Vinyl Acetate Emulsion Polymerization and Copolymerization with Acrylic Monomers

320 Pages·2000·3.82 MB·English

by  Yildirim H. Erbil

Vinyl Acetate
Emulsion
Polymerization
and Copolymerization
With Acrylic
Monomers
H. YILDIRIM ERBIL
CRC Press
Boca Raton London New York Washington, D.C.
© 2000 by CRC Press LLC
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About the Author
H. Yildirim Erbil is a physical chemist with
research interest in the surface properties of poly-
mers. He obtained his B.S. in Chemical Engineer-
ing at Istanbul University in 1977; his M.S. in
Polymer Chemistry at Aston University, England
in 1978; and his Ph.D. in Physical Chemistry at
Istanbul Technical University in 1985. He worked
in the Marmara Research Center of TUBITAK
(National Research Center of Turkey) between
1978-1998, and has been the professor of Physical
Chemistry at Kocaeli University since 1998.
Dr. Erbil has published more than 30 papers
in international journals such as Journal of Phys-
ical Chemistry, Langmuir, Macromolecules, Jour-
nal of Colloid and Interface Science, Colloids Sur-
faces, Polymer, Journal of Applied Polymer
Science, Journal of Food Processing and Preservation, and Journal of Membrane
Science. He is co-author of two chapters in the CRC Handbook of Surface and
Colloid Chemistry, and is the author of Gas Permeability of Plastic Packaging (in
Turkish). He obtained a British Council Scholarship (1982-1983) to do research at
the Aston University, and has twice been awarded The Royal Society Exchange
Scholarship (1998 and 1999-2000) to do research at Nottingham Trent University,
England.
Dr. Erbil has been a consultant to several Turkish companies, including Gumus-
suyu Carpets and Tut Adhesives, and has served as a referee for a number of
international journals. He is a member of the American Chemical Society, Division
of Colloid and Surface Chemistry and the International Association of Colloid and
Interface Scientists.
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Preface
Polyvinyl acetate and vinyl acetate-acrylic copolymer latices are very important in
adhesives, paint, binders for nonwovens, paper and textile additive industries, and
many related industries. Their production is growing steadily in both actual quantities
and different applications. They also possess rather unique properties among emul-
sion polymers in general due to the high water-soluble nature of vinyl acetate
monomer, its high monomer-polymer swelling ratio, and its high chain transfer
constant. However, little work has been done on this subject outside of industrial
laboratories, and comparatively few publications have been made in scientific peri-
odicals. These publications have the disadvantage of presenting fragments of the
field and never the total picture. Although many well-written texts have appeared
on general emulsion polymerization in past years, no monograph devoted to poly-
vinyl acetate based latices has been published; there is only a symposium proceeding
edited by M. S. El-Aasser and J. W. Vanderhoff in 1981. The need for an introductory
and clear text in the field for visitors from industry or university students is quite
evident.
The main objective of this book is to fill the above mentioned gap and provide
a general background on understanding the mechanism and kinetics of emulsion
polymerization initiated in the aqueous phase, and some of the practical problems
of the latex production. This book is written mostly for newcomers to the field. It
is designed as an introduction to research, and as a guide to anyone who wishes to
use its contents in productive work. Throughout the book, considerable attention is
devoted to experimental aspects, the contents of which should also serve as useful
reference sources.
Chapter 1 summarizes the history of emulsion polymerization in general and
the emulsion polymerization of vinyl acetate in particular. A short review of free
radical addition polymerization is also presented to help the understanding of the
kinetics of emulsion polymerization in the following chapters.
Chapter 2 presents essential concepts for the description of emulsion polymer-
ization in general and the emulsion polymerization of water-insoluble hydrophobic
monomers in particular. Inverse emulsion polymerization is also covered in this
chapter.
Homopolymerization of vinyl acetate is treated in Chapter 3. A comprehensive
survey on the open literature is conducted to enable readers to reach the related
publications directly. Branching mechanisms of vinyl acetate homopolymerization,
especially in the presence of polyvinyl alcohol protective colloid, are discussed. A
survey of the literature on radiation-induced vinyl acetate emulsion homopolymer-
ization is also presented.
Chapter 4 deals briefly with the role of the ingredients in vinyl acetate emulsion
homo- and copolymerization. The properties of vinyl acetate monomer and polymer
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and the role and the properties of initiators, emulsifiers, protective colloids, process
water, pH buffers, and ionic strength controllers are also discussed.
Chapter 5 presents the mechanism of vinyl acetate copolymerization with acrylic
ester monomers, monomer reactivity ratios, and a literature survey on the emulsion
copolymerization of vinyl acetate with selected acrylate monomers together with
the results of the comonomer and emulsifier addition strategies and morphology of
particles.
Chapter 6 reviews the most important aspects of the colloidal stability for both
homo- and copolymers. Electrostatic as well as steric stabilization mechanisms and
the reasons for undesired coagulations are discussed. Chapter 7 deals with the
experimental determination of latex properties. Chapter 8 discusses the factors affect-
ing the final properties of both homo- and copolymer latices.
