Bioresource Bioresource Technology Technology 97 (2006) 1086–1091
Review Paper
Castor oil: A vital industrial raw material D.S. Ogunniyi Department of Chemistry, University of Ilorin, Ilorin, Nigeria Received 1 October 2004; received in revised form 24 March 2005; accepted 25 March 2005 Available online 24 May 2005
Abstract
Even though castor oil is inedible, it has long been an article of commerce. This is, in large measure, due to the versatility of the oil. This article discusses the extraction of castor oil and its refining methods and reviews the industrial applications of the oil. Since castor oil is not edible, it could be substituted in many industrial application areas where edible oils are used. An awareness of the various uses of the oil can be used to make a strong case for an increase in its production as a vital raw material for the chemical industries. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Castor oil; Raw material
1. Introduction
The trade in castor oil as an item of commerce goes back to antiquity. The oil is obtained from extracting or expressing the seed of a plant which has the botanical name Ricinus family Eurpho Eurphorbi rbiaca acaee Ricinus communis communis of the family (Kirk-Oth Kirk-Othmer, mer, 1979 1979). ). The oil is not only a naturallyoccurring occurring resource, resource, it is inexpensive inexpensive and environmenenvironmentall tally y frie friend ndly ly.. Cast Castor or oil oil is a visc viscou ous, s, pale pale yell yellow ow non-volatile and non-drying oil with a bland taste and is sometimes used as a purgative. It has a slight characteristi teristicc odour odour while while the crude crude oil tastes tastes slight slightly ly acrid acrid with a nauseating after-taste. Relative to other vegetable oils, it has a good shelf life and it does not turn rancid unless subjected to excessive heat. India is the world s largest largest export exporter er of castor castor oil; oil; other other maj major or produc producers ers are China and Brazil as shown in Table 1. 1. There are different varieties of castor seeds but on the average, they contain about 46–55% oil by weight. Castor seeds are poisonous to humans and animals because they contain ricin, ricinine and certain certain allergens allergens that are Õ
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toxic. If castor seed is accidentally ingested, it will bring about abdominal pain, vomiting and diarrhea. Indeed, as little as 1 mg of ricin can kill an adult. The pure oil however however,, if adminis administer tered ed in recomm recommend ended ed quantit quantities ies,, can be used as a laxative. It is noteworthy that the quality of seed oil is hardly affected by the variation in good or poor seeds. There are numerous other medicinal uses of castor oil but that is not the focus of this discussion. The castor plant grows in the wild in large quantities in most tropical and sub-tropical countries. It is available able at low low cost cost and and the the plan plantt is know known n to toler tolerat atee varying varying weather weather conditions. conditions. Specifically, Specifically, castor castor plant requir requires es a temper temperatu ature re of between between 20 and 26 °C with low humidity throughout the growing season in order to obtain maximum yields. The weather conditions for its growth limit its cultivation to tropical areas of the developing world. Also, the fear of accidental ingestion of the poisonous seed by children does not encourage the use of castor plant for ornamental purposes. Similarly larly,, the the seed seed cake cake is pois poison onou ouss and and cons conseq eque uentl ntly y unsuit unsuitabl ablee as animal animal feed. feed. Indeed Indeed,, some some people people who work with the meal may develop allergic reactions such as asthma. Generally, the toxicity of castor seed is a reas reason on why why US farm farmer erss no long longer er grow grow the the crop crop
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D.S. Ogunniyi / Bioresource Technology 97 (2006) 1086–1091 Table 1 Production volume of castor oil by major producersa Major producers
199 0 00 0 t
Ô
1 9 91 000 t
India China, PR Brazil Thailand E.U.b Others
192 77 77 18 20 54
239 86 73 18 16 52
232 93 54 19 14 49
242 97 28 18 12 41
27 1 97 28 16 14 20
3 33 82 22 14 11 21
34 4 73 21 10 9 22
27 8 83 43 9 10 19
304 80 21 9 7 20
2 94 91 19 7 8 23
32 4 10 5 52 5 8 23
T o t al
438
484
461
438
44 6
483
47 9
44 2
441
4 42
51 7
a b
1 9 92 000 t
Ô
1 99 3 000 t
Ô
1 9 94 000 t
Ô
1995 000 t
Ô
1 9 96 000 t
Ô
Ô
1997 000 t
1998 000 t
Ô
1999 000 t
Ô
Ô
20 00 000 t
Source — Source — http://www.ciara.com.ar/estadize.htm. http://www.ciara.com.ar/estadize.htm. E.U.—European Union.
