Abstract:
A process for introducing a textile treatment material into a textile treatment system, particularly a supercritical fluid carbon dioxide (SCF—CO 2 ) treatment system. The process includes the steps of providing a preparation vessel in fluid communication with a textile treatment system; loading a textile treatment material into the preparation vessel; dissolving or suspending the textile treatment material in near-critical liquid carbon dioxide or supercritical fluid carbon dioxide in the preparation vessel; and introducing the dissolved or suspended textile treatment material into the textile treatment system. The textile treatment material can be selected from a group including a brightening agent, a whitening agent and a dye. A system suitable for use in carrying out the process is also disclosed.

Description:
This application is a Divisional of co-pending U.S. patent application Ser. No. 09/482,371 filed Jan. 13, 2000 now U.S. Pat. No. 6,261,326, herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to generally to textile dyeing and more particularly to the introduction of dyes and other chemicals into a process for dyeing a textile material in a supercritical fluid. 
     BACKGROUND ART 
     It will be appreciated by those having ordinary skill in the art that conventional aqueous dyeing processes for textile materials, particularly hydrophobic textile materials, generally provide for effective dyeing, but possess many economic and environmental drawbacks. Particularly, aqueous dyebaths that include organic dyes and co-solvents must be disposed of according to arduous environmental standards. Additionally, heat must be applied to the process to dry the textile material after dyeing in an aqueous bath. Compliance with environmental regulations and process heating requirements thus drive up the costs of aqueous textile dyeing to both industry and the consuming public alike. Accordingly, there is a substantial need in the art for an alternative dyeing process wherein such problems are avoided. 
     One alternative to aqueous dyeing that has been proposed in the art is the dyeing of textile materials, including hydrophobic textile materials like polyester, in a supercritical fluid. Particularly, textile dyeing methods using supercritical fluid carbon dioxide (SCF—CO 2 ) have been explored. 
     However, those in the art who have attempted to dye textile materials, including hydrophobic textile materials, in SCF—CO 2  have encountered a variety of problems. These problems include, but are not limited to, “crocking” (i.e. tendency of the dye to smudge when the dyed article is touched) of the dye on the dyed textile article; unwanted deposition of the dye onto the article and/or onto the dyeing apparatus during process termination; difficulty in characterizing solubility of the dyes in SCF—CO 2 ; difficulty introducing the dyes into the SCF—CO 2  flow; and difficulty in preparing the dyes for introduction into the dyeing process. These problems are exacerbated when attempts to extrapolate from a laboratory process to a plant-suitable process are made. 
     PCT Publication No. WO 97/13915, published Apr. 17, 1997, designating Eggers et al. as inventors (assigned to Amman and Söhne GmbH and Co.) discloses a system for introducing dye into a CO 2  dyeing process which comprises a bypass flow system associated with the main circulation system that includes a color preparing vessel. The bypass is opened, after a certain temperature and pressure are reached, so that SCF—CO 2  flows through the color preparing vessel and dissolves the previously loaded dye(s). The SCF—CO 2 -containing dissolved dye flows from the bypass back into the main circulation system where it joins the bulk of the SCF—CO 2  flow that is used to accomplish dyeing. 
     PCT Publication No. WO 97/14843, published Apr. 24, 1997, designating Eggers et al. as inventors (assigned to Amman and Söhne GmbH and Co.) discloses a method for dyeing a textile substrate in at least one supercritical fluid, wherein the textile substrate is preferably a bobbin and the fluid is preferably SCF—CO 2 . The disclosed invention attempts to prevent color spots from forming on the textile substrate during dyeing and is directed to ways of incorporating the dye material into the supercritical fluid using the basic bypass system as described above in PCT WO 97/13915. 
     The method involves the use of at least one dye which is contacted with the supercritical fluid as a dye bed, dye melt, dye solution, and/or dye dispersion before and/or during actual dyeing in an attempt to form a stable solution of dye in the supercritical fluid. A stated goal is avoiding the formation of dye agglomerates having a particle size of more than 30 microns, preferably more than 15 microns, in the solution. 
     This invention attempts to accomplish these aims through a variety of embodiments. In one embodiment, the dye bed is provided with inert particles, in particularly glass and/or steel balls, to prevent agglomeration. Alternatively, the dye bed itself can consist of inert particles coated with the dye. SCF—CO 2  is then passed through the dye bed to incorporate the dye within the SCF—CO 2 . 
     However, there are a number of significant drawbacks to this embodiment of the dye introduction method disclosed by Eggers et al. PCT Publication No. WO 97/14843. For example, use of a fixed or fluidized bed to introduce dye into the dyeing system can be hindered if appropriate flow conditions are not present. The dye particles must be at all times in intimate and vigorous contact with the supercritical fluid for effective dissolution. If this is not the case, the dissolution rate will be low and will likely not be complete by the end of the dyeing cycle. 
