Modified polyamide, preparation method thereof and article obtained from said polyamide

1. A polyamide modified by a monofunctional sulfonate compound chemically bonded to the polymer chain, the polyamide comprising at least one unit comprising a sulfonate group of formula (I):

-L-Z-A-Y—SO 3 X  (I)

wherein:

SO 3 X represents SO 3 H or SO 3 M, M is a group which replaces the proto H+ of SO 3 H to form an inactive salified group,

-L-Z— is a radical derived from condensation of two reactive functional groups F 1 and F 2 such that,

F 1 is the precursor of the radical -L- and F 2 the precursor of the radical —Z—,

A is a covalent bond or an aliphatic hydrocarbon radical optionally containing hetero atoms and containing from 1 to 20 carbon atoms, and

Y is a linear or cyclic, aromatic or aliphatic hydrocarbon radical containing at least 2 carbon atoms and optionally containing hetero atoms,

said units being present in a proportion at least equal to 5 mole % relative to the total number of moles of units constituting the polymeric chain, and

wherein the monofunctional sulfonate compound is a monofunctional aromatic compound of formula (II):

wherein:

SO 3 X is as defined above,

—W being -A-F 2 with A as defined above, and

F 2 being selected from the group consisting of —COHal, —COOR, anhydride, —CONRR′, —CO—R, —NRR′, —N═C═O, —OR, —NR—CO—NR′R″, —O—CO—OR, —O—CO—NRR′, —NR—CO—OR′, and —SR, wherein Hal is a halogen and wherein R, R′ and R″, are the same or different, and are a hydrogen atom or a linear or branched alkyl radical containing from 1 to 18 carbon atoms.

2. The modified polyamide as claimed in claim 1 , wherein said units are present in a proportion at least equal to 5 mole % relative to the total number of moles of carboxylic diacid units or of diamine units, and/or of aminocarboxylic acid units in the polymeric chain.

3. The modified polyamide as claimed in claim 1 , wherein M is selected from the alkali and alkaline earth metals.

4. The modified polyamide as claimed in claim 1 , wherein the monofunctional aromatic compound is sodium-3-carboxybenzenesulfonate.

5. A method for preparation of the modified polyamide as claimed in claim 1 , the method comprising introducing a monofunctional aromatic compound of formula (II) into a polymerization medium in a melted state, wherein the functional group can react with an amine or acid functional group.

6. The method as claimed in claim 5 , wherein polymerization of the following monomers is conducted in the melted state:

A) at least one monofunctional compound comprising a sulfonate group, wherein the functional group can react with an amine or acid functional group, and

B) at least one compound or a mixture of compounds selected from:

B1) a mixture of diacid and diamine, and

B2) a lactam or an amino acid,

the molar proportion of monomers A) relative to the monomers B) is at least equal to 5%.

7. The method for preparation of the modified polyamide as claimed in claim 5 , wherein a stoichiometric proportion of acid functional groups and amine functional groups contributed by monomers is introduced into the polymerization medium.

8. A thermoplastic polymer composition comprising:

a. the modified polyamide as claimed in claim 1 ; and

b. a thermoplastic polymer.

9. The thermoplastic polymer composition as claimed in claim 8 , wherein the proportion by weight of modified polyamide in the composition is between 5% and 30%.

10. An article obtained by shaping the polyamide as claimed in claim 1 by molding, injection molding, injection/blow-molding, extrusion/blow-molding, extrusion, spinning or film production.

11. The modified polyamide as claimed in claim 1 , wherein R is an alkyl radical with 1 to 4 carbon atoms.

12. A thermoplastic polymer composition comprising:

a. the modified polyamide obtained by the method as claimed in claim 5 ; and

b. a thermoplastic polymer.