JPH01145663A - Method for producing toner for electrostatic images - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing toner for electrostatic images by a suspension polymerization method.

[Conventional technology]

Conventionally, dry colored fine particles, so-called toner, have been used to visualize the electrostatic charge image formed on the latent image holding surface of a photoreceptor or the like.

Toner particles are manufactured by adding a charge control agent and a coloring agent such as carbon black to a thermoplastic resin, cross-dispersing the resin, cooling it to solidify it, pulverizing it, and classifying it to obtain particles of a predetermined size. The method is common.

Although this manufacturing method can produce quite good toner,
There are also problems such as lack of food.

(1) Depending on the characteristics of the resin, which is the main component, energy consumption may increase during the kneading and pulverization steps, and yields may deteriorate during the classification step due to excessive pulverization, resulting in higher production costs.

+21 The shape of the obtained particles is amorphous, and each particle has a different shape, so the fluidity is poor and the triboelectric charging characteristics of the individual particles are likely to vary.

In order to avoid such problems with conventional methods, a method has been proposed in which toner particles are manufactured from the beginning by suspension polymerization (for example, see Japanese Patent Publication No. 36-70237). Toner particles are obtained by dispersing the additives and a polymerization initiator in a polymerizable monomer to form an oil phase, and then carrying out suspension polymerization in an aqueous phase containing a suspension stabilizer. By simply applying an appropriate shearing force during suspension, fine particles of the desired size for toner can be easily obtained, which simplifies the manufacturing process, consumes less energy, and is advantageous in terms of cost. Since the particle shape is spherical, it also has the advantage of improving toner performance such as fluidity and individual triboelectric charging properties.

[Problem that the invention seeks to solve]

In the suspension polymerization method, the most important point is to uniformly disperse additives such as colorants into monomers. If polymerization occurs without sufficient dispersion, the resulting toner will have these additives unevenly distributed on the surface and inside of individual particles, which may impair the performance necessary for toners such as triboelectric charging properties and transferability. There is.

However, the dyes normally used as colorants for toner
Pigments are highly cohesive fine powders, so it is difficult to uniformly disperse them into monomers, and their stability over time after being dispersed is also poor. Therefore, the coloring agent tends to be unevenly distributed in the particles obtained by polymerization, and if the colorant is extremely unevenly distributed,
Serious defects may occur, such as the presence of transparent particles that do not contain a colorant.

For this reason, various dispersion means or dispersion methods have been studied in order to improve these problems, but so far no satisfactory results have been obtained.

[Failure to solve the problem]

The purpose of the present invention is to improve the above-mentioned problems of suspension polymerization by dispersing a surface-modified colorant in a monomer,
It is an object of the present invention to provide a simple method for producing a fine particulate polymer, especially a dry toner, with no unevenness of colorant.

That is, the gist of the present invention is as follows: 1. An oil phase containing a coloring agent whose surface has been treated with a metal soap and a vinyl monomer is suspended in a state in which it is dispersed in an aqueous phase using a suspension stabilizer. The present invention relates to a method for producing a toner for electrostatic images, which comprises performing polymerization to form toner particles.

The present invention will be explained in detail below.

In the present invention, the colorant is used in a state in which metal soap is contained on the surface of the colorant.

As the coloring agent, known dyes and organic and inorganic pigments can be used. Specifically, carbon blank, Henshishin Yellow, Lake Red C1 Phthalocyanine Blue,
There are many colors such as navy blue.

The metal soap used in the present invention refers to metal salts other than alkali metal salts, such as fatty acids and resin acids, and specifically includes fatty acids such as lauric acid, stearic acid, oleic acid, abietic acid, etc. Aluminum such as resin acid,
Examples include metal salts such as calcium, zinc, barium, and magnesium.

Various methods may be used to treat the surface of the colorant with metal soap as long as the metal soap is distributed on the surface of the colorant. For example, it is also possible to apply or spray the metal soap onto the surface of the colorant. However, a method in which metal soap is deposited on the surface of the colorant is preferable because it can be uniformly distributed on the surface. In this case, the desired metal soap is applied to the surface of the colorant particles by adding and mixing an aqueous alkaline solution of the base acid to the aqueous suspension of the colorant, and then adding a metal salt solution containing the required metal. can be precipitated. Then, the particle size may be adjusted by purifying, drying, and crushing.

In the present invention, it is preferable that the metal soap and the colorant are contained on the surface of the soap in an amount of about 0.1 to 10 wt%. If the content of metal soap is too large, the resulting toner tends to have poor fluidity. It's a moat, the reason that contains too little tends to deteriorate.

The amount of the colorant surface-treated with these metal soaps is preferably 7 to 20 wt%, particularly preferably 3 to 10 wt%, based on the vinyl monomer.

Vinyl monomers are commonly used in the production of toner.
All known vinyl compounds which give polymers by addition polymerization are included. For example, styrene, α-methylstyrene,
Aromatic vinyl compounds such as vinyltoluene; α-unsaturated carboxylic acid esters such as methyl methacrylate, butyl acrylate, and butyl methacrylate; α, β-unsaturated and tolyl compounds such as methacrylatrile and acrylonitrile; halogens such as vinyl chloride Examples include vinyl chloride and others.

These vinyl monomers may be used alone or in combination. Further, it is also possible to use a crosslinkable vinyl compound such as divinylbenzene, and in this case, it is preferable to use θ in a range of 0/~/o wt% relative to the vinyl monomer.

In the present invention, an oil phase containing the above-mentioned colorant and vinyl monomer is dispersed in an aqueous phase, and this is subjected to suspension polymerization to obtain a toner for electrostatic images.

The suspension polymerization method for producing toner is not particularly limited as long as it is carried out by dispersing an oil phase in an aqueous phase using a suspension stabilizer, but examples include: , as follows.

First, a coloring agent surface-treated with the metal soap described above and additives such as a charge control agent and an anti-offset agent, which are used as necessary, are appropriately dispersed in a vinyl monomer using a homomixer, homogenizer, sand mill, etc. After this, a polymerization initiator is usually added to prepare a dispersion of the polymerizable composition (oil phase).

Next, the above dispersion of the oil phase is added to the aqueous phase consisting of water and a suspension stabilizer, and dispersed into oil droplets of 5 to 30 .mu.m using a dispersion means using the above-mentioned homomixer, homogenizer, or the like.

The preferred ratio of the oil phase to the aqueous phase is in the range of 1:/~/near 0, and is set so as not to cause particle aggregation during polymerization. The dispersion liquid in which the oil phase is uniformly dispersed in the water phase is transferred to a polymerization vessel equipped with a stirring device, a condenser, a thermometer, and a nitrogen inlet tube, and the temperature is raised to the temperature at which the polymerization initiator decomposes (KeO~10oC). Then, polymerization is carried out under a nitrogen stream. After the polymerization is completed, the aqueous phase is removed by centrifugation or separation, and after washing with water, alcohol, etc., water is removed by means of spray drying, vacuum drying, etc. to produce the desired toner.

The suspension stabilizer to be present in the suspension polymerization is one that has the effect of protecting the suspended state of the polymerizable composition (oil phase) in the aqueous phase.

Specifically, water-soluble polymeric substances such as polyvinyl alcohol and polyvinylpyrrolidone; inorganic powders that are sparingly soluble in water such as calcium phosphate, calcium carbonate, and silica may be mentioned. It is preferable to use these in an amount of 10 wt% or less based on the aqueous phase.

As mentioned above, it is preferable to use a polymerization initiator during suspension polymerization. This polymerization initiator is selected from organic solvent-soluble polymerization initiators commonly used for radical polymerization of vinyl monomers, such as peroxides such as benzoyl peroxide and lauroyl(-oxide); λ, 2/-azo Bisisobutyronitrile, co,!-azobis-(x,ll
-Azo compounds such as dimethylvaleronitrile 9 are used. Polymerization initiator is 20wt for vinyl type≠1 body
% or less, and more preferably in a range of 0.1 to 10 wt%. Depending on the type of polymerization initiator used, a small amount of an organic solvent inert to the polymerization reaction may be added to the oil phase in order to dissolve the initiator.

