JPH0912610A - Production of fine polymer particle - Google Patents

Abstract

PURPOSE: To produce stably polymer particles having a low molecular weight and a sharp particle diameter distribution and suited as seeds used in seed polymerization. CONSTITUTION: This production process comprises polymerizing an ethylenically unsaturated monomer in an aqueous hydrophilic organic liquid solution in which the monomer is soluble and the formed polymer is insoluble under conditions in which the weight ratio of the polymerization initiator to the monomer is (5-40): (95-60), and the weight ratio of the water to the hydrophilic organic liquid is (1-50):(99-50).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing polymer fine particles having a narrow particle size distribution.

[0002]

2. Description of the Related Art In recent years, applications that require fine particles having a micron size and a narrow particle size distribution have become widespread. Various studies have also been conducted on the manufacturing method thereof. The conventionally known suspension polymerization method can produce only a very wide particle size distribution, and in order to obtain monodisperse particles having a particle size, classification is performed after polymerization. However, classification requires a time-consuming and labor-intensive process. Moreover, it is very difficult to classify small particles of 5 μm or less. On the other hand, emulsion polymerization can produce particles with a narrow particle size distribution, but the particle size is 0.1
Only relatively small ones of 1 μm can be made.

On the other hand, seed polymerization in which a small particle made by soap-free polymerization, dispersion polymerization or the like is used as a seed and an unsaturated monomer is absorbed in the particle to form a desired particle diameter is disclosed in Japanese Patent Publication No. 63-32500 and Japanese Patent Publication 6-924
No. 43 publication. However, the molecular weight of particles obtained by soap-free polymerization or dispersion polymerization is usually 100,000 or more, and the amount of unsaturated monomer absorbed is small, so that there is a problem that particles larger than the seed particles cannot be obtained.

It has been disclosed to lower the molecular weight of seed particles used as a method for increasing the amount of unsaturated monomers absorbed. A method of using a chain transfer agent has been disclosed in order to obtain low-molecular weight particles, but the use of a chain transfer agent causes problems such as a decrease in polymerization rate and coalescence of produced particles.
At present, there is no method for stably producing particles having a desired molecular weight.

[0005]

SUMMARY OF THE INVENTION In view of the above points, the present invention is suitable for seed particles used in seed polymerization,
An object is to provide a method for stably producing particles having a low molecular weight and a small particle size distribution.

[0006]

[Means for Solving the Problems] The present inventors have studied various polymerization methods in order to achieve the above objects. As a result, by adjusting the amount of the initiator of the polymerization system and the amounts of the hydrophilic organic liquid and water, the conditions under which the particle size distribution was narrow and the low-molecular weight fine particles were stably produced were found, and the present invention was completed. .

That is, the present invention is a method of polymerizing an ethylenically unsaturated monomer which is soluble in an aqueous solution of a hydrophilic organic liquid and water but is insoluble in the aqueous solution but does not dissolve the resulting polymer. The polymerization is carried out with the weight ratio of the polymerization initiator to the ethylenically unsaturated monomer and the weight ratio of water to the hydrophilic organic liquid within a specific range. With this configuration, polymer fine particles having a weight average molecular weight of 20,000 or less and a narrow particle size distribution can be stably produced.

The hydrophilic organic liquid used in the present invention may be any one which becomes an aqueous solution when mixed with water,
For example, long-chain alcohols such as methanol, ethanol and isopropyl alcohol, polyhydric alcohols such as ethylene glycol, glycerin and diethylene glycol,
Examples include cellosolves such as methyl cellosolve, cellosolve and butyl cellosolve, and ether alcohols such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether. These hydrophilic organic liquids can be used alone or in combination of two or more kinds. You may.

The hydrophilic organic liquid includes alcohols,
It is possible to control the particle size of the polymer fine particles by using an organic liquid other than ethers together under a mixing condition in which the produced polymer particles are not dissolved.

