Degradable polylactic acid diblock copolymer, preparation method and application to modified polylactic acid

The invention discloses a degradable polylactic acid diblock copolymer, a preparation method and application to modified polylactic acid, solving the problems of instable performance, high preparation cost and unsuitability for industrialized continuous production of modified polylactic resin in the prior art. The preparation method of the degradable polylactic acid diblock copolymer comprises the following steps of: adding dried and dewatered polylactic acid A with an end group being hydroxy into a reaction device under the protection of an inert atmosphere, adding diisocyanate B, heating to 185-190 DEG C, reacting with stirring for 5-8h, adding degradable high polymer C containing hydroxy, reacting with stirring for 1-2h at the temperature of 185-190 DEG C, adding the diisocyanate B, and reacting at the temperature of 185-190 DEG C until the stirring is difficult to obtain the degradable polylactic acid diblock copolymer. The degradable polylactic acid diblock copolymer disclosed by the invention is good in compatibility with the polylactic resin, is used for modifying the polylactic resin, is capable of remarkably improving processing property and mechanical property of the polylactic resin, and has the elongation at break reaching 60 percent.