Chlorine and Bromine Containing Polyols

TCBO is reacted with various polyols (such as carbohydrates), in the presence of cationic catalysts (for example BF3), with the formation of very viscous and high chlorine content polyols (18.3) [14, 22-24]. 

The extremely high viscosities of these polyols lead to difficulties if they are to be used on conventional foaming equipment. TCBO based polyols are not used and are not produced industrially at this moment [3]. 

3 Dibromobutene diol is obtained by the addition of bromine to the triple bond of 2-butyne-1,4- diol (resulting from the addition of formaldehyde to acetylene), as shown in the reaction 18.4. 

The bromine linked to a double bond or linked to an aromatic nucleus are much more stable structures (not easily decomposed to HBr as dibromo neopentylglycol, a saturated aliphatic bromine compound). Thus, a very successful bromine containing diol, produced industrially [4, 24], is based on tetrabromophthalic anhydride. Tetrabromophthalic anhydride is reacted first with diethylene glycol and the resulting half ester is reacted with propylene oxide (PO) (reaction 18.5) [3]. 

The bromine diol (18.5), in combination with sucrose polyols gives rigid PU foams with excellent fire retardancy properties [3, 24]. 

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