JPH035762A - Microcapsule toner and its manufacturing method - Google Patents

Abstract

PURPOSE:To prevent the flocculation and coalescence of the formed capsules by using a core material subjected to a surface reforming by fine inorg. particles specified at the isoelectric point. CONSTITUTION:A shell material is electrostatically charged positive in a phase sepn. process and the pH of the system is an acidic region to neutral region. The fine inorg. particles exhibiting negative chargeability in the deposition pH region of the resin forming the shell material, i.e., the fineinorg. particles having the isoelectric point in at least the acidic pH region (<=7.0 pH) are, therefore, made to exist on the surface of the core material at a certain cover ing rate by noticing the isoelectric point of the fine inorg. particles (the particles are positive-charged in the pH region below the non-load point: isoelectric point and are negative-charged in the pH region above the isoelectric point). The flocculation or coalescence of the formed capsules is obviated and the covering property is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a microcapsule toner used in electrophotography, electrostatic printing, magnetic recording, etc. Relating to a manufacturing method.

[Prior Art] Toner used in the above-mentioned recording methods including electrophotography is produced by pulverizing a molten mixture of a conventional binder resin and a coloring material (and/or a magnetic material if necessary). As an alternative to the so-called pulverized toner, a capsule-type toner with a core made of a material with good fixing properties and a hard resin shell with excellent developability surrounding it is used, mainly for the purpose of improving pressure fixing properties. Various toners have been proposed.

For example, there are capsule toners having a soft material as a core material, as disclosed in Japanese Patent Publication No. 54-8104, and soft resin solution core capsule toners disclosed in Japanese Patent Application Laid-Open No. 51-132838.

On the other hand, in recent years, instead of the heat fixing method, a method of fixing toner using pressure has been attracting attention.

This pressure fixing method does not require a heat source, saves energy, simplifies the device, enables instant copying when the power is turned on, and poses no risk of fire.

This pressure fixing method has drawbacks such as the need to increase the strength of the fixing device, which makes the machine heavy, and the resulting fixed image's fixed surface becomes glossy and paper wrinkles. Therefore, microcapsule toners are being considered that allow for lighter pressure fixing and do not cause problems such as aggregation and fusion.

However, materials that are suitable as toner materials are not necessarily suitable as materials for microcapsule toners. difficult to grant. This difficulty in material selectivity causes problems such as defects in the capsule coating membrane and insufficient mechanical strength of the coating membrane.

The importance of coating microcapsule toners has been emphasized in various development systems. A decrease in the coverage of microcapsule toner results in uneven and unstable charging characteristics.
As a result, a good charging state of the toner particles cannot be achieved. Furthermore, toner aggregation due to seepage of the soft core material and surface protrusion,
This may cause fusion. Furthermore, if the mechanical strength of the capsule membrane is insufficient, the wall material of the microcapsule toner will peel off due to the impact force received during the development process, which will adversely affect the development.

Conventionally, a number of encapsulation production methods have been proposed to solve these problems. For example, spray dryer method, electrostatic coalescence method, submerged drying method, interfacial polymerization method, phase separation method,
In-situ polymerization methods and combinations thereof are disclosed.

The above-mentioned phase separation method is a solution in which the shell material is solubilized using a so-called "good solvent" that exhibits sufficient solubility for the shell material. "Good solvent"
This is a method in which the shell material, which has been dissolved in a good solvent, is precipitated by adding a compatible "non-solvent" and is further coated on the surface of the core particle.

[Problems to be Solved by the Invention] In the above phase separation method, it is essential that the binder constituting the core particles does not dissolve in the good solvent during the process of dispersing the core particles in the good solvent.

If part of the core material were to dissolve in a good solvent, the core material would be mixed into the resulting shell film, resulting in destabilization of the triboelectric properties of the toner and contamination of the sleeve, which is the toner carrier. When the shell material is precipitated by the action of a non-solvent, the so-called free shell, which is composed only of the shell material with high triboelectric charging properties, is likely to cause fogging in the developing process and unevenness of the toner layer on the sleeve. In the phase separation method, the selection of a good solvent and non-solvent for the shell material, as well as the properties of the core material surface relative to the shell material, are important. It is important to.

Another object of the present invention is to provide excellent coating properties without agglomeration or coalescence, no generation of free shells, excellent functional separation, and low cost and reproducibility (productivity). An object of the present invention is to provide a method for producing toner.

