Note: Descriptions are shown in the official language in which they were submitted.
CA 02405649 2002-09-27
PAPERMAIONG FURNISH COMPRISING SOLVENTLESS
CATIONIC POLYMER RETENTION AH) COMBINED WITH
PHENOLIC RESIN AND POLYETHYLENE OXIDE
FIELD OF THE INVENTION
This invention relates to papermaking. ~Viore particularly, it relates to a
papermaking furnish that comprises a solventless cationic polymer retention
aid in
combination with phenolic resin and polyethylene oxide (PEO) to increase
retention
and/or drainage in the furnish.
BACKGROUND OF THE INVENTION
In the manufacture of paper, an aqueous suspension of cellulosic fibers,
optionally
containing a filler and cationic starch, as well as other papermaking
chemicals, is spread
over a wire or cloth and water is removed therefrom to form a fiber web or
sheet. Such
aqueous suspension or slurry is called "papermaking furnish". The removal of
water or
dewatering of the furnish as well as retention of fines, fillers and other
papermaking
chemicals in the paper sheet are very important to the efficient recovery and
production
rate and to the cost of manufacture of the paper and its quality.
It is well known to use a combination of phenolic resin and polyethylene oxide
as
a flocculent to improve retention and drainage in the production of paper and
paperboard,
particularly in newsprint applications where mechanical pulp containing
dissolved
organic contaminants causes some detrimental effects. In such systems, the
phenolic resin
is usually added first to the furnish, before the last shear point, such as a
fan pump, and
PEO is added second, usually near the headbox of the paper machine, in order
to
CA 02405649 2002-09-27
minimize shear. As is known, shearing is provided by one or more of the
cleaning,
mixing and pumping stages in the papermaking process and the shear breaks down
the
flocks formed by the high molecular weight polymer into microflocs, which are
further
agglomerated, for instance with the help of cationic starch.
It has been suggested that the mechanism of the phenolic resin/PEO two-
component retention system consists firstly of adsorption of the phenolic
resin onto fibers
and fines, followed by attachment of PEO to the phenolic hydroxyl groups of
the resin,
forming high molecular weight polymeric networks which serve to retain the
fines and
also promote drainage. Examples of such two-component retention system are
disclosed,
for instance, in U.S. Patents Nos. 4,070,236 and 5,472,570.
The phenolic resin/PEO two-component system has the advantage of being
independent of most dissolved and colloidal contaminants in the water circuit
because it
functions by a hydrogen-bonding mechanism. In contrast, cationic
polyacrylamides,
which are also commonly used as retention aids, are adversely affected by
dissolved and
colloidal contaminants found in mechanical pulp.
In addition, the phenolic resin/PEO two-component system has several other
advantages over cationic polyamides, including more favorable effects on the
final sheet
formation and a better pitch control, which refers to its ability to fix
organic contaminants
in the paper sheet rather than allowing them to deposit on the mill fabrics
and machinery,
thereby causing eventual shutdowns.
Nevertheless, despite the above advantages, the phenolic resin/PE0 retention
and
drainage system has not been adopted in mills producing grades such as highly
filled
specialty mechanical paper, fine paper (where mechanical pulp from softwood
does not
2
CA 02405649 2002-09-27
form a large part of the furnish), and tissue and packaging papers. In these
areas, cationic
polyacrylaxnides are the predominant treatment.
The main reason for the lack of success of the phenolic resin/PEO system in
the
above areas is the reduced performance owing to the lack of organic
contaminants in
these furnishes compared to the softwood mechanical pulp used in many
newsprint
applications. These contaminants provide a part of the network mechanism by
which this
retention system functions and their absence in other furnishes such as
sulphate pulp and
recycled and deinked pulp has led to the predominance of other retention
systems,
especially cationic polyacrylamides. In addition it has been found that
residual silicate in
the pulp from some bleaching and de-inking operations sometimes has an adverse
effect
on polyethylene oxide causing a loss of retention or drainage. (c.f. Rahman
and Tay
Tappi Proceedings, 1986 Papertnakers Conference, p 189-198).
There is thus a need for an improved phenolic resin/PEO based retention system
that would alleviate the above mentioned disadvantages and increase retention
and
drainage, particularly in furnishes such as sulphide pulp and recycled and de-
inked pulp.
OBJECTS AND SUMMARY OF THE INVENTION
Is is an object of the present invention to provide a papermaking fiunish with
increased retention rate and drainage based on the phenolic resin/PE0
retention system.
