Polylactic acid film and preparation method thereof

Abstract

The invention relates to a polylactic acid film. The polylactic acid film comprises an inner layer prepared from a polylactic acid copolymer, at least one middle layer mainly prepared from cellulose and chitin, and at least one surface layer prepared from a polylactic acid copolymer; and based on a weight of the surface layer, the surface layer contains 0.05%-0.6% by weight of crosslinked polymer spherical particles having particle diameters of 2-6 [mu]m, and the middle layer is located between the inner layer and the surface layer. The invention also relates to a preparation method of the polylactic acid film. The preparation method comprises the steps of performing co-extrusion cast compounding on the inner layer, the middle layer and the surface layer, and performing biaxial stretching to obtain the polylactic acid film. According to the multi-layer co-extruded film containing the polylactic acid polymer and the cellulose-chitin prepared by the invention, the friction coefficient is reduced, the adhesion is reduced, the heat sealing property is increased, electrostatic formation and film dust collection are reduced, the film has high biodegradability, the cellulose-chitin layer has a crystal structure through which gas cannot pass, the crystal structure can effectively resist invasion of oxygen, and the prepared film is more suitable as a packaging film for fresh food.

Description

technical field [0001] The invention belongs to the technical field of film preparation, and in particular relates to a polylactic acid film and a preparation method thereof. Background technique [0002] Polylactic acid is a biodegradable or compostable polymer produced by the polycondensation of lactic acid. The monomer used to produce polylactic acid has two optically active isomers, namely D-lactic acid and L-lactic acid. When the two isomers are combined and polymerized, their relative amounts produce a variety of polymers with varying degrees of crystallinity (amorphous to semi-crystalline), crystallization behavior, and melting points. Polymers of this type are available from Cargill-Dow and representative commercially available polymer grades are PLA4042.TM. and PLA4060.TM. Both resins were prepared by combining different ratios of two optical isomers of lactic acid, L-lactic acid and D-lactic acid. The relative proportions of the two isomers control the final cry...

AI Technical Summary

Problems solved by technology

Therefore, its use has several disadvantages: most of the benefits provided by the particles are lost due to their incorporation inside the film away from the surface; larger quantities of anti-blocking particles must be used than required to improve the surface properties, which leads to The cost increases and will limit the use of expensive but highly effective additives, such as spherical cross-linked silicone resins, such as Tospearl.TM., or cross-linked acrylic spheres, such as Epostar.TM.; use additional non-functional Reactive particles will increase the amount of light scattering as measured by film haze and reduce the value and aesthetic appeal of the film and affect the ability to display the packaged product

[0011] Although the preparation of cellulose film has been realized at present, the film prepared by it has the disadvantages of poor stretchability, easy damage, high rejection rate, etc., and there is no report that cellulose and chitin can be used to prepare film together