U.S. patent application number 10/095217 was filed with the patent office on 2002-10-03 for process for the production of paper.
Invention is credited to Hallstrom, Hans, Sikkar, Rein, Struck, Oliver.
Application Number | 20020139502 10/095217 |
Document ID | / |
Family ID | 27239749 |
Filed Date | 2002-10-03 |
United States Patent
Application |
20020139502 |
Kind Code |
A1 |
Hallstrom, Hans ; et
al. |
October 3, 2002 |
Process for the production of paper
Abstract
The present invention relates to process for the production of
paper from a suspension containing cellulosic fibers, and optional
fillers, comprising adding to the suspension drainage and retention
aids comprising a cationic organic polymer and anionic
microparticulate material, forming and dewatering the suspension on
a wire, wherein the cationic organic polymer has a non-aromatic
hydrophobic group. The invention further relates to a cationic
vinyl addition polymer comprising in polymerized form at least one
non-cationic monomer having a non-aromatic hydrophobic group and at
least one cationic monomer.
Inventors: |
Hallstrom, Hans; (Nacka,
SE) ; Sikkar, Rein; (Floda, SE) ; Struck,
Oliver; (Duren, DE) |
Correspondence
Address: |
Lainie E. Parker
Akzo Nobel Inc.
7 Livingstone Avenue
Dobbs Ferry
NY
10603
US
|
Family ID: |
27239749 |
Appl. No.: |
10/095217 |
Filed: |
March 11, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10095217 |
Mar 11, 2002 |
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09674201 |
Dec 6, 2000 |
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09674201 |
Dec 6, 2000 |
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PCT/SE99/00678 |
Apr 26, 1999 |
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60083253 |
Apr 27, 1998 |
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Current U.S.
Class: |
162/168.3 ;
162/173; 162/181.6 |
Current CPC
Class: |
D21H 17/375 20130101;
D21H 17/24 20130101; D21H 21/10 20130101; D21H 17/01 20130101; D21H
23/10 20130101; D21H 17/32 20130101; D21H 17/28 20130101; D21H
17/68 20130101; D21H 23/08 20130101; D21H 11/14 20130101; D21H
17/455 20130101 |
Class at
Publication: |
162/168.3 ;
162/173; 162/181.6 |
International
Class: |
D21H 021/00; D21H
021/10; D21H 017/07; D21H 017/46 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 1998 |
EP |
98850067.4 |
Claims
1. A process for the production of paper from a suspension
containing cellulosic fibres, and optional fillers, comprising
adding to the suspension drainage and retention aids comprising a
cationic organic polymer and anionic microparticulate material,
forming and dewatering the suspension on a wire, characterised in
that the cationic organic polymer has a non-aromatic hydrophobic
group.
2. A process according to claim 1, characterised in that the
cationic organic polymer is a vinyl addition polymer comprising in
polymerized form one or more monomers comprising at least one
cationic monomer having a non-aromatic hydrophobic group.
3. A process according to claim 1 or 2, characterised in that the
cationic organic polymer is a vinyl addition polymer comprising in
polymerized form at least one non-cationic monomer having a
non-aromatic hydrophobic group and at least one cationic
monomer.
4. A process according to claim 1, 2 or 3, characterised in that
the hydrophobic group is attached to a nitrogen or oxygen which, in
turn, is attached to the polymer backbone via a chain of atoms.
5. A process according to claim 1, 2, 3 or 4, characterised in that
the hydrophobic group is an alkyl group containing from 3 to 12
carbon atoms.
6. A process according to any of the preceding claims,
characterised in that the cationic organic polymer is an
acrylamide-based polymer.
7. A process according to any of the preceding claims,
characterised in that the cationic organic polymer comprises in
polymerized form a cationic monomer having a non-aromatic
hydrophobic group represented by the general formula (I): 6wherein
R.sub.1 is H or CH.sub.3; R.sub.2 and R.sub.3 are each an alkyl
group having from 1 to 2 carbon atoms; A is O or NH; B is an
alkylene group of from 2 to 8 carbon atoms or a hydroxy propylene
group; R.sub.4 is a substituent containing an alkyl group
containing from 4 to 8 carbon atoms; and X.sup.- is an anionic
counterion.
8. A process according to any of the preceding claims,
characterised in that the cationic organic polymer comprises in
polymerized form a non-ionic monomer having a non-aromatic
hydrophobic group represented by the general formula (IV): 7wherein
R.sub.1 is H or CH.sub.3; A is O or NH; B is an alkylene group of
from 2 to 8 carbon atoms or a hydroxy propylene group or,
alternatively, A and B are both nothing whereby there is a single
bond between C and N (O.dbd.C--NR.sub.8R.sub.9); R.sub.8 and
R.sub.9 are each H or a substituent containing an alkyl group
having from 1 to 6 carbon atoms, at least one of R.sub.8 and
R.sub.9 being a substituent containing an alkyl group having from 2
to 6 carbon atoms.
9. A process according to any of the preceding claims,
characterised in that the cationic organic polymer comprises in
polymerized form a non-ionic monomer having a non-aromatic
hydrophobic group represented by the general formula (V): 8wherein
R.sub.1 is H or CH.sub.3; A is O; B is an alkylene group of from 2
to 4 carbon atoms; n is an integer of at least 1; R.sub.10 is alkyl
having at least 2 carbon atoms.
10. A process according to any of the preceding claims,
characterised in that the cationic organic polymer is a vinyl
addition polymer prepared from a monomer mixture comprising from 5
to 25 mole % of monomer having a non-aromatic hydrophobic group,
and from 95 to 75 mole % of other copolymerizable monomers.
11. A process according to any of the preceding claims,
characterised in that the anionic microparticulate material is
selected from silica-based particles and bentonite.
12. A process according to any of the preceding claims,
characterised in that the drainage and retention aids further
comprises a low molecular weight cationic organic polymer.
