The Dispersion Triangle for Carbon Black Pigments
Transcript of The Dispersion Triangle for Carbon Black Pigments
CHALLENGE
TESTED
BEYOND
DURABLE
MICRO
MATTERS
COMPOUND
KNOWLEDGE
FAMILIAR
BONDS
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The Dispersion Triangle for Carbon Black Pigments
Richard Abbott
Natalie Harris and Josh Baugh
September 8th 2021
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Table of Contents
INTRODUCTION
DISPERSION TRIANGLE CONCEPT
PIGMENT SELECTION
FORMULATION
DISPERSION PROCESS
WHY USE THE CONCEPT ?
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Dr. RI CHARD ABBOTT
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• Pri nci pal Sci ent i s t ( Coat i ngs ) wi t h over 20 years of
worki ng wi t h carbon bl ack i n a vari et y of l i qui d sys t ems.
• Based at Bi rl a Carbon headquart ers & t echni cal cent er s i nce
2003.
• Respons i bl e f or devel opi ng new carbon bl acks and
l everagi ng exi s t i ng product s i nt o new and di f f erent
appl i cat i ons .
• Cont act s : Ri chard. Abbot t@adi t yabi rl a. com
• Nat al i e. Harri s@adi t yabi rl a. com
• J osh. Baugh@adi t yabi rl a. com
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Introduction
• Today we will be discussing the concept of the performance triangle.
• In turn we will cover
• Pigment selection
• Formulation
• Dispersion
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Pigment Selection
• For carbon blacks there are four fundamental properties that help determine the end performance
• Particle size distribution
• Aggregate size and shape distribution
• Pore size distribution
• Surface chemistry distribution
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Full Shade/Masstone Performance
Surface Area (Particle size) is the primary determinant of color performance.
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200
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0 50 100 150 200 250 300 350 400
Jetn
ess
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STSA m2/g
TreatedUntreated
• Sol vat ed CAB Formul at i on.
• Di spers i on vi a chi ppi ng on 2 rol l mi l l
• The chi p approach ensures a hi gh l evel of
di spers i on
15 g CAB chi p ( 15- 40% CB)
60 g N- but yl acet at e
75 g 3/32 s t eel shot
1 hour shake t i me
• Hi gher surf ace area gi ves hi gher J et ness .
• Sol vent borne f ormul at i on, so t he ef f ect of
t reatment becomes very apparent at hi gh surf ace
area.
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Tinting Product Selection Involves Trading Off Strength and Tone
-5.00
-4.00
-3.00
-2.00
-1.00
0.00
0.0 40.0 80.0 120.0 160.0 200.0
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Tinting Strength (%)
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Pigment Selection Additional Criteria
• Aggregate size and shape distribution
Higher structure carbon blacks will create a higher viscosity, as well as providing an easier dispersion. This will usually come at a minor cost in color performance.
• Pore size distribution
Outside of conductive coatings, this is not normally an important parameter
• Surface chemistry distribution
Post-treated carbon blacks have an acidic surface. This is important in how the pigment interacts with other formulation ingredients
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Formulation
• The formulation chosen has a major effect on the performance of the carbon black
• Some general comments
• Ensure adequate levels of dispersant (in terms of %SOP)
• Check dispersant/resin compatibility
• In solventborne applications, post-treated/acidic products tend to perform better than untreated products
• Good color/dispersion in a concentrate/grind doesn’t necessarily mean good color in a final coating.
