LIMITING ORIFICE DRYING OF CELLULOSIC FIBROUS STRUCTURES, APPARATUS THEREFOR, AND CELLULOSIC FIBROUS STRUCTURES PRODUCED THEREBY

摘要

A method and apparatus for drying of a cellulosic fibrous structure having const ant basis weight and/or density or multiple regions varying in basis weight and/or density. Such a cellulosic fibrous struct ure may have a nonuniform moisture distribution prior to drying by the disclosed method and apparatus. An equally or more unifor m moisture distribution is achieved by providing a micropore medium in the air flow path which has a greater flow resistance than the interstices between the fibers in the cellulosic fibrous structure web. The micropore medium is the limiting orifice i n the air flow used in the drying process. The micropore medium may be executed in a laminate of plural laminae, each of succes sively increasing or decreasing pore size. This arrangement provides the advantage that minimal sagging or deformation of each l amina into the next coarser lamina occurs and lateral air flow between the micropore medium and the cellulosic fibrous structu re is reduced. The micropore medium may be disposed either upstream or downstream in the air flow path of the cellulosic fi brous structure to be through-air dried.