extensively. The total world production of seeds is estimated ma ted at one one mil millio lion n tonn tonnes es and and the the oil oil extr extract acted ed is about 500,000 tonnes. tonnes. Information Information about about the agriculagricultural tural produc production tion of castor castor oil is availab available le from from past past work (Roetheli (Roetheli et al., 1991; Woodend, 1993), 1993 ), and other publications (Weiss, (Weiss, 1971, 1983). 1983). The objective of this review was to highlight the various uses of castor oil in chemical production. Being a non-edible oil, its increased creased cultivation, cultivation, especially in developing developing countries, countries, and its use can free up some edible oils used in industry for human consumption. consumption.
2. Extraction Extraction
The extraction of oil from castor seed is by one or a combination combination of mechanical mechanical pressing and solvent solvent extracextraction. In mechanical pressing, the seeds are crushed and then adjusted to low moisture content by warming in a steam-jacketed vessel. Thereafter, the crushed seeds are loaded into hydraulic presses and they are pressed by mechanical means to extract oil. The oil from mechanical pressing pressing has light light colour colour and low free fatty fatty acids acids (Kirk-Othmer, 1979). 1979). However, mechanical pressing will only only remo remove ve abou aboutt 45% 45% of the the oil oil pres presen entt and and the the remaining oil in the cake can be recovered only by solvent extraction. extraction. In the solvent solvent extraction extraction method, the crushed seeds are extracted with a solvent in a Soxhlet extrac extractor tor or commer commercial cial extrac extractor tor.. Solven Solvents ts used used for extra extract ctio ion n incl includ udee hept heptan ane, e, hexa hexane ne and and petro petroleu leum m ethers.
dal matter by settling and filtration, (b) neutralizing the free fatty acid by alkali, (c) removing coloured matter by bleaching, and (d) deodorizing by treatment with steam at high high temp temper erat atur uree and and low low pres pressu sure. re. The The gene genera rall method of refining used for edible oils is applicable to castor oil.
4. Properties Properties
Castor oil, like all other vegetable oils, has different physic physical al and chemica chemicall proper properties ties that that vary with the method of extraction. Cold-pressed castor oil has low acid value, low iodine value and a slightly higher saponification value than solvent-extracted oil, and it is lighter in colour. Typical properties are given in Table 2 while representative composition of the oil is given in Fig. 1. 1. The chemistry of castor oil is centered on its high content of ricinoleic acid and the three points of functionali tionality ty existin existing g in the molecule. molecule. These These are: are: (1) the carboxyl group which can provide a wide range of esterifications; (2) the single point of unsaturation which can be altered by hydrogenation or epoxidation or vulcanization; and (3) the hydroxyl group which can be acetylated or alkoxylated, may be removed by dehydration to increase the unsaturation of the compound to give a semi-dr semi-dryin ying g oil. oil. The hydrox hydroxyl yl positio position n is so reactiv reactivee the molecule can be split at that point by high-temperature pyrolysis and by caustic caustic fusion fusion to yield useful products of shorter chain length. The presence of hydroxyl grou group p on cast castor or oil oil adds adds extr extra a stab stabil ilit ity y to the the oil oil and and its deri deriva vati tives ves by prev preven enti ting ng the the forma formati tion on of
3. Refining
As in othe otherr vege vegetab table le oils, oils, it is usua usuall to refin refinee the the crude oil obtained from either mechanical pressing or solvent extraction. The main aim of refining is to remove impurities (e.g., colloidal matter, free fatty acid, colouring matter matter)) and other other undesi undesirab rable le constit constituen uents, ts, thus thus making making the oil more more resista resistant nt to deteri deteriorat oration ion during during storage. Refining includes: (a) removing solid and colloi-
Table 2 Characteristics of castor oil grades Properties
Cold-pressed oil
Solvent-extracted oil
Dehydrated oil
Spec Specifi ificc grav gravit ity y Acid value Iodine value (W (W ijij) Saponification value
0.96 0.961– 1–0. 0.9 963 3 82–88 1 79 –18 5
0.95 0.957– 7–0. 0.9 963 10 80–88 1 7 7 – 1 82
0.92 0.926– 6–0. 0.93 937 7 6 125– 14 5 18 5– 18 8
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stored for about 90 days. The reduction of these values is due to the reaction between hydroxyl and carboxyl groups in the oil molecule to form estolides.
