Abstract:
Apparatus and method for removing an ink image from a plastic substrate, particularly a plastic container such as a cup, are provided. A solvent capable of solvating the ink image is utilized in order to de-ink articles so that they can be recycled and re-imprinted thereby reducing waste associated with printing line start up. As the articles may be intended for use with food and beverage products, a safe and non-toxic solvent may be selected. However, to ensure that the article is not contaminated with foreign materials prior to human use, the de-inked article may undergo a rinse and drying operation to remove solvent residues and UV light treatment to eliminate any harmful microorganisms that may be present on the article&#39;s surfaces.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/482,096, filed May 3, 2011, which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is directed toward a process and apparatus for removing ink from plastic materials, such as plastic films and food and beverage containers. In certain embodiments, the ink to be removed has been applied to the plastic material by dry offset printing, although other types of ink and printing processes may also be used. 
         [0004]    2. Description of the Prior Art 
         [0005]    The startup of a dry offset printing line, including the change-over from printing one type of image to another, is generally considered an art form as it involves a number of manual adjustments to the line including the positioning of the various plates and color usage. Further, it is not uncommon for any printing operation to produce misprinted items or have over-runs in terms of quantities of products printed. These operations typically result in the creation of 4-7% scrap product (based upon the total product to be printed). The scrap plastic is traditionally ground up and resold for non-food and beverage applications. As the cost of raw materials, particularly plastics, continues to rise, the production of high levels of scrap material can prove quite costly. 
         [0006]    U.S. Pat. No. 5,830,836 is directed toward compositions and methods for removal of polymeric coatings, such as paint, enamel, lacquer, varnish, a sealant, or the like, from non-porous surfaces, such as metal, certain stone, acrylic siding, and may be the surface of an aircraft, a car, or a building. Particularly, a peroxide-based solution having a pH of about 6.5 to 11.0 is used. This solution may also comprise a surfactant such as between 1-5% by weight of a linear alkyl ethoxylate, and significant quantities of benzyl alcohol and various glycols. The solution is preferably mixed up just prior to use and remains useful for only about 24 hours. 
         [0007]    U.S. Pat. No. 6,147,041 is directed toward a removable ink composition and a process for removing the ink from printed articles. The ink removal process generally comprises applying a 1-3% solution of sodium hydroxide at a temperature of 80-90° C. onto a plastic bottle, for example, containing an image printed thereupon. The solution is then permitted to contact the plastic substrate for 20-30 minutes. 
         [0008]    U.S. Pat. No. 6,663,929 is directed toward removing ink from labels, made from a heat-shrinkable polymer film, by contacting the film with a hot alkaline solution (3% sodium hydroxide, at 90-95° C. for 30 minutes. 
         [0009]    U.S. Pat. No. 6,803,085 is directed toward a method of removing an “ink-only” label from a plastic substrate without destructive treatment of the substrate. The label is removed by exposing the label and substrate to a pre-rinse solution comprising 1-5% sodium hydroxide at 60° C. Next, the substrate is soaked in a similar sodium hydroxide-based solution for between 40-110 seconds wherein the labels are completely removed. The substrate is then rinsed with 30° C. water. 
         [0010]    U.S. Patent No. 7,416,612 is directed toward a process for removing paint from a plastic substrate so that the substrate can be repainted for reuse. The process involves immersing the coated plastic substrate into a first aqueous fluid that contains benzyl alcohol, glycolic acid, sodium lauryl sulphate, 2-mercaptobenzothiazole, and xylene, and has a temperature of 140-180° F. After this immersion step, the plastic can either be rinsed off and reused, or it can be immersed in a second fluid comprising a blend of biodegradable, non-regulated solvents and emulsifiers, such as ethylene glycol, monoethyl or diethyl ether, and a dibasic ester. 
         [0011]    As can be seen, a number of these references utilize caustic or hazardous compounds. 
