| 摘要 |
1,133,668. Polyisocyanate. ALLIED CHEMICAL CORP. 16 May, 1966 [17 May, 1965; 11 June, 1965], No. 21689/66. Heading C2C. [Also in Division C3] A liquid polyisocyanate, said to be storagestable, is prepared by treating a toluenediamine mixture (<1�5 wt. per cent o-) with a molar excess of phosgene, heating to cause complete phosgenation, and removing toluenadiisocyanates by distillation until the residue has an amine equivalent 90-125, a viscosity 20- 10,000 c.p.s. at 25� C. and a 20-55 wt. per cent concentration of hexane-insoluble congeneric solutes. The starting material may be recovered as distilland by fractionating a predominantly mdiamine in a column of at least 23 theoretical plates under subatmospheric pressure which is below 120 mm. Hg absolute at the top, while maintaining a reflux ratio of at least 15: 1. |
