KR100347315B1 - Method for producing non-magnetic mono-constitution black toner - Google Patents

Abstract

PURPOSE: Provided is a method for producing non-magnetic mono-component black toner which has excellent surface smoothness by fusion and sphericalization of the respective toner particles. CONSTITUTION: The method includes (i) emulsion polymerizing 50 to 95 % by weight of a aromatic vinyl monomer, 5 to 50 % by weight of an acrylic monomer to prepare a copolymeric latex having an average molecular weight of 5000 to 100000, (ii) adding carbon black which is surface-treated by oxidation and a charge controlling agent to form primary particles having a size of 2 micron or less, (iii) inducing secondary cohesion of the particles at a temperature lower than the glass transition temperature of the resin to form secondary particles having a size of 5 to 15 micron, and (iv) inducing fusion and sphericalization of the particles at a temperature higher than the glass transition temperature of the resin.

Description

Manufacturing method of nonmagnetic monocomponent black toner

The present invention relates to a method for preparing toner particles, and more particularly, to a toner particle, characterized in that the colorant and charge control agent are added to the emulsion polymer latex to agglomerate the latex, and then a suspension stabilizer is added to fuse and spherically form the toner particles. It is about a method.

In general, electrophotographic toners such as copiers, printers, and fax machines are colored particles having a particle size of about 10 microns, and require various physical properties such as colorability, electrical characteristics, flow characteristics, and thermal characteristics.

Toner is divided into one component and two components, magnetic and non-magnetic, and among them, non-magnetic one-component toner is widely used in printers because it can colorize and form an image in a small device. . Conventional methods for producing such toner particles include a colorant, a charge control agent, a wax, a plasticizer, a fluidity improver, etc., to a binder resin, which is a thermoplastic resin, and melt-kneading with an extruder to form a uniform composition, followed by fine grinding at high speed. In most cases, the following classifier was used to obtain only particles of a desired size. However, the toner by the pulverization method has a disadvantage in that fluidity is low due to non-uniform particle size and shape, and offset and blocking phenomenon tends to occur, as well as toner due to high resolution of recent printers and copiers. In the overall process, such as grinding and sorting to obtain small particles of about 5 to 11 microns in particle size, the yield is very low, such as 70% or less, which is a significant economic disadvantage.

Recently, in order to solve the problems of the pulverization method has been proposed a method for producing colored particles directly in the polymerization process without going through the melt kneading and crushing process, the polymerization method is not only possible to yield more than 95% toner It has the advantage of being able to produce any size without any limitation on the size of the particles.

Suspension polymerization methods known from Korean Patent Publication No. 92-7327, Japanese Patent Laid-Open No. 6-282110, and U.S. Patent No. 4,794,065 have the advantages of a simple process and high yield, but the toner produced by the suspension polymerization method There is a problem in cleaning the toner which is not spherical while being completely spherical and having high flow.

Meanwhile, according to Japanese Patent Laid-Open No. 63-282750, Japanese Patent Laid-Open No. 5-107813, US Patent No. 5,278,020, and US Patent No. 5,366,841, which employ an emulsion polymerization method, the manufacturing process has a rather complicated disadvantage, As high as 95%, the particle shape can be adjusted in various ways, so that the balance of fluidity, fixability and cleaning property of the toner can be maintained. However, in the case of the magnetic polymerization toner containing a large amount of colorant, the emulsion polymerization methods may produce black particles by adding a colorant to the emulsion-polymerized latex, but when producing a non-magnetic black toner having a relatively low content of colorant, As described in Patent Nos. 5,278,020 and 5,366,841, an anion emulsifier and an expensive cationic emulsifier must be used simultaneously.

In addition, Japanese Patent Laid-Open No. 63-282750 and Japanese Patent Laid-Open No. 5-107813 propose to polymerize by further using a polymerization monomer having an acidic or basic polar group. There is a problem that the polymerization stability is lowered during emulsion polymerization.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-described problems, by preparing an emulsion polymer latex having a specific range of molecular weight, and then adding an additive such as carbon black or a charge control agent that is acidified to the polymerized latex to form latex particles. It is to provide a method for producing a non-micron monocomponent black toner at the level of several microns by inducing agglomeration and then adding a suspension stabilizer to improve the shape and surface of the particles.

1 and 2 are micrographs of the black toner particles obtained by Example 1.

