N1TTAL 2015
CROATIAIY ACADEMY OF EF{GINEERING
Ann. 2015 Croat. ,{cad. Eng.
rssN
1332-34&2
AI{I\UAL 2OI5
OF THE CROATIAN ACAI}EMY
OF EISGII$EERII\G
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CAETS
Zagreb,2$16
lmage Inpainting Methods
Annual
20 1 5
of the Croatian Academy ol
Engineering
157
r Homogeneols
Dil1irional Conference CAIP
2000 with anisotropic
Scientific paper
rzlel Ed. Berlin.
leumann, and B. Doerr,
g', in Scale Space and
stein, A. M. Bronstein,
to find sparse data for
on and Pattern Recog-
Eds. Berlin.
,'Understanding, optiJ. Comput. Vis., vol.
iimages', IEEE Trans.
I
Prints Obtained by Varying
the Voltage in IEP Technology
Recy_c[i_ng th_e
Z. Bolan(.nl'., I. Bolania Mirkovidl., I. Majn
rCroatian Academy of Engineering
2University of Zagreb, Faculty
of Graphic Arts
video', IEEE Trans.
With the development of digital printing technology, the amount of
digital prints in waste paper is rapidly increasing. At the same time.
it has been difficult to detach the Electrolnk in liquid electrophotography printing (LEP), from fibers with the same deinking processes used for conventional inks. Because of the different characteristics of Electrolnk, it has been difficult to collect, recycle and
deink. The prints obtained by varying the voltage of the processing
drum, reverse roller and a squeegee roller in the LEp technology on
the mechanism and effrciency of the deinking flotation process and
characteristics ofthe recycled fibers is presented in these afticle.
rngular coding', IEEE
/er adaptive triangula-
pic triangulations', in
2009, pp. 23431318.
dimensional pattem)',
:ipe de la flexion des
Mathdmatique Anal.
Research results indicate that by increasing negative voltage of the
processing drum and reverse roller an increase occurs in the dirl
count on handsheets obtained from fibres after disintegration, while
the results related to the squeegee roller are inversely proportional.
An increase is observed, specific for each of the stages, in the area
of dirt > 0.04 mm'zwith the increase of negative voltage. The range
of dirt sizes that can be removed by flotation is restricted to between
0.050 and 0. 150 mm2. Dirt below 0.04 mm2cannot individually resolved, they stili adsorb light and hence contribute a greyness or
overall loss of brightness to the handsheet. The paper discusses the
inter-dependability of the distribution the size and area of dirt on
handsheets obtained from the deinking flotation process with regard
to the change in voltage of the processing drum, reverse roller and
squeegee roller in printing. The ERIC and handsheet brightness results explain the efficiency of the recycling process well and confirm
the results obtained by implementing other methods.
removal algorithms',
ariation flow', Dilfer
pic diftusion', IEEE
istic edge-preserving
no. 2, pp. 298-311,
ment of higher order
ntpttter Science, vol.
, 200s, pp. 451-458.
processing', I/zeor
rpolation data in irn-
Key v,ords:
LEP technology, recycling, image analysis, ERIC, brightness
rn of distinct points.
Conference on Fasl
i
^rie2i
l
-305.
.zbolanca@hatz.hr,
ibolanca@grthr, i.majnaric@grf.hr
Bolanda,,Z., et. al.: Recycling the prints Obtained by
in LEP Techrology
1. lntroduction
Annual 2015 ofthe Crr
showed that a di
case two flotatio
Digital printing contributes to sustainable development (Gmelin, Senring,
2014).
This printing technique, in comparison to some conventional printing
techniques
has the advantage of having a less harmful influence on the
environment mainly
due to its ability to be ready faster along with the absence
of plate making and its
related chemicals, materials, emissions and wastes (carver,
cuiary, 20rr; Kadam
et aL.,2009 Lasage, Schoonenberg, 2010).
With the developrnent of digital printing technology. the amount of digital
prints in
waste paper is rapidly increasing. At the same time, it has been
diificult to cletach
the Electroink in liquid electrophotography printing (LEp), from
fibers w.ith the
same deinking processes used for conventionul inkr
2000;
Bolanda et al.,
lnotunju,
2000; carre, Mangin 2002; smitz. Fischer 2004; Fischer, 2008)
Because of the
different characteristics of Electrolnk, it has been diffrcult to collect,
recycle and
deink.
