Complex pigment compositions for coating of paper

Complex pigment compositions for the coating of paper, comprising an aqueous phase, at least one pigment of mineral origin, a binding agent, optionally various customary additives, and a dispersing agent comprised of carboxyl-containing polymers which are water soluble and are converted to form salts. The polymers are obtained by known polymerization processes. The dispersing agent PA1 (a) has a specific viscosity (measured on the sodium salt) of between 0.25 and 2; and PA1 (b) is converted to the salt form to the extent of at least 60% by at least one salt-forming agent which has a polyvalent function. These complex pigment compositions have very low viscosities. They may also simultaneously contain diverse pigments, such as kaolin, titanium dioxode, and calcium carbonate, without suffering the usual increase in viscosity and the risk of setting.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to complex pigment compositions for the coating of 
paper, containing a high concentration of one or more pigments having a 
viscosity which is low and is stable with time. 
2. Discussion of the Background 
Those skilled in the art have for a long time had available pigment 
compositions for the coating of paper. These compositions contain 
pigments, ordinarily of a known type such as kaolin, comprised of more or 
less substantial quantities of clays, an aqueous phase in which the 
pigments are dispersed, a binding agent of natural origin which may be 
water-dispersed or water-soluble (e.g. starch, casein, or 
carboxymethylcellulose), and/or a synthetic binding agent (e.g. 
styrene/butadiene emulsions, styrene/acrylate emulsions, or vinyl 
copolymer emulsions), and a dispersing agent (e.g. a polyphosphate). 
There has been rapid development in paper coating techniques due to 
advancement of the relevant techniques and improvement in coating speeds. 
As a result, there has come about a requirement that pigment compositions 
for coating paper must also contain the minimum possible amount of water, 
in order to reduce the heat energy consumed in drying, and in order to 
attain the most favorable rheological characteristics for the coating 
operation. These characteristics are a low viscosity and high velocity 
gradient, so that coating can be accomplished very rapidly; or to enable 
low shear stress via an always-low viscosity, for easy handling of the 
coating composition, particularly during sieving operations prior to the 
coating operation. 
Pigment compositions for the coating of paper have themselves undergone 
major evolution in recent years in response to technical progress (major 
increases in coating speed) and to needs relating to productivity, 
quality, and cost. Beside the reduction of the amount of water, 
improvements have come in the form of increased concentration of the 
pigment materials, and particularly in the use of alkali metal or ammonium 
polyacrylates as dispersants. This enables pigments to be maintained in a 
dispersed state, after being mechanically comminuted, so that the coating 
composition is sufficiently fluid. 
In this connection, French Patent No. 2,185,721 describes pigment 
compositions for coating paper, wherein the dispersant is chosen from the 
acrylic acid polymers completely neutralized by an alkaline sodium 
hydroxide solution. However, such dispersants have major disadvantages in 
that they have been found to be difficult to use in certain pigment 
compositions currently used for coating paper. In particular, they have 
been shown to be sensitive to pH variation in the aqueous phase of the 
pigment dispersion in the ionic environment of the compositions, resulting 
in rapid and irreversible increases in viscosity, and in some cases bulk 
setting of the coating composition. 
The pigment compositions for the coating of paper which are presently 
available have advanced pigment formulations. They increasingly often 
employ mixtures of pigments which are no longer comprised solely of kaolin 
or of kaolin and clays, but are comprised of kaolin and/or pigmented 
calcium carbonate and/or talc and/or titanium dioxide, whereby the ionic 
state of the aqueous phase is changed. Accordingly, the abovementioned 
increases in viscosity (and in certain cases the abovementioned setting) 
occur during preparation of these pigment compositions and during mixing 
of the pigment compositions prior to their being applied to coat paper 
and/or being stored. In particular, these adverse phenomena occur in the 
case of mixtures of pigments. 
Thus, the known dispersants as employed are incapable of eliminating the 
problems caused by the presence of mixtures of pigments which are more or 
less compatible with each other, in the pigment compositions for coating 
paper. Nonetheless, these mixtures are required in the compositions for 
reasons of improving the quality of the paper after coating. 
The present Applicant, in another area of technology, had previously 
encountered the phenomenon of viscosity increase during crushing and 
grinding of mineral materials in aqueous medium, and had successfully 
proposed the use of a "comminution agent", a ethylenic polymer. This 
enabled the concentration of mineral matter in the suspension fed to the 
crushing and grinding operation to be increased, while maintaining a low 
viscosity which was stable with time during the comminution and the 
prolonged (1 month) storage of the suspensions of comminuted materials. 
In this connection, French Patent No. 2,531,444 describes a comminution 
agent comprised of a polymer and/or copolymer of ethylenic acids, wherein 
the acid functions are partially neutralized by at least one neutralizing 
agent having at least one monovalent function, wherewith the degree of 
neutralization may be between 0.40 and 0.96, preferably between 0.50 and 
0.75. Here the nature of the neutralizing cation is not essential. Rather, 
the important characteristic is the amount of free acidity following the 
neutralization. 
However, when this comminution agent is introduced into a pigment 
composition comprised of a high concentration of pigments (e.g. 70%) 
comprising a single pigment (e.g. kaolin) or a plurality of pigments (e.g. 
pigmented calcium carbonate and titanium dioxide) for coating paper, the 
comminution agent causes a substantial increase in the viscosity and 
indeed in certain extreme cases it causes the composition to set, even 
though one would expect just the opposite, i.e., a lowering of the 
viscosity, based on the behavior of the polymeric agent as a comminution 
agent. 
French Patent No. 2,539,137 describes a comminution agent comprised of a 
polymer and/or copolymer of ethylenic acids, wherein the acid functions 
are completely and simultaneously neutralized by at least one neutralizing 
agent having a monovalent function and at least one other neutralizing 
agent having a polyvalent function. The monovalent-type neutralizing agent 
comprises between 40 and 95%, preferably between 60 and 90%, and the 
polyvalent-type neutralizing agent comprises between 60 and 5%, preferably 
between 40 and 10% of the total neutralizing agent. 
However, when this comminution agent is employed as a dispersant in pigment 
compositions for coating of paper according to the prior art method, the 
compositions comprising a very high concentration of one pigment (e.g., 
kaolin, such as "Dinkie A lump", at a concentration of 68%) or of a 
mixture of a plurality of pigments (e.g., calclum carbonate and titanium 
dioxide), a rapid and irreversible change of the rheological 
characteristics of the compositions occurs. In particular a substantial 
increase in viscosity occurs, and in certain cases bulk setting, 
particularly in the case of a mixture of pigments, even if it is a mixture 
of two pigments with one present in a very small proportion. 
