A novel composite board of mineral wool, perlite, and cellulosic newsprint fibers for use primarily as a ceiling tile is disclosed. The board displays virtually no sag (less than 200 mils) when exposed to high temperature and high humidity while displaying quite acceptable strength. The board is manufactured...http://www.google.es/patents/US5134179?utm_source=gb-gplus-sharePatente US5134179 - Composite fiberboard and process of manufacture
