Sept., 1921
T H E JOC'RNAL OF IXLICSTRIAI, AiVD E.\-GINEEXING
CHEMISTRY
831
European Practice in Cellulose Acetate and Dopes During the War By Philip Drinker Laboratory of Applied Physiology, H a r v a r d Medical School, Boston, Massachusetts.
A l t h o u g h ninny sitbstances have been suggested and inany formulas deleloped for the coating and preservation of airplane fabrics, with the exception of the relatively noninfiarninable cellulose esters typified by the cellulose acetates, none have received governmental recognition for any extended period of time. I n this connection, the cellulose nitru tes h a r e received but minor consideration, primarily on awount of their greater inflammability, combined with the fact that they do not exhibit properties other than those shox? n by the corresponding acetic esters. An historical account of the development of airplane dopes necessarily involves an account, first, of the trial and rejwtion of cellulose ester substitutes. and secondly, of the impro~ementof the many combinations and modifications in which cellulose acetate enters as the primarily solid constitnent. So far as the writer is aware, the most complete and comprehensive data on the general subject of airplane dopes and cellulose acetate thermoplastic combinations are contained in a 1050-sheet tjpewritten Report 10,086 of E. C. Worden. made in 1915, and the 5040-sheet typewritten Report 13,228,Kith index, of E. C. Worden, Philip Drinker, J. S. Buford, Leo Rutstein, and R. G. Dart,+ made in 1919, to the Bureau of Aircraft Production in Washingtonrepoi ts einbodyii7g the results of extruded investigations made by the writers abroad and in the United States. Many of the facts and figures incorporated in this article have been abstrackd froin these reports.
tined for the front to be coated with acetate dopes, nitro dopes being liinited to training planes. This procedure was identical with that of the British.
COMMERCIAL DE\ ELOPRfETT O F c1:1 LLLOSE -1CEThTC Prior to the summer of 1914, cellulose acetate was manufactured in commercially interesting quantities by only three European firms, cix.; the B a j er Conipany at Leverkusen, the Societe Chimique des Usines du RhSne a t Lyons, and the Cellonite Company (Dreyfus Bros.) at Basle. Bayer acetate was used by certain British firms and is reliably reported as being satisfactory, while that furnished by the French companq- was also received with favor. I n F';.ance the Usiiies du RhBne product was in general use, so that the outbreak of hostilities found the British depending for their supply on their French Allies and on the product of a neutral couiitry, no adequate supply of German acetate having been accnmulated. As the \\Tar progressed and their aircraft program augmented, the French required more and more of their own product, with the result that shipments to Great Britain were reduced to a minimum. The British program called for an ninouiit of acetate soon evident t o be f a r in excess of the assured supply, coming a s i t did from outside sources. This state of affairs resulted in negotiations with the Dreyfus BIOS.' wherehy the election of a large plant for the manufacture of cellulose acetate was undertaken a t 111 ICurope, a t least, the term d o p e n a s in use in 1914* Sponden, England. This plant also included a synthetic a s indicating the iiitrocellulose and cellulose acetate solu- acetic acid and acetic anhydride unit. To assure further tions which are applied to airplane fabrics to impart in- their own supply, a similar but smaller Dreyfus plant was creased tensile strength, tautness, and resilience, and to in- built by the French at Rouen, while plans for n Dreyfus crease impermeability. Present practice requires the sev- p l m t a t Milan were laid down by the Italians. This examem1 coatings to give a total weight increase to the fabric ple was later followed by the United States at Cumberland, of approximately 2 ousces per rquz!,lc >7au.d (60 t o 70 Md. Throughout the war, the French used the Usines du RhBne product in g i eater gart-a !irodv,ct characterized by grams per square meter), and i.3 retpili their protecti.de its uniformity in the chemical and phvsical qualities essenbeneficial qualities on exposure to atmo;pheric wea thcring conditions, usually for periods of 60 to 90 days. These tial for dopes. With the completion of the Dreyfus English plant, British dopes were made almost solely from this specifications are the outgrowth of experience duriiiq the latter source of acetate, a state of affairs prevailing a t war, at the commencement of which requirements w w e the close of the war when a standard dope formula, obligless rigorous. atory for all manufacturers, had been developed. That the 9 n accounL 01 m e various ereiicn aopes nas Deen grven Dreyfuss acetate successfully met the specifications for by M. I)eschjensP2 who records the use of nitroceilulose this standard dope over an extended period is sufficient conting, in 1596, on a balloon destined for polar exploration. proof of its uniformity. In tlits case the dope was purely for protection and not for The cellulose acetate resources of Germany have been taut+ning effects. Substitutes such as casein, glue, gelatin, st:irch pastes, rubber, etc., have been tried a t various times, said to be greater than those of the Sllies. The acetate of the Bayer Coinpany has already been mentioned as one of in both England and France, but their use has never passed llie three ( y p ~ sproduced i n Europe a t