HK1148569B - Splitter pump - Google Patents

Description

Separation pump

This application is a divisional application with application number 200580034034.1. The application date of the parent case is 8/5/2005; the invention relates to a method for extracting nylon from waste materials.

The present application claims the benefit of the filing date of provisional application serial No. 60/599,624, filed on 8/5/2004.

Technical Field

The present invention relates to an improved process for extracting nylon from waste materials, including mixing waste materials, such as floor coverings, which reduces degradation of nylon polymers to low molecular weight polymers, oligomers and monomers. The process involves contacting the waste material with a polar solvent, or mixture thereof, at elevated pressure.

Background

Nylon is widely used as a fiber in the production of woven fabrics, and in the production of floor coverings, such as broadloom carpet and carpet tiles. When used in floor coverings, nylon is typically present primarily as part of one or more layers of a multi-layer product. Large amounts of floor covering material are replaced each year, with the result that the used material is often discarded to landfills. Because of environmental and economic concerns with such waste materials, there is a need for an economical method of recovering and reusing used or discarded floor covering materials. However, because these materials often contain complex compositions or layers that are difficult to separate into their constituent components, the recycling process of these materials also often results in agglomerated products that are much less valuable than their individual components. In many cases, the value of the recycled product may be equal to or less than the value of the original starting material. The downcycling of this nature is environmentally and economically wasteful. Since the downcycled product is not as valuable as the original starting material, or even the original input to the production of the original waste material, economic value is lost. Because the product of the downcycling does not make full use of its constituents, additional component materials must be produced and used, creating an additional environmental burden that makes it particularly heavy, as these constituent materials are typically petrochemical based.

As a result of these considerations, there is a need in the art for a method that can economically separate and recycle one or more components of a floor covering material. In particular, there is a need in the art for a method that enables the separation and recycling of nylon used in floor covering materials, and in particular nylon used in the upper or warp-faced fabric layers of such floor covering materials, in such a way that the value and utility of the nylon is not degraded.

Methods of recovering nylon tend to fall into two significant categories. In one category are processes in which nylon is deliberately depolymerized to monomers or oligomers thereof, which can then be reused by repolymerization. In general, in order to make reuse more predictable, the aim is to decompose the polymer into monomers as much as possible. However, the processes in this category are disadvantageous because depolymerization is expensive and may lead to side reactions that reduce the amount of available monomer, reduce efficiency, and require additional depolymerization and energy consumption to make up for the losses. In addition, depolymerization of nylon 6, 6 by ammonolysis results in the production of Hexamethylene Diamine (HDMA), but requires an additional source of hexanoic acid to obtain nylon 6, 6, since hexanoic acid cannot be economically recovered from the depolymerization process.

In another category is a process for the recovery of nylon wherein the nylon is not depolymerized so that it can be reused without repolymerization. Generally, the purpose of this method is to extract or dissolve the nylon and thus separate from the other components of the floor covering material, with minimal polymer decomposition. The nylon is then usually 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 diminishing the value of the sexual cycle nylon. At least in part because some polymer decomposition almost always occurs due to the elevated temperatures required to facilitate dissolution or extraction on an economically relevant time scale.

For example, due to the high temperatures involved, nylon fibers that are subjected to dissolution or extraction type recycling processes can have their molecular weight reduced by the initial extrusion process to produce fibers. The molecular weight will be further reduced during conventional extrusion or dissolution processes and, as noted previously, will be further reduced if the nylon is re-extruded into fibers. This cumulative decomposition would render the molecular weight of nylon unsuitable for reuse as a fiber suitable for flooring applications.

Another disadvantage of both types of nylon recycling processes is that they either use raw materials having a non-nylon waste content exceeding that required by the process, or they go to great lengths to obtain relatively pure or colorless nylon raw materials. In the case of composite products, such as flooring materials like carpets and carpet tiles, the presence of fibers, backing materials, pigments, binders, etc. can complicate the efforts of nylon recycling, requiring physical and/or chemical separation of these materials from the nylon prior to any particular processing of the nylon fibers.

There is therefore a need in the art for a nylon recycling process that: which does not require depolymerization, does not significantly reduce the molecular weight of the recycled nylon polymer, and can be used to prepare nylons suitable for extrusion into fibers for use as raw nylon, which have been previously extruded into fibers, and particularly nylons obtained from flooring materials, without the need for undue separation of other components from the raw materials, such as by steps other than air elutriation.

Disclosure of Invention

In one embodiment, the present invention is directed to a method of accomplishing this need. Nylon, which may be obtained in the form of waste material, such as waste carpet material (obtained, for example, from post consumer carpet, carpet tile, or other floor covering, or as edge bands produced in the production of carpet or carpet tile), is contacted with a solvent or solvent mixture comprising an alcohol at elevated temperature and pressure. The use of high pressure has been found to unexpectedly reduce the temperature and dissolution time at which the nylon in the waste material is effectively dissolved in the solvent mixture. At least in part as a result of this reduction in dissolution temperature, nylon can dissolve at a degradation level where its molecular weight is greatly reduced. For applications in carpet materials, the molecular weight maintenance enables the process to effectively use nylon extruded into fibers, such as found in carpets, and the step in which the nylon can be extruded into fibers again. In fact, the process of the present invention allows the nylon present in the carpet material to be recycled without degrading the sexual cycle. While this process may use nylon separated from the other composite components, this need does not occur for commonly used carpet materials.

