JPH0261646A - Production of encapsulated toner - Google Patents

Abstract

PURPOSE:To improve fixability and a preservable property at a high temp. by forming the film of the resin particle layer of a resin emulsion flocculated around emulsifying liquid drops while removing the volatile solvent from the dispersion obtd. by flocculating the resin particles of a resin emulsion around the emulsifying liquid drops in the emulsifying liquid. CONSTITUTION:The resin emulsion is mixed with the emulsifying liquid obtd. by mixing and stirring the liquid dissolved or dispersed with toner components for electrophotography by the volatile solvent at <=100 deg.C b. p. and the water dissolved with an ag. water soluble high-polymer soln. to flocculate the resin particles of the resin emulsion around the emulsifying liquid drops in the emulsifying liquid. The film is formed of the resin particle layer of the resin emulsion flocculated around the emulsifying liquid drops which the volatile solvent is removed from the resulted dispersion. The surfaces of the core particles essentially consisting of the soft polymer having properties sufficient to maintain the fixability to a base are coated uniformly with the material having the high glass transition temp. or high melting point in this way, by which the fixability and the preservable property at a high temp. are improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a toner for electrostatic charge development used in electrophotography, electrostatic recording, and electrostatic printing, which can be fixed by pressure or heat under weak pressure. This relates to a manufacturing method.

(Prior Art) As a copying method using electrophotography, an electrostatic latent image is formed by various means on a photoreceptor using a photoconductive substance.
A common method is to then develop the latent image using toner, transfer it to paper, and then fix it to obtain a copy.

In this copying method, methods for fixing the toner image include a heating fixing method using an oven or a heated roll, and a pressure fixing method for fixing the toner image by applying pressure.

Nowadays, due to faster copying speed, lower power consumption, smaller size, and the spread of electrophotographic terminal printers, there are advantages such as copying without waiting time when the power is turned on, and a simple fixing device. Heat roller fixing and pressure fixing at low temperatures are becoming popular.

However, with these fixing methods, sufficient fixing performance cannot be obtained depending on the conventional toner. This is because in order to obtain sufficient fixing performance at low temperatures, it is necessary to use a material with a low Tg or low melting point as the binder resin, but this not only poses problems in the storage stability of the toner, but also causes contamination of the carrier during development. There are also problems such as fusion to the surface of the photoreceptor.

The toner used in the pressure fixing method is one that undergoes plastic deformation under a predetermined pressure (approximately 3 to 300 kg/c++1), specifically waxes such as polyethylene wax, polyolefin wax, and polyamide wax. However, among the above-mentioned waxes, those with a low softening point have a low compression yield value and good fixing properties, but they have problems in crushability during toner production, toner storage stability, etc.

It is impossible to solve these problems with toner produced by conventional pulverization methods.

Therefore, research has recently been carried out on so-called capsule-type toners, which are composed of a soft core material and a hard outer shell.

As a method for producing toner using a microencapsulation method, there is an interfacial polymerization method using a polymer synthesis reaction, 1n.
- Situ polymerization method Polymerization amount 1985-70851>, encapsulation method by spray drying using a polymer emulsion (JP-A-51-124435, JP-A-521081)
34), Spray drying method (Japanese Patent Application Laid-Open No. 1986-1990)
977), an in-liquid curing coating method that uses a method of changing the properties of polymers, and a coacervage coating method that performs phase separation from an organic or aqueous solution (Japanese Patent Application Laid-Open No. 48-80478).
), etc., but in the conventional method, the core material,
There are restrictions on the materials that can be selected as the shell material, it is difficult to form a uniform shell film, it is difficult to produce toner with a uniform particle size, and the process is complicated due to the use of organic solvents. There is.

In order to fix at low temperatures or relatively low pressure and maintain fluidity as a powder without thermal aggregation during storage or in the developing machine, it is extremely important to have a uniform capsule structure and control the shell membrane. However, it is impossible to create a toner having the above structure and performance using conventional methods, and a capsule toner that is practically satisfactory has not yet been obtained.

(Problems to be Solved by the Invention) The object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide a new manufacturing method capable of controlling a uniform capsule structure, a shell film, and a toner particle size, especially at low temperatures and/or low temperatures. It is an object of the present invention to provide a method for producing a toner that exhibits good fixing properties under pressure and has good storage stability at high temperatures.

(Another Means for Solving the Problems) The object of the present invention is to prepare a liquid in which an electrophotographic toner component is dissolved or dispersed with a volatile solvent having a boiling point of 100°C or less, and a liquid in which an aqueous solution of a water-soluble polymer is dissolved. a step of mixing and stirring to emulsify the above emulsion, a step of mixing a resin emulsion into the emulsion obtained in the emulsification step, and a step of coagulating resin particles of the resin emulsion around the emulsified droplets in the emulsion; This is achieved by a method for producing a capsule toner, which comprises a step of forming a resin particle layer of the aggregated resin emulsion around the emulsified droplets while removing a volatile solvent from the dispersion obtained in the aggregation step.

