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60 Acetylene

V. IMPORTANT CHEMICAL follows: 1981 (50); 1984 (55); 1987 (60). Union Carbide
USES FOR ACETYLENE produced ∼65% of this total, which was used internally
in its battery division.
As shown in Tables II and III, there has been steady growth
in the production of acetylene-based specialty chemicals.
B. Vinyl Fluoride
These products comprise acetylene black, vinyl fluo-
ride, vinyl ethers, Reppe chemicals, and miscellaneous The principal use for this specialty monomer is the produc-
acetylenic alcohols and diols. Reppe products consist tion of polyvinyl fluoride (PVF), a polymer considerably
mainly of butyne-1,4-diol, propargyl alcohol (1-propyn- more stable than polyvinyl chloride (PVC). The use of
3-ol), butane-1,4-diol, butyrolactone, tetrahydrofuran, PVF in exterior coatings for aluminum siding, steel build-
pyrrolidone, vinylpyrrolidone, N-methylpyrrolidone, ing panels, hardboard siding, and asbestos-impregnated
polyvinylpyrrolidone, polyvinyl ethers, and copolymers. felt roofing continues to grow. PVF was introduced by
Butane-1,4-diol has emerged as the most important Du Pont in 1963 under the registered trademark Tedlar.
user of acetylene for acetylenic chemicals and derived In 1966 acetylene consumption for PVF production was
products. Its usage in specialty polymers and chemicals estimated to be ∼1 million pounds and by 1984 it was
increased steadily during the 1977–1979 period from 6–9 million pounds, showing steady growth.
82 to 92% of total acetylene consumption (74 million Vinyl fluoride is produced by the addition of hydrogen
pounds in 1979). The principal uses for butanediol are in fluoride to acetylene in the presence of a mercuric salt
polybutylene terphthalate and other engineering plastics, catalyst deposited on carbon. The intermediate vinyl flu-
besides polyurethanes. By 1984 the total acetylene oride is not isolated due to the difficulty of separating it
usage for acetylenic chemicals had been estimated to be from acetylene. The resulting difluoroethane (DFE) is in
115 million pounds. turn cracked to vinyl fluoride and the evolved hydrogen
fluoride is recycled:

A. Acetylene Black
C 2 H 2 + 2HF → [H 2 C CHF] → CH 3 CHF 2
Vinyl fluoride DFE
This unique, conductive form of carbon is made by the

exothermic decomposition of acetylene: DFE → H 2 C CHF + HF.
800 C
◦
C 2 H 2 −−→ 2C + H 2 . The principal U.S. producers of vinyl fluoride and PVF
are Du Pont (Louisville, KY) and Diamond Shamrock
The reaction is highly exothermic and the evolved heat (Houston, TX). The intermediate DFE is also important
(∼55,000 cal/g) is used to maintain the pyrolysis temper- for the manufacture of vinylidene fluoride, as shown in
the next section.
ature. Preferred processes involve (1) continuous explo-
sion of acetylene at 1–2 atm using an electric spark and
(2) decomposition via the electric arc. C. Vinylidene Fluoride (Vinylidene Difluoride)
The principal uses of acetylene black are in the man-
Vinylidene fluoride (VDF), a monomer, can be produced
ufacture of dry cell batteries and the fabrication of
from DFE via chlorination and cracking or from 1,1,
conducting rubber and plastic sheeting and molded plas-
1-trifluoroethane:
tics. Although acetylene black is too expensive to com-
pete with petrochemical carbons in large-volume polymer C 2 H 2 + 2HF → CH 3 CHF 2 →
Cl 2
compounding, it has carved out for itself a growing spe-

cialty market in conductive applications. Acetylene con- H 3 C—C(Cl)F 2 → H 2 C CF 2 (1)
CDFE VDF
sumption (in estimated millions of pounds) for acetylene
blackgrewsteadilyfrom1967to1984intheUnitedStates:
CH 3 CF 3 → H 2 C CF 2 + HF (2)
1967 (10); 1979 (19); 1980 (20); 1984 (23).
Producers of acetylene black are Shawinigan (Canada), At present the preferred starting material for VDF
Union Carbide (Ashtabula, OH, and Ponce, P. R.), and production is 1-chloro-1,1-difluoroethane (CDFE), also
Gulf (Cedar Bayou, TX). The Gulf production facility known as refrigerant 142b. Numerous other intermediates
went on stream in 1979 and is rated at 15–20 million have been described for the preparation of VDF. The prin-
pounds/year. The markets for batteries and conducting cipal use for this monomer is the production of polyviny-
polymer composites grew significantly from the mid- lene difluoride (PVDF, PVF 2 ). The polymer is semicrys-
1980s, and acetylene black participated in this growth. talline and has the following desirable properties; high
The total production of acetylene black from all sources mechanical and impact strength, resistance to most chemi-
(millions of pounds) from 1981 to 1987 is estimated as cals, very high dielectric constant, and excellent resistance