JPH0335660B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a toner using a seed polymerization method, and more particularly, to a method for producing a capsule toner that can be fixed at low temperatures and has excellent storage stability. [Prior Art] In recent years, electrophotographic methods, electrostatic printing methods, electrostatic recording methods, etc. are used to form electrostatic images based on image information, and this is developed with developer toner to form toner images. It is widely practiced to form a visible image by transferring this toner image onto a transfer paper or the like and then fixing it. Conventionally, toner for electrostatic image development has been widely used in powder form, which is obtained by finely pulverizing a mixture of a thermoplastic resin as a binder and a colorant such as carbon black dispersed therein. If it is a two-component toner, it is mixed and stirred with a carrier such as iron powder or glass beads, or if it is a one-component toner containing fine magnetic powder, it is stirred by itself. The toner image is triboelectrically charged and the electrostatic force is used to develop an electrostatic image, and the resulting toner image is transferred, for example, and then heated and fixed using a heating roller or the like. However, in such toners, due to triboelectric charging, toner particles are crushed during agitation to produce fine powder toner, resulting in poor visible image quality or the need to replace the toner with a new one prematurely. In addition, since fixing is achieved by a heat fixing method, a long waiting time is required until the temperature of the fixing device rises to the required set temperature, and a large amount of time is required for heating. This has led to problems such as rapid deterioration of the photoreceptor and the like due to the fact that a large amount of energy is required or a high-temperature heat source is incorporated into the machine. Therefore, by lowering the temperature at which the toner softens and fixes,
If the toner is fixed at a low temperature, the above-mentioned problems will not occur, but the storage stability of the toner will be poor, and development such as blocking will easily occur at high temperatures. Therefore, there is a strong desire to develop toners that have good storage stability and are fixed at low temperatures. Conventionally, in order to meet this requirement, a so-called capsule toner, in which a toner made of a soft resin is wrapped in a hard resin, has been known. For example, JP-A-58-
It is described in No. 176642, No. 48-90977, and Japanese Patent Publication No. 53-8493. However, manufacturing using the spray drying method described in these places a burden on the manufacturing equipment, and synthesis using the coacelpation method or phase separation method has disadvantages such as limited polymer composition and the need to use a large amount of sieve. There is. Therefore, seed polymerization is a simple encapsulation method that does not use these methods. The seed polymerization method has already been described in JP-A-59-62870 and JP-A-59-61843. [Problems to be Solved by the Invention] However, the reality is that toners that are fixed at low temperatures and have good storage stability have not been obtained using known methods. Therefore, the technical object of the present invention is to provide a method for manufacturing a toner that is fixed at low temperatures and has excellent storage stability, and also to provide a method for manufacturing a toner that does not require complicated equipment. [Means for Solving the Problems] As a result of intensive research, the present inventor has developed a toner material obtained by suspension polymerizing a toner material containing a vinyl monomer (A), a polymerization initiator, and a colorant in water. In a toner manufacturing method that includes a step of suspending fine particles in water, using the fine particles as core particles, and growing the vinyl monomer (B) by adsorbing the core particles, the vinyl monomer (B) is used as the core particle. has higher hydrophilicity than the vinyl monomer (A) that forms the Tg when the vinyl monomer (B) is polymerized.
The present inventors have discovered that the above-mentioned problems can be solved by a method for producing a toner for hot roller fixing, which is characterized in that Tg is higher than the Tg of the resin in the core particles, and the present invention has been achieved. In other words, it is an extremely easy idea to use fine particles (toner) containing a soft resin as seeds and wrap them in a polymer with a higher Tg, so that the monomer is dropped and the particles grow. However, the added vinyl monomer penetrates into the inside of the particles, and as a result, there is a possibility that a clear core-shell structure may not be formed, or even that the core and wall may be reversed. For example, Tsunetaka Matsumoto et al.
