JP2718725B2 - Manufacturing method of toner - Google Patents

Description

The present invention relates to a method for producing a toner. More specifically, the present invention relates to a method for manufacturing a toner for developing an electrostatic image used in electrophotography, electrostatic recording, and the like.

(B) Conventional technology In recent years, an electrostatic image of an image to be transferred is formed by an electrophotographic method or an electrostatic recording method, and this is visualized with a developing toner, transferred to a transfer paper or the like, and then fixed. A method of performing a visible image by performing the method is widely adopted.

The toner used for developing the electrostatic image includes a two-component toner mixed with a carrier such as iron powder or glass beads, and a one-component toner that does not require a carrier. In any of these toners, usually a thermoplastic resin as a binder, a carbon black, a coloring agent such as a dye / pigment, and a charge control agent, and in the case of a magnetic toner, a magnetic substance and the like are further added and mixed. It is manufactured by melting, kneading, pulverizing and classifying.

As described above, the toner produced through the pulverizing step is indefinite in shape and therefore poor in fluidity, and gives an undesirable result in terms of storage stability. Therefore, a method of adding a fine powder of silica or the like as an external additive to the toner surface has been adopted. However, since the step of adding the external additive is a separate step,
In addition to an increase in cost, the fluidity of the resulting toner is not sufficient. Therefore, recently, a method of producing a spherical toner by a solution-based production method (hereinafter referred to as a solution method) such as a submerged drying method and a suspension polymerization method, which does not require the above-mentioned pulverization step and external additive addition step, has been proposed. It has been studied and attempts have been made to improve shelf life and other properties and to reduce costs.

As a fixing method, fusion of toner with a heat roller is generally used.However, fixing by a heating method has disadvantages such as a large power consumption and a warm-up because a heat source is required. doing. In order to solve such a drawback, researches for energy saving by toner having a low fixing temperature, energy saving by adopting a pressure fixing method, and zero warm-up time have been actively conducted. Each of these uses a low molecular weight polymer or wax and is a toner that undergoes plastic deformation at low temperature or pressure. If such a toner is manufactured by a pulverization method, fusion of the binder due to heat is likely to occur during the pulverization, and it is very difficult to stably manufacture the toner. For this reason, the production of these toners is mainly studied by a solution method such as a submerged drying method and a suspension polymerization method.

(C) Problems to be Solved by the Invention The principle of the method for producing a toner by the above solution method is that a binder resin and a toner additive are dissolved or dispersed in a water-insoluble solvent, and the mixed solution is dispersed in water. The solvent is volatilized by heating and stirring. Accordingly, spherical toner particles can be obtained.

However, in the production of the toner by the above solution method, the dispersibility of the toner additive dispersed in the finally obtained toner becomes a major problem. For example, the surface of carbon black is oxidized, and a hydroxyl group, a carbonyl group, and a carboxyl group are formed on the surface. For this reason, in the hydrophobic medium used in the above-mentioned solution method, the toner easily aggregates and does not show good dispersibility during the production of the toner, and the resulting toner becomes non-uniform. In addition, carbon black transfers to an aqueous dispersion phase during production due to its hydrophilicity, causing the generation of fine powder, the aggregation of carbon black on the toner surface, and the like, causing inconvenience in toner characteristics. This is the same for the magnetic material. In addition, polyethylene and polypropylene are often used as waxes, but they are often not dissolved in a hydrophobic solvent, and are dispersed in the toner with the particle size of the raw material. Is increased.

As described above, in the toner production by the solution method,
The good and fine dispersion of the above-mentioned toner additives insoluble in a solution has become a serious problem.

(D) Means for Solving the Problems The present invention has been made in view of such circumstances, and in a solution method, which is a highly versatile method for producing a spherical toner, a method for producing the spherical toner by using the toner additive in the toner. An object of the present invention is to provide a method for producing a toner capable of obtaining good dispersibility.

The inventors of the present invention have found that, among toner additives insoluble in a hydrophobic solvent, carbon black and a magnetic substance which are hydrophilic and have poor dispersibility in a hydrophobic solvent are surface-modified by melt-kneading with a binder resin. Quality and improved dispersibility. Further, the present invention has been completed by noting that an organic additive such as a wax is pulverized by melt-kneading with a binder resin to reduce the particle size.

