December, 1926
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
not only been met, but are excelled in most of the goods placed on the market. By 1921 the volume of the business amounted to about 140,000 pounds and has increased since that time. These colors are mainly used in the ice-cream, confectionery, and soft-drink trade. Education and legislation have practically eliminated the use of color to mask inferiority or impart a “bloom of youth” to the salmon or chicken that had grown hoary with age in the cold-storage plant. The standards of fixed by law for the colors are fully described in the pub!ications of the U. s. Department of Agriculture. Briefly stated, they are as follows: (1) Arsenic content must be less than 1/700,000. ( 2 ) Must be free from heavy metals according t o the authorized test.
(3)
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Must be structurally true to type.
v2ih,’,
CC‘:pmination
~ ~ O ’ ’ ~ ~ ’ ~ ~ ; ~ ~ ~ p ; f with other ( 5 ) Decomposed dyes and other organic impurities must be reduced to a minimum, (6) Insoluble matter must in no case exceed 0.3 per cent.
As stated before these requirements are than met by the producers today. The list now contains an assortment of colors that fully meets the esthetic requirements in the tinting of our confectionery and other products, including many of the demands of the cosmetic trade. Authentic certified colors bearing the official lot number and the name of a reputable manufacturer are products that have met the high standards of purity demand by the Government and Can be used with impunity.
Progress in the Development and Manufacture of Vat Colors in America By 0. M. Bishop and J. H. Sachs F,. I. D U PONTDE
NBMOURS & Co., WILMINGTON, DEL.
Y THE term “vat color” is meant a dyestuff that in covering perhaps 50 acres had won an economic race against its stable form is insoluble in water and in dilute 500,000 acres devoted to the culture of indigo in Asia. At the beginning of the present century indigo and its alkaline or acid solutions, but which on alkaline reduction passes into a form which is readily soluble in dilute substitution products were the only known vat colors of alkali. In former times the reduction of indigo was brought commercial importance. Scarcely one year of the new cenabout by fermentation, and from the fact that this process tury had elapsed, however, when Rohn brought forth the was carried out in large wooden or earthenware containers epoch-making discovery of indanthrene and flavanthrene. called vats the term “vat color” is derived. In the reduced These were vat colors, differing from indigo in that they form these colors are substantive to animal or vegetable possessad not only a different carbon skeleton but also a that of anthraquinone. fibers, and because in this form they are so unstable the different chromophore-namely, simple process of allowing free access of air to the dyed At this time there was no I. G. in Germany and compefibers is sufficient to oxidize the color into its original in- tition between the various color manufacturers was keen. They all took up the scent of new vat colors. In 1905, soluble form. This class of colors, which has been known from antiquity, Friedlaender discovered thioindigo. The way was thereincludes both indigo, the king of dyestuffs, and the much- fore open in two directions for the synthesis of new and prized Tyrian purple of the Phoenicians. The former, varied colors of this class. It thus comes about that even in spite of the accomplishments of the synthetic organic a t the present time practically all of the known vat colors chemists, still retains its premier position. The latter, can be divided into two groups-the indigoids and the anthrasynthesized and catalogued early in the twentieth century, quinones. During the next ten years an enormous number has long since succumbed to colors which are much its su- of new products were uncovered, the majority of which were of no commercial importance. However, many of them perior in shade and fastness. With the advent of the synthetic organic chemist came possessed valuable properties and were thercfore commerthe downfall of the natural dyestuffs. The extract of leaf, cially produced and marketed by the Badische Company bark, and root was replaced by thz magic touch of chemistry under the name Indanthrene: by the Rayer Company under upon the vegetation of geological age, stored up within the the name Algol; by the Meister, Lucius & Briining Company earth awaiting the key that would unlock its riches to man- under the name of Helindon; by the Society of Chemical kind. The madder industry of southern Europe was over- Industry, Basle, under the names of Ciba and Cibanone; thrown in 1869 by the work of Caro and Liebermann in and finally by the Cassella Company under the name of Germany and Perkin in England on the constitution and Hydron. According to the Norton’s census, during the synthesis of alizarin. Likewise, about twenty-five years fiscal year of 1913-1914 there were imported into the United later the long and painstaking work of Bayer on the constitu- States 1,232,002 pounds of fifty-eight different anthration of indigo bore fruit in the first successful commercial quinone vat colors and 305:171 pounds of thirty-six different production of this color. As early as 1882, when Bayer indigoids, indigo itself excluded. In Table I are given the and Drewson’s synthesis from o-nitrobenzaldehyde promised twelve colors imported in the largest amounts in that year. success