     Moreover, promotion of a high convective mass transfer coefficient (i.e., intimate and vigorous mixing) can result in substantial pressure losses through the dye-add vessel. Because of their relatively low viscosity values, supercritical fluids are easily diverted to areas of lower resistance, which can lead to mechanical problems such as channeling and stagnation. Channeling refers to the development of a fluid path, or channel, through a particulate bed that circumvents uniform flow throughout the bed; i.e., a stream of fluid develops through the bed such that the flow in the region where the stream exists is greater than the flow of fluid in the rest of the bed. In this case, the particles not in the channel are not properly contacted by the fluid. These conditions, in turn, result in dye particles not being contacted in a manner that will allow substantially complete dissolution. 
     Insuring the proper flow conditions when using fluidized dye beds, fixed dye beds, or dye bed holding devices requires very careful and complex design of the internals of the dye-add vessel in order to assure good mixing and to avoid mechanical flow problems without excessive pressure drop. Indeed, it is likely that dye bed holding devices that are chambered to force uniform flow of fluid through the bed, such as those proposed for use in dye introduction by Eggers et al., PCT Publication No. WO 97/14843, also suffer very high pressure losses. 
     Another drawback arises when the fluidized and fixed dye bed is installed in the system in a bypass loop. Since the dye dissolution process is rate limiting, this arrangement couples the dyeing process to the dye dissolution process, which is generally undesirable. In contrast, the dye should be introduced at a rate consistent with dyeing the textile material as rapidly as possible but also in a level manner. 
     An alternative embodiment of the dye injection method disclosed by Eggers et al. PCT Publication No. WO 97/14843 involves injection of the dye as a melt incorporated in an inert gas, preferably nitrogen or carbon dioxide (with property of being inert for these two gases being a function of the process conditions). It has been observed by the present applicants that melting of disperse dyes can lead to decreased solubility in SCF—CO 2 . This circumstance indicates that the applicability of this embodiment of the disclosed dye injection method is limited. 
     Yet another embodiment of the dye introduction method disclosed by Eggers et al. PCT Publication NO. WO 97/14843 involves delivery of the dye into the supercritical fluid flow as a solution or suspension. When a solution is being injected and water-soluble dyes are being used, the recommended injection solvent is water. For water-insoluble dyes, a variety of common nontoxic injection solvents are suggested, with acetone, which readily dissolves disperse dyes, being foremost. The water-insoluble dyes are injected as a solution or suspension in the chosen solvent. In the case that a suitable nontoxic solvent cannot be found or the required amount of solvent is so great that it adversely affects the dyeing process, injection of a dispersion, preferably an aqueous dispersion, is recommended. 
     This embodiment of the method disclosed by Eggers et al. PCT Publication No. WO 97/14843 also suffers from several drawbacks. Firstly, water is an anti-solvent in SCF—CO 2  when used with disperse dyes. Thus, for SCF—CO 2 , the presence of water results in a significantly impaired dyeing process to the extent that it is questionable whether dyeing could be accomplished at all. At best, the action of water in the SCF—CO 2  would cause the dye to reside in the dyeing process as dispersion. In the worst case, the dye would exist as an unstable suspension with unsuitable properties for dyeing. Secondly, in the case that a suitable SCF—CO 2 /water/dye dispersion was obtained, the SCF—CO 2  dyeing process would be similar to the conventional aqueous process, the replacement of which is a desired goal in the art. 
     Poulakis et al.,  Chemiefasern/Textilindustrie,  Vol. 43-93, February 1991, pages 142-147 discuss the phase dynamics of supercritical carbon dioxide. An experimental section describing an apparatus and method for dyeing polyester in supercritical carbon dioxide in a laboratory setting is also presented. Thus, this reference only generally describes the dyeing of polyester with supercritical carbon dioxide in the laboratory setting and is therefore believed to be limited in practical application. 
     U.S. Pat. No. 5,199,956 issued to Schlenker et al. on Apr. 6, 1993 describes a process for dyeing hydrophobic textile material with disperse dyes by heating the disperse dyes and textile material in SCF—CO 2  with an azo dye having a variety of chemical structures. The patent thus attempts to provide an improved SCF—CO 2  dyeing process by providing a variety of dyes for use in such a process. 