Another object of the present invention is to provide a capsule toner that has excellent charging characteristics, maintains its initial characteristics even when used continuously for a long period of time, and is free from toner aggregation, fusion, and image density reduction.

[Means and effects for solving the problems] The capsule toner of the present invention was developed to achieve the above-mentioned object, and is composed of core particles and a shell material covering the core particles. It is characterized by the presence of inorganic fine particles having an isoelectric point of pl+7.0 or less near the surface of the material.

The capsule toner manufacturing method of the present invention is characterized in that the shell material is precipitated and coated on the surface of the core particle by utilizing the equilibrium between the protonated product and the aprotonated product of the shell material. More specifically, there is a dispersion step in which core particles coated with the inorganic particles are dispersed in an aqueous medium in which the shell material is dissolved in an acidic PL+ region, and the pi of the dispersion obtained in the above dispersion step is This method is characterized by comprising the step of coating the surface of the core particle with the shell material by changing the pit region from the core particle to the pit region where the shell material precipitates.

According to the research conducted by the present inventors, it has become clear that the characteristics of the capsule shell material, the core material surface, and the encapsulation solvent are important factors in determining the coverage of the capsule membrane.

The microcapsule toner of the present invention focuses on the properties of the core material surface, and by surface-modifying the core material particle surface with inorganic fine particles having an isoelectric point of pH 7.0 or higher, the coverage of the capsule film is dramatically improved. This is a groundbreaking thing.

The method for producing microcapsule toner of the present invention is based on acidic pH.
This method is characterized by the use of a vine shell material that undergoes protonation in the aqueous medium and dissolves in an aqueous medium, and encapsulation is performed by changing p) l toward alkalinity up to the pH region where the shell material precipitates. be. That is, before the pH range where the shell material undergoes phase separation and coacervation droplets (droplets of the shell material) are generated, it is considered that the material that receives proton addition is positively charged. It is thought that the phase-separated shell material becomes unstable in the medium as the polarity (pH) of the medium (encapsulation solvent) changes, and it adheres to the core surface and solidifies.

However, this phase lI! It is very difficult to control the adhesion of the shell material to the core surface due to a number of factors such as the polarity of the solvent at about 1A, its rate of change, and the rate of change.

Therefore, in the encapsulation method of the present invention, the present inventors created an electrostatic effect between the shell material and the core surface to improve the adhesion of the shell material to the core surface. It has been found that this method improves the properties and prevents the occurrence of free shells.

As described above, in the capsule toner manufacturing method of the present invention, the shell material is positively charged during the phase separation process. Also, as a system, 1. pH is in the acidic to neutral range. From this, it can be seen that in the pHlE range below the isoelectric point (no charge point, second isoelectric point) of inorganic fine particles, the particles are positively charged, and at the pH point above the isoelectric point.
Focusing on inorganic fine particles that are negatively charged in the pl+ region where the resin that is the shell material is precipitated, i.e., at least in the acidic pH 1i region (pH 7,
It has become clear that the above-mentioned electrostatic effect can be obtained by allowing a material having an isoelectric point (0 or less) to exist on the surface of the core material at a certain coverage rate.

As the bad material used in the present invention, any soft solid substance that exhibits favorable fixing properties can be used. Such substances include waxes (beeswax, carnauba wax, microcrystalline wax, etc.), higher fatty acids (stearic acid, valmitic acid, lauric acid, etc.), higher fatty acid metal salts (aluminum stearate, lead stearate, stearin). barium acid, magnesium stearate, zinc stearate, zinc palmitate, etc.), higher fatty acid derivatives (methyl hydroxystearate, glycerol monohydroxystearate, etc.), polyolefins (low molecular weight polyethylene, low molecular weight polypropylene, polyethylene oxide, polyisobutylene, polytetrafluoroethylene, etc.), olefin copolymers (ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-chloride) vinyl copolymer, ethylene-vinyl acetate copolymer, ionomer resin, etc.), styrenic resin (low molecular weight polystyrene, styrene-butadiene copolymer (monomer I! amount ratio 5-30:95-7)
o), styrene-acrylic compound copolymer, etc.), epoxy resin, polyester resin (acid value 1O or less), rubbers (isobutylene rubber, nitrile rubber, chlorinated rubber, etc.)
, polyvinylpyrrolidone, polyamide, coumaron-indene resin, methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, phenol-modified terpene resin, silicone resin, etc., and these can be used alone or in combination. .

