Plastics Ε. L KROPA and Ε. Ε. McSWEENEY Battelle Memorial Institute, Columbus, Ohio
w ITH the general recognition that the volume of plastics manufac ture may be an index of the stand ard of living, one wonders whether a plastics or polymer index might not be used rather than information that Russia has produced 1.1 billion pounds of resin, and that Japan's plastic production goal is 400,000 tons. This plastic index might be a ratio of the volume production of anydesignated country divided by the population, with, perhaps, suitable corrections for the amounts of im ported and exported products ap plied to the volume. Simple arithmetic shows that the current U. S. consumption of plas tics is about 25 pounds per capita. With the increasing attention given to the use of plastics in building and in the widest variety of household uses, it is easy to see why projections of future uses of plastics are generally very optimistic. There are rosy predictions for the use of various foams derived from urethanes, phenolics, and vinyls. The plastics potential in building trades was the theme of a symposium held by the Commercial Chemical Development Association, with spe cial attention directed toward the use of not only foams, but also adhesives and surface coatings. This increasing demand appears to have been insufficient to push the consumption in 1958 over that of the record 4.3 billion pounds in 1957. Nor is it particularly consoling to sales managers who can total up pro duction capacity of a variety of plas tics to considerably more than the current demand. This has naturally led to an in creasing attempt to integrate as far as possible, as evidenced by the continuing interest of many major plastics manufacturers, in large con suming industries such as production of film. This market, which is a magnet for machinery as well as raw materials, encompasses not only the older materials such as cello30 A
phane, cellulose acetate, polystyrene, and polyethylene, but newer items such as oriented polypropylene and high-density polyethylene. The ad vent of high-clarity polyethylene film of both low and high density augurs increased competition for cellophane and cellulose acetate. This same trend toward emphasis on production of film has caused a number of paper companies to add film-processing activities to their corporate structures as a hedge against competition for paper. The need to close the gap between production and sales has intensified technical service and applications re search in most companies. It is ironical, but possibly somewhat typi cal of this industry, that the sudden craze of the younger generation to balance by spectacular gyrations cir cular specimens of rigid polyethylene and other materials has probablydone as much in the past year to close this gap as any of the well planned and executed development programs. Raw Materials
Whether or not plastics production is a standard-of-living index, the volume of plastics is closely allied to the health and well-being of the chemical industry. Thus, problems of oversupply plague the raw material supplier also. Concrete illustrations of this were reductions in the price of such stable raw materials as formaldehyde and pentaerythritol, as well as a general consternation caused by the announcement that one new supplier to an already oversupplied phthalic anhydride market intended to bring his production in at a price very substantially lower than the current market. Still, the large size of the plastics market and its future growth are great incentives for raw material manufacturers to develop new ma terials which may find a place in it, as well as to improve current prod ucts and processes. Among the in teresting new materials announced
INDUSTRIAL AND ENGINEERING CHEMISTRY
were a group of fluorine derivatives. Three new fluoro alcohols containing 7, 9, and 11 carbon atoms were re cently added to the already avail able C 3 and C 5 compounds. Some new fluorocarbon dienes were also announced. Of particular interest is 1,1,2,3-tetrafluoro-l ,3-butadiene, which polymerizes and copolymerizes readily, so that its use in high polymer systems can be easily en visioned. Several other materials which have been in the development stage for a number of years became commer cially available, including so-called Isosebacic acid, which is essentially a mixture of scbacic, 2,5-diethyladipic, and 2-ethylsuberic acids, pro duced by dimerization of butadiene using sodium as a catalyst. Methylbutynol and methylpentynol were also added to the growing list of commercially available acety lene derivatives. Inasmuch as acetylene itself re mains the basic raw material for almost the complete spectrum of vinyl compounds, any new synthe sis or process improvement has manypotential ramifications in resin tech nology. The dilemma involving two different processes, carbide and na tural gas, has not been resolved. The bulk of calcium carbide remains an obstacle in large-scale operation; on the other hand, manufacture from natural gas requires the lo cation of plants close to available gas supplies. In an effort to reduce cost, National Carbide, a unit of Air Reduction, plans to produce cal cium oxide from its waste hydroxide.
