Abstract:
Method for producing pigment nano-particles may include vaporizing a pigment precursor material; drawing the vaporized pigment precursor material into a precipitation conduit; contacting the vapor in the precipitation conduit with a collection fluid at a first location within the precipitation conduit, the contacting cooling the vapor and precipitating pigment nano-particles, the contacting occurring in the absence of a temperature change in the vapor at locations within the precipitation conduit that are upstream of the first location; and collecting the pigment nano-particles in a collection fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application claims priority to United States provisional patent application entitled “Pigment Size Reduction Apparatus And Method” of Joel A. Taube, Ser. No. 60/344,681, filed on Nov. 6, 2001, which is hereby incorporated herein by reference for all that it discloses. 
    
    
     FIELD OF INVENTION 
     This invention generally pertains to pigments, and more specifically, to apparatus and methods for producing pigment nano-particles. 
     BACKGROUND 
     Nano-particles (i.e., particles having average sizes less than about 1 micrometer) are known in the art and are of interest because size and structure dramatically change the properties of the material. For example, the extremely large surface area to weight ratio of nano-particles allows nano-particles to interact with their surroundings very quickly. Nano-particles of pigment material are of particular interest in the inkjet printer industry for use with high-quality printers having many small (e.g., nano-scale) delivery orifices. 
     Pigment nano-particles can be produced using a primarily mechanical process in which the pigment precursor material is ground in a mill (e.g., a ball mill) until particles of the desired size are produced. Such grinding processes, however, are energy intensive, require substantial amounts of time, and typically result in the production of a powder having undesirable, larger size particles. Such larger size particles must be separated from the pigment nano-particles before use. In addition, the abrasive materials used in such milling and grinding processes may also contaminate the pigment nano-particle material. Consequently, such grinding processes generally are not conducive to the large-scale production of a highly pure pigment nano-particle material. 
     Consequently, a need remains for a method and apparatus for producing pigment nano-particles that does not suffer from the shortcomings of the prior art methods and apparatus. Such a method and apparatus should be capable of producing large quantities of pigment nano-particle material at low cost. Ideally, such a method and apparatus should be less sensitive to certain process parameters than other systems, thereby allowing the method and apparatus to be more easily practiced on a large scale (i.e., commercial) basis. Additional advantages could be realized if the method and apparatus produced pigment nano-particles in a relatively narrow size range, with a minimum amount of larger sized particles and/or contaminant materials. 
     SUMMARY OF THE INVENTION 
     An embodiment of apparatus for producing pigment nano-particles may comprise a furnace having a vapor region, the furnace vaporizes a pigment precursor material. A precipitation conduit open to the vapor region of the furnace receives vapor from the pigment precursor material. A collection fluid port opening into the precipitation conduit delivers a collection fluid into contact with the vapor in the precipitation conduit, the vapor condensing to form the pigment nano-particles. A collection system in fluid connection with the precipitation conduit collects the pigment nano-particles in the collection fluid. 
     An embodiment of a method for producing pigment nano-particles may comprise vaporizing a pigment precursor material to form a vapor; drawing the vapor into a precipitation conduit, rapidly condensing the vapor in the precipitation conduit to form the pigment nano-particles, contacting the pigment nano-particles with a collection fluid in the precipitation conduit, and collecting the pigment nano-particles in the collection fluid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative and presently preferred embodiments of the invention are shown in the accompanying drawings in which: 
         FIG. 1  is a schematic representation of the apparatus for producing pigment nano-particles according to one embodiment of the invention; 
         FIG. 2  is a cross-sectional view of a portion of the precipitation conduit in which the pigment nano-particles are formed; 
         FIGS. 3(   a ) and  3 ( b ) are scanning electron microscope images of pigment nano-particle material produced according to the teachings of the present invention; 
         FIG. 4  is a schematic representation of another embodiment of the apparatus for producing pigment nano-particles; 
         FIG. 5  is a cross-sectional view of a portion of the precipitation conduit in which the pigment nano-particles are formed according to the embodiment of the apparatus shown in  FIG. 4 ; and 
         FIG. 6  is a schematic representation of another embodiment of the apparatus for producing pigment nano-particles. 
