Purification of tris{8 1-(2-methyl) aziridinyl{9 phosphine oxide
United States Patent [191 Law [451 Apr. 1, 1975 PURIFICATION OF TRISIl-(Z-METHYL) AZIRIDINYL1PHOSPHINE OXIDE [75] Inventor: Ronald D. Law, Brigham City, Utah [73] Assignee: Thiokol Corporation, Bristol, Pa.  
 [22] Filed: Jan. 14, 1974 [21] Appl. N0.: 432,936  
 [52] U.S. Cl. 260/239 EP, 260/705 [51] Int. Cl. C07f 9/56 [58] Field of Search 260/239 EP [56] References Cited UNITED STATES PATENTS 3,359,259 l2/l967 Ham 260/239 EP Primary E.taminerAlton D. Rollins Assistant ExaminerMark L. Bench Attorney, Agent, or Firm-Thomas W. Brennan [57] ABSTRACT 8 Claims, No Drawings PURIFICATION OF TRISI I-(Z-METHYL) AZIRIDINYLIPHOSPHINE OXIDE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to a purification process for a phosphorus heterocyclic oxide, in particular, an extraction process for tris[ l-( 2- methyl)aziridinyllphosphine oxide.  
 2. Description of the Prior Art Trisl l-(Z-methyl)aziridinyHphosphine oxide, re-  
 ferred herein as MAPO, is a high boiling, thermally unstable, toxic, oily liquid, used to cross link polymers. It, however. has contaminants that cause cracking of the cross linked polymers, particularly, carbo&#39;xyl terminated polymers used in propellants when its impurity level is greater than 0.3 wt percent for chlorine and 4.0 wt percent for other impurities These cracks widen under thermal stress causing propellants to burn rapidly and unevenly which results in missile misfiring and failure. Removal of these contaminants from large batches as by vacuum distillation at 0.15 mm Hg and 90-92C is too expensive and hazardous for commercial application, for MAPO rapidly decomposes in the present of heat to toxic, flammable products.  
  The extractive process described herein overcomes these problems and is based on the discovery that water preferentially retains chlorine impurities, that organic solvents such as benzene, chloroform and mixtures of chloroform and carbon tetrachloride preferentially retain the other impurities, and that methylene chloride retains MAPO and is readily removed.  
 SUMMARY OF THE INVENTION The process comprises the steps of dispersing contaminated tris l-(2-methyl)aziridinyl phosphinc oxide (MAPO) in a liquid organic solvent selected from benzene, chloroform and mixtures of chloroform and carbon tetrachloride, extracting a portion of MAPO from the solvent with the water, extracting a portion of MAPO from the water with methylene chloride, and removing the methylene chloride from the MAPO.  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS The purification process is an extractive process based on the discovery that water preferentially retains the chlorine impurities, that benzene, chloroform, and mixtures of chloroform and carbon tetrachloride preferentially retain the other impurities, and that methylene chloride retains tris [l-(2- methyl )aziridinyl lphosphine oxide (MAPO) and is easily removed from MAPO. The process comprises the essential steps of dispersing the contaminated MAPO in a liquid organic solvent selected from benzene, chloroform, and mixtures of chloroform and carbon tetrachloride, extracting a portion of the MAPO from the liquid organic solvent with water, extracting a portion of the MAPO from the water with methylene chloride, and removing the methylene chloride from the MAPO.  
  The term extracting and the various extractive proeesses are used as described by Lyman C. Craig and David Craig, Laboratory lirlraction and Coumercurrenr Distribution, in Technique of Organic Chemistry, ed. by A. Weissberger, NY, Interscience Publishers, Inc., Vol. III. Part l, 1956, p. l49-394. For example, the step of extracting a portion of the MAPO from the liquid organic solvent with water essentially consists of contacting the organic phase with the water phase during which contact a portion of MAPO transfers across the boundary where the two phases meet, and a portion of the impurities also transfers, but the ratio of the amount of impurities to the MAPO retained by the organic phase is greater than the ratio for the water phase. The same phenomenon occurs at the point of contact between the water phase and the methylene chloride phase when extracting a portion of the MAPO from the water phase with methylene chloride except that the ratio of chlorine to MAPO is greater in the water phase than in the methylene chloride phase. Consequently, when these steps are combined in an extractive purification the MAPO in the methylene chloride phase has less impurities than the initial MAPO used.  