SUMMARY OF THE INVENTION 
Accordingly, the object of the invention is to remedy the disadvantages 
described above, by providing complex pigment compositions for coating 
paper, in which a dispersant is introduced which provides a viscosity 
which is low and is stable with time, and which also provides excellent 
compatibility of the pigments and prevents setting. 
This object and other objects which will become apparent from the following 
specification have been achieved by the complex pigment compositions for 
coating paper of the present invention, comprising an aqueous phase, at 
least one pigment of mineral origin, a binding agent, and further 
comprising a dispersing agent comprised of carboxyl-containing polymers 
which are water soluble and are converted to form salts, wherein the 
dispersing agent: 
(a) has a specific viscosity (measured on the sodium salt) of between 0.25 
and 2; and 
(b) is converted to the salt form to the extent of at least 60% of the 
carboxyl groups by at least one salt forming agent which has a polyvalent 
function.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
To better understand the invention, one should recall that a polyvalent 
salt-forming agent has the ability to associate with as many carboxyl 
functions of the polymer as its cation has valences. 
Also, to indicate all the importance and value of the invention, it is 
useful to specify that the term "complex pigment compositions" is 
understood to mean pigmented formulations containing a pigment at a higher 
concentration than in the prior art, or containing a mixture of a 
plurality of pigments the incompatibility of which is clearly evidenced in 
the presence of a dispersant of the prior art type. 
Among the pigments employed alone or in mixtures withi the scope of the 
invention, are kaolins, titanium oxides, talcs, natural or precipitated 
carbonates, aluminum hydroxides, satin white (hydrated double sulfate of 
aluminum and calcium), and natural or synthetic gypsums. 
Research was conducted into dispersants for pigment compositions for the 
coating of paper, and numerous industrial tests were carried out, whereby 
it was observed and later verified that it is possible to devise pigment 
compositions which have higher concentrations of dry matter than have been 
attained according to the prior art. These compositions are of complex 
formulation, employing mixtures of pigments, and have a viscosity which is 
low and is very stable with time, and accordingly, these compositions do 
not set. 
These conditions are achieved when the dispersant is a water-soluble 
carboxyl-containing polymer wherein at least 60% of the carboxylic 
functions are salts of an appropriate salt-forming agent which has a 
polyvalent function, wherewith at least 60% of the carboxylate salt groups 
are formed with the agent. In contrast, the polymer would cause the 
viscosity of the pigment composition to increase and in some cases would 
cause them to set, if unconverted or particularly if converted to the salt 
form entirely with a monovalent salt-forming agent, and if used in 
unconverted or monovalently converted form as a dispersant in complex 
pigment compositions for coating paper. 
The carboxyl-containing polymers comprising the dispersant of the present 
invention result from polymerization in the presence of transfer agents, 
according to known methods, in aqueous medium, or in alcohol or 
water-alcohol or aromatic or aliphatic medium, of at least one of the 
following monomers: (meth)acrylic acid, itaconic acid, crotonic acid, 
fumaric acid, maleic anhydride, isocrotonic acid, aconitic acid, mesaconic 
acid, sinapic acid, undecylenic acid, angelic acid, and hydroxyacrylic 
acid. 
The carboxyl-containing polymer may also contain at least one of the 
following comonomers: acrolein, acrylamide, acrylonitrile, esters of 
(meth)acrylic acid (in particular, methyl (meth)acrylate, ethyl 
(meth)acrylate, propyl (meth)acrylate, and dimethylaminoethyl 
(meth)acrylate), imidazoles, vinylpyrrolidone, vinylcaprolactam, ethylene, 
propylene, isobutylene, diisobutylene, vinyl acetate, styrene, 
alpha-methylstyrene, and methyl vinyl acetone. 
The transfer agents employed in the polymerization are those well known in 
the art, e.g. isopropanol, tertiary dodecylmercaptan, thioglycolic acid 
and its esters, n-dodecylmercaptan, 2-mercaptopropionic acid, and 
thiobisethanol. 
The polymerization medium may be water, methanol, ethanol, propanol, 
isopropanol, one or more of the butanols, dimethylformamide, 
dimethylsulfoxide, tetrahydrofuran, acetone, methyl ethyl ketone, ethyl 
acetate, butyl acetate, hexane, heptane, benzene, toluene, xylene, acetic 
acid, tartaric acid, lactic acid, citric acid, gluconic acid, 
glucoheptonic acid, halogenated solvents (such as carbon tetrachloride, 
chloroform, dichloromethane, or chloromethane), ethers of ethylene glycol, 
and ethers of propylene glycol. 
The water-soluble carboxyl-containing polymers according to the invention 
generally have a specific viscosity (measured on the sodium salt) which is 
preferably between 0.30 and 1.0. 
The specific viscosity, .eta., of the carboxyl-containing polymers and/or 
copolymers is determined as follows: 
A solution of the 100% neutralized carboxyl-containing polymer and/or 
copolymer (neutralized by sodium hydroxide for the purposes of this 
measurement) is prepared by dissolving 50 g of the dry polymer and/or 
copolymer in 1 liter of a solution of 60 g NaCl in distilled water. Then, 
using a capillary viscometer with a Baume constant of 1.05.times.10.sup.-4 
placed in a thermostat bath at 25.degree. C., the time of outflow of a 
given volume of the solution containing the alkaline carboxyl-containing 
polymer and/or copolymer is measured, as well as the time of outflow of 
the same volume of aqueous NaCl solution without the polymer and/or 
copolymer. The specific viscosity is then defined as follows: 
##EQU1## 
The capillary tube is ordinarily chosen such that the outflow time of the 
NaCl solution without the polymer and/or copolymer is about 90-100 sec, at 
which point the measurement of the specific viscosity is very precise. 
The salt-forming agent having a polyvalent function is chosen from among 
the group of compounds having at least one divalent alkaline-earth cation, 
in particular calcium, magnesium, zinc, copper, or lead cations, and the 
group of compounds having at least one trivalent cation, in particular, 
aluminum and chromium cations, and the group of compounds having at least 
one of the cations of higher valence. 
