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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 18, No. 12
The Contribution of the Dyestuff Industry in the Development of the Rubber Industry By Donald H. Powers E. I.
DU
PONTDE NBYOURS & Co., INC., WILMINGTON, DEL.
I
N THE rapid development of the rubber industry syn-
thetic organic chemicals have played an important part, and it is in the development, manufacture, and study of these products that the dyestuff industry has contributed. The importance of these compounds has grown rapidly in the past ten years, until a t the present time they are undoubtedly the most important single contributor to the success and size of this industry. One of the first references to the use of rubber in this country is a footnote in one of the Rev. Joseph Priestley’s articles in which he mentions “a substance excellently adapted to the purpose of wiping from paper the marks of a black lead pencil.” This material, which sold for six dollars a cubic inch, came to be called “rubber” on account of this peculiar property. All the pioneer investigators recognized that this new substance possessed remarkable qualities but were limited by its high price, uncertain supply, and principally by its variability with temperature. The early rubber goods were brittle when cold and sticky when warm. With the discovery of vulcanization by Goodyear and Hancock almost one hundred years ago, rubber showed its first signs of being of technical importance. Vulcanization, discovered by heating the rubber with sulfur in the presence of an accelerator, converted it from a plastic to an elastic state. The vulcanized rubber was much less sensitive to variation in temperature, was mechanically superior in elasticity and strength, and had a much higher resistance to tear and abrasion. Vulcanized rubber gradually became of increasing importance, especially in the manufacture of footwear and mackintoshes, until fifty years ago the value of rubber goods made in this country had reached $25,000,000. For the next forty years this value practically doubled every ten years. But in the past eleven years the rubber industry has passed through one of the most spectacular advances in business history. The total value of rubber products has increased from $300,000,000 in 1914 to an estimated $1,500,000,000’ in 1925, a growth of 500 per cent; yet the total number of persons employed has decreased during this period, so that the efficiency of this industry is over five times that of 1914. Organic Accelerators
The one discovery of this century that has contributed more than any other to the rapid development of the rubber industry is the use of the organic accelerator. Over 90 per cent of the rubber goods now on the market is vulcanized with the aid of these compounds. Not only do they speed up three- to fivefold the rate at which the rubber is vulcanized, which in itself yields an enormous saving, but further, the resulting rubber goods show superior wearing qualities, greater resistance to aging, and much more “life.” Only about one per cent of an organic accelerator is needed and it is estimated that this use (by shortening greatly the time of vulcanizing and yielding a more lasting product) annually awes the motorist and the rubber industry $100,000,000. The rubber industry first recognized the value of organic accelerators just twenty years ago, but it was not until ten years ago that their use became a t all widespread. At 1 The report of the Rubber Association gives $1,142,096,000for 1925, which is estimated as 75 per cent of the total industry.
first the dyestuff industry supplied the intermediates. I t was not long, however, before they manufactured finished accelerators, as they felt that their experience in the making of dyestuffs peculiarly fitted them for this work. They established research laboratories which on the one hand worked out processes which made it possible to offer organic accelerators of a purity rivaling the C. P. chemicals, and on the other hand, studied hundreds of organic compounds for their effect on the rate of vulcanization. As a result of this study entirely new organic accelerators have been developed and placed on the market and still more active bodies under investigation are designed to meet the changing requirements of the rubber industry. The approximate annual consumption of organic accelerators is estimated a t over six million pounds, with a value above $5,000,000. In referring back to the gain effected by the use of accelerators it is evident that this investment by the rubber industry of $5,000,000 yields a saving of twenty times that amount. It is interesting to note that not only was aniline one of the first organic compounds shown to possess accelerating action but at the present time aniline derivatives constitute 75 per cent of the forty-odd accelerators now on the market. All types of accelerators of commercial application may be listed under six heads, five of which start from aniline. AMINEs-Aniline itself still has some application, but its use has been limited by its poisonous character and relatively weak activity. THIomEAs-These products, such as thiocarbanilide and di-o-tolyl thiourea, which may be prepared from aniline or o-toluidine and carbon disulfide, were first used as nonvolatile nonpoisonous substitutes for aniline. They still enjoy a limited use, but on account of their relatively low activity they have been almost entirely replaced by the newer and faster accelerators. GUANIDINES-This is the most important class of organic accelerators on the market and their volume equals over 50 per cent of the total accelerator sales. Diphenylguanidine and di-otolyl guanidine may be considered the reaction products of a cyanogen halide with aniline and toluidine, respectively. As marketed, they