U.S. patent application number 11/782872 was filed with the patent office on 2008-01-17 for cellulosic product and process for its production.
This patent application is currently assigned to Akzo Nobel N.V.. Invention is credited to Jerker Nilsson, Marek Tokarz.
Application Number | 20080011438 11/782872 |
Document ID | / |
Family ID | 32717633 |
Filed Date | 2008-01-17 |
United States Patent
Application |
20080011438 |
Kind Code |
A1 |
Tokarz; Marek ; et
al. |
January 17, 2008 |
CELLULOSIC PRODUCT AND PROCESS FOR ITS PRODUCTION
Abstract
The present invention relates to a process for the production of
a cellulosic product which comprises (i) providing an aqueous
cellulosic suspension; (ii) adding to the suspension a clay having
3R.sub.2 stacking; and (iii) dewatering the obtained suspension.
The invention also relates to a process for the production of a
cellulosic product which comprises (i) providing an aqueous
cellulosic suspension; (ii) adding to the suspension a cationic
clay; (iii) adding to the suspension one or more drainage and
retention aids comprising at least one cationic polymer; and (iv)
dewatering the obtained suspension. The invention further relates
to a cellulosic product comprising clay having 3R.sub.2
stacking.
Inventors: |
Tokarz; Marek; (Kungalv,
SE) ; Nilsson; Jerker; (Goteborg, SE) |
Correspondence
Address: |
AKZO NOBEL INC.
INTELLECTUAL PROPERTY DEPARTMENT
120 WHITE PLAINS ROAD 3RD FLOOR
TARRTOWN
NY
10591
US
|
Assignee: |
Akzo Nobel N.V.
Velperweg 76
Arnhem
NL
6824 BM
|
Family ID: |
32717633 |
Appl. No.: |
11/782872 |
Filed: |
July 25, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10717276 |
Nov 18, 2003 |
7303654 |
|
|
11782872 |
Jul 25, 2007 |
|
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60427618 |
Nov 19, 2002 |
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Current U.S.
Class: |
162/164.4 ;
162/166; 162/181.8 |
Current CPC
Class: |
D21H 17/68 20130101;
Y10T 428/24455 20150115 |
Class at
Publication: |
162/164.4 ;
162/166; 162/181.8 |
International
Class: |
D21H 17/68 20060101
D21H017/68 |
Claims
1.-8. (canceled)
9. A process for the production of paper which comprises (i)
providing an aqueous cellulosic suspension; (ii) adding to the
suspension a clay having 3R.sub.2 stacking, the clay being added in
an amount of at least about 0.01% by weight, calculated as dry clay
on dry cellulosic suspension; and (iii) dewatering the obtained
suspension.
10. The process according to claim 9, wherein the clay is
cationic.
11. The process according to claim 9, wherein the clay is
hydrotalcite.
12. The process according to claim 9, wherein it further comprises
adding to the suspension one or more drainage and retention
aids.
13. The process according to claim 12, wherein the drainage and
retention aids comprise cationic polymer and anionic material.
14. The process according to claim 13, wherein the drainage and
retention aids comprise cationic polymer and anionic silica-based
particles.
15. The process according to claim 13, wherein the drainage and
retention aids comprise cationic polymer and anionic clay of
smectite type.
16. The process according to claim 12, wherein the drainage and
retention aids comprise cationic and anionic organic polymers.
17. The process according to claim 13, wherein the cationic polymer
is cationic starch or cationic acrylamide-based polymer.
18. The process according to claim 16, wherein the cationic polymer
is cationic starch or cationic acrylamide-based polymer.
19. The process according to claim 13, wherein the cationic polymer
contains one or more aromatic groups.
20. The process according to claim 9, wherein it further comprises
adding to the suspension one or more sizing agents.
21. A process for the production of paper which comprises (i)
providing an aqueous cellulosic suspension; (ii) adding to the
suspension a cationic clay in an amount of at least about 0.01% by
weight, calculated as dry clay on dry cellulosic suspension; (iii)
adding to the suspension one or more drainage and retention aids
comprising at least one cationic polymer, the cationic polymer
being added in an amount of at least about 0.001% by weight, based
on dry cellulosic suspension, (iv) dewatering the obtained
suspension.
22. The process according to claim 21, wherein the clay has
3R.sub.2 stacking.
23. The process according to claim 21, wherein the drainage and
retention aids comprise cationic polymer and anionic silica-based
particles.
24. The process according to claim 23, wherein the silica-based
particles have a specific surface area above 100 m.sup.2/g
25. The process according to claim 23, wherein the silica-based
particles are present in a sol having an S-value in the range of
from 8 to 50%,
26. The process according to claim 21, wherein the drainage and
retention aids comprise cationic polymer and anionic clay of
smectite type.
27. The process according to claim 21, wherein the drainage and
retention aids comprise cationic and anionic organic polymers.
28. The process according to claim 21, wherein the cationic polymer
is cationic starch or cationic acrylamide-based polymer.
29. The process according to claim 23, wherein the cationic polymer
is cationic starch or cationic acrylamide-based polymer.
30. The process according to claim 21, wherein the cationic polymer
contains one or more aromatic groups.
31. The process according to claim 21, wherein it further comprises
adding to the suspension one or more sizing agents.
32. The process according to claim 21, wherein the cellulosic
suspension contains filler.
33. A process for the production of paper which comprises (i)
providing an aqueous suspension containing cellulosic fibres, and
optional filler; (ii) adding to the suspension a cationic clay
having 3R.sub.2 stacking, the clay being added in an amount of at
least about 0.01% by weight, calculated as dry clay on dry
suspension; (iii) adding to the suspension at least one cationic
polymer in an amount of at least about 0.001% by weight, based on
dry suspension; (iv) adding to the suspension anionic silica-based
particles in an amount of at least about 0.001% by weight, based on
dry suspension; and (v) dewatering the obtained suspension.
34. The process according to claim 33, wherein it further comprises
adding to the suspension one or more sizing agents.
35.-40. (canceled)
Description
[0001] This application claims priority based on U.S. Provisional
Patent Application No. 60/427,618, filed Nov. 19, 2002
[0002] The present invention relates to a process for the
production of a cellulosic product which comprises treating
cellulosic fibres with clay having 3R.sub.2 stacking, and to a
process for the production of a cellulosic product which comprises
treating cellulosic fibres with cationic clay. The invention also
relates to a cellulosic product comprising clay having 3R.sub.2
stacking.
BACKGROUND OF THE INVENTION
[0003] Pulp suspensions are widely used for making cellulosic
products such as, for example, pulp and paper, and contain, apart
from cellulosic fibres, also compounds which have a negative impact
on the production process. Such compounds are found both in
cellulosic suspensions originating from virgin pulp and from
recycled pulp.
[0004] In virgin pulp suspensions such disturbing/detrimental
substances are primarily hemicellulose, lignin as well as
lipophilic and hydrophilic extractives. Apart from the cellulose,
these substances are to a varying extent dissolved or colloidally
dispersed into the process waters during the pulping and bleaching
operations. Compounds which are released during pulping and
bleaching operations are commonly referred to as pitch. Examples of
pitch include wood resins such as lipophilic extractives (fatty and
resin acids, sterols, stearyl esters, triglycerides), and also
fats, terpenes, terpeniods, waxes, etc.
[0005] In recycled pulp suspensions the compounds having a negative
influence on the paper making process mainly consist of glues,
hot-melt plastics inks and latex, just to mention a few
compounds--which are commonly referred to as stickies. Apart from
pitch and stickies the suspension also contains charged
contaminants like salts and various wood polymers of which the
charged, low charged or non-charged compounds compete with the
cellulose with respect to the adsorption and interaction with added
performance chemicals such as drainage and retention aids, sizing
agents, etc. Usually such disturbing compounds are referred to as
anionic trash.
[0006] All of the above-mentioned compounds interfere with the pulp
and paper making processes in various ways. For instance, some of
them precipitate due to changes in the properties of the pulp
suspension and are eventually deposited on various mechanical parts
of the paper machine such as, for example, screens and felts. Over
time, the deposits will lead to breakdowns on the paper machine
often in form of breaking of the paper web, whereby the paper
machine has to be stopped for cleaning. Furthermore, paper mills
tend to re-circulate the white water to a greater extent than
previously, which increases the presence of disturbing and
detrimental substances in the suspension.
[0007] Various additives have been used in order to decrease the
negative impact of the above-mentioned detrimental/disturbing
substances. For example, talc has been widely used for adsorbing
pitch and stickies. Also various types of clays have been employed
for reducing the impact of detrimental compounds.
[0008] Japanese laid-open patent application No. 1985-94687 relates
to a pitch-adsorbing agent containing hydrotalcite.
SUMMARY OF THE INVENTION
[0009] The present invention is generally directed to a process in
which cellulosic fibres are treated with a clay having 3R.sub.2
stacking. The present invention is also generally directed to a
process in which cellulosic fibres are treated with a cationic
clay. Furthermore, the invention is directed to a process for the
production of a cellulosic product which comprises adding a clay
having 3R.sub.2 stacking to an aqueous suspension containing
cellulosic fibres. The present invention is further generally
directed to a cellulosic product comprising a clay having 3R.sub.2
stacking.
[0010] The present invention further relates to a process for the
production of a cellulosic product which comprises (i) providing an
aqueous suspension containing cellulosic fibres; (ii) adding to the
suspension a clay having 3R.sub.2 stacking and optionally one or
more drainage (dewatering) and retention aids; and (iii) dewatering
the obtained suspension. The invention further relates to a process
for the production of a cellulosic product which comprises (i)
providing an aqueous suspension containing cellulosic fibres; (ii)
adding to the suspension cationic clay; (iii) adding to the
suspension one or more drainage (dewatering) and retention aids
comprising at least one cationic polymer; and (iv) dewatering the
obtained suspension. The cellulosic product produced is preferably
pulp and/or paper.