The degree of salt-forming of the dispersant according to the invention by 
at least one salt-forming agent having a polyvalent function may be 
between 60% and 100% inclusive. 
After the salts are formed with at least 60% of the acid sites by at least 
one salt-forming agent having a polyvalent function, the remaining acid 
sites may be maintained in the acid state or may be converted to salts 
according to the prior art, i.e., using a salt-forming agent having a 
monovalent function, e.g., an alkali cation, in particular a cation of 
lithium, sodium, or potassium, or similarly ammonium or a quaternary 
amine. 
The dispersant is introduced into the pigment compositions at a 
concentration of 0.1-1.5 wt. %, preferably 0.15-1.0 wt. % based on the 
weight of the dry pigments. 
In addition to the dispersant, the compositions are comprised of pigments, 
alone or in mixtures, chosen from among those known in the art (e.g., 
kaolin, calcium carbonate, talc, titanium dioxide, and aluminum 
hydroxide). 
The pigment compositions according to the invention are also comprised of 
at least one binder and/or water retention agent, chosen from among the 
binders of natural or synthetic origin, e.g. natural-type binders such as 
starch, carboxymethylcellulose, and polyvinyl alcohol, all used in aqueous 
solution and serving simultaneously as water retention agents, and 
synthetic-type binders such as styrene-butadiene copolymers or 
styrene-acrylate copolymers, with all of these copolymers being employed 
in aqueous emulsion. 
The binder and/or water retention agent is introduced in the pigment 
compositions according to the invention in the amount of 7-20 wt. % based 
on the weight of dry pigments. 
The pigment compositions according to the invention may also contain the 
usual additives, in known fashion, e.g. antifoaming agents, bluing agents, 
biocides, colorants, alkaline hydroxides, etc. 
The usual additives are introduced in the pigment compositions according to 
the invention in the amounts required in each specific case to obtain the 
desired formulation properties. These effective amounts are known in the 
art. 
In practice, the pigment compositions according to the invention may 
contain the following ingredients (figures given are wt. % with respect to 
the dry, anhydrous mineral pigment component): 
(a) Dispersant, in the amount of 0.10-1.5%, preferably 0.15-1.0%; 
(b) Binder and/or water retention agent, in the amount of 7-20%; 
(c) Optionally, usual additives, in the known amounts. 
The pigment compositions are prepared according to methods known in the 
art. 
The pigment compositions according to the invention represent substantial 
advances over the prior art in the technical area of paper coating, for 
the reasons that they contain a complex pigment formulation (mixture of 
pigments), at a high concentration, and they have optimal rheological 
characteristics for the coating operation, namely low viscosity under high 
velocity gradients, as well as having optimal rheological characteristics 
for the materials handling operations such as sieving and pumping, i.e., 
low viscosities and low shear stresses are maintained. 
Other features of the invention will become apparent in the course of the 
following descriptions of exemplary embodiments which are given for 
illustration of the invention and are not intended to be limiting thereof. 
EXAMPLES 
EXAMPLE 1 
The object of this Example is to illustrate differences in characteristics 
between the invention and the prior art. 
Pigment compositions for the coating of paper were prepared by known 
methods. One such group of compositions was prepared using known 
dispersants, and another such group was prepared using dispersants 
according to the invention. 
In a first set of tests (Tests 1 and 2), for a given pH traditionally used 
in the paper industry, the optimal concentration interval of the 
dispersant in the compositions was determined so as to yield a very low, 
constant viscosity. 
In Test 1, pigment compositions were used wherein the pigment, Dinkie A 
lump kaolin (supplied by the firm English China Clay, of Great Britain) 
was suspended in the amount of 71 wt. % in water (based on the total 
weight of the suspension) in the presence of increasing amounts of sodium 
polyacrylate (100% converted to salt form, with specific viscosity 0.4), 
which is a dispersant representing the prior art. 
In Test 2, pigment compositions were used wherein the same pigment 
suspension was used but in the presence of increasing amounts of an 
acrylic polymer with specific viscosity 0.4 (converted to salt form in the 
amount of 70% by Ca.sup.+2 and in the amount of 30% by Na.sup.+), which is 
a dispersant according to the invention. 
The pH of the compositions was controlled at 7.4.+-.0.1. 
The Brookfield viscosities of all these pigment compositions were measured 
at 10 and 100 rpm and at forces appropriate to the viscosities. The 
viscosities were measured with the aim of devising the optimum 
preparation. 
All the results for these compositions are presented in Table 1 and FIG. 1. 
TABLE I 
______________________________________ 
Tabulated data are Brookfield 
viscosities (centipoise) 
Amount of dispersant used, dry 
wt. % (based on dry weight of 
Rpm of Brookfield 
pigments) 
Test No. 
viscometer 0.20% 0.22% 0.25% 0.28% 
______________________________________ 
Test 1 10 T/mn 1,100 1,200 1,400 1,800 
Prior Art 
100 T/mn 400 410 450 510 
Test 2 10 T/mn 1,100 900 980 1,000 
Invention 
100 T/mn 390 340 340 380 
______________________________________ 
Table 1 shows that, at equal concentrations of the dispersants: 
(a) the viscosity of the pigment compositions is always lower with the 
dispersant according to the invention; 
(b) the viscosity of pigment compositions according to the invention does 
not change between dispersant concentrations of 0.22 and 0.25 wt. % (dry 
weight basis), which is the most favorable use interval. At the same time, 
the viscosity of prior art compositions increases with the amount of 
dispersant. 
In a second group of tests (Tests 3 and 4), a pH interval was studied for a 
given concentration of dispersant, which corresponds to the pH of 
components used in the paper industry for preparing coating compositions. 
It is known that the pH of kaolin coating-compositions used in the prior 
art is controlled at about 7.3, which is the value at which the viscosity 
is the lowest. It is further known that adjusting the pH of the various 
components of the coating compositions avoids shocks resulting from pH 
differences, which are manifested as an undesirable increase in viscosity. 
Test 3 concerns pigment compositions containing Dinkie A lump kaolin 
suspended in the amount of 71 wt. % in water (based on the total weight of 
the suspension) in the presence of the same sodium polyacrylate (100% 
converted to salt form) as was used in Test 1. The polyacrylate is a 
dispersant according to the prior art, the dispersant being present in the 
compositions in the amount of 0.25 wt. % (dry weight basis, based on the 
weight of the pigments). The pH of the compositions ranged from 7.35 to 
10.25. 
