Paper making and fiber liberation – Processes and products – With coating after drying
Reexamination Certificate
1997-06-20
2001-07-03
Silverman, Stanley S. (Department: 1731)
Paper making and fiber liberation
Processes and products
With coating after drying
C162S136000, C162S164100, C162S181100, C162S203000
Reexamination Certificate
active
06254725
ABSTRACT:
BACKGROUND OF THE INVENTION
Heretofore, it has been known to make lightweight, high bulk paper. For example, see U.S. Pat. No. 5,283,129, the teachings of which are incorporated herein by reference. However, that patent achieves high bulk by using coating that tends to be bulkier than conventional coating.
Other prior art attempts have been used to make high bulk coated paper by utilizing lower than conventional supercalendering nip pressures. However, these papers generally had low gloss, usually well below a 75° TAPPI gloss of 40, namely about 35. Consolidated Papers, Inc., the assignee of the present invention, had commercially sold similarly made lower gloss, high bulk papers as early as 1993. Such lower gloss paper is not acceptable for many publication purposes, such as magazines where lightweight, high bulk paper, with high gloss and good print gloss has been desired and sought for years due to ever increasing mailing rates.
BRIEF SUMMARY OF THE INVENTION
A method and apparatus is disclosed for making a high bulk, coated paper of a unique structure with the coating forming a lower portion of the total caliper and the paper base forming a higher portion of the total caliper than conventionally made coated paper of the same weight. This approach provides a bulkier, coated paper. The process includes the steps of using furnish with a high percentage, say over 50%, and preferably in a range of 55 to 75%, with a target of 60 to 65%, of mechanical pulp, or other similar pulps described herein, applying that furnish to two or twin wire papermachines, preferably with a gap former, coating the paper with a coating containing a plastic pigment in a concentration of 4 or more parts, and preferably 7 or more parts per 100 parts of coating pigment, and calendering the coated paper at a loading less than conventional supercalender loading. The use of mechanical pulp in the base sheet and a high content of plastic pigment in the coating gives a good surface finish that is easily calendered, either by lower pounds per linear inch supercalendering or hot-soft calendering to a high gloss acceptable to most publishers interested in lightweight coated paper for magazines or other similar uses. Preferably, the finished coated paper will have a 75° TAPPI gloss of 40 or above. The method or process and apparatus of the present invention can also be used to make other than lightweight grades of coated paper such as ultra lightweight coated paper. While the invention is directed toward coated paper for offset printing, it can be utilized for other coated papers for gravure, flexographic or letterpress printing.
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Berger Bernard J.
Lau Ralph L.
Munce Martin E.
Consolidated Papers Inc.
Halpern Mark
Pyle & Piontek
Silverman Stanley S.
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