Kellogg's Oblad Improving chlorine economics
Dr. Oblad says that Kel-Chlor suits two broad use areas, production of chlorine itself and use of chlorine in industrial chlorination reactions, the largest of which is vinyl chloride production. He states the new process "can improve the economics of making chlorine compounds and has the possibility of making chlorine the coproduct on a large scale by nonelectrolytic methods. It can thus alleviate the problems of caustic-chlorine imbalance and adjust caustic production to meet market requirements."
BUTYL RUBBER:
for sealants with its low-molecularweight butyls. A major target for the product is a sealant in insulated window glass. Other promising markets are coatings, adhesives binders, blends with other elastomers, and electrical uses. The polymer is a semiliquid that can be cured in two separate ways. For room temperature cures a twopart system can be adjusted to cure in hours or weeks. The addition of paraquinone-dioxime plus an oxidizer to the copolymer effects a cure. It can also be cured with sulfur in a conventional system. Enjay describes the process to make the new butyl as cationic polymerization. High-molecular-weight butyl contains from 0.8 to 2.0% isoprene whereas the low-molecular-weight species contains about 4.2% isoprene. Since isoprene poisons the aluminum chloride polymerization catalyst used to make butyl rubber, it was necessary to develop a different catalyst system for the new product. In regular butyl rubber production, isobutylene and isoprene in methyl chloride are chilled to - 1 4 0 ° F. before polymerization. Enjay says that the polymerization temperature for low-molecular-weight butyls is higher. In the finishing stage, solvent is evaporated under conditions of low heat and high vacuum, the company says. Worldwide production of butyl rubbers for 1968 was about 500 million pounds, 80% of which went to tires and tire products. U.S. butyl consumption in 1968 was 198 million pounds. It should grow about 4 % a year for the next four years.
Enjay Aims at Sealants Enjay Chemical has developed a semiliquid copolymer of isobutylene and isoprene for the competitive sealants and adhesives market. The firm will build a fully integrated plant at Bay town, Tex., to produce the lowmolecular-weight butyl polymer. The plant will use an Enjay-developed process of cationic polymerization that differs significantly from the conventional process for making highmolecular-weight butyl rubber. Enjay will offer its low-molecularweight butyl in two forms. The nonchlorinated form will be called LM Butyl and will sell for 65 cents a pound. A chlorinated product will be named LM Chlorobutyl and will be priced at 75 cents a pound. About 30 million pounds per year of prepolymer are sold to the sealant market, according to Enjay. The value of this market is $25 million annually and it is growing about 15% a year. Marketing department manager Jim Fusco says Enjay hopes to capture about 2 5 % of the new growth
Enjay's LM butyl Inspecting for cracks
POLYETHYLENE:
Low-Density Startup Phillips Petroleum's process to make low-density polyethylenes at low pressure moves into commercialization at its Adams Terminal complex near Houston, Tex. The new process under startup will be used in part of a 78 million pound-per-year plant which the company had announced previously as a high-density polyethylene plant. Phillips has disclosed no details of the process other than that it will operate at 500 to 600 p.s.i., instead of 10,000 to 30,000 p.s.i., the conventional pressure range for making lowdensity polyethylene. The pressure of 500 to 600 p.s.i. is 40 to 50% higher than literature values of 300 to 450 p.s.i. for Phillips' high-density polyethylene process using solution technology. Phillips' suspension process for high-density polyethylene apparently operates at pressures even lower than those used for the solution process. To date, Phillips has received no patents on its new process. As a result, the company isn't looking to license the process. Medium-density polyethylene resins can also be made by this process, Phillips says. Commercially, many medium-density (0.93 to 0.94 specific gravity) resins are made by blending low- (0,91 to 0.93 specific gravity) and high-density (0.94 to 0.96-f specific gravity) resins. The blending step, which can add significantly to processing costs, thus could be eliminated. Physically, the plant using the new process looks similar to plants which make polyethylene by Phillips' lowpressure process and built in the past two or three years. Apparently, Phillips has achieved low density at low pressure through modification of catalysts, not through reactor or process flow changes. In conventional high-pressure processes to make low-density polyethylenes, a free-radical polymerization is used, which is initiated by an organic peroxide or an azo compound. Highdensity polyethylene is made using catalysts such as chromium oxides on silica-alumina (Phillips process) or aluminum alkyls plus titanium chlorides (Ziegler catalysts). Phillips may have found a way to operate a free-radical polymerization of ethylene at low pressure, suggest some polymer chemists. Or, they have found an ionic (catalytic) polymerization to give the low density along with other desired properties. In any case, keeping straight what the relations of density and pressure of the processes are has become more complicated. APRIL 21, 1969 C&EN 15
