Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PRESS FELT CONDITIONER FOR NEUTRAL
AND ALKALINE PAPERMAKING SYSTEMS
FIELD OF THE INdENTION
The present invention relates to inhibiting the deposition
of particulate materials in the press felts of a papermaking
operation. Specifically, this invention pertains to the use of a
press felt conditioner directed at controlling the deposition of
polymerically flocculated particulate materials in neutral to
alkaline papermaking systems.
I0 BACKGROUND OF THE INIfENTION
In a paper manufacturing process, ionically charged, rela-
tively high molecular weight, water soluble polymers are often
emplq~ed to enhance retention of cellulosic fibers, fines, and
.inorganic fillers. The addition of these polymers produces a
cleaner process stream by reducing the solids level in the process
filtrate. The high molecular weight, ionically charged polymers
control solids by adsorbing onto solid particulate surfaces in the
papermaking furnish slurry and invoking charge newt ralixation
(coagulation) and/or bridging (flocculation) mechanisms which cause
the solid particles to flocculate. The flocculate can be retained
by the formed mat of cellulosic fibers more easily than smaller
individual particles. However, these flocculated particulate
materials can be transferred from the surface of the sheet to the
papermachine press felts. In the flocculated state, the particles
cannot pass through the fine, porous structure of the press felts)
and become entrapped therein. If not controlled by adequate felt
IO conditioning practices, these agglomerated particulate substances
can severely impair the ability of the press felts to absorb water
thereby requiring reduced production rates and shortening the
useful.life of the felts. In addition, it has been found that
common polymeric retention aids can render normally effective prior
15 art felt conditioners useless or marginally effective.
Typical polymers employed as retention aids are generally
relatively high in molecular weight; far example, copolymers made
from monomers such as; acrylic acid, acrylamide, dimethyl/diallyl
ammonium chloride, dimethylamine, epichlorohydrin, and ethylene
20 diamine. Typically, polymeric retention aids have average
molecular weights greater than 1,000,000 and can range up to around
ZO,OQA,000 for anionically charged polymers and up to 15,000,000
forrcationically charged polymers. These ionically charged poly-
mers adsorb onto the various solid particulate surfaces within the
25, papermaking furnish causing flocculation.
'~~ a~~~
In neutral and alkaline papermaking (pH approximately s.0 -
8.5), the utilization of polymeric retention aids is particularly
critical for efficient operation. Without them, such common system
additives as cellulosic reactive sizes, Alkenyl Succinic Anhydride
(ASA) and Alkene Ketene Dimer (AKD), can cycle up on the process
system and hydrolyze causing numerous operational problems, particu-
larly in the press section. Subsequently, most of the particulates
that are transferred from the sheet to the press felts in the neu-
tral and alkaline papermaking system are generally in a flocculated
IO state and are therefore too large to easily pass through a press
felt. Subsequently, these contaminants are either embedded into the
felt structure or transferred back to the sheet and cause spots,
holes, etc., ar deposit in the dryer section and cause problems
there. Because of their size', they are relatively unresponsive to
prior art felt conditioning treatments.
In addition to the aforementioned contaminants, most press
felts associated with coated alkaline fine paper experience exces-
sive filling due to white pitch deposition. This arises from
natural wood resins such as fatty esters, fatty acids,, resin acids
ZO and othertypical papermaking furnish components .such as sizing
agents, alumina and fiber fines. The paper coating binders such as
polyvinyl acetate or styrene butadiene latices and inorganic coating
pigments such as clay, calcium carbonate and titanium dioxide also
contribute to,the felt filling. If not effectively controlled by
adequate chemical and mechanical press felt conditioning practices,
this high level of contaminating material plugging or filling the
_g_ ~~".~a~~~~i
paper machine press felt severely impairs their water absorbancy
capability, which in turn, reduces paper machine production
rates, produces paper quality defects and/or requires the
premature removal and replacement of the expensive felts.
.Chemical analyses of used press felts associated with
coated neutral and alkaline papermaking also reveal a number of
,, polymerically flocculated components. Significant quantities of
inorganic fillers such as calcium carbonate, clay and titanium
dioxide are typically found in addition to normally smaller
amounts of sizing agents and wood pitch components.
While various anionic or nonionic surfactant-type felt
conditioners commonly employed in the art demonstrate substantial
efficacy for conditioning press felts subject to wood pitch
and/or paper sizing agent-related contamination, they have proven
to possess limited efficacy against white pitch contamination at
commercially viable treatment dosage levels.
DESCRIPTION OF THE RELATED ART
Processes to inhibit contamination deposition in pape,r-
maE~ng felts are known in the art. U.S. Pat. No. 4,715,931,
Shellhamer et al., discloses a process for inhibiting aluminum
hydroxide deposition in papermaking systems which comprises
adding to the felts a hydroxylated carboxylic acid. The use of
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~~~ i~~r~~
the carboxylic acid in combination with surfactants, such as octyi
phenol ethoxylates, nonyl phenol ethoxylates and others listed
therein inhibit aluminum hydroxide deposition and associated
organic contaminants.
