Dimensionally stable filter plate free from asbestos - based on magnesia cement, cellulose fibre, wood filler and inorganic filler

摘要

Filter plate contains 42-70 wt.% magnesia cement (I) with a MgO:MgCl2 wt. ratio of 2-4:1 (2.5-3.6:1), 8-36 (20-30)% long- fibre cellulose (II), 4-20 (6-12) % finely divided wood filler (III) (wood chips and/or saw dust with a max. particle length of under 12 mm) and 0.5-12 (2-10)% finely-divided asbestos-free inorganic filler (s) (IV) with a bulk density of max. 0.3 esp. kieselguhr (IVA) and/or pumice powder (IVB). The wt. ratio of MgO:organic filler is 1:1-1.8 (1:1.1-1.5). The filter plate can be made easily and economically and has good dimensional stability and filtering properties. It is useful in the food and drink and chemical industries. Pref. the filter plate also contains 2-5% water glass. Pt of (II) can be replaced by an equa. wt. of long-fibre vegetable material. The plate has a density of 0.5-0.8 (0.55-0.75) if hardened under pressure or 0.70-0.925 if hardened without applying pressure.