         [0012]    Further, a number of the processes described the above references are quite time consuming. Accordingly, there is a need to develop a quick, safe, and bio-friendly way to de-ink plastic articles so that they may be reused. The present invention seeks to avoid use of hazardous chemicals by providing a method of de-inking plastic articles using a safe and bio-friendly solvent. Additionally, the present invention provides an apparatus that can de-ink plastic articles in a timely, efficient, and automated manner. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention provides a method of removing the ink from synthetic resin material surfaces, such as the surfaces of thin or flexible films or the surfaces of containers formed from synthetic resin materials, such as plastics, thereby allowing the synthetic resin material to be passed through a printing line again and eliminating the production of scrap material that often accompanies printing line start up. In certain embodiments, the process involves three primary steps. First, a solvent is applied to the synthetic resin material in order to solvate the ink printed thereon while the synthetic resin material is scrubbed to aid in the removal of the ink. Next, the synthetic resin material is sent through a water wash cycle to remove ink and solvent residues. Finally, the synthetic resin material is dried. The synthetic resin material emerges from this process ready for re-printing. 
         [0014]    The present invention also provides an apparatus for removing ink from synthetic resin materials. In certain embodiments, the apparatus includes a loading station that loads a synthetic resin material having an ink printed thereon onto the apparatus; a solvent application station that applies organic solvent to the synthetic resin material, where the organic solvent is capable of solvating the ink image; a rinsing station that applies water to the synthetic resin material to remove the solvent residues therefrom; a drying station that removes water from the synthetic resin material; and an unloading station that off loads the de-inked containers from the apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic diagram of an exemplary de-inking apparatus according to the present invention; 
           [0016]      FIG. 2  is a perspective view of a container-handling device according to one embodiment of the present invention; 
           [0017]      FIG. 3  is a diagram of a solvent application station for use with an apparatus according to the present invention; 
           [0018]      FIG. 4  is a diagram of the scrubbing station of  FIG. 3  shown in contact with a container being de-inked; 
           [0019]      FIG. 5  is a diagram of a rinsing station for use with an apparatus according to the present invention; 
           [0020]      FIG. 6  is a diagram of another rinsing station for use with an apparatus according to the present invention; 
           [0021]      FIG. 7  is a diagram of a drying station for use with an apparatus according to the present invention; and 
           [0022]      FIG. 8  is a diagram of a dry buffing station for use with an apparatus according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    The present invention provides methods and apparatus for removing ink from synthetic resin material surfaces, particularly ink printed upon a container surface, such as a cup, which will be used to illustrate the principles of the present invention. Although, it is within the scope of the invention for the methods and apparatus described herein to be adapted for use on other types of printed surfaces such as on synthetic resin material webs, sheets, and films, such as banner material and lids. Therefore, the following discussion should be taken as illustrative and not as limiting the scope of the present invention in any way. In certain embodiments, an ink image is printed upon the outer surface of a substantially cylindrical or frustoconical container. The container is formed from a synthetic resin material such as a polyolefin (e.g., polyethylene or polypropylene), biopolymers (e.g., plant-based materials including starch-containing plastics), or polyesters (e.g., polyethylene terephthalate). The container outer surface, particularly at least that portion containing the printed image, is generally smooth and non-porous. In certain embodiments, this aspect excludes containers created from highly porous materials such as polystyrene as the ink, when printed thereupon, penetrates into the material&#39;s pores. 
         [0024]    The ink image can be applied to the synthetic resin material surface through any number of recognized means, such as screen printing or dry offset printing. The inks can be any ink suitable for use in these printing methods, including UV-curable inks. As noted above, the start up of a printing line in order to print a certain image onto the outer surface of a container is not an exact science and involves a fair amount of trial and error in order to pin point the precise printing parameters needed to produce an acceptable product. This trial and error process generates large quantities of printed products whose printed images are not of a quality suitable for delivery to a customer. The present invention allows for the inferior images on these products to be removed and the containers to be recycled back through the printing line thereby substantially eliminating much of the waste associated with printing start up. 