That is, the present invention 1) emulsion copolymerization of 95 to 50% by weight of the aromatic vinyl monomer, 5 to 50% by weight of the acrylic monomer to prepare a copolymer latex having a weight average molecular weight of 5,000 to 100,000; 2) adding acidified surface treated carbon black and a charge control agent at room temperature to obtain colored primary aggregated particles of 2 microns or less; 3) inducing secondary aggregation below the glass transition temperature of the resin to prepare secondary aggregate particles of 5 to 15 microns; 4) A method of manufacturing a nonmagnetic one-component toner, comprising the step of injecting a stabilizer to induce fusion and spheronization of secondary aggregated particles above a glass transition temperature.

Hereinafter, the present invention will be described in detail.

As the polymerization monomer that can be used in the present invention, an aromatic vinyl monomer and an acrylic monomer are basically used, and when necessary, a monomer copolymerizable with the aromatic vinyl monomer and an acrylic compound may be used. Aromatic vinyl monomers include styrene, alpha methyl styrene, p-methyl styrene, o-methyl styrene, m-methyl styrene, halogenated styrene, alpha or beta vinyl naphthalene, and the acrylic monomers include methyl methacrylate, ethyl methacrylate, Butyl methacrylate, ethylhexyl acrylate, glycidyl methacrylate and the like. And ethylenically unsaturated monomer copolymerizable with these is acrylonitrile, methacrylonitrile, butadiene, etc.

As the polymer latex produced by the monomer, a polymer latex consisting of a styrene-acrylic copolymer, a styrene-butadiene copolymer, a styrene-butadiene-acrylonitrile copolymer, and a mixture of one or more selected from these analogs and the like can be used. Among these, a styrene-acrylic copolymer is most preferable when considering the balance of thermal characteristics, fixing characteristics, and the like of the toner.

The molecular weight of the polymer greatly affects the aggregation of the latex, preferably 5,000 to 100,000, more preferably 5,000 to 50,000, based on the weight average molecular weight. If the molecular weight is less than 5,000, not only is it difficult to manufacture by emulsion polymerization method, but the charging property of the toner is poor, and if the molecular weight is more than 100,000, the fusion and spheronization after the second agglomeration are impossible, so that the surface of the toner particles is rough. The fluidity drops significantly.

Examples of the emulsifier used in the present invention include potassium stearate, sodium oleate, potassium rosinate, sodium rosinate, sodium lauryl sulfate, sodium octyl sulfate, sodium dodecylbenzenesulfonate, and sodium toluene sulfo. Anionic emulsifiers, such as nate, potassium stearyl phosphate, sodium diisobutyl sulfosuccinate, are suitable. Moreover, nonionic emulsifiers, such as ethylene glycol stearate, polyoxyethylene nonyl phenyl ether, octylphenoxy polyethyloxy ethanol, can be used in combination with the anion emulsifier mentioned above. The amount of the emulsifier used during the emulsion polymerization is generally preferably 0.5 to 3.0 parts by weight based on the total weight of the monomers. If the amount of the emulsifier is less than 0.5 parts by weight, the polymerization stability is lowered and coagulated products are more likely to occur. If the amount of the emulsifier is more than 3.0 parts by weight, latex agglomeration is insufficient to leave unaggregated particles, and electrical properties and fluidity of the toner particles are reduced. It may cause a deterioration.

The polymerization initiator for the emulsion polymerization is not particularly limited, but generally used water-soluble pyrolytic initiators or redox-based initiators can be used. Water-soluble pyrolytic initiators include potassium persulfate, 2,2-azobis- (2-amidinopropane) dihydrochloride, and the redox-based initiators in combination with ferrous sulfate, dextrose, sodium pyrophosphate and the like. Cumene hydroperoxide, diisopropylene benzene hydroperoxide, p-mentane hydroperoxide and the like.

Examples of the chain transfer agent include mercaptans such as tertiary dodecyl mercaptan, normal dodecyl mercaptan, and tertiary butadimer captan, halogenated hydrocarbons such as carbon tetrachloride, alpha methyl styrene duplex, terpinolene, dipentene, and gamma terpitene. Etc. can be used. The content of the molecular weight modifier is important for controlling the molecular weight and the molecular weight distribution, and an appropriate content is preferably used 0.2 to 0.5 parts by weight based on the entire monomer mixture. If the added amount is less than 0.2 parts by weight, the molecular weight control ability is insufficient, which may cause cohesiveness, offset, and fixability. If the content is more than 5.0 parts by weight, the polymerization rate is slowed, the productivity is lowered, and the polymerization stability is lowered. There is a problem that occurs.

