Raw Materials of the Plastics Industry GUSTAWS J. ESSE1JEN AND FREDERICK S. BACON Gusitavus J. Eseelen, Inc., Boston,
P
S
WIFT expansion of the plastics industry has created new demands for raw materials in ever-increasing quantities. The hundred fold growth of the industry during the past fifteen years has n o t o n l y m a g n i f i e d markets for familiar materials but has required the production on a huge scale of numbers of materials entirely new in commerce. The effects of this rapidly growing demand are vitally important in the economic picture of chemical industry. On the question of raw material supply often depends the choice of one plastic or another for a specified purpose. When huge tonnages of intricate synthetics must serve as intermediates for further processing, the user may well examine the raw material situation carefully before committing himself to a particular plastic. The purpose of this article is to survey some of the more important economic factors which must be considered in such an analysis. For c o n v e n i e n c e two principal classes of synthetic resins may be set up: (1) those derived from coal tar and (2) t h o s e u t i l i z i n g p r o d u D t s of noncoal-tar origin. The second
(Lower) BULLETMICROPHONE The brilliant Beetle resin colors give more life to the speaker’s table a t banquets, etc., and also permit better photographs t o be taken of the microphone. This latter point IS unusual but im ortant. This unit will photograph excellently and act as a n advertisement for t%e producing company. It is made by Transducer, Inc.
class may be still further subdivided into (a) plastics based on cellulose and plant products; (b) those derived primarily from the hydrocarbons of petroleum, natural gas, and acetylene; and (c) the urea resins and those derived from rubber and alkyl chlorides. In the final analysis, all the raw materials now used in making the synthetic resins can be obtained from a few natural products-cellulose, coal, salt, sulfur, water, air, and limestone. There is no reasonable likelihood that a shortage or a market for them great enough to force wide fluctuations of price will occur. I n some instances it is more convenient to utilize petroleum and natural gas as sources of the same types of intermediate compounds as those from coal; hence in the United States these crude materials must also be considered. It is important to note this interchangeability in view of the frequent controversies regarding the life of our petroleum reserves. Obviously, the plastics industry is unlikely to find itself limited by the supply of its fundamental crude materials.
LIGHTFOR A Bus The outer frame is made of aluminum and the light-diffusing panel of Beetle resin. a small transparent window of glass is designed t o direct the light ddwnward on the seat and the whole panel distributes light throughout the bus. The complete,assembly weighs a little more than 12 ounces and, because of ita light weight and strength, provides additional safety t o t,he occupants of the bus. The Beetle panel waa molded by the Waterbury Button Company. Courtesy, American Cyanamid Company
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Rather, the limits already encountered are set by the abilities of chemical technology to elaborate these crudes into the intermediate forms required in resin manufacture. These intermediate products are much more liable to be affected by the law of supply and demand with its fluctuating prices. I n this class should be included phenol, phthalic anhydride (the true intermediates are benzene and naphthalene, respectively), formaldehyde, urea, ethylene, acetylene, and others. A myriad of organic materials used as plasticizers and blending agents are also among the intermediates, but they are so numerous that they can hardly be more than mentioned in this paper.
