Continuous Emulsion Polymerization as Alternative for Industrial Batch Processes

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Continuous Emulsion Polymerizationas Alternative
for Industrial Batch Processes

• Multi Disciplinary Project Group 1

Ard Koeken Maurice Warnier Raoul Martens Sander
Peeters Tim Baks (speaker) Twan van Veggel
(speaker)

Eindhoven, 6 March, 2001
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Contents

• Objectives
• Introduction
• Introduction on Emulsion Polymerization
• Conventional (Semi-)Batch Reactor System
• Seed Reactors
• Main Reactor Configuration
• On-line Monitoring
• Conclusion
• Recommendations
• Questions

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Objectives
Objective of this project is to investigate the
possibility of switching from relatively large
(semi-) batch processes to smaller continuous
processes for the production of latexes on
industrial scale
(Nomura, 1986)
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Introduction

• Emulsion polymerization
• Homopolymerization of styrene
• Copolymerization of styrene and butylacrylate
• Latex product, feed-stock for paint industry
• 40,000 metric tonnes/yr
• Flexibility
• Small particle size distribution
• High monomer conversion
• Solids content of end product 50
• Average composition of copolymer chains 1 to 1
  molar ratio

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Introduction on Emulsion Polymerization (1)

• Three different stages
• Nucleation of particles
• Particle growth in presence of monomer droplets
• Particle growth in absence of monomer droplets

(Thoenes, 1991)
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Introduction on Emulsion Polymerization (2)

• Smith-Ewart Case II
• Poor water-solubility of monomers
• Ñ equals 0.5
• Radical desorption rate is negligible
• Penultimate Unit Model
• Propagation rate depends on ultimate and
  penultimate unit in active chain
• Eight different propagation steps

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Conventional (Semi-)Batch Reactor System

• Two tanks each 30 m3
• Batch cycle time 5-12 hr (incl. cleaning)
• Flexible
• Reactor Fouling
• Heat transfer (small A/V ratio)
• Outside cooling-loop
• Well-established design rules available

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Seed ReactorsGeneral introduction

• Formation of polymer particles separated from
  growth of polymer particles already formed
• Particle size distribution important
• Number of particles important
• Conversion less important
• Particle size less important
• Dialyses not required

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Continuous Stirred Tank Reactor

• Split-feed system
• reduce fouling by filled reactor, feed location,
  smooth surface, proper agitation, cooling jacket
• broader residence distribution
• A/V heat transfer ratio less favorable than tube
• flexibel
• easy design rules available
• off-spec min. 4 residence times

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Pulsed Packed Column Reactor

• Split system
• turbulence by pulsating membrane, prevents
  deemulsification
• reduce fouling by turbulence
• smallest residence distribution, broadening can
  be decreased by proper packing material
• good heat transfer characteristics A/V ratio,
  radial mixing due to turbulence
• flexibel?
• design rules available
• off-spec 2-3 residence times

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Pulsed Tubular Reactor

• Split feed system
• turbulence by pulsating membrane, prevents
  deemulsification
• reduce fouling by turbulence, coating
• small residence distribution compared to CSTR
• good heat transfer characteristics A/V ratio,
  radial mixing due to turbulence
• quite flexibel
• design rules available
• off-spec min. 2 residence times

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Characteristics of various seed reactors
Np,batch 2.51020
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Main Reactor Configuration

• Homopolymer styrene
• Number of particles 5.01020 m-3
• Particle size 150 nm
• End-product 50 wt solids

• Cascades of 6 CSTRs
• Size CSTR 10 m3
• Monomer conversion 95
• Temperature 50 C
• Fouling idem seed CSTR
• Total Mean Residence time 8.5 hr

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On-line Monitoring Techniques
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Conclusions

• PPC reactor has smallest Particle Size
  Distribution
• PPC has good heat transfer characteristics
• Large A/V ratio
• Radial mixing
• Seed reactor PPC
• Main reactor configuration cascade CSTRs
• Heat transfer major problem in reactor scale-up

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Recommendations

• Economic feasibility study
• Legal, safety, environmental aspects
• Fouling of reactors
• Residual monomer removal
• Parallel reactor systems offer greater
  flexibility
• PPC as seed reactor and main reactor
  configuration
• in one PPC
• two PPCs in series

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Questions