Heat-expandable microspheres and their uses

Abstract

The purpose of the present invention is to provide: thermally expandable microspheres which maintain high expansibility even after heating for a long period of time; and uses of the same. Disclosed are thermally expandable microspheres which contain a thermoplastic resin and a siloxane-based substance (A) that has a volatilization amount of 2 wt% or more when heated at 150°C for 24 hours. The thermally expandable microspheres each internally contain the substance (A). It is preferable that the substance (A) has a kinematic viscosity of 0.1-100 mm2 / s at 25°C, and it is also preferable that the substance (A) is composed of at least one substance that is selected from among organodisiloxanes, organotrisiloxanes and organopolysiloxanes.

Description

[Technical Field]

[0001] The present invention relates to heat-expandable microspheres and uses thereof. [Background technology]

[0002] Heat-expandable microspheres are fine particles that expand when heated, and are used in a wide range of applications, such as design additives for foaming inks and wallpapers, and weight-reducing agents for resins and paints. Heat-expandable microspheres are widely known as microparticles having a thermoplastic resin shell and encapsulating an expanding agent whose boiling point is equal to or lower than the softening point of the thermoplastic resin constituting the shell. For example, Patent Document 1 discloses microspheres using a vinylidene chloride copolymer, an acrylonitrile copolymer, or an acrylic ester copolymer as the thermoplastic resin and a hydrocarbon such as isobutane or isopentane as the expanding agent. Patent Document 2 discloses heat-expandable microspheres containing isododecane as the expanding agent and exhibiting expandability after heating at 150°C for 5 minutes. Heat-expandable microspheres are generally used by blending them with other base materials and expanding the blend when the blend is heated, which allows the base material to have design properties, cushioning properties, etc., and to be made lighter. When blends containing heat-expandable microspheres are heated, the heating process may require multiple heating steps, and heat-expandable microspheres whose expandability does not decrease even after multiple heating steps are desired. However, although the heat-expandable microspheres disclosed in Patent Document 1 can be efficiently expanded at relatively low heating temperatures, at higher temperatures or for long heating times, their heat resistance is insufficient, leading to a phenomenon known as "settlement," in which they significantly shrink upon heating, resulting in insufficient expandability. Furthermore, the heat-expandable microspheres disclosed in Patent Document 2 remain expandable even after heating at 150°C for 5 minutes, but their expandability decreases and cannot be maintained sufficiently after long heating times. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japan Special Publication No. 42-26524 [Patent Document 2] International Publication No. 2016 / 0932220 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide heat-expandable microspheres that maintain high expandability even after heating for a long period of time, and uses thereof. [Means for solving the problem]

[0005] As a result of extensive research, the present inventors have found that the above problems can be solved by using heat-expandable microspheres containing a specific substance, and have arrived at the present invention. That is, the present invention includes the following aspects.

[0006] <1> Heat-expandable microspheres comprising a thermoplastic resin and a siloxane-based substance (A) that volatilizes by 2% by weight or more when heated at 150°C for 24 hours, the substance (A) being encapsulated within the heat-expandable microspheres. <2> The substance (A) has a kinematic viscosity at 25°C of 0.1 to 100 mm 2 / s, <1> The heat-expandable microspheres according to claim 1. <3> The substance (A) is at least one selected from organodisiloxanes, organotrisiloxanes, and organopolysiloxanes. <1> or <2> The heat-expandable microspheres according to claim 1. <4> The weight ratio of the substance (A) in the heat-expandable microspheres is 1 to 70 wt %. <1> ~ <3> 1. The heat-expandable microspheres according to any one of claims 1 to 9. <5> The thermoplastic resin is a polymer of a polymerizable component containing at least one selected from a nitrile-based monomer, a carboxyl group-containing monomer, a (meth)acrylic acid ester-based monomer, a styrene-based monomer, a (meth)acrylamide-based monomer, and a vinylidene halide-based monomer. <1> ~ <4> 1. The heat-expandable microspheres according to any one of claims 1 to 9. <6> <1> ~ <5> 2. Hollow particles which are expanded bodies of the heat-expandable microspheres according to any one of the preceding items. <7> <6> and fine particles attached to the outer surface of the outer shell of the hollow particle. <8> <1> ~ <5> The heat-expandable microspheres according to any one of the preceding claims. <6> and the hollow particles described in <7> 2. A composition comprising at least one fine particle-coated hollow particle selected from those described in 1. and a base component. <9> <8> A molded article obtained by molding the composition according to claim 1. [Effects of the Invention]

[0007] The heat-expandable microspheres of the present invention maintain high expandability even when heated for a long period of time. The hollow particles of the present invention are expanded versions of the heat-expandable microspheres, and therefore are lightweight with reduced shrinkage. The fine particle-coated hollow particles of the present invention contain the above hollow particles, and therefore are lightweight with reduced shrinkage. The composition of the present invention contains at least one selected from the group consisting of the heat-expandable microspheres, the hollow particles, and the fine particle-coated hollow particles, and therefore allows for the stable production of lightweight molded articles. The molded article of the present invention is obtained by molding the above composition, and is therefore lightweight and has excellent heat resistance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of heat-expandable microspheres. [Figure 2] FIG. 2 is a schematic diagram showing an example of fine particle-coated hollow particles. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Thermally expandable microspheres] The heat-expandable microspheres of the present invention (hereinafter sometimes simply referred to as microspheres) contain a thermoplastic resin and a siloxane-based substance (A) that volatilizes at least 2% by weight when heated at 150°C for 24 hours, and the microspheres encapsulate the siloxane-based substance (A). The microspheres as a whole exhibit heat expandability (the property that the entire microspheres expand when heated). The heat-expandable microspheres of the present invention may be in the following embodiment 1 or embodiment 2. Aspect 1: A shell containing a thermoplastic resin and a physical property (A) contained in the shell Mode 2: Thermoplastic resin having two or more pores inside, and containing substance (A) in the pores

[0010] The first embodiment has a core-shell structure having an outer shell 6 containing a thermoplastic resin and a core 7 containing substance (A) as shown in FIG. Furthermore, when the microspheres of the present invention are those of the first embodiment, the effects of the present invention are exhibited, and the hollow particles, which are expanded bodies of the microspheres, are preferred in that they have elasticity.

