ASC Fall Conference October 18, 2016 NonMigratory Surfactants in Emulsion Polymerization By : Dr. Steven Y. Chan
Agenda Introduction Surfactants in Emulsion Polymerization NonMigratory Surfactants (NMS) Reactivity of NMS Dry Film Properties (Clear) Performance Testing in PSA Conclusion
Introduction Global Adhesives and Sealant Market by 2020 15 million metric tons/ $60 billion Waterborne Systems Replacing Solventborne as Result of VOC Directives and Legislation Majority of Waterborne Systems Utilize Emulsion Polymers WB Pressure Sensitive Adhesives at $8.5 billion by 2020 Tends to have Worse Water Resistance Presence of water sensitive materials like surfactants
Surfactants In Emulsion Polymerization Adsorption on Surface and Interfaces Particle Size Nucleation and Colloidal Stability Energy Barrier to Prevent Particle Flocculation or Coagulation D.C. Blackley Emulsion Polymerization, Theory and Practice, London: Applied Science Publishers., 1975
Conventional Surfactants Physical Adsorption via Hydrophobic Interaction (Weak) Emulsion Stability Failure Desorption of surfactant due to external stresses Shear, temperature, formulation ingredients Water Sensitivity Release of surfactant during drying/film formation Surfactant accumulation Surface effects gloss, adhesion, blocking & water resistance Bulk effects water uptake, protection, pigment binding, swelling
Non Migratory Surfactants (NMS) CoPolymerizable Surfactants Irreversibly Grafted through Covalent Linkage Strong Chemical Bond Gives Superior Colloidal Stability No Surfactant Release During Drying Homogeneous Distribution of Surfactant Improves Dry Film Properties
NonIonic NMS NonIonic Polymerizable Surfactant (NNMS) Alkenyl/Carboxyl Functional Ethoxylate Molecular Weight of 1100 (NNMS1) and 1600 (NNMS2) (EO)nX Steric Stabilizers COOH Steric Stabilization
Anionic NMS Anionic Polymerizable Surfactants (ANMS) Modified Alcohol Ethoxylate Phosphate Ester Electrostatic and Steric Stabilizer Efficient during particle nucleation and growth stage (EO) n OPO 3 H Electrostatic Repulsion
Experimental Seeded SemiContinuous Emulsion Polymerization Insitu or separate seed Neat monomer feed or preemulsion feed Process Optimization ph control to avoid aqueous phase polymerization Semicontinuous feed to avoid excessive burial of surfactant Starved feed conditions to maximize grafting
Surfactant Reactivity BA/MMA/AA, Conventional Anionic in Seed Stage, N NMS1 in PreEmulsion Unreacted Surfactant Separated from Polymer with Ultrafiltration and Quantified via HPLC 70% of NNMS1 Reacted after postcooking with monomer starved conditions Xaccum 1 0.8 0.6 0.4 0.2 End of feeding time Feed 4 hr Xsurf 4 hr Feed 2 hr Xsurf 2 hr 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Relative Time
Reactivity of ANMS BA/MMA/MAA, All ANMS Emulsion 45% Polymer Solids and 2.5 phm or 1.14wt% Surfactant on total Unreacted Surfactant Separated via Ultracentrifugation and Quantified via ICPMS Only 0.096 wt % Recovered or 8.5% >90% ANMS Reacted
NMS Effect on Reaction Kinetics 500 M. Wt., g/mole x10 3 450 400 350 300 250 200 150 100 50 Mn Mw SAT = Saturated Alcohol Ether Phosphate Allyl/Propenyl = Competitive Reactive Surfactants 0 Degradative Chain Transfer Observed for Competitive Allylic and Propenylic NMS Surfactants Resulting in Lower Molecular Weight
Surfactant Exhudation AFM of Styrene Acrylic Film Dried and Washed with Water NPE30 NNMS1 Pinholes Observed None
Transmission Haze (%) Better Water Whitening 100 90 80 70 60 50 40 30 20 10 0 0 1 24 Immersion time (hrs) ANMS R ANMS ISO Linear Linear: 1 days ANMS, KPS initiated, ANMS R, tbpb initiated vs linear and isobranched alcohol ether phosphates, all 2.5 phm ANMS : 7 days
Lower Water Transmission Rate BA/MMA/AA Latex Film High Water Diffusion Rates with Conventional Surfactant Suggest Poor Protective Properties Air Substrate Upper Lower Water Transmission Rates Lower Interface Upper Interface NPE30 14.11 183.5 SLS 13.6 103.4 NNMS1 9.84 35.77 NNMS2 13.92 34.31
Improved Water Repellency Water Runs Off much Faster from a Film Based on ANMS ANMS NaDPDS Contact Angle : ANMS = 71, Conventional = 43 for Sodium Alkyl Diphenyl Disulfonate (r)
Increased Hydrophobicity in Acrylic Emulsion Contact angle of water droplets on dried emulsion films prepared with different emulsifiers 76.2 78.4 91.4 Conventional Competitive Maxemul 6106 Higher contact angle indicates more hydrophobic film, leading to better water resistance
Lower Foam 50 ml of Emulsion in a 4 oz Jar Hand Shaken 5 times ANMS NaDPDS
NMS in PSA Shear Strength Tensile Strength (kn) or inplane Cohesion Failure Test Conditions Films obtained from a 60/40 PSA/Ethanol mix Applied on polyester substrate Cured for 5 at 120 C and 24hrs at ambient Contact area: 20mm x 20mm, 5 kg loaded for 60 sec
Max load (N) Max load (N) Improved Shear Strength Effects of Film Thickness and Polymer Composition Wet film thickness from 50 to 200 µm, dry films obtained from a 60/40 PSA/Ethanol mix Surfactant @ 3.21 phm 300 250 200 150 100 BA/MMA/MAA/HEA 300 250 200 150 100 50 0 BA/MMA/MAA Wet film thickness Allylic NPEs ANMS Wet film thickness ANMS 3.21 HEA free A3232 HEA free Higher shear strength for ANMS vs allylic NMS and conventional
Conclusion NonMigratory Surfactants are Effective in Emulsion Polymerization Chemically Grafted to Emulsion Particles Improved Performance in Dried Film Water whitening, water retention, WTR, high contact angle, lower foaming tendency Better Properties in PSA Water immersion, cohesion Improve the Performance of Waterborne Systems to the Next Level that Conventional Surfactants cannot.
Acknowledgement Jo Grade from Gouda, Netherland Nathan Noyes, New Castle, DE
Thank You!