Note: Descriptions are shown in the official language in which they were submitted.
CA 02876609 2014-12-12
IMPROVED METHOD FOR MANUFACTURING PAPER USING A CATIONIC
POLYMER OBTAINED BY HOFMANN DEGRADATION
The invention relates to an improved process for manufacturing paper, board or
the like
using at least one cationic polymer obtained by Hofmann degradation and that
makes it
possible to increase the content of fillers in said papers or boards, while
retaining
advantageous physical strength properties. Another subject of the invention is
the papers
or boards obtained by this process.
The polymers obtained by Hofmann degradation are chemical compounds commonly
used in the paper manufacturing industry. For example, document WO 2011/015783
describes in particular cationic (co)polymers derived from acrylamide obtained
by a
Hofmann degradation. These compounds are added as drainage aids to thin
stocks, or for
improving the dry strength performances, also to thin stocks.
The composition of most of the fibre suspensions used in the manufacture of
paper
contain, following a direct addition or indirect addition (by use of recycled
papers),
inorganic fillers such as clays, kaolins, calcium carbonate or else titanium
dioxide.
Industrially, the most commonly used fillers are calcium carbonates, whether
they are in
ground form (referred to as GCC for ground calcium carbonate), or else in
precipitated
form (referred to as PCC for precipitated calcium carbonate). Currently,
regarding the
significant increase in the price of paper fibres, there is a growing interest
in substituting,
in the sheet, a portion of the fibre with less expensive mineral fillers.
Conventionally, retention aids are used in order to increase the overall
retention in the
sheet (FPR: first pass retention) and in particular the retention of fillers
(FPAR: first pass
ash retention). Chemically, these retention aids are, generally, polymers of
high
molecular weight (i.e. greater than 1 million g/mol), such as acrylamide
copolymers.
These polymers may be combined with microparticulate inorganic compounds
(bentonite,
colloidal silica).
However, the increase in the content of fillers, to the detriment of the
fibres, with this
very widespread technology has a tendency to deteriorate the physical
properties of the
paper. The amount of fillers incorporated into the sheet is therefore limited
due to
strength constraints.
The retention aids conventionally used are added to the thin stock, i.e. a
fibre suspension
containing from 0.1 to 1.5% solids. They make it possible to improve filler
retention, i.e.
CA 02876609 2014-12-12
2
to optimize the amount of filler used. Their role consists in particular in
retaining the
fillers in the paper and thus in reducing the amount of fillers discharged
into the white
waters resulting from the drainage of the sheet during the formation thereof
on the wire.
Document WO 2009/036271 describes a process that makes it possible to increase
the
filler content in the paper by pre-flocculation of the filler slurry in the
presence of two
flocculants injected successively, and combined with an overall (first-pass)
retention aid
added in the vicinity of the head box. However, this technique remains
difficult to
implement due to the multitude of compounds added according to a well-defined
sequence.
Documents US 2006/0024262 and US 2009/0272506 describe a treatment using an
amphoteric polyvinylamine (PVA) resulting from the hydrolysis of an N-
vinylformamide
(NVF) base copolymer.
Document US 2012/073774 Al describes a process involving the addition of a
cationic
polymer and of an aqueous suspension of sizing agent. The cationic polymer is
preferably
a polyvinylamine that can be obtained in particular by hydrolysis or by the
Hofmann
degradation reaction. These two compounds are typically incorporated into the
thin stock.
They make it possible to reduce the adhesion of the sheet of paper to the
wire, during
drying.
Although these processes make it possible to introduce an advantageous filler
content
into the sheet while maintaining acceptable physical properties, they
nevertheless have
limits. There is therefore a need to further increase the amount of fillers
without however
deteriorating the physical properties of the paper.
A problem that the invention proposes to solve relates in particular to the
optimal
increase in the amount of fillers, or filler content, in the sheets of paper
or the boards,
while retaining satisfactory physical properties.
