Acoustic ceiling tiles made with paper processing waste

An acoustic panel comprising:

• from 0 to about 75 wt % mineral wool;
• inorganic materials selected from the group consisting of gypsum, clay, calcium carbonate and mixtures thereof, wherein the acoustic panel comprises from more than 0 to about 30 wt % gypsum;
• from more than 0 to about 15 wt % binder selected from the group consisting of starch, a combination of starch and cellulosic fibers, latex, kraft paper gel and mixtures thereof;
• from about 25 to about 70 wt % perlite;
• from more than 0 to 40 wt % paper sludge obtained from pulp and paper processing waste, said paper sludge including about 18 to about 24 wt % cellulosic fiber and also including inorganic material selected from the group consisting of clay, calcium carbonate and mixtures thereof, and wherein about 20 wt % to about 80 wt % of the inorganic materials in the acoustic panel are provided by the paper sludge.

A process for manufacturing acoustic panels in a water-felting process, the process comprising:

• forming an aqueous slurry comprising
• expanded perlite,
• inorganic material selected from the group consisting of calcium sulfate, calcium carbonate, clay and mixtures thereof,
• cellulosic fibers, and
• binder selected from the group consisting of starch, a combination of starch and cellulosic fibers, latex, kraft paper gel and mixtures thereof,
• wherein about 25 wt % to about 100 wt % of the cellulosic fiber and about 20 wt % to about 80 wt % of the inorganic material are provided by paper sludge derived from pulp and paper processing waste, said paper sludge including cellulosic fiber and inorganic material selected from the group consisting of clay, calcium carbonate and mixtures thereof;
• continuously flowing the slurry onto a moving foraminous support wire to form a cake;
• dewatering the cake to form a base mat such that the cake has a drain time of less than 20 seconds;
• and
• drying the base mat to produce acoustical tile.