CORE-SHELL PARTICLES COMPRISING CORE AGGREGATED CORE IN WHICH FLUORINE-BASED RESIN PARTICLES are AGGREGATED AND SHELL LAYER

Abstract

The present disclosure relates to a novel core-shell particle in which an aggregate-type core formed by aggregation of fluorine-based resin particles and a shell layer formed by close aggregation of acrylic resin particles are formed, and a method for producing the same, the core-shell particles not only have significantly good flowability and excellent storage stability, but also have better binder properties than individual polytetrafluoroethylene particles.

Description

Technical Field

[0001] This disclosure relates to aggregated core-shell particles, comprising an aggregated core in which fluorine-based resin particles are aggregated and a shell formed of acrylic resin particles on the surface of the aggregated core, the aggregated core-shell particles having excellent flowability, excellent storage resistance (storage characteristics) and excellent fibrillation. Background Technology

[0002] Fluorine-based resins can be used in a variety of applications due to their electrical, thermal, and binding properties, such as various adhesives, processing aids, and flow agents. For example, fluorine-based resins can be used as various materials for electrode binders, anti-drip agents, powder coating materials, fiber coating materials, or automotive parts.

[0003] However, fluorine-based resins have the problem of poor flowability during processes such as transportation, storage, processing, or stirring. When fluorine-based resins in resin (granular or powder) form undergo such processes, the low flowability problem of fluorine-based resins usually manifests as premature agglomeration of the resins during processes such as transportation, processing, storage, or stirring.

[0004] To address the low flowability issue of fluorine-based resins while simultaneously achieving higher performance, studies have been conducted to modify the surface of fluorine-based resins or to form a shell on the surface of fluorine-based resins using resins with different surface properties.

[0005] However, Patent Document 1 (Japanese Patent Publication No. JP 2019-112620 A) discloses core-shell particles having a core containing a perfluoropolymer and a shell containing a non-fluorine-based resin, but the technology still has limitations, namely that the fluorine-based resin still has insufficient binder properties and insufficient flowability.

[0006] In addition to the problems mentioned above, the core-shell particles in which the shell is formed by a non-fluorine-based resin on conventional fluorine-based particles also have low storage tolerance, to the point that they are impractical for commercial use, because the particles agglomerate together to form lumps when high loads are applied during storage.

[0007] Therefore, there is a need for core-shell particles containing fluorine-based resins that exhibit significantly superior flowability, excellent storage resistance (storage properties), and simultaneously excellent binder properties. Summary of the Invention

[0008] Technical issues

[0009] One aspect of this disclosure is to provide novel core-shell particles that address the problems of low flowability, low binder properties, and low storage stability of conventional single fluorine-based resin particles and single-type core-shell particles coated with a shell formed by polymerization on the surface of single fluorine-based resin particles. The novel core-shell particles comprise an aggregated core in which fluorine-based resin particles are aggregated and acrylic resin particles aggregated and formed on the surface of the aggregated core.

[0010] Another aspect of this disclosure is to provide a method for producing core-shell particles, each core-shell particle comprising an aggregated core in which fluorine-based resin particles are aggregated together, and an outer shell layer on the surface of the aggregated core formed by the aggregation of acrylic resin particles.

[0011] Another aspect of this disclosure is to provide core-shell particles and a method for producing the same, wherein fluorine-based resin particles can readily aggregate, maintain the form of an aggregated core of aggregated fluorine-based resin particles, and can form a shell.

[0012] Technical solution

[0013] In one general aspect, the core-shell particles comprise: an aggregated core formed by the aggregation of fluorine-based resin particles to each other; and a shell formed by the aggregation of acrylic resin particles to each other on the surface of the aggregated core, wherein the average particle size (D50) of the core-shell particles is from 500 μm to 3,000 μm.

[0014] In one embodiment of this disclosure, the fluorine-based resin particles may comprise a fluorine-based polymer formed by polymerizing one or more fluorinated monomers selected from vinylidene fluoride, vinyl fluoride, trifluorochloroethylene, tetrafluoroethylene, perfluoroalkyl vinyl ethers, and hexafluoropropylene.

[0015] In one embodiment of this disclosure, the fluorine-based polymer can be formed by polymerizing one or more of tetrafluoroethylene, perfluoroalkyl vinyl ether and hexafluoropropylene.

[0016] Acrylic resin particles may contain one or more of the following: methyl methacrylate homopolymers; and acrylic copolymers of methyl methacrylate and one or more comonomers, wherein the one or more comonomers are selected from ethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, and styrene-based monomers.

[0017] In one embodiment of this disclosure, the acrylic resin particles may comprise an acrylic copolymer.

[0018] In one embodiment of this disclosure, based on 100% by weight of total polymeric units, the acrylic copolymer may have 70% by weight to 99.9% by weight of methyl methacrylate polymeric units.

[0019] In one embodiment of this disclosure, the aggregate nucleus may be in the form of an aggregate in which fluorine-based resin particles with an average particle size (D50) of 0.01 μm to 100 μm are tightly aggregated together, and the average particle size of the aggregate nucleus may be from 200 μm to 2,500 μm.

[0020] In one embodiment of this disclosure, the average particle size (D50) of the fluorine-based resin particles can be from 0.1 μm to 50 μm.

[0021] In one embodiment of this disclosure, the thickness of the shell can be from 50 μm to 500 μm.

[0022] In one embodiment of this disclosure, the average particle size (D50) of the acrylic resin particles can be from 0.01 μm to 100 μm.

[0023] In one embodiment of this disclosure, the average particle size (D50) of the acrylic resin particles can be from 0.1 μm to 50 μm.

[0024] In one embodiment of this disclosure, the core-shell particles may include a shell layer in an amount ranging from 1% to 50% by weight, based on the total weight of the core-shell particles.

[0025] In one embodiment of this disclosure, the aggregate nucleus may be covered with a shell covering 90% or more of its entire surface area.

[0026] In one embodiment of this disclosure, the aggregate nucleus may be covered with a shell over 100% of its entire surface area, except for the voids between acrylic resin particles.

[0027] In one embodiment of this disclosure, the core-shell particles may contain one or more coagulants selected from acetate, sulfate, and nitrate.

[0028] In one embodiment of this disclosure, if measured 100 times at 0.3 rpm using a dynamic powder flow analyzer manufactured by Mercury Scientific Inc., the core-shell particles may have a shear force (cohesive thickness) between the static core-shell particles and the flowing core-shell particles of 50 mJ / kg or less.

[0029] In one embodiment of this disclosure, if measured 100 times at 0.3 rpm using a dynamic powder flow analyzer manufactured by Mercury Scientific Inc., the core-shell particles may have a cohesive breakage energy (breakage energy) of 100 mJ / kg or less required for static core-shell particle formation collapse.

[0030] In one embodiment of this disclosure, as measured using a powder rheometer manufactured by Freeman Technology Ltd., core-shell particles may have a total flow energy (basic flowability energy, BFE) of 1,000 mJ or less and a cohesive energy (specific energy, SE) of 10 mJ / kg or less.

[0031] In another general aspect, the mixture contains the aforementioned core-shell particles.

[0032] In one embodiment of this disclosure, the mixture may contain an electrode active material.

[0033] In one embodiment of this disclosure, the mixture may contain core-shell particles in an amount ranging from 0.1% to 20% by weight, based on the total weight of the mixture.

[0034] In one embodiment of this disclosure, 95% by weight or more of the mixture may be retained on a 6.3 mm sieve.

[0035] In yet another general aspect, a method for producing core-shell particles includes: forming an aggregate core in which fluorine-based resin particles are aggregated by adding a first dispersion solution in which fluorine-based resin particles are dispersed to an aqueous solution containing an organic solvent and a coagulant; and forming a shell by adding a second dispersion solution in which acrylic resin particles are dispersed to the aqueous solution in which the aggregate core is formed, causing the acrylic resin particles to aggregate on the surface of the aggregate core, wherein the average particle size (D50) of the aggregate core is from 200 μm to 2,500 μm.

[0036] In one embodiment of this disclosure, the organic solvent may be a C1-C7 aliphatic alcohol, a C1-C4 alkyl acetate, or a mixture thereof.

[0037] In one embodiment of this disclosure, the aqueous solution may comprise deionized water and an organic solvent mixed in a weight ratio of 1:0.1 to 9.

[0038] In one embodiment of the invention, the coagulant may be selected from one or more of acetate, sulfate and nitrate.

[0039] In one embodiment of this disclosure, the coagulant may be contained in an aqueous solution at a concentration of 0.1% to 5% by weight.

[0040] In one embodiment of this disclosure, when forming aggregate cores, a first dispersion solution may be added in an amount of 10 to 60 parts by weight based on 100 parts by weight of an aqueous solution.

[0041] In one embodiment of this disclosure, the stirring speed can be from 100 rpm to 1,000 rpm when forming aggregate cores.

[0042] In one embodiment of this disclosure, fluorine-based resin particles can aggregate at temperatures ranging from 40°C to 90°C when forming aggregate nuclei.

[0043] In one embodiment of this disclosure, the solid content of the first dispersion solution can be from 30% to 80% by weight, based on the total weight of the first dispersion solution.

[0044] In one embodiment of this disclosure, fluorine-based resin particles can aggregate at 50°C to 90°C when forming aggregate nuclei.

[0045] In one embodiment of this disclosure, the solid content of the second dispersion solution can be from 10% by weight to 50% by weight, based on the total weight of the second dispersion solution.

[0046] In one embodiment of this disclosure, in a method for producing core-shell particles, a first dispersion solution and a second dispersion solution may be added at a weight ratio of 1:0.1 to 1.5.

[0047] Beneficial effects

[0048] In one embodiment of this disclosure, when measured between core-shell particles using the measurement methods defined herein, the core-shell particles may have a flowability shear force (cohesive thickness) of 50 mJ / kg or less, 30 mJ / kg or less, and preferably 25 mJ / kg or less, and may have a cohesive breaking energy (breaking energy) of 100 mJ / kg or less, 70 mJ / kg or less, preferably 65 mJ / kg or less, and more preferably 50 mJ / kg or less. Therefore, the core-shell particles can exhibit significantly superior flowability and will not agglomerate during processes such as transportation, processing, storage, or stirring.

[0049] In one embodiment of this disclosure, in a storage stability assessment measured by the measurement methods defined in this disclosure, there is no agglomeration caused by the aggregation of core-shell particles, and therefore the core-shell particles can be used even after long-term storage.

[0050] In one embodiment of the invention, since the core-shell particles have the significantly superior binder properties and fibrillation as defined in the invention, mixtures containing them as binders can be provided. In particular, the core-shell particles can be used as binders for electrode active materials.