The present invention proposes an improved process for manufacturing paper,
board and
the like, comprising the addition, to a fibre suspension, of at least one
polymer obtained
by Hofmann degradation, characterized in that the polymer obtained by Hofmann
degradation is cationic, and added before the fan pump of the thick stock with
the white
waters.
CA 02876609 2014-12-12
3
More specifically, the present invention relates to a process for
manufacturing a sheet of
paper and/or board and the like, according to which, in a plant comprising a
fan pump
and a head box:
- a cellulose fibre suspension, referred to as thick stock, is
prepared, into which
fillers are advantageously introduced;
- the white waters resulting from the drainage of the sheet are
introduced into the
thick stock;
- the mixture thus obtained is homogenized in the fan pump;
- the thin stock resulting from the homogenization is transferred to
the head box;
- the sheet is formed;
- the sheet is dried.
This process is characterized in that, before homogenization of the mixture in
the fan
pump, that is to say before the fan pump, a cationic copolymer obtained by
Hofmann
degradation reaction is introduced into the white waters and/or the thick
stock and/or the
mixture formed by the white waters and the thick stock.
With regard to the prior art, it is quite surprising to observe that a
cationic version of the
polymer obtained by Hofmann degradation, when it is introduced into the
process as
mentioned above, can lead to better performances than the amphoteric versions
in terms
of filler retention while retaining very good physical strength properties.
Another subject of the present invention is the papers or boards obtained
capable of being
obtained according to this process.
Without being tied to any one theory, the Applicant considers that the
cationic polymer
obtained by Hofmann degradation may act as an activator of affinities between
the fillers
and the fibres, which enables the fillers to be retained quantitatively in the
paper sheet
from the moment of the formation of the paper network. Furthermore, this very
good
affinity appears to strengthen the cohesion of the structure of the paper
sheet, thus giving
it unequalled physical strength relative to the percentage of filler present
in the sheet.
As mentioned above, in a process for manufacturing paper, board or the like,
the white
waters are added to the thick stock before the fan pump. Once mixed, the stock
forms a
thin stock which, at the outlet of the fan pump, goes to the head box where
the wet sheet
is formed before being dried. Generally, a shearing step is provided between
the fan
pump and the head box: this is the pressure screen. The fillers are added
generally in
CA 02876609 2014-12-12
4
slurry form to the thick stock. However, these fillers may originate from a
raw material
that contains fillers, for example deinked stocks, broke stocks/sized stocks,
etc.
The thick stock, or thick fibre suspension generally contains between 2% and
5% solids.
As already indicated, the cationic polymer obtained by Hofmann degradation may
be
introduced into the process in the thick stock and/or in the white waters
and/or in the
mixture of the two before the fan pump.
Conventionally, the fillers are added, especially in slurry form, before the
fan pump. They
are added to the thick stock and/or the white waters and/or the mixture of the
two, in one
or more additions. The fillers are nevertheless usually advantageously added
to the thick
stock.
In a first embodiment, the polymer is added in the immediate vicinity of the
filler
introduction point or points.
In a second embodiment, the cationic polymer is introduced at the same time as
the
fillers. Advantageously, it is introduced in this case into the filler slurry
or during the
preparation thereof.
When the polymer is introduced into the white waters, it is advantageously
introduced
just before the mixing thereof with the thick stock.
A filler "slurry" denotes an aqueous dispersion containing fillers. Generally
a slurry
contains more than 10% fillers by weight.
The improved process according to the invention may also comprise the
addition, to the
papermaking sequence, of any other mineral compound or natural or synthetic
polymer
well known to a person skilled in the art. Mention will be made, non-
limitingly, of the
addition of at least one additive selected from the group comprising
coagulants (PAC
(polyaluminium chloride), polyDADMAC, polyamine), retention aids (anionic,
cationic
or amphoteric polymers, bentonites, siliceous materials), dry strength agents
(DSRs - dry
strength resins) (native starch, cationic starch, polyvinylamine) or else
drainage aids
(polyethyleneimine).