A further object is to provide a method of increasing retention rate and
drainage in
a papermaking furnish while also maintaining good sheet quality at reduced
cost.
A still further object is to provide a papermaking furnish based on the
phenolic
resin/PEO retention system which would be suitable for producing highly filled
specialty
mechanical paper, fine paper and tissue and packaging papers.
3
CA 02405649 2002-09-27
Other objects and advantages will become apparent from the following
description of the invention.
The applicants have surprisingly discovered that a retention aid consisting of
a
solventless cationic polymer, which is in the form of an oil-free, water-
soluble polymeric
dispersion, combined with phenolic resin, such as phenol formaldehyde resin,
provides
increased retention rate and drainage as well as other advantages, such as
reduced cost,
when used in conjunction with polyethylene oxide (PEO). When the solventless,
cationic
polymer retention aid and phenolic resin are added to the furnish, they form a
structure
which gives a significantly improved reaction with polyethylene oxide when it
is added
to the furnish. Retention, namely fiber retention, filler retention, and COD-
retention
(natural resins and other organic contaminants) and drainage are increased to
the extent
that the above areas of fine paper, recycle packaging grades and other types
of paper
production become viable areas when this system is used. Additionally
increased filler
and fines retention is obtained over that which would be achievable using the
PEO and
phenolic resin combination alone or using the solventless cationic polymer
alone.
The solventless, cationic polymer retention aids suitable for the purposes of
the
present invention are characterizied by the fact that they do not contain any
oil-phase.
They are liquid, aqueous, solventless dispersions of cationic polymers with
typical charge
densities of between 20 and 75% mole percent, solids content between 2 and
70%, and
viscosities in water at 1% of between 2000 and 20000 mPa sec.
The synthesis of such polymeric dispersions is described, for example, in U.
S.
Patent No. 5,480,934 where it is also indicated that they can be used as a
retention agent
in paper production, as a soil improvement agent or as a dispersing agent.
However, no
4
CA 02405649 2002-09-27
suggestion is made in this patent that they could be employed as a component
of the
phenolic resin/PE0 system, resulting in the above mentioned advantages.
The solventless cationic polymer retention aid and phenolic resin may enter
the
furnish separately at two different points of addition or together at the same
point of
addition, i.e. they can be used in sequence or together, and their combination
reacts much
more favourably with PEO than if either component is used alone. The
solventless
cationic polymer retention aid and the phenolic resin can be added to the
furnish either
before or after PEO addition.
Solventless cationic polymers are suitable for the purposes of the present
invention regardless of the number, type or concentration of the monomers used
to make
them and they can be in the form of a liquid or dried to a powder. Examples of
such
polymers are those marketed by Degussa under trade names Praestaret K-325 and
Praestaret K-350 as well as Praestol E-125 and Praestor E-150.
Thus, the present invention provides a papermaking furnish comprising a
combination of a solventless cationic polymer retention aid with phenolic
resin and
polyethylene oxide, as a retention system for retaining fines, fillers and
other
papermaking chemicals in the paper sheet.
In a preferred application, the amount of the solventless cationic retention
aid is
0.05 kg/ton to 10 kg/ton based on the weight of dry fibers; the amount of
phenolic resin is
0.05 kg/ton to 10 kg/ton of actual resin in the as-supplied material per ton
of dry fibers;
and the amount of polyethylene oxide is 5 g/ton to 500 g/ton based on the
weight of dry
fibers, the "ton" being a metric tonne.
The preferred ratio of solventless cationic polymer retention aid to phenolic
resin
CA 02405649 2002-09-27
is from 200:1 to 1:200; that of phenolic resin to FEO from I 00:1 to 1:100 and
that of
solventless cationic polymer retention aid to PEO is from I :2000 to 2000:1.
The invention also includes a method of increasing retention rate and drainage
in
a papermaking furnish by adding to the furnish an effective amount of a
solventless
cationic polymer retention aid in combination with phenolic resin and
polyethylene
oxide. The ei~ective amount will depend on the type of pulp being dewatered
and on the
other additives being used. It can readily be established by trial and error
before
establishing the appropriate amount for a given furnish. The preferred amounts
are those
already indicated above.
In a further embodiment of the present invention, it has been found that a
further
increase in sheet drainage and machine speed are achieved when the solventless
cationic
polymer retention agent is added last, after the PEO addition and after the
last point of
shear.
