U.S. patent application number 11/926277 was filed with the patent office on 2008-11-06 for pigments for colored paper.
This patent application is currently assigned to NanoPaper, LLC. Invention is credited to Michael C. Berg, William A. Mowers, David S. Soane.
Application Number | 20080271865 11/926277 |
Document ID | / |
Family ID | 39272606 |
Filed Date | 2008-11-06 |
United States Patent
Application |
20080271865 |
Kind Code |
A1 |
Soane; David S. ; et
al. |
November 6, 2008 |
PIGMENTS FOR COLORED PAPER
Abstract
Compositions and methods of producing colored paper products and
agents for making such products are disclosed. Surface-modified
pigments can be manufactured to provide selected coloring in a
paper product. The pigment can include filler particles that are
bound to one or more dye components with a coupling agent, such as
a silane coupling agent or a polymer such as a polycation. The
pigment can also be formulated to produce a paper product with
better particulate and/or fines retention, and/or higher strength
by including components that can interact favorably with the fibers
of a paper material. The surface-modified pigments can also be
utilized to make coloring formulations such as inks for printers
and other applications.
Inventors: |
Soane; David S.; (Chestnut
Hill, MA) ; Berg; Michael C.; (Somerville, MA)
; Mowers; William A.; (Lynn, MA) |
Correspondence
Address: |
NUTTER MCCLENNEN & FISH LLP
WORLD TRADE CENTER WEST, 155 SEAPORT BOULEVARD
BOSTON
MA
02210-2604
US
|
Assignee: |
NanoPaper, LLC
Cambridge
MA
|
Family ID: |
39272606 |
Appl. No.: |
11/926277 |
Filed: |
October 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60855023 |
Oct 27, 2006 |
|
|
|
Current U.S.
Class: |
162/162 |
Current CPC
Class: |
D21H 17/56 20130101;
D21H 21/28 20130101; D21H 17/37 20130101; D21H 17/29 20130101; D21H
17/67 20130101 |
Class at
Publication: |
162/162 |
International
Class: |
D21H 21/28 20060101
D21H021/28 |
Claims
1. A colored paper product, comprising: pulp comprising a plurality
of fibers; and surface-modified pigment particles imparting color
to the paper product, the surface-modified pigment particles
comprising: (i) a filler particle embedded within the pulp, (ii) at
least one dye component adapted to provide a selected color to the
paper product, and (iii) a coupling agent binding the at least one
dye component and the filler particle together.
2. The colored paper product of claim 1, wherein the coupling agent
is directly bound to the filler particle by at least one of
covalent bonding, non-covalent bonding, electrostatic forces, Van
der Waals forces, hydrogen bonding, and intermolecular forces.
3. The colored paper product of claim 1, wherein the pulp comprises
cellulosic-based fibers.
4. The colored paper product of claim 1, wherein the filler
particle of the surface-modified pigment particles comprises at
least one of a biopolymer, a bio-oligomer, metal oxide, silaceous
material, and calcium carbonate.
5. The colored paper product of claim 1, wherein the filler
particle of the surface-modified pigment particles comprises an
inorganic surface.
6. The colored paper product of claim 5, wherein the inorganic
surface comprises at least one of calcium carbonate, kaolin, and
titanium dioxide.
7. The colored paper product of claim 5, wherein the inorganic
surface of the surface-modified pigment particles comprises sites
attached to the coupling agent by reaction of a hydroxide group of
the inorganic surface.
8. The colored paper product of claim 1, wherein the coupling agent
comprises a silane group reacted to attach the coupling agent and
the filler particle together.
9. The colored paper product of claim 8, wherein the coupling agent
further comprises a reactive group including at least one of an
acrylate, an amine, an amino, a carboxyl, a thiol, an epoxy, an
isocyano group, and a hydroxyl, the reactive group reacted to bind
the reactive group and the filler particle together.
10. The colored paper product of claim 1, wherein the coupling
agent comprises a polyelectrolyte.
11. The colored paper product of claim 10, wherein the
polyelectrolyte comprises a polycationic polymer.
12. The colored paper product of claim 11, wherein the polycationic
polymer comprises at least one of an amine-containing polymer and a
cationic starch.
13. The colored paper product of claim 12, wherein the
amine-containing polymer comprises at least one of chitosan,
polyalkyleneimine, polyvinyl amine, and polyallyl amine.
14. The colored paper product of claim 11, further comprising: an
anionic component adapted to couple the anionic component and the
polycationic polymer together.
15. The colored paper product of claim 14, wherein the anionic
component is adapted to bind the at least one dye component and the
polycationic polymer together.
16. The colored paper product of claim 15, wherein the anionic
component is a polyanion.
17. The colored paper product of claim 15, wherein the anionic
component comprises another coupling agent including a silane
group.
18. The colored paper product of claim 1, wherein the at least one
dye component comprises at least one of halogenotrizine,
carboxypyridinium-substituted triazine, trihalogenopyrimidine,
dichloroquinoxaline, vinyl sulfone, halotriazine,
anthraquinone-like structure, azo dye, triaryl dye, and metal
complex.
19. The colored paper product of claim 1, wherein the at least one
dye component comprises at least one of a fluorescent dye, a
phosphorescent dye, a photochromic dye, a thermochromic dye, a
FD&C dye, a whitener, a brightener, a light stabilizer, and an
ultraviolet light stabilizer.
20. The colored paper product of claim 1, wherein the
surface-modified pigment particles are adapted so that at least one
surface-modified pigment particle and at least one fiber of the
pulp are bound together.
21. The colored paper product of claim 20, wherein the
surface-modified pigment particles include coupling agent binding
the filler particle and at least one fiber of the pulp
together.
22. The colored paper product of claim 20, wherein the
surface-modified pigment particles further comprise a
functionalizing polymer binding the filler particle and at least
one fiber of the pulp together.
23. The colored paper product of claim 22, wherein the
functionalizing polymer and the coupling agent are attached
together.
24. The colored paper product of claim 23, wherein the
functionalizing polymer and the coupling agent are directly
attached together.
25. The colored paper product of claim 22, wherein the
functionalizing polymer and the filler particle are bound together
by at least one of covalent bonding, non-covalent bonding,
electrostatic forces, Van der Waals forces, hydrogen bonding, and
intermolecular forces.
26. The colored paper product of claim 22, wherein the
functionalizing polymer comprises at least one of an
amine-containing polymer, a glycoaminoglycan, an amino-containing
polymer, and an imine-containing polymer.
27. The colored paper product of claim 1, wherein the
surface-modified pigment particles further comprise an intermediary
component binding the coupling agent and filler particle
together.
28. The colored paper product of claim 1, wherein the
surface-modified pigment particles further comprise an intermediary
component binding the coupling agent and the at least one dye
component together.
29-54. (canceled)
55. A method of producing a colored paper product, comprising:
producing a surface-modified pigment by binding filler particles
and at least one dye component together using a coupling agent;
mixing the surface-modified pigment with pulp comprising a
plurality of fibers to produce a papermaking dispersion; and
forming the colored paper product using the papermaking
dispersion.
56. The method of claim 55, further comprising: binding the filler
particles and at least one fiber of the pulp together.
57. The method of claim 55, wherein the step of producing the
surface-modified pigment begins before the step of mixing the
surface-modified pigment with pulp.
58. The method of claim 55, wherein the steps of producing the
surface-modified pigment and mixing the surface-modified pigment
with pulp occur substantially simultaneously.
59. The method of claim 55, wherein the step of producing the
surface-modified pigment comprises adjusting color of the paper
product by selecting the amount of coupling agent relative to the
at least one dye component.
60. The method of claim 55, wherein the step of producing the
surface-modified pigment comprises encapsulating the filler
particles with a polycation.
61. The method of claim 60, wherein the step of encapsulating the
filler particles comprises attaching the polycation and the filler
particles together with the coupling agent.
62. The method of claim 60, wherein the polycation is the coupling
agent.
63. The method of claim 62, further comprising: coupling the at
least one dye component and the polycation together before
encapsulating the filler particles with the polycation.
64. The method of claim 60, wherein the step of encapsulating the
filler particles comprises self assembling the polycation on a
surface of the filler particles.
65. The method of claim 60, further comprising: binding an anionic
component to the polycation.
66. The method of claim 55, wherein the coupling agent comprises a
silane group.
67-76. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of a U.S.
Provisional Patent Application filed on Oct. 27, 2006 and bearing
Ser. No. 60/855,023, the text of which is incorporated herein by
reference in its entirety.
[0002] The present application is also related to U.S. Patent
Application Publication Number US 2007/0107635 A1, bearing Ser. No.
11/501,463, filed Aug. 9, 2006, entitled "Dye-Attached and/or
Surface Modified Pigments"; and an international patent application
bearing application number PCT/U.S.07/03159, filed Feb. 5, 2007,
entitled "Functionalization of Paper Components." Both of these
related applications are hereby incorporated by reference
herein.
FIELD OF THE APPLICATION
[0003] The present application relates to materials and processes
for modifying paper products, e.g., making colored paper.
