United States Patent (19) (11) 4,171,296

Connelly et al. 45) Oct. 16, 1979

(54) METHOD OF HYDROLYZING 58) Field of Search ..................... 260/29.6 H, 29.6 E,
POLYACRYLAMDE 260/29.6 N, 29.6AT, 29.6 HN, 29.6 WQ
(75) Inventors: Lawrence J. Connelly, Oak Lawn; (56) References Cited
Edward G. Ballweber, Glenwood, U.S. PATENT DOCUMENTS
both of Ill.
2,892,825 6/1959 Boettner .............................. 260/89.5
(73) Assignee: Nalco Chemical Company, Oak 3,284,393 1 1/1966 Vanderhoff ................. 260/29.6 HN
Brook, Ill. 3,624,019 11/1971 Anderson .................... 260/29.6 HN
21) Appl. No.: 947,905 3,784,597 1/1974 Fujimoto ........................ 260/80.3 N
22 Filed: Oct. 2, 1978 Primary Examiner-Paul R. Michl
Attorney, Agent, or Firm-John G. Premo; Robert A.
Miller
Related U.S. Application Data
(63) Continuation of Ser. No. 912,652, Jun. 5, 1978, which is (57) ABSTRACT
a continuation-in-part of Ser. No. 840,446, Oct. 7, 1977, Polyacrylamide dispersed in a polymeric latex may be
abandoned, which is a continuation of Ser. No. hydrolyzed by the use of an alkali stable organic surfac
705,652, Jul. 15, 1976, abandoned, which is a continua tant followed by the reaction of the polyacrylamide
tion-in-part of Ser. No. 514,961, Oct. 15, 1974, Pat. No. with an alkali metal hydroxide or quaternary ammo
3,998,777. nium hydroxide.
(51) Int. C.’.............................................. C08 L 33/26
52) U.S. C. ........................................... 260/29.6 WQ 11 Claims, No Drawings
 4, 171,296
1 2
METHOD OF HYDROLYZING OBJECTS
POLYACRYLAMIDE It is therefore an object of this invention to provide a
method of hydrolyzing polyacrylamide.
This is a continuation of copending Ser. No. 912,652 It is also an object of this invention to provide a
filed June 5, 1978, which in turn is a continuation-in-, method of hydrolyzing polyacrylamide, which is in the
part of copending Ser. No. 840,446 filed Oct. 7, 1977, form of a polymeric latex.
Flow abandoned, which in turn is a continuation of co Another object of this invention is to provide a stable
pending Ser. No. 705,652 filed July 15, 1976, now aban polymeric latex of hydrolyzed polyacrylamide by the
doned, which in turn is a continuation-in-part of co O addition of an alkali stable organic surfactant prior to
pending Ser. No. 514,961 filed Oct. 15, 1974, now U.S. the hydrolysis.
Pat. No. 3,998,777. A further object is to provide an alkali stable organic
INTRODUCTION surfactant for use in hydrolyzing polyacrylamide.
A still further object is to provide a stable polymeric
This invention concerns a method of hydrolyzing 15 latex of hydrolyzed polyacrylamide for use in second
polyacrylamide to provide a polymer which has been ary and tertiary oil recovery, clarification of turbid
found to be useful in thickening and flocculation appli aqueous solutions and for thickening and dewatering of
cations. In particular, aqueous solutions of the hydro industrial and sewage wastes.
lyzed polyacrylamide of this invention have been found Other objects will appear hereinafter.
to provide excellent results in the thickening and dewa THE INVENTION
tering of industrial wastes, sewage wastes, and clarifica
tions of turbid aqueous solutions. In addition the hydro This invention provides a method of hydrolyzing
lyzed polyacrylamide is used in secondary and tertiary polyacrylamide comprising the steps of:
oil recovery processes to helf increase the amount of (A) Forming a polymeric latex comprising a water
crude oil recovered from underground oil-bearing for 25 in-oil emulsion which contains dispersed therein finely
rations. The use of the polymer in this oil recovery divided polyacrylamide;
process is becoming quite widespread in view of the (B) Adding to the polymeric latex an alkali stable
current need to meet our crude oil requirements. organic surfactant capable of forming a water-in-oil
Typically these polymers are available as powders or emulsion; and
as finely divided solids, which are dissolved in water to 30 (C) Reacting the polymeric latex containing the or
form aqueous solutions for use in the desired applica ganic stabilizer with an alkali metal hydroxide or qua
tion. Great difficulty has been experienced in dissolving ternary ammonium hydroxide to form a hydrolyzed
the dry polymers, particularly hydrolyzed polyacryl polyacrylamide.
amide due to its slow dissolution time and because the
dry polymer is not readily dispersable in water. The dry 35 THE POLYMERC LATEX
polymer has a tendency to form lumps when placed in A polymeric latex is formed which comprises a wa
contact with water. These lumps often taken quite a ter-in-oil emulsion containing dispersed therein finely
long period of time to dissolve, sometimes as long as divided polyacrylamide. These polymeric lattices and
6-0 hours. their method of production are described in U.S. Pat.
