Novel method for recovering calcium lactate by hydrolysis of waste polylactic acid material

Abstract

The present invention relates to a novel method for producing calcium lactate by chemical depolymerization of waste polylactic acid materials to realize recovery of the waste polylactic acid material. The method is characterized by using 1-ethyl-3-methylimidazolium acetate and 1-butyl-3-methylimidazolium acetate which have certain solubility and are easy to reuse as a reaction medium and a catalyst; performing a hydrolysis reaction at 110-130 DEG C; adding a certain amount of calcium carbonate after the reaction; filtering; distilling the filtrate under reduced pressure to remove water and then adding an appropriate amount of absolute ethyl alcohol, separating calcium lactate by crystallization, filtering, drying to get calcium lactate, and separating the filtrate by distillation to recover ethanol and ion liquid for recycling and reusing. The yield of calcium lactate is above 90%. Compared with a conventional method, the present invention is characterized by: (1) having no need of using a conventional alkali catalyst, and significantly improving the problems of equipment corrosion and wastewater discharging; and (2) overcoming the problem that the ionic liquid cannot be reused in the background art, because the ionic liquid having a certain solubility for the polylactic acid material is used as the reaction medium and the catalyst, on the one hand the reaction conditions are eased, on the other hand the ionic liquid can be reused.

Description

technical field [0001] The invention relates to a new method for chemically depolymerizing waste polylactic acid materials and recovering calcium lactate by using ionic liquid as a reaction medium and a catalyst. technical background [0002] Polylactic acid (PLA) is an excellent bio-based polymer material with good biocompatibility and biodegradability, which is a potential substitute for petroleum-based polymers such as polyester and polystyrene, and can be widely used in industrial , packaging and pharmaceutical industries. In recent years, with the increasing shortage of petroleum resources and the continuous development of PLA production technology, the production and consumption of PLA have grown rapidly, and the rapid increase in PLA production and sales will lead to more and more waste PLA. Although PLA can be degraded under natural conditions, but the degradation cycle is too long, and its waste stacking or landfill will take up a lot of space and pollute the envir...

AI Technical Summary

Problems solved by technology

On the other hand, since the ionic liquid with a certain solubility to the polylactic acid material is used as the reaction medium and catalyst, the reaction conditions are eased, and the ionic liquid can be reused, which overcomes the problem that the catalyst cannot be reused in the background technology

[0006] The purpose of the present invention is to provide a new method for recovering calcium lactate by catalytic hydrolysis of waste PLA, which overcomes the shortcomings of traditional methods such as consumption of a large amount of traditional strong alkali, serious equipment corrosion and environmental pollution, non-recyclable catalysts, and harsh reaction conditions.

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