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High Color Carbon Blacks: Waterborne Ladder study shows expected high dispersant demand for optimum performance
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2.50
2.70
2.90
3.10
3.30
3.50
3.70
3.90
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Jet
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s H
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Dispersant Amount Wt %
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Solventborne Automotive:Fall off in performance at different loadings reflects different surface characteristics
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0% 20% 40% 60% 80% 100% 120%
Jet
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Dispersant Amount
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Effect of Dispersant Choice: WB Automotive Large swings in both jetness and bluetone
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3.49
3.02 3.042.94
2.61
3.93
3.64
2.81
-0.42
-0.05 -0.05
0.09
-0.40
-0.18 -0.19
-0.08
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L b
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Effect of Dispersant Choice : Leather CoatingPredominantly a let down effect
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6.27
10.99
6.51
5.565.83
4.89
5.66
0.90
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1.001.12
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Reference "Drop In" A B C Y Z
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Dispersion
• Dispersion covers
• Pigment wetting
• Dispersion process
• Time/Energy
• Media Size and density (if applicable)
• Pre-mixing/bead breakdown (if applicable)
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Stages of Dispersion Process
Premixing Deagglomeration Depends on
- Premixing
- Deagglomeration
- Letdown
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Premix Equipment
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• Wetting is the first step in the dispersion process
• Breakdown of beads and agglomerates in to smaller fractions
• Removal of entrained air from the surface of the carbon black and replacing it with liquid vehicle
• Millbase viscosity and equipment geometry is important
• Geometry should promote rolling laminar flow (Doughnut Effect)
• High peripheral speed generates shear within liquid
• Viscosity too low = splashing, aeration and bubbles
• Viscosity too high = lack of movement, low transmission of mechanical energy
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Low & Medium Viscosity Milling Equipment
• Bead or shot mills spin pegs or disks at high speed in a cylindricalchamber partially filled with small beads or shot
• Small dense beads provide a degree of impact as well as shear
• Ball mills use larger tumbling balls to crush the pigment
• Ball mills are older, batch technology but still very effective
• Attritors fall mid way between the two techniques
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Bead MillingSelection Considerations for high color milling
• Energy density
• Usually dictated by cooling capability, a smaller chamber will allow for higher energy densities, which is a significant help to dispersing higher color pigments
• Hydraulic packing
• How is the mill preventing hydraulic packing of the media, close fitting blades, back flow pumping or other characteristics
• Screen size
• Single/multiple pass versus recirculation
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• Standard Laboratory Shaker
• Finer media gives rise to a jettercoating
• Beaded products will need to be broken down before grinding with fine media
• Finer media has higher risk of hydraulic packing
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Media Size and DensityMedia type has significant impact on color development
0 2 4 6 8 10
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Milling Time
0.6 - 0.8 mm
1.0 - 1.2 mm
1.8 - 2.0 mm
1.7 - 2.4 mm
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0 2 4 6 8 10 12 14 16 18
Jetn
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Dispersion time h
• Standard Laboratory Shaker
• 0.6 - 0.8 mm Zirconia beads
• With a well matched dispersant even 16 hours of shaking has not reached the ultimate level of performance
• For production efficiency there will be a time/energy and performance balance that will be particular to any given location and product
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High Color Carbon Blacks Take a lot of time/energy to disperse fully
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Summary
• We discussed the concept of the performance triangle.
• Covering in turn
• Pigment selection
• Formulation
• Dispersion
• But why this concept, why tie them together ?
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Considering all parts of the triangleEnables proper product selection for any given application
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220 240 260 280 300 320 340 360 380 400 420
Mass Market
Premium
Best Current
Future Need
My Color Space Market
280 – 320 Mass Market Black
330 - 350 Premium Black
370 – 380 Best Current
400 + Future Need
Different High Color Products and their positioning
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What about constraints ?
• As a formulator, constraints are common. You must use pigment X, or the production time is limited so you can only disperse for Y time
• Ultimate example – Military paint
• Pigment and formulation specified
• Performance range also specified.
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Dr. RI CHARD ABBOTT
Thank you and Any Questions ?
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• Pri nci pal Sci ent i s t ( Coat i ngs ) wi t h over 20 years of
worki ng wi t h carbon bl ack i n a vari et y of l i qui d sys t ems.
• Based at Bi rl a Carbon headquart ers & t echni cal cent er s i nce
2003.
• Respons i bl e f or devel opi ng new carbon bl acks and
l everagi ng exi s t i ng product s i nt o new and di f f erent
appl i cat i ons .
• Cont act s : Ri chard. Abbot t@adi t yabi rl a. com
• Nat al i e. Harri s@adi t yabi rl a. com
• J osh. Baugh@adi t yabi rl a. com
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Thank You
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