U.S. Pat. No. 3,624,019, Anderson et al, discloses a Nos. 3,284,393 and 3,624,019. These Patents are incor
polymeric latex comprising a water-in-oil emulsion porated herein by reference.
which contains dispersed therein finely divided parti The molecular weight of the polyacrylamide may
cies of a water-soluble vinyl addition polymer. A pre vary over a wide range, i.e., 10,000-25,000,000. The
ferred polymer disclosed therein is polyacrylamide. The invention, however, finds its greatest usefulness when
enaulsions containing polymer described therein are 45 the molecular weight of the polyacrylamide is in excess
stable and when inverted in the presence of water, the of 1 million.
poiymer goes into solution in a very short period of time The oils used in preparing the polymeric latex may be
as compared to the dissolution of a dry solid polymer. A selected from a large group of organic liquids which
water-in-oil polymerization process and method for include liquid hydrocarbons and substituted liquid hy
raaking latex polymers is disclosed in Vanderhoff et al, 50 drocarbons. A preferred group of organic liquids are
J.S. Pat. No. 3,284,393. the hydrocarbon liquids which include both aromatic
It would be desirable to provide a hydrolyzed poly and aliphatic compounds such as benzene, Xylene, tolu
acrylanide polymer in the form of the polymeric latex ene, mineral oils, kerosenes, and naphthas. A particu
described above. However, up to this time it has not, larly useful oil from the standpoint of its physical and
been possible to hydrolyze a polymeric latex of poly 55 chemical properties is the branch-chain isoparaffinic
acrylamide. During the hydrolysis reaction the poly solvent sold by Humble Oil and Refining Company
meric latex becomes unstable and the polymer present under the trade name ISOPAR M. Typical specifica
in the polymeric latex coagulates and precipitates out of tions of this narrow-cut isoparaffinic solvent are set
the water-in-oil emulsion thereby producing a commer forth below in Table I.
cially useless product. 60
TABLE I
This invention provides a method of hydrolyzing
poiyacrylamide which is present in the form of a poly Specification Properties
Min
imum Maximum Test Method
freric latex by the addition of an organic stabilizer or
alkali stable organic surfactant to the polymeric latex Gravity, API at 60/60' F.
Color, Saybolt
48.0
30
510 ASTM D 287
ASTM D 156
prior to the hydrolysis. By the addition of the organic 65 Aniline Point, F. 185 ASTM D 611
stabilizer, it is therefore possible to perform the hydro Sulfur, ppm O ASTM D 1266
iysis to provide a polymeric latex of hydrolyzed poly Distiliation, F. ASTM D 86
acrylamide which is stable. IBP 400 410
 4,171,296
4.
TABLE I-continued 15.0% by weight based on the polymeric latex. The
Min
preferred concentration is from 0.5 to 3.0% by weight.
Specification Properties imum Maximum Test Method Another embodiment of this invention involves the
Dry Point 495
forming of the polymeric latex which comprises a wa
Flash Point, F. (Pensky- 160 ASTM D93 ter-in-oil emulsion which contains dispersed therein
Martens closed cup). finely divided polyacrylamide and the organic stabilizer
Nephelometric mod. formed by the reaction of an aliphatic hydrocarbon
alcohol having from 10–20 carbon atoms with from
The amounts of the components in the polymeric 2-10 moles of ethylene oxide per mole of the alcohol.
latex may vary over a wide range. However, generally O This polymeric latex is then reacted with a hydrolysis
agent to form a hydrolyzed polyacrylamide. The ad
the polymeric latex is composed of 20-50% by weight
of water, 10-40% by weight of oil and 20-40% by vantage of this embodiment of the invention is that
weight of polyacrylamide. It is generally necessary to there is one less step in the method. The organic stabi
employ an oil soluble emulsifying agent in order to 15 lizer being already present in the polymeric latex.
