Moldable two-way stretch polypropylene film as well as preparation method and application thereof

Abstract

The invention discloses a moldable two-way stretch polypropylene film as well as a preparation method and application thereof. The moldable two-way stretch polypropylene film comprises a first moldable layer, a second moldable layer, a polypropylene core layer and a polypropylene surface layer; the moldable two-way stretch polypropylene film is prepared by the first moldable layer, the second moldable layer, the polypropylene core layer and the polypropylene surface layer through a coextrusion two-way stretch process. Compared with a traditional moldable two-way stretch polypropylene film, themoldable two-way stretch polypropylene film has the advantages that the appearance is good, surface scalding cannot be generated in film preparation and laser mold pressing processes, the film preparation and mold pressing speed is higher, the film heat shrinkage is lower, and the thickness uniformity is higher.

Description

technical field [0001] The invention relates to a biaxially stretched polypropylene film and its preparation method and application, more specifically, relates to a moldable biaxially stretched polypropylene film and its preparation method and application. Background technique [0002] At present, cigarette labels, wine labels, medicine boxes, toothpaste boxes, etc., which contain laser anti-counterfeiting or decorative patterns, are usually made of moldable thermoplastic materials through molding machines for molding and post-processing, especially because of high molding efficiency. The soft pressing process with wide width and rapid development of seamless plate transfer technology is more common, and the molded base film used is usually a biaxially oriented polypropylene film with a total thickness of 15-60 μm. This kind of film usually has a three-layer structure, that is, a moldable layer, a core layer, and a surface layer. The thickness of the moldable layer is usuall...

AI Technical Summary

Problems solved by technology

The main reason why ethylene-propylene binary copolymer is usually not used as the moldable layer is that its relatively high melting point (above 139°C) and softening temperature (above 120°C) limits the molding process speed

However, the film using ethylene-propylene-butene terpolymer as the moldable layer also has two problems in the preparation process: one is that when biaxially stretched, the molded surface is easily scalded by the roller (usually limiting the practicality of the film surface). Temperature ≤ 125 ℃), in order to avoid scalding and reduce the preheating temperature, it will lead to insufficient energy of the core layer polypropylene, the difficulty of stretching will increase, and the production has to be slowed down; second, when producing films with a thickness of more than 40 μm, due to chilling During casting, the cooling of the core layer is not as good as the surface, and crystals that are not conducive to stretching are formed. In addition, the low temperature of the molding surface and the insufficient energy of the core layer lead to difficult stretching, which increases the internal stress and causes the thermal shrinkage of the film. high rate

In the subsequent laser embossing process, due to the large lateral shrinkage of the film and the low preheating temperature of the molded surface, the speed of laser embossing is seriously restricted, which not only affects the quality of the film, but also restricts the production efficiency of the film. , becoming a bottleneck for the improvement of the quality and production efficiency of holographic laser embossed films

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