U.S. patent application number 15/428389 was filed with the patent office on 2017-08-17 for additives for papermaking.
The applicant listed for this patent is NANOPAPER, LLC. Invention is credited to Gangadhar Jogikalmath, Andrea Schneider, David S. Soane.
Application Number | 20170233947 15/428389 |
Document ID | / |
Family ID | 49758891 |
Filed Date | 2017-08-17 |
United States Patent
Application |
20170233947 |
Kind Code |
A1 |
Jogikalmath; Gangadhar ; et
al. |
August 17, 2017 |
ADDITIVES FOR PAPERMAKING
Abstract
The invention is directed to systems for papermaking comprising
a first population of fibers dispersed in an aqueous solution and
complexed with an activator, and a second population of composite
additive particles bearing a tethering material, wherein the
addition of the second population to the first population attaches
the composite additive particles to the fibers. The invention also
encompasses methods for manufacturing a paper product.
Inventors: |
Jogikalmath; Gangadhar;
(Cambridge, MA) ; Schneider; Andrea; (Hyde Park,
MA) ; Soane; David S.; (Palm Beach, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NANOPAPER, LLC |
Cambridge |
MA |
US |
|
|
Family ID: |
49758891 |
Appl. No.: |
15/428389 |
Filed: |
February 9, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14571154 |
Dec 15, 2014 |
9587353 |
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15428389 |
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PCT/US13/45582 |
Jun 13, 2013 |
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14571154 |
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61660146 |
Jun 15, 2012 |
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61759550 |
Feb 1, 2013 |
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Current U.S.
Class: |
162/175 |
Current CPC
Class: |
D21H 13/24 20130101;
D21H 13/14 20130101; D21H 13/26 20130101; D21H 17/21 20130101; D21H
17/72 20130101; D21H 17/67 20130101; D21H 21/16 20130101; D21H
17/69 20130101; D21H 17/74 20130101; D21H 17/34 20130101; D21H
17/28 20130101; D21H 19/12 20130101; D21H 17/675 20130101; D21H
11/20 20130101; D21H 15/10 20130101; D21H 17/375 20130101; D21H
17/37 20130101; D21H 17/63 20130101; D21H 17/70 20130101 |
International
Class: |
D21H 17/28 20060101
D21H017/28; D21H 21/16 20060101 D21H021/16; D21H 15/10 20060101
D21H015/10; D21H 17/21 20060101 D21H017/21; D21H 17/34 20060101
D21H017/34; D21H 17/63 20060101 D21H017/63; D21H 17/67 20060101
D21H017/67; D21H 17/69 20060101 D21H017/69; D21H 19/12 20060101
D21H019/12; D21H 13/14 20060101 D21H013/14; D21H 17/37 20060101
D21H017/37 |
Claims
1. A system for papermaking, comprising: a first population of
fibers dispersed in an aqueous solution and complexed with an
activator, and a second population of composite additive particles
bearing a tethering material, wherein the addition of the second
population to the first population attaches the composite additive
particles to the fibers by the interaction of the activator and the
tethering material.
2. The system of claim 1, wherein the first population comprises
cellulosic fibers.
3. The system of claim 1, wherein the first population comprises
synthetic fibers.
4. The system of claim 1, wherein the composite additive particles
comprise a particle selected from the group of a PCC particle, a
TiO2 particle, a magnetic particle, and a silver colloid
particle.
5. The system of claim 1, wherein the composite additive particles
comprise a latex component and a starch component.
6. An oil and/or grease resistant paper product, comprising: the
system of claim 1, wherein the composite additive particles
comprise a hydrophobic starch, and an oil and/or grease-resistant
coating.
7. A method for manufacturing a paper product, comprising:
activating a first population of fibers in a liquid medium with an
activator, forming a second population of composite additive
particles, treating the second population with a tethering material
to form tether-bearing composite additive particles, wherein the
tethering material is capable of interacting with the activator,
adding the second population to the activated population of fibers
to form a treated paper matrix, and forming the treated paper
matrix to manufacture the paper product.
8. The method of claim 7, wherein the first population comprises
cellulosic fibers.
9. The method of claim 7, wherein the first population comprises
synthetic fibers.
10. The method of claim 7, wherein the composite additive particles
comprise a particle selected from the group of a PCC particle, a
TiO2 particle, a magnetic particle, and a silver colloid
particle.
11. The method of claim 7, wherein the composite additive particles
comprise a latex component and a starch component.
12. The method of claim 7, further comprising: adding an oil and/or
grease resistant coating to the paper matrix, wherein the paper
matrix comprises tether-bearing composite additive particles that
comprise a hydrophobic starch.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 14/571,154, filed on Dec. 15, 2014, which is a continuation of
International Application No. PCT/US13/45582, which designated the
United States and was filed on Jun. 13, 2013, published in English,
which claims the benefit of U.S. Provisional Application Ser. No.
61/660,146, filed Jun. 15, 2012 and U.S. Provisional Application
Ser. No. 61/759,550 filed Feb. 1, 2013. The entire contents of the
above applications are incorporated by reference herein.
FIELD OF THE APPLICATION
[0002] This application relates generally to making high-strength
paper products with specific functionalities.
BACKGROUND
[0003] Many paper applications require not only high strength but
also functionalities that provide the paper article with moisture,
oil and grease, mold and fire resistance, increased brightness, or
other specialized functionalities like antimicrobial properties or
magnetic properties. Certain of these products are currently
manufactured by imparting paper a coating in a secondary process.
In one approach for adding functionality to the paper surface, the
sizing process uses cooked starch solutions with additives (such as
brightening agents, clays, hydrophobicizing compounds) to impart
surface functionality to the paper. In the sizing process, the wet
web is first dried to a pre-set moisture content and/or is re-wet
to achieve uniform moisture content throughout; then the material
is fed into a size press where a high loading of gelatinized starch
with additives is applied to the paper surface; then the material
is dried again. This process involves a number of downstream
processes that can be inefficient. Inefficiencies result from the
number of steps involved in preparing the substrate, cooking the
starch and applying it to form the finished product. A considerable
amount of energy is required for these steps, which adds to the
costs of the process.
[0004] For certain paper products, functionalities can be added by
incorporating additives into the fibrous matrix during the
papermaking process. Particulate additives can be introduced into
the paper web, substituting for some of the pulp that might be used
otherwise. These particulate fillers can create, for example, a
bulky final paper product that creates the impression of higher
quality through its tactile properties while minimizing the use of
expensive pulp. Particulate fillers can also be used to impart
other specialized properties besides bulk. For example, particulate
additives can include filler particles, or other particles,
suitable for use papermaking or a final paper product can include
mineral particles such as calcium carbonate, dolomite, calcium
sulfate, kaolin, talc, titanium dioxide, silica, aluminum
hydroxide, and the like. Particles can be formed from inorganic or
organic materials, and may be solid or porous. Organic particles
may be polymeric, optionally crosslinked, and may be elastomeric. A
wide variety of particles known in the art can be incorporated into
the finished paper product to improve performance attributes such
as brightness, opacity, smoothness, ink receptivity, fire
retardance, water resistance, bulk, and the like.
[0005] Precipitated Calcium Carbonate (PCC) is particularly useful
as a particulate filler additive where high opacity, brightness and
maintenance of caliper are required. Higher PCC contents replace
expensive pulp improving the profitability of paper. Although PCC
contents as high as 15% are often used in papermaking, the first
pass retention of the filler is poor, so that a significant amount
can be lost from the paper product during the papermaking process.
The PCC that is incorporated into the paper product also leads to
weaker sheets, because the particles themselves disrupt the
hydrogen bonding between cellulose fibers. Higher ash content
(>15%) is highly desired in the paper industry, where ash
content indicates the amount of filler in a paper.
[0006] In another embodiment, TiO2 particles are highly desired as
particulate fillers to improve the opacity and brightness beyond
what is achievable using PCC. The TiO2 particles due to their small
size and high refractive index are capable of scattering light and
improving the opacity of the paper containing them. As the TiO2
particles are many times more expensive than PCC, improvement in
retention is highly desired. Although flocculants can be used to
improve the retention of TiO2, the flocculated TiO2 particles do
not possess the same optical properties as the individual TiO2
platelets. It would be advantageous to combine TiO2 particles with
other particles to form a composite that separates individual TiO2
particles and allows them to retain their optical
characteristics.
