JP4655711B2 - Method for producing magnetic composite particles - Google Patents

Description

  The present invention relates to a method for producing a magnetic composite particle. The magnetic composite particles can be used in a wide range of fields such as biochemical carriers, paints, paper, electronic materials, electrophotography, cosmetics, pharmaceuticals, agricultural chemicals, foods, and catalysts.

As a method for producing particles having a relatively uniform particle size distribution and complexing a magnetic material, magnetic fine particles are physically placed on the surface of a uniform particle size mother particle obtained by emulsion polymerization or suspension polymerization. A method of forming a coating layer by adsorbing has been proposed. For physical adsorption, the mother particles and magnetic fine particles are stirred at high energy in a container with a stirring blade in a stream of air with a peripheral speed of the stirring blade of 15 m / sec or higher. It is effective to make them collide. When the surface of the mother particle is adsorbed with surfactants, oligomers, low molecular weight components, etc., there are many cases where it becomes an inhibitor of complexation, and it is desirable that these do not exist. However, in emulsion polymerization and suspension polymerization in the step of obtaining mother particles, it is common to use a surfactant as a stabilizer. In order to reduce or remove these, a purification step such as centrifugation or dialysis is performed. It was carried out. The problem is that this purification process is complicated.
JP 2004-205481 A

  The present invention proposes a method for efficiently obtaining magnetic composite particles using uniform particle size mother particles that can eliminate the purification step in the production of magnetic particles.

  In the present invention, a monomer is produced by polymerizing the monomer in a proportion of 0.01 parts by weight or less based on 100 parts by weight of the monomer. On the surface of the obtained mother particle, The present invention provides a method for producing magnetic composite particles, comprising a step of physically adsorbing magnetic fine particles.

  The average particle diameter of the mother particles used in the present invention is 0.4 to 200 μm, preferably 0.5 to 100 μm, more preferably 1.5 to 50 μm. The CV (Coefficient of Variation) value of the mother particles is 20% or less, preferably 15% or less, more preferably 10% or less. When the average particle diameter of the mother particles is less than 0.4 μm, for example, the collision energy due to high-speed stirring of the particles is insufficient, and it becomes difficult to adsorb magnetic fine particles. On the other hand, when the average particle diameter of the mother particles exceeds 200 μm, the characteristics as fine particles are lost. On the other hand, if the CV value is out of the above range, the uniformity of the particle diameter of the obtained magnetic composite particles becomes insufficient.

  The mother particles used in the present invention are polymer particles obtained by polymerization, and as such polymers, vinyl polymers are particularly preferred, and vinyl monomers used for the production thereof are styrene, α-methylstyrene, Aromatic vinyl monomers such as halogenated styrene and divinylbenzene, vinyl esters such as vinyl acetate and vinyl propionate, unsaturated nitriles such as acrylonitrile, methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2 -Ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, cyclohexyl acrylate, Such as ethylenically unsaturated carboxylic acid alkyl esters such as Russia hexyl methacrylate can be exemplified. This vinyl polymer may be a homopolymer or a copolymer composed of two or more monomers selected from the vinyl monomers. Also, the above vinyl monomers and conjugated diolefins such as butadiene and isoprene, acrylic acid, methacrylic acid, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide, 2-hydroxyethyl acrylate A copolymer with a copolymerizable monomer such as 2-hydroxyethyl methacrylate, diallyl phthalate, allyl acrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, or the like can also be used.

  It is desirable to obtain the mother particles of the present invention by soap-free emulsion polymerization without using a surfactant during polymerization. Soap-free emulsion polymerization is described, for example, in J. Org. Polym. Sci. Chem. Ed. 14, 2193 (1977), polymer chemistry, 22, 481 (1965), polymer theory, 32, 229 (1975), polymer theory, 32, 522 (1975), and the like. Although a small amount of surfactant can be used from the viewpoint of polymerization stability and particle size control, the upper limit is 0.01 parts by weight with respect to 100 parts by weight of the monomer. If it is used in excess of this, the surfactant is adsorbed on the particle surface and becomes an inhibitor of the magnetic substance complexation.

  The average particle size and particle size distribution in the present invention are obtained by randomly measuring the particle size of 100 particles on an electron micrograph.

