Bentonite is a natural occurrence material dominantly the Clay Mineral Montmorillonite. It is having a layered structure that possesses High Swelling properties and High Cation exchange capacities. When in contact with water it expands up to Twenty to Forty times its dry volume. Depending upon the dominant exchangeable cations present the clay may be referred as Calcium Bentonite or Sodium Bentonite, the two varieties exhibiting different properties and thus, uses. There are three main characteristics of Bentonite that make it commercially useful. They include Thixotropy, Swelling, and Adsorption.
Inorganic Thickeners – Bentonite
Hydroxylgel (Partial Replacement of Organic Thickener in Water Base formulation)
Bentonite is a clay generated frequently from the alteration of volcanic ash, consisting predominantly of smectite minerals, usually montmorillonite. Other smectite group minerals include hectorite, saponite, beidelite and nontronite. Rheology plays a major role in production and application stage of paints. Bentonite clay based thickening agent is generally use to modify the viscosity of paints since it is more economical and environmentally friendly compared to polymer based thickening agant. Thickener additives not only behave like rheology modifiers but also affect some properties such as gloss and hiding power of paint by modifing dispersion of primary pigments & extenders in paint formulations.
KEY BENEFITS :
- Excellent thickening agent.
- Excellent suspending and binding agent.
- Excellent thixotrophy reducing sags and drips.
- Low shear viscosity and prevent settling.
- Used as a binder to adhere the various fluxing materials and acts as a suspending agent in the coating solution.
- Exhibits a higher degree of shear thinning.
- High adsorption capacity ensures quick paste.
- Increase the consistency, makes spreading and removal eraser.
Paints : Dyes and Polishes: Due to its thixotropic properties, bentonite and organoclays function as a thickening and/or suspension agent in varnishes, and in water and solvent paints. Its adsorption properties are appreciated for the finishing of indigo dying cloth, and in dyes (lacquers for paints & wallpapers).
Foundry : Bentonite is used as a bonding material in the preparation of molding sand for the production of iron, steel and non-ferrous casting. The unique properties of bentonite yield green sand moulds with good flowability, compactability and thermal stability for the production of high quality castings.
Cat Litter : Bentonite is used for cat litter, due to its advantage of absorbing refuse by forming clumps (which can be easily removed) leaving the remaining product intact for further use.
Pelletizing : Bentonite is used as a binding agent in the production of iron ore pellets. Through this process, iron ore fines are converted into spherical pellets, suitable as feed material in blast furnaces for pig iron production, or in the production of direct reduction iron (DRI).
Construction and Civil Engineering : Bentonite in civil engineering applications is used traditionally as a thixotropic, support and lubricant agent in diaphragm walls and foundations, in tunnelling, in horizontal directional drilling and pipe jacking. Bentonite, due to its viscosity and plasticity, also is used in Portland cement and mortars.
Environmental Markets : Bentonite’s adsorption/absorption properties are very useful for wastewater purification. Common environmental directives recommend low permeability soils, which naturally should ontain bentonite, as a sealing material in the construction and rehabilitation of landfills to ensure the protection of groundwater from the pollutants. Bentonite is the active protective layer of geosynthetic clay liners.
Drilling : Another conventional use of bentonite is as a mud constituent for oil and water well drilling. Its roles are mainly to seal the borehole walls, to remove drill cuttings and to lubricate the cutting head.
Oils/Food Markets : Bentonite is utilized in the removal of impurities in oils where its adsorptive properties are crucial in the processing of edible oils and fats (Soya/palm/canola oil). In drinks such as beer, wine and mineral water, and in products like sugar or honey, bentonite is used as a clarification agent.
Agriculture : Bentonite is used as an animal feed supplement, as a pelletizing aid in the production of animal feed pellets, as well as a flowability aid for unconsolidated feed ingredients such as soy meal. It also is used as an ion exchanger for improvement and conditioning of the soil. When thermally treated, it can be used as a porous ceramic carrier for various herbicides and pesticides.
Pharmaceuticals : Cosmetics and Medical Markets: Bentonite is used as filler in pharmaceuticals, and due to its absorption/adsorption functions, it allows paste formation. Such applications include industrial protective creams, calamine lotion, wet compresses, and antiirritants for eczema. In medicine, bentonite is used as an antidote in heavy metal poisoning. Personal care products such as mud packs, sunburn paint, baby and facepowders, and face creams may all contain bentonite.
Detergents : Laundry detergents and liquid hand cleansers/soaps rely on the inclusion of bentonite, in order to remove the impurities in solvents and to soften the fabrics.
Paper : Bentonite is crucial to paper making, where it is used in pitch control, i.e. absorption of wood resins that tend to obstruct the machines and to improve the efficiency of conversion of pulp into paper as well as to improve the quality of the paper. Bentonite also offers useful de-inking properties for paper recycling. In addition, acid-activated bentonite is used as the active component in the manufacture of carbonless copy paper.
Catalyst : Chemically-modified clay catalysts find application in a diverse range of duties where acid catalysis is a key mechanism. Most particularly, they are employed in the alkylation processes to produce fuel additives.