MXPA99007624A - Carpet recycling process for nylon containing carpeting_ - Google Patents

Abstract

This invention comprises recyclingand recovery processes for rugs, flooring, carpeting, carpet materials, and all other textiles particularly from waste carpet containing both synthetic and natural fibers and for backing materials, and more particularly for the separation and recovery of various nylon polymers as well as other polymeric fibers and materials for recovery and reuse.

Description

PROCESS OF RECYCLING CARPETS FOR CARPETS CONTAINING NYLON FIELD OF THE INVENTION The invention comprises methods and processes for recycling carpets containing nylon, which includes stepped separation using a combination of solvent or selective solvent methods and control temperatures. The steps include: 10 a. reduce the size of the carpet to a granular shape; b. wash and / or filter, as necessary, to remove inert solids, dirt and fillers; and c. Separate in stepped form the various types of backing fibers, adhesives. BACKGROUND OF THE INVENTION The use of synthetic fibers has increased in many areas of technology. Among those areas that have had an increase very large and varied are carpets, area rugs, carpets and include all types of floor coverings. The teachings and publications in this field and related fields are quite extensive and describe details to separate, reconstitute, recover, purify and in a varied way to treat and manage "> used materials and carpets and include natural and synthetic fibers in the processing and recovery steps .. More specifically, US Patent No. 3,006,867 (Simon) discloses a method for reconstituting a synthetic plastic, such as and including nylon from of waste materials and used and include textile waste that have nylon fibers.The method consists of dissolving the waste material of synthetic plastic in formic acid, mixing a hydrocarbon selected from n-hexane, cyclohexene, n-heptane, cyclohexane, hexene , benzene and toluene with the formic acid-plastic solution in an amount sufficient to form an azeotropic mixture, then heat the azeotropic mixture at a temperature sufficient to vaporize the azeotropic mixture and remove (recover) the vapors from the distillation zone to allow back the synthetic plastic that is being recovered U.S. Patent Nos. 4,003,880; 4,003,881; 4,118, 187 and 4,137,393 (Sidebotham et al.) Describe various methods for recovering polyester from dyed polyester fibers as in fabrics, textiles, carpets and commercial products. Only polyesters are involved in the recovery steps. Although the conditions and procedural steps vary in the patent descriptions, there are certain steps that are described and used in all the processes of these patents. The steps generally include: 1. contacting collections of yarns, fibers and fabrics, including polyester fibers dyed with a dye separation solvent for the polyester polymer, which preferably is not a solvent for the remaining constituents at a temperature below which the polyester fiber dissolves and above the crystal network structure of the polyester fibers swells in order to release the dye, thus separating the dye from the polyester fibers; 2. remove the excess dye separation solvent that contains dye, which is not absorbed by the fibers and fabrics; 3. contacting the fibers (which may contain residual dye separation solvents) with the sufficient addition of a primary solution solvent under selective dissolution conditions for polyester fibers; 4. remove undissolved fibers or other impurities from the solution; and 5. separating the solvent or solvents from the polyester by evaporating the solvent from the dissolved and / or molten polyester without the precipitation of the polyester from the solution. It is important and significant to note that none of these recovery methods describe or suggest any step or detailed recovery procedure for nylon. Rather, they are limited to specific dissolution techniques for the recovery of unrelated polymer, polyester. In another US patent Year. 4,064,079 (Sidebotham et al.) Describes a modified polyester recovery method, which does not include a dye removal step from the polyester fibers. The US patents A. Nos. 5,240,530 and 5,288,349 (Fink) teach a method of recycling and recovery of carpets, wherein the portions of the carpet are initially ground and melted to form a supply material. Carpets that contain different types of materials are mechanically ground, so that the length of fiber contained is reduced between 0.635 and 0.15875 cm. These fibers are then separated in an aqueous bath based on the specific gravity. None of these patents teaches or suggests separating the nylon fibers from the polyester fibers by subjecting the mixed fibers to water and then to heat, nor are extraction steps described. The patent of E.U. A. No. 5,294,384 (David et al.) Discloses a method for converting the waste material to a thermoplastic composition. As a starting material, carpet samples (waste) can have any pile weight and can also be composed of inhomogeneous blends of components. The samples are melt mixed with or without a compatibilizer on a temperature scale of 250 ° C to about 260 ° C and at a pressure of about 24.605 to 31,635 kg / cm2 and a shear rate of about 200-400 / sec.; most preferably this step is carried out in a twin screw extruder. The mixtures thus formed are then formed into pellets or processed into other commercially acceptable forms. Mixture compositions that are described include blends of nylon, SBR latex and inorganic fiber. By using the method described in this patent, no attempt is made (no steps included) to separate the fiber mixture into its consistent parts or fractions; rather, the mixtures are merely transformed to a different mixture having a different form of the starting components. In the patent of E.U. A. No. 5,370,757 (Corbon et al.) Describes a carpet product, which has two distinct sections, an upper section constructed entirely of nylon (Nylon 6) and a lower section. The upper section in this way is easily removed from the lower section for replacement without causing any damage to the lower section. After said removal, the upper section can then be recycled to e-caprolactam for reuse in the Nylon 6 carpet or can be used in other Nylon 6 products. In addition, the US patent. A. No. 5,342,854 (Serod) describes a method for separating and recovering polyester from polyester / cotton blends. The polyester / cotton materials are cut and shredded into small pieces and then dried. These dried pieces are placed in a vessel containing a sulfone solvent such as alkylsulfone having from 1 to 10 carbon atoms and heated to 150 ° C. This mixture is impregnated (with stirring) for about 90 minutes at this temperature. Then, the temperature of the mixture was raised to 190 ° C and remained so for about another 35 minutes. The polyester-containing solvent is then separated for another treatment to precipitate the recovered polyester. There are no methods or steps described to separate the polyester from any other polymer system or other polymeric fibers. The patent of E.U. A. No. 5,198,471 does not teach a process related to this invention. There is no description of nylon fibers, or any of the solvents. In the patent of E.U. A. No. 3,696,058 (Tate) describes a process for recovering solid scratch thermoplastic polymers such as polyamides and polyesters. The process includes the following steps: a. dissolving said thermoplastic polymer in hexafluorisopropanol; b. filter said solvent solution; c. mix the polymer solution with an excess of water at a temperature of 60 to 100 ° C; and d. separating the precipitated polymer from water, wherein the thermoplastic polymer is selected from the group consisting of polyamide, polyester, polyacrylonitrile and polyacetal. In this patent, the solvents used for the polymer are fluoroalcohols. It has been known to use formic acid and sulfuric acid as well as various types of solvents such as, for example, ethylene glycol, propylene glycol, meta-cresol and various triglycerides and fatty acids to dissolve polymeric materials as a production step of polyamide fibers. casting including nylon fibers.

