Cashew nut-shell liquid

Other higher boiling phenolic bodies obtainable from coal tar distillates are sometimes used in the manufacture of oil-soluble resins. Mention may also be made of cashew nut shell liquid which contains phenolic bodies and which is used in certain specialised applications. 

During the past four decades phenolic resins have become of increased significance in rubber compounding. For example, the resin based on cashew nut shell liquid, which contains phenolic bodies such as anacardic acid (Figure 23.23), may, when blended with hexamine, be incorporated into nitrile rubber (butadiene-acrylonitrile rubber). 

Structural carbon shapes fabricated by heating coke with a mixture of tar and pitches are porous and are made impermeable by impregnation with a resin (usually a phenolic resin). Cashew nut shell liquid resin is used when resistance to alkalis and acids is required. 

Resol resins thermoset on heating and are used for adhesives. Novolacs require a further source of formaldehyde in the form of hexamethylenetetramine to produce molding powders. Phenolic moldings are resistant to heat, chemicals, and moisture with good electrical and heat insulation qualities. Complex phenols from, e.g., cashew-nut shell liquid, are used in making brake... 

Indian Cashew Nut Shell Liquid—A Versatile Industrial Raw Material of Great Promise—Regional Research Laboratory, Trivandrum and Cashew Export Promotion Council, Ernakulam (1983). 

Development of Value Added Polymer Resins Products from Cashew Nut Shell Liquid, Project report No. RT.09/MO/50, Regional Research Laboratory, Trivandrum (1987). 

Cardanol, a main component obtained by thermal treatment of cashew nut shell liquid (CNSL), is a phenol derivative having mainly the meta substituent of a C15 unsaturated hydrocarbon chain with one to three double bonds as the major. Since CNSL is nearly one-third of the total nut weight, a great amount of CNSL is obtained as byproducts from mechanical processes for the edible use of the cashew kernel. Only a small part of cardanol obtained in the production of cashew kernel is used in industrial fields, though it has various potential industrial utilizations such as resins, friction-lining materials, and surface coatings. Therefore, development of new applications for cardanol is very attractive. 

Figure 10.2 Major components of cashew nut shell liquid.

Several small molecule modulators (SMM) of p300 and PCAF have been developed (Varier et al, 2004). Recently, the first naturally occurring HAT inhibitor anacardic acid was isolated from cashew nut shell liquid, which inhibits the HAT activity of both p300 and PCAF very effectively (Balasubramanyam et al, 2003). By using anacardic acid as a synthon, an amide derivative of anacardic acid, CTPB, has been synthesized, which is the only known small molecule activator of any histone acetyltransferase, in this case, p300. However, cells are impermeable or... 

Synthesis Epoxy resins consisting ofglycidyl ether, ester and amines are generally prepared by the condensation reaction between diol, dibasic acid or amine and epichlorohydrin in the presence of sodium hydroxide with the elimination of hydrochloric acid. The commercially available epoxy resins are, however, made by the reaction of epichlorohydrin and bisphenol-A. Cashew nut shell liquid (CNSL)-based novolac epoxy resins have also been reported [342]. 

Another source of oil, but of very different composition than the previously described oils, is cardanol oil, the major component of cashew nut shell liquid. This is a low-value side product of the mechanical processing of the cashew nut and is therefore a widely available source of cardanol oil. Cardanol oil is a mixture of 3-pentadecylphenol with either a saturated alkyl chain or a one-, two-, or threefold unsaturated alkyl chain (Fig. 10). 

Cashew nut shell liquid (CNSL) is the exudate from the cashew nut shell. It is mainly phenolic in nature. Industrially used for making polymeric resins etc. A bath of the CNSL is traditionally used for heating the whole nuts with shells. 

Long-chain alkylphenols present in natural cashew nut shell liquid have been chromatographed on argen-tated silica gel G [10% (w/w) silver nitrate] with di-ethylether-light petroleum-formic acid (30 70 1) as eluent for the separation of unsaturated constituents. 

Friction dusts are cured coarse powders composed of polymerized cashew nut shell liquids. These materials are added to friction materials to confer friction stability, resiliency, and noise damping. Rubber and abrasive modified friction dusts are also available. Friction dusts tend to absorb solvents, causing the friction material to spring back after forming. This limits the use of cashew friction dusts to dry mixes or solvent-free wet mixes. 

This is one of the most widely distributed plants cultivated to obtain cashew nut. The phenolic lipid is only a by-product known as cashew nut shell liquid (CNSL). The nut, attached to the base of the cashew nut apple consists of an ivory-colored kernel covered by a thin brown membrane (testa) and enclosed by an outer porous shell, the mesocarp which is about 3 mm thick with a honey-comb structure where the reddish brown liquid (CNSL) is stored [91]. The major components of CNSL are a phenolic acid, anacardic acid, a dihydric phenol, cardol with traces of mono hydric phenol, cardanol, and 2-methyl cardol [92-95]. 

AR occur in cashew nut shells as a fraction of other oil components like cardols, cardanols and anacardic acid. A comparative study on the extraction of cashew nut shell liquid (CNSL) was presented by Shobha and Ravindranath (50). The study involved the extraction of the cashew nut shell by supercritical CO2 or pentane. The pentane extraction was carried out on 50g steamed or fresh cashew nut shells in lOOmL solvent. Supercritical CO2 extraction was performed on 300g freshly broken cashew nut shells at 25 MPa and 40 C with the CO2 flow kept at 4-5Kg/h for 17,5h with extract collection every 2.5h. The resorcinolic lipid fraction obtained by supercritical CO2 represented 82% of the equivalent obtained by pentane extraction of fresh cashew nut shells and 70% of the extraction of steamed material. Despite this appreciable variation on the ratio of the total cardols and cardanols from one mediod to other, the relative proportion of the enomers in each group was very similar (50). Generally, the extraction yield obtained by supercritical CO2 was lower (= 60%) than that obtained by the classical solvent extraction methods (50), however, the product was nearly colorless. One of the major problems in the industrial application of CNSL is the very dark brown color of the solvent extracted product. 

The amount of resorcinolic lipids in plant and microbial sources varies considerably depending on the source. The most prominent source of resorcinolic lipids (cardol and methylcardol), as well as of other phenolic lipids, is the oil obtained from extraction of the shell of cashew nuts, Anacardium occidentale, (up to 20% of resorcinolic lipids). The oily extract from the roasting of cashew nuts (Cashew Nut Shell Liquid) is one of the most important sources of these compounds for formaldehyde polymerisation in industry [1,2,11,114], Other plant sources contain amounts of resorcinolic lipids that vary from 0.01% to 0.1% with rye grains as the richest [101,115-120] while bacterial sources, depending on the family and strain contain up to 6% of various resorcinolic lipid derivatives [105]. 

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