[0007] Other particulate fillers can be added to the paper product
to impart specific, desirable properties. As an example, magnetic
or paramagnetic particles can be incorporated into the paper to
form a magnetic or a magnetizable paper. As another example,
colloidal silver particles can be introduced into a paper product
to impart antimicrobial properties. A large number of additives can
be contemplated that are available in particulate form, including
additives that impart oil or grease resistance, optical
brightening, ink binding, dust control, water repellency,
stiffness, biocidal properties, bioactive properties (e.g., a
biomolecule for controlled release), adhesive properties,
diagnostic sensing, filtration assist, targeted
capture/sequestration, and the like. For particulate additives,
proper distribution within the paper matrix is important. For
particulate additives that are expensive, proper retention is also
important. And with the addition of any additive, its impact on the
strength, stiffness and bulk of the final paper product must be
considered.
[0008] A variety of other additives can be used to impart desirable
properties to paper products, but face some of the same challenges:
retention, distribution and impact on paper quality. Some other
additives used presently to impart various functionalities to paper
include synthetic fibers (imparting strength and hydrophobicity and
absorbency characteristics), latex colloids (imparting properties
such as hydrophobicity, oil and grease resistance, mold resistance,
fire retardancy, impact resistance), etc. These components have
poor affinity to pulp fibers, though, owing to lack of functional
groups capable of interacting with cellulose fibers. As an example,
latex colloids are particularly useful for imparting resilience,
barrier properties, bulk, impact resistance, damping, and the like.
Latex particles that are micron or submicron sized (typically 100
nm particles) suspended in an aqueous solution are particularly
suited for use in papermaking. However, latex is typically
water-insoluble, and can be integrated only with great difficulty
into an aqueous process like papermaking.
[0009] It is desirable, therefore, to have a process where an
additive capable of delivering added functionality can be mixed
with pulp fibers in the wet-end of papermaking such that the
additive becomes an integral part of it. It is desirable that such
additives be distributed evenly and appropriately within the paper
matrix, and that the additives be retained on the product and not
lost in the whitewater. It is further desirable to introduce such
additives so that they preserve the strength and resiliency of the
final paper product.
[0010] As an example, there exists a particular need in the art for
systems and methods that incorporate and retain colloidal latex
particles in the wet end so that high amounts of these fillers are
dispersed uniformly in the paper providing paper with desired
functionalities. These colloidal latex fillers should, desirably,
be incorporated so that they are stably anchored to the pulp
fibers, allowing them to expand or gelatinize during paper
manufacturing without being dislodged. In this manner, the fillers
can occupy the interstitial spaces between cellulose fibers more
completely, improving the properties of the paper product.
Furthermore, it is known that high filler content has a detrimental
effect on the strength of the wet web before it is dried because
the fillers act as spacers and interfere with fiber-fiber bonding.
An efficient retention system that attaches the latex fillers to
fibers durably in the wet web can advantageously enhance wet web
strength during processing by allowing fiber-fiber bonding to
proceed unimpeded.
SUMMARY
[0011] Disclosed herein in embodiments systems for papermaking,
comprising a first population of fibers dispersed in an aqueous
solution and complexed with an activator, and a second population
of composite additive particles bearing a tethering material,
wherein the addition of the second population to the first
population attaches the composite additive particles to the fibers
by the interaction of the activator and the tethering material. In
embodiments, the first population comprises cellulosic fibers. In
embodiments, the first population comprises synthetic fibers. In
embodiments, the composite additive particles comprise a particle
selected from the group of a PCC particle, a TiO2 particle, a
magnetic particle, and a silver colloid particle. In embodiments,
the composite additive particles comprise a latex component and a
starch component. Further disclosed herein are oil and/or grease
resistant paper products comprising the system as described above,
wherein the composite additive particles comprise a hydrophobic
starch, and an oil and/or grease-resistant coating.
[0012] Also disclosed herein, in embodiments, are methods for
manufacturing a paper product, comprising activating a first
population of fibers in a liquid medium with an activator, forming
a second population of composite additive particles, treating the
second population with a tethering material to form tether-bearing
composite additive particles, wherein the tethering material is
capable of interacting with the activator, adding the second
population to the activated population of fibers to form a treated
paper matrix, and forming the paper matrix to manufacture the paper
product. In embodiments, the first population comprises cellulosic
fibers. In embodiments, the first population comprises synthetic
fibers. In embodiments, the composite additive particles comprise a
particle selected from the group of a PCC particle, a TiO2
particle, a magnetic particle, and a silver colloid particle. In
embodiments, the composite additive particles comprise a latex
component and a starch component. In other embodiments, the methods
further comprise adding an oil and/or grease resistant coating to
the paper matrix, wherein the paper matrix comprises tether-bearing
composite additive particles that comprise a hydrophobic
starch.
BRIEF DESCRIPTION OF THE FIGURES
[0013] FIG. 1 shows a photograph of samples of latex and cationic
starch in water.
[0014] FIG. 2 shows a graph of normalized load for pulp controls
vs. experimental preparations.
[0015] FIG. 3 shows a table indicating hydrophobicity for various
samples.
[0016] FIG. 4 shows a graph of normalized load for pulp controls
vs. experimental preparations.
[0017] FIG. 5 shows a table indicating hydrophobicity for various
samples.
[0018] FIG. 6 shows a graph of normalized load for pulp controls
vs. experimental preparations.
[0019] FIG. 7 shows a table indicating hydrophobicity for various
samples.
[0020] FIG. 8 shows a graph of normalized load for pulp plus
additive controls vs. experimental preparations.
[0021] FIG. 9 shows a flow chart for a papermaking process.
DETAILED DESCRIPTION
[0022] Disclosed herein are systems and methods for attaching
additives to cellulose fibers in a paper product. In embodiments,
the additives are combined to form composite particles, and the
composite particles are attached to the cellulose fibers. Composite
particles can be formed by attaching two or more additives to each
other; the composite particles can then be attached to the
cellulose fibers. Three steps can be performed to effect the
attachment of composite particle to cellulose fibers. In one step,
the cellulose fibers are modified by the attachment of an agent,
called an "activating agent" or "activator" that prepares the
surface of the fibers for attachment to a suitably-modified
composite particle. In another step, the composite particle is
formed as will be described in more detail below. The composite
particle is then modified by attaching a tethering agent to the
particle, where the tethering agent has a particular affinity for
the activating agent attached to the paper fibers. The
tether-bearing composite additive particles are then admixed with
the activated fibers, so that the activating agent and the
tethering agents interact: this interaction durably affixes the
composite additive particles bearing the tethers to the fibers
bearing the activators. In embodiments, the cellulose fibers can be
treated with a cationic polymer of a specific molecular weight and
composition as an activator, and the composite additive particles
are treated with an anionic polymer as a tethering agent; these
separately-treated populations are then combined so that the
composite additive particles are attached to the pulp fibers. In
embodiments, the combination of these processes can be referred to
as an "Anchor-Tether-Activator," or "ATA" system. In this system,
the cellulose fibers are treated with the activator, as will be
described below in more detail; the composite additive particle
acts as an "anchor particle" that is treated with the tethering
agent. The tether-bearing anchor particles, when mixed with the
activated cellulose fibers, become attached thereto, so that the
composite additive particles become durably affixed to the
cellulose and appropriately distributed throughout the cellulose
matrix.
[0023] In embodiments, the tethering agent also acts to attach the
component additives to each other to form a composite additive
particle. This use of the tethering agent can allow the creation of
composite particles from components that have no intrinsic
attraction to each other. For example, PCC and TiO2 can be combined
to form a composite additive particle using the tethering agent as
a "glue" to hold the components together as a composite. Or, for
example, TiO2 can be combined with another additive, such as clay,
to form a composite additive particle, using the tether as a "glue"
to hold the composite together. The composite additive particle,
thus treated with the tethering agent, forms a tether-bearing
composite particle that is affixable to the activator-treated
cellulose fibers in the anchor-tether-activator system as described
herein.
