Process for polymerization in a fluidized bed reactor
First Claim
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1. A process for polymerization in a gas phase reactor, the process comprising:
- a) fluidizing a bed of polymer particles in a reactor with a gas mixture comprising ethylene and one or more alpha olefin at a first hydrogen concentration [H2]A;
b) introducing a single site catalyst system to the reactor to initiate a polymerization reaction;
c) polymerizing the ethylene and the one or more alpha olefin at a first reactor temperature, TA to give a first ethylene copolymer with a first melt index, I2A, a first melt flow ratio, (I21/I2)A, and a first density, dA, until at least one reactor bed volume has turned over, where a reactor bed volume is defined as the volume of the reactor from a reactor distributor bed plate to the top of the fluidized bed; and
d) subsequently reducing the hydrogen concentration and the reaction temperature to a second hydrogen concentration [H2]B and a second reactor temperature TB, respectively, to give a second ethylene copolymer with a second melt index, I2B, a second melt flow ratio, (I21/I2)B, and a second density, dB;
wherein the first melt index, I2A is greater than the second melt index, I2B.
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Abstract
A polymerization process for stable gas phase reactor start-up when making ethylene copolymers having relatively high molecular weight distribution and melt flow ratio.
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25 Claims
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1. A process for polymerization in a gas phase reactor, the process comprising:
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a) fluidizing a bed of polymer particles in a reactor with a gas mixture comprising ethylene and one or more alpha olefin at a first hydrogen concentration [H2]A; b) introducing a single site catalyst system to the reactor to initiate a polymerization reaction; c) polymerizing the ethylene and the one or more alpha olefin at a first reactor temperature, TA to give a first ethylene copolymer with a first melt index, I2A, a first melt flow ratio, (I21/I2)A, and a first density, dA, until at least one reactor bed volume has turned over, where a reactor bed volume is defined as the volume of the reactor from a reactor distributor bed plate to the top of the fluidized bed; and d) subsequently reducing the hydrogen concentration and the reaction temperature to a second hydrogen concentration [H2]B and a second reactor temperature TB, respectively, to give a second ethylene copolymer with a second melt index, I2B, a second melt flow ratio, (I21/I2)B, and a second density, dB;
wherein the first melt index, I2A is greater than the second melt index, I2B. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification