JPH02241538A - Preparation of aqueous resin particle for shell material of microcapsule toner - Google Patents

Abstract

PURPOSE:To obtain aqueous resin particles excellent in charge characteristics and having durability and heat resistance by polymerizing a composition consisting of a polymerizable monomer, a cationic polymer and a polymerization initiator under a specific condition. CONSTITUTION:A composition consists of a polymerizable monomer such as styrene or ethylene, a cationic polymer dissolved in said monomer and charged positively such as dimethylaminoethyl acrylate and a polymerization initiator dissolved in said monomer but undissolved in an aqueous medium such as 1,1'-azobis (cyclohexane-1-carbonitrile) and is polymerized in the aqueous medium under a condition of pH 1-6. By this method, it is unnecessary to use a usual emulsifier, a water-soluble polymerization initiator and a water-soluble high- molecular emulsifier. As a result, particles excellent in charge characteristic, having no depleted parts and excellent in durability and heat resistance as the shell material of microcapsule toner are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing aqueous resin particles for shell material of microcapsule toner that are positively charged in an aqueous medium. More specifically, the present invention relates to a method for producing aqueous resin particles by an emulsifier-free emulsion polymerization method, so-called soap-free emulsion polymerization method, which does not use a water-soluble polymerization initiator.

[Prior Art] Conventionally, methods for producing aqueous resin particles include (1) a method for producing resin particles by emulsion polymerization using a surfactant;

(2) A method for producing aqueous resin particles by a soap-free emulsion polymerization method using a water-soluble polymerization initiator.

(3) A method for producing aqueous resin particles by a soap-free emulsion polymerization method using a hydrophilic polymerizable 14-monomer and a water-soluble polymerization initiator.

(4) A method for producing water-based resin particles using a water-soluble polymer emulsifier.

etc.

Of these, in (1) and (4), it is difficult to completely remove the surfactant and polymer emulsifier, and when the resulting aqueous resin is used as a microcapsule toner, these residues pose a problem. The image density cannot be obtained.

In addition, in (2), the usable polymerization initiators are limited to 3 to 4 types, and the conditions for the polymerization reaction are also limited, so particles with desired characteristics may not be obtained. When microcapsule toner particles for electrophotography are produced by this method, the TL load cannot be sufficiently imparted to the particles, which may cause problems in image density in electrophotography.

In (3), there is a problem in that it is difficult to obtain a uniform polymer by copolymerizing a hydrophilic monomer with a hydrophobic monomer such as styrene or methyl methacrylate.

[Three Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing resin particles for microcapsule toner. Another object of the present invention is to use microcapsules without using ordinary emulsifiers, without using water-soluble polymerization initiators, and without using water-soluble polymer emulsifiers. It is an object of the present invention to provide a method for producing aqueous resin particles that have excellent charging characteristics when used as a toner shell material, have no defective parts, and have excellent durability and heat resistance.

[Means and effects for solving the problem] As a result of intensive research, the present inventor has found that at least a polymerizable monomer and a positively charged polymer dissolved in the monomer (hereinafter referred to as a cationic polymer) , and a polymerization initiator that is soluble in the monomer and insoluble in the aqueous medium, in the aqueous medium p)II.
It has been found that the object of the present invention can be achieved by a method for producing aqueous resin particles for a shell material of a microcapsule toner, which is characterized in that polymerization is carried out under conditions of .about.6.

The present invention will be explained in more detail below. In the following description, "%" and "1 part" expressing quantitative ratios are based on weight in °C unless otherwise specified.

The polymerizable monomers used in the present invention are described below.

That is, for example, styrene, 0-methylstyrene, m
-Methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3.4-dichlorostyrene, p-ethylstyrene, 2
．． 4-dimethylstyrene, p-n-butylstyrene,
Styrene and its derivatives such as p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene; Ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; Vinyl esters such as vinyl acetate, vinyl propionate, and vinyl benzoate Class: Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, acrylic Methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate,
Acrylic acid esters such as 2-chloroethyl acrylate and phenyl acrylate; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; and Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone: Vinylnaphthalenes include acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.

