JPH0268565A - One-component magnetic developer - Google Patents

Abstract

PURPOSE:To facilitate dispersion of magnetic powder into a binder resin and to obtain an image having a good printing density by previously coating the magnetic powder of the one-component magnetic developer which consists of the binder resin and magnetic powder and is produced by heating and melting, kneading, pulverizing and classifying with the triazine thiol compd. expressed by the prescribed general formula. CONSTITUTION:The one-component magnetic developer which consists of the binder resin and the magnetic powder is produced by heating and melting, kneading, pulverizing and classifying and is used in an electrophotographic method, electrostatic recording method or electrostatic printing method. The magnetic powder of such magnetic developer is previously coated with the triazine thio component expressed by the general formula. In this formula, R1, R2 denote a group contg. polymerizable active double bonds in at least one therein; X denotes hydrogen or alkali metal. The dispersion of the magnetic powder in the binder resin is facilitated and the quality of the good printing density which is free from scumming is obtd. without decreasing the mol. wt. of the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrostatic image developer used in electrophotography, electrostatic recording, electrostatic printing, etc., and particularly to a -component magnetic developer.

2. Description of the Related Art Conventionally, the following methods have been used to produce magnetic toner. That is, magnetic powder, resin, and other components necessary to ensure printing quality are mixed, uniformly pulverized and mixed using a mixer such as a high-speed mixer, ball mill, or tumbler mixer, and this pulverized mixture is passed through a heated roll or kneader. Alternatively, it is economical to obtain magnetic toner by heating and kneading with an extruder, uniformly dispersing magnetic powder and other insoluble components in the resin, pulverizing with a jet mill or other means, and then classifying to a predetermined particle size distribution. This is the most effective method when considering the following. However, in the magnetic toner manufacturing method as described above, the following points remain to be solved.

First, the high viscosity of the resin does not wet the surface of the magnetic powder during heating and cross-talk, making it difficult to disperse the powder uniformly.
There is a drawback that the composition of each toner particle deviates significantly from the desired composition, making it impossible to obtain the desired print quality. Furthermore, due to poor wetting, destruction progresses from the interface between the resin and magnetic powder during the pulverization process, which exposes the magnetic powder to the toner surface, lowering the specific resistance of the magnetic toner, and resulting in a lower transfer rate, resulting in a lower transfer rate. This results in the disadvantage that a print density of 100% cannot be obtained.

Furthermore, in the case of a -component developer, there is a drawback that the print density is lower than that of a two-component developer under high temperature conditions, and this is caused by a decrease in specific resistance due to the above-mentioned magnetic powder being exposed on the toner surface. In addition to this, it is thought that the moisture absorption of the magnetic powder further promotes the decrease in specific resistance.

What the invention seeks to solve: Various attempts have been made to solve the above-mentioned problems. For example, in order to improve the wettability between magnetic powder and resin, there is a method of coating the magnetic powder with a polymer resin in advance (Japanese Patent Publication No. 53-81125, etc.), a method of coating with a titanium-based coupling agent (Japanese Patent Publication No. 59-81, etc.). -7311N, etc.), a method of coating with a low molecular weight fluorine compound (Japanese Patent Publication No. 59-8821, etc.), and a method of coating with a lubricant such as stearic acid (Japanese Patent Publication No. 57-12146, etc.). .

However, when treated with a lubricant such as a fluorine compound or stearic acid, although the dispersibility is improved, the wettability with the resin deteriorates due to the low energy surface, and the magnetic powder is exposed during pulverization. Furthermore, since the adhesion to magnetic powder is weak, it has the disadvantage that it may break off during stirring. In addition, in the titanium coupling treatment, it is necessary to add and react in an amount that is stoichiometrically correct with respect to the OH group concentration on the entire surface of the magnetic powder. Otherwise, if it is added in excess, for example, the titanium coupling agent itself has hydrolyzability, which will actually impair the moisture resistance. Therefore, it is necessary to accurately grasp the OH group concentration in the magnetic powder, but it is extremely difficult to actually grasp the OH group concentration.

