RECYCLING OF WASTE COATING COLOR
Cross-Reference to Related Applications
This Application is a Continuation in Part of pending US Patent Application serial
number 1/854,044 filed on September 12, 2007.
Statement Regarding Federally Sponsored Research or Development
Not Applicable.
Background of the Invention
This invention relates to methods and compositions useful in the treatment and
recycling of waste coating color that is generated in paper coating processes. Coatings are
commonly used during the papermaking process to improve the optical and printing properties of
the resulting paper. Coating colors or formulations commonly include pigments, binders, and
other minor additives. Pigments can represent as much as 95% of the solids in the coating
formulation and contain calcium carbonate, kaolin clay, titania, talc, plastic pigments, silica,
alumina, or mixtures thereof. Binders typically represent from 5% to 25% of the solids in the
coating formulation and are natural or synthetic polymers that bridge the pigment particles in the
coating to give the coating cohesive strength and flexibility. The most typical natural binder is
starch, while typical synthetic binders are styrene-butadiene copolymers, styrene-acrylate
copolymers, polyvinyl alcohol, and polyvinyl acetate. Minor additives usually make up about 1%
of the solids in the coating formulation and consist of a variety of chemicals that serve many
purposes in the coating. Possible additives are insolubilizers, optical brighteners, dispersants,
lubricants, defoamers, rheology modifiers, dyes, and microbiocides. The coating forms a layer on
the outside of the sheet of paper. This improves its opacity, brightness, smoothness, and print
quality compared to an uncoated sheet.
Unfortunately, significant amounts of waste coating color are generated in typical
paper coating processes. This waste is a result of coating that has been added to the process but
which for one reason or another does not end up coating the paper surface. In some cases this
waste can be as much as 4% of the total applied coating. Common practice is to dewater and
compact this waste coating and to simply dump it into landfills or burn it. Many mills use
hundreds of thousands, if not millions of tons of coating, resulting in tens of thousands of tons of
waste being generated annually. This results in both terrible environmental costs as well as a
significant waste of economic resources. Thus there is clear need and novel
utility in a method of recycling coating waste generated in a papermaking process. The art
described in this section is not intended to constitute an admission that any patent, publication or
other information referred to herein is "Prior Art" with respect to this invention, unless
specifically designated as such. In addition, this section should not be construed to mean that a
search has been made or that no other pertinent information as defined in 37 CFR § 1.56(a)
exists.
Brief Summary of the Invention
At least one embodiment of the invention is directed towards a method of
incorporating waste coating in a paper sheet of a papermaking process. The method comprises
the steps of: ) providing a furnish comprising at least cellulose fibers and water, filler particles,
and waste coating from a previous papermaking coating process, 2) mixing the waste coating and
the fresh filler particles to form a mixture, 3) optionally adding a defoamer to the mixture, 4)
adding a cationic agent to the mixture, 5) adding a first flocculating agent to the mixture in an
amount sufficient to mix uniformly without causing significant flocculation of the filler and
coating waste, the first flocculating agent being a flocculant; 6) adding a second flocculating
agent to the mixture after adding the first flocculating agent, in an amount sufficient to initiate
flocculation of the filler and coating waste in the presence of the first flocculating agent, the
second flocculating agent being of opposite charge to the first flocculating agent, the flocculated
mixture of fresh filler and coating waste defining a filler material, 7) optionally, shearing the
flocculated mixture of fresh filler and coating waste to provide floes having the desired particle
size, and 8) mixing the filler material within the furnish.
The waste coating may comprise water and water may be a majority of the mass of
the waste coating. The coating waste may comprise at least one pigment from the list consisting
of: precipitated calcium carbonate, ground calcium carbonate, kaolin clay, titanium dioxide,
plastic pigments, and any combination thereof. The coating waste may comprise at least one
binder from the list consisting of: starch, styrene-butadiene resin, styrene-acrylate copolymer,
styrene-acrylic acid resin, and any combination thereof. The cationic agent may be one selected
from the list consisting of: a starch, a flocculant, a coagulant, and any combination thereof. The
first flocculating agent may be selected from the group consisting of cationic, anionic, nonionic,
zwitterionic and amphoteric polymers. The second flocculating agent may be selected from the
group consisting of microparticles, coagulants and cationic, anionic, nonionic, zwitterionic and
amphoteric polymers and mixtures thereof. The second flocculating agent and first flocculating
agent may be oppositely charged. The first flocculating agent may be anionic and the second
flocculating agent may be cationic. The preflocculated mixture of coating waste and fresh filler
may have a median particle size of 0-70 u . Substantially 00% of the coating pigments and
binders may be flocculated with the filler material. The solids content of the coating waste may
be between 0.5% and 10%. The relative amounts of filler particles and coating particles are
between 50 to 98% filler particles and 2% to 50% waste coating particles.
