This invention discloses a process for the polymerization of acrylamide and for the copolymerization of acrylamide with other monomers. It employs molecular weight jumpers that greatly enhance the molecular weight of the polymer formed. These high molecular weight acrylamide polymers offer outstanding advantages as enhanced oil recovery injection water viscosifiers.

BACKGROUND OF THE INVENTION 
After using conventional pumping techniques very large amounts of oil in a 
given reservoir remain unrecovered. In an attempt to recover this vast 
quantity of unpumped petroleum many enhanced oil recovery (EOR) techniques 
have been developed. The water flooding method is a very common EOR 
technique that has been in use for some time. Water flooding is a 
secondary oil recovery technique that is chiefly of importance when the 
natural production of a well has ceased--that is, when petroleum can no 
longer be pumped from the well economically using conventional pumping 
techniques. The term "secondary recovery" as used herein, refers to all 
petroleum recovery operations used in such areas when spontaneous 
production of the well can no longer be effected. It includes what is 
sometimes known in the industry as "tertiary recovery," which is a later 
stage which begins when the petroleum reservoir is substantially "flooded 
out" and a large amount of water may be produced before any oil is 
recovered. Thus, primary recovery is when a well spontaneously flows using 
conventional pumping techniques and secondary recovery begins when primary 
recovery is no longer feasible and continues for as long as there is any 
petroleum in the well which can be economically or feasibly removed. 
The water flooding technique comprises injecting water into a petroleum 
deposit through at least one input well (injection well), thereby causing 
the petroleum to flow from that area for collection through at least one 
output well. In the simplest recovery method a number of wells are drilled 
on the circumference of a circle and a final well is drilled in the 
center. Water is then pumped into one or more of the wells, typically the 
ones on the circumference, under high pressure and forced through the 
petroleum-bearing formations, usually porous rock strata. The petroleum 
remaining in the strata is forced out by the oncoming water and removed 
through the output well, usually the one at the center of the circle. More 
typically an array of injection and production (output) wells are 
established over an oil field in a manner that will optimize this 
secondary recovery technique by taking into account the geological aspects 
of that particular field. Ideally, the water should displace 100 percent 
of the petroleum in the oil field. Even though water may pass through a 
deposit, the inherent incompatibility of oil and water, variation in 
reservoir rock, including permeability variation, faults and shale 
barriers may result in some regions of the reservoir rock being by-passed 
so that large oil bearing areas in the deposit remain untouched. This 
results in less than 100 percent of the residual oil in the reservoir 
being recovered. The ability of water, or any other fluid, to displace oil 
is related to that fluid's mobility ratio. Every fluid has a specific 
mobility in an oil deposit, which can be defined as the ease with which 
that fluid flows through a porous medium divided by the viscosity of that 
fluid. A mobility ratio is the ratio of the mobility of two fluids: for 
example, oil and water. If a fluid flows much more easily than oil through 
a reservoir, it will readily bypass oil deposits within the reservoir 
rather than pushing them toward producing wells. Thus, fluids with low 
mobility ratios are greatly preferred for enhanced oil recovery 
applications. Recovery by water flooding techniques is greatly facilitated 
if the mobility of the petroleum relative to the injection water is at a 
maximum. This is frequently accomplished by increasing the viscosity of 
the aqueous medium and decreasing the visocisity of the petroleum, by the 
addition of suitable chemical agents. Thus, a thickener is ordinarily 
added to the water while a thinning agent may be charged into the 
petroleum. 
High molecular weight (above about 1,000,000) water soluble polymers are 
generally added to the injection water used in EOR applications to improve 
the mobility ratio of the water to the oil. A very large increase in water 
viscosity can be obtained when certain polymers are added in minor amounts 
(100 ppm to 1500 ppm). Two general types of polymers are currently being 
used as injection water viscosifiers, they are polyacrylamides and 
polysaccharides. In general, partially hydrolyzed and anionic 
polyacrylamides are used, but cationic polyacrylamides have also been used 
in a limited number of cases. The mobility ratio improvement obtained 
using polyacrylamides decreases with water salinity and divalent ion 
concentration. Therefore, a fresh water source (total dissolved solids 
less than 10,000 ppm) has traditionally been necessary for the effective 
use of polyacrylamides in EOR applications as viscosifiers. The 
environment into which the polyacrylamide solution is injected has 
traditionally also been required to be substantially free of salts in 
order to be effective. 
SUMMARY OF THE INVENTION 
This invention reveals a process for the synthesis of ultra-high molecular 
weight polyacrylamide. This ultra-high molecular weight polyacrylamide has 
excellent properties as an injection water viscosifier for EOR 
applications. Even though polyacrylamide synthesized by utilizing the 
process of this invention is sensitive to metal salts its viscosity in 
aqueous solutions is sufficient to allow for its use in salty environments 
(in the presence of brine). Such ultra-high molecular weight 
polyacrylamide is also of great value in environments that are 
substantially free of salts since its ability to viscosify water per unit 
weight is greater than polyacrylamide of lesser molecular weight. 
The process of this invention is also applicable in copolymerizations of 
acrylamide with other vinyl monomers. For example, in some cases it is 
desirable to copolymerize acrylamide with a metal salt of 
2-acrylamido-2-methyl propane sulfonic acid (AMPS) in order to make the 
polymer being synthesized more resistant to hydrolysis (decomposition by 
reaction with water). 
This invention more specifically discloses a process for the 
homopolymerization of acrylamide and for the copolymerization of 
acrylamide with vinyl monomers; comprising: initiating said 
homopolymerization or said copolymerization with a redox system and 
carrying out said homopolymerization or said copolymerization in an 
aqueous reaction medium in the presence of a molecular weight jumper of 
the structural formula: 
##STR1## 
wherein M represents a member selected from the group consisting of Na, K, 
and NH.sub.4 ; and wherein Z and Z' can be the same or different and 
represent a member selected from the group consisting of Na, K, NH.sub.4, 
alkyl groups containing from 10 to 40 carbon atoms, aryl groups containing 
from 10 to 40 carbon atoms, alkyl-ether groups containing from 10 to 40 
carbon atoms, and aryl-ether groups containing from 10 to 40 carbon atoms. 
DETAILED DESCRIPTION 
Ultra-high molecular weight polyacrylamide and acrylamide copolymers can be 
synthesized in an aqueous medium or in a water-in-oil dispersion utilizing 
the process of the invention. Polyacrylamide has the structural formula: 
##STR2## 
wherein n is an integer. Acrylamide copolymers are polymers that contain 
at least about 40 percent by weight acrylamide repeat units (repeat units 
which are derived from acrylamide). The remaining repeat units in 
acrylamide copolymers are vinyl monomer repeat units (repeat units which 
are derived from vinyl monomers other than acrylamide). These repeat units 
differ from the vinyl monomers that they were derived from in that their 
vinyl carbon-carbon double bond has been consumed in the polymerization. 
For example, if N,N-dimethylacrylamide is copolymerized with acrylamide 
the N,N-dimethacrylamide repeat units will have the structural formula: 
##STR3## 
and the resulting acrylamide/N,N-dimethylacrylamide copolymer produced 
will have the structural formula: 
##STR4## 
wherein n and m are integers and wherein indicates that the 
distribution of repeat units derived from acrylamide and 
N,N-dimethylacrylamide can be random. 
The vinyl monomers that can be employed in copolymerizations with 
acrylamide must contain at least one vinyl group (CH.sub.2 .dbd.CH--). 
These vinyl monomers generally contain from 2 to 16 carbon atoms. Such 
vinyl monomers can also contain nitrogen, oxygen, halogens, sodium, 
calcium, and potassium. The maximum amount of a vinyl monomer that can be 
copolymerized with acrylamide to produce a useful polymer will vary 
greatly. A person skilled in the art will be able to ascertain this amount 
through routine experimentation. Generally, such acrylamide coplymers will 
contain no more than about 50 percent by weight vinyl monomer repeat 
units. In some cases the amount of vinyl monomer repeat units that it is 
desirable to incorporate into the polymer will be less than 5 percent by 
weight, based upon the total repeat units in the polymer. In many cases 
vinyl monomers can be polymerized into acrylamide copolymers without 
necessarily improving or adversely affecting the properties of the polymer 
produced. Alpha-olefins and lightly halogenated .alpha.-olefins containing 
from 2 to 16 carbon atoms are examples of such vinyl monomers that do not 
greatly affect the properties of the polymer produced when they are 
copolymerized with acrylamide in small quantities. Since aliphatic vinyl 
monomers have a low solubility in water it generally will not be possible 
to polymerize large quantities of such monomers into the acrylamide 
copolymers of this invention by employing an aqueous polymerization system 
without utilizing soaps. 
