Fatty acids dimerisation

The simplest polyamines are the aliphatic types such as diaminoethane, but these readily carbonate when exposed to the atmosphere as a thin him, so adducts (pre-reacted epoxy polyamines) are preferred. An alternative system is the polyaminoamides which are made by reacting dimerised fatty acids with an excess of polyamine. These themselves act as corrosion inhibitors and are noted for excellent adhesion. 

The synthesis of dimeric fatty acids is based on the reaction between a fatty acid with one double bond (oleic acid) and a fatty acid with two double bonds (linoleic acid) or three double bonds (linolenic acid), at higher temperatures in the presence of solid acidic catalysts (for example montmorillonite acidic treated clays). Dimerised fatty acids (C36) and trimerised fatty acids (C54) are formed. The dimer acid is separated from the trimeric acid by high vacuum distillation. By using fatty dimeric acids and dimeric alcohols in the synthesis of polyesters and of polyester polyurethanes, products are obtained with an exceptional resistance to hydrolysis, noncrystalline polymers with a very flexible structure and an excellent resistance to heat and oxygen (Chapter 12.5). Utilisation of hydrophobic dicarboxylic acids, such as sebacic acid and azelaic acid in polyesterification reactions leads to hydrolysis resistant polyurethanes. 

Dimerised Fatty Acids Technology for Use in Polyurethanes, UNICHEMA, Chicago, IL, USA, 2000. 

Polymers Unsaturated fatty-acid chains offer opportunities for polymerisation that can be exploited to develop uses in surface coatings and plastics manufacturing. Polyunsaturated fatty acids can be dimerised to produce feedstocks for polyamide resin (nylon) production. Work is also ongoing to develop polyurethanes from vegetable oils through manipulation of functionality in the fatty-acid chains, to produce both rigid foams and elastomers with applications in seals, adhesives and moulded flexible parts (see Chapter 5 for more information). 

The construction and properties of monolayers has been well documented by Kuhn (1979) and the photochemical reactions which occur in such systems reviewed (Whitten et al., 1977). Molecules in monolayers are usually ordered and in the case of rru/i -azastilbenes irradiation of the ordered array produces excimer emission and dimers (Whitten, 1979 Quina et al, 1976 Quina and Whitten, 1977). This contrasts with what is found when the fra/jj-isomers of such compounds are incorporated into micelles. In such systems the predominant reaction is cis-trans isomerisation excimer emission is lacking. It is suggested that the lack of isomerisation in the fatty acid monolayers is due to the tight packing and consequent high viscosity of such systems. Styrene also dimerises in a fatty acid monolayer. Interestingly, the products formed on photo-oxidation of protoporphyrins are dependent upon whether the reaction is carried out in a monolayer or a micelle (Whitten et al., 1978). Zinc octa-ethylporphyrin exhibits excimer emission in monolayers (Zachariasse and Whitten, 1973). Porphyrins are photoreduced by amines in monolayers (Mercer-Smith and Whitten, 1979). Electron-transfer reactions have been carried out with monolayers of stearic acid containing chlorophyll and electron acceptors such as quinones (Janzen et al., 1979 Janzen and Bolton, 1979). 

Dimerisation of Unsaturated Fatty Acids - Polyols Based on Dimeric Acids... 

Thus, the dimerisation of unsaturated fatty acids takes place at higher temperatures in the presence of catalysts (for example acidic clays, montmorillonite type). One molecule of oleic acid (having one double bond) reacts with one mol of linoleic acid (having two double bonds) and this forms a dimeric acid with a cycloaliphatic structure. 

Epoxidation, hydroformylation, dimerisation, thiol-ene coupling, oxidative cleavage, and olefin metathesis attack the double bonds of unsaturated oils, fatty acids, or fatty acid esters. These reactions have been exploited for the synthesis of interesting monomers from renewable resources [1-3,13,14]. 

Dimerisation of monounsaturated fatty acids has been exploited to prepare monomers bearing two carboxylic functions and, after reduction, the corresponding diols [2], i.e., potential monomers for the synthesis of polyesters, polyamides, polyethers and polyurethanes incorporating long aliphatic motifs. Scheme 2.7 shows two possible mechanisms associated with this reaction (i.e., ene- or carbonation coupling), which is inevitably accompanied by further additions to give trimers and oligomers, if not carried out under finely controlled conditions. 

To illustrate the recently discovered pathways to functional monomers, Meier and colleagues studied the synthesis of a long-chain diester from a (o-hydroxy fatty acid derived from palmitic acid. The idea was to transform the (0-hydroxyl function into a mesylate, followed by an elimination reaction to prepare the (O-unsaturated fatty acid methyl ester (FAME), which was dimerised by a SM coupling to obtain the desired C30 diester (Scheme 5.5) [14]. This macromonomer was then polymerised with diols and diamines to prepare long-chain polyesters and polyamides (PA) with interesting thermal properties, such as a melting temperature (T ) of 109 °C for the polyester and 166 °C for the PA. 

The chemistry of fatty acids is far more complex than might be imagined from this brief description, with features such as micellisation in aqueous solution and dimerisation in organic solvent being important factors likely to affect coating behaviour. Unfortunately these aspects have largely been overlooked in this context. For a... 

Figure 3.17 Dimerisation of dienoic fatty acids to cyclohexene derivatives.

G. Dimerisierung F. dimerisation D. is the formation of a new product by reaction of two identical compounds. Unsaturated - fatty acids are dimerized or oligomerized to - dimer acid and oligomers. The reaction can by used also to dimerize unsatuiated - fatty alcohols or fatty acid esters. The reaction is a tool to get difunctionality (- polymers from fats and oils). 

The specification discloses a method for vulcanising an elastomer using as the cure promoter the monomeric distillate by-product from the clay-based dimerisation of an unsaturated fatty acid mixture, preferably a tall oil fatty acid mixture. The distillate provides a cost-effective alternative to conventional fatty acid promoters. 

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