[0051] In one embodiment of this disclosure, a method for producing core-shell particles may include: forming an aggregated core composed of fluorine-based resin particles aggregated together, and forming an acrylic shell comprising acrylic resin particles. This method not only provides easy processability, productivity, and economic feasibility, but also produces core-shell particles with excellent flowability and low agglomeration, excellent storage stability, and excellent binder properties.

[0052] In one embodiment of this disclosure, in a method for producing core-shell particles, an aggregate-type nucleus, which is a core in the form of fluorine-based resin particles aggregated together, can form an aggregate of fluorine-based resin particles aggregated together, and the average particle size of the aggregate-type nucleus and the core-shell particles comprising it can be easily adjusted even through a simple process.

[0053] Therefore, since the entire surface of the aggregated core particles is covered by the shell particles with a uniform thickness, the core-shell particles can have excellent flowability and excellent storage stability, and can maintain the excellent binder properties of fluorine-based resin particles, thus allowing users to control the point at which the fluorine-based resins become fibrillated as expected.

[0054] Therefore, core-shell particles can be used as anti-drip agents, powder coating materials, fiber coating materials, automotive parts, or electrode binders. Attached Figure Description

[0055] Figure 1 The aggregated core-shell particles of Example 1 are shown.

[0056] Figure 2 A single core-shell particle of Comparative Example 1 is shown.

[0057] Figure 3 This is an image of the aggregate nucleus of Example 1, taken using an optical microscope.

[0058] Figure 4 The image shows the aggregate nucleus of Example 1, taken using a scanning electron microscope.

[0059] Figure 5 Images of the core-shell particles of Example 1, taken by scanning electron microscopy (SEM).

[0060] Figure 6 The image is a scanning electron microscope image taken after cutting the core-shell particles of Example 1, used to determine the formation of the nuclear aggregate portion and shell layer of the core-shell particles.

[0061] Figure 7 Images of the core-shell particles of Example 1 before and after cutting, taken by energy-dispersive X-ray spectroscopy (SEM-EDX).

[0062] Figure 8 Images of the particles remaining on the sieve after the storage stability assessment are shown: Figure 8 (a) is an image of aggregate-type core-shell particles from Example 1; Figure 8 (b) is an image of a single core-shell particle from Comparative Example 1; and Figure 8 (c) is an image of a single PTFE particle from Comparative Example 2.

[0063] Figure 9 Image of a kneaded mixture containing aggregated core-shell particles of Example 1 after sieving, taken by scanning electron microscopy (SEM).

[0064] Figure 10 Image of a kneaded mixture containing individual core-shell particles of Comparative Example 1 after sieving, taken by scanning electron microscopy (SEM). Detailed Implementation

[0065] In the following text, core-shell particles and methods for their production will be described. In this context, unless otherwise specified, all technical and scientific terms used herein have their general meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and descriptions of known functions and configurations that unnecessarily obscure the spirit of this disclosure will be omitted in the following description.

[0066] Furthermore, unless the context clearly indicates otherwise, the singular form used in this disclosure may be intended to include the plural form.

[0067] Furthermore, unless otherwise stated in this disclosure, the units used herein are based on weight; for example, unless otherwise specified, % or ratios are expressed as weight%, and temperatures are expressed as °C.

[0068] Furthermore, the numerical ranges used in this disclosure include upper and lower limits and all values ​​within those ranges, increments derived from the form and span logic of the defined ranges, all values ​​with double constraints, and all possible combinations of upper and lower limits within numerical ranges defined in different forms.

[0069] Unless otherwise expressly defined in this specification, values ​​outside the range that may occur due to experimental error or rounding are also included in the defined range.

[0070] The term “comprising” as used in this disclosure is an open-ended description and has the same meaning as terms such as “including,” “containing,” “having,” or “characterized in,” and does not exclude elements, materials, or processes not further listed.

[0071] In this disclosure, the term "(meth)acrylate" may mean "acrylate" or "methacrylate".

[0072] The core-shell particles according to this disclosure will be described below.

[0073] In one aspect of this disclosure, the core-shell particles may include an aggregated core formed by the aggregation of fluorine-based resin particles and a shell formed by the aggregation of acrylic resin particles on the surface of the aggregated core.

[0074] Compared to conventional fluorine-based resins (powders or granules) and conventional fluorine-based resin granules coated with resins other than fluorine resins, core-shell particles with this structure can unexpectedly exhibit significantly superior flowability and excellent binder properties.

[0075] In one embodiment of this disclosure, such as Figure 1 As shown, the core-shell particle 100 may include an aggregate core 10 formed by the aggregation of fluorine-based resin particles 11 to each other and a shell 20 formed by the close aggregation of acrylic resin particles 21 to each other on the surface of the aggregate core 10.

[0076] Compared to conventional fluorine-based resins (powders or granules) and conventional fluorine-based resin granules coated with different resins, core-shell particles with this structure can unexpectedly exhibit significantly superior flowability and excellent binder properties.

[0077] In one embodiment of this disclosure, such as Figure 1 As shown, the core-shell particle 100 may include an aggregate core 10 formed by the aggregation of fluorine-based resin particles 11 to each other and a shell 20 formed by the close aggregation of acrylic resin particles 21 to each other on the surface of the aggregate core 10.

[0078] In one implementation scheme, such as Figure 2 As shown, the conventional single-core-shell particle 200 described above can have a structure in which a polymeric shell 40 formed by polymerizing monomers is formed on the surface of a single fluorine-based resin particle 30.

[0079] Compared to monolithic core-shell particles 200 in which a polymeric shell 40 is formed on a single fluorine-based resin particle 30, core-shell particles 100 can exhibit significantly improved flowability and excellent storage resistance, while also possessing superior binder properties. Therefore, core-shell particles 100 are preferred because they offer excellent processability.

[0080] In one embodiment of this disclosure, the fluorine-based resin particles may be in the form of particles containing a fluorine-based resin. The fluorine-based resin is not particularly limited, as long as it is fibrillable, and may include, for example, fluorine-based polymers formed by polymerizing one or more fluorine-based monomers selected from vinylidene fluoride, vinyl fluoride, trifluorochloroethylene, tetrafluoroethylene, perfluoroalkyl vinyl ethers, and hexafluoropropylene.

[0081] In another embodiment of this disclosure, the fluorine-based monomer may be one or more perfluorinated monomers selected from tetrafluoroethylene, perfluoroalkyl vinyl ethers and hexafluoropropylene.

[0082] Fluorine-based polymers can possess high heat resistance, excellent fibrillation properties, and excellent adhesive properties, and therefore can be used as anti-drip agents, powder coating materials, fiber coating materials, automotive parts, or electrode adhesives. Fluorine-based polymers formed by polymerizing the above-mentioned perfluorinated monomers can have further improved heat resistance, further improved adhesive properties, and excellent fibrillation properties, and therefore can be used particularly as electrode adhesives; however, this disclosure is not limited thereto.

[0083] In one embodiment of this disclosure, the fluorine-based polymer is not particularly limited, as long as it does not impair the physical properties of the core-shell particles to be produced; however, as a non-limiting example, the fluorine-based polymer can be obtained by further polymerizing the fluorine-based monomer with one or more α-olefin-based monomers without fluorine substituents, said one or more α-olefin-based monomers without fluorine substituents selected from ethylene, propylene, n-butene and methyl methacrylate.

[0084] As a fluorine-based polymer, from the viewpoint of obtaining further improved binder properties of the produced core-shell particles, it is preferable to use homopolymers of the aforementioned fluorine-based monomers; however, the aforementioned α-olefin-based monomers may also be further included in the fluorine-based polymer.

[0085] For example, when the fluorine-based polymer is a copolymer that also contains α-olefin-based monomers, the amount of polymeric units derived from fluorine-based monomers may be 70% by weight or more based on 100% by weight of total polymeric units; and in another embodiment, this amount may be 80% by weight or more, or 90% by weight or more. While there is no upper limit, this amount may be less than 100% by weight or 99% by weight or less. Core-shell particles containing fluorine-based resins that satisfy the above range of polymeric units may have even more significantly superior heat resistance and binder properties, and are therefore preferred. More preferably, the fluorine-based polymer may be polytetrafluoroethylene (PTFE), and PTFE satisfies the above range of polymeric units and is formed by polymerizing perfluorinated monomers, and is therefore the preferred embodiment; however, this disclosure is not limited thereto.

[0086] In one embodiment of this disclosure, the fluorine-based resin particles may contain one or more of a plasticizer, emulsifier, heat stabilizer and lubricant, as long as it does not impair the physical properties of the core-shell particles to be produced.

[0087] Depending on the material used in anti-drip agents, powder coating materials, fiber coating materials, automotive parts, or electrode binders, fluorine-based resin particles may also contain the above additives to provide optimal physical properties for each material.

[0088] In one embodiment of this disclosure, the average particle size (D50) of the fluorine-based resin particles can be 0.01 μm or greater, 0.05 μm or greater, 0.10 μm or greater, 0.15 μm or greater, or 0.20 μm or greater, and 90.00 μm or less, 80.00 μm or less, 70.00 μm or less, 60.00 μm or less, 50.00 μm or less, 40.00 μm or less, 30.00 μm or less, 20.00 μm or less, 15.00 μm or less, 10.00 μm or less, 8.00 μm or less, 7.00 μm or less, 6.00 μm or less, or 5.00 μm or less. For example, the average particle size (D50) can be 0.01 μm to 100.00 μm, 0.01 μm to 50.00 μm, 0.01 μm to 30.00 μm, 0.01 μm to 20.00 μm, 0.01 μm to 10.00 μm, 0.01 μm to 5 μm, 0.05 μm to 5 μm, or 0.1 μm to 5 μm.

[0089] Fluorine-based resin particles that meet the above average particle size range can aggregate well to form aggregated cores. Therefore, the core-shell particles containing them can have significantly better flowability, better storage stability and better binder properties, and are therefore preferred; however, this disclosure is not limited thereto, as long as the fluorine-based resin particles can aggregate to form aggregated cores without impairing the physical properties of the core-shell particles containing them.

[0090] In another embodiment of this disclosure, from the viewpoint that the core-shell particles containing fluorine-based resin particles have further improved flowability, excellent processing characteristics and excellent binder properties, the average particle size (D50) of the fluorine-based resin particles may preferably be 0.1 μm to 1 μm or 0.1 μm to 0.5 μm; however, the average particle size (D50) is not limited thereto.

[0091] In one embodiment of this disclosure, the aggregate nucleus may be in the form of an aggregate in which fluorine-based resin particles with an average particle size in the above range are tightly aggregated together, and the average particle size (D50) of the aggregate nucleus may be from 200 μm to 2,000 μm.

