The Effect of Double Bonds Present in the
Surfactant on the Deinking Efficiency of
Xerographic Paper
L. MARCHILDON, B. BONNELLY and M. LAPOINTE
The use of stearic acid, which has no
double b o d in its carbon chain, removes
much more ink from the fibre in the pulper
and gives the best overall eficiency of deinkh g (pulping and flotation) compared with
oleic or linoleic acid. The separation of ink
from the fibres and the overall eficiency of
the deinking process increase with the addition of silicate for unsaturated fatty acids
with two double bonds. Thispaper examines
also the influence of the number of separated
ink particles on the optical properties of the
papel:
INTRODUCTION
This paper is a continuation of the
report presented at the Asian Pacific Waste
Paper Conference [I] and at New Orleans
TAPPI Pulping Conference in 1988 [2]. In
Canada and the US,there is a possibility of
shortages in wood supply in the future, especially with softwood species. The cost of
wood and its transport increases every year,
and companies are searching for new raw
materials; some are looking seriously at fast
$rowing trees to replace black spruce, bal-
4
L. Marchildon, B. Bonnelly
and M. Lapointe
Centre de recherche en pates et
papiers
Universit6 du Quebec
B Trois-RiviBres
C.P. 500
Trois-Rivihres, Que.
G9A 5H7
Sam, etc.; others are investigatingthe use of double bonds; oleic acid one cis double bond
at the 9 position; and linoleic acid has two
secondary fibres.
In secondary fibres, because of the cis double bonds at the 9 and 12 positions.
growth rate of reprography, paper printed by The influenceof these agentson the physical
this process seems to be of increasingimpor- and optical properties of the pulps produced
tance for recycling. The rate of utilization in was examined; the number and the size of
the USA was 943 000 tons in 1977 and is the particles separated (or removed) from
predicted to attain 1.3 million tons in the fibres, and the efficiency of flotation in
1990 [3]. Worldwide, in the early 1980s, terms of cleanlinessand reduction of the ink
3 million tons of this grade of paper were surface area were also evaluated.
consumed [4]. This rate of consumption
shows a great potential for reclaiming a Experimental Procedures
The paper was slushed in a laboratory
high-quality fibre such as that used in
pulper; the pulping time was 30 min, so that
xerographicpaper.
In starting these studies, we had to the fibres were well separated from one
bear in mind that the reuse of secondary another and the chemical products had suffibres in fine kraft and specialty grades will ficient time to react. The concentration of
depend on the cleanliness and brightness of surface-active agent was kept constant at
the final pulp; two processes can be used to 1%, and differentsurface-activeagents were
obtain the required standardof quality, flota- used. Sodium silicate was added at 0 to 3%,
tion and washing deinking. In the present the pH being maintained at 10.5. The other
work, flotationdeinking only was examined. parameters were kept constant, consistency
Attention was concentratedon the ef- 2%, temperature 20°C. The choice of 20°C
fect of the nature of the surface-activeagent, was based on work done by Pfalzer [6] and
expressed as the number of double bonds Smith [7].
Flotation deinking was carried out in
present in a linear carbon chain, on the
removal of ink from the fibre and its elimina- a standard Voith laboratory cell (shown in
tion from the suspension. Bechstein [5] Fig. 1); calcium chloridewas added to mainstates that the presence of double bonds on tain 180 ppm of hardness expressed as ppm
the carbon chain of the surface-activeagent of CaCO3. The temperature was 20°C as in
favours its collecting power that influences the pulping sequence, but the consistency
the efficiency of elimination of the ink par- was reduced to 0.4% to diminish the interticles by the flotationprocess. Three surface- ference with the fibres; the time of aeration
active agents consisting of 18 carbon was set at 10 min.
aliphatic acids were studied stearic, oleic
The measured ink particles are those
and linoleic acids. Stearic acid contains no separated from the fibre during the pulping
i
90
VOITH CELL
0
STEARIC
A
LINOLEIC
0
0
6. F.
d.
OLEIC
A.
F.
h
s?
v
FOAM
GATE
(0
$I-
‘..*...-...............