Test 4 concerns pigment compositions containing Dinkie A lump kaolin 
suspended in the amount of 71 wt. % in water (based on the total weight of 
the suspension) in the presence of the same (calcium/sodium) polyacrylate 
as was used in Test 2. The polyacrylate is a dispersant according to the 
invention, the dispersant being present in the said compositions in the 
amount of 0.25 wt. % (dry weight basis, based on the weight of the 
pigments). The pH of the compositions ranged from 7.35 to 10.25. 
The Brookfield viscosities of these pigment compositions (Tests 3 and 4) 
were measured as per Tests 1 and 2. 
All the results for these compositions are presented in Table II and FIG. 
2. 
Table II reveals that, for increasing pH of the given pigment compositions 
with the same concentration of the respective dispersants: 
(a) the viscosity of the compositions according to the invention is always 
less than that of the compositions according to the prior art, regardless 
of pH; and 
(b) the viscosity of the compositions according to the invention is stabile 
regardless of pH, while the viscosity of the prior art compositions 
increases with pH. 
TABLE II 
______________________________________ 
Tabulated data are Brookfield 
viscosities (centipoise) 
Rpm of Brookfield 
pH 
Test No. 
viscometer 7.35 7.8 8.3 9.3 10.25 
______________________________________ 
Test 3 10 T/mn 1,400 1,400 1,500 
1,750 
2,350 
Prior Art 
100 T/mn 450 440 450 500 630 
Test 4 10 T/mn 940 950 950 1,000 
1,360 
Invention 
100 T/mn 320 340 340 350 400 
______________________________________ 
EXAMPLE 2 
The purpose of this Example is to illustrate the invention. The Example 
concerns preparation of pigment compositions for the coating of paper, 
using dispersants comprising acrylic polymers having specific viscosities 
(measured on the sodium salts) in the preferred range of 0.3 to 1, in 
which the polymers have been converted to the salt form to the extent of 
at least 60% by at least one salt-forming agent having a divalent 
function. 
Comparative Test 5 concerns a pigment composition for coating paper, 
comprised of titanium dioxide ("Anatase", supplied by Thann et Mulhouse) 
in the amount of 72 wt. % (based on the total weight of the composition), 
in the presence of dispersants in the amount of 0.35 wt. % (based on the 
weight of pigment), the dispersants being namely acrylic polymers 
completely converted to the salt form by sodium ions as per the prior art. 
Tests 6-24 concern pigment compositions for coating paper as per Test 5 but 
with the dispersants being acrylic polymers converted to the salt form to 
the extent of at least 60% by a salt-forming agent having a divalent 
function (see Table III). 
The Brookfield viscosities of all these pigment compositions (Tests 6-24) 
were measured at 10 and 100 rpm and at forces appropriate to the 
viscosities. The viscosities were measured with the aim of devising the 
optimum preparation. 
Further, in order to demonstrate the possible adverse effects produced in 
industrial installations, in particular in piping, pumps, and storage 
tanks, by successive passage of different compositions through such 
installations, e.g. one based on calcium carbonate and the other on 
titanium dioxide, the two compositions were tested in the laboratory for 
their compatibility. The test consisted of the following. 
A very small quantity (1 wt. % based on the weight of the TiO.sub.2) of an 
aqueous suspension of finely ground calcium carbonate ("H-90", supplied by 
Omya France) was introduced into a pigment composition based on titanium 
dioxide, with the concentration of the calcium carbonate in the aqueous 
calcium carbonate suspension being 75 wt. % (based on the total weight of 
the suspension). The changes in viscosity of the pigment composition were 
observed which could lead to setting. 
All the parameters and results with respect to the above-described 
compositions are given in Table III. 
TABLE III 
__________________________________________________________________________ 
Pigment Compositions comprising 
titanium 
dioxide ("Anatase", supplied by Thann 
et 
Mulhouse) in the amount of 72 wt. % of 
the 
Dispersant total weight of the pigment 
composition. 
(acrylic polymer) Viscosity (centipoise) 
Salt-forming 
Degree of conversion 
At 10 rpm (of 
At 100 rpm (of 
Compatibility with 
Test No. 
Specific Viscosity 
agent to salt form (1 = 100%) 
viscosimeter) 
viscosimeter) 
calcium 
__________________________________________________________________________ 
carbonate 
Test 5 
0.40 Na.sup.+ 
1 Not measurable (composition 
Setting 
Prior Art too thick) 
Test 6 
0.40 Ca.sup.2+ 
1 2,200 385 No increase in 
Invention viscosity 
Test 7 
0.40 Ca.sup.2+ /Na.sup.+ 
0.70/0.3 3,800 650 No increase in 
Invention viscosity 
Test 8 
0.40 Ca.sup.2+ /Na.sup.+ 
0.55/0.45 Thick, of pasty consistency 
No increase in 
Prior Art viscosity 
Test 9 
0.40 Mg.sup.2+ 
1 4,500 750 Viscosity increase 
Invention less than 20% 
Test 10 
0.40 Mg.sup.2+ /Na.sup.+ 
0.7/0.3 12,200 1,380 Viscosity increase 
Invention less than 20% 
Test 11 
0.40 Mg.sup.2+ /Na.sup.+ 
0.6/0.4 24,000 3,200 Viscosity increase 
Invention less than 20% 
Test 12 
0.55 Ca.sup.2+ 
1 1,400 250 No increase in 
Invention viscosity 
Test 13 
0.55 Ca.sup.2+ /Na.sup.+ 
0.70/0.3 2,600 450 No increase in 
Invention viscosity 
Test 14 
0.55 Ca.sup.2+ /Na.sup.+ 
0.6/0.4 5,400 875 No increase in 
Invention viscosity 
Test 15 
0.55 Mg.sup.2+ 
1 1,900 345 No increase in 
Invention viscosity 
Test 16 
0.55 Mg.sup.2+ /Na.sup.+ 
0.7/0.3 2,650 455 No increase in 
Invention viscosity 
Test 17 
0.55 Mg.sup.2+ /Na.sup.+ 
0.6/0.4 2,700 470 No increase in 
Invention viscosity 
Test 18 
0.70 Ca.sup.2+ 
1 1,600 310 No increase in 
Invention viscosity 
Test 19 
0.70 Ca.sup.2+ /Na.sup.+ 
0.765/0.235 2,000 350 No increase in 
Invention viscosity 
Test 20 
0.70 Ca.sup.2+ /Na.sup.+ 
0.7/0.3 2,500 440 No increase in 
Invention viscosity 
Test 21 
0.70 Ca.sup.2+ /Na.sup.+ 
0.6/0.4 3,450 600 No increase in 
Invention viscosity 
Test 22 
0.70 Mg.sup.2+ 
1 2,000 410 No increase in 
Invention viscosity 
Test 23 
0.70 Mg.sup.2+ /Na.sup.+ 
0.7/0.3 2,400 435 No increase in 
Invention viscosity 
Test 24 
0.70 Mg.sup.2+ /Na.sup.+ 
0.6/0.4 2,650 455 No increase in 
Invention viscosity 
__________________________________________________________________________ 
By comparison of Test 5 with Tests 6-24, Table III shows the following: 
(a) the major decrease in viscosities of the pigment compositions, which 
are only down into the measurable range with the inventive dispersant, and 
are beyond measurability with the prior art dispersant. The pigments may 
be used at the given concentration (72 wt. %) with the invention, but not 
with the prior art; 
(b) the very beneficial influence of conversion of the dispersants to salts 
with at least 60% of the carboxyl groups converted to salt form by means 
of a polyvalent salt-forming agent; and 
(c) the high compatibility of the pigments studied ("Anatase" TiO.sub.2 and 
calcium carbonate), for the pigment compositions according to the 
invention. 
