Dimeric fatty alcohols

In polymer applications derivatives of oils and fats, such as epoxides, polyols and dimerizations products based on unsaturated fatty acids, are used as plastic additives or components for composites or polymers like polyamides and polyurethanes. In the lubricant sector oleochemically-based fatty acid esters have proved to be powerful alternatives to conventional mineral oil products. For home and personal care applications a wide range of products, such as surfactants, emulsifiers, emollients and waxes, based on vegetable oil derivatives has provided extraordinary performance benefits to the end-customer. Selected products, such as the anionic surfactant fatty alcohol sulfate have been investigated thoroughly with regard to their environmental impact compared with petrochemical based products by life-cycle analysis. Other product examples include carbohydrate-based surfactants as well as oleochemical based emulsifiers, waxes and emollients. 

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. 

Soybean oil may be hydrolyzed into glycerol and fatty acids, or soybean oil soap-stocks (foots) may be acidified to produce fatty acids. Crude soybean fatty acids are used to make adhesive tape, shaving compounds, textile water repellents, carbon paper, and typewriter ribbons. Consumption of fatty acids in the United States, Western Europe, and Japan was 2.3 MMT (2.5 million t) in 2001. These soybean fatty acids can be separated into various fractions by distillation, and are used in candles, crayons, cosmetics, polishes, buffing compounds, and mold lubricants. These fatty acids can be converted to FAME by esterification, alkyl epoxy esters by epoxidation, fatty alcohols by hydrogenation (Kreutzer, 1983 Voeste Buchold, 1983), and dimer and trimer acids by conjugation or amines and amides as shown in Fig. 17.7 (Maag, 1983). 

Fatty acid esters are generally obtained from the transesterification of fats and oils with a lower alcohol, e.g. methanol, along with glycerol. More than 90% of all oleochemical reactions (conversion into fatty alcohols and fatty amines) of fatty acid esters (or acids) are carried out at the carboxy functionality. However, transformation of unsaturated fatty acid esters by reactions of the carbon-carbon double bond, such as hydrogenation, epoxidation, ozonolysis, and dimerization, are becoming increasingly of industrial importance. Here we will discuss another catalytic reaction of the carbon-carbon double bond, viz. the olefin metathesis reaction, in which olefins are converted into new products via the rupture and reformation of carbon-carbon double bonds [2]. Metathesis of unsaturated fatty acid esters provides a convenient route to various chemical products in only a few reaction steps. 

Polymerization esters alcohols Epoxides Branched chain fatty acids Dimeric fatty acids Mono- and bicyclic compounds Aromatic compounds Compounds with trans double bonds Hydrogen, CO2... 

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). 

Faraday, in 1834, was the first to encounter Kolbe-electrolysis, when he studied the electrolysis of an aqueous acetate solution [1], However, it was Kolbe, in 1849, who recognized the reaction and applied it to the synthesis of a number of hydrocarbons [2]. Thereby the name of the reaction originated. Later on Wurtz demonstrated that unsymmetrical coupling products could be prepared by coelectrolysis of two different alkanoates [3]. Difficulties in the coupling of dicarboxylic acids were overcome by Crum-Brown and Walker, when they electrolysed the half esters of the diacids instead [4]. This way a simple route to useful long chain l,n-dicarboxylic acids was developed. In some cases the Kolbe dimerization failed and alkenes, alcohols or esters became the main products. The formation of alcohols by anodic oxidation of carboxylates in water was called the Hofer-Moest reaction [5]. Further applications and limitations were afterwards foimd by Fichter [6]. Weedon extensively applied the Kolbe reaction to the synthesis of rare fatty acids and similar natural products [7]. Later on key features of the mechanism were worked out by Eberson [8] and Utley [9] from the point of view of organic chemists and by Conway [10] from the point of view of a physical chemist. In Germany [11], Russia [12], and Japan [13] Kolbe electrolysis of adipic halfesters has been scaled up to a technical process. 

A number of different dimers and ohgomers are produced from fatty acids and alcohols. These are branched-chain compounds with significantly lower melting points than straight chain structures of similar molecular weight. Fully saturated dimers... 

