Shaped plastic abrasive elements - cong. urea-formaldehyde, abrasive and hardener

摘要

Shaped plastic abrasive element comprises a mixt. of a urea-formaldehyde resin, an abrasive agent and a hardener. Pref. the mixt. contains 40-70 wt. % (esp. 55-65 wt. %) urea-HCHO resin, 30-60 wt. % (esp. 20-35 wt. %) abrasive agent and 4-8 wt. %. (esp. 5.5-6 wt.%) hardener. The abrasive agent may be kieselguhr, ground quartz alumina, silicon-carbide, or a mixt. of such abrasives, and may be in granulate form. The mixt. pref. also contains 5-15 wt. % of urea, which may be in powder or crystalline form. The hardener is pref. present in amt. of 1/10 of the wt. of the urea-HCHO resin. The use of urea-formaldehyde resin as carrier avoids the disadvantage of foam-formation previously obtd. with polyester resins, and moreover not lead to the same difficult pollution problems as polyesters media.