5. Dehydration Dehydration
Fig. 1. Equation showing showing the constitution of castor oil.
hydroperox hydroperoxides. ides. The ricinoleic ricinoleic acid comprises over 89% of the fatty acid of the oil. Other fatty acids present are linoleic (4.2%), oleic (3.0%), stearic (1%), palmitic (1%), dihy- droxystearic acid (0.7%), linolenic acid (0.3%), and eicosanoic acid (0.3%). Castor oil consists mainly of esters of 12-hydroxy12-hydroxy-9-octa 9-octadecen decenoic oic acid (ricinoleic (ricinoleic acid); thus the presence of hydroxyl groups and double bonds makes the oil suitable for many chemical reactions and modifications (see Table 3). 3). The oil is characterized by high viscosity although this is unusual for a natural vegetable etable oil. oil. This This behavi behaviour our is due largely largely to hydrog hydrogen en bonding of its hydroxyl groups. It is soluble in alcohols in any proportion but it has only limited solubility in aliphatic petroleum solvents. Although castor oil is a unique naturally-occurring polyhy polyhydro droxy xy compou compound, nd, a limi limitat tation ion of the oil is the slight slight reducti reduction on of its hydrox hydroxyl yl value value and acid value value on storage; both values may change by about 10% if
Castor oil has only one double bond in each fatty acid chain and, so, is classified as a non-drying oil. However, it can be dehydrated to give semi-drying or drying oil which is used extensively in paints and varnishes. It must be noted that coatings that incorporate castor oil alone will never achieve complete cure through oxidative crosslinking as do coatings that contain oil with multiple double bonds in their fatty acid components. As the name implies implies,, dehydr dehydratio ation n involv involves es the removal of water from the fatty acid portion of the oil. Being a polyhydroxy compound, its hydroxyl functionality can be reduced through dehydration or increased by interes interester terific ificatio ation n with with a polyhy polyhydric dric alcoho alcohol. l. The dehydration process is carried out at about 250 °C and in the presence of catalysts catalysts (e.g., concentrate concentrated d sulphuric sulphuric acid, activated earth) and under an inert atmosphere or vacuum. Under this condition of dehydration, the hydroxyl group and an adjacent hydrogen atom from the C-11 or C-13 position of the ricinoleic acid portion of the molecule is removed as water (see Fig. 2). 2). This yields a mix mixtu ture re of two two acid acids, s, each each cont contai ainin ning g two two doub double le bonds but in one case, they are conjugated. The presence
Table 3 Various reactions of castor oil
Ester linkage
Nature of reaction
Added reactants
Type of products
Hydrolysis Esterification Alc oh oho ly lysi s
Acid, enzyme, or Twitchell reagent catalyst Monohydric alcohols Glyce ro rol , glyc ol ols , pe nt ntae ry rythr it ito l,l, an d oth er er compounds Alkalies, alkalies plus metallic salts Na reduction Alkyl amines, alkanolamines, and other compounds
Fatty acids, glycerol Esters Mono- and diglycerides, diglycerides, monoglycols, etc. Soluble soaps, insoluble soaps Alcohols Amine salts, amides
Saponification Reduction Amidation Double bond
Oxidation, polymerization Hydrogenation Epoxidation Halogenation Addition reactions Sulphonation
Heat, oxygen, crosslink agent Hydrogen (moderate pressure) Hydrogen peroxide Cl2, Br2, I2 S, maleic acid H2SO4
Polymerized oils Hydroxystearates Epoxidized oils Halogenated Halogenated oils Polymerized oils, factice Sulphonated Sulphonated oils
Hydr Hydroxy oxyll group group
Dehyd Dehydrat ratio ion, n, hydrol hydrolysi ysis, s, distillation Caustic fusion Pyrolysis Halogenation Alkoxylation E st ster ifi ific at atio n
