Soap and detergents

Soap was known to man before the new era of chronology. The earliest written mention of soap in European countries is found in the Roman scientist Pliny the Elder (23-79 gg.), Who wrote about the ways of cooking soap with saponification of fats. Moreover, he wrote about a hard and soft soap, obtained using soda and potash, respectively. Pollutants are very diverse, but they are often poorly soluble or insoluble in water. Such substances, as a rule, are hydrophobic, as they are not wetted by water and do not interact with it. Therefore, we need a variety of detergents. A good washing system must perform a dual function: remove contamination from the surface to be cleaned and transfer it to an aqueous solution. Therefore, the molecule of the detergent must have a hydrophobic and hydrophilic parts. The hydrophobic moiety of the detergent molecule has the ability to interact with the surface of a hydrophobic contaminant. The hydrophilic part of the detergent interacts with water, penetrates into it and carries with it a particle of a contaminant attached to the hydrophobic end.

Soap was known to man before the new era of chronology

Soap making in Europe developed in France, Italy, Greece, Spain, Cyprus, in areas cultivating olive trees. But, despite the rather well-developed soap industry, the chemical nature of the soap preparation processes was not clear. Only at the turn of the 18th and 19th centuries. The chemical nature of fats was clarified and the reaction of their saponification clarified. In 1779 Swedish chemist Scheele showed that the interaction of olive oil with lead oxide and water produces a sweet and water-soluble substance. The decisive step in the study of the chemical nature of fats was made by the French chemist Chevrel. He discovered stearic, palmitic and oleic acids, as products of decomposition of fats when they are saponified with water and alkalis. The sweet substance obtained by Scheele was Chevrel called glycerol. Forty years later, Berthelot established the nature of glycerin and explained the chemical structure of fats. Glycerin is a trihydric alcohol. Fats are esters of glycerol (glycerides) of heavy monobasic carboxylic acids, mainly palmitic CH3(CH2)14COOH, stearic CH3(CH2)16COOH and oleic CH3(CH2)7CH=CH(CH2)7COOH. Artificial, i.e., synthetic, fatty acids are derived from petroleum paraffin by catalytic oxidation with air oxygen. The paraffin molecule is broken in various places during oxidation, and therefore a mixture of acids is obtained, which are divided into fractions. In the production of soap, two fractions are used: C10-C16 and C17-C20. In the laundry soap, synthetic acids are introduced in an amount of 35-40%.

In the composition of various fats come in different ratios of palmitic, stearic, oleic and other acids. In vegetable (liquid), unsaturated acids (containing ethylenic bonds) predominate, and in animals (solid) - limiting, ie, not containing double bonds. The requirements for solid animal fats are greater than in plant foods. Therefore, the liquid plant is converted to solid catalytic hydrogenation.

To produce soap, naphthenic acids are also used, which are released during the purification of petroleum products (gasoline, kerosene, etc.). For this purpose, the petroleum products are treated with a solution of sodium hydroxide and an aqueous solution of sodium salts of naphthenic acids is obtained. This solution is evaporated and treated with common salt, as a result of which a misty mass of dark color - tolonaflu emerges on the surface of the solution. For cleaning, soap is treated with sulfuric acid, that is, they are displaced from the salts themselves by naphthenic acids. This water insoluble product is called asidol or asidol-uslonafth. Directly from the aspidol, it is possible to produce only liquid or, as a last resort, a mild soap. It has an oil smell, but it has bactericidal properties.

In the production of soap for a long time using rosin, which is obtained when processing sap of coniferous trees. Rosin is composed of a mixture of resin acids containing about 20 carbon atoms in the chain. In the formulation of laundry soap, usually 12-15% of rosin is administered from the mass of fatty acids, and not more than 10% in the formulation of toilet soaps. The introduction of rosin in large quantities makes the soap soft and sticky.

The process of producing soap consists of chemical and mechanical stages. In the first stage (cooking soap), an aqueous solution of sodium salts (less often potassium) of fatty acids or their substitutes (naphthenic, resin) is obtained. In the second stage, these salts are mechanically treated - cooling, drying, mixing with various additives, finishing and packaging.

Soap brewing is finished by treating soap solution (soap glue) with excess alkali (NaOH) or NaCl solution. As a result, a concentrated layer of soap, called the core, emerges on the surface of the solution. The soap obtained in this way is called sound, and the process of its isolation from the solution is by salting or salting out. During salting out, the concentration of soap increases and its purification from protein, coloring and mechanical impurities - so get the laundry soap.

To get a very clean and light soap, it is cleaned (grinded) by transferring again into the solution by boiling with hot water and re-salting out. As a result of grinding, the soap acquires greater uniformity, lower viscosity and proper plasticity. To make toilet soap in a cleaned sound soap, reduce the water content from 30 to 12%. Then perfume fragrances, bleaches, dyes, etc. are introduced into it. Good sorts of toilet soap contain up to 50% of soap obtained from imported coconut or palm oil. The most expensive toilet soap is entirely made from coconut oil.

In addition to using soap as a detergent there is also a less harmless use of it. Aluminum soap (aluminum salts of a mixture of fatty and naphthenic acids) is used to produce certain types of napalm - gasoline, thickened with aluminum soap.

At present, the chemical industry produces a large number of different synthetic detergents (washing powders). Of greatest practical importance are compounds containing a saturated hydrocarbon chain of 10-15 carbon atoms, one way or another associated with a sulfate or sulfonate group.

The production of synthetic detergents is based on cheap raw materials, or rather on oil and gas products. Many of the synthetic detergents are equally well washed in both soft and hard water. Some products are suitable even for washing in sea water. Synthetic detergents act not only in hot water, as is typical for household soap, but also in water at relatively low temperatures, which is important when washing fabrics from artificial fibers. Finally, the concentration of synthetic detergents even in soft water can be much lower than the soap obtained from fats.

After several washings, white fabric products turn yellow or gray. To eliminate appearing shades and introduce into synthetic detergents optical brighteners. Their effect is that they absorb ultraviolet light (with a wavelength of ~ 360 nm) and again emit the absorbed energy by fluorescence in the blue region of the visible spectrum (at 430-440 nm). The resulting "blue" product compensates for yellowing and makes the product visually whiter.