A METHOD OF IMPROVING DEWATERING EFFICIENCY,
INCREASING SHEET WET WEB STRENGTH, INCREASING SHEET
WET STREGNTH AND ENHANCING FILLER RETENTION IN
PAPERMAKING
Background of the Invention
This invention relates to a method of improving dewatering
efficiency, increasing sheet wet web strength, increasing sheet wet strength and
enhancing filler retention in a papermaking process. Typically in a papermaking
process chemicals are added in the wet end to assist in the dewatering of the slurry,
increasing retention and improving wet or dry sheet strength. The wet end of the
papermaking process refers to the stage in the papermaking process where the fiber
is dispersed in the water in the slurry form. The fiber-water slurry then go through
drainage and dewatering process to form a wet web. The solid content after this wet
formation process is about 50%. The wet web is further dried and forms a dry sheet
of paper mat. Paper mat comprises water and solids and is commonly 4 to 8%
water. The solid portion of the paper mat includes fibers (typically cellulose based
fibers) and can also include filler.
Fillers are mineral particles that are added to paper mat during the
papermaking process to enhance the resulting paper's opacity and light reflecting
properties. Some examples of fillers are described in US Patent Number 7,21 1,608.
Fillers include inorganic and organic particle or pigments used to increase the
opacity or brightness, reduce the porosity, or reduce the cost of the paper or
paperboard sheet. Some examples of fillers include one or more of: kaolin clay, talc,
titanium dioxide, alumina trihydrate, barium sulfate, magnesium hydroxide,
pigments such as calcium carbonate, and the like.
Calcium carbonate filler comes in two forms, GCC (ground calcium
carbonate) and PCC (precipitated calcium carbonate). GCC is naturally occurring
calcium carbonate rock and PCC is synthetically produced calcium carbonate.
Because it has a greater specific surface area, PCC has greater light scattering
abilities and provides better optical properties to the resulting paper. For the same
reason however, PCC filled paper mat produces paper which is weaker than GCC
filled paper in dry strength, wet strength and wet web strength.
Filler is generally much smaller than fiber, therefore, filler has much
larger specific surface area than fiber. One of the challenges people found to increase
filler content in the sheet is that high filler content decreases the efficiency of wet
end chemicals, such as dewatering aids, wet web strength aids and wet strength aids.
This invention is to provide novel filler pretreatment, so that it reduced the
adsorption of wet end chemicals onto filler surface, therefore, increased the
efficiency of wet end chemicals such as dewatering aids, wet web strength aids and
wet strength aids.
Paper wet web strength is very critical for paper producers because
increased paper wet web strength would increase machine runnability and reduce
sheet breaks and machine down time. Paper wet web strength is a function of the
number and the strength of the bonds formed between interweaved fibers of the
paper mat. Filler particles with greater surface area are more likely to become
engaged to those fibers and interfere with the number and strength of those bonds.
Because of its greater surface area, PCC filler interferes with those bonds more than
GCC.
Paper dewatering efficiency is also very critical for paper producers
because decreased dewatering efficiency in wet wed would increase steam demand
for drying operation, reduce machine speed and production efficiency. Dewatering
aids are widely used to improve dewatering efficiency for reducing energy
consumption, increasing machine speed and production efficiency.
Brief Summary of the Invention
To satisfy the long-felt but unsolved needs identified above, at least
one embodiment of the invention is directed towards a method of papermaking
comprising filler, the method comprising the steps of: providing a blend of filler
particles, at least one drainage additive or wet web strength additive or wet strength
aid, and cellulose fiber stock,
treating the filler particles with a composition of matter in the absence of
cellulose fiber stock,
combining the filler particles with the cellulose fiber stock,
treating the combination with at least one wet strength aid or wet web
strength additive or drainage additive, and
forming a paper mat from the combination,
wherein at least 10% of the filler particles are precipitated calcium carbonate and at
least 10% of the filler particles are ground calcium carbonate, the cellulose fiber
stock comprises a plurality of cellulose fibers and water, and the composition of
matter enhances the performance of the wet strength aid or wet web strength additive
or drainage additive in the paper mat.
and wherein at least some of the composition of matter is added to the filler
with a rotating admixing apparatus, the apparatus having a distribution head, which
is rotated by a drive, is arranged in a container containing a slurry of the filler
particles, and is associated with a rotational plane, and the distribution head has,
along a circumference thereof, which surrounds a rotational axis, distributed outlets
from which the composition is passed into the slurry and mixing blades,
characterized in that the outlets are formed as openings and the mixing blades are
formed as strips extending transverse to the rotational plane and having a length
equal at least half of an inner diameter of the slurry pipe;
and delivering the composition to the distribution head for admixing
the composition to the filler slurry.
Additional features and advantages are described herein, and will be
apparent from, the following Detailed Description.
Brief Description of the Drawings
A detailed description of the invention is hereafter described with
specific reference being made to the drawings in which:
FIG. 1 is an cross sectional illustration of a device used to feed the
invention to a slurry of filler particles.
FIG. 2 is an exploded view of a cross sectional view of a device used
to feed the invention to slurry of filler particles.
For the purposes of this disclosure, like reference numerals in the
figures shall refer to like features unless otherwise indicated. The drawings are only
an exemplification of the principles of the invention and are not intended to limit the
invention to the particular embodiments illustrated.
Detailed Description of the Invention
In at least one embodiment of the invention is a method of making
paper which comprises filler. In at least one embodiment of the invention the method
of papermaking comprises the steps of: creating a filler blend of PCC and GCC in
which PCC comprises at least 10% by mass of the filler and GCC comprises at least
10% of the filler mass, pre-treating at least some of the filler particles with a coating
that decreases the adhesion between a wet web strength additive or drainage aid or
wet strength aid and the filler particles, and adding both the filler blend and the wet
web strength additive or drainage aid or wet strength aid to the paper mat.
It has been known for some time that adding wet web strength
additives or drainage aid or wet strength aid to paper mat increases the wet web
strength of the resulting paper or enhances drainage or improves machine speed and
runnability or enhance sheet wet strength. Some examples of wet strength aids, wet
web strength additives and drainage aids are described in US Patents 7,125,469,
7,615,135 and 7,641,776.
Unfortunately it is not practical to add large amounts of wet strength
aids or wet web strength additives or drainage aids to compensate for the weakness
due to large amounts of filler in paper mat. One reason is because those additives
are expensive and using large amounts of additives would result in production costs
that are commercially non-viable. In addition, adding too much additive negatively
affects the process of papermaking and inhibits the operability of various forms of
papermaking equipment. Furthermore cellulose fibers can only adsorb a limited
amount of wet strength aid or wet web strength additive or drainage aid. This
imposes a limit on how much additive can be used. One reason why this is so is
because wet strength aid or wet web strength additive or drainage aid tend to
neutralize the anionic fiber/ filler charges and when these charges are neutralized
further adsorption of those additives is inhibited.
Adding filler to the paper mat also reduces the effectiveness of the
wet strength aid or wet web strength additive or drainage aid. Those additives have
a tendency to coat the filler particles. The more filler particles present, the more
additive coats the filler particles, and therefore there is less wet strength aid or wet
web strength additive or drainage available to bind the cellulose fibers together.
Because there is a maximum amount of wet strength aid or wet web strength
additive or drainage that can be added, more filler has always meant less effective
strength additive. This effect is more acute with PCC than GCC because PCC's
higher surface area becomes more coated with the additives than GCC.
In at least one embodiment of the invention at least some of the filler
particles are pre-treated with a composition of matter to at least partially prevent the
adherence of wet strength aid or wet web strength additive or drainage aid to the
filler particles. The pre-treatment contemplates entirely coating some or all of one or
more filler particles with the composition of matter. In the alternative, the pretreatment
contemplates applying the composition of matter to only a portion of one
or more of the filler particles, or completely coating some filler particles and
applying the composition of matter to only a portion of some other particles. In at
least one embodiment the pre-treatment is performed with at least some of the
compositions of matter described in US Patent Number 5,221,435 and in particular
the cationic charge-biasing species described therein. In at least one embodiment the
pre-treatment is performed with a diallyl - N,N-disubstituted ammonium halideacrylamide
copolymer described in US Patent Number 6,592,718.
While pre-treating filler particles is known in the art, prior art
methods of pre-treating filler particles are not directed towards affecting the
adhesion of the wet strength aid or wet web strength additive or drainage aid to the
filler particles. In fact, many prior art pre-treatments increase the adhesion of the
strength additive to the filler particles. For example, US Patent Number 7,21 1,608
describes a method of pre-treating filler particles with hydrophobic polymers. This
pre-treatment however does nothing to the adhesion between the strength additive
and the filler particles and merely repels water to counterbalance an excess of water
absorbed by the strength additive. In contrast, the invention decreases the
interactions between the wet strength aid or wet web strength additive or drainage
aid and the filler particles and results in an unexpectedly huge increase in paper
strength, sheet dewatering and machine runnability.
When comparing wet tensile strength of a given paper versus the
percentage of filler relative to the total solid portion of the paper mat used to produce
the given paper, the results clearly illustrates that sheet had very weak wet strength
without addition of wet strength aid 63700 (temporary wet strength aid). Velox
could significantly increase sheet wet strength. Filler pretreatment alone did not
increase sheet wet strength. However, filler pretreatment further enhance Velox
performance which resulted in higher sheet wet strength.
When comparing wet web tensile strength of a given paper versus the
percentage of filler relative to the total solid portion of the paper mat used to produce
the given paper, the relationship between increasing filler content and decreasing
paper wet web strength is a linear relationship. Without the addition of Nalco
dewatering aid (wet web strength aid) 63700, paper sheet had very poor wet web
strength. Sheet wet web strength could be significantly improved by the using of
Nalco dewatering aid 63700. Filler pretreatment alone had negligible effect on paper
wet web strength. However, filler pretreatment could further boost the performance
of Nalco dewatering aid 63700, and additional 20% wet strength improvement was
achieved by the filler pretreatment at the lower ash content. As for the higher ash
content, the performance of 63700 was boosted even higher than 20%. This is
because the reduced effectiveness of the strength additive trapped against the filler
particles was released by the filler pretreatment.
At least some of the fillers encompassed by this invention are well
known and commercially available. They include any inorganic or organic particle
or pigment used to increase the opacity or brightness, reduce the porosity, or reduce
the cost of the paper or paperboard sheet. The most common fillers are calcium
carbonate and clay. However, talc, titanium dioxide, alumina trihydrate, barium
sulfate, and magnesium hydroxide are also suitable fillers. Calcium carbonate
includes ground calcium carbonate (GCC) in a dry or dispersed slurry form, chalk,
precipitated calcium carbonate (PCC) of any morphology, and precipitated calcium
carbonate in a dispersed slurry form. The dispersed slurry forms of GCC or PCC are
typically produced using polyacrylic acid polymer dispersants or sodium
polyphosphate dispersants. Each of these dispersants imparts a significant anionic
charge to the calcium carbonate particles. Kaolin clay slurries also are dispersed
using polyacrylic acid polymers or sodium polyphosphate.
In at least one embodiment, the treating composition of matter is any
one of or combination of the compositions of matter described in US Patent
6,592,718. In particular, any of the AcAm/DADMAC copolymer compositions
described in detail therein are suitable as the treating composition of matter. An
example of an AcAm/DADMAC copolymer composition is product# Nalco -4690
from Nalco Company of Naperville, Illinois (hereinafter referred to as 4690).
The treating composition of matter can be a coagulant. The
coagulants encompassed in this invention are well known and commercially
available. They may be inorganic or organic. Representative inorganic coagulants
include alum, sodium aluminate, polyaluminum chlorides or PACs (which are also
known as aluminum chlorohydroxide, aluminum hydroxide chloride, and
polyaluminum hydroxychloride), sulfated polyaluminum chlorides, polyaluminum
silica sulfate, ferric sulfate, ferric chloride, and the like and blends thereof.
Some organic coagulants suitable as a treating composition of matter
are formed by condensation polymerization. Examples of polymers of this type
include epichlorohydrin-dimethylamine (EPI-DMA), and EPI-DMA ammonia
crosslinked polymers.
Additional coagulants suitable as a treating composition of matter
include polymers of ethylene dichloride and ammonia, or ethylene dichloride and
dimethylamine, with or without the addition of ammonia, condensation polymers of
multifunctional amines such as diethylenetriamine, tetraethylenepentamine,
hexamethylenediamine and the like with ethylenedichloride and polymers made by
condensation reactions such as melamine formaldehyde resins.
Additional coagulants suitable as a treating composition of matter
include cationically charged vinyl addition polymers such as polymers, copolymers,
and terpolymers of (meth)acrylamide, diallyl-N,N-disubstituted ammonium halide,
dimethylaminoethyl methacrylate and its quaternary ammonium salts,
dimethylaminoethyl acrylate and its quaternary ammonium salts,
methacrylamidopropyltrimethylammonium chloride, diallylmethyl(betapropionamido)
ammonium chloride, (beta-methacryloyloxyethyl)trimethyl
ammonium methylsulfate, quaternized polyvinyllactam, vinylamine, and acrylamide
or methacrylamide that has been reacted to produce the Mannich or quaternary
Mannich derivatives. Preferable quaternary ammonium salts may be produced using
methyl chloride, dimethyl sulfate, or benzyl chloride. The terpolymers may include
anionic monomers such as acrylic acid or 2-acrylamido 2-methylpropane sulfonic
acid as long as the overall charge on the polymer is cationic. The molecular weights
of these polymers, both vinyl addition and condensation, range from as low as
several hundred to as high as several million. Preferably, the molecular weight range
should be from about 20,000 to about 1,000,000. In at least one embodiment, the
pre-treatment is preformed by a combination of one, some, or all of any of the
compositions of matter described as suitable compositions of matter for pre-treating
the filler particles.
In at least one embodiment, the wet strength aid or wet web strength
additive or drainage aids carries the same charge as the composition of matter
suitable for treating the filler particles. When the two carry the same charge, the
filler additive is less likely to adsorb wet strength aid, wet web strength additive or
drainage aid on its surface. Wet strength aids, wet web strength additives or
drainage aids encompassed by the invention include any one of the compositions of
matter described in US Patent 4,605,702 and US Patent Application 2005/0161 181
Al and in particular the various glyoxylated Acrylamide/DADMAC copolymer
compositions described therein. An example of a glyoxylated
Acrylamide/DADMAC copolymer composition is product# Nalco 63700 (made by
Nalco Company, Naperville, Illinois). Another example of is amine-containing
polymers including allylamine/acrylamide copolymers and polyvinylamines; one
more example is Polyamide-Polyamine-Epichlorohydrin (PAE)
In at least one embodiment, the fillers used are PCC, GCC, and/or
kaolin clay. In at least one embodiment, the fillers used are PCC, GCC, and/or
kaolin clay with polyacrylic acid polymer dispersants or their blends. The ratio of
wet strength additive or wet web strength aid or drainage additive relative to solid
paper mat can be 3kg of additive per ton of paper mat.
