METHOD OF COATING SHEET MATERIAL WITH A COMPOSITION CONTAINING MICROCAPSULES AND SHEET MATERIAL OBTAINED BY THIS METHOD

摘要

1476787 Coated paper; generating foam WIGGINS TEAPE Ltd 20 June 1975 [4 July 1974] 29729/74 Headings B1C and B2E [Also in Division D2] A microcapsule-coated paper for use in pressure sensitive copying systems is made by first foaming a coating composition containing the microcapsules and a particulate stilt material, applying the foamed composition to the paper, metering the composition on the web to a desired coatweight by means of a metering member in contact with the composition on the web, and drying the composition to leave an unfoamed coating on the web. The metering member may be a rigid or flexible blade, a Meyer bar, or roll. The stilt materials may be cellulose fibre floc, granular starch particles, granular synthetic polymers, hollow or liquid-containing capsules of a size greater than the microcapsules, or particulate mineral materials e.g. talc, or pigments. A foaming agent e.g. polyvinyl alcohol, gelatin, casein, soyabean extract, saponin, surfactants may be used. The binder may itself produce an adequate foam. Examples of such binders are the proteins specified above and polyvinyl alcohol. Foaming apparatus. Coating composition in tanks 16, 17 is pumped to a vortex cleaner 19 into which air is introduced via line 20. The mixture is then passed to a high shear mixer 23 to produce a foamed composition. The bubble size of the foam is made smaller by passage of the foamed composition through nozzles 24 and tubes 25, and the resulting foamed composition is passed to a fountain applicator 14 for application to a web 2. In an alternative arrangement (Fig. 3 not shown) a coating composition is foamed with air in a closed in-line mixer, e.g. a closed tank containing a rotatable paddle, and the resulting composition is pumped through a foam generator to a fountain applicator.