Tubular polymerization reactors and polymers made therein
AssigneeExxonMobil Chemical Patents Inc.
InventorJan Cyriel Donck
Life of this patent
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Abstract
Tubular reactor apparatus and processes are provided for improved polymerization including using chain transfer agents and multiple monomer feeds spaced lengthwise along the tubular reactor providing high conversions of monomer into polymer. The invention also relates to polymers made from such a tubular reactor apparatus and processes including those polymers having a low haze value, a density over 0.92 g/cm3 and/or having terminal carbonyl groups. The apparatus and methods uncouple or reduce the dependency between the monomer concentration and transfer agent concentration. The uncoupling in other embodiments may also be varied leading to multiple desirable effects.
Claims13
A tubular polymerization reactor apparatus comprising:
- a) a source of fresh monomer;
- b) first and second compressor stages for compressing monomer;
- c) a reactor tube;
- d) multiple feeds, spaced lengthwise along the reactor tube for supplying monomer to the reactor;
- e) multiple free-radical or catalyst injection positions spaced lengthwise along the tubular reactor for causing monomer to be converted into polymer inside the tubular reactor;
- f) separators for receiving a monomer-polymer mixture from the reactor tube and separating said mixture into a volatile monomer-rich phase and molten polymerization phase;
- g) conduits for recycling the monomer-rich phase to the first and/or second compressor stages for recycling unreacted monomer to the reactor tube;
- and
- h) a source of transfer agent for modifying the molecular weight of the polymer for compression and feeding to the reactor tube;
- wherein compressor means is provided for compressing a transfer agent rich stream separately from a transfer agent-poor monomer stream and means is provided for feeding the compressed transfer agent rich stream to a polymerization reaction zone upstream of at least one reaction zone receiving the transfer agent-poor stream containing less than 30 wt. % of the transfer agent relative to the transfer agent rich stream.
A process for the polymerization of ethylene comprising:
- combining fresh monomer and recycled monomer and compressing the combined monomer and supplying the monomer using multiple feeds to multiple reaction zones in a tubular reactor for polymerization by a free radical initiator to form a monomer-polymer mixture;
- separating the mixture into a volatile monomer-rich phase and molten polymer-rich phase;
- recycling for compression said monomer-rich phase and supplying said monomer-rich phase to the reactor;
- and
- introducing transfer agent into the reactor to modify the molecular weight of the polymer;
- wherein the transfer agent comprises a chain terminating transfer agent having a transfer coefficient of greater than 0.01, said transfer agent being in a transfer agent rich stream separately from a transfer agent-poor monomer stream of the transfer agent, to a polymerization reaction zone upstream of at least one downstream reaction zone receiving the transfer agent-poor stream comprising less than 30% of the transfer agent relative to the transfer agent rich stream so as to achieve a depletion in the concentration of the transfer agent in said at least one downstream reaction zone.
Dependencies are inferred from the claim text.