WO2010011102A2 - Method of preparing latex whereby molecular weight of latex can be adjusted by viscosity control - Google Patents

Method of preparing latex whereby molecular weight of latex can be adjusted by viscosity control Download PDF

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Publication number
WO2010011102A2
WO2010011102A2 PCT/KR2009/004129 KR2009004129W WO2010011102A2 WO 2010011102 A2 WO2010011102 A2 WO 2010011102A2 KR 2009004129 W KR2009004129 W KR 2009004129W WO 2010011102 A2 WO2010011102 A2 WO 2010011102A2
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WO
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Prior art keywords
stirring
latex
emulsion
preparing
rpm
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PCT/KR2009/004129
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French (fr)
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WO2010011102A3 (en
Inventor
Il Hyuk Kim
Dong Won Kim
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Samsung Fine Chemicals Co., Ltd.
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Publication of WO2010011102A2 publication Critical patent/WO2010011102A2/en
Publication of WO2010011102A3 publication Critical patent/WO2010011102A3/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/12—Polymerisation in non-solvents
    • C08F2/16—Aqueous medium
    • C08F2/22—Emulsion polymerisation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/01—Processes of polymerisation characterised by special features of the polymerisation apparatus used
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F257/00—Macromolecular compounds obtained by polymerising monomers on to polymers of aromatic monomers as defined in group C08F12/00
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
    • C08F265/04—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00 on to polymers of esters

Definitions

  • the present invention relates to a method of preparing latex, and more particularly, to a method of preparing a latex whereby the molecular weight of the latex may be adjusted, the method including preparing a mixture including a monomer, a surfactant, water, and at least one additive, and preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture.
  • Methods of preparing latex can be classified into various methods according to methods of polymerizing monomers to be used in the latex.
  • latex is produced by introducing a mixture of a monomer and additives into a reactor, or by using a pre-emulsion.
  • a molecular weight modifier is generally used in the preparation of a pre-emulsion. If a monomer is polymerized without using a molecular weight modifier, latex may have a very high weight average molecular weight of 200,000 or greater. Thus, in commercial fields where low molecular weight latex is required, the molecular weight modifier is excessively used to reduce the molecular weight of the latex. In addition, the molecular weight of latex may be adjusted by controlling the rate at which monomers are added and the amount of a polymerization initiator.
  • the molecular weight of latex may be adjusted to a desired level using a molecular weight modifier, too much molecular weight modifier is often used, andalso the price of the molecular weight modifier is very high. Even though the molecular weight of latex may also be adjusted by regulating the rate at which the monomers are added, reaction heat is rapidly increased, thereby causing unsafe operating conditions, and side reactions of polymers are induced, thereby increasing a gel portion. Even though the molecular weight of latex may also be slightly reduced by controlling the amount of the polymerization initiator, the effects thereof are negligible.
  • the molecular weight of latex may be adjusted by varying the amount of the molecular weight modifier without changing the amount of the other components, or by varying the amount of the other components without changing the amount of the molecular weight modifier.
  • the present invention provides a method of preparing a latex whereby the molecular weight of the latex may be adjusted, the method including preparing a mixture including a monomer, a surfactant, water, and at least one additive, and preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture.
  • the present invention also provides a method of inexpensively preparing a latex.
  • the present invention also provides a method of preparing latex whereby the yield of the latex increases without changing the properties of the latex.
  • the present invention also provides a method of preparing a latex that provides good working conditions and is environmentally friendly.
  • a method of preparing a latex including: preparing a mixture including a monomer, a surfactant, water, and at least one additive; preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture; and polymerizing the monomer contained in the pre-emulsion.
  • the preparing the pre-emulsion may include: at least two stirring operations selected from F1 st to Fm th stirring operations performed for F1 st to Fm th stirring time periods at F1 st to Fm th stirring speeds and S1 st to Sn th stirring operations performed for S1 st to Sn th stirring time periods by increasing a stirring speed from zero to S1 st to Sn th stirring speeds; and non-stirring operations performed for Z1 st to Zp th time periods between the every two consecutive stirring operations, wherein m, n, and p are each independently a natural number and m and n may be each independently in the range of 2 to 10.
  • the F1 st to Fm th stirring speeds and the S1 st to Sn th stirring speeds may be each independently in the range of 1 to 10,000 rpm, and the F1 st to Fm th stirring time periods, the S1 st to Sn th stirring time periods, and the Z1 st to Zp th time periods are each independently in the range of 1 to 3,600 seconds.
  • the stirring speed acceleration of the S1 st to Sn th stirring operations may be 50 rpm per 0.1 to 600 seconds.
  • the viscosity of the pre-emulsion may be in the range of 20 to 700 mpa ⁇ s in the preparing the pre-emulsion.
  • a method of preparing a toner including the method of preparing the latex.
  • FIG. 1 is a graph illustrating the preparation of a pre-emulsion by stirring in a method of preparing a latex according to an embodiment of the present invention.
  • the method of preparing a latex includes: preparing a mixture including a monomer, a surfactant, water, and at least one additive, preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture; and polymerizing the monomer contained in the pre-emulsion by adding a polymerization initiator thereto.
  • the preparing the pre-emulsion may include: at least two stirring operations selected from F1 st to Fm th stirring operations performed for F1 st to Fm th stirring time periods at F1 st to Fm th stirring speeds
  • m, n, and p may be each independently a natural number.
  • the m and n may be each independently in the range of 2 to 10, but are not limited thereto.
  • the preparing the pre-emulsion may include the stirring operations in the order of a plurality of F1 st to Fm th stirring operations (S F1 to S Fm ) and a plurality of S1 st to Sn th stirring operations (S S1 to S Sn ), but is not limited thereto.
  • the monomer may include one or more monomers; for example, 1 to 10 types of monomers, preferably, 1 to 5 types of monomers may be used.
