Coal as a Source Material for the Plastics IndustrvJ
REGINALD L. WAKEMAN Mellon Institute, Pittsburgh, Penna.
B. H. WEIL Gulf Research & Development Company, Pittsburgh, Penna.
A reported total of 437,800,000 pounds of synthetic resins, exclusive of cellulose derivatives, were produced in 1941 as compared with only 13,450,000 pounds in 1927. As late as 1940, however, plastics output was still less than 0.5 per cent of steel production. Coal has long been the chief source for plastics intermediates, basic materials being light oil and coal tar, water gas, and coke itself. Some 7 per cent of the benzene produced, 86 per cent of the tar acids (natural and synthetic), 66 per cent of the naphthalene, and all of the coumarone-indene from light oil and coal tar went into 1941 production of phenolics, nylon, polystyrene, alkyds, and coumarone-indene resins. Of 1941 formaldehyde production, close to 75 per cent was consumed by such resins as the phenolics, ureas, and melamines. Intermediates for methylcellulose and the methacrylates were also produced from water gas. Acetylene from calcium carbide is a source for numerous thermoplastics, although coal competes with petroleum hydrocarbons in this field. Both acrylonitrile for synthetic rubber and melamine are produced from coke through calcium cyanamide. While petroleum derivatives, agricultural products, and natural resins will provide keen competition, a sound program of research should enable coal to play a vital role in the future expansion of the plastics industry.
H E plastics industry today stands on the threshold of a new e' ra. Extolled in 1941 as ideal substitutes for metals needed in our defense program, plastics found themselves pushed into the limelight of public regard at a time when the over-all picture was not clearly understood, when present shortages of plastic raw materials were not yet envisioned. Neither was it seen that the greater part of plastics production would soon be required first by our defense and then by our war efforts. Moreover, little attention was paid to the contrast in size between the plastics and metals industries. In 1940 pl&stics production reached a then all-time high of a reported 232,785 tons, as contrasted with 60,406,000 gross tons of steel, 206,280 tons of aluminum, 433,065 tons of lead, 724,192 tons of zinc, and 873,377 tons of copper. Yet all-plastic automobile bodies and airplane fuselages were the order of the day in newspapers throughout the country, and manufacturers of all types of metal products turned the attention of their research divisions to the substitution of plastics for metals. When these facts became evident, the resultant confusion tended to obscure indications of healthy growth of the industry. While output, especially in 1942, has been hampered by material shortages, the industry has seen its products successfully adapted to thousands of new applications; i t has seen huge plants go up which will provide an undreamed of abundance of raw materials when these substances are no longer required by war, and it has learned under duress to accomplish such feats of economy that inexpensive plastics after the war will constitute a sustained threat to the use of metals for many applications. The plastics industry today, however, is no longer a relatively unimportant factor in our economy. A quick glance a t the picture in the fairly normal year of 1940 dispels such an idea. For in that year, according to the U. S. Tariff Commission, 276,814,000 pounds of synthetic resins for plastics were produced, while the Bureau of the Census reported an additional production of 11,915,290 pounds of cellulose nitrate plastics and 23,850,000 pounds of cellulose acetate plastics, the value of these products totaling nearly $100,000,000. Table I shows that these figures delineate no
freak year; they are but the culmination of a period of rapid but steady growth which went on to reach a new peak in 1941, despite the handicap of raw material shortages. It should further be considered that the plastics industry, being chemical by nature, is intimately interlinked with certain other chemical industries, especially rayon and synthetic rubber. For, of the 451,204,000 pounds of rayon yarn produced in 1941, 163,745,000 pounds were of the cellulose acetate variety, almost identical in composition with the cellulose acetate plastics and sharing their complexities of manufacture and economics. Furthermore, the rapidly budding synthetic rubber industry can hardly be distinguished from the plastics industry in many phases. Its Thiokol, Koroseal, Resistoflex, and numerous other types are really rubberlike plastics, while both industries have in common similar problems of polymerization, compounding, and processing, in addition t o using large quantities of the same raw materials. Butadiene itself, the basic raw material for the chief types of synthetic rubber, the Bunas, has recently been the topic of numerous patents for the production of various new plastics. This prospective 1,000,000-ton-peryear industry, linked as it is with plastics, will serve again to show the important position already attained by plastics in our economic picture. It is now timely to consider the dominant role which coal plays as raw material in the production of essential intermediates for nearly all synthetic resins and plastics. In such fields as polyamides i t reigns supreme; in others, like the phenolics, its rule is almost undisputed, but in still other realms such as the methacrylates and vinyl polymers its sway h w been effectively challenged and its kingdom so successfully invaded by petroleum and petroleum gases that the demarcation of territory belonging to each raw material source is often well nigh impossible.