are of high uniformity and rival the C. P. chemicals in their purity. Their wide use may be attributed t o their relatively high activity, freedom from tendency to prevulcanize, and t o the superior qualities of the accelerated stocks. Other guanidines having a wide use analogous in their preparation and activity to the two mentioned above are di-p-tolylguanidine, dixylylguanidine (in England) and phenyltolylguanidine. Triphenylguanidine, which may be prepared from aniline and thiocarbanilide, is a somewhat weaker accelerator than the disubstituted guanidines mentioned, but its volume reaches approximately 10 per cent of total accelerator sales. ALDEHYDE AMINES-AS regards numbers, this class of accelerators far outranks all the rest, comprising over 50 per cent of the total on the market, with each year seeing ne% additions. One of the earlier members is the condensation product of formaldehyde and aniline, and this, with the toluidine derivatives, still has a limited use. At present the acetaldehyde aniline condensation product is the most important member of this family and is sold as a resinous product under a variety of names. Just as acetaldehyde aniline gives a better accelerator than formaldehyde aniline, so the use of higher aldehydes gives still more powerful accelerators. As a supply of the higher aldehydes such as butyraldehyde and heptaldehyde becomes available, we find corresponding aldehyde aniline derivatives placed on the market. These compounds have been extensively studied, and will no doubt continue t o provide new accelerators for several years to come. MERCAPTO BENzoTHULzoLES-This class of organic compounds may be considered as derivatives of aniline or its homo-
December, 1926
INDUSTRIAL AND ENGINEERING CHEMISTRY
logs, carbon disulfide, and sulfur. These products heretofore have been limited in their use but will undoubtedly find wider adaptability. It is interesting t o note t h a t aniline and carbon disulfide give thiocarbanilide, which is a very weak accelerator, yet aniline, carbon disulfide, and sulfur give mercapto benzothiazole, which is a very powerful accelerator. The metallic salts and oxidation products of the mercapto benzothiazoles are also good accelerators. THIvRAMs-These particular organic compounds are classed a s ultra-accelerators and are prepared from dimethylamine, diethylamine or piperidine, and carbon disulfide. The best known ones are tetramethylthiuram disulfide and tetramethylthiuram monosulfide. However, the very activity of these ultra-accelerators has limited their use. While no direct comparison is possible, the two compounds just mentioned are approximately ten times as fast as most of the accelerators covered in the first four groups. These ultra-accelerators are growing in popularity and finding wider use, especially in the boot and shoe trade. I n passing it may be mentioned t h a t the xanthates, which are prepared from alcohol, carbon disulfide, and alkali, are of theoretical interest inasmuch as they are among the few nonnitrogenous accelerators of practical value.
The use of organic accelerators has made possible a far wider application of rubber and in the automobile field we have an interesting illustration of this trend. With the development of balloon tires, rubber suspension springs, and sponge rubber cushions we have reached the tinie when we are literally "riding on rubber." Antioxidants
When rubber goods came to be made so that they would wear longer, it became necessary to make them withstand deterioration longer. As a result of years of research it was shown that the deterioration of rubber was due in part to its oxidation and that any prevention of oxidation cut down markedly its rate of deterioration. It was further shown that a relative measure of the rate at which a piece of rubber would deteriorate could be determined with a fair degree of accuracy by accelerated aging tests. These tests comprised heating a slab of the rubber in an oven a t 70°, 80°, or 90' C. for a given number of days or in an oxygen bomb a t 60" to 90' C. for a given number of hours. It was shown that in certain types of stocks 4 days in the oven a t 70" C. was approximately equivalent to 2 years' natural aging, and 10 hours in an oxygen bomb a t 300 pounds pressure a t 60" C. was approximately equal to one year of natural aging. By means of these accelerated aging tests it was possible to study a large number of organic compounds in a short time and select from this number those of particular value for natural aging tests. Hundreds of organic compounds were prepared and tested by the dyestuff industry to study their effect on the rate of the deterioration of the rubber and also to gain further insight into the exact mechanism of this deterioration. As a result of these studies, products were found which retarded the rate of aging in certain stocks as much as sixfold. It meant converting a stock, which would be markedly deteriorated before it was half worn out, into a stock that would show little signs of aging during its entire life. It has been pointed out that this possibility of now obtaining a good aging rubber may greatly increase its use and also open new fields such as the building trade. These organic antioxidants have been found to be extremely active, and 1 to 5 per cent is all that is required in the majority of stocks. While antioxidants have found their principal demand in the tire industry, the advantages of their use in household goods are obvious and their spread to this field is only a question of time. An instance of a recent important demand for antioxidants is in tubes for passenger busses. The ordinary tube deteriorates completely in many cases within aweek, but by the use of the organic antioxidant tubes are now on the market which show practically no deterioration during their life.
