Manufacturing method for magnetic beads

Abstract

The present invention provides a method for manufacturing magnetic beads with improved magnetic particle collection capabilities. [Solution] A method for producing magnetic beads, comprising the steps of (A) dispersing a monomer mixture containing monomers, magnetic particles, and an emulsifying stabilizer in an aqueous medium by a membrane emulsification method to obtain a suspension, and (B) suspend polymerization of the monomers in the suspension.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing magnetic beads. [Background technology]

[0002] As a technology relating to magnetic beads containing polymers and magnetic particles, for example, the technology described in Patent Document 1 is known.

[0003] Patent Document 1 describes a method for producing magnetic polymer particles, characterized by mixing 100 parts by weight of a radically polymerizable vinyl monomer containing 1 to 20% by weight of an unsaturated carboxylic acid with 5 to 200 parts by weight of a magnetic material, dispersing the mixture in water, polymerizing it with an oil-soluble initiator, and then treating the resulting particles with an organic base and / or a water-soluble solvent. According to the method for producing magnetic polymer particles described in Patent Document 1, it is stated that particles with a large number of useful carboxyl groups on their surface and a high surface charge can be obtained. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-87711 [Overview of the project] [Problems that the invention aims to solve]

[0005] This invention provides a method for manufacturing magnetic beads with improved magnetic particle collection capabilities. [Means for solving the problem]

[0006] According to the present invention, a method for manufacturing magnetic beads as shown below is provided.

[0007] [1] The process involves (A) dispersing a monomer mixture containing monomers, magnetic particles, and an emulsifying stabilizer in an aqueous medium using a membrane emulsification method to obtain a suspension. A method for producing magnetic beads, comprising the step (B) of suspend polymerization of the monomer in the suspension. [2] The method for producing magnetic beads according to [1], wherein the emulsifying stabilizer contains an aliphatic higher alcohol. [3] The method for producing magnetic beads according to [2], wherein the aliphatic higher alcohol comprises at least one selected from the group consisting of lauryl alcohol, cetanol, and myristyl alcohol. [4] A method for producing magnetic beads according to any one of [1] to [3], wherein the content of the emulsifying stabilizer in the monomer mixture is 0.05% by mass or more and 10% by mass or less, when the total content of all components in the monomer mixture is 100% by mass. [5] A method for producing magnetic beads according to any one of [1] to [4], wherein the monomer comprises a (meth)acrylate monomer. [6] The method for producing magnetic beads according to [5], wherein the (meth)acrylate monomer includes methyl (meth)acrylate. [7] The (meth)acrylate monomer comprises monomer (a), The method for producing magnetic beads according to [5] or [6], wherein the monomer (a) comprises at least one selected from the group consisting of n-butyl (meth)acrylate, t-butyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, glycidyl (meth)acrylate, and trifluoroethyl (meth)acrylate. [8] A method for producing magnetic beads according to any one of [1] to [7] above, wherein the monomer includes a polyfunctional monomer. [9] A method for producing magnetic beads according to any one of the above [1] to [8], wherein the membrane emulsification method is a direct membrane emulsification method.

[10] A method for producing magnetic beads according to any one of [1] to [9], wherein the volume-average particle size (MV) calculated from the volume-based particle size distribution obtained by the laser diffraction-scattering method of the magnetic beads is 10 μm or more and 50 μm or less. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for manufacturing magnetic beads with improved magnetic particle collection capabilities. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below. Unless otherwise specified, the numerical range "A to B" represents A or greater and B or less. In this embodiment, the notation "(meth)acrylate" represents a concept that encompasses both methacrylate and acrylate. The same applies to similar notations such as "(meth)acrylic acid".

[0010] [Manufacturing method for magnetic beads] Magnetic beads containing polymers and magnetic particles are known. Magnetic beads are used, for example, in diagnostic agents, bacterial isolation, cell culture, drug delivery, magnetic toners, magnetic inks, magnetic paints, and the like.

[0011] In the process of compounding the raw magnetic particles with a polymer in the manufacturing method of magnetic beads, for example, in addition to the target magnetic beads formed by compounding magnetic particles and polymer, beads that do not contain magnetic particles or contain very few magnetic particles (hereinafter also referred to as impurity beads) may be obtained. When the total of the target magnetic beads and impurity beads is used as a baseline, if the proportion of impurity beads is high, it leads to a decrease in the yield of the final magnetic beads. This invention provides a method for manufacturing magnetic beads with improved magnetic particle collection capabilities.

