Note: Descriptions are shown in the official language in which they were submitted.
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Process for sizin pcLaper
The present invention refers to a process for sizing paper which comprises
adding to a suspension containing cellulosic fibres, and optional fillers, an
anionic or
cationic sizing dispersion, and a sizing promoter comprising a cationic
organic polymer
having one or more aromatic groups; and an anionic polymer having one or more
aromatic groups being a step-growth polymer, a polysaccharide and a naturally
occurring
aromatic polymer, forming and draining the obtained suspension, wherein the
sizing
dispersion and sizing promoter are added separately to the aqueous suspension.
Backgroud
Dispersions or emulsions of sizing agents are used in papermaking in order to
give paper and paper board improved resistance to wetting and penetration by
various
liquids. The sizing dispersions are usually added to an aqueous suspension
containing
cellulosic fibres, optional fillers and various additives. The aqueous
suspension is fed into
a headbox ejecting the suspension onto a wire where a wet web of paper is
formed. To
the suspension is further commonly added compounds such as starches and
microparticulate materials which facilitate the dewatering of the suspension
on the wire.
The water drained from the wire, referred to as white water, is usually partly
recirculated
in the papermaking process. The cellulosic suspension contains a certain
amount of non-
fibrous material, for example fillers, charged polymers, sizing agents and
various charged
contaminants, i.e. anionic trash, electrolytes, colloidal substances, etc..
The non-fibrous
material has an influence on the sizing efficiency and commonly impairs the
sizing
efficiency. High amounts of charged compounds such as high contents of salts
in the
suspension renders a suspension which is increasingly difficult to size, i.e.
to obtain a
paper with satisfactory sizing properties. Other compounds contained in the
suspension
which deteriorates sizing are various lipophilic wood extractives which may
come from
recycled fibres and mechanical pulps. An increased amount of added sizing
agent often
improve sizing, however, leading to higher costs as well an increased
accumulation of
sizing agents in the white water. The accumulation of non-fibrous material as
well as any
other component present in the suspension will be even more pronounced in
mills where
white water is extensively recirculated with the introduction of only low
amounts of fresh
water into the papermaking process. Thus, it is an objective of the present
invention to
further improve sizing. Another objective of the present invention is to
improve sizing
when sizing aqueous cellulosic containing suspensions having high conductivity
ans/or
high amounts of lipophilic wood extractives. Yet further objectives will
appear hereinafter.
US 6001166 refers to aqueous alkyl diketen dispersions containing cationic
starch and anionic dispersants such as lignin sulphonic acids, condensates of
naphthalenesulphonic acid and formaldehyde.
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WO 0023651 relates to anionic and cationic sizing dispersions containing
ketene
dimers and at least an anionic dispersing agent.
EP 984101 discloses sizing compositions comprising ketene dimers or acid
anhydrides and a complexing agent selected from aminopolycarboxylic acids, N-
bis-or tris- ((l. 2-dicraboxylethoxy) ethyl) amines and phosphonic acids.
US 5972094 refers to sizing compositions comprising a thermoplastic resin
selected from the group consisting of thermoplastic rosins, thermoplastic
hydrocarbon resins, thermoplastic polyamides and thermoplastic amide waxes.
US 5595629 discloses a paper making process comprising forming an aqueous
cellulosic paper making slurry and adding a cationic polymer and an anionic
polymer to the slurry to increase retention and/or drainage. The anionic
polymer
comprises a formaldehyde condensate of a naphthalene sulfonic acid salt.
Invention
It has been found that the, present invention surprisingly solves the problems
outlined in the application. More specifically, the invention relates to a
process
for sizing paper which comprises adding to an aqueous suspension containing
cellulosic fibres, and optional fillers, an anionic or cationic sizing
dispersion, and
a sizing promoter comprising a cationic organic polymer having one or more
aromatic groups and an anionic polymer having one or more aromatic groups, the
anionic polymer being a step-growth polymer, a polysaccharide or a naturally
occurring aromatic polymer, forming and draining the obtained suspension,
whe.rein the sizing dispersion and sizing promoter are added separately to the
aqueous suspension.
Sizing dispersion
The sizing agent comprised in the anionic or cationic sizing dispersion used
in
the process aecording to the present invention is suitably any sizing agent
rendering paper or board with enhanced resistance to wetting and penetration
of
liquids, such as non-cellulose-reactive agents including rosins, e. g.
fortified
andlor esterified rosins, waxes, fatty acids and resin acid derivatives, e. g.
fatty
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amides and fatty esters, e. g. glycerol triesters of natural fatty acids,
and/or
cellulose-reactive agents. Preferably, the sizing dispersion contains
cellulose-
reactive : sizing agents. The cellulose-reactive sizing agents comprised in
the
sizing dispersion can be selected from any cellulose-reactive agents known in
the
art. Suitably, the sizing agent is selected from hydrophobic ketene dimers,
ketene
multimers, acid anhydrides, organic isocyanates, carbamoyl chlorides. and
mixtures thereof, preferably ketene dimers and/or acid anhydrides. Suitably
the
ketene dimers have the general formula (IA) below, wherein R' and RZ represent
saturated or unsaturated hydrocarbon groups, usually saturated hydrocarbons,
the
hydrocarbon groups suitably having from 8 to 36 carbon atoms, usually being
straight or branched chain alkyl groups having 12 to 20 carbon atoms, such as
hexadecyl and octadecyl groups. The ketene dimers can be liquid at ambient
temperature, i. e. at 25'C, suitably at 20 C. Commonly, the acid anhydrides
can
be characterised by the general formula (IIA) below, wherein R3 and R4 can be
identical or different and represent saturated or unsaturated hydrocarbon
groups
suitably containing from 8 to 30 carbon atoms, or R3 and R4 together with the-
C-
O-C- moiety can form a 5 to 6 membered ring, optionally being further
substituted with hydro- carbon groups containing up to 30 carbon atoms.
