Method for producing hollow resin particles

Abstract

The present invention provides a method for producing hollow resin particles having a shell containing a resin and a hollow portion surrounded by the shell, the method comprising: a mixed solution preparation step of preparing a mixed solution containing a polymerizable monomer, a hydrophobic organic solvent, a polymerization initiator, and an aqueous medium; a suspension step of preparing a suspension in which droplets of a polymerizable monomer composition containing the polymerizable monomer, the hydrophobic organic solvent, and the polymerization initiator are dispersed in the aqueous medium by suspending the mixed solution; a polymerization step of preparing a precursor composition containing precursor particles having a hollow portion and containing the hydrophobic organic solvent in the hollow portion by supplying the suspension to a polymerization reaction; a floatation separation step of floatation-separating the precursor particles in the precursor composition; and a solvent removal step of removing the hydrophobic organic solvent contained in the precursor particles while the precursor particles are floatation-separated.

Description

Technical Field

[0001] This invention relates to a method for manufacturing hollow resin particles. Background Technology

[0002] Hollow resin particles, manufactured by polymerizing polymerizable monomers, are particles with cavities inside. Compared to solid particles whose interior is filled with resin, they can scatter light well and reduce light transmittance. Therefore, they are widely used as organic pigments and masking agents with excellent optical properties such as opacity and whiteness in applications such as water-based coatings and paper coating compositions. Furthermore, they can also be used as additives (additives added to resins used for molding) for molding bodies such as light reflectors, heat insulation materials, and sound insulation materials.

[0003] As a technology for hollow resin particles, for example, Patent Document 1 describes a method for manufacturing hollow resin particles, which is a method for manufacturing hollow resin particles having a shell containing resin and a hollow part surrounded by the shell. The method includes a mixture preparation step, a suspension step, a polymerization step, and a flotation separation and cleaning step. The flotation separation and cleaning step is a process of flotation separation and cleaning by removing the metal components in the precursor composition while flotating and separating the precursor particles in the precursor composition obtained in the polymerization step. The flotation velocity V of the precursor particles in the precursor composition at 25°C, calculated by a specific formula (1), is 0.1 m / h or more.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent document 1: Japanese Patent Application Publication No. 2023-067861. Summary of the Invention

[0007] The problem the invention aims to solve

[0008] According to the manufacturing method described in Patent Document 1, hollow resin particles with low residual metal content can be manufactured with high production efficiency. However, the inventors conducted in-depth research and found that, depending on the structure of the hollow resin particles, the composition of the shell, and the removal conditions of the hydrophobic organic solvent, the hollow resin particles sometimes break when using the manufacturing method described in Patent Document 1.

[0009] Therefore, the inventors investigated the removal conditions of hydrophobic organic solvents and found that removing the hydrophobic organic solvents encapsulated within the precursor particles in the presence of an aqueous medium could prevent the breakage of the hollow resin particles. However, in the method of removing hydrophobic organic solvents in the presence of an aqueous medium, excessive foaming is easily generated during the removal of the hydrophobic organic solvents. This necessitates limiting the supply of hollow resin particles to the solvent removal equipment or restricting the removal conditions of the hydrophobic organic solvents to stable conditions. As a result, the productivity of hollow resin particles tends to deteriorate.

[0010] The present invention was made in view of the current situation, and its object is to provide a method for manufacturing hollow resin particles that can suppress foaming when removing hydrophobic organic solvents and can manufacture hollow resin particles with high productivity.

[0011] Solution for solving the problem

[0012] In order to achieve the above-mentioned objective, the inventors conducted in-depth research and found that the above-mentioned objective can be achieved by a manufacturing method having a flotation separation step that separates precursor particles in a precursor composition from the surface, and a solvent removal step that removes the hydrophobic organic solvent contained in the precursor particles while the precursor particles are in a state of flotation separation. Thus, the present invention was completed.

[0013] That is, according to the present invention, the following manufacturing method is provided.

[0014] [1] A method for manufacturing hollow resin particles, comprising a shell containing resin and a hollow portion surrounded by the shell, comprising the following steps: a mixture preparation step, preparing a mixture containing a polymerizable monomer, a hydrophobic organic solvent, a polymerization initiator and an aqueous medium; a suspension step, preparing a suspension in which droplets of a polymerizable monomer composition containing the polymerizable monomer, the hydrophobic organic solvent and the polymerization initiator are dispersed in the aqueous medium by suspending the mixture; a polymerization step, preparing a precursor composition containing precursor particles having a hollow portion and containing the hydrophobic organic solvent within the hollow portion by supplying the suspension to a polymerization reaction; a flotation separation step, separating the precursor particles in the precursor composition by flotation; and a solvent removal step, removing the hydrophobic organic solvent contained within the precursor particles while the precursor particles are separated by flotation.

[0015] [2] The method for manufacturing hollow resin particles according to [1] further comprises: a cleaning step, wherein the hollow resin particles obtained in the solvent removal step, having had the hydrophobic organic solvent encapsulated in the precursor particles removed, are cleaned.

[0016] [3] The method for manufacturing hollow resin particles according to [1] or [2] further comprises: a drying step, wherein the hollow resin particles obtained in the solvent removal step, having the hydrophobic organic solvent encapsulated in the precursor particles, are dried.

[0017] [4] In the method for manufacturing hollow resin particles according to any one of [1] to [3], in the above-mentioned flotation separation process, after pressurizing the above-mentioned precursor composition, the pressure is reduced from the pressurized conditions, thereby causing the above-mentioned precursor particles to float.

[0018] [5] In the method for manufacturing hollow resin particles according to any one of [1] to [4], in the solvent removal step, the hydrophobic organic solvent contained in the precursor particles is removed under a pressurized environment of 0.1 to 2.0 MPa.

[0019] [6] In the method for manufacturing hollow resin particles according to any one of [1] to [5], in the solvent removal step, the hydrophobic organic solvent contained in the precursor particles is removed under a gas flow.

[0020] [7] The method for manufacturing hollow resin particles according to any one of [1] to [6] is a process of separating the precursor particles into an upper layer (A) and a lower layer (B) containing a smaller proportion of precursor particles than the upper layer (A) by causing the precursor particles to float.

[0021] [8] According to the method for manufacturing hollow resin particles as described in [7], the upper layer (A) contains 0.1 to 70 parts by volume of gas relative to 100 parts by volume of the precursor particles in the upper layer (A).

[0022] [9] According to the method for manufacturing hollow resin particles as described in [7] or [8], the volume (V) of the precursor particles in the upper layer (A) is... Ap ) relative to the volume of the aqueous medium (V Aw ) and the volume (V) of the precursor particles Ap The total proportion of [V] Ap / (V Aw +V Ap The percentage is over 40%, and the volume (V) of the precursor particles in the lower layer (B) is also higher. Bp ) relative to the volume of the aqueous medium (V Bw ) and the volume (V) of the precursor particles Bp The total proportion of [V] Bp / (V Bw +V Bp The percentage is below 20%.

[0023]

[10] According to the method for manufacturing hollow resin particles according to any one of [7] to [9], the average specific gravity (D) of the upper layer (A) is... A The average specific gravity (D) relative to the lower layer (B) mentioned above. B The proportion of ) [D A / D B [Greater than 0.3 and less than 0.97]

[0024]

[11] In the method for manufacturing hollow resin particles according to any one of [7] to

[10] , in the solvent removal step, while removing the hydrophobic organic solvent encapsulated in the precursor particles, an aqueous medium with a conductivity of 2 μS / cm or less is added to the upper layer (A) and the aqueous medium is discharged from the lower layer (B).

[0025]

[12] According to the method for manufacturing hollow resin particles described in [4], the pressure conditions in the above-mentioned floating separation process are 0.1 to 2.0 MPa using a gauge pressure gauge.

[0026]

[13] In the method for manufacturing hollow resin particles according to any one of [1] to

[12] , the proportion of crosslinking monomer in 100% by mass of the above polymeric monomer is 40% by mass or more and 100% by mass or less.

[0027]

[14] The method for manufacturing hollow resin particles according to any one of [1] to

[13] further comprises a dispersing stabilizer.

[0028] Invention Effects

[0029] According to the present invention, a method for manufacturing hollow resin particles is provided that can suppress foaming during the removal of hydrophobic organic solvents and can manufacture hollow resin particles with high productivity. Detailed Implementation

[0030] The manufacturing method of the present invention is a method for manufacturing hollow resin particles having a shell containing resin and a hollow portion surrounded by the shell. The manufacturing method of the present invention includes the following steps:

[0031] (A) Mixture preparation process: preparing a mixture containing polymerizable monomers, hydrophobic organic solvents, polymerization initiators and aqueous media;

[0032] (B) Suspension process: by suspending the above mixture, a suspension is prepared in which droplets of a polymerizable monomer composition containing the above polymerizable monomer, the above hydrophobic organic solvent and the above polymerization initiator are dispersed in the above aqueous medium.

[0033] (C) Polymerization step, in which the above suspension is fed into a polymerization reaction to prepare a precursor composition containing precursor particles, the precursor particles having a hollow portion and containing the above hydrophobic organic solvent within the hollow portion.

[0034] (D) A flotation separation process, in which the precursor particles in the precursor composition are flotated and separated.

[0035] (E) Solvent removal process: under the condition that the precursor particles are floated and separated, the hydrophobic organic solvent contained in the precursor particles is removed.

[0036] The manufacturing method of the present invention is a method for manufacturing hollow resin particles having a shell (outer shell) containing resin and a hollow portion surrounded by the shell. In the present invention, the hollow portion is a hollow space that is clearly distinguishable from the shell of the hollow resin particle formed of resin material. The shell of the hollow resin particle may be a shell with a porous structure, in which case the hollow portion has a size that is clearly distinguishable from the numerous tiny spaces uniformly dispersed within the porous structure.

[0037] The hollow portion of the hollow resin particles can be confirmed, for example, by SEM observation of the particle cross-section or by TEM observation of the particles directly. Furthermore, the hollow portion of the hollow resin particles is typically filled with a gas such as air. Moreover, the hollow resin particles obtained by the manufacturing method of the present invention are typically hollow resin particles whose shells do not have connecting holes or shell defects, and whose hollow portions are isolated from the outside of the particle through the shell. However, they can also be hollow resin particles whose shells have one or more connecting holes, and whose hollow portions are connected to the outside of the particle through these connecting holes.

[0038] (A) Mixture preparation process

[0039] The mixture preparation step in the manufacturing method of the present invention is a step of preparing a mixture containing a polymerizable monomer, a hydrophobic organic solvent, a polymerization initiator and an aqueous medium.

[0040] [Polymerizable monomers]

[0041] Polymerizable monomers are polymerizable monomers used to form the shell of hollow resin particles. Examples of polymerizable monomers include crosslinked monomers and non-crosslinked monomers. Non-crosslinked monomers are polymerizable monomers having only one polymerizable functional group, while crosslinked monomers are polymerizable monomers having two or more polymerizable functional groups and forming crosslinks in the resin through polymerization. Compounds with olefinic unsaturated bonds as polymerizable functional groups are typically used as polymerizable monomers.

[0042] In this invention, the crosslinking monomer has multiple polymerizable functional groups, thus enabling the monomers to connect with each other and increasing the crosslinking density of the shell, which is therefore preferred. Furthermore, by using the crosslinking monomer in combination with the non-crosslinking monomer, the mechanical properties of the shell of the obtained hollow resin particles can be improved.

[0043] Crosslinking monomers can be classified according to the number of functional groups they can polymerize. Furthermore, crosslinking monomers can be classified into crosslinking monomers containing aromatic groups and crosslinking monomers without aromatic groups. Examples of crosslinking monomers include: divinylbenzene, divinylbiphenyl, divinylnaphthalene, diallyl phthalate, and other bifunctional crosslinking monomers containing aromatic groups; and (meth)acrylates [meaning allyl acrylate and / or allyl methacrylate]. [The same applies below], ethylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, bisphenol A di(meth)acrylate, polyphenylene ether with vinyl-terminated ends, and polyphenylene ether with methacrylic acid-terminated ends, etc., are bifunctional crosslinking monomers without aromatic groups; trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol poly(meth)acrylate, etc., are trifunctional or higher crosslinking monomers. Among these, bifunctional crosslinking monomers containing aromatic groups are preferred, as are bifunctional crosslinking monomers without aromatic groups; more preferably, divinylbenzene, ethylene glycol di(meth)acrylate, and pentaerythritol di(meth)acrylate are preferred; even more preferably, divinylbenzene and ethylene glycol di(meth)acrylate are preferred; and particularly preferably, divinylbenzene and ethylene glycol dimethacrylate are preferred. Furthermore, from the viewpoint of readily obtaining a precursor composition with cohesive properties, crosslinking monomers containing aromatic groups can also be used. These crosslinking monomers can be used individually or in combination of two or more.

[0044] Non-crosslinkable monomers refer to compounds having only one polymerizable functional group. Specifically, examples include monovinyl monomers, and more specifically, examples include hydrophilic and non-hydrophilic monomers. Hydrophilic monomers preferably have a solubility in water of 1% by mass or more, and non-hydrophilic monomers preferably have a solubility in water of less than 1% by mass.