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R u b b e r Colors
One of the most recent developments in synthetic dyes is their application to rubber goods. The dyestuff industry, already supplying accelerators and antioxidants, turned its attention to the further applications of organic zompounds and found that the high percentages of inorganic pigments previously used for coloring rubber goods could be replaced by small percentages of organic dyestuffs. Not only was it possible to obtain stocks correspondingly freer from inert filler but a far wider variety of shades and much brighter ones were available. With inorganic pigments the rubber industry was limited to relatively few shades and in many cases as high as 10 per cent was required. It is possible to replace this pigment by even less than 1 per cent of organic dyestuff and in some cases obtain a still brighter shade. The selection of a dyestuff for rubber requires an entirely new set of criteria and relatively few successfully pass all of them. A few of the more important ones, especially those differing from the usual standards, will be mentioned. ABILITYTO WITHSTANDVULCANIZATION-The first essential of a rubber color is that it must withstand hot or cold vulcanization. I n hot vulcanization the color is heated well over 250" F., in many cases by direct steam in a stock containing free sulfur and metallic oxides. Few will withstand this treatment and still hold their brilliancy and shade, more failing in this test than in any other. I n cold vulcanization the color must withstand sulfur chloride fumes without loss of brilliancy. Few are the colors which will withstand both hot and cold vulcanization. EFFECTON CURE-organic accelerators are in many cases basic substances and the presence of acidic colors may markedly retard their action. Further, it is preferable t h a t the organic color should have no accelerating effect as special adjustments would be necessary in the amounts of accelerator used for every variation in the per cent of color. DIsPERsIoN-The organic colors, unless they are soluble in the rubber hydrocarbon, must be in a very fine state of division, as complete dispersion is absolutely necessary. Certain colors are excluded entirely because of a tendency to agglomerate and to give a spotted instead of a uniform stock. Many dyestuffs which are not fast when added directly t o the rubber become so if they are first mixed with some inorganic filler such as China clay and then added to the rubber. NON-MIGRATIONAND NoN-BLOOMING-Sulfur, when Used in relatively high percentages, has a tendency t o bloom, so t h a t fine crystals cover the surface giving a black stock a gray appearance. In the case of colors this blooming is much more objectionable, as this surface color rubs off and stains whatever comes in contact with it. The color must not migrate from a colored part of the rubber t o a non-colored part. This migration appears to be a function of the solubility of the color in rubber and an insoluble organic color is usually found t o be non-migrating. BLEEDING-Rubber colors must be absolutely non-bleeding, and a color which may not be fast t o washing in textiles does not necessarily bleed when used in a rubber stock. As the inorganic pigments do not bleed, it is essential that the organic colors which may be used to replace them should be non-bleeding. FASTNESS To SUNLIGHT-while a great many colored rubber goods are rarely exposed t o the sunlight, others are exposed t o it for long periods of time and must not fade. As the rubber colors in many cases are textile colors, their light fastness has already been determined and it is possible to select colors which will withstand sunlight. BRnLIANcY-This is one of the most important factors in selectinga color for rubber. I n a great many cases where hot vulcanization does not absolutely destroy the shade, nevertheless the heating with sulfur deadens it. I n practically all stocks containing organic colors the shade of the goods is distinctly different after curing. It has been found possible, however, to obtain colors of practically every shade which do hold their brilliancy, and the bright varicolored bathing caps, shoes, and wraps we see along the beaches are testimony of this fact. CosT-Another factor which must be considered is cost, b u t the high tinctorial power of the organic dyes and relatively high cost of the high-grade inorganic pigments makes this factor less important than it would a t first appear. I n selecting a color for rubber all these numerous requirements must be considered, and relatively few dyes pass them all. Many of the organic colors are lakes, but valuable colors have been
INDUSTRIAL A N D EiYGINEERING CHEMISTRY
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found in almost every class of dyestuff. While the use of organic colors has been primarily for the bright-colored goods, their use in the replacement of inorganic pigments is growing apace.
Service
I n the development of organic chemicals for the rubber industry the dyestuff industry established, under the guidance of men trained in the rubber industries, technical laboratories thoroughly equipped to study the compounding, curing, and testing of all types of stocks. The work in these laboratories is not only devoted to the development and application of organic compounds, but also studies factory problems of diverse nature and in many cases offers recommendations as to compounding and curing. While reports are heard from time to time to the effect that the rubber industry has reached its peak, yearly production continues to mount and new uses, many of which are of great importance, have been developed. A few of the more
VOl. 18, N o . 12
+interestingrecently developed uses and processes for handling rubber are: the electrodeposition of rubber on all types of surfaces, the introduction of Revertex, a highly concentrated latex, the Peachey process which makes it possible to waterproof delicate fabrics, the increasing demand for rubber tiling and paving, the development of a hard-rubber substitute for wood, the growing use of sponge rubber, and the varicolored sport and beach accessories. From a position of supplying accelerator intermediates the dyestuff industry has reached the stage where they not only supply practically all of the organic intermediates and a large share of the synthetic organic chemicals, but they also are investigating and offering new products as well as new uses for them. Thus, the contributions of the dyestuff industry have helped to make possible the development of superior rubber products which cost less, look better, and last longer.
