KR20100115147A - Method for preparing toner - Google Patents

Abstract

PURPOSE: A method for manufacturing a toner is provided to reduce energy by lowering temperature of fusion step and to improve dispersibility of wax in toner particles. CONSTITUTION: A method for manufacturing a toner comprises: a step of mixing latex dispersing liquid, coloring agent dispersing liquid and wax dispersing liquid; and a step of adding coagulant to form toner particles. The fusion stem is performed at latex glass transition temperature + 15°C to wax melting temperature and pH 4-5. The toner has a core-shell structure.

Description

Method for preparing toner {Method for preparing toner}

The present invention relates to a manufacturing method of a toner by emulsion coagulation, and more particularly, toner that can save energy, improve dispersibility of wax in toner particles, and prevent leakage of wax out of toner particles. It relates to a method for producing.

Generally, toner is prepared by adding a colorant, a charge control agent, a wax, or the like to a thermoplastic resin serving as a binder resin. Further, in order to impart fluidity to the toner or to improve physical properties such as charge control or cleaning property, fine inorganic metal powders such as silica and titanium oxide may be added to the toner as an external additive. As toner production methods, there are physical methods such as grinding method and chemical methods such as suspension polymerization method and emulsion aggregation method.

Among these, the emulsion agglomeration method (see US Patent Nos. 5,916,725, 6,268,103, etc.) consists of preparing a fine emulsion resin particle composition through an emulsion polymerization reaction, and then agglomerating the composition together with pigments in a separate dispersion. . This method has the advantage of making the toner particles spherical by improving the problems such as high cost, wide particle size distribution, and the like in the pulverization method, and adjusting the coagulation conditions.

In general, in the toner manufacturing method by emulsion coagulation, the binder resin, the colorant, and the wax, which are present in the latex phase, are agglomerated with a coagulant and then fused to prepare final toner particles. More specifically, mixing the latex dispersion, the colorant dispersion, and the wax dispersion for the core, adding and homogenizing a flocculant to the mixture, agglomerating the homogenized mixture to form toner particles, the aggregated toner particles Fusing; And cooling the fused toner particles. At this time, when the aggregated toner particles reach a predetermined size in order to fuse the aggregated toner particles, the growth of the particles is stopped and then raised. Generally, in order to shorten the time taken for the fusion, the elevated temperature is performed at 95 to 98 ° C. which is much higher than the glass transition temperature of the binder resin (latex). The wax melted at this temperature greatly increases the fluidity, resulting in uneven wax distribution in the toner particles as the wax particles agglomerate with each other, thereby increasing the amount of wax leaking to the surface of the toner particles. Thus, when an excessive amount of wax is present on the surface of the toner particles, it is possible to contaminate the developing roll, the photoconductor, the carrier, and other parts and surfaces in the electrophotographic image forming apparatus.

Accordingly, the present invention provides a method for producing a toner by emulsifying a toner, in which energy consumption is reduced, wax has excellent dispersibility in toner particles, and minimizes the leakage of wax to the toner particle surface. For the purpose of

In order to solve the above problems, the present invention,

Mixing the latex dispersion, the colorant dispersion, and the wax dispersion;

Adding a coagulant to the mixture and coagulating to form toner particles; And

In the toner manufacturing method comprising fusing the aggregated toner particles, the fusing step is performed at a pH of 4 to 5 in the temperature range of Tg (glass transition temperature) of the latex + 15 ℃ ~ melting point of the wax It provides a method characterized in that.

According to one embodiment of the present invention, the pH may be adjusted by adding an acid in the fusion step.

According to another embodiment of the present invention, the temperature may be raised to 75 to 90 ℃ in the fusion step.

According to another embodiment of the present invention, the toner may have a core-shell structure.

According to the production method of the present invention, the image quality can be improved by saving energy, improving the dispersibility of the wax in the toner particles, and preventing wax leakage to the toner particle surface.

Hereinafter will be described in detail with respect to a preferred embodiment of the present invention.

The toner manufacturing method according to the present invention comprises the steps of mixing a latex dispersion, a colorant dispersion, and a wax dispersion; Adding a coagulant to the mixture and coagulating to form toner particles; And fusing the aggregated toner particles, wherein the fusing step is performed at a pH of 4 to 5 in the temperature range of Tg (glass transition temperature) of the latex + 15 ° C. to the melting point of the wax. Characterized in that it is carried out.