In one particular embodiment, the process according to the invention comprises
the
addition of at least one cationic polymer obtained by Hofmann degradation
before the fan
CA 02876609 2014-12-12
pump, and of at least one aciylamide-based cationic polymer to the thin stock,
that is to
say after the fan pump. Preferably, this acrylamide-based cationic polymer has
a
molecular weight of greater than 1 million g/mol.
5 The amount of cationic polymer obtained by Hofmann degradation introduced
according
to the process of the invention is between 50 and 4000 g of active polymer per
tonne of
dry stock (g/t). Preferably, the amount introduced is between 100 g/t and 1000
g/t.
The Hofmann degradation is a reaction discovered by Hofmann at the end of the
nineteenth century, which makes it possible to convert an amide into a primary
amine by
eliminating carbon dioxide. The reaction mechanism is given in detail below.
In the presence of a base (sodium hydroxide) a proton is removed from the
amide.
0 H 0
/
OH-
11
R-C-N R-C--H
\H -H20
The amidate ion formed then reacts with the active chlorine (C12) of the
hypochlorite
(e.g.: NaCIO, which is in equilibrium: 2 NaOH + Cl2 <=> NaC10+ NaC1+ H20) to
give an
N-chloramide. The base (NaOH) removes a proton from the chloramide to form an
anion.
The anion loses a chloride ion to form a nitrene, which undergoes a
rearrangement to an
isocyanate.
0
*
________________________ R-171-C-5
Via reaction between the hydroxide ion and the isocyanate, a carbamate is
formed.
+ OH- ______________________ R-NH -002
After decarboxylation (elimination of CO2) starting from the carbamate, a
primary amine
is obtained.
H+
R-NH -0O2 )11.- R-NH2
CO2
For the conversion of all or some of the amide functions of an acrylamide
(co)polymer to
amine functions, 2 main factors are involved (expressed as molar ratios).
These are: -
CA 02876609 2014-12-12
6
Alpha = (alkali and/or alkaline-earth metal hypohalide/acrylamide) and - Beta
= (alkali
and/or alkaline-earth metal hydroxide /alkali and/or alkaline-earth metal
hypohalide).
The cationic polymers obtained by Hofmann degradation used in the process
according to
the invention are advantageously selected from the polymers described in
document WO
2011/015783.
They are obtained by Hofmann degradation on a precursor based on acrylamide or
derivatives, otherwise referred to as base (co)polymer, previously modified
with at least
one polyfunctional compound containing at least 3 identical or different
heteroatoms that
each have at least one mobile hydrogen.
The heteroatoms may be: N, S, 0 and P.
The polyfunctional compounds may especially be oligomers, polymers or carbon-
based
chains comprising at least three carbon atoms.
In one advantageous embodiment, the polyfunctional compound may be selected
from
the group comprising polyethyleneimines (PEls), polyamines (primary or
secondary),
polyallylamines, polyamine amides (PAAs), polythiols, polyalcohols, polyamide-
epichlorohydrin (PAE) resins, and mixtures thereof.
In one preferred embodiment, the polyfunctional compound incorporated may be
polyethyleneimine (PEI) or a polyamine amide (PAA).
In practice, the polymer obtained at the end of the Hofmann reaction could be
branched,
owing to branching of the base polymer. In other words, it is the branched
nature of the
base copolymer which will impart its branched state to the final polymer.
In one preferred embodiment, the polymer is obtained by Hofmann degradation
reaction
in the presence, as hypohalide, of an alkali metal hypochlorite,
advantageously sodium
hypochlorite.
According to another feature, the hypohalide/nonionic monomer Alpha
coefficient
(expressed as molar ratio) used for the preparation of the polymers of the
invention is
greater than 0.3, or even greater than 0.5, advantageously between 0.8 and 1
inclusive.
CA 02876609 2014-12-12
7
According to another feature, the Hofmann degradation product is produced at a
concentration of greater than 4% by weight, preferably greater than 5%,
advantageously
greater than 7%.
