Method of thickening solutions using normally nongelling clays

Normally nongelling montmorillonite clay is treated to have gelling characteristics by drying the clay to 10 to 15 percent free moisture and grinding the clay to at least 100 percent finer than 45 microns. To thicken an aqueous solution, the clay is dispersed in water with a chemical dispersant and the predispersion is agitated in the aqueous liquid with a flocculent. To thicken an organic liquid, the dried and ground clay is stirred into the liquid with a surfactant.

BACKGROUND OF THE INVENTION 
This invention relates to gelling clays and, more particularly, to a method 
of treating normally nongelling clays so that they may be used as gelling 
agents for thickening aqueous and organic liquid systems. 
Certain clay mineral products are known as gelling clays. Such clays are 
used for thickening drilling muds, liquid animal feeds, suspension 
fertilizers, asphalt cutbacks and oil base foundry sand binders, and are 
also used for stabilizing coal/oil mixtures. 
Typical gelling clays include Wyoming bentonite, attapulgite, sepiolite, 
and hectorite. These gelling clays can be used to thicken water by 
stirring a prescribed amount of clay into the water. The amount of 
thickening achieved is a direct function of the amount of clay used and 
the amount of work put into the system by agitation shear. These same 
clays can be used to thicken organic liquids by pretreating the clays with 
certain organic surfactants prior to agitating into the liquid, or by 
adding the clays to the liquid at the same time as the surfactant and 
accomplishing interaction of the clay and surfactant in situ. 
Of the above clays, Wyoming bentonite and hectorite are platy clays that 
are able to imbibe water and swell to achieve their thickening effect. 
Swelling is an inherent property of these clay minerals because of the 
cations (type of cation) between adjacent platelets which are of a type 
(NA+ for example) that allows them to take up water. When the ionic 
content of the water is high, they will not imbibe water and thus are not 
thickeners for salt-containing solutions. 
Attapulgite, sepiolite and palygorskite are acicular clay minerals that can 
be made to thicken water by merely stirring them into the water. 
Thickening is achieved with these minerals by the individual needles being 
separated and interacting in an extended gal structure to thicken the 
continuous water phase. Because of their method of building viscosity, 
this group of minerals will effectively thicken water solutions containing 
high ionic concentrations; e.g., saturated NaCl, gypsum, MgSO.sub.4, etc., 
and are commonly used commercially when contamination with these materials 
is encountered. 
All of these clay minerals can be predispersed in water with a chemical 
dispersant such as sodium hexametaphosphate sold under the tradename 
Calgon by Merck, TSPP (tetrasodium pyrophosphate) and certain phosphate 
glasses, and used as thickeners by reflocculating the clay by either 
adding a neutralizing agent for the dispersant (salts containing Ca++, 
Al+++ or other polyvalent cations) or adding enough ionic material to 
collapse the double layer. Water systems thickened with platy gelling 
grade minerals such as Wyoming bentonite tend to be unstable when high 
concentrations of ionic materials or lower concentrations of polyvalent 
cations are added. Water systems thickened with reflocculated acicular 
clays not only tend to be more stable but also exhibit a higher gelling 
efficiency than when the same liquids are thickened with dry (undispersed) 
clay additions. 
Certain montmorillonite type clays that occur in the region of Ochlocknee, 
Ga. are classified as nonswelling clays because they show little ability 
to thicken or gel water. This is a result of the ionic types (Al.sup.+3 
and some Ca.sup.+2) existing between their plates which do not permit an 
autogenous imbibing of water or swelling. In fact these clays will not gel 
water even with high-shear agitation. The clays are mined commercially and 
are thermally and mechanically processed to produce granular absorbants 
that are sold as oil and grease absorbants, pet litters, agricultural 
chemical carriers, etc.. 
SUMMARY OF THE INVENTION 
According to the present invention, I have discovered that montmorillonite 
type clays may be treated so as to provide them will gelling 
characteristics. To make the clays suitable as gellants in aqueous 
systems, the clays are dried to 10 to 15 percent free moisture and ground 
to essentially 100 percent finer than 45 microns. The dried and ground 
clay is dispersed in water with a chemical dispersant and thereafter the 
mixture is added to the system to be gelled along with a flocculent of a 
type which neutralizes the dispersing ability of the dispersant. 
