Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
162 55, D21L 502
The toners used for printing in the electrophotography processes such as xerography or laser printing are removed from copy paper. In the process, the paper is pulped to form an aqueous slurry. The toner is removed from the paper with a dual system of a collector and a collecting chemical.
The best collectors have solubility parameters similar to the toners so that the softened toner is slightly soluble in the collector. These include polystyrene, polyvinyl chloride and polyacrylates, e.g., polymethyl methacrylates. Other collectors which are operable but less satisfactory are polyurethane and polypropylene. The collector is in the form of prills, beads or sheets. The specific collector will depend upon the specific chemicals in the toner.
There are a number of requirements for the collecting chemical. It should be substantially insoluble in water. It should have a melting point that is at or below the approximate softening point of the toner or collector. It should be a saturated aliphatic primary alcohol, a mixture of such alcohols, an unsaturated aliphatic primary alcohol, a mixture of such unsaturated alcohols, a saturated secondary alcohol, a saturated aliphatic primary hydrocarbon, a mixture of such hydrocarbons, or a mixture of hydrocarbons and alcohols.
The process is operable at or above the melting point of the collecting chemical, and at a temperature at which the toner is softened, generally 38.degree.-75.degree. C.
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Smith William F.
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