Vinyl monomers with the structural formula: 
##STR5## 
wherein R, R', R" can be the same or different and represent a hydrogen 
atom, a methyl group, or an ethyl group; wherein X represents --NH-- or 
--O--; wherein A represents an alkylene group containing from 1 to 4 
carbon atoms; wherein M represents Na, K, Ca, or NH.sub.4 ; and wherein n 
is 1 or 2, are the preferred vinyl monomers for the copolymerizations of 
this invention. If M is Na, K, or NH.sub.4, then n will be 1 and if M is 
Ca, then n will be 2. Repeat units derived from vinyl monomers of this 
type tend to make the copolymer produced more resistant to hydrolysis. It 
is generally preferred for R to be an hydrogen atom or a methyl group. The 
alkylene group (represented as A) can be a straight chain or branched. 
A representative example of a straight chain alkylene group is shown in the 
following structural formula: 
EQU --CH.sub.2 --CH.sub.2 --CH.sub.2 -- 
A representative example of a branched chain alkylene group is shown in the 
following structural formula: 
##STR6## 
The most preferred vinyl monomers for copolymerization into acrylamide 
copolymers are metal and ammonium salts of 2-acrylamido-2-methylpropane 
sulfonic acid (AMPS). Copolymers of this type have a very high viscosity 
in fresh water, maintain excellent viscosities in saline solutions and are 
resistant to hydrolysis. Sodium AMPS (sodium 
2-acrylamido-2-methylpropanesulfonate), potassium AMPS (potassium 
2-acrylamido-2-methylpropanesulfonate), ammonium AMPS (ammonium 
2-acrylamido-2-methylpropanesulfonate) and calcium AMPS (calcium 
2-acrylamido-2-methylpropanesulfonate) are all useful as monomers in the 
synthesis of ultra-high molecular weight acrylamide copolymers. 
##STR7## 
The aqueous polymerizations of this invention are carried out in an aqueous 
reaction medium comprising: water, monomers, a redox initiator system, and 
a molecular weight jumper. 
Ultra-high molecular weight polyacrylamide and acrylamide copolymers can be 
synthesized in an aqueous medium over a very wide temperature range (from 
about -20.degree. C. to about 40.degree. C.). The monomer charge 
concentration used in an aqueous solution synthesis of polyacrylamide and 
acrylamide copolymers can be varied over a wide range from as low as about 
2 weight percent to as high as about 60 weight percent of the total 
reaction medium (monomers, water, initiators, molecular weight jumper, 
etc.). Generally, it is preferred to use a monomer charge concentration 
(total concentration of all monomers in the aqueous reaction medium) in 
the range of 15 to 55 weight percent. For example, 80 parts of water, 19 
parts of acrylamide and 1 part of sodium AMPS (20 weight percent monomer 
charge concentration) can be employed in the polymerization recipe 
utilized in the synthesis of ultra-high molecular weight copolymers of 
acrylamide and sodium AMPS. 
The amount of metal or ammonium AMPS useful in such copolymerizations can 
range from as low as 0.01 weight percent to as high as 50 weight percent 
of the total monomer charge. In such copolymerizations generally from 5 
weight percent to 20 weight percent of a metal or ammonium AMPS will be 
employed based upon the total monomer charge if a copolymer which is 
resistant to hydrolysis is desired. 
The ultra-high molecular weights that are attained by practicing the 
process of this invention are achieved through the use of molecular weight 
jumpers. These molecular weight jumpers must be present in the reaction 
medium during the course of the polymerization. 
