# Patent

## Title
Systems and methods for pulsed direct current magnetic actuated milling of pigment dispersions

## Abstract

A system for pigment milling includes a pulsing direct current (DC) source that generates a DC pulse, an electromagnetic field generating subunit that includes an electromagnetic coil coupled to the pulsing DC source to receive the DC pulse and to generate a magnetic field, and a rotating container subunit that includes a container for holding magnetic particles and ink pigment particles in an ink carrier, and a rotating subunit to rotate the container. A portion of the container is disposed within the electromagnetic coil and generation of the magnetic field causing motion of the magnetic particles thereby dispersing the ink pigment particles within the ink carrier.

## Background
BACKGROUND
Embodiments disclosed herein relate to systems and methods for pigment processing, particularly for toner applications. More particularly, embodiments disclosed herein relate to the use of magnetic actuated milling to facilitate making pigment dispersions.
Pigment dispersions are an important component in the preparation of emulsion aggregation (EA) toner. In order for pigment particles to form aggregates with the latex particles, the pigment particles are ideally smaller or at least comparable in size to the latex particles. Pigments are usually dispersed in a medium and milled until average pigment particle size is in a range from about 100 nm to about 200 nm.
Conventional pigment dispersion processes may be energy intensive and lengthy and the cost associated with their preparation can be as high as 50% of the total pigment dispersion cost. For pigment dispersion utilizing an in-line rotor-stator type homogenizer, the length of process time may exceed four hours. Among CMYK pigments, carbon black is one of the easiest and least expensive pigments to disperse, while colored pigments, such as magenta and yellow pigments, are harder to disperse and hence longer milling times are typically required.
Several types of solenoids or AC motors have been used to provide an alternating magnetic field to drive the movement of magnetic particles for milling. The electromagnetic forces provided by AC solenoids are generally weak, on the order of about 400 Gauss. Additionally, both switching relay and coils tend to heat up in just minutes in such devices rendering longer milling times impractical. While cooling may be possible, relays and coils are often too well insulated to be cooled effectively.
There remains a need to develop a dispersion technology which reduces processing time and cost, without sacrificing benchmark material properties (e.g., small size and relatively narrow particle size distribution).
SUMMARY
In some aspects, embodiments herein relate to systems for pigment milling comprising a pulsing direct current (DC) source that generates a DC pulse, an electromagnetic field generating subunit comprising an electromagnetic coil coupled to the pulsing DC source to receive the DC pulse and to generate a magnetic field, and a rotating container subunit comprising a container for holding a plurality of magnetic particles and a plurality of ink pigment particles in an ink carrier, and a rotating subunit to rotate the container, wherein a portion of the container is disposed within the electromagnetic coil and generation of the magnetic field causes motion of the plurality of magnetic particles thereby dispersing the plurality of ink pigment particles within the ink carrier.
In some aspects, embodiment herein relate to methods of milling a pigment comprising providing a container, the container including a plurality of ink pigments, a plurality of magnetic particles, and an ink carrier, generating a DC pulse by a direct current (DC) source, providing the DC pulse to an electromagnetic coil to generate a magnetic field, and rotating the container by a rotating subunit, wherein a portion of the container is disposed within the electromagnetic coil and generation of the magnetic field causes motion of the plurality of magnetic particles thereby dispersing the plurality of ink pigment particles within the ink carrier.



BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present embodiments, reference may be made to the accompanying figures.
FIG. 1 shows a block diagram of a pulsing direct current electromagnet subunit with pulsing direct current source and coil, along with a container-rotating subunit, in accordance with embodiments disclosed herein;
FIG. 2 shows a block diagram of the pulsing direct current electromagnet subunit of FIG. 1 with components making up the pulsing direct current source and connectivity to the coil, in accordance with embodiments disclosed herein;
FIG. 3 an exemplary circuit diagram of a direct current source and coil that make up the pulsing direct current electromagnet subunit in accordance with the present embodiments, in accordance with embodiments disclosed herein;
FIG. 4 shows an exemplary prototype direct current source for the pulsing direct current electromagnet subunit in accordance with embodiments disclosed herein;
FIG. 5 shows an exemplary working prototype electromagnetic coil (wrapped) which is connected to the pulsing direct current source of FIG. 4, in accordance with embodiments disclosed herein;
FIG. 6 shows a close-up of the coil and of FIG. 5, in accordance with embodiments disclosed herein;
FIG. 7 shows a graph of particle size and particle size distribution of a magenta pigment dispersion prepared using systems and methods in accordance with embodiments disclosed herein;
FIG. 8 shows a plot of effective particle diameter d50 of magenta pigment of FIG. 7, as a function of time using systems and methods in accordance with embodiments disclosed herein;
FIG. 9 shows a graph of particle size and particle size distribution of yellow pigment dispersion prepared using systems and methods in accordance with embodiments disclosed herein;
FIG. 10 shows a plot of effective particle diameter d50 of yellow pigment of FIG. 9, as a function of time using systems and methods in accordance with embodiments disclosed herein.