In a still further embodiment of this invention, the filler is pretreated with
the
solventless cationic polymer retention aid before it is added to the stock.
This
pretreatment is a preflocculation approach and it results in a better
dispersion of the filler
throughout the stock, better finesJfiller retention and better opacifying
properties. The
pretreated filler is dosed into the stock before the last point of shear and
the PEO is
preferably dosed near the head box, thus capturing the filler particles as
well as other
fines and fibers in an apparent network structure.
In summary, this invention utilizes the synergism between the phenolic resin
and
the solventless cationic polymer retention aid to enhance the performance with
polyethylene oxide and to allow the use of polyethylene oxide and phenolic
resin in a
CA 02405649 2002-09-27
wider range of applications, as well as improving existing newsprint
applications.
Furthermore, the synergistic phenolic resin/ solventless cationic polymer
retention aid
combination gives further beneficial effects if the solventless cationic
polymer retention
aid is premixed with the filler prior to dosing into the stock and reaction
with
polyethylene oxide. These effects have been confirmed with acidic and neutral
furnishes
and a variety of fillers including kaolin, calcite, bentonite and titanium
dioxide.
The practice of this invention enables the benefits of polyethylene oxide to
be
realized in more papermaking applications than is possible at present. These
benefits
include a more favourable sheet formation than that produced by polyacrylamide
retention agents, an ability to fix pitch contaminants in the sheet and the
generally lower
dosage rate than with polyacrylamide systems, leading to potentially lower
steam
consumption in the driers because of the smaller amount of bound water. Other
benefits
obtained by the practice of this invention are its favourable reaction with
starch, and its
ability to provide a superior flocculating pretreatment of the filler in order
that the
activated filler be more fully dispersed throughout the stock prior to its
capture by the
addition of the polyethylene oxide component. The provision of a superior
flocculating
pretreatment of the filler allows the filler to attain its best opacifying
power while at the
same time its capture by polyethylene oxide ensures good filler retention.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention will now be described with reference to
the drawings, in which:
Fig. 1 is a schematic representation of an arrangement in which the
solventless
polymer and the phenolic resin are introduced together into the papermaking
furnish;
7
CA 02405649 2002-09-27
Fig. 2 is a schematic representation of an arrangement in which the
solventless
polymer and the phenolic resin are introduced separately from one another into
the
papermaking furnish;
Fig. 3 is a schematic representation of an arrangement in which the
solventless
polymer is added last into the papermaxing furnish; and
Fig. 4 is a schematic representation of an arrangement in which the filler is
pretreated with the solventless polymer.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described with reference to the appended drawings
which illustrate some preferred embodiments thereof and in which the same
elements are
identified by the same reference numbers.
Thus, Fig. 1 illustrates a schematic arrangement of a papermaking process in
which the fan pump 10 forms the last point of shear after which the furnish
proceeds to
the screen 12 and from the screen to the hea~dbox 14. In this embodiment, the
solventless
polymer and the phenolic resin are introduced together into the furnish
between the fan
pump 10 and the screen 12 before the introduction of PEO.
According to the embodiment of Fig. 2, the solventless polymer is added to the
furnish in advance of the fan pump 10 and prior to the introduction of the
phenolic resin
and PEO which are added between the fan pump 10 and the screen 12. The
solventless
polymer is added here as a fiber pretreatment micropolymer.
In the embodiment of Fig. 3, the solventless polymer is added last after the
screen
12 and just in advance of the headbox 14. It acts here as a drainage aid.
Finally, in the embodiment of Fig. 4, the solventless polymer is added as a
filler
R
CA 02405649 2002-09-27
pretreatment in advance of the fan pump 10. Here, the phenolic resin is also
added in
advance of the fan pump 10, but after the pretreated filler. PEO is added
between the fan
pump 10 and the screen 12.
It should be noted that the illustrated arrangements are in no way limitative.
EXAMPLES
To test the various features of the present invention described above, the
following laboratory test procedures were used.
For retention without pad formation and turbidity tests a Dynamic drainage jar
(DDJ) was used with a baffled cylinder and the speed of the stirrer was set at
between
500 and 1000 rpm.
For retention with pad formation, drainage, and formation tests a Dynamic
Drainage Analyzer (DDA) was used. The objective in using the DDA was to be
able to
come as close to papermaking conditions as possible. The DDA is conceived to
measure
drainage rates through a forming pad. As a result, the measured retention is
higher than
I S that obtained using the dynamic drainage jar (DDJ), where no pad is
formed. Since a pad
is formed in the experiment, the formation of the formed wet sheet can also be
obtained.
