Suspensions bentonite

In low sohds muds, vinyl acetate—maleic anhydride copolymers were once used to extend or enhance the viscosity of bentonite suspensions (141). This function is largely performed by polyacrylamides. The vinyl acetate—maleic anhydride copolymers can also have a flocculating effect on drill sohds. Concentrations generally are quite low (0.14—0.57 kg/m (0.05—0.2 Ib/bbl)). 

Complexes of tetravalent zirconium with organic acids, such as citric, tartaric, malic, and lactic acids, and a complex of aluminum and citric acid have been claimed to be active as dispersants. The dispersant is especially useful in dispersing bentonite suspensions [288]. Polymers with amine sulfide terminal moieties are synthesized by using aminethiols as chain transfer agents in aqueous addition polymerizations. The polymers are useful as mineral dispersants [1182]. 

NMRD studies (0.01-30 MHz) on bentonite suspensions showed that the water-proton spin-lattice relaxation rates are dominated by magnetic interactions with paramagnetic centers entrapped in the mineral matrix (89). The 1/Ti values were linearly dependent on the concentration of the... 

In colloidal suspensions of anisotropic particles, the static structure factor plays a prominent role in particle size analysis. We have used transient electric birefringence (TEB) and electron microscopy, in addition to laser light scattering, to correlate our analysis of particle size distributions of bentonite suspensions. The complementary nature of TEB and photon correlation spectroscopy (PCS) in particle size analysis will be discussed. 

High voltage square pulses from 0.5 to 3-3 KV/cm with pulse widths of around 2 msec were applied to the five bentonite suspensions. The pulse traces and the signal from the photomultiplier tube were simultaneously recorded at a resolution of 1024 points each in the transient recorder using a sample time increment of 40 usee and displayed on an oscilloscope. After 10 passes the data were transferred to the microcomputer and saved on floppy disk for subsequent analysis. The entire measurement sequence for one sample took a few minutes. 

The normalized results for one bentonite suspension measured at two different scattering angles are shown to be self-consistent in figure 4. 

Figure 3. Zimin plot of bentonite suspensions using = 514.5 nm. The numbers denote concentrations as shown in Table I (LLS).

Band broadening HDC, 259-260 sedimentation FFF, 223 Batch polymerization, latex, 266-267 Bentonite suspensions dynamic light-scattering... 

FIG. 13 The amount of NaCl needed to flocculate a clay (i.e., sodium bentonite suspension) as a function of the polyelectrolyte concentration (i.e., sodium car-boxymethylcellulose). The inserted figure is an enlargement of the initial addition of the polyelectrolyte. The lines are redrawn from An Introduction to Clay Colloid Chemistry by van Olphen [51]. 

Creep Curves Fig. 4 shows the creep curves for the formulations containing 30 and 45 g dm bentonite. Suspensions containing less than 30 g dm bentonite did not give a measurable creep curve. The creep curves shown in Fig. 4 are typical of those obtained with viscoelastic systems. They consist of three regions (a) directly after the application of the stress one observes a rapid elastic deformation resulting in an elastic compliance (instantaneous shear modulus = T/y =... 

Ippolito, M. Rheology of disperse systems-influence of NaCl on the viscous properties of aqueous bentonite suspensions. In Rheology Volume 2 Fluids Astarita, G.,... 

Aqueous bentonite suspensions may be sterilized by autoclaving. The solid material may be sterilized by maintaining it at 170°C for 1 hour after drying at 100°C. 

Aqueous bentonite suspensions retain their viscosity above pH 6, but are precipitated by acids. Acid-washed bentonite... 

The antimicrobial efficacy of cationic preservatives may be reduced in aqueous bentonite suspensions, but nonionic and anionic preservatives are unaffected. ... 

Harris WA. The inactivation of cationic antiseptics by bentonite suspensions. Aust J Pharm 1961 42 583—588. 

Benna, M. et al.. Effect of pH on rheological properties of purified sodium bentonite suspensions, 7. Colloid Interf. Sci., 218, 442, 1999. 

Petkanchin I, Suong T. Influence of the pH on the electric light scattering of palygorskite and bentonite suspensions. J Colloid Interface Sci 1985 108 553-555. 

Fig. 9a,b. Microscopic observations in polarized light of the textures of the aqueous clay suspensions a nematic threaded texture of a bentonite suspension (concentration 0.044 g/cm magnification 50x) b detail of a 1/2 disclination hne (arrow) in a laponite suspension (concentration 0.034 g/cm magnification lOOx) (Reprinted from [50], copyright (1996) from the American Chemical Society)... 

Heath and Tadros (75) showed that the addition of poly (vinyl alcohol) (PVA) to bentonite suspensions increased the yield stress and plastic viscosity for polymer concentrations up to about 5 g/L. At this PVA concentration only about 25% of the surface of the bentonite was covered with polymer. For higher polymer concentrations, the plastic viscosity and yield stress decreased with increasing polymer concentration. Heath and Tadros explain the increased yield stress and plastic viscosity by the flocculation of the bentonite by the PVA via a bridging mechanism. 

Figure 19. Rheograms of bentonite suspensions (40 g/L) in the presence of various sodium chloride concentrations and values of pH. (Reproduced with permission from reference 75. Copyright 1983 Academic.)...

Despite the low levels of adsorption, the anionic polymers have a significant effect on the rheology of the bentonite suspensions. Figure 22 shows the dependence of the Bingham yield stress rG on bentonite concentration with and without added dispersants. Rabaioli et al. found the dependence of rG on the volume fraction of bentonite 0 to be... 

Figure 22. Dependence of Bingham yield stress and storage modulus (G ) on bentonite content of bentonite suspensions in the presence of various additives. (Reproduced with permission from reference 78. Copyright 1993 Society of Petroleum Engineers.)...

Figure 46 shows the dependence of V30 on CMC polymer content at a fixed bentonite content. At I = 0, where the CMC polymers are fully extended, there is no effect of Mw on V30, although only 1 g/L of any of the CMC polymers causes V30 to decrease by a factor of 2 over the neat bentonite suspension. An effect of Mw and/or charge density of the polymer (degree of substitution) is observed for I = 0.5 molar. 

The polyacrylate polymers and a derivative of a vinyl acetate maleic anhydride copolymer cause V30 to decrease monotonically with increasing polymer concentration, similar to the CMC polymers (Figure 46). The polymers PVA and poly(vinyl pyridinium) (PVP) hydrochloride markedly increased V30 at low concentration at concentrations above 1 g of polymer per gram of added bentonite PVA functions as a static fluid loss additive. The maximum in the API fluid loss at low PVA concentrations approximately coincides with the maximum in the yield stress and plastic viscosity found by Heath and Tadros (75). The increased static fluid loss is consistent with Heath and Tadros s conclusion that bentonite is flocculated by low concentrations of PVA. The concentration of PVA required to decrease V30 below that of the neat bentonite suspension is significantly larger than the concentration of CMC, where effective static fluid loss control can be achieved at polymer bentonite weight ratios of about 0.1 g/g. More effective fluid loss control has been achieved with other synthetic polymers such as poly(vinyl sulphonate)-poly(vinyl amide) copolymer (40) and other sulphonated polymers (39). 

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