| abstract |
A "cold-processed" thermoset plastic pencil lead is produced by extruding a composition formed by blending a mixture of a marking material, a phenolic novolac resin, a hardening agent, a plasticizer, and a lubricant. Blending, billeting, and extruding operations are performed at material temperatures that, in general, do not exceed about 200 DEG F. The extrudate is cured at higher temperatures of, for example, 260 DEG F. to 325 DEG F. |