EXAMPLE 3 
The object of this Example is to demonstrate the universal character of the 
invention for the use of pigment compositions comprising titanium dioxide 
of diverse origins. 
For this purpose, pigment compositions for coating paper, in which the 
pigment comprises titanium dioxide (namely "AHR", supplied by Tioxide, for 
Tests 25-27; and "TiO.sub.2 A", supplied by Kronos, for Tests 28-30), were 
prepared by known methods. The pigment was suspended in water in the 
amount of 72 wt. % of the weight of the suspension, and was used in the 
presence of a dispersant which was either: 
(i) a sodium polyacrylate (specific viscosity 0.4; degree of conversion to 
salt form=100%), for the tests representing the prior art (Tests 25-6, 
28-9); or 
(ii) an acrylic polymer (specific viscosity 0.4) which had been converted 
to salt form to the extent of 70% of the carboxyl groups by Ca.sup.++ and 
to the extent of 30% of the carboxyl groups by Na.sup.+, for the tests 
representing the invention (Tests 27 and 30). 
The viscosities were measured and the compatibilities were tested, in the 
same manner as in Example 2, for all the pigment compositions. 
All the results with respect to the abovedescribed compositions are given 
in Table IV. 
TABLE IV 
__________________________________________________________________________ 
Pigment Compositions comprising 
titanium 
Dispersant dioxide in the amount of 72 wt. 
% of the 
(acrylic polymer) total weight of the pigment 
composition. 
Type of Salt- Amount of dispersant 
Viscosity (centipoise) 
Compatability 
Titanium 
forming 
Degree of conversion 
(dry wt. % based on 
At 10 rpm (of 
At 100 rpm 
with calcium 
Test No. 
Dioxide 
agent to salt form (1 = 100%) 
dry weight (of pigment 
viscometer) 
viscometer) 
carbonate 
__________________________________________________________________________ 
Test 25 
"AHR" Na.sup.+ 
1 0.1 2,750 520 Setting 
Prior Art 
Supplied by or congealing 
the firm 
Tioxide 
Test 26 
"AHR" Na.sup.+ 
1 0.35 14,600 2,700 Setting 
Prior Art 
Supplied by or congealing 
the firm 
Tioxide 
Test 27 
"AHR" Ca.sup.2+ /Na.sup.+ 
0.7/0.3 0.35 3,400 610 No increase 
Invention 
Supplied by in viscosity 
the firm 
Tioxide 
Test 28 
"A" Na.sup.+ 
1 0.1 Thick, of pasty 
Settingency 
Prior Art 
Supplied by or congealing 
the firm 
Kronos 
Test 29 
"A" Na.sup.+ 
1 0.35 Thick, of pasty 
Settingency 
Prior Art 
Supplied by or congealing 
the firm 
Kronos 
Test 30 
"A" Ca.sup.2+ /Na.sup.+ 
0.7/0.3 0.35 2,450 440 No in- 
Supplied by crease in 
the firm viscosity 
Kronos 
__________________________________________________________________________ 
Table IV confirms the conclusions drawn from Table III of Example 2, which 
particularly favor the invention. 
EXAMPLE 4 
This Example enables the universal character of the invention to be 
illustrated by employing kaolin in the pigment compositions, the kaolin 
being used as an example of pigments of different origin than the pigment 
used in Example 1. 
For this purpose, pigment compositions for the coating of paper were 
prepared by known methods, which were based on the kaolin "Alphacoat" 
(supplied by Anglo American Clays Corp.) plus a dispersant, one 
composition with a dispersant representing the prior art, and one with a 
dispersant according to the invention. 
Test 31 concerns pigment compositions comprised of "Alphacoat" kaolin 
suspended in water in the amount of 68 wt. % kaolin (based on the total 
weight of the suspension), plus a dispersant according to the prior art, 
namely a sodium polyacrylate (specific viscosity 0.4) introduced into the 
compositions in a series of increasing amounts expressed in units of dry 
wt %. 
Test 32 concerns pigment compositions comprised of the same "Alphacoat" 
kaolin suspended in the same concentration in water, plus a dispersant 
according to the invention, namely an acrylic polymer (specific viscosity 
0.4) converted to salt form to the extent of 70% of the carboxyl groups by 
Ca.sup.++ and 30% of the carboxyl groups by Na.sup.+, which was 
introduced into the compositions in a series of increasing amounts. 
The pH of these compositions was controlled at 7.1.+-.0.1 
The Brookfield viscosities of all these pigment compositions were measured. 
The results are given in Table V and FIG. 3. 
TABLE V 
__________________________________________________________________________ 
Tabulated data are Brookfield 
viscosities (centipoise) 
Amount of dispersant used, dry wt. % 
Rpm of Brookfield 
(based on dry weight of pigments) 
Test No. 
viscometer 0.10% 
0.15% 
0.18% 
0.20% 
0.22% 
__________________________________________________________________________ 
Test 31 
10 T/mn 
2,500 
2,550 
3,000 
2,300 
2,850 
Prior Art 
100 T/mn 
560 
530 630 600 615 
Test 32 
10 T/mn 
1,850 
1,900 
1,850 
2,400 
2,300 
Invention 
100 T/mn 
460 
470 450 470 450 
__________________________________________________________________________ 
Table V confirms the conclusions derived from Table 1 (which concerns a 
Dinkie A lump kaolin). 