[0024] In embodiments, the components of the composite additive
particle can be attached to each other intrinsically. In one
embodiment, for example, starch granules and PCC particles can be
mixed together physically to form a composite particle slurry. PCC
is slightly cationic at the pH used for papermaking, which makes it
easier to bond with anionic starch granules. With neutral or
uncharged starch granules, PCC can be mixed at high shear to form a
composite additive particle slurry that can then be modified with
tethering agent.
[0025] As another example, colloidal latex particles can interact
electrostatically with granular starch of opposite charge resulting
in a composite latex/starch additive particle. The composite
latex-starch additive particle can then be treated with a tethering
agent as described herein, and affixed to the activated cellulose
fibers. When prepared and deployed in accordance with these systems
and methods, such a composite latex/starch additive can then used
as functional additive with appropriate chemistry to improve
bonding and retention in the pulp in the wet-end of papermaking. In
embodiments, the granular starch particles can be used to deliver
the latex into the papermaking web so that they are distributed
throughout the fibrous matrix. Attached to the starch granules by
electrostatic attraction, the latex particles then become embedded
uniformly in the fibrous web. As the starch granules gelatinize
during the papermaking process, they further spread the attached
latex particles throughout the paper and onto the surface of the
paper. These latex particles, depending on their melting or
softening point, may then be advantageously incorporated in the
final paper product, for example, forming a film in the paper
during the paper drying process or otherwise imparting desirable
latex properties to the final paper product.
[0026] In embodiments, latex polymers are selected that are
oppositely charged from the starch granule that is selected to form
the composite. Thus, latex/starch composites are formed and
stabilized by electrostatic forces. As used herein, the term
"latex" refers to a lyophobic colloidal suspension of a synthetic
polymer in a liquid phase which is produced by a polymerization
reaction ex vivo. The term "latex polymer" or "latex particle"
refer to the polymeric material suspended in such a colloidal
suspension. Examples of latex polymers or particles include
styrene-butadiene rubber, acrylonitrile butadiene styrene, acrylic
polymers, polyvinyl acetate polymers, and the like.
[0027] For the uses as disclosed herein, a suitable latex can be
chosen from a wide variety of polymers. Some species of latex are
inert polymers (Polyvinylacetate) while some are reactive (acrylic
based), capable of flowing and crosslinking in the high temperature
encountered in the drying section of paper making. Latex can also
be selected according to the properties of its component polymers.
For example, a useful latex can be comprised of glassy polymers
such as polystyrene when stiffness is required, or rubbery polymers
such as styrene-butadiene copolymers, when flexibility is required.
In embodiments, a cationic latex is used that can be combined with
a negatively charged starch particle.
[0028] Composite starch-latex additive particles as described
herein can then be attached to the fibrous matrix formed by the
papermaking process. The composite starch-latex particles, however,
lack strong affinity to the natural and/or synthetic fibers used to
form the paper web. Hence, additional steps as disclosed herein can
be performed to attach the composite starch-latex particles to the
fibrous web.
[0029] In embodiments, three steps as described previously can be
performed to effect this attachment. In one step, the fibers are
modified by the attachment of an agent, called an "activating
agent," that prepares the surface of the fibers for attachment to a
suitably-modified composite starch-latex particle. In another step,
the starch-latex particle is modified by attaching a tethering
agent to the particle, where the tethering agent has a particular
affinity for the activating agent attached to the paper fibers. The
tether-bearing starch-latex particles are then admixed with the
activated fibers, so that the activating agent and the tethering
agents interact: this interaction durably affixes the composite
particles bearing the tethers to the fibers bearing the activators.
In embodiments, these systems and methods can be used to treat
fibers used in papermaking with a cationic polymer of a specific
molecular weight and composition as an activator, to treat
composite starch-latex granules with an anionic polymer as a
tethering agent, and to combine these separately-treated
populations so that the starch granules are attached to the pulp
fibers.
1. Activation
[0030] As used herein, the term "activation" refers to the
interaction of an activating material, such as a polymer, with
suspended particles or fibers in a liquid medium, such as an
aqueous solution. An "activator," for example an "activator
polymer," can carry out this activation. In embodiments, high
molecular weight polymers can be introduced into the particulate or
fibrous dispersion as activator polymers, so that these polymers
interact, or complex, with the dispersed particles or fibers. The
polymer-fiber complexes interact with other similar complexes, or
with other fibers, and form agglomerates.
[0031] This "activation" step can function as a pretreatment to
prepare the surface of the suspended material (e.g., fibers) for
further interactions in the subsequent phases of the disclosed
system and methods. For example, the activation step can prepare
the surface of the suspended materials to interact with other
polymers that have been rationally designed to interact therewith
in a subsequent "tethering" step, as described below. Not to be
bound by theory, it is believed that when the suspended materials
(e.g., fibers) are coated by an activating material such as a
polymer, these coated materials can adopt some of the surface
properties of the polymer or other coating. This altered surface
character in itself can be advantageous for retention, attachment
and/or dewatering.
[0032] In another embodiment, activation can be accomplished by
chemical modification of the suspended material. For example,
oxidants or bases/alkalis can increase the negative surface energy
of fibers or particles, and acids can decrease the negative surface
energy or even induce a positive surface energy on suspended
material. In another embodiment, electrochemical oxidation or
reduction processes can be used to affect the surface charge on the
suspended materials. These chemical modifications can produce
activated particulates that have a higher affinity for tethered
anchor particles as described below.
[0033] Suspended materials suitable for modification, or
activation, can include organic or inorganic particles, or mixtures
thereof. Inorganic particles can include one or more materials such
as calcium carbonate, dolomite, calcium sulfate, kaolin, talc,
titanium dioxide, sand, diatomaceous earth, aluminum hydroxide,
silica, other metal oxides and the like. Organic particles can
include one or more materials such as starch, modified starch,
polymeric spheres (both solid and hollow), carbon based
nanoparticles such as carbon nanotubes and the like. Particle sizes
can range from a few nanometers to few hundred microns. In certain
embodiments, macroscopic particles in the millimeter range may be
suitable.
[0034] In embodiments, suspended materials may comprise materials
such as lignocellulosic material, cellulosic material, minerals,
vitreous material, cementitious material, carbonaceous material,
plastics, elastomeric materials, and the like. In embodiments,
cellulosic and lignocellulosic materials may include wood materials
such as wood flakes, wood fibers, wood waste material, wood powder,
lignins, wood pulp, or fibers from woody plants.
[0035] The "activation" step may be performed using flocculants or
other polymeric substances. Preferably, the polymers or flocculants
can be charged, including anionic or cationic polymers.
[0036] In embodiments, anionic polymers can be used, including, for
example, olefinic polymers, such as polymers made from
polyacrylate, polymethacrylate, partially hydrolyzed
polyacrylamide, and salts, esters and copolymers thereof, such as
sodium acrylate/acrylamide copolymers, sulfonated polymers, such as
sulfonated polystyrene, and salts, esters and copolymers thereof.
Suitable polycations include: polyvinylamines, polyallylamines,
polydiallyldimethylammoniums (e.g., the chloride salt), branched or
linear polyethyleneimine, crosslinked amines (including
epichlorohydrin/dimethylamine, and
epichlorohydrin/alkylenediamines), quaternary ammonium substituted
polymers, such as (acrylamide/dimethylaminoethylacrylate methyl
chloride quat) copolymers and
trimethylammoniummethylene-substituted polystyrene, and the like.
Nonionic polymers suitable for hydrogen bonding interactions can
include polyethylene oxide, polypropylene oxide,
polyhydroxyethylacrylate, polyhydroxyethylmethacrylate, and the
like. In embodiments, an activator such as polyethylene oxide can
be used as an activator with a cationic tethering material in
accordance with the description of tethering materials below. In
embodiments, activator polymers with hydrophobic modifications can
be used. Flocculants such as those sold under the trademark
MAGNAFLOC.RTM. by Ciba Specialty Chemicals can be used.
