Diisocyanate prepolymer

Table 3-2. Chemical Identity of Hexamethylene Diisocyanate Prepolymers...

Hexamethylene diisocyanate is a highly reactive synthetic chemical that is widely used in the production of polyurethane materials. There is no natural somee of HDI. All of the potential exposures to this compound are associated with the production, handling, use, and disposal of HDI and HDI-containing products or materials. Exposures to HDI are often associated with exposures to its prepolymers, especially to a trimeric biinetic prepolymer of HDI (HDI-BT) (see Figure 5-Ia), whieh is widely used as a hardener in automobile and airplane paints, and whieh typieally contains 0.5-1% unreacted HDI (Alexandersson et al. 1987 Hulse 1984 Karol and Hauth 1982). There is evidence that diisocyanate prepolymers may induce asthma at the same or greater frequency as the monomers (Seguin et al. 1987) therefore, there is a need to assess the potential for human exposme to prepolymeric HDI as well as monomeric HDI. Except for limited data on occupational exposures, no information was foimd in the available literature related to the potential for human exposure to prepolymers of HDI. 

The polyol, the chain extender, and any catalysts are mixed and stored as a separate item. The second item, the diisocyanate prepolymer, is kept as a "B" part until the material is ready for use. When the two parts are mixed, the chain extension and cross-linking take place simultaneously. Methylene diisocyanate and a catalyst such as an organic tin or bismuth salt provide the... 

Temperature rise after 1 min in °C. 1 M solution diisocyanate prepolymer/hydroxyl in dioxane. Start reaction temperature 25-27 °C. Complete reaction 35 temperature rise according to FTIR. Catalyst 2 weight % based on solution. Metal content of solution (derived from catalyst) shown in Table... 

BuOH = 1-butanol, EG = ethylene glycol, ETOH = 2-ethoxyethanol, EtSOH = 2-ethylthioethanol, DMAOH = j6-dimethylaminoethanol, HEAC = 2-hydroxyethyl acetate, NPG = neopentylglycol. Toluene diisocyanate prepolymer (80% 2,4-TDI 20% 2,6-TDI) 91 %, trimethy-lolpropane 9 %... 

Sandler [11] also reported that poly-2-oxazolidones can be prepared by the reaction of trimerized isocyanates, i.e., isocyanurates on reaction with diepoxides. A variety of poly-2-oxazolidones have been reported (see Table IX). The reactions can be used to cure diisocyanate prepolymers as an alternate cure method to the diamines. Some typical preparations are reported in Table IX. 

The liquid feedstock consists of an extended diisocyanate prepolymer and a caprolactone-based triol. The feed enters the reactor at 318 K with an initial reactive group concentration of 2.64 X lO g-equiv/m. The feed flow rate is 1.05 m / min. What reactor volumes are required in each case At what rate must thermal energy be removed to keep the system isothermal What is the effluent temperature when the reactor operates adiabatically ... 

Two-component reactive quasi-prepolymer liquid adhesives where one component forms the polyol prepolymer stream and the other the diisocyanate prepolymer stream. 

Preparation of poly(ethylene glycol)-diisocyanate prepolymer... 

Nonaromatic isocyanates such as isophorone diisocyanate (IPDI), hexamethylene diisocyanate prepolymers, and dicyclohexylmethane diisocyanate prepolymers have also gained some importance. Guidelines for the use of isocyanates are given in [27]. 

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