Transformation-stable composition comprising viscous polyamide, production thereof and use of same
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.
1. A method for forming a composition which exhibits a good melt viscosity and which is stable during transformation comprising the step of combining:
about 50 ppm to about 5000 ppm of at least one catalyst,
about 0.05% to about 1% of at least one copper-based heat stabilizer,
and about 0.1% to about 3% of at least one oligo- or polycarbodiimide with a matrix comprising at least one polyamide;
wherein said melt viscosity is from about 13,000 to about 23,000 Pas, as determined by oscillatory rheology at 270° C. at 10 rad/sec while flushing with nitrogen with 5% deformation and shearing of 10 sec-1 between two parallel plates with a diameter of 25 mm, and
wherein said stable in transformation means that the melt viscosity does not change by more than 70% as a function of time between 1 minute and 30 minutes during a melt process,
wherein the catalyst is chosen from phosphoric acid (H 3 PO 4 ), phosphorous acid (H 3 PO 3 ), hypophosphorous acid (H 3 PO 2 ) or a mixture of these,
wherein the copper-based heat stabilizer comprises copper iodide,
wherein the polyamide is chosen from: PA 11, PA 12, 11/10.T, PA 10.10, PA 10.12.
2. The method 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 method as claimed in claim 1 , wherein said composition additionally exhibits a resistance to thermal oxidation.
4. The method as claimed in claim 1 , wherein the proportion by weight of catalyst is comprised of about 100 ppm to about 3000 ppm, with respect to the total weight of the composition.
5. The method as claimed in claim 1 , wherein the proportion by weight of copper-based heat stabilizer is comprised of about 0 .05% to about 0.3%, with respect to the total weight of the composition.
6. The method as claimed in claim 5 , copper-based heat stabilizer further comprises potassium iodide.
7. The method as claimed in claim 1 , wherein the proportion by weight of oligo- or polycarbodiimide is comprised of about 0.5 to about 2% with respect to the total weight of the composition.
8. The method as claimed in claim 1 , wherein the polyamide exhibits a M.p. comprised of 160° C. to 290° C., determined according to the standard ISO 11357-3 (2013).