the outbreak of the beyond the experimental stage, and, a t the outbreak of the war. Personal Tisits 1 j E. C. T'VordelP and the \Triter,' war, the use of nitroccllulosc and cellulose acetate dopes 011 behalf of the Bureau of Aircraft Production, to a mas firmly established in Europe and existed to a certain extent i n the United Slates. A s a result of its greater in- sinall plant u t illainz showed an additional source which is known to have been utilized by the Gernians during the R:imin:ibility, ilie nitrocellulose product mas soon rejected war. Samples of gelatin-coated gas-mask eye pieces, made by the French. while, as the war progressed. the British of cellulose acetate, from tile dlrtieiiqesellscliaft f i n Anilin progrmn called for a like procedure when adequate supplies Fabriliation mere also 01 s e n ed froin time to time. Fabrics of celluiose acetate were available. Marked preference was from Gernian and ilustri,in planes invariably showed cellua190 ~ h o w iby ~ the Italians for cellulose acetate dopes. The e x m ~ l i l eof the other Allies mas later followed by the United lose acetate dope, and, knowing their plant resources, it is States, the American program calling for all planes des- but reasonable to presume they had no special difficulties In meeting requirements, although no reliable data are Piesented before t h e Section of Cellulose Chemistry at the 61st :ivailable LO us on thejr cellulose acetate output. All the Meeting of t h e American Chemical Society, Rochester, N. Y , April 26 t o 29, 1921. [?]ants known to have been engaged in its production mere e Published by permission of t h e Chief of -4ir Service, U. S. Army. located far froin the front, and evidences of destruction of ' Xiituber i n t e x t refer t o Bibliography at end of paper
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their chemical factories by Allied aircraft were not apparent. I n fact, the general atmosphere of the enemy chemical plants, a s disclosed from visits to their factories in the occupied region, was decidedly one of prosperity and preparedness for the future. CHEMICALCHARACTERISTICS OF CELLULOSE ACETATE Of the many variations in processes used for the production of cellulose acetate all employ the same basic principles, uix.; acetylation of cellulose by glacial acetic acid and acetic anhydride in the presence of a catalyst such as sulfuric acid. The Dreyfus processes' involve the use of paper 8s the preferred source of cellulose, while it is understood that the Societe Chimique des Usines clu RhBnes employs a long-staple cotton, previously treated. For airplane dope, in both cases the objective is an acetone-soluble acetate, between the diacetate and triacetate in acetic conieiit, which is attained by acetylation temperature control Rnd the subsequent ripening process. I n an exhaustive stndy of the subject, E. C. Worden8 has traced the devcilopment of cellulose acetate from the carbohydrate acetglat ions of Schutzwberger through to the modern period, and has pointed out the iinportance of the Dreyfus discoveries in the development of this art. In this article, he shows that the acetates preferred for photograph films and artificial filaments differ fundamentally from the product used for dopes, the former demanding clarity a s an essential characteristic, while the latter must possess relatively %renter tensile strength, clarity of the dope film bring of less importance. Primary acetates, possessing acetone soluhility as a perinanent characteristic, and having passed through the chloroiorm-soluble stage, are among the qualities necessarj for dopes in \.\ hich chlorinated solvenls do not enter. M. Ost,'O C. Cross and E. Bevan,ll and G. J. Esselen, Jr.IZhave contributed to the literature on this subject, the last author discussing the colloidal nature of the cellulose acetate molecule and distinguishing the chloroform and acetone-soluble acetates by the solvents which may be employed. Of the Usines du Rh6ne and Dreyfus products, the former generally possessed the inore rapid acetone solubiIity, due perhaps to finer state of mechanical division of the particles. Dreyfus aimed to produce an acetate of relatively higher viscosityln which could be applied in a threecoat doping scheme, and which would give a film of tensile strength equal to that formerly attained by applying as many as six coats. This resulted in a substantial solvent economy so iniperative in the successful prosecution of the British aircraft program. SOLVENTS, DILUESTS, PLASTICIZERS, ASD PIGMENTS The selection of solvents and solvent conibinations was determined by each country primarily from the resources available, a condition which prevailed throughout the war, aiid which underwent a gradual development resulting in the ultimate adoption of standard formulas. Since over fifty different solvent combinations-a nuinher of them secret-emanating from the Allied governments and from firms supplying dope, were suggested and used a t one time or another, a detailed historical account would be inexpedient. The subject can well be covered in a review of the essential points of difi'erence of the various combinations, a s their use developed during the course of the war. The use of tetrachloroethane a s a solvent was prohibited by France, and later by Great Britain, because of its toxicity and tendency towards decomposition, as result of which 1he fabric: %vas materially weakened. Actual fatalities14 ~57eretraced to the toxicity of this solvent. The work of W.
