United States Patent
`Birch
`
`[19]
`
`Patent Number:
`[11]
`[45] Date of Patent:
`
`4,530,979
`Jul. 23, 1985
`
`[54] CONTINUOUS POLYMERIZATION OF
`WATER-MISCIBLE POLYMERS
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`[75]
`
`Inventor:
`
`James R. Birch, Midland, Mich.
`
`[73] Assignee:
`
`The Dow Company, Midland, Mich.
`
`[21]
`
`Appl. No.: 504,762
`
`[22J
`
`Filed:
`
`Jun. 15, 1983
`
`[51]
`[52J
`
`[58]
`
`Int. Cl.3
`U.S. Cl.
`
`Field of Search
`
`C08F 2/16
`526/64; 526/62;
`526/88
`526/62, 64, 88
`
`526/64
`526/64
`526/64
`
`4,110,521
`8/1978 Barnett
`4,143,222
`3/1979 Goretta
`4,331,787
`5/1982 Fairchok
`Primary Examiner-Paul R. Michl
`[57]
`ABSTRACT
`A continuous adiabatic process for preparing water(cid:173)
`miscible and water-soluble polymers wherein an aque(cid:173)
`ous solution containing monomer and an initiator sys(cid:173)
`tem is passed through a reactor and reacted to yield a
`rapid increase in viscosity as polymerization occurs.
`The polymer product exhibits consistent cross-sectional
`properties in the reactor over time and moves slowly
`and easily through the reactor as a plug.
`
`7 Claims, No Drawings
`
`SNF Exhibit 1027, Page 1 of 5
`
`

`
`1
`
`CONTINUOUS POLYMERIZATION OF
`WATER-MISCIBLE POLYMERS
`
`4,530,979
`
`2
`continuous process for polymerizing water-miscible
`monomers to form water-soluble polymers that have
`high molecular weights, which process comprises a
`compact, simple, self-contained and energy efficient
`5 system without
`the use of water-immiscible solvents
`and lubricants.
`
`BACKGROUND OF THE INVENTION
`This invention relates to the polymerization of water(cid:173)
`miscible monomers in aqueous solution.
`Most water-soluble polymers, particularly polymers
`of acrylamide, acrylic acid and their water-miscible
`derivatives have been employed commercially as addi- 10
`tives in the manufacture of paper products, as water
`purification coagulants, as dispersing agents, and as
`treating agents in a wide variety of applications.
`Of the various methods employed to polymerize wa(cid:173)
`ter-miscible monomers, the aqueous solution polymeri- 15
`zation method in a batch mode is most commonly em(cid:173)
`ployed because it is inexpensive and can provide water(cid:173)
`soluble polymers having high molecular weight.
`In
`such a method,
`the concentrations of monomer and
`resulting polymer in aqueous solution are maintained as 20
`high as possible in order to reduce the amount of water
`that is subsequently removed from the resulting poly(cid:173)
`mer product. Unfortunately, the high viscosities of the
`resulting polymer solution, even at fairly low conver(cid:173)
`sion, limit the initial monomer concentration to below a 25
`2 or 3 weight percent concentration. This concentration
`limit leads to poor reactor utilization and the high vis(cid:173)
`cosity leads to poor reactor heat
`transfer due to the
`inability to stir the contents.
`The problems that result from the high viscosities of 30
`relatively dilute aqueous solutions of such water-soluble
`polymers have been solved by suspending or emulsify(cid:173)
`ing the aqueous solution of water-miscible monomer in
`a water-immiscible organic liquid and forming a rela(cid:173)
`tively unstable suspension or a relatively stable emul- 35
`sion of the desired water-soluble polymer. Methods of
`practicing such suspension or emulsion polymerization
`are described in U.s. Pat. Nos. 2,982,749 and 3,284,393,
`respectively. These methods significantly increase the
`concentration of monomer and resulting polymer in the 40
`suspension or emulsion as compared to the amount of
`monomer or polymer present in the aforementioned
`batch techniques while maintaining workable viscosi(cid:173)
`ties. Unfortunately, the cost incurred in employing such
`processes is high due to the use of organic solvents 45
`which are not recovered or reused. It has also been
`difficult to practice such methods in a continuous man(cid:173)
`ner.