Thus, according to the present invention, a toner component composed of a binder resin and a toner additive is melt-kneaded in advance, and then this is substantially incompatible with water and dissolves the binder resin. Is prepared by dissolving or dispersing in a solvent that does not dissolve the toner, and then dispersing the toner preparation in an aqueous system, followed by heating and stirring to evaporate the solvent to obtain spherical toner particles. Is done.

The method of the present invention is characterized in that in a method for producing toner particles by a solution method, a toner component is melt-kneaded prior to mixing into a solution.

In the method of the present invention, the toner component includes a resin for a binder and a toner additive. The above-mentioned toner additive refers to a colorant, a charge controlling agent, a wax, etc. which can be usually added to a resin for a binder in the art. Typical examples of the toner component include 80 to 90% by weight of a resin for a binder, 5 to 15% by weight of a coloring agent such as a dye / pigment, 1 to 5% by weight of a charge controlling agent, and wax added as necessary. One composed of 1 to 5% by weight is exemplified. As the resin for the binder, polystyrenes,
Styrene-based copolymers such as styrene-methacrylate and acrylate copolymers, polyvinyl chloride, polyvinyl acetate, polymethacrylate, epoxy resin, polyester resin, polyamide resin, polyethylene, polyurethane, ethylene-vinyl acetate Thermoplastic resins such as copolymers, petroleum resins, and paraffin wax are used alone or in combination. As the colorant, conventionally known dyes and pigments such as carbon black, nigrosine dye, and phthalocyanine pigment are used alone or in combination. Examples of the charge control agent include an electron-donating nigrosine dye and a quaternary ammonium salt for the positive polarity toner, and an electron-accepting organometallic complex and an aliphatic metal salt for the negative polarity toner. Can be Further, a general fluidizer, a magnetic substance, or the like may be further used for the toner component. Examples of the fluidizing agent include colloidal silica.On the other hand, examples of the magnetic substance include ferrite, iron, including magnetite, cobalt, and a metal, alloy, or compound containing a ferromagnetic element such as nickel. No. The particle size of the colorant used is several tens to several hundreds
Å is preferred.

In the method of the present invention, the toner component as described above is prepared by melt-kneading. For the melt kneading, it is preferable to use a pressure kneader or the like, and the melt kneading temperature is equal to or higher than the softening point of the resin, preferably 100 to 300 ° C.

In the present invention, the toner component prepared by melt-kneading as described above is dissolved or dispersed in a hydrophobic solvent that has substantially no compatibility with water and that can volatilize relatively easily, thereby preparing the toner. Liquid. Organic solvents such as toluene, chloroform and diethyl ether are suitable as the hydrophobic solvent in the toner preparation liquid, and these can be used alone or in any combination. The hydrophobic solvent is used in an amount sufficient to form toner particles in the below-described dispersion in water. That is, in a usual solution method (drying method in liquid, suspension polymerization method, etc.), a granular solid material having an arbitrary particle size and surface shape and having appropriate strength as toner particles is obtained in a solution. Used in sufficient quantity to generate.

In the present invention, the toner preparation liquid is dispersed in an aqueous system so as to form oil droplets of a predetermined size, and is manufactured into spherical toner particles by a known method such as a so-called in-liquid drying method. In the above-mentioned dispersion in an aqueous system, a dispersion stabilizer known in the art may be used. The dispersion stabilizer is added to an aqueous system so that oil droplets composed of a toner preparation liquid can be stably dispersed in the aqueous system. Water-soluble polymers such as commonly used polyvinyl alcohol and polyvinylpyrrolidone, and carbonic acid Insoluble inorganic salts such as calcium and tricalcium phosphate can be used. The above-mentioned dispersion stabilizer is usually used so that it can be contained in an aqueous system by several weight% to several tens weight%.

In the above-mentioned dispersion, the size of each oil droplet toner preparation liquid formed in the aqueous system is usually adjusted to several μm to several tens μm. It is preferable to use a homogenizer for this adjustment. In this case, 5000 to 10000 rpm, more preferably 700
The high-speed rotation of 0 to 8000 rpm achieves the above-mentioned size adjustment and uniform dispersion. The dispersion in which the above-mentioned uniform dispersion has been achieved is subjected to drying conditions. This drying is achieved by heating the dispersion at a predetermined temperature for a predetermined time while maintaining stirring. The temperature is not higher than the boiling point of the dispersion medium and the hydrophobic solvent used, and is preferably not higher than the glass transition temperature of the binder resin used. For example, when toluene is used as the hydrophobic solvent and a glass transition temperature of 60 ° C. is used as the binder resin,
The drying temperature is 50-60 ° C, and the heating time is 1-3
Time is up. The stirring speed at the time of drying does not need to be particularly high, and is preferably, for example, 100 to 1000 rpm so as to promote the evaporation of the hydrophobic solvent.

