U.S. patent application number 11/040579 was filed with the patent office on 2005-07-28 for process for making paper.
Invention is credited to Covarrubias, Rosa Maria.
Application Number | 20050161183 11/040579 |
Document ID | / |
Family ID | 34807199 |
Filed Date | 2005-07-28 |
United States Patent
Application |
20050161183 |
Kind Code |
A1 |
Covarrubias, Rosa Maria |
July 28, 2005 |
Process for making paper
Abstract
Methods for making paper or paperboard are described. One
preferred method comprises forming a treated pulp by added to a
papermaking pulp a synthetic layered silicate, a peptizer and at
least one polymer. The synthetic layered silicate preferably
comprises a synthetic hydrous sodium lithium magnesium silicate and
the polymer is selected from cationic, nonionic and amphoteric
polymers. The peptizer is preferably an inorganic polyphosphate
peptizer and is contained in certain commercial synthetic layered
silicate products. The inventor has surprisingly found that the
peptizer provides significant improvements in drainage, retention
and turbidity, thereby improving the papermaking process and the
paper or paperboard product.
Inventors: |
Covarrubias, Rosa Maria;
(Bartlett, TN) |
Correspondence
Address: |
KILYK & BOWERSOX, P.L.L.C.
53 A EAST LEE STREET
WARRENTON
VA
20186
US
|
Family ID: |
34807199 |
Appl. No.: |
11/040579 |
Filed: |
January 21, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60538622 |
Jan 23, 2004 |
|
|
|
Current U.S.
Class: |
162/158 ;
162/164.1; 162/168.3; 162/181.6; 162/183 |
Current CPC
Class: |
D21H 21/10 20130101;
D21H 23/14 20130101; D21H 17/68 20130101; D21H 17/66 20130101; D21H
17/375 20130101; D21H 17/455 20130101 |
Class at
Publication: |
162/158 ;
162/164.1; 162/181.6; 162/168.3; 162/183 |
International
Class: |
D21H 017/74 |
Claims
What is claimed is:
1. A method of making paper or paperboard comprising: (a) forming a
treated pulp by adding to a papermaking pulp a synthetic layered
silicate, a peptizer and at least one polymer, the synthetic
layered silicate comprising a synthetic hydrous sodium lithium
magnesium silicate and the at least one polymer comprising one or
more members of the group consisting of cationic polymers, nonionic
polymers and amphoteric polymers under cationic conditions; and (b)
forming the treated pulp into said paper or paperboard.
2. The method of claim 1, wherein the synthetic layered silicate
comprises laponite.
3. The method of claim 1, wherein the synthetic layered silicate is
added to the pulp in an amount of at least about 0.05 pound on a
dry basis, per ton of pulp based on the dried solids weight of the
pulp.
4. The method of claim 1, wherein the synthetic layered silicate is
added to the pulp in an amount of from about 0.1 pounds to about
5.0 pounds on a dry basis, per ton of pulp based on the dried
solids weight of the pulp.
5. The method of claim 1, wherein the synthetic layered silicate is
added to the pulp in an amount of from about 0.2 pounds to about
1.0 pounds on a dry basis, per ton of pulp based on the dried
solids weight of the pulp.
6. The method of claim 1, wherein the peptizer comprises an
inorganic polyphosphate peptizer.
7. The method of claim 1, wherein the peptizer comprises
tetrasodium pyrophosphate.
8. The method of claim 1, wherein the synthetic layered silicate is
added to the pulp in the form of an aqueous dispersion and wherein
the dispersion contains said inorganic polyphosphate peptizer in an
amount sufficient to maintain said dispersion in the form of a sol
for a predetermined period of time.
9. The method of claim 5, wherein the aqueous dispersion contains
said synthetic layered silicate in an amount of up to about 10 wt
%.
10. The method of claim 1, wherein the cationic polymer is present
and comprises a synthetic nitrogen-containing cationic polymer.
11. The method of claim 1, wherein the cationic polymer is present
and comprises one or more members of the group consisting of
cationic polyacrylamides and copolymers thereof; and cationic
diallyldimethylammonium chloride and copolymers thereof.
12. The method of claim 1, wherein the cationic polymer is present
and is added to the pulp in an amount of at least about 0.01 pound
on a dry basis, per ton of pulp based on the dried solids weight of
the pulp.
13. The method of claim 1, wherein the cationic polymer is present
and is added to the pulp in an amount of from about 0.1 pound to
about 5 pounds on a dry basis, per ton of pulp based on the dried
solids weight of the pulp.
14. The method of claim 1, wherein the cationic polymer is present
and is added to the pulp in an amount of from about 0.2 to about 2
pounds on a dry basis, per ton of pulp based on the dried solids
weight of the pulp.
15. The method of claim 1, further comprising shearing the pulp in
one or more shear stages including a final high shear stage in
which the pulp is passed through a screen prior to entering a
headbox of a papermaking apparatus.
16. The method of claim 15, wherein the polymer is added to the
pulp before the final high shear stage and wherein the synthetic
layered silicate is added to the pulp after the final high shear
stage.
17. The method of claim 15, wherein the synthetic layered silicate
is added to the pulp before the final high shear stage and wherein
the polymer is added to the pulp after the final high shear
stage.
18. A paper or paperboard made according to the method of claim
1.
19. A papermaking apparatus comprising a supply of synthetic
layered silicate, a supply of a papermaking pulp, a device for
feeding the synthetic layered silicate from the supply of synthetic
layered silicate to the supply of papermaking pulp, a supply of a
retention system polymer, a device for feeding the retention system
polymer from the supply of retention system polymer to the
papermaking pulp, and a device for forming the pulp into a paper or
paperboard after treatment with the synthetic layered silicate and
the retention system polymer, wherein said retention system polymer
is a cationic polymer, a nonionic polymer, or an amphoteric polymer
under cationic conditions, or combinations thereof and wherein the
synthetic layered silicate comprises a synthetic hydrous sodium
lithium magnesium silicate and is fed to the papermaking pulp in
the form of an aqueous dispersion which also includes an inorganic
polyphosphate peptizer.
20. The apparatus of claim 19, wherein the device for forming the
pulp comprises a blend chest in communication with the supply of
treated pulp, a fan pump in communication with the blend chest, a
screen in communication with the fan pump, and a head box in
communication with the screen.
21. The apparatus of claim 20, wherein a supply tank is provided
for holding a supply of the pulp, and the communication between the
supply tank and the blend chest includes a refining apparatus for
refining the pulp before entering the blend chest.
22. The apparatus of claim 20, further comprising a white water
silo, wherein the white water silo has an inlet in communication
with said blend chest, an inlet in communication with the head box,
and an outlet in communication with the fan pump.
23. The apparatus of claim 22, further comprising one or more
refiners for refining the pulp prior to forming the pulp in the
head box.
24. A paper or paperboard made from a drained paperweb, the
paperweb comprising a treated pulp, the treated pulp comprising
cellulosic fibers, synthetic hydrous sodium lithium magnesium
silicate, at least one retention system polymer and an inorganic
polyphosphate peptizer, said retention system polymer comprising a
cationic polymer, a nonionic polymer, or an amphoteric polymer
under cationic conditions, or combinations thereof.
Description
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of prior U.S. Provisional Patent Application No.
60/538,622 filed Jan. 23, 2004, which is incorporated in its
entirety by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to papermaking pulps,
papermaking processes employing the pulps, papermaking apparatus
and paper and paperboard products made from the pulps. More
particularly, the present invention relates to treating papermaking
pulp with at least one microparticle-containing retention aid
system.
BACKGROUND OF THE INVENTION
[0003] Retention aid systems containing microparticles and other
particulate materials have been added to papermaking pulps as
process aids to improve retention and other properties such as
formation and drainage. For example, U.S. Pat. No. 5,194,120 to
Peats et al., incorporated herein by reference in its entirety,
describes a retention aid system comprising a cationic polymer and
an amorphous metal silicate material. One type of silicate material
mentioned by Peats et al. system is Laponite.RTM., a synthetic
layered silicate. According to Peats et al., the use of a retention
aid system comprising an amorphous metal silicate material and a
cationic polymer provides several advantages, including improved
retention, drainage and formation while minimizing the amount of
polymer and amorphous metal silicate added to the pulp.
[0004] The microparticle component of the retention aid system is
typically added to the papermaking pulp in the form of a low
viscosity aqueous colloidal dispersion, i.e. a sol. One problem
with microparticle sols employed in papermaking pulps is
instability. Because of the instability of sols used in connection
with papermaking pulps, the sols are often made on-site for
immediate delivery to a papermaking process. A need exists for a
stable microparticle sol retention aid for use in papermaking
processes which can be formed off-site, exhibits a long shelf life,
and can be shipped to a papermaking plant for immediate or future
use in a papermaking process.
[0005] A need also exists for a papermaking pulp that exhibits even
better drainage and retention of fines during a papermaking
process.
SUMMARY OF THE INVENTION
[0006] The present invention relates to the use of a combination of
synthetic layered silicate microparticles, a peptizer and at least
one polymer as a retention aid system for a papermaking pulp or
stock. The synthetic layered silicate is preferably a synthetic
hydrous sodium lithium magnesium silicate and is preferably added
to the papermaking pulp in the form of an aqueous colloidal
dispersion which also contains the peptizer. The polymer can be a
cationic polymer, a nonionic polymer, or an amphoteric polymer used
under cationic conditions. The polymer is preferably a synthetic
nitrogen-containing cationic polymer, for example, a cationic
polyacrylamide. If nonionic, the polymer can be, for example, a
nonionic polyacrylamide or a polyethylene oxide.
[0007] The peptizer is present in the microparticle dispersion for
the purpose of maintaining the dispersion in the form of a sol and
to prevent the dispersion from setting to a gel for a predetermined
period of time. This permits the formation of relatively
concentrated microparticle sols which can be formed off-site, which
exhibit a relatively long shelf life and can be shipped to the
papermaking plant for immediate or future use.
[0008] The inventor has unexpectedly found that certain
microparticle dispersions which include a peptizer also provide
significant improvements over microparticle dispersions which do
not employ a peptizer. For example, the inventor has found that the
use of a retention aid including a microparticle dispersion
containing synthetic hydrous sodium lithium magnesium silicate and
a peptizer significantly improves retention of fines, drainage and
formation, thereby providing enhancements in the papermaking
process and in the paper product.
[0009] In one aspect, the present invention provides a method of
making paper or paperboard comprising: (a) forming a treated pulp
by adding to a papermaking pulp a synthetic layered silicate, a
peptizer and at least one polymer, the synthetic layered silicate
comprising a synthetic hydrous sodium lithium magnesium silicate
and the at least one polymer comprising one or more members of the
group consisting of cationic polymers, nonionic polymers and
amphoteric polymers under cationic conditions; and (b) forming the
treated pulp into said paper or paperboard.
[0010] In another aspect, the present invention provides a
papermaking apparatus comprising a supply of synthetic layered
silicate, a supply of a papermaking pulp, a device for feeding the
synthetic layered silicate from the supply of synthetic layered
silicate to the supply of papermaking pulp, a supply of a retention
system polymer, a device for feeding the retention system polymer
from the supply of retention system polymer to the papermaking
pulp, and a device for forming the pulp into a paper or paperboard
after treatment with the synthetic layered silicate and the
retention system polymer, wherein said retention system polymer is
a cationic polymer, a nonionic polymer, or an amphoteric polymer
under cationic conditions, or combinations thereof and wherein the
synthetic layered silicate comprises a synthetic hydrous sodium
lithium magnesium silicate and is fed to the papermaking pulp in
the form of an aqueous dispersion which also includes an inorganic
polyphosphate peptizer.
[0011] In yet another aspect, the present invention provides a
paper or paperboard made from a drained paperweb, the paperweb
comprising a treated pulp, the treated pulp comprising cellulosic
fibers, synthetic hydrous sodium lithium magnesium silicate, at
least one retention system polymer and an inorganic polyphosphate
peptizer, said retention system polymer comprising a cationic
polymer, a nonionic polymer, or an amphoteric polymer under
cationic conditions, or combinations thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will now be described, by way of example only,
with reference to the accompanying drawings in which:
[0013] FIG. 1 is a flow chart showing a papermaking process
according to an embodiment of the present invention;
[0014] FIG. 2 is a flow chart showing a papermaking process
according to another embodiment of the present invention;
[0015] FIG. 3 is a flow chart showing a papermaking process
according to yet another embodiment of the present invention;
[0016] FIG. 4 is a flow chart showing a papermaking process
according to yet another embodiment of the present invention;
[0017] FIG. 5 is a flow chart showing a papermaking process
according to yet another embodiment of the present invention;
[0018] FIG. 6 is a bar graph showing the time to achieve drainage
of 200 ml of filtrate from paperwebs made of various exemplary and
comparative paperstock formulations;
[0019] FIG. 7 is a bar graph comparing the turbidity of various
exemplary and comparative paperstock formulations;
[0020] FIG. 8 is a bar graph showing the % total first pass
retention (TFPR) of various exemplary and comparative paperstock
formulations;
[0021] FIG. 9 is a plot of time vs. volume showing the drainage of
various exemplary and comparative paperstock formulations;
[0022] FIG. 10 is a bar graph showing the drainage in seconds of
various exemplary and comparative paperstock formulations; and
[0023] FIG. 11 is a bar graph showing the retention for various
exemplary and comparative paperstock compositions.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0024] The present invention relates to the use of a retention aid
system for a papermaking pulp, the system comprising a synthetic
layered silicate, a peptizer and at least one polymer. More than
one type of microparticle, more than one type of peptizer and more
than one type of polymer can be used in the process of the
invention. Paper and paperboard products made according to the
method preferably exhibit excellent opaqueness and/or other
desirable physical properties. Sheets of pulp from which the paper
and paperboard products are made preferably exhibit excellent
drainage and/or excellent retention of pulp fines.
