Paper pencil lead

Abstract

The present invention concerns an extrudable, unexpanded paper pencil lead, comprising, by weight relative to the total weight of the lead; between 40 and 60%, and advantageously between 44 and 50%, of graphite; between 15 and 40%, and advantageously between 20 and 35%, of a polyolefin; between 5 and 15%, and advantageously between 6 and 10%, of a colorless mineral filler; between 5 and 20%, and advantageously between 5 and 15%, of carbon black coated with or mixed with a polyolefin wax or a polyolefin; between 0 and 16%, and advantageously between 5 and 15%, of an additive. It further concerns the paper pencil comprising a lead according to the invention.

Description

technical field [0001] The present invention relates to an extrudable polymer-based lead for a paper pencil having improved erasability. Background technique [0002] Polymer-based refills for paper pencils are known to those skilled in the art. [0003] In particular, patent application US 2011 / 0118383 describes such a cartridge. [0004] However, this refill must contain palm oil in order to improve its manufacturing method by extrusion. In addition, this oil makes it possible to improve the optical density of marks left on paper with a paper pencil. However, this has the opposite effect on the erasing efficiency of the marking: due to the use of this fatty substance, the carbon black present in the lead penetrates deeply into the paper and is difficult to erase. In addition, there is a risk of embrittlement of the refill since palm oil reduces its mechanical properties. [0005] To improve erasure, the carbon black content of the lead of a paper pencil can be reduced,...

AI Technical Summary

Problems solved by technology

However, it is not a pencil lead as it is not intended to be used with or inserted into a sheath

Additionally, the carbon black used was not premixed with the polyolefin wax or polyolefin prior to addition to the composition, potentially causing erasability issues