[0011] Thermoplastic resins are resins that have the property of softening when heated. The thermoplastic resin is not particularly limited, but examples thereof include acrylic resins, acrylic acid resins, nitrile resins, vinyl chloride resins, vinylidene chloride resins, urethane resins, styrene resins, amide resins, ester resins, ether resins, olefin resins, cellulose resins, etc. These thermoplastic resins may be used alone or in combination of two or more, or may be copolymers. In terms of achieving the effects of the present invention, the thermoplastic resin preferably contains at least one selected from an acrylic resin, an acrylic acid resin, a nitrile resin, a vinylidene chloride resin, a styrene resin, and an amide resin, and more preferably a copolymer thereof.

[0012] The thermoplastic resin is preferably a polymer obtained by polymerizing a polymerizable component. The polymerizable component includes a monomer component and may include a crosslinking agent. The monomer component refers to a polymerizable monomer having one polymerizable double bond and is capable of addition polymerization. The crosslinking agent refers to a polymerizable monomer having multiple polymerizable double bonds and is capable of introducing a crosslinked structure into a thermoplastic resin.

[0013] The monomer component is not particularly limited, and examples thereof include nitrile monomers such as acrylonitrile, methacrylonitrile, and fumaronitrile; carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, maleic acid, itaconic acid, fumaric acid, citraconic acid, and chloromaleic acid; halogenated vinyl monomers such as vinyl chloride; halogenated vinylidene monomers such as vinylidene chloride; vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl butyrate; methyl (meth)acrylate, ethyl (meth)acrylate, and the like. (Meth)acrylic acid ester monomers such as butyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate; dimethyl itaconate, diethyl itaconate, and itaconic acid Complete esterification products of unsaturated polycarboxylic acids such as dipropyl and dimethyl maleate; methylene lactone monomers such as α-methylene-γ-valerolactone, γ-methyl-α-methylene-γ-butyrolactone, α-methylene-γ-butyrolactone, β-methyl-α-methylene-γ-butyrolactone, and γ,γ-dimethyl-α-methylene-γ-butyrolactone; (meth)acrylamide monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; N-phenylmaleimide, N-cyclohexyl methyl acrylate ... Examples of suitable monomers include maleimide monomers such as hexylmaleimide; styrene monomers such as styrene and α-methylstyrene; ethylenically unsaturated monoolefin monomers such as ethylene, propylene, and isobutylene; vinyl ether monomers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl ketone monomers such as vinyl methyl ketone; N-vinyl monomers such as N-vinylcarbazole and N-vinylpyrrolidone; and vinylnaphthalene salts. These monomers may be used alone or in combination of two or more. (Meth)acrylic refers to acrylic or methacrylic.

[0014] The polymerizable component is not particularly limited, but it is preferable from the viewpoint of expandability that the monomer component contains at least one selected from nitrile-based monomers, carboxyl group-containing monomers, (meth)acrylic acid ester-based monomers, styrene-based monomers, vinyl ester-based monomers, acrylamide-based monomers, and vinylidene halide-based monomers.

[0015] The polymerizable component preferably contains a nitrile monomer as a monomer component, because the resulting heat-expandable microspheres have improved gas barrier properties and expansion performance. Nitrile monomers such as acrylonitrile and methacrylonitrile are readily available and are preferred because they can further improve gas barrier properties. When the polymerizable component contains a nitrile monomer as a monomer component, the weight ratio of the nitrile monomer in the polymerizable component is not particularly limited, but is preferably 20 to 100% by weight, more preferably 30 to 99.99% by weight, even more preferably 50 to 99.9% by weight, and particularly preferably 70 to 99% by weight.

[0016] The polymerizable component preferably contains a carboxyl group-containing monomer as a monomer component, since the resulting heat-expandable microspheres have improved heat resistance. Acrylic acid and methacrylic acid are preferred as carboxyl group-containing monomers because they are readily available and further improve heat resistance. Furthermore, some or all of the carboxyl groups in the carboxyl group-containing monomer may be in the form of a carboxyl salt during or after polymerization. When the polymerizable component contains a carboxyl group-containing monomer as a monomer component, the weight ratio of the carboxyl group-containing monomer in the polymerizable component is not particularly limited, but is preferably 5 to 70% by weight, more preferably 10 to 65% by weight, even more preferably 20 to 60% by weight, and particularly preferably 30 to 55% by weight.

[0017] When the polymerizable component contains a carboxyl group-containing monomer as a monomer component, the polymerizable component may further contain a monomer having a group reactive with a carboxyl group as a monomer component, which is preferable in that the heat resistance of the resulting heat-expandable microspheres is improved.

[0018] The group that reacts with a carboxyl group is not particularly limited, but examples thereof include a methylol group, a hydroxyl group, an amino group, an epoxy group, and an isocyanate group. The monomer having a group reactive with a carboxyl group is not particularly limited, but examples thereof include N-methylol(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, vinyl glycidyl ether, propenyl glycidyl ether, glycidyl(meth)acrylate, glycerin mono(meth)acrylate, 4-hydroxybutyl acrylate glycidyl ether, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, and p-hydroxystyrene, and these monomers may be used alone or in combination. Note that the term "(meth)acrylic" refers to either acrylic or methacrylic, and the term "(meth)acrylate" refers to either acrylate or methacrylate.

[0019] It is preferable that the polymerizable component contains vinylidene chloride as a monomer component, since this improves the gas barrier properties. It is preferable that the polymerizable component contains at least one selected from a (meth)acrylic acid ester monomer and a styrene monomer as a monomer component, since this makes it easier to control the thermal expansion characteristics. It is preferable that the polymerizable component contains a (meth)acrylamide monomer as a monomer component, since this improves heat resistance.

[0020] The weight proportion of at least one selected from vinylidene chloride, a (meth)acrylic acid ester monomer, a styrene monomer, and a (meth)acrylamide monomer in the polymerizable component is not particularly limited, but is preferably 80% by weight or less, more preferably 50% by weight or less, and particularly preferably 30% by weight or less.

