What is new in the castor industry may not be related as much to REAC-NONS as to APPLICATIONS. Obviously the oleochemical industry is involved with new castor applications. But of equal importance is recognition of proven features from older

technology that may still be utilized. These and new castor derivatives are experiencing greater acceptance in the worldwide expansion of oleochemical products.

Unlike the reaction section it is not possible to present the applications on the basis of tonnage. In general they appear according to volume, to a certain extent, but diversity of use and performance properties are also governing factors.

Castor Oil and Derivatives in Liquid Carbon Dioxide

Castor oil, heptaldehyde and heptyl alcohol were included in a study of the mutual solubility of liquid carbon dioxide with each of 261 other substances. The solubility of carbon dioxide in each substance was determined as was the solubility of each substance in carbon dioxide. Triangular graphs were prepared for 464 ternary systems (347).

This was a project to establish fundamental properties for advanced research in physical properties of organic chemicals

Castor Oil is Non Toxic

Extensive historical use of castor oil for internal consumption and topical application has established it as safe. As an added measure of safety an investigation was conducted by feed studies in a national toxicology program of the US Department of Health and Human Services (National Institutes of Health). In 1990 the feed studies concluded there were "no significant adverse effects of castor oil administration in these Studies in rats or mice." Exposure to castor oil at dietary concentrations as high as 10% in 90-day studies did not affect survival or body weight gains (345).

Fatty Acid Composition

An intensive examination of this subject was undertaken at the University of Bombay, India (278). This included a thorough historical review of prior work on the subject. AJso included were;- an in depth discussion of analytical methods normally applicable to ricinoleic acid, interference reactions related to the hydroxyl group and unsaturation, examination of the methyl esters, influence of estolide formation, and estimation of the dihydroxy acid content.

Castor Oil: Properties and Characteristics

Castor oil characteristics, particularly alcohol solubility, was reported in 1929. In fact, it also included examination of bulk oil in 1919, as well as the comparison of the characteristics of fresh oil against oil in ten months storage. At the time the examinations included refractive index, viscosity, acidity, Halphen number, acetyl value, specific gravity, Wijs iodine value and acetic acid solubility all of which are listed. From a historical standpoint, it is interesting to note the contrast between current test procedures and those used over 60 years ago (142).

An interesting practical thesis on castor oil properties and utilization is presented in a 1952 review. Much of the subject matter is now outdated by technical changes since then (7). However, it is recommended for the clear, concise and practical description of basic properties and characteristics of castor oil and its derivatives.

This approach to the chemistry of castor oil refers to good quality oil, frequently identified as "No. 1" castor oil, an expression accepted by the major operators in each producing country. No. I castor oil is an international standard, representing quality that is generally usable for the reactions and applications described in this publication. In certain instances, an oil of better quality is required.

Castor Oil: Stability to Oxygen

Castor oil and many of its derivatives are stabilized by the hydroxyl group, which is beta to the double bond. This hydroxyl group protects the double bond by preventing the formation of hyperperoxides sterically and inductively preventing the formation of peroxides, the intermediate chemical species that form the oxidation of double bonds.

The kinetics of peroxide formation is the method by which oxidative stability of a vegetable oil is measured.

Data on oxidative stability is derived from an American Oil Chemists method, Active Oxygen Method (AOM). A sample of vegetable oil is heated to 970C while air is bubbled through it. 'ne AOM number for each vegetable oil is the number of hours the sample took to reach a peroxide value of 70 meqs. , Olive oil is the nearest stable vegetable oil after castor oil because, like castor oil, it is predominately mono-unsaturated but is unlike soy and sunflower oils that are polyunsaturated.

However, olive oil lacks a stabilizing factor like castor oil's hydroxyl group. As a result, castor oil is approximately four times more stable than olive oil (279).

Derivative

What is castor oil?

Basically the significant factors that characterize castor oil are the following:

It is the only commercial source of a hydroxylate(i fatty acid or, ricinoleic acid, also known as hydroxyoleic acid.
High purity of the key component, ricinoleic acid, comprises 89-90% of the fatty acid composition of castor oil.
Uniformity,- unusual in vegetable oils the ricinoleic acid content exists year after year with very little variation in good crops or in poor. As an example, for years castor oil was employed as a standard viscosity reference by the U.S. Bureau of Standards.
Castor oil is non-toxic, a renewable resource, and biodegradable.

