METHOD FOR SURFACE APPLICATION OF PROTECTIVE DEVICE ABOVE PERFORATION MADE BY PAPER-MAKING MACHINE Russian patent published in 2022 - IPC B42D25/29 B42D25/346 D21H27/00 

FIELD: paper industry.

SUBSTANCE: group of inventions relates to sheet material containing a protective device, to a protected or valuable document containing fibrous sheet material, to a method for the surface application of a protective device, as well as to fibrous sheet material prepared in accordance with such a method. In this case, sheet material (110) has opposite surfaces, a recess in one opposite surface and one or more through perforations (111) that pass from the recess through another opposite surface of fibrous sheet material, wherein one or more through perforations are through perforations formed during the manufacture of paper, wherein fibers pass in one or more holes bounded by the mentioned one or more through perforations, wherein sheet material contains fibrous subdomain (114), which is located below the recess and which surrounds the mentioned one or more through perforations, and an adjacent area of the main mass located next to the mentioned recess and fibrous subdomain; protective device (112) of surface application, located in the recess above the mentioned one or more through perforations; and interface zone (117) between the protective device of surface application and the fibrous subdomain and the area of the main mass. By means of the method for the present invention, a through perforation is performed in the formed fibrous canvas before it becomes sufficiently compacted, and then, the protective device is applied to the fibrous canvas. The application of the protective device and then additional compaction of the area under the device at this stage of paper making, when fibers cannot be displaced, significantly reduces the probability of that the through perforation will be closed or blocked.

EFFECT: documents manufactured in accordance with the method for the present invention, when conducting a test for imitation of circulation, demonstrate minimal damage in an interface zone of paper with a protective device; in addition, protective devices of surface application demonstrated acceptable levels of ink adhesion during gravure printing, and paper had a higher tensile strength in the transverse direction and much less translucency on their opposite sides.

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