During polymerization, polymerization is carried out in the presence of the following crosslinking agent,
It may also be a crosslinked polymer.

Divinylbenzene, divinylnaphthalene, divinyl ether, divinyl sulfone, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate methacrylate, 1.
6 = hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2°bis(4-methacryloxyjethoxyphenyl)propane, 2,2゛bis(4-acryloxy) (jetoxyphenyl)propane, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, dibromneopentyl glycol dimethacrylate, and general crosslinking agents can be used as appropriate.

The above-mentioned cationic polymer dissolved in the monomer contains a positively charged polymerizable monomer (hereinafter referred to as a cationic polymer) described below. That is, for example, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, vinylpyridine, vinylimidazole, dimethylaminomethylstyrene, etc. In these cationic monomers, methyl group, ethyl group , may be quaternary ammoniumated with a butyl group, a benzyl group, or the like.

Examples of the above-mentioned polymerizable monomer that copolymerizes with the cationic monomer include styrene, O-methylstyrene, m-
Methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene,
3.4-dichlorostyrene, p-ethylstyrene, 2.
4-dimethylstyrene, p-n-butylstyrene, I)
-Styrene and derivatives thereof such as -tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene; ethylene, Ethylenically unsaturated monoolefins such as propylene, butylene, and isobutylene; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; Vinyl esters such as vinyl acetate, vinyl propionate, and vinyl benzoate; Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate,
Isobutyl methacrylate, n-octyl methacrylate,
Dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, methyl acrylate, ethyl acrylate, acrylic acid n
- Acrylic acid esters such as butyl, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; vinyl methyl ether , vinyl ethers such as vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylaterile, acrylamide, etc. be.

The cationic polymer is produced, for example, by solution polymerization in an organic solvent using an azo polymerization initiator. That is, the above-mentioned cationic monomer, a polymerizable monomer that copolymerizes with the above-mentioned cationic monomer, and an azo polymerization initiator are polymerized in an organic solvent.

Here, as the azo polymerization initiator, for example, 1.1'-
Azobis(cyclohexane-1-carbonitrile), 2
, 2°-azobisisobutyronitrile, 2.2′-azobis(2,4-dimethylvaleronitrile), etc. are used. Examples of the organic solvent used include aromatics such as toluene and xylene, alcohols, and ketones.

- Aromatics, especially toluene, are preferably used for boat fishing.

The proportion of the cationic monomer in the cationic polymer is preferably 3 to 80%, more preferably 7 to 70%. This is because if the cationic monomer content is less than 3%, sufficient positive chargeability cannot be imparted, and 8C%
If the content is above, even if sufficient positive chargeability can be imparted, the solubility in an aqueous medium becomes too strong, making it impossible to achieve the object of the present invention.

In the present invention, the cationic polymer and the polymerizable monomer are preferably mixed so that the former accounts for 5 to 80%, more preferably 10 to 70%.

This is because if the content of the cationic polymer is less than 5%, sufficient positive chargeability cannot be imparted to the aqueous resin particles, and if the content is more than 80%, the cationic polymer and the polymerizable monomer The viscosity of the mixture with
Aqueous resin particles cannot be obtained.

In the present invention, the molecular weight of the cationic polymer is 2000 to tooooo as measured by weight average molecular weight by GPC.
, preferably 5,000 to 50,000
This is the case when G. If the weight average molecular weight of the cationic polymer is less than 2,000, the solubility in an aqueous medium will be strong and the object of the present invention cannot be achieved;
If it is more than 0,000, it is virtually impossible to dissolve and mix with the polymerizable monomer.

Polymerization initiators that are not soluble in the aqueous medium used in the present invention include the following.

That is, for example, 1.1°-azobis(cyclohexane-1-carbonitrile), 2.2°-azobisisobutyronitrile, 2,2′-azobis(2,4-dimethylvaleronitrile), 2.2 Examples of polymerization initiators include ゛-azobis(4-methoxy-2,4-dimethylvaleronitrile), dicumyl peroxide, dilauroyl peroxide, benzoyl peroxide, tolyl peroxide, and chlorobenzoyl peroxide. 0 in the mixture of polymer and cationic polymer.
．． It is preferable to add it in an amount of 1 to 20%, more preferably 0.5 to 15%. If the amount of the polymerization initiator added is less than 0.1%, it is difficult to complete the polymerization reaction, and if it is added in an amount of 20% or more, it is difficult to control the polymerization reaction.