13. A process according to any of the preceding claims,
characterised in that the suspension that is dewatered on the wire
has a conductivity of at least 2.0 mS/cm.
14. A process according to any of the preceding claims,
characterised in that the process further comprises dewatering the
suspension on a wire to obtain a wet web of paper and white water,
recirculating the white water and optionally introducing fresh
water to form a suspension containing cellulosic fibres, and
optional fillers, to be dewatered, wherein the amount of fresh
water introduced is less than 30 tons per ton of dry paper
produced.
15. A process according to any of the preceding claims,
characterised in that less than 10 tons of fresh water is
introduced into the process per ton of dry paper produced.
16. A cationic vinyl addition polymer comprising in polymerized
form at least one non-cationic monomer having a non-aromatic
hydrophobic group and at least one cationic monomer.
17. A cationic vinyl addition polymer according to claim 16,
characterised in that the hydrophobic group is attached to a
nitrogen or oxygen which, in turn, is attached to the polymer
backbone via a chain of atoms.
18. A cationic vinyl addition polymer according to claim 16 or 17,
characterised in that the hydrophobic group is an alkyl group
containing from 3 to 12 carbon atoms.
19. A cationic vinyl addition polymer according to claim 16, 17 or
18, characterised in that the cationic vinyl addition polymer is an
acrylamide-based polymer.
20. A cationic vinyl addition polymer according to claim 16, 17, 18
or 19, characterised in that the cationic vinyl addition polymer
comprises in polymerized form a non-ionic monomer having a
non-aromatic hydrophobic group represented by the general formula
(IV): 9wherein R.sub.1 is H or CH.sub.3; A is O or NH; B is an
alkylene group of from 2 to 8 carbon atoms or a hydroxy propylene
group or, alternatively, A and B are both nothing whereby there is
a single bond between C and N (O.dbd.C--NR.sub.8R.sub.9); R.sub.8
and R.sub.9 are each H or a substituent containing an alkyl group
having from 1 to 6 carbon atoms, at least one of R.sub.8 and
R.sub.9 being a substituent containing an alkyl group having from 2
to 6 carbon atoms.
21. A cationic vinyl addition polymer according to any of claims 16
to 20, characterised in that the cationic vinyl addition polymer
comprises in polymerized form a non-ionic monomer having a
non-aromatic hydrophobic group represented by the general formula
(V): 10wherein R.sub.1 is H or CH.sub.3; A is O or NH; B is an
alkylene group of from 2 to 4 carbon atoms; n is an integer of at
least 1; R.sub.10 is alkyl having at least 2 carbon atoms.
22. A cationic vinyl addition polymer according to any of claims 16
to 21, characterised in that the cationic vinyl addition polymer
comprises in polymerized form a cationic monomer represented by the
general formula (I): 11wherein R.sub.1 is H or CH.sub.3; R.sub.2
and R.sub.3 are each H or an alkyl group having from 1 to 3 carbon
atoms; A is O or NH; B is an alkylene group of from 2 to 4 carbon
atoms or a hydroxy propylene group; R.sub.4 is a non-aromatic
hydrocarbon group containing from 4 to 8 carbon atoms; and X.sup.-
is an anionic counterion.
23. A cationic vinyl addition polymer according to any of claims 16
to 22, characterised in that the cationic vinyl addition polymer
comprises in polymerized form a cationic monomer represented by the
general formula (III): 12wherein R.sub.1 is H or CH.sub.3; R.sub.2
and R.sub.3 are each H or an alkyl group having from 1 to 3 carbon
atoms, suitably 1 to 2 carbon atoms; A is O or NH; B is an alkylene
group of from 2 to 8 carbon atoms, suitably 2 to 4 carbon atoms, or
a hydroxy propylene group; R.sub.7 is H, an alkyl group having from
1 to 3 carbon atoms, a benzyl group or a phenylethyl group; and
X.sup.- is an anionic counterion.
24. A cationic vinyl addition polymer according to any of claims 16
to 23, characterised in that the cationic vinyl addition polymer is
prepared from a monomer mixture comprising from 5 to 25 mole % of
non-ionic monomer having a non-aromatic hydrophobic group, and from
95 to 75 mole % of other copolymerizable monomers.
Description
[0001] This invention relates to papermaking and more specifically
to a process for the production of paper in which a cationic
organic polymer having a hydrophobic group and an anionic
microparticulate material are added to a papermaking stock. The
process provides improved drainage and retention.
BACKGROUND
[0002] In the papermaking art, an aqueous suspension containing
cellulosic fibres, and optional fillers and additives, referred to
as stock, is fed into a headbox which ejects the stock onto a
forming wire. Water is drained from the stock, through the forming
wire so that a wet web of paper is formed on the wire, and the web
is further dewatered and dried in the drying section of the paper
machine. Water obtained by dewatering the stock, referred to as
white water, which usually contains fine particles, e.g. fine
fibres, fillers and additives, is usually recirculated in the
papermaking process. Drainage and retention aids are conventionally
introduced into the stock in order to facilitate drainage and
increase adsorption of fine particles onto the cellulosic fibres so
that they are retained with the fibres on the wire. Cationic
organic polymers like cationic starch and cationic acrylamide-based
polymers are widely used as drainage and retention aids. These
polymers can be used alone but more frequently they are used in
combination with other polymers and/or with anionic
microparticulate materials such as, for example, anionic inorganic
particles like colloidal silica and bentonite.
[0003] U.S. Pat. Nos. 4,980,025; 5,368,833; 5,603,805; 5,607,552;
and 5,858,174; as well as International Patent Application No. WO
97/18351 disclose the use of cationic and amphoteric
acrylamide-based polymers and anionic inorganic particles as stock
additives in papermaking These additives are among the most
efficient drainage and retention aids now in use. Similar systems
are disclosed in European Patent Application No. 805,234.