In addition, in order to adjust the molecular weight of the polymer to a predetermined range,
Chain transfer agents such as dodecyl mercaptan may also be used.

In addition, a charge control agent, an offset inhibitor, and other additives may be used in the polymerizable composition forming the oil phase.

As the charge control agent, all those conventionally used for the purpose of imparting triboelectric charging properties to toner can be used. in particular,
Examples of positively chargeable toners include nigrosine dyes and polyamine resins, and negatively chargeable toners include metal-containing azo dyes containing chromium, iron, and the like. The amount used is preferably 7 to 5 wt% based on the vinyl monomer.

As the offset preventing agent, conventionally known ones are used in order to improve the releasability of the toner from the heat roll fixing device. Examples include polyolefins such as low molecular weight polyethylene and polypropylene. The offset inhibitor is 10wL% based on the vinyl monomer.
It is preferable to add and use it below.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. In the examples, "parts" indicate "parts by weight."

Example Coloring obtained by precipitating zinc stearate on the surface of styrene, 7.2 parts of n-butyl acrylate, Mitsubishi Carbon Black #30 (Mitsubishi Chemical Industries @g, r Mitsubishi Carbon Black is a registered trademark) 3 parts of the agent sample (containing about 3 wt% zinc stearate) and 1 part of the nigrosine dye (trade name: Bontron N0II, Orient Chemical Co., Ltd.) were put into a multi-disperser (manufactured by Mitamura Riken) at about 000 rpm. After dispersing for 30 minutes at a rotational speed of 1.2.
Three parts of 2'-azobisinbutyronitrile was dissolved to form an oil phase mixture.

On the other hand, polyvinyl alcohol (trade name GM
-/II, i% aqueous solution of Japan Synthetic Chemical System 9 1gO
section was used.

To disperse the oil phase into the aqueous phase, a TK homomixer (manufactured by Tokushu Kika Kogyo) was used at a rotational speed of about 0.

rpm for 15 minutes. Then, mix the dispersion with a stirrer,
The mixture was transferred to a stainless steel polymerization vessel equipped with a thermometer and a nitrogen inlet tube, and heated at 0.degree. C. under a nitrogen stream for 3 hours while stirring at a rotational speed of about 500 rpm to complete polymerization.

The polymer particles were separated as a solid from the obtained polymer solution using a centrifugal separator, and after repeated washing with water and drying in vacuum, toner particles having a particle size distribution of 5 to 20 μm were obtained.

When the toner particles were observed under a microscope, it was found that no unevenness of carbon black or the like was observed in any of the particles, indicating that the toner particles were well dispersed.

In addition, 5 parts of this toner and iron powder carrier (product name TEFV
-2sO/Hiro00, Nippon Steel Powder Co., Ltd.) qs part was mixed to prepare a developer, and the charge amount of this developer by the blow-off method was OμC/r.

Furthermore, when a photocopying test was conducted using the above-mentioned developer using a commercially available copying machine using an organic photoconductor as a photoreceptor, clear images were obtained.

[Comparative example]

A toner was prepared in the same manner as in the example except that Mitsubishi carbon black #30 not treated with zinc stearate was used as a comparative example.

Microscopic observation of the obtained toner revealed that carbon black was extremely unevenly distributed within the toner particles, and the dispersion state was not good.

A developer was prepared in the same manner as in the example, but the amount of charge was as low as 10 .mu.c7y or less, and even in the actual photographic test, there was a lot of fog and the image was unclear.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to produce a fine particulate polymer suitable as a toner for electrostatic images with no uneven distribution of additives and excellent shape properties through a relatively simple process. . Therefore, the present invention is extremely useful industrially.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - Others/names

Claims (1)

[Claims] (1) An oil phase containing a colorant and a vinyl monomer whose surface has been surface-treated with metal soap is dispersed in an aqueous phase using a suspension stabilizer, and suspension polymerization is performed to form toner particles. 1. A method for producing an electrostatic image toner, the method comprising: