Magnet, curable composition containing the same, and method for manufacturing the magnet

Abstract

The present application relates to a magnet, a curable composition comprising the same, and a method for manufacturing the magnet. The magnet of the present application can have an excellent calorific value and can uniformly maintain the calorific value at the same time. In the magnet of the present application, the calorific value characteristic can be freely adjusted. The curable composition of the present application can be easily cured by utilizing a magnet that satisfies all characteristics. The method of the present application can simply produce a magnet that satisfies all characteristics.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0158213, filed on December 2, 2019, and Korean Patent Application No. 10-2019-0158214, filed on December 2, 2019, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0004] The present application relates to magnets, curable compositions containing the same, and methods for making the magnets. Background Art

[0005] Magnets (specifically, so-called "nanomagnets" with sizes ranging from tens to hundreds of nanometers) have the characteristic of generating heat when an alternating magnetic field is applied. Therefore, magnets are used in various fields, such as the rapid curing of thermosetting resins, thermal processing of polymers, and hyperthermia anti-cancer treatment.

[0006] The heat generation characteristics of a magnet vary depending on external conditions, such as the strength, output, or frequency of the alternating magnetic field applied to the magnet. Furthermore, the heat generation characteristics also vary depending on the inherent characteristics of the magnet itself, such as its size, shape, size distribution, composition, and magnetic properties (coercivity, saturation magnetization value, residual magnetization value, etc.). Therefore, magnets with the same composition and particle characteristics can have different heat generation characteristics.

[0007] In order to easily control the calorific value by induction heating, it is important that the magnet has excellent heat generation efficiency, but the heat generation characteristics need to be uniformly achieved. Summary of the Invention

[0008] Technical issues

[0009] One object of the present application is to provide a magnet having an excellent calorific value and at the same time being able to maintain the calorific value uniformly.

[0010] An object of the present application is to provide a magnet in which heat generation characteristics can be freely adjusted.

[0011] An object of the present application is to provide a curable composition that can be easily cured using a magnet that satisfies all characteristics.

[0012] One object of the present application is to provide a method for simply producing a magnet that satisfies all properties.

[0013] Technical Solution

[0014] Among the physical properties mentioned in the present application, if the measuring temperature and / or pressure affect the physical properties, the physical properties mean physical properties measured at room temperature and / or normal pressure unless otherwise specified.

[0015] In the present application, the term "room temperature" is a natural temperature without special heating and / or cooling, which may be any temperature within the range of about 10°C to 30°C, or a temperature around 25°C or 23°C.

[0016] In the present application, the term "normal pressure" refers to a pressure without special pressurization and / or reduction, which may generally be around one atmosphere, such as atmospheric pressure.

[0017] The present application relates to magnets.

[0018] In the present application, a magnet is a material exhibiting magnetism, which may mean a material capable of generating heat when an electromagnetic field of predetermined conditions is applied from the outside.

[0019] In the present application, a magnet may optionally be referred to as a “nanomagnet.” This may mean that the magnet has a size of a nanometer unit, specifically, a size of several nm to several hundred nm.

[0020] In the present application, the magnet is a composite material comprising magnetic particles and a surface treatment agent introduced onto the surface of the magnetic particles. In the present application, a magnet suitable for the purpose can be provided by controlling the properties of suitable magnetic particles and / or the selection and combination of the surface treatment agent and its composition.

[0021] The present inventors have determined that when size-related properties of magnetic particles are determined under specific conditions and combined with a surface treatment agent, excellent calorific value can be exhibited and uniformly maintained when an electromagnetic field is applied to a magnet, and have completed the present invention.

[0022] The magnetic particles contain crystals whose sizes are within a specific range. The size of the crystals contained in the magnetic particles is within a range of 10 nm to 40 nm. In another example, the size of the crystals can be 15 nm or larger, or 20 nm or larger, and can be 37 nm or smaller, or 35 nm or smaller.

[0023] In one example, when the magnetic particles have a constant average particle size, as the size of the crystals increases within the above range of the crystal size, the calorific value of the magnet including the magnetic particles may be higher.

[0024] When the multiple sizes of crystals present in the magnetic particles are not constant, the size of the crystals may refer to the maximum size, minimum size, or average size of the crystals. The size of the crystals can be measured by X-ray diffraction analysis of the magnetic particles or magnetic powder, and as a specific measurement method, the method described in the Examples below can be applied.

[0025] Furthermore, the magnetic particles have an average particle size within a specific range. Specifically, the magnet of the present application contains magnetic particles with an average particle size within a range of 20 nm to 300 nm. In this case, the magnet can exhibit a high calorific value when an external magnetic field is applied, and the calorific value can be uniformly maintained.

[0026] In another example, the average particle size of the magnetic particles can be 30 nm or greater, 40 nm or greater, 50 nm or greater, 60 nm or greater, 70 nm or greater, or 80 nm or greater, and can be 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less, 250 nm or less, 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less, 190 nm or less, 180 nm or less, 170 nm or less, 160 nm or less, 150 nm or less, 140 nm or less, 130 nm or less, or 120 nm or less.

[0027] The method for measuring the average particle size of the magnetic particles is not particularly limited. For example, the average particle size of the magnetic particles can be measured by preparing a magnet containing the magnetic particles and then analyzing an electron microscope photograph of the magnet.

[0028] In addition, the magnet of the present application contains magnetic particles whose coefficient of variation of particle size is within a specific range. Therefore, it can have a uniformly high calorific value when an external magnetic field is applied. Specifically, the coefficient of variation of the particle size of the magnetic particles is in the range of 5% to 30%. In the present application, the coefficient of variation of any factor can mean the ratio of the standard variation of the factor to the average value of the factor, expressed as a percentage. That is, in the magnet, it can mean the ratio (SV / M) of the standard deviation (SV) of the particle size of the magnetic particles to the average value (M) of the particle size of the magnetic particles. The coefficient of variation of the particle size of the magnetic particles can be estimated by electron micrographs obtained for the magnet.

[0029] Therefore, such a magnet of the present application can generate heat with a high calorific value and uniformly maintain the calorific value when an external magnetic field is applied: the magnet contains magnetic particles and (4) a surface treatment agent introduced onto the surface of the particles, wherein the magnetic particles (1) have crystals with a size within a specific range, (2) an average particle size within a specific range and at the same time (3) a coefficient of variation of the particle size within a specific range.

[0030] As magnetic particles, multi-domain magnetic particles containing two or more magnetic domains can be applied. Multi-domain magnetic particles are magnetic particles having such characteristics: when no external magnetic field is applied, the magnetic domains (or crystals) are randomly arranged, and when an external magnetic field is applied, they can be magnetized along the direction of the applied magnetic field. Here, the meaning of the random arrangement of magnetic domains (or crystals) can mean that the directions of the magnetic forces are different from each other and are in an unoriented state, but the true (net) value of the magnetization intensity is substantially close to 0, so that macroscopically, it is considered to be in a non-magnetic state. The magnetic particles can be superparamagnetic particles.

[0031] As used herein, the term "magnetic domain" generally refers to a region in which magnetization directions differ from one another within a magnetic particle. In this context, when a magnetic particle has two or more magnetic domains, the domains can be strongly magnetized by an external alternating magnetic field to generate vibrational heat, while when the magnetic field is removed, the particle returns to its original magnetic domain state, thereby forming magnetic particles having a residual magnetization strength with low hysteresis loss.

[0032] Whether a magnetic particle is a multi-domain magnetic particle can generally be determined by its particle size. For example, if the magnetic particle has a particle size Ds or greater that satisfies the following equation 1, it is generally expected that the magnetic particle is a multi-domain magnetic particle:

[0033] [Equation 1]

[0034]

[0035] In Equation 1, the variables have the following meanings:

[0036] *μ0: magnetic permittivity in vacuum (1.26Y10 -6 H / m)

[0037] *M s : Saturation magnetization of magnetic particles (unit: A / m or emu / g)

[0038] *A: Exchange stiffness of magnetic particles (unit: J / m)

[0039] *a: Lattice constant of magnetic particles (unit: m)

[0040] In Equation 1, variables other than the vacuum magnetic permittivity, namely, the saturation magnetization, exchange stiffness, and lattice constant of the magnetic particles, may vary depending on the specific type of magnetic particles. Therefore, after examining each numerical value of the magnetic particles to be used, the size of the magnetic particles is controlled to be Ds or larger, which is obtained by substituting the numerical value into Equation 1 above. This allows the formation of magnetic particles having multiple magnetic domains.

[0041] That is, when the magnetic particles used in the present application are multi-domain magnetic particles, the magnetic particles may have a particle size of Ds or more obtained according to the above equation 1. Generally, when the particle size of the magnetic particles exceeds Ds, the coercive force of the magnetic particles tends to decrease, and the magnetic particles used in the present application may have a particle size within the range of coercive force to be described below.

[0042] Such magnetic particles behave like those without magnetism when no external magnetic field is applied, so when a magnet containing magnetic particles is applied to, for example, a composition, the magnet can also exist in a state uniformly dispersed in the composition.

[0043] Magnetic particles do not generate heat through so-called eddy currents or hysteresis losses. However, they can be adjusted so that the hysteresis losses of the magnetic particles themselves are low and essentially only the saturation magnetization value exists, enabling vibrational heat generation. For example, when an external electromagnetic field is applied, the magnetic particles vibrate due to their coercive force, thus generating heat.

[0044] When a magnet satisfies the above conditions, specifically when it comprises magnetic particles and a surface treatment agent introduced onto the surfaces of the magnetic particles, wherein the magnetic particles comprise crystals and / or magnetic domains having a size within the above range, the average particle size of the magnetic particles is within the above range, and the coefficient of variation of the particle size of the particles satisfies all of the above conditions, the magnet or magnetic powder comprising the magnet has the advantage of exhibiting excellent calorific value, and also exhibiting uniformly excellent calorific value. Specifically, a magnet satisfying the above conditions can have an appropriate number of magnetic domains and an appropriate coercive force. Therefore, when an electromagnetic field is applied, vibration heat can be generated due to the low coercive force and the plurality of magnetic domains. Moreover, since the saturation magnetization intensity can be limited to a value while reducing the hysteresis loss of the magnetic particles themselves, heat can be generated stably and uniformly when an electromagnetic field is applied. At the same time, when any of the above conditions is not met, for example, the magnet does not contain a surface treatment agent, or even if it contains a surface treatment agent, the surface treatment agent is first introduced into the crystals constituting the magnetic particles rather than the surface of the magnetic particles, or it has particle characteristics outside the range of the crystal size and average particle size of the magnetic particles, or the coefficient of variation of the particle size as described above, there may be such a problem: its calorific value under certain magnetic field application conditions is low, or even if the calorific value is high, it cannot be maintained uniformly.

[0045] When controlling the thermal properties of a magnet, the size of the magnetic particles themselves and the size of the crystals and / or magnetic domains that make up the particles are also important, but it is also preferable to appropriately control the ratio between them. For example, the ratio (B / A) of the average particle size (B) of the magnetic particles to the crystal size (A) of the magnetic particles can be in the range of 1.5 to 10. In another example, the ratio can be 2 or more or 2.5 or more, and can be 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3.5 or less, or 3.3 or less.

