Grinding tactile material

of all the different types of products that are ground in a blending medium grinder, many do not have the desired fluidity. These non-Newtonian products include color paint, varnish and pigment slurry. They usually contain large aggregates and wrinkled polymer structures. These polymers, including polylytes, are often used to moisturize particles in suspensions and are used as dispersants. The solid content is usually much greater than
40%
(mass ratio), which means that aggregation is more likely to occur because of the low amount of liquid used to wet particles. These factors affect fluidity and increase viscosity due to increased solid surface area during grinding. As the particles are smaller, the adhesion increases, further aggravating the re-accumulation. One of the main reasons for the high solid content is that processes such as drying are expected, so drying requires less energy.need to apply high shear stress when starting to flow the material, due to the structure mentioned above. Therefore, this material needs to carefully select the equipment and process parameters. In addition to the energy input, the size of the grinding beads and the speed of production, the fineness requirements and the operating status of the grinder are important. Strong shear stress must be maintained after start-up to achieve a reasonable grinding progress and maintain viscosity under control. This is achieved by adjusting the end speed of the grinder or by cutting the product before it enters the grinder by using a gear pump and a high shear speed. Short hoses and pipes should be used to reduce the likelihood of increased structure and viscosity mentioned above. This paper describes the grinding parameters of the tact denatured pigment slurry.allexperiments are conducted in a recycling mode, as shown in
1
1. Using
Promass 83I25
measures yield online by measuring complementary forces, as well as the density and viscosity of the products entering the grinder. In order to create shear stress in the product, use
Gebr. The
T4-95G-GKGM

gear pumps produced
Steimel Co., Ltd. Particle
was performed
the Mastersizer 2000, which was tested using the principle of light scattering. The instrument's red laser is used for the measurement of particles with a particle size greater than
1um
, and the blue laser is used for the measurement of particles with a particle size of less than
1um
. More than
90%
of particles in the product have a particle size below
1um
before grinding, which means that particle dispersion is greater than "real grinding". To check the fluidity of offline products, the viscosity
is measured us
ing a rotary viscosity meter
ROTO VISCO 1
produced by the company theermo Haake
. Pigment slurry is produced on medium grain size product grinders (figure
2

WABDYNO
®
-MILL ECM Poly
).are given below:
flow
500 kg/h
and
4000 kg/h
;
end speed:
10.9 m/s
;
sizes:
0.8 mm,
later
0.3 mm
;.
Grinding time:
4
hours in two sizes;
batch:
100 kg
.。 Results and discussionAs a particle size than energy input functionexperiments were conducted using grinding beads with diameters of
0.8 mm
and
0.3 mm
. Figure
3
shows
D90
particle size
,
corresponding to the function of energy input at different grinding beads.the
0.8mm
grinding bead grinding resultsin the energy input of up to
500 kJ/kg
, in fact, the grinding beads using
0.8mm
have no grinding effect. At
500-700 kJ/kg
, the particle size increases temporarily. This is the main occurrence of go-to aggregation and particle wetting signs. The particle size drops below
700nm at
700-1,700kJ/kg
for
energy
. In this area, some "real grinding process" may occur. When
1,700 kJ/kg
, the particle size hardly decreases. This is likely to be a sign of reggregation, as the surface area of the particles increases due to a "real grinding process" and the surface area needs more liquid to wet the particles.the
0.3 mm
grinding bead grinding resultswith
0.8mm
grinding bead grinding, to a diameter of
0.3mm
grinding beads. With smaller size grinding beads, grinding progresses rapidly, with energy inputs of up to
250kJ/kg
. The final particle diameter obtained with a smaller grinding bead is less than
500nm
. However, when it exceeds
1,500kJ/kg
, the measured particle size no longer decreases, or even rises slightly, and there are signs of re-accumulation. viscosity and fluidity in order to learn more about the grinding and dispersion process, pay close attention to viscosity and fluidity. Figure
4
shows the flow curve, in which the shear stress τ and viscosity η of the raw material are a function of the shear rate at a temperature of
30
γ degrees C. The flow
and
curve of the material after 4 hours of grinding are shown in
5
5. Start by increasing the shear rate and

