Thermally expandable microcapsules

Abstract

This invention provides thermally expandable microcapsules that achieve both excellent foaming properties and blackness, a foaming masterbatch using the thermally expandable microcapsules, a foamed molded body, and hollow particles. The invention relates to a thermally expandable microcapsule containing a volatile expanding agent as a core agent within a shell. The shell contains a black material and a polymer compound. In the cross-section of the shell, when the thickness from the outer surface to the inner surface is set to 0-100%, at least 50% of the black material is present in the region within 15% from the outer surface.

Description

Technical Field

[0001] This invention relates to thermally expandable microcapsules that can achieve both excellent foaming properties and blackness, foaming masterbatches using the thermally expandable microcapsules, foamed molded articles, and hollow particles. Background Technology

[0002] Thermally expandable microcapsules are used in a wide range of applications as design-enhancing agents and lightweight agents, and are also used in coatings for lightweight purposes, such as foaming inks and wallpapers.

[0003] Thermally expandable microcapsules, which contain a volatile expander that becomes gaseous at temperatures below the softening point of the shell polymer, are well known as such microcapsules.

[0004] As such thermally expandable microcapsules, for example, Patent Document 1 discloses thermally expandable microcapsules containing carbon black as a black material inside the shell.

[0005] In addition, Patent Document 2 discloses thermally expandable microcapsules containing carbon black as a black material and polyvinyl butyral as a dispersant inside the shell.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2021 / 221160

[0009] Patent Document 2: International Publication No. 2022 / 230994 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the thermally expandable microcapsules described in Patent Documents 1 and 2 have the problem of increased blackness but decreased foaming performance. In particular, when the shell of the thermally expandable microcapsules becomes thinner after foaming, the black material inside the shell becomes the starting point for core leakage, resulting in the thermally expandable microcapsules not being able to expand fully.

[0012] The purpose of this invention is to provide thermally expandable microcapsules that can achieve both excellent foaming properties and blackness, foaming masterbatches using the thermally expandable microcapsules, foamed molded articles, and hollow particles.

[0013] Methods for solving problems

[0014] This disclosure 1 relates to a thermally expandable microcapsule containing a volatile expanding agent as a core agent within a shell. The shell contains a black material and a polymer compound. In the cross-section of the shell, when the thickness from the outer surface to the inner surface is set to 0 to 100%, more than 50% of the black material is present in a region within 15% from the outer surface.

[0015] This disclosure 2 relates to the thermally expandable microcapsules described in this disclosure 1, wherein the black material is selected from at least one of carbon-based black pigments, oxide-based black pigments, and nitride-based black pigments.

[0016] This disclosure 3 relates to the thermally expandable microcapsules described in disclosure 1 or 2, wherein the content of the aforementioned black material is 0.1% by weight or more and 20% by weight or less relative to the total thermally expandable microcapsule.

[0017] This disclosure 4 relates to thermally expandable microcapsules described in any one of disclosures 1 to 3, wherein the primary average particle size of the black material is 10 nm or more and 80 nm or less.

[0018] This disclosure 5 relates to the thermally expandable microcapsules described in disclosure 2, wherein the carbon-based black pigment is carbon black.

[0019] This disclosure 6 relates to thermally expandable microcapsules described in any one of disclosures 1 to 5, wherein more than 70 percent of the aforementioned black material is present in a region within 15 percent of the outer surface.

[0020] This disclosure 7 relates to thermally expandable microcapsules as described in any one of disclosures 1 to 6, wherein more than 30% of the aforementioned black material is present in a region within 10% from the outer surface.

[0021] This disclosure 8 relates to a foaming masterbatch containing thermally expandable microcapsules and a thermoplastic resin as described in any one of disclosures 1 to 7.

[0022] This disclosure 9 relates to a foamed molded article made using thermally expandable microcapsules as described in any one of disclosures 1 to 7 or a foaming masterbatch as described in disclosure 8.