aldehyde, usually formaldehyde. The demand for phenol in America for this purpose has long exceeded the quantity that can be produced by refining from coal-tar distillates. For many years phenol has been synthesized from benzene by chlorination and subsequent hydrolysis at high pressures or by sulfonation, followed by alkali fusion. The manufacture of the 43,400,000 pounds of synthetic phenol in the United States in 1935 required roughly 43,000,000 pounds of benzene, 60,000,000 pounds of 5 per cent oleum, 10,000,000 pounds of chlorine, and 120,000,000 pounds of sodium hydroxide. I n 1935 about 29,000,000 pounds or 67 per cent of the phenol produced went into resins. Today, however, in less than two years, the demand has been so great that there is a shortage in the supply, and the two TABLEI. RAW MATERIALS FOR PRODUCTION OF SYNTHETIC largest producers have enlarged their plants so that a total RESINS of about 30,000,000 pounds could be manufactured in 1937. Air : Limestone : In England a new 1500-ton (per year) synthetic phenol Ammonia for urea Calcium carbide plant is being built. Nitric acid Acetylene This shortage is due not so much to the lack of benzene Acetic acid Cellulose: as to the lack of manufacturing equipment for converting it Petroleum: Cellulose acetate Ethylene to phenol. The benzene production (not including motor Cellulose nitrate Ketene Ethylcellulose and other ethers fuel) in this country is more than sufficient to take care of Salt : the production of phenol as indicated by the following Coal: Sodium hydroxide Ben~ene figures (thousands of pounds) : Chlorine Phenol Naphthalene Phthalic anhydride Calcium carbide Acetylene Acetic acid Ethylene Carbon monoxide Methanol Formaldehyde
Hydrochloric acid Sodium polysulfide Sulfur: Sulfuric acid Sodium polysulfide Water: Hydrogen Ammonia Methanol Formaldehyde Ethylene Acetylene
Year 1933 1934 1935
Coal-Tar Resins The coal-tar resins are the most important class today in quantity, value, and variety of usefulness. Within this class resins of three principal subclasses are recognized : phenolics (including phenols, cresols, and xylenols), phthalic anhydride resins, and miscellaneous which includes styrene, coumarone, etc. U. S. Tariff Commission figures1 on the coal-tar resins produced in the United States during 1933, 1934, and 1535 appear in the following table :
-
1933
Phenolios: Cast Other Phthalio derivatives Cresols and xylenols
25,163 9,931 6,535
Maleio, styrene, santolites, etc. Total coal-tar resins
1934 1935 1000 pounds
3$;gg ] {2i’igi lS:219 34313 10,887
l6:654
1936 69,382 46,952 Included in phenolics
3,623 ... 177 -0
41,629
56,060
90,913
116,334
Of the 116,334,000 pounds of coal-tar resins produced in 1936, approximately 53 per cent was used in paints, varnishes, and lacquers, and 21 per cent in molding compounds. Of the resin used in the paint, varnish, and lacquer industry, about one-third was phenolics and two-thirds, phthalic derivatives.
Phenolic Resins Phenolic resins are produced by the interaction of phenol or one of its homologs such as cresol, xylenol, etc., with an 1 Produotion and Sales of Dyes and Other Synthetic Organic Chemioals in the U. S., 1933, 1934, and 1935, Govt. Printing Office, Washington. D. C.
Benzene 145,365 178,650 180,795
Phenol 33,220 44,935 43,420
The shortage in England has caused some agitation for the use of cresylic acids in resin manufacture, since they are available in quantity from the low-temperature carbonization of coal. Whether or not these compounds will become factors remains to be seen. The supply of benzene is largely limited by the capacity of by-product coke ovens. Although this supply appears to be adequate a t the moment for the demands of the synthetic resin industry, it is one of the raw material factors which must be followed carefully. Other possible sources of benzene have been suggested but none are as yet of commercial significance. Among them may be mentioned the cracking of certain petroleum crudes which, under proper conditions, are said to yield moderate amounts of aromatic hydrocarbons, including a recoverable percentage of benzene. Recent advances in the polymerization of olefins from cracked petroleum gases have also resulted in the production of varying percentages of aromatics. Formaldehyde is the most important aldehyde employed in resin manufacture. It is made by oxidation of methanol in turn synthesized from hydrogen and carbon monoxide. Some 52,250,000 pounds of 40 per cent formaldehyde (21,000,000 pounds CH,O) were synthesized in the United States during 1933, although not all of it was used in resins. Each thousand pounds of phenol used for resin production requires about 1500 pounds of 40 per cent formaldehyde, depending somewhat on the type of resin produced.
Alkyd Resins Phthalic anhydride resins, otherwise known as the alkyds or glyptals, are especially valuable in protective coatings (paints, varnishes, and lacquers) as indicated by the use of 33,227,000 pounds for this purpose in 1935. The production of these resins in 1935 amounted to 225 per cent of the 1934 production, and this had increased in 1936 to 381 per cent of the 1934 figure. The alkyd resins are made by the reaction of a polybasic acid with a polyhydric alcohol. Phthalic anhydride, made by the catalytic oxidation of naphthalene with air, is the most important acid, although maleic acid is used to some extent.
