I&EC REPORTS & COMMENTS A red-letter year in rubber chemistry? Trained brain power-key
to industrial health
New solar energy unit for sea-water desalination
ETHYLENE-PROPYLENE ELASTOMERS CAN NOW INVADE TIRES Adding a nonconjugated diene to the initial polymerization step has made terpolymers that can be sulfur-cured by Conventional techniques When D u Pont and Enjay began to produce ethylene-propylene terpolymer (EPT) late last year, rubber chemistry passed another milestone. The major technical problem with E P elastomers has been making them sulfur-curable by conventional techniques. This has led to much study of possible third components as the linking agent for the ethylene and propylene. Typically EPT polymers contain from 40% to 60% ethylene or propylene and up to 5y0 of a third component, usually a nonconjugated diene. Montecatini’s licensee, Columbian Carbon, has announced that it is using cyclooctadiene, Enjay may be using dicyclopentadiene, and Naugatuck likely uses divinylbenzene. Du Pont could be using 1,4-hexadiene, a fact which would be significant, since it is the only reported company to be using a linear nonconjugated diene. A readily sulfur-curable E P polymer would need built-in unsaturated sites which would act as activated centers needed to achieve the essential cross linking necessary for a good workable elastomer. Cross linking (curing) has been achieved by peroxides in conjunction with accelerating agents. T h e action is primarily a series of free-radical formations and subsequent terminations, giving rise to a suitable elastomer, sometimes with a n objectionable processing odor. Coupled with the odor problem was the necessity for equip-
ment other than that used in conventional rubber curing. The use of diene in the initial polymerization step furnishes the necessary reaction site for the linking of ethylene and propylene to the terpolymer. Successful sulfur curing is achieved when the terpolymer, either cyclic or linear, contains only one bond which is terminal. This is preferred because if both bonds were terminal, the initial polymerization step would tend to use all of the bonds as cyclic structures and to contaminate the elastomer with in-
soluble fractions of cross-linked materials, thereby reducing the residual unsaturation necessary for good sulfur-curing characteristics. Unconjugated dienes are even more important to successful sulfur curing, since screening by intervening groups renders these nonterminal bonds unreactive to copolymerization, while allowing them to be vulcanized later by normal sulfur curing agents. The catalysts used in these processes are the usual Ziegler aluminum isoalkylates and vanadium tetrachloride or its derived oxychloride. The organic portion may be isobutyl,
An outstanding property of the terpolymer is that it gives good uulcanizates, euen when heavily loaded with black and oil. As represented here, 700parts of polymer, 400parts of black, and 730 parts of oil give a vulcanizate having a tensile strength of 7000p.s.i.
VOL
56
NO. 2
FEBRUARY 1964
11
Size Requirements Getting Tougher? Sturtevant Air Separators Increase 40 to 400 Mesh Output as Much as 300%
Closed-circuit air separation is of proved advantage in reduction processes. Result is a better, more uniform product. Grinding mills perform at top efficiency, output frequently increases as much as 30096, power costs drop as much as 50%. Precise separation of all dry powdered materials. Sturtevants currently classify sulfur, soybeans, phosphate, chocolate, feldspar, sand and aggregates, pigments, limestone fillers, flour, abrasives, plastics, gypsum, ceramics, cement and other products. Improve screening - Sturtevant Air Separators prevent blinding by removing undesirable tailings or fines from screen feed loads. Works Like Winnowing Done in a Whirlwind Sturtevant Air Separators do a mechanical job of winnowing. Precise control of whirlwind air currents and centrifugal force results in the desired size being lifted into fines cone, oversize falling into tailings cone. A 16 ft. Sturtevant, for example, has taken a feed rate of 800 tph, containing only a small percentage of desired fines, and delivered 30 tph 90% 200 mesh, recirculating the oversize through the grinding circuit. Send for Bulletin No. 087.
