High-molecular weight long-chain branched crystalline polylactic acid material and preparation method thereof

Abstract

The invention discloses a high-molecular weight long-chain branched crystalline polylactic acid material and a preparation method thereof. The preparation method comprises the following steps of: 1) adding 0.1 to 1 percent of protonic acid catalyst into aqueous solution of lactic acid or mixed solution of the aqueous solution of the lactic acid and silicon dioxide nano particle silica sol containing 0.1 to 10 weight percent of lactic acid, and dehydrating to obtain a product I; 2) adding 0.4 to 2 molar percent of dibasic acid or anhydride into the product I, and reacting to obtain a product II; 3) adding 0.1 to 1 weight percent of lewis acid catalyst into the product II, performing melt polycondensation, and adding 0.1 to 5 weight percent of crystallization accelerator to obtain terminal carboxyl group crystalline polylactic acid prepolymers; and 4) reacting diglycidyl ester and the terminal carboxyl group crystalline polylactic acid prepolymers in a molar ratio of 0.8:1-1.2:1 to obtain the high-molecular weight long-chain branched crystalline polylactic acid material. The preparation method has the advantages of simplicity, short reaction time, high efficiency, low cost and environmental friendliness and capability of contributing to realizing commercialization.

Description

technical field [0001] The invention relates to a biodegradable polymer material and a preparation method thereof, in particular to a high molecular weight long-chain branched crystalline polylactic acid material and a preparation method thereof. Background technique [0002] Polylactic acid is an important class of bio-based / biodegradable polymer materials. After its products are discarded or their service life ends, they can be finally degraded into carbon dioxide and water under natural composting conditions or in vivo environments. Therefore, polylactic acid can replace some petroleum-based non-degradable polymers, used as packaging materials, fibers, and also as medical materials. Although the application prospects are very attractive, and a certain scale of industrial production has been achieved at home and abroad, polylactic acid materials are still far from realizing large-scale applications. There are two main reasons for this: first, the production cost is high an...

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Problems solved by technology

However, the price of diisocyanate is high and toxic; it is easy to react with water, which is not conducive to storage; the property is too active, and it is prone to side reactions; The amount of recovery is very large; the obtained polylactic acid is actually a kind of polyester polyurethane, and the existence of urethane bonds will affect its degradability to a certain extent; in addition, the heat resistance of the obtained product is not good, which is not conducive to subsequent processing, and its impact resistance Sex can also be improved

Diacyl chloride chain extension reactions are performed in solution and produce a corrosive by-product, hydrogen chloride, making them unsuitable for large-scale production

Bisoxazolines are expensive and currently have limited use

Since the terminal functional groups of commercial polylactic acid (polylactic acid obtained by ring-opening polymerization) are mainly hydroxyl groups, and the reactivity between hydroxyl groups and epoxy groups is low, the reaction must be carried out at a high temperature of 190-210 ° C, and a large amount of anti-oxidant is required. Oxygen to inhibit high temperature thermal degradation, thereby increasing production costs

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