[0045] Examples of hydrophilic monomers include monomers containing acidic groups, hydroxyl groups, amide groups, and polyoxyethylene groups, which are monomers with hydrophilic groups.

[0046] Acid-containing monomers refer to monomers that contain acidic groups. The acidic groups mentioned here also include either proton donor groups (Brønsted acidic groups) or electron pair acceptor groups (Lewis acidic groups). By using acid-containing monomers as hydrophilic monomers, the heat resistance of the resulting hollow resin particles can be further improved.

[0047] There are no particular limitations on monomers containing acidic groups, as long as they have acidic groups. Examples include monomers containing carboxyl groups and monomers containing sulfonic acid groups.

[0048] Examples of carboxyl-containing monomers include: olefinic unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butene tricarboxylic acid; and monoalkyl esters of unsaturated dicarboxylic acids such as monoethyl itaconic acid, monobutyl fumarate, and monobutyl maleate. Among these, acrylic acid, methacrylic acid, and maleic acid are preferred, and acrylic acid and methacrylic acid are more preferred.

[0049] Examples of monomers containing sulfonic acid groups include styrene sulfonic acid.

[0050] Examples of hydroxyl-containing monomers include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate.

[0051] Examples of monomers containing amide groups include acrylamide and dimethylacrylamide.

[0052] Examples of polyoxyethylene monomers include methoxy polyethylene glycol (meth)acrylate.

[0053] Examples of non-hydrophilic monomers include: methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, methoxy polyethylene glycol (meth)acrylate, ethoxy polyethylene glycol (meth)acrylate, propoxy polyethylene glycol (meth)acrylate, butoxy polyethylene glycol (meth)acrylate, hexoxy polyethylene glycol (meth)acrylate, octoxy polyethylene glycol polypropylene glycol (meth)acrylate, lauroxy polyethylene glycol (meth)acrylate, stearoxy polyethylene glycol (meth)acrylate, phenoxy polyethylene glycol polypropylene glycol (meth)acrylate, and polyethylene glycol mono(meth)acrylate. Acrylic monovinyl monomers such as acrylates, polypropylene glycol mono(meth)acrylate, polyethylene glycol propylene glycol mono(meth)acrylate, polyethylene glycol tetramethylene glycol (meth)acrylate, propylene glycol polybutylene glycol mono(meth)acrylate, monoethylene glycol mono(meth)acrylate, 2-aminoethyl(meth)acrylate, etc.; aromatic vinyl monomers such as styrene, ethylvinylbenzene, vinyltoluene, α-methylstyrene, p-methylstyrene, halostyrene, etc.; monoolefin monomers such as ethylene, propylene, butene, etc.; diene monomers such as butadiene, isoprene, etc.; vinyl acetate and other carboxylic acid vinyl ester monomers; halogenated vinyl monomers such as vinyl chloride; vinylidene dihaloethylene monomers such as vinylidene chloride; vinylpyridine monomers, etc.

[0054] Non-crosslinking monomers can be used alone or in combination of two or more.

[0055] The proportion of crosslinking monomers in 100% by mass of the polymerizable monomers is preferably 40% by mass or more and 100% by mass or less, more preferably 50% by mass or more and 100% by mass or less, further preferably 70% by mass or more and 100% by mass or less, and particularly preferably 80% by mass or more and 100% by mass or less. Furthermore, the proportion of non-crosslinking monomers in 100% by mass of the polymerizable monomers is preferably 0% by mass or more and 60% by mass or less, more preferably 0% by mass or more and 50% by mass or less, further preferably 0% by mass or more and 30% by mass or less, and particularly preferably 0% by mass or more and 20% by mass or less. By ensuring the proportion of crosslinking monomers is within the above range, the crosslinking monomer units constitute a sufficiently large proportion of the shell of the hollow resin particles, resulting in a densely distributed covalent network within the shell. Consequently, the particles exhibit excellent strength, are not easily broken, and are not easily deformed by externally applied heat. On the other hand, when the proportion of non-crosslinking monomers is within the above range, it is easier to suppress the formation of interconnecting pores and shell defects in the shell.

[0056] In the mixture preparation step of the manufacturing method of the present invention, the content of polymerizable monomers (total amount of crosslinked monomers and non-crosslinked monomers) in the prepared mixture is not particularly limited. From the viewpoint of balancing the porosity, particle size and mechanical strength of hollow resin particles, it is preferably 15 to 55% by mass, more preferably 25 to 50% by mass, relative to 100% by mass of the total mass of the components in the mixture other than the aqueous medium.

[0057] [Hydrophobic organic solvents]

[0058] In this invention, a hydrophobic organic solvent is used as a non-polymerizable organic solvent that is poorly soluble in water. The hydrophobic organic solvent functions as a spacer material that forms hollow spaces within the particles.

[0059] There are no particular limitations on the use of hydrophobic organic solvents; hydrocarbon solvents are preferred. Specific examples include: saturated hydrocarbon solvents such as pentane, butane, n-hexane, cyclohexane, heptane, and octane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; and highly volatile solvents such as carbon disulfide and carbon tetrachloride. These hydrophobic organic solvents can be used individually or in combination of two or more.

[0060] As a hydrophobic organic solvent, the proportion of saturated hydrocarbon solvent in 100% by mass of the total hydrophobic organic solvent is preferably 50% by mass or more. This allows for sufficient phase separation within the droplets of the polymerizable monomer composition prepared in the suspension process described later, easily yielding hollow resin particles with only one hollow portion, and suppressing the formation of porous particles. From the viewpoint of further suppressing the formation of porous particles and from the viewpoint of easily achieving uniformity of the hollow portions of each hollow resin particle, the proportion of saturated hydrocarbon solvent in 100% by mass of the total hydrophobic organic solvent is preferably 60% by mass or more, more preferably 80% by mass or more.

[0061] Furthermore, as a hydrophobic organic solvent, a hydrocarbon solvent with 5 to 8 carbon atoms is preferred. Hydrocarbon solvents with 5 to 8 carbon atoms are easily encapsulated within the precursor particles during the polymerization process described later, and can be easily removed from the precursor particles during the solvent removal process described later. Among these, hydrocarbon solvents with 6 to 8 carbon atoms are more preferred, and hexane, heptane, and cyclohexane are even more preferred.

[0062] Furthermore, from the viewpoint that hydrophobic organic solvents are easy to remove in the solvent removal process described later, hydrophobic organic solvents with a boiling point of 99°C or less at atmospheric pressure are preferred, and hydrophobic organic solvents with a boiling point of 98°C or less are more preferred. On the other hand, from the viewpoint that they are easy to encapsulate in precursor particles, hydrophobic organic solvents with a boiling point of 30°C or more at atmospheric pressure are preferred.

[0063] Furthermore, in this invention, the hydrophobic organic solvent is a mixed solvent containing multiple hydrophobic organic solvents. When there are multiple boiling points, the boiling point of the hydrophobic organic solvent refers to the boiling point of the solvent with the highest boiling point among the solvents contained in the mixed solvent, that is, the highest boiling point among multiple boiling points.

[0064] Furthermore, the relative permittivity of the hydrophobic organic solvent at 20°C is preferably 3 or less. The relative permittivity is one of the indicators of the polarity of a compound. When the relative permittivity of the hydrophobic organic solvent is sufficiently small to be below 3, it can be considered that phase separation occurs rapidly in the droplets of the polymerizable monomer composition prepared in the suspension process described later, and hollow spaces are easily formed.

[0065] Examples of hydrophobic organic solvents with a relative permittivity of 3 or less at 20°C include pentane (1.8), hexane (1.9), heptane (1.9), octane (1.9), cyclohexane (2.0), benzene (2.3), and toluene (2.4) (the values ​​in parentheses are the relative permittivity values). Regarding the relative permittivity at 20°C, values ​​can be found in well-known literature (e.g., "Basic Handbook of Chemistry," revised 4th edition, edited by the Japanese Chemical Society, Maruzen Co., Ltd., published September 30, 2016, pp. II-498 to II-503), as well as other technical information. Methods for determining the relative permittivity at 20°C include, for example, the relative permittivity test performed based on section 23 of JISC 2101:1999 with the measurement temperature set to 20°C.

[0066] The porosity of hollow resin particles can be adjusted by changing the amount of hydrophobic organic solvent in the mixture. In the polymerization process described later, the polymerization reaction is carried out with the hydrophobic organic solvent encapsulated within droplets of the polymerizable monomer composition. Therefore, there is a tendency that the higher the content of the hydrophobic organic solvent, the higher the porosity of the resulting hollow resin particles.

[0067] Relative to 100 parts by mass of the total polymerizable monomers, the content of hydrophobic organic solvent in the mixture is preferably 50 to 500 parts by mass, more preferably 60 to 400 parts by mass, even more preferably 80 to 350 parts by mass, and particularly preferably 100 to 300 parts by mass. By setting the content of the hydrophobic organic solvent within the above range, the porosity can be appropriately increased while maintaining the strength of the hollow resin particles.

[0068] [Polymerization initiator]

[0069] In this invention, an oil-soluble polymerization initiator is preferably used as the polymerization initiator. By using an oil-soluble polymerization initiator as the polymerization initiator, the polymerization initiator can be appropriately introduced into the interior of the droplets of the polymerizable monomer composition in the suspension obtained in the suspension process described later.

[0070] There are no particular restrictions on oil-soluble polymerization initiators, as long as they are lipophilic polymerization initiators with a solubility of less than 0.2% by mass in water. Examples of oil-soluble polymerization initiators include benzoyl peroxide, lauroyl peroxide, tert-butyl peroxide-2-ethylhexanoate, 2,2'-azobis(2,4-dimethylpentanonitrile), and azobisisobutyronitrile.

[0071] The content of the polymerization initiator relative to 100 parts by mass of the total polymerizable monomers in the mixture is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 2 to 12 parts by mass. By keeping the content of the polymerization initiator within the above range, the polymerization reaction is fully carried out, and the possibility of residual polymerization initiator after the polymerization reaction is completed is small. In addition, the possibility of unexpected side reactions is also small.

[0072] [Aqueous medium]

[0073] As an aqueous medium, media selected from water, hydrophilic solvents, and mixtures of water and hydrophilic solvents can be cited.

[0074] There are no particular limitations on hydrophilic solvents, as long as they are fully mixed with water without phase separation. Examples include alcohols such as methanol and ethanol; tetrahydrofuran (THF); and dimethyl sulfoxide (DMSO). These hydrophilic solvents can be used individually or in combination of two or more.

[0075] In aqueous media, water is preferred due to its polarity. When using a mixture of water and a hydrophilic solvent, from the viewpoint of appropriately forming droplets containing a polymerizable monomer composition comprising a polymerizable monomer, a hydrophobic organic solvent, and a polymerization initiator, it is preferable that the overall polarity of the mixture does not become too low. When using a mixture of water and a hydrophilic solvent, it is preferable that the mixing ratio (mass ratio) of water to hydrophilic solvent is water:hydrophilic solvent = 99:1 to 50:50.

[0076] Furthermore, in the mixture preparation step of the manufacturing method of the present invention, in addition to the polymerizable monomer, hydrophobic organic solvent, polymerization initiator, and aqueous medium, a dispersion stabilizer is preferably used. That is, the mixture preparation step is preferably a step of preparing a mixture containing polymerizable monomer, hydrophobic organic solvent, polymerization initiator, aqueous medium, and dispersion stabilizer. By including a dispersion stabilizer, the dispersion stability of the polymerizable monomer composition droplets in the suspension step described later can be further improved.

[0077] The dispersing stabilizer is a compound used in the suspension process described later to disperse droplets of a polymeric monomer composition in an aqueous medium. It can be any of the inorganic or organic dispersing stabilizers.

[0078] Examples of inorganic dispersing stabilizers include colloidal silica, magnesium hydroxide, calcium phosphate, calcium carbonate, barium sulfate, calcium oxalate, calcium carbonate, magnesium carbonate, barium carbonate, tricalcium phosphate, aluminum hydroxide, magnesium hydroxide, iron hydroxide, hydroxyapatite, diatomaceous earth, clay, and bentonite.

[0079] In addition, examples of organic dispersion stabilizers include methylcellulose, hydroxypropyl methylcellulose, carboxymethylcellulose, and starch.

[0080] Among these, from the viewpoint of high dispersion stabilization effect and easier control of droplet size in polymeric monomer compositions containing polymeric monomers, hydrophobic organic solvents, and polymerization initiators, inorganic dispersion stabilizers are preferred. Among inorganic dispersion stabilizers, metal-containing dispersion stabilizers are preferred, and water-insoluble inorganic metal salts are more preferred. Furthermore, as water-insoluble inorganic metal salts, those with a solubility of 0.5 g or less in 100 g of water are preferred; examples include magnesium hydroxide, calcium hydroxide, barium hydroxide, and calcium phosphate, among which magnesium hydroxide is more preferred. Dispersion stabilizers can be used alone or in combination of two or more.