I&EC REPORTS
since longer alkyl groups I tend to restrict electronic and catalytic activity. T h e speed of the polymerization reaction is influenced by the degree of subdivision of the active surface with which the unsaturated compounds are brought into contact. For instance, the surface active catalyst can be adsorbed on cryolite or on a finely divided filler such as silica or carbon black. The silica can consist of either a three dimensional cross-linked network or a lattice distorted by the presence of an element of variable valence. These catalysts must be used in strict absence of oxygen, water, or other material with which they can react. For this reason the solvents in which they are used are greatly limited. The preferred solvents are saturated aliphatic hydrocarbons and nonreactive halogen compounds such as tetrachloroethylene and chlorobenzenes. All monomers and solvents used in the polymerization process must also be free of compounds containing active hydrogen such as alcohols, amines, and acids as well as oxygen, peroxides, ethers, esters, ketones, and sulfides. The lower specific gravity of these raw EPT polymers (0.84 to 0.86) compares favorably to those of natural rubber and SBR (0.93 and 0.94, respectively) and promises to make EPT competitive in many applications on strictly a weight basis. These EPT elastomers, free of the objectionable odor characteristics of peroxide-induced cures and readily processed on conventional rubber mill equipment, offer excellent resistance to ozone attack due to their basic unsaturated nature and the fact that the carbon-to-carbon double bond cure site is isolated from the main saturated chain. Oxidative attack at the sulfur-containing cross link or at double bonds not involved in the cross-linking reaction is sufficiently distant from the saturated chain to avoid its destruction and the 1
STURTEVANT MILL COMPANY 105 Clayton st.,B o s t o n , M a s s . Crushers
Grinders Micron.Grinders Separators Granulators Conveyars Elevators Circle No. 73 on Readers’ Service card
Blenders
12
INDUSTRIAL AND ENGINEERIN
CHEMISTRY
associated degradation of physical properties. EPT polymers are expected to win a share of the nontire rubber market in the automotive accessories, hoses, household appliances, and rubber coated fabrics. However, they are not now designed to compete with the specialty rubbers such as urethane, chlorosulfonated polyethylene, and silicones. Tire producers continue to stress that the problem of tack must be overcome before a mass-produced complete EPT tire is ready for the market. Some say, however, that use can be made of the material’s ozone resistance to build better crack resistant walls for present-day tires. The advent of a complete EPT tire combined with increasing supply is expected to lower the announced 30 cents per pound (dry basis) price schedule. L. CRITIDES
SOLAR ENERGY IN DISTILLATION OF SEA WATER Research continues in use of the sun’s energy for desalinating sea water. T h e techniques reported are based generally on the simple principle of evaporation, and another optimistic-looking project was recently reported by the University of Arizona’s Institute of Atmospheric Physics. With the support of the Office of Saline Water and in collaboration with the University of Sonora, the Institute has begun test operations of a pilot plant at Puerto Penasco, Sonora, Mex. Fresh water produced by this test installation, estimated at 2000 to 3000 gallons per day, will be made available to the city’s hospitals and schools. However, after about a year of experimentation, the project is expected to provide data needed for constructing a full-scale 1 million gallon-per-day plant. The process is patterned after a smaller plant developed recently at
I&EC R E P O R T S
the University of Arizona. Sea water, about two inches deep, is moved slowly through three long shallow collectors, having a surface area of about 9000 square feet and made of redwood lined with plastic film. T o prevent evaporation each collector is covered with a plastic film. For the water to move from the entrance of the first collector to the exit of the third requires about one hour which is long enough for heat from the sun’s rays to raise the temperature of the water to 150’ to 160’ F., or even higher. At these temperatures no insolvable salt deposition problems are anticipated. Sea water thus heated is then pumped through insulated pipe from the exit of the last collector to the top of a 45-foot evaporation tower. From this height it is tumbled down through a series of 2-inch carbonfilled polyethylene Pall rings. Warm air forced up through the tower carries water vapor to an adjoining condensation tower, also 45 feet high, from which it is collected as fresh water. Cold sea water, pumped through coils in the condensation tower, cools the water vapor, is in turn heated itself, and then passes to the redwood collectors. The spent brine from which fresh water has been removed is pumped back to the sea. Part d the water heated during sunlight is transferred to steel underground storage tanks and then cycled when desired. A major question this installation can answer is whether or not the comparatively high initial capital investment cost justifies research in this direction, or whether the “greenhouse” type of evaporator is more feasible. The greenhouse desalination unit, as the name implies, is mplsiy a large glass enclosure heated by solar energy. An experimental unit of this type is now operating a t E. XELLER Daytona Beach, Fla.
QUALITY- MADE is meaningful when describing any product bearing t h e Hackney trademark, famous in industry for more t h a n 61 years. For example, the deep drawing of alloy steels t o uniform close tolerances in forming rugged, safe, high-pressure cylinders. Every Hackney cylinder shell is made by this technique-deep drawn t o final size and shape between precision dies and mandrels. T h e results: smooth, strong cylinders without excess weight, which are easy t o maintain; less costly t o ship; easier t o handle. Quality is a goal for our engineers, regardless of the Hackney products t o be made. Write for further information on any of these Hackney products: Compressed Gas Cylinders -; Pressure Vessels -; Transports for LPgas -, carbon dioxide -, other liquefied gases -; Shapes and Shells for missiles -, or industrial equipment
-.
