| 摘要 |
1,144,607. Web coating apparatus. CELLOPHANE INVESTMENT CO. Ltd. 4 May, 1966 [4 May, 1965], No. 19784/66. Heading D1L. A method of coating a hydrophilic sheet material comprises applying an aqueous dispersion of a coalescable coating composition to one surface of the material and passing the coated material through a path whilst supported on the uncoated surface to prevent curling of the edges, the path being long enough to coalesce the coating, applying an aqueous dispersion of a coalescable coating composition to the second surface of the sheet material and passing the coated material through a second path whilst supported on the first coated side, the path being long enough to coalesce the coating, and then drying the coated material. The coating composition is preferably an aqueous dispersion containing 33.3% by weight of solids, and may be a dispersion of a copolymer of vinylidene chloride with one or more copolymerisable monomers. in which the vinylidene chloride content exceeds 85% by weight. The hydrophilic sheet material may be regenerated cellulose film, hydroxyethyl cellulose film, carboxymethyl cellulose film, cellulose ether film or paper. In apparatus for carrying out the method, the aqueous coating composition is applied by means of a roller dipping into a trough containing the composition, and the applied coating is doctored by means of an air-knife. Each path through which the material passes subsequent to the coating operation comprises a series -of spaced rotatable guide rollers arranged on the line of an arc. Spreading rollers may be arranged between the guide rollers. The coated. material is dried by passage through a hotair dryer, the material passing vertically upwards and downwards through the dryer whilst hot air is directed symmetrically at both surfaces. After passage over cooling rollers, the coated sheet material is wound on a take-up reel. |