In the present invention, the pH of the aqueous medium is measured at 20°C,
It is preferably between 1 and 6, and the aqueous resin particles of the present invention cannot be stably produced even under strong acidity where the pH is less than 1 or under weak acidity where the pH is 6.

Note that the pH of the aqueous medium is preferably adjusted with hydrochloric acid, acetic acid, etc., and pl-1 may be stabilized using a buffer solution.

The aqueous resin particles of the present invention have a diameter of 500 μm to 0.01 LLm.
Although the particle size can be adjusted to any value between 100 μm and 0.01 μm, it is preferable to
More preferably, the particle size is 50 μm to 0.1 μm.

The aqueous resin of the present invention can be prepared at any solid content concentration of 50% or less based on the aqueous medium, but is preferably prepared at a solid content concentration of 5 to 35%. When the solid content concentration exceeds 50%, heat generation due to the polymerization reaction of the polymerizable monomer increases and becomes difficult to control, and furthermore, scale generation due to aggregation between resin particles increases, which poses a problem.

In addition, in the present invention, a polymerization initiator that does not dissolve in an aqueous medium has a solubility in an aqueous medium of 1 when measured at 20°C.
% or less.

The aqueous resin particles of the present invention are microcapsule core particles 1
0.1 to 50 parts, preferably 1 to 30 parts. If the amount of particles is less than 0.1 part, the core particles will not be encapsulated substantially, and if the amount of aqueous resin particles is more than 50 parts, the core particles will significantly agglomerate together during encapsulation, making it unsuitable for practical use as a microcapsule toner. Cannot be used on top.

The particle size ratio of the wall material particles and the core material particles is such that the particle size of the core material particles is 1.
If so, it should be between 1/1000 and 1/1,
More preferably, it is between 11,500 and 1/2. If the particle size ratio of aqueous resin particles and core material particles is 1,
/1000, that is, if the aqueous resin particles are too small, even if a capsule wall can be formed on the surface of the core material particles, the durability and storage stability of the microcapsule toner will be significantly inferior, and the aqueous resin particles will be 1/1 If the particles become larger, that is, if the water-based resin particles are too large, even if the water-based resin particles can adhere to the surface of the core material particles, they will not form a dense and strong capsule wall, and this will also significantly reduce durability. It turns out.

The average particle diameter of the core material particles may be in the range of 1 to 30 μm, more preferably in the range of 5 to 20 μm.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Synthesis of cationic polymer (1) Dimethylaminoethyl methacrylate 35 parts Styrene 65 parts 2.2°-azobisisobutyronitrile 8 parts The above polymerizable monomer composition 5.0 kg was mixed with toluene at 12.0°C. mixed with 20f2
After confirming that the polymerization initiator is completely dissolved and a homogeneous solution is formed, gradually heat the solution to 78° C. while stirring while flowing nitrogen. Once the temperature reaches 78°C, the polymerization reaction is carried out at that temperature for 6 hours, and then heated until the solvent toluene refluxes and kept in that state for 1 hour.

Thereafter, the solvent is distilled off along with the unreacted polymerizable monomer to concentrate. Further, by drying under reduced pressure at 120° C. for 24 hours, a cationic polymer (1) was obtained.

As a result of elemental analysis, it was found that 34.7% of dimethylaminoethyl methacrylate was contained.

Synthesis of cationic polymer (2) Diethylaminoethyl methacrylate 25 parts Methyl methacrylate 75 parts 2.2°-7 zobisisobutyronitrile 5 parts Cationic polymers other than the above polymerizable monomer composition were used. In the same way as merging (1),
A polymer was obtained. This is the cationic polymer (2) of the present invention.
shall be.

As a result of elemental analysis, it was found that the content of diethylaminoethyl methacrylate was 25.3%.

