Modified polyamide composition

1. A method of increasing glass transition temperature of a polyamide composition, the method comprising including an effective amount of a sulfonated aliphatic compound or a sulfonated aromatic compound as an agent to increase the glass transition temperature of the polyamide;

wherein the polyamide composition comprises a polyamide modified by a sulfonated aliphatic compound or a sulfonated aromatic compound, said compound being chemically bonded to a polymer chain of the polyamide, wherein said modified polyamide is a polycondensate of at least a linear carboxylic diacid and a linear or cyclic diamine, and is present in an amount from 30% to 95% by weight relative to the total weight of the composition, wherein the polyamide is selected from the group consisting of polyamide 66, polyamide 610, polyamide 612, polyamide 1212, polyamide 46, polymethxylyene diamine (MXD6), polyamide 66/6T, mixtures thereof, and copolymers thereof;

one or more fibrous reinforcing agent, wherein said reinforcing agent is present in an amount from 1% to 60% by weight relative to the total weight of the composition; and

optionally an additive;

wherein the sulfonated compound comprises at least one SO 3 X functional group, wherein SO 3 X represents SO 3 H or SO 3 M; and M is a group which replaces the proton H+ of SO 3 H to form an inactive salified group; and

wherein the polyamide composition is moldable.

2. A polyamide composition comprising a mixture of:

a polyamide modified by a sulfonated aliphatic compound or a sulfonated aromatic compound, said compound being chemically bonded to a polymer chain of the polyamide, wherein said modified polyamide is a polycondensate of at least a linear carboxylic diacid and a linear or cyclic diamine, and is present in an amount from 30% to 95% by weight relative to the total weight of the composition, wherein the polyamide is selected from the group consisting of polyamide 66, polyamide 610, polyamide 612, polyamide 1212, polyamide 46, polymethxylylene diamine (MXD6), polyamide 66/6T, mixtures thereof, and copolymers thereof;

one or more fibrous reinforcing agent, wherein said reinforcing agent is present in an amount from 1% to 60% by weight relative to the total weight of the composition; and

optionally an additive;

wherein the sulfonated compound comprises at least one SO 3 X functional group, wherein SO 3 X represents SO 3 H or SO 3 M; and M is a group which replaces the proton H+ of SO 3 H to form an inactive salified group; and

wherein the polyamide composition is moldable.

3. The composition as claimed in claim 2 , wherein the sulfonated compound is a sulfonated aromatic compound.

4. The composition as claimed in claim 2 , wherein the sulfonated compound is chemically bonded to the polyamide chain to form a covalent bond via at least one functional group capable of reacting with the amine functional group or carboxylic add functional group of at least one monomer of the polyamide.

5. The composition as claimed in claim 4 , wherein the sulfonated compound is located in the polymer chain of the polyamide or at the chain end of the polyamide.

6. The composition as claimed in claim 2 , wherein the sulfonated compound is represented by the general formula (I):

(Z) n —Y—(SO 3 X) m   (I)

wherein

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

m is between 1 and 10;

Y is a linear or cyclic, aromatic or aliphatic hydrocarbon radical containing from 2 to 100 carbon atoms, and capable of containing hetero atoms

Z is a functional group capable of reacting with the amine or carboxylic acid functional groups of the monomers of the polyamide; and

n lies between 1 and 10.

7. The composition as claimed in claim 2 , wherein the sulfonated compound is selected from the group consisting of: sodium 5-sulfoisophthalic acid, lithium 5-sulfoisophthalic acid, sodium-4-carboxybenzene sulfonate, sodium-3-carboxybenzene sulfonate, sodium-2-carboxybenzene sulfonate, lithium-3-carboxybenzene sulfonate, potassium-3-carboxybenzene sulfonate, sodium-3-carbomethoxybenzene sulfonate, potassium-2-carbopropoxy-benzene sulfonate, sodium-2-carbomethoxyethylbenzene sulfonate, potassium-3-aminomethylbenzene sulfonate, sodium-2-aminoethylbenzene sulfonate and potassium-3-aminopropylbenzene sulfonate.

8. The composition as claimed in claim 2 , wherein the modified polyamide comprises from 0.1% to 70 mol % of sulfonate unit relative to the total number of moles of units constituting the polymer chain.

9. The composition as claimed in claim 2 , wherein the modified polyamide is obtained by addition of the sulfonated compound in polymerization of the polyamide in the melted state, in the presence of at least one monomers of the polyamide.

10. The composition as claimed in claim 2 , wherein the modified polyamide is obtained by addition of the sulfonated compound hot-mixed with a formed polyamide or a partially formed polyamide.

11. The composition as claimed in claim 2 , wherein the fibrous reinforcing agentis selected from the group consisting of: glass fibers, carbon fibers, natural fibers, aramid fibers, nanotubes, hemp, and flax.

12. The composition as claimed in claim 2 , wherein the additives are selected from the group consisting of: lubricants, fire retardants, plasticizers, nucleating agents, impact modifiers, catalysts, light stabilizers, heat stabilizers, antioxidants, antistatic agents, colorants, matting agents, and molding aid additives.

13. An article obtained by shaping of a composition as claimed in claim 2 by a process of molding or extrusion.

14. The composition as claimed in claim 4 , wherein the at least one functional group capable of reacting with the amine or carboxylic acid functional groups is selected from the group consisting of amine, carboxylic acid, aldehyde, anhydride, a hydroxyl, a ketone and derivatives thereof.

15. The composition as claimed in claim 8 , wherein the modified polyamide comprises from 0.1 mol % to 70 mol % of sulfonate unit relative to the total number of moles of diacid or diamine and/or amino acid units in the polymer chain.

16. The composition as claimed in claim 2 , wherein the polyamide obtained by polycondensation of at least one linear dicarboxylic acid with at least one linear or cyclic diamine is selected from the group consisting of polyamide 66, polyamide 610, polyamide 612, polyamide 1212, polyamide 46, and polymethxylylene diamine (MXD6).

17. The composition as claimed in claim 2 , wherein the composition has an increased glass transition temperature relative to a comparable composition not containing the sulfonated aliphatic, compound or the sulfonated aromatic compound.

18. The composition as claimed in claim 2 , wherein the composition has an increased elastic modulus relative to a comparable composition not containing the sulfonated aliphatic compound or the sulfonated aromatic compound.

19. The composition as claimed in claim 2 , wherein the modified polyamide is present in an amount of from 40% to 80% by weight relative to the total weight of the composition.