`Water-soluble polymers can be prepared in a continu(cid:173)
`ous manner using a tubular reactor as described in U.s. 50
`Pat. No.4, 110,521. Static mixers are used to promote
`plug flow and heat transfer while running the polymeri(cid:173)
`zation isothermally. The continuous tubular reactors
`enjoy cost and utilization advantages over batch pro(cid:173)
`cesses but, unfortunately, such processes require costly 55
`temperature control systems, costly static mixing ele(cid:173)
`ments, and high pressures to force highly viscous gels
`through the system. U.S. Pat. No. 4,331,787 offers a
`partial solution to the requirement of high pressure that
`forces the resulting polymer through the system by 60
`employing a water-immiscible fluid to lubricate the
`flow of emulsified polymer gels during continuous tubu(cid:173)
`lar polymerization. Unfortunately, such a process still
`requires pressure to force the polymer through the
`system, and the addition of a lubricant can contaminate 65
`the polymer product and add to processing costs.
`In view of the aforementioned deficiencies of the
`prior art methods,
`it
`is highly desirable to provide a
`
`SUMMARY OF THE INVENTION
`The present invention is a continuous adiabatic pro(cid:173)
`cess for preparing water-soluble polymers wherein an
`aqueous solution containing a water-miscible monomer
`mixture together with suitable initiators
`is passed
`through a reactor. The monomer mixture is sufficiently
`reactive as to effect a rapid increase in viscosity as said
`monomer mixture is subjected to conditions sufficient to
`polymerize the monomer in the reactor thereby forming
`the desired polymer product which exhibits consistent
`cross-sectional properties in the reactor over time. The
`product
`so formed moves
`consistently and easily
`through the reactor as a plug.
`By the term "plug" is meant that the polymer product
`passing through the reactor exhibits a flat cross-sec(cid:173)
`tional velocity profile and undergoes minimal amounts
`of axial backmixing. The monomers are sufficiently
`reactive to rapidly polymerize within the reactor as the
`monomers are subjected to conditions sufficient to poly(cid:173)
`merize said monomers. Thus, factors such as tempera(cid:173)
`ture, initiator type, etc., as well as monomer purity or
`quality can affect the type of product formed. Also, the
`process can be carried out in a continuous manner to
`produce a polymer which is high in molecular weight
`yet contains no water-insoluble gels. The process of this
`invention requires no reactor internals to promote mix(cid:173)
`ing, heat transfer or plug flow and, thus, consequently
`operates at relatively low pressure.
`The polymers prepared in accordance with the prac(cid:173)
`tice of this invention are useful in the same applications
`as similar water-soluble polymers prepared by conven(cid:173)
`tional polymerization methods. Examples of such appli(cid:173)
`cations include additives for the manufacture of paper,
`agents for the treatment of sewage and industrial waste
`waters, thickeners, dispersing agents, mobility control
`agents, and the like.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`Water-miscible monomers suitably employed in the
`practice of this invention are those ethylenically unsatu(cid:173)
`rated monomers which are sufficiently water-miscible
`to form a single aqueous phase when 5 weight parts of
`the monomer are dispersed in water. Such monomers
`readily undergo addition polymerization to form poly(cid:173)
`mers which are at least inherently water-dispersible and
`preferably water-soluble. By "inherently water-dispers(cid:173)
`ible" is meant that the polymer, when contacted with an
`aqueous medium, will disperse therein without the aid
`of surfactants to form a colloidal dispersion of the poly(cid:173)