Surprisingly, high ionic content aqueous systems gelled with this type of 
predispersed montmorillonite clay exhibit good stability. The same dried 
and ground clay may be also utilized as a gellant for organic liquids when 
stirred into the liquid with a suitable surfactant. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Tests which I have carried out so far in practicing the present invention 
have been with aluminum and calcium montmorillonite clays. The aluminum 
montmorillonite clays were from Ochlocknee, Ga. Table I sets forth a 
typical chemical analysis of the aluminum montmorillonite clay. Although 
the constituents listed in the table are represented as percentages of 
oxides, the constituents are actually present in the clay as complex 
alumino silicates. The percentages appearing in Table I are based upon a 
volatile free basis (1200.degree. F.). 
TABLE I 
______________________________________ 
Constituents PERCENT 
______________________________________ 
Si as SiO.sub.2 
69.49 
Fe as Fe.sub.2 O.sub.3 
7.94 
Al as Al.sub.2 O.sub.3 
16.65 
Ti as TiO.sub.2 
0.56 
Ca as CaO 0.04 
Mg as MgO 1.78 
Na as Na.sub.2 O 
0.15 
K as K.sub.2 O 0.06 
C as CO.sub.2 0.15 
S as SO.sub.2 2.63 
P as P.sub.2 O.sub.5 
0.55 
TOTAL 99.90 
______________________________________

The following describes several tests which have been conducted to 
demonstrate the utilization of the present invention for thickening 
aqueous systems. 
EXAMPLE 1 
A crude clay from an Ochlocknee aluminum montmorillonite deposit was 
crushed to 100 percent finer than 6 mesh, dried in a 105.degree. F. oven 
to 12 percent free moisture content and ground through a hammer mill to 
about 100 percent through 325 mesh (45 microns). The final free moisture 
of the powdered clay was 10.5 percent. Dispersions of this clay were made 
up as shown in Table II using TSPP as the dispersing agent. Mixing 
equipment used was a medium-shear Sterling Multimixer. Processing 
consisted of dissolving the TSPP in the water or urea solution while 
stirring, adding the clay and continuing agitation until all of the 
powdered clay had dispersed--about 10 minutes. 
TABLE II 
__________________________________________________________________________ 
Clay Dispersions and Evaluations 
Samples (each formulation expressed in parts by weight) 
A B C D E F G H I 
__________________________________________________________________________ 
Constituents 
Water 299.5 299.0 298.5 298.0 297.5 297.0 -- 300.0 
-- 
20% Urea Solution 
-- -- -- -- -- -- 298.0 -- 300.0 
TSPP 0.5 1.0 1.5 2.0 2.5 3.0 2.0 -- -- 
Clay 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 
100.0 
400.0 400.0 400.0 400.0 400.0 40.0 400.0 400.0 
400.0 
Comments Dispersed 
Dispersed 
Dispersed 
Dispersed 
Dispersed 
Dispersed 
Dispersed 
Settled 
Settled 
/Evaluations: Out Out 
Brookfield 
400/120 
140/120 
140/120 
140/120 
120/116 
120/108 
220/160 
-- -- 
Visc., cps. 
10/100 RPM 
Suspension Test 
Initial 750 900 1000 1200 1200 1700 1200 300 350 
Brookfield 
Visc., cps. 
60 RPM 
__________________________________________________________________________ 
Tests which I will hereinafter call the Suspension Tests were performed for 
evaluation of the 25 percent predispersions (PD clay) shown in Table II. 
In the tests a simulate 3-10-27 suspension fertilizer was used made with 
the following ingredients: 
______________________________________ 
Water 190 g 
PD Clay 80 g (2% clay on a dry basis) 
10-34-0 295 g 
Powdered KCl 435 g 
1000 g 
______________________________________ 
The product 10-34-0 is an ammonium phosphate solution in water made with a 
TVA pipe reactor. It contains about 60% polyphosphate. Each test was run 
in a Waring blender with the speed controlled by a variable transformer 
(Powerstat). While running at 100 volts, the water and PD clay sample were 
mixed for one minute. The 10-34-0 was added while stirring and was stirred 
for three minutes. The KCl flocculent was added and the voltage was 
increased to 120 volts. After all of the KCl had been incorporated, the 
mix was stirred for 5 minutes at 120 volts. The Brookfield viscosity at 60 
RPM's was determined after processing. Each finished sample was stored in 
a 1000 ml cylinder overnight and examined for settling, supernatant liquid 
(SN) and sediment after storage. Each sample was made uniform and 
rechecked for Brookfield viscosity after desired storage periods; e.g., 24 
hrs., 48 hrs., 1 week, 1 month, etc. A minimum viscosity of 1200 cp in the 
Suspension Test is acceptable. As seen in Table II, samples D-G met or 
exceeded this minimum figure. Thus, TSPP levels of 1.5 percent to 3.0 
percent (based on the clay weight) performed satisfactorily in the clay 
dispersions tested. 
