Polyacrylamide hydrolyzed

Hydrolyzed Polyacrylamide. HPAM (6) can be prepared by a free-radical process ia which acrylamide is copolymerized with incremental amounts of acryUc acid or through homopolymerization of acrylamide followed by hydrolysis of some of the amide groups to carboxylate units. 

Polymers in Solution. Polyacrylamide is soluble in water at all concentrations, temperatures, and pH values. An extrapolated theta temperature in water is approximately —40° C (17). Insoluble gel fractions are sometimes obtained owing to cross-link formation between chains or to the formation of imide groups along the polymer chains (18). In very dilute solution, polyacrylamide exists as unassociated coils which can have an eUipsoidal or beanlike stmcture (19). Large aggregates of polymer chains have been observed in hydrolyzed polyacrylamides (20) and in copolymers containing a small amount of hydrophobic groups (21). 

Anionic and nonionic polyacrylamides effectively remove suspended soHds such as silt and clay from potable water. SuppHers provide special grades which meet EPA/FDA regulations for residual acrylamides. A recent pubHcation (102) states that hydrolyzed polyacrylamides with narrow interchain charge distributions provide better performance in flocculation of clay. These polymers were prepared by alkaline hydrolysis. (See Flocculating agents.)... 

The most commonly used polymers are partially hydrolyzed polyacrylamides (32). The optimum degree of hydrolysis depends on the apphcation, injection water composition, and reservoir conditions (33,34). More salt-tolerant acrylamide copolymers may permit this technology in higher salinity injection water (35). Eield apphcations of cross-linked xanthan gum have also been reported (36). 

Postpolymerization Reactions. Copolymers can also be formed by postpolymetization reactions on polymers. A well-known example is the partial hydrolysis of polyacrjiamide (PAM) to hydrolyzed polyacrylamide (HPAM). The product becomes a random copolymer of acrylamide and acryUc acid (44) (see Acrylamide polya rs). 

The polymerization of acrylamide in aqueous solutions in the presence of alkaline agents leads to the ob-tainment of partially hydrolyzed polyacrylamide. The polymerization process under the action of free radicals R (formed on the initiator decomposition) in the presence of OH ion formed on the dissociation of an alkali addition (NaOH, KOH, LiOH), and catalyzing the hydrolysis can be described by a simplified scheme (with Me = Na, K, Li) ... 

Nondispersed Inhibited Systems. In these systems, the nondispersed character of the fluids is reinforced by some inhibition system, or combination of systems, such as (1) calcium ions, lime or gypsum (2) salt-sodium chloride or potassium chloride (3) polymers such as Polysaccharides, polyanionic cellulose, hydrolyzed polyacrylamide. 

G.L. Griffith W.L. Schwoyer, USP 3457128 (1969) CA 71, 72517 (1969). Particulate self-explosive nitrated materials, such as Nitro-starch, PETN, TNT,.and their mixts, can be made relatively safe to handle and transport thru formation of a uniform nongelled aq slurry containing 10—50% water and 0.5—10% partially hydrolyzed polyacrylamide suspending agent having 0.1—50% free acid, and = 50% unhydrolyzed amide groups, and a mw of 1,000,GOO-... 

Such slurries are especially useful for transporting expl sensitizers used in aq slurry blasting agents. Thus, a mixt was prepd by stirring together 66% dry Nitrostarch, 39.8% water, and 0.2% Polyhall 295 (a commercial partiaily hydrolyzed polyacrylamide of mw... 

Capryloamphoglycinate, cocoamphodiacetate, disodium cocoamphodiacetate, lauroamphoacetate, sodium capryloamphohydroxypropyl sulfonate, sodium mixed Cg amphocarboxylate, and alkylamphohydroxypropyl sulfonate Polyvinylpyrrolidone, polyvinyl alcohol, starches, cellulosic material, or partially hydrolyzed polyacrylamide, and polypropylene glycol, or a betaine [43]... 

Aqueous solutions of polyacrylamide may be used as plugging solutions for high-permeability formations. Partially hydrolyzed polyacrylamide polymer also has been used [1211] and completely hydrolyzed polyacrylonitrile has been proposed [1427]. 

Partially hydrolyzed polyacrylamides, carboxymethylcellulose, polysaccharides, and acrylamido methylpropane sulfonate have been screened to investigate the performance of aluminum citrate as a chelate-type crosslinker. An overview of the performance of 18 different polymers has been presented in the literature [1646]. The performance of the colloidal dispersion gels depends strongly on the type and the quality of the polymer used. The gels were mixed with the polymers at two polymer concentrations, at three polymer-to-aluminum ratios, and in different concentrations of potassium chloride. The gels were quantitatively tested 1,7, 14, and 28 days after preparation. 

Among the oxidative breakers, alkali, metal hypochlorites, and inorganic and organic peroxides have been described in literature. These materials degrade the polymer chains by oxidative mechanisms. Carboxymethylcellulose, guar gum, or partially hydrolyzed polyacrylamides were used for testing a series of oxidative gel breakers in a laboratory study [180]. 

