CHEM 550 Formulation of Modern Coatings Spring Coating Additives

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1 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 ppt 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 ppt California Polytechnic State University 1

2 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 ppt 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 ppt California Polytechnic State University 2

3 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 ppt California Polytechnic State University 3

4 Types of Surfactants: Anionic Alkyl Benzene Sulfonates Fatty Alcohol Sulfates Sodium Dodecyl Sulfate Alkylphenol Ether Sulfates Provide electrostatic stabilization in waterborne coatings ppt 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 - ppt California Polytechnic State University 4

5 Functions of Surfactants Solubilization Emulsification Wetting Dispersing Foaming and Defoaming Antistatic Activity ppt 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 3x x10-3 4x x x x x x10-2 ppt00 10 Swarup and Schoff, POC, 23, 1-22 (1993) 10 California Polytechnic State University 5

6 Calculation of HLB: From Structural Group Contributions HLB = 7 + ΣH - ΣL Hydrophilic Groups Lipophilic Groups Group H Number Group L Number NaOOC CH HOOC CH HO O = CH (CH 2 CH 2 O) (CH 2 C( )HO) 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 Detergents Solubilizaers ppt California Polytechnic State University 6

7 Oil-in in-water emulsion Water-in in-oil emulsion ppt 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 ppt California Polytechnic State University 7

8 Rheology Modifiers Aqueous Cellulosics Other Carbohydrates Associative Thickeners Inorganics Non-Aqueous Organo-clays Hydrophobic Fumed Silica Castor Oil Derivatives ppt Inorganic Rheology Modifiers Inorganic Ultra-Fine Clays (Laponites) Other Inorganics (Smectite Clays, Attapulgite) + + Positive Edges & Negative Faces Weak Structure, Highly Shear Thinning ppt California Polytechnic State University 8

9 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 ppt Effect of Molecular Weight on Thickening HMW LMW Shear-thinning Newtonian ppt California Polytechnic State University 9

10 Effect of HEC on Coating Viscosity Airflex 809 / Natrosol 250HR Semi-gloss Formulation 44 Wt.%; 25 PVC with HEC 0.66Wt.% 10 2 Eta (A ) [P] Aq. HEC 1.0Wt.% Control Formulation No Thickener 10-1 ppt 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

11 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 ppt California Polytechnic State University 11

12 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.% ppt 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) ppt California Polytechnic State University 12

13 Syneresis ppt 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) ppt California Polytechnic State University 13

14 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 C 18 = O - H- H = O 18 ; R R = C 7 -C 36 ; x = ; 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 ppt California Polytechnic State University 14

15 10 2 Viscosities of Aq.. Thickener Solutions Aqueous Thickener Solutions Natrosol 250HR 1.0% Eta (A ) [P] HEUR SCT % HASE TT % HEUR RM % 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 Semi-gloss Formulation 44 Wt.%; 25 PVC with Acrysol SCT Wt.% Eta (A ) [P] 10 1 Acrysol SCT Wt.% R ate [s -1 ] ppt California Polytechnic State University 15

16 Comparison of HEC and Assoc. Thickeners HEC Glass, Fernando, Jongewaard, and Brown, J. Oil Colour Chem. Assoc., 67, 256 (1984) ppt Thickening Efficiency - HSV HEC Glass, Fernando, Jongewaard, and Brown, J. Oil Colour Chem. Assoc., 67, 256 (1984) ppt California Polytechnic State University 16

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 ppt 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 ppt California Polytechnic State University 17

18 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 ppt Associative Thickening Mechanisms Effect of Adsorption 5nm 50nm 0 No Adsorption Viscosity 5nm Layer Adsorption % Volume Solids 64 50nm Layer Adsorption ppt California Polytechnic State University 18

19 Sensitivity of Associative Thickeners Performance Sensitivity to Formulation Variables - Major Drawback of Associative Thickeners Latex Particle Characteristics Surfactants Dispersants Cosolvents ppt 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 VAcr Vinyl-Acrylic ppt00 38 Fernando, Wickmann, Louie, and Chelius, ICE Proceedings, California Polytechnic State University 19

20 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, Thickener Sensitivity to Dispersant Tamol 731 Addition to 0.75% Natrosol Solution 1.00E+04 Viscosity, centipoise 1.00E E E E E-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% ppt California Polytechnic State University 20

21 Thickener Sensitivity to Surfactant Tergitol 15S7 Addition to 0.75% Natrosol Solution Viscosity, centipoise E-2 1.0E-1 1.0E+0 1.0E+1 1.0E+2 1.0E+3 Shear Rate, s % 0.10% 2.00% ppt 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 (OCH 2 CH 2 ) 4 OH (OCH 2 CH 2 ) 40 OH C 9 H 9 C 9 H 9 ppt California Polytechnic State University 21

22 Assoc. Thickener Sensitivity to Surfactant in 90 KU & 105 KU Formulations HEUR 200 HEUR 708 HEC Surfactant Wt.% KU Wt.% KU Wt.% KU NP NP NP NP ppt Thickener Sensitivity to Surfactant Tergitol 15S7 Addition to Acrysol 0.5% Solution Viscosity, centipoise E-2 1.0E-1 1.0E+0 1.0E+1 1.0E+2 1.0E+3 Shear Rate, s % 0.10% 2.00% ppt California Polytechnic State University 22

23 Thickener Sensitivity to Surfactant Tergitol 15S7 Addition to 0.5% HASE 935 Solution Viscosity, centipoise Shear Rate,s % 1.0% 2.0% 3.0% 4.0% 5.0% Tergitol Concentration ppt Thickener Sensitivity to Surfactant Polymer / surfactant complex formation ppt California Polytechnic State University 23

24 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] ppt Thickener Sensitivity to Dispersant Tamol 731 Addition to 0.5% Acrysol Solution 1.00E+05 Viscosity, centipoise 1.00E E E E E E E E E E E+03 Shear Rate, s-1 0% 0.025% 0.05% 0.075% 0.1% 0.2% 0.5% ppt California Polytechnic State University 24

25 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 ppt Thickener Sensitivity to Dispersant increase ph add dispersant poly (sodium methacrylate) Acrysol TT-615 Alkali-Swellable, Associative ppt California Polytechnic State University 25