TRANSFORMATION-STABLE COMPOSITION COMPRISING VISCOUS POLYAMIDE, PRODUCTION THEREOF AND USE OF SAME

Abstract

The invention relates to the use of at least one catalyst, at least one copper heat stabiliser and at least one oligo- or poly-carbodiimide with a matrix including at least one polyamide, in order to form a composition that has a good melt viscosity and is stable during transformation, in particular during extrusion.

Claims

1. The use of at least one catalyst, of at least one copper-based heat stabilizer and of at least one oligo- or polycarbodiimide with a matrix comprising at least one polyamide, in order to form a composition which exhibits a good melt viscosity and which is stable in transformation, especially in extrusion.

2. The use as claimed in claim 1, wherein said melt viscosity of said composition is substantially constant between 1 minute and at least 5 minutes.

3. The use as claimed in claim 1, wherein said composition additionally exhibits a resistance to thermal oxidation.

4. The use as claimed in claim 1, wherein said composition exhibits a melt viscosity of approximately 13,000 to approximately 23,000 Pa.Math.s, as determined by oscillatory rheology at 270° C. at 10 rad/sec while flushing with nitrogen with 5% deformation and shearing of 10 sec.sup.−1 between two parallel plates with a diameter of 25 mm.

5. The use as claimed in claim 4, wherein said melt viscosity is comprised of approximately 13,000 to approximately 23,000 Pa.Math.s for at least 30 minutes, as determined by oscillatory rheology at 270° C. at 10 rad/sec while flushing with nitrogen with 5% deformation and shearing of 10 sec.sup.−1 between two parallel plates with a diameter of 25 mm.

6. The use as claimed in claim 1, wherein the proportion by weight of catalyst is comprised of approximately 50 ppm to approximately 5000 ppm, with respect to the total weight of the composition.

7. The use as claimed in claim 1, wherein the catalyst is chosen from phosphoric acid (H.sub.3PO.sub.4), phosphorous acid (H.sub.3PO.sub.3), hypophosphorous acid (H.sub.3PO.sub.2) or a mixture of these.

8. The use as claimed in claim 1, wherein the proportion by weight of copper-based heat stabilizer com is comprised of approximately 0.05% to approximately 1%, with respect to the total weight of the composition.

9. The use as claimed in claim 8, copper-based heat stabilizer is a mixture of potassium iodide and copper iodide.

10. The use as claimed in claim 1, wherein the proportion by weight of oligo- or polycarbodiimide is comprised of approximately 0.1 to approximately 3%, with respect to the total weight of the composition.

11. The use as claimed in claim 10, wherein the oligo- or polycarbodiimide is chosen from a Stabilizer, a Stabaxol®, or a mixture of these.

12. The use as claimed in claim 1, wherein the thermoplastic polymer is a polyamide chosen from an aliphatic polyamide, a cycloaliphatic polyamide, an aromatic polyamide or a mixture of these.

13. The use as claimed in claim 12, wherein the polyamide exhibits a M.p. comprised of 160° C. to 290° C., determined according to the standard ISO 11357-3 (2013).

14. The use as claimed in claim 12 wherein the polyamide is chosen from: PA 11, PA 12, 11/10.T, PA 10.10, PA 10.12 and the copolyamides 11/12 having either more than 90% of units 11 or more than 90% of units 12.

15. A viscous composition which is stable in transformation as defined in claim 1, wherein it comprises, with respect to the total weight of the composition: a. 20.5 to 99.845% by weight of at least one polyamide; b. 0.005 to 0.5% by weight of at least one catalyst; c. 0.05 to 1% by weight of at least one copper-based heat stabilizer; d. 0.1 to 3% by weight of at least one oligo- or polycarbodiimide; e. 0 to 15% of at least plasticizer; f. 0 to 30% of at least one polyolefin; g. 0 to 30% of at least one additive.

16. The composition as claimed in claim 15, wherein it consists of: a. 64.5 to 98.745% by weight of at least one polyamide b. 0.005 to 0.5% by weight of at least one catalyst; c. 0.05 to 1% by weight of at least one copper-based heat stabilizer; d. 0.1 to 3% by weight of at least one oligo- or polycarbodiimide; e. 1 to 30% of at least one polyolefin; f. 0.1 to 1% of at least one additive.)