[0081] Furthermore, from the viewpoint of further improving the dispersion stabilization effect, it is preferable to use the dispersion stabilizer in the form of a dispersion or solution by dispersing or dissolving it in an aqueous medium. That is, in the mixture preparation step of the manufacturing method of the present invention, it is preferable to mix the dispersion stabilizer with the polymerizable monomer, the hydrophobic organic solvent and the polymerization initiator in the form of a dispersion or solution to obtain the mixture.

[0082] Furthermore, the aqueous medium can be selected from water, hydrophilic solvents, and mixtures of water and hydrophilic solvents. As for the hydrophilic solvent, there are no particular restrictions as long as it is a hydrophilic solvent that can be fully mixed with water without phase separation. Examples include alcohols such as methanol and ethanol; tetrahydrofuran (THF); and dimethyl sulfoxide (DMSO).

[0083] In aqueous media, water is preferred due to its polarity. When using a mixture of water and a hydrophilic solvent, from the viewpoint of appropriately forming droplets containing a polymeric monomer composition and a hydrophobic organic solvent, it is preferable that the overall polarity of the mixture does not become too low. When using a mixture of water and a hydrophilic solvent, it is preferable that the mixing ratio (mass ratio) of water to hydrophilic solvent is water:hydrophilic solvent = 99:1 to 50:50.

[0084] When preparing a dispersion or solution of the dispersion stabilizer, the mixing ratio of the dispersion stabilizer to the aqueous medium, measured by weight (dispersion stabilizer: aqueous medium), is preferably 0.7:100 to 7:100, more preferably 1.0:100 to 4.0:100, and even more preferably 1.4:100 to 3:100. By maintaining the mixing ratio of the dispersion stabilizer to the aqueous medium within the above range, the dispersion stabilization effect can be more appropriately improved.

[0085] In the mixture preparation step of the manufacturing method of the present invention, the above-mentioned components can be mixed by stirring or the like to obtain a mixture. At this time, in addition to the above-mentioned components, other materials may be mixed as needed. According to the mixture preparation step of the manufacturing method of the present invention, an oil phase containing polymerizable monomers, hydrophobic organic solvents, and lipophilic materials such as polymerization initiators can be dispersed at a particle size of several millimeters in an aqueous phase containing an aqueous medium and a dispersion stabilizer used as needed, to form a mixture. The dispersion state of these components in the mixture can be observed even with the naked eye, depending on the type of each component.

[0086] Furthermore, in the preparation process of the mixture, from the viewpoint that the composition of the shell portion can be made more uniform, it is preferable to prepare the mixture by pre-preparing an oil phase containing a polymerizable monomer, a hydrophobic organic solvent and a polymerization initiator, and mixing it with a dispersion or solution formed by dispersing or dissolving a dispersion stabilizer in an aqueous medium.

[0087] (B) Suspension Process

[0088] The suspension process is a process of preparing a suspension in an aqueous medium by suspending the mixture obtained in the above-mentioned mixture preparation process, thereby dispersing droplets of a polymeric monomer composition containing polymeric monomers, hydrophobic organic solvents and polymerization initiators.

[0089] The method for suspending droplets used to form polymerizable monomer compositions is not particularly limited, but a method using a stirring device capable of strong stirring to stir the mixture obtained in the above-mentioned mixture preparation step is preferred. As for the stirring device used in the suspension step, there are no particular limitations; for example, a stirring device equipped with stirring blades or a rotor and a supply tank for supplying the mixture to the stirring device can be used. Furthermore, as for the stirring device, any device with stirring blades or a rotor is acceptable; there are no particular limitations. From the viewpoint of efficiently forming a suspension, a stirring device having a combination of a rotor and a stator with comb-shaped concentric rings, rotating the rotor at high speed, causing the dispersion to flow from the inside of the rotor to the outside of the stator, and stirring the dispersion in the gap between the rotor and the stator.

[0090] Examples of mixers with such a structure include inline emulsifying dispersers, such as the "Cavitron" (manufactured by Eurotec Corporation), "Milder" (manufactured by Pacific Machinery Co., Ltd.), "Ebara Milder" (manufactured by Ebara Corporation), "TK Pipeline Homomixer" (manufactured by Special Machinery Industry Co., Ltd.), "Colloid Mill" (manufactured by Kobe Steel PANTECH Co., Ltd.), "Slasher" (manufactured by Nippon Kogyo Co., Ltd.), "Trigonal Wet Micronizer" (manufactured by Mitsui Miike Chemical Machinery Co., Ltd.), and "Fine Flow Mill" (manufactured by Pacific Machinery Co., Ltd.).

[0091] In the suspension step of the manufacturing method of the present invention, a suspension containing droplets of the polymeric monomer composition comprising the aforementioned oleophilic material is uniformly dispersed in an aqueous medium. Such droplets of the polymeric monomer composition are difficult to observe with the naked eye, but can be observed, for example, using a known observation machine such as an optical microscope. Furthermore, during the suspension step, phase separation occurs within the droplets of the polymeric monomer composition, causing the low-polarity hydrophobic organic solvent to accumulate inside the droplets. As a result, the resulting droplet distribution is as follows: the hydrophobic organic solvent is distributed inside, and the material other than the hydrophobic organic solvent is distributed around its periphery.

[0092] (C) Polymerization process

[0093] The polymerization process is a process of preparing a precursor composition containing precursor particles by feeding the suspension prepared in the suspension process above into a polymerization reaction, wherein the precursor particles have a hollow portion and the hollow portion contains a hydrophobic organic solvent.

[0094] In the polymerization process, the polymerizable monomers in a droplet containing a hydrophobic organic solvent polymerize to form precursor particles having a shell and a hollow portion filled with the hydrophobic solvent, wherein the shell contains a resin that is a polymer of the polymerizable monomer.

[0095] In the polymerization process, droplets of the polymerizable monomer composition are supplied to the polymerization reaction while encapsulated in a hydrophobic organic solvent. This facilitates polymerization while maintaining the shape of the precursor particles and allows for easy adjustment of the particle size and porosity. Furthermore, because the polymerizable monomer and the hydrophobic organic solvent are used in combination, the hydrophobic organic solvent has low polarity relative to the shell of the precursor particles, making it less likely to bind to the shell. Therefore, sufficient phase separation easily occurs, resulting in only a hollow core.

[0096] The polymerization method is not particularly limited and can be, for example, batch, semi-continuous, or continuous. The polymerization temperature is preferably 40–90°C, more preferably 50–80°C. Furthermore, the polymerization reaction time is preferably 1–48 hours, more preferably 3–24 hours.

[0097] A precursor composition can be obtained by polymerization process, in which precursor particles containing hydrophobic solvents are dispersed in an aqueous phase with an aqueous medium as the main component.

[0098] An antifoaming agent may be added to the obtained precursor composition. There are no particular limitations on the antifoaming agent; examples include polyether-based antifoaming agents, mineral oil-based antifoaming agents, and alcohol-based antifoaming agents. Water-soluble antifoaming agents such as polyether-based and alcohol-based antifoaming agents are preferred from the perspective of minimizing residue residue in hollow resin particles. Since antifoaming agent residue in hollow resin particles can cause an increase in the dielectric loss tangent of the hollow resin particles, polyether-based antifoaming agents are particularly preferred from the perspective of minimizing the increase in the dielectric loss tangent of the hollow resin particles.

[0099] The amount of defoamer added is not particularly limited. From the viewpoint of further effectively suppressing foaming during the removal of hydrophobic organic solvents, it is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the precursor composition. On the other hand, from the viewpoint of reducing the residual amount of defoamer and suppressing the rise of the dielectric loss tangent of the hollow resin particles, it is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 0.5 parts by mass or less. In addition, defoamer may also be added in the flotation separation process or solvent removal process described later. In this case, the total amount of defoamer added relative to 100 parts by mass of the precursor composition is preferably within the above-mentioned range.

[0100] (D) Flotation Separation Process

[0101] The flotation separation process is a process that separates precursor particles from the precursor composition obtained through the polymerization process by flotation.

[0102] There are no particular limitations on the method for flotating and separating precursor particles in the precursor composition, and examples include: methods for attaching air bubbles to the precursor particles, and methods for adjusting the composition of the mixture used in the mixture preparation process to make the specific gravity of the precursor particles less than that of the aqueous medium. Among these, from the viewpoint of being able to flotate and separate precursor particles with high efficiency, the method of attaching air bubbles to the precursor particles is preferred.

[0103] There are no particular limitations on the method for attaching bubbles to the precursor particles, but a pressurization-depressurization operation is preferred, which involves depressurizing the pressurized conditions after pressurizing the precursor composition. Specifically, in the flotation separation step, the precursor particles are preferably floated by depressurizing the pressurized conditions after pressurizing the precursor composition (pressurization-depressurization operation). This pressurization-depressurization operation can uniformly generate fine bubbles, enabling efficient flotation and separation of the precursor particles. Furthermore, while the reason for generating bubbles through the pressurization-depressurization operation may not be entirely clear, it is presumed that during pressurization in the pressurization-depressurization operation, a portion of the gas in the gas layer inside the container dissolves in the aqueous medium, and during subsequent depressurization, at least a portion of the gas dissolved in the aqueous medium vaporizes.

[0104] When performing pressurization and depressurization operations, the pressure (gauge pressure) during pressurization is preferably 0.1 to 2.0 MPa, more preferably 0.1 to 1.0 MPa. By setting the pressure during pressurization to the lower limit or above, a large number of fine bubbles can be generated uniformly during depressurization, enabling efficient flotation and separation of precursor particles, and further suppressing foaming during the removal of hydrophobic organic solvents in the solvent removal process. On the other hand, by setting the pressure during pressurization to the upper limit or below, excessive foaming caused by pressurization and depressurization operations can be suppressed, allowing for a relatively larger amount of precursor composition supplied to the flotation separation equipment, thereby further improving productivity.

[0105] As a pressurization method, injecting compressed gas into the system is preferred. Examples of compressed gases include air, oxygen, nitrogen, and argon, among which inert gases are preferred, and nitrogen is more preferred.

[0106] The preferred temperature and pressure conditions during pressurization are such that the saturated solubility of the gas in water within the gas layer of the container is in the range of 0.0001 g / 100 g water to 0.01 g / 100 g water. By employing these conditions, a large number of fine bubbles can be generated uniformly during depressurization, enabling the precursor particles to float and separate with high efficiency, and further suppressing foaming during the removal of hydrophobic organic solvents in the solvent removal process.

[0107] The pressurization time is preferably in the range of 1 to 10 minutes.

[0108] When performing pressurization and depressurization operations, the pressure during depressurization is not particularly limited as long as it is lower than the pressure under pressurization conditions (pressure during pressurization). It can be higher than atmospheric pressure or lower than atmospheric pressure. The pressure during depressurization is preferably lower than atmospheric pressure, more preferably lower than 110 kPa in absolute pressure, and even more preferably lower than 105 kPa in absolute pressure. By keeping the pressure during depressurization below the above-mentioned upper limit, a large number of fine bubbles can be generated uniformly during depressurization, enabling efficient flotation and separation of precursor particles, and further suppressing foaming during the removal of hydrophobic organic solvents in the solvent removal process. Furthermore, the lower limit of the pressure during depressurization is not particularly limited; for example, it can be 1 kPa or higher.

[0109] The decompression time is preferably in the range of 1 to 10 minutes.

[0110] During pressurization and depressurization operations, the temperature within the system during heating and depressurization is preferably 20–90°C, more preferably 20–80°C, further preferably 20–70°C, even more preferably 20–60°C, particularly preferably 20–50°C, and most preferably 20–40°C. By keeping the temperature within the system below the above-mentioned upper limits, excessive foaming caused by pressurization and depressurization operations can be suppressed, allowing for a relatively larger amount of the precursor composition supplied to the flotation separation equipment, thereby further improving productivity.

[0111] In the flotation separation process, the pressurization and depressurization operation can be performed only once, or it can be performed multiple times.

[0112] The preferred flotation separation process is as follows: by causing the precursor particles to float, they are separated into an upper layer (A) and a lower layer (B) containing a smaller proportion of precursor particles than the upper layer (A).

[0113] The upper layer (A) is formed above the lower layer (B) and contains a higher proportion of precursor particles than the lower layer (B).

[0114] The upper layer (A) contains precursor particles and an aqueous medium. The volume (V) of the precursor particles in the upper layer (A) is... Ap ) relative to the volume of the aqueous medium (V Aw ) and the volume (V) of the precursor particles Ap The total proportion of [V] Ap / (V Aw +V ApThe concentration of the solvent used is preferably 40% or more, more preferably 45% or more, further preferably 50% or more, particularly preferably 55% or more, and most preferably 60% or more. If the above proportions are within the above ranges, foaming during the removal of hydrophobic organic solvents in the solvent removal process can be further suppressed, and productivity can be further improved. Furthermore, the upper limit of the above proportions is not particularly limited, but is preferably 80% or less. The above proportions can be adjusted by adjusting the flotation separation conditions, such as the pressure / depression operation conditions. In addition, the above proportions can be determined using the methods described in the examples.