  • the monomer may include at least one selected from the group consisting of acrylate ester, methacrylate ester, styrene, vinyl ester of an aliphatic acid, ethylenically unsaturated carboxylic acid, and a known cross-linking agent, but is not limited thereto.
  • the ethylenically unsaturated carboxylic acid may be acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, or the like.
  • the cross-linking agent may be divinyl benzene, divinyl toluene, diacrylate, or dimethacrylate.
  • the monomer may include two or more monomers.
  • the monomer may be styrene, butyl acrylate, glycidyl methacrylate, 2-carboxyethyl acrylate, 1,10-dodecanediol dimethacrylate, or mixtures thereof.
  • the amount of the monomer may be in the range of 40 to 70 wt%, for example 60 to 70 wt% of the pre-emulsion (i.e., the mixture). If the amount of the monomer is less than 40 wt% of the pre-emulsion, productivity of the latex may decrease. On the other hand, if the amount of the monomer is greater than 70 wt% of the pre-emulsion, solid content may increase, and thus stability of latex particles may be reduced.
  • the surfactant may include at least one selected from the group consisting of a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant.
  • nonionic surfactant examples include polyvinyl alcohol, polyacrylic acid, methyl cellulose, ethyl cellulose, propyl cellulose, hydroxylethyl cellulose, carboxymethyl cellulose, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene octylphenyl ether, polyoxyethylene stearyl ether, polyoxyethylene norylphenyl ether, ethoxylate, phosphate norylphenols, triton, and dialkylphenoxypoly(ethyleneoxy)ethanol.
  • anionic surfactant examples include sodium dodecyl sulfate, sodium dodecyl benezene sulfonate, sodium dodecyl naphthalene sulfate, dialkyl benzenealkyl sulfate, and sulfonate.
  • cationic surfactant examples include alkyl benzene dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, and distearyl ammonium chloride.
  • amphoteric surfactant examples include amino acid amphoteric surfactant, betaine amphoteric surfactant, lecitin, taurin, cocoamidopropylbetaine, and disodium cocoamphodiacetate.
  • the surfactants described above may be used alone or in combinations.
  • the amount of the surfactant may be in the range of 0.5 to 1.5 wt% of the pre-emulsion (i.e., the mixture). If the amount of the surfactant is less than 0.5 wt% of the pre-emulsion, the monomers may not form stable particles during the preparation of the pre-emulsion. On the other hand, if the amount of the surfactant is greater than 1.5 wt% of the pre-emulsion, physical properties of the latex may be changed since too much surfactant is used.
  • the water may be purified water such as deionized water, but is not limited thereto.
  • the amount of water may be in the range of 25.0 to 40.0 wt% of the pre-emulsion. If the amount of water is less than 25.0 wt% of the pre-emulsion, the pre-emulsion may not be easily formed. On the other hand, if the amount of water is greater than 40.0 wt% of the pre-emulsion, particles formed of the monomers become unstable, and thus induce phase separation.
  • the additive may include a molecular weight modifier, i.e., a chain transfer agent.
  • the molecular weight modifier is used to adjust the molecular weight of the latex, and may include at least one selected from the group consisting of dodecanethiol, butanethiol, isooctyl-3-mercaptopropionate (IOMP), 2-methyl-5-t-butylthiophenol, carbon tetrachloride, and carbon tetrabromide.
  • the amount of the molecular weight modifier may be in the range of 0.1 to 2.0 wt% of the pre-emulsion. If the amount of the molecular weight modifier is less than 0.1 wt% of the pre-emulsion, the molecular weight of the latex may not be easily adjusted and thus a desired molecular weight may not be obtained.
  • the amount of the molecular weight modifier is greater than 2.0 wt% of the pre-emulsion, some of the molecular weight modifier may remain unreated, and thus the unreacted molecular weight modifier may deteriorate properties of the latex.
  • the monomer, the surfactant, water, and at least one additive are mixed and stirred to prepare a pre-emulsion.
  • the method of preparing the pre-emulsion may include various methods such as a method that is used when a solid content of 50 wt% or greater is required, and another method that is used when a low solid content and a good compatiabilty among monomers are required.
  • methods of preparing a pre-emulsion may be classified into the following three methods:
  • the surfactant is dissolved in water to form a micelle.
  • a pre-emulsion may be formed by stirring the micelle structure.
  • hydrophobic monomers enter the center of the micelle, i.e., inside of the micelle, by stirring to form a pre-emulsion.
  • the viscosity of the pre-emulsion may vary according to the preparation method, the shape of a stirrer, stirring speeds, stirring time periods, and dwelling time of the mixture in a reactor.
  • the viscosity of the pre-emulsion is a factor influencing the molecular weight of the latex.
  • the preparation of the pre-emulsion may include the stirring operation as shown in FIG. 1 in order to obtain reproducible molecular weight of the latex.
  • FIG. 1 is a graph illustrating the preparation of a pre-emulsion by stirring in a method of preparing a latex according to an embodiment of the present invention.
  • the preparing the pre-emulsion includes a F1 st stirring operation (S F1 ) performed for a F1 st time period (T F1 ) at a F1 st stirring speed (V 1 ), a F2 nd stirring operation (S F2 ) performed for a F2 nd time period (T F2 ) at a F2 nd stirring speed (V 1 ), a S1 st stirring operation (S S1 ) performed for a S1 st time period (T S1 ) by increasing a stirring speed from zero to a S1 st stirring speed (V 2 ), a S2 nd stirring operation (S S2 ) performed for a S2 nd time period (T S2 ) by increasing a stirring speed from zero to a S2 nd stirring speed (V 2 ), a F3 rd stirring operation (S F3 ) performed for a F3 rd time period (T F3 ) at a F3 rd stirring
  • the F1 st , F2 nd , and F3 rd stirring speeds (V 1 or V 3 ) and the S1 st and S2 nd stirring speed (V 2 ) may respectively be in the range of 1 to 10,000 rpm, for example, 250 to 1,000 rpm. If the stirring speeds (V 1 , V 2 , and V 3 ) are less than 1 rpm, the mixture is not sufficiently mixed so that the phases of the pre-emulsion are separated from each other. If the stirring speeds (V 1 , V 2 , and V 3 ) are greater than 10,000 rpm, the pre-emulsion may be too viscous and thus the molecular weight of the latex may be too high.
