Heat-expandable microspheres and their uses

Abstract

To provide a thermally expandable microsphere having excellent dispersibility in a polar liquid, and applications thereof.MEANS FOR SOLVING THE PROBLEM: A thermally expandable microsphere contains an outer shell containing thermoplastic resin, and a foamer that is included in the outer shell and is heated to be vaporized. The thermoplastic resin is a polymer of a polymerizable component containing a monomer (A). The monomer (A) is a compound having one polymerizable carbon-carbon double bond and having five or more oxygen atoms in each molecule.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Heat-expandable microspheres, which have a thermoplastic resin shell and a blowing agent encapsulated inside, are generally called heat-expandable microspheres (heat-expandable microcapsules). Heat-expandable microspheres are microspheres that have the characteristic of expanding when heated. These heat-expandable microspheres are used in a wide range of applications, for example, by blending them into a substrate. Heat treatment during molding causes the heat-expandable microspheres to expand simultaneously with molding, thereby not only reducing the weight of the molded product but also imparting design features, cushioning properties, etc. to the molded product. To ensure the expansion function of heat-expandable microspheres, the thermoplastic resin used for their shells must generally have gas barrier properties. For example, heat-expandable microspheres have been disclosed that use a shell made of a vinylidene chloride copolymer, an acrylonitrile copolymer, an acrylic copolymer, or the like, and that use a hydrocarbon, such as isobutane or isopentane, as the blowing agent (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 3,615,972 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although the heat-expandable microspheres disclosed in Patent Document 1 exhibit sufficient expansion behavior, they have poor dispersibility in polar liquids such as water, and it has been confirmed that the heat-expandable microspheres undergo significant aggregation in liquids. An object of the present invention is to provide heat-expandable microspheres having excellent dispersibility in polar liquids, and uses thereof. [Means for solving the problem]

[0005] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by heat-expandable microspheres comprising a shell containing a thermoplastic resin obtained by polymerizing a specific polymerizable component and a blowing agent encapsulated in the shell and vaporized by heating, and have arrived at the present invention based on this finding.

[0006] That is, the present invention relates to heat-expandable microspheres comprising a shell containing a thermoplastic resin and a blowing agent encapsulated in the shell and vaporized by heating, wherein the thermoplastic resin is a polymer of a polymerizable component containing a monomer (A), and the monomer (A) is a compound having one polymerizable carbon-carbon double bond and five or more oxygen atoms in the molecule.

[0007] The heat-expandable microspheres of the present invention preferably satisfy at least one of the following requirements 1) to 5). 1) The content of the monomer (A) in the polymerizable component is 5% by weight or more. 2) The monomer (A) has an ester bond in the molecule, and an oxygen atom other than the carbonyl moiety of the ester bond is bonded to the following group (a1): Group (a1): a group having a linear structural portion and / or a branched structural portion and having two or more carbon atoms 3) The polymerizable component further contains a nitrile monomer. 4) The polymerizable component further contains a carboxyl group-containing monomer other than the monomer (A). 5) The polymerizable component further contains a (meth)acrylic acid ester monomer other than the monomer (A).

[0008] The hollow particles of the present invention are expanded versions of the above-mentioned heat-expandable microspheres. The fine particle-coated hollow particles of the present invention comprise the above hollow particles and fine particles that are adhered to the outer surface of the outer shell of the hollow particles.

[0009] 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 a base component. The composition of the present invention is obtained by molding the above composition. [Effects of the Invention]

[0010] The heat-expandable microspheres of the present invention have excellent dispersibility in polar liquids. The hollow particles of the present invention are obtained from the above-mentioned heat-expandable microspheres as raw materials and therefore have excellent dispersibility in polar liquids. The microparticle-coated hollow particles of the present invention are obtained from the above-mentioned heat-expandable microspheres as raw materials, and therefore have excellent dispersibility in polar liquids. 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 resin hollow particles, and therefore can give a lightweight molded article. The molded article of the present invention is lightweight. [Brief explanation of the drawings]

[0011] [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

[0012] [Thermally expandable microspheres] The heat-expandable microspheres of the present invention comprise a shell containing a thermoplastic resin and a blowing agent encapsulated in the shell and vaporized by heating. The heat-expandable microspheres exhibit heat expandability (the property that the entire microsphere expands upon heating) throughout the microspheres. As shown in FIG. 1, the heat-expandable microspheres of the present invention have a core-shell structure consisting of an outer shell 6 and a blowing agent (core) 7 .

[0013] The thermoplastic resin forming the shell of the heat-expandable microspheres of the present invention is a polymer obtained by polymerizing a polymerizable component. The polymerizable component is a component that essentially contains a monomer component and may contain a crosslinking agent. The monomer component refers to a monomer having one polymerizable carbon-carbon double bond and is a component capable of addition polymerization. The crosslinking agent refers to a monomer having at least two polymerizable carbon-carbon double bonds and is a component that introduces a crosslinked structure into the thermoplastic resin.

[0014] The polymerizable component contains a monomer (A). The monomer (A) is a compound having one polymerizable carbon-carbon double bond and five or more oxygen atoms in the molecule, and is classified as a monomer component. The monomer (A), which is a compound having five or more oxygen atoms in the molecule, has sufficient polarity, which is believed to enable control of the polarity of the resulting thermoplastic resin. This is believed to enable the heat-expandable microspheres to have excellent dispersibility in polar liquids.

[0015] The number of oxygen atoms in the molecule of monomer (A) is 5 or more, preferably 5 to 40. When the number of oxygen atoms is 40 or less, the polarity of monomer (A) is not excessive, and heat-expandable microspheres having an outer shell with appropriate polarity tend to be obtained efficiently. The upper limit of the number of oxygen atoms is more preferably 35, even more preferably 30, particularly preferably 25, and most preferably 20. On the other hand, the lower limit of the number of oxygen atoms is preferably 6, more preferably 7, and particularly preferably 8.

