PIGMENTS FOR COLORED PAPER

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims the benefit of a U. S. Provisional Patent

Application filed on October 27, 2006 and bearing serial number 60/855,023, the text of which is incorporated herein by reference in its entirety.

The present application is also related to U.S. Patent Application Publication Number US 2007/0107635 Al , bearing serial number 11/501 ,463, filed August 9, 2006, entitled "Dye- Attached and/or Surface Modified Pigments"; and an international patent application bearing application number PCT/US07/03159, filed February 5, 2007, entitled "Functionalization of Paper Components." Both of these related applications are hereby incorporated by reference herein.

FIELD OF THE APPLICATION

The present application relates to materials and processes for modifying paper products, e.g., making colored paper.

BACKGROUND 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. 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

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.

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. 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.

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. 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.

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.

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.

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.

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

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.

FIG. 1 illustrates schematically a system for attaching a reactive dye to a particle, consistent with an embodiment of the present invention.

FIG. 2 illustrates schematically a system for attaching a reactive dye to a coated particle, consistent with an embodiment of the present invention.

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

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. 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 Unless the context of use suggests otherwise, the following definitions apply to the terms and phrases used throughout the present application.

The terms "a" and "an" are interchangeable and are the same as the phrase "one or more."

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

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

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 λi 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

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.

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 nonaqueous 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.

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

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.

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. 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 cKaracteristics. 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.

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") ,dy ^e s, which are approved for use in foods, drugs, and cosmetics subject to U.S. Food and Drug Administration regulations.

Coupling Agents and Functional Groups

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.

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. 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.

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.

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.

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. 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.

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.

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

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

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 1 18 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

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-containmg polymers

discussed elsewhere within the present application can also be incorpo rated. 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.

In other embodiments, a surface-modifed 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 ami no -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 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.

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).

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 ₂ ), secondary (--NHR ₂ ), and/or tertiary amine (--NR 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. 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.

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. 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 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)

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

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.

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.

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 functional ized 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.

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.

Methodsfor Forming Paper Products with Surface-Modified Pigments

Some embodiments are directed to methods of forming paper products using surface-modified pigments described throughout Ihe 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.

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. 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 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. 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.

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.

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 sμch 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.

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 fijler 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. 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.

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. 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

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.

Chemicals used in the following experiments included the following: Chitosan cgl 10 (Primex, Siglufjodur, Iceland); Softwood (Georgia-Pacific, Neenah, WI); Kaolin

(Engelhard Corporation (now BASF Catalysts), Iselin, NJ); 3-aminopropyltrimethoxy silane (Gelest, Morrisville, PA); PRO Intense Blue 406 MX reactive dye (Pro Chemical & Dye, Somerset, MA); PRO Turkey Red 320 MX reactive dye (Pro Chemical & Dye, Somerset, MA); PRO Sun Yellow 108 MX reactive dye (Pro Chemical & Dye, Somerset, MA); PRO Deep Navy 414 MX reactive dye (Pro Chemical & Dye, Somerset,

MA); Silicon dioxide (Nanostructured & Amorphous Materials Inc., Los Alamos, NM); Calcium carbonate (Spectrum Chemicals Cl 078, Gardena, CA); Low methoxy pectin (CPKelco Genu Pectin (Citrus) Type USP/100, Nijmegen, The Netherlands); Xanthan gum (EMD Chemicals XXl 110-1; Gibbstown, NJ); NaOH (Spectrum Chemicals S 1303, Gardena, CA); 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 PXl 834-1, Darmstadt, Germany).

Example 1. Blue kaolin with silane linker 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 (n) washed with brine solution until the filtrate was clear, then (in) washed with water to πnse away brine, then (iv) washed with isopropyl alcohol to remove water The pigments were then placed in a 55°C vacuum oven After drying overnight, blue pigments were obtained

Example 2 Blue silica with silane linker

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- aminopropyltπmethoxy 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 (n) washed with brine solution until the filtrate was clear, then (in) washed with water to πnse away brine, then (iv) washed with isopropyl alcohol to remove water The pigments were then placed in a 55°C vacuum oven After drying overnight, blue pigments were obtained

Example 3 Red kaolin with silane linker

Kaolin pigments that were red in color were prepared by mixing 20 g of kaolin particles, 4 0 mL of 3 -aminopropyltπmethoxy 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 (π) washed with brine solution until the filtrate was clear, then (in) washed with water to rinse away brine, then (iv) washed with isopropyl alcohol to remove water The pigments were then placed m a 55 ⁰ C vacuum oven After drying overnight, red pigments were obtained

Example 4 Blue kaolin with silane linker and chitosan coating

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 a2 0% CGI lO 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

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% CGl 10 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

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% CGl 10 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 ⁰ C vacuum oven. After drying overnight, blue pigments were obtained.

Example 7. Blue silica with chitosan linker

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% CGl 10 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 ih a 55 ⁰ C vacuum oven. After drying overnight, blue pigments were obtained.

Example 8. Blue calcium carbonate with chitosan linker

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% CGl 10 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°C vacuum oven. After drying overnight, blue pigments were obtained.

Example 9. Blue calcium- carbonate with chitosan linker and chitosan coating

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% CGIlO chitosan solution (solution was made by dissolving chitosan into acidic water) was slowly added.

Example 10. Blue low methoxy pectin

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 3x with acetone to remove any unreacted dye. After drying overnight in a 55°C vacuum oven, a polymer blue in color was obtained.

Example 11. Yellow low methoxy pectin

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 3x with acetone to remove any unreacted dye. After drying overnight in a 55°C vacuum oven, a polymer yellow in color was obtained.

Example 12. Blue xanthan gum

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 3x with acetone to remove any unreacted dye. After drying overnight in a 55 ⁰ C vacuum oven, a polymer blue in color was obtained.

Example 13. Blue calcium carbonate with chitosan and pectin

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% CGl 10 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°C vacuum oven. After drying overnight, blue pigments were obtained.

Example 14. Pulp slurry

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

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% CGI lO 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

Handsheets were prepared using a Mark V Dynamic Paper Chemistry Jar and Hand-Sheet Mold from Paper Chemistry Laboratory, Inc. (Larchmont, NY). 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

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

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

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

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

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

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

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.

[0001] 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. What is claimed is: