Manufacturing method for magnetic beads

Abstract

The present invention provides a method for manufacturing magnetic beads that can narrow the particle size distribution of the resulting magnetic beads. [Solution] A method for producing magnetic beads comprising a polymer and magnetic particles, comprising the steps of: (A) dispersing a monomer mixture containing monomers 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 Initiative] [Problems that the invention aims to solve]

[0005] The present invention provides a method for manufacturing magnetic beads that can narrow the particle size distribution of the resulting magnetic beads. [Means for solving the problem]

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

[0007] [1] A method for manufacturing magnetic beads comprising a polymer and magnetic particles, The process involves (A) dispersing a monomer mixture containing monomers 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] A method for producing magnetic beads according to [1], wherein the monomer comprises a (meth)acrylate monomer. [3] The (meth)acrylate monomer comprises monomer (a), The method for producing magnetic beads according to [2], 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. [4] The method for producing magnetic beads according to [3], wherein the content of monomer (a) in the monomer mixture is 0.01% by mass or more and 15% by mass or less, when the total content of all components in the monomer mixture is taken as 100% by mass. [5] A method for producing magnetic beads according to any one of the above [2] to [4], wherein the (meth)acrylate monomer comprises methyl (meth)acrylate. [6] A method for producing magnetic beads according to any one of [1] to [5], wherein the monomer comprises a monomer (b) having a carboxyl group. [7] The method for producing magnetic beads according to any one of [1] to [6], wherein the monomer mixture contains the magnetic particles. [8] A method for producing magnetic beads according to any one of the above [1] to [7], wherein the membrane emulsification method is a direct membrane emulsification method. [9] D is calculated from the volume-based particle size distribution obtained by the laser diffraction and scattering method of the magnetic beads. 50The method for producing magnetic beads according to any one of [1] to [8], wherein the particle diameter is 10 µm or more and 50 µm or less.

[10] The method for producing magnetic beads according to any one of [1] to [9], wherein the coefficient of variation (CV) in the volume-based particle size distribution of the magnetic beads obtained by laser diffraction-scattering method is 42% or less.

Effects of the Invention

[0008] According to the present invention, there can be provided a method for producing magnetic beads that can narrow the particle size distribution of the resulting magnetic beads.

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described. Unless otherwise specified, "A to B" indicating a numerical range represents not less than A and not more than B. The notation "(meth)acrylate" in the present embodiment represents a concept including both methacrylate and acrylate. The same applies to similar notations such as "(meth)acrylic acid".

[0010] [Method for Producing Magnetic Beads] Magnetic beads containing a polymer and magnetic particles are known. Magnetic beads are used in, for example, diagnostic reagents, bacterial separation, cell culture, drug delivery, magnetic toners, magnetic inks, magnetic coatings, and the like. For example, in magnetic beads applied to flow cytometers, it may be required to narrow the particle size distribution of the magnetic beads. The present invention provides a method for producing magnetic beads that can narrow the particle size distribution of the resulting magnetic beads.

[0011] As a method for obtaining magnetic beads having a narrow particle size distribution, for example, a method of classifying magnetic beads can be mentioned. However, if the method for producing magnetic beads includes a classification step, productivity such as a decrease in yield may be reduced. According to the magnetic bead manufacturing method of this embodiment, even if the magnetic bead manufacturing method does not include a classification step, the particle size distribution of the resulting magnetic beads can be narrowed. However, the magnetic bead manufacturing method of this embodiment is not limited to a magnetic bead manufacturing method that does not include a classification step.

[0012] The method for producing magnetic beads according to this embodiment is a method for producing magnetic beads comprising a polymer and magnetic particles, comprising the steps of (A) dispersing a monomer mixture containing monomers in an aqueous medium by a membrane emulsification method to obtain a suspension, and (B) suspend polymerization of the monomers in the suspension.

[0013] The following describes in detail each step of the manufacturing method for magnetic beads according to this embodiment.

[0014] <Steps for preparing a monomer mixture> The method for manufacturing magnetic beads in this embodiment preferably includes a step of preparing a monomer mixture. The step of preparing the monomer mixture is performed before step (A).

