Desktop version

Home arrow Environment

Seed Oil-Derived Polyols

The convergence of advanced industrial biotechnology and advanced chemical manufacturing techniques has opened up an opportunity to develop agricultural-based polyol feedstocks. Whereas most polyols are originally derived from C2 and C3 components of natural gas, the use of seed oils provides an additional source of hydrocarbon with either intrinsic hydroxyl functionality or with an olefin reactive handle to create isocyanate reactive groups. Modern agroscience has at the same time been developing genetic variants that more ideally suit chemical industry requirements for cost-competitive feedstocks. Table 2.10 provides a list of seed oils and their fatty acid composition [91]. The fatty acid compositions can vary around these average values depending on the soil and growing conditions. There are many other seed oils that have been the subject of their potential for use in making polyols based on availability or uniqueness of fatty acid composition. Figure 2.39 shows the structure of the fatty acid components. The seed oil contains the fatty acid components in the form of a triglyceride (Fig. 2.40). The triglyceride can be modified for use from its native form by transforming the olefin groups to hydroxyl groups, for instance. Alternatively, the fatty acids can be freed of the glycerine via alcoholysis or hydrolysis to form the ester or acid, respectively [92]. If the native triglyceride is used, the hydroxyl equivalent weight of the polyol will be the molecular weight divided by the average hydroxyl functionality on the triglyceride. The molecular weight between cross-links in the final

TABLE 2.10 Fatty acid composition of common seed oils used for polyester polyol synthesis

Fatty acid

High oleic

Modified

composition (%)

Soy

Sunflower

sunflower

Canola

canola

Castor

Palmitic

11

6

3

4

4

1

Stearic

5

5

1

2

2

1

Oleic

22

18

93

61

78

5

Linoleic

54

69

1

21

13

2

Linolemc

8

2

0

11

2

1

Ricinoleic

90

Structure of fatty acid components of seed oils.

FIGURE 2.39 Structure of fatty acid components of seed oils.

Illustrative triglyceride structure showing oleic, stearic and hnolenic esters.

FIGURE 2.40 Illustrative triglyceride structure showing oleic, stearic and hnolenic esters.

polyurethane will be very inhomogeneous as some arms of the triglyceride will be stearate or palmitate and have no hydroxyl functionality, and some may have as many as three hydroxyls with only a few carbon atoms between them.

Castor oil from the castor bean is a unique substrate since it is the triglyceride of ricinoleic acid, which, as can be seen in Figure 2.39, is already hydroxyl functionalized. This allows the unmodified castor oil to be used in some applications with no thermochemical transformation required [93].

 
< Prev   CONTENTS   Next >

Related topics