To determine if predispersion samples E and G could be made to gel more 
efficiently, they were restirred for 5 minutes on a high-shear Waring 
blender. The Suspension Test viscosities obtained after this additional 
processing are shown in Table III. 
TABLE III 
______________________________________ 
Initial Brookfield Viscosities 
at 6 RPM, cp 
Processing Sample E Sample G 
______________________________________ 
Medium-Shear Mixing 
1200 1200 
Medium-Shear plus 
1950 1950 
high-shear mixing 
______________________________________ 
The foregoing indicates that additional high-shear mixing during the 
preparation of predispersions improves the performance of the PD clay. 
EXAMPLE 2 
As shown in Table II, initial work on the predispersed montmorillonite was 
carried out at a 25 percent clay level. To determine if other clay levels 
would be preferable, the clay of Example 1 was predispersed at 25 percent, 
30 percent and 35 percent levels with 3 percent TSPP (% on clay weight). 
Formulations and evaluation results are shown in Table IV. Processing was 
under medium-shear conditions. The amount of clay on a dry basis was 
adjusted to 2 percent in all of the Suspension Tests by adjusting the 
amount of PD clay added. While all three predispersions performed well in 
the Suspension Tests, Sample B was the most satisfactory predispersion. 
TABLE IV 
______________________________________ 
Effect of Clay Concentration 
on Viscosity of Predispersions 
SAMPLES 
25% 30% 35% 
A B C 
______________________________________ 
Constituents 
Water 297 g 276.4 g 255.8 g 
TSPP 3 g 3.6 g 4.2 g 
Clay 100 g 120.0 g 140.0 g 
400 g 400.0 g 400.0 g 
Predispersion 
Characteristics: 
Appearance Thin Med. Visc. 
Thick 
Brookfield Visc., cp 
120/116 3000/1500 10,500/5200 
10/100 RPM 
Evaluation: 
Suspension Test 
Brookfield Visc., 
cp, 60 RPM 
Initial 1700 2000 1800 
Aged 24 hrs. 
1800 2100 2150 
no SN, no SN, no SN, 
no sed. no sed. no sed. 
______________________________________ 
EXAMPLE 3 
To determine the effect of extrusion and extrusion plus soda ash addition 
on the thickening ability of the montmorillonite clay, crude from Example 
1 was pugged with enough water to increase the FM (free moisture) to 51 
percent. The extrudate was dried to 15 percent FM in a 105.degree. F. oven 
and hammer mill ground. The ground clay was predispersed at 30 percent 
solids with 3 percent TSPP (% on clay weight) and evaluated with the 
Suspension Test. It was noted that the extruded clay dispersed easier than 
the previously evaluated unextruded clay. Suspension Test viscosities on 
the extruded clay were 2050 cp initially and 2250 cp in 24 hours; on the 
extruded plus one percent soda ash treated clay were 2300 initially and 
2350 cp after 24 hours. Because of the easier predispersion, both of these 
techniques appear worthwhile. 
EXAMPLE 4 
A second crude montmorillonite sample was processed as described in Example 
1. This was checked for viscosifying properties in a series of qualifying 
tests normally used for colloidal attapulgite. Such tests are the Firetrol 
Test, the TVA Q-Test and the API Yield Test. Suspension Tests were also 
performed. Results of the tests on undispersed clay, a 30 percent 
predispersion dispersed with 3 percent TSPP (% based on the clay weight) 
and Min-U-Gel 200, a colloidal attapulgite, are shown in Table V. 
