I&EC REPORTS & COMMENTS Polybutadiene-a
heavy duty rubber
C ske oven benzene-co mpeti tive again? Radioisotopes as a new process tool
NEW RUBBER FROM AN OLD SBR PLANT In 1963, stereo-speczj'ic rubber will account for a n estimated 7.6% of the total rubber market If a company has acquired the know-how for putting into commercial production two new rubbers it has discovered, and also owns one of the largest SBR plants in the country, what is the next step? Goodrich-Gulf found itself in precisely such a position. T h e two new rubbers were the stereo-regular cis configurations of 1,4-~olybutadieneand -polyisoprene. T h e plant is a 37acre installation containing three parallel production lines, purchased in 1956 from the Government for $11 million. Either rubber can be made by converting SBR facilities, and arguments in favor of conversion were convincing. Two of the three lines in the SBR plant were operating but, even though SBR is the most widely used synthetic rubber, the third was standing idle. World capacity for SBR exceeds demand by a large margin. Also, many market experts believe that because of price stability, better physical properties, and for national defense reasons, use of stereo-specific rubbers will become more prevalent in the future. Last, but not least, cost of conversion was less than that for buiIding entirely new facilities-about $225 to $300 per ton of annual capacity compared to $300 to $350. For a 10,000-ton plant the saving would amount to a half to three quarters of a million dollars. Having decided to convert the idle SBR line, the company faced the next question : Which rubber should be put into production? Polyisoprene is the nearest equivalent to natural
minor alterations were required. From the start it has produced consistently high quality rubber well within specifications. I n addition, the process is flexible. It can accommodate a variety of solvents, catalysts, manufacturing conditions, and even eventual closed-loop computer control. Personnel for the new line plus the two SBR lines numbers only
rubber, but it has not clearly emerged as a general purpose rubber. Polybutadiene was chosen for two main reasons: Price of the feed stock is lower and company engineers had unshakable confidence that performance of the polybutadiene, particularly in wear resistance, would be superior and thereby create substantial markets, both in this country
Old SBR polymerization reactors were retained. process requires fewer reactors
and abroad. Undeniably, however, another contributing factor was that the company owns half of the largest butadiene plant in the country. Having made these two major decisions, some of the best engineering talent available was put to work on the conversion project. After a year and a half, the line was put on stream, almost exactly within engineering predictions. Only a few
Because reaction time is shorter, the new
about 720, half of which are for maintenance; thus the lines are automatic to a high degree. A chief advantage of conversion is that the product can be dewatered, dried, and packaged with the old equipment. T h e major changes required were because the Ziegler catalyst system used (cobalt-alkyl aluminum) requires anahydrous conditions. I n the old process, the feed VOL. 5 5
NO. 1
JANUARY 1963
11
I&EC R E P O R T S is a water-monomer-soap emulsion and the reactor product is rubber particles suspended in the emulsion. I n contrast, the feed for the new process is a hydrocarbon-solvent system from which water must be removed completely, and the reactor product is a clear viscous cement containing about 1570 of dissolved rubber. The new reaction is carried out either batchwise or continuously in a series of reactors. Goodrich - Gulf claims several unique properties for the new cis-l,4polybutadiene, called Ameripol CB. I t has a high cis content: 987, compared with 96 to 97y0for natural rubber and a maximum of 947, for other polybutadienes. Unlike other polybutadienes, it can be used as the only rubber in a compound as well as blended with either natural rubber
ever, the product cannot replace natural rubber gum stocks for making items such as rubber bands, surgical gloves, or swimming caps. Low hysteresis heat build-up makes this rubber useful for vibration dampeners and shock absorbers, but the major advantages will be probably for heavy duty uses such as truck tires, conveyor belts, power transmission belting, hose covers, and chute liners. I n tests where tires have been run more than 7 million miles, treads of this rubber blended with either SBR or natural rubber lasted 25 to 3570 longer, and treads made solely of this rubber lasted twice as long. An important factor is that advantages over other rubbers become more marked as severity of wear conditions increases. Also, because of outstanding low temperature performance, the rubber has potential military use in arctic cliE. KELLER mates and for aircraft.
COKE OVEN BENZENE REFINING CONTINUES TO IMPROVE
The new rubber, clear and light colored, is dried with old SBR dryers
or SBR. Chemical structure is precise and impurity content is low. Also, tack and processability are good-it accepts carbon black and other agents generally better than either SBR or natural rubber. T h e new rubber has a number of properties claimed either to equal or surpass those of natural rubber, which the company hopes will earn an outstanding reputation for the product. For example, it resists aging and oxidation better and resilience is higher. Resistance to hysteresis heat build-up is equal or better and flexibility is retained a t temperatures far below those where other rubbers become brittle. HOW12
Refiners of coke oven benzene who use the sulfuric acid wash process now seem to have upgraded its performance to where it can hold its own, not only against hydrogen refining but also against petroleum benzene. Latest step forward comes from Rheinelbe Bergbau, Gelsenkirchen, West Germany, which has revealed some details of its new plant in Gelsenkirchen. Coke oven benzene refiners have in the past 10 years turned more and more to hydrogen refining to produce benzene pure enough to compete against oil sources for chemical uses. But a hydrorefining plant takes a larger investment than acid refining, and potentially valuable olefins such as cyclopentadiene, styrene, and indenes are lost in the process. Some European refiners have improved their acid refiningDutch State Mines and APV, Ltd., for example-but only four new acid process plants have been built in Europe since 1952.
