Polycarbonate polyol

The specialty class of polyols includes poly(butadiene) and polycarbonate polyols. The poly(butadiene) polyols most commonly used in urethane adhesives have functionalities from 1.8 to 2.3 and contain the three isomers (x, y and z) shown in Table 2. Newer variants of poly(butadiene) polyols include a 90% 1,2 product, as well as hydrogenated versions, which produce a saturated hydrocarbon chain [28]. Poly(butadiene) polyols have an all-hydrocarbon backbone, producing a relatively low surface energy material, outstanding moisture resistance, and low vapor transmission values. Aromatic polycarbonate polyols are solids at room temperature. Aliphatic polycarbonate polyols are viscous liquids and are used to obtain adhesion to polar substrates, yet these polyols have better hydrolysis properties than do most polyesters. 

Polyesters and polycarbonate polyols show improved resistance to oxidative attack, compared with that of the polyethers. Stress relation studies run at 130°C, comparing a urethane based on a poly(oxypropylene) polyol and a urethane based on poly(butane adipate) polyol show that, after 60 h, the urethane based on PPG lost most of its strength, while the polyester retained most of its strength [83], Urethanes made from poly(butadiene) polyols are also susceptible to oxidation, but they show good resistance to air-oven aging with antioxidants present (see p. 290 in [45],... 

Bayer MaterialScience (Germany) in the Project "Dream Production" combines part of waste streams of coal-fired power plants, CO2, with the production of polymers. The target is the design and development of a technical process able to produce C02-based polyether polycarbonate polyols on a large scale. The first step was to convert the C02 in new polyols, and these polyols showed similar properties such as products already on the market and can be processed in conventional plans as well (Figure 22). 

New polyols, such as polycarbonate polyols (Duracatb, PPG Ind. Inc.), hydantoin-containing polyols (Dantocol DHE, Lonza Inc.), polyo-lefinic polyols (Poly bd, Atochem Co.) and its hydrogenated polyols, i.e.. Polytail (Mitsubishi Chemical Corp.) are now available as conunercial products. An application of polyolefinic polyols for foams has recently been reported (119). The chemical structures of the above polyols are shown below ... 

Polycarbonate polyols have a structure, characterised by the aliphatic carbonic ester groups, as repeated units (Figure 8.4). 

A second method for polycarbonate polyol synthesis is the ring opening polymerisation of cyclic carbonates of 5-6 members, initiated by various polyols as starters (reaction 8.38) [68-76]. 

Alkyl carbonates are relatively labile concerning the hydrolysis reaction. Surprisingly, polycarbonate polyols give PU that are extremely resistant to hydrolysis, superior to those PU derived from polyesters based on adipic acid and diethylene glycol. The explanation of this paradox, mentioned before, is that between the hydrolysis products of polycarbonate polyols, acidic groups which are able to further catalyse hydrolysis reactions are not formed. The products of polyester polyol hydrolysis are diacids and glycols. The products of polycarbonate polyols hydrolysis are carbon dioxide (a gas which is eliminated easily) and glycols [76] ... 

Preparation 5-2 In a reaction vessel equipped with a dropping funnel, a thermometer, a water-cooled reflux condenser, a stirrer, a temperature regulator and a nitrogen inlet tube, 230.0 y of a polycarbonate polyol (DURANOL T5651), 126.3 g of acetone and 0.06 g of dibutyltin dilaurate were added. The contents were heated to 40°C and sufficiently mixed. Then, 87.5 g of hexamethylene diisocyanate was added to the reaction vessel from the dropping funnel at 40°C over a period of 60 min. The residual hexamethylene diisocyanate in the dropping funnel was rinsed into the reaction vessel with 7.5 g of acetone. 

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