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1. Homepage : http://www.nanotech.or.kr Resin-Fortified Emulsion Polymerizations Doug-Youn Lee (polylab1@yonsei.ac.kr) Nanosphere Process & Technology Laboratory Department of Chemical Engineering, Yonsei University

2. Emulsion Polymerization • Production • Billions of metric tons/year • Advantages • - High rate of polymerization • - High molecular weights • - Low viscosity • - Excellent heat transfer • - High conversions • - Continuous production possibility

3. Applications of Latexes • Synthetic elastomer • Surface coatings • Adhesive • Carpet backing • Paper additives & coatings • Well-characterized monodisperse particle for fundamental colloid research • Medical uses • Diagnostic test • Smart bombs • Pore size measurements • Electron microscope calibration standards • Mortar reinforcement

4. Drawbacks of Emulsion Polymers • Wetting and adherency problems • Low gloss or mudcaking of resulting films • Mechanical instability • Freeze-thaw instability • Shear thinning property • Poor physical properties of the resulting films Disadvantage of Surfactants • Poor water and corrosion resistance of resulting films • Poor adhesion especially to metal surfaces

5. Resin-Fortified Emulsion Polymers • Fine particle size emulsions • Excellent film property • High gloss property • Newtonian-like rheological property • Excellent mechanical stability and • freeze-thaw stability • Excellent wetting property Resin-fortified Emulsion Latex • Emulsion Polymer • High Molecular Weight • Toughness • Mechanical Strength • Low Mw Resin • Stability • Physical properties • Alkali Dispersibility • Gloss • Crosslinkability • etc.

6. Resin-Fortified Emulsion Polymerization Aggregate of Fuctional Resins in Aqueous Phase Resin-Fortified Latex Particles Fig. Schematic Representation of Emulsion Polymerization of Styrene in the Presence of Carboxylated Alkali-Soluble Resin.

7. Alkali-Soluble Resin (ASR) • Type of ASRs • - Acrylic Resin (St/AMS/AA or BA/AA etc.) • - SMA (Styrene Maleic Anhydride) Resin • - EAA (Ethylene Acrylic Acid) Resin • - Polyurethane Resin, etc. • Number Average Molecular Weight : 500 - 20,000 • (Preferably : 2,000 - 4,000) • Acid Number : 50 - 300 • Soluble or Dispersible in Water or Alkali • Useful as Emulsifier, Leveling agent, and Film-former • *acid number: the number of mg of KOH required to neutralize 1g of resin

8. Acrylic Resin • Low Mw Polymer Containing Carboxyl Groups • - poly(styrene/alpha-methylstyrene/acrylic acid) (SAA) • (St : AMS : AA = 35 : 33 : 32) • - Mn : 4,300 , Mw : 8,600 , PDI : 2.0 • Acid Number : 190 • Tg : 115 oC • Soluble in water and amine or alcohol, etc • Useful as emulsifier, leveling agent, and • film-former • Applications • - Floor Polishing • - Adhesive • - Paper Coating & Metal Coating • - Binder & Sizing • - etc. Fig. Schematic Representation of Low MW SAA.

9. Properties and Characteristics of SAA • Pigment Dispersion • High Gloss & Excellent Clarity • Transfer Property & Printability • Solublility - soluble in water and amine or alcohol, MEK etc. • Compatibility - excellent compatibilty with styrene-acrylic emulsions, as well as SMA and maleic resins. • Viscosity Stability • Applications - multi-functional properties in water and solvent based ink and coatings. - source of carboxyl functionality so that inks and coatings can be further crosslinked to provide heat and chemical resistance.

10. SAA Resin-Fortified Emulsion Polymer System • Excellent stability and physical properties • System having most of the advantages of both bulk and emulsion polymer system without their disadvantages • Fine particle size emulsions • Excellent film property • High gloss property • Newtonian-like rheological property • Excellent mechanical stability and • freeze-thaw stability • Excellent pigment dispersity and • wetting property Latex Particle

11. SAA Resin-Fortified Emulsion Polymer System Fig. TEM photographs of PMMA latex prepared with 35 wt % of SAA.

12. Applications of SAA Resin-Fortified Polymer System • Graphic Art • Ink Binder • Pressure Sensitive Adhesive - Excellent adhesion • Paper Coating - High gloss property - Crosslinkable W. J. Blank, R. E. Layman, US patent 4,151,143 (1979) S. L. Tsaur, US patent 4,820,762 (1989) G. R. Frazee, US patent 4,845,149 (1989)