The molecular weight jumpers that are useful in the practice of this 
invention have the structural formula: 
##STR8## 
wherein M represents a member selected from the group consisting of Na, K, 
and NH.sub.4 ; and wherein Z and Z' can be the same or different and 
represent a member selected from the group consisting of Na, K, NH.sub.4, 
alkyl groups containing from 10 to 40 carbon atoms, aryl groups containing 
from 10 to 40 carbon atoms, alkyl-ether groups containing from 10 to 40 
carbon atoms, and aryl-ether groups containing from 10 to 40 carbon atoms. 
In most cases wherein Z is Na, K, or NH.sub.4 ; Z' will be an alkyl group, 
an aryl group, an alkyl-ether group or an aryl-ether group. In the 
converse situation wherein Z' is Na, K, or NH.sub.4 normally Z will be an 
alkyl group, an aryl group, an alkyl-ether group or an aryl-ether group. 
These molecular weight jumpers are generally prepared by reacting maleic 
anhydride with an appropriate alcohol containing at least 10 carbon atoms 
followed by the addition of a metal bisulfite, such as sodium bisulfite. A 
general description of this synthesis technique is given in U.S. Pat. Nos. 
2,028,091 and 2,176,423 which are incorporated herein by references in 
their entirety. 
Alkyl-ether groups are aliphatic hydrocarbon radicals that contain one or 
more "oxy" linkages (--O--). 
Some representative examples of alkyl-ether groups include: 
EQU --CH.sub.2 --CH.sub.2 --O--(CH.sub.2).sub.10 --CH.sub.3 
EQU --CH.sub.2 --(O--CH.sub.2).sub.8 --(CH.sub.2).sub.5 --CH.sub.3 
##STR9## 
Aryl-ether groups are aromatic hydrocarbon radicals that contain one or 
more "oxy" linkages (--O--). The term alkyl group as used herein includes 
what is sometimes referred to as a cycloalkyl group. In other words the 
term alkyl group as used herein includes all aliphatic hydrocarbon 
radicals including those with straight chain branched chain, and cyclic 
(ring) structures. The aryl groups normally employed contain an aliphatic 
component and are sometimes referred to as aralkyl groups. 
The preferred molecular weight jumpers for use in this invention are those 
wherein Z and Z' are selected from the group consisting of Na; K; NH.sub.4 
; alkyl groups containing from 12 to 30 carbon atoms; alkyl-ether groups 
of the structural formula: 
##STR10## 
wherein T and T' can be the same or different and represent a hydrogen 
atom, a methyl group, or an ethyl group, wherein a and b are integers, 
wherein indicates that the distribution of repeat units can be in any 
order, and wherein the alkyl-ether group contains from 12 to 30 carbon 
atoms; aryl-ether groups of the structural formula: 
##STR11## 
wherein T and T' can be the same or different and represent a hydrogen 
atom, a methyl group, or an ethyl group, wherein a, b, and c are integers, 
wherein indicates that the distribution of repeat units can be in any 
order, wherein chain linkages through the benzene ring can be in an ortho, 
meta, or para orientation, and wherein the aryl-ether group contains from 
12 to 30 carbon atoms. 
In the most preferred molecular weight jumpers for use in this invention Z' 
is Na or K and Z is an alkyl group containing from 12 to 15 carbon atoms 
or an aryl-ether group with the structural formula: 
##STR12## 
wherein d is an integer from 1 to 6, wherein e is an integer from 2 to 10, 
and wherein f is an integer from 1 to 20, and wherein the sum of d, e, and 
f (d+e+f) is from 12 to 24. Some representative examples of molecular 
weight jumpers that are most preferred for use in this invention include: 
Aerosol.TM. A-102 (sold by American Cyanamid) which has the structural 
formula: 
##STR13## 
wherein x is 4 or 5 and wherein y is 10 to 12; and bis-n-tridecyl sodium 
sulfosuccinate which has the structural formula: 
##STR14## 
The polymerizations of this invention can be carried out in an aqueous 
reaction medium to obtain ultra-high molecular weight polyacrylamide and 
acrylamide copolymers. These polymerizations can be initiated by the 
addition of a redox system to a mixture of water, the monomers, and the 
molecular weight jumper which forms an aqueous reaction medium. It is not 
necessary for the molecular weight jumper to be present at the time that 
the polymerization is first initiated (it can be added later), but it is 
generally desirable for the molecular weight jumper to the present from 
the start of the polymerization. 
