Thermally-expandable microcapsule

Abstract

The present invention provides: thermally-expandable microcapsules that can achieve both excellent foamability and blackness; and a foamable master batch, a foam-molded body, and hollow particles, in all of which the thermally expandable microcapsules are used. The present invention pertains to thermally-expandable microcapsules each comprising a shell in which a volatile expansive agent is encapsulated as a core agent. The shell contains a black coloring material and a polymer compound. In a cross-section of the shell, when the thickness direction from the outer surface to the inner surface is defined as ranging from 0% to 100%, a region within 15% from the outer surface includes at least 50% of particles of the black coloring material.

Description

Thermally Expandable Microcapsules

[0001] The present invention relates to a thermally expandable microcapsule that can achieve both excellent expandability and blackness, and to an expandable masterbatch, foamed molded article, and hollow particles that use the thermally expandable microcapsule.

[0002] Thermally expandable microcapsules are widely used as design-imparting agents and weight-reducing agents, and are also used in foaming inks, wallpapers, and other lightweight coating materials. Widely known thermally expandable microcapsules contain a thermoplastic shell polymer encapsulating a volatile expanding agent that becomes gaseous at temperatures below the softening point of the shell polymer.

[0003] As examples of such thermally expandable microcapsules, Patent Document 1 discloses a thermally expandable microcapsule containing carbon black as a black material inside the shell, and Patent Document 2 discloses a thermally expandable microcapsule containing carbon black as a black material and polyvinyl butyral as a dispersant inside the shell.

[0004] International Publication No. 2021 / 221160 International Publication No. 2022 / 230994

[0005] However, the thermally expandable microcapsules described in Patent Documents 1 and 2 have a problem in that while the blackness is improved, the foaming performance is reduced. In particular, when the shell becomes thinner after foaming of the thermally expandable microcapsules, the black material present inside the shell becomes a starting point for core loss, resulting in insufficient expansion.

[0006] An object of the present invention is to provide a thermally expandable microcapsule that can achieve both excellent expandability and blackness, and an expandable masterbatch, foamed molded article, and hollow particles that use the thermally expandable microcapsule.

[0007] Disclosure 1 relates to a thermally expandable microcapsule having a shell encapsulating a volatile expansion agent as a core agent, the shell containing a black material and a polymer compound, and in a cross section of the shell, when the thickness from the outer surface to the inner surface is 0 to 100%, 50% or more of the black material by number is present within a region of 15% or less from the outer surface. Disclosure 2 relates to the thermally expandable microcapsule according to Disclosure 1, in which the black material is at least one selected from the group consisting of carbon-based black pigments, oxide-based black pigments, and nitride-based black pigments. Disclosure 3 relates to the thermally expandable microcapsule according to Disclosure 1 or 2, in which the content of the black material is 0.1% by weight or more and 20% by weight or less, based on the entire thermally expandable microcapsule. Disclosure 4 relates to the thermally expandable microcapsule according to any one of Disclosures 1 to 3, in which the black material has an average primary particle diameter of 10 nm or more and 80 nm or less. Disclosure 5 relates to the thermally expandable microcapsules according to Disclosure 2, wherein the carbon-based black pigment is carbon black. Disclosure 6 relates to the thermally expandable microcapsules according to any one of Disclosures 1 to 5, wherein 70% or more by number of the black material is present within 15% of the region from the outer surface. Disclosure 7 relates to the thermally expandable microcapsules according to any one of Disclosures 1 to 6, wherein 30% or more by number of the black material is present within 10% of the region from the outer surface. Disclosure 8 relates to a foamable masterbatch containing the thermally expandable microcapsules according to any one of Disclosures 1 to 7 and a thermoplastic resin. Disclosure 9 relates to a foamed molded article produced using the thermally expandable microcapsules according to any one of Disclosures 1 to 7 or the foamable masterbatch according to Disclosure 8. Disclosure 10 relates to hollow particles produced by thermally expanding the thermally expandable microcapsules according to any one of Disclosures 1 to 7, wherein a black material is attached to or partly embedded in the outer surface of a shell containing a polymer compound. The present invention will be described in detail below.

[0008] The shell constituting the thermally expandable microcapsule according to one embodiment of the present invention contains a black material and a polymer compound. In a cross section of the shell, assuming a thickness of 0 to 100% from the outer surface to the inner surface, 50% or more of the black material is present within 15% of the thickness from the outer surface. Having 50% or more of the black material present within 15% of the thickness from the outer surface enables excellent blackness and foamability to be achieved. In particular, when the shell thins after foaming, the black material present inside the shell is prevented from becoming a source of core loss, enabling sufficient expansion. The black material exhibits its black color by absorbing all light rays, including those in the visible light range of sunlight. While typical black pigments exhibit their black color by absorbing light in the visible light range (approximately 380 to 780 nm), they also absorb light in the near-infrared range, including the wavelength range of 800 to 1,400 nm, which contributes significantly to heat generation. Furthermore, when determining whether 50% or more by number of the black material is "present within 15% of the area from the outer surface," the "percentage (%) from the outer surface where 50% or more by number of the black material is present" is measured, and if the measured value includes decimal points, all decimal points are rounded up to make the determination (the same applies to the preferred range). For example, if the measured value is 15.5%, the decimal points are rounded up to "16%" and the determination is made. Furthermore, the percentages (%) from the outer surface where "70% or more by number of the black material," "30% or more by number of the black material," and "80% or more by number of the black material," which will be described later, are present are handled in the same way as "50% or more by number of the black material."

[0009] In the present invention, it is preferable that 50% or more by number of the black material is present in a region within 13% from the outer surface, and more preferably within 11%. The lower limit of the region from the outer surface within which 50% or more by number of the black material is present is not particularly limited, but is preferably 1%.

[0010] In the present invention, it is preferable that 70% or more of the black material is present within a region of 15% from the outer surface, and more preferably within a region of 12%. The lower limit of the region from the outer surface within which 70% or more of the black material is present is not particularly limited, but is preferably 1%. It is also preferable that 30% or more of the black material is present within a region of 10% from the outer surface, and more preferably within a region of 5%. It is also preferable that 30% or more of the black material is present within a region from the outer surface within which 30% or more of the black material is present, but is preferably 1%. Furthermore, in the present invention, it is preferable that 80% or more of the black material is present within a region of 18% from the outer surface.

[0011] The area (% value) from the outer surface where 50% or more of the black material is present can be measured as follows (the same applies to the area from the outer surface where 70% or more, or 30% or more of the black material is present). First, the thermally expandable microcapsules are added to an embedding resin (e.g., Oken Epok 812, manufactured by Oken Shoji Co., Ltd.) so that the content is 3% by weight, and dispersed to prepare a thermally expandable microcapsule-embedded resin. A thin film is prepared from the obtained embedding resin using a microtome (EM UC7, manufactured by LEICA), and when observed with a transmission electron microscope (ARM-200F, manufactured by JEOL Ltd.), a shell cross section of any part of the thermally expandable microcapsule with the largest diameter is photographed. Next, the photographed cross-sectional photograph is subjected to image analysis to obtain an image (thermally expandable microcapsule extracted image) in which the black material, thermally expandable microcapsules, and inner surface (shell / core interface) are extracted. Image analysis was performed using the three-dimensional image analysis software Dragonfly (manufactured by Object Research Systems) and the open source image analysis software Fiji (ImageJ). The black material was extracted from the cross-sectional image by image segmentation (identification) using Dragonfly's deep learning (algorithm: U-Net). The cross-sectional image was also binarized using Fiji to extract the thermally expandable microcapsules and inner surface (shell / core interface). Then, a Distance Map was performed on the extracted image of the thermally expandable microcapsules to obtain a distance map image from the outer surface. Image Calculator was then performed on the distance map image and the extracted inner surface image, and Histogram was then performed to obtain distance distribution data from the outer surface to the inner surface. The average value of this distance distribution was taken as the shell thickness. In addition, Image Calculator processing is performed on the distance map image and the black material extraction image, and then Analyze Particles is executed to obtain distance data from the outer surface of the black material. The average value of the distance data in each black material area is taken as the distance from the outer surface of each black material. The position of each black material from the outer surface of the shell is then calculated using the following formula.Location of black material from outer surface (%) = distance from outer surface of black material (pixels) / shell thickness (pixels) × 100. In the location distribution from the outer surface of the black material, the location from the outer surface of the black material where the cumulative frequency of the number is 50% (or 70%, 30%) is defined as the region (% value) from the outer surface. In this invention, the total number of black material present inside the shell (part or all of the black material embedded in the shell) is defined as "100% by number," and black material attached to the outer or inner surface of the thermally expandable microcapsule is not calculated as black material present within a specific region from the outer surface. In addition, "outer surface" means the outer surface of the shell.