`mer in the aqueous medium. Preferably, such polymers
`are sufficiently water-soluble in that they will form at
`least a 5 weight percent solution when dissolved in
`water. Exemplary water-miscible monomers include
`the water-miscible ethylenically unsaturated amides
`such as acrylamide, methacrylamide and fumaramide;
`water-miscible N-substituted ethylenically unsaturated
`amides such as N-(N' ,N'-dialkylaminoalkyl)acrylamide,
`e.g., N-(N',N'-dimethylaminomethyl)acrylamide
`and
`quaternized derivatives thereof such as N-(N',N',N'-
`
`SNF Exhibit 1027, Page 2 of 5
`
`

`
`4,530,979
`
`5
`
`3
`trimethylammonium methyl)acrylamide chloride and
`N-substituted alkylol acrylamide such as N-methylol
`acrylamide; ethylenically unsaturated carboxylic acids
`such as acrylic acid, methacrylic acid, fumaric acid and
`the like; ethylenically unsaturated quaternary ammo(cid:173)
`nium compounds such as vinylbenzyl trimethylammo(cid:173)
`nium chloride; sulfoalkyl esters of carboxylic acids such
`as 2-sulfoalkyl methacrylate as well as the alkali metal
`and ammonium salts thereof; aminoalkyl esters and
`quaternary ammonium alkyl of unsaturated carboxylic
`acids such as 2-aminoethyl methacrylate and 2-(N,N,N(cid:173)
`trimethylammonium)ethyl methacrylate chloride; vinyl
`aryl sulfonates such as vinylbenzene sulfonate as well as
`the alkali metal and ammonium salts thereof; diallyl
`quaternary ammonium compounds such as dimethyl
`diallyl ammonium chloride and diethyl diallyl ammo(cid:173)
`nium chloride; N-(sulfoalkyl)acrylamides and metha(cid:173)
`crylamides such as N-(2-sulfo-l, l-dimethylethyl)acryla(cid:173)
`mide; ethylenically unsaturated amines such as allyl and
`diallylamine and the like. Of the foregoing water-misci(cid:173)
`ble monomers, acrylamideand the water-miscible de(cid:173)
`rivatives of acrylamide as well as acrylic acid and meth(cid:173)
`acrylic acid and mixtures of such monomers are pre(cid:173)
`ferred. Especially preferred are acrylamide and mix(cid:173)
`tures of acrylamide and acrylic acid containing from
`about 10 to about 30 weight percent of acrylic acid. It is
`also desirable to employ a mixture of monomer and
`sodium carbonate as, for example, acrylamide and so(cid:173)
`dium carbonate, sodium bicarbonate, soluble hydrox(cid:173)
`ides and the like to yield a partially hydrolyzed poly(cid:173)
`mer.
`Normally, such polymerization is carried out in the
`presence of a polymerization initiator capable of gener(cid:173)
`ating free radicals. Exemplary polymerization initiators
`include the inorganic persulfates such as potassium per(cid:173)
`sulfate, ammonium persulfate and sodium persulfate,
`azo catalyst such as azobisisobutyronitrile and dimethyl
`azoisobutyrate; organic peroxygen compounds such as
`benzyl peroxide,
`t-butyl peroxide, diisopropylbenzene
`hydroperoxide and t-butyl hydroperoxide. Of these
`.initiators, the organic peroxygen compounds are pre(cid:173)
`ferred. Particularly preferred are combinations of these
`peroxygen compounds with reducing agents to provide
`conventional redox catalyst systems. Examples of such
`reducing agents are sodium bisulfite, sodium borohy(cid:173)
`dride, ferrous chloride, and the like. Preferred initiator
`systems include mixtures of t-butyl peroxide, sodium
`persulfate and sodium bisulfite. Also preferred is a mix(cid:173)
`ture of t-butyl peroxide and sodium borohydride. In
`addition to the aforementioned ingredients,
`the poly(cid:173)
`merization recipe desirably includes a chelating reagent
`such as the penta sodium salt of diethylenetriamine
`pentaacetic acid, ethylene diamine tetraacetic acid, or
`any reagent that is effective in sequestering free ions
`such as ferrous or cuprous ions which interfere with
`polymerization processes.
