Resin composition, prepreg, and molded article

Abstract

Provided are: a resin composition which is capable of producing a molded body having excellent lightweight properties and suppressed deterioration in physical properties; and a prepreg and a molded body which are produced using the resin composition. The present invention relates to a resin composition containing: hollow particles having a shell containing a resin and a hollow portion surrounded by the shell, the porosity being 50% or more, the volume average particle diameter being greater than 1.0 [mu] m and 20.0 [mu] m or less, and the volume average particle diameter being greater than 1.0 [mu] m and not greater than 20.0 [mu] m; the amount of epoxy groups per unit area as determined from the epoxy value and the specific surface area of the hollow particles is 1.0 [mu] mol / m2 or more, and a matrix resin having a functional group capable of reacting with an epoxy group is contained as the matrix resin.

Description

Technical Field

[0001] The present invention relates to a resin composition containing hollow particles, and a prepreg and a molded article produced using the resin composition. Background Art

[0002] Because hollow particles have a void inside, they are added to resins, coatings, and various molded articles for purposes such as weight reduction, thermal insulation, and lowering the dielectric constant. Their applications span a wide range of fields, including automobiles, bicycles, aviation, electrical and electronics, construction, home appliances, containers, stationery, tools, and footwear.

[0003] Materials for the hollow particles include resins such as vinyl resins, acrylic resins, epoxy resins, polyurethane resins, and melamine resins, as well as inorganic materials such as silica. Resin compositions containing such hollow particles in a matrix resin such as a thermosetting resin or a thermoplastic resin, or fiber-reinforced molded articles containing such hollow particles in a fiber-reinforced plastic (FRP), are widely used in various fields.

[0004] For example, Patent Document 1 discloses a coating agent and a masterbatch, wherein the coating agent contains hollow particles and a thermosetting resin or a thermoplastic resin, wherein the hollow particles have a shell comprising a cross-linked copolymer derived from a copolymer, wherein the copolymer is composed of a radically reactive monomer having at least one epoxy group or oxetane group, and a radically reactive monomer having at least one silyl group.

[0005] Patent Document 2 discloses a low dielectric material in which hollow epoxy resin fine particles are dispersed in an insulating resin.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 5992598;

[0009] Patent Document 2: Japanese Patent No. 4955960. Summary of the Invention

[0010] Problems to be solved by the invention

[0011] However, resin compositions to which hollow particles are added for weight reduction or the like have a problem in that physical properties related to resistance to external forces, such as tensile modulus and tensile strength, are reduced compared to compositions without hollow particles.

[0012] An object of the present invention is to provide a resin composition capable of producing a molded article having excellent lightness and suppressed deterioration in physical properties; and to provide a prepreg and a molded article produced using the resin composition.

[0013] Solutions for solving problems

[0014] The present inventors have discovered that, in a resin composition comprising hollow particles whose shells are formed of a resin, when the hollow particles have a specific amount or more of epoxy groups on the outer surface and the matrix resin has functional groups capable of reacting with the epoxy groups, deterioration in the physical properties of a molded body comprising a cured product of the resin composition is suppressed, thereby completing the present invention.

[0015] That is, the present invention provides the following resin composition.

[0016] [1] A resin composition comprising hollow particles and a matrix resin,

[0017] The hollow particles have a shell containing a resin and a hollow portion surrounded by the shell, a porosity of 50% or more, a volume average particle size of greater than 1.0 μm and less than 20.0 μm, and an epoxy group amount per unit area calculated by the following formula (A) based on the epoxy value and specific surface area of ​​the hollow particles is 1.0 μmol / m 2 above,

[0018] Formula (A):

[0019] Epoxy group content (μmol / m 2 )=epoxy value (μmol / g) / specific surface area (m 2 / g)

[0020] The base resin contains a base resin having a functional group capable of reacting with an epoxy group.

[0021] [2] The resin composition according to [1], wherein the functional group possessed by the matrix resin is at least one selected from a hydroxyl group, an amino group, an epoxy group, a carboxyl group, a carboxylic anhydride group, a thiol group, an isocyanate group, and a silanol group.

[0022] [3] The resin composition according to [1] or [2], comprising at least one selected from epoxy resins, benzoxazine resins, cyanate resins, polyimide resins, silicone resins, polyester resins, liquid crystal polymers (LCPs), modified polyolefin resins, polyphenylene ether resins, thiol resins, polyurethane resins, polyurea resins, and raw material compounds of these resins as the above-mentioned matrix resin.

[0023] [4] The resin composition according to any one of [1] to [3], wherein the shell of the hollow particles comprises a polymer of a radical polymerizable monomer as the resin.

[0024] [5] The resin composition according to [4], wherein the content of the crosslinking monomer containing two or more radical polymerizable groups in one molecule is 50% by mass or more in 100% by mass of the radical polymerizable monomer.

[0025] [6] The resin composition according to any one of [1] to [3], wherein the shell of the hollow particles contains a cured product of an epoxy resin as the resin.

[0026] [7] The resin composition according to [6], wherein the content of the crosslinkable epoxy resin containing two or more epoxy groups in one molecule is 50% by mass or more in 100% by mass of the epoxy resin.

[0027] [8] The resin composition according to any one of [1] to [7], wherein the total content of the surfactant and the water-soluble polymer stabilizer present on the surface of the hollow particles is 100 ppm or less.

[0028] Furthermore, the present invention provides the following prepreg and thermoplastic prepreg.

[0029] [9] A prepreg obtained by impregnating a base material with the resin composition according to any one of [1] to [8] and then heating and drying the resin composition.

[0030]

[10] A thermoplastic prepreg obtained by impregnating a base material with the resin composition according to any one of [1] to [8].

[0031] Furthermore, the present invention provides the following molded article.

[0032]

[11] A molded article comprising a cured product of the resin composition according to any one of [1] to [8].

[0033] Effects of the Invention

[0034] As described above, the present invention provides a resin composition that is lightweight and less susceptible to degradation of physical properties. Furthermore, the present invention provides a prepreg formed by impregnating a substrate with the resin composition and then heating and drying, or a thermoplastic prepreg formed by impregnating a substrate with the resin composition, and a molded article comprising a cured product of the resin composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram illustrating an example of a method for producing hollow particles used in the present invention.

[0036] Figure 2 This is a diagram illustrating an example of a stirring device used in the solvent removal step. DETAILED DESCRIPTION

[0037] Hereinafter, the resin composition, prepreg, and molded article of the present invention will be described in detail.

[0038] In the present invention, "to" in a numerical range means that the numerical values ​​described before and after it are included as the lower limit and the upper limit.

[0039] 1. Resin composition

[0040] The resin composition of the present invention is characterized by comprising hollow particles and a matrix resin.

[0041] The hollow particles have a shell containing a resin and a hollow portion surrounded by the shell, a porosity of 50% or more, a volume average particle size of greater than 1.0 μm and less than 20.0 μm, and an epoxy group amount per unit area calculated by the following formula (A) based on the epoxy value and specific surface area of ​​the hollow particles is 1.0 μmol / m 2 above,

[0042] Formula (A):

[0043] Epoxy group content (μmol / m 2 )=epoxy value (μmol / g) / specific surface area (m 2 / g)

[0044] The base resin contains a base resin having a functional group capable of reacting with an epoxy group.

[0045] The resin composition containing hollow particles is compared with the situation that does not contain hollow particles, and the physical property related to the intensity of external force such as tensile elastic modulus, tensile strength etc. when making the molded body usually reduces.This is thought to be the peeling of the interface of the matrix resin and hollow particles caused by the insufficient adhesion of hollow particles and matrix resin or the insufficient dispersion of hollow particles.In contrast, in the molded body that the resin composition of the present invention is solidified, even if containing hollow particles, the reduction of physical property can be suppressed.In the resin composition of the present invention, the particle diameter of hollow particles is appropriate large and the hollow particles with epoxy group are close to the polarity of the matrix resin with above-mentioned functional group, and thus the affinity of both is high, so the dispersibility of hollow particles is excellent.And then, if the resin composition of the present invention is solidified, the epoxy group that hollow particles have on the surface reacts with the functional group that matrix resin has and forms covalent bond. Therefore, in the molded article of the resin composition of the present invention, the hollow particles are uniformly dispersed, and the surfaces of the hollow particles are cross-linked with the matrix resin, thereby making the interface between the hollow particles and the matrix resin excellent in adhesion and not easily peeling off.

[0046] Furthermore, in the resin composition of the present invention, the hollow particles have a sufficiently high porosity of 50% or more, and the hollow particles are not easily broken, easily maintaining their pores. Therefore, the hollow particles provide an excellent lightweighting effect. It is speculated that the hollow particles are not easily broken because the epoxy groups on the surface of the hollow particles react with the functional groups of the matrix resin, forming a three-dimensional cross-linked structure near the surface of the hollow particles. Furthermore, in the molded article of the resin composition of the present invention, the hollow particles are evenly dispersed, making it easier to apply pressure evenly during pressurization, thereby further suppressing the breakage of the hollow particles.

[0047] Hereinafter, the hollow particles contained in the resin composition of the present invention, the production method thereof, and the matrix resin will be described in detail.

[0048] [Hollow particles]

[0049] The hollow particles used in the present invention are particles having a shell (outer shell) containing a resin and a hollow portion surrounded by the shell, and have epoxy groups on the outer surface of the shell.

[0050] The hollow particles used in the present invention have an epoxy group amount per unit area calculated from the epoxy value and specific surface area of ​​the hollow particles using the following formula (A): 2 above.

[0051] Formula (A):

[0052] Epoxy group content (μmol / m 2 )=epoxy value (μmol / g) / specific surface area (m 2 / g)

[0053] In the present invention, the epoxy value of the hollow particles is measured by a potentiometric titration method in accordance with JIS K 7236. The epoxy value has two significant figures and the epoxy group weight is rounded to one decimal place.

[0054] In the present invention, the specific surface area of ​​the hollow particles can be calculated using the following formula (B) based on the volume average particle size and the apparent density D1 of the hollow particles, assuming the hollow particles are spherical. In the following formula (B), the values ​​of the volume average particle size and the apparent density D1 are rounded to two significant figures, and the specific surface area is rounded to two decimal places.

[0055] Formula (B):

[0056] Specific surface area (m 2 / g) = 6 / (volume average particle size (m) × apparent density D1 (g / m 3 ))

[0057] The above-mentioned epoxy group content can be used as an indicator of the amount of epoxy groups present on the outer surface of the hollow particles. In the hollow particles used in the present invention, the epoxy group content only needs to be 1.0 μmol / m 2 From the perspective of improving the adhesion between the hollow particles and the matrix resin to suppress the degradation of the physical properties when the molded body is formed, and suppressing the breakage of the hollow particles to improve the weight reduction effect, 3.0 μmol / m 2 More preferably, 5.0 μmol / m 2 The upper limit of the epoxy group content is not particularly limited, but is preferably 1000 μmol / m from the perspective of suppressing a decrease in the strength of the particles due to an inadequate cross-linking reaction of the epoxy group. 2 Below, more preferably 750 μmol / m 2 Below, more preferably 500 μmol / m 2 the following.

[0058] As the resin contained in the shell of the hollow particles, for example, a polymer of a radical polymerizable monomer, a cured product obtained by curing an epoxy resin with a curing agent, and a mixture thereof are preferably used.

[0059] When the shell comprises a polymer of a radically polymerizable monomer, the epoxy groups present on the outer surface of the hollow particle shell are preferably epoxy groups contained in a portion of the monomer units constituting the polymer. Furthermore, in the polymer of a radically polymerizable monomer, the epoxy groups contained in the monomer units may be epoxy groups previously contained in the raw monomers, or may be epoxy groups introduced into a portion of the monomer units through a modification treatment or the like after polymerization.

[0060] When the shell includes a cured product of an epoxy resin, the epoxy groups on the outer surface of the shell of the hollow particle are preferably epoxy groups that remain without undergoing a polymerization reaction.

[0061] In addition, examples of mixtures of polymers of radically polymerizable monomers and cured products of epoxy resins include, for example, composite resins obtained by polymerizing radically polymerizable groups and then conducting a cross-linking reaction of epoxy groups in a mixture containing a radically polymerizable monomer and a polymerization initiator thereof, an epoxy resin and a curing agent thereof, or in a mixture containing a monomer having both a radically polymerizable group and an epoxy group, a polymerization initiator, and a curing agent.

[0062] The shell of the hollow particles may further contain additives other than the resin, within a range that does not impair the effects of the present invention. When the shell contains additives, the content of the resin in the shell is preferably 96% by mass or greater, more preferably 97% by mass or greater, even more preferably 98% by mass or greater, and even more preferably 99% by mass or greater.

[0063] In the hollow particles used in the present invention, the hollow portion is a hollow space clearly distinguishable from the shell. The shell of the hollow particle may have a porous structure. In this case, the hollow portion has a size that can be clearly distinguished from the multiple microscopic spaces uniformly dispersed within the porous structure. From the perspective of mechanical strength, the hollow particles used in the present invention preferably have a dense shell.

[0064] Furthermore, from the viewpoint of lightness, the hollow particles used in the present invention preferably have their hollow portions filled with a gas such as air.

[0065] The hollow particles used in the present invention may have one or two or more hollow portions. From the perspective of maintaining a good balance between high porosity and mechanical strength, they preferably have only one or two hollow portions, and more preferably have only one hollow portion. The proportion of the hollow particles used in the present invention having only one or two hollow portions is preferably 90% or more, more preferably 95% or more. Furthermore, the proportion of the particles having only one hollow portion is preferably 90% or more, more preferably 95% or more.

[0066] Furthermore, the shell of the hollow particles used in the present invention and, when the hollow particles have two or more hollow parts, the partition walls separating adjacent hollow parts may be porous, but are preferably dense from the viewpoint of strength.

[0067] The shape of the hollow particles used in the present invention may be, for example, spherical, ellipsoidal, or irregular. From the viewpoint of dispersibility, strength, and pressure resistance of the hollow particles, spherical is preferred.

[0068] An example of the shape of the hollow particles used in the present invention is a bag composed of a thin membrane and bulging due to gas, and its cross-sectional view is as follows: Figure 1 The hollow particles 10 in (4) are shown. In this example, a thin membrane is provided on the outside, and the inside is filled with gas.

[0069] The hollow portion of the hollow particles can be confirmed by, for example, observing a cross section of the particles with an SEM or directly observing the particles with a TEM. The shape of the hollow particles can be confirmed by, for example, observing the hollow particles with an SEM or a TEM.

[0070] The hollow particles used in the present invention may contain a small amount of particles with low roundness due to particle breakage, deformation, etc. as impurities. From the viewpoints of the dispersibility, strength, and pressure resistance of the hollow particles, as well as the lightness of the hollow particles, the proportion of particles with a roundness of 0.85 or less in 100% by mass of the hollow particles is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 4% by mass or less.

[0071] Particles with a roundness of 0.85 or less are typically deformed or cracked, such as by dents, and are sometimes referred to as "irregular-shaped particles" in the present invention. Such irregular-shaped particles have lower porosity than spherical hollow particles, resulting in inferior lightweight properties. Therefore, by reducing the proportion of irregular-shaped particles contained in the hollow particles, the lightweight properties of the hollow particles can be improved.

[0072] Furthermore, irregularly shaped particles tend to aggregate more easily than spherical particles when dispersed in a matrix resin, resulting in poor dispersibility. Therefore, reducing the proportion of irregularly shaped particles contained in hollow particles can improve the dispersibility of the hollow particles.

[0073] Furthermore, irregularly shaped particles are susceptible to localized external pressure, resulting in lower pressure resistance compared to spherical particles. When irregularly shaped particles are dispersed in a matrix resin, they tend to form aggregates, which are susceptible to external pressure, further degrading pressure resistance. Therefore, reducing the proportion of irregularly shaped particles within hollow particles can improve their pressure resistance.

[0074] Circularity is defined as the value obtained by dividing the diameter of a circle having the same area as the projected image of the particle (equivalent circular area diameter) by the diameter of a circle having the same circumference as the projected image of the particle (equivalent circular perimeter diameter). If the particle is a perfect sphere, the circularity is 1. The more complex the surface shape of the particle, the smaller the circularity value.

[0075] The average circularity of the hollow particles used in the present invention may be 0.950 to 0.995.

[0076] In the present invention, the circularity is measured using a flow particle imaging measurement device at an image resolution of 0.185 μm / pixel.

[0077] As a flow-type particle imaging measurement device, for example, the "IF-3200" manufactured by JASCO INTERNATIONAL Co., Ltd. can be preferably used. The measurement sample is prepared, for example, by adding 0.10 to 0.12 g of hollow particles to an aqueous solution of sodium linear alkylbenzene sulfonate (concentration 0.3%) and dispersing the resulting mixture in an ultrasonic cleaner for 5 minutes.

[0078] The average circularity is defined as the average value of the circularities of 1,000 to 3,000 particles selected at random.

[0079] The hollow particles used in the present invention have a porosity of 50% or more. This allows the hollow particles to be lightweight and have excellent thermal insulation properties. The porosity of the hollow particles used in the present invention is preferably 60% or more, more preferably 65% ​​or more.

[0080] The upper limit of the porosity of the hollow particles is not particularly limited, but is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less, from the perspective of suppressing a decrease in the strength of the hollow particles and making them less likely to break.

[0081] The porosity of the hollow particles was calculated based on the apparent density D1 and true density D0 of the hollow particles.

[0082] The apparent density D1 of the hollow particles is measured as follows. First, a volume of 100 cm 3 Fill the volumetric flask to about 30 cm 3 The mass of the hollow particles was accurately weighed. Next, isopropyl alcohol was accurately filled to the mark in the volumetric flask filled with the hollow particles, while being careful not to introduce air bubbles. The mass of isopropyl alcohol added to the volumetric flask was accurately weighed, and the apparent density D1 (g / cm2) of the hollow particles was calculated based on the following formula (I): 3 ).

[0083] Formula (I)

[0084] Apparent density D1 = [mass of hollow particles] / (100-[mass of isopropyl alcohol] / [specific gravity of isopropyl alcohol at the measurement temperature])

[0085] The apparent density D1 corresponds to the specific gravity of the entire hollow particle when the hollow portion is regarded as a part of the hollow particle.

[0086] The true density D0 of the hollow particles is measured as follows. After the hollow particles are crushed in advance, a 100 cm 3 A volumetric flask is filled with about 10 g of hollow particle fragments, and the mass of the filled fragments is accurately weighed. Then, isopropyl alcohol is added to the volumetric flask in the same manner as the above-mentioned apparent density measurement, and the mass of isopropyl alcohol is accurately weighed. The true density D0 (g / cm2) of the hollow particles is calculated based on the following formula (II): 3 ).

[0087] Formula (II)

[0088] True density D0 = [mass of hollow particle fragments] / (100 - [mass of isopropyl alcohol] / [specific gravity of isopropyl alcohol at the measurement temperature])

[0089] The true density D0 corresponds to the specific gravity of the shell portion alone in the hollow particle. As can be seen from the above measurement method, when calculating the true density D0, the hollow portion is not considered as part of the hollow particle.