Digital printing equipment manufacturers and the International Association
of the
Deinking Industry GNGEDE) have different opinions on the deinkabiliry
of digital
prints' During DRUPA 2008, HP claimed that the 4.0 version
of Electrolnk is as
deinkable as dry toners. INGEDE issued a press release stating that
the claims were
incomect (INGEDE, 2008). Digital printing equipment manuficturers
also question
the relevance of the single-step laboratory test of the INGEDE
11 method, claiming
thai it does not reflect the industrial conditions of two-loop deinking (INGEDE
200 I ; wripp201 0). A revision of the INGEDE I 1 method
was done with the criteria of the pH after pulping and before the flotation was added (INGEDE,
2012).
The results of the research conducted showing the effect of kneading
and the 2'd
flotation on significantly reducing the total dirt area to a level uelow
zoo ppm as
the proposed laboratory target were published up until DRUPA 2012 (Hewlett-Packard Indigo, 2012). The new generation of Electrolnk produces
smaller
specks after pulping. Specks which are effectively broken up
by dispersion are
floatable in a second flotation loop (Hewlett-paciard Indigo, 2012; putz
et al.,
2008). Hewlett-Packard is engaged in research to ensure that the
deinkability of
current recycled paper streams is maintained as the percentage of
digital prinis in
the deinking mill furnish increases
Cl.{g et a1.,2009).
The aim of the research is to understand how ink and paper interaction
for liquid
electrophotography affect the flotation deinking process. Hp Indigo plans
to iest
Electrolnk 4.0 under NewPage Duluth recycled paper mill simulated
conditions.
The composition of furnish for the deinking trial was 5% Elechol
nk and 95%
mixed office waste recovered paper (Macias, 2010). The pilot scale
simulation
Both Mittelstadt
IIPMA (Mittelst
including sodiun
ic surfactant, an
to achieve ink p
interaction with
Ng and a group
achieved excelle
the fellow assoc
a). The optimiz
dynamics simul
good recyclabili
Bhattacharyya a
can be extender
found a direct r
contamination a
they presented i
electrophotogra
The results sho'
in deinking and
Zhang and the
loop deinking 1
in between two
sisted of mixe'
amounts of liq
process succesr
photography pr
The aim of our
in the printing
recycling (Bolr
ther research c,
1.80, and 2.001
tic of recycled
of deinking flc
intermediate cture in the dor
cltage in LEp,Technology
::
::
.
n, Senring, Z0l4).
rrinting techniques
rvlronment mainly
ate making and its
dry,2011; Kadam
of digital prints in
difficult to detach
m fibers with the
00; Bolanda et al.,
i) Because of the
'llect, recycle and
ssociation of the
kability of digital
t
I Electrolnk is
as
rt the claims were
rers also question
method, claiming
inking (INGEDE
with the crite_
GEDE. 2012).
ne
rding and the 2"d
low 200 ppm as
'A 2012 (Hewlrroduces smaller
1, dispersion are
)12; Putz et a1.,
: deinkability of
digital prints in
rction for liquid
go plans to test
ated conditions.
rolnk and 95%
cale simulation
showed that a dirt count is similar
to that in a mixed office waste
fumish. In this
case two flotations were conducted.
I
I
f
i
i
r
I
I
Both Mittelstadt and co-authors
deveroped modified alkaline
deinking chemistry
HPMA (Miftelstadt et al., 2010;
rr,roain"a .rr.,,rrty^ui.. ,ruoirronur
including sodium hydroxide ,na
,ooJ- silicate with ihe sutstitution of achemicals
non-ionic surfactant' an emulsifier for
atty
The result orilr"
composition
to achieve ink particulates with the ""io
is
desired ,rr. ,urrg.-unj"i"rical
p.orria" the interfacial
interaction with foam fo, r"moual
J** flotation.
Ng and a group of co-authors adapted
H.ES from a lab scale to a pilot scare
and
achieved excellent recyclabiliry
.t
a1.,.2010). During ;;n,,"r research
t*t
Ng and
the fellow associates adapted
upgs"rr"- a lab scare to a pilot scare (Ng
et ar.,2010
a)' The optimization of HpES ir
ur.i.t.o by advancea'.oi."utu, modelring
and
dynamics simulation. using Hp
h;;; print in mixed-offiL waste has achieved
good recyclability on a pilot
scale.