In at least one embodiment at least some of the filler particles are pretreated
using a rotating admixing apparatus. A rotating admixing apparatus
comprises a distribution head which is constructed and arranged to rotate as it
disperses the treating chemicals to the filler particles. In at least one embodiment the
rotating admixing apparatus is the device described in US Patent 5,993,670. The
apparatus can admix flocculant liquid(s) to a process stream, in which a distribution
head, which is rotated by a drive, is arranged in a pipe/conduit, through which a
slurry of filler particles flows, and is associated with a rotational plane, and the
distribution head has, along a circumference thereof, which surrounds a rotational
axis, distributed flocculant outlets and mixing blades, and is connected with a
flocculant liquid delivery conduit.
In at least one embodiment the invention also relates to the
use of the apparatus of admixing the flocculant liquid, which is formed by a
mixture of an active agent and water and of which n parts are added to 100
parts of the filler slurry, with the flocculant liquid added to the 100 parts of
the slurry containing a necessary amount a of the active agent.
There exist cases, when an apparatus for admixing is located,
in the direction of the filler slurry flow, downstream of a delivery pump or a
centrifuge and which mixes a flocculant liquid and the filler with each other
with good results. However, there exists a noticeable number of cases when
this is not the case and when the admixing apparatus fails to effect a
satisfactory mixing of the flocculant liquid and the filler. In a known
apparatus of the above-mentioned type (DE-05 40 29 824), the flocculant
outlets are formed as holes or nozzles, and each mixing blade is formed as a
journal-like projection, with the dimensions of the mixing blade and the
outlet in a direction transverse to the rotational plane being very small in
comparison with the width of the filler slurry stream. In some cases the
admixture of the flocculant liquid to the slurry, which is obtained with this
apparatus is insufficient, i.e., the added flocculant liquid is not sufficiently
uniformly distributed in the slurry stream behind the apparatus and is not
contained in the slurry in the quantity necessary for a satisfactory
flocculation.
Therefore, an object of the invention is an apparatus of the above-described
type with which a better admixing of the flocculant liquid to the slurry is
achieved. The apparatus according to the invention, which achieves this
object, is characterized in that the flocculant outlets are formed as slots and
the mixing blades are formed as strips, which extend transverse to the
rotational plane and have a length equal at least a half of the width of the
slurry stream.
In at least one embodiment only one, some, or all of the
chemicals added in the pre-treatment process are added with the rotating
apparatus.
In at least one embodiment the construction of the distribution
head of the apparatus permits to achieve an improved admixture and
distribution of the flocculant liquid in the slurry. The flocculant liquid exits
from every slot in a form of a broad strip into which a following mixing
blade is inserted in a direction opposite to the rotational direction and which
pulls the flocculant liquid along its edge as a foggy strip through the slurry.
The flocculant liquid is delivered through the slots as an interrupted torrent
into the slurry, and the slots and strips are arranged one after another in the
rotational direction. The dimensioning of the length of the slots and the
blades is effected in accordance with the diameter of the stream or of the
distribution head.
In at least one embodiment, the flocculant slots and the stripshaped
blades can extend both in the direction of the slurry stream and
substantially perpendicular to the slurry stream. An another embodiment of
the invention is possible in which the rotational axis of the mixing head
extends at an angle to the slurry stream. As a rule, however, the rotational
plane of the mixing head extends substantially in the direction of the slurry
stream.
Each slot is formed, e.g., of two or more slot sections arranged
in a row. It is, however, particularly effective and advantageous when each
slot is continuous along its entire length. This prevents clogging and an
undesirable high exit velocity of the flocculant liquid.
Each strip-shaped mixing blade is divided, e.g., along its
length, with radial incisions in a comb-like fashion. However, if is
particularly effective and advantageous when each strip-shaped mixing blade
is continuous over its length. This improves the rigidity of the strip-shaped
mixing blades and improves the mixing action.
The cross-section of each outlet slot can be changed along its
length for controlling the amount of the emerging flocculant liquid. It is
particular effective and advantageous when the cross-section of each outlet
slot is increased, when viewed along its length, toward the middle. This
shape of the outlet slots is used when the slots extend transverse to the
stream direction, as in the middle of the slurry pipe, there is more slurry than
at the sides. With a uniform slot width, a uniform delivery of the flocculant
into the slurry is achieved.
In at least one embodiment the slots, which form an outlet for
the flocculant liquid, have, e.g., a width of 7-9 mm. The greater is the amount
of the flocculant liquid to be delivered in a unit of time, the wider the slots
are, and the smaller is the amount of the flocculant liquid to be delivered in a
unit of time, the narrower they are.
It is particularly effective and advantageous when the edge of
each strip-shaped mixing blade extend approximately parallel to the inner
contour of the slurry pipe, forming a clearance therebetween. The elongate
strip-shaped mixing blades extending in a radial direction improve the
admixing action. However, a clearance should remain between the mixing
blade and the slurry conduit, with the clearance being sufficiently large to
permit passing of stone pieces present in the slurry.
This clearance is particularly important and is large when the
strip-shaped mixing blades extend transverse to the stream. When the stripshaped
mixing blades extend transverse to the stream, the clearance
preferably is smaller in the direction of the rotational axis than in the
direction transverse to the rotational axis.