FEBRUARY, 1938 Year 1930 1933 1934 1935 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY Phthalic Anhydride Produoed ,--IO00 5,614 14,075 20,680 23,421 31,244
Estd. Naphthalene Used pounds5,600 14,000 20,500 23,200 31,000
The growth of the demand for alkyd resins, and in turn the increased demand for naphthalene, has seriously affected the naphthalene market. Even before alkyd resins came into the picture, large quantities of naphthalene were consumed for intermediates in the dyestuff industry as well as in smaller quantities for other purposes. The United States production of naphthalene’ is as follows (in thousand pounds): Year 1932 1933 1934 1935
Produced in U. 8. 13,600 30,620 37,922 47,653
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cal process for this recovery and is planning a factory to cost close to a million dollars for the recovery of styrene. The synthetic methods of producing styrene usually involve first the production of ethylbenzene which is then dehydrogenated by pyrolysis to give styrene. The sulfonamide resins are water-white products of good light stability which are produced in limited quantity by the interaction of substituted toluene sulfonamides with formaldehyde. These resins are finding increasing use in lacquers. The coumarone and indene resins are manufactured in large volume from certain fractions of coal-tar distillates by polymerization with acid catalysts. They find extensive use in the paint, varnish, and linoleum or floor-covering industries.
Imported
Estd. Requirements for Phthalic Anhydride
Plastics from Cellulose
4i,Qi5 48,455
14,ijijo 20,500 23,200
One of the natural products which, through synthesis and processing, is consumed in huge quantities is cellulose. Whether obtained from cotton, wood, or other sources which today are under intensive investigation, the quantity available is practically unlimited, and the quantities used are sufficiently large so that the purification costs are relatively low. Nitrocellulose, discovered by Hyatt in 1868, is the oldest of the cellulose plastics and is produced in large tonnage in the United States. In 1936, 16,934,850 pounds were manufactured; about 12,900,000 pounds were used in pyroxylin plastics. For this purpose about 4,300,000 pounds of camphor were required, which today is being made synthetically both in the United States and Germany. The production of nitrocellulose also draws heavily on the heavy chemical industries for nitric and sulfuric acids. At present the acid manufacturers have no difficulty in meeting the requirements for nitrating acid, and the future need not concern
...
I n 1936 the German Government placed heavy restriction on the exportation of naphthalene from Germany. The resulting decrease in importation of this commodity into the United States was soon reflected in the spot market by an advance in price from 3.75 cents per pound in 1932 to over 7 cents per pound early in 1937 for the refined grade. From 1930 to 1936 the domestic production of phthalic anhydride increased 5.6 fold. I n addition to phthalic anhydride, a polyhydric alcohol, glycerol, or glycol is required to form these resins. The rapid growth in the demand for glycerol has also caused shortages from time to time in the market because its production depends upon operations in which it is a by-product. The glycols, being synthetic, are not so limited, and new methods of making glycerol are being actively sought to free it from the limitations inherent in its production as a byproduct of soap and fatty acid manufacture. Both Germany and Italy have done intensive research along this line; an announcement has recently been made of a synthetic process that will provide adequately for Germany’s glycerol requirements. The possible production of phthalic anhydride resins are thus a t present limited from two sides. Phthalic anhydride is made from naphthalene, which in turn comes from coal tar. The United States is an importer of crude naphthalene, principally from Germany and Groat Britain, and thus foreign conditions affect its price. Among the possible new sources of naphthalene suggested is the thermal treatment of natural gas which, under proper conditions, is said to produce both naphthalene and anthracene. Similarly, glycerol production, limited by other factors and largely used for other purposes, hinders by its lack of flexibility the more rapid expansion of these resins.
