CNSL is extracted from the outer shell of the cashew nut obtained from the cashew nut tree, Anacardium Occidentale L. CNSL is a mixture of phenolic compounds and the compounds which can be present in varying proportions include anacardic acid, cardanol, cardol, and 2-methyl cardol. Each of these compounds has a 15 carbon (pentadecyl) side chain, and each compound can occur with this side chain fully saturated, or in one of three forms of unsaturation; monoene, unsaturated at the 8′ position, diene, unsaturated at the 8′ and 11′ positions, and triene, unsaturated at the 8′, 11′, and 14′ positions. CNSL is available as natural CNSL and also as so-called “technical CNSL”. The ratio of the components present in the two forms differs because there is a heating step during the formation of technical CNSL which causes the decarboxylation of some or all of the anarcardic acid which increases the proportion of cardanol. This heating step also leads to the formation of some polymerised material.
The presence of phenol groups means that CNSL can be used to form adhesives analogous to phenol formaldehyde adhesives by reacting with aldehydes in the presence of an acid or base catalyst. The presence of unsaturated groups in the side chains of compounds present in CNSL means that polymerisation can also take place under acidic conditions without any other reactants being added.
CNSL, once polymerised with acids to a solid form, is crushed and used for many purposes, e.g. in the manufacture of clutch facings and linings. CNSL is not water-soluble and is not easily dispersed in water. The reaction of CNSL with aldehydes in the presence of sodium hydroxide gives at the earliest stages of the reaction a viscous mix which is not easily handled and makes it very difficult to make large scale use of alkali catalysed resins made from CNSL.
It would be more commercially advantageous if CNSL could be converted to a form where it can be more easily dispersed in water, and made either wholly or partially water-soluble.