[0025] The synthetic layered silicate preferably comprises a
synthetic hydrous sodium lithium magnesium silicate which is
manufactured and sold under the trademark Laponite.RTM. by Rockwood
Additives Limited of Widnes, Cheshire, United Kingdom. These
synthetic hydrous sodium lithium magnesium silicates are
synthesized by combining salts of sodium, magnesium and lithium
with sodium silicate at carefully controlled rates and
temperatures. This produces an amorphous precipitate which is then
partially crystallized under high temperature and pressure. The
resulting product is filtered, washed, dried and milled to give a
fine white powder.
[0026] For greater certainty, the terms "synthetic hydrous sodium
lithium magnesium silicate" and "hydrous sodium lithium magnesium
silicate" as used herein include silicates which are identified by
CAS No. 533320-86-8 and have the following typical chemical
analysis (wt %): SiO.sub.2 59.5; MgO 27.5; Li.sub.2O 0.8; Na.sub.2O
2.8; loss on ignition 8.2. Such silicates typically comprise a free
flowing white powder having a bulk density of 1,000 kg/m.sup.3;
surface area (BET) of 370 m.sup.2g; pH (2% suspension) of 9.8;
sieve analysis (<250 .mu.m) of 98%; and moisture content of
10%.
[0027] For greater certainty, the terms "synthetic hydrous sodium
lithium magnesium silicate" and "hydrous sodium lithium magnesium
silicate" as used herein do not include synthetic layered silicates
identified by the TSCA name "hydrous sodium lithium magnesium
fluorosilicate" and by CAS No. 64060-48-6 and which have the
following typical chemical composition (wt %--dry basis): SiO.sub.2
51.0; MgO 25.0; Li.sub.2O 1.3; Na.sub.2O 6.0; P.sub.2O.sub.5 3.3; F
5.0; loss on ignition 8.4.
[0028] The synthetic layered silicate microparticles can be added
in any amount sufficient to improve the retention of fines or
drainage or to reduce turbidity when the pulp or stock is formed
into a wet sheet or web. Preferably, the microparticles are added
in an amount of at least about 0.05 lb/ton (0.02 kg/tonne) of
paperstock, based on the dried solids weight of both the
microparticles and the paperstock. More preferably, the
microparticles are added in an amount of from about 0.1 lb/ton
(0.05 kg/tonne) of paperstock to about 5.0 lb/ton (2.3 kg/tonne) of
paperstock, for example, from about 0.2 lb/ton (0.09 kg/tonne) to
about 1.0 lb/ton (0.5 kg/tonne), based on dried solids weight of
the paperstock. For purposes of this patent application, the terms
"furnish", "pulp", "stock", and "paperstock" are used
interchangeably.
[0029] Preferably, the synthetic layered silicate is added to the
pulp in the form of an aqueous, colloidal dispersion of relatively
low viscosity. A colloidal dispersion having these characteristics
is known as a "sol". In addition to the synthetic layered silicate,
the dispersion preferably also contains a peptizer in an amount
sufficient to maintain the dispersion in the form of a sol for a
predetermined period of time. The peptizer essentially stabilizes
the sol to prevent it from setting to a gel for a period of time
which depends at least partially on the concentration of the
synthetic layered silicate. This permits the dispersion to be
formed off-site in a reasonable concentration and then shipped to
the paper making plant for immediate or future use.
[0030] The peptizer is preferably a water soluble salt which
enhances dispersion of the synthetic layered silicate, more
preferably a sodium salt selected from the group comprising sodium
carbonate, sodium metaphosphates, sodium polyacrylates, sodium
hydroxide, sodium chloride, sodium polyphosphates and sodium
pyrophosphates. In particularly preferred embodiments of the
present invention, the peptizer is an inorganic polyphosphate, more
preferably tetrasodium pyrophosphate. The preferred peptizer,
tetrasodium pyrophosphate, is present in certain grades of hydrous
sodium lithium magnesium silicate available from Rockwood Additives
Limited, including Laponite RDS, Laponite XLS and Laponite DS. One
particularly preferred grade of Laponite is Laponite RDS which
comprises synthetic hydrous sodium lithium magnesium silicate (CAS
No. 53320-86-8) in combination with about 5 wt% tetrasodium
pyrophosphate. Laponite RDS sols containing about 10wt%
concentration of Laponite are stable for about 3 days. Preferably,
the sol has a laponite concentration of up to about 6 wt % which is
stable for at least about 90 days. Sols having a microparticle
concentration in this range exhibit sufficiently long shelf to
allow them to be formed off-site for shipment and subsequent use in
a papermaking process.
[0031] As mentioned above, the inventor has unexpectedly discovered
that certain microparticle dispersions which include a peptizer
also provide significant improvements over microparticle
dispersions which do not employ a peptizer. In particular, the
inventor has found that the inclusion of a peptizer in the
microparticle dispersion significantly improves retention of fines,
drainage and formation, thereby providing enhancements in the
papermaking process and in the paper product. For example, the
inventor has found that Laponite RDS, which contains the peptizer
tetrasodium pyrophosphate (TSPP), provides significantly enhanced
drainage and retention, with lower turbidity, than equivalent
amounts of Laponite RD.
[0032] Without being bound by theory, it is believed that when the
TSPP is blended and dissolved in a colloidal dispersion of
Laponite, the pyrophosphate ions become associated with the
positively charged edges of the Laponite crystals, making the whole
particle negatively charged. This effectively increases the
negative charge on the Laponite crystals and causes them to have a
greater attraction to cationic particles present in the papermaking
process.