As the above-mentioned organic liquid, hydrocarbons such as hexane, octane, petroleum ether, cyclohexane, benzene, toluene and xylene, halogenated hydrocarbons such as carbon tetrachloride, trichloroethylene and tetrabromoethane, ethyl ether, Ethers such as dimethyl glycol, trioxane, tetrahydrofuran, methylal,
Acetals such as diethyl acetal, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexane, butyl formate, butyl acetate, ethyl propionate, esters such as cellosolve acetate, acids such as formic acid, acetic acid and propionic acid, nitropropene , Sulfur- and nitrogen-containing organic compounds such as nitrobenzene, dimethylamine, monoethanolamine, pyridine, dimethylsulfoxide, and dimethylformamide.

The amount of water mixed with the hydrophilic organic liquid is
When the amount is small, the particles are coalesced during the polymerization, and when the amount is large, the molecular weight of the produced particles is increased. Therefore, the weight ratio of the hydrophilic organic liquid and water is limited to 99 to 50: 1 to 50. Preferably 99-60: 1-40, more preferably 99.5-
75: 0.5 to 25.

The aqueous solution used in the present invention contains S
O_Four ^2-, NO^2-, PO_Four ^3-, Cl^-, Na ⁺, Mg²⁺,
Ca²⁺, Polymerization in the presence of other inorganic ions
You may go.

The ethylenically unsaturated monomer used in the present invention is soluble in hydrophilic organic liquids such as styrene and α.
-Styrene derivatives such as methylstyrene, p-methylstyrene, p-chlorostyrene and chloromethylstyrene; vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated nitriles such as acrylonitrile;
(Meth) acrylic acid such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, stearyl acrylate, stearyl methacrylate Examples thereof include ester derivatives, which may be used alone or in combination of two or more kinds.

The amount of the ethylenically unsaturated monomer added is
It is determined according to the particle size of the target polymer particles, and the higher the concentration of the unsaturated monomer in the aqueous solution, the larger the diameter of the produced particles, and the lower the value, the smaller.

In order to make the particle diameters uniform, the weight ratio of the hydrophilic organic liquid to the ethylenically unsaturated monomer is 99 to 40: 1.
About 60 is suitable.

The polymerization initiator used in the present invention is not particularly limited as long as it can be used in the radical polymerization which is dissolved in the aqueous solution of the hydrophilic organic liquid, and examples thereof include benzoyl peroxide, lauroyl peroxide and orthochloroperoxide. Benzoyl, orthomethoxybenzoyl peroxide, 3,5,
Organic peroxides such as 5-trimethylhexanoyl peroxide, t-butylperoxy-2-ethylhexanoate, di-t-butylperoxide, azobisisobutyronitrile, azobiscyclohexacarbonitrile,
Examples thereof include azo compounds such as azobis (2,4-dimethylbereronitrile) and persulfide initiators such as potassium persulfate.

The amount of the above-mentioned polymerization initiator may be determined according to the molecular weight of the intended polymer particles and the decomposition temperature of the polymerization initiator. When the amount is small, the molecular weight does not decrease sufficiently, and when the amount is large, the molecular weight decreases and the particles formed. Or
Since the polymerization rate becomes too high and stable polymerization cannot be performed, the weight ratio of the unsaturated monomer to the initiator is 95 to 6
It is limited to 0: 5-40.

In the aqueous solution used in the present invention, a dispersion stabilizer may be used in order to stabilize the dispersion of the above-mentioned ethylenically unsaturated monomer and the polymer fine particles produced, and for example, as the dispersion stabilizer. , Acrylic acid, methacrylic acid and their derivatives, acids such as itaconic acid, crotonic acid, maleic acid, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, diethylene glycol monoacrylic acid ester, diethylene glycol monomethacrylic acid ester, Glycerin monoacrylate,
Acrylic monomers having hydroxyl groups such as glycerin monomethacrylic acid ester, N-methylol acrylamide, N-methylol methacrylamide, ethers such as vinyl alcohol or vinyl methyl ether, vinyl propyl ether, or vinyl acetate, vinyl propionate, Esters with vinyl alcohol such as vinyl butyrate,
Acrylamide, methacrylamide or methylol compounds thereof, acid chlorides such as acrylic acid chloride and methacrylic acid chloride, vinylpyridine, vinylpyrrolidone, vinylimidazole, ethyleneimine and other nitrogen atom or a monomer having a heterocycle thereof. (Co) polymers may be mentioned.