At least one embodiment of the invention is directed towards a sheet of paper
manufactured in a papermaking process according to the above method.
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 a graph showing the particle size distribution of waste coating used in the
invention.
FIG. 2 is a table of the physical properties of paper made according to the
invention.
FIG. 3 is a graph showing the particles contained in the supernatant of the
untreated mixture.
FIG. 4 is a graph showing the relative fluorescence from OBA in paper made
according to the invention.
FIG. 5 is an electron micrograph of filler material used in the invention.
FIG. 6 is a graph showing the amount of deposit present in the invention.
FIG. 7 is a graph showing the relative strength of paper made according to the
invention.
Detailed Description of the Invention
The following definitions are provided to determine how terms used in this
application, and in particular how the claims, are to be construed. The organization of the
definitions is for convenience only and is not intended to limit any of the definitions to any
particular category.
For purposes of this application the definition of these terms is as follows:
"Binder" means natural or synthetic polymers that bridge the pigment particles
the coating to give the coating cohesive strength and flexibility.
"Coating, coating formulation, or coating color" means a mixture of water,
pigments, binders, and other minor additives.
"Coagulant" means a composition of matter having a higher charge density and
lower molecular weight than a flocculant, which when added to a liquid containing finely divided
suspended particles, destabilizes and aggregates the solids through the mechanism of ionic charge
neutralization.
"Defoamer" means a material added to a coating color or to the papermaking
process that reduces the generation of foam and/or the persistence of foam. Defoamers are
usually blends of any or all of the following components: organic or inorganic hydrophobic
particulates, spreading agents, and surfactants in oil or a water carrier. Specific chemicals often
used in defoamer formulations are silica particles, hydrophobically-modified silica particles,
polyethylene glycol (PEG) esters and amides, fatty acids, fatty amides, fatty alcohols, and
alkoxylated nonionic surfactants.
"Filler" means a material which as a result of the papermaking process becomes
positioned within the resulting paper for the purposes of reducing the cost by replacing more
expensive fiber components, Filler often increase the opacity, increase the brightness, and/or
increase the smoothness of the resulting paper.
"Flocculant" means a composition of matter having a low charge density and a
high molecular weight (in excess of 1,000,000) which when added to a liquid containing finely
divided suspended particles, destabilizes and aggregates the solids through the mechanism of
interparticle bridging.
"Flocculating Agent" means a composition of matter which when added to a
liquid destabilizes and aggregates colloidal and finely divided suspended particles in the liquid;
flocculants and coagulants can be flocculating agents.
"GCC" means ground calcium carbonate, which is manufactured by grinding
naturally occurring calcium carbonate rock.
"PCC" means precipitated calcium carbonate which is synthetically produced.
"Pigment" means a solid, particulate material that makes up as much as 95% of a
coating formulation, which as a result of the papermaking process, becomes engaged to the
outside of the resulting paper for the purpose of improving the optical and printing properties of
the resulting paper.
In the event that the above definitions or a description stated elsewhere in this
application is inconsistent with a meaning (explicit or implicit) which is commonly used, in a
dictionary, or stated in a source incorporated by reference into this application, the application
and the claim terms in particular are understood to be construed according to the definition or
description in this application, and not according to the common definition, dictionary definition,
or the definition that was incorporated by reference. In light of the above, in the event that a tenn
can only be understood if it is construed by a dictionary, if the term is defined by the Kirk-Othmer
Encyclopedia of Chemical Technology, 5th Edition, (2005), (Published by Wiley, John & Sons,
Inc.) this definition shall control how the tenn is to be defined in the claims.
Numerous materials are commonly used as pigments, binders, and fillers.
Pigments can represent as much as 95% of the solids in the coating formulation and are often
calcium carbonate, kaolin clay, titania, talc, plastic pigments, silica, alumina, or mixtures thereof.
