Appeal No. 1997-4290
Application No. 08/218,647
The chelation stage is followed by bleaching with a peroxide containing compound,
followed by bleaching with ozone and followed by bleaching with peroxide
containing compound. (p. 2, l. 58 to p. 3, l. 7, and p. 3, ll. 52 to 54). Andersson
‘590 discloses the viscosity and brightness of the pulp is improved if the ozone
bleaching is preceded by bleaching with a peroxide containing compound. (p. 3, ll.
7 to 9). Andersson ‘590 discloses washing can occur before and after the respective
stages. Andersson ‘590 discloses the spent liquor and washing water can be
recycled. (p. 3, ll. 22 to 27). Andersson ‘590 discloses the hydrogen peroxide can
be used in amounts ranging from 2 to 50 kg/ton of dry pulp, preferably from 3 to 35
kg/ton of dry pulp. (p. 3, ll. 46 to 54). Example 3 describes a process which
includes chelation treatment stage, a first peroxide treatment stage, an ozone
treatment stage and a second peroxide treatment stage. Example 3 differs from the
invention of claim 18 in that the first peroxide treatment stage contains more
peroxide than the second peroxide treatment stage.
Lachenal is directed to a process of bleaching mechanical wood pulp.
Mechanical wood pulp is described as “high yield wood pulps, generally exceeding
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