Aniline resins.
Resins obtained by condensing aniline and formaldehyde have been developed in recent years. Much of the research on this type of resin was done in Switzerland by the Ciba Co., which holds a number of patents on it. The Swiss product, called Cibanite, has excellent electrical and mechanical properties. At least one domestic manufacturer is licensed under the Swiss-owned patents.
Citric acid resins.
Considerable interest has recently been manifest in synthetic resins derived from citric acid. The sharp decline in the price of citric acid, as a result of large scale synthesis from sugar has placed it within the realm of possibility as a raw material for synthetic resins.
The citric acid resins, classed as alkyd resins, are obtained by condensing citric acid and glycerin. Commercial production is said to have started in Europe, but there is no known domestic production as yet.
Diphenyl resins.
A series of products known as Aroclors and made by chlorinating diphenyl are available in commercial quantities.
Diphenyl was commercially produced for the first time by Swann Research, Inc., at Anniston, Ala., about 1928. The demand for it as a heat-transfer medium resulted in large scale output. Later it was found that certain of the chlorinated compounds of diphenyl possess valuable resin properties.
The Aroclors range from a clear mobile oily liquid to an amber colored transparent solid. They are thermoplastic, do not polymerize or oxidize, and are therefore nondrying. They may be dissolved in varnish oils, such as tung oil and linseed oil, to give varnishes which are resistant to alkali and water. The diphenyl resins are good adhesives on metal and glass and give strong joints between such surfaces. They have a high dielectric constant, resistivity, and a low power factor. Their chief use is in wire insulation.