[0033] The polymer is preferably added to the papermaking pulp
before addition of the microparticles, though any order of addition
can be used. Preferably, the polymer can be any polymer which does
not adversely affect the formation of pulp or paper and may
preferably comprise a coagulant and/or a flocculant. Preferably,
the polymer is a medium to high molecular weight synthetic polymer,
for example, a cationic nitrogen-containing polymer such as a
cationic polyacrylamide or a copolymer thereof, or a cationic
diallyldimethylammonium chloride or a copolymer thereof.
[0034] The polymer can be cationic, nonionic, or amphoteric. If
amphoteric, the polymer is preferably used under cationic
conditions. At least one other polymer of any kind can be used in
addition to the polymers recited above so long as the at least one
other polymer does not substantially adversely affect the retention
properties of the present invention. The at least one other polymer
can preferably be a polyamidoamineglycol (PAAG) polymer.
[0035] The polymer preferably has a molecular weight in the range
of from about 100,000 to about 25,000,000, and more preferably from
about 500,000 to about 18,000,000, though other molecular weights
are possible to achieve the intended effect.
[0036] The polymer can preferably be a high molecular weight linear
cationic polymer or a crosslinked polyethylene oxide. Exemplary
high molecular weight linear cationic polymers and shear stage
processing suitable for use in the pulps and methods of the present
invention are described in U.S. Pat. Nos. 4,753,710 and 4,913,775
to Langley et al., both of which are incorporated herein in their
entireties by reference.
[0037] The polymer is preferably added before at least one of the
significant shear steps of the papermaking process and may be added
in more than one step. The microparticles can be added before or
after the various significant shear steps of the papermaking
process. According to some embodiments of the present invention,
the polymer can be added before the microparticles and before at
least one significant shear step in the papermaking process. If the
polymer is added before the microparticles, the microparticles can
be added before or after a final shear step of the papermaking
process. Although it is preferable to add the polymer to the
papermaking pulp before the last shear point in the papermaking
process, the polymer can be added after the last shear point.
[0038] The microparticles preferably form bridges or networks
between various particles. The polymer is preferably partially
attached (e.g., adsorbed) onto the surfaces of particles within the
stock and can provide sites of attachment.
[0039] Aqueous cellulosic papermaking pulp or stock can be treated
by first adding the polymer to the pulp or stock, followed by
subjecting the paper stock to high shear conditions, followed by
the addition of the microparticles prior to sheet formation. As
discussed above, the polymer can be cationic, nonionic, or
amphoteric under cationic conditions. Alternatively, the polymer
can be added simultaneously with the synthetic layered silicate
microparticles.
[0040] Preferred cationic polyacrylamides for use as the retention
system polymer are described in more detail below. If a cationic
polyacrylamide is used as the cationic polymer, the cationic
polyacrylamide can have a molecular weight in excess of 100,000,
and preferably has a molecular weight of from about 500,000 and
18,000,000. The combination of the polymer and the synthetic
layered silicate microparticles preferably provides a suitable
balance between freeness, dewatering, fines retention, good paper
formation, strength, and resistance to shear.
[0041] The polymer composition of the retention system is added in
an amount effective to preferably improve the drainage or retention
of the pulp compared to the same pulp but having no polymer
present. The polymer is preferably added in an amount of at least
about 0.01 pound of polymer per ton (0.005 kg/tonne) of paperstock,
based on the weight of dried solids of both the polymer and the
paperstock. More preferably, the polymer is added in an amount of
from about 0.1 lb/ton (0.05 kg/tonne) of paperstock to about 5
lb/ton (2.3 kg/tonne) of paperstock, even more preferably from
about 0.2 lb/ton (0.09 kg/tonne) to about 2 lb/ton (1 kg/tonne)
based on the dried solids weight of the paperstock, though other
amounts can be used.
[0042] If the polymer is cationic, any cationic polymer or mixture
thereof can be used and preferably conventional cationic polymers
commonly associated with papermaking can be used in the pulps or
stocks of the present invention. Examples of cationic polymers
include, but are not limited to, cationic starches and cationic
polyacrylamide polymers, for example, copolymers of an acrylamide
with a cationic monomer, wherein the cationic monomer may be in a
neutralized or quaternized form. Nitrogen-containing cationic
polymers are preferred. Exemplary cationic monomers which may be
copolymerized with acrylamide to form preferred cationic polymers
useful according to the present invention, include amino alkyl
esters of acrylic or methacrylic acid, and diallylamines in either
neutralized or quaternized form. Exemplary cationic monomers and
cationic polyacrylamide polymers are described in U.S. Pat. No.
4,894,119 to Baron, Jr., et al., which is incorporated herein in
its entirety by reference.
[0043] The polymer may also be a polyacrylamide formed from
comonomers that include, for example,
1-trimethylammonium-2-hydroxypropylmethacrylat- e methosulphate.
Other examples of cationic polymers, include, but are not limited
to, homopolymers of diallylamine monomers, homopolymers of
aminoalkylesters of acrylic acids, and polyamines, as described in
U.S. Pat. No. 4,894,119. Co-polymers, ter-polymers, or higher forms
of polymers may also be used. Further, for purposes of the present
invention, a mixture of two or more polymers may be used.
[0044] In embodiments wherein the polymer contains a cationic
polyacrylamide, nonionic acrylamide units are preferably present in
the copolymer, preferably in an amount of at least about 30 mol %
and generally in an amount of no greater than 95 mol %. From about
5 mol % to about 70 mol % of the polymer is preferably formed from
a cationic comonomer.
[0045] The papermaking pulp or stock can be any conventional type,
and, for instance, can contain cellulose fibers in an aqueous
medium at a concentration of preferably at least about 50% by
weight of the total dried solids content in the pulp or stock. The
retention system of the present invention can be added to many
different types of papermaking pulp, stock, or combinations of
pulps or stocks. For example, the pulp may comprise virgin and/or
recycled pulp, such as virgin sulfite pulp, broke pulp, a hardwood
kraft pulp, a softwood kraft pulp, mixtures of such pulps, and the
like.
[0046] The retention aid system can be added to the pulp or stock
in advance of depositing the pulp or stock onto a papermaking wire.
The pulp or stock containing the retention aid system has been
found to exhibit good dewatering during formation of the paperweb
on the wire. The pulp or stock also exhibits a desirable high
retention of fiber fines and fillers in the paperweb products under
conditions of high shear stress imposed upon the pulp or stock.
[0047] In addition to the retention aid system used in accordance
with the present invention, the papermaking pulp or stock according
to the present invention may further contain other types of
microparticles. One or more different types of secondary
microparticle additives, different from the synthetic layered
silicate microparticles, may be added to the pulp at any time
during the process. The secondary microparticle additive can be a
natural or synthetic hectorite, bentonite, zeolite, non-acidic
alumina sol, or any conventional particulate additives as are known
to those skilled in the art. Exemplary synthetic microparticles are
described in U.S. Pat. Nos. 5,571,379 and 5,015,334, which are
incorporated herein in their entireties by reference.
