ES317145A1 - Improvements in the orientation of polypropylene film or ribbon - Google Patents

Abstract

A film or ribbon of a polymeric composition comprising polypropylene is drawn in one direction at least 6 times its original length at a draw rate which is at least 70,000% per minute, and which may be e.g. 1,000,000% per minute. The film may be drawn between two rollers set close together (Figs. 1 and 2, not shown) the first roller 3 or 9 heating the film to drawing temperature with or without ancillary infra-red heating 101 and 1011 and the second roller 4 cooling it to below drawing temperature or the film may pass through a bath 11 of a cooling medium, e.g. water, in which the second roller 12 is partly immersed. The above two rollers may be placed between or form part of nip or capstan roller systems. In another method (Fig. 3, not, shown) the film is heated to a temperature below the draw temperature by the feed roller 14 with or without ancillary infrared heaters 20 and 21. and shortly before reaching the cooling roller is heated by a concentrated beam of rays from an infra-red heater 16. The film before treatment may be in smectic or crystalline form. The resultant oriented film has high strength in the direction of drawn and adequate strength in the transverse direction it may show no tendency to fibrillation in the transverse direction. " Polypropylene " includes propylene co-polymers, e.g. with ethylene the polymer may contain additives, e.g. dyes, pigments, antistatic,agents. antiblocking agents and oxidants and modifiers, e.g. polyterpenes.