The magnetic fine particles used in the present invention are not particularly limited, but iron oxide-based substances are typical, and MnFe ₂ O ₄ (Mn = Co, Ni, Mg, Cu, Li _0.5 Fe _{0. 5} ) or the like, magnetite represented by Fe ₃ O ₄ , or γFe ₂ O ₃ . In particular, γFe ₂ O ₃ and Fe ₃ O ₄ are preferable as magnetic materials having strong saturation magnetization and low residual magnetization.

  The magnetic fine particles used in the present invention preferably have an average particle size of 1/5 or less, more preferably 1/10 or less, and even more preferably 1/20 or less of the average particle size of the mother particles. When the average particle diameter of the magnetic fine particles exceeds 1/5 of the average particle diameter of the mother particles, it is difficult to form a coating layer having a uniform and sufficient thickness on the surface of the mother particles.

  In the present invention, the ratio of the mother particles to the magnetic fine particles (mother particles: magnetic fine particles) is preferably 95: 5 to 20:80 by weight. When the amount of magnetic fine particles is less than this range, the composite effect is reduced. When the amount of magnetic fine particles is larger than this range, the amount of the mother particles becomes excessive, and the number of magnetic fine particles that are not combined increases.

  The magnetic fine particles used in the present invention are preferably those whose surfaces are hydrophobized from the viewpoints of affinity and compatibility between the mother particles and the monomer monomer used in the subsequent step. Examples of the method for hydrophobizing the surface of the magnetic fine particles include a method in which a compound having an extremely high affinity portion and a hydrophobic portion in the molecule is brought into contact with and bonded to the magnetic fine particles. it can. Examples of such compounds include silane compounds represented by silane coupling agents. Hydrophobization with silane compounds is excellent in chemical resistance, especially alkali resistance, and peeling of the magnetic material due to dropping of the hydrophobized layer during use, problems of deterioration of magnetic performance, or detached magnetic material and surface activity It is possible to effectively prevent the occurrence of a problem that contaminants enter the system due to the floating agent. Further, in the present invention, it can be said that the hydrophobized magnetic fine particles are sufficiently hydrophobized when they can be satisfactorily dispersed in, for example, toluene.

  Examples of silane compounds represented by silane coupling agents include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and γ-glycid. Oxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, dodecyltrimethoxysilane, Hexyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, dodecyltrichlorosilane, hexyltrichlorosilane, methyltrichlorosilane, phenyltrichlorosilane, etc. The

  As a method for bonding these silane compounds to magnetic fine particles, for example, magnetic fine particles and a silane compound are mixed in an inorganic medium such as water or an organic medium such as alcohol, ether, ketone, ester, and stirred. After heating, the magnetic fine particles are separated by decantation or the like and the inorganic medium or the organic medium is removed by drying under reduced pressure. Alternatively, the magnetic fine particles and the silane compound may be directly mixed and heated to bond them together. In these means, the heating temperature is usually 30 to 100 ° C., and the heating temperature is about 0.5 to 2 hours. The amount of the silane compound used is appropriately determined depending on the surface area of the magnetic fine particles, but is usually 1 to 50 parts by weight, preferably 2 to 30 parts by weight with respect to 100 parts by weight of the magnetic fine particles.

  In order to form a coating layer of magnetic fine particles on the surface of the mother particles by the method of the present invention, first, the mother particles and the magnetic fine particles are mixed, and the magnetic fine particles are physically adsorbed on the surface of the mother particles. The physical adsorption method described in the present invention refers to an adsorption method and a bonding method that do not involve a chemical reaction. In principle, hydrophobic / hydrophobic adsorption, melt bonding or adsorption, fusion bonding or adsorption, hydrogen bonding, This refers to van der Waals coupling. As an example of using hydrophobic / hydrophobic adsorption, the surface of the mother particle and the surface of the magnetic fine particles are selected to be hydrophobic or hydrophobized, and dry blended, or the mother particles and magnetic fine particles are selected. And a method of volatilizing the solvent under mixing conditions after sufficiently dispersing in a well-dispersible solvent such as toluene and hexane without attacking both. It is also possible to make a composite using fusion bonding or adsorption, fusion bonding or adsorption by selecting a material or solvent that slightly dissolves the surface of the mother particle and the surface of the magnetic fine particles and / or selecting the temperature conditions during mixing. is there.