DETAILED DESCRIPTION
In the following description, reference is made to the accompanying drawings, which form a part hereof and which illustrate several embodiments. It is understood that other embodiments may be utilized and structural and operational changes may be made without departure from the scope of the present disclosure. The same reference numerals are used to identify the same structure in different figures unless specified otherwise. The structures in the figures are not drawn according to their relative proportions and the drawings should not be interpreted as limiting the disclosure in size, relative size, or location.
Embodiments herein provide systems and methods for pigment milling using direct current pulsing electromagnets with magnetic particles to assist in milling.
Thus, in some embodiments, there are provided devices for pigment milling using pulsed direct current (DC) electromagnets. Such devices may be employed in pigment milling methods which benefit from reduced cycle time while avoiding issues in similar magnetic actuated methods, such as rapid heat accumulation as observed in alternating current (AC)-based devices. Further advantages include potentially lower cost due to reduced process cycle time. The systems and methods disclosed herein are provided with containers/vessels that rotate when in use, further improving milling effectiveness. Those skilled in the art will appreciate, however, that depending on the material being milled, rotation of the container may be entirely optional. Thus, for example, with materials that are easier to mill, magnetic actuated mixing alone may be sufficient. The systems and methods disclosed herein may be adapted to a continuous emulsion aggregation toner process scheme. Overall, the methods disclosed herein provide improved performance over previously known methods. These and other advantages will be apparent to those skilled in the art.
In embodiments, there are provided systems for pigment milling comprising a pulsing direct current (DC) source that generates a DC pulse, an electromagnetic field generating subunit comprising an electromagnetic coil coupled to the pulsing DC source to receive the DC pulse and to generate a magnetic field, and a rotating container subunit comprising a container for holding a plurality of magnetic particles and a plurality of ink pigment particles in an ink carrier, when in use, a portion of the container is disposed within the electromagnetic coil, and a rotating subunit to rotate the container; wherein when in use, generation of the magnetic field causes motion of the plurality of magnetic particles thereby dispersing the plurality of ink pigment particles within the ink carrier.
In embodiments, there are provided systems for pigment milling comprising a pulsing direct current (DC) source that generates a DC pulse, an electromagnetic field generating subunit comprising an electromagnetic coil coupled to the pulsing DC source to receive the DC pulse and to generate a magnetic field, and a rotating container subunit comprising a container for holding a plurality of magnetic particles and a plurality of ink pigment particles in an ink carrier, and a rotating subunit to rotate the container, wherein a portion of the container is disposed within the electromagnetic coil and generation of the magnetic field causes motion of the plurality of magnetic particles thereby dispersing the plurality of ink pigment particles within the ink carrier.
Referring now to FIG. 1, there is shown a pigment milling system 100 comprising a pulsing DC source 110 which is coupled to an electromagnetic field generating subunit comprising an electromagnetic coil 120 coupled to pulsing DC source 110. A rotating container subunit 130 comprises a container 140 for holding a plurality of magnetic particles and a plurality of ink pigment particles in an ink carrier. As indicated at least a portion of container 140 is disposed with electromagnetic coil 120. In embodiments, the portion of container 140 disposed within electromagnetic coil 120 is centered, in other embodiments, container 140 is offset from center. In embodiments, the portion of container 140 that is disposed within electromagnetic coil 120 includes the entire portion of container 140 up to the level of the ink carrier fluid. In embodiments, the entirety of container 140 is disposed within electromagnetic coil 120. In some embodiments, system 100 may be configured to oscillate container 140 to variable depths within electromagnetic coil 120. This motion of container 140 along the axis of electromagnetic coil 120 may be performed in addition to or in lieu of rotating container 140.
In embodiments, container 140 is cylindrical, although its geometry can be any desired geometry including rectangular prism, conical, cubical prism, triangular prism, hexagonal prism, or even spherical.
Rotating container subunit 130 further comprises a rotating subunit 150 to rotate container 140. In use, the system thus provides for simultaneous rotation of container 140 while delivering periodic DC pulse to electromagnetic coil 120 with concomitant generation of a high strength magnetic field. The combined actions may provide exceptional shearing power to mill particles effectively via chaotic motion of the plurality of magnetic particles present in container 140. Those skilled in the art will recognize that with the high magnetic field strength generated in electromagnetic coil 120, ink pigments that are easier to disperse, such as carbon black, may allow the system to run without the use of rotating subunit 150. In accordance with such embodiments, system 100 for milling easily dispersed pigments may completely exclude rotating subunit 150. Thus, for easily milled pigments, the system has the further advantage of reducing mechanically driven components susceptible to wear.
In embodiments, rotating subunit 150 may rotate container 140 clockwise and in other embodiments counter-clockwise.
Referring now to FIG. 2, there is shown a more detailed block diagram of pulsing DC source 110 which includes an alternating current source 200 and a voltage rectifier 210 that converts a voltage provided by AC source 200 to a DC voltage. In embodiments, voltage rectifier 210 further multiples the DC voltage. Voltage rectifier 210 may be configured to double, treble, or quadruple the DC voltage. Those skilled in the art will appreciate that any degree of DC voltage amplification may be selected with appropriate circuitry.
In embodiments, pulsing DC source 110 further includes one or more capacitors 220 to store the DC voltage. Other storage means may be provided besides a bank of capacitors, such as supercapacitors, ultracapacitors and other systems having larger capacitance in smaller sizes. In embodiments, pulsing DC source 110 further includes a switching circuit 230 to receive the DC voltage from the one or more capacitors 220 and provide the DC pulse which is coupled to the electromagnetic coil 120. Referring to FIG. 3, switching circuit 230 may be turned off and on according to a duty cycle generated by one or more relays 230a/230b to maintain a target operating temperature of electromagnetic coil 120. In embodiments, the one or more relays 230a/230b provides the DC pulse with a duration of 0.4 to 0.6 seconds. Those skilled in the art will recognize that this range of pulse times is merely exemplary and other acceptable pulse durations may be fall outside this range while still allowing for acceptable operating temperatures.
The length of the pulse allowable may be determined for a given system based on a target operating temperature. The theoretical heat generated from the coil for a given pulse time may be calculated and a pulse time appropriately selected to meet a target operating temperature. The power consumed in a DC electromagnet is due to the resistance of the windings, and is dissipated as heat. Since the magnetic field is proportional to the product NI, the number of turns in the windings N and the current I can be chosen to minimize heat losses, as long as their product is constant. Power dissipation, P=I2R, increases with the square of the current but only increases approximately linearly with the number of windings. Using these relationships the measurable rate of heat dissipation, an optimal DC pulse duration may be selected for a given system.
Thus, in some embodiments, the DC pulse may have a duration of less than 0.4 seconds, such as 0.3, 0.2, 0.2, or 0.05 seconds, including any fractional value in between. Such conditions may be selected where lower coil operating temperatures may be desirable. In other embodiments, the DC pulse may have a duration longer than 0.6 seconds, such as 0.7, 0.8, 0.9, 1.0, or 1.5 seconds, and so on, including any fractional value in between. Such conditions may be selected where higher coil operating temperatures may be acceptable.
In embodiments, the one or more relays 230a/230b cause an off time with no DC pulse from 0.6 to 0.8 seconds. Thus, in an exemplary embodiment, there is no DC pulse for approximately 0.6 sec (i.e., this is trigger pulse off time). This gives the capacitor bank enough time to re-charge and in the exemplary arrangement in the Example below represents a useful time setting. In embodiments, the off time may also be useful to allow heat dissipation. If the capacitor bank is altered, then the off time may be altered accordingly; thus, in embodiments, the off time may be less than 0.6 seconds, such as 0.5, 0.4, or 0.3 seconds and so on, including any fractional value in between. Other alterations to the capacitor bank may provide a desirable increase in the off time greater than 0.8 seconds, such as 0.9, 1.0, or 1.1 seconds and so on, including any fractional value in between.
In embodiments, system 100 can used carry out milling in excess of six hours. For the purpose of pigment milling, methods employing the systems disclosed herein may provide significant particle size reduction was achieved in as little as one hour. In embodiments, this is a substantial time savings compared to conventional milling methods. Further particle size reduction can be achieved after three hours and six hours of milling. In the exemplary working embodiment in the Example below, a maximum temperature of the coil after six of continuous operation was approximately 50° C. This is within beneficial operating conditions and allows for milling times heretofore not as effectively achieved in purely mechanical systems.
Referring to FIGS. 2 and 3, pulsing dc source 110 may comprise one or more load protecting features 205 (FIG. 2), which may include, for example, one or more lamps (205a, FIG. 3) and/or fuses (205b, FIG. 3).
Referring back to FIG. 1, system 100 may further comprise a cooling subunit 160 directed to cool electromagnetic coil 120. In embodiments, cooling subunit 160 is on separate circuitry from DC source 110. In embodiments, cooling subunit 160 is also on separate circuitry from rotating container subunit 150. In still further embodiments, cooling subunit 160 may be connected to the circuitry of either DC source 110 or rotating subunit 150. In embodiments, cooling subunit 160 is a fan. In other embodiments, cooling subunit 160 may be a chilled jacket (such as a chilled glycol jacket) wrapped around electromagnetic coil 120 with circulating pump.
In embodiments, the electromagnetic coil generates a field strength in a range from about 4000 to about 6000 Gauss. Those skilled in the art will recognize that these field strengths are merely exemplary and that electromagnetic coil and the voltage of the DC pulse may be altered as desired to achieve field strengths outside this range. Thus, in embodiments, the field strength may be 3000 or 2000 Gauss or 7000 or 8000 Gauss, including any value in between and fractions thereof.
In embodiments, there are provided methods of milling a pigment comprising providing a pigment milling system comprising a pulsing direct current (DC) source that generates a DC pulse, an electromagnetic field generating subunit comprising an electromagnetic coil coupled to the pulsing DC source to receive the DC pulse and to generate a magnetic field, and a rotating container subunit comprising a container, a portion of the container being disposed within the electromagnetic coil, and a rotating subunit to rotate the container, the process further comprising adding to the container a plurality of ink pigments, a plurality of magnetic particles, and an ink carrier, and operating the pulsing DC electromagnet subunit and container rotating subunit for a sufficient period of time to obtain milled ink pigment particles of a target effective diameter in a dispersion; wherein generation of the magnetic field causes motion of the plurality of magnetic particles thereby dispersing the plurality of ink pigment particles within the ink carrier.
