Patent ID: 8784716

Claim:
A process of supplying a thermoplastic polymer film with longitudinal orientation comprising the steps of: reducing a width of a film in a reduction zone comprising at least one pair of curved mutually intermeshing grooved rollers or curved intermeshing sets of discs to form a regular pattern of longitudinally extending pleats, where the width reduction occurs gradually within the reduction zone, where a length of the reduction zone is no shorter than half of an original width of the film, and where the reduction zone length is limited by an upstream roller or roller assembly and a downstream roller or roller assembly installed having varying directions of their respective axis of rotation from a central direction at the middle of the film forming an angle of 90° with a machine direction and gradually changing towards edges of the film to forward the film in a converging manner within the reduction zone, and solid state stretching in one or more short zones between and/or on two or more stretching rollers or bars, where the stretching zones are adapted to fully straighten out the pleats by the inherent tendency in the polymer material making up the film to contract transversely, while being stretched longitudinally.