DETAILED DESCRIPTION OF THE INVENTION
[0011] It has surprisingly been found that the negative impact on
pulp and paper making processes by the presence of disturbing and
detrimental substances in aqueous cellulosic pulp suspensions,
specifically problems caused by pitch and stickies, can be reduced
by treating cellulosic fibres with a clay according to the
invention.
[0012] It has surprisingly also been found that the addition to
cellulosic suspensions of a clay according to the invention,
specifically a cationic and/or 3R.sub.2 clay, in conjunction with
additives used for pulp and paper making not only allows for
adsorption and removal of disturbing substances, but it also
improves the performance of the additives used in the process, as
compared to the situation when the clay is not added. Examples of
such additives for which improved performance is observed include
retention and dewatering aids, sizing agents, etc. preferably, the
clay is used together with one or more drainage and retention aids
comprising at least one cationic polymer. Thus, the present
invention provides improved drainage (dewatering) and retention in
pulp and paper making processes as well as improved sizing in paper
making processes, while simultaneously further reducing the content
of disturbing and detrimental substances in the cellulosic
suspension.
[0013] The clay according to the invention can be derived from
naturally occurring clays, chemically and/or physically modified
naturally occurring clays, and synthetic clays. Naturally occurring
clays normally have an essentially crystalline structure. However,
synthetically obtained clays may also additionally contain
amorphous material having essentially the same chemical composition
as the crystalline structures. The amount of amorphous material
present in synthetic clay depends mainly on the reaction parameters
used. The term "clay", as used herein, refers to clays having
essentially crystalline structure and also to clays containing both
crystalline and amorphous structures.
[0014] Clays are characterised by a layered structure wherein atoms
within the layers (lamellae) are cross-linked by chemical bonds,
while the atoms of adjacent layers interact mainly by physical
forces. The layers of the clay may be non-charged or charged
depending on the type of atoms present in the layers. If the layers
are charged, then the space between these layers, also designated
as the interlayer space, contains ions which have the opposite
charge with respect to the charge of the layers. The term "cationic
clay", as used herein, refers to clays having positively charged
layers and anions present in the interlayer space. The term
"anionic clay", as used herein, refers to clays having negatively
charged layers and cations present in the interlayer space. Usually
the ions in the interlayer space are exchangeable.
[0015] The clays according to the invention can virtually have any
anion, optionally also water molecules, present in the interlayer
space. Examples of common anions that can be present in the
interlayer space include NO.sub.3.sup.-a, OH.sup.-, Cl.sup.-,
Br.sup.-, I.sup.-, CO.sub.3.sup.2-, SO.sub.4.sup.2-,
SiO.sub.3.sup.2-, CrO.sub.4.sup.2-; BO.sub.3.sup.2-, MnO.sub.4--,
HGaO.sub.3.sup.2, HVO.sub.4.sup.-, and ClO.sup.4-, as well as
pillaring or intercalating anions such as V.sub.10O.sub.28.sup.6-
and MO.sub.7O.sub.24.sup.6-, mono-carboxylates like acetate,
dicarboxylates such as oxalate, and alkyl sulphonates such as
lauryl sulphonate; usually hydroxide and carbonate. Naturally
occurring clays of the invention commonly have carbonate anions in
the interlayer space.
[0016] The layer or lamella of the clay suitably comprises at least
two different metal atoms having different valences. Suitably, one
metal atom is divalent and the other metal atom is suitably
trivalent. However, the layer may also comprise more than two metal
atoms. The charge of the layer is governed by the ratio of metal
atoms having different valences. For instance, a higher amount of
trivalent metals will render a layer having an increased density of
the positive charge. Suitably, the clay of the invention comprises
layers containing divalent and trivalent metals in a ratio so that
the overall charge of the layers is cationic, and the interlayers
comprise anions. Preferably, the layers essentially consist of
divalent and trivalent metals in such a ratio that the overall
charge of the layers is cationic.
[0017] Synthetically produced and naturally occurring clays
according to the invention can be characterised by the general
formula:
[M.sub.m.sup.2+M.sub.n.sup.3+(OH).sub.2m+2n]X.sub.n/z.sup.Z-.bH.sub.2O,
wherein m and n, independently of each other, are integers having a
value such that m/n is in the range of from 1 to 10, preferably 1
to 6, more preferably 2 to 4 and most preferably values around 3; b
is an integer having a value in the range of from 0 to 10, suitably
a value from 2 to 6, and often a value about 4; X.sub.n/z.sup.Z- is
an anion where z is an integer from 1 to 10, preferably from 1 to
6, suitable X.sub.n/z.sup.Z- including NO.sub.3.sup.-, OH.sup.-,
Cl.sup.-, Br.sup.-, I.sup.-, CO.sub.3.sup.2-, SO.sub.4.sup.2-,
SiO.sub.3.sup.2-, CrO.sub.4.sup.2-, BO.sub.3.sup.2-,
MnO.sub.4.sup.-, HGaO.sub.3.sup.2-, HVO.sub.4.sup.-,
ClO.sub.4.sup.-, pillaring and intercalating anions such as
V.sub.10O.sub.28.sup.6- and MO.sub.7O.sub.24.sup.6-,
mono-carboxylates like acetate, dicarboxylates such as oxalate, and
alkyl sulphonates such as lauryl sulphonate; M.sup.2+ is a divalent
metal atom, suitable divalent metal atoms including Be, Mg, Cu, Ni,
Co, Zn, Fe, Mn, Cd, and Ca, preferably Mg; M.sup.3+ is a trivalent
metal atom, suitable trivalent metal atoms including Al, Ga, Ni,
Co, Fe, Mn, Cr, V, Ti and In, preferably Al. Preferably, the
divalent metal is magnesium and the trivalent metal is aluminum,
rendering the general formula:
[M.sub.m.sup.2+M.sub.n.sup.3+(OH).sub.2m+2n]X.sub.n/z.sup.Z-.bH.sub.2O.
[0018] According to one preferred embodiment of the invention, the
clay is cationic. Examples of suitable cationic clays according to
the invention include hydrotalcite, manasseite, pyroaurite,
sjogrenite, stichtite, barbertonite, takovite, reevesite,
desautelsite, motukoreaite, wermiandite, meixnerite, coalingite,
chloromagalumite, carrboydite, honessite, woodwardite, iowaite,
hydrohonessite, mountkeithite, etc. Examples of terms also used to
describe these clays include hydrotalcite-like compounds and
layered double hydroxide compounds.
[0019] According to another preferred embodiment of the invention,
the clay has a specific stacking, namely a 3R.sub.2 stacking; this
type of clay is herein also referred to as "3R.sub.2 clay". The
3R.sub.2 clay is preferably cationic, and the clay can be any of
those mentioned above. Preferably, the clay is
magnesium-aluminum-containing 3R.sub.2 clay. The 3R.sub.2 clay
suitably has a three-layer repeat. The 3R.sub.2 stacking polytype
of clay has a different layer arrangement/stacking than the
3R.sub.1 stacking polytype, herein also referred to as "3R.sub.1
clay". The 3R.sub.1 and 3R.sub.2 clays can be distinguished from
each other by X-ray diffraction/reflections patterns by the
intensities of the 107 and 108 d.sub.hkl reflections. The 3R.sub.2
clay has a stronger d.sub.hkl 107 reflection close to 45.degree. 2
theta (according to Drits and Bookin), whereas the 3R.sub.1 clay
has a stronger d.sub.hkl reflection close to 47.degree. 2 theta
(the d.sub.hkl 108 reflection). The presence of peaks at both
45.degree. 2 theta and 47.degree. 2 theta indicates the presence of
a mixture of 3R.sub.1 and 3R.sub.2 clays. It is understood that the
precise 2 theta values for the 107 and 108 d.sub.hkl reflections
will depend on the lattice "a" and "c" structural parameters for
the clay, for example Mg--Al clay. Of course, there are some other
differences in the X-ray diffraction patterns as well, but it is
believed that this is the best range of the d.sub.hkl reflections
to make such a distinction. Furthermore, the clay having 3R.sub.2
stacking has a different morphology compared to that of
conventional 3R.sub.1 clays, as can be detected by the SEM
examinations. The 3R.sub.2 clay appears to have a structure with
irregular flake-like platelets which are randomly agglomerated,
whereas the conventional and prior art 3R.sub.1 clays have regular
well-formed layers of platelets which are arranged in the usual
book-stack form.
[0020] Clays having 3R.sub.2 stacking according to the invention
can be prepared by hydrothermal treatment (solvo thermal) of a
slurry containing an aluminium source and a magnesium source.
Examples of suitable clays having 3R.sub.2 stacking, e.g. Mg--Al
clays, according to the invention and methods for their preparation
include those disclosed in International Patent Application
Publication No. WO 01/12550, the disclosure of which is hereby
incorporated herein by reference.
[0021] According to one preferred embodiment of the invention, the
clay having 3R.sub.2 stacking is added to an aqueous suspension
containing cellulosic fibres in a process for the production of a
cellulosic product like pulp and paper. It has been observed that
if the 3R.sub.2 clay is added to such a suspension, improved
removal of disturbing substances such as pitch and stickies is
achieved over the addition of conventional clay having 3R.sub.1
stacking.