     U.S. Pat. No. 5,250,078 issued to Saus et al. on Oct. 5, 1993 describes a process for dyeing hydrophobic textile material with disperse dyes by heating the disperse dyes and textile material in SCF—CO 2  under a pressure of 73 to 400 bar at a temperature in the range from 80° C. to 300° C. Then the pressure and temperature are lowered to below the critical pressure and the critical temperature, wherein the pressure reduction is carried out in a plurality of steps. 
     U.S. Pat. No. 5,578,088 issued to Schrell et al. on Nov. 26, 1996 describes a process for dyeing cellulose fibers or a mixture of cellulose and polyester fibers, wherein the fiber material is first modified by reacting the fibers with one or more compounds containing amino groups, with a fiber-reactive disperse dyestuff in SCF—CO 2  at a temperature of 70-210° C. and a CO 2  pressure of 30-400 bar. Specific examples of the compounds containing amino groups are also disclosed. Thus, this patent attempts to provide level and deep dyeings by chemically altering the fibers prior to dyeing in SCF—CO 2 . 
     U.S. Pat. No. 5,298,032 issued to Schlenker et al. on Mar. 29, 1994 describes a process for dyeing cellulosic textile material, wherein the textile material is pretreated with an auxiliary that promotes dye uptake subsequent to dyeing, under pressure and at a temperature of at least 90° C. with a disperse dye from SCF—CO 2 . The auxiliary is described as being preferably polyethylene glycol. Thus, this patent attempts to provide improved SCF—CO 2  dyeing by pretreating the material to be dyed. 
     Despite extensive research into SCF—CO 2  textile dyeing processes, there has been no disclosure of a suitable method for introducing dyes or other textile treatment materials into such processes. An environmentally and economically sound method for introducing dyes or other textile treatment materials would be particularly desirable in the plant-scale application of a SCF—CO 2  textile dyeing process. Therefore, the development of such a method meets a long-felt and significant need in the art. 
     DISCLOSURE OF THE INVENTION 
     A process for introducing a textile treatment material into a textile treatment system is disclosed. The process comprises: (a) providing a preparation vessel in fluid communication with a textile treatment system; (b) loading a textile treatment material into the preparation vessel; (c) dissolving or suspending the textile treatment material in near-critical liquid carbon dioxide or supercritical fluid carbon dioxide in the preparation vessel; and (d) introducing the dissolved or suspended textile treatment material into a textile treatment system. A system suitable for use in carrying out the process is also disclosed. 
     The process and system of the present invention are preferred for use with a textile treatment system that utilizes SCF—CO 2  as a treatment medium. Optionally, the textile treatment material can be selected from a group including, but not limited to, a brightening agent, a whitening agent, a dye and combinations thereof. 
     Accordingly, it is an object of the present invention to provide an improved process and system for introducing dyes or other textile treatment materials into a textile treatment system, preferably a SCF—CO 2  textile treatment system. 
     It is another object of the present invention to provide an environmentally benign process and system for introducing dyes or other textile treatment materials into a textile treatment system, preferably a SCF—CO 2  textile treatment system. 
     It is another object of the present invention to provide a process and system for introducing dyes or other textile treatment materials into a textile treatment system, preferably a SCF—CO 2  textile treatment system, that reduces the loss of such textile treatment materials in a textile processing operation. 
     It is yet another object of the present invention to provide a process and system for introducing dyes or other textile treatment materials into a textile treatment system, preferably a SCF—CO 2  textile treatment system, that can be isolated from the textile treatment system to thereby facilitate addition of dyes and other textile treatment materials thereto. 
     It is a further object of the present invention to provide an improved process and system for introducing dyes or other textile treatment materials into a textile treatment system, preferably a SCF—CO 2  textile treatment system, in accordance with an introduction profile that facilitates correspondence between the introduction rate and an appropriate dyeing rate. 
     It is a further object of the present invention to provide an improved process and system for introducing dyes or other textile treatment materials into a textile treatment system, preferably a SCF—CO 2  textile treatment system, at an introduction point where there is high fluid shear to ensure proper mixing of the introduced treatment material into the textile treatment system. 
     It is yet a further object of the present invention to provide an improved process and system for introducing dyes or other textile treatment materials into a textile treatment system, preferably a SCF—CO 2  textile treatment system, that utilizes supercritical fluid and/or near-critical liquid carbon dioxide as a solvent for the dye or other textile treatment material. 
