1. Formulating High-Performance Waterborne Epoxy Coatings
M.J. Watkins,
D.J. Weinmann, J.D. Elmore
Presented at a meeting of the
Thermoset Resin Formulators Association
Hyatt Regency Montréal
September 11-12, 2006

2. Mythbusters Myth #1 “Waterborne epoxy coatings can never match the
performance of solvent based systems”
Myth #2
“I know how to formulate other waterborne systems,
So I can use all my current tricks and additives to
formulate waterborne epoxies”

3. “Devil is in the Details”
(and the details are in the paper)
This presentation will
Define achievable high performance
Outline general formulation techniques
Please see paper for specific recommendations

4. Topics Waterborne epoxy types Type 5 waterborne epoxy performance
Stoichiometry effects
Pot life issues
Components (cosolvents, pigments, additives, etc.)
Dispersing pigments
Pigment selection

5. Waterborne Epoxy Types
Best Performance
Non-ionic aqueous dispersions
Solid resin dispersions

6. Type 5 Epoxy Resin Dispersion
Name: EPI-REZ 6520-WH-53
Description: Modified 1001-type
EEW, g/eq, solids:
Viscosity, cP*: < 3000
Solids, % weight:
Lb./Gal:
VOC Cosolvent: PM (<4%)
* Brookfield, #5 spindle, 20 rpm, 25 °C.

7. Type 5 Curing Agent Dispersion
Name: EPIKURE 6870-W-53
Description: Modified polyamine adduct
AHEW, g/eq, solids:
Viscosity, cP*: ,000
Solids, % weight:
Lb./Gal:
VOC Solvent: None
* Brookfield, #5 spindle, 20 rpm, 25 °C.

8. Performance of White Enamels

9. Discernable End Potlife20 30 40 50 60 70 80 90
100
110
120 1 2 3 4 5 6
Time, hours, After Mixing A + B
Viscosity, KU / 60° Gloss Value
60° Gloss
Viscosity
Semi-Gel

10. 2000 Hour Salt Spray 3 mils DFT on cold-rolled steel
SB epoxy / polyamide
Type 5 WB system
3 mils DFT on cold-rolled steel

11. Epoxy / Amine Ratio Effects on Performance
(Stoichiometry)
Higher epoxy level gave improved:
Higher curing agent level gave improved:
Pot life
Cure rate
Acid resistance
Gloss
Alkali resistance
Adhesion
Water resistance
Abrasion resistance
Humidity resistance
Solvent resistance
Corrosion resistance
Stain resistance

12. Effects of Epoxy/Curing Agent Ratio

13. Effects of Epoxy/Curing Agent Ratio

14. Pot Life Characterization
End of Pot Life
Viscosity Increase Above Application Limit
Significant Change in Gloss (10 Units Lower at 60°)
Decrease or Loss of Cure (Hardness)

15. Factors Affecting Pot Life

16. Cosolvents Functions Coalescing aids Freeze-thaw stabilizers
Leveling agents
Pigment wetters
Foam control
Performance Effects
Dry time
Gloss
Hardness development
Final film properties

17. Cosolvents Glycol ethers are most versatile
Ethylene glycol ethers are suitable
Propylene glycol ethers are preferred for
non-HAP status
Diacetone alcohol can be useful
Partition between water and resin phases
Slow and dynamic process

18. Cosolvents Others – see paper for details Alcohols Aromatics Ketones
Glycol ether acetates

19. Total Hansen Solubility Parameter, cgs units
Cosolvent Selection (based on results with Type 5) 8
8.5 9
9.5 10
10.5 11
11.5 12
12.5
100
125
150
175
200
225
250
275
300
Total Hansen Solubility Parameter, cgs units
DPNP
DPTB EM EE EH
EEH DM DE DP DB
Boiling Point, °C
DPNB
TPNB
PPh PM PE
PNP
PTB
PNB
DPM EB EP
Poor Coalescing
Good Coalescing
TPM
DAA
MnAK

20. Freeze-Thaw Resistance
Adding glycol ethers and/or alcohols
Reduces freezing point
Promotes recovery of frozen material
25-30%v of total volatiles provides resistance
to 1-3 Cycles
Examples: ethylene glycol monopropyl ether
(EP), or methanol
1:1 blend of DAA / PnB (Type 5 )

21. Liquid Resins as Alternative Coalescing Aids
Increase solids
Decrease VOC
Increase gloss
Liquid aromatic epoxy resin (e.g. EPON™ 828)
Liquid aliphatic epoxy resin (e.g EPONEX™ 1510)
Glycidyl neodecanoate (e.g. Cardura™ E10P)
Low viscosity – easy to disperse in W/B epoxy
Best performance
Improved leveling and gloss
Improved mar and early water resistance

22. Coalescence Properties
2 µm
Type 2 System
Avg. surface roughness = 25X
Type 5 System
Avg. surface roughness = 1.25X
SB Epoxy
Avg. surface roughness = 1X

