Swellable clay

U.S. 5135675 (1992) [65] Elliot et al. (Lever Bros.) Swellable clay, sulfonated polymer, and multivalent cations Good salt tolerance bleach stability shear thinning... 

The multilayered swellable clay particles are overall negatively charged, as shown by electrokinetic studies [64,65], Hence bentonites are quite compatible with anionic-based detergents. 

Some patents or applications employ prior art AST compositions to obtain use features providing enhanced performance or utility. Synergistic thickening is observed, for example, when associative ASTs are combined with various other components, for example, with surfactants (82), with water-swellable clay minerals (111), or with nonionic associative thickeners 112, 113), Witiak and Dupre (114) disclose utility of AST latices in acidic media. This utility is accomplished by neutralization to a pH above 6.5 followed by reduction to some lower pH in the presence of surfactant. In spite of the low pH, the surfactant prevented coagulation on reacidification. 

Addition of a suspending (antisettling) agent to reduce settling caking or claying. This is achieved by addition of thickeners (such as xanthan gum, hydro-xyethyl cellulose, silica or swellable clays). 

Several other thickeners may be used Swellable clays, such as sodium montmor-illonite (commercially known as Bentopharm ). These clay particles consist of very thin plates and they can produce a gel in the continuous phase by a mechanism known as House-of-Card structure. The plates have negative surfaces and positive edges and they produce the House-of-Card structure by edge-to-face association. Fumed silica, such as AerosU 200 (manufactured by DeGussa), can also be used. These finely divided particles produce gels in the continuous phase by association between the particles forming chains and cross-chains. 

Fine inorganic materials such as swellable clays and finely divided oxides (silica or alumina), when added to the dispersion medium of coarser suspensions, can eliminate claying or caking. These fine inorganic materials form a three-... 

The originally hydrophilic surface of the layer silicates is hydrophobiz by the adsorption of cationic and non-ionic surfactants resulting in an expanded interlayer of the swellable clay minerals. 

Smectites are water swellable clays that have a platy structure. Smectite is the mineralogical term for a group of clays, which includes montmorillonite, hectorite, and saponite. Most smectites are more commonly known under the geological term bentonite. By convention, bentonite is understood to be an ore or product with a substantial smectite content. The range of possible chemical variations in the basic smectite trilayer lattice starts with montmorillonite, the high-aluminum end member. Montmorillonite is composed of a central alumina octahedral layer sandwiched between tetrahedral silica layers. This is identical to the dioctahedral pyrophyllite structure except for small... 

Sorption depends on Sorption Sites. The sorption of alkaline and earth-alkaline cations on expandable three layer clays - smectites (montmorillonites) - can usually be interpreted as stoichiometric exchange of interlayer ions. Heavy metals however are sorbed by surface complex formation to the OH-functional groups of the outer surface (the so-called broken bonds). The non-swellable three-layer silicates, micas such as illite, can usually not exchange their interlayer ions but the outside of these minerals and the weathered crystal edges ("frayed edges") participate in ion exchange reactions. 

Platelets are held together by cations. They impart a positive charge to the edge of the particles. These interlayer cations play a key role in the physicochemical properties of bentonite and in the stability of aqueous dispersions. Normally calcium is predominant and the clay swells to a moderate extent when dispersed in water. When Ca ions are replaced by Na, e.g., by reacting with Na2CC>3, the bentonite is said to be activated. This activation makes the clay much more swellable. 

At the other end of the smectite series are the high-magnesium members, hectorite and saponite. These clays possess a talc structure, with a trioctahedral magnesia l er sandwiched between the silica layers. Swellability results from minor substitution of aluminum for silicon in saponite or Hthimn for magnesium in hectorite. As with montmorillonite, the type of exchangeable cation determines the degree of swelling. Hectorite also has partial substitution of lattice hydroxyls by fluorine. 

Tseng et al., 2001 Xu et al., 2001) This is based on a solvent system in which the polymer or pre-polymer is soluble and the clay is swellable. The layered silicate is first swollen in a solvent such as water, chloroform or toluene. When the polymer and clay solutions ate mixed, the polymer chains intercalate and displace the solvent within the interiayerof the clay. Upon solvent removal, the irrterealated stmcture remains, resrrlting in PCN rrraterials. 

This method uses a solvent system in which the rubber is soluble and the layered silicate is swellable. The organically modified layered silicate is first swollen and comes apart in the solvent. The rubber is then dissolved in solvent and added to the solution. Upon solvent removal, the clay layers reassemble around the polymer, resulting in rubber-clay nanocomposite. 

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