A particularly effective and advantageous embodiment of the
invention is obtained, when the direction of rotation of the distribution head
drive can be changed. In the apparatus according to the invention, the mixing
blade is relatively large or protrudes with respect to the slurry pipe crosssection,
so that a danger of clogging with hard pieces and of accumulation of
fibers or threads exists if the distribution head rotates in the same direction
for a long time. The rotation in opposite directions prevents such clogging
and accumulation.
One, two, and/or more flocculant outlets can be provided, e.g.,
between two mixing blades. However, it is particularly effective and
advantageous when outlet slots and strip-shaped mixing blades alternate in
the rotational direction. This also improves the admixing process. Over the
distribution head, in the rotational direction, there are provided two or more
outlet slots and two or more strip-shaped mixing blades.
It is further particularly effective and advantageous when the
inner cross-section of the slurry pipe, in the region of the distribution head, is
similar to the further inner cross-section of the slurry pipe. The apparatus
according to the invention thus eliminates the narrowing of the slurry pipe
and an associated with it increase of the flow velocity of the slurry. The
distribution head already forms a greater narrowing of the cross-section
available for the slurry.
It is particularly effective and advantageous when the
distribution head is formed as a cylindrical tubular section and/or when the
outer diameter of the distribution head is equal at least to 0.4 of the inner
diameter of the slurry pipe. This simplifies the construction and improves the
rigidity of the distribution head, with the shape of the outlet slots and the
strip-shaped mixing blades presenting an increased demand to the rigidity of
the distribution head.
A particularly effective and advantageous embodiment of the
invention is formed when the distribution head passes into a rotatably
supported connection tube which extends away from the slurry pipe and
which is connected to the drive and with a flocculant liquid delivery conduit,
and is further provided with inlet openings and is ratably supported in a
connection chamber into which the flocculant liquid delivery conduit opens.
This manner of delivery of the flocculant liquid to a rotatable distribution
head permits to insure an increased rigidity of the connection tube and its
support with simple means. This becomes possible in the apparatus
according to the present invention due to the "stone crushing" cooperation of
the strip-shaped mixing blades and the slurry pipe.
For a satisfactory delivery of the flocculant liquid(s) through
the outlet slots, the flow cross-section, which is available for the flocculant
liquid(s), is very important. In one embodiment of the invention, all of the
outlet slots together have a cross-section which is smaller than the preceding
flow cross-section of the flocculant liquid. The entire cross-section of the
inlet opening is not smaller than the flow cross-section in the delivery
conduit and in the connection tube. The flow cross-section in the distribution
head and in the connection tube are similar. The arrangement of the
connection tube in a sealed connection chamber enables to optimize the flow
cross-section of the flocculant liquid.
It is particularly effective and advantageous when a check
valve is arranged in the flocculant liquid delivery conduit when the flocculant
liquid in front of the check valve is not under pressure, e.g., when the
flocculant liquid pump does not operate, the slurry can penetrate into the
outlet slots. The sealings and the bearings in the connection chamber remain
lubricated with the flocculant liquid when the flocculant liquid from the
flocculant liquid pump is not under pressure any more.
A particular effective and advantageous embodiment of the
invention is obtained when the distribution head is driven with a rotational
speed of 700-2,500 revolution/min preferably, 1,000-2,000 revolution/min.
At this relatively high rotational speed, a desired improved admixing and
distribution of the flocculant liquid in the slurry takes place. At the too low
rotational speed, below 500 revolution/min, the strip or the stream of the
flocculant liquid break off. However, a big speed requires too high expenses
in order to achieve the desired effect. In a known apparatus (DE-05 4029824)
of the above-described type, the flocculant is available which is stored in a
reservoir. It is further known (DE-05 39 0 1 292) to add fresh water to a
flocculant available in a liquid or powder form to obtain about 1% of a
flocculant parent solution. The flocculant parent solution is then mixed, at a
filling station, with 4-10 volume parts of make-up water to obtain a
flocculant in a form of a so-called commercial solution. This flocculant is
added in the amount of 18-20% of the amount of the filler slurry is added to
the slurry, i.e., about 20 parts of the flocculant liquid in a form of flocculant
agent is added to 100 parts of filler particles. At that, the flocculant—
containing slurry, i.e., the conditioned filler, contains 1/6 of liquid added by
admixing of the additionally added flocculant liquid.
In a known application, for the additional processing of the
flocculant agent a large amount of water is used, which is expensive. For
processing, in addition to the apparatus for obtaining the parent solution, an
apparatus for obtaining the commercial solution is needed, which results in
additional expenses associated with the apparatus and in additional expenses
associated with the driving of the apparatus. The flocculant and its water are
delivered until they mix up with the slurry, and the delivery require energy,
which is costly. The water component of the flocculant must be delivered,
together with the slurry, to filter presses, pass through the filter presses and,
finally, purified again. Thus, in a known application, additional increased
expenses are associated with the water contained in the flocculant liquid.
Therefore, an object of the invention is to so improve the
process described above that the expenses associated with the use of the
flocculant liquid or increase of its water content, are eliminated. This object
is achieved according to the invention by so designing the above-described
apparatus according to the invention that maximum 3t of the flocculant liquid
need be provided for lOOt of filler slurry.