23. Defoamers
Suppress Foam Generation During Manufacturing, Filling, Tinting, and Application
Selection Considerations
Empirically determined
Optimize level (avoid stability & application problems)
Must remain active for desired shelf life
Most effective if portion added to grind & remainder to letdown
Required level is approximately 0.5% of paint volume

24. Defoamers Useful Generic Types  Silicone Based  Oil Based
Possible Problems Due to Improper Choice or High Use Levels
Pigment flocculation Incompatibility
Poor Color acceptance Cratering (fish eyes)
Poor inter-coat adhesion Water sensitivity

25. Cure Catalysts/Accelerators
Positive functions
Decrease time to achieve desired hardness
Improves early solvent resistance
Negative functions
Shortens pot life
Decrease water & acid resistance
Most effective
Tertiary Amines such as 2,4,6-Tris(Dimethylaminoethyl)Phenol
Effect of an Accelerator on the Hardness Development 2H J B J F B J B B
Pencil Hardness J 3B B 5B J
Accelerated Control B
Control
<6B 24 48 72
Time, Hours, After Coating

26. Flash Rust Inhibitors
Occurs on ferrous substrates under high relative humidity
Effectiveness depends on % solids. Adding water can
reduce effectiveness.
Nitrite salts (Ca or K salts preferred).
Several common inhibitors ineffective or incompatible  lead naphthanate  chromates or dichromates  tertiary amines
Use in curing component for stability
Minimize levels to avoid water sensitivity

27. Adhesion Promoters Benefits Improved substrate wetting and adhesion
Especially galvanized steel, cold rolled steel, and aluminum
Less effective on blasted or phosphated steel
Faster cure & hardness development
Incorporate in epoxy during pigment grind
Improved corrosion resistance
Chemical Structure is Important
Use Epoxy-functional, triethoxy- or diethoxymethyl- silanes for best shelf stability.
Aminosilanes contribute to yellowing
Methoxysilanes hydrolyze and give poor adhesion

28. Mar and Slip Agents
May Improve Abrasion Resistance and Early Water Resistance
Useful Types
Polydimethylsiloxanes
Wax Dispersions
Micronized Polyethylene Dispersions
Silicones

29. Fungicides and Mildewcides
Generally not required for waterborne epoxy
systems
Can cause instability

30. Viscosity Do not over-dilute the curing agent. Can hard settle
Do not add cosolvent to curing agent. Can destabilize
For stability, component viscosity >65 KU at 25°C
DO NOT use latex viscosity control agents
Often neurtalized with NH3 or amines
React with epoxy
Viscosity build, gel or coagulation & pigment kick-out

31. Thixotropes / Thickeners
Used for component stability and sag resistance
Modified hydroxyethyl cellulosics
Modified clays
HEUR thickeners for component stability and grind
viscosity

32. Dispersing Pigments Disperse pigments, modifying resins, & additives
directly into the epoxy resin dispersion
Water-only pigment dispersions may use too much
surfactant & give poor performance
Dispersing pigments in W/B curing agent may lead
to poor stability
Can disperse pigments in low viscosity polyamide.
Then let down with W/B curing agent

33. Pigments Dispersants Use in grind for epoxy resin dispersion stability
Useful Dispersant Types
Non-ionics, e.g. poly(ethylene oxide) types best
Neutralized acid-functional acrylics – risky
Avoid ionic dispersants (cause gel and kick-out)
Primary Uses
Pre-wetting pigments when grinding in epoxy
Stabilize dispersion during storage

34. Pigment Selection Guidelines
Low Oil and Water Absorption
Low Soluble Salt Content
Low Ionic Character
Extender Pigments
Variety of Shapes and Sizes
Anti-Corrosive Pigments
Acceptable Water Solubility
pH >6

35. Extender Pigments
+ recommended not recommended

36. Corrosion Inhibitors Zn-modified Al triphosphate
Sr phosphosilicate
Zn phosphate
Zn phosphate complex
Ca phosphosilicate
Ca ion-exchange silica
Al-Zn phosphate hydrate
Zn/silicate-modified Al triphosphate

37. Corrosion Inhibitors Not Recommended Ca or Ba metaborate Zn borate
Zn phospho oxide complexes
High ionic character
Poor stability

38. Corrosion Inhibitors in Type 5 Epoxy
Zinc Phosphate Strontium/Zinc Calcium Phosphate
Phosphosilicate
Information provided by Halox®

39. Corrosion Inhibitors in Type 5 Epoxy
Blank Calcium Phosphate Ca Phosphate
+ organic
Information provided by Halox®

40. Conclusions Realities – Not Myths
High-performance waterborne epoxy coatings can
be formulated which match or exceed solvent
based coatings at attractively low VOC
In order to achieve high performance, components
and formulating techniques specific to waterborne
epoxy must be used

41. What is HEXION?
Thermoset Resins
June, 2005