Appeal No. 1998-2217
Application No. 08/644,555
Discussion
The claimed invention relates to a method for using the
“wet-pressing” method to produce high bulk tissue. According
to appellants, there are two distinct drawbacks in using the
"wet-pressing" method to produce tissue products
(Specification, pp. 1-2).
First, pressing the tissue web while wet densifies
the web significantly. As the web is dried, the
dried sheet retains this high density (low bulk)
until it is creped. Creping is necessary to attempt
to undo what the wet-pressing has done to the sheet.
. . .
A second drawback, shared by conventional wet-
pressing and through-air-drying processes is the
high energy costs necessary to dry the web from a
consistency of about 35 percent to a final dryness
of about 95 percent. This second drawback has
recently been addressed in the manufacture of high
density paper products by the advent of the high
intensity extended nip press. This device employs
an extended nip length and heat to more efficiently
dewater the wet web up to exit consistencies of
about 60 percent. Such devices have been
successfully used for making paperboard, but have
not been used to make low density paper products
such as tissues because the high pressures and
longer dwell times in the extended nip press serve
to further densify the sheet beyond that experienced
by conventional tissue wet-pressing methods. This
increase in density is detrimental to the quality of
the resulting tissue products because creping cannot
completely overcome the added increase in sheet
density.
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