JPH0364767A - Production of polymerized toner - Google Patents

Abstract

PURPOSE:To stably maintain a polymn. system and to obtain the optimum grain size, satisfactory triboelectric chargeability and moisture resistance, high image density and a stable image by using modified starch as a suspension stabilizer. CONSTITUTION:Modified starch is used as a suspension stabilizer. In general, starch has characteristics of colloid and the viscosity of an aq. starch soln. is relatively high. When a polymerized toner is produced by suspension polymn., starch covers liq. particles having complex viscoelastic characteristics like protective colloid and prevents the aggregation of the liq. particles in the middle and final stages of polymn. in which the stability of the polymn. system is lowest. By modifying starch, the performance of a surfactant is rendered and suspension stabilizing ability by which the liq. particles are kept stable in the desired particle size until polymn. is finished can be rendered. The polymn. system can stably be maintained and the optimum grain size, satisfactory triboelectric chargeability and moisture resistance, high image density and a stable image are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a polymerized toner produced by suspension polymerization.

[Prior Art] Conventionally, toners used in electrophotography are produced by kneading additives such as a coloring agent such as carbon black and a charge control agent in a thermoplastic resin and uniformly dispersing the mixture. It is manufactured by the so-called pulverization method, in which the toner is pulverized using a pulverizer and classified into particle sizes suitable for toner using a classifier. Toner produced by this pulverization method has several problems.

That is, in a toner manufactured using this pulverization method, the material must have brittleness so that it can be easily pulverized to some extent. However, the use of such brittle materials causes the problem that the toner is too finely powdered. As a result, in order to finally obtain a toner with an appropriate particle size distribution, a large amount of fine powder must be removed, which increases manufacturing costs.

Further, such toner may be further pulverized in the developing device of a copying machine during the process of continuous copying, which poses a practical problem. In addition, if a material with a low melting point or pressure fixing material is used for the toner in order to improve heat fixing properties, the toner may fuse in the crushing device or classification device, making continuous production impossible. cause problems.

In order to solve these problems of the pulverization method, a polymerized toner has been proposed in which the toner is directly produced by polymerizing polymerizable monomers using a suspension polymerization method (Japanese Patent Publication No.
-14895, JP-A No. 57-53756, etc.).

When obtaining a toner by a conventional general suspension polymerization method, a monomer composition containing at least a polymerizable monomer and mainly carbon black as a colorant is combined with a water-miscible monomer composition containing a suspension stabilizer. The polymerization initiator is granulated to the toner particle size using an appropriate stirrer in a medium, etc., and the radicals generated when the previously added polymerization initiator or the newly added polymerization initiator is decomposed by heat. Polymerizable monomers are polymerized to form a polymer to produce a polymerized toner. In other words, since this suspension polymerization method does not include a pulverization step, the polymerized toner does not need to be brittle, and since its shape is spherical, the polymerized toner has excellent fluidity and has uniform triboelectric charging properties. It has certain characteristics.

However, in the production of polymerized toner by suspension polymerization, the dispersed phase (monomer phase) contains at least a colorant in addition to the polymerizable monomer, and further contains polymerizable monomers such as a charge control agent and a low molecular weight wax. Because the droplets of the monomer composition contain toner constituents that are insoluble in the toner, the viscoelastic properties of the monomer composition during the polymerization process change in a complicated manner due to the dispersibility and polymerization inhibition of these toner constituents, and furthermore, the toner composition Since the desired particle size is approximately 5 to 20 μm, the behavior is completely different from that of suspension polymerization, which has conventionally been carried out industrially. Therefore, when producing a polymerized toner by a suspension polymerization method, selection of a suspension stabilizer becomes an important issue. In other words, the suspension stabilizer has a large effect on the particle size, particle size distribution, yield, post-processing method, etc. In particular, the suspension stabilizer stabilizes droplets having a desired particle size in the toner until the end of polymerization. It has been determined that there is a need for a suspension stabilizer that has a large suspension stabilizing ability and is also easy to remove after polymerization, that is, has good washability. Conventional suspension stabilizers include, for example, polyvinyl alcohol, poly(meth)acrylic acid and salts thereof, polystyrene sulfonic acid and salts thereof, water-soluble polymers such as casein and gelatin, calcium carbonate, tertiary calcium phosphate, metal powder, etc. Although inorganic solid fine powders and the like have been used, the current situation is that they do not satisfy the necessary properties as described above.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing a polymerized toner that solves the above-mentioned problems. That is, an object of the present invention is to provide a method for producing a polymerized toner using a suspension polymerization method,
It is possible to stably complete the polymerization without coalescence of droplets, and obtain a polymerized toner with a desired particle size in a high yield. Furthermore, a polymerized toner with good triboelectric charging properties, properties, fluidity, and storage stability can be obtained. The object of the present invention is to provide a manufacturing method that can obtain the desired results.