Synthesis of cationic polymer (3) Dimethylaminomethylstyrene 12 parts Styrene 88 parts Benzoyl peroxide 3 parts Above polymerizable monomer composition 5
．． Mix 0 kg with toluene 12.i, put it in a container of 21 and stir. After confirming that the polymerization initiator is completely dissolved and a homogeneous solution is formed, the mixture is heated to 80°C under stirring while flowing nitrogen.
Heat gradually until Once the temperature reaches 80°C, the polymerization reaction is carried out at that temperature for 10 hours, and then heated until the solvent toluene refluxes and kept in that state for 1 hour.

Thereafter, the solvent is distilled off along with the unreacted polymerizable monomer to concentrate. Further, by drying under reduced pressure at 120° C. for 24 hours, a cationic polymer (3) was obtained.

As a result of elemental analysis, it was found that 10.8% of dimethylaminomethylstyrene was contained.

Synthesis of Cationic Polymer (4) Vinylimidazole 45 parts Styrene 55 parts 1.1°-azobis(cyclohexane 5 parts 1-carbonitrile) 5.0 kg of the above polymerizable monomer composition was mixed with toluene I5.
After confirming that the 0 polymerization initiator is completely dissolved and a homogeneous solution is obtained, the solution is gradually heated to 95° C. under stirring while flowing nitrogen. Once the temperature reaches 95°C, the polymerization reaction is carried out at that temperature for 8 hours, then heated until the solvent toluene refluxes and kept in that state for 1 hour, after which the solvent is distilled together with the unreacted polymerizable monomer. Remove and concentrate. The cationic polymer (
4) was obtained.

Furthermore, as a result of elemental analysis, vinylimidazole was found to be 4
It was found that the content was 2.6%.

Production of aqueous resin particles (1) Cationic polymer (1) 40 parts Styrene 58 parts Divinylbenzene 2 parts 2.2゛-azobis(2
, 4-dimethyl, 2 parts of valeronitrile) Ion-exchanged water 51 adjusted to pH 2.0 with hydrochloric acid is charged into a reaction vessel having a volume of 1 lOIt. under stirring at room temperature.
When 2.0 kg of the above polymerizable monomer solution composition is added dropwise over 20 minutes, a milky white emulsion is obtained. Next, it is heated to 60°C, held at that temperature for 8 hours, further heated to 80°C, kept for 1 hour, and then cooled to room temperature. The resulting resin particle aqueous solution was passed through a +00 mesh sieve to remove a small amount of resin particle aggregates. This is referred to as the aqueous resin particle (1) of the present invention.

In addition, the average particle diameter measured by Coulter N4 type is 0.1
It was 5±0.03 μm. In addition, the solid content determined by concentrating and drying a certain amount of aqueous resin particle liquid was 27.7
%, and the polymerization yield was 98.1%.

Production of aqueous resin particles (2) Cationic polymer (2) 20 parts styrene 75 parts ethyl acrylate 5 parts divinylbenzene
1.5 parts 2.2'-Azobisisobutyronitrile 4 parts Ion-exchanged water 5I2 adjusted to p) 12.0 with hydrochloric acid is charged into a reaction vessel having a volume of 10. While stirring at room temperature, 1.0k of the above polymerizable monomer solution composition
g dropwise over 20 minutes to obtain a milky white emulsion.

Then, it was heated to 78°C and kept at that temperature for 8 hours,
Further, the mixture was heated to 90° C., kept for 1 hour, and then cooled to room temperature. The resulting resin particle aqueous solution was passed through a 100-mesh sieve to remove a small amount of resin particle aggregates. This is referred to as the aqueous resin particle (2) of the present invention.

In addition, the average particle diameter measured by Coulter N4 type is 0.0
It was 5±0.01 μm. In addition, the solid content determined by concentrating and drying a certain amount of aqueous resin particle liquid was 15.9
%, and the polymerization yield was 96.3%.

