JP3149984B2 - Filtration method for polymer resin particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for filtering polymer resin particles, and more particularly to a filtration method useful for separating and recovering resin particles obtained by a dispersion polymerization method.

[0002]

2. Description of the Related Art A polymer dispersant which dissolves in a hydrophilic organic liquid is added to a hydrophilic organic liquid, and the resulting polymer is dissolved in the organic liquid. The so-called dispersion polymerization method, in which at least one kind of a vinyl monomer that hardly dissolves is added and polymerized, is well known. According to this polymerization method, spherical resin particles having a small particle size and a narrow particle size distribution can be obtained. .

[0003] Spherical particles having such a small particle size and a narrow particle size distribution develop, for example, an electrostatic latent image (electrostatic image) formed on an electrophotographic photosensitive member or an electrostatic recording member. Is useful for dry toners. That is, a small particle size toner obtained by coloring and drying resin particles produced by a dispersion polymerization method in a hydrophilic organic liquid is expected to achieve high image quality.

However, in the production of toner having a small particle size by the dispersion polymerization method, the resin particles obtained by the polymerization method have a small particle size, a narrow particle size distribution, and are substantially spherical. When the particles are separated and recovered from the dispersion system by filtration, if filtration is performed through a normal filter cake layer, the resin particles aggregate within the filter cake layer, and the filtration speed becomes extremely slow. There is a problem that filtration becomes impossible. The dispersed polymerized resin cake formed by the ordinary filtration operation is subsequently dried, but in order to obtain small-sized dried resin particles (powder), the aggregated dry powder must be crushed. No. However, this agglomerated dry powder usually has poor crushing properties, and has a disadvantage that it is difficult to obtain a particle size distribution and a particle shape in a dispersed state.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problem, that is, to provide a polymer resin particle in a hydrophilic organic liquid obtained by a dispersion polymerization method through a usual filter cake layer. It is an object of the present invention to provide a filtration method capable of preventing resin particles from agglomerating inside a cake layer and preventing a reduction in filtration speed when performing filtration. Another object of the present invention is to obtain a powder by drying a resin cake obtained by a filtration operation, which has a good crushing property, and is close to a particle size distribution and a particle shape in a simple and dispersed state. It is an object of the present invention to provide a filtration method capable of producing a resin cake from which powder in a state can be obtained.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a coagulation preventing liquid that does not dissolve the resin particles is added to the dispersion containing the polymer resin particles, and then the mixture is filtered. The inventors have found that the above-mentioned object is achieved, and have completed the present invention.

That is, according to the present invention, a polymer resin particle which is separated by filtering a dispersion system in which a polymer resin particle which is swollen or hardly dissolved in the organic liquid is dispersed in the hydrophilic organic liquid is separated. In the filtration method, a method for filtering polymer resin particles is provided, wherein water , which is a liquid for preventing aggregation that does not dissolve the polymer resin particles , is added to the dispersion system and then filtered.

Hereinafter, the method for filtering polymerized resin particles of the present invention will be described in detail. In the present invention, the stock solution to be filtered is a dispersion containing resin particles produced by the dispersion polymerization method. That is, according to the dispersion polymerization method,
A polymer dispersant which dissolves in the organic liquid is added to the hydrophilic organic liquid, and the polymer which dissolves in the organic liquid but swells or hardly dissolves in the organic liquid is further added thereto. Resin particles are produced by adding and polymerizing at least one of the monomers (hereinafter, the resin particles thus obtained are referred to as resin particles A). In the present invention, the dispersion system thus formed is intended. And Further, a dispersion system in which resin particles are produced in advance by using a polymer having a smaller particle size distribution but narrower than the target particle size and growing in the above system is also included in the scope of the present invention. In this case, the monomer used for the growth reaction may be the same monomer as that used for producing the seed particles or another monomer, but the polymer must not be dissolved in the hydrophilic organic liquid.