Numerous redox initiator systems can be employed to initiate the 
polymerizations of this invention. For example, the polymerizations of 
this invention can be initiated by utilizing metal persulfate/sodium 
metabisulfite redox initiators, Cu.sup.2+ /peroxydiphosphate redox 
initiators, KMnO.sub.4 /glucose redox initiators, and Cu.sup.3+ 
/hydroperoxide redox initiators. Ferrous sulfate heptahydrate, 
FeSO.sub.4.7H.sub.2 O, has also been used in conjunction with paramenthane 
hydroperoxide as a redox initiation system in the polymerizations of this 
invention. Potassium persulfate and ammonium persulfate can be used with 
great success as redox initiators when used in conjunction with sodium 
metabisulfite. Various metal persulfates (for example sodium and 
potassium) and ammonium persulfate (hereinafter the term metal persulfates 
will be meant to include ammonium persulfate) can be employed as redox 
initiators when used in conjunction with sodium metabisulfite, sodium 
thiosulfate, and sodium dithionite. These redox initiator components can 
be employed at levels from about 0.0001 weight percent to about 0.05 
weight percent based upon the total weight of the aqueous reaction medium. 
It is generally preferred for the initiator components to be employed at 
levels from about 0.0005 weight percent to 0.01 weight percent based upon 
the total weight of the aqueous reaction medium. The most preferred level 
for the initiator components is from 0.001 weight percent to 0.005 weight 
percent based upon the total aqueous reaction medium. Optimal results are 
obtained a concentration of about 0.002 weight percent of each of the 
redox initiating components (based upon the total weight of the aqueous 
reaction medium) in homopolymerizations of acrylamide and in 
copolymerizations containing large amounts of acrylamide in comparison to 
other monomers. 
The temperature range over which the polymerizations of this invention can 
be conducted is from about -20.degree. C. to about 40.degree. C. The 
preferred temperature range is from -5.degree. C. to 20.degree. C. with 
the most preferred temperature being from -2.degree. C. to 5.degree. C. 
The reaction time allowed for the polymerization to occur (time period 
between the initiation of the polymerization and its termination) is 
generally in the range of about 0.5 to 18 hours. However, in most cases a 
reaction time of 1.5 to 3 hours can be employed. This reaction time will 
vary with the temperature at which the polymerization is conducted with 
the type of redox initiator system employed and with the level of 
initiator used. 
It is sometimes desirable to use deionized water in the preparation of the 
aqueous reaction medium used in the polymerizations of this invention. For 
best results oxygen which is dissolved in the water and monomers should be 
removed before polymerization. This can be accomplished by sparging the 
monomers and water used in the reaction medium with an inert gas or 
nitrogen. 
The amount of molecular weight jumper that can be employed in the aqueous 
reaction media of this invention will generally range from about 2 weight 
percent to about 20 weight percent based on the total weight of the 
reaction medium. Lesser amounts of molecular weight jumper can be used, 
but by employing less than 2 percent by weight of the molecular jumper in 
a reaction medium only minimal increases in the molecular weight of the 
polyacrylamide or acrylamide copolymer being synthesized will result. On 
the other hand, greater amounts (20 weight percent) of molecular weight 
jumper can also be employed, but such use of addtional molecular weight 
jumper generally does not result in molecular weights that are greater 
than those observed when more moderate amounts of molecular weight jumper 
is used. In other words, a molecular weight maximum is reached and the use 
of additional amounts of molecular weight jumper will not result in 
significant increases in molecular weight above this maximum. The 
molecular weight maximum is generally reached at a molecular weight jumper 
level in the reaction media of 8 to 12 phm (parts per 100 parts of monomer 
by weight). 
The preferred amount of molecular weight jumper for use in the aqueous 
reaction media of this invention ranges from 4 weight percent to 15 weight 
percent. The most preferred amount of molecular weight jumper for use in 
the reaction media of this invention ranges from 10 weight percent to 12 
weight percent based upon the total weight of the reaction media. 
