JPH04351605A - Preparation of fine polymer particle - Google Patents

Abstract

PURPOSE:To produce fine polymer particles having a monodisperse particle diameter distribution and an average particle diameter in a specific range. CONSTITUTION:A hydrophobic monomer is polymerized in the presence of poly(methacrylic acid) using a free-radical polymerization initiator in a solvent that dissolves both the monomer and poly(methacrylic acid) but does not dissolve a polymer of the monomer, thereby giving fine polymer particles. As the initiator is used a compound that is soluble in the solvent and capable of generating a free radical. The fine polymer particles produced by this method have a monodisperse particle diameter distribution and an average particle size not less than 0.05mum but less than 1mum.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine polymer particles having a monodisperse particle size distribution and an average particle size of 0.05 μm or more and less than 1 μm. These polymer particles are used in a wide range of applications, such as diagnostic particle carriers and liquid chromatography column packing materials.

0002

[Prior Art] Monodisperse polymer fine particles are used as diagnostic fine particle carriers, diagnostic reagent carriers, column packing materials for liquid chromatography, fillers for paints, various spacers, particles for electrophotographic toners, etc. It is used.

[0003] For example, diagnostic microparticle carriers are usually used as test reagents by immobilizing antigens, antibodies, etc. on the particle surface. When this diagnostic microparticle dispersion (diagnostic latex) is mixed with a body fluid such as blood or urine, the antigens, antibodies, etc. immobilized on the surface of the microparticles react with specific substances in the sample body fluid and aggregate. Immunological tests are performed by determining the presence or absence of agglutination and measuring the degree of agglutination. The main conditions required for such diagnostic microparticle carriers include uniform particle size, particularly true spherical monodisperse microparticles.

[0004] Monodisperse polymer fine particles are known to have various particle sizes depending on the purpose of use, but for example, the one widely used as diagnostic latex is 1 μm in diameter.
0.05μ, as seen in those less than m
Polymer particles having an average particle diameter of 1 μm or more and less than 1 μm are in great demand for applications such as diagnostic microparticle carriers, column packing materials, and various spacers. However, with the conventional method, particles with a monodisperse particle size distribution and an average particle size of 0.05 μm or more1
It is very difficult to produce polymer microparticles in the sub-μm range.

Conventionally, as a method for obtaining monodisperse polymer fine particles, for example, polymer particles prepared by a normal emulsion polymerization method are used as seed (polymerization seed) particles, and then a monomer, a surfactant, and a polymerization initiator are added to the seed particles. A seed polymerization method is known in which the particle size of seed particles is increased by adding and polymerizing various polymerization auxiliary materials such as agents. However, in this method, when surfactants, polymerization initiators, etc. are added in excess, new polymer particles are generated, which impairs the monodispersity of the particle size distribution of the obtained polymer. Therefore, the amount of surfactant is usually adjusted to be around the critical micelle-forming concentration of surfactant in the polymerization system, but under these conditions, the growing polymer particles become extremely unstable colloidally. ,
It becomes easier to form aggregates. Therefore, in order to suppress the generation of aggregates, careful attention is required during polymerization operations such as stirring.

[0006] Furthermore, a part of the surfactant and reaction initiator added during latex production are exposed on the surface of the polymer particles obtained by the emulsion polymerization method. For example, when used as a diagnostic microparticle carrier,
It affects the sensitization of antigens and antibodies, and also has an adverse effect on the stability of reagents.

[0007] As another method for obtaining polymer fine particles having a monodisperse particle size distribution, soap-free polymerization is known, which does not use a surfactant and uses sodium styrene sulfonate, which has emulsifying power, instead. . However, in this method, the particle size of the obtained polymer varies slightly depending on dissolved oxygen, inorganic salts, etc. contained in the polymerization system, so reproducibility is poor and it is unsuitable for industrial production. Furthermore, since the reaction system does not use a surfactant, it is colloidally unstable, and the monomer concentration must usually be kept at 10% by weight or less, which is also problematic from an economic standpoint.

[0008] Sufficient monodispersity cannot be achieved by a method of classifying polymer particles having a wide molecular size distribution obtained by a conventional suspension polymerization method.

[0009] In recent years, a dispersion polymerization method has been proposed as a method for easily producing monodisperse polymer particles. However, this dispersion polymerization method is a polymerization method that utilizes polymer precipitation in an organic solvent, and the molecular weight of the precipitated polymer in an organic solvent is generally larger than that in aqueous polymerization. The particle size is usually 1 to several μm. Moreover, the surface of the polymer particles obtained by the dispersion polymerization method is covered with the dispersion stabilizer used, so it can be used in applications that require purification of the particles, such as diagnostic microparticle carriers, liquid chromatography columns, etc. It cannot be used as a filler, filler for paint additives, etc. In addition, since a water-soluble polymer is used as a dispersion stabilizer, the surface of the polymer particles is hydrophilic to a considerable extent, and when such particles are used in electrophotographic toners, the particle surface becomes The amount of charge decreases, making it impossible to obtain a clear image.