THE INVENTION
[0004] According to the present invention it has been found that
improved drainage and retention can be obtained by using drainage
and retention aids comprising a cationic organic polymer having a
hydrophobic group and an anionic microparticulate material. More
specifically, the present invention relates to a process for the
production of paper from a suspension containing cellulosic fibres,
and optional fillers, which comprises adding to the suspension a
cationic organic polymer and an anionic microparticulate material,
forming and dewatering the suspension on a wire, wherein the
cationic organic polymer has a non-aromatic hydrophobic group. In a
preferred aspect of the invention, the process further comprises
forming and dewatering the suspension on a wire to obtain a wet web
containing cellulosic fibres, or paper, and white water,
recirculating the white water and optionally introducing fresh
water to form a suspension containing cellulosic fibres, and
optional fillers, to be dewatered to form paper, wherein the amount
of fresh water introduced is less than 30 tons per ton of dry paper
produced. The invention thus relates to a process as further
defined in the claims.
[0005] The process of this invention results in improved drainage
and/or retention and hereby the present process makes it possible
to increase the speed of the paper machine and to use lower a
dosage of additives to give a corresponding drainage and retention
effect, thereby leading to an improved papermaking process and
economic benefits. The process of this invention is suitably used
for the treatment of cellulosic suspensions in closed mills wherein
the white water is repeatedly recycled with the introduction of
only low amounts of fresh water. The process is further suitably
applied to papermaking processes using cellulosic suspensions
having high salt contents, and thus having high conductivity
levels, for example processes with extensive white water recycling
and limited fresh water supply and/or processes using fresh water
having high salt contents.
[0006] The cationic organic polymer having a hydrophobic group
according to this invention, herein also referred to as "main
polymer", can be linear, branched or cross-linked, e.g. in the form
of a microparticulate material, preferably essentially linear.
Preferably the main polymer is water-soluble or water-dispersable.
The hydrophobic group of the main polymer is non-aromatic and it
can be a pendent group attached to the polymer backbone (main
chain) or, preferably, a hydrophobic group attached to a
heteroatom, e.g. nitrogen or oxygen, the nitrogen optionally being
charged, which heteroatom, in turn, can be attached to the polymer
backbone, for example via a chain of atoms. The hydrophobic group
has at least 2 and usually at least 3 carbon atoms, suitably from 3
to 12 and preferably from 4 to 8 carbon atoms. The hydrophobic
group is suitably a hydrocarbon chain. Examples of suitable
hydrophobic groups include linear, branched and cyclic alkyl groups
like ethyl; propyl, e.g. n-propyl and iso-propyl; butyl, e.g.
n-butyl, iso-butyl and t-butyl; pentyl, e.g. n-pentyl, neo-penyl
and iso-pentyl; hexyl, e.g. n-hexyl and cyclohexyl; heptyl, e.g.
n-heptyl and cycloheptyl, octyl, e.g. n-octyl; nonyl, e.g. n-nonyl;
decyl, e.g. n-decyl; undecyl, e.g. n-undecyl and dodecyl, e.g.
n-dodecyl. The linear and branched chain alkyl groups are generally
preferred.
[0007] The main polymer can be selected from homopolymers and
copolymers prepared from one or more monomers comprising at least
one monomer having a hydrophobic group, suitably an ethylenically
unsaturated monomer, and the main polymer is preferably a vinyl
addition polymer. The term "vinyl addition polymer", as used
herein, refers to a polymer prepared by addition polymerization of
vinyl monomers or ethylenically unsaturated monomers which include,
for example, acrylamide-based and acrylate-based monomers.
According to a first embodiment of this invention, suitable main
polymers include cationic vinyl addition polymers obtained by
polymerizing a cationic monomer having a non-aromatic hydrophobic
group or a monomer mixture comprising such a monomer. Preferably
the cationic monomer having a non-aromatic hydrophobic group is
represented by the general formula (I): 1
[0008] wherein R.sub.1 is H or CH.sub.3; R.sub.2 and R.sub.3 are
each H or, preferably, an alkyl group having from 1 to 3 carbon
atoms, suitably 1 to 2 carbon atoms; A is O or NH; B is an alkylene
group of from 2 to 8 carbon atoms, suitably 2 to 4 carbon atoms, or
a hydroxy propylene group; R.sub.4 is a substituent containing a
hydrophobic group, suitably a non-aromatic hydrocarbon group
containing at least 2 carbon atoms, suitably from 3 to 12 and
preferably from 4 to 8 carbon atoms; and X.sup.- is an anionic
counterion, usually a halide like chloride. The group R.sub.4
usually comprises and, preferably, is selected from any of the
linear, branched or cyclic alkyl groups mentioned above and the
total number of carbon atoms of the groups R.sub.2, R.sub.3 and
R.sub.4 is usually at least 4, suitably at least 5 and preferably
at least 6. Examples of suitable cationic monomers having a
non-aromatic hydrophobic group include
(meth)acryloxyethyl-N,N-dimethyl-N-n-butylammonium chloride,
(meth)acryloxyaminoethyl-N,N-dimethyl-N-n-butylammonium chloride,
(meth)acryloxypropyl-N, N-dimethyl-N-t-butyl-ammonium chloride,
(meth)acryloxyaminopropyl-N,N-dimethyl-N-t-butylammonium chloride,
(meth)acryloxyaminopropyl-N,N-dimethyl-N-n-hexylammonium chloride,
(meth)acryloxyethyl-N,N-dimethyl-N-n-hexylammonium chloride,
(meth)acrytoxyethyl-N,N-dimethyl-N-methylcyclohexylammonium
chloride, and
(meth)acryloxyaminopropyl-N,N-dimethyl-N-methylcyclohexylammonium
chloride.