13. Resin-Fortified PSA Formulation Table Basic Recipe of PSA in the Presence of ASR Components Wt % D.D.I Water 49.14 Alkali-Soluble Resin(ASR) [poly(BA(70%)/AA(30%)] Mn: 2000 11.93 Ammonium Hydroxide (NH4OH) 2.39 Nonionic Surfactant 0.48 Monomer MMA(10)/2-EHA(77)/BA(10)/TEGDA(3) 35.81 Initiator Ammonium Persulfate 0.25

14. Advantages of Resin-Fortified PSA • Excellent water resistance, tack and adhesion • Fine particle size emulsions • Emulsion viscosities which can be varied from low to high with no sacrifice in stability • Emulsion viscosities which are stable under high shear conditions in roll coating operation - Newtonian-like flow characteristics • Low foam production which is desirable in roll coating operation

15. Emulsion Polymerization Using SAA Resin

16. Aggregate Formation of SAA in Aqueous Solution 75 .8 • The increase in pyrene solubility with • SAA concentration indicated the formation • of SAA aggregates like micelles in aqueous • solution. • Also, a gradual decrease and leveling off of • surface tension indicated that SAA formed • aggreagtes. 70 .6 65 60 .4 UV Absorbance Surface Tension (dyne/cm) 55 .2 • Critical Micelle Concentration • : 10-2 wt % 50 45 0.0 -6 -5 -4 -3 -2 -1 0 10 10 10 10 10 10 10 SAA Concentration (wt%) Fig. UV absorbance of pyrene at 360nm and surface tension of SAA solution as a function of SAA concentration. (wt% based on total)

17. Excess Addition of Neutralization Agent Low Degree of Neutralization Solubilizing ability, Physicochemical Properties Degree of Neutralization (%) Effect of Neutralization Degree on Emulsion Kinetics Degree of Neutralization of SAA Resin

18. Emulsion Polymerization Using ASR as Emulsifier 1. Formation of Aggregates C O O H H O O C Important Factors determining the Characteristics of Aggregates 1. Acid Number 2. Degree of Neutralization 3. Molecular Weight & Structure 4. Temperature,…, etc. C O O H C O O H Neutralization H O O C C O O H 2. Emulsion Latexes in the Presence of ASR ASR Grafted ASR : Monomer Polymerization Swelling Core/Shell Morphology . Monomer-swollen Polymer Particle Free Radical ( j > z-mer)

19. Figure TEM photographs of PMMA latex prepared with 35 wt % of ASR: degree of neutralization of ASR; (a) 80 %, (b) 100 %.

20. Particle Size of Polystyrene Particles • The PS latex particle size decreased • with increasing the concentration of • ASR • This result was similar to that obtained • in the emulsion polymerization using • conventional surfactant Fig. Polystyrene latex particle size as a function of SAA concentration (wt % based on monomer).

21. 1st, 2nd developed solvent 10 10 Glass Box ASR ASR TLC Column PS PS & ASR-g-PS ASR-g- PS 0 0 1st Ammonia Water 2nd Toluene 1st 2nd Grafting Reaction of SAA TLC-FID Separation Technique Iatroscan MK-5 TLC/FID analyzer - This result indicated that the grafting of PS to SAA occurred during emulsion polymerization Fig. TLC-FID chromatographic scanning showing separation of the polystyrene latexes into three components; the ungrafted ASR, ungrafted polystyrene, and the ASR-grafted polystyrene.

22. Latex Particle Stabilized with SAA Stabilization Mechanism - Electrosteric Stabilization • In emulsion polymerization using SAA, • SAA containing a large number of carboxyl • groups results in electrosterically stabilized • latexes Fig. Schematic Representation of Latex ParticleGrafted and Adsorbed with Alkali-Soluble Resin.

23. Zeta-Potential of SAA-Fortified Latex Particle • SAA was adsorbed and grafted on the • surface of the final latex particle, which • resulted in small-sized carboxylated latex • The zeta potentials of final latexes • showed high values due to SAAs which • were concentrated on the surface of • latex particle Fig. pH dependence of zeta-Potential of PS Latex Particle Prepared at Different Concentration of SAA

24. Rate of Polymerization - Reaction Calorimetric Technique Measure heat of reaction, ,from reaction calorimeter Rate of Polymerization, Rp Calorimetric Conversion : heat of reaction (J/s) : calorimetric conversion : total volume of water (L) : evolution of heat of reaction : heat of polymerization of styrene (J/mol) : overall calorimetric conversion of the final latex

25. Rp in SDBS vs. SAA Systems The kinetic of emulsion polymerization using SAA and conventional ionic emulsifier was conducted to study directly any effect of SAA. • Average Partcle Size • Dn ([SDBS] = 10 wt %) = 54 nm • Dn ( [SAA] = 15 wt %) = 52 nm • Despite the almost same particle size • Rp in SAA system was lower than that • in SDBS system. • This result can be explained by the adsorp • -tion of SAA onto the latex particles, which • can influence the entry and exit of radicals. • Rp is proportional to average number of • radicals per particle. Fig. Rate of polymerization in emulsion polymerization of styrene using SDBS and SAA respectively.