The core material of the capsule toner of the present invention generally contains various dyes and pigments as colorants. Examples of such dyes and pigments include carbon black, nigrosine dye,
Lamp Black, Sudan Black SM, First Yellow G1 Benzidine Yellow Pigment Yellow
India First Orange, Irgazine Red, Paranitroaniline Red, Toluidine Red, Carmine FB, Permanent Bordeaux FRR, Pigment Orange R1 Lysol Red 2G, Lake Red C, Rhodamine FB, Rhodamine B Lake, Methyl. Violet B Lake, Phthalocyanine Blue Pigment Blue Brilliant Green B1 Phthalocyanine Green, Oil Yellow GG, Zapon Fast Yellow CGG, Kayaset Y963, Kayaset YG
, Sumiblast Yellow GG, Zapon First Orange RR, Oil Scarlet, Sumiblast Orange G1 Orazole Brown B, Pomelo First Scarlet CG, Eisenspiron Red BEH, Oil Pink OP, etc. can be applied.

Since the microcapsule toner of the present invention is used as a magnetic toner, magnetic powder may be contained in the core material. As such magnetic powder, a substance that is magnetized when placed in a magnetic field is used. These include powders of ferromagnetic metals such as iron, cobalt, and nickel, or alloys and compounds such as magnetite, hematite, and ferrite. The content of this magnetic powder is preferably 15 to 180 i% based on the weight of the toner.

Furthermore, 50 to 150 parts is preferable.

The core particles used in the present invention can be manufactured using the materials described above and by various manufacturing methods.

Such core particle manufacturing methods include, for example, the electrostatic nization method described in JP-A-58-216736, which applies a DC voltage and discharges the core material from a disk atomizer, and the core particle manufacturing method using a two-fluid nozzle. JP-A-59-12 to form
The melt spray method described in JP-A No. 0263, and the suspension granulation method described in JP-A-59-127062, which involves granulation in an aqueous medium, are preferably used. The method is not limited.

The average particle size of the core particles used in the present invention is preferably 0.4 to 99 μm, more preferably 4 to 19 μm, as a volume average particle size.

According to the present invention, inorganic fine particles are externally added to the core material particles obtained as described above, and the inorganic fine particles are attached to the surface of the core material particles.

The inorganic fine particles used in the present invention include titanium dioxide,
Any inorganic fine powder having an isoelectric point of pH 7.0 or lower, such as chromium oxide, silica, manganese oxide, and tungsten oxide, can be used.

However, since the same structure differs depending on the isoelectric ignition, the manufacturing method of the inorganic fine powder, the manufacturer, the raw material, the place of production, etc., it is necessary to measure it in advance. The method is as follows:
Examples include potentiometric titration, Zeku potential, etc., and the p++ value at which the inflection point of the potentiometric titration curve becomes zero, the zeta potential, can be regarded as the isoelectric point.

Further, the size of the inorganic fine particles is preferably smaller than that of the core particles, and those having a specific surface area of 50 to 400 m''/g by the BET method using N2 adsorption are preferably used.

In the present invention, these inorganic fine particles are externally added and mixed using a coffee mill grinder, Henschel, etc. powder temperature mixing, a grinder, a surface modification device, a bipridizer-atomizer, etc. The amount added is approximately 30% of the core material surface.
The amount that can cover the above is preferably 0601 to 60% by weight based on the weight of the core material, although it depends on the particle size of the inorganic fine particles.
It is preferably about 1.0 to 10% by weight and the coverage is more preferably 60% or more.

By such external addition mixing operation, the inorganic fine particles are attached to the core particles in a state where they are embedded in the surface or surface layer.

As a method for causing the inorganic "!L-through-particles to be present on the surface of the core material, other methods that occur during the granulation process may be used.

On the other hand, as the shell material used in the present invention, one should be selected that has good mechanical strength and thermal properties, and has excellent triboelectric charging properties when formed into a toner. In addition, the shell material used in the present invention is limited to those that form a proton adduct with a base and have the property of being soluble in an aqueous solvent.

Specifically, resins composed of the following monomers can be used.