[0012] Methods for making 50% or more of the black material present within 15% of the region from the outer surface (similar methods for making 70% or more, or 30% or more of the black material present within a predetermined range from the outer surface) include mixing the black material, dispersant, dispersion aid, and medium to prepare a black material dispersion, and then mixing it with an aqueous dispersion medium or an oil-based mixture; changing the composition and amount of the black material (type, average primary particle size), dispersant, dispersion aid, and medium; or adjusting the preparation time when mixing the black material, dispersant, dispersion aid, and medium to prepare a black material dispersion. In particular, the location of the black material can be suitably adjusted by using a method for separately preparing a black material dispersion by mixing the black material, dispersant, dispersion aid, and medium (the same as the monomer).

[0013] The preferred lower limit of the OD value of the black material is 1.5, and the preferred upper limit is 5.0. By setting it within the above range, it is possible to obtain a black coating film and a black matrix that combine high light-blocking properties and jet blackness. The OD value of the black material refers to the OD value measured when an acrylic resin (coating film thickness 1 μm) containing 50% by weight of the black material is used. In this specification, the optical density (OD value) is the intensity of light incident on an optical density variable element, expressed as I ０ , the transmitted light intensity is I Ｔ When X = -log(I Ｔ / I ０The optical density (OD value) can be measured using a color difference meter, a Macbeth densitometer, or the like.

[0014] Examples of the black material include black pigments, black dyes, and black conductive polymers. Among these, black pigments are preferred. Examples of the black pigment include inorganic black pigments such as carbonaceous black pigments, oxide-based black pigments, and nitride-based black pigments, as well as organic black pigments. Among these, at least one selected from the group consisting of carbonaceous black pigments, oxide-based black pigments, and nitride-based black pigments is preferred. Examples of the carbonaceous black pigment include carbon black, graphite, activated carbon, graphene, and carbon nanotubes. Among these, carbon black is preferred. Examples of the oxide-based black pigment include titanium black, iron oxide, magnetite, and cuprous oxide (cuprous oxide), as well as composite oxide black pigments containing copper and chromium, copper and manganese, copper, iron and manganese, or cobalt, chromium, and iron as the main metal components. Examples of the nitride-based black pigment include zirconium nitride. Examples of the organic black pigment include aniline black (C.I. Pigment Black 1). Among these, carbon black is more preferred because it has excellent heat resistance, excellent dispersibility in resins, and the ability to impart a uniform black color. Furthermore, black pigments having aromatic functional groups are preferred as the black pigment. By using the black pigment having aromatic functional groups, the aromatic functional groups of the black pigment interact with the aromatic groups of the compound containing an aromatic group and a nitrogen atom in the molecule, improving the dispersibility of the black pigment and increasing the degree of blackness. Examples of black pigments having aromatic functional groups include carbon black and carbon nanotubes (both of which have aromatic functional groups).

[0015] Examples of the black dye include inorganic black dyes and organic black dyes. Of these, organic black dyes are preferred. Examples of the inorganic black dye include metal complex azo black dyes. Examples of the metal complex azo black dye include NeoSuper Black C-832 (product name Solvent Black 27, manufactured by Chuo Synthetic Chemical Industry Co., Ltd.).

[0016] Examples of the organic black dye include disazo black dyes, azine black dyes, phthalocyanine black dyes, anthraquinone black dyes, and indigoid black dyes. Examples of the disazo black dye include Chuo Sudan Black 141 (product name: Solvent Black 3, manufactured by Chuo Synthetic Chemical Industry Co., Ltd.). Examples of the azine black dye include ChuoBlack F5 (product name: Solvent Black 7, manufactured by Chuo Synthetic Chemical Industry Co., Ltd.).

[0017] Examples of the black conductive polymer include polythiophene, polydopamine, polypyrrole, polyaniline, polyphenylene vinylene, polyphenylene, polyacetylene, polyquinoxaline, polyoxadiazole, polybenzothiadiazole, etc., and polymers having a plurality of these conductive skeletons, etc. Among these, polythiophene and its derivatives are preferred, and poly(3,4-ethylenedioxythiophene) [PEDOT], poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) [PEDOT / PSS], and polythienothiophene are particularly preferred.

[0018] Among the black materials, particulate black materials (black fine particles) are preferred. The black fine particles preferably have a number average particle diameter (primary average particle diameter) of 1 μm or less, more preferably 5 nm or more and 100 nm or less, even more preferably 10 nm or more and 80 nm or less, and particularly preferably 15 nm or more and 75 nm or less. By ensuring this range, the black fine particles are dispersed in the resin, resulting in a uniform hue (black). The primary average particle diameter can be measured by observation using a transmission electron microscope (TEM).

[0019] The preferred lower limit of the content of the black material is 0.1 wt % relative to the total weight of the thermally expandable microcapsules, and the preferred upper limit is 20 wt %. By setting the content at 0.1 wt % or more, fusion between the thermally expandable microcapsules in the resin during molding can be suppressed. By setting the content at 20 wt % or less, the strength of the shell against melt-kneading during molding can be increased, and light-blocking properties and appearance performance can be further improved. A more preferred lower limit is 0.3 wt %, an even more preferred lower limit is 0.5 wt %, a particularly preferred lower limit is 1 wt %, and the most preferred lower limit is 3 wt %, and a more preferred upper limit is 15 wt %, an even more preferred upper limit is 10 wt %, and an even more preferred upper limit is 7 wt %. The content of the black material can be determined, for example, by heating the thermally expandable microcapsules in a nitrogen atmosphere to 600°C at 10°C / min, holding the temperature for 10 minutes, then lowering the temperature to 400°C at 10°C / min and holding the temperature for 10 minutes, switching the atmosphere to air, heating the microcapsules in air to 1000°C, and holding the temperature for 10 minutes. The content of the black material can be determined from the weight loss between 400°C and 1000°C.

[0020] The black material has a specific surface area of ​​500 m ２ / g or less, and more preferably 300m ２ The lower limit of the specific surface area is not particularly limited, but from the viewpoint of increasing the degree of blackness, it is 1 m ２ / g or more, and ２ / g or more is more preferable. By setting it within the above range, the black material is dispersed in the resin, and the hue (black) becomes uniform. The specific surface area can be measured by measuring a nitrogen adsorption isotherm using a surface area / pore size analyzer (NOVA4200e, manufactured by Quantachrome Instruments) and calculating the specific surface area of ​​the black material from the measurement results in accordance with the BET method.

[0021] The shell constituting the thermally expandable microcapsule according to one embodiment of the present invention contains a polymer compound. The polymer compound is preferably a polymer of a monomer composition containing a nitrile-based monomer and a monomer having a carboxyl group.

[0022] The nitrile monomer is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, and mixtures thereof. Among these, acrylonitrile and methacrylonitrile are particularly preferred. These may be used alone or in combination of two or more.

[0023] The preferred lower limit of the content of the nitrile monomer in the monomer composition is 40% by weight, and the preferred upper limit is 90% by weight. By making it 40% by weight or more, the gas barrier properties of the shell can be improved and the expansion ratio can be increased. By making it 90% by weight or less, heat resistance can be improved and yellowing can be prevented. The more preferred lower limit is 50% by weight, and the more preferred upper limit is 80% by weight.

[0024] Examples of the carboxyl group-containing monomer include a radically polymerizable unsaturated carboxylic acid monomer having a carboxyl group and 3 to 8 carbon atoms. Specific examples include unsaturated dicarboxylic acids and their anhydrides, and monoesters and derivatives of unsaturated dicarboxylic acids. These may be used alone or in combination of two or more. Examples of the unsaturated dicarboxylic acids include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, as well as maleic acid, itaconic acid, fumaric acid, citraconic acid, and chloromaleic acid. Examples of the monoesters of unsaturated dicarboxylic acids include monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate. Among these, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid are particularly preferred.

