Cationcally dispersed slurries of calcined kaolin clay

A stable fluid acidic concentrated aqueous slurry of positively charged particles of a calcined kaolin clay pigment wherein the dispersant is a water-soluble organic cationic material, such as a quarternary ammonium polyelectrolyte.

FIELD OF THE INVENTION 
This invention relates to aqueous slurries of calcined clay pigments. 
BACKGROUND OF THE INVENTION 
Kaolin clay pigments used by the paper and paint industry are available in 
both uncalcined and calcined grades, both of which bear a negative charge 
when dispersed in water. When preparing aqueous coating or paper filling 
compositions containing such pigments, it is frequently desirable to 
provide the clay in the form of a concentrated suspension (slurry) which 
is sufficiently fluid at both high and low rates of shear to be handled by 
conventional mixers and pumps. 
In the manufacture of paper and paper board, it is wellknown to incorporate 
quantities of inorganic fillers into the fibrous web in order to improve 
product quality. Titanium dioxide is widely used to improve brightness and 
opacity, but it is an expensive pigment. In recent years, considerable 
efforts have been made to develop satisfactory replacements for titanium 
dioxide. Substantially anhydrous kaolin clays prepared by partially or 
fully calcining a fine particle size fraction of crude kaolin clay is now 
a replacement pigment of choice. Calcined kaolin clay opacifying pigments, 
such as the products supplied under the registered trademarks ANSILEX and 
ANSILEX 93 by Engelhard Corporation are exemplary. These products are 
substantially anhydrous white pigments and are widely used as fillers in 
paper sheets and paper board, as a coating pigment for paper, and as a 
pigment in paints and other filled systems. They consist of aggregates of 
clay particles, and exhibit exceptionally high light-scattering and 
opacifying characteristics when incorporated as a filler into paper. The 
particle size of these pigments is typically at least 65 percent by weight 
finer than 2 micrometers equivalent spherical diameter (ESD), and at least 
50 percent by weight finer than 1 micrometer. The pigments exhibit low 
Valley abrasion values, generally less than 50 mg., and usually below 30 
mg. 
It is desirable to be able to ship high solids slurries of calcined clay 
pigments in tank cars. A high degree of fluidity is required as it is with 
conventional hydrated kaolin pigments. In many instances, slurry shipments 
must be sufficiently fluid to flow out of tank cars under the influence of 
gravity alone. Such phenomena as thickening, gel formation, and 
sedimentation are undesirable because they impair or prevent gravity flow. 
When the kaolin is not calcined and has a limited content of particles 
larger than 2 micrometers (equivalent spherical diameter), is relatively 
simple to produce a stable high solids (70 percent) suspension of the 
clay. A powerful anionic deflocculant such as a polyacrylate salt or 
tetrasodium pyrophosphate (TSPP) is added to a filter cake of acid 
negatively charged particles of clay, the cake being at about 60 percent 
solids, and additional dry clay is incorporated with agitation until the 
suspension has the desired high solids content. The TSPP is usually 
employed in an amount within the range of 0.3 percent to 0.5 percent based 
on the dry clay weight. This corresponds to the use of 6 to 10 lbs. 
TSPP/ton of clay. Typically, the pH of such slurries is in the range of 
6.5 -8.5. Such suspensions are stable in the sense that there is minimal 
settling of particles to form a dense sediment and minimal formation of a 
clear or cloudy supernatant liquid layer when the suspension is allowed to 
stand. This is attributable to the fact that suspensions of the fine 
kaolin clay are fairly viscous and contain only small amounts of coarse 
particles. Few particles of clay, if any, have sufficient mass to settle 
under the influence of gravity. 
However, when clay pigments contain significant amounts of coarse 
particles, especially particles larger than 2 micrometers, and the content 
of ultrafine particles is low, there is a marked tendency of coarse 
particles to settle out of deflocculated suspensions of the clay. For 
example, 70 percent solids deflocculated suspensions of filler grades of 
hydrated kaolin clay tend to form hard sediments during shipment or 
storage. These filler clays usually contain at least 20 percent by weight 
of particles larger than 5 micrometers and at least 35 percent larger than 
2 micrometers. 