~ Drainage
Drainage in the DDA is measured as the time from the start of the run until
air
starts being sucked through the sheet and it is automatically computed to
within one
hundredth of a second. The drainage is affected by many factors, for example
grammage,
vacuum, sample volume, type of stock, temperature, wire, and chemicals. It is
usually
desirable to use the same furnish consistency as in the mill. However, for
furnishes with
high freeness and fast drainage it can improve the experimental accuracy if a
higher
9
CA 02405649 2002-09-27
solids content or larger sample volume is used. The opposite is true of a low
freeness
fiunish.
~ Retention
Retention is defined as the amount of fiber retained on the wire compared to
the
amount of fiber going through. The retention in DDA experiments is inherently
higher
than on a paper machine. However, it correlates very well with the values
found with a
Britt jar.
The present invention will be illustrated by the following examples, however,
without being restricted thereto.
EXAMPLE 1
A 1.06% cellulosic fibre slurry consisting of 50% TMP (thermo mechanical pulp
- hydrosulfite bleached), 20% DIP (de-inked pulp) and 30% broke was taken from
a
newsprint mill. The slurry had a clay filler content of 20%. The pH of the
slurry was set
at 4.5.
For retention and turbidity tests a Dynamic drainage jar (DDJ) was used with a
baffled cylinder and the speed of the stirrer was set at 550 rpm. A 500 ml
sample was
used for testing. FPR indicates the first pass retention.
For drainage, formation, and retention (with pad formation) tests a Dynamic
Drainage Analyzer (DDA) was used with a bailed cylinder and the speed of the
stirrer
was set at 1000 rpm. A 800 ml sample was used for testing. The vacuum was set
at 500
mBar.
CA 02405649 2002-09-27
Tables l and 2 below show the results when conventional phenol formaldehyde
resin-polyethylene oxide retention system is compared to phenol formaldehyde
resin-
polyethylene oxide - solventless cationic polymer flocculant retention system.
In the
tables the turbidity is indicated in nephelometric turbidity units (ntu).
TABLE 1. DDJ TESTll~IG
ProductProduct ProductProductProductProduct R- TurbidityNormalizied
ntu Cost
Name Dose Name Dosage Name Dosage (h) (O to
(9It) (qlt) (plt) 100)
Blank 0 0 0 0 0 43.58~G28S 0
Solventless
Polymer
Flocculent
added
before
nol'a;
resin
and
PEO
solventless,200 phenoAc240 polyethylene30 45.85%2T5 38.4
cationic resin o~dde
polymer400 240 30 48.02%248 62.3
retention600 240 30 46.33%258.6 68.2
aid 800 240 30 46.50%229.6 84.0
1000 240 30 48.83%227 100.0
Solventless
Polymer
Floccul~t
added
after
henolic
resin
and
PEO
phenobc240 Polyethylene30 solventless,200 45.08%248.5 36.4
resin obde cationic
240 30 polymer400 45.2T%247 52.3
retention
aid
240 30 600 4b.88%238 68.2
240 30 800 4T.11%235 84.1
240 30 1000 4T.36%234.5 100.0
8olventless locculaM
Polymer added
F between
lic
resin
and
PEO
phenoUc240 Solventless,200 polyethylene30 45.80%248.5 38.4
resin cationic opde
240 polymer400 30 46.88%248 52.3
240 retention600 30 46.24%243.5 88.2
aid
240 800 30 46.30%228 84.1
240 1000 30 46.34%222 100.0
phanolic
rosin
and
PEO
alone
solventless,0 phenoAc240 polyethylene30 43.86 242 20.5
cationic0 resin 480 obde 60 44.07%240 40.8
polymer0 T20 90 44.23%238 61.4
retention0 980 120 44.66%231 81.8
aid
Solventless
Polyrrwr
Flocculant
alone
solventiess,200 phenoGc0 polyethylene0 42.92%280 15.9