  The extractive process using this invention may be a discontinuous one, that is a single contact between the different phases is made, or a multiple discontinuous process, that is a multiple number of contacts are made between the phases, or a continuous extractive process, that is the phases flow counter current to each other. These different ways are described in the reference of L. Craig and D. Craig cited above.  
  The examples described below are based on a discontinuous extractive process and show that almost 50 percent of the impurities are removed. The imine assay is determined from quantitative reaction of thiocyanic acid with Z-methyl aziridine rings, which assay is significant to the nearest 0.1 percent.  
 EXAMPLE l 100 grams of tris[l-(2-methyl)aziridinyl1phosphine oxide dispersed in 300 ml of chloroform was extracted with 300 ml of water in a-separatory funnel, and the water phase extracted with two 600 ml portions of methylene chloride which were combined and evaporated off to about 300 ml by boiling on a hot plate. The remaining solvent was removed by evaporation in a rotating evaporator under vacuum for two hours at 50C. The final traces of solvent were removed by bubbling dry nitrogen through the product for 2 hours at 70C. The yield was 20 grams. Chemical analysis before and after purification gave the following results:  
 K of impurities Before After removed Imine Assay 92.2?! 96.0% Polymer Impurities 7.8% 4.0% 499! Total Chlorine 0.58% 0.30% 48% Hydrolyzahle Chlorine 0.47% 0.25% 4771 Moisture 0.2091 (H87! 10% EXAMPLE 2 bubbling dry nitrogen through the product for 4 hours at 60C. The yield was 59 grams. Chemical analysis before and after purification gave the following values:  
  7: of impurities Before After removed lmine Assay 92.271 96.171  
 Polymer lmpurities 7.871 3.97: 5071 Total Chlorine 0.58% 0.2771 53% Hydrolyzable Chlorine 0.477: 0.21% 55% Moisture 0.207: 01371 35% EXAMPLE 3 Impurities Before After Removed lmine Assay 92.271 95.4% Polymer Impurities 7.871 4.6% 417! Total Chlorine 0.5871 0.42% 387: Hydrolyzahle Chlorine 0.47?! 0.357: 257: Moisture 0.2071 0.07% (357! The invention as described is not to be limited only by these examples but by the claims as set forth below.  
 I claim:  
 1. A process for removing impurities from contaminated tris[l-(2-methyl)aziridinyllphosphine oxide, which comprises:  
 dispersing the contaminated tris[ l-(2- methyl)aziridinyllphosphine oxide in an organic solvent selected from the group consisting of benzene, chloroform, and mixtures of chloroform and carbontetrachloride, extracting a portion of the tris[ l-(Z- methyl)aziridinyl]phosphine oxide from the organic solvent with water,  
 extracting a portion of the tris[ l-( 2- methyl)aziridinyl]phosphine oxide from the water with methylene chloride, and  
 removing the methylene chloride from tris[ l-(2- methyl)aziridinyl]phosphine oxide.  
 2. The process as described in claim 1, wherein the step of removing the methylene chloride comprises:  
 evaporating off the methylene chloride until a trace amount remains mixed with the tris[l-(2- methyl)aziridinyl]phosphine oxide, and passing an inert gas through the tris[l-(2- methyl)aziridinyllphosphine oxide until the trace amount of methylene chloride is removed.  
  3. The process as recited in claim 1 wherein the organic solvent is a mixture of chloroform and earbontet rachloride.  
  4. The process as recited in claim 3 wherein the step of removing the methylene chloride comprises:  
 evaporating off the methylene chloride until a trace amount remains mixed with the tris[l-(Z- methyl )aziridinyljphosphine oxide, and passing an inert gas through the tris[l-(2-&#39; methyl)aziridinyljphosphine oxide until the trace amount of methylene chloride is removed. 5. The process as recited in claim 1, wherein the organic solvent is benzene.  
  6. The process as recited in claim 5, wherein the steps of removing the methylene chloride comprises;  
 evaporating off the methylene chloride until a trace amount remains mixed with the tris[l-(2- methyl )aziridinyl1phosphine oxide, and passing an inert gas through the tris[l-(2- methyl)aziridinyl1phosphine oxide until the trace amount of methylene-chloride is removed. 7. The process as recited in claim 1, wherein the organic solvent is chloroform.  
  8. The process as recited in claim 7, wherein the step of removing methylene chloride comprises:  
 evaporating off the methylene chloride until a trace amount remains mixed with the tris[l-(2- methyl)aziridinyllphosphine oxide, and passing an inert gas through the tris[l-(2- methyl)aziridinyljphosphine oxide until the trace amount of methylene chloride is removed.