Bhattacharyya and severar
co-authors used near-neutrar
deinking chemistry _ H'ES
can be extended to obtain gooa
oeinking results for traditional
offset inks. They
found a direct correlation b-etrve.n
irt"^
effects
irr"
ink-particle
contamination and its particle
"rr"-ical
"" et ar.,2011). speck
size distributions
(Bhatt u"nunau
Berow
they presented a comparative
study oithe atkaline and n"uiiuideinking
of indirect
electrophotography prints with
r^""i^
The results show that the.preferred;p;i;"
"rsubstrates fgh;tt""lr".ry a et al., 2012).
of neutral chemistry is always successful
in deinking and that alkaline
compticated.
"h"*i;il;
zhang and the colraborating authors
describe the design of a laboratory
"t
scale two_
loop deinking process with the
inclusion
ijr.
rir"u,
kneading
step
in between two flotation steps
ir 1Jg]"-snJ
Qn^,g
,"-pi"s for recycling con_
sisted of mixed office waie una
"t-^1.,2013)..rrr"
#*tur.s of mixed offic'e waste with various
amounts of liquid electrophotography
prints. It was our.-.a that the
two_loop
process successfully brings
the dirt area-for mixed om..
*uri.
with
liquid
electrophotography prints to a satisfactory
level.
The aim of our extensive research
was to determine the influence
of the conditions
in the printing process of indirect
,"
;;;frb"tiveness
of prints
recycling (Bolanda Mirkovii, Boranda,
"r..t.prrotography
zbos, eolun!" nai.to,rii et al., 2014).
ther research concentrated on
the
i-pu"iorriquid
Fur_
toner density (D r.2a,1.40,7.60,
.ith;iff.;;nt printing substrates on the characteris_
tic of recvcled fibres (Bolanda
Mi.k";;;, ;; aL,2009).Furrhermore, the mechanism
of deinking flotation was presented
in relation to the changes in temperature
of the
intermediate
1.80, and 2.00) in combination
cyrinder (Boianda v"t"r*
ture in the domain from 125
"c, 130
.,
ar.,2012).ny-in"r"u.rng
the tempera_
"c, l3S oC,740.i r"J i+s oc, an increase
Amual 2015 of the Cr(
elimination in the flotation
of dirt area is obseled, which in turn influences their
process.ontheotherhand,byincreasingthetemperature,theincreaseofcolour
quality'
gum.,t volume of prints is obserued, i'e' higher reproduction
Theprintsobtainedbyvaryingthevoltageoftheprocessingdtum,reverseroller
the mechanism and efftciency of the
and squeegee roller in the LEP technology on
the recycled fibers is presented in
deinking flotation process and characteristics of
these article.
the printing process conditions on
The results is contributed to the explanation of
the area of reused materials acceptthe deinkability of prints and can be applied in
the postulates of
ing the cradle-to-cradle concept which takes into consideration
ecological sustainable development'
The process of
J
charge the Photc
printing form wi
toner on the Prin
This paper show
ysis related to th
ticles need be i
squeegee roller t
ating a very thir
the paPer directl
Phase of develc
processing drun
Phase
of develc
processing drur
rr rl, -^^ ^C^-^^
tlltisc drur vr
AII
2. Materials and methods
chronized and t
Indigo based LEP technology' HP
The samples were made on the Turbo Stream HP
the transfer of a liquid toner'
Indigo printing is an offset process which involves
and thence to the printing
from the imaging drum to a heated olfsetting blanket
Machine calibrr
1. Voltage
of th
1, samPles:
substrate.
pI
z
2. Voltage of tt
ples: b,,br,b
Toger ospaper
3. Voltage
Chargrng
of t
(series 3, sa
4) 'r'
Ynn
L(lt
Irnagng
q,L
9)q)
Toner
The printing
wedge in the
control, textua
1
v'
.=
During the ex1
varied, while t
bration of the
*-*
Latent irnage
{toner particles + liquid canis)
Squeege*
rsu€r
Developnrg systsrn
Fig.
1
-
Indirect LEP technology (Majnari6' 2007)
ness and the t
and a 3D gam
Liquid Electr<
volatile miner
bltage in LEp Technology
ion in the flotation
increase of colour
a,lity.
rum, reverse roller
rd efficiency of the
rers is presented in
cess conditions on
I materials accept_
r the postulates of
The process of printing which
uses the. LEp technorogy has the
foilowing steps:
charge the photoconductor drum,
illumination the printing form,
colouration the
printing form with riquid toner,
t uor[. the toner to the printing substrate,
fix the
toner on the printing substrate,
and clean the printing form from
residue ink.