cationic resin o~ade
polymer400 0 0 43.82%280 31.8
retention800 0 0 44.22%288 4T.7
aid 800 0 0 46.26~fiZT8 83.8
1000 0 0 46.82%275 78.6
11
CA 02405649 2002-09-27
TABLE 2. DDA TESTING
ProductProductProductProductProductProductRstwrtionDrainpeNomwlizad
Cost
Name Dose Name DosaOe Name Dosage (9G) (sac) (0 to
(~ (0It) (yltj 100)
Blank 0 0 0 0 0 78.14 57.50 0
Solventless
Polymer
Flocculant
added
before
Phenolic
resin
and
PEO
soNet4less,500 phenolic240 polyethylene30 78.14 58.28 66.8
resin
cationic oxide
polymer500 800 100 78.10 86.10 100
retention1000 240 30 78.08 64.14 82.6
aid
Solventless
Polymer
Flocculant
added
after
Phenolic
resin
and
PEO
phenolic240 polyethylene30 solvenbess,500 77.68 58.84 55.8
re8i11 0xid8 CatIOnIC
480 80 polymer500 78.25 68.97 74.7
240 30 reter~lon1000 81.70 58.80 92.6
aid
800 100 500 83.28 60.32 100.0
entlsssolymer
P FlocculaM
added
between
Phsnolic
rosin
and
PEO
pherwlic240 soAror~s,500 poHethylene30 78.84 65.63 55.8
resin cationic oxide
240 polymer1000 30 78.95 66.20 82.8
retention
aid
Phenolic
resin
and
PEO
alone
phenollo24o polyethylene30 77.86 56.44
resin la.o
oxide
480 60 80.27 66.47
37.8
800 100 83.38 48.86
63.2
ventlessolymer
P alone
soNenUess,200 phsno~c0 polyethylene0 76.08 57.76 14.7
resin
cationic oxide
polymer400 0 0 77.32 58.82 29.5
retention600 0 0 77.27 55.56 44.2
aid
800 0 0 77.28 65.88 68.9
1000 0 0 77.54 58.34 73.6
EXAMPLE 2
A 0.992% cellulose fibre slurry consisting of 10% Kraft and 90% TMP (thermo
mechanical pulp - hydrosulfite bleached) was taken from a specialty newsprint
mill. The
slurry had a clay filler content of 10%. The pH of the slurry was set at 6.0
For drainage, formation, and retention (with pad formation) tests a Dynamic
Drainage Analyzer (DDA) was used with a baffled cylinder and the speed of the
stirrer
was set at 1000 rpm. A 800 ml sample was used for testing. The vacuum was set
at 500
mBar.
12
CA 02405649 2002-09-27
Table 3 below shows the results when conventional phenol formaldehyde resin-
polyethylene oxide retention system is compared to phenol formaldehyde resin-
polyethylene oxide - solventless, cationic polymer flocculant retention
system.
TABLE 3. DDA TESTING
ProductProductProductProductP~~- p~~ R Drairw0eNon~nalizsd
Name Doss Name Dosa~s Name Dosa~a (9G) (sec) Cost
(~ (p/t) (~
0 to
100
Blank 0 0 0 0 0 78.87 83.93 0
Solventless
Polymer
Flocculant
added
before
Phenolic
resin
and
PEO
SoIveMless,350 phenouc1000 Polyethylene125 83.88 38.70 83.1
cationic resin obde
polymer350 600 150 83.60 37.20 73.2
retention475 700 175 83.40 34.70 89.3
aid
Phenolic
resin
and
PEO
alone
phenolic polyetfiylene150 81.12 48.60
0 30.3
resin o~dde
1000 200 82.2b 58.20
7T.8
1500 150 83.16 46.30
86.4
200o ms so.s~ s~.ro
~oo.o
IveMless
Polymer
alone
Solven>less,500 phenolic0 , polyethylene0 81.60 36.b0 29.2
cationic resin obde
polymer1000 0 0 80.88 51.00 ti8.4
retention
aid
EXAMPLE 3
A 1.12% cellulose fibre slurry consisting of 5% Kraft, 70% TMP (thermo
mechanical pulp - hydrosulfite bleached) and 25% deinked pulp (DIP) was taken
from a
specialty newsprint mill using recycled fibres. The slurry had a clay filler
content of 30%.
The pH of the slurry was set at 6.2
For retention and turbidity tests a Dynamic drainage jar (DDJ) was used with a
baffled cylinder and the speed of the stirrer was set at 550 rpm. A 500 ml
sample was
used for testing. FPR refers to the first pass retention and FPAR the first
pass ash
retention.