80
&..e........
a..,!?
............*
A m o m 0
A
*.-a.
........
I
CY
oc
IECIRCUIA TlON
m
70
4000
0
8000
NUMBER
Fig. 1. Laboratory Voith Cell (17 L).
Fig. 2. Brightness in relation to the number of ink particles.
//
90
A
’ a00
0
*..................... 4...........A .*.........@...”..........*
.....
.....
A
A
A
0
8000
(0
W
1
Foc
undw
2
LL
0
80
’
I
I
:
0
STEARIC
W
A
LINOLEIC
3= 2000
0
OLEIC
0
E. F.
m
A. F.
I
I
0
I
4000
I
8000
Total
NUMBER
-.rpparc
_-
__
~
3
4
Fig. 4. Particle size distribution by class after pulping.
total surfaceoccupied by the free ink without
any dilution.
RESULTS AND DISCUSSION
Optical Properties
of the Deinked Pulps
In Figs. 2 and 3, the circles, the triangles and the squares represent, respectively, data obtained with stearic, linoleic and
oleic acid; the open symbols are used for
results obtained before the flotationprocess,
and the filled ones after flotation. The letters
B.F. and A.F. refer to the terms “Before
Flotation” and “After Flotation”,respectively.
Brightness
Figure 2 points out that the brightness
varies with the number of ink particles in the
pulp before and after flotation; the kind of
surface-active agent has no influence. The
flotation process increases significantly the
brightness of the pulp. After pulping or
before flotation, the handsheets contain
PAPER SCIENCE VOL. 19 NO. 4 JULY 1993
J J
2
CLASS
Fig. 3. Opacity in relation to the number of ink particles.
process or the ink particles retained in the
pulp suspension after the flotation process.
The number and the size of the ink particles
are measured through samples prepared as
follows. Two grams (b.d.) of pulp at known
consistency are taken after the pulping or the
flotation step and diluted to 0.01% consistency. B o hundred millilitres of the final
dilution are taken for each filtration on a
millipore filter, and four millipore filters are
prepared in the same way.
An area 1.6 cm2 is measured on each
of four millipore filters. Aphotographic slide
is made for each surface by means of a
camera placed on a stereoscope. The slide i s
then projected onto a screen placed at a fixed
distance, and the number and the size of the
ink particles are measured on the screen. The
actual particle size is obtained by comparison with particles having different
standard sizes which were photographedand
projected the same way. The ink surface area
is the summation of the surface area of each
particle of ink in the measured space multiplied by a dilution factor to represent the
1
many ink spots that absorb light. The flotation process eliminates most of the ink spots
and increases light reflectance and brightness accordingG.
Opacity
The influence on opacity is shown in
Fig. 3. It is obvious that the most important
parameter is the flotation process because
the ink spots and the filler eliminated no
longer interfere with the passage of light
through the sheet. After pulping (before
flotation), we observed that an increase in
the number of ink spots did not affect the
opacity. After flotation, a decrease in their
number and a reduction of the filler content
in the pulp greatly decreased the opacity. As
for the brightness, the kind of surface-active
agent has no influenceon this optical property.
Particle Size Distribution of Ink
Distribution by Class
The histogram in Fig. 4 represents the
granulometric distribution of the ink spots
5157
FE
75
E
v
a
w
9
50
w
0
*
O%S,l.
-+-
E. F.
- TOTAL
3
U
3
.__..
25
_ _ _ CLASS
A. F.
L
0
----- --_____
~*
-
.......
..............................................
- - -- - - - ~ - - - - - - -
-
2
1
0
DOUBLE BONDS
Fig. 5. The total ink surface area before and after flotation vs the
number of double bonds.
0
I
DOUBLE BONDS
-+-
0% Sil.
+
3% LI.
1
i
2
2
3
4
CLASS
Fig. 8. Efficiency of the flotation process in relation to the class
of ink particles.