COMPENDIUM OF THE INVENTION It is an object of this invention to provide a recycling process for carpeting material containing nylon polymers and / or nylon fibers. It is also an object to describe processes for separating and recovering plastic and polymer components from carpets, used carpets, carpet pieces and the like, including blends of synthetic carpeting materials, one or more components or portions containing nylon. Another object is to provide an economical, practical and environmentally acceptable method for recovering components from carpeting materials containing nylon polymers. Another specific object is to recover Nylon 6 and Nylon 6.6 from pieces of carpet containing nylon and used carpets. A further object is to separate and recover nylon polymer from carpets containing other polymers such as polyesters, polyamides, P.E.T. (polyethylene terephthalate) and other polymers as well as natural fibers. Another object is to provide an efficient recycling process for carpet materials containing nylon or any material containing nylon. Other objects will be described in the detailed description of the process of the invention described below.

DESCRIPTION OF THE INVENTION At present, there are a number of different, but related, reasons and objects that make carpet recycling very important. There are environmental as well as economic reasons with respect to recirculation processes and methods. Practical and economical values are advantageous to limit the use of fillers for old and discarded carpets, as well as other useless carpet pieces. Recycling can generally include methods for reprocessing or reconditioning for reuse such as, the conversion of carpets or their components to a new or different product, which may have a different application and generally of lower demand or more generic, or use one or more processes or process steps in a way that recovers all or part of the value of the components. In the processes of this invention, a number of these advantages and objects are achieved. This invention broadly relates to the recycling and recovery of products from carpets, wherein the fibers containing at least substantial amounts of nylon as well as polyester and P.E.T. (polyethylene terephthalate). In addition, acrylic fibers as well as various olefinic resins may be present. Also, in some cases, natural fibers such as cotton and / or wood may also be present. The carpet, which is subjected to recycling, also has a backing material, which may be, for example, polypropylene, polyethylene, acrylic resin, a straw-burlap material commercially known as "JUTE", a mixture of these with possibly other materials in smaller quantities. It is also commonly required that some type of agent "glue" or adhesive is present in a smaller quantity in order to join and safely gather the fibers to the backing. The adhesive during the recovery process becomes part of the inert by-product stream and thus a part of the inert fraction remains. The process of this invention can be advantageous and quite satisfactory to practice with any carpet as the starting material, as long as only a few nylon fibers are present. Nylon can be of the type commercially known as Nylon 6 (poly-6-aminocaproic acid), Nylon 6,6 (poly-hexamethyleneadipamine), Nylon 8 (poly-8-aminocaprylic acid), Nylon 11 (poly-11-aminoinodecanoic acid) ) and Nylon 6,10 (poly-hexamethylene sebacamide). It is not necessary, or at least not practical or highly effective to separate the carpet fibers from the backing ie, since the release of the adhesive from the fibers during the recovery step is effectively achieved. Usually, it is not necessary to remove the adhesive since everything that remains with the fiber will remain as a solid residue in the separation step. In one embodiment of the invention, the milled carpet, preferably mainly comprising nylon-containing fibers, is mixed with a selective solvent. This solvent must be appropriately selected and it is preferred that it be a glycolic compound (polyhydric alcohol) such as ethylene glycol or propylene glycol and it can also be various mixtures of these solvents. This solvent can also be organic formate, such as methyl or ethyl formate, hydrochloric acid, formic acid, methanol, nitric acid, glacial acetic acid, fluorinated alcohols, m-cresol, phenolic