Further, a copolymer of the above monomer and a monomer having an aromatic ring such as styrene or α-methylstyrene, or a derivative of acrylic acid or methacrylic acid such as acrylonitrile, methacrylonitrile or acrylamide can also be used.

Other dispersion stabilizers include polyoxyethylene, polyoxypropylene, polyoxyethylene alkylamines, polyoxyethylene alkylamides,
Polymer dispersion stabilizers such as polyoxyethylenes such as polyoxyethylene alkyl phenyl ether and polyoxyethylene alkyl phenyl ester, and celluloses such as methyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose can be used.

The above-mentioned polymer dispersion stabilizer can be appropriately selected depending on the kind of the hydrophilic organic liquid to be used and the intended polymer particles, but in the sense that the coalescence between the particles is prevented three-dimensionally, it is applied to the surface of the polymer particles. A substance having a high affinity and absorptivity and a high affinity and solubility for a hydrophilic organic liquid is selected.

When the amount of the polymer dispersion stabilizer added is small, the particle size distribution is broadened and the resulting polymer is coalesced. Therefore, when the amount is increased, the viscosity of the aqueous solution is increased and a large amount of power is required for stirring. Therefore, the weight ratio of the ethylenically unsaturated monomer and the polymer dispersion stabilizer is 97-50: 3-
50.

In order to enhance the protective effect, it is desirable that the polymer dispersion stabilizer has a molecular chain of a certain length or more, preferably 10,000 or more.

In the aqueous solution used in the present invention, a metal such as cobalt, iron or aluminum or an alloy thereof, or a metal oxide such as iron oxide, copper oxide or nickel oxide is used in combination with the above polymer dispersion stabilizer. Fine powder, carbon black, nigrosine dye, pigment such as aniline blue, dyes, higher alcohol sulfate ester salt, alkylbenzene sulfonate, α-olefin sulfonate, anionic surfactant such as phosphate ester, alkylamine salt , Amine alcohol fatty acid derivatives, polyamine fatty acid derivatives, imidazoline and other amine type and alkyl trimethyl ammonium salts, dialkyl dimethyl salts, alkyl dimethyl benzyl ammonium salts, pyridium salts, quaternary ammonium salt type cation surfactants such as benzotonium chloride , Fatty acid amide derivative, polyvalent Is advantageous in also narrow the stabilization and particle size distribution of the formed polymer particles with a non-ionic surfactant such as alcohol derivatives.

In the production method of the present invention, in an inert gas,
After the dispersion stabilizer is dissolved in the aqueous solution of the hydrophilic organic liquid, a polymerization initiator, an ethylenically unsaturated monomer, and other necessary additives are added, and the mixture is appropriately stirred (20 to 300 times / rp).
It is carried out by raising the temperature while initiating m) to start the polymerization.

Although a polymerization time of 5 to 40 hours is required to carry out the polymerization in the high polymerization rate region, the polymerization is stopped in the state of a desired particle size and particle distribution, or a polymerization initiator is sequentially added. The polymerization rate can also be increased.

After the completion of the polymerization, the polymer fine particles can be obtained by collecting, washing and drying the polymer slurry by operations such as sedimentation, centrifugation, decantation and the like.

[0028]

Next, embodiments of the present invention will be described. Hereinafter, "parts" means "parts by weight".

Example 1 Polyvinylpyrrolidone (weight average molecular weight of 30,000) 3.6 parts, aerosol OT (anionic surfactant manufactured by Wako Pure Chemical Industries) 0.57 part and V-65
(2,2'-azobis (2,4-dimethylvaleronitrile) 2.86 parts was dissolved in an aqueous solution of 74.0 parts methanol and 10.0 parts ion-exchanged water, and the solution was stirred under a nitrogen stream. Add 14.0 parts of styrene, 60 ℃
The temperature was raised to and the polymerization reaction was carried out for 24 hours.

