JPH0288606A - Production of electrostatic charge controlling resin - Google Patents

Abstract

PURPOSE:To obtain the subject resin, excellent in compatibility with binder resins and useful as electrophotographic toners, etc., by dispersing and polymerizing respective specific oil-soluble and water-soluble monomers in an aqueous mixed solvent in the presence of a dispersion stabilizer and recovering the resultant copolymer in the form of particles. CONSTITUTION:(A) At least one oil-soluble monomer selected from the group consisting of vinyl aromatic hydrocarbon monomers (e.g., styrene) and (meth) acrylic acid esters and (B) at least one water-soluble monomer (e.g., styrenesulfonic acid) having an anionic group, such as sulfonic acid, carboxylic acid or phosphoric acid type group, are dispersed and polymerized in a mixed solvent of water and a water-miscible organic solvent in the presence of a dispersion stabilizer to recover the resultant copolymer of the water-soluble monomer and the oil-soluble monomer in the form of particles. Thereby, the objective resin is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a charge control resin used in electrophotographic toners, etc. This invention relates to a method for producing a charge control resin in the form of easy-to-handle particles, in which an oil-soluble monomer that provides a good polymer and a water-soluble monomer that provides a good charging property are copolymerized in a predetermined ratio. .

(Prior Art) In general, a method of mixing and dispersing dyes in binder resins is widely used for the purpose of imparting chargeability to toners, but many charge control agents such as dyes are mixed with resins. Because there is no compatibility at all, a large amount of charge control agent is mixed with the resin to obtain sufficient chargeability.Furthermore, the charge control agent is dispersed in the resin as particles, so it depends on the quality of the dispersibility. The toner performance varies widely, which poses a major problem in toner manufacturing. In order to solve these problems caused by the dispersibility of particles, we synthesized a copolymer of a monomer with a polar group such as acrylonitrile and a monomer that provides a polymer with good compatibility with the binder resin. The copolymer is called a charge control resin (CCR), and there are examples where it is mixed with a binder resin and used.

Bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization are generally used as polymerization methods for the above CCR (problems to be solved by the invention).The conditions for good OCR include polarity that provides charging characteristics. It is required to contain the group-containing monomer component at an effective concentration and to have high compatibility with the fixing resin (binder resin).

Many monomers and polymers with polar groups have low compatibility with binder resins and polymers that give highly compatible polymers, so in bulk polymerization and suspension polymerization, they form a heterogeneous system before or during polymerization. A copolymer containing many polar units that are incompatible with the binder resin is produced. Solution polymerization causes the same problems as bulk polymerization, but by selecting an appropriate solvent a homogeneous system can be obtained before polymerization. However, even in solution polymerization, the polymer tends to precipitate as the polymerization progresses, and the composition of the precipitated polymer is non-uniform. In order to control polymer precipitation in solution polymerization, it is necessary to make the hold-up extremely small or to reduce the ratio of polar monomers.

In emulsion polymerization, the monomer unit composition of the copolymer produced is
It is possible to control tlJ, but the molecular weight is high and the compatibility with the binder resin is low.

Therefore, an object of the present invention is to provide a method for producing a charge control resin that contains a polar group-containing monomer component that imparts charging properties at an effective concentration and is highly compatible with a fixing resin.

Another object of the present invention is to copolymerize an oil-soluble monomer that provides a polymer with good compatibility with a fixing resin and a water-soluble monomer that provides a good charging property in a predetermined ratio. The present invention provides a method for producing a charge control resin.

Still another object of the present invention is to provide a method for producing a charge control copolymer resin, in which the charge control copolymer resin is obtained in the form of particles that are easy to handle, and the composition of each particle is uniform and uniform. It is in.

(Means for Solving the Problems) According to the present invention, at least one oil-soluble monomer selected from the group consisting of vinyl aromatic hydrocarbon monomers and (meth)acrylic acid esters, and sulfone At least one water-soluble monomer having an acid, carboxylic acid, or phosphoric acid type anionic group is dispersed and polymerized in a mixed medium of water and a water-miscible organic solvent in the presence of a dispersion stabilizer. Provided is a method for producing a charge control resin, which comprises recovering a copolymer of a water-soluble monomer and an oil-bath monomer in the form of particles.

(Function) In the present invention, the oil-soluble monomer consisting of a vinyl aromatic hydrocarbon monomer and (meth)acrylic acid ester is a component that provides a polymer with good compatibility with the fixing resin, while the sulfonic acid , a water-soluble monomer having a carboxylic acid or phosphoric acid type anionic group is a component that imparts charging characteristics (negative charging characteristics) to the copolymer resin.