Methacrylic acid N,N-dimethylaminoethyl ester (
DM), acrylic acid N, N-dimethylaminoethyl ester, methacrylic acid N, N'-diethylaminoethyl ester (DE), acrylic acid N, N-diethylaminoethyl ester, acrylic acid N, N-dibutylaminoethyl ester, methacrylic acid Nitrogen-containing aliphatic molecules such as filN, N-dibutylaminoethyl ester (D[l), methacrylic acid 2-piperidinoethyl ester, and acrylic acid 2-piperidinoethyl ester are preferably used.

Also, vinylpyridine, vinylcarbazole, 5-ethyl-2-vinyl and lysine, 2-methyl-5-vinylpyridine, N,N-divinylaniline, trans-1,2-bis(2-pyridyl)ethylene, 2-vinyl quinoline, 2
-(N,N-dimethylamino)-4-vinylpyrimidine, 4-vinylpyrimidine, 3-cinnamoylpyridine,
Nitrogen-containing aromatic monomers such as 4-methacryloxybenzylideneaniline, diallylmelamine, 2,4-dimethyl-6-vinyl-triazine, 4,6-diami2-vinyltriazine, and N-vinylimidazole are also preferably used.

Examples of monomers that can be combined with the above-described monomers to form a copolymer include the following.

Styrene (St), α-chlorostyrene, α-methylstyrene, allylbenzene, phenylacetylene, vinylnaphthalene, 4-methylstyrene, 2,4-dimethylstyrene, 3-ethylstyrene, 2,4-diethylstyrene, 2- Methoxystyrene, 4-chlorostyrene, 4-
Aromatic polymers such as fluorostyrene, 3-iodostyrene, 4-cyanostyrene, 3-nitrostyrene, etc.
Or ethylenically unsaturated monoolefins such as ethylene, propylene, isoprene (IP), butadiene (BD), butylene, and isobutylene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride: vinyl acetate , vinyl esters such as vinyl propionate and vinyl benzoate; methyl methacrylate (MMA
) Ethyl methacrylate, propyl methacrylate, n-butyl methacrylate (HMA), isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate (2Ell^
), stearyl methacrylate, phenyl methacrylate,
Methyl acrylate, ethyl acrylate, n-acrylate
Acrylic acids or methacrylates such as butyl (B^), isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, etc. Acid esters; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; acrylonitrile (8N
), acrolein, acrylamide, maleic anhydride (
M^), aliphatic vinyl polymers such as timer acid, etc. are preferably used.

Furthermore, the shell material used in the present invention is not limited to the above-mentioned resin composed of 1,000 yen, but may also include polyester, polycarbonate, polysulfonate, polyamide, polyurethane, polyurea, epoxy resin, rosin, Homopolymers or copolymers of modified rosins, Derben resins, phenolic resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, melamine resins, polyether resins such as polyphenylene oxide, or thioether resins, etc. It is also possible to use combination.

More preferable examples of the shell material used in the present invention include St-MMA-DM copolymer, St-MMA-D
Ternary copolymers such as E copolymer and 5t-2EII^-DM copolymer; St-MMA-2EIIA-DM copolymer, St-MMA-BMA-D&l copolymer, St-MM
A-BD-DM copolymer, St-MMA-IP-DM copolymer, St- to N-MM^-DM copolymer, etc., quaternary elements in which the function (C) is composed of two 1,000 units. Examples include copolymers.

Further, the average particle size (volume average particle size) of the encapsulated toner in the present invention is usually 0.5 to 100 μm, preferably 5 to 20 μm.

In the present invention, the above-described shell material is provided in the state of a solution dissolved in an aqueous medium set in an acidic pl+ region for the coating process of the core particles.

In the encapsulation step, in addition to removing the base in the aqueous medium, the pl+ of the system is changed to the p11 region where the shell material becomes insoluble (deprotonation), and the shell material is precipitated to cover the core material.

The aqueous medium used in the present invention is preferably a highly polar solvent that dissolves the shell material as a protonated product in the presence of a base. Specifically, a mixed solvent of the following solvents and water is used. can do.

Glycerin, ethylene glycol, methanol, ethanol, propylene glycol, furfuryl alcohol,
Examples include benzyl alcohol, n-propyl alcohol, allyl alcohol, isopropyl alcohol, cyclohexanol, and butyl alcohol. These solvents and water are mixed and used within a compatible range.