[0022] The clay is suitably mixed with cellulosic fibres by being
added to an aqueous suspension containing cellulosic fibres (herein
also referred to as "aqueous cellulosic suspension" and "cellulosic
suspension") either as a slurry (suspension) or powder, which can
be easily dispersed in water. The suspension or powder of clay may
further also contain other components such as, for example,
dispersing and/or protecting agents, which can contribute to the
overall effect of the clay. Such agents can have non-ionic, anionic
or cationic character. Examples of suitable protective agents or
colloids include water-soluble cellulose derivatives, e.g.
hydroxyethyl- and hydroxypropyl-, methylhydroxypropyl- and
ethyl-hydroxyethyl-cellulose, methyl- and carboxymethylcellulose,
gelatine, starch, guar gum, xanthan gum, polyvinyl alcohol, etc.
Examples of suitable dispersing agents include, non-ionic agents,
e.g. ethoxytated fatty acids, fatty acids, alkyl phenols or fatty
acid amides, ethoxylated and non-ethoxylated glycerol esters,
sorbitan esters of fatty acids, non-ionic surfactants, polyols
and/or their derivatives; anionic agents, e.g. as alkyl or
alkylaryl sulphates, sulphonates, ethersulphonates, polyacrylic
acid; and cationic agent, e.g. esterquats obtained by reacting
alkanolamines with mixtures of fatty acids and dicarboxylic acids,
optionally alkoxylating the resulting esters and quatemising the
products, quatemised fatty acid amides, betaines, dimethyl dialkyl
or dialkylaryl ammonium salts, and cationic gemini dispersing
agents.
[0023] The clay can be added at any point in the cellulosic product
production process starting from the point where wood chips are
disintegrated up to the point in the process where dewatering of
the cellulosic suspension takes place. The cellulosic product can
be in any form such as, for example, in the form of a web or sheet,
e.g. pulp sheets and paper sheets.
[0024] According to a preferred embodiment of the invention, the
clay is added to a cellulosic suspension of a pulp making process.
The clay can be added prior to or after the pulping process which
can be kraft, mechanical, thermo-mechanical, chemomechanical,
chemo-thermo-mechanical pulping processes. The clay can be added
just before the pulping process or directly to the pulping process,
such as to the digester. However, it is preferred that the clay is
added to the cellulosic suspension subsequent to chemical digestion
such as after the brown stock washer, or after refining of
(chemo-)mechanical pulp. Usually, the cellulosic pulp is bleached
in a multi stage bleaching process comprising different bleaching
stages and the clay can be added to any bleaching sequence.
Examples of suitable bleaching stages include chlorine bleaching
stages, e.g. elementary chlorine and chlorine dioxide bleaching
stages, non-chlorine bleaching stages, e.g. peroxide stages like
ozone, hydrogen peroxide and peracetic acid, and combinations of
chlorine and non-chlorine bleaching and oxidizing stages,
optionally in combination with reducing stages like treatment with
dithionite. The clay can be added to the cellulosic suspension
directly to a bleaching stage, preferably to the mixer prior to the
bleaching tower, at any point between the bleaching and washing
stages, and also to a washing stage where the clay may be partly or
wholly removed, e.g. in the displacement section.
[0025] According to another preferred embodiment of the invention,
the clay is added to a cellulosic suspension of a paper making
process. The clay can be added to the cellulosic suspension at any
point of the paper making process such as to the thick stock, thin
stock, or to the white water before it is recycled, e.g. prior to
the thin stock feed box. Preferably, the clay is added to the thick
stock. The cationic clay can also be added to more than one point
of the pulp and/or paper making processes. For instance, in
integrated pulp and paper mills, the clay can be added in the
process for pulp production, and optionally also in the process for
paper production, and one or more drainage and retention aids can
be added in the process for paper production. Such processes can
include dewatering the cellulosic suspension containing clay,
diluting the suspension obtained, adding to the diluted suspension
one or more drainage and retention aids and dewatering the
suspension containing the drainage and retention aids.
[0026] The term "paper", as used herein, include not only paper and
the production thereof, but also other cellulosic fibre-containing
sheet or web-like products, such as for example board and
paperboard, and the production thereof. The process can be used in
the production of paper from different types of aqueous suspensions
of cellulosic (cellulose-containing) fibres and the suspensions
should suitably contain at least 25% by weight and preferably at
least 50% by weight of such fibres, based on a dry substance. The
cellulosic fibres can be based on virgin and/or recycled fibres,
and the suspension can be based on fibres from chemical pulp such
as sulphate, sulphite and organosolve pulps, mechanical pulp such
as thermo-mechanical pulp, chemo-thermo-mechanical pulp, refiner
pulp and ground wood pulp, from both hardwood and softwood, and can
also be based on recycled fibres, optionally from de-inked pulps,
and mixtures thereof. If recycled fibres are used the suspended,
recycled fibres are commonly treated in order to separate the
non-fibre components such as, for example, printing inks and
various paper surface treatment compounds, e.g. latex from the
fibres. In a preferred embodiment, the clay is suitably added to
such a de-inking treatment process.
[0027] According to the invention, the clay is suitably added to
the cellulosic suspension in an amount of from about 0.01% by
weight to about 5% by weight, preferably form about 0.05% by weight
up to about 2% by weight, calculated as dry clay on a dry
cellulosic suspension.
[0028] The present invention also relates to a process for the
production of a cellulosic product, e.g. pulp and paper, which
comprises adding to the suspension a clay having 3R.sub.2 stacking
and optionally one or more drainage (dewatering) and retention
aids. In a preferred embodiment, the drainage and retention aids
comprise at least one cationic polymer. It is preferred that the
clay and drainage and retention aids are used in a process for the
production of paper. The term "drainage and retention aid", as used
herein, refers to a component (agent, additive) which, when being
added to an aqueous cellulosic suspension, give better drainage
and/or retention than is obtained when not adding said component.
The term "cationic polymer", as used herein, refers to an organic
polymer having one or more cationic groups, preferably an overall
cationic charge. The cationic polymer may also contain anionic
groups, and such polymers are commonly also referred to as
amphoteric polymers.
[0029] The cationic polymer according to the invention can be
derived from natural and synthetic sources. Examples of suitable
cationic polymers derived from natural sources include
polysaccharides, e.g. starches, guar gums, celluloses, chitins,
chitosans, glycans, galactans, glucans, xanthan gums, pectins,
mannans, dextrins, preferably starches and guar gums. Examples of
suitable starches include potato, corn, wheat, tapioca, rice, waxy
maize, barley, etc. Examples of suitable synthetic, cationic
polymers include chain-growth polymers, e.g. vinyl addition
polymers like acrylate-, acrylamide- and vinylamide-based polymers,
and step-growth polymers, e.g. polyurethanes. Suitably, the
cationic polymer is selected from polysaccharides, e.g. starches,
and vinyl addition polymers, e.g. acryl-amide-based polymers, and
mixtures thereof.
[0030] The cationic polymer, specifically cationic polysaccharides
and vinyl addition polymers, may also comprise aromatic groups
which can be present in the polymer backbone or, preferably, the
aromatic groups can be a pendent group attached to or extending
from the polymer backbone or be present in a pendent group that is
attached to or extending from the polymer backbone (main-chain).
Examples of suitable aromatic groups include aryl, aralkyl and
alkaryl groups, e.g. phenyl, phenylene, naphthyl, phenylene,
xylylene, benzyl and phenylethyl; nitrogen-containing aromatic
(aryl) groups, e.g. pyridinium and quinolinium, as well as
derivatives of these groups, preferably benzyl. Examples of
cationically charged groups that can be present in the cationic
polymer as well as in monomers used for preparing the cationic
polymer include quaternary ammonium groups, tertiary amino groups
and acid addition salts thereof.
[0031] The cationic organic polymer having an aromatic group is
preferably a polysaccharide represented by the general structural
formula (I): ##STR1## wherein P is a residue of a polysaccharide;
A.sub.1 is a group attaching N to the polysaccharide residue,
suitably a chain of atoms comprising C and H atoms, and optionally
0 and/or N atoms, usually an alkylene group with from 2 to 18 and
suitably 2 to 8 carbon atoms, optionally interrupted or substituted
by one or more heteroatoms, e.g. O or N, e.g. an alkyleneoxy group
or hydroxy propylene group (--CH.sub.2--CH(OH)--CH.sub.2--);
K.sub.1 and K.sub.2 are each H or, preferably, a hydrocarbon group,
suitably alkyl, having from 1 to 3 carbon atoms, preferably 1 to 2
carbon atoms; Q is a substituent containing an aromatic group,
suitably a phenyl or substituted phenyl group, which can be
attached to the nitrogen by means of an alkylene group usually
having from 1 to 3 carbon atoms, suitably 1 to 2 carbon atoms, and
preferably Q is a benzyl group (--CH.sub.2--C.sub.6H.sub.5); n is
an integer, usually from about 2 to about 300,000, suitably from 5
to 200,000 and preferably from 6 to 125,000 or, alternatively,
K.sub.1, K.sub.2 and Q together with N form a aromatic group
containing from 5 to 12 carbon atoms; and X.sup.- is an anionic
counterion, usually a halide like chloride. Suitable
polysaccharides of the general formula (I) include those mentioned
above. Cationic polysaccharides according to the invention can also
contain anionic groups, preferably in a minor amount. Such anionic
groups may be introduced in the polysaccharide by means of chemical
treatment or be present in the native polysaccharide.