[0090] The porosity (%) of the hollow particles is calculated from the apparent density D1 and true density D0 of the hollow particles by the following formula (III).

[0091] Formula (III)

[0092] Porosity (%) = 100 - (apparent density D1 / true density D0) × 100

[0093] The volume average particle size of the hollow particles used in the present invention is greater than 1.0 μm and is not more than 20.0 μm. As a lower limit, from the perspective of improving the dispersibility of the hollow particles, it is preferably 1.5 μm or more, more preferably 2.0 μm or more. As an upper limit, from the perspective of suppressing the reduction in the strength of the molded body, it is preferably 17.5 μm or less, more preferably 10.0 μm or less, and even more preferably 5.0 μm or less.

[0094] The particle size distribution (volume average particle size (Dv) / number average particle size (Dp)) of hollow particle is not particularly limited, is preferably more than 1.1 and below 2.5, more preferably more than 1.1 and below 2.0.If this particle size distribution is below the above-mentioned upper limit, then can obtain the particle that the deviation of performance between particles is little.In addition, if this particle size distribution is below the above-mentioned upper limit, then for example, when using for example resin combination of the present invention to manufacture flaky molded article, can manufacture the product of uniform thickness.

[0095] The volume average particle size (Dv) and number average particle size (Dp) of the hollow particles can be obtained by, for example, the following method: the particle size of the hollow particles is measured by a particle size distribution measuring device based on the Coulter counter method, and the number average and volume average are calculated respectively, and the obtained values ​​are used as the number average particle size (Dp) and volume average particle size (Dv) of the particles. Particle size distribution is the value of volume average particle size divided by number average particle size. The Coulter counter method is a method for measuring particle diameter by a resistance method known as the Coulter principle.

[0096] The hollow particles used in the present invention are not particularly limited, but the thermal decomposition starting temperature is preferably 345°C or higher, more preferably 350°C or higher. When the thermal decomposition starting temperature is above the lower limit, excellent heat resistance is achieved. The upper limit of the thermal decomposition starting temperature of the hollow particles is not particularly limited, and may be, for example, 400°C or lower.

[0097] In the present invention, the thermal decomposition starting temperature of the hollow particles is the temperature at which the weight decreases by 5%, and can be measured using a TG-DTA apparatus under a nitrogen atmosphere at a nitrogen flow rate of 230 mL / min and a heating rate of 10°C / min.

[0098] The total content of the surfactant and the water-soluble polymer stabilizer (hereinafter referred to as " surfactant etc. ") present in the particle surface in the hollow particle used in the present invention is preferably less than 100ppm, more preferably less than 70ppm, further preferably less than 50ppm, and more preferably less than 30ppm. In addition, the water-soluble polymer stabilizer can be any one of organic or inorganic. If the content of the surfactant etc. present in the surface of the hollow particle is below the above-mentioned upper limit, the reduction of the reactivity of the hollow particle and the matrix resin is suppressed, so the adhesion of the hollow particle and the matrix resin is improved, as a result, the reduction of the physical property when making molded body is suppressed, and in addition, the crushing of the hollow particle is suppressed, and the lightweight effect improves. By only using an inorganic dispersion stabilizer as a dispersion stabilizer in the manufacture of the hollow particle described later, the content of the surfactant etc. present in the hollow particle surface can be made less than the determination limit.

[0099] In the present invention, the content of surfactants etc. present on the surface of hollow particles refers to the ratio of the mass of surfactants etc. present on the surface of hollow particles to the mass of the hollow particles. The surfactants etc. present on the surface of hollow particles can be extracted by, for example, ultrasonic treatment of the hollow particles in water. The type and mass of the surfactants etc. extracted into water can be determined according to the 1 The peak position and peak intensity of the H-NMR spectrum are determined. In this method, the measurement limit of the amount of the surfactant and the like present on the surface of the hollow particles is usually 0.05 ppm.

[0100] In the resin composition of the present invention, the content of the hollow particles is not particularly limited. As a lower limit, it is preferably 5% by mass or more, more preferably 10% by mass or more, and as an upper limit, it is preferably 50% by mass or less, more preferably 30% by mass or less, further preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the total solid content of the resin composition.

[0101] In addition, in the resin composition of the present invention, the content of hollow particles can be appropriately adjusted according to the type of base resin and the purpose of the resin composition of the present invention, and is not particularly limited. The lower limit is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 20 parts by mass or more, relative to 100 parts by mass of the base resin. The upper limit is preferably 60 parts by mass or less, and more preferably 55 parts by mass or less.

[0102] If the content of the hollow particles is above the above lower limit, the lightweight effect brought by the hollow particles is excellent. If the content of the hollow particles is below the above upper limit, the resin composition can be fully contained with the matrix resin, thereby suppressing the reduction of the physical properties when making the molded body and improving the mechanical strength.

[0103] [Method for producing hollow particles]

[0104] The hollow particles can be produced by, for example, a production method based on a suspension polymerization method as described below.

[0105] As one embodiment of the method for producing hollow particles, there can be mentioned, for example, a method for producing hollow particles having the following steps:

[0106] A step of preparing a mixed solution comprising a polymerizable compound, a hydrophobic solvent, a dispersion stabilizer, and an aqueous medium, wherein the polymerizable compound is selected from at least one of a free radical polymerizable monomer and an epoxy resin;

[0107] a step of preparing a suspension containing polymerizable droplets of the polymerizable compound and the hydrophobic solvent dispersed in the aqueous medium by suspending the mixed liquid;

[0108] a step of subjecting the suspension to a polymerization reaction to prepare a precursor composition in which precursor particles are dispersed in the aqueous medium, wherein the precursor particles have a hollow portion surrounded by a shell containing a resin and the hollow portion is filled with the hydrophobic solvent; and

[0109] a step of removing the hydrophobic solvent from the precursor particles.

[0110] In the present invention, hollow particles whose hollow parts are filled with a hydrophobic solvent are considered to be intermediates of hollow particles whose hollow parts are filled with a gas, and are sometimes referred to as “precursor particles.” In the present invention, a “precursor composition” refers to a composition containing the precursor particles.

[0111] In the above-described production method, a suspension comprising polymerizable droplets dispersed in an aqueous medium is prepared by suspending a mixture containing a polymerizable compound, a hydrophobic solvent, a dispersion stabilizer, and an aqueous medium. The polymerizable droplets have a distribution structure in which the polymerizable compound and the hydrophobic solvent undergo phase separation, with the polymerizable compound being preferentially present on the surface and the hydrophobic solvent being preferentially present in the center. When this suspension is subjected to a polymerization reaction, a solidified material begins to precipitate on the surface of the polymerizable droplets. As the polymerization reaction proceeds, the entire surface of the droplets solidifies, forming a shell, resulting in hollow particles having a hollow portion filled with the hydrophobic solvent.

[0112] Above-mentioned manufacture method comprises the operation of preparing mixed solution, the operation of preparing suspension, the operation that suspension is supplied to polyreaction and the operation of removing hydrophobic solvent from precursor particles, and also can further comprise the operation except these.In addition, as long as technically feasible, also can carry out simultaneously as a operation two or more of above-mentioned each operation and other additional operation, can also exchange order and carry out.For example, also can carry out simultaneously the mode of suspending simultaneously while dropping into the material of preparation mixed solution, carry out preparation and suspension of mixed solution simultaneously in an operation.

[0113] As a preferred example of the method for producing the hollow particles used in the present invention, there can be mentioned a method comprising the following steps.

[0114] (1) Mixed liquid preparation process

[0115] A step of preparing a mixed solution comprising a polymerizable compound, a hydrophobic solvent, a dispersion stabilizer, and an aqueous medium;

[0116] (2) Suspension process

[0117] a step of suspending the mixed solution to prepare a suspension containing polymerizable liquid droplets of a polymerizable compound and a hydrophobic solvent dispersed in an aqueous medium;

[0118] (3) Polymerization process

[0119] a step of subjecting the suspension to a polymerization reaction to prepare a precursor composition in which precursor particles are dispersed in an aqueous medium, wherein the precursor particles have a hollow portion surrounded by a shell containing a resin and the hollow portion is filled with a hydrophobic solvent; and

[0120] (4) Solvent removal process

[0121] a step of removing the hydrophobic solvent from the precursor particles.

[0122] Figure 1 This is a schematic diagram showing an example of the production method of the present invention. Figure 1 (1) to (4) in the figure correspond to the above steps (1) to (4). The white arrows between the figures indicate the order of the steps. Figure 1 The schematic diagrams are merely for explanation, and the manufacturing method of the present invention is not limited to the method shown in the drawings. In addition, the structure, size, and shape of the materials used in the manufacturing method of the present invention are not limited to the structure, size, and shape of the various materials in these drawings.

[0123] Figure 1(1) is a schematic cross-sectional view showing one embodiment of a mixed solution in the mixed solution preparation step. As shown in the figure, the mixed solution includes an aqueous medium 1 and a low-polarity material 2 dispersed in the aqueous medium 1. Here, the low-polarity material 2 refers to a material with low polarity that is not easily miscible with the aqueous medium 1. In the present invention, the low-polarity material 2 includes a polymerizable compound and a hydrophobic solvent, etc.

[0124] Figure 1 (2) is a schematic cross-sectional view showing an embodiment of a suspension in the suspension step. The suspension includes an aqueous medium 1 and polymerizable droplets 3 dispersed in the aqueous medium 1. The polymerizable droplets 3 contain a polymerizable compound and a hydrophobic solvent, etc., but the distribution within the droplets is uneven. The polymerizable droplets 3 have the following structure: a hydrophobic solvent 4a and a material 4b other than the hydrophobic solvent and containing a polymerizable compound undergo phase separation, the hydrophobic solvent 4a being predominantly present in the center, the material 4b other than the hydrophobic solvent being predominantly present on the surface, and a dispersion stabilizer (not shown) being attached to the surface.

[0125] Figure 1 (3) is a schematic cross-sectional view showing an embodiment of a precursor composition of precursor particles obtained by a polymerization process, which contains a hydrophobic solvent in a hollow portion. The precursor particles 5 have a shell 6 containing a resin and a hollow portion filled with a hydrophobic solvent 4a. The shell 6 forming the outer surface of the precursor particles 5 is formed by polymerizing the polymerizable compound contained in the above-mentioned polymerizable droplets 3. Figure 1 In (3), the precursor particles 5 are dispersed in the aqueous medium 1 .

[0126] Figure 1 (4) is a schematic cross-sectional view showing an embodiment of the hollow particles obtained in the solvent removal step. In the solvent removal step, by removing the hydrophobic solvent from the precursor particles, hollow particles 10 having a shell 6 containing a resin and a hollow portion 7 filled with gas can be obtained. Figure 1 In (4), the hollow particles 10 are separated from the aqueous medium 1 and exist in the gas.

[0127] Hereinafter, the above four steps and other steps will be described in sequence.

[0128] (1) Mixed liquid preparation process

[0129] This step is a step of preparing a mixed solution containing a polymerizable compound, a hydrophobic solvent, a dispersion stabilizer, and an aqueous medium. The mixed solution may further contain other materials within a range that does not impair the effects of the present invention.

[0130] The materials of the mixed liquid are described in order: (A) polymerizable compound, (B) hydrophobic solvent, (C) polymerization initiator, (D) curing agent, (E) dispersion stabilizer, and (F) aqueous medium.

[0131] (A) Polymerizable compound

[0132] As polymerizable compounds, for example, free radical polymerizable monomers and epoxy resins can be preferably used. Free radical polymerizable monomers are preferred because they can form hollow particles with a uniform shell and excellent pressure resistance, while epoxy resins are preferred because they can easily introduce epoxy groups into the outer surface of the hollow particles.

[0133] (A-1) Radical polymerizable monomer

[0134] A radical polymerizable monomer refers to a compound having a radical polymerizable group. In the present invention, a radical polymerizable monomer may be simply referred to as a "polymerizable monomer." As the radical polymerizable group, from the perspective of excellent reactivity, at least one selected from a (meth)acryloyl group, a vinyl group, and an allyl group is particularly preferred, and at least one selected from a (meth)acryloyl group and a vinyl group is more preferred.

[0135] In addition, in the present invention, a polymerizable monomer having only one free radical polymerizable group in one molecule is referred to as a non-crosslinking monomer, and a polymerizable monomer having two or more free radical polymerizable groups in one molecule is referred to as a crosslinking monomer. Crosslinking monomers can form crosslinks in the polymer through free radical polymerization. In addition, the crosslinking monomer becomes the crosslinking monomer unit in the shell, and the non-crosslinking monomer becomes the non-crosslinking monomer unit in the shell.

[0136] In the present invention, a polymerizable monomer composed of carbon and hydrogen is referred to as a hydrocarbon monomer, a crosslinkable monomer composed of carbon and hydrogen is referred to as a crosslinkable hydrocarbon monomer, and a non-crosslinkable monomer composed of carbon and hydrogen is referred to as a non-crosslinkable hydrocarbon monomer. Furthermore, a polymerizable monomer having a (meth)acryloyl group as a free radical polymerizable group is referred to as an acrylic monomer, a crosslinkable monomer having a (meth)acryloyl group as a free radical polymerizable group is referred to as a crosslinking acrylic monomer, and a non-crosslinking monomer having a (meth)acryloyl group as a free radical polymerizable group is referred to as a non-crosslinking acrylic monomer. In a crosslinkable acrylic monomer, it suffices if at least one free radical polymerizable group is a (meth)acryloyl group, and preferably all free radical polymerizable groups are (meth)acryloyl groups.

[0137] In the present invention, (meth)acrylate refers to acrylate and methacrylate, (meth)acrylic acid refers to acrylic acid and methacrylic acid, and (meth)acryloyl refers to acryloyl and methacryloyl.

[0138] In the present invention, it is preferred that the radical polymerizable monomer include an epoxy group-containing monomer and an epoxy group-free monomer in combination.

[0139] [Epoxy-containing monomers]

[0140] Examples of epoxy-containing monomers include epoxy-containing (meth)acrylates such as glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and epoxycyclohexyl methyl (meth)acrylate; epoxy-containing styrenes such as p-vinylbenzyl glycidyl ether; epoxy-containing olefins such as 3,4-epoxy-1-pentene, 3,4-epoxy-1-butene, 4,5-epoxy-2-pentene, and 3,4-epoxy-1-vinylcyclohexene; and epoxy-containing ethers having a radically polymerizable group such as allyl glycidyl ether, vinyl glycidyl ether, 4-vinylcyclohexyl glycidyl ether, cyclohexenyl methyl glycidyl ether, and allylphenyl glycidyl ether. These epoxy-containing monomers can be used alone or in combination of two or more.

[0141] Among them, from the viewpoint of reactivity, epoxy-group-containing (meth)acrylates are preferred as the epoxy-group-containing monomer, and glycidyl (meth)acrylate is particularly preferred.

[0142] [Contains no epoxy monomer]

[0143] The epoxy-free monomer can be a crosslinking monomer or a non-crosslinking monomer that does not contain epoxy groups. As the epoxy-free monomer, preferably at least comprising a crosslinking monomer. By comprising a crosslinking monomer, it is easy to form a hollow portion in the particle, and then, when the suspension is supplied to the polymerization reaction, the crosslinking density of the solidified material (polymer) separated out on the surface of the droplet increases, and then the precipitate is also crosslinked to each other, and therefore the crosslinking density of the shell can be improved. Therefore, by comprising a crosslinking monomer as the epoxy-free monomer, it is easy to form a shell with excellent strength. In addition, the hollow particle easily becomes spherical, easily forms a hollow portion clearly distinguished from the shell in the particle.

[0144] Examples of the crosslinking monomer include aromatic divinyl monomers such as divinylbenzene, divinylbiphenyl, and divinylnaphthalene; linear or branched dienes such as butadiene, isoprene, 2,3-dimethylbutadiene, pentadiene, and hexadiene; and alicyclic dienes such as dicyclopentadiene, cyclopentadiene, and ethylenetetracyclododecene; crosslinking macromonomers such as polybutadiene, polyisoprene, block copolymers of styrene and butadiene (SBS), and block copolymers of styrene and isoprene (SIS); and crosslinking hydrocarbon monomers such as allyl (meth)acrylate, vinyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 3-(meth)acryloyloxy-2-hydroxypropyl (meth)acrylate. Cross-linking acrylic monomers such as 1,3-bis(methacryloyloxy)-2-hydroxypropane, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol poly(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, and ethoxylates thereof; and cross-linking macromonomers such as polyphenylene ether modified with vinyl groups at both ends and polyphenylene ether modified with (meth)acrylic acid at both ends. These cross-linking monomers can be used alone or in combination of two or more.

[0145] Among these, crosslinkable monomers are preferably crosslinkable hydrocarbon monomers and crosslinkable acrylic monomers from the viewpoint of increasing the strength of the hollow particles. Aromatic divinyl monomers are particularly preferred as the crosslinkable hydrocarbon monomer, and divinylbenzene is particularly preferred.

[0146] Furthermore, from the perspective of increasing the strength of the hollow particles, the crosslinking monomer preferably contains at least a bifunctional crosslinking monomer, and preferably contains a combination of a bifunctional crosslinking monomer and a trifunctional or higher crosslinking monomer. When a bifunctional crosslinking monomer and a trifunctional or higher crosslinking monomer are contained in combination, the content of the bifunctional crosslinking monomer in 100% by mass of the crosslinking monomer is not particularly limited. From the perspective of increasing the strength of the hollow particles, the lower limit is preferably 60% by mass or more, more preferably 70% by mass or more, and the upper limit is preferably 95% by mass or less, more preferably 85% by mass or less.

[0147] Examples of the non-crosslinking monomer include aromatic monovinyl monomers such as styrene, vinyltoluene, α-methylstyrene, p-methylstyrene, ethylvinylbenzene, ethylvinylbiphenyl, and ethylvinylnaphthalene; linear or branched monoolefins such as ethylene, propylene, and butene; and alicyclic monoolefins such as vinylcyclohexane, norbornene, tricyclododecene, and 1,4-methano-1,4,4a,9a-tetrahydrofluorene; and non-crosslinking hydrocarbon monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, t-butylaminoethyl (meth)acrylate, 2-aminoethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, propoxy 1,2-Butoxy polyethylene glycol (meth)acrylate, 1,2-Butoxy polyethylene glycol (meth)acrylate, 1,2-Hexyl polyethylene glycol (meth)acrylate, 1,2-Octyl polyethylene glycol polypropylene glycol (meth)acrylate, 1,2-Lauryl polyethylene glycol (meth)acrylate, 1,2-Stearyl polyethylene glycol (meth)acrylate, 1,2-Phenoxy polyethylene glycol polypropylene glycol (meth)acrylate, 1,2-Polyethylene glycol mono(meth)acrylate, 1,2-Polypropylene glycol mono(meth)acrylate, 1,2-Polyethylene glycol mono(meth)acrylate, 1,2-Polyethylene glycol mono(meth)acrylate, 1,2-Polyethylene glycol mono(meth)acrylate, 1,2-Polyethylene glycol mono(meth)acrylate, Non-crosslinking acrylic monomers such as glycol tetramethylene glycol (meth)acrylate, propylene glycol polybutylene glycol mono(meth)acrylate, and monoethylene glycol mono(meth)acrylate; carboxylic acid vinyl ester monomers such as vinyl acetate; halogenated aromatic vinyl monomers such as halogenated styrene; halogenated vinyl monomers such as vinyl chloride; vinylidene halide monomers such as vinylidene chloride; non-crosslinking macromonomers such as polystyrene terminally modified with (meth)acrylic acid and polymethyl methacrylate terminally modified with (meth)acrylic acid, etc.

