CA1054017A - Method for thickening clays using water-in-oil emulsions of acrylamide polymers - Google Patents

Abstract

ALVIN J, FRISQUE
ARTHUR R. McDERMOTT

METHOD FOR
THICKENING CLAYS USING
WATER-IN-OIL EMULSIONS
OF ACRYLAMIDE POLYMERS

ABSTRACT OF THE DISCLOSURE

A process is disclosed for the thickening of clays, humates, lignosulfonates and minerals using water-in-oil emulsions of a finely divided acrylamide polymer.

Description

INTRODUCTION
This invention relates to a new and improved method for thickening clays through the use of a water-in-oil emulsion of a finely divided acrylami~e polymer. This is accomplished by adding the water-in-oiL emulsion o~ the acrylamide polymer directly to a clay powder with agitation. The oil phase of the water-in-oil emulsion serves as a carrier, causing the polymer particles to be uniformly dispersed throughout the clay. This clay-polymer slurry, depending on the concentration of the polymer within the slurry, can be either mixed with more clay or used as is. ~he clay-polymer slurry is then added to water where the polymer emulsion contained in the clay inverts, causing the polymer to solublize, giving a rapid .increase of the viscosity of the clay-polymer-water slurry to produce a thickened clay.
-The use of water-soluble acrylamide polymers as thickening agents, is well-known in the art. Commercially, these polymers are available in two forms: as a dilute liquid: and as a solid.
The dllute liquid acrylamide polymer solutions, have two disadvantages. one, due to the viscosity of the high molecular weight material in water, they must be shipped as extremely dilute solutions, usually within the range of 0.5 to 3% polymer solids. ;
Also, because they are so dilute, they cannot be used l`n~application where a more concentrated solution is desired. The solid acrylamide polymers are most often available commercially as powders or as finely divided solids. DUe to their large particle `,` .
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Isize~ a lO0 mesh particle, being on the order of a 150 microns9 it lis difficult to dispexse these polymers uniformily in clay solutions : ¦ In order to assure uniform distxibution, they must be dissolved in ¦water. Although the various polymers used are soluble in water, di~ficulty is often exper:ienced in preparing aqueous polymer solutions because of slow dissolution, and because the solid polymer i5 not readily dispersable in water. Furthermoreg dispersior of solid polymers in water is hindered by their tendency to clump ¦or remain as agglomerates on contact with water. Lumps of solid ¦polymer immediately form by the agglomerating. Although many of the ¦~
` ¦lumps ara eventually dissolved by continued agitation, it is ¦frequently impractical to agitate the solution for a sufficiently ¦long period of time to obtain complete dissolution.
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The method of this invention involves an improved method for thickening clays through the use of water-in-oil emulsions of ;~
a finely divided acryIamide polymer. The method of this invention involves adding a water-in-oil emulsion of a fiAely divided acrylamide polymer to a clay powder followed by agitation to evenly disperse the emulsion in the clay. The slurry so formed may be added to water whereupon the polymer inverts or may be added to more clay powder which is in turn added to water. The metho~ ~of this invention provides to the art a new and improved method for a preparing thickened clay solutions in a short period of time, as well as providiny a clay-polymer dispersion which can be inverted into water to produce a thickened clay.