High solids deflocculated suspensions of calcined clay pigments having 
particle size distributions similar to those of uncalcined filler clays 
tend to form hard sediments during storage. Furthermore, calcined clay 
pigments have unusual rheological properties and the problem of producing 
stable high solids suspensions is even more difficult than when a typical 
uncalcined clay is involved. Relatively coarse particle size calcined 
kaolin clay products such as SATINTONE.RTM. clay usually cannot even be 
prepared into suspensions containing more than 60 percent solids by 
conventional techniques without producing systems which are highly 
dilatant. In the case of ultrafine low abrasion grades, such as 
ANSILEX.RTM. pigment, fluid suspensions containing more than about 50 
percent solids cannot be prepared without impairing the opacifying 
capacity of the material by subjecting the pigment to excessive mechanical 
action in dry or wet state. Dilatant systems obtained by slurrying 
ultrafine particle size grades of calcined kaolin clay resemble quicksand. 
When a stirring rod is dropped into a fluid concentrated slurry of 
calcined clay, it may be impossible to extricate the stirring rod unless 
the stirring rod is removed very slowly. The shearing force applied to the 
suspension results in the conversion of the originally fluid system into a 
mass which becomes increasingly viscous as the rate of shear increases. 
Processing equipment such as mixers and pumps would be damaged by such 
highly dilatant suspensions or the equipment would stop operating. 
A conventional method of maintaining various particulate solids in 
suspension in fluid media is to thicken the suspending media with suitable 
colloidal additives. This principle has been advocated to prevent 
sedimentation in high solids suspensions of filler grades of uncalcined 
clay. In accordance with the teachings of U.S. Pat. No. 3,130,063 to 
Millman et. al., an organic polymeric thickening agent, preferably CMC, is 
added to a previously deflocculated suspension of coarse filler clay in 
amount sufficient to thicken (and thereby stabilize) the suspension. 
Anionic dispersants (deflocculating agents) are used. However, organic 
polymers such as CMC are subjected to bacterial degradation. Consequently, 
clay slurries stabilized with such polymers may arrive at their 
destination in the form of gray or black masses having a putrid odor. 
Obviously, it is desirable to avoid stabilizing a deflocculated clay 
suspension with such thickening agents since preservatives are costly. 
It has been suggested (U.S. Pat. No. 3,014,836 to Proctor) to reduce the 
viscosity of calcined clay pigments by milling the calcined clay under wet 
or dry conditions. The preferred procedure, as set forth in the patent, is 
to deflocculate a 55 percent to 60 percent solids suspension of the 
calcined clay with a conventional amount of a dispersant (0.3 percent 
TSPP) and ball mill the suspension for 12 to 24 hours. The slip of 
ballmilled clay is then flocculated by adding acid or alum. The 
flocculated calcined clay is subsequently dried and then it is mixed with 
water and dispersing agent to produce a 70 percent solids suspension. 
Proctor did not attempt to produce directly the desired 70 percent solids 
suspensions of calcined clay and he was not concerned with the 
sedimentation properties of his suspensions. Furthermore, Proctor did not 
address the problem resulting from the fact that milling would impair the 
opacifying properties of the clay. 
Similarly, U.S. Pat. No. 3,754,712 to Cecil is concerned with a method for 
preparing fluid high solids suspensions of calcined clay which are stable 
without the necessity of adding colloidal thickening agents. Cecil's 
process involves pebble milling a slurry of anionically dispersed calcined 
clay and gradually adding more clay to increase solids while the slurry is 
being milled. Cecil et. al. did not consider the fact that the milling 
impaired opacification. See also U.S. Pat. Nos. 4,118,245, (Hamil, et. 
al.) and 4,118,246 (Horzepa et. al.) Among the known dispersants disclosed 
in U.S. Pat. No. 4,118,246 are condensed phosphate, amino hydroxy 
compounds such as 2-amino, 2-methyl, 1-propanol (AMP), sodium citrate and 
sodium naphthalene formaldehyde condensates, alone or in combination. 
Marchetti et. al., U.S. Pat. No. 4,118,247 addresses the problem unique to 
the preparation of slurries of acidic, acid-treated montmorillonite clay 
pigments. A combination of condensed phosphate and AMP or other amino 
alcohol is used as the dispersant. In a preferred embodiment, the slurries 
also contain calcined kaolin clay pigments in major or minor amounts. We 
have carried out tests using procedures of U.S. Pat. No. 4,118,247 and 
found that anionic dispersions are formed. 