Vol. 13, No. 9
\\'illcox, B. Spillsbnry, and T. Leggels showed that a characteristic type of toxic jaundice, affecting the liver, developed from inhaling tetrachloroethane fumes. Both countries, and Italy a s well, prohibited the use of chlorine substitution products, a n example followed later by the United States. Consequent to these discoveries, the British enforced rigid ventilation of their doping shops and required at least thirty changes of air per hour. Somewhat before our entry into the war, the French mere using a four-coat dope designed for purposes of camouflage, which at that time was considered by them to be indispensable. A typical French dope, patented under the trade name of Acellos by Nauton Freres et de Marsac, the patentee being their chemist, T. Tesse,l6 was in special favor, while I,. Clement and 0. Riviere" produced a somewhat similar product. I n AceZEos dope the scratch coat contained 3 to 5 per cent acetate and was low in high boiling solvents, by which means greater tautening effects were said to be produced. The second and third coats required 8 to 9 per cent acetate and about 2 per cent of mineral or metallic pigments, t h e vehicle for which was usually eugenol, while other high boilers and pdasticieers, such a s benzyl alcohol, triacetin, isoeugenol, carvacrol, safrol, isosafrol, methyleugenol, and glyceryl benzoate, could be employed. The fourth and final coat required about 8 per cent acetate, while the high boilers were again cut down. The under surfaces of the planes received second and third coats of aluniinium color and upper surfaces were given a variegated camouflage scheme intended to resemble the enrth's surface. Planes used in night flying were colored dark, the dopes being applied exactly a s were those for the day planes. None of the French plnnes destined for the f r o m received a varnish coating of either oil o r nitrocellulose base. This treatment was claimed t o impart special characteristics of tautness aiid to increase invisibility of the plane from both above and below, a n idea which gradually lost fa\or until, a t the end of the mar, the French followed the British example and adopted colorless dopes with a finishing coat of khaki color on upper surfaces. Byitisli practice went through a similar but seemingl> more logically coijrdinated and technically controlled development. While the French relied mainly on methyl acetate of local innnufacture for their low boiling solvent, the British had recourse priiicipally to acetone, furnished in large part by the United States and Canada. In a general report, J. Rnmsbottom2 discusses cellulose acetate solvents and poiiirs out the latent solvent effects of a mixture of benzene and alcohol, each of which in itself is a non-solvent at ordinary temperatures, a point mentioned later by G. J. Esselen, Jr.I8 EEorts to obtain a satisfactory threecoat standard formula requiring the maximum amounts of the iioii-pyroligneous products, ethyl alcohol and benzene, resulted in 1916 in a British formula1.18 in which acetone, methyl acetate, ethyl formate, or methylethylketone could be used a s the low boiling solvents, alcohol and benzene as the diluents, benzjl alcohol a s high boiler, and triacetin and triphenyl phosphate as softeners.'# To these lists the French added a locally manufactured low boiling product, known a s C.G.H., which consisted in a mixture of approximately 70 per cent methyl acetate, 16 per rent acetone, 12 per cent methyl alcohol, and 2 per cent water. I n addition to the high boiling solvents already mentioned, the French suggested acetoacetic ester and furfurol, and towards the end of the war, amyl and isobutyl alcohol,*' of which a French firm offered a consiclerable supply. r)echitns3 mentions their having investigated i n addition the following substances : methyl, ethyl, amyl,
Sept., 1921
T H E J O U R N A L OF I N D U S T R I A L A N D ElLTGlNEERIhTG C H E M I S T R Y
and butyl lactates and oxalates, glycol diacetin, benzylidene diacetate, diphenyltolyurea, and cresol,la none of which passed beyond experimental stages. CyclohexanoL and cyclohexanonez3 were also suggested froin both Rritish and French sources, but were never used in any quantity, although said to be efficient. Acetic and formic acids were used experimentally as solvents and did not appear to weaken the fabric materially.% Unlike the British, the French dopes contained no solid softeners such as triphenyl phosphate, although the French had attempted using both this and tricresyl phosphate, principally as fire retardants.m Having adequate supplies of phenol, the Italians generally used a sinall percentage of this substance-2 to 3 per cent, depending on the type of fabric for which the dope was destined, Their formulas, like several of the French ones, were varied somewhat in winter and summer to compensate for rapidity of solvent evaporation. The Italians permitted a certain latitude in the choice of low boiling solvent combinations and also used no tricresyl or tripheiiyl phosphates. The United States developed a standard four-coat scheme in which the scratch coat contained a small percentage of phenol and nspthalene, and, a s antacid, a small percentage of urea or dicyanodiamide. For t h e three subsequent coats, there was included in the formula about 7 per cent of diacetone alcohol, principally to prevent blushing, with small amounts of benzyl acetate and benzoate. The United States’ formula embraces the greatest number of ingredients, but it must be remembered that this formula was based on supply and economy in local resources. GERMANAND AUSTRIANPRACTICE Critical periodic examinations of enemy fabric obtained from captured or destroyed aircraft, both lighter- and heavier-than-air, disclosed a few important points differentiatiug their fabric and dope from those of the Allies. The enemy planes were frequently camouflaged in multicolored dyes, printed on the fabric i n polygonal designs. The airplane fabric was usually linen, showing evidences of heavy calendering, with a thread count averaging about 55 to 65 per inch for the warp and 45 t o 55 in the weft. The tensile strength gave average minimum figures of 70 to 80 pounds per linear inch in the warp and 65 to 75 pounds in the weft, but i t must be remembered that these figures