| 摘要 |
Paper of enhanced smoothness and printability is produced by applying onto each of the opposed surfaces of a forwardly moving dry web of paper a number of superposed layers of aqueous coating composition comprising mineral pigment and adhesive without intermediate calendering, the adhesive in the last coating being greater in amount by weight of the pigment than that of the preceding coating and comprising principally a synthetic aqueous polymeric dispersion, each layer of coating being separately wiped and levelled by trailing-blade coating means and separately heat-dried before application of a succeeding coating. Each of the surfaces may have been smoothed prior to the appreciation of the layers of aqueous coating composition. Each of the surfaces may be a machine-glazed surface. Each of the opposed surfaces of a newly formed paper web may be smoothed while moist in contact with heated routing surfaces before application of the layers of aqueous coating composition. Two superposed layers of aqueous coating composition may be applied to each of the surfaces of the web of paper. The amount of polymeric material in the first coating may be from 10 to 25% by weight of the pigment and that of the second coating may be from 30 to 100% by weight of the pigment. The paper may have about 92% of its surface topographic discontinuities (peaks and valleys) not greater than 15 to 20 microns in height and depth. The mineral pigment may be clay, calcium carbonate, titanium dioxide or mixtures thereof. The coating composition may contain enzyme converted or oxidized starches, dextrines, casein, zeim derived from corn and soybeam, alpha protein or mixtures thereof, carboxymethyl cellulose, polyvinyl alcohol, acrylic resin, vinyl acetate-acrylic e.g. acrylonitrile copolymer, vinylidene chloride-vinyl chloride copolymer, and copolymers of styrene or acrylonitrile with butadiene, polybutadiene, polyethylene, polyvinyl butyral, polychloroprene, vinyledene chloride-acrylonitrile and polymers and copolymers of acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile. |