In addition, due to cross-wire crushing and classification, molecular chain scission of the resin occurs during cross-wire, which is an essential problem when manufacturing toner.
The molecular weight after kneading is lower than the molecular weight of the resin before kneading,
For this reason, there are problems such as excessive pulverization during pulverization, resulting in a decrease in yield, and the possibility of hot offset occurring at the toner fixation stage. As mentioned above, this molecular chain scission has an antinomic relationship with the dispersibility of magnetic powder and the like. For this reason, in the past, a resin with a large molecular weight was used in advance to allow for molecular chain scission during kneading, and the molecular weight was adjusted to the desired molecular weight after kneading under conditions that could obtain sufficient dispersibility. The current situation is that However, the cause of resin molecular chain scission is a complex intertwining of the crosstalk conditions (temperature set at 9 rotations, crosstalk mechanism remains) and toner composition, and it is difficult to find the optimal conditions, and even if the optimal conditions are not found. Even if the toner composition is changed, the settings must be reset every time the toner composition is changed or the kneading machine is changed, which is extremely inconvenient in terms of manufacturing.

The present invention solves the above problems, and provides magnetic powder with good dispersibility, excellent adhesion to the matrix resin, and no decrease in specific resistance under high humidity conditions.
A further object of the present invention is to provide a one-component magnetic developer in which the molecular weight of the resin does not decrease during crosstalk.

Means for Solving am In order to solve the above problems, the present invention consists of at least a binder resin and a magnetic powder, which are heated and melted and kneaded.

A one-component magnetic developer produced by pulverization and 9 classifications, wherein the magnetic powder has a general formula (wherein R1 and R2 are at least one group containing a polymerizable active double bond, and X is hydrogen or an alkali metal. It is pre-coated with a triazinethiol compound.

Specific examples of the triazinethiol compound used in the present invention include the following.

H2 S Na S Na Effect The dissociation constant of the thiol group of the triazinethiol compound used in the present invention is Pk, approximately 4 to 6.5, Pk, 2
is approximately 12 and is an acidic substance such as hydrogen sulfide, and it is known that this thiol group can easily react with metals and their oxides to form stable metal salts with strong adhesion. Therefore, inventions based on conventional techniques, such as Japanese Patent Application Laid-Open No. 59-8821, Japanese Patent Application Laid-Open No. 57-1214,
It is possible to prevent the coating film from being chipped due to poor adhesion with magnetic powder, such as in Publication No. 6.

Further, it is possible to prevent moisture from entering through the interface between the coating film and the magnetic powder, and a stable resistivity value can be obtained even in high humidity. Further, since the triazinethiol compound does not have hydrolyzability, its tolerance can be used more advantageously than the titanium coupling agent, even when it is added in excess, for example.

In addition, the chemical structure of the triazinethiol compound used in the present invention, excluding the thiol group, has good wettability with commonly used binder resins, which increases the uniform dispersibility of the magnetic powder and makes each toner particle uniform. It is possible to obtain toner particles having a suitable composition.

Furthermore, since the triazinethiol compound has at least an active double bond in its molecule, it polymerizes and becomes integrated with the binder resin through a mechanochemical reaction or thermal reaction during heating, melting, and kneading. When pulverized, the magnetic powder is broken from the interface between the magnetic powder and the binder resin, and the magnetic powder is not exposed, making it possible to greatly improve hygroscopicity.

Furthermore, it has been found that in the present invention, the molecular chains of the binder resin are not substantially cut during heating, melting, and kneading as in the prior art. The reason for this is not necessarily clear, but it is thought that in the past, mechanochemically or thermally generated radicals were captured by a substance that acted as a chain transfer agent, resulting in a decrease in molecular weight. It is thought that the generated radicals undergo a chain reaction with the active double bond in the triazinethiol compound, and no substantial decrease in molecular weight occurs. Therefore, according to the present invention, it is possible to eliminate the conventional problem of using a resin having a high molecular weight in consideration of molecular chain scission in the kneading process.

Examples of the binder resin that can be used in the present invention include styrenes such as styrene, chlorostyrene, and α-methylstyrene, and methyl acrylate.