[0016] The monomer (A) is not particularly limited, but is preferably a compound having an ester bond in the molecule, in which an oxygen atom other than the carbonyl moiety in the ester bond is bonded to the following group (a1), in that the polarity of the resulting thermoplastic resin can be efficiently controlled. Group (a1): a group having a linear structural portion and / or a branched structural portion and having two or more carbon atoms

[0017] When the monomer (A) has an ester bond, the number of ester bonds is not particularly limited, but is preferably 1 to 15. The upper limit of the number of ester bonds is more preferably 10, even more preferably 8, particularly preferably 6, and most preferably 4. On the other hand, the lower limit of the number of ester bonds is more preferably 2. When the monomer (A) has an ester bond, the monomer (A) may be a derivative of a (meth)acrylic acid ester. The monomer (A) may contain a sulfur atom and / or a phosphorus atom, or may not contain a sulfur atom and / or a phosphorus atom.

[0018] When the monomer (A) has a group (a1), the number of carbon atoms in the group (a1) is not particularly limited, but from the viewpoint of achieving the effects of the present invention, it is 2 to 150. The upper limit of the number of carbon atoms is more preferably 125, even more preferably 85, particularly preferably 65, and most preferably 45. On the other hand, the lower limit of the number of carbon atoms is more preferably 3, even more preferably 4, and particularly preferably 5. In addition, when the monomer (A) has the group (a1), the group (a1) may or may not have a polymerizable carbon-carbon double bond. In terms of achieving the effects of the present invention, the group (a1) preferably does not have a polymerizable carbon-carbon double bond.

[0019] The straight-chain structural portion and / or branched structural portion of group (a1) contains carbon atoms. The number of carbon atoms in the straight-chain structural portion and / or branched structural portion is not particularly limited, but is preferably 2 to 150 in terms of achieving the effects of the present invention. The upper limit of the number of carbon atoms is more preferably 120, even more preferably 80, particularly preferably 60, and most preferably 40. On the other hand, the lower limit of the number of carbon atoms is more preferably 3, even more preferably 4, and particularly preferably 5. The linear structural portion and / or branched structural portion of the group (a1) may contain a carbon atom and further an oxygen atom.

[0020] The group (a1) may have at least one selected from an alkoxy group, a phenoxy group, a carboxyl group, and a hydroxyl group. The group (a1) preferably has at least one selected from an alkoxy group, a phenoxy group, a carboxyl group, and a hydroxyl group, which allows for more efficient control of the polarity of the thermoplastic resin. The alkoxy group preferably has 1 to 20 carbon atoms.

[0021] The monomer (A) may have an oxyalkylene structure in its molecule, although there are no particular limitations on the number of carbon atoms in the structure. In the case where the oxyalkylene structure is present, there are no particular limitations on the number of carbon atoms in the structure, but from the viewpoint of achieving the effects of the present invention, it is preferably 2 to 4, and more preferably 2 to 3. When the monomer (A) molecule has an oxyalkylene structural portion, the number of oxyalkylene structural units is not particularly limited, but is preferably 1 to 30. The upper limit of the number of structural units is more preferably 20, even more preferably 15, and particularly preferably 10. On the other hand, the lower limit of the number of structural units is more preferably 2, and even more preferably 3. When the molecule of the monomer (A) contains an oxyalkylene structure, the oxyalkylene structure is preferably in the group (a1).

[0022] The monomer (A) may be an alkylene oxide adduct and / or a lactone adduct. If the monomer (A) is the above compound, it is preferred in terms of compatibility with the organic base material components. The number of moles of alkylene oxide added in the monomer (A) is not particularly limited, but is preferably in the same numerical range as the number of oxyalkylene structural units described above. In the present invention, the number of moles of alkylene oxide added means the average number of moles of alkylene oxide added. The number of carbon atoms in the alkylene oxide is not particularly limited, but is preferably 2 to 4, and more preferably 2 to 3.

[0023] The number of moles of lactone added in the monomer (A) is not particularly limited, but is preferably 1 to 15. The upper limit of the number of moles added is more preferably 10, even more preferably 8, particularly preferably 6, and most preferably 4. On the other hand, the lower limit of the number of moles added is more preferably 2. In the present invention, the number of moles added of lactone means the average number of moles added of lactone. The number of carbon atoms in the lactone is not particularly limited, but is preferably 4 to 15, more preferably 5 to 10, even more preferably 6 to 9, and particularly preferably 6 (caprolactone).

[0024] Examples of the monomer (A) include alkoxypolyoxyalkylene mono(meth)acrylates such as methoxypolyethylene glycol mono(meth)acrylate, methoxypolypropylene glycol mono(meth)acrylate, methoxypolybutylene glycol mono(meth)acrylate, methoxypolyethylene glycol-polypropylene glycol mono(meth)acrylate, methoxypolyethylene glycol-polybutylene glycol mono(meth)acrylate, methoxypolypropylene glycol-polybutylene glycol mono(meth)acrylate, octylpolyethylene glycol mono(meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, and stearoxypolyethylene glycol mono(meth)acrylate; phenoxy Examples of suitable monomers include phenoxypolyoxyalkylene mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate; polyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono(meth)acrylate, polyethylene glycol-polypropylene glycol mono(meth)acrylate, polyethylene glycol-polybutylene glycol mono(meth)acrylate, and polypropylene glycol-polybutylene glycol mono(meth)acrylate; mono(2-acryloyloxyethyl succinate; and polylactone mono(meth)acrylates such as ω-carboxy-polycaprolactone mono(meth)acrylate. In the present invention, the term "(meth)acrylate" refers to either acrylate or methacrylate. These monomers (A) may be used alone or in combination of two or more.

[0025] The weight proportion of the monomer (A) in the polymerizable components is not particularly limited, but is preferably 5% by weight or more. When the weight proportion is 5% by weight or more, the resulting thermoplastic resin tends to have sufficient polarity. The upper limit of the weight proportion is preferably 100% by weight, more preferably 90% by weight, even more preferably 80% by weight, particularly preferably 70% by weight, and most preferably 50% by weight. On the other hand, the lower limit of the weight proportion is more preferably 10% by weight, even more preferably 15% by weight, particularly preferably 20% by weight, and most preferably 25% by weight.

