1306 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 32, NO. 10

A series of maroon pigments was formulated in an alkyd resin-nitrocellulose lacquer with a small amount of aluminum powder as the extender and exposed on steel panels as in the previous series. This set included an azo pigment dyestuff (toluidine type), a precipitated azo dye (litho1 type), and a thioindigo red (vat dye). After 12-month exposure in Florida both azo maroons had faded badly, while the vat dye was in practically perfect condition. The vat dye exhibited no bronzing under severe buffing, which is an important prop- erty of a maroon.

Certain Prussian blues have been found to drift in shade when used as a tint in lacquer. Milori blue, which is greener in shade, does not show this tendency. Since vat violets do not drift, it was possible to shade Milori blue with a vat violet to match the shade of Prussian blue and have a nondrifting combination.

Printing inks containing (a) rhodamine phosphotungstate and (b) a thioindigo pink were made up on the following for- mula: 1 part color, 5 titanium dioxide, 4 zinc oxide, and 15 lithographic varnish. Prints on paper were exposed to the rays of a carbon arc for 50 hours. The rhodamine phospho- tungstate faded badly, while the vat dye faded only slightly. Although this method of determining fade is not necessarily a true measure of the relative out-of-door fastness properties of the two colors, the obvious advantage of the vat dye does carry over into practical trial.

Vat dyes are fast to alkali and, when formulated with a fast vehicle, can be used for soap wrappers and linoleum where there is a definite need (particularly for reds) to meet this requirement.

Bronzing is, of course, undesirable.

In the case of beater dyeing of high-grade white papers, vat blues and violets in highly dispersed form can be used to advantage. They are extremely light-fast even in the small amounts used and can be produced sufficiently fine to prevent specking.

I n order to demonstrate the point that vat dyes stand- ardized for textiles do not always produce maximum pigment results, wall paper brush-outs using a clay-glue size were made with (a) a thioindigo pink standardized for the textile trade and (b) the same color reduced in particle size by wet grinding. These brush-outs containing the same amounts of vat dye show that b has approximately twice the tinctorial strength of a. This effect is apparently due to a decrease in the aggre- gate size by grinding. Pigment a settles out of a water slurry rapidly, while 6 stays suspended more or less indefinitely,

The foregoing survey shows that, in spite of a relatively high pigment cost, vat dyes may fit into certain gaps in the present line of pigments and assist in the solution of problems which cannot be easily solved without them. Particularly in the case of pale tints in which only a small quantity of vat color is required, this may be an economical solution to ai problem.

Acknowledgment The writer wishes to acknowledge assistance given by

D. H. Parker and other members of the staff of Krebs Pig- ment and Color Corporation.

PRESENTED before the Division of Paint and Varnish Chemistry a t the 99th Meeting of the American Chemical Society, Cincinnati, Ohio.

Cashew Nut Shell Liquid M. T. HARVEY AND S . CAPLAN, Harvel Research Corporation, Irvington, N. J.

IQUID from the shells of the cashew nut, once an un- desirable by-product of the cashew kernel industry of southern India, has become a valuable raw material in

the manufacture of numerous industrial products. Poly- merization products of this oil, alone and in combination with other materials, have found their way into such diverse uses as insulating varnishes, typewriter rolls, oil- and acid-proof cold- setting cements, industrial floor tile, and automobile brake linings. Industrial uses of shell liquid have kept pace with the gradual growth of the Indian kernel trade which, in imports to the United States alone, grew from 100,000 pounds in 1923 to 27,000,000 pounds in 1937. Up to the present time recovery of shell oil is incidental to the kernel extraction, and much of the oil is wasted. The oil cells of the cashew nut shell are honeycombed and prevent ready removal of a kernel, and the natives have resorted to a crude charring process to destroy the cell wall which permits the oil from the ruptured cell to es- cape. Newer methods of treatment, employing extraction with hot oils, have been developed which remove 50 per cent of the available shell oil. As the ratio of kernel to oil, on a weight basis, is approximately 1 to 1, the oil in the shells of the cashew kernels imported into the United States during 1937 alone amounted to 27,000,000 pounds. Added to this is the potential supply of oil from the large portion of cashew nuts consumed by the natives of India. An estimated quantity (8) of shelled kernels available for shipment during 1938 was put a t 58,000,000 pounds, and with efficient extrac-

L tion methods, 29,000,000 pounds of oil should be available for commercial purposes yearly.

