Note: Descriptions are shown in the official language in which they were submitted.
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Cationised Pol~accharide Product
The present invention relates to a cationised polysaccharide product, which
has
one or more substituents having an aromatic group and one or more substituents
having
no aromatic group, a method for the preparation of the cationised
polysaccharide product,
use of the cationised polysaccharide pr-oduct and a papermaking process in
which the
cationised polysaccharide product is used as an additives to an aqueous
cellulosic
suspension.
Background
In the papermaking art, an aqueous suspension containing cellulosic fibres,
and
optional fillers and additives, referred to as the 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. Drainage and retention aids are
widely used
in the papermaking process and examples of such aids are cationic and
amphoteric
polysaccharides like cationic starches and cationic guar gums. The
polysaccharides can
be used alone or in combination with other polymers and/or with anionic
microparticulate
materials such as, for example, anionic inorganic particles like colloidal
silica. Cationic
and amphoteric polysaccharides are also widely used as dry strength agents.
International.Patent Application WO 99/55964 discloses cationic or amphoteric
polysaccharides having hydrophobic groups for use as additives in papermaking
and as
dry-strength agents for the paper produced.
U.S. Patent Nos. 4,388,150, 4,755,259, 4,961,825, 5,127,994, 5,643,414,
5,447,604, 5,277,764, 5,607,552, 5,603,805, and 5,858,174, and European Patent
No.
500,770 disclose the use of cationic and/or amphoteric polysaccharides and
anionic
inorganic particles as stock additives in papermaking.
The cationic groups of cationised polysaccharides can be obtained by the
reaction of a polysaccharide with a quaternising agent. Examples of
cationisation
processes using such agents are known from U.S. Patent Nos. 2,876,217,
3,422,087,
4,785,087, 5,827,372 and European Patent Nos. 303,039; 400,361; 737,210 and
874,000.
It would be advantageous to be able to provide drainage and retention aids
with
improved performance. It would also be advantageous to be able to provide a
papermaking process with improved drainage and/or retention performance. It
would
further be advantageous to be able to produce a paper with improved dry
strength
properties.
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2
The Invention
In accordance with the present invention there is generally provided a
cationised
polysaccharide product comprising at least one first substituent having an
aromatic group
and at least one secorid substituent having no aromatic group. There is also
provided a
cationised polysaccharide product comprising at least one first substituent
having an
aromatic group and at least one second substituent having no aromatic group,
wherein
the polysaccharide has a molar ratio of first substituent to second
substituent within the
range of from 10:1 to 1:10. There is also provided a cationised polysaccharide
product
comprising one or more polysaccharides having at least one first substituent
having an
aromatic group and one or more polysaccharides having at least one second
substituent
having no aromatic group. There is further provided a cationised
polysaccharide product
comprising at least one first substituent having an aromatic group and at
least one
second substituent having no aromatic group, wherein the polysaccharide has a
degree
of aromatic substitution (DSA~) within the range of from 0.0005 to 2.0 and a
degree of non-
aromatic substitution (DS~on-Ar) within the range of from 0.0005 to 2Ø There
is also provided
a cationised polysaccharide product obtainable by reacting one or more
polysaccharides
with at least one first aromatic agent and at least one second non-aromatic
agent,
wherein the first aromatic agent and second non-aromatic agent are reacted in
a molar
ratio within the range of from 10:1 to 1:10. There is also provided a
cationised
polysaccharide product obtainable by reacting a first polysaccharide with at
least one first
aromatic agent, reacting a second polysaccharide with at least one second non-
aromatic
agent, and then mixing the polysaccharides obtained.
The present invention also generally relates to a method for the preparation
of a
cationised polysaccharide product comprising reacting one or more
polysaccharides with
at least one aromatic agent and at least one non-aromatic agent. The invention
further
relates to a method for the preparation of a cationised polysaccharide product
comprising
reacting one or more polysaccharides with at least one first aromatic agent
and at least
one second non-aromatic agent, wherein the first aromatic agent and second non-
aromatic agent are reacted in a molar ratio within the range of from 10:1 to
1:10. The
invention further relates to a method for the preparation of a cationised
polysaccharide
product comprising reacting a first polysaccharide with at least one aromatic
agent,
reacting a second polysaccharide with at least one second non-aromatic agent,
and then
mixing the polysaccharides obtained.
The present invention further relates to a process for production of paper
from
an aqueous suspension containing cellulosic fibres, and optionally fillers,
which
comprises adding to the suspension a cationised polysaccharide product
comprising a
polysaccharide having (i) at least one first substituent having an aromatic
group, and (ii)
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3
at least one second substituent having no aromatic group, forming and draining
the
suspension on a wire. The invention also relates to a process for production
of paper from
an aqueous suspension containing cellulosic fibres, and optionally fillers,
which
comprises adding to the suspension a cationised polysaccharide product
comprising (i) at
least one polysaccharide having at least one first substituent having an
aromatic group
and (ii) at least one polysaccharide having at least one second substituent
having no
aromatic group, wherein one or both of the polysaccharides according to (i)
and (ii) are
cationic and/or amphoteric; forming and draining the suspension on a wire. The
invention
further relates to a process for production of paper from an aqueous
suspension
containing cellulosic fibres, and optionally fillers, which comprises
separately adding to
the suspension (i) at least one polysaccharide having at least one first
substituent having
an aromatic group; and (ii) at least one polysaccharide having at least one
second sub-
stituent having no aromatic group, wherein one or both of the polysaccharides
according
to (i) and (ii) are cationic and/or amphoteric; forming and draining the
suspension on a wire.
Detailed Description of the Invention
The cationised polysaccharide ~ product according to this invention has
unexpectedly been found to improve the dry strength properties of paper
produced. It has
also been found that the cationised polysaccharide product according to the
invention
improves drainage and/or retention when used as additives to cellulosic
suspensions in
papermaking processes.
The cationised polysaccharide product according to this invention is suitably
water-dispersible or, preferably, water-soluble. The cationised polysaccharide
product can
comprise one or more polysaccharides of the same or different type. The
polysaccharides
can be derived from any of the polysaccharides known in the art including, for
example,
starches, gums, celluloses, chitins, chitosans, glycans, galactans, glucans,
pectins,
mannans, dextrins, preferably starches and gums, and mixtures thereof.
Examples of
suitable starches include potato, corn, wheat, tapioca, rice, waxy maize,
etc., preferably
potato and corn. Examples of suitable gums are guar gums, tamarind gums,
locust bean
gums, tars gums, karaya, okra, acacia, xanthan gums etc., preferably guar
gums.
The cationised polysaccharide product comprises one or more polysaccharides
which are cationic and/or amphoteric, i.e. polysaccharides having one or more
cationic
groups. Examples of suitable cationic groups include sulphonium groups,
phosphonium
groups, tertiary amino groups and quaternary ammonium groups, preferably,
quaternary
ammonium groups. The polysaccharides may also contain one or more anionic
groups.
Examples of suitable anionic groups include phosphate, phosphonate, sulphate,
sulphonate
and carboxylic acid groups, preferably phosphate groups and sulphonate groups.