BACKGROUND
[0004] Many paper and paperboard products are derived from
cellulosic materials. The strength of these composites is due to
inter-fiber hydrogen bonds, which are inherently weak and easily
broken. Thus, strength additives are incorporated during some
fabrication processes to increase paper strength. These additives,
and the processes that utilize them, add steps and cost to the
production.
[0005] Producing colored paper involves additional challenges. In
order to make colored paper, dyes and other ingredients are
typically mixed in-line during the fabrication process. It is
difficult to obtain consistent colors, though, because a minimal
change in dye concentration may significantly affect the final
color of the product. Thus considerable operator skill is required
so that colors are reproducible across lots. In addition, dyes will
impart color to the processing equipment during a given dye run, so
that changing from one color lot to another must be preceded by an
elaborate cleaning protocol that is time-consuming and expensive.
There remains a need in the art for products and processes that
reduce costs, increase efficiency, and decrease waste while
increasing paper strength and optimizing color.
SUMMARY
[0006] Some embodiments are directed to a paper product, such as a
colored paper product. The paper product can include pulp
comprising a plurality of fibers (e.g., cellulosic-based fibers
and/or other fibers used in paper products). Surface-modified
pigment particles can also be included. Such particles can impart a
selected color to a paper product. Surface-modified pigment
particles can include a filler particle, which can be embedded with
the pulp. A coupling agent can be used to bind one or more dye
components and the filler particle together. Filler particles can
include one or more of a biopolymer, a bio-oligomer, metal oxide,
silaceous material, and calcium carbonate. Filler particles, which
can optionally be nanoparticles or other sized particles, can also,
or alternatively, include an inorganic surface such as calcium
carbonate, kaolin, titanium dioxide, or combinations thereof. Such
particles can comprise sites attached to the coupling agent by
reaction of a hydroxide group on the particle surface. In some
embodiments, the coupling agent is directly bound to the filler
particle by at least one of covalent bonding, non-covalent bonding,
electrostatic forces, Van der Waals forces, hydrogen bonding, and
intermolecular forces.
[0007] Dye components can be adapted to provide the selected color
to the paper product, and can include any appropriate material for
imparting coloration to paper. In some embodiments, the dye
component can be any of halogenotrizine,
carboxypyridinium-substituted triazine, trihalogenopyrimidine,
dichloroquinoxaline, vinyl sulfone, halotriazine,
anthraquinone-like structure, azo dye, triaryl dye, metal complex,
and combinations thereof. The dye component can also include any
combination of a fluorescent dye, a phosphorescent dye, a
photochromic dye, a thermochromic dye, a FD&C dye, a whitener,
a brightener, a light stabilizer, and a ultraviolet light
stabilizer.
[0008] Coupling agents for use with embodiments disclosed herein
can be in a variety of forms and interact with the surface-modified
pigment particles in a variety of manners. For instance, the
coupling agent(s) can use one or more intermediary agent(s), which
can couple the coupling agent to the particle, or can couple
another component (e.g., one or more dye components) to the
coupling agent, or both. In some embodiments, the coupling agent
comprises a multifunctional coupling agent or a polymer. In some
embodiments, a coupling agent can include a silane group that can
react to attach to a filler particle either directly or indirectly.
Coupling agents can also, or alternatively, include a reactive
group including at least one of amine, thiol, epoxy, isocyanate, or
hydroxyl; the reactive group reacted to attach to the filler
particle. In some embodiments, the coupling agent can comprise a
polymer, such as a polyelectrolyte (e.g., a polycationic polymer).
Examples of polycationic polymers include any combination of
amine-containing polymers, such as chitosan, polyalkyleneimine,
polyvinyl amine, and polyallyl amine, and a cationic starch. An
anionic component can also be added such as to couple together with
the polycation. The anionic component can be adapted to bind the
anionic component and one or more dye components, or other
components, together so as to couple such components to the filler
particle. Examples of anionic components can include anionic
polymers or a coupling agent that can optionally include a silane
group.
[0009] In some embodiments, the surface-modified pigment particles
can be bound together with other paper components, such as a fiber
of the paper's pulp. For instance, the coupling agent (e.g., an
amine-containing polymer such as chitosan) can act to bind a filler
particle and a fiber directly or indirectly together. In another
instance, a functionalizing agent, such as a polymer, can be
included with a surface-modified pigment particle to aid binding of
the particle (or components thereof) and a fiber together. A
functionalizing agent (e.g., polymer) can be attached together with
the coupling agent and/or can be directly attached together with a
filler particle. The attachment can be by covalent bonding,
non-covalent bonding, electrostatic forces, Van der Waals forces,
hydrogen bonding, intermolecular forces, and combinations of such
named mechanisms, among others. Examples of functionalizing
polymers include an amine-containing polymer, a glycoaminoglycan,
an amino-containing polymer, and an imine-containing polymer.
[0010] Other embodiments of the invention are directed to slurries
that can be used to make paper products such as colored paper
products. The slurry can include an aqueous medium, which can be
used to disperse the other paper components. Other components can
include pulp having a plurality of fibers, and a surface-modified
pigment mixture. Such a mixture, which can be used to impart a
selected color to a paper product, can include filler particles,
one or more dye components, and a coupling agent adapted to bind
the dye component(s) and the filler particles together. The
components of such slurries, such as the surface-modified pigments,
pulps, filler particles, dye components, and coupling agents, can
include any of such components as disclosed herein.
[0011] Additional embodiments of the invention are drawn to
surface-modified pigment, and formulations that utilize such
pigments such as ink formulations that are dispersed in an aqueous
medium. Surface-modified pigment particles can include a plurality
of pigment particles having a fiber affinity component, such as a
polycation, coupled together with the pigment particle. The fiber
affinity component, such as a polycation, can act to bind the
particles with the fibers of a paper-based material. For example,
when used in an ink formulation, a polycation can act to improve
binding between the ink formulation and the paper relative to not
having the polycation in the ink formulation. Though a variety of
pigment particles can be utilized, in some embodiments the
surface-modified pigment particles can be comprised of filler
particles having one or more dye components bound together with a
coupling agent (e.g., a polycation). The types of surface-modified
pigment particles that can be utilized, and the components of such
particles, include the variety of types and components disclosed
herein.
[0012] Further embodiments are drawn toward methods of producing a
colored paper product. A surface-modified pigment can be produced
by binding filler particles and one or more dye components together
using a coupling agent such as a polymer or a material having a
silane group. For example, the filler particles can be encapsulated
with a polycation, where the polycation can be attached using the
coupling agent or the polycation can be the coupling agent itself.
The surface-modified pigment can be combined with pulp comprising
fibers so as to produce a papermaking dispersion. A colored paper
product can be then be formed from the papermaking dispersion.
[0013] In some of the method embodiments, the filler particles can
bind to a fiber of the dispersion, which can result in a stronger
final paper product and/or increased retention of fillers (and
associated components thereof) and/or fines. As well, the color of
a paper product can be adjusted by selecting the relative amount of
coupling agent to dye component(s). Anionic components can be bound
to a polycation to provide additional functionality, for
example.
[0014] The steps of producing the surface-modified pigment and
combining the pigment with pulp can be practiced sequentially, or
substantially simultaneously (e.g., a mixture of components to
become the surface-modified pigment can be combined with the fibers
to make a reacting papermaking dispersion). As well, portions of a
surface-modified pigment particle can be manufactured and coupled
together with a filler particle, or other paper components such as
fibers, before remaining portions of the pigment particle are
completed. Alternatively, or in addition, the surface-modified
pigment can be assembled in a variety of manners, e.g., a dye
component can be coupled together with a polycation before the
polycation encapsulates (such as by self assembly upon the surface)
a filler particle, or the dye can be coupled after the polycation
is attached to a filler particle.
BRIEF DESCRIPTION OF THE FIGURES
[0015] The objects and features disclosed in the present
application can be better understood with reference to the drawings
described herein, and the claims. The drawings are not necessarily
to scale, emphasis instead generally being placed upon illustrating
one or more principles of the invention. In the drawings, like
numerals are used to indicate like parts throughout the various
views. While the invention is particularly shown and described
herein with reference to specific examples and specific
embodiments, it should be understood by those skilled in the art
that various changes in form and detail may be made therein without
departing from the spirit and scope of the invention.
[0016] FIG. 1 illustrates schematically a system for attaching a
reactive dye to a particle, consistent with an embodiment of the
present invention.
[0017] FIG. 2 illustrates schematically a system for attaching a
reactive dye to a coated particle, consistent with an embodiment of
the present invention.
[0018] FIG. 3 illustrates schematically another system for
attaching a reactive dye to a coated particle, consistent with an
embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0019] Embodiments of the invention are drawn to various aspects of
papermaking, such as improving engineering properties of
paper-based materials, improving the process efficiency of such
operations, imparting color or other appearance features to
paper-based materials, and/or decreasing waste production during
papermaking operations. In some embodiments, processes and
materials used in paper manufacturing utilize surface-modified
filler particles to achieve changes in properties of the resulting
paper-based material. Several embodiments utilize surface-modified
pigment particles to impart a selected color in a paper-based
material, for example either throughout the paper and/or when such
surface-modified pigment particles are used in an ink
formulation.
