ZA200303327B - Method of extracting nylon from waste materials. - Google Patents
Method of extracting nylon from waste materials. Download PDFInfo
- Publication number
- ZA200303327B ZA200303327B ZA200303327A ZA200303327A ZA200303327B ZA 200303327 B ZA200303327 B ZA 200303327B ZA 200303327 A ZA200303327 A ZA 200303327A ZA 200303327 A ZA200303327 A ZA 200303327A ZA 200303327 B ZA200303327 B ZA 200303327B
- Authority
- ZA
- South Africa
- Prior art keywords
- nylon
- alkanol
- solvent
- containing solvent
- pressure
- Prior art date
Links
- 229920001778 nylon Polymers 0.000 title claims description 87
- 239000004677 Nylon Substances 0.000 title claims description 82
- 238000000034 method Methods 0.000 title claims description 53
- 239000002699 waste material Substances 0.000 title claims description 14
- 239000002904 solvent Substances 0.000 claims description 33
- 239000000463 material Substances 0.000 claims description 30
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 25
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 21
- 239000000203 mixture Substances 0.000 claims description 13
- 229920002302 Nylon 6,6 Polymers 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 230000003247 decreasing effect Effects 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 3
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical class CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims 1
- 150000002334 glycols Chemical class 0.000 claims 1
- 229920005862 polyol Polymers 0.000 claims 1
- 150000003077 polyols Chemical class 0.000 claims 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical class CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims 1
- 238000004090 dissolution Methods 0.000 description 11
- 239000000835 fiber Substances 0.000 description 8
- 239000000047 product Substances 0.000 description 8
- 230000015556 catabolic process Effects 0.000 description 6
- 238000004064 recycling Methods 0.000 description 6
- 239000011877 solvent mixture Substances 0.000 description 6
- 239000002131 composite material Substances 0.000 description 5
- 239000000470 constituent Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 description 4
- 239000000178 monomer Substances 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 238000001125 extrusion Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- 235000011037 adipic acid Nutrition 0.000 description 2
- 239000001361 adipic acid Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000029087 digestion Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical compound NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- -1 and in particular Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012943 hotmelt Substances 0.000 description 1
- 239000010812 mixed waste Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003348 petrochemical agent Substances 0.000 description 1
- 239000002798 polar solvent Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Landscapes
- Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
Description
. ‘
METHOD FOR EXTRACTING NYLON FROM WASTE MATERIALS
This application claims benefit of provisional U.S. application Serial No. . 60/245,006, filed November 1, 2000, the entire contents of which are incorporated by ’ 5 reference. ‘
1. Field of the Invention
The present invention relates to improved processes for extracting nylon from waste materials, including mixed waste materials such as floor coverings, such that degradation of the nylon polymer into lower molecular weight polymers, oligomers, and monomers is decreased. The process involves contacting the waste materials with polar solvents, or mixtures thereof at high pressures. 2. Description of Related Art
Nylon is widely used as a fiber, both in the production of textile cloths, and in the production of floor covering materials, such as broadloom carpet and carpet tile. When used in floor covering materials, the nylon is usually predominantly present as part of one or more layers of a multilayered product. Large quantities of floor covering materials are replaced each year, with the resulting used materials often discarded to landfills. Because of environmental and economic concerns about this waste material, there has been a need for an economical process for recovering and reusing used or discarded floor covering materials. However, because these materials often contain complicated composites or laminates that are difficult to separate into their constituent components, recycling processes for these materials too often result in conglomerated products whose value is considerably lower than that of their individual constituents. In some cases, the value of the product of recycling may be equal to or less than the value of the original starting material. Downcycling of this nature is both environmentally and economically wasteful.
Because the downcycled product is not as valuable as the original starting material, or ‘ even of the original inputs to the production of the original waste material, economic ; 30 value is lost. Because the downcycled product does not make the best use of its i WO 02/36668 PCT/US01/15639 constituents, additional constituent materials must be produced and used, generating an additional environmental burden made particularly heavy because these constituent materials are often based on petrochemicals. . As a result of these considerations, there is a need in the art for processes that can economically separate and recycle one or more of the components of floor covering ) materials. In particular, there is a need in the art for processes that allow for the separation and recovery of nylon used in floor covering materials, and in particular, of nylon used in the topcloth or facecloth layers of these floor covering materials, in such a way that the value and usefulness of the nylon is not degraded.
