Coating Additives Antisettling agents Catalysts and driers Corrosion inhibitors Coalescing agents Coupling agents Defoamers Flatting agents Lubricants, wax Stabilizers Thickeners Crosslinking agents Dispersants Flow control agents Plasticizers Surfactants UV absorbers & stabilizers ppt00 1 1 Stabilizers for Improved Weathering Improve exterior durability Color, gloss, mechanical property retention Various types available Usually used in combination UV absorbers Preferentially absorb UV Prevent free radical formation Hindered amine light stabilizers (HALS) Quickly remove free radicals Antioxidants Reduce oxidation of polymer binder Also used to prevent skinning in can ppt00 2 2 California Polytechnic State University 1
Other Additives Flash rust inhibitors: Prevent rust during application and drying of waterborne coatings Freeze thaw stabilizers: Prevent freezing of paint and / or coagulation of coating at low temperatures Water scavengers: React with or adsorb water to make it unavailable in the coating Moisture cure urethanes Zinc rich coatings Lubricants: Improve feel, slip, mar resistance Biocides; Anti-microbials: Prevention of mildew growth in can ppt00 3 3 Recommendations for Additives Usage Keep it simple Know all the components of the coating Try to solve the performance problem without additives first Use additives only when necessary A simple formulation is easier to prepare and troubleshoot Additives solve and create problems Consult with the additive supplier ppt00 4 4 California Polytechnic State University 2
Dispersant Chemistry (-CH 2 -C-) x (CH 2 ) y - C=O O- Na + (-CH 2 -C-) x Tamol 731 C=O Tamol 850 O- Na + ppt00 5 Na + O _ Na + O _ O=P O P=O O O Na + Na + TSPP 5 Types of Surfactants: Nonionic Alkylphenol Ethoxylates (APE) Igapel, Triton Acetylenic Diols Surfynol EO/PO Block Copolymers Pluronics HO R CH CH 2 C C OH O(CH 2 CH 2 O) X H C CH3 C OH CH 2 CH CH CH 2 O CH 2 CH 2 O CH CH 2 O H a b a Provide steric stabilization in waterborne coatings Often used with anionics ppt00 6 6 California Polytechnic State University 3
Types of Surfactants: Anionic Alkyl Benzene Sulfonates Fatty Alcohol Sulfates Sodium Dodecyl Sulfate Alkylphenol Ether Sulfates Provide electrostatic stabilization in waterborne coatings ppt00 7 7 Types of Surfactants: Cationic and Zwitterionics Cationic Example: CTAB (Cetyl trimethyl ammonium bromide Pigment Dispersion Germicidal Activity Br - N+ C 16 H 33 Zwitterionic Example: N-alkyl betains Rarely used in coatings RN + ( ) 2 CH 2 COO - ppt00 8 8 California Polytechnic State University 4
Functions of Surfactants Solubilization Emulsification Wetting Dispersing Foaming and Defoaming Antistatic Activity ppt00 9 9 CMC Values of Surfactants Surfactant Alkyl Group (R) R(OCH 2 CH 2 ) 6 OH R(OCH 2 CH 2 ) 9 OH ROSO - 3 Na + C 18 C 16 Nonionics 3x10-7 9x10-6 5x10-7 2x10-7 Anionics 3x10-4 5x10-4 C 14 1x10-5 3x10-3 C 12 8x10-5 9x10-5 1x10-2 RCOO - Na + 1x10-3 3x10-3 7x10-3 2x10-2 RNH + 3 Cl - RN( ) + 3 Cl - Cationics 3x10-4 0.9x10-3 4x10-4 1.4x10-3 3.6x10-3 3.7x10-2 1.6x10-2 1.8x10-2 ppt00 10 Swarup and Schoff, POC, 23, 1-22 (1993) 10 California Polytechnic State University 5
