Abstract:
A process and an apparatus for treating large articles to impart color or performance enhancing additives to the article in which a treatment system which includes: (i) a coloring solution and/or a solution containing at least one performance enhancing additive, (ii) water, and (iii) a solvent such as ethylene glycol monobutyl ether and diethylene glycol is applied to the article. The apparatus is made up of (a) a spray enclosure sized to contain the article(s) to be treated; (b) dispensing means, such as nozzles, which are configured to dispense sequentially, hot solution (i), hot solution (ii) and hot water (iii) directly onto the article surface(s); (c) means for securing and transporting the article to be treated into and out of the spray enclosure (such as a trolley system); and at least three closed vessels capable of delivering enough hot saturated coloring and/or performance enhancing solution, hot dye-free rinse solution and deionized water, respectively, with sufficient pressure to form small droplets from the spray nozzles, to thoroughly cover and rinse articles contained in the enclosure.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a process and to an apparatus for treating, preferably by spraying, an article which is preferably a polymeric material, to impart color and/or to enhance the properties of that article. 
       BACKGROUND INFORMATION 
       [0002]    In the course of dyeing materials, particularly plastics, it is sometimes desirable to color very large and heavy articles such as coated glass sheets, plastic sheets, furniture, large volume water bottles and automobile windows. Some of these articles may be large, e.g., up to 5 feet wide by 10 feet long, and weigh in excess of 300 pounds. In these instances, it is more economical and environmentally attractive to color large articles using spray processes because spray processes significantly reduce the required volume of coloring solution and eliminate the need for large volume dipping tanks. Hence vessels containing the dye solutions, as well as ancillary equipment such as pumps and heaters, can be smaller, and consequently, less expensive. Also, the smaller quantities of dye-containing solution discarded as the result of a color change can be reclaimed more efficiently. 
         [0003]    In addition to using less solution, spray processes also allow large articles to be easily transported via a simple conveyer into an enclosed spray apparatus where both coloring and subsequent rinsing take place. Once coloring and rinsing are completed, the articles are simply conveyed out of the spray apparatus for drying and packaging. In contrast, if similarly sized articles are immersed in coloring solutions, expensive cranes, requiring buildings with high bay areas, must be used to convey and lift heavy articles into and out of huge vats of hot solution. Moreover, these vats open to the atmosphere and create a potential for introducing vapors into the environment. Also, there is a problem with solution cross-contamination as the articles are lifted from one vat to another, dripping solution as they move. Another objection to the immersion technique is that due to their size, the articles cannot be moved in and out of the vats quickly enough to avoid non-uniformity in the color. 
         [0004]    U.S. Pat. No. 6,994,735 describes a method of spraying dye solutions onto plastic articles to add color to the article. However, no apparatus for performing such operations is described. 
         [0005]    It would be desirable to have an efficient apparatus for spraying dye-containing solutions and associated rinse solutions onto relatively large substrates. 
       SUMMARY OF THE INVENTION 
       [0006]    Accordingly, the present invention provides a process and an apparatus for treating large articles, preferably by spraying, with (1) a coloring system containing dye and/or a solution containing performance enhancing materials, (2) water, and (3) solvent(s) such as ethylene glycol monobutyl ether and diethylene glycol. The apparatus of the present invention includes an enclosure or vessel sized to contain an article to be treated with means for dispensing (e.g., by spraying through nozzles) the coloring and/or performance enhancing solution sequentially onto the article to be colored, means for securing the article to be treated and means for transporting the article to be treated into and out of the enclosure. The treatment system is applied to the article to be treated in the following sequence: first, hot dye-containing solution and/or hot solution containing performance enhancing material(s); second, hot dye-free solution; and third, hot water directly onto the article surface(s). The preferred means for securing and transporting the article to be treated is a trolley system designed to securely hold and transport large and heavy articles into the spray vessel for subsequent treatment with color and/or performance enhancing solution and rinse solutions. The means for dispensing the coloring system are connected to three or more closed vessels. Each of the closed vessels must be capable of delivering enough of a hot treatment system component with sufficient pressure that small droplets will be released from the dispensing means in an amount sufficient to either color, enhance or rinse the substrate being colored. The apparatus of the present invention must include at least one closed vessel for a saturated dye-containing solution or a solution containing a performance enhancing additive, at least one closed vessel for a hot dye-free rinse solution and at least one closed vessel for hot deionized water. Optional vessel(s) for collection of discarded solutions for reclamation may also be included in the apparatus of the present invention. 