In embodiments, the sufficient period of time is in a range from about five minutes to about six hours. In embodiments, the target effective diameter is suitable for forming a toner. In embodiments, the average pigment particle size is in a range from about 100 nm to about 200 nm. In embodiments, a time to mill the plurality of ink pigments is shorter than when using alternating current actuated magnetic milling.
In embodiments, there are provided pulsing direct current (DC) electromagnets comprising a pulsing DC source to generate a DC pulse comprising an alternating current source and a voltage rectifier that converts a voltage provided by the AC source to a DC voltage, the voltage rectifier further multiplying the DC voltage, one or more capacitors to store the DC voltage, and a switching circuit to receive the DC voltage from the one or more capacitors, the switching circuit being turned off and on according to a duty cycle generated by one or more relays, the pulsing DC electromagnet further comprising an electromagnetic coil coupled to the pulsing DC source to receive the DC pulse and to generate a magnetic field, wherein when in use a field strength of the magnetic field is in a range from about 4000 Gauss to about 6000 Gauss.
In embodiments, the duty cycle generated by the one or more relays allows operation of the DC electromagnet in excess of six hours without adverse performance due to excessive heat generation. In embodiments, the pulsing DC electromagnet further comprises one or more load protecting features.
Embodiments herein provide a pulsing magnetic field to drive the chaotic motion of magnetic particles to generate shearing throughout a container/vessel, thus providing uniform dispersion of materials, such as ink pigments, within a very short time frame. The present embodiments may eliminate the need for complex layouts of pipes, pumps, impellers, and material transfer commonly required for the preparation of pigment dispersions. Moreover, the present systems and methods are generic for any type or geometry design of reaction vessels, and can be readily optimized to fit any set up.
In embodiments, there is provided a method for preparing pigment dispersions using magnetic actuated mixing. A dry pigment is loaded in a solvent, such as water, an organic solvent or mixtures thereof, into the vessel. In embodiments, the pigment is selected from the group consisting of a blue pigment, a black pigment, a cyan pigment, a brown pigment, a green pigment, a white pigment, a violet pigment, a magenta pigment, a red pigment, an orange pigment, a yellow pigment, and mixtures thereof. In embodiments, systems and methods disclosed herein are particularly suited to mill pigments that are otherwise challenging to mill, such as yellow and magenta pigments. In embodiments, the pigment/water mixture comprises the pigment and water in a weight ratio of from about 5% to about 80%, or from about 10% to about 50%, or from about 15% to about 25%.
The magnetic particles may be comprised of, paramagnetic, ferrimagnetic, ferromagnetic or antiferromagnetic materials. The magnetic particles may further be comprised of a material selected from the group consisting of Fe, Fe2O3, Ni, CrO2, Cs, and the like or mixtures thereof. In embodiments, the magnetic particles have a nonmagnetic coating. In other embodiments, the magnetic particles can also be encapsulated with a shell, for example, a polymeric shell comprising, in embodiments, polystyrene, polyvinyl chloride, TEFLON®, PMMA, and the like and mixtures thereof. The magnetic particles may have a diameter of from about 5 nm to about 50 μm, or from about 10 nm to about 10 μm, or from about 100 nm to about 5 μm. The volume percentage of magnetic particles can be chosen based on different applications or processes. In embodiments, the volume percentage of magnetic particles used for milling may also vary depending on the different application or process for which the pigment particles are being used. For example, from about 5% to about 80%, or from about 10% to about 50%, or from about 15% to about 25% magnetic particles may be added to the vessel.
The magnetic field may have a strength of from about 500 Gauss to about 50,000 Gauss, or from about 1000 Gauss to about 20,000 Gauss, or from about 2000 Gauss to about 15,000 Gauss. The present embodiments are able to drive chaotic or random motion of magnetic particles across the whole solution. This type of random motion generates maximized shearing and impacting effects on the pigment particles and helps facilitate a uniform milling of the materials to achieve required particle size. If micro sized magnetic particles are used, due to the large surface contact area between micro magnetic particles and the solution, micro milling due to enhanced local interactions significantly produces homogeneous and global milling. The present embodiments thus provide small particles on the nano to micro scale and uniform distribution. The present embodiments also provide for the potential of higher viscosity (for example, a viscosity of from about 0.1 cP to about 100,000 cP at 25° C.) mixing if the exposed magnetic field is large.
Another advantage of the present method and system is the reduction of mechanical components and thus maintenance, which significantly reduces the cost of the system. The present embodiments are also free of noise or have reduced noise.
The container/vessel may have the magnetic particles already pre-loaded in the vessel or the magnetic particles may be loaded into the vessel after the pigment/water mixture. A surfactant may be optionally added to the pigment/water mixture in the vessel. In embodiments, the surfactant is selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, and combinations thereof. A pigment dispersion with the desired particle size is then achieved by continued mixing of the magnetic particles through application of the pulsing magnetic field. A reduction in pigment particle size is achieved with continued mixing. The duration and speed of mixing may be dependent on the pigment particle size desired. In embodiments, the pigment particle size achieved may be from about 5 nm to about 300 nm, or from about 10 nm to about 200 nm, or from about 100 nm to about 150 nm. The magnetic particles can then be collected for re-use, for example, with the aid of a permanent magnet.
In embodiments, the pigment dispersion made by methods disclosed herein can be used to prepare a toner comprising a resin composition.
The resin composition may comprise one or more resins, such as two or more resins. The total amount of resin in the resin composition can be from about 1% to 99%, such as from about 10% to about 95%, or from about 20% to 90% by weight of the resin composition.
A resin used in the method disclosed herein may be any latex resin utilized in forming Emulsion Aggregation (EA) toners. Such resins, in turn, may be made of any suitable monomer. Any monomer employed may be selected depending upon the particular polymer to be used. Two main types of EA methods for making toners are known. First is an EA process that forms acrylate based, e.g., styrene acrylate, toner particles. See, for example, U.S. Pat. No. 6,120,967, incorporated herein by reference in its entirety, as one example of such a process. Second is an EA process that forms polyester, e.g., sodio sulfonated polyester. See, for example, U.S. Pat. No. 5,916,725, incorporated herein by reference in its entirety, as one example of such a process.
Illustrative examples of latex resins or polymers selected for the non-crosslinked resin and crosslinked resin or gel include, but are not limited to, styrene acrylates, styrene methacrylates, butadienes, isoprene, acrylonitrile, acrylic acid, methacrylic acid, beta-carboxy ethyl arylate, polyesters, known polymers such as poly(styrene-butadiene), poly(methyl styrene-butadiene), poly(methyl methacrylate-butadiene), poly(ethyl methacrylate-butadiene), poly(propyl methacrylate-butadiene), poly(butyl methacrylate-butadiene), poly(methyl acrylate-butadiene), poly(ethyl acrylate-butadiene), poly(propyl acrylate-butadiene), poly(butyl acrylate-butadiene), poly(styrene-isoprene), poly(methyl styrene-isoprene), poly(methyl methacrylate-isoprene), poly(ethyl methacrylate-isoprene), poly(propyl methacrylate-isoprene), poly(butyl methacrylate-isoprene), poly(methyl acrylate-isoprene), poly(ethyl acrylate-isoprene), poly(propyl acrylate-isoprene), poly(butyl acrylate-isoprene); poly(styrene-propyl acrylate), poly(styrene-butyl acrylate), poly(styrene-butadiene-acrylic acid), poly(styrene-butadiene-methacrylic acid), poly(styrene-butyl acrylate-acrylic acid), poly(styrene-butyl acrylate-methacrylic acid), poly(styrene-butyl acrylate-acrylonitrile), poly(styrene-butyl acrylate-acrylonitrile-acrylic acid), and the like, and mixtures thereof. The resin or polymer can be a styrene/butyl acrylate/carboxylic acid terpolymer. At least one of the resin substantially free of crosslinking and the crosslinked resin can comprise carboxylic acid in an amount of from about 0.05 to about 10 weight percent based upon the total weight of the resin substantially free of cross linking or crosslinked resin.
The monomers used in making the selected polymer are not limited, and the monomers utilized may include any one or more of, for example, styrene, acrylates such as methacrylates, butylacrylates, δ-carboxy ethyl acrylate (β-CEA), etc., butadiene, isoprene, acrylic acid, methacrylic acid, itaconic acid, acrylonitrile, benzenes such as divinylbenzene, etc., and the like. Known chain transfer agents, for example dodecanethiol or carbon tetrabromide, can be utilized to control the molecular weight properties of the polymer. Any suitable method for forming the latex polymer from the monomers may be used without restriction.
The resin that is substantially free of cross linking (also referred to herein as a non-crosslinked resin) can comprise a resin having less than about 0.1 percent cross linking. For example, the non-crosslinked latex can comprise styrene, butylacrylate, and beta-carboxy ethyl acrylate (beta-CEA) monomers, although not limited to these monomers, termed herein as monomers A, B, and C, prepared, for example, by emulsion polymerization in the presence of an initiator, a chain transfer agent (CTA), and surfactant.
The resin substantially free of cross linking can comprise styrene:butylacrylate:beta-carboxy ethyl acrylate wherein, for example, the non-crosslinked resin monomers can be present in an amount of about 70 percent to about 90 percent styrene, about 10 percent to about 30 percent butylacrylate, and about 0.05 parts per hundred to about 10 parts per hundred beta-CEA, or about 3 parts per hundred beta-CEA, by weight based upon the total weight of the monomers, although not limited. For example, the carboxylic acid can be selected, for example, from the group comprised of, but not limited to, acrylic acid, methacrylic acid, itaconic acid, beta carboxy ethyl acrylate (beta CEA), fumaric acid, maleic acid, and cinnamic acid.
In a feature herein, the non-crosslinked resin can comprise about 73 percent to about 85 percent styrene, about 27 percent to about 15 percent butylacrylate, and about 1.0 part per hundred to about 5 parts per hundred beta-CEA, by weight based upon the total weight of the monomers although the compositions and processes are not limited to these particular types of monomers or ranges. In another feature, the non-crosslinked resin can comprise about 81.7 percent styrene, about 18.3 percent butylacrylate and about 3.0 parts per hundred beta-CEA by weight based upon the total weight of the monomers.
The initiator can be, for example, but is not limited to, sodium, potassium or ammonium persulfate and can be present in the range of, for example, about 0.5 to about 3.0 percent based upon the weight of the monomers, although not limited. The CTA can be present in an amount of from about 0.5 to about 5.0 percent by weight based upon the combined weight of the monomers A and B, although not limited. The surfactant can be an anionic surfactant present in the range of from about 0.7 to about 5.0 percent by weight based upon the weight of the aqueous phase, although not limited to this type or range.
