Inverse microsuspension polymerisation of aqueous acrylic acid using redox initiators

283 Pages·2017·5.84 MB·English

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Inverse microsuspension
polymerisation of aqueous
acrylic acid using redox
initiators
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• A Doctoral Thesis. Submitted in partial fulfilment of the requirements
for the award of Doctor of Philosophy of Loughborough University.
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Publisher: (cid:13)c Zuifang Liu
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I I I 111111111111111111111111
INVERSE MICROSUSPENSION
POLYMERISATION OF AQUEOUS ACRYLIC ACID
USING REDOX INITIATORS
by
ZUIFANGLIU
A Doctoral Thesis
Submitted in partial fulfilment of the requirements
for the award of
Doctor of Philosophy
of the Loughborough University
28 November, 1997
. ,..' .. '"
© by Zuifang Liu (1997)

ACKNOWLEDGEMENT
I am greatly indebted to my supervisor, Professor B. W. Brooks, for his invaluable
guidance and continuous encouragement throughout the course of research.
I wish to thank Scott Bader Company Limited for the financial support of this project.
Thanks must go to Mr. K. Cheasman and Dr. 1. Peard in Scatt Bader Company
Limited for the fruitful discussion on the experimental results.
I also wish to thank all the technicians in the Department of Chemical Engineering of
the University for their kindly help in my research. Special thanks go to Mr. A. Milne
for his help in the experimental work; to Mr. D. Smith for his valuable advice in the
development of HPLC technique; to Mr. T. Neale for his help in the construction of
temperature control system of polymerisation apparatus; to Mr. S. Graver for printing
the photographs of SEM and TEM images.
Many thanks should go to Mr. J. Bates in IPTME of the University for his help in
developing SEM and TEM techniques.
SUMMARY
In an inverse microsuspension polymerisation initiated by a redox pair, at least one
component of the redox pair must be segregated from the monomer initially to restrict
the extent of polymerisation before the dispersion is established. Normally, the
monomer and the oxidant in aqueous solution are dispersed in an oil phase, and the
aqueous reductant is separately added to start polymerisation. Thus, the reaction
system initially consists of two types of aqueous drop and the distribution of reactants
is heterogeneous in nature. In the literature, no report to date has been found
concerning the mechanistic aspects of this polymerisation process. The present work
concerns polymerisation of aqueous acrylic acid in drops that are dispersed in a
paraffinic oil and stabilised with a non-ionic surfactant. A sodium metabisulphitel
potassium bromate redox initiation system is used. Drop mixing in agitated
dispersions has been investigated by examining the aqueous drop behaviour in
simulation systems using various developed techniques. The evolution of aqueous
drop size and size distribution has been characterised throughout the course of
polymerisation using a freeze-fracture technique with electron microscope. The
variations of polymerisation rate, limiting conversion, final particle size and size
distribution have been investigated by altering several key parameters, such as
agitation intensity, volume and composition of the aqueous reductant and ways of
adding the aqueous reductant. Aqueous polymerisation of acrylic acid in a single
phase, initiated by the redox pair, has been also studied and a reaction scheme has
been proposed. Kinetic relationships for polymerisations in both an aqueous
homogeneous medium and a heterogeneous medium have been obtained and
rationalised in terms of mechanism. A new hypothesis for the polymerisation process
has been developed which differs from both conventional suspension and emulsion
polymerisations. It is believed that the polymerisation takes place in the aqueous drops
as a result of continuous simultaneous coalescence and break-up of the different types
of aqueous drops. The surfactant has important effects on the course of
polymerisation. A preliminary model has been developed for describing this specific
polymerisation process. The publications arising from the present project are listed in
Appendix VIII.
11
CONTENTS
Acknowledgements
Summary ii
List of Figures ix
List of Tables xiv
Chapter 1 INTRODUCTION 1
1.1 Definition of Terms 1
1.2 Research Background and Objective 3
1.3 Thesis Organisation 7
Chapter 2 LITERATURE REVIEW 9
2.1 Polymerisation of Acrylic Acid 9
2.2 Redox Initiators 13
2.3 Inverse Heterogeneous Polymerisation 18
2.3.1 Main Components and Their Effects 19
2.3.1.1 Monomer 19
2.3.1.2 Emulsifier (Surfactant, Stabiliser) 21
2.3.1.3 Initiator(s) 26
2.3.1.4 Dispersion Media 28
2.3.1.5 Other Components 30
2.3.2 Mechanism, Kinetics and Modelling 31
2.3.2.1 Polymerisation Using Oil-soluble Single-component Initiator 32
2.3.2.2 Polymerisation Using Water-soluble Single-component Initiator 37
2.3.2.3 Polymerisation Using Redox Initiators 38
2.3.2.4 Inverse Microemulsion Polymerisation 40
2.4 Drop Mixing in Agitated Liquid-liquid Systems 42
Chapter 3 PRELIMINARY INVESTIGATIONS ON DROP BEHAVIOUR
IN INVERSE DISPERSION 49
iii
3.1 Introduction 49
3.2 Methodology 50
3.2.1 Optical Microscopy 50
3.2.1.1 Colouring Method 51
3.2.1.2 Acid Indication Method 52
3.2.1.3 Precipitation Method 52
3.2.1.4 Limitation of Optical Microscopy 54
3.2.2 Light Scattering 57
3.2.3 Electron Microscopy 58
3.2.3.1 Transmission Electron Microscopy 58
3.2.3.2 Scanning Electron Microscopy 59
3.2.4 Viscosity Method 61
3.3 Results and Discussion 62
3.3.1 Stability ofInverse Dispersion 62
3.3.2 Addition of Pure Water to Inverse Dispersion 62
3.3.3 Evolution of Drop Size and Its Distribution 64
3.4 Conclusions 66
Chapter 4 POLYMERISATION APPARATUS AND ITS OPERATION 68
4.1 Design of Polymerisation Apparatus 68
4.1.1 Design of Reactor 68
4.1.2 Design of Stirrer and Baffles 70
4.1.3 Temperature Controlling System 78
4.2 Polymerisation in Inverse Microsuspension 80
4.2.1 Materials 80
4.2.2 Inverse Microsuspension Polymerisation Procedure 81
4.3 Polymerisation in Aqueous Solution 82
4.3.1 Materials 82
4.3.2 Aqueous Polymerisation Procedure 83
4.4 Polymerisation Monitoring 83
4.4.1 Determination of Monomer Conversion and Polymerisation Rate 83
4.4.1.1 High Pressure Liquid Chromatography 84
iv