         [0007]    Each means for dispensing a component of the treatment system (also referred to herein as a “nozzle”) is designed to disperse solution at a temperature sufficient to color or treat the article to be treated. The nozzles are configured inside the enclosure or vessel in which the treatment system is to be dispensed so that the entire surface of the article to be colored or covered with solution containing performance enhancing additive will receive dispensed treatment system components. The enclosure includes an outlet through which dye-containing and/or performance enhancing solution may be removed from the enclosure and recycled back to the supply vessel where the solution is reheated and re-saturated with dye or performance enhancing additive before being returned to the spray enclosure containing the article to be treated. Recycling is continued until the article is the desired color or the desired amount of performance enhancement has been attained. The treated article is then rinsed, first, with dye-free solvent followed by a water rinse. When a color or additive change is required, the discarded dye-containing or performance enhancing additive-containing solution may be transferred to a vessel for discarded solutions for reclamation. The dye-free solvent rinse solution falls to the spray enclosure outlet from which it is then transported to a discarded solution vessel for reclamation. Waste rinse water is also removed from the spray enclosure at the enclosure outlet, treated to remove low levels of residual organic compounds and discarded into a waste water treatment facility. 
         [0008]    These and other aspects of the present invention will become more readily apparent from the following drawing, detailed description and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]      FIG. 1  illustrates an apparatus within the scope of the present invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0010]    As used herein in the specification and claims, including as used in the examples and unless otherwise expressly specified, all numbers may be read as if prefaced by the word “about”, even if the term does not expressly appear. Also, any numerical range recited herein is intended to include all sub-ranges subsumed therein. 
         [0011]    The present invention provides a process and an apparatus for preparing and applying, preferably by spraying, a coloring or performance enhancing system which includes at least one coloring agent or dye-containing solution and/or a performance enhancing additive or solution containing at least one performance enhancing additive and associated rinse solutions onto a material to be treated which is preferably a polymeric material such as a polycarbonate, a polyurethane, a polyester (preferably a glycolized polyester), a polymethylmethacrylate (acrylic), a nylon, a thermoplastic polyurethane, a polyvinylchloride, a polycarbonate/acrylonitrile butadiene styrene (ABS) blend, a polycarbonate/polyester blend or an ABS. 
         [0012]    The coloring agent(s) or dye(s) suitable for use in the process and apparatus of the present invention include, for example, conventional dyes such as fabric dyes and disperse dyes as well as dyes that are known in the art to be suitable for tinting polymeric materials such as polycarbonates. Specific examples of suitable disperse dyes include Disperse Blue #3, Disperse Blue #14, Disperse Yellow #3, Disperse Red #13 and Disperse Red #17. Dyestuffs are generally used either as a sole dye constituent or as a component of a dye mixture depending upon the color desired. Thus, the term “dye” as used herein includes “dye mixture”. Solvent dyes may also used in dying operations conducted in accordance with the process of the present invention in the apparatus of the present invention. Some examples of suitable solvent dyes include Solvent Blue 35, Solvent Green 3 and Acridine Orange Base. Water-insoluble azo, diphenylamine and anthraquinone compounds; acetate dyes, dispersed acetate dyes, dispersion dyes and dispersol dyes, specific examples of which include Dystar&#39;s Palanil Blue E-R150 (anthraquinone/Disperse Blue) and DIANIX Orange E-3RN (azo dye/CI Disperse Orange 25) may also be used in the practice of the present invention. Acid dyes, such as those used for dying nylon, as well as reactive dyes sold under the trade name Reactint for use with polyurethanes and polyurethane blends, are also suitable for use in the practice of the present invention. 
         [0013]    The apparatus of the present invention is also suitable for spraying solutions containing additives which enhance the performance characteristics of the article to be treated. Suitable performance enhancing additives include: photochromic dyes, UV-stabilizers, antistatic agents, flame retardants, mold release agents, antimicrobials, and other performance improving additives. 