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Thus ~his invention seeks to provide a process for the thickening of clays which compris~s the steps of:
A. adding from 1.0 to 40% by weight of a water-in~oil emulsion :
of a finely divided acrylamide polymer to a clay powder, said water-in-oil emulsion containing 15 to 40% by weig}lt of an acrylamide polymer;
, B. agitating the mixture to produce a homogeneous concentrated :
slurry o.f the clay and polymer;
C. adding a quantity of the slurry of Step ~ to a volume of ~ ;
water to produce a slurry containing from 0.1 to 10% by weight pol~ner; :
. D. inverting the water-in-oil emulsion of a finely divided ~ ;~
acrylamide polymer contained in the slurry of Step C to produce a thickened : clay.
As a preferred embodiment this invention seeks to provide a ~ ;
process for the thickening of clays which comprises the steps of:
A. adding to the clay powder from 1 to 40% by weight of a water-: in-oil emulsion of a finely divided acrylamide polymer, said emulsion con-`~ taining 15 to 40% by weight of an acrylamide polymer;
; B. agitating the mixture to produce a homogeneous concentrated .
slurry of the clay; ~ .
C. adding the concentrated slurry of Step B to a quantity of :~-clay powder with agitation so as to produce a clay rich slurry;
D. adding to the clay rich slurry of Step C a quanti~y of water so that the total polymer concentration is reduced to between 0.1 to 10% by ::1 weight; and then~
E. inverting the water-in-oil emulsion of a finely divided :~ acrylamide polymer contained in the clay slurry to produce a thickened clay.
~ The polymers most commonly used in the application of this `~ in~ention are acrylamide polymers which include polyacrylamide and its water-soluble nonionic, cationic or anionic copolymeric derivatives such as, ~ for instance, acrylic acid, methacrylic acid, itaconic acid, dimethyl-aminoethylmethacrylate, acrylonitrile and styrene . .

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~4~:~L7 land styrene. The copolymers contain from about 5 to 95% by weight ¦f acrylamide. l~he molecular weights of such polymers exceed , 500,000.
A polymer also useul in the practice of this invention :is hydrolyzed polyacrylamide which has from 1 to 50% of the original carboxami.de groups hydrolyzed to carboxyl groups.
l~e molecular weight of the polymers described above may vary over a wide range, e.g., 10,000 to 25 million. The preferred polymer has a molecular weight'in excess, of 1 million. `
In'general, the polymer emulsions axe stable yet at the same time contain relatively large amounts,of pol~mer. The polymers dispersed in the emulsion are quite stable when the particle si~e of the polymer is within the range of 2 millimicrons up to about 5 microns. The preferred particle size is within the range of , 5 millimicrons and 3 microns.
It is extremely important for the purposes of our invention that particle size is kept as small as,posslble. This is due to the fact that the small particles are more easily blended in a uniform fashion than large particles.
The stable water-in-oil emulsion comprises:
~' ' 1. An aqueous phase; '

2. A hydrophobic liquid, and

3. A water-in-oil emulsifying agent. _,~
; The polymer-containing emulsion of this invention is comprised of an aqueous phase ranging between 30 and 95% by weight ~, of the emulsion. The aqueous phase is defined as the sum of the polymer or copolymer and the water present in the composition. The ~-,` -4- ', " ~' :`" . `'~
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preferred range is between70 and 90% by wei~ht of th~ emulsion.
The most preferred range is betweell 7~ and 80~ by weig]lt of the emulsion.
¦ The prcsent invelltion has a polymer concentration between 10 and 50% by weight of the emulsion. A preforred range is between 25 and ~0% by weight of the emulsion. The most preferred range is between25 and 35% by weight of the emulsion.
The organic or oil phase of the emulsion is comprised of an inert hydrophobic liquid The hydrophobic liquid usually comprises between 5 and 7~/oby weight of the emulsion. The preferrec range is between 5 and 30% by weight of the emulsion. The most preferred range is between 20 and 30% by weight of the emulsion.
The oils used in preparing these emulsions may be ~elected from a large group of organic liquids which include liquid hydrocarbons and substituted liquid hydrocarbons. Prefarred ~` groups of organic liquids are hydrocarbon liquids whic~ include blends of aromatic and aliphatic hydrocarbon compounds, which contair contain from 4 to 8 carbon atoms. Thus, such organic hydrocarbon liqulds as benzene, xylene, toluene, mineral oils kerosenes, ~ ;
naphtha, and in certain instances, petroleums may be used. A
particularly useful oil from the standpolnt of its physical and chemical properties is the branch-chain isoparafinnic solvent sold by Humble Oil and ~efinery Company under the tradename~iXsopar M~o .
Typical specifications of this narrow-cut isoparaffinic solvent are set forth below in Table I.
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Specificati.on ProPerties Minim~ Maximum Test Method Gravity, API at 60/60F 48.0 51.0 ASTM D 287 Color, Saybolt 30 - ASq~ D 156 Aniline point, F 185 - ASTM D 611 Sulur~ ppm - 10 ASqM D 1266 (~ephelometric mod.) Distillation, F