α-methylene resin group monocarboxylic acid esters such as ethyl acrylate, n-butyl acrylate, methyl methacrylate, and ethyl methacrylate, vinyl nitriles, vinyl ethers, vinyl pyridines, N-vinyl cyclic compounds, vinyl ketones , unsaturated hydrocarbons, etc., or a copolymer or mixture of two or more thereof.

Examples of the magnetic powder that can be used in the present invention include triiron tetroxide powder, iron sesquioxide powder, chromium iron oxide powder, and chromium powder.

The above are the essential components of the present invention, but if necessary, coloring pigments, resistance control materials, charge control agents, offset inhibitors, etc. may be added.

Example Specific examples of the present invention will be described below.

Example-1 Magnetite powder (EPT-1000:
(manufactured by Toda Kogyo) 500r and 0.3wt of exemplified compound (1)
%, immersed in tetrahydrofuran solution at 45°C with stirring.
After processing for 12 minutes, the sample was washed with methanol and dried at room temperature. 45 parts by weight of the obtained treated magnetite, 45 parts by weight of styrene-acrylic resin (HIMER 388-100, manufactured by Sanyo Chemical Co., Ltd.), and low molecular weight polypropylene (Viscol 4) were added.
40P: made by Sanyo Kasei Co., Ltd.) 4 parts by weight, carbon black (H^-44 made by Mitsubishi Kasei Co., Ltd.) 5 parts by weight, (Subiron Black THR: made by Hodogaya Kaji Co., Ltd.) 1 part by weight were added, and Hensel After pre-dispersion in a mixer, a twin-screw extruder (PCH30,
After cooling, it was heated and melted and kneaded using a jet mill (Labojet, manufactured by NPK) and an air classifier <M
DS (manufactured by NPK), and the average particle size was 11.
A 5μ magnetic toner was obtained. 0.3 parts by weight of hydrophobic silica (Aerosil R-972) was added to 100 parts by weight of this magnetic toner.
: manufactured by Nippon Aerosil Co., Ltd.) was added externally as sample-1.

Example 2 Sample 2 was obtained in the same manner as in Example 1, except that the reaction conditions were 55°C and 16 minutes using Exemplified Compound (4).

Example-3 Sample-3 was obtained in the same manner as in Example-1 except that the reaction conditions were 30° C. and 20 minutes using Exemplary Compound 16).

Comparative Example A comparative sample was obtained in the same manner as in Example-1 except that the magnetite of Example-1 was left untreated.

When the dispersibility of the above samples was evaluated using the dispersity index q of a thin film formed on a glass plate, samples 1 to 3 of Examples according to the present invention showed good dispersion at q = 40 to 50. , in the comparative sample, q = 110 to 120, and 2 μm
Many of the above aggregates remained.

Further, the sample was left at 35° C./85% RH for 168 hours, then molded into a disk, electrodes were attached, and the specific resistance was measured by comparing with the initial value. The results are shown in Table 1.

Table 1 As shown in Table 1, it can be seen that the comparative samples had lower initial resistivity and poorer moisture resistance than the samples according to the present invention.

Table 2 shows the production rate of fine powder of 5μ or less and the weight average molecular weight before and after heating and melting crosstalk by GPC (gel permeation glomerography).

Table 2 As shown in Table 2, Samples 1 to 3 according to the present invention have a low proportion of over-pulverized products, and also show that the decrease in molecular weight due to heating and melt-kneading is substantially small.

Effects of the Invention As described above, according to the present invention, it is possible to easily disperse magnetic powder into a binder resin, which has been difficult in the past, and to do so without reducing the molecular weight of the resin. Furthermore, since the resistivity of the toner can be kept substantially constant regardless of the environment, when used for developing electrostatic images, it is possible to obtain good quality print density without scumming.

Agent Hiroshi Mori Moto

Claims (1)

[Scope of Claims] 1. A one-component magnetic phenomenon agent comprising at least a binder resin and magnetic powder, and produced by heating melting, kneading, pulverization, and classification, wherein the magnetic powder has the general formula ▲ mathematical formula, chemical formula , tables, etc. ▼ (However, R_1 and R_2 are groups containing a polymerizable active double bond on at least one side, and X is hydrogen or an alkali metal.) A one-component magnetic developer coated in advance with a triazinethiol compound. agent.