[0025] The preferred lower limit of the content of the carboxyl group-containing monomer in the monomer composition is 5% by weight, and the preferred upper limit is 50% by weight. By setting the content to 5% by weight or more, the maximum foaming temperature can be increased, and by setting the content to 50% by weight or less, the foaming ratio can be improved. The more preferred lower limit is 10% by weight, and the more preferred upper limit is 30% by weight.

[0026] The monomer composition preferably contains a crosslinkable monomer having two or more double bonds in the molecule. The crosslinkable monomer functions as a crosslinking agent. By containing the crosslinkable monomer, the strength of the shell can be increased, making the cell walls less likely to break during thermal expansion.

[0027] Examples of the crosslinkable monomer include monomers having two or more radically polymerizable double bonds, and specific examples include divinylbenzene, di(meth)acrylate, and tri- or higher functional (meth)acrylates. Examples of the di(meth)acrylate include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Other examples include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane di(meth)acrylate, and dimethylol-tricyclodecane di(meth)acrylate. Furthermore, di(meth)acrylate of polyethylene glycol having a weight average molecular weight of 200 to 600 may also be used. Examples of the trifunctional (meth)acrylate include trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, triallyl formal tri(meth)acrylate, etc. Examples of the tetrafunctional or higher (meth)acrylate include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc. Among these, trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and bifunctional (meth)acrylates such as polyethylene glycol provide relatively uniform crosslinking to the acrylonitrile-based shell.

[0028] The preferred lower limit of the content of the crosslinkable monomer in the monomer composition is 0.1 wt%, and the preferred upper limit is 1.0 wt%. By setting the content of the crosslinkable monomer to 0.1 wt% or more, the effect as a crosslinking agent can be fully exerted, and by setting the content of the crosslinkable monomer to 1.0 wt% or less, the expansion ratio of the thermally expandable microcapsules can be improved. The more preferred lower limit of the content of the crosslinkable monomer is 0.15 wt%, and the more preferred upper limit is 0.9 wt%.

[0029] The monomer composition preferably contains other monomers in addition to the nitrile monomer, the carboxyl group-containing monomer, and the crosslinkable monomer. The inclusion of the other monomers improves the miscibility of the thermally expandable microcapsules with matrix resins such as thermoplastic resins, resulting in foamed molded articles using the thermally expandable microcapsules with excellent appearance. Examples of the other monomers include (meth)acrylic acid esters as well as vinyl monomers such as vinyl chloride, vinylidene chloride, vinyl acetate, and styrene. These may be used alone or in combination of two or more. Among these, (meth)acrylic acid esters are preferred, with alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate, and alicyclic, aromatic, and heterocyclic methacrylates such as cyclohexyl methacrylate, benzyl methacrylate, and isobornyl methacrylate being particularly preferred.

[0030] The preferred lower limit of the content of the other monomer in the monomer composition is 0.1 wt %, and the preferred upper limit is 25 wt %. By making the content of the other monomer 0.1 wt % or more, the dispersibility of the composition using the thermally expandable microcapsules can be improved, and by making it 25 wt % or less, the gas barrier properties of the cell wall can be improved, and the thermal expandability can be improved. The more preferred lower limit of the content of the other monomer is 0.3 wt %, and the more preferred upper limit is 22 wt %.

[0031] The monomer composition may contain a thermosetting resin in addition to the nitrile monomer, the carboxyl group-containing monomer, the crosslinkable monomer, and other monomers. Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, urea resin, polyimide resin, and bismaleimide resin. Among these, epoxy resin and phenol resin are preferred.

[0032] The epoxy resin is not particularly limited, and examples thereof include bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, dicyclopentadiene epoxy resins, and glycidylamine epoxy resins. Examples of the phenol resins include novolac phenol resins, resol phenol resins, and benzylic ether phenol resins. Of these, novolac phenol resins are preferred.

[0033] The thermosetting resin preferably has two or more functional groups reactive with carboxyl groups per molecule. Having two or more functional groups reactive with carboxyl groups can further strengthen the curing properties of the thermosetting resin. In particular, when the monomer composition contains a monomer having a carboxyl group, the heat generated during heating and foaming causes the carboxyl group and the thermosetting resin to bond more strongly, significantly improving heat resistance and durability. The thermosetting resin preferably does not have a radically polymerizable double bond.

[0034] Examples of the functional group reactive with the carboxyl group include a glycidyl group, a phenol group, a methylol group, and an amino group. Of these, a glycidyl group is preferred. The functional groups reactive with the carboxyl group may be the same or two or more different groups.

[0035] The preferred lower limit of the content of the thermosetting resin in the monomer composition is 0.01 wt %, and the preferred upper limit is 30 wt %. By making the content of the thermosetting resin 0.01 wt % or more, it is possible to improve compression resistance during heat foaming. By making the content of the thermosetting resin 30 wt % or less, the gas barrier properties of the shell are improved, and foaming properties are improved. A more preferred lower limit is 0.1 wt %, and a more preferred upper limit is 15 wt %.

[0036] A polymerization initiator is added to the monomer composition to polymerize the monomers. Suitable examples of the polymerization initiator include dialkyl peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, and azo compounds. Specific examples include dialkyl peroxides such as methyl ethyl peroxide, di-t-butyl peroxide, and dicumyl peroxide; and diacyl peroxides such as isobutyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and 3,5,5-trimethylhexanoyl peroxide. Other examples include t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, and 1,1,3,3-tetramethylbutyl peroxyneodecanoate. Other examples include peroxyesters such as cumyl peroxy neodecanoate and (α,α-bis-neodecanoylperoxy)diisopropylbenzene; bis(4-t-butylcyclohexyl)peroxydicarbonate, di-n-propyl-oxydicarbonate, and diisopropyl peroxydicarbonate. Further examples include peroxydicarbonates such as di(2-ethylethylperoxy)dicarbonate, dimethoxybutyl peroxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate. Additionally, other examples include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 1,1'-azobis(1-cyclohexanecarbonitrile).

[0037] The weight-average molecular weight of the polymer compound constituting the shell preferably has a lower limit of 100,000 and an upper limit of 2,000,000. If it is less than 100,000, the strength of the shell may decrease, whereas if it exceeds 2,000,000, the strength of the shell may become too high, resulting in a decrease in the expansion ratio.

[0038] The shell constituting the thermally expandable microcapsule according to one embodiment of the present invention preferably further contains at least one inorganic compound selected from the group consisting of Si-based compounds and Mg-based compounds. By containing the inorganic compound, it is possible to suppress fusion of the thermally expandable microcapsules in the resin during molding. Note that the inorganic compound is different from the black material.

[0039] The Si-based compound and Mg-based compound preferably contain an oxide, hydroxide, carbonate, or hydrogencarbonate of silicon or magnesium. These Si-based compounds and Mg-based compounds may be used alone or in combination of two or more.

[0040] Examples of the Si-based compounds include colloidal silica, silicate sol, No. 3 water glass, sodium orthosilicate, sodium metasilicate, etc. Among these, colloidal silica is preferred. Examples of the Mg-based compounds include magnesium oxide, magnesium hydroxide, magnesium oxide hydroxide, hydrotalcite, dihydrotalcite, magnesium carbonate, basic magnesium carbonate, magnesium calcium carbonate, magnesium phosphate, magnesium hydrogen phosphate, magnesium pyrophosphate, magnesium borate, etc. Among these, magnesium hydroxide is preferred.

[0041] Other examples of the inorganic compounds that may be added include calcium phosphate, aluminum hydroxide, ferric hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, etc. Furthermore, inorganic salts such as sodium chloride and sodium sulfate, alkali metal nitrite, stannous chloride, stannic chloride, potassium dichromate, etc. may also be added as needed.

[0042] The inorganic compound is preferably in the form of fine particles. When the inorganic compound is in the form of fine particles, the primary particle diameter is preferably 0.5 μm or less, more preferably 5 to 100 nm (0.1 μm). By keeping the diameter within this range, fusion between thermally expandable microcapsules in the resin during molding can be suppressed. The primary particle diameter can be measured by observation using a transmission electron microscope (ARM-200F, manufactured by JEOL Ltd.).

[0043] The content of the inorganic compound is 0.01% by weight, preferably 7% by weight, of the total thermally expandable microcapsules. By making the content 0.01% by weight or more, it is possible to suppress fusion of the thermally expandable microcapsules in the resin during molding. By making the content 7% by weight or less, it is possible to further improve the resin dispersibility during molding. A more preferred lower limit is 0.3% by weight, and a more preferred upper limit is 5% by weight. The content of the inorganic compound can be calculated from the weights of the monomer composition, volatile expanding agent, and black material that form the thermally expandable microcapsules.

[0044] The weight ratio of the inorganic compound to the black material (inorganic compound / black material) is preferably 0.001 to 400. By making it 0.001 or more, it is possible to suppress fusion between thermally expandable microcapsules in the resin during molding. By making it 400 or less, it is possible to further improve resin dispersibility during molding, and also to further improve light blocking properties and appearance performance. A more preferred lower limit is 0.3, an even more preferred lower limit is 0.5, a more preferred upper limit is 300, an even more preferred upper limit is 200, an even more preferred upper limit is 100, a particularly preferred upper limit is 90, and an especially preferred upper limit is 80.

[0045] The shell may contain a metal cation. When the copolymer constituting the shell contains a carboxyl group, the metal cation reacts with the carboxyl group to ionically crosslink the copolymer, improving heat resistance and enabling the formation of thermally expandable microcapsules that do not burst or shrink for long periods of time at high temperatures. Furthermore, since the elastic modulus of the shell is less likely to decrease even at high temperatures, the thermally expandable microcapsules do not burst or shrink even when subjected to molding processes that apply strong shear forces, such as kneading, calendaring, extrusion, and injection molding. The aforementioned ionic crosslinking refers to the formation of crosslinks between free carboxyl groups present as side chains of the copolymer. The number of carboxyl groups arranged per monovalent metal cation varies depending on the metal type.

[0046] The metal cation is not particularly limited as long as it reacts with the carboxyl groups of the copolymer to ionically crosslink the copolymer, and examples thereof include ions of Li, Na, K, Zn, Mg, Ca, Ba, Sr, Mn, Al, Ti, Ru, Fe, Ni, Cu, Cs, Sn, Cr, and Pb. These may be used alone or in combination of two or more. Among these, Ca, Zn, and Al ions are preferred, with Zn ions being particularly preferred. When two or more of the metal cations are used, the combination is not particularly limited, but it is preferable to use an alkali metal ion in combination with a metal cation other than the alkali metal. The presence of the alkali metal ion activates functional groups such as carboxyl groups, thereby promoting the reaction between the metal cations other than the alkali metal and the carboxyl groups of the copolymer. Examples of the alkali metal include Na, K, and Li.

[0047] The shell may further contain, as necessary, a stabilizer, an ultraviolet absorber, an antioxidant, an antistatic agent, a flame retardant, a silane coupling agent, a coloring agent, and the like.

[0048] In one embodiment of the thermally expandable microcapsules of the present invention, a volatile expanding agent is encapsulated in the shell as a core agent. The volatile expanding agent is a substance that becomes gaseous at a temperature below the softening point of the polymer that constitutes the shell, and a low-boiling organic solvent is suitable. Examples of the volatile expanding agent include low-molecular-weight hydrocarbons such as ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, petroleum ether, isooctane, octane, decane, isododecane, dodecane, and hexanedecane. Also, CCl ３ F, CCl ２ F ２ , CClF ３ , CClF ２ -CClF ２ and chlorofluorocarbons such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, trimethyl-n-propylsilane, and tetraalkylsilanes such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane. Among these, isobutane, n-butane, n-pentane, isopentane, n-hexane, isooctane, isododecane, and mixtures thereof are preferred. These volatile expanding agents may be used alone or in combination of two or more. Furthermore, as the volatile expanding agent, a thermally decomposable compound that is thermally decomposed into a gaseous form by heating may be used.

[0049] In the thermally expandable microcapsules according to one embodiment of the present invention, among the above-mentioned volatile expanding agents, it is preferable to use low-boiling hydrocarbons having 5 or less carbon atoms. By using such hydrocarbons, it is possible to obtain thermally expandable microcapsules with a high expansion ratio and rapid expansion start. Furthermore, a thermally decomposable compound that decomposes into a gaseous form when heated may be used as the volatile expanding agent.

[0050] The thermally expandable microcapsules according to one embodiment of the present invention preferably have an optical density (OD value) of 0.5 or more. By setting the OD value to 0.5 or more, a black coating film or black matrix that combines high light-blocking properties and jet blackness can be obtained. A more preferred lower limit is 0.8, and a more preferred upper limit is 1.6. The optical density (OD value) can be measured using a Macbeth densitometer or the like.

[0051] The thermally expandable microcapsules according to one embodiment of the present invention have a maximum foaming temperature (Tmax) of preferably 170°C or higher. By setting the temperature at 170°C or higher, heat resistance is improved, and rupture and shrinkage of the thermally expandable microcapsules can be prevented when a composition containing the thermally expandable microcapsules is applied in a high temperature range. Furthermore, aggregation of the thermally expandable microcapsules during application can be suppressed, resulting in a good appearance. A more preferred lower limit is 180°C, and a preferred upper limit is 240°C. In this specification, the maximum foaming temperature refers to the temperature at which the diameter of the thermally expandable microcapsules reaches its maximum (maximum displacement) when the diameter of the thermally expandable microcapsules is measured while being heated from room temperature.

[0052] In the thermally expandable microcapsules according to one embodiment of the present invention, the maximum displacement (Dmax) measured by thermomechanical analysis preferably has a lower limit of 10 μm. When the Dmax is 10 μm or more, the expansion ratio improves and the desired expansion performance is obtained. A more preferred lower limit is 20 μm, an even more preferred lower limit is 100 μm, and an even more preferred lower limit is 300 μm. The preferred upper limit of the maximum displacement is 2000 μm, a more preferred upper limit is 1800 μm, and an even more preferred upper limit is 1500 μm. The maximum displacement refers to the value at which the diameter of a predetermined amount of thermally expandable microcapsules as a whole is maximum when the diameter of the predetermined amount of thermally expandable microcapsules is measured while heating the microcapsules from room temperature.

[0053] The upper limit of the foaming initiation temperature (Ts) is preferably 185° C. By setting the temperature to 185° C. or less, foaming becomes easy and a desired foaming ratio can be achieved. The lower limit is preferably 130° C., and the upper limit is more preferably 180° C.

[0054] The preferred lower limit of the volume-average particle diameter of the thermally expandable microcapsules according to one embodiment of the present invention is 5 μm, and the preferred upper limit is 45 μm. When the diameter is 5 μm or more, the resulting molded product has a moderate amount of bubbles, resulting in a sufficient expansion ratio. When the diameter is 45 μm or less, the resulting coated product has a moderate amount of bubbles, resulting in a good appearance. A more preferred lower limit is 7 μm, and a more preferred upper limit is 35 μm. The volume-average particle diameter of the thermally expandable microcapsules can be measured using a laser diffraction / scattering particle size distribution analyzer or the like. Furthermore, the thickness of the shell constituting the thermally expandable microcapsules according to one embodiment of the present invention is preferably 2 μm or more and 6 μm or less. The shell thickness can be measured simultaneously when measuring the area (% value) from the outer surface where 50% or more of the black material is present by number.

[0055] The method for producing the thermally expandable microcapsules according to one embodiment of the present invention is not particularly limited, but they can be produced, for example, by carrying out the steps of preparing a black material dispersion containing a black material, a pigment derivative, a dispersant, and a medium, preparing an aqueous dispersion medium containing an inorganic compound, mixing the black material dispersion with an oily mixture containing a monomer composition and a volatile expanding agent, and dispersing the mixture in the aqueous dispersion medium, and polymerizing the monomer. The monomer composition may contain the nitrile monomer, a monomer having a carboxyl group, a crosslinkable monomer, or other monomers.