Pressed Steel Tank Company Exnort Division, 1445
S. 66th
St., Milwaukee 14, Wisconsin, U.S.A.
Cable Address: SEAMLESS, Milwaukee Manufacfurer of Hackney Products Since 1902
(Continued on Fagc 74)
CONTAINERS AND PRESSURE VESSELS FOR GASES, LIQUIDS AND SOLIDS Circle NO. 517 on Readers’ Service Card VOL. 5 6
NO. 2
FEBRUARY 1964
13
I&EC R E P O R T S
RESEARCH AND INDUSTRIAL HEALTH
T h e distressed area of the future may well be one which Lacks centers of graduate education and reseurchJohn F. Kennedy Because of our inescapable dependence on modern science and technology, we must regard trained brain power as a precious natural resource. The extent to which we discover and encourage growth of intellectual activity will determine our success or failure in meeting problems posed during the remainder of this troubled 20th century. This was the main theme in an address delivered recently by Glenn T. Seaborg, Chairman of the AEC, before a group of engineers. I n America, Dr. Seaborg went on to say, it was the engineer who was architect of our industrial revolution, but in the future it will be the scientist as well as the engineer who guides industrial growth. But they must be educated. In the past, the engineer’s education prepared him well for his tasks, but it did not stress fundamentals of why and how a device or principle worked. Then beginning with Tt‘orld War 11, engineers were faced no longer only with problems of building a new machine patterned on the old or a new bridge patterned on age-old bridge-building techniques. Rather, they had to design, build, and operate a totally new machine or device. The nuclear reactor was born; radar came of age; digital and analog computers were developed ; and automatic control systems were developed. Recognition that these events required changes in education was not long in coming, and the need for more graduate study having several objectives was realized: a more general and fundamental understanding of not only the science underlying a specific field, but also that underlying related fields; more general and powerful methods of 14
analysis; capacity to read with understanding advanced work, both classic and contemporary; and courage, imagination, and technical capacity to make new advances, and know the methods as well as failures and successes involved. These objectives of graduate study should be applied to undergraduate study as well. This means that each course must be sufficiently fundamental and based on scientific principle, so that it remains reasonably valid during the professional lifetime of the student. Such courses should provide the basis for communication and cooperation with nearly all other branches of science or engineering. Nevertheless, even the most thorough preparation along these lines will not guarantee against the need for “re-treading.” The growth of basic science is now progressing so rapidly that even these graduates will have to go back to school in one way or another to keep pace. \’arious means for continuous education are being used more and more, such as interchange between industries and universities by faculty industrial leaves and consulting programs, and visiting periods in the universities for industrial people. Meetings, sponsored by professional societies, between industries and universities are being encouraged, and also more special meetings such as summer institutes. Undoubtedly this trend will accelerate. What this trend means is that the engineer of today, in his partnership with the scientist, can no longer be content merely to preserve and extend in a gradual fashion his technological inheritance. H e must force his technology as rapidly as new developments in basic science allow him to. And further, if he is imaginative and creative, he will call frequently on the scientist to explore areas heretofore neglected, because the needed knowledge is not available. But to fulfill this function, he must be broadly educated.
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
These changes that so radically affect engineering education will inevitably have an impact on the nation’s industrial picture. In his message to Congress on Aid to Education, the late President Kennedy said, “TYe need more graduate centers, and they should be better distributed geographically-. N e w industries increasingly gravitate to or are innovated by, strong centers of learning and research.” The truth of this statement is reflected by the industrial complexes that have grown up in Massachusetts and California which do have these centers of higher learning and which have received a major share of Governmental defense contracts. Many complaints have been voiced by this alledged preferential distribution of Government contracts. However, these contracts are generally of an advanced scientific and technological character. Contract awards can be often equated simply to the scientific and technical competence residing in a particular geographical area, and it is the outstanding educational institutions which are capable of attracting this manpower. They can retrain and redirect talents and create new, fresh competence through education and graduation of capable students. The answer to the complaints about preferential distribution of Government contracts is to begin now with a vigorous program to place universities in these by-passed areas, and thereby create the scientific and technological base for economic well-being. However, this is easier said than done. Such centers of higher learning are not created overnight. The strong centers on the West Coast and New England have been 30 years in the making and they continue to forge ahead with vigorous consistent programs for improvement. Their position of excellence is therefore a moving target and only a moderate support program cannot keep abreast E RELLER of this progress.