[0037] In embodiments, activators such as polymers or copolymers
containing carboxylate, sulfonate, phosphonate, or hydroxamate
groups can be used. These groups can be incorporated in the polymer
as manufactured. Alternatively they can be produced by
neutralization of the corresponding acid groups, or generated by
hydrolysis of a precursor such as an ester, amide, anhydride, or
nitrile group. The neutralization or hydrolysis step could be done
on site prior to the point of use, or it could occur in situ in the
process stream.
[0038] The activated suspended material (e.g., fiber) can also be
an amine functionalized or modified. As used herein, the term
"modified material" can include any material that has been modified
by the attachment of one or more amine functional groups as
described herein. The functional group on the surface of the
suspended material can be from modification using a multifunctional
coupling agent or a polymer. The multifunctional coupling agent can
be an amino silane coupling agent as an example. These molecules
can bond to a material's surface and then present their amine group
for interaction with the particulate matter. In the case of a
polymer, the polymer on the surface of a suspended fiber or
particle can be covalently bound to the surface or interact with
the surface of the particle and/or fiber using any number of other
forces such as electrostatic, hydrophobic, or hydrogen bonding
interactions. In the case that the polymer is covalently bound to
the surface, a multifunctional coupling agent can be used such as a
silane coupling agent. Suitable coupling agents include isocyano
silanes and epoxy silanes as examples. A polyamine can then react
with an isocyano silane or epoxy silane for example. Polyamines
include polyallyl amine, polyvinyl amine, chitosan, and
polyethylenimine.
[0039] In embodiments, polyamines (polymers containing primary,
secondary, tertiary, and/or quaternary amines) can also
self-assemble onto the surface of the suspended particles or fibers
to functionalize them without the need of a coupling agent. For
example, polyamines can self-assemble onto the surface of the
particles or fibers through electrostatic interactions. They can
also be precipitated onto the surface in the case of chitosan for
example. Since chitosan is soluble in acidic aqueous conditions, it
can be precipitated onto the surface of suspended material by
adding a chitosan solution to the suspended material at a low pH
and then raising the solution pH.
[0040] In embodiments, the amines or a majority of amines are
charged. Some polyamines, such as quarternary amines are fully
charged regardless of the pH. Other amines can be charged or
uncharged depending on the environment. The polyamines can be
charged after addition onto the suspended particles or fibers by
treating them with an acid solution to protonate the amines. In
embodiments, the acid solution can be non-aqueous to prevent the
polyamine from going back into solution in the case where it is not
covalently attached to the particle or fiber.
[0041] The polymers or particles can complex via forming one or
more ionic bonds, covalent bonds, hydrogen bonding and combinations
thereof, for example. Ionic complexing is preferred.
[0042] To obtain activated suspended materials, the activator could
be introduced into a liquid medium through several different means.
For example, a large mixing tank could be used to mix an activating
material with fine particulate materials. Activated particles or
fibers are produced that can be treated with one or more subsequent
steps of attachment to tether-bearing anchor particles.
2. Tethering
[0043] As used herein, the term "tethering" refers to an
interaction between an activated suspended particle or fiber and an
additive particle, herein termed an anchor particle (as described
below). The additive particle, for example, a composite additive
particle, ("anchor particle") can be treated or coated with a
tethering material. The tethering material, such as a polymer,
forms a complex or coating on the surface of the anchor particles
such that the tethered anchor particles have an affinity for the
activated suspended material. In embodiments, the selection of
tether and activator materials is intended to make the two solids
streams complementary so that the activated particles or fibers in
the suspension become tethered, linked or otherwise attached to the
anchor particle.
[0044] In accordance with these systems and methods, the tethering
material acts as a complexing agent to affix the activated
particles or fibers to the additive particle anchor material. In
embodiments, a tethering material can be any type of material that
interacts strongly with the activating material and that is
connectable to an anchor particle. Composite latex-starch particles
are an example of an additive particle or anchor particle that can
be treated with a tethering agent.
[0045] In embodiments, various interactions such as electrostatic,
hydrogen bonding or hydrophobic behavior can be used to affix an
activated complex to a tethering material complexed with an anchor
particle.
[0046] For use in papermaking, an anchor particle can be selected
from any particulate matter that is desirably attached to cellulose
fibers in the final paper product. The tether-bearing anchor
particle comprising the desirable additive can then interact with
the activated cellulose fibers in the wet paper stream. As an
example, starch granules can be used as an anchor particle to be
attached to the cellulose fibers, as is described in more detail
below. Or, as described herein, composite latex-starch granules can
be used as anchor particles, to be attached via tethering agents to
activated cellulosic or synthetic fibers.
[0047] In embodiments, polymers such as linear or branched
polyethyleneimine can be used as tethering materials. It would be
understood that other anionic or cationic polymers could be used as
tethering agents, for example polydiallyldimethylammonium chloride
(poly(DADMAC)). In other embodiments, cationic tethering agents
such as epichlorohydrin dimethylamine (epi/DMA), styrene maleic
anhydride imide (SMAI), polyethylene imide (PEI), polyvinylamine,
polyallylamine, amine-aldehyde condensates, poly(dimethylaminoethyl
acrylate methyl chloride quaternary) polymers and the like can be
used. Advantageously, cationic polymers useful as tethering agents
can include quaternary ammonium or phosphonium groups.
Advantageously, polymers with quaternary ammonium groups such as
(poly(DADMAC)) or epi/DMA can be used as tethering agents. In other
embodiments, polyvalent metal salts (e.g., calcium, magnesium,
aluminum, iron salts, and the like) can be used as tethering
agents. In other embodiments cationic surfactants such as
dimethyldialkyl(C8-C22)ammonium halides,
alkyl(C8-C22)trimethylammonium halides,
alkyl(C8-C22)dimethylbenzylammonium halides, cetyl pyridinium
chloride, fatty amines, protonated or quaternized fatty amines,
fatty amides and alkyl phosphonium compounds can be used as
tethering agents. In embodiments, polymers having hydrophobic
modifications can be used as tethering agents.
[0048] The efficacy of a tethering material, however, can depend on
the activating material. A high affinity between the tethering
material and the activating material can lead to a strong and/or
rapid interaction there between. A suitable choice for tether
material is one that can remain bound to the anchor surface, but
can impart surface properties that are beneficial to a strong
complex formation with the activator polymer. For example, a
polyanionic activator can be matched with a polycationic tether
material or a polycationic activator can be matched with a
polyanionic tether material. In one embodiment, a poly(sodium
acrylate-co-acrylamide) activator is matched with a chitosan tether
material.
[0049] In hydrogen bonding terms, a hydrogen bond donor should be
used in conjunction with a hydrogen bond acceptor. In embodiments,
the tether material can be complementary to the chosen activator,
and both materials can possess a strong affinity to their
respective deposition surfaces while retaining this surface
property.
[0050] In other embodiments, cationic-anionic interactions can be
arranged between activated suspended materials and tether-bearing
anchor particles. The activator may be a cationic or an anionic
material, as long as it has an affinity for the suspended material
to which it attaches. The complementary tethering material can be
selected to have affinity for the specific anchor particles being
used in the system. In other embodiments, hydrophobic interactions
can be employed in the activation-tethering system.
3. Retention and Incorporation in Papermaking
[0051] It is envisioned that the complexes formed from the additive
or composite additive ("anchor") particles and the activated
fibrous matter can form a homogeneous part of a fibrous product
like paper. In embodiments, the interactions between the activated
suspended fibers and the tether-bearing anchor particles can
enhance the mechanical properties of the complex that they form.
For example, an activated suspended material can be durably bound
to one or more tether-bearing anchor particles, so that the
tether-bearing anchor particles do not segregate or move from their
position on the fibers. Increased compatibility of the activated
fine materials with a denser (anchor) matrix modified with the
appropriate tether polymer can lead to further mechanical stability
of the resulting composite material. For example, using
latex-starch composites as tether-bearing anchor particles permits
the latex to attach durably to the paper fibers; the gelatinization
of the starch combined with the melting of the latex allows the
flowable latex to permeate the paper fibers and impart desirable
properties thereto.