[0092] In another embodiment of this disclosure, the average particle size (D50) of the aggregate nuclei can be 200 μm or greater, 300 μm or greater, 400 μm or greater, 500 μm or greater, 600 μm or greater, or 700 μm or greater, and 1,800 μm or less, 1,500 μm or less, 1,300 μm or less, 1,200 μm or less, or 1,000 μm or less. For example, the average particle size (D50) can be from 200 μm to 1,800 μm, 200 μm to 1,500 μm, 200 μm to 1,000 μm, 500 μm to 1,000 μm, or 700 μm to 1,000 μm.

[0093] Aggregate nuclei with an average particle size in the above range are covered by a shell covering 90% or more of their entire surface area, and the core-shell particles comprising them not only exhibit significantly superior flowability and storage resistance, but also excellent binder properties, and therefore can be used as, for example, electrode binders and powder coating materials. Preferably, the shell is formed by covering the entire surface of the aggregate nucleus.

[0094] Since the shell is formed by the aggregation of acrylic resin particles with physical properties that are completely different from those of fluorine-based resin particles, core-shell particles can have significantly better flowability and excellent binder properties.

[0095] In one embodiment of this disclosure, the acrylic resin particles may comprise one, two, or more of a homopolymer of methyl methacrylate and an acrylic copolymer, said acrylic copolymer being formed by copolymerizing methyl methacrylate with one, two, or more of a comonomer selected from ethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, and α-styrene.

[0096] In another embodiment of this disclosure, the acrylic resin particles may comprise an acrylic copolymer.

[0097] There are no particular limitations on acrylic resin particles, as long as they do not impair the physical properties of the shell and core-shell particles formed therefrom. However, acrylic copolymers formed by polymerizing methyl methacrylate with the above comonomers can more easily form a shell, and the resulting core-shell particles can exhibit significantly superior flowability and excellent storage resistance (storage properties); therefore, such acrylic copolymers are preferred.

[0098] In one embodiment of this disclosure, the acrylic copolymer contained in the acrylic resin particles may be an acrylic copolymer formed by copolymerizing methyl methacrylate with a comonomer selected from n-butyl methacrylate, tert-butyl methacrylate and isobutyl methacrylate.

[0099] In another embodiment, the acrylic copolymer may preferably be a methyl methacrylate-n-butyl acrylate copolymer, but is not limited thereto.

[0100] In one embodiment of this disclosure, based on 100% by weight of total polymer units, the acrylic copolymer may have an amount of 70% by weight to 99.9% by weight of methyl methacrylate polymer units; and in another embodiment, the amount may be 80% by weight to 99.9% by weight, 80% by weight to 95% by weight, 80% by weight to 90% by weight, or 80% by weight to 85% by weight.

[0101] Acrylic copolymers that meet the above range of polymerization units can be preferably used to form the shell of core-shell particles, because the core-shell particles containing them can have excellent storage resistance and flowability.

[0102] In one embodiment of this disclosure, the acrylic resin particles may contain one or more additives selected from plasticizers, emulsifiers, heat stabilizers and lubricants, provided that the additives do not impair the physical properties of the core-shell particles to be produced.

[0103] Depending on the material in which the produced core-shell particles are used, such as anti-drip agents, powder coating materials, fiber coating materials, automotive parts, or electrode binders, acrylic resin particles may also contain the above additives to provide optimal physical properties for each material.

[0104] In one embodiment of this disclosure, the average particle size (D50) of the acrylic resin particles can be 0.01 μm or greater, 0.05 μm or greater, or 0.10 μm or greater, and 100.00 μm or less, 80.00 μm or less, 70.00 μm or less, 60.00 μm or less, 50.00 μm or less, 30.00 μm or less, 20.00 μm or less, 10.00 μm or less, 7.00 μm or less, or 5.0 μm or less. For example, the average particle size (D50) can be 0.01 μm to 100.00 μm, 0.05 μm to 100.00 μm, 0.1 μm to 100.00 μm, 0.1 μm to 50 μm, 0.1 μm to 20 μm, 0.1 μm to 10.00 μm, or 0.1 μm to 5.00 μm.

[0105] Acrylic resin particles with an average particle size within the above range can aggregate on the surface of the aggregate core to more easily form a shell, thus the produced core-shell particles can have significantly improved flowability; therefore, such acrylic resin particles are preferred.

[0106] In another embodiment of this disclosure, the average particle size of the acrylic resin particles may be 0.1 μm to 1 μm or 0.5 μm to 1 μm, but is not limited thereto, from the perspective of making it easier to form a shell on the surface of the core aggregate.

[0107] In one embodiment of this disclosure, the core-shell particles may contain one or more coagulants selected from acetate, sulfate, and nitrate.

[0108] In the production method described below, the coagulant used for the core-shell particles can aggregate fluorine-based resin particles to form an aggregated core, and can aggregate acrylic resin particles on the surface of the formed aggregated core to form a shell.

[0109] Furthermore, the core-shell particles may contain residual coagulant from the production methods described below, thereby allowing fluorine-based resin particles and acrylic resin particles to remain in aggregated form, and such core-shell particles may be preferred; however, this disclosure is not limited thereto.

[0110] The coagulant is described in more detail in the following method for producing core-shell particles, therefore its detailed description is omitted.

[0111] In one embodiment of this disclosure, the thickness of the shell layer of the core-shell particle can be 50 μm to 500 μm, 300 μm or less, 200 μm or less, 150 μm or less, or 100 μm or less; and can be, for example, 50 μm to 200 μm, 50 μm to 150 μm, or 50 μm to 100 μm, or a value in the intermediate range between the upper and lower limits above.

[0112] Surprisingly, core-shell particles having a shell layer that meets the above thickness range can maintain the excellent binder properties of fluorine-based resin particles and can have even more significantly improved flowability and excellent storage resistance, and are therefore preferred; however, this disclosure is not limited thereto, as long as the desired physical properties in this invention are met.

[0113] The thickness of the shell layer of core-shell particles was measured using the measurement method defined in this invention. Specifically, the thickness was measured at five locations using a scanning electron microscope (SEM) at a magnification of 50×, and the average value was calculated.

[0114] In one embodiment of the invention, the average particle size (D50) of the core-shell particles can be 500 μm or greater, 520 μm or greater, 600 μm or greater, 620 μm or greater, 700 μm or greater, 830 μm or greater, 900 μm or greater, 930 μm or greater, 950 μm or greater, 960 μm or greater, 974 μm or greater, 984 μm or greater, 1,000 μm or greater, 1,020 μm or greater, 1,040 μm or greater, 1,051 μm or greater, 1,100 μm or greater, 1,103 μm or greater, or 1,166 μm or greater, and 3,000 μm or less, 2,500 μm or less, 2,000 μm or less, 1,800 μm or less, 1,750 μm or less, 1,600 μm or less. The particle size can be 500 μm or smaller, or 1,500 μm or smaller. For example, the average particle size (D50) can be 500 μm to 3,000 μm, 500 μm to 2,000 μm, 500 μm to 1,500 μm, or 1,000 μm to 1,500 μm. The average particle size (D50) of the core-shell particles can be adjusted by regulating the average particle size of the aggregated core and the thickness of the shell, and can be easily adjusted according to the stirring speed in the production method described below.

[0115] Core-shell particles meeting the above average particle size range can be incorporated into powder coating materials or electrode binders with high dispersibility and can possess the excellent flowability and excellent binder properties described above, thus making them preferred. However, since the average particle size can be adjusted by the user according to the intended use of the core-shell particles, the average particle size of the core-shell particles is not limited to the above range.

[0116] In one embodiment of this disclosure, when measured by the above-described average particle size measurement method, the average particle size span value of the core-shell particles can be 1.50 or less, 1.45 or less, 1.43 or less, 1.40 or less, 1.38 or less, 1.35 or less, 1.33 or less, 1.31 or less, 1.30 or less, 1.27 or less, 1.26 or less, 1.25 or less, 1.24 or less, 1.23 or less, or 1.20 or less, and 1.05 or more, 1.10 or more, or 1.15 or more. For example, the span values ​​can be 1.05 to 1.50, 1.05 to 1.45, 1.05 to 1.40, 1.05 to 1.38, 1.05 to 1.33, 1.05 to 1.30, 1.05 to 1.27, 1.05 to 1.26, 1.05 to 1.23, or 1.05 to 1.20.

[0117] Even with an average particle size of 500 μm or larger as described above, core-shell particles can have an average particle size distribution with a span value of 1.5 or smaller. Therefore, since core-shell particles can have a highly uniform average particle size, they can be used as materials for adhesives, powder coating materials, fiber coating materials, or automotive parts.

[0118] In one embodiment of the invention, the core-shell particles may contain a shell layer in an amount of 1% to 50% by weight, based on the total mass of the core-shell particles, and the amount of the shell layer is preferably 1% to 30% by weight, and more preferably 10% to 30% by weight, from the viewpoint of achieving excellent flowability and binder properties.

[0119] Core-shell particles containing a shell in the above range can simultaneously satisfy significantly superior flowability and excellent binder properties, and therefore can be used particularly as electrode binders; however, this disclosure is not limited thereto, as long as the desired physical properties of the present invention are met.

[0120] In one embodiment of this disclosure, the aggregate nucleus may be covered with a shell covering 90% or more, preferably 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, or 98% or more of its entire surface area.

[0121] Since the shell can form well on aggregated nuclei, core-shell particles can have excellent flowability, excellent handleability and excellent storage stability, and are therefore preferred.

[0122] In one embodiment of this disclosure, the aggregate nucleus may be covered with a shell over 100% of its entire surface area, except for the voids between acrylic resin particles.

[0123] Core-shell particles can have a clearly defined structure of aggregated core and shell, such as Figure 7 As shown in the image obtained by energy-dispersive X-ray spectroscopy (SEM EDX), the aggregated core is formed from fluorine-based resin particles, and the shell is formed from acrylic resin particles. Furthermore, because the shell is formed on 100% of the surface of the aggregated core, the core-shell particles exhibit significantly superior flowability and storage stability, along with excellent binder properties.

[0124] The method for producing core-shell particles will be described below.

[0125] In one aspect of this disclosure, core-shell particles can be produced by: forming an aggregate core in which the fluorine-based resin particles are aggregated by adding a first dispersion solution in which fluorine-based resin particles are dispersed to an aqueous solution containing an organic solvent and a coagulant; and forming a shell by adding a second dispersion solution in which acrylic resin particles are dispersed to an aqueous solution in which the aggregate core is formed, causing the acrylic resin particles to aggregate on the surface of the aggregate core.

[0126] The method for producing core-shell particles is not a conventional method of coating individual fluorine-based resin particles with acrylic resin or modifying the surface of individual fluorine-based resin particles. That is, this disclosure provides core-shell particles comprising an aggregated core formed by the aggregation of fluorine-based resin particles and a shell formed by the aggregation of acrylic resin particles on the surface of the aggregated core.