[0032] The cationic organic polymer having an aromatic group may
also be a chain-growth polymer. The term "chain-growth polymer", as
used herein, refers to a polymer obtained by chain-growth
polymerisation, also being referred to as chain reaction polymer
and chain reaction polymerisation, respectively. Examples of
suitable chain-growth polymers include vinyl addition polymers
prepared by polymerisation of one or more monomers having a vinyl
group or ethylenically unsaturated bond, for example a polymer
obtained by polymerising a cationic monomer or a monomer mixture
comprising a cationic monomer represented by the general structural
formula (II): ##STR2## wherein L.sub.3 is H or CH.sub.3; L.sub.1
and L.sub.2 are each H or, preferably, a hydrocarbon group,
suitably alkyl, having from 1 to 3 carbon atoms, preferably 1 to 2
carbon atoms; A.sub.2 is O or NH; B.sub.2 is an alkyl or alkylene
group having from 2 to 8 carbon atoms, suitably from 2 to 4 carbon
atoms, or a hydroxy propylene group; Q is a substituent containing
an aromatic group, suitably a phenyl or substituted phenyl group,
which can be attached to the nitrogen by means of an alkylene group
usually having from 1 to 3 carbon atoms, suitably 1 to 2 carbon
atoms, and preferably Q is a benzyl group
(--CH.sub.2--C.sub.6H.sub.5); and X.sup.- is an anionic counterion,
usually a halide like chloride.
[0033] Examples of suitable monomers represented by the general
formula (II) include quaternary monomers obtained by treating
dialkylaminoalkyl (meth)acrylates, e.g. dimethyl-aminoethyl
(meth)acrylate, diethylaminoethyl (meth)acrylate and
dimethylaminohydroxy-propyl (meth)acrylate, and dialkylaminoalkyl
(meth)acrylamides, e.g. dimethylaminoethyl (meth)acrylamide,
diethylaminoethyl (meth)acrylamide, dimethylaminopropyl
(meth)-acrylamide, and diethylaminopropyl (meth)acrylamide, with
benzyl chloride. Preferred cationic monomers of the general formula
(I) include dimethylaminoethylacrylate benzyl chloride quaternary
salt and dimethylaminoethylmethacrylate benzyl chloride quaternary
salt. The monomer of formula (II) can be copolymerized with one or
more non-ionic, cationic and/or anionic monomers. Suitable
copolymerizable non-ionic monomers include (meth)-acrylamide;
acrylamide-based monomers like N-alkyl (meth)acrylamides,
N,N-dialkyl (meth)acrylamides and dialkylaminoalkyl
(meth)acrylamides, acrylate-based monomers like dialkylaminoalkyl
(meth)acrylates, and vinylamides. Suitable copolymerizable cationic
monomers include acid addition salts and quaternary salts of
dimethylaminoethyl (meth)acrylate and diallyldimethylammonium
chloride. The cationic organic polymer may also contain anionic
groups, preferably in a minor amount. Suitable copolymerizable
anionic monomers include acrylic acid, methacrylic acid and various
sulphonated vinylic monomers such as styrenesulphonate. Preferred
copolymerizable monomers include acrylamide and methacrylamide,
i.e. (meth)acrylamide, and the cationic or amphoteric organic
polymer is preferably an acrylamide-based polymer.
[0034] Cationic aromatic vinyl addition polymers according to this
invention can be prepared from a monomer mixture generally
comprising from 1 to 99 mole %, suitably from 2 to 50 mole % and
preferably from 5 to 20 mole % of cationic monomer having an
aromatic group and from 99 to 1 mole %, suitably from 98 to 50 mole
%, and preferably from 95 to 80 mole % of other copolymerizable
monomers which preferably comprises acrylamide or methacrylamide
((meth)acrylamide), the monomer mixture suitably comprising from 98
to 50 mole % and preferably from 95 to 80 mole % of
(meth)acrylamide, the sum of percentages being 100.
[0035] Examples of suitable aromatic cationic step-growth polymers
according to the invention include cationic polyurethanes, which
can be prepared from a monomer mixture comprising aromatic
isocyanates and/or aromatic alcohols. Examples of suitable aromatic
isocyanates include diisocyanates, e.g. toluene-2,4- and
2,6-diisocyanates and diphenyl-methane-4,4'-diisocyanate. Examples
of suitable aromatic alcohols include dihydric alcohols, i.e.
diols, e.g. bisphenol A, phenyl diethanol amine, glycerol
monoterephthalate and tri-methylolpropane monoterephthalate.
Monohydric aromatic alcohols such as phenol and derivatives thereof
may also be employed. The monomer mixture can also contain
non-aromatic isocyanates and/or alcohols, usually diisocyanates and
diols, for example any of those known to be useful in the
preparation of polyurethanes. Examples of suitable monomers
containing cationic groups include cationic diols such as acid
addition salts and quaternisation products of N-alkandiol
dialkylamines and N-alkyl dialkanolamines like
1,2-propanediol-3-dimethylamine, N-methyl diethanolamine, N-ethyl
diethanolamine, N-propyl diethanolamine, N-n-butyl diethanolamine
and N-t-butyl diethanolamine, N-stearyl diethanol-amine and
N-methyl dipropanolamine. The quaternization products can be
derived from alkylating agents like methyl chloride, dimethyl
sulphate, benzyl chloride and epichlorohydrin.
[0036] Examples of suitable cationic organic polymers having an
aromatic group that can be used according to the present invention
include those described in International Patent Application
Publication Nos. WO 99/55964, WO 99/55965, WO 99/67310 and WO
02/12626, which are hereby incorporated herein by reference.
[0037] The weight average molecular weight of the cationic polymer
can vary within wide limits dependent on, inter alia, the type of
polymer used, and usually it is at least about 5,000 and often at
least 10,000. More often, it is above 150,000, normally above
500,000, suitably above about 700,000, preferably above about
1,000,000 and most preferably above about 2,000,000. The upper
limit is not critical; it can be about 200,000,000, usually
150,000,000 and suitably 100,000,000.
[0038] The cationic organic polymer, such as polysaccharides and
vinyl addition polymers, can have a degree of cationic substitution
(DS.sub.C) varying over a wide range dependent on, inter alia, the
type of polymer used; DS.sub.C can be from 0.005 to 1.0, usually
from 0.01 to 0.5, suitably from 0.02 to 0.3, preferably from 0.025
to 0.2; and the degree of aromatic substitution (DS.sub.Q) can be
from 0.001 to 0.5, usually from 0.01 to 0.5, suitably from 0.02 to
0.3 and preferably from 0.025 to 0.2. In case the cationic organic
polymer contains anionic groups, the degree of anionic substitution
(DS.sub.A) can be from 0 to 0.2, suitably from 0 to 0.1 and
preferably from 0 to 0.05, the cationic polymer having an overall
cationic charge. Usually the charge density of the cationic polymer
is within the range of from 0.1 to 6.0 meqv/g of dry polymer,
suitably from 0.2 to 5.0 and preferably from 0.5 to 4.0.
[0039] According to a preferred embodiment of the invention, the
drainage and retention aid comprises, in addition to the cationic
polymer, also an anionic material. Examples of suitable anionic
materials include anionic microparticulate materials, e.g. anionic
inorganic and organic particles, and anionic organic polymers, e.g.
anionic vinyl addition polymers such as anionic acrylamide-based
polymers.
[0040] Anionic inorganic microparticulate materials that can be
used include anionic silica-based particles and anionic clays of
the smectite type. It is preferred that the anionic inorganic
particles are in the colloidal range of particle size. Anionic
silica-based particles, i.e. particles based on SiO.sub.2 or
silicic acid, are preferably used and such particles are usually
supplied in the form of aqueous colloidal dispersions, so-called
sols. Examples of suitable silica-based particles include colloidal
silica and different types of polysilicic acid, either homo- or
co-polymerised. The silica-based sols can be modified and contain
other elements, e.g. aluminium, boron, nitrogen, zirconium,
gallium, titanium and the like, which can be present in the aqueous
phase and/or in the silica-based particles. Suitable silica-based
particles of this type include colloidal aluminium-modified silica
and aluminium silicates. Mixtures of such suitable silica-based
particles can also be used. Drainage and retention aids comprising
suitable anionic silica-based particles include those disclosed in
U.S. Pat. Nos. 4,388,150; 4,927,498; 4,954,220; 4,961,825;
4,980,025; 5,127,994; 5,176,891; 5,368,833; 5,447,604; 5,470,435;
5,543,014; 5,571,494; 5,573,674; 5,584,966; 5,603,805; 5,688,482;
and 5,707,493; which are hereby incorporated herein by
reference.
[0041] Anionic silica-based particles suitably have an average
particle size below about 100 nm, preferably below about 20 nm and
more preferably in the range of from about 1 to about 10 nm. As
conventional in the silica chemistry, the particle size refers to
the average size of the primary particles, which may be aggregated
or non-aggregated. The specific surface area of the silica-based
particles is suitably above 50 m.sup.2/g and preferably above 100
m.sup.2/g. Generally, the specific surface area can be up to about
1700 m.sup.2/g and preferably up to 1000 m.sup.2/g. The specific
surface area is measured by means of titration with NaOH in a well
known manner, e.g. as described by G. W. Sears in Analytical
Chemistry 28 (1956): 12, 1981-1983 and in the U.S. Pat. No.
5,176,891. The given area thus represents the average specific
surface area of the particles.
[0042] According to a preferred embodiment of the invention, the
anionic silica-based particles have specific surface area within
the range of from 50 to 1000 m.sup.2/g, preferably from 100 to 950
m.sup.2/g. Sols of silica-based particles of these types also
encompass modifications, for example with any of the elements
mentioned above. Preferably, the silica-based particles are present
in a sol having an S-value in the range of from 8 to 50%,
preferably from 10 to 40%, containing silica-based particles with a
specific surface area in the range of from 300 to 1000 m.sup.2/g,
suitably from 500 to 950 m.sup.2/g, and preferably from 750 to 950
m.sup.2/g, which sols can be modified as mentioned above. The
S-value can be measured and calculated as described by Iler &
Dalton in J. Phys. Chem. 60 (1956), 955-957. The S-value indicates
the degree of aggregation or microgel formation and a lower S-value
is indicative of a higher degree of aggregation.