[0009] The main polymer can be a homopolymer prepared from a
cationic monomer having a non-aromatic hydrophobic group or a
copolymer prepared from a monomer mixture comprising a cationic
monomer having a non-aromatic hydrophobic group and one or more
copolymerizable monomers. Suitable copolymerizable non-ionic
monomers include monomers represented by the general formula (II):
2
[0010] wherein R.sub.1 is H or CH.sub.3; A is O or NH; B is an
alkylene group of from 2 to 8 carbon atoms, suitably 2 to 4 carbon
atoms, or a hydroxy propylene group or, alternatively, A and B are
both nothing whereby there is a single bond between C and N
(O.dbd.C--NR.sub.5R.sub.6)- ; R.sub.5 and R.sub.6 are each H or a
substituent containing a hydrophobic group, suitably a hydrocarbon
group, preferably alkyl, having from 1 to 6, suitably from 1 to 4
and usually from 1 to 3 carbon atoms. Examples of suitable
copolymerizable monomers of this type include (meth)acrylamide;
acrylamide-based monomers like N-alkyl (meth)acrylamides and
N,N-dialkyl (meth)acrylamides, e.g. N-n-propylacrylamide,
N-isopropyl (meth)acrylamide, N-n-butyl (meth)acrylamide,
N-isobutyl (meth)acrylamide and N-t-butyl (meth)acrylamide; and
dialkylaminoalkyl (meth)acrylamides, e.g. dimethylaminoethyl
(meth)acrylamide, diethylaminoethyl (meth)acrylamide,
dimethylaminopropyl (meth)acrylamide and diethylaminopropyl
(meth)acrylamide; acrylate-based monomers like dialkylaminoalkyl
(meth)acrylates, e.g. dimethylaminoethyl (meth)acrylate,
diethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate
and dimethylaminohydroxypropyl acrylate; and vinylamides, e.g.
N-vinylformamide and N-vinylacetamide. Preferred copolymerizable
non-ionic monomers include acrylamide and methacrylamide, i.e.
(meth)acrylamide, and the main polymer is preferably an
acrylamide-based polymer.
[0011] Suitable copolymerizable cationic monomers include the
monomers represented by the general formula (III): 3
[0012] wherein R.sub.1 is H or CH.sub.3; R.sub.2 and R.sub.1 are
each H or, preferably, an alkyl group having from 1 to 3 carbon
atoms, suitably 1 to 2 carbon atoms; A is O or NH; B is an alkylene
group of from 2 to 8 carbon atoms, suitably 2 to 4 carbon atoms, or
a hydroxy propylene group; R.sub.7 is H, a hydrocarbon group,
suitably alkyl, having from 1 to 3 carbon atoms, suitably 1 to 2
carbon atoms, or 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, for
example a benzyl group (--CH.sub.2--C.sub.6H.sub.5) or a
phenylethyl group (--CH.sub.2--CH.sub.2--C.sub.6H.sub.5); and
X.sup.- is an anionic counterion, usually methylsulphate or a
halide like chloride. Examples of suitable cationic copolymerizable
monomers include acid addition salts and quaternary ammonium salts
of the dialkylaminoalkyl (meth)acrylamides and dialkylaminoalkyl
(meth)acrylates mentioned above, usually prepared using acids like
HCl, H.sub.2SO.sub.4, etc., or quaternizing agents like methyl
chloride, dimethyl sulphate, benzyl chloride, etc.; and
diallyldialkylammonium halides like diallyidimethylammonium
chloride. Copolymerizable anionic monomers like acrylic acid,
methacrylic acid, various sulfonated vinyl addition monomers, etc.
can also be employed and, preferably, in minor amounts.
[0013] According to a second embodiment of this invention, suitable
main polymers include cationic vinyl addition polymers obtained by
polymerizing a monomer mixture comprising at least one non-cationic
ethylenically unsaturated monomer having a non-aromatic hydrophobic
group and at least one cationic ethylenically unsaturated monomer,
the non-aromatic hydrophobic group being as defined above, and this
invention further relates to a cationic vinyl addition polymer
having a non-aromatic hydrophobic group, its preparation and use,
as further defined in the claims. Suitable non-cationic monomers
having a non-aromatic hydrophobic group include non-ionic monomers,
preferably a non-ionic monomer represented by the general formula
(IV): 4
[0014] wherein R.sub.1 is H or CH.sub.3; A is O or NH; B is an
alkylene group of from 2 to 8 carbon atoms, suitably 2 to 4 carbon
atoms, or a hydroxy propylene group or, alternatively, A and B are
both nothing whereby there is a single bond between C and N
(O.dbd.C--NR.sub.8R.sub.9)- ; R.sub.8 and R.sub.9 are each H or a
substituent containing a hydrophobic group, suitably a hydrocarbon
group, preferably alkyl, having from 1 to 6 carbon atoms, at least
one of R.sub.8 and R.sub.9 being a substituent containing a
hydrophobic group, suitably an alkyl group, having from 2 to 6 and
preferably 3 to 4 carbon atoms. The total number of carbon atoms of
the groups R.sub.8 and R.sub.9 is usually at least 2, suitably at
least 3 and notably from 3 to 6. Examples of suitable
copolymerizable monomers of this type include acrylamide-based
monomers like N-alkyl (meth)acrylamides, e.g. N-ethyl
(meth)acrylamide, N-n-propyl (meth)acrylamide, N-isopropyl
(meth)acrylamide, N-n-butyl (meth)acrylamide, N-t-butyl
(meth)acrylamide, N-isobutyl (meth)acrylamide, N-n-butoxymethyl
(meth)acrylamide, and N-isobutoxymethyl (meth)acrylamide;
N-alkylaminoalkyl (meth)acrylamides; N,N-dialkylaminoalkyl
(meth)acrylamides, as well as acrylate-based monomers like
N-alkylaminoalkyl (meth)acrylates and N,N-dialkylaminoalkyl
(meth)acrylates, e.g. t-butylamino-2-ethyl (meth)acrylate.
