VERFAHREN ZUR HERSTELLUNG VON EXPANDIERBAREN POLYMILCHSÄURE-HALTIGEN GRANULATEN

摘要

The invention relates to a method for producing expandable granulates containing polylactic acid, having a bulk density of between 500 - 800 kg/m3, comprising the following steps: a) melting and mixing the components i) between 59.9 and 79.9 wt. %, relative to the total weight of components i) to iii), of polylactic acid, ii) between 20 and 40 wt. %, relative to the total weight of components i) to iii), of a polybutylene succinate, polybutylene succinate co-adipate, polybutylene succinate co-sebacate, polybutylene adipate co-terephthalate or polybutylene sebacate-co-terephthalate, iii) between 0.1 and 2 wt. %, relative to the total weight of components i) to iii), of a chain extender, and iv) between 0 and 10 wt. %, relative to the total weight of components i) to iii) of at least one additive, b) mixing v) between 3 and 7 wt. %, relative to the total weight of components i) to iv), of a physical blowing agent, into the melted polymer mass, by means of a static or dynamic mixer, at a temperature of at least 140°C, c) discharging the mixture via a nozzle plate with boreholes, the diameter on the nozzle outlet being a maximum of 1.5 mm, and d) granulating the melted mass containing the blowing agent directly behind the nozzle plate, under water, at a pressure of between 1 and 25 bar and e) coating the thus obtained granulates vi) having 0.1 to 0.45 wt.%, relative to the total weight of the granulates, amorphous polylactic acid which is introduced to the granulates by means of an aqueous dispersion. The invention also relates to expandable granulates containing polylactic acid obtained according to said method and moulded parts produced therefrom.