[0046] As long as the magnetic particles can generate heat by applying an electromagnetic field, i.e., induction heating, their chemical composition is not particularly limited. For example, the magnetic particles may include a compound represented by the following formula 1:

[0047] [Formula 1]

[0048] MX a O b

[0049] In Formula 1, M is a metal or metal oxide, X includes Fe, Mn, Co, Ni or Zn, and satisfies |a×c|=|b×d|, where c is the cationic charge of X and d is the anionic charge of oxygen. In one embodiment, M in Formula 1 can be Fe, Mn, Mg, Ca, Zn, Cu, Co, Sr, Si, Ni, Ba, Cs, K, Ra, Rb, Be, Li, Y, B, or an oxide thereof. For example, when X a O b When X is Fe2O3, c can be +3 and d can be -2. a O b When Fe3O4, it can be expressed as FeOFe2O3, so that c can be +2 and +3, respectively, and d can be -2. The structure of the compound of the magnetic particle is not particularly limited as long as it satisfies the above formula 1, and it can be, for example, FeOFe2O3.

[0050] The magnetic particles may be made of the compound of Formula 1 above, or may include a compound in which the compound of Formula 1 is doped with an inorganic material. The inorganic material may include a monovalent to trivalent cationic metal or an oxide thereof, and two or more of a plurality of cationic metals may also be used.

[0051] As described above, the magnetic particles may exist in the form of clusters. Specifically, as described above, the magnetic particles contain a plurality of crystals having a size within a specific range, wherein such crystals may be clustered to form magnetic particles. That is, the magnetic particles may exist in the magnet in the form of clusters in which crystals (or magnetic domains) are formed. In this case, the reduction in calorific value caused by the aggregation of the magnetic particles can be prevented.

[0052] In the magnet, the magnetic particles are surface-treated with an appropriate surface treatment agent. The surface treatment of the magnetic particles can be performed using a compound (surface treatment agent) that can be introduced onto the surface of the magnetic particles. That is, as described above, the magnet contains magnetic particles and a surface treatment agent introduced onto the surface of the magnetic particles.

[0053] In this application, the terms "introduction," "anchoring," "interaction," or "binding" when referring to the surface treatment of a magnet are intended to refer to the formation of a bond between the magnetic particles and the surface treatment agent, or between the surface treatment agents. However, the term "bond" as used herein includes all known bonds capable of connecting two components, such as covalent bonds, ionic bonds, hydrogen bonds, coordination bonds, and / or van der Waals bonds.

[0054] In one embodiment, a precursor of magnetic particles or a compound having functional groups capable of strongly binding to the surface of magnetic particles can be used as a surface treatment agent. Compounds having such functional groups can include compounds having phosphate groups, carboxyl groups, sulfonic acid groups, amino groups, and / or cyano groups. Therefore, the magnetic particles or precursors of magnetic particles are surface-treated with a material having such functional groups, i.e., a surface treatment agent.

[0055] In the present application, as compounds that can be used as surface treatment agents, polyol-based compounds, polysiloxane-based compounds, alkylphosphoric acid-based surface treatment agents (for example, compounds of the following formula A), alkylcarboxylic acid-based surface treatment agents (for example, compounds of the following formula B), alkylsulfonic acid-based surface treatment agents, acid compounds containing other long-chain alkyl groups, acrylic copolymers containing acidic functional groups or amino groups, aromatic acid-based surface treatment agents, or block copolymers containing acidic functional groups or amino groups, etc. can be used.

[0056] [Formula A]

[0057]

[0058] [Formula B]

[0059]

[0060] [Formula C]

[0061]

[0062] In formulae A to C, R1 to R3 are each independently an alkyl group, an arylalkyl group, an alkoxy group, or an arylalkoxy group.

[0063] The alkyl group or alkoxy group that may be included in the above formulae A to C can be exemplified by an alkyl group or alkoxy group having a carbon number in the range of 6 to 24. In addition, in another example, the carbon number of the alkyl group or alkoxy group may be 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more, 19 or more, 20 or more, 21 or more, 22 or more, or 23 or more, or may be 23 or less, 22 or less, 21 or less, 20 or less, 19 or less, 18 or less, 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, or about 7 or less.

[0064] The alkyl group or alkoxy group that may be included in the above formulae A to C may be exemplified by an aryl group having about 6 to 13 carbon atoms, and for example, a benzyl group, a phenyl group, or the like may be applied.

[0065] Furthermore, in another example, as surface treatment agents, (a) phosphate salts of oligomers or polymers containing amino groups, such as phosphate salts of polyamines optionally modified with fatty acids or alkoxylated (especially ethoxylated), phosphate salts of epoxide-polyamine adducts, phosphate salts of acrylate or methacrylate copolymers containing amino groups, or phosphate salts of acrylate-polyamine adducts can also be used; (b) monoesters or diesters of phosphoric acid, such as monoesters or diesters of phosphoric acid esters with alkyl, aryl, aralkyl or alkylaryl alkoxylates (for example, nonylphenol ethoxylates, isotridecanol ethoxylates or butyl alcohol-initiated alkylene oxide monoesters or diesters) or with polyesters (for example, lactone polyols). (c) acidic dicarboxylic monoesters, for example acidic dicarboxylic monoesters (especially those of succinic acid, maleic acid or phthalic acid) with alkyl, aryl, aralkyl or alkylaryl alkoxylates (for example nonylphenol ethoxylate, isotridecanol ethoxylate or butanol-initiated alkylene oxide polyethers); (d) polyurethane-polyamine adducts; (e) polyalkoxylated monoamines or diamines (for example ethoxylated oleylamine or alkoxylated ethylenediamine) or (f) reaction products of monoamines, diamines, polyamines or amino alcohols with unsaturated fatty acids, and reaction products of unsaturated 1,2-dicarboxylic acids, their anhydrides and their salts with alcohols and / or amines, etc.

[0066] Such a surface treatment agent is known as a commercially available product, and for example, a surface treatment agent known as the following product name can be used: for example BYK-220S、BYK-P 9908、BYK-9076、BYK-9077、BYK-P 104、BYK-P104 S、BYK-P 105、BYK-W 9010、BYK-W 920、BYK-W 935、BYK-W 940、BYK-W 960、BYK-W 965、BYK-W 966、BYK-W 975、BYK-W 980、BYK-W 990、BYK-W 995、BYK-W 996、BYKUMEN、BYKJET9131、LACTIMON、ANTI-TERRA-202、ANTI-TERRA-203、ANTI-TERRA-204、ANTI-TERRA-205、ANTI-TERRA-206、ANTI-TERRA-207、ANTI-TERRA-U 100、ANTI-TERRA-U 80、ANTI-TERRA-U、LP-N-21201、LP-N-6918、DISPERBYK、DISPERBYK-101、DISPERBYK-102、DISPERBYK-103、DISPERBYK-106、DISPERBYK-107、DISPERBYK-108、DISPERBYK-109、DISPERBYK DISPERBYK-110、DISPERBYK-111、DISPERBYK-112、DISPERBYK-115、DISPERBYK-116、DISPERBYK-118、DISPERBYK-130、DISPERBYK-140、DISPERBYK-142、DISPERBYK-145、DISPERBYK-160、DISP DISPERBYK-161、DISPERBYK-162、DISPERBYK-163、DISPERBYK-164、DISPERBYK-165、DISPERBYK-166、DISPERBYK-167、DISPERBYK-168、DISPERBYK-169、DISPERBYK-170、DISPERBYK-171、DI DISPERBYK-174、DISPERBYK-176、DISPERBYK-180、DISPERBYK-181、DISPERBYK-182、DISPERBYK-183、DISPERBYK-184、DISPERBYK-185、DISPERBYK-187、DISPERBYK-190、DISPERBYK-191、DISPERBYK-192, DISPERBYK-193, DISPERBYK-194, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2008, DISPERBYK-2009, DISPERBY K-2010, DISPERBYK-2020, DISPERBYK-2025, DISPERBYK-2050, DISPERBYK-2070, DISPERBYK-2090, DISPERBYK-2091, DISPERBYK-209 5. DISPERBYK-2096, DISPERBYK-2150, DISPERBYK-2151, DISPERBYK-2152, DISPERBYK-2155, DISPERBYK-2163, DISPERBYK-2164, DIS PERBLAST-1010, DISPERBLAST-1011, DISPERBLAST-1012, DISPERBLAST-1018, DISPERBLAST-I or DISPERBLAST-P (BYK-Chemie, Wesel). ,

[0067] For proper surface treatment, a surface treatment agent having an acid value or an amine value within a specific range may be used. In one example, the surface treatment agent may have an acid value within a range of 10 mgKOH / g to 400 mgKOH / g, or an amine value within a range of 5 mgKOH / g to 400 mgKOH / g.

[0068] In another example, the acid value of the surface treatment agent may be about 20 mgKOH / g or more, 30 mgKOH / g or more, 40 mgKOH / g or more, 50 mgKOH / g or more, 60 mgKOH / g or more, 70 mgKOH / g or more, 80 mgKOH / g or more, or 90 mgKOH / g or more, or may be about 390 mgKOH / g or less, 380 mgKOH / g or less, 370 mgKOH / g or less, 360 mgKOH / g or less, 350 mgKOH / g or less, 340 mgKOH / g or less, 330 mgKOH / g or less, 320 mgKOH / g or less, 310 mgKOH / g or less, 300 mgKOH / g or less, 290 mgKOH / g or less. KOH / g or less, 280 mgKOH / g or less, 270 mgKOH / g or less, 260 mgKOH / g or less, 250 mgKOH / g or less, 240 mgKOH / g or less, 230 mgKOH / g or less, 220 mgKOH / g or less, 210 mgKOH / g or less, 200 mgKOH / g or less, 190 mgKOH / g or less, 180 mgKOH / g or less, 170 mgKOH / g or less, 160 mgKOH / g or less, 150 mgKOH / g or less, 140 mgKOH / g or less, 130 mgKOH / g or less, 120 mgKOH / g or less, 110 mgKOH / g or less, or about 100 mgKOH / g or less.

[0069] In another example, the amine value of the surface treatment agent can be about 10 mgKOH / g or more, about 15 mgKOH / g or more, about 20 mgKOH / g or more, 30 mgKOH / g or more, 40 mgKOH / g or more, 50 mgKOH / g or more, 60 mgKOH / g or more, 70 mgKOH / g or more, 80 mgKOH / g or more, or 90 mgKOH / g or more, or can be about 390 mgKOH / g or less, 380 mgKOH / g or less, 370 mgKOH / g or less, 360 mgKOH / g or less, 350 mgKOH / g or less, 340 mgKOH / g or less, 330 mgKOH / g or less, 320 mgKOH / g or less, 310 mgKOH / g or less, 300 mgKOH / g or less. KOH / g or less, 290 mgKOH / g or less, 280 mgKOH / g or less, 270 mgKOH / g or less, 260 mgKOH / g or less, 250 mgKOH / g or less, 240 mgKOH / g or less, 230 mgKOH / g or less, 220 mgKOH / g or less, 210 mgKOH / g or less, 200 mgKOH / g or less, 190 mgKOH / g or less, 180 mgKOH / g or less, 170 mgKOH / g or less, 160 mgKOH / g or less, 150 mgKOH / g or less, 140 mgKOH / g or less, 130 mgKOH / g or less, 120 mgKOH / g or less, 110 mgKOH / g or less, or about 100 mgKOH / g or less.