         [0014]    The apparatus of the present invention is also suitable for applying, preferably by spraying, solutions containing both a coloring agent and an additive to enhance the performance of the material to be colored which is preferably a plastic. The apparatus of the present invention is also suitable for applying separately one or more solutions containing a coloring agent and one or more other solutions containing performance enhancing additives. 
         [0015]    The apparatus of the present invention is also suitable for applying, preferably by spraying, any associated rinsing liquids required to produce a clean, market ready article. 
         [0016]    The enclosure in which the article to be treated is positioned may be made of any material which will withstand the operating conditions and exposure to the solutions being applied to the article being treated. It is preferred that the walls of the enclosure be made of a transparent material such as tempered glass, so that the progress of the treatment, particularly treatment to impart color to the article may be observed. However, progress of the treatment may also be monitored by video camera or visually through small ports in the door(s) or side(s) of the enclosure. 
         [0017]    All of the vessels, nozzles, and interconnecting piping are fabricated of materials which do not absorb dyes or additives from the solution. Examples of suitable materials include: stainless steel, aluminum, glass and plastics such as crystalline polyesters or polyolefins. As used herein, the term “materials which do not absorb dyes or additives from solution” will be used to denote any of these materials. Preferably, the components of the apparatus are made of stainless steel. 
         [0018]    Referring now to  FIG. 1 , which illustrates an embodiment of the present invention in which the article to be treated is being treated to impart color to that article. The dye-free solution is typically formulated with water and organic solvents such as ethylene glycol butyl ether, diethylene glycol ethylether, diethylene glycol butylether, propylene glycol propylether, dipropylene glycol propylether and tripropylene glycol propylether and diethylene glycol. U.S. Pat. Nos. 6,733,543; 6,749,646; 6,929,666; 6,949,127; 6,994,735; and 7,094,263 disclose particularly advantageous formulations for producing such dye-free solutions and each of these disclosures is incorporated herein by reference. The dye-free solution components are mixed and heated in a closed insulated vessel  5  to a maximum temperature of 95° C. This solution is used directly as the dye-free rinse solution, and as a solvent feedstock useful for formulating dye-containing solutions in closed vessel  10 , as described below. 
         [0019]    To formulate the dye-containing solution, the dye-free solution contained in vessel  5  is transferred by pump  15  to vessel  10 , fitted with a second pump  20 , heater  25  and bag filter  30  in a piping arrangement that continuously circulates the solution in vessel  10  from the bottom of vessel  10  through the heater  25  and bag filter  30 , respectively, and returns the solution back to vessel  10 . The filter bag  35  contains dye that, over the course of a few minutes, saturates the circulating dye-free solution and produces the hot, dye-containing solution required for practicing the present invention. Each of U.S. Pat. Nos. 6,733,543; 6,749,646; 6,929,666; 6,949,127; 6,994,735; and 7,094,263 describes in detail processes for producing such dye-containing and performance-enhancing additive solutions, and is incorporated herein by reference. The dye-containing solution is transferred using pump  20  from vessel  10  through spray enclosure inlet  40 . 
         [0020]    The spray enclosure  45  is vented to a condenser system  50  sized to condense solvent vapors and return the resulting liquid to a reclamation vessel  55 , while allowing air to be channeled through a roof vent. Optionally, the spray enclosure  45  is double insulated and has supplemental pad heaters attached to its walls as an aid to maintaining the temperature of the dye-containing solution during the spraying operation. Additionally, an optional heater and fan may be attached to the spray enclosure  45  to concurrently heat the air and article to be colored  60  inside the enclosure  45  to a predetermined temperature before the dye-containing solution is applied to the article  60 . 
         [0021]    Article(s)  60  is mounted on a fixture attached to a trolley  65 . The trolley  65 , with the article(s)  60  attached, is moved into the spray enclosure  45  through door  70 . A continuous rubber seal  75  permits ingress and egress of the trolley while keeping the enclosure  45  sealed. 
         [0022]    The door  70  is secured and hot dye-containing solution is transferred from vessel  10  by pump  20  to spray enclosure  45  via the inlet manifold  40  and header system  80 . The pump  20 , used to transfer the dye-containing solution from the solution vessel  10  to the spray enclosure  45 , controls the solution flow rate through the piping, and consequently, the pressure of the solution as it enters the header  80  and exits the nozzles  85 . The article  60  is positioned in front of the nozzles  85  so that the entirety of one or both of the surfaces of the article  60  is/are covered with coloring solution exiting from the nozzles  85 . 