The poly-
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4
saccharides may also contain one or more non-ionic groups. If present, the
anionic groups
can be native or introduced by means of chemical treatment in conventional
manner. Native
potato starch contains a substantial amount of covalently bound phosphate
monoester
groups. In amphoteric polysaccharides, cationic groups are preferably present
in a
predominant amount.
The cationised polysaccharide product of this invention contains one or more
polysaccharides having one or more substituents. As used herein, the term
"substituent"
means a group of atoms that is not present in the native polysaccharide but
usually has
been introduced by chemical treatment. Preferably the substituents are derived
from an
agent, as described herein, the substituent being formed by reacting the
polysaccharide with
the agent. As used herein, the term "first substituent" means a substituent
which has an
aromatic group, and the term "second substituent" means a non-aromatic
substituent which
has no aromatic group. The substituents can be attached to a heteroatom, e.g.
oxygen or
nitrogen, present in the polysaccharide. Heteroatoms such as oxygen or
nitrogen can. also
be present in the substituents. In a preferred embodiment, the first
substituent contains a
heteroatom, preferably a nitrogen atom. In another preferred embodiment, the
second
substituent contains a heteroatom, preferably a nitrogen atom. The heteroatom
of the first
and second substituents can be charged, for example when it is nitrogen, e.g.
ammonium
ion, or potentially charged, e.g. nitrogen that is present in an amine group
that can be
rendered cationic by protonation; or uncharged, e.g. heteroatoms present in
amide, ester or
ether groups. The heteroatoms of the substituents can be attached to the
polysaccharide for
example via a chain of atoms. In a preferred embodiment of the invention, the
cationised
polysaccharide product comprises a polysaccharide which has two or more
substituents,
at least one first substituent and at least one second substituent.
In the first substituent having an aromatic group, the aromatic group can be
selected from aryl and aralkyl groups, e.g. phenyl, phenylene, naphthyl,
phenylene, xylylene,
benzyl and phenylethyl; nitrogen-containing aromatic (aryl) groups, e.g.
pyridinium and
quinolinium, as well as derivatives of these groups where one or more
substituents attached
to said aromatic groups can be selected from hydroxyl, halides, e.g. chloride,
nitro, and
hydrocarbon groups having from 1 to 4 carbon atoms.
In a preferred embodiment of the invention, the first substituent having an
aromatic
group has the following general structural formula (I):
R~ (I)
1 X
_A_N+_Rz
I
RAr ,
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wherein A is a group attaching N to a polysaccharide, suitably a chain of
atoms comprising
C and H atoms, and optionally O and/or N atoms, usually an alkylene group with
from 2 to
18 and suitably 2 to 8 carbon atoms, optionally interrupted or substituted by
one or more
heteroatoms, e.g. O or N, e.g. an alkyleneoxy group or hydroxy propylene group
(-CH2-
5 CH(OH)-CH2-); R~ and RZ are individually H or, preferably, a hydrocarbon
group, suitably
alkyl having from 1 to 3 carbon atoms, preferably 1 or 2 carbon atoms; RAr is
an aromatic
group containing at least 1 to 18 carbon atoms, suitably 1 to 15 and
preferably 1 to 12
carbon atoms preferably aralkyl groups, e.g. benzyl and phenylethyl groups;
or,
alternatively, R~, R2, and RAr together with N form a cyclic aromatic group,
suitably having 5
to 12 carbon atoms; and X is an anionic counterion, usually a halide like
chloride.
Preferably, the first substituent having an aromatic group is -CHz-CH(OH)-CH~-
N+((CHs)a)CHzCsHs CI-.
In the second substituent having no aromatic group, the substituent can be
selected from aliphatic groups and alicyclic groups. Examples of suitable
aliphatic groups
and alicyclic groups include linear, branched and cyclic alkyl groups like
methyl, 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; octyl,
e.g. n-octyl; decyl,
e.g. n-decyl; dodecyl, e.g. n-dodecyl; tetradecyl and octadecyl.
In a preferred embodiment of the invention, the second substituent having no
aromatic group has the following general structural formula (II):
R3 (II)
I X
-B_N+-R4
I
Rnon-Ar
wherein B is a group attaching N to a polysaccharide, suitably a chain of
atoms comprising
C and H atoms, and optionally O and/or N atoms, usually an alkylene group with
from 2 to
18 and suitably 2 to 8 carbon atoms, optionally interrupted or substituted by
one or more
heteroatoms, e.g. O or N, e.g. an alkyleneoxy group or hydroxy propylene group
(-CH2-
CH(OH)-CH2-); R3 and R4 are individually H or, preferably, a hydrocarbon
group, suitably
alkyl having from 1 to 3 carbon atoms, preferably 1 or 2 carbon atoms; Rnon-ar
is a non-
aromatic group containing at least 1 to 18 carbon atoms, suitably 1 to 15,
preferably 1 to
12 and most preferably 1 to 4 carbon atoms, the group suitably being as
defined above;
or, alternatively, R3 and R~, optionally together with R~o~Ar, together with N
form a cyclic
group, suitably having 5 to 12 carbon atoms; and X is an anionic counterion,
usually a
halide like chloride. Preferably, the second substituent having no aromatic
group is -CH2--
CH(OH)-CH2--N+((CH3)3) CI-.
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6
Particularly suitable polysaccharide products according to the invention
include
polysaccharides with at least one first substituent having aromatic groups
represented by
the general structural formula (III):
R, (III)
I X
(P-A-IV+--Rz)n
I
RAr
and at least one second substituent with no aromatic groups represented by the
general
structural formula (I~:
Rs
I X
(P-B-N+-R4)m
I
Rnon-Ar
wherein P is a residue of a polysaccharide; A, B, R,, Rz, R3, R4 , RAr, Rnon-
Ar and X are as
defined above, n and m are individually integers from about 1 to about
1,200,000, suitably
from 5 to 600,000 and preferably from 6 to 300,000.
In a preferred embodiment of the invention, the cationised polysaccharide
product comprises a polysaccharide having at least one cationic first
substituent and at
least one cationic second substituent, e.g. as described above. In another
preferred
embodiment, the cationised polysaccharide product comprises a first
polysaccharide
having at least one cationic first substituent, e.g. as described above, and a
second
polysaccharide having at least one cationic second substituent, e.g. as
described above.
The first and second polysaccharides can be selected from any of the
polysaccharides
defined above.
The cationised polysaccharide product according to the invention has a molar
ratio
of first substituent to second substituent which can be from 10:1 to 1:10,
usually from 7:1
to 1:7, suitably from 5:1 to 1:5, preferably from 3:1 to 1:3, and most
preferably from 2:1 to
1:2.
