new generation calcium carbonate

8/9/2019 New generation calcium carbonate

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NEW GENERATION OF CALCIUM CARBONATE

K.K.Mishra

20 Microns Ltd., Mumbai, India

GENERAL OUTLOOK

Paint, as an aesthetic and protective material, has undergone significant transformation over the years from

being just a colour to a performance specific composite material. With this change, the ingredients of paint

have evolved into more sophisticated functional raw materials. Extenders once considered as mere fillers are

today looked upon as functional input to the paint contributing to rheology, adhesion, gloss control, hiding and

PV optimi!ation. "his situation necessitates up gradation of techni#ues and for the characteri!ation of

extenders.

$%&' paint makers still believe that fillers, (extenders, minerals) are of little importance, low cost and widely

available products. *ut extenders should no longer be viewed in such terms. "hey have a functional purpose

in the paint end product and their properties and #ualities will substantially affect this product. Paint makers

must expand and moderni!e their production facilities to cope with increasing technological sophistication. +n

trying to cut costs, raw materials will be a key consideration. $any paint makers have successfully decreased

the use of expensive titanium dioxide by partial replacement of white extenders which are properly ground to

the extent of submicrons to -microns average particle si!e.

FUNCTIONAL EXTENDERS

Extender pigment or simply extenders are also so called because such materials are used to Extend/ the

effect of expensive white and coloured pigments, so cheapening the paint formulation. 0owever, it is now

recogni!ed that extender pigments contribute much more to paint properties. areful selection of the type and

#uantity of extenders can affect such features in paints 1 coating as2

3. 4pacity or hiding.

-. 5loss or sheen.

6. 7low, leveling and smoothness.

8. 9urability and appearance of the paint film.

:. Pigment settlement on storage.

6. *arriers effect and water permeability etc.

onventionally, extenders have been characteri!ed employing simple techni#ues like visual colour

assessment, sieving, specific gravity, oil and water demand, p0 and microscopic examination. "hese tests do

give very useful information to the paint formulator in deciding upon fundamental formulation parameters like

PV, weight per liter, finish and the like. 0owever, if one desires to establish the closer relationship between

characteristics of the extenders on one hand and various paint making, application and performance

parameters on the other, then the use of modern analytical techni#ues become unavoidable. "hese

techni#ues possess the capability to look at the micro structure of extenders in terms of si!e, shape, surface

chemistry and crystallography. orrelations established between different extender parameters and a paint

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performance property enables the technologist to diagnose the cause of the #uality or performance problem.

$ore importantly, it provides predictive capability to envisage performance of a paint which incorporates

certain type of extenders.

While examining various modern techni#ues, it is important to take over view of various particle si!e analysis

techni#ues like, electron microscopy forms a very important tool for examination of particle shape which has

significant bearing on ;0E4;7%E 7+&+=0.

7or the sake of simplicity the term Extenders/ will be retained in this article, but it is used in the widest sense.

"he main difference between a pigment and an extender is that pigments impart colour and hiding power to

the paint where as extenders have little or no hiding power themselves. "he manufacturers of mineral

extenders are generally re#uired to give high technical service back up, and bear above average the ;19

costs. "he efficient processing is important, as is the ability to upgrade and modify products term as a New

Generation Extenders by usin u!tra"ine rindin techno!oy without any o#ersi$ed %artic!es &nib

"ree', ca!cinin or sur"ace modi"ications.

FUNCTIONAL PERPORTIES OF EXTENDERS=election of extenders by the paint maker depends on a number of factors2

GENERAL

"he colour should be bright, clear, intense and reproducible. +t depends on the mineral, chemical composition,

the brightness, the cleanliness and the intensity on the difference between the refractive indices of pigment

extenders and medium, and on particle si!e and si!e distribution, particle shape and crystal habit. "he opacity

or hiding power is a function of the difference between refractive indices of the pigment and dispersion

medium. *oth pigments and extenders are opa#ue as dry powders, but when dispersed in media, pigments

are opa#ue in both organic and a#ueous media, whereas the extenders are practically transparent in organic

media but opa#ue in a#ueous media. "his is because the refractive indices of extenders are very close to

those of oils and resins.

Extenders have a low refractive index, similar to that of binders and so are effectively transparent. "hey are

usually white or offwhite and contribute either no color or an undesirable one to paint film. 0ow, then, can

extenders increase the efficacy of pigments if they possess neither of the basic properties re#uired. ? "here

are five aspects to consider2

1. PARTICLE SIZE DISTRIBUTION.

"he particle si!e is very important and it is one of the properties which can be altered substantially by the

processor. 0iding power and tinting strength are both related to the particle si!e. "he particle si!e also

influences gross consistency and settlement. Particle si!es have directly corelation with surface area of

the particle which effects viscosity, flow characteristics, dispersion stability and oil absorption. Particle

shape effects flow characteristics settlement and film durability.

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2. HIGH BRIGHTNESS.

"hey should be as bright as possible so that no pigment is, as it were, wasted covering the unwanted

colour of the extender. "he brightness depends on the chemical composition of the deposit. =ometimes

the colour can be improved by washing or flotation.

3. HINDER RE-AGLOMERATION.

"his is done by introducing sufficient physical barriers so that the likelihood of two pigment particlescolliding and reagglomerating in the li#uid paint system is reduced.

4. IMPROVED PIGMENT DISPERSION.

"hey help to break down the pigment agglomerates. +t has been calculated that if all the titanium dioxide

used were perfectly dispersed, the world demand for titanium dioxide would fall to about 38@ of the

present usage. +t is evident that extender producers can help a lot here.