Extensive references to the original literature are cited whenever possible
throughout the text. This contribution cannot claim to be completely comprehensive;
it is an attempt to join the fragments in order to see the total picture and judge the
importance of the related factors. I am greatly indebted to my colleagues who
encouraged me to write this book, and to my wife Ayse and my children for their
patience and understanding throughout its preparation.
H. Yildirim Erbil
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Contents
1 Introduction
1.1 History of Emulsion Polymerization
1.2 History of Emulsion Polymerization of Vinyl Acetate
1.3 A Short Review of the Free Radical Addition Polymerization
1.3.1 Initiation
1.3.2 Propagation
1.3.3 Termination
1.3.3.1 Biradical Coupling
1.3.3.2 Disproportionation
1.3.4 Degree of Polymerization
1.3.5 Chain Transfer
References
2 General Emulsion Polymerization
2.1 Basic Aspects
2.2 Emulsion Polymerization of Hydrophobic Monomers
2.2.1 Smith-Ewart Kinetic Theory
2.2.2 Gardon Kinetic Theory
2.2.3 Other Kinetic Effects
2.2.3.1 The Effect of Electrolyte Concentration
2.2.3.2 Effect of the Structure of the Emulsifier
2.2.3.3 The Effect of Nonionic Emulsifiers
2.2.3.4 Monomer Solubilization and the Duration
of Interval I
2.2.3.5 The Effect of Monomer-to-Water Ratio
2.2.3.6 The Effect of Temperature
2.2.3.7 The Effect of Agitation
2.2.3.8 The Effect of Conversion
2.2.3.9 Gel Effect
2.3 Inverse Emulsion Polymerization
References
3 Emulsion Homopolymerization of Vinyl Acetate
3.1 General Aspects
3.2 Literature Survey on the Mechanism of Vinyl
Acetate Emulsion Homopolymerization
3.3 Branching Mechanisms in Vinyl Acetate Emulsion
Polymerization
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3.4 Radiation-Induced Vinyl Acetate Emulsion Polymerization
References
4 Properties and Roles of Ingredients in Vinyl Acetate Emulsion
Homopolymerization
4.1 Vinyl Acetate Monomer
4.1.1 Synthesis and Manufacture of Vinyl Acetate Monomer
4.1.2 Physical Properties of Vinyl Acetate Monomer
4.1.3 Chemical Properties of Vinyl Acetate Monomer
4.1.3.1 Hydrolysis of Vinyl Acetate
4.1.3.2 Transesterification of Vinyl Acetate
4.1.3.3 Addition Reactions
4.1.3.4 Oxidation of Vinyl Acetate
4.1.3.5 Decomposition of Vinyl Acetate
4.1.3.6 Other Reactions of Vinyl Acetate
4.1.4 Inhibition of Vinyl Acetate Monomer
4.1.5 Storage and Handling of Vinyl Acetate Monomer
4.1.5.1 Bulk Storage in the Plant
4.1.5.2 Materials of Construction
4.1.5.3 Tank Cars, Trucks, and Drums
4.1.5.4 Physiological Properties
4.1.6 Analysis of Vinyl Acetate Monomer
4.2 Polyvinyl Acetate Polymer
4.2.1 Physical and Mechanical Properties
4.2.2 Solubility in Solvents and Fractionation
4.2.3 Polymer Molecular Weight Determination
by Viscometry
4.2.4 Hydrolysis
4.2.5 Mechanical and Thermal Degradation
4.2.6 Light Stability and Biological Degradation
4.3 Initiators
4.3.1 Thermal Dissociation Type Free Radical Initiators
4.3.1.1 Persulfates
4.3.1.2 Peroxides
4.3.2 Redox Type Free Radical Initiators
4.3.2.1 Persulfate–Bisulfite
4.3.2.2 Peroxide–Iron (II) Salt
4.3.3 Other Free Radical Initiators
4.3.4 Other Methods of Initiation
4.4 Water
4.5 Emulsifiers
4.5.1 Anionic Emulsifiers
4.5.1.1 Sodium Alcohol Sulfate
4.5.1.2 Alkyl Aryl Sodium Sulfonate
4.5.1.3 Dialkyl Ester of Sodium Sulfosuccinic Acid
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4.5.1.4 Fluorinated Anionic Emulsifiers
4.5.1.5 Phosphate Ester Anionic Emulsifiers
4.5.2 Cationic Emulsifiers
4.5.3 Nonionic Emulsifiers
4.5.3.1 Polyoxyethylenated Alkylphenol Nonionic
Emulsifiers
4.5.3.2 Polyoxyethylenated Alcohol Nonionic
Emulsifiers
4.5.3.3 Ethylene Oxide–Propylene Oxide Block
Copolymer Nonionic Emulsifiers
4.5.3.4 Other Nonionic Emulsifiers
4.5.4 Amphoteric Emulsifiers
4.6 Protective Colloids
4.6.1 Polyvinyl Alcohol
4.6.2 Hydroxyethyl Cellulose
4.7 pH and Ionic Strength Controllers
4.8 Others
4.8.1 Chain Transfer Agents
4.8.2 Retarders
