Formulating High-Performance Waterborne Epoxy Coatings Presented at a meeting of the Thermoset Resin Formulators Association Hyatt Regency Montréal September 11-12, 2006 M.J. Watkins , D.J. Weinmann, J.D. Elmore
Jan 19, 2016
Formulating High-Performance Waterborne Epoxy Coatings
Presented at a meeting of the Thermoset Resin Formulators Association
Hyatt Regency MontréalSeptember 11-12, 2006
M.J. Watkins, D.J. Weinmann, J.D. Elmore
Mythbusters
“Waterborne epoxy coatings can never match theperformance of solvent based systems”
Myth #1
Myth #2
“I know how to formulate other waterborne systems,So I can use all my current tricks and additives to formulate waterborne epoxies”
“Devil is in the Details”(and the details are in the paper)
This presentation will
1. Define achievable high performance
2. Outline general formulation techniques
Please see paper for specific recommendations
Topics
• Waterborne epoxy types
• Type 5 waterborne epoxy performance
• Stoichiometry effects
• Pot life issues
• Components (cosolvents, pigments, additives, etc.)
• Dispersing pigments
• Pigment selection
Waterborne Epoxy Types
Best Performance Non-ionic aqueous dispersions Solid resin dispersions
Primers and topcoats
Amine dispersionSolid epoxy dispersion
5
Flooring, masonry coatings
Amine dispersionLiquid or liquid
emulsion4
Low yellowing topcoats
Carboxy-functional acrylic dispersion
Liquid or solid emulsion
3
Light – to medium-duty metal primers
Water soluble amine
Solid dispersion2
Flooring, masonry coatings
Water soluble amine
Liquid or liquid emulsion
1
Typical ApplicationCuring Agent FormResin FormType
Primers and topcoats
Amine dispersionSolid epoxy dispersion
5
Flooring, masonry coatings
Amine dispersionLiquid or liquid
emulsion4
Low yellowing topcoats
Carboxy-functional acrylic dispersion
Liquid or solid emulsion
3
Light – to medium-duty metal primers
Water soluble amine
Solid dispersion2
Flooring, masonry coatings
Water soluble amine
Liquid or liquid emulsion
1
Typical ApplicationCuring Agent FormResin FormType
Type 5 Epoxy Resin DispersionType 5 Epoxy Resin Dispersion
* Brookfield, #5 spindle, 20 rpm, 25 °C.
Name:Name: EPI-REZ 6520-EPI-REZ 6520-WH-53WH-53Description: Modified 1001-Description: Modified 1001-typetypeEEW, g/eq, solids:EEW, g/eq, solids: 550 550Viscosity, cP*:Viscosity, cP*: << 3000 3000Solids, % weight:Solids, % weight: 53.0 53.0Lb./Gal:Lb./Gal: 9.0 9.0VOC Cosolvent:VOC Cosolvent: PM (<4%) PM (<4%)
Type 5 Curing Agent Type 5 Curing Agent DispersionDispersion
* Brookfield, #5 spindle, 20 rpm, 25 °C.
Name:Name: EPIKURE 6870-W-53EPIKURE 6870-W-53Description: Description: Modified polyamine Modified polyamine adductadductAHEW, g/eq, solids:AHEW, g/eq, solids: 225 225Viscosity, cP*:Viscosity, cP*: 8,000 8,000Solids, % weight:Solids, % weight: 53 53Lb./Gal:Lb./Gal: 9.1 9.1VOC Solvent:VOC Solvent: None None
Performance of White Enamels
Discernable End Discernable End PotlifePotlife
20
30
40
50
60
70
80
90
100
110
120
0 1 2 3 4 5 6Time, hours, After Mixing A + B
Vis
cosi
ty,
KU
/ 6
0° G
loss
Val
ue
60° Gloss
Viscosity
Semi-Gel
2000 Hour Salt Spray
3 mils DFT on cold-rolled steel
SB epoxy / polyamide Type 5 WB system
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
Wat
er I
mm
ers
ion
, hrs
.
J
J
J
J
0
200
400
600
800
1000
1200
IncreasingAmine:Epoxy Weight Ratio
(Solids Basis)
JJ
J
J
0
200
400
600
800
1000
1200
Sal
t S
pra
y, h
rs.
IncreasingAmine:Epoxy Weight Ratio
(Solids Basis)
Wat
er I
mm
ers
ion
, hrs
.
J
J
J
J
0
200
400
600
800
1000
1200
IncreasingAmine:Epoxy Weight Ratio
(Solids Basis)
JJ
J
J
0
200
400
600
800
1000
1200
Sal
t S
pra
y, h
rs.
