Crystallization soaps

CS 68 Crystal Soap 1.10 (paste) blend of acid soap... 

The first application described was as temperature sensors by using a chiral nematic liquid crystal, which displays different colors at different temperatures. It is also worth noting that many common fluids are in fact liquid crystals. Soap, for instance, is a liquid crystal, and forms a variety of liquid crystal phases depending on its concentration in water. 

Austria. The Statistische Nachrichten (3), issued monthly, gives statistics on population, labor conditions, production, foreign trade, and wholesale prices. Production figures are given for caustic soda, chlorine, carbon dioxide, calcium carbide, lime-ammonium nitrate, acetylene (dissolved), oxygen, soda crystals, soaps and detergents, cellulose, rayon, and magnesite. 

After interesterification has proceeded to the desired point, the catalyst is destroyed by adding water and carbon dioxide. Carbon dioxide buffers the caustic to a lower pH and minimizes saponification of the lard. The neutralized lard is heated to melt the trisaturated glyceride crystals. Soaps are removed by conventional water washing and centrifuging, and the lard is dried in a continuous-vacuum drier. A basic flow chart for the process is shown in Fig. 12-8. 

CgHeOa. White crystals m.p. 37°C, b.p. 263°C. Occurs associated with vanillin. Obtained on oxidation of various natural products such as piperine. Used extensively in soap perfumery. 

Potassium biduoride crystals may break down to a fine white powder that is readily airborne. In this form, the salt is quite irritating to the nasal passages, eyes, and skin. Therefore, the hands and eyes should be protected and acid dust masks should be worn while handling, as an acid duoride KHF2 can cause superficial hydroduoric acid-type bums. Areas of skin that have been in contact with potassium biduoride should be washed as soon as possible with mildly alkaline soaps or borax-containing hand cleaners. If there has been contact with the eyes, they should be washed well with water and a physician should be consulted. 

Amphiphilic Molecules. In just about all cases of lyotropic Hquid crystals, the important component of the system is a molecule with two very different parts, one that is hydrophobic and one that is hydrophilic. These molecules are called amphiphilic because when possible they migrate to the iaterface between a polar and nonpolar Hquid. Soaps such as sodium laurate and phosphoHpids such as a-cephalin [5681-36-7] (phosphatidylethanolamine) (2) are important examples of amphiphilic molecules which form Hquid crystal phases (see Lecithin Soap). 

Fig. 13. Lyotropic liquid crystal structures (a) micelle formed by a typical soap (b) vesicle formed by a typical phospholipid.

These structures are commonly referred to as hexagonal Hquid crystals. As the surfactant concentration is further increased, the tubules expand in a second direction to form large, stacked lamellar sheets of surfactants, commonly referred to as lamellar Hquid crystals. These Hquid crystals are very important in soap making. 

For sodium palmitate, 5-phase is the thermodynamically preferred, or equiUbrium state, at room temperature and up to - 60° C P-phase contains a higher level of hydration and forms at higher temperatures and CO-phase is an anhydrous crystal that forms at temperatures comparable to P-phase. Most soap in the soHd state exists in one or a combination of these three phases. The phase diagram refers to equiUbrium states. In practice, the drying routes and other mechanical manipulation utilized in the formation of soHd soap can result in the formation of nonequilibrium phase stmcture. This point is important when dealing with the manufacturing of soap bars and their performance. 

Other factors also impact the type of crystals formed upon cooling of hot soap. Water activity or moisture content contribute to the final crystal state as a result of the different phases containing different levels of hydration. Any additive that changes the water activity changes the crystallization pathway. For example, the addition of salt reduces the water activity of the mixture and pushes the equiUbrium state toward the lower moisture crystal stmcture. Additionally, the replacement of sodium with other counter cations influences the crystallization. For example, the replacement of sodium with potassium drives toward the formation of 5-phase. 

In the presence of excess fatty acid, different soap crystalline phase compounds can form, commonly referred to as acid—soaps. Acid—soap crystals are composed of stoichiometric amounts of soap and fatty acid and associate in similar bilayer stmctures as pure soap crystals. There are a number of different documented acid—soap crystals. The existence of crystals of the composition 2 acid—1 soap, 1 acid—1 soap, and 1 acid—2 soap has been reported (13). The presence of the acid—soaps can also have a dramatic impact on the physical and performance properties of the finished soap. The presence of acid—soaps increases the plasticity of the soap during processing and decreases product firmness, potentially to the point of stickiness during processing. Furthermore, the presence of the acid—soap changes the character of the lather, decreasing the bubble size and subsequently increasing lather stabiUty and... 

It would be incomplete for any discussion of soap crystal phase properties to ignore the colloidal aspects of soap and its impact. At room temperature, the soap—water phase diagram suggests that the soap crystals should be surrounded by an isotropic Hquid phase. The colloidal properties are defined by the size, geometry, and interconnectiviness of the soap crystals. Correlations between the coUoid stmcture of the soap bar and the performance of the product are somewhat quaUtative, as there is tittle hard data presented in the literature. However, it might be anticipated that smaller crystals would lead to a softer product. Furthermore, these smaller crystals might also be expected to dissolve more readily, leading to more lather. Translucent and transparent products rely on the formation of extremely small crystals to impart optical clarity. 

Black Liquor Soap Acidulation. Only two-thirds of a typical black Hquor soap consists of the sodium salts of fatty acids and resin acids (rosin). These acids are layered in a Hquid crystal fashion. In between these layers is black Hquor at the concentration of the soap skimmer, with various impurities, such as sodium carbonate, sodium sulfide, sodium sulfate, sodium hydroxide, sodium Hgnate, and calcium salts. This makes up the remaining one-third of the soap. Cmde tall oil is generated by acidifying the black Hquor soap with 30% sulfuric acid to a pH of 3. This is usually done in a vessel at 95°C with 20—30 minutes of vigorous agitation. Caution should be taken to scmb the hydrogen sulfide from the exhaust gas. 

The long reaction time needed for this apparendy simple neutralization is on account of the phase inversion that takes place, namely, upon dilution, the soap Hquid crystals are dispersed as micelles. Neutralization of the sodium ions with sulfuric acid then reverses the micelles. The reverse micelles have a polar interior and a hydrophobic exterior. They coalesce into oil droplets. 

The use of high concentrations of vanillin in soap perfumery can cause discoloring effects over time, dark or black spots appear on the soap and foaming power is reduced. In some cases, however, the use of Rhodiarome ethylvanillin is possible, because ethylvanillin [121 -32-4] does not cause the same discoloration problems and, being at least three times more powerful than vanillin, can be used alone. Some surprising cases show that with oak or tree mosses and large amounts of methyl ionones, the soap perfume may look fine and have a low discoloration, and yet over time vanillin crystals can appear on the soap itself. 

Crystallization generally involves the evaporation and subsequent cooling of a solution to the point of supersaturation, whereupon the formation of crystals takes place. Modern technology often focus on the control of crystal size, since product demands frequently are rigorous in this regard. The process of crystallization is often conducted in evaporators. As in the evaporation of salt and in the recovery of salt and glycerin in soap manufacturing, salt separators are used to remove crystallized materials as rapidly as it settles. 

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