[0021] As described above, the polymerizable component may contain a crosslinking agent, which is preferable in terms of improving heat resistance. The crosslinking agent is not particularly limited, and examples thereof include alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5 pentanediol di(meth)acrylate, and 2-methyl-1,8 octanediol di(meth)acrylate; Polyethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, PEG#1000 di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol#400 di(meth)acrylate, polypropylene glycol#700 di(meth)acrylate, polytetramethylene glycol di(meth)acrylate Polyalkylene glycol di(meth)acrylates such as ethoxylated bisphenol A di(meth)acrylate, polytetramethylene glycol #650 di(meth)acrylate, and ethoxylated polypropylene glycol #700 di(meth)acrylate; ethoxylated bisphenol A di(meth)acrylate (EO addition 2-30); propoxylated bisphenol A di(meth)acrylate; propoxylated ethoxylated bisphenol A di(meth)acrylate; glycerin di(meth)acrylate; polybutadiene di(meth)acrylate; polyisoprene di(meth)acrylate; 2-hydroxypropyl ... Oxy-3-acryloyloxypropyl methacrylate;Dimethylol-tricyclodecane di(meth)acrylate;Divinylbenzene;Ethoxylated glycerin triacrylate;1,3,5-Tri(meth)acryloyl hexahydro-1,3,5-triazine;Triallyl isocyanurate;Pentaerythritol tri(meth)acrylate;Trimethylolpropane tri(meth)acrylate;1,2,4-Trivinylbenzene;Ditrimethylolpropane tetra(meth)acrylate;Pentaerythritol tetra(meth)acrylateExamples of the crosslinking agent include a bifunctional crosslinking agent such as dipentaerythritol hexa(meth)acrylate, a trifunctional crosslinking agent, and a tetrafunctional or higher crosslinking agent, and these crosslinking agents may be used alone or in combination of two or more.

[0022] The weight proportion of the crosslinking agent in the polymerizable component is not particularly limited, but is preferably 0 to 10% by weight, more preferably 0.1 to 7% by weight, even more preferably 0.2 to 5% by weight, particularly preferably 0.3 to 3% by weight, and most preferably 0.3 to 2% by weight.

[0023] The weight proportion of the thermoplastic resin in the heat-expandable microspheres is not particularly limited, but is preferably 10 to 99% by weight, more preferably 20 to 98% by weight, even more preferably 30 to 97% by weight, particularly preferably 40 to 95% by weight, and most preferably 50 to 95% by weight.

[0024] The heat-expandable microspheres of the present invention may be surface-treated with an organic compound containing a metal belonging to Groups 3 to 12 of the periodic table, or may be crosslinked by carboxyl groups and metal ions.

[0025] The heat-expandable microspheres of the present invention may contain a component having thermosetting properties. The thermosetting component is not particularly limited, and examples thereof include thermosetting silicones such as silicone rubber, silicone resin, and silicone oligomer; epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, dicyclopentadiene type epoxy resin, and glycidylamine type epoxy resin; phenol resins such as novolac type phenol resin, resol type phenol resin, and benzylic ether type phenol resin; melamine resin, urea resin, polyimide resin, and bismaleimide resin; and the like, which may be used alone or in combination of two or more.

[0026] The heat-expandable microspheres of the present invention contain a siloxane-based substance (A) that volatilizes by 2% by weight or more when heated at 150°C for 24 hours. The heat-expandable microspheres are capable of expanding due to the volatility of the substance (A).

[0027] The substance (A) has a structure in which a silicon atom is bonded to an organic group, with the main skeleton being a siloxane bond in which a silicon atom is bonded to an oxygen atom. The substance (A) having the above structure tends to remain inside the heat-expandable microspheres, resulting in high expandability. Even when the shell softens due to prolonged heating, the substance (A) remains inside the shell because of the siloxane bond, preventing penetration through the shell resin. This allows the heat-expandable microspheres to maintain high expandability even after prolonged heating. Furthermore, the inclusion of substance (A) in the heat-expandable microspheres allows them to maintain high expandability even after reheating.

[0028] Furthermore, substance (A) has a volatilization amount of 2% by weight or more when heated at 150°C for 24 hours. When the volatilization amount is 2% by weight or more, the internal pressure of the microspheres can be maintained high during heating, resulting in highly expandable microspheres. The volatilization amount is preferably (1) 5 to 100% by weight, (2) 10 to 100% by weight, (3) 15 to 100% by weight, (4) 20 to 100% by weight, (5) 30 to 100% by weight, (6) 40 to 100% by weight, or (7) 50 to 100% by weight (the larger the number in parentheses, the more preferable it is). The amount of volatilization of substance (A) when heated at 150°C for 24 hours can be confirmed by placing 1 g of substance (A) in a stainless steel evaporating dish with a diameter of 95 mm and a depth of 10 mm, leaving it in a thermostatic bath at 150°C for 24 hours, and measuring the weight loss before and after leaving it.

[0029] The substance (A) is not particularly limited, but it is preferably a liquid at 25°C. The kinematic viscosity of the substance (A) at 25°C is not particularly limited, but is preferably 0.1 to 1000 mm 2 / s, more preferably 0.2 to 500 mm 2 / s, more preferably 0.3 to 100 mm2 / s, particularly preferably 0.4 to 50 mm 2 / s, most preferably 0.5 to 30 mm 2 The kinematic viscosity of the substance (A) at 25°C is measured using an Ostwald viscometer.

[0030] Although there are no particular limitations on the substance (A), it is preferable that the volatilization amount be 1% by weight or more when left standing for 24 hours at 25° C. The volatilization amount is preferably (1) 2 to 100% by weight, (2) 3 to 100% by weight, (3) 5 to 100% by weight, (4) 7 to 100% by weight, and (5) 10 to 100% by weight in that order (the larger the number in parentheses, the more preferable it is). The amount of volatilization of substance (A) when left standing at 25°C for 24 hours can be confirmed by placing 1 g of substance (A) in a stainless steel evaporating dish with a diameter of 95 mm and a depth of 10 mm, leaving it standing in a thermostatic bath at 25°C for 24 hours, and measuring the weight loss before and after leaving it standing.