  • the F1 st , F2 nd , and F3 rd stirring time periods (T F1 , T F2 , and T F3 ) and the S1 st and S2 nd stirring time periods (T S1 and T S2 ) may be each independently in the range of 1 to 3,600 seconds, for example, 5 to 300 seconds.
  • the Z1 st , Z2 nd , Z3 rd , and Z4 th time periods (T Z1 , T Z2 , T Z3 , and T Z4 ) may be each independently in the range of 1 to 3,600 seconds, preferably 2 to 600 seconds, and more preferably 2 to 300 seconds.
  • the Z1 st , Z2 nd , Z3 rd , and Z4 th time periods (T Z1 , T Z2 , T Z3 , and T Z4 ) are less than 1 second, the viscosity of the pre-emulsion may not be sufficiently increased.
  • the Z1 st , Z2 nd , Z3 rd , and Z4 th time periods (T Z1 , T Z2 , T Z3 , and T Z4 ) are greater than 3,600 seconds, the phases of the pre-emulsion may be separated from each other.
  • the F3 rd stirring time period (T F3 ) may be in the range of 30 to 60 minutes, but is not limited thereto.
  • the stirring speed acceleration of the S1 st and S2 nd stirring operations may be 50 rpm per 0.1 to 600 second, for example, 50 rpm per 100 to 500 seconds.
  • the preparing the pre-emulsion is performed by sequentially performing the F1 st stirring operation (S F1 ) ⁇ the non-stirring operation (S Z1 ) ⁇ the F2 nd stirring operation (S F2 ) ⁇ the non-stirring operation (S Z2 ) ⁇ the S1 st stirring operation (S S1 ) ⁇ the non-stirring operation (S Z3 ) ⁇ the S2 nd stirring operation (S S2 ) ⁇ the non-stirring operation (S Z4 ) ⁇ the F3 rd stirring operation (S F3 ).
  • the present invention is not limited thereto.
  • the preparing the pre-emulsion may include 2 to 10 F1 st to F2 nd stirring operations (S F1 and S F2 ), 2 to 10 S1 st to S2 nd stirring operations (S S1 and S S2 ), a single F3 rd stirring operation (S F3 ), and non-stirring operations (S Z1 to S Zp ) between the every two consecutive stirring operations.
  • the viscosity of the pre-emulsion may be in the range of 20 to 700 mpa ⁇ s. If the viscosity of the pre-emulsion is less than 20 mpa ⁇ s, the phases of the pre-emulsion are separated from each other and thus properties of the product polymer are changed. On the other hand, if the viscosity of the pre-emulsion is greater than 700 mpa ⁇ s, the pre-emulsion may be too viscous and thus the molecular weight of the latex may be too high.
  • the monomer contained in the pre-emulsion having a controlled viscosity is polymerized using a polymerization initiator, e.g., potassium persulfate.
  • a polymerization initiator e.g., potassium persulfate.
  • the polymerization initiator may be added during the preparation of the pre-emulsion, or after the preparation of the pre-emulsion and before the polymerization.
  • the weight average molecular weight (Mw) of the latex may be in the range of 500 to 5,000,000, for example, 20,000 to 100,000.
  • the molecular weight distribution (PDI) of the latex may be in the range of 1.5 to 3.5, for example, 2.0 to 3.2.
  • the particle size of the latex may be in the range of 20 to 500 nm, for example, 150 to 300 nm.
  • the particle size distribution of the latex may be in the range of 1.0 to 5.0, for example, 1.15 to 1.5.
  • the glass transition temperature (Tg) of the latex may be in the range of 58 to 68 °C , for example, 60 to 65 °C .
  • the molecular weight of the latex may be adjusted using a small amount of the molecular weight modifier; that is, the amount of the molecular weight modifier may be in the range of 0.1 to 2.0 wt% of the pre-emulsion. Furthermore, since a small amount of molecular weight modifier is used, the amount of gas discharged to the surrounding environment may be reduced, and thus the method is environmentally friendly.
  • the present invention also provides a method of preparing a toner using the latex prepared using the method according to the embodiment described above. That is, the toner may be prepared by mixing the latex, a coloring agent, and at least one additive, and then aggegating, coalescing, cleaning and drying the mixture.
  • the second reactor was heated to 75 °C , and stirred at 75 °C under the stirring conditions below to control the viscosity of the pre-emulsion. That is, the viscosity of the pre-emulsion was controlled under the stirring conditions described with reference to FIG. 1.
  • the viscosity measured using a Brookfield Viscometer using No. 1 spindle at a rotation speed of 10 rpm was 50 ⁇ 20 mpa ⁇ s.
  • the viscosity was an average of viscosities of 4 pre-emulsion samples. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG.
  • the pre-emulsion was added at a flow rate of 103.49 ml/min to the first reactor maintained at 75 °C to perform the polymerization for 3 hours, thus completing the preparation of a latex.
  • the molecular weight of the latex was measured using gel permeation chromatography (GPC), Waters 515 HPLC Pump, Waters 2410 Differential Refractometer, and Waters 717plus Autosampler.
  • the particle size of the latex was measured using capillary hydrodynamic fractionation (CHDF) 2000.
  • the glass transition temperature (Tg) was measured using differential scanning calorimetry (DSC) produced by TA Instrument by heating the latex from room temperature to 250 °C at a rate of 10 °C /min, rapidly cooling the latex to room temperature at a rate of 50 °C /min, and heating the latex to 250 °C at a rate of 10 °C /min.