13
CA 02405649 2002-09-27
Table 4 below shows the results when conventional phenol formaldehyde resin-
polyethylene oxide retention system is compared to phenol formaldehyde resin-
polyethylene oxide - solventless, cationic polymer flocculant retention
system.
TABLE 4. DDJ TESTING
ProductProductproductProductProductProductFPRlFPARTurbidityNormalized
ntu
Name Dose Name DosaOa Name DosaOa (%) Cost
(plt) (~ (~
O to
100
Blank 0 0 0 0 0 35.6!46.488.1 0
Solventless
Polymer
Flocculant
added
bofore
lic
r~ssin
and
PEO
solveMless,300 phenouc420 polyethylene60 48.0158.238.2 8T.8
cationic resin obde
polymer
retention
aid
SoIveMlass
Polymer
Fkxwlant
added
after
olio
resin
and
PEO
phenolic420 polyethylene60 soHerriless,300 42.2!56.634.1 87.8
resin oxide cationic
polymer
retention
aid
SoNaMless
Polymer
Flocculant
added
between
nolic
resin
and
PEO
phenolic420 soNerdless,300 polyethylene60 45.4157.836.2 87.8
resin cationic o~dde
polymer
retention
aid
phenolic
resin
and
PEO
alone
soNeMless,0 phenolic0 polyethylene60 37.1147.835.7 26.2
cationic resin oxide
~
polymer 420 60 42.8164.840.7 60.1
reterttion 700 100 41.3143.342.6 100.0
aid
Solventiess
Polyrrwr
Flocculant
alone
solventiess,300 phenoGc0 polyethylene0 41.1143.335.2 3T.8
cationic resin o~dde
polymer
retention
aid
For this same mill, the polymer was tested on the machine. The solventless,
cationic flocculant was added before the phenolic resin and PEO (in the thick
stock). The
table below shows the results when conventional phenol formaldehyde resin-
polyethylene oxide retention system is compared to phenol formaldehyde resin-
polyethylene oxide - solventless, cationic polymer flocculant retention
system. All
14
CA 02405649 2002-09-27
relevant machine parameters and polymer dosages are tabulated below in Table
5.
TABLE 5. MACHINE PARAMETERS - BEFORE AND AFTER ADDITION
OF THE SOLVENTLESS CATIONIC POLYMER RETENTION AID.
Parameter Without solventless With solventless
cationic cationic polymer
polymer retention aid retention aid
Grade 643.01 643.01
Gramma a m2 41 41
S eed m/min 813 855
De-inked u1 DIP 0 0
Softwood bleached kraft 25.2 25
SBK
1 st section Steam kPa 114 100
2nd section Steam kPa 177 210
3rd section Steam kPa 273 258
Head Box consistenc % 1.154 1.02
White water consistenc 0.686 0.537
%
First ass retention % 40.66 47.1
Head box ash content % 14.87 8.43
White water ash content 21.1 13.23
%
First ass ash retention 12.3 17.44
%
of ash in the sheet 3 2.3
of alphatex clay added 2.01 1.89
to
headbox
Cationic demand me/l 286 213
Headbox turbidit ntu 121 43
White water turbidit ntu 90 32
Solventless cationic polymer0 300
dosa a /T
Phenolic resin dosa a /T 560 235
Coa ulant dosa a IT 210 0
Pol eth lens oxide dosa 59 38
a /T
Cost Decrease % ---- -12.60%
The saving of 12.60% in the cost of production represents a considerable
advantage in papermaking.
CA 02405649 2002-09-27
The above results clearly indicate that the solventless cationic polymer-
phenolic
resin-PEO combination is the best system to use based on relative costs. The
retention
systems using the phenolic resin/PE0 in combination with the solventless
cationic
polymer yield the highest DDJ and DDA fines retention, the lowest turbidities
and the
best drainage rate - a clear indication of the programs ability to retain
fines and colloidal
substances. This is especially true for the following addition sequence:
solventless
cationic polymer/phenolic resin/polyethylene oxide. In contrast the
solventless cationic
polymer or the phenolic resin/polyethylene oxide system used alone result in
lower
retentions and/or higher turbidities.
From these results it can be concluded that not only is there a synergy
between the
phenolic resin/PEO system and the solventless cationic polymer, but also that
it is the
most cost effective system.
It should be noted that this invention is not limited to the specific
embodiments
described and exemplified above, but that various modification obvious to
those skilled
in the art can be made without departing from the invention and the scope of
the
following claims.
1~