According to 2007), when emulsion polymerized ethyl acrylate (particle size approximately 0.1 μm) is used as a core and styrene is added dropwise to grow particles, the resulting particles are formed using polystyrene as a core in the opposite order of addition. , it is reported that polyacrylate was used as the exterior wall. If methyl methacrylate, which has approximately the same hydrophilicity as polyethyl acrylate, is used instead of styrene as a monomer to be added later, in the order of addition,
It has been reported that particles with polyethyl acrylate in the core and methyl methacrylate in the outer wall are formed. As a result of conducting research with reference to this report, the present inventor found that toner particles with a diameter of 5 to 15 μm exhibited similar effects, and that a monomer with a higher Tg and higher hydrophilicity than the core material was used in soft particles. By adsorbing the toner and carrying out seed polymerization, it was possible to obtain a toner that can be fixed at a low temperature and has good durability, leading to the present invention. The present invention will be explained in detail below. The core particles used in the present invention contain a resin and a colorant. As the coloring agent, dyes, pigments, magnetic substances, etc. are used, and in the case of a two-component developer using a toner and a carrier, a paint or a pigment is used, and a magnetic substance may be added if necessary. Further, in the case of a one-component developer that does not use a carrier, it is necessary to use a magnetic material to make a one-component magnetic toner. Specific examples of dyes and pigments include carbon black, nigrosine dye (CI No. 50415B), aniline blue (CI No. 50405), calco oil blue (CI No. azoicBlue3), and chrome yellow (CI
No.14090), Ultramarine Blue (CINo.
77103), DuPont Oil Red (CINo.26105),
Orient Oil Red #330 (CINo.60505). Quinoline Yellow (CINo.47005), Methylene Blue Chloride (CINo.52015), Phthalocyanine Blue (CINo.74160), Malachite Green Oxalate (CINo.42000), Lamp Black (CINo.
77266), rose bengal (CI No. 45435), oil black, azo oil black, and others can be used alone or in combination. These colorants are used in toner as a final product.
It may be contained in a proportion of about 3 to 20% by weight. Magnetic materials include ferrite, magnetite, iron, cobalt, nickel, and other ferromagnetic metals or alloys, or compounds containing these elements, or materials that do not contain ferromagnetic elements but can be made by applying appropriate heat treatment. Mention may be made of alloys which become ferromagnetic over time, such as alloys of the type called Heusler alloys containing manganese and copper, such as manganese-copper-aluminum, manganese-copper-tin, or chromium dioxide, among others. Specifically, as magnetite, EPT-
1000, EPT-500, MRMB-450 (manufactured by Toda Kogyo Co., Ltd.), BL-100, BL-120, BL-200, BL-
220, BL-500, BL-520, BL-SP, RB-BL,
RB-20 (manufactured by Titanium Kogyo Co., Ltd.) and the like are preferably used. These colorants may be added not only to the core particles but also dissolved in the vinyl resin monomer added later. As the resin contained in the core particles, thermoplastic resins such as polyethylene, polypropylene, vinyl acetate, ethylene-vinyl acetate copolymer, polyester, and vinyl resin are preferably used, and the glass transition point of the thermoplastic resin is 50°C or lower. is preferred, and more preferably 40°C or lower. The optimum toner for pressure fixing is one with a temperature of -30°C to 40°C. The Tg of the vinyl resin added later and used as the outer wall is
The temperature is preferably 60°C or higher, preferably 70 to 120°C. In the case of vinyl resin, Tg can be substituted with an approximate solution obtained based on the values listed in polymer handbooks, etc., without relying on actual measurements. For example, in the case of styrene-ethyl acrylate copolymer (70:30 volume ratio), St (Tg 100°C) and EA (Tg -24°C) are calculated using the volume ratio to give a Tg of 62.8°C. Examples of vinyl monomers include styrene, p-methylstyrene, p-tert-butylstyrene, p-methoxystyrene, p-phenylstyrene, 3,4
-dichlorostyrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-acrylate
-Octyl, dodecyl acrylate, acrylic acid 2
-ethylhexyl, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate,
methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate,
Examples include lauryl methacrylate, stearyl methacrylate, and phenyl methacrylate. The glass transition point and degree of hydrophilicity may be adjusted by combining these monomers. Further, a portion of the vinyl resin contained in the core particles may be crosslinked using a crosslinking agent such as divinylbenzene or ethylene glycol dimethacrylate. Alternatively, a graft polymer may be obtained by polymerizing in the presence of liquid butadiene or unsaturated polyester. Furthermore, a wax such as low molecular weight polyethylene or carnauba wax, or a release agent such as silicone oil (to prevent part of the melted toner from adhering to the surface of the fixing roller) may be added to the core particles. The present invention is a seed polymerization method in which core particles are suspended in water and monomers are added afterwards. Dispersion stabilizers may be used to stably suspend the core particles. An activator or an inorganic fine powder can be used for this purpose.