In addition, the copolymer of the invention may have a cationic charge density
preferably
greater than 2 meq/g and advantageously greater than 5 meq/g.
The polymer used in the process according to the invention is advantageously
obtained by
Hofmann degradation reaction on a base copolymer comprising:
- at least 5 mol% of a non-ionic monomer selected from the group comprising
acrylamide (and/or methacrylamide), N,N-dimethylacrylamide and/or
acrylonitrile, preferably acrylamide,
- at least 0.001 mol% of at least one additional polyfunctional compound
selected
from the group comprising polyethyleneimine, polyamine (primary or
secondary), polyallylamine, polythiols, advantageously polyethyleneimine,
- optionally at least:
o one unsaturated cationic ethylenic monomer, preferably selected from
the group comprising monomers of dialkylaminoalkyl
(meth)acrylamide, diallylamine and methyldiallylamine type and the
quaternary ammonium or acid salts thereof. Mention will be made, in
particular, of dimethyldiallylammonium chloride (DADMAC),
acrylamidopropyltrimethylammonium chloride (APTAC) and/or
methacrylamidopropyltrimethylammonium chloride (MAPTAC),
o and/or one nonionic monomer preferably selected from the group
comprising N-vinyl acetamide, N-vinyl formamide, N-
vinylpyrrolidone and/or vinyl acetate.
Advantageously, the base polymer is branched and preferably consists of the
following
three types of compounds:
- acrylamide,
- polyethyleneimine, and
- at least one unsaturated cationic ethylenic comonomer, selected from
the group
comprising monomers of dialkylaminoalkyl (meth)acrylamide, diallylamine and
methyldiallylamine type and the quaternary ammonium or acid salts thereof,
preferably diinethyldiallylammonium chloride.
It is important to note that, in combination with these monomers, it is also
possible to use
water-insoluble monomers such as acrylic, allyl or vinyl monomers comprising a
CA 02876609 2014-12-12
8
hydrophobic group. During their use, these monomers will be employed in
amounts
generally of less than 20 mol%, preferably less than 10 mol%. They may be
selected
preferably from the group comprising acrylamide derivatives, such as N-
alkylacrylamides, for example N-tert-butylacrylamide, octylacrylamide and also
N,N-
dialkylacrylam ides such as N,N-dihexylacrylamide, etc.
In one preferred embodiment, the precursor based on acrylamide or derivatives
(otherwise referred to as base polymer on which the Hofmann degradation is
carried out)
incorporates, at its very heart, at least polyethyleneimine (PEI);
- the hypohalide/nonionic monomer Alpha coefficient used for the preparation
of
the polymers of the invention is between 0.8 and 1 inclusive;
- the base copolymer is branched.
The branching may be carried out preferably during (or optionally after) the
polymerization of the "base" copolymer, in the presence of a polyfunctional
branching
agent and optionally a transfer agent. A nonlimiting list of branching agents
is found
below: methylenebisacrylamide (MBA), ethylene glycol diacrylate, polyethylene
glycol
dimethacry late, diacrylamide, cyanomethyl acrylate, vinyloxyethyl acry late
or
methacrylate, triallylamine, formaldehyde, glyoxal, compounds of glycidyl
ether type
such as ethylene glycol diglycidyl ether, or epoxies or any other means well
known to a
person skilled in the art that permit crosslinking.
In practice, the branching agent is advantageously introduced in a proportion
of five to
fifty thousand (5 to 50 000) parts per million by weight relative to the
active material,
preferably 5 to 10 000, advantageously 5 to 5000 parts per million by weight.
Advantageously, the branching agent is methylenebisacrylamide (MBA).
The incorporation of the additional polyfunctional compound within the base
copolymer
may be carried out in the reaction medium before or during the polymerization
of the
monomers constituting the base (co)polymer, or by any other method of grafting
to the
finished base copolymer.
Preferably, the additional polyfunctional compound is mixed with a comonomer
before
polymerization.