26. Radical Diffusion in SDBS and SAA Systems Electrosteric Layer Monomer Swollen Polymer Particle monomeric radical monomeric radical SDBS(Anionic Surfactant) System SAA System • Thin Electrical Double Layer • Higher radical entry rate • Thicker Electrosteric Layer (Hairy Structure) • Decrease in radical entry in the electrosterically • stabilized latex is ascribed to hairy layer around • the particle surface.

27. n Calculation in SDBS vs. SAA Systems • It was assumed that the system enters • Interval III after the maximum heat of • polymerization. • Rate expression for emulsion polymn. • n for the SAA system is lower than • that for the SDBS system. • This supports that SAA has an influence • on radical entry & exit, which lowers the • average number of radicals per particle. Fig. Average number of radicals per particle ( n ) vs. conversion in emulsion polymerization of styrene using SDBS and SAA respectively.

28. Effect of SAA Concentration on Rp 54 52 50 48 Particle Size [Dn (nm)] 46 44 42 40 10 15 20 25 30 35 40 SAA Concentration • Although a decrease in particle size was • observed, the Rp decreased with increasing • SAA concentration. • This result is quite different from that of • conventional emulsion polymerization of • styrene run earlier. Fig. Rate of polymerization in emulsion polymerization of styrene for different concentration of SAA. (wt% based on monomer)

29. Radical Diffusion For Different SAA Concentrations Monomer Swollen Polymer Particle monomeric radical monomeric radical Low Concentration SAA System High Concentration SAA System • Thin electrosteric SAA Layer • Relatively higher radical entry rate • Thicker electrosteric SAA Layer • More difficult for radicals to reach the particles • This effect lowers the average number of • radicals per particle.

30. Effect of % Neutralization of SAA on Rp • With increasing the neutralization • degree of SAA, the Rp of styrene decreased. • The increase in Rp may be explained by • the solubilizing ability of SAA aggregate • and the radical entry into the particle. • As the degree of neutralization increased, • the SAA micelles of low neutralization is • less efficient in capturing radicals and solu- • bilizing the monomer. Fig. Rate of polymerization in emulsion polymerization of styrene for different degree of neutralization of SAA.

31. Emulsion Polymerization Using SAA Resins Effect of Neutralization Degree Note: Low rate of instantaneous termination or radical exit from the particle may be due to viscose and dense shell C B A Rp & n increased Rp & n increased Low Degree of Neutralization Excess Addition of Neutralization Agent Degree of Neutralization (%)

32. Effect of Electrolyte Contents on Rp • Significant increase in Rp as the electrolyte • contents increased with little change in • particle size. • Effect of electroytes • - solubilization ability of SAA aggregates • - capture efficiency of radical • The effect was explained as a consequence • of an increase in solubilization ability of • SAA aggregates and enhanced rate of radical • entry. Fig. Rate of polymerization vs. time in emulsion polymerization of styrene for different electrolyte contents. [SAA]=15 wt %(wt% based on monomer)

33. Film Formation & Properties

34. Dynamic Mechanical Property for Blend System • The spectrum shows distinct • relaxations due to immiscibility • between PBMA and SAA Fig. Dynamic mechanical properties of 10 wt% SAA-blended PBMA latex film as a function of temperature; storage modulus (E’); damping curve (tan).

35. Atomic Force Microscopy Nanoscope III AFM (Digital Instruments, Inc, USA) Figure Schematic of an atomic force microscopy (AFM) showing the force sensing cantilever.

36. AFM Images of PBMA+10%SAA Before Annealing Fig. Atomic force micrographs of PBMA latex film containing 10% SAA before annealing.

37. AFM Images of PBMA+10%SAA, 90oC for 10min Fig. Three-dimensional AFM surface images of PBMA latex film containing 10% SAA and annealed for 10 min at 90 oC.