By such a dispersion polymerization method, resin particles A having a small particle size and a narrow particle size distribution can be obtained. Preferred resin particles A have a volume average particle diameter (Dv) and a number average particle diameter (Dp).
Are in the range of 1.00 ≦ (Dv / Dp) ≦ 1.20, and Dv is 1 to 10 μm. When such resin particles A are used as base particles, a toner capable of achieving high image quality can be obtained, and therefore, the resin particles A are very useful for toner.

Examples of the hydrophilic organic liquid used as a dispersion medium containing dispersed polymer particles, that is, a hydrophilic organic liquid used as a diluent for a monomer used for forming seed particles and for performing a growth reaction of seed particles, include, for example, methyl Alcohol, ethyl alcohol, denatured ethyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, sec-butyl alcohol, tert-amyl alcohol, 3-pentanol, octyl alcohol, benzyl alcohol, cyclohexanol, full Alcohols such as furyl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, glycerin, and diethylene glycol; methyl cellosolve, cellosolve, isopropyl cellosolve, butyl cellosolve, and ethylene Glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, and ether alcohols such as diethylene glycol monoethyl ether. These organic liquids can be used alone or in a mixture of two or more.

An organic liquid other than alcohols and ether alcohols, which is used in combination with the above-mentioned alcohols and ether alcohols under various conditions under which the polymer particles of the organic liquid do not have solubility. By changing the SP value and changing the polymerization conditions, it is possible to suppress the size of the produced particles, the coalescence of seed particles, and the generation of new particles. As the organic liquid used in combination in this case,
Hexane, octane, petroleum ether, cyclohexane,
Hydrocarbons such as benzene, toluene and xylene; halogenated hydrocarbons such as carbon tetrachloride, trichloroethylene and tetrabromoethane; ethers such as ethyl ether, dimethyl glycol, trioxane and tetrahydrofuran; acetal such as methylal and diethyl acetal Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexane; esters such as butyl formate, butyl acetate, ethyl propionate and cellosolve acetate; acids such as formic acid, acetic acid and propionic acid;
Examples thereof include sulfur- and nitrogen-containing organic compounds such as nitropropene, nitrobenzene, dimethylamine, monoethanolamine, pyridine, dimethylsulfoxide, and dimethylformamide.

The solvent mainly composed of a hydrophilic organic liquid is used as a solvent containing SO ₄ ion (-2 valence), NO ₂ ion (-1 valence), PO
₄ ions (-3 valence), Cl ion (-1 valence), Na ion (+1 valence), K ion (+1 valence), Mg ion (+2 valence)
), Ca ions (+2 valence), and other inorganic ions may be used for the polymerization. Further, the type and composition of the mixed solvent at the start of polymerization, during the polymerization, and at the end of the polymerization may be changed to adjust the average particle size, particle size distribution, drying conditions and the like of the polymer particles to be produced.

In producing the resin particles A by dispersion polymerization, a polymer dispersant is added to the hydrophilic organic liquid. However, the dispersion system targeted in the present invention may or may not contain a polymer dispersant. Suitable examples of the polymer dispersant used at the time of producing seed particles or producing growing particles include, for example, the following.

Acids such as acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride; acrylic monomers containing a hydroxyl group; For example, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, γ-hydroxypropyl acrylate, γ-hydroxypropyl methacrylate, 3-chloro-2 acrylate -Hydroxypropyl,
3-chloro-2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerin monoacrylate, glycerin monomethacrylate, N-methylol acrylamide, N-methylol methacrylamide, etc .; vinyl alcohol or Ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, etc .; esters of vinyl alcohol and compounds containing a carboxy group, such as vinyl acetate, vinyl propionate, vinyl butyrate, etc .; acrylamide, methacrylamide , Diacetone acrylamide or their methylol compounds; acid chlorides such as acrylic acid chloride and methacrylic acid chloride Homopolymers or copolymers such as those having a nitrogen atom or a heterocycle thereof such as vinylpyridine, vinylpyrrolidone, vinylimidazole and ethyleneimine; polyoxyethylene, polyoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine Polyoxyethylenes such as, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene steacrylphenyl ether, and polyoxyethylene nonylphenyl ether;
And celluloses such as methylcellulose, hydroxyethylcellulose and hydroxypropylcellulose.

