GB1327433A - Method of calendering paper - Google Patents

Abstract

1327433 Calendering paper EASTMAN KODAK CO 9 Nov 1970 [10 Nov 1969] 53289/70 Heading D2A The density and smoothness of a paper web is increased by passing it, while it contains at least 2% by weight of water, through the nip between calender rolls which have hard, smooth, non-resilient surfaces, which exert pressure in the range from 10,000 to 50,000 lbs/ins<SP>2</SP> on the paper and said surfaces of which are maintained at a temperature in the range from 250‹F to 500‹F, the actual water content of the web, the actual pressure exerted by the rolls on the paper and the actual temperature of said surfaces being such that the paper does not blister on; passing through the nip. The web to be treated may have an opaque porous structure or it may be well formed and dense, have a basis weight of 40 lbs. per sq. ft. or be fairly closed in structure and non-porous. In the latter case, for example, the arc over which web-to-heated roll contact occurs is restricted by fly rolls and these are preferably positioned so that the web moves to and from the nip in a plane whereby contact is only at the nip. The rolls may be of cast iron or steel and they may be heated by passing steam or other heated fluid through passages in them or by electrical heating coils in them. The calender may have two or more rolls. The web may be passed successively through two or more nips at which successively increasing pressures are exerted on it. The web speed may be as low as 10 ft per min or as high as 2000 ft per min. The calender may form part of a paper-making machine or it may be a separate unit. The calender shown in Fig. 3 comprises rolls 10 to 24, the rolls 14 and 16 being at a high temperature, e.g. 300‹F, and the other rolls being at a low temperature, e.g. room temperature. Fly rolls 28, 30 prevent the web 26 from wrapping around the rolls 14, 16. More than two high temperature rolls may be provided. with further associated fly rolls. The calender is loaded through roll 10 and driven through roll 24. The finished paper may be used in the production of photographic papers, i.e. carrying one or more lightsensitive silver halide emulsion layers, especially papers intended for manufacture of photographic paper base of the resin coated type used for photographic papers used in diffusion transfer processes.