TA! __ Printing Textile Fa rics with Xerography td/3 BY W. W. CARR. F. L. COOK, W. R. LANIGAN, M. E. SIKORSKI and W. C. TINCHER, Georgia Institute of Technology. Atlanta ver the past few years, the textile Background rapidly. Thus the time available for devel- 0 industry has moved toward quick oping the charged pattern is extremely response, just-in-time delivery and shorter Applications of Chemicals to short. Since much of the fabric to be process runs to facilitate frequent style Textiles Without the Use of Liquids printed contains cotton, the charge dissi- and color changes. Reduced process effi- The textile xerographic investigation was pation problem would have to be solved. ciency accompanies short runs unless part of a larger project (I), funded by the The other problem is related to the nature changeover downtime is small. Processes U.S. Department of Energy (DOE), in of the fabric surface. Developing the such as continuous carpet dyeing have which several techniques for applying charge image without the entrapment of been modified to minimize time required chemicals to textiles without the use of toner in uncharged regions of the fabric for changeover. However, current fabric liquids were investigated. The objective of would probably be difficult. Sincexerogra- printing systems do not lend themselves to the project was to develop techniques for phy is a highly developed technology for rapid changeover. reducing the energy consumed by the paper printing without these problems, it Rotary screen printing, currently the textileindustry in wet processing. Muchof was the method of choice. predominant method of fabric printing, the energy utilized in wet processes goes has several disadvantages. Color and pat- toward heating and evaporating water. Xerography tern changes require long process set up Energy conservation research has led to a time. Screen production is slow and expen- reduction in thequantity of water required Advantages/Disadvantages 11 sive. Screens have relatively short lives and in wet processing; however, liquids are still Xerography has several potential advan- require considerable storage space when used. Further reductions in energy con- tages for printing fabrics. One is informa- not being used. Thus a new technology for sumption are possible by the complete tion storage can be either optical or com- fabric printing is needed that will permit elimination of liquids. puterized, eliminating the need for large frequent style and color changes with storage space for screens. Since the system minimum downtime for changeover and New Technologies can be computerized, fast style and color will allow computer storage of design Fabric printing was one area selected for changeover are possible. Another is the information. Xerographic printing has the study in the DOE project. Technologies potential for producing color using three potential of meeting these requirements. eliminating water from fabric printing primaries. Theresolution needed for print- whilc having promise of relieving response ing apparel fabrics should be attainable time and information storage problems and image development can be achieved associated with screen printing were con- without the use of solvents. Pigments, sidered.Twomajorcandidates wereinkjet which are generally much less expensive printing and electrophotography. Al- ABSTRACT than dyes and offer better lightfastness though ink jet printing has promise, disad- and other properties, can be used for A three-phase investigation of the use of vantages are associated with it. The major coloration. Washing and drying following xerography for color printing of textiles one is that it is liquid based which elimi- printing is eliminated. has been conducted. Phase I studied the nated it as a candidate for the DOE While xerography has much promise feasibility of using xerography to project. Other disadvantages include: high for fabric printing, current technology has produce clear prints on textiles and to resolution needed for apparel is probably been developed for paper printing. Fabric identify textile toner candidates. Phase unattainable; insoluble dyes such as dis- II demonstrated continuous xerographic, printing has requirements beyond those single-color printing of polyester/cotton perse dyes and pigments are not compati- for paper printing. Xerographic paper sheeting fabric. Phase 111 involved scale ble with the technique; dyes used in the printing systems have been designed pri- up to continuous three-foot wide, process must have the proper textile char- marily for operating in the batch mode (a three-color, complex textile printing. acteristics and influence on rheology; and single sheet is normally printed) and for Textile color xerography was shown to the use of three primaries to produce color fairly narrow widths (usually 8%inches). be a feasible route to waterless, complex is probably not attainable. Fabric printing systems will need to print Printing of fabrics with plgment and Electrophotography (2) involves the much wider webs in a continuous