[0026] The polymerizable component may contain, as a monomer component, a monomer component other than the monomer (A) (hereinafter, sometimes simply referred to as other monomer component). Examples of other monomer components include nitrile monomers such as acrylonitrile, methacrylonitrile, fumaronitrile, and maleonitrile; halogenated vinyl monomers such as vinyl chloride; halogenated vinylidene monomers such as vinylidene chloride; vinyl ester monomers other than monomer (A) such as vinyl acetate, vinyl propionate, and vinyl butyrate; unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, and maleic acid, itaconic acid, fumaric acid, and citraconic acid. Carboxyl group-containing monomers other than monomer (A) such as unsaturated dicarboxylic acids such as maleic acid, chloromaleic acid, anhydrides of unsaturated dicarboxylic acids, and unsaturated dicarboxylic acid monoesters such as monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, Examples of the monomer include (meth)acrylic acid ester monomers other than monomer (A) such as acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate; (meth)acrylamide monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; maleimide monomers such as N-phenylmaleimide and N-cyclohexylmaleimide; 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 vinyl naphthalene salts. The carboxyl groups of the carboxyl group-containing monomer may be partially or entirely neutralized during or after polymerization. In the present invention, acrylic acid and methacrylic acid may be collectively referred to as (meth)acrylic acid, and (meth)acrylic means either acrylic or methacrylic.These other monomer components may be used alone or in combination of two or more.

[0027] The polymerizable component may further contain a nitrile monomer as a monomer component, which is preferred because it improves the solvent resistance of the heat-expandable microspheres. When the polymerizable component contains a nitrile monomer, the weight percentage of the nitrile monomer in the polymerizable component is not particularly limited, but is preferably 5 to 95% by weight. The upper limit of this weight percentage is more preferably 90% by weight, even more preferably 85% by weight, particularly preferably 80% by weight, and most preferably 75% by weight. On the other hand, the lower limit of this weight percentage is more preferably 10% by weight, even more preferably 15% by weight, particularly preferably 20% by weight, and most preferably 25% by weight.

[0028] The nitrile monomer preferably contains acrylonitrile and / or methacrylonitrile, since this improves the expansion performance. When the nitrile monomer contains acrylonitrile, the weight ratio of acrylonitrile in the nitrile monomer is not particularly limited, but is preferably 5% by weight or more. The upper limit of this weight ratio is preferably 100% by weight, more preferably 90% by weight, and even more preferably 80% by weight. On the other hand, the lower limit of this weight ratio is more preferably 10% by weight, and particularly preferably 20% by weight. When the nitrile monomer contains methacrylonitrile, the weight ratio of methacrylonitrile in the nitrile monomer is not particularly limited, but is preferably 5% by weight or more. The upper limit of this weight ratio is preferably 100% by weight, more preferably 90% by weight, and particularly preferably 80% by weight. On the other hand, the lower limit of this weight ratio is more preferably 10% by weight, and particularly preferably 20% by weight.

[0029] The polymerizable component may further contain a carboxyl group-containing monomer other than the monomer (A) as a monomer component. The inclusion of a carboxyl group-containing monomer other than the monomer (A) is preferred because it improves the stretchability of the resulting thermoplastic resin during thermal expansion. When the polymerizable component contains a carboxyl group-containing monomer, the weight percentage of the carboxyl group-containing monomer in the polymerizable component is not particularly limited, but is preferably 5 to 90% by weight. The upper limit of this weight percentage is more preferably 80% by weight, even more preferably 75% by weight, particularly preferably 70% by weight, and most preferably 65% ​​by weight. Meanwhile, the lower limit of this weight percentage is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight.

[0030] The polymerizable component may further contain a (meth)acrylic acid ester monomer other than the monomer (A) as a monomer component, which is preferable because it improves the heat resistance of the heat-expandable microspheres. When the polymerizable component contains a carboxyl group-containing monomer, the weight percentage of the carboxyl group-containing monomer in the polymerizable component is not particularly limited, but is preferably 5 to 60% by weight. The upper limit of the weight percentage of the carboxyl group-containing monomer is more preferably 50% by weight, even more preferably 40% by weight, particularly preferably 35% by weight, and most preferably 30% by weight. On the other hand, the lower limit of the weight percentage of the carboxyl group-containing monomer is more preferably 10% by weight, even more preferably 15% by weight.

[0031] The polymerizable component may further contain a vinylidene halide monomer as a monomer component. The inclusion of a vinylidene halide monomer is preferred because it improves the gas barrier properties of the thermoplastic resin forming the shell of the heat-expandable microspheres. When the polymerizable component contains a vinylidene halide monomer, the weight ratio of the vinylidene halide monomer in the polymerizable component is not particularly limited, but is preferably 5 to 55 wt %.

[0032] As described above, the polymerizable component may contain a crosslinking agent. By using a crosslinking agent for polymerization, the resulting heat-expandable microspheres can be effectively expanded by heat, since the retention of the encapsulated blowing agent (encapsulation retention) during thermal expansion is suppressed. The crosslinking agent is not particularly limited, and examples thereof include aromatic divinyl compounds such as divinylbenzene; allyl methacrylate, triacrylformal, triallyl isocyanate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polytetramethylene glycol diacrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and the like. Examples of suitable crosslinking agents include polyfunctional (meth)acrylate compounds such as ol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, and tricyclodecane dimethanol di(meth)acrylate. These crosslinking agents may be used alone or in combination of two or more.

[0033] The crosslinking agent may be omitted, but its amount is not particularly limited and is preferably 0 to 5.0 parts by weight, more preferably 0.01 to 3.0 parts by weight, even more preferably 0.02 to 2.0 parts by weight, and particularly preferably 0.05 to 1.5 parts by weight, per 100 parts by weight of the monomer component. If the content of the crosslinking agent exceeds 5.0 parts by weight, the expansion performance of the heat-expandable microspheres may decrease.

[0034] The blowing agent is a component that vaporizes when heated. When the blowing agent is encapsulated in the outer shell of the heat-expandable microspheres, the heat-expandable microspheres as a whole exhibit heat-expandability (the property of expanding the entire microsphere when heated).

[0035] The blowing agent is not particularly limited, and examples thereof include linear hydrocarbons such as 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, isotridecane, 4-methyldodecane, isotetradecane, isopentadecane, isohexadecane, 2,2,4,4,6,8,8-heptamethylnonane, isoheptadecane, and isooctadecane; Examples of suitable blowing agents include branched hydrocarbons such as isonadecane and 2,6,10,14-tetramethylpentadecane; hydrocarbons such as cyclododecane, cyclotridecane, hexylcyclohexane, heptylcyclohexane, n-octylcyclohexane, cyclopentadecane, nonylcyclohexane, decylcyclohexane, pentadecylcyclohexane, hexadecylcyclohexane, heptadecylcyclohexane, and octadecylcyclohexane; petroleum ether; halides thereof; fluorine-containing compounds such as hydrofluoroethers; tetraalkylsilanes; and compounds that undergo thermal decomposition upon heating to produce gas. The blowing agent may be linear, branched, or alicyclic, with aliphatic blowing agents being preferred. These blowing agents may be used alone or in combination.

[0036] The average particle size of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 0.5 to 200 μm. An average particle size of 0.5 μm or more tends to improve the expansion performance of the heat-expandable microspheres, while an average particle size of 200 μm or less tends to improve the expansion stability of the heat-expandable microspheres. The upper limit of the average particle size is more preferably 150 μm, even more preferably 100 μm, particularly preferably 75 μm, and most preferably 50 μm. The lower limit of the average particle size is more preferably 1 μm, even more preferably 1.5 μm, particularly preferably 2 μm, and most preferably 5 μm. The average particle size of the heat-expandable microspheres is determined by the method described in the Examples of the present invention.

[0037] The coefficient of variation (CV) of the particle size distribution of heat-expandable microspheres is not particularly limited, but is preferably not more than 50%, more preferably not more than 45%, and particularly preferably not more than 40%. The coefficient of variation (CV) is calculated using the following formulas (1) and (2).

[0038]

number

[0039] The encapsulation rate of the blowing agent is defined as the percentage of the weight of the blowing agent encapsulated in the heat-expandable microspheres relative to the weight of the heat-expandable microspheres. There are no particular limitations on the encapsulation rate of the blowing agent, but it is preferably 1 to 50% by weight, more preferably 2 to 45% by weight, even more preferably 5 to 40% by weight, and particularly preferably 10 to 35% by weight. The encapsulation rate of the blowing agent in the heat-expandable microspheres is determined by the method described in the Examples of the present invention.

[0040] The expansion start temperature of thermally expandable microspheres (T s ) is not particularly limited, but is preferably 80°C or higher, more preferably 90°C or higher, even more preferably 100°C or higher, particularly preferably 110°C or higher, and most preferably 120°C or higher. If the expansion initiation temperature of heat-expandable microspheres is lower than 80°C, the heat-expandable microspheres may not have sufficient heat resistance. The upper limit of the expansion initiation temperature of heat-expandable microspheres is preferably 300°C. Maximum expansion temperature of thermally expandable microspheres (T max ) is not particularly limited, but is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, particularly preferably 130°C or higher, and most preferably 140°C or higher. The upper limit of the maximum expansion temperature is preferably 350°C. If the maximum expansion temperature of heat-expandable microspheres is lower than 100°C, sufficient heat resistance may not be obtained, and if it exceeds 350°C, a sufficient expansion ratio may not be obtained. The expansion onset temperature (T s ) and maximum expansion temperature (T max ) is obtained by the method described in the examples of the present invention.

[0041] The maximum volume expansion ratio of the heat-expandable microspheres is not particularly limited, but is preferably at least 3, more preferably at least 5, even more preferably at least 10, particularly preferably at least 15, and even more preferably at least 20. The upper limit of the maximum expansion ratio is preferably 200.

[0042] The heat-expandable microspheres of the present invention have excellent dispersibility in polar liquids and are therefore suitable for use in pastes such as vinyl chloride paste, and liquid compositions such as EVA emulsions, acrylic emulsions, and solvent-based binders. They can also be used in molding processes such as injection molding, extrusion molding, press molding, kneading molding, calendar molding, blow molding, compression molding, vacuum molding, and thermoforming.

[0043] [Method for producing heat-expandable microspheres] The method for producing heat-expandable microspheres of the present invention comprises the steps of dispersing an oily mixture containing a polymerizable component, a blowing agent, and a polymerization initiator in an aqueous dispersion medium and polymerizing the polymerizable component (hereinafter, sometimes simply referred to as the polymerization step).

[0044] 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.

[0045] 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).

[0046] The amount of polymerization initiator is not particularly limited, but is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, and most preferably 0.2 to 5 parts by weight, per 100 parts by weight of the polymerizable component. If the weight ratio is less than 0.05% by weight, unpolymerized polymerizable component may remain, making it difficult to stably produce the desired heat-expandable microspheres. If the weight ratio exceeds 10% by weight, heat resistance may decrease.

[0047] In the polymerization process, the aqueous dispersion medium is a medium for dispersing an oily mixture essentially containing a polymerizable component and a blowing agent, and is primarily composed of water such as ion-exchanged water. The aqueous dispersion medium may further contain an alcohol such as methanol, ethanol, or propanol, or a hydrophilic organic solvent such as acetone. In the present invention, "hydrophilic" means a state in which the aqueous dispersion medium can be freely mixed with water. The amount of the aqueous dispersion medium used is not particularly limited, but it is preferable to use 100 to 1,000 parts by weight of the aqueous dispersion medium per 100 parts by weight of the polymerizable component.

[0048] 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, sodium carbonate, etc. These electrolytes may be used alone or in combination of two or more. The content of the electrolyte is not particularly limited, but it is preferable that the content be 0.1 to 50 parts by weight per 100 parts by weight of the aqueous dispersion medium.

[0049] The aqueous dispersion medium may contain at least one water-soluble compound selected from 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, potassium dichromate, alkali metal nitrite, metal (III) halide, boric acid, water-soluble ascorbic acids, water-soluble polyphenols, water-soluble B vitamins, and water-soluble phosphonic acids (salts). Water-soluble in the present invention means that 1 g or more of the compound dissolves in 100 g of water.

[0050] 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 particularly preferably 0.001 to 0.05 part by weight, per 100 parts by weight of the polymerizable component. If the amount of the water-soluble compound is too small, the effects of the water-soluble compound may not be fully obtained. On the other hand, if the amount of the water-soluble compound is too large, the polymerization rate may decrease or the amount of the polymerizable component (raw material) remaining may increase.