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Light oil, coal tar, coke, and water gas all contribute their share to the plastics industry.
Plastics Derived from Light Oil and Coal Tar The essential components of light oil and coal tar which pass into large-volume plastics are benzene, naphthalene, the tar acids, and coumarone-indene fractions. Cyclopentadiene and dicyclopentadiene have attracted some attention and will probably receive more in the future, although as yet their polymerization and condensation products can scarcely be considered big-volume plastics. Toluene also finds limited use in the production of sulfonamide-formaldehyde resins for lacquer and adhesive formulation. Figure 1 shows the 1941 production of these basic raw materials for large-volume plastics, together with the estimated amount of each consumed by the plastics industry. The remarkable increase in demand for coal tar chemicals by the plastics industry during the past quarter of a century is especially spectacular in the cases of phenol and naphthalene. Prior to the first ITorld War, our annual production of phenol, entirely natural, was in the order of a million pounds a year, with consumption not much in excess of 5 million pounds, supplied largely by imports. Military demands during that war caused the introduction of synthetic phenol processes and a vastly increased production which attained 107 million pounds in 1918. Upon cessation of hostilities, stocks on hand amounted to some 35 million pounds, several times the normal civilian demand in those days. Synthetic operations stopped, and production in 1919 dropped to only 1.5 million pounds. The subsequent rapid increase in demand, much of it occasioned by the phenomenal increase in importance of phenolic resins, is apparent from the production figures of Table 11.
FIGURE 1 . 1941 P R O D U C T I O N O F COALT A R C H E M I C A L S AND THEIRCONSVMPTION BY THE PLASTICS INDUSTRY
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Historically, tar acids have played a fundamental role in the development of the plastics industry, for Bakelite, the first purely synthetic resin, was originally manufactured exclusively from natural phenol. During the war of 1914-18 when phenol became scarce, the cresols and xylenols were investigated and found to yield resins of excellent merit, so that their use was continued after the Armistice. Appropriately treated to maintain a low o-cresol content, they still play an important part in the production of phenolic resins today, especially those used for laminating. Of the total reported 1941 production of 157 million pounds of phenolic resins, some 99 million pounds were derived from phenol alone and the remainder from cresols, cresylic acid, and xylenols, alone or mixed with phenol. This would have required some 96 million pounds of phenol and 36 million pounds of cresols and xylenols. The cresols and xylenols were almost entirely natural in origin, but petroleum cresylic acids give promise of future usage. In the peacetime pursuits of the nation, the plastics industry is by far the largest consumer of phenol, having accounted for over 7 5 per cent of last year’s production of approximately 130 million pounds. It is obvious, therefore, that current military demands for this chemical have dislocated the production of phenolic resins. Russia’s request last fall for over 100 million pounds of phenol in 1942 left plastics manufacturers gasping for breath. Current operations are being greatly expanded both by increased volume from existing plants and by extensive new construction. Present phenol production is estimated to be about 25 per cent natural, the remainder synthetic. I n the latter case benzene is universally the basic raw material employed. It is converted to phenol either by sulfonation and subsequent caustic fusion, the earliest synthetic process; by chlorination and later hydrolysis according to the Dow process; or by reaction with hydrogen chloride and air, followed by hgdrolysis, according to the Raschig process operated by Durez. Of the 75 per cent of 1941 phenol production estimated t o have been synthetic, some 15 per cent was made by the recent Raschig method, while the rest was manufactured by the other two processes. On the basis of present-day operatiom1 methods, about 68 million tons of coal were required to supply the phenol for last