Patent GB-520255-A (GB)
Title: Separation of polymerisable organic compounds
IPC: C07C7/00
Filed: 1938-10-17
Abstract: 520,255. Recovering volatile liquids. DU PONT DE NEMOURS & CO., E. I. Oct. 17, 1938, No. 30069. Convention date, Oct. 15, 1937. [Class 32] [Also in Group IV] Volatile constituents are separated from a liquid composition containing a heat-polymerizable unsaturated organic compound by bringing an inert gas into contact with said composition to entrain the volatile constituents, the temperature being maintained below that at which the polymerizable compound is polymerized in substantial amount (1.5 per cent.), and separating the gas with entrained constituents from the liquid. The invention is particularly applicable to the separation of monofrom divinylacetylene, of divinylacetylene from an oily acetone-soluble polymer thereof, and of vinylacetylene from its hydrogen halide addition products. Two or more stripping columns may be used, the liquid composition passing down through these in series against an upward current of inert gas, the entrained volatile constituents being condensed out from the gas leaving each column. A liquid composition containing 10-15 per cent. oily divinylacetylene polymers, 80-85 divinylacetylene, and 5 per cent. xylene may be treated using nitrogen as inert gas and a stripping temperature of 20-45‹C. The columns may contain close fitting spirals to distribute the liquids over the walls or may be plain or packed. Hydrogen, carbon dioxide and the inert gases of Group O may also be used. Pressure is usually normal or slightly above. In the polymerization of acetylene to give mainly mono- or di-vinylacetylene, acetylene is fed to reactor 1, Fig. 2, which may contain aqueous cuprous and ammonium chlorides at 45-100‹C. The exit gases pass to 0‹C. condenser 4, water separating as the bottom layer in separator 5 and being returned to the reactor. A second liquid layer rich in divinylacetylene (DVA) generally forms and is drawn off at 9 and passed to stripping column 21. A gaseous mixture of acetylene and monovinylacetylene (MVA) leaves at 10 and, where MVA is the desired product, passes to -65 to -75‹C. condenser 11, acetylene being vented at 13 and recycled, and the condensed MVA containing some DVA passing to column 17 which is at 18-25‹C. MVA is vented at 18 and the residual crude DVA is fed to stripping column 21 where it meets an upward current of acetylene which entrains MVA. The gases are returned to the system at 28 and DVA leaves the column at 29. When DVA is the main product, the acetylene and MVA leaving at 10 are returned direct by valve 30 to the reactor 1. Examples are given. In the production of chloroprene from vinylacetylene, the latter may be stripped from the product using acetylene, advantageously at 20-45‹C. Acetylene is polymerized in reactor 2, Fig. 3, water is removed from the products in drier 3, acetylene removed in 5 and 7, and the monovinylacetylene vaporized in 13. It is fed to reactor 16 and reacted with hydrogen chloride, the product containing chloroprene (CD) being liquefied in condenser 20 and fed to a column 21 at 30-35‹C. Part of the MVA is vaporized and returned by pipe 23. The liquid passes to a stripping column 25 where acetylene entering at 29 entrains MVA and is returned via reflux condenser 31 and lines 32, 34. Chloroprene leaves at 36. Other inert gases may be used in the stripping stage. Thus nitrogen may be introduced into column 25 at 37, the exit gases passing by line 32 and valve 33 to a condenser 39 where nitrogen and MVA are separated and returned. The reflux condenser 31 may be omitted allowing some chloroprene to be stripped with the MVA. The two are condensed in 39 and added to the condensate from condenser 20 at 44. Other hydrogen chloride or bromide addition products may be prepared similarly.