[0015] 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.

[0016] 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.

[0017] The (meth)acrylate monomer preferably includes monomer (a) from the viewpoint of narrowing the particle size distribution of the resulting magnetic beads. 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 isobornyl methacrylate and t-butyl methacrylate, and even more preferably comprising isobornyl methacrylate.

[0018] In this embodiment, if the monomer mixture contains monomer (a), the particle size distribution of the resulting magnetic beads can be made narrower. The reason for this is not clear, but the inventors speculate that monomer (a) is a highly hydrophobic monomer, and if the monomer mixture contains monomer (a), the irregular fragmentation of the monomer mixture within the pores of the porous membrane used in step (A) is suppressed, and the particle size of the monomer mixture droplets in the suspension can be made more uniform, thus making the particle size distribution of the resulting magnetic beads narrower.

[0019] The content of monomer (a) in the monomer mixture of this embodiment is preferably 0.01% to 15% by mass, more preferably 0.1% to 14% by mass, and even more preferably 0.5% to 12% by mass, from the viewpoint of narrowing the particle size distribution of the resulting magnetic beads, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0020] The (meth)acrylate monomer preferably contains methyl (meth)acrylate, and more preferably contains methyl methacrylate.

[0021] The content of methyl (meth)acrylate in the monomer mixture of this embodiment is preferably 30% to 75% by mass, more preferably 40% to 70% by mass, and even more preferably 45% to 63% by mass, from the viewpoint of narrowing the particle size distribution of the resulting magnetic beads, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0022] The content of monomer (a) in the monomer mixture of this embodiment is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 25 parts by mass or less, and even more preferably 1 part by mass or more and 20 parts by mass or less, from the viewpoint of narrowing the particle size distribution of the resulting magnetic beads, when the content of methyl (meth)acrylate in the monomer mixture is 100 parts by mass.

[0023] 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.

[0024] 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.

[0025] The content of monomer (b) in the monomer mixture of this embodiment is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 45% by mass or less, and even more preferably 10% by mass or more and 40% by mass or less, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The content of the polyfunctional monomer in the monomer mixture of this embodiment is preferably 1% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and even more preferably 8% 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 monomer mixture of this embodiment preferably contains monomer (a) and methyl (meth)acrylate, from the viewpoint of narrowing the particle size distribution of the resulting magnetic beads. The monomer mixture of this embodiment more preferably comprises monomer (a), methyl (meth)acrylate, and monomer (b) from the viewpoint of narrowing the particle size distribution of the resulting magnetic beads and further improving heat resistance, etc., and even more preferably comprises monomer (a), methyl (meth)acrylate, monomer (b), and a polyfunctional monomer.

[0031] The monomer mixture of this embodiment preferably 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The content of magnetic particles in the monomer mixture of this embodiment is preferably 0.05% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less, and even more preferably 0.5% by mass or more and 2% by mass or less, when the total content of all components in the monomer mixture is taken as 100% by mass.

[0037] 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(2,4-dimethylvaleronitrile).

[0038] 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.

[0039] 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.

[0040] 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.

[0041] <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).

[0042] 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.

[0043] 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.

[0044] 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 5% by mass or less, and even more preferably 1% by mass or more and 3% by mass or less, when the total content of all components in the aqueous medium is taken as 100% by mass.

[0045] 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.

[0046] When the aqueous medium of this embodiment contains a surfactant, the surfactant content in the aqueous medium of this embodiment is preferably 0.01% by mass or more and 3.0% by mass or less, more preferably 0.05% by mass or more and 1.0% by mass or less, and even more preferably 0.1% 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.

[0047] 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.

[0048] 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.

[0049] The method for preparing the aqueous medium is not particularly limited; for example, each component can be mixed in any way.

[0050] <Step (A) to obtain the suspension> The method for producing magnetic beads in this embodiment includes step (A) of dispersing a monomer mixture containing monomers in an aqueous medium by a membrane emulsification method to obtain a suspension. The method for manufacturing magnetic beads according to this embodiment, by including step (A), can narrow the particle size distribution of the resulting magnetic beads.