         [0025]    In one embodiment of the present invention, a solvent is applied to the outer surface of the container containing the ink image. The solvent is capable of solvating the ink which has been cured upon the container surface. Therefore, the solvent must be capable of weakening the adherence of the ink to the container surface. The solvent may be applied by dipping the container in the solvent, spraying the solvent onto the container, or wiping the container surface with a solvent-laden textile material. It is important that the particular method of solvent application not scratch or de-gloss the container itself thereby rendering the container unsuitable for reuse. The solvent selected may be any solvent capable of de-adhering the ink from the surface of the container on which it is printed. However, the ink image should be un-varnished, that is, there should be no varnish or clear coat applied on top of the ink image. In certain embodiments, particularly those applications wherein the plastic material is to be used on food and beverage containers, the solvent is a non-toxic, environmentally friendly material. Although, the requirement for a non-toxic solvent may be lessened when the target substrate is not going to be used for this purpose. In particular embodiments, the solvent comprises an organic solvent that is non-corrosive, non-flammable, and does not contain any EPA Hazardous Air Pollutants. Exemplary solvents that may be used in with methods according to the present invention include those selected from various classes of chemicals such as esters (e.g., alkyl esters), ketones, glycols, glycol ethers, halogenated solvents, aromatics, alcohols, aliphatic hydrocarbons, amines, and terpenes. More specifically, the solvent is selected from the group consisting of amyl propionate, butyl butyrate, alkyl lactates, ethyl hexyl acetate, dibasic esters, methyl soyate, ethyl soyate, cyclohexanone, methyl ethyl ketone, dipropylene glycol, dipropylene glycol methyl ether, diethylene glycol butyl ether (DGBE), trichloroethylene, xylene, ethanol, 2-propanol, tetrahydrofurfuryl alcohol, hexane, mineral spirits, monoethanolamine, d-limonene, dimethyl formamide, n-methyl pyrrolidone, propylene carbonate, and combinations thereof. In still another embodiment, the solvent is an alkyl ester solvent having the general formula RCOOR′, wherein R and R′ are independently selected from C1-C10 alkyl groups and R contains at least one hydroxyl group. One particular solvent that has been found to produce acceptable results is Substi-Solve, available from Flexocleaners.com, Bellport, N.Y. 
         [0026]    The solvent may also comprise a surfactant to assist in the de-inking process. Any surfactant capable of aiding in the removal of the ink can be used, including anionic, cationic, nonionic, zwitterionic, amphoteric, and ampholytic surfactants. Exemplary anionic surfactants comprise various sulfate, sulfonate, and carboxylate compounds. Exemplary amphoteric surfactants comprise amine oxides. Exemplary zwitterionic surfactants comprise derivatives of secondary and tertiary amines, such as betaine compounds. Exemplary cationic surfactants comprise alkoxylated amines. Exemplary nonionic surfactants comprise alcohol alkoxylates. In one embodiment, the nonionic surfactant comprises from about 0 to about 9% of C9-C11 alcohol alkoxylates. In a preferred embodiment, the nonionic surfactant comprises from about 0 to about 9% of C9-C11 alcohol ethoxylates. 
         [0027]    In one embodiment, solvent application is carried out using a mechanical scrubbing device. The mechanical scrubbing device may comprise a textile material, such as wool or cotton felt, onto which the solvent is directly applied. Then, the textile material, which may be in the form of a movable belt or roller, is brought into contact with the container and the image is effectively “scrubbed” from the outer surface of the container. During this scrubbing operation, at least some of the ink is transferred from the container to the scrubbing device. However, particles of ink may remain loosely adhered to the container as a result of surface tension interactions between the particles and the container. These particles, along with any solvent residues are removed in subsequent processing steps described below. 
         [0028]    Although not required, to aid in the ink removal, the container, and particularly the surface of the container bearing the image may be heated. In certain embodiments, the container is heated to a temperature of between about 100° to about 185° F., or between about 110° to about 175° F., or between about 130° to about 170° F. The heating can be accomplished by a variety of means. In one embodiment the heating involves directing heated air onto the outer surface of the container. 
         [0029]    Next, the solvent, and any ink residues, are rinsed from the surface of the container. Any rinsing process capable of removing the solvent and ink residues from the container can be used. For example, the rinsing step may employ application of water to the container surface by methods similar to those used to apply the solvent. Alternatively, the rinsing step may employ other methods than those used to apply solvent to the container, such as contacting the container with a water-laden sponge, or spraying water directly onto the container. 
         [0030]    Following the rinsing step, the containers can be dried by any number of means, such as application of heated air, buffing with a dry cloth or sponge, or a combination thereof. The containers may also be sanitized at this stage, such as through application of UV light, in order to kill bacteria present on the containers. 
         [0031]    The present invention may also be used to de-ink post-consumer synthetic resin articles. For example, synthetic resin material containers that have been used by consumers can be de-inked, reprinted, and recycled for further consumer use. In such embodiments, the interior or non-printed surfaces of the containers will need to be cleaned as a part of the overall recycling process. 