Ink Surface Area
Total Ink Surface After
Pulping and Flotation
The total ink surface area is the summation of the surface area of each particle of
ink, separated from the fibres during pulping
or not removed during the flotation process,
of four surfaces of 1.6 cm2leach of millipore
filter [S-111. In Fig. 5, the total ink surface
area in mm2 after pulping and flotation is
related to the number of double bonds for the
case when 0% sodium silicate was added in
the Beinking process. The solid line represents the results before flotation and after
pulping; the dashed line is after flotation.
Before flotation it can be observed that the
ink surface area, in other words the ink
separated from the fibres during pulping,
increases with the absence of double bonds.
The use of a soap of stearic acid,
which has no double bonds in its carbon
chain, removed much more ink from the
fibres than oleic or linoleicacid. The last two
agents removed approximately the same
--
1
DOUBLE BONDS
2
CLASS 1
Fig. 6. The ink surface area before flotation (by class) vs double
bonds.
2
Fig. 7. Ink surface area (total and class 4 Ink particles) in relation
to the number of double bonds and % of silicate.
by class before flotation for the experiments
performed with 0% silicate and the three
surfactants. The number of ink particles of
each class is shown on the vertical axis. On
the x-axis, the class is shown by a number;
each class refers to a spread of particle size.
Class 1 represents particles smaller than
30pm; class 2 particles a size between
30 and 70 pn; class 3, those between 70 and
130 pm; and class 4 comprises particles
greater than 130 pm. The number of small
particles removed from the fibre was a lot
larger than the number of big ones. We observed also that stearic acid, the surfactant
without double bonds, produced a greater
quantity of total separated ink spots. The
presence of one double bond (oleic acid)
gave a slightly lower result. Linoleic acid,
with two double bonds, separated approximately half the number of ink spots
from the fibre that were removed by stearic
acid. Oleic acid gave more particles of class
1; for the three other classes, stearic acid
showed the best result expressedas the number of ink spots removed.
CLASS 4
.. CLASS 3
(I)
-
I-
D
amount of ink from the fibres. Based on ink
surface area, there was very little difference
in the removal of ink in ?e flotation process
due to the type of surface active agent. The
flotation process reduced the ink surface
area by 95 to 99%.
Ink Surface Area of Class 1 to 4
After Pulping
Figure 6 shows the relationship between the number of double bonds and the
surface area of ink particles present in the
pulp before flotation. The relationship for
particles of class 4 is similar to that of the
total ink surface area. However, the surface
area of class 4 (i.e., particles of diameter
bigger than 130 Fm) is lower by 5 to 10 mm2
compared to the total surface. This 5 to
10 mm2 is the sum of the surface area of
particles included in classes 1 to 3. These
three classes contain approximately 10% of
the ink removed from the fibre. The kind of
surface-activeagent has no significanteffect
on the ink surface area of these classes. The
vnL
iq
. I I I I Yi q w
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
- ..
type of soap affects only the area corresponding to the particles of class four.
>
0
Z
Influence on the Ink Surface
Area of Double Bonds in the
Fatty Acid Soap Used in the
Pulping Process
Figure 7 illustrates the total ink surface area after pulping in relation to the
percentage of silicate used and the type of
surface-activeagent at a 1% addition level.
The bullet and the filled triangle represent
the total ink surface with 0 and 3%of sodium
silicate added, respectively. The separation
of ink from the fibres, represented by the ink
surface area, increases with the addition of
silicate for unsaturated fatty acids. In the
absence of double bonds or with only one,
the silicate has little or no effect; with two
double bonds the ink surface area increases
by 20%. This augmentation is mainly due to
an increased number of ink particles in class
4 represented by the crosshatched area.
Decrease of Ink Surface Area
in the Flotation Process
Flotation was carried out with the
pulp suspension from the pulping step, but
the consistency was reduced to 0.4%. The
concentrations of different surface active
agents and sodium silicate are as in the pulping step. In our experiments, we observed
that the percentage of ink particles
eliminated by flotation increased with size.
The reduction of ink surface area, as shown
in Fig. 8, is 92,96,98 and loo%, respectively, for ink particles of class 1, 2, 3 and 4. It
is indeed preferable to have ink particles of
class 3 and 4, or larger than 70 pm, if we want
to achieve the cleanest pulp.