[0023] This disclosure 10 relates to a hollow particle which is formed by thermally expanding a thermally expandable microcapsule as described in any one of disclosures 1 to 7, wherein a black material is attached to the outer surface of the shell containing a polymer compound or a portion of the black material is embedded therein.

[0024] The present invention will now be described in detail.

[0025] The shell constituting the thermally expandable microcapsule, as one embodiment of the present invention, contains a black material and a polymer compound. In the cross-section of the shell, when the thickness from the outer surface to the inner surface is set to 0-100%, at least 50% of the black material is present in a region within 15% of the outer surface. By ensuring that at least 50% of the black material is present in the region within 15% of the outer surface, excellent blackness and foaming properties can be achieved. In particular, when the shell thins after the thermally expandable microcapsule foams, it prevents the black material present inside the shell from becoming the starting point for core leakage, allowing it to expand sufficiently.

[0026] It should be noted that the aforementioned black material appears black by absorbing all light rays in sunlight, including the visible light region. While typical black pigments absorb light in the visible light region (approximately 380–780 nm) to appear black, they also absorb light in the near-infrared region, including wavelengths from 800–1,400 nm, which contribute significantly to heat.

[0027] Furthermore, when determining whether 50% or more of the black material "exists in the area within 15% from the outer surface," the percentage (%) of "50% or more of the black material existing from the outer surface" is measured. If the measured value includes a decimal point, all decimal places are rounded up for determination (the same applies to preferred ranges). For example, if the measured value is 15.5%, the decimal places are rounded up to "16%" for determination.

[0028] Furthermore, the percentage (%) of "more than 70% of black material", "more than 30% of black material", and "more than 80% of black material" from the outer surface mentioned later shall be treated in the same way as the case of "more than 50% of black material".

[0029] In this invention, preferably, more than 50% of the aforementioned black material is present in a region of 13% or less from the outer surface, and more preferably in a region of 11% or less.

[0030] It should be noted that there is no particular limitation on the lower limit related to the area from the outer surface that is present in more than 50% of the aforementioned black material, but it is preferably 1%.

[0031] In this invention, it is preferable that 70% or more of the aforementioned black material is present in a region of 15% or less from the outer surface, and more preferably in a region of 12% or less. It should be noted that there is no particular limitation on the lower limit related to the region of 70% or more of the aforementioned black material present from the outer surface, but it is preferably 1%.

[0032] Furthermore, it is preferable that at least 30% of the aforementioned black material is present in a region of 10% or less from the outer surface, and more preferably in a region of 5% or less. It should be noted that there is no particular limitation on the lower limit related to the region from the outer surface where at least 30% of the aforementioned black material is present, but 1% is preferred.

[0033] Furthermore, in this invention, it is preferable that at least 80% of the aforementioned black material is present in the region within 18% from the outer surface.

[0034] The percentage of the black material present at 50% or more, starting from the outer surface, can be determined as follows (the same applies to the percentage of the black material present at 70% or more, and 30% or more, starting from the outer surface).

[0035] First, thermally expandable microcapsules were added to an embedding resin (e.g., Oken Epok 812, manufactured by Oken Shoji Co., Ltd.) at a content of 3% by weight to disperse them, thus preparing a thermally expandable microcapsule embedding resin. Thin films were fabricated from the obtained embedding resin using a microtome (EM UC7, manufactured by LEICA Co., Ltd.). When observed using a transmission electron microscope (ARM-200F, manufactured by NEC Corporation), cross-sectional images of the shells of any portion of the thermally expandable microcapsules with the largest diameter were taken.

[0036] Next, image analysis was performed on the captured cross-sectional photographs to obtain images of the extracted black material, thermally expandable microcapsules, and inner surface (shell / core interface) (images of extracted thermally expandable microcapsules). Image analysis was performed using the 3D image analysis software Dragonfly (made by Object Research Systems) and the open-source image analysis software Fiji (ImageJ). For the cross-sectional images, Dragonfly's deep learning algorithm (U-Net) was used to extract the black material through image segmentation (recognition). Additionally, Fiji was used to extract the thermally expandable microcapsules and inner surface (shell / core interface) through binarization processing for the cross-sectional images.