[0043] According to another preferred embodiment of the invention,
the silica-based particles are selected from polysilicic acid,
either homo- or co-polymerised, having a high specific surface
area, suitably above about 1000 m.sup.2 .mu.g. The specific surface
area can be within the range of from 1000 to 1700 m.sup.2/g and
preferably from 1050 to 1600 m.sup.2/g. The sols of modified or
co-polymerised polysilicic acid can contain other elements as
mentioned above. In the art, polysilicic acid is also referred to
as polymeric silicic acid, polysilicic acid microgel, polysilicate
and polysilicate microgel, which all are encompassed by the term
poly-silicic acid used herein. Aluminium-containing compounds of
this type are commonly also referred to as polyaluminosilicate and
polyaluminosilicate microgel, which are both, encom-passed by the
terms colloidal aluminium-modified silica and aluminium silicate
used herein.
[0044] According to yet another preferred embodiment of the
invention, the drainage and retention aid comprise anionic clay of
the smectite type. Examples of suitable smectite clays include
natural clays such as montmorillonite/bentonite, hectorite,
beidelite, nontronite and saponite, as well as synthetic
smectite-like clays such as laponite, etc., preferably bentonite
and especially such bentonite which after swelling preferably has a
surface area of from 200 to 800 m.sup.2/g. Suitable anionic clays
include those disclosed in U.S. Pat. Nos. 4,753,710; 5,071,512; and
5,607,552, which are hereby incorporated herein by reference. Also
mixtures of anionic silica-based particles and anionic clays of the
smectite type can be employed.
[0045] Anionic organic polymers according to the invention contain
one or more negatively charged (anionic) groups. Examples of groups
that can be present in the polymer as well as in the monomers used
for preparing the polymer include groups carrying an anionic charge
and acid groups carrying an anionic charge when dissolved or
dispersed in water, the groups herein collectively being referred
to as anionic groups, such as phosphate, phosphonate, sulphate,
sulphonic acid, sulphonate, carboxylic acid, carboxylate, alkoxide
and phenolic groups, i.e. hydroxy-substituted phenyls and
naphthyls. Groups carrying an anionic charge are usually salts of
an alkali metal, alkaline earth or ammonia.
[0046] Anionic organic particles that can be used according to the
invention include cross-linked anionic vinyl addition polymers,
suitably copolymers comprising an anionic monomer like acrylic
acid, methacrylic acid and sulfonated or phosphonated vinyl
addition monomers, usually copolymerised with non-ionic monomers
like (meth)acrylamide, alkyl (meth)-acrylates, etc. Useful anionic
organic particles also include anionic condensation polymers, e.g.
melamine-sulfonic acid sols.
[0047] Further anionic polymers that can form part of the drainage
and retention system include vinyl addition polymers comprising an
anionic monomer having carboxylate groups like acrylic acid,
methacrylic acid ethylacrylic acid, crotonic acid, itaconic acid,
maleic acid and salts of any of the foregoing, anhydrides of the
diacids, and sulfonated vinyl addition monomers, such as sulfonated
styrene, usually copolymerised with non-ionic monomers like
acrylamide, alkyl acrylates, etc., for example those disclosed in
U.S. Pat. Nos. 5,098,520 and 5,185,062, the teachings of which are
hereby incorporated herein by reference The anionic vinyl addition
polymers suitably have weight average molecular weights from about
50,000 to about 5,000,000, typically from about 75,000 to about
1,250,000.
[0048] Examples of suitable anionic organic polymer further include
step-growth polymers, chain-growth polymers, polysaccharides,
naturally occurring aromatic polymers and modifications thereof.
The term "step-growth polymer", as used herein, refers to a polymer
obtained by step-growth polymerisation, also being referred to as
step-reaction polymer and step-reaction polymerisation,
respectively. The anionic organic polymers can be linear, branched
or cross-linked. Preferably the anionic polymer is water-soluble or
water-dispersable. In a preferred embodiment, the anionic organic
polymer also contains one or more aromatic groups.
[0049] Anionic organic polymers having aromatic groups contain one
or more aromatic groups of the same or different types. The
aromatic group of the anionic polymer can be present in the polymer
backbone or in a substituent group that is attached to the polymer
backbone (main chain). Examples of suitable aromatic groups include
aryl, aralkyl and alkaryl groups and derivatives thereof, e.g.
phenyl, tolyl, naphthyl, phenylene, xylylene, benzyl, phenylethyl
and derivatives of these groups.
[0050] Examples of suitable anionic aromatic step-growth polymers
include condensation polymers, i.e. polymers obtained by
step-growth condensation polymerisation, e.g. condensates of an
aldehyde such as formaldehyde with one or more aromatic compounds
containing one or more anionic groups, and optional other
co-monomers useful in the condensation polymerisation such as urea
and melamine. Examples of suitable aromatic compounds containing
anionic groups comprises benzene and naphthalene-based compounds
containing anionic groups such as phenolic and naphtholic
compounds, e.g. phenol, naphthol, resorcinol and derivatives
thereof, aromatic acids and salts thereof, e.g. phenylic, phenolic,
naphthylic and naphtholic acids and salts, usually sulphonic acids
and sulphonates, e.g. benzene sulphonic acid and sulphonate, xylen
sulphonic acid and sulphonates, naphthalene sulphonic acid and
sulphonate, phenol sulphonic acid and sulphonate. Examples of
suitable anionic step-growth polymers according to the invention
include anionic benzene-based and naphthalene-based condensation
polymers, preferably naphthalene-sulphonic acid based and
naphthalene-sulphonate based condensation polymers.
[0051] Examples of further suitable anionic step-growth polymers
having aromatic groups include addition polymers, i.e. polymers
obtained by step-growth addition polymerisation, e.g. anionic
polyurethanes, which can be prepared from a monomer mixture
comprising aromatic isocyanates and/or aromatic alcohols. Examples
of suitable aromatic isocyanates include diisocyanates, e.g.
toluene-2,4- and 2,6-diisocyanates and
diphenylmethane-4,4'-diisocyanate. Examples of suitable aromatic
alcohols include dihydric alcohols, i.e. diols, e.g. bisphenol A,
phenyl diethanol amine, glycerol monoterephthalate and
trimethylolpropane monoterephthalate. Monohydric aromatic alcohols
such as phenol and derivatives thereof may also be employed. The
monomer mixture can also contain non-aromatic isocyanates and/or
alcohols, usually diisocyanates and diols, for example any of those
known to be useful in the preparation of polyurethanes. Examples of
suitable monomers containing anionic groups include the monoester
reaction products of triols, e.g. trimethylolethane,
tri-methylolpropane and glycerol, with dicarboxylic acids or
anhydrides thereof, e.g. succinic acid and anhydride, terephthalic
acid and anhydride, such as glycerol monosuccinate, glycerol
monoterephthalate, trimethylolpropane monosuccinate,
trimethylolpropane monoterephthalate,
N,N-bis-(hydroxyethyl)-glycine, di-(hydroxymethyl)propionic acid,
N,N-bis-(hydroxyethyl)-2-aminoethanesulphonic acid, and the like,
optionally and usually in combination with reaction with a base,
such as alkali metal and alkaline earth hydroxides, e.g. sodium
hydroxide, ammonia or an amine, e.g. triethylamine, thereby forming
an alkali metal, alkaline earth or ammonium counter-ion.
[0052] Examples of suitable anionic chain-growth polymers having
aromatic groups include anionic vinyl addition polymers obtained
from a mixture of vinylic or ethylenically unsaturated monomers
comprising at least one monomer having an aromatic group and at
least one monomer having an anionic group, usually co-polymerised
with non-ionic monomers such as acrylate- and acrylamide-based
monomers. Examples of suitable anionic monomers include
(meth)acrylic acid and paravinyl phenol (hydroxy styrene).
[0053] Examples of suitable anionic polysaccharides having aromatic
groups include starches, guar gums, celluloses, chitins, chitosans,
glycans, galactans, glucans, xanthan gums, pectins, mannans,
dextrins, preferably starches, guar gums and cellulose derivatives,
suitable starches including potato, corn, wheat, tapioca, rice,
waxy maize and barley, preferably potato. The anionic groups in the
polysaccharide can be native and/or introduced by chemical
treatment. The aromatic groups in the polysaccharide can be
introduced by chemical methods known in the art.
[0054] Naturally occurring aromatic anionic polymers and
modifications thereof, i.e. modified naturally occurring aromatic
anionic polymers, according to the invention include naturally
occurring polyphenolic substances that are present in wood and
organic extracts of bark of some wood species and chemical
modifications thereof, usually sulphonated modifications thereof.
The modified polymers can be obtained by chemical processes such
as, for example, sulphite pulping and kraft pulping. Examples of
suitable anionic polymers of this type include lignin-based
polymers, preferably sulphonated lignins, e.g. ligno-sulphonates,
kraft lignin, sulphonated kraft lignin, and tannin extracts.
[0055] The weight average molecular weight of the anionic polymer
having aromatic groups can vary within wide limits dependent on,
inter alia, the type of polymer used, and usually it is at least
about 500, suitably above about 2,000 and preferably above about
5,000. The upper limit is not critical; it can be about
200,000,000, usually about 150,000,000, suitably about 100,000,000
and preferably about 10,000,000.