The present invention may be viewed as a method of recycling nylon comprising:

contacting the nylon with the alkanol-containing solvent at an elevated temperature and at a pressure greater than the equilibrium pressure of the alkanol-containing solvent at the elevated temperature;

removing the alkanol-containing solvent comprising dissolved nylon from any undissolved solids;

the temperature and pressure of the alkanol-containing solvent containing the dissolved nylon are reduced to precipitate the dissolved nylon. The nylon recovered thereafter may be further treated by filtration, washing, etc., and reused.

The increase in pressure of the mixture of nylon and alkanol-containing solvent may be accomplished by adding an inert gas to the dissolution vessel or line, which is the desired pressure stage vessel or plug flow heat exchanger. Alternatively, the increase in pressure of the solvent mixture may be accomplished by increasing the head pressure of the solvent mixture pumped into the reactor. For example, the cross-sectional area of the vessel through which solvent is added to the reactor may exceed the cross-sectional area of the vessel through which solvent is removed from the reactor, creating a head pressure in the reactor sufficient to reduce the nylon dissolution temperature and thus the reactor temperature, as described herein.

The process of the present 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 and broken carpet or carpet tiles, or selvedges obtained during the production of these materials. In particular, the method has been found to be very beneficial for carpet tiles, since these materials are typically composite structures having many layers. The process of the invention provides the additional benefit of easier separation of these layers and in many cases waste material is present in the dissolution process using recycled nylon and the remaining layers of material that have been separated. This gives the significant advantage of recycling these additional components much more efficiently.

In addition, in order to make the recycling process economically viable, it has been found that the treatment of the solvent in contact with the solvent requires careful handling, particularly since the process is often carried out at relatively high temperatures and pressures. This knowledge has already been disclosed in the prior art. For example, heating any nylon fiber mixture and solvent mixture to a dissolution temperature must be conducted under conditions and using processing equipment that avoid or reduce the tendency of aggregated and precipitated fibers or particles to clog processing equipment and piping. The present invention includes embodiments that minimize or avoid this blockage, enabling the process to be completed in a more efficient manner.

One of the process features that help provide reduced clogging is the high velocity, high recycle ratio of the portion of the solvent and nylon particles or fibers that exit the mixer before heating the mixture to the dissolution temperature. High speed may be maintained by, for example, a screw pump adapted with its inlet in the pump throat (pumpthroat). The recirculation flow remains a constant circulation, with a high velocity flow through the mixer outlet, the line to the pump, and the pump itself. It is desirable that the flow be a stirring plug flow and maintaining this type of flow prevents or minimizes agglomeration and plugging of process equipment.

Another method feature that helps reduce clogging is the use of a plug flow heat exchanger to heat the solvent/nylon mixture to the dissolution temperature. This avoids the use of shell and tube heat exchangers or other heat exchanger designs in which sharp bends, headers or manifolds, obstructions and other components provide opportunities for nylon particles to settle and clog equipment. Examples of plug flow heat exchangers include coil exchangers, stacked tube exchangers, jacketed plug flow reactors, plate and frame exchangers and other designs that render the process mixture turbulent.

Another method feature that increases the efficiency of the nylon recovery process is the use of a high efficiency filtration system to concentrate the nylon precipitated from solution. Examples include membrane filtration, ultrafiltration, reverse osmosis, and similar high efficiency separation techniques. One example of such a method is a vibratory shear enhanced process membrane filter ("VSEP"). Another example is a filter press. Both techniques substantially increase the solids content of the process stream, making subsequent dryer separations more efficient without sacrificing product (i.e., without significant product loss).

In one embodiment, the present invention relates to a process for recovering nylon from a nylon-containing material by:

contacting the nylon-containing material with the alkanol-containing solvent in a mixing vessel, wherein at least a portion of the mixture of the nylon-containing material and the alkanol-containing solvent is withdrawn from the mixing vessel and returned to the mixing vessel at a high flow rate;

increasing the temperature and pressure of the mixture until the pressure reaches a pressure above the equilibrium pressure of the alkanol-containing solvent at the elevated temperature, thereby dissolving the nylon in the alkanol-containing solvent;

removing the alkanol-containing solvent comprising dissolved nylon from any undissolved solids; and are

The temperature, or pressure, or both, of the alkanol-containing solvent comprising the dissolved nylon is reduced to precipitate the dissolved nylon.

In another embodiment, the invention relates to a method of increasing the toughness of nylon by:

dissolving raw nylon fibers in an alkanol-containing solvent at an elevated temperature and a dissolution pressure greater than the equilibrium flow pressure of the solvent at the dissolution temperature;

filtering undissolved solids from the solution;

precipitating nylon from the solution by reducing the temperature, pressure, or both of the solution to form a precipitated mixture;

concentrating the precipitated mixture by removing solvent from the precipitated mixture to form a concentrated mixture;

drying the concentrated mixture to form solid nylon;

the solid nylon is extruded into a fiber having an increased tenacity over the tenacity of the raw nylon fiber.

