High-melt-strength propylene/ethylene/butene copolymer and preparation method thereof

[0071] The polymerization reaction was carried out on a polypropylene pilot plant. Its main equipment includes prepolymerization reactor, first loop reactor and second loop reactor. Polymerization method and steps are as follows:

[0072] (1) Prepolymerization reaction:

[0073] The main catalyst (titanium-containing solid catalyst active component) is obtained by the method described in Example 1 of Chinese Patent CN93102795, its Ti content: 2.4wt%, Mg content 18.0wt%, di-n-butyl phthalate content: 13wt %.

[0074] The main catalyst, co-catalyst (triethylaluminum), and the first external electron donor (dicyclopentyldimethoxysilane, DCPMS) are pre-contacted at 10°C for 20 minutes, and then continuously added to the pre-polymerization reactor for pre-polymerization. In the polymerization reaction, the prepolymerization is carried out in the environment of the propylene liquid phase body, the temperature is 15° C., and the residence time is about 4 minutes. Under this condit...

[0083] With embodiment 1, just the ethylene addition in the first loop reactor becomes 30000ppm, and the butene addition becomes 15mol%; The ethylene addition in the second loop reactor becomes 30000ppm, and the butene addition is adjusted to 15mol%. At the same time, the amount of hydrogen in the second loop reactor was adjusted to 9300 ppmv.