Standard Methods for the Sampling and Analysis of Commercial Fats and Oils' A. C. S. Committee on Analysis of Commercial Fats and Oils HE first report of the Committee on Analysis of Commercial Fats and Oils of the AMERICANCHEMICALSOCIETYwas adopted April 14, 1919, by unanimous vote. The present revision of these methods, together with a number of new methods, was adopted unanimously in February, 1926. W. D. RICHARDSON, Chairman Swift & Company, Chicago, Ill. W. H. IRWIN, Secrerary Swift & Company, Chicago, Ill. R. W. BAILEY Stillwell & Gladding, New York City T.c. LAW Walton Bldg., Atlanta, Ga. C. P. LONG Globe Soap Co., Cincinnati, Ohio H. J. MORRISON Procter & Gamble, Ivorydale, Ohio
J. R. POWELL Armour & Company, Chicago, Ill.
L. M. TOLMAN United Chemical & Organic Products Co., Hammond, Ind. H. P. TREVITHICK New York Produce Exchange, New York, N. Y. J. J. VOLLBRTSEN Armour & Company, Chicago, Ill. DAVID WESSON Southern Cotton Oil Co., New York, N. Y.
. . . . *.........
Former Members of the Committee W. J. GASCOYNE R. J. QUI" W. J. Gascoyne & Co., Baltimore, The Mathieson Alkali Works, Md. Inc., New York City E. TWITCHBLL I.'KATz Wilson & Co., Chicago, Ill. Emery Candle Co., Cincinnati, Ohio A. LOWENSTEIN PAULRUDNICK Wilson & Co., Chicago, Ill. Armour & Company, Chicago, Ill.
Scope, Applicability, and Limitations of the Methods SCOPE
These methods are intended to aid in determining the commer-cial valuation of fats and fatty oils in their purchase and sale, based on the fundamental assumption commonly recognized in the trade-namely, t h a t the product is true to name and is not adulterated.
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APPLICABILITY The methods are applicable in commercial transactions involving fats and fatty oils used in the soap, candle, and tanning industries, t o edible fats and oils, and t o fats and fatty oils in1 Approved by the Supervisory Committee on Standard Methods of Analysis of the American Chemical Society.
tended for lubricating and burning purposes. The methods are applicable to the raw oils used in the varnish and paint industry with the exceptions noted under Limitations, but special methods have not been included.
LIMITATIONS The methods have not been developed with special reference to waxes (beeswax, carnauba wax, wool wax, etc.), although some of them may be found applicable to these substances. The Committee considers the a'ijs method superior t o the Hanus method for the determination of iodine number of linseed oil as well as other oils, although the Hanus method has been considered standard for some time and has been adopted by the American Society for Testing Materials and in various specifications. It has been customary t o use the Hub1 method for the determination of iodine value of tung oil (China wood oil), but the Committee's work indicates that the Wijs method is just a s satisfactory.
Sampling TANK CARS WHILE LOADING-Sample shall be taken a t discharge of 1. SAMPLING pipe where i t enters tank-car dome. The total sample taken shall be not less than 60 pounds (23 kg ), and shall be a composite of small samples of about 1 pound (450 grams) each, taken a t regular intervals during the entire loading period. When the material flows freely and is not liable to clog, a sample may be taken continuously through a pet cock attached a t a suitable point on the discharge line or pump, the pet cock to be '/r-inch size or larger and to be kept flowing continuously during the pumping period and so regulated as to produce a sample of not less than 50 pounds (23 kg.) to represent the tank car. The sample thus obtained shall be thoroughly mixed and uniform 3-pound (1.3 kg.) portions placed in air-tight 3-pound metal containers. At least three such samples shall be p u t up, one for the buyer, one for the seller, and the third t o be sent to a referee chemist in case of dispute. All samples are to be promptly and correctly labeled and sealed. 2. SAMPLINGFROM CAR O N TRACK-(a) When contents are solid. Live steam must not be turned into tank cars or coils before samples are drawn, a s there is no certain way of knowing when coils are free from leaks. If water is present under the solid material, this must be noted and estimated separately. The sample is taken by means of a large tryer measuring about 2 inches (5 cm.) across and about one and one-half times the depth of the car in length. Several tryerfuls are taken vertically and obliquely toward the ends of the car until 50 pounds are accumulated, when the sample is softened, mixed, and handled a s under (1). I n case the contents of the tank car have become very hard, as in winter weather, so t h a t i t is impossible to insert the tryer,