TABLE V 
______________________________________ 
Gelling Properties of Ochlocknee Montmorillonite 
SAMPLES 
Dry 30% PD Min-U-Gel 
Mont. Clay Mont. Clay 
200 
______________________________________ 
FM, % 16.3 -- 13.4 
API Yield 
(Bbl/T) 
Fresh Water 
42 -- (1) 124 
Salt Water 
5 88 105 
Firetrol 100 5980 (2) 1800 
Test 
(B. Visc., 
cp, 60 RPM) 
TVA Q-Test 
25 215 240 
(B. Visc., 
cp, 100 RPM) 
Suspension 
800 2000 2400 
Test settled 
(B. Visc., 
out 
cp, 60 RPM) 
Comments nongelling fair to good 
good gelling 
clay gelling clay 
clay in fresh 
in ionic water and 
systems ionic systems 
______________________________________ 
NOTE: 
(1) no gelling, approx. visc. of water 
(2) stiff gel 
EXAMPLE 5 
Tests have also been conducted on two calcium montmorillonite samples 
obtained from the Source Clay Minerals Repository, Department of Geology, 
University of Missouri, Columbia, Mo. The samples were (1) STx-1 Ca 
Montmorillonite (White), Gonzales County, Tex. and (2) SAz-1 Ca 
Montmorillonite (Cheto), Apache County, Ariz. They are standard reference 
clay minerals, are nonswelling and are described in detail in "Data 
Handbook for Clay Materials and Non-Metallic Minerals," edited by Van 
Olphen and Fripiat, Pergamon Press (1979). Their nonswelling non-gelling 
characteristics were established by stirring a 30% by weight slurry in 
distilled water with a Sterling multimixer for 10 minutes. No gel 
resulted. Similar results were noted when Waring Blender mixing was tried. 
Samples STx-1 and SAz-1 were predispersed at the 25% level with 3% TSPP 
(based on the clay weight) in water with a Sterling multimixer using 5 
minutes stirring. The predispersed clays were then checked with the 
Suspension Test. Evaluation results are shown in Table VI. 
TABLE VI 
______________________________________ 
Properties of Calcium Montmorillonites 
Ca. Mont. 
Ca. Mont. 
STx-1 SAz-1 
______________________________________ 
Initial Evaluations 
FM, % 10.5 10.9 
Dry Screen +325, % 
10.0 12.5 
(Alpine) 
API Yields: bbl/ton 
Salt water No gelling 
No gelling 
Fresh water " " 
Suspension Test 
Brookfield Visc. 
at 60 RPM in cps 
Dry Clay 200 100 
Predispersed Clay 
1300 500 
______________________________________ 
Because SAz-1 showed poor results it was evaluated further by making up a 
second 25% predispersion in water with higher-shear mixing equipment, a 
Waring Blender. The TSPP content was increased to 5% (based on the clay 
weight). This predispersion was checked with the Suspension Test and gave 
a 60 RPM Brookfield viscosity of 1100 cps. These results indicate that Ca 
montmorillonites also are susceptible to the processing techniques of this 
invention. 
While not bound by this theory, it is believed that the predispersion of 
the nonswelling, nongelling montmorillonite clay with chemical dispersants 
in water under conditions of medium shear or high shear results in a 
delaminating type of cleavage across the "C" axis of the clay crystal 
which generates many thinner flakes. When the thin flakes adsorb 
dispersant, they are charged up and exhibit the low viscosities 
characterisitc of mineral dispersions. However, when the protective charge 
mechanism is destroyed by floccing the clay particles, the particles 
interact to give a viscosity-producing gel structure. 
Floccing of the clay predispersion may be accomplished by one of dispersant 
neutralizers such as soluble polyvalent cations (salts containing Ca++, 
Al+++, for example) which react with the dispersant, or high ionic 
concentrations (K+, NH.sub.4 +, Na+ for example) to collapse the charge 
layer of the dispersed particles. 
Various inorganics have been used for many years as gelling agents for 
organic liquids such as petroleum fractions (naphthas, mineral spirits, 
lube oils) alkyd resins, alcohols, polyethers and many others. Mineral 
gellants have included etherified hydrophobic amorphous silicas 
(Estersils), amorphous silica aerogels and fumed silicas treated with 
cationic surfactants, Wyoming bentonite clay reacted with amine salts or 
quaternary nitrogen compounds (Bentones), hectorite clay reacted with 
quaternary nitrogen compounds, and colloidal attapulgite treated with 
imidazolines or alkanolamides. Oils gelled with clay/surfactant 
combinations have many things in common--the resultant gels are 
thixotropic, pseudo-plastic, exhibit good gel strenghts and are very heat 
resistant. Heat resistance is very important in such applications as high 
temperature greases. Recently a new application has been devised for 
attapulgite/surfactant gelled oils. They are coal/oil mixtures (C/OM) 
which consist of about 50 percent finely ground coal dispersed in fuel oil 
with the attapulgite clay/surfactant as a gellant for the oil phase in 
order to suspend the coal particles. 