Calcium carbonate, for example, can be used as a pigment or filler. In prior art applications,
fillers (such as calcium carbonate) are particles typically from 1 to 8 microns in size, This size
often represents a compromise with fine particles scattering light more efficiently and large
particles interfering less with the strength of the paper.. Pigment particles used in coatings tend
to be smaller than fillers, with as much as 95% by mass smaller than 2 microns. Binders
typically represent from 5% to 25% of the solids in the coating formulation and are natural or
synthetic polymers that bridge the pigment particles in the coating to give the coating cohesive
strength and flexibility. The most typical natural binder is starch, while typical synthetic binders
include styrene-butadiene copolymers, styrene-acrylate copolymers, polyvinyl alcohol, and
polyvinyl acetate. Minor additives usually make up about 1% of the solids in the coating
formulation and consist of a variety of chemicals that serve many purposes in the coating.
Possible additives are insolubilizers, optical brighteners, dispersants, lubricants, defoamers,
rheology modifiers, dyes, and microbiocides. Coating formulations usually contain 20% to 50%
water by mass. Most of this water must be removed in the coating process through absorption
into the paper structure and radiant drying. The coating forms a layer on the outside of the sheet
of paper. This improves its opacity, brightness, smoothness, and print quality compared to an
uncoated sheet.
Numerous technical problems discourage the reuse of waste coatings as either
fillers or coatings. After a paper coating process, the waste coatings are present as dilutions in
varying amounts of wash water. Waste coatings are poor candidates for fillers because they have
a high foaming tendency, are strongly anionic and difficult to retain in the papermaking web, and
contain a large amount of hydrophobic binder particles that tend to agglomerate in the white
water and deposit on papermaking equipment. Additionally, they have a small size and tend to
weaken the paper significantly. They are poor candidates for coatings because of their low and
inconsistent concentration. This results in inconsistent rheology leading to poor coater
runnability and poor coating quality.US Patents 5,830,364, 6,159,381, and 6,214,166 describe
attempts to recover one or more portions of the waste coating from a papermaking process, but do
not adequately address the problems inherent in waste coatings and do not teach a cost effective
recovery process.
n at least one embodiment waste coatings are used as filler in a papermaking
process. This is accomplished by mixing the waste coating with fresh filler and treating the
mixture to negate the various technical problems. In at least one embodiment the mixture
comprises between 50 to 98% fresh properly sized filler particles and 2% to 50% smaller waste
coating solids.
In at least one embodiment the treatment comprises adding a defoaming agent to
the mixture, adding a cationic coagulant to the mixture, and preflocculating the mixture. When
preflocculated, the mixed waste coating and fresh filler particles are agglomerated through
treatment with coagulants and/or flocculants.
n at least one embodiment, at least some of the coating is binder and the
preflocculation results in the agglomeration containing substantially all of the latex that was
present in the coating waste. This results in turning waste latex from a liability to an asset. As a
material which is highly hydrophobic by nature, waste latex can agglomerate from dilute
solutions and ultimately deposits on papermaking equipment, resulting in low papermaking
efficiency and quality problems with the finished paper. In this case however, because all of the
latex is incorporated within the agglomerates, the process equipment is not clogged and the latex
instead further enhances the strength properties of the paper by helping bind mineral particles to
each other and to paper fibers.
In at least one embodiment the treatment comprises adding a defoaming agent to
the mixture, adding a cationic coagulant to the mixture, and combining the mixture with at least
one item selected form the list consisting of starch, coagulant, flocculant, and any combination
thereof.
In at least one embodiment the preflocculation process comprises the steps of:
a) providing an aqueous dispersion of filler and coating waste;
b) adding a first flocculating agent to the dispersion in an amount sufficient to mix
uniformly in the dispersion without causing significant flocculation of the filler and coating
particles, the first flocculating agent being a flocculant;
c) adding a second flocculating agent to the dispersion after adding the first
flocculating agent, in an amount sufficient to initiate flocculation of the filler and coating
particles in the presence of the first flocculating agent, the second flocculating agent being of
opposite charge to the first flocculating agent; and
d) optionally, shearing the flocculated dispersion to provide a dispersion of fillercoating
waste floes having the desired particle size.
In at least one embodiment the preflocculation process comprises the steps of:
a) providing an aqueous slurry of anionically dispersed coating waste and undispersed or
dispersed filler particles;
b) adding a low molecular weight composition to the dispersion, the added low
molecular weight composition at least partially neutralizing the charge in the
dispersion;
c) adding a first flocculating agent to the dispersion under conditions of high mixing, the
first flocculating agent being a flocculant;
d) adding a second flocculating agent to the dispersion under conditions of high mixing,
the second flocculating agent comprising an item selected from the list consisting of: a
flocculent, a coagulant, a microparticle, and any combination thereof; and
e) optionally, shearing the flocculated dispersion to provide a dispersion of filler and
coating floes having the desired particle size.