a r e taken from used fabrics which had undoubtedly deteriorated to an appreciable extent, so t h a t the tensile strength figures a r e probably lorn. I n most instances the doped fabrics were covered with an alcohol-soluble varnish, colorless or pigmented, showing a dry weight increase due t o t h e varnish of anything from 0.5 to 2 ounces per square yard. The dope films were of notably Iess weight t h a n those used by the Allies and were in t h e neighborhood of 1 t o 1.5 ounces per square yard. Comparative analyses of scrap Allied fabric showed at least 2 ounces of dope film per square yard and frequently more. A few German fabrics showed evidences of chlorinated compounds as cellulose acetate softeners, but extraneous m a t t e r was, in general, not found to be present. METHODS OF APPLYINQ DOPES Siuce the major percentage of ingredients of both cellulose acetate and nitrocellulose dopes is made up of low !soiling hygroscopic liquids, their evaporation is rapid, a n effect in some measure retarded by the addition of softeners and high boiling solvents. I n both types of dope the cellulose Ester can readily be precipitated by the addition of water, .which explains the formation of the white spots or
833
blushing so familiar on fabrics doped in damp and excep tionally drafty doping shops. Directions by the manufacturers and by all the governments required the dopes to be applied to dry fabric, while the United States alone enf o i ~ e dany attempt a t humidity control, the European Allies merely suggesting its advisability. Great Britain and the United States both required special brushes, approximately 4 inches wide with 2-inch bristles firmly fixed in the stock, a special brush wash being supplied in which the brushes were kept when not in use. Special cans were provided by Great Britain and the United States, these being designed to hold a conveniently portable quantity of dope of which a minimum of surface was exposed. Towards the end of the war a British firm developed a type of brush, through the handle of which dope was fed b9 air pressure, the dope being contained in a standard 10-gallon (Imperial) can. This brush, however, received no general usage. Both British and French made it a practice to save the skins or films which formed on the edges of the dope cans, these films being furnished to the manufacturers, who again used them, with judicious blending, in making up fresh dope. Cellulose acetate doped fabrics, unprotected by a varnish coating, temporarily lose their tautness on becoming soaked, the tautness again becoming normal on the fabric’s drying. This effect was most noticeable on French planes doped according to their four-coat scheme which required no varnish and no solid softeners. H. GaultAe and the writer have taken advantage of this in a patent application for a process in which fabric, both linen and cotton, is mechanically coated with a cellulose acetate dope by spreading machine, for example, on both surfaces. When a wing or other member is to be covered the doped fabric is soaked in water and applied, moist, to the frame. When dried and varnished the fabric attains the required degree of tautness, while at the same time other properties conferred by dopes applied i n the conventional manner a r e claimed to be eqnaled. The signing of the armistice prevented further investigations as to the value of this process, although laboratory and large-scale tests gave every indication that it had decided practical commercial possibilities for aircraft and possibly for other industries. Great Britain and the United States very generally applied varnish covers and the colors for the insignia or identification innrks by a i r brush. This method of application can be used for oil or nitrocellulose varnishes with equal facility, but no cellulose acetate dope which could be sprayed was developed, although a certain amount of experimental work mas done.2T
EFFECTOF SUNLIQHT ON DOPEDFABRICS It has been shown how important a factor was the question of supply in determining the various dopes used by the Allies; no less important mas this same factor in standardizing the types of fabric. I n place of line the United States gave precedence to a mercerized cotton of the type developed through the investigations of the Bureau of Standards, notably by E. Wa1enZ8 This cotton fabric fulfilled the specifications of the Allied countries, although its general acceptance and recognition was slow. I n England linen made from Irish flax was preferred although cotton had fairly general acceptance, while France used .. mien, cotton, and silk. From her own resources Italy obtained silk, and both France and Italy, purely from economic reasons, used considerable quantities of this fabric in spite of its high cost. It has been stated that both France and Great Britain abandoned the use of tetrachloroethane as a cellulose acetate
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T H E J O U R N A L O F I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
solvent in dopes because of its toxicity and tendency to deconipose. The cause of this decomposition was frequently ascribed to sunlight, although investigations a t the beginning of the war do not appear to have been carried out t o prow this point. The fact that both nitro and acetate doped fabrics gradually deteriorated, with a consequent loss in imperineability and tensile strength, was well recognized, but lio meaiiS of retardation by agents, other than varnish, appears t o have been attempted. During 1918, F. Aston, a t the Royal Aircraft Establishment, England, showed that the destructive action of snnlight o n fabric, not the dope filin, was principally due to ullraviolet light of wave lengths lying between 2950 and 4000 p, and that the effect of these rays could be diminished by interposing an impervious layer or pigmented film. After testing various media, Aston showed that their coateffectively impeded the destructive action ing, P . C . of sunlight. This particular varnish has a base of nitrocellulose and khaki colored pigments of yellow ocher and lamp black, rendered plastic in a vehicle of castor oil. One coat of this varnish was applied by hand or air brush on upper suraces of British planes. Following hston’s work, it was shown by