[0012] As used herein, the improvement of magnetic particle collecting property means reducing the proportion of impurity beads based on the total of target magnetic beads and impurity beads in the step of compositing raw material magnetic particles and a polymer.

[0013] The method for producing magnetic beads according to the present embodiment comprises: step (A) of dispersing a monomer mixture containing a monomer, magnetic particles and an emulsion stabilizer in an aqueous medium by a membrane emulsification method to obtain a suspension; and step (B) of subjecting the monomer in the suspension to suspension polymerization.

[0014] Hereinafter, each step of the method for producing magnetic beads of the present embodiment will be specifically described.

[0015] <Step of preparing monomer mixture> The method for producing magnetic beads according to the present embodiment preferably includes a step of preparing a monomer mixture. The monomer mixture of the present embodiment contains a monomer, magnetic particles, and an emulsion stabilizer. The step of preparing the monomer mixture is performed before step (A).

[0016] The monomer mixture of the present embodiment contains an emulsion stabilizer. When the monomer mixture contains an emulsion stabilizer, the collecting property of magnetic particles can be improved.

[0017] The reason why the inclusion of an emulsion stabilizer in the monomer mixture can improve the collecting property of magnetic particles is not clear, but the present inventors speculate as follows. When the monomer mixture contains an emulsion stabilizer, the emulsion stabilizer functions as a protective film at the interface between the oil phase (monomer mixture) and the aqueous phase (aqueous medium) when the suspension is formed. This makes it easier for magnetic particles to be encapsulated in the oil phase, thereby improving the collecting property of magnetic particles.

[0018] The emulsifying stabilizer in this embodiment is not particularly limited and includes, for example, at least one selected from the group consisting of aliphatic higher alcohols, polyvinyl alcohols, and cellulosic compounds, and preferably includes an aliphatic higher alcohol from the viewpoint of further improving the magnetic particle collection ability.

[0019] The aliphatic higher alcohol is not particularly limited, but from the viewpoint of further improving the magnetic particle collection ability, it preferably includes at least one selected from the group consisting of lauryl alcohol, cetanol, and myristyl alcohol, and more preferably includes lauryl alcohol.

[0020] The amount of emulsifying stabilizer in the monomer mixture of this embodiment is preferably 0.05% to 10% by mass, more preferably 0.1% to 9% by mass, and even more preferably 0.3% to 8% by mass, when the total amount of components in the monomer mixture is taken as 100% by mass, from the viewpoint of further improving the magnetic particle collection ability.

[0021] The monomer mixture of this embodiment contains monomers. The monomer in this embodiment is not particularly limited as long as it contains a polymerizable group. The polymerizable group includes, for example, at least one selected from the group consisting of vinyl group, vinylidene group, and (meth)acryloyl group. The monomer of this embodiment includes, for example, at least one selected from the group consisting of (meth)acrylate monomers, styrene monomers, and vinyl monomers, and preferably includes a (meth)acrylate monomer.

[0022] The (meth)acrylate monomer includes, for example, at least one selected from the group consisting of alkyl (meth)acrylate, hydroxyalkyl (meth)acrylate, and aminoalkyl (meth)acrylate.

[0023] The (meth)acrylate monomer preferably contains methyl (meth)acrylate, and more preferably contains methyl methacrylate.

[0024] The methyl (meth)acrylate content in the monomer mixture of this embodiment is preferably 20% to 90% by mass, more preferably 30% to 85% by mass, and even more preferably 35% to 80% by mass, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0025] The (meth)acrylate monomer preferably includes monomer (a) from the viewpoint of further improving the stability of the suspension. Monomer (a) comprises at least one selected from the group consisting of n-butyl (meth)acrylate, t-butyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, glycidyl (meth)acrylate, and trifluoroethyl (meth)acrylate, preferably comprising at least one selected from the group consisting of n-butyl methacrylate, t-butyl methacrylate, dodecyl methacrylate, stearyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, glycidyl methacrylate, and trifluoroethyl methacrylate, more preferably comprising at least one selected from the group consisting of t-butyl methacrylate and isobornyl methacrylate.

[0026] The content of monomer (a) in the monomer mixture of this embodiment is preferably 0.01% to 25% by mass, more preferably 0.1% to 20% by mass, even more preferably 1% to 18% by mass, and even more preferably 3% to 15% by mass, when the total content of all components in the monomer mixture is taken as 100% by mass, from the viewpoint of further improving the stability of the suspension.

[0027] The monomer of this embodiment preferably includes monomer (b) having a carboxyl group. The monomer (b) having a carboxyl group preferably further comprises at least one selected from the group consisting of a vinyl group, a vinylidene group, and a (meth)acryloyl group, and more preferably further comprises a (meth)acryloyl group.