Production of microcapsule toner (1) Polyester (composition, terephthalic acid: isophthalic acid: ethylene glycol: trimethylolpropane = 45:1
0:30:15) 100 parts magnetic material
70 parts low molecular weight polypropylene
A mixture consisting of 4 parts (Viscol 660P manufactured by Sanyo Chemical Industries) was heated and kneaded with a roll. After allowing it to cool, it was coarsely crushed, further finely crushed using a jet mill, and classified using an air classifier, resulting in a volume average particle size of 11.6 μm.
Core material particles (1) were obtained.

The aqueous resin particles of the present invention (
1) was mixed and dispersed in 15 parts in terms of solid content. Next 5
Spray drying was carried out using a spray dryer at an inlet temperature of 160° C. and an outlet temperature of 90° C., and a crosslinked resin coating layer mainly composed of the emulsion-constituting copolymer was provided around the core particles. This is referred to as the microcapsule toner (1) of the present invention.

Colloidal silica (Aerosil R-972) was added to the capsule toner (1) thus obtained, and 1000 images were printed using a copying machine NP-3525 (manufactured by Canon). It was confirmed that the film had good density and development durability.

In addition, in order to examine the thermal fixability in detail, we prepared a separate fixing unit for the copying machine and used this separate fixing unit to fix an unfixed image on a separately prepared transfer paper, and no offset phenomenon occurred over a wide temperature range. The fixing properties were also excellent.

Further, this capsule toner was left in an atmosphere at 45°C for a long time, but no blocking or caking was observed.

Production of microcapsule toner (2) Styrene/butyl acrylate/divinylbenzene copolymer (composition ratio 77:22.5:0.5)
100 parts magnetic material 70
A microcapsule toner (2) was obtained in the same manner as in Example 1, except that aqueous resin (2) was used and core particles consisting of 4 parts of low molecular weight polypropylene (Viscol 660P manufactured by Sanyo Chemical Industries, Ltd.) were used. When the same image quality evaluation and blocking test as for microcapsule toner (1) was conducted, good results were obtained.

Production of Microcapsule Toner (3) The core particles used in the production of Microcapsule Toner (1) and Aerosil #300 were mixed and stirred, and the surface thereof was coated with silica. 10 kg of this slurry containing 1.0 kg of core material particles was placed in a 204 container and stirred at room temperature.
I adjusted it to be H.

Aqueous resin particles (1) in the suspension dispersion of the core material particles (1)
) was added under stirring. After continuing stirring for 1 hour, it was heated to 50°C and kept at that temperature for 2 hours.

After cooling to room temperature, it was filtered and dried. When the surface of the particles was observed using an electron microscope, it was confirmed that the particles were covered with wall material particles.

This is referred to as microcapsule toner (3).

Good results were obtained when image quality evaluation and blocking test were conducted in the same manner as for microcapsule toner (1).

Comparative Example 1 A zero-polymerizable monomer solution composition in which the production of aqueous resin particles was attempted in exactly the same manner as in the production example of aqueous resin particles (1), except that the aqueous medium, ion-exchanged water, was adjusted to pH 7.6. The state of dispersion of the substance in the aqueous phase was extremely unstable, and it was not possible to obtain aqueous resin particles.

Comparative Example 2 Polymerization was carried out in exactly the same manner as in the production example of aqueous resin particles (1) except that 0.5 part of sodium dodecylbenzenesulfonate was added as an emulsifier and the pH of the aqueous phase was not adjusted. Aqueous resin particles (2) were obtained.

A comparative microcapsule toner was obtained by the spray drying method in the same manner as the production of microcapsules (1) except that this comparative resin particle (2) was used, and image density and durability evaluation were performed. was extremely low.

[Effects of the Invention] The present invention is characterized in that it does not use ordinary emulsifiers, water-soluble polymerization initiators, water-soluble polymer emulsifiers, etc., and is excellent in producing resin particles for microcapsule toner. A method of manufacturing resin particles has been provided.

Claims (1)

[Claims] 1) A monomer composition consisting of at least a polymerizable monomer, a positively charged polymer that dissolves in the monomer, and a polymerization initiator that dissolves in the monomer but does not dissolve in the aqueous medium. A method for producing aqueous resin particles for a shell material of a microcapsule toner, which comprises polymerizing in a medium at a pH of 1 to 6.