on a commercial scale, the attention of the foremost Table I Pounds color manufacturers in Germany was directed towards this Indigo 8,507.359 goal. Thousands upon thousands of dollars were spent 478.980 Indanthrene blue GCD 187,379 Indanthrene blue R S in research work. Other thousands were poured out in 75,192 Indanthrene yellow G 72,227 Indanthrene green B plant development. That these thousands were not spent Indanthrene violet RR 68,419 in vain can be appreciated by the fact that, whereas in 53,610 Indigo MLB (brominated indigo) Indanthrene golden orange R 50,496 1895 Germany imported indigo to the extent of about five Indanthrene black B 50.034 39,393 Helindone pink millions of dollars, in 1905 she exported indigo to the extent Indanthrene claret B extra 28,728 of almost seven millions of dollars. Plant sites in Germany Helindone violet B 28,607
B
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It is needless to stmatehere the causes which led to the establishment of a dyestuff industry in America. Once started it was realized that if the industry were to be permanent it would have to he complete-that is, it would be compelled to supply the textile industry with a full line of colors. This realization brought about the beginning of the vat dye industry in America.
Indigo As early as 1916 ideas were entertained as to the possible manufacture of indigo, but it was not until the latter part of this year that active work on this color was started. How rapidly this work was advanced can be appreciated from the fact that the year 1917, witnessed the production of 274,771 pounds of this, the most important of all dyestuffs in this country. Within a year three different concerns were engaged in its manufacture, and the production in 1918 reached the appreciable figure of 3,083,888 pounds, the average selling price of which was about 88 cents per pound. Table I1 will illustrate the remarkable progress made year by year in the manufacture of this color. Table I1 Year 1917 1918 1919 1920 1921 1922 1923 1924 1925
Production Pounds 274,771 3,083,888 8 863 824 18:178:231 6,673.968 15,850,752 28,347,259 19,996,703 29,121,817
Average selling price Cents
...
88
59 74 45 24 23 22 15 (estimated)
Anthraquinone Colors We now come to the development of vat colors other than indigo. For about fifteen years these colors, especially those derived from anthraquinone, had held unquestioned supremacy where fastness and brilliancy of shade were desired. The American public had found that fast colors, fast in every sense of the word, could be obtained. And it might be said here that in the experience of the writers the demand for fast colors is increasing year by year. From the manufacturing standpoint, as is often the case in other fields, the things most to be desired are the most difficult of obtainment. Perhaps no other class of colors has offered so many difficulties and complexities of manufacture as the anthraquinone vat colors. Active work looking to the manufacture of these colors in America was begun late in 1917 and from the start two major difficulties presented themselves: (1) the meager and indefinite disclosures relating to methods for the synthesis of these colors and their intermediates which were available in the patent and chemical literature; and (2) the lack of raw materials, especially anthracene. Meagerness of Literature Disclosures
As far as the first difficulty is concerned, the fact was quickly recognized that the patent and chemical literature could not be relied upon to furnish workable processes whereby these products could be made. Of course, by following the examples and directions disclosed in the patents, more or less, usually the latter, of the desired product resulted. I n most of the patents it is the product and not the process by which it is obtained that is claimed, and it is for this reason more than any other that they were practically useless as working recipes. But while pointing out the inadequacy of the German-owned patents as recipes fCr manufacture, we cannot pass by without a word of commendation for the purely scientific work of Scholl and his co-workers on the constitution and synthesis of many of the highly complex anthraquinone derivatives. His work
Vol. 18, No. 12
deserves to be better known and furnishes us here in America an excellent example as to the close relation between the university and industry in Germany. Scholl was not much concerned with yields, however, neither were the attorneys who drew up the German-owned patents, and it is by yields alone that a chemical industry can live. Speaking now for one concern that entered this field, it was therefore necessary to plunge headlong into the most lowly form of research work-namely, the study of times, temperatures, and the various proportions and concentrations of. the reacting materials. This work sufficed to draw up tentative recipes for the small-scale or semiworks production of the most important of the anthraquinone vat colors and their intermediates, and it was pushed so rapidly that within a year and a half-that is, by midsummer of 1919-small amounts of the blue GCD, dark blue BO, violet R, green B, and yellow G of American manufacture were available to the textile industry. Lack of Raw Materials