The polymerization temperature in the emulsion polymerization used in the present invention is not particularly limited and is preferably in the range of 50 to 85 ° C., which are ordinary conditions. If the temperature is less than 50 ° C, the polymerization reaction rate is slow, and the practicality is lowered. If the temperature is higher than 85 ° C, the amount of coagulated product is increased due to the weakening of the polymerization system stability, and the yield is decreased.

As the colorant, dyes and pigments such as carbon black and acetylene black are commonly known, but the colorant used in the present invention should be acidified surface treated carbon black. The reason for this is that when neutral and alkaline carbon blacks are used, not only the coloring is poor, but the agglomeration desired in the present invention is hardly induced, so that black particles of several microns cannot be obtained. The particle size of the carbon black is preferably 100 μm or less, and commercially available acidified surface treated carbon black is available from various companies, for example, Black Boats 1300 manufactured by Cabot, Monarch. 1000 (MONARCH 1000), Mogul L (MOGUL L), Degussa's Printex 150T (PRINTEX 150T), Special Black 4 (SPECIAL BLACK 4), Special Black 4A (SPECIAL BLACK 4A), Raven 7000 (RAVEN) 7000), RAVEN 5000 ULTRA, MITSUBISHI's ME 100S, # 2400 (MA100S, # 2400), and the like. The content of the colorant is preferably 3 to 10% by weight based on the solids content of the polymer latex as is commonly known.

As charge control agents, nigrosine, indolin, quaternary ammonium salts, salicylic acid-based metal crystals, metal-azo compounds, and the like are commercially available. Orient's Bontron N-01, Bontron Y-07 (BONTRON N-07), Bontron E-84 (BONTRON E-84), Bontron S-34 (BONTRON S-34), copycharge NEX (COPYCHARGE NEX), copy charge COPYCHARGE NX, COPYCHARGE PSY, COPYBLUE PR, BASF's Neozapon Black X-51, Hodogaya and many others. The commercially available can be purchased and used, the content of the charge control agent is preferably 0.5 to 2.0% by weight based on the emulsion polymer solids.

The colored fine particles are prepared through a two-step agglomeration process and a spheroidization process. The colored and primary agglomerates are carried out at room temperature, the second agglomeration is carried out below the glass transition temperature (Tg) of the resin, and then a suspension stabilizer is added to the glass transition temperature. The temperature is raised to above to induce fusion and spheronization of the secondary aggregated particles.

Referring to the manufacturing process of the aggregated particles of the present invention in detail.

In the coloring and first coagulation step, a colorant, a charge control agent, and the like are added to the latex polymerized at room temperature and stirred at a high speed for at least 1 hour. In this step, the acidified surface treated carbon black, which is a colorant, acts as a flocculant. In other words, the emulsifier present in the polymerized latex and the acidified surface treatment portion of the surface of the carbon black form crosslinking, so that uniform coloring and aggregation occurs. Aggregated particles at this time usually have a size of 2 microns or less in diameter. When the first aggregated aggregate is heated to below the glass transition temperature of the resin and sufficiently stirred for 30 minutes or more, secondary aggregated particles in which the primary aggregated particles are aggregated again can be obtained. Usually, particles of 5 to 15 microns can be obtained. have. The temperature at this time has the preferable range of Tg-15 degreeC-Tg. If the temperature is less than Tg-15 ℃, the agglomeration time is too long or the aggregation is insufficient to leave the non-aggregated particles, the diameter of the aggregated particles is less than 5㎛ too small, the coagulation rate when the temperature exceeds Tg Is too fast and there is a problem that the aggregated particles are too large with a diameter of 15㎛ or more.

Suspension stabilizer is introduced to completely melt the inside of the secondary aggregated particles and at the same time smooth the surface of the aggregated particles. Secondary agglomerated particles can be used as toner, but the first agglomerated particles are not completely fused at the time of second agglomeration, so the particles are likely to be broken by the toner feed roller during printing, and the fluidity is very poor due to the rough surface. Blocking is likely to occur.