[0015] Further suitable non-cationic monomers having a non-aromatic
hydrophobic group include non-ionic monomers represented by the
general formula (V): 5
[0016] wherein R.sub.1 is H or CH.sub.3; A is O or NH; B is an
alkylene group of from 2 to 4 carbon atoms, suitably 2 to 3 carbon
atoms, preferably ethylene (--CH.sub.2--CH.sub.2--) or propylene
(--CH.sub.2--CH(CH.sub.3)-- or --CH(CH.sub.3)--CH.sub.2--); n is an
integer of at least 1, suitably from 2 to 40 and preferably 3 to
20; R.sub.10 is a substituent containing a hydrophobic group,
suitably alkyl, having at least 2 carbon atoms, suitably from 3 to
12 and preferably from 4 to 8 carbon atoms. Examples of suitable
copolymerizable monomers of this type include alkyl (mono-, di- and
polyethyleneglycol) (meth)acrylates and alkyl (mono-, di- and
polypropyleneglycol) (meth)acrylates, e.g. ethyltriglycol
(meth)acrylate and butyldiglycol (meth)acrylate.
[0017] The cationic monomer can be selected from any of the
cationic monomers mentioned above, including the cationic monomers
represented by the general formulae (I) and (III) as well as
diallyldialkylammonium halides like diallyidimethylammonium
chloride. The monomer mixture according to the second embodiment
may also comprise other copolymerizable monomers such as, for
example, the non-ionic monomers represented by the general formula
(II) above which may not have a hydrophobic group, suitably
acrylamide and methacrylamide, and the anionic monomers mentioned
above.
[0018] Main 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 25 mole % of
monomer having a non-aromatic hydrophobic group, and from 99 to 1
mole %, suitably from 98 to 50 mole % and preferably from 95 to 75
mole % of other copolymerizable monomers which preferably comprises
acrylamide or methacryl-amide ((meth)acrylamide), the monomer
mixture suitably comprising from 98 to 50 mole % and preferably
from 95 to 75 mole % of (meth)acrylamide, the sum of percentages
being 100. According to the first embodiment of this invention, the
monomer having a non-aromatic hydrophobic group is cationic.
According to the second embodiment of this invention, the monomer
having a non-aromatic hydrophobic group is non-cationic and the
monomer mixture thus also comprises a copolymerizable cationic
monomer which suitably is present in an amount of from 2 to 50 mole
% and preferably from 5 to 25 mole %.
[0019] The main polymer according to this invention can be prepared
by polymerization of monomers in known manner and the
polymerization is suitably carried out in an aqueous or inverse
emulsion phase. The monomer(s) used, including the monomer having a
hydrophobic group described above, are preferably at least in part
soluble in the aqueous phase. Polymerization processes are
generally known in the art and reference is made to Encyclopedia of
Polymer Science and Engineering, Vol. 1-18, John Wiley & Sons,
1985, which is hereby incorporated herein by reference. The
polymerization is suitably initiated in an aqueous phase containing
monomers, a conventional free-radical polymerization initiator and
optionally chain-transfer agent for modifying the molecular weight
of the polymer, and is suitably carried out in the absence of
oxygen in an inert gas atmosphere, for example under nitrogen. The
polymerization suitably takes place under stirring at temperatures
between 20 and 100.degree. C., preferably between 40 and 90.degree.
C.
[0020] Usually the charge density of the main polymer is from 0.2
to 5.0 meqv/g of dry polymer, suitably from 0.6 to 3.0. The weight
average molecular weight of synthetic main polymers is usually at
least about 500,000, suitably above about 1,000,000 and preferably
above about 2,000,000. The upper limit is not critical; it can be
about 30,000,000, usually 25,000,000 and suitably 20,000,000.
[0021] The main polymer of this invention may be in any state of
aggregation such as, for example, in solid form, e.g. powders, in
liquid form, e.g. solutions, emulsions, dispersions, including salt
dispersions, etc. When being added to the stock, the main polymer
is suitably in liquid form, e.g. in the form of an aqueous solution
or dispersion.
[0022] The anionic microparticulate material according to this
invention can be selected from inorganic and organic particles.
Anionic inorganic particles that can be used according to the
invention include anionic silica-based particles and 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. The silica-based sols can also
be modified and contain other elements, e.g. aluminium and/or
boron, 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 are 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.
[0023] Anionic silica-based particles suitably have an average
particle size below about 50 nm, preferably below about 20 nm and
more preferably in the range of from about 1 to about 10 nm. As
conventional in 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 can be measured by means of titration with NaOH in
known manner, e.g. as described by Sears in Analytical Chemistry
28(1956):12, 1981-1983 and in U.S. Pat. No. 5,176,891. The given
area thus represents the average specific surface area of the
particles.
[0024] In a preferred embodiment of the invention, the anionic
inorganic particles are silica-based particles having a 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 these types also encompass modified sols like
aluminium-containing silica-based sols and boron-containing
silica-based sols. Preferably, the silica-based particles are
present in a sol having an S-value in the range of from 8 to 45%,
preferably from 10 to 30%, 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 with aluminium and/or boron
as mentioned above. For example, the particles can be
surface-modified with aluminium to a degree of from 2 to 25%
substitution of silicon atoms. The S-value can be measured and
calculated as described by Iter & Dalton in J. Phys. Chem.
60(1956), 955-957. The S-value indicates the degree of aggregate or
microgel formation and a lower S-value is indicative of a higher
degree of aggregation.
[0025] In yet another preferred embodiment of the invention, the
silica-based particles are selected from polysilicic acid and
modified polysilicic acid having a high specific surface area,
suitably above about 1000 m.sup.2lg. 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 polysilicic acid
can contain other elements, e.g. aluminium and/or boron, which can
be present in the aqueous phase and/or in the silica-based
particles. In the art, polysilicic acid is also referred to as
polymeric silicic acid, polysilicic acid microgel, polysilicate and
polysilicate microgel, which are all encompassed by the term
polysilicic acid used herein. Aluminium-containing compounds of
this type are commonly also referred to as poly-aluminosilicate and
polyaluminosilicate microgel, which are both encompassed by the
terms colloidal aluminium-modified silica and aluminium silicate
used herein.
