PRODUCTION
Goodyear makes Natsyn in two 500 gal. reactors· The re actor at left is presently being used for reaction, the
other as a holding tank for finished cement. The 10 hp. motors above the reactors drive turbine type mixers
G o o d y e a r Explains Natsyn Process C o m p a n y talks a b o u t polyisoprene pilot plant; is to d e v e l o p a continuous process Λ SOFT, darkish material—a carbon copy of natural rubber—oozes from an extruder in spaghetti-like strands while a sharp knife slices down to cut the strands into pellets. Nearby, a baling machine squashes the pellets into 50 pound bales. A worker wraps the bales in brown paper and marks the package with the date and the batch number. Later, the package 1 will he mixed with other materials and molded to form tires. The scene is the Goodyear Tire & Rubber Co., Akron. Ohio. For over a year, Goodyear bas been making pilot plant batches of r/.v-l,4-poly isoprene— the polymer which duplicates natural rubber. Now, in the January issue of Industrial & Engineering Chemistry, Goodyear s G. T. Winchester tells some of the details of the Goodyear process. The Natsyn pilot plant (Natsyn is 50
C&EN
JAN.
19,
19 59
goal
Goodyenv's trade name for polyiso prene rubber) has two purposes: to make material for product evaluation, and to give data which Goodyear even tually will use to design a commercial unit. T h e process is a straightfor ward batch operation. Goodyear mixes isoprene monomer with a hydro carbon solvent, adds a catalyst, lets the mixture react at moderate temperature 1 and pressure, and removes the solvent. Although Goodyear prefers to use a Ziegler catalyst, the plant is designed to use either Ziegler-type or lithiumderived catalysts. • Pitfalls. Though the process can he simply stated on paper, in practice it has its share of pitfalls. Raw ma terials must he extremely pure since oxv^on and some unsaturated com pounds poison the catalyst, and even traces of water will spoil the reaction.
Near the end of the reaction, the ce ment—the mixture of polyisoprene and solvent—has such a high viscosity that heat transfer and agitation are difficult. And process conditions must be con trolled carefully to get the most de sirable poly nier structure and molecu lar weight. Goodyear buys petroleum-derived isoprene and distills it just before use. Likewise, the solvent is distilled to make sure that no impurities are pres ent. Almost any straight-chain hydro carbon will work, although Goodyear prefers to use one like n-pentane which has a boiling point close to that of isoprene. Isoprene and solvent are measured by weight, mixed, and dried in a silica gel oi ah unit. The Natsyn plant has four stainless steel reactors which are identical ex cept for size, and which can be used interchangeably. Two 26 gal. reactors are used mainly to try out new process conditions. The larger. 500 gal. re actors make the polymer used for test tires. The reaction starts as soon as catalvst is added to the monomer-
solvent mix. Heat from t h e exothermic polymerization is removed by water or brine eire'iîating in the jacket of the reactor, a..d Goodyear finds 5()° C. to be Λ flood average reaction tempera ture. A lower t e m p e r a t u r e gives poK mers of higher molecular weight. But this advantage is offset, Ooodyear be lieves, by increased catalyst consump tion and slower reaction rates. • Viscosity P r o b l e m . The operator checks the cement s solids content every two hours. At about 7 ' ' solids it is quite viscous and. though tbixotropie. is still difficult to eool. On the 500 gal. reactors, Goodyear uses tur bine t\pe mixers driven by 10 hp. motors. Actual viscosity during the polymerization hasn't been measured, but a 15' '* solids sample tested in the lab measured 100,000 centipoises. Be cause of this high viscosity, the first few runs in the Xatsyn plant were stopped at 15' < solids. But with its experience, Goodyear now operates to 2o(/t solids and hopes t h a t this figure can be pushed higher in the hiture. Higher solids content increases the amount of polymer per batch and cuts down the quantity of solvent that must be stripped off. T h e batch is pumped from the re actor into a holding tank where catalvst deactivator and antioxidant are added. Solvent is taken off in an ex truder rather than a d r u m dryer or similar kind of equipment. The ex truder offers a convenient way to get a closed system for good solvent re covery. Vaporized solvent is con densed, distilled, and is ready for re-use. Goodyear feels that the Xatsyn plant has already gone a long way toward closing the gap between research lab and commercial production. But the job is far from complete. Says Goodyear's Winchester: " J u s t a s manufac ture of SBR went from a batch to a continuous process, polyisoprene no doubt will be m a d e some day by a mere efficient continuous method. This is the next step for the Goodyear pilot plant."
• New t e s t for c h r o m a î e in water comes from Betz Laboratories. The test, says Betz, eliminates all liquid reagents except sodium thiosulfate. The new reagents used: sulfamic acid, iodide crystals·, and Betz Starramic indicator. Chromate can be titrated to as low as 10 p.p.m. as C r 0 4 , Betz says.
syntron
vibra-Flow
V I B R A T O R Y FEEDERS
u υτ
accelerate
COSTS
ana
production
— b y providing an efficient, high capacity, flow controlled method of trans ferring bulk materials from storage hoppers to process equipment or from one operation to another. Uses for SYNTRON Vibratory Feeders in the chemical processing and allied industries are almost unlimited—packaging, bagging, mixing, weighing etc. Feed rate is instantly adjustable—material fiow is smooth and uniform. 3600 efficient, powerful controlled electromagnetic vibrations per minute moves even hard-to-handle materials. This principle eliminates mechanical wearing parts a n d assures dependability and low maintenance. SYNTRON Vibratory Feeders can solve most of your bulk materials feed mg
ρ rob I Write for information and specification literature.
S Y N T R O N COMPANY 416 Lexington Avenue
-
Homer City, Ponna.
Other SYNTRON Equipment of proven dependable Quality
VIBRATING SCREENS
BIN VIBRATORS
FLOW C O N T R O L VALVES
, f / ^ f
VIBRATORY PACKERS
MECHANICAL S H A F T SEALS
*J
JA-4M. 19. t ' ^ 9
.
