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Introduction
Laponite is a synthetic layered silicate with a structure
resembling that of the natural claymineral hectorite. It is used as
a cost-effective rheological additive in a wide range ofwaterborne
systems including surface coatings and household and personal care
products.
The unsurpassed shear thinning properties of Laponite make it
ideally suited for thestabilisation of water based concentrated
pigment slurries and dispersions without causingexcessive increase
in viscosity.
As a synthetic product manufactured by a controlled batch
process product consistency is
excellent and Laponite is completely free of crystalline silica
impurities found in naturallyoccurring clays.
Laponite disperses readily in water without the need for high
shear mixing to form clear,colourless, sols or gels. Because it is
a wholly inorganic material it is not damaged by microbialattack
and is non-flammable. The viscosity of formulations stabilized by
Laponite is notaffected by changes in temperature.
Stabilization of concentrated aqueous pigment slurries using
Laponite
Concentrated pigment slurries are used in a wide range of
industrial application areas includingsurface coatings, paper,
textiles, leather, construction and plastics.
The problem of settling of pigment solids in these slurries can
be overcome by addition of arheology modifier such as a cellulose
ether. This will impart anti-settling properties by thickeninga
formulation across the shear rate range.
A novel, alternative approach is to use Laponite. At
concentrations of, typically, less than 0.2%,Laponite will develop
viscosity at very low shear rates giving excellent anti-settling
properties
during storage and transport. This viscosity build developed by
Laponite is easily broken downwith a minimum of shear to give
readily flowable slurries with improved application properties.
Laponite has been used successfully to stabilise aqueous
pigmentconcentrates with the following materials:
iron oxide
titanium dioxide
kaolin
tinting pigment pastes
aluminosilicates
carbon black
conductive micas
synthetic organic pigments
calcium carbonate
pearlescent pigments
metallic pigments
-aluminium-bronze
-zinc
-nickel
-stainless steel etc.
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Laponite grades and method of addition
Two grades of Laponite are available for stabilization of
pigment slurries.
Laponite RD - a rapidly dispersing gel forming grade which
should be added to water at the
beginning of the formulation and allowed to fully hydrate before
addition of other ingredients.
Laponite RDS - a rapidly dispersing sol forming grade which can
be made into a low viscosityconcentrated stock dispersion at up to
10% solids. Laponite RDS is modified with apolyphosphate dispersing
agent to delay rheological activity until it is added as a
dispersion intothe pigment slurry. The unique sol forming
properties of Laponite RDS allow it to be used as apost-additive or
corrective thickener and also in water-lean formulations. The stock
dispersion
may be prepared in advance and then added to successive
production batches of a formulation.
Both Laponite RD and Laponite RDS should be pre-dispersed in
water and allowed to fullyhydrate to form clear dispersions before
use.
Laponite disperses readily in tap water at ambient temperature.
The use of high shear mixersor chemical dispersants is not required
to fully disperse Laponite .
Example starter formulation60% iron oxide pigment slurry for
concrete
Order of addition % weight
water 38.3
Laponite RD 0.1Dispex N40 1.2Texanol 0.2sodium carbonate 0.2iron
oxide pigment 60.0
ProcedureDisperse Laponite RD in water, mixing for 10 mins at
600rpm using a Cowles (sawtooth)blade. Add Dispex N40, Texanol and
Na2C03and mix for 5 mins. Then add pigment powder, in-
creasing mixer speed as solids content increases.
Viscosity : 350 cP (Brookfield LV 60rpm)pH : 10.1
An alternative procedure using Laponite RDS
Prepare the dispersion of pigment with dispersant, coalescent
and pH adjustment. Add 1 part
of a 10% solids dispersion of Laponite RDS in water to 99 parts
of pigment slurry (w/w).Mix for 5 minutes.
% Concentrationin premix
Dispersion andhydration time
Laponite RD 0.25 10 minutes
Laponite RD 2 15 minutes
Laponite RDS 10 40 minutes
example recommended dispersion and hydration times (20c)
Laponite grades and method of addition
Two grades of Laponite are available for stabilization of
pigment slurries.