For example, sodium dodecylbenzenesulfonate,
Active agents such as sodium pentadecyl sulfate, sodium octyl sulfate, sodium allyl-alkyl-polyether sulfonate, sodium laurate, sodium caprylate, calcium oleate, tricalcium phosphate, barium sulfate, aluminum hydroxide, silica, etc. There is an inorganic fine powder. To make the core particles, a vinyl monomer is mixed with a colorant using a suspension polymerization method (for example, Japanese Patent Application Laid-Open No. 57-229641).
If the method described in Japanese Patent No. 57-233363 is adopted, the seed polymerization step can be carried out continuously, which is advantageous in terms of synthesis. Examples of the vinyl monomer added later after the core particles are dispersed in water include the above-mentioned vinyl monomers, but the Tg must be higher than that of the resin of the core particles, preferably 60°C or higher. Since they are more hydrophilic than the resin used for the core particles, copolymers mainly containing methyl methacrylate, ethyl methacrylate, methyl acrylate, acrylonitrile, p-cyanostyrene, styrene, etc. are preferred. Here, hydrophilicity is relative compared to the resin of the core particle. For example, when the core particle is made using a hydrophobic monomer such as 2-ethylhexyl acrylate, it is Even substances that are generally known as hydrophobic substances can be used in the present invention as they have relatively high hydrophilicity. The hydrophilicity of the monomer added later should normally be compared with that of the resin in the core particle, but it is necessary to compare the hydrophilicity of the monomer constituting the resin contained in the core particle and the monomer added later. Can be compared and substituted.
Relative hydrophilicity can be compared based on the solubility of each monomer in water, but Hansh
(Chem Reviews Vol 71.525 (1971), Taneichi Kubota, Hiroshi Terada et al. (Chemistry Domain Increase No. 122, "Structure-Activity Relationships of Drugs"), calculated from the hydrophobic parameter π value of each substituent. partition coefficient by
It is also possible to obtain logP and use that instead. Here, the distribution coefficient P is defined as follows. P=Co/Cw Co=concentration of substance in n-octanol phase Cw=concentration of substance in aqueous phase In other words, it is the distribution coefficient of a certain substance when an equilibrium state between n-octanol and water is reached. The difference _{π π _ _}

〔Example〕

Examples of the present invention will be described below, but the embodiments of the present invention are not limited to these. Example 1 Styrene (Tg 100℃) 95g, 2-ethylhexyl acrylate (Tg - 50℃) 70g, carbon black "MONARCH880" (manufactured by Kayabot Corporation) 15
5 g of 2,2'-azobis(2,4-dimethylvaleronitrile) were mixed and dispersed using a sand stirrer to obtain a polymerizable composition. This was added in an amount of 15% by weight to an aqueous colloid solution containing 2% by weight of calcium phosphate and 0.02% by weight of sodium dodecylbenzenesulfonate, and the particle size was adjusted to 6 to 12 μm using a TK homogiator (manufactured by Tokushu Kika Kogyo Co., Ltd.). to obtain a suspension. This suspension was then heated to 60°C.
was heated for 20 hours to polymerize and obtain a dispersion of core particles. Next, add 1.0g of benzoyl peroxide to this.