Processes for recovering nylon tend to fall into two distinct categories. In one category are processes where the nylon is deliberately depolymerized into monomer or oligomers thereof, which can then be reused by repolymerization. In general, the goal is to reduce as much of the polymer to monomer as possible, in order to make reuse more predictable. However, processes in this category are disadvantageous because depolymerization is expensive, and can lead to side reactions that decrease the amount of monomer available, reducing efficiency, and requiring additional depolymerization and energy consumption to make up for the loss. In addition, depolymerization of nylon 6,6 requires the separation of hexamethylenediamine (HDMA) and adipic acid, or further reaction to convert adipic acid to HDMA, which is difficult and expensive.
In the other category are processes where the nylon is recovered without depolymerization, so that it can be reused without repolymerization. In general, the goal of such processes is to extract or dissolve the nylon with minimal polymer breakdown.
The nylon is then generally obtained in solid form so that it can be reused. Conventional dissolution or extraction type processes can be difficult, if not impossible, to use without downcycling the value of the nylon. At least part of the reason for this is that some polymer breakdown almost always occurs.
For example, nylon fiber that is to be subjected to a dissolution or extraction type recovery process will have had its molecular weight reduced by the original extrusion ‘ process, due to the high temperatures involved. Molecular weight will be reduced further during the conventional extraction or dissolution process, and will be even further reduced if the nylon is to be re-extruded back into fiber. This cumulative breakdown will render the molecular weight of the nylon inappropriate for reuse as fibers.
Another disadvantage of both types of nylon recycling processes is their need for : relatively pure nylon feedstocks. In the case of composite products, such as floor coverings like carpet and carpet tile, the presence of fillers, backing materials, adhesives, ) etc. can complicate the nylon recycling effort, requiring that these materials be physically and/or chemically separated from the nylon prior to any nylon-specific processing.
There is therefore a need in the art for a nylon recycling process that does not require depolymerization, that does not significantly degrade the molecular weight of the nylon polymer recovered, and that is useful to prepare nylon suitable for extrusion into fiber using as a feedstock nylon that has previously been extruded into fiber, and in particular, nylon that has been obtained from floor covering material, without the need to delaminate or otherwise physically separate other components from the feedstock.
The process of the invention fulfills this need. Nylon, which may be obtained in the form of waste material, such as waste or scrap floor covering material (obtained, e.g., from used carpet, carpet tile, or other floor covering, or as selvedge produced in the manufacture of carpet or carpet tile), is contacted with a solvent or solvent mixture containing an alcohol at an elevated temperature, and at an elevated pressure. The use of an elevated pressure has been found to unexpectedly decrease the temperature at which the nylon in the waste material will effectively dissolve in the solvent mixture. At least in part as the result of this decrease in dissolution temperature, the nylon can be dissolved with a substantially decreased degradation of its molecular weight. This preservation of molecular weight allows the process to be effectively used with nylon that has been extruded into fiber, such as that found in floor coverings, and produces nylon that can again be extruded into fiber, for use in floor coverings. In effect, the process of the invention allows the nylon present in floor coverings to be recycled without being ‘ downcycled. Although the process can be used with nylon that has been separated from other composite material components, this need not occur with commonly used floor covering materials.
The invention can be viewed as a method for recovering nylon, including: . contacting the nylon with an alkanol-containing solvent at elevated temperature and at a pressure higher than the equilibrium pressure of the alkanol-containing solvent at ) the elevated temperature; removing alkanol-containing solvent containing dissolved nylon from any undissolved solids; decreasing the temperature of the alkanol-containing solvent containing dissolved nylon to precipitate the dissolved nylon. The recovered nylon can then be further processed by filtration, washing, etc., and reused.
The increase in pressure of the nylon and alkanol-containing solvent mixture can be accomplished by introducing inert gas into the dissolution vessel, which is desirably a pressure vessel. Alternatively, the increase in pressure of the solvent mixture can be accomplished by increasing the head pressure of the solvent mixture pumped into the reactor. For instance, the vessel through which solvent is introduced to the reactor could have a cross-sectional area that exceeds that of the vessel through which solvent is withdrawn from the reactor, creating a pressure head in the reactor sufficient to lower the nylon dissolution temperature, and thus the reactor temperature, as described herein.
The method of the invention is suitable for recovering nylon from waste materials, and is particularly suitable for use with nylon-containing floor covering waste materials, such as used or scrap carpet or carpet tile, or selvedge obtained during production of these materials. In particular, use of the method with carpet tile has been found to be very beneficial, since these materials are typically composite structures having a number of laminated layers. The method of the invention provides the additional benefit of making separation of these laminated layers easier, and in many cases the waste materials emerge from the dissolution process with the nylon removed and the remaining layers of materials already separated. This confers apparent advantages in making the recycling of ’ these additional components much more efficient.
