The 20th INTERNATIONAL DAAAM SYMPOSIUM
"Intelligent Manufacturing & Automation: Theory, Practice & Education"
25-28th November 2009, Vienna, Austria
RECYCLING OF WASTE PAPER WITH DIFFERENT DENSITY OF LIQUID TONER
BOLANCA MIRKOVIC, I[vana]; MAJNARIC, I[gor]; BOLANCA, Z[denka] & GRGASOVIC, A[nte]
1. INTRODUCTION
¶
The effectiveness of the deinking process in paper
recycling depends on numerous factors. The following ones
have to be mentioned: the printing technique, the ink
characteristics, the properties of the printing substrate and the
components of the coating. The other influential factors are the
kind and quantity of chemicals used in different phases of the
process as well as the chemical and physical conditions of the
system such as pH value, consistency of fiber suspension,
defibering time and the hydrodynamic factors of the flotation
process (Lassus, 2000).
The size, shape and the surface properties of the dispersed
ink particles, the air volume and the size of the air bubbles have
special importance for the effectiveness of deinking flotation.
The effectiveness of the process depends on the ability of the
printing ink adherence on air bubbles and the strength of this
bond in order to prevent their detaching and rebinding to the
cellulose fibers (Renner, 2009; Carre, 2008).
In the described problems, the majority of authors
researched the hydrodynamic factors of the process and the
influence of chemical and physical conditions of the system on
the process effectiveness, while the influence of the printing
techniques and the conditions in printing process haven’t been
studied much (Li et al., 2007, Zhao et al., 2004).
The investigation results of the liquid toner density of
ElectroInk on the effectiveness of the print recycling have been
presented. Deinking process mechanism in relation to the
characteristics of the printing substrates used in printing is
discussed. In scientific sense, the work is the contribution to the
explanation of the print deinking mechanism in relation to the
liquid toner concentration in combination with the coated and
uncoated printing substrates.
The recent investigations have proved the bad
effectiveness of print recycling made in the technique of digital
offset printing. The investigations have to prove if it is possible
to contribute to solve the mentioned problem by choosing the
conditions in different phases of indirect electrophotographic
printing (scorotrone voltage, laser strength, offset cylinder
voltage, concentration of the liquid toner etc.). The
investigation results can be applied in the production of the
recycled papers, in formulation of new printing materials and in
the design of graphic products taking into consideration the
postulates of the sustainable development.
2. EXPERIMENTAL
¶
The prints made on digital offset machine Turbo Stream HP
Indigo were used for analysis. The printing form contained
different printing elements: standard CMYK step wedge in the
range from 10-100% tone value, standard ISO illustration for
the visual control, textual positive and negative microelements,
wedges for determination the greyness and the standard wedge
with 378 patches for production of ICC profiles and 3D gamut.
Five different densities of liquid ElectroInk (D 1.20 - 2.00)
were used in combination with the printing substrate as follows.
The fine art paper (Symbol Gloss) and the wood free natural
paper (Acroprint), all the products of the firm Fedrigoni, were
used as the printing substrates. Papers do not differ in their
basic chemical composition of the paper raw materials. The
only difference is in the finishing process referring to coating.
For print recycling the method of alkaline chemical
deinking flotation was used, which was described in details in
the previous work (Bolanca & Bolanca, 2005). The handsheets
were made using a laboratory sheet former, according to
standard method T 205.
For determining ISO brightness of the recycled fibres the
spectrophotometer DataColor, Elrepho 450X was used.
Residual toner size, toner dirt particles number and toner area
were assessed with image analysis software Spec*Scan,
Apogee System. This system is utilizing scanner to digitize
image. Threshold value (100), white level (75) and black level
(65) were chosen after comparing computer images to
handsheet.
3. RESULTS AND DISCUSSION
For observing and explaining the deinking flotation
process, the image analysis method and the brightness of
handsheet have been chosen. In figure 1 the count of dirt
particles (toner particles) on handsheet made from the fibres
obtained from print recycling with different liquid toner
concentrations is presented.
The investigation results show the trend of dirt particles
increase on handsheet after flotation in the function of the
concentration increase of the ink carrier in ElectroInk when the
uncoated paper was used for printing (628-1024). However,
when the paper coated on both sides was used for printing the
unc…
1000
Count of
dirt…
Abstract: The investigation results of the liquid toner density of
ElectroInk in indirect electrophotographic printing on the print
recycling effectiveness are presented in this work. The deinking
process mechanism in relation to the substrate characteristics
used in printing is discussed. In the scientific sense the work is
a contribution to the explanation of the print deinking
mechanism in relation to the concentration of the liquid toner
in combination with the coated and uncoated printing
substrate. Almost linear relationship of the ElectroInk
concentration, the number of particles and the area size they
occupy on handsheet after recycling, when the print was made
on the uncoated paper has been determined. Such relationship
was not determined when the print was made on the coated
substrate.