Influence of Double Bonds
in the Fatty Acid Soap and of
Silicate in the Flotation Process
In Fig. 9, the pqcentage of ink surface
area removed by flotation, or the overall
efficiency of the flotation process, is shown
on the ordinate. As we did not know how
much ink was present on the fibre before
pulping, we took as reference the greatest
surface area of ink particles separated from
the fibre during pulping. This value was
obtained with stearic acid. On the abscissa is
shown the number of double bonds in the
fatty acid soap used. The other parameter is
the percentage of silicate added.
Stearic acid (without double bonds)
with or without silicate eliminates approximately 98% of the ink present in the
stock suspension. The global efficiency of
the deinking process (pulping and flotation)
is superior with stearic acid, even if the two
other surfactants work slightly better in the
flotation stage. They have, however, a much
lower efficiency in the removal of ink from
fibre in the repulping stage (Fig. 5). The
assistanceof silicate increases the efficiency
of the flotation process when the surfactant
has two double bonds. Sixty-five percent of
the ink is eliminated with linoleic acid (two
double bonds) with no silicate; however,
w
I
100
0
LL
LL
W
-1
$
CT
w
>
0
8
I
“
t
l.S%SIi.
-&-
3% Sil.
1
0
0% SII.
*
2
DOUBLE BONDS
I
Fig. 9. Efficiencyofthe deinking process in relation to the number of double bonds and
‘YOof silicate.
with the addition of 3% silicate, 85% of the
ink is removed.
CONCLUSIONS
The flotation process applied to
xerographic paper increases pulp brightness
from 80 to 89%, and reduces the opacity
from 88 to 81.5% depending on the conditions of operation. These changes are essentially attributed to the elimination of ink
particles by the flotation process.
Stearic acid, with no double bonds in
the carbon chain of the soap, increases the
ease of separationof ink from the fibre in the
pulping stage; however, the presence of at
least one double bond in the chain permits a
better elimination of ink by flotation. The
efficiency of the flotation process, however,
is not increased by using a soap containing
two double bonds instead of one.
For the overall deinking process
(pulping and flotation), stearic acid gives the
best performance. The overall efficiency of
thedeinking process, when using a soap with
two double bonds, is increased by the addition of sodium silicate.
REFERENCES
1. MARCHILDON, L., LAPOINTE, M. and
BONNELY, B., “Deinking by Flotation of
Paper Printed by Xerography”, Asian
Pacific Waste Paper Conference, Taipei,
Taiwan (Apr. 11-13, 1989).
2. MARCHILDON, L., LAPOINTE, M. and
BONNELY, B., “The Deinking of
Xerographic Paper by Flotation”, TAPPI
Pulping Conf., New Orleans, Book 1: 81-94,
(Oct. 1988).
3. FRANKLIN, W., “Waste Paper Recycling:
Its Present and Future Status”, Pulp Paper
53( IO): 182-187 (1979).
4. NIELSEN, N., “Reprography”, Pulp Paper
Chem. & Chem. Technol. 4(24):2277-23 I7
(1983).
5. BECHSTEIN, G., “Performance of Collectors in the Deinking-Flotation Process”,
Zellstoaund Papier 2 1 :297-306 ( 1972).
6. PFALZER, L., “Deinking of Xerographic
and Carbonless Copy Papers”, Tappi J.
62(7):27-30 (1979).
7. SMITH, M., “The Deinking of Xerographic
Waste Paper by Dispersed Air Flotation and
Side-Hill Screen Washing”, Independent
Study A-291. Inst. Paper Chemistry (Apr.
15, 1983).
I
’
8. CHABOT, B., “L‘impact de la quantit.5
d’agent floculant et de la temp&”
d‘ophtion sur la grosseur des particules
d’encre flotees”, MCmoire de maihise,
Universitk du QuCbec B Trois-Rivikres (Feb.
1988).
9. MARCHILDON, L., LAPOINTE, M. et
CHABOT, B., “Le dksencrage du papier
journal par la technique de flottation”, Conf.
Tech. Estivale, Pointe-au-Pic, 38-41 (May
1987).