[0031] There are no particular limitations on the substance (A) as long as it has a volatilization amount of 2% by weight or more when heated at 150°C for 24 hours. Examples of suitable substances include organodisiloxanes such as hexamethyldisiloxane, tetramethyldisiloxane, triethyltrimethyldisiloxane, hexaethyldisiloxane, hexamethoxydisiloxane, hexaphenyldisiloxane, pentamethyldisiloxane, and tetramethyldiphenyldisiloxane; Siloxane, octamethyltrisiloxane, hexamethylcyclotrisiloxane, ethyltrisiloxane, methyltris(dimethylsiloxy)silane, tris(dimethylsilyloxy)phenylsilane, methyltris(trimethylsiloxy)silane, 1,1,1,3,5,5,5-heptamethyltrisiloxane, phenyltris(trimethylsilyloxy)silane, dimethylbis(dimethylsilyloxy)silane, hexamethyltrisiloxane, methyltris(dimethylsiloxy)phenylsilane, methyltris(trimethylsiloxy)silane, methyltris(trimethylsilyloxy)silane, methyltris(trimethylsilyloxy)silane, methyltris(trimethylsilyloxy)silane, methyltris(trimethylsilyloxy)phenyl ... Organotrisiloxanes such as octamethylcyclotetrasiloxane, dodecamethylcyclohexasiloxane, dodecamethylpentasiloxane, decamethyltetrasiloxane, methylpolysiloxane, methylphenylpolysiloxane, decamethylcyclopentasiloxane, methylhydrogenpolysiloxane, caprylyl methicone, triethoxysilylethyl polydimethylsiloxyethyl dimethicone, triethoxysilylethyl polydimethylsiloxyethylhexyl dimethicone, ethylmethicone, and modified silicone oils; triethoxycaprylylsilane; polymethylhydrosiloxane, and the like, and these may be used alone or in combination of two or more. There are no particular restrictions on the substance (A), but it is preferably at least one selected from organodisiloxanes, organotrisiloxanes, and organopolysiloxanes, as this increases the vapor pressure when heated. There are no particular restrictions on the substance (A), but it is preferable that it does not have a polymerizable carbon-carbon double bond.

[0032] The weight percentage of the substance (A) in the heat-expandable microspheres is not particularly limited, but is preferably 1 to 70% by weight, more preferably 3 to 60% by weight, even more preferably 5 to 50% by weight, particularly preferably 8 to 40% by weight, and most preferably 10 to 35% by weight. When the weight percentage is 1% by weight or more, the expandability tends to be improved. When the weight percentage is 70% by weight or less, the expandability tends to be maintained even after heating for a long period of time. The weight ratio of the substance (A) in the heat-expandable microspheres is determined by the method described in the Examples.

[0033] The heat-expandable microspheres of the present invention may contain a substance (B) other than the substance (A), which is a component that volatilizes upon heating. The substance (B) is not particularly limited, and examples thereof include linear hydrocarbons such as methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, and nanodecane; isobutane, isopentane, isohexane, isoheptane, isooctane, isononane, isodecane, isododecane, 3-methylundecane, and isotridecane. Branched hydrocarbons such as hexane, 4-methyldodecane, isotetradecane, isopentadecane, isohexadecane, 2,2,4,4,6,8,8-heptamethylnonane, isoheptadecane, isooctadecane, isonadecane, and 2,6,10,14-tetramethylpentadecane; cyclododecane, cyclotridecane, hexylcyclohexane, heptylcyclohexane, n-octylcyclohexane, cyclopentadecane, and nonylcyclohexane hydrocarbons such as petroleum ether, and petroleum fractions such as normal paraffin and isoparaffin having an initial boiling point of 150 to 260°C and / or a distillation range of 70 to 360°C; halides of hydrocarbons having 1 to 12 carbon atoms such as methyl chloride, methylene chloride, chloroform, and carbon tetrachloride; fluorine-containing compounds such as hydrofluoroethers; silanes having an alkyl group having 1 to 5 carbon atoms such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane; and compounds that undergo thermal decomposition upon heating to produce gas, such as azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, and 4,4'-oxybis(benzenesulfonylhydrazide), and these may be used alone or in combination of two or more. The heat-expandable microspheres of the present invention may contain, in addition to the substance (A), a substance (C) that volatilizes in an amount of less than 2% by weight when heated at 150°C for 24 hours.

[0034] The volume average particle size of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 0.1 to 500 μm, more preferably 0.5 to 300 μm, even more preferably 1 to 200 μm, particularly preferably 3 to 100 μm, and most preferably 5 to 50 μm. The volume-average particle size of the heat-expandable microspheres of the present invention is measured by the method described in the Examples.

[0035] The expansion starting temperature (Ts) of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 120 to 350°C, more preferably 140 to 340°C, even more preferably 150 to 330°C, and particularly preferably 150 to 320°C.

[0036] The maximum expansion temperature (Tmax) of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 150 to 400°C, more preferably 160 to 370°C, even more preferably 170 to 350°C, and particularly preferably 180 to 340°C. The expansion starting temperature (Ts) and maximum expansion temperature (Tmax) of the heat-expandable microspheres are measured by the methods described in the examples.

[0037] The maximum expansion displacement (Hmax1) of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 100 μm or more, more preferably 200 μm or more, even more preferably 300 μm or more, and particularly preferably 500 μm or more. The maximum expansion displacement (Hmax2) of the heat-expandable microspheres of the present invention after heating for 2 hours at a temperature 50°C lower than their expansion-initiation temperature is not particularly limited, but is preferably at least 100 μm, more preferably at least 200 μm, even more preferably at least 300 μm, and particularly preferably at least 500 μm. The maximum expansion displacement of the heat-expandable microspheres of the present invention and the heated product thereof is measured by the method described in the examples.

[0038] The heat-expandable microspheres of the present invention maintain high expandability even after prolonged heating. Therefore, compounds containing the heat-expandable microspheres of the present invention can maintain their expandability even when subjected to multiple heating processes or prolonged heating processes. Furthermore, shrinkage of the resulting expanded body is suppressed even when subjected to extensive thermal history. This maintains the shape of the pores introduced by the expansion of the heat-expandable microspheres, allowing for the stable production of lightweight molded bodies. This makes the heat-expandable microspheres suitable for molding processes such as injection molding, extrusion molding, kneading molding, calendar molding, blow molding, compression molding, vacuum molding, and thermoforming. They can also be used by mixing with pastes such as vinyl chloride pastes and liquid compositions such as EVA emulsions, acrylic emulsions, and urethane binders. They can also be incorporated into coatings to create textures and improve design.