In the conventional method for producing toner by emulsion coagulation, the temperature at the time of fusing is raised to a high temperature of 96 ° C. or more, which is much higher than the glass transition temperature of latex (binder resin), thereby increasing the circularity of the toner particles and shortening the time taken for fusing. It was. However, when the temperature is raised to an excessively high temperature, there is a problem that wax particles are agglomerated due to excessive fluidity of the molten wax, resulting in poor dispersibility of the wax in the toner particles and excessive leakage of wax on the surface of the toner particles, causing image contamination. . On the other hand, when the temperature at the time of fusing is made 75 degreeC or more and 90 degrees C or less, not only will fusion time become too long, but also the roundness of a toner particle may not reach a desired level. Therefore, in the present invention, by controlling the pH of the reaction solution immediately before the fusion occurs, it is possible to achieve the desired circularity of the toner particles in a short time while fusing at a lower temperature than in the conventional method.

In the toner manufacturing method of the present invention, a toner particle is prepared by adding and homogenizing a flocculant to a mixture of a latex (binder resin) dispersion, a colorant dispersion, and a wax dispersion. That is, the latex dispersion, the colorant dispersion and the wax dispersion are mixed in a reactor, and then a flocculant is added to homogenize at a stirring linear speed of 1.0 to 2.0 m / s at pH 1.5 to 2.3 and 20 to 30 ° C. for 10 to 100 minutes. The reactor is heated to 48 to 53 ° C, stirred at a stirring linear speed of 1.5 to 2.5 m / s, and coagulated.

The agglomerated toner particles undergo a step of stopping the growth of the toner particles, a fusion step of the toner particles that have stopped growing, and a cooling and drying step to obtain desired toner particles. The dried toner particles may be externally treated with silica or the like to adjust the charge amount and the like to prepare a final laser printer toner.

In the fusion step, the temperature of Tg (glass transition temperature) of the binder resin (latex) + 15 ° C. to the melting point of the wax is raised, and then the pH is adjusted to 4-5 immediately before the fusion. Preferably the temperature in the fusion step is raised to 75 to 90 ℃, more preferably 80 to 85 ℃. The pH can be adjusted by adding acid to the reaction solution. Thus, by adjusting the pH at the time of fusion, even if the temperature rise temperature at the time of fusion is reduced, desired roundness of toner particles can be obtained within a short time.

The manufacturing method of the toner of the present invention can also be applied to a toner having a core-shell structure. In the case of producing a toner having a core-shell structure, a flocculant is added to a mixture of a latex dispersion, a colorant dispersion and a wax dispersion for the core and homogenized. After the coagulation step, a primary coagulation toner is prepared, and a latex dispersion for shell is added to the obtained primary coagulation toner to form a shell layer, followed by a fusion step.

The binder resin included in the latex dispersion that can be used in the toner manufacturing method of the present invention is one or two or more polymerizable selected from vinyl monomers, polar monomers having a carboxyl group, monomers having an unsaturated polyester group, and monomers having a fatty acid group. It can be prepared by polymerizing monomers.

In order to proceed with the polymerization, a polymerization initiator is generally used, and such polymerization initiators include benzoyl peroxide and azo polymerization initiators.

Macromonomers such as polyethylene glycol ethyl ether methacrylate, polyethylene glycol methyl methacrylate, polyethylene glycol methyl acrylate, and the like may be used to control the number average molecular weight and glass transition temperature (Tg) of the binder resin, and divinyl benzene. Chain transfer agents such as 1-dodecanethiol and the like can be used.

The amount of the macromonomer added is preferably 0.3 to 30 parts by weight based on 100 parts by weight of the binder resin.

Some of the binder resins may be selected and further reacted with a crosslinking agent, and an isocyanate compound, an epoxy compound, or the like may be used as the crosslinking agent.

A crosslinking resin is formed by the crosslinking reaction of the binder resin and the crosslinking agent, and the content of the crosslinking resin contained in the toner is generally 5 to 30 parts by weight based on 100 parts by weight of the uncrosslinked binder resin. When the content of the crosslinked resin is less than 5 parts by weight, it is not preferable because the molecular weight decreases and the fixing temperature range is narrowed. When the content of the crosslinked resin is more than 30 parts by weight, the resin becomes too hard and does not benefit low temperature fixability.

The colorant may be used as the pigment itself or in the form of a pigment masterbatch in which the pigment is dispersed in the resin.

The pigment may be appropriately selected from black pigments, cyan pigments, magenta pigments, yellow pigments, and mixtures thereof, which are commonly used pigments.

