| abstract |
Process for preparing a propylene copolymer in the presence of a catalyst (1). The copolymer has excellent flow properties and an MFR value of 10 g/10 mins. or more. The catalyst (1) comprises (A) a solid-titanium component contg. as main components Mg cpds., Ti cpds., Mg, Ti, halogens and a polycarboxylic acid ester, (B) organo aluminium cpds., and (C) organo silica cpds. represented by the formula SiR11m(OR12)4-m, where R11 is an alkyl or alkyl gp., R12 is a hydrocarbon gp. and m is 1-2. The process is a two step polymerisation consisting of a first polymerisation step and a subsequent polymerisation step. The first polymerisation step comprises at least two stages and propylene is polymerised or copolymerised in this step. The crystalline propylene polymer obtd. from the first stage has a limiting viscosity (eta)FC of 1.8 dl and that obtd. from the second stage has (eta)xc = 0.7-2.0 dl/g (measured in decalin at 135 deg.C). The ratio (eta)FC/(eta)xc = should be 0.9 or less. In the second polymerisation step propylene and alpha-olefin in the molar ratio of 10/90-90/10 are random omega-polymerised in the presence of crystalline propylene polymer. |