compounds, chloroform-methanol, lithium methanol chloride , potassium thiocyanate, benzyl alcohol, butanediol-1, 1, dimethyl sulfoxide, triethylene glycol and tetraethylene glycol. It has been found through real testing and experimentation that glycerol is the most effective solvent and is preferred for the isolation and recovery of the nylon components in the fibers. It has been found that it is the most environmentally condescending solvent of those listed. The basis for the separation of the types of nylon fractions (Nylon 6 and Nylon 6,6) is the relative solubility of the two types in the solvent, depending on the temperature. In this way, the different types can be identified, separated and removed by varying the temperature. The Nylon 6 fraction is soluble at 155 ° C, while the Nylon 6,6 is soluble at 195 ° C, all nylon polymers will be dissolved. Afterwards, the mixture is cooled and Nylon 6,6 will not be soluble and can be separated and removed as a solid. Additional cooling at approximately 150 ° C will cause Nylon 6 to separate and can be removed as a solid. The process can also be performed by selectively heating the fibers in solution. At a temperature of about 150 ° C, Nylon 6 will be dissolved and then separated with glycerol and Nylon 6,6. This is the remaining solid, which has not been heated to a sufficiently high temperature to dissolve. The nylon that is recovered as a solution in glycerol or other organic solvent can be easily recovered through precipitation after cooling, followed by washing with water, while the solid nylon polymer is separated from the liquid solution. The many advantages include the ability to separate nylon polymers from other polymers, adhesives and fibers, using environmentally acceptable and safe steps to recover relatively pure, clean nylon polymers. Although the advantage is that there is a relatively simple, economical and effective step, which is easily included to separate Nylon 6 and Nylon 6,6 and recover both in a pure form. The following Examples are typical processes for the recovery of the products according to the invention, but are in no way intended to limit the process of the invention and its products.

EXAMPLES EXAMPLE 1 This process and its steps refer to the recovery of nylon, particularly Nylon 6,6, both domestic and commercial carpets. The carpet containing Nylon 6,6 is dissolved in a hot, highly pure glycerol at elevated temperatures. At high temperatures, nylon is oxidized with oxygen and / or hydrolysis with water. To prevent oxidation, several stabilizers can be added to the solvent. Alternatively, working under a nitrogen environment provides effective protection against nylon degradation from both oxidation and hydrolysis. After dissolution, the solution is quickly removed to a dry container, where it is rapidly cooled to 40 ° C or lower. The solution was washed with water to remove glycerol prints, then filtered and finally dried under vacuum at 40 to 60 ° C to recover the nylon polymer. The following is an example of the method used to practice the recovery and recycling process: 1. 1200 ml of pure glycerol was heated and kept at 205 ° C and 1 ATM of pressure in an equipped, stirred vessel, where it is uniformly agitated at a moderate speed. 2. Meanwhile, a constant stream of nitrogen is applied to the solvent as it is heated to purge any residual oxygen. 3. 100 grams of the Dupont Stainmaster carpet was added to the solvent. 4.- The initial carpet fiber was sampled and found to be Nylon 6 with a relative viscosity of 1.7. 5. Fifteen (15) minutes later, all the nylon dissolved, the solution was pumped out of the heating vessel through a heated stainless steel pipe with a diameter of 0.635 cm into a dry flask which is seated in a bath of water. ice. 6. When the solution is cooled to 40 ° C or below, it was washed with water at a ratio of 20: 1 by volume and filtered for final washing. 7. For the final wash, potassium iodide (Kl) was added to the water as a thermal stabilizer for future processing. 8. The final solution was filtered and the cake was dried in a furnace purged with nitrogen, then under vacuum, allowed to dry at 45 ° C for 3 days. 9. The final material was verified for its purity and relative viscosity (RV). The final material exhibited an increase in the relative viscosity at 2.21.

