The use of synthetic fibers has increased in many areas of technology. Among those areas which has had a very great and varied increase is carpets, area rugs, carpeting and include all types of floor coverings. The teachings and publications in this and related fields are quite extensive and describe details for separating, reconstituting, recovering, purifying and variously treating and handling used textiles and carpeting and include natural and synthetic fibers in the processing and recovery steps.
The objective is to to provide a recycling process for carpeting material containing nylon polymers and/or nylon fibers.
Another specific objective is to recover Nylon 6 and Nylon 6,6 from nylon containing carpet scraps and used carpeting.
A further object is to separate and recover nylon polymer from carpeting containing other polymers such as polyesters, polyamides, P.E.T. (poly-ethylene terepthtalate) and other polymers as well as natural fibers.
This process and the steps thereof relate to the recovery of nylon, particularly Nylon 6,6 both from home and commercial carpets. Carpet containing Nylon 6,6 is dissolved in a hot, highly pure glycerol at elevated temperatures. At high temperatures, nylon oxidizes with oxygen and/or hydrolysis with water. To prevent oxidation various stabilizers may be added to the solvent. Alternatively, working under a nitrogen environment renders an effective protection against nylon degradation from both oxidation and hydrolysis.
Upon dissolution, the solution is quickly withdrawn to a dry vessel where it is quickly cooled to 40 degrees Celsius or lower. The solution is washed with water to remove traces of glycerol, then filtered, and lastly dried under vacuum at 40 to 60 degrees Celsius to recover the nylon polymer. The following is an example of the method used in practicing this recovery and recycling process:
1. 1200 ml of pure glycerol is heated to and maintained at 205 C. and 1 ATM. of pressure in a stirrer equipped vessel where it is uniformly stirred at a moderate speed.
2. Meanwhile, a constant stream of nitrogen gas is applied to the solvent as it heats up to purge out any residual oxygen.
3. 100 grams of Dupont Stainmaster carpet is added to the hot solvent.
DUPONT STAINMASTER-NYLON CARPETS
4. The initial carpet fiber is sample and found to be Nylon 6 with a relative viscosity of 1.7.
5. 15 minutes after all the nylon is dissolved, the solution is pumped out of the heating vessel via a heated 0.25 inch diameter stainless steel pipe into a dry flask that is sitting in an ice bath.
6. When the solution cools down to 40 C. or below it is washed with water at a ratio of 20:1 by volume and filtered, for the final wash.
7. For the final wash potassium iodine (KI) is added to the water as a heat stabilizer for future processing.
8. The final solution is filtered and the cake is dried in an oven purged with nitrogen then under vacuum allowed to dry at 45 C. for three days.
9. The final material is checked for its purity and relative viscosity (RV). The final material exhibited an increase in relative viscosity to 2.21.