AMENDED SHEET
The invention involves the use of a solvent or mixture of solvents, containing a lower alkanol, to dissolve nylon, which is desirably in the form of nylon 6,6, but which may include other nylons or combinations thereof. The nylon, which may be ground, comminuted, chopped or otherwise modified in size, may be added as waste or scrap floor covering material, such as carpet or carpet tile, or as some other composite material, or as essentially pure nylon, is contacted with the solvent or solvent mixture in a pressure vessel. The pressure vessel is heated to a temperature of about 130 °C to about 155 °C, more particularly to about 145 °C, and held at this temperature for a period of time sufficient to dissolve the desired yield of nylon. Surprisingly, this use of increased pressure allows operation at temperatures below 160 °C.
The pressure vessel is maintained at a pressure higher than the equilibrium pressure for the solvent system at the selected temperature. One technique for increasing the pressure is to introduce a sufficient quantity of inert gas, such as nitrogen, argon, etc. into the pressure vessel. For example, at a temperature of about 150 °C, the equilibrium pressure of an ethanol/water solvent system will be approximately 100 psig (689.47 kPa).
This pressure can be increased by an amount ranging from about 250 psig (1723.69 kPa) to about 600 psig (4136.85 kPa), more particularly from about 250 psig (1723.69 kPa) to about 400 psig (2757.90 kPa), by adding inert gas, such as N,, to the pressure vessel prior to reaction. Alternatively, the pressure in the vessel can be increased by increasing the head pressure of the solvent system entering the reactor. This can be done, e.g., by removing liquid from the reactor through a vessel having a smaller cross-sectional area than the vessel delivering solvent to the reactor. This increased pressure allows increased and faster dissolution of the nylon into the solvent system as compared to the dissolution level and rate at the equilibrium pressure for that temperature. Put another way, for the same dissolution level, the invention allows the process to be operated at a lower temperature than would an equilibrium pressure process, or even a slightly elevated (e.g., 50 psig (344.74 kPa)) pressure process. Degradation of the nylon is thus decreased, resulting in a higher quality product that is suitable for extrusion into fiber.
In addition, the process of the invention results in a nylon product that is enriched in high molecular nylon, as compared to conventional processes that are not carried out at
AMENDED SHEET in part from better or more complete dissolution of low molecular weight nylon fractions,
J which then remain in solution as the higher molecular weight nylon fractions precipitate out.
The invention can be more clearly understood by reference to the following
Examples, which are not intended to limit the scope of the invention in any way.
EXAMPLE 1
A series of tests were conducted wherein nylon yarn or nylon chips were tested to determine a baseline relative viscosity. Nylon chips were also dissolved in a methanol/water mixture, the nylon recovered, and its relative viscosity measured. A number of nylon-containing carpet tiles (designated as Sample Nos. 1-6) were chopped up and placed into a pressure vessel to which 400 ml of an alkanol solvent and 100 m] water were added as indicated below, and the mixture heated and pressurized as indicated below. The solution was removed from the pressure vessel into another vessel, where it was cooled until nylon precipitated. This nylon was then tested for relative viscosity using the same method that was used for the nylon yarn or chips. The results are indicated below.
Samples Digestion Solvent Final Pressure, Relative
Temp., °C (80% psig Viscosity
Concentration) (kPa)
Nylon 6,6 Yam | Not digested
Standard PA 66 | Not digested
Standard PA 66 205 (1413.42) 1 165 99% 140 (965.26) 40
Isopropanol 2 165 Denatured 400 (2757.90) 37
Ethanol 3 175 Denatured 150 (1034.21) 34
Ethanol
Pure Ethanol _| 150 (1034.21 5 155 Denatured 400 (2757.90) 44
Ethanol 6 [155 | PucEthwol | 450010260
Pure Ethanol _| 400 (2757.50) [8 | 15 | PucEtano | 400@5700)
AMENDED SHEET
EXAMPLE 2
A similar procedure to that used in Example 1 was followed, using two samples from the same carpet tile or broadloom carpet, and varying the pressure thereof. The results are reported below. Where “Methanol” and “Pure Ethanol” are indicated, 400 ml. of these solvents were mixed with 100 ml of water. Where “100% Methanol” is indicated, water was not included in the mixture. Samples 1 and 3 were taken from carpet tile, Sample 2 was taken from broadloom carpet, and Sample 4 was taken from hotmelt precoated carpet.