In another embodiment, the invention relates to a method of increasing the molecular weight of a starting nylon by:

dissolving raw nylon fibers in an alkanol-containing solvent at an elevated temperature and a dissolution pressure greater than the equilibrium flow pressure of the solvent at the dissolution temperature;

filtering undissolved solids from the solution;

precipitating nylon from the solution by reducing the temperature, pressure, or both of the solution to form a precipitated mixture;

concentrating the precipitated nylon by removing the solvent from the precipitated mixture to form a concentrated mixture;

drying the concentrated mixture to form a solid nylon having a molecular weight substantially exceeding that of the starting nylon.

In another embodiment, the present invention relates to an apparatus for recovering nylon from a nylon-containing material, comprising:

a mixing vessel adapted to mix a nylon-containing material and a liquid solvent;

a high flow rate separation pump system in liquid communication with the mixing vessel adapted to remove a portion of the contents of the mixing vessel and return to the mixing vessel at high speed;

a pressurized heat exchanger, a separation pump, or both in liquid exchange with the mixing vessel adapted to heat the mixture of nylon and solvent from the mixing vessel to an elevated temperature at a pressure above the equilibrium stream pressure of the solvent;

a filtration system in liquid exchange with the pressurized heat exchanger adapted to remove undissolved solids from the fluid stream;

a precipitator in liquid exchange with the filtration system, the pressurized heat exchanger, or both, adapted to reduce the pressure of the fluid stream, reduce the temperature of the fluid stream, or both;

a concentrator in liquid exchange with the precipitator adapted to remove solvent from the mixture of precipitated nylon and solvent and increase the solids content of the mixture

A dryer in liquid exchange with the concentrator is adapted to dry the mixture of nylon and solvent. The pump system generally comprises two pumps: a high flow rate recirculation pump, and a second pump adapted to remove a portion of the fluid and add it to the heat exchanger while increasing its pressure. The high flow rate recirculation pump is typically in fluid communication with the mixing vessel outlet (on the inlet side of the recirculation pump) and a second pump (on the outlet side of the recirculation pump). The second pump is typically in fluid communication with a high flow rate recirculation pump (on the second pump inlet side) and a heat exchanger and mixing vessel recirculation inlet (on the second pump outlet side).

In another embodiment, the present invention relates to a pump of the following type suitable for a second pump in a split pump system having:

a propulsion chamber, comprising:

a distal end;

a proximal end;

a propulsion chamber rotor extending through at least a portion of the propulsion chamber;

a propulsion chamber stator surrounding the propulsion chamber rotor and disposed between the distal end and the proximal end of the propulsion chamber;

an inlet chamber in fluid communication with the proximal end of the pusher lumen;

a side inlet opening in fluid communication with the inlet chamber;

a side recirculation outlet opening in fluid communication with the inlet chamber;

a method outflow port in fluid communication with the distal end of the propulsion lumen;

a drive shaft connected to the propulsion chamber rotor.

The process of the present invention results in significant advantages because the nylon obtained has a higher molecular weight than the starting nylon. It is unclear whether this is a result of retention of low molecular weight nylon chips or a result of nylon chain elongation or cross-linking during the process. It is clear that high molecular weight nylon has high tenacity when extruded into fibers, making the material produced by this process very suitable for reuse as fibers. As a result, the process of the present invention recycles nylon without degrading the recycled nylon and provides a sustainable method of reusing nylon for carpet fibers.

Drawings

FIG. 1(A) is a schematic diagram of one embodiment of the process of the present invention.

FIG. 1(B) is a continuation of the schematic diagram of the process of FIG. 1(A) in accordance with one embodiment of the present invention.

Fig. 1(C) is a continuation of the schematic diagram of the process of fig. 1(a) according to another embodiment of the present invention.

FIG. 1(D) is a continuation of the schematic diagram of the process of FIG. 1 (C).

Fig. 2 shows an embodiment of the separation pump according to the invention. Fig. 2(a) is a left side view of the pump according to the present invention. Fig. 2(B) is a left sectional view of the pump shown in fig. 2 (a).

Detailed Description

In general, the process of the present invention involves the use of a solvent or solvent mixture comprising a lower alkanol to dissolve nylon at a pressure above the equilibrium flow pressure of the solvent at the dissolution temperature. Desirably the nylon is in the form of nylon 6, but may include other nylons or combinations thereof. Nylon, which may be ground, pulverized, chopped or otherwise altered in size, may be contacted with a solvent or solvent mixture in a dissolution vessel or pipe, as a waste or small piece floor covering, such as a carpet or carpet tile, or as some other composite material, or as a substantially pure nylon addition. In order to achieve and maintain dissolution without clogging the process lines, a high flow rate of recycled fiber/solvent slurry is used in the mixing step. A high pressure pump may be used to increase the pressure of the process stream above the equilibrium stream pressure of the solvent. After heating/dissolution in a dissolution vessel or conduit, such as a plug flow heat exchanger, the nylon/solvent solution is recrystallized or precipitated and dried using a high efficiency drying process, which may precede a process that increases the solids content of the process stream, such as VSEP, filter press, or a combination of these. The drying process may include a rotary flash dryer, tray dryer, horizontal plow dryer, Bry-Air dryer, and/or other drying devices, all of which may be operated under an inert gas environment or under sufficient vacuum to maintain a relatively oxygen-free environment. The resulting recrystallized nylon has a very high molecular weight, excellent tenacity, and is generally well suited for spinning into fibers; the process thus represents a means of sustainable recycling of nylon fiber from waste carpeting without degrading the recycled fiber.

In a particular embodiment, the carpet product stock, consisting of the primary carpet backing of the nylon 6, 6 fiber tufts, is sheared using a rotating cylinder shear blade, which cuts the fibers to the same length. Placing the nylon fiber into a vacuum system of a shearing blade to pump the sheared nylon fiber from the base fabric; the fibers were captured by a vacuum system and bagged, pressed, and baled.

The dissolution vessel is maintained at a pressure above the equilibrium pressure for the solvent system at the selected temperature. For example, at a temperature of about 150 ℃, the equilibrium pressure of the ethanol/water solvent system will be about 100 psig. The pressure in the vessel can be increased to about 300psig to 600psig, more specifically about 300psig to about 500psig, even more specifically about 400psig to about 500 psig. One technique for increasing the pressure is to increase the head of the solvent system entering the vessel. This may be done, for example, by removing liquid from the vessel through a conduit having a smaller cross-sectional area than the conduit conveying the dissolved solution to the reactor, or by a high pressure pump to drive the process flow through a pressure control valve or fine orifice plate, by adding an inert gas, such as N, to the dissolution vessel or conduit before or during dissolution₂And (4) finishing. Alternatively, the pressure in the vessel may be increased by adding a sufficient amount of an inert gas, such as nitrogen, argon, etc., to the dissolution vessel.

The dissolution vessel is heated to a dissolution temperature of from about 130 ℃ to about 155 ℃, more particularly from about 135 ℃ to about 145 ℃, and even more particularly from about 140 ℃ to about 145 ℃, and held at that temperature for a period of time to dissolve the desired yield of nylon. Surprisingly, the use of increased pressure enables operation at temperatures below 160 ℃.

This increased pressure significantly enables increased and accelerated dissolution of nylon into the solvent system compared to the dissolution level and speed at equilibrium pressure for a certain temperature. In other words, the present invention enables the process to be operated at a temperature below the equilibrium pressure process, or even slightly elevated (e.g., 50psig) pressure process, for the same level of dissolution. Thus reducing nylon degradation resulting in higher amounts of product suitable for extrusion into fibers. More particularly, the process of the present invention results in a nylon product rich in high molecular weight nylon as compared to conventional processes which are not carried out under increased pressure.

Suitable solvents and solvent mixtures include lower alkanols, mixtures thereof, and mixtures of lower alkanols and water. More particularly, suitable lower alkanols include methanol, ethanol, propanol, butanol, and mixtures thereof. Mixtures of methanol and water or ethanol and water have been found to be particularly suitable. In particular, mixtures of ethanol and water are desirable because the use of ethanol involves reduced environmental and regulatory concerns compared to the use of other alkanols. When mixed with water, the alkanol is typically used in a ratio of alkanol to water ranging from about 40% to about 90%. In particular, a mixture of 80% ethanol and water has been found suitable for most applications. Desirably, the solvent or solvent mixture is substantially free of (i.e., contains no more than about 1%) glycerol or other polyol. Water has been found to make the process more economical and it is believed that the dissolution time for some alkanols to dissolve is reduced.

For example, after the carpet pieces are dissolved, the mixture is removed from the dissolution vessel in a dissolution vessel or dissolution conduit (e.g., a plug flow heat exchanger). The hot solution is filtered to remove undissolved components and the solution is cooled to about 120 ℃ to about 130 ℃ at atmospheric pressure to recrystallize or precipitate from dissolved nylon. The nylon is filtered from the remaining solution leaving any oil, lubricant, and plasticizer, paint and other impurities in the solution. As the nylon/solvent solution cools, the high molecular weight nylon will precipitate first and can therefore be filtered from the solution while maintaining the temperature of the solution at about 120 ℃ to about 130 ℃. This allows low molecular weight materials resulting from previous extrusion or any small degradation of molecular weight to remain in solution or to be expelled out of the nylon product. The solvent mixture may be recovered by evaporation and/or distillation, as the solution also retains some of the dissolved components (e.g., plasticizers, lubricants, and coatings) that may be present in the floor covering material. The precipitated nylon is then washed with a clean, hot alkanol/water mixture and dried, for example, in a vacuum oven.

It has been found that the use of increased pressure allows the dissolution or extraction temperature to be below 160 ℃ while maintaining the relative viscosity (indicative of molecular weight) of the nylon at an acceptable level for fiber extrusion applications. While not wishing to be bound by any theory, it is believed that this effect should result at least in part from better or more complete dissolution of the low molecular weight nylon fraction, which then remains in solution as the high molecular weight nylon fraction precipitates out.

In addition, it has been found that dissolution can be enhanced by separating the mixing and heating processing steps, performing these functions in separate process equipment, and recycling a stream of solvent/nylon mixture, which includes primarily the solvent and undissolved solids of nylon and other materials. The recycle stream is pumped at a relatively high velocity from the mixing vessel back into the mixing vessel by a pump. The velocity of the mixture is sufficient to provide plug flow through the recirculation loop, desirably turbulent plug flow. For further processing, the process stream is separated from the recycled material; recycling the material in this way in the mixing tank keeps the nylon particles and fibers from settling and clogging the pump system, tank outlet and piping. The recycle ratio (volume ratio recycled to total volume) is not particularly critical, but may generally be in the range of about 0.971-0.981.