[0051] The aqueous dispersion medium may contain a dispersion stabilizer or a dispersion stabilization aid in addition to the electrolyte and the water-soluble compound. Examples of the dispersion stabilizer include tricalcium phosphate, magnesium pyrophosphate obtained by a metathesis method, calcium pyrophosphate, colloidal silica, alumina sol, magnesium hydroxide, etc. These dispersion stabilizers may be used alone or in combination of two or more. The amount of the dispersion stabilizer is preferably 0.05 to 30 parts by weight, more preferably 0.2 to 20 parts by weight, based on 100 parts by weight of the polymerizable component.

[0052] The dispersion stabilization aid is not particularly limited, and examples thereof include surfactants such as polymer-type dispersion stabilization aids, cationic surfactants, anionic surfactants, zwitterionic surfactants, nonionic surfactants, etc. These dispersion stabilization aids may be used alone or in combination of two or more.

[0053] The aqueous dispersion medium is prepared, for example, by blending water (ion-exchanged water) with a water-soluble compound and, if necessary, a dispersion stabilizer and / or a dispersion stabilization assistant, etc. The pH of the aqueous dispersion medium during polymerization is appropriately determined depending on the types of the water-soluble compound, dispersion stabilizer, and dispersion stabilization assistant.

[0054] In the production method of the heat-expandable microspheres of the present invention, the polymerization may be carried out in the presence of sodium hydroxide and zinc chloride. In the method for producing the heat-expandable microspheres 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. In the polymerization step, a chain transfer agent, an organic pigment, an inorganic pigment or inorganic particles whose surface has been treated to be hydrophobic, or the like may also be used.

[0055] In the polymerization step, the oily mixture is suspended and dispersed in an aqueous dispersion medium so as to prepare spherical oil droplets having a predetermined particle size. Examples of methods for suspending and dispersing the oily mixture include a method of stirring with a homomixer (e.g., manufactured by Primix Corporation) or the like, a method using a static dispersing device such as a static mixer (e.g., manufactured by Noritake Co., Ltd.), a membrane emulsification method, an ultrasonic dispersion method, and other common dispersion methods. The aqueous suspension containing the oily mixture dispersed in the aqueous dispersion medium as oil globules is then heated to initiate suspension polymerization. During the polymerization reaction, the aqueous suspension is preferably stirred, and the stirring may be gentle enough to prevent the floating of the monomer components and the settling of the heat-expandable microspheres after polymerization.

[0056] 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 time for maintaining the reaction temperature is preferably about 0.1 to 20 hours. The initial polymerization pressure is not particularly limited, but is 0 to 5.0 MPa, and more preferably 0.1 to 3.0 MPa, in gauge pressure.

[0057] The obtained slurry is filtered using a centrifuge, pressure press, vacuum dehydrator, etc. to obtain a wet powder with a moisture content of 10 to 50% by weight, preferably 15 to 45% by weight, and more preferably 20 to 40% by weight. The obtained wet powder is then dried using a tray dryer, indirect heating dryer, fluidized bed dryer, vacuum dryer, vibration dryer, flash dryer, etc. to obtain a dry powder. The moisture content of the obtained dry powder is preferably 8% by weight or less, more preferably 5% by weight or less. To reduce the content of ionic substances, the obtained wet or dry powder may be washed with water and / or redispersed, then re-filtered and dried. Alternatively, the slurry may be dried using a spray dryer, fluidized bed dryer, or the like to obtain a dry powder. The wet or dry powder can be selected appropriately depending on the intended use.

[0058] [Hollow particles] The hollow particles of the present invention are particles obtained by thermally expanding the heat-expandable microspheres described above, and when they are incorporated into compositions or molded articles, they exhibit excellent material properties. The hollow particles of the present invention are particles obtained by thermally expanding heat-expandable microspheres, which have an outer shell containing a thermoplastic resin obtained by polymerizing a specific polymerizable component and a blowing agent encapsulated in the outer shell, and therefore have excellent dispersibility when mixed with a base component.

[0059] The hollow particles of the present invention can be obtained by thermally expanding the heat-expandable microspheres described above, preferably at a temperature of 80 to 450°C. The thermal expansion method is not particularly limited and may be either a dry thermal expansion method or a wet thermal expansion method. Examples of dry thermal expansion methods include the method described in JP-A-2006-213930, particularly the internal injection method. Other dry thermal expansion methods include the method described in JP-A-2006-96963. Examples of wet thermal expansion methods include the method described in JP-A-62-201231.

[0060] The true specific gravity of the hollow particles of the present invention is not particularly limited, but is preferably 0.001 to 0.60. When the true specific gravity is 0.001 or more, the outer shell has a sufficient thickness, which tends to suppress settling. On the other hand, when the true specific gravity is 0.60 or less, the effect of reducing the specific gravity is sufficiently obtained, and when a composition is prepared using the hollow particles, the physical properties of the composition and molded article tend to be sufficiently maintained. The upper limit of the true specific gravity is more preferably 0.50, even more preferably 0.40, particularly preferably 0.30, and most preferably 0.20. On the other hand, the lower limit of the true specific gravity is more preferably 0.003, even more preferably 0.005, and particularly preferably 0.01. The true specific gravity of the hollow particles is measured by the method described in the examples.

[0061] [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 outer shell of the hollow particle. For example, as shown in FIG. 2, the hollow particles are formed of microparticles (4 and 5) attached to the outer surface of the outer shell (2) of the hollow particle (1). The term "adhesion" as used herein means that the fine particles 4 and 5 may simply be adsorbed onto the outer surface of the shell 2 of the hollow particle (as in the state of fine particle 4 in Figure 2), or may mean that the thermoplastic resin constituting the shell near the outer surface is melted by heating, causing the fine particle filler to sink into the outer surface of the shell of the hollow particle and become fixed thereto (as in the state of fine particle 5 in Figure 2). The particle shape of the fine particles may be either irregular or spherical. By adhering the fine particles to the hollow particles, scattering of the hollow particles can be suppressed, improving handling, and also improving dispersibility in base components such as binders and resins.

[0062] 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 spherical, needle-like, or plate-like. The inorganic substance constituting the fine particles is not particularly limited, but examples thereof include wollastonite, sericite, kaolin, mica, clay, talc, bentonite, alumina silicate, pyrophyllite, montmorillonite, calcium silicate, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, glass flakes, boron nitride, silicon carbide, silica, alumina, mica, titanium dioxide, zinc oxide, magnesium oxide, zinc oxide, hydrosaltite, carbon black, molybdenum disulfide, tungsten disulfide, ceramic beads, glass beads, quartz beads, and glass microballoons.

