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History of Printing Toner
Toner is a powder used in laser printers and photocopiers to form the printed text and images on the paper. In its early form it was simply carbon powder. Then, to improve the quality of the printout, the carbon was melt-mixed with a polymer. Toner particles are melted by the heat of the fuser, and bind to the paper.
In earlier machines, this low-cost carbon toner was poured by the user from a bottle into a reservoir in the machine. Current machines feed directly from a sealed cartridge, which is usually a proprietary design. Although manufacturers go to great lengths to frustrate the process, empty cartridges are sometimes refilled by third-party vendors.
Modern toners intended for use in color copiers and printers come in cyan, magenta, yellow and black (CMYK).
Composition, size and manufacture
The specific polymer used varies by manufacturer but can be a styrene acrylate copolymer, a polyester resin, a styrene butadiene copolymer, or a few other special polymers. Toner formulations vary from manufacturer to manufacturer and even from machine to machine. Typically formulation, granule size and melting point vary the most.
Originally, the particle size of toner averaged 14-16 micrometres or greater. To improve image resolution, particle size was reduced, eventually reaching about 8-10 micrometres for 600 dots per inch resolution. Further reductions in particle size producing further improvements in resolution are being developed through the application of new technologies such as Emulsion-Aggregation. Toner manufacturers maintain a quality control standard for particle size distribution in order to produce a powder suitable for use in their printers.
Toner has traditionally been made by compounding the ingredients and creating a slab which was broken or pelletized, then turned into a fine powder with a controlled particle size range by air jet milling. This process results in toner granules with varying sizes and aspherical shapes. To get a finer print, some companies are using a chemical process to grow toner particles from molecular reagents. This results in more uniform size and shapes of toner particles. The smaller, uniform shapes permit more accurate color reproduction and more efficient toner use.
Toner can be washed off skin and garments with cold water. Hot or warm water softens the toner, causing it to bond in place. Toner fused to skin eventually wears off, or can be partially removed using an abrasive hand cleaner. Toner fused to clothing usually cannot be removed.
Toner particles have electrostatic properties by design and can develop static-electric charges when they rub against other particles, objects, or the interiors of transport systems and vacuum cleaner hoses. Because of this and the small particle size, toner should not be vacuumed with a conventional home vacuum cleaner. Static discharge from charged toner particles can ignite dust in the vacuum cleaner bag or create a small explosion if sufficient toner is airborne. This may damage the vacuum cleaner or start a fire. Toner particles are so fine that they are poorly filtered by household vacuum cleaner filter bags and can blow through the vacuum motor or into the room.
If toner spills into the laser printer, a special type of vacuum cleaner with an electrically conductive hose and a high efficiency (HEPA) filter may be needed for effective cleaning. These are called Electrostatic discharge-safe (ESD-safe) or toner vacuums. Similar HEPA-filter equipped vacuums should be used for clean-up of larger toner spills.
Unfused toner is easily cleaned from most water-washable clothing. Because toner is a wax or plastic powder with a low melting temperature, it must be kept cold while cleaning. The washing machine should be filled with cold water before adding the garment. Two complete wash cycles improves the chances of success. The first may use hand wash dish detergent, the second may use regular laundry detergent. Residual toner floating in the rinse water of the first cycle will remain in the garment and may cause permanent graying. A clothes dryer or iron should not be used until all toner has been removed.
As a fine powder, toner can remain suspended in the air for some period, and is considered to have health effects comparable to inert dust. It can be an irritant to people with respiratory conditions such as asthma or bronchitis. Following studies on bacteria in the 1970s that raised concerns about health effects resulting from pyrrole, a contaminant created during manufacture of the carbon black used in black toner, manufacturing processes were changed to eliminate pyrol from the finished product.
According to recent research, some laser printers emit submicrometer particles which have been associated in other environmental studies with respiratory diseases.
An unpublished study at the University of Rostock in Germany is reported to have found that the microscopic particles in toners are carcinogenic, similar to asbestos. Several technicians who had been working with printers and copiers on a daily basis were observed for several years. They showed increased lung problems.
Repackaging - Toner Refill
Several toner manufacturers offer toner in wholesale quantities. Typically, bulk loose toner is sold in barrels or 10 kg (22-pound) bags. Remanufacturers use the bulk toners to refill used empty toner cartridges. Some also replace worn parts in more complex cartridges.
Remanufactured toner cartridges are also available to the average consumer. Remanufactured cartridges are generally only available from on-line shops, however some electronic stores have begun to stock remanufactured toner cartridges. Sold at a lower cost than original toner cartridges, these cartridges have been recycled and refilled.
Recycling of pre-consumer waste toner is practiced by most manufacturers. Classifying toner to the desired size distribution produces off-size rejects, but these become valuable feedstocks for the compounding operation, and are recycled this way. Post-consumer waste toner appears primarily in the cleaning operation of the photo-printing machine. In early printers, as much as 20 to 25% of feed toner would wind up in the cleaner sump and be discarded as waste. Improved printer efficiencies have reduced this waste stream to lower levels. Some printer designs have attempted to divert this waste toner back into the virgin toner reservoir for direct reuse in the printer; these attempts have met with mixed success. Some consideration and fewer industry attempts have been made to reclaim waste toner by cleaning it and "remanufacturing" it.
Most toner goes to printed pages, a large fraction of which are ultimately recycled in paper recovery and recycling operations. Removal of toner from the pulp is not easy, and toner formulations to ease this step have been reported. Hydrolyzable, water-soluble, and caustic-soluble toner resins have been reported, but do not appear to enjoy widespread application. Recovery of waste toner with other inks and resins from paper recycling plants occurs as sludge, a low-value off-product.
In the UK, large compatible ink cartridge manufacturers like Jet Tec have implemented recycling toner recycling programmes in order to receive back empty cartridges for refilling of HP, Lexmark, Dell, etc cartridges, as no compatible version is readily available.