Calculation of HLB: From Structural Group Contributions HLB = 7 + ΣH - ΣL Hydrophilic Groups Lipophilic Groups Group H Number Group L Number NaOOC - 19.0 CH- 0.47 HOOC - 2.1 CH 2 0.47 HO - 1.9 0.47 -O - 1.3 = CH - 0.47 -(CH 2 CH 2 O) - 0.36 -(CH 2 C( )HO) - 0.11 ppt00 11 Patton, Paint Flow and Pigment Dispersion, Wiley (1979) 11 HLB HLB (hydrophile-lipophile balance) is related to the proportion of hydrophilic (water loving) and lipophilic (oil loving) groups in the surfactant molecule HLB system is an indicator of how nonionic surfactants behave HLB Range Application 4-6 Water-in-oil emulsifiers 7-9 Wetting Agents 8-18 Oil-in-water emulsifiers 13-15 Detergents 10-18 Solubilizaers ppt00 12 12 California Polytechnic State University 6
Oil-in in-water emulsion Water-in in-oil emulsion ppt00 13 13 Wetting Agents Spreading Coefficient must be positive for spontaneous wetting S w/s = γ sa (γ sw + γ wa ) air water solid CH3 CH CH 2 C C C C CH 2 CH OH OH Tetramethyldecynediol Surfynol 104 bis(2-ethylhexyl)sulfosuccinate Aerosol OT ppt00 14 14 California Polytechnic State University 7
Rheology Modifiers Aqueous Cellulosics Other Carbohydrates Associative Thickeners Inorganics Non-Aqueous Organo-clays Hydrophobic Fumed Silica Castor Oil Derivatives ppt00 15 15 Inorganic Rheology Modifiers Inorganic Ultra-Fine Clays (Laponites) Other Inorganics (Smectite Clays, Attapulgite) + + Positive Edges & Negative Faces Weak Structure, Highly Shear Thinning ppt00 16 16 California Polytechnic State University 8
Cellulosic Thickeners OR H CH2 O O H ( ) HO n OR H H R = -CH2CH2OH = Hydroxyethyl R = -CH2COONa = Carboxymethyl R = - C2H5, -CH2CH2OH,= Ethyl, Hydroxyethyl R = - CH3, -CH2CH2OH,= Methyl, Hydroxyethyl ppt00 17 17 Effect of Molecular Weight on Thickening HMW LMW Shear-thinning Newtonian ppt00 18 18 California Polytechnic State University 9
Effect of HEC on Coating Viscosity 10 4 10 3 Airflex 809 / Natrosol 250HR Semi-gloss Formulation 44 Wt.%; 25 PVC with HEC 0.66Wt.% 10 2 Eta (A ) [P] 10 1 10 0 Aq. HEC 1.0Wt.% Control Formulation No Thickener 10-1 ppt00 19 10-2 10-2 10-1 10 0 10 1 10 2 10 3 R ate [s -1 ] 19 Cellulosics -Thickening Mechanisms A. Contribution to Hydrodynamic Volume B. Chain Entanglements B. LSV Viscosity HSV ppt00 20 Molecular Weight 20 California Polytechnic State University 10
Cellulosics - Thickening Mechanisms C. Depletion Flocculation Lower Total Entropy Higher Total Entropy Non-Adsorbing Polymer Causes Depletion Flocculation & Aggregation Leading to 1) Viscosity Changes 2) Phase Separation (Syneresis( Syneresis) ppt00 21 G = H - T S 21 Effect of Particle Flocculation / Aggregation on Viscosity Non-aggregated Viscosity Aggregated % Volume Solids 64 ppt00 22 22 California Polytechnic State University 11
Cellulosic Thickeners Viscosity HMW HEC MMW HEC LMW HEC LSV - Low Shear Viscosity Thickener Wt.% Viscosity HMW HEC MMW HEC LMW HEC HSV - High Shear Viscosity Thickener Wt.% ppt00 23 23 Cellulosics - Advantages & Disadvantages Advantages - Cellulosics are Low Cost Universal Thickeners Based on Natural Resources Disadvantages: Poor Leveling (High LSV; Yield Stress) Reduction of Gloss (Depletion Flocculation; Poor Leveling) Roller Spatter (Extensional Viscosity) Water Sensitivity (WSP Hydrophilicity) Bio-degradation (Enzyme Attack on beta 1-4 Linkage) Syneresis (Depletion Flocculation) ppt00 24 24 California Polytechnic State University 12
Syneresis ppt00 25 25 Associative Thickeners First Introduced to Coating Industry in Late 1970s Several Different Types Currently in the Market HEUR (Hydrophobically-Modified Ethoxylated Urethanes) HASE (Hydrophobically-Modified Alkali-Swellable Emulsions) HMHEC (Hydrophobically-Modified HEC) HMPE (Hydrophobically-Modified Polyether) HEAT (Hydrophobically-Modified Aminoplast Ether) ppt00 26 26 California Polytechnic State University 13
