Method of recycling high relative viscosity nylon
The disclosed method relates to a method of recycling high relative viscosity nylon. The process involves melting a base polyamide with a dry blended mixture of dicarboxylic acid and a second polyamide. The disclosed method provides a process of controlling the relative viscosity of the combined polyamides and, in various aspects, the second polyamide may be nylon plop or other polyamide having high relative viscosity.
1. A method of reducing the relative viscosity (RV) of a polyamide melt, the method comprising:
treating a first polyamide having a RV of 45 or greater with an additive mixture comprising an organic dicarboxylic acid and a second polyamide, wherein the particle size distribution of the organic dicarboxylic acid component is characterized by >94% by weight of particles scaling <710 microns, dry-blended with a second polyamide, where the second polyamide is characterized by >97 wt % of particles scaling >300 microns and ≤3 wt % of particles scaling <300 microns, and wherein greater than 50 wt % of the additive mixture is the second polyamide; and
melting the first polyamide treated with the additive mixture.
2. The method of claim 1 , wherein 0.01 wt % to 1.0 wt % of a combination of the first polyamide and the additive mixture is the organic dicarboxylic acid.
3. The method of claim 1 , wherein 0.05 wt % to 0.5 wt % of a combination of the first polyamide and the additive mixture is the organic dicarboxylic acid.
4. The method of claim 1 , wherein 0.1 wt % to 0.5 wt % of a combination of the first polyamide and the additive mixture is the organic dicarboxylic acid.
5. The method of claim 1 , wherein the organic dicarboxylic acid is a linear dicarboxylic acid having a formula HO 2 C—(CH 2 ) n —CO 2 H, wherein n is an integer from 0 to 12.
6. The method of claim 1 , wherein the polyamide is derived from a diamine monomer and a dicarboxylic acid monomer, and the dicarboxylic acid monomer is the same as the organic dicarboxylic acid.
7. The method of claim 1 , wherein the organic dicarboxylic acid is adipic acid.
8. The method of claim 1 , wherein the first polyamide is nylon-6,6.
9. The method of claim 1 , wherein either the first or the second polyamide is a mixture of one or more of nylon waste fibers, nylon pellets, nylon plop, post-consumer nylon, post-industrial nylon, nylon having an RV of from ≥50 to ≤70, and nylon having an RV of from ≥70 to ≤140.
10. The method of claim 1 , wherein either the first or the second polyamide has an RV of 60 or greater.
11. The method of claim 1 , wherein either the first or the second polyamide has an RV of 75 or greater.
12. The method of claim 1 , wherein either the first or the second polyamide is a mixture of one or more polyamide components, wherein at least one polyamide component has an RV of 60 or greater and is greater or equal to 30 wt % of the polyamide mixture.
13. The method of claim 1 , wherein either the first or the second polyamide is a mixture of one or more polyamide components, wherein at least one polyamide component has an RV of 75 or greater and is greater or equal to 30 wt % of the polyamide mixture.
14. The method of claim 1 , wherein either the first or the second polyamide is a mixture of one or more polyamide components, wherein at least one polyamide component has an RV of 60 or greater and is greater or equal to 50 wt % of the polyamide mixture.
15. The method of claim 1 , wherein either the first or the second polyamide is a mixture of one or more polyamide components, wherein at least one polyamide component has an RV of 75 or greater and is greater or equal to 50 wt % of the polyamide mixture.
16. The method of claim 1 , wherein either the first or the second polyamide is a mixture of one or more polyamide components, wherein at least one polyamide component has an RV of 60 or greater and is greater or equal to 75 wt % of the polyamide mixture.
17. The method of claim 1 , wherein either the first or the second polyamide is a mixture of one or more polyamide components, wherein at least one polyamide component has an RV of 75 or greater and is greater or equal to 75 wt % of the polyamide mixture.
18. The method of claim 1 , wherein at least 20 wt % of either the first or the second polyamide is granulated nylon plop.
19. The method of claim 1 , wherein ≤1% wt. of particles of the second polyamide have a major dimension of ≤106 microns in size.
20. The method of claim 1 , further comprising forming pellets from the melted first polyamide treated with the additive mixture, wherein over multiple performances of the method a maximum variation in RV of the pellets is less than a maximum variation in RV of control pellets formed from melting of the first polyamide that is not treated with the additive mixture.
21. The method of claim 20 , where the maximum variation in the RV value of the pellets is from ≥0.01% to ≤50% of the maximum variation in RV of the control pellets.
22. The method of claim 20 , wherein the multiple performances of the method are twenty performances of the method.
23. The method of claim 20 , wherein the maximum variation in RV of the pellets is at least 5 less than the maximum variation in RV of the control pellets.