KR20100048071A - Method for preparing toner having narrow particle size distribution - Google Patents

Abstract

PURPOSE: A producing method of a toner is provided to produce the toner with the little contents of fine powder by controlling a physical parameter at a cohesion process. CONSTITUTION: A producing method of a toner comprises the following: mixing a latex dispersion solution, a colorant dispersion solution and a wax dispersion solution; homogenizing the mixture by adding a coagulant to the mixture; forming a toner particle by cohering the mixture; fusing the toner particle; and cooling the toner particle. The homogenizing process is performed by stirring the mixture after adding the coagulant at 20~30 deg C.

Description

Method for preparing toner having narrow particle size distribution}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing toner by emulsion aggregation, and more particularly, to a method for producing a toner having a narrow particle size distribution.

Generally, toner is prepared by adding a colorant, a charge control agent, a release agent, 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 or 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 non-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.

In the electrophotographic image forming apparatus, the size and particle size distribution of the toner particles affect the resolution of the final printed image. The narrower the particle size distribution of the toner particles and the smaller the particle size, the higher the resolution of the final printed image can be achieved. Recently, there is a growing interest in manufacturing a toner capable of realizing high resolution according to demands of consumers and industries requiring high resolution images.

In the case of toner synthesized by emulsion coagulation, toner particles are formed by agglomeration of submicron-sized particles, and the particle size distribution, shape, and structure of the toner are adjusted by adjusting the mixing, pH, temperature, agitation speed, reaction time, etc. of appropriately formulated raw materials. It is manufactured by control. In general, the toner manufactured in this way enables high quality output by optimizing the resin design compared to other types of laser printer toners, and reduces the consumption of the toner according to the particle size, improves the transfer efficiency by controlling the shape of the toner, and in production. Significant increases in demand are expected in the future as environmental loads can be reduced in all aspects of use and disposal.

Particularly, in the method of manufacturing toner by emulsion coagulation, the coagulation process of latex dispersion, wax dispersion and colorant dispersion can be precisely controlled to produce toner particles having a desired particle size with a narrow particle size distribution. It is a very demanding situation.

In general, in the toner production method by emulsion coagulation, the particle size is greatly deteriorated from the initial reaction coagulation step to the coagulation finishing step, and the fine powder tends to increase significantly.

Accordingly, an object of the present invention is to provide a method capable of producing a high quality toner having a narrow particle size distribution and a fine powder content with a reproducible reaction at a minimum management cost by adjusting physical parameters in the coagulation step of the toner manufacturing method by emulsion coagulation. It is done.

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

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

Homogenizing by adding a flocculant to the mixture;

Agglomerating the homogenized mixture to form toner particles;

Fusing the aggregated toner particles; And

In the manufacturing method of the toner comprising the step of cooling the fused toner particles,

The step of homogenizing by adding the flocculant provides a method characterized in that it consists of stirring at a temperature of 20 to 30 ℃.

According to one embodiment of the invention, the step of homogenizing by adding the flocculant may be carried out for 10 to 100 minutes.

According to another embodiment of the present invention, the viscosity of the reaction solution in the step of homogenizing by adding the flocculant may be 50 to 200cps.

According to another embodiment of the present invention, the step of homogenizing by adding the flocculant may be performed at a stirring linear speed of 1.0 to 2.0 m / s.

According to another embodiment of the present invention, the latex dispersion may include a latex styrene residue.

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

According to the manufacturing method of the present invention, toner particles having a narrow particle size distribution and a uniform surface shape can be provided while reflecting the process independently of the conventional particle size distribution control technology and calculating the synergistic effect. It is possible to manufacture high reaction reproducibility and high quality toner particles on the basis of the management cost.

