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US 4,154,899 AGranted
Production of porous, smooth, coated paper using high solids water-based coating compositions in blade coating apparatus
AssigneePotlatch Forests, Inc.
InventorsRobert V. Hershey, Gerald M. Hein
Life of this patent
Estimating the term…
Abstract
The process of producing a porous, smooth, easy finishing coated paper utilizing high solids water-based coating compositions (e.g. 68-73% solids) having certain rheological and viscosity characteristics in blade coating apparatus on paper webs moving at speeds above 500 feet per minute (e.g. moving at 1500 to 3500 feet per minute). The coating compositions are substantially free of protein adhesives and contain clay as a coating pigment.
Claims19
A process for coating paper which comprises:
- (a) introducing into a blade coating station of a blade-coating apparatus, an aqueous coating composition with a solids content within the range of 67-73 weight-%, a Brookfield viscosity of 1000 to 30,000 centipoise at 122.degree. F., and a rheology within the maximum and minimum rheologies shown in the drawing, said coating composition consisting essentially of:
- (1) paper coating pigment material comprising at least one-third by weight of clay particles, at least 80% by weight of the remaining two-thirds of said pigment material comprising pigment particles smaller than 2 microns equivalent spherical diameter as determined by settling techniques, at least 90% by weight of said pigment material being selected from the group of pigments consisting of clay, calcium carbonate, titanium dioxide, hydrated alumina, barium sulphate, ground limestone, and mixtures thereof;
- and
- (2) from 5 to 30 parts by weight of water soluble or water dispersible, non-protein adhesive per 100 parts by weight of said pigment material, all on a dry basis;
- (b) maintaining said aqueous coating composition at said blade coating station at or above the minimum rheology shown in the drawing and at a solids level within the said range of 67-73 weight-% while passing a paper web at a speed of at least 500 feet per minute past said blade coating station and applying said aqueous coating composition to said moving web at said blade coating station;
- the rheology maintained at said blade coating station being selected to maximize porosity and blister resistance properties of the resulting coated paper without producing blade scratches on said coated paper;
- and
- (c) recovering a coated paper web with porosity and blister resistance properties superior to a coated web coated in the same manner but with a relatively lower rheology and relatively lower solids content, as compared to the rheology and solids content maintained at said blade coating station.
5 more elements
A process for coating paper which comprises:
- (a) preparing a plurality of aqueous coating compositions differing from one another in solids content, each coating composition having a solids content within the range of 67-73 weight-% and a Brookfield viscosity of 1,000 to 30,000 centipoise at 122.degree. F.;
- each coating composition consisting essentially of:
- (1) paper coating pigment material comprising at least one-third by weight of clay particles, at least 80% by weight of the remaining two-thirds of said pigment material comprising pigment particles smaller than 2 microns equivalent spherical diameter as determined by settling techniques, at least 90% by weight of said pigment material being selected from the group of pigments consisting of clay, calcium carbonate, titanium dioxide, hydrated alumina, barium sulphate, ground limestone, and mixtures thereof;
- and
- (2) from 5 to 30 parts by weight of water soluble or water dispersible, non-protein adhesive per 100 parts by weight of said pigment material, all on a dry basis;
- (b) selecting a said aqueous coating composition from among said plurality of coating compositions in accordance with the maximum and minimum rheologies shown in the drawing to maximize porosity and blister resistance properties in the coated paper without producing blade scratches during blade coating;
- (c) introducing essentially the selected aqueous coating composition into a blade coating station of a blade coating apparatus;
- (d) maintaining the said selected aqueous coating composition at a said blade coating station at or above the minimum rheology shown in the drawing and at a solids level above 67 weight-% while passing a paper web at a speed of at least 500 feet per minute past said blade coating station and applying the said selected aqueous coating composition to said moving web at said blade coating station;
- (e) recovering a paper coated web essentially free of blade scratches which has porosity and blister resistance properties superior to a coated paper web coated in the same manner but with a relatively lower rheology and relatively lower solids content as compared to the rheology and solids content maintained at said blade coating station.
6 more elements
Dependencies are inferred from the claim text.