Catalyst (plus heat)
Dehydrated castor oil, octadecadienoic acid Sebacic acid, capryl alcohol Undecylenic acid, heptaldehyde Halogenated Halogenated castor oils Alkoxylated castor oils Alkyl and alkylaryl esters, phosphate phosphate esters Urethane polymers Sulphated castor oil (Turkey red oil)
Urethane reactions Sulphation http://www.groshea.com.. Source: Source : http://www.groshea.com
NaOH High heat PCl5, POCl3 Ethylene and/or propylene oxide Ac et eti cc-, ph os osp ho hor ic ic-, mal ei eic -, -, phth al ali c anhydrides Isocyanates H2SO4
D.S. Ogunniyi / Bioresource Technology 97 (2006) 1086–1091
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Fig. 3. Production Production of sebacic acid and capryl alcohol from castor castor oil.
Fig. 2. Equation showing showing the dehydration of ricinoleic acid.
of an acid containing conjugated double bonds results in an oil oil rese resembl mblin ing g tung tung oil oil in some some of its its prop proper ertie ties. s. Thus, Thus, castor castor oil, which which is non-dr non-dryin ying, g, can be treate treated d and converted into a semi-drying or drying oil known as dehydrated castor oil.
6. Industrial uses
Although castor oil is not edible, it is more versatile than other vegetable oils as it is widely used as a starting material for many industrial chemical products because of its unique structure. It is one of those vegetable oils that have found usage in many chemical industries. It is a raw material for paints, coatings, inks, lubricants and a wide variety of other products. Becau Because se of its hydr hydrox oxyl yl func functi tion onali ality ty,, the the oil oil is suitable for use in isocyanate reactions to make polyurethane elastomers (Quipeng (Quipeng et al., 1990), 1990), polyurethane milla millabl blee (Kirk Kirk-Oth -Othmer mer,, 197 1979; 9; Yeg Yegane aneh h and Meh Mehdidizadeh, 2004), 2004), castables (Heiss, (Heiss, 1960; Lyon and Garret, 1973), 1973 ), adhe adhesi sive vess and and coat coatin ings gs (Ye Yead adon on et al al., ., 19 1959 59;; Trevino and Trumbo, 2002; Somani et al., 2003 ), interpenetr penetratin ating g polymer polymer networ network k from from castor castor oil-ba oil-based sed polyurethan polyurethanee (Pat Patel el and Suthar, Suthar, 198 1988; 8; Xie and Guo Guo,, 2002)) and 2002 and poly polyur uret etha hane ne foam foam ( Eh Ehrli rlich ch et al al., ., 19 1959 59;; Ogunniyi et al., 1996). 1996). Some semi-rigid foams that have potential uses in thermal insulation were produced when castor castor oil/pol oil/polyet yether her mix mixtur turee was reacted reacted with with toluen toluenee diisocyanate (Ogunniyi (Ogunniyi et al., 1996). 1996 ). Sebacic Sebacic acid, a 10-carbon 10-carbon dicarboxylic dicarboxylic acid, is manufact factur ured ed by heat heatin ing g cast castor or oil oil to high high tempe tempera ratu tures res (about (about 250 °C) with with alka alkali. li. This This trea treatm tment ent resu results lts in saponification of the castor oil to ricinoleic acid that is then cleaved to give capryl alcohol (2-octanol) and sebacic acid (see Fig. 3). 3). The preparation of sebacic acid and 2-octanol from castor oil has been reported (Vasishtha ( Vasishtha et al., 1990). 1990). Although the sebacic acid yields are low, this route has been found to be cost competitive. Sebacic acid and hexamethylene diisocyanate react through condensation densation polymerizatio polymerization n to produce produce nylon-6,10. nylon-6,10. Fur-