The transfer agent may especially be chosen, non-limitingly, from the group
comprising
isopropyl alcohol, sodium hypophosphite and mercaptoethanol.
=
CA 02876609 2014-12-12
9
The copolymer used as a base for the Hofmann degradation reaction does not
require the
development of a particular polymerization process. The principal
polymerization
techniques, well known to a person skilled in the art, and which may be used
are:
precipitation polymerization, emulsion (aqueous or inverse) polymerization,
which may
or may not be followed by a distillation and/or spray-drying step, and
suspension
polymerization or solution polymerization, these two techniques being
preferred.
It is also possible to add to the base copolymer solution, before or during
the Hofmann
degradation reaction, certain compounds which are capable of reacting with the
isocyanate functions of the polymer generated during the degradation.
Generally, these
are molecules bearing nueleophilic chemical functions such as hydroxyl
functions or
amine functions. As examples, the compounds in question may therefore be of
the family
of: alcohols, polyols, polyamines, polyethyleneimines.
The incorporation of salts of polyvalent cationic ions, as mentioned in
document WO
2010/061082 by the applicant, may also be carried out.
As already specified, the Hofmann reaction requires the conversion of the
amide
functions to amine functions involving 2 main factors (expressed as molar
ratios):
- Alpha = (alkali and/or alkaline-earth metal
hypochlorite/(meth)acrylamide); and
- Beta = (alkali and/or alkaline-earth metal hydroxide/alkali and/or
alkaline-earth
metal hypochlorite).
Starting from a "base" copolymer solution described above having a
concentration
between 10% and 40% by weight, preferably between 15% and 25%, the molar
quantity
of total amide functions is determined. The level of Alpha degradation is then
chosen,
which makes it possible to determine the dry quantity of alkali and/or
alkaline-earth metal
hypohalide and then the Beta coefficient is chosen, which makes it possible to
determine
the dry quantity of alkali and/or alkaline-earth metal hydroxide.
A solution of alkali and/or alkaline-earth metal hypohalide and alkali and/or
alkaline-
earth metal hydroxide is then prepared from the alpha and beta ratios.
According to the
invention, the reactants preferably used are sodium hypochlorite (bleach) and
caustic
soda (sodium hydroxide).
In order to stabilize the amine functions that will be produced, it is
optionally possible to
add, to the reactor containing the base polymer, one (or optionally several)
quaternary
ammonium derivative(s) as is described in document JP 57077398 and is well
known to a
CA 02876609 2014-12-12
person skilled in the art, the purpose of which is specifically to prevent the
reaction
between the amine functions and the residual amide functions. Furthermore, it
will be
noted that the addition of these agents may be carried out separately,
simultaneously, as a
mixture or not, in any order of introduction and at one or more injection
points.
5
The increase in cationicity of the base copolymer takes place during the
Hofmann
degradation, via the use of an alkali or alkaline-earth metal hypohalide.
Similarly, although prepared in solution, the polymers of the invention may
also be
10 proposed in solid form. Under these conditions, the solid form contains
not only the
copolymer, but also a proportion of salt obtained at the end of the Hofmann
degradation
reaction. In practice, they are obtained, inter alia, by processes that
consist in drying the
aforementioned solution. The main separation techniques then used are those of
spray
drying (which consists in creating a cloud of fine droplets in a hot gas
stream for a
controlled duration), drum drying, fluid bed dryers, etc.
The incorporation of the cationic polymer obtained by Hofmann degradation will
be
carried out with conventional means known to a person skilled in the art.
The process according to the invention will be able to be used with all types
of stock:
virgin fibre (kraft, bisulphite, etc.) stocks, recycled fibre stocks, deinked
stocks,
mechanical and therrnomechanical stocks, etc.
As regards the fillers, they may be all the types of fillers that can be
selected from the
group comprising clays, kaolins, ground calcium carbonate (GCC), precipitated
calcium
carbonate (PCC), titanium dioxide, and mixtures thereof. The fillers will be
able to be
added in various forms, the slurry form being the most widely encountered.