[0051] Membrane emulsification is a method of preparing suspensions using porous membranes. The membrane emulsification method in this embodiment may be, for example, a direct membrane emulsification method or a membrane emulsification method accompanied by pre-emulsification. However, from the viewpoint of further simplifying the manufacturing process by omitting the preparation step of the pre-emulsified emulsion, a direct membrane emulsification method is preferred. Direct membrane emulsification is a method of obtaining a suspension by directly dispersing a monomer mixture in an aqueous medium through a porous membrane. The membrane emulsification method with pre-emulsification is a method in which a pre-emulsified emulsion, prepared by mixing a monomer mixture with an aqueous medium under mild conditions, is passed through a porous membrane to obtain a suspension.

[0052] The porous membrane is not particularly limited, but it includes at least one selected from the group consisting of, for example, glass porous membranes (e.g., SPG membranes) and PTFE membranes, and preferably includes glass porous membranes.

[0053] The pore size of the porous membrane is not particularly limited, but may be, for example, 1 μm to 50 μm, 2 μm to 30 μm, or 3 μm to 10 μm.

[0054] In the direct membrane emulsification method, the flow rate when directly dispersing a monomer mixture in an aqueous medium through a porous membrane is, for example, 1 μL / (min·cm). 2 ) or more 500μL / (min cm 2 ) or less, and 2 μL / (min·cm 2 ) or more 500μL / (min cm 2 ) or less, and 5 μL / (min·cm 2 ) or more 200μL / (min cm 2) may be 10 μL / (min·cm 2 ) or more and 100 μL / (min·cm 2 ) or less. Here, the flow rate refers to 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 refers to the area of the porous membrane that is in contact with the aqueous medium during membrane emulsification.

[0055] The mixing ratio of the monomer mixture to the aqueous medium, by mass ratio, is, for example, monomer mixture:aqueous medium = 1:99 to 25:75.

[0056] <Step (B) of subjecting a monomer to suspension polymerization> The method for producing magnetic beads according to the present embodiment includes step (B) of subjecting a monomer in a suspension to suspension polymerization.

[0057] In step (B), the polymerization conditions are not particularly limited, and for example, conditions may be: temperature: 50°C or higher and 90°C or lower, time: 1 hour or longer and 30 hours or shorter.

[0058] <Other Steps> The method for producing magnetic beads according to the present embodiment may further include other steps. Examples of other steps include a step of separating magnetic beads from a suspension, a step of acid-washing the magnetic beads, and the like. Examples of the method for separating magnetic beads from a suspension include centrifugation, magnetic separation, and the like. Furthermore, if the suspension of this embodiment does not contain magnetic particles, after obtaining polymer particles in step (B), magnetic beads can be obtained by, for example, performing a step to compound the obtained polymer particles with magnetic particles. Examples of methods for compounding polymer particles with magnetic particles include adding magnetic particles externally to polymer particles. Examples of methods for adding magnetic particles externally to polymer particles include chemically bonding magnetic particles to the surface of polymer particles using polymer particles as a core and magnetic particles as a shell, adsorbing magnetic particles to the surface of polymer particles using a surfactant, and seed polymerization of monomers and magnetic particles using polymer particles as seeds.

[0059] The method for manufacturing magnetic beads in this embodiment preferably does not include a classification step, from the viewpoint of further improving productivity. In this embodiment, the classification step refers to the step of separating magnetic beads with a particle size of a certain size or larger from magnetic beads with a particle size of a certain size or smaller. For example, a filtration step performed after step (B) for the purpose of removing aggregates does not fall under the classification step of this embodiment.

[0060] [Magnetic beads] The following describes preferred embodiments of magnetic beads obtained by the magnetic bead manufacturing method of this embodiment.

[0061] 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.

[0062] The polymer in the magnetic beads of this embodiment is a polymer of the monomer of this embodiment.

[0063] 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.

[0064] 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 an ethynyl group, a propargyl group, a trimethylsilylethynyl group, a cyclooctinyl group, an azacyclooctinyl group, and a dibenzocyclooctinyl group, and preferably includes an ethynyl group.

[0065] 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.