The applicant has filed a patent application for a method for producing polymer particles having a monodisperse particle size distribution by dispersion polymerizing a hydrophobic monomer in the presence of polymethacrylic acid using a radical initiator. (Unexamined Japanese Patent Publication No. 1-2)
No. 49806), although this method can obtain relatively large polymer particles of 1 to 20 μm, it is not possible to obtain fine polymer particles having an average particle size of 0.05 μm or more and less than 1 μm. Under these circumstances, there is a need for a method for easily producing polymer fine particles having a monodisperse particle size distribution.

[0011]

[Problems to be Solved by the Invention] An object of the present invention is to obtain particles that have a monodisperse particle size distribution and have an average particle size within the range of 0.05 μm or more and less than 1 μm by a method that is simpler than conventional methods. An object of the present invention is to provide a method for producing polymer fine particles.

[0012] As a result of intensive research to overcome the problems of the prior art, the present inventors found that when carrying out dispersion polymerization of hydrophobic monomers in the presence of polymethacrylic acid, the radical polymerization initiator The inventors have discovered that the above object can be achieved by using a compound that is soluble in a solvent and has the ability to generate radical ions, and based on this knowledge, the present invention has been completed.

[0013]

Thus, according to the present invention, hydrophobic monomers are dissolved in the presence of polymethacrylic acid in a solvent that dissolves them but does not dissolve the polymer of the hydrophobic monomers. A method for producing a particulate polymer by performing polymerization using a radical polymerization initiator, characterized in that a compound soluble in the solvent and capable of generating radical ions is used as the radical polymerization initiator. A method for producing fine polymer particles having a particle size distribution and an average particle size within a range of 0.05 μm or more and less than 1 μm is provided. The present invention will be explained in detail below.

(Hydrophobic monomer) The hydrophobic monomer used in the present invention has a solubility in water of 5% by weight at 20°C.
less than 1% by weight, preferably less than 1% by weight of monomer.

Specific examples of hydrophobic monomers include, for example:
Styrene, α-methylstyrene, p-methylstyrene,
Aromatic vinyl monomers such as chloromethylstyrene, halogenated styrene, divinylbenzene; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate , (meth)acrylic acid esters such as stearyl (meth)acrylate, ethylene glycol di(meth)acrylate, and glycidyl (meth)acrylate; and conjugated diolefins such as butadiene and isoprene.

These monomers are usually used alone or in combination of two or more so that the glass transition temperature of the resulting polymer is higher than room temperature. Among these, aromatic vinyl monomers are particularly preferred.

(Polymethacrylic acid) In the present invention,
Polymethacrylic acid is used as a dispersion stabilizer. Polymethacrylic acid is not limited by its manufacturing method, but
Viscosity measured with a B-type viscometer of 0% by weight aqueous solution (20°C,
Rotor #2, measured at 60 rpm) is 100-500,
000cps, preferably 50,000-150,00
It is 0 cps.

The amount of polymethacrylic acid used is usually 1 to 40 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the hydrophobic monomer component. If it is less than 1 part by weight, polymerization stability during polymerization will deteriorate and a large amount of coagulum will be generated. If more than 40 parts by weight is used, it will be uneconomical, the monomer concentration will be low and productivity will be reduced, and when polymethacrylic acid is removed after polymerization, the operation will be complicated, etc. There's a problem.

Polymethacrylic acid may be polymerized by adding separately polymerized polymethacrylic acid to the reaction system together with a hydrophobic monomer; It may be obtained by polymerizing a methacrylic acid monomer prior to polymerizing the methacrylic acid monomer.

(Solvent) In the present invention, as a solvent,
A solvent is used that dissolves the hydrophobic monomer, polymethacrylic acid and polymerization initiator, but does not dissolve the resulting polymer particles.

Specific examples of such solvents include lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol; ketones such as acetone and methyl ethyl ketone; and heterocyclic compounds such as pyridine, pyrrole, and tetrahydrofuran. ; Aliphatic hydrocarbons such as n-hexane and cyclohexane; Aromatic hydrocarbons such as benzene and toluene; Organic solvents such as halogenated hydrocarbons such as methylene chloride and chloroform. Among these, lower alcohols are preferred. These organic solvents may be used alone or in combination of two or more. In addition, depending on the case, water may be used in combination.

The amount of the solvent used is not particularly limited, but is usually 100 to 2 parts by weight per 100 parts by weight of the hydrophobic monomer component.
000 parts by weight, preferably in the range of 500 to 2000 parts by weight. If the amount of solvent used is too small, the monomer concentration during polymerization will be high, resulting in a large amount of aggregate formation, while if it is too large, it will be economically disadvantageous.