Test 33 concerns pigment compositions comprised of the same "Alphacoat" 
kaolin in water suspension in the same (68 wt. %) concentration, and 
further comprised of a prior art dispersant which is the same as that of 
Test 31, which is introduced into the compositions in a dry weight 
concentration of 0.25 wt. % (based on the dry weight of the pigment). The 
pH of the compositions is varied in a series ranging from 6.7 to 10.25. 
Test 34 concerns pigment compositions comprised of the same "Alphacoat" 
kaolin in water suspension in the same (68 wt. %) concentration, and 
further comprised of a dispersant according to the invention which is the 
same calcium/sodium polyacrylate as that of Test 32, which is introduced 
into the compositions in a dry weight concentration of 0.25 wt. % (based 
on the dry weight of the pigment). The pH of the compositions is varied in 
a series ranging from 6.5 to 10.0. 
The results for these pigment compositions are given in Table VI and FIG. 
4. 
TABLE VI 
______________________________________ 
Rpm of 
Brookfield Tabulated data are Brookfield 
Test No. 
viscometer viscosities (centipoise) 
______________________________________ 
pH 
6.7 7.1 7.8 8.9 9.4 10.25 
______________________________________ 
Test 33 
10 T/mn 1,650 2,550 
1,400 1,400 
1,650 
2,100 
Prior Art 
100 T/mn 400 530 335 320 360 430 
______________________________________ 
pH 
6.5 7.0 7.1 8.25 8.8 10.0 
______________________________________ 
Test 34 
10 T/mn 1,650 1,900 
1,300 1,000 
1,050 
1,150 
Invention 
100 T/mn 405 470 335 265 275 290 
______________________________________ 
Table VI provides grounds for the same conclusions as Table II (which 
concerns a Dinkie A lump kaolin). 
EXAMPLE 5 
This Example illustrates the invention in comparison to the prior art. The 
Example concerns preparation of pigment compositions for coating paper, 
making use of dispersants comprising acrylic polymers with specific 
viscosity 0.4 (measured on the sodium salt). 
Tests 35 and 37 concern aqueous pigment compositions for coating paper, 
comprised of a natural calcium carbonate (supplied by Omya; BET specific 
surface 7 m.sup.2 /g--Test 35) or of a precipitated calcium carbonate 
("Socal P3" supplied by Solvay; BET specific surface 14 m.sup.2 /g--Test 
37), in the presence of a dispersant, i.e., the above-described acrylic 
polymer, which is completely converted to salt form by sodium ion, as per 
the prior art. 
Tests 36 and 38 concern aqueous pigment compositions for coating paper 
according to the invention which are comprised of the same calcium 
carbonates as used in Tests 35 and 37, respectively, in the presence of a 
dispersant i.e., the above-described acrylic polymer, which is converted 
to salt form to the extent of 70% of the carboxyl groups by Ca.sup.++ and 
to the extent of 30% by Na.sup.+. 
The results for these compositions are given in Table VII. 
Comparison of the prior art tests (Tests 35 and 37) with the tests 
according to the invention (Tests 36 and 38) confirms the important 
benefits obtained from the invention, particularly when there is a 
substantial increase in the BET specific surface of the pigments. It is 
clear that high surface area leads to problems which are familiar in the 
art. 
TABLE VII 
__________________________________________________________________________ 
Dispersant Viscosity 
(centipoise) 
(acrylic polymer) 
Weight Percent of the 
Degree of Amount of Pigment 
pigment composition 
Type of 
Salt- conversion to 
Amount of Dispersent 
(wt. % based on the 
At 10 
At 100 rpm 
mineral 
forming 
salt form 
(dry wt. % based on dry 
total weight of the 
(of (of 
Test No. 
pigment 
agent (1 = 100%) 
weight of pigment) 
aqueous pigment suspension) 
viscometer) 
viscometer) 
__________________________________________________________________________ 
Test 35 
Natural 
Na.sup.+ 
1.0 0.25 73 1,150 300 
Prior Art 
calcium 
Test 36 
carbonate 
Ca.sup.2+ /Na.sup.+ 
0.7/0.3 
0.25 73 1,100 290 
Invention 
Test 37 
Precipi- 
Na.sup.+ 
1.0 0.80 68 1,000 300 
Prior Art 
tated 
Test 38 
calcium 
Ca.sup.2+ /Na.sup.+ 
0.7/0.3 
0.80 68 300 170 
Invention 
carbonate 
__________________________________________________________________________ 
EXAMPLE 6 
This example illustrates the use of a dispersant according to the invention 
in an aqueous pigment composition, which is an acrylic polymer (specific 
viscosity 0.4) partially converted to the salt form by Ca.sup.++ (to the 
extent of 70% of the carboxyl groups), with the remaining --COOH groups 
being unconverted. 
In this connection, Test 39 concerns preparation of an aqueous pigment 
composition comprising TiO.sub.2 in the amount of 72 wt. % (based on the 
total weight of the pigment composition suspension), the TiO.sub.2 being 
the product "Anatase" of the firm Thann et Mulhouse,. The pigment 
composition further comprises a dispersant (the above-described acrylic 
polymer, but with Ca.sup.++ /--COOH=0.7/0.3) which is present in the 
amount of 0.35 wt. % (based on the dry weight of the pigment). 
The results for this composition and for the comparison composition (the 
prior art Test 5) are given in Table VIII. 
TABLE VIII 
______________________________________ 
Dispersant 
(acrylic polymer) 
Degree of Viscosity (centipoise) 
Salt- conversion 
of the pigment compositions 
forming to salt form 
At 10 rpm (of 
At 100 rpm (of 
Test No. 
agent (1 = 100%) 
viscometer 
viscometer) 
______________________________________ 
Test 5 Na 1 Not measureable - 
Prior Art composition too 
thick 
Test 39 
Ca.sup.2+ / 
0.7/0.3 5,000 780 
Invention 
--COOH 
______________________________________ 
Thus, as long as the dispersant (acrylic polymer) is converted to salt form 
to the extent of at least 60% of the carboxyl groups by a salt-forming 
agent having a polyvalent function, the presence of free carboxylic acid 
groups does not detract from the beneficial effects noticed for the 
pigment compositions according to the invention. 