  • DSC differential scanning calorimetry
  • the acid value and stability of the latex were also measured.
  • the stability was measured by identifying whether viscous oligomer residues remain in the upper layer of the latex.
  • a latex was prepared in the same manner as in Example 1, except that the viscosity of the pre-emulsion was changed to 300 ⁇ 20 mpa ⁇ s by varying the stirring conditions. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1.
  • a latex was prepared in the same manner as in Example 1, except that the viscosity of the pre-emulsion was changed to 400 ⁇ 10 mpa ⁇ s by varying the stirring conditions. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1.
  • a latex was prepared in the same manner as in Example 1, except that the viscosity of the pre-emulsion was changed to 500 ⁇ 20 mpa ⁇ s by varying the stirring conditions. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1.
  • a latex was prepared in the same manner as in Example 1, except that the viscosity of the pre-emulsion was changed to 600 ⁇ 10 mpa ⁇ s by varying the stirring conditions. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1.
  • a latex was prepared in the same manner as in Example 1, except that 8.5 g of 1-dodecanethiol, constituting a molecular weight modifier, which is greater than that used in Example 1, was used, and a pre-emulsion having a viscosity of 50 ⁇ 50 mpa ⁇ s was prepared by stirring the mixture including the 1-dodecanethiol at 1000 rpm for 10 seconds. Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
  • a latex was prepared in the same manner as in Comparative Example 1, except that the stirring was performed for 60 seconds, and a pre-emulsion having a viscosity of 100 ⁇ 70 mpa ⁇ s was prepared. Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
  • a latex was prepared in the same manner as in Comparative Example 1, except that the stirring was performed for 90 seconds, and a pre-emulsion having a viscosity of 150 ⁇ 65 mpa ⁇ s was prepared. Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
  • the viscosity of the latex prepared according to Examples 1 to 5 has an error range of ⁇ 10 to ⁇ 30 mpa ⁇ s, and thus high reproducibility was identified.
  • defect rates of the pre-emulsion caused when the viscosity of the pre-emulsion is not within the range described above may be reduced, and thus the yield of the latex having the desired molecular weight may increase.
  • the desired molecular weight of the latex may be obtained by controlling the viscosity of the pre-emulsion even though a small amount of the molecular weight modifier is used.
  • the latex may also have excellent stability.
  • the properties of the latex, such as the glass transition temperature Tg, the particle size, and the acid value were not changed by controlling the viscosity of the pre-emulsion.
  • the viscosity of the latex has an error range of ⁇ 50 ⁇ 70 mpa ⁇ s, and thus low reproducibility was identified. Furthermore, the viscosity of the pre-emulsion was controlled by the conventional stirring methods during the preparation of the pre-emulsion, and thus the molecular weight of the latex varies greatly. In addition, the latex had poor ( ⁇ ) stability.

Abstract

Provided is a method of preparing a latex. The method includes: preparing a mixture including a monomer, a surfactant, water, and at least one additive; preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture; and polymerizing the monomer contained in the pre-emulsion.

Description

METHOD OF PREPARING LATEX WHEREBY MOLECULAR WEIGHT OF LATEX CAN BE ADJUSTED BY VISCOSITY CONTROL Technical Field
The present invention relates to a method of preparing latex, and more particularly, to a method of preparing a latex whereby the molecular weight of the latex may be adjusted, the method including preparing a mixture including a monomer, a surfactant, water, and at least one additive, and preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture.
Background Art
Methods of preparing latex can be classified into various methods according to methods of polymerizing monomers to be used in the latex. Generally, latex is produced by introducing a mixture of a monomer and additives into a reactor, or by using a pre-emulsion.
In order to control the molecular weight of latex, a molecular weight modifier is generally used in the preparation of a pre-emulsion. If a monomer is polymerized without using a molecular weight modifier, latex may have a very high weight average molecular weight of 200,000 or greater. Thus, in commercial fields where low molecular weight latex is required, the molecular weight modifier is excessively used to reduce the molecular weight of the latex. In addition, the molecular weight of latex may be adjusted by controlling the rate at which monomers are added and the amount of a polymerization initiator.
Even though the molecular weight of latex may be adjusted to a desired level using a molecular weight modifier, too much molecular weight modifier is often used, andalso the price of the molecular weight modifier is very high. Even though the molecular weight of latex may also be adjusted by regulating the rate at which the monomers are added, reaction heat is rapidly increased, thereby causing unsafe operating conditions, and side reactions of polymers are induced, thereby increasing a gel portion. Even though the molecular weight of latex may also be slightly reduced by controlling the amount of the polymerization initiator, the effects thereof are negligible.
Techniques of preparing latex using a pre-emulsion are disclosed in European Patent Publication No. 1708036 and U.S. Patent No. 6503680. These patent publications disclose polymerization of a pre-emulsion including a monomer, water, a surfactant, and additives by semi-continuously introducing the pre-emulsion into a reactor. According to the methods, the molecular weight of latex may be adjusted by varying the amount of the molecular weight modifier without changing the amount of the other components, or by varying the amount of the other components without changing the amount of the molecular weight modifier.
 Technical Problem
The present invention provides a method of preparing a latex whereby the molecular weight of the latex may be adjusted, the method including preparing a mixture including a monomer, a surfactant, water, and at least one additive, and preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture.
The present invention also provides a method of inexpensively preparing a latex.
The present invention also provides a method of preparing latex whereby the yield of the latex increases without changing the properties of the latex.
The present invention also provides a method of preparing a latex that provides good working conditions and is environmentally friendly.
 Technical Solution
According to an aspect of the present invention, there is provided a method of preparing a latex, the method including: preparing a mixture including a monomer, a surfactant, water, and at least one additive; preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture; and polymerizing the monomer contained in the pre-emulsion.