`The amount of oxidizing agent employed in the poly(cid:173)
`merization process is between about 100 and about 2000
`ppm based on the weight of the monomer. It is most
`desirable that
`the amount of initiator be sufficient
`to 60
`prevent slow polymerization and, hence, yield a high
`rate of conversion of monomer to polymer in order that
`the polymer product will gel and lead to uniform flow
`through the reactor. However,
`it
`is desirable that the
`amount of initiator not be too high as to result in the
`formation of a low molecular weight polymer product.
`The amount of reducing agent employed is preferably
`in the range from about 0 to about 30 ppm based on the
`
`4
`weight of the monomer. As with the oxidizing agents,
`an excessive amount of reducing agent will
`lead to a
`low molecular weight polymer product.
`The amount of monomer employed in the polymeri-
`zation process is between about 6 and about 30, more
`preferably between about IS and about 30, weight per(cid:173)
`cent based on the weight of the monomer and the total
`aqueous feed. The amount of monomer or mixture of
`monomers depends on the type of monomer employed.
`10 It is desirable that the monomer result in a water-soluble
`polymer of sufficient molecular weight to form a thick
`gel product. It
`is desirable that
`the concentration of
`monomer be great enough in order that
`the polymer
`product will gel and lead to uniform flow of the gel
`15 through the reactor. It is critical in the process of this
`invention that the monomer be sufficiently reactive to
`rapidly gel,
`thus, building up viscosity quite rapidly.
`Thus, if "plug" flow is not established, channeling of
`reactants through the reactor and pressure surging oc-
`20 cur. Such occurrences lead to gel products which are
`inconsistent in their properties. In addition, the concen(cid:173)
`tration of monomer should be great enough to exhibit a
`temperature rise in the reactor which will lead to high
`polymer conversion. However, it is desirable that the
`25 concentration of monomer not be too high, as the result(cid:173)
`ing high adiabatic temperatures in the reactor can lead
`to low molecular weight products or excessive polymer
`product degradation.
`In addition, an extremely high
`monomer concentration can require excessive pressure
`30 to force the polymer product through the reactor.
`The system employed in the process of this invention
`most advantageously includes a neutralization reactor
`equipped with a jacket, agitator and various shot tanks.
`To this reactor is added the monomer mix. The system
`35 is also equipped with several feed tanks for the monO(cid:173)
`mer mix and each of the various initiators. It is prefera(cid:173)
`ble that
`the feed tanks be equipped with pressure
`gauges, level transmitters, vacuum lines, nitrogen inlets
`for providing pressure to the system and sparging tank
`40 contents, and pumping apparatus for forcing reactants
`into a mixing chamber. The reactants are forwarded to
`a primary reactor which is operated adiabatically and
`insulated to minimize heat loss during operation. At the
`primary reactor exit the system can be equipped with a
`45 means for injecting and mixing additional
`initiator to
`decompose residual, unreacted monomer. A series of
`static mixing elements leading to a secondary reactor is
`It is desirable that
`usually satisfactory.
`temperature
`probes be present in the system in order to monitor
`50 various temperatures in the primary reactor, the static
`mixer elements and the secondary reactor. The product,
`which is a gel, exits the secondary reactor through a
`control valve in order that back pressure on the system
`can keep the reactor hydraulically full. Although any
`55 material which is relatively inert to the reactants and
`which can tolerate the pressures experienced within the
`system can be employed in constructing the system, the
`preferred materials used to construct
`the system are
`stainless steel alloys.
`The primary and secondary reactors employed in the
`polymerization process of this invention are of sufficient
`cross-sectional area as to lead to slow axial velocities
`which are typically less than about 5 meters per hour. It
`is most preferred that the cross-sectional shape of the
`65 reactors is circular. The overall geometry of the reac(cid:173)
`tors can vary depending upon the desired operating
`pressures,
`the monomer mix,
`initiator,
`levels and the
`product desired. Most preferably, the reactor is tubular
`
`SNF Exhibit 1027, Page 3 of 5
`
`

`
`4,530,979
`
`5
`in shape. The residue time of the primary reactor is
`typically sufficient for high conversion to occur; gener(cid:173)
`ally from 1 to 4 hours.
`The length of the reaction time is not particularly
`critical so long as the mixture remains in the reactor for 5
`a time sufficient to polymerize essentially all monomer.
`Normally,
`residence times range from about 0.5 to
`about 4, preferably from about 1 to about 2, hours.
`Accordingly, the length and diameter (volume) of the
`reactor are sufficient to attain the aforementioned resi- 10
`dence times.
`In the process of this invention, an aqueous monomer
`mix is prepared and fed into a feed tank. In a like man(cid:173)
`ner, a separate feed tank(s) is prepared containing se(cid:173)
`questering and chelating agents, oxidizing agents and 15
`reducing agents. The contents of each of the feed tanks
`are mixed with one another and fed into a primary
`reactor which has been described hereinbefore. Poly(cid:173)
`merization and gelation occurs rapidly in the reactor
`leading to a temperature rise therein. The rapid viscos- 20
`ity buildup in the reactor is believed to cause the viscous
`gel to move slowly through the reactor as a "plug." It
`is believed that the shear thinning nature of the gel will
`enhance the plug flow effect since the high shear stress
`at
`the wall of the reactor will
`lead to a lower local 25
`viscosity which thus promotes slippage at the wall.
`It is desirable that the gel move through the reactor
`as a "plug" having a flat cross-sectional velocity profile
`in order that there exist minimal amounts of axial back(cid:173)
`mixing. The lack of backmixing of polymer with reac- 30
`tants leads to a narrow residence time of reactants in the
`reactor. This results in consistent polymerization prod(cid:173)
`ucts over time.
`The temperatures employed in the practice of this
`invention are not particularly critical and are generally 35
`those conventionally employed in polymerizing such
`water-miscible monomers. Preferably, such tempera(cid:173)
`tures range from about 10° to about 100° C., most pref(cid:173)
`erably from about 25° to about 60° C. The maximum
`temperature will depend upon the initial monomer con- 40
`centration as the reactor operates adiabatically. In most
`instances, it is desirable to polymerize the monomer in
`two stages, an initial stage wherein the monomer is
`subjected to temperatures less than 70° C., preferably
`from about 25° to about 55° c., and a second stage 45
`wherein the mixture is subjected to temperatures in
`excess of 70° c., preferably from about 75° to about 100°
`C. In order to practice this two-stage procedure, it is
`desirable to pass the mixture through two reactors, an
`initial or a primary reactor operating at a temperature 50
`below 70° C., and subsequent or secondary reactor
`operating at a temperature in excess bf 70° C. It is found
`that the employment of this two-stage polymerization
`procedure improves the physical properties of the poly(cid:173)
`mer. The secondary reactor is typically the same size 55
`and design as the primary reactor and is employed to
`maintain high temperatures necessary to reduce the
`amount of residual, unreacted monomer to acceptable
`levels. It is understood, however, that the temperature
`is governed by the adiabatic character of the process 60
`and the particular monomer combination which is used.
`The temperature most advantageously should not ex(cid:173)
`ceed about 90° C. in order that polymer product degra(cid:173)
`dation does not occur.
`Recovery of the polymer from the reactor is readily 65
`achieved since the resulting polymer gel flows readily
`through the reactor. Thus, the polymer can be recov(cid:173)
`ered as a solid by conventional drying techniques or
`
`6
`transferred directly to a continuous dilution device. If
`the polymer is to be stored as a powder or similar finely
`divided particulate matter, it is advantageous to subject
`it to air drying to prevent subsequent agglomeration of
`the particulate. Accordingly, recovery of the polymer
`is generally achieved according to conventional tech(cid:173)
`niques.