others, notably the French, that the action of sunlight was more serious on silk than on cotton or linen, a point of interest to the Italians and A three-coat pigmented doped1 was suggested by the British for Handley-Page night bombers, the resultant color scheme being much like that already in use by them a t the time, except that under surfaces were also colored. The formula used for these pigmented dopes mas very close to their standard and differed from the French colored dopes principally in the use of triphenyl phosphate, of which the British made much point. Although the British pigmented dopes showed coiisiderable promise, they had received but limited application a t the signing of the armistice. SOLVENT RECOVERY~~ Solvents lost in the doping of aircraft fabrics were relatively small, coinpared with the solvents used in the manufacture of nitrocellulose powder, and it was quite natural that their recovery was of secoiidary importance in the question of solvent economy. By the centralization of plants engaqed in covering aiid doping airplane parts, solvent recovery was in a fair way towards practical realization at the close of Lhe \.\iar, so that a brief account will be given of two processes used in Europe. L. Cleinent and C. Riviere attempted recovery by scrubbing the solvent vapors in cold water, a small plant for this purpvse being built near Paris. The, airplane wings were placed in horizontal troughs, of convenient height for the workers to cloyc, nnd the solsent vapors were drawn by fan down through a pipe running along the floor and thence to a scrubbiiig tower where the vapors niet a descending shower of cold water, contact surface being furnished by coke. A number of doping troughs were connected iu parallel t o the vnpor pipe, each trough having a damper for connecting inlo the system. Rolling curtains were placed aero% the end of each, and as doping progressed one curtain was rolled up mid the other unrolled, thus affording a slight degree of control on the solvent content of the air entering the scrubber. The aqueous solutions a t the bottom of the scrubber contained approximately 2 t o 3 per cent of recoverable solvents with a total j;ield of about 30 per cent. The solvents cnptured FT ere necessarily limited to the water-soluble, although the solubility of such substances h S benstne, o ~ i i n a r i l ymater-insoluble, is enhmced by the 1wesenc.e o i benzene solvents which in theinselvee are water-soluble. It is understood that the inventors
Vol. 13, No. 9
c1:iinied better yields could be effected, but no evidence a~ililablelo the writer shows that this mas accoinplished o n a scale of commercial interest. For the recovery of ether-alcohol in the gelatinization and drying of nitrocellulose pov-cler, the process of J . Bregeat,*’ which utilizes cresol, received extensive application during the war. I t had been shown that certain phenolic bodies formed addition products with solvents such as acetcneY’ which could be liberated on heating, the coniplex dissociating into its original components. Bregeat used this basic principle in attempting a substitute for sulfuric acid as an agent for ether-alcohol recovery, and first suggested the sulfonic acid of benzene but later found that cresol alone served as well and, in addition, mas cheap and available in large quantities, The inventor claims the possible recovery of a number of volatile solvents, among which are the methyl, ethyl, and amyl alcohols and acetates. acetone, benzene, toluene, xylene, and chloroform, from which it will be seen that the process is of interest in the cellnlose acetate industries. Yields of 75 per cent of the solvents entering the system are guaranteed, while 92 per cent yields are said actually to have been obtained, figures which are supported by 31. D e s c h i e n ~ . ~ ~ The success of his French plants, notably at Ripault, Sevran-Livry, and Toulouse, was such that Bregeat’s process was recognized in Italy and England, where plants were built for ether-alcohol recovery. At H. M. Factory, Gretna, England,’: sulfuric acidSo had been aLiantloned aiid an experimental cresol plant installed, independent of Bregeat’s engineering supervision. This plant proved so successful that a larger unit was undertaken, but mas not firiehed until t l e close of the war. The plants built by Bregeat usually include three scrubbing towers in which a large contact surface is obtained by a system of horizontal lattices of wood, scrubbing taking place on the countercurrent principle. At Gretna, rotary scrubbers made by the Whessoe Foundry Company were used, these being built up in twelve compartments giviiig a twelve-stage absorption. Contact surface was obtained by V-shaped wooden sectors, about one-quarter of an inch in thickness and sufficieiitly close together t o pick up a film of cresol through which the solvent vapor passed as the scrubber slowly rotated. F o r tlie liberation of ether-alcohol from cresol, Bregont usually employs heat alone, while at Gretna live stearn was considered essential. I n either case the distilled solvents are subsequently rectified, while the cresol is returned to tlie scrubbers. It has been shown in aircraft manufacturing that the weight decrease of freshly doped fabric proceeds a t a fairly uuifc;im rate for the first 15 to 20 minutes, after which solvent evaporation rapidly falls off. Tests, with cresol as the absorbent and using the standard British dope (D.lOO specification), shoffed a yield of 50 to 60 per cent, with reliable indications that this would be exceeded in largascale operations. Whether the fabric be doped in a verticd position from both sides a t once or horizontally, is of no ii!oinent as regards the effect of the dope, but the former rnelhod is more rapid and will therefore give greater concenty;uion of the solvent vapors in the air passing to tile scrubbers. Vrrtiml doping was adopted by the T‘oisin Coinpnny in whoat: aircraft works, near Paris, a Bygent recovepy plant mas completed a t the signing of the armistyce. With Iocally devised improvements in the doping wbinets, all such modifications having as an objective t w increased solvent concentration entering the scrubbers, this plant possessed the equipment then believed the best obtainable and endorsed by the Allied services.