O( CHEM 550 Formulation of Modern Coatings Spring 2006 Associative Thickeners - HEUR Type = O R-N-C-(O-CH 2 -CH 2 ) x -[O-C-N-R -N-C-(O-CH 2 -CH 2 ) x ] n -O-C-N-R - H R, R R = C 12 12 -C 18 = O - H- H = O 18 ; R R = C 7 -C 36 ; x = 90-455; n = 1-41 = O H- ppt00 27 Acrysol QR-708 Acrysol RM-8 Acrysol RM-825 (C 12 H 25 Terminal Hydrophobes; 40,000 Approx. M.W.) Acrysol RM-2020 UCAR SCT-275 Acrysol SCT-275 (Comb-type; 100,000 Approx.. M.W.) 27 Associative Thickeners - HASE Type Acrysol TT-615 Alkali-Swellable, Associative Thickener Dispersion at High Concentration (30%) As ph increases (-CH 2 -C-) (-CH 2 -CH-) (-CH 2 -C-) C=O C=O C=O OH OC 2 H 5 O ( CH 2 CH 2 20 C 18 H 37 ppt00 28 28 California Polytechnic State University 14
10 2 Viscosities of Aq.. Thickener Solutions Aqueous Thickener Solutions Natrosol 250HR 1.0% Eta (A ) [P] 10 1 10 0 HEUR SCT-275 1.0% HASE TT-935 1.0% HEUR RM2020 4.0% 10-1 10-2 10-1 10 0 10 1 10 2 10 3 ppt00 29 R ate [s -1 ] 29 Effect of HEUR 275) Coating Viscosity SCT-275 Solution / 0.5% SCT-275 in 809 Semi-Gloss Paint 10 3 10 2 Semi-gloss Formulation 44 Wt.%; 25 PVC with Acrysol SCT275 0.5Wt.% Eta (A ) [P] 10 1 Acrysol SCT275 1.0Wt.% 10 0 10-1 10-2 10-1 10 0 10 1 10 2 10 3 R ate [s -1 ] ppt00 30 30 California Polytechnic State University 15
Comparison of HEC and Assoc. Thickeners HEC Glass, Fernando, Jongewaard, and Brown, J. Oil Colour Chem. Assoc., 67, 256 (1984) ppt00 31 31 Thickening Efficiency - HSV HEC Glass, Fernando, Jongewaard, and Brown, J. Oil Colour Chem. Assoc., 67, 256 (1984) ppt00 32 32 California Polytechnic State University 16
Associative Thickeners - HEUR Association Modes Many Association Modes Possible Depending on Molecular Architecture Adsorption Hydrophobic Ion-Dipole Self Association Intra-Molecular Inter-Molecular Mix Micelle Formation ppt00 33 33 Associative Thickeners - HEUR Association Modes Many Association Modes Possible Depending on Molecular Architecture Adsorption Hydrophobic Ion-Dipole Self Association Intra-Molecular Inter-Molecular Mix Micelle Formation ppt00 34 34 California Polytechnic State University 17
Associative Thickeners - HEUR Association Modes Many Association Modes Possible Depending on Molecular Architecture Adsorption Hydrophobic Ion-Dipole Self Association Intra-Molecular Inter-Molecular Mix Micelle Formation ppt00 35 35 Associative Thickening Mechanisms Effect of Adsorption 5nm 50nm 0 No Adsorption Viscosity 5nm Layer Adsorption % Volume Solids 64 50nm Layer Adsorption ppt00 36 36 California Polytechnic State University 18
Sensitivity of Associative Thickeners Performance Sensitivity to Formulation Variables - Major Drawback of Associative Thickeners Latex Particle Characteristics Surfactants Dispersants Cosolvents ppt00 37 37 Assoc. Thickener Sensitivity to Latex Surface Stabilization Latex Polymer Composition Particle Size(nm) Protective Colloid Non-Ionic Surfactants Anionic Surfactants Acid Monomer VAE155 Vinyl Acetate (87) Ethylene (13) VAEVCl Vinyl Acetate (36) Ethylene (24) Vinyl Chloride (39) VAE145 Vinyl Acetate (85) Ethylene (15) EVCl Ethylene (15) Vinyl Chloride (85) 155 Yes Yes No No 154 No Yes Yes Yes 145 No Yes No Yes 131 No No Yes Yes UrAcr Urethane-Acrylic 85 No No No Yes Acr All-Acrylic 130 -- -- -- -- VAcr Vinyl-Acrylic 149 -- -- -- -- ppt00 38 Fernando, Wickmann, Louie, and Chelius, ICE Proceedings, 2000 38 California Polytechnic State University 19