[0037] Then, a distance map was performed on the extracted images of the thermally expandable microcapsules to obtain a distance map image from the outer surface. After performing Image Calculator on the distance map image and the extracted inner surface image, a Histogram was performed to obtain the distance distribution data from the outer surface to the inner surface. The average value of this distance distribution was taken as the shell thickness. Additionally, after performing Image Calculator on the distance map image and the extracted black material image, Analyze Particles was performed to obtain the distance data of the black material from the outer surface. The average value of the distance data in each region of the black material was taken as the distance of each black material from the outer surface.

[0038] Then, the location of each black material from the outer surface of the shell is calculated according to the following formula.

[0039] Presence of black material from the outer surface (%) = Distance of black material from the outer surface (pixel) / Shell thickness (pixel) × 100

[0040] Then, in the distribution of the black material's presence locations from the outer surface, the black material's presence locations from the outer surface with a cumulative frequency of 50% (or 70%, 30%) are taken as the regions (% values) from the outer surface.

[0041] It should be noted that, in this invention, the total amount of black material existing inside the shell (where part or all of the black material is embedded within the shell) is defined as "100%". Black material adhering to the outer or inner surface of the thermally expandable microcapsules is not counted as black material existing in a specific percentage area from the outer surface. In addition, "outer surface" refers to the outer surface of the shell.

[0042] As a method for ensuring that at least 50% of the aforementioned black material exists in the region within 15% from the outer surface (the same applies to methods for ensuring that at least 70% and at least 30% of the black material exists in the region within a specified range from the outer surface), adjustments can be made in the following ways: preparing a black material dispersion by mixing the black material, dispersant, dispersing aid, and medium, and then mixing it with an aqueous dispersion medium or an oily mixture; changing the composition and amount of the black material (type, primary average particle size), dispersant, dispersing aid, and medium; and adjusting the preparation time when preparing a black material dispersion by mixing the black material, dispersant, dispersing aid, and medium. In particular, by further adjusting the black material dispersion by mixing the aforementioned black material, dispersant, dispersing aid, and medium (a substance identical to the monomer), the presence position of the aforementioned black material can be appropriately adjusted.

[0043] The preferred lower limit for the OD value of the aforementioned black material is 1.5, and the preferred upper limit is 5.0. By setting it within the above range, a black coating film and a black matrix that balance high opacity and deep blackness can be obtained.

[0044] The OD value of the aforementioned black material refers to the OD value obtained when measuring an acrylic resin (coating thickness 1 μm) containing 50% by weight of the aforementioned black material.

[0045] It should be noted that, in this specification, optical density (OD value) refers to the value when the incident light intensity of the optical density changing element is set to I0 and the transmitted light intensity is set to I... T When, X = -log(I) T The value X is represented by / I0).

[0046] It should be noted that optical density (OD value) can be measured using a colorimeter, Macbeth density meter, etc.

[0047] Examples of black materials include black pigments, black dyes, and black conductive polymers. Among these, black pigments are preferred.

[0048] In addition to inorganic black pigments such as carbon-based black pigments, oxide-based black pigments, and nitride-based black pigments, organic black pigments can also be cited as examples of the aforementioned black pigments. Among them, at least one selected from carbon-based black pigments, oxide-based black pigments, and nitride-based black pigments is preferred.

[0049] Examples of carbon-based black pigments include carbon black, graphite, activated carbon, graphene, and carbon nanotubes. Among these, carbon black is preferred.

[0050] In addition to titanium black, iron oxide, magnetite, and cuprous oxide (copper monoxide), other examples of oxide-based black pigments include composite oxide black pigments with copper and chromium, copper and manganese, copper and iron and manganese, and cobalt, chromium and iron as the main metal components.

[0051] Examples of nitride-based black pigments include zirconium nitride.

[0052] Examples of organic black pigments include aniline black (CI Pigment Black 1).

[0053] In addition to its excellent heat resistance, carbon black is preferred in terms of its excellent dispersibility in resin and its ability to impart a homogeneous black color.