     
    
    
     DETAILED DESCRIPTION 
     Apparatus  10  ( FIG. 1 ) is shown and described herein as it may be used to produce pigment nano-particles  12  ( FIG. 2 ) from a precursor material  14 . Briefly, apparatus  10  for producing pigment nano-particles  12  may comprise a furnace  16  having a vapor region  18 . Precursor material  14  is fed into the furnace  16  and vaporized. In one embodiment, the precursor material  14  may be sublimated (i.e., converted directly to a vapor or gas state from a solid state without passing through a liquid state), although the invention is not limited to such an embodiment. A precipitation conduit  20  open to vapor region  18  receives the vapor  22  from the vaporizing precursor material  14 ′. The vapor  22  condenses in the precipitation conduit  20  and forms the pigment nano-particles  12 . Precipitation conduit  20  is connected to a collection system  24  which collects the pigment nano-particles  12 . 
     Precipitation conduit  20  is shown in more detail in  FIG. 2 . A collection fluid port  30  opens into the precipitation conduit  20  and discharges collection fluid  32  into the precipitation conduit  20 , preferably as a fine mist or fluid stream. As will be described in greater detail below, the collection fluid  32  may be used to rapidly cool the vapor  22 , causing the vapor  22  to condense and form pigment nano-particle material  12  in the precipitation conduit  20 . The pigment nano-particle material  12  is suspended in the collection fluid  32  and carried through the precipitation conduit  20  to the collection system  24 . 
     Again with reference to  FIG. 1 , the collection system  24  may comprise a collection drum  26  and a pump  28  fluidically connected through the collection drum  26  to the precipitation conduit  20 . The pump  28  draws or pumps the vapor  22  from the vapor region  18  into the precipitation conduit  20 , where it condenses and forms the pigment nano-particle material  12 . The pump  28  then draws or pumps the pigment nano-particle material  12  suspended in the collection fluid  32  into the collection drum  26 . 
     Apparatus  10  may be operated as follows to produce pigment nano-particles  12 . A suitable pigment precursor material  14  is fed into the furnace  16 , where it is vaporized to produce vapor  22 . The vapor  22  is generally formed in the vapor region  18  of the furnace  16 . Depending on various design considerations, a carrier gas  34  may be introduced into vapor region  18  to enhance flow of the vapor  22  into the precipitation conduit. 
     Pump  28  may be activated to draw the vapor  22 , and the carrier gas  34  where provided, from the vapor region  18  into the precipitation conduit  20 . The vapor  22  condenses in the precipitation conduit  20  to form the pigment nano-particle material  12 . For example, the vapor  22  flowing into precipitation conduit  20  may come into contact with collection fluid  32 , which rapidly cools the vapor  22  (i.e., substantially adiabatically), precipitating the pigment nano-particle material  12 . The precipitated pigment nano-particle material  12  is generally suspended within the collection fluid  32 , although some of the pigment nano-particle material  12  may also be entrained in the carrier gas  34 . The slurry containing the precipitated pigment nano-particle material  12  and carrier gas  34  are carried through the precipitation conduit  20  and ultimately collected by collection system  24 . 
     Advantages of the present invention include, among others, the ability to produce large quantities of highly-pure pigment nano-particle material at low cost and on a shorter production schedule. The present invention is also relatively simple to construct, easy to operate, and is not overly sensitive to certain process parameters. Consequently, the present invention is ideally suited for use in large-scale (i.e., commercial) applications. Furthermore, the design of apparatus  10  allows ready removal of any pigment nano-particle material which may accumulate on the internal components of the system. 
     The pigment nano-particle material itself is a high-quality product that requires little or no additional processing before it may be used, making it particularly useful for use in, among other applications, high-quality inkjet printers. In addition, the purity of the pigment nano-particle material produced according to one embodiment of the invention gives it a “richer” color than what has been conventionally produced. 
     Having briefly described the method and apparatus according to one embodiment of the present invention, as well as some of the more significant features and advantages, the various embodiments of the method and apparatus for producing pigment nano-particles of the present invention will now be described in detail. 
     Referring to  FIG. 1 , one embodiment of apparatus  10  is shown and described herein as it may be used to produce pigment nano-particles  12  from a precursor material  14 . Apparatus  10  may comprise a furnace  16  having a vapor region  18 . The furnace  16  is suitable for receiving a supply of the precursor material  14  and vaporizing it. 
     In the embodiment shown and described herein, the furnace  16  comprises a rotary tube furnace having one or more electric heating elements  40 . Preferably, the furnace  16  has three heating zones  41 ,  42 ,  43 , although other embodiments are also contemplated as being within the scope of the invention. Electric heating elements  40  are used to elevate and maintain the temperature inside each of the heating zones  41 – 43  at level(s) sufficient to vaporize the pigment precursor material  14 . 