As the acidic substance used in the present invention, inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, and succinic acid can be used.As the basic substance used in the present invention, sodium hydroxide can be used. Inorganic bases such as , potassium hydroxide, calcium hydroxide, and aqueous ammonia, and organic bases such as ethylenediamine, diethylenetriamine, and triethylenediamine are preferably used.

[Examples] The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto.

Example 1 The core material is Hiwax 200P (manufactured by Mitsui Petrochemicals) 2
0 parts, 80 parts of paraffin wax 155 (Japanese Ruso), and 5 parts of phthalocyanine blue were melted and mixed at 150°C.
After granulation with a spray dryer, dry classification yielded spherical particles with a particle size of 10.3μ±5.0μ.

To 1 kg of the core material, 20 g of wood-philic silica having an isoelectric point of PB4.2 (actually measured by potentiometric titration) was externally added and mixed using a Henschel mixer model 10B (Mitsui Miike Seisakusho) at a scale of 10 for 2 minutes.

When the core material obtained here was observed with an electron microscope, it was found that silica was uniformly adhered to the surface of the core material, and its coverage was good.
, N-dimethylaminoethyl ester copolymer.

The aqueous medium used for encapsulation was a 1:2 mixed solvent of water and ethanol, and acetic acid was added as an acid to dissolve the shell material.

Here, as a base, 0. IN-sodium hydroxide was gradually added dropwise to phase separate the shell material and cover the core material to obtain a capsule toner.

Moreover, the precipitation p11 region of this shell material is pl+6.2 to 7
．． 0, and the zeta potential of the core material coated with silica fine powder in this pt+ region was negative. When the microcapsule toner obtained as described above was observed using an electron microscope, it was found that the capsule film had complete coverage and no free shells were generated. Further, when this toner and carrier were mixed and an image was produced, the image obtained was good and the toner was also excellent in durability.

Example 2 A capsule toner was obtained in the same manner as in Example 1, except that titanium oxide with an isoelectric point of pH 6.5 was used as the core surface modifying material.

The obtained microcapsule toner had the same characteristics as in Example 1.
The coverage of the capsule membrane was good, and no free shells were observed. Further, when image printing was carried out, the obtained image was good. It also had excellent durability.

Example 3 A capsule toner was obtained in the same manner as in Example 1, except that hydrophobic silica having an isoelectric point of pH 5.5 was used as the core surface modifying material.

The obtained microcapsule toner had the same characteristics as in Example 1.
The coverage of the capsule membrane was good, and no free shells were observed. Further, when image printing was performed, the obtained image was good. °The toner also had excellent durability.

Example 4 As a core material surface modification material, manganese oxide with an isoelectric point p old, 0 was used at a concentration of 4.0% per 1 kg of core material! A capsule toner was obtained in the same manner as in Example 1 except that i amount % was used.

The obtained microcapsule toner had the same characteristics as in Example 1.
The capsule membrane had excellent coverage and no free shells were observed. Further, when image printing was carried out, the obtained image was good. The toner also had excellent durability.

Comparative Example 1 As a surface-modified inorganic fine powder for the core material, the isoelectric point is 11 II
Example 1 except that alumina of 9 and 5 was used.
Encapsulation was performed in the same way.

The microcapsule toner obtained as a result had poor coverage, and as a result of zero-image printing with free shells, the resulting image had low density, poor image quality, and poor durability. It was also inferior to

[Effects of the Invention] As described above, according to the present invention, in phase separation method encapsulation using equilibrium between protonated and aprotonated products of the shell material, the surface of the core material is inorganic with an isoelectric point pl+7.0 or less. By using a core material surface-modified with fine particles, it is possible to provide a microcapsule toner with excellent coating properties, no generation of free shells, and excellent functional separation due to the aggregation and coalescence of the capsules produced.

Claims (2)

[Claims] (1) A microcapsule toner comprising a core material and a shell material covering the core material, and inorganic fine particles having an isoelectric point of pH 7.0 or less are present near the surface of the core material. (2) A dispersion step of dispersing core material particles coated with inorganic particles with an isoelectric point of pH 7.0 or less in an aqueous medium in which the shell material is dissolved in an acidic pH region, and the dispersion obtained in the dispersion step. A method for producing a microcapsule toner, comprising the step of coating the surface of core particles with a shell material by changing the pH of the liquid to a pH range in which the shell material precipitates from the dispersion.