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