Methods for preparing polyamide compositions
View Patent ↗A polyamide composition is formed by combining a phosphorous containing catalyst with monomer starting materials under conditions suitable to cause polymerization of the monomer starting material into a low molecular weight polyamide material. The polyamide material, which may include remaining or residual catalyst, is then further polymerized via solid state polycondensation at a temperature suitable to form a high molecular weight polyamide material. The presence of the catalyst results in increased solid state polymerization rate and a final polyamide material composition with increased viscosity and a higher molecular weight.
1. A method of forming a high viscosity polyamide material comprising:
combining at least one lactam monomer, and a sufficient amount of at least one phosphorous containing catalyst to provide a mixture with an initial catalyst concentration of at least 1 ppm phosphorous;
reacting the mixture under temperature conditions suitable to form a low viscosity polyamide material;
removing extractables from the polyamide material, wherein at least 0.1 ppm phosphorous remains in the polyamide material after said removing step; and
subjecting the washed polyamide material to conditions suitable for causing solid state polymerization to increase the viscosity of the polyamide material.
2. The method of claim 1 , further comprising, after said reacting step and prior to said removing step, of quenching the reaction at a viscosity of about 50 FAV.
3. The method of claim 2 , wherein said step of subjecting the washed polyamide material to conditions suitable for solid state polymerization comprises increasing the viscosity to a viscosity higher than about 50 FAV.
4. The method of claim 1 , wherein the at least one monomer comprises caprolactam.
5. The method of claim 1 , wherein the phosphorous containing catalyst comprises hypophosphorous acid.
6. The method of claim 1 , wherein the reacting step is carried out at a temperature that is at least as high as the melting temperature of the resulting polymer.
7. The method of claim 1 , wherein the low viscosity polyamide material has an FAV of less than 90 FAV prior to solid state polymerization.
8. The method of claim 1 , wherein the polyamide material is washed in a solution comprising hot water to remove extractables.
9. The method of claim 1 , wherein at least 0.5 ppm phosphorous remains after removing extractables.
10. The method of claim 1 , wherein at least 1 ppm phosphorous remains after removing extractables.
11. The method of claim 1 , wherein the initial catalyst concentration is from about 1 ppm phosphorous to about 30 ppm phosphorous.
12. The method of claim 1 , wherein after the removing extractables step, a residual phosphorous content in the polyamide material is from about 0.1 ppm to about 15 ppm phosphorous.
13. The method of claim 1 , wherein solid state polymerization occurs at a temperature between about 140° C. and about 200° C.
14. The method of claim 1 , wherein solid state polymerization occurs at a temperature of no less than 165° C. to about 200° C.
15. The method of claim 1 , wherein solid state polymerization occurs at a rate of at least 9.6 FAV/hour.
16. The method of claim 1 , wherein the polyamide material after solid state polymerization has a viscosity that is at least 15 FAV greater than the viscosity prior to solid state polymerization.
17. The method of claim 1 , wherein the polyamide material after solid state polymerization has a viscosity that is at least 30 FAV greater than the viscosity prior to solid state polymerization.
18. A method of forming a high viscosity polyamide material comprising:
reacting at least one lactam monomer and water under temperature conditions suitable to form a low viscosity polyamide melt;
adding a sufficient amount of at least one phosphorous containing catalyst to the melt such that the melt has an initial catalyst concentration of at least 10 ppm phosphorous;
forming a solid polyamide material from the polyamide melt; and
subjecting the solid polyamide material to conditions suitable for causing solid state polymerization to increase the viscosity of the polyamide material.
19. The method of claim 18 , further comprising a step, prior to said subjecting step, of removing extractables from the solid polyamide material, wherein at least 0.1 ppm phosphorous remains in the polyamide material after said removing step.
20. A method of forming a high viscosity polyamide material comprising:
reacting at least one lactam monomer and water under temperature conditions suitable to form a low viscosity solid polyamide material;
removing extractables from the solid polyamide material;
applying a phosphorous containing catalyst to the solid polyamide material; and
subjecting the solid polyamide material to conditions suitable for causing solid state polymerization to increase the viscosity of the polyamide material.