[0020] In some embodiments, the surface-modified pigment particles
can comprise filler particles that can have one or more dye
components that are bound together with the filler particle using a
coupling agent. A dye component can be selected to impart a desired
coloration to the particles, and hence a paper-based product. Such
embodiments are potentially advantageous in reducing wasted use of
dyes during paper or ink production. Since dyes are typically
liquid-based materials that are soluble in a papermaking mixture,
excess dye is often used in coloration of paper components. By
using a surface-modified pigment, where the particles are not
soluble in the papermaking mixture, loss of coloration materials
can be reduced. In other embodiments, a surface-modified pigment
particle can include a polyelectrolyte bound to the particle
surface. Such polyelectrolytes can be adapted to bind together with
fibers (e.g., cellulose-based fibers) of a paper or paper mixture,
which can result in enhanced properties such as paper strength.
These aspects and others are discussed in further detail
herein.
DEFINITIONS
[0021] Unless the context of use suggests otherwise, the following
definitions apply to the terms and phrases used throughout the
present application.
[0022] The terms "a" and "an" are interchangeable and are the same
as the phrase "one or more."
[0023] The terms "attach," "bind," and "bound" are synonymous with
each other and refer to a coupling between entities. Such coupling
can either be direct, such as a polymer sharing a covalent chemical
bond with a surface site of a particle together, or can be
indirect, such as coupling a polymer and a surface site together
using an intermediary agent which is directly coupled to the
polymer and the surface site (e.g., a bifunctional coupling agent).
Binding between entities can occur by any feasible mechanism
consistent with an embodiment of the invention. Accordingly,
non-limiting mechanisms by which chemical entities can be bound
together include covalent bonding, non-covalent bonding,
electrostatic (or ionic) forces, Van der Waals forces, hydrogen
bonding, other intermolecular forces, and combinations of the
listed mechanisms.
[0024] The phrase "pigment particle" refers to one or more
particles that are used to impart coloration. A pigment particle
can be based from organic and/or inorganic materials, and can be
chosen to be insoluble in a given medium, such as an aqueous
solution and/or a mixture from which paper can be manufactured.
[0025] The term "polymer" refers to a molecule comprising a
plurality of repeat units or monomers. A polymer can comprise one
or more distinct repeat units. For example, a "copolymer" refers to
a polymer having two or more distinct repeat units. Repeat units
can be arranged in a variety of manners. For example, a homopolymer
refers to a polymer with one type of repeat unit where the repeat
units are adjacently connected. In another example, a plurality of
different repeat units can be assembled as a copolymer. If A
represents one repeat unit and B represents another repeat unit,
copolymers can be represented as blocks of joined units (e.g.,
A-A-A-A-A-A . . . B-B-B-B-B-B . . . ) or interstitially spaced
units (e.g., A-B-A-B-A-B . . . or A-A-B-A-A-B-A-A-B . . . ), or
randomly arranged units. Of course, these representations can be
made with 3 or more types of repeat units as well. In general,
polymers (e.g., homopolymers or copolymers) include macromolecules
in a broad range of configurations (e.g., cross-linked, linear,
and/or branched). The polymer can be disposed in a variety of
mixture dispositions such as solutions, melts, and/or gels. A gel
refers to a state where a mixture of polymer and liquid has at
least some properties that make the mixture behave more like a
solid than a viscous liquid (e.g., the mixture exhibits
elasticity). A polyelectrolyte refers to a polymer where one or
more of the repeat units includes an ionic group. Accordingly, such
groups can be charged in an aqueous solution. When the ionic groups
include a cationic group, the polyelectrolyte can be referred to as
a "polycation." When the ionic groups include an anionic group, the
polyelectrolyte can be referred to as a "polyanion." In some
instances, the polyelectrolyte can also have a net zero charge.
Colored Paper Products
[0026] Some embodiments are directed to paper products, and in
particular paper products with a selected color. Paper products
include the range of paper, paper-board, and other paper-based
materials that can be manufactured. In some instances, the paper
product can include pulp in the form of a plurality of fibers and
surface-modified pigment particles for imparting color to the paper
product. The surface-modified pigment particles can include filler
particles, such as those typically utilized in paper manufacturing
(e.g., inorganic particles like precipitated calcium carbonate
(herein "PCC") or silicon dioxide). One or more dye components can
also be included, which can be bound together with one or more of
the filler particles using one or more coupling agents. In some
embodiments, the dye can be durably, if not substantially
permanently, bound together with the filler particle (e.g., the dye
can be substantially attached to, and remains unremoved from, a
filler particle during a papermaking process). Thus, such
embodiments can advantageously reduce the loss of excess dye
components inherent when excess soluble dye liquid is employed for
paper coloration. In addition, such embodiments can potentially
produce a richer set of pigments for use with paper that correspond
with useable dyes.
[0027] Other embodiments can be directed to slurries, or other
types of mixtures of components, that can be used to form paper
products (e.g., paper products with a selected coloration). The
slurry often times includes an aqueous medium, though non-aqueous
mediums and mixed media systems (e.g., surfactant can be present to
form micelles) can also be utilized. The slurry can include pulp
having a plurality of fibers dispersed in the medium. A mixture for
producing surface-modified pigments can also be included in the
slurry. Such a mixture can include filler particles and one or more
dye components for selectively coloring the filler particles. A
coupling agent can also be present in the mixture. The coupling
agent can be chosen to bind the dye component(s) and the filler
particles together. Thus, in some embodiments, the surface-modified
pigment mixture can impart a selected color to a paper product
formed from such slurries.
[0028] More detailed descriptions of particular aspects of
embodiments of paper products and slurries are discussed herein. It
is understood that these aspects are individually or
combinatorially interchangeable, and can be additionally inserted,
or deleted from, various embodiments of the invention. For example,
the use of a particular aspect of a coupling agent in a
paper-forming slurry can also be used in a resulting paper product,
regardless of whether it is explicitly stated in the present
application. In another example, more than one type of coupling
agent can be employed in an embodiment where the coupling agent can
be selected from any of the coupling agents disclosed herein.
Indeed, those skilled in the art will recognize that minor changes
and modifications of disclosed aspects of the invention can be
performed without undue experimentation. All such variations are
within the scope of the present application.
Component Descriptions
[0029] Paper products and slurries for making such products, among
other embodiments, can utilize pulps that are typically utilized in
conventional paper manufacturing. Thus, the pulp utilized in some
embodiments disclosed herein can comprise fibers such as
cellulose-based fibers, and can also include other components
typically found in pulps/fibers used to make paper products (e.g.,
filler additives). In many embodiments, the fibers of the pulp can
have a net negative charge. Such net charge can be utilized
advantageously in some embodiments to cause electrostatic
attraction of cationic moieties such as polycations. Though any
type of compatible fiber material can be utilized in a pulp, in
some embodiments the fibers of a pulp exclude the presence of
synthetic fibers such as polymer-based fibers (e.g., aromatic amide
fibers). Thus, some embodiments utilize pulps that include
substantially naturally-occurring fibers. Other embodiments,
however, can utilize pulps that include synthetic fibers such as
polymer-based fibers (e.g., aromatic amide fibers) or other types
of synthetic fibers.
[0030] As well for papermaking purposes, filler particles can be
made into surface-modified pigments (e.g., colored pigments), can
be used in unmodified form, or can comprise a mixture of modified
and unmodified particles, which can be used in various embodiments
described herein. Such filler particles can comprise any number of
materials. Non-limiting examples include polymers, biopolymers,
bio-oligomers, metal oxides, calcium carbonate silicas, inorganic
components, and mixtures of such materials. Particles commonly used
in the paper industry include those made from materials such as
kaolin, calcium carbonate, and titanium dioxide; such particles can
also be used with the embodiments disclosed herein. In particular
embodiments, the filler particles have a surface comprising one or
more the listed materials herein. For instance, filler particles
with an inorganic surface (e.g., metal oxide surface) can be used
in particular embodiments to bind together with selected coupling
agents. The selected coupling agents can aid in binding a dye
component or some other component (e.g., a functionalizing polymer
such as an amine-containing polymer to aid binding of a
surface-modified pigment to pulp fibers) to improve interactions
with pulp fibers or to add other beneficial properties such as
enhanced pigment particle, other filler components, and/or fines
retention. For example, the coupling agent can attach to the
particle surface via a reaction with a hydroxide group previously
residing on the particle surface or as part of the unreacted
coupling agent. In some embodiments, filler particles can have a
net negative charge on their surfaces for binding with cationic
entities such as polycations.
[0031] In embodiments, filler particles may be of any shape,
including substantially spherical, amorphous, cylindrical,
plate-like, flake-like, or any other geometry. Particles may be
selected for physical properties desirable in papermaking,
including porosity, strength, opacity, or other characteristics. In
embodiments, the particles may have average dimensions from 3-200
microns, or from 5-100 microns; in some embodiments the average
dimension (e.g., diameter, radius, or effective dimension based on
some type of surface area measurement) can be the average of the
largest dimension of the particles. In embodiments, the particle
may be a nanoparticle. As used herein, the term nanoparticle
applies to a particle having at least one dimension measuring less
than 100 nm on average. It is understood that while embodiments
herein refer to surface-modified filler particles that include a
bound dye component, dye components can also be bound to other
substrates to form surface-modified substrates to form a
surface-modified pigment (e.g., a coating material), which can be
used to replace surface-modified pigment particles in some
embodiments described herein.
