Process for producing moldings with an increase in the melt stiffness
A process for producing moldings with condensing-up of a polyamide molding composition by means of a compound having at least two carbonate units, wherein a) a polyamide molding composition is made available, b) a mixture of the polyamide molding composition and the compound having at least two carbonate units is prepared, c) the mixture is, if appropriate, stored and/or transported and d) the mixture is subsequently processed to produce the molding, with the condensing-up occurring only in this step, and the molding is a hollow body or hollow profile having an external diameter of at least 30 mm and a wall thickness of at least 1 mm, effects a significant increase in the melt stiffness combined with moderate processing presssures, which considerably simplifies the production of these moldings.
1. A process for producing a molding, comprising:
(a) preparing a mixture of a polyamide molding composition and a compound having at least two carbonate units without permitting condensing-up by melt mixing of the polyamide molding composition by the compound having at least two carbonate units and without permitting the polyamide molding composition or the compound having at least two carbonate units to melt, during preparation of the mixture;
(b) optionally storing the mixture; and
(c) feeding the mixture into an extruder configured to form the molding and operating the extruder under conditions that cause condensing-up of the polyamide molding composition by the compound having at least two carbonate units to produce the molding;
wherein the molding is a hollow body or hollow profile having an external diameter of at least 30 mm and a wall thickness of at least 1 mm.
2. The process as claimed in claim 1 , wherein the polyamide has been prepared using a diamine or polyamine as regulator.
3. The process as claimed in claim 1 , wherein the compound having at least two carbonate units is used as a masterbatch.
4. A molding produced by the process as claimed in claim 1 .
5. The molding as claimed in claim 4 , which is a gas pipe, an offshore pipeline, a supply line, a cable conduit, a filling station supply line, a ventilation line, an air intake pipe, a tank filling port, a storage vessel or a fuel tank.
6. The molding as claimed in claim 4 , in which the wall has a multilayer structure.
7. The process as claimed in claim 1 , wherein the hollow body or hollow profile has an external diameter of at least 60 mm.
8. The process as claimed in claim 1 , wherein the hollow body or hollow profile has an external diameter of at least 110 mm.
9. The process as claimed in claim 1 , wherein the hollow body or hollow profile has wall thickness of at least 6 mm.
10. The process as claimed in claim 1 , wherein the hollow body or hollow profile has wall thickness of at least 6 mm.
11. The process as claimed in claim 1 , wherein said polyamide molding composition has a Mn of greater than 5,000.
12. The process as claimed in claim 1 , wherein said polyamide molding composition has a Mn of greater than 8,000.
13. The process as claimed in claim 1 , wherein said polyamide of said polyamide molding composition has at least 30% end groups present as amino end groups.
14. The process as claimed in claim 1 , wherein said polyamide of said polyamide molding composition has at least 50% end groups present as amino end groups.
15. The process as claimed in claim 1 , wherein said polyamide of said polyamide molding composition has at least 70% end groups present as amino end groups.
16. The process as claimed in claim 1 , wherein said at least one compound having at least two carbonate units is used in a ratio of from 0.005 to 10% by weight based on said polyamide molding composition.
17. The process as claimed in claim 1 , wherein said at least one compound having at least two carbonate units is used in a ratio of from 0.01 to 5.0% by weight based on said polyamide molding composition.
18. The process as claimed in claim 1 , wherein said at least one compound having at least two carbonate units is used in a ratio of from 0.05 to 3% by weight based on said polyamide molding composition.
19. The process as claimed in claim 1 , wherein said polyamide molding composition is in the form of pellets.