[0054] Furthermore, the black pigment described above is preferably a black pigment having aromatic functional groups. By using the aforementioned black pigment having aromatic functional groups, the aromatic functional groups of the black pigment interact with the aromatic groups of compounds containing aromatic groups and nitrogen atoms within the molecule, thereby improving the dispersibility of the black pigment and enhancing its blackness.

[0055] Examples of black pigments with aromatic functional groups include carbon black and carbon nanotubes (both of which have aromatic functional groups).

[0056] Examples of black dyes include inorganic black dyes and organic black dyes. Among them, organic black dyes are preferred.

[0057] Metal complex salt azo dyes can be cited as examples of the aforementioned inorganic black dyes.

[0058] Examples of the aforementioned metal complex salt azo black dyes include NeoSuper Black C-832 (trade name Solvent Black 27, manufactured by Central Synthetic Chemicals).

[0059] Examples of organic black dyes include: diazo black dyes, azine black dyes, phthalocyanine black dyes, anthraquinone black dyes, and indigo black dyes.

[0060] Examples of the aforementioned diazo-based black dyes include Chuo Sudan Black 141 (trade name SolventBlack 3, manufactured by Central Synthetic Chemicals).

[0061] Examples of azine-based black dyes include ChuoBlack F5 (trade name Solvent Black 7, manufactured by Central Synthetic Chemicals Co., Ltd.).

[0062] Examples of the aforementioned black conductive polymers include: polythiophene, polydopamine, polypyrrole, polyaniline, polyphenylene oxide, polyphenylene, polyacetylene, polyquinoxaline, polyoxadiazole, polybenzothiadiazole, and polymers having multiple of these conductive backbones. Among these, polythiophene and its derivatives are preferred, and poly(3,4-ethylenedioxythiophene) [PEDOT], poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) [PEDOT / PSS], and polythiophene-thiophene are particularly preferred.

[0063] Among the aforementioned black materials, particulate black materials (black particles) are preferred.

[0064] As for the aforementioned black microparticles, the number-average particle size (primary average particle size) of the primary particles is preferably 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 setting them within the above range, the black microparticles are dispersed in the resin, and the color tone (black) becomes uniform.

[0065] The aforementioned average particle size can be determined by observation using a transmission electron microscope (TEM).

[0066] The preferred lower limit of the content of the aforementioned black material relative to the total thermally expandable microcapsules is 0.1% by weight, and the preferred upper limit is 20% by weight. By setting it to 0.1% by weight or more, the fusion of the thermally expandable microcapsules in the resin during molding can be suppressed. By setting it to 20% by weight or less, the shell's resistance to melt mixing during molding can be improved, and further, the light-blocking properties and appearance properties can be improved. A more preferred lower limit is 0.3% by weight, a more preferred lower limit is 0.5% by weight, a particularly preferred lower limit is 1% by weight, the most preferred lower limit is 3% by weight, a more preferred upper limit is 15% by weight, a more preferred upper limit is 10% by weight, and an even more preferred upper limit is 7% by weight.

[0067] It should be noted that regarding the content of the black material, for example, if thermally expandable microcapsules are heated to 600°C at a rate of 10°C / min under a nitrogen atmosphere and held for 10 minutes, then cooled to 400°C at a rate of 10°C / min and held for 10 minutes, and then the atmosphere is switched to air, and the temperature is raised to 1000°C under air and held at 1000°C for 10 minutes, the weight reduction at the 400°C to 1000°C temperature range can be used to determine the content.

[0068] For the aforementioned black material, the preferred specific surface area is 500 m². 2 / g or less, more preferably 300m 2 / g or less. There is no particular limitation on the lower limit of specific surface area, but from the viewpoint of improving blackness, 1m² is preferred. 2 / g or more, preferably 5m 2 / g or more. By setting it within the above range, the black material is dispersed in the resin, and the hue (black) becomes uniform.

[0069] The specific surface area can be determined as follows: the adsorption isotherm of nitrogen is measured using a surface area / pore size analyzer (NOVA4200e, Quantachrome Instruments). Based on the measurement results, the specific surface area of ​​the black material is calculated according to the BET method.