[0048] In addition to the synthetic layered silicate microparticles
retention aid system used in accordance with the present invention,
the papermaking pulps or stocks according to the present invention
may further contain a coagulantiflocculant retention system having
a different composition than the retention system of the present
invention.
[0049] The papermaking pulps of the present invention may also
contain a conventional papermaking pulp-treating enzyme that has
cellulytic activity. Preferably, the enzyme composition also
exhibits hemicellulytic activity. Suitable enzymes and
enzyme-containing compositions include those described in U.S. Pat.
Nos. 5,356,800 and 6,342,381 to Jaquess, and International
Publication No. WO 99/43780, all incorporated herein in their
entireties by reference. Other exemplary papermaking pulp-treating
enzymes are BUZYME.TM. 2523 and BUZYME.TM. 2524, both available
from Buckman Laboratories International, Inc., Memphis, Tenn. A
preferred cellulytic enzyme composition preferably contains from
about 5% by weight to about 20% by weight enzyme. The preferred
enzyme composition can further contain polyethylene glycol,
hexylene glycol, polyvinylpyrrolidone, tetrahydrofuryl alcohol,
glycerine, water, and other conventional enzyme composition
additives, as for example, described in U.S. Pat. No. 5,356,800.
The enzyme may be added to the pulp in any conventional amount,
such as in an amount of from about 0.001 % by weight to about
0.100% by weight enzyme based on the dry weight of the pulp, for
example, from about 0.005% by weight to about 0.05% by weight.
[0050] In one preferred embodiment of the present invention, an
enzyme composition is included in the pulp or stock and contains at
least one polyamide oligomer and at least one enzyme. The polyamide
is present in an effective amount to stabilize the enzyme.
Exemplary enzyme compositions containing polyamide oligomers and
enzymes are described in International Published Application No. WO
99/43780, which is incorporated herein in its entirety by
reference.
[0051] If an enzyme composition is included, it can include a
combination of two or more different enzymes. The enzyme
composition can include, for example, a combination of a lipase and
a cellulase, and optionally can include a stabilizing agent. The
stabilizing agent may be a polyamide oligomer as described
herein.
[0052] One particular additive for use according to the methods of
the present invention is a cationic starch. Cationic starch may be
added to the pulp or stock of the present invention to form a
starch treated pulp. Starch may be added at one or more points
along the flow of papermaking pulp through the papermaking
apparatus or system of the present invention. For instance,
cationic starch can be added to a pulp at about the same time that
the acidic aqueous alumina sol is added to the pulp. Preferably, if
a cationic starch is employed, it is added to the pulp or combined
with the pulp prior to introducing the synthetic layered silicate
microparticles to the pulp. The cationic starch can alternatively
or additionally be added to the pulp after the pulp is first
treated with an enzyme, a coagulant, or both. Preferred cationic
starches include, but are not limited to, potato starches, corn
starches, and other wet-end starches, or combinations thereof.
[0053] Conventional amounts of starch can be added to the pulp. An
exemplary amount of starch that can be used according to the
present invention is from about 5 to about 25 pounds per ton based
on the dried solids weight of the pulp.
[0054] A biocide may be added to the pulp in accordance with
conventional uses of biocides in papermaking processes. For
example, a biocide may be added to the treated pulp in a blend
chest after the pulp has been treated with the optional enzyme and
polymer. Biocides useful in the papermaking pulps according to the
present invention include biocides well known to those skilled in
the art, for example, biocides available from Buckman Laboratories
International, Inc., Memphis, Tenn., such as BUSAN.TM.
biocides.
[0055] The pulps or stocks of the present invention may
additionally be treated with one or more other components,
including polymers such as anionic and non-ionic polymers, clays,
other fillers, dyes, pigments, defoamers, pH adjusting agents such
as alum, microbiocides, and other conventional papermaking or
processing additives. These additives can be added before, during,
or after introduction of the synthetic layered silicate
microparticles. Preferably, the synthetic layered silicate
microparticles are added after most, if not all, other additives
and components are added to the pulp. Thus, the synthetic layered
silicate microparticles can be added to the papermaking pulp after
the addition of enzymes, coagulants, flocculants, fillers, and
other conventional and non-conventional papermaking additives.
[0056] The addition of the retention system in accordance with the
present invention can be practiced on most, if not all,
conventional papermaking machines.
[0057] A flow chart of a papermaking system for carrying out one of
the methods of the present invention is set forth in FIG. 1. It is
to be understood that the system shown is exemplary of the present
invention and is in no way intended to restrict the scope of the
invention. In the system of FIG. 1, an optional supply of enzyme
composition at a desired concentration is combined with a flowing
stream of papermaking pulp to form a treated pulp. The supply of
pulp shown represents a flow of pulp, as for example, supplied from
a pulp holding tank or silo. The supply of pulp shown in FIG. 1 can
be a conduit, holding tank, or mixing tank, or other container,
passageway, or mixing zone for the flow of pulp. The supply of
enzyme composition can be, for example, a holding tank having an
outlet in communication with an inlet of a treated pulp tank.
[0058] The pulp treated with the enzyme composition is passed from
the treated pulp tank through a refiner and then through a blend
chest where optional additives, for example, a biocide, may be
combined with the treated pulp. The refiner has an inlet in
communication with an outlet of the treated pulp tank, and an
outlet in communication with an inlet of the blend chest.
[0059] According to the embodiment of FIG. 1, the pulp treated in
the blend chest is passed from an outlet of the blend chest through
a communication to an inlet of a machine chest where optional
additives may be combined with the treated pulp. The blend chest
and machine chest can be of any conventional type known to those
skilled in the art. The machine chest ensures a level head, that
is, a constant pressure on the treated pulp or stock throughout the
downstream portion of the system, particularly at the head box.
[0060] From the machine chest, the pulp is passed to a white water
silo and then to a fan pump. The retention system polymer of the
present invention is preferably introduced into the flow of pulp
between the silo and the fan pump. The supply of retention system
polymer composition can be, for example, a holding tank having an
outlet in communication with a line between the white water silo
and the fan pump. As pulp passes from the fan pump to a screen, the
synthetic layered silicate microparticles are preferably added.
Conventional valving and pumps used in connection with introducing
conventional additives can be used. The screened pulp passes to a
head box where a wet papersheet is made on a wire and drained. In
the system of FIG. 1, drained pulp resulting from papermaking in
the headbox is recirculated to the white water silo.