17. The composition as claimed in claim 15, wherein it consists of: a. 49.50 to 97.745% by weight of at least one polyamide; b. 0.005 to 0.5% by weight of at least one catalyst; c. 0.05 to 1% by weight of at least one copper-based heat stabilizer; d. 0.1 to 3% by weight of at least one oligo- or polycarbodiimide; e. 1 to 15% of at least plasticizer; f. 1 to 30% of at least one polyolefin; g. 0.1 to 1% of at least one additive.

18. The composition as claimed in claim 15, wherein the polyamide is chosen from an aliphatic polyamide, a cycloaliphatic polyamide, an aromatic polyamide or a mixture of these.

19. The composition as claimed in claim 15, wherein the polyamide exhibits a M.p. comprised of 160° C. to 290° C., determined according to the standard ISO 11357-3 (2013).

20. The composition as claimed in claim 15, wherein the polyamide is chosen from: PA 11, PA 12, 11/10.T, PA 10.10, PA 10.12 and the copolyamides 11/12 having either more than 90% of units 11 or more than 90% of units 12.

21. The composition as claimed in claim 15, wherein the catalyst is chosen from phosphoric acid (H.sub.3PO.sub.4), phosphorous acid (H.sub.3PO.sub.3), hypophosphorous acid (H.sub.3PO.sub.2) or a mixture of these.

22. The composition as claimed in claim 15, wherein the copper-based heat stabilizer is a mixture of potassium iodide and copper iodide.

23. The composition as claimed in claim 15, wherein the oligo- or polycarbodiimide is chosen from a Stabilizer, a Stabaxol®, or a mixture of these.

24. The use of a composition as defined in claim 15 for forming a structure, such as: a flexible pipe intended for the transportation of gas or for the exploitation of offshore oil deposits; a flexible pipe for motor vehicles, for refrigeration, for air conditioning or for ducts produced by extrusion-blow molding for supplying with air; and a hollow body, a molding or a sports item.

25. The use as claimed in claim 24, wherein the a flexible pipe intended for the transportation of gas or for the exploitation of offshore oil deposits exhibits a good resistance to thermal oxidation and a resistance to hydrolysis.

26. The use as claimed in claim 24 wherein the pipe exhibits a working temperature of at least 70° C. for 20 years.

27. The use as claimed in claim 24, wherein the structure is a pipe is intended for the transportation of gas.

28. The use as claimed in claim 24 the structure is a flexible pipe intended for the exploitation of offshore oil deposits.

29. The use as claimed in claim 24 the structure is a flexible pipe for motor vehicles, in particular for the transportation of fuel (gasoline, diesel, biodiesel or ethanol), for refrigeration, for air conditioning or for ducts produced in particular by extrusion-blow molding for supplying with air.

30. A flexible pipe intended for the transportation of gas or for the exploitation of offshore oil deposits, or for motor vehicles, in particular for the transportation of fuel (gasoline, diesel, biodiesel or ethanol), for refrigeration, for air conditioning or for supplying with air, as defined in claim 24.

31. The flexible pipe as claimed in claim 30, wherein said layer is the layer in contact with the fluid and intended for the transportation of gas.

32. The flexible pipe as claimed in claim 31, wherein it can additionally comprise at least one second layer, in particular made of thermoplastic.

33. The flexible pipe as claimed in claim 30, wherein said layer is the internal layer of a flexible pipe intended for the exploitation of offshore oil deposits.

34. The pipe as claimed in claim 30, wherein said layer is the external layer of a flexible pipe intended for the exploitation of offshore oil deposits.

35. The pipe as claimed in claim 30, wherein it comprises an internal layer and an external layer which consist of the composition, said internal and external layers consisting of the same composition or each consisting of a different composition.

Description

DESCRIPTION OF THE FIGURES

[0253] FIG. 1 exhibits the oscillatory rheology at 270° C. (frequency: 10 rad/s, 5% deformation, shearing 10 s.sup.−1) from 0 to 30 minutes.

[0254] The graph exhibits the analysis time in seconds on the abscissa and the viscosity in Pa.Math.s on the ordinate.

[0255] At 1800 seconds, from the top downwards:

[0256] Catalyzed PA 11 (600 ppm H.sub.3PO.sub.4).

[0257] Catalyzed PA 11 (600 ppm H.sub.3PO.sub.4)+1% Stabilizer 9000.