This paper shows the results
of the research c_onducted regarding
the sample anal_
ysis related to the third,
development stpe in LEp t""i,rror"ogv,
where
-oii
pigment par_
ticles need be isorated f.om tire
tiqrria
uy ur"
,qr""g". ro,er. The
ink on photoconductor, thus cre-
squeegee roller reduces the
"uoi",
total amount of
liquid
ating a very thin rayer on printing
.uf.our.r. The photoconductor drum pressures
the paper directly, thus obtainirg
ird_i""liry print.
Phase of development is carried
out in thre.e separate parts: developing
with the
processing drum, developing
with reverse roners and fixing with
squeegee roller.
:P technology. Hp
of a liquid toner,
ce to the printing
Phase of developing is conducted
in three separate parts: the developing
with the
processing drum, deveroping
with ."u..."..oil.r, und fixing with
squeegee
roiler.
All these aforementioned aiJinct pu.ts
of tt d"""r;p;;;;;se are perfbrmed
syn_
chronized and they are the subject'oir"r"ur.'
".
pr.."nt"iin
,t
i,
pupur.
Machine calibration is followed
by test printing:
1' voltage of the processing
drum: -200
l, samples: zr,&t,d:,aoi ur)
v,-2g0v -350v
_430v and _500v (series
2' voltage of the reveise rolrers: c\',
-50\,: -i25v,
Lvv r. att., _250v
' -r t ) -zXav,and
-z
(series 2, sam_
ples: b, br. br bo b. )
,
3' voltage of the squeegee rolrer:
-1250 v, -1300v -r350v. _1400v
and _1450v
(series 3, samples: c,, cr, c:.
co i cr)
nging
totrer
liquid cajrierj
During the experimentar printing,
onry one parameter in the printing
process was
varied, while ail other parameters
remained ionstant u, a"nnJj
by the initial cali_
bration of the printing machine.
The printing adifferent printing elements: a standard
cMyK step
"o^llu.tned
wedge in the l0%-100%o
tone uuru".uing., a standard
ISo illustration for visual
control, textuar positive and
ffiJ#
negative micioelem"ntr, *"Jg.,
ro, a.t.r_ining grey_
tJ"";^i?'o'.0 wedge *itn :zs pui"hes
ror ihe
of rcc profiles
p;;;;;;,
Liquid Electrolnk was used. It
contains 5 o%. monomer pigment
paste, 94 % highry
volatile mineral oil and about
l u" ug;ftfo. in"r"uring
(Landa
"r"*i"-.Jnductivity
162
Bolanda, 2., et' al': Rec
the Prints Obtained
Varying the Voltage in LEP Technology
etal.,1988).Theparticlesarel-2pminsize,dispersedinliquidmedium,which
for increasing electric conducresults in a high-qu ality 2400 dpi print. The agents
to their positive side and
tivity are highly polar molecules that receive G pigments
furn toward less negative electrostatic field'
substrate has high brightness (
ing on HP Indigo press that improve adhesion. This
-
L
CJ
cL
800
=
E
E
-lJ
.g
papel because the liquid toner
In LEP technology problem were with printing on
coated paper designed for printdid not always adhere uniformly to it. It was used
ISO brightness
Annual 2015 ofthe Cr
(}
F
Ttx}
600
soo
400
300
2U)
93%).
dernking flotation was used' DurFor the recycling of the prints alkaline chemical
hydroxide 1o%, hydroing,rr" prot.*r lhe following chemicals were used: sodium
and a surface active substance
gen peroxide 1ol0, sodium sJicate 2yo,DTqA0.2o/o
disintegration phase is 10%' while
0.4 %.The consisteo"y ortrt" suspension in the
in the flotation phase the consistency is 0'6%'
of
deinked pulp' with the usage
The handsheets were made from non-deinked and
to the standard ISO 5269 (ISO 5269-2'
trre nupid-rllthen sheet former, according
of the optical charac2002).The following values were used for the measurement
and deinked pulp: the diffuse
teristics of iaboratory handsheets from non-deinked
residual ink concentrareflectance factor according to ISO 2410, effective
blue
tion-E,RICaccordingtoTAPPIT56Tpm-97(ISo24]0.1,2009;TAPPIT567om09, 2009).
100
o
Fig.2-Totaldirt
Research resul
drum, and reve
disintegration
versely propor
negative volta
voltage Prints
lowest negativ
to b,).