[0061] In the embodiment shown in FIG. 2, the synthetic layered
silicate microparticles are added first to the refined treated pulp
between the white water silo and the fan pump. The retention system
polymer is added after the fan pump and before the screen.
[0062] Another embodiment of the present invention is shown in FIG.
3. A pulp optionally treated with a cationic starch is refined,
passed to a blend chest, passed to a machine chest, and then passed
to a white water silo. Between the white water silo and the fan
pump the retention system polymer is preferably added to the pulp.
The synthetic layered silicate microparticles are preferably added
after the pulp passes through the screen and just prior to sheet
formation in the head box.
[0063] The apparatus of the present invention can also include
metering devices for providing a suitable concentration of the
synthetic layered silicate microparticles or other additives to the
flow of pulp.
[0064] A cleaner, for example, a centrifugal force cleaning device,
can be disposed between, for instance, the fan pump and the screen,
according to any of the embodiments of FIGS. 1-3 above.
[0065] FIGS. 4 and 5 are flow charts illustrating the polymer and
microparticle addition steps in two particularly preferred
embodiments of the present invention. It will be appreciated that
FIGS. 4 and 5 illustrate only those components (i.e. fan pump,
screen and headbox) and addition steps which are necessary to
describe the polymer and microparticle addition steps in these
preferred processes, and that the processes and apparatus
illustrated in FIGS. 4 and 5 may preferably include some or all of
the optional additives, apparatus components and/or process steps
shown in FIGS. 1 to 3 and described above.
[0066] The pulp passes through the apparatus of FIGS. 4 and 5 in
the direction indicated by the arrows, passing through the fan pump
and the screen on its way to the headbox. The pulp is sheared by
both the fan pump and the screen, however the shear applied to the
pulp by the screen is greater than that applied by the fan pump, so
that the screen is the final high shear stage in the papermaking
process prior to entry of the pulp into the headbox of the
papermaking apparatus.
[0067] In both FIGS. 4 and 5, a coagulant polymer is preferably
added before the fan pump. The coagulant preferably comprises a
relatively low molecular weight, cationic, high charge density
polymer to scavenge and collect colloidal particles, primarily
anionic fibers and fillers. The colloidal particles are coagulated
to form macro-colloids which are larger in size and more easily
retained in the sheet upon drainage. The coagulant is preferably a
polyamine or diallyidimethylammonium chloride (DADMAC) polymer, or
copolymers thereof. A particularly preferred coagulant for use in
the processes illustrated in FIGS. 4 and 5 is BUFLOC.TM. 5376,
available from Buckman Laboratories International, Inc., which is a
cationic DADMAC having a 95% charge density and a molecular weight
of about 500,000. The coagulant polymer is preferably added to the
pulp in an amount of from about 0.05 to about 1.0 kg/tonne of pulp
on a dry basis, more preferably from about 0.1 to about 0.5
kg/tonne and even more preferably about 0.3 kg/tonne.
[0068] The processes of FIGS. 4 and 5 both include the addition of
a microparticle-containing retention aid system comprising a
retention system polymer and a microparticle. The microparticle is
a synthetic layered silicate, more preferably a synthetic hydrous
sodium lithium magnesium silicate, and even more preferably a
synthetic hydrous sodium lithium magnesium silicate in combination
with a peptizer, the most preferred peptizer being tetrasodium
pyrophosphate. The microparticle preferably comprises one or more
of Laponite RDS, XLS and DS, and more preferably comprises Laponite
RDS. The microparticle is preferably added in an amount of from
about 0.1 to about 1.0 kg/tonne of pulp on a dry basis, more
preferably from about 0.2 to about 0.6 kg/tonne and even more
preferably about 0.4 kg/tonne.
[0069] The retention system polymer is preferably a flocculant and
may preferably comprise any of the synthetic nitrogen-containing
cationic polymers described above. A particularly preferred
retention system polymer is BUFLOC.TM. 5511, available from Buckman
Laboratories International, Inc., which is a cationic
polyacrylamide having a molecular weight of about 10,000,000. The
retention system polymer is preferably added to the pulp in an
amount of about 0.05 to 1.0 kg/tonne of pulp on a dry basis, more
preferably from about 0.05 to about 0.5 kg/tonne and even more
preferably from about 0.1 to about 0.2 kg/tonne.
[0070] The flow charts of FIGS. 4 and 5 differ from one another in
the order of addition of the retention system polymer and the
microparticle. In FIG. 4, the microparticle is added before the
screen, more preferably between the fan pump and the screen, while
the retention system polymer is added after the screen, more
preferably between the screen and the head box. In FIG. 5, the
order of addition is reversed, with the polymer being added before
the screen, more preferably between the fan pump and the screen,
and the microparticle being added after the screen, more preferably
between the screen and the head box. The order of addition in FIG.
5 is preferred.
[0071] The invention is further described in the following
examples.
EXAMPLES
[0072] In the examples below, various components used in the
examples are abbreviated. In the examples, the components
identified as "RD", "RDS" and "JS" are Laponite RD, Laponite RDS
and Laponite JS respectively, available from Rockwood Additives
Limited. Laponite RD is a hydrous sodium lithium magnesium
silicate; Laponite RDS is a hydrous sodium lithium magnesium
silicate with tetrasodium pyrophosphate; and Laponite JS is a
hydrous sodium lithium magnesium fluorosilicate with tetrasodium
pyrophosphate. When followed by a numerical value, for example,
"RDS 0.5", the numerical value represents the amount of pounds on a
dry basis of the Laponite microparticles per ton of paperstock
based on the dried solids weight of the paperstock.
[0073] In the examples below, the abbreviations "B 594" and "594"
represent BUFLOC.TM. 594, available from Buckman Laboratories
International, Inc., which is a high molecular weight cationic
polyacrylamide having an average molecular weight of from about
5,000,000 to about 7,000,000 units and a 21% charge density. When
followed by a numerical value, for example, "594 0.5", the
numerical value represents the amount of pounds on a dry basis of
the Bufloc 594 polymer per ton of paperstock based on the dried
solids weight of the paperstock.
[0074] The abbreviations "B 5511" and "5511" represent BUFLOC.TM.
5511, available from Buckman Laboratories International, Inc.,
which is a cationic polyacrylamide having a molecular weight of
about 10,000,000. When followed by a numerical value, for example,
"5511 0.5", the numerical value represents the amount of pounds on
a dry basis of the Bufloc 5511 polymer per ton of paperstock based
on the dried solids weight of the paperstock.