The content of the colorant may be sufficient to color the toner to form a visible image by development, for example, preferably 1 to 20 parts by weight based on 100 parts by weight of the binder resin.

On the other hand, a charge control agent and the like may be used as the additive.

As the charge control agent, both an ancillary charge control agent and an antistatic charge control agent may be used. Examples of the charge control agent include an organometallic complex or a chelate compound; Metal-containing salicylic acid compounds; And organometallic complexes of aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids may be used, and any known ones are not particularly limited. As the antistatic charge control agent, a product modified with nigrosine and a fatty acid metal salt thereof, an onium salt containing a quaternary ammonium salt, or the like may be used alone or in combination of two or more thereof. Such a charge control agent charges the toner stably and at high speed by the electrostatic force, thereby stably supporting the toner on the developing roller.

The content of the charge control agent included in the toner is generally within the range of 0.1 parts by weight to 10 parts by weight based on 100 parts by weight of the total toner composition.

As the wax can improve the fixability of the toner image, polyalkylene waxes such as low molecular weight polypropylene and low molecular weight polyethylene, ester wax, carnauba wax, paraffin wax and the like can be used. The amount of wax contained in the toner is generally within the range of 0.1 part by weight to 30 parts by weight with respect to 100 parts by weight of the total toner composition. When the content of the wax is less than 0.1 parts by weight, it is not desirable to realize an oilless fixation capable of fixing the toner particles without using oil, and when the content of the wax exceeds 30 parts by weight, the toner is agglomerated when stored. This is undesirable because it can be caused.

In addition, the additive may further include an external additive. The external additive is to improve the fluidity of the toner or to control the charging characteristics, and includes large particle size silica, small particle size silica, and polymer beads.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these embodiments.

(Production of Latex Dispersion for Core)

A 3-liter reactor with a stirrer, thermometer and condenser was installed in the oil bath. 660 g and 3.2 g of distilled water and surfactant (Dowfax 2A1) were added to the reactor thus installed, and the reactor temperature was increased to 70 ° C. and stirred at a speed of 100 rpm. Then 13.5 g of potassium persulfate was added as an initiator. Then, as monomers, ie styrene 838g, 322g butyl acrylate, 37g 2-carboxyethyl acrylate and 22.6g 1,10-decanediol diacrylate, 507.5g distilled water, 22.6g surfactant (Dowfax 2A1), macromonomer 53 g of polyethylene glycol ethyl ether methacrylate and 18.8 g of 1-dodecanethiol as a chain transfer agent were stirred at 400 to 500 rpm for 30 minutes with a disk-type impeller, and then slowly added to the reactor for 1 hour. After the reaction was performed for about 8 hours and then slowly cooled to room temperature to complete the reaction.

After completion of the reaction, the glass transition temperature (Tg) of the latex (binding resin) was measured using a differential scanning calorimeter (DSC), and the temperature was 57 ° C. The number average molecular weight of the binder resin was measured by gel permeation chromatography (GPC) using a polystyrene reference sample. As a result, the number average molecular weight was 15,000.

Preparation of Latex Dispersion for Shell

2,200 g of deionized water was added to a 4 liter reactor, and the mixture was heated to 80 ° C. while stirring while purging N ₂ . Thereafter, 390 g of styrene monomer, 145 g of butyl methacrylate, 20 g of methacrylic acid, and 10 g of epoxy acrylate were completely dissolved after stirring, and a mixture of 10% of all monomers of the mixture was first introduced into a heated reactor. Subsequently, an initiator solution in which 16 g of potassium sulfate was dissolved in 140 g of deionized water was added thereto, followed by reaction for 10 minutes. The remaining 90% of the monomer mixture was added dropwise when the polymer in the reactor showed suspension. The reaction product was added dropwise for 2 hours, and when the addition of the monomer was completed, the reaction was allowed to proceed for an additional 4 hours and finished to prepare a latex dispersion for shell.

(Production of Colorant Dispersion)

Into a 3-liter reactor equipped with a stirrer, a thermometer, and a condenser, 540 g of cyan pigment (from ECB303, Japan), 27 g of surfactant (Dowfax 2A1), and 2,450 g of distilled water were added, followed by predispersion while stirring slowly for about 10 hours. Was performed. After pre-dispersion for 10 hours, using Ultimaizer (Amtech Co.) was dispersed for 4 times until the particle size to 200nm or less at 1500bar. As a result, a cyan pigment dispersion was obtained.

