JPH01182856A - Production of developer for electrophotography - Google Patents

Abstract

PURPOSE:To efficiently obtain a toner of small grain sizes by incorporating a material which generates gas by heating into a raw material at the time of producing toner lumps, then foaming the raw material by heating so that cells of specific size exist in the toner lumps. CONSTITUTION:The material which generates the gas by heating is mixed with the ordinary raw material consisting of a resin, coloring agent, charge control agent, offset preventive agent, etc., and the mixture is heated to foam during the process of kneading to obtain the hard sponge-like toner lumps 1 contg. 10-60vol.% cells 2 having 1-50mum diameter; thereafter, the lumps are ground. The mechanical strength and physical bond of the binder resin of the toner 1 are weakened by the presence of the cells 2 in the case of pulverizing the lumps by, for example, a jet mill, etc. The grinding of the toner lumps with the smaller energy is thereby enabled and the toner of the small grain sizes is produced efficiently at the low cost.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an electrophotographic developer.

(Prior Art) The following steps are required to produce an electrophotographic developer.

First, a resin that softens when heated, a coloring agent, a charge control agent,
The mixture obtained by mixing anti-offset agents, etc. in a preliminary mixer such as a ball mill, V-shaped mixer, or S-shaped mixer is kneaded in a double-arm kneader, triple roll, co-kneader, pressure kneader, etc. The mixed substance is coarsely pulverized using a pulverizer such as a hammer mill to obtain coarse toner particles having a diameter of 1% 3 II. After adding external additives thereto, the toner particles are dispersed using a ball mill or the like, and the toner coarse particles are further pulverized using a jet mill and then classified using an air classifier to obtain a toner having a predetermined particle size.

In recent years, as the resolution of copiers, printers, etc. has improved, it has become necessary to reduce the particle size of toner (small particle size refers to a diameter of 10 caps or less). When pulverizing toner −
A jet mill is used in the membrane, but the practical limit of fine pulverization with a jet mill is pulverization up to a diameter of 7 mm, and if the particle size is smaller than that, the yield of the sample will drop significantly. , leading to an increase in costs.

Separately, since the residual rate of external additives is significantly reduced during the pulverization process f using a jet mill, it is necessary to increase the amount of external additives added, which increases the cost of raw materials.

(Problems to be Solved by the Invention) As explained above, it is difficult to efficiently obtain small particle sizes using conventional developer manufacturing methods, and the residual rate of external additives is low, making them difficult to utilize effectively. The problem was that it was difficult.

The present invention has been made in consideration of these problems, and has been made for the purpose of efficiently obtaining toner having a small particle size while making effective use of external additives.

[Structure of the invention]

(Means and Effects for Solving the Problems) The present invention provides a method for producing an electrophotographic developer, which comprises finely pulverizing a toner mass containing 10 to 60 volumetric air bubbles with a diameter of 1-5Q/Am. It is.

That is, in the present invention, resin 1 colorant, charge control agent,
A substance that generates gas when heated is mixed with ordinary raw materials such as an offset inhibitor, and foamed by heating during the crosstalk process to obtain a hard sponge-like toner mass, which is then crushed. When pulverized using a jet mill or the like, the presence of air bubbles significantly weakens the mechanical strength and physical bond of the binder resin of the toner. Therefore, it is possible to perform pulverization with less energy, and toner can be manufactured efficiently and at low cost. Separately, when external additives are added and dispersed after coarse pulverization in the toner manufacturing process, the presence of fine bubbles in the toner mass causes the external additives to be dispersed in the bubbles, so even if pulverized with a jet mill etc. Raw materials can be used effectively without losing external additives. In addition,
The toner particle size is about 7 to 12-50% volume average particle size.

A feature of the present invention is that fine air bubbles with a diameter of 1 to 50 Am are created in the mixed material by heating during kneading in the toner manufacturing process.
If 0 to 60 parts by volume are generated, this is the case.

If the diameter of the generated bubbles is less than IAm, the particles will be over-pulverized and the particle size distribution will become broad. If the bubble size is 5 o 11 m or more, the efficiency of crushability will not improve. Furthermore, when the number of bubbles generated is 10 parts by volume or less, the efficiency of crushability does not improve. Furthermore, if 60 parts by volume or more of bubbles are present, the volume of the foam-to-wire crosstalk increases, and the amount of crosstalk is reduced, resulting in a decrease in productivity.