[0028] Monomer (b) comprises, for example, at least one selected from the group consisting of (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinic acid, mono-2-(methacryloyloxy)ethyl phthalate, and mono-2-(acryloyloxy)ethyl phthalate, preferably comprising 2-(meth)acryloyloxyethyl succinic acid, and more preferably comprising 2-methacryloyloxyethyl succinic acid.

[0029] The content of monomer (b) in the monomer mixture of this embodiment is preferably 0.1% by mass or more and 50% by mass or less, more preferably 1% by mass or more and 30% by mass or less, and even more preferably 3% by mass or more and 20% by mass or less, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0030] The monomers in this embodiment preferably include polyfunctional monomers. A polyfunctional monomer is a monomer containing two or more polymerizable groups. Since polyfunctional monomers function as crosslinking agents, including a polyfunctional monomer in the monomer mixture of this embodiment can further improve the heat resistance of the resulting magnetic beads.

[0031] The polymerizable group of the polyfunctional monomer preferably comprises at least one selected from the group consisting of a vinyl group, a vinylidene group, and a (meth)acryloyl group, and more preferably comprises a (meth)acryloyl group.

[0032] The polyfunctional monomer includes, for example, at least one selected from the group consisting of ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, and N,N'-methylenebis(acrylamide), preferably including ethylene glycol di(meth)acrylate, and more preferably including ethylene glycol dimethacrylate.

[0033] The content of the polyfunctional monomer in the monomer mixture of this embodiment is preferably 0.1% by mass or more and 60% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and even more preferably 2% by mass or more and 45% by mass or less, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0034] The monomer mixture of this embodiment preferably includes methyl (meth)acrylate, monomer (b), and a polyfunctional monomer, from the viewpoint of further improving the magnetic particle collection ability and further improving heat resistance, etc. The monomer mixture of this embodiment preferably comprises methyl (meth)acrylate, monomer (a), monomer (b), and a polyfunctional monomer, from the viewpoint of further improving the magnetic particle collection ability and the stability and heat resistance of the suspension.

[0035] The monomer mixture of this embodiment contains magnetic particles. The magnetic particles in this embodiment are not particularly limited as long as they are magnetic particles, but for example, they include at least one selected from the group consisting of magnetite (Fe3O4), maghemite (γ-Fe2O3), hematite (α-Fe2O3), manganese ferrite (MnFe2O4), cobalt ferrite (CoFe2O4), nickel ferrite (NiFe2O4), copper ferrite (CuFe2O4), Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg ferrite, Li ferrite, Cu-Zn ferrite, and goethite (FeO(OH)), preferably at least one selected from the group consisting of magnetite and maghemite, and more preferably magnetite.

[0036] The magnetic particles in this embodiment may be modified with, for example, a coupling agent or the like. The magnetic particles of this embodiment preferably include magnetic particles modified with at least one selected from the group consisting of fatty acids and silane coupling agents, and more preferably include magnetic particles modified with a silane coupling agent.

[0037] The fatty acid of this embodiment includes, for example, at least one selected from the group consisting of oleic acid, stearic acid, palmitic acid, linoleic acid, and palmitoleic acid.

[0038] The silane coupling agent of this embodiment includes, for example, at least one selected from the group consisting of 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, p-styryltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0039] The particle size of the magnetic particles in this embodiment is preferably 1 nm to 5000 nm, more preferably 3 nm to 1000 nm, and even more preferably 10 nm to 300 nm. Here, the particle size of magnetic particles refers to the value measured by a transmission electron microscope (TEM), specifically, the value obtained by performing image analysis on a TEM image and calculating the arithmetic mean of the particle sizes of any 10 magnetic particles.

[0040] The content of magnetic particles in the monomer mixture of this embodiment is preferably 0.1% to 10% by mass, more preferably 0.5% to 8% by mass, and even more preferably 1% to 6% by mass, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0041] The monomer mixture of this embodiment preferably further comprises a polymerization initiator. The polymerization initiator preferably includes a thermal polymerization initiator, and more preferably includes a thermal radical polymerization initiator. The thermal radical polymerization initiator includes, for example, at least one selected from the group consisting of azo polymerization initiators and peroxides, and more preferably includes an azo polymerization initiator. The azo polymerization initiator includes, for example, at least one selected from the group consisting of 2,2′-azobis(isobutyronitrile), 2,2′-azobis(2-methylbutyronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobis(cyclohexane-1-carbonnitrile), and azobis(isobutyric acid)dimethyl, and preferably includes 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile).