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Briquetting appears to be the key to the process. Concurrently there are developments in the gas picture. Eastman has designed a new acetylene-ethylene process which is stated to be different from those currently employed and involves a specially designed furnace which operates at 2500° C. One possibility for a cure of the oversupply of phthalic anhydride is indicated by the interest in the Henkel process for rearrangement of the potassium salts of phthalic and isophthalic acids to the corresponding terephthalate. However, handling the potassium salts at 400° C. presents difficult corrosion problems which first must be overcome. On the other hand, some of the new processes of oxidation of mixed xylenes may only contribute to additional supplies of terephthalic and add to the glut of phthalic itself. Polyethylene
Among the plastic materials, poly, ethylene remains the most active. Several new plants were completed, while others are still projected into 1959 and 1960. When planned facilities are all completed, total capacity for high- and low-pressure material will be about 1.5 billion , pounds. As the 1958 consumption will at best be in the vicinity of a billion pounds, it is easy to understand the substantial price decreases during the year, with the low- and high-pressure materials now down to 35 and 43 cents, respectively. With at least four suppliers now furnishing material ranging from 0.92 to 0.96 in density and 0.2 to 30 in melt index, the user is confronted with an almost bewildering number of available materials. When to this is added the possibility of blends as well as the use of scrap, one must sympathize with the men faced with making choices. Of course, price, which sometimes narrows the choice, is still one of the most significant properties. However, when the more rigid high density materials can be used in thinner sections at an appreciable saving in weight, even this factor becomes very complicated. And the increasing availability of polypropylene only confuses the picture further. Among the newer varieties of polyethylene are high-melting-point
I/EC ANNUAL REVIEW waxes designed for use in hot-melt coatings and for slush molding. Vulcanized material produced by irradiation remains the one significant use of radiation in the plastics industry. But its use in electrical insulation may be challenged by insoluble polyethylene, compounded with carbon black and cured by peroxide, which possesses unusual heat resistance, suggesting the production of cable coating which would be insulation and jacket simultaneously. Other varieties of polyethylene are directed toward fire resistance; greater ability to be joined by adhesives; coatings for tanks, pipes, and valves; and even purging resins. The last variety is designed to reduce waste during interrupted operation in extrusion and injection molding. Activities in the development of new catalyst systems have been very intense. Most attention has been given to the so-called heterogeneous systems, and a better understanding of their mechanisms is resulting. On the other hand, a completely soluble catalyst comprising tetraphenyltin and aluminum and vanadium halides has resulted in a unique product which may require distinction between polymethylene and polyethylene. This variety of polymer contains only one methyl group in about 2000 carbon units. Structure of polymer is also of paramount importance in the basic patent on linear polyethylene which was assigned to Du Pont and is the subject of a pending suit with Phillips. There is obviously much speculation about the validity of the patent and the ultimate outcome of the suit, which undoubtedly will not be known for a number of years. Polypropylene
Polypropylene, the new petrochemical plastic which has been discussed so widely in polymer literature during the last few years, made its commercial debut in 1957. Humble Oil and Refining Co. will begin producing in 1959. This is of particular interest, since Humble has completely bypassed ethylene to get into the polyolefin field via propylene. Presumably Sun Oil will also follow this route, while several of the current
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polyethylene producers will add polypropylene to their line. U. S. markets seem to favor film and molding as principal outlets, while foreign producers put more stress on fibers. Difficulty in dyeing may have been the principal deterrent here. If so, introduction of dye sites by grafting or the use of soluble dyes may increase fiber interest. Intensive investigations are being conducted in industrial laboratories in an effort to extend the isotactic polymerization principle to polar monomers. There was comparatively easy extrapolation of stereospecific catalysts to other hydrocarbons; as a result, several companies are known to be pursuing research on high melting, isotactic polystyrene. However, entirely new systems have bad to be designed for polar-containing materials. Success has been achieved with methyl methacrylate, using Grignard reagents or 9-fluorenyllithium. Lithium dispersions have also yielded a crystalline poly(tert-hutyl acrylate). One could not help but note certain remarkable parallelisms between enzyme catalysis and stereospecific polymerization. The concept of templates and the prosthetic groups is well known in biology. The template concept was used, during the year, to direct the polymerization of diolefins; the template employed was the canal which exists in the urea (or thiourea) crystaL Such a template holds the monomer rigidly in position, and if the system is then exposed to radiation, the positioned monomer can be linked together only in the preferred direction. After polymerization, the urea is flushed out. Among the polymers produced by this method is frans-polybutadiene as a hard, tough, crystalline solid. Certain more conventional templates from proteins and polypeptides are being employed in Russia as membranes which act as molecular sieves, permitting a rapid purification of natural products such as insulin and streptomycin. Outside of polyethylene, the greatest growth potential is still focused on glass-reinforced polyester resins. Over 90% of the reinforced resin bonding utilizes styrene-modified, unsaturated alkyd. Various modiVOL. 5 1 , NO. 1
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T H E GOODYEAR T I R E &
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Polyester p a c k a g i n g filn i has been d e v e l o p e d
fications are being introduced for specialized applications, such as the use of acrylic systems to secure good color retention and the modification with triallyl cyanurate to achieve improved heat resistance. Epoxies are still of paramount interest for some uses such as pipe. A new allhydrocarbon resin which shows considerable promise is being developed by Esso. The greatest single outlet for such reinforced plastics is in the transportation field in both boats and automobiles. It was estimated that 40,000 boats were produced last year. Military applications are not being overlooked, such as in radomes, in rocket motors, and as storage containers for high-pressure fuels; Other directions in which the polyesters appear to be expanding are in the construction field, and a new type of simulated stone has been produced. The roof of the U. S. Pavilion at the Brussels World Fair contained about 100,000 square feet of such reinforced resin. Other large-scale consumer goods on the horizon are reinforced swimming pools.
