GB456855A - Improvements in and relating to transparent films of rubber hydrochloride - Google Patents

Abstract

Films of high transparency are obtained by spreading a solution of rubber hydrochloride on a surface, evaporating solvent from the exposed surface of the film material, and then smoothing out irregularities in the surface of the resulting film while it contains not more than 15 per cent of solvent. The smoothing treatment may be carried out before or after the film is removed from the forming surface. Smoothing may be effected by passing the film into pressure contact with a highly polished heated surface, such as a pressure roll. A steel roll may be caused to contact with the <PICT:0456855/IV/1> surface of the film from which solvent has been evaporated and the film may be supported by a rubber covered roll, a hard rubber roll, or other resilient surface. In an example, a solution of a partially saturated rubber hydrochloride dissolved in benzene is spread out as a thin film on an endless smooth belt so as to produce a continuous film. The greater part of the solvent is evaporated with the aid of a forced draught and the film containing 5--15 per cent of solvent is then passed between highly polished heated pressure rolls which may be engraved so as to impress or emboss a figure or design on the film. As shown, rubber hydrochloride solution is fed through pipe 3 on to the endless belt 1 provided with a hood 2 to carry off solvent vapour. The thickness of film is regulated by a spreader 4. The film 5 is stripped from the belt and passed through pressure rolls 6, 7 where irregularities in the surface are smoothed out. The film then passes through a festoon drier 8. Specification 437,304, [Group V], is referred to The Specification as open to inspection under Sect. 91 describes also the application of the process to the manufacture of films from other materials including other rubber derivatives such as halogenated rubber. This subject-matter does not appear in the Specification as accepted.