[0075] In samples where both a polymer and a microparticle
component are added, the order of addition is specified. For
example, the abbreviation "B 5511 0.5/RDS 0.5" indicates that the
polymer component Bufloc 5511 is added to the furnish before the
microparticle component Laponite RDS. This simulates a papermaking
process in which the polymer is added prior to the final high shear
stage (typically before the screen) and the microparticle is added
after the final high shear stage (typically between the screen and
the headbox). Similarly, the abbreviation "RDS 0.5/B 5511 0.5"
indicates that the polymer component Bufloc 5511 is added to the
furnish after the microparticle component Laponite RDS. This
simulates a papermaking process in which the microparticle is added
prior to the final high shear stage (typically before the screen)
and the polymer is added after the final high shear stage
(typically between the screen and the headbox).
Example I
Drainage and Turbidity Tests
[0076] Tests were conducted at a paper mill. Drainage was performed
using a small screen through which 500 ml samples were drained
using a modified Schopper Riegler method. Mixing was carried out in
a food blender.
[0077] Equipment used for the modified Shopper Riegler drainage
test included the following: a Modified Schopper Riegler (MSR); a
1000 ml graduated cylinder; a stopwatch; a 5-gallon (18.9 I)
plastic bucket; wires for MSR; a vacuum flask and funnel (for
retention); Whatman ashless filter papers (for ash retention); a
turbidity meter; a hemocytometer; and a microscope.
[0078] Samples to be tested were taken from the headbox of the
papermaking apparatus. For each test, 1000 ml was required. Because
temperature has an impact on drainage, each test was run
immediately after the sample was taken. For lab studies with the
retention aids, the furnish was kept at the same temperature as the
headbox temperature.
[0079] If the MSR was cold and the sample was hot, the MSR was
warmed up by running hot water over the outside and inside of the
MSR. If no hot water was available, cold water was used. All tests
were conducted in the same way. It was imperative that the MSR wire
was devoid of any fibers or fines. The wire was backflushed with
water before the test was run. Uniform fiber, fines, and filler
distribution in the sample was ensured by agitating the fiber
slurry in the bucket 1000 ml of the slurry was measured in a
graduated cylinder and poured into the MSR while holding the
plunger down. The graduated cylinder was placed under the MSR. The
plunger was then released and the stop watch started at the same
time. The time required for drainage of the sample in incremental
units of 100 ml was measured and recorded. The incremental units of
100 ml chosen were purely empirical. For example, very slow
draining stock samples were instead measured at 100, 150, and 200
ml drainage times. Sometimes several tests were needed to determine
the starting volume tests. The different levels of polymers in the
various samples were compared, and for this purpose, furnish
samples were obtained from the machine before addition of the
retention/drainage aid. Drainage and retention values were compared
against blank furnishes to determine improvement. To measure
retention performance, the MSR filtrate was filtered through a
pre-weighed filter paper, dried in an oven at from 105.degree. C.
to 120.degree. C. and weighed again. The weight difference was
recorded in mg/ml.
[0080] Drainage times were compared based on different levels of
additives (i.e. polymer and/or microparticle) in the furnish.
Drainage times were recorded in seconds for each volume level. The
total suspended solids were estimated with a turbidity meter. The
filtrate could also have been filtered to determine suspended
solids. Solids contents of MSR filtrate could be reported in mg/ml
and used to indicate the retention capabilities of different
systems, with lower numbers indicating better retention.
[0081] For repeated tests, the sample was taken from the same place
along the papermaking system. It was ensured that the furnish
composition was the same for the repeated test. Repeated tests that
did not agree within reason with a corresponding original test were
suspect.
[0082] The MSR was kept clean and constantly rinsed with water to
keep residual fibers from building up on the sides. The screen was
periodically cleaned to remove resin build-up, and brushed clean
with a mild detergent. The wires were checked to make sure bent or
damaged wires were not used. All tests were conducted in the same
manner and at the same consistency.
[0083] The paper mill employed a newsprint furnish comprising 70 wt
% thermomechanical pulp (TMP) and 30% de-inked pulp (DIP). The pulp
had a headbox conductivity of 1,000 microsiemens, a cationic demand
of 0.15 ml/l of 0.001N solution and a consistency of 0.65. The
headbox pH of the paperstock was 4.83. Additives combined with the
paperstock included calcined clay as a filler in an amount of 2 wt
% based on the dried solids weight of the paperstock. The calcined
clay was present in the DIP component.
[0084] Polymer was added to the paperstock in varying amounts up to
0.75 lb/ton (0.35 kg/tonne) of paperstock, based on the dried
solids weight of both the polymer and the paperstock.
[0085] The microparticle was added to the paperstock in varying
amounts up to 1.0 lb/ton (0.46 kg/tonne). All microparticle dosages
were calculated on dry basis.
[0086] The results of the tests are shown in Tables 1 and 2 below.
(Table 1 will contain the drainage/turbidity data and Table 2 will
contain the retention data). In Table 1, the column headings "100",
"150", "200" and "250" represent the number of milliliters of
filtrate collected that drained through the wire. The corresponding
numbers underneath the column headings represent the number of
seconds needed for the respective number of milliliters (ml) of
filtrate to drain through the wire and be collected. For example,
in the first entry of Table 1, the paperstock identified as
"Blank", (having no microparticle retention system) required 27
seconds for 100 ml of filtrate to be drained through the forming
wire and collected, required 58 seconds for 150 ml of filtrate to
be collected, and required 90 seconds for 200 ml of filtrate to be
collected. In Table 1 the turbidity, measured in units of
nephelometric turbidity unites (NTU), is listed in the last column.
For each of the various samples tested and reported in Table 1
which include both a microparticle additive and a polymer, the
order of addition is specified in the table. For example, in
samples 5 to 7 and 11 to 13 of Table 1, the polymer was added
first. In samples 8 to 10 the microparticle was added first.
1TABLE I Drainage and Turbidity Sample Sample 100 150 200 250 No.
Composition* ml. ml. ml. ml. Turbidity 1 Blank 27 58 90 141 249 2 B
5511 0.25 25 55 87 129 193 3 B 5511 0.5 22 46 76 112 211 4 B 5511
0.75 24 49 78 112 210 5 B 5511 0.5/RDS 0.5 17 38 64 93 114 6 B 5511
0.5/RDS 0.75 15 31 52 75 70 7 B 5511 0.5/RDS 1 13 29 48 72 91 8 RDS
0.5/B 5511 0.5 14 30 50 70 97 9 RDS 0.75/B 5511 0.6 15 30 50 70 94
10 RDS 1/B 5511 0.7 13 28 46 64 101 11 B 5511 0.5/RD 0.5 15 45 74
102 150 12 B 5511 0.5/RD 0.75 15 39 64 94 129 13 B 5511 0.5/RD 1 14
34 55 83 91 14 Blank 2 29 58 93 139 241 *All sample compositions in
lb/ton
[0087] The data shown in Table 1 is graphically represented in
FIGS. 6 and 7.