[0148] These non-crosslinking monomers can be used alone or in combination of two or more.

[0149] Among these, the non-crosslinkable monomer is preferably a non-crosslinkable hydrocarbon monomer, more preferably an aromatic monovinyl monomer, and still more preferably styrene and ethylvinylbenzene, from the viewpoint of improving the strength of the hollow particles.

[0150] When a free radical polymerizable monomer is used as a polymerizable compound, the content of the crosslinking monomer in 100% by mass of the free radical polymerizable monomer is preferably 50% by mass or more, more preferably 55% by mass or more. If the content of the crosslinking monomer is above the above lower limit, the strength of the shell is improved and the hollow particles are easy to maintain a high porosity. On the other hand, the performance of the hollow particles can sometimes be improved by combining a crosslinking monomer and a non-crosslinking monomer as a free radical polymerizable monomer. When a non-crosslinking monomer is included, the content of the crosslinking monomer in 100% by mass of the free radical polymerizable monomer is preferably 95% by mass or less, more preferably 90% by mass or less.

[0151] The content of each monomer in 100% by mass of the radical polymerizable monomer corresponds to the content of each monomer unit in 100% by mass of all monomer units of the polymer contained in the shell.

[0152] In addition, in 100% by mass of the free radical polymerizable monomer, the content of the epoxy group-containing monomer is preferably 5% by mass or more, more preferably 10% by mass or more. If the content of the epoxy group-containing monomer is above the above lower limit, the epoxy group amount of the hollow particles easily falls within the above range. On the other hand, from the aspect of suppressing the reduction in the strength of the hollow particles, in 100% by mass of the free radical polymerizable monomer, the content of the epoxy group-containing monomer is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0153] Furthermore, from the perspective of excellent reactivity and increased strength of the hollow particles, the total content of the acrylic monomer and the hydrocarbon monomer in 100% by mass of the radical polymerizable monomer is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and particularly preferably 100% by mass.

[0154] (A-2) Epoxy resin

[0155] Epoxy resin refers to a low-molecular-weight or high-molecular-weight compound having at least one epoxy group in one molecule and capable of curing by forming a crosslinked network through reaction of the epoxy groups.

[0156] The epoxy resin is not particularly limited, and examples thereof include bixylene-type epoxy resins, bisphenol AD-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, bisphenol AF-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, phenol novolac-type epoxy resins, naphthol novolac-type epoxy resins, tert-butyl-catechol-type epoxy resins, naphthalene-type epoxy resins, naphthol-type epoxy resins, anthracene-type epoxy resins, glycidylamine-type epoxy resins, glycidyl ester-type epoxy resins, cresol novolac-type epoxy resins, bisphenol A novolac-type epoxy resins, phenol aralkyl-type epoxy resins, biphenyl-type epoxy resins, biphenyl-type epoxy resins. Aralkyl epoxy resins, phenylaralkyl epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro-ring-containing epoxy resins, cyclohexane epoxy resins, cyclohexanedimethanol epoxy resins, naphthylene ether epoxy resins, trimethylol epoxy resins, tetraphenylethane epoxy resins, isocyanurate epoxy resins, phenolphthalimidine epoxy resins, phenolphthalein epoxy resins, rubber-modified epoxy resins such as silicone-modified epoxy resins, ε-caprolactone-modified epoxy resins, brominated epoxy resins such as tetrabromobisphenol A diglycidyl ether, and the like. These epoxy resins can be used alone or in combination of two or more.

[0157] From the viewpoint of easily allowing the epoxy group content of the hollow particles to fall within the above range and improving the shell strength, the epoxy resin preferably contains a crosslinkable epoxy resin (multifunctional epoxy resin) having two or more epoxy groups in one molecule.

[0158] The crosslinkable epoxy resin is not particularly limited, and preferably used are, for example, biphenyl aralkyl epoxy resins, phenyl aralkyl epoxy resins, biphenyl epoxy resins, naphthalene epoxy resins, dicyclopentadiene epoxy resins, rubber-modified epoxy resins such as silicone-modified epoxy resins, ε-caprolactone-modified epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, alicyclic multifunctional epoxy resins, glycidyl ester multifunctional epoxy resins, glycidyl amine multifunctional epoxy resins, heterocyclic multifunctional epoxy resins, etc. The crosslinkable epoxy resins can be used alone or in combination of two or more.

[0159] As the epoxy resin, at least one selected from bisphenol A epoxy resin, dicyclopentadiene epoxy resin, naphthalene epoxy resin, and rubber-modified epoxy resin can be preferably used.

[0160] In addition, as the epoxy resin, from the perspective that the epoxy group content of the hollow particles easily falls within the above-mentioned range, the epoxy value is preferably 0.1 mmol / g or more, more preferably 0.25 mmol / g or more, further preferably 0.5 mmol / g or more, further preferably 1.0 mmol / g or more, and particularly preferably 2.0 mmol / g or more.

[0161] When an epoxy resin is used as the polymerizable compound, the content of the cross-linking epoxy resin in 100% by mass of the epoxy resin is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass, from the perspectives of improving the strength of the shell, facilitating the maintenance of a high porosity of the hollow particles, and facilitating the epoxy group content of the hollow particles to fall within the above-mentioned range.

[0162] The polymerizable compound contained in the mixed liquid is preferably selected from at least one of the above-mentioned free radical polymerizable monomers and epoxy resins. From the perspective of easily increasing the epoxy group content of the hollow particles, it is preferred to contain at least epoxy resin. A higher epoxy group content in the hollow particles tends to increase the adhesion between the hollow particles and the matrix resin, which can easily suppress the degradation of physical properties when formed into a molded article, and can easily suppress the breakage of the hollow particles, thereby improving the lightweighting effect.

[0163] Furthermore, from the viewpoint of suppressing side reactions in the shell forming step (polymerization step), it is more preferable to use only one of the above-mentioned radical polymerizable monomer or the above-mentioned epoxy resin.

[0164] The content of the polymerizable compound in the mixed liquid is not particularly limited. From the perspective of the balance between the porosity, particle size and mechanical strength of the hollow particles, it is preferably 15 to 50 mass %, more preferably 20 to 40 mass %, relative to 100 mass % of the total mass of the components in the mixed liquid excluding the aqueous medium.

[0165] Furthermore, in the obtained hollow particles, from the perspective of suppressing a decrease in strength, the total content of the polymerizable compound and the polymerization initiator and curing agent described later is preferably 96% by mass or more, more preferably 97% by mass or more, relative to 100% by mass of the total mass of the solid components excluding the hydrophobic solvent in the material serving as the oil phase in the mixed liquid.

[0166] In the present invention, the solid content refers to all components excluding the solvent, and liquid monomers and the like are included in the solid content.

[0167] (B) Hydrophobic solvent

[0168] The hydrophobic solvent used in the production method of the present invention is a non-polymerizable organic solvent that is poorly soluble in water.

[0169] The hydrophobic solvent functions as a spacer, forming hollow spaces within the particles. In the suspension step described below, a suspension of polymerizable droplets containing the hydrophobic solvent dispersed in an aqueous medium is obtained. During the suspension step, phase separation occurs within the polymerizable droplets, resulting in the low-polarity hydrophobic solvent tending to concentrate within the droplets. Ultimately, within the polymerizable droplets, the hydrophobic solvent is distributed within them according to their polarity, while other materials other than the hydrophobic solvent are distributed around them.

[0170] Furthermore, in the polymerization step described below, an aqueous dispersion containing precursor particles containing a hydrophobic solvent can be obtained. That is, the hydrophobic solvent is concentrated inside the particles, and hollow portions filled with the hydrophobic solvent are formed inside the obtained precursor particles.

[0171] The hydrophobic solvent is not particularly limited and can be appropriately selected from known hydrophobic solvents. Examples thereof include esters such as ethyl acetate and butyl acetate; ether esters such as propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate; and hydrocarbon solvents. Hydrocarbon solvents are particularly preferred, and hydrocarbon solvents having 5 to 8 carbon atoms are more preferred.

[0172] Examples of hydrocarbon solvents include aliphatic hydrocarbons including chain hydrocarbon solvents such as pentane, hexane, heptane, octane, 2-methylbutane and 2-methylpentane, paraffin solvents, and cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane and cycloheptane; and aromatic hydrocarbons such as benzene, toluene and xylene.

[0173] These hydrophobic solvents can be used alone or in combination of two or more.

[0174] In order to facilitate phase separation between the polymerizable compound and the hydrophobic solvent in the polymerizable droplets during the suspension step, the hydrophobic solvent is preferably an organic solvent having a lower solubility in water than the crosslinkable monomer or crosslinkable epoxy resin contained in the polymerizable compound.

[0175] Furthermore, when the polymerizable compound contains a hydrocarbon monomer at a ratio of greater than 50% by mass, the hydrophobic solvent is preferably a chain hydrocarbon solvent, more preferably a chain hydrocarbon solvent having 5 to 8 carbon atoms, and further preferably at least one selected from pentane, hexane, heptane, and octane. When the polymerizable compound contains an acrylic monomer at a ratio of greater than 50% by mass, the hydrophobic solvent is preferably a cyclic hydrocarbon solvent, more preferably a cyclic hydrocarbon solvent having 5 to 8 carbon atoms, and further preferably at least one selected from cyclohexane, methylcyclohexane, and cycloheptane. When the polymerizable compound contains an epoxy resin at a ratio of greater than 50% by mass, the hydrophobic solvent is preferably an aromatic hydrocarbon solvent, more preferably an aromatic hydrocarbon solvent having 5 to 8 carbon atoms, and further preferably at least one selected from benzene, toluene, and xylene.

[0176] In addition, the boiling point of the hydrophobic solvent is not particularly limited. From the perspective of easy removal in the solvent removal step described later, it is preferably 130°C or lower, more preferably 120°C or lower, and further preferably 100°C or lower. On the other hand, from the perspective of easy inclusion in the precursor particles, it is preferably 50°C or higher, more preferably 60°C or higher.

[0177] In addition, when the hydrophobic solvent is a mixed solvent containing multiple hydrophobic solvents and has multiple boiling points, it is preferred that the boiling point of the solvent with the highest boiling point among the solvents contained in the mixed solvent is below the above-mentioned upper limit value, and it is preferred that the boiling point of the solvent with the lowest boiling point among the solvents contained in the mixed solvent is above the above-mentioned lower limit value.

[0178] Furthermore, the hydrophobic solvent preferably has a relative dielectric constant of 2.5 or less at 20°C. The relative dielectric constant is one of the indicators that indicates the polarity of a compound. It is believed that when the relative dielectric constant of the hydrophobic solvent is sufficiently low, 2.5 or less, phase separation rapidly proceeds within the polymerizable droplets, facilitating the formation of hollow portions.

[0179] Examples of hydrophobic solvents having a relative dielectric constant of 2.5 or less at 20° C. are as follows. The values ​​in parentheses are relative dielectric constants.

[0180] Pentane (1.8), hexane (1.9), heptane (1.9), octane (1.9), cyclohexane (2.0), toluene (2.4).

[0181] Regarding the relative dielectric constant at 20°C, reference can be made to values ​​described in known literature (e.g., "Basic Handbook of Chemicals," edited by the Chemical Society of Japan, 4th revised edition, Maruzen Co., Ltd., published on September 30, 1993, pp. II-498 to II-503) and other technical information. Examples of methods for measuring the relative dielectric constant at 20°C include a relative dielectric constant test conducted in accordance with JIS C 2101:1999, Section 23, with the measurement temperature set at 20°C.

[0182] In the present invention, the content of the hydrophobic solvent in the mixed solution is not particularly limited. From the perspective of easily controlling the particle size of the hollow particles and easily maintaining the strength of the hollow particles while improving the porosity, it is preferably 100 parts by mass or more and 650 parts by mass or less, more preferably 120 parts by mass or more and 500 parts by mass or less, and further preferably 140 parts by mass or more and 400 parts by mass or less, relative to 100 parts by mass of the polymerizable compound. In addition, the porosity of the hollow particles can be adjusted by the amount of the hydrophobic solvent in the mixed solution. In the polymerization step described later, the oil droplets containing the polymerizable compound, etc., are subjected to polymerization reaction in a state in which the hydrophobic solvent is contained. Therefore, the more the content of the hydrophobic solvent, the higher the porosity of the hollow particles obtained.

[0183] (C) Polymerization initiator

[0184] When the mixed liquid contains a radical polymerizable monomer as the polymerizable compound, the mixed liquid preferably contains a polymerization initiator for the radical polymerizable monomer.

[0185] As the polymerization initiator, an oil-soluble polymerization initiator is preferably used. As long as the oil-soluble polymerization initiator is a lipophilic polymerization initiator with a solubility in water of 0.2% by mass or less, there is no particular limitation, and examples thereof include organic peroxides such as benzoyl peroxide, lauroyl peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxydiethylacetate, and tert-butyl peroxypivalate; azo compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile), azobisisobutyronitrile, and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). As the oil-soluble polymerization initiator, an organic peroxide is particularly preferably used. When an organic peroxide is used as the polymerization initiator, it is easy to reduce the residual amount of unreacted free radical polymerizable monomers, and the polymerization initiator or its decomposition products.

[0186] The content of the polymerization initiator is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and even more preferably 1 to 5 parts by mass relative to 100 parts by mass of the radical polymerizable monomer. If the content of the polymerization initiator is above the lower limit, the polymerization reaction can proceed sufficiently. If the content of the polymerization initiator is below the upper limit, the possibility of residual polymerization initiator after the polymerization reaction is completed is small, and the possibility of unexpected side reactions is also small.

[0187] (D) Curing agent

[0188] When the mixed liquid contains an epoxy resin as a polymerizable compound, the mixed liquid preferably contains a curing agent for the epoxy resin. As the curing agent, a known curing agent for epoxy resin can be used, and a compound containing active hydrogen can generally be used.

[0189] The curing agent is not particularly limited, and examples thereof include amine curing agents, acid anhydride curing agents, thiol curing agents, phenol curing agents, naphthol curing agents, benzoxazine curing agents, cyanate curing agents, and carbodiimide curing agents. Among them, amine curing agents are particularly preferably used due to their high reactivity with epoxy resins.

[0190] In addition, the curing agents can be used alone or in combination of two or more.

[0191] Examples of the amine curing agent include polyamine compounds such as ethylenediamine, tetramethylenediamine, hexamethylenediamine, phenylenediamine, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, norbornanediamine, isophoronediamine, phenylenediamine, and polyetheramine; 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1,2-dimethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, Imidazole compounds such as 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolium-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolium-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methyl-4'-methylimidazolium-(1')]-ethyl-s-triazine, 2-phenylimidazole isocyanuric acid adduct, and 2-methylimidazole isocyanuric acid adduct; piperazine compounds such as piperazine, 2-methylpiperazine, and 2,5-dimethylpiperazine; and amino group-containing prepolymers such as amino adducts of epoxy resins. In particular, at least one selected from polyamine compounds and imidazole compounds is preferred.

[0192] The content of the curing agent is not particularly limited and can be appropriately adjusted by the type of curing agent, etc., and is preferably 0.01 to 1000 parts by mass, more preferably 0.02 to 900 parts by mass, further preferably 0.04 to 800 parts by mass, and even more preferably 1 to 150 parts by mass relative to 100 parts by mass of the epoxy resin. If the content of the curing agent is above the lower limit, the crosslinking reaction of the epoxy group can proceed sufficiently. If the content of the curing agent is below the upper limit, the epoxy group content of the hollow particles tends to fall within the above range.

[0193] (E) Dispersion stabilizer

[0194] The dispersion stabilizer is an agent that disperses the polymerizable droplets in the aqueous medium during the suspension step. Examples of the dispersion stabilizer include inorganic dispersion stabilizers, organic or inorganic water-soluble polymer stabilizers, and surfactants.

[0195] In the present invention, an inorganic dispersion stabilizer is preferably used as the dispersion stabilizer from the viewpoints of easily controlling the particle size of droplets in the suspension, facilitating removal of the dispersion stabilizer by a washing step, and preventing the shell from becoming too thin and thus reducing the strength of the hollow particles.

[0196] Examples of the inorganic dispersion stabilizer include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate, and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, and iron hydroxide; and inorganic compounds such as silicon dioxide. These inorganic dispersion stabilizers can be used alone or in combination of two or more.

[0197] As the inorganic dispersion stabilizer, an inorganic dispersion stabilizer that is poorly soluble in water can be preferably used. Here, poorly soluble in water preferably means that the solubility in water at 25° C. is less than 1 g / L.

[0198] As the poorly water-soluble inorganic dispersion stabilizer, metal hydroxides are particularly preferred, and magnesium hydroxide is more preferred.

[0199] In the present invention, it is particularly preferred to use the sparingly water-soluble inorganic dispersion stabilizer in a state dispersed in an aqueous medium in the form of colloidal particles, that is, in a colloidal dispersion containing the sparingly water-soluble inorganic dispersion stabilizer colloidal particles. This allows the inorganic dispersion stabilizer to be easily removed in the washing step described below.

[0200] The colloidal dispersion containing the sparingly water-soluble inorganic dispersion stabilizer colloidal particles can be prepared by, for example, reacting at least one selected from alkali metal hydroxides and alkaline earth metal hydroxides with a water-soluble polyvalent metal salt (excluding alkaline earth metal hydroxides) in an aqueous medium.

[0201] Examples of the alkali metal hydroxide salt include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. Examples of the alkaline earth metal hydroxide salt include barium hydroxide, calcium hydroxide, etc.

[0202] The water-soluble polyvalent metal salt may be any water-soluble polyvalent metal salt other than the compounds belonging to the above-mentioned alkaline earth metal hydroxide salts. Examples thereof include magnesium metal salts such as magnesium chloride, magnesium phosphate, and magnesium sulfate; calcium metal salts such as calcium chloride, calcium nitrate, calcium acetate, and calcium sulfate; aluminum metal salts such as aluminum chloride and aluminum sulfate; barium salts such as barium chloride, barium nitrate, and barium acetate; and zinc salts such as zinc chloride, zinc nitrate, and zinc acetate. Among these, magnesium metal salts, calcium metal salts, and aluminum metal salts are preferred, magnesium metal salts are more preferred, and magnesium chloride is particularly preferred.