[0070] The shell of the thermally expandable microcapsule, which is one embodiment of the present invention, contains a polymer compound.

[0071] The polymer compound described above is preferably a polymer of a monomer composition containing a nitrile monomer and a monomer having a carboxyl group.

[0072] The aforementioned nitrile monomers are not particularly limited, and examples include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaric acid, or mixtures thereof. Acrylonitrile and methacrylonitrile are particularly preferred. They can be used alone or in combination of two or more.

[0073] The preferred lower limit for the content of nitrile monomers in the above monomer composition is 40% by weight, and the preferred upper limit is 90% by weight. Setting it to 40% by weight or more improves the gas barrier properties of the shell and increases the foaming ratio. Setting it to 90% by weight or less improves heat resistance and prevents yellowing. A more preferred lower limit is 50% by weight, and a more preferred upper limit is 80% by weight.

[0074] As the aforementioned monomers containing carboxyl groups, for example, free radical polymerizable unsaturated carboxylic acid monomers having carboxyl groups and having 3 to 8 carbon atoms can be used.

[0075] Specifically, examples include unsaturated dicarboxylic acids, their anhydrides or monoesters of unsaturated dicarboxylic acids, and their derivatives, which can be used alone or in combination of two or more.

[0076] Examples of unsaturated dicarboxylic acids include: acrylic acid, methacrylic acid, ethylacrylic acid, crotonic acid, cinnamic acid, maleic acid, itaconic acid, fumaric acid, citraconic acid, chloromaleic acid, etc.

[0077] Examples of monoesters of the aforementioned unsaturated dicarboxylic acids include: monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconic acid, monoethyl itaconic acid, and monobutyl itaconic acid.

[0078] Among them, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid are particularly preferred.

[0079] The preferred lower limit for the content of the carboxyl-containing monomer in the above monomer composition is 5% by weight, and the preferred upper limit is 50% by weight. By setting it to 5% by weight or more, the maximum foaming temperature can be increased, and by setting it to 50% by weight or less, the foaming ratio can be increased. A more preferred lower limit is 10% by weight, and a more preferred upper limit is 30% by weight.

[0080] The above monomer composition preferably contains a crosslinking monomer having two or more double bonds within the molecule. This crosslinking monomer acts as a crosslinking agent. By containing this crosslinking monomer, the shell strength is enhanced, and the capsule wall is less prone to rupture during thermal expansion.

[0081] As crosslinking monomers, examples include monomers having two or more free radical polymerizable double bonds, such as divinylbenzene, di(meth)acrylate, and (meth)acrylate with three or more functions.

[0082] Examples of the aforementioned di(meth)acrylates 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, glycerol di(meth)acrylate, trimethylolpropane di(meth)acrylate, and dimethyloltricyclodecane di(meth)acrylate. Furthermore, di(meth)acrylates of polyethylene glycol with a weight-average molecular weight of 200 to 600 can also be used.

[0083] Examples of trifunctional (meth)acrylates include: trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and triallyl formaldehyde tri(meth)acrylate. Examples of quadrifunctional or higher (meth)acrylates include pentaerythritol tetra(meth)acrylate and dipentaerythritol hexa(meth)acrylate.

[0084] Among them, trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and difunctional (meth)acrylates such as polyethylene glycol are cross-linked relatively uniformly in a shell mainly composed of acrylonitrile.

[0085] The preferred lower limit of the content of the crosslinking monomer in the above monomer composition is 0.1% by weight, and the preferred upper limit is 1.0% by weight. By making the content of the crosslinking monomer 0.1% by weight or more, its effect as a crosslinking agent can be fully exerted, and by making the content of the crosslinking monomer 1.0% by weight or less, the foaming ratio of the thermally expandable microcapsules can be improved. The more preferred lower limit of the content of the crosslinking monomer is 0.15% by weight, and the more preferred upper limit is 0.9% by weight.