T. Chen, W. Pu, K. Ping, and Z. Ye. The rheological behavior of partially hydrolyzed polyacrylamide (HPAM) solutions in reservoir. J Southwest Petrol Inst, 19(3) 2A-3A, 28-34, August 1997. 

Friction reducers such as partially hydrolyzed polyacrylamide may also be used in drilling fluids (19). They allow fluid to be circulated through the well bore more easily thereby reducing horsepower requirements for the circulating pumps and thus decreasing well treatment costs. 

Cationic polyacrylamide may be used in the initial treatment stages to promote rapid polymer adsorption (201). Adjustment of the pH may allow deeper penetration of the fluids in an aluminate crosslinking system prior to gelation (202). A process involving injection of alternate slugs of stoichiometrically equivalent amounts of partially hydrolyzed polyacrylamide and Al O ) has been evaluated in the laboratory permeability of sana packs were reduced by more than 96% (203). Mixtures of Al(IIl) and Zr(IV) have also been evaluated as partially hydrolyzed polyacrylamide crosslinkers (204). 

Chromium crosslinked gels prepared from a 3 1 blend of partially hydrolyzed polyacrylamide and guar gum have been found to have a higher strength and stability than gels prepared from the partially hydrolyzed polyacrylamide alone (222). 

The first mobility control agents were partially hydrolyzed polyacrylamides having molecular weights of 1-5x10 (254-259) and... 

Compared to partially hydrolyzed polyacrylamide, xanthan gum is more expensive, more susceptible to bacterial degradation, and less stable at elevated temperatures (1). However, xanthan gum is more soluble in saline waters, particularly those containing divalent metal ions generally adsorbs less on rock surfaces and is substantially more resistant to shear degradation (1,34). The extensional viscosity of the semi-rigid xanthan molecule is less that that of the flexible polyacrylamide (263). 

Electrostatic repulsion of the anionic carboxylate groups elongates the polymer chain of partially hydrolyzed polyacrylamides increasing the hydrodynamic volume and solution viscosity. The extensional viscosity is responsible for increased resistance to flow at rapid flow rates in high permeability zones (313). The screen factor is primarily a measure of the extensional (elonga-tional) viscosity (314). The solution properties of polyacrylamides have been studied as a function of NaCl concentra-tion and the parameters of the Mark-Houwink-Sakaruda equation calculated... 

As far as neighboring group inhibition is concerned, sequence distribution can play an important role, e.g. Morowetz [5] showed that partially hydrolyzed polyacrylamide hydrolyzes more slowly than an acrylic acid copolymer of the same charge. The former has a more even distribution of groups leading to a greater proportion of the least reactive BAB triad (where A are the acrylamide and B are the acrylic acid moieties). 

Kowblansky et A1 (19) have also measured the intrinsic viscosity of hydrolyzed polyacrylamide of a given molecular weight as a function of r for a - 1 and their results can be fitted by the expression ... 

The strong interaction of polyvalent cations with polyions is well known to strongly alter the rheological properties of hydrolyzed polyacrylamide used in the tertiairy oil recovery process (1-4). The influence of divalent cations have already been studied(5-7) but the role played by the presence of small quantities of aluminium ions has never been investigated. 

Most polymers used in oil field operations and resource recovery are synthetic. The man-made materials in common use are polyO-amidoethylene) ( = polyacrylamide ), poly( 1-amidoethylene-r-( sodium 1-carboxylatoethylene ) ( = partially hydrolyzed polyacrylamide ), poly(l-amidoethylene-r-( sodium 1-(2-methylprop-1N-yl-1-sulfonate)amidoethylene) (AMPS-acrylamide copolymer), and xanthan gum. Xanthan gum is a synthetic because no one finds a pool or river contaminated with Xanthomonas compestris that experiences the right sequence of solute to naturally produce the exocellular gum polymer. A fermenter is a man made object, a tree is not. 

Polymers Polyacrylamide and hydrolyzed polyacrylamide were prepared by the American Cyanamid Company specifically for this project, starting with l C labelled monomer. The radioactivity level of the monomer was kept below 0.20 mC /g in order to avoid significant spontaneous polymerization, utilizing a copper inhibitor. The homopolymer was synthesized by free radical solution polymerization in water at 40°C, using monomer recrystallized from chloroform, an ammonium persulfate-sodium metabisulfite catalyst system, and isopropanol as a chain transfer agent. Sodium... 

Figure 2. Adsorption and flocculation obtained with Na-kaolinite at pH 4.5 as a function of dosage of 33% hydrolyzed polyacrylamide (HPAM 0.4-33).

The presence of excess salt, particularly of bivalent inorganics can reduce the electrostatic repulsion between the anionic polymer and the kaolinite particles and enhance flocculation (24,25). The optimum flocculation of fine coal and coal refuse (which contained 13 to 65% clays) obtained by Lewellyn and Wang(24) with hydrolyzed polyacrylamide containing 70% acrylate in fact might have resulted from the use of recycled water which contained 55 ppm Ca and 30 ppm Mg. Other works in literature have reported maximum flocculation of kaolinite to occur with 30% hydrolyzed polyacrylamide (5,6,10,26,27). Such differences in reported results could easily result from variations in water chemistry, originating either with the water used or with dissolved organics released by the mineral itself. 

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