Acountoftheresidualdirtparticlesandareawereassessedusing.spec*S:11|ogeesystemimageanalysissoftware(TAPPIT563-08/R,2012).Thissystemuttvalue (i00), white level (75)
lizes a scanner to oigi;ui2" an image. The threshold
and black level (65)
iere
to the handchosen after comparing the computer images
sheets.
2. Results and discussion
and contribute to optimizIn order to determine the impact of the printing substrate
of
the reseolrch was conducted of the impact
ing LEP technology pri,',
'ety"ting-,
the development process (processing
voltage change i" ,u*ff. priniing, t-hroughout
recycled fibre characteristics'
drum, reverse roller, ,i,,.tgt" 'Jt"t;, on the
before and after the flotation of
Figure 2 presents the total dirl count of handshets
and highest negative voltage used
prints of each of the ,;;pl" series for the lowest
in printing.
The lowest to1
fibres with the
highest total c
prints with the
lowest efficier
for the prints
the highest e1
voltage (46.2(
Figure 3 shor
of prints for t
The dirt taker
integrating
pr
119.875 mm:
compared to
e in LEP Technology
medium, which
:lectric conducositive side and
Annual 2015 ofthe Croatian Academy
163
(u
.o
E
3
c
.g
-E
E
the liquid toner
;igned for PrintLigh brightness (
ofEngineering
o
F
r
aoo
Before flotation
t]After flotation
7W
600
500
400
300
zo0
was used. Durxrde lo/o, hYdro-
I
active substance
se is 1070, while
100
o
a1
a5
b1
b5
c1
c5
Samples
Fig. 2 - Total dirt count versus voltage of the processing drum, reverse roller and squeegee roller on
handsheets from t-rbers after pulping and after flotation
vith the usage of
69 (ISO s269-2,
e optical characpulp: the diffuse
Ll
ink
concentra-
APPI T 567 om-
g Spec*Scan AP-
This system uti, white level (75)
rages to the hand-
fibute to oPtirnizt of the imPact of
rocess (processing
rcteristics.
ler the flotation of
,ative voltage used
Research results show that by increasing the negative voltage of the processing
drum, and reverse roller the dirt count on handsheets resulting from the fibres after
disintegration is reduced, while the results related to the squeegee roller are inversely proportional. The highest-level fragmentation is achieved with the lowest
negative voltage prints of the reverse rollel fbllowed by the lowest negative
voltage prints of the processing drum (lower by 8.7 o/o compared to b,) and the
lo'west negative voltage prints of the squeegee roller (lower by 58.3 Yo compared
to b,).
The lowest total dir-t number is found on the handsheet made from recycled prints
fibres with the Iowest negative squeegee roller voltage (total numbero,: 227). The
highest total dirt number is found on the sheets made from recycled fibres of the
prints with the lowest negative voltage processing drum (total number",: 610). The
lowest efficiency of removal the number of dirt by deinking flotation was achieved
for the prints made at the lowest negative voltage processing drum (17.6 %), while
the highest efficiency was achieved for the prints with the largest reverse roller
voltage (46.2%).
Figure 3 shows the total dirl area of sheets obtained before and after the flotation
of prints for the lowest and highest negative voltage used in printing.
The dirt takes the largest area on the handsheet made from fibres obtained by disintegrating prints made at the highest negative voltage of the reverse roller (b , :
119.875 mm2) The difference versus other samples series being 75.8 oh higher
compared to prints bl 60.8 Yo higher compared to a, or 63.5 % higher compared to
\64
Bolanda,
2., et. al.'. Recycling
th9
!llt'
'' .
t40
N
E
E
900
Befiire tlolJimh
-3aoo
'---nAfte+Jlstation
120
fi;
(u
Annual 2015 ofthe
the Voltage rn LEP
Obtnqgq by-Vatv
E
3zoo
L
(u
f
t
100
=
co
o
F
66m
BO
G
Esoo
F
60
400
40
300
20
2m
oi
a1
a5
b1
b5
c1
1m
c5
Samples
0
Fig.3_Totaldirtareaonhandsheetsfromfibersafterpulpingv.ersusvoitageoftheprocessing
drum, reverse roller and squeegee roller
5
Fig
r..ar.^*^-^ irlt chnrrtd
Jriuuru he noted
that lhe area taken bv dirr on the handsheet. as
negative voltage in the processsien in Figure 3, increases with the increase in the
ing drum, reverse roller, and squeegee roller'
C
.r Ul Lll€i IrlUr!r
Thelowestefficiencyofremovaltheareatakenbythedirtonthehandsheet
lowest
for the prints made at the
by the deinking flotaiion process was obtained
oA),
and the highest efftciency was
nlgative voltage of the ..u.rr. roller (10.9
of the squeegee roller
achieved with the print at the lowest negative voltage
(53.2%).