[0127] Unlike conventional monomorphic core-shell particles that contain only fluorine-based resin particles, these core-shell particles can exhibit significantly superior flowability and storage stability, while also possessing excellent binder properties, thus making them suitable for use as anti-drip agents, powder coating materials, fiber coating materials, automotive parts, and electrode binders.

[0128] Furthermore, in the method for producing core-shell particles, fluorine-based resin particles aggregate to form an aggregated core, and then acrylic resin particles aggregate on the surface of the core aggregate to form a shell, thus obtaining the following unexpected properties.

[0129] That is, as described above, each core-shell particle has an aggregated core in which fluorine-based resin particles are aggregated and a shell coated with acrylic resin particles. Therefore, the core-shell particles do not agglomerate with each other and have significantly improved flowability. They also have excellent storage stability because the core-shell structure is well maintained during multi-layer stacking packaging due to the shells aggregated on the surface.

[0130] Furthermore, when forming an aggregate-type fluorine-based resin core and an acrylic resin particle shell, it is possible to produce core-shell particles that do not essentially have individual fluorine-based resin particles (primary particles, i.e., non-aggregated particles) or individual acrylic particles. This method can have the advantages of high cost-effectiveness and high productivity because the method for separating solids is simple.

[0131] In the formation of aggregate nuclei, an aqueous solution containing an organic solvent can be used, thus maintaining polarity, allowing for the formation of uniform aggregates, and preventing residual non-aggregated fluorine-based resin particles.

[0132] Furthermore, in the core-shell particles formed in an aqueous solution containing an organic solvent, the fluorine-based resin particles substantially aggregate to form an aggregated core, and a shell layer formed by the aggregation of only acrylic resin particles is formed on the surface of the aggregated core, making it possible to produce core-shell particles with a clear distinction between the core and shell portions.

[0133] In one embodiment of this disclosure, the organic solvent may be a C1-C7 aliphatic alcohol, a C1-C4 alkyl acetate, or a mixture thereof, preferably a C1-C7 aliphatic alcohol, and more preferably methanol, ethanol, or butanol.

[0134] The aforementioned aliphatic alcohols can have excellent miscibility with water and can more easily maintain the polarity of the aqueous solution when forming aggregate nuclei through the aggregation of fluorine-based resin particles and when forming shells through the aggregation of acrylic resin particles, and are therefore preferred; however, this disclosure is not limited thereto.

[0135] In one embodiment of this disclosure, in the formation of aggregate cores, the aqueous solution may contain deionized water and an organic solvent in a weight ratio of 1:0.1 to 9, preferably 1:0.3 to 9, and more preferably 1:0.3 to 5 or 1:0.3 to 1.

[0136] In the case of an aqueous solution in which deionized water and water are mixed in the above weight ratio, aggregated cores can be formed by the aggregation of fluorine-based resin particles, and shells can be formed by the aggregation of acrylic resin particles, so that core-shell particles in which the aggregated cores and shells can be clearly distinguished can be formed, and such an aqueous solution is preferred.

[0137] In one embodiment of this disclosure, as described above, the coagulant may be selected from one, two, or more of acetate, sulfate, and nitrate.

[0138] Coagulants can be used without restriction, provided they are known to those skilled in the art. For example, coagulants can be inorganic acids, such as sulfuric acid, hydrochloric acid, phosphoric acid, or nitric acid; organic acids, such as acetic acid; alkali metal halides, such as sodium or potassium halides; salts of alkali metals with inorganic acids; or salts of alkali metals with organic acids.

[0139] In another embodiment of this disclosure, the coagulant may be calcium acetate hydrate or aluminum nitrate hydrate, but is not limited thereto, as long as the fluorine-based resin particles and the acrylic resin particles can aggregate with each other to produce core-shell particles.

[0140] In one embodiment of this disclosure, the coagulant may be contained in an aqueous solution at a concentration of 0.1% to 5% by weight, preferably 0.1% to 3% by weight, and more preferably 0.1% to 1% by weight.

[0141] Core-shell particles produced in aqueous solutions containing coagulants at concentrations within the above range are preferred because they allow the formation of a shell layer on the surface of the aggregated core, in which acrylic resin particles aggregate well with each other. Furthermore, deterioration of the physical properties of the core-shell particles due to excessive coagulant can be prevented; however, the coagulant can be used without limitation, as long as aggregated core-shell particles can be produced.

[0142] Of course, in the formation of the aggregated core and shell of core-shell particles, a coagulant can also be used to allow fluorine-based resin particles and acrylic resin particles to aggregate well with each other. Furthermore, as mentioned above, the coagulant can be retained in the core-shell particles to be produced, thereby maintaining the form of an aggregated core of fluorine-based resin particles and a shell formed by the aggregation of acrylic resin particles on the surface of this aggregated core, and thus such core-shell particles are preferred; however, this disclosure is not limited thereto.

[0143] In one embodiment of this disclosure, since the fluorine-based resin particles dispersed and contained in the first dispersion solution during the formation of the aggregate nucleus have the same monomer composition and average particle size (D50) as the fluorine-based resin particles described above, a detailed description thereof is omitted.

[0144] In one embodiment of this disclosure, the solids content of the first dispersion solution may be from 30% to 80% by weight, based on the total weight of the first dispersion solution, and in another embodiment, the solids content may be from 30% to 70% by weight or from 40% to 65% by weight, but is not limited thereto. As mentioned above, many commercial products are available as the first dispersion solution, and the first dispersion solution can be prepared by using such commercial products or by polymerization; therefore, further description thereof is omitted.

[0145] In one embodiment of this disclosure, in the formation of aggregate cores, a first dispersion solution may be added in an amount of 10 to 60 parts by weight based on 100 parts by weight of an aqueous solution, and in another embodiment, the first dispersion solution may be added in an amount of 10 to 50 parts by weight, 10 to 40 parts by weight, or 10 to 30 parts by weight.

[0146] When an aggregate core is formed by adding a first dispersion solution having a solid content within the above range to an aqueous solution, the aggregate core and the core-shell particles containing it can be produced with a target average particle size, and excellent agitation and processability can be achieved during production; and therefore such formation is preferred.

[0147] In one embodiment of this disclosure, the first dispersion solution may be a product obtained by emulsion polymerization or suspension polymerization of a fluorine-based polymer, may contain deionized water as a solvent, and may contain emulsifiers, dispersants, dispersing aids, chain transfer agents, initiators, etc., but is not limited thereto, as long as they are known to those skilled in the art.

[0148] In one embodiment of this disclosure, during the formation of aggregate cores, the stirring speed can be from 100 rpm to 1,000 rpm, preferably 800 rpm or less, 700 rpm or less, and more preferably 500 rpm or less, or 200 rpm or more, and can satisfy the numerical range defined by the upper and lower limits of the above range.

[0149] In the formation of aggregate nuclei, the stirring speed can adjust the average particle size of the aggregate nuclei. That is, in the method for producing core-shell particles, the average particle size (D50) of each of the aggregate nuclei to be produced and the core-shell particles containing them can be easily adjusted by controlling the stirring speed.

[0150] Therefore, aggregated cores and core-shell particles containing them formed at stirring speeds within the above range can have a target average particle size and are therefore preferred; however, since the stirring speed can be controlled by those skilled in the art based on the target average particle size, this disclosure is not limited thereto.

[0151] In one embodiment of this disclosure, fluorine-based resin particles can aggregate at 40°C to 90°C during the formation of aggregate nuclei, and in another embodiment, fluorine-based resin particles can aggregate at 50°C to 90°C, 60°C to 90°C, 60°C to 80°C, or 60°C to 70°C.

[0152] When fluorine-based resin particles aggregate at temperatures within the above range, aggregate nuclei can be formed well with excellent aggregation ability, and the fluorine-based resin particles do not become entangled due to fibrillation. This allows aggregate nuclei to be formed in the form in which the fluorine-based resin particles aggregate with each other, as per the objectives of this disclosure; therefore, such aggregation is preferred. However, this disclosure is not limited thereto, as long as the physical properties of the core-shell particles to be produced are not impaired.

[0153] In one embodiment of this disclosure, during the formation of the aggregate core, fluorine-based resin particles can be aggregated to prepare a dispersion in which the aggregate core is dispersed, and the solid content of the dispersion can be from 5% to 50% by weight based on the total mass of the dispersion in which the aggregate core is dispersed, and in another embodiment, the solid content can be from 10% to 40% by weight or from 10% to 30% by weight.

[0154] In the formation of aggregate nuclei, after the fluorine-based resin particles aggregate, the aggregate nuclei can be dispersed in an aqueous solution in an amount of 5% to 50% by weight. This indicates that the added fluorine-based resin particles aggregate well without residue to form aggregate nuclei.

[0155] Furthermore, when forming the shell as described below, an aqueous solution in which the aggregate nucleus is dispersed with a solid content within the above range can allow acrylic resin particles to aggregate well on the surface of the aggregate nucleus to form a shell, and is therefore preferred; however, this disclosure is not limited thereto, as long as the physical properties of the core-shell particles to be produced are not impaired.

[0156] Therefore, in the formation of aggregate nuclei, the average particle size of the aggregate nuclei can be adjusted by controlling the stirring speed, the solid content of the first dispersion solution and the aggregation reaction temperature, and as mentioned above, the average particle size (D50) can be from 200 μm to 2,500 μm, and in another embodiment, the average particle size (D50) can be from 200 μm to 2,000 μm, 200 μm to 1,800 μm, 200 μm to 1,500 μm, 200 μm to 1,000 μm, 500 μm to 1,000 μm, or 700 μm to 1,000 μm.

[0157] The surface of aggregate-type nuclei with an average particle size in the above range can be covered with a shell covering 90% or more, preferably 95% or more, and most preferably 100% of the total area. The core-shell particles containing the shell can have significantly excellent flowability and excellent processability, and due to good fibrillation, they can also have excellent binder properties, and therefore can be used as electrode binders, powder coating materials, etc.

[0158] In one embodiment of this disclosure, during the formation of the shell, a second dispersion solution in which acrylic resin particles are dispersed can be added to an aqueous solution in which the above-mentioned aggregate core is formed, so that the acrylic resin particles aggregate on the surface of the aggregate core to form a shell.

[0159] The second dispersion solution can be prepared by polymerizing acrylic resin particles using emulsion polymerization or suspension polymerization, and therefore can contain water as a solvent, acrylic resin particles, and may also contain emulsifiers, dispersants, chain transfer agents and initiators.

[0160] In the method for preparing the second dispersion solution, the second dispersion solution can be prepared by emulsion polymerization in the preparation example described below, and since this is a known technique, its detailed description is omitted.

