Biopolymers - Food and Industrial Bioproducts and Bioprocessing - page 271

11.3.1.1 Polymers from soybean oil

Soybean oil is a vegetable oil dominating today's food oil market. About 80% of the
soybean oil produced each year is used for human food; another 6% is used for animal feed,
while the remainder (14%) serves non-food uses (soaps, fatty acids, lubricants, coatings,
etc.)(Valverde et al ., 2008). Another increasingly important non-food use of soybean oil is
biodiesel production (in 2007 about 80% of the vegetable oil used to produce biodiesel was
soybean oil in the United States).
Soybean oil is less expensive than corn, safflower, and sunflower oils. It also has a higher
level of unsaturation (typical composition: 53% linoleic, 21% oleic, 8% linolenic, 10%
palmitic, and 5% stearic) (Meier et al ., 2007) compared to some other vegetable oils. Crude
soybean oil contains approximately 95-97% triacylglycerides, making it a potential
candidate as a renewable macromonomer for the polymer industry.
The double bonds present on the fatty acid chains can undergo cationic or radical
polymerization processes. The reactivity towards different polymerization techniques depends
on the number and position of the double bonds; hence conjugated double bonds are more
reactive. Henna and co-workers (2007) prepared a copolymer of conjugated low-saturation
soybean oil, acrylonitrile, and either divinylbenzene or dicyclopentadiene via free-radical
polymerization. The resulting transparent yellow polymers exhibited 10% weight loss in the
dicyclopentadiene and divinylbenzene at 402-428 and 370-391 °C, respectively. Complete
conversion of conjugated low-saturation soybean oil was achieved when the oil concentration
was kept between 40 and 65%.
An important application of soybean oil is its conversion to polyols and use for PU foam
synthesis (Figure 11.7 ).
Soybean oil was converted into polyols to improve its reactivity with isocyanate and used
to synthesize PUs via hydroformylation and subsequent hydrogenation reactions. John and
co-workers (2002) used three different polyols made from soybean oil triacylglycerides for
PU synthesis with TDI and MDI and studied their reactivities and foam formation, and

O OH

G O

O

G = Glycerol

1. Epoxidation
2. Ring-opening

O

G

O

Soybean oil

1. Hydroformylation
2. Reduction

1. Ozonolysis
2. Reduction

O

O

G O

OH

G O

OH

Figure 11.7 Different ways to prepare polyols for PU synthesis from soybean oil (G: glycerol moiety
with two more fatty acid derivatives attached).