After completion of the dispersion, the particle size of the cyan pigment particles was measured using a Multisizer 2000 (manufactured by Malvern Corporation), and the D50 (v) was 170 nm. Here, D50 (v) refers to a particle size corresponding to 50% of the volume average particle diameter, that is, a particle size corresponding to 50% of the total volume when the volume is accumulated from small particles by measuring the particle diameter.

(Production of Wax Dispersion)

After adding 65 g of surfactant (Dowfax 2A1) and 1,935 g of distilled water to a volume 5 liter reactor equipped with a stirrer, a thermometer, and a condenser, the mixture was slowly stirred at a high temperature for about 2 hours. Mp: 95 ° C.) was charged into the reactor. The mixture was dispersed for 30 minutes using a homogenizer (IKA, T-45). As a result, a wax dispersion was obtained.

After completion of the dispersion, the particle size of the dispersed particles was measured using a Multisizer 2000 (manufactured by Malvern Corporation), and the D50 (v) was 320 nm.

(Production of Toner Particles)

3300 g of the latex dispersion for cores, 530 g of a colorant dispersion, and 590 g of a wax dispersion were added to a 20 liter reactor, followed by mixing at room temperature and stirring at 120 rpm. As a flocculant, 970 g of a 2: 1 (mass ratio) mixture of 0.3N HNO ₃ and PSI (Poly Silicato Iron) was added. The temperature of the reactor was raised to 57 ° C., followed by stirring at 140 rpm to effect aggregation. Aggregation was continued until D50 became 6.45 ~ 6.50㎛, and the stirring speed was increased to 170rpm, and 1280g of the latex dispersion for shell was added, and then the stirring speed was lowered to 140rpm. 900 g of 1N sodium hydroxide aqueous solution was added to the reactor, and the mixture was stirred at 120 rpm until pH 4, and at 100 rpm until pH 7. The temperature of the reactor was raised to 80 ° C. while the stirring speed was lowered to 80 rpm, and then 0.3N HNO ₃ was added to adjust the pH to 5 to fuse the toner particles. Fusion was continued until the circularity was 0.970.

The temperature of the reactor was then cooled to 40 ° C., the toner was separated using a filtration device (device name: Tumbler Screen), and then the separated toner was washed with 0.3 N HNO ₃ aqueous solution and rewashed five times with distilled water to form a surfactant. All of the backs were removed. Thereafter, the washed toner particles were dried in a fluidized bed dryer at a temperature of 40 ° C. for 5 hours to obtain dried toner particles.

Example 2

Toner particles were obtained in the same manner as in Example 1, except that the temperature was raised to 75 ° C. and the pH was adjusted to 4.0 in the fusion step.

Example 3

Toner particles were obtained in the same manner as in Example 1, except that the temperature was raised to 80 ° C. and the pH was adjusted to 4.0 in the fusion step.

Example 4

Toner particles were obtained in the same manner as in Example 1, except that the temperature was raised to 90 ° C. and the pH was adjusted to 4.0 in the fusion step.

Comparative Example 1

Toner particles were obtained in the same manner as in Example 1, except that the temperature was raised to 96 ° C. without adjusting the pH in the fusion step (pH 7).

Comparative Example 2

Toner particles were obtained in the same manner as in Example 1, except that pH was not adjusted (pH 7) in the fusion step.

Hereinafter, the physical properties of the toner particles prepared in the above Examples and Comparative Examples were evaluated by the following method.

GSDp and GSDv of the toner particles in Examples 1 to 4 and Comparative Examples 1 to 2 were measured by using an average particle diameter using a Multisizer ™ 3 Coulter Counter ^의 of Beckman Coulter Inc. Obtained by Formulas 1 and 2. In the multisizer, an aperture is 100 μm, and an appropriate amount of a surfactant is added to 50-100 ml of ISOTON-II (Beckman Coulter Co., Ltd.), which is an electrolyte, and 10-15 mg of the measurement sample is added thereto. Samples were prepared by dispersing the dispersion machine for 5 minutes.

[Equation 1]

(p : 입자수)GSDp =

(p: number of particles)

[Equation 2]

(v : 부피)GSDv =

(v: volume)

Circularity was measured using FPIA-3000 (manufactured by Sysmex, Japan). In the circularity measurement using FPIA-3000, the measurement sample was prepared by adding an appropriate amount of a surfactant to 5 to 10 ml of distilled water, adding 10 to 20 mg of toner particles thereto, and then dispersing in an ultrasonic disperser for 1 minute. The circularity is automatically obtained from FPIA-3000 by the following equation.