[0056] When producing thermally expandable microcapsules, which are one embodiment of the present invention, a step of preparing a black material dispersion containing a black material, a pigment derivative, a dispersant, and a polymerizable monomer (medium) is carried out. Specifically, for example, a black material, a dispersant, a pigment derivative, a polymerizable monomer, and optionally a polymerization initiator are added to a container, and the mixture is dispersed using a disperser to prepare a black material dispersion containing the black material, the pigment derivative, the dispersant, and the polymerizable monomer.

[0057] The dispersant functions to suppress aggregation of the black material and improve dispersion stability. The dispersant generally consists of a unit that easily adsorbs to the black material and a unit that easily adsorbs to substances other than the black material, such as polymerizable monomers (i.e., has affinity for substances other than the black material). Each unit may be contained within a single dispersant structure. Alternatively, polymers composed of the respective units may be condensed (chemically bonded). Furthermore, the monomers that form the respective units may be copolymerized. Alternatively, the dispersant may be prepared by other methods or a combination of these methods. The dispersant generally preferably comprises an adsorbent moiety that easily adsorbs to the black material or pigment and a side chain moiety that solvates with solvents, such as polymerizable monomers. Examples of the adsorbent moiety include a moiety containing a polar functional group, such as an amino group, an imino group, a carboxyl group, a sulfonic acid group, or a hydroxyl group, or a moiety containing an aromatic ring. Examples of the side chain moiety include a polyalkylene moiety, a polyoxyalkylene moiety, a polyether moiety, a polyester moiety, a polyamide moiety, a poly(meth)acrylic moiety, or a polyurethane moiety. Examples of the dispersants include polyacrylic, polyether, polyurethane, polyamide, polyimide, poly(meth)acrylic acid, poly(maleic anhydride) and other polycarboxylic acid dispersants, polyamine, and polyester dispersants having poly(meth)acrylate, polylactone, polyalkylene oxide, or the like as the main chain or side chain, as well as dispersants having a quaternary ammonium salt or the like incorporated therein. These dispersants can be used alone or in combination of two or more. Examples of the polyether dispersants include polyoxyalkylene, polyether phosphate ester amine, polyether phosphate ester, and polyether ester acid amine. Examples of the polyester dispersants include polycaprolactone and polylactic acid.Examples of dispersants in which a unit that is easily adsorbed to the black material and a unit that has affinity for substances other than the black material are chemically bonded include condensates of polycaprolactone and polyalkyleneimine, condensates of polycaprolactone and polyallylamine, condensates of polylactide and polyalkyleneimine, condensates of polylactide and polyallylamine, and amine salts of polyether ester acids. Commercially available dispersants include polyurethane-based dispersants such as Disperbyk-161, 166, and 167 manufactured by BYK Japan, and Solsperse 55000 and 76500 manufactured by Lubrizol Japan; polycarboxylic acid-based dispersants such as Disperbyk-106, 110, and 111, Solsperse 36000 and 41000, and EFKA-5060 manufactured by BASF Japan; polyamine-based dispersants such as Disperbyk-116 and 130, Solsperse 24000, 32000, 33000, 35000, 86000, J200, and EFKA-4046, and Ajinomoto Fine-Techno Co., Ltd.'s Ajisper PB821, PB822, PB824, and PB881; and carboxyl group-containing dispersants. Examples of polymer-based dispersants include FLOWLEN G-700, FLOWLEN G-900, and FLOWLEN GW-1500 manufactured by Kyoeisha Chemical Co., Ltd.; examples of polyester-based dispersants include Solsperse 35000, Solsperse 39000, and T-6000, T-8000E, and T-9100 manufactured by Kawaken Fine Chemicals Co., Ltd.; examples of polyacrylic-based dispersants include Efka 4701, Efka 4585, and Efka 4780 (manufactured by BASF), DISPERBYK-2012 (manufactured by BYK), FLOWLEN DOPA-35, FLOWLEN DOPA-17HF, and FLOWLEN DOPA-15BHFS (manufactured by Kyoeisha); and examples of polyether-based dispersants include Disparlon 234 and Disparlon 325 (manufactured by Kusumoto Chemicals Co., Ltd.). Among these, Solsperse J200, Solsperse 35000, and Solsperse 39000 are more preferred from the viewpoint of dispersibility of the black material.

[0058] The preferred lower limit of the content of the dispersant is 0.01 wt % relative to the total black material dispersion, and the preferred upper limit is 20 wt %. By setting the content at 0.01 wt % or more, aggregation of the black material can be suppressed. By setting the content at 20 wt % or less, aggregation of the black material due to interactions between dispersants can be suppressed. A more preferred lower limit is 0.1 wt %, an even more preferred lower limit is 0.3 wt %, a more preferred upper limit is 15 wt %, an even more preferred upper limit is 10 wt %, and an even more preferred upper limit is 5 wt %.

[0059] The pigment derivative (dispersion aid) is a compound in which an acidic or basic group is introduced as a substituent into a pigment molecule. The inclusion of a pigment derivative acts as a dispersing aid, adjusting the dispersibility of the black material and the properties of the resulting thermally expandable microcapsules. Examples of pigments that form the base structure of the pigment derivative include phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, perylene pigments, diketopyrrolopyrrole pigments, azo pigments, benzimidazolone pigments, dioxazine pigments, quinophthalone pigments, and isoindoline pigments. Examples of the substituent include sulfonic acid groups, sulfonic acid bases, sulfonic acid amide groups, phthalimidomethyl groups, amino groups, imino groups, nitro groups, carboxyl groups, amide groups, hydroxyl groups, and phosphate groups. Among these, derivatives of phthalocyanine pigments, quinacridone pigments, azo pigments, and diketopyrrolopyrrole pigments are preferred, and at least one derivative selected from the group consisting of azo pigments and phthalocyanine pigments is preferred. Use of a pigment derivative having such a base skeleton can improve the dispersibility and dispersion stability of the black material, and can further improve the foamability and blackness when formed into thermally expandable microcapsules.

[0060] The preferred lower limit of the content of the pigment derivative is 0.001 wt % relative to the total black material dispersion, and the preferred upper limit is 20 wt %. By setting the content at 0.001 wt % or more, aggregation of the black material can be suppressed. By setting the content at 20 wt % or less, aggregation of the black material due to interactions between the pigment derivatives can be suppressed. A more preferred lower limit is 0.01 wt %, an even more preferred lower limit is 0.1 wt %, a more preferred upper limit is 15 wt %, an even more preferred upper limit is 10 wt %, and an even more preferred upper limit is 5 wt %.

[0061] The black material dispersion liquid contains a medium. The medium is not particularly limited as long as it is a medium capable of dispersing the black material, but is preferably a polymerizable monomer. The polymerizable monomer is preferably a radical polymerizable monomer, and is preferably a nitrile monomer or a monomer having a carboxyl group. The polymerizable monomer may be the same as or different from the above-mentioned monomer.

[0062] When producing thermally expandable microcapsules according to one embodiment of the present invention, a step of preparing an aqueous dispersion medium is carried out. Specifically, for example, an aqueous dispersion medium containing a black material and an inorganic compound is prepared by adding water, an inorganic compound, and, if necessary, a co-stabilizer to a polymerization reaction vessel.

[0063] Examples of the auxiliary stabilizer include a condensation product of diethanolamine and an aliphatic dicarboxylic acid, a condensation product of urea and formaldehyde, etc. Further examples include polyvinylpyrrolidone, polyethylene oxide, polyethyleneimine, tetramethylammonium hydroxide, gelatin, methylcellulose, polyvinyl alcohol, dioctyl sulfosuccinate, sorbitan ester, various emulsifiers, etc.

[0064] In addition to the co-stabilizer, a condensation product or a water-soluble nitrogen compound may be added. As the condensation product, a condensation product of diethanolamine and an aliphatic dicarboxylic acid is preferred, and a condensation product of diethanolamine and adipic acid or a condensation product of diethanolamine and itaconic acid is particularly preferred.

[0065] Examples of the water-soluble nitrogen compounds include polyvinylpyrrolidone, polyethyleneimine, polyoxyethylene alkylamine, polydialkylaminoalkyl(meth)acrylates such as polydimethylaminoethyl methacrylate and polydimethylaminoethyl acrylate, polydialkylaminoalkyl(meth)acrylamides such as polydimethylaminopropyl acrylamide and polydimethylaminopropyl methacrylamide, polyacrylamide, polycationic acrylamide, polyamine sulfone, and polyallylamine. Among these, polyvinylpyrrolidone is preferably used.