[0258] Catalyzed PA 11 (600 ppm H.sub.3PO.sub.4)+1% Stabilizer 9000+0.25% iodine 201:

[0259] curve of the invention, the only one having a viscosity of between 13 000 and 23 000 Pa.Math.s.

[0260] Non-catalyzed PA 12+1% Stabilizer 9000+0.25% iodine 201.

[0261] Non-catalyzed PA 11+1% Stabilizer 9000.

[0262] Catalyzed PA 11 (600 ppm H.sub.3PO.sub.4)+0.25% iodine 201.

[0263] Non-catalyzed PA 11.

EXAMPLES

[0264] Products Used

[0265] The polyamides used are PA 11 (Besno, sold by Arkema), PA 12 (Aesno, sold by Arkema), PA 10.10 (sold by Arkema: Hiprolon 200) and PA 10.12 (sold by Arkema: Hiprolon 400).

[0266] The copper-based heat stabilizer is PolyAdd P201 from Polyad Services (iodine 201).

[0267] The carbodiimide used is Stabilizer® 9000 (poly(1,3,5-triisopropylphenylene-2,4-carbodiimide), sold by Raschig, or TCC, sold by Teijin.

[0268] The catalyst used is H.sub.3PO.sub.3 or H.sub.3PO.sub.4.

[0269] Anox® NDB TL89: organic stabilizer of phenol phosphite type, sold by Chemtura.

[0270] BBSA: n-butylbenzenesulfonamide, sold by Proviron.

[0271] EPR 1801: polyolefin (maleic anhydride-functionalized ethylene copolymer), sold by Exxon.

[0272] Fusabond® 493: polyolefin (anhydride-functionalized ethylene copolymer), sold by DuPont.

Example 1

Determination of the Melt Viscosity of Polyamides of the Invention with or without Catalyst in the Presence or not of a Copper-Based Stabilizer and/or of a Carbodiimide

[0273] The tests (mixture of PA with or without catalyst, to which a copper-based stabilizer and/or a carbodiimide are or are not added) are carried out on an Xplore MC15 micro compounder equipped with 111 and 123 screws (screw profile 2).

[0274] The flat temperature profile at 270° C. is programmed.

[0275] The various mixtures are produced with a screw speed of 100 rpm and a recirculation time of 25 minutes, to which the machine feed time, i.e. between 1′30 and 2′, has to be added.

[0276] The tests are carried out while flushing with nitrogen (0.5 bar).

[0277] The normal force is measured in N. It represents the change in the melt viscosity.

[0278] The viscosity at T0 and its change at T+30 minutes are determined by plate-plate oscillatory rheology.

[0279] Plate-plate: 30 min at 270° C. 10 rad/sec 5% deformation according to the following operating conditions:

[0280] Appliance: Physica MCR301

[0281] Geometry: parallel plates with a diameter of 25 mm

[0282] Temperatures: 270° C.

[0283] Frequency: 10 rad.s.sup.−1

[0284] Duration: 30 minutes

[0285] Atmosphere: Flushing with nitrogen.

[0286] Shearing of 10 s.sup.−1

Example 1.1

PA 11, PA 12 and PA 10.10 without Catalyst: with or without Copper-Based Heat Stabilizer and/or Carbodiimide

[0287] The percentages are shown by weight.

[0288] The melt viscosity is determined at T0 and after 30 minutes.

[0289] The inherent viscosity is determined in m-cresol according to the standard ISO 307-2007.

[0290] The method is well known to a person skilled in the art. The standard ISO 307-2007 is followed but with the solvent being changed (use of m-cresol instead of sulfuric acid) and the temperature being 20° C.

TABLE-US-00001 PA 11 PA 11 PA 11 Inherent viscosity 1.45 1.45 1.45 Catalyst — — — Copper-based heat — 0.25% iodine 0.25% iodine stabilizer 201 201 Carbodiimide — — 1% Stabilizer 9000 Plate-plate 270° C. 10 rad/sec Pa .Math. s Pa .Math. s Pa .Math. s (melt viscosity) T0 384 No RIV 5350 After 30 min 807 No RIV 5278 Comment Too fluid Too fluid Too fluid

[0291] “No RIV” means that there is no rise in viscosity.

[0292] A PA 11, without catalyst, with a relatively high inherent viscosity (1.45, extrusion grade), is not viscous enough, whether with copper-based stabilizer alone or copper-based stabilizer and carbodiimide.