ther thermo more re,, the the este esters rs of seba sebacic cic acid acid also also are are used used as plasticizers for vinyl resins and in the manufacture of diocty dioctyll sebacat sebacate—a e—a jet lubrica lubricant nt and lubrica lubricant nt in airaircooled cooled combust combustion ion motors motors.. Capryl Capryl alcoho alcoholl is used used in plastic plasticizer izerss in the form of dicapr dicapryl yl esters esters of variou variouss dibasic acids. The pyrolysis of castor oil at 700 °C under reduced pres pressu sure re has has been been used used to obta obtain in hept heptal alde deyd ydee and and undecylenic acid (Das ( Das et al., 1989) 1989) (Fig. 4). 4). Undecylenic Undecylenic acid and heptaldehyd heptaldehydee are important intermediates intermediates in the preparation of perfume formulations. When undecylenic acid is mixed with isobutylamine, an insecticidal syne synerg rgist ist is obta obtain ined ed.. Hept Heptald aldeh ehyd ydee can can be furt further her hydrogenated to produce alcohol for use as a plasticizer. In addition, undecylenic acid is used in preparing athlete s foot remedy. Also, the synthesis of E -2-Nonenal, -2-Nonenal, an ingred ingredient ient of natura naturall flavour flavourss and fragra fragrance ncess has been reported (Kula ( Kula et al., 1994). 1994). In order to obtain x-aminoundeca -aminoundecanoic noic acid (Brydson,, 197 son 1975; 5; Sau Saunde nders, rs, 198 1988 8 ), cast castor or oil oil is subj subjec ected ted to methanolysis to yield methyl ester of ricinoleic acid by the route shown in Fig. 4. 4. In the first step, the pyrolysis of methyl ricinoleate is carried out at about 500 °C to Õ
Fig. 4. Production Production of x-aminoundecanoic acid from castor oil.
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give n-hepta -heptalde ldehyd hydee and methyl methyl undecy undecylen lenate ate.. The methyl undecylenate is hydrolysed to give undecylenic acid acid,, whic which h is trea treate ted d with with hydr hydrog ogen en brom bromide ide in a non-po non-polar lar solvent solvent in the presen presence ce of peroxid peroxide. e. Under Under these conditions, reverse Markownikoff Markownikoff addition occurs occurs and the main product is x-bromounde -bromoundecanoic canoic acid. The produc productt is then then treate treated d with with amm ammonia onia to give give x-aminoun nounde deca cano noic ic acid acid,, whic which h is a crys crysta tall llin inee soli solid. d. Aminoundecanoic acid is the starting material for nylon-11. It is claimed that a French company produces nylon-11 by this route (Kovaly ( Kovaly,, 1982 1982). ). Another characteristic of castor oil is the hydrogen bonding of its hydroxyl group; this confers a high viscosity on the oil. This property makes the oil useful as a comp compon onen entt in blen blendin ding g lubr lubric ican ants ts ( Kirk-Othmer, 1979). 1979 ). The castor cake is mainly used as a fertilizer. It is unsuita unsuitable ble as an animal animal feed feed becaus becausee of the presence presence of toxic protein called ricin and toxic allergen often referred to as CBA (castor bean allergen). However, it is noteworthy noteworthy that none of the toxic components components is carried into the oil. Some methods reported for the detoxification of the cake include treatment with ammonia, caustic soda, lime and heat (Kirk-Othmer, (Kirk-Othmer, 1979; Weiss, 1971; Gardener, Garden er, 1960; Horton and Williams, 1989 1989). ). When the cake is steamed, the ricin is detoxified and the allergen is inactivated. Although the use of detoxified cake as cattle feed has been reported (Woodend, ( Woodend, 1993), 1993 ), extreme caution and experimentation are desirable before the cake is fed to farm animals. Another method of detoxifying castor seed meal involved the wet mixing with sal ( Shorea robusta) robusta) seed meal so that the toxic constituents of castor seed were neutralized by tannins. (Ghandi ( Ghandi et al., 1994). 