[0066] An aqueous dispersion medium containing the inorganic compound, co-stabilizer, and optionally a dispersant is prepared by blending the inorganic compound, co-stabilizer, and dispersant with deionized water, and the pH of the aqueous phase is determined appropriately depending on the types of inorganic compound and co-stabilizer used. For example, when a Si-based compound such as colloidal silica is used as the inorganic compound, polymerization is carried out using an acidic aqueous dispersion medium, and to make the aqueous dispersion medium acidic, an acid such as hydrochloric acid is added as necessary to adjust the pH of the system to 3 to 4. On the other hand, when a Mg-based compound such as magnesium hydroxide or calcium phosphate is used as the inorganic compound, polymerization is carried out using an alkaline aqueous dispersion medium adjusted to a pH of 8 to 11.

[0067] Next, in the method for producing thermally expandable microcapsules, a step of dispersing an oily mixture containing a monomer composition and a volatile expanding agent and a black material dispersion in an aqueous dispersion medium is carried out. Specifically, the oily mixture containing a monomer composition and a volatile expanding agent and the black material dispersion are mixed and dispersed in the aqueous dispersion medium. In this step, the monomer composition, the volatile expanding agent, and the black material dispersion may be separately added to the aqueous dispersion medium to prepare the oily mixture in the aqueous dispersion medium. However, typically, the three are mixed in advance to form a black material-containing oily mixture, which is then added to the aqueous dispersion medium. In this case, the oily mixture and the aqueous dispersion medium may be prepared in separate containers, and the oily mixture may be dispersed in the aqueous dispersion medium by stirring in the separate containers, and then added to the polymerization reaction vessel. In this step, an inorganic compound can be present on the aqueous dispersion medium side at the interface between the oil droplets of the black material-containing oily mixture and the aqueous dispersion medium. As a result, the inorganic compound can be present on the surface of the resulting thermally expandable microcapsules. Furthermore, in this process, the black material is present on the black material-containing oily mixed liquid side at the interface between the oil droplets consisting of the black material-containing oily mixed liquid and the aqueous dispersion medium, and as a result, in the shell of the obtained thermally expandable microcapsules, when the thickness from the outer surface to the inner surface is 0 to 100%, 50% or more of the black material can be present in a region within 15% from the outer surface. Note that a polymerization initiator is used to polymerize the above monomer, and the polymerization initiator may be added to the black material-containing oily mixed liquid in advance, or may be added after stirring and mixing the aqueous dispersion medium and the black material-containing oily mixed liquid in a polymerization reaction vessel.

[0068] Examples of a method for emulsifying and dispersing the black material-containing oily mixture in an aqueous dispersion medium to a predetermined particle size include a method of stirring with a homomixer (for example, manufactured by Tokushu Kika Kogyo Co., Ltd.) or a method of passing the mixture through a static dispersion device such as a line mixer or an element-type static disperser. The aqueous dispersion medium and the polymerizable mixture may be supplied separately to the static dispersion device, or a dispersion liquid that has been mixed and stirred in advance may be supplied.

[0069] The thermally expandable microcapsules according to one embodiment of the present invention can be produced by subjecting the dispersion obtained through the above-described steps to a step of polymerizing the monomers by heating, and a step of washing. The thermally expandable microcapsules produced by this method have a high maximum foaming temperature, excellent heat resistance, and do not burst or shrink even when coated at high temperatures.

[0070] The present invention also includes a foamable masterbatch containing the above-mentioned thermally expandable microcapsules and a thermoplastic resin (base resin).

[0071] The thermoplastic resin used for the base resin is not particularly limited, and any thermoplastic resin commonly used in foam molding can be used. Specific examples of the thermoplastic resin include polyolefins such as low-density polyethylene (LDPE) and polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), vinyl chloride, polystyrene, thermoplastic elastomers, and ethylene-methyl methacrylate copolymer (EMMA). Among these, LDPE, EVA, and EMMA are preferred because of their low melting points and ease of processing. These resins may be used alone or in combination of two or more.

[0072] The content of the thermally expandable microcapsules in the foamable masterbatch is not particularly limited, but the preferred lower limit is 10 parts by weight and the preferred upper limit is 90 parts by weight per 100 parts by weight of the thermoplastic resin.

[0073] The method for producing the expandable masterbatch is not particularly limited, but examples include pre-kneading raw materials such as a base resin such as a thermoplastic resin and various additives using a co-rotating twin-screw extruder or the like. The mixture is then heated to a predetermined temperature, a blowing agent such as thermally expandable microcapsules is added, and the resulting mixture is further kneaded. The resulting mixture is then cut into pellets of the desired size using a pelletizer to form a masterbatch. Alternatively, a pellet-shaped masterbatch may be produced by kneading raw materials such as a base resin such as a thermoplastic resin and thermally expandable microcapsules using a batch kneader and then granulating them using a granulator. The kneader is not particularly limited as long as it can knead the materials without destroying the thermally expandable microcapsules, and examples include a pressure kneader and a Banbury mixer.

[0074] The present invention also provides a foamed molded article obtained using the thermally expandable microcapsules or expandable masterbatch. In particular, the thermally expandable microcapsules can be suitably used in applications requiring post-processing at high temperatures, allowing for the production of foamed sheets with high appearance quality, such as uneven surfaces, and suitable for applications such as residential wallpaper. Specifically, the thermally expandable microcapsules or the expandable masterbatch containing the thermally expandable microcapsules are kneaded with a matrix resin and then molded to obtain a foamed molded article.

[0075] The molding method for the foamed molded article is not particularly limited, and examples thereof include kneading molding, calendar molding, extrusion molding, injection molding, etc. In the case of injection molding, the process is not particularly limited, and examples thereof include the short-short method in which a resin material is partially placed in a mold and foamed, and the core-back method in which the mold is fully filled with the resin material and then opened to the desired foaming point.

[0076] Another aspect of the present invention is a hollow particle obtained by thermally expanding the thermally expandable microcapsule of the present invention, in which a black material is attached to or partly embedded in the outer surface of a shell containing a polymer compound. Another aspect of the present invention can exhibit excellent blackness. The hollow particle of another aspect of the present invention can be produced, for example, by heating the thermally expandable microcapsule of the present invention and thermally expanding it. In this other aspect of the present invention, the shell configuration, black material, and polymer compound are the same as those of the thermally expandable microcapsule of the present invention, and therefore description thereof will be omitted.

[0077] According to the present invention, it is possible to provide a thermally expandable microcapsule that can achieve both excellent expandability and blackness, and a expandable masterbatch, a foamed molded product, and hollow particles using the thermally expandable microcapsule. Furthermore, according to the present invention, it is possible to provide a thermally expandable microcapsule that has a small difference in blackness before and after expansion.

[0078] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0079] (Example 1) (Preparation of thermally expandable microcapsules) Carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Corporation, primary average particle size 24 nm, specific surface area 110 m) was used as a black material. ２A carbon black dispersion was prepared by adding 0.13 parts by weight of carbon black (1000 ppm / g), 0.026 parts by weight of Solsperse 39000 (a polyester-based dispersant manufactured by Lubrizol Nippon Co., Ltd.) as a carbon black dispersant [polymer dispersant], 0.0065 parts by weight of Solsperse 5000S (a phthalocyanine-based pigment derivative manufactured by Lubrizol Nippon Co., Ltd.) as a dispersing aid, and 30 parts by weight of methacrylonitrile and 20 parts by weight of acrylonitrile as a medium, and dispersing the mixture using a bead mill. An aqueous dispersion medium was prepared by adding 300 parts by weight of water, 10 parts by weight of colloidal silica (20% by weight manufactured by Asahi Denka Co., Ltd.) and 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF) as dispersion stabilizers, and 1.8 parts by weight of 1N hydrochloric acid to a polymerization reaction vessel. Next, an oily mixture consisting of a volatile expanding agent, 30 parts by weight of methyl methacrylate, 20 parts by weight of methacrylic acid, 50.2 parts by weight of carbon black dispersion, and polymerization initiator (0.8 parts by weight of 2,2'-azobisisobutyronitrile, 0.6 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile)) in the blending ratio shown in Table 1 was added to an aqueous dispersion medium and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, charged into a nitrogen-substituted pressure polymerization vessel, and reacted at 60°C for 21 hours under pressure (0.5 MPa), to obtain a reaction product. The resulting reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules.

