Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 9, pp. 1444−1446.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © T.N. Poyarkova, S.V. Zhdanova, I.N. Pugacheva, S.S. Nikulin, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 9,
AND POLYMERIC MATERIALS
Coagulating Effect of Alkali Metal Chlorides on Polystyrene
and Butadiene–Styrene Latexes
T. N. Poyarkova
, S. V. Zhdanova
, I. N. Pugacheva
, and S. S. Nikulin
Voronezh State University, Voronezh, Russia
Voronezh State University of Engineering Technologies, Voronezh, Russia
Received March 30, 2012
Abstract—The coagulating power of lithium, sodium, and potassium chlorides in rubber recovery from SKS-30
ARK latex at 20, 40, and 60°С and from a model polystyrene latex was studied. The electrokinetic potential of
the polystyrene latex at various concentrations (5, 20, 80 mM) of the chlorides added was measured.
Rubbers prepared by emulsion copolymerization play
an important role in world’s industry. The key step in
production of these rubbers is their recovery from latexes
using mineral salts in the presence of sulfuric acid.
Numerous coagulating agents, both inorganic and
organic, have been reported [1–3]. However, their use
is restricted by problems arising with them under real
industrial conditions. For example, aqueous solutions of
protein coagulants are unstable in storage, especially at
elevated temperatures . Other coagulating agents are
expensive and are in short supply, which limits prospects
for their commercial use.
Today the major amount of rubber is recovered in the
presence of NaCl and sulfuric acid . However
in use of cheap alternative salts (e.g., natural sylvinite
containing NaCl and about 20–40% KCl) stimulates
studies of the behavior of latexes in the presence of
chlorides other than NaCl. It is known that lithium fairly
widely occurs in the nature in the form of minerals
(spodumene, lepidolite, petalite, etc., the majority of
which are silicates) . The content of Li in the Earth
crust is higher than that of Hg, Ag, Pb, and Sn. In the
lyotropic series of alkali metals, the ionic radius (pm)
varies signiﬁ cantly: from 68 for Li
to 98 for Na
132 for K
. This fact should inevitably affect the ability
of salts of these cations for latex coagulation.
In this study we examined the rubber recovery from latex
using not only sodium chloride, but also potassium and
lithium chlorides. Their use in this process is of scientiﬁ c
and practical interest, but was not studied previously.
The coagulation of the industrial latex was performed
as follows . A vessel placed in a thermostat was
loaded with a butadiene–styrene rubber latex (dry
residue 21.7 wt %), kept at the preset temperature for
10–15 min, and combined under continuous stirring with
a deﬁ nite amount of an aqueous electrolyte solution.
After introducing the coagulant, the system was stirred
for approximately 1 min, after which an acidifying agent
was added (~2.0 wt % aqueous solution of sulfuric acid)
in an amount of approximately 12 kg (t rubber)
resulting rubber crumb was separated from the serum,
washed with water, and dried at 75–80°С.
The coagulating performance was evaluated
gravimetrically (from the relative amount of the
rubber crumb formed) and visually (from the serum
The coagulating effect of lithium, sodium, and
potassium chlorides was also studied with a model
polystyrene latex (PSL) synthesized in the presence of