Patent Application
20080076056
These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.
A method to prepare a toner composition by using a continuous reactor according to an exemplary embodiment of the present general inventive concept may include polymerizing a first monomer and a second monomer in the continuous reactor in the presence of a polymerization initiator, and adding a releasing agent, a colorant, and a charge control agent thereto.
The continuous reactor is a vessel in which a product of a reaction moves in a designated direction in a continuous stream to thereby perform a continuous reaction, and from which the product can be extruded through an outlet formed in one side of the reactor.
The continuous reactor 1 may include a first inlet 10, a second inlet 11, a reaction tub 20, and an outlet 30.
The reactants, i.e., the first and second monomers, the polymerization initiator, the releasing agent, the colorant, and the charge control agent, inflow through the first and second inlets 10 and 11 into the reactor.
According to an embodiment of the present general inventive concept, the first monomer inflows through the first inlet 10 and the second monomer flows through the second inlet 11. In a case where the second monomer is introduced into the reactor through the first inlet 10, the first monomer can be introduced into the reactor through the second inlet 11. That is to say, the different monomers may be introduced through different inlets, respectively. Alternatively, the first and second monomers may be introduced through the same inlet. While
The first monomer and the second monomer can be sequentially inputted into the continuous reactor 1. These monomers are polymerized in the reaction tub 20 and extruded through the outlet 30. Compared with a simultaneous input of the first and second monomers, sequentially inputting the first and second monomers enables an easier adjustment of a polymerization start time point and an easier differentiation of an input time of the monomers in consideration with a reaction rate of each monomer, thereby guiding the reaction to promote polymerization.
By adjusting the input times of the monomers, the first and second monomers can be polymerized into one of a random copolymer, a block copolymer, and a graft copolymer.
In a random copolymer, monomeric units are at random sites of a polymer. In a block copolymer, monomeric units repeat at a fixed ratio. In a graft copolymer, a monomer is polymerized and other monomers are polymerized with the polymerized chain in a branch shape.
If the first monomer and the second monomer are simultaneously inputted through one inlet, a ratio of random copolymers in a polymer increases. Meanwhile, if the first and second monomers are sequentially or separately inputted, a ratio of block copolymers in a polymer increases. In a case of a polymer blend where monomers are simply polymerized together, the resultant polymer blend typically has degraded properties compared with properties of each of the monomers. On the other hand, in a case of a random copolymer and a graft copolymer, properties of each monomer are blended to create different properties. In case of a block copolymer, where each monomer is polymerized in block unit, properties of individual monomer are retained.
Therefore, the block copolymer may be more desirable than the other copolymer types because the polymer is produced while keeping desirable properties of every monomer in it. Accordingly, the monomers may be sequentially input to obtain a high block copolymer ration.
Any monomers suitable for the binder resin of a toner may be used as the first and second monomers. Examples of such monomers include, but are not limited to, polyester, styrene, divinyl benzene, n-butyl acrylate, metacrylate, and (meta) acrylic acid. Monomers may be used singly or in combination.
However, polyester- and styrene-acryl based monomers are often blamed for a production of environmentally harmful substances, for example, catalysts used in the polymerization (tin group, heavy metals, e.g., Co, Ni, and VI) or volatile organic compounds produced from non-reacted monomers.
Therefore, the first and second monomers may be aliphatic polyester. For example, the monomers used in the present general inventive concept may be lactam monomers or lactone monomers. Here, examples of the lactam monomers include ω-lauryl lactam, ε-caprolactam, and mixtures thereof. Examples of the lactone monomers include ε-caprolactone, butyrolactone, and mixtures thereof.
Among the lactone monomers, ε-caprolactone for example is an aliphatic ester monomer as a crystal polymer with a cyclic structure. This monomer compound is a human eatable/non-toxic, environmentally friendly, and biodegradable substance, and improves a fixability of toner particles.
Among the lactam monomers, ω-lauryl lactam has an aliphatic amide ring structure, and is a most moisture-insensitive and reactive among the amide-based compounds. Thus, it serves to improve an endurance of the toner.
Additionally, a polymerization initiator can be inputted to polymerize the first monomer and the second monomer. For example, an anion based polymerization initiator can be used, such as, sodium hydroxide.
Besides the polymerization initiator, a cocatalyst may be used. The cocatalyst is an element that is added to increase a catalyst activity, or to control/change a reaction caused by a catalyst. For example, N-acetyl caprolactam can be used as a cocatalyst.
As aforementioned, after putting the first monomer, the second monomer, and the polymerization initiator in the continuous reactor 1 to cause the polymerization reaction, a releasing agent, a colorant, and a charge control agent are inputted to the toner particles as internal additives.
Even though the releasing agent, the colorant, and the charge control agent may be introduced through the first inlet 10 and the second inlet 11, they may be inputted only through the second inlet 11 in consideration of the reaction time of the first monomer.
The releasing agent improves a releasability between a roller and a toner when a toner image is transferred onto a recording medium to prevent a toner offset. Many times, the recording medium is adhered to the roller because of the toner, so the recording medium is easily caught in the middle. This is why the releasing agent may be added to the toner composition.
Typically used releasing agents are a polyolefin group having low molecular weight, a silicon group having a softening point by the application of heat, a fatty acid amid group, and wax. Among these, commercially made wax is easy to get.
Examples of wax as a releasing agent of a toner component are natural waxes including waxes from a plant, such as, carnauba wax and bayberry wax, and waxes from an animal, such as, beeswax, shellac wax, and supermaceti wax; mineral waxes, such as, montan wax, ozokerite wax, and ceresin wax; and synthetic waxes, such as, paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, acrylate wax, fatty acid amid wax, silicon wax, and polytetrafloroethylene wax. These waxes may be used singly or in mixture of two or more.
The colorant is a substance exhibiting color of toner particles. Colorants are largely divided into dye colorants and pigment colorants. Any widely used commercial colorant can be used as a toner colorant in the present general inventive concept. For example, pigment colorants with excellent thermal stability and lightproofness may be used.
Examples of such pigment colorants for use in the present general inventive concept include, but are not limited to, azo pigments, phthalocyanine pigments, basic dyes, quinacridone pigments, dioxazine pigments, diazo pigments, chromate, ferrocyanices, oxide, selenium sulfide, sulfate, silicate, carbonate, phosphate, metal powder, and carbon black.
The charge control agent is employed to control a quantity of electric charge on toner particles (also called a charge assistant, charge directing agent, and so on). Depending on the charge (positive or negative) of the toner particles, different kinds of charge control agents can be used.
Examples of a negative charge control agent include azo dyes, salicylic acid metal complexes containing a metal like chrome, iron and zinc, and so on. Examples of a positive charge control agent include nigrosine, quaternary ammonium salts, triphenylmethane derivatives, and so on.
A conductive polymer, e.g., polyaniline, polypyrol, and polythiophene, may be used as the charge control agent. For example, liquid polythiophene with an excellent charge control performance can be used to ensure uniform chargeability.
In Example 1, a toner composition is prepared using a continuous reactor according to an embodiment of the present general inventive concept, and in Example 2 a toner composition is prepared with a different content ratio of monomers according to the present general inventive concept. The following examples are aimed to be illustrative of the present general inventive concept. However, they should not be construed as limiting the scope of this general inventive concept.
In preparing the first monomer, 6.340 mol of ω-lauryl lactam, 0.1250 mol of sodium hydroxide, and 0.097 mol of N-acetylcaprolactam were mixed in a dry box, under an inert gas (Ar) atmosphere. Later, the mixture was inputted through the first inlet at a speed of 1.3 kg/hr by using a solid type feeder.