It is also effective to realize compounding by applying a physically strong force from the outside. For example, a mortar, an automatic mortar, a ball mill, a blade pressurizing powder compression method, a mechanochemical effect such as a mechanofusion method, or a jet mill or a hybridizer using a high-speed airflow impact method. It is desirable that the physical adsorption force is strong in order to efficiently and firmly perform the composite. As the method, the peripheral speed of the stirring blade is preferably 15 m / second or more, more preferably 30 m / second or more, and further preferably 40 to 150 m / second in a vessel with a stirring blade. If the peripheral speed of the stirring blade is lower than 15 m / second, sufficient energy for forming the coating layer may not be obtained. In addition, although there is no restriction | limiting in particular about the upper limit of the circumferential speed of a stirring blade, It determines automatically from points, such as an apparatus to be used and energy efficiency.
Also, the composite can be performed a plurality of times using the same or different types of magnetic fine particles and / or non-magnetic fine particles, and magnetic composite particles comprising a multilayered coating layer having a plurality of coating layers can be produced. . For example, after forming a first coating layer using mother particles and magnetic fine particles, polymer particles are further added and physically adsorbed on the first coating layer to form a second coating layer. And a several coating layer can be formed by repeating this as needed. As described above, polymer particles, preferably thermoplastic polymer particles, are preferably used as components of the non-magnetic fine particles used when forming the coating layer having a multilayer structure. The thermoplastic polymer particles can be appropriately selected from the vinyl polymers according to the purpose. The thermoplastic polymer particles preferably have a particle size of 1 to 60% of the particle size of the mother particles, a weight average molecular weight of 10,000 to 1,000,000, and an acrylic material. The addition amount of these polymer components is preferably 100 parts by weight or less with respect to 100 parts by weight of the base particles. In this case, if the type of the polymer that is non-magnetic fine particles is changed to the mother particles, it becomes easy to adhere by frictional charging and the formation of the coating layer becomes easier.
Next, a polymer layer (hereinafter also referred to as “coating polymer layer”) formed on the coating layer for coating will be described.

  Such a polymer layer comprises a copolymerizable monomer as a main raw material and a polymerization initiator as a secondary raw material in the presence of particles having a coating layer formed on the surface of the mother particles (hereinafter referred to as “magnetic material-coated particles”). , Emulsifiers, dispersants, surfactants, electrolytes, cross-linking agents, molecular weight regulators and the like are added as necessary, and polymerization is performed in a liquid. By forming the coating polymer layer by polymerization in this way, it is possible to introduce a desired functional group onto the surface of the polymer layer, and the surface processability is excellent.

  As a component of the polymer layer, a vinyl polymer is particularly preferable, and vinyl monomers used for the production thereof are aromatic vinyl monomers such as styrene, α-methylstyrene, halogenated styrene, divinylbenzene, vinyl acetate, Vinyl esters such as vinyl propionate, unsaturated nitriles such as acrylonitrile, methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, ethylene glycol di Ethylenically unsaturated carboxylic acid alkyls such as acrylate, ethylene glycol dimethacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, etc. It can be exemplified esters and the like. This vinyl polymer may be a homopolymer or a copolymer composed of two or more monomers selected from the vinyl monomers.

  In addition, the vinyl monomers and conjugated diolefins such as butadiene and isoprene, acrylic acid, methacrylic acid, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, diallyl phthalate, allyl acrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, styrenesulfonic acid and its sodium salt, 2-acrylamido-2-methylpropanesulfonic acid and its sodium salt, Copolymers with copolymerizable monomers such as isoprene sulfonic acid and its sodium salt should also be used. Can.

  The polymerization initiator is preferably an oil-soluble polymerization initiator from the viewpoint of solubility in water. When a water-soluble polymerization initiator is used, there is a tendency that not only polymerization on the surface of the composite particles but also a large amount of new particles in which only a hydrophobic polymerization monomer not containing magnetic substance-coated particles is polymerized.

  Examples of oil-soluble polymerization initiators include benzoyl peroxide, lauroyl peroxide, tertiary butyl peroxy 2-ethylhexanate, 3,5,5-trimethylhexanoyl peroxide, azobisisobutyronitrile and other peroxide compounds and azo compounds. Can be mentioned.

  Water-soluble initiators include potassium persulfate, ammonium persulfate, persulfates such as sodium persulfate, hydrogen peroxide, 2-2 azobis (2-aminopropane) mineral acid salt, azobiscyanovaleric acid and its alkali metal salts, and Examples thereof include ammonium salts, and redox initiators in which persulfate, hydrogen peroxide salt and sodium bisulfite, sodium thiosulfate, ferrous chloride, etc. are combined. Among them, persulfate is preferably used. . The ratio of these polymerization initiators to the whole monomer is preferably in the range of 0.01 to 8% by weight.