         [0032]    The following description illustrates an exemplary de-inking system according to one embodiment of the present invention. It is to be understood, however, that this embodiment is illustrative of the principles of the present invention and should not be taken as limiting the overall scope thereof. Turning first to  FIG. 1 , a de-inking apparatus  10  is shown comprising a rotatable container-handling device  12 . Device  12  comprises a rotatable hub  14  having a plurality of mandrels  16  disposed thereon. An alternate view of device  12  is depicted in  FIG. 2 . As explained further below, rotation of hub  14  serves to advance the container to be de-inked through a plurality of stations where the container is subjected to a particular operation. Other configurations to advance a synthetic resin material container through a plurality of stations are also within the scope of this invention, even though not depicted in the Figures. For example, in certain embodiments, apparatus  10  may be configured to advance a container through a plurality of stations arranged in a substantially linear manner, as opposed to the illustrated circular manner. 
         [0033]    Device  12  further comprises a rotatable disk  18  that is operably coupled to a motor  20 . Motor  20  and rotates disk  18  about a first axis (shown in  FIG. 1  as counter-clockwise in direction). Disk  18  provides motive force for causing each of mandrels  16  to rotate about a second axis disposed at approximately 90° (i.e., perpendicularly) from the first axis. Rotational force from disk  18  is transmitted to mandrels  16  by a friction material  22  such as a rubber material, particularly neoprene rubber. 
         [0034]    Returning now to  FIG. 1 , cups  24  are fed to a loading station  26  by a conveyor assembly  28 . Conveyor assembly  28  comprises three flighted screws  30  arranged in a triangular configuration. Note, one of screws  30  is disposed beneath the stack of cups  24  and is not visible in  FIG. 1 . To load a cup  24  onto a mandrel  16 , the screws  30  are advanced and a cup is ejected onto mandrel  16 . Mandrels  16  may be equipped with suction to secure cups  24  thereto as hub  14  rotates between a plurality of stations. In addition to supporting the interior surface of the cup, mandrel  16  also prevents the inside of cup  24  from coming into contact with the solvent and rinse fluids that will be used during the de-inking process. Thus, contamination of these surfaces due to the de-inking process is avoided, as is the necessity to cleanse the interior of the cups prior to reprinting. 
         [0035]    Once a cup  24  has been loaded onto a mandrel  16 , hub  14  rotates (in a clockwise manner as depicted in the  FIG. 1 ) to a solvent application station where solvent is applied to cup  24 .  FIG. 3  illustrates an exemplary solvent application station  32 . Solvent application station  32  comprises a scrubbing assembly  34  which includes a cleaning belt  36  entrained about a series of rollers  38 . One of rollers  38  is coupled to a motor (not shown) for powered rotation of belt  36 . Rollers  38  and belt  36  are attached to a carriage  40  which is slidably mounted on a linear bearing slide assembly  42 . Assembly  42  is affixed to a steel mounting base  44 . An air cylinder  46  is used to shift carriage  40  on slide assembly  42 . A perforated tube  4848  is used to apply solvent to belt  36  either by dripping or spraying. However, it is within the scope of the present invention for the solvent to be applied directly to container  24 . Belt  36  can be made from a textile material, and in certain embodiments, comprises cotton or wool. Solvent application station  32  may also comprise a heat source  50 , such as an infrared heat element or conduit for dispersing hot air. Although not required, it has been discovered that raising the temperature of the synthetic resin material assists with the ink removal process, particularly the ease and speed with which the ink is removed. Thus, heat source  50  may be used to raise the temperature of cup  24  as discussed previously. 
         [0036]    As illustrated in  FIG. 4 , scrubbing assembly  34  is moved into engagement with cup  24 . When hub  14  rotates a cup  24  to solvent application station  32  for de-inking, air cylinder  46  raises the carriage  40  placing belt  36  in contact with the spinning cup  24 . Thus, solvent, which has been applied to belt  36  by tube  48 , is applied onto cup  24  and belt  36  simultaneously scrubs ink from the cup. Periodically, belt  36  can be removed from carriage  40  for cleaning. 
         [0037]    After cup  24  has been scrubbed, air cylinder  46  lowers carriage  40  back to the configuration shown in  FIG. 3 . Cup  24  is now ready to be advanced to the next station. In certain embodiments, cup  24  is advanced to a second solvent application station  52 . This solvent application station is provided to ensure complete ink removal from the cups. However, it is understood that this additional station need not necessarily be included if a single solvent application station can adequately perform the de-inking operation. Solvent application station  52  can be configured similarly to solvent application station  32 , although one of skill in the art can appreciate alternate belt configurations should spacing be an issue. 
         [0038]    Following solvent application station  52 , hub  14  rotates so that cup  24  is delivered to a rinse station  54 . Exemplary rinse stations are illustrated in  FIGS. 5 and 6 . Turning first to  FIG. 5 , water or other rinsing fluid is supplied by a perforated tube  56  and applied to a belt  58  entrained about two rollers  60 , one of which is driven by a drive motor (not shown). Note, it is also within the scope of the present invention for the water to be directly applied to cup  24 . Rollers  60  may shiftable so that belt  58  can be brought into and out of contact with cup  24 . At rinse station  54 , at least a portion of the solvent and solid ink residues on cup  24  are removed. The belt  58  can comprise any water absorbent material, and may be identical to belt  36  used in solvent application station  32 . Alternatively, belt  58  can be replaced with a sponge material attached to a single roller  60 . An example of such an assembly is shown in  FIG. 7  and described further below. 
         [0039]    Turning now to  FIG. 6 , an alternate rinse station  62  is illustrated. Rinse station  62  may be configured similarly to solvent application station  32 , with the exception that heat source  50  is removed. Rinse station  62  is labeled with the same reference numerals as solvent application station  32  and operates in a similar manner except that a rinsing fluid, such as water, is dispensed from tube  48 . 
         [0040]    In operation, and as illustrated in  FIG. 1 , two rinse stations  54  and  62 , for example, may be employed. Although, it is within the scope of the present invention for only one rinse station to be employed, or that a single rinse station configuration ( 54  or  62 ) be employed. However, dual rinse stations can help ensure complete removal of solvent and ink residues from cup  24  as the belt from a single rinse station can become saturated with solvent and ink particles thus reducing the rinsing efficacy. 
         [0041]    After the solvent and ink residues are removed, hub  14  rotates so as to deliver cup  24  to a drying station  64 . An exemplary drying station  64  is illustrated in  FIG. 7 . Drying station  64  comprises an absorbent material, such as a sponge  66 , disposed on a shiftable roller  68 . Sponge  66  can be cylindrical in shape or frustoconical so as to more readily mate with cup  24 . After hub  14  rotates to deliver cup  24  to the drying station  64 , roller  68  shifts upward into contact with cup  24  so that sponge  66  can absorb water present on the surface of the cup. After a sufficient contact time, roller  68  is shifted downwardly and sponge  66  is brought out of contact with cup  24 , and hub  14  is again free to rotate cup  24  to the next station. Drying station  64  is also equipped with a bar  70  that comes into contact with sponge  66  when roller  68  is shifted downwardly. In this downward configuration, roller  68  continues rotation and sponge  66  impinges upon bar  70 , which operates to squeeze water from the sponge. By removing water from sponge  66  in this manner, the sponge&#39;s absorptive capacity is maintained and water can be efficiently removed from the surface of cup  24 . 
         [0042]    Next, hub  14  rotates so as to deliver cup  24  to a dry buff station  72 , an exemplary configuration of which is depicted in  FIG. 8 . Dry buff station  728  comprises a buffing material  74  disposed on a roller  76 . The buffing material generally comprises an absorptive material capable of removing any final water residues from the cup. In certain embodiments, the buffing material can be wool, cotton, or another textile material. As cup  24  enters dry buff station  72  and contacts buffing material  74 , any residual moisture remaining on the cup  24  is absorbed by the buffing material  74 . In certain embodiments, a heat source may supply heat to buffing material  74  and/or cup  24  to enhance final drying of the cup. In some embodiments, a UV light source (not shown) can be supplied as a part of station  72  so as to irradiate the de-inked surface of the cup  24  and kill germs or bacteria residing thereon. 
         [0043]    After being buffed, hub  14  rotates yet again and delivers the de-inked cup  24  to an unloading station  78  where the cup  24  is removed from mandrel  16 . A burst of positive pressure air from mandrel  16  can dislodge cujp  24  therefrom and place it into contact with a conveyor  80 , such as a belt-type conveyor. Conveyor  80  forms a stack of de-inked cups  24  that are ready to be re-printed. In certain embodiments, cups  24  need not be stacked and can be directly fed to a printing press.