Manufacturing Operations The raw commercial cashew shell liquid, almost solely im-

ported from southwest India, is received in 55-gallon drums and then stored in 25,000-gallon tanks a t the processing plant of the Irvington Varnish and Insulator Company, a t Irvington, N. J. As usual the samples for test purposes are taken prior to any chemical processing. Testing consists of determination of moisture, iodine number, and polymeriza- tion. There are two main specifications for cashew liquid: The iodine number (Wijs) must be over 250, and the material must polymerize to a rubbery mass when heated with a small amount of acid.

The first step in the processing of the oil consists of a light chemical treatment with materials such as hydrocarbon sul- fates and sulfuric acid. This performs two important func- tions; mineral salts are precipitated and there is a reduction in the content of skin vesicant present in cashew shell oil. While still hot, the charge is passed through a plate-and- frame filter press, using wool felt as the filter cloth, and the filtrate is pumped to an intermediate storage tank. The precipitate thus separated has been analyzed and found to consist mainly of the salts of ammonium, calcium, and po- tassium.

OCTOBER, 1940 INDUSTRIAL AND ENGINEERING CHEMISTRY 1307

I n addition to the precipitation of salts, the chemical treat- ment is accompanied by evolution of hydrogen sulfide, and provision is made for proper venting. The reduction of the sulfur content has been found to correspond roughly to the removal of the agent responsible for the skin irritation. By “skin irritation” is meant not merely the corrosive action a t point of application, but the spreading action with formation of blisters a t points some distance removed from point of con- tact (a vesicant action characteristic of poison ivy and other members of the anacardiaceae family). It is interesting to note in this connection, that oil extracted from poison ivy leaves also evolves hydrogen sulfide upon similar treatment. Whether the evolution of hydrogen sulfide during the chemi- cal treatment is actually indicative of the decomposition of a vesicative compound or whether i t is simply a coincidence remains unproved. However, such chemical treatment does greatly reduce the irritating action of the oil, as has been proved by many tests on persons of known sensitivity. This treatment affects only a small percentage of the total oil, since the quantity of oil recovered is nearly equal in weight to the original oil, and the physical constants have not changed appreciably as shown in Table I.

TABLE I. PHYSICAL CONSTANTS OF THE OIL BEFORE AND AFTER CHEMICAL TREATMENT

Raw Oil Treated Oil Iodine No. (Wijs) 269 254 Refractive index, 20’ C. 1.5158-1.5162 1.5212-1.5218 Acetyl value 173 156 Sp. gr., 25’/15O C. 0,958 0.960 Saponification Pr-0. 19.6 2 9 . 7 Viscosity a t 25’ C., centipoise8 400 435

Polymerization The subsequent processing of the oil may take one of sev-

eral courses depending upon the particular application of the finished product. I n general, one of two possibilities exists; the first utilizes the unsaturated nature of the oil and the second makes use of the fact that cashew nut shell liquid is comprised almost entirely of an unsaturated organic compound having a phenolic radical attached.

Alkyl sulfates are used as polymerizing agents in most cases since they are readily soluble in the cashew liquid and allow better control of polymerization reactions than would be possible with an immiscible agent such as sulfuric acid. The polymerized product, when cool, is a thick liquid which easily reacts with aldehydes at room temperature. Aldehyde- reacted material sets to a hard infusible mass, possessing ex- treme resistance to alkalies, acids, and oils. The aldehyde employed for this purpose is usually paraformaldehyde. Reaction rates of the polymerized cashew liquid and the aldehyde can be greatly retarded by increasing the pH value of the oil, and in plant operation the speed of setting is con- trolled by the addition of varying amounts of an alkaline ma- terial to the hot polymerization charge before it is discharged to storage. The aldehyde product is finding application as binder for industrial flooring, particularly in chemical plants and as a tank lining where it is troweled on in the form of a cement. I ts other properties, such as good moisture and elec- trical resistance, have led to its extensive application in elec- trical insulation. Unlike most phenolaldehyde resins, the cashew-aldehyde polymer softens slightly a t elevated tempera- tures and becomes rubbery, even though the product has been cured by baking. This behavior, coupled with low libera- tion of volatile matter at elevated temperatures, has led to the development of a unique industrial application-i. e., as organic fillers for brake linings. It confers high frictional power on a brake lining together with long wear.

When paraformaldehyde is used as a reactant, the product is hard. If hexamethylenetetramine is employed, the result- ing slabs are not hard but are rubbery. The latter product can be milled and in admixture with rubber is used for the manufacture of typewriter platens. Owing to the superior oil resistance of this rubbery polymer as compared with natural rubber, it is a useful blending agent for some of the other more expensive oil-resistant synthetic rubbers.