     Some of the objects of the invention having been stated herein above, other objects will become evident as the description proceeds, when taken in connection with the accompanying drawings as best described herein below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of a prior art system for introducing textile treatment materials into a SCF—CO 2  textile dyeing process; 
     FIG. 2 is a schematic of a system for introducing textile treatment materials into a textile treatment system wherein the system utilizes a stirred dye-add vessel in accordance with a process of the present invention; 
     FIG. 3 is a schematic of a system for introducing textile treatment materials into a textile treatment system wherein the system utilizes a circulated dye-add loop in accordance with a process of the present invention; 
     FIG. 4 is a schematic of a syringe pump with mechanical piston and circulation pump for use in a system for introducing textile treatment materials into a textile treatment system in accordance with the present invention; 
     FIG. 5 is a schematic of a syringe pump with mechanical piston and magnetically coupled stirrer for use in a system for introducing textile treatment materials into a textile treatment system in accordance with the present invention; 
     FIG. 6 is a schematic of a syringe pump with mechanical piston and no agitation for use in a system for introducing textile treatment materials into a textile treatment system in accordance with the present invention; 
     FIG. 7 is a schematic of a syringe pump with an inert fluid piston and magnetically coupled stirrer for use in a system for introducing textile treatment materials into a textile treatment system in accordance with the present invention; and 
     FIG. 8 is a schematic of a syringe pump with an inert fluid piston and no agitation for use in a system for introducing textile treatment materials into a textile treatment system in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the following terms are believed to be well-understood in the art, the following definitions are set forth to facilitate explanation of the invention. 
     The terms “supercritical fluid carbon dioxide” or “SCF—CO 2 ” are meant to refer to CO 2  under conditions of pressure and temperature which are above the critical pressure (P c =about 73 atm) and temperature (T c =about 31° C.). In this state the CO 2  has approximately the viscosity of the corresponding gas and a density which is intermediate between the density of the liquid and gas states. 
     The terms “near-critical liquid carbon dioxide” or “NCL—CO 2 ” are meant to refer to liquid CO 2  under conditions of pressure and temperature which are near the critical pressure (P c =about 73 atm) and temperature (T c =about 31° C.). 
     The term “textile treatment material” means any material that functions to change, modify, brighten, add color, remove color, or otherwise treat a textile material. Examples comprise UV inhibitors, lubricants, whitening agents, brightening agents and dyes. Representative fluorescent whitening agents are described in U.S. Pat. No. 5,269,815, herein incorporated by reference in its entirety. The treatment material is, of course, not restricted to those listed herein; rather, any textile treatment material compatible with the introduction and treatment systems is envisioned in accordance with the present invention. 
     The term “dye” is meant to refer to any material that imparts a color to a textile material. Preferred dyes comprise sparingly water-soluble or substantially water-insoluble dyes. More preferred examples include, but are not limited to, forms of matter identified in the  Colour Index,  an art-recognized reference manual, as disperse dyes. Preferably, the dyes comprise press-cake solid particles which has no additives. 
     The term “disperse dye” is meant to refer to sparingly water soluble or substantially water insoluble dyes. 
     The term “sparingly soluble”, when used in referring to a dye, means that the dye is not readily dissolved in a particular solvent at the temperature and pressure of the solvent. Thus, the dye tends to fail to dissolve in the solvent, or alternatively, to precipitate from the solvent, when the dye is “sparingly soluble” in the solvent at a particular temperature and pressure. 
     The term “hydrophobic textile fiber” is meant to refer to any textile fiber comprising a hydrophobic material. More particularly, it is meant to refer to hydrophobic polymers which are suitable for use in textile materials such as yarns, fibers, fabrics, or other textile material as would be appreciated by one having ordinary skill in the art. Preferred examples of hydrophobic polymers include linear aromatic polyesters made from terephathalic acid and glycols; from polycarbonates; and/or from fibers based on polyvinyl chloride, polypropylene or polyamide. A most preferred example comprises one hundred fifty denier/34 filament type 56 trilobal texturized yarn (polyester fibers) such as that sold under the registered trademark DACRON® (E.I. Du Pont De Nemours and Co.). Glass transition temperatures of preferred hydrophobic polymers, such as the listed polyesters, typically fall over a range of about 55° C. to about 65° C. in SCF—CO 2 . 
     The term “crocking”, when used to describe a dyed article, means that the dye exhibits a transfer from dyed material to other surfaces when rubbed or contacted by the other surfaces. 
     Following long-standing patent law convention, the terms “a” and “an” mean “one or more” when used in this application, including the claims. 
     A critical step in the treating of textile materials in a supercritical fluid (e.g., SCF—CO 2 ) involves the introduction of textile treatment material (e.g., dyes and other chemicals). Current introduction methods employed in SCF—CO 2  textile dyeing systems are somewhat similar to those used in commercial aqueous dyeing systems. 
