KR100942677B1 - Washing method of chemically polymerized toner - Google Patents

Abstract

The present invention relates to a method for cleaning a polymerized toner which can significantly reduce drying time. The polymerized toner cleaning method of the present invention removes a dispersant from toner particles by adding an acidic or alkaline solution to a dispersion solution in which emulsion polymerization or suspension polymerization is completed. First step; A second step of dispersing the toner slurry in distilled water and repeatedly washing the toner slurry; A third step of washing the toner slurry repeatedly washed with distilled water with an organic solvent or a mixed solvent of an organic solvent and water; A fourth step of removing water from the toner slurry washed with the organic solvent or a mixed solvent of organic solvent and water using a filtration device; And a fifth step of drying the filtered toner composition.

Toner Wash, Polymerized Toner

Description

WASHING METHOD OF CHEMICALLY POLYMERIZED TONER

1 is a graph showing the reduction rate of the washing solution of Examples 1 to 3 and Comparative Example 1.

The present invention relates to a method for cleaning a polymerized toner, and more particularly, to a method for cleaning a polymerized toner that can significantly reduce the drying time of a toner slurry.

In general, toner refers to functional fine particles prepared by dispersing a pigment, a charge control agent, or the like in a polymer resin, and adding an internal additive such as wax and an external additive such as silica. Used as a developer. Recently, as computer document creation has become commonplace, the demand for an image forming apparatus such as a printer has soared, and the demand for a toner used in the image forming apparatus has soared.

In general, the most well-known toner manufacturing method is a pulverization method in which a toner is prepared by melt-mixing or extruding an additive such as a pigment, a charge control agent, a wax, and the like into a binder resin prepared by chemical polymerization, and mechanically pulverizing it. to be. However, the pulverization method requires complicated steps such as polymerization, melt-mixing, and pulverization, which makes the manufacturing process complicated, high energy consumption, and mechanically pulverizes the toner particles, thereby providing a wide particle size distribution and sharp edges. There are disadvantages in that the shape of the toner particles, such as eggplants, is irregular, so that problems in print quality are likely to occur.

The developed toner manufacturing method for overcoming the disadvantages of such a pulverization method is a polymerization method, and the polymerization method produces toner particles using a polymerization reaction without using mechanical grinding. The production of the toner by the polymerization method has the advantage that the particle size hardening and the particle shape control are easy.

The polymerization method is divided into emulsion polymerization method and suspension polymerization method. Among them, emulsion polymerization method is a method of emulsifying additives such as pigments, waxes and charge control agents in advance, and then dispersing the monomers together in water to polymerize them. The use of OH has the advantage that the structure and size of the toner particles can be controlled by adjusting conditions such as temperature and time during polymerization. In the suspension polymerization method, a monomer mixture is prepared by uniformly dissolving or dispersing various additives such as a monomer, a pigment, a wax, and a charge control agent, and putting the same into an aqueous dispersion containing a dispersant and applying a shear force to polymerize the suspension. The method has the advantage that the manufacturing process is simple, and spherical toner particles of about 10 micrometers, which are sizes suitable for use as toners, can be produced. Polymerized toner is capable of achieving a higher resolution than pulverized toner, and is highly demanded due to its excellent quality reproducibility.

On the other hand, the polymerization process is carried out after the completion of the polymerization reaction, the acid is added to favor the dispersion, NaOH used to remove the dispersant, the emulsion polymer produced as a side reactant, suspended solids not formed completely spherical and unreacted Monomers, dimers, etc. must be removed. This is because if the above materials are not removed properly, the toner properties such as low temperature fixability and chargeability are deteriorated.

Korean Patent Laid-Open No. 10-2006-0041017 discloses a conventional method for cleaning a polymerized toner. Looking at the conventional polymerized toner cleaning method in detail as follows. First, when polymerization of the toner is completed, the dispersant is removed from the surface of the toner by a suitable method, and the toner composition is separated from the reaction solution to obtain a toner slurry. For example, when colloidal silica is used as a dispersant, the colloidal silica may be removed from the surface of the toner by adding and stirring the NaOH solution to the solution containing the polymerized toner (dispersant removing step). It is dispersed in distilled water, and distilled water including the toner slurry is separated using a centrifugal separator. After decondensing the toner slurry separated by the above process, the remaining solution is redispersed and the process of centrifugation-decondensation is repeated to sufficiently purify (washing step). When the cleaning is completed, the water is removed by filtration to obtain a toner cake (filtration step). The toner cake is placed in a vacuum oven and dried to obtain the final toner particles (drying step).

 Since the cleaning method for the polymerized toner as described above uses water as the cleaning solvent, the time required for drying the toner is long. Therefore, there is a problem that the overall process time required for toner production increases, and as a result, productivity decreases. In addition, when water is used as the washing solvent as described above, since the organic matters are difficult to be completely removed, the unreacted or side reactions may remain in the toner and deteriorate the toner properties.

