WATER-DISPERSIBLE COPOLYAMIDE

1 . A water-dispersible copolyamide comprising at least four different polyamide units, in which:

at least one of said polyamide units includes at least one sulfonate group, said polyamide sulfonate unit being present in a content of at least 15% by weight; and

at least two of said polyamide units are derived from aliphatic monomers;

it being understood that said copolyamide does not include more than 20% by weight of caprolactam-based unit, that it has a glass transition temperature of between 10° and 140° C. as measured by DSC according to the standard NF EN ISO 11 357-2 with a heating rate of 20° C./minute, and an inherent viscosity of greater than 0.4 dl/g as measured by applying the standard ISO 307:2007, but at 20° C. in a solution at 0.5% by weight in m-cresol.

2 . The water-dispersible copolyamide as claimed in claim 1 , comprising at least five different polyamide units.

3 . The water-dispersible copolyamide as claimed in claim 2 ,

in which the copolyamide is of formula (I):

in which:

A is a unit obtained from at least one lactam or aminocarboxylic acid comprising at least 6 carbon atoms;

X 1 Y 1 is a unit obtained from an aliphatic, cycloaliphatic, heterocyclic or arylaliphatic diamine X 1 and from an aliphatic or aromatic dicarboxylic acid Y 1 ;

X 2 Y 2 is a unit obtained from an aliphatic, cycloaliphatic, heterocyclic or arylaliphatic diamine X 2 and from an aliphatic or aromatic dicarboxylic acid Y 2 ;

X 3 Y 3 is a unit obtained from an aliphatic, cycloaliphatic, heterocyclic or arylaliphatic diamine X 3 and from an aliphatic or aromatic dicarboxylic acid Y 3 ; and

X 4 Z is a unit obtained from an aliphatic, cycloaliphatic, heterocyclic or arylaliphatic diamine X 4 including 4 to 12 carbon atoms and a sulfonate compound Z chosen from aromatic dicarboxylic acid sulfonates, aliphatic sulfonates or esters thereof, including 4 to 18 carbon atoms and bearing at least one group of formula SO 3 − X + in which X may be a hydrogen, a quaternary ammonium group or a monovalent metal.

4 . The copolyamide as claimed in claim 1 , not including more than 10% by weight of cycloaliphatic diamine residues.

5 . The water-dispersible copolyamide as claimed in claim 3 , in which A is a lactam or an aminocarboxylic acid including 10 to 12 carbon atoms, respectively, notably chosen from 11-aminoundecanoic acid and lauryllactam.

6 . The water-dispersible copolyamide as claimed in claim 3 , in which X 1 , X 2 , X 3 and X 4 are identical or different, and chosen from 1,2-ethylenediamine, 1,6-hexamethylenediamine, 1,9-nonanediamine and 1,10-decanediamine.

7 . The water-dispersible copolyamide as claimed in claim 3 , in which Y 1 and Y 2 are identical or different, and chosen from adipic acid, azelaic acid, sebacic acid and dodecanedioic acid.

8 . The water-dispersible copolyamide as claimed in claim 3 , in which Y 3 is isophthalic acid.

9 . The water-dispersible copolyamide as claimed in claim 1 , in which the sulfonate compound is chosen from the sodium, lithium or potassium salt of 5-sulfoisophthalic acid and the sodium, lithium or potassium salt of the methyl diester of 5-sulfoisophthalic acid.

10 . The water-dispersible copolyamide as claimed in claim 3 , comprising 0 to 30% by weight of unit A, 0 to 30% by weight of unit X 1 Y 1 , 0 to 30% by weight of unit X 2 Y 2 , 0 to 30% by weight of unit X 3 Y 3 and 15% to 70% by weight of unit X 4 Z, it being understood that said copolyamide includes at least four different polyamide units.

11 . The water-dispersible copolyamide as claimed in claim 1 , comprising at least 40% by weight of aromatic units.

12 . The water-dispersible copolyamide as claimed in claim 1 , having a glass transition temperature of between 11° and 130° C.

13 . The water-dispersible copolyamide as claimed in claim 1 , having an inherent viscosity of greater than 0.5 dl/g.

14 . A process for manufacturing a water-dispersible copolyamide as claimed in claim 1 , comprising the steps of:

a. providing monomers chosen, respectively, from a lactam, an aminocarboxylic acid, and a diamine and a diacid, in suitable number and proportions;

b. polycondensation of the monomers, where appropriate, in the presence of one or more catalysts and/or chain limiters under conditions suitable for obtaining said copolyamide; and

c. where appropriate, granulation of said copolyamide.

15 . A composition comprising the water-dispersible copolyamide as claimed in claim 1 , which is notably in filament form.