[0066] The content of magnetic particles 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, and even more preferably 8% to 15% 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 content of the magnetic beads is considered as 100% by mass.

[0067] The magnetic beads of this embodiment may contain components other than polymers and magnetic particles.

[0068] D is calculated from the volume-based particle size distribution obtained by the laser diffraction / scattering method of the magnetic beads of this embodiment. 50The particle size is preferably 10 μm to 50 μm, more preferably 15 μm to 40 μm, and even more preferably 20 μm to 35 μm.

[0069] D is calculated from the volume-based particle size distribution obtained by the laser diffraction / scattering method of the magnetic beads of this embodiment. 10 The particle size is preferably 5 μm to 40 μm, more preferably 8 μm to 30 μm, and even more preferably 10 μm to 25 μm.

[0070] D is calculated from the volume-based particle size distribution obtained by the laser diffraction / scattering method of the magnetic beads of this embodiment. 90 The particle size is preferably 10 μm to 60 μm, more preferably 20 μm to 55 μm, and even more preferably 25 μm to 50 μm.

[0071] The span value in the volume-based particle size distribution obtained by the laser diffraction-scattering method of the magnetic beads of this embodiment ((D 90 -D 10 ) / D 50 From the viewpoint of narrowing the particle size distribution, the particle size ratio is preferably 1.00 or less, more preferably 0.95 or less, even more preferably 0.90 or less, even more preferably 0.80 or less, and even more preferably 0.70 or less, and the lower limit is not particularly limited, but may be, for example, 0.40 or more, 0.50 or more, or 0.55 or more.

[0072] The coefficient of variation (CV) in the volume-based particle size distribution obtained by the laser diffraction-scattering method of the magnetic beads of this embodiment is preferably 42% or less, more preferably 40% or less, even more preferably 35% or less, even more preferably 30% or less, and even more preferably 28% or less, from the viewpoint of narrowing the particle size distribution, and the lower limit is not particularly limited, but may be, for example, 10% or more, or 15% or more.

[0073] The volume-based particle size distribution obtained by the laser diffraction / scattering method of the magnetic beads in this embodiment specifically refers to the particle size distribution obtained by the following [method].

[0074] [method] A magnetic bead dispersion with a concentration of 1% by mass is used as the measurement sample. The measurement sample is subjected to ultrasonic dispersion treatment using an ultrasonic cleaner for 3 minutes. After ultrasonic dispersion treatment, the particle size distribution of the measurement sample is measured using a laser diffraction particle size distribution analyzer to obtain a volume-based particle size distribution. Here, a magnetic bead dispersion with a concentration of 1% by mass can be, for example, a magnetic bead aqueous solution with a concentration of 1% by mass in which the solvent is water.

[0075] [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 have a narrow particle size distribution, and are therefore 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.

[0076] [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.

[0077] 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.

[0078] 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.

[0079] 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]

[0080] 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.

[0081] First, we will explain the manufacturing process of magnetic particles modified with the silane coupling agent used as a raw material.

[0082] 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.

[0083] [Example 1] <Steps for preparing a monomer mixture> 1.9 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.), and 0.57 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 were mixed, and 0.06 parts by mass of 2,2′-azobis(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, 0.04 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 disruptor, 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.

[0084] <Steps for preparing an aqueous medium> Separately, 94.6 parts by mass of deionized water was added, and 0.03 parts by mass of sodium nitrite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 0.2 parts by mass of sodium dodecyl sulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 2.3 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.

[0085] <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.

[0086] <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.

[0087] <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.

[0088] [Examples 2-4] Magnetic beads for Examples 2 to 4 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 Industry Co., Ltd. Isobornyl methacrylate corresponds to monomer (a) in this embodiment. In the <Preparation of Monomer Mixture> step, isobornyl methacrylate was mixed with methyl methacrylate, etc., before adding the polymerization initiator.