[0293] The addition of 0.25% of iodine 201 does not increase the viscosity.

[0294] The addition of carbodiimide provides a rise in melt viscosity which, however, is not sufficient for the transformation of the product.

TABLE-US-00002 PA 12 PA 12 Inherent viscosity 1.60 1.60 Catalyst — — Copper-based heat — 0.25% iodine 201 stabilizer Carbodiimide — 1% Stabilizer 9000 Plate-plate 270° C. 10 rad/sec Pa .Math. s Pa .Math. s (melt viscosity) T0 7152 9000 After 30 min 7800 10000 Comment Too fluid Too fluid

[0295] A PA 12 (Aesno from Arkema without chain-limiting agent), without catalyst, with a high inherent viscosity (1.6), is not viscous enough even with addition of copper-based stabilizer and carbodiimide.

[0296] The addition of carbodiimide provides a rise in melt viscosity which, however, is not sufficient for the transformation of the product.

TABLE-US-00003 PA 10.10 PA 10.10 PA 10.10 Inherent viscosity 1.35 1.35 1.35 Catalyst — — — Copper-based heat — 0.25% iodine 0.25% iodine stabilizer 201 201 Carbodiimide — — 1% Stabilizer 9000 Plate-plate 270° C. 10 rad/sec Pa .Math. s Pa .Math. s Pa .Math. s (melt viscosity) T0 1650 No RIV 7685 After 30 min 2648 No RIV 9635 Comment Too fluid Too fluid Too fluid

[0297] A PA 10.10, with a medium inherent viscosity (1.35), is too fluid, whether with copper-based stabilizer to which carbodiimide has or has not been added.

[0298] Consequently, the problem of the melt inherent viscosity cannot be solved by increasing the starting inherent viscosity.

Example 1.2

PA 11, PA 10.10 and PA 10.12 with Catalyst: with or without Copper-Based Heat Stabilizer and/or Carbodiimide

[0299] The percentages are shown by weight.

TABLE-US-00004 Catalyzed PA Catalyzed PA PA 11 11 11 Inherent viscosity 1.45 1.45 1.45 Catalyst 600 ppm 600 ppm 600 ppm H.sub.3PO.sub.4 H.sub.3PO.sub.4 H.sub.3PO.sub.4 Copper-based heat — 0.25% iodine 0.25% iodine stabilizer 201 201 Carbodiimide — — 1% Stabilizer 9000 Plate-plate 270° C. Pa .Math. s Pa .Math. s Pa .Math. s 10 rad/sec (melt viscosity) T0 13500 1550 19000 After 30 min 30000 7300 23000 Comments Too much Too fluid Invention change Change after 21 000, i.e. +  5% 400 sec 55% Change after 30 min 148% 22%

[0300] A PA 11 with a relatively high inherent viscosity (1.45; extrusion grade) is sufficiently viscous in the molten state at T0 (i.e., a melt viscosity of greater than or equal to approximately 13 000 Pa.Math.s) but changes too much since the melt viscosity is very markedly greater than 23 000 Pa.Math.s).

[0301] The addition of a heat stabilizer to the catalyzed PA 11 does not make it possible to improve the viscosity, quite the opposite since the latter falls drastically, stopping even the rotation.

[0302] On the other hand, the addition of a heat stabilizer and carbodiimide makes it possible not only to obtain a melt viscosity of greater than or equal to approximately 13 000 Pa.Math.s but a melt viscosity which is also stable for at least 30 minutes.

TABLE-US-00005 PA 10.10 PA 10.10 PA 10.10 Inherent viscosity 1.45 1.45 1.45 Catalyst 2000 ppm 2000pm 2000 ppm H.sub.3PO.sub.4 H.sub.3PO.sub.4 H.sub.3PO.sub.4 Copper-based heat — 0.2% iodine 0.2% iodine stabilizer 201 201 Carbodiimide — — 1% Stabilizer 9000 Plate-plate 270° C. 10 rad/sec Pa .Math. s Pa .Math. s Pa .Math. s (melt viscosity) T0 9369 10200 13357 After 30 min 12805 16400 20313 Comment Too fluid Too fluid Invention Change after 30 min 52%

[0303] A PA 10.10 with an inherent viscosity of 1.45 comprising only a catalyst is not sufficiently viscous in the molten state at T0 (i.e., a melt viscosity of less than 13 000 Pa.Math.s).