Dry point - 495 Flash point, F
(Pensky-Martens closed cup) 160 -. ASTM D 93 .
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~LoS~7 Any conventional water-in-oil emulsif7ing agent can be used such as sorbitan monostearate, sorbitan monooleate, and the so-called low HLB
materials which are all documented in the literature and are summarized in the ~tlas ~ILB Surfactant Selector. ~lthough the mentioned emulsifiers are usad Ln producing good water-in-oil emulsions, other surfactants may be used as long as they are c~pable of producing these emulsions. The water-in~oil emulsifying agent is usually present :in amounts ranging between 0.1 and 5.0% by weight of the emulsion. The preferred range is between 1.0 and 3.o% by weight of the emulsion. The most preferred range is between 1.2 and 2.0% by weight of the emulsion.
The polymers contemplated for use~in this invention may be synthesized in emulsion form as described in Vanderhoff et al, United States 3,284,393. The polymerization technique set forth in Vanderhoff is generally followed in preparing polymeric latexes used in this invention.
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Also contemplated in the practice of this invention is the -~ preparation of suitable water-in-oil emulsions of water-soluble polymers by the methods described in Anderson et al, United States 3,624,019 and 3,734,873.
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- ~ The water-in-oil emulsion used in the practice of this invention exhibits the unique ability of rapidly dissolving into aqueous solution.