1994 ). In addition, some people in parts of South-Eastern Nigeria have long developed a method for treating and detoxi detoxifyi fying ng the unextr unextract acted ed seed seed that that is subseq subsequen uently tly used used as food food seas season oning ing know known n as ogiri-igbo (Weiss, 1971; Okagbue, 1993). 1993 ). In this case, the method used to detoxi detoxify fy castor castor seed seed involve involvess ferment fermentati ation. on. The seeds seeds are first dehulled and boiled in water for about 18 h. The boiled seeds are cooled and wrapped together with banana leaves and allowed to ferment in the fire place for for abou aboutt five five days days.. The The ferm fermen ente ted d seed seedss are are then then mashed by pounding using a mortar and pestle. This is followe followed d by additio addition n of ash from burnt burnt palm kernel kernel husk which gives it a dark colour. The dark, mashed product is allowed to mature for a further period of five days after which it is packaged for sale. It is believed that most of the detoxification takes place during fermentation and it leads to the elimination of the toxic factor factors. s. Microb Microbiolo iologica gicall studie studiess have have shown shown that that the bacteria involved are spore-forming bacteria, especially members of the genus Bacillus (Odunfa, 1985). 1985 ). Castor oil has been used as a plasticizer for celluloid and in lacquers but the blown oil has been discovered to
perform better. Blown or oxidized castor oil is prepared by blowing air or oxygen into it at temperatures of 80– 130 °C, with or without catalyst to obtain oils of varying viscosity. The blown oil is used widely as a plasticizer in lacquers, artificial leathers, hydraulic fluids and adhesives (Kirk-Othmer, (Kirk-Othmer, 1979; Weiss, 1971). 1971). Castor Castor oil also can be modifie modified d by reduct reduction ion with hydrogen hydrogen to produce produce hydrogenate hydrogenated d castor castor oil (HCO), which which is a waxwax-lik likee ma mate teri rial al with with melt meltin ing g poin pointt of 86 °C. Hydrogenated Hydrogenated castor oil is used in cosmetics, cosmetics, hair dressing, dressing, ointments, ointments, preparation preparation of hydrostearic hydrostearic acid and its derivatives; and in certain cases as wax substitutes tutes and and for for polis polishe hes. s. Some Sometim times es HCO is used used as a paint additive, solid lubricant, lubricant, pressure pressure mould release agent in the manufacture of formed plastics and rubber goods (Kirk-Othmer, (Kirk-Othmer, 1979; Weiss, 1971). 1971). Anothe Anotherr produc productt formed formed from from the modific modificatio ation n of castor oil is sulphated sulphated castor oil (also known as ‘‘Turkey red oil’’). oil’’). Sulpha Sulphated ted castor castor oil is prepar prepared ed by adding adding concen concentrat trated ed sulphu sulphuric ric acid acid to castor castor oil at 25–30 25–30 °C for several hours, followed by washing and neutralizing with sodium hydroxide solution. It is an active wetting agent. agent. As such, it is used extensively extensively in dyeing and in finishing of cotton and linen. Generally, the ability of castor oil and some of its derivatives to wet surfaces make them useful as excellent carriers of pigments and dyes. Also, the action of sulphuric acid on castor oil produces a useful useful emulsifi emulsifier er for certain certain insecticid insecticidal al oils (Kirk( KirkOthmer, 1979; Weiss, 1971). 