In preparing the second monomer, 2.09 mol of ε-caprolactone, and with respect to a total weight of the two monomers, 2 wt % carnauba wax as a releasing agent, 3 wt % of carbon black as a colorant, and 1 wt % of liquid polythiophene as a charge control agent were inputted through the second inlet. Polythiophene in a liquid phase contains 1.2 to 2.2% of solid, and features a viscosity of 10 to 30 mPa·s, a pH value of 3 to 8, and a density of 0.900 to 0.926 g/cm3. The ε-caprolactone, the releasing agent, the colorant, and the charge control agent were preheated at about 100° C., and were inputted into the reactor using a liquid feeder.
A twin screw extruder was used as the continuous reactor under controlled conditions. In detail, a barrel temperature was set to 195° C., a screw speed was set to 150 rpm, and inflow speeds at the first and second inlets were set to 1.3 kg/hr and 1.5 kg/hr, respectively.
Under the above conditions, a mean residence time in the extruder was approximately 400 sec. The mixture was pulverized in a Bantam-mill pulverizer to produce medium pulverized particles of about 1-2 mm in size, and further pulverized in a Super-rotor to produce super fine pulverized particles of about 15 μm in size. Last, toner particles of less than 5 m in size were classified by centrifugal force to thereby obtain a particle size of about 8.0±0.5 μm.
Next, as external additives, 1.0-1.6% of coarse SiO2, 0.8-1.3% of fine powder SiO2, 0.1-0.3% of a metal oxide (TiO2, Al2O3 and the like), and 0.1-0.3% of polymer bead (melamine group, PMMA group) were added and mixed in Henschel mixer at 3500-3800 rpm for 7-10 minutes, and screened.
When thermal analysis was done using a DSC (Differential Scanning Calorimetry), crystalline melting points were 60° C., 80° C., and 170° C., respectively.
Because ε-caprolactone, carnauba wax, and ω-lauryl lactam are all crystalline substances, melting points do not exist when the conventional amorphous polymer resin binder was used, and one can observe a very wide range of fixing properties. However, when the lactam-lactone copolymer was used, as in this example, a very narrow range of fixing properties can be realized during fixing an image. Therefore, the method to prepare a toner composition according to the present general inventive concept can be advantageously used for an engine requiring a very short fixing time, such as, a high-speed image forming device.
Toner particles were obtained in the same manner as in Example 1 except that 6.01 mol of ε-caprolactone was inputted through the second inlet.
Properties of toner compositions thus prepared in Examples 1 and 2 were evaluated as follows:
100 ml of ink compositions prepared according to Examples 1 and 2 were put into a heat-resistance glass bottle, respectively, sealed and kept in a 60° C. constant temperature vessel. Two months later, an existence of sediments on the bottom was checked and an evaluation was made as follows. The results are provided in Table 1 below.
For the fixability test, a solid image was measured by taping, and expressed in percentage. The endurance test was conducted in an H/H environment (32° C./80%) in reference to an image formation damage phenomenon of a solid image in a 16 PPM class image forming device (2% coverage black image, 3.0K print cartridge).
The evaluation results are shown in Table 1.
As described above, by using the continuous reactor, lactone and lactam monomers, and polythiophene in liquid phase as the charge control agent, the resultant toner compositions exhibited a superior fixability and endurance. In addition, as can be seen in the result for Example 2, fixability was improved even more when the content of ε-caprolactone was increased.
As explained above, according to the present general inventive concept, the toner composition can be manufactured in a continuous stream. Also, without degrading physical properties of the toner composition, it is easy to control over the toner composition at the same time. Further, the molecular weight of the toner composition is easily controlled, thereby improving an overall preparation process of the toner composition.
Moreover, the toner composition of the present general inventive concept is more environmentally friendly and features excellent performance as it is made from materials that are environmentally friendly, have enhanced fixability and endurance, and exhibit excellent charge control performances.
Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-094400 | Sep 2006 | KR | national |
