English Indian Clays Ltd Kaolin as High Performance Extender Pigment for Coatings S.V.Kamalesh
Sep 12, 2014
English Indian Clays Ltd
Kaolin as High Performance Extender Pigment for Coatings
S.V.Kamalesh
A brief on EICL
English Indian Clays Ltd, part of Karan Thapar Group was incorporated in 1963 in technical collabration with English China clays Ltd ,UK ,the pioneer and the then world leader in kaolin processing
EICL's clay bussiness is the largest integrated clay facility in Asia, mining and refining high end Hydrous clay and calcined clay
EICL has been ranked as the 9th largest kaolin processing company in the world by IM
EICl operation are multi location with an installed capacity of 240,000 Mt/annum
EICL philosophy is to be a solution provider to customers through value enhancing product and service
Extender Pigments Functional Properties in Coatings
The choice of extenders in Paints are influenced by the following considerations
1. Aesthetic Properties - Control Gloss, Sheen, Matt , Enhance Opacity, Brightness, Provide texture &smoothness
2. Processing & Wet Paint - Ease of Dispersion, Viscosity, Flow and Levelling, Sedimentation / settling properties
3.Mechanical & Physical - Hardness, Impact Resistance, Film Reinforcement, Porosity, Cracking and Checking
resistance
4. Performance& ressistance - Abrasion, Burnishing and Scrub resistance, properties Permeability, Corrossion & Chemical and
Electrical property insulation and conductivity
5. Other factor - Cost control
Extender pigments functional
properties in coatings The functional properties of extender pigments in
coatings are characterized by its
Particle shape
Particle size distribution
Physical properies
Specific gravity ,Bulk densiy Oil absorption,Hardness
Surface Area
Chemical composition
Extender Type - particle shape
• Kaolin - Platy
• Calcite - Nodular
• Talc - Platy
• Baryte - Nodular
• Mica - Platy
• Silica - Nodular
• Wollastonite- Acicular
Kaolin (China clay )
Kaolin is formed by the hydrothermal degradation of Feldspar rock and the mineral is called Kaolinite
Kaolin is mostly of hydrated alumino-silicate with a chemical formula Al2O3.2SiO2.2H2O
The particles have a platy structure and belong to the phylosilicate family.
Under SEM it appears as stacks of Hexagonal platelets. It is crystalline in nature and occur as very fine particle.
SEM of Hydrous kaolin
TEM kaolinite
Kaolin classification Kaolin can be broadly classified as primary or secondary Primary kaolin deposits are insitu formations – these
contain impurties, mainly quartz, mica,silica and alkaline metals.
Secondary kaolin deposits are those which have been have been transported by receding water and deposited down stream. These have relatively low impurties.
Secondary kaolin is also less abrasive than primary kaolin and is finer.
EICL Kaolin is a Secondary kaolin
Features of Kaolin
Kaolin is characterised by the following properties
Platy structure
Surface charge
Fine particle size
Chemically inertness over a wide pH range
Kaolin as extender pigment in Paints EICL Kaolin deposits are considered to one of the best in
the world in terms of purity, fineness and colour. EICL Kaolin imparts the following properties to Paint formulations
Good Dispersibility in water based system,and better processibility
Good Opacity ,Gloss & Brushability
Higher viscosity, Better water holding
Good filling property
Anti settling property
Anti sagging properties
10 5 2 1 0.530
40
50
60
70
80
90
100
110
PSD of EICL hydrous grades
Cumulative finer mass % Vs Diameter
BCKDLC-90HibriteSupershine plusSuperlustreNanokaolin
Particle Diameter (micron)
Ma
ss %
Functional properties Enhancement
The restructring of kaolin by the following technique enhances its functional properties in coatings
Delamination Calcination Chemical modification
Non delaminated
Partially delaminated
Fully delaminated
Delaminated kaolin
Advantage of Delaminated Kaolin in paint
EICL delaminated clay DLC 90 offer the following advantage in coatings Improved Opacity and Gloss Improved Tinting strength Better WashabilityImproved Enamel hold out Controlled penetration of water/ vapour with improved barrier resistance
DLC90 usage - Types of paint
• DLC 90 is used both in Architectural and Industrial coatings.
• It is recommended for use in the following paints
Water base paint Interior Wall paint Exterior House paints
Solvent base - Anti-corrosive primer Stain blocking Primers Industrial Primers
Calcined kaolin Produced by high
temperature treatment of processed kaolin
The crystalline structure of kaolin undergoes change into an amorphous one, with a microvoids with entrapped air.
These microvoids facilitate light scattering and contribute to opacity
Calcined Kaolin
The Optical properties of Kaolin are enhanced by the calcination process
The enhancement of optical properties of the Kaolin by the calcination process gives the opportunity to rationalises the TiO2 content in the paint formulation using calcined kaolin
Calcined Kaolin
In addition it imparts the following properties
Improved Whiteness
Improved Dry film hardness
Wet Scrub resistance
Film reinforment by bridging
Gloss control in Industial coating
Cost effective formulation by TiO2 Saving
Fine grade Calcined clay Himafine
Titaniumdioxide is one among the major pigments consumed in the paint industry Paint formulators have always worked at different ways to optimise TiO2 content without deterioration in final paint properties
EICl has brought out the ultra fine grade calcined clay Himafine that is designed to reduce more TiO2 content and bring down the cost of water based formulation
Himafine
Himafine is derived from specially refined hydrous clay selected to achieve highest optical properties and dispersion.
Himafine has a narrow PSD distribution with d50 of 0.8 micron
The finePSD effectively space the TiO2 particle in the paint formulation achieving higher hiding power with lower TiO2 content
Himafine usage
Himafine is recommended for usage in
Water based Interior Emulsion paints Water based Exterior Emulsion paints Traffic paints (water & Solvent base ) Coil coating (industrial )
NEW PRODUCTS UNDER DEVELOPMENT
New products
EICL R&D has now embarked on the development of a set of new generation products,by engineering the size and morphology of the kaolin,surface modification or nanosizing This product are designed to impart higher value addition to the Paint industryin terms of either
Cost advantage -bringing down the effective cost of paint formulations
Process advantage- facilitating easier processing and saving in energy cost
Enhancement in quality performance- enhancing the application performance of the coating or as a combination of these
New products
The following are the new products now under development for the Paint Industry
• Silica coated clay – Silstar
• Surface modified clay Visfine,Amfil
• Nano Clay -Nanocaliber
1. Silica Coated Clay - Silstar
Concept Retaining the benefit of Kaolin in interior emulsion paint
(Improved opacity, storage stability ,anti-settling ,anti-sagging properties etc ) re -engineered the kaolin to to improve the exterior durability through chemical bonding of silica
Since the coating is done using an active silica material, the skin formed is dense, amorphous and hydrated giving a strong bonding on the surface of the core
This silica coated Kaolin can be used as an opacifying extender pigment in Exterior paint formulation for partial replacement of Titanium dioxide
Diagrammatic representation of silica coating
CORE CLAY
SILSTAR
std Silstar silstar % TiO2 replacement 0 5 10Water 25 25 25Natrasol 250 HBR 0.5 0.5 0.5Indofil 850 0.3 0.3 0.3AMP 95 0.3 0.3 0.3Ammonia 0.4 0.4 0.4Defoamer 0.3 0.3 0.3Biocide 0.3 0.3 0.3TiO2 (R) 20 19 18Silica 10 micron 8 5 5Silstar 0 4 5Water 11 11 11Ethylene glycol 1 1 1Texanol 1 1 1Acrylic emulsion 32 32 32Total weight 100 100 100
Partial Replacement of TiO2 with Silstar
Dry film properties Std 5 %TiO2 Repl 10 % TiO2 Repl
Brightness ISO 89 88.9 88.7
Whitness 88 87.6 87.5
Gloss 24 26 27
Contrast ratio (Opacity) 94.5 94.8 94.5
1400 1450 1420
Tinting Strength Comparable to Std comparable to std
comparable to std comparable to std
Wet scrub resistance ( cycle to fail )
Accelarated weather Test ( 1000 hrs ) colour differnce ,chalking ,fading
Benefits
The above application studies, show that ~10% TiO2
can be replaced by Silstar .
