ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 9, pp. 1472!1475. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + V.D. Koshevar, V.G. Shkadretsova, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 9, pp. 1436 !1439.
AND INDUSTRIAL INORGANIC CHEMISTRY
Low-Temperature Preparation and Properties of
Shell Filler Pigments
V. D. Koshevar and V. G. Shkadretsova
Institute of General and Inorganic Chemistry, National Academy of Sciences of Belarus, Minsk, Belarus
Received November 30, 2006
Abstract-The effect of various factors (temperature of drying of the core substance, polymer concentration,
concentration of coloring component, mechanical treatment procedures) on the preparation and properties of
shell filler pigments was examined.
Much attention is given today in many countries
to the development of nontraditional methods for pro-
duction of pigments in the core, microencapsulated,
and hollow forms. It is known that the main functions
of pigments (ensuring the required optical density of
a medium, color, etc.) are associated with optical phe-
nomena: reflection, absorption, and scattering of light.
These phenomena mainly occur in the surface layer.
Therefore, to save raw materials (especially nonfer-
rous metal compounds), it is appropriate to use a
cheap material as a core and form on its surface a thin
film (several tens of nanometers thick) of a more ex-
pensive coloring substance. Synthesis of core3shell
particles attracts particular interest in materials science
[1, 2], because such structures are potential building
blocks for the preparation of composite materials with
periodically modulated structure, composition, and
Here we report experimental data on the prepara-
tion and properties of coloring shell powders. Their
formation is based on controllable heterocoagulation
followed by baking at temperatures not exceeding
As a modifying material we used SiO
mean diameter 33 4 mm, prepared from phosphoric
acid production waste [TU RB (Technical Specifica-
tion of Belarus Republic) 00 203 714 006394], and a
shell-forming dispersion of polymers and coloring
substances. As polymeric components we used latexes
of butadiene3styrene, acrylic, and styrene3acrylate
copolymers. As coloring agents we used aqueous
dispersion of organic dyes, scarlet [TU (Technical
Specification) 6-14-946387] and blue (TU 2463-125-
05-05 800 14232003).
Before deposition of the shell, the surface of core
particles was etched in 5% H
, washed with water
to pH 537 of wash waters, and dried at 03200oC.
Shell powders were prepared from a mixed disper-
sion of a latex, a core-forming complex, and a color-
ing agent by various procedures: in a high-speed
mechanical mixer, in a SAND ball planetary mill, and
in a UZDI-1UCh.2 ultrasonic disperser.
The heterocoagulate was heat-treated in a thermo-
stat at 50oC for 2 h. Then, to check the strength of
adhesion of the shell to the core, the heterocoagulate
was washed in water at 20oC for 24 h. After washing,
the shell powders were dried in air at 20oC.
The stability of the color of the resulting coloring
powder depends on the adhesion of the shell to the
core and on the water permeability of the shell. These
properties were estimated by turbidimetric measure-
ment of the optical density of water from washing of
the heterocoagulate. The higher the optical density
of the wash water relative to the reference (distilled
water), the lower the adhesion and the higher the
water permeability of the shell. The optical density
was measured with a KFK-3 photoelectric colorimeter
at actinic wavelengths.
The sedimentation stability of the shell powders
obtained was studied by the joint sedimentation meth-
od. For this purpose, 1% aqueous dispersions were
placed in a graduated cylinder, and the shift of the
dispersion medium3dispersed phase boundary was
monitored up to complete clarification.