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; Homogenizing by adding a flocculant to the mixture; Agglomerating the homogenized mixture to form toner particles; Fusing the toner particles which have stopped growing; And cooling the fused toner particles, wherein the homogenizing by adding the flocculant comprises stirring at a temperature of 20 to 30 ° C. In the conventional method for preparing toner by emulsion coagulation, temperature is not varied separately in the homogenization process through stirring after addition of the coagulant, thereby causing severe temperature variation according to seasons, thereby degrading product quality. That is, when the temperature of the stirred reaction solution is lower than 20 ° C, the particle size distribution is widened (GSDp value increases) and the fine powder increases, and when the temperature of the stirred reaction solution is higher than 30 ° C, the aggregation proceeds. There is a problem that the average particle size increases.

Homogenizing by adding the flocculant is preferably performed for 10 to 100 minutes. If it is shorter than 10 minutes, the homogenization of the reaction solution is not sufficient, so that the formation of particles is uneven, and if it is longer than 100 minutes, no more homogeneous effect can be observed, and the time required for the manufacturing process may increase.

In the present invention, the viscosity of the reaction solution can be kept constant by adjusting the temperature of the reaction solution within a predetermined range in the homogenization process after adding the flocculant, thereby achieving a narrow particle size distribution and a reduction in the fine amount of the desired toner particles in the flocculation process. Can be. The viscosity of the reaction solution in the step of adding and mixing the flocculant may be 50 to 200 cps as measured using a Brookfield viscometer lv set No. 3 spindle. In addition, the homogenizing by adding the flocculant may be performed at a stirring linear speed of 1.0 to 2.0 m / s. If the speed is less than 1.0 m / s, the reaction solution may not be sufficient homogenization heat transfer may not be properly, if larger than 2.0 m / s bubbles may occur and the reaction may not occur homogeneously.

In the toner manufacturing method of the present invention, a toner particle is prepared by adding a coagulant to a mixture of a latex dispersion, a colorant dispersion, and a wax dispersion, homogenizing (HOMO), and then performing an aggregation step (Agg). 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 1.0 to 2.5 m / s, and coagulated.

The aggregated toner particles stops toner particle growth (Freezing: Frz); Fusing the toner particles which have ceased growth; And cooling and drying the fused toner particles 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.

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. Then, the first flocculation toner is prepared by going through a flocculation step, and a latex shelling (LS) is added to the obtained first flocculation toner by adding a latex dispersion for a shell, followed by a fusion step.

The binder resin included in the latex that can be used in the toner manufacturing method of the present invention is one or two or more polymerizable groups 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 a monomer. Specific examples of the polymerizable monomer include styrene monomers of styrene, vinyltoluene and α-methylstyrene; Acrylic acid, methacrylic acid; Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate (Meth) acrylic acid derivatives of dimethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, and methacrylamide; Ethylenically unsaturated monoolefins of ethylene, propylene, butylene; Vinyl halides of vinyl chloride, vinylidene chloride and vinyl fluoride; Vinyl esters of vinyl acetate and vinyl propionate; Vinyl ethers of vinyl methyl ether and vinyl ethyl ether; Vinyl ketones of vinyl methyl ketone and methyl isopropenyl ketone; 2-vinylpyridine, 4-vinylpyridine, nitrogen-containing vinyl compound of N-vinylpyrrolidone, and the like, but are not necessarily limited thereto.

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

More specifically, the polymerization initiator may be, for example, an azo polymerization initiator such as 2-2'-azobisisobutylonitrile; Ketone peroxides such as methyl ethyl ketone peroxide; Peroxy ketals such as 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane; hydroperoxides such as t-butylhydroperoxide; Dialkyl peroxides such as di-t-butylperoxide; Diacyl peroxides such as isobutyl peroxide; Peroxy dicarbonates such as di-isopropylperoxy dicarbonate; Sulfonyl peroxides such as acetylcyclohexylsulfonyl peroxide; And peroxy esters such as t-butylperoxy acetate.

As the macromonomer added to adjust the number average molecular weight and glass transition temperature (Tg) of the binder resin, polyethylene glycol ethyl ether methacrylate, polyethylene glycol methyl methacrylate, polyethylene glycol methyl acrylate, and the like may be used. As the chain transfer agent, divinyl benzene, 1-dodecanethiol, or the like may 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, it is not preferable because 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.

