DEFOAMING THE SCIENCE Theory, Experiment and Applications. Peter R. Garrett. CRC Press. Taylor & Francis Group, an informa business

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1 THE SCIENCE OF DEFOAMING Theory, Experiment and Applications Peter R. & CRC Press Francis Group Boca Raton London NewYork CRC Press is an imprint of the Taylor & Francis Group, an informa business

2 Contents Preface Author xxiii xxv Chapter 1 Some General Properties of Foams Introduction Structure of Foams Foam Films Surface Tension Gradients and Foam Film Stability Drainage Processes in Foam Films Disjoining Forces and Foam Film Stability Processes Accompanying Aging of Foam Capillary Pressure Gradients Foam Drainage Bubble Coarsening (Diffusional Disproportionation) Summarizing Remarks 28 Acknowledgment 29 References 29 Chapter 2 Experimental Methods for Study of Foam and Antifoam Action Introduction Measurement of Foam Bartsch Method: Hand Shaking Measuring Cylinders Automated Shake Tests Ross-Miles Method Tumbling Cylinders Gas Bubbling Direct Air Injection Measurement of Bubble Size Distributions Observations with Single Foam Films Scheludko Cells Films Containing Antifoam Drops Measurement of Disjoining Pressure Isotherms of Air-Liquid-Air Foam Films Dippenaar Cell Large Vertical Films 45 xiii

3 xiv Contents 2.4 Air-Water-Oil Pseudoemulsion Films Direct Observation of Pseudoemulsion Films Measurement of Disjoining Pressure Isotherms for Air-Water-Oil Pseudoemulsion Films Direct Measurements of Pseudoemulsion Film Rupture Pressures Spreading Behavior of Oils Summarizing Remarks 53 References 54 Chapter 3 Oils at Interfaces: Entry Coefficients, Spreading Coefficients, and Thin Film Forces Introduction Classic Entry and Spreading Coefficients Generalized Entry Coefficients, Pseudoemulsion Films, and Thin Film Forces Definitions Case Where Generalized Entry Coefficient, g > Case Where Generalized Entry Coefficient, Eg< Magnitude of Generalized Entry Coefficients Mode of Rupture of Pseudoemulsion Films Disjoining Pressures and Stability of Pseudoemulsion Films Surface Tension Gradients and Stability of Pseudoemulsion Films Generalized Spreading Coefficients and Thin Film Forces Spreading Behavior of Typical Antifoam Oils on Aqueous Surfaces Hydrocarbon Oils Spreading and Wetting Behavior of Hydrocarbons on Surface of Pure Water Complete and Pseudo-Partial Wetting Behavior of Hydrocarbons on the Surfaces of Aqueous Surfactant Solutions Non-Spreading (Partial Wetting) by Hydrocarbons on the Surfaces of Aqueous Surfactant Solutions Polydimethylsiloxane Oils Complete and Pseudo-Partial Wetting Behavior of Polydimethylsiloxanes on the Surfaces of Pure Water and Aqueous Surfactant Solutions 96

4 Contents xv Rates of Spreading of Polydimefhylsiloxanes on the Surfaces of Pure Water and Aqueous Surfactant Solutions Effect of Spread Hydrocarbon and Polydimethylsiloxane Oils on the Stability of Pseudoemulsion Films Non-Equilibrium Effects due to Surfactant Transport Summarizing Remarks 108 References 110 Chapter 4 Mode of Action of Antifoams Introduction Antifoam Effects due to Solubilized Oils Effect on Foamability of Mesophase Precipitation in Aqueous Surfactant Solutions Surface Tension Gradients and Theories of Antifoam Mechanism General Considerations Surface Tension Gradients Induced by Spreading Antifoam Elimination of Surface Tension Gradients Oil Bridges and Antifoam Mechanism Oil Bridges in Foam Films Line Tensions and Antifoam Behavior of Oil Lenses Oil Bridges in Plateau Borders and Stability of Pseudoemulsion Films Antifoam Behavior of Emulsified Liquids Antifoam Effects of Neat Oils in Aqueous Foaming Systems Early Work Short-Chain Alcohols n-alkanes Neat Polydimethylsiloxane Oils Antifoam Effects of Neat Oils in Non-Aqueous Foaming Systems Partial Miscibility and Antifoam Effects Origins of Partial Miscibility in Binary Liquid Mixtures Systems with Lower Critical Temperatures Systems with Higher Critical Temperatures 198