[0161] In one embodiment of this disclosure, the average particle size (D50) of the acrylic resin particles dispersed in the second dispersion solution can be from 0.01 μm to 100 μm, which can provide effects on the production method in addition to the physical property effects of the core-shell particles produced as described above.

[0162] Acrylic resin particles with an average particle size in the above range are preferred because they can provide the effect of good aggregation of acrylic resin particles to uniformly form a shell in the production process; however, this disclosure is not limited thereto, as long as the shell can be formed on the aggregate core.

[0163] In one embodiment of this disclosure, the combination of monomers to be polymerized and polymerization units of acrylic resin particles dispersed in a second dispersion solution has been described above, and therefore its detailed description is omitted.

[0164] In one embodiment of this disclosure, the solid content of the second dispersion solution may be from 10% to 50% by weight, based on the total weight of the second dispersion solution, and in another embodiment, the solid content may be from 10% to 40% by weight, from 10% to 30% by weight, or from 10% to 20% by weight.

[0165] A second dispersion solution with a solid content within the above range is preferred because it allows for better shell formation on the surface of the aggregate core and leaves fewer acrylic resin particles, thus providing excellent productivity.

[0166] In one embodiment of the invention, in the method for producing core-shell particles, the weight ratio of the first dispersion solution to be added to the second dispersion solution can be 1:0.1 to 1.5, preferably 1:0.4 to 1.5, and more preferably 1:0.5 to 1.2.

[0167] Core-shell particles produced by adding the first and second dispersion solutions in the above-mentioned weight ratios are preferred because, as mentioned above, based on the total mass of the core-shell particles, the core-shell particles can contain the shell layer in an amount of 1% to 50% by weight, 1% to 30% by weight, or 10% to 30% by weight, thereby providing both excellent flowability and binder properties.

[0168] Therefore, core-shell particles can simultaneously satisfy significantly superior flowability and excellent binder properties, and thus can be used particularly as electrode binders; however, this disclosure is not limited thereto, as long as the desired physical properties of the invention are met.

[0169] In one embodiment of this disclosure, acrylic resin particles may aggregate at 50°C to 90°C during shell formation, and in another embodiment, the shell may be formed by forming acrylic resin particles at 70°C to 85°C.

[0170] Forming the shell at temperatures within the above range is preferred because it preserves the form of aggregate nuclei, allows for uniform shell formation, and does not impair the physical properties of the acrylic resin particles.

[0171] Therefore, core-shell particles can have an aggregate core in which fluorine-based resin particles aggregate with each other and a shell formed by acrylic resin particles aggregated on the surface of the aggregate core (two-dimensional core-shell particles), and can simultaneously have significantly superior flowability, superior storage stability and superior binder properties compared to conventional single-type fluorine-based resin particles and conventional core-shell particles in which single-type fluorine-based resin particles are coated with acrylic resin.

[0172] In one embodiment of this disclosure, as measured by the measurement method defined in this invention, core-shell particles may have a molecular weight distribution of 50.0 mJ / kg or less, 49.1 mJ / kg or less, 40.0 mJ / kg or less, 30.0 mJ / kg or less, 25.0 mJ / kg or less, 24.5 mJ / kg or less, 24.0 mJ / kg or less, 23.0 mJ / kg or less, 22.3 mJ / kg or less, 22.2 mJ / kg or less, 22.0 mJ / kg or less, 21.4 mJ / kg or less, 21.0 mJ / kg or less, 20.9 mJ / kg or less, 20.0 mJ / kg or less, 19.0 mJ / kg or less, 18.5 mJ / kg or less, 18.4 mJ / kg or less, 18.0 mJ / kg or less, 17.6 mJ / kg or less. The flowability shear force (cohesive thickness) can be mJ / kg or less, 17.5 mJ / kg or less, 17.3 mJ / kg or less, 17.0 mJ / kg or less, 16.4 mJ / kg or less, or 16.0 mJ / kg or less, and although there is no lower limit, the flowability shear force (cohesive thickness) can be 5.0 mJ / kg or greater, or 10.0 mJ / kg or greater. For example, the flowability shear force of core-shell particles can be from 5 mJ / kg to 50 mJ / kg, 5 mJ / kg to 40 mJ / kg, 5 mJ / kg to 30 mJ / kg, 5 mJ / kg to 20 mJ / kg, or 10 mJ / kg to 20 mJ / kg.

[0173] Furthermore, in one embodiment of this disclosure, as measured by the same measurement method as the flowability shear force measurement method, the core-shell particles may have a cohesive breaking energy (breaking energy) of 100 mJ / kg or less, 80 mJ / kg or less, 76.8 mJ / kg or less, 70.0 mJ / kg or less, 65.0 mJ / kg or less, 61.5 mJ / kg or less, 60.0 mJ / kg or less, 59.3 mJ / kg or less, 55.2 mJ / kg or less, 52.8 mJ / kg or less, 50.1 mJ / kg or less, 50.0 mJ / kg or less, 49.8 mJ / kg or less, or 49.5 mJ / kg or less, and although there is no lower limit, the cohesive breaking energy (breaking energy) may be 20.0 mJ / kg or greater, or 30.0 mJ / kg or greater. For example, the cohesive breaking energy of core-shell particles can be 20 mJ / kg to 100 mJ / kg, 20 mJ / kg to 80 mJ / kg, 20 mJ / kg to 70.0 mJ / kg, 20 mJ / kg to 65 mJ / kg, 20 mJ / kg to 60 mJ / kg, 20 mJ / kg to 55 mJ / kg, 20 mJ / kg to 51 mJ / kg, 20 mJ / kg to 50 mJ / kg, or 30 mJ / kg to 50 mJ / kg.

[0174] The fluidity shear force (cohesive thickness) of core-shell particles can be the shear force between static and flowing particles during drum rotation, and the cohesive breakage energy (breakage energy) can be the energy required for static particles to form a collapse. Therefore, fluidity shear force (cohesive thickness) and cohesive breakage energy (breakage energy) can indicate the dynamic fluidity of core-shell particles.

[0175] Core-shell particles can have significantly low interparticle cohesion, with flowability shear force (cohesive thickness) and cohesive breakage energy (breakage energy) within the aforementioned range. Therefore, core-shell particles can remain agglomerated during processes such as transportation, processing, storage, or stirring, and thus can exhibit significantly superior flowability.

[0176] In one embodiment of this disclosure, as measured by the measurement methods defined in this disclosure, core-shell particles may have a flow characteristic energy (basic flow energy, BFE) of 1,000 mJ or less, 800 mJ or less, 700 mJ or less, 680 mJ or less, 644 mJ or less, 621 mJ or less, 617 mJ or less, 604 mJ or less, 600 mJ or less, 576 mJ or less, 556 mJ or less, 550 mJ or less, 512 mJ or less, 500 mJ or less, or 498 mJ or less, and although there is no lower limit, the flow characteristic energy may be 200 mJ or more, 300 mJ or more, or 400 mJ or more. The fluidity characteristics of core-shell particles can be 200 mJ to 1,000 mJ, 200 mJ to 800 mJ, 200 mJ to 700 mJ, 200 mJ to 600 mJ, 200 mJ to 550 mJ, 300 mJ to 550 mJ, or 300 mJ to 400 mJ.

[0177] In another embodiment of this disclosure, core-shell particles may have a cohesive energy (specific energy, SE) of 10.0 mJ / g or less, 6.0 mJ / g or less, 5.0 mJ / g or less, 4.3 mJ / g or less, 4.0 mJ / g or less, 3.9 mJ / g or less, 3.8 mJ / g or less, 3.6 mJ / g or less, 3.5 mJ / g or less, or 3.2 mJ / g or less, as measured by the same measurement method as the flow property energy (basic flow energy, BFE). Although there is no lower limit, the cohesive energy may be 1.0 mJ / g or greater, 2.0 mJ / g or greater, or 3.0 mJ / g or greater.

[0178] Within the range of the above-mentioned flowability energy and cohesive energy, core-shell particles can have low static flowability because acrylic resin particles aggregate on the surface of the aggregate core to uniformly cover the surface, thereby preventing the fluorine-based resin particles contained in the aggregate core from prematurely undergoing fibrillation. As a result, core-shell particles can have excellent flowability and excellent storage stability.

[0179] Therefore, core-shell particles can contain a shell layer uniformly formed by the aggregation of acrylic resin particles on the surface of the aggregate core, thereby preventing the fluoropolymer from undergoing premature fibrillation. As a result, core-shell particles can simultaneously exhibit significantly superior static and dynamic flowability during processing, and can also have excellent storage stability because they do not form lumps even after long-term storage.

[0180] That is, in one embodiment of this disclosure, the core-shell particles may have excellent storage stability as measured by the measurement methods defined in this disclosure, which may mean that there is no clumping between the core-shell particles when placed under constant pressure.

[0181] The superior storage stability of core-shell particles is evaluated by allowing the particles to stand at constant pressure and measuring the degree to which the particles aggregate to form clumps. These core-shell particles can exhibit superior storage stability without clumping, compared to conventional monotype fluorine-based resin particles and monotype core-shell particles in which the surface of the monotype fluorine-based resin particles is coated with an acrylic resin.

[0182] Therefore, core-shell particles not only have excellent flowability without pre-agglomeration, but also excellent long-term stability, because core-shell particles do not agglomerate with each other even when placed (stacked) under constant pressure for a long period of time.

[0183] In one aspect of this disclosure, a mixture comprising core-shell particles may be provided.

[0184] Core-shell particles can exhibit excellent flowability without pre-agglomeration, and when used as a binder, they can exhibit excellent fibrillation, making the composition contained in the mixture difficult to separate.

[0185] In one embodiment of this disclosure, the mixture may contain core-shell particles in an amount of 0.1% to 20% by weight, based on the total weight of the mixture, and in another embodiment, the mixture may contain core-shell particles in an amount of 1% to 10% by weight; however, this disclosure is not limited thereto.

[0186] Because core-shell particles have excellent binder properties, kneaded mixtures containing core-shell particles in amounts within the above range can allow the contained particles to be well bonded to maintain their shape.

[0187] In one embodiment of this disclosure, the mixture may contain an electrode active material.

[0188] Core-shell particles can be used as binders in various fields such as coatings, anti-drip agents, powder coating materials, fiber coating materials, or automotive parts, but they can be used particularly as binders for electrode active materials because core-shell particles can bond electrode active materials and thus provide excellent retention of the mixture.

[0189] There are no particular limitations on the electrode active material, as long as it is known to those skilled in the art. However, it can be, for example, a positive electrode active material comprising a lithium complex metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum, which is a compound capable of reversibly inserting and deintercalating lithium; and a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon or carbon composite material, which can be used alone or in mixtures of both or more thereof.

[0190] In one embodiment of this disclosure, the mixture may also contain a conductive agent.