Titanium oxide or carbon black may be used as the black pigment. As the cyan pigment, a copper phthalocyanine compound and a derivative thereof, an anthrakin compound, a basic dye rate compound, or the like can be used. As the magenta pigment, condensed nitrogen compounds, anthraquines, quinacridone compounds, base dye rate compounds, naphthol compounds, benzo imidazole compounds, thioindigo compounds, or perylene compounds may be used. As the yellow pigment, a condensed nitrogen compound, an isoindolinone compound, an anthrakin compound, an azo metal complex, or an allyl imide compound may be used.

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.

Example 1

(Production of Latex Dispersion for Core)

A 3-liter reactor equipped with a stirrer, thermometer, and condenser was installed in the oil bath, a heat transfer medium. 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. Subsequently, as monomers, that is, 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 binder resin was measured using a differential scanning calorimeter (DSC), and the temperature was 62 ° 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 50,000.

Preparation of Latex Dispersion for Shell

2,200 parts by weight of deionized water was added to a 4 liter reactor, and the mixture was heated to 80 ° C while stirring while purging N ₂ . Then, 390 parts by weight of styrene monomer, 145 parts by weight of butyl methacrylate, 20 parts by weight of methacrylic acid, and 10 parts by weight of epoxy acrylate were mixed and stirred to completely dissolve the mixture of 10% of the total monomers of the monomers. Into the heated reactor. Subsequently, an initiator solution in which 16 parts by weight of potassium sulfate was dissolved in 140 parts by weight 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 was added dropwise for 2 hours, and when the addition of the monomer was completed, the reaction proceeded for an additional 4 hours and terminated 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 (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 10 hours of predispersion, the mixture was dispersed for 4 hours using Bizmill (Zeta RS, Netzsch, Germany). 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, and then wax (NOF Japan, WE-5). 1,000 g was charged to 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), and the D50 (v) was 320 nm.

(Production of Toner Particles)

Example 1

60.0 parts by weight of the latex dispersion for the core, 5.0 parts by weight of the colorant dispersion and 10 parts by weight of the wax dispersion were added to a 70-liter reactor, followed by mixing at 80 rpm for about 15 minutes at room temperature. 2.0 parts by weight of a mixed solution of PSI (Poly Silicato Iron) and nitric acid (PSI / 0.3M HNO ₃ = 1/2) was added as a flocculant, and then the pH was 1.5 at 30 ° C. at 80 rpm at 1.32 m / sec. Mix at ˜2.3. The temperature of the reactor was raised to 51 ° C., followed by stirring at 100 rpm to effect aggregation. Aggregation was continued until the average particle diameter became 6.3 to 6.4 μm, and then the stirring speed was increased to 120 rpm, while 25 parts by weight of the latex dispersion for shell was added over about 20 minutes, and then the stirring speed was lowered to 100 rpm. Stirring was continued until the average particle diameter became 6.7˜6.9 μm, and 1N aqueous sodium hydroxide solution was added to the reactor, followed by stirring at 70 rpm until pH 4 and at 60 rpm until pH 7. The temperature of the reactor was raised to 96 ° C. while maintaining the stirring speed so as to fuse the toner particles. When the circularity was measured using FPIA-3000 (sysmex, Japan), the temperature was 0.971. The temperature of the reactor was cooled to 40 ° C, the pH was adjusted to 9.0, and the toner was used by using nylon mesh (pore size: 20 µm). After separation, the separated toner was washed four times with distilled water, washed with 0.3 N aqueous nitric acid solution, adjusted to pH 2.0, and washed again with distilled water four times to remove all surfactants. Thereafter, the washed toner particles were dried in a fluid bed dryer at a temperature of 40 ° C. for 5 hours to obtain dried toner particles.

Example 2

Toner particles were prepared in the same manner as in Example 1, except that the temperature of the reactor was 25 ° C. in the stirring step after the flocculant was added.

Example 3

Toner particles were prepared in the same manner as in Example 1, except that the temperature of the reactor was 30 ° C. in the stirring step after the flocculant was added.