(Left) METAL PANELCOATED WITH HASTOLITE BAKELITE RESIN STILLRETAINS ITSORIGINAL GLOSSAFTER Two YEARS IN GASOLINE, HOTSALTWATER,AND MOISTAIR (Right) USCOATED REVERSESIDE OF METALPANELSHOWS RUSTING,PITTING,AND SCALING
Other Coal-Tar Resins Other coal-tar resins are the s t y r e n e s (now being r e c o v e r e d from manufactured gas), the sulfonamides, and those derived from coumarone and indene. Styrene may be synthesized in many ways, but the yield is usually not very high. It is present in the drip oil of carbureted water-gas plants and a potentially large source is available there, but recovery costs are a t present high. It is reported that one large company has developed an economi-
Courtesy, Bakelite Corporation
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INDUSTRIAL AND ENGINEERING CHEMISTRY (Top)
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PACKAGES FOR EXPENSIVE JEWELRY MADE OF BEETLEREGIS
Beetle is suitable for this application because i t provides a colorful background a ainst whlch the contents may be displayed safely%ecause of ita strength and shock resistance, and a medium for unusual package designs. These boxes were molded by the Rathbun lIolding Corporation. Courtesy, Amerrcan C y a n a m i d C o m p a n y
(Center) PHOSOQRAPH RECORDS,BEER CAN LIKISGS, SLIDERTLES, I NT E R L I N E R s FOR ‘STARCHLESS” COLLARS, CLOTH,SUN VISORS AND Box SHOETOES, AS KELL AS THE ADHESIVE FOR SEALIITG ?VfILK CARTONS ARE MADE FROM V’IKYLITE RESIS-s Courtesy. Carbide ‘t Carbon Chemicals Corporation
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us, since there are indications that other materials of more general adaptability to new molding processes are making inroads on nitrocellulose as a plastic. Cellulose acetate is being used in increasing amounts as a plastic, as indicated by the consumption for this purpose of 2,482,111 pounds in 1933, 4,826,347 in 1934, and 13,036,497 in 1936. It is primarily dependent on cheap glacial acetic acid. The production of acetic acid in any quantity is assured by the catalytic synthesis from acetylene and new extraction processes from hardwood distillates. Acetic anhydride is also used in large quantities in the production of cellulose ncctate (for synthetic fibers as well as plastic); 116,460,000 pounds were produced in 1935. It is today being produced commercially by one large organic chemical manufacturer by the interaction of ketene and glacial acetic acid. The development of the commercial production of ketene is a noteworthy step in American chemical industry. The use of cellulose acetate as a molding compound requires the use of large quantities of plasticizers. Those widely used for this p u r p o s e a r e the dialkyl phthalates, phthalyl glycolates, sulfonamides, and triphenyl and tricresyl p h o s p h a t e s The phthalyl glycolates and dialkyl phthalates are both phthalic anhydride derivatives, and their production also depends on a steady supply of both anhydride and naphthalene. TriDlienrl Dhowhates rewire Dhenol, which in turn adds to-the shortage of-phenol available for resin manufacture. Another cellulose derivative, ethylcellulose, which is now available in commercial quantities from more than one source, is finding a place for itself1 in the plastic industry and, like cellulose acetate, is well adapted for injection molding. Ethyl chloride, which is allowed to react with soda cellulose to form ethylcellulose, is today potentially available in large quantities, the raw materials being
.
(Bottom) POLYSTYRENE MOLDINGMATERIAL Bakelite polyst rene possesses a loss factor of less than 0 00053 a power factor of less than 0.0002 and a dTelectric constant of 2.60 a t 60 1000 a i d 1 00’0 000 cycles. I t s dielectric strengih is more than 500 volts per mil, its resishvity iOs mepbhm’-cm., and its arc resistance 240-250 seconds. Teats indicate that no noticeable change occurs in electrical properties with a n increase in temperature or humidity. The polystyrene provides uniformity in molding, freedom from crazing or surface difficulties, permanence of dimension, and high resistance to water acids and alkalies I t s durability and toughness are indicated by its A. 9. T. M. impact’etrenith of 0.16 t o b.20 foot pound, flexural strength of more thFn 7000 pounds per square inch, and tensile strength of 5000 t o 5500 pounds per square inch.
Courtesy, Bakelite
Corporation
FEBRUARY, 1938
INDUSTRIAL AND ENGINEEREW CHEMISTRY
ethylene and hydrochloric acid. Increased demand for ethylcellulose would, therefore, be taken care of without much difficulty. Alarge demand for ethyl chloride would in turn require larger volumes of ethylene which is now, as pointed out earlier in the paper, available in large quantities in the cracked gases from petroleum refining, and can also be obtained through the hydrogenation of coal. Chlorine and hydrochloric acid can be obtained in practically any quantity; the supply is limited only by the production capacity of suitable equipment in the chemical manufacturing industry. I n some industries hydrochloric acid is a by-product.