This is an investigative move aimed at providing up-to-date information on the utilization of castor oil in the modern world of oleochemicals. 'ne undertaking seems well placed because castor is certainly one of the earliest and most prominent participants in the field of oleochemicals

Effect on Skin

Non-comedogenicity is castor oit's least understood or appreciated benefit. Comedogens are defined as cosmetics or cosmetic ingredients that exacerbate or contribute to acne and are an important factor for dermatologists and consumers alike. To overcome this growing concern, cosmetic manufacturers are formulating products with noncomedogenic emollients. Castor oil and its derivatives are recognized as non-comedogens and emollients

General

There is no attempt at "teaching" the chemistry of castor oil; that is the responsibility of academia. The objective is to review the known and established technology, publications and patents, and to provide an extensive bibliography, all in a single compact publication.

It is a summary of the known reactions involving castor oil and its derivatives. Of greater importance is the information on uses and applications.

Castor oil has relatively high purity, (high for a naturally occurring material). Thus, it can be subjected efficiently to a number of chemical processes to yield high purity chemical derivatives. The chemical bases for such reactions are the three points of functionality existing in ricinoleic acid:

(a) The carboxyl or ester group

(b) The single point of unsaturation

This functionality may be utilized as follows:

1) At the carboxyl position, through a wide range of esterifications.

2) The hydroxyl group can be acetylated or alkox\llated.

3) The unsaturation can be altered by hydrogenation or epoxidation.

4) The hydroxyl group can be removed by dehydration to increase the linsaturation of the compound thus yielding a drying/polymeri7ing oil.

5) The hydroxyl position is so reactive, the molecule can be split at that point by high temperature pyrolysis and by caustic fusion yielding four useful products of shorter chain length.

Introduction

It is hoped this information will be of use to the entire castor industry,- the growers, producers of oil and processors who supply oil and derivatives to the market. Castor oil is one of the earliest and perhaps most impressive participants in the oleochemical industry.

It is equally important that this publication provide to the scientific community a better understanding of the diverse potential for castor oil.

Castor has transcended that period from early "arts and craftsmanship" to the present where chemical science is no longer black magic or secret formulas. As the oleochemical age advanced it became more important to know how a product is made, why it works and how. It is the objective of this project to identify these details.

In the absence of both time and technical proficiency, this is not the occasion to attempt a teaching program in organic chemistry and the reactions of vegetable oils. That effort rightfully belongs to academia and research institutions.

Castor's experience as an oleochemical follows a meaningful pattern within the chemical industry;-constant changes, with some of the old important processes and products being replaced by the new. In contrast, over the years some products that were in decline have been revived with the Introduction of new technology and applications. Separately, new market demands have placed heavy pressure on castor chemistry which has responded with great vigor.

Castor oil is a most unusual product. Among all the vegetable oils it is, by far, more versatile. Most oils are concentrated in one or two applications, such as for edible purposes (cottonseed, soya, corn, peanut, rapeseed, canola, sunflower, coconut and palm, for example). Many of these are interchangeable according to economic factors. Some have other uses, as in coatings, inks lubricants, detergents and soaps. In contrast, castor has considerably more uses, with a wide diversity of commercial applications,- all directly related to the unique hydroxy fatty acid structure.

Pigment and Dye Dispersing Properties

Castor oil and many of its derivatives (esters, hydrogenates and ethoxylates) are well known for their ability to wet surfaces thus acting as excellent carriers of pigments and dyes. Typical examples are colors for food stuffs, plastics, lipstick, paints, lacquers, coatings, inks, sealants, adhesives and color concentrates for plastics.

Reactions

Many castor reactions are utilized in current commercial practice,- as described in the pages that follow. There are, however, certain limiting factors that must be recognized. An important example is the formation of estolides which result from a linkage between hydroxyl and carboxyl groups;- the hydroxyl in ricinoleic acid actually forming an ester with the carboxyl. This takes place on storage, with the reaction decline of both hydroxyl value and acid value. The change is well known with commercial ricinoleic acid,- the two values can change by 5%-10% within 90 days from original production.

The subject of castor estolides is reviewed by Modak and Kane (67) which has an important list of references.

There are instances where theoretically sound reaction mechanisms cannot be undertaken because of this interference.