Further, the hydrophilic monomer and styrene, α
-Having a benzene nucleus such as methylstyrene and vinyltoluene, a derivative thereof or a copolymer such as acrylonitrile, methacrylonitrile, or an acrylic acid or methacrylic acid derivative such as acrylamide; further, a crosslinkable monomer such as ethylene glycol dimethacrylate; Copolymers with diethylene glycol dimethacrylate, allyl methacrylate, divinylbenzene and the like can also be used.

In the present invention, the resin particles A formed by dispersion polymerization consist of a vinyl polymer.
The raw material vinyl monomer is soluble in the hydrophilic organic liquid. Specific examples of the vinyl monomer in this case include the following.

Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene,
p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p -Methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,
Styrenes such as 4-dichlorostyrene; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-acrylate
-Octyl, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-methyl methyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, N-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc. α-methyl fatty acid monocarboxylic acid esters; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; vinyl chloride, vinyl chloride Single or mixed mixtures of vinyl halides such as lidene, vinyl bromide and vinyl fluoride, and mixtures thereof with monomers containing 50% by weight or more and copolymerizable with them.

The polymer constituting the resin particles may be polymerized in the presence of a so-called cross-linking agent having two or more polymerizable double bonds in order to increase the offset resistance. Preferred crosslinking agents include divinylbenzene, divinylnaphthalene and aromatic divinyl compounds that are derivatives thereof, other ethylene glycol dimethacrylate, diethylene glycol methacrylate, triethylene glycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate, tert-butyl. All divinyl compounds such as aminoethyl methacrylate, tetraethylene glycol methacrylate, diethylenic carboxylic acid esters such as 1,3-butanediol dimethacrylate, N, N-divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone, and three or more Compounds having a vinyl group are mentioned, and these are used alone or in a mixture.

When the growth polymerization reaction is subsequently performed using the seed particles thus cross-linked, the inside of the growing polymer particles becomes cross-linked. On the other hand, when the above-mentioned crosslinking agent is contained in the vinyl monomer solution used for the growth reaction, a polymer having a cured particle surface is obtained.

When the resin particles A are used as the base particles for toner, the resin particles A are dispersed in an organic solvent which does not dissolve the resin particles A, and a dye is dissolved in the solvent before and after the dispersion. Is used. A dispersion containing resin particles colored by infiltrating into the resin particles (hereinafter referred to as colored particles B) is used. In this case, the dye used for dyeing includes the solubility [D ₁ ] of the dye in the organic solvent used and the solubility [D ₂ ] of the dye in the resin constituting the resin particles A.
And the ratio [D ₁ ] / [D ₂ ] is preferably 0.5 or less. In addition, the solubility here is defined as what was measured at the temperature of 25 degreeC. The solubility of the dye in the resin has exactly the same definition as the solubility of the dye in the solvent, and means the maximum amount of the dye that can be contained in the resin in a compatible state.

As the organic solvent used for dyeing the resin particles A with the dye, those which do not dissolve or slightly swell the resin particles A to be used, specifically, the solubility parameter of the organic solvent [SP Value] and the [SP value] of the resin particles used are 1.0 or more, preferably 2.
Zero or more are used. For example, for styrene / acrylic resins, alcohols such as methyl alcohol, ethyl alcohol and n-propyl alcohol having a high [SP value] are used. Of course, if the difference in [SP value] is too large, the wetting of the resin particles A becomes poor, and good dispersion of the resin particles cannot be obtained.
Value] difference is preferably 2 to 5. From the viewpoint that the separation treatment of the resin particles A is not required, it is very preferable to use the same organic solvent as the hydrophilic organic liquid at the time of dispersion polymerization.

