Preparation method of multi-layer coextrusion bidirectionally-stretched composite thin film

Abstract

The invention relates to a preparation method of a multi-layer coextrusion bidirectionally-stretched composite thin film, which is prepared through combination of two-step stretching including tubular-film synchronous stretching and flat-film stretching. The method, being direct at the composite thin film, includes the steps of: 1) performing first-time synchronous fusion stretching to extruded film bubbles in both longitudinal and transversal directions through a coextrusion tubular-film shaping process to prepare a tubular thin film, and flatly folding the tubular thin film to form double-layer or single-layer film sheets, wherein under the flatly folding status, if the temperature of an extruded film bubble inner layer material reaches or is lower than the glass transition temperature of the material, the double-layer film sheet is formed, or if the temperature of the extruded film bubble inner layer material is higher than fusion point of the material, the single-layer film sheet is formed; and 2) pre-treating the double-layer or single-layer film sheets, and performing flat-film stretching to the double-layer or single-layer film sheets to complete second-time longitudinal non-fused stretching; and 3) finally performing post-treatment to the double-layer or single-layer film sheets to obtain the bidirectionally-stretched composite thin film.

Description

technical field [0001] The invention relates to a preparation method of a multilayer co-extruded biaxially stretched composite film. Background technique [0002] Tube-film synchronous stretching and flat-film biaxial stretching are two commonly used biaxially stretched plastic film production processes, both of which have their own advantages and disadvantages. [0003] The simultaneous stretching of the tubular film method completes the longitudinal and transverse bidirectional stretching of the film when the tubular film bubble is formed by inflation. The principle of this method is to extrude a tubular object first, and then cool the tubular object with a water bath. Between the first and second pair of nip rollers, the transverse stretching is formed by properly adjusting the air pressure state in the film bubble, and the longitudinal stretching is This is achieved by adjusting the speed difference between the first and second pair of nip rollers. The stretched film p...

AI Technical Summary

Problems solved by technology

Flat film biaxial stretching includes synchronous stretching method and two-step stretching method. The film produced by synchronous stretching method has uniform performance and non-contact stretching, but the mechanical structure of the production equipment is complicated, the flexibility is low, and the production speed is low. ; The film produced by the two-step stretching method has excellent flexibility, good thickness uniformity and low shrinkage, but the performance is uneven