1. A PRESSURE-SENSITIVE ADHESIVE PRODUCT HAVING AS A BACKING, A FLEXIBLE BONDED SHEET COMPRISING A FIBROUS PAPER WEB OF AN INITIALLY POROUS MATERIAL, THE FIBERS OF WHICH ARE BONDED TOGETHER INTERNALLY OF WEB BY PARTICLES OF AN IMPREGNATING AGENT WHICH HAS ENTERED THE PORES OF THE WEB, SATURATING IT TO THE EXTENT OF FROM ABOUT FORTY TO ABOUT SIXTY PER CENT OF ITS WEIGHT, SAID IMPREGNATING AGENT COMPRISING PER HUNDERED PARTS OF ITS WEIGHT: FROM ABOUT FIFTEEN TO ABOUT FIFTY PARTS OF BUTADIENE STYRENE COPOLYMER AVERAGING AT LEAST ABOUT TWENTY PER CENT STYRENE AND AT LEAST ABOUT FORTY PER CENT BUTADIENE, FROM ABOUT TEN TO ABOUT FORTY PARTS OF A BUTADIENE STYRENE COPOLYMER COMPRISING AT LEAST ABOUT FIVE PER CENT BUTADIENE AND AT LEAST ABOUT EIGHTY-FIVE PER CENT STYRENE AND FROM ABOUT FIFTY TO ABOUT EIGHTY PARTS OF A BUTADIENE ACRYLONTRILE COPOLYMER COMPRISING AT LEAST ABOUT FORTY PER CENT BUTADIENE AND AT LEAST ABOUT FORTY PER CENT ACYLONITRILE, THE PARTICLES OF SAID COPOLYMERS BEING PREDOMINANTLY LESS THAN FOUR MICRONS IN DIAMETER, AND NORMALLY TACKY AND PRESSURESENSITIVE BUTADIENE TYPE ADHENSIVE COATED ONTO SAID BACKING; SAID BACKING BEING CHARACTERIZED BY HIGH TENSILE STRENGTH AND GREAT RESISTANCE TO FORCE EXERTED BY THE PRESSURE-SENSITIVE ADHESIVE TENDING TO SEPARATE AND DELAMINATE SAID BACKING AND TO SEPARATE SAID ADHESIVE FROM SAID BACKING WHEN THE PRODUCT IS SEPARATED FROM ROLLS OR STACKS THEREOF.