[0086] The monomer composition described above preferably contains monomers other than the aforementioned nitrile monomers, monomers with carboxyl groups, and crosslinking monomers. By containing the aforementioned other monomers, the compatibility of the thermally expandable microcapsules with matrix resins such as thermoplastic resins becomes good, and the foamed articles using these thermally expandable microcapsules have excellent appearance.

[0087] Other monomers mentioned above, besides (meth)acrylates, include vinyl chloride, vinylidene chloride, vinyl acetate, styrene, and other vinyl monomers. They can be used alone or in combination of two or more. Among these, (meth)acrylates are preferred, and particularly preferred are alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate, or methacrylates containing alicyclic, aromatic, or heterocyclic rings such as cyclohexyl methacrylate, benzyl methacrylate, and isobornyl methacrylate.

[0088] The preferred lower limit for the content of the other monomers in the above-described monomer composition is 0.1% by weight, and the preferred upper limit is 25% by weight. By setting the content of the other monomers to 0.1% by weight or more, the dispersibility of the composition using thermally expandable microcapsules can be improved; by setting it to 25% by weight or less, the gas barrier properties of the capsule wall can be improved, and the thermal expansion properties can be enhanced. The more preferred lower limit for the content of the other monomers is 0.3% by weight, and the more preferred upper limit is 22% by weight.

[0089] In addition to the aforementioned nitrile monomers, monomers with carboxyl groups, crosslinking monomers, and other monomers, the monomer compositions may also contain thermosetting resins.

[0090] Examples of thermosetting resins include epoxy resins, phenolic resins, melamine resins, urea resins, polyimide resins, and bismaleimide resins. Among these, epoxy resins and phenolic resins are preferred.

[0091] The epoxy resins mentioned above are not particularly limited, and examples include: bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol linear phenolic type epoxy resin, cresol linear phenolic type epoxy resin, dicyclopentadiene type epoxy resin, glycidylamine type epoxy resin, etc.

[0092] Examples of phenolic resins include linear phenolic resins, methyl phenolic resins, and benzyl ether phenolic resins. Among these, linear phenolic resins are preferred.

[0093] The aforementioned thermosetting resin preferably has two or more functional groups that react with carboxyl groups in one molecule. Having two or more of these carboxyl-reactive functional groups makes the curing properties of the thermosetting resin more stable. In particular, when the aforementioned monomer composition contains a monomer with a carboxyl group, the carboxyl group bonds more firmly to the thermosetting resin through the heat generated during foaming, significantly improving heat resistance and durability.

[0094] It should be noted that the above-mentioned thermosetting resins preferably do not have double bonds that are capable of free radical polymerization.

[0095] Examples of functional groups that react with the carboxyl group include glycidyl, phenolic, hydroxymethyl, and amino groups. Glycidyl is preferred. The same functional group or two or more functional groups can be used as the functional group that reacts with the carboxyl group.

[0096] The preferred lower limit of the content of the thermosetting resin in the above monomer composition is 0.01% by weight, and the preferred upper limit is 30% by weight.

[0097] By making the content of the above-mentioned thermosetting resin 0.01% by weight or more, the compressibility during heat foaming can be improved. By making the content of the above-mentioned thermosetting resin 30% by weight or less, the gas barrier properties of the shell are improved and the foaming properties are enhanced. A more preferred lower limit is 0.1% by weight, and a more preferred upper limit is 15% by weight.

[0098] To polymerize the above monomers, a polymerization initiator is added to the above monomer composition.

[0099] As polymerization initiators, suitable materials include, for example, dialkyl peroxides, diacyl peroxides, peroxide esters, peroxydicarbonates, azo compounds, etc.

[0100] Specific examples include: dialkyl peroxides such as methyl ethyl peroxide, di-tert-butyl peroxide, and diisopropylbenzene peroxide; diacyl peroxides such as isobutyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and bis(3,5,5-trimethylhexanoyl) peroxide.

