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The Role of Thickeners in Optimising Coatings Formulation
Clemens Auschra, Immanuel Willerich, Iván García Romero, Hunter He, Robert Reichardt, Cindy Muenzenberg, Elena Martinez
ChinaCoat, December 2014
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Outline
� Rheology in waterborne coatings
� Influence of rheology modifiers and latex binder
� Interior paints: comparison of different rheology modifiers
� Rheology modifiers: new developments
� Outlook
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Importance of rheology on paint application
ICIStormerBrookfield
Controlled Stress Rheometer
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High PVC paint: typical composition
Water
FillersTiO2Binder
~35%
~18%~10%
� paint rheology is influenced by many components:� main influence by: rheology modifier, latex, pigments & their interactions
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Theory: Rheology of disperse systems
Hard sphere models
liquid
particles: latex, fillers, pigments
“Ideal“ suspension- low concentration- uniform spheres- no interactions
particle
interactions
“Real“ suspensions- different particles, size, shape,..- high concentration- with interactions
ηr =ηsuspension
ηliquid
= 1 + 2.5 Φ
ηr =ηsuspension
ηliquid
= 1 + 2.5 Φ + K Φ2
(Φ = volume fraction particles)
Paint: -> effective volume fraction Φeff of latex influenced by surface chemistry-> interaction between particles + interaction with additives:
associative rheology modifiers, dispersants, surfactants
….
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Polymer Binders
Benchmark dispersion polymer binders used in this study
Binder Region Chemistry SolidsParticle Size
(DLS)MFFT Remark
SA-1 Asia styrene / acrylate 50% 158 nm ~16°Cexcellent water resistance
& hydrolytic stability
SA-2 Asia styrene / acrylate 48% 148 nm ~24°C excellent scrub resistance
AC-3 NAFTA all acrylic 50% 126 nm ~10 °Csuitable for zero VOC paints
excellent cleanability
AC-4 Europe all acrylic 50% 198 nm ~2°Csuitable for low VOC paints
broad formulation latitude
Binder Region Chemistry SolidsParticle Size
(DLS)MFFT Remark
SA-1 Asia styrene / acrylate 50% 158 nm ~16°Cexcellent water resistance
& hydrolytic stability
SA-2 Asia styrene / acrylate 48% 148 nm ~24°C excellent scrub resistance
AC-3 NAFTA all acrylic 50% 126 nm ~10 °Csuitable for zero VOC paints
excellent cleanability
AC-4 Europe all acrylic 50% 198 nm ~2°Csuitable for low VOC paints
broad formulation latitude
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pure Latex @ 40% solids, pH = 8.5
0
100
200
300
Vis
co
sit
y [
mP
as
]
Shear rate [1/s]
binder SA-2
binder AC-4
binder AC-3
binder SA-1
Binder Chemistry Particle size
Pseudoplasticity
Index
η(0.1 s-1) / η(1000 s-1)
SA-2 styrene / acrylate 148 nm 12.4
AC-4 all acrylic 198 nm 4.2
AC-3 all acrylic 126 nm 2.6
SA-1 styrene / acrylate 158 nm 2.8
Binder Chemistry Particle size
Pseudoplasticity
Index
η(0.1 s-1) / η(1000 s-1)
SA-2 styrene / acrylate 148 nm 12.4
AC-4 all acrylic 198 nm 4.2
AC-3 all acrylic 126 nm 2.6
SA-1 styrene / acrylate 158 nm 2.8
Rheology of pure binders
� No simple correlation to latex monomer chemistry or particle size
� latex SA-2 with higher hydrodynamic effective volume fraction: Φeff
� No simple correlation to latex monomer chemistry or particle size
� latex SA-2 with higher hydrodynamic effective volume fraction: Φeff
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Rheology modifiers
Three different classes studied
Hydrophilic backbone
Hydrophobes
Alkali-soluble backboneCO2H CO2H CO2HCO2H
Associative
HASE HEUR
emulsion: pH <5
pH > 7
COO- COO- COO-
formulation:Non-Associative
ASE
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Rheology Modifiers
Benchmark low shear rheology modifiers used in this study
Rheology
ModifierChemistry Product form pH Solids
Viscosity
(mPas)
HASE
associative anionic polyacrylate
(hydrophobe modified alkali swellable
emulsion copolymer)
aqueous
emulsion~3.5 35% ~5
HEUR
associative nonionic polyurethane
(hydrophobe modified polyethyleneoxide
urethane copolymer)
aqueous
solution~7 30% ~2700
ASEanionic polyacrylate
(alkali swellable emulsion copolymer)
aqueous
emulsion~3.5 30% ~40
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Binary system: latex (40%) + rheology modifier (0.28%)
Low shear thickening efficiency
� Different response depending on latex type
� HASE most efficient
� Different response depending on latex type
� HASE most efficient
Thickening Efficiency :
TE =η(Latex + Rheology Modifier)
η(pure Latex)
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Binary system: latex (40%) + rheology modifier (0.28%)
Impact on low shear and high shear viscosity
� HASE most efficient
� HEUR more balanced
� ASE more pseudoplastic
� HASE most efficient
� HEUR more balanced
� ASE more pseudoplastic
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Associative rheology modifiers
Thickening mechanism of HEUR
How to study the interaction between colloid particles and the rheology modifier?How to study the interaction between colloid particles and the rheology modifier?