It was found out, that the use of the distribution head of the
apparatus according to the invention permits to eliminate the water
component of the flocculant liquid without the elimination of the
effectiveness of the flocculant liquid admixed to the slurry. Whereas in the
know application in order to achieve a predetermined effect with a
predetermined amount of the additive, a large amount of the water
component is necessary, this is not necessary when the inventive apparatus is
used. The water component of the flocculant liquid can be reduced to a very
large extent, so that the expenses associated with this water content are
correspondingly eliminated. As less water is necessary, less water need be
pumped, and less water need be purified.
The improved effectiveness achieved by the invention can be
explained, without claiming that the explanation is correct, as follows: The
particular shape of the mixing blade of the inventive apparatus breaks the
filler slurry particles of the slurry to a great extent, and the resulting broken
pieces form open fissures. The particular shape of the flocculant outlets
insures that the flocculant liquid takes a shape of a large surface veil which
cover the freshly opened fissures so that the mixing of the filler and the
flocculant intensifies. The flocculant liquid in accordance with the invention
is already admixed in a finely distributed state so that it is not necessary the
additive to further dilute in a large amount of water, i.e., to increase the water
component of the flocculant liquid. Thus, according to a particular effective
and advantageous embodiment of the invention, the flocculant liquid is used
as a parent solution, with the additive being mixed with water in a single
step. With this embodiment, additional stations for further mixing with water
are eliminated.
Referring now to FIG.s 1 and 2 it is shown in at least one
embodiment that the apparatus may be mounted on a filler slurry carrying
conduit/pipe 1 through which a filler slurry flows in a direction of arrow 2.
The apparatus may be mounted on the slurry pipe 1 by means of an elongate
flange 3 and includes a connection chamber 4 projecting from the flange 3.
From the connection chamber 4, a distribution head 6 extends into the slurry
pipe 1 and is rotated by a drive 7 provided at the opposite end of the chamber
4 and formed as an electromotor. A flocculant liquid conduit 8 opens into the
chamber 4, and a check valve 9 is located in the conduit 8. The distribution
head 6 forms outlet slots 10 and carries mixing strip shaped blades (11).
A sleeve 14 supports a connection tube 15 in a shaft extension
12 which extends from the drive 7, and in the end wall of the connection
chamber 4, there is provided an axial face seal 16 through which the shaft
extension 13 extends. The connection tube 15 has a plurality of elongate
entrance openings 17 through which flocculant flows into the connection
tube from the connection chamber. The connection tube 15 projects into
connection chamber 4 through a plain bearing sleeve 5 provided in the flange
3, with the tubular- shaped distribution head 6 forming an integral part of the
tube 15. The distribution head 6 is associated with a rotational plane 18
designated with a dash line. Each mixing blade 11 forms an arcuate edge 19
which, in a corresponding position of the blade, limits a slot 20 with respect
to the slurry pipe 1, which has a circular cross-section.
The foregoing may be better understood by reference to the
following example, which is presented for purposes of illustration and is not
intended to limit the scope of the invention.
Example 1
l(i) Filler pre-treatment:
A blend of filler particles was obtained from a paper mill. The blend
filler was a mixture of 50% PCC and 50% 100% GCC. The filler blend was diluted
to 20% solid content with tap water. 200 mL of the diluted filler blend was placed in
a 500 mL glass beaker. Stirring was conducted for at least 30 seconds prior to the
addition of coagulant. The stirrer was a EUROSTAR Digital overhead mixer with a
R1342, 50 mm, four-blade propeller (both from IKA Works, Inc., Wilmington,
North Carolina). A coagulant solution was slowly added after the initial 30 seconds
of mixing under stirring with 800rpm. The coagulant solution used was 4690. The
dose of coagulant was lkg/ton based on dry filler weight. Stirring continued at 800
rpm until all the coagulant was added. Then the stirring speed increased to 1500 rpm
for one minute.
l(ii) Use of filler:
Furnish was prepared by disintegrating commercial bleached
hardwood dry lap. The mixture of 50% PCC and 50% GCC was added to pulp
furnish to achieve different filler content in the sheet. 200ppm Nalco 61067 was
used as retention aid. For the pretreatment evaluation, filler mixture was pretreated
using Nalco coagulant 4690 before filler was added into the furnish. During the
handsheet preparation, 3kg/ton Nalco 63700 was added to improve the sheet wet
web strength. We tried to evaluate the effect of filler pretreatment on the press
dewatering performance of 63700 by measuring sheet wet web strength. Handsheets
were pressed to a certain solid content (50%) by controlling the same pressure level
at 60 degree C, and the time required to completely break up wet sheet in water
under the shear force of lOOORPM was recorded to compare sheet wet web strength,
which was expected to indirectly reflect press dewatering. The results indicate that
sheet wet web strength could be significantly improved by the addition of 63700.
Filler pretreatment could further boost sheet wet web strength by additional 20% at
the lower ash content. As for the higher ash content, the performance of 63700 was
even higher than 20%.
Example 2
A machine trial was run in which a papermaking machine made
GAB300 with machine speed of 900m/min. A composition was provided whose
cellulose fibers were 14% MXW; 3% coated broke; 17% SOW; 12% Uncoated
Broke, 44% DIP and 10% ONP. The furnish also contained GCC. During the trial,
all the wet end additives including 15/ton Nalco press dewatering aid 63700,
retention aids, sizing agents, and cationic starches were kept constant.