Courtesy, Ircinglon Varnish & Insulator Company RESIN-COLLECTING SYSTEM PRJOR TO BAGGING

Another polymerization product of cashew shell liquid is a rubbery material resulting from a more thoroughgoing acid polymerization. Its low susceptibility to oxidation has enabled its use as a replacement for rubber in certain types of brake lining, in storage battery separators, and as blending agent for synthetic rubbers, particularly for the production of hard stocks. A mixture of the alkyl-sulfate-polymerized and aldehyde-polymerized cashew liquid has been calendered on cloth, and this “rubberized” fabric shows no signs of cracking or checking after a period of four years.

Aldehyde Condensation The reaction product of formaldehyde and cashew shell

liquid behaves as a drying oil, particularly when a trace of copper is present. Such a product is not subject to saponifica- tion, and varnishes and paints containing cashew liquid as the main constituent of the vehicle are especially resistant to alkali. Such paints are particularly adapted to applications where an alkali-resistant surface coating is desired, as in ce- ment paints. Baking such films confers upon them the addi- tional property of solvent resistance, and this is of specia! importance in such applications as surfacing of laboratory table tops and coating paper liners in bottle caps.

Another feature of the cashew liquid-formaldehyde con- densation product is the relative flexibility of the film after baking. This is in contrast to the brittleness of condensation

1308 INDUSTRIAL AND ENGINEERING ClTl3MISTHY VOI.. 32, NO. 10

products of the lower plieiiols. Combi- nations of cashew liquid and lower phenols therefore lead to formaldehyde resins of enhanced toughness. Combination resins are being used as bindcrs not only for brake linings, but also for laminated paper products; particularly xhere cold punching stock is desired.

Solid condensation products, suitable for molding povden, are also obtained by tho reaction of furfural with mixtures of cashew liquid and the lower phenols.

Distillation A large portion of shell liquid consists

of a single phenol, anacardic acid. The distillate of the shell liquid is an

a.mber-colored liquid, and has most of the properties and reactivity of shell oil with certain important exceptions. It cannot be polymerized so easily or completely to the rubbery state as em the original ma- terial. Its sulfate polymer, however, shows the same reactivity with aldehydes at room temperature as does the corresponding product from the whole oil. In addition, its lighter color and freedom from shrinkage on setting permit several special applies, tions. A mixture of the sulfate polymer of the distilled oil and paraformaldehyde is used in the nianiifacture of water-resistant plywood since it sets a t rooin temperature and w n he used in the same manner as a water-soluble glue. The reaction product of the sulfate, or preliminary, polymer of the distilled oil with hexamethylenetetra- mine is not a rubbery product but a plastic resin. When completely cured this material sets to a flexible mass and is used as a calen- dering compound for cloth and as a plasti- cizer for other resins.

Reaction of the distillate with formalde- hyde leads to B plastic condensation product which differs from the formaldehyde con- densation product of the whole cashew liquid in its much slower speed of conver- sion to the infusible form. Tllis perniitv the manufacture of a product of wrying degrees of polymerization from a liquid to a plastic solid. An outstanding property of these aldehyde condensation products of the distillate is their ready solubility in petroleum solvenb. Such solutions are being widely used, for example, for the impregnation of electrical coils, since the petroleum solvent does not attack the enamel which constitutes the sole insulation of the wire. Another application is its use as an alkali-resistant oil-soluble blending agent for alkyd resin varnishes and wire enamels.

Residue The distillation residue is both phenolic

a i d unsaturated. It reacts slowly at room temperature with aldehydes and may be polymerized, for example, with sulfuric acid or diethyl sulfate. Characteristic of both the a ldehyde r eac t ion p r o d u c t s

OCTOBER, 1940 INDUSTRIAL AND ENGINEERING CHEMISTRY 1309

and the acid polymers of the residue is their high heat re- sistance and extremely low volatile loss a t temperatures around 350” C. For this reason they are being largely used as frictional elements in brake linings, in the form both of plastic resins and of inert ground fillers. The same property is the basis of its use as a cement for mica in certain types of spark plugs.

Chemical Structure and Reactions In 1847 Stadeler (7) published the results of his researches

on the composition of an oil extracted with ether from the shells of cashew nuts. His work indicated that the extracted oil contained two distinct compounds. To one of these, which constituted about 90 per cent of the total oil, he assigned the formula C4H3,,05 and the name “anacardic acid”; the re- maining 10 per cent he called “cardol” and stated that its formula was C42H3104. Recalculation of these formulas, using Stadeler’s own combustion data but employing more recent values for the atomic weights of the elements, would represent anacardic acid as CuHeoOr, and cardol as C42H~104. The former, according to this early investigator, was a fatty acid similar in its behavior to oleic acid.

