Eraser and process for its manufacture
AssigneeJ. S. Staedtler
InventorWerner Handl
Life of this patent
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Abstract
An eraser based on polyvinyl chloride having particles of a crosslinked polymeric natural or synthetic rubber embedded in the polyvinyl chloride structure. Such erasers have high strength and good aging resistance. Additionally, conventional softeners in the eraser do not undergo significant migration and consequently, the eraser does not smudge. A process for manufacturing the eraser is also disclosed.
Claims2
A method for the manufacture of an eraser based on polyvinyl chloride or polyvinyl chloride copolymer comprising preparing a polyvinyl chloride plastisol or polyvinyl chloride-copolymer plastisol in connection with unvulcanized synthetic or natural rubber, wherein first a pourable or flowable homogeneous substance is produced from mixing the polyvinyl chloride plastisol or polyvinyl chloride-copolymer plastisol and the rubber, and this substance is then fed into an extruder which has varying temperature ranges which increase from approximately 90.degree. to 135.degree. C. and from whose nozzle the cured or vulcanized eraser strand emerges and is cut into usable eraser size pieces after passing through a cooling zone.
A method for the manufacture of an eraser based on polyvinyl chloride or polyvinyl chloride copolymer comprising preparing a polyvinyl chloride plastisol or polyvinyl chloride copolymer plastisol, mixing an unvulcanized rubber selected from the group consisting of natural rubber, butadiene styrene or butadiene acrylonitrile, in with said plastisol to produce a dry, flowable mixture, extruding this mixture at vulcanizing temperatures in an extruder whose temperature range increases toward the exit as follows:
- 90.degree./110.degree./120.degree./130.degree. and 135.degree. C., and cutting into usable eraser size pieces after passing through a cooling zone.
Dependencies are inferred from the claim text.