[0039] [Method for producing heat-expandable microspheres] The method for producing heat-expandable microspheres of the present invention includes, for example, a step of dispersing an oily mixture containing a polymerizable component, a substance (A), and a polymerization initiator in an aqueous dispersion medium and polymerizing the polymerizable component (hereinafter, sometimes simply referred to as a polymerization step).

[0040] The polymerization initiator is not particularly limited, but examples thereof include commonly used peroxides and azo compounds. Examples of peroxides include peroxydicarbonates such as diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and dibenzyl peroxydicarbonate; diacyl peroxides such as dilauroyl peroxide and dibenzoyl peroxide; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; peroxyketals such as 2,2-bis(t-butylperoxy)butane; hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; dialkyl peroxides such as dicumyl peroxide and di-t-butyl peroxide; and peroxyesters such as t-hexyl peroxypivalate and t-butyl peroxyisobutyrate. Examples of azo compounds include 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), and 1,1'-azobis(cyclohexane-1-carbonitrile).

[0041] The amount of the polymerization initiator to be added is not particularly limited, but is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, and even more preferably 0.2 to 5 parts by weight, relative to 100 parts by weight of the polymerizable component.

[0042] In the production method of the present invention, it is preferable to prepare an aqueous suspension by dispersing the oily mixture in an aqueous dispersion medium, and then polymerize the polymerizable component. The aqueous dispersion medium is a medium containing water, such as ion-exchanged water, as a main component for dispersing the oily mixture, and may further contain alcohols, such as methanol, ethanol, and propanol, or hydrophilic organic solvents, such as acetone. The term "hydrophilic" in the present invention means a state in which the aqueous dispersion medium can be arbitrarily mixed with water. The amount of the aqueous dispersion medium used is not particularly limited, but is preferably 100 to 1,000 parts by weight per 100 parts by weight of the polymerizable component.

[0043] The aqueous dispersion medium may further contain an electrolyte. Examples of the electrolyte include sodium chloride, magnesium chloride, calcium chloride, sodium sulfate, magnesium sulfate, ammonium sulfate, and sodium carbonate. These electrolytes may be used alone or in combination of two or more. The content of the electrolyte is not particularly limited, but is preferably 0.1 to 50 parts by weight per 100 parts by weight of the aqueous dispersion medium.

[0044] The aqueous dispersion medium may contain at least one water-soluble compound selected from the group consisting of water-soluble 1,1-substituted compounds having a structure in which a hydrophilic functional group selected from a hydroxyl group, a carboxylic acid (salt) group, and a phosphonic acid (salt) group and a heteroatom are bonded to the same carbon atom, polyalkyleneimines having a structure in which an alkyl group substituted with a hydrophilic functional group selected from a carboxylic acid (salt) group and a phosphonic acid (salt) group is bonded to a nitrogen atom, water-soluble ascorbic acids, water-soluble polyphenols, water-soluble B vitamins, potassium dichromate, alkali metal nitrites, metal (III) halides, boric acid, and water-soluble phosphonic acids (salts). In the present invention, water solubility refers to a state in which 1 g or more of the compound dissolves in 100 g of water. The amount of the water-soluble compound contained in the aqueous dispersion medium is not particularly limited, but is preferably 0.0001 to 1.0 part by weight, more preferably 0.0003 to 0.1 part by weight, and even more preferably 0.001 to 0.05 part by weight, relative to 100 parts by weight of the polymerizable component.

[0045] The aqueous dispersion medium may contain a dispersion stabilizer or a dispersion stabilization aid in addition to the electrolyte and the water-soluble compound. The dispersion stabilizer is not particularly limited, but examples thereof include tribasic calcium phosphate, magnesium pyrophosphate obtained by a metathesis method, calcium pyrophosphate, colloidal silica, alumina sol, magnesium hydroxide, and the like, and these dispersion stabilizers may be used alone or in combination of two or more. The amount of the dispersion stabilizer to be added is not particularly limited, but is preferably 0.05 to 100 parts by weight, more preferably 0.2 to 70 parts by weight, per 100 parts by weight of the polymerizable component. The dispersion stabilization aid is not particularly limited, and examples thereof include polymer-type dispersion stabilization aids, and surfactants such as cationic surfactants, anionic surfactants, zwitterionic surfactants, and nonionic surfactants, and these dispersion stabilization aids may be used alone or in combination of two or more.

[0046] The aqueous dispersion medium is prepared, for example, by blending water (ion-exchanged water) with an electrolyte, a water-soluble compound, a dispersion stabilizer, a dispersion stabilization assistant, etc., as necessary. The pH of the aqueous dispersion medium during polymerization is determined appropriately depending on the types of the water-soluble compound, dispersion stabilizer, and dispersion stabilization assistant.

[0047] In the method for producing heat-expandable microspheres of the present invention, polymerization may be carried out in the presence of sodium hydroxide or sodium hydroxide and zinc chloride. In the production method of the present invention, an oily mixture is suspended and dispersed in an aqueous dispersion medium so as to prepare spherical oil droplets having a predetermined particle size.

[0048] Examples of methods for suspending and dispersing an oily mixture include general dispersion methods such as stirring with a homomixer (e.g., manufactured by Primix Corporation), using a static dispersion device such as a static mixer (e.g., manufactured by Noritake Engineering Co., Ltd.), membrane suspension, and ultrasonic dispersion. The suspension polymerization is then initiated by heating the dispersion in which the oily mixture is dispersed as oil globules in the aqueous dispersion medium. During the polymerization reaction, the dispersion is preferably stirred, and the stirring may be gentle enough to prevent the floating of the monomers and the settling of the heat-expandable microspheres after polymerization.

[0049] The polymerization temperature can be freely set depending on the type of polymerization initiator, but is preferably controlled within the range of 30 to 100°C, and more preferably 40 to 90°C. The reaction temperature is preferably maintained for about 1 to 20 hours. The initial polymerization pressure is not particularly limited, but is in the range of 0 to 5 MPa, and more preferably 0.1 to 3 MPa, in gauge pressure.