     An exemplary prior art system is shown schematically in FIG.  1  and generally designated  10 . As shown in FIG. 1, dyeing system  10  comprises a dyeing vessel  12 , a dyeing circulation loop  14 , a dyeing loop circulation pump  16 , a dye-add vessel  18 , and a series of SCF—CO 2  flow control valves  20 . Dye is introduced into system  10  by placing it in dye-add vessel  18 , which can accommodate flow of SCF—CO 2 . SCF—CO 2  flow is mediated by circulation pump  16 . At the appropriate time in the dyeing process, a portion of the main SCF—CO 2  flow (represented by arrows in FIG. 1) is diverted from dye circulation loop  14  via valves  20  into dye-add vessel  18  in order to effect dissolution of the dye. The diverted SCF—CO 2  flow, laden with dissolved dye, then re-enters and mixes with the main SCF—CO 2  flow in loop  14  for use in dyeing the textile material, which is placed in vessel  12 . 
     In marked contrast to prior art methods and systems, the textile treatment material introduction process and system of the present invention decouple the textile treatment material dissolution process from the treatment process. The dye introduction rate is used to effect control over the dyeing rate in order to minimize non-uniform dyeing behavior, such as shading and streaking. As such, the dye introduction rate is varied to achieve amounts of dye in solution ranging from near zero up to the equilibrium value at each set of dyeing conditions (CO 2  density and temperature). Though a variety of solvents or carrier fluids can be used in the method and system of the present invention, the preferred preparation fluid is pure CO 2  in supercritical or near-critical liquid form. 
     The dye is introduced as a solution or suspension (dispersion) in SCF—CO 2  or NCL—CO 2 , depending on the required dye injection rate and the degree of solvency of SCF—CO 2  in the textile treatment system at the existing treatment conditions. As such, the use of surfactants or dispersing chemicals is not required in the introduction process and system of the present invention. However, co-solvents or surfactants may optionally be used to enhance dye solubility and dispersing agents may optionally be used to facilitate the establishment of stable suspensions of textile treatment materials in CO 2 . 
     Preferably, the textile treatment material introduction process and system of the present invention is used in conjunction with a method for treating a textile material using supercritical fluid carbon dioxide (SCF—CO 2 ). More preferably, the textile treatment material introduction method and system of the present invention are used in the treatment of a hydrophobic textile material, such as polyester, in SCF—CO 2 . However, application of the process and system of the present invention to other textile treatment processes and systems is contemplated. 
     For example, the method and system of the present invention also can be used with conventional aqueous dyeing processes. This is particularly the case with respect to treatment materials that are sparingly soluble in water. The textile treatment material introduction method and system of the present invention are used to predissolve such treatment materials, and the treatment materials are then introduced into a conventional aqueous dyebath. The use of environmentally hazardous organic co-solvents is thus avoided. 
     The textile treatment material introduction process and system of the present invention facilitate introduction of a textile treatment material, such as a dye, into a textile treatment process in that the treatment material is already dissolved or suspended when it contacts the solvent used in the treatment process. Thus, problems, such as agglomeration of particles, that have been observed in prior art processes, including particularly prior art SCF—CO 2  dyeing processes, are avoided. 
     Referring now again to the drawings, a preferred embodiment of the textile treatment material introduction system of the present invention is generally designated  30  in FIG.  2 . Referring to FIG. 2, system  30  introduces textile treatment materials dissolved or suspended in NCL—CO 2  or SCF—CO 2  into a textile treatment system  32  (similar to the prior art system shown in FIG.  1 ), which preferably comprises a SCF—CO 2  textile treatment system. System  30  comprises dye-add or preparation vessel  34 , positive-displacement metering pump  36 , line sections  38  and  40 , control valves  42 ,  43  and  44 , filter  46  and return line  48 . Treatment system  32  comprises a treatment vessel  50 , a circulation loop  52  and a circulation pump  54 . 
     Continuing with reference to FIG. 2, a textile treatment material is placed in preparation vessel  34 , which is equipped with a stirring device  56  capable of thoroughly mixing the contents of vessel  34 . Stirring device  56  comprises a motor-driven fan, but may also comprise a motor-driven shaft, a rotatably mounted shaft, or any other suitable stirring device as would be apparent to one of ordinary skill in the art after reviewing the disclosure of the present invention. Other stirring devices include a fan, propeller or paddle that is magnetically coupled to a motor rather than coupled to the motor by a solid shaft. Another approach, though mechanically more difficult, comprises placing the dye bed within a holding container within the preparation vessel that is both permeable to flow of the SCF—CO 2  and capable of being agitated within the fluid. The permeable holding container can thus be adapted for rotation via the flow of SCF—CO 2  to provide mixing of the dye bed with the SCF—CO 2 . Such devices, and equivalents thereof, thus comprise “stirring means” and “mixing means” as used herein and in the claims. 