HEUR-2020 (1.0wt.%)/Latex (30wt.%) Aqueous Blends Viscosity (mpa s) 1.E+04 1.E+03 1.E+02 1.E+01 - VAE155; -VAEVCl + -VAE145; - EVCl -UrAcr; -Acr -VAcr 1.E+00 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Shear Rate (s -1 ) ppt00 39 Fernando, Wickmann, Louie, and Chelius,ICE Proceedings, 2000 39 Thickener Sensitivity to Dispersant Tamol 731 Addition to 0.75% Natrosol Solution 1.00E+04 Viscosity, centipoise 1.00E+03 1.00E+02 1.00E+01 1.00E+00 1.0E-2 1.0E-1 1.0E+0 1.0E+1 1.0E+2 1.0E+3 Shear Rate, s-1 0% 0.025% 0.05% 0.075% 0.1% 0.2% 0.5% ppt00 40 40 California Polytechnic State University 20
Thickener Sensitivity to Surfactant Tergitol 15S7 Addition to 0.75% Natrosol Solution 1000000 Viscosity, centipoise 100000 10000 1000 100 10 1 1.0E-2 1.0E-1 1.0E+0 1.0E+1 1.0E+2 1.0E+3 Shear Rate, s-1 0.00% 0.10% 2.00% ppt00 41 41 Associative Thickener Sensitivity to Surfactant - Example Flat (57PVC) formulations with small-particle (100nm), all-acrylic latex Surfactant type varied; amount constant (4.28x10-4 moles/100g) Tergitol NP-40 Tergitol NP-4 Thickeners added to adjust Stormer Viscosity at Target Kus 90 105 (OCH 2 CH 2 ) 4 OH (OCH 2 CH 2 ) 40 OH C 9 H 9 C 9 H 9 ppt00 42 42 California Polytechnic State University 21
Assoc. Thickener Sensitivity to Surfactant in 90 KU & 105 KU Formulations HEUR 200 HEUR 708 HEC Surfactant Wt.% KU Wt.% KU Wt.% KU NP-40 1.16 86 0.61 90 0.38 86 NP-4 0.56 89 0.40 86 0.32 80 NP-40 1.50 102 0.77 102 0.47 105 NP-4 0.77 104 0.57 100 0.43 100 ppt00 43 43 Thickener Sensitivity to Surfactant Tergitol 15S7 Addition to Acrysol 0.5% Solution 1000000 Viscosity, centipoise 100000 10000 1000 100 10 1 1.0E-2 1.0E-1 1.0E+0 1.0E+1 1.0E+2 1.0E+3 Shear Rate, s-1 0.00% 0.10% 2.00% ppt00 44 44 California Polytechnic State University 22
Thickener Sensitivity to Surfactant Tergitol 15S7 Addition to 0.5% HASE 935 Solution Viscosity, centipoise 200000 150000 100000 50000 0 Shear Rate,s -1 0.08 8.00 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 7000 6000 5000 4000 3000 2000 1000 0 Tergitol Concentration ppt00 45 45 Thickener Sensitivity to Surfactant Polymer / surfactant complex formation ppt00 46 46 California Polytechnic State University 23
Tint Base Viscosity - Discussion Viscosity of a Tint-Base containing associative thickeners is highly sensitive to colorants Light colors vs deep tones This is related to assoc. thickeners sensitivity to surfactants Approaches to address the problem Over-thicken tint base Use thickener blends New class of assoc. thickeners [Steinmetz, FSCT Symposium on Waterborne Coatings: Meeting the Challenges, May, 2002] ppt00 47 47 Thickener Sensitivity to Dispersant Tamol 731 Addition to 0.5% Acrysol Solution 1.00E+05 Viscosity, centipoise 1.00E+04 1.00E+03 1.00E+02 1.00E+01 1.00E+00 1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 Shear Rate, s-1 0% 0.025% 0.05% 0.075% 0.1% 0.2% 0.5% ppt00 48 48 California Polytechnic State University 24
O( CHEM 550 Formulation of Modern Coatings Spring 2006 Associative Thickeners - HASE Type Acrysol TT-615 Alkali-Swellable, Associative Thickener Dispersion at High Concentration (30%) As ph increases (-CH 2 -C-) (-CH 2 -CH-) (-CH 2 -C-) C=O C=O C=O OH OC 2 H 5 O ( CH 2 CH 2 20 C 18 H 37 ppt00 49 49 Thickener Sensitivity to Dispersant increase ph add dispersant poly (sodium methacrylate) Acrysol TT-615 Alkali-Swellable, Associative ppt00 50 50 California Polytechnic State University 25