I
P. V. SMITH,
Jr.
Esso Research and Engineering Co., Linden, N. J,
Some Developments in Polymers from Petroleum
A of the huge and ever-growing volume of petrochemicals hi.\joR
FRACTIOS
finds its \vay into polymeric materials of one kind or another. I n 1958. about 20 billion pounds could be so classified. Synthetic rubber. nylon. polyethylene, and vinyl are terms recognized and accepted in most households in this country: and there are few major chemical. oil. or rubber companies which are not actively interested in one or more polymers derived from petroleum raw materials. This article discusses briefly five polymeric products which are in the market development stage: one elastomer and four oily polymers. For many years. a variety of butyl rubber polymers. differing in molecular !\-eight and degree of unsaturation. have been commercially available, and have been exploited \\-here air retention, high tcmperaturc stability. or ozone resistance is of importance. A broader spectrum of uses has been denied butyl because of its incompatibility \iith SBR and natural rubber, which has required stringent segregation in users' factories. its slower cure rates. and difficulties connected with rhe dispersion of fillers and their effect on die mechanical properties of the rubber. Now a chlorine-containing copolymer of isobutylene and isoprene (MD-551) has been developed which overcomes these difficulties and offers a number of other advantages. I t has exceptional high temperature and flexural stability as well as outstanding ozone resistance. X'ulcanization may be effected with a wide variety of cross-linking systems to give products having excellent processing characteristics. It promises to be an exceedingly interesting neiv elastomer. The more rapid cure rate can be demonstrated by a simple sulfur-Tellurac recipe. A useful 300% modulus value of 1600 is achieved in 35 minutes a t 307' F. lvith MD-551, in contrast to 85 minutes \vith regular butyl. With this same formulation, the rate of cure increases fairly linearly with the increasing chlorine content of the polymer. Similarly, retention of tensile strength after heat aging for 7 2 hours at 300' F. also improves with increasing chlorine content. This is a very tough aging test
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and, under comparable conditions. both SBR and natural rubber give decidedly inferior performances. Still another property of the ne\< polymer Lvhich improves with increasing chlorine content is rebound. An increasr of 2.5yGover regular butyl rubber is achieved by a polymer containing 1 ..5ycchlorine. T h e flex resistance of MD-531 is better than SBR and equivalent to natural rubber. Only one third the shape distortion encountered with SBR is observed with the neiv polymer. Its heat build-up during flexing is comparable to that of natural rubber. and no vulcanizate degradation occurs. as u i t h regular butyl. General1 elastomer warrants conside applications \\,here ozone resistance. flex resistance. and or high temperature stability are of importance. For several years. this company has been interested in new outlets for butadiene. One investigation has resulted in a family of four polymeric materials based largely on butadiene. Lvhich appear to have outstanding promise in a variety of application fields. The parent material. C-oil (E-l l ) . a sodium-catal~-red copolyrncr of butadiene and styrene. is a viscous oil of 8000 to 10,000 molecular weight. having a high degree of unsaturation. The olefinic character is approximately evenly divided bet\\ een internal double bonds and side vinyl groups. The benzene rings. together Ivith the unsaturation, make the parent copolymer a highly reactive producr ichich can be modified in many ivays. .A simple chemical reaction results in the material designated as E-1 1-K; varying degrees of oxidation give two butoxy products, iMD-423 and MD-424. A comparison of properties of interest in surface coaxing applications sho\vs that the E-11 products are soluble in aliphatic hydrocarbons and insoluble in oxygenated solvents; the reverse is true -411 dissolve for the butoxy resins. readily in aromatic hydrocarbons. Acid numbers range from 0 for E-1 1 to 16 for MD-424. .411 three derivatives give excellent pigment wetting because of their increased polarity. T h e tw'o butoxy products are easily compatible with a wide range of surface coating
INDUSTRIAL AND ENGINEERING CHEMISTRY
materials. including ureas, melamines. triazines, alkyds, phenolics. ester gums. nitrocellulose. vinyls. polyamides. and vegetable oils. More work has bren done in the protective coating field than in any other to date. Great promise in a \vide variety of applications has been demonstrated. These products are about equivalent to the epoxies in chemical resistance. are easier to apply. and have a lower specific gravity and a loLver cost per pound. They are somewhat less amenable to chemical curing than thc epoxies. Of the remaining indicated uses. glass fiber-reinforced laminates probably hold the biggest potential from a volume standpoint. Laminates as strong as the epoxies and cheaper than the polyesters are readily obtained. In most applications. a normal oxidative type of cure is employed. Several other methods of curing arc of interest. A purely thermal cure is possible by simply impinging a flame on the coated surface; this gives a tremmdously tough film with outstanding chemical resistance. Two-second exposure at 800' F. \\-ill cure a 3-mil film to a S\vard hardness of 40. Such a film !vi11 withstand a 180" bend over a ')*-inch mandrel and 60 inch-pounds of impact without failure even at -40' F. S o other polymer rested, including phenolics. alkyds. epoxies. and ureas. can be satisfactorily flame-cured \\-ithout failure due to blistering. crawling. or burning. This technique is of particular interest for can coatings and continuous pipe coatings, \\-here coating speed and quality are of utmost importance. Another interesting technique for curing butoxy products is the use of sulfur dioxide. Exposure to as little as sulfur dioxide in air will give a dustfree film in a half hour. Acceptable hardnesses are obtained in about one fifth of the time of conventional commercial enamels. A \side variety of other chemical curing agents are effective. including polyisocyanates.
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RECEIVED for review December 23, 1958 ACCEPTED January 8, 1959 Division of Petroleum Chemistry, Symposium on Recent Developments in Chemicals from Petroleum, 133rd Meeting, ACS, San Francisco, Calif., April 1958.