Resins from Lignin Lignin from wood should be given consideration, since it is available in unlimited quantities and the supply is constantly being replenished by new growth. By hydrolysis of sawdust or digestion with aniline, plastic products of limited color range can be produced which will mold by hot pressing. The very low cost of production (estimated a t from 1 to 4 cents per pound) should open up a large field for the utilization of lignin, provided aging and other properties of the product can be made competitive with commercial plastics now in use. Partial chlorination of sawdust has also been tried, but the last traces of chlorine are difficult to remove and have a tendency t o attack metal molds.
Resins from Noncoal-Tar Sources Of the noncoal-tar resins, the most important next to the cellu€ose derivatives are those of the urea-formaldehyde and vinyl types. The former, made from urea and formaldehyde, are unrestricted by their raw materials since urea is freely synthesized from carbon dioxide and ammonia, and formaldehyde uses carbon monoxide and hydrogen as its prime raw materials, I n 1933 production of these resins amounted to 3,234,000 pounds, a n a m o u n t which h a d grown to 4,203,000 pounds in 1935.' It is significant to note that the total production of all resins of noncoal-tar origin in 1933 was barely 3,333,000 pounds, little more than that of urea resins. However, in 1936, the production of all noncoal-tar resins had risen to more than 15,500,000 pounds through the introduction of other types. Included in the increase are the vinyl resins derived from vinyl chloride, and vinyl acetate, in turn synthesized from ethylene or acetylene; the acrylic resins, including both t h e a c r y l a t e s which may be derived from ethylene or acetylene; and the a-methacrylates which are usually derived from acetylene. The vinyl acetate polymers may be made either from e t h y l e n e b y treating with a halogen, followed by sodium acetate which removes the halogen and forms the unsaturated acetic acid ester (United States process), or by the addition of acetic acid to acetylene in the p r e s e n c e of a mercury catalyst (Canada and Germany). The v i n y l h a l i d e s m a y be formed either from e t h y l e n e , through the action of p o t a s s i u m
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hydroxide on the dihalides, or by the addition of hydrohalide to acetylene. They are both readily polymerized to form resins. A recent development which shows marked promise is the formation of the acetals of polyvinyl alcohol. Polyvinyl alcohol is prepared by the hydrolysis of polyvinyl acetate. The alcohol is then treated with an aldehyde such as formaldehyde, acetaldehyde, or butyraldehyde, in the presence of an acid catalyst, to give solid, water-insoluble, tough resinous products. As these products develop, the demand for acetic acid as well as ethylene and acetylene will naturally increase. None of them, however, are dependent solely on petroleum since they can all be made from coal, salt, water, and lime, the basic raw materials. The potential demand for acetylene, however, is already so great that sources other than the time-honored calcium carbide are being actively sought. I n Germany considerable quantities of acetylene, with hydrogen as a by-product, are being produced by the thermal decomposition of methane. A number of derivatives of terpenes, abietic acid, and other natural products elaborated by further synthetic steps are also produced in relatively small volume. Petroleum resins first reached commercial importance in 1936. They are formed by the interaction of diolefins, monoolefins, and aromatic hydrocarbons obtained from cracked distillates, and are used by varnish and enamel manufacturers.
Plastics Resembling Rubber Turning from the synthetic resins as commonly considered, we find a rapid development and growth among the so-called synthetic rubbers, prominent among which are Buna in Germany, and Neoprene and Thiokol in the United States.
