JPS6360906B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrostatic image developing toner for developing electrostatic images formed in electrophotography, electrostatic printing, electrostatic recording, or the like. Generally, as a toner for developing an electrostatic image, a powder formed by dispersing or containing a colorant and a charge control agent in binder resin particles is widely used. So-called magnetic toners containing the above have also come into practical use. As the binder resin, vinyl resin, phenolic resin, epoxy resin, polyurethane resin, cellulose resin,
Synthetic resins such as polyether resins and polyester resins or natural resins are used, but vinyl resins and divinyl resins in particular have a wide range of selection due to their many monomer compositions, and the molecular weight can also be adjusted at will. Therefore, it is most widely used as a binder resin for toners because it can easily impart the necessary properties as a binder resin for toners. By the way, vinyl resins or divinyl resins are usually synthesized by a suspension polymerization method, an emulsion polymerization method, or a bulk polymerization method. Among these, the emulsion polymerization method has the following advantages: Binder resins for toners are used because they are easy to mix with colorants such as carbon black, charge control agents, and other additives in the production of toners because the polymerization products are fine particles. It is advantageous compared to other methods as a manufacturing method. However, since the emulsion polymerization method is a method in which water-insoluble monomers are emulsified and dispersed in water using an emulsifier and then polymerized, it is impossible to avoid the inclusion of impurities caused by the emulsifier in the polymerized product. Moreover, since these impurities have an adverse effect on the properties of toner, it has been considered that the resin obtained by this emulsion polymerization method cannot be suitably used as a binder resin for toner. That is,
As the emulsifier, fatty acid potassium salt, fatty acid sodium salt, disproportionated rosin acid potassium salt, sodium alkylbenzene sulfonate, etc. are used, and the amount used is about 2 to 5 parts by weight per 100 parts by weight of the monomer. These emulsifiers or substances produced therefrom, such as fatty acid calcium salts, disproportionated rosin acid calcium salts, fatty acid aluminum salts, disproportionated rosin acid calcium salts, Aluminum salts of rosin acid, organic acids such as fatty acids, and other substances are contained as impurities in the polymer in an amount of about 3 to 8% by weight, and when a resin made of the polymer is used as a binder resin for toner, the impurities are This adversely affects the triboelectric properties, durability, etc. of the toner. Furthermore, for the same reason, when a resin obtained by emulsion polymerization is used as a binder resin for a toner, the resulting toner also has the disadvantage of promoting so-called toner filming. This toner filming is a phenomenon in which a part of the components contained in the toner transfers and adheres to the surface of the electrostatic image support, the surface of the carrier particles that constitute the developer together with the toner, or the surface of the developing sleeve during development, resulting in a thin film. This is a phenomenon of forming layers. The present invention has been made based on the above circumstances, and its object is to provide a toner for developing electrostatic images using a resin synthesized by an emulsion polymerization method as a binder resin, and which does not have the above-mentioned drawbacks. It is on offer. This purpose is to provide an electrostatic image developing toner in which the binder resin contains a polymer synthesized by emulsion polymerization using an emulsifier, in which the polymer is added to the emulsion obtained by emulsion polymerization with a coagulant. The resin can be obtained by coagulating the resin by adding , and then treating the coagulated resin with an alkaline aqueous solution, or by adding the emulsion obtained by emulsion polymerization to the coagulation solvent to coagulate the resin. This is achieved by a toner for developing an electrostatic image, characterized in that the content of impurities due to the emulsifier in the polymer is 1.2% by weight or less based on the binder resin. According to the present invention, as will be clear from the description of the examples below, the