`The polymers prepared by the process of this inven(cid:173)
`tion can be used in industrial applications as such poly(cid:173)
`mers have previously been employed. For example,
`such polymers can be used as thickeners, dispersants,
`coagulants, and the like in a wide variety of industrial
`applications. An especially preferred use of the poly(cid:173)
`mers is as a mobility control agent in enhanced oil re(cid:173)
`covery applications. It is possible to dilute the resulting
`gel directly to field-use conditions directly from the
`polymerization system. Thus, shipping costs associated
`with delivering the polymer to the point of use are
`significantly reduced. In addition, it is possible to pre(cid:173)
`pare a polymer at a particular site which can be specifi(cid:173)
`cally designed for
`the particular conditions under
`which it will be used.
`The following examples are given to illustrate the
`preferred embodiments of the invention and should not
`be construed as limiting its scope. Unless otherwise
`indicated, all parts and percentages are by weight.
`
`EXAMPLE 1
`A feed solution of monomer mix is prepared by add(cid:173)
`ing into a small batch reactor 7200 grams of a 50 percent
`acrylamide solution, 1080 grams of sodium carbonate,
`and 6280 grams of filtered water. The mixture is agi(cid:173)
`tated for 30 minutes, transferred by vacuum to a storage
`tank, and deoxygenated by recirculating the tank con(cid:173)
`tents with nitrogen until the oxygen level is below 0.5
`ppm. The monomer feed tank is pressurized with nitro(cid:173)
`gen.
`A second feed solution comprising an oxidizer mix is
`prepared by adding 10.3 grams of a 70 percent t-butyl
`hydroperoxide solution, 36 grams of a 40 percent solu(cid:173)
`tion of the pentasodium salt of a diethylenetriamine
`pentaacetic acid, and 2571 grams of filtered water. The
`mixture is capped, shaken, transferred to a separate feed
`tank, deoxygenated by sparging with nitrogen for 30
`minutes, and the feed tank is pressurized with nitrogen.
`A third feed solution comprising a reducer mix is
`prepared by adding 0.06 gram of a 12 percent sodium
`borohyride solution, 21.2 grams of a 50 percent sodium
`hydroxide solution, and 2571 grams of filtered water.
`The mixture is capped, shaken, transferred to a separate
`feed tank, deoxygenated by sparging with nitrogen for
`30 minutes, and the feed tank is pressurized with nitro(cid:173)
`gen.
`The three feed solutions are pumped into a rotary
`mixing device at the rate of 1286 gramslhour for the
`monomer mix and 107 grams/hour for each of the oxi(cid:173)
`dizer and reducer mixes. The solutions are mixed briefly
`and the mixture is allowed to flow into a stainless steel
`main reactor 4 inches in diameter and 24 inches long. At
`steady state, the main reactor temperature exotherms to
`60° C. and the pressure is 170 psig. The viscous gel is
`transferred to a secondary reactor that has dimensions
`similar to the main reactor. The temperature in the
`secondary reactor is 85° C. and the pressure is 50 psig.
`Each of the reactors is electrically traced and insulated
`to minimize heat losses. The average residence time of
`monomer or polymer in each of the reactors is 2 hours.
`
`SNF Exhibit 1027, Page 4 of 5
`
`

`
`4,530,979
`
`7
`The gel exiting the secondary reactor is 29.2 percent
`solids, contains 0.03 percent residual monomer, and has
`undergone 14 percent hydrolysis. The 0.3 percent solu(cid:173)
`tion viscosity of the polymer as determined using an
`Ostwald Viscometer (25 0 C., 4 percent sodium chloride
`solution) is 9.6 cps.
`
`EXAMPLE 2
`A feed solution of monomer mix is prepared as fol(cid:173)
`lows by adding into a small batch reactor 2341 grams of
`a 50 percent acrylamide solution, 505 grams of acrylic
`acid, 513 grams of a 50 percent aqueous sodium hydrox(cid:173)
`ide solution, and 1782 grams of filtered water. The
`mixture is agitated for 30 minutes, transferred by vac(cid:173)
`uum to a storage tank, and deoxygenated by recirculat(cid:173)
`ing the tank contents with nitrogen until the oxygen
`level is below 0.5 ppm. The monomer feed tank is pres(cid:173)
`surized with nitrogen.