The polymer-containing emulsion, releases the polymer into water in the presence of a surfactant, electrolite, or upon physical manipulation such .
as high shear mixing, in a very short period of time. This inversion technique is described in Anderson et al, United States 3,624,019 and ~ ~
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lOS4~7 TIIE METHOD
Once the water-in-oil emulsion of a ~inely divided acryl-amide polymer is prepared, it is added to a clay powder. The sub-stance used as the clay may include clays, humates, soils, lignosul-onates, and minerals, Preferably the water~in-oll emulsion of the pOlylller i5 added to the clay in a weight percent from 1 to 40/~
based on the dry clay powder. This mixture is ~hen agitated ~o produce a homogeneous concentrated slurry of the clay. ~t low polymer levels, the clay totally absorbs the hydrophobic li~uid phase from the water~in-oil emulsion of the finely divided vinyl addition polymer. Usually this treated clay still has the appear-ance of a dry powder. It is only when the clay is contacted with water that the instant thickening properties appear.
- The oil used in preparing the water-in-oil emulsion servec as a carrier or the polymer and provides for much easier dispersior ~hat will be possible using a dry pol~ner of equivalent particle size, After this concentrated slurry of the clay-polymer is formed, it may be added directly to water to produce a thickened clay with the polymer concentration being rom 0.1 to 10% by weight of th~
aqueous solution, In the preferred embodiment of our invention the concentrated clay-p~lymer slurry is added to an additional quantity of clay power, with agitation9 so as to produce a clay-rich slurry which upon addition of water will produce a thickened clay o the desired polymer concen~ration without excessive dilution, When water in the presence of a hydrophilic surfactant is added to the clay-polymer slurry, the polymer within the emulsion inverts, caus-ing an almost ins~antaneous thickening effect, Typically, in the final thickened clay slurry the pol~ner concentration should be in the range of 0.1 ~o 10% with the clay cDmprisin~ a substantial portion of the mixture.
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The polymer contained within the clay-rich slurry may be inverted by the use of a surfactant. The surfactant so employed may be added to the aqueous solution into which the clay-polymer slurry wil:L be added, or to the water_in-oil cmuLsion of a Einely di~ided acrylamide polymer, beEore its addition to the cLay to render it self-inverting upon contact with water.
The surfactant may be present in amounts ranging from .01 to 50% by weight based on the polymer contained in the 0 water-in-oil emulsion. However, generally the surfactant concentration is within the range 1.0 to 10% by weight based on polymer.
` The preferred surfactants are hydropholic and are 1` further characteri~ed as being water-soluble. Any hydrophilic-type surfactant surh as etho~lated nonyl phenols, ethoxylated nonyl phenol formaldehyde resins, dioctyl esters of sodium sulfosuccinate, and octyl phenol polyethoxyethanol can be used~ Basically, any anionic, cationic or nonionic surfactant can be employed in this invention. The surfactants are fully o disclosed in U.S. 3j624,019.
The surfactants chosen, however, should be tried on a case-by-case basis due to variances in the water-in-oil emulsions, the salt content, and pH of the inorganic nitrate - salt slurries~ and the water-in-oil emulsifier used originally~The method of this invention thus allows for the rapid preparation of thickened clays, which may be done using the clay and a water_in-oil emulsion~,of a finely divided acrylamide polymer, or in the field, using a clay-rich slurry.
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~ZZlls~ol7 The amount of pol~ner, clay, and water used, will depend on the ; desired viscosity of the thickened clay. The use of more water will cause a decrease in viscosity. The use of greater amounts of polymer and greater amounts of clay will cause an increase in the viscosity. The following c~amples are offercd to illustrate our invention.
EXAMPLk'Z 1 ISOPAR ~Z 27.6 grams Sorbitan Monostearate 1.65 grams Water 40.20 grams Acrylamide 36.51 grams SZodium Hydroxide 2.29 grams 2,2'azobis (isobutyronitrile)0.0~ grams The sorbitan monostearate was dissolved in the ISOPAR M* and the ~ ;
resulting solution was poured into a two liter glass reactor fitted with a ~10 stirrer, thermometer, and nitrogen purge. The monomer solution was prepared by dissolving the acrylamide in water. The pH of the monomer solution was adjusted to 8.5 with sodiuZm hydroxide. The monomer solution was added to the organic phase with rapid agitation. The reactor was purged for 30 minutes after which time the 2Zl2~azobis (isobutyronitrile) dissolved in .:
acetone was added to the mixture. The emulsion was heated to 60C with agitation. The reaction proceeded for 2-1/2 hours at which time it had reached completion. The resulting product was a stable emulsion.

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¦ EX~MPLE 2 Acrylamide-acrylic acid emulslon reci~e:
ISOPAR M 28.10 grams Sorbitan Monostearate 1.85 grams Water 40.00 grams Acrylamide 33.90 grams Acry]ic Acid 2.40 grams Sodium Hydroxide 2.30 grams 2,2'a~obis (isobutyronitrile) 0.07 grams As in ~xample 1, the sorbitan monostearate was dissolved in the ISOPAR M and the resulting solution was poured into a two liter glass reactor fitted with a stirrer, thermometer, and nitrogen purge. The monomer solution was prepared by dissolving the acrylamide and acrylic acid in watex. The pH of the monomer solution was adjusted to 8.5 with sodium hydroxide. Th~ monomer solution was added to the organic phase with rapid agitation. The reactor was purged for 30 minutes after which time the 2,2'azobis (isobutyronitrile) dissolved in acetone was added to the mixture.
The emulsion was heated to 60C with agitation. The reaction pro~
ceeded for 2-1/2 hours at which time it had reached completion.
The re ul~ing product was a stable emu1sion:

