High molecular-weight-polyacrylamide powders

The rate of polymer dissolution is an important property that impacts high-molecular-weight polyacrylamide availability and performance commercially. Polymer particle size distribution in dry powder polymers and the polymer solids content and level of activating surfactant in inverse emulsion polymers are factors that impact polymer dissolution. The rate of polymer dissolution is typically determined by following the rate at which the viscosity in a polymer solution builds during dissolution. 

Poly(ethylene oxide)s [25372-68-3] are made by condensation of ethylene oxide with a basic catalyst. In order to achieve a very high molecular weight, water and other compounds that can act as chain terminators must be rigorously excluded. Polymers up to a molecular weight of 8 million are available commercially in the form of dry powders (27). These must be dissolved carefliUy using similar techniques to those used for dry polyacrylamides. Poly(ethylene oxide)s precipitate from water solutions just below the boiling point (see Polyethers, ethylene oxide polymers). 

Retention and flow characteristics of a solution containing Pusher 700 , a high-molecular-weight, partially hydrolyzed polyacrylamide, were studied in an 86-md core made by compacting Teflon powder. The quantity of polymer retained during linear displacement experiments ranged from 10 to 21 pgm/gm for polymer concentrations of 100 to 500 ppm in 2-percent NaCl solutions. Nearly all retention was attributed to mechanical entrapment because of low polymer adsorption on the Teflon surface. Flow rate affected polymer retention. An increase in velocity was accompanied by polymer retention. Polymer was expelled when the flow rate was reduced. Inaccessible pore volume was about 19 percent of the total pore volume. 

Low molecular weight (1000—5000) polyacrylates and copolymers of acryflc acid and AMPS are used as dispersants for weighted water-base muds (64). These materials, 40—50% of which is the active polymer, are usually provided in a Hquid form. They are particularly useful where high temperatures are encountered or in muds, which derive most of their viscosity from fine drill soHds, and polymers such as xanthan gum and polyacrylamide. Another high temperature polymer, a sulfonated styrene maleic—anhydride copolymer, is provided in powdered form (65,66). AH of these materials are used in relatively low (ca 0.2—0.7 kg/m (0.5—2 lb /bbl)) concentrations in the mud. 

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