[0052] For papermaking, cationic and anionic polymers for
activators and tethering agents (respectively) can be selected from
a wide variety of available polymers, as described above. In
embodiments, starch granules used to form starch-latex composites
can be used in their native state, or they can be modified with
short amine side-groups, with amine polymers, or with hydrophobic
side groups (each a "modified starch"). The presence of amines on
the surface of the starch granules can help in attaching an anionic
tethering polymer.
[0053] For activating the cellulose fibers, cationic polymers can
be used. The polycation can be linked to the fiber surface using a
coupling agent, for example a bifunctional crosslinking agent such
as a carbonyldiimidazole or a silane, or the polyamine can
self-assemble onto the surface of the cellulose fiber through
electrostatic, hydrogen bonding, or hydrophobic interactions. In
embodiments, the polyamine can spontaneously self-assemble onto the
fiber surface or it can be precipitated onto the surface. For
example, in embodiments, chitosan can be precipitated on the
surface of the cellulose fibers to activate them. Because chitosan
is soluble only in an acidic solution, it can be added to a
cellulose fiber dispersion at an acidic pH, and then can be
precipitated onto the surface of the cellulose fibers by slowly
adding base to the dispersion until chitosan is no longer soluble.
In embodiments, a difunctional crosslinking agent can be used to
attach the polycation to the fiber, by reacting with both the
polycation and the fiber.
[0054] In other embodiments, a polycation such as a polyamine can
be added directly to the fiber dispersion or slurry. For example,
the addition level of the polycation can be between about 0.01% to
5.0% (based on the weight of the fiber), e.g., between 0.1% to 2%.
For example, if the cellulose fiber population is treated with a
polyamine like polyDADMAC, a separately treated population of
tether-bearing starch granules can be mixed in thereafter,
resulting in the attachment of the starch-latex composites to the
cellulose fibers by the interaction of the activator polymer and
the tether polymer. In embodiments, starch-latex composites can be
treated with a variety of anionic polymers, such as anionic
polyacrylamide, which then act as tethers.
[0055] Starch that is to be treated in accordance with these
systems and methods can be further derivatized or coated with
moieties that impart desirable properties, e.g., hydrophobicity,
oleophobicity or both. Starches thus modified may be also termed
"modified starches." Preferred oil resistant coating formulations
are aqueous solutions of cellulose derivatives such as
methylcellulose, ethyl cellulose, propyl cellulose, hydroxypropyl
methyl cellulose, hydroxyethyl methyl cellulose, ethylhydroxypropyl
cellulose, and ethylhydroxyethyl cellulose, cellulose acetate
butyrate, which may further comprise polyvinyl alcohol and/or its
derivatives. Another group of preferred oil resistant coating
compositions are latex emulsions such as the emulsions of
polystyrene, styrene-acrylonitrile copolymer, carboxylated
styrene-butadiene copolymer, ethylene-vinyl chloride copolymer,
styrene-acrylic copolymer, polyvinyl acetate, ethylene-vinyl
acetate copolymer, and vinyl acetate-acrylic copolymer. The starch
granule thus coated with grease resistant formulations could be
attached to the activated pulp fibers via tethering, such that the
surface segregation of the starch granule will modify the surface
of the paper product.
[0056] In embodiments, the presence of hydrophobic starch also
improves the hydrophobicity of the resulting paper without needing
an internal sizing such as alkyl succinic anhydride (ASA), alkyl
ketene dimer (AKD) or Rosin. The gelatinized hydrophobic starch
sizes the entire thickness of the paper. This property is useful in
reducing the coating requirements in making coated sheets. The
coating applied using a roller or a metering bar or any such
methods, would remain on the surface of the paper and not
impregnate the bulk of the paper thus needing less coating to
achieve the same amount of gloss and surface finish.
[0057] In other embodiments, the addition of a coating agent to the
starch can improve its mechanical properties such as bending
stiffness or tensile strength, or could improve its optical
properties (e.g., TiO2 nanoparticles bound to starch).
4. Surface Treatments Combined with Paper Products
[0058] In embodiments, paper products formed in accordance with
these systems and methods can be combined with specific surface
treatments or coating agents to improve desirable properties of the
finished paper sheet. For example, oil and/or grease resistant
(OGR) properties can be imparted into the finished paper sheet by
adding an OGR coating agent to a paper product being formed as
disclosed above.
[0059] OGR coatings are used in a variety of commercial
applications, including paper and board used in food packaging.
Many of these treatments or coatings use fluorinated materials, and
others use high amounts of polyolefins or other plastics. Concerns
by consumers and regulatory agencies are driving the search for
alternative coating materials. In addition to concerns regarding
the safety of fluorinated materials, polyolefins or other plastics
often make the paper non-recyclable, or too brittle to allow
folding or creasing of the treated paper. For these reasons and
others, alternative coating materials can be employed that
withstand the penetration of oil or grease, while being acceptable
to a wider base of consumers. It is desirable that this OGR coating
be aqueous-based for use in certain papermaking processes. The
coating process using aqueous solutions is often performed using
size presses, roll presses, etc., which force the aqueous coating
material through the paper substrate. Presently, the coating
material has to penetrate the entire paper sheet to achieve a
satisfactory coating. Therefore, more coating solution is required
than would be needed if the solution just remained on the surface.
Saturating the paper sheet with the coating solution also requires
a prolonged drying period for the paper sheet. A number of
conventional approaches have been employed to reduce the
penetration of the coating solution into the paper web, but these
have various drawbacks.
[0060] Hydrophobic starches, whether gelatinized or ungelatinized,
have been used to increase the water holdout of the paper product,
thereby reducing the ingress of the aqueous coating solution. The
retention of these materials on the paper web is typically poor,
though, with non-uniform dispersion on the cellulose fibers. This
results in a paper product that can have undesirable mechanical
and/or surface properties, along with poor water holdout. In
addition, the poor retention leads to a large amount of starch
being lost in the whitewater effluent instead of sticking to the
paper web. This whitewater contamination has deleterious
environmental effects.
[0061] Attachment of hydrophobic starches to the paper web as
described herein produces good retention of the hydrophobic
starches on the cellulose fibers, with markedly less starch loss as
compared to conventional techniques. The even and durable
distribution of the hydrophobic starch within the paper product
results in uniform physical and mechanical properties. The presence
of the hydrophobic starch throughout the interior of the paper
product also resists the incursion of the aqueous OGR coating.
Thus, the OGR coating stays on the surface, so that a smaller
amount of coating material is required to produce OGR properties in
the paper product. In addition, since the OGR coating does not
penetrate the paper matrix, it is easier to dry than conventional
OGR products where the coating saturates the entire cellulosic web.
Use of the systems and methods disclosed herein for hydrophobic
starch attachment can result in more efficient and cost-effective
production of OGR specialty paper products that retain advantageous
physical and mechanical properties.
[0062] OGR agents suitable for these applications include, for
example: polyvinyl alcohol, polyvinyl acetate, acrylic emulsions,
emulsions of polyethylene or polyolefins, cellulose esters, such as
cellulose acetate, celluloseacetatae butyrate, cellulose
propionate, carboxy methyl cellulose acetate butyrate and cellulose
ethers such as methyl cellulose, ethyl cellulose, hydroxypropyl
methylcellulose, and the like.
[0063] In embodiments, the OGR agent would be added to the
papermaking process inline in a size press or offline using either
a size press or a doctor blade or flexo press or other gravure roll
application processes. An illustrative flowchart for adding
hydrophobic starch according to the previously described systems
and methods is set forth in FIG. 9.
[0064] In certain embodiments, an OGR agent can be combined with
another agent to impart further desirable properties to the surface
of the paper sheet. For example, an OGR agent can be combined with
fillers such as calcium carbonate, clay, silica, or various
functional additives (e.g., food additives including antioxidants).
In one embodiment, an exfoliated clay additive can be combined with
the OGR agent, or added separately during the papermaking process.
The exfoliated clay additive can be prepared in various ways as
would be understood by those of ordinary skill in the art. For
example, a formulation comprising exfoliated clay can be prepared
by combining an acrylic emulsion and polyethylene glycol diglycidyl
ether as a plasticizer with an exfoliated clay suspension in water,
mixing them under sonication or vigorous stirring. The same
formulation can also be made without the clay just by mixing the
acrylic emulsion with the plasticizer to yield flexible oil and
grease resistant films on paper surface when combined with the
systems and methods for hydrophobic starch attachment as set forth
above.