[0115] The weight percentage of precursor particles in the overall precursor particles used in the flotation separation process, and the precursor particles contained in the upper layer (A), is preferably 80% by weight or more, more preferably 90% by weight or more. If the weight percentage of precursor particles contained in the upper layer (A) is within the above range, foaming during the removal of hydrophobic organic solvents in the solvent removal process can be further suppressed, and productivity can be further improved. The above percentage can be adjusted by adjusting the flotation separation conditions, such as the pressure / depression operation conditions.

[0116] The upper layer (A) preferably also contains gas. The upper layer (A) is preferably a layer of foam containing precursor particles, an aqueous medium and gas.

[0117] The upper layer (A) preferably contains 0.1 to 70 parts by volume of gas relative to 100 parts by volume of precursor particles in the upper layer (A), more preferably 10 to 70 parts by volume of gas, and even more preferably 20 to 70 parts by volume of gas. If the amount of gas in the upper layer (A) is within the above range, the amount of precursor composition supplied to the flotation separation equipment can be relatively increased, and foaming during the removal of hydrophobic organic solvents in the solvent removal process can be further suppressed, thereby further improving productivity. The amount of gas in the upper layer (A) can be adjusted by adjusting the flotation separation conditions, such as the pressure / depression operation conditions. Furthermore, the amount of gas in the upper layer (A) can be measured according to the method described in the examples.

[0118] The lower layer (B) is formed below the upper layer (A) and contains a smaller proportion of precursor particles than the upper layer (A).

[0119] The lower layer (B) contains an aqueous medium. The lower layer (B) may also contain precursor particles. The volume (V) of the precursor particles in the lower layer (B) is... Bp ) relative to the volume of the aqueous medium (V Bw ) and the volume (V) of the precursor particles Bp The total proportion of [V] Bp / (V Bw +V BpThe content is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. The above proportion can be adjusted by adjusting the floating separation conditions, such as the pressure / depression operation conditions. Furthermore, the above proportion can be determined by the method described in the examples.

[0120] The weight percentage of precursor particles in the lower layer (B) of the total precursor particles used in the flotation separation process is preferably 20% by weight or less, more preferably 10% by weight or less. If the weight percentage of precursor particles in the lower layer (B) is within the above range, foaming during the removal of hydrophobic organic solvents in the solvent removal process can be further suppressed, and productivity can be further improved. The above percentage can be adjusted by adjusting the flotation separation conditions, such as the pressure / depression operation conditions.

[0121] The lower layer (B) is generally not substantially gas-free. The gas content of the lower layer (B) is usually less than 0.1 parts by volume per 100 parts by volume.

[0122] After separation, a boundary layer (C) can form between the upper layer (A) and the lower layer (B). The boundary layer (C) is the volume (V) of the precursor particles within it. Cp ) relative to the volume of the aqueous medium (V Cw ) and the volume (V) of the precursor particles Cp The total proportion of [V] Cp / (V Cw +V Cp Layers with a percentage greater than 20% and less than 40%.

[0123] Through the flotation separation process, the precursor composition is preferably separated into two or three layers consisting of an upper layer (A), a lower layer (B), and a boundary layer (C) formed as appropriate.

[0124] The volume percentage of the upper layer (A) in the precursor composition after flotation separation is preferably 60% by volume or less, more preferably 20% to 60% by volume, and even more preferably 40% to 60% by volume. If the volume percentage of the upper layer (A) is below the above-mentioned upper limit, the amount of precursor composition supplied to the flotation separation equipment can be relatively increased, thereby further improving productivity.

[0125] The volume ratio of the lower layer (B) in the precursor composition after flotation separation is preferably 39% by volume or more, more preferably 39 to 80% by volume, and even more preferably 39 to 60% by volume. If the volume ratio of the lower layer (B) is above the above lower limit, the amount of precursor composition supplied to the flotation separation equipment can be relatively increased, thereby further improving productivity.

[0126] The total volume ratio of the upper layer (A) and the lower layer (B) in the precursor composition after flotation separation is preferably 95% by volume or more, more preferably 97% by volume or more. If the above volume ratio is within the above range, foaming during the removal of hydrophobic organic solvents in the solvent removal process can be further suppressed, and productivity can be further improved.

[0127] The volume percentage of the boundary layer (C) in the precursor composition after flotation separation is preferably 5% by volume or less, more preferably 3% by volume or less. If the volume percentage of the boundary layer (C) is within the above range, foaming during the removal of hydrophobic organic solvents in the solvent removal process can be further suppressed, and productivity can be further improved.

[0128] The volume ratio of the upper layer (A), lower layer (B), and boundary layer (C) in the precursor composition after flotation separation can be adjusted by regulating the flotation separation conditions, such as the pressure / decompression operation. Furthermore, the aforementioned ratio can be determined using the methods described in the examples.

[0129] The average specific gravity (D) of the upper layer (A) A The average specific gravity (D) relative to the lower layer (B) B The proportion of ) [D A / D B The ratio is typically less than 1, preferably greater than 0.3 and less than 0.97, more preferably greater than 0.3 and less than 0.80, and even more preferably greater than 0.3 and less than 0.67. If the above ratio is within the above range, foaming during the removal of hydrophobic organic solvents in the solvent removal process can be further suppressed, and productivity can be further improved. The above ratio can be adjusted by adjusting the flotation separation conditions, such as the pressure / depression operation conditions. Furthermore, the above ratio can be determined using the method described in the examples.

[0130] Defoamers may also be added to the precursor composition after flotation separation. The defoamer may be added to any of the upper layer (A), lower layer (B), and boundary layer (C), preferably at least to the upper layer (A). Furthermore, the method of addition is not particularly limited, but it is preferable to spray the defoamer, diluted as needed, from the top of the upper layer (A).

[0131] There are no particular limitations on defoamers, and examples include polyether-based defoamers, mineral oil-based defoamers, and alcohol-based defoamers. Among these, water-soluble defoamers such as polyether-based and alcohol-based defoamers are preferred from the perspective of minimizing residue residue in hollow resin particles. Since defoamer residue in hollow resin particles can cause an increase in the dielectric loss tangent of the particles, polyether-based defoamers are particularly preferred from the perspective of minimizing the increase in the dielectric loss tangent of the hollow resin particles.

[0132] The amount of defoamer added is not particularly limited. From the viewpoint of further effectively suppressing foaming during the removal of hydrophobic organic solvents, it is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the precursor composition before flotation separation. On the other hand, from the viewpoint of reducing the residual amount of defoamer and suppressing the rise of the dielectric loss tangent of the hollow resin particles, it is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 0.5 parts by mass or less. In addition, the defoamer may be added in the polymerization step described above or the solvent removal step described later. In this case, the total amount of defoamer added relative to 100 parts by mass of the precursor composition before flotation separation is preferably within the above range.

[0133] (E) Solvent Removal Process

[0134] The solvent removal process is a process of removing the hydrophobic organic solvent contained within the precursor particles while they are floating and separated. The manufacturing method of the present invention is a method for removing solvent from precursor particles that have floated and separated during the flotation separation process while maintaining the precursor particles in a floating and separated state.

[0135] The manufacturing method of the present invention, by including such a solvent removal step, can suppress foaming during the removal of hydrophobic organic solvents, thereby enabling a relatively increased amount of hollow resin particles supplied to the solvent removal equipment, or allowing the use of removal conditions that promote the removal of hydrophobic organic solvents. As a result, according to the manufacturing method of the present invention, hollow resin particles can be manufactured with high productivity. Furthermore, according to the manufacturing method of the present invention, breakage of hollow resin particles during the removal of hydrophobic organic solvents can be prevented.

[0136] In the solvent removal process, there is no particular limitation on the method for removing the hydrophobic organic solvent contained in the precursor particles, but it is preferable to replace the hydrophobic organic solvent contained in the precursor particles with gas by heating the precursor particles.

[0137] The preferred heating temperature in the solvent removal process is higher than the boiling point of the hydrophobic organic solvent under the pressure environment of the solvent removal process, and higher than the boiling point of the aqueous medium under the same pressure (T). b The temperature should be lower than that of the aqueous medium. Furthermore, the boiling point of hydrophobic organic solvents is generally lower than that of aqueous media. The heating temperature in the solvent removal process is preferably lower than the boiling point (T0) of the aqueous medium under the pressure environment of the solvent removal process. b The temperature range is 1°C to 50°C lower, more preferably 2°C to 35°C lower, and even more preferably 5°C to 20°C lower. By keeping the heating temperature in the solvent removal process within the above range, foaming during the removal of hydrophobic organic solvents can be further suppressed, and productivity can be further improved.

[0138] The pressure in the solvent removal process can be any of atmospheric pressure, pressurized pressure, or depressurized pressure. It is particularly preferred to remove the hydrophobic organic solvent encapsulated within the precursor particles under pressure during the solvent removal process. The pressurization condition, measured using a gauge pressure gauge, is preferably 0.1–2.0 MPa, more preferably 0.3–1.5 MPa, and even more preferably 0.7–1.0 MPa. By maintaining the pressure in the solvent removal process within the above range, foaming during the removal of hydrophobic organic solvents can be further suppressed, thereby further improving productivity.

[0139] The heating time in the solvent removal process can be determined based on the removal level of the target hydrophobic organic solvent. The removal level of the target hydrophobic organic solvent can be, for example, a level where the amount of hydrophobic organic solvent in the hollow resin particles is 0.01 g / g or less. Furthermore, the removal level of the target residual monomer can be, for example, a level where the amount of residual monomer in the hollow resin particles is 0.001 g / g or less. The heating time for such a removal level is typically around 10 to 60 hours. Additionally, the amounts of hydrophobic organic solvent and residual monomer in the hollow resin particles can be determined according to the method described in the examples.

[0140] In the solvent removal process, it is preferable to remove the hydrophobic organic solvent encapsulated within the precursor particles under a gas stream. Specifically, it is preferable to perform gas injection and gas discharge in the upper gas phase of the precursor composition after flotation separation. Removing the hydrophobic organic solvent under a gas stream can promote the removal of the hydrophobic organic solvent and further improve productivity.

[0141] When removing hydrophobic organic solvents under a gas stream, inert gases such as nitrogen or argon are preferred. Using inert gases improves the electrical insulation properties of the resulting hollow resin particles.

[0142] When removing hydrophobic organic solvents under a gas stream, the gas flow rate is preferably determined based on the volume (V0) of the precursor composition before flotation separation. The gas flow rate is preferably at least 0.5 times (0.5V0 / min or more) the volume (V0) of the precursor composition before flotation separation per minute, and more preferably at least 1.0 times (V0 / min or more) the volume (V0) per minute. By keeping the gas flow rate within the above range, the removal of hydrophobic organic solvents can be promoted, and productivity can be further improved.

[0143] In the solvent removal process, when removing the hydrophobic organic solvent encapsulated within the precursor particles, it is preferable to perform a cleaning operation in which an aqueous medium with a conductivity of 2 μS / cm or less is added to the upper layer (A) while the aqueous medium is discharged from the lower layer (B). By performing such a cleaning operation, the residual metal content of the obtained hollow resin particles can be reduced, and the electrical insulation can be improved.

[0144] Furthermore, in the manufacturing method of the present invention, the cleaning operation described above is omitted; instead, the hollow resin particles are cleaned in a cleaning step following the solvent removal step. This reduces the residual metal content of the obtained hollow resin particles and improves electrical insulation. On the other hand, by performing the cleaning operation described above in the solvent removal step of the manufacturing method of the present invention, even if the cleaning time in the cleaning step following the solvent removal step is shortened or the cleaning step following the solvent removal step is omitted, the residual metal content of the obtained hollow resin particles can be reduced, and electrical insulation can be improved. In other words, by performing the cleaning operation described above in the solvent removal step of the manufacturing method of the present invention, hollow resin particles with low residual metal content and excellent electrical insulation can be manufactured with very high productivity.

[0145] In the cleaning operation, an aqueous medium (hereinafter sometimes referred to as cleaning water) with a conductivity of 2 μS / cm or less is used as the cleaning water. There is no particular limitation on the conductivity of the cleaning water as long as it is 2 μS / cm or less, but 1 μS / cm or less is preferred. By keeping the conductivity of the cleaning water within the above range, the cleaning efficiency can be improved. The temperature of the cleaning water is preferably within the above-mentioned temperature range, which is also the heating temperature in the solvent removal process, and more preferably the same as the heating temperature in the solvent removal process.

[0146] There are no particular limitations on the method of adding cleaning water to the upper layer (A), but it is preferable to add the cleaning water from the top of the upper layer (A). The cleaning water added from the top of the upper layer (A) moves through the upper layer (A) to the lower layer (B). At this time, by dispersing or dissolving the metal components in the upper layer (A) in the cleaning water moving in the upper layer (A), the metal components can be removed from the upper layer (A) with high efficiency. As a result, hollow resin particles with low residual metal content and excellent electrical insulation properties can be manufactured with very high productivity.

