POLYMER MIXTURE HAVING IMPROVED RHEOLOGICAL PROPERTIES AND IMPROVED SHRINKING BEHAVIOUR

The invention relates to a thermoplastic polymer mixture containing m, m representing a natural number higher than 1, polymers Pn wherein n represents a natural number between 1 and m, and at least one recurring functional group contained in the Pn polymer chain, said group(s) having the structure -(R )x-C(O)-(R )y- wherein x and y independently represent 0 or 1, and x+y=1, and R , R independently represent oxygen or nitrogen linked into the main polymer chain. The polymers Pn differ in terms of at least one characteristic related to molecular weight. The polymer mixture has a number average molecular weight Mn(P)1, a weight average molecular weight Mw(P)1, a Z average molecular weight Mz(P)1, a heterogeneity index Mw(P)1/Mn(P)1, and a molecular weight Mp(P)1 defined according to DIN 55672-2 in hexafluoroisopropanol as an elution agent. After maintaining the polymer mixture at the melting point of the same, defined according to ISO 11357-1 and 11357-3, for five minutes, the polymer mixture has a number average molecular weight Mn(P)2, a weight average molecular weight Mw(P)2, a Z average molecular weight Mz(P)2, a heterogeneity index Mw(P)2/Mn(P)2, and a molecular weight Mp(P)2 defined according to DIN 55672-2 in hexafluoroisopropanol as an elution agent. The values Mn(P)2, Mw(P)2, Mz(P)2, Mw(P)2/Mn(P)2 and Mp(P)2 lie within the triple replication standard deviation sigma (r) in relation to Mn(P)1, Mw(P)1, Mz(P)1, Mw(P)1/Mn(P)1 and Mp(P