[0191] There are no particular limitations on conductive agents, as long as they are conductive and do not cause chemical changes in the battery, and examples include graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers such as carbon fibers or metal fibers; metal powders such as fluorinated carbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0192] In one embodiment of the invention, as measured by the measurement method defined in the invention, the weight percentage of the mixture containing core-shell particles as a binder retained on a 6.30 mm sieve may be 90% by weight or more, preferably 95% by weight or more, more preferably 98% by weight or more, and most preferably 100% by weight.

[0193] Core-shell particles can bind particles contained in a mixture due to their excellent binder properties and fibrillation, thereby allowing the mixture to retain its shape. In particular, core-shell particles can have even better binder properties for electrode active materials, and thus enable the preparation of mixtures that retain 90% by weight or more on a 6.30 mm sieve. Therefore, the above mixture can be used as a binder for electrode active materials.

[0194] That is, because core-shell particles can have the aforementioned significantly superior flowability and excellent storage stability, they can be used in conventional applications using fluorine-based resins, such as anti-drip agents, powder coating materials, fiber coating materials, or automotive parts. In particular, because core-shell particles can have the aforementioned significantly superior flowability and excellent storage stability, and can have binder properties superior to those of pure fluorine-based resins, they can be used as electrode binders.

[0195] In the following description, core-shell particles will be described in more detail with reference to embodiments. However, the following embodiments are provided only as a reference for a detailed explanation of this disclosure, and this disclosure is not limited thereto and may be implemented in various forms. Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Additionally, the terminology used in the description of this disclosure is only for the purpose of effectively describing particular embodiments and is not intended to limit the scope of this disclosure.

[0196] [Measurement Method]

[0197] 1. Measurement of weight-average molecular weight (Mw) [kg / mol]

[0198] To measure the molecular weight of the non-fluorine-based resin, 10 mg of the extracted non-fluorine-based resin was dissolved in 10 ml of tetrahydrofuran (THF) and filtered using a 0.2 μm Teflon filter. The molecular weight was then measured using a gel permeation chromatography (GPC) instrument manufactured by Waters.

[0199] 2. Measurement of glass transition temperature (Tg) [°C]

[0200] The glass transition temperature of non-fluorine-based resins was measured for two cycles at a heating rate of 10 °C / min using a Q20 DSC (differential scanning calorimeter) manufactured by TA Instruments. The glass transition temperature was then calculated from the inflection point of the second cycle using the semi-Cp method.

[0201] 3. Measurement of the ratio of fluorine-based resins to non-fluorine-based resins

[0202] Weight loss was measured by heating 10 mg of dried granules to 600 °C at a rate of 10 °C / min using a thermogravimetric analysis (TGA). The ratio of fluorine-based to non-fluorine-based resins was measured based on the degree of weight loss, taking advantage of the initial thermal decomposition of the non-fluorine-based resin. In the case of mono-core-shell granules, 20 g of acetone was added to 10 g of mono-core-shell granules, the mixture was shaken, and then the mixture was added dropwise to 400 g of methanol to obtain a precipitated non-fluorine-based resin. The precipitated non-fluorine-based resin was separated using a vacuum filter, washed three times with methanol, and then vacuum-dried in an oven at 25 °C for 24 hours.

[0203] 4. Measurement of average particle size and particle size distribution

[0204] Particle size distribution was measured using a wet method with a laser diffraction particle size distribution analyzer (Malvern Panalytical, MASTERSIZER 3000hydro). The D50 value was used as the average particle size, which is the average particle size based on volume-based measurements (where "D50" corresponds to 50% of the cumulative fraction, Dn refers to the particle size corresponding to n% of the cumulative fraction). In the measurement of average particle size, the span value was used as the particle size distribution, calculated by the particle size distribution analyzer using the (D90-D10) / D50 method. Furthermore, images of the core-shell particles were obtained using a scanning electron microscope (SEM). Figure 5 The average particle size (D50) of the core-shell particles was determined to be similar to the average particle size (D50) of the acrylic resin particles measured above.

[0205] 5. Structural analysis of core-shell particles

[0206] To analyze the structure of the core-shell particle, the particle was photographed using a scanning electron microscope. Furthermore, to clearly distinguish between the aggregated core and shell, bisections of the core-shell particle were photographed using a scanning electron microscope. The photographs of the core-shell particle and the bisectioned core-shell particle are shown below. Figure 6 In this study, image measurement methods were used to measure the shell thickness of 10 particles and obtain their average values, as well as cross-checking using core-shell particles and particle size.

[0207] Furthermore, to measure the size and shell surface distribution of the aggregated core-shell particles prepared in the examples and comparative examples, images of each particle were taken 10 times using a scanning electron microscope (SEM) to measure the visually observed average diameter, and the average diameter was determined to be similar to the average particle size (D50) measured above. The surface coverage level of the core-shell was visually observed and classified as follows:

[0208] ○: For example, visually observed coverage of 90% or more of the nuclear surface;

[0209] △: such as visual observation covering 90% to 30% of the nuclear surface; and

[0210] X: 30% or less of the surface of the nucleus as observed by visual inspection.

[0211] Furthermore, to determine whether the aggregated core and shell of the core-shell particles prepared in Example 1 were clearly formed, energy-dispersive X-ray spectroscopy (SEM-EDX) was used to image the core-shell particles and bisected core-shell particles, and the results are shown in... Figure 7 middle.

[0212] 6. Analysis of storage stability

[0213] 10 g of each particle sample was loaded into a stainless steel container, and the container was placed at 20°C for 4 hours while a pressure of 11.3 kg was applied. Afterward, the particles remaining in the stainless steel container were removed to prepare particle clumps. The particles were then placed on sieves with a 2 mm mesh opening, 0.6 mm mesh openings, and 0.2 mm mesh openings. The particle clumps placed on the sieves were then crushed for 1 minute using a vibrating sieve (Haver & Boecher OHG, EML200 Premium), and the weight of the crushed particle clumps was measured and calculated using Equation 1 below. Figure 8 The image shows the particles remaining after sieving.

[0214] [Equation 1]

[0215] Storage stability (%) = [Mass of crushed particulate matter (g) / Mass of initial particulate matter (g)] × 100

[0216] 7. Measurement of total kinetic energy and cohesive energy of particles

[0217] The flowability and cohesive energy of the particles were measured using a powder rheometer (Freeman Technology Ltd., FT4). Specifically, in the method for measuring the flowability and cohesive energy of the particles, after filling a cylindrical tube with a diameter of 50 mm with particles, an impeller was rotated at a tip speed of 100 mm / s (8 times), 70 mm / s (1 time), 40 mm / s (1 time), or 10 mm / s (1 time) while the particles were repeatedly moved up and down in the cylindrical tube. The total flow energy (basic flow energy, BFE) was measured when the particles moved downwards in the cylindrical tube, and the cohesive energy (specific energy, SE) was measured when the particles moved upwards. Both BFE and SE were measured during a total of 11 up-and-down movements of the particles in the cylindrical tube, and their average values ​​were calculated.

[0218] 8. Measurement of particle flowability, shear force, and cohesive force

[0219] The flowability shear force and cohesive force of particles were measured using a dynamic powder flow analyzer (Mercury, Revolution). Specifically, after filling a 100 cc drum with 25 cc of particles, the drum was rotated at 0.3 rpm, and the potential energy of the particles in the drum was measured using a camera. Then, the average cohesive thickness (the shear force between static and flowing particles during drum rotation) and breakup energy (the energy required for static particles to form a collapse) of the particles in the drum were calculated after 100 collapses (the phenomenon where particles rise and collapse with the drum) occurred in the drum.

[0220] 9. Measurement of adhesive properties and fibrillation

[0221] To evaluate the fibrillation of the particles, a mixture was prepared comprising 96 wt% of active material (NCM622 (nickel / cobalt / manganese = 6 wt% / 2 wt% / 2 wt%)), 2 wt% of conductive agent (Ketjen Black), and 2 wt% of particles from the following examples and comparative examples as binders.

[0222] Subsequently, the mixture was pulverized using a Kochstar (KSEBD-1500) at 24,000 rpm, and after pulverization, it was kneaded for 3 minutes using a batch mixer (HAAKE, Rheomix 600) at an internal temperature of 150°C and a rotation speed of 15 rpm. Images of the kneaded mixture containing the core-shell particles of Example 1 were then captured by scanning electron microscopy (SEM) and are shown below. Figure 9 Images of the kneaded mixture containing individual core-shell particles of Comparative Example 1, captured by scanning electron microscopy (SEM), are shown below. Figure 10 middle.

[0223] In addition, the total mass of the kneaded samples was measured, and the kneaded mixture was first sieved using a sieve with a mesh opening of 6.3 mm, and then second sieved using a sieve with a mesh opening of 4.75 mm. Based on the first and second sieves described above, the binder properties were detailed as follows: The percentage by weight of kneaded samples with a size of 6.3 mm or larger (retained on the first sieve), the percentage by weight of kneaded samples with a size of 4.75 mm or larger but smaller than 6.3 mm (retained on the second sieve), or the weight of kneaded samples with a size smaller than 4.75 mm (not retained on either the first or second sieve) were determined based on the total weight of the kneaded samples.

[0224] Preparation of acrylic resin particles

[0225] [Preparation Example 1]

[0226] 744.4 g of deionized water, 115.2 g of methyl methacrylate (MMA), and 28.8 g of n-butyl acrylate (nBA) were added to a 1 L reactor. 11.6 g of Tergitol TMN-100X (90% aqueous solution) manufactured by DOW as an emulsifier, 0.14 g of ammonium persulfate as an initiator, and 0.32 g of n-octylthiol as a chain transfer agent were added. The mixture was heated to 75 °C while stirring at 230 rpm and bubbling with nitrogen. After reaching 75 °C (the polymerization temperature), nitrogen bubbling was stopped, and the polymerization reaction was carried out for 3 hours. The mixture was then cooled to room temperature to prepare a second dispersion solution containing acrylic resin particles. The results obtained by analyzing the weight-average molecular weight, glass transition temperature, and average particle size are shown in Table 1.

[0227] [Preparation Example 2]

[0228] The procedure was carried out in the same manner as in Preparation Example 1, except that 100.8 g of methyl methacrylate (MMA), 21.6 g of methacrylic acid (MAA), and 21.6 g of n-butyl acrylate (nBA) were added as monomers, and other components were used in the same amounts. The results obtained by analyzing the weight-average molecular weight, glass transition temperature, and average particle size are shown in Table 1.

[0229] [Preparation Example 3]

[0230] The same procedures as in Preparation Example 1 were followed, except that 115.2 g of methyl methacrylate (MMA) and 28.8 g of styrene were added as monomers, and other components were used in the same amounts. The results obtained by analyzing the weight-average molecular weight, glass transition temperature, and average diameter are shown in Table 1.

