A process produces a body of a belt (10) for a paper, board, pulp or tissue machine, the body having an inner surface and an outer surface. The process includes producing a modified polyurethane by adding a polydialkylsiloxane having at least one functional group to a manufacturing process of a polyurethane in order to obtain the modified polyurethane, which modified polyurethane is a polyurethane matrix having a covalent bond with the polydialkylsiloxane, and forming the body of the belt, wherein the body is the modified polyurethane. The belt (10) is for a paper, board, pulp, or tissue machine, or for a shoe press and a sleeve roll.