(57) A neutral or alkaline paper having highly uniform tone, higher bursting point and
greater opacity is described. The manufacturing process consists primarily in neutralizing
to a pH of 7 or more and acid mixture of fibers, sizing agents and aluminium sulphate
with alkaline-earth metal oxides or hydroxides and their derivates. The mixture so
neutralized allows the use of calcium carbonate as a filler in the stock, resulting
in greater ingredient retention and a lesser amount of fines in the water, this residual
water being a clear water that can be recycled. The substitution of clays by calcium
carbonate reduces or eliminates machinery wear. Implementation of the process does
not require using additional, new or different manufacturing equipment while it implies
an immediate reduction in costs.
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