[0203] The method for reacting at least one selected from the above-mentioned alkali metal hydroxides and alkaline earth metal hydroxides with the above-mentioned water-soluble polyvalent metal salt in an aqueous medium is not particularly limited, and for example, an aqueous solution of at least one selected from the above-mentioned alkali metal hydroxides and alkaline earth metal hydroxides can be mixed with an aqueous solution of the water-soluble polyvalent metal salt.

[0204] Furthermore, colloidal silica can also be used as a colloidal dispersion containing colloid particles of an inorganic dispersion stabilizer that is poorly soluble in water.

[0205] Examples of organic water-soluble polymer stabilizers include polyvinyl alcohol, polycarboxylic acids (polyacrylic acid, etc.), celluloses (hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, etc.), polyvinyl pyrrolidone, polyacrylimide, polyethylene oxide, and poly(hydroxystearic acid-g-methyl methacrylate-co-methacrylic acid) copolymers.

[0206] Examples of the inorganic water-soluble polymer stabilizer include sodium tripolyphosphate.

[0207] The surfactant refers to a compound having both a hydrophilic group and a hydrophobic group in one molecule, and examples thereof include ionic surfactants such as well-known anionic surfactants, cationic surfactants, and amphoteric surfactants; and nonionic surfactants.

[0208] Furthermore, the solubility of the water-soluble polymer stabilizer and surfactant in water at 25° C. is usually 1 g / L or more.

[0209] The content of the dispersion stabilizer is not particularly limited, but is preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the total mass of the polymerizable compound and the hydrophobic solvent. By setting the dispersion stabilizer content above the lower limit, the polymerizable droplets can be fully dispersed in the suspension without agglomeration. On the other hand, by setting the dispersion stabilizer content below the upper limit, an increase in the viscosity of the suspension during granulation can be prevented, thereby avoiding the problem of the suspension clogging the granulator.

[0210] The content of the dispersion stabilizer is preferably 0.5 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the aqueous medium.

[0211] In the hollow particles of the present invention, from the aspect of the reduction of the reactivity of the hollow particles and the matrix resin, the adhesion of the hollow particles and the matrix resin, the reduction of the physical property when the molded body is suppressed, and the aspect of the reduction of the crushing of the hollow particles and the improvement of the lightweight effect, the residual amount of the dispersion stabilizer is less and more preferred, and most preferably does not contain a dispersion stabilizer. Particularly, the residual amount of the water-soluble polymer stabilizer and the surfactant is less and more preferred, and preferably does not contain a water-soluble polymer stabilizer and a surfactant. By only using an inorganic dispersion stabilizer as a dispersion stabilizer, it is possible to obtain hollow particles in which the water-soluble polymer stabilizer and the surfactant are all less than the detection limit.

[0212] (F) Water-based media

[0213] In the present invention, the aqueous medium refers to a medium selected from water, a hydrophilic solvent, and a mixture of water and a hydrophilic solvent.

[0214] When a mixture of water and a hydrophilic solvent is used, it is important that the polarity of the mixture as a whole does not become too low from the perspective of forming polymerizable droplets. In this case, the mass ratio of water to hydrophilic solvent (water:hydrophilic solvent) can be set to 99:1 to 50:50, for example.

[0215] The hydrophilic solvent in the present invention is not particularly limited as long as it is fully miscible with water without phase separation. Examples of the hydrophilic solvent include alcohols such as methanol and ethanol; tetrahydrofuran (THF); and dimethyl sulfoxide (DMSO).

[0216] The content of the aqueous medium is not particularly limited. From the viewpoint of ensuring that the particle size and porosity of the hollow particles are within the preferred ranges described below, the lower limit is preferably 200 parts by mass or more, more preferably 400 parts by mass or more, and even more preferably 600 parts by mass or more, relative to 100 parts by mass of the total amount of the polymerizable compound, polymerization initiator, and curing agent contained in the mixed liquid, and the upper limit is preferably 1000 parts by mass or less, and more preferably 800 parts by mass or less.

[0217] The mixed liquid may further contain other materials different from the materials (A) to (F) described above, within a range not impairing the effects of the present invention.

[0218] A mixed solution can be obtained by mixing the above-mentioned materials with other materials as needed and stirring them appropriately. In this mixed solution, an oil phase containing lipophilic materials such as (A) the polymerizable compound, (B) the hydrophobic solvent, (C) the polymerization initiator, and (D) the curing agent is dispersed in particles of approximately several millimeters in an aqueous phase containing (E) the dispersion stabilizer and (F) the aqueous medium. The dispersion state of these materials in the mixed solution can be observed visually, depending on the type of materials.

[0219] In the mixed solution preparation step, the mixed solution can be obtained by simply mixing the above-mentioned materials with other materials as needed and stirring them appropriately. From the perspective of easily achieving a uniform shell, it is preferred to separately prepare an oil phase containing a polymerizable compound and a hydrophobic solvent, and an aqueous phase containing a dispersion stabilizer and an aqueous medium, and then mix them to prepare the mixed solution. In the present invention, a colloidal dispersion in which a poorly water-soluble inorganic dispersion stabilizer is dispersed in the form of colloidal particles in an aqueous medium can be preferably used as the aqueous phase.

[0220] By separately preparing the oil phase and the water phase in advance and then mixing them, hollow particles having a uniform composition of the shell portion can be produced, and the particle size of the hollow particles can also be easily controlled.

[0221] (2) Suspension process

[0222] The suspending step is a step of preparing a suspension in which polymerizable liquid droplets containing a hydrophobic solvent are dispersed in an aqueous medium by suspending the mixed liquid.

[0223] The suspension method for forming the polymerizable droplets is not particularly limited, and a known suspension method can be employed. Examples of dispersers used to prepare the suspension include horizontal or vertical inline dispersers such as the Milder manufactured by Ohyo Kiko Co., Ltd., the Cavitron manufactured by Eurotec Co., Ltd., and inline dispersers manufactured by IKA (e.g., the DISPAX-REACTOR (registered trademark) DRS); and emulsifying dispersers such as the HOMOMIXER MARK II series manufactured by Plemix Co., Ltd.

[0224] In the dispersion for preparing a suspension, from the perspective of ensuring that the particle size of the hollow particles is within the preferred range described above, the tip speed of the blade of the rotating portion of the disperser is preferably 5 m / s or more, more preferably 10 m / s or more, and even more preferably 15 m / s or more. On the other hand, from the perspective of reducing the proportion of irregular-shaped particles, the tip speed is preferably 90 m / s or less, more preferably 89 m / s or less, and even more preferably 88 m / s or less.

[0225] In the suspension prepared in the suspension step, polymerizable droplets containing the lipophilic material and having a particle size of approximately 1 to 20 μm are uniformly dispersed in the aqueous medium. While these polymerizable droplets are difficult to observe with the naked eye, they can be observed using known observation equipment such as an optical microscope.

[0226] During the suspension process, phase separation occurs in the polymerizable droplets, so the low-polarity hydrophobic solvent tends to concentrate inside the droplets. As a result, the resulting droplets contain the hydrophobic solvent inside and materials other than the hydrophobic solvent around them.

[0227] The polymerizable liquid droplets dispersed in the aqueous medium are formed by surrounding an oil phase containing a polymerizable compound and a lipophilic material such as a hydrophobic solvent with a dispersion stabilizer.

[0228] When a free radical polymerizable monomer is used as the polymerizable compound and an oil-soluble polymerization initiator is used as the polymerization initiator, the oil-soluble polymerization initiator generates polymerization-initiating free radicals within the polymerizable droplets, which are microscopic oil droplets. Consequently, precursor particles of the target particle size can be produced without excessive growth of the microscopic oil droplets. In suspension polymerization methods using such oil-soluble polymerization initiators, there is no opportunity for the polymerization initiator to come into contact with the free radical polymerizable monomer dispersed in the aqueous medium. Therefore, the use of an oil-soluble polymerization initiator can suppress the production of excess resin particles as byproducts, such as small, dense particles, in addition to the target hollow resin particles.

[0229] (3) Polymerization process

[0230] This step is a step of subjecting the suspension obtained in the suspending step to a polymerization reaction to prepare a precursor composition containing precursor particles having a hollow portion surrounded by a shell containing a resin and filled with the hydrophobic solvent.

[0231] In this step, the shell portion of the polymerizable liquid droplets containing the hydrophobic solvent inside is polymerized, so that a hollow portion filled with the hydrophobic solvent is formed inside the obtained precursor particles.

[0232] In the polymerization step, the polymerization method is not particularly limited, and for example, a known polymerization method such as a batch method (intermittent method), a semi-continuous method, and a continuous method can be adopted.

[0233] The polymerization temperature is not particularly limited, but is preferably 60° C. or higher, more preferably 70° C. or higher, and even more preferably 80° C. or higher from the perspective of sufficient polymerization reaction. It is preferably 95° C. or lower from the perspective of suppressing evaporation of the aqueous medium.

[0234] The polymerization reaction time is not particularly limited, but is preferably 5 hours or more, more preferably 10 hours or more, from the perspective of sufficient polymerization reaction. From the perspective of production efficiency, it is preferably 60 hours or less, more preferably 48 hours or less, and even more preferably 36 hours or less.

[0235] The suspension during the polymerization reaction is usually stirred. The stirring power is not particularly limited, but is preferably 0.01 kW / m 3 More than 0.02kW / m 3 More than, more preferably 0.03kW / m 3 From the perspective of reducing the proportion of irregular particles, it is preferably 0.20 kW / m 3 Below, more preferably 0.10kW / m 3Below, more preferably 0.05kW / m 3 the following.

[0236] (4) Solvent removal process

[0237] This step is a step of removing the hydrophobic solvent from the precursor particles.

[0238] As methods for removing the hydrophobic solvent from precursor particles, for example, there can be cited: (i) a method in which, after removing the hydrophobic solvent from the precursor particles in the slurry by introducing a gas into the slurry-like precursor composition, solid-liquid separation is performed to remove the aqueous medium remaining in the hollow particles in the gas, thereby obtaining hollow particles whose hollow portions are filled with gas; (ii) a method in which, after solid-liquid separation of the slurry-like precursor composition, the hydrophobic solvent in the precursor particles is removed in the gas, thereby obtaining hollow particles whose hollow portions are filled with gas; and (iii) a method in which, under a predetermined pressure (high pressure, normal pressure, or reduced pressure), the hydrophobic solvent is distilled off from the precursor particles contained in the slurry-like precursor composition.

[0239] The above method (i) and the above method (ii) are particularly preferred from the viewpoint of excellent removal efficiency of the hydrophobic solvent, and the above method (i) is more preferred from the viewpoint of removing impurities together with the hydrophobic solvent.

[0240] In the above method (i), as a method for removing the hydrophobic solvent from the precursor particles in the slurry, a method in which a gas is bubbled into the precursor composition while stirring the slurry in a stirring tank to remove the hydrophobic solvent from the precursor particles is particularly preferred. This method can produce hollow particles whose hollow portions are filled with the bubbled gas.

[0241] Blast gas into the precursor composition can be carried out by, for example, directly importing gas into the precursor composition, i.e., directly blowing gas into the precursor composition. Alternatively, the precursor composition can be stirred in a stirred tank having a liquid phase portion and a gas phase portion that comprise the precursor composition, so that the gas in the gas phase portion is blasted into the precursor composition. From the aspect of efficiently removing impurities such as unreacted polymerizable monomers remaining in the hydrophobic solvent and the precursor particles enclosed in the precursor particles, it is particularly preferred that gas is directly imported into the precursor composition while stirring the precursor composition in the stirred tank with the gas phase portion, thus blasting gas into the precursor composition. In addition, the gas phase portion in the stirred tank is preferably filled with the gas that is blasted into the precursor composition in advance.

[0242] The gas blown into the precursor composition is preferably at least one selected from an inert gas and air, and more preferably an inert gas. Examples of the inert gas include nitrogen, argon, and helium, with nitrogen being particularly preferred.

[0243] From the perspective of efficiently removing the hydrophobic solvent contained in the precursor particles, the treatment time for blowing gas into the precursor composition is preferably 2 hours or more, more preferably 5 hours or more, further preferably 10 hours or more, and further preferably 15 hours or more. From the perspective of manufacturing efficiency, it is preferably 72 hours or less, and more preferably 60 hours or less.

[0244] On the other hand, when the polymerization reaction time in the above-mentioned polymerization step is 50 hours or more, even if the time of the bubbling treatment in the solvent removal step is less than 2 hours, the hydrophobic solvent contained in the precursor particles can be fully removed. When the polymerization reaction time in the above-mentioned polymerization step is 50 hours or more, the time of the bubbling treatment in the solvent removal step is preferably 20 minutes or more, more preferably 30 minutes or more.

[0245] The stirring power when stirring the precursor composition is not particularly limited, but is preferably 0.01 kW / m from the perspective of efficiently removing the hydrophobic solvent contained in the precursor particles. 3 More than 0.02kW / m 3 More than, more preferably 0.03kW / m 3 From the perspective of reducing the ratio of irregular-shaped particles and suppressing the foaming of the precursor composition, the preferred speed is 0.60 kW / m 3 Below, more preferably 0.55kW / m 3 Below, more preferably 0.50kW / m 3 Below, more preferably 0.20kW / m 3 Below, particularly preferably 0.10kW / m 3 Below, can also be 0.05kW / m 3 the following.

[0246] From the aspect of efficiently removing the hydrophobic solvent enclosed in the precursor particles, it is preferably carried out under a pressure of more than 20kPa and less than 300kPa to the precursor composition by bubbling gas, more preferably under a pressure of more than 40kPa and less than 200kPa. In addition, from the aspect that yield can be improved, it is preferably carried out under a pressure above the above-mentioned lower limit, and from the aspect that the ratio of irregular-shaped particles can be reduced, it is preferably carried out under a pressure below the above-mentioned upper limit. Wherein, from the aspect that the removal efficiency of the hydrophobic solvent is excellent, it is preferably carried out under a pressure below atmospheric pressure to the precursor composition by bubbling gas, more preferably carried out under a reduced pressure of less than 60kPa. On the other hand, from the aspect that suppresses the foaming of the precursor composition, it is preferably carried out under a pressurization of more than 150kPa. By suppressing the foaming of the precursor composition when bubbling, the yield of hollow particles can be improved. In addition, the above-mentioned pressure can be the internal pressure of the agitated tank.

[0247] The flow rate of the gas introduced into the stirring tank is not particularly limited. From the perspective of efficiently removing the hydrophobic solvent contained in the precursor particles, the flow rate per unit time is preferably 4 L / min or more, more preferably 8 L / min or more, and even more preferably 10 L / min or more. The flow rate per unit volume is preferably 200 L / (min·m 3 ) or more, more preferably 8000 L / (min·m 3 ) or more, more preferably 10000 L / (min·m 3 The upper limit of the gas flow rate is based on cost reduction. For example, as a flow rate per unit time, it can be less than 10,000 L / min, and as a flow rate per unit volume, it can be 500,000 L / (min·m 3 )the following.

[0248] When using a stirring tank having a capacity of 3 to 15,000 L, the flow rate of the gas is preferably within the above range.

[0249] The stirring tank preferably has a liquid phase containing the precursor composition and a gas phase. This is because if the stirring tank has a gas phase, the hydrophobic solvent contained in the precursor particles can be transferred to the gas phase, thereby improving the removal efficiency.

[0250] From the perspective of being able to efficiently remove the hydrophobic solvent contained in the precursor particles, the ratio of the liquid phase to the entire stirring tank is preferably 30% by volume or more and less than 80% by volume.

[0251] As a method for directly introducing gas into the precursor composition, for example, the gas is preferably introduced directly into the precursor composition within the stirred tank from the side or bottom, and more preferably from the bottom of the stirred tank. Here, the bottom of the stirred tank refers to the portion visible when looking up at the stirred tank in use. The stirred tank is typically cylindrical, and in a cylindrical stirred tank, the bottom surface located on the lower side in the direction of gravity is the bottom, and is also the deepest portion.

[0252] When introducing gas directly into the precursor composition, it is preferable to introduce the gas closer to the deepest part of the stirring tank because the gas can be more uniformly blown into the precursor composition. When the gas is uniformly blown into the precursor composition, the hydrophobic solvent removed from the precursor particles is more easily transferred to the gas phase above, thereby improving the removal efficiency.

[0253] Furthermore, from the perspective of easily and uniformly blowing gas into the precursor composition, the introduction of gas into the precursor composition is preferably performed toward the center of the region occupied by the precursor composition within the stirred tank. That is, when the gas is introduced from the bottom of the stirred tank, it is preferably introduced in the direction opposite to the direction of gravity.

[0254] In addition, in the present invention, the direction of gravity is not necessarily on the same straight line as the direction of gravity, and an axial deviation of, for example, within 30 degrees is allowed.

[0255] On the other hand, sometimes the yield of hollow particles can be increased by introducing gas only into the gas phase in the stirring tank and stirring the precursor composition in the stirring tank instead of directly introducing gas into the precursor composition, thereby blowing the gas in the gas phase into the precursor composition.

[0256] This process can be performed using, for example, Figure 2 In addition, Figure 2 The diagram is only for illustration, and the stirring device used in the solvent removal process of the present invention is not limited to the stirring device shown in the diagram. In addition, the structure, size and shape of the stirring device used in the solvent removal process of the present invention are not limited to Figure 2 The structure, size and shape shown.

[0257] exist Figure 2 In the stirring device shown, if the precursor composition as a slurry liquid is injected into the supply tank 12, the precursor composition is supplied from the supply tank 12 to the stirring tank 11 via the supply line 16. The method of supplying the precursor composition is not particularly limited, and a method using a liquid feeding pump can be mentioned. The precursor composition is supplied to the stirring tank 11 via an internal nozzle (not shown). The precursor composition 20 in the stirring tank 11 is stirred by rotating a rotor (not shown) provided in the stirring tank 11.

[0258] Gas can be introduced into the stirring tank 11 from the gas inlet 13a, 13b or 13c of the stirring tank 11. The gas inlet 13a is provided at the bottom of the stirring tank 11, and the gas inlet 13b is provided at the side of the stirring tank 11. When the gas is introduced from the gas inlet 13a or 13b, the gas can be directly blown into the precursor composition 20 in the stirring tank 11 and bubbling is performed. The gas inlet 13c is provided at the upper part of the stirring tank 11. When the gas is introduced from the gas inlet 13c, the gas is blown into the gas phase portion 21 in the stirring tank 11. By stirring the precursor composition 20 in the stirring tank 11, the gas in the gas phase portion 21 is blown into the precursor composition 20.

[0259] exist Figure 2In the stirring device shown, the precursor composition 20 stirred in the stirring tank 11 is returned from the outlet 14 to the stirring tank 11 via the circulation line 17 a , the supply tank 12 , and the supply line 16 , thereby circulating the precursor composition 20 in the stirring device.