In addition to the control of inorganic contaminants,
pitch formation is of concern in papermaking systems. Filler
materials can become trapped within the organic matrix formed by
pitch coalescence compounding deposition problems. Methods of
controlling the pitch deposition formation are known in the art.
U.S. Pat. No. 4,184,912, Payton, discloses a method of preventing
pitcy formation by dispersing and emulsifying pitch particles in
the pulp furnish to an exceptionally fine state and uniformally
distributing the particles throughout the finished paper. The
pitch deposition is controlled by the addition of a three com-
ponent formulation comprising a nonionic surfactant plus an
anionic surfactant and a low molecular weight anionic polymer.
The three component mixture is added to the papermaking pulp
system at a point.prior to where pitch deposits normally form.
In U.S. Pat. No. 3,992,249, Farley, a process for inhibiting pitch
deposition is disclosed wherein the pulp is washed with an aqueous
solution of anionic polymer having between 25 to 85 mole percent.
hydrophobic-oleophilic linkages and 15 to TO mole percent hydro-
philic acid linkages to complex with the pitch. The pitch-polymer
complex is washed away with water.
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'~;~~ ~~~~~~a
U.S. Pat. No. 3,873,417, Otrhalek et al., discloses a pitch
and pigment dispersant which comprises a neutralized solution of
polymer prepared by free radical polymerization of an'alpha, beta
unsaturated acid with an alkyl ester and an allyl alcohol.
Another pitch control process is disclosed in U.S. Patent
No. 3,398,047, Michalski. The patentee teaches that the use of an
organic polydentate ligand such as aminopolycarboxylic acids, and
an organic sulfonate offer an efficient pitch deposition inhibitor.
Of further interest is U.S. Patent No. 3,582,461, Lipowski et al.,
which discloses a pitch control process utilizing a dicyandiamide-
formaldehyde condensate compound.
U.S. Patent No. 3,642,572, Endres et al., discloses that
polyamidoamines are useful not only as flocculants, but also as
retention aids and dewatering agents in papermaking processes.
Additional polyamines are disclosed by Ziemann et al., in U.S.
Patent No. 3,893,885 as being useful as retention aids and
dewatering agents.
Some treatment programs are directed specifically at the
reduction of contaminants within the felt or other sheet farming
surfaces. EP 0359590, Aston et al., addresses the control of
deposits on and within papermill felts by employing the use of a
cationic polymer in conjunction with nonionic or cationic surface
tants. The base products used to create the cationic polymers
preferably contain amine groups. U.S. Patent No. 4,895,622,
~~C'~~~'~~~
Barnett et al., discloses a felt conditioner comprising a
relatively low molecular weight anionic organic polymer and a
hydrophilic anionic or nonionic surfactant. The polymers
preferably contain acrylic acid or methacrylic acid moieties.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed toward inhibiting
the deposition of polymerically flocculated particulate
material in a felt in the press section of a papermaking
system. Several functionally similar members of fatty acid
imidazolines are surprisingly effective when employed as felt
conditioning agents for inhibiting contamination of press
felts subjected to the aforementioned flocculated particulate .
substances. An effective inhibiting amount of these felt
conditioning agents may be metered into one or more fresh
water showers directed onto a press felt on its runs between
the press nip and the vacuum or uhle box utilized for
dewatering the treated felts.
Also surprisingly, other types of fatty acid imida-
zolines did not produce positive results when employed as felt
conditioners.
Examples of highly effective fatty acid imidazolines
that can be utilized in accordance with this invention are
represented by the general structure:
~ H2
~---C CH2
PI - CH2CH20H
where R is an alkyl hydrophobe, radical with a preferred carbon chain
length of C12 or greater, more preferably C18.
Fatty acid imidazolines, according to this invention, will
provide for an effective continuous press felt conditioning treat-
ment when the press felts are subjected to significant quantities of
the aforementioned polymerically flocculated particulate substances
originating from coated neutral and alkaline pH papermaking
furnishes, with or without sizing agent being present. The choice
of the fatty acid imidazoline appears to be critical and the imida-
zoline embodied in this invention may fall within a hydrophobe
carbon chain length of C12 or greater with the preferred
hydrophobe chain length of C18.
Furthermore, it is also believed that the embodied invention
can also be effectively used to prevent these same types of contami-
nant~.=from building up on paper machine press section press rolls
whet fed continuously through an aqueous shower directed upon the
press rolls. .In either case, the required amount or concentration
of fatty acid imidazoline will depend on, among other things, the
volume of shower water employed, the production rate, and the
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concentration of poiymerically flocculated contaminants. Generally
the total concentration of fatty acid imidazoline added to the
aqueous showering medium is from 10 to 1500 parts per million parts
of the aqueous medium. Preferably, they are added at concentrations
from 100 parts to 300 parts per million parts o~f aqueous. showering
medium..
.. In order to more clearly illustrate the present invention
the following data were generated. The following examples are
included as illustrations of the present invention and should not be
construed as limiting the scope thereof.
EXAMPLES
The examples contained herein will demonstrate the
unexpected superior responses produced by the present invention.