These aqueous polymerizations which yield ultra-high molecular weight 
polyacrylamide and acrylamide copolymers result in the formation of a 
water soluble gel-like mass. This water soluble polymer must be dissolved 
in additional water in order to be utilized as a viscosifier for EOR 
applications. These polymers should be dissolved in an appropriate amount 
of water to provide a polymer concentration that will result in the 
desired visocisity for the injection water. Obviously the viscosity of the 
injection water increases with increasing polymer concentrations. 
Generally it will be desirable to have an injection water visocisity 
(Brrokfield) of about 2 to about 30 cP (centipoise) for EOR applications. 
When preparing these solutions care should be taken so as to prevent shear 
forces from causing molecular fracture in the polymer chains of these 
polymers. In order to prevent molecular fracture when dissolving these 
polymers in water vigorously mixing, shaking, etc. should generally be 
avoided. The occurrence of such molecular fracture induced by shearing 
forces can significantly reduce the molecular weight of the polymer and 
therefore its usefulness as an EOR viscosifier (viscosities would be 
reduced). In order to dissolve these polymers in water they must be 
allowed to dissolve over a very long period of time. Ultra-high molecular 
weight acrylamide copolymers and ultra-high molecular weight 
polyacrylamide are very valuable as EOR injection water viscosifiers since 
their ultra-high molecular weight allows them to viscosify an aqueous 
solution to a given viscosity at lower polymer concentrations than do 
corresponding acrylamide polymers of lesser molecular weight. The ability 
of an EOR polymer to viscosify water increases with increasing molecular 
weight; therefore, the molecular weight jumpers of this invention are very 
valuable because they can be used to increase the molecular weight of 
polyacrylamide and acrylamide copolymers. 
The polyacrylamide and acrylamide copolymers of this invention can also be 
synthesized in an aqueous reaction medium utilizing water-in-oil 
dispersion polymerization techniques. The ultra-high molecular weight 
polymers produced in an aqueous reaction media by water-in-oil dispersion 
polymerization techniques are in the form of a liquid (in contrast to the 
gel-like mass formed in standard aqueous polymerizations). This liquid can 
easily be further diluted to the desired polymer concentration for use as 
injection water for EOR applications. This further dilution can be 
achieved almost immediately upon mixing with additional water. The 
ultimate properties of the acrylamide copolymers and polyacrylamide 
produced by water-in-oil dispersion polymerizations are equivalent to the 
properties of their counterparts produced by standard aqueous 
polymerization (they have the same excellent properties as EOR 
viscosifiers). Water-in-oil dispersion polymerization offers a very 
substantial advantage over standard aqueous polymerization in that the 
ultra-high molecular weight polymers produced can be easily and rapidly 
dissolved (further diluted) in the injection water. 
The water-in-oil dispersion synthesis of polyacrylamide and acrylamide 
copolymers is run utilizing the same monomer charge composition, redox 
initiators, and reaction conditions as is used in the standard aqueous 
polymerization synthesis of these ultra-high molecular weight polymers. In 
water-in-oil dispersion polymerization in addition to the reagents used in 
standard aqueous polymerizations, there is also present an oil and 
normally a dispersing agent. Some representative examples of oils that can 
be used are kerosene, diesel fuel, pentane, hexane, decane, pentadecane, 
benzene, toluene, 2,4-dimethylhexane, mineral oil (liquid petrolatum), and 
3-ethyloctane. This is certainly not an exhaustive list of the oils that 
can be employed. Most alkanes containing 5 or more carbon atoms will work 
very well as will most aromatic hydrocarbons. Alkanes should not be used 
since they can react in the polymerization. The dispersing agents are 
nonionic surfactants that are soluble in hydrocarbons and insoluble in 
water. Some representative examples of dispersing agents that may be used 
in water-in-oil dispersion polymerization include polyethers, such as 
Igepal CO-430.TM. (GAF Corp.); polyglycerol oleates, such as 
Witconol-14.TM. (Witco Chemical Company); and polyglycerol stearates, such 
as Witconol-18L.TM. (Witco Chemical Company). 