[0026] Clays of the smectite type that can be used in the process
of the invention are known in the art and include naturally
occurring, synthetic and chemically treated materials. Examples of
suitable smectite clays include montmorillonite/bentonite,
hectorite, beidelite. nontronite and saponite, preferably bentonite
and especially such bentonite which after swelling preferably has a
surface area of from 400 to 800 m.sup.2/g. Suitable clays are
disclosed in U.S. Pat. Nos. 4,753,710; 5,071,512; and 5,607,552,
which are hereby incorporated herein by reference.
[0027] Anionic organic particles that can be used according to the
invention include highly 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 copolymerized with nonionic monomers
like (meth)acrylamide, alkyl (meth)acrylates, etc. Useful anionic
organic particles also include anionic condensation polymers, e.g.
melamine-sulfonic acid sols.
[0028] In addition to the cationic organic polymer having a
hydrophobic group and the anionic microparticulate material, the
drainage and retention aids (agents) according to the present
invention may also comprise further components such as, for
example, low molecular weight cationic organic polymers and/or
aluminium compounds. The term "drainage and retention aids", as
used herein, refers to two or more components (aids, agents or
additives) which, when being added to a stock, give better drainage
and/or retention than is obtained when not adding the
components.
[0029] Low molecular weight (hereinafter LMW) cationic organic
polymers that can be used include those commonly referred to and
used as anionic trash catchers (ATC). ATC's are known in the art as
neutralizing and/or fixing agents for 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 an
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. In relation to the molecular
weight of the main polymer, the molecular weight of the LMW
cationic organic polymer is usually lower, it is suitably at least
2,000 and preferably at least 10,000. The upper limit of the
molecular weight is usually about 700,000, suitably about 500,000
and preferably about 200,000.
[0030] Aluminium compounds that can be used according to this
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, organic acids
such as citric acid and oxalic acid.
[0031] The components of drainage and retention aids according to
the invention can be added to the stock in conventional manner and
in any order. It is preferred to add the main polymer to the stock
before adding the anionic microparticulate material, even if the
opposite order of addition may be used. It is further preferred to
add the main polymer before a shear stage, which can be selected
from pumping, mixing, cleaning, etc., and to add the anionic
particles after that shear stage. When using an LMW cationic
organic polymer and/or an aluminium compound, such components are
preferably introduced into the stock prior to introducing the main
polymer and anionic microparticulate material. Alternatively, the
LMW cationic organic polymer and the main polymer can be introduced
into the stock 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.
[0032] The components of the present drainage and retention aids
are added into the stock to be dewatered in amounts which can vary
within wide limits depending on, inter alia, type and number of
components, type of furnish, filler content, type of filler, point
of addition, salt content, etc. Generally the components are added
in an amount that give better drainage and/or retention than is
obtained when not adding the components. The main polymer is
usually added in an amount of at least 0.001%, often at least
0.005% by weight, based on dry stock substance, and the upper limit
is usually 3% and suitably 1.5% by weight. The anionic
microparticulate material is usually added in an amount of at least
0.001% by weight, often at least 0.005% by weight, based on dry
substance of the stock, and the upper limit is usually 1.0% and
suitably 0.6% by weight. When using anionic silica-based particles,
the total amount added is suitably within the range of from 0.005
to 0.5% by weight, calculated as SiO.sub.2 and based on dry stock
substance, preferably within the range of from 0.01 to 0.2% by
weight. When using an LMW cationic organic polymer in the process,
it can be added in an amount of at least 0.05%, based on dry
substance of the stock to be dewatered. Suitably, the amount is in
the range of from 0.07 to 0.5%, preferably in the range from 0.1 to
0.35%. When using an aluminium compound in the process, the total
amount introduced into the stock to be dewatered is dependent on
the type of aluminium compound used and on other effects desired
from it. It is for instance well known in the art to utilise
aluminium compounds as precipitants for rosin-based sizing agents.
The total amount added is usually at least 0.05%, calculated as
Al.sub.2O.sub.3 and based on dry stock substance. Suitably the
amount is in the range of from 0.5 to 3.0%, preferably in the range
from 0.1 to 2.0%.
[0033] The process of the invention is preferably used in the
manufacture of paper from a suspension containing cellulosic
fibres, and optional fillers, having a high conductivity Usually,
the conductivity of the stock that is dewatered on the wire is at
least 0.75 mS/cm, suitably at least 2.0 mS/cm, preferably at least
3.5 mS/cm. Very good results have been observed at conductivity
levels above 5.0 mS/cm and even above 7.5 mS/cm. Conductivity can
be measured by standard equipment such as, for example a WTW LF 539
instrument supplied by Christian Berner. The values referred to
above are suitably determined by measuring the conductivity of the
cellulosic suspension that is fed into or present in the headbox 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),
where the various salts can be based on mono-, di- and multivalent
cations like alkali metals, e.g. Na.sup.+ and K.sup.+, alkaline
earths, e.g. Ca.sup.2+ and Mg.sup.2+, aluminium ions, e.g.
Al.sup.3+, Al(OH).sup.2+ and polyaluminium ions, and mono-, di- and
multivalent anions like halides, e.g., Cl.sub.- sulfates, e.g.
SO.sub.4.sup.2- and HSO.sub.4.sup.-, carbonates, e.g.
CO.sub.3.sup.2- and HCO.sub.3.sup.-, silicates and lower organic
acids. The invention is particularly useful in the manufacture of
paper from stocks having high contents of salts of di- and
multivalent cations, and usually this content is at least 200 ppm,
suitably at least 300 ppm and preferably at least 400 ppm. The
salts can be derived from the cellulosic fibres and fillers used to
form the stock, in particular in integrated mills where a
concentrated aqueous fibre suspension from the pulp mill normally
is mixed with water to form a dilute suspension suitable for paper
manufacture in the paper mill. The salt may also be derived from
various additives introduced into the stock, from the fresh water
supplied to the process, or be added deliberately, 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.
