Patent ID: 6096168
Filing Date: 2000-08-01
Classification: B31F,D21F,D21G,D21H

Abstract:
An improved process for production of a creped paper sheet suitable for use as a bathroom tissue, towel, napkin, and facial tissue having a basis weight of about 7 to 40 pounds for each 3000 square foot ream and having a specific caliper from about 2 to 7 mils per 8 sheets per pound per 3000 square foot ream comprising the steps of:forming a nascent cellulosic web on a foraminous surface;adhering said nascent cellulosic web to the surface of a Yankee dryer;drying the nascent cellulosic web while in contact with the Yankee dryer to reduce the moisture content of the cellulosic web; and creping the cellulosic web from the Yankee dryer;wherein the improvement comprises:(i) providing an undulatory creping member disposed to crepe said dried cellulosic web from said Yankee dryer,said undulatory creping member comprising:an elongated blade adapted to be engagable against, and span the width of, said Yankee dryer, said blade having:a rake surface defined thereupon, extending generally outwardly from said Yankee when said blade is engaged against said Yankee and extending across substantially the width of said Yankee,a relief surface defined thereupon generally adjacent to the portion of said Yankee dryer from which said dried cellulosic web has been creped when said blade is engaged against said Yankee and extending across substantially the width of said Yankee,the intersection between said rake surface and said relief surface defining a serrulated engagement surface formed along the length of an elongated edge thereof, said serrulated engagement surface being adaptable to be engaged against the surface of said Yankee drying cylinder in surface-to-surface contact, said serrulated engagement surface constituting a spaced plurality of nearly planar crescent-shaped bands of width "".delta."", depth "".lambda."" and span "".sigma."" interspersed with, and inter-connected by, a plurality of substantially co-linear rectilinear elongate regions of width "".epsilon."" and length ""l"", the initial width "".epsilon."" of the substantially rectilinear elongate regions being substantially less than the initial width "".delta."" of the nearly planar crescent-shaped bands of the serrulated engagement surface;said relief surface being configured so as to form a highly relieved foot contiguous to each nearly planar crescent-shaped band of the serrulated engagement surface;the length ""l"" of each of said plurality of substantially co-linear rectilinear elongate regions being between about 0.002 inch and 0.084 inch and the span "".sigma."" of each of said plurality of nearly planar crescent-shaped bands being between about 0.01 inch and 0.095 inch, the depth "".lambda."" of each of said plurality of nearly planar crescent-shaped bands being between about 0.0080 inch and 0.0500 inch; and controlling the creping geometry such that:(a) the resulting web exhibits from about 10 to about 150 crepe bars per inch, said crepe bars extending transversely in the cross machine direction and (b) said sheet exhibits undulations extending longitudinally in the machine direction, the number of longitudinally extending undulations per inch being from about 10 to about 50 and wherein the nascent web is subjected to overall compaction while the percent solids is less than fifty percent by weight.