[Means for Solving the Problems] In order to solve the problems faced by the conventional technology, the present inventors, as a result of intensive research, have found that the polymerization system can be stably maintained by using modified starch as a suspension stabilizer. The present inventors have found that the method is extremely effective in achieving the above objectives because a skewer can be obtained and the resulting polymer particles have good washability.

That is, the present invention provides a method for producing a polymerized toner obtained by suspension polymerizing a monomer composition containing at least a polymerizable monomer and a colorant, the method comprising using modified starch as a suspension stabilizer. A method for producing a polymerized toner characterized by the following.

The present invention will be explained in more detail below. In the following description, "%" and "part" expressing quantitative ratios are based on weight unless otherwise specified.

In general, starch has colloidal properties and the viscosity of an aqueous solution is relatively high. Therefore, when producing polymerized toner by suspension polymerization, droplets with complex viscoelastic properties are covered with a protective colloid. It can be expected to have the effect of preventing droplets from coalescing between the middle and final stages of polymerization, when the polymerization system is most unstable. The present invention
We have discovered that by further modifying starch, which has these properties, we can impart surfactant properties and give it a large suspension stabilizing ability that stabilizes droplets at the desired particle size until the end of polymerization. be.

Examples of the modified starch used in the present invention include etherified starch, esterified starch, oxidized starch, crosslinked starch, and graft copolymers with vinyl compounds, among which etherified starch and esterified starch are preferred. .

Specifically, the etherified starch includes, for example, an alkyl group such as a methyl group or an ethyl group, an allyl group such as a propenyl group, an aryl group, an alkylamino group such as an aminoethyl group,
It is possible to use etherified starches into which various functional groups have been introduced, such as hydroxyalkyl groups such as hydroxyethyl groups and hydroxypropyl groups, cyanoalkyl groups such as cyanoethyl groups, and carboxyalkyl groups such as carboxymethyl groups. Here, the degree of substitution (degree of etherification) of the etherified starch is 0.01-
:, 5 is particularly preferable.

On the other hand, esterified starch includes saturated aliphatic carboxylic acid esters such as formic acid ester, acetic acid ester, propionic acid ester, and acetic acid ester, unsaturated aliphatic carboxylic acid ester such as propenoic acid ester, propic acid ester, and even benzoic acid ester. Acid esters such as 1)-toluenesulfonic esters, nitric esters, sulfuric esters, phosphoric esters, etc. can be used. Here, the degree of substitution (degree of esterification) of the esterified starch is 0.0% per glucose group of the starch molecule. Particularly preferred is O1 to 2.5.

The degree of etherification and the degree of esterification are determined by known analytical chemistry methods, such as determining the degree of etherification by quantifying nitrogen in cyanoethylated starch by elemental analysis.

The above modified starches can be used alone or in combination of two or more in various compositions as required. The amount of modified starch used is such that the concentration in the continuous phase (aqueous phase) is 0.1% to 40%, preferably 1% to 20%.

Next, materials constituting the monomer composition for producing the polymerized toner in the present invention will be explained.

First, as the main component of the monomer composition used in the method for producing a polymerized toner of the present invention, for example, the following polymerizable monomers can be used.

Examples of such polymerizable monomers include styrene, 0-
Methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene,
p-Chlorstyrene, 3゜4-dichlorostyrene, p-
Ethylstyrene, 2゜4-dimethylstyrene, p-n-
Butylstyrene, p-tert-butylstyrene, p-
n-hexylstyrene, p-n-octylstyrene, p
- Styrene and its derivatives such as n-nonylstyrene and p-n-decylstyrene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride Vinyl halides such as vinyl acetate, vinyl propionate, vinyl benzoate; organic acid vinyl esters such as methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, methacrylic acid Methacrylic acid and its derivatives such as n-octyl, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; acrylic acid,
Methyl acrylate, ethyl acrylate, n-acrylate
Butyl, isobutyl acrylate, propyl acrylate,
Acrylic acid and its derivatives such as n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; vinyl methyl ether, vinyl ethyl ether, vinyl isobutyether , etc.; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc.;

Examples include N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone; vinylnaphthalenes; and polymerizable monomers such as acrylonitrile, methacrylonitrile, and acrylamide. These heptanomers can be used alone or in combination of two or more in various compositions as necessary.