##STR15## 
These dispersing agents (nonionic surfactants) are added to the oil that 
will be used in the water-in-oil dispersion polymerization. Normally, the 
oil used in such dispersion polymerizations will contain from about 2 to 
about 10 weight percent of the dispersing agent. Normally, the aqueous 
reaction medium used in these water-in-oil dispersion polymerizations will 
contain 25 weight percent of the oil containing the dispersing agent based 
on the total aqueous reaction medium. Even more oil can be used in such 
water-in-oil dispersion polymerization with a corresponding increase in 
the amount of dispersing agent used but generally it will not be 
advantageous to use larger amounts of the oil. Good results can be 
obtained using an aqueous reaction medium comprising about 25 weight 
percent monomers, about 50 weight percent water, and about 25 weight 
percent oil. A charge composition containing less than 25 weight percent 
monomers can be used, however, it will not normally be advantageous to use 
lesser quantities of the monomers. 
It is often desirable to use deionized water in such water-in-oil 
dispersion polymerizations. Oxygen which is dissolved in the monomers, 
water, and oil should be removed before polymerization. This can be 
accomplished by sparging the monomers, water, and oil with an inert gas or 
nitrogen. Such a mixture of monomers, water, and oil is vigorously mixed 
to obtain the water-in-oil dispersion. The dispersion is brought to the 
desired temperature (normally about 0.degree. C.) and the initiator 
components are added. The aqueous reaction medium containing the redox 
initiators system is normally stirred or in some alternative way agitated 
during the course of the polymerization. 
After the desired reaction time the polymerization can be terminated by 
adding a shortstopping agent, such as methylether hydroquinone; however, 
this will normally not be necessary. Normally, this reaction time will be 
from about 1.5 to about 3 hours. The desired reaction time will vary with 
reaction temperature, initiator concentration, and the degree of 
polymerization desired. Normally, it will be desirable to allow the 
polymerization to go to completion (until the monomer supply is 
essentially exhausted). 
In the polymerizations of this invention yields are essentially 
quantitative (in excess of 99 percent). The percentage of repeat units by 
weight derived from a monomer in a polymer will be equal to the percentage 
by weight of that monomer in the aqueous reaction medium used in the 
synthesis of that polymer.

The present invention will be described in more detail in the following 
examples. These examples are merely for the purpose of illustration and 
are not to be regarded as limiting the scope of the invention or the 
manner in which it may be practiced. Unless specifically indicated 
otherwise, all parts and percentages are given by weight. 
EXAMPLES 1 THROUGH 10 
A series of 10 vials were charged with 50 percent aqueous acrylamide 
solutions. These acrylamide monomer solutions were degassed by a 
continuous nitrogen sparge. Three different molecular weight jumpers were 
deaerated under aspirator vacuum for a minimum of 3 hours. 
Table I indicates which molecular weight jumper was added to each of the 
vials and the amount of it employed. Examples 1, 5, and 9 served as 
controls wherein no molecular weight jumper was added. In the examples 
wherein a molecular weight jumper was added, it was charged into the vial 
under a nitrogen atmosphere just after cessation of sparging and 
immediately before addition of the redox initiator system. 
These polymerizations were initiated by injecting equivalent amounts of 
sodium meta-bisulfite, Na.sub.2 S.sub.2 O.sub.5, and ammonium persulfate, 
(NH.sub.4).sub.2 S.sub.2 O.sub.8, into each of the vials. In these 
examples 0.01 percent of sodium meta-bisulfite and 0.01 percent of 
ammonium persulfate, based upon the total weight of the aqueous reaction 
medium, was added to each of the vials. All of these polymerizations were 
conducted with the vials being immersed in an ice water bath for a period 
of at least 12 hours. These polymerizations resulted in the production of 
polymer cements. 
Aqueous brine solutions having a polymer concentration of 2500 ppm (parts 
per million) were prepared by placing the proper amount of polymer cement 
from each of the vials in 400 ml (milliliters) of brine water and waiting 
for complete dissolution which took several days. One-hundred percent 
monomer conversion was assumed in the preparation of these solutions. The 
brine water solutions employed in these examples contained 3 percent NaCl 
and 0.3 percent CaCl.sub.2. Brookfield viscosities were then determined 
for each of the polymer-brine solutions with the results being given in 
Table I. 