The results were obtained utilizing a continuous press felt
conditioning test apparatus and a~simulated caated alkaline fine
paper contaminant system. The testing incorporates a clean (unused)
press felt sample of known initial weight and air permeability
placed on a heavy-mesh support screen through which the treated or
untr~ted contaminant solution is pressed. The simulated coated
alts-line fine papermaking contaminant test slurry consisted of the
following: ~ .
_1o-
Ingredient Concentration
(PPm)
Ground Calcium Carbonate 375.00
Clay , 125.00
Fatty ester/fatty acid pitch mixture 50.00
*Coating solids (cured, redispersed 1596 slurry) 300.00
Alkaline Size (ASA/starch, 1:3 ratio, 1096 slurry) 48.75
Cationic Retentian Aid (High Molecular freight,
Cationic Polyacrylamide) 2.00
* Pre-cured casting formulation contains:
5~ PVAc latex, 5% S8R latex, 32~ Clay,
8~ Ti02 and 50~ water
Table 1 contains data generated in this slurry syst em
showing the performance characteristics of several commercially
available surfactants and polymers as defined below, employed in the
art for continuous or intermittent conditioning of paper machine
press felts in comparison to the fatty acid imidazolines according
to the invention. Table 2 s~immarizes data generated to evaluate the
effectiveness of the present invention in the same slurry sy stem
excluding the alkaline size.
As can be seen from Tables 1 and 2, the results show that in
two critical test parameters, namely percent weight gain and percent
permeability loss, the values for the fatty acid imidazolines with a
hydrd~hobe carbon chain length of C12 to C18 were significantly
lower than the control or any other surfactant or polymer commonly
employed in the continuous or intermittent conditioning of paper
machine felts.
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Examples are listed below of the conventional surfactants
known in the art which were compared against the fatty acid r
imidazolines of the present invention:
Alkyl or dialkyl phenol ethoxylates represented by the
general structure: '
.. R p OCH2CHZ)nOH
R
where,
R = H or alkyl group
R' = H or alkyl group
n = moles of ethylene oxide;
Sodium lignosulfonates;
Ethoxylated secondary alcohols;
Quaternary imidazolines;
Phosphate esters;
Polymethylnapthalene sulfonates;
Polyacrylic acid; and
Sodium alkylnapthalene sulfonate.
~~~W
TA6LE 1
Performance of various surfactants and fatty acid imidazolines in a
felt conditioning test system utilizing a simulated polymerically
(retention aid) flocculated coated alkaline fine paper contaminant
system (with sizing agent present).
CONDITIONING % WT. GAIN % PEPMEABILITY
AGENT OF TEST FELT LOSS
(over clean control) (over clean control)
Untreated Control 24.4 83.4
Fatty Acid Imidazoline
H.ydrophobe carbon chain length
a) Clg 4.1 38.1
b) C16 5.7 41.4
c) C12 13.6 54.2
~ d) C$ 26.I 81.2
Quaternized Fatty Imidazoline
~i_ydrophobe carbon chain le~th
a) C18 22.2 71.2
"b) C16 19.4 73.3
-,~_ .
Phosphate ester ~ 16.1 59.9
Sodium Lignosulfonate ' 23.8 79.6
Palymethylnapthalene Sulfonate I9.2 61,8
Ethoxylated nonyl phenol 18.9 56.9
E~hoxylated octyl phenol * 19.1 70.6
Polyacrylic acid ~ 27.4 80.5
* Untreated Control Data were: 28.3% Wt. Gain and 84.4%
Permeabi 1 i~ty- Loss
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TALE 2
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i:)s9 :v:'~~:)
Performance of various surfactants and fatty acid imidazolines in a
felt conditioning test system utilizing a simulated polymerically
(retention aid) flocculated coated alkaline fine paper (no sizing
agent employed) contaminant system.
CONDITIONING % WT. GAIN % PERMEABILITY
,. AGENT OF TEST FELT LOSS
(over c lean control) (over clean control)
Untreated Control 27.9 80.4
Fatty Acid Imidazoline
Hvdroohobe carbon chain len th
a) C18 6.5 44.8
b) C16 6.2 33.9
c) C12 16.1 52.4
d) C8 30.3 84.7
Quaternized Fattv lmi~a'gline
Hvdrophobe carbon chain length
a) C18 21.0 68.2
.b) C16 23.1 71.0
Phosphate ester 20
4
. 75.0
Sodium Lignosu'lfonate 20
1
. 74.2
Polymethylnapthalene Sulfonate 20
2
. 77.1
Ethoxylated nonyl phenol 17
1
. 68.8
Ethoxylated octyl phenol 19
1
. 70.6
Polyacrylic acid 20
3
. 70.9
Sodium alkyl napthalene sulfonate19
7
. 75.6
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It is clear that the process of the present invention
provides a significant positive felt conditioning response to
prevent the aforementioned polymerically flocculated particulate
substances from depositing in the felts, regardless of whether a
sizing agent is present or not.
While this invention has been described with respect~to
particular embodiments thereof, it is apparent that numerous other
forms and modifications of the invention will be obvious to those
skilled in the art. The appended claims and this invention should
be construed to cover all such otivious forms and modifications which
are within the true spirit and scope of the present invention.