year’s phenolics, while about 57 million tons supplied the tar acids for other types of phenolics derived from phenol homologs. These two figures are, of course, not additive, since coal yields benzene, phenol, and cresylic acids simultaneously in most recovery systems. Phenolic resins are utilized in an infinite variety of ways which may be generally classified under molding powders, laminated articles, casting resins, coating materials, bonding agents, and miscellaneous uses. In 1937 phenolic resins utilized in molding compounds accounted for 40 per cent of the total, those for laminated products some 25 per cent, and those for other applications about 35 per cent, of which 25 per cent went into surface coatings. The peacetime applications of molded phenolics range all the way from electrical fixtures and telephone sets to radio cabinets, pipestems, and coffins. Ash trays, juke boxes, fan supports, and many other nonessential civilian uses are now banned for the duration, and phenolics have been drafted for gunstocks, trench mortar shell nosepieces, and an infinite variety of more prosaic but vital applications in instrument housings and electrical parts of all types of land, sea, and aircraft of the armed forces. Laminated phenolics, since their birth, have found essential electrical and mechanical applications in industry. Recent years have seen water-lubricated bearings for rolling mills, cement mixers, paper machinery, and turbines come to the fore. Laminated phenolics, no less than their molded brethren, have gone to war and occupy a position of importance in
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diamine were utilized in the production of 8 million pounds TABLE I. UNITED STATES PRODUCTION OF RESINS AND PLASTICS~ of nylon last year which, in turn, would have required about Synthetic Organic Resins b , Cellulose Plastics e, 6.8 million tons of coal, passing through phenol. It is underYear Lb. Lb.
stood that the current shortage of phenol has led to the introduction of a process for the manufacture of adipic acid directly from benzene. Benzene also serves as raw material for other plastics intermediates besides phenol which, although small in volume thus far, possess enormous potentialities. Among these chemicals, styrene is one of the most important. It is produced largely by pyrolysis of ethylbenzene, the product of a Friedel-Crafts reaction between benzene and ethylene or ethyl alcohol. It should be noted, however, that a competitive operation yields styrene by pyrolysis of petroleum oils, and this process is now in commercial development, supplying considerable amounts of styrene. Polystyrene, although the first synthetic resin discovered in the laboratory (dating back to 1839), is one of the most recent to achieve success in this country. It was produced to the extent of some 5 million pounds in 1941, which would have required the recovery of benzene TABLE 11. UNITED STATES PRODUCTION AND SALES OF PHENOL", from about 1.6 million tons of coal. With the current development of synthetic rubber, styrene as one of the comIN THOUSANDS OF POUNDS ponents of Buna S will become a large-tonnagb chemical, a c Sales Year Production Quantity Unit value fact which will be reflected in increased production of poly1917 64,147 64.147 $0.37 styrene plastics in molded, extruded, and film form. I n 106,794 0.35 1918 106,794 1,544 1,544 0.10 1919 Germany it is today one of the most available plastics, and is 1923 3,311 2,180 0.27 utilized for many applications where cellulose acetate is used 14,734 8,524 1925 0.21 5,480 0.18 1926 8,691 in the United States. It has been freely predicted that, 1927 8,041 4,595 0.15 10,227 1928 7,746 0.12 because of the increased production of styrene caused by the 19,939 1929 24,178 0.11 rubber industry, polystyrene will be one of the most avail21,147 17,715 1930 0.11 1931 17.981 14.002 0.10 able and least expensive plastics in this country after the 13,965 12,181 1932 0.10 33,220 27,923 0.10 1933 present war. 36,241 1934 44,935 0.11 Benzene can also serve as a source of butadiene for synthetic 1935 43,419 34,575 0.10 48,724 40,942 0.10 1936 rubber in a process using cyclohexane as intermediate. It 65,690 57.176 0.11 1937 32,196 1938 44,548 0.11 was originally planned to produce some 40,000 tons of buta59.857 1939 68,577 0.10 diene per year by this method, but current shortages of 96,155 