Examples of acid anhydrides which are used commercially include alkyl and
alkenyl succinic anhydrides and particularly isoocta- decenyl succinic
anhydride:
(IA) R' HC C CH R2 (ILA) II 11
I I 0 R3-C O C R4
Suitable ketene dimers, acid anhydrides and organic isocyanates include the
compounds disclosed in US 4522686. Examples of suitable carbamoyl chlorides
include those disclosed in US3887427.
The process according to the present invention comprises adding to a
suspension
containing cellulosic fibres an anionic or cationic aqueous sizing dispersion,
i. e.
the dispersing and/or stabilising agents present in the dispersion which can
be
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referred to as the dispersing system have an overall anionic or cationic
charge,
respectively. The dispersing system can include any agent facilitating the
formation of a dispersion or emulsion such as dispersing and/or stabilising
agents
exemplified by polyelectrolytes, surfactants and electrolytes. Anionic aqueous
sizing dispersions may comprise cationic compounds, i. e. cationic
polyelectrolytes (cationic or amphoteric polyelectrolytes with an overall
cationic
charge) and/or cationic surfactants and/or any other cationic compound known
to
the skilled person provided that the overall charge of the dispersing system
is
anionic. Cationic aqueous sizing dispersions, on the other hand, can comprise
anionic compounds, i. e. anionic polyelectrolytes (anionic or amphoteric
polyelectrolytes with an overall anionic charge) and/or anionic surfactants
and/or
any other anionic compound known to the skilled person provided that the
overall charge of the dispersing system is anionic. The anionic or cationic
charge
of the sizing dispersion can be detennined by means of a ZetaMaster S version
PCS.
According to a preferred embodiment of the present invention the anionic or
cationic sizing dispersion contains a cationic organic polymer having one or
more aromatic groups and/or an anionic polymer having one or more aromatic
groups. The cationic organic
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polymer and the anionic polymer can be any of those described hereinafter
comprised in the
sizing promoter.
The anionic or cationic sizing dispersion added to the suspension can have a
sizing
agent content from 0.1 to 50 % by weight based on total dispersion/emulsion,
suitably over
20% by weight. Dispersions comprising ketene dimer sizing agents may have
ketene dimer
contents from 5 up to 50 % by weight based on total dispersion, preferably
from 10 up to
35% by weight. Dispersions, or emulsions, comprising acid anhydride sizing
agents may
have acid anhydride contents from 0.1 up to 30 % by weight based on total
dispersion/emulsion, suitably from 1 up to 20 % by weight. Dispersions
containing non-
cellulose reactive sizing agents suitably have sizing agent contents from 5 up
to 50 % by
weight, preferabiy from 10 up to 35 % by weight. If an anionic and/or a
cationic polymer
having one or more aromatic groups are comprised in the sizing dispersion they
are suitably
present in an amount of from about 0.1 % by weight up to about 15 % by weight
based on
sizing agent.
The amount of sizing agent added to the aqueous suspension containing
cellulosic fibres can be from 0.01 to 5 % by weight, suitably from 0.05 to 1.0
% by weight,
based on dry weight of cellulosic fibres and optional fillers, where the
dosage is dependent
on the quality of the pulp or paper to be sized, the sizing agent and the
level of sizing.
According to the present invention an anionic or cationic sizing dispersion
and a
sizing promoter comprising a cationic organic polymer having one or more
aromatic
groups and an anionic polymer having one or more aromatic groups being a step-
growth
polymer, a polysaccharide or a naturally occurring aromatic polymer are added
separately
to the aqueous suspension. Although the sizing dispersion may contain the same
polymers as comprised in the sizing promoter, significant improvements
regarding sizing,
is only observed when the sizing promoter and the sizing dispersion are added
separately
to the cellulosic suspension. By separate addition is meant that the sizing
dispersion
which may comprise any of the polymers of the sizing promoter and the sizing
promoter
are added at different locations to the cellulosic suspension (thin stock) or
at substantially
the same location but timely separated. Furthermore, the cationic organic
polymer and
the anionic polymer forming the sizing promoter are suitably also added
separately.
Preferably, the anionic polymer is added to the suspension after both the
sizing
dispersion and the cationic organic polymer.
According to a preferred embodiment of the present invention the process fo.ra
sizing paper comprises adding to an aqueous suspension containing cellulosic
fibres, and
optional fillers, an anionic or cationic sizing dispersion comprising a sizing
agent and an
anionic polymer having one or more aromatic groups being a step-growth
polymer, a
polysaccharide or a naturally occurring aromatic polymer, the amount of added
sizing
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agent to the suspension,being from about 0.01 % up to about 5.0 % by weight
based on
dry fibres; and a sizing promoter comprising a cationic polymer having one or
more
aromatic groups being suitably a cationic polysaccharide or a cationic vinyl
addition
polymer, and an anionic polymer having one or more aromatic groups being a
step-
5 growth polymer, a polysaccharide or a naturally occurring aromatic polymer,
the amount
of cationic polymer added to the suspension being from about 0.001 % up to
about 3.0 %
by weight based on dry fibres, and the amount of anionic polymer added to the
suspension being from about 0.001 % up to about 3.0 % by weight based on dry
fibres,
forming and draining the obtained suspension, wherein the sizing dispersion
and the
sizing promoter are added separately to the aqueous suspension.
According to yet another preferred embodiment of the invention the anionic or
cationic sizing dispersion comprises a sizing agent, a cationic organic
polymer having
one or more aromatic groups, such as a cationic polysaccharide or a cationic
vinyl
addition polymer, and an anionic polymer having one or more aromatic groups
being a
step-growth polymer, a polysaccharide or a naturally occurring aromatic
polymer suitably
the anionic polymer being a step-growth polymer or a naturally occurring
aromatic
polymer.