[0147] The addition of cleaning water is preferably performed by spraying. Adding cleaning water by spraying effectively maintains the state in which the precursor particles float and separate. As a result, foaming during the removal of hydrophobic organic solvents is suppressed while increasing the contact frequency between the particles and the cleaning water, thereby improving cleaning efficiency.

[0148] As a method for discharging the aqueous medium from the lower layer (B), it is preferable to discharge the clarified liquid from the bottom of the container where the precursor composition has been added.

[0149] The operation of adding cleaning water to the upper layer (A) and the operation of draining the water medium from the lower layer (B) can be performed once, multiple times, or continuously.

[0150] In the solvent removal process, it is preferable to continuously or intermittently add cleaning water to the upper layer (A) and discharge the aqueous medium from the lower layer (B) for at least a portion of the time during the removal of the hydrophobic organic solvent encapsulated in the precursor particles. It is preferable to continuously or intermittently perform this operation throughout the entire period of removing the hydrophobic organic solvent encapsulated in the precursor particles.

[0151] In this case, it is preferable that the amount of cleaning water added to the upper layer (A) per unit time is approximately equal to the amount of aqueous medium discharged from the lower layer (B). Here, the amount of cleaning water added to the upper layer (A) and the amount of aqueous medium discharged from the lower layer (B) per unit time are preferably determined based on the volume (V0) of the precursor composition before flotation separation. These amounts are preferably 0.01 to 2.00 times (0.01V0 / h to 2.00V0 / h) of the volume (V0) of the precursor composition before flotation separation per hour, and more preferably 0.5 to 1.5 times (0.5V0 / h to 1.5V0 / h) of the volume (V0) of the precursor composition before flotation separation per hour.

[0152] Defoamers can also be added to the system during the solvent removal process. The defoamer can be added to any of the upper layer (A), lower layer (B), and boundary layer (C), preferably at least to the upper layer (A). Furthermore, the method of addition is not particularly limited; the defoamer, diluted as needed, can be sprayed from the top of the upper layer (A). Additionally, when performing the above-described cleaning operation, the defoamer can also be added together with the cleaning water.

[0153] As a defoamer, the same defoamer that can be used in the flotation separation process can be cited, and the preferred defoamer is also the same. The amount of defoamer added is not particularly limited, but from the viewpoint of further effectively suppressing foaming during the removal of hydrophobic organic solvents, it is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the precursor composition before flotation separation. On the other hand, from the viewpoint of reducing the residual amount of defoamer and suppressing the rise of the dielectric loss tangent of the hollow resin particles, it is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 0.5 parts by mass or less. Furthermore, a defoamer may also be added in the above-mentioned polymerization process or solvent removal process. In this case, the total amount of defoamer added relative to 100 parts by mass of the precursor composition before flotation separation is preferably within the above-mentioned range.

[0154] (F) Other processes

[0155] The manufacturing method of the present invention may also include other steps besides the above-described mixture preparation step, suspension step, polymerization step, flotation separation step and solvent removal step.

[0156] (F-1) Cleaning process

[0157] The manufacturing method of the present invention preferably further includes a cleaning step. The cleaning step is a process of cleaning the hollow resin particles obtained in the solvent removal step, from which the hydrophobic organic solvent encapsulated within the precursor particles has been removed. By including the cleaning step in the manufacturing method of the present invention, the residual metal content of the obtained hollow resin particles can be reduced, thereby improving electrical insulation.

[0158] When using a dispersant stabilizer, it is preferable to use an acid or alkali in the cleaning process to remove any residual dispersant stabilizer. When the dispersant stabilizer used is acid-soluble, it is preferable to use an acid-washing solvent to remove the hollow resin particles obtained in the process. Conversely, when the dispersant stabilizer used is alkali-soluble, it is preferable to use an alkaline-washing solvent to remove the hollow resin particles obtained in the process.

[0159] For example, when using an acid-soluble dispersion stabilizer, it is preferable to add acid to the system containing hollow resin particles and an aqueous medium to adjust the pH to 6.5 or lower, more preferably 6 or lower, for cleaning. As the added acid, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, as well as organic acids such as formic acid and acetic acid, can be used. Sulfuric acid is particularly preferred due to its high removal efficiency of the dispersion stabilizer and low burden on manufacturing equipment.

[0160] In the cleaning process, it is preferable to clean the hollow resin particles obtained in the solvent removal process with cleaning water. As the cleaning water, it is preferable to use the same cleaning water used in the cleaning operation during the solvent removal process. Furthermore, if cleaning with the aforementioned acid or alkali is performed, it is preferable to subsequently clean the hollow resin particles obtained in the solvent removal process with cleaning water. By cleaning the hollow resin particles with cleaning water, the residual metal content of the obtained hollow resin particles can be reduced, and the electrical insulation can be improved.

[0161] In the cleaning process, solid-liquid separation is preferably performed to separate and recover the cleaned hollow resin particles obtained in the cleaning process from the aqueous medium. Examples of solid-liquid separation methods include centrifugation, filtration, and settling, with centrifugation and filtration being preferred.

[0162] Furthermore, the hollow resin particles recovered through solid-liquid separation can be further washed with cleaning water. By repeatedly performing cleaning with cleaning water and solid-liquid separation in this way, the residual metal content of the obtained hollow resin particles can be reduced, and the electrical insulation can be improved. Cleaning with cleaning water and solid-liquid separation can be repeated until the conductivity of the aqueous medium removed during solid-liquid separation (the filtrate in the case of solid-liquid separation by filtration) becomes, for example, below 10 μS / cm.

[0163] Furthermore, in the absence of a cleaning step in the manufacturing method of the present invention, solid-liquid separation is preferably performed in order to separate and recover the hollow resin particles obtained in the solvent removal step from the aqueous medium.

[0164] (F-2) Drying process

[0165] The manufacturing method of the present invention preferably further includes a drying step. The drying step is a process of drying the hollow resin particles obtained in the solvent removal step above, after removing the hydrophobic organic solvent encapsulating the precursor particles. Alternatively, when the manufacturing method of the present invention includes the cleaning step above, the drying step may also be a process of drying the cleaned hollow resin particles recovered in the cleaning step.

[0166] As a drying method, there are no particular limitations as long as the method can remove the aqueous medium. Examples of drying methods include vacuum drying, heating drying, airflow drying, and combinations thereof.

[0167] As for the drying conditions when using the heat drying method, there are no particular limitations as long as the aqueous medium can be removed. The drying temperature is not particularly limited, but is preferably 50–250°C, more preferably 75–220°C, and even more preferably 100–200°C. The drying time is not particularly limited, but is preferably 1–48 hours, more preferably 3–24 hours. Furthermore, the drying environment is not particularly limited and can be appropriately selected according to the intended use of the hollow resin particles. Examples of suitable drying environments include air, oxygen, nitrogen, and argon.

[0168] (F-3) Hollow section re-replacement process

[0169] The hollow section re-displacement process involves replacing the gas or liquid inside the hollow resin particles with other gases or liquids. This displacement alters the internal environment of the hollow resin particles, allows for the selective encapsulation of molecules within the particles, or enables the modification of the internal chemical structure of the particles to suit specific applications.

[0170] Hollow resin particles

[0171] The shape of the hollow resin particles obtained by the manufacturing method of the present invention is not particularly limited as long as a hollow portion is formed inside. The external shape of the hollow resin particles is not particularly limited, but a spherical shape is preferred from the perspective of ease of manufacturing. Furthermore, the hollow resin particles obtained by the manufacturing method of the present invention may have one or more hollow portions, but to maintain a good balance between high porosity and mechanical strength, it is preferable to have only one hollow portion. Additionally, the shell of the hollow resin particles, and the barrier walls separating adjacent hollow portions in the case of two or more hollow portions, can be porous. The average sphericity of the hollow resin particles obtained by the manufacturing method of the present invention is preferably 0.950 to 0.995.

[0172] Furthermore, the morphology of the hollow resin particles can be confirmed by observing the particles, for example, using SEM or TEM. Additionally, the internal shape of the hollow resin particles can be confirmed by, for example, SEM observation of the particle cross-section or TEM observation of the particles.

[0173] The volume average particle size (Dv) of the hollow resin particles obtained by the manufacturing method of the present invention is preferably 1 to 50 μm, more preferably 2 to 50 μm, and even more preferably 3 to 50 μm. Furthermore, the particle size distribution (volume average particle size (Dv) / number average particle size (Dp)) is preferably 1.05 to 2.0, more preferably 1.05 to 1.5, and even more preferably 1.05 to 1.3. The volume average particle size (Dv) and number average particle size (Dp) of the hollow resin particles can be determined, for example, by using a laser diffraction particle size distribution measuring device to measure the particle size of the hollow resin particles, calculating their number average and volume average respectively, and using the obtained values ​​as the number average particle size (Dp) and volume average particle size (Dv) of the particle. The particle size distribution is the value obtained by dividing the volume average particle size by the number average particle size.

[0174] Furthermore, the porosity of the hollow resin particles obtained by the manufacturing method of the present invention is preferably 50% or more, more preferably 50-95%, and even more preferably 55-90%. By maintaining the porosity within the above range, the hollow resin particles can be made into hollow resin particles with excellent lightweight, heat resistance, and thermal insulation properties. In addition, the porosity (%) of the hollow resin particles can be calculated based on the apparent density D1 and true density D0 of the hollow resin particles using the following formula. In other words, the porosity of the hollow resin particles can be considered as the proportion of the hollow portion in the specific gravity of the hollow resin particles.

[0175]

[0176] As for the uses of the hollow resin particles obtained by the manufacturing method of the present invention, examples include their use as additives in various fields such as automobiles, electrical, electronics, construction, aviation, and aerospace, as well as in components such as low dielectrics, heat insulation materials, sound insulation materials, and reflective materials; food containers; shoes such as sports shoes and slippers; household appliance parts; automobile parts; stationery; and tools.

[0177] In particular, in the manufacturing method of the present invention, when one or both of the cleaning operation and the cleaning process in the solvent removal step described above are performed, the amount of residual metal is reduced, and hollow resin particles with excellent electrical insulation properties can be manufactured with high productivity. The hollow resin particles thus obtained can preferably be used as additives in the electrical or electronic fields to achieve low transmission loss. For example, such hollow resin particles are preferably used as electronic circuit board materials; specifically, by containing hollow resin particles in the insulating resin layer of the electronic circuit board, the transmission loss of the electronic circuit board can be reduced.

[0178] Furthermore, the hollow resin particles obtained by the manufacturing method of the present invention are also preferably used as additives in semiconductor materials such as interlayer insulating materials, dry film resists, solder resists, bonding wires, bonding sheets, magnetwires, semiconductor sealing materials, epoxy sealing materials, molded underfill, underfill, die bond paste, buffer coats, copper-clad laminates, flexible substrates, high-frequency device modules, antenna modules, and automotive radar. Among these, they are particularly preferred as additives in semiconductor materials such as interlayer insulating materials, solder resists, bonding sheets, magnetwires, epoxy sealing materials, underfill, buffer coats, copper-clad laminates, flexible substrates, high-frequency device modules, antenna modules, and automotive radar. Additionally, a bonding sheet refers to an insulating adhesive layer forming material used to bond conductor layers to organic insulating layers in the manufacture of multilayer printed wiring substrates.

[0179] Furthermore, the hollow resin particles obtained by the manufacturing method of the present invention, when added to molded articles, exhibit excellent performance as lightweight materials, heat insulation materials, sound insulation materials, shock-absorbing materials, light diffusing agents, etc., and are therefore preferably used as additives for molded articles. For example, they can be used as additives for resin molded articles. In addition, they can also be contained as fillers in fiber-reinforced molded articles formed using resin and reinforcing fibers. Moreover, when the hollow resin particles obtained by the manufacturing method of the present invention are used as light diffusing agents, they are preferably used as additives for light diffusing materials such as light diffusing films or light diffusing plates.

[0180] Furthermore, the hollow resin particles obtained by the manufacturing method of the present invention have high porosity, are not easily broken, and have excellent heat resistance, thus meeting the requirements for heat insulation and cushioning properties of primer materials, as well as the heat resistance required for thermal paper applications. In addition, the hollow resin particles obtained by the manufacturing method of the present invention are also useful as plastic pigments with excellent gloss and hiding power.

[0181] Furthermore, the hollow resin particles obtained by the manufacturing method of the present invention can be encapsulated with useful components such as fragrances, pharmaceuticals, pesticides, and ink components through impregnation treatment, depressurization or pressurization impregnation treatment, etc., and can therefore be used for various purposes depending on the components contained inside.

[0182] The hollow resin particles obtained by the manufacturing method of the present invention are also preferably used as rust inhibitors. Since the hollow resin particles obtained by the manufacturing method of the present invention are also useful as additives that reduce electrical conductivity, coatings containing, for example, the hollow resin particles obtained by the manufacturing method of the present invention can be used as rust-preventive coatings (coating substrates, lubricating coatings, etc.) to improve the corrosion resistance and rust prevention of steel and other materials. Furthermore, rust-preventive additives can also be encapsulated within the hollow resin particles added to rust-preventive coatings.

