| 摘要 |
<p>Ceramic-free calcined pencil leads disclosed contain graphite, binder and opt. additives. Binders consist of addn. cpds. of (1) polyethylene oxide., pref. having mol. wt. 100000-5,000,000, with (2), alginate salts, cellulose glycolate salts, lignin sulphonic acid, lignin sulphonates, novolacs, phenol-HCHO resins, phenol-HCHO-urea resins, phenol resols, or their mixts.. Leads are esp. fine leads, for writing. Hardness and elasticity of end-prod. can be predetermined. Binders retain water and give it up gradually. Lead blanks have a uniform pore structure. Leads are not distorted. Dia. is unchanged.</p> |