[0056] The anionic polymer having aromatic groups can have a degree
of anionic substitution (DS.sub.A) varying over a wide range
dependent on, inter alia, the type of polymer used; DS.sub.A is
usually from 0.01 to 2.0, suitably from 0.02 to 1.8 and preferably
from 0.025 to 1.5; and the degree of aromatic substitution
(DS.sub.Q) can be from 0.001 to 1.0, usually from 0.01 to 0.8,
suitably from 0.02 to 0.7 and preferably from 0.025 to 0.5. In case
the anionic polymer contains cationic groups, the degree of
cationic substitution (DS.sub.C) can be, for example, from 0 to
0.2, suitably from 0 to 0.1 and preferably from 0 to 0.05, the
anionic polymer having an overall anionic charge. Usually the
anionic charge density of the anionic polymer is within the range
of from 0.1 to 6.0 meqv/g of dry polymer, suitably from 0.5 to 5.0
and preferably from 1.0 to 4.0.
[0057] Examples of suitable aromatic, anionic organic polymers that
can be used according to the present invention include those
described in U.S. Pat. Nos. 4,070,236 and 5,755,930; and
International Patent Application Publication Nos. WO 95/21295, WO
95/21296, WO 99/67310, WO 00/49227 and WO 02/12626, which are
hereby incorporated herein by reference.
[0058] Further to the above mentioned cationic and anionic drainage
and retention aids, low molecular weight cationic organic polymers
and/or inorganic aluminium compounds can also be used as drainage
and retention aids.
[0059] Low molecular weight (hereinafter called LMW) cationic
organic polymers that can be used in conjunction with the
dewatering and retention aid include those commonly referred to and
used as anionic trash catchers (ATC). ATC's are known in the art as
neutralising and/or fixing agents for disturbing/detrimental
anionic substances present in the stock and the use thereof in
combination with drainage and retention aids often provide further
improved drainage and/or retention. The LMW cationic organic
polymer can be derived from natural or synthetic sources, and
preferably it is a LMW synthetic polymer. Suitable organic polymers
of this type include LMW highly charged cationic organic polymers
such as polyamines, polyamidoamines, polyethyleneimines, homo- and
copolymers based on diallyidimethyl ammonium chloride,
(meth)acrylamides and (meth)acrylates, vinylamide-based and
polysaccarides. In relation to the molecular weight of the
retention and dewatering polymers, the weight average molecular
weight of the LMW cationic organic polymer is preferably lower; it
is suitably at least about 2,000 and preferably at least about
10,000. The upper limit of the molecular weight is usually about
2,000,000, to about 3,000,000. Suitable LMW polymers may have a
weight average molecular weight of from about 2,000 up to about
2,000,000.
[0060] Aluminium compounds that can be used as ATC's, according to
the invention include alum, aluminates, aluminium chloride,
aluminium nitrate and polyaluminium compounds, such as
polyaluminium chlorides, polyaluminium sulphates, polyaluminium
compounds containing both chloride and sulphate ions, polyaluminium
silicate-sulphates, and mixtures thereof. The polyaluminium
compounds may also contain other anions than chloride ions, for
example anions from sulfuric acid, phosphoric acid, and organic
acids such as citric acid and oxalic acid.
[0061] According to one preferred embodiment of the invention, the
drainage and retention aid comprises a cationic polymer and an
anionic inorganic microparticulate material, suitably anionic
silica-based particles or anionic clay of the smectite type.
According to another preferred embodiment of the invention, the
drainage and retention aid comprises a cationic polymer and an
anionic vinyl addition polymer, suitably an anionic
acrylamide-based polymer. According to yet another preferred
embodiment of the invention, the drainage and retention aid
comprises a cationic polymer comprising aromatic groups. According
to yet another preferred embodiment of the invention, the drainage
and retention aid comprises a cationic polymer comprising aromatic
groups and an anionic polymer comprising aromatic groups.
[0062] The components of drainage and retention aids can be added
to the cellulosic suspension in conventional manner and in any
order. When using an anionic micro-particulate material, it is
preferred to add the cationic polymer to the suspension before
adding the microparticulate material, even if the opposite order of
addition may be used. It is further preferred to add the cationic
polymer before a shear stage, which can be selected from pumping,
mixing, cleaning, etc., and to add the anionic compound after that
shear stage. When using an LMW cationic organic polymer and/or an
aluminium compound, such components are preferably introduced into
the suspension prior to introducing the cationic polymer and
anionic component, if used. Alternatively, the LMW cationic organic
polymer and cationic polymer can be introduced into the suspension
essentially simultaneously, either separately or in admixture, e.g.
as disclosed in U.S. Pat. No. 5,858,174, which is hereby
incorporated herein by reference.
[0063] If the clay according to the invention is used together with
a drainage and retention aid, the clay can be added to the
suspension prior to or after the addition of the drainage and
retention aid. However, it is preferred that the cationic clay is
added prior to the addition of drainage and retention aid and other
performance chemicals. Suitably, the clay is added to the thick
stock, or to the thin stock, and the drainage and retention aid is
added to the thin stock. The clay can also be added to the
re-cycled white water. If two or more drainage and retention aids
are used, i.e. a cationic polymer together with an anionic
material, e.g. silica-based particles, or anionic organic polymer,
the clay may be added to the cellulosic suspension (stock) prior
to, after or in between the addition of the drainage and retention
aids, or together with any of the drainage and retention aids. The
clay may also be added at several locations in the process, e.g. to
the thick stock and again to the thin stock prior to the addition
of drainage and retention aid.
[0064] The drainage and retention aid(s) according to the invention
can be added to the stock to be dewatered in amounts which can vary
within wide limits depending on, inter alia, type and number of
components, type of cellulosic suspension, salt content, type of
salts, filler content, type of filler, point of addition, degree of
white water closure, etc. Generally, the retention and drainage
aid(s) are added in amounts that give better drainage and/or
retention than is obtained when not adding the components. The
cationic polymer is usually added in an amount of at least about
0.001% by weight, often at least about 0.005% by weight, based on
dry cellulosic suspension, and the upper limit is usually about 3%
and suitably about 1.5% by weight. Commonly applied addition
amounts of cationic polymer are from about 0.01% up to about 0.5%
by weight. Anionic materials, e.g. anionic silica-based particles,
anionic clays of the smectite type and anionic organic polymers,
are usually added in an amount of at least about 0.001% by weight,
often at least about 0.005% by weight, based on dry cellulosic
suspension, and the upper limit is usually about 1.0% and suitably
about 0.6% by weight.
[0065] When using an LMW cationic organic polymers in the process,
they can be added in an amount of at least about 0.001% by weight,
based on dry cellulosic suspension. Suit-ably, the amount is in the
range of from about 0.07 up to about 0.5%, preferably in the range
from about 0.1 up to about 0.35%. When using an aluminium compound
in the process, the total amount introduced into the stock to be
dewatered depends on the type of aluminium compound used and on
other effects desired from it. It is for instance well known in the
art to utilize aluminium compounds as precipitants for rosin-based
sizing agents. The total amount added is usually at least about
0.05% by weight, calculated as Al.sub.2O.sub.3 and based on dry
cellulosic suspension. Suitably the amount is in the range of from
about 0.5 u to about 3.0%, preferably in the range from about 0.1
up to about 2.0%.
[0066] Further additives which are conventional in papermaking can
of course be used in combination with the additive(s) according to
the invention, such as, for example, dry strength agents, wet
strength agents, optical brightening agents, dyes, sizing agents
like rosin-based sizing agents and cellulose-reactive sizing
agents, e.g. ketene dimers and succinic anhydrides, etc. The
cellulosic suspension, or stock, can also contain mineral fillers
of conventional types such as, for example, kaolin, china clay,
titanium dioxide, gypsum, talc and natural and synthetic calcium
carbonates such as chalk, ground marble and precipitated calcium
carbonate.
[0067] Furthermore, the process can also be useful in the
manufacture of paper from cellulosic suspensions having high
conductivity. In such cases, the conductivity of the suspension
that is dewatered on the wire is usually at least 1.0 mS/cm,
suitably at least 2.0 mS/cm, and preferably at least 3.5 mS/cm.
Conductivity can be measured by standard equipment such as, for
example, a WTW LF 539 instrument supplied by Christian Bemer. The
values referred to above are suitably determined by measuring the
conductivity of the cellulosic suspension that is fed into or
present in the head box of the paper machine or, alternatively, by
measuring the conductivity of white water obtained by dewatering
the suspension. High conductivity levels mean high contents of
salts (electrolytes) which can be derived from the materials used
to form the cellulosic suspension, from various additives
introduced into the cellulosic suspension, from the fresh water
supplied to the process, etc. Further, the content of salts is
usually higher in processes where white water is extensively
recirculated, which may lead to considerable accumulation of salts
in the water circulating in the process.
[0068] The present invention further encompasses paper making
processes where white water is extensively recycled, or
recirculated, i.e. with a high degree of white water closure, for
example where from 0 to 30 tons of fresh water are used per ton of
dry paper produced, usually less than 20, suitably less than 15,
preferably less than 10 and notably less than 5 tons of fresh water
per ton of paper. Recycling of white water obtained in the process
suitably comprises mixing the white water with cellulosic fibres
and/or optional fillers to form a suspension to be dewatered;
preferably it comprises mixing the white water with a suspension
containing cellulosic fibres, and optional fillers, before the
suspension enters the forming wire for dewatering. The white water
can be mixed with the suspension before, between, simultaneous with
or after introducing the clay and optional drainage and retention
aid(s) of this invention. Fresh water can be introduced in the
process at any stage; for example, it can be mixed with cellulosic
fibres in order to form a suspension, and it can be mixed with a
thick suspension containing cellulosic fibres to dilute it so as to
form a thin suspension to be dewatered, before, simultaneous with
or after mixing the suspension with white water.