[0032] In embodiments, one or more dye components can be bound to
one or more substrates (e.g., filler particles) to produce a
manufactured colorant. As discussed in the present application, a
dye component refers to a colorant, which can be bound to a filler
particle or other substrate to form a surface-modified filler
particle. In some embodiments, a dye component can be a reactive
dye. As used herein, the term "reactive dye" refers to a
chromophore containing one or more moieties that is/are capable of
reacting with, or otherwise binding to, a substrate, such as a
fiber or a particle. Some dye components can include a vinyl
sulfone. In certain embodiments, the dye component can include a
halotriazine, for example, a chlorotriazine. In embodiments, the
dye component can include one or more of the following: a
monohalogenotriazine, a dihalogenotrizine, a
carboxypyridinium-substituted triazine, a trihalogenopyrimidizine,
and/or a dichloroquinoxaline. The dye component can also include a
fluorescent dye, a phosphorescent dye, a photochromic dye, a
thermochromic dye, a whitener, a brightener, a light stabilizer,
and/or a ultraviolet light stabilizer. Anionic dyes can also be
utilized as a dye component. Anionic dyes include acid dyes having
a variety of structures, for example anthraquinone-like structures,
azo dyes, triaryl dyes, and metal complex dyes. Other anionic dyes
include Food, Drug, and Cosmetic (herein "FD&C") dyes, which
are approved for use in foods, drugs, and cosmetics subject to U.S.
Food and Drug Administration regulations.
Coupling Agents and Functional Groups
[0033] In embodiments, surface modified pigments and surface
modification processes described herein can include the use of a
variety of types of coupling agents to bind one or more dye
components or other components, and filler particles or other
substrates together. It is understood that coupling agents can act
to bind dye component(s) and filler particles in a variety of
configurations. For instance, the coupling agent can be directly
bound to the filler particle and dye component to cause coupling.
In another instance, one or more intermediary components can bind
the particle and coupling agent together, with a dye component
directly bound to the coupling agent. In yet another instance, one
or more intermediaries can bind the dye component(s) and coupling
agent together, with the coupling agent directly bound to the
particle. Other instances can use intermediaries, same or
different, to connect the coupling agent and dye component, and the
particle and coupling agent. It is also understood that while many
embodiments specifically discuss coupling of dye components, other
components can also be bound with coupling agents. These variations
and others, including ones understood by a skilled artisan, are all
within the scope of the present invention.
[0034] In some instances, a multifunctional coupling agent can be
employed to functionalize a filler particle to bind a dye component
or other material (e.g., a polycation) thereto. As used herein, the
phrase "multifunctional coupling agent" refers to agents which
include at least two distinct types of functional groups that can
be used to bind to other entities (e.g., a filler particle surface
and/or a dye component). Examples of multifunctional coupling
agents include an agent with a silicon atom or silane group for
direct linkage to the surface of a filler particle or other
substrate. The multifunctional coupling agent can be a
small-molecule, an oligomer, or even a polymer.
[0035] Though much of the following description is with reference
to functional groups on a multifunctional coupling agent, it is
understood that such groups can be utilized on other coupling
agents as well. Indeed, such groups can be utilized on other
coupling agents within the scope of the present application.
[0036] In some embodiments, the multifunctional coupling agent can
include a silicon-containing group and at least one other different
type of functional group. Examples of other functional groups
include an amine group, an amino group, an epoxy group, a hydroxyl
group, a thiol group, an acrylate group, a carboxyl group, and/or
an isocyano group. In one embodiment, the silicon-containing group
can be a silane group. Instances of such groups can include an
isocyanosilane, for example, a trialkoxy isocyanosilane such as
trimethoxy isocyanosilane, triethoxy isocyanosilane, and/or
triisopropoxy isocyanosilane. In certain embodiments, the
multifunctional coupling agent may include an aminosilane, for
example, a trialkoxy aminosilane such as triethoxy
aminopropylsilane and/or trimethoxy aminopropyl silane. In certain
embodiments, the multifunctional coupling agent may include an
epoxy siloxane. The coupling agent can include triethoxy
methacryloxypropyl silane. Though in many instances a
multifunctional coupling agent is embodied as a bifunctional
coupling having one silane group and one other group, it is
understood that a multifunctional coupling agent can have one or
more silicon-containing groups, and/or one or more other functional
groups. It should also be understood that certain embodiments of
multifunctional coupling agents need not include a silicon atom or
a silane group.
[0037] To illustrate some aspects of the invention, a
multifunctional coupling agent can bond with the surface groups on
filler particles, and can have one or more functionalities, which
can be located on a free end, that can connect with a dye
component. For instance, a bifunctional coupling agent can have one
group that can react with the surface of a filler particle and a
different group that can react with a reactive dye component. In
one example, when a filler particle having a metal oxide surface is
utilized, a multifunctional coupling agent can include a
hydrolysable silane or hydroxyl silane as one group to react with
the metal oxide surface. An amine, thiol, epoxy, isocyanate, or
hydroxyl group can be used as another group to bind a reactive dye
to the particle. For instance, an alkoxy, halo, hydroxyl, or other
group on the silane can form a bond with the particle surface. The
other group can be on another end of the coupling agent to react
with the reactive dye. Moieties including, but not limited to, a
primary amine, a secondary amine, and/or an alcohol group, may
react to a dye containing a chlorotriazine.
[0038] Though in the above illustration covalent bonding can cause
connection of a functional group of a coupling agent with a
particle surface and/or dye component, it should be understood that
the functional group of a multifunctional coupling agent can induce
binding by other mechanisms as well. The functional group can
covalently link the dye to the particle surface; alternatively, the
linkage may be non-covalent, ionic (e.g., electrostatic forces), or
via Van der Waals forces, hydrogen bonds, and/or other
intermolecular forces.
[0039] FIG. 1 depicts schematically an illustrated embodiment of
the invention. As shown, a filler particle 12 according to
compositions and methods described herein can be attached to a
coupling agent 14, with a linkage 30 formed between the coupling
agent 14 and the particle 12. The coupling agent 14 can include a
free end 18, providing a site for attachment of a reactive dye 20.
As illustrated, the reactive dye 20 can include a chromaphore 22
and a reactive moiety 24. The reactive moiety 24 of the reactive
dye 20 can attach to the free end 18 of the coupling agent 14,
forming a linkage 28 that attaches the reactive dye 20 to the
particle 12 via the coupling agent 14.
[0040] While in some embodiments a dye component can directly bind
with a multifunctional coupling agent, in other embodiments the dye
component can be bound to a coupling agent through one or more
intermediary entities. For example, the number of amine groups on a
particle surface available for reaction with a dye component (or
even other types of components) can be increased by using a
coupling agent with a functional group that reacts with amines and
first attaching an amine-containing polymer to the coupling agent
for subsequent reaction with the reactive dye. For instance, a
polyamine such as chitosan, branched polyethylenimine, or polyallyl
amine can be reacted onto an isocyano or epoxide group of a
multifunctional coupling agent (that is attached to the particle)
for subsequent reaction to a reactive dye. In another instance, a
number of alcohol groups available for dye interaction can be
enhanced. In one example, a cellulosic polyanion can be attached to
a filler particle surface with alcohol moieties using a
multifunctional coupling agent including acid groups capable of
reacting with the alcohol groups on the particle surface. Hydroxyl
groups of the polyanion can be reacted with a reactive dye to
complete the surface-modification of the particles. It is
understood that a coupling agent can be adapted to bind with
components other than a dye component to provide additional
functional advantages in a paper-based product. For instance, when
chitosan is bound to a filler particle using a coupling agent, the
free amines can be used to interact with the fibers of a paper
product, as opposed to binding with a dye component, to increase
the retention of the filler particle and/or fines, which can
increase the strength of a resulting paper material.
[0041] In some embodiments, a second multifunctional coupling
agent, which can be distinct from a first multifunctional coupling
agent, can be utilized to bind another component to a filler
particle, such as a different type of dye component or a polymer
for enhancing paper component strength or properties (e.g.,
hydrophobicity). Such a second multifunctional coupling agent can
utilize any of the binding mechanisms previously discussed, such as
covalent, non-covalent, ionic, or via Van der Waals forces,
hydrogen bonds, and/or other intermolecular forces. It is also
possible that no second coupling agent is utilized. In such an
instance, moieties of the additional component bind to moieties of
the first multifunctional coupling agent, or bind directly with
moieties on a filler particle surface. The moities on the particle
surface can either be inherent to the surface, or the surface can
be modified in some other fashion. It is also contemplated that
additional multifunctional coupling agents can also be used with
various embodiments of the present invention.
[0042] While some embodiments herein contemplate the use of a
multifunctional coupling agent that can bind directly with a
surface of a filler particle, practice of the invention is not
necessarily limited to such embodiments. Some instances can utilize
a filler particle that includes a coating layer on the particle's
surface. A multifunctional coupling agent, which can be bound to a
dye component or other component, can be attached to the coating
layer, thus providing the connection between the component and the
filler particle. FIG. 2 provides one specific illustration of this
arrangement.
[0043] As depicted in FIG. 2, a coating layer 116 can be deposited
onto the surface of a particle 112, forming a coated particle 110.
Methods for depositing the coating layer 116 onto the particle 112
may include electrostatic interaction, spray drying, precipitation,
or chemical reaction involving covalent, non-covalent, ionic or van
der Waals forces, or the like. Many methods for depositing the
coating layer 116 will be familiar to skilled artisans. The coating
layer 116 can then provide a nexus for attachment 130 of a coupling
agent 114. The coupling agent 114 can have a free end 118 that
permits attachment of a reactive dye 120. The reactive dye 120 can
comprise a chromaphore 122 and a reactive moiety 124. As shown in
FIG. 2, the reactive moiety 124 can attach to the free end 118 of
the coupling agent 114, thereby forming a linkage 128. In some
embodiments, the reactants can be reacted sequentially, for
example, so that the coating layer 116 is first deposited on the
particle 112, followed by the deposition of the coupling agent 114,
followed by the attachment of the reactive dye 120 to the coupling
agent 114 free ends 114. In other embodiments, some or all of the
reactants may be mixed together initially, with the products of
these mixtures then being reacted together.
[0044] In some embodiments, a coating layer can comprise one or
more layers of polymers. For example, amine-containing polymers can
be directly deposited onto a particle surface without the use of an
intermediary, a technique useful for many types of particles,
including calcium carbonate and metal oxides. Amine-containing
polymers useful for this technique may include a number of polymers
containing primary or secondary amines. Examples include chitosan,
branched polyethylenimine, linear polyethylenimine, and polyallyl
amine. Other aspects of amine-containing polymers discussed
elsewhere within the present application can also be incorporated.
To accomplish the direct deposit of an amine-containing polymer
onto the surface of the particle, a number of methods may be used,
including electrostatic interaction, spray drying, or precipitating
the polyamine out of solution onto the particle by adjusting the
pH. For example, chitosan may be deposited onto a particle by
slowly raising the pH until chitosan is insoluble. It is understood
that a variety of components can be linked to a coating layer
beyond a coupling agent. For example, in some instances a reactive
dye can be coupled to one or more free amines of the polyamine
without the use of a coupling agent. Other components include
polyanions or other groups capable of binding with an amine group,
for example.
[0045] In other embodiments, a surface-modified substrate (e.g.,
filler particle) can include a multifunctional coupling agent and a
functionalizing component, where the functionalizing component
binds to the surface of the filler particle. Though the
functionalizing component can bind to the surface using an
intermediary such as a multifunctional coupling agent, in some
embodiments the functionalizing component binds directly to the
surface of the filler particle. Such functionalizing components can
serve to enhance the properties of a resultant paper product in
terms of its appearance, strength, and/or other properties. In some
embodiments, the functionalizing component can be one or more
functionalizing polymers. Such polymers can include any of the
polymers described herein that can act as a coupling agent, for
example. In one instance, the polymer can be a polycation such as
an amine-containing polymer, a glycoaminoglycan, an
amino-containing polymer, and an imine-containing polymer. Such
polymers can be advantageous since the amine groups can act as
sites of interaction, allowing the binding of entities such as
reactive dyes to further enhance pigment coloration abilities, or
fibers of a paper pulp to enhance the overall strength of the paper
material.
Polymeric Coupling Agents
[0046] In some embodiments, the coupling agent can be a polymer,
such as a polyelectrolyte (e.g., a polycation). Polymer coupling
agents can differ from multifunctional coupling agents in that the
polymer may not have a plurality of different functional groups to
bind with various entities, though polymers with multifunctional
groups for binding can also be utilized. In some embodiments, the
polymer coupling agent can bind to the surface of a filler particle
directly. Such binding can occur by any number of mechanisms such
as electrostatic forces, Van der Waals forces, covalent bonding, or
other intermolecular forces. For example, the polymer can include
silane groups (or other silicon-containing groups) capable of
binding to a filler particle surface (e.g., having a metal oxide
surface) by reacting with a surface site. In another example, a
polycation with amine-containing groups can bind with a negatively
charged surface of a filler particle. One or more dye components,
and/or other components, can also bind with the polymer to create
binding between the component(s) and the filler particles.
[0047] A variety of polymers can be utilized as a coupling agent.
In some embodiments, the polymers can have an amine group, an
amino-group, an imine group, or a combination of such groups. Other
polymers can include hydroxyl groups, where entities can be
attached at the hydroxyl sites. Particular embodiments utilize
polycations as a coupling agent. Such embodiments can be beneficial
for creating binding with substrates and particle surfaces that
have a net negative charge. Accordingly, some embodiments can
advantageously utilize polymers that are polycationic (e.g.,
amine-containing polymers such as chitosan).
[0048] In general, amine-containing polymers (also referred to as
polyamines herein) for use with compositions and methods disclosed
herein include at least one primary (--NH.sub.2), secondary
(--NHR.sub.2), and/or tertiary amine (--NR.sub.3) group. Such
polymers can also, or alternatively, include a quaternary ammonium
cation or a quaternary ammonium salt moiety. The amine groups of an
amine-containing polymer can include charged and/or uncharged
groups. Examples of amine-containing polymers can include chitosan,
polyalkyleneimine, polyvinyl amine, and polyallyl amine. In some
embodiments, a surface-modified pigment particle with an attached
polymer can be treated or washed with an acidic solution or
compound, such as an acidic solution comprising an inorganic acid,
to create a charged group (e.g., an amine group) and/or a stable
salt complex. Such polymers can be in the form of an amine salt,
and may include salts formed with formic, acetic, succinic, citric,
lactic, maleic, fumaric, palmitic, cholic, pamoic, mucic,
d-glutamic, d-camphoric, glutaric, glycolic, phthalic, tartaric,
lauric, stearic, salicyclic, methanesulfonic, benzenesulfonic,
paratoluenesulfonic, sorbic, puric, benzoic, cinnamic and the like
organic acids. A particular polymer can be in the form of an amine
hydrochloric acid salt. An acidic solution for use can be at a
concentration that facilitates the formation of the charged amine
group, but may not be at a concentration that would remove the
amine group or other moieties from the polymer.
[0049] Examples of polymers for use in compositions and methods
disclosed herein can include glycoaminoglycans such as
polysaccharides, gums, starch or cationic derivatives thereof, that
include an amine group. For instance, such polymers can include
chitosan, hyaluronic acid, chrondoitin sulfate, and certain
proteins or polypeptides. As used herein, "polysaccharide" is
understood to mean a biological polymer having sugar subunits, for
example, a starch or a cellulose, or a derivative of such a
biological polymer; chitosan, pectin, or carboxymethyl cellulose
are specific examples.
[0050] Other polymers for use in these systems and methods include
polyalkyleneamines (PAA) such as tetrabutylenepentamine,
polyalkyleneimines (PAI), polyethyleneamine (PEA) such as
triethylenetetramine (TETA) and teraethylenepentamine (TEPA), and
polyethyleneimines (PEI) such as linear polyethyleneimine (LPEI),
branched polyethyleneimine (BPEI), polyallylamines, and
polyvinylamines. Branched polyethylenimine, for example, may have
at least moderate branching. In certain embodiments, film-forming
polymers are used, which can facilitate attachment of the polymer
onto the particles (e.g. "wrapping" of the polymer onto the
particles). Still other polymers useful in these systems and
methods can include poly(amido-amine) dendrimers,
poly(alkylamino-glucaramide), and linear polymers with a single
primary, secondary or tertiary amine group attached to the polymer
units, such as poly(dimethylaminoethyl methacrylates),
dimethylamino dextran, and polylysines.
[0051] In some embodiments, a natural or synthetic polyelectrolyte
can be used as a coupling agent where the polyelectrolyte includes
one or more silicon-containing groups (e.g., silane groups). For
example, the polyelectrolyte can include an aminosilane polymer,
which can optionally be dispersed in an aqueous medium. The silane
groups can allow the polyelectrolyte to bind to the filler
particle, and the amino groups can induce binding with one or more
dye components (e.g., by reacting with a reactive dye). The
resultant surface-modified pigment particles can serve as pigments
that can be used to change the color of a resulting paper product.
The new pigment made according to these methods can also retain
residual functional groups (e.g., amine groups) by not saturating
the coupling agent with dye molecules. The remaining amine groups
can act to bind with fibers of a paper pulp to enhance the strength
and/or weight of a resulting paper product.
[0052] Polymers (e.g., polycations) that contain hydroxyl groups
for dye reaction can also be attached to reactive dyes or other
components, as can cationic polymers where the amines are left free
to preserve the cationic nature of the polymer (either using
stoichiometry or doing the reaction while the amine is charged).
The dyed polycation can then be coated onto the particle surface
directly using electrostatic interactions or by precipitation. The
dyed polycation may also be coupled to the surface of the particle
using a coupling agent. Multilayers of dyed or undyed polycations,
and dyed or undyed polyanions can be built on the surface if
desired to deepen the color of the particle through sequential
addition of the polycations and polyanions. Embodiments using
multiple layers of polycations and polyanions can enhance the
amount of polyelectrolyte available for interacting with other
entities (e.g., by increasing the surface area available).