[0304] The addition of a heat stabilizer does not make it possible to achieve a sufficient melt viscosity.

[0305] On the other hand, the addition of a heat stabilizer and carbodiimide makes it possible not only to obtain a melt viscosity of greater than or equal to approximately 13 000 Pa.Math.s but a melt viscosity which is also stable for at least 30 minutes.

TABLE-US-00006 PA 10.12 PA 10.12 PA 10.12 Inherent viscosity 1.4 1.4 1.4 Catalyst 100 ppm 100 ppm H.sub.3PO.sub.3 100 ppm H.sub.3PO.sub.3 H.sub.3PO.sub.3 Copper-based heat — 0.2% iodine 201 0.2% iodine 201 stabilizer Carbodiimide — — 1% Stabilizer 9000 Plate-plate 270° C. Pa .Math. s Pa .Math. s Pa .Math. s 10 rad/sec (melt viscosity) T0 6156 9000 17653 After 30 min 27558 17000 19772 Comment Too fluid Too fluid and too Invention and too much change much change Change after 30 min 347% 89% 12%

[0306] In the same way, with a PA 10.12 with an inherent viscosity of 1.4 comprising only a catalyst, the melt viscosity at T0 is too low (less than 13 000 Pa.Math.s).

[0307] The addition of a heat stabilizer does not make it possible to achieve a sufficient melt viscosity.

[0308] On the other hand, the addition of a heat stabilizer and carbodiimide makes it possible not only to obtain a melt viscosity of greater than or equal to approximately 13 000 Pa.Math.s but a melt viscosity which is also stable for at least 30 minutes.

Example 2

Influence of the Presence of Catalyst and of the Proportion of a Copper-Based Stabilizer and/or Carbodiimide on the Rheological Properties of the Polyamides of the Invention

Example 2.1

[0309] The percentages are shown by weight.

[0310] The polyamide used for all the tests of this example is PA 11 with an inherent viscosity of 1.45 as above.

TABLE-US-00007 Copper- based heat stabilizer Catalyst (Iodine 201) Carbodiimide Viscosity (ppm) % by weight % by weight Rheology stability 0 0 0 − ++ 0 0 1 − ++ 0 0 1.5 + + 0 0 2 + + 600 0 0 + − 600 0 1 − − 600 0.25 0 − + 600 0.25 1 ++ ++ The remainder to 100% is, in each case, the percentage by weight of PA 11. “−” means that the value obtained is insufficient for the transformation “+” means that the value is borderline for the transformation “++” means that the value obtained is comfortable for the transformation

[0311] This example shows that the most important aspect for the transformation is not the inherent viscosity value but the value of the melt viscosity with the catalyst/copper-based heat stabilizer/carbodiimide combination.

Example 2.2

The Polyamide used for all the Tests of this Example is PA 11.

[0312] The percentages shown are by weight.

TABLE-US-00008 Plate-plate at Inherent viscosity T0 PA 11 + 600 ppm H.sub.3PO.sub.4 1.77 15000 Noncatalyzed PA 11 + 1% 1.80 6600 Stabilizer ® 9000 Noncatalyzed PA 11 + 1.5% 2.25 12130 Stabilizer ® 9000 PA 11 + 600 ppm H.sub.3PO.sub.4 + 2.30 20000 1% Stabilizer ® 9000 + 0.25% iodine 201

[0313] There is no correlation between the viscosity in solution (inherent viscosity in meta-cresol) and the melt viscosity. This can be explained by the polydispersity index representative of the branchings.

Example 3

Evaluation of the Compositions of the Invention Additionally Comprising Polyolefins and/or Plasticizers and/or Additives: Thermal Behavior at 140° C.

[0314] The proportions shown are percentages by weight, with respect to the total weight of the composition.

[0315] Test on twin-screw at 280° C. -300 rev/min under vacuum-600 mmHg (Werner 40) at 60 kg/h.

[0316] The PA base is dried (moisture content<0.1%).