(Radical Polymerization Initiator) The radical polymerization initiator used in the present invention is a compound that is soluble in the solvent used and has the ability to generate radical ions.

When a conventional radical polymerization initiator such as an organic peroxide type such as benzoyl peroxide as disclosed in JP-A-1-249806 or an azonitrile type such as azobisisobutyronitrile is used, Polymer particles having a relatively large particle size are obtained, making it impossible to obtain polymer fine particles as the object of the present invention.

Specific examples of compounds having the ability to generate radical ions used in the present invention include persulfates such as potassium persulfate and ammonium persulfate; 4,4'-azobis-4-cyanovaleric acid, 2, 2'-Azobis-
Mention may be made of 2-amidinopropane hydrochloride,
It is not limited to these.

[0026] The amount of the polymerization initiator used in the present invention is not particularly limited and may be selected appropriately taking into consideration the molecular weight of the desired polymer, but it is limited to 100 parts by weight of the hydrophobic monomer component. , usually 0.1 to 10 parts by weight.

(Polymerization method) In the method of the present invention, in a solvent that dissolves both the hydrophobic monomer and polymethacrylic acid, a polymerization initiator having a radical ion generating ability is used.
The hydrophobic monomer is polymerized. The order of addition of each component is
Although not particularly limited, polymerization is usually carried out by adding a polymerization initiator to a solution in which a hydrophobic monomer and polymethacrylic acid are dissolved in a solvent.

The polymerization reaction temperature is not particularly limited and may be appropriately selected depending on the polymerization initiator used.
It is in the range of 0 to 100°C.

After the polymerization reaction is completed, the polymer particles are separated by filtration, centrifugation, or the like. If necessary, polymethacrylic acid on the surface of the polymer fine particles can be removed,
As a result, the surface of the polymer fine particles easily changes from a hydrophilic surface to a hydrophobic surface of the polymer fine particles themselves. As a method for this purpose, a conventional method for purifying polymer particles such as centrifugation, dialysis using a semipermeable membrane, ultrafiltration method, etc. may be employed.

In order to completely remove the polymethacrylic acid on the surface of the polymer particles, it is preferable to suspend the polymer particles in water and centrifuge the suspension.
It is preferable to adjust the pH of the particle suspension to the alkaline side using a base such as sodium hydroxide, since this improves the solubility of polymethacrylic acid.

[0031] Polymethacrylic acid is removed by this purification operation because polymethacrylic acid does not normally have α-hydrogen, which serves as a grafting point, so polymethacrylic acid and hydrophobic monomer are not copolymerized. Therefore, it is thought that this is because the water-soluble polymethacrylic acid present on the particle surface is separated from the particle by centrifugation or the like.

In the method of the present invention, after the initially added hydrophobic monomer has been polymerized, 100 parts by weight of the hydrophobic monomer (and, if necessary, a polymerization initiator) is added to the monomer component. (in the range of 0.1 to 10 parts by weight) to continue the polymerization.

The additionally added hydrophobic monomer may be the same as or different from the hydrophobic monomer originally used, but it must be soluble in the organic solvent used. The amount is preferably 150 parts by weight or less, more preferably 100 parts by weight, based on 100 parts by weight of the polymer particles obtained in the initial polymerization.
Parts by weight or less. If more than 150 parts by weight is added later, the added monomer creates new particles, impairing the monodispersity of the particle diameter of the polymer fine particles.

According to the method of the present invention, particles having a monodisperse particle size distribution with a weight average particle size/number average particle size of less than 1.2, and
Average particle size (weight average particle size and number average particle size) is 0.0
Polymer fine particles having a size in the range of 5 μm or more and less than 1 μm are obtained.

[0035]

[Examples] The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Note that parts and percentages in the examples are based on weight unless otherwise specified.

The method for measuring physical properties is as follows. (1) Polymerization conversion rate by weight method. (2) Average particle size Unless otherwise specified, the average particle size was measured using an LPA3000/3100 submicron particle size analyzer (manufactured by Otsuka Electronics). (3) Amount of acid groups on the particle surface 2 g of polymer particles were added to 48 g of distilled water, and 0.1
After adding N sodium hydroxide solution until the pH reached 12 and stirring for 6 minutes, conductivity titration (CM-117, manufactured by Kyoto Denshi Co., Ltd.) was performed by adding 0.5 ml of 0.1 N hydrochloric acid aqueous solution every 30 seconds. Calculate from the amount of hydrochloric acid consumed corresponding to the inflection point of the titration curve. (4) Using a thermogravimetric change thermobalance (manufactured by Shimadzu Corporation; TGA-50),
Under a nitrogen atmosphere, the temperature at which the polymer weight decreased by 1% and 5% was measured at a heating rate of 10° C./min.

