I/EC
by R. W . Lerner, Anderson Chemical Div., Stauffer Chemical Co.
Safety
Titanium Trichloride Handling Techniques
Successful described
procedures
here can help
you avoid injury and costly
serious accidents
^^IULIO NATTA, using titanium trichloride as a p o l y m e r i z a t i o n catalyst, a n d K a r l Ziegler, using alum i n u m alkyls, led t h e w a y to p r o d u c t i o n of stereo-specific polymers. Since these discoveries, i n d u s t r y has a d o p t e d t h e Z i e g l e r - N a t t a cocatalyst system for t h e low t e m p e r a t u r e a n d pressure p o l y m e r i z a t i o n of olefins. T i t a n i u m trichloride is a c h e m ically reactive m e t a l h a l i d e commerically i m p o r t a n t as a cocatalyst in the m a n u f a c t u r e of stereo-regular
Transfer of Small Quantities from Drum Lots Transfer apparatus is screwed t o the flange on the drum h e a d . Nitrogen pressure on the drum is released at this point a n d the drum is then secured in an inverted a n d elevated working position. A polyethylene b a g containing loosely c a p p e d l a b o r a t o r y containers is attached t o the lower portion of the transfer apparatus using several turns of plastic electrical t a p e . The ball valve (3) is adjusted to the open position a n d vacuum a p p l i e d to evacuate the system to a pressure of about 1 mm. of mercury. The valve (1 ) on the vacuum line is then closed a n d nitrogen introduced through a valve (2) into the system to inflate the plastic b a g . Alternate
polymers. T h e r e are two forms c o r r e s p o n d i n g to the p r o d u c t o b t a i n e d by h y d r o g e n a n d a l u m i n u m r e d u c t i o n of t i t a n i u m t e t r a c h l o r i d e . T h e c h e m i c a l properties of t i t a n i u m trichloride themselves give a clue to t h e need for special h a n d l i n g techniques to preserve its effectiveness as a catalyst for olefin polym e r i z a t i o n . E q u a l l y i m p o r t a n t , personnel h a n d l i n g this chemically r e active m e t a l h a l i d e m u s t be p r o t e c t e d against direct c o n t a c t of t h e m a t e r i a l
vacuum a n d nitrogen cycles a r e r e p e a t e d until the transfer a p p a r a t u s is thoroughly p u r g e d o f residual w a t e r a n d moisture. At this point the b a l l valve (3) is closed a n d the slide valve (4) on the drum o p e n e d , allowing a portion o f the drum contents to fill the upper portion o f the transfer assembly. The slide valve (4) m a y then be closed a n d the b a l l valve (3) opened until the titanium trichloride flows into the plastic b a g . The o p e r a t o r may then fill the sample container b y manipulating through the plastic bag. A pneumatic v i b r a t o r may b e used to facilitate the passage o f the solid through the transfer apparatus. After the transfer o f the metal halide into the l a b o r a t o r y container is completed, this container in the plastic b a g is then tightly closed a n d the ball valve (3) closed. The plastic b a g a n d the contents a r e removed from the transfer assembly. The l a b o r a t o r y container is immediately isolated a n d sealed, using plastic electrical t a p e a n d w a x . Residual titanium trichloride in the plastic b a g should b e placed in a well ventilated area for disposal. Dissolution in isopropyl alcohol or acetone effectively removes this residual material a n d the solution may be flushed a w a y using water. Titanium trichloride in a l a b o r a t o r y container m a y b e transferred into a vacuum d r y b o x for further sampling. Proper d r y - b o x transfer techniques include •
•
•
•
70 A
INDUSTRIAL AND ENGINEERING CHEMISTRY
Evacuation of the system to 50-micron vacuum t o remove residual o x y g e n a n d moisture f o l l o w e d b y pressurization to atmospheric pressure using an inert gas such as nitrogen Use of neoprene r u b b e r - t y p e gloves in the d r y b o x glove ports to minimize diffusion o f o x y g e n a n d w a t e r into the working a r e a o f the d r y b o x W e a r i n g of surgeon-type rubber gloves while operator's hands a r e inserted into the glove ports t o prevent skin moisture from contacting the d r y - b o x glove Maintenance o f a slight inert gas pressure in the working a r e a o f the d r y b o x
Transfer of Large Quantities from Steel Drums Transfer fittings are attached to the titanium trichloride storage drum and the inert gas pressure vented (open valve 1 ) while the drum is in an upright position (close valve 1 ). The storage drum is then inverted and elevated directly over the ball valve assembly attached to the receiver.