[0050] The slurry obtained after the polymerization step is filtered using a centrifuge, a pressure press, a vacuum dehydrator, or the like to form a cake-like substance having a moisture content of 10 to 50% by weight, preferably 15 to 45% by weight, and more preferably 20 to 40% by weight. The cake-like substance is then dried using a tray dryer, an indirect heating dryer, a fluidized bed dryer, a vacuum dryer, a vibration dryer, a flash dryer, or the like to form a dry powder having a moisture content of 6% by weight or less, preferably 5% by weight or less, and more preferably 4% by weight or less. To reduce the content of ionic substances such as electrolytes, the cake-like product may be washed with water or redispersed, filtered, and dried. Alternatively, the slurry may be dried using a spray dryer, fluidized bed dryer, or the like to obtain a dry powder.

[0051] [Hollow particles] The hollow particles of the present invention are expanded versions of the heat-expandable microspheres described above. The hollow particles are lightweight and exhibit excellent material properties when incorporated into compositions or molded articles.

[0052] The hollow particles of the present invention are not particularly limited, but can be obtained by thermally expanding the above-mentioned heat-expandable microspheres, preferably at a temperature of 100 to 500° C. The thermal expansion method is not particularly limited, and may be either a dry thermal expansion method or a wet thermal expansion method.

[0053] The volume average particle size of the hollow particles of the present invention is not particularly limited as it can be freely designed depending on the application, but is preferably 0.2 to 3000 μm, more preferably 1 to 1000 μm.

[0054] The true specific gravity of the hollow particles of the present invention is not particularly limited, but is preferably 0.005 to 0.8, more preferably 0.01 to 0.6, even more preferably 0.015 to 0.5, and particularly preferably 0.020 to 0.4. If the true specific gravity is 0.005 or more, deformation of the hollow particles tends to be suppressed, and if the true specific gravity is 0.8 or less, the hollow particles tend to function more efficiently as a weight-reducing agent. The true specific gravity of the hollow particles of the present invention is measured by the method described in the Examples.

[0055] [Hollow particles with fine particles attached] The microparticle-coated hollow particles of the present invention comprise the hollow particles described above and microparticles attached to the outer surface of the shell of the hollow particle. As shown in Figure 2, the microparticle-coated hollow particles may be composed of microparticles (4 or 5) attached to the outer surface of the shell 2. The term "attached" here means that the microparticles may simply be adsorbed onto the outer surface of the shell 2 of the hollow particle (the state of microparticle 4 in Figure 2), or may mean that the thermoplastic resin forming the shell near the outer surface is melted by heating, causing the microparticles to sink into the outer surface of the shell of the hollow particle and become fixed thereto (the state of microparticle 5 in Figure 2).

[0056] Various types of fine particles can be used, and may be made of either inorganic or organic materials. The shape of the fine particles may be amorphous or spherical. Examples of the shape of the fine particles include spherical, needle-like, and plate-like. The fine particles are not particularly limited, but when the fine particles are organic, examples include metal soaps such as sodium carboxymethylcellulose, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, nitrocellulose, hydroxypropyl cellulose, sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, carboxyvinyl polymer, polyvinyl methyl ether, magnesium stearate, calcium stearate, zinc stearate, barium stearate, and lithium stearate; synthetic waxes such as polyethylene wax, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, and hydrogenated castor oil; (meth)acrylic resins, polyamide resins, polyimide resins, urethane resins, polyethylene resins, polypropylene resins, and fluorine-based resins. When the fine particles are inorganic, examples thereof include talc, mica, clay, bentonite, wollastonite, sericite, kaolin, alumina silicate, pyrophyllite, montmorillonite, carbon black, molybdenum disulfide, tungsten disulfide, graphite fluoride, calcium fluoride, boron nitride, silicon carbide, silica, alumina, mica, colloidal calcium carbonate, calcium silicate, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, calcium hydroxide, calcium phosphate, magnesium hydroxide, magnesium phosphate, barium sulfate, titanium dioxide, magnesium oxide, zinc oxide, hydrosaltite, ceramic beads, glass flakes, glass beads, quartz beads, and glass microballoons. The inorganic or organic material constituting the fine particles may be treated with a surface treatment agent such as a silane coupling agent, paraffin wax, fatty acid, resin acid, urethane compound, or fatty acid ester, or may be untreated.

[0057] The volume average particle size of the fine particles is preferably 1 / 10 or less of the volume average particle size of the fine particle-coated hollow particles, where the average particle size refers to the average particle size of the primary particles.

[0058] The weight ratio of the fine particles to the total fine particle-coated hollow particles is not particularly limited, but is preferably 20 to 95% by weight, more preferably 20 to 90% by weight, even more preferably 40 to 85% by weight, and particularly preferably 40 to 80% by weight.

[0059] The true specific gravity of the fine particle-coated hollow particles of the present invention is not particularly limited, but is preferably 0.01 to 0.8. If the true specific gravity is 0.03 or more, deformation of the hollow particles tends to be suppressed, and if the true specific gravity is 0.8 or less, the hollow particles tend to function more efficiently as a weight-reducing agent.

[0060] When the fine particle-coated hollow particles of the present invention are blended with the compositions described below, they are useful as coating compositions or adhesive compositions. The fine particle-coated hollow particles can be obtained, for example, by heating and expanding fine particle-coated heat-expandable microspheres. A preferred method for producing fine particle-coated hollow particles includes a step of mixing heat-expandable microspheres with fine particles (mixing step), and a step of heating the mixture obtained in the mixing step to a temperature above the softening point to expand the heat-expandable microspheres and to cause fine particles to adhere to the outer surfaces of the resulting hollow particles (adhesion step).