EXAMPLE 2 This process and its steps refer to the recovery of Nylon 6 and Nylon 6,6 from both domestic and commercial carpets. The carpet containing Nylon 6 and Nylon 6,6 was dissolved in hot, highly pure glycerol at elevated temperatures. To avoid oxidation, stabilizers were added to the solvent. Alternatively, work under a nitrogen environment causes effective protection against nylon degradation. After dissolution at 165 ° C, the solution containing Nylon 6 is quickly removed to a dry container, while the undissolved residue containing Nylon 6,6 is dissolved in a second vessel at 200 ° C and removed to its Clean dry container. The two containers containing nylon were rapidly cooled to 40 ° C. The solid particles were washed independently of one another to remove any trace of glycerol. The polymer was then filtered and dried under vacuum at 40 to 60 ° C to recover the pure nylon polymer. The polymer is then verified for the relative viscosity and purity using scanning calorimetry. Nylon 6,6 and Nylon 6 exhibited an individual fusion peak confirming the melting point of the pure components by proving that the separation of the polymer was performed accurately.

Claims (18)

1. - A process for separating nylon from carpet containing nylon, which comprises dissolving the nylon in the carpet in a solvent at least at the dissolution temperature of the nylon in the solvent, removing the solvent containing the nylon from the remaining solid residue , and cool the solvent-nylon solution to precipitate and recover the nylon.

2. The process according to claim 1, wherein at least two types of nylon are present in the carpet, wherein only a first type of nylon is initially recovered by dissolving the first type of nylon in a solvent at least at the dissolution temperature of the first type of nylon in the solvent, but below the dissolution temperature of remaining types of nylon, remove the solvent containing the first dissolved type of nylon from any remaining solid residue, and repeat the solution for each of the remaining types of nylon.

3. The process according to claim 1, wherein at least two types of nylon are present in the carpet, wherein at least two types of nylon are dissolved in a solvent at least at a temperature where all the nylon types are dissolved; cooling the solvent to a temperature at which a type of nylon is precipitated, but above the dissolution temperature of the remaining types of nylon; remove the precipitate; and then cooling the solvent to a temperature at which another type of nylon is precipitated and repeating the precipitate removal and the cooling steps, until all types of nylon have been precipitated.

4. The process according to claim 2, wherein two types of nylon are present in the carpet.

5. The process according to claim 4, wherein the two types of nylon are Nylon 6 and Nylon 6.6.

6. The process according to claim 3, wherein two types of nylon are present in the carpet.

7. The process according to claim 6, wherein the two types of nylon are Nylon 6 and Nylon 6.6.

8. The process according to claim 1, which further comprises reducing the carpet to a granulated particle form before dissolving the nylon.

9. The process according to claim 8, which further comprises separating the inert solids and non-fibrous fillers from the carpet before dissolving the nylon.

10. The process according to claim 1, wherein the carpet contains at least one other fiber.

11. The process according to claim 10, wherein at least said other fiber comprises a synthetic polymer fiber.

12. The process according to claim 11, wherein at least that other fiber is a polyester.

13. The process according to claim 11, wherein at least said other fiber is a polyamide.

14. - The process according to claim 11, wherein at least that other fiber is a terephthalate polymer.

15. The process according to claim 11, wherein at least said other fiber comprises a natural fiber.

16. The process according to claim 1, wherein the solvent is glycerol.

17. The process according to claim 1, wherein the solvent is ethylene glycol.

18. The process according to claim 1, wherein the solvent is propylene glycol.