Halogen-containing polyurethanes

Phosphorus compounds should be added to an extent of 1.5 to 2 per cent of phosphorus content in the foam. Above this level, no further flammability reduction is gained. Even 1 per cent of phosphorus is satisfactory in the presence of 10 to 15 per cent of chlorine, and in fact, the phosphorus level can be decreased to 0.5 per cent at 4 to 7 per cent content of bromine. Halogen-containing polyurethane foams are preferably supplemented with antimony trioxide synergent. 

Halogenated 2-propanol derivatives, eg, l,3-dichloro-2-propanol [96-23-1], are generally prepared from glycerol [56-81-5] (qv). These materials are used in the preparation of halogen-containing phosphates to plasticize and lower the flammability of plastics, eg, polyurethanes and ceUulosics. 

Whilst rigid closed-cell polyurethanes are excellent thermal insulators they do suffer from a limited and often unsatisfactory level of fire resistance, even in the presence of phosphorus-containing and halogen-containing fire retardants. Considerable promise is now being shown by the polyisocyanurates, which are also based on isocyanate chemistry. 

Halogen-containing borate ester such as tris(2,3-dibromopropyl)borate [B(OCH2CHBrCH2Br)3] is reportedly used in polyurethanes, unsaturated polyesters, and epoxy novolacs.89 More recently, it was also claimed to be used in cotton textiles.89... 

The volume leaders among fire retardants with 35 million pounds were the three phosphate plasticizers for PVC tricresyl phosphate, cresyl diphenyl phosphate and triphenyl phosphate. The remaining 6 million pounds were made up of octyl diphenyl phosphate, tributyl phosphate, tri(dibromopropyl) phosphate, tri(dichloropropyl) phosphate and tri-(chloroethyl) phosphate. Polymeric phosphorus and phosphorus halogen-containing additives are used in concentrations of 3-25 p.p.h. in polyesters, flexible and rigid polyurethane foam, and phenolics. 

Flammability. Rigid polyurethane foams, along with other organic plastics, have been the subject of much work in the field of flame retardance. A variety of phosphorus and/or halogen containing additives (reactive and non-reactive) are now available which improve the flame resistance of polyurethane foams. The choice of additives and of test methods is however best decided upon in the light of the application envisaged. Table 7 shows some typical properties. 

Polyurethane foams for building purposes are normally of the rigid kind used for roof and wall insulation. Polyols containing halogen or phosphoms are used to increase the fire resistance of the foam. 

NLO materials (16 and 17) (Fig. 13) have been obtained from polyurethanes by the incorporation of sidechains with boron chromophores.37 The dihydroxy ligand of an azobenzene ligand containing a dimesityl boron acceptor was reacted in a polycondensation fashion with the diisocyanate groups of the polyurethanes to yield the desired polymers. Halogen displacement and transmetallation reactions have been utilized in the development of extended ir-conjugated systems of tri-9-anthrylborane with dendritic structures.38 In one (18) (Fig. 14) of the novel compounds, three identical... 

The next major improvement was the development of combustion modified PU foam. The original CMHR polyurethane foam was developed in the USA (26) and contained hydrated alumina and halogenated flame retardants but was made in a single operation. It was used in institutions, public buildings, hotels etc. but its high density and less than optimum physical properties... 

Such diisocyanates can lead to polyurethanes. The first fluorinated polyurethane was patented in 1958 [74], An interesting survey [75] details the comparison of the reactivity of fluorinated diols about that of non halogenated ones for the preparation of such polymers. The first one which contained fluorine was synthesized by reaction of hexafluoropentanediol and hexamethylene diisocyanate [76] ... 

Clariant is the world s largest manufacturer of ammonium polyphosphate, which is the basis of its Exolit AP halogen-free intumescent flame retardants. They cut down smoke emission, evolve no corrosive gases and are recommended for both thermoplastic (including polyolefin and polyurethane) and thermosetting polymers. Exolit AP 750 is used to make injection moulded PP electrical parts and weatherable items that contain a HALS stabiliser. Ammonium polyphosphate is recommended for certain types of wood-plastic composite. 

With a patented [1], proprietary surface modification, rubber particles are rendered compatible with polyurethanes. One surface modification is a controlled oxidation of the outermost molecules on each rubber particle. The treatment chemistry involves the reaction of halogen- and oxygen-containing gases with the rubber backbone to form pendant polar functional groups. Figure 1. In fact, the rubber surface becomes so hydrophilic that the treated particles are readily wetted by water. 

---