HETEROPHASIC PROPYLENE COPOLYMER

The invention relates to a process for the preparation of a final heterophasic propylene copolymer (A) having a final melt flow rate in the range from 65 to 110 dg/min as measured according to ISO1133 at 230 ºC and 2.16 kg, comprising visbreaking an intermediate heterophasic propylene copolymer (A') having an intermediate melt flow rate, which intermediate melt flow rate is lower than the final melt flow rate, to obtain the final heterophasic propylene copolymer, wherein the intermediate heterophasic propylene copolymer (A') consists of: (a) a propylene-based matrix, wherein the propylene-based matrix consists of a propylene homopolymer, wherein the melt flow rate of the propylene-based matrix is in the range from 75 to 85dg/min as measured according to ISO1133 at 230 ºC and 2.16 kg, (b) a dispersed ethylene-α-olefin copolymer, wherein the amount of ethylene incorporated into the ethylene-α-olefin copolymer is in the range from 45 to 55wt% based on the ethylene-α-olefin copolymer, wherein the amount of ethylene-α-olefin copolymer is less than 15wt% and at least 10 wt% based on the intermediate heterophasic propylene copolymer, wherein the melt flow rate of the ethylene-α-olefin copolymer is in the range from 0.50 to 2.0 dg/min as calculated using formula (I), wherein MFR heterophasic is the melt flow rate of the intermediate heterophasic propylene copolymer measured according to ISO1133 (2.16kg/230°C), MFR PP is the MFR of the propylene-based matrix of the intermediate heterophasic propylene copolymer measured according to ISO1133 (2.16kg/230°C), matrix content is the amount of the propylene-based matrix in the intermediate heterophasic propylene copolymer and rubber content is the amount of the dispersed ethylene-α-olefin copolymer in the intermediate heterophasic propylene copolymer, wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-α-olefin copolymer in the intermediate heterophasic propylene copolymer is 100 wt% based on the intermediate heterophasic propylene copolymer. L'invention concerne un processus de préparation d'un copolymère de propylène hétérophasique final (A) ayant un indice de fluidité final de 65 à 110 dg/min tel que mesuré selon la norme ISO1133 à 230 °C et 2,16 kg, comprenant la viscoréduction d'un copolymère de propylène hétérophasique intermédiaire (A') ayant un indice de fluidité intermédiaire, lequel indice de fluidité intermédiaire est inférieur à l'indice de fluidité final, p