[0101] Other examples include: tert-butyl peroxypentanoate, tert-hexyl peroxypentanoate, tert-butyl peroxyneodecanate, tert-hexyl peroxyneodecanate, 1-cyclohexyl-1-methylethyl peroxyneodecanate, and 1,1,3,3-tetramethylbutyl peroxyneodecanate.

[0102] Other examples include: cumyl peroxynedecanoate, (α,α-bis-neodecanoyl peroxy)diisopropylbenzene, etc.; bis(4-tert-butylcyclohexyl)dicarbonate peroxide, di-n-propyl dicarbonate peroxide, diisopropyl dicarbonate, etc.

[0103] In addition, examples include: di(2-ethylethyl peroxide) dicarbonate, dimethoxybutyl peroxide dicarbonate, di(3-methyl-3-methoxybutyl peroxide) dicarbonate, and other peroxide dicarbonates.

[0104] In addition, examples include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylpentanitrile), 2,2'-azobis(2,4-dimethylpentanitrile), and 1,1'-azobis(1-cyclohexanenitrile).

[0105] The preferred lower limit of the weight average molecular weight of the polymer compound constituting the aforementioned shell is 100,000, and the preferred upper limit is 2,000,000. If it is less than 100,000, the strength of the shell may decrease in some cases; if it exceeds 2,000,000, the strength of the shell may become excessively high, resulting in a decrease in expansion ratio in some cases.

[0106] The shell of the thermally expandable microcapsule according to one embodiment of the present invention preferably further contains at least one inorganic compound selected from Si-based compounds and Mg-based compounds.

[0107] By containing the aforementioned inorganic compound, welding between thermally expandable microcapsules in the resin during molding can be suppressed.

[0108] It should be noted that the aforementioned inorganic compound is different from the aforementioned black material.

[0109] As the aforementioned Si-based compounds and Mg-based compounds, preferred are compounds containing silicon and magnesium oxides, silicon and magnesium hydroxides, silicon and magnesium carbonates, or silicon and magnesium bicarbonates.

[0110] These Si-based compounds and Mg-based compounds may be used alone or in combination of two or more.

[0111] Examples of the aforementioned Si-based compounds include, in addition to colloidal silica, silicic acid sol, etc., No. 3 water glass (Japanese: 3号水ガラス), sodium orthosilicate, sodium metasilicate, etc. Among these, colloidal silica is preferred.

[0112] Examples of the aforementioned Mg-based compounds include magnesium oxide, magnesium hydroxide, magnesium oxyhydroxide (Japanese: 水酸化酸化マグネシウム), hydrotalcite, dihydrotalcite (Japanese: ジハイドロタルサイト), magnesium carbonate, basic magnesium carbonate, magnesium calcium carbonate, magnesium phosphate, magnesium hydrogen phosphate, magnesium pyrophosphate, magnesium borate, etc. Among these, magnesium hydroxide is preferred.

[0113] As the aforementioned inorganic compound, for example, calcium phosphate, aluminum hydroxide, iron hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, etc. may also be added. In addition, inorganic salts such as sodium chloride and sodium sulfate, alkali metal nitrites, stannous chloride, tin chloride, potassium dichromate, etc. may also be added as needed.

[0114] As the aforementioned inorganic compound, a particulate inorganic compound is preferred.

[0115] When the aforementioned inorganic compound is in particulate form, the primary particle size is preferably 0.5 μm or less, more preferably 5 to 100 nm (0.1 μm). By setting it within the above range, the fusion of thermally expanding microcapsules in the resin during molding can be suppressed. The aforementioned primary particle size can be measured by observation using a transmission electron microscope (ARM-200F, manufactured by Nippon Egis Corporation).

[0116] The content of the aforementioned inorganic compound is 0.01% by weight relative to the total thermally expandable microcapsules, with a preferred upper limit of 7% by weight. By setting it to 0.01% by weight or more, the fusion of the thermally expandable microcapsules in the resin during molding can be suppressed. By setting it to 7% by weight or less, the resin dispersibility during molding can be further improved. A more preferred lower limit is 0.3% by weight, and a more preferred upper limit is 5% by weight.