[0183] The hollow resin particles obtained by the manufacturing method of the present invention can be mixed with resin and rubber to form resin compositions and rubber compositions.

[0184] The resin composition can be a liquid resin composition or a resin molded body. Examples of liquid resin compositions include, for example, a liquid resin composition comprising a liquid base resin before curing, a liquid resin composition formed by dissolving or dispersing the components in a solvent, or a liquid resin composition in which the base resin is a thermoplastic resin and the resin composition is liquefied by melting the resin. Examples of resin molded bodies include, for example, resin molded bodies formed from such liquid resin compositions using known methods.

[0185] The matrix resin contained in the resin composition is not particularly limited and can be, for example, a thermosetting resin or a thermoplastic resin. Furthermore, the resin contained in the resin composition can be an unreacted monomer, prepolymer, or macromonomer, or a polymer, or a precursor to a cured resin such as polyamic acid. The matrix resin contained in the resin composition can also be a matrix resin containing a thermoplastic elastomer as a resin. Furthermore, the resin composition can also be a resin composition containing rubber.

[0186] As a thermosetting resin, any known thermosetting resin can be used without particular limitation, such as phenolic resins, melamine resins, urea resins, unsaturated polyester resins, epoxy resins, polyurethane resins, silicone resins, alkyd resins, thermosetting modified polyphenylene ether resins, thermosetting polyimide resins, benzoxazine resins, urea-formaldehyde resins, allyl resins, aniline resins, maleimide resins, bismaleimide triazine resins, liquid crystal polyester resins, vinyl ester resins, unsaturated polyester resins, cyanate ester resins, and polyetherimide resins. These thermosetting resins can be used individually or in combination of two or more.

[0187] As a thermoplastic resin, any known thermoplastic resin can be used without particular limitation, such as: polyolefins such as polypropylene and polyethylene; polyamides such as PA6, PA66, and PA12; polyimide, polyamide-imide, polyether-imide, polyetherketone-ketone, polyvinyl chloride, polystyrene, poly(meth)acrylate, polycarbonate, polyvinylidene fluoride, acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene copolymer (AS), polyphenylene ether, polyphenylene sulfide, polyester, polytetrafluoroethylene, thermoplastic elastomers, etc. These thermoplastic resins can be used alone or in combination of two or more.

[0188] In applications requiring low dielectric constants or low dielectric loss tangents, insulating resins such as epoxy resins, thermosetting modified polyphenylene ether resins, thermosetting polyimide resins, silicone resins, benzoxazine resins, melamine resins, urea-formaldehyde resins, allyl resins, phenolic resins, unsaturated polyester resins, polyurethane resins, and aniline resins are preferred. Epoxy resins, thermosetting polyimide resins, modified polyphenylene ether resins, silicone resins, benzoxazine resins, and melamine resins are particularly preferred. These insulating resins can be used individually or in combination of two or more.

[0189] As thermoplastic elastomers, thermoplastic elastomers that have traditionally been used as molding resins can be used, such as polyurethane-based elastomers, styrene-based elastomers, olefin-based elastomers, amide-based elastomers, and ester-based elastomers. Thermoplastic elastomers are materials that typically exhibit rubber-like elasticity at room temperature (25°C) and can be plasticized and molded at high temperatures. Thermoplastic elastomers can be used alone or in combination of two or more types.

[0190] The matrix rubber and resin composition contained in a rubber composition are not particularly limited in their types of rubber, but examples include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and ethylene-propylene-diene terpolymer (EPDM). Rubber can be used alone or in combination with two or more types.

[0191] The resin content in 100% by mass of the total solids of the resin composition is not particularly limited, but is preferably 50% to 95% by mass or less. If the resin content is within the above range, the effects of low dielectric loss tangent based on hollow resin particles can be fully utilized, while the moldability of the resin composition and the mechanical strength of the resulting molded article are also excellent.

[0192] The rubber content in 100% by mass of the total solids of the rubber composition is not particularly limited, but is preferably 50% to 95% by mass or less. If the rubber content is within the above range, the effects of low dielectric loss tangent based on hollow resin particles can be fully utilized, while the moldability and rubber elasticity of the rubber composition are also excellent.

[0193] Depending on the type of resin or rubber, the resin composition or rubber composition may further contain additives such as curing agents, curing catalysts, or initiators to carry out the curing reaction. Examples of curing agents include amines, acid anhydrides, imidazoles, thiols, phenols, naphthols, benzoxazines, cyanate esters, and carbodiimides. The content of the curing agent is not particularly limited; for example, it may be 5 to 120 parts by weight relative to 100 parts by weight of the resin or rubber.

[0194] The content of hollow resin particles obtained by the manufacturing method of the present invention in the resin composition or rubber composition is not particularly limited, but is preferably 5 to 50% by mass. If the content of hollow resin particles is within the above range, the effects of low dielectric loss tangent based on hollow resin particles can be fully utilized, and the moldability of the composition and the mechanical properties of the resulting molded article are also excellent.

[0195] Without impairing the effects of the present invention, the resin composition and rubber composition may further contain, as needed, additives such as compatibilizers, ultraviolet absorbers, colorants, heat stabilizers, and fillers, as well as solvents. Furthermore, the resin composition may further contain organic or inorganic fibers such as carbon fibers, glass fibers, aramid fibers, and polyethylene fibers.

[0196] The resin composition and rubber composition can be obtained, for example, by mixing hollow resin particles, resin, rubber, and additives and solvents as needed, obtained by the manufacturing method of the present invention. For example, if the resin in the resin composition is a thermoplastic resin, it can also be mixed by adding hollow resin particles and additives as needed to molten thermoplastic resin and then melting and kneading them. Furthermore, the resin composition can be, for example, a liquid resin composition, or a resin molded body formed by molding a liquid resin composition using known methods.

[0197] There is no particular limitation on the method of manufacturing the resin composition from the liquid resin composition. For example, the resin molded body can be obtained by applying a liquid resin composition containing hollow resin particles in a liquid matrix resin before the curing reaction, or by dissolving or dispersing the components in a solvent, to a support, and then drying and curing as needed.

[0198] Examples of materials that can be used as the support structure include resins such as polyethylene terephthalate and polyethylene naphthalate; and metals such as copper, aluminum, nickel, chromium, gold, and silver. These supports can also be supports with a surface coated with a release agent.

[0199] As a method for applying liquid resin compositions, known methods can be used, such as dip coating, roller coating, curtain coating, mold coating, slot coating, gravure coating, etc.

[0200] Furthermore, a resin molded article can also be obtained by impregnating a substrate with a liquid resin composition and then drying and curing it as needed. Examples of substrates include inorganic fibers such as carbon fiber, glass fiber, metal fiber, and ceramic fiber; and organic synthetic fibers such as polyamide fiber, polyester fiber, polyolefin fiber, and Novoloid phenolic fiber, with glass fiber (glass cloth) being particularly preferred. Furthermore, the form of the substrate is not limited, and woven fabrics, nonwoven fabrics, etc., can be used.

[0201] When the liquid resin composition contains a solvent, it is preferable to dry the resin composition after the above-mentioned coating or impregnation. The drying temperature is preferably a temperature at which the base resin does not cure, typically 20°C or higher and 200°C or lower, preferably 30°C or higher and 150°C or lower. Furthermore, the drying time is typically 30 seconds or higher and 1 hour or lower, preferably 1 minute or higher and 30 minutes or lower.

[0202] The curing reaction of the resin composition is carried out by a method corresponding to the type of resin, and is not particularly limited. When the resin is included and cured by heating, the heating temperature used for the curing reaction can be appropriately adjusted according to the type of resin, and is not particularly limited, but is generally 30°C or higher and 400°C or lower, preferably 70°C or higher and 300°C or lower, more preferably 100°C or higher and 200°C or lower. Furthermore, the curing time is preferably 5 minutes or more and 5 hours or less, preferably 30 minutes or more and 3 hours or less. The heating method is not particularly limited; for example, an electric oven can be used.

[0203] In addition, the liquid resin before the curing reaction, as well as the resin dissolved or dispersed in the solvent, can be either a thermosetting resin or a thermoplastic resin.

[0204] Alternatively, the resin molded body can be obtained by molding a liquid resin composition containing a thermoplastic resin as the resin and the resin being melted into the desired shape using known molding methods such as extrusion molding, injection molding, compression molding, etc.

[0205] The shape of the resin molded article is not particularly limited, and it can be made into various moldable shapes, such as sheets, films, plates, tubes, and other three-dimensional shapes. Furthermore, when the resin molded article contains fibers, the fibers can be in the form of non-woven fabric. Additionally, when the resin molded article contains fibers, it can also be a molded article made by adding hollow resin particles obtained by the manufacturing method of the present invention to a fiber-reinforced plastic containing the aforementioned resin and fibers.

[0206] Examples of uses for resin compositions and rubber compositions include, for instance, the use of hollow resin particles obtained by the manufacturing method of the present invention described above, where the resin composition and rubber composition can be used.

[0207] Example

[0208] The present invention is further illustrated by the following examples and comparative examples, but the invention is not limited to these examples. Furthermore, unless otherwise specified, "parts" and "%" are weight-based. Various measurements are performed according to the following methods.

[0209] <Method for collecting samples from the upper (A) and lower (B) layers after flotation separation>

[0210] Before the flotation separation, a preliminary test was conducted to estimate the height of the lower layer (B) after flotation separation. In the preliminary test, a small sample was collected from the homogenized precursor composition before flotation separation. After measuring the sample volume (V0'), the sample was centrifuged, and the volume of the clarified liquid layer after centrifugation (V0') was measured. B '). Calculate the volume of the clarified liquid layer (V). B The ratio of ') to the sample volume (V0') [V B On the other hand, the height (H0) of the precursor composition before floating and separation is measured, and this height (H0) is multiplied by the aforementioned ratio [V]. B [ / V0], calculate the estimated height of the lower layer (B) after it floats and separates.

[0211] Next, after buoyancy separation, samples were collected from the pressure vessel using a long needle syringe. The water depth in the pressure vessel was divided into 10 equal parts from the top to the bottom, and small samples were collected at each of these 10 divisions. Additionally, samples were collected from heights other than the upper part of the pressure vessel where only gas was present. Furthermore, samples from three points that closely approximate the estimated height of the lower layer (B) determined in the preliminary test were excluded. Then, from the remaining samples, the sum of samples collected from the upper layer (A) was used as the upper layer (A) sample, and the sum of samples collected from the lower layer (B) was used as the lower layer (B) sample, and the following measurements were performed.

[0212] <Acquisition of mass and volume data sets for upper (A) and lower (B) layers>

[0213] First, the sample in the upper layer (A) is divided into two parts, namely sample (A1) and sample (A2).

[0214] Determine the mass (m) of the sample (A1) A The volume (V) of gas in the sample (A1) is determined using the following steps. Ag ), the volume of the aqueous medium (V) Aw ) and the volume (V) of the precursor particles Ap In addition, the bulk density of sample (A1), the specific gravity of the aqueous medium in sample (A1), the specific gravity of the shell of the precursor particles, and the specific gravity of the hydrophobic organic solvent encapsulated in the precursor particles were determined in advance.

[0215] First, the sample (A1) was heated at 105°C for 2 hours to remove gases and volatile components, thereby obtaining the shell (solid component) of the precursor particles in the sample (A1), and its mass (m) was determined. As Then, calculate the mass (m) of the components other than the solid components in the sample (A1). A -m As), the mass (m) of the liquid components (aqueous medium and hydrophobic organic solvent encapsulated in precursor particles) in the sample (A1). Al ).

[0216] Next, the mass (m) of the hydrophobic organic solvent in sample (A1) is determined using the following steps. Ao First, the mass of sample (A2) was determined. Next, 1 g of sample (A2) and 4 g of acetone (as extraction solvent) were measured into a 100 cc sample vial and subjected to ultrasonic treatment for 5 minutes. The treated liquid was transferred into a disposable syringe and filtered through a 0.50 μm membrane filter. The filtered liquid was then analyzed by gas chromatography. The mass of the hydrophobic organic solvent in sample (A2) was determined according to a pre-prepared standard curve of the hydrophobic organic solvent encapsulated within the precursor particles. Then, the ratio of the mass of the hydrophobic organic solvent in sample (A2) to the mass of sample (A2) was calculated as the mass ratio of the hydrophobic organic solvent in the upper layer (A). Based on this mass ratio of the hydrophobic organic solvent in the upper layer (A) and the mass of sample (A1) (m... A ), calculate the mass (m) of the hydrophobic organic solvent in sample (A1). Ao ).

[0217] Furthermore, based on the mass (m) of the liquid component in sample (A1) Al ) and the mass (m) of the hydrophobic organic solvent Ao The difference between the samples (A1 and A2) is used to calculate the mass (m) of the aqueous medium in the sample (A1). Aw Based on the mass (m) of the aqueous medium in sample (A1). Aw Calculate the volume (V) of the aqueous medium in sample (A1) by determining the specific gravity of the aqueous medium in sample (A1) and the specific gravity of the aqueous medium in sample (A1). Aw ).

