JPH0689082B2 - Method for producing monodisperse polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field The present invention uses a seed polymerization method to obtain a number average particle size of 2.0 to 50.
The present invention relates to a method for producing a monodisperse polymer latex having a narrow particle size distribution of 0 μm.

2. Description of the Related Art Conventionally, an emulsion polymerization method and a suspension polymerization method are mentioned as a method for producing a spherical polymer latex. Regarding the particle size and particle size distribution, generally, in the emulsion polymerization method, a monodisperse polymer latex can be obtained by properly setting the conditions, but only a particle size of 1 μm or less can be obtained. On the contrary, in the suspension polymerization method, a wide range of particle diameters of several microns to several millimeters can be obtained, but it is impossible to obtain a uniform particle diameter.

As an improvement of these methods, JP-A-58-106554
As described in the publication, a method for obtaining a monodisperse polymer by seed polymerization has been proposed. That is, it is a method in which polymer fine particles of about 0.5 μm are first prepared by emulsion polymerization, and then the polymer fine particles are enlarged and grown by polymerization.

On the other hand, as a method for obtaining micron-sized monodisperse polymer particles by one-step polymerization, J. Polym. Sci. Polym, Lett. Ed, Vol.
23, p103-108 (1985), a solution-based dispersion polymerization method is known. According to this method, polymer particles are obtained by dissolving the monomer in a solvent that dissolves the monomer but not the polymer, and polymerizing in the solvent.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the method by the seed polymerization is 0.5 μm.
Since seed polymerization is carried out starting from the emulsion polymerization latex before and after, a particle growth step of two or more steps is required in order to prepare a latex of 5 to 10 μm, and the length of the step complicates the production equipment, It has a drawback that it causes a decrease in economic efficiency. Further, the above-mentioned solution-based dispersion polymerization method has an advantage that polymer fine particles having a uniform particle size distribution of about 10 μm at the maximum can be obtained. The distribution changes greatly, especially like electrophotographic toner,
It is difficult to use for applications that require rheology control. Furthermore, there is a problem in that safety is caused by using a solvent, or auxiliary equipment such as recovery of the solvent is required.

The present invention has been made in view of the above problems.
Therefore, an object of the present invention is to provide a method for economically producing monodisperse polymer particles having a particle size of 2 to 50 μm by a simple process.

The present inventors focused their research on the fact that polymerization in an aqueous medium is possible, the process is simple, the economy is excellent, and the molecular weight and the molecular weight distribution can be controlled. As a result, the present invention has been completed.

Means and Actions for Solving Problems The method for producing monodisperse polymer fine particles of the present invention comprises a vinyl aromatic compound, one or more monomers selected from the group consisting of acrylic acid esters and methacrylic acid esters. In the presence of a surfactant, as a polymerization initiator persulfate 10
^-1 to 10 ^-3 mol / and divalent metal sulfate as electrolyte
A first step of producing a latex of polymer fine particles having a number average particle size of 1.0 to 10.0 μm and a particle size distribution with a standard deviation of 1.25 or less by a Coulter counter, which is emulsion-polymerized using 10 ⁻² to 10 ⁻⁴ mol / Impregnating the polymer fine particles (hereinafter referred to as “seed particles”) with a polymerization initiator,
Then, a latex of polymer fine particles having a number average particle size of 2.0 to 50.0 μm and a standard deviation of 1.25 or less by a Coulter counter is produced by polymerizing one or more vinyl monomers.

Next, the present invention will be described in detail.

In the first step of the present invention, first, the number average particle size is 1.0 to 1
Standard deviation of 1.25 with 0.0μm and Coulter counter
A latex of polymer particles having the following particle size distribution is produced. That is, one or more monomers selected from the group consisting of vinyl aromatic compounds, acrylic acid esters and methacrylic acid esters are polymerized in an aqueous medium in the presence of a polymerization initiator and a surfactant.

At this time, known surfactants can be used, but it is preferable to use the succinic acid ester derivative represented by the following general formula (I).

(In the formula, R ₁ and R ₂ are the same or different and each represent a substituted or unsubstituted alkyl group having 4 to 8 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted cyclohexyl group.) The addition amount of the succinic acid ester derivative is appropriately set, but it is particularly preferable to use it in the aqueous solution concentration range of 0.04 to 0.8 g / dl.