Suitably, the cationic polymer having one or more aromatic groups is a
cationic
polysaccharide having the structural formula (I):
R, (I)
1 x
P(-A-Nf-R2)n
1
R3
wherein P is a residue of a polysaccharide; A is a chain of atoms comprising C
and H atoms
attaching N to the polysaccharide residue, R, and R2 are each H or a
hydrocarbon group,
R3 is an aromatic hydrocarbon group, n is an integer from 2 up to 300000, and
X is an
anionic counter ion; or vinyl addition polymer obtained by polymerising a
cationic monomer
or a monomer mixture comprising a cationic monomer represented by the general
formula
(II):
CH2 = C- Rj R2 (II) ~'
1 1 +
O=C-A,-B,-N -Q X
1
R3
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wherein R, is H or CH3; R2 and R3 are each an alkyl group having from 1 to 3
carbon atoms,
A, is 0 or NH, B, is an alkylene group having from 2 to 8 carbon atoms or a
hydroxy
propylene group, Q is a substituent containing an aromatic group, and X is an
anionic
counterion. More preferably, the cationic polymer having one or more aromatic
groups is a
cationic polysaccharide having the structural formula (I):
R, (1)
1 X
P-(-A-N+-R2)n
I
R3
wherein P is a residue of a polysaccharide; A is a chain of atoms comprising C
and H atoms
attaching N to the polysaccharide residue, R, and R2 are each H or a
hydrocarbon group,
R3 is an aromatic hydrocarbon group, n is an integer from 2 up to 300000, and
X is an
anionic counter ion.
Cationic organic polymer having one or more aromatic qroups
The cationic organic polymer of the sizing promoter and suitably present in
the
sizing dispersion can be derived from natural or synthetic sources, and can be
linear,
branched or cross-linked. Preferably the cationic polymer is water-soluble or
water-
dispersable. Examples of suitable cationic polymers include cationic
polysaccharides,
e.g. starches, guar gums, celluloses, chitins, chitosans, glycans, galactans,
glucans,
xanthan gums, pectins, mannans, dextrins, preferably starches and guar gums,
suitable
starches including potato, corn, wheat, tapioca, rice, waxy maize, barley,
etc.; cationic
synthetic organic polymers such as cationic chain-growth polymers, e.g.
cationic vinyl
addition polymers like acrylate-, acrylamide- and vinylamide-based polymers,
and cationic
step-growth polymers, e.g. cationic polyurethanes. Cationic organic polymers
selected
from polysaccharides, i.e. starches , and cationic vinyl addition polymers
like acrylamide-
based polymers having an aromatic group are particularly preferred.
The aromatic group of the cationic organic polymer can be present in the
polymer
backbone or in a substituent. group that is attached to the polymer backbone
(main chain),
preferably in a substituent group. Examples of,suitable aromatic groups
include aryl, aralkyl
and alkaryl groups, e.g. phenyl, phenylene, naphthyl, xylylene, benzyl and
phenylethyl;
preferably benzyl, nitrogen-containing aromatic (aryl) groups, e.g. pyridinium
and
quinolinium, as well as derivatives of these groups. Examples of cationically
charged gr9ups
that can be present in the cationic polymer as well as in monomers used for
preparing the
cationic polymer include quaternary ammonium groups, tertiary amino groups and
acid
addition salts thereof.
According to a preferred embodiment the cationic organic polymer having an
aromatic group is selected from cationic polysaccharides. The aromatic group
of the
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polysaccharide can be attached to a heteroatom, e.g. nitrogen or oxygen,
present in the
polysaccharide, the heteroatom optionally being charged, for example when it
is a nitrogen.
The aromatic group can also be attached to a group comprising a heteroatom,
e.g. amide,
ester or ether, which groups can be attached to the polysaccharide
backbone(main=chain),
for example via a chain of atoms. Example of suitable aromatic groups and
groups
comprising an aromatic group include 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
Preferably, the cationic organic polymer is selected from cationic
polysaccharides having the general structural formula (I):
R, (I)
P-(-A-N+-R2)n
I
R3
wherein P is a residue of a polysaccharide; A is a group attaching N to the
polysaccharide
residue, suitably a chain of atoms comprising C and H atoms, and optionally 0
and/or N
atoms, usually an alkylene group with from 2 to 18 and suitably 2 to 8 carbon
atoms,
optionally interrupted or substituted by one or more heteroatoms, e.g. 0 or N,
e.g. an
alkyleneoxy group or hydroxy propylene group (- CH2- CH(OH) - CH2 -); R, and
R2
are each H or, preferably, a hydrocarbon group, suitably alkyl, having from 1
to 3 carbon
atoms, suitably 1 or 2 carbon atoms; R3 is suitably an aromatic hydrocarbon
group
including aralkyl groups, e.g. benzyl and phenylethyl groups; n is an integer
from about 2
to about 300,000, suitably from 5 to 200,000 and preferably from 6 to 125,000
or,
alternatively, Rl, R2 and R3 together with N form a aromatic group containing
from 5 to 12
carbon atoms; and X is an anionic counterion, usually a halide like chloride.
The aromatic group modified cationic polysaccharide can have a degree of
substitution varying over a wide range; the degree of cationic substitution
(DSc) can be from
0,01 to 0,5, suitably from 0,02 to 0,3, preferably from 0,025 to 0,2, the
degree of aromatic
substitution (DSAI) can be from from 0,01 to 0,5, suitably from 0,02 to 0,3,
preferably from
0,025 to 0,2, and the degree of anionic substitution (DSA) can be from 0 to
0,2, suitably from
0 to 0,1, preferably from 0 to 0,05.
