Biodegradable polymeric mixture and method for its preparation

A method for preparation of a biodegradable polymer blend, the biodegradable polymer blend comprising at least one component (A), at least one component (B), and at least one component (D), wherein

• component (A) includes polymers based on lactic acid, wherein the polymers based on lactic acid comprise homopolymers of PLLA, PDLA, as well as their copolymers, or mixtures of their homopolymers, mixtures of their homopolymers and copolymers, or mixtures of their copolymers;
• component (B) includes thermoplastic starch (TPS), representing a mixture of starch, at least one plasticizer from the group of substances (C), and at least one modifier from the group of substances (E), wherein the at least one plasticizer from the group of substances (C) comprises OH groups, and wherein the at least one modifier from the group of substances (E) reacts with the OH groups of the at least one plasticizer from the group of substances (C);
• group of substances (C) includes plasticizers for starch;
• group of substances (E) includes modifiers, wherein the modifiers comprise saturated or unsaturated carboxylic acids, dicarboxylic acids, tricarboxylic acids or polycarboxylic acids, saturated or unsaturated anhydrides, and mixed anhydrides of carboxylic acids, substances containing isocyanate groups, substances containing expoxide groups, acyl halides, acyl imidazoles, acylphosphates, thioesters of acids, or a combination thereof;
• component (D) includes homopolymers or copolymers of polyhydroxyalkanoates (PHAs), and/or their mixtures;
• and
• the biodegradable polymer blend optionally contains component (F) and component (G), wherein
• component (F) includes plasticizers for PLA and/or for PHA, and
• component (G) comprises inorganic fillers, organic fillers, compatibilizers, interphase agents, pigments, dyes, nucleating agents, processing aids, anti-block additives, slip additives, cross-linking additives, foaming agents, antistatic additives, flame retardants, antidegradants, other additives, other modifiers, or a combination thereof,
• wherein the biodegradable polymer blend is prepared in a such way that components (A) and (B) are blended, wherein component (B) is present in the blend at least in one phase of the mixing process where simultaneously at least one component (B) and at least one component (A) are blended, and this phase of the blending process precedes by at least one phase that blending phase of the blending process where component (D) is added to the blending process, and the optional component (F) and the optional component (G) can be added to the blend in any one or multiple phases of the blending process, either in one or in multiple doses.