[0069] The invention is further illustrated in the following
Examples which, however, are not intended to limit the same. Parts
and % relate to parts by weight and % by weight, respectively,
unless otherwise stated.
EXAMPLE 1
[0070] An Al--Mg clay having the 3R.sub.2 stacking (CC-14, Akzo
Nobel Catalyst B.V.) was compared to a commercial talc (Finntalc
PO.sub.5 from Omya) in terms of pitch adsorption. The method of
evaluation of pitch adsorption of mineral powder was a variation of
a procedure outlined by D. A. Hughes in Tappi (July 1977, vol. 60,
No. 7, p. 144-146). Firstly, samples of synthetic pitch were
prepared by adding potassium hydroxide (1 M) to a mixture of 0.65 g
of gum rosin and 0.35 g of oleic acid until saponification
resulted. Denatured ethanol was subsequently added to dissolve the
synthetic pitch.
[0071] Pitch adsorption test procedure: 35 ml of distilled water
was first added to a glass centrifuge tube followed by the addition
of 1 ml of the synthetic pitch solution and 10 ml of clay having
the 3R.sub.2 stacking (2.5% dry content). The pH of the synthetic
pitch slurry was adjusted to 6.5 with sulphuric acid. The mixture
was subsequently stirred for 2 minutes and centrifuged for 20
minutes at 4500 rpm. The supernatant was thereafter poured off and
discarded and the tube was dried over night at 60.degree. C. After
drying, the 10 ml of a chloroform-acetic anhydride (1:1) reagent
was added to the tube and stirred to release the adsorbed pitch.
The tube was then centrifuged for 20 minutes effecting that the
clear reagent remained at the top of the tube. The reagent was
thereafter poured into a small beaker and 10 drops of conc.
sulphuric acid were added. After a period of 4 minutes the liquid
was measured on an UV-vis spectrophotometer set at 400 nm whereby
the absorbance value was compared to absorbance values of known
quantities of pitch. Similar test was also performed for the sample
of Finntalc P05. The pitch adsorption results are summarised in
Table 1, in which `Pitch Addition` refers to the amount of pitch,
in mg, added per gram of adsorbent; talc or clay, and `Pitch
Adsorption` refers to the amount of pitch, in mg, adsorbed per gram
of adsorbent; talc or clay. TABLE-US-00001 TABLE 1 Pitch Adsorption
[mg/g] Clay Clay Pitch Talc (CC-14) Talc (CC-14) Test Addition
[0.16 [0.16 [0.08 [0.08 No. [mg/g] mg/ml] mg/ml] mg/ml] mg/ml] 1 0
0 0 0 0 2 2 1.2 2 1.2 2 3 4 2.3 4 1.2 4 4 6 3 6 1.5 6 5 8 3.1 7.5
1.6 8 6 10 4 9 2 10 7 12 4.3 10 2.1 11.5 8 14 4.2 10.1 2.2 13 9 16
4.5 10.1 2 13 10 18 4.7 11 2.4 13
[0072] As shown by Table 1, the clay having the 3R.sub.2 stacking
has a significantly improved adsorption capability as compared to
talc.
EXAMPLE 2
[0073] In this example, the pitch adsorption characteristics of an
Al--Mg cationic clay having the 3R.sub.1, stacking, (CC-8, Sud
Chemie) was compared to an Al--Mg cationic clay having the 3R.sub.2
stacking (CC-17, Akzo Nobel Catalyst B.V.).
[0074] Two mixtures of synthetic pitch were prepared, one
containing oleic acid and gum rosin (Pitch No. 1)--of example 1,
and a further synthetic pitch mixture containing abietic acid. The
abietic acid containing pitch (Pitch No. 2) was prepared by mixing
1 g of abietic acid and 1M potassium hydroxide until saponification
occurred. Denaturated ethanol (250 ml) was added to dissolve the
synthetic pitch. The same pitch adsorption test procedure as
outlined in Example 1 was used. The results are summarized in
Tables 1 and 2. TABLE-US-00002 TABLE 2 Pitch Addition (Pitch No. 1)
Pitch Adsorption [mg/g] Test No. [mg/g] CC-8 (3R.sub.1) CC-17
(3R.sub.2) 1 0 0 0 2 8 5.4 7.1 3 16 9.64 14.1 4 32 21.5 29 5 48
34.4 41
[0075] TABLE-US-00003 TABLE 3 Pitch Addition (Pitch No. 2) Pitch
Adsorption [mg/g] Test No. [mg/g] CC-8 (3R.sub.1) CC-17 (3R.sub.2)
1 0 0 0 2 8 4.45 6.07 3 16 11.1 13.8 4 32 26.5 30.3 5 48 40.3
47.5
[0076] As shown by Tables 2 and 3, the clay with 3R.sub.2 stacking
adsorbed abietic acid and the gum rosin as well as the oleic acid
mixture to a significantly higher degree than the cationic clay
having the 3R.sub.1, stacking.
EXAMPLE 3
[0077] The adoption of stickies (hot-melts) of an Al--Mg cationic
clay having the 3R.sub.2 stacking (CC-14, Akzo Nobel Catalyst B.V.)
was compared to talc (Finntalc P05, Omya) using the TOC Instrument
(Dohrman DC190). The TOC (Total Organic Carbon) was determined by
combustion at 800.degree. C. whereby the carbon was oxidised to
carbon dioxide and then analysed by means of the IR-spectroscopy
method. The results are summarised in Table 4, in which `Stickies
Addition` refers to the amount of stickies, in mg, added per gram
of adsorbent; clay or talc, and `Stickies Adsorption` refers to the
amount of stickies, in mg, adsorbed per gram of adsorbent; talc or
clay. TABLE-US-00004 TABLE 4 Stickies Adsorption [mg/g] Talc CC-14
Talc CC-14 Stickies [0.16 [0.16 [0.08 [0.08 Test Addition mg/ml]
mg/ml] mg/ml] mg/ml] No. [mg/g] hotmelt hotmelt hotmelt hotmelt 1 0
0 0 0 0 2 2 1.3 2 1.5 2 3 4 1.8 4 1.8 4
EXAMPLE 4
[0078] Drainage performance by incorporation of the clay having the
3R.sub.2 stacking in a dewatering and retention aid was evaluated
by means of a Dynamic Drainage Analyser (DDA), available from
Akribi Kemikonsulter AB, Sweden, which measures the time for
draining a set volume of stock through a wire when removing a plug
and applying vacuum (0.35 bar) to that side of the wire which is
opposite to the side on which the stock is present. First pass
retention was evaluated by means of a nephelometer by measuring the
turbidity of the filtrate, the white water, obtained by draining
the suspension.
[0079] The furnish used was based on a de-inking pulp from a
newspaper mill having consistency of 30 g/liter, conductivity of
around 1500 .mu.S/cm and the pH of 7. Sample of an Al--Mg cationic
clay having the 3R.sub.2 stacking (CC-9, Akzo Nobel. Catalyst B.V.)
was added to the pulp suspension. The furnish was then mixed with a
magnetic stirrer and the dwell/contact time of the stock and
cationic clay was from 30 min. up to 1 hour. Thereafter the furnish
was diluted with water (approx. 1:10) before making the DDA
test.
[0080] The stock/furnish samples were put into the baffled DDA-jar
at time 0. Next the retention/dewatering chemicals were added in
the following order: i) after 15 seconds 0.8 kg/ton of dry pulp of
polyacrylamide (Eka PL 1510), ii) after another 15 seconds (30
seconds from the start) 0.4 kg/ton of dry pulp of anionic
silica-based particles (Eka NP 780), iii) after another 15 seconds
draining of the suspension while automatically recording the
drainage time.
[0081] The filtrate samples from the drainage tests were evaluated
with respect to the pitch adsorption. The adsorption was assumed to
correlate to UV-vis spectrophotometer absorbance at 280 nm of the
filtrate and the decrease in UV-vis absorbance was referred to as
Pitch reduction. The results are set forth in Table 5.
TABLE-US-00005 TABLE 5 Addition of Test No. CC-9 [kg/t] Drainage
time [s] Pitch reduction [%] 1 0 9.3 -- 2 5 6.04 19.8 3 10 5.63
21.4
[0082] Table 5 clearly shows that the addition of CC-9 to the
suspension reduces the drainage time and that the filtrate contains
less pitch as the CC-9 is added to the suspension.
EXAMPLE 5
[0083] In this example an Al--Mg cationic clay having the 3R.sub.1
stacking (CC-12) was compared to an Al--Mg cationic clay having the
3R.sub.2 stacking (CC-18) with respect to drainage. The same
furnish and procedure as described in Example 4 was used. Table 6
summarized the results. TABLE-US-00006 TABLE 6 Drainage time [sec.]
Test No. CC Dosage [kg/t] CC-12 (3R.sub.1) CC-18 (3R.sub.2) 1 0
16.2 16.2 2 2 15 13.1 3 5 14.9 13.2 4 10 14.8 11.9
[0084] From table 6 it is evident that the addition of the clay
having the 3R.sub.2 stacking further improves drainage compared to
the cationic clay having the 3R.sub.2, stacking.
