| 摘要 |
<p>In the recovery of pure dissocyanates consisting of (i) 2,4-diisocyanato-toluene and its mixts. with upto 35 wt.% w.r.t total mixt. of 2,6-diisocyanato-toluene, (ii) 1,6-diisocyanato-hexane and (iii) 1-isocyanato -3,3,5-trimethyl -5-isocyanato -methyl-cyclohexane from conc. solns. of the phosgenation prods. of the diamines corresp. to the diisocyanates, in industrial-grade chlorobenzene and/or o-dichloro-benzene, the solns. obtd. in the phosgenation of the diamines, and contg. 40-98 wt.% solvent, are conc. by distn. to a residual solvent content of 2-15 wt.% and opt. also freed from pt. of the diisocyanate formed. The concentrates obtd. are mixed intimately, at -20 to +130 deg.C, with aliphatic hydrocarbons liq. at room temp. and/or with aliphatic ethers liq. at room temp., as extractants, to form a liq. 2-phase mixt. Wt. ratio extractant:concentrate is 0.5:1 to 30:1. After the phase sepn. the liq. phases formed are sepd. from one another. The pure diisocyanate is recovered from the lighter liq. phase by distilling off the solvent and extractant present. The sepd. heavy phase is opt. charged to a renewed extn.</p> |