The ricinoleic acid structure explains why it cannot be refined or purified by distillation by the conventional commercial procedure for purifying other fatty acids. III distillation the hydroxyl-acid linkage produces an alteration so the product is no longer ricinoleic acid. In fact, the estolide formation becomes one stage in the conversion to dehydrated castor fatty acids, the process for which is explained in this section.

The reactions are presented in order according to actual castor tonnage consumed. It is difficult to compare hydrogenated castor with polyamide 11. The latter is the larger, producing one finished product by one manufacturer. There are numerous hydrogenaters, worldwide. Their product is an intermediate for several different end products. The volume of the two is comparable and polyamide is arbitrarily placed first.

The Principal Castor Reactions

Pyrolysis, Polyamide 11

Hydrogenation

Dehydration

Caustic Fusion, Sebacic Acid

Undecylenic Acid*

Heptaldehyde*

Sulfation/Sulfonation

Alkoxylation

Oxidation/Polymerization

Esterification

Dimerization**

Quarternaries

Engineering Resins (Interpenetrating Networks)

Miscellaneous

*Also by-products from pyrolysis

**From Dehydration

Some Background

Castor oil occurs in the seed of the castor plant, ricinus communis L. (Eurphorbiaceae Family), growing in most tropical and subtropical areas.

Castor seeds are toxic, containing a highly poisonous protein, ricin, and a highly allergenic material identified as CB-LA.

Neither is carried into the oil but remain in the by-product meal after extraction. Details concerning both toxic components and the process for detoxification and deallergenation of castor meal are present in ICOA Technical Bulletin No. 1.

At the turn of the century, castor consumption was limited to a rather crude type of lubrication, production of soap and Turkey Red Oil (sulfonated castor). Later the blown oils and ester-, came into common use as plasticizers. Dehydrated castor oil soon appeared, followed by the polyamide 11 reaction, producing a nylon polymer of considerable import as a synthetic fiber and engineering resin. From World War 11 and the 1950's to the current scene there have been in any changes; some of the products have declined, being replaced in the name of progress. Others expanded and came along to the present with several new and significant developments.

It is interesting to note that castor oil itself seldom appears in the marketplace alone or at a high concentration. Two exceptions are the traditional bottle available in tile pharmacy (pure castor oil) and lipstick which generally will contain 30-40%. In practically all other instances, the presence of castor oil or its derivatives will be in the range of 1/2 to 10 percent of the finished product offered in the market. Never is there a label or advertising statement claiming,- "contains castor oil" or contains of ricinoleic acid"! The important point for the reader to understand clearly is that the reason for the castor (or derivative) presence is performance. That presence is justified simply because the product’s total performance is largely dependent on its castor component .

The Basic Properties of Castor Oil

Several universal specifications are in effect, including those of the American Oil Chemists Society (AOCS), The American Society for Testing Materials (ASTM), The U.S. Pharmacopeia (USP), the U.S. National Formulary (N.F.). Similarly there are applicable specifications for Great Britain, France, Germany and Japan. All are useful and in most cases interchangeable. The point is that quality standards are universally applicable. The following is an example.

A typical specification, that of the ASTM, is presented below with the observation that is quite similar to the others listed above:

Acid Value	2.0 Max
Clarity	Clear
Color (Gardner)*	2 Max
Hydroxyl Value	160-168
Loss on Heating, %	0.3 Max
Refractive Index 250C	1.4764-1.4778
Saponification Value	176-184
Solubility in Alcohol	Complete
Specific Gravity 25cC/25oC	0.957-0.961
Unsaponiflable matter, %	0.7 Max
Viscosity Stokes	6.3-8.9
Iodine Value	83-88

*Color is often expressed in terms of the Lovibond Scale.

Other standards are also applied, such as optical rotation, peroxide value, and light absorption, the latter being particularly useful as an indication of special heat treatment in processing the oil (which might be undesirable for pharmaceutical purposes).

The Bleaching of Castor Oil

The decolorization of castor oil differs from other vegetable oils primarily due to the hydroxyl group. Bleaching clays and carbon are used but certain clays of the acid type can promote chemical dehydration of the oil (conversion to a drying oil). Accordingly, an examination of several clays was undertaken, indicating appropriate choices (204). The tests were applied to both hydraulic pressed oil and extracted oil. In some cases the hydroxyl value was increased slightly.