EXAMPLES
The following examples are presented to describe embodiments and utilities of the
invention and are not meant to limit the invention unless otherwise stated in the claims.
Example 1:
A waste coating color sample was obtained from a paper mi l. The solids level of
the waste coating color was 5.76%. A fresh filler with 18% solids was also obtained from the
same mill, and it was Albacar LO, manufactured by Specialty Minerals Inc. (SMI). The waste
coating color was then mixed with fresh filler in a mass ratio of 20/80. Tap water was added to
the mixture to make the solids content 10%. 300 ml of the mixture was stirred at 800 rpm. A
significant amount of foam was generated by the stirring. Enough silicone-based defoaming agent
was added to eliminate the foam. 5.5 lb/ton of Nalco coagulant DEVI 20 was added slowly into
the mixture, followed by 5 lb/ton Nalco flocculating agent DEV1 5. Then 3.0 lb/ton Nalco
flocculating agent DEV125 was slowly added into the mixture. All the chemical dosages were
based on product mass per ton of solids in the coating waste/filler mixture. The dosages of the
coagulant and flocculating agents were carefully chosen to minimize foaming. After the addition
of flocculating agent DEVI 25, the mixture was stirred at 500 rpm for 2 minutes. Figure 1 shows
the particle size distributions of waste coating color only, fresh filler only, the mixture of waste
coating color and fresh filler, and the treated mixture. After treatment, the particle size was
significantly larger, which is believed to be beneficial for improving sheet strength. Coagulant
DEVI 20 is a cationic poly(diallyldimethylammonium chloride) with a RSV of about 0.7 dL/g,
available from Nalco Company, Naperville, L, USA. Flocculating agent DEVI 15 is an anionic
sodium acrylate-acrylamide copolymer with an RSV of about 32dL/g and a charge content of 29
mole percent, available from Nalco Company, Naperville, IL, USA. Flocculating agent DEV125
is a cationic acrylamide-dimethylaminoethyl acrylate-methyl chloride quaternary salt copolymer
with an RSV of about 25 dL/g and a charge content of 10 mole percent, available from Nalco
Company, Napervi!le, IL, USA..
Examples 2, 3 and 4 were performed to demonstrate that binders contained in the
waste coating color were deposited onto the pigment or filler surfaces after the treatment.
Example 2:
Samples of 20/80 mixture of waste coating color and fresh filler before and after
the treatment described in Example 1 were centrifuged at 1500 rpm for 15minutes. After
centrifugation, the supernatant of the untreated mixture was turbid, while the supernatant of the
treated mixture was clear. The particle size distribution of the particles contained in the
supernatant of the untreated mixture was shown in Figure 3. It is believed that the size of the
particles is consistent with binders from the waste coating color.
Example 3:
3mI of 0.1% Nile red solution in ethanol were added into 3 ml supernatant from
the centrifuged untreated mixture described in Example 2 and the fluorescence spectrum was
taken. After subtracting the fluorescence from OBA (optical brightening agent) contained in the
solution, there was a significant fluorescence emission, as shown in Figure 4. The same
experiment was al o conducted for the supernatant of the centrifuged treated mixture described in
Example 2 . There was no fluorescence detectable, and the result was also shown in Figure 4.
Nile red dye emits fluorescence when it is adsorbed on a hydrophobic solid. Therefore, the result
indicates that substantially all the hydrophobic materials contained in the waste coating pigment
were not in the supernatant after the treatment.
Example 4:
10 mΐ of 0.1% Nile red solution in ethanol were mixed with 3 ml slurry of the
treated mixture described in Example 1. The fluorescence images of the particles were taken
using a confocal laser scanning microscope with laser excitation at 488 n and a 530 nm long
pass filter on the emission. At the same time, a reflected light image of the same filler particles
was taken. The results are shown in Figure 5. The images clearly show that the hydrophobic
binder particles were deposited on the filler surfaces.