[0070] In the present application, the term "amine value" means a ratio of the amount of KOH used for titration when an amino group (NH2, -NHR or -NR2) contained in a surface treatment agent is titrated with KOH (a numerical value in mg indicating the amount of KOH consumed when 1 g of the surface treatment agent is titrated).

[0071] In the present application, the term "acid value" means the ratio of the amount of KOH used for titration when an acidic functional group (-COOH, etc.) contained in a surface treatment agent is titrated with KOH (a numerical value in mg indicating the amount of KOH consumed when 1 g of the surface treatment agent is titrated).

[0072] The acid value can be measured by dissolving the sample in a solvent (a mixed solvent in which diethyl ether and ethanol are mixed at a volume ratio of 2:1 (diethyl ether:ethanol)) and using an automatic potentiometric titrator (Mettler, G10S). Potentiometric titration is performed with an ethanol solution (potassium hydroxide-ethanol solution) in which KOH is dissolved so that the concentration of the sample becomes about 0.1 mol / L, and the amount of potassium hydroxide-ethanol solution required for neutralizing the sample is measured. The acid value can then be calculated by the following formula A:

[0073] [Formula A]

[0074] Acid value = (B × f × 5.611) / S

[0075] In formula A, B is the amount of potassium hydroxide-ethanol solution used for titration (unit: mL), f is the factor of 0.1 mol / L potassium hydroxide-ethanol solution, and S is the mass of the solid content of the sample (g).

[0076] After placing a sample in an amount of about 0.5 g in a flask and dissolving it in neutralized acetone, and then cooling the solution and titrating it with 0.1N HCl using a bromophenol blue indicator until the color changes from blue to yellow, the amine value (mgKOH / g) can be obtained by the following formula B:

[0077] [Formula B]

[0078] Amine value = number of moles of 0.1N HCl solution × 100 × 5.61 / sample weight × NV

[0079] In the above formula B, NV is non-volatile, ie, solid content, which can be obtained in the following manner.

[0080] A sample in an amount of about 0.8 to 1.0 g is weighed on a tin lid of 7.5 cm in diameter, spread evenly, and then dried in an air circulation drying oven at 125° C. for 60 minutes, and NV can be obtained by the following formula C.

[0081] [Formula C]

[0082] NV (unit: %) = final weight (weight after drying) / initial weight (weight before drying) × 100

[0083] At the same time, in order to ensure the desired physical properties (viscosity, etc.), it is also preferable to appropriately control the properties of the surface treatment agent. For example, the weight average molecular weight (Mw) of the surface treatment agent can be 20,000 or less. The "weight average molecular weight" is a standard polystyrene conversion value measured by GPC (gel permeation chromatography). In another example, the weight average molecular weight of the surface treatment agent can be about 19,000 or less, 18,000 or less, 17,000 or less, 16,000 or less, 15,000 or less, 14,000 or less, 13,000 or less, 12,000 or less, 11,000 or less, 10,000 or less, 9,000 or less, 8,000 or less, 7,000 or less, 6,000 or less, 5,000 or less, 4,000 or less, 3,000 or less, 2,000 or less, or 1,000 or less, and can also be 100 or more, 200 or more, 300 or more, 400 or more, 500 or more, 600 or more, 700 or more, 800 or more, 900 or more, or 1,000 or more. It may vary depending on the type of the surface treatment agent, but as the molecular weight of the surface treatment agent applied within the above range increases, the size of crystals constituting the magnetic particles may tend to relatively decrease.

[0084] In the present application, the magnet can also be formed by applying a method of allowing a functional group present in a compound having a specific functional group, specifically, an anchoring functional group, to interact with the magnetic particles, or when the surface treatment agent does not have a functional group, by introducing the functional group into the surface treatment agent via a known chemical method and then allowing it to interact with the magnetic particles.

[0085] The ratio of the surface treatment agent in the magnet is not particularly limited, and it can be added to the extent that a magnet that can meet the aforementioned conditions (such as the size of the magnetic domains and / or the average particle size of the magnetic particles) can be produced. For example, in the magnet, the surface treatment agent can be included in a ratio within the range of 0.01 parts by weight to 30 parts by weight relative to 100 parts by weight of the magnetic particles. At this ratio, a magnet with desired thermal properties can be obtained. In another example, the ratio can be 0.1 parts by weight or greater, 1 part by weight or greater, 2 parts by weight or greater, 3 parts by weight or greater, or 4 parts by weight or greater, and can be 27 parts by weight or less, 25 parts by weight or less, 23 parts by weight or less, 21 parts by weight or less, or 20 parts by weight or less. On the other hand, the ratio of the surface treatment agent does not significantly affect the average particle size of the preformed magnetic particles, so that when the ratio of the surface treatment agent exceeds the appropriate range, specifically, even if the ratio exceeds the above range, it does not affect the physical properties of the magnetic particles, such as size.

[0086] Unless otherwise specified in the present application, the unit "parts by weight" means a weight ratio between components.

[0087] There is no particular limitation on the method for surface treating magnetic particles with a surface treatment agent to obtain a magnet. For example, the magnetic particles are mixed with the surface treatment agent in a suitable environment, such as in the presence of a solvent, thereby causing interaction between the magnetic particles and the surface treatment agent, and forming a bond between the magnetic particles and the surface treatment agent as described above. Such a surface treatment agent can be present on the surface of the magnetic particles, specifically on the periphery of the magnetic particles. In addition, the magnet can be manufactured by applying the detailed method of the present application described below.

[0088] The magnetic particles may be subjected to a surface treatment in addition. In this case, the surface treatment agent described above may be referred to as a primary surface treatment agent, and the surface treatment agent used for the additional surface treatment may be referred to as a secondary surface treatment agent. That is, in one example, the magnet of the present application may further comprise a surface treatment agent (primary surface treatment agent) or a secondary surface treatment agent that forms a bond with the magnetic particles. That is, when the magnet further comprises a secondary surface treatment agent, the secondary surface treatment agent may be introduced onto the surface of the magnetic particles and / or onto the surface of the primary surface treatment agent treated on the surface of the magnetic particles.

[0089] When such a secondary surface treatment agent is primarily applied to a magnet, it is generally used to impart dispersion stability, cohesiveness, and anti-sedimentation properties to the magnet, rather than to control the particle properties of the magnetic particles that constitute the magnet. Furthermore, the properties of the secondary surface treatment agent can be appropriately modified depending on the compatibility with the material that can be mixed with the magnet, the function of the material, and the like.

[0090] A polymer compound can be used as a secondary surface treatment agent. For example, a polymer compound having a weight average molecular weight in the range of about 1,000 to 500,000 can be used as a secondary surface treatment agent. In the case where the secondary surface treatment agent is a polymer compound, in another example, its molecular weight (Mw) can be about 1500 or more, 2000 or more, 2500 or more, 3000 or more, 3500 or more, 4000 or more, 4500 or more, 5000 or more, 5500 or more, 6000 or more, 6500 or more, 7000 or more, 7500 or more, 8000 or more, 8500 or more, 9000 or more, 9500 or more, 10000 or more, 12000 or more, 14000 or more, or In some embodiments, the present invention may be 16,000 or greater, 18,000 or greater, 19,000 or greater, or 20,000 or greater, or may be 450,000 or less, 400,000 or greater, 350,000 or less, 300,000 or less, 250,000 or less, 200,000 or less, 150,000 or less, 100,000 or less, 90,000 or less, 80,000 or less, 70,000 or less, 60,000 or less, 50,000 or less, 40,000 or less, 30,000 or less, or about 25,000 or less.

[0091] The polymer compound that can be used as the secondary surface treatment agent may be a polyurethane-based surface treatment agent, a polyurea-based surface treatment agent, a poly(urethane-urea)-based surface treatment agent, and / or a polyester-based (particularly, a branched polyester-based) surface treatment agent. As the secondary surface treatment agent, the polymer compound described above may include a compound containing a functional group that interacts with the primary surface treatment agent and / or the magnetic particles. Alternatively, if the polymer compound does not contain a functional group, the secondary surface treatment may be performed by introducing such a functional group into a specific polymer compound and applying the compound thereto.

[0092] As a secondary surface treatment agent, a compound having a functional group that interacts with the primary surface treatment agent and / or magnetic particles can be used, and such functional groups can be exemplified by the aforementioned phosphate group, carboxyl group, sulfonic acid group, amino group and / or cyano group, or a secondary amine group or a tertiary amine group or an amino group, or a urea bond, etc., but are not limited thereto.

[0093] In one example, as a secondary surface treatment agent, a polymer containing urea units and / or urethane units may also be used.

[0094] Here, the urea unit may be represented by the following formula D, and the urea unit may be represented by the following formula E:

[0095] [Formula D]

[0096]

[0097] In Formula D, R4 to R7 are each independently a hydrogen atom or an alkyl group, and L1 and L2 are each independently an aliphatic, alicyclic or aromatic divalent residue.

[0098] [Formula E]

[0099]

[0100] In Formula E, R8 and R9 are each independently a hydrogen atom or an alkyl group, and L3 and L4 are each independently an aliphatic, alicyclic or aromatic divalent residue.

[0101] The unit of Formula D is a so-called urea unit, which can be a reaction product of a polyamine and a diisocyanate compound. Thus, for example, in Formula D above, L1 can be a structure derived from the diisocyanate compound participating in the reaction, and L2 can be a structure derived from the polyamine participating in the reaction. Here, the "derived structure" in the case of L1 can be a structure derived from the diisocyanate compound other than the isocyanate group, and in the case of L2 can be a structure derived from the portion of the polyamine compound other than the amine group (-NH2).

[0102] The unit of Formula E is a so-called urethane unit, which can be a reaction product of a polyol and a diisocyanate compound. Thus, for example, in Formula E above, L3 can be a structure derived from the diisocyanate compound participating in the reaction, and L4 can be a structure derived from the polyol participating in the reaction. Here, the "derived structure" in the case of L3 can be a structure derived from the diisocyanate compound other than the isocyanate group, and in the case of L4 can be a structure derived from the portion of the polyol other than the hydroxyl group (-OH).

[0103] The diisocyanate compound capable of forming the structures of Formulae D and E may be exemplified by toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoboron diisocyanate, tetramethylxylene diisocyanate, or naphthalene diisocyanate, but is not limited thereto.

[0104] In addition, the polyamine capable of forming the structure of Formula D may be exemplified by alkylenediamines having an alkylene unit containing 1 to 20, 1 to 16, 1 to 12, 1 to 8, or 1 to 4 carbon atoms, such as ethylenediamine or propylenediamine, but is not limited thereto.

[0105] In addition, the polyol capable of forming the structure of Formula E may be exemplified by an alkylene glycol having an alkylene unit containing 1 to 20, 1 to 16, 1 to 12, 1 to 8, or 1 to 4 carbon atoms, such as ethylene glycol or propylene glycol, but is not limited thereto.

[0106] Therefore, polyurethane and / or polyurea or poly(urethane-urea) prepared by appropriately combining the above-mentioned known monomers can be used as a secondary surface treatment agent. If necessary, it can also be used after necessary functional groups are introduced into the polyurethane and / or polyurea or poly(urethane-urea) by known chemical methods.

[0107] As the secondary surface treatment agent, a compound having or not having an appropriate acid value and / or amine value may be applied depending on the type of compound to be mixed with the magnet. In one example, the secondary surface treatment agent may have an acid value in the range of 10 mgKOH / g to 400 mgKOH / g, or an amine value in the range of 5 mgKOH / g to 400 mgKOH / g.

[0108] In another example, the acid value of the surface treatment agent may be about 20 mgKOH / g or greater, 30 mgKOH / g or greater, 40 mgKOH / g or greater, 50 mgKOH / g or greater, 60 mgKOH / g or greater, 70 mgKOH / g or greater, 80 mgKOH / g or greater, or 90 mgKOH / g or greater, or may be about 390 mgKOH / g or less, 380 mgKOH / g or less, 370mgKOH / g or less, 360mgKOH / g or less, 350mgKOH / g or less, 340mgKOH / g or less, 330mgKOH / g or less, 320mgKOH / g or less, 310mgKOH / g or less, 300mgKOH / g or less, 290mgKOH / g or less, 280mgKOH / g or less, 270mgKOH / g or less, 260mgKOH / g or less, 250mgKOH / g or less, 240mgKOH / g or less, 230mgKOH / g or less, 220mgKOH / g or less, 210mgKOH / g or less, 200mgKOH / g or less, 190mgKOH / g or less, 180mgKOH / g or less, 170mgKOH / g or less, 160mgKOH / g or less, 150mgKOH / g or less, 14 0 mgKOH / g or less, 130 mgKOH / g or less, 120 mgKOH / g or less, 110 mgKOH / g or less, 100 mgKOH / g or less, 90 mgKOH / g or less, 80 mgKOH / g or less, 70 mgKOH / g or less, 60 mgKOH / g or less, 50 mgKOH / g or less, 40 mgKOH / g or less, or about 30 mgKOH / g or less.

[0109] In another example, the amine value of the surface treatment agent can be about 10 mgKOH / g or greater, about 15 mgKOH / g or greater, about 20 mgKOH / g or greater, 30 mgKOH / g or greater, 40 mgKOH / g or greater, 50 mgKOH / g or greater, 60 mgKOH / g or greater, 70 mgKOH / g or greater, 80 mgKOH / g or greater, or 90 mgKOH / g or greater, or can be about 390 mgKOH / g or greater. H / g or less, 380mgKOH / g or less, 370mgKOH / g or less, 360mgKOH / g or less, 350mgKOH / g or less, 340mgKOH / g or less, 330mgKOH / g or less, 320mgKOH / g or less, 310mgKOH / g or less, 300mgKOH / g or less, 290mgKOH / g or less, 280mgKOH / g or less, 270mgKOH / g or less, 260 mgKOH / g or less, 250 mgKOH / g or less, 240 mgKOH / g or less, 230 mgKOH / g or less, 220 mgKOH / g or less, 210 mgKOH / g or less, 200 mgKOH / g or less, 190 mgKOH / g or less, 180 mgKOH / g or less, 170 mgKOH / g or less, 160 mgKOH / g or less, 150 mgKOH / g or less The present invention relates to an aqueous solution of at least 1,400 mgKOH / g or less, or about 1,400 mgKOH / g or less, 1,600 mgKOH / g or less, 1,200 mgKOH / g or less, 1,100 mgKOH / g or less, 1,200 mgKOH / g or less, 1,100 mgKOH / g or less, 1,200 mgKOH / g or less, 1,100 mgKOH / g or less, 1,200 mgKOH / g or less, 1,200 mgKOH / g or less, 1,100 mgKOH / g or less, 1,200 mgKOH / g or less, 1,200 mgKOH / g or less, 1,100 mgKOH / g or less, 1,200 mgKOH / g or less, 1,200 mgKOH / g or less, 1,

[0110] In another example, the secondary surface treatment agent can be a compound with no acid value and / or amine value. In this application, no acid value or amine value means an acid value or amine value of about 5 mgKOH / g or less, 4 mgKOH / g or less, 3 mgKOH / g or less, 2 mgKOH / g or less, 1 mgKOH / g or less, or 0.5 mgKOH / g or less, or substantially 0 mgKOH / g. As described above, when the magnet is blended with epoxy resin, etc., a surface treatment agent without any acid value and / or amine value may be effective.

[0111] As the secondary surface treatment agent, a branched polyester surface treatment agent, which is called a so-called branched polyester-based dispersant, or the like can also be used.

[0112] In the magnet, the secondary surface treatment agent may be included in a ratio of 0.01 to 30 parts by weight relative to 100 parts by weight of the magnetic particles. At such a ratio, a magnet having desired properties can also be formed. In another example, the ratio may be approximately 0.5 parts by weight or greater, 1 part by weight or greater, 1.5 parts by weight or greater, 2 parts by weight or greater, 2.5 parts by weight or greater, 3 parts by weight or greater, 3.5 parts by weight or greater, 4 parts by weight or greater, 4.5 parts by weight or greater, or 5 parts by weight or greater, or may be approximately 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, approximately 13 parts by weight or less, approximately 12 parts by weight or less, or approximately 10 parts by weight or less.

[0113] The method of surface treating the magnetic particles with the secondary surface treatment agent is not particularly limited. For example, a magnet can be prepared by mixing the magnetic particles (or magnetic particles treated with the primary surface treatment agent) with the secondary surface treatment agent in an appropriate environment such as a solvent.

[0114] The magnet of the present application comprises a plurality of magnetic particles, so that in one embodiment, it can exist in powder form. In this case, when the magnet of the present application is used, for example, to cure a curable (particularly a thermosetting) resin, when the magnet exists in powder form, the magnet can maintain an excellent dispersion state in a composition having the resin and the magnet, thereby having the advantage that the curing of the resin can proceed more smoothly.

[0115] The magnet of the present application can exhibit excellent magnetic and thermal properties.

[0116] In one example, the magnet may have a saturation magnetization value within a specific range. The saturation magnetization value of the magnet may be within a range of 20 emu / g to 150 emu / g. When the saturation magnetization value of the magnet is within the above range, when an electromagnetic field is applied to the magnet, heat can be generated by vibration between the magnet, specifically, magnetic particles contained in the magnet, rather than by eddy currents of the magnet, thereby generating a large amount of heat uniformly.

[0117] In one example, the magnet may have a coercive force within a specific range. Specifically, the coercive force of the magnet may be in the range of 1 kOe to 200 kOe. Here, the term "coercive force" may mean the strength of the critical magnetic field required to reduce the magnetization intensity of the magnetic particles to zero. That is, even when the magnetic field is removed, the magnet magnetized by the external magnetic field maintains a certain degree of magnetization state, wherein the strength of the magnetic field that can make the magnetization degree zero by applying a reverse magnetic field to the magnet thus magnetized is called coercive force. Coercive force can be a standard for distinguishing between soft magnetic materials and hard magnetic materials, and the magnet of the present application can be a soft magnetic powder. In the present application, by adjusting the coercive force of the magnet within the above-mentioned range, the magnetic conversion of the magnet can be more easily achieved, and therefore, the vibration heat of the desired degree in the present application can be generated.

[0118] In the present application, the physical properties of the magnet can be measured using a VSM (vibrating sample magnetometer). VSM is a device that measures the magnetization value of a sample by recording the magnetic field applied by a Hall probe and recording the electromotive force obtained by Faraday's law when vibration is applied to the sample. According to Faraday's law, it can be seen that if the N pole of the bar magnet points to the coil and is pushed toward the coil, the ammeter moves and current flows through the coil. The resulting current is called the induced current, which is generated by the induced electromotive force. VSM is a method of detecting the induced electromotive force to measure the magnetization value of the sample by the electromotive force, and the induced electromotive force is generated in the detection coil when the sample is vibrated by such a basic working principle. The magnetic properties of the material can be measured simply as a function of magnetic field, temperature and time, and rapid measurement is possible under a magnetic force as high as 2 Tesla (T) and in a temperature range of 2K to 1273K.

[0119] The magnet of the present application may also have a specific surface area within a specific range. Specifically, the magnet of the present application may have a specific surface area within 3m 2 / g to 25m 2 The BET specific surface area is in the range of 1.5 ~ 2.5 g / cm2.

[0120] In the present application, the BET specific surface area may be the specific surface area of ​​magnetic particles measured according to the BET (Brunauer-Emmett-Teller) adsorption isotherm equation, specifically, an adsorption isotherm equation introduced as a model for multilayer adsorption. The parameters of the BET equation and the method for measuring the specific surface area using the BET equation are well known in the industry. The BET specific surface area can be used to determine the size of the pores formed by the magnetic particles in the magnet, the size of the magnetic particles, the particle size distribution of the magnetic particles, and the like.

[0121] The magnets of the present application may also have excellent thermal properties. For example, the magnets may have a SAR value of 60 W / g or greater calculated according to the following equation 2:

[0122] [Equation 2]

[0123] SAR=CiXmXΔT / Δt

[0124] In the above equation 2, SAR means the calorific value of the magnetic fluid in which the magnet is dissolved in water, Ci is the specific heat of water as the solvent of the magnetic fluid, which is 4.184 J (g×K); m is the ratio (mi / ma) of the weight of water (mi, unit: g) as the solvent of the magnetic fluid to the weight of the magnet (ma, unit: g); ΔT is the temperature increase (unit: K) of the magnetic fluid when an alternating magnetic field is applied to 0.35 mL of the magnetic fluid under the conditions of a current of 120.4 A and 310 kHz at a temperature of 294 K for 60 seconds; and Δt is the time for which the alternating magnetic field under the above conditions is applied to the magnetic fluid, which is 60 seconds.

[0125] When the alternating magnetic field of certain intensity is applied on the magnet of specific amount, SAR value is the standardized value of the heat produced by magnet.Should be understood that, if above value is at least 60W / g, then desired thermal characteristic can be realized in the present application.In another example, SAR value can be 63W / g or larger, 65W / g or larger, 67W / g or larger or 70W / g or larger, and can be 120W / g or smaller, 115W / g or smaller or 110W / g or smaller.Especially, the upper limit of SAR value also can change according to the solvent type for measuring this value.In addition, in the present application, water is used as solvent to measure SAR value, and wherein the upper limit (120W / g) of numerical value can mean the SAR value that can occur at maximum when the solvent for measuring this value is water.

[0126] Since magnets exhibit excellent thermal properties when an external force, specifically an external magnetic field, is applied, they can be advantageously used to cure thermosetting polymers (or resins).

[0127] Thus, in another aspect, the present application relates to a curable composition.

[0128] The curable composition may mean a composition that can be cured by an external force such as heat application or light irradiation, etc. Therefore, the curable composition of the present application includes at least a material that can be cured by an external force.

[0129] Curable composition comprises curable resin and magnet.In addition, the magnet applied to curable composition is the magnet of the present application.Therefore, even in the description of curable composition of the present application, all descriptions to magnetic properties can be applied.At this moment, the magnet in the composition can show suitable dispersion, and therefore, even if curable composition has low viscosity and fluidity, it can also be used for curing process.

[0130] For example, at a shear ratio of 100 seconds-1 The viscosity of the curable composition at room temperature can be 10,000 cP or less, measured under conditions of . In another example, the viscosity of the curable composition can be 9500 cP or less, 9,000 cP or less, 8500 cP or less, 8,000 cP or less, 7500 cP or less, 7,000 cP or less, 6500 cP or less, 6,000 cP or less, 5500 cP or less, 5,000 cP or less, 4500 cP or less, 4,000 cP or less, 3,000 cP or less, 2,000 cP or less, 1,000 cP or less, 900 cP or less, or 800 cP or less, or can also be 1 cP or more, 2 cP or more, 3 cP or more, 4 cP or more, 5 cP or more, 6 cP or more, 7cP or greater, 8cP or greater, 9cP or greater, 10cP or greater, 15cP or greater, 20cP or greater, 25cP or greater, 30cP or greater, 35cP or greater, 40cP or greater, 45cP or greater, 50cP or greater, 55cP or greater, 60cP or greater, 65cP or greater, 70cP or greater, 75cP or greater, 80cP or greater, 85cP or greater, 90cP or greater, 95cP or greater, or 100cP or greater, 1000cP or greater, 1500cP or greater, 2000cP or greater, 2500cP or greater, 3000cP or greater, 3500cP or greater, or 4000cP or greater.

[0131] The curable composition of the application can be an insulating composition. That is, curable composition can have insulation or can form a cured product showing insulation after solidification. In the application, term "insulation" means such a situation: the dielectric breakdown strength as determined by ASTM D149 standard is 10kV / mm or larger, 11kV / mm or larger, 12kV / mm or larger, 13kV / mm or larger, 14kV / mm or larger, 15kV / mm or larger, 16kV / mm or larger, 17kV / mm or larger, 18kV / mm or larger, 19kV / mm or larger or 20kV / mm or larger. Therefore, curable composition of the present invention itself can show above dielectric breakdown strength or can be cured to form a cured product showing above dielectric breakdown strength. The higher the value of dielectric breakdown strength, the more excellent the insulation, wherein the upper limit is not particularly limited, but in an example, the upper limit can be about 50kV / mm or less, 45kV / mm or less, 40kV / mm or less, 35kV / mm or less, 30kV / mm or less, 25kV / mm or less or 20kV / mm or less.Dielectric breakdown strength is the value measured according to ASTM D149 standards for the cured product of the curable composition in film form or the curable composition in film form, and unless otherwise stated, units are kV / mm.Dielectric breakdown strength can be achieved by being adjusted to the type and / or ratio of the curable resin and / or magnet of the component of curable composition.

[0132] The type of curable resin that can be included in the curable composition is not particularly limited. For example, as the curable resin, a so-called "thermosetting resin" that participates in a curing reaction by applying heat can be used. In addition, the curable resin is a so-called insulating resin, and a resin that can exhibit the above-mentioned insulating properties (dielectric breakdown strength) before and / or after curing can be used.

[0133] The curable resin may include a curable functional group. Specifically, the curable functional group may be exemplified by an alkenyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, an acryloyloxyalkyl group, a methacryloyloxyalkyl group, an epoxy group, an oxetane group, an alkenyl group, a hydrogen atom bonded to a silicon atom, an isocyanate group, a hydroxyl group, a phthalonitrile group, or a carboxyl group, but is not limited thereto.

[0134] Unless otherwise specified, "alkenyl" means an alkenyl group having 2 to 20, 2 to 16, 2 to 12, 2 to 8, or 2 to 4 carbon atoms. An alkenyl group may be linear, branched, or cyclic, and may be optionally substituted with one or more substituents.

[0135] Unless otherwise specified, "epoxy group" may refer to a cyclic ether having three ring-constituting atoms or a monovalent moiety derived from a compound containing a cyclic ether. Epoxy groups may be exemplified by glycidyl, epoxyalkyl, glycidyloxyalkyl, or alicyclic epoxy groups. Here, alicyclic epoxy groups may refer to a monovalent residue derived from a compound containing an aliphatic hydrocarbon ring structure and containing a structure in which two carbon atoms forming the aliphatic hydrocarbon ring also form an epoxy group. As the alicyclic epoxy group, an alicyclic epoxy group having 6 to 12 carbon atoms may be exemplified, and for example, 3,4-epoxycyclohexylethyl and the like may be exemplified.

[0136] The specific type of curable resin is not particularly limited. For example, the curable resin may be a resin having a linear or branched structure containing the above-mentioned curable functional group, and specifically, polysiloxane resin, polyimide, polyetherimide, polyesterimide, acrylic resin, vinyl-based resin, olefin resin, polyurethane resin, isocyanate resin, acrylic resin, polyester resin, phthalonitrile resin, polyamic acid, polyamide or epoxy resin, etc. can be exemplified.

[0137] The content of the magnet in the curable composition is not particularly limited. The content of the magnet in the curable composition can be considered for making the relevant curable composition, and specifically the heat required for curing the curable resin is suitably regulated. In an example, relative to the curable resin of 100 weight portions, the curable composition can include a magnet having a content of 0.01 weight portion to 60 weight portions. In another example, the ratio of the magnet can be approximately 0.5 weight portion or larger, or approximately 1 weight portion or larger, approximately 3 weight portions or larger, or approximately 5 weight portions or larger, or approximately 55 weight portions or smaller, approximately 50 weight portions or smaller, approximately 45 weight portions or smaller, approximately 40 weight portions or smaller, approximately 35 weight portions or smaller, approximately 30 weight portions or smaller, approximately 25 weight portions or smaller, approximately 20 weight portions or smaller, approximately 15 weight portions or smaller, or approximately 10 weight portions or smaller. The curable resin for calculating the reference of the magnet content comprises the component in resinous state, and is not in resinous state but can form the component of resin by solidification.

[0138] In addition to the above components, the curable composition may further comprise any additives required in the curable composition. Such additives may be exemplified by curing agents or catalysts for assisting the curing of the curable resin, initiators such as free radical initiators or cationic initiators, thixotropic agents, leveling agents, defoaming agents, antioxidants, substances that generate free radicals, organic and inorganic pigments or dyes, dispersants, various fillers such as thermally conductive fillers or insulating fillers, functional polymers or light stabilizers, and the like.

[0139] The magnets satisfying the above-mentioned characteristics have excellent thermal properties, so that when used in a curable composition in this manner, they can provide various advantages for curing the curable composition. For example, through the use of the magnets, the curable composition of the present application can be cured at a high speed and, in addition, can be cured with an excellent filling rate even in a narrow curing space.

[0140] Subsequently, the method for manufacturing the magnet will be described in more detail.

[0141] The present inventors have found that when a magnet is produced by applying a specific method, a magnet exhibiting the above-mentioned characteristics can be obtained with higher yield, in an easy manner, etc., and have completed the present invention.

[0142] The method for manufacturing a magnet of the present application includes at least: a first step of generating crystals of magnetic particles using a specific raw material; a second step of clustering the crystals generated in the first step; and a third step of mixing the raw material with the clustered crystals with a surface treatment agent. The method of the present application performs at least the steps in the above order.

[0143] In the first step, a raw material containing a magnetic particle precursor and a polar solvent is heated to form crystals. When the raw material, containing at least the magnetic particle precursor and the polar solvent, is heated, crystals forming the magnetic particles are formed. Specifically, when the raw material is heated, the polar solvent acts as a reducing agent, causing hydrolysis and condensation reactions in the magnetic particle precursor, resulting in the formation of an amorphous solid. Subsequently, continued heating causes the amorphous solid to undergo a phase transition and become crystalline.

[0144] The magnetic particle precursor may refer to a material capable of forming magnetic particles through a specific reaction. The reaction of generating magnetic particles using the magnetic particle precursor is performed by heating a raw material containing at least the magnetic particle precursor and an organic solvent.

[0145] The description of the magnetic particles is the same as above. Any precursor for the magnetic particles can be used without limitation, as long as it is a compound capable of forming magnetic particles through hydrolysis, dehydration, reduction, or phase transformation of the precursor. For example, when the magnetic particles are FeOFe2O3, the precursor for the magnetic particles can be FeCl3, Fe(NO3)3, Fe(CO)5, Fe(NO3)2, Fe(SO4)3, or Fe(AcAc)3 {iron(III) acetylacetonate}.

[0146] The content of the magnetic particle precursor can also be adjusted appropriately. For example, the content of the magnetic particle precursor in the raw material can be in the range of 0.025M to 0.125M. In another example, the content can be 0.03M or greater, 0.04M or greater, or 0.05M or greater, and can be 0.120M or less, 0.115M or less, or 0.1M or less.

[0147] The organic solvent contained in the raw material may be, for example, a polar organic solvent. As the polar organic solvent, any known polar solvent may be used without limitation as long as it can dissolve the magnetic particle precursor at an appropriate level.

[0148] Polar organic solvents can be used as reducing agents for magnetic particle precursors. Therefore, polar organic solvents may also be optionally referred to as "reducing polar solvents". "Polar solvent" may mean a solvent having a dielectric constant in the range of about 75 to 85 at a specific temperature, such as 25°C. From the perspective of smoothly dissolving the precursor of the magnetic particles in the raw material and applying the reducing agent for the phase change of the magnetic particle precursor to the magnetic particles, specifically the reduction reaction of the magnetic particle precursor, it is advantageous to apply a polyol as the organic solvent. Therefore, the raw material may contain a magnetic particle precursor and a polyol. A polyol is a compound having two or more hydroxyl groups (-OH).

[0149] As the polyol, there can be used so-called low molecular weight polyols such as ethylene glycol, glycerin, butanediol, trimethylolpropane; and high molecular weight polyols such as polyethylene glycol and methoxypolyethylene glycol, etc. Here, the low molecular weight polyol may refer to a monomolecular polyol, and the high molecular weight polyol may refer to a polyol having a molecular weight (weight average molecular weight) of 2,000 or less among the high molecular weight polyols.

[0150] The raw material may contain an organic solvent (e.g., a polyol) as a major component. That is, the content of the organic solvent in the raw material may be 50% or greater, 55% or greater, 60% or greater, 65% or greater, 70% or greater, 75% or greater, 80% or greater, 85% or greater, or 90% or greater, and may be approximately 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less, based on weight.

[0151] The method of the present application includes a step (second step) of clustering the crystals produced in the first step. Clustering can refer to a unit in which crystals or magnetic domains are densely aggregated (or agglomerated) to form a particle unit. In the method of the present application, magnetic particles are formed by forming crystals of magnetic particles using a magnetic particle precursor in the first step, and clustering the crystals in the second step.

[0152] The method for clustering the crystals is not particularly limited. For example, the crystals can be clustered by heat-treating (or heating) the product obtained in the first step (i.e., the raw material in which the crystals are formed) at a predetermined temperature. Based on the heat treatment results, the crystals formed in the first step form clusters to form magnetic particles. The specific process of the second step will be described below.

[0153] The method of the present application includes a step (third step) of mixing the raw materials that have passed the first and second steps with a surface treatment agent. As the surface treatment agent, all of the above can be used. When the raw materials that have passed the first and second steps are mixed with the surface treatment agent, a magnet containing magnetic particles and the surface treatment agent introduced into the particle surface is produced, wherein the magnetic particles have crystals of a specific size and have an average particle size and a particle size variation coefficient within a specific range.

