Method and apparatus for manufacturing papers with watermarks or patterns and paper thus manufactured

摘要

A method for producing watermarks or patterns in paper and cardboard which can be performed during a process for manufacturing the paper or cardboard comprises the following steps: preparing a primary fibrous mix of cotton cellulose based on alpha-cellulose with the addition of sulfate cellulose; preparing a secondary fibrous mix which has substantially the same composition as the primary mix but to which an adapted dye and/or pigment has been added; spreading the resulting fluid mix on a moving formation board of a paper manufacturing plant, so as to obtain a layer of very moist cellulose pulp designed to be dehumidified and stabilized along a preset path on the formation table; applying a jet or jets of secondary fibrous mix to the relatively fluid layer of primary fibrous mix so as to produce a recess as a consequence of the lateral displacement, with respect to each jet, occurring in the layer of primary fibrous mix, the recess being filled with the secondary fibrous mix by the respective jet; and amalgamating the material of the applied secondary mix so as to form a uniform agglomarate with the material of the primary mix.