The cationised polysaccharide product can have a degree of substitution
varying
over a wide range; the degree of cationic substitution (DSO) can be from 0,005
to 2,0, suit-
ably from 0,01 to 1,0, and preferably from 0,02 to 0,5; the degree of aromatic
substitution
(DSAr) can be from 0.0005 to 2.0, usually from 0.001 to 1.0, suitably from
0.005 to 0.5, and
preferably from 0.01 to 0.5; the degree of non-aromatic substitution (DSnon-
Ar) can be from
0.0005 to 2.0, usually from 0.001 to 1.0, suitably from 0.005 to 0.5, and
preferably from 0.01
to 0.5; and the degree of anionic substitution (DSA) can be from 0 to 2.0,
suitably from 0 to
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7
1,0, preferably from 0 to 0,5. Usually the charge density of the cationised
polysaccharide
product is within the range of from 0.01 to 6.0 meq/g of dry polysaccharide,
suitably from
0.02 to 5.0 and preferably from 0.05 to 4Ø
The cationised polysaccharide product may consist or essentially consist of
one
or more polysaccharides according to the invention. The cationised
polysaccharide
product normally contains a liquid, usually water, and it is usually an
aqueous cationised
polysaccharide product.
In a preferred embodiment of the invention, the cationised polysaccharide
product is in the form of a powder. The powder may contain less than 30% by
weight of
an aqueous phase, preferably less than 25% by weight, most preferably less
than 20% by
weight based on the total weight of the polysaccharide product.
In another preferred embodiment of the invention, the cationised
polysaccharide
product is in the form of an aqueous slurry. The dry content of the
polysaccharide in the
aqueous slurry can be within the rage of from 10 to 55% by weight, suitable
from 20 to 50%
by weight, preferably from 25% to 45% by weight, based on the total weight of
the
polysaccharide product.
In yet another preferred embodiment of the invention, the cationised
polysaccharide product is in the form of an aqueous solution. The dry content
of the
cationised polysaccharide product in aqueous solution can be within the rage
of from 10 to
50% by weight by weight, suitably from 15 to 45%, preferably from 20 to 40% by
weight,
based on the total weight of the dry polysaccharide product.
The present invention also relates to a method for the preparation of a
cationised
polysaccharide product and a cationised polysaccharide product obtainable by
the method.
The polysaccharides to be subjected to modification can be non-ionic, anionic,
amphoteric
or cationic, and the polysaccharides are reacted with aromatic agents and/or
non-aromatic
agents, which can be non-ionic, cationic or anionic. The polysaccharides can
be selected
from any of the polysaccharides known in the art including, for example,
starches, gums,
celluloses, chitins, chitosans, glycans, galactans, glucans, pectins, mannans,
dextrins,
preferably starches and gums, and mixtures thereof. Examples of suitable
starches include
potato, corn, wheat, tapioca, rice, waxy maize, etc., preferably potato and
corn. Examples of
suitable gums are guar gums, tamarind gums, locust bean gums, tars gums,
karaya, okra,
acacia, xanthan gums etc., preferably guar gums. The non-ionic agents and
cationic agents
may ~ be reaction products obtained by reaction of halohydrin, epihalohydrin
and
epichlorohydrin with secondary or tertiary amines. The cationic agents can
also comprise
quaternary agents. The anionic agents comprise aromatic or non-aromatic agents
containing phosphate, phosphonate, sulphate, sulphonate or carboxylic acid
groups. The
aromatic agent can be reacted with one or more polysaccharides before the
polysaccharide
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8
is reacted with the non-aromatic agent, simultaneously, in reversed order or
separately in
case of at least two polysaccharides. In case of separate reactions of at
least two
polysaccharides, at least one polysaccharide is reacted with an aromatic agent
and at least
one polysaccharide is reacted with a non-aromatic agent, then the obtained
polysaccharides
are mixed. The cationised polysaccharide products can be obtained by reaction
with the
agents in aqueous suspension, pulverulent mixture, aqueous solution or aqueous
alcoholic
suspension under alkaline conditions. In a preferred embodiment of the present
invention
the cationised polysaccharide product can be obtained by reaction with one or
more cationic
agents, e.g. aromatic cationic agents and/or non-aromatic cationic agents.
Aromatic agents of the invention include non-ionic agents, cationic agents,
and
anionic agents. Examples of suitable agents include:
(I) Non-ionic aromatic agents such as substituted succinic anhydrides having
an
aromatic group; aralkyl halides, e.g. benzyl chloride and benzyl bromide;
ethers,
e.g. phenyl glycidyl ether and benzyl glycidyl ether; the reaction products of
epichlorohydrin and dialkylamines having at least one substituent comprising
an
aromatic group.
Cationic aromatic agents such as, the reaction product of epichlorohydrin and
tertiary amines having one or more aromatic groups as defined above, including
alkaryldialkylamines, e.g. dimethylbenzylamine; arylamines, e.g, pyridine and
quinoline. Suitable cationic agents of this type include halohydroxypropyl-N,N-
dialkyl-N-alkarylammonium halides and N-glycidyl-N-(alkaryl)-N,N-dialkyl-
ammonium chloride, e.g. N-(3-chloro-2-hydroxypropyl)-N-(alkaryl)-N,N-di(lower
alkyl)ammonium chloride where the alkaryl and lower alkyl groups are as
defined
above, particularly N-(3-chloro-2-hydroxypropyl)-N-benzyl-N,N-dimethylammonium
chloride; and N-(3-chloro-2-hydroxypropyl) pyridinium chloride. The aromatic
cationic agent is preferably 3-chloro-2-hydroxypropyl dimethyl benzyl ammonium
chloride or 2,3-epoxipropyl dimethyl benzyl ammonium chloride.
(III) Anionic aromatic agents include agents having an aromatic group
attached, such
agents can be, for example, phosphate, phosphonate, sulphate, sulphonate or
carboxylic acid groups and they are preferably phosphate groups, phosphonate
groups or sulphonate groups, e.g. phenyl phosphonic acid and phenyl phosphonic
sulphonic acid.
Non-aromatic agents of the invention include non-ionic agents, cationic
agents, and
anionic agents. Examples of suitable agents include:
(I) Non-ionic non-aromatic agents such as alkylene oxides, e.g. propylene
oxide,
butylene oxide and iso-butylene oxide; alkylene ethers, e.g. butyl glycidyl
ether;
alkyl halides, e.g. decyl bromide and docecyl bromide; the reaction products
of
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9
epichlorohydrin and dialkylamines having at least one substituent comprising a
non-aromatic hydrocarbon group as defined above, including 3-dialkylamino-1,2-
epoxypropanes.
(II) Cationic non-aromatic agents such as, for eXample, the reaction product
of
epichlorohydrin and tertiary amines having non-aromatic hydrocarbon groups as
defined above, including trialkylamines. Suitable cationic agents of this type
include
2,3-epoxypropyl trialkylammonium halides and halohydroxypropyl trialkyl-
ammonium halides, e.g. N-(3-chloro-2-hydroxypropyl)-N-(alkyl)-N,N-di(lalkyl)-
ammonium chloride and N-glycidyl-N-(alkyl)-N,N-di(alkyl)ammoniumchloride where
the non-aromatic hydrocarbon group as defined above, notably octyl, decyl,
dodecyl and octadecyl, and the alkyl is methyl, ethyl, propyl or butyl,
preferably
methyl or ethyl. Preferred non-aromatic hydrocarbon cationic agents include 3-
chloro-2-hydroxypropyl trimethyl ammonium chloride or 2,3-epoxipropyl
trimethyl
ammonium chloride.