.
Expected cost advantage is ~5 % from the intial formulation cost
2. Surface Modified Clays
Surface modified clay EICL R&D has developed the technology for surface
modificationof kaolins in collabration with NIIST (CSIR). With this we are introducing Surface Mod clays for High performance coating
Application
High Performance Industrial Solvent Based Paints
Key Characteristics
Compatible with resin matrix
Easy dispersion
Hydrophobicity in the coated surface
Surface modified clay
Advantages in Paints
Reduces processing time and power cost by 10 %
Enhance the performance of coating and thereby extend the durability of the coating period by 10 to15 %
Advantages in Processing
• The surface modification of kaolin, reduces surface energy and allows better wetting with resin media and facilitates easier dispersion into the matrix.
and lowers the resin / filler mix viscosities , resulting in improved mechanical properties
• The easier dispersion reduces processing time by 10% of normal processing time with attendant saving in power / energy cost.
Paint Performance
Surface modified clays imparts the following performance enhacement to the coated surface
Water resistance Chemical resistance Corrosion resistance Exterior durability Film integrity
Types of paint
Surface modified clays are used in the following types of paint
High solid polyester coating High Solid Epoxy coaing Two pack poly urethane enamel High Performance specaility coating Marine coating
Type of Surface modification
The type of coating system determines the selection of the modifying chemicals such as
• Vinyl silanes
• Amino Silica
• Epoxy silane
• Mercapto silane
3. Nano kaolin
Nano Technology
Nanotechnology deals with the the fact that properties of materials can change drastically when the size fall below approximately 100 nanometer at least in one dimesion Nanoscale material have already found application in several areas in industry and they are very promising for coating application Nano particle can improve the properties of coating system in several ways
Nano is one thousandth of a micron
Particles with below 100nm in any one dimesion is
reffered as nano material
Nano Clay / Kaolin
The mechanism of functioning of Nano clay in coating film is based on the following structural aspects of Nanoclay /polymer hybrid
High Interfacial area High Aspect ratio Relatively inert in chemical nature
Nano Clay /Kaolin
Unlike other fillers Clay particle at nano size posses some unique charactertics
Nano clay particle are in platelet form with thickness < 10 nm and width 150 -200 nm
High aspect ratio 75 – 100 and impart some anisotropic charactertics to the film
Benefits with Nano clays
Incorporation of nano materials is expected to give the following novel properties in coating film
High Mechanical strength
Abrasion, Scratch and wear resistance,Impact resistance
Improved barrier properies
Anti-corrosion Film Durability Enhanced Heat resistance Higher electrical conductivity
Potential Applications
Nano clays will give advantages in Industrial Speciality coatings such as :
Scratch resistant Clear coating Anti corrosive coating Abrasion and wear reistance coating
d = > 500 nm
t = > 100 nm
d ≤ 500 nm
t = < 100 nm
D 50
= < 100 nm; t = 40-60 nmChemically modified surface
Nanokaolin- the Concept....................
Nano Kaolin100 nm
EICL Nano kaolins
As the first stage of development of Nano Kaolins, the process capability for making a product with d50 of 300 nm, has been achieved.
In the subsequent stages, we are planning to develop process capability for a d 50 of 200, 100 and lower nano meters.
Product with d 50 of 200 nm has been developed in the lab.
Regular grade Kaolin - Water base Paint - Distemper, Emulsion Solvent base Paint - Primer,Under coat
Premium grade Kaolin - Solvent base Paint - Enamel
Specialty grade Kaolin - Industrial Automotive Electro deposition primer,
Surface coated Kaolin - Exterior Emulsion paint
Surface modified Kaolin - High performance protective coating
Kaolin variants usage in coatings
Nano Kaolin - Industrial High performance protective clear coating
Calcined Kaolin - Interior / Exterior Emulsion paint
Concluding...Concluding...
Kaolin is a versatile extender pigment,which apart from giving good performance in paint films ,also gives ample opportunity for value addition by physical , structural and chemical modification with enhanced performance in paints.
EICL will continue to work with paint formulators , evolving such innovative product ideas for the benefit of the paint industry