emulsifier or emulsifier in the binder resin can be By controlling the content of impurities generated from this to 1.2% by weight or less, the adverse effects of the impurities on the performance of the toner can be substantially eliminated. Examples of the method for producing the binder resin of the toner according to the present invention include the following. (1) At the stage where the emulsion polymerization process is completed, a coagulant such as sulfuric acid is added to the emulsion containing the particulate resin to break the bond between the resin and the emulsifier, coagulate the resin, and then A method in which the resin is treated with an alkaline aqueous solution, then washed with water and solidified. (2) A method in which an emulsion containing particulate resin is added to a coagulation solvent such as alcohol at the stage where the emulsion polymerization process has been completed, the resin is coagulated, and then dehydrated and solidified. Specific examples of resins obtained by the above method and used as binder resins in the present invention include styrene-acrylic resins, styrene-butadiene resins, acrylonitrile-styrene-butadiene resins, acrylonitrile-styrene resins, and vinyl chloride resins. etc. can be mentioned. In the binder resin of the toner of the present invention, examples of emulsifiers that constitute impurities whose content should be limited as described above include potassium salts of fatty acids, sodium salts of fatty acids, potassium salts of disproportionated rosin acids, sodium alkylbenzenesulfonates, etc. can be mentioned. In the present invention, the binder resin may be composed only of a resin having a small impurity content as described above, but the binder resin may also be a mixture with other resins. As other resins, those synthesized by suspension polymerization or bulk polymerization, natural resins, etc. can be used. Specific examples thereof include styrene-acrylic copolymer resins, polyester resins, polyether resins, polyurethane resins, rosin-modified phenolic resins, cellulose resins, and epoxy resins. Although it is possible to reduce the content of the impurities in the entire binder resin by mixing other resins that are not based on the emulsion polymerization method, it is possible to reduce the content of the impurities in the entire binder resin. It is desirable that the mixing ratio of the other resin be less than 40% by weight of the binder resin so that the advantages are not diminished. In the present invention, it is sufficient that the content of impurities in the binder resin is 1.2% by weight or less, and if this content is further reduced, the effect will be improved, but the degree of improvement is not so large. The toner of the present invention contains other toner components, that is, a coloring agent such as a pigment or a dye, and additives such as a charge polarity control agent, which are contained as necessary, in particles made of the binder resin as described above. When it is made into a magnetic toner, fine magnetic powder is dispersed therein. Here, the particle size of the toner particles is usually 1 to 50 microns, especially 3 microns.
~20 microns. Specific examples of the above colorants include carbon black, nigrosine dye (CI No. 50415B), aniline blue (CI No. 50405), and calco oil blue (C.
I.No.azoec Blue3), Chrome Yellow (CINo.
14090), Ultramarine Blue (CINo.77103),
DuPont Oil Red (CI No. 26105), Quinoline Yellow (CI No. 47005), Methylene Blue Chloride (CI No. 52015), Phthalocyanine Blue (C.
I.No.74160), malachite green oxalate (CINo.42000), lamp black (CINo.77266),
Mention may be made of Rose Bengal (CI No. 45435), mixtures thereof, and others. These colorants need to be contained in a sufficient proportion so that a visible image of sufficient density is formed by development, and usually 1 to 100 parts by weight of the binder resin.
The content is said to be about 20 parts by weight. Specific examples of magnetic materials used in the case of magnetic toner include metals made of ferromagnetic elements such as iron, cobalt, and nickel, including ferrite and magnetite; alloys or compounds containing these; Alloys that do not contain magnetic elements but become ferromagnetic through appropriate heat treatment, such as manganese-copper-aluminum or Heusler alloys containing manganese and copper such as manganese-copper-tin. Chromium dioxide, etc. may be mentioned.
The content ratio of these fine magnetic powders is 20 to 70% by weight, preferably 40 to 70% by weight based on the entire toner.