(III) Anionic non-aromatic agents such as, for example, agents containing
phosphonate
groups, e.g. aminochloroethane diethylphosphonic acid; agents containing
sulphate
groups, e.g. sulfamic acid or S03 complexes such as S03TMA (trimethylamine),
S03pyridine; agents containing sulfoalkyl groups, e.g. 2-chloroethane-
sulfonates
and 3-chloro-2-hydroxypropanesulfonate; agents containing carboxylic alkyl
groups, e.g. salts of 1-halocarboxylic acid such as sodium monochloroacetate
or
sodium chloropropionate; agents containing sulfocarboxyl groups, e.g. 3-chloro-
2-
sulfopropionic acid; lactones like propionolactone or butyrolactone,
acrylonitrile,
acid anhydrides such as malefic anhydride, succinic anhydride, phthalic
anhydride
and the like.
Examples of suitable agents, cationic or amphoteric polysaccharides and
cationisation methods include those described in U.S. Patent Nos. 2,876,217
3,422,087,
4,687,519, 4,785,087, 5,129,989, 5,463,127 and 5,827,372; International Patent
Applications WO 94124169, WO 99155964, European Patent Application Nos. 0 189
935, 0
303 039, 0 400 361, 0 737 210 and 0 874 000; and S.P. Patel, R.G. Patel and
V.S. Patel,
Starch/Starke, 41 (1989), No. 5, pp. 192-196, the teachings of which are
hereby incorporated
herein by reference.
The method of the invention comprises reacting one or more polysaccharides
with
(i) at least one first aromatic agent, and (ii) at least one second non-
aromatic agent, at
least one of the first and second agents comprising a cationic agent. In a
preferred
embodiment of the invention, one or more polysaccharides are reacted with at
least one
first aromatic agent and at least one second non-aromatic agent to form a
cationised
polysaccharide product. In another preferred embodiment of the invention, one
or more
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first polysaccharides are reacted with at least one first aromatic agent, and
one or more
second polysaccharides are reacted with at least one second non-aromatic
agent, and
then the polysaccharides obtained are then mixed to form a cationised
polysaccharide
product. The first and second polysaccharides can be selected from any of the
5 polysaccharides defined above. In a further preferred embodiment of the
invention, one
or more polysaccharides are reacted with at least one cationic first aromatic
agent, and at
least one cationic second non-aromatic agent. The agents are reacted in a
molar ratio of
aromatic agents to non-aromatic agents that can be within the range of from
10:1 to 1:10,
usually from 7:1 to 1:7, suitably from 5:1 to 1:5, preferably from 3:1 to 1:3,
and most
10 preferably from 2:1 to 1:2.
The method may also comprise crosslinking of the polysaccharides, e.g. by
reaction with epichlorohydrin according to European Patent No. 0 603 727,
which renders
a higher molecular weight to the polysaccharides and a viscosity increase when
the
polysaccharides are in solution or slurry. The increase of the viscosity is
within the range
of from of about 5% to 500%, preferably from about 10% to 400%, and the
crosslinking
effect provided by the crosslinking agent is within the range of from about 2%
to 85%,
preferably from about 2% to 60% and more preferably from about 5% to 50%
Breakdown
Viscosity.
The method may also comprise degradation of the polysaccharides by acid
hydrolysis, by the use of peroxides, sodium hypochlorite (NaClO), ozon or
enzymes,
which renders a lower molecular weight to the polysaccharides and thereby a
decrease of
the viscosity when the polysaccharides are in solution or slurry. The
polysaccharide
viscosity can be decreased to viscosities, suitably within the range of from
95% to 0.1 %,
preferably from 80% to 1 % and more preferably of 60% to 5% of the viscosity
before
degradation.
The method may also comprise both crosslinking and degradation of the
polysaccharides, and thereby provide a cationised polysaccharide product in
solution or
slurry with controlled viscosity.
The present invention further relates to a papermaking process in which one or
more cationised polysaccharide products of the invention are added to an
aqueous
suspension containing cellulosic fibres, or stock, to be dewatered. The
cationised
polysaccharide products according to the invention can be employed in the
papermaking
process as drainage and retention aids and as dry strength agents. The term
"drainage
and retention aid", as used herein, refers to one or more components (aid,
agent or
additive) which when being added to an aqueous cellulosic suspension, give
better
drainage and/or retention than is obtained when not adding said one or more
components. The term "dry strength agent", as used herein, refers to one or
more
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11
components (aids, agents or additives) which, when being added to a stock,
give better
dry strength of the paper produced than is obtained when not adding said one
or more
components.
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 additive to give a corresponding drainage and
retention effect,
thereby leading to an improved papermaking process and economic benefits.
Further
benefits observed with the present invention include improved dry strength of
the paper
produced using the cationised polysaccharide product. Hereby it is possible to
use a lower
dosage of dry strength agent to give a corresponding paper dry strength
effect. It is also
possible to use high dosages of the cationised polysaccharide product without
overcharging the fibre material in order to increase the paper strength and
thereby paper
quality, since the cationised polysaccharide products according to the
invention are very
effective also at relatively low cationicity. The process of this invention
can be utilised for
the treatment of cellulosic suspensions in mills with relatively closed water
loops, 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.
The cationised polysaccharide product according to the invention can be used
in
conjunction with additional additives that are beneficial to the overall
drainage and/or
retention and/or dry strength performance of the process and/or paper
produced, thereby
forming drainage and retention aids as well as dry strength aids comprising
two or more
components. Examples of suitable stock additives of this type include anionic
materials,
e.g. anionic inorganic materials such as, for example, microparticulate
materials, e.g.
silica-based particles and clays of smectite type, and anionic organic
materials such as,
for example, anionic organic polymers such as condensation polymers, addition
polymers,
step-growth polymers, chain-growth polymers, polysaccharides containing
anionic groups,
synthetic polymers having an aromatic group, naturally occurring aromatic
polymers, and
modifications thereof. The term "step-growth polymer", as used herein, refers
to a polymer
obtained by step-growth polymerisation, also being referred to as step-
reaction polymer and
step-reaction polymerisation, respectively. Addition polymers are polymers
obtained by step-
growth addition polymerisation, e.g. anionic polyurethanes which can be
prepared from a
monomer mixture comprising aromatic isocyanates and/or aromatic alcohols.
Condensation
polymers i.e. polymers obtained by step-growth condensation polymerisation,
e.g.
condensates of an aldehyde such as formaldehyde with one or more aromatic
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12
compounds, and optional other co-monomers useful in the condensation
polymerisation
such as urea and melamine. Chain-growth polymers are prepared by
polymerisation of one
or more monomers having a vinyl group or ethylenically unsaturated bond.
Anionic inorganic materials 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 Si02 or silicic acid, are preferably used and such
particles are usually
supplied in the form of aqueous colloidal dispersions, so-called sots.
