Process for preparing polyamide granules and uses
The subject matter of the present invention is a process for preparing polyamide granules having heat-resistance properties, and also the use of these granules, in particular in the aid of the manufacture of yarns for airbags or for tyre cords. More specifically, the invention relates to a process for preparing polyamide granules having heat-resistance properties by wet impregnation of the granules with an aqueous solution comprising at least one heat stabilizer.
1. A process for preparing polyamide granules with heat resistance properties, comprising:
contacting the polyamide granules with a single aqueous solution comprising at least one heat stabilizer under a controlled atmosphere of inert gas, wherein the contacting is performed on stirred granules;
wherein a total amount of an aqueous solution relative to the polyamide granules is less than or equal to 1% by weight; and
wherein the heat stabilizer is a mixture of alkali metal or alkaline-earth metal halide and of copper halide; and
subjecting the polyamide granules comprising the heat stabilizer to a solid-phase post-condensation step, without drying the polyamide granules before the solid-phase post-condensation step.
2. The process as claimed in claim 1 , wherein the alkali metal halide is potassium or sodium iodide.
3. The process as claimed in claim 1 , wherein the copper halide is copper iodide.
4. The process as claimed in claim 1 , wherein the heat stabilizer is a mixture of potassium iodide and copper iodide.
5. The process as claimed in claim 1 , wherein the ratio between the number of moles of halide and the number of moles of copper is greater than or equal to 7/1.
6. The process as claimed in claim 4 , wherein the copper iodide is present in an amount of less than or equal to 6% by weight in the single aqueous solution of potassium iodide at 50% by weight.
7. The process as claimed in claim 1 , further comprising performing a step of rinsing the polyamide granules with water after contacting the polyamide granules with the single aqueous solution.
8. The process as claimed in claim 1 , wherein the total amount of the aqueous solution relative to the polyamide granules is between 0.15% and 1% by weight.
9. The process as claimed in claim 1 , wherein the polyamide in the polyamide granules is polyamide 66.
10. The process as claimed in claim 1 , wherein the contacting of the polyamide granules with the single aqueous solution is performed by spraying of the single aqueous solution.
11. The process as claimed in claim 7 , wherein the total amount of the aqueous solution relative to the polyamide granules includes the amounts of the single aqueous solution and the water from the rinsing step.