The polysaccharides can be prepared by subjecting a polysaccharide to cationic
and aromatic modification in known manner using one or more agents containing
a
cationic group and/or a aromatic group, for example by reacting the agent with
the
polysaccharide in the presence of an alkaline substance such as an alkali
metal or
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alkaline earth metal hydroxide. The polysaccharide to be subjected to cationic
and aromatic modification can be non-ionic, anionic, amphoteric or cationic.
Suitable modifying agents include non-ionic agents such as, for example
aralkyl
halides, e. g. benzyl chloride and benzyl bromide; the reaction products of
epichlorohydrin and dialkylamines having at least one substituent comprising
an
aromatic group as defined above, including 3-dialkylamino-1, 2-epoxypropanes;
and cationic agents such as, for example, the reaction product of
epichlorohydrin
and tertiary arnines having at least one substituent comprising an aromatic
group
as defined above, including alkaryldialkylamines, e. g. dimethylbenzylamine ;
arylamines, e. g. pyridine and quinoline.
Suitable cationic agents of this type include 2,3-epoxypropyl trialkylammonium
halides and halohydroxypropyl trialkylammonium halides, e. g. N- (3-chloro-2-
hydroxypropyl)-N- (hydrophobic alkyl)-N, N-di (lower alkyl) ammonium
chloride and N-glycidyl-N- (hydrophobic alkyl)-N, N-di (lower alkyl)
ammonium chloride where the aromatic group is as defined above, notably octyl,
decyl and dodecyl, and the lower alkyl is methyl or ethyl ; and halo-
hydroxypropyl-N, N-dialkyl-N-alkarylammonium halides and N-glycidyl-N-
(alkaryl)-N, N- dialkylammonium 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. Generally, when using a non-ionic
aromatic agent, the polysaccharide is suitably rendered cationic by using any
of
the cationic agents known in the art before or after the hydrophobic
modification.
Examples of suitable cationic andlor aromatic modifying agents, aromatic group
modified polysaccharides and methods for their preparation include those
described in U. S. Patent Nos. 4,687,519 and 5,463,127 ; International Patent
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Application WO 94/24169, European Patent Application No. 189 935; and S. P.
Patel, R. G. Patel and V. S. Patel, Starch/Starke, 41 (1989), No. 5, pp. 192-
196.
According to yet another preferred embodiment the cationic organic polymer is
selected from homopolymers and copolymers prepared from one or more
monomers comprising at least one monomer having an aromatic group, suitably
an ethylenically unsaturated monomer. The synthetic polymer may be branched
linear or branched. The aromatic group of the synthetic polymer can be present
in
the polymer backbone or, preferably, it can be a pendant group attached to or
extending from the polymer backbone or be present in a pendent group that is
attached to or extending from polymer backbone. Suitable aromatic (aryl)
groups
include those comprising a phenyl group, optionally substituted, a phenylene
group, optionally substituted, and a naphthyl group, optionally substituted,
for
example groups having the general formulae-C6H5,-C6H4-,
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-C6H3-, and -C6H2-, e.g. in the form of phenylene (-C6H4-), xylylene
(-CH2-C6H4-CH2-), phenyl (-C6H5), benzyl (-CH2-C6H5), phenethyl (-CH2CH2-
C6H5),
and substituted phenyl (for example -CsH4-Y, -C6H3Y2, and -C6H2Y3) where one
or
more substituents (Y) attached to the phenyl ring can be selected from
hydroxyl, halides,
e.g. chloride, nitro, and hydrocarbon groups having from 1 to 4 carbon atoms.
Preferably, the cationic polymer is a vinyl addition polymer. The term "vinyl
addition polyme-" as used herein, refers to a polymer prepared by addition
polymerisation
polymerization of one or more vinyl monomers or ethylenically unsaturated
monomers
which include, for example, acrylamide-based and acrylate-based monomers.
Suitably,
the cationic polymer is selected from cationic vinyl addition polymers
obtained by
polymerising a cationic monomer or a monomer mixture comprising a cationic
monomer
represented by the general formula (II):
CHZ = C- Rj R2 (I I)
1 1
O=C-A,-B,-N -Q X
I
R3
wherein R, is H or CH3; R2 and R3 are each or, preferably, an alkyl group
having from 1 to 3
carbon atoms, usually 1 to 2 carbon atoms; A, is 0 or NH; B, is an alkylene
group having
from 2 to 8 carbon atoms, suitably from 2 to 4 carbon atoms, or a hydroxy
propylene group;
Q is a substituent containing an aromatic group, suitably a phenyl or
substituted phenyl
group, which can be attached to the nitrogen by means of an alkylene group
usually having
from 1 to 3 carbon atoms, suitably 1 to 2 carbon atoms, and preferably Q is a
benzyl group
(- CH2- C6H5); and X is an anionic counterion, usually a halide like chloride.
Examples of
suitable monomers represented by the general formula (II,) include quatemary
monomers
obtained by treating dialkylaminoalkyl (meth)acrylates, e.g.
dimethylaminoethyl (meth)-
acrylate, diethylaminoethyl (meth)acrylate and dimethylaminohydroxypropyl
(meth)acrylate,
and dialkylaminoalkyl (meth)acrylamides, e.g. dimethylaminoethyl
(meth)acrylamide, diethyl-
aminoethyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, and
diethylamino-
propyl (meth)acrylamide, with benzy( chloride` Preferred cationic monomers of
the general
formula (II) include dimethylaminoethylacrylate benzyl chloride quaternary
salt and
dimethylaminoethylmethacrylate benzyl chloride quatemary salt.