Since these oil-soluble monomers and water-soluble monomers are mutually immiscible, in the present invention, a mixed medium of water and a water-miscible organic solvent is used as the polymerization medium. Here, water naturally dissolves water-soluble monomers, while water-miscible organic solvents dissolve oil-soluble media, and both monomers are present in these mixed media. Dissolve to form a homogeneous solution phase. By coexisting a dispersion stabilizer in this solution phase and performing polymerization, the oil-soluble monomer and the water-soluble monomer are contained in a set amount ratio, and in the form of particles, the mutual composition of the particles is A remarkable feature is that a charge control resin with uniform and -like characteristics is produced. The resulting charge control resin has excellent charging properties and also has excellent compatibility with the fixing resin.

In the polymerization system of the present invention, the reaction proceeds through solution polymerization at the initial stage of polymerization, producing a low molecular weight copolymer having a monomer unit composition commensurate with the reactivity ratio. As the polymerization progresses, this copolymer tends to precipitate, but since a dispersion stabilizer is present in this polymerization system, it is thought that some of them coalesce to form relatively stable dispersed particles. These dispersed particles. Since it is a copolymer of an oil-soluble monomer and a water-soluble monomer, it simultaneously absorbs the unreacted oil-soluble monomer and water-soluble monomer in the continuous phase, and also generates particles. However, it has been recognized that a copolymer having a relatively uniform composition is produced, and in the present invention, even if a combination of monomers having completely different solubilities and significantly different reactivity ratios is produced, the composition of the particles is uniform and - The formation of such a copolymer was discovered as an experimental result, and although the theoretical explanation is still insufficient, it exists as a homogeneous solution phase in which both polymers are dissolved in a mixed medium. This seems to be related to the fact that the copolymer produced in the intermediate stage of polymerization exists as stable dispersed particles in this solution phase, and the monomer is effectively incorporated into these dispersed particles. .

(Preferred Embodiment of the Invention) The oil-soluble monomer used in the present invention is a vinyl aromatic hydrocarbon or (meth)acrylic acid ester.

As a vinyl aromatic monomer, in the formula, R1 is a hydrogen atom, a lower alkyl group, or a halogen atom, and FL2 is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, a nitro group, or a vinyl group. , vinyl aromatic hydrocarbons such as styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o-
, m-, p-chlorostyrene, p-ethylstyrene, and divinylbenzene alone or in combination of two or more.

Moreover, as a (meth)acrylic acid ester monomer, the formula, eH2=C-GO-0-R4...(2) In the formula, R5
is a hydrogen atom or a lower alkyl group, and R4 is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, or a vinyl ester group. Acrylic monomers such as methyl acrylate, ethyl acrylate, acrylic butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate,
2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-hydroxyacrylate,
Examples include butyl δ-hydroxyacrylate, ethyl β-hydroxymethacrylate, ethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate.

On the other hand, water-soluble monomers have sulfonic acid, phosphoric acid, and carboxylic acid type anionic groups, and these acid groups can be used in the form of alkali metal salts such as sodium salts, ammonium salts, amine salts, etc. May be in salt form or free acid form,
Suitable examples thereof are styrene sulfonic acid, sodium styrene sulfonate, 2-acrylamido 2-methylpropanesulfonic acid, 2-acid phosphooxypropyl methacrylate, 2-acid phosphooxyethyl methacrylate, 3-chloro 2-acid phosphooxypropyl These include methacrylate, acrylic acid, methacrylic acid, fumaric acid, crotonic acid, tetrahydroterephthalic acid, itaconic acid, and maleic acid.

The composition ratio of the oil-soluble monomer and the water-soluble monomer is preferably determined so as to have good compatibility with the fixing resin and to obtain sufficient charging ability, and is generally 70:30 to 99:1, particularly 70:30 to 99:1. It is preferable to use a weight ratio of 80:20 to 98:2.

The water-miscible organic solvent used in the present invention includes lower alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone, methyl ethyl ketone, and methyl butyl ketone; ethers such as tetrahydrofuran and dioxane; ethyl acetate. and amides such as dimethylformamide are appropriately selected and used depending on the type of monomer used.

The ratio of water to water-miscible organic solvent used varies depending on the type of solvent and monomer, but is generally 40:60 to 5:95. In particular, the composition ratio may be selected from a weight ratio of 30:0 to 10:90 so as to form a homogeneous solution phase as a whole. The ratio of the mixed medium to the monomer is preferably 0.5 to 50 times by weight, particularly 5 to 25 times by weight per monomer.

