Patent GB-1327073-A (GB)
Title: Method and apparatus for coating paper
IPC: D21H/
Filed: 1970-08-24
Abstract: 1327073 Coating webs COMBINED PAPER MILLS Inc 24 Aug 1970 [22 Aug 1969 (2)] 40571/70 Heading D1L [Also in Division B2] Apparatus for coating paper comprises as shown in Fig. 3 comprises a power-driven roller 31 and a second roller 30 arranged in operation of the appartus to engage a continuous moving web 12 of paper which is in contact with the first roller and to form with the web an area containing pool of primary coating liquid 37 to be applied to the front side of the web, a further roller 40 arranged in contact with roll 30 to form a pin area 42 between them, means 45 for supplying a barrier liquid to the nip area and maintaining a pool 41 of the barrier liquid in the nip area so that barrier liquid can be applied by the first roller to the back side of the web to provide a barrier coat which prevents strike-through of the primary coating liquid applied to the front side of the web. Roller 30 may have a hard surface while the second roller 31 may have a deformable surface formed from rubber. The further roller 40 may also have a deformable surface. Roll 31 can be disengaged from roller 30 by lever system 34 and similarly roller 40 may be moved to disengaged position 47 when not in operation. A roller 48 which may be grooved along its surface in spiral fashion is disposed downstream from the rollers 30 and 31 to impart a. spreading force to the web after application of the primary coating liquid so as to remove possible wrinkles in the web caused by expansion due to the wetting action of the primary coating liquid. A positioning roller 35 is disposed upstream from the engagement of rollers 30 and 31 so as to place the moving web in peripheral contact with roller 30 above the area of engagement of the two rolls. Roller 30 is driven by any conventional means. The rotational motion for roller 31 is obtained and controlled by a drive that senses the amount of force required to keep and, through its own servo mechanism which adds or subtracts power, maintains the desired differential between the rotational speed of rollers 30 and 31. The paper may be discharged from a Fourdrinier paper-making machine and then subjected to a series of pressing operations and to drying means before the application of a coating to the first side of the web and the application of the barrier liquid medium to the second side of the web, the coated web thereafter being subjected to further drying means and conditioning operation such as calendering prior to reeling. The barrier liquid medium may comprise water, an aqueous starch solution, an aqueous solution of adhesive, or an adhesive-pigment system in water. The arcuate length of the lap of the moving web on the roller 30 may be varied by displacing the positioning roll with respect to roller 30. In operation roller 31 turns at a slower rate than roller 30 and roller 40 runs at a lower surface speed than roller 30. The coating material applied at nip 36 may be an aqueous suspension of clay and other mineral pigments with adhesives used in the paper coating industry. Other materials mentioned as being applied at either nip area 41 or nip area 36 include two solutions, methyl cellulose solutions, polyvinyl chloride, polyvinyl acetate. The application of these materials is said to increase the adhesion of subsequently applied coatings such as clay.