Polyols vegetable oils

By chemical recovery of polyester [poly(ethylene terephthalate) (PET)] (Chapter 16) and PU wastes, by alcoholysis or by aminolysis (Chapter 20), new polyols are obtained that can be used in rigid PU foam fabrication. The vegetable oil polyols, obtained by chemical transformation of the double bonds in vegetable oils in various hydroxyl groups are a very attractive route to obtain polyols from renewable resources (Chapter 17). 

Synthesis of Vegetable Oil Polyols by using Reactions Involving Ester Groups... 

Generally the resulting vegetable oil polyols are greases, with an hydroxyl number of around 180-200 mg KOH/g and a functionality of 3.8-4.1 OH groups/mol. The reactions... 

The typical alkyd resin (see above) is eomprised of three basic components an aromatic diacid such as phthalic anhydride which together with a polyol such as glycerol, forms the backbone of the resin molecule and along which are distributed the fatty acids derived from vegetable oils. The solubility, film hardness and colour of alkyd resins depend on the nature of the modifying fatty acid which in most cases contributes some colour to the film. 

Fatty Acid Esters and Fatty Alcohols Fatty acid esters are obtained by transesterification of triglycerides (vegetable oils) or by esterification of fatty acid with alcohol or polyols. Fatty alcohols are obtained by hydrogenation of esters on metal catalysts. Fatty acid esters and fatty alcohols are useful platform molecules to prepare surfactants, emulsifier, lubricants and polymers. 

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 hydrogenation step following hydroformylation serves two important purposes. It reduces the aldehyde intermediate product to the desired primary alcohol functional group, which is the primary site of reactivity of the polyol with isocyanates. It also reduces the residual olefins in the FAMEs to saturated hydrocarbons, thus eliminating the pathway to Hock degradation and odor development, which is inherent to other processes that leave fatty acid unsaturation in the polyols. This step eliminates the typical vegetable oil odor from the final namral oil polyols of this process. 

Fig. 22 Respirometry of vegetable oil-based polyurethanes made from the following polyols triolein-met arrowhead), soy-HF (filled square), soy-met 180 (open diamond), soy-met 206 (open circle), and linseed met (open square). Also shown is ESO/BF3 polymer (open triangle) and soybean oil control (filled circle). Temperature was increased from 30°C to 55°C on day 71. Note that hydroxyl number of 180 has the functionality of 3.3 and that of hydroxyl 206 is 4.0. Met refers to polyol made from ESO and methanol HF refers to polyol from hydroformylation and reduced ESO. Reproduced from [152] by permission of Journal of Polymers and the Environment...

Polyols. The polyols for urethane foams are oligomers or polymeric compounds having at least two hydroxyl groups. Such polyols include polyether polyols, polyester polyols, hydroxyl-terminated polyolefins and hydroxyl-containing vegetable oils. 

Other Polyols, Hydroxyl-containing vegetable oils such as castor oil were used for producing semi-flexible foams in the initial stage of the urethane foam industry, but they have not been used much in recent years. 

Synthetic ester-based hydraulic fluids are used where application of vegetable oil-based products is limited due to their lower chemical stability however, then-high cost has limited their use. The most commonly used synthetic esters are polyol esters, such as those based on trimethylolpropane and pentaerithritol. 

The vitality of this field is further demonstrated by a continuous search for original ways of exploiting vegetable oils. Examples include self-healing elastomers in which fatty acids play a central role [46] the esterification of cellulose with fatty acids to give thermoplastic materials [47] the synthesis of a saturated aliphatic diisocyanate from oleic acid and its subsequent use in the preparation of fully biobased polyurethanes in conjunction with canola oil-derived polyols [48] and novel elastomers from the concurrent cationic and ring-opening metathesis polymerization of a modified linseed oil [49]. 

Vegetable oils and fats are very important resources for polyols. The vegetable oils such as soybean oil, castor oil, sunflower oil, palm oil, rapeseed oil, olive oil, linseed oil and so on, with a worldwide production of around 110 milions t/year (in 2000) [10,12, 21, 22], are used mainly in human food applications (76%), in technical applications (19.5% only 7.5% is converted into soaps, and 10.5% is used in oleochemical industry) and 1.5% in other applications. Soybean oil is the most important vegetable oil produced worldwide, representing 25% from the total oils and fats, the second place being occupied by palm oil (18%) [10, 12, 21, 22, 24-26]. 

The unsaturated vegetable oils, having double bonds but without hydroxyl groups, are transformed by various chemical reactions into polyols, which by reaction with isocyanates are transformed into PU. 

The reactions of vegetable oil transformations in polyols are divided into two important groups ... 

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