INSULATION. Slot cell Insulation made of glass fabric coated with Du Pont's Pyre M.L. polyimide and Pyre M.L. enamel-coated magnet wire are used in this armature. After inspection the armature, for a Bendix a.c. brushless generator, is immersed in Pyre M.L. insulating varnish

be used for lamination by conven­tional techniques.

Du Pont's Η-film can be laminated, metalized, formed, punched, or ad­hesive coated. In addition, a heat-sealable modification is available which consists of Teflon-FEP fluoro-carbon resin bonded to either one or both sides of the H-film. Du Pont says major outlets for the film will be electrical insulation where tempera­ture stability is important, such as wire and cable wrap, motor slot liners, flexible printed circuits, and magnetic-and pressure-sensitive tapes. The company is presently fabricating its polymer SP into parts trade-named Vespel. These include items such as compressor vanes, sleeve bearings, ball-bearing cages, seals, valve seats, piston rings, and diamond abrasion wheels in which the polyimide resin is used as a binder. Fabrication of polyimides is difficult because of their high viscosity and thermal stability, thus intricate parts cannot be pro­duced. Du Pont says it uses a heat-pressure process similar to that used in powder metallurgy. The firm has no plans as yet to sell either polymer SP resin or Vespel parts commercially.

Adhesives. Most firms are examin­ing polyimides for use as adhesives because of their high tensile shear strengths at temperatures up to 370° C. Some applications under study are bonding metal to metal, film to film, and film to metal. Devel­opment work is also under way for polyimides as heat-resistant coatings for uses such as coatings on the wings of high-speed aircraft.

Production. Polyimides are pro­duced by reacting the dianhydride of an aromatic tetrabasic acid with an aromatic diamine. The dianhydride most commonly used is pyromellitic dianhydride (PMDA), derived from the oxidation of durene. Other pos­sible materials include Amoco's tri-mellitic anhydride (TMA), which it uses for its polyimide-polyamide, and Gulf Oil's developmental chemical, benzophenone tetracarboxylic dian­hydride (BTDA). Du Pont was the sole supplier of PMDA, but in 1963 the company claimed there was no commercial market for the material and stopped offering it for sale. Du Pont, however, does make PMDA for its own use and continues to offer limited quantities to its customers.

Du Pont's withdrawal from the mar­ket has sparked activity by some com­panies to consider producing PMDA. The first new entry in the market will be Princeton Chemical Research, which says it will produce commercial quantities of PMDA by the end of 1964 at its 400,000 pound-a-year plant at Princeton, N.J. Enjay Chemi­cal, a supplier of durene, says it is actively pursuing the upgrading of its durene into various outlets, includ­ing PMDA.

Patents. The patent situation in polyimides is cloudy. There have been no patents issued in the U.S. regarding either composition of matter or end use, although most firms doing work with polyimides have patent ap­plications pending. Some companies believe that more than one composi-tion-of-matter patent will be issued.

Borden Plans to Buy Smith-Douglass Deal would involve about $72 million worth of Borden stock Borden plans to acquire the fertilizer company, Smith-Douglass. The trans­action, subject to approval by Smith-Douglass stockholders, would involve an exchange of stock. If the deal is approved, Borden will acquire Smith-Douglass for the equivalent of about $72 million.

Rumors that Smith-Douglass would be taken over by another company have been rife for several years. One of the earliest rumors was that Smith-Douglass would merge with Parke-Davis. Merger negotiations between the two companies did take place, but they fell through.

About a year ago, when the big petroleum companies started buying fertilizer companies—Cities Service got Tennessee Corp., Continental Oil bought American Agricultural Chemi­cal, and Socony-Mobil acquired Vir­ginia-Carolina—Smith-Douglass was linked at one time or another with nearly all the major petroleum com­panies. But Smith-Douglass* major stockholders held out for various reasons.

Under the terms of Borden's acqui­sition agreement, Borden would issue 0.9 share of Borden common stock for each share of Smith-Douglass common stock. If, at the time of acquisition, the market value of Borden stock is below $77.75 a share, Borden would issue sufficient additional shares to provide $70 a share for Smith-Doug­lass common, up to a maximum of 0.95 share of Borden for each share of Smith-Douglass.

Smith-Douglass had 1,025,012 com­mon shares outstanding on July 31, 1963. Borden's stock has been selling recently for about $75 a share.

Fertilizer Interest. Smith-Douglass, headquartered in Norfolk, Va., is one of the oldest fertilizer companies in the U.S. Net sales for the year ended July 31, 1963 (the latest year for which figures are available) were just under $65 million. Net income for the same period was $3.5 million.