10. MARCHILDON, L., LAPOINTE, M. and
CHABOT, B., “The Influence of Particle
Size in Flotation Deinking of Newsprint”,
74th Ann. Mtg., Tech. Sect., CPPA,
Preprints, p. 61-66 (1988).
11. MARCHILDON, L., LAPOINTE, M. et
CHABOT, B., “Le dksencrage en
laboratoire du papierjoumal par la technique
de flottation”, J. prifes papiers 4(1):25-29
(Feb. 1988).
The Mechanical Permanence of Paper:
A Literature Review
N. GURNAGUL, R.C./HOWARD, X. ZOU, T. UESAKAand D.H. PAGE
Librarians and archivists are concemed about bookpages that become brittle
&disintegrate as a consequenceof ageing.
i%ishas resulted in an increased demandfor
paper with good mechanical permunence,
i.e. paper that retains its strength properties
with ageing. This report reviews the literature on thefactors that affect the mechanical
permanence of papex
standard specifies that the paper must have
a minimum cold extract pH of 7.5, an
alkaline reserve equivalent to 2% calcium
carbonate, must not contain any
groundwood or unbleached pulp, should
have an initial folding endurance of 30
double-folds (at 1 kg tension) in the cross
direction and a tear resistance in the machine
direction of 24-50 g (for 30-60 Ib paper).
This standard has recently been revised as
follows: paper stock requirement has been
INTRODUCTION
Librarians and archivists are con- changed to less than 1% lignin in place of the
cerned about the rapid deteriorationof books 1984specification of no groundwood or unand documents printed on acid paper. Such bleached pulp; in addition, the folding enconcerns have been reflected in a recent durance test has been dropped due to the
government decision to print publications it inherent variability of the test [3].
Standards on permanence are also
expects to be retained for information or
historical purposes on alkaline-based being issued by other organizations such as
the International Standards Organization
paper [11.
A Canadian standard for permanent (ISO) [4] and the American Societyfor Testpaper is not yet available. For the time being, ing and Materials (ASTM) [5]. Like the
paper for government publications must ANSI standard, these have similar requiresatisfy the 1984 version of the American ments with regard to lignin content, pH and
National Standards Institute (ANSI) alkaline reserve.
A number of good reviews exist on
specifica- tions for permanence [2]. This
paper permanence [6-111; however these do
not necessarily focus on the issues raised in
N. Gumagul, R.C. Howard,
the standards for permanence such as the
X. Zou, T. Uesaka and
effect of pulp type. This review covers the
D.H. Page
literature from 1895 to the present with an
Paprican
aim to reveal the anecdotal and scientific
570 St. John’s Blvd.
basis for the specifications outlined in the
Pointe-Claire, Que.
various standards for paper permanence.
H9R 3J9
4
J160
DEFINITION OF PERMANENCE
Permanence was defined in the early
1920s as “the degree to which paper resists
chemical action which may result from impurities in the paper itself, or agents from the
surrounding air” [ 121. This lead to the emphasis on high fibre “purity”, Le. a high
a-cellulose content as one of the requirements for permanence [131.
In the definition of permanence, it is
important to specify the end-use requirements for the paper. Far most end-use applications the retention of strength
properties, i.e. “mechanical permanence”, is
of prime importance since book pages have
to remain intact during hand1ing:Of secondary importance are the aesthetic properties
of the sheet such as colour, i.e. “optical
permanence”. As a large body of literature
exists on the optical permanence of paper,
this review will be confined to the existing
literature on mechanical permanence.
ACCELERATED AGEING TESTS
Since the processes of ageing under
ambient conditions are extremely slow, the
only approach to a scientific study of ageing
is some form of an accelerated ageing test.
The question is how best to accelerate the
processes occurring during natural ageing,
without inducing artificial effects.
The basis for accelerated ageing tests
JOURNAL OF PULP AND PAPER SCIENCE: VOL. 19 NO. 4 JULY 1993
,
I
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Volume 19, No. 4, July 1993
ISSN 0317 882X
Published by the Technical Section, Canadian Pulp and Paper Association
,