     Continuing with reference to FIG. 2, in operation the preparation vessel  34  of system  30  is sealed and charged with NCL—CO 2  or SCF—CO 2 . The amount of CO 2  initially charged and the state of CO 2  (i.e., NCL—CO 2  or SCF—CO 2 ) depends on the CO 2  density desired at the introduction conditions. If a co-solvent, surfactant or dispersing agent is to be used, it is charged along with the textile treatment material, or introduced with a metering pump (not shown in FIG. 2) into the preparation vessel  34  at some point in the textile treatment material preparation process. The contents of the preparation vessel  34  are then heated with mixing to the introduction conditions (i.e., CO 2  density and temperature), which is contemplated to be a pressure that is near the textile treatment system pressure. 
     Preferably, introduction system  30 , and particularly preparation vessel  34 , is isolated from treatment system  32  when the solution or suspension of textile treatment material is prepared. Control valves  42 ,  43  and  44  are used to isolate preparation vessel  34  and thus can be opened and closed for reversibly isolating preparation vessel  34 . Any other suitable structure, such as other valves, piping or couplings, as would be apparent to one of ordinary skill in the art after reviewing the disclosure of the present invention may also be used to isolate, preferably to reversibly isolate, preparation vessel  34 . Such devices and structures, and equivalents thereof, thus comprise “isolation means” as used herein and in the claims. 
     Continuing with FIG. 2, depending on the introduction conditions and amount of textile treatment material present, the textile treatment material resides in a suspension or in a combination of solution and suspension. If introducing of a textile treatment material solution is desired, the fluid is removed from preparation vessel  34  via line section  38 , which is equipped with a filter  46 , and via control valve  42 . The filtering media of filter  46  has pore sizes predetermined from the particle size distribution and solubility characteristics of the textile treatment material. If introducing of a textile treatment material suspension or combination of textile treatment material solution and suspension is desired, the fluid is removed from the preparation vessel  34  via line section  40  and control valve  43 . 
     Continuing with reference to FIG. 2, positive-displacement metering pump  36  introduces the textile treatment material-laden NCL—CO 2  or SCF—CO 2  into the circulation loop  52  of treatment system  32  using a introducing rate profile that is consistent with producing uniformly-treated textile materials in minimum processing time. In a preferred embodiment, pump  36  shown in FIG. 2 comprises a positive displacement pump with a reciprocating piston. Other representative pumps include a syringe type pump employing a mechanical piston (FIGS. 4-6) as described below and a syringe type pump employing an inert fluid as a piston (FIGS. 7 and 8) as described below. Thus, devices such as pumps, nozzles, injectors, combinations thereof, and other devices as would be apparent to one of ordinary skill in the art after reviewing the disclosure of the present invention, and equivalents thereof, comprise “introducing means” as used herein and in the claims. 
     Mixing of the preparation vessel  34  is continued throughout the introduction cycle via mechanical stirring with stirring device  56 . Introducing of the textile treatment material-laden NCL—CO 2  or SCF—CO 2  occurs at an introduction point  58  in the circulation loop  52  where fluid shear is very high. For example, point  58  may lie before or after circulation pump  54  or in a mixing zone that contains static mixing elements (not shown in FIG. 2) in order to facilitate mixing with the treatment medium (e.g. SCF—CO 2 ) flowing in circulation loop  52  of treatment system  32 . The term “high fluid shear” refers to a turbulent flow or a flow with high rate of momentum transfer. Preferably, the term “high fluid shear” refers to a flow having a Reynolds number greater than 2300, and more preferably, greater than 5000. 
     When the textile treatment material is introduced as a solution from preparation vessel  34  into a SCF—CO 2  treatment system  32 , CO 2  makeup to introduction system  30  occurs via return line  48 . This action is taken in order to maintain the CO 2  density in introduction system  30 . Makeup of CO 2  involves opening the control valve  44  in the return line  48  such that SCF—CO 2  is diverted from circulation loop  52  to preparation vessel  34  in quantities sufficient to maintain the operating pressure of the introduction system  30 . Thus, control valve  44  and return line  48 , or any other suitable structure, such as other valves or couplings, as would be apparent to one of ordinary skill in the art after reviewing the disclosure of the present invention may be used to divert SCF—CO 2  to preparation vessel  34 . Such devices and structures, and equivalents thereof, thus comprise “diverting means” as used herein and in the claims. 
     When textile treatment material is dosed as a suspension into the treatment system  32 , introduction system  30  operates with full or partial CO 2  makeup via return line  48 . When textile treatment material introducing is performed without CO 2  makeup, the control valve  44  in return line  48  remains closed throughout the introduction cycle, and preparation vessel  34  is emptied of its contents during the introduction cycle. For introduction of suspension with full makeup, control valve  44  operates as described above. In the case of partial makeup, control valve  44  is operated intermittently to return SCF—CO 2  from circulation loop  52  to preparation vessel  34 ; i.e., preparation vessel  34  is partially emptied and then refilled with return SCF—CO 2 . 