[0231] [Table 1]

[0232]

[0233] Preparation of core-shell particles

[0234] [Example 1]

[0235] 291.2 g of deionized water, 291.2 g of methanol, and 4.5 g of calcium acetate monohydrate (Ca(OAc)2*H2O) as a coagulant were added to a 1 L reactor. The mixture was stirred at 300 rpm, and the reactor temperature was heated to 60 °C. Using a dropping funnel, 168 g of an aqueous dispersion of polytetrafluoroethylene (PTFE) (Chemours, DISP30, average particle size (D50): 0.22 μm, solids content: 63.5%) as the first dispersion solution was added dropwise to the heated reactor at a rate of 5.6 g / min to form aggregate nuclei in the solvent of the reactor.

[0236] Subsequently, 157 g of the dispersion solution of Preparation Example 1 was continuously added dropwise to the reactor at a rate of 15.8 g / min using a dropping funnel to form a shell layer on the surface of the aggregated core, and the mixture was aged at 80°C for 1 hour. After aging, the mixture was cooled to room temperature, thoroughly washed with deionized water, and dried in a vacuum oven at 50°C for 24 hours to obtain core-shell particles.

[0237] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0238] [Example 2]

[0239] 320.0 g of deionized water, 320.0 g of methanol, and 6.9 g of calcium acetate monohydrate (Ca(OAc)2*H2O) as a coagulant were added to a 1 L reactor. The mixture was stirred at 300 RPM, and the reactor temperature was heated to 60 °C. Using a dropping funnel, 189.0 g of an aqueous dispersion of polytetrafluoroethylene (PTFE) (Chemours, DISP30, average particle size (D50): 0.22 μm) was added dropwise to the heated reactor as the first dispersion solution at a rate of 6.3 g / min to form aggregate nuclei in the reactor solvent.

[0240] Subsequently, 78.8 g of the dispersion solution of Preparation Example 1 was continuously added dropwise to the reactor at a rate of 7.9 g / min using a dropping funnel to form a shell on the aggregate core, and the mixture was aged at 80°C for 1 hour. After aging, the mixture was cooled to room temperature, thoroughly washed with deionized water, and dried in a vacuum oven at 50°C for 24 hours to obtain core-shell particles.

[0241] That is, the steps are carried out in the same manner as in Example 1, except that the first dispersion solution and the dispersion solution of Preparation Example 1 are added at a weight ratio of 1:0.42.

[0242] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0243] [Example 3]

[0244] The steps were performed in the same manner as in Example 1, except that the reactor stirring speed was set to 200 rpm.

[0245] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0246] [Example 4]

[0247] The steps were performed in the same manner as in Example 1, except that the reactor stirring speed was set to 500 rpm.

[0248] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0249] [Example 5]

[0250] The steps were performed in the same manner as in Example 1, except that a dispersion solution with a solid content of 63.5% was used as the first dispersion solution by dispersing PTFE particles (Sigma-Aldrich) with an average particle size of 40 μm in deionized water.

[0251] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0252] [Example 6]

[0253] The steps were performed in the same manner as in Example 1, except that a dispersion solution with a solid content of 63.5% was used as the first dispersion solution by dispersing PTFE particles (Sigma-Aldrich) with an average particle size of 1 μm in deionized water.

[0254] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0255] [Example 7]

[0256] The steps were performed in the same manner as in Example 1, except that the dispersion solution of Preparation Example 2 was used instead of the dispersion solution of Preparation Example 1.

[0257] Subsequently, the physical properties of the prepared aggregate-type nuclei were measured using the above measurement methods, and are shown in Tables 3 and 4.

[0258] [Example 8]

[0259] The steps were performed in the same manner as in Example 1, except that the dispersion solution of Preparation Example 3 was used instead of the dispersion solution of Preparation Example 1.

[0260] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0261] [Example 9]

[0262] The procedure was performed in the same manner as in Example 1, except that an aqueous solution containing deionized water and methanol in a weight ratio of 1:0.43 was used by adding 407.7 g of deionized water and 174.7 g of methanol.

[0263] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0264] [Example 10]

[0265] The steps were performed in the same manner as in Example 1, except that ethanol was used instead of methanol as the organic solvent.

[0266] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0267] [Example 11]

[0268] The steps were performed in the same manner as in Example 1, except that 7.1 g of aluminum nitrate nonahydrate was added instead of calcium acetate monohydrate (Ca(OAc)2*H2O) as a coagulant, so that the coagulant concentration in the aqueous solution was 1.20 by weight.

[0269] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0270] [Comparative Example 1]

[0271] A PTFE aqueous dispersion (Chemours, DISP-30) with an average particle size of 0.21 μm, a solids content concentration of 30%, and a standard specific gravity (SSG) of 2.16 to 2.22 was prepared. Subsequently, 2448.0 g of the PTFE dispersion and 48.96 g of a 90% aqueous solution of polyethylene glycol trimethyl nonyl ether with a molecular weight of 384 g / mol exhibiting hydrophilic ethylene glycol repeating units were added to a 4 L reactor, and the mixture was heated to 75 °C while stirring at 350 rpm and bubbling with nitrogen. After raising the temperature to 75 °C, nitrogen bubbling was stopped, and after 15 minutes, a monomer mixture consisting of 223.20 g of methyl methacrylate (MMA), 55.08 g of n-butyl acrylate (nBA), and an additional 0.40 g of n-octyl mercaptan as a chain transfer agent was added dropwise over 15 minutes. Fifteen minutes after adding the monomer mixture solution, 68.4 g of distilled water and an aqueous solution of 0.92 g of potassium persulfate were added dropwise to the reactor over approximately 10 minutes. After the addition of potassium persulfate was complete, the polymerization reaction was carried out for 3 hours, and then the mixture was cooled to 30°C to obtain a white emulsion. Furthermore, the emulsion was freeze-dried at -60°C at 10 mTorr for 72 hours to obtain a white powder.

[0272] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0273] [Comparative Example 2]

[0274] The polytetrafluoroethylene (PTFE) powder (Chemours, 601X) with an average particle size similar to that of the aggregate nuclei in Example 1 was used. According to the measurements in the TDS, the average particle size (D50) of the PTFE powder (Chemours, 601X) was 532 μm.

[0275] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0276] [Comparative Example 3]

[0277] The steps were performed in the same manner as in Example 1, except that no organic solvent was added to the reactor and 582.4 g of deionized water was used.

[0278] Subsequently, the physical properties of the prepared aggregate-type nuclei were measured using the above measurement methods, and are shown in Tables 3 and 4.

[0279] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0280] [Comparative Example 4]

[0281] The steps were performed in the same manner as in Example 1, except that no coagulant was used.

[0282] Subsequently, the physical properties were measured using the above measurement methods, and the results are shown in Tables 3 and 4.

[0283] [Comparative Example 5]

[0284] 291.2 g of deionized water, 291.2 g of methanol, and 4.5 g of calcium acetate monohydrate (Ca(OAc)₂*H₂O) as a coagulant were added to a 1 L reactor. The mixture was stirred at 300 RPM, and the reactor temperature was heated to 60 °C. 168.0 g of an aqueous dispersion of polytetrafluoroethylene (PTFE) (Chemours, DISP30, average particle size (D50): 0.22 μm) as the first dispersion solution was added dropwise to the heated reactor at a rate of 5.6 g / min using a dropping funnel to obtain aggregate nuclei in the reactor solvent. The resulting reaction mixture was maintained at 60 °C for 10 min, then cooled to room temperature, and the aggregate nuclei were thoroughly washed with deionized water and dried in a vacuum oven at 50 °C for 24 h to obtain particles.

[0285] That is, in Example 1, only aggregate nuclei without a shell were prepared. Subsequently, physical properties were measured using the methods described above, and are shown in Tables 3 and 4.

[0286] [Table 2]

[0287]

[0288] [Table 3]

[0289]

[0290] [Table 4]

[0291]

[0292] Figure 3 A photograph of the aggregate nucleus of Example 1 taken using an optical microscope, and Figure 4 This is a photograph of the aggregate nucleus of Example 1 taken using a scanning electron microscope. (Refer to...) Figure 3 and Figure 4 It can be determined that in Example 1, the fluorine-based resin particles aggregated well, and thus the aggregate nuclei were well formed.

[0293] Figure 5The image shows an aggregate nucleus of Example 1 taken using a scanning electron microscope, and refers to... Figure 6 It can be determined that in the core-shell particles of Example 1, the acrylic shell aggregates and the shell is well formed.

[0294] also, Figure 6 The image shows a core-shell particle of Example 1 after it has been cut in half, taken using a scanning electron microscope, and is shown in reference to... Figure 6 It can be determined that in the core-shell particles of Example 1, the aggregated core and shell are formed in a way that can be clearly distinguished.

[0295] To determine the formation of core-shell particles in Example 1 such that the aggregated core and shell are clearly distinguishable, SEM-EDX images of the core-shell particles of Example 1 are shown. Figure 7 The PTFE resin particles are shown in dark gray (essentially blue), while the acrylic resin particles of Preparation Example 1 are shown in light gray (essentially green). It can be determined that only the PTFE resin particles are distributed in the aggregate core, and only the acrylic resin particles are distributed in the shell, thus indicating a perfect core-shell particle morphology. Furthermore, refer to... Figure 7 The SEM-EDX images confirmed that in the core-shell particles of Example 1, the shell completely covers 100% of the total surface area of ​​the aggregate nucleus.

[0296] Therefore, referring to Table 3, it is determined that in each of Examples 1 to 11, fluorine-based resin particles aggregate with each other to form an aggregate core, and acrylic resin particles aggregate on the surface of the formed aggregate core to form a shell, thereby forming a core-shell particle consisting of an aggregate core formed by well-aggregated fluorine-based resin particles and a shell formed by well-aggregated acrylic resin particles.

[0297] Furthermore, referring to Table 3, when examining the core-shell particles prepared in Examples 3 and 4, it was determined that the average particle size of the aggregated core and the average particle size of the core-shell particles could be adjusted by controlling the stirring speed. Also, referring to Example 2, it was determined that the amount of shell could be adjusted by adjusting the amount of polytetrafluoroethylene (PTFE) aqueous dispersion solution and acrylic resin particle solution.

[0298] Furthermore, as can be seen from Table 3, when examining the core-shell particles of Examples 5 and 6, it can be determined that even when the average particle size of the fluorine-based resin particles is changed, the fluorine-based resin particles aggregate well, and aggregated cores and core-shell particles including them can be prepared.

[0299] Furthermore, as can be seen from Table 3, it is determined that an acrylic resin particle prepared by further adding styrene or (meth)acrylic acid can form a shell, as in the core-shell particles of Examples 7 and 8.