It is. The toner of the present invention can be manufactured by a conventional method. That is, the above-mentioned binder resin is mixed with a colorant, magnetic fine powder, or other additives, and the mixture is dispersed for 24 hours using a ball mill, kneaded using hot rolls, etc., and after cooling, the resulting agglomerate is pulverized. The toner of the present invention is obtained by taking out particles having a desired particle size. As described above, in the toner of the present invention, the main component of the binder resin is synthesized by the emulsion polymerization method, so it is easy to manufacture and mix with a colorant, etc. Moreover, the emulsifier in the binder resin Since the content of impurities is 1.2% by weight or less, no adverse effects appear in practice, and it has sufficiently good properties and can form good visible images over many times. Examples of the present invention will be described below, but the present invention is not limited thereto. Furthermore, “department”
represents parts by weight. Example 1 [Production of binder resin] (Dispersion medium) Water 180 parts (monomer) Butadiene 10 parts Styrene 90 parts (emulsifier) Fatty acid potassium salt 2.2 parts Disproportionated rosin acid potassium salt 2.2 parts Potassium phosphate 0.4 parts ( (Polymerization initiator system) Ferrous sulfate 0.005 part Paramethane hydroperoxide 0.02 part t-dodecyl mercaptan 0.5 part The above formulation was placed in a 20 volume autoclave purged with nitrogen gas, and the emulsion polymerization method was used to adjust the temperature. The polymerization reaction was carried out at 5°C, and when the conversion rate reached 70%, 0.2 parts of polymerization terminator N,N'-diethylhydroxyamine was added to stop the reaction, so that the weight average molecular weight M _w was 110000.
A latex emulsion of styrene-butadiene copolymer was obtained. This latex contains an emulsifier and impurities produced therefrom. Collect this latex so that the solid content is 1 kg, and add 20 ml of sulfuric acid aqueous solution with a specified concentration of 0.01 N to this latex.
was added to solidify the resin while stirring. The resin obtained here contained 5.0% by weight of impurities. A portion of this resin was divided and placed in 20 degrees of warm water (temperature: 80°C), and 33 ml of a sodium hydroxide aqueous solution with a specified concentration of 12N was added to this and stirred for 20 minutes. This removed some of the impurities. Impurity removal treatment was carried out by making the material water-soluble and then washing it with water. The resin obtained here has an impurity content ratio of
It was 2.0% by weight. A portion of the resin thus obtained was divided and subjected to the same impurity removal treatment as described above to obtain a resin containing 1.2% by weight of impurities. After dividing a part of the resin in this way, the same impurity removal process was repeated two more times.
Resin containing 0.7% by weight of impurities and the same
0.3% by weight of resin was obtained. The impurity content ratio obtained as above is
5.0% by weight, 2.0% by weight, 1.2% by weight, 0.7% by weight,
Using 0.3% by weight of each of the five types of resin as a binder resin, 100 parts of the binder resin and 5 parts of the colorant carbon black were mixed and dispersed, kneaded, pulverized, and classified in a conventional manner to obtain an average particle size. Five types of toner having a diameter of 15 microns were obtained. 5 parts of each of the toners obtained here are transferred to an iron powder carrier.
95 parts to make a total of 5 types of developers, and each of them was subjected to a continuous copying test using an electrophotographic copying machine "U-Bix V" (manufactured by Konishiroku Photo Industry Co., Ltd.) to determine the number of durable copies. I asked for it. Here, the durable number of copies is determined based on the degree of fog in the copied image caused by deterioration of the toner's triboelectric charging characteristics, toner filming on the photoreceptor, which is an electrostatic image support, and the like. The degree of fog produced was defined as a fog value of 0.20, and the number of times a practically valuable copy image was formed was adopted. The results are shown in the table below.

[Table] As is clear from the results in this table, the toner of the present invention in which the content of impurities in the binder resin is 1.2% by weight or less can provide a dramatically greater number of durable copies. Example 2 The latex produced in Example 1 was sampled so that the weight of the solid content was 1 kg, and this was dropped into 20% ethyl alcohol, solidified while stirring, and the solid content was separated and washed with water. A resin containing 1.0% by weight of impurities was obtained. Using this resin as a binder resin, a toner was produced in the same manner as in Example 1 and subjected to a continuous copying test.
It was over 20,000.

Claims (1)

[Scope of Claims] 1. An electrostatic image developing toner in which the binder resin contains a polymer synthesized by emulsion polymerization using an emulsifier, wherein the polymer is an emulsion obtained by emulsion polymerization. A process of coagulating the resin by adding a coagulant to the resin and then treating the coagulated resin with an alkaline aqueous solution, or a process of coagulating the resin by adding an emulsion obtained by emulsion polymerization to a coagulation solvent. 1. A toner for developing an electrostatic image, characterized in that the content of impurities due to the emulsifier in the polymer is 1.2% by weight or less based on the binder resin.