[Technical field]
The present patent application relates to a process for manufacturing aminocarboxylic acids, notably
10-aminodecanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid. It also relates to a
process for producing polyamide or copolyamide from said aminocarboxylic acids.
[Prior art]
Aminocarboxylic acids such as 10-decanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic
acid are monomers of use in particular in the manufacture of long-chain polyamides such as
polyamide 10, polyamide 11 and polyamide 12, respectively.
The excellent thermal and mechanical properties of these polyamides and also their chemical
resistance make them advantageous for various applications, notably in motor vehicles, sports
equipment, coatings or 3-D printing. One increasingly valued advantage of these polyamides is the
fact that their monomers can be obtained from products of plant origin and that are therefore
renewable.
Thus, 11-aminoundecanoic acid is attainable from castor oil by transesterification in the presence of
methanol and subsequent pyrolysis. The methyl 10-undecenoate obtained is hydrolysed to 10-
undecenoic acid which can be brominated at the chain end by a step of hydrobromination. The 11-
bromoundecanoic (or ω-bromoundecanoic) acid obtained can then be subjected to a step of
ammonolysis by reaction with ammonia to give 11-aminoundecanoic acid and ammonium bromide.
The hydrobromination step is described for example in French patent FR 928265 A. Hydrobromic acid
is made to act on 10-undecenoic acid in solution in an organic solvent in the presence of a catalyst
such as benzoyl peroxide.
French patent FR 951932 proposes to increase the yield of 11-bromoundecanoic acid to around 80%
using hydrobromic acid in excess and a hydrocarbon solvent such as benzene, toluene, petroleum
ether or chlorinated hydrocarbons.
According to European patent EP 3 030 543 B1, it is also possible to use other solvents when the
reaction is carried out in two steps, the first step consisting in mixing, in a first reactor, 10-
undecenoic acid and hydrobromic acid in the form of a liquid stream in turbulent flow and the
second step consisting in continuing the reaction in a second reactor in transitional or laminar flow.
Patent applications FR 928265 and EP 235 866 B1 describe the conversion of 11-bromoundecanoic
acid to 11-aminoundecanoic acid by treatment with an aqueous solution of ammonium hydroxide.
The 11-aminoundecanoic acid formed is separated from the ammonium bromide formed.
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Application WO 2018/080869 A1 describes the synthesis of 10-aminodecanoic acid from 9-decenoic
acid obtained from a palm oil composition. In particular, the hydrobromination of 9-decenoic acid is
carried out by bubbling gaseous hydrogen bromide through a solution of 9-decenoic acid in toluene
in the presence of benzoyl peroxide at a temperature of from 5°C to 15°C. After washing, drying and
purification in hexane, the yield of 10-bromodecanoic acid is 64%. The 10-bromodecanoic acid can
react with 28% ammonium hydroxide at ambient temperature then at 45°C to form 10-
aminodecanoic acid, which is recovered by crystallization at ambient temperature then filtration,
washing and drying.

CLAIMS
1. Process for producing an aminocarboxylic acid of formula (I) below:
NH3-CH2-(CH2)n-COOH (I)
in which n is an integer from 7 to 12, preferably from 8 to 10, comprising the following steps:
(i) reacting the unsaturated carboxylic acid of formula (II) below:
CH=CH-(CH2)n-1-COOH (II)
with hydrogen bromide (HBr) to form the ω-bromoalkanoic acid of formula (III) below:
Br-CH2-(CH2)n-COOH (III);
(ii) reacting the ω-bromoalkanoic acid of formula (III) obtained with ammonia in aqueous solution to
form a reaction mixture comprising the aminocarboxylic acid of formula (I) and ammonium bromide;
(iii) separating the reaction mixture of the aminocarboxylic acid of formula (I) and an aqueous
solution rich in ammonium bromide;
(iv) bringing the aqueous solution rich in ammonium bromide obtained into contact with sodium
hydroxide to form ammonia and an aqueous solution rich in sodium bromide;
(v) purifying the aqueous solution rich in sodium bromide obtained in order to eliminate the organic
impurities;
(vi) bringing the purified aqueous solution rich in sodium bromide obtained into contact with
chlorine to form bromine and an aqueous solution rich in sodium chloride;
(vii) reacting the bromine obtained with hydrogen to form hydrogen bromide; and
(viii) recycling the hydrogen bromide obtained to step (i).
2. Process according to Claim 1, in which bromides originating from another process are added
to the solution rich in ammonium bromide or sodium bromide of step (iv).
3. Process according to Claim 1 or 2, in which bromine originating from another process is
added to the bromine obtained in step (vi).
4. Process according to one of Claims 1 to 3, in which step (v) of purifying the aqueous solution
of bromides makes it possible to reduce the TOC by a factor of more than 5.
5. Process according to one of Claims 1 to 4, in which step (vi) is performed with a bromide
solution having less than 2%, and preferably less than 1% and advantageously less than 0.5%
of TOC.
6. Process according to one of Claims 1 to 5, in which step (v) is carried out by acidification of
the aqueous solution rich in sodium bromide resulting from step (iv) followed by a
decantation of the oily phase formed.
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7. Process according to Claim 6, in which the aqueous solution rich in sodium bromide resulting
from step (iv) is acidified by addition of acid to a pH of between 3 and 5.
8. Process according to one of Claims 1 to 7, in which step (v) comprises a subsequent step (va)
in which the oily phase formed in step (v) is subjected to an extraction operation to obtain an
aqueous solution enriched in sodium bromide, which is sent back to step (iv) or (vi), in
particular by liquid/liquid extraction.
9. Process according to one of Claims 1 to 5, in which step (v) is carried out by neutralization of
the aqueous solution rich in sodium bromide followed by a liquid/liquid extraction.
10. Process according to Claim 9, in which the aqueous solution rich in sodium bromide is
neutralized in step (v) to a pH between 3 and 10, in particular by addition of an aqueous
solution of hydrochloric acid, of hydrobromic acid, of sulfuric acid or of a mixture thereof.
11. Process according to one of Claims 1 to 5, in which step (v) is carried out by adsorption on an
adsorbent material, in particular chosen from mineral materials such as activated carbon; a
silica or an alumina or a mixture thereof; organic materials such as adsorbent
macrocrosslinked resins or ion-exchange resins.