[0065] A sheet prepared in accordance with these systems and
methods can display advantageous properties such as oil resistance,
for example oil resistance when measured in terms of 3M kit test or
ANSI test or a boat test. In addition, the process for
manufacturing such a paper product would have further advantages.
such as requiring less OGR formulation to achieve a given degree of
oil resistance (as measured for example by 3M kit score or ANSI
score), faster post size-press drying owing to lower moisture
absorption within the interior of the paper.
EXAMPLES
[0066] Materials
[0067] Market softwood and hardwood pulp
[0068] Recycled brown pulp
[0069] Poly(diallyldimethylammonium chloride), Hi Molecular Weight,
20 wt % in water (polyDADMAC), Sigma-Aldrich, St. Louis, Mo.
[0070] MagnaFloc 919, Ciba Specialty Chemicals Corporation,
Suffolk, Va.
[0071] STA-LOK 300 Starch, Tate & Lyle, Decatur, Ill. (cationic
starch)
[0072] COSEAL 30061A Anionic Latex, Rohm & Haas, Philedelphia,
Pa.
[0073] ChitoClear Chitosan CG-10, Primex, Siglufjordur, Iceland
[0074] Polyethylene fibers PEFYB-00620, MiniFibers, Inc., Johnson
City, Tenn.
[0075] Modified Polyethylene fibers PEFYB-ONL490, MiniFibers, Inc.,
Johnson City, Tenn.
[0076] Polypropylene fibers ("PP"), PEFYB-00Y600, MiniFibers, Inc.,
Johnson City, Tenn.
[0077] PES/Nylon pie wedge bicomponent cut fibers
[0078] Precipitated Calcium Carbonate (PCC), Sigma-Aldrich, St.
Louis, Mo.
[0079] Douglas Pearl Starch (unmodified corn starch), Penford
Products, Cedar Rapids, Iowa
[0080] Iron (III) Oxide, <5 um, 99.9%, Sigma-Aldrich, St. Louis,
Mo.
[0081] Hydrophobic starch Gum 270 Ethylated Starch (Penford
Products, Centennial, Colo.)
[0082] Acrylic resin--Michelman (Cincinnati, Ohio) Micryl 766R
[0083] Poly(propylene glycol), diglycidyl ether--Sigma Aldrich (St.
Louis, Mo.) 406740
[0084] BASF Montmorillonite Clay--F100
[0085] Aldrich Montmorillonite clay
[0086] Sodium phosphate, monobasic dehydrate
[0087] Sodium hydroxideDeionized water
Example 1
Control Virgin Pulp
[0088] A 0.5% slurry was prepared by blending 3.5% by weight
softwood and hardwood pulp mixture (in the ratio of 20:80) in
water.
Example 2
Control Recycled Pulp
[0089] A 0.5% slurry was prepared by blending 22.5% recycled brown
pulp in water.
Example 3
Handsheet Preparation
[0090] Handsheets were prepared using a Mark V Dynamic Paper
Chemistry Jar and Hand-Sheet Mold from Paper Chemistry Laboratory,
Inc. (Larchmont, N.Y.). Handsheets were prepared without addition
of polymers as controls, using the pulps prepared as described in
Example 1 and 2. Handsheets were prepared with the addition of
polymers as experimental samples, as described below.
[0091] For preparing each experimental handsheet, the appropriate
volume of 0.5% pulp slurry prepared in accordance with Examples 1
or 2 (as applicable) was activated with up to 2% of the selected
polymer(s) (based on dry weight), as described below in more
detail. Polymer additions were performed at 5 minute intervals.
This polymer-containing slurry was diluted with up to 3 L of water
and added to the handsheet maker, where it was mixed at a rate of
1100 RPM for 5 seconds, 700 RPM for 5 seconds, and 400 RPM for 5
seconds. The water was then drained off. The subsequent sheet was
then transferred off of the wire, pressed and dried.
[0092] For preparing sheets containing low melting point synthetic
fibers PEFYB-00620, PEFYB-0NL490, PEFYB-00Y600, as described below
in Example 9, the sheets were dried as described above and then
heated further to ensure melting of the synthetic fibers.
Example 4
Tensile Test
[0093] Tensile tests were conducted on control and experimental
samples using an Instron 3343. Samples of handsheets for tensile
testing were initially cut into 1 in wide strips with a paper
cutter, and then attached within the Instron 3343. The gauge length
region was set at 4 in and the crosshead speed was 1 in/minute.
Thickness was measured to provide stress data as was the weight to
be able to normalize the data by weight of samples. The strips were
tested to failure with an appropriate load cell. At least three
strips from each control or experimental handsheet sample were
tested and the values were averaged together.
Example 5
Preparation Of Latex-Coated Starch
[0094] StaLok 300 cationic starch was dispersed in water in slurry
form such that the solids content was about 20%. COSEAL 30061A
anionic latex was added to the cationic starch, up to 50% by weight
of starch. The latex is spontaneously self-assembled on the starch
surface resulting in a clear solution when the starch settles down.
By contrast, the latex solution without starch remains milky white,
as shown in FIG. 1.
Example 6
Preparation Of Latex-Coated Starch with Tether
[0095] StaLok 300 cationic starch was dispersed in water in slurry
form such that the solids content was about 20%. COSEAL 30061A
anionic latex was added to the cationic starch, up to 50% by weight
of starch. MagnaFloc 919 was then added 0.1% by weight as a
tethering agent.
Example 7
Process for Preparing Handsheets from Activated Pulp and
Latex-Coated Starch (with and without Tether)
[0096] 800 mL of a 0.5% pulp slurry prepared in accordance with
Example 1 or 2 (as applicable) was initially provided. The pulp
slurry was activated with 0.1% by fiber weight polyDADMAC.
Separately, tethered cationic starch granules were prepared as a
slurry in accordance with Example 5 and 6. Each slurry was mixed
for 5 minutes and then combined and mixed for another 5 minutes
using an overhead stirrer. Handsheets were then produced by the
method in Example 3. The final basis weight was approximately 80
gsm for these handsheets.
Example 8
Preparation of Synthetic Fibers with and Without Tether
[0097] PEFYB-00620, PEFYB-0NL490, PEFYB-00Y600, and PES/Nylon
Bicomponent Fibers (and mixtures of two or more of the previous)
were dispersed in water in slurry form such that the solids content
was about 20%. In samples containing a tether, MagnaFloc 919 was
then added 0.1% by weight as a tethering agent.
Example 9
Process for Preparing Handsheets from Activated Pulp and Tethered
Synthetic Fibers
[0098] 800 mL of a 0.5% pulp slurry prepared in accordance with
Example 1 or 2 (as applicable) was initially provided. The pulp
slurry was activated with 0.1% by fiber weight polyDADMAC.
Separately, synthetic fibers and tethered synthetic fibers were
prepared as a slurry in accordance with Example 8. Each slurry was
mixed for 5 minutes and then combined and mixed for another 5
minutes using an overhead stirrer. Handsheets were then produced by
the method in Example 3. The final basis weight was approximately
80 gsm for these handsheets.
Example 10
Preparation of Chitosan Solution
[0099] CG-10 was added to water to make a 1% by weight slurry of
chitosan. Strong acid was added dropwise to the slurry with
stirring until the solution reached a pH of 2.5 and the chitosan
was dissolved.
Example 11
Preparation of Coated Synthetic Fibers with Chitosan
[0100] PEFYB-00620, PEFYB-0NL490, PEFYB-00Y600, and PES/Nylon
Bicomponent Fibers (and mixtures of two or more of the previous)
were dispersed in water in slurry form such that the solids content
was about 20%. A strong acid was then added to the slurry to bring
the pH below 2.5. The solution in Example 9 was added to the
synthetic fiber slurry so that the chitosan was 1% by weight of the
synthetic fibers. The pH was then raised back to 8-9 with a strong
base to precipitate any unbound chitosan.