Embodiments of the process can be more clearly understood with reference to fig. 1(a), 1(B) and 1(C), which provide schematic illustrations of two embodiments of the process of the present invention. In both embodiments, in mixer 1 is a mixed nylon-containing feedstock 2, solvent 3, and inert gas feed 4. Solvent 3 and nylon-containing feedstock 2 are mixed under pressure and a portion of the mixture is removed as mixture effluent stream 5 by pump 5 a. The effluent stream 5b from pump 5a is fed to a separation pump 6 which separates the stream into a high flow rate recycle stream 7 (which is returned to mixer 1), and a low flow rate process stream 9 (which is pumped by separation pump 6 into heat exchange system 10). Recycle stream 7 is treated at relatively high linear velocities; stream 9 is separated from stream 7, typically at a significantly lower flow rate. To achieve a stirring plug flow and reduce the chance of nylon fibers or particles in the flow settling and clogging the process equipment, both are pumped through a pipe having a relatively smooth inner surface, such as a pipe filled with a shaped iron.

Process stream 9 passes through heat exchange system 10 where it is heated by a working fluid added via inlet stream 11 (desirably steam) and withdrawn via outlet stream 12 (desirably condensate). The heated mixture 13 and at least a portion (desirably a majority) of the nylon of process stream 9 dissolved in solvent 3 exit heat exchange system 10. The heated mixture 13 may also contain particles of undissolved materials such as carpet backing, plasticizers, reinforcing fibers, fillers, and the like. These particulate materials are filtered from solution by a strainer/filter system 14 so that the filtered stream 15 is primarily dissolved nylon and solvent. Additionally, to help reduce the amount of undissolved material that flows through the system 15, the ground and/or air elutriated waste carpeting may be thoroughly rinsed in water or other rinsing liquid to remove as much particulate material as possible prior to being added to the mixer.

The filtered stream 15 is then added to a precipitator where dissolved nylon is precipitated from solution. Since the solution is under relatively high pressure, for precipitation, if a cooling operation is not desired, it may be advantageous to use a flash precipitator, which removes nylon from the solution by reducing the pressure of the solution. The resulting suspension of precipitated nylon and solvent may be removed from the settler as effluent stream 17 and optionally a portion of such streams 18, 20 may be recycled to the settler by pump 19 to agitate the slurry and avoid precipitation of the nylon product.

The non-recycled portion 21 of the precipitated discharge suspension passes through the filtration system 22 where it is concentrated and the solvent permeate stream 33 is removed. The unwashed concentrate stream 27 is added to the wash tank 24 where it is washed with a wash liquid 25, typically a water and solvent mixture similar to that used in a mixer. In the embodiment of the invention schematically shown in fig. 1(B), scrubber discharge streams 26, 28 are recycled to filtration system 22 by a scrubber tank recycle pump 29. The filtration system 22 re-concentrates the wash stream and the re-concentrated wash stream is then fed to a dryer 31 where residual solvent and water are removed. In the embodiment of the invention schematically illustrated in fig. 1(C), the unwashed concentrate stream 27 is added to another filtration system 22a, which may be the same or a different type than filtration system 22, where it is reconcentrated and the permeate stream 33a is removed. The washed, concentrated, and dried product 32 is removed from the dryer 31, shown in fig. 1(D) for an embodiment of the invention. In order to remove as much of the undesired contaminants, solvents, water, etc., as possible, it will be recognized by those skilled in the art that it may be necessary and desirable to include further washing and/or re-concentration steps prior to drying.

The solid nylon produced from the present process has a molecular weight sufficiently high for high value applications (e.g., fiber spinning) and low value applications (e.g., injection molding). And it has been found that surprisingly the nylon produced by this process can be processed into nylon fibers having a tenacity considerably higher than those obtained by using new nylon, and wherein when a mixture with new materials is used, the tenacity increases when the fraction of nylon recycled in the fibers increases.

The mixer 1 may be a pressure-rated vessel operating as a stirred tank with an inlet for nylon sheet material 2, solvent 3 and inert gas 4 (e.g. nitrogen) to surround the tank. The tank will be equipped with a passageway or other inlet for a motorized stirrer and an outlet and inlet for the removal and addition of the recirculating mixture. The solvent 3 is typically an alkanol and water, for example ethanol and water, for example an 80: 20v/v mixture of ethanol and water. The waste material 2 may be waste from carpet or carpet tiles and may be cut or ground pieces or scraps, such as selvedges, or in the form of large pieces. The use of ground crumb is particularly suitable for the process of the invention. In addition, although not strictly necessary, it may still be particularly advantageous to at least partially separate the nylon from other waste materials by elutriating the permeate debris, flushing it to remove non-nylon particles, or some combination of these. For example, the crumb may be elutriated first, for example by air elutriation, to mostly separate the nylon from the PVC and other materials, and the nylon may be washed to remove small particles, such as PVC or calcium carbonate filler particles.

The mixture of solvent and nylon-containing material 5 (which may consist essentially of nylon, or may be a mixture of nylon and insoluble materials such as carpet backing, plasticizer, etc.) is removed from the mixer through an outlet valve and recycled and disposed of by pump 5 a. The pump is desirably a centrifugal or other type of pump suitable for producing high flow rates, and may have size reduction capabilities (e.g., so-called "chopper" or shear centrifugal pumps). The discharge from the high flow pump 5a passes through a second stage pump 6, which recirculates a portion of its influent back into the mixing apparatus at a flow rate and/or linear velocity similar to that delivered by the pump 5 a. In which another part of the influent is pumped by pump 6 as effluent to the next stage at a low flow rate and linear velocity.