[0260] Figure 2 The stirring device shown further has a spray mechanism 15. Figure 2 In the stirring device shown, a portion of the precursor composition 20 stirred in the stirring tank 11 can be supplied from the outlet 14 to the spray mechanism 15 via the circulation line 17 b and sprayed toward the liquid surface 20 a of the precursor composition 20 in the stirring tank 11 .

[0261] Furthermore, the internal pressure of the stirring tank 11 can be adjusted by adjusting the flow rate of the precursor composition discharged from the stirring tank 11 .

[0262] During the period of bubbling gas into the precursor composition, it is preferred to repeat the process of supplying the gas from the supply tank to the stirred tank, stirring the gas in the stirred tank, and then discharging the gas into the supply tank, so that the precursor composition circulates within the stirring device. This allows efficient removal of the hydrophobic solvent contained within the precursor particles. The flow rate of this circulation is not particularly limited.

[0263] When bubbling gas into the precursor composition, it is preferred that a portion of the precursor composition is supplied from the stirring tank to the spray mechanism and sprayed onto the liquid surface of the precursor composition in the stirring tank. This allows efficient removal of the hydrophobic solvent contained in the precursor particles, thereby shortening the bubbling treatment time.

[0264] The precursor composition can be sprayed continuously or intermittently while the gas is being blown into the precursor composition, with continuous spraying being particularly preferred. When the precursor composition is sprayed intermittently, it is preferred that the precursor composition be sprayed until the foaming disappears when the liquid level rises due to foaming of the precursor composition. The amount of sprayed precursor composition is not particularly limited.

[0265] Furthermore, from the perspective of reducing the residual amount of the hydrophobic solvent, the temperature at which the gas is bubbled into the precursor composition is preferably at least the temperature obtained by subtracting 35°C from the boiling point of the hydrophobic solvent, more preferably at least the temperature obtained by subtracting 30°C from the boiling point of the hydrophobic solvent, and even more preferably at least the temperature obtained by subtracting 20°C from the boiling point of the hydrophobic solvent. Here, when the hydrophobic solvent is a mixed solvent containing multiple hydrophobic solvents and has multiple boiling points, the boiling point of the hydrophobic solvent in the solvent removal step 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 the multiple boiling points.

[0266] Furthermore, the temperature when blowing the gas into the precursor composition is usually set to a temperature equal to or higher than the polymerization temperature in the above-mentioned polymerization step.

[0267] The temperature when the gas is blown into the precursor composition is not particularly limited, and may be 50 to 100°C.

[0268] In the above method (ii), after the solid-liquid separation of the slurry-like precursor composition, the precursor particles are dried in a gas, and the hydrophobic solvent contained in the precursor particles is removed in the gas. As a result, the hydrophobic solvent inside the precursor particles is replaced with the gas, and hollow particles filled with gas can be obtained.

[0269] " in gas " in this process strictly refers to the outside of precursor particles does not have the environment of liquid component completely and the outside of precursor particles only has the environment of the minute amount of liquid component that does not affect the degree of removing hydrophobic solvent. " in gas " can also be said to be the state that precursor particles are not present in the slurry, can also be said to be the state that precursor particles are present in dry powder. That is, it is important to remove the hydrophobic solvent under the environment that precursor particles are in direct contact with the gas outside.

[0270] The method for removing the hydrophobic solvent in the precursor particles in a gas is not particularly limited, and a known method can be employed, such as reduced pressure drying, heat drying, airflow drying, or a combination of these methods.

[0271] In particular, when using a heat drying method, the heating temperature must be at least the boiling point of the hydrophobic solvent and at or below the maximum temperature at which the shell structure of the precursor particles does not collapse. Therefore, depending on the shell composition of the precursor particles and the type of hydrophobic solvent, the heating temperature can be, for example, 50 to 200°C, 70 to 200°C, or even 100 to 200°C.

[0272] In addition, pre-drying may be performed. For example, pre-drying can be performed by drying with a drying device such as a dryer or a drying appliance such as a hand dryer.

[0273] By the drying operation in the gas, the hydrophobic solvent inside the precursor particles can be replaced by the gas outside, and as a result, hollow particles can be obtained in which the hollow portion is occupied by the gas.

[0274] The drying environment is not particularly limited and can be appropriately selected according to the purpose of the hollow particles. Examples of drying environments include air, oxygen, nitrogen, argon, etc. In addition, after the hollow particles are temporarily filled with gas, the hollow particles can be dried under reduced pressure to obtain a temporarily vacuum hollow particle.

[0275] (5) Cleaning process

[0276] The above-mentioned production method preferably further comprises a washing step for removing the dispersion stabilizer.

[0277] The cleaning step is preferably carried out by, for example, repeating the following series of operations twice or more: adding an acid or a base to the slurry-like precursor composition or the aqueous dispersion of the hollow particles after the solvent removal step, thereby dissolving the dispersion stabilizer contained in the hollow particles or precursor particles in the aqueous medium, then separating the hollow particles or precursor particles from the aqueous medium, then dispersing the separated hollow particles or precursor particles in ion exchange water and re-slurrying them, and then separating the hollow particles or precursor particles.

[0278] Performing the washing step on the hollow particles after removing the hydrophobic solvent from the precursor particles is preferable because the hollow particles are less likely to aggregate during washing, and the particles can be thoroughly washed, resulting in improved cleaning properties.

[0279] In order to remove more of the dispersion stabilizer remaining in the hollow particles or precursor particles, the following series of operations is preferably repeated three or more times in the washing step: the hollow particles or precursor particles separated after the addition of acid or alkali are dispersed in ion-exchanged water and re-slurried, followed by separation of the hollow particles or precursor particles. This operation is more preferably performed four or more times, and even more preferably five or more times. The upper limit is not particularly limited, but from the perspective of ease of production, it can be, for example, ten or fewer times, or eight or fewer times.

[0280] When the dispersion stabilizer used is an inorganic dispersion stabilizer soluble in acid, it is preferred to add an acid. When the dispersion stabilizer used is an inorganic dispersion stabilizer soluble in alkali, it is preferred to add an alkali.

[0281] When the dispersion stabilizer used is an acid-soluble inorganic dispersion stabilizer, an acid is added to the slurry-like precursor composition or the aqueous dispersion of the hollow particles after the solvent removal step to adjust the pH to preferably 6.5 or less, more preferably 6 or less. The acid to be added includes inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid; and organic acids such as formic acid and acetic acid. Sulfuric acid is particularly preferred from the perspectives of high dispersion stabilizer removal efficiency and minimal burden on production equipment.

[0282] The method for separating hollow particles or precursor particles from an aqueous medium, i.e., the method for solid-liquid separation is not particularly limited, and examples thereof include centrifugation, filtration, and static separation. Filtering is particularly preferred because it is easy to operate and has a high removal efficiency for a dispersion stabilizer. Furthermore, when performing solid-liquid separation, the hollow particles or precursor particles obtained by filtration are preferably dehydrated by a known method.

[0283] As the filtration method, any method such as natural filtration (normal pressure filtration), reduced pressure filtration, pressurized filtration, centrifugal filtration, etc. can be used. In terms of efficiently removing the dispersion stabilizer remaining in the hollow particles or precursor particles, pressurized filtration is particularly preferred.

[0284] In the production method of the present invention, the operation of separating the hollow particles or precursor particles from the aqueous medium is performed multiple times in the washing step. Preferably, pressure filtration is performed at least once, and more preferably, pressure filtration is performed throughout the operation of separating the hollow particles or precursor particles from the aqueous medium.

[0285] (6) Drying process

[0286] The above-mentioned production method may further include a drying step for removing moisture remaining in the hollow particles. The method for drying and removing moisture remaining in the hollow particles is not particularly limited, and the same method as the method for drying the precursor particles in a gas in the method (ii) of the above-mentioned solvent removal step can be used. In the drying step, the dehydrated filter cake of the hollow particles is generally dried.

[0287] The water content of the hollow particles before drying used in the drying step is usually 40 to 80%. In the present invention, the water content is calculated by the following formula (IV).

[0288] Formula (IV)

[0289] Moisture content (%) = {(w1-w2) / w1}×100

[0290] In the above formula (IV), w1 represents the mass of the measurement sample, and w2 represents the mass of the measurement sample after being dried at 200°C for 12 hours and then cooled to 25°C.

[0291] (7) Others

[0292] In addition to the above-mentioned steps (1) to (6), a particle internal replacement step may be added. The particle internal replacement step is a step in which the gas or liquid inside the hollow particle is replaced with another gas or liquid. This replacement can change the environment inside the hollow particle, selectively enclose molecules inside the hollow particle, or modify the chemical structure inside the hollow particle to suit the intended use.

[0293] [Matrix resin]

[0294] The resin composition of the present invention includes a matrix resin having a functional group capable of reacting with an epoxy group. The reaction between the epoxy group and the functional group of the matrix resin may be a reaction to form a covalent bond.

[0295] From the viewpoint of reactivity, the functional group capable of reacting with the epoxy group is preferably at least one selected from a hydroxyl group, an amino group, an epoxy group, a carboxyl group, a carboxylic anhydride group, a thiol group, an isocyanate group and a silanol group. Among them, from the perspective of a high-strength cross-linking reaction with the epoxy group on the surface of the hollow particles, the functional groups possessed by the matrix resin are particularly preferably epoxy groups, amino groups, hydroxyl groups, carboxyl groups and carboxylic anhydride groups.

[0296] As the matrix resin having a functional group capable of reacting with an epoxy group, it is preferred to use, for example, at least one selected from epoxy resins, benzoxazine resins, cyanate resins, polyimide resins, silicone resins, polyester resins, liquid crystal polymers (LCP), modified polyolefin resins, polyphenylene ether resins, thiol resins, polyurethane resins, polyurea resins, and raw material compounds of these resins. Preferably, according to the use of the resin composition of the present invention, these matrix resins are appropriately selected and used. Among them, it is particularly preferred to include at least one selected from epoxy resins, benzoxazine resins, polyimide resins, polyester resins, liquid crystal polymers (LCP), modified polyolefin resins, polyphenylene ether resins, and raw material compounds of these resins as the matrix resin.

[0297] Examples of the epoxy resin include the same epoxy resins as those that can be used in the hollow particles described above.

[0298] The epoxy resin used as the matrix resin preferably has an epoxy equivalent of 1000 or less, more preferably 500 or less, in order to obtain a cured product with a high crosslinking density. The lower limit of the epoxy equivalent of the epoxy resin is not particularly limited, and may be, for example, 100 or more.

[0299] Benzoxazine resins and polyphenylene ether resins are preferably used as the base resin having a hydroxyl group.

[0300] The benzoxazine resin is not particularly limited, but a known compound having two or more dihydrobenzoxazine rings in one molecule can be preferably used, and examples thereof include Pd-type benzoxazine and Fa-type benzoxazine.

[0301] The polyphenylene ether resin is not particularly limited, and known resins containing a polyphenylene ether skeleton can be used, such as poly(2,6-dimethyl-1,4-phenylene) ether, an alloy polymer of poly(2,6-dimethyl-1,4-phenylene) ether and polystyrene, and an alloy polymer of poly(2,6-dimethyl-1,4-phenylene) ether and a styrene-butadiene copolymer.

[0302] Polyimide resins are obtained by the imidization reaction of polyamic acid. Polyamic acid has an amide bond and a carboxyl group. Polyamic acid is obtained by the reaction of a tetracarboxylic acid component such as tetracarboxylic dianhydride, tetracarboxylic acid, or a tetracarboxylic acid diester, and a diamine component.

[0303] A tetracarboxylic acid component and a diamine component, which are raw material compounds of the polyimide resin, are preferably used as a base resin containing a carboxyl group or a carboxylic anhydride group and a base resin containing an amino group, respectively.

[0304] As a tetracarboxylic acid component, benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, pyromellitic acid and its dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid and its dianhydride, etc. are mentioned, for example.

[0305] As a diamine component, p-phenylenediamine, 4,4'-diaminodiphenyl ether, etc. are mentioned, for example.

[0306] As polyester resins and liquid crystal polymers (LCP), polyester resins and liquid crystal polymers (LCP) having at least one functional group selected from hydroxyl groups, carboxyl groups and amino groups derived from raw materials at the polymer terminals are preferably used. In addition, polyester resins and liquid crystal polymers (LCP) generally have alkoxycarbonyl groups. The above-mentioned functional groups present at the polymer terminals of polyester resins and liquid crystal polymers (LCP) react with epoxy groups present on the surface of hollow particles. Through this reaction, a portion of the epoxy groups on the surface of the hollow particles becomes hydroxyl groups, which react with the alkoxycarbonyl groups of polyester resins and liquid crystal polymers (LCP) to form a stronger cross-linked structure.

[0307] The polyester resin is not particularly limited, and a saturated or unsaturated polyester resin can be used.

[0308] As the modified polyolefin resin, it is preferable to use a modified polyolefin resin into which a functional group capable of reacting with an epoxy group is introduced by modification. The modified polyolefin resin can be appropriately selected from known resins having a polyolefin skeleton.

[0309] As the modified polyolefin resin, for example, a carboxylic acid-modified polyolefin resin into which a carboxyl group or a carboxylic anhydride group is introduced is preferably used.

[0310] The carboxylic acid-modified polyolefin resin can be obtained, for example, by grafting at least one selected from α,β-unsaturated carboxylic acids and their anhydrides onto a polyolefin resin. Examples of α,β-unsaturated carboxylic acids and their anhydrides include (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and their anhydrides. Maleic anhydride and maleic acid are particularly preferred, and maleic anhydride is more preferred.

[0311] As the carboxylic acid-modified polyolefin resin, commercially available products such as the UMEX series manufactured by Sanyo Chemical Industries, Ltd. may be used.

[0312] The acid value of the carboxylic acid-modified polyolefin resin is preferably 3 mgKOH / g or higher, more preferably 10 mgKOH / g or higher, and even more preferably 15 mgKOH / g or higher. The upper limit is preferably 150 mgKOH / g or lower, more preferably 120 mgKOH / g or lower, and even more preferably 100 mgKOH / g or lower.

[0313] Furthermore, as the modified polyolefin resin, an epoxy-modified polyolefin resin into which an epoxy group is introduced is also preferably used.

[0314] The epoxy-modified polyolefin resin can be obtained by copolymerizing a polymerizable monomer containing an olefin and an epoxy group-containing monomer, for example. Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, allyl glycidyl ether, and epoxybutene.

[0315] As the epoxy-modified polyolefin resin, commercially available products such as MODIPER (registered trademark) A4100, A4300, and A4400 manufactured by NOF Corporation may be used.

[0316] Cyanate resins are preferably used as the base resin having an isocyanate group. Examples of cyanate resins include novolac-type cyanate resins, bisphenol A-type cyanate resins, bisphenol E-type cyanate resins, bisphenol F-type cyanate resins, tetramethylbisphenol F-type cyanate resins, and dicyclopentadiene-type cyanate resins.

[0317] The polyurethane resin is obtained by the reaction of a polyol component having a hydroxyl group and a polyisocyanate component having an isocyanate group.

[0318] A polyol component and a polyisocyanate component, which are raw material compounds of the polyurethane resin, are preferably used as a base resin containing a hydroxyl group and a base resin containing an isocyanate group, respectively.

[0319] Examples of the polyol component include ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, sucrose, polyoxypropylene triol, and polyester polyol.

[0320] Examples of the polyisocyanate component include aliphatic polyisocyanates and aromatic polyisocyanates.

[0321] Examples of the aliphatic polyisocyanate include polyisocyanates having a chain structure, such as tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate; and polyisocyanates having a cyclic structure, such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane.

[0322] Examples of the aromatic polyisocyanate include tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-dibenzyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyl diphenylmethane diisocyanate, tetraalkyl diphenylmethane diisocyanate, and α,α,α,α-tetramethylxylylene diisocyanate.

[0323] The polyurea resin is obtained by the reaction of a polyisocyanate component having an isocyanate group and a polyamine component having an amino group.

[0324] A polyisocyanate component and a polyamine component, which are raw material compounds of the polyurea resin, are preferably used as the base resin containing an isocyanate group and the base resin containing an amino group, respectively.

[0325] Examples of the polyisocyanate component include the same ones as those used for the polyurethane resin.

[0326] Examples of the polyamine component include bifunctional polyamines such as ethylenediamine, propylenediamine, pentamethylenediamine, isophoronediamine, xylylenediamine, diphenylmethanediamine, hydrogenated diphenylmethanediamine, hydrazine, and poly(propylene glycol)diamine; and trifunctional or higher polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and polyamidepolyamine.

[0327] Silicone resins are preferably used as the base resin having silanol groups. As the silicone resins, any curing reaction type such as addition type, condensation type, ultraviolet curing type, electron beam curing type, and solventless type can be used. Examples of commercially available curable silicone resins include KS-774, KS-775, KS-778, KS-779H, KS-847, KS-847T, KS-856, X-62-2422, and X-62-2461 manufactured by Shin-Etsu Chemical Co., Ltd.; DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, and DKQ3-210 manufactured by Dow Corning Asia; YSR-3022, TPR-6700, TPR-6720, and TPR-6721 manufactured by Toshiba Silicone Corporation; and SD7220, SD7226, and SD7229 manufactured by Dow Corning.

[0328] A thiol resin is preferably used as the base resin having a thiol group.

[0329] Examples of the thiol resin include thiol compounds such as trimethylolpropane tris(3-mercaptopropionate), pentaerythritol 3-mercaptopropionate, dipentaerythritol hexa(3-mercaptopropionate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, polyethylene glycol = bis(3-mercaptopropionate), and pentaerythritol tetrapropylthiol.

[0330] In addition, polyphenylene sulfide resin is preferably used as a thiol resin because it has a thiol group derived from the raw material at the polymer terminal. The polyphenylene sulfide resin is not particularly limited, and a known resin containing a polyphenylene sulfide skeleton can be used. Polymers similar to polyphenylene sulfide (for example, polyphenylene sulfide ketone PPSK, polyphenylene sulfide sulfone PPSS, polybiphenylene sulfide (PBPS), etc.) are also included in the polyphenylene sulfide resin.

[0331] The resin composition of the present invention may further contain a base resin having no functional group as the base resin. As the base resin having no functional group, for example, bismaleimide resin, hydrocarbon resin, etc. are preferably used.

[0332] In resin combination of the present invention, the content of matrix resin is not particularly limited, in the whole solid components of 100 mass % of resin combination, as lower limit, preferably more than 30 mass %, more preferably more than 40 mass %, further preferably more than 50 mass %, as upper limit, preferably below 95 mass %, more preferably below 90 mass %.If the content of matrix resin is more than the above-mentioned lower limit, the reduction of the physical property of resin combination can be suppressed, moldability is improved, and mechanical strength is improved.If the content of matrix resin is below the above-mentioned upper limit, hollow particles can be fully contained, and the lightweight, heat-insulating effects of the resin combination therefore brought by hollow particles are excellent.