0.09 1940 1941 130,000b ... benzene have occasioned abandonment of this program. According to the U. S. Tariff Commission. Benzene and, particularly, naphthalene, rank high as b Chem. & Met. Eng., 49, No. 2, 94 (1942). essential raw materials for the production of alkyds which, nonexistent in 1925, now equal the phenolics in importance and rival them in volume. I n 1941 the production of alkyd airplane pulleys, fair-leads, and tracks, for example, in resins from phthalic anhydride reached a reported total of soldiers' helmet liners and in numerous electrical control 128 million pounds and from maleic anhydride, 9.5 million panels. Phenolic-bonded plywood, closely related to lamipounds. These acid anhydrides are produced by catalytic nated products, is a field of intense current activity. Millions oxidation of naphthalene and benzene, respectively. Here of feet of resin-bonded plywood have gone into flooring, again it is interesting to note the increased demand for phthalic control surfaces, and leading wing edges of military planes. anhydride occasioned by the plastics industry. Prior to Bomb-bay doors and shaped plywood noses are in production the first World War this chemical was made by sulfuric acid on certain planes, while struts and supports are widely used. oxidation of naphthalene in the presence of mercury and sold So-called all-plastic planes built of plywood seem yet to be in for as much as $4.25 per pound. Following the introduction the future, save for a few experimental trainers. Their of the Gibbs and Conover catalytic oxidation process, probirth expectancy, however, is excellent. duction steadily increased until it reached approximately Phenolic coatings are also vital to the war effort, being used 80 million pounds last year, at an average sales price of 15 on equipment of all the armed services. An interesting cents per pound. I n 1941 some 60 million pounds of phthalic development of recent years has been Revolite phenolicanhydride were consumed in the manufacture of alkyd resins. coated fabric which, suitably gummed on the reverse side, This would have accounted for about 55 million pounds of serves as a tape to seal, protect, and simultaneously camounaphthalene, produced from 24 million tons of coal. Maleic flage tanks and planes in transit across both oceans. The anhydride consumed by the plastics industry in the manushipment of a single Airacobra requires 2960 yards of onefacture of alkyds required approximately 1.2 million tons of inch tape; larger planes require much more. coal to yield the necessary amount of benzene for its synthesis Until recently, the phenolic resins were the only important by oxidation. outlet for phenol in the plastics industry, save in plasticizers. Glycerol, or an equivalent polyhydric alcohol, is the other The latter, of course, require considerable amounts of both essential component of alkyds. Drying .oils or drying oil phenol and cresol, particularly as phosphates. The introacids are usually employed as modifiers, while other addiduction of nylon, however, added another large-volume tional components sometimes include rosin, other natural plastic to the list of phenol consumers, for its essential interresins, and phenol. Alkyds have become indispensable in mediates, adipic acid and hexamethylene diamine, are both the formulation of synthetic coatings. I n combination with derived from phenol. It is estimated that some 5 million nitrocellulose, phenolic resins, or urea resins, they find extenpounds of adipic acid and 4 million pounds of hexamethylene sive application in quick-drying interior finishes, in automo1927 13,452,000 d 1928 20,411,000 d 1929 33,036.000 d 1930 30,868,000 d 1931 36,179,000 d 1932 30,937,000 d 1933 45,200,000 15,825,000 e 1934 59,915,000 1935 95,133,000 26,695,000e 1936 132,913,000 1937 163,03 1,000 37,047,000 1938 130,359,000 d 1939 213,028.000 34,169,000 1940 276,814,000 35,765,000 1941 437,800,000/ 55.000,oooa 0 Production totals are not directly additive, as figures for cellulose plastics are not for net resin content. b According t o the U. S. Tariff Commission. c According t o the U. S. Bureau of the Census. d Figures not available. e Figures do not include cellulose acetate plastics consumed by producers. f Preliminary U. 9.Tariff Commission total. Estimated>by authors; includes estimates for ethylcellulose and methylcellulose plastics.
