Metal soaps
When metallic soaps are salts of fatty acids , and salts of resin and naphthenic acids with metals referred to excluding the sodium and potassium salts. The water-soluble fatty acid salts of the sodium and potassium salts are called soaps and are described there.
properties
Metal soaps are poorly soluble in water, but are good in organic solvents such as benzene or fatty oils . They usually colloidal and surface-active properties and therefore serve as emulsifiers for water-in-oil - emulsions (W / O emulsions). They are used as additives for lubricants and for W / O emulsions in the cosmetic field. Metal soaps serve as release agents or flow aids in the course of technical processes or as an aid for their products. Some metal soaps have catalytic properties and are used as color binders or as activators e.g. B. used in rubber vulcanization .
| Examples of metallic soaps | |
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| Example zinc soap : hydrophobic alkyl radical (left) and hydrophilic carboxylate group on a blue background . |
Example lithium soap : hydrophobic alkyl radical (left) and hydrophilic carboxylate group highlighted in blue .
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Manufacturing
Metal soaps are manufactured industrially from alkali or ammonium soaps by precipitation with the corresponding inorganic metal salts or by reacting carboxylic acids with metal hydroxides or oxides.
Technically important carboxylic acids
The salts are often based on higher (long-chain) fatty acids like stearic acid , palmitic acid and lauric acid and unsaturated fatty acids like linolenic acid and oleic acid . In addition, hydroxycarboxylic acids such as ricinoleic acid and its hydrogenated form 12-hydroxystearic acid are also used. Metal soaps can also be based on naphthenic acids , tall oil and resin acids .
use
- Calcium stearate is the basis of Stauffer grease, which is used as a lubricating and sealing grease. Calcium stearate is also used to harden wax candles. As thickeners in greases are often lithium soaps used.
- Metal soaps are used as release agents and lubricants in plastics processing.
- Metal soaps are used for dry impregnation in dry cleaning .
- Aluminum stearate , magnesium stearate and zinc stearate are used as pharmaceutical excipients in the manufacture of ointments, powders and tablets.
- Aluminum soaps were used as a thickener in the manufacture of the warfare agent napalm .
- Surcharge for silicone grease
- Metal soaps are used as a siccative (drying agent ) for oil paints to polymerize the paints. Cobalt , manganese and lead soaps are used here. Zinc salts such as zinc stearate are used for rubber vulcanization .
- Copper naphthenates are used as wood preservatives .
See also
Individual evidence
- ↑ a b Hans-Dieter Jakubke, Ruth Karcher (Ed.): Lexicon of Chemistry , Spectrum Academic Publishing House, Heidelberg, 2001.
- ↑ Der Brockhaus, Science and Technology , FA Brockhaus, Mannheim; Spectrum Academic Publishing House, Heidelberg, 2003.
literature
- Theo Mang, Wilfried Dresel, Lubricants and Lubrication , Wiley-VCH, Weinheim, 2001, p. 603 ff.