[0063] The organic substance constituting the microparticles is not particularly limited, but examples thereof include sodium carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, ethylcellulose, nitrocellulose, hydroxypropylcellulose, sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, carboxyvinyl polymer, polyvinyl methyl ether, magnesium stearate, calcium stearate, zinc stearate, polyethylene wax, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, hydrogenated castor oil, (meth)acrylic resin, polyamide resin, silicone resin, urethane resin, polyethylene resin, polypropylene resin, and fluorine-based resin. 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.

[0064] The average particle size of the fine particles is not particularly limited, but is preferably 0.001 to 30 μm, more preferably 0.005 to 25 μm, and particularly preferably 0.01 to 20 μm. The average particle size is the cumulative 50% particle size on a volume basis measured by laser diffraction. The ratio of the volume average particle diameter of the fine particles to the volume average particle diameter of the hollow particles (volume average particle diameter of fine particles / volume average particle diameter of hollow particles) is not particularly limited, but from the viewpoint of the adhesion of the fine particles to the surfaces of the hollow particles, it is preferably 1 or less, more preferably 0.1 or less, and even more preferably 0.05 or less.

[0065] The weight percentage of the fine particles in the total fine particle-coated hollow particles is not particularly limited, but is preferably 95% by weight or less, more preferably 90% by weight or less, particularly preferably 85% by weight or less, and most preferably 80% by weight or less. If the weight percentage exceeds 95% by weight, the amount of fine particle-coated hollow particles added when preparing a composition using the fine particle-coated hollow particles becomes large, which may be uneconomical. The lower limit of the weight percentage of the fine particles is preferably 10% by weight, more preferably 20% by weight, particularly preferably 30% by weight, and most preferably 40% by weight.

[0066] The true specific gravity of the fine particle-coated hollow particles is not particularly limited, but is preferably 0.01 to 0.60. When the true specific gravity is 0.01 or more, the outer shell has a sufficient thickness, which tends to suppress settling. On the other hand, when the true specific gravity is 0.60 or less, the effect of reducing the specific gravity is sufficiently obtained, and when a composition is prepared using the fine particle-coated hollow particles, the physical properties of the composition and molded article tend to be sufficiently maintained. The upper limit of the true specific gravity is more preferably 0.40, particularly preferably 0.30, and most preferably 0.20. On the other hand, the lower limit of the true specific gravity is 0.07, and particularly preferably 0.10.

[0067] The microparticle-coated hollow particles of the present invention can be obtained, for example, by heating and expanding microparticle-coated heat-expandable microspheres. A preferred method for producing microparticle-coated hollow particles includes a step of mixing heat-expandable microspheres with microparticles (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 microparticles to adhere to the outer surfaces of the resulting hollow particles (adhesion step).

[0068] The mixing step is a step of mixing the heat-expandable microspheres and the fine particles. The weight ratio of the fine particles to the total weight of the heat-expandable microspheres and fine particles in the mixing step is not particularly limited, but is preferably 95% by weight or less, more preferably 90% by weight or less, particularly preferably 85% by weight or less, and most preferably 80% by weight or less. When this weight ratio is 95% by weight or less, the obtained fine particle-coated hollow particles tend to be lightweight and have a sufficient effect of reducing the specific gravity. The lower limit of this weight ratio is preferably 5% by weight, more preferably 10% by weight, particularly preferably 20% by weight, and most preferably 30% by weight.

[0069] The device used to mix the heat-expandable microspheres and fine particles in the mixing step is not particularly limited, and can be a device equipped with a very simple mechanism such as a container and a stirring blade. Alternatively, a general powder mixer capable of shaking or stirring may also be used. Examples of powder mixers include powder mixers capable of rocking or stirring, such as ribbon mixers and vertical screw mixers. In recent years, more efficient and multifunctional powder mixers incorporating a stirring device have been introduced, such as the Super Mixer (manufactured by Kawata Co., Ltd.), the High Speed ​​Mixer (manufactured by Fukae Co., Ltd.), the New Gram Machine (manufactured by Seishin Enterprise Co., Ltd.), and the SV Mixer (manufactured by Kobelco Eco Solutions Co., Ltd.), and these may also be used.

[0070] The adhering step is a step in which the mixture containing heat-expandable microspheres and fine particles obtained in the mixing step is heated to a temperature above the softening point of the thermoplastic resin constituting the shell of the heat-expandable microspheres. In the adhering step, the heat-expandable microspheres are expanded and the fine particles are adhered to the outer surface of the shell of the resulting hollow particles. Heating can be carried out using a general contact heat transfer or direct heating type mixing dryer. There are no particular limitations on the functions of the mixing dryer, but it is preferable that it has the ability to adjust the temperature, disperse and mix the raw materials, and, in some cases, a pressure reducing device or a cooling device to accelerate drying. There are no particular limitations on the device used for heating, but examples include a Lödige Mixer (manufactured by Matsubo Corporation) and a Solid Air (Hosokawa Micron Corporation). The heating temperature condition depends on the type of heat-expandable microspheres, but is preferably set to the optimum expansion temperature, preferably 70 to 250°C, more preferably 80 to 230°C, and even more preferably 90 to 220°C.

[0071] [Composition and Molded Article] The composition of the present invention contains at least one selected from the group consisting of the heat-expandable microspheres, hollow particles, and fine particle-coated hollow particles described above, 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; thermoplastic resins such as 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), polybutylene terephthalate (PBT), polyacetal (POM), and polyphenylene sulfide (PPS); thermoplastic elastomers such as olefin-based elastomers and styrene-based elastomers; polyvinylidene fluoride, polytetrafluoroethylene, vinyl fluoride, and the like. Examples of suitable substrates include fluorine-containing resins such as vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, hexafluoropropylene-tetrafluoroethylene copolymer, and ethylene-tetrafluoroethylene; bioplastics such as polylactic acid (PLA), cellulose acetate, PBS, PHA, and starch resin; sealing materials such as silicones, modified silicones, polysulfides, modified polysulfides, urethanes, acrylics, polyisobutylenes, and butyl rubbers; liquid components such as emulsions and plastisols of urethanes, ethylene-vinyl acetate copolymers, vinyl chlorides, and acrylics; inorganic materials such as cement, mortar, and cordierite; and organic fibers such as cellulose, kenaf, bran, aramid fibers, phenolic fibers, polyester fibers, acrylic fibers, polyolefin fibers such as polyethylene and polypropylene, polyvinyl alcohol fibers, and rayon. These substrate components may be diluted, dissolved, or dispersed in water or an organic solvent. These base components may be used alone or in combination of two or more.