The timing of suspension stabilizer can be divided into pre-coagulation, post-aggregation, and post-aggregation.In the case of pre-aggregation or post-aggregation, a significant amount of the used suspension stabilizer is coagulated in the continuous coagulation process. As the particles enter the particles, the efficiency as a stabilizer during fusion and spheronization is reduced. In other words, it is most preferable to introduce the suspension stabilizer immediately after fusion and spheronization after the second aggregation.

Suspension stabilizers used in the present invention include polyvinyl alcohol, hydroxyethyl cellulose, carboxylated methyl cellulose, silica, calcium phosphate, and the like. It is preferable to use. The reason for this is that polyvinyl alcohol and cellulose are used to have a wider particle size distribution, and stabilizers remain on the surface of the particles, thereby degrading charging characteristics as toners. In order to prevent additional agglomeration at the time of use, more than 10% by weight should be used, and this is because there is a problem that must be removed because it affects the toner charging characteristic when remaining. On the other hand, when silica is used, there is no problem in stability even when a small amount is used, and there is no need to additionally add silica after drying because silica is used as a fluidity improving agent. The amount of the suspension stabilizer silica is preferably 0.5 to 5% by weight relative to the emulsion polymer solid, and commercially available silica is Aerosil series manufactured by Degussa.

Silica as a suspension stabilizer can be added in dry powder state, but if it is put in dry powder state, the efficiency as a stabilizer is decreased. Therefore, it is prepared in a colloidal state uniformly dispersed in pure water using a high speed stirrer, and then added. It is preferable.

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

Example 1

Emulsification polymerization was carried out using a reactor having a capacity of 500 ml equipped with a stirring device, a heating device, a cooling device, a condenser, a temperature controller, and a device capable of continuously adding raw materials such as monomers and initiators. First, a monomer mixture of 17 g of styrene, 3 g of butyl acrylate, 0.6 g of tertiary decelercaptan, 130 g of deionized water, and 1 g of sodium lauryl sulfate were added thereto, and the temperature of the reactor was raised to 60 ° C. while stirring at 250 rpm. When the temperature inside the reactor reached 60 ° C, an initiator aqueous solution in which 0.5 g of potassium sulfate was dissolved in 20 g of deionized water was added, and the first stage polymerization was initiated to react for 30 minutes. After the completion of the first stage reaction, a mixed solution of 68 g of styrene, 12 g of butyl acrylate and 2.4 g of tertiary dodecyl mercaptan was continuously added to the reactor in a constant amount for 120 minutes while maintaining the temperature inside the reactor at 70 ° C. The polymerization was carried out in two steps while being added. After the addition of each raw material, the reaction was continued for an additional 60 minutes and then cooled to terminate the reaction. As a result of analysis, the solid content of the latex copolymer was 39.8%, the glass transition temperature was 65 ° C, and the weight average molecular weight was 18,000.

25 parts by weight of the polymer latex, 0.5 parts by weight of carbon black (PRINTEX 150T, manufactured by Degus), 0.1 part by weight of chromium-azo compound (BONTRON S-34, product of Orient), and 65 parts by weight of deionized water were added thereto. Stirred at 2,000 rpm for 1 hour with a high speed stirrer. As a result, primary aggregated particles were uniformly colored in whole, and micrographs showed that there was no coagulated latex and the average was less than 1 micron. The primary agglomerate was gradually heated to 60 ° C. while continuing stirring at 1,000 rpm, followed by further stirring for 2 hours to obtain a secondary agglomerate. The average particle diameter of this secondary aggregated particle was 10 micrometers, as can be seen through the micrograph shown in FIG. 2 g of silica (Aerosil R972) was added to 98 g of distilled water, and 10 parts by weight of a silica dispersion dispersed at 5000 rpm for 1 minute with a homogenizer was added to the secondary agglomerate, and the temperature of the system was stirred at 500 rpm using a stirrer. The temperature was raised to and maintained for 2 hours to induce sphericalization at the same time as fusion between primary particles. Microscopic observation showed no further aggregation and fusion and spheronization occurred as shown in FIG. 2, resulting in smooth surfaces.

