Cardanol Manufacturing Process

Cardanol Manufacturing Process

The present invention provides a process for the production of color-stable cardanol. In addition, products derived from the cardanol produced by this process, particularly phenalkamines, are color-stable.

It has surprisingly been found that this can be achieved by subjecting crude Cashew nut shell liquid CNSL to a special chemical treatment and subsequent distillation. In a preferred embodiment the distillate may then be subjected to a further treatment with chemical adsorbents.
The key steps of the process according to the invention are as follows:

1. Distillation, more particularly short-path distillation, of crude CNSL(cashew nut shell liquid)
2. Reaction of the distillate (“crude cardanol”) with boric acid
3. Distillation of the reaction mixture of step 2, more particularly short-path distillation.
If desired, the main fraction of step 3 may be after-treated with small quantities of adsorbents and/or reducing agents. This is an optional measure.

The present invention relates to a process for the production of a color-stable composition containing cardanol and cardol, in which

1. crude CNSL (cashew shell nut liquid) is first subjected to distillation, more particularly short-path distillation,
2. the distillate obtained is reacted with boric acid and
3. a distillation is then carried out, low-boiling fractions first being removed and the main fraction representing the target product (the color-stable cardanovcardol composition).

The Cashew nut shell liquid CNSL used in the process according to the invention is of natural origin. It is obtained by extraction from the shells of cashew nuts (i.e. nuts of the cashew tree ) and can vary in its composition. Typically, it contains 60-65% cardanol, 2-10% cardol, 10-15% oligomers/polymers and 0-2% 2-methylcardanol and anacardic acid.
The process according to the invention provides a color-stable composition containing cardanol and cardol. This composition is not only color-stable in storage, the phenalkamines produced from it are also. In addition, the composition is distinguished by the fact that it has better dermatological compatibility than known commercially available products, so that handling and transportation are safer.
In a preferred embodiment, the main fraction of step 3 of the process according to the invention is after-treated with small quantities of adsorbents and/or reducing agents. A further increase in color stability is achieved by the use of adsorbents and/or reducing agents.

Its production by distillation from crude Cashew nut shell liquid CNSL involves losses of value because part of the cardanol is lost through polymerization so that, ultimately, the yield of cardanol in the distillate is only 50-60%.

The initially pale yellowish cardanol/cardol mixture changes during storage, rapidly turning brown in color. This unwanted change in color is attributed to the presence of cardol.

Products ensuing from the cardanol/cardol mixture also undergo unwanted changes in color during storage.

It has also been proposed to improve the color stability of cardanol/cardol mixtures by reducing the cardol content by special measures. To this end, it has been proposed first to react the cardol present in the Cashew nut shell liquid CNSL largely selectively with aldehydes, amines or bases and hydroxides of alkali and alkaline earth metals and then to distil off the unreacted cardanol.

Source from Inventor: Setsuo Sato, Wanderson Bueno De Almeida Fiho, Ramiro Carielo Bueno