When the resin particles A dispersed in the hydrophilic organic liquid (including the colored resin particles B ... the same applies hereinafter) are subjected to a filtration operation through a filter cake layer for washing or concentration, Although the resin particles A hardly dissolve in the organic liquid (including the case of the organic solvent..., The same applies hereinafter), since the surface is very swelled, if it is pressurized by filtration or compacted, The swollen outer surface near the very surface of the resin particle A inside the cake layer is united with the surface of another adjacent resin particle A, and an aggregate is generated. For this reason, the filtration speed is reduced, and the filtration is severely stopped. It is considered that this does not depend on the size or shape of the resin particles A, but depends on the hardness of the resin particles A and the very small solubility (swellability) in the organic liquid.
The reason is also apparent from the fact that the other resin particles C having the same size and shape as the resin particles A but having a small swelling property to the organic liquid did not show an extremely low filtration rate.

In the present invention, in order to solve the problem, a liquid for preventing aggregation that does not dissolve the resin particles A is added to the dispersion system, and then a filtration operation is performed. That is, in the present invention, by adding the aggregation preventing liquid to the dispersion system,
The swellability of the resin particles A in the organic liquid is reduced, and as a result, a reduction in the filtration speed of the resin particles A is prevented.

This liquid for preventing liquid is a liquid having an ability to prevent aggregation of the resin particles A at the time of filtration and at the time of drying the filter cake, and has a [SP value] higher than that of the above-mentioned hydrophilic organic liquid or dyeing / use solvent. It is sufficient that the organic solvent is large and is soluble in the organic liquid or the solvent for dyeing. Specifically, water is mentioned.

The reason that the addition of the coagulation preventing liquid reduces the swelling of the resin particles A into the organic liquid is that the organic liquid and the resin particles A slightly swell, The swelling of the resin particles A into the organic liquid is extremely smaller than the swelling of the resin particles A into the organic liquid. Further, from the condition that the organic liquid is soluble with the anti-agglomeration liquid, the anti-agglomeration liquid added to the organic liquid reacts with the organic liquid dissolved into the particle surface, as if it were very thin on the particle surface. The state is as if a film of the aggregation preventing liquid was formed. Therefore, the resin particles A have less swelling on the surface as in the case of being dispersed in the aggregation preventing liquid, and the filterability is improved as in the case of the resin particles C.

The amount of the aggregation-preventing liquid to be added may be any as long as the surface of all of the resin particles A can be covered with a single-molecule-preventing liquid film. And 10% or more, more preferably 30% or more of the organic liquid, depending on the ratio of the organic liquid. However, an increase in the amount of the anti-agglomeration liquid increases the amount of treatment and decreases the efficiency in drying, so that it is desirable to minimize the amount.

It is very preferable to stir the dispersion after adding the aggregation preventing liquid. This has the effect of shortening the time required for the uniform diffusion of the anti-agglomeration liquid into the organic liquid and effectively promoting the reaction with the organic liquid dissolved into the resin particle surface. Can be reduced.

[0028]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. The parts and percentages shown below are based on weight.

Example 1 Styrene / acrylic resin particles dispersed and polymerized in methanol had a volume average particle size Dv = 5.80 μm, Dv / Dp
= L. It was 15. Add oil black 80 to this dispersion.
3 (manufactured by Orient Chemical Co., Ltd.) was added in the form of powder while stirring gradually, and the mixture was stirred at room temperature for 7 hours to obtain dyed resin particles.
In the obtained slurry, water 3 was added to 10 parts of methanol.
Water (particularly dyed resin particles: methanol: water = 4: 10: 3). Next, in order to remove unreacted substances (monomer, dispersant, etc.) at the time of polymerization, solid-liquid separation was performed by Nutsche filtration. As a result, the result shown by curve 1 in FIG. 1 was obtained as the state of filtration. Was. That is, although the filtration rate tended to decrease with an increase in the cake thickness, the filtration did not completely stop.

Example 2 Dyeing resin particles were obtained in the same manner as in Example 1. In the obtained slurry, dyed resin particles: methanol: water = 4:
Water was added to give 6.5: 6.5. Next, in order to remove unreacted substances (monomer, dispersant, etc.) during polymerization,
When solid-liquid separation was performed by Nutsche filtration, FIG.
The result shown by curve 2 was obtained, and the filtration speed was almost the same as in Example 1.