Example 5:
The purpose of example 5 was to demonstrate that treated mixtures of the waste
coating color and fresh filler described in Example 1 do not cause any deposits. 1400 ml of 0.6%
solids cellulose fiber furnish was stirred at 300 rpm. The furnish was composed of 25% softwood
and 75% hardwood. 30% by mass filler was then added to the furnish. The filler tested in the
experiment was 00% waste coating color, a 20/80 mass ratio of waste coating color and fresh
filler, and a treated 20/80 mass ratio of waste coating color and fresh filler. The treatment
process was described in Example 1. A Nalco DRM probe was inserted into the furnish to record
the amount of deposit on the probe surface. The Nalco DRM probe is a treated quartz crystal
microbalance for measuring microgram quantities of deposition, as described in US Patent
7,842,165. About 30 minutes later, 5 lb/ton Nalco coagulant N-2030 was added into the furnish
to help neutralize the anionic charge associated with the waste coating color. (This would be done
to improve retention of these components on a papermachine.) Nalco coagulant N-2030 is a
cationic poly(diallyldimethylammonium chloride) with a RSV of about 0.7 dL/g, available from
Nalco Company, Naperville, TL, USA. The dosage of N-2030 was based on product mass per ton
of total solids in the furnish. The results were shown in Figure 6. After injection of 5 lb/ton N2030
to the furnish containing 100% waste coating color, deposits were significant. For the
furnish containing a 20/80 mass ratio of waste coating color and fresh filler, the deposits were
less, but still significant. However, for the furnish containing the treated mixture of waste coating
color and fresh filler, there was no significant amount of deposits recorded.
Example 6:
The purpose of example 6 was to demonstrate the impact of the treated mixture of
waste coating color and fresh filler on physical properties of handsheets. The filler and waste
coating studied in this example were the same as described in Example 1: an untreated 20/80
mass ratio of waste coating color and fresh filler, a treated 20/80 mass ratio of waste coating
color and fresh filler, and 100% fresh filler. The process of treating 20/80 mass ratio of waste
coating color and fresh filler was described in example 1. Thick stock with a consistency of 2.5%
was prepared from 75% eucalyptus hardwood dry lap pulp and 25% pine softwood dry lap pulp.
Both the hardwood and softwood were refined to 400 ml Canadian Standard Freeness (TAPPI
Test Method T 227 om-94) in a Valley Beater (from Voith Sulzer, Appleton, WI). The thick
stock was diluted with tap water to 0.6% consistency. Handsheets were prepared by mixing the
proper amount of 0.6% consistency furnish and fillers at 800 rpm in a Dynamic Drainage Jar with
the bottom screen covered by a solid sheet of plastic to prevent drainage. The target basis weight
of the handsheet was 80 gsm. Different amounts of filler were added into the furnish to change
the filler content of the handsheet. The Dynamic Drainage Jar and mixer are available from Paper
Chemistry Consulting Laboratory, Inc., Carmel, NY. 30 s after mixing, 12 lb/ton Stalok 400
starch (available from Tate and Lyle, Decatur, IL) and 2 lb/ton Nalsize ® 7542 (available from
Nalco Company, Naperville, IL, USA) ASA emulsion were added into the furnish. The ASA
emulsion was prepared in the following procedure: 28 g Nalsize ® 7542 was added to 186 g of
6.0% solids Stalok 400 starch solution and 66 g deionized water to bring the total weight of
solution to 280 g in a 300 ml Oster® blending cup. This mixture was agitated at high speed for 90
seconds using an Osterizer® blender. The emulsion was post-diluted with Stalok 400 starch
solution to bring the mass ratio of starch to ASA to 3:1. At 45 s mixing, 1 lb/ton cationic
flocculant Nalco 61067 was added. Flocculant Nalco 6 1067 is a cationic acrylamidedimethylaminoethyl
acrylate-m ethyl chloride quaternary salt copolymer with an RSV of about 25
d g and a charge content of 10 mole percent, available from Nalco Company, Naperville, IL,
USA. For the mixture of 20/80 waste coating color/fresh filler, 2 lb/ton Nalco coagulant 2030
(available from Nalco Company, Naperville, IL, USA) was also added at 15 s after mixing.