The Teflon bellows is then bolted securely to the ball valve assembly on the receiver and pneumatic vibrators are attached (valves 9 and 10 closed). At this point, valves 3 and 5 are connected to the vacuum inert-gas manifold (valve 6, 7 , and 8 closed). Vacuum is a p p l i e d to the transfer assembly (valves 2 , 3, 4 , 5, 6 open) until a minimum pressure is obtained (close valve 6 at this point). The system is then pressured with inert gas (valve 8 open) to 5 pounds g a g e pressure (close valve 8). Alternate evacuations and pressuring are then performed to insure removal of residual o x y g e n and moisture from the assembly. Valves 2, 3, 4 , and 5 are closed and the v i b r a t o r started (valves 9 and 10 open). The slide valve (valve 11) is slowly o p e n e d followed b y opening ball valves 2 and 4 . The transfer of titanium trichloride from the storage container into the receiver proceeds until the desired quantity of titanium trichloride has been transferred. The titanium trichloride storage drum may be suspended from a scale during the transfer operation to enable the o p e r a t o r to follow the course of transfer. After the transfer is completed, slide valve 1 1 is closed f o l l o w e d b y ball valves 2 and 4 , respectively. Valves 9 and 10 a r e closed and the Teflon bellows is then disconnected from ball valve assembly. The titanium trichloride storage drum is then placed in an upright position and pressured to 5 pounds g a g e pressure (valve 1 open) with inert gas (value 1 closed) to protect the contents of the drum. The transfer assembly may be then removed from the storage drum, washed with acetone to remove residual titanium trichloride and d r i e d for re-use. After clean-up and d r y i n g , the transfer apparatus may be conveniently stored in a plastic b a g in readiness for further use.
with the skin and inhalation of the corrosive vapor. Exposure of titanium trichloride to excess moisture and oxygen results in the production of finely divided titanium dioxide and hydrogen chloride gas. Formation of the metal oxide under these conditions yields a dense white smoke. Exposure of the metal halide to trace amounts of oxygen and water results in the formation of titanium tetrachloride and titanium oxychloride. H a n d l i n g Procedures
Titanium trichloride may be successfully handled in the laboratory or plant providing that the material is isolated from water and oxygen. A positive pressure of nitrogen over the material at all times protects the metal halide from contact with the two afore-mentioned reactants. Nitrogen containing less than 20 p.p.m. of oxygen and a —85° F. dew point has been found to be satisfactory for this purpose. Laboratory-size quantities of titanium
trichloride may be obtained commercially in glass screw-capped bottles whose lid is taped and waxed as a protection against atmospheric contamination, or small quantities of the material may be drawn from commercially available drum lots. In transfers of drum quantities of titanium trichloride, operating personnel should wear acid-resistant coverall-type suits and rubberized gloves to protect them from corrosive vapors and direct contact with the material. Face shields, hard hats, safety toe shoes and dust respirators should also be worn. An acid- or demand-type gas mask should be used if spills occur. Commercial quantities of titanium trichloride may be stored in the manufacturer's steel drums under 5-pound gage pressure, using an inert gas without loss of catalytic activity. These containers should be periodically checked to make certain that a minimum of 5 pounds of pressure exists in the drums. Alternately the drums may be connected to an inert gas manifold to
ensure a constant supply of gas pressure to the container. The containers should be maintained at approximately 20° C. Excessive heat may cause pressure build-up and subsequent loss of a portion of the protective atmosphere. No loss in catalytic activity was observed from material stored for one year. Accidental spills of titanium trichloride should be isolated from the source by manipulation of appropriate valves. The residue should then be flushed away using copious quantities of water by an operator wearing the protective clothing heretofore described and including an acid-dust type of gas mask. Adequate ventilation should be available to disperse the corrosive fumes.
Our authors like to hear from readers. If you have questions or comments, or both, send them via The Editor, l/EC, 1155 16th Street N.W., Washington 6, D. C. Letters will be forwarded and answered promptly. VOL. 53, NO. 12
·
DECEMBER 1961
71 A