The present invention also constitutes the discovery that properly prepared 
aluminum montmorillonite clay can be used in this application and in other 
organic liquid-gelling applications along with surfactants to achieve 
excellent results. The following examples are illustrative of my 
invention. 
EXAMPLE 6 
Montmorillonite clays prepared as described in Example 1 were checked for 
gelling properties in #6 fuel oil by dissolving Amine T (the imidazoline 
of tallow fatty acid and aminoethylethanolamine) at 180.degree. F., adding 
the clay while stirring with a double bladed Sterling Multimixer and 
continuing mixing until the clay is gelled (approximately 5 minutes). 
Formulations made on three montmorillonite clay samples and an attapulgite 
clay control plus evaluation results are shown in Table VII. 
TABLE VII 
______________________________________ 
Clay Gels in #6 Fuel Oil 
Attapulgite 
Montmorillonite Clay Sample 
Clay Samples Min-U-Gel 
Constituents: 
A B C FG 
______________________________________ 
#6 Fuel Oil 
433.5 g 433.5 
g 433.5 
g 433.5 
g 
Amine T 16.5 g 16.5 g 16.5 g 16.5 g 
Clay 
A (Mont.) 50.0 g -- -- -- 
B (Mont.) -- 50.0 g -- -- 
C . . . (Mont.) 
-- -- 50.0 g -- 
Min-U-Gel FG* 
-- -- -- 50.0 g 
500.0 g 500.0 
g 500.0 
g 500.0 
g 
Appearance Med. Med. to Med. No thickening 
thin thick 
Brookfield Visc. in cp: 
Initial 
at 180.degree. F. 
10 RPM 7200 5400 10400 -- 
100 RPM 1332 1080 1580 -- 
Aged 2 weeks 
at 180.degree. F. 
10 RPM 8800 4800 9200 -- 
100 RPM 1800 1140 1920 -- 
Aged 1 Month 
at 180.degree. F. 
10 RPM 3800 1400 4300 -- 
100 RPM 840 480 930 -- 
______________________________________ 
*A finelyground, colloidal attapulgite clay 
EXAMPLE 7 
Montmorillonite clay was processed as in Example 1. The clay was pregelled 
in #6 fuel oil using Amine T as the surfactant as described in Example 6 
with the order of addition listed in Table VIII. Next, 50 percent of a 
Kentucky bituminous coal ground to 80 percent -200 mesh was added with 
additional stirring. Formulations tried and evaluation results are shown 
in Table VIII. Note that Samples A and B in Table VIII contained a 
solution of Amine T (10%). The extra water is lost during processing and 
storage. Sample C was processed with undilute Amine T. The best results 
were achieved with Sample C; second best was Sample A, and Sample B was 
successful if used within two weeks of processing. 
TABLE VIII 
______________________________________ 
50% C/OM Stabilized 
With Montmorillonite Clay and Amine T 
SAMPLES 
Constituents 
A B C 
______________________________________ 
6 Fuel Oil 100.0 g 100.0 
g 100.0 
g 
Amine T 16.6 g 8.3 g -- 
(10% Solution) 
Amine T -- -- 0.83 g 
Clay 5.0 g 2.5 g 2.5 g 
Oil 143.3 g 148.3 
g 148.3 
g 
Coal 250.0 g 250.0 
g 250.0 
g 
Comments: 
Clay, % 1 0.5 0.5 
Clay/ 3/1 3/1 3/1 
Surfactant 
Ratio 
Evaluations: 
(Stored and Evaluated at 160.degree. F.) 
Brookfield Visc., cps. 
Initial 15,200/3640 
3400/1580 5200/1700 
10/100 RPM 
24 hrs., 19,000/4900 
4400/2000 6400/2400 
10/100 RPM v. thick no sed. no sed. 
1 Week, 15,200/4000 
2800/1880 5200/2440 
10/100 RPM 
2 Weeks, 15,000/4000 
2600/1920 2800/2080 
10/100 RPM 
1 Month, 8000/3300 hard sedi- 1200/1400 
10/100 RPM no SN, ment no SN, 
no sed. no sed. 
______________________________________ 
Thus, in conclusion, the present invention constitutes the discovery that 
the previously held assumption that nongelling montmorillonite clays 
cannot be used as gellants because of their generally accepted nongelling 
characteristics is false. Special processing and formulation of such clays 
in accordance with the invention described herein renders the clays 
suitable for gelling both aqueous and organic liquid systems.