Biologically degradable polymer mixture

A biologically degradable polymer dispersion consisting essentially of a mixture of thermoplastically processable starch and at least one hydrophobic polymer, characterized by the fact that the hydrophobic polymer is biologically degradable and processable thermoplastically and the mixture contains a phase mediator, said starch being present in the dispersion as the dispersed phase and the hydrophobic polymer as a hydrophobic continuous phase and the phase mediator molecularly coupling the two phases, wherein the hydrophobic polymer is selected from the group consisting of a cellulose derivative having a degree of substitution .ltoreq.2, an aliphatic polyester and a hydrophobic protein and wherein the combined water content of the dispersion components prior to mixing is less than 1% by weight, said thermoplastically processable starch obtained by mixing at a water content of less than 1% by weight based on the weight of the mixture, of native starch or a derivative thereof with 15 to 40% by weight of at least one plasticizing or swelling agent adapted to at least slightly swell or dissolve the starch or derivative.