Importance

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Abstract

A method of and apparatus for applying coating liquid to a web of paper traveling over a web supporting surface at speeds of 3,000, 4,000 and more feet per minute to produce a coated web free of streaking and other imperfections comprises apparatus for and the sequential steps of distributing coating liquid in a turbulent state over the supported web through a limited application zone within a very short dwell time of the turbulent liquid on the web; subjecting the coating liquid on the supported web to an initial doctoring by means of a primary doctor blade biased under pressure against the coated web at the rear edge of the application zone to form on the web downstream from the zone a relatively quiescent layer of coating liquid having a wet film thickness sufficiently in excess of the final wet film thickness to accommodate a subsequent final wet film doctoring of the coating liquid on the web; and, at a location downstream and isolated from the application zone, subjecting the relatively quiescent layer of excess coating liquid on the supported web to a final doctoring by means of a final doctor blade biased under pressure against the coated web to remove the excess coating from the web and to level and smooth the coating retained on the web to final wet film thickness and smoothness. The method and apparatus of the present invention produces essentially a constant paper smoothness in relation to web speed at which it was coated and subsequently supercalandered, i.e., smoothness does not decrease at higher web speeds, and produces higher gloss with less decline in gloss at higher web speeds.

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First Claim