JPS60243664A - Preparation of toner for electrostatic charge image development - Google Patents

Abstract

PURPOSE:To obtain a toner causing no uneveness of color, and having superior fluidity and charge stability by carrying out suspension polymn. of a prepolymer converted to a specified degree of polymn. obtd. by polymerizing a polymerizable monomer together with dehydrated carbon black until the content of the residual monomer attains a specified value, and weshing obtd. polymer suspension. CONSTITUTION:Dehydrated carbon black is added to a polymerizable monomer, and the monomer is polymerized by heating to obtain a prepolymer having <=40% conversion. Obtained prepolymer is added to an aq. suspension contg. a radical polymn. initiator and the aq. suspension is stirred violently to obtain a suspension contg. dispersed oil particles having toner size particle diameter. Then, the polymn. is proceeded for the suspension until the content of the residual polymerizable monomer attains <=0.5%, and obtd. polymer is washed with acid and then with water to obtain a toner. By proceeding the polymn. to <=0.5% residual monomer content, the odor, instability of charging property, and dispersion of softening temp. of the toner can be eliminated. If calcium phosphate is used in combination with sodium alkylbenzene sulfonate simultaneously for the dispersed system, the fluidity of the toner is improved because of the superior suspending effect and easily removable effect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a toner, and more particularly, to a method for producing a toner for developing electrostatic images that has fluidity, charging stability, and is free from irregularities in color.

The so-called pulverization method toner, which is manufactured by kneading media, pigments, etc. like a turret, and then pulverizing them, requires complicated equipment processes to obtain the desired toner, and is an expensive process. However, it also had drawbacks in terms of powder properties, such as poor fluidity.

On the other hand, for example, Japanese Patent Publication No. 56-102
No. 51 and No. 43-10799 propose a toner manufacturing method called a polymerization method, but while these methods improve the drawbacks of the pulverization method, on the other hand, the charging characteristics are unstable. In addition, new drawbacks such as color unevenness were observed, and it cannot be said that it was a success.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing toner by a polymerization method, which overcomes the drawbacks of the prior art.

An overview of the toner manufacturing method according to the present invention will be explained as follows.

Carbon black is used as a pigment suitable for the polymerization method, but by adding dehydration treatment before use, the dispersion effect of the polymerizable monomer (hereinafter simply referred to as monomer) is improved, and the pigment is dispersed. The resulting monomers are polymerized by heating to obtain a prepolymer with a conversion rate of 40 or less. This prepolymer with a radical polymerization initiator added and dispersed therein is added to an aqueous solution containing a calcium phosphate salt and a surfactant, and is vigorously stirred to form oil droplets having the toner particle size.

Next, suspension polymerization is performed until the residual monomer becomes 0.5% or less, and then the dispersant (calcium phosphate salt, surfactant 2) is removed by acid washing and water washing to produce the desired toner. Consists of.

Next, a supplementary explanation will be given regarding the configuration of the present invention.

In the production of toner by the polymerization method of the present invention, it is important to use pigments appropriately. That is, it is important to perform dehydration treatment before adding it to the monomer. Specifically, the dehydration treatment can be accomplished by carefully heating and drying until the water content becomes 0.1% or less. If this dehydration treatment is not performed, the dispersion effect in the monomer will be poor, resulting in uneven color and eventually unstable charging properties.

Typical examples of monomers used in the present invention include the following, which can be used alone or in combination in copolymerization.

Styrene, 0-methylstyrene, m-methylstyrene,
Styrenic monomers such as p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert7'tylstyrene, p-phenylstyrene, o-lystyrene, l-chlorostyrene, p-chlorostyrene; methyl acrylate , ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, tetravir methacrylate, n-butyl methacrylate, methacrylate Acrylic acid or methacrylic acid monomers such as inbutyl acid, n-octyl methacrylate, ethyl methacrylate, 2-ethylhexyl methacrylate, and stearyl methacrylate: ethylene, tetrapyrene, butylene, vinyl chloride, vinyl acetate, acrylonitrile.

In the toner manufacturing method according to the present invention, in addition to the selection of carbon black, the conversion rate of the prepolymer is also important in obtaining the desired toner. In order to improve the dispersibility of carbon black into monomers, it is preferable to increase the conversion rate of the prepolymer, but oh! 'If the conversion rate is increased too much, it becomes difficult to obtain a spherical toner with good fluidity, as particles become highly distorted in the subsequent turbidity step. The preferred conversion rate of the prepolymer in the present invention is 40 or less, and K is preferably 35.
less than or equal to Here, the conversion rate as used in the present invention refers to the rate at which a monomer is converted into a polymer.

In the present invention, a radical polymerization initiator is mixed and dispersed in this prepolymer.

Examples of the radical polymerization initiator used in the present invention include peroxide-based initiators such as benzoyl peroxide, lauroyl peroxide, and stearyl peroxide; 'P2.2'-azobisisobutyronitrile;
An azobis-based initiator such as 2,2'-7zobis(2,4-dimethylvaleronitrile) is used.

In order to adjust the charge in the present invention, a dye called a charge adjustment agent can be added to the needle for the time being.
Decapolar or unipolar dyes can be used depending on the purpose.

Next, in the present invention, a dispersion in which a radical polymerization initiator or a charge control agent is mixed and dispersed in a prepolymer is added to an aqueous solution containing a specific suspending and dispersing agent.

In order to obtain a toner, the role of this suspension dispersant (hereinafter simply referred to as a dispersant) is also important. For example, polyvinyl alcohol, which is generally known, has an excellent effect on the dispersion of suspended particles and can be used in this method, but it is difficult to remove the residual dispersant in the subsequent process, and the resulting Containing toner may cause images to become smudged or unclear.

Therefore, it is important to select a dispersant that has excellent suspension and dispersion ability and is easy to remove in the subsequent process, and in the present invention, it has been found that a combination of calcium phosphate salt and a surfactant such as sodium alkylbenzenesulfonate is excellent. . If this system is used, the harmful effects of residual dispersant can be avoided by acid washing and water washing, and a toner with good fluidity can be obtained.

In order to obtain toner-sized oil droplet dispersed particles by adding the above dispersion to an aqueous solution containing the above dispersant, vigorous stirring is required, for example, a shear force of 102 to 108 dynes/crn.
The dispersion machine used for this purpose is preferably a dispersion machine that can stir the soil vigorously to make the oil droplets into fine particles in the water.
J1! A homogenizer such as an iTK homomix mycolloider can be used.

The resulting suspension is then subjected to turbidity polymerization. In this case, suspension polymerization can be carried out at a temperature higher than the decomposition temperature of the initiator described above, but a temperature of 40 to 150 C is usually preferred. Further, during this suspension polymerization, the above-mentioned dispersant may be added as desired. This can prevent the dispersed particles from re-agglomerating. Naturally, monomer residue is unfavorable for suspension polymerization, and a high monomer residue rate may cause agglomeration when removing the dispersant, odor after the toner is formed, unstable chargeability, and low softening temperature. 0 as it causes variation.
．． It is important to lower the monomer residual rate to below 5%.

In order to keep the suspension and dispersion state stable and to lower the monomer residual rate, the first half of the reaction (conversion rate below 90) is kept at a low temperature (40 to 80).
C) It has been found that in the latter half of the reaction, it is preferable to use a multi-stage polymerization method such as polymerization at Bi temperature (80 to 150 tl:'). The dispersant of the polymer obtained by the suspended 81i1 polymerization is removed by acid washing and water washing to obtain a toner.

The toner obtained by the present invention has a high yield of particles of 5 to 20μ in excess of 95% in the polymerization stage, has an almost spherical shape even when observed under a microscope, and has excellent fluidity, charging stability, color tone, etc. I was able to obtain.

The present invention will be described in more detail below based on Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Example 1 Carbon black MOG [LL (manufactured by Cabot -5,
0) was open-dried at 110C for 48 hours (moisture content: 0.05 weight), 10 parts were mixed with 75 parts of styrene, and acrylic r.
! After mixing 25 parts of R2-ethylhexyl in a flask, the mixture was heated at 130C for 1.5 hours to obtain a prepolymer with a conversion rate of 25%. 2 for 100 parts of this prepolymer.
5 parts of 2'-azobisisobutyronitrile, 1 part of 2,2'-azobis-(2,4-dimethylvaleronitrile), charge control agent (Subiron Black T manufactured by Hodogaya Chemical Co., Ltd.)
RH) was added and mixed and dispersed for 1 hour. This material was added to a dispersion consisting of 630 parts of water, 20 parts of tribasic calcium phosphate, and 0.1 part of sodium dodecylbenzenesulfonate, and added to T' manufactured by Tokushu Kika Kogyo Co., Ltd. using a homomixer.
A suspension containing oil droplet particles having an average particle size of 12 μm was obtained by vigorously dispersing at 00 rpm. This was transferred to an autoclave equipped with a stirrer, and 60 parts were reacted for 3 hours. The temperature was further raised, and 90 parts were reacted for 1 hour. The mixture was cooled, taken out of the system, and excess hydrochloric acid was added to dissolve tricalcium phosphate. After washing and drying, a spherical toner having an average particle size of 12 μm was obtained. This toner was almost spherical, had no color unevenness, and had a residual monomer concentration of 50 ppm as determined by gas chromatography.

3 parts of the above toner and Japanese iron powder carrier TV-18297
After adjusting the developer, Ricoh FT=6200
When we evaluated the image using a copy machine, the clarity was high.
There was no capri, and stable images were obtained.

Comparative Example 1 In the same manner as in Example 1, except that the carbon black of Example 1 was used at a water content of 1.0% by weight without a dehydration step, the toner had uneven color like a soccer ball, and The j image was also unclear.

Comparative Example 2 In a system similar to Example 1, except that polyvinyl alcohol was used instead of tricalcium phosphate and sodium dodecylbenzenesulfonate, a flat polymer was formed in the toner, and the toner could not be rinsed with water. Even after returning it, the washing was insufficient, the charging property was poor, and the image evaluation showed that there was a lot of scumming.

Example 2 MA-600 (Mitsubishi Gas Chemical -3,0) was used as a substitute for the carbon black in Example 1, n-butyl methacrylate was used as a substitute for 2-ethylhexyl acrylate, and the prepolymer conversion rate was The same procedure as in Example 1 was carried out except that 5% was used.

As a result, the average particle size was 10μm, and the residual monomer was 1330p.
pm, an almost perfectly spherical toner with no color unevenness was obtained.

When image evaluation was performed under the same conditions as in Example 1, good images were obtained with no difference in quality.

Example 3 80% p-methylstyrene was used as a substitute for methyl/ in Example 1.
Example 1 was repeated except that 20 parts of 2-ethylhexyl methacrylate were used.

A spherical toner with an average particle size of 10 μm and a residual monomer content of 2000 ppm with no color unevenness was obtained.

Example 4 Orient Chemical 5-3 was used instead of the charge control agent in Example 1.
Example 1 was carried out in the same manner as in Example 1 except that 3 parts of 1 were used.

A spherical toner with an average particle diameter of 11 μm, a residual monomer content of 750 ppm, and no uneven color was obtained. Images with no problems such as clarity and fog were obtained.

Patent applicant: Showa Denko Co., Ltd. Representative patent attorney Yoshihiro Sato

Claims (1)

[Claims] Add dehydrated carbon black to a polymerizable monomer, polymerize it by heating to obtain a prepolymer with a conversion rate of 40% or less, and add the obtained prepolymer to an aqueous suspension containing a radical 1 initiator. Then, the aqueous solution is vigorously stirred to obtain a suspension containing toner-sized oil droplet dispersed particles, and the suspension is then subjected to suspension polymerization until the residual polymerizable monomer becomes 0.5% or less. . A method for producing a toner for developing an electrostatic image, characterized in that the obtained polymer is washed with acid and washed with water to obtain a toner.