As a means for generating the above bubbles, for example, 60S-
An example of this method is to add a substance that generates a gas upon vaporization or decomposition at 180° C. in an amount calculated according to the effective amount of gas released when the raw materials are premixed.

Double-arm kneader, three-roll kneader, coneater, pressure kneader
Bubbles can be easily generated in the toner mass by cross-talking and heating at an appropriate temperature. 60～
Substances that vaporize or generate gas upon decomposition at 180°C are shown below.

Inorganic substances include bicarbonates of alkali metals such as sodium and potassium, bicarbonates of heavy metals such as mercury and cadmium, ammonium hydrogen carbonate, ammonium carbonate, and ammonium nitrate. Organic substances include azide compounds, azobisisobutyronitrile, azodicarbonamide, Schifumi nyl sulfone-disulfohydrazine, 4,4'-oxybis(
benzenesulfohydrazide), allylbis(sulfohydrazide), 5-morpholine-N,N'-dimethyl-N,
N'-dinitrothyrephthalamide, diaminobenzene,
These include Freon 11, Freon 12, and Freon 114.

In addition, external additives added and dispersed after coarse grinding include hydrophobic silica, metal oxides such as aluminum oxide, titanium oxide, etc.
Minerals such as mica and myra, PMMA.

These are spherical resin particles such as Teflon and styrene. These particle sizes are 0.02 μm-511 m. Examples of resins and mixtures thereof to be foamed include monopolymers of styrene and substituted products thereof such as polystyrene, poly-P-chlorostyrene, and polyvinyltoluene, such as styrene-P-chlorostyrene copolymers.

Styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer,
Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer.

Styrene-vinylethyl ether copolymer, styrene-
vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-imprene copolymer, styrene-acrylonitrile indene copolymer, styrene-maleic acid copolymer, styrene-nystyl maleate copolymer,
or polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, etc.
Single or Can be used in combination.

(Example) The present invention will be described in detail below.

Polyester resin (KTR-2150: manufactured by Kao) 93 parts by weight Blue pigment (KBN: manufactured by Dainichiseika) 4 parts by weight Polypropylene wax (660P: manufactured by Sanyo Chemical) 3 parts by weight Sodium hydrogen carbonate 10 parts by weight Mixture of the above composition were premixed in a ball mill for 2 hours, and then kneaded and foamed in a pressure kneader at 140°C for 20 minutes and 100°C to obtain a spongy mixed material. In this mixed material, there were 40 parts by volume of 50-sized bubbles with a diameter of 1 μm.

Next, this spongy mixed material was cooled and coarsely ground using a hammer mill. To 100 parts by weight of this coarsely ground material, 3 parts of hydrophobic silica (U-972: manufactured by Nippon Aerosil Co., Ltd.) was externally added as an external additive, mixed for 30 minutes with a V-type mixer, finely pulverized with a jet mill, and further dried. A toner with a 50% average particle size of 7- was obtained by classifying with a wind classifier (8 with a particle size distribution of 3 to 131 tm).
(including 11m bubble).

The yield of the obtained toner was 50%, and the residual rate of externally added silica was 60%. In addition, the set pressure during crushing is
It was 5y+. After pulverization, the toner contains a diameter of 3 g.
Air bubbles of n-B gn were present.

Comparative Example Polyester resin (KTR-2150: manufactured by Kao) 93 parts by weight Blue pigment (KBN: Dainichiseikasai) 4 parts by weight Polypropylene wax (660P: manufactured by Sanyo Kasei) 3 parts by weight A mixture having the above composition was prepared in the same manner as in the example. As a result, a toner having a 50% average particle size of 7 caps was obtained. There are 111 m in the kneaded material after kneading.
~50 #1 had less than 10 parts by volume of bubbles.

The yield of the obtained toner was 22%, and the residual rate of externally added silica was 25%. In addition, the set pressure during crushing is 7
~Met.

〔Effect of the invention〕

As explained above, according to the present invention, the pulverization efficiency is improved and an electrophotographic developer having a small particle size can be easily obtained. In addition, the efficiency of using external additives is high, which greatly contributes to reducing manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the toner.

Claims (2)

[Claims] (1) A method for producing an electrophotographic developer, which comprises pulverizing a toner mass containing 10 to 60% by volume of air bubbles with a diameter of 1 to 50 μm. (2) The electrophotographic developer according to claim 1, characterized in that, when producing the toner mass, a substance that generates gas when heated is mixed into the raw material, and foamed by heating to cause air bubbles to exist in the toner mass. Method for manufacturing the agent.