[0089] [Comparative Example 1] 3.3 parts by mass of methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 0.42 parts by mass of ethylene glycol dimethacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.94 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 were mixed, and 0.29 parts by mass of 2,2′-azobis(2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a polymerization initiator. The mixture was treated in an ultrasonic bath (manufactured by Yamato Scientific Co., Ltd., tabletop ultrasonic cleaner, product name: CPX5800H-J) to completely dissolve the polymerization initiator. 0.24 parts by mass of magnetic particles (median diameter 146 nm) modified with a silane coupling agent were added, and the mixture was treated in the ultrasonic bath for 15 minutes to completely disperse the magnetic particles modified with the silane coupling agent, obtaining a monomer mixture.

[0090] Separately, 0.03 parts by mass of sodium nitrite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a four-neck separable flask. Next, an aqueous solution of deionized water and 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 (an aqueous solution prepared so that 92.8 parts by mass of deionized water and 2.0 parts by mass of polyvinyl alcohol) was placed in the four-neck separable flask, and the mixture was processed by rotating the stirring blade at 150 rpm using a Three One Motor (manufactured by AS ONE Corporation) to obtain an aqueous medium.

[0091] The monomer mixture obtained above was added to the resulting aqueous medium, and the mixture was stirred in an ice bath at 3000 rpm for 5 minutes using a rotor / stator homogenizer (manufactured by IKA Japan Co., Ltd., product name: T18 digital ULTRA-TURRAX, shaft generator: S18N-19G) to obtain a suspension in which the monomer mixture was dispersed as droplets in the aqueous medium.

[0092] The obtained suspension was subjected to the same operations as in Example 1, namely <Monomer suspension polymerization step: step (B)> and <Purification step>, to obtain the magnetic beads of Comparative Example 1.

[0093] [Comparative Example 2] Magnetic beads of Comparative Example 2 were obtained in the same manner as in Comparative Example 1, except that the monomer mixture and aqueous medium were formulated as shown in Table 1.

[0094] [measurement] The following measurements were performed on the magnetic beads obtained in each example and comparative example. The results are shown in Table 1.

[0095] <Particle size 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 sample after ultrasonic dispersion treatment, the volume-based particle size distribution was measured using a laser diffraction particle size distribution analyzer (Beckman Coulter, product name: LS 13 320), and the coefficient of variation (CV) and D were determined. 10 Particle size, D 50 Particle size, D 90 Particle size, span value ((D 90 -D 10 ) / D 50 The following values ​​were calculated for each of them.

[0096] <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.

[0097] [Table 1]

[0098] Table 1 shows that the magnetic beads of the example have a smaller coefficient of variation (CV) compared to the magnetic beads of the comparative example. In other words, the manufacturing method of the magnetic beads of this embodiment allows for a narrower particle size distribution of the resulting magnetic beads.

Claims

1. A method for manufacturing magnetic beads comprising a polymer and magnetic particles, The process involves (A) dispersing a monomer mixture containing monomers 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 monomer includes a (meth)acrylate monomer.

3. The (meth)acrylate monomer comprises monomer (a), The method for producing magnetic beads according to claim 2, 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.

4. The method for producing magnetic beads according to claim 3, wherein the content of monomer (a) in the monomer mixture is 0.01% by mass or more and 15% by mass or less, when the total content of all components in the monomer mixture is taken as 100% by mass.

5. A method for producing magnetic beads according to any one of claims 2 to 4, wherein the (meth)acrylate monomer comprises methyl (meth)acrylate.

6. A method for producing magnetic beads according to any one of claims 1 to 4, wherein the monomer comprises a monomer (b) having a carboxyl group.

7. A method for producing magnetic beads according to any one of claims 1 to 4, wherein the monomer mixture contains the magnetic particles.

8. A method for manufacturing magnetic beads according to any one of claims 1 to 4, wherein the aforementioned membrane emulsification method is a direct membrane emulsification method.

9. D is calculated from the volume-based particle size distribution obtained by the laser diffraction and scattering method of the magnetic beads. ５０ A method for producing magnetic beads according to any one of claims 1 to 4, wherein the particle size is 10 μm or more and 50 μm or less.

10. A method for manufacturing magnetic beads according to any one of claims 1 to 4, wherein the coefficient of variation (CV) of the volume-based particle size distribution obtained by the laser diffraction / scattering method of the magnetic beads is 42% or less.

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