[0061] [Composition and Molded Article] The composition of the present invention contains at least one material selected from the group consisting of the above-mentioned heat-expandable microspheres, hollow particles, and fine particle-coated hollow particles (hereinafter sometimes simply referred to as particulate material), and a base component. The base material component is not particularly limited, and examples thereof include rubbers such as natural rubber, butyl rubber, silicone rubber, and ethylene-propylene-diene rubber (EPDM); thermosetting resins such as unsaturated polyester, epoxy resin, and phenolic resin; waxes such as polyethylene wax and paraffin wax; ethylene-vinyl acetate copolymer (EVA), ionomer, polyethylene, polypropylene, polyvinyl chloride (PVC), acrylic resin, thermoplastic polyurethane, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polystyrene (PS), polyamide resin (nylon 6, nylon 66, etc.), polycarbonate, polyethylene terephthalate (PET), and polybutylene terephthalate. Examples of the base material include thermoplastic resins such as polybutadiene rubber (PBT), polyacetal (POM), and polyphenylene sulfide (PPS); thermoplastic elastomers such as olefin elastomers and styrene elastomers; bioplastics such as polylactic acid (PLA), cellulose acetate, polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), and starch resins; sealing materials such as silicones, modified silicones, polysulfides, modified polysulfides, urethanes, acrylics, polyisobutylenes, and butyl rubbers; urethane-based, ethylene-vinyl acetate copolymer-based, vinyl chloride-based, and acrylic coating components; emulsions; and inorganic materials such as cement, mortar, and cordierite. These base material components may be used alone or in combination of two or more.

[0062] The composition of the present invention can be prepared by mixing a base component with a granular material. Alternatively, the composition obtained by mixing a base component with a granular material can be further mixed with another base component to prepare the composition of the present invention. The content of the particulate material is not particularly limited, but is preferably 0.1 to 70 parts by weight, more preferably 0.5 to 65 parts by weight, and even more preferably 1 to 60 parts by weight, relative to 100 parts by weight of the base component.

[0063] The method for producing the composition of the present invention is not particularly limited, but is preferably a method of mixing using a kneader, roll, mixing roll, mixer, single-screw kneader, twin-screw kneader, multi-screw kneader, or the like. The uses of the composition of the present invention are not particularly limited, but examples thereof include molding compositions, coating compositions, clay compositions, fiber compositions, adhesive compositions, and powder compositions.

[0064] The composition of the present invention may be a molding masterbatch. When the molding masterbatch contains heat-expandable microspheres, the base component preferably softens or melts at a temperature lower than the expansion initiation temperature of the heat-expandable microspheres contained therein. Examples of base components that soften or melt at a temperature lower than the expansion initiation temperature of heat-expandable microspheres include waxes such as polyethylene wax and paraffin wax; thermoplastic resins such as ethylene-vinyl acetate copolymer (EVA), polyethylene, modified polyethylene, polypropylene, modified polypropylene, modified polyolefin, polyvinyl chloride (PVC), acrylic resin, thermoplastic polyurethane, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polystyrene (PS), polycarbonate, polyethylene terephthalate (PET), and polybutylene terephthalate (PBT); ionomer resins such as ethylene-based ionomers, urethane-based ionomers, styrene-based ionomers, and fluorine-based ionomers; and thermoplastic elastomers such as olefin-based elastomers, styrene-based elastomers, and urethane-based elastomers. The molding masterbatch can be used when producing a resin molded article by a method such as extrusion molding, injection molding, or press molding, and is suitably used as a method for introducing pores into a resin molded article.

[0065] The molded article of the present invention is obtained by molding the composition described above. Examples of the molded article of the present invention include coating films and molded articles. The molded article of the present invention has improved physical properties such as light weight, porosity, sound absorption, heat insulation, low thermal conductivity, low dielectric constant, designability, impact absorption, strength, chipping resistance, etc. Furthermore, a molded article containing an inorganic substance as a base component can be further fired to obtain a ceramic filter or the like. [Example]

[0066] Examples of the heat-expandable microspheres of the present invention will now be described in detail. The present invention is not limited to these examples. In the following examples and comparative examples, "%" means "% by weight" unless otherwise specified. Furthermore, for the sake of simplicity, heat-expandable microspheres will sometimes be referred to as "microspheres."

[0067] [Measurement of Volume Average Particle Diameter of Heat-Expandable Microspheres] The volume average particle diameter was measured using a laser diffraction scattering particle size distribution analyzer (MT3000II) manufactured by Microtrack Bell Co., Ltd. The D50 value obtained by volume-based measurement was used as the volume average particle diameter.

[0068] [Measurement of the expansion starting temperature (Ts), maximum expansion temperature (Tmax), and maximum expansion displacement (Hmax) of heat-expandable microspheres] A DMA (DMA Q800, manufactured by TA Instruments) was used as the measurement device. 1.0 mg of microspheres was placed in an aluminum cup with a diameter of 6.0 mm and a depth of 4.8 mm, and an aluminum lid (diameter 5.6 mm, thickness 0.1 mm) was placed on top of the microsphere layer to prepare a sample. The sample height was measured while a force of 0.01 N was applied from above using a pressure probe. The sample was heated from 20°C to 400°C at a heating rate of 10°C / min while a force of 0.01 N was applied using the pressure probe, and the displacement of the pressure probe in the vertical direction was measured. The temperature at which displacement in the forward direction began was defined as the expansion onset temperature (Ts), and the temperature at which the maximum expansion displacement (Hmax) was reached was defined as the maximum expansion temperature (Tmax).

[0069] [Expansion evaluation of heat-expandable microspheres] (Expansion evaluation) The maximum expansion displacement (Hmax1) obtained during the measurement of the maximum expansion temperature (Tmax) of the heat-expandable microspheres was evaluated as follows. ◎ (Excellent): 500 μm≦Hmax1 ○(slightly better): 50 <Hmax1<500μm × (inferior): Hmax1≦50 (Expansion evaluation after heating) 1 g of microspheres was heated for 2 hours in an oven set at a temperature 50°C lower than the expansion onset temperature (Ts). The expansion behavior of the heated product was measured in the same manner as in the above-mentioned method for measuring the maximum expansion temperature (Tmax) of heat-expandable microspheres, and the maximum expansion displacement (Hmax2) obtained was evaluated as follows: ◎ (Excellent): 500 μm≦Hmax2 ○(slightly better): 50 <Hmax2<500μm × (inferior): Hmax2≦50

[0070] [Measurement of the weight proportion of substance (A) in heat-expandable microspheres] 0.1 g of heat-expandable microspheres and 10 mL of methanol were added to a vial, which was then sealed and mixed uniformly to disperse the mixture. The resulting mixture was allowed to stand at 25°C for 12 hours. The mixture was filtered to recover the filtrate, which was then diluted 10-fold with methanol. 1 μL of the diluted solution was used as a sample for GC-MS analysis (Agilent 7890A GC) to determine the weight percentage of substance (A) in the heat-expandable microspheres.

