Cleansing

Cleansing of materials (substrates) implies the removal of soil and stains. A wide variety of stains and substrates are encountered. For instance, textiles may be of natural origin such as cotton, wool, or natural silk, or are made of synthetic fibers, such as nylon, polyester, or polyacryl. Cotton is cellulose that has an intermediate hydrophobicity wool and natural silk are proteins, both rather hydrophobic and in most cases negatively charged. Synthetic fibers are usually polymers of which the backbone is characterized by a series of repeating units such as peptide units (in nylon), ester bonds (in polyesters), and cyan groups (in polyacryl). 

Stains may be even more diverse ranging from very hydrophobic (soot, grease, and oil), amphiphilic (proteinaceous stains), to hydrophilic (clay, sand, cement). 

The stains may further be negatively or positively charged. Because of the diversity of both the substrates and the staining agents, a wide variety of interactions (dispersion interaction, hydrogen bonds. Coulomb interaction, and hydrophobic interaction) may play a role in the adhesion of the staining materials to the substrate. 

As a rule, a cleansing procedure comprises two steps (a) detachment of the stain from the substrate and (b) prevention of readhesion of the stain onto the substrate. Detachment of the stain F from the substrate S in an (aqueous) medium L occurs spontaneously if (at constant p and T) 

A negative value for AG may be achieved by supplying a surfactant to L that adsorbs at the FL and SL interfaces, thereby lowering and y. Ranoval of liquid-Uke stains from the voids between the fibers of the substrate uiay be further enhanced by capillary penetration, as described by Equation 8.20. 

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Coke (deposited on the catalyst) which is burned in the regenerator producing energy (electricity, steam) and the necessary heat for the reaction. Produced gases are cleansed when necessary of SOj and NO as well as particles of entrained catalyst. 

Gas-phase reactions play a fundamental role in nature, for example atmospheric chemistry [1, 2, 3, 4 and 5] and interstellar chemistry [6], as well as in many teclmical processes, for example combustion and exliaust fiime cleansing [7, 8 and 9], Apart from such practical aspects the study of gas-phase reactions has provided the basis for our understanding of chemical reaction mechanisms on a microscopic level. The typically small particle densities in the gas phase mean that reactions occur in well defined elementary steps, usually not involving more than three particles. 

A wide class of aiyl-based quaternary surfactants derives from heterocycles such as pyridine and quinoline. The Aralkyl pyridinium halides are easily synthesized from alkyl halides, and the paraquat family, based upon the 4, 4 -bipyridine species, provides many interesting surface active species widely studied in electron donor-acceptor processes. Cationic surfactants are not particularly useful as cleansing agents, but they play a widespread role as charge control (antistatic) agents in detergency and in many coating and thin film related products. 

The most widely used cleansing agent is the chromic acid cleaning mixture. It is essentially a mixture of chromic acid (CrOj) and concentrated sulphuric acid, and possesses powerful oxidising and solvent properties. Two methods of preparation are available —... 

The formation of micelles and their properties are responsible for the cleansing action of soaps Water that contains sodium stearate removes grease by enclosing it m the hydrocarbon like interior of the micelles The grease is washed away with the water not because it dissolves m the water but because it dissolves m the micelles that are dis persed m the water Sodium stearate is an example of a soap sodium and potassium salts of other C12-C1S unbranched carboxylic acids possess similar properties... 

Detergents are substances including soaps that cleanse by micellar action A large number of synthetic detergents are known One example is sodium lauryl sulfate Sodium lauryl sulfate has a long hydrocarbon chain terminating m a polar sulfate ion and forms soap like micelles m water... 

Detergents are designed to be effective in hard water meaning water containing calcium salts that form insoluble calcium carboxylates with soaps These precipitates rob the soap of Its cleansing power and form an unpleasant scum The calcium salts of synthetic deter gents such as sodium lauryl sulfate however are soluble and retain their micelle forming ability even m hard water... 

Potassium and sodium salts of long chain carboxylic acids form micelles that dissolve grease (Section 19 5) and have cleansing properties The carboxylic acids obtained by saponification of fats are called fatty acids... 