In accordance with U.S. Pat. No. 4,107,325 to Eggers, aqueous slurries 
containing 50 percent or more of calcined clay are prepared by employing a 
mixture of the calcined clay with a significant amount of uncalcined 
kaolin clay. Practice of the invention necessitates the use of large 
amounts of additives including dispersants (and suspending agents). This 
technique necessitates dilution of the calcined clay with substantial 
amounts of hydrated clay and thus limits the utility of the products for 
some end use applications. Furthermore, the high solids slurries were 
undesirably dilatant. 
U.S. Pat. No. 3,804,65 to Kaliski teaches the use of combinations of 
normally-used anionic dispersants along with nonionic surfactants and 
cationic surfactants to provide a stable pigment slurries. The slurries 
are only usable at high pH, at least 8 or higher, and preferably 8.5 to 
11. In some cases pH values as high as 13 are stated to be desirable. 
An object of the instant invention is to overcome the limitations of prior 
art processes for manufacturing high solids slurries of calcined kaolin 
clay. 
THE INVENTION 
We have discovered a simple method for preparing high solids suspensions of 
calcined clay which are stable without the necessity of adding a colloidal 
thickening agent and have minimal dilatancy. 
Stated briefly, in accordance with this invention, a calcined kaolin clay 
pigment is mixed with water to provide an acidic slurry containing a 
dispersant effective amount of a water-soluble cationic organic material, 
thereby converting the calcined clay from its initially negatively charged 
state to positively charged state. 
This invention provides a cationic pigment which is dispersed 
(deflocculated) in water at an acid pH. Anionic dispersion requires a 
near-neutral or alkaline pH. Slurries of the invention are thus 
particularly useful in systems where dispersion at an acid pH is 
necessary. 
In a preferred embodiment of the invention, the calcined clay pigment is a 
fine particle size low abrasion material. See, for example, U.S. Pat. No. 
3,586,523 (Fanselow et. al.), the teachings of which are incorporated 
herein by cross-reference. 
A preferred cationic dispersant is a diallyl ammonium polymer salt. 
The present invention utilizes a cationic rather than an anionic dispersant 
such as are invariably used alone or in some cases with an amino alcohol 
to disperse clay, resulting in an acidic, rather than a neutral or mildly 
alkaline slurry. 
Slurry shipments of anionic calcined ultrafine clay pigments at 50 percent 
solids require the presence of thickening agents to prevent settling of 
the particles. Slurries of the invention would not require the presence of 
a suspending agent. 
Slurry shipments of calcined kaolin gradually increase in viscosity with 
time. Cationically dispersed calcined kaolin appears to be viscosity 
stable with time. 
The invention potentially affords a host of other benefits. For example, 
calcined kaolin that has been dispersed cationically will co-flocculate 
with cellulose fibers since, under normal papermaking conditions, the 
fibers are negatively charged. The positive and negative particulates 
attract each other and stick together. This phenomenon suggests that a 
cationic calcined kaolin could be a "self-retaining" filler and would not 
require the addition of retention aids. The use of retention aids by a 
papermaker is troublesome since they are expensive and the addition rate 
for maximum retention is difficult to control. 
Previous publications have described the use of cationic coating 
formulations based on calcium carbonate, hydrated kaolin and mixtures 
thereof and claimed for them certain advantages over the normal anionic 
coating formulations. A cationic calcined kaolin could be added directly 
to a cationically dispersed coating formulation without the user having to 
pretreat the calcined kaolin to render it cationic. (A normal anionically 
dispersed kaolin, when added to a cationic formulation, would flocculate 
the system giving a high viscosity, unworkable paste.) 
Current practice in the electrodeposition of paints is to deposit the 
pigment and binder particles from a suspension in which all the particles 
are cationically dispersed. Anionically dispersed pigments are difficult 
to convert to the cationic form since relatively large amount of a 
cationic compound are required to overcome the anionic particle charge. A 
pigment with a high cationic charge could be added to the 
electrodeposition system without the cost of additional chemicals and 
without the danger of flocculation. 
The preferred diallyl polymer salt used in practice of the invention 
provides an electrically conductive film when the aqueous solution is 
dried. It is believed that treatment of calcined kaolin would give a 
product of greater electrical conductivity. This could have advantages in 
certain non-impact printing processes which required a coated paper with 
some degree of electrical conductivity.

