Melt flow index determination in polymer process control
AssigneePorpoise Viscometers Limited
InventorsAlan George, Peter Harper
Life of this patent
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Abstract
Closed-loop feedback control of (continuous) catalytic polymerisation, by regulating the introduction of a Chain Transfer Agent (CTA) to a reactor, and so polymer chain length formation; through responsive (on-line) MFI determination, of a reactor polymer sample, using an MFI measurement viscometer (70) with dual measurement dies (91, 93), for extended measurement range.
Claims26
A method of closed-loop regulation of polymerization in a reactor using a chain transfer agent (CTA) to determine average polymer chain length, the method comprising the following steps:
- (a) periodically selecting, isolating, and conditioning of discrete samples of polymer output from said reactor;
- (b) measuring samples of viscometric melt flow index (MFI) values directly and on-line;
- (c) comparing a directly measured sample MFI value and a desired target reactor polymer output MFI value;
- and
- (d) periodically adjusting supply of said CTA to said reactor responsive to ongoing comparing carried out at step (c).
A polymerization reactor control apparatus, including:
- a supply of chain transfer agent (CTA) coupled to a CTA flow meter and a CTA flow regulator intermediate said supply and a reactor;
- a CTA flow comparator, coupled to a CTA concentration set point unit and to a CTA concentration controller;
- wherein discrete samples of polymer output from said reactor are periodically selected, isolated, and conditioned;
- an MFI comparator coupled to an MFI set point unit, and to a viscometer to measure samples of viscometric melt flow index (MFI) values directly and on-line;
- wherein a supply of said CTA provided to said reactor is periodically adjusted and CTA concentration of said reactor is closed-loop controlled by said CTA flow regulator as a function of sample MFI determination by said viscometer.
The polymerization reactor control apparatus;
- a funnel having an input coupled to an output of said cyclone separator;
- a ram compaction chamber coupled to an output of said funnel;
- a compaction ram, movable within said ram compaction chamber;
- a melted, coupled to said ram compaction chamber;
- a gear pump coupled to an output of said melted;
- and
- a measurement die block, coupled to an output of said gear pump;
- wherein determination of melt flow index (MFI) is carried out on sample material from said cyclone separator following collection, mixing, and temperature pre-conditioning in said funnel, said sample material being discharged into said compaction chamber, and consolidated by said compaction ram upon said melted, whereupon said gear pump delivers a conditioned sample melt stream to said die block for MFI test flow measurement.
A viscometer for MFI determination in a reactor polymerization control method that includes use of a chain transfer agent (CTA) to determine average polymer chain length by (a) periodically selecting, isolating, and conditioning discrete samples of polymer output from a reactor;
- (b) measuring samples of viscometric melt flow index (MFI) values directly and on-line;
- (c) comparing a directly measured sample MFI value and a desired target reactor polymer output MFI value;
- and (d) periodically adjusting supply of said CTA to said reactor responsive to ongoing comparing carried out at step (c);
- the viscometer including:
- a die block;
- a rotary diverter valve disposed within said die block;
- at least first and second angled capillaries defied in said die block;
- at least first and second measurement dies, selectively coupleable to a chosen one of said first and second angled capillaries so as to selectictively divert samples of polymer output by said reactor, subject to differential respective pressure heads (Px, Py);
- wherein conditioning of MFI viscometric testing can occur without interruption to measure any change in said pressure heads (Px, Py).
A polymer reactor process control method, comprising the steps of:
- applying a chain transfer agent (CTA) to a reactor to control a polymerization reaction within said reactor;
- measuring melt flow index (MFI) of a pre-conditioned sample of polymer output from said reactor;
- determining a CTA concentration correction according to a preceding sample MFI determination;
- applying said CTA concentration correction;
- measuring effect of applying said CTA concentration correction upon sampled MFI obtained at said output from said reactor;
- and
- continuing successive output sampling MFI measurement and attendant CTA flow adjustment to stabilize output of said reactor to a desired MFI target criteria.
A polymerization process control method for use with a reactor, the method including the following steps:
- controlling melt flow index (MFI) on a polymer output from said reactor,
- selecting, conditioning, and measuring successive sample from said reactor, said samples having been isolated from said reactor;
- carrying out at least one of purging and neutralizating a chain transfer action (CTA) associated with said reactor to accomplish at least one of suppressing ongoing reactivity, promoting stability of said samples, and enhancing representation of polymer output from said reactor;
- and
- subsequent to a flushing of said samples, determining MFI using at least one of a neutralizing agent, and an anti-oxidizing agent;
- wherein said determining MFI is carried out with a repetition selected from periodically and continuously such that adjustment to flow of said CTA is maintained and adjustment to conditions in said reactor and output of said polymer are controlled such that output characteristics of said polymer are substantially pre-determined.
A method to control melt flow index (MFP) in a polymer output from a reactor selected from a reactor group consisting of continuous, catalyzed, and slurry-phase, the method including the following steps:
- using and measuring a concentration of a chain transfer agent (CTA) by conducting gas chromatography on process environment within said reactor;
- measuring actual CTA flow to said reactor;
- determining MFI for a selected discrete sample of polymer output from said reactor;
- comparing sampled determined said MFI with a desired target MFI set point;
- generating from a result of said comparing a target CTA concentration set point;
- comparing actual CTA concentration, with said CTA concentration set point;
- and
- adjusting, CTA concentration in response to actual CTA concentration, actual CTA flow, and CTA concentration set point, by adjusting CTA flow to said reactor.
A method of closed loop control of melt flow index (MFI) in a continuous catalyzed polymerization process in a reactor, the method comprising the following steps:
- (a) measurement of a chain transfer agent (CTA) flow to said reactor, and adjustment of said flow directly upstream from a location of said measurement;
- (b) taking discrete samples of polymer output from said reactor, and on-line viscometric sample measurement of said MFI;
- (c) comparing sample measurement of said MFI with an MFI set-point;
- (d) using a CTA concentration controller to generate a concentration set-point using output from a comparison of said MFI;
- and
- (e) adjusting concentration of said CTA responsive to CTA concentration, to said flow, and to determinants of said set-point.
Dependencies are inferred from the claim text.