Chemical Engineering March 2021 - 26

Technology Profile
Acrylonitrile Butadiene Latex Production
By Intratec Solutions
itrile rubber (also known
as NBR, acrylonitrile butadiene
rubber, acrylonitrile
butadiene latex, Buna-N) is
a synthetic polymer made of monomers
1,3-butadiene and acrylonitrile.
This rubber is known for its resistance
to chemicals, oils and fuels.
NBR is produced with a wide range
of molecular weights and monomer
ratios, so basic polymer properties
can vary greatly.
N
NBR is primarily used in applications
where good oil resistance is required,
such as rubber seals and O-rings,
hose and belting stock and blowout
preventers or packers (in oil drilling).
NBR is also used in molding miscellaneous
parts, rubber latex products,
sponge applications, gaskets, pump
stators, safety gloves and footwear.
Additionally, NBR is used in modifying
plastics, adhesives, cements, sealants,
coatings and friction materials.
The process
The present analysis discusses an
industrial process for acrylonitrile
butadiene latex production. The process
comprises two major sections:
(1) polymerization; and (2) monomers
recovery (Figure 1).
Polymerization. Polymerization occurs
in continuously stirred, jacketed
tank reactors connected in series. To
maintain a low reaction temperature,
all reactors are cooled by means of
ammonia vaporization. Acrylonitrile
and butadiene are mixed with an
emulsifier, demineralized water and
other chemicals to form the emulsion
that will be fed to the polymerization
reactors. Downstream, a " shortstop "
Butadiene plant
(for addtional
purification / out
of scope)
Acrylonitrile
Butadiene
Acrylonitrile,
naphtha
Steam cracking,
extraction,
polymerization
Ethylene, propylene,
pyrolysis gas, fuel
Acrylonitrile,
butadiene
Polymerization
n Raw material n Process n Main product
FIGURE 2. The most common NBR latex production pathways are shown here
agent is mixed with the emulsion in
order to stop reaction at the desired
conversion. This avoids gel formation.
Monomers recovery. The latex generated
in polymerization reactors is
flashed at atmospheric pressure and
then under vacuum. Residual butadiene
vapors are compressed and then
cooled for condensation. The condensed
stream is directed to a decanter
for water removal. Recovered
butadiene is recycled to a butadiene
plant, where butenes are separated,
so the recovered butadiene can be
reused in the NBR latex plant. The
degassed latex is pumped and fed to
a vacuum plate column, where residual
acrylonitrile monomer is stripped
by contacting the latex with steam
entering the column bottom. Stripped
acrylonitrile is recycled to the polymerization
stage. The latex is mixed
with an antioxidant agent and finally
blended into a homogeneous emulsion
before being sent to storage facilities
as the finished latex product.
Production pathways
Nitrile rubber latex production basically
consists of the emulsion polymerization
of 1,3-butadiene and acrylonitrile,
so different NBR manufacturing
5
CW
ST
2
4
Water
Emulsifier, catalyst
and other chemicals
26
1
ST
Shortstop
agent
3
ST
6
NBR latex
FIGURE 1. The diagram shows a
process for the production of acrylonitrile
butadiene latex
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Wastewater
7
8
routes are related to different sources
of the monomers used. The most typical
NBR latex production routes are
based on acrylonitrile produced via
ammoxidation of propylene and butadiene
produced via isolation from C4
steam-cracker fractions (Figure 2).
Economic performance
The total operating cost (raw materials,
utilities, fixed costs and depreciation
costs) estimated to produce
NBR latex was about $2,000 per
ton of NBR latex in the first quarter
of 2017. The analysis was based on
a plant constructed in the U.S. with
capacity to produce 35,000 metric
tons per year of acrylonitrile butadiene
latex.
This column is based on " Acrylonitrile
Butadiene Latex Production
- Cost Analysis, " a report published
by Intratec. It can be found at: www.
intratec.us/analysis/nitrile-rubberproduction-cost.
n
Edited
by Scott Jenkins
Editor's note: The content for this column is supplied by Intratec
Solutions LLC (Houston; www.intratec.us) and edited by Chemical
Engineering. The analyses and models presented are prepared on
the basis of publicly available and non-confidential information. The
content represents the opinions of Intratec only. More information
about the methodology for preparing analysis can be found, along
with terms of use, at www.intratec.us/che.
1. Polymerization reactors
2. Ammonia refrigeration
3. Butadiene flash
4. Steam stripping
5. Butadiene recovery
6. Latex blending
7. Cooling tower
8. Boiler
CW Cooling water
ST Steam
NBR latex
Ammoxidation,
polymerization
Acetonitrile,
hydrogen cyanide
Propylene,
butadiene
http://www.intratec.us/analysis/nitrile-rubber http://www.intratec.us http://www.intratec.us/che http://WWW.CHEMENGONLINE.COM
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