maintain a stable emulsion. The amount of emulsifying THE HYDROLYSIS
agent needed to provide an emulsion will have to be The polymeric latex containing the organic stabilizer
determined by routine experimentation. As a general is reacted with a hydrolysis agent. The hydrolysis
rule it may be said that the amount of oil-soluble emulsi agents may be alkali metal hydroxides or quaternary
fier may range from 0.1 to 30% by weight based on the 20 ammonium hydroxides. Typically, alkali metal hydrox
weight of oil. To produce stable emulsions the amount ides include lithium, sodium and potassium hydroxides.
of emulsifier will normally be within the range of A typical quaternary ammonium hydroxide is tetra
3-15% by weight of the oil. The preferred emulsifiers methyl ammonium hydroxide.
are the so-called low HLB materials which are well
documented in the literature and are summarized in the 25 In the practice of the invention the hydrolysis agent
Atlas HLB Surfactant Selector. Although these emulsi used should be added to the polymeric latex as an aque
fiers are useful in producing good water-in-oil emul ous solution slowly and with mixing. The preferred
sions, other surfactants may be used as long as they are hydrolysis agents used in the invention are alkali metal
capable of producing these emulsions. For instance, hydroxides and more specifically sodium, potassium,
certain high HLB surfactants are capable of producing 30 and lithium hydroxides with the most preferred being
stable water-in-oil emulsions. A typical low HLB emul about a 50% aqueous solution of the alkali metal hy
sifier is sorbitan monooleate. Other emulsifiers are dis droxide. The concentration of the solution of the alkali
cussed in U.S. Pat. No. 3,284,393. metal hydroxide is within the range of 0.2-30% by
The emulsions may be prepared by any one of a num weight based on the polymeric latex and preferably
ber of methods. One particular method is that taught in 35 4-12% by weight based on the polymeric latex. How
U.S. Pat. No. 3,284,393. In addition, the emulsions may
ever, the percentage of hydrolysis agent used will al
be prepared by using high-speed agitation or ultrasonic ways vary to the degrees of hydrolysis desired with
techniques. higher percentage of the hydrolysis agent being used
for higher degrees of hydrolysis.
THE ALKALISTABLE ORGANIC 40 While solutions of about 50% concentration of the
SURFACTANT Alkali metal hydroxides are convenient to use, it is
important to note that higher or lower concentrations
The organic surfactants used in this invention must be of alkali metal hydroxides in aqueous media may be
alkali stable and capable of forming a water-in-oil emul used. Conditions favoring lower concentration of the
sion. Any compound meeting these requirements may hydrolysis agent include the desire for low levels of
be used, however due to variations in the polymeric hydrolysis and stability factors. Conditions favoring
latex, and hydrolysis agents, each organic stabilizer higher concentrations include the desire for a high de
should be tried first on a small sample and be used on a gree of hydrolysis without excessive dilution, and for
case by case basis. stability reasons.
The organic stabilizer typically used is formed by the 50 The hydrolysis may be conducted at room tempera
reaction of an aliphatic hydrocarbon alcohol having ture but more favorable results are obtained at elevated
from 10-20 carbon atoms with from 2-10 moles of eth temperatures. Generally the reaction maybe performed
ylene oxide per mole of the alcohol. Preferably the within the range of from 10-70° C. The preferred tem
alcohol will have from 12-18 carbon atoms and will be perature range is from 35-55 C. The length of time for
reacted with 2-4 moles of ethylene oxide per mole of 55 hydrolysis depends upon the reactants, their concentra
the alcohol. tion, reaction conditions and the degree of hydrolysis
A preferred organic surfactant is formed by the reac desired. It has been experimentally determined that
tion of one mole of oleyl alcohol with two moles of polyacrylamide may be hydrolyzed according to the
ethylene oxide to form polyoxyethylene (2) oleyl alco procedure set forth herein to a degree of between
hol. Another preferred organic stabilizer is formed by 60 5-80%. Depending upon the reaction conditions de
the reaction of one mole of lauryl alcohol with four scribed above, typically a 20-60% hydrolysis is ob
moles of ethylene oxide to form polyoxyethylene (4) tained, with the preferred range being 30-50%. This
lauryl ether. These compounds are well known and hydrolysis procedure and all of the reaction conditions
their preparations are commonly known to those skilled and ranges described herein apply to both embodiments
in the art. 65 of this invention: that is, (1) the formation of the poly
In the preferred embodiment of this invention, the meric latex with the alkali stable organic surfactant and
organic surfactant is added to the polymeric latex and (2) the addition of the alkali stable organic surfactant to
thoroughly mixed in a concentration of from 0.10 to a polymeric latex. With the use of the organic surfac
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4,171,296
6
tant, it is possible to hydrolyze the polymeric latex of PAR M solvent having an average molecular weight of
polyacrylamide. 175 to 180. This was then added to 1 liter of a mixed
The hydrolyzed polyacrylamide is dispersed solvent containing 50% each by volume of acetone and
throughout the water-in-oil emulsion, similar to those methanol, filtered and dried 16 hours under vacuum at
emulsions disclosed in Anderson et al, U.S. Pat. No. 5 40' C.