1971 ). Even though a small amount is involved, about 0.7 parts per hundred of castor oil is added to latex or wet rubber rubber to promote promote crumbling crumbling and thus thus produc producee the crum crumb b rubb rubber er grad gradee (Rubb Rubber er Res Resear earch ch Ins Institu titute te of Malaysia, Malay sia, 1966 1966). ). Dehydrated castor oil (DCO) is used in the preparation of alkyd resins (Ogunniyi (Ogunniyi and Njikang, 2000) 2000 ) that are are in turn turn used used for for pain paints, ts, enam enamels els,, lacq lacque uers rs and and varnis varnishes hes with high high gloss, gloss, good good adhesi adhesion on and wetting wetting qualities. It has advantages over tung oil because it is non-ye non-yellow llowing ing (We Weiss iss,, 19 1971 71). ). The The vulc vulcan aniz izat atio ion n of DCO with sulphur has been reported (Botros ( Botros and Meinecke,, 1987 necke 1987): ): factice factice,, the resulti resulting ng produc product, t, has been found found to be a rubber rubber additive additive with with antiozo antiozonan nantt and good flow properties. Castor oil is used in the preparation of brake fluids; as an ingredient for soaps, lubricants, inks, paint and varnishes; and as the main ingredient in motor oils for high high speed speed automo automobile bile engine engines. s. Other Other miscella miscellaneo neous us appl applic icat atio ions ns of casto castorr oil oil are are in the the form formul ulati ation on of cathartic, cathartic, the formulation formulation of contraceptiv contraceptivee creams, creams, as a component of synthetic flower scents, the preparation of bland emollient to treat skin diseases, and for inducing labour in pregnancy at term. Castor oil-based syntheti theticc dete deterg rgen ents ts are are less less pron pronee to foam foaming ing and and the the disposal of the detergent is hastened since microbiological breakdown is simplified. Since DCO contains unsat-
D.S. Ogunniyi / Bioresource Technology 97 (2006) 1086–1091
urated acids, it is felt that epoxidation of DCO should be feasible (Kirk-Othmer, (Kirk-Othmer, 1979; Weiss, 1971). 1971 ). If DCO is epox epoxid idize ized, d, the the prod produc uctt can can be eval evalua uate ted d in poly poly (vinyl (vinyl)) compou compounds nds as a plasti plasticize cizer/st r/stabi abilize lizerr with the possibility that epoxidized castor oil may be capable of replacing epoxidized soybean oil. It must be noted that edible oils such as soybean oil are useful in industrial production, but they are in short supply in Africa. The poss possib ibili ility ty of usin using g nonnon-ed edib ible le oil oil such such as DCO for for industrial production will make available nutritious oil such as soybean oil for human consumption.
7. Conclusions
Ther Theree is no doub doubtt that that cast castor or oil oil is an impo import rtan antt renewable resource. This is evident from the fact that much has been written about the oil and it is certain certain that more literature will still be written. In this short review, the various uses of castor oil have been outlined. However, it must be realized that there are other chemicals that can be produced from castor oil that have not been mentioned. This is because such chemicals are not yet produced in commercial quantities. In many countries with little or no petrochemical feedstock, castor oil will come in handy as a versatile renewable resource. Such oil, with a variety of uses, will be a suitable substitute in indu indust stria riall prod produc uctio tion n wher wheree ma many ny edib edible le oils oils are are being used. Generally, it is considered that non-edible oils should be exploited as far as it is possible so that edible oils can be freed for human consumption. This is especially important in developing countries where food security poses a challenge.
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