The separator pump 6 is desirably a single or dual rotor screw pump, such as a MOYNO progressive cavity pump, particularly a MOYNO L series pump, which has been modified to have an inlet and an outlet at the suction throat (suction) of the pump. Through which a high flow rate of effluent from pump 5a passes. Part of the inflow is passed through the propulsion chamber part of the pump 6 and pumped through the stator and conveyed by other lines to the remaining process steps. This fraction is provided by a fraction of the influent at a significantly reduced flow rate and linear velocity. The remainder of the inflow passes through the throat (throat) of the pump 6 and not through the propulsion chamber portion of the pump and is pumped out through the outflow opening opposite the inlet opening in the region of the pump throat. This stream is returned to the mixing vessel as a recycle stream at a high flow rate.

Fig. 2 illustrates one embodiment of a separation pump 6 suitable for use in the process of the present invention. The use of inlet opening 201, corresponding outlet opening (also in the pump throat area), and process flow outlet opening 203 in pump throat area 205 helps to reduce clogging caused by nylon fiber or particle agglomeration. Also, the pump can operate at relatively high pressures and produce a linear velocity high enough to produce a stirring plug flow of the mixture or suspension in the process stream exiting the stator 209 through the outlet 203. As indicated, a substantial portion of the pump effluent is recycled back to the mixing vessel. Deep recirculation of the mixture helps to maintain the nylon fibers or particles in suspension and limits agglomeration. Part of the pump effluent is separated from the recirculation stream by a passage through stator 209 and discharge outlet 203, and then through process heat exchange system 10. The opening 207 is used to clean the pump and is typically kept closed during pump operation.

Fig. 2A shows a left side view of the embodiment of the separation pump 6 described above. It should be understood that the right view is a mirror image of the left view. The pump is driven by a motor connected to a drive shaft 211 (not shown) that is connected to a link 213 (in fig. 2B) that extends through the pump throat region 205. The link is connected to a rotor 215 (fig. 2B), which creates a propulsion chamber 217 (fig. 2B) connected to the stator 209. A similar outlet opening opposite the inlet 201 enables a portion of the influent material to be recirculated out of the pump while a portion is diverted through the rotor/stator combination and exits the pump through the outlet 203. A split pump according to an embodiment of the invention can be manufactured by modifying a series L Moyno thrust cavity pump by drilling holes on either side of the pump throat, welding suitable flanges around the opening, as indicated in fig. 2A, and closing the raw material inlet at the top of the pump.

Heat exchange system 10 can include one or more heat exchangers that allow for continuous plug flow of the mixture while increasing its temperature to the dissolution temperature, generally from about 130 ℃ to about 155 ℃, more particularly from about 135 ℃ to about 145 ℃, even more particularly in the temperature range from about 140 ℃ to about 145 ℃, and at a pressure above the equilibrium vapor pressure of the solvent. Typical pressures range from about 300psig to about 600psig, more particularly from about 300psig to about 400psig, and even more particularly from about 400psig to about 500 psig. Suitable heat exchangers include stacked tube heat exchangers or jacketed plug flow reactors, coil heat exchangers, and other exchanger designs that enable plug flow at high pressures. For example, one or more coil exchangers, in which process fluid is passed through smooth tube sidewalls and steam is passed through the shell, may be used to heat the process stream to solution temperatures, particularly in small scale processes. A stacked tube heat exchanger or a jacketed plug flow reactor may be used with steam or other heat transfer fluid flowing through the jacket, particularly in large scale processes. An important feature of the heat exchanger is that it does not require process flow through manifolds, headers, shrink tubes, expanders or other flow obstructions that may cause slurry material to accumulate prior to nylon dissolution. It has been found that the use of, for example, laminated tube heat exchangers with seamless central tubes with complete flow jackets is particularly suitable in this respect, since they do not cause any significant agglomeration of the dissolving pulp.

It is desirable that the residence time in the heat exchanger be long enough to allow most or all of the nylon to dissolve. The residence time may vary depending on other parameters such as the amount of solids in the mixture, flow rate, dissolution temperature, pressure, etc., but is generally at least 60s, more particularly at least about 180s for 2% nylon solids. The minimum residence time will increase with increasing solids loading.

Any remaining particulate residual material after dissolution may be removed from the process stream by filtration system 14, desirably including one or more filters and strainers. For example, a primary filter may be used to remove large particles, such as those above 100 μm, followed by a finer filter to remove smaller particles, such as those of about 1 μm. For effective filtration, the process stream can be split and passed through two or more filter canisters, as necessary.