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CYCLOPENTADIENE 8 OICYCLOPENTADI €NE
Hydronaphtholene
Coumarone Indene Resins
RESINSAND PLASTICS DERIVED FROM COALTARAND LIGHT OIL FIGURE2. SYNTHETIC
bile and refrigerator lacquers, and now in all manner of coating materials for the Army and Navy. I n addition to its use in the manufacture of alkyd resins, phthalic anhydride is also consumed in volume for the manufacture of plasticizers, especially dibutyl phthalate, which is compounded with thermoplastics in molding powders and sheets and is employed in the formulation of synthetic lacquers. This plasticizer is being utilized in such ever-increasing quantity for military purposes, among which the manufacture of smokeless powder ranks first, that it may curtail the production of cellulose acetate and acetate-butyrate plastics. A new plastic derived from phthalic anhydride by reaction with allyl alcohol has made its appearance this year. Much promise is held for this material, especially for can linings. Present development, however, is said t o be exclusively for military purposes. The highly unsaturated naphtha cut from light oil contains much indene and coumarone, and these products are polymerized, usually with sulfuric acid, to yield resins ranging in color from light amber to dark black and in melting point from molasseslike sirups a t room temperature to friable solids melting a t 150" C. or above. They have found extensive use in rubber compounding, terrazzo floor tile, printing inks, paints, lacquers, and chewing gum. Hydrogenated products have recently appeared on the market. Several more or less similar resins of comparable thermoplastic characteristics are also produced by modification with phenols. Polymerization of cyclopentadiene and dicyclopentadiene, condensation of naphthalene and formaldehyde, and polymerization of partially hydrogenated naphthalenes have also, in times past, yielded small amounts of analogous resins. These related products are all small-production items a t present. The volume of coumarone resins manufactured last year is estimated a t 30 million pounds which, by a rough estimate, would have required recovery of the indenecoumarone fraction from by-product coking of nearly 100 million tons of coal. About 90 million tons of coal were coked in 1941, of which some 90 per cent, or approximately 80 million tons, were handled in by-product ovens. Hence it is apparent that most of the indene-coumarone fraction recoverable from by-product operations was utilized last year by the plastics industry. These resins have found only limited military application so far.
All the various ways thus far discussed in which the plastics industry draws upon derivat,ives of by-product coking operations are summarized in Figure 2.
Plastics Derived from Water Gas Water gas, derived chiefly from coke, is no less essential as a raw material for the plastics industry than coal tar and light oil. I n the case of the phenolic resins, for example, coal serves not only as a source of tar acids and synthetic phenol, but also, through water gas, as the most important source of formaldehyde. This chemical, now also made in limited amounts by direct oxidation of natural gas, is still produced mainly by oxidation of synthetic methanol. While some methanol is produced from water gas originating with methane, that actually used by formaldehyde producers presumably comes from coal. In 1941 the total formaldehyde production for all purposes was about 277 million pounds (basis 40 per cent). Of this, about 150 million pounds found its way into phenolic plastics and approximately 60 million pounds into other types of plastics. Of the latter, the ureas are most important, These plastics, not produced in this country before 1929, were made to the extent of about 35 million pounds last year, some 50 per cent going into molding powders and 50 per cent into lacquers and adhesives. They are used extensively in molded housings, buttons and buckles, light shades and reflectors, electrical fixtures (especially where nontracking is important), and in a miscellany of novelty applications. I n combination with alkyds they have become indispensable in white lacquers, especially refrigerator enamels. Urea adhesives, both cold and hot setting, have gained ground in a spectacular manner since their introduction in this country about three years ago; they now are used in considerable volume in plywood manufacture. The urea resins are produced by the reaction of urea with formaldehyde. Coal serves not only as the principal source of formaldehyde, but also of carbon for urea which is the product of the interaction of carbon dioxide and ammonia. Ammonia is, of course, also a product of coal distillation. Other applications of formaldehyde in synthetic and semisynthetic resins include the hardening of casein to a plastic used principally in buttons and buckles; the conversion of casein to artificial wool, of which some 5 million pounds will
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be made in the United States during 1942; the manufacture of melamine resins, new light-colored thermosetting molding and laminating resins of superior heat and moisture resistance; and the production of toluenesulfonamide resins and several other small-volume plastics and resins, including polyvinyl formal, the coating material employed in the fabrication of Formex magnet wire. Methanol is an intermediate in the production of other chemicals besides formaldehyde which are absorbed in the manufacture of plastics. It is converted to methyl chloride which, in turn, enters into the production of methylcellulose used largely as a paper size and textile treating agent. Some 72 tons of coal were required for the production of water gas, which by this tortuous path, finally appeared on the market as methylcellulose last year. This corresponds to an estimated 500,000-pound production. Furthermore, by high-pressure reaction with carbon dioxide, methanol yields acetic acid, used in the manufacture of cellulose acetate. Indirectly through a formate, carbon monoxide from water gas is reacted with ammonia to yield formamide, which is subsequently dehydrated to hydrogen cyanide, used in increasing amounts to produce acetone cyanohydrin which is then converted to methyl methacrylate and polymerized. Figure 3 summarizes the relation between coal and plastics produced from chemicals derived from water gas.
