On-line Particle Size
Analysis in Toner
Production
In the toner industry, there is a 13
long-standing trend toward manu-
facturing products with a smaller Toner 1
particle size. Smaller particles, 12 Toner 2
while more challenging to handle, Toner 3
are necessary for enhanced print 11 Model
Percentage of Particles < 5 μm D50 Insitec Data (μm)
(Particle Counter)
Toner 4
resolution. A resolution of 600 dpi,
for example, requires a toner particle 10
size of approximately 8 μm. While
the mean size of toner particles five 9
years ago was about 11 μm, the cur-
rent mean size is approximately 8
8 to 9 μm. This trend seems likely 7. 5 8. 5 9. 5 10.5
to continue, so that by the end of D50 Particle Counter Data (μm)
the decade it is expected that the
average toner particle size will be
between 5 and 6 μm.
Toners can be manufactured 30
by milling extruded toner pellets
that are produced from a poly- 25
mer blend incorporating pigments
and other additives. Controlling 20
this milling process to meet customers’ increasingly demand- 15
ing specifications is a challenge. Toner 1
Underprocessing, which can lead 10 Toner 2
to the presence of large particles or Toner 3
excessive fines, compromises prod- 5 Model
uct quality. On the other hand,
0
overprocessing is costly, since mill- 0 0.5 1 1.5 2 2.5 3 3. 5 4
ing is energy
intensive. An Percentage Volume < 5 μm (Insitec)
added compli- Figure 2: Particle size distribution correlation output classifier sampling of line 4
cation is that for D50
with decreasing
particle size, the dispersion
process associated with conventional particle-sizing techniques
becomes more arduous, making
the analytical procedure more
time-consuming.
At Toshiba Dieppe, toners are
produced on a series of parallel milling lines. To improve the
control of these lines and decrease the analytical burden associated with increased control, the
company has invested in a pair
of Insitec systems from Malvern
Instruments. The first of these
on-line laser-diffraction particle
11. 5
Figure 1: Particle size distribution correlation between the particle counter and the
Malvern Insitec D50 output classifier
Percentage of Particles < 5 ∧μm = 9.7275 × Per∼centage Volume < 5 μm 0.6939 R2 0.93
in 2001 and the second in 2004. A third installation
is planned.
Operation at Toshiba Dieppe
From 1993 to 2000, particle size measurements were
taken once an hour at Toshiba Dieppe. The shift supervisor used a Panorama supervisory control and
data acquisition (SCADA) system to control the process by manipulating parameters such as pressure, rotor speed, mill feed rate, and current. Historically, the
supervisor was inundated with information on which
to base process changes. Subsequently, a change in
philosophy limited the control parameters to the most
relevant variables. These variables included the particle size output from the process, the finished particle
size being a function of all the process parameters recorded by the Panorama software.