5 xvi Contents 4.7 Inert Hydrophobic Particles and Capillary Theories of Antifoam Mechanism for Aqueous Systems Early Work Experimental Observations Concerning Contact Angles and Particle Bridging Mechanism Theoretical Considerations Concerning Particle Geometry and Contact Angle Conditions for Antifoam Action by Smooth Particles Particles with Curved Surfaces and No Edges Particles with Edges Models of Foam Film Rupture by Particles Using Surface Energy Minimization Effect of Rugosities on Antifoam Action of Particles Rugosities and Stability of Air-Water-Solid Films Particle Size and Kinetics of Foam Film... Rupture Antifoam Effects of Calcium Soaps Melting of Hydrophobic Particles and Antifoam Behavior Mixtures of Hydrophobic Particles and Oils as Antifoams for Aqueous Systems Antifoam Synergy Early Patent Literature Role of Oil in Synergistic Oil-Particle Antifoams Early Hypotheses Concerning Role of Particles in Synergistic Oil-Particle Antifoams Role of Particles in Synergistic Oil-Particle Antifoams Experimental Observation Spherical Particles, Spread Oil Layers, and Rupture of Pseudoemulsion Films Smooth Particles with Edges in Absence of Spread Oil Layers Smooth Particles with Edges in Presence of Spread Oil Layers Rough Particles with Many Edges Antifoam Dimensions and Kinetics Summarizing Remarks 292 Acknowledgments 295 Appendix References 302

6 Contents xvii Chapter 5 Effect of Antifoam Concentration on Volumes of Foam Generated by Air Entrainment Phenomenology Introduction Dispersion of Single Antifoam Mixed Dispersions of Two Antifoams Relative Effectiveness of Antifoam Entities and Foam Structure Statistical Theory of Antifoam Action Assumptions Factors Determining Number of Antifoam Entities in Foam Film Calculation of Volume of Air in Foam in Presence of Antifoam Limitations of Theory Summarizing Remarks 336 Appendix 5.1 Effect of Excluded Volume on Antifoam Concentration in a Film Exhibiting Reynolds Drainage 338 A5.1.1 Mean Flow Velocity of Antifoam Entities 338 A5.1.2 Effect of Excluded Volume on Antifoam Concentration in a Draining Film 339 References 341 Chapter 6 Deactivation of Mixed Oil-Particle Antifoams during Dispersal and Foam Generation in Aqueous Media Introduction Deactivation of Antifoam Effect of Polydimethylsiloxane Oils without Particles Early Work with Hydrophobed Silica Polydimethylsiloxane Antifoams Separation of Silica from Oil Equilibration and Deactivation Deactivation, Emulsification, and Drop Sizes Deactivation of Hydrophobed Silica Polydimethylsiloxane Antifoam by Disproportionation Experimental Evidence Theoretical Considerations Concerning Deactivation by Disproportionation Effect of Oil Viscosity on Deactivation of Hydrophobed Silica-Polydimethylsiloxane Antifoams Deactivation in Other Types of Oil-Particle Antifoams Theories of Foam Volume Growth in Presence of Deactivating Antifoam 368

7 xviii Contents Antifoam-Bubble Heterocoalescence-Kinetic Model of Pelton and Goddard for Foam Generation by Sparging Modified Antifoam-Bubble Heterocoalescence- Kinetic Model Using a Statistical Distribution of Antifoam Drops over Bubbles Combination of Kinetic Model of Antifoam Deactivation with Kinetic Model of Antifoam Action Combination of Kinetic Model of Antifoam Deactivation by Disproportionation with Empirical Expression for Antifoam Action Summarizing Remarks 383 Acknowledgment 386 References 386 Chapter 7 Mechanical Methods for Defoaming Introduction 389 Devices Defoaming Using Rotary Designs of Rotary Devices Described in Scientific Literature Commercial Rotary Defoamers Defoaming Mechanisms of Rotary Devices Role of Centrifugal Force Role of Shear and Impact Forces on Bubbles in Mechanical Defoaming Defoaming by Inherent Liquid Spray Defoaming Using Ultrasound Brief History of Defoaming by Ultrasound Defoaming Mechanism of Ultrasound Defoaming Using Packed Beds of Appropriate Wettability Summarizing Remarks 422 Appendix References 428 Chapter 8 Antifoams for Detergent Products Introduction Powders for Machine Washing of Laundry Front-Loading Drum-Type Textile Washing Machines Use of Fatty Acids and Soaps Use of Non-Soap Particulate Antifoams Use of Hydrocarbon-Hydrophobic Particle Mixtures 441