Soaps (Section 19 5) Cleansing substances obtained by the hydrolysis of fats m aqueous base Soaps are sodium or potassium salts of unbranched carboxylic acids having 12-18 carbon atoms... 

Miscellaneous Natural Abrasives. Powdered feldspar [68476-25-5] is used as a mild abrasive in cleansing powders, and clays are sometimes used in polishing powders. StauroHte [12182-56-8] is a complex hydrated aluminosiHcate of kon, of high density (3.74—3.83 g/mL) and a hardness of 7 to 8 on Mohs scale. It is primarily used as a sandblasting grit, but siHcosis hazards had cut production in 1987 about 25% compared to that... 

Bisacodyl (9) is a contact laxative that may be given orally or rectaHy. It is often used for evacuation of the bowel prior to surgery or diagnostic examination. It may obviate the need for a cleansing enema. 

Gel Shampoos. These shampoos are generally versions of the clear product but consist of higher concentrations of the cleansing and thickening agents. They are usually packaged in tube form for dispensing purposes. 

Anionic Surfactants. In terms of general usage in cosmetic products, the anionics are by far the most widely used and are chiefly found in shampoo systems. They provide the formulator with the basic conditions for preparing these products, ie, foaming, cleansing, and solubiHty. 

The most widely used alkyl sulfate in shampoo preparation is lauryl sulfate. The alkyl component of this sulfate ranges from C-10 to C-18 with a predominance of the C-12 (lauryl) component. By distillation of the fatty alcohol, certain cuts can be obtained which offer the best effects in foaming, cleansing, and rinsing properties for the alkyl sulfate preparation. The range which appears to be most desirable is between C-12 and C-16. Lauryl sulfate detergents are available in various salt forms with the sodium, ammonium, and triethanolamine types being used most frequently in shampoos. 

Nonionie Detergents. Nonionic surfactants rarely are used as the primary cleansing additives ia shampoos. They are generally poor foaming, but have value as additives to modify shampoo properties, eg, as viscosity builders, solubilizers, emulsifiers, and conditioning aids. 

Shampoo Additives. Although the primary function of a shampoo is for cleansing, a number of additives are kicluded ki thek formulation to enhance and improve properties of the product. 

The Food, Dmg and Cosmetics Act defines a cosmetic as a substance intended to be mbbed, poured, sprinkled, or sprayed on, introduced into, or otherwise appHed to the human body or any part thereof for cleansing, beautifying, promoting attractiveness, or altering the appearance. A dmg is defined as an article intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in humans or other animals, and articles intended to affect the stmcture or any function of the body of humans or other animals. 

The 35 and 50% H2O2 concentrations are used for most industrial appHcations. The standard grades contain sufficient stabilizers to ensure safety. Grades having lower stabilizer content and evaporative residue are available for specialty uses and for aseptic cleansing of containers in food processing and marketing. 

Separate ketdes and backwash towers are frequendy used to convert ion-exchange resins from one ionic form to another prior to packaging, and to cleanse the resin of chemicals used in the functionalization reactions. Excess water is removed from the resin prior to packaging by a vacuum drain. Both straight line filters and towers or columns are used for this purpose. 

Microcapsules are used in several film coatings other than carbonless paper. Encapsulated Hquid crystal formulations coated on polyester film are used to produce a variety of display products including thermometers. Polyester film coated with capsules loaded with leuco dyes analogous to those used in carbonless copy paper is used as a means of measuring line and force pressures (79). Encapsulated deodorants that release their core contents as a function of moisture developed because of sweating represent another commercial appHcation. Microcapsules are incorporated in several cosmetic creams, powders, and cleansing products (80). 

Translating odor modifiers into consumer products results in forms, such as soHds, Hquids, and aerosols, for a market defined as products "for the nose." This includes products that cover up or eliminate odors, perfume the home, or cleanse the air. Such products thus defined were reported to have sales in 1992 of just under 2 biUion. The categories of this market can be broken out as traditional air fresheners, cat Utter products, aroma care, air purification, and disinfectant in both consumer and industrial appUcations. 

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