Diisocyanate Drying

The polyurea is prepd by dissolving equivalent amounts of the monomers (80g total wt) in dime thylformamide. Using separate solns, 125ml of the diisocyanate is slowly added to 120ml of the amine soln while keeping the temp below 20°. After standing 18 days at RT, most of the dimethylformamide is vacuum evapd at 50° and the syrupy residue is kept at 50° for 48 hrs. Acet diln is followed by filtration, then pptn in ice w. The product is vacuum steam distd at 30° then dried over P2Os... 

A three-necked flask equipped with a condenser and stirrer was charged with the PET depolymerization product (0.05 mol of BHET and dimer in the ratio of 80 to 20 wt%), 0.05, 0.10, and 0.15 mol of e-caprolactone (in separate experiments), and 0.1 wt% of dibutyltin dilaurate. The reaction mixture was heated at 150°C for 2 h. The resulting co-oligomer (0.01 mol) was dissolved in 500 mL of tetrahydrofuran in a three-necked flask equipped with a condenser and a stirrer. After the temperature was raised to 67°C, a solution of 0.01 mL of hexamethylene diisocyanate in 50 mL of tetrahydrofuran was added dropwise. After heating and stirring the reaction mixture for 12 h, it was cooled and precipitated in ether. The polyurethane precipitate was collected by filtration and dried at 70°C for 12 h. 

Materials and Purification. Chemicals were purchased from Aldrich chemical company and used as received unless otherwise noted 1,1,1,3,3,3-hexamethyl disilazane, ethylene glycol, triphosgene, poly(ethylene oxide) (MW = 600), poly(tetramethylene oxide) (MW = 1000), poly(caprolactonediol) (MW = 530), toluene diisocyanate (TDI), anhydrous ethanol (Barker Analyzed), L-lysine monohydride (Sigma) and methylene bis-4-phenyl isocyanate (MDI) (Kodak). Ethyl ether (Barker Analyzer), triethylamine and dimethyl acetamide were respectively dried with sodium, calcium hydride and barium oxide overnight, and then distilled. Thionyl chloride and diethylphosphite were distilled before use. 

The above prepolymer on treatment with 2 as the chain extender in dry DMF did not proceed at ambient temperature. The mixture had to be heated to 60°C for 3 h before the reaction was complete. After curing at 60°C for 24 h, the yellow, translucent block polyurethane film (BPUR2) again showed the absence of the —NCO peak in the IR spectrum indicating that curing had been complete. The fact that a higher temperature had to be used in the case of 2 as the chain extender compared to 1 is in keeping with the lower order of reactivity of diols with diisocyanates as compared to diamines with diisocyanates. 

This intermediate for the preparation of ethylene diisocyanate exploded violently during isolation [1], Previously the almost dry solid had exploded violently on stirring with a spatula [2]. 

Polyurethane networks were prepared from polyoxypropylene (POP) triols(Union Carbide Niax Polyols) after removal of water by azeotropic distillation with benzene. For Niax LHT 240, the number-average molecular weight determined by VPO was 710 and the number-average functionality fn, calculated from Mjj and the content of OH groupSj determined by using excess phenyl isocyanate and titration of unreacted phenyl isocyanate with dibutylamine, was 2.78 the content of residual water was 0.02 wt.-%. For the Niax LG-56, 1 =2630, fn=2.78, and the content of H2O was 0.02wt.-%. The triols were reacted with recrystallized 4,4"-diphenylmethane diisocyanate in the presence of 0.002 wt.-% dibutyltin dilaurate under exclusion of moisture at 80 C for 7 days. The molar ratio r0H = [OH]/ [NCO] varied between 1.0 and 1.8. For dry samples, the stress-strain dependences were measured at 60 C in nitrogen atmosphere. The relaxation was sufficiently fast and no extrapolation to infinite time was necessary. 

Lithium aluminum hydride Lithium hydride Methyl isocyanate Methylaluminum sesquibromide Methylaluminum sesquichloride Methyldichlorosilane Methylene diisocyanate Methylpentaldehyde Methyltrichlorosilane Mono-(trichloro)-tetra-(mono-potassium dichloro)-penta-s-triazinetrione, dry Monochloro-s-triazinetrione acid Octadecyltrichlorosilane Phenyl trichlorosilane Phosphorus oxychloride Phosphorus pentachloride Phosphorus pentasulfide... 