Comparative Example 1 Dyed resin particles were obtained in the same manner as in Example 1. Methanol was additionally added to the obtained slurry so that the dyeing resin particles: methanol = 4: 13. Next, in order to remove unreacted substances (monomer, dispersant, etc.) at the time of polymerization, solid-liquid separation was performed by Nutsche type filtration. Was. The result is shown by curve 5 in FIG. When the cake on the filter paper when filtration became impossible was observed with a microscope, it was found that there was no single particle, and the cake was united as if they were fused together.

Example 3 After the separated resin particles obtained in Example 1 were washed, they were redispersed so that the washed resin particles: methanol: water = 4: 10: 3. When this slurry was subjected to solid-liquid separation by Nutsche filtration, there was little tendency for the filtration rate to decrease due to an increase in the number of cake layers, and the filtration could be performed at almost the same filtration rate until the end. The result is shown by curve 3 in FIG.

Further, the obtained filter cake was air-dried and then pulverized. When the weight particle size distribution of the obtained powder was measured,
The result shown in FIG. 2 was obtained. As shown in FIG. 2, the particle size distribution of this powder was narrow, and the shape of the powder was close to the shape of the resin particles in a state of being dispersed in methanol.

Example 4 After the separated resin particles obtained in Example 1 were washed, they were redispersed so that the washed resin particles: methanol: water = 4: 6.5: 6.5. When this slurry was subjected to solid-liquid separation by Nutsche filtration, there was little tendency for the filtration rate to decrease due to an increase in the number of cake layers, and the filtration could be performed at almost the same filtration rate until the end. Also, no difference was found in the filtration rate between Example 3 and Example 4. The result is shown by curve 4 in FIG.

Comparative Example 2 After the separated resin particles obtained in Example 1 were washed, they were redispersed so that the ratio of washed resin particles: methanol = 4: 13. When this slurry was subjected to solid-liquid separation by Nutsche filtration, it was found that the filtration rate tended to decrease as the thickness of the cake layer increased. However, it was not impossible to filter. The result is shown by curve 6 in FIG.

Further, the obtained filter cake was air-dried and then pulverized. When the weight particle size distribution of the obtained powder was measured,
The result shown in FIG. 3 was obtained. As shown in FIG. 3, the particle size distribution of this powder was wide, and the powder was amorphous.

[0037]

According to the present invention, there is provided a filtration method comprising the steps of: filtering polymer resin particles which are swelled or hardly dissolved in a hydrophilic organic liquid; In the filtration method, after adding a liquid for preventing aggregation that does not dissolve the polymerized resin particles to the dispersion system and then performing filtration, it is possible to prevent swelling of the resin particles inside the filter cake layer, Aggregation and fusion of the resin particles are prevented, and as a result, a reduction in filtration speed can be prevented. Further, in the filtration method of the present invention, since the bonding between the resin particles in the filter cake is weakened, according to the present method, when the cake is dried to obtain powder, the crushability is good, Further, a filter cake from which powder having a shape close to primary particles can be easily obtained can be produced.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a filtration amount and a filtration time in Examples and Comparative Examples.

FIG. 2 shows a weight particle size distribution chart of a dried and pulverized product of the filter cake obtained in Example 3.

FIG. 3 shows a weight particle size distribution diagram of a dried and pulverized product of the filter cake obtained in Comparative Example 2.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-97704 (JP, A) JP-A-3-66705 (JP, A) JP-A-3-6205 (JP, A) JP-A-63-1988 43907 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 6/00-6/28

Claims (1)

(57) [Claims] 1. A method for filtering polymerized resin particles, comprising filtering and separating a dispersion system in which polymerized resin particles which are swollen or hardly dissolved in the organic liquid are dispersed in a hydrophilic organic liquid. A method for filtering polymerized resin particles, comprising adding water , which is a liquid for preventing aggregation that does not dissolve the resin particles, to the dispersion system, and then filtering.