DETAILED DESCRIPTION 
Coarse particle size calcined clay within the scope of the invention may 
contain from 0 percent to 30 percent by weight of particles larger than 5 
micrometers (ESD) and at least 35 percent larger than 2 micrometers. The 
invention is of special benefit when used with low abrasion ultrafine 
particle size calcined clay (e.g., calcined clay in which about 88 percent 
is finer than 2 micrometers and at least about 50 percent is finer than 1 
micrometer), exemplified by ANSILEX.RTM. and ANSILEX 93 pigments. 
As used in this specification, the term "calcined kaolin clay pigment" 
shall include kaolin clays which have been heated to over 400.degree. C. 
to render same dehydroxylated. The term thereby embraces fully calcined 
kaolins-which usually have been heated above 980.degree. C. exotherm, as 
well as so-called "metakaolin," which results from heating to lower 
temperatures below the exotherm. Reference is made to Fanselow et. al., 
U.S. Pat. No. 3,586,823 and to Morris U.S. Pat. No. 3,519,453; Podschus, 
U.S. Pat. Nos. 3,021,195 and 3,309,214, and British Pat. No. 1,181,491 
some of which are concerned with kaolins pigments which are calcined at 
lower temperatures and which therefore can be regarded as metakaolins. 
Generally, the pH of calcined pigments (20 percent solid slurries with no 
added dispersant, using deionized water to form slurries) is in the range 
of 4 to 7, more usually 5 to 6. 
Prior to slurry formation according to our invention, the calcined clay may 
be blended with minor amounts (e.g., 1 percent to 20 percent based on the 
weight of the clay) of mineral pigments such as titania or uncalcined 
kaolin. Calcium carbonate, another commonly used pigment, tends to 
dissolve at acidic pH values. 
The process of the present invention is conveniently carried out by adding 
a dispersant effective amount of the cationic compound to the required 
amount of water for the desired solids in a container equipped with a 
stirrer. Once the cationic dispersant has dissolved, the calcined kaolin 
is added slowly with sufficient agitation to give a smooth, uniform, fluid 
suspension. If necessary, the slurry may be passed through a sieve to 
remove any undispersed aggregates or coarse impurities. If the slurry is 
at about 50 percent solids, it may be shipped to the user at these solids 
in tank cars or trucks. Should a dry cationic product be desired, the 
slurry may be dried using spray driers or other commonly used drying 
techniques. 
Presently preferred dispersants are water soluble cationic 
polyelectrolytes. See, for example, U.S. Pat. No. 4,174,279. Cationic 
polyelectrolytes are characterized by a high density of positive charge. 
Positive charge density is calculated by dividing the total number of 
positive charges per molecule by the molecular weight. Generally the high 
charge density of polyelectrolytes exceeds 1.times.10.sup.-3 and such 
materials do not contain negative groups such as carboxyl or carbonyl 
groups. In addition to the alkyl diallyl quarternary ammonium salts, other 
quarternary ammonium cationic polyelectrolytes are obtained by 
copolymerizing aliphatic secondary amines with epichlorohydrin. See U.S. 
Pat. No. 4,174,279. Still other water-soluble cationic polyelectrolytes 
are poly(quarternary ammonium) polyester salts that contain quarternary 
nitrogen in a polymeric backbone and are chain extended by the groups. 
They are prepared from water-soluble poly(quarternary ammonium salts) 
containing pendant hydroxyl groups and bifunctionally reactive chain 
extending agents; such polyelectrolytes are prepared by treating an N, N, 
N.sup.(1), N.sup.(1) tetraalkylhydroxyalkylenediamine and an organic 
dihalide such as a dihydroalkane or a dihaloether with an epoxy 
haloalkane. Such polyelectrolytes and their use in flocculating clay are 
disclosed in U.S. Pat. No. 3,663,461. Other water soluble cationic 
polyelectrolytes are polyamines. Polyamines are usually supplied 
commercially under trade designations; chemical structure and molecular 
weight are not provided by the suppliers. 
Cationic dispersants used in practice of this invention also include low 
molecular weight polyamines (e.g., ethylene diamine or hexamethylene 
diamine), long carbon chain amines or quarternary ammonium salts (e.g., 
"ditallowdimethyl" ammonium chloride). 