Among the above heptanomers, styrene or styrene derivatives can be used alone or in combination with other heptanomers as polymerizable monomers to develop toners.

As the colorant used in the present invention, carbon black is suitable for use in black toner.

The carbon black used in the present invention includes:
Although it can be used without any restrictions on number average particle size, oil absorption, pH, etc., commercially available products include the following.

For example, REGAL 4 manufactured by Cabot, USA.
00.660, 330. 300, 5RF-S.

STERLIILG S OLV, NS
,R;:F Ronbia Carbon Nippon Nakamade U-Pen (RA
VEN) H2O, MT-P, 410,420.430
゜450.500, 760.780, 1000.103
5.1060.1080. #10B manufactured by Mitsubishi Chemical Corporation,
Examples include #5B, #40, #24008°MA-100; and the like.

Further, these carbon blacks may be used alone or in combination of two or more in various compositions.

As the coloring agent for color toners other than carbon black, there is used a coloring agent that can be dispersed in the monomer composition and exhibits a clear color with excellent stability over time when used as a toner. Such colorants include phthalocyanine pigments, rhodamine lake pigments, azo lake pigments,
Examples include iron oxide, titanium oxide, alumina, barium sulfate, and the like.

The amount of the colorant added is 1 to 40 parts, preferably 5 to 20 parts, based on 100 parts of the polymerizable monomer.

In the present invention, in order to improve heat fixability and offset resistance, low softening point compounds with mold release properties such as waxes such as paraffin wax, and low molecular weight polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene are used. It may also be added to the monomer composition.

Further, in the present invention, in order to improve blocking resistance and durability, a crosslinking agent may be added and suspension polymerization may be carried out. As such a crosslinking agent, a known crosslinking agent such as divinylbenzene can be added to the monomer composition.

Furthermore, in the present invention, a known charge control agent can be added to the monomer composition if necessary. Such charge control agents include metal complexes of organic compounds having carboxyl groups, sulfonic acid esters, or nitrogen-containing groups, metal-containing dyes, and the like.

Note that the surface of the polymerized toner particles may be treated with a solution of the charge control agent dissolved in an organic solvent.

The polymerization initiator used in the present invention is preferably soluble in the polymerizable monomer.

Such polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-(2,4-
dimethylvaleronitrile), 2゜2'-azobis-4-
Methoxy-2,4-dimethylvaleronitrile, other azo or diazo polymerization initiators; Examples include benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxy carbonate, and other peroxide polymerization initiators. Peroxide-based polymerization initiators decompose and produce carboxylic acids such as benzoic acid as by-products, which may have an adverse effect on toner storage stability, and also have drawbacks such as the generation of aromatic odors. It is preferable to use an azo polymerization initiator.

In the present invention, it is preferable to use two or more of the above polymerization initiators in combination in various compositions for the purpose of controlling the molecular weight and molecular weight distribution or for the purpose of controlling the reaction time. Furthermore, a water-soluble initiator such as ammonium persulfate or potassium persulfate may be used in combination, if necessary.

The amount of the polymerization initiator used is usually 0.1 to 20 parts, preferably 1 to 10 parts, based on 100 parts of the polymerizable monomer. If the amount of the polymerization initiator is less than 0.1 part, the polymerization time will be long and the molecular weight of the polymerization product will be too high. Also, on the other hand,
If the amount of the polymerization initiator exceeds 20 parts, the molecular weight of the polymerization product will become too low, which is not preferable.

In the polymerization method of the present invention, a polymerized toner is produced using a suspension liquid in which a monomer composition having the composition as described above is dispersed in a continuous phase (aqueous phase). Here, surfactants can be added to the suspension in order to better control the particle size of the polymerized toner particles. In other words, by making the droplets finer through the action of the surfactant, and by holding the droplets like a protective colloid with the modified starch and stabilizing the suspension, polymerized toner with smaller particle sizes can be efficiently produced. You can.

As such a surfactant, any known surfactant can be used regardless of the type, such as cationic, anionic, or nonionic. Note that the amount of surfactant used is based on the continuous phase (
The concentration in the aqueous phase is 0.001% to 1.5%, preferably 0.005 to 1.0%.