In order to solve the above problems, the present invention further includes a washing step using an organic solvent or a mixed solvent of water and an organic solvent in the conventional toner cleaning process, thereby shortening the drying time of the toner, thereby improving productivity and economic efficiency of producing a polymerized toner. The purpose of the present invention is to improve the characteristics of the polymerized toner by improving the efficiency of the reaction product and by easily removing side reactions such as unreacted monomers or dimers.

In order to achieve the above object, the present invention further includes the step of using an organic solvent or a mixed solvent of organic solvent and water as a washing solution instead of distilled water in the cleaning step of the conventional polymerization toner, so as to drastically reduce the drying time of the toner It is characterized by that.

The polymerized toner cleaning method of the present invention includes a first step of removing the dispersant from toner particles by adding an acidic solution or an alkaline solution to a dispersion solution in which emulsion polymerization or suspension polymerization is completed; A second step of dispersing the toner slurry in distilled water and repeatedly washing the toner slurry; A third step of washing the toner slurry repeatedly washed with distilled water with an organic solvent or a mixed solvent of an organic solvent and water; A fourth step of removing water from the toner slurry washed with the organic solvent or a mixed solvent of organic solvent and water using a filtration device; And a fifth step of drying the filtered toner composition.

In this case, the mixing ratio of the water and the organic solvent is preferably 1:99 to 99: 1, and the organic solvent is preferably an alcohol such as ethanol or methanol.

Hereinafter, the polymer toner cleaning method of the present invention will be described in more detail.

(1) dispersant removal step

When the polymerization reaction is completed, an acidic solution or an alkaline solution is added to the dispersion solution and stirred for a predetermined time to remove the dispersant from the surface of the toner composition. When the dispersant removal is completed, the dispersion solution is filtered to obtain a toner slurry.

(2) distilled water washing step

Next, after dispersing the toner slurry in distilled water, a solution in which the toner slurry is dispersed (hereinafter referred to as "distilled water washing solution") is put in a centrifugal separator and the toner slurry is washed by separating the solid and liquid components. Distilled water washing step is to dissolve and remove the dispersant remaining on the surface of the toner particles, and to lower the ionic conductivity of the toner, using distilled water or water as the washing solvent.

The distilled water washing step is preferably repeated several times. If it is determined that the toner slurry is sufficiently washed by repeating distilled water washing several times, the toner slurry is separated from the distilled water washing solution through filtration.

(3) organic solvent washing step

The toner slurry separated from the distilled water washing solution is washed with an organic solvent or a mixed solvent of water and an organic solvent (hereinafter referred to as "organic solvent"). The washing method is the same as the distilled water washing step. That is, after dispersing the toner slurry in an organic solvent, the solution (hereinafter referred to as " organic washing solution ") is put into a centrifugal separator and the toner slurry is washed by separating the solid and liquid components.

The organic solvent washing step may be repeatedly performed. However, when the number of washing of the organic solvent increases, the toner agglomeration may occur and the quality of the toner may be deteriorated. Therefore, the organic solvent washing step may be performed once after the distilled water washing step.

As the organic solvent, a pure organic solvent may be used, or a mixed solvent of water and an organic solvent may be used. When a pure organic solvent is used, the solvent has a high volatility, and thus has an advantage of shortening the drying time. However, agglomeration of toner may occur. When using a mixed solvent of water and an organic solvent, the mixing ratio of the water and the organic solvent is preferably 1:99 to 99: 1.

 As the organic solvent, it is preferable to use an organic solvent having a high volatility such as alcohol such as methanol and ethanol.

(4) filtration step

After the organic solvent washing step is completed, the organic washing solution is filtered using a filtration filter to obtain a toner cake. At this time, the filtration filter preferably has a hole of 3 to 10 ㎛ size.

(5) drying step

The toner cake obtained through the filtration step is put into a vacuum oven and dried to obtain final toner particles.

After the washing step using the organic solvent as a washing solvent after washing the distilled water as described above, the toner drying time can be significantly reduced due to the strong volatility of the organic solvent. In addition, since the organic components of subreactants such as NaOH, unreacted monomers, and dimers used for dispersant separation are more soluble in organic solvents than distilled water, a purified toner composition can be obtained better than when washed only with distilled water. have.

Hereinafter, the present invention will be described in more detail with reference to Examples. The following Examples are merely examples of the present invention, and the present invention is not limited by the following Examples.

Preferred Embodiment

Comparative example

NaOH is added to the dispersion solution containing the toner composition prepared by emulsion polymerization or suspension polymerization to bring the concentration to 2.2N. The solution is stirred for 4 hours to remove a dispersant such as silica from the surface of the toner particles and then filtered to obtain a toner slurry.