The resin can be a polyester resin such as an amorphous polyester resin, a crystalline polyester resin, and/or a combination thereof. The polymer used to form the resin can be a polyester resin described in U.S. Pat. Nos. 6,593,049 and 6,756,176, the disclosures of each of which are hereby incorporated by reference in their entirety. Suitable resins also include a mixture of an amorphous polyester resin and a crystalline polyester resin as described in U.S. Pat. No. 6,830,860, the disclosure of which is hereby incorporated by reference in its entirety.
The resin can be a polyester resin formed by reacting a diol with a diacid in the presence of an optional catalyst. For forming a crystalline polyester, suitable organic diols include aliphatic diols with from about 2 to about 36 carbon atoms, such as 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol and the like; alkali sulfo-aliphatic diols such as sodio 2-sulfo-1,2-ethanediol, lithio 2-sulfo-1,2-ethanediol, potassio 2-sulfo-1,2-ethanediol, sodio 2-sulfo-1,3-propanediol, lithio 2-sulfo-1,3-propanediol, potassio 2-sulfo-1,3-propanediol, mixture thereof, and the like. The aliphatic diol may be, for example, selected in an amount of from about 40 to about 60 mole percent, such as from about 42 to about 55 mole percent, or from about 45 to about 53 mole percent (although amounts outside of these ranges can be used), and the alkali sulfo-aliphatic diol can be selected in an amount of from about 0 to about 10 mole percent, such as from about 1 to about 4 mole percent of the resin (although amounts outside of these ranges can be used).
Examples of organic diacids or diesters including vinyl diacids or vinyl diesters selected for the preparation of the crystalline resins include oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, dimethyl fumarate, dimethyl itaconate, cis, 1,4-diacetoxy-2-butene, diethyl fumarate, diethyl maleate, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, cyclohexane dicarboxylic acid, malonic acid and mesaconic acid, a diester or anhydride thereof; and an alkali sulfo-organic diacid such as the sodio, lithio or potassio salt of dimethyl-5-sulfo-isophthalate, dialkyl-5-sulfo-isophthalate-4-sulfo-1,8-naphthalic anhydride, 4-sulfo-phthalic acid, dimethyl-4-sulfo-phthalate, dialkyl-4-sulfo-phthalate, 4-sulfophenyl-3,5-dicarbomethoxybenzene, 6-sulfo-2-naphthyl-3,5-dicarbomethoxybenzene, sulfo-terephthalic acid, dimethyl-sulfo-terephthalate, 5-sulfo-isophthalic acid, dialkyl-sulfo-terephthalate, sulfoethanediol, 2-sulfopropanediol, 2-sulfobutanediol, 3-sulfopentanediol, 2-sulfohexanediol, 3-sulfo-2-methylpentanediol, 2-sulfo-3,3-dimethylpentanediol, sulfo-p-hydroxybenzoic acid, N,N-bis(2-hydroxyethyl)-2-amino ethane sulfonate, or mixtures thereof. The organic diacid may be selected in an amount of, for example, from about 40 to about 60 mole percent, in embodiments from about 42 to about 52 mole percent, such as from about 45 to about 50 mole percent (although amounts outside of these ranges can be used), and the alkali sulfo-aliphatic diacid can be selected in an amount of from about 1 to about 10 mole percent of the resin (although amounts outside of these ranges can be used).
Examples of crystalline resins include polyesters, polyamides, polyimides, polyolefins, polyethylene, polybutylene, polyisobutyrate, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, polypropylene, mixtures thereof, and the like. Specific crystalline resins may be polyester based, such as poly(ethylene-adipate), poly(propylene-adipate), poly(butylene-adipate), poly(pentylene-adipate), poly(hexylene-adipate), poly(octylene-adipate), poly(ethylene-succinate), poly(propylene-succinate), poly(butylene-succinate), poly(pentylene-succinate), poly(hexylene-succinate), poly(octylene-succinate), poly(ethylene-sebacate), poly(propylene-sebacate), poly(butylene-sebacate), poly(pentylene-sebacate), poly(hexylene-sebacate), poly(octylene-sebacate), poly(decylene-sebacate), poly(decylene-decanoate), poly(ethylene-decanoate), poly(ethylene dodecanoate), poly(nonylene-sebacate), poly(nonylene-decanoate), copoly(ethylene-fumarate)-copoly(ethylene-sebacate), copoly(ethylene-fumarate)-copoly(ethylene-decanoate), copoly(ethylene-fumarate)-copoly(ethylene-dodecanoate), alkali copoly(5-sulfoisophthaloyl)-copoly(ethylene-adipate), alkali copoly(5-sulfoisophthaloyl)-copoly(propylene-adipate), alkali copoly(5-sulfoisophthaloyl)-copoly(butylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(pentylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(hexylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(octylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(ethylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(propylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(butylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(pentylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(hexylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(octylene-adipate), alkali copoly(5-sulfoisophthaloyl)-copoly(ethylene-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(propylene-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(butylenes-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(pentylene-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(hexylene-succinate), alkali copoly(5-sulfoisophthaloyl)-copoly(octylene-succinate), alkali copoly(5-sulfo-isophthaloyl)-copoly(ethylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(propylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(butylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(pentylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(hexylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(octylene-sebacate), alkali copoly(5-sulfo-isophthaloyl)-copoly(ethylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(propylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(butylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(pentylene-adipate), alkali copoly(5-sulfo-isophthaloyl)-copoly(hexylene-adipate), poly(octylene-adipate), wherein alkali is a metal like sodium, lithium or potassium. Examples of polyamides include poly(ethylene-adipamide), poly(propylene-adipamide), poly(butylenes-adipamide), poly(pentylene-adipamide), poly(hexylene-adipamide), poly(octylene-adipamide), poly(ethylene-succinimide), and poly(propylene-sebecamide). Examples of polyimides include poly(ethylene-adipimide), poly(propylene-adipimide), poly(butylene-adipimide), poly(pentylene-adipimide), poly(hexylene-adipimide), poly(octylene-adipimide), poly(ethylene-succinimide), poly(propylene-succinimide), and poly(butylene-succinimide).
The crystalline resin can be present, for example, in an amount of from about 5 to about 50 percent by weight of the toner components, such as from about 10 to about 35 percent by weight of the toner components (although amounts outside of these ranges can be used). The crystalline resin can possess various melting points of, for example, from about 30° C. to about 120° C., in embodiments from about 50° C. to about 90° C. (although melting points outside of these ranges can be obtained). The crystalline resin can have a number average molecular weight (Mn), as measured by gel permeation chromatography (GPC) of, for example, from about 1,000 to about 50,000, such as from about 2,000 to about 25,000 (although number average molecular weights outside of these ranges can be obtained), and a weight average molecular weight (Mw) of, for example, from about 2,000 to about 100,000, such as from about 3,000 to about 80,000 (although weight average molecular weights outside of these ranges can be obtained), as determined by Gel Permeation Chromatography using polystyrene standards. The molecular weight distribution (Mw/Mn) of the crystalline resin can be, for example, from about 2 to about 6, in embodiments from about 3 to about 4 (although molecular weight distributions outside of these ranges can be obtained).
Examples of diacids or diesters including vinyl diacids or vinyl diesters used for the preparation of amorphous polyesters include dicarboxylic acids or diesters such as terephthalic acid, phthalic acid, isophthalic acid, fumaric acid, dimethyl fumarate, dimethyl itaconate, cis, 1,4-diacetoxy-2-butene, diethyl fumarate, diethyl maleate, maleic acid, succinic acid, itaconic acid, succinic acid, succinic anhydride, dodecylsuccinic acid, dodecylsuccinic anhydride, glutaric acid, glutaric anhydride, adipic acid, pimelic acid, suberic acid, azelaic acid, dodecane diacid, dimethyl terephthalate, diethyl terephthalate, dimethylisophthalate, diethylisophthalate, dimethylphthalate, phthalic anhydride, diethylphthalate, dimethylsuccinate, dimethylfumarate, dimethylmaleate, dimethylglutarate, dimethyladipate, dimethyl dodecylsuccinate, and combinations thereof. The organic diacid or diester can be present, for example, in an amount from about 40 to about 60 mole percent of the resin, such as from about 42 to about 52 mole percent of the resin, or from about 45 to about 50 mole percent of the resin (although amounts outside of these ranges can be used).
Examples of diols that can be used in generating the amorphous polyester include 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, 2,2-dimethylpropanediol, 2,2,3-trimethylhexanediol, heptanediol, dodecanediol, bis(hydroxyethyl)-bisphenol A, bis(2-hydroxypropyl)-bisphenol A, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, xylenedimethanol, cyclohexanediol, diethylene glycol, bis(2-hydroxyethyl)oxide, dipropylene glycol, dibutylene, and combinations thereof. The amount of organic diol selected can vary, and can be present, for example, in an amount from about 40 to about 60 mole percent of the resin, such as from about 42 to about 55 mole percent of the resin, or from about 45 to about 53 mole percent of the resin (although amounts outside of these ranges can be used).
Polycondensation catalysts which may be used in forming either the crystalline or amorphous polyesters include tetraalkyl titanates, dialkyltin oxides such as dibutyltin oxide, tetraalkyltins such as dibutyltin dilaurate, and dialkyltin oxide hydroxides such as butyltin oxide hydroxide, aluminum alkoxides, alkyl zinc, dialkyl zinc, zinc oxide, stannous oxide, or combinations thereof. Such catalysts may be used in amounts of, for example, from about 0.01 mole percent to about 5 mole percent based on the starting diacid or diester used to generate the polyester resin (although amounts outside of this range can be used).
Suitable amorphous resins include polyesters, polyamides, polyimides, polyolefins, polyethylene, polybutylene, polyisobutyrate, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, polypropylene, combinations thereof, and the like. Examples of amorphous resins which may be used include alkali sulfonated-polyester resins, branched alkali sulfonated-polyester resins, alkali sulfonated-polyimide resins, and branched alkali sulfonated-polyimide resins. Alkali sulfonated polyester resins may be useful in embodiments, such as the metal or alkali salts of copoly(ethylene-terephthalate)-copoly(ethylene-5-sulfo-isophthalate), copoly(propylene-terephthalate)-copoly(propylene-5-sulfo-isophthalate), copoly(diethylene-terephthalate)-copoly(diethylene-5-sulfo-isophthalate), copoly(propylene-diethylene-terephthalate)-copoly(propylene-diethylene-5-sulfoisophthalate), copoly(propylene-butylene-terephthalate)-copoly(propylene-butylene-5-sulfoisophthalate), copoly propoxylated bisphenol-A-fumarate)-copoly(propoxylated bisphenol A-5-sulfo-isophthalate), copoly(ethoxylated bisphenol-A-fumarate)-copoly(ethoxylated bisphenol-A-5-sulfo-isophthalate), and copoly(ethoxylated bisphenol-A-maleate)-copoly(ethoxylated bisphenol-A-5-sulfo-isophthalate), wherein the alkali metal is, for example, a sodium, lithium or potassium ion.
An unsaturated amorphous polyester resin can be used as a latex resin. Examples of such resins include those disclosed in U.S. Pat. No. 6,063,827, the disclosure of which is hereby incorporated by reference in its entirety. Exemplary unsaturated amorphous polyester resins include, but are not limited to, poly(propoxylated bisphenol co-fumarate), poly(ethoxylated bisphenol co-fumarate), poly(butyloxylated bisphenol co-fumarate), poly(co-propoxylated bisphenol co-ethoxylated bisphenol co-fumarate), poly(1,2-propylene fumarate), poly(propoxylated bisphenol co-maleate), poly(ethoxylated bisphenol co-maleate), poly(butyloxylated bisphenol co-maleate), poly(co-propoxylated bisphenol co-ethoxylated bisphenol co-maleate), poly(1,2-propylene maleate), poly(propoxylated bisphenol co-itaconate), poly(ethoxylated bisphenol co-itaconate), poly(butyloxylated bisphenol co-itaconate), poly(co-propoxylated bisphenol co-ethoxylated bisphenol co-itaconate), poly(1,2-propylene itaconate), and combinations thereof. A suitable polyester resin can be a polyalkoxylated bisphenol A-co-terephthalic acid/dodecenylsuccinic acid/trimellitic acid resin, or a polyalkoxylated bisphenol A-co-terephthalic acid/fumaric acid/dodecenylsuccinic acid resin, or a combination thereof.