Examples of suitable
silica-based particles include different types of polymerised silicic acid,
either
homopolymerised or co-polymerised. The silica-based particles and/or sots can
be modified
and contain other elements, e.g. aluminium, nitrogen 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.
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 suitably is at least 50 m2lg and preferably at
least 100 m~/g.
Generally, the specific surface area can be up to about 1700 m2/g and
preferably up to 1000
mz/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. Patent No. 5,176,891. The given area thus represents the average specific
surface
area of the particles.
Suitably the silica-based particles are contained in a sol. The sol may have
an S-
value in the range of from 5 to 80%, suitably from 5 to 50%, preferably from 8
to 45%, and
most preferably from 10 to 30%. Calculation and measuring of the S-value can
be
performed as described by Iler & 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.
Suitably the silica-based particles have a molar ratio Si20:Na20 less than 60,
usually within the range 5 to 60, and preferably within the range from 8 to
55.
Suitable anionic silica-based particles used as retention and/or drainage aid
are
disclosed in U.S. Patent 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.
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13
Anionic polymers that can be used according to the invention can be selected
from
step-growth polymers, chain-growth polymers, polysaccharides, naturally
occurring aromatic
polymers and modifications thereof. The anionic polymers can be linear,
branched or cross-
linked. Preferably the anionic polymer is water-soluble or water-dispersible.
Examples of
anionically charged groups that can be present in the anionic polymer as well
as in the
monomers used for preparing the anionic polymer include groups carrying an
anionic charge
and acid groups carrying an anionic charge when dissolved or dispersed in
water, the
groups herein collectively being referred to as anionic groups, such as
phosphate,
phosphonate, sulphate, sulphonic acid, sulphonate, carboxylic acid,
carboxylate, alkoxide
and phenolic groups, i.e. hydroxy-substituted phenyls and naphthyls. Groups
carrying an
anionic charge are usually salts of an alkali metal, alkaline earth or
ammonia.
Examples of suitable anionic step-growth polymers include condensation
polymers,
suitable aromatic compounds containing anionic groups comprises benzene and
naphthalene-based compounds containing anionic groups such as phenolic and
naphtholic compounds, e.g. phenol, naphthol, resorcinol and derivatives
thereof, aromatic
acids and salts thereof, e.g. phenylic, phenolic, naphthylic and naphtholic
acids and salts,
usually sulphonic acids and sulphonates, e.g. benzene sulphonic acid and
sulphonate,
xylen sulphonic acid and sulphonates, naphthalene sulphonic acid and
sulphonate,
phenol sulphonic acid and sulphonate.
Examples of further suitable anionic step-growth polymers include addition
polymers, e.g. anionic polyurethanes which can be prepared from a monomer
mixture
comprising aromatic isocyanates and/or aromatic alcohols. Examples of suitable
aromatic
isocyanates include diisocyanates, e.g. toluene-2,4- and 2,6-diisocyanates and
diphenyl-
methane-4,4'-diisocyanate. Examples of suitable aromatic alcohols include
dihydric alcohols,
i.e. diols, e.g. bisphenol A, phenyl diethanol amine, glycerol
monoterephthalate and tri-
methylolpropane monoterephthalate. Monohydric aromatic alcohols such as phenol
and
derivatives thereof may also be employed. The monomer mixture can also contain
non-
aromatic isocyanates and/or alcohols, usually diisocyanates and diols, for
example any of
those known to be useful in the preparation of polyurethanes. Examples of
suitable
monomers containing anionic groups include the monoester reaction products of
triols, e.g.
trimethylolethane, trimethylolpropane and glycerol, with dicarboxylic acids or
anhydrides
thereof, e.g. succinic acid and anhydride, terephthalic acid and anhydride,
such as
glycerol monosuccinate, glycerol monoterephthalate, trimethylolpropane
monosuccinate,
trimethylolpropane monoterephthalate, N,N-bis-(hydroxyethyl)-glycine, di-
(hydroxy-
methyl)propionic acid, N,N-bis-(hydroxyethyl)-2-aminoethanesulphonic acid, and
the like,
optionally and usually in combination with reaction with a base, such as
alkali metal and
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14
alkaline earth hydroxides, e.g. sodium hydroxide, ammonia or an amine, e.g.
triethylamine, thereby forming an alkali metal, alkaline earth or ammonium
counter-ion.
Examples of suitable anionic chain-growth polymers include anionic vinyl
addition
polymers obtained from a mixture of vinylic or ethylenically unsaturated
monomers
comprising at least one monomer having an aromatic group and at least one
monomer
having an anionic group, usually co-polymerised with non-ionic monomers such
as acrylate-
and acrylamide-based monomers. Examples of suitable anionic monomers include
(meth)acrylic acid and paravinyl phenol (hydroxy styrene).
Examples of suitable anionic polysaccharides include starches, gums,
celluloses,
chitins, chitosans, glycans, galactans, glucans, pectins, mannans, dextrins,
preferably
starches and gums, and mixtures thereof. Examples of suitable starches include
potato,
corn, wheat, tapioca, rice, waxy maize, etc., preferably potato and corn.
Examples of
suitable gums are guar gums, tamarind gums, locust bean gums, tars gums,
karaya, okra,
acacia, xanthan gums etc., preferably guar gums. The anionic groups in the
polysaccharide
can be native and/or introduced by chemical treatment.
Naturally occurring aromatic anionic polymers and modifications thereof, i.e.
modified naturally occurring aromatic anionic polymers, according to the
invention include
naturally occurring polyphenolic substances that are present in wood and
organic extracts of
bark of some wood species and chemical modifications thereof, usually
sulphonated
modifications thereof. The modified polymers can be obtained by chemical
processes such
as, for example, sulphite pulping and Kraft pulping. Examples of suitable
anionic polymers of
this type include lignin-based polymers, preferably sulphonated lignins, e.g.
ligno-
sulphonates, kraft lignin, sulphonated kraft lignin, and tannin extracts.
The average molecular weight of the anionic polymer can vary within wide
limits
dependent on, inter alia, the type of polymer used, and usually it is at least
about 500,
suitably above about 2,000 and preferably above about 5,000. The upper limit
is not
critical; it can be about 200,000,000, usually 150,000,000, suitably
100,000,000 and
preferably 10,000,000.
The anionic polymer can have a degree of anionic substitution (DSA) varying
over a wide range dependent on, inter alia, the type of polymer used; DSA is
usually from
0.01 to 2.0, suitably from 0.02 to 1.8 and preferably from 0.025 to 1.5; and
the degree of
aromatic substitution (DSA~) can be from 0.001 to 1.0, usually from 0.01 to
0.8, suitably
from 0.02 to 0.7 and preferably from 0.025 to 0.5. In case the anionic polymer
contains
cationic groups, the degree of cationic substitution (DSO) can be, for
example, from 0 to
0.2, suitably from 0 to 0.1 and preferably from 0 to 0.05, the anionic polymer
having an
overall anionic charge. Usually the anionic charge density of the anionic
polymer is within
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the range of from 0.1 to 6.0 meqv/g of dry polymer, suitably from 0.5 to 5.0
and preferably
from 1.0 to 4Ø
Examples of suitable anionic aromatic polymers that can be used according to
the
present invention include those described in U.S. Patent Nos. 4,070,236 and
5,755,930; and
5 International Patent Application Publication Nos. WO 95/21295, WO 95/21296,
WO
99/67310, and WO 00/49227, which are hereby incorporated herein by reference.