The cationic vinyl addition (synthetic cationic) polymer can be a homopolYmer
prepared from a cationic monomer having an aromatic group or a copolymer
prepared from
a monomer mixture comprising a cationic monomer having an aromatic group and
one or
more copolymerizable monomers. Suitable copolymerizable non-ionic monomers
include
monomers represented by the general formula (III):
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CH2 = C- R4 R5 (I II)
I I
O=C-AZ-BZ-N
5 1
R6
wherein R4 is H or CH3; R5 and R6 are each H or a hydrocarbon group, suitably
alkyl, having
from I to 6, suitably from 1 to 4 and usually from I to 2 carbon atoms; A2 is
0 or NH; B2 is
10 an alkylene group of from 2 to 8 carbon atoms, suitably from 2 to 4 carbon
atoms, or a
hydroxy propylene group or, alternatively, A and B are both nothing whereby
there is a
single bond between C and N(0=C - NR5R6). Examples of suitable copolymerizable
monomers of this type include (meth)acrylamide; acrylamide-based monomers like
N-alkyl
(meth)acrylamides and N,N-dialkyl (meth)acrylamides, e.g. N-n-
propylacrylamide, N-
isopropyl (meth)acrylamide, N-n-butyl (meth)acrylamide, N-isobutyl
(meth)acrylamide and N-
t-butyl (meth)acrylamide; and dialkylaminoalkyl (meth)acrylamides, e.g.
dimethylaminoethyl
(meth)acrylamide, diethylaminoethyl (meth)acrylamide, dimethylaminopropyl
(meth)acryl-
amide and diethylaminopropyl (meth)acrylamide; acrylate-based monomers like
dialkyl-
aminoalkyl (meth)acrylates, e.g. dimethylaminoethyl .(meth)acrylate,
diethylaminoethyl
(meth)acrylate, t-butylaminoethyl (meth)acrylate and
dimethylaminohydroxypropyl acrylate;
and vinylamides, e.g. N-vinylfomiamide and N-vinylacetamide. Preferred
copolymerizable
non-ionic monomers include acrylamide and methacrylamide, i.e.
(meth)acrylamide, and the
main polymer is preferably an acrylamide-based polymer.
Suitable copolymerizable cationic monomers include the monomers represented by
the general formula (IV):
CH2 = C - R, R8 (IV)
~ ~ .
0=C-A3-B3-N* -Ria X-
1
R9
wherein R7 is H or CH3; Ra, R9 and Rlo are each H or, preferably, a
hydrocarbon group,
suitably alkyl, having from 1 to 3 carbon atoms, usually 1 to 2 carbon atoms;
A3 is 0 or NH;
B3 is an alkylene group of from 2 to 4 carbon atoms, suitably from 2 to 4
carbon atoms, or a
hydroxy propylene group, and X is an anionic counterion, usually
methylsulphate or a halide
like chloride. Examples of suitable cationic copolymerizable monomers include
acid addition
salts and quaternary ammonium salts of the dialkylaminoalkyl (meth)acrylates
and d'alkyl-
aminoalkyl (meth)acrylamides mentioned above, usually prepared using acids
like HCI,
H2SO4, etc., or quaternizing agents like methyl chloride; dimethyl sulphate,
etc.; and diallyl-
dimethylammonium chloride. Preferred copolymerizable cationic monomers include
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dimethylaminoethyl (meth)acrylate methyl chloride quatemary salt and
diallyldimethyl-
ammonium chloride. Copolymerizable anionic monomers like acrylic acid,
methacrylic acid,
various sulfonated vinyl addition monomers, etc. can also be employed and,
preferably; in
minor amounts.
The cationic vinyl addition polymer can be prepared from a monomer mixture
generally comprising from 1 to 99 mole%, suitably from 2 to 50 mole% and
preferably from 5
to 20 mole% of cationic monomer having an aromatic group, preferably
represented by the
general formula (II), and from 99 to 1 mole%, suitably from 98 to 50 mole%,
and preferably
from 95 to 80 mole% of other copolymerizable monomers which preferably
comprises
acrylamide or methacrylamide ((meth)acrylamide), the monomer mixture suitably
comprising
from 98 to 50 mole% and preferably from 95 to 80 mole% of (meth)acrylamide,
the sum of
percentages being 100.
The cationic polymer can also be selected from polymers prepared by
condensation reaction of one or more monomers containing an aromatic group.
Examples of
such monomers include toluene diisocyanates, bisphenol A, phthalic acid,
phthalic
anhydride, etc., which can be used in the preparation of cationic
polyurethanes, cationic
polyamideamines, etc.
Alternatively, the organic polymer can be a polymer subjected to aromatic
modification using an agent containing an aromatic group. Suitable modifying
agents of this
type include benzyl chloride, benzyl bromide, N-(3-chloro-2-hydroxypropyl)-N-
benzyl-N,N-
dimethylammonium chloride, and N-(3-chloro-2-hydroxypropyl) pyridinium
chloride. Suitable
polymers for such an aromatic modification include vinyl addition polymers. If
the polymer
contains a tertiary nitrogen which can be quaternized by the modifying agent,
the use of
such agents usually results in that the polymer is rendered cationic.
Alternatively, the
polymer to be subjected to aromatic modification can be cationic; for example
a cationic vinyl
addition polymer.
Usually the charge density of the vinyl addition polymer is within the range
of from
0.1 to 6.0 meqv/g of dry polymer, suitably from 0.2 to 4.0 and preferably from
0.5 to 3Ø
The weight average molecular weight of synthetic polymers is usually at least
about
500,000, suitably above about 1,000,000 and preferably above about 2,000,000.
The upper
limit is not critical; it can be about 50,000,000, usually 30,000,000 and
suitably 25,000,000.
Anionic polymer having one or more aromatic groups ;1
4
The anionic polymer having an aromatic group comprised in the sizing promoter
and optionally comprised in the sizing dispersion of the present invention is
a step-growth
polymer, a polysaccharide or a naturally occurring aromatic polymer. The term
"step-growth
polymer", as used herein, refers to a polymer obtained by step-growth
polymerization, also
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12
being referred to as step-reaction polymer and step-reaction polymerization,
respectively.