[0042] The content of the polymerization initiator in the monomer mixture of this embodiment is preferably 0.05% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 8% by mass or less, and even more preferably 0.5% by mass or more and 5% by mass or less, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0043] The monomer mixture of this embodiment may also contain an organic solvent and a hydrophobic polymer, etc. The organic solvent includes, for example, at least one selected from the group consisting of hexadecane, tetrahydrofuran, N,N-dimethylformamide, 4-methyl-2-pentanol, 1,2-dichloroethane, toluene, and heptane. The hydrophobic polymer includes, for example, at least one selected from the group consisting of polystyrene and polymethyl methacrylate.

[0044] The method for preparing the monomer mixture is not particularly limited, but is preferably a method in which the following steps (i) to (iii) are carried out sequentially. (i) Mix the monomer components. (ii) Dissolve the polymerization initiator in the mixed monomer components. (iii) Magnetic particles are added to the monomer components, and the magnetic particles are dispersed to obtain a monomer mixture.

[0045] <Steps for preparing an aqueous medium> The method for manufacturing magnetic beads according to this embodiment preferably includes a step of preparing an aqueous medium. The step of preparing the aqueous medium is performed before step (A).

[0046] The aqueous medium in this embodiment is not particularly limited as long as it is an aqueous medium that can be used in suspension polymerization. The aqueous medium in this embodiment contains water, preferably deionized water.

[0047] The aqueous medium in this embodiment preferably contains a dispersion stabilizer. The dispersion stabilizer is not particularly limited, but preferably includes a polyvinyl alcohol-based dispersion stabilizer, and more preferably includes a partially saponified polyvinyl alcohol-based dispersion stabilizer.

[0048] The content of the dispersion stabilizer in the aqueous medium of this embodiment is preferably 0.05% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 8% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less, when the total content of all components in the aqueous medium is taken as 100% by mass.

[0049] The aqueous medium in this embodiment may or may not contain a surfactant. The surfactant is not particularly limited, but preferably includes anionic surfactants, and more preferably includes sodium dodecyl sulfate.

[0050] When the aqueous medium of this embodiment contains a surfactant, the surfactant content in the aqueous medium of this embodiment is preferably 0.001% by mass or more and 3.0% by mass or less, more preferably 0.005% by mass or more and 1.0% by mass or less, and even more preferably 0.01% by mass or more and 0.5% by mass or less, when the total content of all components in the aqueous medium is taken as 100% by mass.

[0051] The aqueous medium in this embodiment may or may not contain a polymerization inhibitor. If the aqueous medium of this embodiment contains a polymerization inhibitor, it can suppress emulsion polymerization that occurs concurrently in suspension polymerization. The polymerization inhibitor is not particularly limited, but preferably contains an inorganic salt, more preferably a nitrite, and even more preferably sodium nitrite.

[0052] If the aqueous medium of this embodiment contains a polymerization inhibitor, the content of the polymerization inhibitor in the aqueous medium of this embodiment is preferably 0.001% by mass or more and 1.0% by mass or less, more preferably 0.005% by mass or more and 0.5% by mass or less, and even more preferably 0.01% by mass or more and 0.1% by mass or less, when the total content of all components in the aqueous medium is taken as 100% by mass.

[0053] The method for preparing the aqueous medium is not particularly limited; for example, each component can be mixed in any way.

[0054] <Step (A) to obtain the suspension> The method for producing magnetic beads according to this embodiment includes step (A) of dispersing a monomer mixture containing monomers, magnetic particles, and an emulsifying stabilizer in an aqueous medium by a membrane emulsification method to obtain a suspension.

[0055] Membrane emulsification is specifically a method for preparing a suspension using a porous membrane. The membrane emulsification method of the present embodiment may be, for example, a direct membrane emulsification method or a membrane emulsification method involving pre-emulsification, but is preferably a direct membrane emulsification method from the viewpoint that the production process can be further simplified by omitting the step of preparing a pre-emulsified emulsion. Direct membrane emulsification is specifically a method for obtaining a suspension by directly dispersing a monomer mixture into an aqueous medium through a porous membrane. A membrane emulsification method involving pre-emulsification is a method for obtaining a suspension by passing a mixed liquid obtained by pre-mixing a monomer mixture and an aqueous medium through a porous membrane.

[0056] The porous membrane is not particularly limited, and includes, for example, at least one selected from the group consisting of glass porous membranes (e.g., SPG membranes), PTFE membranes, and the like, and preferably includes a glass porous membrane.

