Polyurethane catalysts Blowing

The aromatic polyols resulting from the reaction can be mixed with commercial polyols, blowing agents, surfactants, catalysts, and polymeric isocyanates to produce a rigid polyurethane foam. n compared w control foams produced from commercially available polyester polyols, the foams produced from reclaimed materials were found to have essentially the same properties. 

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. 

The production of polyurethane involves the controlled polymerization of an isocyanate, a long-chain-backbone polyol and a shorter-chain extender or cross-linker. The reaction rates can be controlled through the use of specific catalyst compounds, well known in the industry, to provide sufficient time to pour or otherwise transfer the mix and to cure the polymer sufficiently to allow handling of the freshly demolded part. The use of blowing agents allows the formation of a definite cellular core (thus the term microcellular elastomer ) as well as a non-porous skin, producing an integral sandwich-type cross section. 

The proper balance between viscosity and gas evolution can be controlled by a number of factors such as a suitable type and concentration of catalyst and surfactant, the presence of a nucleating agent (not always necessary) (17,18) and control of reaction temperature (or exotherm). Additional factors that must be considered are the use of a suitable chemical blowing agent, which is especially important for the production of thermoplastic foams, and the formation of oligomers (prepolymers) which exhibit higher viscosities than monomers in the preparation of thermoset foams (e.g. polyurethane foams). 

Preparation. Polyurethane foams (often referred to as urethane foams) are prepared by the reaction of a polyisocyanate with a polyol in the presence of a blowing agent, a surfactant, and a catalyst without external heating of the foaming system. The principle of preparation of urethane foams is based on the simultaneous occurrence of two reactions, i.e., polyurethane formation and gas generation in the presence of catalyst and surfactant, as shown below ... 

Polyurethane Foams. Rigid polyurethane foam can be prepared by the reaction of a polyisocyanate, a polyol, a blowing agent, a catalyst and a surfactant. Detailed explanation of these foams are described in the sections on Rigid Urethane Foams and Miscellaneous Urethane Foams earlier in this chapter. 

Di-n-butyltin catalysts are being used in the preparation of polyurethane foams. Most polyurethane foams utilize aromatic isocyanates such as toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI) as the isocyanate, and a polyester or polyether polyols as the coreactant. Tertiary amine catalysts are used to accelerate the reaction with water and formation of the carbon dioxide blowing agent. To achieve a controlled rate of reaction with the polyol, an organotin catalyst can be used. Polyurethane foams are not only applied in place, but are also cast in a factory as slabstocks. These foam slabs are then cut for use in car seats, mattresses, or home furnishings. DBTDL is an excellent catalyst in high resiliency slabstock foams. DBTDL shows an excellent reaction profile for this application replacement for DBTDL in such an end-use is difficult and requires a substantial reformulation of the foam. 

Bis(dimethylaminoethyl)ether and other blowing catalysts for polyurethane... 

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