[0333] In addition, in the 100 mass% of the matrix resin contained in the resin composition of the present invention, from the perspective of improving the close adhesion between the hollow particles and the matrix resin and suppressing the reduction in physical properties when the molded body is made, and suppressing the breakage of the hollow particles and improving the lightweight effect, the content of the matrix resin having a functional group capable of reacting with an epoxy group is preferably 10 mass% or more, more preferably 50 mass% or more, further preferably 70 mass% or more, and even more preferably 90 mass% or more.

[0334] In addition, the matrix resins can be used alone or in combination of two or more.

[0335] [Curing agent]

[0336] The resin composition of the present invention may further contain a curing agent for curing the matrix resin.

[0337] The curing agent is not particularly limited, and a known curing agent can be appropriately selected and used according to the type of the matrix resin. Examples of the curing agent for the epoxy resin include the same curing agents as those that can be used for the hollow particles.

[0338] When the curing agent has a functional group capable of reacting with an epoxy group, the resin composition of the present invention is preferred from the viewpoint of further suppressing deterioration in physical properties.

[0339] The content of the curing agent is not particularly limited, and may be, for example, 1 to 120 parts by mass relative to 100 parts by mass of the base resin.

[0340] [catalyst]

[0341] The resin composition of the present invention may further contain a catalyst for curing the above-mentioned matrix resin.

[0342] Examples of catalysts used in the imidization reaction of polyamic acid include combinations of organic acid anhydrides and organic bases. Examples of organic acid anhydrides include acetic anhydride, propionic anhydride, maleic anhydride, and phthalic anhydride. Examples of organic bases include heterocyclic compounds such as pyridine and picoline; and tertiary amines such as triethylamine and N,N-dimethylaniline.

[0343] When the catalyst has a functional group capable of reacting with an epoxy group, the resin composition of the present invention is preferred from the viewpoint of further suppressing deterioration in physical properties.

[0344] The content of the catalyst is not particularly limited and can be appropriately adjusted according to the type of the base resin.

[0345] [other]

[0346] The resin composition of the present invention may further contain a solvent. As the solvent, a known solvent can be used, and the solvent can be appropriately selected according to the type of the matrix resin.

[0347] The resin composition of the present invention may further contain additives such as a curing accelerator, a filler, a coupling agent, a stress reducing agent, a defoamer, a leveling agent, a UV absorber, a foaming agent, an antioxidant, a colorant, a heat stabilizer, and a flame retardant as needed, within the scope of not impairing the effects of the present invention. In addition, examples of fillers include inorganic or organic microparticles and fibers.

[0348] In the resin composition of the present invention, the total content of the hollow particles, the matrix resin and the curing agent contained in 100% by mass of the total solid content of the resin composition is not particularly limited. From the perspective of easily improving the physical properties of the molded body, it is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0349] [Method for producing resin composition]

[0350] The resin composition of the present invention is obtained by mixing the above-mentioned hollow particles, the matrix resin and other components added as needed. The mixing method is not particularly limited, and can adopt a method using, for example, a planetary mixer, a ball mill, a bead mill, a planetary mixer, a roller mill or other known mixing device. The resin composition of the present invention obtained using such a mixing device is generally a liquid resin composition (resin varnish).

[0351] Alternatively, when the matrix resin is a thermoplastic resin, the resin composition of the present invention can also be obtained by melt-kneading the hollow particles, the matrix resin, and other components added as needed to form pellets. The melt-kneading is preferably performed under conditions that melt the matrix resin without destroying the hollow particles. For example, the melt-kneading temperature is preferably within a range of 30 to 300°C. It is believed that in the pelletized resin composition of the present invention thus obtained, at least a portion of the hollow particles are cross-linked with the matrix resin.

[0352] [Application of resin composition]

[0353] The resin composition of the present invention may be used, without particular limitation, in various fields such as automobiles, bicycles, aviation, aerospace, railway vehicles, ships, construction, electrical equipment, electronics, sporting goods, footwear, household appliances, stationery, and tools, and is preferably used in various components requiring mechanical properties and lightweighting. Furthermore, the resin composition of the present invention is also preferably used in buoyancy materials such as filaments and syntactic foams for 3D printers.

[0354] 2. Prepreg

[0355] The prepreg of the present invention can be, for example, a prepreg obtained by impregnating a substrate with the liquid resin composition (resin varnish) of the present invention and then heating and drying. The prepreg of the present invention thus obtained generally contains a semi-cured product of the resin composition of the present invention. It is believed that in this semi-cured product, at least a portion of the hollow particles are cross-linked with the matrix resin.

[0356] Alternatively, the prepreg of the present invention may be a thermoplastic prepreg formed by impregnating a substrate with the granular resin composition of the present invention. The thermoplastic prepreg can be obtained, for example, by impregnating a substrate with a molten resin composition of the present invention and then cooling and solidifying the resin composition. In the cooled and solidified resin composition contained in the thermoplastic prepreg of the present invention thus obtained, it is also considered that at least a portion of the hollow particles are cross-linked with the matrix resin.

[0357] Since the prepreg of the present invention contains the hollow particles of the present invention, it is excellent in lightness and has suppressed deterioration in physical properties.

[0358] The substrate used for the prepreg is not particularly limited, and examples thereof include inorganic fibers such as carbon fibers, glass fibers, metal fibers, and ceramic fibers, or organic synthetic fibers such as polyamide fibers, polyester fibers, polyolefin fibers, and novoloid fibers. The form of the substrate is not particularly limited, and fabrics, non-woven fabrics, etc. can be used. Glass cloth (glass fiber) is particularly preferred from the perspective of mechanical strength.

[0359] As the thickness of the substrate, for example, a substrate having a thickness of 0.04 mm to 0.3 mm can be generally used.

[0360] The method of impregnating the substrate with the resin composition is not particularly limited, and examples thereof include a method of immersing the substrate in the resin composition and a method of coating the substrate with the resin composition. The impregnation may be repeated multiple times as necessary.

[0361] The method of heat drying is not particularly limited, as long as it is a method that makes the liquid matrix resin into a semi-cured state (B-stage state), and it can be carried out using, for example, an oven. The heating temperature is not particularly limited and can be, for example, 20°C to 200°C, 50°C to 200°C, 100°C to 180°C or 150°C to 170°C. The heating time is not particularly limited and can be, for example, 1 minute to 1 hour or 5 minutes to 40 minutes. Heat drying can be carried out in stages by changing the temperature. In addition, before heat drying, natural drying can be carried out as pre-drying.

[0362] When producing a thermoplastic prepreg, the temperature at which the resin composition of the present invention is melted is not particularly limited and can be adjusted so that the hollow particles in the resin composition are not destroyed while the resin composition of the present invention is melted. The temperature is preferably within the range of 30 to 300°C.

[0363] 3. Molded body

[0364] The molded article of the present invention is characterized by comprising a cured product of the resin composition of the present invention. It is believed that in this cured product, at least a portion of the hollow particles are cross-linked with the matrix resin. The cured product of the resin composition of the present invention may be, for example, a cured product of a thermosetting resin cured by heating, or a cured product of a thermoplastic resin cured by cooling.

[0365] When curing a resin composition, generally when curing a thermosetting resin, curing is preferably performed in an inert atmosphere from the viewpoint of suppressing changes in the properties of a molded article.

[0366] The molded article of the present invention is a structure obtained by molding the resin composition of the present invention under conditions where at least a portion of the epoxy groups contained in the hollow particles of the resin composition of the present invention react with the functional groups of the matrix resin. The molded article of the present invention is obtained by, for example, heating and drying the liquid resin composition of the present invention and then performing heat and pressure molding. Alternatively, the molded article of the present invention can also be obtained by molding the granular resin composition of the present invention using a known method. The molded article of the present invention is obtained by heating and pressurizing the prepreg of the present invention.

[0367] Since the molded article of the present invention contains the hollow particles of the present invention, it is excellent in lightness and the deterioration of physical properties is suppressed.

[0368] In the molded body of the present invention, the content of hollow particles is not particularly limited. On a mass basis, the lower limit is preferably 5 mass % or more, more preferably 10 mass % or more, and further preferably 20 mass % or more. The upper limit is preferably 50 mass % or less, more preferably 40 mass % or less, and further preferably 30 mass % or less.

[0369] In addition, the content of hollow particles in the molded product of the present invention is preferably 20 volume % or more, more preferably 30 volume % or more, and further preferably 40 volume % or more as the lower limit, and is preferably 90 volume % or less, more preferably 80 volume % or less, and further preferably 70 volume % or less as the upper limit, based on volume.

[0370] When the content of the hollow particles is at least the above lower limit, the lightness of the molded article can be improved, and when the content of the hollow particles is at most the above upper limit, deterioration in the physical properties of the molded article can be suppressed.

[0371] In the molded body of the present invention, the content of the matrix resin is not particularly limited. From the perspective of suppressing the reduction of the physical properties of the molded body and improving the mechanical strength, it is preferably 20 volume % or more, more preferably 30 volume % or more. From the perspective of fully containing hollow particles, it is preferably 90 volume % or less, more preferably 80 volume % or less.

[0372] Furthermore, when the matrix resin contained in the resin composition of the present invention is cured by an additive such as a curing agent, the matrix resin contained in the molded article of the present invention may contain the additive such as the curing agent.

[0373] The molded article of the present invention may contain reinforcing fibers, that is, may be a fiber-reinforced molded article.

[0374] The reinforcing fibers are not particularly limited, and examples thereof include organic or inorganic reinforcing fibers such as carbon fibers, glass fibers, aramid fibers, polyethylene fibers, cellulose nanofibers, alumina fibers, boron fibers, Tyranno fibers, SiC fibers, and liquid crystal polymer (LCP) fibers. Carbon fibers are particularly preferred due to their excellent mechanical properties, thermal oxidation resistance, and dimensional stability.

[0375] The form of the reinforcing fibers is not particularly limited, and for example, reinforcing fibers processed into a woven fabric, a nonwoven fabric, a mat, etc. can be used. The reinforcing fibers may be long fibers or short fibers.

[0376] Furthermore, the reinforcing fibers may be used as a base material of the prepreg, or may be contained as a filler.

[0377] When the molded article of the present invention contains reinforcing fibers, the content of the reinforcing fibers is not particularly limited, but the lower limit is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 30% by volume or more, and the upper limit is preferably 60% by volume or less, more preferably 50% by volume or less.

[0378] When the content of the reinforcing fibers is at least the above lower limit, the strength of the molded product can be further improved, while when the content of the reinforcing fibers is at most the above upper limit, the hollow particles and the matrix resin can be sufficiently contained.

[0379] When determining the mass-based content of the hollow particles in the fiber-reinforced molded article, first, the content (mass %) of the resin component in the fiber-reinforced molded article is calculated using the following formula (1) based on the mass of the fiber-reinforced molded article and the mass of the reinforcing fibers in the fiber-reinforced molded article. Next, the mass-based content (mass %) of the hollow particles can be calculated using the following formula (2) based on the content (mass %) of the resin component and the content (mass %) of the hollow particles in the solid content of the resin composition impregnated with the reinforcing fibers.

[0380] Here, the resin component refers to the total amount of materials constituting the fiber-reinforced molded body excluding the reinforcing fibers, and typically refers to the total amount of the matrix resin and hollow particles in the fiber-reinforced molded body.

[0381] The fiber-reinforced molded article used to determine the mass-based content of hollow particles may be a fiber-reinforced molded article after solvent removal. An intermediate product such as a prepreg can be used to determine the content of hollow particles contained in a finished product obtained by curing the prepreg.

[0382] Formula (1)

[0383] Resin component content (mass %) = {(mass of fiber-reinforced molded body - mass of reinforcing fibers) / mass of fiber-reinforced molded body} × 100

[0384] Formula (2)

[0385] Content of hollow particles (mass %) = content of resin component (mass %) × content of hollow particles in the solid content of the resin composition impregnated with the reinforcing fiber (mass %) / 100

[0386] The volume-based content of the hollow particles in the fiber-reinforced molded body can be calculated by, for example, calculating the volumes of the hollow particles, matrix resin, and reinforcing fibers constituting the fiber-reinforced molded body using the following equations (3), (4), and (5), and then using the calculated values ​​using the following equation (6).

[0387] Formula (3)

[0388] Volume of hollow particles = content of hollow particles (mass %) / specific gravity of hollow particles (g / cm 3 )

[0389] Formula (4)

[0390] Volume of matrix resin = content of matrix resin (mass %) / specific gravity of matrix resin after curing (g / cm 3 )

[0391] Formula (5)

[0392] Volume of reinforcing fiber = content of reinforcing fiber (mass %) / specific gravity of reinforcing fiber (g / cm 3 )

[0393] Formula (6)

[0394] Content of hollow particles (volume %) {volume of hollow particles / (volume of hollow particles + volume of matrix resin + volume of reinforcing fibers)}×100

[0395] In addition, the "content (mass %) of hollow particles" used in the above formula (3) is a value obtained by the above formula (2).

[0396] The "content (mass %) of the matrix resin" used in the above formula (4) is calculated by the following formula (7).

[0397] Formula (7)

[0398] Matrix resin content (mass %) = resin component content (mass %) × matrix resin content (mass %) in the solid content of the resin composition impregnated with the reinforcing fiber / 100)

[0399] Here, the "content (mass %) of the resin component" is a value obtained by the above-mentioned formula (1).

[0400] In addition, the specific gravity of the matrix resin after curing (g / cm 3 )" can be a value of true density obtained by the same method as for the hollow particles for a cured product of a composition obtained by removing the hollow particles from the resin composition impregnated with reinforcing fibers.

[0401] The "reinforcement fiber content (mass %)" used in the above formula (5) can be calculated by the following formula (8).

[0402] Formula (8)

[0403] Reinforcement fiber content (mass %) = (mass of reinforcing fiber / mass of fiber-reinforced molded body) × 100

[0404] The tensile modulus of the molded article of the present invention is not particularly limited. As a lower limit, it is preferably 13 GPa or more, more preferably 14 GPa or more, and as an upper limit, it is preferably 30 GPa or less, more preferably 25 GPa or less. However, the tensile modulus of the molded article of the present invention may also vary depending on the type of matrix resin. For example, the tensile modulus of the molded article of the present invention using epoxy resin as the matrix resin is preferably 16 GPa or more, more preferably 17 GPa or more, and further preferably 18 GPa or more, as an upper limit, preferably 25 GPa or less, and more preferably 23 GPa or less. The tensile modulus of the molded article of the present invention using unsaturated polyester resin as the matrix resin is preferably 7 GPa or more, more preferably 7.2 GPa or more, as an upper limit, preferably 20 GPa or less, and more preferably 10 GPa or less. The tensile modulus of the molded article of the present invention using modified polyolefin resin as the matrix resin is preferably 5.5 GPa or more, more preferably 5.7 GPa or more, as an upper limit, preferably 20 GPa or less, and more preferably 10 GPa or less.

[0405] The tensile strength of the molded article of the present invention is not particularly limited. As a lower limit, it is preferably 350 MPa or more, more preferably 400 MPa or more, and as an upper limit, it is preferably 650 MPa or less, more preferably 600 MPa or less. However, the tensile strength of the molded article of the present invention may also vary depending on the type of base resin. For example, the tensile strength of the molded article of the present invention using epoxy resin as the base resin is preferably 440 MPa or more, more preferably 450 MPa or more, as a lower limit, and preferably 650 MPa or less, more preferably 600 MPa or less as an upper limit. The tensile strength of the molded article of the present invention using unsaturated polyester resin as the base resin is preferably 80 MPa or more, more preferably 85 MPa or more, as an upper limit, preferably 200 MPa or less, more preferably 150 MPa or less. The tensile strength of the molded article of the present invention using modified polyolefin resin as the base resin is preferably 70 MPa or more, more preferably 73 MPa or more, as an upper limit, preferably 150 MPa or less, more preferably 100 MPa or less.

[0406] In the present invention, the tensile modulus and tensile strength of the molded article are measured in accordance with JIS K 7165:2008.

[0407] The shape of the molded article of the present invention is not particularly limited and may be any shape that can be molded, such as a sheet, film, plate, or tube or any other three-dimensional shape.

[0408] The method for producing the molded article of the present invention is not particularly limited, and examples thereof include a method including a step of curing the resin composition of the present invention.

[0409] As a method for curing the resin composition of the present invention, for example, when the resin composition of the present invention is a resin varnish, there can be mentioned a method of heat-drying the resin composition of the present invention and then performing heat-pressing molding.

[0410] The heat drying method is not particularly limited and may be the same as the heat drying method used in producing a prepreg using a resin varnish.

[0411] The method of heat and pressure molding is not particularly limited, and it can be carried out, for example, using a hot press. The temperature, pressure and time during heat and pressure molding are not particularly limited, and can be appropriately set according to the type and content of the matrix resin, the shape of the molded body, etc. For example, the temperature can be set to 100°C to 250°C or 120°C to 220°C, and the pressure can be set to 0.5MPa to 5.0MPa. The treatment time of heat and pressure is not particularly limited, and can be set to, for example, 1 minute to 5 hours or 1 hour to 3 hours. In addition, the heat and pressure treatment can also be carried out in stages by changing the temperature or pressure.

[0412] When the resin composition of the present invention is in a pellet form, the step of solidifying the resin composition of the present invention may be, for example, a step of melting the pelletized resin composition and then cooling and solidifying it.

[0413] Examples of uses of the molded article of the present invention include the same uses as those of the resin composition of the present invention described above.

[0414] Example

[0415] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, parts and % are by mass unless otherwise specified.

[0416] [Example 1]

[0417] 1. Preparation of hollow particles

[0418] (1) Mixed liquid preparation process

[0419] First, mix the following materials to form the oil phase.

[0420] 32.4 parts of divinylbenzene (DVB)

[0421] 1.3 parts of ethyl vinyl benzene (EVB)

[0422] 5.0 parts of glycidyl methacrylate

[0423] 0.89 parts of tert-butyl peroxydiethyl acetate

[0424] 61.3 parts of hydrophobic solvent (heptane)

[0425] Next, in a stirred tank, to an aqueous solution prepared by dissolving 19.59 parts of magnesium chloride (water-soluble polyvalent metal salt) in 225 parts of ion-exchanged water, an aqueous solution prepared by dissolving 13.72 parts of sodium hydroxide (alkali metal hydroxide) in 55 parts of ion-exchanged water was slowly added under stirring to prepare a magnesium hydroxide colloid (a poorly water-soluble metal hydroxide colloid) dispersion (10 parts of magnesium hydroxide) as an aqueous phase.

[0426] A mixed liquid is prepared by mixing the obtained aqueous phase with the oil phase.

[0427] (2) Suspension process

[0428] The mixed solution obtained in the mixed solution preparation step was suspended by stirring for 1 minute using an emulsifying disperser (manufactured by Plemicus Co., Ltd., product name: HOMOMIXER) at a tip speed of 88 m / s in the rotating part to prepare a suspension in which polymerizable liquid droplets containing a hydrophobic solvent were dispersed in water.