Plastics Derived from Coke I n addition to its use in the production of water gas, coke serves directly as a source material for a large number of synthetic organic chemicals of which an ever-increasing number find their way into the plastics industry either as plasticizers or in the manufacture of the resins themselves. Coke is, routed into plastics manufacture by either of two main highways through calcium carbide-namely, acetylene and calcium cyanamide. The latter is a source of cyanide, used in the manufacture of acrylonitrile, one of the components of oil-resistant Buna N and Hycar. This type of oil-resistant rubber was first produced in this country in commercial quantities late in 1940. Cyanide can also serve as intermediate in the manufacture of methacrylonitrile which, in turn, is converted to methyl methacrylate and polimerized to the highly transparent plastics-Lucite, Plexiglas, and Crystalite. It is probable, however, that a considerable fraction of these plastics is produced from hydrogen cyanide obtained by catalytic dehydration of formamide, derived from
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carbon monoxide and ammonia. The methacrylates, although produced in smaller volume than the more timehonored plastics, have become well known because of their spectacular clarity which permits a large number of unique optical and decorative applications. Today they are indispensable in airplane wind screens. It is estimated that about 5 million pounds of methacrylates were produced in this country last year. For their manufacture, intermediates from 25,000 tons of coal were required in addition to those derived from petroleum. Calcium cyanamide is the only source of dicyandiamide, and this chemical, in turn, is now converted to melamine, the intermediate which, upon reaction with formaldehyde, yields the new melamine resins. These products are now going solely into war applications, except for small amounts being used for experimental work. They will undoubtedly increase in favor after the war. Chemicals derived from calcium carbide through acetylene are numerous. With a few notable exceptions-nitrocellulose, rubber derivatives, and polyvinylidene chloride-they enter into the production of all the thermoplastics to a greater or less extent. This picture, however, is far from clear because of the fact that petroleum products, especially natural and cracked gases, likewise provide huge amounts of many of these chemicals. I n some instances products which can be derived from one source can be produced at almost the same figure from the other. Among the thermoplastics, cellulose acetate is by far the most important. Acetic acid and acetic anhydride are both required for its manufacture. I n 1940 the production of cellulose acetate for all purposes, including acetate yarn, was 175 million pounds, a then all-time high reflected in a 30-million-pound increase in acetic acid and its anhydride over the preceding year. Cellulose acetate molding powders are used in the fabrication of an infinite variety of articles for the home, office, and automobile which do not require high-temperature or solvent resistance. I n transparent sheeting it has opened extensive markets in the packaging field. I n filament form it has become well established as an artificial silk, a use which is expanding annually. Coldstretched acetate yarn is an innovation which has been used in such military applications as balloon and parachute fabrics. Acetic anhydride is produced from acetylene by pyrolysis of ethylidene diacetate and by controlled oxidation of acetaldehyde, but still larger volumes come from ketene, obtained by pyrolysis of acetone. The latter, once a large-volume
Ce IIulore
Met hocrylote
Alcohol
FXQURE 3. SYNTHETIC RESINSAND PLASTICS DBRIVED FROM WAWR GAS
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FIGURE 4. SYNTHETIC RESINSAND PLASTICS D ~ R I V EDIRECTLY D FROM COKE
acetylene derivative, is now largely obtained from the propylene content of cracked gases, although it is probable that some still comes from coal as well as from the fermentation of cornstarch, an operation which has persisted, for better or worse, since its introduction during the first World War. Acetic acid likewise is produced from acetylene by hydration to acetaldehyde, followed by oxidation. But some acetic acid is also produced by oxidation of ethanol, and small amounts are still obtained as a by-product of wood distillation. Its manufacture from methanol by reaction with carbon dioxide is a recent innovation which has already been mentioned. It is estimated that somewhere around 5000 tons of coal were coked in 1941 for conversion t o acetylene consumed in the production of acetic acid and its anhydride, destined for the manufacture of cellulose acetate plastics, exclusive of acetate yarn. Either acetylene or ethylene can serve as the source of vinyl chloride and vinyl acetate, intermediates required for the production of vinyl resins. Polyvinyl chloride has found favor as an oil- and oxidation-resistant rubber substitute and as a water- and oilproof coating material for cloth such as Korosealed goods. As an electrical insulator it has few equals. Because of its resistance not only t o the elements but also to fire, almost its entire production has been used by the Army and Navy during the past year, especially in the manufacture of degaussing cables. I n the past vinyl chloride has been produced largely from ethylene derived from petroleum, but this situation has changed with the opening of recent plants. The cost of vinyl chloride produced from acetylene is about the same as that made from