[0218] Furthermore, based on the mass (m) of the hydrophobic organic solvent in sample (A1) Ao ) and the specific gravity of another hydrophobic organic solvent, calculate the volume (V) of the hydrophobic organic solvent in the sample (A1). Ao Furthermore, in all embodiments, the specific gravity of the aqueous medium in sample (A1) is 1, and the specific gravity of the precursor particle shell is also approximately 1. Therefore, based on their specific gravity and the mass (m) of the components in sample (A1) other than the hydrophobic organic solvent (aqueous medium and precursor particle shell), A -m Ao ), calculate the volume (V) of the aqueous medium in sample (A1). Aw ) and the volume of the shell of the precursor particle (V As The sum of (V) Aw +V As ).

[0219] Then, the sum of the volumes (V) of the hydrophobic organic solvent, the aqueous medium, and the shells of the precursor particles in the sample (A1) is calculated. Ao +V Aw +V As Based on the sum of these volumes and the volume of the aqueous medium (V) calculated above, Aw ), calculate the sum of the volumes of the hydrophobic organic solvent and the shell of the precursor particles in the sample (A1) (V Ao +V As ), that is, the volume (V) of the precursor particles in the sample (A1). Ap Furthermore, based on the mass (m) of the sample (A1) A ) and the bulk density of sample (A1), calculate the volume of sample (A1), and subtract the volume of the aqueous medium in sample (A1) from it (V Aw ) and the volume (V) of the precursor particles Ap ), thereby calculating the volume (V) of gas in the sample (A1). Ag ).

[0220] Furthermore, the samples in the lower layer (B) were measured in the same manner as those in the upper layer (A). Then, based on the mass and volume data obtained from the above measurements, the following values ​​were calculated.

[0221] 1. The amount of gas in the upper layer (A) (relative to the volume of gas in 100 volume parts of the precursor particles in the upper layer (A)).

[0222] 2. The volume (V) of the precursor particles in the upper layer (A) Ap ) relative to the volume of the aqueous medium (V Aw ) and the volume (V) of the precursor particles Ap The total proportion of (the proportion of particles in the upper layer (A)) [V] Ap / (V Aw +V Ap )).

[0223] 3. The volume (V) of the precursor particles in the lower layer (B) Bp ) relative to the volume of the aqueous medium (V Bw ) and the volume (V) of the precursor particles Bp The total proportion of (particle proportion of lower layer (B)) [V] Bp / (V Bw +V Bp )).

[0224] 4. The average specific gravity (D) of the upper layer (A) A The average specific gravity (D) relative to the lower layer (B) B The ratio of the upper layer (A) to the lower layer (B) [D] A / DB ].

[0225] Furthermore, in Example 1, for each sample collected in small quantities at various heights after dividing the water depth of the pressure vessel into 10 equal parts from the top to the bottom, the ratio of the precursor particle volume to the total volume of the aqueous medium and the precursor particle volume was calculated. The results showed that this ratio was consistently significantly higher than 40% or significantly lower than 20%. Similarly, for samples collected in Examples 2-12, this ratio was also consistently significantly higher than 40% or significantly lower than 20%. Therefore, it can be determined that in Examples 1-12, the volume ratio of the layer (boundary layer (C)) with a ratio greater than 20% and less than 40% is essentially zero.

[0226] <Volume ratio of upper layer (A) and lower layer (B)>

[0227] The volume ratio of the upper layer (A) and lower layer (B) in the precursor composition after flotation separation is determined by the following method. First, the entire amount of the precursor composition after flotation separation is slowly poured into a graduated cylinder. Next, the volumes of the precursor composition after flotation separation, the upper layer (A), and the lower layer (B) in the graduated cylinder are visually read. Then, the volume ratio of the upper layer (A) and lower layer (B) in the precursor composition after flotation separation is calculated.

[0228] <Foaming Inhibition Level in Solvent Removal>

[0229] The foaming inhibition level in solvent removal is evaluated according to the following criteria. A lower amount of particles leaking out of the pressure vessel indicates a higher foaming inhibition level. Furthermore, a lower amount of particles leaking out of the pressure vessel indicates a higher yield and higher productivity. Moreover, from the viewpoint of relatively increasing the amount of hollow resin particles supplied to the solvent removal equipment, or adopting removal conditions that promote the removal of hydrophobic organic solvents, a lower amount of particles leaking out of the pressure vessel also indicates higher productivity.

[0230] A: Foaming was well suppressed, and no particles leaked out of the pressure vessel during solvent removal.

[0231] B: Foaming is well suppressed, and during solvent removal, the amount of particles leaking out of the pressure vessel is greater than 0% by weight and less than 0.1% by weight relative to the total amount of particles in the system (converted to the weight of the hollow resin particles obtained).

[0232] C: Foaming is sufficiently suppressed, and during solvent removal, the amount of particles leaking out of the pressure vessel is more than 0.1% by weight and less than 1% by weight relative to the total amount of particles in the system (converted to the weight of the hollow resin particles obtained).

[0233] D: Insufficient foaming suppression; during solvent removal, the amount of particles leaking out of the pressure vessel is more than 1% by weight and less than 5% by weight relative to the total amount of particles in the system (converted to the weight of the hollow resin particles obtained).

[0234] E: Insufficient foaming suppression; during solvent removal, the amount of particles leaking out of the pressure vessel is more than 5% by weight and less than 10% by weight relative to the total amount of particles in the system (converted to the weight of the hollow resin particles obtained).

[0235] F: Insufficient foaming suppression; during solvent removal, the amount of particles leaking out of the pressure vessel is more than 10% by weight relative to the total amount of particles in the system (converted to the weight of the hollow resin particles obtained).

[0236] Solvent Removal Grades in Solvent Removal Processes

[0237] At the end of the solvent removal process, a small amount of hollow resin particles floating on the lower layer (B) is collected, and the amount of solvent in the hollow resin particles is determined by headspace gas chromatography. Then, the solvent removal level in the solvent removal process is evaluated according to the following criteria.

[0238] A: The amount of solvent is less than 0.01g relative to 1g of collected hollow resin particles.

[0239] B: The amount of solvent is greater than 0.01g relative to 1g of collected hollow resin particles.

[0240] <Removal levels of residual monomers in the solvent removal process>

[0241] At the end of the solvent removal process, a small amount of hollow resin particles floating on the lower layer (B) are collected, and the amount of residual monomer in the hollow resin particles is determined by headspace gas chromatography. Then, the removal level of residual monomer in the solvent removal process is evaluated according to the following criteria.

[0242] A: The amount of residual monomer is less than 0.001g relative to 1g of collected hollow resin particles.

[0243] B: The amount of residual monomer is greater than 0.001g relative to 1g of collected hollow resin particles.

[0244] <Cleaning time for the cleaning process>

[0245] In the cleaning process, the number of treatments (addition of ion-exchange water, elimination of coagulation, and filtration) required to achieve a conductivity of less than 10 μS / cm in the filtrate is evaluated according to the following criteria. Fewer treatments indicate a shorter cleaning time and better hollow resin particle production.

[0246] A: Less than once.

[0247] B: 2 or more times but less than 4 times.

[0248] C: 5 times or more.

[0249] <Residual Metal Content in Hollow Resin Particles>

[0250] Wet decomposition of 10g of precisely weighed hollow resin particles was performed using a microwave apparatus (PerkinElmer Multiwave 3000). The decomposition products were analyzed by ICP emission spectroscopy using an ICP emission spectrometer (PerkinElmer Optima 2100 DV) to determine the total mass of metals. Furthermore, the metal species were identified by elemental analysis using X-ray fluorescence (XRF). The ratio of the total mass of metals in the decomposition products to the mass of the hollow resin particles was calculated as the metal content in the hollow resin particles.

[0251] <Moisture content of hollow resin particles>

[0252] First, accurately weigh 10 μl of pure water using a microsyringe. Calculate the water content (mg) per 1 ml of Karl Fischer reagent based on the reagent titration amount required to remove this water. Next, accurately weigh 100–200 mg of hollow resin particles and place them at 30°C and 80% RH for 2 hours. Then, thoroughly disperse them in a measuring flask using a magnetic stirrer for 5 minutes. Next, begin the titration using a Karl Fischer moisture meter (Kyoto Electronics Industry Co., Ltd., MKA-3p). Determine the required Karl Fischer reagent titration amount (ml) and calculate the water content and moisture percentage of the hollow resin particles using the following formula. Then, evaluate the moisture percentage according to the following criteria.

[0253]

[0254] A: Moisture content is less than 1%.

[0255] B: The moisture content is above 1%.

[0256] <Dielectric loss tangent (Df) of hollow resin particles>

[0257] The dielectric loss tangent of hollow resin particles was measured using a measuring device (AET Corporation, model: ADMS01Nc) at a frequency of 1 GHz and room temperature (25°C). A lower dielectric loss tangent indicates better electrical insulation.

[0258] <Porosity of hollow resin particles>

[0259] The apparent density D1 and true density D0 of the hollow resin particles were measured. Then, the porosity (%) was calculated according to the following formula.

[0260]

[0261] <Example 1>

[0262] (1) Mixture preparation process

[0263] First, the following materials were mixed to prepare the oil phase.

[0264] Divinylbenzene (crosslinked hydrocarbon monomer) 37.5 parts;

[0265] 1.6 parts of ethyl vinylbenzene (monofunctional hydrocarbon monomer);

[0266] 0.89 parts of tert-butyl perethyl acetate (oil-soluble polymerization initiator);

[0267] 60.8 parts of heptane (a hydrophobic organic solvent).

[0268] Next, in a stirred tank, an aqueous solution of sodium hydroxide (alkali metal hydroxide) dissolved in 11.0 parts of 55 parts of ion-exchanged water was gradually added to a solution of magnesium chloride (a water-soluble polyvalent metal salt) dissolved in 225 parts of ion-exchanged water while stirring, to prepare a magnesium hydroxide colloidal (water-insoluble metal hydroxide colloid) dispersion (8 parts magnesium hydroxide). The resulting aqueous dispersion of magnesium hydroxide was used as the aqueous phase. A mixed solution was prepared by mixing the obtained aqueous phase and the oil phase.

[0269] (2) Suspension process

[0270] Using an emulsifying disperser (manufactured by PRIMIX Co., Ltd., product name: HOMOMIXER), the mixture obtained in the above-mentioned mixture preparation process was stirred for 1 minute at a speed of 4000 rpm, thereby performing suspension treatment to prepare a suspension in which droplets of a polymerizable monomer composition containing a hydrophobic organic solvent are dispersed in water.

[0271] (3) Polymerization process

[0272] The suspension obtained in the above suspension process is fed into a cylindrical pressure vessel. Then, under a nitrogen atmosphere, the temperature is raised to 80°C, and the suspension is stirred at 80°C for 24 hours to carry out a polymerization reaction. Through this polymerization reaction, a slurry containing precursor particles encapsulating a hydrophobic organic solvent dispersed in water is obtained, i.e., the precursor composition. Furthermore, the polymerization conversion rate is approximately 100%, and the composition of the monomers used is substantially the same as that of the monomers in the formed resin. (The same applies in Examples 2-12.)

[0273] (4) Flotation Separation Process

[0274] The pressure vessel was cooled to 30°C. Next, compressed nitrogen was injected into the upper part of the pressure vessel, pressurizing it to 0.3 MPa (gauge pressure) and maintaining this pressure for 5 minutes. Then, the gas in the upper part of the pressure vessel was released, depressurizing it to 10 kPa (absolute pressure) and maintaining this pressure for 5 minutes. This pressurization and depressurization process generates bubbles in the precursor composition. These bubbles adhere to the outer surface of the precursor particles, becoming integrated with them and rising to the surface. As a result, the precursor composition separates into an upper layer (A) and a lower layer (B). The upper layer (A) is a foam layer containing water, precursor particles, and gas.

[0275] Various measurements were performed according to the above method. The amount of gas in the upper layer (A) was 41 parts by volume relative to 100 parts by volume of precursor particles in the upper layer (A). The particle ratio of the upper layer (A) [V] Ap / (V Aw +V Ap The particle ratio of the lower layer (B) is 65%. Bp / (V Bw +V Bp The particle ratio of the lower layer (B) is 0-1%. (Additionally, in Examples 2-12, the particle ratio of the lower layer (B) is [V]). Bp / (V Bw +V Bp The specific gravity ratio of the upper layer (A) to the lower layer (B) is also 0-1%. A / D B The value was 0.33. Furthermore, in the precursor composition after flotation separation, the upper layer (A) had a volume ratio of 60% by volume, and the lower layer (B) had a volume ratio of 40% by volume.