Sept., 1921 RECOVERY OF
T H E J O U R N A L OF I N D U S l R I A L A N D ENGINEERING C H E M I S T R Y CELLULOSE
ACETATEF R O M FAERIC
SCR-4P
835
AIRPLANE
T o alleviate its shortage, investigatioas were undertaken both by independent firms and by the Allied governments towards the recovery of cellulose acetate from discarded airplane fabric, with the object of its resolution as such or mixed in part with fresh acetate. Mention has been made of the fact that the French used only cellulose acetate dupes on all planes, while the British used nitrocellulose dopes 011 training planes and finished off the S-U. S. P a t e n t 1 030 311 (1912) . 1 1 9 1 439 ( 1 9 1 4 ) . 1 258,913, 1,216,462 (1915) ; U.' S. kppl. Ser. 3$,7d7 (i915) ; Brit. 'Pa'tent 25,combat planes Tyith a nitrocellulose varnish for protection 893 ( 7 9 1 2 ) . 13 696 (1914) . 7,763, 7,773, 8,046, 1 0 8 2 2 ( 1 9 1 5 ) * against ultraviolet light. Of the two systems, the French 128,911 ( l Q i 9 );' French P a t k n t 437 240 (1911) ' 473,'390, 477,620: 436 (1914) . Addn. 20 072 ( 1 9 i 5 ) to 473 3'99 ( 1 9 1 4 ) * Swlss afforded the better opportunity for cellulose acetate 're- 478 P a t k n t 59,412 ( i m ). S_S,690, 71,696 (1914) ;'71,991, 77,6b3, q 108 ( 1 9 1 5 ) : D. R . P.' 208,879 (1910). D. R. P. Anm. ( J u n e 20 covery, inasmuch a s the British required the separation of 1913) . ( J u n e 1 2 , 1 9 1 4 ) ; ( J u n e 1 2 , $915) ; Can P a t e n t 139,048 the two esters. (19125. Of the several recovery processes suggested, all operated 9-E. Worden, J . Hoc. Chem. I71d., 3 8 ( 1 9 1 9 ) , 370t. on the extraction principle and differed only in the choice 10-Z nngeu;. O h e m . 3 2 ( 1 9 1 9 ) 6 6 7 6 8 2 . abst. C . A . , 13 (1919),'2670; J . Soc. C'he?;. I n d . , 38 (1819): 335;. of solvents and in certain details of mechanical manipu1 1 - 4 . Soc. Duers Uoiour., 36 ( 1 9 2 0 ) , 19. The Soci6tB Generale d u Coton IndustrielZ1 lation. 12-J. J??& Eng. Chem., 12 (19201, 8 0 1 ; C h e m . M e t . m y . , 23 suggested the use of cresol or furfurol as solvents, but it (19201, 861. is understood that the former alone was used. This pro13-Eritish Air Board Specification D-6, J u n e 1918. cess requires extraction at temperatures i n the neighbor14-The L m c e t , December 26, 1914. hood of 40" C., filtration of suspended mineral pigments, 15-2'roiss. dlerl. Soc. L o i i d . 38 (1915). 129. See also TV. Wilcox. and precipitation of the cellulose acetate by benzene, fol- Brit. N e d . J., PeDrunrl! 2 6 . 19'36. T. Legge, J . J n d . H~/,G.,2 ( 1 9 2 0 ) . 0. A . , 15 (1021), 282. 1 2 1 ; abst. lowed by its purification with steam under reduced pressure, 16--Rrit. P a t e n t 124 7 6 3 124,844, 126,989 (1916) : 131,309 by which means it is claimed the acetate is not injured. (1918); J . Soc. C h e m . I?&., 58 ( 1 9 1 9 ) , 319a, 5 3 h , 7 5 9 ~ ;C . A . , 13 (1919), 1771. The acetate thus recovered is undoubtedly degraded to a certain extent, but i t is claimed to be satisfactory for dopes 17-U. S. P a t e n t 1,173 9 3 1 . Fr P a t e n t 4 6 1 088 479 387 ; absr. Bull. soc. encozw. i n d . nali., i z i ( i g i 4 1 , 1871 ; ' J . Boo. Ohem. ~ n d . , when mixed with fresh acetate. 33, (1914), 3 2 0 . 3 4 ( 1 9 1 5 ) 7 5 : 3 5 ( 1 9 1 6 ) , 4 6 5 , , 1 1 6 4 ' C A 9 J. Lumsden and R. Mackensie3* proposed the use of (19151, 1253 ; Id, ( 1 9 1 6 ) , l i 0 4 , 2308. See also .C7?zmze &'titrhst'&e 1 (3018) 5 6 0 ; 3 ( l 9 2 0 ) , 440. .4. Fuchs, C h m i e & iizdustri?, 5 solvents such as acetone for extracting the cellulose acetate. (i920), i67. I n one sense this would be a n improvement over cresol, as 1 8 4 . Z%d. Eizg. Chem., 10 ( 1 9 1 8 ) , 135. the acetate need not be precipitated from solution but 19-British Air Board Specification D-100, March 1918. fresh dope could be made up with this a s a basis. 