negative volti
lower negativ
bo and b, inct
a b5-br: 358
imental condi
A
ur*'
-
13.6:
A significant
from fibres
negative voltages proThe flotation efficiency increases by prints with increasing
:
.5'e"/:'ar: 52'8o/o:br: l0'90/o'b': 42'3Yo)'
cessing drum and u."*rr" roller (ai
negative voltage causes
us opiosed to the squeegee roller'where the increasing
:
:
flotaiion efficiency deceases (c, 4l'3o/o, c, 34'10/o).
detailed analysis of the dirt numThe results obtained indicate the need for a more
as shown in Figure 4'
ber and area, throughout the whole measuring range'
a
the reverse ro
and A br-b, =
The results c
ment. The pt
rotation, the
photoconduc
v
v
trolnk is injt
-50V-125v,-200Y,and-250V,adecreasewasobservedinthedirtnumberon in
of decrease in the dirt count varies
handsheets after pulping. However, the trend
processing drum
of
monitored series. By Increasing the negative voltage
_the
as follows:
count,
dirt
in the
throughout the measured range, a decrease occurs
the
increasing
By
L a;ar: 125, t ur-.u :-2t3,"A"u;ur: 315 and A ?,_-dt': 328'
cessing drun
power of the
to the values of -200
By increasing the negative voltage of the processing drum
to the values of 0
roller
-2g0 v _350 V _430 V, and -50d V, and or tn. reverse
drum, creatir
ing elements
of ink on the
the voltage c
165
Amual 2015 of the Croatian Academy of Engineering
rge in LEP Technology
900
-Tenore-fTulion
rTotal
L
-LAfter$otation-
-3aoo
140
d
dirt number
E
120 E
dirt area,
E
Szoa
ro-
(u
-fsl3l
t
100
;600
k
!
-ct
80-fit
fit
6soo
F
v
o
400
60
300
F
40
zffi
20
100
0
a1
: of the processing
a2
a4
a3
a5
b1
b2
b3
b4
bs
Sarnples
Fig. 4 - Dirt number and dirt area on handsheets from fibers after pulping
the handsheet, as
3e in the process-
+L^ L^-.{.1^-^+
-.^
, t I tl lL
li4lluJu! l
r
ade at the lowest
st efftciency was
)
squeegee roller
five voltages pro-
.9%o,br:42.3%),
/e voltage causes
of the dirt numr Figure 4.
s
values of-200 V
the values of 0 V
re dirt number on
irt count varies in
processing drum
)ount, as follows:
By increasing the
negative voltage ofthe reverse roller, a higher decrease in the dirt count occurs at
lower negative values, compared to series I samples, while the values for samples
bo and b, increased compared to b, (A b, b,: 221, L br-b,: 362, Lb;br: 337,
A b5-bi - 358).By increasing the negative voltage of the processing drum, in experimental conditions, the dirr area on handsheets after pulping is generally increased:
:
ar{,: 23.131 mnf.
with
handsheets made
A significantly higher increase of the dirl area is observed
from fibres after pulping the prints obtained by an increase in negative voltage of
Lu;ur:
13.631mm2, A ar-a,
:
15,132 mm2, A a*-a, :13,572 mm2, A
I 8.3 I I mm2, A br-b,
the reverse roller: A br-b,
and A b, b,
89,7 12 mm2.
:
:
51.1 12 mm2, A bo-br
:
68.91 1 mm2
The results obtained may be explained by the principle of liquid toner development. The processing drum stands next to the photoconductor. Due to adversary
rotation, the processing drum does not come into contact with the surface of the
photoconductor. There is a vety nalrow gap between them into which the Electrolnk is injected. During printing, negative voltage is formed on the processing
drum, creating electrostatic field with the photoconductor. In order for virtual printing elements to adhere the ink, they need to be more electropositive than the processing drum. With an increase in the negative voltage of the processing drum, the
power of the electrostatic field increases, resulting in an increase in the application
of ink on the printing element. Hence, the thickness of ink on the prints depends on
the voltage of the processing drum.