The preparing the pre-emulsion may include: at least two stirring operations selected from F1st to Fmth stirring operations performed for F1st to Fmth stirring time periods at F1st to Fmth stirring speeds and S1st to Snth stirring operations performed for S1st to Snth stirring time periods by increasing a stirring speed from zero to S1st to Snth stirring speeds; and non-stirring operations performed for Z1st to Zpth time periods between the every two consecutive stirring operations, wherein m, n, and p are each independently a natural number and m and n may be each independently in the range of 2 to 10.
The F1st to Fmth stirring speeds and the S1st to Snth stirring speeds may be each independently in the range of 1 to 10,000 rpm, and the F1st to Fmthstirring time periods, the S1st to Snth stirring time periods, and the Z1st to Zpth time periods are each independently in the range of 1 to 3,600 seconds.
The stirring speed acceleration of the S1st to Snth stirring operations may be 50 rpm per 0.1 to 600 seconds.
The viscosity of the pre-emulsion may be in the range of 20 to 700 mpaㆍs in the preparing the pre-emulsion.
According to an aspect of the present invention, there is provided a method of preparing a toner including the method of preparing the latex.
 Description of Drawings
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawing in which:
FIG. 1 is a graph illustrating the preparation of a pre-emulsion by stirring in a method of preparing a latex according to an embodiment of the present invention.
 Mode for Invention
Hereinafter, the present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown
A method of preparing a latex according to an embodiment of the present invention will be described in detail.
The method of preparing a latex according to an embodiment of the present invention includes: preparing a mixture including a monomer, a surfactant, water, and at least one additive, preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture; and polymerizing the monomer contained in the pre-emulsion by adding a polymerization initiator thereto.
The preparing the pre-emulsion may include: at least two stirring operations selected from F1st to Fmth stirring operations performed for F1st to Fmth stirring time periods at F1st to Fmth stirring speeds
and S1st to Snth stirring operations performed for S1st to Snth stirring time periods
by increasing a stirring speed from zero to S1st to Snth stirring speeds; and non-stirring operations performed for Z1st to Zpth time periods between the every two consecutive stirring operations. In this regard, m, n, and p may be each independently a natural number.
In the preparing the pre-emulsion, the m and n may be each independently in the range of 2 to 10, but are not limited thereto. In this regard, the preparing the pre-emulsion may include the stirring operations in the order of a plurality of F1st to Fmth stirring operations (SF1 to SFm) and a plurality of S1st to Snth stirring operations (SS1 to SSn), but is not limited thereto.
The method of preparing a latex according to the present embodiment will be described in more detail.
In the preparing the mixture, the monomer may include one or more monomers; for example, 1 to 10 types of monomers, preferably, 1 to 5 types of monomers may be used. The monomer may include at least one selected from the group consisting of acrylate ester, methacrylate ester, styrene, vinyl ester of an aliphatic acid, ethylenically unsaturated carboxylic acid, and a known cross-linking agent, but is not limited thereto. The ethylenically unsaturated carboxylic acid may be acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, or the like. The cross-linking agent may be divinyl benzene, divinyl toluene, diacrylate, or dimethacrylate. The monomer may include two or more monomers. The monomer may be styrene, butyl acrylate, glycidyl methacrylate, 2-carboxyethyl acrylate, 1,10-dodecanediol dimethacrylate, or mixtures thereof. The amount of the monomer may be in the range of 40 to 70 wt%, for example 60 to 70 wt% of the pre-emulsion (i.e., the mixture). If the amount of the monomer is less than 40 wt% of the pre-emulsion, productivity of the latex may decrease. On the other hand, if the amount of the monomer is greater than 70 wt% of the pre-emulsion, solid content may increase, and thus stability of latex particles may be reduced.
The surfactant may include at least one selected from the group consisting of a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant.
Examples of the nonionic surfactant include polyvinyl alcohol, polyacrylic acid, methyl cellulose, ethyl cellulose, propyl cellulose, hydroxylethyl cellulose, carboxymethyl cellulose, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene octylphenyl ether, polyoxyethylene stearyl ether, polyoxyethylene norylphenyl ether, ethoxylate, phosphate norylphenols, triton, and dialkylphenoxypoly(ethyleneoxy)ethanol. Examples of the anionic surfactant include sodium dodecyl sulfate, sodium dodecyl benezene sulfonate, sodium dodecyl naphthalene sulfate, dialkyl benzenealkyl sulfate, and sulfonate. Examples of the cationic surfactant include alkyl benzene dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, and distearyl ammonium chloride. Examples of the amphoteric surfactant include amino acid amphoteric surfactant, betaine amphoteric surfactant, lecitin, taurin, cocoamidopropylbetaine, and disodium cocoamphodiacetate.
The surfactants described above may be used alone or in combinations. The amount of the surfactant may be in the range of 0.5 to 1.5 wt% of the pre-emulsion (i.e., the mixture). If the amount of the surfactant is less than 0.5 wt% of the pre-emulsion, the monomers may not form stable particles during the preparation of the pre-emulsion. On the other hand, if the amount of the surfactant is greater than 1.5 wt% of the pre-emulsion, physical properties of the latex may be changed since too much surfactant is used.
In addition, the water may be purified water such as deionized water, but is not limited thereto. The amount of water may be in the range of 25.0 to 40.0 wt% of the pre-emulsion. If the amount of water is less than 25.0 wt% of the pre-emulsion, the pre-emulsion may not be easily formed. On the other hand, if the amount of water is greater than 40.0 wt% of the pre-emulsion, particles formed of the monomers become unstable, and thus induce phase separation. The additive may include a molecular weight modifier, i.e., a chain transfer agent.