[0057] The pore diameter of the porous membrane is not particularly limited, and may be, for example, 1 µm or more and 50 µm or less, 2 µm or more and 30 µm or less, or 3 µm or more and 10 µm or less.

[0058] In the direct membrane emulsification method, the flow rate when directly dispersing the monomer mixture into the aqueous medium through the porous membrane is, for example, 1 µL / (min·cm 2 ) or more and 500 µL / (min·cm 2 ) or less, 2 µL / (min·cm 2 ) or more and 500 µL / (min·cm 2 ) or less, 5 µL / (min·cm 2 ) or more and 200 µL / (min·cm 2 ) or less, or 10 µL / (min·cm 2 ) or more and 100 µL / (min·cm 2 ) or less. Here, the above flow rate means the flow rate of the monomer mixture flowing per minute per unit area [cm 2 of the porous membrane. In addition, the area of the porous membrane means the area of the porous membrane that is in contact with the aqueous medium during membrane emulsification.

[0059] The mixing ratio of the monomer mixture to the aqueous medium is expressed as a mass ratio, for example, monomer mixture:aqueous medium = 1:99 to 25:75.

[0060] <Step (B) of suspension polymerization of monomers> The method for producing magnetic beads in this embodiment includes a step (B) of suspension polymerization of monomers in a suspension.

[0061] In step (B), the polymerization conditions are not particularly limited, but for example, they can be set to a temperature of 50°C or higher and 90°C or lower, and a time of 1 hour or higher and 30 hours or lower.

[0062] <Other processes> The method for manufacturing magnetic beads according to this embodiment may further include other steps. Other processes include, for example, separating the magnetic beads from the suspension and acid washing the magnetic beads. Methods for separating magnetic beads from a suspension include, for example, centrifugal separation and magnetic separation.

[0063] [Magnetic beads] The following describes preferred embodiments of magnetic beads obtained by the magnetic bead manufacturing method of this embodiment.

[0064] The magnetic beads of this embodiment include a polymer and magnetic particles. The magnetic beads of this embodiment preferably contain magnetic particles inside the polymer.

[0065] The polymer in the magnetic beads of this embodiment is a polymer of the monomer of this embodiment.

[0066] The magnetic beads of this embodiment preferably contain at least one selected from the group consisting of carboxyl groups, alkynyl groups, azide groups, hydroxyl groups, amino groups, and epoxy groups on the surface of the magnetic beads, more preferably contain at least one selected from the group consisting of carboxyl groups, alkynyl groups, and azide groups, and even more preferably contain carboxyl groups.

[0067] The alkynyl group may be a substituted or unsubstituted linear alkynyl group, or a substituted or unsubstituted cyclic alkynyl group. The alkynyl group includes, for example, at least one selected from the group consisting of ethynyl group, propargyl group, trimethylsilylethynyl group, cyclooctinyl group, azacyclooctinyl group, and dibenzocyclooctinyl group, and preferably includes an ethynyl group.

[0068] When magnetic beads contain functional groups as described above on their surface, it becomes possible to immobilize a target substance (hereinafter referred to as the target substance) by reacting it with a substance that can bond to the functional groups. Magnetic beads containing such functional groups are preferable from the viewpoint of enabling applications in the medical and bio-fields, such as diagnostic agents.

[0069] The magnetic particle content in the magnetic beads of this embodiment is preferably 1% to 40% by mass, more preferably 2% to 30% by mass, even more preferably 3% to 20% by mass, even more preferably 8% to 15% by mass, and even more preferably 11% to 14% by mass, from the viewpoint of improving the magnetic properties of the magnetic beads and increasing the functional groups on the surface of the magnetic beads, when the total amount of magnetic beads is considered to be 100% by mass.

[0070] The magnetic beads of this embodiment may contain components other than polymers and magnetic particles.

[0071] The volume-average particle size (MV) of the magnetic beads in this embodiment is preferably 10 μm or more and 50 μm or less, more preferably 15 μm or more and 45 μm or less, and even more preferably 20 μm or more and 42 μm or less. The volume-average particle size (MV) of magnetic beads is defined as the volume-average particle size obtained when a 1% by mass magnetic bead dispersion is used as a measurement sample, ultrasonically dispersed using an ultrasonic cleaner for 3 minutes, and the particle size distribution of the sample after ultrasonic dispersion is measured using a laser diffraction particle size distribution analyzer. Here, the 1% by mass magnetic bead dispersion can be, for example, a 1% by mass aqueous magnetic bead solution in which the solvent is water.