     In the case of full or partial makeup to introduction system  30  when NCL—CO 2  is utilized in system  30 , the pressure of the returning SCF—CO 2  stream is reduced substantially across control valve  44  and return line  48  to match the near-critical liquid pressure in preparation vessel  34 . 
     Referring now to FIG. 3, an alternative embodiment of the textile treatment material introduction system  30  shown in FIG. 2 is disclosed and generally designated  60 . In alternative embodiment  60 , treatment materials are introduced in NCL—CO 2  or SCF—CO 2  into textile treatment system  62 , which preferably comprises a SCF—CO 2  textile treatment process. System  60  comprises dye-add or preparation vessel  64 , positive-displacement metering pump  66 , line sections  68  and  70 , control valves  72 ,  73  and  74 , filter  76  and return line  78 . Treatment system  62  comprises a treatment vessel  80 , a circulation loop  82  and a circulation pump  84 . 
     Textile treatment material is placed in the preparation vessel  64  of system  60 . Preparation vessel  64  is equipped with a mixing loop  86  as shown in FIG.  3 . Thus, mixing of the preparation vessel  64  is continued throughout the introducing cycle via fluid circulation (demonstrated by arrows in FIG. 3) by circulation pump  88  through mixing loop  86 . Such devices and structures, and equivalents thereof, thus comprise “circulation means” and “mixing means” as used herein and in the claims. Other aspects of alternative embodiment  60  function as described above, including the introduction of treatment material at high fluid shear introduction point  90 . 
     Referring again to FIGS. 2 and 3, the method and system of the present invention also contemplate treating a textile material after introduction of a textile treatment material from the introduction system to the treatment system. The treatment system comprises a treatment vessel, a circulation loop, and a circulation pump. In a preferred embodiment, the treatment system comprises a SCF—CO 2  treatment system. A textile material, such as a hydrophobic textile fiber, is placed in the treatment vessel. A solution or suspension of treatment material is introduced into the treatment system at an introduction point from the introduction system as described above. The flow, represented by arrows in FIGS. 2 and 3, of the medium used in the treatment system (e.g. SCF—CO 2  flow) is mediated by the circulation pump. The circulation pump directs the flow of treatment medium, which now includes the solution or suspension of treatment material, along the circulation loop to the treatment vessel. In accordance with a preferred embodiment of the present invention, if a suspension is introduced into the treatment circulation loop, the conditions in the loop are such that the suspended material is rapidly dissolved in the treatment flow of supercritical fluid and not carried further as a suspension. Thus, the introduction is preferably made into an area of high shear to promote rapid mixing and dissolution of any undissolved treatment material particles. Within the vessel the treatment material contacts the textile material for a suitable time to impart the desired characteristics to the textile material. 
     Referring now to FIG. 4, an embodiment of a syringe pump suitable for use as an introducing means in accordance with the present invention is disclosed and is generally designated  100 . Syringe pump  100  comprises syringe pump body  102 , piston  104 , high pressure hose section  106 , circulation pump  108 , and high pressure hose section  110 . Syringe pump body  102  comprises an internal void space  112  in which piston  104  is slidably mounted. Piston  104  comprises an axial channel  114  through which the flow  116  (represented by arrows in FIG. 4) of SCF CO 2  travels within syringe pump  100 . 
     Continuing with FIG. 4, circulation pump  108  is connected to syringe pump body  102  via high pressure hose sections  106  and  110 . Circulation within syringe pump  100  is thus provided via circulation pump  108 . Treatment material-laden SCF CO 2    118  enters syringe pump  100  from a preparation system via line  120  and valve  122 . Circulation, or other type of agitation, is preferred if further dissolution of the dye is being accomplished or if an unstable suspension of the dye is being introduced. If circulation or agitation is not required (e.g., when introducing a stable suspension of the dye), an inert gas piston might be substituted for the mechanical piston, as discussed below and as shown in FIGS. 7 and 8. Syringe pump  100  then propels treatment material-laden SCF CO 2    118  into a treatment system via line  124  and valve  126 . 