TABLE I 
______________________________________ 
M W Jumper Brookfield 
Example 
M W Jumper.sup.a 
Level (phm).sup.b 
Viscosity (cP).sup.c 
______________________________________ 
1 Aerosol .TM. A-102 
0 4.5 
2 Aerosol .TM. A-102 
0.8 5.6 
3 Aerosol .TM. A-102 
2.0 8.3 
4 Aerosol .TM. A-102 
10.0 20.5 
5 Aerosol .TM. A-103 
0 7.5 
6 Aerosol .TM. A-103 
0.8 8.5 
7 Aerosol .TM. A-103 
2.0 20.5 
8 Aerosol .TM. A-103 
10.0 19.5 
9 TR-70.sup.d 0 6.2 
10 TR-70 2 16.3 
______________________________________ 
.sup.a M W Jumper = Molecular Weight Jumper 
.sup.b phm = parts per onehundred parts monomer 
.sup.c cP = centipoise 
.sup.d TR70 = bisn-tridecyl sodium sulfosuccinate 
Aerosol.TM.A-103 has the structural formula: 
##STR16## 
wherein n is 8 or 9. 
The very dramatic effect that the molecular weight jumpers of this 
invention have on molecular weight is apparent when Examples 1, 5 and 9 
which were controls and did not contain any molecular weight jumper are 
compared with the examples wherein a molecular weight jumper was present 
during the polymerization. Actually in these examples Brookfield 
viscosities were determined instead of molecular weights. However, 
Brookfield viscosities are of perhaps greater importance in the 
characterization of an EOR polymer than is molecular weight. In any case, 
increases in Brookfield viscosities are indicative of increases in the 
molecular weight of the polymer in the solution being tested. 
The presence of Aerosol.TM.A-102 during the homopolymerization of 
acrylamide resulted in more than quadrupling the Brookfield viscosity of 
the brine solution prepared from the polyacrylamide produced (compare 
Example 1 with Example 4). It should be noted that these Brookfield 
viscosities were run under very harsh conditions since they were conducted 
with the polyacrylamide being dissolved in brine. The presence of brine 
severely reduces the viscosity of aqueous polyacrylamide solution. If 
these Brookfield viscosities would have been run in pure water they would 
have been substantially higher. However, such a brine solution simulates 
the harsh conditions often encountered in actual EOR applications. 
EXAMPLES 11 through 16 
The procedure specified in Examples 1 through 10 was employed in these 
examples except that a copolymerization of acrylamide monomer with sodium 
AMPS was conducted which was initiated with Na.sub.2 S.sub.2 O.sub.5 and 
(NH.sub.4).sub.2 S.sub.2 O.sub.8 at a level of 0.002 weight percent each 
based upon the total weight of the aqueous reaction medium. The aqueous 
reaction mediums employed in these polymerizations contained an acrylamide 
monomer concentration of 3.5M (molar) and a sodium AMPS concentration of 
0.5M. Aerosol.TM.A-202 was used as the molecular weight jumper in these 
experiments and was employed at the level shown in Table II, which is 
expressed as a volume percent based upon the total aqueous reaction 
medium. The Brookfield viscosities shown in Table II were determined in a 
brine solution using the technique specified in Examples 1 through 10. The 
very dramatic effect that Aerosol.TM.A-102 has on the molecular weight can 
readily be seen by analyzing Table II. It is apparent that this molecular 
weight jumper increases Brookfield viscosities very substantially. At a 
concentration of 5 volume percent in the aqueous reaction medium the 
Brookfield viscosity attained was almost 8 fold what is was when the 
polymerization was done in the absence of a molecular weight jumper 
(compare Example 11 with Example 15). 
TABLE II 
______________________________________ 
M W Jumper Level 
Brookfield Viscosity 
Example (Volume %) (cP) 
______________________________________ 
11 0 3.4 
12 1 5.9 
13 2 6.6 
14 3 9.7 
15 5 26.2 
16 10 24.9 
______________________________________ 
While certain representative embodiments and details have been shown for 
the purpose of illustrating the invention, it will be apparent to those 
skilled in this art that various changes and modifications may be made 
therein without departing from the scope of the invention.