As the dispersion stabilizer, polymeric dispersion stabilizers soluble in the mixed medium mentioned above, such as polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, (meth)acrylic acid-(meth) ) Acrylic acid ester copolymer, acrylic acid-vinyl ether copolymer, methacrylic acid-styrene copolymer, carboxymethyl cellulose,
Preferably, polyethylene oxide, polyacrylamide, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, etc. are used, but nonionic or anionic surfactants can be used. The dispersion stabilizer is preferably present in the system in an amount of 0.01 to 10% by weight, especially 0.1 to 3% by weight.

As a polymerization initiator, azo compounds such as azobisisobutyronitrile, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-
Those soluble in water-insoluble monomers such as peroxides such as butyl peroxide, benzoyl peroxide, and lauroyl peroxide are used. In addition, combinations of ionizing radiation such as gamma rays, accelerated electron beams, ultraviolet rays, and various photosensitizers are also used.

The amount of the polymerization initiator such as an azo compound or peroxide may be a so-called appropriate amount of catalyst, and is generally 0.1 to 1 per monomer charged.
Preferably, it is used in an amount of 0% by weight. Polymerization temperature and time are
Any known method may be used, generally at a temperature of 40 to 100°C.
Polymerization for 50 to 50 hours is sufficient. Incidentally, the reaction system may be stirred gently so that a homogeneous reaction occurs as a whole.Also, in order to prevent the polymerization from being inhibited by oxygen, the reaction system may be replaced with an inert gas such as nitrogen to carry out the polymerization. You can also

CCR produced by polymerization generally has a particle size of 0.1 to 1.
These particles have a relatively uniform particle size distribution of 0 μm, particularly 0.5 to 7 μm. Since the polymerized product after the reaction is obtained in the form of granules having the above particle size range, the resulting particles are passed through a sieve, washed with water or a suitable solvent if necessary, and dried to obtain a CCR for toner.

The CCR of the present invention is blended in an amount of 0.5 to 50% by weight, particularly 1 to 20% by weight, with respect to a toner fixing resin known per se such as a styrene resin or an acrylic resin.
can be used.

(Effects of the invention) The CCR obtained by the dispersion polymerization method of the present invention has good compatibility with the binder resin, and since it has become particles of about 1 μm at the end of polymerization, it can be easily dispersed when mixed with the binder resin. and dissolve. Furthermore, since it has a very small molecular weight, it dissolves well in styrene monomers, and its viscosity does not increase, so it can be applied to toner production using polymerization methods. Of course, since it dissolves well in the binder resin and powder, it is uniformly dispersed in the toner particles and is extremely effective in imparting chargeability.

(Examples) Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples.

Example 1 20 g of polyacrylic acid was dissolved in a mixed solvent of 1600 g of isopropyl alcohol and 400 g of water, 200 g of styrene, 25 g of sodium styrene sulfonate and 10 g of azobisisobutyronitrile were added thereto, and the mixture was heated with nitrogen in a separable flask. The reaction was carried out at 80° C. for 12 hours while stirring at 150 rpm under air flow to complete the polymerization. When the emulsion thus obtained was observed with an optical microscope, particles of around 3 μm were found to be formed.

This emulsion is centrifuged to separate particles.
A white powder was obtained. Analysis of this styrene-sodium styrene sulfonate copolymer by thin layer chromatography using silica gel as an adsorbent and ethyl acetate as a developing solvent revealed that it was a copolymer with an almost uniform monomer composition. Met. In addition, the molecular weight is based on the assumption by GPC that Mn is 2.
400, Mw was 6100.

10 parts by weight of the above styrene-sodium styrene sulfonate copolymer (Tg = 6
5℃, Mn=10000. Mw=120000) Carbon black 10 parts by weight These were melt-kneaded, pulverized, and classified to give a toner having an average particle size of 10 μm. When this toner and ferrite carrier were mixed and used as a developer in a DC-1205 and a copying test was conducted, it scattered at high temperatures (35°C, I'LH 85%) and at low temperatures and low humidity (10°C, RH 45%). No problems such as fogging or changes in image density occurred. Further, this developer showed a high amount of charge under these environments, and the rise in charge was also extremely high. Furthermore, as a result of measuring the charge amount distribution of this developer using a toner charge amount measuring device, the charge distribution was extremely sharp, and there was no uncharged toner or reverse polarity toner.