We turn now to the second major difficulty, the lack of raw materials. Anthraquinone, the starting point or primary intermediate necessary for the building up of its derivatives or complexes can be made in two ways-namely, (1) by the oxidation of anthracene, and (2) by the condensation of benzene and phthalic anhydride by means of aluminum chloride to o-benzoylbenzoic acid, and the splitting off of water from this compound to form anthraquinone. In looking for a source of this material both methods presented difficulties, both of which will be briefly discussed. When coal tar is distilled, that fraction passing over from about 270" to 400" C. is called the anthracene fraction. The pitch or residue left a t 400" C. is hard and brittle and unsuited for roofing or road-making purposes. If the distillation is discontinued at 270' C. there is obtained a soft pitch which is ideal for both of these purposes. In Europe very little pitch or tar is used in road-making and furthermore hard pitch is utilized in the manufacture of briquets. Therefore, whereas in Europe, the tar distillers find it economical to remove the anthracene from the tar, in this country it was found that if anthracene were removed the pitch was useless, and the former product had to stand the loss incurred by this waste. This, of course, resulted in a very high priced anthracene. Another difficulty arose in the use of the anthracene method-namely, the lack of an American production of pyridine, a solvent which is almost indispensable for the purification of crude anthracene to a stage'where it can be successfully oxidized to anthrsquinone. In spite of these difficulties and the resulting high price of anthracene, the first vat colors made in this country were made from anthraquinone, which in its turn resulted from the oxidation of anthracene. This condition did not long obtain, however, for as early as 1917 Gibbs and his co-workers in the Color Laboratory in Washington had shown that phthalic anhydride could be obtained by passing the vapors of naphthalene over suitable catalysts. As a result of his work the total requirements of phthalic anhydride in this country are today made by this process and a t such a cost that synthetic anthraquinone-anthraquinone derived from phthalic anhydride-has, a t least for the time being, thrown the oxidation of anthracene into the discard. Time alone wilI tell whether or not this change will be permanent, for the factors involved are so numerous and complicated that another five-year period may again witness a change back to the older method of producing anthraquinone by the oxidation of anthracene. Disregarding anything that may develop along this line in the future, there is no doubt a t this time as to:the economic importance of the catalytic synthesis of
INDUSTRIAL A N D ENGINEERING CHEMISTRY
December, 1926
phthalic anhydride and of anthraquinone. These achievements will always occupy a high place in the history of the American dye industry. First Colors Produced As stated before, the first successful commercial production of vat colors other than indigo and its derivatives was accomplished in the summer of 1919. In view of the fact that, of the vat colors imported in the fiscal year 1913-1914, those derived from @-aminoanthraquinoneand benzanthrone seemed to be of especial importance, these were taken up first. By the summer of 1920, or one year later, the following colors of American manufacture were available: Blue RS Blue GCD Dark blue BO Yellow G
Green B Black B Violet RR Brown B
They were marketed by the E. I. du Pont de Nemours & Company under the name of Ponsol, and by the Newport Chemical Company under the name of Anthrene. In this discussion neither term will be employed but it may be safely recorded that from this time (1920) until the present, with few exceptions, every color introduced has been made by both firms. Improvement Due to Research Speaking again for one concern that entered this field,
it is readily admitted that the quality of the colors produced in the early stages of manufacture left much to be desired. This fact is emphasized by a comparison of the quality of the standards then in use with our present standards. But the faults of the colors then produced were recognized, and the more they were apparent, the greater was the effort expended in their remedy. Consequently, along with work looking to the production of a larger line of colors there wm conducted most careful and thorough research on those colors already manufactured on the plant scale. In some periods, when critical situations arose relating to production colors, work on the new developments was suspended pending the solution of the difficulties. This method of procedure, which holds good even a t the present time, has revealed many secrets and uncovered many facts that have resulted in higher yields, better quality, and, of equal importance, simplified and more easily controlled plant operations. There is no doubt that of all factors contributing to the development of an American vat dye industry, pure chemical research has contributed more than any other to the progress that has been made. The most difficult chemical operations can be carried out on a larger scale without difficulty if the chemical process is right, and if control tests by which the course of the reaction can be followed are available. The Engineer's Contributions In giving first place to pure research as a factor in the establishment of this industry we do not mean to reflect upon the contributions made by the engineer. The reactions by which these colors are made are in some cases so severe that great skill and ingenuity had to be exercised in the design and installation of equipment in which they could be carried out. Two illustrations will suffice to make plain the difficulties along this line which were overcome. (1) The best method for the preparation of chloroanthraquinones consists in boiling together a solution of the alkali metal salt of the corresponding anthraquinonesulfonic acid and sodium chlorate, with the gradual addition of concentrated aqueous hydrochloric acid to the mixture. The reaction is very simple when carried out in the laboratory in a glass fla& fitted with a glass stirrer and with a Bunsen burner