The Chemistry of Castor Oil

It is not intended to engage in a complex highly scientific dissertation on the subject. However, the effort will be facilitated by a brief reminder of castor's triglyceride structure showing, graphically, the carbon chains, hydroxyl groups and unsaturation. The properties of castor oil are unique and may be described as its "Fingerprints." Castor oil is glyceryl triricinoleate and the difference between it and glyceryl trioleate (olive oil) is attributable to these "Fingerprints":

Ricinoleic Acid (12-hydroxyoleic) 89-90%

Molecular weight 928.5

Hydroxyl value 164

Iodine value 86

The Investigative Procedure

This study concentrates on two sections. The first, REAC-HONS, reviews those basic chemical conversion processes that are currently in use. Some are old, having been active for over fifty years; others are more recent, being developed as recently as the last twenty years. The listing of twelve basic reactions is not based on a historical priority, but is related to the market demand of the 1980's and 1990's. The largest use of castor oil, worldwide in one product, is described first, followed by the others in declining order.

The second section reports on APPLICATIONS with coverage following the pattern of usage according to worldwide market demand. This section examines the direct use of castor oil, unaltered, and the derivatives as described in the REACTIONS section.

It cannot be denied that some reactions may be in use under little known, unpublicized or proprietary processes. Similarly, there can be applications utilizing castor oil or its derivatives whereby the castor presence is not identified.

Throughout this treatise, the expressions relate to castor oil, ricinoleic acid, hydrogenated oil, dehydrated oil, etc., etc. It should be understood the chemical breakdown of castor also includes sebacic acid, undecylenic acid, heptaidehyde and others. 'I'hese, are included in both REACTIONS and APPLICATIONS.

In several instances useful information was found in technical literature issued by certain chemical manufacturers. They discovered attractive properties with castor based components were observed, giving reason for recommending them in combination with their products. Such information was included in this project only after clear evidence revealed that actual laboratory tests supported the claims.

In addition to the scientific literature and patent search, another useful source is technical service literature and commercial catalogs issued by certain members of the ICOA which supply the oil and derivative types reported here.

Alberdingk Iloley GmbH, Germany

Baker Castor Oil Co (now Caschem) USA

Caschem Inc., USA

Elf-Atochem, France

ITOH Oil Manuficturing Co., Japan

Jayant Oil Mills, India

Thai Castor Oil Industries Co., Thailand

This project includes an extensive bibliography,- almost 400 entries. The readers interest may be further investigated by pursuing the original source material, identified by a number in parentheses ( ), which lists author, title, Publication and date.

For convenience in studying this report, there are certain sources that contain good basic information almost of the encyclopedic nature. These are listed below and recommended as good references for castor oil and in some cases, for chemical information on fits and oils in general. They are included in title Bibliography.

Kirk-Othmer (1)

Bailey's Industrial Oil and Fat Products (2)

Naughton (3)

Achaya (4)

Binder, Applewhite, Kohler and Goldblatt (5)

Achaya, Craig and Youngs (6)

Pryde (14)

'ne Merck Index (351)

Johnson and Fritz (75)

Schwitzer (297)

A general reference on castor (349), published in 1991 is one of the most recently issued publications. In contrast, an interesting practical thesis on castor oil properties and utilization was published (London) in a 1952 review. Much of the subject matter is now outdated by technical changes of the last 50 years. However, it is recommended for the clear, concise and practical description of basic properties and characteristics of castor oil and its derivatives. Useful background information covers several applications. Emphasis is placed on wetting, emulsification and lubricity as well as the conversion to a drying oil and a nylon type polyamide (7).

Hopefully this undertaking will stimulate the scientific recognition of the potential for castor oil, particularly at the time of importance for all renewable resources that are inherently biodegradable.

The Mechanics of this Project

The objective was to gather all possible information from published texts, scientific articles and reports, patents and general industrial sources. The constraints of time and personal language limitations made it necessary to restrict the investigative effort to publications in English.

Each source was studied after which the important subject matter was abstracted and recorded under suitable subtitles in the two sections, REACTIONS and APPLICATIONS. The overall picture is described in two sections; the first describes the 12 leading reactions in which castor is involved, the second covering the numerous applications which use castor oil or its derivatives. There are subsections in APPLICATIONS, simply to group together those subtitles of common interest; for example there are two groups under grease production and several groups under dehydrated castor oil and fatty acids.

It is acknowledged that some duplication of statements will be found. This is intentional and not an oversight. When a particular product has proficiency in more than one application, each must be mentioned separately. For example, this will occur with a derivative that is both a plasticizer and lubricant