Such amorphous resins can have a weight average molecular weight (Mw) of from about 10,000 to about 100,000, such as from about 15,000 to about 80,000.
An example of a linear propoxylated bisphenol a fumarate resin that can be used as a latex resin is available under the trade name SPARII from Resana S/A Industrias Quimicas, Sao Paulo Brazil. Other propoxylated bisphenol a fumarate resins that can be used and are commercially available include GTUF and FPESL-2 from Kao Corporation, Japan, and EM181635 from Reichhold, Research Triangle Park, N.C., and the like.
Suitable crystalline resins that can be used, optionally in combination with an amorphous resin as described above, include those disclosed in U.S. Patent Application Publication No. 2006/0222991, the disclosure of which is hereby incorporated by reference in its entirety. In embodiments, a suitable crystalline resin can include a resin formed of dodecanedioic acid and 1,9-nonanediol.
Such crystalline resins can have a weight average molecular weight (Mw) of from about 10,000 to about 100,000, such as from about 14,000 to about 30,000.
For example, a polyalkoxylated bisphenol A-co-terephthalic acid/dodecenylsuccinic acid/trimellitic acid resin, or a polyalkoxylated bisphenol A-co-terephthalic acid/fumaric acid/dodecenylsuccinic acid resin, or a combination thereof, can be combined with a polydodecanedioic acid-co-1,9-nonanediol crystalline polyester resin.
The resins can have a glass transition temperature of from about 30° C. to about 80° C., such as from about 35° C. to about 70° C. The resins can have a melt viscosity of from about 10 to about 1,000,000 Pa*S at about 130° C., such as from about 20 to about 100,000 Pa*S. One, two, or more toner resins may be used. Where two or more toner resins are used, the toner resins can be in any suitable ratio (e.g., weight ratio) such as, for instance, about 10 percent (first resin)/90 percent (second resin) to about 90 percent (first resin)/10 percent (second resin). The resin can be formed by emulsion polymerization methods.
The resin can be formed at elevated temperatures of from about 30° C. to about 200° C., such as from about 50° C. to about 150° C., or from about 70° C. to about 100° C. However, the resin can also be formed at room temperature.
Stirring may be used to enhance formation of the resin. Any suitable stirring device may be used. In embodiments, the stirring speed can be from about 10 revolutions per minute (rpm) to about 5,000 rpm, such as from about 20 rpm to about 2,000 rpm, or from about 50 rpm to about 1,000 rpm. The stirring speed can be constant or the stirring speed can be varied. For example, as the temperature becomes more uniform throughout the mixture, the stirring speed can be increased. However, no mechanical or magnetic agitation is necessary in the method disclosed herein.
Solvent
Any suitable organic solvent can be contacted with the resin in the resin composition to help dissolve the resin in the resin composition. Suitable organic solvents for the methods disclosed herein include alcohols, such as methanol, ethanol, isopropanol, butanol, as well as higher homologs and polyols, such as ethylene glycol, glycerol, sorbitol, and the like; ketones, such as acetone, 2-butanone, 2-pentanone, 3-pentanone, ethyl isopropyl ketone, methyl isobutyl ketone, diisobutyl ketone, and the like; amides, such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, 1,2-dimethyl-2-imidazolidinone, and the like; nitriles, such as acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, benzonitrile, and the like; ethers, such as ditertbutyl ether, dimethoxyethane, 2-methoxyethyl ether, 1,4-dioxane, tetrahydrohyran, morpholine, and the like; sulfones, such as methylsulfonylmethane, sulfolane, and the like; sulfoxides, such as dimethylsulfoxide; phosphoramides, such as hexamethylphosphoramide; benzene and benzene derivatives; as well as esters, amines and combinations thereof, in an amount of, for example from about 1 wt % to 99 wt %, from about 20 wt % to 80 wt %, or from about 20 wt % to about 50 wt %.
The organic solvent can be immiscible in water and can have a boiling point of from about 30° C. to about 100° C. Any suitable organic solvent can also be used as a phase or solvent inversion agent. The organic solvent can be used in an amount of from about 1% by weight to about 25% by weight of the resin, such as from about 5% by weight to about 20% by weight of the resin, or from about 10% by weight of the resin to about 15% by weight of the resin.
A neutralizing agent can be contacted with the resin in the resin composition to, for example, neutralize acid groups in the resins. The neutralizing agent can be contacted with the resin as a solid or in an aqueous solution. The neutralizing agent herein can also be referred to as a “basic neutralization agent.” Any suitable basic neutralization reagent can be used in accordance with the present disclosure.
Suitable basic neutralization agents include both inorganic basic agents and organic basic agents. Suitable basic agents include, for example, ammonium hydroxide, potassium hydroxide, sodium hydroxide, sodium carbonate, sodium bicarbonate, lithium hydroxide, potassium carbonate, potassium bicarbonate, combinations thereof, and the like. Suitable basic agents also include monocyclic compounds and polycyclic compounds having at least one nitrogen atom, such as, for example, secondary amines, which include aziridines, azetidines, piperazines, piperidines, pyridines, pyridine derivatives, bipyridines, terpyridines, dihydropyridines, morpholines, N-alkylmorpholines, 1,4-diazabicyclo[2.2.2]octanes, 1,8-diazabicycloundecanes, 1,8-diazabicycloundecenes, dimethylated pentylamines, trimethylated pentylamines, triethyl amines, triethaholamines, diphenyl amines, diphenyl amine derivatives, poly(ethylene amine), poly(ethylene amine derivatives, amine bases, pyrimidines, pyrroles, pyrrolidines, pyrrolidinones, indoles, indolines, indanones, benzindazones, imidazoles, benzimidazoles, imidazolones, imidazolines, oxazoles, isoxazoles, oxazolines, oxadiazoles, thiadiazoles, carbazoles, quinolines, isoquinolines, naphthyridines, triazines, triazoles, tetrazoles, pyrazoles, pyrazolines, and combinations thereof. The monocyclic and polycyclic compounds can be unsubstituted or substituted at any carbon position on the ring.
The basic agent can be used as a solid such as, for example, sodium hydroxide flakes, so that it is present in an amount of from about 0.001% by weight to 50% by weight of the resin, such as from about 0.01% by weight to about 25% by weight of the resin, or from about 0.1% by weight to 5% by weight of the resin.
As noted above, the basic neutralization agent can be added to a resin possessing acid group. The addition of the basic neutralization agent may thus raise the pH of an emulsion including a resin possessing acid group to a pH of from about 5 to about 12, in embodiments, from about 6 to about 11. The neutralization of the acid groups can enhance formation of the emulsion.
The neutralization ratio can be from about 25% to about 500%, such as from about 50% to about 450%, or from about 100% to about 400%.
Surfactant
As discussed above, a surfactant can be contacted with the resin prior to formation of the resin composition used to form the latex emulsion. One, two, or more surfactants can be used. The surfactants can be selected from ionic surfactants and nonionic surfactants. The latex for forming the resin used in forming a toner can be prepared in an aqueous phase containing a surfactant or co-surfactant, optionally under an inert gas such as nitrogen. Surfactants used with the resin to form a latex dispersion can be ionic or nonionic surfactants in an amount of from about 0.01 to about 15 weight percent of the solids, such as from about 0.1 to about 10 weight percent of the solids.
Anionic surfactants that can be used include sulfates and sulfonates, sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkyl sulfates and sulfonates, acids such as abietic acid available from Aldrich, NEOGEN®, NEOGEN SCTM obtained from Daiichi Kogyo Seiyaku Co., Ltd., combinations thereof, and the like. Other suitable anionic surfactants include, DOWFAXTM 2A1, an alkyldiphenyloxide disulfonate from The Dow Chemical Company, and/or TAYCA POWER BN2060 from Tayca Corporation (Japan), which are branched sodium dodecyl benzene sulfonates. Combinations of these surfactants and any of the foregoing anionic surfactants can be used.
Examples of cationic surfactants include, but are not limited to, ammoniums, for example, alkylbenzyl dimethyl ammonium chloride, dialkyl benzenealkyl ammonium chloride, lauryl trimethyl ammonium chloride, alkylbenzyl methyl ammonium chloride, alkyl benzyl dimethyl ammonium bromide, benzalkonium chloride, C12, C15, C17 trimethyl ammonium bromides, combinations thereof, and the like. Other cationic surfactants include cetyl pyridinium bromide, halide salts of quaternized polyoxyethylalkylamines, dodecylbenzyl triethyl ammonium chloride, MIRAPOL and ALKAQUAT available from Alkaril Chemical Company, SANISOL (benzalkonium chloride), available from Kao Chemicals, combinations thereof, and the like. A suitable cationic surfactant includes SANISOL B-50 available from Kao Corp., which is primarily a benzyl dimethyl alkonium chloride.
Examples of nonionic surfactants include, but are not limited to, alcohols, acids and ethers, for example, polyvinyl alcohol, polyacrylic acid, methalose, methyl cellulose, ethyl cellulose, propyl cellulose, hydroxyl ethyl cellulose, carboxy methyl cellulose, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene octyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene stearyl ether, polyoxyethylene nonylphenyl ether, dialkylphenoxy poly(ethyleneoxy) ethanol, combinations thereof, and the like. Commercially available surfactants from Rhone-Poulenc such as IGEPAL CA-210TM, IGEPAL CA-520TM, IGEPAL CA-720TM, IGEPAL CO-890TM, IGEPAL CO-720TM, IGEPAL CO-290TM, IGEPAL CA-210TM, ANTAROX 890TM and ANTAROX 897TM can be used.
The choice of particular surfactants or combinations thereof, as well as the amounts of each to be used, are within the purview of those skilled in the art.
Preparation of Toner
A latex emulsion can be used to form a toner, such as an EA toner. The latex emulsion can be added to a pre-toner mixture, such as before particle aggregation in the EA coalescence process. The latex or emulsion, as well as a binder resin, a wax such as a wax dispersion, a colorant, and any other desired or required additives such as surfactants, may form the pre-toner mixture.
The pre-toner mixture can be prepared, and the pH of the resulting mixture can be adjusted, by an acid such as, for example, acetic acid, nitric acid or the like. The pH of the mixture can be adjusted to be from about 4 to about 5, although a pH outside this range can be used. Additionally, the mixture can be homogenized. If the mixture is homogenized, homogenization can be accomplished by mixing at a mixing speed of from about 600 to about 4,000 revolutions per minute, although speeds outside this range can be used. Homogenization can be accomplished by any suitable means, including, for example, an IKA ULTRA TURRAX T50 probe homogenizer.
Aggregation
Following the preparation of the above mixture, including the addition or incorporation into the pre-toner mixture of the latex emulsion produced by the methods disclosed herein, an aggregating agent can be added to the mixture. Any suitable aggregating agent can be used to form a toner. Suitable aggregating agents include, for example, aqueous solutions of a divalent cation or a multivalent cation material. The aggregating agent can be, for example, polyaluminum halides such as polyaluminum chloride (PAC), or the corresponding bromide, fluoride, or iodide, polyaluminum silicates such as polyaluminum sulfosilicate (PASS), and water soluble metal salts including aluminum chloride, aluminum nitrite, aluminum sulfate, potassium aluminum sulfate, calcium acetate, calcium chloride, calcium nitrite, calcium oxylate, calcium sulfate, magnesium acetate, magnesium nitrate, magnesium sulfate, zinc acetate, zinc nitrate, zinc sulfate, zinc chloride, zinc bromide, magnesium bromide, copper chloride, copper sulfate, and combinations thereof. The aggregating agent can be added to the mixture at a temperature that is below the glass transition temperature (TG) of the resin.
The aggregating agent can be added to the mixture used to form a toner in an amount of, for example, from about 0.01 percent to about 8 percent by weight, such as from about 0.1 percent to about 1 percent by weight, or from about 0.15 percent to about 0.8 percent by weight, of the resin in the mixture, although amounts outside these ranges can be used. The above can provide a sufficient amount of agent for aggregation.
To control aggregation and subsequent coalescence of the particles, the aggregating agent can be metered into the mixture over time. For example, the agent can be metered into the mixture over a period of from about 5 to about 240 minutes, such as from about 30 to about 200 minutes, although more or less time can be used as desired or required. The addition of the agent can occur while the mixture is maintained under stirred conditions, such as from about 50 revolutions per minute to about 1,000 revolutions per minute, or from about 100 revolutions per minute to about 500 revolutions per minute, although speeds outside these ranges can be used. The addition of the agent can also occur while the mixture is maintained at a temperature that is below the glass transition temperature of the resin discussed above, such as from about 30° C. to about 90° C., or from about 35° C. to about 70° C., although temperatures outside these ranges can be used.
The particles can be permitted to aggregate until a predetermined desired particle size is obtained. A predetermined desired size refers to the desired particle size to be obtained as determined prior to formation, and the particle size being monitored during the growth process until such particle size is reached. Samples can be taken during the growth process and analyzed, for example with a Coulter Counter, for average particle size. The aggregation thus can proceed by maintaining the elevated temperature, or slowly raising the temperature to, for example, from about 30° C. to about 99° C., and holding the mixture at this temperature for a time from about 0.5 hours to about 10 hours, such as from about hour 1 to about 5 hours (although times outside these ranges may be utilized), while maintaining stirring, to provide the aggregated particles. Once the predetermined desired particle size is reached, then the growth process is halted. The predetermined desired particle size can be within the desired size of the final toner particles.
The growth and shaping of the particles following addition of the aggregation agent can be accomplished under any suitable conditions. For example, the growth and shaping can be conducted under conditions in which aggregation occurs separate from coalescence. For separate aggregation and coalescence stages, the aggregation process can be conducted under shearing conditions at an elevated temperature, for example, of from about 40° C. to about 90° C., such as from about 45° C. to about 80° C. (although temperatures outside these ranges may be utilized), which can be below the glass transition temperature of the resin as discussed above.
Once the desired final size of the toner particles is achieved, the pH of the mixture can be adjusted with a base to a value of from about 3 to about 10, such as from about 5 to about 9, although a pH outside these ranges may be used.
The adjustment of the pH can be used to freeze, that is to stop, toner growth. The base utilized to stop toner growth can include any suitable base such as, for example, alkali metal hydroxides such as, for example, sodium hydroxide, potassium hydroxide, ammonium hydroxide, combinations thereof, and the like. In embodiments, ethylene diamine tetraacetic acid (EDTA) may be added to help adjust the pH to the desired values noted above.
Core—Shell Structure
After aggregation, but prior to coalescence, a resin coating can be applied to the aggregated particles to form a shell thereover. Any resin described above as suitable for forming the toner resin can be used as the shell.
Resins that can be used to form a shell include, but are not limited to, crystalline polyesters described above, and/or the amorphous resins described above for use as the core. For example, a polyalkoxylated bisphenol A-co-terephthalic acid/dodecenylsuccinic acid/trimellitic acid resin, a polyalkoxylated bisphenol A-co-terephthalic acid/fumaric acid/dodecenylsuccinic acid resin, or a combination thereof, can be combined with a polydodecanedioic acid-co-1,9-nonanediol crystalline polyester resin to form a shell. Multiple resins can be used in any suitable amounts.
The shell resin can be applied to the aggregated particles by any method within the purview of those skilled in the art. The resins utilized to form the shell can be in an emulsion including any surfactant described above. The emulsion possessing the resins can be combined with the aggregated particles described above so that the shell forms over the aggregated particles. In embodiments, the shell may have a thickness of up to about 5 microns, such as from about 0.1 to about 2 microns, or from about 0.3 to about 0.8 microns, over the formed aggregates, although thicknesses outside of these ranges may be obtained.
The formation of the shell over the aggregated particles can occur while heating to a temperature of from about 30° C. to about 80° C. in embodiments from about 35° C. to about 70° C., although temperatures outside of these ranges can be utilized. The formation of the shell can take place for a period of time of from about 5 minutes to about 10 hours, such as from about 10 minutes to about 5 hours, although times outside these ranges may be used.
For example, the toner process can include forming a toner particle by mixing the polymer latexes, in the presence of a wax dispersion and a colorant with an optional coagulant while blending at high speeds. The resulting mixture having a pH of, for example, of from about 2 to about 3, can be aggregated by heating to a temperature below the polymer resin Tg to provide toner size aggregates. Optionally, additional latex can be added to the formed aggregates providing a shell over the formed aggregates. The pH of the mixture can be changed, for example, by the addition of a sodium hydroxide solution, until a pH of about 7 may be achieved.
Coalescence
Following aggregation to the desired particle size and application of any optional shell, the particles can be coalesced to the desired final shape. The coalescence can be achieved by, for example, heating the mixture to a temperature of from about 45° C. to about 100° C., such as from about 55° C. to about 99° C. (although temperatures outside of these ranges may be used), which can be at or above the glass transition temperature of the resins used to form the toner particles, and/or reducing the stirring, for example, to a stirring speed of from about 100 revolutions per minute to about 1,000 revolutions per minute, such as from about 200 revolutions per minute to about 800 revolutions per minute (although speeds outside of these ranges may be used). The fused particles can be measured for shape factor or circularity, such as with a Sysmex FPIA 2100 analyzer, until the desired shape is achieved.
Higher or lower temperatures can be used, it being understood that the temperature is a function of the resins used for the binder. Coalescence may be accomplished over a period of from about 0.01 hours to about 9 hours, such as from about 0.1 hours to about 4 hours (although times outside of these ranges can be used).
After aggregation and/or coalescence, the mixture can be cooled to room temperature, such as from about 20° C. to about 25° C. The cooling can be rapid or slow, as desired. Suitable cooling methods include introducing cold water to a jacket around the reactor. After cooling, the toner particles can be washed with water, and then dried. Drying can be accomplished by any suitable method for drying including, for example, freeze-drying.
Wax
A wax can be combined with the latex or emulsion, colorant, and the like in forming toner particles. When included, the wax can be present in an amount of, for example, from about 1 weight percent to about 25 weight percent of the toner particles, such as from about 5 weight percent to about 20 weight percent of the toner particles, although amounts outside these ranges can be used.
Suitable waxes include waxes having, for example, a weight average molecular weight of from about 500 to about 20,000, such as from about 1,000 to about 10,000, although molecular weights outside these ranges may be utilized. Suitable waxes include, for example, polyolefins such as polyethylene, polypropylene, and polybutene waxes such as commercially available from Allied Chemical and Petrolite Corporation, for example POLYWAXTM polyethylene waxes from Baker Petrolite, wax emulsions available from Michaelman, Inc. and the Daniels Products Company, EPOLENE N-15TM commercially available from Eastman Chemical Products, Inc., and VISCOL 550-PTM, a low weight average molecular weight polypropylene available from Sanyo Kasei K. K.; plant-based waxes, such as carnauba wax, rice wax, candelilla wax, sumacs wax, and jojoba oil; animal-based waxes, such as beeswax; mineral-based waxes and petroleum-based waxes, such as montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax; ester waxes obtained from higher fatty acid and higher alcohol, such as stearyl stearate and behenyl behenate; ester waxes obtained from higher fatty acid and monovalent or multivalent lower alcohol, such as butyl stearate, propyl oleate, glyceride monostearate, glyceride distearate, and pentaerythritol tetra behenate; ester waxes obtained from higher fatty acid and multivalent alcohol multimers, such as diethyleneglycol monostearate, dipropyleneglycol distearate, diglyceryl distearate, and triglyceryl tetrastearate; sorbitan higher fatty acid ester waxes, such as sorbitan monostearate, and cholesterol higher fatty acid ester waxes, such as cholesteryl stearate. Examples of functionalized waxes that can be used include, for example, amines, amides, for example AQUA SUPERSLIP 6550TM, SUPERSLIP 6530TM available from Micro Powder Inc., fluorinated waxes, for example POLYFLUO 190TM, POLYFLUO 200TM, POLYSILK 19TM, POLYSILK 14TM available from Micro Powder Inc., mixed fluorinated, amide waxes, for example MICROSPERSION 19TM also available from Micro Powder Inc., imides, esters, quaternary amines, carboxylic acids or acrylic polymer emulsion, for example JONCRYL 74TM, 89TM, 130TM, 537TM, and 538TM, all available from SC Johnson Wax, and chlorinated polypropylenes and polyethylenes available from Allied Chemical and Petrolite Corporation and SC Johnson wax. Mixtures and combinations of the foregoing waxes can be used. Waxes can be included as, for example, fuser roll release agents.
Colorant
The toner particles described herein can further include colorant. Colorant includes pigments, dyes, mixtures of dyes, mixtures of pigments, mixtures of dyes and pigments, and the like made in accordance with the methods disclosed herein. Suitable colorants include those comprising carbon black, such as, REGAL 330® and Nipex 35. Colored pigments, such as, cyan, magenta, yellow, red, orange, green, brown, blue or mixtures thereof can be used. The additional pigment or pigments can be used as water-based pigment dispersions. Suitable colorants include inorganic pigments and organic pigments. Examples of pigments include SUNSPERSE 6000, FLEXIVERSE and AQUATONE, water-based pigment dispersions from SUN Chemicals; HELIOGEN BLUE L6900TM, D6840TM, D7080TM, D7020TM, PYLAM OIL BLUETM, PYLAM OIL YELLOWTM and PIGMENT BLUE ITM available from Paul Uhlich & Company, Inc.; PIGMENT VIOLET ITM, PIGMENT RED 48TM, LEMON CHROME YELLOW DCC IO26TM, TOLUIDINE REDTM and BON RED CTM available from Dominion Color Corporation, Ltd., Toronto, Ontario; NOVAPERM YELLOW FGLTM and HOSTAPERM PINK ETM from Hoechst; CINQUASIA MAGENTATM available from E.I. DuPont de Nemours & Co., and the like. Examples of magenta pigments include 2,9-dimethyl-substituted quinacridone, an anthraquinone dye identified in the Color Index as CI 60710, CI Dispersed Red 15, a diazo dye identified in the Color Index as CI 26050, CI Solvent Red 19 and the like. Illustrative examples of cyan pigments include copper tetra(octadecylsulfonamido) phthalocyanine, a copper phthalocyanine pigment listed in the Color Index as CI 74160, CI Pigment Blue, Pigment Blue 15:3, Pigment Blue 15:4, an Anthrazine Blue identified in the Color Index as CI 69810, Special Blue X-2137 and the like. Illustrative examples of yellow pigments are diarylide yellow 3,3-dichlorobenzidene acetoacetanilide, a monoazo pigment identified in the Color Index as CI 12700, CI Solvent Yellow 16, a nitrophenyl amine sulfonamide identified in the Color Index as Foron Yellow SE/GLN, CI Disperse Yellow 3,2,5-dimethoxy-4-sulfonanilide phenylazo-4′-chloro-2,5-dimethoxy acetoacetanilide and Permanent Yellow FGL.
