Mfg. structured surface on coating of paper or foil - by two successive coatings of different thickness and polymer concn.

摘要

Structured surface is produced on a sheet of paper or foil by multiple coating. Firstly a solvent mixt. contg. dissolved polymer is applied as a thin coating onto the (moving) paper or foil and at least partly dried. This is followed (immediately) by a second, thicker coating of a liq. which may be the same as the first but pref. has a greater concn. of polymer in the solvent, after which a first drying phase (5) is applied for both the coatings in which the rate of drying is regulated by the flow rate of air and its temp. so that the upper, second layer (3) achieves the desired surface structure (6) without a too rapid increase in the concn. of the polymer and without too much formation of skin. Pref. a first solvent and at least one other solvent are mixed in proportions by which the steepness of the flanks of the minute cells of the structured surface can be regulated (according to the relevant proportions) and thus the roughness can be regulated. Used for the prodn. of a semi-matt or similar surface on paper or similar foil, with the attendant advantages of insensitivity to scratching, lack of reflection, etc. The method enables the following three parameters to be independently regulated. The total thickness of the dry coating; the roughness depth of the surface; and the dia. of the minute surface cells.