Table Of ContentEMULSION POLYMERIZATION
OF VINYL ACETATE
Papers based on a symposium on Emulsion Polymerization of Vinyl Acetate
held between 10 and 11 April 1980 at the Emulsion Polymers Institute,
Lehigh University, Bethlehem, Pennsylvania, USA
Emulsion Polymerization
of Vinyl Acetate
Edited by
MOHAMED S. EL-AASSER
and
JOHNW. VANDERHOFF
Co-directors,
Emulsion Polymers Institute, Lehigh University,
Bethlehem, Pennsylvania, USA
APPLIED SCIENCE PUBLISHERS
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APPLIED SCIENCE PUBLISHERS, INC.
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British Library Cataloguing in Publication Data
Emulsion polymerization of vinyl acetate.
1. Vinyl polymers -Congresses
2. Polymers and polymerisation-Congresses
I. El-Aasser, Mohamed S.
II. Vanderhoff, John W.
547'.28 QD281.P6
ISBN-13: 978-94-009-8116-4 e-ISBN-13: 978-94-009-8114-0
DOl: 10.1 007/978-94-009-8114-0
WITH 65 TABLES AND 108 ILLUSTRATIONS
© APPLIED SCIENCE PUBLISHERS LTD 1981
Softcover reprint of the hardcover 1s t edition 1981
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Introduction
It is particularly appropriate that this symposium on the emulsion polymeriza
tion of vinyl acetate was held in recognition of the industrial importance of
poly(vinyl acetate) and vinyl acetate copolymers, and their rather unique
properties among emulsion polymers in general. Poly( vinyl acetate) latexes
were the first synthetic polymer latexes to be made on a commercial scale:
their production using polyvinyl alcohol as emulsifier began in Germany
during the mid-1930s and has continued to the present day, growing steadily
with the years. Indeed, poly(vinyl acetate) latexes prepared with polyvinyl
alcohol are still one of the mainstays of the adhesives industry. With the
passing of time, however, vinyl acetate copolymers have been developed:
copolymers with maleate esters such as dibutyl maleate, acrylate esters such as
ethyl acrylate and butyl acrylate, versatic acid esters, and, more recently,
ethylene. These versatile copolymers have found increasing use in more
sophisticated adhesives with specialized properties, adhesives for clay coatings
on paper, carpet backing, and interior and exterior paints. Thus more than
45 years after the first commercial production of vinyl acetate latexes, their
use is still growing, both in actual quantities and different applications.
The industrial importance of vinyl acetate latexes makes the mechanism
and kinetics of their emulsion polymerization of practical as well as scientific
interest. However, little work was done on this subject outside industrial
circles, and although vinyl acetate latexes were the first to be produced com
mercially, it was the butadiene-styrene copolymer latexes that provided the
stimulus for development of the mechanism and kinetics of emulsion poly
merization. The forced development of these copolymers in the Office of
Rubber Reserve Program of World War II, not only resulted in the rapid
development of emulsion polymerization processes to make synthetic rubber,
but also gave the first coherent account of the mechanism by emulsion poly-
v
vi INTRODUCTION
merization that produces latex polymer particles of ca. O·lllm from monomer
droplets of 1-10 Ilm. This was the concept of initiation of polymerization in
monomer-swollen emulsifier micelles advanced by Harkins1 and developed
quantitatively by Smith and Ewart? This latter theoretical development, with
its succ~ssful use of the Smith-Ewart Case 2 in explaining the emulsion poly
merization of styrene, stimulated research in many other monomers. It was
soon found that the Smith-Ewart Case 2 fitted the emulsion polymerization
of styrene in only a narrow range of conditions and fitted the emulsion poly
merization of other monomers even more poorly. However, the stimulus
provided by the simplicity of the resulting kinetic equations resulted in the
investigation of many other monomers, including vinyl acetate.
The early workers (French3 and O'Donnell et al.4) interpreted their
results for vinyl acetate in terms of the Smith-Ewart Case 2, but their
conversion-time curves were determined gravimetrically, with relatively few
points which could be well represented by a straight line. Thus these data
were interpreted in accord with the initiation-in-micelles hypothesis despite
some evidence to the contrary in industrial circles. Certainly, the traditional
polyvinyl alcohol emulsifier did not lend itself well to interpretation in terms
of concentrations above and below the critical micelle concentration.
Soon, however, PriestS pointed out for vinyl acetate, as did Jacobi6 for
vinyl chloride, that initiation in micelles did not fit the experimental evidence
and proposed that initiation occurred in the aqueous phase. Initiation in the
aqueous phase was not considered important in the emulsion polymerization
of styrene, but vinyl acetate is about 100 times more soluble in water than
styrene, so that a primary radical formed in the water phase could add
monomer units much more readily. These oligomeric radicals thus formed
would grow until they reached their solubility limit in water and then precipi
tate to nucleate a latex particle. In some cases, these particles upon precipitation
would be destabilized and flocculate with other such particles or with particles
formed earlier.
This concept was expanded and confirmed experimentally by Stannett
et al., 7 Napper and Alexander,S and Dunn and Tylor.9
At the same time, the hypothesis of initiation in the adsorbed emulsifier
layer was developed by Medvedev,lO and some time later the hypothesis of
initiation in small monomer droplets was proposed.ll At one time or another,
all four of these mechanisms of particle initiation-monomer-swollen micelles,
aqueous phase, adsorbed emulsifier layer, and monomer droplets-have been
proposed to explain the experimental results obtained for vinyl acetate.