[0276] (5) Solvent removal process

[0277] By injecting compressed nitrogen gas into the pressure vessel from the top, the pressure vessel is pressurized, and simultaneously heated. The internal pressure of the pressure vessel is adjusted to 0.9 MPa (gauge pressure), and the temperature inside the pressure vessel is adjusted to a level lower than the boiling point of water under the pressure environment inside the pressure vessel (T0). b Temperature 2℃ lower (T) b-2℃). Next, while maintaining the internal pressure and temperature, nitrogen is injected and discharged into the upper gas phase section of the pressure vessel to create a nitrogen flow environment inside the pressure vessel. The nitrogen flow rate is set to be equal to the volume (V0) of the precursor composition before flotation separation per minute (i.e., V0 / min). Then, ion-exchanged water (conductivity: 1 μS / cm) is injected from the top of the pressure vessel to perform a cleaning operation, spraying it onto the upper layer (A) while simultaneously discharging the clarified liquid from the bottom of the pressure vessel. The temperature of the ion-exchanged water is set to be equal to the temperature inside the pressure vessel. The injection rate of the ion-exchanged water and the discharge rate of the clarified liquid are both set to be equal to the volume (V0) of the precursor composition used per hour (i.e., V0 / h).

[0278] By continuously performing the above operation for 30 hours, hollow resin particles with the hydrophobic organic solvent removed were obtained, floating on the lower layer (B). At the end of the above operation, the clarified liquid was collected from the bottom of the pressure vessel, and the conductivity was measured, which was 100 μS / cm. Following the above method, the foaming inhibition level in solvent removal, the removal level of hydrophobic organic solvent and residual monomer in the solvent removal process, and the yield of hollow resin particles at the end of the solvent removal process were evaluated. The results are shown in Table 1.

[0279] (6) Cleaning process

[0280] Release the pressure inside the pressure vessel while cooling the temperature to 25°C. Add dilute sulfuric acid to the pressure vessel to adjust the pH to below 5.5, and clean at 25°C for 10 minutes. Discharge all components from the pressure vessel, remove water by filtration, and recover the solid component containing hollow resin particles. Add ion-exchange water to the recovered solid component and slurry again. Stir the slurry to eliminate the aggregation of hollow resin particles, and then separate it into filtrate and filter residue containing hollow resin particles by filtration. If the conductivity of the filtrate exceeds 10 μS / cm, repeat the series of treatments consisting of adding ion-exchange water, eliminating aggregation, and filtration. After each filtration, measure the conductivity of the filtrate. The series of treatments is terminated when the conductivity of the filtrate reaches below 10 μS / cm. Then, evaluate the cleaning time of the cleaning process according to the above method. The results are shown in Table 1.

[0281] (7) Drying process

[0282] The filter residue containing hollow resin particles obtained in the above cleaning process was dried at 40°C for pre-drying. Then, it was heated at 200°C for 12 hours under vacuum conditions using a vacuum dryer, thereby obtaining the hollow resin particles of Example 1. Observation of the obtained hollow resin particles using a scanning electron microscope confirmed that the hollow resin particles were spherical and had a hollow portion. Furthermore, it was confirmed that the shells of the hollow resin particles were not damaged. (In addition, it was confirmed in the following examples that the obtained hollow resin particles were spherical and had a hollow portion, and the shells were not damaged.) The residual metal content, moisture content, dielectric loss tangent (Df), and porosity of the hollow resin particles obtained in Example 1 were determined. The results are shown in Table 1.

[0283] <Examples 2-5>

[0284] The temperature, pressure, and depressurization conditions in the flotation separation process (4) were changed as described in Table 1, except that hollow resin particles were obtained in the same manner as in Example 1. Measurements and evaluations were performed in each process in the same manner as in Example 1. The results are shown in Table 1.

[0285] <Example 6>

[0286] In step (5), the solvent removal process, no cleaning operation (spraying of ion-exchange water and discharge of clarified liquid) was performed. Otherwise, hollow resin particles were obtained in the same manner as in Example 1. Measurements and evaluations were performed in each step in the same manner as in Example 1. The results are shown in Table 1.

[0287] <Example 7>

[0288] In the solvent removal step (5), nitrogen was not injected and the environment inside the pressure vessel was not made into a nitrogen flow environment. Otherwise, hollow resin particles were obtained in the same manner as in Example 1. In addition, in the solvent removal step, gas was vented in order to maintain the internal pressure. In each step, the measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0289] <Example 8>

[0290] In step (5), the solvent removal process was carried out without pressurizing the pressure vessel (gauge pressure set to 0 MPa). Otherwise, hollow resin particles were obtained in the same manner as in Example 1. Measurements and evaluations were performed in each step in the same manner as in Example 1. The results are shown in Table 1.

[0291] <Example 9>

[0292] The mixture preparation process (1) to the washing process (6) were performed in the same manner as in Example 1, thereby obtaining hollow resin particles as filter residue. The residual metal content and moisture content of the obtained hollow resin particles were evaluated according to the above method. The results are shown in Table 1.

[0293] <Example 10>

[0294] The mixture preparation process (1) to the solvent removal process (5) were performed in the same manner as in Example 1, thereby obtaining hollow resin particles with the hydrophobic organic solvent removed in a state floating on the lower layer (B). The hollow resin particles and the aqueous medium in the pressure vessel were stirred and mixed to obtain slurry-like hollow resin particles. Then, the moisture content was evaluated using the obtained slurry-like hollow resin particles according to the method described above. In addition, the residual metal content was evaluated using the dried hollow resin particles obtained by drying the obtained slurry-like hollow resin particles at 105°C for 2 hours according to the method described above. The results are shown in Table 1.

[0295] <Example 11>

[0296] In step (1), the following materials were mixed to prepare the oil phase, otherwise hollow resin particles were obtained in the same manner as in Example 1. Measurements and evaluations were performed in each step in the same manner as in Example 1. The results are shown in Table 1.

[0297] 24.6 parts of divinylbenzene (crosslinked hydrocarbon monomer);

[0298] 14.5 parts of ethyl vinylbenzene (monofunctional hydrocarbon monomer);

[0299] 0.89 parts of tert-butyl perethyl acetate (oil-soluble polymerization initiator);

[0300] 60.8 parts of heptane (a hydrophobic organic solvent).

[0301] <Example 12>

[0302] In step (1), the following materials were mixed to prepare the oil phase, otherwise hollow resin particles were obtained in the same manner as in Example 1. Measurements and evaluations were performed in each step in the same manner as in Example 1. The results are shown in Table 1.

[0303] 25 parts of ethylene glycol dimethacrylate (containing heteroatom crosslinking monomers);

[0304] 30 parts of trimethylolpropane trimethacrylate (containing heteroatom crosslinking monomers);

[0305] 26 parts of divinylbenzene (crosslinked hydrocarbon monomer);

[0306] 19 parts of ethyl vinylbenzene (monofunctional hydrocarbon monomer);

[0307] 3 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (oil-soluble polymerization initiator);

[0308] 100 parts of hexane (a hydrophobic organic solvent).

[0309] <Comparative Example 1>

[0310] The mixture preparation process (1) to the polymerization process (3) are carried out in the same manner as in Example 1, thereby obtaining a slurry containing precursor particles encapsulated in hydrophobic organic solvent dispersed in water, i.e., a precursor composition. Then, instead of the flotation separation process (4), the solvent removal process (5) is carried out.

[0311] (5) The solvent removal process is carried out through the following steps: Compressed nitrogen is injected into the pressure vessel from the top to pressurize it. Simultaneously, the pressure vessel is heated to adjust the internal pressure to 0.1 MPa (gauge pressure), and the temperature inside the pressure vessel is adjusted to a level lower than the boiling point of water under the pressure environment inside the pressure vessel (T0). b Temperature 2℃ lower (T) b -2℃). Next, while maintaining the internal pressure and temperature, nitrogen is injected and gas is discharged from the upper gas phase section inside the pressure vessel to create a nitrogen flow environment inside the pressure vessel. The nitrogen flow rate is set to be equal to the volume of the precursor composition (volume: V0) supplied per minute for the flotation separation process (i.e., V0 / min). By continuously performing the above operation for 30 hours, a slurry containing hollow resin particles from which hydrophobic organic solvents have been removed is obtained.

[0312] Then, using the obtained slurry, the cleaning steps (6) and (7) were performed in the same manner as in Example 1, except that... In each step, the measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0313] <Comparative Examples 2-3>

[0314] The pressurization conditions in the solvent removal step (5) were changed to those described in Table 1, and hollow resin particles were obtained in the same manner as in Comparative Example 1. Measurements and evaluations were performed in each step in the same manner as in Example 1. The results are shown in Table 1.

[0315] [Table 1]

[0316]

[0317] As can be clearly seen from Table 1, the manufacturing method having a solvent removal process that removes the hydrophobic organic solvent contained within the precursor particles while they are floating and separated can suppress foaming during the removal of the hydrophobic organic solvent and can manufacture hollow resin particles with high productivity (Examples 1 to 12).

[0318] On the other hand, when removing the hydrophobic organic solvent contained within the precursor particles in the state of a slurry in which the precursor particles are dispersed in water without causing the precursor particles to float and separate, excessive foaming occurs during the removal of the hydrophobic organic solvent, making it impossible to manufacture hollow resin particles with high productivity (Comparative Examples 1-3).

Claims

1. A method for manufacturing hollow resin particles, the hollow resin particles having a shell containing resin and a hollow portion surrounded by the shell, the manufacturing method comprising the following steps: The mixture preparation process involves preparing a mixture containing polymerizable monomers, hydrophobic organic solvents, polymerization initiators, and an aqueous medium. The suspension process involves suspending the mixture to prepare a suspension in which droplets of a polymerizable monomer composition containing the polymerizable monomer, the hydrophobic organic solvent, and the polymerization initiator are dispersed in the aqueous medium. The polymerization process involves feeding the suspension into a polymerization reaction to prepare a precursor composition comprising precursor particles having a hollow portion and encapsulating the hydrophobic organic solvent within the hollow portion. The flotation separation process causes the precursor particles in the precursor composition to float and separate. In the solvent removal process, the hydrophobic organic solvent contained within the precursor particles is removed while the precursor particles are being floated and separated.

2. The method for manufacturing hollow resin particles according to claim 1, wherein the manufacturing method further comprises: The cleaning process involves cleaning the hollow resin particles obtained in the solvent removal process, from which the hydrophobic organic solvent encapsulated within the precursor particles has been removed.

3. The method for manufacturing hollow resin particles according to claim 1 or 2, wherein the manufacturing method further comprises: The drying process involves drying the hollow resin particles obtained in the solvent removal process, after removing the hydrophobic organic solvent encapsulated within the precursor particles.

4. The method for manufacturing hollow resin particles according to any one of claims 1 to 3, wherein, In the flotation separation process, the precursor composition is pressurized and then depressurized, thereby causing the precursor particles to float.

5. The method for manufacturing hollow resin particles according to any one of claims 1 to 4, wherein, In the solvent removal process, the hydrophobic organic solvent encapsulated within the precursor particles is removed under a pressurized environment with a gauge pressure of 0.1 to 2.0 MPa.

6. The method for manufacturing hollow resin particles according to any one of claims 1 to 5, wherein, In the solvent removal process, the hydrophobic organic solvent encapsulated within the precursor particles is removed under a gas flow.

7. The method for manufacturing hollow resin particles according to any one of claims 1 to 6, wherein, The flotation separation process is a process of separating the precursor particles into an upper layer (A) and a lower layer (B) containing a smaller proportion of precursor particles than the upper layer (A) by causing the precursor particles to float to the surface.

8. The method for manufacturing hollow resin particles according to claim 7, wherein, The upper layer (A) contains 0.1 to 70 parts by volume of gas relative to 100 parts by volume of the precursor particles in the upper layer (A).

9. The method for manufacturing hollow resin particles according to claim 7 or 8, wherein, The volume (V) of the precursor particles in the upper layer (A) Ap ) relative to the volume of the aqueous medium (V Aw ) and the volume (V) of the precursor particles Ap The total proportion of [V] Ap / (V Aw +V Ap The percentage is over 40%. The volume (V) of the precursor particles in the lower layer (B) Bp ) relative to the volume of the aqueous medium (V Bw ) and the volume (V) of the precursor particles Bp The total proportion of [V] Bp / (V Bw +V Bp The percentage is below 20%.

10. The method for manufacturing hollow resin particles according to any one of claims 7 to 9, wherein, The average specific gravity (D) of the upper layer (A) A The average specific gravity (D) relative to the lower layer (B) B The proportion of ) [D A / D B [Greater than 0.3 and less than 0.97] 11. The method for manufacturing hollow resin particles according to any one of claims 7 to 10, wherein, In the solvent removal process, while removing the hydrophobic organic solvent contained within the precursor particles, an aqueous medium with a conductivity of less than 2 μS / cm is added to the upper layer (A) while the aqueous medium is discharged from the lower layer (B).

12. The method for manufacturing hollow resin particles according to claim 4, wherein, The pressurization conditions in the flotation separation process are 0.1 to 2.0 MPa using a gauge pressure gauge.

13. The method for manufacturing hollow resin particles according to any one of claims 1 to 12, wherein, The proportion of crosslinking monomers in 100% by mass of the polymerizable monomer is 40% by mass or more and 100% by mass or less.

14. The method for manufacturing hollow resin particles according to any one of claims 1 to 13, wherein, The mixture also contains a dispersing stabilizer.

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