Patented Jan. 5, 1937 , 2,067,013.

2,067,013 PROCEss FoR PRODUCING THE DIsobruM - SALT of IMIDoDICARBOXYLIC ACID

Robert B. MacMullin, Niagara Falls, N.Y., as: signor to The Mathieson Alkali Works, Inci; : New York, N.Y., a corporation of Virginia. No Drawing. Application october 2, 1935, v- Serial No. 43,178

...... "...... 3 Claims. (C1, 260-12) My invention relates to the production of the half of the nitrogen is evolved as ammonia to the compound having the formula: substantial exclusion of carbon dioxide and water vapor, as follows: - ...... o 5 5 Na-O-O N H. The heating may be carried out under atmos Na-O-CC pheric pressure, sub-atmospheric pressures or O pressures somewhat higher than atmospheric 105. 0- i. - pressure. The compound so produced, disodium which is hereinafter referred to as disodium ini imidodicarboxylate, is a solid, stable at tempera dodicarboxylate. More particularly my inven tures up to 200° C., and is less hygroscopic than tion relates to the production of disodium imido Sodium carbamate. It has valuable detergent and dicarboxylate by: heating Sodium carbamate. anti-acid properties. It is an advantageous 5. This application is in part a continuation of my household cleanser. It hydrolyzes, in water, to prior co-pending application, Serial No. 607,510, Sodium bicarbonate and ammonium hydroxide, filed April 25, 1932. It has been proposed to prepare disodium ini as follows: dodicarboxylate by heating Sodium carbamate at temperatures of 200° C. and upwards. I have dis (NaCO2)2NH-3H2O->2NaHCO3--NH4OH 20 covered, however, that disodium imidodicarboxyl ate can be prepared by heating dry sodium carba By heating this compound in the presence of wa mate in a dry atmosphere at temperatures below ter or water vapor, it may be converted to anhy 200° C. Temperatures of 100°-190° C. may be used drous Sodium carbonate, Na2CO3, or to sodium. in carrying out the process of my invention. Sesquicarbonate, NaHCO3. Na2CO3.2H2O. By heat 2 Temperatures of 125°-150° C. are advantageous, a ing this compound to temperatures above 200° C., temperature of 140°-150° C. being particularly it may be converted to mixtures of sodium car advantageOuS. bonate and Sodium cyanate, NaOCN. I am aware While conversion of sodium carbamate to di that there have hitherto been suggestions that 30 sodium imidodicarboxylate can be effected at dry sodium carbamate is converted to sodium 30 temperatures of 200° C. and upwards, Several ad cyanate to the exclusion of other products, by vantages are to be obtained by carrying out the heating. These Suggestions are not in accord conversion according to the process of my in with the facts. vention. Disodium imidodicarboxylate is stable The following tabulations are reproduced to attemperatures up to 200 C., but attemperatures illustrate the effect of heat on sodium carbamate: 35 of about 200° C. it decomposes to form. Sodium carbonate and sodium cyanate. The use of tem TABLE I peratures of 200° C. and upwards involves danger of decomposition of the desired product, requiring Wapor pressure NaCONE 40 40 critical control of reaction conditions to avoid ex cess decomposition. Again, maximum dissocia tion of the sodium carbamate to disodium imido Temp. C. Dynamic Static dicarboxylate takes place at a temperature of 140°-150° C. It will thus be seen that the process PNH, Poo P. P of my invention affords advantages both with re lam-ma-re-m-m-m-m- 45 90. 87.2 min. 59.3 146, 5 161.3 spect to the extent of conversion of sodium car 135-140. ------|------About 710 bamate to disodium imidodicarboxylate and de 160 ------>1850 mm. composition of the formed product. Further, these advantages are obtained while requiring less 50 critical control of the reaction conditions, an From the above table it will be apparent that 50 important advantage in itself. the dissociation temperature of the sodium car When dry sodium carbamate, NaCO2NH2, is bamate is just Slightly above 140° C., because at heated to the temperatures employed in the proc the temperature of 140° C. the pressure had nearly approximated that of the atmosphere, 55 56 ess of my invention in a dry atmosphere, one 2 2,067,013 TABLE II tion with the following example but it will be Effect of heating NaCO2NH2 under NH3 pressure understood that the example is merely illustrative Note: Original PNH3=100 lb/sq. in... gauge of the invention and not limiting: 5 Eacample I N Max Max. E. 0. preSS. eat 100 parts of sodium carbamate consisting of trap. lbs./sq. ing NaCONH 84.6% (by weight) NaCO2NH2, 8.5% NaHCO3 and . (hrs.) 6.9% H2O are spread in a thin layer on the trays Original.------100 ------100 of a drying cabinet or other suitable apparatus, 10 E.: 90 275 19 100 the temperature of which can be controlled, and 2. 150-180 400 5. - 0 10 3------350-400 550 4 0 heated to a temperature of 140° C. for approxi - - - - 450-500 600 ... 8 0. mately one hour while circulating dry air over the material. The ammonia, given off into the l5 Percent of Na as circulating air may be removed and recovered by absorption in Water, for example. 81.4 parts of a li product containing approximately 93% disodium (NaCO)NH Na,CO. NaCNO NaCN imidodicarboxylate are obtained. The presence of moisture is undesirable as it O 0 0 0. 0 O causes the evolution of excessive amounts of am 73 13 14 monia, giving rise to side reactions. The heating 20 33 51 16 of the Sodium carbamate may be carried out in a 0. 77 21 dry atmosphere comprising air, ammonia, nitro gen, or carbon dioxide, for example. From Table I it Will be seen that Sodium car I claim: 25 bamate dissociates at about 145 C. when heated even in the absence of air to give off ammonia and . 1. A process for producing disodium imidodi 25 some carbon dioxide. The higher the temper carboxylate comprising heating dry sodium car ature the greater will be the proportion of am banate to a temperature at which nitrogen is monia, to carbon dioxide. Table II shows the evolveddry atmosphere. as ammonia not exceeding 190° C. in a 30 results of heating sodium carbamate under an 2. A process for producing disodium imidodi original NH3 pressure of 100 lbs./sq. in... gauge. carboxylate comprising heating dry sodium car 30 From the table it is seen that Sodium carbamate bamate to a temperature of 100°-190° C. in a dry undergoes no change upon being heated to 90° C. atmosphere. but that its dissociation to form (NaCO2)2NH has 35 passed its peak at 150°-180° C. In the last ex 3. A process for producing disodium imidodi carboxylate comprising heating dry sodium car 35 ample of Table II fusion of the mixture oc bamate to a temperature of 140°-150° C. in a dry curred. atmosphere. - My invention Will noW be illustrated in connec - . . . ROBERT B. MACMULLIN.