Example 2 20 g of polymethacrylic acid was dissolved in a mixed solvent of 600 g of methanol i and 400 g of water, and 200 g of methyl methacrylate, 25 g of sodium vinylphosphonate and 10 g of azobisisobutyronitrile were added thereto, and the mixture was poured into a separable flask of 31. The reaction was carried out at 60° C. for 12 hours while stirring at 150 rpm under a nitrogen stream to complete the polymerization. The emulsion thus obtained was observed under an optical microscope, and it was found that particles with a diameter of about 1 μm were formed. This emulsion was centrifuged to separate particles to obtain a white powder. This methyl methacrylate-sodium vinylphosphonate copolymer was analyzed by thin layer chromatography under the same conditions as in Example 1, and as a result, it was found to be a copolymer with a nearly uniform monomer composition. Also, the molecular weight is GP
As measured by C, Mn is 18600 and Mw is 14200.
It was 0.

Styrene 60 parts by weight n-butyl methacrylate 30 parts by weight Polymerization initiator
(AIBN) 4 parts by weight The above composition was used as a polymerizable mixture, and the polymerizable composition was added to a dispersion medium consisting of 400 parts by weight of water and 10 parts by weight of polyvinyl alcohol.
1.8 parts by weight of maleic acid was dissolved in the suspension, followed by normal stirring at 80° C. under a nitrogen atmosphere and polymerization for 5 hours. After taking out the particles, they were washed with warm water, filtered, and dried to obtain a toner.

When the particle size distribution of this toner was measured using a Coulter counter, the volume average diameter was 10.8 μm and 5 μm.
The following fine powder toners had a content of 0.5% or less. This toner and ferrite carrier were mixed, frictionally stirred, and the toner charge amount was measured by the blow-off method.-17
, 5 μc/g.

Also. The charge distribution of this developer was measured using a toner charge amount measuring device. As a result, the charge distribution was extremely sharp, and there was no uncharged toner or toner of opposite polarity.

Example 3 20 g of acrylic acid-methyl methacrylate copolymer was dissolved in a mixed solvent of 1600 g of ethanol and 400 g of water, and 200 g of methyl methacrylate was added thereto.

25 g of sodium methacrylate and 10 g of benzoyl peroxide were added, and the reaction was carried out at 70° C. for 12 hours with stirring at 150 rpm under a nitrogen stream in a 31 separable flask to complete polymerization. When the emulsion thus obtained was observed with an optical microscope, it was found that particles of approximately 2 μm were formed. This emulsion was centrifuged to separate particles to obtain a white powder. This methyl methacrylate-sodium methacrylate copolymer was prepared in Example 1.
As a result of analysis using thin layer chromatography under the same conditions as
was a copolymer with a nearly uniform monomer composition.

In addition, the molecular weight was determined by GPC, and Mn was 25.80.
0, Mw was 129,000.

Solvent Blue 25 10 parts by weight These were melt-kneaded, pulverized, and classified to give a toner having an average particle size of 10 μm. This toner and ferrite carrier are mixed and loaded as a developer into a modified DC-1205 machine, and OHP
A copying test was conducted using film. The obtained image had excellent translucency and good image quality.

Comparative Example 1.200g of styrene and 22g of sodium styrene sulfonate in a mixed solvent of 1600g of 4-dioxane and 400g of water
5 g and 10 g of azobisisobutyronitrile were added and charged into a No. 31 separable flask, and the mixture was stirred at 150 rpm at 80° C. under a nitrogen stream to attempt homogeneous solution polymerization. At the initial stage of polymerization, the flask was a transparent homogeneous system, but as the polymerization progressed, the system gradually became cloudy. It was not possible to separate the precipitate from the polymer thus obtained by filtration or centrifugation. Therefore, all of the polymer was poured into a large amount of methanol to separate the polymer. As a result of analyzing this polymer by thin layer chromatography under the same conditions as in Example 1, a styrene-sodium styrene sulfonate copolymer was detected; A mixture of styrene homopolymers and water-soluble sodium styrene sulfonate homopolymers were also detected.

The polymer synthesized in this way has very poor compatibility with the binder resin, so it could not be sufficiently dispersed in the resin. Furthermore, it cannot be used as a material for polymerized toners because it is not completely soluble in oil-soluble monomers such as styrene.

Claims (1)

[Claims] (1) At least one oil-soluble monomer selected from the group consisting of vinyl aromatic hydrocarbon monomers and (meth)acrylic acid esters, and an anionic group of sulfonic acid, carboxylic acid, or phosphoric acid type. The water-soluble monomer and the oil-soluble monomer are polymerized in a mixed medium of water and a water-miscible organic solvent in the presence of a dispersion stabilizer. 1. A method for producing a charge control resin, which comprises recovering a copolymer in the form of particles.