Preferably, the anionic polymer comprised in the promoter is a step-growth
polymer, a
polysaccharide or a naturally occun-ing aromatic polymer with the proviso that
the anionic
polymer is not a melamine sulphonic acid condensation polymer. The anionic
polymer may
be a step-growth polymer or a naturally occurring aromatic polymer. The
anionic polymers
according to the invention can be linear, branched or cross-linked. The
anionic polymer is
commonly water-soluble or water-dispersable. The anionic polymer is preferably
organic.
Preferred anionic aromatic polymers are naphthalene sulphonate condensation
polymers
like condensated naphthalene sulphonate, and modified lignin polymers, e.g.
lignin
sulphonate.
The aromatic group of the anionic polymer can be present in the polymer
backbone or in a substituent group that is attached to the polymer backbone
(main chain).
Examples of suitable aromatic groups include aryl, aralkyl and alkaryl groups
and derivatives
thereof, e.g. phenyl, tolyl, naphthyl, phenylene, xylyiene, benzyl,
phenylethyl and derivatives
of these groups. 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 polymerization products according to
the
present invention include condensation polymers, i.e. polymers obtained by
step-growth
condensation polymerization, e.g. condensates of an aldehyde such as
formaldehyde with
one or more aromatic compounds containing one or more anionic groups,
specifically
condensated naphthalene sulphonate type polymers, and optional other co-
monomers
useful in the condensation polymerization such as urea. Examples of suitable
aromatic
compounds containing anionic groups include phenolic and naphtholic compounds
such
as phenol, naphthol, resorcinol and derivatives thereof, aromatic acids and
salts thereof
such as 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 polymerization products
according
to the present invention include addition polymers, i.e: polymers obtained by
step-growth
addition polymerization, e.g. anionic polyurethanes prepared from a monomer
mixture
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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
derivaties 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-aminoethanesulfonic acid, and
the like,
optionally and usually in combination with reaction with a base, such as
alkali metal and
alkaline earth hydroxides, e.g. sodium hydroxide, ammonia or an amine, e.g.
triethylamine, thereby forming an alkali metal, alkaline earth or ammonium
counter-ion.
Examples of suitable anionic chain-growth polymerization products according to
the
invention 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-polymerized
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, guar gums,
celluloses, chitins, chitosans, glycans, galactans, glucans, xanthan gums,
pectins, mannans,
dextrins, preferably starches, guar gums and cellulose derivatives, suitable
starches
including potato, corn, wheat, tapioca, rice, waxy maize and barley,
preferably potato. The
anionic groups in the polysaccharide can be native and/or introduced by
chemical treatment.
The aromatic groups in the polysaccharide can be introduced by chemical
methods known
in the art. .41
Examples of suitable (modified) naturally occurring aromatic anionic polymers
of
this invention include Kraft lignin, such as modified lignin polymers like
lignin adducts co-
polymerised with formaldehyde and sulphonated lignin, e.g. lignin sulphonate
and tannin
extracts, i.e. naturally occuring polyphenolic substances that are present in
the organic
extracts of bark of some wood species.
Suitably, the anionic polymer having an aromatic group is selected from step-
growth polymers, polysaccharides and naturally occurring aromatic polymer.
Condensated
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naphthalene sulphonate type polymers like condesated naphthalene sulphonate
and
modified lignin polymers such as lignin sulphonates are preferred.
The weight 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 1,000,000.
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 (DSQ) 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 (DSc) can be, for
example, from 0 to
0.2, suitably from 0 to 0.1 and preferably from 0 to 0.05, the anionic polymer
having an
overall anionic charge. Usually the anionic charge density of the anionic
polymer is within
the range of from 0.1 to 6.0 meqv/g of dry polymer, suitably from 0.5 to 5.0
and preferably
from 1.0 to 4Ø
The cationic organic polymer having an aromatic group and the anionic polymer
having an aromatic group of the sizing promoter can be added to the aqueous
suspension
(stock) in any order separately from the addition of the sizing dispersion and
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
polymers are added in
an amount that give better sizing than is obtained when not adding them and
usually the
cationic organic polymer is added to the stock prior to adding the anionic
polymer. The
cationic polymer 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
2.0% by weight. The anionic polymer 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.
Apart from the cationic organic poaymer and the anionic polymer the sizing
promoter may contain other compounds which improve the sizing efficiency such
as anionic
microparticulate materials, e.g., silica-based particles and clays of smectite
type, low
molecular weight cationic organic polymers, aluminium compounds like alum,
aluminates,
aluminium chloride, aluminium nitrate and polyaluminium compounds, such as
poly-
aluminium chlorides, polyaluminium sulphates, polyaluminium compounds
containing both
chloride and sulphate ions, polyaluminium silicate-sulphates and mixtures
thereof, anionic
vinyl addition polymers and combinations thereof.
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The process of the invention is preferably used in the manufacture of paper
from a
suspension containing cellulosic fibers, and optional fillers, having a high
conductivity.
Usually, the conductivity of the stock is at least 0.20 mS/cm, suitably at
least 0.5 mS/cm,
preferably at least 3.5 mS/cm. Very good sizing results have been observed at
conductivity
5 levels above 5.0 mS/cm and even above 7.5 mS/cm. Conductivity can be
measured by
standard equipment such as, for example a WfW 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
10 suspension. High conductivity levels mean high contents of salts
(electrolytes), where the
various salts can be based on mono-, di- and multivalent cations like alkali
metals, e.g. Na+
and K, alkaline earths, e.g. Ca2' and Mgz+, aluminium ions, e.g. AI3+,
AI(OH)2" and
polyaluminium ions, and mono-, di- and multivalent anions like halides, e.g.,
CI-, sulfates,
e.g. S042' and HS04 , carbonates, e.g. C032' and HC03 , silicates and lower
organic acids.