In emulsion polymerization, the surfactant properties required to increase the particle size and maintain monodispersity are 1) have a higher surface tension than commonly used sodium dodecyl sulfate, etc. The conditions are that the number of repetitions of generation / disappearance is as small as possible, and 3) the surface charge is sufficient. The above 1) is a condition for controlling polydispersion (generation of fine particles) by generating conditions for increasing the particle size, and 3) is polydispersion by preventing interparticle bonding (for coarse particles). This is a condition for controlling (generation). The surfactant represented by the general formula (I) is
These conditions are satisfied, and there is an advantage that the generation-disappearance of the emulsion is less repeated as compared with a linear activator such as sodium dodecyl sulfate.

In the present invention, a persulfate-based initiator is used as the polymerization initiator, and for example, potassium persulfate, ammonium persulfate and the like are most preferably used. In that case, it is necessary to use the aqueous solution in the concentration range of 10 ⁻¹ to 10 ⁻³ mol /. Outside this range, seed particles with a predetermined particle size and standard deviation cannot be obtained.

Further, in the present invention, as the electrolyte, divalent metal sulfate such as cuprous sulfate (CuSO ₄ ) and ferrous sulfate (FeSO ₄ ) is used, whereby the average particle size of the polymer fine particles is The larger the particle size, the sharper the particle size distribution. It is necessary to use the concentration of the electrolyte in the range of 10 ⁻² to 10 ⁻⁴ mol /. If it deviates from this range, seed particles having a predetermined particle size and average deviation cannot be obtained.

Further, a water-soluble polymer such as an acrylic acid-maleic acid copolymer or a vinyl acetate-maleic acid copolymer may be used as a dispersion stabilizer together with the succinic acid ester derivative represented by the general formula (I). . In that case, the surface tension is preferably 40 to 75 dynes / cm.

The polymerization temperature is 40 to 90 ° C, preferably 45 to 75 ° C.

The monodisperse latex prepared in the first step is purified by ultrafiltration, dialysis, etc. to remove the remaining polymerization initiator, surfactant and the like.

In the second step, the seed particles obtained in the first step are enlarged. First, the seed particles are impregnated with the polymerization initiator. As the method of impregnation, for example,
It is common to add a vinyl monomer solution of an oil-soluble polymerization initiator to a suitable aqueous solution of a surfactant to form an emulsion, and add the latex containing the seed particles obtained in the first step to the emulsion. The polymerization initiator and the vinyl monomer are thereby impregnated in the seed particles via the aqueous phase. At this time, it is necessary to adjust the molecular weight of the seed particles so that the seed particles are easily expanded by the vinyl monomer. The number average molecular weight is 50,000 or less, preferably 30,000 or less, and more preferably 10,000 or less.

It is necessary to use a polymerization initiator that does not decompose during impregnation or has a very low decomposition rate. For example, the decomposition temperature of the polymerization initiator is a 10-hour half-life temperature,
It is preferably 55 to 90 ° C. If this decomposition temperature is lower than 55 ° C, the vinyl monomer cannot be suppressed from polymerizing during the impregnation operation, and if it is higher than 90 ° C, the reaction temperature in the subsequent polymerization reaction should be increased. Will be required. The most preferred and commonly used of such are lauroyl peroxide and benzoyl peroxide.

The amount of the polymerization initiator used is in the range of 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the vinyl monomer used.

The impregnation operation is usually performed at a temperature in the range of room temperature to 40 ° C.
It takes 5 to 20 hours.

In order to maintain the dispersion stability in the impregnation operation, it is necessary to add an appropriate surfactant and dispersion stabilizer. As such a surfactant, one having a surface tension as low as possible,
For example, it is preferable that the surface tension of a 0.1% aqueous solution by the Dunui method is 35 dynes / cm or less. For example, those represented by the following general formula can be given.

(In the formula, each of R ₁ and R ₂ represents an alkyl group having 9 to 20 carbon atoms.) Specific examples include those represented by the following general formula.