ethylene. Some 10 million pounds of polyvinyl chloride were produced last year, requiring the consumption of about 1600 tons of coal. Vinyl acetate, on the other hand, is largely made from acetylene by addition of acetic acid, its production from ethylene being feasible but probably slightly less economical. Vinyl acetate is used in copolymers with vinyl chloride which are fabricated as molding powders, sheets, calendered sheeting, and extruded yarns. It also serves as adhesive in certain limited applications when polymerized alone, and as the basis of polyvinyl butyral safety-glass interlayer. It is estimated that a million pounds of vinyl acetate resins were produced last year, requiring the use of 650 tons of coal, while an estimated 7 million pounds of polyvinyl butyral resins were made, utilizing about 7000 tons of coal. In spite of the shutdown of the automobile industry, largevolume military uses for polyvinyl butyral have now been
developed, such as the production of waterproof fabrics of all types. Acetylene from coke is also the source of neoprene synthetic rubber, for the production of about 13 million pounds of which in 1941 some 11,000 tons of coal were required. Small amounts of S-D-0 obtained as a by-product from neoprene manufacture also represent still another resinous product derived from coal. Cellulose acetobutyrate, cellulose acetopropionate, and ethylcellulose are still other semisynthetic resins that utilize chemicals which, although derived chiefly from petroleum, are also manufactured in lesser volume from coal through acetylene, Figure 4 summarizes the relation between coke and the plastics industry.
Conclusions Coal is thus an important source material for the plastics 'industry. Plastics made from coal intermediates have shown each year a healthy rate of increased production. It seems proper to envision much greater expansion after the war. But the coal industry must take cognizance here, as in other chemical industries which use its products, of the recent but already important factor of competition with petroleum and natural gas hydrocarbon derivatives. Petroleum chemicals have already taken over a sizable portion of the intermediates business, especially in the field of thermoplastics. Large quantities of acetic anhydride, acetone, butyraldehyde, ethyl alcohol, ethyl chloride, formaldehyde, hydrogen chloride, methyl methacrylate, methanol, methyl chloride, styrene, vinyl chloride, and vinylidene chloride are now coming from petroleum hydrocarbons, and the petroleum chemical industry shows no intention of resting on its laurels. The present crisis has brought new factors into play. The shortage of benzene occasioned by the demand for production of synthetic rubber has made extraction of quantities of benzene from petroleum distillates a certainty. Production of some acetylene from petroleum hydrocarbons, long a matter of increasingly close economics, is now projected. These two hydrocarbons from petroleum will provide increasing competition in the manufacture of such important intermediates as acetic acid, adipic acid, hexamethylene diamine, maleic anhydride, phenol, styrene, and vinyl acetate. The coal industry's domination of the phenolic resin field may also soon be challenged not only by phenol from petroleum
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INDUSTRIAL AND ENGINEERING CHEMISTRY
benzene, but likewise by increasing quantities of petroleum cresylic acids. It is of interest to note that in 1941 the plastics industry consumed intermediates which required as raw materials some 700 million cubic feet of natural gas for methane, 2.9 billion cubic feet of propane for ethylene, 270 million cubic feet of propane-butane mixtures, 70 million cubic feet of propylene, and 150,000barrels of petroleum. The quantities soon to be required for synthetic rubber will make most of these amounts fade into insignificance. Nor should the coal industry expect competition from only one quarter. Agricultural products may be expected to play an increasingly important role in the plastics industry of tomorrow. Brazil is keen about a large program for the production of plastics from coffee. Soybean resins have already entered the field. Patents appear in great numbers for the production of plastics from cottonseed hulls, corn proteins, and bagasse. In the synthetic rubber picture, butadiene from alcohol and other agricultural products is now a certainty. Waste sulfite liquors and exploded wood
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chips are constantly contributing larger volumes of lignin plastics. Similarly, the plastics industry may expect to see a continued use of products derived from the naval stores industry. The coal industry need not necessarily suffer from this competition, even though prices will undoubtedly resume their downward trend after the war and the markets for some intermediates may be lost. The prospects for a tremendous increase in the volume of plastics production will render the future for coal derivatives extremely bright if every effort is made to maintain research, reduce basic costs of manufacture, increase yields, and produce a varied and flexible number of intermediates. Research must continue to be the watchword of the day! PEEBI~NTED as part of the Symposium on Uses of Coal by Various Industries before the Division of Gas and Fuel Chemistry at the 104th Meeting of the AMIH~RICAN CHEMICAL SOCIETY. Buffalo, N. Y . Joint oontribution from the Pittsburgh Equitable Meter Company's Industrial Fellowship at Mellon Institute and the Chemical Engineering Laboratory of the Gulf Research and Development Company.