[0072] The composition of the present invention can be prepared by mixing at least one selected from heat-expandable microspheres, hollow particles, and microparticle-coated hollow particles with the above-mentioned base component. Alternatively, the composition obtained by mixing at least one selected from heat-expandable microspheres, hollow particles, and microparticle-coated hollow particles with a base component can be further mixed with another base component to prepare the composition of the present invention. In addition to at least one selected from heat-expandable microspheres, hollow particles, and microparticle-coated hollow particles, and the base component, the composition of the present invention may contain other components, such as plasticizers, fillers, colorants, high-boiling organic solvents, and adhesives, as appropriate depending on the intended use.

[0073] In the composition of the present invention, the total content of the heat-expandable microspheres, hollow particles, and microparticle-coated hollow particles is not particularly limited, but is preferably 0.05 to 750 parts by weight per 100 parts by weight of the base component. A total content of 0.01 part by weight or more tends to result in a sufficiently lightweight molded product. On the other hand, a total content of 750 parts by weight or less tends to result in improved uniform dispersion of at least one selected from the group consisting of the heat-expandable microspheres, hollow particles, and microparticle-coated hollow particles. The upper limit of this total content is more preferably 700 parts by weight, even more preferably 650 parts by weight, particularly preferably 600 parts by weight, and most preferably 500 parts by weight. On the other hand, the lower limit of this total content is more preferably 0.1 parts by weight, even more preferably 0.2 parts by weight, particularly preferably 0.5 parts by weight, and most preferably 1 part by weight.

[0074] The method for preparing the composition of the present invention is not particularly limited, and any conventionally known method may be used, such as a method of mechanically mixing the components uniformly using a mixer such as a homomixer, static mixer, Henschel mixer, tumbler mixer, planetary mixer, kneader, roll, mixing roll, mixer, single-screw kneader, twin-screw kneader, or multi-screw kneader. Examples of the composition of the present invention include a rubber composition, a molding composition, a coating composition, a clay composition, an adhesive composition, and a powder composition.

[0075] 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 molded articles and coating films. 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, design, impact absorption, and strength, and also has the effect of having an excellent appearance. [Example]

[0076] Examples of the heat-expandable microspheres of the present invention are described below in detail. However, the present invention is not limited to these examples. In the following examples and comparative examples, "%" means "% by weight" and "parts" means "parts by weight" unless otherwise specified. The heat-expandable microspheres described in the following Examples and Comparative Examples were measured for physical properties and evaluated for performance in the following manner. Hereinafter, heat-expandable microspheres will sometimes be referred to as "microspheres" for simplicity.

[0077] [Measurement of mean particle size (D50) and particle size distribution of heat-expandable microspheres] The measuring device used was a Microtrac particle size distribution analyzer (model 9320-HRA) manufactured by Nikkiso Co., Ltd., and the D50 value determined by volume-based measurement was taken as the average particle size.

[0078] [Expansion start temperature of thermally expandable microspheres (T s ), and maximum expansion temperature (T max ) Measurement A DMA (DMA Q800, manufactured by TA Instruments) was used as the measuring device. 0.5 mg of microspheres was placed in an aluminum cup with a diameter of 5.6 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 300°C at a temperature increase 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 (T s ) and the maximum displacement (H max ) is the maximum expansion temperature (T max ) was decided.

[0079] [Water content of thermally expandable microspheres (C w1 ) Measurement The measurement was carried out using a Karl Fischer moisture meter (Model MKA-510N, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). The moisture content (wt%) of the heat-expandable microspheres was measured using the formula C w1 It was decided.

[0080] [Measurement of the encapsulation ratio (C1) of the blowing agent in heat-expandable microspheres] 1.0 g of heat-expandable microspheres was placed in a stainless steel evaporating dish with a diameter of 80 mm and a depth of 15 mm, and its weight (W1(g)) was measured. 30 ml of acetonitrile was added to disperse the microspheres uniformly, and the microspheres were left to stand at room temperature for 24 hours. After drying under reduced pressure at 130°C for 2 hours, their weight (W2(g)) was measured. The encapsulation rate (C1) of the blowing agent in the heat-expandable microspheres is calculated by the following formula: C1(weight%)=100×{100×(W1-W2) / 1.0-C w1 } / (100-C w1 ) (In the formula, the water content of thermally expandable microspheres C w1 was measured by the above method.)

[0081] [Measurement of true specific gravity] The true specific gravity of the heat-expandable microspheres, hollow particles, or fine particle-coated hollow particles (hereinafter sometimes simply referred to as particle samples) was measured by the following method. The true specific gravity 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%. Specifically, a 100 mL volumetric flask was emptied, dried, and then weighed. The weighed volumetric flask was then filled with isopropyl alcohol exactly up to the meniscus, and the weight of the volumetric flask filled with 100 mL of isopropyl alcohol (WB2) was then weighed. The 100 mL volumetric flask was also emptied, dried, and then weighed. The weight of the volumetric flask filled with the particle sample (WS2) was then weighed. The volumetric flask filled with the particle sample was then filled with isopropyl alcohol exactly up to the meniscus, taking care not to trap air bubbles, and the weight (WS3) was then weighed. The obtained WB1, WB2, WS1, WS2, and WS3 were then introduced into the following equation to calculate the true specific gravity (d) of the particle sample. d={(WS2-WS1)×(WB2-WB1) / 100} / {(WB2-WB1)-(WS3-WS2)}

[0082] [Measurement of true specific gravity of expanded heat-expandable microspheres] A flat-bottomed box measuring 12 cm in length, 13 cm in width, and 9 cm in height was made from aluminum foil, and 1.0 g of heat-expandable microspheres was uniformly placed inside and covered with aluminum foil. The covered box was placed in a gear oven and heated for 1 minute at the maximum expansion temperature of the heat-expandable microspheres described above to obtain an expanded product. The true specific gravity of the resulting expanded hollow particles was measured using the method described above.