[0053] In some embodiments where a polymer acts as a coupling
agent, the polymer can attach to surface sites of the filler
particle in a sparse manner, or can be attached in a manner that
the polymer can encapsulate the filler particle. For example, when
applied to papermaking, techniques for encapsulation of filler
particles with polycations (natural or synthetic) can involve such
methods as slowly precipitating, spray drying, or using any known
encapsulation technique to coat the polycation onto the particle.
Using the techniques described herein, or using other techniques
including those familiar to skilled artisans, additional
polyelectrolytes can be added to further increase the performance
properties of the paper or help balance the charge of the paper
stock. For example, this can be done by further encapsulating the
particle or adding it to the stock slurry.
[0054] In embodiments where a filler particle can use a polymer as
a coupling agent, a dye component (e.g., a reactive dye) can be
attached to the polymer to form a surface-modified pigment
particle. In some embodiments, the dye component is directly
attached to the polymer coupling agent without any other
intermediary component, such as reacting at an amine site of an
amine-containing polycation. Such a dye component can be bound to
the polymer before the polymer is bound to the filler particle,
after the polymer is bound to the filler particle, or during a
process in which all components are mixed in a reaction broth and
binding of the components occurs substantially simultaneously. With
the use of an anionic dye component, binding to a polycationic
coupling agent can be performed through the electrostatic
interactions between the dye and polymer. Multiple layers of
polycations and anionic dyes can be used to deepen the color of the
particle.
[0055] FIG. 3 schematically illustrates particular embodiments of
the invention. As shown, a polymer-bound dye 210 may be formed by
combining a reactive dye 220 comprising a chromophore 222 and a
reactive moiety 224 with a binding polymer 214. The binding polymer
214 can have a free end 218 or a plurality of free ends 218 that
can attach to the reactive moiety 224 of the reactive dye 220. In
embodiments, each of the free ends 218 may be adapted for binding
to a single reactive dye 220 or to a plurality of different
reactive dyes 220. The polymer-bound dye 210 can be attached to a
particle 216. Optionally a coating or a series of coatings (not
shown) may be attached to the particle 216, using methods such as
those described herein. In such cases, the polymer-bound dye 210
can be attached to the coating (not shown), as described
previously. In some embodiments, an attachment 228 between the
reactive dye 220 and the binding polymer 214 can be formed first,
and then an attachment 230 between the polymer-bound dye 210 and
the particle 216 or the coated particle (not shown) can be formed.
In some embodiments, multiple layers of polymer-bound dyes 210 or
other polymers (not shown) can be deposited on the particle 216
using the aforesaid methods.
[0056] In some embodiments, other components can bind to the
polymer coupling agent. Such components can include polymers and
other molecules capable of binding with the polymer coupling agent.
For instance, when the coupling agent is a polycation, an anionic
component can be adapted to couple with the polycation. The anionic
component can be used to bind to one or more dye components or
other entities. Examples of anionic components include a
multifunctional entity with a negatively charged moiety, a
polyanion, and appropriately functionalized multifunctional
coupling agents as described in the present application (e.g., a
silane coupling agent). Polyanions, such as a cellulosic or
starch-based polymer, can be advantageously utilized when the
coupling agent is a polycation due to the affinity between the
polymers. Without being bound by any particular theory, anionic
polymers such as cellulosic or starch-based polymers (e.g., pectin,
carboxy methyl cellulose, xanthan gum, and the like) can react with
a dye component at one or more hydroxyl groups, leaving the acid
group free to preserve the anionic character of the polymer. The
reaction product can then be precipitated onto (e.g.,
electrostatically deposited onto) or otherwise attached to a
particle which has been coated with a polycation such as
amine-containing polymer. Polycations can be bound to the filler
particle using a multifunctional coupling agent or some other
mechanism such as electrostatic interactions. In related
embodiments, alternating layers of polycations and dyed polyanions
can be repeated applied to a filler particle surface to increase
the color intensity if desired. Though these embodiments have been
described using dye components bound to the additional component
(e.g., polyanion), it is understood that other types of entities
can also be bound such as other polymers or components that can
enhance the strength or appearance properties of a resulting paper
product.
[0057] In some embodiments, a polycation can be applied onto a
colored particle surface, for example as a layer, to enhance
interactions with anionic pulp fibers. For instance, a polycation
layer can lead to better retention of fillers and/or pigments in
paper products, leading to reduced filler/pigment use during
papermaking processes. Also such polycations can increase strength
properties of the paper product when incorporated into the pulp
sheet relative to not using such polycations. Indeed, these
potential advantages are also accrued in other embodiments of the
present invention where a surface-modified filler particle includes
a component (e.g., a polycation) that can interact favorably with
fibers of a paper pulp. The polycation can be a polyamine including
chitosan, branched polyethylenimine, linear polyethylenimine, and
polyallyl amine. The polyamine can be deposited onto the surface of
the particle using electrostatic interactions, spray drying, by
precipitating the polyamine out of solution onto the particle by
adjusting the pH, or other suitable techniques. For example,
chitosan can be deposited onto the particle by slowly raising the
pH until chitosan is insoluble. In some embodiments, the polycation
layer can be thin, e.g., approximately the wavelength of visible
light or smaller (less than about 500 nm), such that the color
particle surface is not affected significantly, if at all
visually.
Methods for Forming Paper Products with Surface-Modified
Pigments
[0058] Some embodiments are directed to methods of forming paper
products using surface-modified pigments described throughout the
present application. Papermaking processes, including those
understood by one skilled in the art, can be adapted with the
teachings herein to practice various aspects of the invention
described herein.
[0059] Some embodiments of the invention are directed to methods
for producing a paper product (e.g., a paper product with a
selected color). Surface-modified pigments, and mixtures for making
such pigments, can be produced such that one or more components
bind with filler particles (e.g., a dye component using a coupling
agent). Surface-modified pigments, and their corresponding
mixtures, can be mixed with a pulp having fibers to make a
papermaking dispersion. In some circumstances, the filler particles
of the surface-modified pigments can bind to one or more pulp
fibers, resulting in a strengthened paper product and/or one that
retains fines to a larger degree. The dispersion can then be formed
into a sheet of paper or other paper-based material, for example by
using techniques for molding or drawing the dispersion into an
appropriate form. The sequence in which such operations are
performed can be in any appropriate manner for forming a
papermaking mixture or paper-based material. For instance, all of
the components (such as particles, coupling agent and dye) can be
added in one step to the reactor, while in other embodiments, the
particles can be functionalized with dye and or other components,
and then subsequently added to the other papermaking materials
(e.g., pulp and additional fillers etc.). The components of the
papermaking mixture include any permutation and combination of
materials as disclosed in the present application.
[0060] For uses in the papermaking industry, the compositions and
methods described herein can further include adding other
substances to a slurry before forming the sheet to boost
interactions of the surface-modified filler particles with the pulp
fibers. In some embodiments, additives such as additional
cellulosic or starch polymers or synthetic ionic strength enhancers
may be used. For example polymers such as a cationic starch can
increase the strength of a final paper product. In another example,
polyacrylic acid copolymers can be added to aid charge balance or
help retain cationic filler particles and/or surface-modified
pigments. Wet strength chemicals such as melamine-formaldehyde
resins, urea-formaldehyde resins, and epoxidized
polyamine-polyamide resins can also be used. In other embodiments,
dyed cellulosic or starch polymers can be added to impart color and
strength to the paper. In embodiments, paper formed according to
these compositions and methods can be coated with an oppositely
charged polymer or with amine reactive polymers to impart strength,
or the paper may be coated with a polymer imparting hydrophobicity
or superhydroyphobicity to enhance the product's release
characteristics.
Surface-Modified Pigments
[0061] Some embodiments of the present invention are directed to
surface-modified pigment particles, which can be added to a
papermaking slurry to color a paper product or used in an ink to be
applied to a paper. In general, such surface-modified pigments can
enhance the appearance or quality of a paper product created by
using such a pigment, or can result in an ink formulation that can
have superior properties such as increased affinity for the fibers
of paper. In some embodiments, the surface-modified pigments can
include pigment particles that have a fiber-affinity component
bound to the pigment particles. Fiber-affinity components include
materials such as polymers, and in particular polycations as
disclosed throughout the present application. For example, a
polycation, such as but not limited to chitosan or a cationic
starch, can be attached or encapsulated onto the particles to form
a polycation overcoat on the pigment. A fiber-affinity component
can be adapted to improve binding of the pigment particles with the
fibers of a paper-based product, which can result in the enhanced
retention of pigment particles, other fillers, and/or fines during
paper making and/or increased strength of the paper product.
[0062] Pigments that can be utilized with the above-described
embodiment include the range of pigments known to those skilled in
the art, as well as the surface-modified pigments described in the
present application. Accordingly, in some embodiments, a pigment
particle can comprise at least one dye component and a coupling
agent to bind the dye component(s) to a filler particle. The
arrangements and types of filler particles, dye components, and
coupling agents include all those described in the various
embodiments within the present application. For example, the
coupling agent can be a multifunctional coupling agent, or a
polyelectrolyte. Particular polyelectrolytes include
polyelectrolytes having an isocyanosilane or another silane.
