C&EN PROGRESS REPORT
INDUSTRIAL CHEMICAL SPECIALTIES
Companies added these products to their lines during the past month Company Acheson Colloids Co. Port Huron, Mich. Dow Chemical Co. Midland, Mich. Durez Plastics North Tonawanda, N.Y. E. I. du Pont Co. Wilmington, Del. E. F. Houghton & Co. Philadelphia, Pa. M & Τ Chemicals, Inc. Rahway, N.J. Nopco Chemical Co. Newark, N.J. General Electric Co. Waterford, N.Y.
Material Tetrafluoroethylene lubricant (Emralon 315) Coalescing agent (Dalpad A) Fire-retardant resin (Hetron 197) Nonfoaming surfactant (Zonyl A) Rust preventive (Rust Veto) Strippable packaging (Unichrome 4417) Liquid dispersant (Nopcosant L) Liquid silicone rubber (RTV-30)
Features and Uses Useful on glass substrates where a trans lucent, low-friction coating is needed Low-temperature film-forming aid for paint systems Resin for tanks and ductwork has distor tion temperature of 310° F. Stable in solutions of strong acids, bases, and salts Aerosol spray deposits a transparent film for up to two years' protection Vinyl foam plastisol expands when cured, strips easily from surfaces Disperses pigments, fillers, and other insoluble fine particles in water Cures at room temperature when catalyst is added
Available in commercial quantities unless otherwise noted.
Product Mix Data Aid Photochlorination With such data, Diamond Alkali gets a range of products and greater efficiency in p-xylene reaction Determination of the product mix dur ing photochlorination of p-xylene per mits Diamond Alkali to make more than just the key intermediate for the company's highly successful Dacthal herbicide. By knowing the make up of the reaction mixture at any time, Diamond can make other chloro-pxylenes, used as intermediates for other products. And the data will reveal changes in conditions needed for optimum reaction efficiency. Product distribution data obtained during early stages of photochlorina tion also allow "impurities" to be de tected more readily, according to Dr. R. H. Lasco, R. L. Urbanowski, and W. N. Wheeler of Diamond. The impurities, unwanted products, result from side reactions in the ring or in Friedel-Crafts condensations. Iron as ferric chloride catalyzes these side reactions, as does free chlo rine in the reaction mixture, Mr. Wheeler told the American Institute of Chemical Engineers, meeting in New Orleans. Glass-lined reactors keep metal contamination to a mini mum. Free chlorine is minimized by 52
C&EN
MARCH
2 5, 1963
control of process variables such as temperature, light intensity, and chlo rine dispersion, and by keeping out oxygen. Product distribution is changed only slightly by these vari ables and by pressure about 25 p.s.i.g. In Diamond's plant (near Houston, Tex.) for making Dacthal, dimethyl tetrachloroterephthalate, p-xylene is photochlorinated to hexachloro-pxylene, which is converted to terephthaloyl chlorine by fusion with terephthalic acid. More chlorination makes tetrachloroterephthaloyl chlo ride, which is esterified with methanol. Only Way. Photochlorination is the only way in which chlorine can be di rected onto the substituent groups of p-xylene in high yield, Mr. Urbanowski says. Increased light intensity im proves yield and quality of the hexachloro-p-xylene as would be expected, but its effect diminishes. In its plant, Diamond uses two 2100-watt mer cury vapor lamps in each 500-gal. reactor to get good yield and quality. Most of the useful light of these lamps has a wave length of 3660 A. During photochlorination, the prod
uct volume increases as does the mass. Because of this, the reactors at the plant are partially filled with p-xylene and a vapor space exists in which the light is unshielded. Diamond obtains high quality hexachloro-p-xylene by adjusting light intensity, temperature, and chlorine feed rate to get almost 100% efficiency in chlorine utilization. Because temperatures of 120° C. or higher increase Friedel-Crafts conden sations, Diamond starts the photo chlorination at about 90° C. As the amount of chlorinated product in creases, the temperature is increased in steps coinciding with amount of chlorine consumed. When about 3 moles of chlorine per mole of p-xylene have been added, the temperature is held at about 120° C. Chlorine feed rate is directly gov erned by the actual rate at which chlorine reacts and by the rate at which the heat of chlorination can be removed. Unless materials other than water are used for cooling the reactors, the maximum chlorine feed rate is 2 moles per hour per mole of p-xylene. Optimum operating conditions and results for a small or medium capacity commercial plant are, according to Mr. Wheeler: 70 to 80% utilization of chlorine feed, 26 to .30 hr. batch re action time, 85 to 95% hexachloro-pxylene from p-xylene.