They will be
able to be prepared with or without dispersant, away from or on the paper
manufacturing
site.
The cationic polymer obtained by Hofmann degradation will be able to be
prepared in the
vicinity of the papermaking machine.
The examples below make it possible to illustrate the invention, but have no
limiting
nature.
CA 02876609 2014-12-12
11
Polymer A:
Cationic polymer A is obtained by a Hofmann degradation reaction (alpha = 1)
on a base
copolymer (20% base copolymer solution), of acrylamide (70 mol%) and of
dimethyl-
diallylammonium chloride (DADMAC) (30 mol%) that is branched (MBA: 600
ppm/active material) modified with a polyethyleneimine polymer (of Polymin HM
type
by BASF), in an amount of 5% active material.
In order to do this, the polyethyleneimine is mixed with the DADMAC monomer
and the
MBA in the reactor.
The acrylamide will be incorporated by flowing continuously, over 2 h, into a
reaction
medium maintained at 85 C. The polymerization is catalyzed in the presence of
SPS
(sodium persulphate) and MRS (sodium metabisulphite), catalysts that are well
known to
a person skilled in the art. The precursor polymer thus obtained has a
viscosity of
5500 cps (25 C. Brookfield LV3, 12 rpm).
The Hofmann degradation itself takes place in the same way as in example 1 of
the
document WO 2010/061082 by the applicant, by carrying out a complete Hofmann
degradation. The cationic acrylamide-derived copolymer thus prepared has a
bulk
viscosity of 35 cps (25 C, Brookfield IN 1 , 60 rpm) and a concentration of
8.5% active
material.
Polymer B:
Cationic polymer B is obtained by a Hofmann degradation reaction (alpha = 1)
on a base
copolymer (20% active material), of acrylamide (60 mol%), of acrylic acid (10
mol%)
and of dimethyldiallylammonium chloride (DADMAC) (30 mol%) that is branched
(MBA: 600 ppm/active material) modified with a polyethyleneimine polymer (of
Polymin HM type by BASF), in an amount of 5% active material.
In order to do this, the polyethyleneimine is mixed with the DADMAC monomer
and the
MBA in the reactor.
The acrylamide and the acrylic acid will be incorporated by flowing
continuously, over
2 h, into a reaction medium maintained at 85 C. The polymerization is
catalyzed in the
presence of SPS and MBS, catalysts that are well known to a person skilled in
the art.
The precursor polymer thus obtained has a viscosity of 4500 cps (25 C,
Brookfield LV3,
12 rpm).
CA 02876609 2014-12-12
12
The Hofmann degradation itself takes place in the same way as in example I of
the
document WO 2010/061082 by the applicant, by carrying out a complete Hofmann
degradation. The cationic acrylamide-derived copolymer thus prepared has a
bulk
viscosity of 55 cps (25 C, Brookfield LV1, 60 rpm) and a concentration of 9%.
These polymers will be compared to (1) a high molecular weight
acrylamide/ADAME
MeC1 powder copolymer (FO 4190 PG I, from SNF Floerger), standard retention
aid, and
(2) Luredur PR 8351 from BASF, amphoteric copolymer based on PVA (resulting
from
the hydrolysis of NVF), current reference as filler retention aid and aid for
maintaining
DSR performances.
Procedure for evaluating the dry strength
Paper handsheets are produced with an automatic dynamic handsheet former.
The stock slurry is produced by disintegrating dry stock in order to obtain a
final
concentration of 3%.
The necessary amount of stock is withdrawn so as to obtain, in the end, a
sheet having a
basis weight of 60 g/m2.
The concentrated stock is introduced into the chest of the dynamic handsheet
former and
stirred therein. Added to this stock is a slurry of fillers, injected at the
same time as (but
separately from) polymer A, B or Luredur PR 8351 from BASF. This stock is then
diluted to a concentration of 0.32%.
In manual mode, the stock is pumped to the level of the nozzle in order to
prime the
circuit.
