METHOD FOR RECYCLING A POLYAMIDE COMPRISING A PRETREATMENT STEP

1 . A method of recovery of the monomers from a polyamide (PA), comprising the following steps:

a) a product (P) comprising a polymeric component comprising the polyamide (PA) is put into contact with at least one inorganic salt (A*) to reduce partly or totally the crystallinity of the polyamide (PA), step a) being performed with the polymeric component of product (P) being in the molten form and the inorganic salt (A*) being selected in the group of the inorganic salts of alkaline metals, the inorganic salts of alkaline-earth metals and the inorganic salts of Zn;

b) the mixture obtained at the end of step a) is optionally treated so as to remove from the molten mixture at least one solid material;

c) the hydrolysis of the molecules of polyamide(s) present in the mixture obtained at the end of step a) or optional step b), is performed in an aqueous medium either (i) by an acidic or basic hydrolysis involving an acid (Ac) or a base (Ba), or (ii) by an enzymatic hydrolysis;

d) a stream (S) comprising the diacid (A), the diamine (B), each of these two compounds being either in their free form or in the form of a salt, is recovered at the end of step c) and is further processed in order to separate and recover the diacid (A), and the diamine (B).

2 . The method according to claim 1 , wherein:

the polyamide (PA) comprise at least 50.0 mol % of recurring units (R PA ) formed from the condensation of at least diacid (A) and at least diamine (B), this proportion being based on the total amount of recurring units in the polyamide (PA); or

the recurring units of the polyamide (PA) consist of recurring units (R PA ) formed from the condensation of at least diacid (A) and at least diamine (B).

3 . The method according to claim 2 , wherein the recurring units (R PA ) are according to formula (F) below:

wherein R a and R b , equal to or different from each other, are divalent hydrocarbon groups selected in the group of aliphatic, alicyclic, cycloaliphatic and aromatic groups.

4 . The method according to claim 1 , wherein the polyamide (PA) is prepared by polycondensation of:

at least one diacid (A) selected in the group of C 2 -C 18 aliphatic diacids; diacids of formula HOOC-Cy-COOH where Cy is a C 3 -C 6 non-aromatic cycle optionally substituted by C 1 -C 10 alkyl groups; isophthalic acid and terephthalic acid; and

at least one diamine (B) selected in the group consisting of C 2 -C 18 aliphatic diamines, C 4 -C 18 cycloaliphatic diamines and C 8 -C 18 arylaliphatic diamines.

5 . (canceled)

6 . The method according to claim 1 , wherein the polyamide (PA) is selected in the group of polyamides X. Y where X is an aliphatic diamine represented by general formula (II) H 2 N-Alk-NH 2 , where Alk is a C 2 -C 18 linear or branched alkylene group and Y is an aliphatic diacid represented by general formula (I) HOOC-Alk-COOH, wherein Alk is a C 1 -C 16 linear or branched alkylene group.

7 . The method according to claim 1 , wherein the polyamide (PA) is selected in the group consisting of polyamide 6.6, polyamide 6.9, polyamide 6.10, polyamide 6.12, polyamide 10.10, polyamide 4.6, polyamide 4.9, polyamide 4.10, polyamide 12.12, polyamide 10.12, polyamide MXD6, polyamide MXD6/PXD6, polyamide MXD6/MXDI, polyamide 6T/66, polyamide 6T/6I/66, polyamide 6T/6I and mixtures thereof.

8 . (canceled)

9 . The method according to claim 1 , wherein the proportion of polyamide (PA) in product (P) is at least 30.0 wt. %.

10 . (canceled)

11 . The method according to claim 1 , wherein the anion of the inorganic salt (A*) is chloride or nitrate selected in the group of CaCl 2 , CaCl 2 ), xH 2 O, Ca(NO 3 ) 2 , Ca(NO 3 ) 2 , xH 2 O, LiCl, ZnCl 2 , MgCl 2 wherein x is an integer between 1 and 6, and combination of two or more of said inorganic salts.

12 . (canceled)

13 . The method according to claim 1 , wherein the proportion of inorganic salt (A*) is:

less than 60.0 wt %, this proportion in wt % being expressed as the weight of inorganic salt (A*) relative to the total weight of polyamide (PA)+inorganic salt (A*); and/or

at least 5.0 wt %, this proportion in wt % being expressed as the weight of inorganic salt(s) (A*) relative to the total weight of polyamide (PA)+inorganic salt (A*).

14 . The method according to claim 1 , wherein at the end of step a), the crystallinity of the polyamide (PA) is reduced by a ratio r of at least 25%, r being defined as: r=(Hm of polyamide (PA)−Hm at the end of step a))/Hm of polyamide (PA)×100, Hm being determined by DSC.

15 . The method according to claim 1 , wherein at the end of step a), the number average molecular weight (Mn) of the polyamide (PA) is reduced by a ratio r* of at least 20.0%, r* being defined as: r=(Mn of polyamide (PA) Mn at the end of step a))/Mn of polyamide (PA))×100.

16 . The method according to claim 1 , wherein the degree of conversion R of polyamide (PA) achieved at the end of hydrolysis step c) is at least 90.0 mol %.

17 . The method according to, wherein step c) is an acidic hydrolysis, performed at a pH lower than 6.0, a basic hydrolysis performed at a pH higher than 8.0, or an enzymatic hydrolysis performed in the presence of at least one enzyme selected in the group of enzymes that are suitable to break the —NH—CO— bond of the polyamide(s).

18 . (canceled)

19 . (canceled)

20 . (canceled)

21 . (canceled)

22 . The method according to claim 1 , wherein further processing of the stream (S) is based on at least one crystallization step and/or at least one distillation step.

23 . The method according to claim 17 , wherein the hydrolysis is an acidic hydrolysis and where the diacid (A) and the salt of the diamine (B) which are present in the stream (S) are separated and where the salt of diamine (B) having been separated reacts with an inorganic base of formula XOH, X being Li, Na, K or a combination of two or more of these cations to release the diamine (B).

24 . The method according to claim 1 , wherein the hydrolysis in step c) is performed at a pH lower than 6.0 or higher than 8.0.