After the reaction was completed, the polymer fine particles were isolated by centrifugation, washed with methanol several times, and then dried under reduced pressure. The particle size and particle size distribution of the polymer fine particles were measured by gel permeation chromatography (GPC) from the molecular weight and the average value of 100 arbitrary particles in an electron micrograph. Each value was as follows. The Cv value is a coefficient of variation of the diameter of particles and its unit is “%”. Weight average molecular weight (Mw) 11300, number average molecular weight (Mn) 3440 Average particle size 1.32 μm Cv value 2.5

(Example 2) The methanol of Example 1 was replaced with 82
The same procedure as in Example 1 was repeated except that 2 parts of water and 2 parts of water were used. Each value was as follows. Weight average molecular weight (Mw) 5600 Number average molecular weight (Mn) 1900 Average particle size 1.42 μm Cv value 2.8

(Example 3) The procedure of Example 1 was repeated, except that 64 parts of ethanol and 20 parts of water were used as the methanol of Example 1. Each value was as follows. Weight average molecular weight (Mw) 12100 Number average molecular weight (Mn) 3650 Average particle size 1.30 μm Cv value 3.0

(Example 4) The procedure of Example 1 was repeated except that the amount of the polymerization initiator in Example 1 was changed to 1.43 parts. Each value was as follows. Weight average molecular weight (Mw) 18300 Number average molecular weight (Mn) 4410 Average particle size 1.22 μm Cv value 3.0

Example 5 The procedure of Example 1 was repeated, except that the amount of the polymerization initiator used in Example 1 was 4.29 parts, the amount of methanol was 74 parts, and the polymerization temperature was 50 ° C. Each value was as follows. Weight average molecular weight (Mw) 9200 Number average molecular weight (Mn) 3220 Average particle size 1.46 μm Cv value 2.8

Comparative Example 1 The procedure of Example 1 was repeated, except that 84 parts of ethanol was used as the methanol of Example 1 and water was not used. The particles produced during the polymerization were coalesced into a viscous polymer, and the particles could not be collected.

(Comparative Example 2) The methanol of Example 1 was replaced with 84
Parts, except that water was not used and the polymerization temperature was 45 ° C., and the same procedure as in Example 1 was carried out. There were many coalescents, and the particles had a wide particle size distribution. The respective values were as follows: Weight average molecular weight (Mw) 7450 Number average molecular weight (Mn) 2920 Average particle size 3.5 μm Cv value 10.5

Comparative Example 3 The procedure of Example 1 was repeated except that 0.286 parts of azoisobutyronitrile was used as a polymerization initiator, 84 parts of methanol was used, and the polymerization temperature was 70 ° C. Although the particle size was monodisperse, the particles had a large molecular weight. The values were as follows: Weight average molecular weight (Mw) 80250 Number average molecular weight (Mn) 41110 Average particle size 1.80 μm Cv value 2.8

[0038]

Since the production method of the present invention has the above-mentioned constitution, it is possible to stably produce polymer fine particles having a low molecular weight and a narrow particle size distribution. The obtained polymer fine particles are polymerized into particles having a desired particle size by seed polymerization, and have functionality such as electrophotographic toner, spacers in liquid crystal displays, optical fibers, microsphere lenses such as optical connectors, and latex reagents. It can be used for microspheres and the like.

Claims (1)

[Claims] 1. A method for polymerizing an ethylenically unsaturated monomer, which is soluble in an aqueous solution of a hydrophilic organic liquid but is insoluble in the resulting polymer, but is insoluble in the resulting polymer, wherein the polymerization is soluble in the aqueous solution. The weight ratio of the initiator to the ethylenically unsaturated monomer is 5 to 40:95 to 60, and the weight ratio of the amount of water to the hydrophilic organic liquid is 1 to 50:99 to 50. A method for producing fine polymer particles.