EXAMPLE 6
[0085] The drainage enhancing effect of the Al--Mg cationic clay
having the 3R.sub.2 stacking (CC-22) was here evaluated. The same
furnish and procedure as described in example 4 was used, except
that different drainage and retention aids were used. In this
example, 0.4 kg/ton of dry pulp of Percol 63 (a cationic
polyacrylamide from CIBA) and 2 kg/ton of dry pulp of Hydrocol SW
(bentonite clay of the smectite type from CIBA) were added in a
similar manner. TABLE-US-00007 TABLE 7 Drainage time [sec.] CC
Dosage [kg/t] CC-22 (3R.sub.2) 0 11.2 2 9.1 10 8.1
[0086] Table 7 demonstrates that the performance of a dewatering
and retention aid comprising addition of cationic PAM and bentonite
clay to a suspension is improved by the addition of an Al--Mg
cationic clay of the 3R.sub.2 type.
EXAMPLE 7
[0087] The adsorption of Pressure-Sensitive Adhesives stickies of
an Al--Mg cationic clay having the 3R.sub.2 stacking (CC-17, Akzo
Nobel Catalyst B.V.) was evaluated and compared with talc (Finntalc
P05, Omya). Pressure-Sensitive Adhesives stickles are found in
office waste furnishes as labels, tapes, self-sealing envelopes and
Post-it.RTM. notes.
[0088] 60 g of Post-it.RTM. (notes having one side totally covered
with the adhesive (Tappi journal vol. 79 no 7 Jul. 1996) were cut
into small squares and soaked in 1.5 l of cold tap water for 24
hours. 0.5 l of a salt solution containing CaCl.sub.2.2H.sub.2O,
Na.sub.2SO.sub.4 10H.sub.2O and tap water was added to the
water-paper mixture to simulate the paper mill conditions, such as
pH and conductivity. The mixture was then disintegrated in a
standard pulp disintegrator for 30000 revolutions. Fibres and fines
larger than 25 um were removed by filtration. The filtrate was
heated in a water bath to 60 C. The pH varied between 6.8 and 7.4.
To the filtrate samples was added Al--Mg clay having a 3R.sub.2
stacking and Talc (P05). After addition of CC-17 and talc the
filtrate was mixed with a magnet stirrer and the dwell time of the
CC-17 and talc was 60 min. The adsorption test was carried out by
centrifugation 30 min 4500 rpm. The supernatant was then poured off
and TOC was measured. Table 8 shows the results of adsorption of
pressure sensitive adhesive. TABLE-US-00008 TABLE 8 Test No. Talc
[kg/t] CC-17 [kg/t] TOC [ppm] 1 0 0 550 2 5 525 3 10 498 4 20 400 5
5 401 6 10 292 7 20 115
[0089] As shown by table 8, the adsorption of pressure sensitive
adhesives is significantly improved when adding CC-17 compared to
talc.
EXAMPLE 8
[0090] In this example, sizing performance was evaluated. A furnish
from a liquid packaging board mill was treated with an Al--Mg
cationic clay having the 3R.sub.2 stacking (CC-22, Akzo Nobel
Catalyst B.V.) and with talc (Finntalc P05, Omya) respectively.
Size and retention chemicals were added and hand sheets were made
(SCAN-C 26:76). Sizing of the sheets was measured as Cobb 60 values
(SCAN-P 12:64).
[0091] The furnish used was a thick-stock from a LPB mill,
containing bleached soft- and hardwood pulp. This furnish was
stirred and heated to 50.degree. C. The chemicals were added and
the furnish was treated for 30 minutes. The thick stock was then
diluted with tap water to a consistency of 5 g/L. This furnish had
a pH of 8 and a conductivity of 0.7 mS/cm. Before sheet making, 0.3
kg/ton of dry pulp of AKD (Keydime C223, Eka Chemicals), 8 kg/ton
of dry pulp of cationic starch (Perlbond 970) and 0.5 kg/ton of dry
pulp of silica-based particles (Eka NP 590, Eka Chemicals) were
added. The sheets had a basis weight of approximately 73 g/m.sup.2.
Table 9 shows the sizing results obtained by addition of different
amounts of talc and CC-22 to the liquid packaging board furnish.
TABLE-US-00009 TABLE 9 Test No. Talc [kg/t] CC-22 [kg/t] Cobb 60 1
0 0 40 2 1 44 3 5 60 4 1 35 5 5 34
[0092] The sizing performance improved when CC-22 was used over
talc.
EXAMPLE 9
[0093] performance was evaluated with higher additions of Al--Mg
cationic clay having the 3R.sub.2 stacking (CC-22, Akzo Nobel
Catalyst B.V.) and talc (Finntalc P05, Omya), respectively. Hand
sheets were made, and sizing was measured as Cobb 60 (SCAN-P 12:64)
values.
[0094] The furnish used was a thick stock from a LPB mill
containing hydrogen peroxide bleached soft- and hardwood sulphate
pulp at .about.4% consistency. This furnish was stirred and heated
to 50.degree. C. Cationic clay or talc were added and the furnish
was treated for 20 minutes. The thick stock was then diluted with
bleach filtrate to .about.3.9 g/l consistency. To the furnish AKD,
1.6 kg/t rosin size, 1.6 kg/t alum, 5.0 kg/t cationic starch and
0.35 kg/t silica-based particles (Eka NP 590, Eka Chemicals) were
added before making hand sheets (Rapid-Kothen former). The sheets
had a basis weight of approximately 100 g/m.sup.2. Table 10
summarized the sizing results obtained by sizing the liquid
packaging board furnish. TABLE-US-00010 TABLE 10 Test No. AKD
[kg/t] Talc [kg/t] CC-22 [kg/t] COBB 60 1 0 0 0 258 2 0.5 0 0 250 3
0.8 0 0 131 4 1 0 0 59 5 1.4 0 0 39 6 0.5 5 0 211 7 0.8 5 0 115 8 1
5 0 61 9 1.4 5 0 39 10 0.5 0 10 198 11 0.8 0 10 87 12 1 0 10 45 13
1.4 0 10 33
[0095] Table 10 shows that the sizing performance was improved
(lower Cobb 60 values) using CC-22 compared to talc.
EXAMPLE 10
[0096] This example was made in a pulp mill. Chemical pulp from the
dewatering headbox of the pulp machine was treated with an Al--Mg
cationic clay having the 3R.sub.2 stacking (CC-22, Akzo Nobel
Catalyst B.V.). The turbidity of the pulp filtrate was then
measured, see table 11.
[0097] The pulp used was a bleached eucalyptus fibre suspension at
.about.1.2% consistency. This pulp was stirred and heated at
60.degree. C. The cationic clay was added and the pulp was treated
for 30 minutes. The pulp was then filtrated through a Brift-Jar
with a 200 mesh wire (76.2 .mu.m hole diameters). The filtrate was
analysed for turbidity in a Hach 2100P turbidity meter. Table 11
shows the results in terms of turbidity of the filtrate
TABLE-US-00011 TABLE 11 Test No. CC-22 [kg/t] Turbidity [NTU] 1 0
53 2 2 43 3 5 23
[0098] The turbidity of the filtrate improved (decreased) when
treating a chemical pulp with CC-22.
EXAMPLE 11
[0099] This example was made in a TMP pulp mill. Thermomechanical
pulp (TMP) was dewatered or washed after hydrogen peroxide
bleaching. The filtrate is often referred to as bleach filtrate.
TMP bleach filtrate water was stirred and heated at 50.degree. C.
The TMP bleach filtrate water was treated for 30 minutes with an
Al--Mg cationic clay having the 3R.sub.2 stacking (CC-22, Akzo
Nobel Catalyst B.V.). This water was centrifuged and the clear
phase was measured for turbidity by being analysed for absorption
in a Lasa 10 spectrophotometer at 700 nm wavelength. Table 12 shows
the results. TABLE-US-00012 TABLE 12 Test No. CC-22 [kg/t]
Absorption [700 nm] 1 0 0.506 2 10 0.377
[0100] The absorption in the clear phase improved (decreased) when
treating TMP bleach water with CC-22.
EXAMPLE 12
[0101] This example was made in a de-inked pulp (DIP) mill. Pulp
from the DIP plant was treated with an Al--Mg cationic clay having
the 3R.sub.2 stacking (CC-22, Akzo Nobel Catalyst B.V.). The
turbidity of the pulp filtrate was then measured, see table 13.
[0102] The pulp used was a taken from between the disc filter and
the screw press in the DIP plant. The pulp had a consistency of
.about.7%, and was diluted with tap water to .about.4.2%. This pulp
was stirred and heated at 50.degree. C. The clay was added and the
pulp was treated for 30 minutes. The pulp was then filtrated
through a GF/A glass fibre filter (.about.2 .mu.m hole diameters).
The filtrate was analysed for turbidity in a Hach 2100P turbidity
meter. Table 13 shows the results. TABLE-US-00013 TABLE 13 Test No.
CC-22 [kg/t] Turbidity [NTU] 1 0 71.8 2 2 63.5 3 5 42.3
[0103] The turbidity of the filtrate improved (decreased) when
mixing de-inked pulp with CC-22 before filtering.
EXAMPLE 13
[0104] Pulp from a de-inked pulp (DIP) mill was treated with an
Al--Mg cationic clay having the 3R.sub.2 stacking (CC-22, Akzo
Nobel Catalyst B.V.) in a manner similar to Example 12. The
turbidity of the pulp filtrate was then measured and is summarized
in Table 14. TABLE-US-00014 TABLE 14 test CC-22 [kg/t] Turbidity
[NTU] 1 0 18 2 5 15 3 10 11
[0105] The turbidity of the filtrate improves (decreases) when
treating a de-inked pulp by adding CC-22 to it before
filtering.
* * * * *