A number of new epoxy-containing resin intermediates derived from olefins and peracetic acid have been added to the established bisphenol A-epichlorohydrin condensation product. Among the promising new candidates is epoxide-201—3,4-epoxy - 6 - methylcyclohexylmethyl - 3,4-epoxy-6-methylcyclohexane carboxylate. This resin intermediate is claimed to have superior color stability to the phenolic counterpart. Among the more attractive features is a much higher concentration of epoxide residues, permitting a more tightly woven structure possessing a higher heat distortion. The higher concentration of functional groups also allows more rapid reaction with hardeners.
The developments were not limited to manipulation of resin raw materials; during the year a three-way spray gun was introduced to permit the simultaneous deposition of glass fiber resin and catalysts, eliminating tedious, messy hand layup. During the operation, glass fiber is chopped and ejected, and this stream meets the other two components in mid-
A number of other new aliphatic epoxides are also being projected— for example, dicyclopentadiene dioxide, vinylcyclohexene monoxide, vinylcyclohexene dioxide, and styrène oxide. A new tetrafunctional phenolic epoxide which forms the basis of resins with improved heat distortion has also been disclosed.
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air. Utilization of reinforcing agents other than glass also continues to receive attention. The use of synthetic fibers is well known. The reinforcing agent which could open up entirely new markets is metal fiber. Even metal-coated glass fibers are being evaluated as reinforcing agents. Epoxies
INDUSTRIAL AND ENGINEERING CHEMISTRY
Recent commercial development interest has been directed toward the spraying of high-solid films containing no solvent. In this way thick coatings may be applied in a single application. Still another development which may open many new outlets comprises the epoxy polystyrene blend ; this composition on heating yields an expanded plastic. Among the more unusual applications of epoxide resins has been the production of a pavement which minimizes automobile skidding. This development, which started in factory floors, has graduated into roads and may prove effective on wet pavement. Along with ureas, cyclic ureas, triazones, and melamines, epoxides have been evaluated for textile finishing. Thus far, the nitrogen analog of the epoxide—namely, the aziridinyl ring system—has found more favor. Tris (1-aziridinyl) phosphine oxide (APO) not only yields a shrink- and crease-proof fabric but also imparts some flame resistance to cotton fabric. Such a procedure is more durable than other systems used in the past. Actually, the entire field of "minimum care" cottons is receiving attention from industry and from government laboratories. Major emphasis is directed toward compositions containing no nitrogen or at least a nitrogen structure which would not absorb chlorine. Such nitrogenous substances react with bleaching agents, and on subsequent ironings, liberated hydrochloric acid tenders the fabric. Among the nonnitrogenous reagents in addition to the epoxides are the acetals, both the glycol acetals and pentaerythritol . acetals. Dichloropropanols, reacted with sodium hydroxide and padded onto cotton, seemingly result in some type of reaction between the organic halide and cotton. Some much more efficient chemical system may be required to maximize crease resistance. Nylon
Nylon plastics have attracted new raw material manufacturers and new producers of molding compounds. Entered in the caprolactam sweepstakes are not only the established factors such as Du Pont and Allied; also Commercial Solvents has stated that it will be producing this monomer before the end of the year. Pre-
sumably this development is a technical dividend from its knowledge of nitroparaffins. Spencer Chemical, in combination with Industrial Rayon, intends to build a large caprolactam manufacturing unit. In addition, Foster-Grant is tooling to manufacture the polymer on a substantial scale, primarily for molding and extruding applications. A spectacular assignment projected for coated nylon fabrics involves plastic barges. Sausageshaped, collapsible tubes are being considered for the transportation of oils, chemicals, and even bulk foods. Because of the estimated large savings in equipment, capital, and transportation costs, a number of firms in this country, in England, and in Germany are experimenting with such one-way barges for both lake and ocean transportation. When filled, these containers are practically submerged and appear to ride the heavy seas successfully. Urethanes