[0154] If the raw materials are not mixed with the surface treatment agent, or even if they are mixed with the surface treatment agent, but the raw materials and the surface treatment agent are mixed before the second step, specifically during the first step or during the process of clustering of the crystals produced in the first step, it is impossible to produce a magnet with the above-mentioned properties. Magnets produced in this manner have a form in which the surface treatment agent is not introduced, or even if the surface treatment agent is introduced, it is introduced to the surface of the crystals constituting the magnetic particles rather than the surface of the magnetic particles. Such magnets do not exhibit the desired thermal properties used in this application.

[0155] The method of this application also specifies the timing for mixing the surface treatment agent. This allows for the production of magnets with the aforementioned properties. Specifically, in the third step, by crystallizing the magnetic particle precursor, clustering the crystals, and then mixing with the surface treatment agent, a magnet with the desired thermal properties can be produced.

[0156] Hereinafter, each step of each method of the present application will be described in more detail.

[0157] The method of the present application can perform a phase transition reaction from a magnetic particle precursor to magnetic particles in the first step, specifically, a reduction reaction. The reaction to magnetic particles occurs through hydrolysis, dehydration, and reduction of the magnetic particle precursor. Therefore, the raw materials used in the first step may include additional materials in addition to the magnetic particle precursor and polar solvent.

[0158] In the first step, the hydrolysis of the magnetic particles can be performed. Therefore, the reaction of the magnetic particle precursor to form crystals can be carried out at least in the presence of an aqueous solvent. That is, the raw materials applied in the first step can also contain an aqueous solvent.

[0159] As the aqueous solvent, water or other polar solvents can be applied, and typically, water can be exemplified.

[0160] The ratio of the aqueous solvent is not limited. For example, the raw material may contain an aqueous solvent content in the range of 1 volume % to 30 volume % relative to the volume of the organic solvent. In another example, the content may be 2 volume % or greater, 3 volume % or greater, 4 volume % or greater, or 5 volume % or greater, and may be 25 volume % or less, 20 volume % or less, or 15 volume % or less.

[0161] The phase transition of the magnetic particle precursor to the magnetic particles, specifically, the reduction reaction, can be performed by a reaction between the magnetic particle precursor and a base. Therefore, the raw material may further contain a base (basic compound) in addition to the magnetic particle precursor, the organic solvent, and the aqueous solvent.

[0162] The type of base used in the method of the present application is not particularly limited. As the base, compounds showing alkalinity known in the art can be used without limitation, that is, compounds that can release hydroxide ions (-OH) or absorb hydrogen ions (H) in aqueous solution. + ) or a compound having a pH greater than about 7. As the base, for example, a strong basic compound such as sodium oxide and potassium hydroxide; or a weak basic compound such as sodium carbonate, sodium bicarbonate, cesium carbonate, calcium carbonate, ammonia water or sodium acetate can be used, and in the example of the present application, sodium acetate is used as the base.

[0163] The content of alkali in the raw material is also non-limiting. The raw material can include alkali in a range of 0.4M to 2.0M. In another example, the content can be 0.5M or greater, 0.6M or greater, or 0.7M or greater, and can be 1.9M or less, 1.8M or less, 1.7M or less, 1.6M or less, 1.5M or less, 1.4M or less, 1.3M or less, 1.2M or less, or 1.1M or less.

[0164] In the method of the present application, the first to third steps represented by the above steps, specifically the step of forming magnetic crystals, the step of clustering the crystals, and the step of treating the surface of the magnetic particles, can each be performed at a temperature within a specific range for a certain time range.

[0165] In the method of the present application, the first step can be performed at a temperature within the range of 50°C to 90°C. That is, the first step can be performed while heating the raw materials to a temperature within this range. The crystals constituting the magnetic particles can be appropriately formed within this temperature range. In another example, the temperature conditions of the first step can be 55°C or higher, 60°C or higher, 65°C or higher, or 70°C or higher, and can be 85°C or lower, 80°C or lower, 75°C or lower, or 70°C or lower.

[0166] In the method of the present application, the first step can be performed through at least two processes. For example, the first step can be performed by a method including: (1-a) raising the temperature of the raw material to a temperature within a range of 50°C to 90°C; and (1-b) maintaining the temperature of the heated raw material for a period of time within a range of 30 minutes to 120 minutes. That is, when heating the raw material to form crystals from the precursor of the magnetic particles, maintaining the raw material heated to a specific temperature at that temperature for an appropriate period of time allows for smoother formation of magnetic domains (or crystals).

[0167] In another example, the elevated temperature of the feedstock in process (1-a) may be 55°C or higher, 60°C or higher, 65°C or higher, or 70°C or higher, and may be 85°C or lower, 80°C or lower, 75°C or lower, or 70°C or lower.

[0168] The time for maintaining the temperature of the heated raw material in process (1-b) can be 35 minutes or longer, 40 minutes or longer, 45 minutes or longer, 50 minutes or longer, 55 minutes or longer, or 60 minutes or longer, and can be 110 minutes or shorter, 100 minutes or shorter, 90 minutes or shorter, 80 minutes or shorter, 70 minutes or shorter, or 60 minutes or shorter.

[0169] The temperature increase rate for increasing the temperature of the raw material in process (1-a) can also be appropriately adjusted. For example, in the method of the present application, process (1-a) in the first step can be performed at a temperature increase rate within a range of 0.5°C / min to 2°C / min.

[0170] In the method of the present application, the second step, specifically the step of aggregating the crystals produced in the first step, can also be performed at a temperature within a specific range. For example, in the method of the present application, the second step can be performed at a temperature in the range of 170°C to 210°C. Within this temperature range, magnetic particles having a particle size that satisfies the above-mentioned average value and coefficient of variation while having magnetic domains of the above-mentioned size can be appropriately formed. In another example, the temperature condition of the second step can be 175°C or higher, 180°C or higher, 185°C or higher, or 190°C or higher, and can be 205°C or lower, 200°C or lower, 195°C or lower, or 190°C or lower.

[0171] In the method of the present application, the second step may also be performed through at least two processes similar to the first step.

[0172] For example, the second step can be performed by a method comprising: (2-a) raising the temperature of the raw material to a temperature within the range of 170°C to 210°C; and (2-b) maintaining the temperature of the raised raw material for a period of time within the range of 12 hours to 80 hours. Specifically, by maintaining the raw material heated to a specific temperature at that temperature for an appropriate period of time during the process of clustering the crystals, clustering of the crystals can proceed more smoothly.

[0173] In another example, the temperature increased in process (2-a) may be 175°C or higher, 180°C or higher, 185°C or higher, or 190°C or higher, and may be 205°C or lower, 200°C or lower, 195°C or lower, or 190°C or lower.

[0174] In another example, the time for maintaining the temperature of the heated raw material in process (2-b) may be 16 hours or longer, 20 hours or longer, or 24 hours or longer, and may be 64 hours or shorter, 48 hours or shorter, 32 hours or shorter, or 24 hours or shorter.

[0175] The temperature increase rate for increasing the temperature of the raw material in process (2-a) can also be appropriately adjusted. For example, in the method of the present application, process (2-a) in the second step can be performed at a temperature increase rate within a range of 1.5°C / min to 5°C / min.

[0176] In the method of the present application, the third step, specifically, the step of mixing the crystallized clusters with the surface treatment agent, can also be performed within a specific temperature range. In the method of the present application, the third step can be performed at a temperature within the range of 50°C to 90°C. Within the above temperature range, the interaction between the magnetic particles and the surface treatment agent can proceed smoothly. In another example, the temperature can be 55°C or higher, 60°C or higher, 65°C or higher, or 70°C or higher, and can be 85°C or lower, 80°C or lower, 75°C or lower, or 70°C or lower.

[0177] As the surface treatment agent, for example, a powdered surface treatment agent can be used. In this case, the surface treatment agent can be dissolved in a solvent such as water and applied as a solution. From the perspective of ensuring that the powdered surface treatment agent functions smoothly and that the reaction is stable, the third step of mixing the powdered surface treatment agent with the magnetic particles can be performed within the above-mentioned temperature range.

[0178] In the method of the present application, the third step can also be performed as a more detailed process similar to the first and second steps. Specifically, in the method of the present application, the third step can be performed by at least the following process: mixing the raw material that has passed the second step with a surface treatment agent, cooling the raw material mixed with the surface treatment agent to a temperature within a specific range, and maintaining the cooled raw material at this temperature for a specific time. That is, in the method of the present application, the third step can include: (3-a) mixing the raw material that has passed the second step with the surface treatment agent; (3-b) cooling the raw material mixed with the surface treatment agent to a temperature within a range of 50°C to 90°C; and (3-c) maintaining the cooled raw material for a period of time within a range of 30 minutes to 120 minutes.

[0179] There is no particular restriction on the type, application amount, etc. of the surface treatment agent applied in process (3-a). As the surface treatment agent, the surface treatment agent of the above type can be applied. In the method of the present application, the surface treatment agent can be mixed in a content within the range of 0.01 to 30 parts by weight relative to 100 parts by weight of the magnetic particle precursor in process (3-a). In another example, the content of the surface treatment agent can be 0.1 parts by weight or greater, 1 part by weight or greater, 2 parts by weight or greater, 3 parts by weight or greater, or 4 parts by weight or greater, and can be 27 parts by weight or less, 25 parts by weight or less, 23 parts by weight or less, 21 parts by weight or less, or 20 parts by weight or less. In the method of the present application, the surface treatment agent is added after the magnetic crystallization clustering, and the surface treatment agent does not affect the size of the average particle diameter of the magnetic particles (crystallized clusters) thus formed, so that even if the content of the surface treatment agent exceeds an appropriate value, factors such as the size of the magnetic particles are not affected.

[0180] Since the temperature for clustering the crystals in the second step is higher than the temperature for mixing the surface treatment agent in the third step, a cooling process can generally be performed in the third step. For example, the cooling temperature in process (3-b) may be in the range of 50°C to 90°C. In another example, the temperature may be 55°C or higher, 60°C or higher, 65°C or higher, or 70°C or higher, and may be 85°C or lower, 80°C or lower, 75°C or lower, or 70°C or lower.

[0181] In process (3-b), the temperature reduction rate for cooling the raw material can also be appropriately adjusted. For example, in the method of the present application, process (3-b) in the third step can be performed at a temperature reduction rate within a range of 1.5°C / min to 5°C / min.

[0182] As described above, the magnet manufactured by the method of the present application may further include another surface treatment agent, such as the aforementioned secondary surface treatment agent. Therefore, the method of the present application may further include a step of performing a secondary surface treatment with a secondary surface treatment agent after the third step. As the secondary surface treatment agent, the secondary surface treatment agent mentioned in the description of the magnet may be used as is.

[0183] Specifically, the method of the present application may further include a step (fourth step) of mixing the magnetic particles surface-treated in the third step with a secondary surface treatment agent that can be combined with the surface treatment agent. For example, by mixing the magnetic particles surface-treated in the third step with the secondary surface treatment agent and then reacting them at an appropriate temperature for an appropriate time, a magnet that is further surface-treated with the secondary surface treatment agent can be produced.