`A second feed solution comprising an oxidizer mix is
`prepared by adding 0.707 gram of a 70 percent t-butyl
`hydroperoxide solution, 9.9 grams of a 40 percent solu(cid:173)
`tion of the pentasodium salt of a diethylenetriamine
`pentaacetic acid, 0.1485 gram of sodium persulfate, and
`3142 grams of filtered water. The mixture is capped,
`shaken, transferred to a separate feed tank, deoxygen(cid:173)
`ated by sparging with nitrogen for 30 minutes, and the
`feed tank is pressurized with nitrogen.
`A third feed solution comprising a reducer mix is
`prepared by adding 0.02 gram of sodium persulfate and
`3142 grams of filtered water. The mixture is capped, 30
`shaken, transferred to a separate feed tank, deoxygen(cid:173)
`ated by sparging with nitrogen for 30 minutes, and the
`feed tank is pressurized with nitrogen.
`The three feed solutions are pumped into a rotary
`mixing device at the rate of 643 grams/hour for the
`monomer mix and 357 grams/hour for each of the oxi(cid:173)
`dizer and reducer mixes. The solutions are mixed briefly
`and the mixture is allowed to flow into a stainless steel
`main reactor 4 inches in diameter and 24 inches long. At
`steady state, the main reactor temperature exotherms to 40
`60 0 C. and the pressure is 135 psig. A mix of 59.4 grams
`of sodium sulfite and 1257 grams of water is pumped
`into the gel at a rate of 143 grams/hour and mixed with
`a series of Ross LPD static mixers. The viscous gel is
`
`8
`then transferred to a secondary reactor that has dimen(cid:173)
`sions similar to the main reactor. The temperature in the
`secondary reactor is 85 0 C. and the pressure is 50 psig.
`Each of the reactors is electrically traced and insulated
`5 to minimize heat losses. The average residence time of
`monomer or polymer in each of the reactors is 2 hours.
`The gel exiting the secondary reactor is 15.4 percent
`solids and contains 0.03 percent residual monomer. The
`0.3 percent solution viscosity of the polymer as deter(cid:173)
`10 mined using an Ostwald Viscometer (25 0 C., 4 percent
`sodium chloride solution) is 4.6 cps.
`What is claimed is:
`1. A continuous adiabatic process for preparing wa(cid:173)
`ter-miscible high molecular weight polymers which
`15 comprises passing an aqueous solution containing a
`water-miscible monomer mixture together with suitable
`initiators through a reactor, said monomer mixture
`being sufficiently reactive as to effect a rapid increase in
`viscosity as said monomer mixture is subjected to condi-
`20 tions sufficient to polymerize the monomer in the reac(cid:173)
`tor,
`thereby forming the desired polymer product
`which exhibits consistent cross-sectional properties in
`the reactor over time, wherein said product so formed is
`in the form of a gel and moves consistently and easily
`25 through the reactor as a plug.
`2. A process of claim 1 wherein said reactor is tubular
`in shape.
`3. A process of claim 1 wherein the polymer is water(cid:173)
`soluble.
`4. A process of claim 3 wherein the monomer mixture
`comprises acrylamide or a mixture of acrylic acid and
`acrylamide.
`5. A process of claim 1 wherein said aqueous solution
`comprises from about 6 to about 30 weight percent
`35 monomer based on the total weight of the aqueous
`solution.
`6. A process of claim 1 wherein said polymer product
`is passed through a secondary reactor to reduce the
`amount of residual, unreacted monomer.
`7. A process of claim 1 wherein said aqueous solution
`comprises from about 15 to about 30 weight percent
`monomer based on the total weight of the aqueous
`solution.
`
`*
`
`*
`
`*
`
`*
`
`*
`
`45
`
`50
`
`55
`
`60
`
`65
`
`SNF Exhibit 1027, Page 5 of 5