[0071] [Measurement of true specific gravity of hollow particles] The true specific gravity of the hollow particles was measured by the immersion method (Archimedes method) using isopropyl alcohol in an atmosphere with an ambient temperature of 25°C and a relative humidity of 50%.

[0072] Example 1 To 600 g of ion-exchanged water, 150 g of sodium chloride, 50 g of colloidal silica containing 20% ​​by weight of the active ingredient, 4.0 g of polyvinylpyrrolidone, and 1.0 g of ethylenediaminetetraacetic acid tetrasodium salt were added, and the pH of the resulting mixture was adjusted to 2.0-3.0 to prepare an aqueous dispersion medium. Separately, 4 g of acrylonitrile, 114 g of methacrylonitrile, 153 g of methacrylic acid, 15 g of methacrylamide, 15 g of styrene, 0.06 g of 1,9-nonanediol diacrylate, and decamethyltetrasiloxane (volatilization amount when heated at 150°C for 24 hours: 100% by weight, kinematic viscosity at 25°C: 1.5 mm 2 An oily mixture was prepared by mixing 30 g of PEG-100 / s and 8 g of a solution containing 50% by weight of the active ingredient di-sec-butyl peroxydicarbonate. The aqueous dispersion medium and the oil mixture were mixed, and the resulting mixture was dispersed in a homomixer to prepare a suspension. The suspension was transferred to a 1.5 L pressure reactor and purged with nitrogen. The initial reaction pressure was adjusted to 0.2 MPa, and polymerization was carried out at 60°C for 20 hours with stirring. The resulting product was filtered and dried to obtain heat-expandable microspheres 1. The resulting heat-expandable microspheres 1 had the same configuration as the above-mentioned configuration 1, and their physical properties were measured to evaluate their expandability. The results are shown in Table 1.

[0073] <Examples 2 to 7, Comparative Examples 1 and 2> Heat-expandable microspheres were obtained in the same manner as in Example 1, except that the oily mixtures were changed as shown in Tables 1 and 2. The physical properties of the obtained heat-expandable microspheres were measured, and their expandability was evaluated. The results are shown in Tables 1 and 2. In Tables 1 and 2, Mode 1 indicates the above Mode 1, and Mode 2 indicates the above Mode 2. Table 3 shows details of the raw materials used in the examples and comparative examples.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Table 3]

[0077] The heat-expandable microspheres of Examples 1 to 7 expanded well even after prolonged heating and exhibited excellent expansion retention. On the other hand, the heat-expandable microspheres of Comparative Example 1 showed no expansion after prolonged heating and exhibited poor expansion retention. The heat-expandable microspheres of Comparative Example 2 did not show any expansion initiation temperature or maximum expansion temperature, and no expansion was observed. Furthermore, no expansion was observed even after prolonged heating.

[0078] Example A The heat-expandable microspheres 1 obtained in Example 1 were heated in an oven at 200°C for 2 hours and then at 280°C for 2 minutes to obtain hollow particles A. The true specific gravity of the obtained hollow particles A was 0.05, indicating that lightweight hollow particles were obtained.

[0079] <Comparative example B> The heat-expandable microspheres 3 obtained in Comparative Example 1 were heated in an oven at 200°C for 2 hours and then at 280°C for 2 minutes to obtain hollow particles B. The true specific gravity of the obtained hollow particles B was 0.98, and they were hardly expanded.

[0080] Heat-expandable microspheres 1 of Example 1 expanded well even after prolonged heating, yielding lightweight hollow particles, whereas heat-expandable microspheres 3 of Comparative Example 1 showed reduced expansion after prolonged heating, failing to yield hollow particles. [Industrial Applicability]

[0081] The heat-expandable microspheres of the present invention maintain high expandability even after prolonged heating. Therefore, when a compound containing the heat-expandable microspheres is heated, the compound can maintain its expandability even after multiple heating steps or long-term heating steps. Therefore, the compound can be suitably used in processing steps that involve significant thermal history. The heat-expandable microspheres, hollow particles, and microparticle-coated hollow particles of the present invention have excellent heat resistance and can be used as compounding agents in various products such as paints, coating compositions, films, and molded articles. [Explanation of symbols]

[0082] 1 Hollow particles with fine particles attached 2 Outer shell (shell) 3 Hollow part 4 Microparticles (adsorbed state) 5. Microparticles (embedded, fixed) 6. Shell containing thermoplastic resin 7 Core containing substance (A)

Claims

1. A thermoplastic resin; and a siloxane-based substance (A) that volatilizes in an amount of 5 to 100% by weight when heated at 150°C for 24 hours. The heat-expandable microspheres contain the substance (A).

2. The heat-expandable microspheres according to claim 1, wherein the volatile content of the substance (A) when heated at 150°C for 24 hours is 10 to 100% by weight.

3. The substance (A) has a kinematic viscosity at 25°C of 0.1 to 100 mm ２ The heat-expandable microspheres according to claim 1 or 2, wherein the average molecular weight of the heat-expandable microspheres is 1 / s.

4. 3. The heat-expandable microspheres according to claim 1, wherein the substance (A) is at least one selected from the group consisting of organodisiloxanes, organotrisiloxanes, and organopolysiloxanes.

5. 3. Heat-expandable microspheres according to claim 1, wherein the weight ratio of the substance (A) in the heat-expandable microspheres is 1 to 70% by weight.

6. 3. The heat-expandable microspheres according to claim 1, wherein the thermoplastic resin is a polymer of a polymerizable component containing at least one monomer selected from the group consisting of a nitrile monomer, a carboxyl group-containing monomer, a (meth)acrylic ester monomer, a styrene monomer, a (meth)acrylamide monomer, and a vinylidene halide monomer.

7. Hollow particles, which are expanded bodies of the heat-expandable microspheres according to claim 1.

8. A microparticle-coated hollow particle comprising the hollow particle according to claim 7 and microparticles attached to the outer surface of the outer shell of the hollow particle.

9. A composition comprising at least one selected from the group consisting of the heat-expandable microspheres according to claim 1 or 2, the hollow particles according to claim 7, and the fine particle-coated hollow particles according to claim 8, and a base component.

10. A molded article obtained by molding the composition according to claim 9.

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