Key words: electrophotographic printing, liquid toner,
recycling, image analysis, brightness
¶
100
10
1
1
Density
of
2
1 liquid
1 toner
1
Fig.1 Count of dirt particles on the handsheet made after
flotation
uncoa…
Area of dirt
particle/ mm2
100
10
1
1
toner
1Density
1 of liquid
1
2
.
.
Fig. 2 Area of the
on. the handsheet after flotation
. dirt particles
.
number of dirt particles of ElectroInk on handsheet varied and
there is no expressed trend in relation to the toner concentration
used in the printing phase (673-892). The difference in the total
number of the dirt particles on handsheet in relation to the
printing substrates used for prints intended for the deinking
flotation can be seen. There is greater number of particles on
handsheet obtained from the fibres of print recycling where the
prints were made on paper coated on both sides (79,9-86,1 % in
relation to D 1,20-2,00).
The investigation results show that greater handsheet area
is covered with toner particles when the coated paper was used
for printing (27,0-77,3 % in relation to D 1,20 do 2,00). The
obtained results show that there is the need for particle size
analysis according to classes in order to understand the process.
The investigation results on handsheet before print flotation
obtained from the uncoated paper show greater number of
particles of greater classes than 0,04mm2, i.e. the particles
visible with naked eye in relation to the handsheet obtained
from the fibres of the prints printed on coated paper (34,6-68,4
% for D from 1.20-2,00).
One of the conditions for the removal of the toner particles
in the flotation process is the fragmentation of toner particles as
well as their size. The number of particles on handsheet before
flotation decreases at 77,3- 90,0% in relation to the density of
toner used for print preparation when the uncoated paper was
used for printing. By using the paper coated on both sides the
removal of particles by flotation, in the described experimental
conditions, decreases drastically (the decrease is about 10
times). The brightness of handsheet is in accordance with the
presented results, so higher values were obtained for the
recycled fibres of prints made on uncoated paper in accordance
with the concentration of ElectroInk used in printing (D 1,202.00 uncoated paper, brightness 91,0-86,8, coated paper,
brightness 86,4-81.0)
The removal of ink from the substrate, in deinking process
depends on characteristics of the printing substrate. With prints
made on coated paper there is no contact between ink and
fibers. The paper coating disintegrates as the recovered paper is
pulped and fragments of the ink film are released. Opposite to
the uncoated paper, the adhesion of ink on paper depends on the
surface structure, ashes content, fiber types and the mechanism
of ink drying in the printing process.
4. CONCLUSION
Fig. 3 Distribution of the dirt particles on the handsheet before
flotation (the ancoated paper was used for printing, D=1,80).
Fig. 4 Distribution of the dirt particles on the handsheet before
flotation (the ancoated paper was used for printing, D=1,80)
Fig. 5 Distribution of the dirt particles on the handsheet after
flotation (the coated paper was used for printing, D=1,80)
Based on the investigation results described in the
experimental conditions, the following conclusions can be
made. By the application of different concentration of ink
carrier in liquid ElectroInk, in the process of indirect
electrophotographic printing, the number and the size of toner
particles on handsheet made from the fibres of the deinking
fotation phase can be influenced. The described phenomenon,
the type of the substrate, i.e. the coating on paper used in
printing is under greater influence.
The results justify the creation of statistic models
including multifactorial analysis and the determination of the
essential conditions in different phases of the indirect
electrophotographic printing (voltage of scorotrone, laser
strength, voltage of the offset cylinder, concentration of the
liquid toner etc.) which leads to the optimization of the
deinking flotation process and to obtaining fibres with better
characteristics. In this sense, the continuation of these
investigations goes on.
5. REFERENCES
Bolanca, I., Bolanca Z., (2005). The Optical Properties of
Deinked Pulp, Journal of Imaginig Science and Technology,
Vol. 49, No. 3, 284-292, ISSN: 1062-3701
Carre, B., (2008). Overview of the Deiking Technology, Final
Conference of COST Action E46, Bordeaux, October 2008,
Lassus, A. (2000). Deinking Chemistry, In: Recycled Fiber and
Deinking, Gӧttsching, L., Pakarinen, H. (Eds.), 241-266,
Fapet Oy, ISBN 952-5216-07-1, Jyvӓskylӓ
Li, G., Xie,X.F., Wang, A.L., Chen, K.F., (2009). Application
of Hydrodynamics in Design of Flotation Deinking Cell, In
New Trends in Fluid Mechanics Research, Zhuang F.G., Li
J.C., (Eds.), pp.459, ISBN 978-3-540-75994-2, Springer,
Berlin
Renner, K., (2000). Deinking Chemistry, In: Recycled Fiber
and Deinking, Gӧttsching, L., Pakarinen, H. (Eds.), 241266, Fapet Oy, ISBN 952-5216-07-1, Jyvӓskylӓ
Zhao, Y., Deng, Y., Zhu, J.Y., (2004). Roles of Surfactants in
Flotation Deinking, Progres in Paper Recycling, Vol 14,
No1, (November, 2004) pp 41-45