# US 4,393,022 A · Eraser and process for its manufacture

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 4,393,022 A
- Document ID: US4393022A
- Status: Granted
- Kind: A
- Application number: 06/318,923
- Filed: 1981-11-06
- Granted: 1983-07-12
- Earliest claimed: 1978-08-25
- Assignees: J. S. Staedtler
- Inventors: Werner Handl
- Web page: https://patentgrep.com/patent/US4393022A

## CPC

- C08L 21/00: Compositions of unspecified rubbers
- B43L 19/0025: {Eraser or rubber material, e.g. comprising hard particles}
- C08L 7/00: Compositions of natural rubber
- C08L 9/02: Copolymers with acrylonitrile
- C08L 9/06: Copolymers with styrene
- C08L 27/06: Homopolymers or copolymers of vinyl chloride
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)
- B43L: ARTICLES FOR WRITING OR DRAWING UPON; {WRITING OR DRAWING AIDS;} ACCESSORIES FOR WRITING OR DRAWING (workshop equipment for marking-out work B25H7/00; teaching hand-writing or drawing G09B11/00)

## 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.

## Claims

### Claim 1

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.

### Claim 2

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.