Chemistry Reference
In-Depth Information
PET is 30-40% more expensive than petroleum PET (US$1.50-1.80 per lb
versus US$1.04-1.23 per lb).
51
Despite the higher costs of bio-based plastics,
there is a driving force in the packaging industry to replace petroleum-based
plastics with a renewable source to achieve a ''green'' rating approval.
49,51,52
7.3.2 Cost and Sources of Citrate Glycerides
The cost of the ''green'' feedstock ingredients is often the deciding factor in
the commercial viability of a bio-plastic.
49,51,53,54
If the cost of the feedstock
chemicals to manufacture a bio-plastic exceeds the cost of purchasing the
commercial plastic polymer it is to replace, it is essentially economically
infeasible to utilize this bio-plastic. Our line of interest is to explore the
possibility of utilizing low-cost and ''green'' feedstocks to manufacture
biodegradable bio-plastics. To this end the citric acid glycerol polyesters
satisfy these two parameters. The cost of carboxylic acids and polyols, see
Table 7.3, varies considerably.
Clearly, citric acid and glycerol are considerably less expensive than other
polyfunctional acids or epoxidized oils (Table 7.3). In fact, citric acid glycerol
polyesters (citrate glycerides) are probably the least expensive of all natural
polyester polymers (Table 7.3). In terms of their ingredient costs, a high-
purity citric acid source costs around US$0.35-0.86 per lb and high purity
glycerol source costs US$0.30-0.43 per lb. Therefore, an equal molar poly-
ester of these two compounds would cost
B
US$0.33 per lb excluding
preparation costs. The ingredient costs for the preparation of other poly-
functional acid glycol polyesters are so prohibitively expensive they cannot
compete in price with current synthetic or natural thermoplastic polymers.
This study is confined to the exclusive discussion of these citrate glycerol
polyesters.
Glycerol is relatively non-toxic, as recognized by the Food and Drug
Administration and is employed in a multitude of food, pharmaceutical,
and industrial products.
55
Glycerol production has mushroomed from
200 000 MT in 2004 to 2.8million MT in 2011 and is projected to increase to
3.0million MT in 2014.
56,57
About two-thirds of all glycerol is produced by
the bio-diesel industry,
56
as a byproduct.
57
Bio-diesel production consumes
10% of the 200million MT of natural oil and fats globally produced.
Table 7.3 Cost of ingredients used to manufacture carboxylic acid glycols.
Ingredient Cost/US$ per lb Purity Source of quote
a
Citric acid 0.35-0.86 499% ref. 72
Adipic acid 0.77-0.82 99% ref. 72
Azelaic acid 8.18-22.00 499% ref. 72
Suberic acid 20.00-45.00 499% ref. 72
Sebacic acid 1.82-2.50 499% ref. 72
Glycerol 0.30-0.43 95% ref. 72
ESBO 1.50-1.62 499% ref. 73
a
Prices presented were accessed on 02/02/14 and sold in ton or more quantities, free on board.