1,000s-1
30s
, then drop to zero. At first there is a need for high shear stress to flow the product, which behaves more like a solid than a liquid, and the viscosity tends to be infinite. When the shear rate reaches
1,000s-1
, the viscosity of the raw material drops to
0.688 pa
.
s
。 The viscosity of the grinding product drops to
.74Pa
.
s
。 addition, the product clearly shows that it has tentacles because the viscosity decreases less when the shear rate decreases than when the shear rate increases. This behavior is due to the time it takes to gather again when the shear stress is reduced after the aggregate is broken. This further demonstrates that the grinding problem at hand is primarily a decentralized one. At the beginning of the grinding process, the original particles need to be moisturized and dispersed in order to break the aggregate. The original particle breaking to a smaller particle size may only occur after dispersion is complete. Once a smaller particle size is obtained, the adhesion between particles also increases, which may result in re-

shown in Figure
3. Due to the large surface area of the finer particles, the viscosity increases at all shear rates, as shown
5
5. the denaturation is more pronounced at higher shear rates, as shown in Figure
6
, the maximum shear rate is
3,000 s-1
instead of
1,000 s-1
. When the shear rate is first increased to
3,000 s-1
, the viscosity is
0.419 pa
.

, when the shear rate decreases, i.e.
30
seconds after
3,000 s-1
, the viscosity drops to
0.096Pa
.
s
。 This means that the longer the material shears, the less time it takes to form a re-aggregation structure such as a cluster, and therefore the less viscosity. It can be concluded that in order to minimize the residual time of low shear areas, shorter hoses and pipes are actually required, as viscosity increases in these areas. 7
shows
effect of yield on viscosity. At a yield of
550 kg/h
, the residual time of the low shear stress area is considerable, and the viscosity measured on the front flow meter of the grinder exceeds
1,400 mPa
.
s
。 Over a certain flow rate, the pigment slurry is continuously sheared in the gear pump and grinder. The minimum shear stress required to exceed the flow limit has actually been given. As a result, the viscosity drops sharply. Product particles are pumped more often through the grinder, the possibility of contact between the grinding beads increases, and the product is cut more often, eventually leading to a decrease in viscosity. A further increase in production would not have a greater impact. The viscosity is maintained at
than 200 mPa
.
s
。 The effect is similar when grinding beads with a diameter of
0.3 mm
, and the minimum viscosity is higher than when larger beads are used, as this results in a lower yield. Higher yields result in smaller grinding beads piling up, resulting in higher wear on the machine's components. study shows that the viscosity and fluidity of particle suspensions depend mainly on the adhesion force
1
. Therefore, particle size, solid content and suspension stability play an important role. Sometimes it can be assumed that when a certain shear rate is reached, the fluidity is Newtonian and the viscosity is constant
1
. However, it is very difficult to tell the actual viscosity of the material in the grinder, because the shear rate in the grinder is much larger than the shear rate obtained using the viscosity meter. Due to tentacles, the residual time of different regions has different effects at different shear rates. For minimal viscosity, a higher shear rate needs to be applied for a period of time. Therefore, it is helpful if the product suspension has been sheared before entering the grinder( e.g. with a blender or gear pump). Increased yields require less time for structures to re-gather, such as aggregates, especially in certain areas such as pipes, hoses, and valves. In order to avoid the accumulation of beads and blockage of the filter, viscosity minimization is particularly necessary for the dispersion process of
2,3
. Higher viscosity also means more energy is needed to transfer the liquid, resulting in an inadequate grinding process
3
. In order to increase shear stress in the product, other parameters that need to be optimized may be end speed. However, the disadvantage of the increase in end speed is that the faster the mechanical components in the grinding cavity are damaged, re-aggregation may also occur due to higher energy inputs, as shown in Figure
3
. Therefore, in these experiments, the end speed is kept constant. conclusion experiments with water-based tact denatured pigment slurry show that the production volume is an important parameter affecting the grinding process of these materials with non-ideal fluidity. By changing the yield, the viscosity can be reduced from
to more than 1,400 mPa
.
s
fell below
300 mPa

s
。 when the size of the grinding beads decreases, the effect decreases because the maximum yield is lower when the beads are not stacked. Since the raw materials are already fairly fine, which means that the adhesion between particles is large, the problem is just dispersal rather than "real grinding". This can also be seen by studying the particle size as a ratio energy input function. Dispersion problems mean that viscosity has a significant effect on the resulting particle size, as particles that are not moisturized and properly dispersed form aggregates that increase viscosity. At higher viscosity, a higher energy input is required to transfer the liquid rather than the grinding process. Beyond a certain point, increasing the ratio of energy inputs will only lead to re-accumulation, as very little energy enters the grinding process and most of the energy is converted directly into heat. the viscosity of the
material,
the viscosity after grinding is large at all shear rates, and the tentacles are more pronounced. The impact of yield indicates that
,
in addition to the shear rate itself, you need to consider regions
with different shear rates,
to keep these regions as low as possible. Therefore, short hoses and pipes are recommended to reduce the re-aggregation and increased viscosity of the structure. Reference 1 Stenger, F; Peukert, W. The Role of Particle Interactions on Suspension Rhe。