Abstract: A film material formed of thermoplastic polymer material is processed so as to have linearly extending regions (A) linked together by linearly extending webs (B), regions (A) and webs (B) each being oriented, the dominant direction of orientation in regions (A) forming an angle (V) to the direction on which (A) extends and webs (B) comprising arrays of linear furrows of thinner material or splits forming angles (U) higher than (V) to the direction in which (A) extends. The method of producing the new film involves passing an orientated film through a pair of intermeshing grooved rollers to cold-stretch the film in a direction at an angle to the predominant original orientation, at least one of the grooved rollers having crests with sharp edges to form the division between regions A and webs B and to stretch the material to form webs B while stretching the material less or not at all to form regions A. Preferably at least one of the grooved rollers has crests with a waved surface shape.

Abstract: Sheet material (4) is stretched transversely into longitudinally extending pleats by passage between intermeshing grooved rollers (A and B) having circularly or helically extending grooves in their surfaces. Each groove is formed of a base (6a,6b) and side walls (5a,5b) inclined outwardly to a peak (7a,7b). Portions of adjacent side walls (5a,5b) are parallel to one another. The peaks are less than about 3 mm apart and the film is stretched by the peaks and is compressed between the side walls by forcing the rollers together. The pleated material is generally then stretched longitudinally substantially to eliminate the pleats and it may then be again stretched transversely between a further set of intermeshing grooved rollers.

Abstract: A coextrusion die for the extrusion of plastics materials in the shape of a tubular film comprising supply means for separately supplying at least two plastics materials to said die, a distribution channel system connected to each supply means, each distribution channel system comprising at least two arched channels provided in different axial planes, the ends of each arched channel being connected to the middle portion of the following arched channel and the distribution channel systems being located at different distances from the center axis of the die, collecting chambers communicating with said distribution channel systems and an annular extrusion slot communicating with the collecting chambers.

Abstract: A coextrusion die for the extrusion of plastics materials in the shape of a tubular film comprising supply means for separately supplying at least two plastics materials to said die, a distribution channel system connected to each supply means, each distribution channel system comprising at least two arched channels provided in different axial planes, the ends of each arched channel being connected to the middle portion of the following arched channel and the distribution channel systems being located at different distances from the center axis of the die, collecting chambers communicating with said distribution channel systems and an annular extrusion slot communicating with the collecting chambers.