Example 2

15 g of styrene and 5 g of butyl methacrylate were added as a polymerization monomer in the emulsion polymerization step, and polymerization was carried out in the same manner as in Example 1 except that 60 g of styrene and 20 g of butyl methacrylate were used in the two-step polymerization. As a result, solid content 39.8%, glass transition temperature 65 ℃, and weight average molecular weight 12,000 were shown. The agglomeration and spheronization step were also carried out in the same manner as in Example 1 to prepare black toner particles, and when observed under a microscope, the average coagulation particle diameter was 9 μm, and the shape thereof was not significantly different from that of Example 1.

Example 3

Polymerization Latex was polymerized in the same manner as in Example 1, except that 18 g of styrene and 2 g of ethylhexyl acrylate were used in the first step polymerization, and 72 g of styrene and 8 g of ethylhexyl acrylate were used in the second step polymerization. As a result, solid content was 39.8%, weight average molecular weight was 22,000, and glass transition temperature was 69 ° C. In addition, except that 10 parts by weight of the silica dispersion in which 1 g of fused and spherical silica (Aerosil R812) was dispersed in 99 g of distilled water, the same experiment was performed as in Example 1. As a result of observation under a microscope, the average cohesive particle diameter was 8 µm and the shape was similar to that of Example 1.

Comparative Example 1

The polymerization was carried out in the same manner as in Example 1, except that no molecular weight modifier tercydodecylmercaptan was used in the emulsion polymerization step. As a result, the solid content of the polymer was 39.8%, the weight average molecular weight was 254,000, the glass transition temperature was 70 ℃. The first coagulation was carried out in the same manner as in Example 1 at room temperature, the second coagulation was carried out at 65 ℃ to produce secondary aggregated particles having an average particle diameter of 8㎛. A silica stabilizer (Aerosil R972) concentration of 2% suspension stabilizer was added thereto, and fusion and spheronization were attempted by raising the temperature to 95 ° C., but the surface state of the particles was the same as that of the secondary agglomerated particles.

Comparative Example 2

The polymer latex was emulsified and polymerized in the same manner as in Example 1, and coloring and aggregation were carried out in the same manner as in Example 1, except that carbon black (MA600, manufactured by Mitsubishi), which was not acidified in the first coagulation step, was used. Tried. However, the carbon black was not evenly dispersed, so that coloring did not occur properly and latex aggregation did not occur.

Comparative Example 3

Polymer latex was polymerized in Example 1, except that 20 parts by weight of a suspension stabilizer silica (Arosil R972) dispersion of 2% concentration was added together with carbon black during the first agglomeration without the addition after the second agglomeration. Aggregation and fusion were performed under the same conditions as in Example 1. As a result, the average particle diameter and particle shape of the secondary aggregated particles were not different from those of Example 1, but the surface after the fusion and spheronization was slightly smoothed, but the average particle diameter was increased to 30 µm and the particle shape was very irregular.

According to the present invention, after preparing an emulsion polymer latex having a specific range of molecular weight, an additive such as carbon black or a charge control agent acidified to the polymerized latex is added to induce flocculation of latex particles, and then a suspension stabilizer is added. As a result, as shown in FIG. 2, fusion and spheronization occur to obtain non-magnetic monocomponent toner particles having a smooth surface.

Claims (3)

1) preparing a copolymer latex having a weight average molecular weight of 5,000 to 100,000 containing 95 to 50% by weight of aromatic vinyl monomer and 5 to 50% by weight of an acrylic monomer by emulsion polymerization; 2) 3 to 10% by weight of carbon black having an acidification surface treatment of 100 μm or less and 0.5 to 2.0% by weight of a charge control agent were added to the emulsion polymer solid to obtain colored primary aggregated particles of 2 microns or less; 3) inducing secondary aggregation below the glass transition temperature of the resin to prepare secondary aggregate particles of 5 to 15 microns; 4) A method of manufacturing a nonmagnetic one-component toner, comprising the step of injecting a stabilizer to induce fusion and spheronization of secondary aggregated particles above a glass transition temperature. The method of manufacturing a nonmagnetic one-component toner according to claim 1, wherein the glass transition temperature, which is a temperature at the time of secondary aggregation, is in the range of Tg-15 占 폚 to Tg. The non-magnetic suspension stabilizer according to claim 1, wherein the suspension stabilizer is selected from the group consisting of polyvinyl alcohol, hydroxyethyl cellulose, carboxylated methylcellulose, silica and calcium phosphate. Method of manufacturing a one-component black toner.

Images