The aforementioned cationic dispersants are known when used at appropriate 
dosages to flocculate negatively charged clays. See, for example, U.S. 
Pat. No. 4,738,726 (Pratt et. al.), and references cited therein. It 
should be noted that as incremental dosages of such cationic materials are 
added to anionically charged particles, the initial effect is that of 
flocculation. As dosages increase beyond the levels at which flocculation 
occurs, dispersion (deflocculation) occurs and the charge on the particles 
becomes positive. 
The amount of cationic dispersant required depends on the nature of the 
cationic dispersant as well as the nature of the surface of the pigment 
particles. In most cases the amount of cationic dispersant used is such 
that the slurry of calcined clay has minimum Brookfield viscosity of 90 
mPa.s measured at 100 rpm. A lower molecular weight diallyl polymer salt 
is less effective in conferring a cationic charge than is the same polymer 
of higher molecular weight. Quarternary ammonium polymers of high charge 
density are more effective than those of lower charge density. Higher 
surface area, fine particles pigments require more dispersant than do 
coarser particles. The magnitude of the anionic charge before treatment 
with the cationic dispersant also affects the amount required. A pigment 
carrying a high anionic charge will require a greater amount of cationic 
dispersant than will a pigment which initially has a lower anionic charge. 
A dimethyl diallyl quarternary ammonium chloride polymer commercially 
available under the trademark designation Polymer 261 LV from the Calgon 
Corporation having a molecular weight estimated to be between 
50,000-250,000 has been found particularly useful in the practice of the 
present invention. 
With commercial calcined pigments, 0.2 to 0.3 percent by weight of Calgon's 
261LV will usually result in a fluid, deflocculated slurry. Higher 
quantities (for example up to about 0.8 percent by weight) may impart 
greater fluidity, especially when the viscosity is measured at high shear 
rates. 
The following examples are given to illustrate the invention. 
EXAMPLE 1 
This example illustrates the preparation of a 50 percent solids content 
slurry of a commercially available calcined kaolin pigment (supplied under 
the trademark ANSILEX 93) using a cationic polyelectrolyte (Calgon 261LV 
polymer) as the dispersing agent. The polymer was supplied in aqueous 
solution containing 42 percent active material. 
In an initial experiment, a slurry was made down by a Kitchen Aid mixer 
(Model K5SS) at the low speed setting for stirring. A dilute solution of 
cationic dispersant was prepared by placing 500.0 grams of deionized water 
and 2.976 grams of Calgon 262LV polymer into the stainless steel bowl 
attachment on the mixer. The two ingredients were stirred for five 
minutes. The total amount of ANSILEX 93 pigment added to the diluted 
polymer solution was 500.0 grams, however, after a substantial amount was 
added gradually, the slurry became thicker. The thickened slurry was 
gradually fluidized by slowly adding 0.36 grams of undiluted polymer to it 
followed by the slow addition of the remaining amount of ANSILEX 93 
pigment. After all of the ingredients were added the slurry was dilatant. 
Stirring continued for another fifteen minutes. The resulting slurry 
contained 0.28 percent Calgon 261LV polymer based on the weight of the dry 
pigment and the slurry solids content was exactly 50.6 percent. 
A portion of the slurry was diluted to exactly 50.0 percent solids content 
with deionized water. Due to the very dilatant nature of the slurry, the 
deionized water was added to the slurry gradually during manual mixing of 
the slurry with a spatula, followed by mixing on a roller mill for fifteen 
minutes. 
Tests were carried out to determine the slurry pH, specific conductivity, 
and Brookfield viscosity at 20 and 100 rpm. 
To determine the effect of extra cationic dispersant on the properties of 
the original slurry, 0.01 percent Calgon 261LV polymer (based on the 
weight of the pigment) was added gradually to the slurry while stirring 
the slurry manually with a spatula, followed by mixing on a roller mill 
for fifteen minutes. 
Tests were carried out again to determine the slurry pH, specific 
conductivity, and Brookfield viscosity. 
Results are summarized in TABLE 1. Data in this table show that when the 
amount of polymer in the original slurry was increased from 0.28 percent 
to 0.29 percent Calgon 261LV polymer (based on the weight of dry pigment), 
the slurry pH remained at 4.0; however, the slurry specific conductivity 
increased from 790 .mu.mhos to 820 .mu.mhos, and the slurry Brookfield 
viscosity increased from 60 cp to 80 cp at 20 rpm and from 94 cp to 114 cp 
at 100 rpm. 
