Page 12 - Academic Press Encyclopedia of Physical Science and Technology 3rd Organic Chemistry

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Encyclopedia of Physical Science and Technology EN001F-4 May 7, 2001 16:19

64 Acetylene

C. Polybutylene Terephthalate VII. SPECIALTY ACETYLENICS
AND DERIVATIVES
Althoughthisengineeringplasticcompeteswithpolyethy-
lene terephthalate (PET), PBT is considered a supe-
Specialty acetylenics and their derivatives have a variety
rior polymer because of its outstanding properties. It is
of uses which are described in the subsections that fol-
produced by ester interchange between dimethyl tereph-
low. Further details are provided in Sections IX–XII. The
thalate and butanediol, while PET is derived from ethylene
production volumes and dollar sales of such products are
glycol as the diol component. PBT is most widely used as
often proprietary and seldom exceed 2–15 million pounds.
a 30% glass-filled blend.
The desirable properties of PBT include excellent
dimensional stability, superior strength and stiffness, A. Vitamins A, E, and K and β-Carotene
exceptional moldability and low mold shrinkage, low
Acetylene is an important building block in the lengthy
creep at elevated temperatures,excellent electrical (dielec-
synthesis of vitamins A, E, and K and β-carotene, all of
tric) properties, and good chemical resistance.
which are important polyterpene compounds. Synthetic
It has end uses in the automotive industry: dielec-
vitamin E, also known as dl-α-tocopherol, has emerged
tric and heat-resistant uses to 300 F; ignition system
◦
as one of the most important vitamins in the world to-
components—distributor caps, coil bobbins, rotors; light
day. Before 1950 its role in nutrition was in dispute, and
sockets; emission control parts; body panels and louvers;
it was not considered an essential vitamin. The synthesis,
transmission components. It is also used in electronics
development, and manufacture of vitamins A and E were
for connectors, switches, relays, cases, and covers. In the
pioneered by Hoffmann–La Roche in Basel, Switzerland
manufacture of appliances, PBT is a component of han-
and Nutley, NJ. Both vitamins are important in animal,
dles, small housings, impellors, and general engineering
human, and pet nutrition. The largest commercial markets
parts; it also has high-voltage applications (resistance to
are animal feeds and supplements. In 1983 the production
arc tracking).
of both synthetic and natural vitamin E was estimated to
The annual growth rate of PBT from 1974 to 1977 was
be 11 million pounds with a value of about $164 million.
∼40%, and in 1984 it was estimated to be 10–15%. If
Vitamin A production is about one-tenth that of vitamin E,
acetylene usage between butanediol and THF production
and that of vitamin K is even less. Vitamin K is used almost
is about equal, then PBT derived from acetylene could be
entirely as an antihemorrhagic agent, while β-carotene
of the order of 200 million pounds/year.
made from vitamin A (trans-retinol) is used as a safe food
colorant. Since β-carotene is metabolized in mammalian
D. Tetrahydrofuran: Commercial Uses organisms partly to vitamin A, it is far more effective than
ordinary yellow food dyes. The technology of vitamins A
DuPontbuiltaTHFproductionfacility inHouston in 1969
and E and flavor–fragrance (F & F) compounds is sum-
based on Reppe technology. The capacity of the plant was marized in Section XI.
increased from 50 million to 90 million pounds annually
by 1973. This plant made Du Pont the largest producer of
THF in the United States. By virtue of the uses summa- B. Flavors and Fragrance Compounds
rized below, THF has been growing at an annual rate of
Although it is possible to produce a variety of F & F com-
7%; by 1979 U.S. production was ∼112 million pounds.
pounds by the reaction of acetylene with C 5 to C 8 ketones
followed by hydrogenation, only a small number of these
1. Continuous top coating of automotive vinyl have attained commercial importance, as shown in the fol-
upholstery via THF–PVC solutions lowing subsections.
2. Coating cellophane with vinylidene copolymers
KOH
3. Coating of PVC and acrylic polymer sheets
R 1 R 2 C O + C 2 H 2 −−−−−→
4. Protective coatings, film casting, printing inks, solvent
adhesives H 2
5. Activating solvent for tetraethyllead manufacture, R 1 R 2 C C CH → R 1 R 2 C CH CH 2
| |
specialty solvent OH OH
6. Polymer intermediate for polyethers, polyurethane
elastomers, spandex fibers
1. Linalool (3,7-Dimethylocta-1,6-dien-3-ol)
To date the Reppe process for both butanediol and THF The fragrance compound linalool is prepared via the
remains dominant. route shown above by the reaction of methylheptenone