166
Bolanda,2., et. al.: Recycling the Prints Obtained by Varying the Voltage in LEP Techrology
The aim of the development process using the reverse roller is getting a clean photoconductor. Therefore, mineral oil is used on the surface of the photoconductor.
An electrostatic field is formed in the contacl zone between the photoconductor and
the reverse roller, much weaker than the field formed between the photoconductor
and the processing dmm. Due to low voltage (0 V -250 V), the reverse roller may
easily become more electropositive than the printing elements, which results in
additional detachment of ink from the photoconductor.A slight change in the voltage of the reverse rolier affects the thickness of ink on the prints.
Varying the voltage of the squeegee roller may result in decreasing the thickness
ink on the photoconductor by over 50 %.
-E
14{l
-{tt
120
ro
1cn
F
L
t
i:
80
aoo
E
7o0
"!
6OO
=
e
-
r dirt nummkrer
>
O.O4 mmz
f] Dirt numkrer < o,o4 mtn2
l
-1l
I
I
40
20
Fig.
6
while
I
il
Area c
and
A b,-bo: 36
bo
The area co'
an increase
r
increase (A
500
Itoo
Larar--2
53.612 mm2
300
200
100
o
a1
Fig. 5
I
I
Since cases were observed in which the dirt number has little change, while at the
same time the dirt area is significantly increased, as was the case with samples b,,
bo and b' the emergence of large, visible dirt can be expected in such cases, which
so
T1
(U
of
can not be removed by flotation nor screening since they are too soft and pass
through screens. This calls for a more detailed analysis of the dirt size, as shown in
Figure 5.
olr
Annual 2015
-
a2
a3
a4
a5
b1
b2
difi < 0.04 r
ries I (A a,2.502 mm2)
3.120 mm2 t
tt3
sarnpres
Dirt number > 0.04 mm2 and < 0.04 mm2 on handsheets from fibers after pulping
With the increase in negative voltage of the processing drum in experimental conditions, a decrease in the dirt number >0.04 mnf occurs on the handsheet made
from fibres after pulping the prints, as follows: A, ar-ar: 3, A &r-dt: 19, A, ar-ao: 40
: 169,
and A a,-a, : 42 and the dirt number < 0.04 mm2 for A' ar-ar: 122, A ar-a,
:
261.
A. ar-ao: 250 and A a,-a,
The trends of sample series 2 differ ffom those of series l. In this case the dirt
number > 0.04 mm2 is increased with an increase in the negative voltage of the
reverse roller by the following amounts: A bri,: 8, A b,-b,: 19, A b4-b1: 40 and
A b.-br :42.The dirt number < 0.04 mm2 has a decreasing trend for b,,b, and br,
In order to c
was used di
number of d
The majorit'
ofthe revers
ative voltagt
voltages all
Large partic
The criteria
centration ([
age in LEP Technology
Amual 2015 of the Croatian Academv of
ling
*
a clean phophotoconductor.
otoconductor and
: photoconductor
lverse roller may
which results in
140
E
F
i
rzo
fit
OJ
€
a
1oo
80
range in the volt-
3
the thickness
of
while at the
with samples b,,
Lnge,
;uch cases, which
.oo soft and pass
size, as shown in
a1
Fig'
6
while.
rber
<
O,O4 mm2
a3
a4
a5
bI
bZ
b3
b4
b5
Samples
-
Area covered by dirt > 0.04 mm'7 and dirt < 0.04 mm2 on handsheets
from fibers after pulping
bo
A br-b4
rmh)er ) O,O4 mm2
a2
b, being slightly higher compared to b. (A b,_br: 22g, Lb,_b,
:T9
364 and A b,-br: 368).
:
378,
The area covered by dirt > 0.04 mm2 on handsheets after pulping
of series I with
an increase of negative voltage of the processing drum
shows a significantly lower
increase (lur_!,: 10-512 mm2,A ?t d,: 13.232 mm2, A zo-.dr:
12.032 mm2,
mm2)
compared
to'r"ii",
(Lb2-bt:
z
zO.3t1
mm2, A br_b, :
!_ur-ur:21.900
S,] AtZ^y7t'z, A-b*-b, :12.lll mm2 and A br-b, : gi.g+t
mmr). The area taken by
dirt < 0.04 mm2 is considerably smaller compared to dirt > 0.04 mm2,
both for se(A a?. a, : l1712 *T,: a, a, : 1.7
myr,
A,
ao*a,:
2.3s0
mm2, A ?., ?r :
l:t^
1
.A.
li mm2,
2.502 mmz) and for series^2^(A-br:U,
: l. l7l
:
A b:b,'
1.901 mm2, A bu_b, :
3.L20 mm2 and A br-b, : 3.273 mm))
_
b4
trS
Sarnples
rrs after pulping
:rperimental con-
: handsheet made
: 19, A ar-ao:40
32, A
a,-a,:
169,
this case the dirl
r-e voltage of the
. .\ b4 br:40 and
d tbr b,.b, and b".