Mixing was stopped at 75 seconds and the furnish was transferred into the deckle
box of a handsheet mold (Adirondack Machine Company, Queensbury, NY). The 8"x 8"
handsheet was formed by drainage through a 00 mesh forming wire. The handsheet was
couched from the sheet mold wire by placing two blotters and a metal plate on the wet handsheet
and roll-pressing with six passes of a 25 lb metal roller. The forming wire and top blotter were
removed and the handsheet and blotter were placed on top of two new blotters. A metal plate
was then placed facing the wire side of the handsheet. Five formed handsheets were stacked on
top of one another in this manner (new blotter, blotter, formed handsheet, and plate) and placed
in the handsheet press (Lorentzen & Wettre, Kista, Sweden) for five minutes at 0.565 MPa. The
handsheet label was placed on the lower-right-wire side of the sheet and this side was in contact
with the dryer surface. Sheets were dried at 220°F for 90 seconds in a single pass using an
electrically heated, rotary drum dryer (Adirondack Machine Company, Queensbury, NY).
The finished handsheets were stored overnight at TARRG standard conditions of
50% relative humidity and 23°C. The basis weight (TAPPI Test Method T 410 om-98), ash
content (TAPPI Test Method T 2 om-93) for determination of PCC content, brightness (ISO
Test Method 2470: 1999), opacity (ISO Test Method 2471 : 1998), formation, tensile strength
(TAPPl Test Method T 494 om-01 ), and z-directional tensile strength (ZDT, TAPPI Test Method
T 541 om-89) of the handsheets were tested. The formation, a measure of basis weight
uniformity, was determined using a Kajaani Formation Analyzer from Metso Automation,
Helsinki, F .
5 Five replicate handsheets were prepared and the sheet properties were averaged
and reported in Table 1. Compared to both untreated 20/80 mixture of waste coating color and
fresh filler and 100% untreated PCC, the treated 20/80 mixture of waste coating color and fresh
filler significantly increased sheet strength (which was also shown in Figure 6 for tensile
strength), and decreased the sheet optical properties slightly. Sheet formation was improved by
10 the treatment of the mixture.
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
s 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
20 incorporated by reference in their entirety.
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 incorporating waste coating in a paper sheet of a papermaking process, the
method comprising:
providing a furnish comprising at least cellulose fibers and water, filler particles, and
waste coating from a previous papermaking coating process
mixing the waste coating and the fresh filler particles to form a mixture,
optionally adding a defoamer to the mixture,
adding a cationic agent to the mixture,
adding a first flocculating agent to the mixture in an amount sufficient to mix uniformly
without causing significant flocculation of the filler and coating waste, the first flocculating agent
being a flocculant;
adding a second flocculating agent to the mixture after adding the first flocculating agent,
in an amount sufficient to initiate flocculation of the filler and coating waste in the presence of
the first flocculating agent, the second flocculating agent being of opposite charge to the first
flocculating agent, the flocculated mixture of fresh filler and coating waste defining a filler
material,
optionally, shearing the flocculated mixture of fresh filler and coating waste to provide
floes having the desired particle size, and
mixing the filler material within the furnish.
2. The method of claim 1 in which the waste coating comprises water and water is a
majority of the mass of the waste coating.
3. The method of claim 1 in which the coating waste comprises at least one pigment from
the list consisting of: precipitated calcium carbonate, ground calcium carbonate, kaolin clay,
titanium dioxide, plastic pigments, and any combination thereof.
4. The method of claim 1 in which the coating waste comprises at least one binder from the
list consisting of: starch, styrene-butadiene resin, styrene-acryiate copolymer, styrene-acrylic acid
resin, and any combination thereof.
5. The method of claim 1 in which the cationic agent is one selected from the list consisting
of: a starch, a flocculant, a coagulant, and any combination thereof.
6. The method of claim 1 wherein the first flocculating agent is selected from the group
consisting of cationic, anionic, nonionic, zwitterionic and amphoteric polymers, the first
flocculant agent being a flocculant
7. The method of claim 1wherein the second flocculating agent is selected from the group
consisting of microparticles, coagulants and cationic, anionic, nonionic, zwitterionic and
amphoteric polymers and mixtures thereof.
8. The method of claim 1 wherein the second flocculating agent a d first flocculating agent
are oppositely charged.
9. The method of claim 9 wherein the first flocculating agent is anionic and the second
flocculating agent is cationic.
10. The method of claim 1 wherein the preflocculated mixture of coating waste and fresh
filler have a median particle size of 10-70 m h.
11. The method of claim 1 in which substantially 100% of the coating pigments and binders
are flocculated with the filler material.
12. The method of claim 2 in which the solids content of the coating waste is between 0.5%
and 10%.
13. The method of claim 1 in which relative amounts of filler particles and coating particles
are between 50 to 98% filler particles and 2% to 50% waste coating particles.
14. A sheet of paper manufactured in papermaking process which includes the method of claim 1.