Among the new modifiers for urethanes in the manufacture of flexible foams are the dimer acid polyesters which react with diisocyanates. Until recently the polyethers were the preferred reactants. In either instance, however, while there has been an increase in the volume of production of urethane foams, the manufacturers appear to be losing ground pricewise. Such a program could prove disastrous, because any such reduction would decrease the amount of service work, and this in turn would decrease new potential outlets. Of the purely technical laboratory developments which were disclosed during the year, interfacial polycondensation is most notable. While somewhat similar techniques had been employed in the past in the preparation of the polyurethanes, sufficient exploration was made of a wide variety of systems composing water-soluble and waterinsoluble monomers to indicate that it is possible with condensation reactions to have a reaction simulating emulsion conditions. Both emulsion and bulk procedures are well recognized in vinyl polymerization, but the laboratory wrinkle of using interfacial condensation techniques allows one to take advantage of the rapid reaction in condensations at interfaces. Advantages
I/EC ANNUAL REVIEW over bulk (melt) polymerization are speed of reaction, simple equipment, less stringent requirements for monomer purity, and more choice of reactants—for example, high melting or even cross-linked structures can be made easily. High-Temperature Materials
The search for high-temperatureresistant materials continues to be spurred on by needs such as items for missile applications. A variety of unusual elements has been incorporated into the more conventional carbon-hydrogen-nitrogenoxygen system. The introduction of chlorine, fluorine, and silicon into this established fraternity passed without major incident. Other candidates demanding admission are phosphorus, boron, aluminum, tin, and a host of others. Phosphoborines, stannosiloxanes, and ferrocene silicones arc being groomed for high-temperature stability applications, as are chlorophenyl and cyanomethylene substituted silicones. It was believed that such candidates would have to be admitted where high-temperature applications were necessary. Surprisingly, the older established membership possessed unusual resiliency and stamina, as witnessed by the use of plastics under the so-called ablation conditions. The asbestos-filled phenolic resin combinations have been employed in the nose cones of intermediate-range missiles. In a sense, however, such high-temperature applications were considered and established for decades in another type of ablation environment—in grindingwheel applications. A new elastomer (Viton), which is resistant to oils, fuels, and solvents at temperatures above 400° F., is a copolymer of vinylidene fluoride with pcrfluoropropylene. Also on the horizon is a new weather-resistant film base utilizing vinyl fluoride. This polymer is reported to possess good transparency and high transmission to ultraviolet light. Along with these developments in the fluorinatcd plastic field, there is a report that the Russians have produced a new fluorine-containing plastic, the nature of which has not been revealed.
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Other new resins noted in this review in past years, which are now being pushed toward commercialization, are Hercules' Pentone (a chlorinated polyether) and Du Pont's Delrin (polyformaldehyde). The initial price of 95 cents per pound for the latter indicates it will be more competitive with nylon than with the polyolefins. Water-Soluble Resins
Water-soluble resins might more properly be designated as gums. But the alternative nomenclature appears more attractive, even though it tends to distort the initial distinction between resins and gums. Since the raw materials and products used to manufacture water-dispersible resins are so closely associated wi*h the. resin industry and resin intermediates, such terminology may be necessary to distinguish these synthetic products from the natural watersoluble counterparts. In the same way that resins may be modified, various water-dispersible functional groups may be introduced into the polymer molecule. These groups may be ionic or nonionic, and by suitable adjustment a wide range of physical properties may be incorporated into the final polymer, permitting it to be more or less sensitive to accompanying ions. The carboxyl group is the preferred ionic residue, and this functional group is introduced by using either acrylic and methacrylic acid or maleic anhydride. Of the nonionic residues a much wider range of components is available, such as the alcohol group, methoxides, pyrrolidonc, and amides. Considerable studies had been carried out in various copolymers of acrylamidc and acrylic acid. Where at one time an ad hoc product was prepared by hydrolyzing polyacrylonitrile, yielding a polymer containing varying amounts of unreacted cyanide, ammonium salt, amide, and acid, the newer products are tailored to adjusted amounts of amide and acid. One of the newer outlets for these water-soluble colloids has been approved for removing the "chill haze" in beer. Polyvinylpyrrolidone will precipitate tannins and other complex proteins from beer and wine. V O L 5 1 , NO. 1
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