8 Contents xix Hydrocarbon Mixtures with Alkyl Phosphoric Acid Derivatives Hydrocarbon Mixtures with Non- Phosphorous-Containing Organic Compounds Use of Polydimethylsiloxane-Based Antifoams General Properties Storage Deactivation and Incorporation in Detergent Powders Dispensing Enhancement of Antifoam Effectiveness Hydrocarbon-Based Simulation of Dimethylsiloxane-Based Antifoams Liquids for Machine Washing of Laundry General Properties Incorporation of Polyorganosiloxane-Hydrophobic Silica Antifoams in Detergent Liquids Machine Dishwashing General Hard-Surface Cleaning Products Summarizing Remarks 471 Appendix References 476 Chapter 9 Control of Foam in Waterborne Latex Paints and Varnishes Introduction Foam and Antifoam Behavior General Considerations Effect of Stratified Layers of Polymer Latex Particles on Foam and Pseudoemulsion Film Stability Specific Issues Concerning Oil-Based Antifoams Incorporation in Paints and Varnishes Defect Formation in Drying Paint Films General Considerations Experimental and Theoretical Studies of Cratering Caused by Marangoni Effect Induced by Spreading Oil Drops Putative Craters Caused by Non- Spreading Oil Drops Bridging Paint Films Summarizing Remarks 499 References 500

9 XX Contents Chapter 10 Antifoams for Gas-Oil Separation in Crude Oil Production Introduction Surface Activity at Gas-Hydrocarbon and Gas-Crude Oil Interfaces Causes of Foam Formation in Gas-Crude Oil Systems Disjoining Pressures Origin of Surface Tension Gradients at Gas-Crude Oil Interfaces Experimental Observations of Foam Behavior Use of Antifoams General Considerations Polydimethylsiloxanes and Substituted Polydimethylsiloxanes Effect of Solubility of Antifoam Oils Mode of Antifoam Action in Crude Oils Other Materials Summarizing Remarks 525 References 526 Chapter 11 Medical Applications of Defoaming Introduction Use of Simethicone Antifoam in Treatment of Gastrointestinal Gas Therapeutic Application Use of Simethicone in Endoscopy Defoaming of Blood during Cardiopulmonary Bypass Surgery Gas Bubble Oxygenators and Use of Antifoams Mechanism of Polydimethylsiloxane- Hydrophobed Silica-Coated Porous Defoamers Polydimethylsiloxane-Hydrophobed Silica Antifoam as Source of Emboli Cardiotomy Defoam ing Defoaming in Cardiopulmonary Bypass Blood Circuits, Which Include Membrane Oxygenators and Cardiotomy/Venous Reservoirs Defoaming Systems Avoiding Use of Polydimethylsiloxane-Based Antifoam Potential Replacements for PDMS- Hydrophobed Silica in Cardiotomy Reservoirs 542

10 Contents xxi Potential Use of Defoamer Elements with High Air-Blood Contact Angles Removal of Gaseous Microemboli Summarizing Remarks 549 References 551 Frequently Used Symbols and Abbreviations 555 Index 559

CHEMISTRY PHYSICAL. of FOODS INTRODUCTION TO THE. CRC Press. Translated by Jonathan Rhoades. Taylor & Francis Croup

CHEMISTRY PHYSICAL. of FOODS INTRODUCTION TO THE. CRC Press. Translated by Jonathan Rhoades. Taylor & Francis Croup Christos Ritzoulis Translated by Jonathan Rhoades INTRODUCTION TO THE PHYSICAL CHEMISTRY of FOODS CRC Press Taylor & Francis Croup Boca Raton London NewYork CRC Press is an imprint of the Taylor & Francis