new generation calcium carbonate
TRANSCRIPT
-
8/9/2019 New generation calcium carbonate
1/17
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
- 1 -
-
8/9/2019 New generation calcium carbonate
2/17
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.
- 2 -
-
8/9/2019 New generation calcium carbonate
3/17
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 $icrons). +n general, the finer the particle si!e, the higher the gloss of
the paint.
alcium carbonate does not contribute significantly to opacity in itself but a new eneration ca!cium
carbonate is said to brin out the opacity of prime white pigments by spacing them correctly. 0igh
brightness and proper micronisation is desirable to improve paint colour characteristics. Properly microni!ed
- 3 -
-
8/9/2019 New generation calcium carbonate
4/17
-
8/9/2019 New generation calcium carbonate
5/17
surface it follows that smaller and more numerous fine particles offer more opportunities for refraction and
thus lead to better coating 4P%+"' and 0+505
-
8/9/2019 New generation calcium carbonate
6/17
*ulk 9ensity loose
(gmJliter)
:GA:A :-A6A 6:A:A 8AA:A
*rightness H8- H8- H-- HA-
4il absorption
(gmJ3AAgm)
-A6 -I: 6:: I::
=pecific surface area
(*E") m-Jgm
68 :D 3-3: ---:
EXPERIMENTAL OB6ECTIVE"he most widely used pigment in the paint industry is titanium dioxide. "he rising titanium dioxide price and
tight supply situation is causing more and more paint manufacturers to seek means of extending this pigment
without loss of opacity or change in colour tone. *ased on the experience and global trend in the industry, we
introduce a New eneration ca!cium carbonate, and our product application center had carried out some
experiment which is subse#uently fallowed by our esteemed paints 1 coating customers.
EXPERIMENT NO. 1
:19I:L 1EL:4EMEN9 5; 9I9:NI(M
-
8/9/2019 New generation calcium carbonate
7/17
EXPERIMENTAL INTRODUCTION
"he standard formulation content DA@ by weight of "i4- and calcium carbonate extender with average
particle si!e of - Fm. means 5 4arbin this experiment -A@ "i4-were replaced by weight by 7a%or!ite 809
as per "able no. -
"he paint was made using a high speed disperser.
T!+/" )$. 1
R! M!&"%'!/ S&!),!%, $%
-
8/9/2019 New generation calcium carbonate
8/17
CONCLUSION
"he partial replacement of titanium dioxide by 7a%orci"ier and 5 4arb in exterior emulsion paint offers cost
savings without affecting the optical or weathering properties adversely.
EXPERIMENT NO. 2
1EL:4EMEN9 5; >?N9AE9I4 :L(MINI(M >ILI4:9E :N< 1E4II9E< 4:L4I(M 4:1-5N:9E -?
7:51LI9E 809 :N< 5 4:1-
T!+/" )$. 2
R! M!&"%'!/ S&!),!%, F$%
-
8/9/2019 New generation calcium carbonate
9/17
-
8/9/2019 New generation calcium carbonate
10/17
T!+/" N$. 3
R! M!&"%'!/ S&!),!%, F$%
-
8/9/2019 New generation calcium carbonate
11/17
EXPERIMENT NO. 4
1EL:4EMEN9 5; 1E;INE< 4AIN: 4L:? -? 7:514I;IE1, 7:51LI9E 809 :N< 5 4:1-.
E=E1IMEN9:L IN915&)"
8DIN 5313 C@2:
R 8G%"")
F'/&"%:
O'/
A+$%0&'$)8G
-
8/9/2019 New generation calcium carbonate
12/17
T!+/" N$. 4
R! M!&"%'!/ S&!),!%, F$%
-
8/9/2019 New generation calcium carbonate
13/17
"i4- @wt. -G.AI -D.AG
Vaporlite HA" @wt. 3.:-
PV @ -A.6 -A.6
=olid vol. @
Wt.@
8G.D
DD.G
8G.D
DD.D
9ensity gmJml 3.-D 3.-D
5%tica! ro%erties & :"ter 2 days dryin at 234''ellowness +ndex -.H -.H
ontrast ratio (8:Fm film) HI.H HI.8
5loss
-AK (after - days) @
-AK (after -G days) @
DAK (after - days) @
DAK (after -G days) @
G:
G3
H3
HA
GD
G-
H-
HA
EXPERIMENT NO.
:19I:L 1EL:4EMEN9 5; 9I9:NI(M
-
8/9/2019 New generation calcium carbonate
14/17
T!+/" N$.
R! M!&"%'!/ S&!),!%,
F$%
-
8/9/2019 New generation calcium carbonate
15/17
F'* 4.ON SITE SATELITE PLANT
2 M'#%$) 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.
- 15 -
-
8/9/2019 New generation calcium carbonate
16/17
+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
I
-
8/9/2019 New generation calcium carbonate
17/17
-. Paper published on 0%;"E;+=%"+4& 47 EQ"E&9E;= *' $49E;& "E0&+R>E= %&9 +"=
4;;E