IncreasingAmine:Epoxy Weight Ratio
(Solids Basis)
Effects of Epoxy/Curing Agent Effects of Epoxy/Curing Agent RatioRatio
Pen
cil
Har
dn
ess
ME
K D
ou
ble
Ru
bs
J
J
J J
B
B
BB
<6B
5B
3B
B
F
2H
J 2 Week Cure
B 24 Hour CureJ
J
J
J
0
40
80
120
160
200
240
IncreasingAmine:Epoxy Weight Ratio
(Solids Basis)
IncreasingAmine:Epoxy Weight Ratio
(Solids Basis)
Pen
cil
Har
dn
ess
ME
K D
ou
ble
Ru
bs
J
J
J J
B
B
BB
<6B
5B
3B
B
F
2H
J 2 Week Cure
B 24 Hour CureJ
J
J
J
0
40
80
120
160
200
240
IncreasingAmine:Epoxy Weight Ratio
(Solids Basis)
IncreasingAmine:Epoxy Weight Ratio
(Solids Basis)
Effects of Epoxy/Curing Agent Effects of Epoxy/Curing Agent RatioRatio
Pot Life Pot Life CharacterizationCharacterization
End of Pot LifeEnd of Pot LifeViscosity Increase Above Application LimitViscosity Increase Above Application LimitSignificant Change in Gloss (10 Units Lower at Significant Change in Gloss (10 Units Lower at
60°)60°)Decrease or Loss of Cure (Hardness)Decrease or Loss of Cure (Hardness)
Factors Affecting Pot LifeFactors Affecting Pot Life
Cosolvents
Functions• Coalescing aids• Freeze-thaw stabilizers• Leveling agents• Pigment wetters• Foam control
Performance Effects• Dry time• Gloss• Hardness development• Final film properties
• 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
Cosolvents
Cosolvents
Others – see paper for details
• Alcohols
• Aromatics
• Ketones
• Glycol ether acetates
Cosolvent Cosolvent SelectionSelection(based on results with Type 5)(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
To
tal H
anse
n S
olu
bili
ty P
aram
eter
, cg
s u
nit
s
DPNP
DPTB
EM
EE
EH
EEH
DM DE
DPDB
Boiling Point, °C
DPNBTPNB
PPh
PM
PE
PNP
PTB PNB
DPMEB
EP
Poor Coalescing
Good Coalescing
TPM
MnAK
DAA
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 )
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
Coalescence Coalescence PropertiesProperties
2 µm
Type 2 SystemAvg. surface roughness = 25X
Type 5 SystemAvg. surface roughness = 1.25X
SB EpoxyAvg. surface roughness = 1X
DefoamersDefoamers
Suppress Foam Generation During Suppress Foam Generation During Manufacturing, Filling, Tinting, and ApplicationManufacturing, Filling, Tinting, and Application
Selection ConsiderationsSelection Considerations– Empirically determinedEmpirically determined– Optimize level (avoid stability & application Optimize level (avoid stability & application
problems)problems)– Must remain active for desired shelf life Must remain active for desired shelf life – Most effective if portion added to grind & remainder Most effective if portion added to grind & remainder
to letdownto letdown– Required level is approximately 0.5% of paint volumeRequired level is approximately 0.5% of paint volume
DefoamersDefoamers
Useful Generic TypesUseful Generic TypesSilicone BasedSilicone Based Oil BasedOil Based
Possible Problems Due to Improper Choice Possible Problems Due to Improper Choice or High Use Levelsor High Use Levels
Pigment flocculationPigment flocculation IncompatibilityIncompatibility
Poor Color acceptancePoor Color acceptance Cratering (fish eyes)Cratering (fish eyes)
Poor inter-coat adhesionPoor inter-coat adhesion Water sensitivityWater sensitivity
Cure Catalysts/AcceleratorsCure Catalysts/Accelerators
Positive functionsPositive functions– Decrease time to achieve Decrease time to achieve
desired hardnessdesired hardness– Improves early solvent Improves early solvent
resistanceresistance Negative functionsNegative functions
– Shortens pot lifeShortens pot life– Decrease water & acid Decrease water & acid
resistanceresistance Most effectiveMost effective
– Tertiary Amines such as 2,4,6-Tertiary Amines such as 2,4,6-Tris(Dimethylaminoethyl)PhenTris(Dimethylaminoethyl)Phenolol
Effect of an Accelerator on Effect of an Accelerator on the Hardness Developmentthe Hardness Development
J
J
J J
B
B
B
B
<6B
5B
3B
B
F
2H
0 24 48 72
Time, Hours, After Coating
J Accelerated Control
B Control
Pen
cil H
ard
nes
s
Flash Rust Flash Rust InhibitorsInhibitors
• Occurs on ferrous substrates under high relative humidityOccurs on ferrous substrates under high relative humidity
• Effectiveness depends on % solids. Adding water can Effectiveness depends on % solids. Adding water can
reduce effectiveness.reduce effectiveness.