The experimental data to be considered are shown in Figure 1. They refer to previously published data on hexamethylene diisocyanate(HDI) reacting with polyoxypropylene(POP) triols and tetrols in bulk and in nitrobenzene(5-7,12) that is, to RA2 + RBj polymerisations. is the molar mass of chains between elastically effective junction points. A/Mj. has been determined directly from small-strain compression measurements on swollen and dry networks using the equations... 

According to O. Bayer, the latter procedure, which is used especially for the preparation of elastomeric polyurethanes, is carried out in two separate stages. First, a carefully dried, relatively low-molecular-weight, aliphatic polyester or polyether with hydroxy end groups is reacted with an excess of diisocyanate. A chain extension reaction occurs in which two to three linear diol molecules are coupled with diisocyanate, so as to yield a linear polymer with some in-chain urethane groups and with isocyanate end groups. 

Polyurethanes (PU s). SL and 4,4 -diphenylmethane diisocyanate (MDI) were dissolved in tetrahydrofuran (THF), and the solution was stirred for 1 hr at 60°C. A THF solution of polyethylene glycol (PEG 400) and diethyl bis(2-hydroxyethyl)aminomethylphosphonate (polyol containing phosphorous) was added to the reaction mixture, and the reaction time was extended for 1 hr. In all reactions, the molar ratio of the total amount of isocyanate groups to the total amount of hydroxyl groups (NCO/OH) was maintained at 1.2. The lignin content in PU was 20 wt%. Each solution was drawn on a glass plate, and allowed to dry for 48 hr. The residual solvent in a sample was removed under vacuum and curing of each PU film was carried out at 120°C for 3 hr under a pressure of 50 kg/cm2. 

To a flask containing a solution of 8.7 gm (0.05 mole) of 2,4-toluene diisocyanate in 200 ml of anhydrous ether is slowly added a mixture of 0.432 gm (0.024 mole) of water, 50 ml of anhydrous ether, and 0.5 ml of pyridine at room temperature. The urea derivative precipitates as a fine powder, and then 10 ml water is added and the mixture stirred for an additional hr. The product is filtered, washed several times with 1 1 anhydrous petroleum ether-diethyl ether, dried to yield the product, m.p. 172°-175°C (% yield not reported). 

To a 500 ml dry, nitrogen-flushed resin kettle equipped with a mechanical stirrer, thermometer, condenser with drying tube, dropping funnel, and heating mantle are added 34.8 gm (0.20 mole) of 2,4-toluene diisocyanate and 0.12 gm... 

The preparation was carried out in a dried 250 ml three-necked flask equipped with a nitrogen inlet, magnetic stirrer, reflux condenser, micro-dropping funnel and recording thermocouple. The reaction flask was immersed in a constant temperature bath (25°C) and 100 ml of the 2,4-tolylene diisocyanate (TDI) were placed into the flask. When constant temperature was reached in the flask, one ml of a solution of a catalyst in acetonitrile was added dropwise to the reaction mixture and the resultant mixture was intensively mixed for 4 hours. The reaction product was analyzed by GPC and the conversion was determined by the dibutylamine method. 

Materials. The flexible polyurethane (polyether) foam, formulated from a polyol, tolylene diisocyanate, emulsifier, catalyst, and blowing agent, was obtained from the Nopco Chemical Co. It had a density of about 1.5 pounds per cubic foot (0.02 gram per cc.) and contained approximately 40 open cells per linear inch. The foam samples were washed in detergent, dried, and weighed before being irradiated. 

Union Carbide also patented a phosgene-free process for making hexamethylene diisocyanates [40] (Scheme5.5). In this later process, 1,6-hexanediamine was reacted with dry-ice, trimethylchlorosilane, and trichlorophenylsilane to form a halosilyl carbamate intermediate and then converted to the corresponding diisocyanate. However, it should be noted that trichlorophenylsilane used in this process is on the EPA s Extremely Hazardous Chemicals List (40 CFR Part 355, Appendix A). 

Specialty Isocyanates. Specialty isocyanates are organic isocyanates having the isocyanate function attached to a carbonyl group or to elements other than carbon. /t-Toluenesulfonyl isocyanate is used as a drying agent for organic solvents. Arenesulfonyl diisocyanates, such as m-phenylenedisulfonyl diisocyanate, are used as monomers for base-soluble polymers. Arenesulfonyl monoisocyanates are used as intermediates for pharmaceuticals and herbicides. 

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