3,624,019. This polymer latex may be inverted in a simi The following table II shows the amount of latex in
lar manner to that disclosed in Anderson et al. The each samples, dried weight, the percent acrylate and
polymer latex releases the hydrolyzed polyacrylamide amide in the product as measured by infra-red analysis
in water in a very short period of time. Generally, a and the viscosity at a concentration of 1.0% in deion
surfactant is added to either the polymer-containing 10 ized water.
emulsion or to the water into which it is to be dissolved. TABLE II
The placement of a surfactant into the water causes the Sample Grams Dried % % Viscosity
emulsion to rapidly invert and release the polymer in No. Latex Weight Acrylate Amide (cps)
the form of an aqueous solution. The surfactants listed 22.68 g. 7.93g. 16 84 10,000
in Anderson et al have been found to easily invert the 15 2 21.80 7.80 26 74. 26,000
hydrolyzed polyacrylamide, however, due to variations 3 23.40 8.80 40 60 25,500
in the polymeric latices surfactants used for inversion
should be tried on a case by case basis. The invention
can be more readily understood by the following exam This example shows the effect of time on the hydrolysis.
ples. 20 EXAMPLE 3
EXAMPLE 1. This example was run the same as Example 2 except
A polyacrylamide latex was prepared for hydrolysis a higher temperature was used, namely 45 to 50° C.
studies. Samples were taken at one hour, two hours, and after
A two liter three-neck reaction vessel was charged 25 about 20 hours. The following Table III shows the
results of the respective samples. The same work-up
with 340 g. of an isoparaffinic solvent previously de was used as in Example 2.
scribed as ISOPARM, and having an average molecu
lar weight of 175-180, and 20 g. of sorbitan monooleate TABLE III
as an emulsifier. To this was added 40g of acrylamide, Sample Weight Dried % % Viscosity
180g of water, 0.4 ml. of 2% EDTA (ethylene diamine 30 No, Latex Weight Acrylate Amide (cps)
tetraacetic acid) and a drop of 50% sodium hydroxide. 1 26.42 g. 10.2g. 36 64 26,500
Over a 30 minute period of time, the temperature was 2 24.50 g. 9.71 g. 37 63 16,500
raised to 30' C. and then to 45' C. within 10 minutes as 3 24.60 9.70 g. 39 61 28,000
10 mls. of 8% vazo catalyst is added. Vazo catalyst is a
well-known catalyst and is 2,2'azobis (isobutronitrile). 35
The amount of catalyst is 0.2% by weight based on the EXAMPLE 4
monomer. After 30 minutes, 200 mls. of a monomer This example uses a different alkali stable organic
solution is added. The monomer solution contains the surfactant. A 500 ml, three necked-distillation flask is
following: equipped with a stirrer, thermometer, sampling tube,
Acrylamide: 360 g. 40 reflux condenser, and a hot water bath. One hundred
Water: 250 g. fifty grams of the latex of Example 1 is charged to the
Boric Acid: 7.2 g. reaction flask. Then, 2.53 g of polyoxyethylene (4)
EDTA: 3.6 ml. lauryl ether is added to the latex at 42-45 C. After
50% sodium hydroxide: 0.5g. stirring for about ten minutes at 400 rp.m., 17.15g. of
The temperature is kept between 43-48 C. for 1, 45 50% sodium hydroxide is added dropwise. A moderate
hours. Then, 200 mls. of the monomer solution is again viscosity increase is noted. The reaction is held at
added. The temperature is kept between 44'-50' C. for 42"-45 C. for one hour. A molderate darkening is ob
1 hours, after which a third addition of 200 mls, of the served. Sample 1 is removed. After another hour, sam
monomer solution is added. After about two hours, the ple 2 is removed. The same work-up is used as in Exam
reaction is stopped and a good latex recovered without 50 ple 2.