Stadeler’s procedure was followed by Ruhemann and Skinner (3) who came to the conclusion that anacardic acid was a hydroxycarboxylic acid having the formula C~ZHSZOS.

More recently an investigation of the structure of anacardic acid was made by Smit (4). Working with oil extracted by ether from the rinds of cashew nuts, he isolated the acid, hydrogenated both the acid and its decarboxylation product, and broke them down by oxidation as well as by destructive distillation over zinc chloride. It is his opinion that anacardic acid is a homolog of salicylic acid, having the unsaturated straight-chain hydrocarbon CI5Hzs attached somewhere on the nucleus.

The portion of cashew nut shell oil termed “cardol” by Stadeler was studied by Spiegel and co-workers (6, 6). Its formula is given as CS2HS003.H20, and although its constitu- tion was not definitely determined, it appeared from their work to be a phenol.

Distillation of Commercial Oil Previous work on the chemical nature of cashew nut shell

oil has been performed on oils obtained from the shells by extraction with solvents. Since the commercial oil is a prod- uct of thermal treatment, i t might be expected to differ chemi- cally from the extracted oil. A comparison of the physical constants of two such oils led Pate1 and his co-workers (2) to the conclusion that the two oils were different, and though the extracted oil contained over 90 per cent of anacardic acid, the oil resulting from the heat treatment contained only 16 per cent.

Commercial shell oil having a density of 0.98 at 20” C. was distilled in vacuo, and an oil of practically constant boil- ing point (225” C. a t 10 mm. mercury pressure) was obtained. Little evolution of any gas, such as carbon dioxide, was noted during the distillation. Similar results were obtained by steam distillation. I n each case the distillate darkened with age, but oxidizing treatment, such as heating with 30 per cent hydrogen peroxide solution followed by redistillation, serves to stabilize the pale yellow color. The physical constants of the distillate are as follows: boiling point, 360” C. a t 760 mm. and 225’ at 10 mm.; density d:’, 0.930; refractive index $2, 1.5113; melting point, below -20” C.

In addition to the main portion of the distillate of constant boiling point, a first fraction of lower boiling material was ob- tained with a nicotinelike odor and a propensity for rapid darkening on exposure to air. This fraction, which amounted to about 5 per cent of the original oil, contained 0.64 per cent nitrogen.

Chemical Structure of Distillate The main portion of the distillate appears to be a single

compound by reason of its constant boiling point and other properties. As already noted, i t reacts with formaldehyde to produce a resinous body. It also reacts with acetyl and ben- zoyl chlorides to form the corresponding esters and with diethyl sulfate to yield an ether. Alkali metal salts have been prepared and found to be insoluble in water. Molecular weight determinations by the cryoscopic method in benzene give the value 278. From this and other experiments in which various compounds were formed, the authors have assigned to the compound, obtainable from commercial cashew nut shell oil to the extent of about 70 per cent, the following structural formula :

OH n The meta position of the side chain was determined by oxida- tion of the ethyl ether to the ether of m-hydroxybenzoic acid. The name “cardanol” has been applied to this compound by the authors to indicate its phenolic nature as well as its origin from the fruit of the Anacardium occidentale.

The fact that the side chain of cardanol contains fourteen carbons and only one double bond is somewhat at variance with the formula assigned to anacardic acid, which constitutes the principal constituent of the oil obtained from the shells of cashew nuts by solvent extraction and which is represented by previous investigators, notably Smit (4) , as having a side chain of fift,een carbons with two double bonds. Whether this represents an actual difference in the composition of the two oils or whether it is due to analytical inexactitude is not cer- tain. In most of the work on the extracted oils, only small quantities of material were employed, whereas in the present investigation, drum lots of the commercial oil were available. Also the quantity of hydrogen absorbed in hydrogenating cardanol proves one bond rather than two.

Chemical Reactions of Cardanol Commercial cashew nut shell oil is nontoxic when tested

on white mice in accordance with the method described by Hale ( I ) . Its only apparent effect when taken internally by human beings is a slight cathartic action. I n cardanol, there- fore, we have a nontoxic phenol which may have interesting physiological applications.