[0300] Therefore, it is determined that the core-shell particles prepared in Examples 1 to 11 have an aggregated core formed by the aggregation of fluorine-based resin particles to each other, and a shell formed by the aggregation of acrylic resin particles to each other on the surface of the aggregated core, thus having a core-shell particle form in which the aggregated core and the shell can be clearly distinguished, and it is also determined that the shell is uniformly formed on the surface of the aggregated core.

[0301] Furthermore, it was determined that the core-shell particles prepared in Examples 1 to 11 formed well, regardless of the average particle size of the fluorine-based resin particles and the acrylic resin particles, and regardless of the monomers used to prepare the acrylic resin particles.

[0302] Furthermore, it was determined that in the core-shell particles prepared in Examples 1 to 11, the average particle size of the core-shell particles, the average particle size of the aggregated core, and the thickness of the shell layer could be easily adjusted by controlling the stirring speed of the reactor and the weight ratio of the first dispersion solution to the second dispersion solution. It was also determined that the span value of the average particle size of the core-shell particles was 1.5 or less.

[0303] Since the average particle size span of the core-shell particles is 1.5 or less, it indicates that the average particle size distribution is significantly narrow, and therefore indicates that the core-shell particles of this disclosure can have a significantly uniform average particle size.

[0304] Therefore, since the core-shell particles according to one embodiment of this disclosure have the above-mentioned physical properties, the core-shell particles can have effects such as excellent flowability, excellent binder properties and excellent storage stability, as will be described below.

[0305] Referring to Examples 1 to 11 in Table 4, it was determined that the aggregated core-shell particles of Examples 1 to 11 have low total flow energy (basic flow energy, BFE) and low cohesive energy (specific energy, SE) as measured by FT4, and it was also determined that the measured cohesive thickness (shear force between static and flowing particles during drum rotation) and breakage energy (energy required for static particles to form collapse) are significantly low in dynamic powder flow measurements using rotation.

[0306] That is, the aggregated core-shell particles prepared in Examples 1 to 11 show that the premature aggregation of fluorine-based resin particles contained in the aggregated core is prevented, and therefore the aggregated core-shell particles can have excellent flowability.

[0307] Furthermore, referring to Table 4, it was determined that the core-shell particles of Examples 1 to 11 not only have the aforementioned excellent flowability, but also excellent storage stability, because even when the core-shell particles are placed under high pressure, agglomeration between the core-shell particles is prevented.

[0308] Furthermore, referring to Table 4, it was determined that the core-shell particles of Examples 1 to 11 not only have the aforementioned excellent flowability and storage stability, but also excellent binder properties, because 95% by weight or more of the electrode mixture containing the core-shell particles used as an electrode binder is retained on the first sieve with an opening of 6.3 mm or larger.

[0309] In contrast, as can be seen from Tables 3 and 4, it was determined that no aggregate nucleus was well formed in Comparative Examples 3 and 4, and furthermore, no shell was formed by the aggregation of acrylic resin particles.

[0310] Therefore, it was determined that the particles in Comparative Examples 3 and 4 were aggregated to such an extent that static flowability measurement by FT4 was impossible, and similarly, in the dynamic powder flow measurement using rotation, the measured cohesive thickness and breakage energy were higher than those of the Examples. Furthermore, referring to Table 3, it was determined that the particles in Comparative Examples 2 and 5, in which no shell layer was formed, had such poor flowability that measurement was impossible.

[0311] Furthermore, as can be seen from Tables 3 and 4, the particles of Comparative Example 1 were determined to be single core-shell particles in which acrylic resin is polymerized on the surface of a single PTFE particle to form a shell layer, and as compared with the examples, these particles have significantly higher interparticle cohesion and lower storage stability, and in particular, have significantly lower binder properties compared with them.

[0312] Therefore, the method for producing core-shell particles can prevent the premature agglomeration of fluorine-based resin particles, thereby enabling significantly superior flowability and storage stability, and achieving binder properties superior to those of conventional monotype core-shell particles. Consequently, core-shell particles can be used as anti-drip agents, powder coating materials, fiber coating materials, automotive parts, or electrode binders.

[0313] In the foregoing, although this disclosure has been described by way of specific matters and limited embodiments and comparative examples, these are provided only to help to fully understand this disclosure. Therefore, this disclosure is not limited to the described embodiments, and various modifications and changes can be made by those skilled in the art based on the description.

[0314] Therefore, the spirit of this disclosure should not be limited to the described embodiments, but rather the claims and all modifications equivalent to or related to the claims are intended to fall within the spirit of the invention.

[0315] (Detailed description of the main elements)

[0316] 100: Core-shell particles

[0317] 10: Aggregate-type nuclei

[0318] 11: Fluorine-based resin particles

[0319] 20: Shell

[0320] 21: Acrylic resin particles

Claims

1. A core-shell particle, comprising: Aggregate nuclei formed by the aggregation of fluorine-based resin particles; and The shell is formed by acrylic resin particles aggregating on the surface of the aggregate core. The average particle size (D50) of the core-shell particles is between 500 μm and 3,000 μm.

2. The core-shell particles of claim 1, wherein the fluorine-based resin particles comprise a fluorine-based polymer formed by polymerizing one or more fluorinated monomers selected from vinylidene fluoride, vinyl fluoride, trifluorochloroethylene, tetrafluoroethylene, perfluoroalkyl vinyl ethers and hexafluoropropylene.

3. The core-shell particles of claim 2, wherein the fluorine-based polymer is formed by polymerizing one or more of tetrafluoroethylene, perfluoroalkyl vinyl ether and hexafluoropropylene.

4. The core-shell particles of claim 1, wherein the acrylic resin particles comprise one or more of the following: methyl methacrylate homopolymer; and acrylic copolymers of methyl methacrylate and one or more comonomers, wherein the one or more comonomers are selected from ethyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and styrene-based monomers.

5. The core-shell particles according to claim 4, wherein the acrylic resin particles comprise acrylic copolymers.

6. The core-shell particles according to claim 4, wherein, based on 100% by weight of total polymer units, the acrylic copolymer has 70% by weight to 99.9% by weight of methyl methacrylate polymer units.

7. The core-shell particles of claim 1, wherein the aggregated core is in the form of an aggregate of fluorine-based resin particles with an average particle size (D50) of 0.01 μm to 100 μm that are tightly aggregated together. The average particle size (D50) of the aggregated nuclei is between 200 μm and 2,500 μm.

8. The core-shell particles of claim 7, wherein the average particle size (D50) of the fluorine-based resin particles is from 0.1 μm to 50 μm.

9. The core-shell particle according to claim 1, wherein the thickness of the shell layer is from 50 μm to 500 μm.

10. The core-shell particles according to claim 1, wherein the average particle size (D50) of the acrylic resin particles is from 0.01 μm to 100 μm.

11. The core-shell particles of claim 10, wherein the average particle size (D50) of the acrylic resin particles is from 0.1 μm to 50 μm.

12. The core-shell particle of claim 1, wherein the core-shell particle comprises the shell layer in an amount of 1% to 50% by weight, based on the total weight of the core-shell particle.

13. The core-shell particle of claim 1, wherein the aggregated core is covered by the shell over 90% or more of its entire surface area.

14. The core-shell particles of claim 13, wherein, except for the voids between the acrylic resin particles, the aggregated core is covered by the shell over 100% of its entire surface area.

15. The core-shell particles of claim 1, wherein the core-shell particles comprise one or more coagulants selected from acetates, sulfates and nitrates.

16. The core-shell particles of claim 1, wherein, based on 100 measurements at 0.3 rpm using a dynamic powder flow analyzer manufactured by Mercury Scientific Inc., the core-shell particles have a shear force (cohesive thickness) of 50 mJ / kg or less between the static core-shell particles and the flowing core-shell particles.

17. The core-shell particles of claim 1, wherein, based on 100 measurements at 0.3 rpm using a dynamic powder flow analyzer manufactured by Mercury Scientific Inc., the core-shell particles have a cohesive breakage energy (breakage energy) of 100 mJ / kg or less required for static core-shell particle formation collapse.

18. The core-shell particles of claim 1, wherein, as measured using a powder rheometer manufactured by Freeman Technology Ltd., the core-shell particles have a total flow energy (basic flow energy, BFE) of 1,000 mJ or less and a cohesive energy (specific energy, SE) of 10 mJ / kg or less.

19. A mixture comprising core-shell particles according to any one of claims 1 to 18.

20. The mixture of claim 19, wherein the mixture further comprises an electrode active material.

21. The mixture of claim 19, wherein the mixture contains the core-shell particles in an amount of 0.1% to 20% by weight, based on the total weight of the mixture.

22. The mixture of claim 19, wherein 95% by weight or more of the mixture is retained on a 6.3 mm sieve.

23. A method for producing core-shell particles, the method comprising: An aggregate nucleus in which the fluorine-based resin particles are dispersed is formed by adding a first dispersion solution therein to an aqueous solution containing an organic solvent and a coagulant. as well as A shell is formed by adding a second dispersion solution containing acrylic resin particles to an aqueous solution in which the aggregate core is formed, causing the acrylic resin particles to aggregate on the surface of the aggregate core. The average particle size (D50) of the aggregated nuclei is 200 μm to 2,500 μm.

24. The method according to claim 23, wherein the organic solvent is a C1-C7 aliphatic alcohol, a C1-C4 alkyl acetate, or a mixture thereof.

25. The method of claim 23, wherein the aqueous solution comprises deionized water and an organic solvent mixed in a weight ratio of 1:0.1 to 9.

26. The method of claim 23, wherein the coagulant is selected from one or more of acetate, sulfate and nitrate.

27. The method of claim 23, wherein the coagulant is contained in the aqueous solution at a concentration of 0.1% to 5% by weight.

28. The method according to claim 23, wherein, When forming the aggregate core, the first dispersion solution is added in an amount of 10 to 60 parts by weight based on 100 parts by weight of the aqueous solution.

29. The method according to claim 23, wherein, The stirring speed is 100 rpm to 1,000 rpm when the aggregate core is formed.

30. The method according to claim 23, wherein, During the formation of the aggregate nucleus, the fluorine-based resin particles aggregate at a temperature between 40°C and 90°C.

31. The method of claim 23, wherein the solid content of the first dispersion solution is from 30% to 80% by weight, based on the total weight of the first dispersion solution.

32. The method according to claim 23, wherein, During the formation of the shell, the acrylic resin particles aggregate at a temperature of 50°C to 90°C to form the shell.

33. The method of claim 23, wherein the solid content of the second dispersion solution is from 10% to 50% by weight, based on the total weight of the second dispersion solution.

34. The method of claim 23, wherein the first dispersion solution and the second dispersion solution are added in a weight ratio of 1:0.1 to 1.5.

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