Recently, chemically prepared toners (CPTs) have been finding their way into an increasing number of electrophotographic printers. Although all these printers claim to utilize CPT as marking particles, the toner composition and manufacturing method used can be very different from each other. The production of conventional melt pulverized toners (MPTs) essentially consists of melt compounding and a pulverization operation of toner ingredients using standard equipment and processes that are similar for most suppliers. Different CPT manufacturers, on the other hand, produce the chemically prepared toners via entirely different approaches. The chemical methods of manufacturing include: suspension polymerization, emulsion aggregation, solvent dispersion, and the like. Each method used in the production of chemically prepared toner has its associated limitations and advantages. Use of polyester as the toner polymer is often desired because of the inherent advantages offered by these resins over styrene-acrylate copolymers. Polyester binders provide a unique melt flow and mechanical toughness that is highly desirable in high-speed digital printing applications. These resins are also more suited for digital printing because of their charging behavior. The CPT process developed at Eastman Kodak Company offers the flexibility of using any soluble polymer as a toner resin or the use of monomers that are suitable for additional polymerization for making linear or crosslinked toners. With this solvent-based process, it is possible to prepare chemical toners that are based on polyester binders, which are uniquely desired in production printing. This manufacturing process is suitable for making chemically prepared toners that have the narrowest particle size distribution in the industry. Shape control is very extensive using this approach, and particle shapes ranging from completely spherical to raisin-like can be prepared easily. The degree of irregularity can be controlled to produce particles that provide optimum performance in the machine. There is a considerable amount of flexibility offered by this solvent-based process. Toner ingredients that are affected or changed by elevated temperatures can be easily incorporated into toners because this toner manufacturing process does not require any heating. This process can be used to tailor-make toners that simplify the equipment design and electrophotographic process to provide a consistent performance in producing high image quality and lower costs for printing.
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