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Order of addition
The usal way of incorporation
of dispersant in a coating formulation would be in three stages:
1. Mix the dispersant in the millbase
solvent or in the resin/solvent mixture
2. Add any other additives
3. Add the pigment, in stages, and disperse in the
normal manner.
In case you want to optimise a P
olymeric dispersant millbase, 4 stages are involved.
The following example explaining using Solsperse products (referred to
as a ladder series)
Stage 1 - Calculation of % AOWP of Polymeric hyperdispersant
The theoretical amount of Polymeric dispersants (Solsperse) agent required
in a millbase is 2mg Polymeric agent per sq. metre pigment surface area.
Example:
Pigment surface area - 70m2/g
Therefore 140mg Polymeric agent/1g pigment are required = 14g agent/100g
pigment i.e. 14% AOWP
Synergists (if required) are used with the Polymeric in ratios between 4
: 1 and 9 : 1 Polymeric : synergist.
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Stage 2 - Determines the higher pigment
content required
(Can be performed on lab. shaker e.g. Red Devil) |
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Using the % AOWP of Polymeric agent (calculated above) + synergist (if
required) prepare a series of millbases with increasing pigment contents
in a GRINDING MEDIUM containing APPROXIMATELY 10% SOLID RESIN. Note: the
ratio of hyperdispersant: pigment must be maintained
The pigment concentration giving the same viscosity as the control should
now be used in Stage 3. |
Stage 3 - Determines optimum amount of
Solsperse Hyperdispersant
(Can be performed
on lab. shaker e.g. Red Devil) |
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Using the higher pigment content established in Stage 2: Carry out a series
of Polymeric agent dosages around the theoretical % AOWP (+ any synergist
required) to optimise the required agent dosage. Determine best hyperdispersant
dosage by measuring desired property. |
Stage 4 - Optimises final pigment concentration
(Should be done in equipment representative of bulk
production) |
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Using the % agent on weight of pigment established in Stage 3: Prepare
final ladder series of pigment contents - maintaining agent: pigment ratio
determined in Stage 3 to determine optimum amount which gives best final
product.
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For technical advices on how to obtain a good
coating dispersion, contact our experts via TechDirect |
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