In order to determine more precisely the number, size and area of dirt
distribution
was used dirl spot size from 0.001-0.006 mm2 to >:5mm2 .
Figure 7 shows the
number of dirl larger than >:5 mm2 for all sample series.
The majority of large dirt >5 mm2 forms with the increase in the
negative voltage
of the reverse roller, while the smallest amount forms with the increase
of the negative voltage of the squeegee roller. One general feature is
that at lower negative
voltages all of the three print series obseryed no dirt size >:
5 mm2 is formed.
Large particles cause optical inhomogeneiqr of handsheets.
The criteria for cleanliness is a minimum dirt count. The
effective residual ink concentration (EzuC) measurement means to relate ink content with
brightness. An ink
1
68
Bolanda,
2., et. al.: Recycling the Prints Obtained by Varying the Voltage in LEP Technology
L-,
c., '
-o
r
Dirt number >O,O5mm2
5o
c
The differenc,
before and afi
recycling pro,
.Es
I
O
al
I
measurement
fective for sul
I
I
a2 a3 a4 a5 b1 b2 b3 b4 b5 c1 c2 c3 c4
c5
Samples
Fig.
7
Dirt number >:5mm2 on handsheets from fibers after pulping prints for series 1, 2 and 3
removal efficiency based on ERIC and dirt count across the different recycling
operations tells what has happen to the ink, because uses refletance measurements
in the infrared area of the spectrum where the absorption coefficient for the ink is
several orders of magnitude greater than the absorption coeffrcient for the fiber,
fillers and other components.
The results presented in Figure B show that the least number of remaining ink particles is found on handsheet made from deinked pulp of b, and b, prints. The largest
difference in brightness was observed with the samples on handsheets before and
after flotation (brightness gain br- 2.0; brightness gain b, :2.9).
r,
a
.,
Annual 2015 oftht
3. Conclus
The depender
and squeegee
efficiency of
fibres.
During the fl
needed for st
printing subsl
to the paper.
alkali can lea
can hydrophi
well as affect
Furthermore,
of LEP prints
80
7a
Relerences
60
t1l
Bhattachar
acid based
national C
50
719-121
40
L2l
30
Bhattachar
digital prir
Fabricatior
20
t3l
Bolanaca l
t4l
Bolanaca l
conditions
t5l
Bolanca N
photograpl
and Tech.
10
o
a5
Fig.8
b1
bs
c1
ERIC on handsheet from fibres before and after flotation
c5
Samples
Baltic Indr
s
in LEP Techrology
Arnual
201 5
of the Croatian Academy of Engineering
169
The differences in the values of effective residual in concentration on handsheets
before and after the deinking flotation are good indicators of the efficiency of the
recycling process and confirm the results obtained by other methods. The ERIC
measurement is dependent on the distribution of ink particle sizes and is most effective for submicron particles.
3. Conclusion
c3 c4
c5
Samples
series 1,2 and
3
lrent recycling
measurements
rt for the ink is
t for the fiber,
aining ink parrts. The largest
:ets before and
The dependence of changes in the voltage of the processing drum, reverse roller
and squeegee roller was determined in the LEP technology on the mechanism and
efficiency of the deinking flotation process and characteristics of the recycled
fibres.
During the flotation process, a slight formation of foam was observed, which is
for successful dirt separation. This might be caused by the coating of the
printing substrate, necessary to improve adhesion and increase the ink's adherence
to the paper. In recycling process dispersants are surface active and together with
alkali can lead to acceptable ink detachment from the coated paper. These species
can hydrophilise ink containing agglomerates and hinder flotation effrciency as
well as affecting foam stability.
needed
Furthermore, the size of Electrolnk dirt also has an important role in the deinking
of LEP prints hence, by reducing dirt, deinking would be easier.
lforsfffiiontes$otatianReferences
tll
Bhattacharyya, M, Manoj, K., Ng, H.,T., Mittelstadt, L., Laurie S., Aronhime M. (2011) Fatqr
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