The molecular weight modifier is used to adjust the molecular weight of the latex, and may include at least one selected from the group consisting of dodecanethiol, butanethiol, isooctyl-3-mercaptopropionate (IOMP), 2-methyl-5-t-butylthiophenol, carbon tetrachloride, and carbon tetrabromide. The amount of the molecular weight modifier may be in the range of 0.1 to 2.0 wt% of the pre-emulsion. If the amount of the molecular weight modifier is less than 0.1 wt% of the pre-emulsion, the molecular weight of the latex may not be easily adjusted and thus a desired molecular weight may not be obtained. On the other hand, if the amount of the molecular weight modifier is greater than 2.0 wt% of the pre-emulsion, some of the molecular weight modifier may remain unreated, and thus the unreacted molecular weight modifier may deteriorate properties of the latex. The monomer, the surfactant, water, and at least one additive are mixed and stirred to prepare a pre-emulsion.
The method of preparing the pre-emulsion may include various methods such as a method that is used when a solid content of 50 wt% or greater is required, and another method that is used when a low solid content and a good compatiabilty among monomers are required.
In particular, methods of preparing a pre-emulsion may be classified into the following three methods:
(1) a method including mixing a monomer, a surfactant, water, and additives, and stirring the mixture.
(2) a method including preparing a first mixture by mixing a monomer and additives, preparing a second mixture by mixing water and a surfactant, adding the second mixture to the first mixture, and stirring the resultant mixture.
(3) a method including preparing a first mixture by mixing a monomer and additives, preparing a second mixture by mixing water and a surfactant, adding the first mixture to the second mixture, and stirring the resultant mixture.
The surfactant is dissolved in water to form a micelle. A pre-emulsion may be formed by stirring the micelle structure. In particular, in an aqueous solution, hydrophobic monomers enter the center of the micelle, i.e., inside of the micelle, by stirring to form a pre-emulsion. In addition, the viscosity of the pre-emulsion may vary according to the preparation method, the shape of a stirrer, stirring speeds, stirring time periods, and dwelling time of the mixture in a reactor. The viscosity of the pre-emulsion is a factor influencing the molecular weight of the latex. Thus, the preparation of the pre-emulsion may include the stirring operation as shown in FIG. 1 in order to obtain reproducible molecular weight of the latex.
FIG. 1 is a graph illustrating the preparation of a pre-emulsion by stirring in a method of preparing a latex according to an embodiment of the present invention.
Referring to FIG. 1, the preparing the pre-emulsion includes a F1st stirring operation (SF1) performed for a F1st time period (TF1) at a F1st stirring speed (V1), a F2nd stirring operation (SF2) performed for a F2nd time period (TF2) at a F2nd stirring speed (V1), a S1st stirring operation (SS1) performed for a S1st time period (TS1) by increasing a stirring speed from zero to a S1st stirring speed (V2), a S2nd stirring operation (SS2) performed for a S2nd time period (TS2) by increasing a stirring speed from zero to a S2nd stirring speed (V2), a F3rd stirring operation (SF3) performed for a F3rd time period (TF3) at a F3rd stirring speed (V3), and non-stirring operations (SZ1,SZ2, SZ3, and SZ4) respectively performed between the every two consecutive stirring operations (SF1, SF2, SS1, SS2, and SF3) for Z1st, Z2nd, Z3rd, and Z4th time periods (TZ1, TZ2, TZ3, and TZ4).
The F1st, F2nd, and F3rd stirring speeds (V1 or V3) and the S1st and S2nd stirring speed (V2) may respectively be in the range of 1 to 10,000 rpm, for example, 250 to 1,000 rpm. If the stirring speeds (V1, V2, and V3) are less than 1 rpm, the mixture is not sufficiently mixed so that the phases of the pre-emulsion are separated from each other. If the stirring speeds (V1, V2, and V3) are greater than 10,000 rpm, the pre-emulsion may be too viscous and thus the molecular weight of the latex may be too high. In addition, the F1st, F2nd, and F3rd stirring time periods (TF1, TF2, and TF3) and the S1st and S2nd stirring time periods (TS1 and TS2) may be each independently in the range of 1 to 3,600 seconds, for example, 5 to 300 seconds. In addition, the Z1st, Z2nd, Z3rd, and Z4th time periods (TZ1, TZ2, TZ3, and TZ4) may be each independently in the range of 1 to 3,600 seconds, preferably 2 to 600 seconds, and more preferably 2 to 300 seconds. If the Z1st, Z2nd, Z3rd, and Z4th time periods (TZ1, TZ2, TZ3, and TZ4) are less than 1 second, the viscosity of the pre-emulsion may not be sufficiently increased. On the other hand, if the Z1st, Z2nd, Z3rd, and Z4th time periods (TZ1, TZ2, TZ3, and TZ4) are greater than 3,600 seconds, the phases of the pre-emulsion may be separated from each other. In addition, the F3rd stirring time period (TF3) may be in the range of 30 to 60 minutes, but is not limited thereto.
The stirring speed acceleration of the S1st and S2nd stirring operations (SS1 and SS2) may be 50 rpm per 0.1 to 600 second, for example, 50 rpm per 100 to 500 seconds.
Referring to FIG. 1, the preparing the pre-emulsion is performed by sequentially performing the F1st stirring operation (SF1) → the non-stirring operation (SZ1) → the F2nd stirring operation (SF2) → the non-stirring operation (SZ2) → the S1st stirring operation (SS1) → the non-stirring operation (SZ3) → the S2nd stirring operation (SS2) → the non-stirring operation (SZ4) → the F3rd stirring operation (SF3). However, the present invention is not limited thereto. The preparing the pre-emulsion may include 2 to 10 F1st to F2nd stirring operations (SF1 and SF2), 2 to 10 S1st to S2nd stirring operations (SS1 and SS2), a single F3rd stirring operation (SF3), and non-stirring operations (SZ1 to SZp) between the every two consecutive stirring operations.
The viscosity of the pre-emulsion may be in the range of 20 to 700 mpa ㆍ s. If the viscosity of the pre-emulsion is less than 20 mpa ㆍ s, the phases of the pre-emulsion are separated from each other and thus properties of the product polymer are changed. On the other hand, if the viscosity of the pre-emulsion is greater than 700 mpa ㆍ s, the pre-emulsion may be too viscous and thus the molecular weight of the latex may be too high.