[0080] (Examples 2 to 6) Thermally expandable microcapsules were obtained in the same manner as in Example 1, except that the black material, polymer dispersant, and dispersion aid were added in the amounts shown in Table 1. In Examples 2 to 6, methacrylonitrile and acrylonitrile were also added as media when preparing the carbon black dispersion.

[0081] (Examples 7 to 14, 25, and 26) Thermally expandable microcapsules were obtained in the same manner as in Example 4, except that the black materials shown in Tables 1 and 2 were used. Details of CB2 to CB9, titanium black, and zirconium nitride are shown below. In Examples 7 to 14, 25, and 26, methacrylonitrile and acrylonitrile were also added as media when preparing the carbon black dispersion. CB2: #2650, manufactured by Mitsubishi Chemical Corporation, primary average particle size 13 nm, specific surface area 370 m２ / g CB3: MA230, manufactured by Mitsubishi Chemical Corporation, primary average particle size 30 nm, specific surface area 74 m ２ / g CB4: MA14, manufactured by Mitsubishi Chemical Corporation, primary average particle size 40 nm, specific surface area 56 m ２ / g CB5: MA285, manufactured by Mitsubishi Chemical Corporation, primary average particle size 40 nm, specific surface area 60 m ２ / g CB6: #95, manufactured by Mitsubishi Chemical Corporation, primary average particle size 40 nm, specific surface area 55 m ２ / g CB7: #240, manufactured by Mitsubishi Chemical Corporation, primary average particle size 45 nm, specific surface area 64 m ２ / g CB8: MA220, manufactured by Mitsubishi Chemical Corporation, primary average particle size 55 nm, specific surface area 36 m ２ / g CB9: #5, manufactured by Mitsubishi Chemical Corporation, primary average particle size 76 nm, specific surface area 29 m ２ / g Titanium black: UF-8, manufactured by Mitsubishi Materials Corporation, primary average particle size 20 nm, specific surface area 25 m ２ / g Zirconium nitride: UB-2, manufactured by Mitsubishi Materials Corporation, primary average particle size 40 nm, specific surface area 40 m ２ / g

[0082] (Examples 15 to 24, 27, 28) Thermally expandable microcapsules were obtained in the same manner as in Example 4, except that the black material, polymer dispersant, dispersing aid, and monomer composition were mixed in the compositions shown in Tables 1 and 2. Details of the polymer dispersant and dispersing aid are shown below. In Examples 15 to 24, 27, and 28, methacrylonitrile and acrylonitrile were also added as a medium when preparing the carbon black dispersion. [Polymer dispersant] Polyacrylic: Efka 4701 (manufactured by BASF) Polyether: Disparlon 234 (manufactured by Kusumoto Chemicals) [Dispersing aid] Azo pigment derivative: Solsperse 22000 (manufactured by Lubrizol Corporation) Quinacridone pigment derivative: sulfonic acid derivative of quinacridone red Diketopyrrolopyrrole pigment derivative: sulfonic acid derivative of diketopyrrolopyrrole

[0083] (Comparative Example 1) Carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Corporation, primary average particle size 24 nm, specific surface area 110 m) was used as a black material. ２A carbon black dispersion was prepared by adding 6.89 parts by weight of carbon black (20% by weight, manufactured by Asahi Denka Co., Ltd.) as a dispersion stabilizer, 1.38 parts by weight of Solsperse 39000 (manufactured by Lubrizol Japan Co., Ltd.), and 30 parts by weight of methacrylonitrile and 20 parts by weight of acrylonitrile as a medium, and dispersing the carbon black using a bead mill. An aqueous dispersion medium was prepared by adding 300 parts by weight of water, 10 parts by weight of colloidal silica (20% by weight, manufactured by Asahi Denka Co., Ltd.) as a dispersion stabilizer, 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF Corporation), and 1.8 parts by weight of 1N hydrochloric acid to a polymerization reaction vessel. Next, an oily mixture consisting of a volatile expanding agent, 30 parts by weight of methyl methacrylate, 20 parts by weight of methacrylic acid, 50.3 parts by weight of carbon black dispersion, and a polymerization initiator (0.8 parts by weight of 2,2'-azobisisobutyronitrile, 0.6 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile)) in the formulation shown in Table 2 was added to an aqueous dispersion medium and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, charged into a nitrogen-substituted pressure polymerization vessel, and reacted at 60°C for 21 hours under pressure (0.5 MPa), to obtain a reaction product. The resulting reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules.

[0084] (Comparative Examples 2 and 3) Thermally expandable microcapsules were obtained in the same manner as in Example 4, except that the black materials shown in Table 2 were used. Note that the titanium black used was the same as in Example 25, and the zirconium nitride used was the same as in Example 26.

[0085] (Comparative Example 4) A polymerization reaction vessel was charged with 300 parts by weight of water and carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Corporation, primary average particle size: 24 nm, specific surface area: 110 m) as a black material. ２4.6 parts by weight of carbon black (1 / g), 0.92 parts by weight of Solsperse 39000 (manufactured by Lubrizol Japan Co., Ltd.) as a dispersant for carbon black [polymer dispersant], 0.23 parts by weight of Solsperse 5000S (phthalocyanine pigment derivative, manufactured by Lubrizol Japan Co., Ltd.) as a dispersing aid, 10 parts by weight of colloidal silica (20% by weight manufactured by Asahi Denka Co., Ltd.) and 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF Corporation) as dispersion stabilizers, and 1.8 parts by weight of 1N hydrochloric acid were charged, and then a volatile expanding agent, 30 parts by weight of methacrylonitrile, 20 parts by weight of acrylonitrile, 30 parts by weight of methyl methacrylate, 20 parts by weight of methacrylic acid, and a polymerization initiator (0.8 parts by weight of 2,2′-azobisisobutyronitrile, 0.6 parts by weight of 2,2′-azobis(2,4-dimethylvaleronitrile)) in the blending ratios shown in Table 2 were added and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, charged into a nitrogen-substituted pressure polymerization vessel, and reacted at 60°C for 21 hours under pressure (0.5 MPa), to obtain a reaction product. The resulting reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules.

[0086] (Comparative Example 5) Carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Corporation, primary average particle size 24 nm, specific surface area 110 m) was used as a black material. ２A carbon black dispersion was prepared by adding 0.13 parts by weight of carbon black (100% wt. / g), 0.026 parts by weight of Solsperse 39000 (a polyester-based dispersant manufactured by Lubrizol Nippon Co., Ltd.) as a carbon black dispersant [polymer dispersant], 0.0065 parts by weight of Solsperse 5000S (a phthalocyanine-based pigment derivative manufactured by Lubrizol Nippon Co., Ltd.) as a dispersing aid, and 50 parts by weight of methyl ethyl ketone as a medium, and dispersing the carbon black using a bead mill. An aqueous dispersion medium was prepared by adding 300 parts by weight of water, 10 parts by weight of colloidal silica (20% by weight manufactured by Asahi Denka Co., Ltd.) and 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF) as dispersion stabilizers, and 1.8 parts by weight of 1N hydrochloric acid to a polymerization reaction vessel. Next, an oily mixture consisting of a volatile expanding agent, 60 parts by weight of methyl methacrylate, 40 parts by weight of methacrylic acid, 50.2 parts by weight of carbon black dispersion, and polymerization initiator (0.8 parts by weight of 2,2'-azobisisobutyronitrile, 0.6 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile)) in the blending ratio shown in Table 2 was added to an aqueous dispersion medium and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, charged into a nitrogen-substituted pressure polymerization vessel, and reacted at 60°C for 21 hours under pressure (0.5 MPa), to obtain a reaction product. The resulting reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules.