The cationised polysaccharide product according to the invention can also be
used in conjunction with other additives, e.g. other polysaccharides,
aluminium
compounds, cationic, non-ionic, and amphoteric synthetic polymers such as, for
example,
10 low molecular weight cationic organic polymers, anionic vinyl addition
polymers and
combinations thereof, including the compounds disclosed in International
Patent
Application Publication Nos. WO 99/55964, WO 99/55965, and WO 02112626 which
are
incorporated herein by reference.
Low molecular weight (hereinafter LMW) cationic organic polymers that can be
15 used according to the invention include those commonly referred to as
anionic trash
catchers (ATC). 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
diallyldimethyl
ammonium chloride, (meth)acrylamides and (meth)acrylates. In relation to the
molecular
weight of the cationised polysaccharide product of this invention, the
molecular weight of the
LMW cationic organic polymer is preferably 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.
Aluminium compounds that can be used according to the invention include alum,
aluminates, aluminium chloride, aluminium nitrate and polyaluminium compounds,
such as
polyaluminium chlorides, polyaluminium sulphates, polyaluminium compounds
containing
both chloride and sulphate ions, polyaluminium silicate-sulphates, and
mixtures thereof. The
polyaluminium compounds may also contain other anions than chloride ions, for
example
anions from sulphuric acid, phosphoric acid, organic acids such as citric acid
and oxalic acid.
The cationised polysaccharide product according to the invention can be added
to
the suspension as a single polysaccharide having both aromatic and non-
aromatic
substituents, or as a composition containing different polysaccharides, one of
which having
at least one first substituent and one of which having at least one second
substituent.
Alternatively, a polysaccharide having at least one first substituent and a
polysaccharide
having at least one second substituent are separately added to the suspension.
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16
The cationised polysaccharide product and anionic material according to the
invention are preferably separately added to the aqueous suspension containing
cellulosic
fibres, or stock. Preferably the cationised polysaccharide product and the
anionic materials
are added to the stock at different positions. The cationised polysaccharide
product and the
anionic materials can be added in any order. Usually the cationised
polysaccharide product
is added to the stock prior to adding the anionic material, although the
reverse order of
addition may also be used. The cationised polysaccharide product can be added
to the
stock to be dewatered in amounts which can vary within wide limits depending
on, inter alia,
type of stock, salt content, type of salts, filler content, type of filler,
point of addition, etc.
Generally the cationised polysaccharide product is added in an amount which
give better
drainage and/or retention than is obtained when not adding them. The
cationised
polysaccharide product is usually added in an amount of at least 0.05%, often
at least 0.1
by weight, based on dry stock substance, whereas the upper limit is usually 5%
and suitably
3% by weight. The anionic material is usually added in an amount of at least
0.001 %, often
at least 0.005% by weight, based on dry stock substance, whereas the upper
limit is usually
3% and suitably 1.5% by weight.
The process of this invention is applicable to all papermaking processes and
cellulosic suspensions,,and it is particularly useful in the manufacture of
paper from a stock
that has a high conductivity. In such cases, the conductivity of the stock
that is dewatered on
the wire is generally at least 0.5 mSlcm, usually at least 1.0 mS/cm, suitably
at least 1.5
mS/cm, and preferably at least 2.0 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) which can be
derived from the materials used to form the stock, from various additives
introduced into the
stock, from the fresh water supplied to the process, etc. Further, the content
of salts is
usually higher in processes where white water is extensively recirculated,
which may lead to
considerable accumulation of salts in the water circulating in the process.
The present invention further encompasses papermaking processes where white
water is extensively recycled, or recirculated, i.e. with a high degree of
white water closure,
for example where from 0 to 30 tonnes of fresh water are used per tonne of dry
paper
produced, usually less than 20, suitably less than 15, preferably less than 10
and notably
less than 5 tonnes of fresh water per ton of paper. Recycling of white water
obtained in the
process suitably comprises mixing the white water with cellulosic fibres
and/or optional fillers
to form a suspension to be dewatered; preferably it comprises mixing the white
water with a
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17
suspension containing cellulosic fibres, and optional fillers, before the
suspension enters the
forming wire for dewatering. The white water can be mixed with the suspension
before,
between, simultaneous with or after introducing the drainage and retention
aids of this
invention. Fresh water can be introduced in the process at any stage; for
example, it can be
mixed with cellulosic fibres in order to form a suspension, and it can be
mixed with a thick
suspension containing cellulosic fibres to dilute it so as to form a thin
suspension to be
dewatered, before, simultaneous with or after mixing the suspension with white
water.
Further additives which are conventional in papermaking can of course be used
in
combination with the cationised polysaccharide product according to the
invention, such as,
for example, other retention and/or drainage aids and other dry strength
agents, wet
strength agents, optical brightening agents, dyes, sizing agents like rosin-
based sizing
agents and cellulose-reactive sizing agents, e.g. alkyl and alkenyl ketene
dimers, alkyl and
alkenyl ketene multimers, and succinic anhydrides, etc. The cellulosic
suspension, or stock,
can also contain mineral fillers of conventional types such as, for example,
kaolin, china
clay, titanium dioxide, gypsum, talc and natural and synthetic calcium
carbonates such as
chalk, ground marble and precipitated calcium carbonate.
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
cellulosic fibre-containing sheet or web-like products, such as for example
board and
paperboard, and the production thereof. The process can be used in the
production of paper
from different types of 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 suspension can be based on fibres from
chemical pulp
such as sulphate, sulphite and organosolv pulps, mechanical pulp such as
thermome-
chanical pulp, chemo-thermomechanical pulp, refiner pulp and groundwood pulp,
from both
hardwood and softwood, and can also be based on recycled fibres, optionally
from de-inked
pulps, and mixtures thereof.
The invention also relates to uses of the polysaccharide product in
papermaking
processes. In a preferred embodiment of this invention, the cationised
polysaccharide
product is capable of functioning as a dry strength agent. In another
preferred
embodiment of this invention, the polysaccharide product is capable of
functioning as
drainage andlor retention aid. In a third preferred embodiment the
polysaccharide product
is capable of functioning as both dry strength agent and drainage and/or
retention aid.
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.
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18
Example 1
Cationic polysaccharide products used in the tests were prepared by reacting
native potato starch with one or more quaternising agents according to the
general
procedure described in EP-A 0 189 935 and WO 99155964. The cationic starches
used in
the tests, hereinafter also collectively referred to as C1, C2, C3 and C4
according to the
invention and ATC1, Ref. 1, Ref. 2, Ref. 3, Ref. 4, Ref. 5, Ref. 6 and Ref. 7
intended for
comparison purposes, were the following:
C1: Cationic starch obtained by quarternisation of native potato starch with 3-
chloro
2-hydroxypropyl dimethyl benzyl ammonium chloride to DSA~ 0.025 and with 2,3
epoxypropyl trimethyl ammonium chloride to DS~o~-Ar 0.025, and DSO was 0.05.
C2: Cationic starch obtained by quarternisation of native potato starch with 3-
chloro-
2-hydroxypropyl dimethyl benzyl ammonium chloride to DSA~ 0.032 and with 2,3-
epoxypropyl trimethyl ammonium chloride to DS~on-ar 0.008, and DSO was 0.04.
C3: Cationic starch mixture containing 1 part starch obtained by
quarternisation of
native potato starch with 3-chloro-2-hydroxypropyl dimethyl benzyl ammonium
chloride to DSO 0.05 mixed with 1 part starch obtained by quarternisation of
native potato starch with 2,3-epoxypropyl trimethyl ammonium chloride to DSO
0.05.
C4: Cationic starch obtained by quarternisation of native potato starch with 3-
chloro-
2-hydroxypropyl dimethyl benzyl ammonium chloride to DSA~ 0.065 and also
modified with 2,3-epoxy-2-methyl-propane to DSnon-Ar 0.01, and DSO was 0.065.
C5: Cationic starch obtained by quarternisation of native potato amylopectin
starch with
3-chloro-2-hydroxypropyl dimethyl benzyl ammonium chloride to DSA~ 0.07 and
with
2,3-epoxypropyl trimethyl ammonium chloride to DSnonAr 0.59, and DSO was 0.66.
C6: Cationic starch obtained by quarternisation of native potato amylopectin
starch with
3-chloro-2-hydroxypropyl dimethyl benzyl ammonium chloride to DSA~ 0.14 and
with
2,3-epoxypropyl trimethyl ammonium chloride to DS~on-ar 0.54, and DSO was
0.68.
ATC1: Cationic polyamine having a molecular weight of about 50,000.
Ref. 1: Cationic starch obtained by quarternisation of native potato starch
with 2,3-
epoxypropyl trimethyl ammonium chloride to DSO 0.08.
Ref. 2: Cationic starch obtained by quarternisation of native potato starch
with 2,3-
epoxypropyl trimethyl ammonium chloride to DSO 0.18.
Ref. 3: Cationic starch obtained by quarternisation of native potato starch
with 3-chloro-
2-hydroxypropyl dimethyl benzyl ammonium chloride to DSO 0.09.
Ref.4: Cationic starch obtained by quarternisation of native potato starch
with 2,3-
epoxypropyl trimethyl ammonium chloride to DSO 0.05.
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19
Ref. 5: Cationic starch obtained by quarternisation of native potato starch
with 3-chloro
2-hydroxypropyl dimethyl benzyl ammonium chloride to DSO 0.05.
Ref 6: Cationic starch obtained by quarternisation of native potato starch
with 2,3-
epoxypropyl trimethyl ammonium chloride to DSC 0.04.
Ref. 7: Cationic starch obtained by quarternisation of native potato starch
with 2,3-
epoxypropyl trimethyl ammonium chloride to DS~on-ar 0.065 and also modified
with 2,3-epoxy-2-methyl-propane to DS~on-a,r 0.01, DStot(non-a,r) 0.075, and
DSO was
0.065.
Ref. 8: Cationic starch obtained by quarternisation of native potato
amylopectin starch with
2,3-epoxypropyl trimethyl ammonium chloride to DSO 0.65.
Ref. 9: Cationic starch obtained by quarternisation of native potato
amylopectin starch with
3-chloro-2-hydroxypropyl dimethyl benzyl ammonium chloride to DSO 0.65.
C1, C2, C3, C4, C5, ATC1, Ref. 1, Ref. 2, Ref. 3, Ref. 4, Ref. 5 and Ref. 6
were all
used as dilute aqueous solutions in all tests.
Anionic components used in the tests were anionic silica sol (A1) and anionic
polycondensate (A2). The anionic components used in the tests were the
following:
A1: Silica sol of the type described in US 5,368,833, having an S-value of 25%
and
containing silica particles with a specific surface area of 900 m2lg which are
surface-modified with aluminium to a degree of 5%.
A2: Anionic polycondensate of formaldehyde with naphthalene sulphonate,
molecular
weight about 20,000.
A1 and A2 were used as sols or dilute aqueous solutions.
Example 2
Dry strength performance was evaluated with a Dynamic Sheet Former
(Formette Dynamique), supplied by Fibertech AB, Sweden, and a Burst Strength
Tester
supplied by Lorentzen & Wettre, Sweden.
The furnish used in the tests was based on 100% by weight of recycled waste
mill furnish. The furnish consistency was 0.5% and the conductivity was
adjusted by
addition of calcium chloride to 2.7 mS/cm and further by sodium chloride to
4.0 mS/cm.
The furnish was stirred with a high shear stirrer at a speed of 700 rpm and
the
starches were added after 0.5 min followed by 5 min of stirring in the mixing
chest.
Paper sheets were formed in the Dynamic Sheet Former by pumping the furnish
from the mixing chest through a traversing nozzle into the rotating drum onto
the water film
on top of the wire, draining the stock to form a sheet, pressing and drying
the sheet. The
sheets were evaluated in the Burst Strength Tester. The burst strength index
increase
values were calculated and compared.
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Table 1 shows Burst Strength Index Increase of the sheets obtained at various
starch dosages, calculated as dry starch on dry stock system.
Table 1
Test Starch Dosage Burst Strength
No. [kg/t] Index
Increase
C1 Ref.1 Ref.2 Ref.3
1 5.0 17.1 8.8 10.7 8.6
2 10.0 20.1 15.7 3.5 9.5
3 20.0 30.4 17.8 18.8 17.3
4 30.0 29.7 15.9 13.5 20.0
5 Example 3
Dry strength perFormance was evaluated using the equipment according to
Example 2. The furnish used in the tests was based on 100% by weight of
recycled waste
mill stock. The thick stock consistency was 3.6% and the conductivity of the
thick stock
was adjusted by addition of calcium chloride to 3.0 mS/cm. The white water
consistency
10 was 0.1 % and the conductivity of the white water was adjusted by addition
of calcium
chloride to 4.0 mS/cm.
The thick stock was stirred with a high shear stirrer at a speed of 700 rpm
and
the starches were added after 0.5min. After 6.5 min the ,thick stock was mixed
with the
white water in the mixing chest for 2 min, creating the furnish.
15 Paper sheets were formed in the Dynamic Sheet Former by pumping the furnish
from the mixing chest through a traversing nozzle into the rotating drum onto
the water film
on top of the wire, draining the stock to form a sheet, pressing and drying
the sheet. The
sheets were evaluated in the Burst Strength Tester. The burst strength index
values were
calculated and compared.
20 Table 2 shows Burst Strength Index of the sheets obtained at various starch
dosages, calculated as dry starch on dry stock system.
Table 2
Test Starch Dosage Burst Strength
No. (kg/t] Index
MN/k
C 1 Ref. 4
1 0 2.37 2.37
2 ~ 5.0 2.77 2.49
3 10.0 2.86 2.47
4 20.0 2.92 2.67
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21
Example 4
Drainage 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.
Retention perFormance was evaluated by means of a nephelometer by measuring
the turbidity of the filtrate, the white water, obtained by draining the
stock. The turbidity was
measure in NTU (Nephelometric Turbidity Units).
The furnish used in the tests was based on 56% by weight of peroxide bleached
TMP/SGW pulp (80/20), 14% by weight of bleached birchlpine sulphate pulp
(60/40)
refined to 200° CSF and 30% by weight of china clay. To the stock was
added a colloidal
fraction, bleach water from an SC mill. Stock consistency was 0.12%.
Conductivity of the
stock was adjusted by addition of calcium chloride to 1.0 mS/cm.
The stock was stirred in a baffled jar at a speed of 1500 rpm throughout the
tests
and chemicals additions were conducted as follows: i) adding cationic starch
to the stock
following by stirring for 30 seconds, ii) adding anionic component to the
stock followed by
stirring for 15 seconds, iii) draining the stock while automatically recording
the drainage
time.
Table 3 shows the dewatering effect at various dosages of cationised starch,
calculated as dry starch on dry stock system, and silica-based particles A1,
calculated as
SiO~ and based on dry stock system.
Table 3
Test Starch A1 Dewatering Turbidity
Dosage Dosage Times NTU
sec
No. (kg/t] ~kg/tl C1 Ref.1 C1 Ref.1
1 0 0 19.4 19.4 90 90
2 5 3 16.5 18.1 57 59
3 10 3 14.5 15.8 47 52
4 15 3 11.4 14.5 43 45
5 20 3 12.0 13.2 40 45
Example 5
Fines retention was measured in the Britt Dynamic Drainage Jar, BDDJ,
available
from e.g. Paper Materials Inc., U.S., which measures the first pass retention
of fines for a set
volume of stock on a wire.
The furnish used in the tests was based on 56% by weight of peroxide bleached
TMPISGW pulp (80/20), 14% by weight of bleached birch/pine sulphate pulp
(60/40)
CA 02500545 2005-03-29
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22
refined to 200° CSF and 30% by weight of china clay. To the stock was
added a colloidal
fraction, bleach water from an SC mill. Stock consistency was 0.5%. The
conductivity bf
the stock was adjusted by addition of calcium chloride to 3.0 mS/cm.
The stock was stirred in a baffled jar at a speed of 1000 rpm throughout the
tests
and chemicals additions were conducted as follows: i) adding polysaccharide to
the stock
following by stirring for 30 seconds, ii) adding anionic inorganic particles
to the stock
followed by stirring for 15 seconds, iii) draining the stock during 30
seconds, recording the
volume and measuring the dry content of that volume.
Table 4 shows the fines retention effect at various dosages of cationised
starch,
calculated as dry starch on dry stock system, and silica-based particles,
calculated as
Si02 and based on dry stock system.
Table 4
Test Starch A1 Fines retention
Dosage Dosage
No. [kglt] [kg/t] C1 Ref 4 Ref 5
1 0 0 13.7 13.7 13.7
2 5 3 41.6 29.3 27.0
3 10 3 47.2 40.6 37.6
4 15 3 52.7 45.9 43.3
Example 6
Drainage and retention performance was evaluated in a manner similar to
Example
4. The furnish used in the tests was based on 70% by weight of bleached
birch/pine
sulphate pulp (60/40) refined to 200° CSF and 30% by weight of calcium
carbonate. To the
stock was added a colloidal fraction, bleach water from an SC mill. Stock
consistency was
0.28%. Conductivity of the stock was adjusted by addition of sodium sulphate
to 0.45 mS/cm
and further by calcium chloride to 2.2 mS/cm.
Table 5 shows the dewatering effect at a constant dosage of cationised starch,
calculated as dry starch on dry stock system, and various dosages of the
anionic
component, A2, based on dry stock system.
Table 5
TestStarch A2 Dewatering Turbidity
Dosage Dosage Times NTU
sec
No. [kg/t] [kglt] C2 Ref.6 C2 Ref.6
1 15 0 18.1 18.1 - -
2 15 1 12.5 17.6 93 118
3 15 2 11.8 16.1 87 109
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23
Example 7
Drainage and retention performance was evaluated in a manner similar to
Example 4. The furnish used in the tests was based on 100% by weight of
unbleached
softwood Kraft pulp. Stock consistency was 0.43%. Conductivity of the stock
was
adjusted by addition of calcium chloride to 5.4 mS/cm.
Table 6 shows the dewatering effect at various dosages of cationised starch,
calculated as dry starch on dry stock system, and silica-based particles,
calculated as
Si02 and based on dry stock system.
Table 6
i
Test Starch DosageA1 Dosage Dewatering
No. [kg/t] [kglt] Times
sec
C3 Ref.4 Ref.5
1 0 2 15.4 15.4 15.4
2 2.5 2 14.1 14.8 14.3
3 5 2 11.6 13.1 12.8
Example 8
Drainage and retention performance was evaluated in a manner similar to
Example
4. The furnish used in the tests 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° CSF and 30% by weight of china clay. To the stock was added a
colloidal fraction,
bleach water from an SC mill. Stock consistency was 0.12%. Conductivity of the
stock was
adjusted by addition of calcium chloride to 3.5mS/cm.
Table 7 shows the dewatering effect at various dosages ~ of cationised starch,
calculated as dry starch on dry stock system, and silica-based particles,
calculated as
Si02 and based on dry stock system.
Table 7
Test Starch DosageA1 Dosage Dewatering Turbidity
No. [kg/t] [kg/t] Time NTU
sec
C4 Ref.7 C4 Ref.7
1 0 0 20.8 20.8 94 94
2 5 3 17.7 17.9 63 64
3 10 3 14.7 17.3 61 ' 61
4 15 3 14.9 19.2 57 64
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24
Example 9
Drainage performance was evaluated in a manner similar to Example 4. The
furnish used in the tests 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° CSF
and 30% by weight of china clay. To the stock was added a colloidal fraction,
bleach water
from an SC mill. Stock consistency was 0.16%. Conductivity of the stock was
adjusted by
addition of calcium chloride to 5.OmS/cm.
Retention performance was evaluated by means of a Hach 2100P by measuring
the turbidity of the filtrate, the white water, obtained by draining the
stock. The turbidity was
measure in NTU (Nephelometric Turbidity Units).
Table 8 shows the dewatering effect at various dosages of cationised starch,
calculated as dry starch on dry stock system.
Table 8
Test Starch Dosage Dewatering
No. k It Times
sec'
C5 C6 Ref.8 Ref.9
1 0 27.6 27.6 27.6 27.6
2 3 15.9 15.5 16.9 22.1
3 5 13.1 12.4 13.5 17.5
Table 9 shows the retention effect at various dosages of cationised starch,
calculated as dry starch on dry stock system.
Table 9
Test Starch Dosage Turbidity
No. k /t NTU
C5 C6 Ref.8 Ref.9
1 0 188 188 188 188
2 3 121 131 131 161
3 5 119 118 130 148