Example 2
Retention Tests
[0088] Britt Jar tests were performed at 1,000 rpm to evaluate
performance of the retention aid system according to the invention
based on increased first pass retention and increased first pass
ash retention. In the Britt Jar, the furnish is under continuous
movement, so no fiber mat is formed and the water can drain
continuously through the wire. This simulates the stock and water
dewatering occurring on the paper machine.
[0089] The furnish used in the Britt Jar tests was identical to the
furnish used in Example 1.
[0090] In the Britt Jar tests, the chemicals are applied in the
correct sequence and the furnish is mixed to a degree to simulate
the treatment of the furnish by paper machine equipment such as fan
pumps and centri-screens. As it is sheared, the stock spends a
second (at the most) actually in the fan pump or the screens.
Another way to simulate the shear and to represent the actual short
contact time is to carry out all chemical mixing outside the Britt
Jar Retention tester. Chemical additive mixing is carried out using
a common household food blender.
[0091] The mixing process is the same for the retention as well as
drainage work.
[0092] All high shear mixing is carried out outside the Britt Jar
using a food blender since this is more representative of the high
shear points in the papermaking process. This also avoids plugging
the Britt Jar wire. Each chemical addition is followed by a short
two-second burst in the food blender. This simulates stock
(including coagulant, starch, high molecular weight polymer) going
through the fan pump.
[0093] To simulate pre-screen addition of polymer or microparticle
component a short one-second burst in the food blender is used. To
simulate post-screen addition of polymer or microparticle the
treated stock sample is poured into a cylinder, followed by
addition of the polymer or microparticle component and inversion of
the Britt Jar four times.
[0094] The following equipment was used in the Brift Jar tests:
Britt Jar tester; wires--80P for newsprint furnishes;
pre-conditioned ashless filter papers--Whatman #41 or 43; diluted
polymer samples; stock sample (at least 20 liters); balance to
0.001 g; buchner funnel; drying oven; furnace for ash
determination; plastic containers with lids; syringes--1, 5, and 10
mL; and a blender--standard household food blender with pulse
feature.
[0095] Each of the stock and polymer samples were prepared as
follows: prepare stock and polymer samples; make sure the wire for
the Britt Jar is wet; set the Britt Jar speed at the required set
point and turn it on; mix chemicals into stock; pour treated stock
into Britt Jar; wait 5 seconds; open clamp and start collecting
filtrate; collect first 100 mL of filtrate; filter the filtrate
through the pre-conditioned filter papers and dry in the oven at
110.degree. C.; and calculate the % TFPR. If required ash the dried
filter papers to determine the % FPAR.
[0096] If required ash the dried filter papers to determine the %
FPAR.
[0097] Calculations 1 1. Consistency = % solids in sample , and is
represented by [ ] symbol = 100 .times. ( wt suspended solids ) / (
wt or vol . of the original sample ) 2. FPR , First Past Retention
= % of HB solids retained in sheet = ( [ HB ] - [ TW ] ) / [ HB ]
.times. 100
Example
[HB]=0.75%, [TW]=0.18%
FPR=100 (0.75-0.18)/0.75=76%
[0098] 3. FPAR, First Pass Ash Retention=([HB ash]-[TW ash])/[HB
ash].times.100
[0099] [HB ash] is determined by ashing the HB, then multiplying
the % ash value by the [HB]. [TW ash] is determined by ashing the
TW, then multiplying the % ash value by the [TW].
[0100] The results of the retention tests are shown below in Table
2.
2TABLE 2 Retention SAMPLE NO. COMPOSITION TFPR/percent 1 Blank
24.22 2 594 0.5 48.99 3 594 0.5/RD 0.5 59.05 4 594 0.5/RD 1 63.26 5
594 0.5/RDS 0.5 65.66 6 594 0.5/RDS 1 71.71
[0101] The data shown in Table 2 is graphically illustrated in FIG.
8.
Example 3
Drainage Tests Comparing Laponite RD, RDS and JS
[0102] Drainage tests were conducted on an alkaline furnish
following the procedure described in Example 1.
[0103] All the samples containing a microparticle also contained a
polymer, Bufloc 5511. In most of these tests, Bufloc 5511 was added
to the furnish before the microparticle. For Laponite RDS, tests
were also conducted with the reverse order of addition.
[0104] The results of the drainage tests are illustrated in FIGS. 9
and 10. As shown in these figures, the furnish containing Laponite
RDS had better drainage properties than the furnish containing
either Laponite JS or Laponite RD. In addition, drainage results
using RDS were better when the polymer (Bufloc 5511) was added
before the Laponite RDS than when Laponite RDS was added last.
Example 4
Retention Tests Comparing Laponite RD, RDS and JS
[0105] Britt Jar tests as described in Example 2 were performed
using various combinations of polymer (Bufloc 5511) and
microparticles. The tests were performed with an alkaline fine
paper furnish comprised of 60% hardwood and 40% softwood, having a
pH of 7.9, conductivity of 670 microsiemens and ash content of 20%
precipitated calcium carbonate (PCC) added at the machine chest in
the paper process. The retention data, including both total first
pass retention (TFPR) and first pass ash retention (FPAR) is shown
below in Table 3 and is also illustrated in FIG. 11.
3TABLE 3 SAMPLE NO. COMPOSITION TFPR/percent FPAR/percent 1 Blank
50.97 18.14 2 5511 0.5 78.72 69.16 3 5511 0.5/JS 0.5 78.93 71.49 4
5511 0.5/JS 0.75 82.80 73.05 5 5511 0.5/RD 0.5 81.44 73.15 6 5511
0.5/RD 0.75 84.99 76.46 7 RDS 0.5/5511 0.5 84.22 79.59 8 RDS
0.75/5511 0.5 86.63 80.58 9 5511 0.5/RDS 0.5 87.21 81.02 10 5511
0.5/RDS 0.75 89.99 82.04
[0106] As shown in Table 3 and FIG. 11, the retention results for
Laponite RDS were better than the results obtained for comparable
concentrations of Laponite JS and Laponite RD. Also, the results
show that addition of Bufloc 5511 followed by addition of Laponite
RDS provided the best results.
[0107] It will be apparent to those skilled in the art that various
modifications and variations can be made to the embodiments of the
present invention without departing from the spirit or scope of the
present invention. Thus, it is intended that the present invention
covers other modifications and variations of this invention within
the scope of the appended claims and their equivalents.
* * * * *