         [0023]    The temperature of the solution entering the nozzle(s)  85  is 30-100° C. at a pressure of 5-50 psi. The solution temperature is dependent on the material being colored, particularly plastic materials being colored. For example, rigid, high heat distortion materials such as polycarbonate are colored above 90° C. while more flexible, rubbery materials color at around 45-60° C. The preferred nozzle  85  pressure is 15-25 psi. 
         [0024]    In the next steps of the process, solution exits the spray vessel  45  through outlet  100 . The exiting solution is continuously recycled via pump  105  back to the dye-containing solution vessel  10  to be reheated and saturated again with dye. The solution is continuously cycled until the article  60  attains the desired color. 
         [0025]    After the article  60  has attained the desired color, the dye-containing solution flow is stopped and hot, dye-free solution rinse is pumped from heated vessel  5  through nozzles  85 , applying dye-free solvent rinse to the article  60  surface(s) to remove any excess dye. The dye-free solution is typically heated to increase cleaning efficiency and to thoroughly remove all article surface dye. The solution temperature is dependent on the material being colored, as described above in the dyeing sequence. Moreover, the temperature of the dye-free rinse solution can be independent of the dye-containing solution. Unlike the dye-containing solution which is circulated continuously back to the source (vessel  10 ) during the coloring operation, the dye-free solution is not circulated back to the source vessel but rather, after one pass through the spray enclosure  45 , is pumped via pump  105  directly to reclamation vessel  55  to be reclaimed. After thorough rinsing of the article, as indicated by the complete removal of dye, the dye-free solution flow is stopped and distilled or deionized water is pumped from a heated vessel  110  through the nozzles  85  onto the article  60  surface(s) to remove traces of residual dye-free solution, leaving the article  60  free of organic solvents but wet with water. Residual water can be wiped away with a soft cloth or blown from the article  60  with compressed air. Another means, albeit slower than wiping or blowing compressed air, is the use of infrared heaters to evaporate the residual water from the article  60  surface(s). 
         [0026]    Nozzles  85  are designed and spaced within spray enclosure  45  to provide maximum solution coverage to the surface(s) of article  60 . The maximum coverage for article  60  when it is in the form of a flat sheet is obtained using a type full-cone nozzle  85 . The nozzle  85 , located 5-8 inches (optimally 6⅞ inches) from the sheet surface, will, at the optimum distance, spray a circular pattern of solution covering an area approximately 21 to 26 inches (optimally 23⅝ inches) in diameter. Consequently, nine of these nozzles  85 , spaced 15 to 20 inches apart (optimally 17¼ inches) on center, will totally cover a 4 feet wide by 4 feet long piece of sheet on one side with sprayed solution. For two sided coloration, a similar configuration of nozzles  85  must be positioned in the spray vessel on the reverse side of the sheet, doubling the total number of required nozzles  85  to eighteen. Assuming the spray enclosure  45  has sufficient width, several nozzle headers, including headers equipped with nozzles on a common header but facing in opposite directions, can optionally be installed to cover multiple sheet pieces with solution in a single operation. 
         [0027]    There are generally significant areas of overlap between the spray nozzles  85  where two nozzles  85  will double the amount of colored solution sprayed on the sheet surface per unit time. Moreover, as the hot color solution droplets impacts the flat sheet surface of article  60 , small rivulets are formed as the droplets coalesce and are pulled by gravity, to the bottom of the flat sheet. It might be expected that these areas will ultimately appear as defects (dark streaks) however, it has been found that the spray process of the present produces sheet articles that are very uniform in color. 
         [0028]    Any of the known dye-containing and dye-free solutions may be used in the process of the present invention. 
         [0029]    In a preferred embodiment of the present invention, the system contains an in-line probe or detector to determine the clean solvent composition. The probe can be a near IR analyzer or other instrument for determining purity. Other analytical techniques for determining the clean solvent composition, such as gas chromatography, can be used, but near IR (NIR) is the most reliable and cost effective means to do this analysis. 
         [0030]    Although it is possible for the process of the present invention to be conducted manually, it is preferred that the coloring process of the present invention be controlled electronically, most preferably, by a human-machine interface (HMI) programmed to sequence valve functions. 
         [0031]    Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.