     It should be noted that the present invention is not limited to use with a rotary tube furnace. Nor does the invention require the use of electric heating elements. Any of a wide range of other furnaces that are now known in the art or that may be developed in the future that are suitable for vaporizing the pigment precursor material  14  may be used according to the teachings of the invention. Examples of other types of furnaces  16  that could be utilized with the present invention include, but are not limited to, muffle furnaces, induction furnaces, vacuum furnaces, and arc furnaces. 
     The pigment precursor material  14  may be delivered to the furnace  16  in any suitable manner. In one embodiment, the pigment precursor material  14  is fed into the furnace  16  in batch mode using a shot feeder  46  ( FIG. 1 ). That is, pigment precursor material  14  is loaded into the shot feeder  46  outside of the furnace  16 , then delivered into the furnace  16 , where the pigment precursor material  14  is emptied from the shot feeder  46 . However, delivery of the pigment precursor material  14  may be accomplished using other suitable delivery systems. In addition, the invention is not limited to a batch mode product delivery schedule. In other embodiments, the pigment precursor material  14  may be continuously fed into the furnace  16 , for example, using a screw-type conveyor system (not shown). Yet other delivery systems may also be used according to the teachings of the invention, some of which will be discussed below with respect to alternative embodiments. 
     As discussed above, the carrier gas  34  may also be delivered into the vapor region  18  of furnace  16 . The carrier gas  34  is preferably an inert gas, such as nitrogen. However, other gases may be used based on the properties of the precursor material  14  and the desired properties of the pigment nano-particles  12 . The use of carrier gas  34  promotes an even flow of the vapor  22  from vapor region  18  into the precipitation conduit  20 , thereby enhancing production of the pigment nano-particles  12 . 
     Precipitation conduit  20  is open to the vapor region  18  of the furnace  16 . The precipitation conduit  20  may comprise a generally elongate, pipe-like inner member  50 , and may be supported along at least a portion of its length by a generally elongate, pipe-like outer member  52 , as best seen in  FIG. 1 . Pipe-like inner member  50  fluidically connects vapor region  18  of the furnace  16  to the collection system  24 . 
     In the embodiment shown and described herein, outer member  52  is generally concentrically aligned with inner member  50  and is separated a spaced distance therefrom so that an insulating space or annulus  54  is defined between the inner and outer members  50  and  52 . The insulating annulus  54  may be maintained under a vacuum to enhance its insulating properties. The insulating annulus  54  is advantageous in that it helps to maintain the inner member  50  at cooler temperatures, thereby discouraging the re-vaporization of the precipitated pigment nano-particle material  12  flowing through the precipitation conduit  20 . 
     It is noted that the inner and outer members  50 ,  52  of precipitation conduit  20  may be fabricated from any of a wide variety of materials (e.g., hightemperature alloys and stainless steels) suitable for the intended application. In addition, the inner and outer members  50 ,  52  may have dimensions that are commensurate with the size (i.e., desired production capacity) of the apparatus  10  for the desired production of pigment nano-particles  12 . In the embodiment shown and described herein, the inner member  50  has an outer diameter of 2.375 inches (6.033 cm) and an inside diameter of about 2.067 inches (5.250 cm) and a wall thickness of about 0.154 inches (0.391 cm). The outer member  52  may have an outer diameter of about 4.5 inches (11.43 cm) and an inside diameter of about 4.26 inches (10.82 cm) and a wall thickness of about 0.12 inches (0.305 cm). Accordingly, the insulating space or annulus  54  will have a thickness of about 0.943 inches (2.395 cm). 
     As was briefly described above, the inner member  50  of precipitation conduit  20  is provided with a collection fluid port  30 . In the embodiment shown and described herein, the collection fluid port  30  is fluidically connected to a supply of collection fluid  32 . The collection fluid port  30  is suitable for discharging the collection fluid  32  into the inner member  50  of precipitation conduit  20 , as shown in more detail in  FIG. 2 . 
     In one embodiment, collection fluid port  30  comprises one or more nozzles that are configured to discharge a spray or a “curtain” of collection fluid into inner member  50  of the precipitation conduit  20 . Preferably the collection fluid  32  is discharged as a fine mist. In addition, the collection fluid  32  preferably sprays through a cross-section of the inner member  50  of precipitation conduit  20  so as to come into contact with most, if not all of the vapor  18  entering the precipitation conduit  20 . 