Further, a neutral salt such as sodium chloride or sodium sulfate may be added to the continuous phase (aqueous phase) for the purpose of preventing emulsification. Also,
Furthermore, a thickener such as glycerin or ethylene glycol may be added for the purpose of preventing coalescence of the monomer composition particles formed in the granulation process.

In the present invention, the suspension polymerization reaction is usually carried out at a polymerization temperature of 5
The temperature is set at 0° C. or higher, taking into consideration the decomposition temperature of the polymerization initiator. If the set temperature is too high, the polymerization initiator will rapidly decompose, which will affect the molecular weight, etc., which is not preferable.

Furthermore, in the present invention, the suspension can be treated with a starch-degrading enzyme after the polymerization is completed. In other words, the viscosity of the suspension decreases due to the action of starch-degrading enzymes, so washing,
The filtration step is facilitated, and the modified starch remaining on the particle surface can be efficiently removed, making it possible to obtain a polymerized toner having superior triboelectric charging properties, moisture resistance, and the like.

Such starch-degrading enzymes include, for example, α-amylase, β-amylase,
- Known enzymes such as amylase can be used, and are used in an amount of 0.005 to 20 parts, preferably 0.01 to 5 parts, per 100 parts of modified starch.

[Example] Hereinafter, the present invention will be specifically explained based on Examples.

<Example 1> Styrene 90. After mixing and dispersing 10 g of n-butyl acrylate and 20 g of carbon black (manufactured by Mitsubishi Kasei Co., Ltd., #40) at room temperature using a paint condensator for about 1 hour, the mixture was placed in a separable flask and heated with nitrogen gas for about 30 minutes. After the substitution, the carbon black was surface-treated with the polymerizable monomer at 100° C. or higher to obtain a surface-treated carbon black.

Surface-treated carbon black obtained above 10° Styrene 85srn-butyl acrylate 15g To the above monomer mixture,
2.5 g of 2'-azobisisobutyronitrile was added and dissolved to prepare a monomer composition.

Next, potato starch 33. was dispersed in 300 mII of water,
Adjust the suspension. Add 10% 20% aqueous sodium hydroxide solution to this suspension. Add and stir vigorously. To this, 32 g of acrylonitrile was added and reacted at room temperature for about 3 hours to obtain a paste-like crude product. The obtained crude product was treated by a conventional method to obtain etherified starch into which cyanoethyl groups were introduced.

The degree of substitution (
The degree of etherification was determined to be 1.0.

This etherified starch20. A continuous phase (aqueous phase) is prepared by dispersing the mixture in 500 μm of distilled water and turning it into a paste. A monomer composition is added to this continuous phase and dispersed for about 20 minutes at 110,000 rpm using a TK homo mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a suspension. This suspension is added to a three-bottle round-bottomed flask with a capacity of 1 liter, equipped with a stirrer, a thermometer, and a reflux condenser, heated to 80° C., and stirred for about 8 hours to the extent that droplets do not precipitate to polymerize.

After polymerization, the polymer particles are washed using an ultrasonic cleaner,
Dehydrated by centrifugation. Thereafter, it was dried at 30° C. for 24 hours to obtain a polymerized toner.

When the particle size of the obtained polymerized toner was measured using a Coulter counter (aperture 100 μm), the volume average particle size of the polymerized toner was 14.5 μm.

When this polymerized toner was observed under an optical microscope (magnification: 450 times), each particle of the toner showed a completely black spherical shape, and no carbon black was found to be ubiquitous within the toner particles.

Furthermore, using this toner, a developer was prepared by mixing it with a non-coated ferrite carrier at a toner concentration of 5%, and a commercially available copying machine (manufactured by Sharp Corporation, 5F-8260) was heated at room temperature of 25%.
When an image formation test was conducted under conditions of .degree. C. and 60% humidity, images with good density and image quality were obtained.

<Example 2> The same procedure as described in Example 1 was carried out except that 0.1 g of sodium dodecylbenzenesulfonate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added to the continuous phase (aqueous phase) to prepare polymerized toner. I got it.

When the particle size of the obtained polymerized toner was measured using a Coulter counter (aperture 100 μm), the volume average particle size of the polymerized toner was 1'2 μm.

When this polymerized toner was observed under an optical microscope (magnification: 450 times), each particle of the toner had a completely black spherical shape, and no carbon black was found to be ubiquitous within the toner particles.