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
Basically, Rheinelbe Bergbau's process refinement consists of adding a fast acid wash of the benzene after the latter has been separated from other aromatics such as toluene and xylene. Key to the extra step is removal of the thiophene by reaction with sulfuric acid while at the same time minimizing benzene-acid reactions to hold losses doivn. According to the company's studies, when strong acid is used, thiophene content drops sharply and in just a few minutes reaches a limiting value not dependent on the starting thiophene content. The stronger the acid, the faster this limit is reached. The company also finds that, at equilibrium, thiophene concentration in the organic phase decreases as acid concentration in the acid phase increases. But low water content in the acid phase increases rate of reaction of benzene with the acid. Req-cling the acid and reinforcing it with oleum or SOY suppresses the benzene-acid reaction. These conditions were therefore chosen : -Temperature, 30" C. -SuIJuric acid, Q6yG, enrzchrd wifli oleum or liquid SOS, recycled -Contact time, 4 inmutes --Aczd-benzene ratio, 6y0 or higher
Benzene treated under these conditions h a s melting points ranging from 5.32" to 5.40" C., total sulfur content from 0.5 to 10 p.p.m., and thiophene contents from 0.5 to 1 p.p.m., exact levels depending on thiophene content prior to treatment. These properties make the benzene suitable for use in most syntheses. Losses from the treatment are less than 1.570,about two thirds of them from benzene-acid reaction. This fast acid wash must be carried out on benzene from which the toluene and xylene have been separated, the company points out. At 30' C., toluene and xylene react faster than benzene with the acid ; losses would thus be too hiqh. Rheinelbe Bergbau has had a unit (Continued on page 74)
HIGH PERFORMANCE DESIGN
MlKRO-PULSAIRE DUST COLLECTOR! 0 NEW RlaHT ANaLE VALVE SYSTIW dawoues compressed alr mqulmentl 0 NEW 8-FT. FILTER ELEMENTS allow 1Ia mom fllter apmclty wlth no l r in lloor meal 0 NEW LOWER INSTALLATION COST PER 84 FT. OF FILTER AREA1 0 NEW PRE-WIRED PANELS as standard aqulpmmt
Jb
w l r h l . 1 1 ~eIimlnta field wiring! 0 NEW LOWER HAINTENkNCE AND INSTALLATION COST1 Now, two engineering developments in the MIKROPULSAIRE-a right angle valve system, and higher capacity 84. filter elements made possible by increased pressure at the filter cleaning jets-bring added economy to the field of dust collection. With a unique, jet-action cleaning principle proved in nearly Zoo0 installations throughout the world, the new im-
proved High Performance Design MIKRO-PULSAIRE now offers new lower cost operation, maintenance and initial installation. Discover why “it’s the pulse that makes the difference”. . . MIKROPRODUCTS we’ll be glad to send you MIKRO-PULSAIRE Bulletin 52-A2. Write today. GRINDING WNVYLYINGCOLLECTING
Menbsr Industrial G I C I e m i I u Illltitutl, lm.
l&EC R E P O R T S based on these studies in commercizl operation for about three years. Thiophene contents and operating losses in the unit are as predicted by the lab and pilot plant data. D . E . GUSIIEE
RADIATION-CATALYZED PROCESS GOES COMMERCIAL DOW Chemical uses y - r a ) s to poduce ethjl bromide from ethjlene and anhydrous HBr Production will begin soon a t Midland, Mich., in the first commercial plant in the United States to use radioisotope radiation as a chemical process catalyst. T h e ne\v process was chosen on its own merits, but Dow regards it as only the beginning of a new production technology using radiation chemistry. I n seeking a better process to replace the old ethanol-HBr system,
Dow looked at several catalyst systems which would promote the reaction between ethylene and hydrogen bromide. Ultraviolet light was considered, too, but the choice was gamma radiation. There are reports of similar work in Japan and in France, but no details are available. A Russian phenol process is thought to depend on arbitrary prices and costs in the state-controlled economy. In the U. S., radioisotopes have limited use in thickness and density gages, food sterilization, and tracer techniques; but up to the present they have not been used directly as sources of process enersy. This would be a new outlet for productive use of waste fission products. Radiation Process. The reaction between hydrogen bromide and ethylene proceeds by a free radical mechanism, initiated by gamma
radiation from a cobalt-60 source. The over-all reaction is: CZH4
+ HBr
Y C2HjBr
, 4
The older ethanol-HBr process is an equilibrium reaction, and forms \cater as one of the reaction products. The radiation-induced process reaction Toes to completion and has no inherent by-products. Yields are nearly quantitative. Product purity is high because both high purity ethylene gas and hydrogen bromide are available from Dow’s Midland chemical complex. In addition, this reaction is very efficient in the
A 30-gallon reaction vessel, made of ‘/d-znch thick nickel metal, is placed 31,12feet below ground leuel zeithin the welded steel shell shown above. T h i s shell i s surrounded by a concrete jacket. Steel boiler plate couers the top of the ieactor and the openang of the pit
On guard just in case! When trouble strikes. emergency action must be ittrviedicife. c o n t a m i n a t i o n f r o m acids, chemicals a n d o t h e r industrial caustics requires first aid n m ’ . . . HAWS Decontamination Booths are your best stand-by protection against serious injury. hlODEL 8600: Fiberglass decontamination booth; spray nozzles and eye/face wash activated by weight o n treadle base.
Siiitr 1909
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DECONTAMINATION BOOTH for complete catalog write
Circle No. 2 on Readers’ Service Card 14
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
use of available radiation energy. T h e company emphasizes that the radiation process does not induce any radioactivity in the product. The highly radioactk-e cobalt-60 is used in the form of small aluminum-clad slugs. These are sealed in stainless steel tubes. A source holder assembly, which is lowered into the center of the reaction vessel, holds up to 30 of these rods. T h e outer surface of the cvlindrical source holder assembly is made of Hastelloy-C. Lead plugs a t top and bottom of the source holder act as shielding while it is in use. ,4 portable lead shielding cask is used to remove the radiation source. J . H. OLIN