     The collection fluid  32  is discharged into the precipitation conduit  20  so that the collection fluid  32  contacts the vapor  22 , causing it to cool. As the vapor  22  cools, the pigment nano-particles  12  precipitate and become suspended in the collection fluid  32 , as illustrated in  FIG. 2 . Some of the precipitated pigment nano-particles  12  may also become entrained in the carrier gas  34 , also as illustrated in  FIG. 2 . 
     Collection fluid  32  may comprise any of a wide range of fluids suitable for effecting the rapid (i.e., substantially adiabatic) cooling of the vapor  22 . In one embodiment, collection fluid  32  is water. However, the collection fluid  32  may also comprise a mixture of fluids, organic fluids (e.g., ethylene-glycol, kerosene), a base, or other fluids suitable for mixing with the pigment nano-particles  12 . The selection of collection fluid  32  may, at least to some extent, be based on the desired characteristics of the pigment nano-particles  12 . Design considerations may also include the desired medium in which the product is collected, as may be specified by the end-user of the pigment nano-particles  12 , among others. 
     The location of the collection fluid port  30  within the precipitation conduit  20  may influence characteristics (e.g., size) of the pigment nano-particles  12  produced by the apparatus  10  according to the present invention. For example, moving the location of the collection fluid port  30  closer to the vapor region  18  of furnace  16  generally results in the production of larger pigment nano-particles  12 . Conversely, moving the location of the collection fluid port  30  away from the vapor region  18  generally results in the production of smaller pigment nano-particles  12 . 
     Other design factors can also affect characteristics of the pigment nano-particles  12 . For example, increasing the flow rate of the collection fluid generally results in the production of larger pigment nano-particles  12 . Alternatively, extending the precipitation conduit  20  at least partially within vapor region  18  of the furnace  16  and positioning the collection fluid port  30  therein may also affect the production of pigment nano-particles  12 . However, we have found that it is generally preferable to position the precipitation conduit  20  and the collection fluid port  30  external to the furnace  16  in the manner shown and described herein. 
     The temperature of the precipitation conduit may also affect characteristics of the pigment nano-particle material  12  that is produced. It is generally preferred, but not required, to position a temperature sensor, such as a thermocouple (not shown) within the interior region of the precipitation conduit  20  at a location downstream from the collection fluid port  30 . The output signal from the thermocouple may be monitored to maintain the temperature of the suspended pigment nano-particle material  12  within a desired temperature range that is appropriate for the particular pigment nano-particles  12  being produced. 
     Since the sizes of the pigment nano-particles produced by apparatus  10  of the present invention are related to several structural and operational parameters of the invention, as described herein, the present invention should not be regarded as limited to any particular parameters or range of parameters for any given structural or operational configuration. 
     Pigment nano-particle material  12  exiting the precipitation conduit  20  (e.g., suspended in the collection fluid  32  and/or entrained in the carrier gas  34 ) is conveyed to a collection system  24 . The collection system  24  is best seen in  FIG. 1  and may comprise a pump  28  and collection drum  26 . The pump  28  draws the vapor  22  from the furnace  16  into the precipitation conduit  20 , where the pigment nano-particles  12  are formed, as previously described. The pump  28  then draws the carrier gas  34  and the collection fluid  32  with the suspended pigment nano-particles  12  into the collection drum  26 . The carrier gas  34  is scrubbed and discharged into the surrounding atmosphere and the pigment nano-particle material  12  is collected in the collection drum  26 . 
     Pump  28  may comprise any of a wide range of gas-state pumping devices that are well-known in the art and readily commercially available. By way of example, the pump  28  may comprise a Leybold vacuum pump/centrifugal blower having a capacity of about 2407 liters per minute (85 cubic feet per minute), commercially available from Leybold Vacuum USA, Inc. (Export, Pa. 15632). Of course, the pump  28  may have a larger or smaller capacity depending on the intended production capacity of apparatus  10 . In another embodiment, the pump  28  may be provided with a variable capacity to allow the user to vary the flow rate of the pump  28  to more easily effect certain changes in the sizes and/or production quantity of the pigment nano-particle material  12 . 