     Referring now to FIG. 5, an alternative embodiment of a syringe pump suitable for use as an introducing means in accordance with the present invention is disclosed and is generally designated  150 . Syringe pump  150  comprises a syringe pump body  152  having an internal void space  154  wherein a syringe pump piston  156  is slidably mounted. Syringe pump piston  156  comprises an axially mounted stirrer shaft  158  having a stirrer shaft magnet  160  mounted at the end of stirrer shaft  158  proximate to stirrer magnet  162 . Stirrer magnet  162  is also mounted within syringe pump piston  156 , and propeller stirrer  164  extends from stirrer magnet  162  into the internal void space  154  of syringe pump  150 . 
     Continuing with FIG. 5, treatment material-laden SCF CO 2    166  enters syringe pump  150  from a preparation system via line  168  and valve  170 . Agitation of treatment material-laden SCF CO 2    166  is accomplished within syringe pump  150  via propeller stirrer  164 . Syringe pump  150  then propels treatment material-laden SCF CO 2    166  into a treatment system via line  172  and valve  174 . 
     Referring now to FIG. 6, yet another alternative embodiment of a syringe pump suitable for use as an introducing means in accordance with the present invention is disclosed and is generally designated  200 . Syringe pump  200  comprises a syringe pump body  202  having an internal void space  204 , and a piston  206  slidably mounted within the interval void space  204  of syringe pump body  202 . Treatment material-laden dye  208  enters syringe pump  200  from a preparation system via line  210  and valve  212 . Syringe pump  200  then propels treatment material-laden SCF CO 2    208  into a treatment system via line  214  and valve  216 . 
     Referring now to FIG. 7, another alternative embodiment of a syringe pump suitable for use as an introducing means in accordance with the present invention is disclosed and is generally designated  250 . Syringe pump  250  comprises pump body  252  having an internal void space  256 , and a high pressure fluid inlet line  254 . A stirrer shaft  258  and a stirrer shaft magnet  260  are mounted at the end of the syringe pump body  252  opposite the line  272  and valve  274  that connect pump  250  with a treatment system. A stirrer magnet  262  is also mounted in pump body  252  proximate to stirrer shaft magnet  260 . A propeller stirrer  264  extends into the internal void space  256  of pump body  252  from stirrer magnet  262 . 
     Continuing with FIG. 7, treatment material-laden SCF C 2    266  enters pump  250  from a preparation system via line  268  and valve  270 . An inert material  278  (designated with a large arrow in FIG.  7 ), such as supercritical fluid nitrogen, is introduced into the internal void space  256  of pump body  252  via inlet line  254  while propeller stirrer  264  stirs the treatment material-laden SCF CO 2    266 . The in-flow inert material  278  drives treatment material-laden SCF CO 2    266  into a treatment system via line  272  and valve  274 . 
     Referring finally to FIG. 8, still another alternative embodiment of a syringe pump suitable for use as an introducing means in accordance with the present invention is disclosed and is generally designated  300 . Syringe pump  300  comprises pump body  302  having an internal void space  306 , and a high pressure inlet line  304  connected at the end of pump body  302  opposite from the line  314  and valve  316  that connect syringe pump  300  with a treatment system. 
     Continuing with FIG. 8, treatment material-laden SCF CO 2    308  enters syringe pump  300  from a preparation system via line  310  and valve  312 . An inert material  318  (designated with a large arrow in FIG.  8 ), such as supercritical fluid nitrogen, is introduced into the internal void space  306  of pump body  302  via high pressure line  304 . Inert material  318  thus drives treatment material-laden SCF CO 2    308  into a treatment system via line  314  and valve  316 . 
     The syringe pumps disclosed in FIGS. 4-8 can also be used in maintaining the SCF—CO 2  density in the preparation vessel by facilitating the addition of fresh SCF—CO 2  to the preparation vessel at the conditions in the preparation vessel without necessarily diverting SCF—CO 2  from the treatment system. For example, additional SCF—CO 2  can be introduced via high pressure lines  106  and/or  110  in FIG.  4 . This approach also adds additional SCF—CO 2  to the treatment system, and the treatment process is altered to include a different treatment process control strategy to accommodate the additional SCF—CO 2 . Thus, the pumps disclosed in FIGS. 4-8 also provide an alternative embodiment of the present invention in which SCF—CO 2  density is maintained in the preparation system without diverting SCF—CO 2  to the preparation vessel from the treatment system. 
     An advantage of the textile treatment material introduction process and system of the present invention is that it is used to introduce a variety of chemicals for treatment of a textile material. Thus, multiple operations can be performed concurrently or sequentially. For example, once a first textile treatment material, such as a dye, is introduced, the introducing system can be isolated and depressurized. Then, another textile treatment material, such as a UV inhibitor, can placed in the preparation vessel for introduction into the treatment system in accordance with the steps described herein above. 
     It will be understood that various details of the invention may be changed without departing from the scope of the invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation—the invention being defined by the claims.