1) Filler retention enhancement:
4690 was gradually increased from 0.5kg/ton to 2kg/ton based on
filler. It was found that online ash content was increased gradually with the addition
of 4690 to the filler pipe. Obviously, 0.7 ash point increase from 15.6% to 16.3%
was obtained through filler pre-treatment. Historically, for the same grade
production, recorded ash content of DCS was about 12% without using Nalco
63700. It should be pointed out that the ash content improvement was only
contributed by filler ply. Therefore, ash content increase in filler ply was supposed
to be about 1.4% because filler ply accounted for half basis weight of the final
product. FPAR was increased from 70% to 75%, which could explain why final ash
content was significantly enhanced.
2) Steam pressure reduction:
It was also found that steam pressure of the pre-dryer was reduced
through filler treatment. Steam pressure was gradually decreased from 2.15 to 2 bar
from 10:30am to 2:00pm. Even though press pressure of the first press section and
press pressure of the second press section were reduced from 550 to 470 and 600 to
580 respectively, the steam pressure only went back to 2.05.
During the trial, the ash content increased from around 15.6% to
16.3% about 1 hour after the filler was pretreated, then was kept at the same level for
several hours. On the other hand, the steam pressure kept decreasing for several
hours until the press load was reduced. This seems to indicate that the steam
reduction was not only from ash content increase. Moreover, the steam demand
reduction of this trial was only from filler ply since 4690 was only applied for this
ply, thus the total steam reduction caused by ash content increase alone should be
less. Therefore, the results illustrated that filler pre-treatment could enhance 63700
performance as press dewatering agent or wet web strength aid.
A person of ordinary skill in the art will recognize that all of the
previously described methods are also applicable to paper mat comprising other noncellulose
based fibrous materials, paper mats comprising a mixture of cellulose
based and non-cellulose based fibrous materials, and/or synthetic fibrous based
materials.
Changes can be made in the composition, operation, and arrangement
of the method of the invention described herein without departing from the concept
and scope of the invention as defined in the claims. While this invention may be
embodied in many different forms, there are described in detail herein specific
preferred embodiments of the invention. The present disclosure is an exemplification
of the principles of the invention and is not intended to limit the invention to the
particular embodiments illustrated. Furthermore, the invention encompasses any
possible combination of some or all of the various embodiments described herein.
All patents, patent applications, and other cited materials mentioned anywhere in this
application or in any cited patent, cited patent application, or other cited material are
hereby incorporated by reference in their entirety. Furthermore this invention
contemplates embodiments which exclude one, some, or all of the compositions,
methods, components, elements, or other portions of any cited material.
The above disclosure is intended to be illustrative and not exhaustive.
This description will suggest many variations and alternatives to one of ordinary
skill in this art. All these alternatives and variations are intended to be included
within the scope of the claims where the term "comprising" means "including, but
not limited to". Those familiar with the art may recognize other equivalents to the
specific embodiments described herein which equivalents are also intended to be
encompassed by the claims.
This completes the description of the preferred and alternate
embodiments of the invention. Those skilled in the art may recognize other
equivalents to the specific embodiment described herein which equivalents are
intended to be encompassed by the claims attached hereto.

Claims
1. A method of papermaking comprising filler, the method comprising the steps
of: providing a blend of filler particles, at least one drainage additive or wet web
strength additive or wet strength aid, and cellulose fiber stock,
treating the filler particles with a composition of matter in the absence of
cellulose fiber stock,
combining the filler particles with the cellulose fiber stock,
treating the combination with at least one wet strength aid or wet web
strength additive or drainage additive, and
forming a paper mat from the combination,
wherein at least 10% of the filler particles are precipitated calcium carbonate and at
least 10% of the filler particles are ground calcium carbonate, the cellulose fiber
stock comprises a plurality of cellulose fibers and water, and the composition of
matter enhances the performance of the wet strength aid or wet web strength additive
or drainage additive in the paper mat.
and wherein at least some of the composition of matter is added to the filler
with a rotating admixing apparatus, the apparatus having a distribution head, which
is rotated by a drive, is arranged in a container containing a slurry of the filler
particles, and is associated with a rotational plane, and the distribution head has,
along a circumference thereof, which surrounds a rotational axis, distributed outlets
from which the composition is passed into the slurry and mixing blades,
characterized in that the outlets are formed as openings and the mixing blades are
formed as strips extending transverse to the rotational plane and having a length
equal at least half of an inner diameter of the slurry pipe;
and delivering the composition to the distribution head for admixing
the composition to the filler slurry.
2. The method of claim 1 in which the paper mat is formed by removing some
of the water from the combination.
3. The method of claim 1 in which at least some of the calcium carbonate is in
one form selected from the list consisting of: undispersed calcium carbonate,
dispersed slurry calcium carbonate, chalk, and any combination thereof.
4. The method of claim 1 in which at least a portion of the calcium carbonate is
in a dispersed slurry calcium carbonate form, the dispersed slurry calcium carbonate
further comprising at least one item selected from: polyacrylic acid polymer
dispersants, sodium polyphosphate dispersants, Kaolin clay slurry, and any
combination thereof.