38. ATR FTIR Spectra (A) before annealing (B) after annealing for 60 min at 90oC (A) (B) 710 to 690 cm-1 region : typical absorption peak for benzene ring 690-710 cm-1 Attenuated total reflectance FTIR: (Perkin-Elmer model 2000) Fig. ATR FTIR spectra showing the 710 to 690 cm-1 region of the air/film interface of PBMA latex film containing 10% SAA.

39. (a) Ungrafted SAA Ungrafted PBMA (b) Ungrafted PBMA SAA-g- PBMA Ungrafted SAA Grafting Reaction in Resin-Fortified Polymer System Grafting Efficiency: 50 - 80% Fig. TLC/FID chromatographic scanning curves of PBMA latex prepared with SAA ; (a) 10 wt % SAA-blended PBMA latex film, (b) 10 wt % SAA-fortified latex film.

40. Dynamic Mechanical Properties of SAA-fortified PBMA Fig. Dynamic mechanical properties of SAA-fortified PBMA latex films as a function of temperature; storage modulus (E); damping curve (tan); (a) 10 wt % of SAA, (b) 20 wt % of SAA

41. Other Resin-Fortified Systems

42. Polyurethane Resin • 1. Basic Urethane Chemistry • Polyaddition between di(poly)ol and di(poly) isocyanate group •  Segmented structure: soft and hard segments •  Various kinds of polyurethanes can be synthesized • 2. Water-soluble Polyurethane Resin • Polyurethane resins have carboxylic acids (DMPA) and they located • randomly at polymer backbone • Characteristics : • Water-dispersible or water-soluble • Low CMC and high solubilizing ability • Molecular Weight: 5,000 - 15,000; • Acid Number: 31 - 50 mg KOH/g PUR

43. Stoichiometric balance in NCO and OH values + Non-reactive polyurethane resin : PUR-750 and PUR-2000 + Excess residual NCO 2-hydroxyethyl methacrylate (HEMA) + Reactive polyurethane resin : PUR-750HEMA Preparation of Polyurethane Resins Synthetic Procedure

44.  Polyurethane Resin Aggregates PUR-750 PUR-2000 TEM Photo of Polyurethane Resins ( 30 K)  Non-reactive type polyurethane resins at 100% neutralization degree  Amorphous structure due to low Mw and low Tg Polyurethane Resin

45. [SDS]o = 5wt.%(monomer) [KPS]o = 0.93mM water [PUR750]o = 5wt.%(monomer) [KPS]o = 0.93mM water Emulsion Polymerization Using Polyurethane Resins Electron Microscopy Analysis Suggested driving forces affecting continuous nucleation 1. Low CMC and small aggregation number of the polyurethane resin 2. High solubilization ability for hydrophobic materials  Remark Self-aggregate of polyurethane molecules can be polymerization locus, even below CMC

46. Properties of Ethylene-Modified Latex Using Ethylene-Acrylic Acid Resin Ethylene-modified Latex • Emulsion Polymer • High Molecular Weight • Toughness • Mechanical Strength • EAA resin • Alkali Dispersibility • Crosslinkability • Barrier • Chemical Resistance [Mn: 18,800, acid number: 140]

47. EAA Resin-Fortified Emulsion Polymer • PAPER COATING • - Excellent water, grease and oil resistance • - Excellent adhesion • - Repulping property • - High gloss property • - Crosslinkable • - High wet strength retention • PAPER AND PAPERBOARD SATURATION AND SIZING • METAL COATING, etc.

48. Latex Particle Size with Concentration of EAA • As the concentration of EAA as a • polymeric emulsifier increases, • particle size is smaller and size • distributionbecomes narrow. • Polydispersityis affected by : • - water solubility of monomer • - concentration of EAA as a • polymeric emulsifier. Figure. Particle size and size distribution of ethylene -modified polystyrene with different EAA concentration at 140% degree of neutralization of EAA.

49. Effect of EAA Concentration on Permeability Table. Permeability of PBMA Films and Pure EAA Film. Permeabilitya (g mm/m2 day) PBMA film EMPB-E20 film EMPB-E40 film EMPB-E60 film EAA film 8.1267 4.2276 3.9046 3.5568 0.2275 a measured at 20oC and 90% RH. b % based on monomer. * All sample drying at 40oC. Figure. Permeability of ethylene-modified PBMA latex film with different EAA concentration.

50. Chemical Resistance The chemical resistance of ethylene-modified PS films is about 20 times higher than that of simple blends. Figure. Weight loss of ethylene-modified PS and the simple blends of PS/EAA as a function of EAA concentration after their immersion to methyl ethyl ketone for 5 hours.