High performance in the synthesis of hydrolytically resistant polyurethanes was obtained by using in the polyesterification reaction, very hydrophobic fatty dimer acids and fatty dimer alcohols, products obtained from vegetable oils (see Chapter 12.5). The use of fatty dimeric acids and fatty dimeric alcohols (obtained by the hydrogenation of dimeric acids or dimeric esters) to build the polyester structure, creates an extremely high hydrophobic environment alongside a low concentration of labile ester bonds. 

The reactive dimer polyamides and fatty amido amines are liquid resins with many of the properties described above for solid polyamides. In addition, they are amine-like in that they are basic and form salts. They are more soluble than solid resins, although alcohols are still primary solvents. 

In Chapter 3 the adsorption isotherms where discussed for some surfactant systems showing the formation of small aggregates (dimers or trimers) within the adsorption layer. There are quite a number of surfactants, which can be described by this model perfectly, for example the homologous series of fatty acids or alcohols or the alkyl sulphates [81],... 

Oxidation causes the formation of hydroperoxides and conjugated compounds, which by cleavage give aldehydes, alcohols, ketones, lactones, acids, esters, and hydrocarbons. Radical mechanisms lead to the formation of dimers, other oligomers, and oxidized TAG. The latter have one or more acyl group with an extra oxygen (hydroxy, keto, epoxy derivatives). Other oxidation products are TAG with short-chain fatty acyl and n-oxo fatty acyl groups. 

The fatty acid spectrum of rice bran oil is 22-25% palmitic acid, 37-41% oleic acid and 37-41% linoleic acid. More recently, interest in rice oil escalated with its identification as a healthy oil that reduces serum cholesterol. Rice bran is a good source of antioxidants including vitamin E and oryzanol (ferulic esters of sterols and triterpene alcohols), cholesterol-lowering waxes and antitumor compounds like rice bran saccharide.Besides applications in nutrition and in phyto-chemicals, rice bran oil has traditionally been used for industrial applications, such as dimer acid manufacturing, depending on pricing for alternative vegetable oils. 

The Si-Cl bond readily undergoes solvolysis reactions with water or alcohols to yield the silanol and silyl ether compounds, respectively. The silanol dimerizes giving a disiloxane with two fatty acid ester units. Using methanol and an excess of hydrosilane under reaction conditions, fatty acid esters with siloxane branches are accessible. 

Figure 3-36. Raman spectra (0-400 cm ) of (a) hexatriacontane, n-C36H74 (b) stearic acid, n-CivHjjCOOH and (c) strearyl alcohol, n-CigH370H. Notice that since fatty acids and alcohols form head-to-head hydrogen-bonded dimers LAM modes extend throughout the whole dimeric system. Thus, the LAM progression shifts toward much lower frequencies than those expected for one isolated chain, approaching the values of hexatriacontane. The lowest frequency strong LAMl mode has its node at the center of the molecule, inside the hydrogen-bonded dimeric structure (see text).

Unsaturated lipids produce qualitatively similar products when thermally oxidized or autoxidized at low temperatures. These include a series of aldehydes, ketones, acids, esters, alcohols, hydrocarbons, lactones, cyclic compounds, dimers and polymers. However, quantitative pattern of the decomposition products formed at high temperatures is different from that of autoxidation, varying widely depending on the nature of the substrate and parameters of heat treatment (Nawar, 1985 Pokorny, 1989). Unsaturated fatty acids are much more susceptible to oxidation than their saturated analogs. According to Frankel (1980), at 25 to 80 °C, relative proportions of isomeric hydroperoxides isolated from each substrate varies with the oxidation temperature, however, their qualitative pattern remains the same. At oxidation temperatures higher than 80°C, isolation and quantitation of hydroperoxide intermediates is difficult due to their extreme heat sensitivity. Furthermore, the primary decomposition products are unstable and rapidly undergo further oxidative decomposition. As the oxidative process continues, a variety of possible reaction mecha-... 

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