Samples Digestion Solvent Final Pressure, | Viscosity Relative
Temp., °C psig (kPa) Number Viscosity
Nylon 6,6 | Not Digested NA NA 135 44
Yarn 66
Standard PA 165 Methanol | 205 (1413.42) 112 34 66 1A 155 100% 210 (1447.89) 141 47
Methanol
Pure Ethanol | 150 (103421) 2A 155 100% 210 (1447.89) 162
Methanol
Pure Ethanol | 150 (103421)
EXAMPLE 3
An 80% mixture of ethanol and water was preheated to the temperatures indicated below, and added all at once to a vessel containing nylon fiber in sufficient amount to provide a 3.5 wt% mixture of solvent and nylon. The mixture was pressurized to the pressure indicated below, and held at pressure for the time indicated below. The liquid was removed from the vessel and cooled in a jacketed vessel to a temperature of 120 °C.
The resulting cooled liquid was filtered to removed precipitated nylon. The undissolved nylon remaining in the first vessel was measured, and a yield of dissolved nylon to total nylon added to the mixture was computed.
AMENDED SHEET
: Run Temperature Pressure psig Time (min.) Yield (%) (°C) (kPa) 300 (2068.47) 300 (2757.90)
GI) 500 (3447.38) 150 (1034.21)
This description of specific embodiments of the invention is intended to enable those of skill in the art to more easily understand the nature of the invention, but not to limit the scope of the appended claims or the range of equivalents thereof. "Comprises/comprising” when used in this specification is taken to specify the presence of stated features integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps or components or groups thereof.
0)
This description of specific embodiments of the invention is intended to enable those of skill in the art to more easily understand the nature of the invention, but not to limit the scope of the appended claims or the range of equivalents thereof.
Claims (1)
- WHAT IS CLAIMED IS:I 1. A method for recovering nylon from a nylon-containing material, comprising: 2 contacting the nylon-containing material with an alkanol-containing solvent at N 3 elevated temperature and at a pressure higher than the equilibrium pressure of the alkanol- 4 containing solvent at the elevated temperature, thereby dissolving the nylon in the ) 5 alkanol-containing solvent; 6 removing the alkanol-containing solvent containing dissolved nylon from any 7 undissolved solids; and 8 decreasing the temperature of the alkanol-containing solvent containing dissolved 9 nylon to precipitate the dissolved nylon.1 2. The method of claim 1, wherein the nylon-containing material comprises a floor 2 covering material.1 3. The method of claim 1, wherein the nylon is nylon 6,6.1 4. The method of claim 1, wherein the alkanol-containing solvent is substantially free 2 of glycols or other polyols.1 5. The method of claim 1, wherein the alkanol-containing solvent comprises an 2 alkanol selected from the group consisting of methanol, ethanol, propanols, butanols, and 3 mixtures thereof.1 6. The method of claim 1, wherein the alkanol-containing solvent comprises a 2 mixture of alkanol and water.1 7. The method of claim 6, wherein the alkanol is present in an amount ranging from 2 about 40 wi% to about 90 wt% of the solvent. ]AMENDED SHEETL 8. The method of claim 7, wherein the alkanol-containing solvent comprises a : mixture of about 80 wt% ethanol in water.9. The method of claim 1, wherein the pressure during the contacting ranges from about 250 psig (2723.69 kPa) to about 600 psig (4136.85 kPa).10. The method of claim 1, wherein the elevated temperature ranges from about 130 °C to about 155 °C.11. The method of claim 10, wherein the elevated temperature is about 145 ° C.12. The method of claim 1, wherein the pressure higher than the equilibrium pressure of the alkanol-containing solvent at the elevated temperature is attained by introducing an inert gas into the reactor.13. The method of claim 1, wherein the pressure higher than the equilibrium pressure of the alkanol-containing solvent at the elevated temperature results at least in part from the pressure head of the alkanol-containing solvent entering the reactor.14. The method of claim 1, wherein the nylon-containing waste material comprises nylon-containing floor covering materials.15. The method of claim 14, wherein the nylon-containing floor covering materials comprise carpet or carpet tile, or mixtures thereof.16. The method of claim 15, wherein the carpet or carpet tile contains nylon 6,6.17. A method according to the invention for recovering nylon from a nylon-containing material, substantially as hereinbefore described and exemplified.18. A method for recovering nylon from a nylon-containing material including any new and inventive integer or combination of integers, substantially as herein described.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US24500600P | 2000-11-01 | 2000-11-01 |
Publications (1)
Publication Number | Publication Date |
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ZA200303327B true ZA200303327B (en) | 2004-03-09 |
Family
ID=32849382
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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ZA200303327A ZA200303327B (en) | 2000-11-01 | 2003-04-30 | Method of extracting nylon from waste materials. |
Country Status (1)
Country | Link |
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ZA (1) | ZA200303327B (en) |
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2003
- 2003-04-30 ZA ZA200303327A patent/ZA200303327B/en unknown
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