4.8.3 Antifoams
4.8.4 Plasticizing and Coalescing Aids
4.8.5 Biocides and Fungicides
4.8.6 Antioxidants and Ultraviolet Light Absorbers
4.8.7 Latex Postadditives
References
5 Vinyl Acetate Copolymerization with Acrylic Monomers
5.1 Modification of Polyvinyl Acetate Latex Properties by
Copolymerization
5.2 Acrylic Monomers
5.2.1 Inhibition of Acrylic Monomers
5.2.1.1 Inhibitor Selection
5.2.1.2 Inhibitor Removal by Distillation
5.2.1.3 Inhibitor Removal by Washing
5.2.1.4 Inhibitor Removal by Ion-Exchange
5.2.2 Acrylic Homopolymer Properties
5.3 Copolymerization and Reactivity Ratios
5.3.1 Copolymerization
5.3.2 Copolymer Composition Equation
5.3.3 Experimental Determination of Reactivity Ratios
5.3.4 Variation of Copolymer Composition with Conversion
5.3.5 The Q-e Scheme
5.3.6 Comonomer and Emulsifier Addition Strategies
5.3.7 Effects of Comonomer Addition Rates
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5.3.7.1 Control of Copolymerization Rate
5.3.7.2 Control of Copolymer Composition
5.3.7.3 Coagulum Formation
5.4 Vinyl Acetate/Acrylic Batch and Semicontinuous Emulsion
Copolymerizations
5.5 Particle Morphology of Copolymers
5.6 Film Properties of Copolymers
References
6 Colloidal Stability of Vinyl Acetate Homo- and Copolymer Latices
6.1 Basic Phonemena
6.1.1 Electrical Double Layer Interaction Energies
6.1.1.1 Surface Charge Density
6.1.1.2 Surface Potential
6.1.2 van der Waals Interaction Energies
6.1.3 Potential Energy Curves
6.2 Steric Stabilization
6.2.1 Mechanism of Steric Stabilization
6.2.2 Steric Interaction Energy
6.2.3 Effect of the Size of Particle and Stabilizing Polymer
6.2.4 Depletion Flocculation
6.3 Coagulation of Polymer Colloids
6.3.1 Coagulation of Electrostatically Stabilized Colloids
6.3.1.1 Critical Coagulation Concentration
6.3.1.2 Effects of Organic Electrolytes
6.3.2 Coagulation of Sterically Stabilized Colloids
6.3.3 Coagulation of Colloids by Freezing and Thawing
6.3.4 Effect of a Shear Gradient on Colloid Stability
6.4 Coagulation during the Process of Particle Formation
6.5 Colloidal Stability of Vinyl Acetate Homo- and Copolymer
Latices
References
7 Experimental Determination of Latex Properties
7.1 Total Solids Content
7.2 Density
7.3 pH
7.4 Viscosity
7.4.1 Brookfield Viscometers
7.4.2 Cone-Plate and Double-Cone Viscometers
7.4.3 Rheogonimeters
7.4.4 Orifice-Type Vicometers
7.5 Surface Tension
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7.6 Mean Particle Size and Particle Size Distribution
7.6.1 Optical Microscopy — Dark Field Microscopy
7.6.2 Electron Microscopy
7.6.3 Fractional Creaming
7.6.4 Soap Titration
7.6.5 Light Scattering
7.6.6 Quasi-Elastic Light Scattering
(Photon Correlation Spectroscopy)
7.6.7 Turbidity
7.6.8 Hydrodynamic Chromatography
7.6.9 Size Exclusion Chromatography
7.7 Free Monomer Content
7.8 Coagulum Content
7.9 Mercaptan Content
7.10 Colloidal Stability
7.10.1 Chemical Stability
7.10.2 Mechanical Stability
7.11 Monomer Conversion during Polymerization
7.12 Latex Cleaning
7.13 Average Molecular Weight and Molecular Weight Distribution
7.13.1 Osmometry
7.13.2 Light Scattering Methods
7.13.3 Viscometry
7.13.4 Ultracentrifugation
7.13.5 Gel Permeation (Size-Exclusion) Chromatography
7.13.6 Field-Flow Fractionation
7.14 Graft and Cross-Linked Polymer Content
7.14.1 Graft Polymer Content
7.14.2 Cross-Linked Polymer Content
7.15 Chemical Composition of Copolymers
7.15.1 Infrared Spectroscopy
7.15.2 Nuclear Magnetic Resonance Spectroscopy
7.15.3 Pyrolysis Gas Chromatography
7.15.4 Chemical Composition Distribution
7.15.5 Monomer Sequence Distribution
7.16 Surface Tension of Dried Latex Films
7.16.1 Critical Surface Tension of Polymer
7.16.2 Surface Tension Components of Polymers
7.17 Thermal Properties of Latex Films
7.18 Mechanical Properties of Latex Films
References
8 Factors Affecting the Final Properties of Polyvinyl Acetate-
Based Latices
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