The soft substances that make up the toner components that become the core particles include:
A resin that softens at a relatively low temperature (preferably 100°C or less) and has a low melt viscosity, or under a predetermined pressure (3 to 300°C).
Resins that undergo plastic deformation at a temperature of about 1 kg/cffl are used, including styrene resins, acrylic resins, styrene acrylic resins, styrene diene resins, epoxy resins, polyester resins, polyamide resins, natural waxes, synthetic waxes, and higher fatty acids. and its derivatives, polyolefins, etc., and these may be used alone or in combination.

As the solvent for dissolving the core particles, there is used a solvent that has a lower boiling point than water, is hydrophobic, and is capable of swelling or dissolving the resin emulsion forming the shell film. For example, low-boiling halogen solvents such as methylene chloride and trichloroethylene can be used.

Water-soluble polymeric substances for emulsifying the core particle solution in water include alkyl cellulose, polyvinyl alcohol, gelatin, starch, carboxymethyl cellulose, polyacrylic acid, polymethacrylic acid, styrene-maleic acid copolymer, polyacrylamide, polyvinyl acetate, etc. These can be used alone or in combination.

As the resin emulsion constituting the shell membrane, one obtained by emulsion polymerization of vinyl monomers by a conventional method can be used. Examples of the vinyl monomer include styrene monomers such as styrene, vinyltoluene, and α-methylstyrene; acrylic acid, methacrylic acid, methyl acrylate,
Ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate,
Derivatives of acrylic acid or methacrylic acid such as 2-ethylhexyl methacrylate, dimethylaminoethyl methacrylate, acrylonitrile, and acrylamide; ethylenically unsaturated monoolefins such as ethylene, propylene, and butylene; vinyl chloride, hnylidene chloride, vinyl fluoride, etc. Vinyl halides; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone and methyl isopropenyl ketone; 2-
Examples include nitrogen-containing vinyl compounds such as vinylpyridine, 4-vinylpyridine, and N-vinylpyrrolidone. These vinyl monomers may be used alone, or a plurality of vinyl monomers may be used in combination and copolymerized. In addition, in addition to these monomers, any crosslinking agent such as aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and derivatives thereof; diethylenically unsaturated carboxylic acid esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate, N, N-
Divinyl compounds such as divinylaniline and divinyl ether and compounds having three or more vinyl groups can be used alone or in combination of two or more.

The shell substance composed of resin particles forms the outer shell of the core particle mainly composed of soft substances, prevents agglomeration during toner storage and thermal aggregation in the developing machine, and improves the fluidity of the powder. It is necessary to have the ability to maintain Therefore, it is preferable that the glass transition temperature of the shell material is 40°C or higher, and the above-mentioned seven-mer composition and molecular weight are preferably set so that the glass transition temperature of the obtained shell material polymer is 40°C or higher.

Furthermore, as another function of the shell material, it is necessary that capsule breakage occurs easily under the pressure of the fixing roll, and taking this point into consideration, styrene monomers are preferred among the above-mentioned seven monomers.

It is effective to use a suitable emulsifier when preparing a resin emulsion. Examples of the emulsifier include sodium dodecylbenzenesulfonate, sodium lauryl sulfate, dialkylsulfosuccinate, potassium oleate, and the like. These may be used alone or in combination.

The amount of emulsifier used is 0.001 to 20 parts by weight, preferably 0.01 to 10 parts by weight per 100 parts by weight of vinyl monomer.

Examples of initiators used in polymerization include persulfates such as potassium persulfate, hydroperoxides such as cumene hydroperoxide and paramenthane hydroperoxide, water-soluble initiators such as redox initiators, and peroxides. Examples include peroxides such as lauryl and benzoyl peroxide, and ab compounds such as azobisisobutyronitrile and azobisisovaleronitrile.

After the resin emulsion is mixed with a dispersion obtained by emulsifying the core particle solution with stirring, the volatile solvent is removed by heating under reduced pressure, etc., thereby obtaining a spherical toner encapsulated with the resin of the resin emulsion. This phenomenon occurs when the resin emulsion aggregates around the emulsified droplets of the core particle solution.
It is presumed that this is caused by the resin emulsion being swollen or dissolved by the volatile solvent during the process of removing the volatile solvent from the emulsified droplets of the core particle solution.

The above-mentioned film formation state differs depending on the type of water-soluble polymer adsorbed on the surface of the core particle droplet, the degree of hydration, and the degree of stability of the resin emulsion in water. Temperature in the mixing stirring system, p
Taking into account the conditions such as H, it is preferable to have resin particles present on the surface of the core particle in a submicron or smaller agglomerated particle size from the viewpoint of uniform encapsulation.

Various pigments can be used in the capsules 1-Q according to the invention. As pigments, for example, titanium oxide, zinc oxide, carbon black, and other various coloring materials can be used to produce black toners and color toners. Furthermore, by incorporating magnetic powder, it can be used as a magnetic toner.