mode. binders. formation of a latent image and trans- The toner requirements for paper printing forming it into a visible image or print. are also quite different from those for KEY TERMS Two types of electrophotography were textile applications. The binders in paper considered for fabric printing: direct im- toners normally consist of styrenejacry- Binders aging on the fabric and xerography. Direct late copolymers with poor adhesion to Colorfastness to Crocking imaging eliminates some of the steps of textile fibers and low drycleaning solvent Electrophotography xerography, but presents two problems not fastness. Printing associated with it. Preliminary tests indi- Triboelectric Attraction Basic Steps Xerography cated that cotton-containing fabrics, un- der standard conditions of 65% relative The basic steps of xerography are illus- humidity and 20C, dissipate charge very trated in Fig. 1. Metal that is electrically May 1991 cm 33 ‘ Color Xerography PC develops the image. The fourth step is Red Toner No. 22-144 (Haloid Xerox the transferring of the developed image to Inc.) and Black Toner Type 10 (Xerox the substrate being printed. The substrate Corp.). These two toners were used to is brought into contact with the PC. The produce prints on fabric which were sub- grounded is coated with a layer of photo- back of the substrate is strongly charged, jected to textile tests. conductor (PC). The first step involves usually by using a corona, so that the toner The carrier components of the two charging the surface of the PC which will transfers to the surface of the substrate. tonerlcarrier systems were isolated by hold a charge in the dark. The charging is The fifth step is fixing the toner to the solvent removal of paper toners. Attempts usually accomplished by passing a corona substrate. The temperature of the toner is were made to make textile developer over the PC surface. The second step raised, causing the resin binder to flow. systems by mixihg the carrier with several involves producing a latent electrostatic Pressure is often used as well as a heat resins and disperse dyes, listed in Table I. image by exposing the PC to light. Since source. Following fixation, the surface of Sublimable disperse dyes were included in light causes the PC to become conductive, the PC is cleaned and the process is the materials considered for toners since charge is drained from the surface in repeated. they had the potential of being used regions that are exposed. This step is without binder for sublimation printing of usually accomplished by reflecting light Phase I 100% polyester fabrics. from an original or passing light through a Objective Tests were performed on two other transparency onto the PC surface. A laser The objectives of Phase I were to investi- paper toners. One was a Kodak magenta driven by a computer can also be used to gate on a bench scale the technical feasi- toner and the other a blue toner provided produce the image. The third step is bility of using xerography to print woven by Hunt Chemical Co. developing the latent image by placing fabrics and to identify binder materials for Research was conducted to identify toner (pigment plus binder) in regions toners meeting textile requirements. commercially available resins suitable for where electrostatic charge is located. De- use as the binder component of developer velopment involves the use of a developer Apparatus systems for xerographic fabric printing. system composed of carrier and toner. The A Haloid single-page batch copier with Over 60 commercially available resins as carrier beads, which usually consist of selenium photoconductive plate was used well as melt blended combinations were metal shot coated with a polymer film, are for printing on 50/50 polyester/cotton screened. The physical/textile properties normally much larger in size than the sheeting fabric (Westpoint Pepperell) and of the resins were compared with a stan- toner particles. The triboelectric charac- for screening potential textile toners. dard screen printing resin currently used teristics of the toner and carrier are such by the textile industry, Hycar 26120. The that when they are thoroughly mixed, they Materials standard is a complex acrylic polymer become oppositely charged and attract Initial tests were performed using paper- produced by BF Goodrich Co. each other. The carriEr is oppositely toners; however, since paper toners have charged from the PC surface. When car- not been designed to meet textile require- Tests rier which holds toner on its surface is ments, screening of binder materials with Wet and dry crockfastness tests c were brought intocontact with the PC, the toner potential of meeting textile requirements performed using AATCC Test Method is attracted to charged regions of the PC. was begun. Two toner/carrier systems 8-1972. Samples produced by the Haloid Transfer of toner to these regions on the designed for paper xerography were used: batch system and by sprinkling powder on polyester/cotton sheeting and curing at L 150C for one to two minutes were tested.