The hot, pressurized, filtered process stream 15 is then passed through a precipitator 16 to precipitate nylon from solution. The precipitator may be a simple flash tank where the low pressure in the flash tank causes the dissolved nylon to precipitate. Alternatively, more complex precipitators, such as forced circulation evaporative crystallizers, thick liquor crystallizers, DTB (draft tube buffer) crystallizers, surface cooling crystallizers, etc., are used to obtain precipitated nylon. Precipitator 16 may be in fluid communication with optional recycle streams 18 and 20, and recycle pump 19. The recycle stream of precipitation and mother liquor may be recycled back to the precipitator to maintain a substantial portion of the solids suspended in the dissolution mixture and prevent the amount of precipitation. Process stream 17 exiting the precipitator typically comprises a suspension of precipitated nylon in a solvent, and the nylon and mother liquor are separated by filtration system 22. The filtration system 22 can be any suitable filtration system; however, reverse osmosis or membrane filtration systems have been found to provide good results. In particular, vibratory shear enhanced process filtration (VSEP), such as produced by New logic research, inc, is particularly suitable for efficiently separating precipitated particulate nylon from precipitated mother liquor. However, the filter press may be used in place, or as an adjunct to the VSEP system, to provide a high solids nylon slurry more suitable for conventional filtration and/or drying to nylon.

In one embodiment of the invention, the precipitated nylon particles are washed with water or other aqueous washing solution and dried. In an exemplary embodiment, a portion of particles 27 are washed with water 25 in a washer 24, and the resulting suspension 26 is recycled by a pump 29 to the filtration system 22 for re-concentration, after which the re-concentrated particles 30 are dried in a dryer 31 to produce a dried nylon product 32.

The dryer 31 may be one or more of various types of dryers available depending on the solids content level of the precipitated nylon slurry obtained by the filtration process. The dryer desirably operates under vacuum or in an inert gas environment, as described above. VSEP systems can typically concentrate the product stream to a solids content of about 5-6%, which is too low for effective operation of many commercially available dryers. The addition of (or replacement by) a filter press can increase the solids content to 25% or more. Higher than about 10% solids, a rotary flash dryer or a paddle dryer can be effectively used. A 10% solids content feed, a rotary flash dryer (APV) can provide a dried product with a volatile content as low as 1.5% or less. Volatile concentrations as low as 0.07% have been obtained using a paddle dryer (Littleford Day) containing an agitated plow and chopper.

As explained above, the process of the present invention uses recycle streams in solvent mixing and crystallization, uses special pumping equipment, and avoids sharp internal edges and bends in processing equipment and piping to reduce fouling of process equipment. Also, it has been found that, unexpectedly, some solvents, such as alkanol solvents, can be substantially absorbed by the nylon fibers or particles in the starting materials during or after the mixing process. As a result, it is desirable to use a relatively high weight ratio of dissolved waste material, typically in the range of about 90 wt.% to about 99 wt.%, based on the total weight of the feed solution/suspension. The use of relatively dilute nylon pulp throughout the process enables the pulp to be more easily pumped.

The present invention may 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 in which nylon yarns or nylon sheets were tested to determine baseline relative viscosity. The nylon tablets were also dissolved in a methanol/water mixture, the nylon recovered, and its relative viscosity determined. A number of nylon-containing carpet tiles (as indicated by sample numbers 1-6) were cut up and placed in a pressure vessel to which 400ml of alkanol solvent and 100ml of water were added as indicated below, and the mixture was heated and pressurized as indicated below. The solution was removed from the pressure vessel to another vessel where it was cooled until the nylon precipitated. The nylon was then tested for relative viscosity using the same method used for nylon yarn or sheet. The results are shown in table 1 below.

TABLE 1

Sample (I)	Steaming temperature of low DEG C	Solvent (80% strength)	Final pressure, psig	Relative viscosity
					Nylon 6, 6 yarn	Is not cooked		NA	44
Standard PA66	Is not cooked		NA	45
					Standard PA66	165	Methanol	205	34
					1	165	99% isopropyl alcohol	140	40
2	165	Denatured ethanol	400	37
					3	175	Denatured ethanol	150	34
4	165	Pure ethanol	150	42
					5	155	Denatured ethanol	400	44
6	155	Pure ethanol	450	48
					7	150	Pure ethanol	400	45
8	145	Pure ethanol	400

Example 2

The procedure followed was similar to that used in example 1, using two samples from the same carpet tile or broadloom carpet, and varying the pressure. The results are reported in table 2 below. When "methanol" or "absolute ethanol" is indicated, 400ml of these solvents are mixed with 100ml of water ("absolute ethanol" only indicates that ethanol is not denatured). When "100% methanol" is indicated, water is not included in the mixture. Samples 1 and 3 were taken from carpet tiles, sample 2 was taken from broadloom carpet, and sample 4 was taken from hot melt precoated carpet.

TABLE 2

Sample (I)	Steaming temperature of low DEG C	Solvent (80% strength)	Final pressure, psig	Viscosity number	Relative viscosity
						Nylon 6, 6 yarn	Is not cooked	NA	NA	135	44
Standard PA66	Is not cooked	NA	NA	137	45
						Standard PA66	165	Methanol	205	112	34
						1A	155	100% methanol	210	141	47
1B	155	Pure ethanol	150	141	47
2A	155	100% methanol	210	162	60
						2B	155	Pure ethanol	150	166	62

Example 3

An 80% mixture of ethanol and water was preheated to the temperature indicated below and the nylon-containing fibers were added at once to the vessel in a sufficient amount to provide a mixture of solvent and nylon 3.5 wt%, which was pressurized to the pressure indicated in table 3 below and maintained at that pressure for the time indicated below. The liquid was removed from the vessel and cooled to a temperature of 120 ℃ in a jacketed vessel. The resulting cooled liquid was filtered to remove precipitated nylon. The remaining undissolved nylon in the first vessel was measured and the yield of dissolved nylon relative to total nylon added to the mixture was calculated.

