Overfeeding type thin film drawing process

Abstract

The invention discloses an overfeeding type thin film drawing process. In the thin film drawing process, the length of a thin film clamped by clamps is larger than the length of chain clamps of a drawing machine, redundant parts are formed between the length of the thin film and the length of the chain clamps in the film clamping, feeding and drawing process, and the redundant parts are accumulated in gaps between the clamps to form wrinkles. By the adoption of the overfeeding type thin film drawing process, the thin film is not accumulated in clamping sections of the clamps and only accumulated in the gaps between the front and back clamps, and when the transversely-drawn thin film shrinks longitudinally, the edges of the film do not shrink longitudinally at the clamping portions of the clamps, the portions, close to the inner side, of the thin film shrink longitudinally, and the longitudinal shrinkage ratio is reduced. The redundant parts, namely the wrinkles are reserved in clamping seams and cut off at the rear edge portion of a transversely-drawing outlet and are not components of products. By the adoption of the overfeeding type thin film drawing process, the stepless adjustment longitudinal shrinkage ratio can be acquired, so that the longitudinal shrinkage ratio of the transversely-drawn thin film is controlled within a controllable range.

Description

technical field [0001] The invention relates to a stretching process, in particular to an overfeeding film stretching process. Background technique [0002] The film stretching process can be divided into sequential stretching and synchronous stretching according to the stretching sequence: successive stretching is to stretch the plastic film thick sheet longitudinally and then transversely. Biaxial stretching is divided into two steps. Of course, it can also be stretched horizontally and then stretched vertically; synchronous stretching is horizontal stretching and longitudinal stretching at the same time. The advantage of synchronous stretching is that the properties of the film in the vertical and horizontal directions are similar. However, the performance of the two directions of successive stretching is quite different. [0003] The film stretching process can be divided into flat stretching and bubble tube stretching according to the stretching method: a flat sheet is...

AI Technical Summary

Problems solved by technology

[0005] There is a problem of increased shrinkage of the film after stretching: polymer materials have a tendency to de-orient after stretching and orientation, which is the main reason for shrinkage

However, it is more difficult to reduce the shrinkage rate in the longitudinal stretching direction, because the heating and shrinkage of the transverse stretching is carried out in the air, and the longitudinal shrinkage is carried out on the rollers, so there are two main problems: one is the height of heating If the temperature is too high, the film will adhere to the roller and cause scald scars; the second is that the longitudinal stretching diaphragm is wrapped on the roller, and the diaphragm between the rollers is too tight to relax and fully retract. After the diaphragm is too loose, the diaphragm cannot cover the roller, and slippage will occur, causing slippage and scratches on the film.

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