[0034] Accordingly, the invention is further suitably used in
papermaking processes where white water is extensively recirculated
(recycled), 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. Recirculation 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 or
after introducing the drainage and retention aids. 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 suspension containing cellulosic fibres to
dilute it so as to form the suspension to be dewatered, before or
after mixing the stock with white water and before, between or
after introducing the drainage and retention aids.
[0035] Further additives which are conventional in papermaking can
of course be used in combination with the additives according to
the invention, such as, for example, dry strength agents, wet
strength agents, sizing agents, e.g. those based on rosin, ketene
dimers and acid anhydrides, optical brightening agents, dyes, 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.
[0036] The process of this invention is used for the production of
paper. The term "paper", as used herein, of course include not only
paper and the production thereof, but also other 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 suspensions of 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 dry substance. The suspensions can be based on fibres from
chemical pulp such as sulphate, sulphite and organosolv pulps,
mechanical pulp such as thermomechanical pulp,
chemo-thermomechanical pulp, refiner pulp and groundwood pulp, from
both hardwood and soft-wood, and can also be based on recycled
fibres, optionally from de-inked pulps, and mixtures thereof.
[0037] 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
[0038] Cationic polymers were prepared by polymerizing a monomer
mixture according to the following general procedure:
[0039] Monomers and an initiator, 2,2'-azobis(2-amidinopropane)
dihydrochloride (Wako V-50) were added to an aqueous phase and
polymerization was carried out for about 24 hours at 45.degree. C.
with stirring under a nitrogen atmosphere. The cationic polymer,
which was obtained as a clear gel, was dissolved in water and used
as an 0.1% aqueous solution.
[0040] Polymers according to the invention, P1 to P5, and polymers
intended for comparison purposes, Ref. 1 and Ref. 2, were prepared
from the indicated monomers in the indicated amounts:
[0041] P1: acrylamide (90 mole %), and
[0042] acryloxyethyl dimethyl n-butylammonium chloride (10 mole
%);
[0043] P2: acrylamide (90 mole %) and
[0044] acryloxyethyl dimethyl methylcyclohexylammonium chloride (10
mole %);
[0045] P3: acrylamide (90 mole %),
[0046] methacryloxyaminopropyl trimethylammonium chloride (5 mole
%), and
[0047] methacryloxyethyl t-butylamine (5 mole %);
[0048] P4: acrylamide (90 mole %),
[0049] methacryloxyaminopropyltrimethylammonium chloride (5 mole
%), and
[0050] N-isopropylacrylamide (5 mole %);
[0051] P5: acrylamide (90 mole %),
[0052] methacryloxyaminopropyltrimethylammonium chloride (5 mole
%), and
[0053] N-t-butylacrylamide (5 mole %);
[0054] Ref. 1: acrylamide (90 mole %), and
[0055] acryloxyethyl trimethylammonium chloride (10 mole %).
[0056] Ref. 2: acrylamide (95 mole %), and
[0057] acryloxyethyl trimethylammonium chloride (5 mole %).
EXAMPLE 2
[0058] Drainage and retention performance was evaluated by means of
a Dynamic Drainage Analyser (DDA), available from Akribi, Sweden,
which measures the time for draining a set volume of stock through
a wire when removing a plug and applying vacuum to that side of the
wire opposite to the side on which the stock is present. First pass
retention was evaluated by measuring, with a nephelometer, the
turbidity of the filtrate, the white water, obtained by draining
the stock.
[0059] The furnish used was based on 56% by weight of peroxide
bleached TMP/SGW pulp (80/20), 14% by weight of bleached birch/pine
sulphate pulp (60/40) refined to 200.degree. CSF and 30% by weight
of china clay. To the stock was added 40 g/l of a colloidal
fraction, bleach water from an SC mill, filtrated through a 5 .mu.m
screen and concentrated with an UF filter, cut off 200,000. Stock
volume was 800 ml, consistency 0.14% and pH 7.0. Conductivity was
adjusted to about 2.5 mS/cm by addition of calcium chloride (400
ppm Ca).
[0060] The stock was stirred in a baffled jar at a speed of 1500
rpm throughout the test and additions were conducted as follows: i)
adding cationic polymer to the stock following by stirring for 30
seconds, ii) adding anionic microparticulate material to the stock
followed by stirring for 15 seconds, iii) draining the stock while
automatically recording the drainage time.
[0061] The cationic polymers tested in this Example were P1 and
Ref. 1 according to in Example 1. The anionic microparticulate
material used in this Example was a sol of silica-based particles
of the type disclosed in U.S. Pat. No. 5,368,833. The sol had an
S-value of about 25% and contained silica particles with a specific
surface area of about 900 m.sup.2/g which were surface-modified
with aluminium to a degree of 5%. The silica-based sol was added to
the stock in an amount of 1.5 kg/ton, calculated as SiO.sub.2 and
based on dry stock system.
[0062] Table 1 shows the drainage time and retention values at
various dosages of P1 and Ref. 1, calculated as dry polymer on dry
stock system (kg/ton).
1TABLE 1 Dewatering time (sec)/ Cationic Turbidity (NTU) at
indicated Polymer dosage Polymer 0.5 kg/t 1.0 kg/t 1.5 kg/t 2.0
kg/t P1 11.6/48 8.9/34 5.8/32 4.7/14 Ref. 1 12.0/57 9.0/49 6.5/36
5.1/28
EXAMPLE 3
[0063] In this test series, dewatering and retention performance
was evaluated according to the procedure described in Example
2.
[0064] The furnish was the same as used in Example 2. Stock volume
was 800 ml, pH about 7 and conductivity was adjusted to 7.0 mS/cm
by addition of calcium chloride (1300 ppm Ca), thus simulating a
high electrolyte content and a high degree of white water
closure.
[0065] The anionic inorganic material according to Example 2 were
similarly used in this Example and was added in an amount of 1.5
kg/ton, calculated as SiO.sub.2 and based on dry stock system.