  As the surfactant, a commonly used anionic surfactant or nonionic surfactant can be used alone or in combination. For example, reactive anionic surfactants include alkali metal salts of higher alcohol sulfates, alkali metal salts of alkylbenzene sulfonic acids, alkali metal salts of succinic acid dialkyl ester sulfonic acids, alkali metal salts of alkyl diphenyl ether disulfonic acids, In addition to anionic surfactants such as sulfuric acid ester salt of oxyethylene alkyl (or alkylphenyl) ether, phosphoric acid ester salt of polyoxyethylene alkyl (or alkylphenyl) ether, formalin condensate of sodium naphthalene sulfonate, etc. S-180A (manufactured by Kao Corporation), Eleminol JS-2 (manufactured by Sanyo Chemical Co., Ltd.), Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adekaria Soap SE-10N (Asahi Denka Kogyo Co., Ltd.) Inc.) Door can be.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, Aqualon RS-20 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adekari Soap NE-20 ( Reactive nonionic surfactants such as Asahi Denka Kogyo Co., Ltd.).

  The method for adding the monomer to the polymerization system in the formation of the coating polymer layer is not particularly limited, and may be any of a batch method, a division method, or a continuous addition method. The polymerization temperature varies depending on the polymerization initiator, but is usually 10 to 90 ° C, preferably 30 to 85 ° C, and the time required for the polymerization is usually about 1 to 30 hours.

  One of the main uses of the magnetic composite particles obtained by the method of the present invention is diagnostic carrier particles. In this application, it is not desirable to elute impurities from the particles, or from the magnetic fine particles themselves, or from the magnetic fine particles. However, the magnetic composite particles obtained in the present invention do not have such inconvenience, and thus are diagnosed. Suitable for medicinal carrier particles. In the use of such diagnostic agent carrier particles, the surface characteristics of the coating polymer layer can be selected according to the purpose.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited by these.
1. Preparation of mother particles (Method of obtaining particles by polymerization without using a surfactant by soap-free emulsion polymerization)
Distilled water (780 g) was charged into a 1 L separable flask, and the temperature was raised to 80 ° C. under an N ₂ gas stream while stirring at 200 rpm. Next, 20 g of a 5% aqueous solution of potassium persulfate as a reaction initiator and 20 g of styrene as a monomer were added and reacted for 2 hours while maintaining 80 ° C. Subsequently, 180 g of styrene monomer was continuously dropped over 3 hours while maintaining 80 ° C. Thereafter, the mixture was reacted for 2 hours while maintaining 80 ° C. and then cooled.
The obtained particles had an average particle size of 0.80 μm and a CV value of 1.5%. This was filtered through a 500 mesh stainless steel wire mesh, and only the particles were collected by centrifugation and dried in a 60 ° C. oven for 24 hours.
2. Covering mother particles with magnetic particles (formation of coating layer)
A ferrite superparamagnetic substance (average) having a hydrophobized surface is obtained by adding acetone to the oil-based magnetic fluid “FV55” (manufactured by Matsumoto Yushi Co., Ltd.) to precipitate and precipitate particles. Particle size: 0.01 μm) was obtained. The obtained magnetic fine particles are added to toluene / water (weight ratio 1: 1), and after sufficiently stirring, the magnetic fine particles are dispersed only in toluene, and the surface is hydrophobic. It was confirmed.

Next, 20 g of magnetic fine particles were mixed with 10 g of the mother particles, and this mixture was mixed with this system using a hybridization system NHS-0 type (manufactured by Nara Machinery Co., Ltd.). Treatment was performed at 100 m / sec (16200 rpm) for 5 minutes.
3. Surface coating polymerization of magnetic material coated particles (formation of coating polymer layer)
30 g of magnetic material coated particles obtained by coating the magnetic particles on the mother particles and 900 g of 0.5% aqueous solution of nonionic emulsifier “Emulgen 150” (manufactured by Kao) as a dispersing agent are charged into a 1 L separable flask. To disperse. To this was added 3 g of styrene as a monomer, 0.9 g of methacrylic acid, and 0.6 g of tertiary butyl peroxy 2-ethylhexanate (manufactured by NOF Corporation; Perbutyl O) as a polymerization initiator. _The reaction was carried out at 80 ° C. for 8 hours under a _two gas stream.
Comparative example