"he extender must itself be easy to disperse. "he individual particles collide with pigment agglomerates,

breaking them up. "he extender must be fine since if it is too coarse it encourages crowding/ thus

defeating the objective. +deally, the pigment particles should be half the wave length of light in diameter

and the distance between them should also be half the wave length of visible light. Please note that we no

longer speak of spacing extenders. "his theory has been proved wrong by simple experiment. +f the

pigment and extender are disperse separately in half of the binder and then subse#uently mixed, there is

only a slight increase in opacity and much less than when the extender and pigment are mixed together in

the first place. "he slight increase in opacity is caused by hindering reagglomeration as mentioned

above.

5. DECREASE CRITICAL PVC.

"hey can decrease the critical PV to below that of the paint so that there is insufficient binder to

completely coat each organic particle. "iny pockets of air are trapped on the surface of some of the

particles, increasing the amount of light diffracted and hence the opacity or hiding power of the paint film.

4f course, this also lowers the scrub resistance and increases the tendency of the film to pick up

atmospheric dirt. "he extender must have a high absorption. =uitable ones are calcined clay or synthetic

aluminium silicate. "his usage is only practical for interior paints and even then it is limited due the poorer

scrub resistance.

A NEW GENERATION CALCIUM CARBONATES LEADING THE FIELD

+n #uantity terms calcite, dolomite and whiting are the most widely used carbonate extender minerals in

paints. alcite is basically used as a pigment extender for the improvement of pigment efficiency because of

the spacing and refractive index. Paint makers may use any grade si!e from a coarser grade (8AA $esh) to a

microni!ed grade (-A $icrons and 3A $icrons). +n general, the finer the particle si!e, the higher the gloss of

the paint.

alcium carbonate does not contribute significantly to opacity in itself but a new eneration ca!cium

carbonate is said to brin out the opacity of prime white pigments by spacing them correctly. 0igh

brightness and proper micronisation is desirable to improve paint colour characteristics. Properly microni!ed

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surface it follows that smaller and more numerous fine particles offer more opportunities for refraction and

thus lead to better coating 4P%+"' and 0+505


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*ulk 9ensity loose

(gmJliter)

:GA:A :-A6A 6:A:A 8AA:A

*rightness H8- H8- H-- HA-

4il absorption

(gmJ3AAgm)

-A6 -I: 6:: I::

=pecific surface area

(*E") m-Jgm

68 :D 3-3: ---:

EXPERIMENTAL OB6ECTIVE"he most widely used pigment in the paint industry is titanium dioxide. "he rising titanium dioxide price and

tight supply situation is causing more and more paint manufacturers to seek means of extending this pigment

without loss of opacity or change in colour tone. *ased on the experience and global trend in the industry, we

introduce a New eneration ca!cium carbonate, and our product application center had carried out some

experiment which is subse#uently fallowed by our esteemed paints 1 coating customers.

EXPERIMENT NO. 1

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EXPERIMENTAL INTRODUCTION

"he standard formulation content DA@ by weight of "i4- and calcium carbonate extender with average

particle si!e of - Fm. means 5 4arbin this experiment -A@ "i4-were replaced by weight by 7a%or!ite 809

as per "able no. -

"he paint was made using a high speed disperser.

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CONCLUSION

"he partial replacement of titanium dioxide by 7a%orci"ier and 5 4arb in exterior emulsion paint offers cost

savings without affecting the optical or weathering properties adversely.

EXPERIMENT NO. 2

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7:51LI9E 809 :N< 5 4:1-

T!+/" )$. 2

R! M!&"%'!/ S&!),!%, F$%


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EXPERIMENT NO. 4

1EL:4EMEN9 5; 1E;INE< 4AIN: 4L:? -? 7:514I;IE1, 7:51LI9E 809 :N< 5 4:1-.

E=E1IMEN9:L IN915&)"

8DIN 5313 C@2:

R 8G%"")

F'/&"%:

O'/

A+$%0&'$)8G


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"i4- @wt. -G.AI -D.AG

Vaporlite HA" @wt. 3.:-

PV @ -A.6 -A.6

=olid vol. @

Wt.@

8G.D

DD.G

8G.D

DD.D

9ensity gmJml 3.-D 3.-D

5%tica! ro%erties & :"ter 2 days dryin at 234''ellowness +ndex -.H -.H

ontrast ratio (8:Fm film) HI.H HI.8

5loss

-AK (after - days) @

-AK (after -G days) @

DAK (after - days) @

DAK (after -G days) @

G:

G3

H3

HA

GD

G-

H-

HA

EXPERIMENT NO.

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T!+/" N$.

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F'* 4.ON SITE SATELITE PLANT

2 M'#%$) S#$0"7-

Providing >ninterrupted supply W55 in slurry form as per the specification attached.

Provide the slurry at the dosage point in the I:@ =olids.

+nstallation of the re#uirement PlantJ$achinery and testing instruments at the site.

;egular running and maintenance of plant.

=torage tank for slurry.

ADVANTAGES OF WET GRINDING PROCESS

Wet ground calcium carbonate is superior to dry ground calcium carbonate.

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+n wet processdue to floatation method it improves2

olour of the material

;educes impurity level

+t helps to produce ultrafine mineral where uniform particle si!e distribution takes place which helps to

dispersion in the end use.

A,(!)&!*" $ "& *%$), C!CO3$("% ,% *%$), C!CO3

this application particle si!e plays major role to achieve end productMs performance ,wet ground processgives the particles of :A to HG@ below - microns and it act as a spacers between tio -particles leading to

increase the efficiency of tio- in paint and coating application 9ue to controlled 1 uniform particle si!e

distribution, it

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new generation calcium carbonate

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