Example 12
Process for Preparing Handsheets from Pulp and Chitosan-Coated
Synthetic Fibers
[0101] 800 mL of a 0.5% pulp slurry prepared in accordance with
Example 1 or 2 (as applicable) was initially provided. Separately,
tethered synthetic fibers were prepared as a slurry in accordance
with Example 10. Each slurry was mixed for 5 minutes and then
combined and mixed for another 5 minutes using an overhead stirrer.
Handsheets were then produced by the method in Example 3. The final
basis weight was approximately 80 gsm for these handsheets.
Example 13
The Effect of Latex-Coated Starch on Strength and
Hydrophobicity
[0102] Samples were prepared as in Example 7, where the amount of
latex-coated and latex-coated tether-bearing starch (StaLok 300)
was 4.25% of the solids weight. The latex-coated starch had been
coated with COSEAL 30061A in accordance with Example 5. The
tether-bearing latex-coated starch had been coated with
COSEAL30061A and then tethered with MagnaFloc 919 in accordance
with Example 6. Samples were made with activator and tether,
without either activator or tether, and with activator alone. For
ATA-treated samples, the tether used on the starch was 0.1%
MagnaFloc 919 by solids and the activator on the pulp was 0.1%
polyDADMAC by solids. The max load for each sample was measured
using an Instron as in Example 4. Data were normalized by the mass
to show load contribution per overall solids weight. Graph 1
(FIG.2) shows the strength data with all of the aforementioned
conditions mentioned in this example. FIG. 2 shows a graph of
normalized max. load examining the effect of pulp with and without
latex-coated starch and with and without the use of ATA. Normalized
loads show that there is no loss or gain in tensile strength with
any of the latex-coated starch conditions (within error).
[0103] The hydrophobicity improvement with the samples above was
also examined. Using handsheet samples prepared as in Example 7,
hydrophobicity was tested by depositing a 25 microliter water
droplet on the surface of the paper and recording the time for the
droplet to completely absorbed by the paper. The results of the
hydrophobicity tests are shown in Table 1 (FIG. 3). These results
demonstrate that the use of the ATA process (and activator-only) to
attach latex-coated starch to pulp fibers improves the water
resistance of the paper by up to 14,500% compared to control
samples having no added latex-coated starch. FIG. 3 shows a table
of normalized water droplet holdout examining the effect of pulp
with and without latex-coated starch and with and without the use
of ATA. Water droplet holdout times show that there is up to a
145.times. gain in droplet holdout time with the use of
latex-coated starch and pulp activator only.
Example 14
The Effect of Tethered Synthetic Fibers on Strength and
Hydrophobicity
[0104] Samples were prepared as in Example 9, where the amount of
tether-bearing synthetic fibers were a total of 15% of the solids
weight. The tether-bearing synthetic fibers had been prepared in
accordance with Example 8. Samples were made both with activator
and tether and without either activator or tether. For ATA-treated
samples, the tether used on the synthetic fibers was 0.1% MagnaFloc
919 by solids and the activator on the pulp was 0.1% polyDADMAC by
solids. The max load for each sample was measured using an Instron
as in Example 4. Data were normalized by the mass to show load
contribution per overall solids weight. Graph 2 (FIG.4) shows the
strength data with all of the aforementioned conditions mentioned
in this example. FIG. 4 shows a graph of normalized max. load
examining the effect of pulp with and without synthetic fibers and
with and without the use of ATA. Normalized loads show that there
is no loss or gain in tensile strength with any of the conditions
(within error). The hydrophobicity improvement with the samples
above was also examined. Using fiber handsheet samples prepared as
in Example 9, hydrophobicity was tested by depositing a 25
microliter water droplet on the surface of the paper and recording
the time for the droplet to completely absorbed by the paper. The
results of the hydrophobicity tests are shown in Table 2 (FIG. 5).
These results demonstrate that the use of synthetic fibers in
combination with pulp fibers improves the water resistance of the
paper by up to 26,600% compared to control samples having no added
synthetic fibers. FIG. 5 shows a table of normalized water droplet
holdout examining the effect of pulp with and without synthetic
fibers and with and without the use of ATA. Water droplet holdout
times show that there is a >266.times. gain in droplet holdout
time with the use of polypropylene fibers under several
conditions.
Example 15
The Effect of Chitosan-Coated Synthetic Fibers on Strength and
Hydrophobicity
[0105] Samples were prepared as in Example 12, where the amount of
chitosan-coated synthetic fibers were a total of 15% of the solids
weight. The chitosan-coated synthetic fibers had been prepared in
accordance with Example 11. The max load for each sample was
measured using an Instron as in Example 4. Data were normalized by
the mass to show load contribution per overall solids weight. Graph
3 (FIG.6) shows the strength data with all of the aforementioned
conditions mentioned in this example. FIG. 6 shows a graph of
normalized max. load examining the effect of pulp with synthetic
fibers with and without the use of chitosan. Normalized loads show
that there is no loss or gain in tensile strength with any of the
conditions (within error).
[0106] The hydrophobicity improvement with the samples above was
also examined. Using recycled fiber handsheet samples prepared as
in Example 12, hydrophobicity was tested by depositing a 25
microliter water droplet on the surface of the paper and recording
the time for the droplet to completely absorbed by the paper. The
results of the hydrophobicity tests are shown in Table 3 (FIG. 7).
These results demonstrate that the use of chitosan-coated synthetic
fibers improves the water resistance of the paper by up to 26,600%
compared to control samples having no synthetic fibers. FIG. 7
shows a table of normalized water droplet holdout examining the
effect of pulp with and without synthetic fibers and with and
without chitosan coating. Water droplet holdout times show that
there is a >266.times. gain in droplet holdout time with the use
of polypropylene fibers coated with chitosan.
Example 16
Control Virgin Pulp (Softwood only)
[0107] A 0.5% slurry was prepared by blending 93% solids content
softwood in water.
Example 17
Preparation of PCC and Pearl Starch with and without Tether
[0108] PCC and Pearl Starch (and mixtures of the two) were
dispersed in water in slurry form such that the solids content was
about 20%. In samples containing a tether, MagnaFloc 919 was then
added 0.05% by weight of solids as a tethering agent.
Example 18
Preparation of a Handsheet with PCC and Pearl Starch
[0109] 600 mL of a 0.5% pulp slurry prepared in accordance with
Example 16 was initially provided. The pulp slurry was activated
with 0.1% by fiber weight polyDADMAC. Separately, starch, PCC, and
tethered starch/PCC were prepared as a slurry in accordance with
Example 17. Each slurry was mixed for 5 minutes and then combined
and mixed for another 5 minutes using an overhead stirrer.
Handsheets were then produced by the method in Example 16. The
final basis weight was approximately 60 gsm for these
handsheets.
Example 19
The Effect of PCC and Pearl Starch on Strength
[0110] Samples were prepared as in Example 18, where the amount of
PCC, Pearl Starch, tether-bearing pearl starch and PCC was between
5% and 30% of the solids weight. The tethered PCC with pearl starch
had been prepared with MagnaFloc 919 in accordance with Example 17.
Samples were made with both activator and tether or with neither
activator nor tether. For ATA-treated samples, the tether used on
the dry-mixed pearl starch and PCC and was 0.05% MagnaFloc 919 by
solids and the activator on the pulp was 0.1% polyDADMAC by solids.
The max load for each sample was measured using an Instron as in
Example 16. Data were normalized by the mass to show load
contribution per overall solids weight. Graph 4 (FIG.8) shows the
strength data with all of the aforementioned conditions mentioned
in this example. As shown in FIG. 8, the ATA treatment improves
retention and reduces the loss of tensile strength at similar
loadings of PCC.
Example 20
Preparation of Iron (III) Oxide with and without Tether
[0111] Iron (III) Oxide particles were dispersed in water in slurry
form such that the solids content was about 20%. In samples
containing a tether, MagnaFloc 919 was then added 0.05% by weight
of solids as a tethering agent.
Example 21
Preparation of a Handsheet with Iron (III) Oxide
[0112] 600 mL of a 0.5% pulp slurry prepared in accordance with
Example 16 was initially provided. The pulp slurry was activated
with 0.1% by fiber weight polyDADMAC. Separately, Iron (III) Oxide
with and without tether were prepared as a slurry in accordance
with Example 20. Each slurry was mixed for 5 minutes and then
combined and mixed for another 5 minutes using an overhead stirrer.