Then, the monomer contained in the pre-emulsion having a controlled viscosity is polymerized using a polymerization initiator, e.g., potassium persulfate.
The polymerization initiator may be added during the preparation of the pre-emulsion, or after the preparation of the pre-emulsion and before the polymerization.
Properties of the latex prepared according to the present embodiment are as follows. That is, the weight average molecular weight (Mw) of the latex may be in the range of 500 to 5,000,000, for example, 20,000 to 100,000. The molecular weight distribution (PDI) of the latex may be in the range of 1.5 to 3.5, for example, 2.0 to 3.2. The particle size of the latex may be in the range of 20 to 500 nm, for example, 150 to 300 nm. The particle size distribution of the latex may be in the range of 1.0 to 5.0, for example, 1.15 to 1.5. The glass transition temperature (Tg) of the latex may be in the range of 58 to 68 ℃ , for example, 60 to 65 ℃ .
According to the method of preparing the latex according to current embodiment, the molecular weight of the latex may be adjusted using a small amount of the molecular weight modifier; that is, the amount of the molecular weight modifier may be in the range of 0.1 to 2.0 wt% of the pre-emulsion. Furthermore, since a small amount of molecular weight modifier is used, the amount of gas discharged to the surrounding environment may be reduced, and thus the method is environmentally friendly.
The present invention also provides a method of preparing a toner using the latex prepared using the method according to the embodiment described above. That is, the toner may be prepared by mixing the latex, a coloring agent, and at least one additive, and then aggegating, coalescing, cleaning and drying the mixture.
The present invention will be described in more detail with reference to the examples below, but is not limited thereto. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.
Examples
Example 1: Preparation of latex (1)
200 g of deionized water and 1.06 g of a surfactant (Dowfax 2A-1, Dow Chemical Company) were added to a double-jacketed reactor (first reactor) equipped with a heat exchanger to control temperature, and the first reactor was heated to 75 ℃ . Then, 6.0 g of potassium persulfate dissolved in 166.6 g of deionized water was added to the first reactor, and the mixture was stirred for 10 minutes.
Then, 319.2 g of styrene, 67.8 g of butyl acrylate, 11.96 g of 2-carboxyethyl acrylate, 1.4 g of 1,10-dodecanediol dimethacrylate, and 5.84 g of 1-dodecanethiol, constituting a molecular weight modifier, were added to a double-jacketed reactor (second reactor) having a structure similar to that of the first reactor. Then, 169.5 g of deionized water and 7.53 g of a surfactant (Dowfax 2A-1, Dow Chemical Company) were further added to the second reactor, and the mixture was stirred to prepare a pre-emulsion. The second reactor was heated to 75 ℃ , and stirred at 75 ℃ under the stirring conditions below to control the viscosity of the pre-emulsion. That is, the viscosity of the pre-emulsion was controlled under the stirring conditions described with reference to FIG. 1. The viscosity measured using a Brookfield Viscometer using No. 1 spindle at a rotation speed of 10 rpm was 50±20 mpa ㆍ s. The viscosity was an average of viscosities of 4 pre-emulsion samples. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1: SF1(V1=200 rpm, TF1=60 sec)→SZ1(0 rpm, TZ1=60 sec)→SF2(V1=200 rpm, TF2=60 sec)→SZ2(0 rpm, TZ2=60 sec)→SS1(V2=300 rpm, TS1=60 sec, 50 rpm/30 sec)→SZ3(0 rpm, TZ3=60 sec)→SS2(V2=300 rpm, TS2=60 sec, 50 rpm/30 sec)→SZ4(0 rpm, TZ4=60 sec)→SF3(V3=300 rpm, TF3=30 min).
Then, the pre-emulsion was added at a flow rate of 103.49 ml/min to the first reactor maintained at 75 ℃ to perform the polymerization for 3 hours, thus completing the preparation of a latex.
Properties of the prepared latex were measured, and the results are shown in Table 1 below. That is, the molecular weight of the latex was measured using gel permeation chromatography (GPC), Waters 515 HPLC Pump, Waters 2410 Differential Refractometer, and Waters 717plus Autosampler. The particle size of the latex was measured using capillary hydrodynamic fractionation (CHDF) 2000. The glass transition temperature (Tg) was measured using differential scanning calorimetry (DSC) produced by TA Instrument by heating the latex from room temperature to 250 ℃ at a rate of 10 ℃ /min, rapidly cooling the latex to room temperature at a rate of 50 ℃ /min, and heating the latex to 250 ℃ at a rate of 10 ℃ /min.
The acid value and stability of the latex were also measured. The stability was measured by identifying whether viscous oligomer residues remain in the upper layer of the latex.
Example 2: Preparation of latex (2)
A latex was prepared in the same manner as in Example 1, except that the viscosity of the pre-emulsion was changed to 300±20 mpaㆍs by varying the stirring conditions. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1. SF1(V1=250 rpm, TF1=60 sec)→SZ1(0 rpm, TZ1=60 sec)→SF2(V1=250 rpm, TF2=60 sec)→SZ2(0 rpm, TZ2=60 sec)→SS1(V2=300 rpm, TS1=60 sec, 50 rpm/30 sec)→SZ3(0 rpm, TZ3=60 sec)→SS2(V2=350 rpm, TS2=60 sec)→SZ4(0 rpm, TZ4=60 sec)→SF3(V3=350 rpm, TF3=30 min).
Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
Example 3: Preparation of latex (3)
A latex was prepared in the same manner as in Example 1, except that the viscosity of the pre-emulsion was changed to 400±10 mpaㆍs by varying the stirring conditions. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1. SF1(V1=300 rpm, TF1=60 sec)→SZ1(0 rpm, TZ1=60 sec)→SF2(V1=300 rpm, TF2=60 sec)→SZ2(0 rpm, TZ2=60 sec)→SS1(V2=300 rpm, TS1=60 sec, 50 rpm/30 sec)→SZ3(0 rpm, TZ3=60 sec)→SS2(V2=350 rpm, TS2=60 sec, 50 rpm/30 sec)→SZ4(0 rpm, TZ4=60 sec)→SF3(V3=350 rpm, TF3=30 min).
Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
Example 4: Preparation of latex (4)
A latex was prepared in the same manner as in Example 1, except that the viscosity of the pre-emulsion was changed to 500±20 mpaㆍs by varying the stirring conditions. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1. SF1(V1=300 rpm, TF1=60 sec)→SZ1(0 rpm, TZ1=60 sec)→SF2(V1=300 rpm, TF2=60 sec)→SZ2(0 rpm, TZ2=60 sec)→SS1(V2=300 rpm, TS2=60 sec, 50 rpm/30 sec)→SZ3(0 rpm, TZ3=60 sec)→SS2(V2=450 rpm, TS2=60 sec, 50 rpm/30 sec)→SZ4(0 rpm, TZ4=60 sec)→SF3(V3=450 rpm, TF3=30 min).
Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
Example 5: Preparation of latex (5)
A latex was prepared in the same manner as in Example 1, except that the viscosity of the pre-emulsion was changed to 600±10 mpa ㆍ s by varying the stirring conditions. Stirring operations for preparing the pre-emulsion were performed in the following order as shown in FIG. 1. SF1(V1=350 rpm, TF1=60 sec)→SZ1(0 rpm, TZ1=60 sec)→SF2(V1=350 rpm, TF2=60 sec)→SZ2(0 rpm, TZ2=60 sec)→SS1(V2=300 rpm, TS1=60 sec, 50 rpm/30 sec)→SZ3(0 rpm, TZ3=60 sec)→SS2(V2=500 rpm, TS2=60 sec, 50 rpm/30 sec)→SZ4(0 rpm, TZ4=60 sec)→SF3(V3=500 rpm, TF3=30 min).
Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
Comparative Example 1: Preparation of latex (6)
A latex was prepared in the same manner as in Example 1, except that 8.5 g of 1-dodecanethiol, constituting a molecular weight modifier, which is greater than that used in Example 1, was used, and a pre-emulsion having a viscosity of 50±50 mpaㆍs was prepared by stirring the mixture including the 1-dodecanethiol at 1000 rpm for 10 seconds. Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
Comparative Example 2: Preparation of latex (7)
A latex was prepared in the same manner as in Comparative Example 1, except that the stirring was performed for 60 seconds, and a pre-emulsion having a viscosity of 100±70 mpa ㆍ s was prepared. Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
Comparative Example 3: Preparation of latex (8)
A latex was prepared in the same manner as in Comparative Example 1, except that the stirring was performed for 90 seconds, and a pre-emulsion having a viscosity of 150±65 mpa ㆍ s was prepared. Properties of the prepared latex were measured in the same manner as in Example 1, and the results are shown in Table 1 below.
In the evaluation of the stability of the latex particles, '○' and '×' of Table 1 are defined as follows.
○: Phase separation was not observed after 24 hours.
×: Phase separation was observed after 24 hours.
Table 1
Figure PCTKR2009004129-appb-T000001
Referring to Table 1, based on the viscosity reproducibility test, the viscosity of the latex prepared according to Examples 1 to 5 has an error range of ±10 to ±30 mpaㆍs, and thus high reproducibility was identified. Thus, in the preparation of latex, defect rates of the pre-emulsion caused when the viscosity of the pre-emulsion is not within the range described above may be reduced, and thus the yield of the latex having the desired molecular weight may increase. Furthermore, the desired molecular weight of the latex may be obtained by controlling the viscosity of the pre-emulsion even though a small amount of the molecular weight modifier is used. The latex may also have excellent stability. The properties of the latex, such as the glass transition temperature Tg, the particle size, and the acid value were not changed by controlling the viscosity of the pre-emulsion.
Referring to Comparative Examples 1 to 3, based on the viscosity reproducibility test using conventional stirring methods, the viscosity of the latex has an error range of ±50~±70 mpaㆍs, and thus low reproducibility was identified. Furthermore, the viscosity of the pre-emulsion was controlled by the conventional stirring methods during the preparation of the pre-emulsion, and thus the molecular weight of the latex varies greatly. In addition, the latex had poor (×) stability.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims (7)

1. A method of preparing a latex, the method comprising:
preparing a mixture comprising a monomer, a surfactant, water, and at least one additive;
preparing a pre-emulsion by controlling the viscosity of the mixture by stirring the mixture; and
polymerizing the monomer contained in the pre-emulsion.
2. The method of claim 1, wherein the preparing the pre-emulsion comprises: at least two stirring operations selected from F1st to Fmth stirring operations performed for F1st to Fmth stirring time periods at F1st to Fmth stirring speeds and S1st to Snth stirring operations performed for S1st to Snth stirring time periods by increasing a stirring speed from zero to S1st to Snth stirring speeds; and non-stirring operations performed for Z1st to Zpth time periods between the every two consecutive stirring operations, wherein m, n, and p are each independently a natural number.
3. The method of claim 2, wherein the F1st to Fmth stirring speeds and the S1st to Snth stirring speeds are each independently in the range of 1 to 10,000 rpm, and the F1st to Fmth stirring time periods, the S1st to Snth stirring time periods, and the Z1st to Zpth time periods are each independently in the range of 1 to 3,600 seconds.
4. The method of claim 2, wherein the stirring speed acceleration of the S1st to Snth stirring operations is 50 rpm per 0.1 to 600 seconds.
5. The method of claim 2, wherein m and n are each independently in the range of 2 to 10.
6. The method of claim 1, wherein the viscosity of the pre-emulsion is in the range of 20 to 700 mpaㆍs.
7. A method of preparing a toner comprising the method of preparing the latex according to any one of claims 1 to 6.
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