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Interactions between latex and rheology modifier
Study be electrophoretic mobility: e.g. HEUR
Mo
bil
ity
low
high
� Latex AC-4 shows weaker
interactions to HEUR
� Latex AC-4 shows weaker
interactions to HEUR
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SA-2
SA-2
SA-1
SA-1
AC-3
AC-3
AC-4
AC-4
Binary system: latex (40%) + rheology modifier (0.28%)
Thickening response of different latex versus HEUR
� Latex AC-4: relative lowthickening with HEUR
� Good response with all otherbinders
� Latex AC-4: relative lowthickening with HEUR
� Good response with all otherbinders
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White base paints used for testing of rheology modifiers
Paint A
interior matt
PVC = 68%
Paint Binterior matt
PVC = 80%
Paint Cgloss paint
PVC = 18%
Paint D
interior matt
PVC = 68%
from region Asia Asia NAFTA Europe
main binder SA-1 SA-2 AC-3 AC-4
rheology modifier in base paint nocellulosic
HECno
cellulosic
HEC
preferred rheology modifier HEUR HEURHEUR-1 (KU)
HEUR-2 (ICI)/
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Comparison: low shear thickening efficiency
Base paints + same active content rheology modifier (0.175%)
Thickening Efficiency :
TE =η(Paint + Rheology Modifier)
η(pure Base Paint)
� HASE: most efficient
� HEUR: balanced efficiency
� Paint D with lowest response
� HASE: most efficient
� HEUR: balanced efficiency
� Paint D with lowest response
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Comparison: overall thickening response
Base paints + same active content rheology modifier (0.175%)
� different response byeach base paint
� Paint D with lowest response
� different response byeach base paint
� Paint D with lowest response
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Paints adjusted with rheology modifier to KU = 100
Rheology of paints: comparison paint A versus paint B
� Low shear thickening: HASE > ASE > HEUR
� HEUR: more newtonian, more balanced
� Low shear thickening: HASE > ASE > HEUR
� HEUR: more newtonian, more balanced
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100
1000
10000
100000
1000000
Vis
co
sit
y [
mP
as
]
Shear rate [1/s]
HASE
HEUR
ASE
base paint A w/o RM
paint A paint B
10
100
1000
10000
100000
1000000
Vis
co
sit
y [
mP
as
]
Shear rate [1/s]
HASE
HEUR
ASE
base paint B w/o RM
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Levelling TestSagging Test
Paint B: application properties versus rheology
Rheology
Modifier
low shear
thickening efficiency
@ 0.1 s-1
Pseudoplasticity
index
η(0.1s-1) / η(1000s-1)
Sagging Test Levelling Test
HASE 4202 54661 no sagging poor
HEUR 824 13602 no sagging good levelling
ASE 2977 33116 no sagging poor
base paint B base paint B+ HEUR + HEUR
Paints adjusted with rheology modifier to KU = 100
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Paint B: adjusted with rheology modifier to KU = 100strain sweep @ 10 rad/s
Dynamic mechanical analysis
0.1
1
10
100
1000
0.001 0.01 0.1 1
G' an
d G
"
[
Pa
]
Strain Amplitude
base paint
HEUR ASE HASE
� Crossover points correlate to levelling performance� Crossover points correlate to levelling performance
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Novel concept: branched and hyperbranched polymer structures
Development of new nonionic rheology modifiers
Hydrophilic backbone
Hydrophobes
HEUR New concepts
� New hydrophobe structures with optimum interaction to latex surface
� Branched polymer architectures: backbone a/o hydrophobes
� New hydrophobe structures with optimum interaction to latex surface
� Branched polymer architectures: backbone a/o hydrophobes
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0.25% thickener actives in a pure acrylic dispersion
Comparison: linear versus hyperbranched HEUR
New nonionic rheology modifiers
� Hyperbranched end groups + high molecular weight:-> significant improved thickening
� Hyperbranched end groups + high molecular weight:-> significant improved thickening
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Properties HEUR 2Hyper-branched,
high molecular weightHyper-branched,
low molecular weight
Viscosity [mPa*s] 1770 2100 1750
Active [%] 1.48 0.95 0.99
Flow & Levelling 1.0 1.0 1.0
Sag [mm] 200 200 200
Flow & leveling: 0.25 = excellent, >4.0mm = badSag: 300µm = excellent, 75µm = bad
Target viscosity: 1700 mPa.s [Brookfield viscosity]
Testing in high PVC pure acrylic paint
New hyperbranched HEUR
� -> significant improved thickening efficiency� -> no compromise in levelling & sag behavior � -> significant improved thickening efficiency� -> no compromise in levelling & sag behavior
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Summary & Outlook
� Binary model systems:► Interaction between latex and rheology modifiers were studied
by rheology and correlated to electrophoretic mobility► Optimum thickener response results with “good fit” of hydrophobe
chemistry to latex surface
� Paints:► Fully formulated paints show similar trends concerning
different classes of rheology modifiers
� New rheology modifiers:► Results from model studies help to design new associative
thickeners with optimum response towards new generationlatex binders
► New hyperbranched HEUR with high efficiency
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Formulation Additives