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furnishing the heat. But glass flasks, glass agitators, and Bunsen burners are out of the question when the required quantities of chloroanthraquinones are reckoned in hundreds of pounds rather than in grams. (2) The best method for the preparation of P-aminoanthraquinone, one of the most important of the anthraquinone intermediates, consists in heating the sodium salt of anthraquinone-@-sulfonic acid (silver salt) with 25 to 28 per cent aqueous ammonia to a temperature of 175-200" C., whereby a pressure of 600 to 1000 pounds per square inch results. Good agitation is absolutely essential. Ammonia gas is both costly and fugitive, and a t the temperature of reaction the molecules get excited. They tend to chase each other out into the wide open spaces where they can cool off. But, thanks to the chemical and design engineers, they are forced to vent their pent-up energy within the reacting mass by separating the sulfonic acid group from anthraquinone and entering it in its place. And thanks again to the same professions, the extremely active and corrosive molecules of the first example are forced to satisfy their appetite upon the anthraquinonesulfonic acid rather than upon the walls of the containing vessel. Increase in Variety and Quantity
It therefore comes about that the chemist, the chemical engineer, and the design engineer have combined their skill in solving the most perplexing problems that have been encountered in the building up of this industry. Their work has resulted in the production today of a complete line of vat colors in America, the quality of which is fully equal and in many cases superior to that of German manufactured color. Table I11 in which is given the colors brought out year after year, illustrates the progress that has been made. There are included two colors which can be classified either as sulfur or vat colors-namely, hydron blue R and hydron blue G, derived from carbazole and ethylcarbazole, respectively. 1917 Indigo Dibromoindigo
... ... ...
Table 111 1919 1920 Blue GCD Blue RS Yellow G Violet RR Dark blue BO Brown B Green B Blue Ra Violet R
1922 Blue GC Blue BCS Jade green
...
...
1923 Golden orange G Blue 3G Pink FFb
1924 Golden orange R R T Golden orange 4R Red B N Orange Rb Scarlet 2B b Blue G" Derivatives of carbazole. b Indigoids.
... ... ...
...
1925 I926 Red violet R R N Pink B Violet Bb Violet Rb
... ... ... ...
.... ...* .
...
I n Table IV are given the production and imports of vat colors other than indigo for the years 1917 to 1925, inclusive. These figures were taken from the Dye Census of the U. S. Tariff Commission. T a b l e IV Production Pounds
Imports Year Pounds 1914 1,945,304 ii,%k25 1917 197,449 191s 1919 389,158 1920 78i,ifi3 1,159,868 1921 1,045,370 345,152a 1,075,992 1922 1,548,519 1,207,554 1,766,383 1923 1,493,851 1,821,319 1924 1925 2,416,890 2,608,361 General business depression and large decline in the manufacture of bromoindigo.
... ...
Developments i n Application t o Textiles These figures illustrate not only the progress made in America in the manufacture of these colors, but also the
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remarkable increase in the quantity consumed in this country. This increase has been brought about by two outstanding developments in the application of these colors to textile fibers and fabrics-namely, (1) their application to silk, and ( 2 ) their application on piece goods by the “pad and jig” method. Both developments are of American origin. Today large quantities of silk and an enormous yardage of cotton piece goods are being dyed with these, the fastest of all dyes. In both cases the manufacturer has played a large part in the solution of the difficulties encountered by the textile people in these two modes of application. Especially is this true in the case of the application of these dyes by the “pad and jig” method, and the problem of producing these colors in a form whereby they could be successfully “padded” was one of the most difficult which the manufacturer was called upon to solve. It will therefore .be discussed briefly. These colors, being insoluble, are for the most part marketed in the paste form and it is in this form only that they can be applied to cotton by either the printing or the padding process. The presence of sand or grit in the paste is fatal to the cotton printer, for his copper printing rolls are easily scratched and each scratch means a corresponding impression in the fabric being printed. Likewise the presence of small particles of dry color, or in fact particles of color that are not of colloidal dimensions, is sufficient to render a paste useless for application by the padding process. Both d%culties have been overcome by the application of the principles of milling and of classification, so that today pastes are being produced in this country which are practically 100 per cent colloidal, which are sand-free, and which the printer and padder can use without fear of scratching his rolls or spotting his fabrics.
