Polyether triols Synthesis

The high MW polyether triols, copolymers of PO-EO are the most important oligo-polyols for PU, having the biggest volume of industrial production. This is the reason why the synthesis of polyether triols, by polymerisation of PO and/or EO and initiated by glycerol, will be presented in detail. 

Synthesis of Polyether Triols Based on Glycerol Homopolymers of PO... 

The synthesis of polyether triols, block copolymers with terminal poly[EO] block is relatively simple in the first step a propoxylated intermediate polyether is synthesised by the polyaddition of PO to the starter (glycerol or propylene glycol). After the addition of the required quantity of PO, the unreacted monomer is eliminated by vacuum distillation and the polymerisation continues by the addition of EO, the second monomer. 

The reactions involved in the synthesis of EO capped polyether triols are ... 

DMC catalysts are considered to be the ones that perform best at this time for PO polymerisation initiated by hydroxyl groups. Bayer developed the first continuous process, with a very high productivity, for the synthesis of polyether polyols with DMC catalysts (IMPACT Catalyst Technology). In a short and simple production cycle, a large variety of polyether diols of very low unsaturation for elastomers, sealants, coatings and low monol content polyether triols destined for flexible polyurethane foams are obtained. This is one of the best developments in the last few years in the field of polyether polyol synthesis [2],... 

For low MW oligomers, (e.g., polyether triols initiated by glycerol with a MW of 600-1000 daltons), the cationic catalysis is used successfully especially in the synthesis of the starters/ precursors for coordinative polymerisation with dimetallic catalysts (DMC) (see Chapter 5). 

By the hydrolysis of a flexible foam based on toluene diisocyanate (TDI) one obtains toluene diamine (2,4 and 2,6 isomers), the polyether triol and, of course, carbon dioxide. The difficulty of the process is the separation of the amine. The amine may be used for TDI synthesis (after a previous purification), or be transformed into a valuable rigid polyol (aminic polyol) by alkoxylation with PO and EO. 

Chem. Descrip. Polyether triol containing primary hydroxyl groups Uses Flow aid, leveling agent, abrasion resist, aid for radiation-curable monomers, urethane and polyester resins, high-solids coatings, polyester resin synthesis reactive modifier for UV cationic cure systems Features Good compat. with resin systems Properties Lt. yel. clear liq. m.w. 240 sp. gr. 1.1 dens. 9.2 Ib/gal vise. 800-900 cps hyd. no. 680-710 pH 6-8 (2%) 0.5% moisture... 

In his synthesis of the polyether antibiotic X-506, Evans4 needed the triol 20 with two of the OH groups protected. He added an allyl group as a nucleophile to open the epoxide 17 at the less hindered end and then protected the two OH groups as an acetal 19 before the third was introduced by ozonolysis and reduction. These two examples emphasise the versatility of the allyl group. 

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