[0072] [Uses of magnetic beads] The applications of the magnetic beads of this embodiment are not particularly limited and can be applied to, for example, diagnostic agents, bacterial isolation, cell culture, drug delivery, magnetic toner, magnetic ink, magnetic paint, etc. The magnetic beads of this embodiment are preferably magnetic beads that can be used in diagnostic reagents. The applications of the magnetic beads in this embodiment preferably do not include at least one application selected from the group consisting of magnetic toner, developer, and electrophotographic carrier.

[0073] [Method for producing dispersion] The method for producing the dispersion of this embodiment includes the steps of obtaining magnetic beads by the method for producing magnetic beads of this embodiment, and mixing the magnetic beads and a solvent to obtain a dispersion.

[0074] The dispersion of this embodiment comprises the magnetic beads of this embodiment and a solvent. The solvent includes, for example, at least one selected from the group consisting of water, methanol, ethanol, isopropyl alcohol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate, and preferably includes water.

[0075] The concentration of the dispersion in this embodiment is, for example, 0.01% by mass or more and 20% by mass or less, preferably 0.1% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 10% by mass or less.

[0076] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. Furthermore, the present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0077] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples unless there is a change in its essence.

[0078] First, we will explain the manufacturing process of magnetic particles modified with the silane coupling agent used as a raw material.

[0079] 60 g of FeCl2·4H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 135 g of FeCl3·6H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a separable flask. Then, 1500 mL of pure water, which had been pre-purged with nitrogen by nitrogen bubbling, was added to dissolve the FeCl2·4H2O and FeCl3·6H2O. 400 mL of 28 wt% aqueous ammonia was then poured into the mixture, and the mixture was stirred at 200 rpm for 30 minutes in a 30°C oil bath to obtain magnetic particles. The obtained magnetic particles were recovered magnetically, the supernatant was removed, and the process of adding water was repeated five times to wash the magnetic particles. The magnetic particles obtained above were magnetically recovered, and water was added to prepare a magnetic particle aqueous slurry so that when the slurry was 100 parts by mass, the amount of magnetic particles in the slurry was 20 parts by mass. 320 g of diethylamine and 64 g of the above magnetic particle aqueous slurry were added to a reaction vessel and treated in an ultrasonic bath for 15 minutes. 9.1 g of distilled water and 31.4 g of 3-methacryloxypropyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) as a silane coupling agent were added and treated in an ultrasonic bath for 30 minutes. The reaction vessel was then placed in a shaker and stirred at 100 rpm for 24 hours. After that, the magnetic particles were recovered by centrifugation. The recovered magnetic particles were washed by adding acetone and repeating the centrifugation process a total of three times. By air drying, magnetic particles modified with the silane coupling agent were obtained.

[0080] [Example 1] <Steps for preparing a monomer mixture> 0.75 parts by mass of methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 0.38 parts by mass of ethylene glycol dimethacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polyfunctional monomer, 0.20 parts by mass of 2-methacryloyloxyethyl succinic acid (manufactured by Kyoeisha Chemical Co., Ltd., product name: Light Ester HOMS(N)) as a monomer (b) having a carboxyl group, and 0.01 parts by mass of lauryl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an emulsifying stabilizer were mixed, and 0.02 parts by mass of 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a polymerization initiator. The mixture was then treated in an ultrasonic bath (manufactured by Yamato Scientific Co., Ltd., tabletop ultrasonic cleaner, product name: CPX5800H-J) to completely dissolve the polymerization initiator. To this, 0.05 parts by mass of magnetic particles (median diameter 146 nm) modified with a silane coupling agent were added and treated for 15 minutes in an ultrasonic bath (Sonic Bio Co., Ltd., sealed ultrasonic disruption device, product name: BIORUPTOR II (TYPE24)) under an ice bath to completely disperse the magnetic particles modified with the silane coupling agent. Furthermore, considering subsequent processes, aggregates of undispersed magnetic particles were removed using a microsyringe filter (Tokyo Glass Instruments Co., Ltd., hydrophobic PTFE, 1.0 μm) to obtain a monomer mixture in which the magnetic particles were uniformly dispersed.

[0081] <Steps for preparing an aqueous medium> Separately, 95.2 parts by mass of deionized water was added, and 0.01 parts by mass of sodium nitrite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 0.10 parts by mass of sodium dodecyl sulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 3.0 parts by mass of partially saponified polyvinyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., degree of saponification: 88 mol%, degree of polymerization: 1500) as a dispersion stabilizer were dissolved in a 300 mL glass beaker to create an aqueous medium.