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The American manufacturer has contributed in another direction to a solution of the difficulties which the textile people encounter in the application of these colors. It is a well-known fact that colors marketed in the paste form are not so easy to apply as are those which come in the powder form. Pastes dry out, they freeze, some settle out, and some ferment. As stated before, pastes are essential for the printing and padding of these colors. But for other methods of application, such as the dyeing of raw stock, powders are preferable to the pastes, provided the powders are available in a foqm whereby they are readily dispersible in water and easily vatted. Therefore, both American manufacturers have placed these colors on the market in the powder form, and it can be stated without fear of contradiction that American-made powders are superior in every respect to those made anywhere else in the world. ConcIusion
This is, very briefly, the story of the progress of the American vat color industry. There are many problems yet to be solved, many yields to be increased, many operating problems to be straightened out, many by-products to be utilized, and finally, as a result of the solution of these difficulties, many costs to be reduced. Furthermore, the American chemist will not be content to follow always in the footsteps of another, to duplicate and to improve upon that which has already been accomplished. He has already launched out into the realm of vat colors that are to be and has brought back into the realm of reality a number of .new vat colors, new, not in the sense of being simply homoIogs of heretofore known colors, but new in every sense of the word. He faces the future with confidence in his ability not only to imitate but also to create.
The Contribution of the Color Laboratory to Industry’ By H. T. Herrick COLORLABORATORY.BUREAUOF CHBHISTRY, WASHINGTON, D. C.
REVIOUS to the beginning of the World War two lines of work relating to dyes were being carried on by the Bureau of Chemistry of the Department of Agriculture. These lines included the work of the Contracts Laboratory on inks, pigments, and similar substances, and that on the certification of food colors. The outbreak of the war brought troubles and complications to all branches of chemical industry, but to none more than the manufacture of dyes. After a hard fight against adverse conditions, most of the dye firms that had made a start during the latter part of the nineteenth century had succumbed, and those which survived were engaged chiefly in the assembly of dyes from German intermediates, the supply of which promptly ceased, along with all dye importations, with the tightening of the British blockade of Germany. As the users of dyes began to feel the pinch, a great call for American-manufactured dyestuffs went up from every side, and the United States Government was importuned to do its share in the rush of dye investigation. Accordingly, Congress, on August 11, 1916, appropriated $50,000 “for investigation and experiment in the utilization for coloring purposes, of raw materials grown or produced in the United States.” As most of the chemists in the government service who
P
1
Contribution No. 125 from the Color Laboratory, Bureau of Chemistry,
Washington, D. C .
had had experience in color work were in the Bureau of Chemistry, the Color Laboratory, as it was called, was assigned to the Department of Agriculture, and work on the new project was started. A building was erected on the Arlington Farm, and plans were made for the laboratory investigation of colors and the substances entering into their composition, and also for the reproduction of laboratory processes on a technical scale. The building, 150 by 70 feet, contains six chemical and physical laboratories, besides offices and a library. All these rooms are on the second floor on one side of the building, with a fully equipped machine shop, storeroom, etc., beneath. Next to the machine shop and storeroom on the ground level is a technical floor, 150 by 40 feet, with a large assortment of chemical apparatus. There is also an auxiliary equipment in the way of a 10-ton crane, a &ton ice machine, and two 100-horsepower boilers. Power is likewise available in any voltage from 6600 volts down. There is a small MG set for producing direct current. Tools for all sorts of research, both in a laboratory and a technical way, are available. Because of the customary delay between making an appropriation and its expenditure, and also because of difficulties arising from war complications, the Color Laboratory personnel did not move to its new building until nearly four years after the first appropriation was made. I n the meantime much valuable work was accomplished under the di-