TABLE 3

Run in	Temperature (. degree.C.)	Pressure (psig)	Time (minutes)	Yield (%)
					1	143	300	37	64
2	143	400	23	82
					3	147	450	23	100
4	150	500	15	100
					5	160	150	45	88

Example 4

Raw material obtained by cutting, vacuum collecting, bagging, and bagging nylon 6, 6 broadloom carpet waste was processed through the apparatus shown in fig. 1. A 10-thread nylon feedstock fiber sample was taken and analyzed to nylon 6, 6. In mixer 1, the feedstock nylon fibers were mixed with ethanol to a concentration of 2.75 weight percent, based on the total weight of the feedstock solution, pressurized to 425-460 psi. Heating in heat exchanger 10 (coil heat exchanger) increased the slurry temperature to 138-. A flow rate of 1.32-1.5gpm through the heat exchanger was used. The solution was strained and precipitated in a crystallization tank at a temperature range of about 115-125 ℃. The nylon suspended in solution is then passed through a first filtration/concentration system (i.e., VSEP) to bring the solution to a solids content of 5 wt.% to 6 wt.%. The dried solids obtained from the previous run were back-mixed to a solids content of 10-15% to allow more efficient operation of the dryer (the process was then modified to add a filter press after VSEP operation to remove the need for back-mixing). Although this means that some solids pass through the dryer multiple times, the results are very good. The material was again filtered through a 100 micron filter.

The 100lbs of nylon powder obtained from this process was further dried and pelletized to obtain a material having a moisture content of 500ppm, and relatively uniform size. And about 70lbs of the pelletized material was extruded through a combination filter (at a back pressure of about 500 psi) and a spinneret over 2-3 hours to obtain nylon fibers. The denier and tenacity of the yarn obtained by this method was tested and reported in table 4 below.

TABLE 4

Fineness of fiber	Toughness
		2429	3.11lb

The fibers were spun into a yarn which was then added to a yarn having a 17oz/yd²Surface weight carpets. No other fibers were used in the yarn to make the carpet face. The yarns were tufted into a rut-duller primary backing using a Glasbec backing.

Various tests were carried out on the carpet obtained by this method, the results of which are summarized in table 5 below.

TABLE 5

Test of	Results
		Art 5yr (dry) maintenance	8.25
Art 5yr (wet) maintenance	8
		Borrough's resistance	9083meg
Delamination-drying	Not separated out
		Fluorine	2322
IBM resistance	3783meg
		Color fastness to light	2-3(60AFUs)
Nitrogen dioxide	4-5(2cy.)
		Color fading by ozone	4-5(2cy.)
Radiation panel	.70
		Radiation panel-15 min	.78
Smoke-combustion	166
		Smoke-fire-4 minutes	131
Smoke-to-come combustion	438
		Smoke-unburned-4 min	66
Coloring (Red dye 40) for 24 hours	10
		Tuft bind-dry	8.66Ib
Vetterman Drum	1.522,000cy.

In addition, the molecular weight of the sheared waste material and the dry nylon obtained by the method, and the nylon pelletized before fiber extrusion were determined as viscosity average molecular weight. The molecular weight of the starting material was determined to be about 30 daltons. 6 nylon samples obtained from the process described above and further dried in an APV spin flash dryer or Littleford Day vacuum dryer, with a molecular weight of about 38 daltons on average. The molecular weight of the pelletized nylon was determined to be about 40 daltons.

Example 5

Nylon 6, 6 obtained from pressurized dissolution of carpet shear waste described above was combined with virgin nylon at different weight ratios, extruded into undrawn and drawn fibers, and evaluated for tenacity and draw. The same evaluation was performed on completely new nylon fibers. The results of the average tenacity and the stretching are provided in table 6 below.

TABLE 6

Sample number	Content-recycled: novel	Tenacity of not stretching	Elongation without stretching	Tensile toughness	Elongation without stretching
						1	25∶75	1.03	437.90	3.56	19.75
2	50∶50	1.01	411.02	3.58	20.33
						3	100∶0	1.04	370.74	3.89	19.88
Control	0∶100	0.937	408.87	2.7-3.2 (Specification)

The data show that, surprisingly, the tenacity of the fibers comprising recycled nylon obtained by the process of the present invention is better than that obtained with the new undrawn nylon fibers and is much better than the commercial specification for drawn nylon fibers. And as the fiber recycle content increases, the tenacity surprisingly improves further.

The description of the specific embodiments of the present invention is intended to make the nature of the present invention easier for those skilled in the art to understand, but not to limit the scope of the appended claims or their equivalents.

Claims (1)

1. A separator pump, comprising:

a propulsion chamber, comprising:

a distal end;

a proximal end;

a propulsion chamber rotor extending through at least a portion of the propulsion chamber;

a propulsion chamber stator surrounding the propulsion chamber rotor and disposed between the distal end and the proximal end of the propulsion chamber;

an inlet chamber in fluid communication with the proximal end of the propulsion lumen;

a side inlet opening in fluid communication with the inlet chamber;

a side recirculation outlet opening in fluid communication with the inlet chamber;

a process stream outlet in fluid communication with the distal end of the pusher lumen; and

a drive shaft connected to the propulsion chamber rotor.