Polyols castor oil

Castor polyols Castor oil (CO) is mainly available in India and Brazil although the USA also produces a considerable quantity. Castor oil is produced either by expression or by solvent extraction from its seeds, also known as castor beans . It is a viscous liquid with a characteristic unpleasant taste and can be made odorless and tasteless by neutralization and subsequent deodorization. The grade of castor oil is decided by its... 

Preparation of polyurethane matrix In a Petri dish, 9.0 g of the polyol of castor oil and 6.0 g of the prepolymer based on MDI were combined to obtain a polyol (castor oil) diisocyanate mass ratio of 1.5 1.0 for all composites. The homogenized mixture was distributed in the mold to fill the entire space of the intermediate plate. Then, the upper plate of the mold was closed and sealed with adhesive tape. After the material was cured for approximately 24 h, the mold was opened. 

The final type of polyurethane available is known as the two-part polyol system. One component contains the isocyanate containing compound such as a prepolymer or adduct and the second component is a hydroxy group terminated resin which may or may not contain a catalyst. The most commonly used hydroxy-terminated components are polyols, castor oil, hydroxy-terminated polyesters and some epoxy resins. By varying the components of such a system a wide range of cured properties can be achieved ranging from high flexibility to very hard or brittle. The curing reactions and properties of the different polyurethanes are summarised in Table 10.9. 

Reactive diluents based on low molecular weight polyester or polyether polyols, castor oil derivatives, oxazolidines and acetoacetate chemistry are commercially available. The reactive diluent not only reduces the viscosity of the system, whilst increasing the solids, but it can also give improvements in resistance properties and durability. The polyester polyols do, however, have an adverse effect on dtying times and hardness of the coating. 

If a branched polyol, usually either castor oil or a simple polyester, is heated with an isocyanate but without chain extenders soft and weak rubbery products are obtained with very low resilience. These materials are useful for encapsulation of electronic components and for printer rollers. 

Polyurethane foams may be rigid, semi-rigid or flexible. They may be made from polyesters, polyethers or natural polyols such as castor oil (which contains approximately three hydroxyl groups in each molecule). Three general processes are available known as one-shot, prepolymer or quasi-prepolymer processes. These variations lead to 27 basic types of product or process, all of which have been used commercially. This section deals only with flexible foams (which are made only from polyesters and polyethers). Since prepolymers and... 

Products intermediate to the flexible and rigid foams may be obtained from castor oil (a trihydroxyl molecule), synthetic triols of moderate molecular weight and polyesters with a moderate amount of trifunctional hydroxyl compound in the strueture. Current practice, however, is to use tipped polyols of the type used for flexible foams with MDI. Semi-rigid foams are used for such purposes as crash pads, car steering wheels and packaging equipment. 

Numerous other polyols are commercially available, some from renewable resources. Urethanes based on castor oil have been used for many years as encapsulants for electronic components, due to their hydrophobic nature [29J. 

Much work has been done on the incorporation of castor oil into polyurethane formulations, including flexible foams [64], rigid foams [65], and elastomers [66]. Castor oil derivatives have also been investigated, by the isolation of methyl ricinoleate from castor oil, in a fashion similar to that used for the preparation of biodiesel. The methyl ricinoleate is then transesterified to a synthetic triol, and the chain simultaneously extended by homo-polymerization to provide polyols of 1,000, 000 molecular weight. Polyurethane elastomers were then prepared by reaction with MDl. It was determined that lower hardness and tensile/elongation properties could be related to the formation of cyclization products that are common to polyester polyols, or could be due to monomer dehydration, which is a known side reaction of ricinoleic acid [67]. Both side reactions limit the growth of polyol molecular weight. 