Handsheets were then produced by the method in Example 16. The
final basis weight was approximately 60 gsm for these
handsheets.
Example 22
Analysis of Magnetization of Iron (III) Oxide Handsheets
[0113] 1'' by 2'' pieces of handsheets with iron (III) oxide
prepared in Example 21 were held to a ceramic magnet to verify
holdout of Iron (III) Oxide in the sheet. Sheets containing as
little as 5% Iron (III) oxide by solids weight held onto the magnet
with no other support.
Example 23
Preparation of Hydrophobic Starch with and without Tether
[0114] Hydrophobic starch granules were dispersed in water in
slurry form such that the solids content was about 20%. In samples
containing a tether, MagnaFloc 919 was then added 0.05% by weight
of solids as a tethering agent.
Example 24
Preparation of a Handsheet with Hydrophobic Starch
[0115] 600 mL of a 0.5% pulp slurry prepared in accordance with
Example 16 was initially provided. The pulp slurry was activated
with 0.1% by fiber weight polyDADMAC. Separately, hydrophobic
starch and tethered hydrophobic starch were prepared as a slurry,
with the tethered samples prepared by adding MagnaFloc 919 at 0.05%
by weight of solids as a tethering agent. Each slurry was mixed for
5 minutes and then combined and mixed for another 5 minutes using
an overhead stirrer. Handsheets were then produced by the method in
Example 3.
Example 25
Acrylic resin
[0116] For this Example, the coating was prepared as follows: a
draw down was performed with the test solution using a 6'' bar with
a 5 mil gap. A single coat of the test solution was applied (unless
otherwise specified) on a basis sheet and left to air dry. In the
examples below, the following test procedures were used: A 23.3%
solids solution was prepared by diluting 4 mL Micryl 766R (35%
solids w/v) with 2 mL water. The ANSI score of the coat was 12
without a crease and 6 with a crease. The boat test was not
performed.
Example 26
OGR coating with Acrylic Resin and Poly(Propylene Glycol)Diglycidyl
Ether Terminated
[0117] A 31.7% solids solution was prepared by dissolving 0.5 g
poly(propylene glycol), diglycidyl ether terminated, in 4 mL of
Micryl 766R and diluting the mixture with 2 mL water. The solution
was coated onto the hydrophobic starch paper made in Example
24.
[0118] The ANSI test was then performed as follows: The ANSI test,
TAPPI test method T 559, which expands upon TAPPI UM 557
"Repellency of Paper and Board to Grease, Oil, and Waxes (Kit
Test)," involved releasing a drop of a mixture of castor oil,
heptane, and toluene (twelve different mixtures are made and
numbered 1-12 based on the aggressiveness of the mixture, with 12
being the most aggressive solvent mixture and aggressiveness being
determined by the percentage of small molecular weight species
having a higher penetration power than the higher molecular weight
fatty acids (here, castor oil)) onto the coating for 15 seconds and
determining if the sheet darkened in color. The score was ranked
from 1-12 (12 is best) and the coating was given the highest number
it passes.
[0119] The ANSI score of the coat was 12 without a crease and 12
with a crease. The boat test (described below in Example 32)
resulted in no grease spots.
Example 27
Preparation of Extractant Solutions
[0120] A solution of 0.141% NaOH was prepared by adding 1.41 g NaOH
to 1 L water and stirring to dissolve all NaOH (basic solution). A
solution of 0.274% NaH.sub.2PO.sub.4.2H.sub.2O was prepared by
adding 2.74 g NaH.sub.2PO.sub.4.2H.sub.2O to 1 L of water and
stirring to dissolve all NaH.sub.2PO.sub.4.2H.sub.2O (phosphate
solution). A solution of NaOH and NaH.sub.2PO.sub.4.2H.sub.2O was
made so that for every two NaOH molecules there is one
NaH.sub.2PO.sub.4.2H.sub.2O molecule. NaOH was chosen to be 0.0353
M, so NaH.sub.2PO.sub.4.2H.sub.2O was added to this solution at
0.0176 M. The resulting solution was 1.41 g NaOH and 2.74 g
NaH.sub.2PO.sub.4.2H.sub.2O in 1 L of water (phosphate/base
solution).
Example 28
Exfoliation of Montmorillonite Clays
[0121] For each clay sample (F100 and Aldrich), four vials were
prepared. To begin, 300 mg of the clay sample was added to each of
the four vials. 15 mL water was added to one of each vial for F100
and Aldrich clay. The remaining three sample vials were also
suspended in 15 mL each of phosphate, phosphate/base and basic
extractant solutions prepared in accordance with Example 27. The
vials were each shaken vigorously for 15 seconds and then placed
into an ultrasonic bath (Model 75T Aquasonic by VWR Scientific
Products) for 30 minutes. The ultrasonicated vials were allowed to
settle for 1 hour and a photograph was taken. By this time, the
water controls had completely settled. Pictures were then taken
periodically to measure the amount of time the exfoliated clays
were stably suspended in solution. After 28 days, the F100 and
Aldrich clays exfoliated with phosphate/base solutions remained
suspended, whereas the rest of the samples settled.
Example 29
OGR Coating with Acrylic Resin and Poly(Propylene Glycol)Diglycidyl
Ether Terminated and Exfoliated Clay
[0122] A 34.3% solids solution was prepared by dissolving 0.5 g
poly(propylene glycol) (200), digycidyl ether terminated and 0.5 g
by dry weight of exfoliated clay solution in 4 mL Micryl 766R under
sonication. The resulting OGR solution was then coated onto the
hydrophobic paper made in Example 24.
Example 30
Fatty Acid Test to Determine the Grease Resistance of Paper and
Paperboard
[0123] The fatty acid test, (developed by Solvay Chemicals utilizes
natural fatty acids to determine the grease resistance of paper. A
set of test solutions is prepared with various amounts of castor
oil, oleic acid, and octanoic acid. Each member of the test
solution set is ranked from 1 to 11, with 1 being the least
aggressive solution (i.e., having a lower percentage of a smaller
molecular weight fatty acid (here octanoic acid) with higher
penetration power than the higher molecular weight fatty acids
(here, castor oil or oleic acid)) and 11 being the most aggressive.
The solutions are heated to 60.degree. C. and a drop of each is
placed on the test paper and the paper is placed in a 60.degree. C.
oven for 5 minutes. After five minutes the drop is wiped off and
the paper is examined. Failure is indicated by the darkening or
discoloring of the test paper. The paper is given the score of the
highest number of solution that can be applied without failure
(i.e., darkening or discoloration after five minutes).
Example 31
Kit Test to Determine the Grease Resistance of Paper and
Paperboard
[0124] The ANSI test, TAPPI test method T 559, which expands upon
TAPPI UM 557 "Repellency of Paper and Board to Grease, Oil, and
Waxes (Kit Test)," was employed in certain examples. The test
involved releasing a drop of a mixture of castor oil, heptane, and
toluene (twelve different mixtures are made and numbered 1-12 based
on the aggressiveness of the mixture, with 12 being the most
aggressive solvent mixture) onto the coating for 15 seconds and
determining if the sheet darkened in color. Failure is indicated by
the darkening or discoloring of the test paper. The paper is given
the score of the highest number of solution that can be applied
without failure, using a ranking from 1-12 (the "Kit Score").
Example 32
Boat Test to Determine the Grease Resistance of Paper and
Paperboard
[0125] The boat test was performed by creating a boat-shaped
construct with the coated sheet so that it can hold oil. To perform
this test, a 5'' by 6'' piece of coated paper was creased in the
middle by applying 20 psi of pressure, and then the edges were
folded up to create a boat-like structure. Palm oil was placed in
the boat and the boat was place in an oven on a piece of paper for
24 hrs at 37.degree. C. The paper underneath the boat was observed
for grease spots after the given time and the number and diameter
of the spots were recorded.
[0126] While this invention has been particularly shown and
described with references to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims.
* * * * *