Finally, 0.3 cc of sulfuric acid (5 percent active solution) was gradually 
added to the slurry to see if the viscosity of the slurry improved; it was 
noted that acid addition thickened the slurry severely. 
TABLE 1 
______________________________________ 
Effects of Additional Cationic Polymer 
on a 50% Solids ANSILEX 93 Slurry Originally Dispersed 
with 0.28% Calgon 261 LV Polymer 
Total 
Calgon 261 LV Slurry Brookfield Viscosity* 
Polymer Slurry Sp. Cond. cp @ 
(% on pigment) 
pH (.mu.mhos) 20 rpm 100 rpm 
______________________________________ 
0.28 4.0 790 60 94 
0.29 4.0 820 80 104 
______________________________________ 
*measured with spindle number 2 at the tenth revolution of the spindle. 
EXAMPLE 2 
This example illustrates the effect of varying the amount of a cationic 
polyelectrolyte (Calgon 261LV polymer) on characteristics and properties 
of nominally 50 percent solids slurries of ANSILEX 93 calcined clay 
pigment as well as some performance properties indicated by black glass 
scattering data. See TABLE II. 
The specified amount of 261LV was dissolved in 250 ml. of deionized water 
in the bowl of a Kitchen-Aid.RTM. mixer. Two hundred and fifty (250) grams 
of oven dried calcined clay was added slowly with moderate mixing until 
all of the clay has been added. When all of the clay had been added, the 
speed of mixing was increased somewhat and continued for an additional 10 
minutes. The samples were then stored in tightly sealed jars until the 
measurements reported in TABLE II were made. Levels of polymer in the 0.05 
percent to 0.25 percent range did not give a fluid mixture since these 
smaller quantities flocculated the clay. 
As the data of TABLE II show, the use of the cationic polymer at levels of 
0.3 percent and above, provided a positively charged, acidic, fluid 
slurry. The opacity, as measured by black glass scattering was improved or 
at least equivalent to that of the anionic product. High shear viscosity, 
as measured by the Hercules viscometer, was improved at the higher levels 
of polymer addition. 
TABLE II 
__________________________________________________________________________ 
EFFECT OF DISPERSING CALCINED CLAY WITH 261 LV CATIONIC POLYELECTROLYTE 
VISCOSITY ZETA FILMS ON BLACK GLASS 
% CATIONIC % B' FIELD 
HERCULES 
pH POTENTIAL 
GLOSS S 457 
POLYELECTROLYTE 
SOLIDS 
(NOTE 1) 
(NOTE 2) 
(NOTE 3) 
(NOTE 4) 
(NOTE 5) 
(NOTE 
S 
__________________________________________________________________________ 
577 
0.00 50.3 145 210 5.48 -51 53 282 191 
0.30 50.9 158 185 3.65 +33 20 316 228 
0.35 51.2 112 245 3.67 +37 38 295 213 
0.40 51.2 92 275 3.82 +37 44 283 200 
0.50 51.1 139 365 3.77 +45 59 270 185 
0.70 50.9 138 505 3.86 +47 57 282 197 
__________________________________________________________________________ 
(1) mPa.s (cp) 100 rpm at given solids. 
(2) rpm for 0.16 Nm (16 "dynes") at 50.0% solids. 
(3) Measured at % solids shown. 
(4) Measured on Lazer Zee Meter, millivolts. 
(5) Tappi 75.degree. gloss, %. 
(6) m.sup.2 /kg 
EXAMPLE 3 
An experiment was carried out to determine if a cationic calcined clay 
would co-flocculate with pulp fibers. If coflocculation occurs, it would 
indicate that a self-retaining cationic filler might be a viable product. 
Pulp was prepared using a WARING BLENDOR.RTM. mixer into which was placed 
deionized water and laboratory filter paper. After about 2 minutes mixing 
at high speed, a uniform dispersion of pulp fibers was obtained. 
Four 100 ml glass cylinders were filled with the mixtures described below: 
1. Deionized water+2 drops (ca. 0.1 ml) of 50 percent solids anionic 
ANSILEX 93 pigment. 
2. deionized water+2 drops (ca. 0.1 ml) of 50 percent solids slurry of 
ANSILEX 93 pigment which had been made cationic by treatment with 0.41 
percent Calgon 261LV. 
3. As 1 (anionic pigment)+anionic pulp fibers. 
4. As 2 (cationic pigment)+anionic pulp fibers. 
The four cylinders were mixed by hand shaking and then allowed to stand 
undisturbed for about 20 minutes. At the end of this time, the samples had 
the following appearance: 
Cylinders 1 and 2 appeared to be composed of a uniform dispersion of clay 
particles which settle only very slowly. This appearance is typical of 
dispersed clay particles and indicates that both the anionic and cationic 
samples were deflocculated. Cylinder 3 (the mixture of anionic pigment 
with the anionic pulp fibers) appeared to be similar to cylinders 1 and 2 
in that the clay was dispersed uniformly. The pulp fibers, being fairly 
large in comparison with the clay, had settled somewhat but appeared to be 
dispersed. Cylinder 4 (the mixture of cationic pigment and anionic fibers) 
showed a markedly different appearance. In the case of cylinder 4, both 
the clay and pulp fibers had settled to the bottom and the supernatant 
liquid was clear and completely free of suspended particles. This behavior 
is typical of flocculated systems and shows that the clay is 
co-flocculating with the paper fibers. 
EXAMPLE 4 
An experiment was performed in the laboratory whereby a slurry of ANSILEX 
93 was prepared at 50 percent solids content using 1 percent Calgon and 2 
percent AMP (2-amino, 2-methyl, 1-propanol propanol) as dispersants. 
Percentages are based on the weight of ANSILEX 93 pigment. Tests were 
carried out to determine slurry pH, Brookfield viscosity, and particle 
charge (zeta potential). A similar experiment is shown in U.S. Pat. No. 
4,118,247 (Marchetti et. al.) Example 11 where 30 parts acid treated 
montmorillonite and 70 parts ANSILEX pigment were used as kaolin pigments. 
The slurry was made down by a Kitchen Aid mixer (Model K5SS) placed on the 
low speed setting number 2. Initially a diluted solution of both 
dispersants was prepared by placing 500.0 grams of deionized water into 
the stainless steel mixing bowl following which 5.000 grams of Calgon was 
added and stirred for five minutes, and 10.526 grams of AMP (95 percent 
active) was then added and stirred for five minutes more. Five hundred 
grams (500.0 g.) of ANSILEX 93 pigment was gradually and continuously 
added to the stirring dispersant solution and the mixing continued for 
another fifteen minutes. The resulting slurry contained exactly 50.0 
percent solids content, and its pH was 10.7. The slurry Brookfield 
viscosity measured with spindle number two was 210 cp at 20 rpm and 144 cp 
at 100 rpm. 
A zeta potential value of -53 mv. (negative 53) was obtained using the 
Lazer Zee Meter Model 501 (PEN KEM Inc.). The sample was prepared by 
diluting a drop of the original 50.0 percent solids slurry with 50 ml of 
the supernatant or "mother liquor" extracted from the slurry by 
centrifugation. 
The slurry shown in Example II, U.S. Pat. No. 4,118,247 prepared at 52.4 
percent solids content (acid treated montmorillonite and ANSILEX) with the 
same amounts and types of dispersants, resulted in a slurry Brookfield 
viscosity of 350 cps at 100 rpm, 420 rpm and 150 cps. The slurry pH was 
7.7. 
pH measurements used in examples were obtained using the conventional glass 
electrode. The pH values reported in the examples were all measured at the 
indicated percent solids. 
The magnitude and sign (positive or negative) of the electrical charge on 
the particles cited in this example and elsewhere herein are measured 
using the Lazer Zee.RTM. meter, Model 501, a product of Pen Kem, Inc. The 
measurement involves the determination of the velocity of migration of 
charged particle under a known potential gradient. The measurement is 
carried out in a dilute suspension of the slurry. From the measured 
electrophoretic velocity, the particle charge (zeta potential) can be 
calculated. Since cationic and anionic particles migrate in opposite 
direction at velocities proportional to the charge, both the magnitude of 
the charge and its sign, either positive or negative, can be measured. 
Other methods of measuring the magnitude and sign of the electrical charge 
on the particles can be used. For example, an acoustphoretic titrator, 
also manufactured by Pen Kem, can be utilized.