EXAMPLE 7 
The object of this Example is comparison of complex pigment compositions 
for coating paper, namely, compositions comprising mixtures of two 
components, according to the prior art and according to the invention. 
Complex pigment compositions were prepared, by known methods, in which the 
dispersant was, in one case, a known type (sodium polyacrylate), and in 
the other case a polymer converted to salt form according to the 
invention, namely, converted to salt form to the extent of 70% of the 
carboxyl groups by Ca.sup.++ and to the extent of 30% by Na.sup.+. 
Test 40 concerns a complex pigment composition according to the prior art, 
comprised of the following: 
(1) Dinkie A lump kaolin in the amount of 70 wt. %, introduced in the form 
of an aqueous suspension comprised of the kaolin in the amount of 71 wt. % 
of the suspension, and containing a dispersant in the form of a sodium 
polyacrylate (specific viscosity 0.4; completely converted to salt form), 
the dispersant being present in the amount of 0.25 wt. % (dry basis, based 
on the dry weight of the kaolin); and 
(2) calcium carbonate pigment in the amount of 30 wt. %, introduced in the 
form of an aqueous suspension comprised of the calcium carbonate in the 
amount of 74.3 wt. % of the suspension, and containing a dispersant in the 
form of an acrylic polymer (specific viscosity 0.56; converted to salt 
form to the extent of 30% of the carboxyl groups by Ca.sup.++ and to the 
extent of 70% by Na.sup.+, according to the prior art) the dispersant 
being present in the amount of 0.6 wt. % (dry basis, based on the dry 
weight of the calcium carbonate). 
Test 41 concerns a complex pigment composition according to the invention, 
comprised of the following: 
(1) Dingie A lump kaolin in the amount of 70 wt. %, introduced in the form 
of an aqueous suspension comprised of the kaolin in the amount of 71 wt. % 
of the suspension, and containing a dispersant in the form of an acrylic 
polymer (specific viscosity 0.4; converted to salt form to the extent of 
70% of the carboxyl groups by Ca.sup.++ and to the extent of 30% by 
Na.sup.+). The dispersant was present in the amount of 0.25 wt. % (dry 
basis, based on the dry weight of the kaolin); and 
(2) calcium carbonate pigment in the amount of 30 wt. %, introduced in the 
form of an aqueous suspension as per Test 40. 
Pigment compositions for coating paper were prepared by adding the 
following to the mixtures of Test 40 (prior art) and Test 41 (invention), 
per 100 parts by weight of dry pigment: 
0.5 parts by weight of a water retention agent (carboxymethylcellulose); 
and 
10.5 parts by weight of a latex, namely an anionic aqueous emulsion of an 
acrylic copolymer having trade name "Acronal S 360 D.RTM.", supplied by 
BASF. 
The pH of these coating compositions was controlled at 8.6.+-.1. The dry 
matter concentration was 69 wt. %. 
The Brookfield viscosities of the coating compositions were measured at 10 
and 100 rpm, under appropriate forces. 
All the results for these compositions are given in Table IX. 
TABLE IX 
______________________________________ 
Brookfield viscosity (centipoise) 
At 10 rpm At 100 rpm 
Test No. (of the viscometer) 
(of the viscometer) 
______________________________________ 
Test 40 16,600 2,880 
Prior Art 
Test 41 11,000 1,900 
Invention 
______________________________________ 
Table IX, showing the comparison between the two paper-coating 
compositions, confirms that at equal concentrations of pigments and 
dispersants the viscosity of the inventive paper-coating composition is 
always much lower (by about 40%) than that of the coating composition 
according to the prior art. 
EXAMPLE 8 
This Example is a comparison of complex pigment compositions for coatin 
paper, namely, compositions comprising mixtures of three components, 
according to the prior art and according to the invention. Complex pigment 
compositions were prepared, by known methods, in which the dispersants 
were, in one group of cases, prior art types, and in the other group of 
cases the dispersants were polymers converted to salt form according to 
the invention. 
Test 42 concerns a complex composition according to the prior art, prepared 
by combining the following ingredients: 
(a) titanium dioxide ("Anatase At1", supplied by the firm Thann et 
Mulhouse) in the amount of 10 wt. % of the composition, introduced in the 
form of an aqueous suspension of which the titanium dioxide comprises 72 
wt. %. The suspension also contains a dispersant in the form of sodium 
polyacrylate (specific viscosity 0.4; degree of conversion to the salt 
form 100% of the carboxyl groups), the dispersant being present in the 
amount of 0.1 wt. % (dry basis, based of the dry weight of the titanium 
dioxide); 
(b) then, calcium carbonate pigment in the amount of 20 wt. % of the 
composition, introduced in the form of the aqueous suspension employed in 
Test 40, with the prior art dispersant; and 
(c) then, kaolin in the amount of 70 wt. % of the composition, introduced 
in the form of the aqueous suspension employed in Test 40, with the prior 
art dispersant. 
Test 43 concerns a complex composition according to the invention, prepared 
by combining the following ingredients: 
(a) titanium dioxide ("Anatase At1", supplied by the firm Thann et 
Mulhouse) in the amount of 10 wt. % of the composition, introduced in the 
form of an aqueous suspension of which the titanium dioxide comprises 72 
wt. %. The suspension also contains a dispersant according to the 
invention, in the form of an acrylic polymer (specific viscosity 0.4 as 
measured on the sodium salt; converted to the salt form to the extent of 
70% of the carboxyl groups by Ca.sup.++ and to the extent of 30% by 
Na.sup.+) in the amount of 0.35 wt. % (dry basis, based on the dry weight 
of the titanium dioxide); 
(b) then, calcium carbonate pigment in the amount of 20 wt. % of the 
composition, introduced in the form of the aqueous suspension employed in 
Test 42 (paragraph (b) thereof); and 
(c) then, kaolin in the amount of 70 wt. % of the composition, introduced 
in the form of the aqueous suspension employed in Test 42 (paragragh (c) 
thereof). 