• Nitrite salts (Ca or K salts preferred). Nitrite salts (Ca or K salts preferred). • Several common inhibitors ineffective or incompatibleSeveral common inhibitors ineffective or incompatible
lead naphthanate lead naphthanate chromates or dichromates chromates or dichromates tertiary amines tertiary amines
• Use in curing component for stabilityUse in curing component for stability
• Minimize levels to avoid water sensitivityMinimize levels to avoid water sensitivity
Adhesion PromotersAdhesion Promoters
BenefitsBenefits– Improved substrate wetting and adhesionImproved substrate wetting and adhesion
Especially galvanized steel, cold rolled steel, and aluminumEspecially galvanized steel, cold rolled steel, and aluminum Less effective on blasted or phosphated steelLess effective on blasted or phosphated steel
– Faster cure & hardness developmentFaster cure & hardness development– Incorporate in epoxy during pigment grindIncorporate in epoxy during pigment grind– Improved corrosion resistanceImproved corrosion resistance
Chemical Structure is ImportantChemical Structure is Important– Use Use EpoxyEpoxy-functional, -functional, triethoxytriethoxy- or - or diethoxymethyldiethoxymethyl- silanes for - silanes for
best shelf stability. best shelf stability. – Aminosilanes contribute to yellowingAminosilanes contribute to yellowing– Methoxysilanes hydrolyze and give poor adhesionMethoxysilanes hydrolyze and give poor adhesion
Mar and Slip Mar and Slip AgentsAgents
May Improve Abrasion Resistance and May Improve Abrasion Resistance and Early Water ResistanceEarly Water Resistance
Useful TypesUseful Types– PolydimethylsiloxanesPolydimethylsiloxanes– Wax DispersionsWax Dispersions– Micronized Polyethylene DispersionsMicronized Polyethylene Dispersions– SiliconesSilicones
Fungicides and Mildewcides
• Generally not required for waterborne epoxy systems
• Can cause instability
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
Thixotropes / Thixotropes / ThickenersThickeners
Used for component stability and sag resistance
• Modified hydroxyethyl cellulosics
• Modified clays
• HEUR thickeners for component stability and
grind viscosity
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
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
Pigment Selection GuidelinesPigment Selection Guidelines
Low Oil and Water Low Oil and Water AbsorptionAbsorption
Low Soluble Salt ContentLow Soluble Salt Content Low Ionic CharacterLow Ionic Character Extender PigmentsExtender Pigments
– Variety of Shapes and Variety of Shapes and SizesSizes
Anti-Corrosive PigmentsAnti-Corrosive Pigments– Acceptable Water Acceptable Water
SolubilitySolubility– pH >6pH >6
Chemical Class Comments Calcium Metasilicate • Acicular shape for film strength Barium Sulfate • High density can be a problem Muscovite Mica (e.g 325 mesh waterground mica)
• Aid in moisture resistance • High oil absorption
Talc (Magnesium Silicate) • Avoid due to high viscosity Ceramic Silica-Alumina • Very low oil absorption
• Aids in pigment packing • dark color limits use to primers
Calcium Carbonate • Ionic content can be a problem China Clay (Aluminum Silicate) • May use to aid in brushability
+ recommended - not recommended
Extender Extender PigmentsPigments
• Zn-modified Al triphosphate
• 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
Corrosion Inhibitors
Corrosion Inhibitors
Not Recommended
• Ca or Ba metaborate
• Zn borate
• Zn phospho oxide complexes
High ionic character
Poor stability
Corrosion Inhibitors in Type 5 Corrosion Inhibitors in Type 5 EpoxyEpoxy
Zinc Phosphate Strontium/Zinc Calcium Phosphate Phosphosilicate
Information provided by Halox®
Corrosion Inhibitors in Type 5 EpoxyCorrosion Inhibitors in Type 5 Epoxy
Blank Calcium Phosphate Ca Phosphate + organic
Information provided by Halox®
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
Conclusions
June, 2005
What is HEXION?
Thermoset Resins