A blotting paper and the forming fabric are placed in the drum of the dynamic
handsheet
former before starting the rotation of the drum at 900 m/min and constructing
the water
wall. Potentially, a retention aid will be injected ten seconds before
starting the sheet
manufacturing cycle. The sheet is then produced (in automatic mode) by 22 to-
and-fro
movements of the nozzle spraying the stock into the water wall. Once the water
is drained
and once the automatic sequence is completed, the forming fabric with the
network of
fibres formed is removed from the drum of the dynamic handsheet former and
placed on
a table. A dry blotting paper is deposited on the side of the mat of wet
fibres and is
CA 02876609 2014-12-12
13
pressed once with a roller. The assembly is turned over and the fabric is
carefully
separated from the fibrous mat. A second dry blotting paper is deposited and
the sheet
(between the two blotting papers) is pressed once under a press delivering 4
bar and is
then dried on a stretched dryer for 9 min at 107 C. The two blotting papers
are
subsequently removed and the sheet is stored overnight in a chamber with
controlled
humidity and controlled temperature (50% relative humidity and 23 C). The dry
strength
properties of all the sheets obtained by this procedure are then evaluated.
The burst index is measured with a Messmer Buchel M 405 bursting strength
tester
(average over 14 measurements).
The dry tensile strength is measured in the machine direction with a
Testometric AX
tensile testing machine (average over 5 samples).
The content of fillers in the sheet is measured using a muffle furnace
according to a
standard procedure for measuring non-organic material (570 C for 5 hours).
The tests are carried out with a stock having a neutral pH and having the
following
composition, by weight relative to the dry weight of the composition: (this
composition
exceeds 100% of material)
- 70% of bleached deciduous tree kraft fibres
- 10% of bleached resinous tree kraft fibres
- 20% of pine-based mechanical stock fibres
30% (by weight relative to the amount of fibres) of natural calcium carbonate
are added
to the stock.
Polymers used alone:
Polymer Polymer dosage Burst index Breaking length %
fillers in sheet
1.51 3.82 16.73%
Polymer A 300 g/t 1.54 3.94 21.62%
Polymer B 300 g/t 1.52 3.92 20.54%
Luredur PR 8351 300 g/t 1.53 3.94 20.51%
Polymer A 600 g/t 1.54 3.95 23.27%
Polymer B 600 g/t 1.53 3.93 21.97%
Luredur PR 8351 600 g/t 1.54 3.95 22.12%
I
CA 02876609 2014-12-12
14
It can be observed that polymer A provides better filler retention but also
better DSR
performances than Luredur PR 8351.
The amphoteric polymer B gives performances equivalent to Luredur PR 8351 but
worse
5 than polymer A.
Polymers combined with a standard retention aid:
Polymer Polymer Retention Retention aid
Burst .. Breaking .. % fillers in
dosage aid dosage index length sheet
F04190
- -
PG1 150 g/t 1.53 3.93
20.02%
FO 4190
- - 300 g/t 1.50 3.74
23.32%
PG1
FO 4190
Polymer A 150 g/t PG1 150 g/t 1.54 3.91 23.10%
FO 4190
Polymer B 150 g/t 150 g/t 1.52 3.91 22.01%
PG1
Luredur PR PG1 FO 4190
8351
150 g/t 150 g/t 1.53 3.92 22.05%
FO 4190
Polymer A 300 g/t 150 g/t I .54 3.93 25.37%
PG1
F04190
Polymer B 300 Wt PG1 150 0 1.53 3.93 23.38%
Luredur PR FO 4190
300 g/t 150 g/t 1.54 3.94 23.44%
8351 PG1
10 In a manner known to a person skilled in the art, the simple use of a
retention aid
provides retention of fillers, but greatly deteriorates the physical
performances.
In combination with a retention aid, polymer A makes it possible to obtain the
highest
amount of fillers in the paper sheet while retaining good physical strength
properties of
15 the sheet.