[0082] <Step to obtain a suspension by membrane emulsification: Step (A)> The above monomer mixture was introduced into a 5 mL gastight syringe (TRAJAN / SGE) using a VAN metal needle (manufactured by Tsubasa Kogyo Co., Ltd., 90° cut tip, 16G x 40, locking base, 61-9093-07). The aqueous medium was stirred at 150 rpm in a general-purpose rotary homogenizer and then mixed using a syringe pump (Harvard, product name: PUMP 11 ELITE) at a flow rate of 10 μL / min (26 μL / min·cm). 2 The above monomer mixture was emulsified through a microglass filter (S.P.G. Techno Co., Ltd., DS08-050N, hydrophilic, pore size: 5 μm) to obtain a magnetic composite emulsion containing magnetic particles as a suspension.

[0083] <Step of suspension polymerization of monomers: Step (B)> The obtained suspension (magnetic composite emulsion) was transferred to a four-necked separable flask, equipped with a stirring blade, a flux condenser, a nitrogen purge tube, and a thermometer. The flask was immersed in a water bath, and nitrogen gas was blown in for 30 minutes while the stirring blade rotated at 150 rpm to replace oxygen with nitrogen. The water bath temperature was then raised to 70°C, and suspension polymerization was carried out for 24 hours to obtain magnetic beads.

[0084] <Purification process> After polymerization, the suspension was passed through a filter (manufactured by Yotoriyama Co., Ltd., 200 mesh) to remove aggregates. Next, the magnetic beads were washed by centrifugation followed by the addition of water three times, followed by the addition of ethanol once, and followed by the addition of water once. Furthermore, magnetic separation was performed using a magnet, and the dried material was transferred to a 50 mL glass bottle. The bottle was then placed in a vacuum apparatus (manufactured by AS ONE Corporation, product name: AVO-250NS-D) and evacuated under reduced pressure using a vacuum pump (manufactured by Sato Vacuum Co., Ltd., product name: P135D, 0.67 Pa or less). Under reduced pressure, the material was vacuum-dried at 50°C overnight to obtain a dried powder. 10 parts by mass of 1 N hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 0.5 parts by mass of the obtained dried powder, and the mixture was exposed to the acid for 60 minutes. Subsequently, the treated magnetic beads were washed and purified by magnetic separation, and finally, water was added and ultrasonic irradiation was performed to obtain a purified suspension. The obtained purified suspension was used as the magnetic beads of Example 1.

[0085] [Examples 2-5 and Comparative Examples 1-3] Magnetic beads for Examples 2-5 and Comparative Examples 1-3 were obtained in the same manner as in Example 1, except that the monomer mixture and aqueous medium were formulated as shown in Table 1. In Table 1, isobornyl methacrylate was manufactured by Tokyo Chemical Industries, Ltd., and t-butyl methacrylate was manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Isobornyl methacrylate and t-butyl methacrylate correspond to monomer (a) in this embodiment. In the <step for preparing the monomer mixture>, isobornyl methacrylate and t-butyl methacrylate were mixed together with methyl methacrylate, etc., before adding the polymerization initiator.

[0086] [Measurement and Evaluation] The magnetic beads obtained in each example and comparative example were subjected to the following measurements and evaluations. The results are shown in Table 1.

[0087] <Volume-average particle size (MV) of magnetic beads> The magnetic beads from each example and comparative example were prepared as a 1% by mass aqueous solution of magnetic beads and used as the measurement sample. The measurement samples were subjected to ultrasonic dispersion treatment for 3 minutes using a tabletop ultrasonic cleaner (manufactured by Yamato Scientific Co., Ltd., product name: CPX5800H-J). For the measurement samples after ultrasonic dispersion treatment, the particle size distribution was measured using a laser diffraction particle size distribution analyzer (Beckman Coulter, product name: LS 13 320), and the volume-average particle size (MV) was calculated.

[0088] <Content of magnetic particles in magnetic beads> A portion of the magnetic beads (purified suspension) from each example and comparative example was pipetted and vacuum-dried to obtain purified suspension powder. The purified suspension powder was subjected to thermogravimetric analysis (TG-DTA). The content of magnetic particles in magnetic beads was determined under the following conditions. Measuring device: 2000SR (manufactured by NETZSCH) Atmosphere: Nitrogen Heating rate: 10℃ / min Sample measuring container: Platinum A platinum cell was placed in which 5 mg of purified suspension powder was placed and set in the measurement unit. The measurement unit was then heated to 800°C while injecting nitrogen. After holding the temperature of the measurement unit at 800°C for 2 minutes, the weight of the residue was taken as the weight of the magnetic particles, and the content of magnetic particles in the magnetic beads was determined.