[0066] The polymers used in this Example were P1, P2 and Ref. 1
according to Example 1. Table 2 shows the dewatering and retention
effect at various dosages of P1, P2 and Ref. 1, calculated as dry
polymer on dry stock system.
2TABLE 2 Dewatering time (sec)/ Cationic Turbidity (NTU) at
indicated Polymer dosage of Polymer 0.5 kg/t 1.0 kg/t 1.5 kg/t 2.0
kg/t P1 11.0/-- 8.7/49 6.3/40 6.0/38 P2 10.7/-- 7.9/50 6.1/43
5.5/32 Ref. 1 12.1/-- 9.5/57 8.8/47 7.8/43
EXAMPLE 6
[0067] In this test series, dewatering and retention performance
was evaluated according to the procedure described in Example
2.
[0068] The furnish was the same as used in Example 2. Stock volume
was 800 ml and pH about 7. Sodium chloride (550 ppm Na) and calcium
chloride were added to the stock to adjusted the conductivity to
5.0 mS/cm (400 ppm Ca) and 7.0 mS/cm (1300 ppm Ca).
[0069] The polymers P2, P3, Ref. 1 and anionic microparticles
according to Example 1 were similarly used in this test series in
conjunction with a low molecular weight cationic polyamine. The
polyamine was added to the stock followed by stirring for 30
seconds before addition of the cationic acrylamide-based polymer.
The polyamine was added in an amount of 3 kg/ton, calculated as dry
polymer on dry stock system. The main polymers P2, P3 and Ref. 1
were added in an amount of 1.5 kg/ton, calculated as dry polymer on
dry stock system.
[0070] Table 5 shows the dewatering and retention effect at various
conductivities and dosages of silica-based particles, calculated as
SiO.sub.2 and based on dry stock system.
3TABLE 5 Test SiO.sub.2 Dewatering time (sec)/Turbidity (NTU)
Series Dosage Conductivity by using the indicated Cationic Polymer
No. (kg/t) (mS/cm) P2 P3 Ref. 1 1 1.5 5.0 6.9/-- --/39 7.2/51 2 1.5
7.0 16.2/-- --/56 24.7/60 3 1.0 7.0 7.8/-- --/50 13.3/55
EXAMPLE 7
[0071] In this test series, dewatering and retention performance
was evaluated according to the procedure described in Example
2.
[0072] The furnish was the same as used in Example 2. Stock volume
was 800 ml and pH about 7. Varying amounts of sodium chloride was
added to the stock to adjust the conductivity to 2.5 mS/cm (550 ppm
Na) (Test Series Nos. 1-3), 5.0 mS/cm (1470 ppm Na) (Test Series
Nos. 4-6) and 10.0 mS/cm (3320 ppm Na) (Test Series Nos. 7-9).
[0073] The cationic polymers used were P1 to P3 and Ref. 1
according to Example. 1. The anionic microparticulate material used
was hydrated suspension of powdered Na-bentonite in water.
[0074] Table 6 shows the dewatering and retention effect at various
dosages of cationic polymer, calculated as dry polymer on dry stock
system, and bentonite, calculated as dry on dry stock system.
EXAMPLE 4
[0075] In this test series, dewatering and retention performance
was evaluated according to the procedure described in Example
2.
[0076] The stock used in this Example was similar to the stock used
according to Example 3 and had a conductivity of about 7.0 mS/cm
(1300 ppm Ca). The anionic inorganic material according to Example
2 was added in an amount of 1.5 kg/ton, calculated as SiO.sub.2 and
based on dry stock system. The polymers used were P3 and Ref. 1
according to Example 1.
[0077] Table 3 shows the results of the dewatering tests at various
dosages of P3 and Ref. 1, calculated as dry polymer on dry stock
system.
4TABLE 3 Cationic Dewatering time (sec) at Polymer dosage of
Polymer 0.5 kg/t 1.0 kg/t 1.5 kg/t 2.0 kg/t P3 13.2 10.0 7.4 5.6
Ref. 1 15.5 12.1 10.6 10.2
EXAMPLE 5
[0078] In this test series, the dewatering performance was
evaluated according to the procedure described in Example 2.
[0079] The stock used in this test series was similar to the one
according to Example 2 and had a conductivity of about 2.5 mS/cm.
The polymers used were P4, P5 and Ref. 2 according to Example 1
which were added in an amount of 2 kg/ton, calculated as dry
polymer on dry stock system. The anionic inorganic material
according to Example 2 was similarly used in this test series.
[0080] Table 4 shows the results of the dewatering tests at various
dosages of anionic inorganic material, calculated as SiO.sub.2 and
based on dry stock system.
5TABLE 4 Cationic Dewatering time (sec) at SiO.sub.2 dosage of
Polymer 0.5 kg/t 1.0 kg/t 1.5 kg/t 2.0 kg/t P4 11.3 10.1 9.8 9.1 P5
11.8 9.5 8.8 8.5 Ref. 2 11.9 10.7 10.3 9.9
[0081]
6TABLE 6 Test Polymer Bentonite Dewatering time (sec)/Turbidity
(NTU) Series Dosage Dosage by using the indicated Cationic Polymer
No. (kg/t) (kg/t) P1 P2 P3 Ref. 1 1 2 4 6.6/25 8.5/-- 7.5/-- 8.9/39
2 2 8 6.3/29 7.9/-- 7.2/-- 8.3/37 3 4 8 4.2/10 4.6/-- 4.9/-- 8.4/15
4 2 4 7.0/30 8.4/-- 8.9/-- 8.8/42 5 2 8 6.6/28 8.0/-- 8.4/-- 8.6/40
6 4 8 4.8/10 5.0/-- 4.8/-- 6.6/28 7 2 4 7.9/22 8.0/-- 8.2/-- 9.1/45
8 2 8 7.4/30 7.2/-- 7.1/-- 8.2/48 9 2 8 5.2/11 4.8/-- 5.2/--
7.5/28
* * * * *