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非常有意思的话题
EP 561225
Polyisocyanates contg. no discoloring components are prepd. by treatment, after phosgenation, with H at 100-180°/3-150 bar for 15-240 min in the presence of catalysts. Treating MDI with H at 160°/30 bar in the presence of a Co-Mn-Ag-Ru/Al2O3 catalyst for 3 h gave MDI with extinction coeff. at 430 and 520 nm 0.21 and 0.020, resp., and transparency at 450, 500, 550, and 600 nm 13, 50, 72, and 78%, resp.; vs. 0.28, 0.046, 10, 42, 63, and 74, resp., without hydrogenation.
GB 1417075
Tolylene diisocyanate (I) [26471-62-5] and 4,4'-diphenylmethane diisocyanate [101-68-8] were decolorized by treatment of the liq. with 1/16 in. 5A mol. sieve pellets in the dark. Further yellowing was reduced by this treatment. Thus, 25 vol. parts of a 6-month old 80:20 mixt. of the 2,4 and 2,6 isomers of I was stored over 2 wt. parts mol. sieve pellets. Coloration was 30 and 20 Hazen units after 24 and 94 hr, resp., over the mol. sieve compared with 40 Hazen units for untreated liq.
DE4215761
The title mixts. are decolorized by treatment with radical-forming azo compds. after removal of excess COCl2 and solvents. Stirring 200 g crude MDI (oligomer content 39.5%) with 0.6 g AIBN at 90° for 3 h gave a product with I color no. 32; vs. 50 before AIBN treatment. |
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材料与化工 322求调剂
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