Chemical Engineering July 2022 - 40

Applied Technologies
One-stage Filtration for Silicone Production
Presented here is a fast and flexible solution that removes solids, traces of water and
gel in a single operation, therefore significantly reducing the time it takes to perform
the process during silicone production
R
eliable silicone manufacturing
operations depend on
a complex network of process
technologies, including,
among other things, the removal
of solids as well as traces of water
and gels from the intermediate silicone
product. Traditionally, this activity
has been a two-stage operation.
However, there is a single-stage
filtration technique that combines
the removal of solids, water and gels
that can enable a manufacturer of
silicone products to streamline its
production activities and enhance
operational efficiency.
Silicone products
Specialty silicones are used in a
broad range of industries. From
adhesives to aerospace, textiles
and transportation, different types
of silicone are crucial to numerous
production processes. Silicones are
contained in a wide variety of enduser
products - cosmetics, toiletries,
lubricants, adhesives and protective
coatings, to name a few.
To meet such widespread applications,
silicone products come in
many different grades, being produced
at highly integrated manufacturing
plants that use multi-stage
processes to deliver consistency
and repeatability. The manufacturing
process is complex and carefully
refined. Silicates in sand or rock
are first processed to obtain silicon.
Chemical reactions then produce
silanes (any of a series of covalently
bonded compounds containing only
the elements silicon and hydrogen)
and, in further steps, polysiloxane
precursors (a group of silicon-based
polymers), which are the basis for
different grades of silicone products.
These precursors contain a silicon-oxygen
backbone along with
other organic components, and can
be processed into silicone oils, resins
and elastomers, among other materials.
The composition of silicone
40
offers several desired performance
characteristics, such as thermal and
oxidative stability, chemical inertness
and excellent dielectric strength.
Silicone production processes
During the production process,
which involves hydrolysis of organohalosilane
(carbosilanes derivatized
with a hydroxy group on the silicon
atom [1]) and condensation of
chemical compounds forming salts,
among other things, silicone manufacturers
have to ensure that any
unwanted residues and particles are
removed, to protect the quality of the
finished product. This requirement is
met through the use of advanced filtration
techniques, which have to be
performed without having any adverse
impact on volume throughput
on the production line. Filtration has
to be carried out to exacting standards,
using equipment that is reliable
and easy to maintain.
Stringent production techniques
One of Europe's silicone manufacturers
came to Eaton Corp. (Bloomfield,
N.J.; www.eaton.com) with
a requirement for a more effective
means of carrying out solid separation,
as well as liquid traces separation
at one of its large production
plants. The company was producing
about 6,614 lb of intermediate
silicone oil at 22 gal/min on a regular
basis. The production process
involved a carbonation technique
using sodium carbonate to neutralize
hydrochloric acid. This process
resulted in the generation of water
residue and solids that need to be
removed in an effective way. Failure
to do so can increase the viscosity of
the final product through the creation
of gel in the silicone - identified as a
highly undesirable outcome.
Historically, a two-stage process is
used. In this process, solids are separated
from the silicone intermediate,
and water residues are removed
Eaton
FIGURE 1. BECO KD 7 depth filter sheets consist
of finely fibrillated cellulose fibers from deciduous
and coniferous trees that provide an especially
high water-retention capacity
using chemical additives. However,
the silicone manufacturer wanted to
implement a more advanced system
that could offer highly controllable removal
of solids, traces of water and
gel particles in a single-stage operation.
By implementing such a unique
approach, the company would be
able to simplify its production processes,
saving time and reducing
by-product waste.
Single-stage filtration process
Engineers from Eaton's Filtration Division
forged a strong customer relationship
with the silicone manufacturer,
working with its technical team
to devise an effective solution. The
answer came with the combination
of BECO depth filter sheets, fitted to
a BECO Compact Plate plate-andframe
filtration system, allowing for
the removal of nearly all water residue
and solids through adsorption,
without causing any significant pressure
drop on the production line.
In laboratory tests with different
types of depth filter sheets, an optimized
solution was jointly developed.
BECO depth filter sheets have a
nominal retention rate ranging from
0.1 to 40 µm, and the analyses identified
BECO KD 7 depth filter sheet
(Figure 1) as the most suitable grade
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JULY 2022
http://www.eaton.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering July 2022

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