[0089] <Magnetic recovery rate and magnetic particle collection efficiency> (Magnetic separation operation) After polymerization, the suspension was passed through a filter to remove aggregates, and a portion of the purified suspension that had undergone the above-mentioned purification step was collected by pipette and used as the sample for magnetic separation. A predetermined concentration of magnetic bead aqueous dispersion (fixed at 7 mL or less), prepared by dispersing the magnetic separation sample using an ultrasonic device, was placed in a 15 mL tube and then set in a PureProteome magnetic stand (for 15 mL tubes, LSKMAGS15). After standing for 2 minutes, the supernatant containing magnetic beads that had not been magnetically collected was separated. Then, the same amount of deionized water was added to the separated volume, and the mixture was thoroughly redispersed using an ultrasonic device. The magnetic bead aqueous dispersion was then set back in the magnetic stand, and the same procedure was repeated a total of four times to recover only magnetic beads with sufficient magnetic force.

[0090] (Calculation of magnetic recovery rate) After the above (magnetic separation operation) was completed, magnetic collection was performed again on the magnetic bead aqueous dispersion using the same method as above (magnetic separation operation). Two samples were used as evaluation samples: the supernatant separated after the second magnetic collection (Sample 1) and the magnetic bead aqueous dispersion to which ion-exchanged water was added after the supernatant was removed after the second magnetic collection (Sample 2). For samples 1 and 2, the particle size distribution was measured using a laser diffraction particle size distribution analyzer (Beckman Coulter, product name: LS 13 320). Next, the number frequency % of particles (target particles) within the target particle size range (5 μm to 20 μm) was calculated for each sample. Then, when the number frequency % of target particles contained in sample 1 was denoted as A and the number frequency % of target particles contained in sample 2 was denoted as B, the calculated value A / (A+B)×100 was defined as the uncollected efficiency %(C), and the calculated value 100-(C) was defined as the magnetic recovery rate (X)[%].

[0091] (Evaluation of magnetic particle collection ability) Based on the calculation of magnetic recovery rate (X) described above, products with a magnetic recovery rate (X) of 90% or higher were rated "AA", those with (X) between 70% and 90% were rated "A", those with (X) between 50% and 70% were rated "B", those with (X) between 20% and 50% were rated "C", and those with (X) below 20% were rated "D". The magnetic particle collection performance was evaluated based on these ratings. Products with a magnetic particle collection performance rating of B or higher were considered acceptable.

[0092] [Table 1]

[0093] Table 1 shows that the magnetic beads of the embodiment exhibit good evaluation results for magnetic particle collection. In other words, the manufacturing method of the magnetic beads of this embodiment can improve the collection of magnetic particles.

Claims

1. The process involves (A) dispersing a monomer mixture containing monomers, magnetic particles, and an emulsifying stabilizer in an aqueous medium using a membrane emulsification method to obtain a suspension. A method for producing magnetic beads, comprising the step (B) of suspend polymerization of the monomer in the suspension.

2. The method for producing magnetic beads according to claim 1, wherein the emulsifying stabilizer comprises an aliphatic higher alcohol.

3. The method for producing magnetic beads according to claim 2, wherein the aliphatic higher alcohol includes at least one selected from the group consisting of lauryl alcohol, cetanol, and myristyl alcohol.

4. The method for producing magnetic beads according to any one of claims 1 to 3, wherein the content of the emulsifying stabilizer in the monomer mixture is 0.05% by mass or more and 10% by mass or less, when the total content of all components in the monomer mixture is 100% by mass.

5. A method for producing magnetic beads according to any one of claims 1 to 3, wherein the monomer comprises a (meth)acrylate monomer.

6. The method for producing magnetic beads according to claim 5, wherein the (meth)acrylate monomer includes methyl (meth)acrylate.

7. The (meth)acrylate monomer comprises monomer (a), The method for producing magnetic beads according to claim 5, wherein the monomer (a) comprises at least one selected from the group consisting of n-butyl (meth)acrylate, t-butyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, glycidyl (meth)acrylate, and trifluoroethyl (meth)acrylate.

8. The method for producing magnetic beads according to any one of claims 1 to 3, wherein the monomer includes a polyfunctional monomer.

9. A method for producing magnetic beads according to any one of claims 1 to 3, wherein the aforementioned membrane emulsification method is a direct membrane emulsification method.

10. A method for manufacturing magnetic beads according to any one of claims 1 to 3, wherein the volume-average particle size (MV) calculated from the volume-based particle size distribution obtained by the laser diffraction / scattering method of the magnetic beads is 10 μm or more and 50 μm or less.

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