     Optional purge valves  60 ,  61 ,  62  may be provided for use in conjunction with pump  28  prior to operation to evacuate apparatus  10 . According to the embodiment shown in  FIG. 1 , purge valves  61 ,  62  may be closed and purge valve  60  opened and pump  28  actuated to evacuate the furnace  16  and precipitation conduit  20 . Purge valve  60  may then be closed and purge valves  61 ,  62  opened so that the collection fluid  32  and carrier gas  34  are diverted through the collection drum  26  during operation. 
     The collection drum  26  serves to retain the pigment nano-particle material  12  and to scrub the carrier gas  34 . During operation, pump  28  draws both the collection fluid  32  and the carrier gas  34  from the precipitation conduit  20  and empties the collection fluid  32  and carrier gas  34  into the collection drum  26 . Discharge is preferably below the surface of a liquid provided in the collection drum  26 . The liquid may be any of a wide range of liquids, such as a mixture of water and ethylene-glycol. The properties of the liquid may depend on various design considerations, such as the desired characteristics of the product as specified by the end-user of the pigment nano-particles  12 , and its properties when mixed with the collection fluid  32 , to name only a few. 
     In any event, the carrier gas  34  is bubbled through the liquid in the collection drum  26  to scrub any pigment nano-particle material  12  from the carrier gas  34 . Carrier gas  34  may then be discharged to the atmosphere, as illustrated by arrow  64  in  FIG. 1 . Collection fluid  32  and the pigment nano-particle material  12  is collected in the collection drum  26 , which may be diverted or drained occasionally to retrieve the pigment nano-particle material  12 . 
     Collection system  24  may also comprise a venturi scrubber  66 . Use of a venturi scrubber  66  may increase the removal efficiency of the pigment nano-particles  12  entrained in the carrier gas  34 . Operation and design of venturi scrubbers  66  is well-known in the art for removing particulates from gas streams. Briefly, the converging walls of the venturi scrubber  66  create a pressure differential through the throat of the venturi scrubber  66 . This, combined with a large surface area for contacting the gas stream (e.g., the carrier gas) with the liquid stream (e.g., the collection fluid) aids in the transfer of particulates from the gas stream to the liquid stream passing therethrough. The higher the pressure drop, the greater the removal efficiency. 
     According to one embodiment, the venturi scrubber  66  is provided upstream from the collection drum  26 . The collection fluid  32  and carrier gas  34  flow from the precipitation conduit  20  through the venturi scrubber  66  before being discharged into the collection drum  26 . Liquid from the collection drum  26  can be recirculated upstream of the venturi scrubber  66  to dilute the collection fluid  32  and increase its ability to entrain more of the pigment nano-particles  12  from the carrier gas  34 . 
     Other systems could also be used to capture the pigment nano-particle material  12  suspended in the collection fluid  32  and/or entrained in the carrier gas  34 . For example, collection system  24  may be provided with a filter (not shown) suitable for removing small particles from the carrier gas  32 . The use and selection of such a filter will depend on design considerations, and may also be governed by certain regulatory requirements governing discharge of process gases to the atmosphere. Since filters for capturing such nano-sized particles are well-known in the art and could be easily provided by persons having ordinary skill in the art after having become familiar with the teachings of the present invention, filters that could be used with the present invention will not be described in further detail herein. 
     Yet other product collection devices and processes can be readily provided, as would be obvious to persons having ordinary skill in the art after having become familiar with the teachings of the present invention. Consequently, the present invention should not be regarded as limited to the particular product collection system  24  shown and described herein. 
     Apparatus  10  may be operated in accordance with the following embodiment of a method for producing pigment nano-particles  12 . As a first step, the apparatus  10  may be evacuated. For example, purge valves  61 ,  62  may be closed and purge valve  60  opened to by-pass the collection drum  26 , and the pump  28  operated to draw carrier gas  34  through the furnace  16  and precipitation conduit  20 . The purge valves  61 ,  62  may then be opened and purge valve  60  closed to divert flow through the collection drum  26  during operation. 
     The pigment precursor material  14  is then fed into the furnace  16  (e.g., in a continuous or batch manner), as discussed above. A pigment precursor material  14  suitable for use with the present invention is copper phthalocyanine crystals, and may be used to produce pigment nano-particles of copper phthalocyanine. 
     Of course other pigment precursor materials are available and could also be used in conjunction with the present invention, as would be obvious to persons having ordinary skill in the art after having become familiar with the teachings of the present invention. For example, pigment nano-particles may be made from proprietary pigment precursor material such as PY14 (yellow), PG7 (green), and 57:1 (red), which are commercially available from Heucotech, Ltd. (Fairless Hills, Pa. 19030). These are merely exemplary of other pigment precursor materials that may be used according to the teachings of the invention and are not intended to limit the scope of the invention. 
     Regardless of the particular pigment precursor material  14  that is used, the furnace  16  heats the pigment precursor material  14  to a temperature in the range of about 540 to 700° C. (with optimum results being obtained within a temperature range of about 680° C.), which is sufficient to vaporize, and in one embodiment sublimate, the pigment precursor material  14  and form a vapor  22  in vapor region  18  of the furnace  16 . 
     The vapor  22  may be combined with a carrier gas  34 , such as nitrogen or any other desired atmosphere, to assist in the flow of the vapor  22  into the precipitation conduit  20 . The vapor  22  (along with the carrier gas  34 ) is drawn into precipitation conduit  20 , for example, under the influence of pump  28 . 
     Upon entering the precipitation conduit  20 , vapor  22  is brought into contact with collection fluid  32  being discharged from the collection fluid port  30 . The collection fluid  32  is considerably cooler (e.g., about 15° C. to 50° C.) than the vapor  22  and causes rapid (i.e., substantially adiabatic) cooling of the vapor  22  and the formation, or precipitation of the pigment nano-particle material  12 . The resulting mixture of precipitate (in the form of the pigment nano-particles  12 ) and collection fluid  32 , along with the carrier gas  34 , continues to be carried through the precipitation conduit  20 , whereupon it is discharged into the collection system  24 . 
     The mixture of pigment nano-particles  12  and collection fluid  32 , along with the carrier gas  34 , which is discharged into the collection system  24  ultimately reaches the collection drum  26 . The collection fluid  32  and carrier gas  34  are discharged below the surface of the liquid in the collection drum  26  so that pigment nano-particle material  12  which may be entrained in the carrier gas  34  can be scrubbed as it bubbles through the liquid. Discharging the collection fluid  32  beneath the surface of the liquid also reduces the re-entrainment of the pigment nano-particle material  12  in the scrubbed carrier gas  34 . 
     From time to time, contents of the collection drum  26  may be diverted or otherwise emptied to retrieve the slurry containing the pigment nano-particles  12 . The carrier gas  34  may be discharged into the surrounding atmosphere. 
       FIGS. 3(   a ) and  3 ( b ) are images of pigment nano-particle material  12  produced by a scanning electron microscope in a process that is commonly referred to as scanning electron microscopy (SEM). As is readily seen in  FIGS. 3(   a ) and  3 ( b ), individual particle of the pigment nano-particle material  12  range from generally cylindrical to generally spherically-shaped configuration. Preferably, most if not all of the pigment nano-particle material is generally spherical in shape. Faster cooling of vapor  18  as it enters the precipitation conduit  20  tends to result in the production of more spherical-shaped pigment nano-particles  12 . 
     The size of the pigment nano-particle material  12  can be expressed in terms of the mean diameter of the particles. The particle size may be determined using scanning electron microscopy, transmission electron microscopy, or a suitable particle size analyzer, such as the laser diffraction particle size analyzer (model no. LA910) commercially available from Horiba Laboratory Products (Irvine, Calif. 92614). The preferred pigment nano-particle material  12  has a diameter of less than about 200 nm, and more preferably a diameter of less than about 100 nm. 
     An alternative embodiment of apparatus  110  is shown and described with respect to  FIG. 4  and  FIG. 5 . It is noted that one-hundred series reference numbers are used to refer to the like elements of this embodiment. 
     According to this embodiment of apparatus  110 , inner member  150  of precipitation conduit  120  is provided with a quench fluid port  180 , as shown in more detail in  FIG. 5 . The quench fluid port  180  is fluidically connected to a supply of quench fluid  182  ( FIG. 4 ) and discharges the quench fluid  182  into the inner member  150  of precipitation conduit  120 . Quench fluid  182  may comprise a fluid suitable for effecting the rapid (i.e., substantially adiabatic) cooling of the vapor  122 , causing the vapor  122  to condense and form pigment nano-particle precipitate  112 . 
