Resin based on two polypropylenes, useful for making stretched films for packaging, with specific ratios of structural viscosity and melting temperature between components

摘要

Resin composition based on polypropylene, for preparation of stretched films, comprises 20-98 weight parts polypropylene-based polymer (A) and 2-80 weight parts second such polymer (B) where (i) the ratio of melt temperatures (Tm) of (A):(B) is below 1 and (ii) the ratio of structural viscosity (eta) of (A):(B) is over 1 but below 10, and the composition has melt index 1-20 g/10 min. Resin composition (X) based on polypropylene (PP), for preparation of stretched films, comprises 20-98 weight parts polypropylene-based polymer (A) and 2-80 weight parts second such polymer (B) where (i) the ratio of melt temperatures (Tm) of (A):(B) is below 1 and (ii) the ratio of structural viscosity (eta) of (A):(B) is over 1 but below 10, and the composition has melt index 1-20 g/10 min. Tm, measured by differential scanning calorimetry, is 140-165 deg C for (A) and 150-170 deg C for (B), and eta, measured in tetralin at 135 deg C, is 1.8-8 dl/g for (A) and 0.8-1.7 dl/g for (B). Independent claims are also included for the following: (a) method for preparing (X); and (b) stretched films produced from (X) by uni- or bi-axial stretching.