By using such a low surface tension surfactant, migration of substances (polymerization initiator, vinyl monomer) from the swollen seed particles to the aqueous phase can be prevented and the generation of fine particles can be controlled. it can.

The dispersion stabilizer needs to have an appropriate adsorption force and spread in water to prevent interparticle aggregation. Known ones can be used. Examples thereof include dispersants such as hydroxyethyl cellulose, polyvinyl alcohol, gelatin, and tricalcium phosphate. Among them, polyvinyl alcohol, particularly those having a polymerization degree of 100 to 900 and a saponification degree of 80 to 95 mol% are preferably used.

After the impregnation with the polymerization initiator is completed, a vinyl monomer is newly added. As the vinyl monomer, one or more selected from vinyl aromatic compounds such as styrene, acrylic acid esters such as methyl methacrylate, methacrylic acid esters, vinyl cyan compounds such as acrylonitrile, and conjugated diolefins such as butadiene. Monomers are used.

These vinyl monomers may be added as they are, but it is preferable to add them in the form of an aqueous emulsion. If desired, the above-mentioned surfactant and dispersion stabilizer are added.

The polymerization is carried out in the form of an aqueous emulsion at a temperature of 50 to 95 ° C. The obtained latex has a core-shell structure having a layer of the vinyl polymer formed in the second step on the surface of the seed particles obtained in the first step, the number average particle size is 2.0 to 50.0 μm and the Coulter counter It is composed of monodisperse vinyl polymer fine particles having a standard deviation of 1.25 or less.

Further, in the second step, it is possible to make it porous by using an appropriate polyfunctional vinyl monomer. Divinylbenzene or the like is preferably used as the polyfunctional vinyl monomer, and is added together with an appropriate solvent when the seed particles are enlarged.
After the completion of the polymerization, the solvent can be removed under reduced pressure to make it porous.

When the present invention is applied to the production of an electrophotographic developer, it is necessary to wear it. As a coloring method, 1) a vinyl monomer-soluble oil-soluble dye is allowed to coexist when the seed particles are enlarged. Method, 2) a method of coating seed particles with a pigment such as carbon black, and then enlarging the seed particles,
3) A method of impregnating an oil-soluble dye with a solvent after completion of the enlargement and removing the solvent after the impregnation, 4) a method of coating the surface of the enlarged particles with a coloring agent by a spray drying method or the like can be used. . However, the coloring method is not limited to the above method, and the coloring agent is not particularly limited.

Examples Hereinafter, the present invention will be described by examples. All of the following examples were carried out in a 5 glass-lined autoclave equipped with a N ₂ inlet, anchor type stirring blade, and temperature controller.

Preparation of seed particles (first step) After putting distilled water 3.2 into the reactor and replacing with nitrogen gas,
The temperature was raised to 50 ° C. To this, an aqueous solution obtained by dissolving 4.32 g of the following compound and 0.72 g of an acrylic acid-maleic acid copolymer (Poise 520 manufactured by Kao Corporation) in 0.2 water was added.

Then, an aqueous solution obtained by dissolving 28.8 g of ammonium persulfate in 0.2 water was added. Furthermore, while adding 400 ml of styrene and 0.6 g of cuprous sulfate, keeping the polymerization temperature at 50 ° C,
Polymerization was carried out for a time. After 5 hours, the temperature was raised to 60 ° C. Styrene 400 ml and t-dodecyl mercaptan 1
2 g of the mixed solution was placed in a dropping funnel and added dropwise in about 2 hours.
The polymerization was further continued, and the polymerization was completed in a total of 26 hours.
The obtained latex was passed through a 200-mesh wire net to remove agglomerates from the latex.

The particle diameter of the obtained polymer fine particles (seed particles) was observed by a scanning electron microscope, and it was confirmed that a monodisperse particle aggregate having a particle diameter of 2.8 μm was obtained. The standard deviation of the particle size distribution measured by a Coulter counter was 1.09. Further, the polymer fine particles have a weight average molecular weight of 72000,
The number average molecular weight was 14,000.

Seed Polymerization (Second Step) The latex obtained in the first step was purified by repeating ultrafiltration and concentration, and finally concentrated to 2700 ml (solid content 20%). Perex TR is added to the obtained concentrated latex.
(Kao Corporation, sodium ditridecyl sulfosuccinate)
0.54 g was added, shaken and stored.

