Diols forming polyester polyols

Figure 15 Reaction of diol with diacid to form polyester polyol.

Dow also developed polyurethane foams from polyols via hydroformylation of fatty acids. The foams have properties which are comparable to foams from petrochemicals in terms of density and flexibility. The advantages of using sustainable feedstocks in viscoelastic foams are increased load bearings and tensile and tear properties [39, 40]. The hydroformylation and consecutive hydrogenation of fatty acids derived from seed oil can also be used to form low viscosity polyester polyols. Therefore, fatty acid methyl esters are transesterified with diols, e.g., glycol (Scheme 12). The polymer contains chemically active hydroxy groups which can be used for polyurethanes in coating applications [41]. 

Propylene oxide is one of the top 50 chemicals. More than 4 million t/a are produced worldwide. It is reacted via polyetherpolyols to form polyurethanes and via propylene glycol to form polyesters 15). Obviously, the polyol and diol functionalities are used to form with diisocyanates derived from diamino compounds polyurethanes and with diacids polyesters, respectively. These functionalities are available from renewable feedstocks carbohydrates, oils and fats, proteins and lignins. 

Basically, flexible polyurethane foams are formed from polyols and isocyanates. The polyols have hydroxyl functionalities of at least 2 if the foam is to be made by a prepolymer process and of 3 or more if the foam is to be made by a "oneshot" process. The prepolymer process proceeds in two distinct steps while in the one-shot process, all reactants are intensively mixed together at the begiiming of the foaming process. Early in the development of urethane foams, the polyols were polyester diols now, however, by far the largest volume of polyols for urethane foams are poly(propylene oxide) polyols or poly(propylene oxide) polyols containing up to 25... 

Polyurethane dispersions are secondary dispersions typically produced by polymerization of isocyanates and diols in organic solvent After polymerization water is added followed by solvent removal. The polyester-polyol component can be designed to form crystalline structures (Fig. 8-25), which make a significant contribution to the internal strength. 

Representative PCL are the diols of MW of 2000-4000 daltons, used in hydrolytically stable PU elastomers. The diols used as starters are DEG, 1,4 butanediol and NPG. The melting point of PCL, of MW of 2000 daltons, is in the range of 40-60 °C and of MW of 1000 daltons in the range of 30-40 °C. If a polyfunctional polyol is used as a starter, polyfunctional PCL polyols are obtained. Thus, by polymerisation of CPL initiated by trimethylolpropane (reaction 8.32) a polyester triol is obtained and initiated by pentaerythritol, a polyester tetraol is formed. It is interesting that some low MW PCL triols with a MW of 300-900 daltons are liquid at room temperature (melting points in the range of 6-16 °C). The viscosities of PCL polyols, at 60 °C, are 40-1600 mPa-s, depending on the polyol structure. 

Urethanes are a reaction product of a diisocyanate and long- and short-chain polyether, polyester, or caprolactone glycols [2]. The polyols and the short-chain diols react with the diisocyanates to form linear polyurethane molecules. This combination of diisocyanate and short-chain diol produces the rigid or hard segment. The polyols form the flexible or soft segment of the final molecule. Figure 8.1 shows the molecular structure in schematic form. 

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