&Quot; (3) "

Circularity = 2 × (area × π) ^1/2 / perimeter

In the above formula, the area means the area of the projected toner, and the perimeter means the circumferential length of the projected toner. This value can range from 0 to 1, the closer to 1, the spherical.

In the table below, the time taken until the circularity was 0.970 was measured and displayed.

In addition, the evaluation method of resin is as follows.

The glass transition temperature (Tg, ° C.) was measured by using a differential scanning calorimeter (Netzsch Co., Ltd.) and heating the sample at 20 ° C. to 200 ° C. at a heating rate of 10 ° C./min, and then at 10 ° C./min. After quenching to < RTI ID = 0.0 > C, < / RTI >

The wax content of the toner surface was expressed as a percentage by measuring the surface concentration of the element from the area of the Micro XPS (Quantom 2000) characteristic photoelectron peak (carbon atom area of the XPS peak).

The toner fixing property is a heating roller method in which a toner image of a sheet to be adhered is pressurized while being pressed against the surface of a heat fixing roller having a surface formed of a material having a mold release property against the toner. Fixability evaluation evaluates fixation rate by measuring the fixation rate on a specific portion of the printed portion of the printer, and then attaching the tape to the portion and comparing the tape before and after the tape operation. The fixing temperature range indicates a temperature range in which the fixing degree is 85% or more, and generally, the fixing temperature and the fixing temperature have a proportional relationship.

The glossiness is obtained by using a glossiness tester (Glassiness Tester) and the glossiness is higher.

The evaluation results are shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 GSDp 1.26 1.26 1.27 1.27 1.27 1.27 GSDv 1.27 1.27 1.27 1.27 1.27 1.27 Circular drawing (0.970)
Reach fusion time 6.5h 10h 5.5h 5h 6h 20h Surface wax content 15% 10% 8% 9% 63% 64% Fusing temperature range 140 ~ 230 ℃ 130 ~ 230 ℃ 130 ~ 230 ℃ 130 ~ 230 ℃ 160 ~ 230 ℃ 160 ~ 230 ℃ Luster 5.5 7.2 7.4 7.0 5.3 5.2

1 is a graph showing a change in the circularity of toner according to the fusion time in the manufacturing method according to Example 1 and Comparative Example 2. As shown in the figure, in the case of Example 1, it can be seen that the circularity increases with time, but in Comparative Example 2, it can be seen that the circularity of the toner does not increase more than a certain level even after elapse of time. have. Therefore, as in the present invention, it can be seen that the pH control in the fusing step has a large influence on the roundness of the toner.

2 is a SEM photograph of toner particles prepared according to Example 1 (FIG. 2A) and Comparative Example 1 (FIG. 2B). As shown in the figure, it can be seen that the toner particles of the present invention fused at a low temperature have no difference in circularity and surface properties as compared with conventional toner particles fused at a high temperature.

3 is a FIB (Focus Beam Ion) photograph obtained on the basis of Example 2, wherein the toner of the manufacturing method of the present invention (FIG. 3A) is a toner of wax rather than the toner of the conventional manufacturing method (FIG. 3B). It can be seen that the dispersibility in the particles is excellent and no agglomeration of wax occurs.

Although the preferred embodiment according to the present invention has been described above, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the protection scope of the present invention should be defined by the appended claims.

1 is a graph showing the circularity of toner particles according to the manufacturing processes of Example 1 and Comparative Example 2. FIG.

2A and 2B are SEM photographs of toner particles prepared according to Example 1 and Comparative Example 1, respectively.

3A and 3B are FIB photographs of toner particles prepared according to Example 2 and Comparative Example 1, respectively.

Claims (5)

Mixing the latex dispersion, the colorant dispersion, and the wax dispersion; Adding a coagulant to the mixture and coagulating to form toner particles; And In the manufacturing method of the toner comprising fusing the aggregated toner particles, The fusing step is characterized in that the Tg (glass transition temperature) of the latex + 15 ℃ characterized in that carried out at a pH of 4 to 5 in the temperature range of the melting point of the wax. The method of claim 1, PH is adjusted by adding acid in the fusion step. The method of claim 1 Toner production method characterized in that the temperature is raised to 75 to 90 ℃ in the fusing step. The method of claim 3, A method of manufacturing a toner, wherein the temperature is raised to 90 ° C to 5 ° C in the fusing step. The method of claim 1, And the toner has a core-shell structure.

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