100 parts of the toner slurry is taken, 500 parts of distilled water corresponding to 5 times is added, and then washed 10 times by centrifugation, followed by filtration. The filtered toner cake is dried in a vacuum oven and the residual weight is measured with drying time. The measured values are shown in Table 1.

Example 1

NaOH is added to the dispersion solution containing the toner composition prepared by emulsion polymerization or suspension polymerization to bring the concentration to 2.2N. The solution is stirred for 4 hours to remove a dispersant such as silica from the surface of the toner particles and then filtered to obtain a toner slurry.

100 parts of the toner slurry obtained by emulsion polymerization or suspension polymerization of the polymerized toner were taken, 500 parts of distilled water corresponding to 5 times was added, and then washed nine times by centrifugation. In the tenth wash, 500 parts of methanol is added instead of distilled water, and the resultant is filtered. The filtered toner cake was dried in a vacuum oven and the residual weight was measured over time. The measured values are shown in Table 1.

Example 2

It is the same as in Example 1 except that 500 parts of a mixed solvent in which methanol and water are mixed in a 1: 1 ratio instead of methanol is added.

Example 3

It is the same as in Example 1 except that 500 parts of a mixed solvent of 1: 1 mixed ethanol and water is added instead of methanol.

Hours (h) Comparative Example 1 Example 1 Example 2 Example 3 Weight (g) Residual Solvent Ratio (%) Weight (g) Residual Solvent Ratio (%) Weight (g) Residual Solvent Ratio (%) Weight (g) Residual Solvent Ratio (%) 0.00 36.15 100.00 59.05 100.00 48.20 100.00 39.58 100.00 0.20 35.63 96.46 55.41 81.76 46.94 92.84 37.99 86.99 0.42 34.76 90.54 52.15 65.43 45.01 81.88 36.28 73.00 0.60 33.35 80.95 48.08 45.04 42.53 67.78 34.49 58.35 0.87 31.30 67.01 44.20 25.60 40.00 53.41 32.66 43.47 1.20 29.20 52.72 41.39 11.52 37.56 39.55 30.92 29.13 1.60 26.78 36.26 39.93 4.21 35.08 25.45 29.07 13.99 1.72 26.04 31.22 39.49 2.00 34.49 22.10 28.58 9.98 2.03 25.16 25.24 39.31 1.10 33.59 16.99 28.11 6.14 2.50 24.18 18.57 39.11 0.10 32.50 10.80 27.72 2.95 3.25 22.74 8.78 39.10 0.05 31.16 3.18 27.45 0.74 3.92 21.74 1.97 39.09 0.00 30.72 0.68 27.38 0.16 4.50 21.55 0.68 39.09 0.00 30.61 0.06 27.38 0.16 6.17 21.47 0.14 39.09 0.00 30.60 0.00 27.37 0.08 7.05 21.47 0.14 39.09 0.00 30.60 0.00 27.36 0.00 10.00 21.46 0.07 39.09 0.00 30.60 0.00 27.36 0.00 25.00 21.45 0.00 39.09 0.00 30.60 0.00 27.36 0.00

As shown in the table, it can be seen that the toners of Examples 1 to 3, which were washed with distilled water and washed with an organic solvent, were much shorter in drying time than the toner of Comparative Example, which was only washed with distilled water.

Meanwhile, FIG. 1 is a graph showing the cleaning solution reduction rate with respect to the drying time of each toner cleaned by the method of Examples 1 to 3 and Comparative Example 1 using the data of Table 1. As can be seen in Figure 1, in the case of the toner of Comparative Example 1 cleaned by the conventional method, it can be seen that the reduction rate of the cleaning solution is slow compared to the toner of Examples 1 to 3 that went through the organic solution cleaning step of the present invention have.

The present invention has the effect of improving productivity by drastically reducing the drying time of the toner by using an organic solvent as a washing solution in the last step of washing.

The present invention has the advantage that by using an organic solvent as the washing solvent, it is easy to remove the side reactions such as unreacted monomers or dimers, organic components such as sodium hydroxide.

Claims (3)

A first step of removing the dispersant from the toner particles by adding an acidic solution or an alkaline solution to the dispersion solution in which the emulsion polymerization or suspension polymerization is completed; A second step of dispersing the toner slurry in distilled water and repeatedly washing the toner slurry; A third step of washing the toner slurry repeatedly washed with distilled water with an organic solvent or a mixed solvent of an organic solvent and water; A fourth step of removing water from the toner slurry washed with the organic solvent or a mixed solvent of organic solvent and water using a filtration device; And a fifth step of drying the filtered toner cake (CAKE), wherein the drying time of the toner slurry is significantly shortened. The method of claim 1, The mixing ratio of the water and the organic solvent is 1:99 to 99: 1, the cleaning step of the polymerized toner. The method of claim 1, And said organic solvent is an alcohol.