CALCIUM CHLORIDE NOMOGRAPHS D. S . DAVIS Michigan Alkali Company, Wyandotte, Mich. ALCIUM chloride, available in large quantities in flake form, finds industrial application as a general dehydrating agent, in the drying of gases, in the manufacture of liquid carbon dioxide, ammonia, and air, in the curing of portland cement concrete, in fireproofing paints, in the manufacture of gunpowder, dry colors, and lakes, in automatic sprinkler solutions, and as a refrigerating brine. It is admirably adapted to the latter use since the specific heats of its aqueous solutions are high enough to ensure the use of moderately small quantities of brine, accidental ammonia leakage does it no harm, it is not particularly corrosive, and its solutions have satisfactorily low freezing points. Large amounts of calcium chloride are used in road treatment for stabilization and dust laying, for ice control on highways, and for the treatment of coal and coke for dustproofing and freezeproofing. Since many of the uses of calcium chloride require brines, hydrometric methods of analysis for control purposes offer obvious advantages. Excellent specific gravity-temperatureconcentration data (1, 3, 4) are available, but these are in tabular form and require inconvenient interpolation. For temperatures between 10' and 30' C. the I. C. T. data (4) can be represented closely by the equations,
C
for c = 6 to 20 s = a + + + p 0.736 )
for c
= 20 to
34
where 6 = specific gravity, 60/60" F. c = concentration of anhydrous CaCll in pure aqueous solutions, a, b = functions of tern erature resulting from Lagrange interpolation (%f and defined by Table I Commercial calcium chloride contains about 1.5 per cent of sodium chloride and thus necessitates adjustment of the quantity e to cover concentrations of anhydrous calcium
chloride in the impure brines using the Dow data (3). The nomographs, based on this correlation, extend the utility of the hydrometric method by permitting reliable graphical interpolations to be made quickly and conveniently. The use of the charts is illustrated as follows: What is the concentration of calcium chloride in a commercial brine when
TABLEI. FUNCTIONS OF TEMPERATURE Temp.,
c.
10 12 14 16 18
a0
22 24 26 28 30
o
a 0 * 9880 0.9878 0.9875 0.9872 0.9869 0,9865 0,9861 0.9857 0.9852 0.9848 0.9842
-
6 t o 20
b
0,009723 0.009690 0.009659 0.009604 0.009632 0.009578 0.009554 0.009529 0,009506 0.009484 0.009465
c = 20 to 34 a b 0.9619 0.010880 0.010851 0.9616 0.9613 0.010826 0.010804 0.9609 0.010783 0.9605 0,9600 0.010765 0.010750 0.9594 0.9588 0.010730 0.010724 0.9581 0.9574 0.010716 0.9565 0.010706
TABLE11. AGREEMENTBETWEEN TABULAR AND CHART DATA Hydrometer Reading 1.071 1.127 1,177 1.231 1.286 1.331 1.068 1,123 1.173 1.226 1,280 1.325 1.060 1.122 1.171 1.223 1,278 1.322
Temp.,
c.
10 10 10 10 10 10 21.1 21.1 21.1 21.1 21.1 21.1 26.7 26.7 26.7 26.7 26.7 26.7
70
Nomograph 8.15 14.05 19.1 24.15 29.1 33.1 8.18 14.35 19.2 24.15 29.1 33.12 8.15 14.4 19.2 24.1 29.2 33.2
CaClt
CaClz Assoc. 8.0 14.0 19.0 24.0 29.0 33.0 8.0 14.0 19.0 24.0 29.0 33.0 8.0 14.0 19.0 24.0 29.0 33.0
