Westvaco Corporation

Hiawatha P Watkins

Bryan J Ortman

Hans W Maurer

Suzanne S Fenton

Douglas W Donigian

A paper rawstock web is wet densified on a papermachine at a moisture content greater than about 20% and less than about 50%, and preferably from about 25-35%, in a calender device at nip pressures greater than about 3000 psi, and preferably within the range of from about 3000-6000 psi, to provide fiber springback resistance and irreversibly smooth surfaces which are substantially resistant to loss of smoothness upon rewetting, as for example in a subsequent surface sizing or coating process. Wet densification according to the present invention produces a web having greater density and increased internal bond strength, as compared with webs treated by conventionally known methods, to achieve the irreversibly smooth surfaces.

Method for providing enhanced smoothness for a paper web

A tandem calender is provided at the output end of a paper machine which includes two single stack nips in-line. The first nip is formed by a pair of steel rolls which are lightly loaded and the second nip is formed by a steel roll and a plastic covered roll which is loaded 2-10 times greater than the first nip.

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Columbia, MD, United States of America

Hiawatha P Watkins