[Example 1] Stirrer, cooling condenser,
The interior of a 2-liter reactor equipped with a nitrogen gas inlet tube and a thermometer was replaced with nitrogen, and 360 g of deionized water, 840 g of ethyl alcohol, and 1 liter of methacrylic acid were placed in the reaction container.
Add 3.3 g and 0.95 g of potassium persulfate to 30
The mixture was stirred for a minute to form a homogeneous mixture.

Next, after bubbling the mixed solution with nitrogen, the reactor was heated to 70° C. to initiate the reaction, which was maintained for 6 hours to complete the polymerization of methacrylic acid. The polymerization conversion rate was about 100%. Next, 66.7 g of styrene was added to the reactor (the catalyst was: potassium persulfate 0
．． 5 parts) After polymerizing styrene at the same temperature for 16 hours, the reaction mixture was cooled to room temperature. Polymerization conversion rate is 9
It was 8.3%.

The resulting polystyrene suspension was centrifuged to precipitate the polymer particles, and the polymer particles were separated by decantation. The polymer particles were poured into distilled water, thoroughly stirred, and then centrifuged again, thereby repeating the purification operation twice.

The obtained polystyrene fine particles were spherical fine particles having a monodisperse particle size distribution with a weight average particle size of 0.47 μm and a number average particle size of 0.44 μm. Furthermore, no polymethacrylic acid was detected on the surface of the polymer fine particles, confirming that the particle surface was polystyrene.

[Comparative Example 1] In place of potassium persulfate, 2,
The weight average particle size was 2.0 in the same manner as in Example 1 except that 0.95 g of 2'-azobisisobutyronitrile was used.
Spherical particles having a monodisperse particle size distribution of 5 μm and a number average particle size of 2.01 μm were obtained. In addition, the particle diameter was measured using Coulter Multisizer (manufactured by Coulter).

[Example 2] After the polymerization of styrene was completed in Example 1, 66.7 g of styrene and 0.5 g of potassium persulfate were further added, and the polymerization was continued for 10 hours. The polymerization conversion rate was 96.4%. Thereafter, the same purification operation as in Example 1 was carried out to obtain a weight average particle size of 0.58 μm.
, Spherical fine particles having a monodisperse particle size distribution with a number average particle size of 0.55 μm were obtained.

[Example 3] After the polymerization of styrene was completed in Example 1, 33.3 g of styrene, 60.7 g of divinylbenzene (manufactured by Wako Pure Chemical Industries, Ltd., purity 55%) and 0.5 g of potassium persulfate were added. was added, and the polymerization was continued for 10 hours. The polymerization conversion rate was 98.2%. Thereafter, the same purification operation as in Example 1 was carried out to obtain a weight average particle size of 0.6.
Spherical fine particles having a monodisperse particle size distribution of 0 μm and a number average particle size of 0.58 μm were obtained.

After vacuum-drying the polymer particles, they were poured into ethylene glycol and toluene, but in each case the liquid became cloudy, confirming that the polymer particles were insoluble in these solvents.

Further, when the thermal weight loss of the polymer fine particles was measured, the 1% weight loss temperature was 310°C, and the 5% weight loss temperature was 360°C.

[Example 4] In place of potassium persulfate, 4,
The weight average particle size was 0 in the same manner as in Example 1 except that 0.1 g of 4'-azobis-4-cyanovaleric acid was used.
．． Spherical fine particles having a monodisperse particle size distribution of 86 μm and a number average particle size of 0.83 μm were obtained.

[Example 5] The same procedure as Example 1 was carried out, except that 3.2 g of ammonium persulfate was used in place of potassium persulfate, with a weight average particle size of 0.23 μm and a number average particle size of 0.
．． Spherical fine particles with a monodisperse particle size distribution of 21 μm were obtained.

[Example 6] The amount of deionized water was 360 g,
Spherical fine particles having a monodisperse particle size distribution of a weight average particle size of 0.68 μm and a number average particle size of 0.65 μm were obtained in the same manner as in Example 1, except that the amount of ethyl alcohol was changed to 840 g.

[0049]

Effects of the Invention According to the present invention, polymer fine particles having a monodisperse particle size distribution and an average particle size within the range of 0.05 μm or more and less than 1 μm can be produced with a simpler operation compared to conventional production methods. Obtainable.

Claims (1)

[Claims] [Claim 1] Hydrophobic monomers are polymerized in the presence of polymethacrylic acid using a radical polymerization initiator in a solvent that dissolves the hydrophobic monomers but does not dissolve the polymer of the hydrophobic monomers to form particles. A method for producing a polymer having a monodisperse particle size distribution and an average particle size distribution characterized by using as a radical polymerization initiator a compound that is soluble in the solvent and has the ability to generate radical ions. Diameter is 0.05μm
A method for producing polymer fine particles having a size of less than 1 μm.