1. Preparation of mother particles (method of obtaining particles by polymerization using a surfactant by general emulsion polymerization)
585 g of distilled water was put into a 1 L separable flask. In a separate container (for example, a 500 ml beaker), 147 g of distilled water, 3 g of 5% aqueous solution of sodium dodecylbenzenesulfonate as a surfactant, and 135 g of styrene as a monomer were directly emulsified by ultrasonication. A 1 L separable flask containing distilled water was stirred at 200 rpm with a squid type stirring blade, and the temperature was raised to 80 ° C. under a N ₂ gas stream. Next, 15 g of a 5% aqueous solution of potassium persulfate as a reaction initiator and 15 g of styrene as a monomer were added and reacted for 2 hours while maintaining 80 ° C. Subsequently, styrene emulsified with a surfactant was continuously dropped into a 1 L separable flask at 80 ° C. for 3 hours. Thereafter, the mixture was reacted for 2 hours while maintaining 80 ° C. and then cooled.
The obtained particles had an average particle size of 0.79 μm and a CV value of 1.9%. This was filtered through a 500 mesh stainless steel wire mesh, and only the particles were collected by centrifugation and dried in a 60 ° C. oven for 24 hours.
2. Covering mother particles with magnetic particles (formation of coating layer)
It carried out by the same method as an Example.
3. Surface coating polymerization of magnetic material coated particles (formation of coating polymer layer)
It carried out by the same method as an Example.

  A test solution containing 1% by weight of the obtained magnetic composite particles in water as a dispersion medium was prepared. 1 ml of this test solution was placed in an Eppendorf tube, and the magnetic capture rate was measured when 4000 gauss magnetism was applied for 1 minute from the lateral direction after stirring. Moreover, the same operation and measurement were performed for 200 mM NaOH aqueous solution as a dispersion medium.

  The magnetic composite particles of the examples had a magnetic capture ratio of 99% by weight or more in any dispersion medium of water and a 200 mM NaOH aqueous solution. This is because the magnetic fine particles are strongly bonded to the mother particles, and the magnetic material does not peel off during the surface coating polymerization of the magnetic material-coated particles, and even under high pH conditions such as a 200 mM NaOH aqueous solution, the magnetic fine particles The magnetic responsiveness is fast because it is stable without desorption from the mother particles.

  On the other hand, in the comparative example, the magnetic capture ratio of 99% by weight or more obtained in all of the examples was not obtained in any dispersion medium of water or 200 mM NaOH aqueous solution. This is because the surface of the mother particle is covered with a surfactant, so the bond with the magnetic fine particles is weak, and the magnetic material is peeled off during the surface coating polymerization of the magnetic material-coated particles, and the magnetic responsiveness in water is low. The magnetic responsiveness was further delayed because the peeling of the magnetic material was accelerated in a 200 mM NaOH aqueous solution. In the comparative example, after the preparation of the mother particles, the performance of the examples can be exhibited by repeatedly performing dialysis and centrifugal purification to remove the surfactant. However, the method of the present invention without this step has an advantage. is there.

Claims (6)

A monomer is produced by polymerizing the monomer in a proportion of 0.01 parts by weight or less with respect to 100 parts by weight of the monomer, and magnetic fine particles are formed on the surface of the obtained mother particle. A method for producing magnetic composite particles, comprising a step of physically adsorbing. _{2. The} method for producing magnetic composite particles according to claim 1, wherein the magnetic fine particles are at least one of γFe ₂ O ₃ and Fe ₃ O ₄ . In any one of Claims 1 to 2,
The method for producing magnetic composite particles, wherein the magnetic fine particles have an average particle diameter that is 1/5 or less of the average particle diameter of the mother particles. In any of claims 1 to 3 ,
The ratio of the said mother particle and the said magnetic body fine particle is a manufacturing method of a magnetic body composite particle which is 95: 5-20: 80 by weight ratio (base particle: magnetic body particle). In any of claims 1 to 4,
The magnetic particles are adsorbed on the mother particles by stirring the mother particles and the magnetic fine particles in a container with a stirring blade at a high speed in an air flow with a peripheral speed of the stirring blade of 15 m / sec or more. A method for producing magnetic composite particles.   A method for producing magnetic composite particles, comprising a step of polymerizing a monomer in the presence of the magnetic composite particles obtained by the production method according to claim 1.