Organic compounds -- part of the class 532-570 series – Organic compounds – Four or more ring nitrogens in the bicyclo ring system
Patent
1984-07-06
1986-05-27
Ford, John M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Four or more ring nitrogens in the bicyclo ring system
544200, C07D25160
Patent
active
045916446
ABSTRACT:
An improved method for the preparation of melamine from urea and/or thermal decomposition products thereof. The melamine reactor synthesis effluent is quenched by means of an aqueous medium to form an aqueous solution or suspension of melamine which is processed and solid product melamine removed therefrom. At least a portion of the melamine solution or suspension is processed in equipment having surfaces exposed to such solution or suspension fabricated from a stainless steel with a ferritic austenitic duplex structure containing, by weight 20 to 30 percent by weight chromium, 1 to 10 percent by weight nickel from 0 to about 10 percent manganese, such that the sum of the nickel plus one-half of the manganese content is within the range of between 4 and 10 percent, 1 to 5 percent by weight molybdenum, 0 to 3 percent by weight copper, not more than 0.1 percent by weight carbon and for the rest iron.
REFERENCES:
patent: 3598818 (1971-08-01), Krekels
patent: 3711479 (1973-01-01), Verstegen et al.
"Corrosion and Corrosion Prevention in Stainless Steel Urea Plants", Chemical Age of India, vol. 26, No. 4, Apr. 1975; De Jonge et al., pp. 249-260.
Hamilton, J. W., Ferralium--The Alternative to Mechanically Weak Austenitic Stainless Steel, Process Engineering, Jan. 1972.
Brochure of Langley Alloys Ltd., entitled "Langley Corrosion Resistance" undated Background Art.
Brochure of Langley Alloys Ltd., (in German) entitled "Ferralium Alloy 255" undated Background Art.
Chemical Abstracts, vol. 80, 1974, p. 168, Abstract No. 29599q.
Chemical Abstracts, vol. 91, 1979, p. 178, Abstract No. 91:7990k.
Dols Hubert J.
Leerschool Joseph F. M.
Ford John M.
Stamicarbon B.V.
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