The following components were charged to the same reactor as in the first step.

The above latex 125 ml Perex TR (Kao Corporation, sodium ditridecyl sulfosuccinate) 0.02% aqueous solution 2340 ml potassium iodide 0.2 g polyvinyl alcohol 120 ml (Kuraray PVA-203) 10% aqueous solution. , Charged to the reactor.

Benzoyl peroxide 12 g Styrene 120 g Perex TR (manufactured by Kao Corporation, sodium ditridecyl sulfosuccinate) 0.02% aqueous solution 240 ml The mixture was stirred at 30 ° C. for 15 hours to complete the impregnation with the polymerization initiator.

Then, for the enlargement of seed particles by polymerization, an emulsion having the following composition was prepared and added to the above reactor.

Styrene 455g Perex TR (Kao Corporation, sodium ditridecyl sulfosuccinate) 0.02% aqueous solution 800ml Kao Perex OTP (sodium dioctyl sulfosuccinate) 7.2g After adding the reaction mixture, start heating the reaction mixture at 75 ° C for 9 hours. Polymerization was carried out. The obtained latex was passed through a 100-mesh wire net to remove agglomerates from the latex. Aggregates
At 10 to 20 g, the polymerization stability was quite good.

When a part of the latex was solidified by freeze-drying and the molecular weight was measured (Toyo Soda HLC802A), the weight average molecular weight was 56400 and the number average molecular weight was 21600. Furthermore, when a part of the latex was taken out and the particle size was observed with a scanning electron microscope, the particle size was 7.5 μm. When the particle size distribution was observed with a Coulter counter, the standard deviation was 1.10 on a number basis and 1.12 on a volume basis.

EFFECTS OF THE INVENTION According to the method for producing polymer fine particles of the present invention, a single particle having an extremely large particle size of about 2.0 to 50.0 μm by emulsion polymerization and a narrow particle size distribution with a standard deviation of 1.25 or less. Dispersible polymer particles can be easily obtained without requiring complicated steps.

And, the polymer fine particles obtained by the present invention, a biological carrier, an immobilized enzyme carrier, an immunoserological diagnostic agent carrier,
It can be applied to carriers for pharmaceutical administration, ion exchange resins, spacers for crystal display, column fillers, electrophotographic developers, paints, etc. Particularly, colored polymer particles can be used as they are as electrophotographic developers. It is advantageous because it can be used.

Claims (5)

[Claims] 1. A vinyl aromatic compound, acrylic acid ester and one selected from the group consisting of methacrylic acid ester or more monomers, the presence of a surfactant, persulfate as the polymerization initiator 10 ^- Emulsion polymerization using ¹ to 10 ^-3 mol / and divalent metal sulfate 10 ^-2 to 10 ^-4 mol / as electrolyte, number average particle size of 1.0 to 10.0 μm and particle size distribution of standard deviation of 1.25 or less by Coulter counter A first step of producing a latex of polymer fine particles having, and a number average particle size of 2.0 to 50.0 by impregnating the polymer fine particles with a polymerization initiator and then polymerizing one or more vinyl monomers. A process for producing monodisperse polymer fine particles, which comprises the second step of producing a latex of polymer fine particles having a standard deviation of 1.25 or less by μm and a Coulter counter. 2. The method for producing monodisperse polymer fine particles according to claim 1, wherein the surfactant used in emulsion polymerization is selected from the compounds represented by the following general formula (I). (In the formula, R ₁ and R ₂ are the same or different and each represents a substituted or unsubstituted alkyl group having 4 to 8 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted cyclohexyl group) 3. The method for producing monodisperse polymer fine particles according to claim 1, wherein the polymer fine particles obtained in the first step have a number average molecular weight of 30,000 or less. 4. The surface tension is 35 dyne / c in the second step.
The method for producing monodisperse polymer fine particles according to claim 1, wherein a surfactant having a m or less is used. 5. The monodispersion according to claim 1, wherein polyvinyl alcohol having a saponification degree of 80 to 95 mol% and a polymerization degree of 100 to 900 is used as a dispersion stabilizer in the second step. Method for producing polymer fine particles.