The resin formed by treating cardanol with formaldehyde is readily soluble in drying oils, no matter what catalyst is used in the reaction with formaldehyde. Even when the cardanol is mixed with twice its weight of cresylic acid and the mixture reacted with formaldehyde using ammonia as a catalyst, an oil-soluble resin results; cresylic acid under the same conditions produces an oil-insoluble resin. This prop- erty of yielding oil-soluble resins has been generally as- cribed to phenols with para substitution, whereas in the case of cardanol we have a meta-substituted phenol, which indi- cates that not only the position but also the chemical com- position of the substituent group is important. These solvent properties of cardanol-formaldehyde resins can be advan- tageously used in alkyd resin reactions wherein the finished product has increased tolerance for petroleum spirits. Car- danol couples through its unsaturated bond with other phe- nols, and the ethers of cardanol react likewise, giving a unique phenol ether which can be sulfonated to obtain excellent wet- ting agents.

Hydrogenated cardanol, by reason of its color, miscibility with a large variety of organic substances, lack of odor, and

1310 INDUSTRIAL AND ENGINEERING CIIEMISTRY VOL. 32, NO. 10

low volatility (boiling point, 380" C.), is apparently well thereby confer greater miscibility with ordinary solvents and fitted for use as a fixative in perfumes. The same properties, greater water resistance on the final resins. These and other coupled with good solvent action on cellulose acetate, should uses await further commercial development of this material. make it suitable for use as a plasticizer for cellulose acetate lacquers and molding compositions.

The alkyl ethers of hydrogenated cardanoi are stable Li terat ure Ci I ed

(I) do, Worth, u. 8. Pub. I i d t h Servioc, ~ ~ i e l i a c Lab. ~di. 88 liquids of high boiling point. The ethyl ether boils at about 365" C, and can be boiled at this temperatllre with no appar- ent change. This compound may find utility as a substitute for mercury in hi-liqiiid boilers, as well as for geueral heat transfer applications. (1913).

by the reaction of cardanol with chloroacetic acid, may be substituted for a portion of the phthalic anhydride in the preparation of alkyd resins and

(1913). (2) Peal. c. K.3 el ai., J . Indian I%*t. SCi.. 5, 152 (1922). (a) Ruhwnenn. 8.. and Skinner, S., J . Chsn . Soo., 51. 663 (1887).

smit, A, $, w,, proc, A&. sei, Ama2e7hm, 34, (5) spiogei. L., and correii. M., &r. deut.

(6) SPieEcl. 12.. and Dobrin. C.. Ibid.. 5, 309-25 (1895). (7) Stncieler. Ann. CAern. u. PFhannacie, 63, 137-64 (1847).

(193,). ees.,23, 356-78

&.,,janoxyacetic u. s. Commoroe, ~ ~ , , ~ ~ ~ ~ ~ 'Round World, *, No, 5, (1838).

Evaporation Rate of Stoddard Dry Cleaning Solvent CHARLES S. LOWE AND A. C. LLOYD National Association of Dyers and Cleaners, Silver Spring, Md.

Apparatus designed by Thorn and Bowman for determining the evaporation rate of solvents at high temperature by passing a measured volume of air through solvent maintained at constant temperature has been utilized, in a modified form, to obtain evaporation curws of dry cleaning solvents. The results with this technique correspond to those obtained under conditions similar to plant practice by following the loss in weight of fabrics containing the solvents and suspended in an oven equipped with air circulation.

Evaporation rates of commercial dry cleaning solvents vary widely. Distillation curves do not provide adequak information as to evaporation characteristics. The effect of small amonnts of fatty acid and mineral oil residues on evaporation rates is shown to he negligible.

HE time required for tho complete evaporation of Stod- dard dry cleaning solvent from cleaned garments so that no trace of solvent odor remains, is largely governed by

the particular solvent being used, and by the temperature and air circulation employed in the drying operation. Under noma1 conditions for deodorizing, exhaust vapors leave the tumbler or drying cabinet at 120-1FO" F., depending on the type of garment, and are accompanied by a rapid flow of air; wide variations in the drying time of Ytoddard solvent

T

from dieerent refineries have been noted. Whcn the drying period is lengthened to provide adequate time to remove a more slowly evaporating solvent completely, more steam and electricity are required to operate the tumbler or cabinet, more stains are probably set owing to long exposure to the heat, the cleaning cycle is longer, arid production is slowed down. This investigation was undertaken to devise a labora- tory test to place such variations on a quantitat.ive hasis, and

firoun~ 1. MODIFIED TXOXN-BOWMAN Am*-

SOLVENT^ AT H I ~ H TEMPERATURES RATUS FOR DETERMINING EYAPORATION RATE OF