Polymer polyols polyurea dispersions

Another family of polyols is the filled polyols.llb There are several types, but die polymer polyols are die most common. These are standard polyether polyols in which have been polymerized styrene, acrylonitrile, or a copolymer thereof. The resultant colloidal dispersions of micrometer-size particles are phase stable and usually contain 20-50% solids by weight. The primary application for these polyols is in dexible foams where the polymer filler serves to increase foam hardness and load-bearing capacity. Other filled polyol types diat have been developed and used commercially (mainly to compete with die preeminent polymer polyols) include the polyurea-based PEID (polyhamstoff dispersion) polyols and the urethane-based PIPA (poly isocyanate polyaddition) polyols. 

Polymer polyols are defined as very fine and stable dispersions of solid polymers (vinylic polymers and copolymers, polyurea, polyurethanes) in liquid polyethers. Currently polymer polyols represent one of the most important group of polyolic intermediates for elastic polyurethanes [1-10]. 

PHD polymer polyols are a special class of filled polyols developed successfully by Bayer, PHD being the abbreviation of the German name polyharnstoff dispersion or polyurea dispersions [67-69]. PHD polyols contain organic urea, oligomeric or polymeric polyurea, finely dispersed in liquid polyether polyols [67-73]. The difference between PHD polyols and graft polyether polyols is the different nature of the solid polymer dispersed (it is a heterocatenary polymer - polyurea - instead of carbocatenary polymer) which is obtained by another synthetic procedure (polyaddition reaction between a diisocyanate and a diamine instead of radical polymerisation). The reaction between the diisocyanate and the diamine, takes place in situ (reaction 6.19), in liquid poly ether. The resultant polyurea being insoluble in polyether, precipitates in the form of very fine particles ... 

An alternative stable interactive organic dispersion in polyol has recently been introduced. This consists of particles of polyurea dispersed in polyol, formed by the in situ polyaddition reaction of isocyanates with amines in a polyol medium, and offers similar advantages to the polymer/polyols. 

More recently, filled polyethers (so called polymer polyols ) have been introduced. These contain dispersed organic filler such as acrylonitrile-styrene copolymer or polyurea, some of which is grafted on to the polyether chain. Filled polyethers are used principally for flexible foams of high resilience. 

Many of the same basic raw materials shown in Table II for RIM fascia systems are also used in high modulus systems. Additionally, however, polyether polyols "filled" with dispersions of polyureas are used( 2) These are the so-called PHD polyols developed by Bayer AG, the PHD being an abbreviation for Polyharnstoff-Dispersion. These polyols provide the same "filler" effect as the graft polyols (Table II) for increasing the modulus of the polymer without increasing the amount of extender. 

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