Indeed, vinyl acetate differs from other monomers in other respects than
its solubility in water: it has a high equilibrium monomer-polymer swelling
INTRODUCTION vii
ratio (values as great as 7 : 1), it has a high transfer constant (ca. 10-3 as com
pared to ca. 10-4 for styrene), and its radical has a strong tendency to abstract
hydrogens from previously formed poly(vinyl acetate) to form branches.
The poly(vinyl acetate) also differs from other polymers. Although gener
ally hydrophobic, it shows some hydrophilic characteristics. It can be solu
bilized in emulsifier solutions, a process that is still not well understood and
whose significance at the earlier stages of emulsion polymerization has not
yet been fully taken into account. Moreover, in the presence of water, it can
hydrolyze to form vinyl alcohol units, which makes the poly(vinyl acetate)
particle, slightly hydrolyzed in this way, somewhat self-stabiliZing in the
absence of emulsifier.
Papers presented on these various aspects of vinyl acetate emulsion poly
merization and the properties and behavior of poly(v inyl acetate) latexes have
usually been presented in symposia and publications dealing with other types
of emulsion polymers. Because these properties are significantly different
from those of other emulsion polymers and because poly(vinyl acetate) has
such strong industrial importance, this symposium was organized to gather
together those who are working in this field, to exchange ideas, to review
progress, to formulate hypotheses, and to determine areas of agreement as
well as areas of disagreement; it is fitting that a symposium was held solely
to discuss those unique properties and problems of vinyl acetate. It is hoped
that the papers presented at the symposium, which are collected in this
volume, will indeed represent the current thinking on vinyl acetate systems
and furnish a starting point for the development of a unified theory which
will reconcile all parameters of vinyl acetate emulsion polymerization with
those of other monomers.
J. W. Vanderhoff
M. S. EI-Aasser
REFERENCES
1. W. D. Harkins,l. Am. Chem. Soc., 69, 1428 (1947).
2. W. V. Smith and R. H. Ewart, J. Chem. Phys., 16,592 (1948).
3. D. M. French,J. Polym. Sci., 32,395 (1958).
4. J. T. O'Donnell, R. B. Mersobian and A. E. Woodward, J. Polym. Sci.,
28, 171 (1958).
5. W. J. Priest,J. Phys. Chem., 56,1077 (1952).
6. B. Jacobi, Angew. Chem., 64,539 (1952).
viii INTRODUCTION
7. V. T. Stannett, M. Litt and R. Patsiga,J. Phys. Chern., 64,801 (1960).
8. D. H. Napper and A. E. A1exander,J. Polyrn. Sci., 61, 127 (1962).
9. A. S. Dunn and P. A. Ty1or, Makrornol Chern., 83,207 (1965).
10. S. S. Medvedev, Proc. Int. Syrnp. Macrornolek. Chern., Prague, 1957,
London and New York, Pergamon Press, p. 174.
11. 1. Uge1stad, M. S. E1-Aasser and 1. W. Vanderhoff,J. Polyrn. Sci., Polyrn.
Letts., 11, 503 (1973).
Contents
Introduction. v
List of Contributors xi
1. Frontiers Between Theory and Industrial Practice in Vinyl Acetate
Polymerizations
Henry Warson
2. The Polymerization of Aqueous Solutions of Vinyl Acetate 11
A. S. Dunn
3. Effects of Particle Number and Initiator Level on the Kinetics of
Vinyl Acetate Emulsion Polymerizations 31
Richard L. Zollars
4. Synthesis Kinetics and Characterization of Poly(Vinyl Acetate)-
Molecular Weight and Long Chain Branching Development 49
A. E. Hamielec
5. Some Surface Chemical Effects on the Capture of Free Radicals-A
Kinetic Parameter Analysis of the LPS Model 63
A. Klein and V. T. Stannett
6. The Reinvestigation of Vinyl Acetate Emulsion Polymerization (1)-
The Rate of Polymerization . 89
K. H. S. Chang, M. H. Litt and M. Nomura
ix
x CONTENTS
7. The Reinvestigation of Vinyl Acetate Emulsion Polymerization
(11)-The Induced Decomposition of Initiator 137
M. H. Litt and K. H. S. Chang
8. The Reinvestigation of Vinyl Acetate Emulsion Polymerization
(lII)-Isotope Effect 159
M. H. Litt and K. H. S. Chang
9. The Radiation Induced Emulsion Polymerization of Vinyl Acetate 173
V. T. Stannett, R. R. Challa, J. H. Drew and E. P. Stahel
10. The Stabilization ofPoly(Vinyl Acetate) Latexes by Polymethacrylic
Acid . 191
W. E. Daniels, J. W. Vanderhoff, C. T. Enos, J. G. Iacoviello,
S. M. Ahmed and J. Frost
11. Particularities of Emulsion Polymerization of Vinyl Acetate in the
Presence of Hydroxyethylcellulose . 203
D. Donescu, Kristiana Go~a, I. Diaconescu, Magdalena Mazare
and Nicoleta Carp
12. Preparation, Characterization and Properties of Vinyl Acetate-
Butyl Acrylate Copolymer Latexes. 215
M. S. EI-Aasser, T. Makgawinata, S. Misra, J. W. Vanderhoff,
C. Pichot and M. F. Llauro
13. Some Studies on Vinyl Acrylic Latex-Surfactant Interactions 253
B. R. Vijayendran, T. Bone and C. Gajria
Index . . 285