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IJ JlOS4~ 7 I EX~MPL~ 3 ¦Acrylaml~e-mcth~cr~lic acid emulsio~ recipe:
¦ ISOPAR M 27.6 grams ¦ Sorbitan Monostearate1;65 grams Water 40.20 grams ¦ Acrylamide 34.51 grams ¦ Meth~crylic Acid2.31 grams ¦ Sodium Hydroxide2.29 grams l 2,2'azobis (isobutyronitrile) 0.07 grams ' ¦ me sorbitan monostearate was dissolved in the ISOPAR M
~nd the xesulting solution was poured into a two liter glass ¦ eactor fitted with a stirrer, thermometer, and nitrogen purge. The ¦ onomer solution was prepared by dissolving the acrylamide and methacrylic acid in water. The pH of the monomer solution was adjusted to 8.5 with sodium hydroxide. The monomer solution was added to the organic phase with rapid agitation. The reactor was purged or 30 minutes a~ter which time the 2,2'azobis ~ ~-(isobutyronitrile) dissolved in acetone was added to the mixture.
The emulsion was heated to 60C with agitation. The reaction pro-ceeded for 2-1/2 hours at which time it had reached completion.
~he resulting produce was a stable emulsion.
This invention is further illustrated by the ollowing !exampS: - ;

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EXA~IPL~ 4 The water-in-oil emulsion of a finely divided acrylamide polymer oE Example 2, was added to Wyoming sodium bentonite at a S% level (1.7%
polymer solids). A 1% solution of the sodium bentonite, in water, containing .17% nonylphenol which had been reacted with 10 moles oE ethylene oxide, increased the viscosity from 50 to 100 cps as a result of this polymer addition. In practice, the 5% slurry of the emulsion in sodium bentonite could be added to more sodium bentonite to achieve any intermediate viscosity.

The water-in-oil emulsion of a finely divided acrylamide polymer of Example 1, was added to a Wyoming sodium bentonite at 5% level (1.68%
pol~ner solids). A 1% solution of this sodium bentonite in water containing 0.15% nonylphenol which had been reacted with 10 moles of eth~lene oxide, increased the viscosit~ from about 50 to about 100 cps as a result of this E polymer addition.

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Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the thickening of clays which comprises the steps of:
A. adding from 1.0 to 40% by weight of a water-in-oil emulsion of a finely divided acrylamide polymer to a clay powder, said water-in-oil emulsion containing 15 to 40% by weight of an acrylamide polymer;
B. agitating the mixture to produce a homogeneous concentrated slurry of the clay and polymer;
C. adding a quantity of the slurry of Step B to a volume of water to produce a slurry containing from 0.1 to 10% by weight polymer;
D. inverting the water-in-oil emulsion of a finely divided acrylamide polymer contained in the slurry of Step C to produce a thickened clay.

2. A process for the thickening of clays which comprises the steps of:
A. adding to the clay powder from 1 to 40% by weight of a water-in-oil emulsion of a finely divided acrylamide polymer, said emulsion containing 15 to 40% by weight of an acrylamide polymer;
B, agitating the mixture to produce a homogeneous concentrated slurry of the clay;
C. adding the concentrated slurry of Step B to a quantity of clay powder with agitation so as to produce a clay rich slurry;
D. adding to the clay rich slurry of Step C a quantity of water so that the total polymer concentration is reduced to between 0.1 to 10% by weight; and then, E. inverting the water-in-oil emulsion of a finely divided acrylamide polymer contained in the clay slurry to produce a thickened clay.

3. The process of claim 1 wherein the particle size of the acrylamide polymer in the water-in-oil emulsion varies from 3 millimicrons to 5 microns,

4. The process of claim 1 wherein the clay is from the group consisting of lignosulfonates, humates, and soils.

5. The process of claim 1 wherein the acrylamide polymer is a copolymer of acrylamide and acrylic acid.

6. The process of claim 1 wherein a hydrophilic water-soluble surfactant capable of inverting the polymer is added at between .1 to 10%
by weight to the oil-in-water emulsion of a finely divided acrylamide polymer.

7. The process of claim 1 wherein a hydrophilic water-soluble surfactant is added to the homogeneous concentrated slurry of the clay and polymer at between .1 to 10% by weight.