[0429] (3) Polymerization process

[0430] The suspension obtained in the above suspension step was heated to 80°C in a nitrogen atmosphere, and the stirring power of the stirring blade was set to 0.04 kW / m 3 The mixture was stirred for 24 hours to carry out a polymerization reaction. Through the polymerization reaction, a slurry liquid in which precursor particles containing a hydrophobic solvent were dispersed in water, that is, a precursor composition, was obtained.

[0431] (4) Solvent removal process

[0432] Solvent removal process Figure 2 The stirring apparatus shown above was used in the following steps: A stirring tank with a capacity of 3.6 L was used as the stirring tank, and the interior of the stirring tank was set to a nitrogen atmosphere when the precursor composition was supplied.

[0433] 2.6 L of the precursor composition obtained in the above polymerization step was supplied from the supply tank to the stirring tank. The stirring power of the stirring blades provided in the stirring tank was set to 0.04 kW / m 3 While stirring the precursor composition in the stirring tank, the temperature of the precursor composition was raised to 95°C, the pressure in the stirring tank was reduced to 40 kPa, and a gas inlet ( Figure 2The gas inlet 13a in the middle is directed in the opposite direction to the gravity direction at a rate of 10 L / min (the gas phase is 1 L, so the flow rate per unit volume is 10000 L / (min·m 3 )) flow rate is blown directly into the precursor composition, while stirring the precursor composition in the stirred tank, thereby carrying out a bubbling treatment for 15 hours. In this treatment, the precursor composition added to the stirred tank is repeatedly stirred in the stirred tank, discharged to the supply tank, and then supplied from the supply tank to the stirred tank again, and circulated in the stirring device. In addition, during this treatment, a portion of the precursor composition added to the stirred tank is supplied to the spray mechanism and continuously sprayed toward the liquid level of the precursor composition in the stirred tank. Through the above treatment, an aqueous dispersion of hollow particles whose hollow portion is filled with nitrogen is obtained.

[0434] (5) Cleaning process

[0435] Dilute sulfuric acid was added to the aqueous dispersion of hollow particles obtained in the solvent removal step at 25°C and stirred for 10 minutes to obtain a pH-adjusted slurry having a pH of 5.5 or less. The pH-adjusted slurry was pressure-filtered and dehydrated while maintaining at 25°C to obtain a dehydrated cake of hollow particles. This series of steps, including washing the dehydrated cake with 400 parts of ion-exchanged water, pressure-filtering, and dehydrating, was repeated six times.

[0436] (6) Drying process

[0437] The dehydrated cake (water content 67%, 2 cm thick) after the above-mentioned washing step was pre-dried in a dryer at a temperature of 40°C, and then heated in a vacuum dryer at 200°C and 4 kPa for 12 hours to remove the moisture remaining in the particles, thereby obtaining hollow particles 1.

[0438] 2. Preparation of resin composition (varnish)

[0439] 50 parts of epoxy resin (manufactured by Daicel Corporation, product name: EHPE3150CE, a mixture of 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol and 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate, epoxy equivalent: 180), 24.9 parts of bisphenol A novolac resin (manufactured by DIC Corporation, product name: PHENOLITE LF-6161, 65% solid content MEK solution) as a curing agent, 0.1 part of 2-ethyl-4-methylimidazole (manufactured by Nacalai Tesque Co., Ltd., product name: 2E4MZ), and 30 parts of methyl ethyl ketone (MEK) were added to a stirring tank and stirred at room temperature for 30 minutes. After stirring, 25 parts of the hollow particles 1 obtained above were added, and the mixture was further stirred for 1 hour to prepare a resin composition (varnish) having a solid content of about 70%.

[0440] 3. Preparation of prepreg

[0441] A carbon fiber (Mitsubishi Chemical Corporation, product name: TR3110MS, thickness: 200 μm, mass per unit area: 200 g / m) cut into 300 mm × 200 mm was used. 2 ) Apply 25 to 30 mL of the resin composition obtained above.

[0442] The carbon fibers coated with the resin composition were suspended, and the excess resin composition was allowed to fall by its own weight to dry naturally (air dry), and then dried in a hot air circulation oven at 140° C. for 30 minutes to obtain a prepreg.

[0443] 4. Production of carbon fiber reinforced plastics (CFRP)

[0444] A PET film (manufactured by NIPA Co., Ltd., product name: SFL, thickness: 50 μm) was placed on a SUS plate, and two sheets of the prepreg laminated above were stacked on top of it. A PET film and then a SUS plate were placed on top of this, and the resulting laminated product was placed in a vacuum press. Heat and pressure molding was performed in the vacuum press at 120°C and 0.5 MPa for 20 minutes. The temperature was then further increased (4°C / min) to 205°C and held for 1 hour. The product was then removed from the vacuum press to produce a plate-shaped carbon fiber reinforced molded product (CFRP).

[0445] [Example 2]

[0446] In the above-mentioned "1. Preparation of hollow particles" of Example 1, except that the amount of free radical polymerizable monomer added to the oil phase in the above-mentioned "(1) Mixed liquid preparation step" was changed according to Table 1, the same procedure as in Example 1 was carried out to obtain hollow particles 2 of Example 2.

[0447] In the above-mentioned "2. Preparation of resin composition (varnish)", "3. Preparation of prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 1, hollow particles 2 were used instead of hollow particles 1. Except for this, the same procedures as in Example 1 were carried out to obtain the resin composition, prepreg and carbon fiber reinforced molded body (CFRP) of Example 2.

[0448] [Example 3]

[0449] In the above-mentioned "1. Preparation of hollow particles" of Example 1, in the above-mentioned "(1) Mixed liquid preparation step", the type and amount of the free radical polymerizable monomer added to the oil phase and the type of the hydrophobic solvent were changed according to Table 1. In the preparation of the aqueous phase, an aqueous solution obtained by dissolving 7.83 parts of magnesium chloride (water-soluble polyvalent metal salt) in 225 parts of ion-exchanged water was added with an aqueous solution obtained by dissolving 5.49 parts of sodium hydroxide (alkali metal hydroxide) in 55 parts of ion-exchanged water to prepare a magnesium hydroxide colloid (a sparingly water-soluble metal hydroxide colloid) dispersion (4 parts of magnesium hydroxide) as the aqueous phase. Except for this, the same procedure as in Example 1 was carried out to obtain hollow particles 3 of Example 3.

[0450] In addition, "EGDMA" shown in Table 1 and Table 2 is ethylene glycol dimethacrylate, and "A-TMMT" is pentaerythritol tetraacrylate.

[0451] In the above-mentioned "2. Preparation of resin composition (varnish)", "3. Preparation of prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 1, hollow particles 3 were used instead of hollow particles 1. Except for this, the same procedures as in Example 1 were carried out to obtain the resin composition, prepreg and carbon fiber reinforced molded body (CFRP) of Example 3.

[0452] [Example 4]

[0453] Hollow particles 4 of Example 4 were obtained in the same manner as in Example 1 except that the "(1) mixed solution preparation step" in the "1. Preparation of hollow particles" of Example 1 was changed to the following step.

[0454] In the mixed liquid preparation step of Example 4, first, the following materials were mixed to form an oil phase.

[0455] Epoxy resin (bisphenol A type epoxy resin, number of epoxy groups per molecule: 2, epoxy value 5.26 mmol / g, product name: jER (registered trademark) 828, manufactured by Mitsubishi Chemical Corporation) 35.7 parts

[0456] 1.49 parts of curing agent (2-ethyl-4-methylimidazole)

[0457] 62.8 parts of hydrophobic solvent (toluene)

[0458] Next, in a stirred tank, to an aqueous solution prepared by dissolving 7.83 parts of magnesium chloride (water-soluble polyvalent metal salt) in 225 parts of ion-exchanged water, an aqueous solution prepared by dissolving 5.49 parts of sodium hydroxide (alkali metal hydroxide) in 55 parts of ion-exchanged water was slowly added under stirring to prepare a magnesium hydroxide colloid (a poorly water-soluble metal hydroxide colloid) dispersion (4 parts of magnesium hydroxide) as an aqueous phase.

[0459] A mixed liquid is prepared by mixing the obtained aqueous phase with the oil phase.

[0460] In the above-mentioned "2. Preparation of resin composition (varnish)", "3. Preparation of prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 1, hollow particles 4 were used instead of hollow particles 1. Except for this, the same procedures as in Example 1 were carried out to obtain the resin composition, prepreg and carbon fiber reinforced molded body (CFRP) of Example 4.

[0461] [Examples 5 to 9]

[0462] In Example 4, except that the types and addition amounts of the epoxy resin and the curing agent were changed according to Table 1, the same procedures as in Example 4 were carried out to obtain hollow particles 5 to 9 of Examples 5 to 9.

[0463] In the above-mentioned "2. Preparation of resin composition (varnish)", "3. Preparation of prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 1, hollow particles 5 to 9 were used instead of hollow particle 1. Except for this, the same procedure as in Example 1 was carried out to obtain resin compositions, prepregs and carbon fiber reinforced molded bodies (CFRP) of Examples 5 to 9.

[0464] In addition, the details of the epoxy resins and curing agents shown in Tables 1 and 2 are as follows.

[0465] · "jER828"

[0466] Bisphenol A epoxy resin, number of epoxy groups per molecule: 2, epoxy value 5.26 mmol / g, product name: jER (registered trademark) 828, manufactured by Mitsubishi Chemical Corporation

[0467] HP7200

[0468] Dicyclopentadiene-type epoxy resin, number of epoxy groups per molecule: 2, product name: EPICLON (registered trademark) HP-7200, manufactured by DIC Corporation

[0469] HP4700

[0470] Naphthalene-type epoxy resin, number of epoxy groups per molecule: 2, epoxy value 3.77 mmol / g, product name: EPICLON (registered trademark) HP-4700, manufactured by DIC Corporation

[0471] ·TSR960

[0472] Flexibility-imparting (solvent-free rubber-modified) epoxy resin, number of epoxy groups per molecule: 2, epoxy value 4.17 mmol / g, product name: EPICLON (registered trademark) TSR-960, manufactured by DIC Corporation

[0473] EXA4850-150

[0474] Soft and tough liquid epoxy resin, number of epoxy groups per molecule: 2, epoxy value 2.22mmol / g, product name: EPICLON (registered trademark) EXA4850-150, manufactured by DIC Corporation

[0475] ·"YX7400"

[0476] Flexible epoxy resin, number of epoxy groups per molecule: 2, epoxy value 2.27 mmol / g, product name: jER (registered trademark) YX7400N, manufactured by Mitsubishi Chemical Corporation

[0477] ·Polyetheramine D230

[0478] Polyetheramine (molecular weight 230), product name: Polyetheramine D230, manufactured by Mitsui Chemicals Fine Co., Ltd.

[0479] "Polyetheramine D2000"

[0480] Polyetheramine (molecular weight 2000), product name: Polyetheramine D2000, manufactured by Mitsui Chemicals Fine Co., Ltd.

[0481] [Comparative Example 1]

[0482] 1. Preparation of Hollow Particles C1

[0483] 50 parts of an epoxy resin (bisphenol A type epoxy resin, product name: jER (registered trademark) 828, manufactured by Mitsubishi Chemical Corporation) and 50 parts of a hydrophobic solvent (toluene) were mixed and stirred to prepare a mixed solution.

[0484] On the other hand, 15 parts of a curing agent (diethylenetriamine) and 2 parts of a water-soluble emulsifier (sodium dodecylbenzenesulfonate) were added to 390 parts of ion-exchanged water to prepare an aqueous phase.

[0485] The entire amount of the mixed solution obtained above was added to the aqueous phase, and forced emulsification was performed using an ultrasonic homogenizer for 60 minutes to prepare a dispersion in which polymerizable droplets having an average particle size of 180 nm were dispersed.

[0486] Next, a 20-liter polymerization vessel equipped with a stirrer, a jacket, a reflux cooler, and a thermometer was used to deoxygenate the vessel. The atmosphere was then replaced with nitrogen to create a nitrogen atmosphere. The resulting dispersion was then added, and the vessel was heated to 80°C to initiate polymerization. Polymerization was continued for 4 hours, followed by a 1-hour aging period, and the vessel was then cooled to room temperature.

[0487] The obtained slurry was dehydrated by a dehydrating device and then vacuum-dried to obtain hollow particles C1.

[0488] The hollow particles C1 correspond to the hollow fine particles (A) used in Example 1 of Patent Document 2.

[0489] In the above-mentioned "2. Preparation of resin composition (varnish)", "3. Preparation of prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 1, hollow particles C1 were used instead of hollow particles 1. Except for this, the same procedures as in Example 1 were carried out to obtain the resin composition, prepreg and carbon fiber reinforced molded body (CFRP) of Comparative Example 1.

[0490] [Comparative Example 2]

[0491] In Comparative Example 1, hollow particles C2 of Comparative Example 2 were obtained in the same manner as in Comparative Example 1, except that the types and addition amounts of the epoxy resin and curing agent, and the amount of the hydrophobic solvent were changed according to Table 1, and the resulting slurry was dehydrated using a dehydrator as described below.

[0492] <Dehydration using a dehydration device>

[0493] The obtained slurry was dehydrated by a dehydrating device to obtain a dehydrated cake of hollow particles. The obtained dehydrated cake was washed with 400 parts of ion-exchanged water and dehydrated by a dehydrating device, and the series of steps was repeated fifteen times.

[0494] In the above-mentioned "2. Preparation of resin composition (varnish)", "3. Preparation of prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 1, hollow particles C2 were used instead of hollow particles 1. Except for this, the same procedures as in Example 1 were carried out to obtain the resin composition, prepreg and carbon fiber reinforced molded body (CFRP) of Comparative Example 2.

[0495] [Reference Example 1]

[0496] In the above-mentioned "2. Preparation of resin composition (varnish)", "3. Preparation of prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 1, hollow particles 1 were not added. Otherwise, the same procedures as in Example 1 were carried out to obtain the resin composition, prepreg and carbon fiber reinforced molded body (CFRP) of Reference Example 1.

[0497] [Example 10]

[0498] 1. Preparation of hollow particles

[0499] Hollow particles 2 were obtained by the same procedure as in Example 2 for producing hollow particles.

[0500] 2. Preparation of resin composition (varnish)

[0501] 100 parts of an unsaturated polyester resin (RIGOLAC 158BQT(N), manufactured by Resonac Co., Ltd., containing hydroxyl groups at the polymer terminals), 1 part of a curing agent (PERMEK N, manufactured by NOF Corporation), and 30 parts of toluene were placed in a stirring tank and stirred at room temperature for 30 minutes. After stirring, 25 parts of the hollow particles 2 obtained above were added, and the mixture was further stirred for 1 hour to produce a resin composition (varnish) having a solids content of approximately 70%.

[0502] 3. Preparation of prepreg

[0503] A carbon fiber (Mitsubishi Chemical Corporation, product name: TR3110MS, thickness: 200 μm, mass per unit area: 200 g / m) cut into 300 mm × 200 mm was used. 2 ) Apply 25 to 30 mL of the resin composition obtained above.

[0504] The carbon fibers coated with the resin composition were suspended, and the excess resin composition was allowed to fall by its own weight to dry naturally (air dry), and then dried in a hot air circulation oven at 140° C. for 30 minutes to obtain a prepreg.

[0505] 4. Production of carbon fiber reinforced plastics (CFRP)

[0506] A PET film (manufactured by NIPA Co., Ltd., product name: SFL, thickness: 50 μm) was placed on a SUS plate, and two sheets of the prepreg laminated above were stacked on top of it. A PET film and then a SUS plate were placed on top of this, and the resulting laminated product was placed in a vacuum press. Heat and pressure molding was performed in the vacuum press at 120°C and 0.5 MPa for 20 minutes. The temperature was then further increased (4°C / min) to 205°C and held for 1 hour. The product was then removed from the vacuum press to produce a plate-shaped carbon fiber reinforced molded product (CFRP).

[0507] [Example 11]

[0508] Hollow particles 6 were obtained by the same procedure as in Example 6.

[0509] The resin composition, prepreg, and carbon fiber reinforced molded product (CFRP) of Example 11 were obtained in the same manner as in Example 10 except that the hollow particles 6 were used instead of the hollow particles 2.

[0510] [Comparative Example 3]

[0511] Hollow particles C1 were obtained by the same procedure as that for producing the hollow particles in Comparative Example 1.

[0512] The resin composition, prepreg, and carbon fiber reinforced molded product (CFRP) of Comparative Example 3 were obtained in the same manner as in Example 10, except that the hollow particles C1 were used instead of the hollow particles 2.

[0513] [Reference Example 2]

[0514] In the above-mentioned "2. Preparation of resin composition (varnish)", "3. Preparation of prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 10, hollow particles 2 were not added. Otherwise, the same procedures as in Example 10 were carried out to obtain the resin composition, prepreg and carbon fiber reinforced molded body (CFRP) of Reference Example 2.

[0515] [Example 12]

[0516] 1. Preparation of hollow particles

[0517] Hollow particles 2 were obtained by the same procedure as in Example 2 for producing hollow particles.

[0518] 2. Preparation of resin composition (particles)

[0519] 90 parts of a polypropylene resin (manufactured by Japan Polypropylene Co., Ltd., product name: MA3), 10 parts of a maleic acid-modified polypropylene resin (manufactured by Sanyo Chemical Industries, Ltd., product name: UMEX1001, acid value: 26 mgKOH / g), and 25 parts of hollow particles 2 were added and mixed using a stirrer. The resulting mixture was then kneaded and extruded using a twin-screw kneader (product name "TEM-35B", manufactured by Toshiba Machine Co., Ltd.) under the following conditions, and pelletized to obtain a pelletized resin composition.

[0520] Mixing conditions: screw diameter 37mm, L / D=32

[0521] Screw speed 250rpm

[0522] Resin temperature 190℃

[0523] Feed rate 20kg / hour

[0524] 3. Preparation of thermoplastic prepreg

[0525] The pelletized resin composition obtained above was heated to 190°C to melt it and cut into 300 mm × 200 mm carbon fibers (Mitsubishi Chemical Corporation, product name: TR3110MS, thickness: 200 μm, mass per unit area: 200 g / m 2 ) Apply 25 to 30 mL of the molten resin composition.

[0526] The carbon fibers coated with the resin composition are suspended, and the excess resin composition is allowed to fall due to its own weight, and then naturally cooled to obtain a thermoplastic prepreg.

[0527] 4. Production of carbon fiber reinforced plastics (CFRP)

[0528] A PET film (manufactured by NIPA Co., Ltd., product name: SFL, thickness: 50 μm) was placed on a SUS plate, and two sheets of the thermoplastic prepreg laminated above were stacked on top of it. The PET film and SUS plate were further placed on top of this, and the resulting laminated product was placed in a vacuum press. Heat and pressure molding was performed in the vacuum press at 120°C and 0.5 MPa for 20 minutes. The temperature was then further increased (4°C / min) to 205°C and held for 1 hour. The product was then removed from the vacuum press and allowed to cool naturally, producing a plate-shaped carbon fiber reinforced molded product (CFRP).

[0529] [Example 13]

[0530] Hollow particles 6 were obtained by the same procedure as in Example 6.