Examples of inorganic pigments include such as, Ultramarine violet: (PV15) Silicate of sodium and aluminum containing sulfur; Han Purple: BaCuSi2O6; Cobalt Violet: (PV14) cobalt phosphate; Manganese Violet: (PV16) Manganese ammonium phosphate; Ultramarine (PB29): a complex naturally occurring pigment of sulfur-containing sodio-silicate (Na8-10Al6Si6O24S2-4); Cobalt Blue (PB28) and Cerulean Blue (PB35): cobalt(II) stannate; Egyptian Blue: a synthetic pigment of calcium copper silicate (CaCuSi4O10); Han Blue: BaCuSi4O10; Prussian Blue (PB27): a synthetic pigment of ferric hexacyanoferrate (Fe7(CN)18). The dye Marking blue is made by mixing Prussian Blue and alcohol; YIn1-xMnxO3: a synthetic pigment made from inserting Mn into the trigonal bipyramidal atomic site of the YInO3 crystal structure. Cadmium Green: a light green pigment consisting of a mixture of Cadmium Yellow (CdS) and Viridian (Cr2O3); Chrome Green (PG17); Viridian (PG18): a dark green pigment of hydrated chromium(III) oxide (Cr2O3); Paris Green: copper(II) acetoarsenite; (Cu(C2H3O2)2.3Cu(AsO2)2); Scheele's Green (also called Schloss Green): copper arsenite CuHAsO3; Orpiment natural monoclinic arsenic sulfide (As2S3); Cadmium Yellow (PY37): cadmium sulfide (CdS); Chrome Yellow (PY34): natural pigment of lead(II) chromate (PbCrO4); Aureolin (also called Cobalt Yellow) (PY40): Potassium cobaltinitrite (Na3Co(NO2)6; Yellow Ochre (PY43): a naturally occurring clay of hydrated iron oxide (Fe2O3.H2O); Naples Yellow (PY41); Titanium Yellow (PY53); Mosaic gold: stannic sulfide (SnS2); Cadmium Orange (PO20): an intermediate between cadmium red and cadmium yellow: cadmium sulfoselenide; Chrome Orange: a naturally occurring pigment mixture composed of lead(II) chromate and lead(II) oxide. (PbCrO4+PbO); Cadmium Red (PR108): cadmium selenide (CdSe); Sanguine, Caput Mortuum, Venetian Red, Oxide Red (PR102); Burnt Sienna (PBr7): a pigment produced by heating Raw Sienna; Carbon Black (PBk7); Ivory Black (PBk9); Vine Black (PBk8); Lamp Black (PBk6); Titanium Black; Antimony White: Sb2O3; Barium sulfate (PW5); Titanium White (PW6): titanium(IV) oxide TiO2; Zinc White (PW4): Zinc Oxide (ZnO)
Other known colorants can be used, such as, Levanyl Black A-SF (Miles, Bayer) and Sunsperse Carbon Black LHD 9303 (Sun Chemicals), and colored dyes, such as, Neopen Blue (BASF), Sudan Blue OS (BASF), PV Fast Blue B2G 01 (American Hoechst), Sunsperse Blue BHD 6000 (Sun Chemicals), Irgalite Blue BCA (CibaGeigy), Paliogen Blue 6470 (BASF), Sudan III (Matheson, Coleman, Bell), Sudan II (Matheson, Coleman, Bell), Sudan IV (Matheson, Coleman, Bell), Sudan Orange G (Aldrich), Sudan Orange 220 (BASF), Paliogen Orange 3040 (BASF), Ortho Orange OR 2673 (Paul Uhlich), Paliogen Yellow 152, 1560 (BASF), Lithol Fast Yellow 0991 K (BASF), Paliotol Yellow 1840 (BASF), Neopen Yellow (BASF), Novoperm Yellow FG 1 (Hoechst), Permanent Yellow YE 0305 (Paul Uhlich), Lumogen Yellow D0790 (BASF), Sunsperse Yellow YHD 6001 (Sun Chemicals), Suco-Gelb L1250 (BASF), SUCD-Yellow D1355 (BASF), Hostaperm Pink E (American Hoechst), Fanal Pink D4830 (BASF), Cinquasia Magenta (DuPont), Lithol Scarlet D3700 (BASF), Toluidine Red (Aldrich), Scarlet for Thermoplast NSD PS PA (Ugine Kuhlmann of Canada), E.D. Toluidine Red (Aldrich), Lithol Rubine Toner (Paul Uhlich), Lithol Scarlet 4440 (BASF), Bon Red C (Dominion Color Company), Royal Brilliant Red RD-8192 (Paul Uhlich), Oracet Pink RF (Ciba-Geigy), Paliogen Red 3871 K (BASF), Paliogen Red 3340 (BASF), Lithol Fast Scarlet L4300 (BASF), combinations of the foregoing and the like. Other pigments that can be used, and which are commercially available include various pigments in the color classes, Pigment Yellow 74, Pigment Yellow 14, Pigment Yellow 83, Pigment Orange 34, Pigment Red 238, Pigment Red 122, Pigment Red 48:1, Pigment Red 269, Pigment Red 53:1, Pigment Red 57:1, Pigment Red 83:1, Pigment Violet 23, Pigment Green 7 and so on, and combinations thereof.
The colorant, for example carbon black, cyan, magenta and/or yellow colorant, may be incorporated in an amount sufficient to impart the desired color to the toner. In general, pigment or dye, may be employed in an amount ranging from about 2% to about 35% by weight of the toner particles on a solids basis, from about 5% to about 25% by weight or from about 5% to about 15% by weight.
In embodiments, more than one colorant may be present in a toner particle. For example, two colorants may be present in a toner particle, such as, a first colorant of pigment blue, may be present in an amount ranging from about 2% to about 10% by weight of the toner particle on a solids basis, from about 3% to about 8% by weight or from about 5% to about 10% by weight; with a second colorant of pigment yellow that may be present in an amount ranging from about 5% to about 20% by weight of the toner particle on a solids basis, from about 6% to about 15% by weight or from about 10% to about 20% by weight and so on.
Other Additives
The toner particles can contain other optional additives, as desired or required. For example, the toner can include positive or negative charge control agents, for example, in an amount of from about 0.1 to about 10 percent by weight of the toner, such as from about 1 to about 3 percent by weight of the toner (although amounts outside of these ranges may be used). Examples of suitable charge control agents include quaternary ammonium compounds inclusive of alkyl pyridinium halides; bisulfates; alkyl pyridinium compounds, including those disclosed in U.S. Pat. No. 4,298,672, the disclosure of which is hereby incorporated by reference in its entirety; organic sulfate and sulfonate compositions, including those disclosed in U.S. Pat. No. 4,338,390, the disclosure of which is hereby incorporated by reference in its entirety; cetyl pyridinium tetrafluoroborates; distearyl dimethyl ammonium methyl sulfate; aluminum salts such as BONTRON E84TM or E88TM (Orient Chemical Industries, Ltd.); combinations thereof, and the like. Such charge control agents can be applied simultaneously with the shell resin described above or after application of the shell resin.
External additive particles can be blended with the toner particles after formation including flow aid additives, which additives can be present on the surface of the toner particles. Examples of these additives include metal oxides such as titanium oxide, silicon oxide, aluminum oxides, cerium oxides, tin oxide, mixtures thereof, and the like; colloidal and amorphous silicas, such as AEROSILRTM, metal salts and metal salts of fatty acids inclusive of zinc stearate, calcium stearate, or long chain alcohols such as UNILIN 700, and mixtures thereof.
In general, silica can be applied to the toner surface for toner flow, tribo enhancement, admix control, improved development and transfer stability, and higher toner blocking temperature. TiO2 may be applied for improved relative humidity (RH) stability, tribo control and improved development and transfer stability. Zinc stearate, calcium stearate and/or magnesium stearate can be used as an external additive for providing lubricating properties, developer conductivity, tribo enhancement, enabling higher toner charge and charge stability by increasing the number of contacts between toner and carrier particles. A commercially available zinc stearate known as Zinc Stearate L, obtained from Ferro Corporation, can be used. The external surface additives can be used with or without a coating.
Each of these external additives can be present in an amount of from about 0.1 percent by weight to about 5 percent by weight of the toner, such as from about 0.25 percent by weight to about 3 percent by weight of the toner, although the amount of additives can be outside of these ranges. The toners may include, for example, from about 0.1 weight percent to about 5 weight percent titanium dioxide, such as from about 0.1 weight percent to about 8 weight percent silica, or from about 0.1 weight percent to about 4 weight percent zinc stearate (although amounts outside of these ranges may be used). Suitable additives include those disclosed in U.S. Pat. Nos. 3,590,000, 3,800,588, and 6,214,507, the disclosures of each of which are hereby incorporated by reference in their entirety. Again, these additives can be applied simultaneously with the shell resin described above or after application of the shell resin.
The toner particles can have a weight average molecular weight (Mw) in the range of from about 17,000 to about 80,000 daltons, a number average molecular weight (Mn) of from about 3,000 to about 10,000 daltons, and a MWD (a ratio of the Mw to Mn of the toner particles, a measure of the polydispersity, or width, of the polymer) of from about 2.1 to about 10 (although values outside of these ranges can be obtained).
While the description above refers to particular embodiments, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of embodiments herein.
The presently disclosed embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of embodiments being indicated by the appended claims rather than the foregoing description. All changes that come within the meaning of and range of equivalency of the claims are intended to be embraced therein.
EXAMPLES
The example set forth herein below is illustrative of different compositions and conditions that can be used in practicing the present embodiments. All proportions are by weight unless otherwise indicated. It will be apparent, however, that the embodiments can be practiced with many types of compositions and can have many different uses in accordance with the disclosure above and as pointed out hereinafter.
The embodiments will be described in further detail with reference to the following examples and comparative examples. All the “parts” and “%” used herein mean parts by weight and % by weight unless otherwise specified.
An exemplary direct current (DC) electromagnet device provided in the Examples below demonstrated a magnetic field strength of about 5,000 Gauss, which compares favorably with the 400 Gauss alternating current (AC) solenoids. In particular, it was shown that using a pulsing direct current electromagnetic generator, a pulsing DC current at 334 volts to the coil could be achieved. Those skilled in the art will appreciate that higher voltages are achievable through circuit modifications and that the device shown in the Examples is merely exemplary. Because the coil has fixed resistance, higher voltage results in higher current and therefore magnetic field strength.
By pulsing the direct current and employing optional fan cooling, the temperature of the coil was successfully maintained at less than about 50° C. Under such conditions, pigment milling may be carried out for as long as required.
FIGS. 3 and 4 show a circuit diagram and working prototype, respectively, of an exemplary embodiment of a pulsing direct current electromagnet subunit developed for pigment milling applications in accordance with embodiments disclosed herein. Referring to the circuit diagram of FIG. 3 and prototype of FIG. 4, a 118 V AC power supply 200 is rectified to DC and the voltage is increased to 334 Volts (via rectifier 210 comprising capacitor 210a and diodes 210b) for charging the capacitor bank 220. A silicon chip relay (SCR) gate 230a, triggered by a timer (relay, 230b) every 0.6 second, allows capacitors 220 to discharge stored energy to the electromagnetic coil for a duration of 0.4 seconds. Two light bulbs (lamps, 205a, along with fuse 205b) are used as safety load for capacitors 220 as well as “charging” and “discharging” indicators. The electromagnetic coil 120 operates on V=IR principle. Because coil resistance (R) is a constant, the higher the voltage, the higher the current. The strength of the magnetic field generated by the coil (H) is determined by the following equation:




  
    H
    →
  
  =
  
    
      number
      ⁢
      
        
      
      ⁢
      of
      ⁢
      
        
      
      ⁢
      
        turns
        ⨯
        current
      
    
    
      coil
      ⁢
      
        
      
      ⁢
      length
    
  




The magnetic field strength, or magnetic flux density, generated by the prototype device is estimated to be about 0.5 Tesla (5000 Gauss). FIG. 5 shows a coil 120 connected to pulsing direct current electromagnet subunit with pigment slurry in vial 140 being milled (coil de-energized). FIG. 6 shows close up view of coil 120 with a pigment slurry in vial 140 being milled (coil energized). In the exemplary working Example below, an optimal position of the vial was protruding approximately 0.5 inches below the bottom of the coil. This position resulted in the most aggressive and chaotic movement of the magnetic particles/pigment during milling.
Method of Preparing Pigment Dispersion
Example 1
Preparation of Magenta Pigment Dispersion in Accordance with Methods and Systems Disclosed Herein
Into a 9 ml vial was added 2.66 g 45 wt % of magenta pigment (PR122) water mixture (containing 9 wt % Tayca power surfactant), 1.31 ml (3.25 g) of 35 micron iron oxide magnetic particles and 1.31 ml (1.82 g) nonmagnetic abrasives Al2O3 (<10 micron) at 50:50 abrasive volume concentration.




  
    Abrasive
    ⁢
    
      
    
    ⁢
    concentration
  
  =
  
    
      Abrasive
      ⁢
      
        
      
      ⁢
      Dry
      ⁢
      
        
      
      ⁢
      Volume
    
    
      
        
          
            Total
            ⁢
            
              
            
            ⁢
            Dry
            ⁢
            
              
            
            ⁢
            Volume
          
        
      
      
        
          
            of
            ⁢
            
              
            
            ⁢
            Milling
            ⁢
            
              
            
            ⁢
            Media
          
        
      
    
  




The vial was then spun at a speed of 50 revolutions per minute under an electromagnetic pulser described above for a total 2 hours, resulting a final magenta pigment dispersion of 178.6 nm, which is comparable to the magenta pigment dispersion used in EA toner. FIG. 7 shows the final particle size and particle size distribution. The particle size of pigment dispersion was also measured at different time interval as shown in FIG. 8. FIG. 7 shows the final particle size and particle size distribution of magenta pigment dispersion from Example 1. FIG. 8 shows the time-D50 plot of magenta pigment samples taken from Example 1.
Example 2
Preparation of yellow pigment dispersion using High-energy Direct Current (D.C.) “Pulsing” Electro-magnetic field generator. Into a 9 ml vial was added 2.66 g 35 wt % of yellow pigment (PY74) water mixture (containing 9 wt % Tayca power surfactant), 1.31 ml (3.25 g) of 35 micron iron oxide magnetic particles and 1.31 ml (1.82 g) nonmagnetic abrasives Al2O3 (<10 micron) at 50:50 abrasive volume concentration.




  
    Abrasive
    ⁢
    
      
    
    ⁢
    concentration
  
  =
  
    
      Abrasive
      ⁢
      
        
      
      ⁢
      Dry
      ⁢
      
        
      
      ⁢
      Volume
    
    
      
        
          
            Total
            ⁢
            
              
            
            ⁢
            Dry
            ⁢
            
              
            
            ⁢
            Volume
          
        
      
      
        
          
            of
            ⁢
            
              
            
            ⁢
            Milling
            ⁢
            
              
            
            ⁢
            Media
          
        
      
    
  




The vial was then spun at 50 rpm under an electromagnetic pulser described above for a total 6 hours, resulting in a final yellow pigment dispersion of 144.7 nm, which meet the target of below 150 nm. FIG. 5 is the final particle size and particle size distribution. The particle size of pigment dispersion was also measured at different time interval as shown in FIG. 9. FIG. 9 shows the final particle size and particle size distribution of yellow magenta pigment dispersion from Example 2. FIG. 10 shows the time-D50 plot of magenta pigment samples taken from Example 2.
It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. Unless specifically recited in a claim, steps or components of claims should not be implied or imported from the specification or any other claims as to any particular order, number, position, size, shape, angle, color, or material.

## Claims

1. A system for pigment milling comprising:
a pulsing direct current (DC) source that generates a DC pulse;
an electromagnetic field generating subunit comprising an electromagnetic coil coupled to the pulsing DC source to receive the DC pulse and to generate a magnetic field; and
a rotating container subunit comprising:
a container for holding a plurality of magnetic particles and a plurality of ink pigment particles in an ink carrier; and
a rotating subunit to rotate the container;
wherein a portion of the container is disposed within the electromagnetic coil and generation of the magnetic field causes motion of the plurality of magnetic particles thereby dispersing the plurality of ink pigment particles within the ink carrier.

2. The system of claim 1, wherein the pulsing DC source includes an alternating current source and a voltage rectifier that converts a voltage provided by the AC source to a DC voltage.

3. The system of claim 2, wherein the voltage rectifier further multiples the DC voltage.

4. The system of claim 3, wherein the pulsing DC source further includes one or more capacitors to store the DC voltage.

5. The system of claim 4, wherein pulsing DC source further includes a switching circuit to receive the DC voltage from the one or more capacitors and provide the DC pulse to the electromagnetic coil.

6. The system of claim 5, wherein the switching circuit is turned off and on according to a duty cycle generated by one or more relays to maintain a target operating temperature of the electromagnetic coil.

7. The system of claim 6, wherein the target operating temperature can be maintained in excess of six hours and milling can be carried during the entire period.

8. The system of claim 6, wherein the one or more relays provides the DC pulse with a duration of 0.4 to 0.6 seconds.

9. The system of claim 6, wherein the one or more relays cause an off time with no DC pulse from 0.6 to 0.8 seconds.

10. The system of claim 1, wherein the pulsing dc source comprises one or more load protecting features.

11. The system of claim 1, further comprising a cooling subunit to cool the electromagnetic coil during operation thereby maintaining a target operating temperature of the electromagnetic coil.

12. The system of claim 1, wherein the electromagnetic coil generates a field strength in a range from about 4000 to about 6000 Gauss.

13. A method of milling a pigment comprising:
providing a container, the container including a plurality of ink pigments, a plurality of magnetic particles, and an ink carrier;
generating a DC pulse by a direct current (DC) source;
providing the DC pulse to an electromagnetic coil to generate a magnetic field; and
rotating the container by a rotating subunit,
wherein a portion of the container is disposed within the electromagnetic coil and generation of the magnetic field causes motion of the plurality of magnetic particles thereby dispersing the plurality of ink pigment particles within the ink carrier.

14. The method of claim 13, wherein the sufficient period of time is in a range from about five minutes to about six hours.

15. The method of claim 13, wherein target effective diameter is suitable for forming a toner.

16. The method of claim 13, wherein the average pigment particle size is in a range from about 100 nm to about 200 nm.

17. The method of claim 13, wherein a time to mill the plurality of ink pigments is shorter than when using alternating current actuated magnetic milling.