20-On use of acetanilide as softener, see B r i t i s h Emaillite ComOther solvents suggested were nitrobenzene, mixtures of pany a n d J. Goldsmith U . S P a t e n t 1 2 9 5 1 9 9 ' B r i t P a t e n t 124 515 abst. J . Soc. b h e m . ' I n d . , 38 '(NiQ), 378a,'472a; 0. A:, 13 methyl and ethyl alcohols and acetates, and tetrachloro- (( 11 99 11 69 )) ,; 1771. ethane. None of these niethods m7ei-e investigated on a scale 21-J. Grolea a n d J . W e y l w , Brit. P a t e n t 123,712 (1318): ahst., of commercial interest over any extended period, mainly J . SOC. Chem. I n d . , 35 ( 1 9 1 9 ) , 714a. 22-See also A. Zimmer J. Bryce a n d G. Dariea I3ilt. P a t e n t because the salvaging of scrap fabric was, at best, ail uii124,807 ( 1 9 1 6 ; abst., J . $0;. C h e m I%d., 38 ( 1 9 1 9 ) , 379n; C . A , , 13 certainty, although the French accumulated a considerable 1771. qunnti ty. 23-Cellon, Ltd., Tyrer & Co., Ltd., T. Tyrer, B r i t . P a t e n t 130,402 SCMMARY
J i n n y processes utilized in the mar for the manufacture and use of cellulose acetate and nitrocellulose dopes for the coating of aircraft fabrics have been made public since the signing of the tmiiistice. Through the issuance of official governineiital publicaKioiis ami articles i n the technical journals, our European allies hare taken a leading part in this coinmeiidable procedure. 111 this brief review a n account is given of the coiiiinerrial development, in Europe, of cellulose acetate, certain of the physical and chemical characteristics reauired for its use in dopes, cellulose acetate solvents, diluents, thermoplastic combinations, pjgmentation, camouflage, application of dopes, and recovery of solvents and cellulose acetate from discurded fabric.
BIBLIOGRAPHY l-.The Chief of t h e Air Service has grnnced permission f o r t h e release of three expurgated Seth of f i e p o r t 13,228, which work is being completed under t h e direction of Mr. E. C. Worden. 2-.J. H a m s b o t t o m , Report of Advisory Committee for Aeronautics (Dritisli), 1914. 3-Rev. CliLint I n d . , 1920 S o . 7 I77 -Fifth KepoGt from t h e ' Select 'Committee on National Expendit u r e ( B r i t i s h P a r l i a m e n t ) , 1918. See also J . Soo. Chenz. Ind!, 3 8 ( 1 9 1 9 ) , 317r. 6-Chern. A g e ( L o n d o n ) , 1 (1919), 275. 6--Oolor T r a d e J., 5 ( 1 9 1 9 ) , 5 0 ; C h e n z . d g e ( L o n d o n ) , 1 ( 1 9 i 9 ) , 279.
.
(915) alrst. J . S O C . O 7 ~ e m .I n d , , 3 8 ( 1 9 1 9 ) , 714a. 13'. Fenton a n d A. B e r r y , Proc. C a m b r i d g e Phil. Soc., 20 %-See ( 1 9 2 0 ) , 16. 25--5. Groves a n d T. W a r d Brit. P a t e n t 128,659 ( 1 9 1 7 ) : abst J . Scc. Chem. I n d . , 38 (1819) ' 6 4 7 a ' 0. A 13 (1919) 3028. S u i : gested zinc chloride and calcidm chldride a; fire r e t a r d k n t s in nitrocellulose dopes. 26-Formerly Chef d e Service Chimiqiie, Section Technique d e I'Aeronautique. 27-See G. W a r d . Brit. P a t e n t 128,655 (1917) ; a b s t , J Sot?. Chem I n d 38 (l919),647a. Chrm.' Iizd.': 3 8 (IOlg), 6 4 i a . 28-Third A ~ i u u a lReport of t h e National d d v i s o r r Cornmittre f o r
heronnutica, 1918. port, 1919. 29--B1Aitish 30-Sce
F o r Walen's article on tapes 'see F o u r t h Re-
E71ur. S t a n d a r d dssoc. Bztlletiiz 83 (April, 19181.
L. Vignon, C o m g t . r e n d . , 170 ( 1 9 2 0 ) , 1322.
31-For a pigmented dope formula, see A . B a r r a n d H. L : w p I l Brit. P a t e n t 136,641 (1918) ; abst., J . Soc. C h e m . I i i d . , 38 ( 1 9 1 9 ) ; 834a. 32-,For physicochemical discussion of refrineration methods see Chz??zw R w d z i s l r h e 1 (1918) 481 ' a b s t C . A., 13 ( 1 9 1 9 ) 304.' F o r other solvent .fecoverg piocessis qee h Worden " Techdology of Cellnlose E s t e r s 1921, I. 2 6 5 3 - 2 5 5 8 . See also Deschiens, R e v . p r o d . c7izm., 2 3 ' (1920), 237.
RI. OPonchon
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
836
34-4. Schmidlin and R. Lang, Be?., 43 (1910), 2806; abst. 0.A., 5 (1911), 4 8 7 ; Be?., 45 (19121, 8 9 9 ; abst., U. A., 6 (19121, 9428. T. Zincke and W. Gaebel, Alcno, 388 (1911-1912)* 2 9 9 ; ab5t.n 0. A., 6 ( 1 9 1 2 ) , 1763. 35-1. Masson and T. McEwan, J . SoC. Chem. Ifid., 4 0 ( 1 9 2 1 ) ,
32t. 36-E.
Barbet e t Fils e t Cie., Brit. Patent 101,723, 101,875
Vol. 13, No. 9
(1916) : 117,269 (1918) ; U. S. Patent 1,326,432: abst.. f. BOO. C h m . m d . , 37 ( 1 9 1 8 ) . 46a; 38 (1919), 521a; 39 ( 1 9 2 0 ) , 145a; 0. A., 11 ( 1 9 1 7 ) , 280; 12 ( 1 9 1 8 ) , 2417. 269 1918)' 37-French Patent 'Ppl' 103,588 38-Brit. Patent 2,365 (1918) ; abst., J . Soc. Ch@n%. I%&, 37 (1918), l l l a .
Motor Fuel from Vegetation' By T. A. Boyd G ~ N E R AMOTORS L RESEAROH CORPORATION, D.iYTON, O H I O
For operating the motors of the country an enormous and ever increasing amount of liquid fuel is required. This amount of fuel is so large that not 011ly has great activity in the production of crude oil been necessary to meet the demand but the reserves of crude oil a r e also being rapidly depleted. The yearly production of petroleum has become so large that exhaustion of its reserves in the United States threatens to occur within a few years. The object of this paper is to present the danger with which motor transportation is threatened, with the hope of directing further attention to a possible means of solving this problem, which i s of such vital importance to the country. THE PRESENT MOTORFUELSITUATION The number of automobiles and trucks in use in the
ninefold, domestic crude oil production has only doubled. The relation between motor vehicles in use, as shown by registration figures, and the production of crude oil is given graphically in Fig. 1. I n Fig. 2 the relative growths of the three factors, motor vehicle registration, crude oil production, and gasoline production, a r e compared with 1909 values. The production of crude oil has increased since 1909 about 140 per cent, and t h a t of gasoline about SO0 per cent, but the number of automobiles registered has increased 2570 Per cent. The normal gasoline content of the crude oil produced
100
80
80 70
60 50 40
30
20
fD
Nf2
1913
Fig. 1-Relation crude oil
&I4
/QI5
I916
/9/7 /9/8 /SB
/$20
between automobiles registered and production
Of
United States has increased from about 1,000,000in 1912 to about 9,000,000 i n 1920, a n average increase of over 1,000.000 n year. Crude oil, the principal source of fuel for motor vehicles, has shown a n increase in domestic production during the same period from about 220,000,000 barrels to 440,000,000barrels a y e a r ; so that, while the number of motor vehicles in use has increased about Readibefore the Cellulose Section at the 61st Meeting of the American Chemical-Society,Rochester, N. Y., April 26 t o 29, 1921.
FIG. 8-PEHCENTAGBINCREASESI N MOTORVEHICLESREGISTERED, PRODUCTION OF CRUDE OIL, AND PRODUCTION OF GASOLINE, COMPARED WITH
1909'
U.
S. Bureau of Mines, Bulletin 191. 1 9 : Automobile Industries (Feb. .17, 1921), 3 0 6 ; recent statistics, U. .S, Bureau of Mines and 1
Geological Survey.
in the United States is around 20 per cent.' The actual production of gasoline has exceeded this percentage of the crude since 1917. Refiners have met the rapidly in* David White, J . 9 o c .
Automotive Eng. 43, (1919), 61.