Amine-containing polymers, including but not limited to
polyethylenimine, poly(allyl amine), chitosan, and many proteins,
can also be used. Amine-containing polymers can be adsorbed
directly to a particle surface, or can be coupled thereto using
another coupling agent, as described elsewhere within the present
application. Free amine groups can be used to tag on dye or
interact with the paper fibers or other paper additives. As well,
alternating layers of polyelectrolytes with opposite net charge can
be applied to the particle surface.
[0063] Fiber-affinity components, such as a polycation adapted to
interact with pulp fibers, can alter the character of the filler
particle surface, and can be used to provide additional
functionality. For example, a polycation can be bound with a dye
component (e.g., reactive or ionic) to provide a selected
coloration to the surface-modified pigment. The dye component can
be bound to the polycation before, after, or during the
polycation's binding with the filler particle. Colored pigments can
also be further treated with another layer on top (e.g., a
biopolymer or polyanion) of the dyed particle or left as is. Such
layering can adapt the features of any of the embodiments herein
particular to adding a layer to a colored pigment.
[0064] As previously mentioned, surface-modified pigments particles
in accord with these embodiments can also be used in ink
formulations. The ink formulation can include a medium (e.g., an
aqueous-based medium) for dispersing the surface-modified pigment
particles in which such particles provide a selected color to the
ink. In one example, silicon dioxide nanoparticles functionalized
with colored dyes can provide high resolution when used in an
inkjet printer. In some embodiments, the pigments can be
functionalized with a polycation to interact favorably with pulp
fibers. For instance, chitosan can be precipitated onto organic or
inorganic pigments. These pigments, which now have a high affinity
for the paper fibers (e.g., cellulose-based fibers), can be used in
inks in printers or as fillers to make colored paper. Accordingly,
such pigments can be superior to conventional dyes due to lower ink
migration once printed on a paper sheet. In addition, such an ink
formulation can be separated from the pulp during a paper recycling
process through addition of salt solution to interrupt the
electrostatic interactions between the polyamine on the particle
surface and the pulp fibers. Small particles such as nanoparticles
(e.g., having an average size of less than 100 nm) can be preferred
to achieve a high print resolution. Pigments produced according to
these systems and methods can be useful in a variety of printing
processes, including at-home printers, office printers and
industrial printers.
[0065] It is understood by those skilled in the art that colored
pigments produced according to these compositions and methods can
be added to the papermaking process stream at any place where
filler particles would typically be added. Such pigments may also
be added to the paper as a coating step, especially when particles
that are normally used in paper coatings form the base particle for
subsequent color attachment as described herein.
[0066] In other embodiments, surface-modified pigment particles can
be further modified by agents prior to, or in the paper making
stream, with anionic or reactive agents to impart properties such
as hydrophobicity. One example of such agents include sizing
agents, which can have aliphatic, fluorinated or siloxane reactive
chemistries. In further embodiments, particles can be
functionalized with polyelectrolytes through self-assembly of the
polyelectrolyte on the surface of the particle or fiber. Subjecting
these moieties to either a polymer of opposite charge to swap ionic
character or form multilayers on the surface or by reacting
chemistries to the functional groups on the polymer the surface
characteristics can easily be altered for use. This process can be
repeated by using polyelectrolytes of opposite charges. As in the
case of this and all of the other embodiments, these functionalized
and/or dyed particles may interact with the pulp fibers and
increase the strength of the paper, increase particle and fines
retention, and reduce amount of materials necessary in the
papermaking process.
[0067] In any of these embodiments, additional polyanions can be
added that will further interact electrostatically with the
functionalized particles. These polyanions may or may not be dyed
with reactive dyes. Also, as would be understood by those of skill
in the art, the particles described herein may be added anywhere in
the papermaking process. For example, the particles can be used as
filler or coating, where such particles can contribute to enhanced
properties in paper, as would be understood by those of ordinary
skill in the art.
[0068] While the present invention has been described in terms of
specific methods, structures, and compositions it is understood
that variations and modifications will occur to those skilled in
the art upon consideration of the present application. As well, the
features illustrated or described in connection with one embodiment
may be combined with the features of other embodiments. Such
modifications and variations are intended to be included within the
scope of the present invention. Those skilled in the art will
appreciate, or be able to ascertain using no more than routine
experimentation, further features and advantages of the invention
based on the above-described embodiments. Accordingly, the
invention is not to be limited by what has been particularly shown
and described, except as indicated by the appended claims. All
publications and references are herein expressly incorporated by
reference in their entirety.
EXAMPLES
[0069] The following examples are provided to illustrate some
aspects of the present application. The examples, however, are not
meant to limit the practice of any embodiment of the invention.
[0070] Chemicals used in the following experiments included the
following: Chitosan cg110 (Primex, Siglufjodur, Iceland); Softwood
(Georgia-Pacific, Neenah, Wis.); Kaolin (Engelhard Corporation (now
BASF Catalysts), Iselin, N.J.); 3-aminopropyltrimethoxy silane
(Gelest, Morrisville, Pa.); PRO Intense Blue 406 MX reactive dye
(Pro Chemical & Dye, Somerset, Mass.); PRO Turkey Red 320 MX
reactive dye (Pro Chemical & Dye, Somerset, Mass.); PRO Sun
Yellow 108 MX reactive dye (Pro Chemical & Dye, Somerset,
Mass.); PRO Deep Navy 414 MX reactive dye (Pro Chemical & Dye,
Somerset, Mass.); Silicon dioxide (Nanostructured & Amorphous
Materials Inc., Los Alamos, N. Mex.); Calcium carbonate (Spectrum
Chemicals C1078, Gardena, Calif.); Low methoxy pectin (CPKelco Genu
Pectin (Citrus) Type USP/100, Nijmegen, The Netherlands); Xanthan
gum (EMD Chemicals XX1110-1; Gibbstown, N.J.); NaOH (Spectrum
Chemicals S1303, Gardena, Calif.); Hydrochloric acid (for chitosan
solutions) (Sigma Aldrich 258148, St. Louis, Mo.); Sodium Chloride
(for brine solution) (Sigma Aldrich, St. Louis, Mo.); Isopropyl
Alcohol (EMD Chemicals PX1834-1, Darmstadt, Germany).
Example 1
Blue Kaolin with Silane Linker
[0071] Kaolin pigments that were blue in color were prepared by
mixing 20 g of kaolin particles, 4.0 mL of 3-aminopropyltrimethoxy
silane, and 0.8 g of PRO Intense Blue 406 MX reactive dye into 400
mL of deionized water. The reaction was allowed to proceed for 4
hours while being stirred. The reaction product was filtered and
(i) washed with water until filtrate was clear; then (ii) washed
with brine solution until the filtrate was clear; then (iii) washed
with water to rinse away brine; then (iv) washed with isopropyl
alcohol to remove water. The pigments were then placed in a
55.degree. C. vacuum oven. After drying overnight, blue pigments
were obtained.
Example 2
Blue Silica with Silane Linker
[0072] Silica pigments that were blue in color were prepared by
mixing 20 g of silicon dioxide particles (having an average
diameter of approximately 15 nm), 4.0 mL of 3-aminopropyltrimethoxy
silane, and 0.8 g of PRO Intense Blue 406 MX reactive dye into 400
mL of deionized water. The reaction was allowed to proceed for 4 h
while being stirred. The reaction product was filtered and (i)
washed with water until filtrate was clear; then (ii) washed with
brine solution until the filtrate was clear; then (iii) washed with
water to rinse away brine; then (iv) washed with isopropyl alcohol
to remove water. The pigments were then placed in a 55.degree. C.
vacuum oven. After drying overnight, blue pigments were
obtained.
Example 3
Red Kaolin with Silane Linker
[0073] Kaolin pigments that were red in color were prepared by
mixing 20 g of kaolin particles, 4.0 mL of 3-aminopropyltrimethoxy
silane, and 0.8 g of PRO Turkey Red 320 MX reactive dye into 400 mL
of deionized water. The reaction was allowed to proceed for 4 hours
while being stirred. The reaction product was filtered and (i)
washed with water until filtrate was clear; then (ii) washed with
brine solution until the filtrate was clear; then (iii) washed with
water to rinse away brine; then (iv) washed with isopropyl alcohol
to remove water. The pigments were then placed in a 55.degree. C.
vacuum oven. After drying overnight, red pigments were
obtained.
Example 4
Blue Kaolin with Silane Linker and Chitosan Coating
[0074] A slurry of blue kaolin particles was created by stirring 5
g of particles from Example 1 into 50 mL of deionized water. To
this vessel, 2.5 mL of a 2.0% CG110 chitosan solution (solution was
made by dissolving chitosan into acidic water) was slowly added. To
this, 0.1 M NaOH was added until the pH reached 8.
Example 5
Blue Silica with Silane Linker and Chitosan Coating
[0075] A slurry of blue silica particles was created by stirring 5
g of particles from Example 2 into 50 mL of deionized water. To
this vessel, 2.5 mL of a 2.0% CG110 chitosan solution (solution was
made by dissolving chitosan into acidic water) was slowly added. To
this, 0.1 M NaOH was added until the pH reached 8.
Example 6
Blue Kaolin with Chitosan Linker
[0076] A slurry of kaolin particles was created by stirring 20 g of
kaolin into 200 mL of deionized water. To this vessel, 10 mL of a
2.0% CG110 chitosan solution (solution was made by dissolving
chitosan into acidic water) was slowly added. To this, 0.1 M NaOH
was added until the pH reached 8. To this vessel, 0.8 g of PRO
Intense Blue 406 MX reactive dye was added. The reaction was
allowed to proceed for 2 hours while being stirred. The reaction
product was filtered and (i) washed with water until filtrate was
clear; then (ii) washed with brine solution until the filtrate was
clear; then (iii) washed with water to rinse away brine; then (iv)
washed with isopropyl alcohol to remove water. The pigments were
then placed in a 55.degree. C. vacuum oven. After drying overnight,
blue pigments were obtained.
Example 7
Blue Silica with Chitosan Linker
[0077] A slurry of silica particles was created by stirring 20 g of
silicon dioxide (having an average diameter of approximately 15 nm)
into 200 mL of deionized water. To this vessel, 10 mL of a 2.0%
CG110 chitosan solution (solution was made by dissolving chitosan
into acidic water) was slowly added. To this, 0.1 M NaOH was added
until the pH reached 8. To this vessel, 0.8 g of PRO Intense Blue
406 MX reactive dye was added. The reaction was allowed to proceed
for 2 hours while being stirred. The reaction product was filtered
and (i) washed with water until filtrate was clear; then (ii)
washed with brine solution until the filtrate was clear; then (iii)
washed with water to rinse away brine; then (iv) washed with
isopropyl alcohol to remove water. The pigments were then placed in
a 55.degree. C. vacuum oven. After drying overnight, blue pigments
were obtained.
Example 8
Blue Calcium Carbonate with Chitosan Linker
[0078] A slurry of calcium carbonate particles was created by
stirring 20 g of calcium carbonate into 200 mL of deionized water.
To this vessel, 10 mL of a 2.0% CG110 chitosan solution (solution
was made by dissolving chitosan into acidic water) was slowly
added. The high pH of the calcium carbonate solution caused the
chitosan to precipitate onto the calcium carbonate particles. To
this vessel, 0.8 g of PRO Intense Blue 406 MX reactive dye was
added. The reaction was allowed to proceed for 2 hours while being
stirred. The reaction product was filtered and (i) washed with
water until filtrate was clear; then (ii) washed with brine
solution until the filtrate was clear; then (iii) washed with water
to rinse away brine; then (iv) washed with isopropyl alcohol to
remove water. The pigments were then placed in a 55.degree. C.
vacuum oven. After drying overnight, blue pigments were
obtained.
Example 9
Blue Calcium Carbonate with Chitosan Linker and Chitosan
Coating
[0079] A slurry of blue calcium carbonate was created by stirring 5
g of particles from Example 8 into 50 mL of deionized water. To
this vessel, 2.5 mL of a 2.0% CG110 chitosan solution (solution was
made by dissolving chitosan into acidic water) was slowly
added.
Example 10
Blue Low Methoxy Pectin
[0080] Blue low methoxy pectin was prepared by first adding 0.5 g
of low methoxy pectin to 100 mL of deionized water. NaOH was then
added to bring the pH up to 8.0 before adding 0.2 g of PRO Deep
Navy 414 MX reactive dye. The reaction was left for one hour. The
dyed pectin solution was then poured into a large volume of acetone
where the dyed pectin precipitated out of the solution. The dyed
pectin was then washed 3.times. with acetone to remove any
unreacted dye. After drying overnight in a 55.degree. C. vacuum
oven, a polymer blue in color was obtained.
Example 11
Yellow Low Methoxy Pectin
[0081] Yellow low methoxy pectin was prepared by first adding 0.5 g
of low methoxy pectin to 100 mL of deionized water. NaOH was then
added to bring the pH up to 8.0 before adding 0.2 g of PRO Sun
Yellow 108 MX reactive dye. The reaction was left for one hour. The
dyed pectin solution was then poured into a large volume of acetone
where the dyed pectin precipitated out of the solution. The dyed
pectin was then washed 3.times. with acetone to remove any
unreacted dye. After drying overnight in a 55.degree. C. vacuum
oven, a polymer yellow in color was obtained.
Example 12
Blue Xanthan Gum
[0082] Blue xanthan gum was prepared by first adding 0.5 g of
xanthan gum to 100 mL of deionized water. NaOH was then added to
bring the pH up to 8.0 before adding 0.2 g of PRO Deep Navy 414 MX
reactive dye. The reaction was left for one hour. The dyed xanthan
gum solution was then poured into a large volume of acetone where
the dyed pectin precipitated out of the solution. The dyed xanthan
gum was then washed 3.times. with acetone to remove any unreacted
dye. After drying overnight in a 55.degree. C. vacuum oven, a
polymer blue in color was obtained.
Example 13
Blue Calcium Carbonate with Chitosan and Pectin
[0083] A slurry of calcium carbonate particles was created by
stirring 5 g of calcium carbonate into 50 mL of deionized water. To
this vessel, 2.5 mL of a 2.0% CG110 chitosan solution (solution was
made by dissolving chitosan into acidic water) was slowly added.
The high pH of the calcium carbonate solution caused the chitosan
to precipitate onto the calcium carbonate particles. To this, 15 mL
of a 2.5% blue-dyed pectin solution (obtained by dissolving polymer
from Example 10 in water) was added. The contents were filtered and
washed with water until filtrate was clear. The pigments were then
placed in a 80.degree. C. vacuum oven. After drying overnight, blue
pigments were obtained.
Example 14
Pulp Slurry
[0084] A 5% slurry was prepared by blending 20 g refurnished
softwood in 400 mL of water. The slurry was diluted to 0.5% pulp by
adding 3.6 L of water.
Example 15
Pulp with Chitosan and Blue Pectin Slurry
[0085] A vessel was filled with 1 L of the pulp slurry prepared in
Example 14. To this vessel, 2.5 mL of a 2.0% CG110 chitosan
solution (solution was made by dissolving chitosan into acidic
water) was slowly added. To this, 0.1 M NaOH was added until the pH
reached 8. To this, 50 mL of a 2.5% blue-dyed low methoxy pectin
solution (obtained by dissolving polymer from Example 10 in water)
was added.
Example 16
Handsheet Preparation
[0086] Handsheets were prepared using a Mark V Dynamic Paper
Chemistry Jar and Hand-Sheet Mold from Paper Chemistry Laboratory,
Inc. (Larchmont, N.Y.). The appropriate volume of 0.5% pulp slurry
was mixed with the appropriate volume of pigment slurry. This
combined slurry was diluted with water up to 2 L and added to the
handsheet maker. The slurry 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.
Example 17
Paper with Blue Kaolin
[0087] Two handsheets were produced according to the method of
Example 16 using 240 mL of the material from Example 14 and 0.6 of
pigment from Example 1 (pigment was first dispersed in 20 mL of
water). The resulting handsheets were blue in color.
Example 18
Paper with Red Kaolin
[0088] Two handsheets were produced according to the method of
Example 16 using 240 mL of the material from Example 14 and 0.6 of
pigment from Example 3 (pigment was first dispersed in 20 mL of
water). The resulting handsheets were red in color.
Example 19
Paper with Blue Kaolin Coated with Chitosan
[0089] Two handsheets were produced according to the method of
Example 16 using 240 mL of the material from Example 14 and 0.3 of
pigment from Example 4 (pigment was first dispersed in 20 mL of
water). The resulting handsheets were blue in color.
Example 20
Paper with Blue Calcium Carbonate
[0090] Two handsheets were produced according to the method of
Example 16 using 240 mL of the material from Example 14 and 0.6 of
pigment from Example 8 (pigment was first dispersed in 20 mL of
water). The resulting handsheets were blue in color.
Example 21
Paper with Blue Calcium Carbonate Coated with Chitosan
[0091] Two handsheets were produced according to the method of
Example 16 using 240 mL of the material from Example 14 and 0.3 of
pigment from Example 9 (pigment was first dispersed in 20 mL of
water). The resulting handsheets were blue in color.
Example 22
Paper with Blue Low Methoxy Pectin
[0092] Two handsheets were produced according to the method of
Example 16 using 300 mL of the material from Example 15. The
resulting handsheets were blue in color.
EQUIVALENTS
[0093] While specific embodiments of the subject invention have
been discussed, the above specification is illustrative and not
restrictive. Many variations of the invention will become apparent
to those skilled in the art upon review of this specification. The
full scope of the invention should be determined by reference to
the claims, along with their full scope of equivalents, and the
specification, along with such variations.
[0094] Unless otherwise indicated, all numbers expressing
quantities of ingredients, reaction conditions, and so forth used
in the specification and claims are to be understood as being
modified in all instances by the term "about." Accordingly, unless
indicated to the contrary, the numerical parameters set forth in
this specification and attached claims are approximations that may
vary depending upon the desired properties sought to be obtained by
the present invention.
* * * * *