Lithium stearate

Lithium hydroxide can be used for preparation of numerous lithium salts. The dominant use is the preparation of lithium stearate [4485-12-5], which is added to lubricating greases in amounts up to about 10% by weight. This salt has very low water solubiHty and extends the acceptable viscosity for the grease to both low and high temperatures (see Lubrication and lubricants). Lithium hydroxide is also used in production of dyes (62) and has been proposed as a source of lithium ion for inhibition of alkaH-aggregate expansive reactivity in concrete (63). 

Dry lubricants are usually added to the powder in order to decrease the friction effects. The more common lubricants include zinc stearate [557-05-17, lithium stearate [4485-12-5] calcium stearate [1592-23-0] stearic acid [57-11-4] paraffin, graphite, and molybdenum disulfide [1317-33-5]. Lubricants are generally added to the powder in a dry state in amounts of 0.25—1.0 wt % of the metal powder. Some lubricants are added by drying and screening a slurry of powder and lubricant. In some instances, lubricants are appHed in Hquid form to the die wall. 

When the catalyst is triethylamine, the yield is nearly 100% cycHc oligomers but if pyridine is used, the polymer is nearly 100% linear. A basic catalyst in the second step, such as lithium stearate or an organic titanate [bis-(acetylacetonato)diisopropoxytitanium], produces a polycarbonate with a molecular weight of 250,000—300,000 when polymerized at 300°C for 30 min. A fiber glass composite has been prepared using this basic procedure (39). 

Greases made with lithium stearate and synthetic oils, such as 2-ethylhexyl sebacate or adipate, are especially applicable to lubrication of bearings that are subjected to both high and low temperatures. An important application is lubrication of antifriction bearings and instruments in aircraft which may encounter temperatures as low as —100° F. at high altitudes. 

Another important compound of lithium is lithium stearate. Lithium stearate is added to petroleum to make a thick lubricating grease. The grease is used in many industrial applications because it does not break down at high temperatures, it does not become hard when cooled, and... 

Anonymous. Final report of the safety assessment of lithium stearate, aluminum distearate, aluminum stearate, aluminum tristearate, ammonium stearate, calcium stearate, magnesium stearate, potassium stearate, sodium stearate, and zinc stearate. ] Am Coll Toxicol 1982 1 143-177. 

Lithium hydroxide monohydrate is industrially important in the manufacture of greases e.g. on the basis of lithium stearate. In the USA more than 60% of all greases are produced with the help of lithium soaps (ca. 25% of total lithium consumption). 

Other important lithium compounds include lithium chloride, which has significant water-absorbing power. This allows for the use of lithium chloride in the manufacture of air conditioning units. Another compound, lithium stearate, is the product of a reaction between stearic acid and lithium hydroxide. This compound is useful as a type of grease able to withstand extremely low temperatures. 

Figure 18-4. Phase diagram for the system lithium stearate-white oil. A Crystalline lithium stearate I. B Crystalline lithium stearate II. C Waxy phase. D Liquid crystal phase. E Isotropic solution. Data by D. B. Cox [7]. ...

K (180 C) in Fig. 18-4 the transition for the system lithium stearate-white oil is at 463 K (190 C). The sharp rise in the bleeding of oil from the lithium 12-hydroxystearate grease is due to transformations to the liquid crystal and the isotropic liquid states. 

Figure 18-9. Roll testing of grease consistency. Gellants A. Lithium stearate. B. Lithium 12-hydroxystearate. C. Calcium tallow soap. D. Sodium tallow-stearate. E. Aluminum stearate. From data by Woods and Trowbridge [23].

Figure 18-10. Flow behavior for lithium stearate grease. From data by Bauer, Finkelstein and Wiberly [26].

Broad-line nuclear magnetic resonance has been used to study melting in stearic acid and a mesomorphic crystalline to waxy) phase transition in lithium stearate. Extensive motion, liquidlike, though less extensive than that in an isotropic free-flowing liquid, takes place within the system below the melting point of stearic acid or the crystalline to waxy phase transition of lithium stearate. The amount of liquid-like character, as measured by the intensity of a narrow component in the NMR spectrum relative to the total intensity of the whole spectrum, depends on the presence of impurities in the system and even more significantly on whether and how many times the sample has been melted. 

Materials. Two different lots of stearic acid were used in the experiments reported here, one purified sample being used for the stearic acid experiments, the other for making lithium stearate. The initial source for both was Eastman Kodak White Label grade, further purified by recrystallization according to the method of Brown and Kolb (6) from freshly distilled reagent grade acetone at — 20°C. 

---