Most of biobased polyols for polyurethanes are synthesized from vegetable oils. In the first part, the present review goes into details of these different synthetic routes to obtain polyols. First, olefinic functionalities of triglycerides could easily be epoxidized, leading to reactive epoxide groups. Second, triglycerides double bonds could undergo a wide ranges of reactions to yield polyols. Finally, the carbonyl group could also be used as a reactive group to yield various polyols. In the second part, the present review is dedicated to the commercial biobased polyols, and, based on the patent literature focuses on the industrial synthetic routes.

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From Vegetable Oils to Polyurethanes: Synthetic Routes to Polyols and Main Industrial Products

Plant oils as platform chemicals for polyurethane synthesis: current state-of-the-art.

Both HCFC- and pentane-blown rigid polyurethane foams have been prepared from polyols derived from soybean oil. The effect of formulation variables on foam properties was studied by altering the types and amounts of catalyst, surfactant, water, crosslinker, blowing agent, and isocyanate, respectively. While compressive strength of the soy foams is optimal at 2 pph of surfactant B-8404, it increases with increasing the amount of water, glycerin, and isocyanate. It also increases linearly with foam density. These foams were found to have comparable mechanical and thermoinsulating properties to foams of petrochemical origin. A comparison in the thermal and thermo-oxidative behaviors of soy- and PPO-based foams revealed that the former is more stable toward both thermal degradation and thermal oxidation. The lack of ether linkages in the soy-based rather than in PPO-based polyols is thought to be the origin of improved thermal and thermo-oxidative stabilities of soy-based foams. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 467–473, 2000

Rigid polyurethane foams based on soybean oil

We synthesized six polyurethane networks from 4,4-diphenylmethane di- isocyanate and polyols based on midoleic sunflower, canola, soybean, sunflower, corn, and linseed oils. The differences in network structures reflected differences in the composition of fatty acids and number of functional groups in vegetable oils and resulting polyols. The number average molecular weights of polyols were between 1120 and 1300 and the functionality varied from 3.0 for the midoleic sunflower polyol to 5.2 for the linseed polyol. The functionality of the other four polyols was around 3.5. Canola, corn, soybean, and sunflower oils gave polyurethane resins of similar crosslink- ing density and similar glass transitions and mechanical properties despite somewhat different distribution of fatty acids. Linseed oil- based polyurethane had higher crosslinking density and higher mechanical properties, whereas midoleic sunflower oil gave softer polyurethanes characterized by lower Tg and lower strength but higher elongation at break. It appears that the differences in properties of polyurethane networks resulted primarily from different crosslinking densities and less from the position of reactive sites in the fatty acids. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 809 - 819, 2004

Effect of structure on properties of polyols and polyurethanes based on different vegetable oils

Four polyols intended for application in polyurethanes were synthesized by oxirane ring opening in epoxidized soybean oil with hydrochloric acid, hydrobromic acid, methanol, and hydrogen The structures of the polyols were characterized by spectroscopic, chemical, and physical methods The brominated polyol had 41 hydroxy groups, whereas the other three polyols had slightly lower functionality The densities, viscosities, viscous-flow activation energies, and molecular weights of the polyols decreased in the following order: brominated > chlorinated > methoxylated > hydrogenated All the polyols were crystalline solids below their melting temperature, displaying multiple melting peaks The methoxylated polyol was liquid at room temperature, whereas the other three were waxes © 2000 John Wiley & Sons, Inc J Polym Sci A: Polym Chem 38: 3900–3910, 2000

Structure and properties of halogenated and nonhalogenated soy-based polyols

Rigid urethane foams were prepared from hydroxymethylated linseed oil and its esters of glycerol, trimethylolpropane and pentaerythritol. These polyols were made by selective hydroformylation with a rhodium-triphenylphosphine catalyst followed by catalytic hydrogenation with Raney nickel. Although the hydroxymethylated linseed monoglyceride by itself yielded a satisfactory foam, better foams were made from all hydroxymethylated linseed derivatives when blended with a low-molecular weight commercial polyol. Linseed-derived foams were compared with foams from equivalent formulations of hydroxymethylated monoolein and castor oil. Hydroxymethylated products yielded polyurethane foams meeting the requirements of commercial products with respect to density, compressive strength and dimensional stability.

Rigid urethane foams from hydroxymethylated linseed oil and polyol esters

Satisfactory rigid polyurethane foams were prepared from diethanolamides of hydroxymethylated oleate, linseed oil, safflower oil and their methyl esters. These foams were improved when the fatty polyols were blended with a commercial, low molecular weight polyol.

T. H. Khoe

Papers

Rigid urethane foams from hydroxymethylated linseed oil and polyol esters

Polyurethane foams from hydroxymethylated fatty diethanolamides