35 g of styrene dissolved therein was added dropwise at 80° C. over 3 hours, and the reaction was continued for an additional 10 hours to complete the polymerization. After cooling, it was treated with hydrochloric acid, filtered and washed, and dried to obtain a toner. A developer consisting of 2 parts of this toner and 100 parts of iron powder carrier was prepared, and U-Bix V
An unfixed toner image was obtained using a modified machine (manufactured by Konishiroku Photo Industry Co., Ltd.). A heat roller whose surface layer is made of Teflon (manufactured by Dapon, polytetrafluoroethylene) and a silicone rubber surface layer "KE-1300RTV" are used.
(manufactured by Shin-Etsu Chemical Co., Ltd.) at a linear speed of 120 mm/sec while changing the temperature of the heat roller every 10 degrees Celsius. A fixed image was obtained. Further, no aggregation was observed even when this toner was left at a high temperature of 55° C. and 60% humidity for 2 hours. Comparative example 1 Styrene 130g, 2-ethylhexyl acrylate 70g, carbon black "MONARCH880"
(manufactured by Kyabot Co., Ltd.) 15g, 2,2'-Azobis (2,
5 g of 4-dimethylvaleronitrile) and 1.0 g of benzoyl peroxide were added and dispersed with a sand stirrer, followed by dispersion with a calcium phosphate dispersion, and suspension polymerization was performed. After reaction at 60℃ for 20 hours,
React at 80℃ for 10 hours, add hydrochloric acid after cooling,
A toner was obtained by filtering and washing with water. When this toner was evaluated in the same manner as in Example 1, it was found that although it was fixed at 120°C, aggregation of the toner was observed after 2 hours at a high temperature of 55°C. Comparative Example 2 100g of styrene, n-butyl acrylate (Tg
-54℃), 15 g of carbon black "MONARCH880", and 5 g of 2,2'-azobis(2,4-dimethylvaleronitrile) were mixed and dispersed using a sand stirrer, and suspended in a calcium phosphate dispersion in the same manner as in Example 1. Turbid polymerization occurred. 60℃
After 20 hours reaction with benzoyl peroxide 1.0
35 g of styrene dissolved in 10 at 80℃
After reacting for a period of time, the mixture was treated with hydrochloric acid and washed with water to obtain a toner. When this toner was evaluated in the same manner as in Example 1, it was found that although fixation was achieved at a roller temperature of 120°C,
In an environmental resistance test at 55°C for 2 hours, toner aggregation was observed. Comparative Example 3 Composition of the resin in Comparative Example 1 (130 g of styrene,
70g of 2-ethylhexyl acrylate), 155g of styrene, 45g of 2-ethylhexyl acrylate
I got toner instead. Although this toner showed no aggregation in the environmental resistance test (55°C and 60% humidity for 2 hours) as in Example 1, a satisfactory fixed image could not be obtained unless the temperature of the heat roller exceeded 150°C. Nakatsuta. Example 2 A toner was obtained by carrying out the same operation as in Comparative Example 2 except that 35 g of styrene was replaced with a mixture of 20 g of styrene and 15 g of methyl methacrylate (Tg 113° C.). This toner is 120℃
It gave a good fixed image, and no aggregation occurred in the environmental resistance test.

Claims (1)

[Claims] 1 Fine particles obtained by suspension polymerizing a toner material containing a vinyl monomer (A), a polymerization initiator, and a colorant in water are suspended in water, and this is used as a core particle. In the method for producing a toner, the vinyl monomer (B) has higher hydrophilicity than the vinyl monomer (A) forming the core particles, and A method for producing a toner for thermal roller fixing, characterized in that the Tg when the vinyl monomer (B) is polymerized is higher than the Tg of the resin in the core particles.