15 The invention is particularly useful in the manufacture of paper from
stocks having high
contents of salts of di- and multivalent cations, and usually the cation
content is at least 200
ppm, suitably at least 300 ppm and preferably at least 400 ppm. The salts can
be derived
from the cellulosic fibres and fillers used to form the stock, in particular
in integrated mills
where a concentrated aqueous fibre suspension from the pulp mill normally is
mixed with
water to form a dilute suspension suitable for paper manufacture in the paper
mill. The salt
may also be derived from various additives introduced into the stock, from the
fresh water
supplied to the process, or be added deliberately, etc. Further, the content
of salts is usually
higher in processes where white water is extensively recirculated, which may
lead to
considerable accumulation of salts in the water circulating in the process.
The present invention further encompasses papermaking processes where white
water is extensively recirculated (recycled), i.e. with a high degree of white
water closure, for
example where from 0 to 30 tons of fresh water are used per ton of dry paper
produced,
usually less than 20, suitably less than 15, preferably less than 10 and
notably less than 5
tons of fresh water per ton of paper. Recirculation of white water obtained in
the process
suitably comprises mixing the white water with.cellulosic fibres and/or
optional fillers to form
a suspension to be sized; preferably it comprises mixing the white water with
a suspension
containing cellulosic fibres, and optional fillers, before the suspension
enters the forming
wire for sizing.
Further additives which are conventional in papermaking can of course be used
in
combination with the additives according to the invention, such as, for
example, additional
dry strength agents, wet strength agents. The cellulosic suspension, or stock,
can also
contain mineral fillers of conventional types such as, for example, kaolin,
china clay, titanium
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16
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 sheet or web-like products, such as for example board and
paperboard, and
the production thereof. The process can be used in the production of paper
from different
types of suspensions of cellulose-containing fibres and the suspensions should
suitably
contain at least 25% by weight and preferably at least 50% by weight of such
fibres,
based on dry substance. The suspensions can be based on fibres from chemical
pulp
such as sulphate, sulphite and organosolv pulps, mechanical pulp such as
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 is particularly useful in
the
manufacture of paper from suspensions based on pulps comprising recycled
fibres and
de-inked pulp, and the content of cellulosic fibres of such origin can be up
to 100%,
suitably from 20% to 100%.
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.
In all examples hereinafter the sizing dispersion and the sizing prompter were
added separately to the cellulosic suspension. Furthermore, in the case the
promoter
comprised more than one polymer having an aromatic group, these polymers were
added
separately to the suspension with respect to each other and to the dispersion.
Example 1
The sizing performance of the process was evaluated by using the cobb 60 test.
An anionic sizing dispersion was prepared containing alkyl ketene dimer,
condensated
naphthalene sulphonate and di(hydrogenated tallow) dimethylammonium chloride.
The
sizing dispersion had an AKD content of 30% and contained 4% of
di(hydrogenated
tallow) dimethylammonium chloride and 6% of condensated naphthalene sulphonate
based on AKD. The sizing dispersion was added to the stock in an amount of 5
kg AKD/
tonne dry stock.
In test 2 the sizing promoter comprised condensated naphtalene sulphonate
(available
under the trade name Tamol ) and a cationic starch with a cationic
substitution DS of
0.065 regarding nitrogen containing benzyl groups. In test 1 cationic starch
without
aromatic groups with a cationic substitution of 0.065 and anionic inorganic
silica particles
provided as a sol, i.e. an anionic non-aromatic polymer, was added to the
furnish.
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The furnish used was based on 80 % by weight of bleached birch/pine (60/40)
sulphate
pulp and 20 % by weight of CaCO3 refined to 200 CSF and containing 0.3 g/litre
stock
Na2SO4, having a conductivity of 461 pS/cm and a pH of 8,1.
Table I
Test no. anionic cationic starch cationic
sizing containing starch
dispersion/ aromatic (without
[kg sizing groups/[kg aromatic
agent/tonne /tonne dry groups)/[kg
dry stock] stock] starch/tonne
dry stock]
test 1 0,5 0 10
test 2 0,5 10 0
Table 1 cont.
Test no. cond. anionic silica cobb
naphtalene particles/[kg 60/[g/m2j
sulphonate/ silica
[kg part./tonne
cond./tonne dry stock]
dry stock]
test 1 0 1 45,2
test 2 1 0 29,3 .
Example 2
The sizing performance of the process was evaluated (cobb 60 test) by adding
the same
anionic sizing dispersion as described in example 1 and a sizing promoter
comprising
cationic starch with a cationic substitution DS of 0.065 regarding nitrogen
containing
benzyl groups and anionic inorganic silica particles (test 1); and a promoter
comprising
condensated naphtalene sulphonate (available under the trade name Tamol 0) and
a
cationic starch with a cationic substitution DS of 0.065 regarding nitrogen
contaiPiing
benzyl groups (test 2). However, calcium chloride was added to the furnish to
adjust the
conductivity to 5000 pS/cm thereby simulating a furnish having high
conductivity.
Table 2
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Test no. anionic sizing cationic cationic
dispersion/ starch starch
[kg sizing containing (without
agent/tonne aromatic aromatic
dry stock] groups /[kg groups)/[kg
/tonne dry starch/tonne
stock] dry stock]
test 1 0,5 10 0
test 2 0,5 10 0
Table 2 cont.
Test no. cond. anionic silica cobb
naphtalene particles/[kg 60/[g/m2]
sulphonate/ silica
[kg part./tonne
cond./tonne dry stock]
dry stock]
test 1 0 1 75
test 2 1 0 27,8
Example 3
The sizing performance was evaluated using a cationic sizing dispersion which
contained
% of alkyl ketene dimer, 2 % of cationic ~starch and 0.6% of sodium
lignosulphonte,
based on AKD. The components and added amount of components comprised in the
15 sizing promoter, apparent from table 3,` included condensated naphtalene
sulphonate,
cationic starch without aromatic groups having a DS of 0.065, cationic starch
contairiing
aromatic groups having a DS of 0.065 and anionic inorganic silica particles
provided as a
sol. The stock used was that of example 2 having a pH of 8.1 and a
conductivity of 5000
pS/cm by the addition of calcium chloride to the stock.