[0184] The amount of the secondary surface treatment agent applied is also non-limiting. In the method of the present application, the secondary surface treatment agent in the fourth step can be mixed in an amount ranging from 0.01 parts by weight to 30 parts by weight relative to 100 parts by weight of the magnetic particle precursor. In another example, the amount of the secondary surface treatment agent applied can be about 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, 2 parts by weight or more, 2.5 parts by weight or more, 3 parts by weight or more, 3.5 parts by weight or more, 4 parts by weight or more, 4.5 parts by weight or more, or 5 parts by weight or more, or can be about 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, about 13 parts by weight or less, about 12 parts by weight or less, or about 10 parts by weight or less.

[0185] In the method of the present application, in addition to the above, known processes required for synthesizing or manufacturing other magnets can also be carried out. For example, in the method of the present application, a process of filtering or extracting only the necessary components (magnets) from a raw material containing a completely synthesized reaction product can be carried out.

[0186] The method of the present application can produce magnets that meet the inherent particle characteristics (magnetic domain and / or crystal size, average particle size and coefficient of variation of magnetic particles, etc.) through the above-mentioned method. In addition, the magnets produced by the method of the present application have characteristics such as coercive force and specific surface area, which have the advantage of having excellent thermal properties when a specific electromagnetic field is applied.

[0187] Beneficial effects

[0188] The magnet of the present application can have an excellent calorific value, and at the same time, can uniformly maintain the calorific value.

[0189] In the magnet of the present application, the calorific value characteristics can be freely adjusted.

[0190] The curable composition of the present application can be easily cured using a magnet that satisfies all of the above characteristics.

[0191] The method of the present application can easily manufacture a magnet that meets all the above characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0192] Figure 1 This is the X-ray diffraction analysis result of Example 2.

[0193] Figure 2 This is the X-ray diffraction analysis result of Comparative Example 2.

[0194] Figure 3 This is a scanning electron microscope (SEM) photograph of Example 1.

[0195] Figure 4 This is a scanning electron microscope (SEM) photograph of Example 2.

[0196] Figure 5 This is a scanning electron microscope (SEM) photograph of Comparative Example 1.

[0197] Figure 6 This is a scanning electron microscope (SEM) photograph of Comparative Example 2.

[0198] Figure 7 Schematic diagram of a stator used to measure fill factor. DETAILED DESCRIPTION

[0199] Hereinafter, the present application will be described in detail by way of examples. However, the protection scope of the present invention is not limited by the examples described below.

[0200] 1. Measurement of crystal size

[0201] The crystal sizes of the magnetic particles in the magnets synthesized in Examples and Comparative Examples were measured according to the following method.

[0202] (1) Using Brucker's XRD-07-D8_Endeavor equipment, according to the equipment manual, the signal intensity was measured in a 2θ diffraction angle section of 10 to 90 degrees on the magnet.

[0203] (2) The size of the crystals was measured by substituting the measurement results within the range of 60.824 to 94.957 degrees, specifically the measurement results within the 2θ range of 62.57 degrees, into the following equation 3. At this time, the half width at the peak was about 4.133 degrees (=0.0721 radians).

[0204] [Equation 3]

[0205] τ=(K×λ) / (β×cos(θ))

[0206] In Equation 3, τ is the size of the crystal, K is the Scherrer constant of 0.94, λ is the wavelength of applied X-rays (unit: nm), β is about 0.0721 radians as the half width of 62.57 degrees, and θ is the Bragg diffraction angle.

[0207] 2. Average particle size and shape analysis of magnetic particles

[0208] The average particle size and shape analysis of the magnetic particles were performed according to the following procedure.

[0209] (1) A magnet was coated on a platinum (Pt) base material using a coater (Sputter Coater 108, Cressington Corporation) in automatic mode for about 60 to 90 seconds to prepare a specimen for SEM imaging.

[0210] (2) Use SEM (FESEM, JSM7610F, JEOL) to take pictures of the sample.

[0211] (3) Evaluate the clustering, particle size characteristics, and coefficient of variation of magnetic particles in the magnet through SEM photographs of the samples.

[0212] 3. Measurement of the calorific value of magnets

[0213] The thermal efficiency (SAR value) of the magnet was measured according to the following steps.

[0214] (1) A solution (magnetic fluid) in which 0.5 g of a magnet (provided that it is an amount excluding the applied amount of the surface treatment agent) is dispersed in 10 g of water is prepared.

[0215] (2) To 0.35 mL of the solution, an alternating magnetic field at a current and frequency of 120.4 A and 310 kHz was applied for about 60 seconds at a temperature of 294 K using a commercially available magnetic field application device, and the temperature of the solution was then measured.

[0216] (3) Calculate the SAR value of the following equation 2 by substituting the result of process (2) into the following equation 2:

[0217] [Equation 2]

[0218] SAR=CiXmXΔT / Δt

[0219] In the above equation 2, SAR means the calorific value of the magnetic fluid in which the magnet is dissolved in water, Ci is the specific heat of water as the solvent of the magnetic fluid, which is 4.184 J (g×K); m is the ratio (mi / ma) of the weight of water (mi, unit: g) as the solvent of the magnetic fluid to the weight of the magnet (ma, unit: g); ΔT is the temperature increase (unit: K) of the magnetic fluid when an alternating magnetic field is applied to 0.35 mL of the magnetic fluid under the conditions of a current of 120.4 A and 310 kHz at a temperature of 294 K for 60 seconds; and Δt is the time for which the alternating magnetic field of the above conditions is applied to the magnetic fluid, which is 60 seconds.

[0220] 4. Curing properties of curable compositions

[0221] The curing properties of the curable compositions were evaluated according to the following procedure.

[0222] (1) The curable composition is injected into a container having a capacity of 1 mL.

[0223] (2) Using a commercially available solenoid coil (winding diameter: 3 cm, number of turns: 3 turns), an electromagnetic field under the conditions of a current of 150 A and a frequency of 310 kHz was applied to the container for 60 seconds.

[0224] (3) Visually inspect whether the composition is cured.

[0225] (4) The relative degree of curing of the cured product formed by curing the composition with respect to the cured product was evaluated by residual enthalpy measured by differential scanning calorimetry (DSC).DSC3+ (Mettler-Toledo) was used as a DSC apparatus.

[0226] 5. Fill rate measurement

[0227] The filling rate in the curing properties of the curable compositions was evaluated in the following order.

[0228] (1) Prepare Figure 7 Specifically, rectangular slots each having a width of 5 mm and a length of about 20 mm are formed radially in the stator.

[0229] (2) Five windings (copper wires having a circular cross-section with a diameter of approximately 4.5 mm) are introduced into each slot of the stator.

[0230] (3) The curable composition is injected into the groove, and the curable composition is filled in the groove while the stator is appropriately tilted.

[0231] (4) Using a commercially available solenoid coil (winding diameter: 3 cm, number of turns: 3 turns), an electromagnetic field under the conditions of a current of 150 A and a frequency of 310 kHz was applied to the stator in which the slots were filled with the curable composition for 60 seconds.

[0232] (5) The stator was cut in a direction perpendicular to the longitudinal direction, and the portion of the cut surface where the cured product was present was inspected using a UV lamp. From this, the filling rate of the cured product was calculated.

[0233] 6. Bond Strength Measurement

[0234] The bonding strength was measured in the following order.

[0235] (1) The curable composition is cured in the same manner as described in the measurement of the filling rate.

[0236] (2) After connecting a Push & Pull Gauge device to a part of the winding, the winding is pulled using the device, and then the force when the winding breaks is measured.

[0237] 7. Measurement of compressive strength

[0238] The compressive strength is measured in the following manner.

[0239] (1) The curable composition was cured in the same manner as described in the measurement of the filling rate.

[0240] (2) After the stator on which the cured product was formed was compressed using a universal testing machine (UTM), its compressive strength was evaluated according to ASTM D 695 standard.

[0241] Example 1. Magnet

[0242] The magnet was manufactured according to the following steps.

[0243] (1) A raw material was prepared by mixing 0.17 mol of a magnetic particle precursor (iron (III) chloride hexahydrate), 160 mL of an aqueous solvent (distilled water), and 1.80 mol of a base (sodium acetate) with 1500 mL of an organic solvent (ethylene glycol).

[0244] (2) At 23°C, the raw material was heated at a temperature increase rate of about 0.8°C / min until the temperature reached 70°C.

[0245] (3) The result of step (2) is maintained at a temperature of about 70° C. for about 1 hour.

[0246] (4) Subsequently, at a temperature of 70°C, the raw material was heated at a temperature increase rate of about 2°C / min until the temperature reached 190°C.

[0247] (5) The result of step (4) is maintained at a temperature of about 190° C. for about 24 hours.

[0248] (6) The product obtained in step (5) was mixed with a surface treatment agent (polyacrylic acid having a weight average molecular weight of about 5,100, Sigma-Aldrich) in an amount of about 4.8 parts by weight relative to 100 parts by weight of the magnetic particle precursor.

[0249] (7) At 190°C, the resultant of step (6) was cooled at a temperature reduction rate of about 3°C / min until the temperature reached 70°C.

[0250] (8) The result of step (7) is maintained at a temperature of about 70° C. for about 2 hours.

[0251] (9) The resultant of step (8) was cooled at 70°C at a temperature reduction rate of about 1°C / min until the temperature reached about 23°C, and the raw material was appropriately filtered to obtain a magnet.

[0252] Examples 2 to 5. Magnet

[0253] A magnet was prepared in the same manner as in Example 1, except that the composition of the raw materials was adjusted as shown in Table 1 below.

[0254] [Table 1]

[0255]

[0256] Comparative Example 1. Magnet

[0257] The magnet was manufactured according to the following steps.

[0258] (1) A raw material was prepared by mixing 0.08 mol of a magnetic particle precursor (iron (III) chloride hexahydrate), 80 ml of an aqueous solvent (distilled water), 1.22 mol of a base (sodium acetate), and 3.5 g of a surface treatment agent (polyacrylic acid with a weight average molecular weight of approximately 5,100, Sigma Aldrich) with 1520 mL of an organic solvent (ethylene glycol).

[0259] (2) At 23°C, the raw material was heated at a temperature increase rate of about 0.8°C / min until the temperature reached 70°C.

[0260] (3) The result of step (2) is maintained at a temperature of about 70° C. for about 1 hour.

[0261] (4) Subsequently, at a temperature of 70°C, the raw material was heated at a temperature increase rate of about 2°C / min until the temperature reached 190°C.

[0262] (5) The result of step (4) is maintained at a temperature of about 190° C. for about 24 hours.

[0263] (6) At 190°C, the resultant of step (5) was cooled at a temperature reduction rate of about 3°C / min until the temperature reached 70°C.

[0264] (7) The result of step (6) is maintained at a temperature of about 70° C. for about 2 hours.

[0265] (8) The result of step (7) was cooled at 70°C at a temperature reduction rate of about 1°C / min until the temperature reached about 23°C, and the raw material was appropriately filtered to obtain a magnet.

[0266] Comparative Examples 2 to 6. Magnets

[0267] A magnet was prepared in the same manner as in Comparative Example 1, except that the composition of the raw materials was adjusted as shown in Table 2 below.

[0268] [Table 2]

[0269]

[0270] The input time and type of the surface treatment agent for the magnets of Examples 1 to 5 and Comparative Examples 1 to 6, and matters for evaluating the characteristics of each magnet are summarized in Tables 3 and 4 below.