[0531] The resin composition, thermoplastic prepreg, and carbon fiber reinforced molded product (CFRP) of Example 13 were obtained in the same manner as in Example 12 except that the hollow particles 6 were used instead of the hollow particles 2.

[0532] [Comparative Example 4]

[0533] Hollow particles C1 were obtained by the same procedure as that for producing the hollow particles in Comparative Example 1.

[0534] The resin composition, thermoplastic prepreg, and carbon fiber reinforced molded product (CFRP) of Comparative Example 4 were obtained in the same manner as in Example 12 except that the hollow particles C1 were used instead of the hollow particles 2.

[0535] [Reference Example 3]

[0536] In the above-mentioned "2. Preparation of resin composition (particles)", "3. Preparation of thermoplastic prepreg" and "4. Preparation of carbon fiber reinforced molded body (CFRP)" of Example 12, hollow particles 2 were not added. Otherwise, the same procedure as in Example 12 was carried out to obtain the resin composition, thermoplastic prepreg and carbon fiber reinforced molded body (CFRP) of Reference Example 3.

[0537] [Measurement of hollow particles]

[0538] The following measurements were performed on the hollow particles produced in each of the Examples and Comparative Examples. The results are shown in Tables 1 and 2.

[0539] 1. Particle size and particle size distribution

[0540] The particle size of the hollow particles was measured using a particle size distribution analyzer based on the Coulter counter method (product name: Multisizer 4e, manufactured by Beckman Coulter). The number average and volume average values ​​were calculated to obtain the number average particle size (Dp) and volume average particle size (Dv). Furthermore, the particle size distribution (Dv / Dp) was obtained by dividing the volume average particle size by the number average particle size.

[0541] The measurement conditions were: pore size: 50 μm, dispersion medium: ISOTONII (product name), concentration: 10%, and number of particles measured: 100,000. Specifically, 0.2 g of the particle sample was placed in a beaker, and an aqueous surfactant solution (product name: DRIWEL, manufactured by Fujifilm Corporation) was added as a dispersant. 2 ml of the dispersion medium was further added to wet the particles, and then 10 ml of the dispersion medium was added. The particles were dispersed using an ultrasonic disperser for 1 minute, and then measured using the aforementioned particle size distribution analyzer.

[0542] 2. Porosity

[0543] 2-1. Measurement of apparent density of hollow particles

[0544] First, to a capacity of 100cm 3 Fill the volumetric flask to about 30 cm 3 The mass of the hollow particles was accurately weighed. Next, isopropyl alcohol was accurately filled to the mark in the volumetric flask filled with the hollow particles, while being careful not to introduce air bubbles. The mass of isopropyl alcohol added to the volumetric flask was accurately weighed, and the apparent density D1 (g / cm2) of the hollow particles was calculated based on the following formula (I): 3 ).

[0545] Formula (I)

[0546] Apparent density D1 = [mass of hollow particles] / (100-[mass of isopropyl alcohol] / [specific gravity of isopropyl alcohol at the measurement temperature])

[0547] 2-2. Measurement of True Density of Hollow Particles

[0548] After the hollow particles are crushed in advance, a 3 A volumetric flask is filled with about 10 g of hollow particle fragments, and the mass of the filled fragments is accurately weighed.

[0549] Then, isopropyl alcohol was added to the volumetric flask in the same manner as in the above-mentioned apparent density measurement, and the mass of isopropyl alcohol was accurately weighed. The true density D0 (g / cm2) of the hollow particles was calculated based on the following formula (II): 3 ).

[0550] Formula (II)

[0551] True density D0 = [mass of hollow particle fragments] / (100 - [mass of isopropyl alcohol] / [specific gravity of isopropyl alcohol at the measurement temperature])

[0552] 2-3. Calculation of porosity

[0553] The porosity of the hollow particles was calculated based on the following formula (III) from the apparent density D1 and true density D0 of the hollow particles.

[0554] Formula (III)

[0555] Porosity (%) = 100 - (apparent density D, / true density D,) × 100

[0556] 3. Determination of epoxy group weight

[0557] 3-1. Determination of epoxy value

[0558] The epoxy value was measured by potentiometric titration in accordance with JIS K 7236. The specific measurement method is as follows.

[0559] About 2g of sample (hollow particles) and 30mL of chloroform were added to a 100mL conical flask and stirred at room temperature (25°C). 20mL of acetic acid and 10mL of tetraethylammonium bromide acetic acid solution (tetraethylammonium bromide / acetic acid=25g / 100mL) as a reaction solution were further added to the conical flask. Potentiometric titration apparatus AT-710 (manufactured by Kyoto Electronics Co., Ltd.) and a composite glass electrode (manufactured by Kyoto Electronics Co., Ltd.) were used to titrate a 0.1mol / L perchloric acid acetic acid solution as a titrant, with the resulting inflection point as the endpoint. In addition to this test, a blank test was performed on a sample solution not containing hollow particles, and the epoxy value of the hollow particles was calculated using the following formula.

[0560] Epoxy value (mmol / g) = {(V1-V0) × N × f} / S

[0561] S: mass of the sample (g)

[0562] V1: Volume of titrant in this test (mL)

[0563] V0: Volume of titrant in blank test (mL)

[0564] N: concentration of titrant (mol / L)

[0565] f: factor of the titrant

[0566] 3-2. Determination of specific surface area

[0567] The specific surface area (m2) of the hollow particles was calculated from the volume average particle size and apparent density D1 of the hollow particles measured above by the following formula (B): 2 / g).

[0568] Formula (B):

[0569] Specific surface area (m 2 / g) = 6 / (volume average particle size (m) × apparent density D1 (g / m 3 ))

[0570] 3-3. Calculation of epoxy group weight

[0571] The epoxy group amount per unit area of ​​the hollow particles (μmol / m2) was calculated by the following formula (A) based on the epoxy value of the hollow particles and the specific surface area of ​​the hollow particles. 2 ).

[0572] Formula (A):

[0573] Epoxy group content (μmol / m 2 )=epoxy value (μmol / g) / specific surface area (m 2 / g)

[0574] In accordance with Rule B of JIS Z8401:1999, the epoxy value is expressed with two significant figures, the unit of "mmol / g" is converted to "μmol / g", and the epoxy group weight is rounded to one decimal place. The volume average particle size and apparent density D1 used in formula (B) above are expressed with two significant figures, the values ​​converted to the above units are used, and the specific surface area is rounded to two decimal places.

[0575] 4. Residual surfactant content

[0576] Accurately weigh 50 ml of ultrapure water and 5 g of hollow particles and mix thoroughly. Irradiate with ultrasound for 30 minutes and filter with a needle membrane filter with a diameter of 0.45 μm. The filtrate is freeze-dried and 1 g of tetramethylsilane (TMS) solvent is added to the residue to dissolve it. 1 H-NMR measurement. 1 A calibration curve based on TMS intensity was created based on the surfactant and water-soluble polymer stabilizer identified by H-NMR spectroscopy, and the amount of surfactant and water-soluble polymer stabilizer extracted from the hollow particle surface was calculated. A calibration curve was created based on the ratio of TMS intensity to the peak intensity of the detected surfactant or water-soluble polymer stabilizer. The ratio of the amount of surfactant and water-soluble polymer stabilizer extracted from the hollow particle surface to the mass of the hollow particle was calculated as the content of surfactant and water-soluble polymer stabilizer present on the hollow particle surface.

[0577] In addition, according to 1 Particles of the surfactant and the water-soluble polymer stabilizer were not detected by H-NMR spectroscopy and were judged as not detected (ND).

[0578] < 1 H-NMR measurement conditions>

[0579] Device name: FT-NMR device

[0580] Resonant frequency: 400MHz

[0581] Measurement mode: 1 H-NMR

[0582] Pulse width: 5.0μs (pulse angle: 90°)

[0583] Measurement range: 26ppm (frequency range: 10500Hz)

[0584] Cumulative times: 1024 times

[0585] Measurement temperature: 40°C

[0586] Solvent: deuterated chloroform (TMS (tetramethylsilane) 1%)

[0587] Reference substance: Peak derived from tetramethylsilane: 0.00 ppm (internal standard method)

[0588] [Measurement of Prepreg or CFRP]

[0589] The following measurements were performed on the prepregs or carbon fiber reinforced molded products (CFRP) produced in each of the Examples and Comparative Examples. The results are shown in Tables 1 and 2.

[0590] 1. Specific gravity

[0591] The specific gravity of CFRP was measured by the water displacement method in accordance with JIS K7112.

[0592] 2. Content of hollow particles and reinforcing fibers based on mass

[0593] The prepregs obtained in each example and comparative example were cut into 150 mm × 150 mm pieces to serve as test prepregs. The mass of the test prepregs was measured. In addition, the mass per unit area of ​​carbon fiber (200 g / m 2 ) is used to calculate the mass of the carbon fibers in the prepreg for measurement. For the prepreg for measurement, the content (mass %) of the resin component in the prepreg is calculated using the above formula (1) based on the mass of the prepreg and the mass of the reinforcing fibers (carbon fibers) in the prepreg. The content (mass %) of the hollow particles is calculated using the above formula (2) based on the content (mass %) of the resin component and the content (mass %) of the hollow particles in the solid content of the resin composition impregnated with the reinforcing fibers. In addition, the mass of the prepreg for measurement is used as the "mass of the fiber-reinforced molded body" in the above formula (1).

[0594] Furthermore, the content (mass %) of the reinforcing fibers in the aforementioned prepreg for measurement was calculated as the ratio of the mass of the reinforcing fibers in the aforementioned prepreg for measurement to the mass of the aforementioned prepreg for measurement.

[0595] Furthermore, the mass-based content of hollow particles and the mass-based content of reinforcing fibers were calculated for six prepregs cut from the prepreg for measurement. The mass-based content of hollow particles and the mass-based content of reinforcing fibers in the fiber-reinforced molded articles obtained in each Example and Comparative Example were calculated as the average of the values ​​obtained for the six prepregs for measurement.

[0596] The mass content of the hollow particles and the reinforcing fibers in the prepreg can be considered to be the same as the mass content of the hollow particles and the reinforcing fibers in the CFRP.

[0597] 3. Content of hollow particles based on volume

[0598] Using the content (mass %) of the hollow particles, the content (mass %) of the matrix resin, and the content (mass %) of the reinforcing fibers in the measurement prepreg used in the above "2. Content of Hollow Particles and Reinforcing Fibers on a Mass Basis", the volume of the hollow particles, the volume of the matrix resin, and the volume of the reinforcing fibers were calculated by the above formulas (3), (4), and (5), and the content (volume %) of the hollow particles on a volume basis was calculated by the above formula (6).

[0599] In addition, the true density of the cured product of the resin composition prepared in Reference Example 1 was measured and used as the "specific gravity of the matrix resin after curing (g / cm 3 )”.

[0600] The volume-based content of the hollow particles in the prepreg can be considered to be the same as the volume-based content of the hollow particles in the CFRP.

[0601] 4. Tensile elastic modulus and tensile strength

[0602] The CFRP obtained in each of the Examples, Comparative Examples, and Reference Examples was cut into test samples at right angles to the fabric winding direction. From these test samples, 130 mm x 15 mm strips were cut, with the fabric winding direction oriented as the minor axis, to prepare test pieces. These test pieces were subjected to tensile testing under the following conditions in accordance with JIS K7165:2008 to determine their tensile modulus and tensile strength.

[0603] Tensile test conditions

[0604] Testing machine: Made by Shimadzu Corporation, model: AG-5kNI

[0605] Load cell: 5t

[0606] Chuck: Wedge type

[0607] Tensile speed: 1mm / min

[0608] Distance between chucks: 60mm

[0609] Temperature: 25℃

[0610] Humidity: 50% RH

[0611] The tensile modulus and tensile strength of CFRP were measured for five test pieces cut from the sample. The tensile modulus and tensile strength of CFRP were calculated as the average of the three measured values, excluding the maximum and minimum values, from the five test pieces.

[0612] [Table 1]

[0613]

[0614] [Table 2]

[0615]

[0616] Tables 1 and 2 show the addition amount (parts by mass) of each material and the results of the above-mentioned measurements.

[0617] SEM observation of the hollow particles obtained in each example revealed that the percentage of particles having only a single hollow portion was 90% or greater. Furthermore, an examination of any 3,000 hollow particles obtained in each example revealed that the percentage of particles having a circularity of 0.85 or less, based on mass, was 10% or less in each example.

[0618] [Investigation]

[0619] As shown in Table 1, the volume average particle size of the hollow particles used in Comparative Examples 1 and 2 was 1.0 μm or less. Therefore, while the CFRPs produced using the resin compositions of Comparative Examples 1 and 2 were lighter than the CFRP of Reference Example 1, which did not contain hollow particles, they also exhibited lower tensile modulus and tensile strength. This reduction in physical properties in the CFRPs of Comparative Examples 1 and 2 is presumably due to the uneven dispersion of the hollow particles in the resin composition due to the small particle size of the hollow particles. Furthermore, the further reduction in physical properties in the CFRP of Comparative Example 1 compared to the CFRP of Comparative Example 2 is presumably due to the fact that the amount of surfactant remaining on the surface of the hollow particles in Comparative Example 1 inhibits the formation of crosslinks through the reaction between the epoxy groups of the hollow particles and the epoxy groups of the matrix resin, resulting in poor adhesion between the hollow particles and the matrix resin.

[0620] In contrast, in each example shown in Table 1, a CFRP was produced using a resin composition comprising hollow particles and an epoxy resin as a matrix resin, wherein the hollow particles had a porosity of 50% or more, a volume average particle size of greater than 1.0 μm and less than 20.0 μm, and an epoxy group content of 1.0 μmol / m 2 As a result, the CFRP produced in each example is lighter than the CFRP of Reference Example 1 that does not contain hollow particles, and furthermore, has higher tensile modulus and tensile strength. These improvements in physical properties of the CFRP in each example are presumably due to the suppression of degradation in physical properties due to aggregation of hollow particles and delamination at the interface between the hollow particles and the matrix resin, and the fact that the added hollow particles have higher tensile modulus and tensile strength than the matrix resin.

[0621] Furthermore, in the production of hollow particles, Examples 4-9, which used epoxy resin as the polymerizable compound, produced CFRP with higher tensile modulus and tensile strength than Examples 1-3, which used a free radical polymerizable monomer. This is presumably because the use of epoxy resin as the polymerizable compound in Examples 4-9 increased the amount of epoxy groups in the hollow particles, resulting in more crosslinks formed by the reaction between the epoxy groups in the hollow particles and the epoxy groups in the matrix resin, improving the adhesion between the hollow particles and the matrix resin.

[0622] In the Examples and Comparative Examples shown in Table 2, the same hollow particles as in Example 2, Example 6, or Comparative Example 1 shown in Table 1 were used, and an unsaturated polyester resin or a modified polyolefin resin was used as the matrix resin having epoxy-reactive functional groups. In the Examples and Comparative Examples using the unsaturated polyester resin, prepregs and CFRPs were prepared using the same procedures as in the Examples and Comparative Examples shown in Table 1. In the Examples and Comparative Examples using the modified polyolefin resin, thermoplastic prepregs were prepared using the pelletized resin compositions, and CFRPs were then prepared using these thermoplastic prepregs.

[0623] As a result, the Examples and Comparative Examples shown in Table 2 also exhibited the same trends as those shown in Table 1. Specifically, while CFRP produced using a resin composition containing the same hollow particles as in Comparative Example 1 was lighter than CFRP without hollow particles, its tensile modulus and tensile strength were also lower. Furthermore, CFRP produced using a resin composition containing the same hollow particles as in Examples 2 or 6 was even lighter than CFRP without hollow particles, resulting in higher tensile modulus and tensile strength. Furthermore, in the production of hollow particles, the tensile modulus and tensile strength of the resulting CFRP were higher in the Examples using epoxy resin as the polymerizable compound than in the Examples using a free radical polymerizable monomer.

[0624] Description of Reference Numerals

[0625] 1: Water-based medium;

[0626] 2: Low polarity materials;

[0627] 3: polymeric droplets;

[0628] 4a: hydrophobic solvent;

[0629] 4b: Materials other than hydrophobic solvents;

[0630] 5: precursor particles;

[0631] 6: Shell;

[0632] 7: hollow part;

[0633] 10: hollow particles;

[0634] 11: stirring tank;

[0635] 12: supply tank;

[0636] 13a, 13b, 13c: gas inlet;

[0637] 14: Export;

[0638] 15: spray mechanism;

[0639] 16: Supply line to the stirring tank;

[0640] 17a, 17b: circulation pipeline;

[0641] 20: Precursor composition;

[0642] 20a: liquid surface of the precursor composition;

[0643] 21: Gas phase section.

Claims

1. A resin composition comprising hollow particles and a matrix resin, The hollow particles have a shell containing a resin and a hollow portion surrounded by the shell, a porosity of 50% or more, a volume average particle size of greater than 1.0 μm and less than 20.0 μm, and an epoxy group amount per unit area calculated by the following formula (A) based on the epoxy value and specific surface area of ​​the hollow particles is 1.0 μmol / m 2 above, Formula (A): Epoxy group weight (μmol / m 2 )=epoxy value (μmol / g) / specific surface area (m 2 / g) The base resin contains a base resin having a functional group capable of reacting with an epoxy group.

2. The resin composition according to claim 1, wherein The functional group of the base resin is at least one selected from the group consisting of a hydroxyl group, an amino group, an epoxy group, a carboxyl group, a carboxylic anhydride group, a thiol group, an isocyanate group, and a silanol group.

3. The resin composition according to claim 1 or 2, wherein The matrix resin comprises at least one selected from epoxy resin, benzoxazine resin, cyanate resin, polyimide resin, silicone resin, polyester resin, liquid crystal polymer (LCP), modified polyolefin resin, polyphenylene ether resin, thiol resin, polyurethane resin, polyurea resin and raw material compounds of these resins.

4. The resin composition according to claim 1 or 2, wherein The shell of the hollow particle contains a polymer of a radical polymerizable monomer as the resin.

5. The resin composition according to claim 4, wherein The content of the crosslinking monomer containing two or more radical polymerizable groups in one molecule is 50% by mass or more in 100% by mass of the radical polymerizable monomer.

6. The resin composition according to claim 1 or 2, wherein The shell of the hollow particle contains a cured product of an epoxy resin as the resin.

7. The resin composition according to claim 6, wherein The content of the cross-linkable epoxy resin containing two or more epoxy groups in one molecule is 50% by mass or more in 100% by mass of the epoxy resin.

8. The resin composition according to claim 1 or 2, wherein The total content of the surfactant and the water-soluble polymer stabilizer present on the surface of the hollow particles is 100 ppm or less. 9 . A prepreg obtained by impregnating a base material with the resin composition according to claim 1 or 2 and then heating and drying the resin composition. 10 . A thermoplastic prepreg, comprising a base material impregnated with the resin composition according to claim 1 .

11. A molded article comprising a cured product of the resin composition according to claim 1 or 2.

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