5. The method of claim 1 in which the blend of filler particles is 50% ground
calcium carbonate and 50% precipitated calcium carbonate.
6. The method of claim 1 in which the composition of matter is a coagulant.
7. The method of claim 1 in which the composition of matter is a coagulant
selected from the list consisting of: inorganic coagulants, organic coagulants,
condensation polymerization coagulants, and any combination thereof.
8. The method of claim 1 in which the composition of matter is a coagulant
having a molecular weight range of between 200 and 1,000,000.
9. The method of claim 1 in which the composition of matter is a coagulant
selected from the list consisting of: alum, sodium aluminate, polyaluminum
chlorides, aluminum chlorohydroxide, aluminum hydroxide chloride, polyaluminum
hydroxychloride, sulfated polyaluminum chlorides, polyaluminum silica sulfate,
ferric sulfate, ferric chloride, epichlorohydrin-dimethylamine (EPI-DMA), EPIDMA
ammonia crosslinked polymers, polymers of ethylene dichloride and
ammonia, polymers of ethylene dichloride, polymers of dimethylamine,
condensation polymers of multifunctional diethylenetriamine, condensation
polymers of multifunctional tetraethylenepentamine, condensation polymers of
multifunctional hexamethylenediamine condensation polymers of multifunctional
ethylenedichloride, melamine polymers, formaldehyde resin polymers, cationically
charged vinyl addition polymers, and any combination thereof.
10. The method of claim 1 in which the composition of matter is an
AcAm/DADMAC copolymer.
11. The method of claim 1 in which the drainage additive or wet web strength
additive or wet strength aid is one selected from the list of: glyoxylated
Acrylamide/DADMAC copolymer, poly-vinylamine, poly-vinylamide, polydiallylamine,
and any combination thereof.
12. The method of claim 1 in which the ratio of drainage additive or wet web
strength additive or wet strength aid relative to the solid portion of the paper mat is
0.3 to 5 kg of strength additive per ton of paper mat.
13. The method of claim 1 in which at least some of the GCC particles are
treated with the composition of matter.
14. The method of claim 1 in which none of the PCC particles are treated with
the composition of matter.
15. The method of claim 1 in which the paper mat has a solid portion and the
filler particles in the paper mat comprise more than 50% of the combined mass of
the solid portion of the paper mat.
16. The method of claim 1 in which the drainage additive or wet web strength
additive or wet strength aid and the composition of matter carry the same charge.
17. The method of claim 1 in which the blend of filler particles further comprises
one item selected from the list consisting of: organic pigment, inorganic pigment,
clay, talc, titanium dioxide, alumina trihydrate, barium sulfate, magnesium
hydroxide, and any combination thereof.
18. A method of papermaking comprising the use of filler, the method
comprising the steps of:
providing a blend of filler particles, at least one drty strength aid, and
cellulose fiber stock,
treating the filler particles with a composition of matter in the absence of
cellulose fiber stock,
combining the filler particles with the cellulose fiber stock,
treating the combination with at least one dry strength aid, and
forming a paper mat from the combination,
wherein at least 10% of the filler particles are in a dispersed slurry calcium
carbonate form,
the cellulose fiber stock comprises a plurality of cellulose fibers and water,
and
the composition of matter enhances the performance of the dry strength aid in
the paper mat
and wherein at least some of the composition of matter is added to the filler
with a rotating admixing apparatus, the apparatus having a distribution head, which
is rotated by a drive, is arranged in a container containing a slurry of the filler
particles, and is associated with a rotational plane, and the distribution head has,
along a circumference thereof, which surrounds a rotational axis, distributed outlets
from which the composition is passed into the slurry and mixing blades,
characterized in that the outlets are formed as openings and the mixing blades are
formed as strips extending transverse to the rotational plane and having a length
equal at least half of an inner diameter of the slurry pipe;
and delivering the composition to the distribution head for admixing
the composition to the filler slurry.
19. A method of increasing the interactions between a drainage additive or wet
web strength additive or wet strength aid and cellulose fibers mixed with filler
particles, the method comprising the steps of:
pre-treating filler particles with a composition of matter in the absence of
cellulose fiber stock,
combining the pre-treated filler particles with cellulose fibers, and
treating the combination with at least one drainage additive or wet web
strength additive or wet strength aid,
wherein the filler particles are selected from the list consisting of precipitated
calcium carbonate, ground calcium carbonate, and any combination thereof, and
the composition of matter inhibits the drainage additive or the wet web
strength additive or wet strength aid from adhering to the filler particles,
and wherein at least some of the composition of matter is added to the filler
with a rotating admixing apparatus, the apparatus having a distribution head, which
is rotated by a drive, is arranged in a container containing a slurry of the filler
particles, and is associated with a rotational plane, and the distribution head has,
along a circumference thereof, which surrounds a rotational axis, distributed outlets
from which the composition is passed into the slurry and mixing blades,
characterized in that the outlets are formed as openings and the mixing blades are
formed as strips extending transverse to the rotational plane and having a length
equal at least half of an inner diameter of the slurry pipe;
and delivering the composition to the distribution head for admixing
the composition to the filler slurry.