(Upper) SMALL ARTICLES MAKD THE BULK OF PHENOLIC PLASTICS USED
UP
Automotive parts electrical fixtures and parts, and bot6le closures together consume about a third of the production of phenolic resins. Courtesy, Resinox Corporatzon
PIPESECTION bHLower) PLANTCOATED EA T - R E PHENOLIC FROM A WITH
HEMICAL
ACTIVE
RESINOID
From a mechanical standpoint these resinoid coatings provide a tenacious durable bond. They are unaffected by extremes of climate, temperature, and humidity. They are resistant to common solvents such as gasoline, alcohol, and acitone, and t o oils grertses, dilute alkaline solutions, or: ganio and mineral acids in moderate concentrations. Recently 8 p e c i a 1 methods and processes have been devised whereby large areas may be poated and baked with resinoid coatings. These methods have enabled large processing equipment to be protected against corrosion. Courtesu, Bakelite Corporation
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Buna, which is being made in increasing quantities in Germany, is a butadiene polymer produced by synthesis from acetylene in the following steps: (a) acetylene to acetaldehyde (b) acetaldehyde to acetaldol, (c) acetaldol to butyleneglycol, (d) butyleneglycol to butadiene, and (e) butadiene to synthetic rubber polymers. The basic raw material is, therefore, available in large quantity and the synthesis is not difficult, although the yields in some of the steps are not high. Until recently all the Buna rubber produced in Germany has been retained by the government for its own use. Neoprene is also derived from acetylene by converting it into vinylacetylene, formed by passing acetylene gas into an acid aqueous solution containing powdered cuprous chloride; it is then converted to chloroprene by the addition of hydrochloric acid and polymerized to a stage which is suitable as a rubber substitute. Xeoprene rubber has already reached a production rate of about 2,000,000 pounds in 1937, and the 1938 production is expected to be several times this amount. Thiokol is an entirely different type of rubber substitute; it is not a polymerized diolefin but a product of the interaction of ethylene dichloride and sodium polysulfide. There is little likelihood of shortage of raw materials for this type because both ethylene dichloride and sodium polysulfide are cheap and available in practically unlimited quantity if the demand arises, Thiokol is exceptionally resistant to hydrocarbon solvents, printing inks, etc., and by compounding with natural rubber markedly increases the latter’s aging properties.
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Resins Derived from Rubber Derivatives which use rubber as the base material and have recently come on the market are Tornesit, a chlorinated rubber used in paint and protective coatings, and Plioform, which is rubber hydrochloride or a similar derivative. These materials are of a plastic nature, but only Plioform is used in molding and then to a limited degree. Plioform can also be sheeted to give Pliofilm, which may be used as a thin foil for wrapping and other purposes. At present rubber is a commodity of unstable price. Consequently, the general adoption of derivatives from it may depend a great deal on the price of natural rubber. There is a trend towards world stabilization of the price of rubber, but this utopia has not yet been reached. Since the synthetic resin industry is fundamentally based on ultimate raw materials which are among the most common and most widely distributed throughout the world, it is apparent that the only serious impediments to its orderly and continued growth are temporary limitations of processing the ultimate crude materials. None of these seems a t all likely to impose more than a passing resistance to the expansion of the plastics industry. Rather, from every point of view continued acceleration of growth seems assured as more resins of greater utility are produced. This growth is importantly stimulating all branches of American chemical industry. RECEIYED October 11, 1937. Presented before the Division of Paint and Varnish Chemistry at the 94th Meeting of the Ameriaan Chemical Society, Rochester, N. Y., September 6 to 10, 1937.
DEVELOPMENTS IN GRINDING---
T
HE story of crushing and pulverizing has been one of slow and steady development dating from prehistoric times, but it received a special impetus with the advent of power generation equipment. During the past decade or two the field has become recognized as important to chemical industries. Although it was well established in the mineral and milling industries, it was barely recognized in the earliest lists of unit operations in chemical engineering. Gradually the rate-controlling feature of surface has become important in the physical and chemical behavior of heterogeneous sys-
LINCOLN T. WORK Columbia University, New York, N. Y.
terns involving at least one solid phase, and grinding to fine size has taken on new importance as a means of creating surface. The tools of measurement have been advanced materially during this time. Fineness over a range of microns to meters is now subject to quantitative evaluation. With this means of measurement available, the grindability of a great diversity of raw mateGals has been escablished with a satisfactory degree of quantitative precision. The basic problems of energy consumption, mill maintenance, and size distribution of product are now open to solution. This paper is an effort to give the present status of crushing and pulverizing and to indicate possible future trends. The few striking developments of recent years are specifically designated by name. As a rule, the developments have been gradual and have consisted in utilizing new materials of construction and in varying the combination of drives, feeders, mills, classifiers, and collectors. No mention is made of several of the well-established mill types, whereas in other cases reference may be made to special features without indicating the specific name of the mill. Only time will SIDEVIEW OF A BARTLETT & SNOW24 X 24 INCH SINGLE-ROLL COAL tell the wisdom of the author’s selection of C R U S H E R WITH PORTION O F S I D E SECTION B R O K E N AWAY T O SHOW THE examples. INTERIOR CONSTRUCTION