     In the embodiment shown and described herein, the supply of quench fluid  182  may comprise liquid nitrogen. An optional accumulator (not shown) may be provided in order to provide optimal quenching performance between the supply of quench fluid  182  and the quench fluid port  180 . The accumulator helps to ensure that the quench fluid  182  is discharged as a liquid, as opposed to a liquid/gas mixture. Alternatively, a liquid/gas mixture can be used if increased flow-rates are desired and the end temperature is maintained within the desired range. 
     Although any suitable quench fluid  182  may be used, it is generally preferable that the quench fluid  182  be a cryogenic fluid. As used herein, the term “cryogenic fluid” refers to liquids that boil at temperatures of less than about 110 K (−163.15° C.) at atmospheric pressure. Cryogenic fluids include, but are not limited to, hydrogen, helium, nitrogen, oxygen, argon air, and methane. 
     Also according to this embodiment, apparatus  110  preferably comprises collection fluid port  130 , which may be arranged downstream from quench fluid port  180  to deliver collection fluid  132  into the precipitation conduit  120 . Again, collection fluid  132  may be any suitable fluid or mixture thereof, including but not limited to water and ethylene-glycol, as discussed above. 
     The collection fluid  132  is discharged into the precipitation conduit  120  in such a manner so that the pigment nano-particles  112  formed by the rapid cooling of vapor  122  by quench fluid  182  become suspended in the collection fluid  132  and can be readily collected by the collection system  124 , as described above. 
     Another alternative embodiment of the apparatus  210  is shown in  FIG. 6 . It is noted that two-hundred series reference numbers are used to refer to the like elements of this embodiment. 
     According to this embodiment of apparatus  210 , pigment precursor material  214  is delivered to the furnace  216  on a continuous basis. The pigment precursor material  214  is stored in a storage chamber  290 , and the carrier gas  234  is introduced into the storage chamber  290 . The pigment precursor material  214  becomes entrained in the carrier gas  234  in storage chamber  290 , and when the pump  228  is operated, it draws the carrier gas  234  and entrained pigment precursor material  214  into the furnace  216 . 
     Of course it is understood that other embodiments and product-delivery schedules may also be used. The embodiment shown in  FIG. 6  is provided merely as illustrative of another embodiment that is suitable for use according to the teachings of the present invention, and is not intended to limit the scope of the invention. 
     EXAMPLE 
     In this example, pigment precursor material comprised 15.3 copper phthalocyanine crystals having a mean size of about 25.9 microns. The pigment precursor material is readily commercially available from Sun Chemical Corporation, Fort Lee, N.J. 07024. The precursor material was provided to an electrically heated furnace of the type described above having a capacity to sublimate or vaporize approximately 5 grams/minute of pigment precursor material. 
     A precipitation conduit having the configuration and dimensions of the precipitation conduit described above was mounted adjacent the vapor region of the furnace. The precipitation conduit was fluidically connected to a collection system. The precursor material was fed into the furnace in batch mode using a shot feeder. In the furnace, the precursor material was heated to a temperature of about 680° C. which was sufficient to sublime the precursor material. 
     Nitrogen carrier gas was provided at about 2–5 liters per minute. A supply of collection fluid (i.e., water and ethylene-glycol mixture) was discharged in accordance with the description provided herein. The pump associated with the product collection apparatus, such as the type described above, was turned on to produce a vacuum of about 10–50 torr. 
     The apparatus started to produce the pigment nano-particle material, which was thereafter captured by the collection system. The flow-rate of the collection fluid was such that the temperature of the slurry containing the pigment nano-particle material  12  as measured by the thermocouple positioned within the precipitation conduit was maintained in the range of about 25° C.±5° C. The apparatus was operated in this manner for a time period of about 16 hours, which resulted in the production of about five gallons of pigment nano-particle material suspended in collection fluid having about 10 wt % pigment nano-particles, 15 wt % ethylene-glycol, and 75 wt % water. The pigment nano-particle material had a mean diameter of less than about 100 nm as determined using a laser diffraction analyzer, such as the type described above. 
     It is readily apparent that the apparatus and process discussed herein may be used to produce large quantities of highly-pure pigment nano-particle material. Consequently, the claimed invention represents an important development in nano-particle technology in general and to pigment nano-particle technology in particular. Having herein set forth preferred embodiments of the present invention, it is anticipated that suitable modifications can be made thereto which will nonetheless remain within the scope of the present invention. Therefore, it is intended that the appended claims be construed to include alternative embodiments of the invention except insofar as limited by the prior art.