[0087] Comparative Example 6 A polymerization reaction vessel was charged with 300 parts by weight of water, 3 parts by weight of carbon black (CB10, Aqua Black #001, manufactured by Tokai Carbon Co., Ltd., primary average particle size 50 nm) as a black material, 10 parts by weight of colloidal silica (20% by weight manufactured by Asahi Denka Corporation) as a dispersion stabilizer, 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF Corporation), and 1.8 parts by weight of 1N hydrochloric acid, and then a volatile swelling agent, 30 parts by weight of methacrylonitrile, 20 parts by weight of acrylonitrile, 30 parts by weight of methyl methacrylate, 20 parts by weight of methacrylic acid, and a polymerization initiator (0.8 parts by weight of 2,2'-azobisisobutyronitrile, 0.6 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile)) in the blending ratio shown in Table 2 were added and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, charged into a nitrogen-substituted pressure polymerization vessel, and reacted at 60°C for 21 hours under pressure (0.5 MPa), to obtain a reaction product. The resulting reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules.

[0088] (Evaluation Method) The performance of the obtained thermally expandable microcapsules was evaluated by the following method. The results are shown in Tables 1 and 2.

[0089] (1) Evaluation of Thermally Expandable Microcapsules (1-1) Average Particle Diameter (Before Foaming) The average particle diameter (volume average particle diameter) of the obtained thermally expandable microcapsules was measured using a laser diffraction / scattering particle size distribution analyzer (LS 13 320, manufactured by Beckman Coulter).

[0090] (1-2) Location of Black Material Thermally expandable microcapsules were added to an embedding resin (Oken Epok 812, manufactured by Oken Shoji Co., Ltd.) so that the particle content was 3% by weight, and dispersed to prepare a thermally expandable microcapsule-embedded resin. A thin film was prepared from the resulting embedded resin using a microtome (EM UC7, manufactured by LEICA), and a transmission electron microscope (ARM-200F, manufactured by JEOL Ltd.) was used to photograph the shell cross section of any part of the thermally expandable microcapsule with the largest diameter when observed. Then, image analysis was performed using the three-dimensional image analysis software Dragonfly (manufactured by Object Research Systems) and the open source image analysis software Fiji (ImageJ). The analysis procedure is as follows. For the cross-sectional image, Dragonfly's deep learning (algorithm: U-Net) was used to extract the black material by image segmentation (identification). Furthermore, for the cross-sectional image, Fiji was used to perform binarization processing to extract the thermally expandable microcapsules and the inner surface (shell / core interface). Then, Distance Map was performed on the thermally expandable microcapsule extracted image to obtain a distance map image from the outer surface. Image Calculator was performed on the distance map image and the inner surface extracted image, and then Histogram was performed to obtain distance distribution data from the outer surface to the inner surface. The average value of this distance distribution was used as the shell thickness. Furthermore, Image Calculator processing was performed on the distance map image and the black material extracted image, and then Analyze Particles was performed to obtain distance data from the outer surface of the black material. The average value of the distance data in each black material region was used as the distance from the outer surface of each black material. The location of each black material from the outer surface of the shell was calculated using the following formula: Location from the outer surface of the black material (%) = Distance from the outer surface of the black material (pixel) / Shell thickness (pixel) × 100. The location from the outer surface of the black material where the cumulative frequency of the number in the location distribution from the outer surface of the black material was 50% was calculated, thereby measuring the proportion (%) from the outer surface where 50% or more of the black material was present by number.In addition, the proportion (%) of the black material from the outer surface where 30% or more of the black material exists was measured by calculating the positions from the outer surface of the black material where the cumulative frequency of the number of particles in the distribution of positions from the outer surface of the black material is 30%. Furthermore, the proportion (%) of the black material from the outer surface where 70% or more of the black material exists was measured by calculating the positions from the outer surface of the black material where the cumulative frequency of the number of particles in the distribution of positions from the outer surface of the black material is 70%.

[0091] (1-3) Measurement of Foaming Initiation Temperature, Maximum Displacement, and Maximum Foaming Temperature The foaming initiation temperature (Ts), maximum displacement (Dmax), and maximum foaming temperature (Tmax) were measured using a thermomechanical analyzer (TMA) (TMA450, manufactured by TA Instruments). Specifically, 25 μg of sample was placed in an aluminum container with a diameter of 7 mm and a depth of 1 mm, and heated from 80°C to 220°C at a heating rate of 5°C / min with a force of 0.1 N applied from above. The displacement in the vertical direction of the measuring probe was measured. The temperature at which the displacement began to increase was defined as the foaming initiation temperature, the maximum value of the displacement was defined as the maximum displacement, and the temperature at the maximum displacement was defined as the maximum foaming temperature. Note that in the foaming ratio described below, when a rating of "x" was given, the foaming initiation temperature, maximum displacement, and maximum foaming temperature were not measured, and the rating was "-."

[0092] (1-4) Average particle size (after expansion), expansion ratio After expansion by heating at 200°C for 3 minutes in a heating oven (PHH-102, manufactured by Espec Corporation), the average particle size (after expansion) of the expanded thermally expandable microcapsules was measured with a laser diffraction particle size distribution analyzer (LS 13 120, manufactured by Beckman Coulter, Inc.). Thereafter, the expansion ratio was calculated from "average particle size (after expansion) / average particle size (before expansion)" and evaluated according to the following criteria.

[0093] 〇〇: 2.5 times or more 〇: 2.0 times or more but less than 2.5 times ×: Less than 2.0 times

[0094] (1-5) L* Value Measurement 100 mg of the obtained thermally expandable microcapsules were weighed into an aluminum pan and heated at 200°C for 3 minutes in a heating oven (PHH-102, manufactured by Espec Corporation) to expand the thermally expandable microcapsules. The expanded microcapsules were transferred to a vial (No. 2, manufactured by AS ONE Corporation), and the L* value (SCE) was measured from the bottom side of the vial using a spectrophotometer (CM-26dG, manufactured by Konica Minolta, Inc.). The obtained L* value (blackness after expansion) was evaluated according to the following criteria. In the above expansion ratio, when the evaluation was "x", the L* value was not measured and the result was rated as "-". Furthermore, for the thermally expandable microcapsules before expansion, the difference between the L* value (blackness before expansion) measured by the above-mentioned method (blackness after expansion - blackness before expansion) was calculated.

[0095] 〇〇: Less than 38 〇: 38 or more but less than 45 △: 45 or more but less than 55 ×: 55 or more

[0096]

[0097]

[0098] According to the present invention, it is possible to provide thermally expandable microcapsules that can achieve both excellent expandability and blackness, as well as expandable masterbatches, foamed molded articles, and hollow particles that use the thermally expandable microcapsules.

Claims

1. A thermally expandable microcapsule in which a volatile expanding agent is encapsulated as a core agent in a shell, the shell containing a black material and a polymer compound, and in which, when the thickness from the outer surface to the inner surface of the cross section of the shell is 0 to 100%, 50% or more of the black material is present in an area within 15% of the outer surface.

2. The thermally expandable microcapsule according to claim 1, wherein the black material is at least one selected from the group consisting of carbon-based black pigments, oxide-based black pigments, and nitride-based black pigments.

3. A thermally expandable microcapsule according to claim 1 or 2, wherein the content of the black material is 0.1% by weight or more and 20% by weight or less based on the total weight of the thermally expandable microcapsule.

4. A thermally expandable microcapsule according to any one of claims 1 to 3, wherein the black material has an average primary particle size of 10 nm or more and 80 nm or less.

5. The thermally expandable microcapsule according to claim 2, wherein the carbon-based black pigment is carbon black.

6. A thermally expandable microcapsule according to claim 1 or 2, wherein 70% or more by number of the black material is present within 15% of the area from the outer surface.

7. A thermally expandable microcapsule according to claim 1 or 2, wherein 30% or more of the black material is present in an area within 10% of the outer surface.

8. A foamable masterbatch comprising the thermally expandable microcapsules according to any one of claims 1 to 7 and a thermoplastic resin.

9. A foamed molded article obtained by using the thermally expandable microcapsules according to any one of claims 1 to 7 or the expandable masterbatch according to claim 8.

10. Hollow particles obtained by thermally expanding the thermally expandable microcapsules according to any one of claims 1 to 7, in which a black material is attached to or partly embedded in the outer surface of a shell containing a polymer compound.

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