Furthermore, when an image formation test was conducted using this toner in the same manner as in Example 1, an image with good density and image quality was obtained.

<Example 3> 45sj of 25g of potato starch! of water to prepare a suspension. To this suspension, 10 g of a 20% aqueous sodium hydroxide solution is added and stirred vigorously.

To this, 10 g of ethylene oxide was added and reacted at room temperature to obtain etherified starch into which hydroxyethyl groups were introduced.

The degree of substitution (degree of etherification) of this etherified starch is Ana
It was 0.09 when analyzed using the method disclosed in Ches+, 28.892 (1956).

After dispersing 10 g of this etherified starch in 500 liters of distilled water and making a paste, 0.1 g of cetyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the continuous phase (
Aqueous phase) was prepared.

Polymerization was carried out in the same manner as in Example 1 except for using the continuous phase (aqueous phase).

After the polymerization is completed, the suspension is made slightly acidic, and then a starch degrading enzyme (
0.6 g of Clystase PA (manufactured by Daiwa Kasei Co., Ltd.) was added, and the mixture was treated at 80°C. A significant decrease in suspension viscosity was observed with the addition of enzyme. After the enzyme treatment, the polymer particles were washed with water and centrifugally dehydrated. Thereafter, it was dried at 30° C. for 24 hours to obtain a polymerized toner.

The particle size of the obtained polymerized toner was measured using a Coulter counter (aperture of 100 μm), and the volume average particle size of the polymerized toner was 12.8 μm.

When this polymerized toner was observed under an optical microscope (magnification: 450 times), each particle of the toner showed a completely black spherical shape, and no carbon black was found to be ubiquitous within the toner particles.

Furthermore, when an image formation test was conducted using this toner in the same manner as in Example 1, an image with good density and image quality was obtained.

<Example 4> Phosphate esterified starch (manufactured by Matsutani Chemical Co., Ltd., Neil Gum A-
115, degree of esterification 0.03) 10 g with distilled water 5
00 After dispersing in a bowl and making a paste, sodium dodecylbenzenesulfonate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) 0.1
g was added to prepare a continuous phase (aqueous phase).

Bontron 5-34 was added to the monomer composition described in Example 1.
(manufactured by Orient Chemical Co., Ltd.) was further added and dispersed to prepare a dispersed phase.

The continuous phase (aqueous phase) and the dispersed phase (uniform monomer composition phase)
A polymerized toner was obtained by performing the same operation as described in Example 1, except for using the following.

When the particle size of the obtained polymerized toner was measured using a Coulter counter (aperture 100 μm), the volume average particle size of the polymerized toner was 12.3 μm.

When this polymerized toner was observed under an optical microscope (magnification: 450 times), each particle of the toner showed a completely black spherical shape, and no carbon black was found to be ubiquitous within the toner particles.

Furthermore, when an image formation test was conducted using this toner in the same manner as in Example 1, an image with good density and image quality was obtained.

Comparative Example> After dispersing 20 g of unmodified potato starch in 500 ml of distilled water, it was made into a paste to prepare a continuous phase (aqueous phase).

Suspension polymerization was carried out in the same manner as in Example 1 except for using the continuous phase, but from the middle to the end of the polymerization, coalescence of the dispersed droplets was observed, and most of them , agglomerated around the stirring blade.

Moreover, the polymer particles obtained without agglomeration did not pass through a 200 mesh sieve (opening diameter: 75 μL, 11), and a polymerized toner could not be obtained.

[Effects of the Invention] Since the polymerized toner of the present invention uses modified starch as a suspension stabilizer, the polymerization system is stably maintained, has an optimal particle size, has good triboelectric charging properties, moisture resistance, etc., and has excellent image quality. A stable image with high density can be provided.

Claims (5)

[Claims] (1) A method for producing a polymerized toner by suspension polymerizing a monomer composition containing at least a polymerizable monomer and a colorant, characterized in that modified starch is used as a suspension stabilizer. A method for producing a polymerized toner. (2) The method for producing a polymerized toner according to claim 1, wherein the modified starch is an etherified starch. (3) The method for producing a polymerized toner according to claim 1, wherein the modified starch is an esterified starch. (4) The method for producing a polymerized toner according to claim 1, wherein a surfactant is used in combination with the modified starch. (5) The method for producing a polymerized toner according to claim 1, characterized in that the suspension is treated with a starch-degrading enzyme after the polymerization is completed.