particles. TABLE IV
The molecular weight was over 5,000,000 and the Sample Weight Dried % % Viscosity
intrinsic viscosity was over 100, No, Latex Weight Acrylate Amide (cps)
EXAMPLE 2 55 21.6 8.9 40 60 26,000
2 21.5 8.0 40 60 26,000
One hundred fifty grams of the latex of Example 1
was charged to a 500 ml. reaction flask. To this was
added 2.52 g of polyoxyethylene (2) oleyl ether and EXAMPLE 5
stirred about 400 rp.m. at room temperature for 25
minutes. Then, at 26 C., 16.95 g. of 50% sodium hy- 60 Another latex was prepared using a greater amount of
droxide was added over a five minute period. The tem emulsifier and alkali stable organic surfactant. A latex
perature increased to 32.5°C. The reaction mixture was was prepared in the same way as Example 1 except that
stirred at about 400 rp.m. After one hour, sample Num instead of 20 g. of sorbitan monooleate, 60 g (15% by
ber 1 was taken. An hour later sample Number 2 was weight) of polyoxyethylene (2) oleyl ether was used.
taken. Eighteen hours later, sample Number 3 was re- 65 EXAMPLE 6
moved,
The samples were worked-up in the following way: After the polymerization of Example 5 was com
A sample of the latex as diluted with 100 ml. of ISO pleted, 50g of the latex was placed in a reaction vessel.
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4,171,296 8
Then, 3.36 g. (20% by weight) of the sodium salt of quaternary ammonium hydroxide whereby a stable
alkyl acryl polyether sulfonate was added as an emulsi water-in-oil emulsion of finely divided hydrolyzed
fier. This emulsifier is sold under tradename of Triton polyacrylamide is formed.
X-200. Thus, the total amount of emulsifier and stabi 2. The method of claim 1 wherein said alkali stable
lizer is 35% by weight based on the polymer. Then, 2.72 5 organic surfactant ranges from 0.5 to 3.0% by weight
g. of 50% sodium hydroxide (10 mole percentage based based on the polymeric latex.
on polyacrylamide) was added and hydrolysis pro 3. The method of claim 1 wherein said alkali stable
ceeded as in Example 2. The polymer as measured by organic surfactant is polyoxyethylene (2) oleyl ether
titration showed 12% acrylate. - formed by the reaction of one mole of oleyl alcohol
EXAMPLE 7
10 with two moles of ethylene oxide.
4. The method of claim 1 wherein said alkali stable
This example was run in the same way as Example 6 organic surfactant is polyoxyethylene (4) lauryl ether
except the amount of 50% sodium hydroxide was 0.91 formed by the reaction of one mole of lauryl alcohol
g. (5 mole percentage based on polyacrylamide). The with four moles of ethylene oxide.
result was that the polymer as measured by titration 15 5. The method of claim 1 wherein said alkali metal
showed 6% acrylate. hydroxide is an aqueous solution of sodium hydroxide
As is readily apparent to anyone skilled in the art, the of about 50 weight percent.
examples demonstrate a useful method for the hydroly 6. The method of claim 1 wherein said alkali metal
sis of polyacrylamide, and produce a stable product hydroxides are from the group consisting of sodium
readily inverted into aqueous solution. 20 hydroxide, potassium hydroxide and lithium hydroxide.
What is claimed is: 7. The method of claim 1 wherein said alkali metal
1. The method of hydrolyzing polyacrylamide which hydroxide is an aqueous solution of about 50% concen
comprises the steps of: tration by weight and said solution ranges from 0.2 to
A. Forming a polymeric latex comprising a water-in 30% by weight based on the polymeric latex.
oil emulsion which contains dispersed therein 25 8. The method of claim 1 wherein said alkali metal
finely divided polyacrylamide and an organic sur hydroxide is in aqueous solution of about 50% concen
factant which is alkali stable and will form a stable tration by weight and said solution ranges from 4 to
water-in-oil emulsion said polymeric latex compris 12% by weight based on the polymeric latex.
ing from 20 to 50% by weight of water, from 10 to 9. The method of claim 1 wherein said polyacryl
40% by weight of oil, and from 20 to 40% by 30 amide is hydrolyzed to from 5 to 80% by weight.
weight polyacrylamide, and from 0.10 to 15% by 10. The method of claim 1 wherein said polyacryl
weight of the alkali stable organic surfactant; and amide is hydrolyzed to from 20 to 60% by weight.
then, 11. The method of claim 1 wherein said polyacryl
B. Reacting said polymeric latex containing the or amide is hydrolyzed kto from. .
30. to . 50% by weight.
ganic stabilizer with an alkali metal hydroxide or 35

45

50

55

65