The synthesis of polylactic acid is divided into direct method and ring-opening method.
At present, industrialized PLA is basically prepared by a ring-opening method. However, the ring-opening method has many reaction steps and high requirements for the purity of the intermediate product lactide, which makes the cost of PLA high.
At the same time, polylactic acid has a large brittleness and poor toughness, which limits its wide application.
the simpler direct method and the synthesis of modified polylactic acid based on the direct method have become one of the research hotspots.
Direct methods include melt polycondensation, melt / solid phase polymerization, solution polymerization and chain extension polymerization.
This subject mainly studies the melt polycondensation, chain extension polymerization of PLA, and the preparation of castor oil-modified PLA-type polyurethanes. Through process optimization and program improvement, a series of brand-new castor oil-modified PLA types with different properties have been prepared. Polyurethane.
The main research contents and conclusions of this paper are divided into four parts. The first part is the preparation of high molecular weight polylactic acid by the melt polycondensation method. Finally, 0.6wt% SnCl2 · 2H2O and TSA (p-toluenesulfonic acid) (SnCl2 · 2H2O / TSA = 1, molar ratio) are obtained by catalytic polymerization of lactic acid at 180 ° C.
PLA with a weight-average molecular weight of 56,000. In the second part, PLA with higher molecular weight was used as raw material, modified by castor oil, HDI (hexamethylene diisocyanate) was used as chain extender, and polylactic acid polyurethane was obtained by bulk polymerization at room temperature.