Well over half of the company's business is in fertilizers. More than a quarter of its business is in animal feed supplements. The company also makes some miscellaneous and indus­trial chemicals.

A U G . 2 4, 1964 C & E N 25

Simon Strauss Donald J. Ramsey

Supports bill ordering Treasury to make Urges switch to some other metal for intensive study of silver problems dimes, quarters, and half-dollars

Industry Battles Coins for Silver Supply Congress postpones showdown on finding solution for silver crisis until next year

Smith-Douglass is a large producer of phosphate rock in Florida. How­ever, the company's Florida phos­phate reserves are not as extensive as some of the other major phosphate companies. Smith-Douglass has about 15 million tons of recoverable ore in Florida. This compares with an esti­mated 100 million tons for American Agricultural Chemical, 80 million tons for Virginia-Carolina, 70 million tons for the Davison division of W. R. Grace, and 60 million tons for Ameri­can Cyanamid. Smith-Douglass also has a joint venture with Magnet Cove Barium, a subsidiary of Dresser In­dustries, to explore the feasibility of mining phosphate rock in North Carolina.

Smith-Douglass has an extensive marketing organization, and a network of plants in the U.S. for making com­plete fertilizers. It also sells feed supplements, such as defluorinated phosphate rock, and a line of insecti­cides, herbicides, defoliants, pesti­cides, a line of specialty fertilizers for lawns and garden, and .other agri­cultural chemicals.

It has an anhydrous ammonia plant in Houston, Tex. It also participates in a joint venture with Illinois Nitro­gen Corp. to make ammonia in Mar­seilles, 111.

How It Fits. There is some question as to just how Smith-Douglass' opera­tions will fit into Borden's operations. If the deal goes through, Borden will make Smith-Douglass a division of Borden Chemical Co. Smith-Doug­lass would continue under its present management, retaining its name.

Borden Chemical makes a line of adhesives, resins, molding powders, solvents, formaldehyde, hexamethyl-ene tetramine, and other chemicals. It and U.S. Rubber jointly own Mono-chem, Inc. Monochem produces acety­lene and vinyl chloride at Geismar, La.

Borden's total chemical sales will probably reach $160 million in 1964. Its total corporate sales will probably reach $1.2 billion. Last year, Bor­den's chemical business advanced to about as much of total company sales as ice cream—about 12%.

Borden's main business is in foods and other nonchemical operations. The company is a big milk processor, but collecting milk from farmers is somewhat different than selling them fertilizers. However, it's possible that Borden may plan to make use of the two different networks of contacts it has with fanners.

The widening gap between supply and demand is creating a crisis for users of silver. The U.S. Treasury is bridging the gap by selling silver to industry from its stocks. But with a crash program to mint more subsidiary coins (dimes, quarters, and half dol­lars) to relieve the current coin shortage, Treasury stocks, estimated at 1.4 billion ounces (troy), may last only four or five years or less.

Several proposals to alleviate the shortage are before Congress. One would raise the so-called monetary value of silver from $1.293 an ounce to $2.5858 an ounce. Another would forbid the Treasury to sell silver bullion. A third would reduce the silver content of coins, and a fourth (H. J. Res. 1140) would order the Treasury to make an intensive study of the problem and report its findings to Congress by Feb. 1, 1965.

Silver producers strongly back the proposed study as a way of bringing the problem into perspective before taking positive action. They also sup­port proposals to raise the monetary value of silver, to forbid Treasury sales of bullion, and to reduce the silver content of coins.

Silver users oppose the proposals supported by producers on the grounds that they are merely devices to boost the price of silver. They want the use of silver in coins abandoned immediately as a way of

funneling the available supply of the metal to industry. They give luke­warm support to the study proposal but fear this will do little but delay action.

Congress will take no action this year to alleviate the silver crisis. Rep. Wright Patman (D.-Tex.), chair­man of the House Banking Commit­tee, which will start silver legislation through Congress, says the committee will consider only H. J. Res. 1140— the study proposal. If this bill clears Congress in the rush for adjournment, it would postpone action until some­time next year. The same result will occur if it fails.

Views. "The time has come to stop using our monetary system as a ve­hicle to give the silver producers higher prices for silver," says Rear Admiral Donald J. Ramsey (USN-Ret.) of the Silver Users Association. If the monetary value of silver were increased to $2.58 an ounce, the mar­ket price of silver would rise to this level from the present $1.29. This increase, for the benefit of foreign producers, holders of silver, specula­tors, and a few domestic producers, could cost industrial users $142 mil­lion a year, he says.

Producers say that an increase in price would stimulate silver produc­tion. Adm. Ramsey challenges this view. An increase in the market price for silver from 90 cents in 1961 to

26 C&EN AUG. 24, 1964