Comparative Example 1

Toner particles were prepared in the same manner as in Example 1, except that the temperature of the reactor was 15 ° C. in the stirring step after the flocculant was added.

Comparative Example 2

Toner particles were prepared in the same manner as in Example 1, except that the temperature of the reactor was 35 ° C. in the stirring step after the flocculant was added.

Assessment Methods

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

The average particle diameter of the toner particles in Examples 1 to 3 and Comparative Examples 1 to 2 was measured using a Beckman Coulter Inc. Multisizer ™ 3 Coulter Counter ^® and GSDp was analyzed. Is calculated directly by Equation 1 below, and the amount of derivative (% of <3 µm) is automatically measured.

In the multisizer, an aperture was 100 μm, and 2 drops of the reaction solution was added to 5 ml of the electrolyte ISOTON-II (Beckman Coulter) to prepare a sample.

[Equation 1]

GSDp = (D84 (number) / D16 (number)) ^1/2

In the above formula, D84 and D16 mean average particle size when the number of particles is quantified to include 84% and 16% of particles, respectively.

Circularity was measured using FPIA-3000 (manufactured by Sysmex, Japan). In the circularity measurement using FPIA-3000, a sample was prepared by adding 10 drops of the reaction solution to 5 ml of the electrolyte ISOTON-II (Beckman Coulter).

The circularity is automatically obtained from FPIA-3000 by the following formula (2).

[Equation 2]

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 addition, the evaluation method of resin is as follows.

The glass transition temperature (Tg, ° C) was measured using a differential scanning calorimeter (Netzsch model name STA409) and the sample was heated at 20 ° C to 200 ° C at a heating rate of 10 ° C / min, and then at a cooling rate of 20 ° C / min. After quenching to 10 ° C., the temperature was again measured at a heating rate of 10 ° C./min.

In the manufacturing method of the toners of Examples 1 to 3 and Comparative Examples 1 and 2, the percentage change of GSDp value and particle size of less than 3 μm was observed as the process proceeded, and the results are shown in Tables 1 and 2 and 1 and 2 are shown.

Referring to Table 1 and Figure 1, when the fusion step through the flocculation process according to the addition of the flocculant, the GSDp in the conventional method increased more than in the mixing step before the flocculant addition in the process according to the present invention in the post-aggregation process It can be seen that the GSDp is greatly reduced. Referring to Table 2 and Figure 2, when the fusion step through the flocculation process according to the flocculant is added, according to the conventional method, the percentage of particles having a particle size of less than 3㎛ increased more than in the mixing step before the flocculant addition, In the following method, it can be seen that rather reduced. Therefore, it can be seen that the toner particles produced by the method of the present invention have a more uniform particle size distribution and a lower content of fine powder as the process proceeds.

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 GSDp according to a manufacturing process of toner particles prepared according to Examples 1, 2 and 3 and Comparative Examples 1 and 2;

FIG. 2 is a graph showing the percentage of particles having a particle size of <3 µm according to the production process of toner particles prepared according to Examples 1, 2, 3 and Comparative Examples 1, 2;

Claims (6)

Mixing the latex dispersion, the colorant dispersion and the wax dispersion; Homogenizing by adding a flocculant to the mixture; Agglomerating the homogenized mixture to form toner particles; Fusing the aggregated toner particles; And In the manufacturing method of the toner comprising the step of cooling the fused toner particles, The homogenizing step of adding the flocculant is characterized in that it consists of stirring at a temperature of 20 to 30 ℃. The method of claim 1, The homogenizing step of adding the flocculant is performed for 10 to 100 minutes. The method of claim 1, The homogenizing step of adding the flocculant is carried out at a stirring linear velocity of 1.0 to 2.0 m / s. The method of claim 1, The viscosity of the reaction solution in the step of homogenizing by adding the flocculant is 50 to 200 cps. The method of claim 1, And the latex dispersion is a latex comprising a styrene moiety. The method of claim 1, And the toner has a core-shell structure.

Images