[0083] <Evaluation of dispersibility in polar liquids> 8.0 g of an aqueous emulsion of ethylene-vinyl acetate copolymer resin (containing ethylene-vinyl acetate copolymer resin composed of 30% by weight of ethylene and 70% by weight of vinyl acetate, at a concentration of 55% by weight based on the total weight of the aqueous emulsion) was added to 0.5 parts of dried heat-expandable microspheres, mixed, and then allowed to stand for 24 hours. After standing, this liquid composition was applied to plain paper using a coater and air-dried at room temperature to form a 100 μm thick EVA coating film containing unexpanded microspheres on the plain paper. The thickness of the EVA coating film was measured at any five points (n1, n2, n3, n4, n5), and the average value, n ave The standard deviation σ was calculated from the following formula: The dispersibility in polar liquids was evaluated according to the following indices. σ=[{(n1-n ave ) 2 +(n2-n ave ) 2 +(n3-n ave ) 2 +(n4-n ave ) 2 +(n5-n ave ) 2 } / 5 (1 / 2) ◎: Standard deviation σ is 0μm or more and 2μm or less 〇: Standard deviation σ is more than 2μm and less than 4μm ×: Standard deviation σ exceeds 4 μm

[0084] Example 1 An aqueous dispersion medium was prepared by dissolving 130 parts of sodium chloride in 500 parts of ion-exchanged water, adding 1.0 part of polyvinylpyrrolidone, 0.05 parts of carboxymethylated polyimine sodium salt, and 65 parts of colloidal silica (effective concentration 20%), and adjusting the pH to 3.0. Separately, 20 parts of methoxypolyethylene glycol monomethacrylate (average number of ethylene glycol constituent units: 4), 25 parts of acrylonitrile, 5 parts of methacrylonitrile, 40 parts of methacrylic acid, 5 parts of methacrylamide, 3 parts of styrene, 2 parts of ethylene glycol dimethacrylate, 2 parts of di-2-ethylhexyl peroxydicarbonate, and 40 parts of 2-methylpentane (isobutane) were mixed to prepare an oily mixture. The aqueous dispersion medium and the oily mixture were mixed, and the resulting mixture was dispersed in a homomixer (TK homomixer, manufactured by Primix Corporation) at a rotation speed of 10,000 rpm for 1 minute to prepare an aqueous suspension. The resulting aqueous suspension was transferred to a 1.5-liter pressure reactor and purged with nitrogen. The initial reaction pressure was adjusted to 0.35 MPa, and the polymerization reaction was carried out at a polymerization temperature of 60°C for 20 hours while stirring at 80 rpm. After polymerization, the product was filtered and dried to obtain heat-expandable microspheres. The physical properties of the resulting heat-expandable microspheres were measured and evaluated. The results are shown in Table 1.

[0085] (Examples 2 to 13, Comparative Examples 1 to 4) In Examples 2 to 13, heat-expandable microspheres were obtained in the same manner as in Example 1, except for the changes shown in Table 1. On the other hand, in Comparative Examples 1 to 4, heat-expandable microspheres were obtained in the same manner as in Example 1, except that the monomer (A) was not used and the conditions were changed as shown in Table 2. The physical properties of the resulting heat-expandable microspheres were measured and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0086] [Table 1]

[0087] [Table 2]

[0088] Heat-expandable microspheres made from monomer (A), which is a compound having one polymerizable carbon-carbon double bond and five or more oxygen atoms in the molecule, have excellent dispersibility in polar liquids and good expansion properties. In contrast, heat-expandable microspheres not containing the monomer (A) have poor dispersibility in polar liquids. [Industrial Applicability]

[0089] The heat-expandable microspheres of the present invention can be used as lightweight materials for putty, paint, ink, sealant, mortar, paper clay, ceramics, etc., and can also be used together with base components to produce molded articles with excellent sound insulation, heat insulation, heat shielding, sound absorption, etc. by molding using injection molding, extrusion molding, press molding, etc. [Explanation of symbols]

[0090] 1 Hollow particles with fine particles attached 2 Outer shell 3 Hollow part 4 Microparticles (adsorbed state) 5. Microparticles (embedded and fixed) 6. Shell 7. Foaming agent (core)< / x>

Claims

1. Heat-expandable microspheres comprising a shell containing a thermoplastic resin and a blowing agent encapsulated in the shell and vaporized by heating, the thermoplastic resin is a polymer of a polymerizable component containing a monomer (A), the monomer (A) is a compound having one polymerizable carbon-carbon double bond and 6 to 40 oxygen atoms in the molecule, the weight ratio of the monomer (A) in the polymerizable component is 5% by weight or more; Thermally expandable microspheres.

2. 2. Heat-expandable microspheres according to claim 1, wherein the weight ratio of the monomer (A) to the polymerizable component is 5 to 80% by weight.

3. 3. The heat-expandable microspheres according to claim 1, wherein the monomer (A) has an ester bond in the molecule, and an oxygen atom other than the carbonyl moiety of the ester bond is bonded to the following group (a1): Group (a1): a group having a linear structural portion and / or a branched structural portion and having two or more carbon atoms

4. The heat-expandable microspheres according to any one of claims 1 to 3, wherein the polymerizable component further comprises a nitrile monomer.

5. 5. Heat-expandable microspheres according to claim 1, wherein the polymerizable component further comprises a carboxyl group-containing monomer other than the monomer (A).

6. The heat-expandable microspheres according to claim 1, wherein the monomer (A) is at least one selected from the group consisting of alkoxypolyoxyalkylene mono(meth)acrylate, phenoxypolyoxyalkylene mono(meth)acrylate, polyalkylene glycol mono(meth)acrylate, mono(2-acryloyloxyethyl)succinate, and polylactone mono(meth)acrylate.

7. Hollow particles which are expanded bodies of the heat-expandable microspheres according to any one of claims 1 to 6.

8. A microparticle-coated hollow particle comprising the hollow particle according to claim 7 and microparticles adhered 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 any one of claims 1 to 6, 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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