[0271] [Table 3]

[0272]

[0273] [Table 4]

[0274]

[0275] The XRD analysis results of the magnets of Example 2 and Comparative Example 2 are shown in Figure 1 and Figure 2 In. According to Figure 1 and Figure 2 It was determined that both the magnets of Example 2 and Comparative Example 2 exhibited a peak with a half-width of 0.0721 radians at a 2θ value of approximately 62.57 degrees. The peak represents the (440) crystal plane of Fe₃O₄. Therefore, this means that the magnetic particles of both Example 2 and Comparative Example 2 contain Fe₃O₄. The size of the magnetic domains in the magnets, measured according to Equation 3 above, was approximately 28.2 nm in Example 2 and approximately 10.5 nm in Comparative Example 2.

[0276] exist Figure 3 and Figure 4 , and SEM images of the magnets of Examples 1 and 2 are shown in FIG. Figure 5 and Figure 6 The SEM images of the magnets of Comparative Examples 1 and 2 are shown in FIG. Figures 3 to 6 It can be seen that when the SEM photograph is examined, the magnetic particles in the magnet of the embodiment have a smoother surface compared to the magnet of the comparative example. It can be determined that the magnetic particles in the magnets of Examples 1 and 2 have a form in which crystals are clustered, each magnetic particle is surface-treated with a surface treatment agent, and each magnetic particle is a multi-domain type with an average particle size of 100 nm and 85 nm. However, in the magnetic particles of the magnets of Comparative Examples 1 and 2, the surface treatment agent is introduced into the surface of the crystals, so that it has a relatively small crystal size compared to the embodiment, and therefore it can be determined that it has a relatively rough surface. That is, it can be seen from the SEM photograph analysis that the magnetic particles in the magnet of the present application have the crystal size and average particle size proposed in the present application, and the magnetic particles are surface-treated with a surface treatment agent.

[0277] Furthermore, it can be seen from the results in Tables 3 and 4 that the magnets of the examples have excellent thermal characteristics (high SAR values).

[0278] Example 6. Curable composition

[0279] A curable composition was prepared by dispersing 5 parts by weight of the magnet of Example 1 in 95 parts by weight of a liquid epoxy resin (a mixture of Kukdo Chemical's KSR-177 product and AKEMA's EH4357 mixed in a weight ratio of 97:3).

[0280] Example 7. Curable composition

[0281] A curable composition was prepared in the same manner as in Example 6, except that the magnet of Example 2 was used instead of the magnet of Example 1.

[0282] Example 8. Curable composition

[0283] A curable composition was prepared in the same manner as in Example 6, except that the magnet of Example 3 was used instead of the magnet of Example 1.

[0284] Example 9. Curable composition

[0285] A curable composition was prepared in the same manner as in Example 6, except that the magnet of Example 4 was used instead of the magnet of Example 1.

[0286] Example 10. Curable composition

[0287] A curable composition was prepared in the same manner as in Example 6, except that the magnet of Example 5 was used instead of the magnet of Example 1.

[0288] Example 11. Curable composition

[0289] A curable composition was prepared by dispersing 5 parts by weight of the magnet of Example 2 in 95 parts by weight of an unsaturated polyesterimide resin (Voltatex 4200, Axalta).

[0290] Example 12. Curable composition

[0291] A curable composition was prepared in the same manner as in Example 11, except that the magnet of Example 4 was used instead of the magnet of Example 2.

[0292] Comparative Example 7. Curable composition

[0293] A curable composition was prepared by dispersing 5 parts by weight of the magnet of Comparative Example 1 in 95 parts by weight of a liquid epoxy resin (a mixture of Kukdo Chemical's KSR-177 product and AKEMA's EH4357 mixed at a weight ratio of 97:3).

[0294] Comparative Example 8. Curable composition

[0295] A curable composition was prepared in the same manner as in Comparative Example 7, except that the magnet of Comparative Example 2 was used instead of the magnet of Comparative Example 1.

[0296] Comparative Example 9. Curable composition

[0297] A curable composition was prepared in the same manner as in Comparative Example 7, except that the magnet of Comparative Example 3 was used instead of the magnet of Comparative Example 1.

[0298] Comparative Example 10. Curable composition

[0299] A curable composition was prepared in the same manner as in Comparative Example 7, except that the magnet of Comparative Example 4 was used instead of the magnet of Comparative Example 1.

[0300] Comparative Example 11. Curable composition

[0301] A curable composition was prepared in the same manner as in Comparative Example 7, except that the magnet of Comparative Example 5 was used instead of the magnet of Comparative Example 1.

[0302] Comparative Example 12. Curable composition

[0303] A curable composition was prepared in the same manner as in Comparative Example 7, except that the magnet of Comparative Example 6 was used instead of the magnet of Comparative Example 1.

[0304] Comparative Example 13. Cured Resin

[0305] A curable composition was prepared in the same manner as in Comparative Example 7, except that no magnet was applied, and cured in an oven to obtain a cured resin.

[0306] Comparative Example 14. Curable composition

[0307] A curable resin was prepared by dispersing 5 parts by weight of the magnet of Comparative Example 2 in 95 parts by weight of an unsaturated polyesterimide resin (Voltatex 4200, Axalta).

[0308] Comparative Example 15. Curable composition

[0309] A curable composition was prepared in the same manner as in Comparative Example 13, except that the magnet of Comparative Example 4 was used instead of the magnet of Comparative Example 2.

[0310] The compositions of the curable compositions of Examples 6 to 12 and Comparative Examples 7 to 15, and matters for evaluating their curing characteristics are summarized and described in the following Tables 5 and 6. In Tables 5 and 6, blank description means that they were not evaluated by the corresponding evaluation method due to insufficient curing.

[0311] [Table 5]

[0312]

[0313] [Table 6]

[0314]

Claims

1. A magnet comprising magnetic particles and a surface treatment agent introduced onto the surface of the magnetic particles, wherein The magnetic particles comprise crystals with a size ranging from 20 nm to 40 nm, The average particle size of the magnetic particles is in the range of 20 nm to 300 nm, The coefficient of variation of the particle size of the magnetic particles is in the range of 5% to 30%, and wherein a ratio B / A of an average particle size B of the magnetic particles to a crystal size A of the magnetic particles is in the range of 1.5 to 5.

2. The magnet according to claim 1, wherein The magnetic particles include a compound represented by the following Formula 1: [Formula 1] in, M is a metal or a metal oxide, X includes Fe, Mn, Co, Ni or Zn, and satisfies |a × c| = |b × d|, where c is the cationic charge of X, and d is the anionic charge of oxygen.

3. The magnet according to claim 1, wherein The surface treating agent has an acid value within a range of 10 mgKOH / g to 400 mgKOH / g, or an amine value within a range of greater than 0 mgKOH / g to 20 mgKOH / g or less.

4. The magnet according to claim 1, wherein The surface treatment agent has a weight average molecular weight of 20,000 or less.

5. The magnet according to claim 1, The surface treatment agent is included in an amount ranging from 0.01 parts by weight to 30 parts by weight relative to 100 parts by weight of the magnetic particles.

6. The magnet according to claim 1, The magnet is in powder form.

7. The magnet according to claim 1, Having a SAR value of 60 W / g or greater according to the following Equation 2: [Equation 2] in, SAR means the calorific value of a magnetic fluid in which the magnet is dissolved in water, Ci is the specific heat of water as a solvent for the magnetic fluid, and Ci is 4.184 J, g × K; m is the ratio mi / ma of the weight mi of the water as a solvent for the magnetic fluid to the weight ma of the magnet, where mi and ma are expressed in g; ΔT is the temperature increase of the magnetic fluid when an alternating magnetic field is applied to 0.35 mL of the magnetic fluid at a temperature of 294 K under the conditions of a current of 120.4 A and 310 kHz for 60 seconds, in K; and Δt is the time for which the alternating magnetic field under the above conditions is applied to the magnetic fluid, and Δt is 60 seconds.

8. A curable composition comprising the magnet according to claim 1 and a curable resin.

9. The curable composition according to claim 8, wherein The curable resin includes an alkenyl group, a (meth)acryloyl group, an epoxy group, an oxetane group, a hydrogen atom bonded to a silicon atom, an isocyanate group, a hydroxyl group, a phthalonitrile group, or a carboxyl group.

10. The curable composition according to claim 8, wherein The curable resin is a polysiloxane resin, a polyimide, a polyetherimide, a polyesterimide, an acrylic resin, a vinyl-based resin, an olefin resin, a polyurethane resin, an isocyanate resin, a polyester resin, a phthalonitrile resin, a polyamic acid, a polyamide, or an epoxy resin.

11. A method for producing a magnet according to any one of claims 1 to 7, comprising: a first step of heating a feedstock comprising a magnetic particle precursor and an organic solvent to produce crystallization; a second step of clustering the crystals produced in the first step; as well as The third step is to mix the raw material having passed the second step with a surface treatment agent.

12. The method for producing a magnet according to claim 11, wherein The content of the magnetic particle precursor in the raw material is in the range of 0.025 M to 0.125 M.

13. The method for producing a magnet according to claim 12, wherein The raw materials also include a base, and The content of the base in the raw material is in the range of 0.4 M to 2.0 M.

14. The method for producing a magnet according to claim 11, wherein The raw materials also include an aqueous solvent, and The content of the aqueous solvent in the raw material is in a range of 1 volume % to 30 volume % relative to the organic solvent.

15. The method for producing a magnet according to claim 11, wherein The first step is performed at a temperature ranging from 50°C to 90°C.

16. The method for producing a magnet according to claim 15, wherein The first step includes: (1-a) a process of increasing the temperature of the raw material to a temperature within a range of 50° C. to 90° C.; and (1-b) maintaining the temperature of the heated raw material for a period of time ranging from 30 minutes to 120 minutes.

17. The method for producing a magnet according to claim 16, wherein The process (1-a) is performed at a temperature increase rate within a range of 0.5°C / min to 2°C / min.

18. The method for producing a magnet according to claim 11, wherein The second step is performed at a temperature in the range of 170°C to 210°C.

19. The method for producing a magnet according to claim 18, wherein The second step includes (2-a) a process of increasing the temperature of the raw material having passed the first step to a temperature within a range of 170° C. to 210° C. and (2-b) a process of maintaining the temperature of the increased raw material for a period of time within a range of 12 hours to 80 hours.

20. The method for producing a magnet according to claim 19, wherein The process (2-a) is performed at a temperature increase rate within a range of 1.5°C / min to 5°C / min.

21. The method for producing a magnet according to claim 11, wherein the third step is performed at a temperature within a range of 50°C to 90°C.

22. The method for producing a magnet according to claim 21, wherein The third step includes: (3-a) a process of mixing the raw material having passed the second step with the surface treatment agent, (3-b) a process of cooling the raw material mixed with the surface treatment agent to a temperature in the range of 50° C. to 90° C., and (3-c) a process of maintaining the cooled raw material for a period of time in the range of 30 minutes to 120 minutes.

23. The method for producing a magnet according to claim 22, wherein The process (3-a) is performed at a temperature decreasing rate within a range of 1.5°C / min to 5°C / min.

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