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Table 3
Test no. cationic cationic cationic
sizing starch starch
dispersion/ containing (without
[kg sizing aromatic aromatic
agent/tonne groups /[kg groups)/[kg
dry stock] /tonne dry starch/tonne
stock] dry stock]
test 1 0,5 0 10
test 2 0,5 10 0
Table 3 cont.
Test no. cond. anionic silica cobb
naphtalene particles/[kg 60/[g/m2]
sulphonate/ silica
[kg part./tonne
cond./tonne dry stock]
dry stock]
test 1 0 1 55
test 2 1 0 27,8
Example 4
An anionic sizing dispersion was prepared containing 8,9 % of a commercial
alkyl ketene
dimer, 0,89 % of an aromat substituted cationic starch having a DS of 0,065
containing
benzyl groups, and 0,22 % of condensated naphthalene sulphonate available
under the
trade name Tamol . The anionic dispersion was added in an amount of 0,0115%
(dry
base) based on the ketene dimer to a cellulosic suspension (dry base)
containing , 30%
Pine, 30% Bee, 40% Eucaluptus, and 15% of precipitated CaCO3. The conductivity
of the
suspension was 500 pS/cm. To the suspension was also added a sizing promoter
containing benzyl substituted starch having a DS of 0.065 and condensated
naphtalene
sulphonate available under the trade name Tamol 0 (test 2).
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To the same suspension was also added the same anionic dispersion. However,
the
sizing promoter added to the suspension contained no aromatic polymers. The
sizing
promoter contained cationic starch with a DS of 0.065 having no aromatic
groups and
anionic inorganic silica particles provided as a sol (test 1). The amounts of
polymers of
5 the promoter and sizing agent (AKD) of the dispersion are given in table 4.
Table 4
Test no. anionic cationic starch cationic starch
sizing containing (without
dispersion/ aromatic aromatic
[kg sizing groups/[kg groups)/[kg
agent/tonne /tonne dry starch/tonne
dry stock] stock] dry stock]
test 1 0.115 0 5
test 1 0.125 0 5
test 1 0.140 0 5
test 2 0.115 5 0
test 2 0.125 5 0
test 2 0.140 5 0
Test no. cond. anionic silica cobb 60/[g/m ]
naphtalene particles/[kg
sulphonate/ silica -~
~
[kg part./tonne dry
cond./tonne stock]
dry stock]
test 1 0 0.120 90.0
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21
test 1 0 0.120 50.0
test 1 0 0.120 29.0
test 2 0.120 0 28.0
test 2 0.120 0 27.0
test 2 0.120 0 25.5
Example 5
In this example the same dispersion and sizing promoters were used as in
example 2
except that the conductivity of the suspension was 5000 pS/cm.
The amounts of polymers of the promoter and sizing agent (AKD) of the
dispersion are
given in table 5.
Table 5
Test no. anionic cationic starch cationic starch
sizing containing (without
dispersion/ aromatic aromatic
[kg sizing groups/[kg groups)/[kg
agent/tonne /tonne dry starch/tonne
dry stock] stock] dry stock]
test 1 0.140 0 5
test 1 0.160 0 5
test 1 0.180 0 5
test 1 0.200 0 5
test 2 0.100 5 0
test 2 0.115 5 0
test 2 0.125 5 0'
test 2 0.140 5 0
Test no. cond. anionic silica cobb 60/[g/m ]
naphtalene particles/[kg
sulphonate/ silica
[kg part./tonne dry
cond./tonne stock]
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dry stock]
test 1 0 0.120 150
test 1 0 0.120 137
test 1 0 0.120 138
test 1 0 0.120 110
test 2 0.120 0 47
test 2 0.120 0 35
test 2 0.120 0 33
test 2 0.120 0 25
Example 6
The sizing performance of the process was evaluated by using the Cobb 60 test.
An
anionic sizing dispersion was prepared containing alkyl ketene dimer,
condensed
naphtalene sulphonate and di(hydrogenated tallow) dimethylammonium chloride.
The
sizing dispersion had an AKD content of 30% and contained 4% of
di(hydrogenated
tallow) dimethylammunium chloride and 6% of condensed naphtalene sulphonate,
based
on AKD. The sizing dispersion was added in an amount of 0.3 kg AKD/ tonne of
dry
stock.
A cationic starch with a cationic substitution DS of 0.065 regarding nitrogen
containing
benzylgruops and a starch with a cationic substitution DS of 0.065 were used
in a
combination of a condensed naphtalene sulphonate and a melamin sulphonate,
respectively.
The furnish used was based on 80% birch/pine (60/40) sulphate pulp and 20% by
weight
oc CaCO3 , refinded to 200 CSF and containing 0.3 g/litre stock giving a
conductivity of
555 S/cm and a pH 8,22.
Table 6
Test no. Anionic Cationic Cationic
sizing starch starch
dispersion containing without
kg/tonne of aromatic aromatic
sizing groups groups
agent/tonne kg/tonne of kg/tonne of
of dry stock dry pulp dry pulp
Test 1 0.3 10
Test 2 0.3 10
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Test 3 0.3 10
Test 4 0.3 10
Test no. cond. melamin Cobb 60
naphtalen sulphonate g/m2
sulphonate
kg/tonne of kg/tonne of
dry pulpl dry pulp
Test 1 1 33
Test 2 1 52
Test 3 1 35
Test 4 1 68
,.;