The above-mentioned pigment may be present anywhere in the capsule toner, inside the core particle, at the core particle/outer shell interface, or in the outer shell. Additives may be included or externally added to control the adhesion to the roll. Additives include metal-containing dyes, dyes such as nigrosine dyes, carbon black, silica, cerium oxide,
Examples include fine inorganic powder such as zinc oxide, long chain fatty acids such as stearic acid and their derivatives, and fine resin powder such as fluororesin.

(Effects of the Invention) According to the production method of the present invention, a soft polymer having sufficient properties to maintain fixing properties to a support under low temperature or low pressure fixing conditions is used as the main component. The surface of the core particle is
A capsule toner having a structure uniformly covered with a substance having a high glass transition temperature or a high melting point and having a uniformly controlled outer shell thickness can be produced.

A toner having such a structure exhibits good fixing properties at low temperatures and/or low pressures, does not cause thermal aggregation during storage or in a developing machine, and has good fluidity as a powder.

(Example) Next, the present invention will be specifically explained with reference to Examples.

Parts are by weight.

Example 1 100 parts of styrene monomer was mixed and dissolved in 200 parts of water, 1 part of sodium lauryl sulfate, and 0.2 part of soda carbonate.
After stirring and emulsifying, add 0.3 parts of potassium persulfate and heat to 50°C.
The mixture was polymerized for 10 hours to obtain a resin emulsion.

A solution obtained by dissolving and dispersing 80 parts of a styrene-butyl acrylate resin with a molecular weight of 5,000 and 20 parts of carbon black in 500 parts of methylene chloride at Tg 20°C was added to a solution in which 4 parts of methyl cellulose was dissolved in 2,000 parts of water, and with strong stirring. Emulsified.

This emulsion was mixed with 300 parts of the resin emulsion with stirring to obtain a dispersion. When this dispersion was observed under an optical microscope, it was confirmed that the resin emulsion was coagulated and adhered around the emulsified droplets.

By heating the above dispersion liquid under reduced pressure, an average particle size of 11.5
A μm capsule toner was obtained. Furthermore, when the obtained particles were cut and observed with a transmission electron rJ4 microscope (TEM), it was found that a uniform film was observed around the core particles, indicating that they were complete capsule particles.

When the toner obtained by the above manufacturing method was applied to a selenium photoreceptor PPC copying machine for copying and fixed with a fixing roller at 150° C., sufficient fixing properties were obtained. Furthermore, we measured the degree of aggregation after storing this toner at 50°C for a day and night.
The degree of aggregation was less than 2%.

Example 2 A solution in which 25 parts of crystalline polyester with a melting point of 40°C and 50 parts of magnetite were dissolved and dispersed in 500 parts of methylene chloride,
A solution prepared by dissolving 4 parts of polyvinyl alcohol in 2000 parts of water was added and emulsified by strong stirring. 300 parts of the resin emulsion was mixed into the emulsion with stirring to obtain a dispersion. When this dispersion was observed under an optical microscope, it was confirmed that the resin emulsion was loosely coagulated and adhered around the emulsified droplets. By heating the above dispersion liquid under reduced pressure, an average particle size of 1
A 0.5 μm capsule toner was obtained. Furthermore, when the obtained particles were cut and observed with a TEM, it was found that an uneven film was observed around the core particles, indicating that they were capsule particles.

The toner obtained by the above manufacturing method was applied to a selenium photoreceptor PPC copying machine and copied at a pressure of 200 kg/c at room temperature.
Fixation was performed with a weight of nt. The resulting image had good fixability, no offset was observed, and was a good image without gloss. Further, this toner did not cause any aggregation after being stored at 50° C. for a day and night.

Comparative Example 1 A toner dispersion was obtained in the same manner as in Example 1 except that no water-soluble polymer was used. In the toner dispersion obtained by the above manufacturing method, a large number of resin emulsions that did not coagulate remain, and as a result of observing the cut surface of the toner with a TEM, many unencapsulated core particles were observed, and uniform capsules were formed. It turned out that no change had been made. Furthermore, agglomeration occurred in the developing machine of the PPC copying machine, and the spikes on the developing roller became uneven, resulting in copies with extremely poor image quality.

Claims (1)

[Claims] a step of mixing and stirring a liquid in which an electrophotographic toner component is dissolved or dispersed with a volatile solvent having a boiling point of 100° C. or less and water in which a water-soluble polymer aqueous solution is dissolved to emulsify;
A step of mixing a resin emulsion with the emulsion obtained in the above emulsification step and aggregating the resin particles of the resin emulsion around the emulsified droplets in the emulsion, and volatilization from the dispersion obtained in the above aggregation step. A method for producing a capsule toner comprising the step of forming a layer of resin particles of an aggregated resin emulsion around the emulsified droplets while removing a solvent.