Test 44 concerns a complex composition according to the invention, prepared 
by combining the following ingredients: 
(a) titanium dioxide ("Anatase At1", supplied by the firm Thann et 
Mulhouse) in the amount of 10 wt. % of the composition, introduced in the 
form of an aqueous suspension of which the titanium dioxide comprises 72 
wt. %. The suspension also contains a dispersant according to the 
invention, in the form of an acrylic polymer (specific viscosity 0.4 as 
measured on the sodium salt; converted to the salt form to the extent of 
70% of the carboxyl groups by Ca.sup.++ and to the extent of 30% by 
Na.sup.+) in the amount of 0.35 wt. % (dry basis, based on the dry weight 
of the titanium dioxide); 
(b) then, calcium carbonate pigment in the amount of 20 wt. % of the 
composition, introduced in the form of the aqueous suspension employed in 
Test 42, with the dispersant according to the prior art; and 
(c) then, kaolin in the amount of 70 wt. %, introduced in the form of an 
aqueous suspension comprised of the kaolin in the amount of 71 wt. % of 
the suspension, and containing a dispersant in the form of an acrylic 
polymer (specific viscosity 0.4; converted to salt form to the extent of 
70% of the carboxyl groups by Ca.sup.++ and to the extent of 30% by 
Na.sup.+) in the amount of 0.25 wt. % (dry basis, based on the dry weight 
of the kaolin). 
Test 45 concerns a complex composition according to the prior art, prepared 
by combining the following ingredients: 
a kaolin in the amount of 70 wt. % of the composition, introduced in the 
form of the aqueous suspension employed in Test 40, with the prior art 
dispersant; 
(b) then, calcium carbonate pigment in the amount of 20 wt. % of the 
composition, introduced in the form of the aqueous suspension employed in 
Test 40, with the prior art dispersant; and 
(c) then, titanium dioxide ("Anatase At1", supplied by the firm Thann et 
Mulhouse) in the amount of 10 wt. % of the composition, introduced in the 
form of an aqueous suspension of which the titanium dioxide comprises 72 
wt. %. The suspension also contains a dispersant in the form of sodium 
polyacrylate (specific viscosity 0.4; degree of conversion to the salt 
form 100% of the carboxyl groups). The dispersant is present in the amount 
of 0.1 wt. % (dry basis, based on the dry weight of the titanium dioxide). 
Test 46 concerns a complex composition according to the invention, prepared 
by combining the following ingredients: 
(a) kaolin in the amount of 70 wt. % of the composition, introduced in the 
form of the aqueous suspension employed in Test 40, with the prior art 
dispersant; 
(b) then, calcium carbonate pigment in the amount of 20 wt. % of the 
composition, introduced in the form of the aqueous suspension employed in 
Test 40, with the prior art dispersant; and (c) then, titanium dioxide 
("Anatase At1", supplied by the firm Thann et Mulhouse) in the amount of 
10 wt. % of the composition, introduced in the form of an aqueous 
suspension of which the titanium dioxide comprises 72 wt. %. The 
suspension also contains a dispersant according to the invention, in the 
form of an acrylic polymer (specific viscosity 0.4 as measured on the 
sodium salt; converted to the salt form to the extent of 70% of the 
carboxyl groups by Ca.sup.++ and to the extent of 30% by Na.sup.+) in the 
amount of 0.35 wt. % (dry basis, based on the dry weight of the titanium 
dioxide). 
Test 47 concerns a complex composition according to the invention, prepared 
by combining the following ingredients: 
(a) kaolin in the amount of 70 wt. %, introduced in the form of an aqueous 
suspension comprised of the kaolin in the amount of 71 wt. % of the 
suspension, and containing a dispersant in the form of an acrylic polymer 
(specific viscosity 0.4; converted to the salt form to the extent of 70% 
of the carboxyl groups by Ca.sup.++ and to the extent of 30% by Na.sup.+) 
in the amount of 0.25 wt. % (dry basis, based on the dry weight of the 
kaolin); 
(b) then, calcium carbonate pigment in the amount of 20 wt. % of the 
composition, introduced in the form of the aqueous suspension employed in 
Test 40, with the dispersant according to the prior art; and 
(c) then, titanium dioxide ("Anatase At1", supplied by the firm Thann et 
Mulhouse) in the amount of 10 wt. % of the composition, introduced in the 
form of an aqueous suspension of which the titanium dioxide comprises 72 
wt. %. The suspension also contains a dispersant according to the 
invention, in the form of an acrylic polymer (specific viscosity 0.4 s 
measured on the sodium salt; converted to the salt form to the extent of 
70% of the carboxyl groups by Ca.sup.++ and to the extent of 30% by 
Na.sup.+) in the amount of 0.35 wt. % (dry basis, based on the dry weight 
of the titanium dioxide). 
After the above various pigment-containing mixtures were prepared, 
corresponding compositions for the coating of paper were prepared by 
adding the following to the mixtures of Tests 42 to 47, per 100 parts by 
weight of dry pigment: 
0.5 parts by weight of a water retention agent (carboxymethylcellulose); 
and 
10.5 parts by weight of the latex described in Example 7, above. 
The pH of these compositions was controlled at 8.6.+-.0.1, and the 
concentration of dry matter was controlled at 68.7.+-.0.2%. 
The Brookfield viscosities of the coating compositions thus prepared were 
measured, at 10 and 100 rpm. 
All the results relating to these compositions are given in Table X. 
From Table X, and by comparison of the tests concerning the prior art and 
the tests concerning the invention, it is seen that: 
(a) With regard to the prior art: The order of addition of the aqueous 
pigment suspensions when preparing the complex compositions for coating of 
paper is important. It can give rise to setting (Test 42) or very high 
viscosity of the composition (Test 45). This indicates incompatibility of 
the various pigments. 
(b) With regard to the invention: The aqueous pigment suspensions produced 
in the presence of at least one dispersant according to the invention are 
compatible among themselves when mixed, due to the presence of the 
inventive dispersant. Regardless of the order of mixing of the pigment 
suspensions, the mixtures do not set or congeal; rather, they impart much 
lower viscosities to the complex compositions thus prepared than result 
under the prior art. 
TABLE X 
______________________________________ 
Brookfield viscosity (centipoise) 
At 10 rpm At 100 rpm 
Test No. (of the viscometer) 
(of the viscometer) 
______________________________________ 
Test 42 SETTING 
Prior Art 
Test 43 11,400 1,920 
Invention 
Test 44 9,600 1,720 
Invention 
Test 45 14,000 2,400 
Prior Art 
Test 46 9,800 1,680 
Invention 
Test 47 9,200 1,560 
Invention 
______________________________________ 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.