TABLE-US-00009 Comp. 1 Comp. 2 Comp. 3 Comp. 4 Inv. 1 Inv. 2 Anox NDB TL89 1.2 BBSA 6 6 10 6 6 6 PA 11 + 600 ppm 82.8 83.8 82.8 83.3 H.sub.3PO.sub.4 Inherent viscosity 1.45 EPR 1801 10 10 10 10 Fusabond 493 10 6 iodine 201 0.2 0.2 0.2 0.2 0.2 PA 11 inherent 82.5 82.5 viscosity 1.45 Stabilizer 9000 0 1.3 1.3 0 1 TCC 0.5 Head pressure 23 35 33 16.5 40 40 (bar) Torque (%) 71 68 63 63 86 82 RCG at 260° C. 5 min 2819 2209 1936 3830 at 100 sec.sup.−1: in Pa .Math. s plate-plate at 10 rad/sec: 13000 10300 9800 1200 14000 13000 T0 at 270° C. in Pa .Math. s plate-plate at 10 rad/sec: 31800 5140 2770 8000 21000 19000 after 30 min at 270° C. in Pa .Math. s Test specimens 720 h >2000 h >2000 h >2000 h ISO 527-2 1BA Half life at 140° C. Corrected 1.72 2.22 2.49 1.50 2.31 2.2 inherent viscosity

[0317] The half life measured with regard to the elongation at break changes from 30 days for the comparative composition 1 (PA 11+600 ppm of catalyst), which does not comprise heat stabilizer and carbodiimide, to 90 days for a composition of the invention simultaneously comprising a catalyst (same proportion as the comparative composition 1), a copper-based stabilizer and a carbodiimide.

[0318] The composition according to the invention is more viscous than the comparative composition 4, the only difference being the presence of carbodiimide in the formulation according to the invention (at T0 and T=30 min).

[0319] Furthermore, the comparative composition 1 exhibits a melt viscosity which a priori seems good (T0=13 000) but which changes much too much up to T=30 min, thus not making it difficult to transform it, in contrast to the composition according to the invention.

[0320] Moreover, the comparative compositions 2 and 3, which do not comprise catalyst but comprise a carbodiimide in a greater proportion than that of the composition of the invention (1.3% instead of 1%), not only have melt viscosities at T=0 which do not reach the required value of 13 000 Pa.Math.s but also are completely devoid of stability since the viscosity at T=30 min strongly decreases.

Example 4

Resistance to Hydrolysis of a Formulation of the Invention (example 3) Compared with that of a Besno P40 TL

[0321]

TABLE-US-00010 Besno Example 3 of the P40 TL invention Thermal stability at 140° C. 700 h 2000 h Half life Resistance to hydrolysis 280 h  950 h 140° C. Volvic water pH 4 Time in order to have 50% absolute of elongation at break Plate-plate viscosity at 270° C. 10 rad/sec, 5% deformation T0 9000 14000 T = 30 min 32000 21000

[0322] The Besno P40 TL product is an Arkema Offshore reference PA11+ H.sub.3PO.sub.4 +plasticizer+heat stabilizer.

[0323] This table shows that the compounds of the invention exhibit a stability to hydrolysis and a melt viscosity which is improved, whatever the time (T=0 or T=30 min).

Example 5

Comparison of the Properties of the Compositions According to the Invention with the Comparative Compositions

[0324]

TABLE-US-00011 Carb. Stab. Cat. % by % by High Stable PA (ppm) weight weight viscosity viscosity Hyd. Ox. PA 0 0 0 − ++ − − 11 PA 0 1 0 + ++ + − 11 PA 0 0 0.2 − ++ + ++ 11 PA 0 1 0.2 + ++ ++ ++ 11 PA 600 0 0 ++ − − − 11 PA 600 0 0.2 − ++ + ++ 11 PA 600 1 0 − − + − 11 PA 600 1 0.2 ++ ++ ++ ++ 11 PA 11: Inherent viscosity 1.45. Cat.: H.sub.3PO.sub.4 catalyst. Carb.: polycarbodiimide Stabilizer 9000. Stab.: Copper-based heat stabilizer (Iodine 201). Hyd.: Resistance to hydrolysis. Ox.: Resistance to oxidation. − means that the value obtained is insufficient for the desired property with regard to the service performances. + means that the value obtained is borderline for the desired property with regard to the service performances. ++ means that the value obtained is comfortable for the desired property with regard to the service performances.

[0325] Only the composition simultaneously comprising a catalyst, a polycarbodiimide and a heat stabilizer makes it possible to obtain a good value for the six properties desired with regard to the service performances.