Laponite RD - a rapidly dispersing gel forming grade which
should be added to water at the
beginning of the formulation and allowed to fully hydrate before
addition of other ingredients.
Laponite RDS - a rapidly dispersing sol forming grade which can
be made into a low viscosityconcentrated stock dispersion at up to
10% solids. Laponite RDS is modified with apolyphosphate dispersing
agent to delay rheological activity until it is added as a
dispersion intothe pigment slurry. The unique sol forming
properties of Laponite RDS allow it to be used as apost-additive or
corrective thickener and also in water-lean formulations. The stock
dispersion
may be prepared in advance and then added to successive
production batches of a formulation.
Both Laponite RD and Laponite RDS should be pre-dispersed in
water and allowed to fullyhydrate to form clear dispersions before
use.
Laponite disperses readily in tap water at ambient temperature.
The use of high shear mixersor chemical dispersants is not required
to fully disperse Laponite .
Example starter formulation60% iron oxide pigment slurry for
concrete
Order of addition % weight
water 38.3
Laponite RD 0.1Dispex N40 1.2Texanol 0.2sodium carbonate 0.2iron
oxide pigment 60.0
ProcedureDisperse Laponite RD in water, mixing for 10 mins at
600rpm using a Cowles (sawtooth)blade. Add Dispex N40, Texanol and
Na2C03and mix for 5 mins. Then add pigment powder, in-
creasing mixer speed as solids content increases.
Viscosity : 350 cP (Brookfield LV 60rpm)pH : 10.1
An alternative procedure using Laponite RDS
Prepare the dispersion of pigment with dispersant, coalescent
and pH adjustment. Add 1 part
of a 10% solids dispersion of Laponite RDS in water to 99 parts
of pigment slurry (w/w).Mix for 5 minutes.
Laponite grades and method of addition
Two grades of Laponite are available for stabilisation of
pigment slurries.
Laponite RD - a rapidly dispersing gel forming grade which
should be added to water at the
beginning of the formulation and allowed to fully hydrate before
addition of other ingredients.
Laponite RDS - a rapidly dispersing sol forming grade which can
be made into a low viscosityconcentrated stock dispersion at up to
10% solids. Laponite RDS is modified with apolyphosphate dispersing
agent to delay rheological activity until it is added as a
dispersion intothe pigment slurry. The unique sol forming
properties of Laponite RDS allow it to be used as apost-additive or
corrective thickener and also in water-lean formulations. The stock
dispersion
may be prepared in advance and then added to successive
production batches of a formulation.
Both Laponite RD and Laponite RDS should be pre-dispersed in
water and allowed to fullyhydrate to form clear dispersions before
use.
Laponite disperses readily in tap water at ambient temperature.
The use of high shear mixersor chemical dispersants is not required
to fully disperse Laponite.
Example starter formulation60% iron oxide pigment slurry for
concrete
Order of addition % weight
water 38.3
Laponite RD 0.1Dispex N40 1.2Texanol 0.2sodium carbonate 0.2iron
oxide pigment 60.0
ProcedureDisperse Laponite RD in water, mixing for 10 mins at
600rpm using a Cowles (sawtooth) blade.Add Dispex N40, Texanol and
Na2C03and mix for 5 mins. Then add pigment powder, increasing
mixer speed as solids content increases.
Viscosity : 350 cP (Brookfield LV 60rpm)pH : 10.1
An alternative procedure using Laponite RDS
Prepare the dispersion of pigment with dispersant, coalescent
and pH adjustment. Add 1 part
of a 10% solids dispersion of Laponite RDS in water to 99 parts
of pigment slurry (w/w).Mix for 5 minutes.
% Concentrationin premix
Dispersion andhydration time
Laponite RD 0.25 10 minutes
Laponite RD 2 15 minutes
Laponite RDS 10 40 minutes
example recommended dispersion and hydration times (20c)