(E) Function According to the present invention, the surface of the additive is modified by mechanochemical action by previously kneading and kneading a toner component composed of a binder resin and a toner additive. The particle size of the agent is reduced to achieve uniform plasticity, and the agent is stably dispersed in a solvent having substantially no compatibility with water.

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

(F) Example An example of the production of the toner according to the present invention will be described below with reference to a submerged drying method.

As shown in FIG. 1, for example, an apparatus used in the submerged drying method has a water tank 1 in which a toner preparation liquid is mixed as oil droplets 3 in water 2 contained in the water tank 1. The one provided with the homogenizer 4 for dispersing, the stirrer 5, and the heater 6 for heating the liquid in the water tank 1 is used.

A method for producing a toner by the above-described apparatus will be described with reference to the flowchart of FIG.

First, a styrene-butyl methacrylate copolymer (glass transition temperature: 60 ° C.) as a binder resin, carbon black (particle size: 250 °) as a colorant, a nigrosine dye as a charge controlling agent, and polyethylene wax were used. Weight ratio: Styrene-butyl methacrylate copolymer: 85.5 parts by weight Carbon black: 10 parts by weight Nigrosine dye: 3 parts by weight Polyethylene wax: Measured by 1.5 parts by weight and heated as shown in FIG. The mixture was melted and kneaded at 200 ° C. for 5 minutes in a pressurized kneader 7 (see FIG. 4A) to obtain a kneaded toner component.

The kneaded toner component is cooled and dissolved and dispersed in a mixed organic solvent of toluene: chloroform = 4: 1 (volume ratio) so as to be 10% by weight of the whole (b), and the toner preparation liquid is dispersed. Obtained.

Next, the toner preparation liquid was dropped into water containing 0.5% by weight of gelatin and stirred at a high speed by a homogenizer 4 rotating at a high speed of 7500 rpm.
(C in the same figure).

Then, by heating with the heater in the water tank
The mixture was heated to 50 ° C. and stirred at a speed of 800 rpm with a stirrer to evaporate the mixed organic solvent from the oil droplets.

Thereafter, the solid matter was separated from the water by filtration (d in the same figure), and the dispersant was removed with hydrochloric acid and dried to obtain an average particle diameter of 10 μm.
Was obtained.

When the inside of the toner particles obtained as described above was observed with a transmission electron microscope after exfoliation,
The dispersibility of carbon black and other additives was very good.

Comparative Example Spherical toner particles were obtained in the same manner as in the above example, except that the same toner component as in the above example was directly dissolved and dispersed in the mixed organic solvent without performing melt kneading. When the toner particles were observed with a transmission electron microscope in the same manner as described above, the carbon black was aggregated to a size of 0.1 to 1 μm, and the dispersibility of the additive was extremely poor.

According to the method of the present invention, spherical toner particles in which additives are well dispersed can be obtained by a submerged drying method.

(G) Effects of the Invention According to the present invention, even in the production of spherical toner particles by a solution method, it is possible to obtain toner particles having a uniform composition in which additives having a problem of dispersibility are uniformly dispersed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used for the submerged drying method, FIG. 2 is a flowchart of the production of a toner by the submerged drying method, and FIG. 3 is a schematic diagram of a pressure type kneader. 1 ... water tank, 2 ... water, 3 ... oil drops, 4 ... homogenizer, 5 ... stirrer, 6, 8 ... heater, 7 ... pressure type kneader.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-57350 (JP, A) JP-A-62-237466 (JP, A) JP-A-62-205365 (JP, A) JP-A-62-237365 72727 (JP, A) JP-A-62-30258 (JP, A)

Claims (1)

(57) [Claims] A toner component comprising a binder resin and a toner additive is melt-kneaded in advance, and then this is substantially incompatible with water and dissolves the binder resin.
Dissolving or dispersing in a solvent that does not dissolve the toner additive to form a toner preparation liquid, and then dispersing the toner preparation liquid in an aqueous system, heating and stirring to volatilize the solvent, thereby producing spherical toner particles. Method.