One of the more advanced technical offerings from castor oil is a line of polyester diols, triols, and higher functional polyols derived from 100% castor oil as products for the preparation of polyurethane prepolymers and elastomers [68]. The Polycin line of polyols are prepared by transesterification of ricinoleic acid and derivatives. The producers (Vertellus) offer diol and triol products, as well as a recently developed series of diol and triol glyceryl ricinoleate esters that are stated to be prepared from 100% castor oil, making them fully renewable in content. The products are recommended for coatings, sealants, and adhesive applications. 

Helling R (2006) Life cycle analysis of polyols from soy oil or castor oil. In Proceedings AlChE 2006, Topical Session 4 Sustainable Biorefineries, 16 November 2006, San Francisco. AlChE, New York... 

ISRO polyol is considered to be a substitute for HTPB binder and propellants based on it are used in sounding rockets (RH-300). Such propellants are also considered as candidate propellants [94] for the booster stages of Polar Satellite Launch Vehicle (PSLV). The easy availability of castor oil coupled with its low cost makes ISRO polyol more attractive compared with current binders [95] like PBAN, CTPB and HTPB. 

While the use of these polyethers is widespread, the goal of discussion is to create a specialty chemical. Propylene- and ethylene-based polyols are produced for physical reasons and will serve as the backbone. Researchers should note, however, that the scope of polyethers and polyesters is much broader when they are willing to sacrifice some physical strength to gain a chemical advantage. To illustrate, we cite a particularly interesting example. Castor oil was a conunon polyol for the production of polyurethanes. It was replaced by less expensive and more predictable polyols in commercial production. Readers should be aware that mixed polyols can be used to advantage. 

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. 

Renewable materials can be used in the preparation of polyurethanes. Glycosides of polytetrahydrofuran have been used with diisocyanates.164 Castor oil (which contains about 2.7 OH per molecule) has also been used.165 Polyols derived from epoxidized soybean oil have been used to make polyurethanes.166 Lactic acid oligomers can be used.167 Wheat Board is made from wheat straw and isocyanates.168 It is said to be lighter and as strong as and more resistant to moisture than conventional particle board. No formaldehyde is needed for this building material. 

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]. 

Castor oil plays a very important role, especially in the earlier stages of the PU industry, even before synthetic polyols were available. Worldwide production of castor oil is around 1,200,000-1,800,000 t/year [76], the world leader in castor oil production being India (750,000 t/year) [76] (India 64%, China 23%, and Brazil 7%). 

Concerning the direct utilisation in rigid PU foams, castor oil has some major disadvantages low functionality, and low hydroxyl number and secondary hydroxyl groups lead to a low reactivity. Castor oil, as sole polyol, leads to semi-flexible to semi-rigid PU foams. 

By mixing castor oil with polyols such as glycerol (for example 75 % castor oil and 25 % glycerol) a higher hydroxyl number polyol mixture is obtained, which leads to rigid PU foams with good physico-mechanical properties [47]. 

By the transesterification of castor oil with polyols with high functionality and high hydroxyl number [29], or by transamidation with poly amines or alkanolamines [29] new polyols are obtained which are of real use in the fabrication of rigid PU foams with good physico-mechanical properties. These polyols are made without PO. 

The polyols that can be used for transesterification with castor oil are glycerol, trimethylolpropane, pentaerythritol, sorbitol, and sucrose. The catalysts of the reaction between castor oil and various polyols are alkali alcoholates, such as sodium methoxide or potassium methoxide. Thus, by the reaction of one mol of castor oil with two mols of glycerol, a mixture of mono, di and triglycerides of ricinoleic acid, having a much higher hydroxyl number than the initial castor oil, of around 420-430 mg KOH/g (reaction 17.5) is obtained. 

The transesterification between castor oil and various polyols is an equilibrium reaction of all the hydroxyl group species from the reaction system with the ester groups. Because no reaction component is removed, the reaction time is in fact the time needed to establish the reaction equilibrium (around 1-2 hours at 90-120 °C). 

Figure 17.7 Structure of polyols resulting from transesterification of castor oil with...

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