[0117] It should be noted that the content of the above-mentioned inorganic compounds can be calculated based on the weight of the monomer composition, volatile expanding agent and black material that form the thermally expandable microcapsules.

[0118] The weight ratio of the inorganic compound to the aforementioned black material (inorganic compound / black material) is preferably 0.001 to 400. Setting it to 0.001 or higher suppresses the fusion of thermally expanding microcapsules in the resin during molding. Setting it to 400 or lower further improves resin dispersibility during molding, and further improves opacity and appearance properties. A more preferred lower limit is 0.3, a more preferred lower limit is 0.5, a more preferred upper limit is 300, a more preferred upper limit is 200, a more preferred upper limit is 100, a particularly preferred upper limit is 90, and an especially preferred upper limit is 80.

[0119] The aforementioned shell may contain metal cations. By including metal cations in the shell, and when carboxyl groups are included in the copolymer constituting the shell, the metal cations react with the carboxyl groups, causing ionic crosslinking of the copolymer. This improves heat resistance, enabling the production of thermally expandable microcapsules that will not rupture or shrink even after prolonged exposure to high temperatures. Furthermore, the elastic modulus of the shell does not easily decrease even in high-temperature regions, thus preventing rupture and shrinkage of the thermally expandable microcapsules even during molding processes such as compounding, calendering, extrusion, and injection molding under strong shear forces.

[0120] It should be noted that the aforementioned ionic crosslinking refers to the formation of crosslinks between free carboxyl groups existing as side chains of the copolymer. It should also be noted that the number of carboxyl groups per monovalent metal cation varies depending on the type of metal.

[0121] The metal cations used are not particularly limited as long as they react with the carboxyl groups of the copolymer to cause ionic crosslinking of the copolymer. Examples include ions of Li, Na, K, Zn, Mg, Ca, Ba, Sr, Mn, Al, Ti, Ru, Fe, Ni, Cu, Cs, Sn, Cr, and Pb. They can be used alone or in combination of two or more. Among them, Ca, Zn, and Al ions are preferred, and Zn ions are particularly suitable.

[0122] It should be noted that there is no particular limitation on the combination of two or more of the above-mentioned metal cations, but it is preferable to use alkali metal ions in combination with metal cations other than the alkali metals mentioned above. By having the ions of the above-mentioned alkali metals, functional groups such as carboxyl groups are activated, which can promote the reaction between metal cations other than the above-mentioned alkali metals and the carboxyl groups of the above-mentioned copolymers.

[0123] Examples of alkali metals mentioned above include Na, K, and Li.

[0124] The shell may further contain stabilizers, ultraviolet absorbers, antioxidants, antistatic agents, flame retardants, silane coupling agents, pigments, etc., as needed.

[0125] As one embodiment of the present invention, the thermally expandable microcapsule contains a volatile expanding agent as a core agent within the aforementioned shell.

[0126] The aforementioned volatile expanding agent is a gaseous substance that becomes gaseous at temperatures below the softening point of the polymer constituting the shell, and is suitable as a low-boiling-point organic solvent.

[0127] Examples of volatile expanding agents include: ethane, ethylene, propane, propylene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, petroleum ether, isooctane, octane, decane, isododecane, dodecane, hexadecane, and other low molecular weight hydrocarbons.

[0128] In addition, examples include: chlorofluorocarbons such as CCl3F, CCl2F2, CClF3, and CClF2-CClF2; and tetraalkylsilanes such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyln-propylsilane. Among these, isobutane, n-butane, n-pentane, isopentane, n-hexane, isooctane, isododecane, and mixtures thereof are preferred. These volatile expanding agents can be used alone or in combination of two or more.

[0129] In addition, as a volatile expanding agent, a thermally decomposable compound that becomes gaseous through thermal decomposition by heating can be used.

[0130] Regarding the thermally expandable microcapsules as an embodiment of the present invention, a low-boiling-point hydrocarbon with 5 or fewer carbon atoms is preferably used as the volatile expanding agent. By using such a hydrocarbon, thermally expandable microcapsules with high foaming ratio and rapid foaming initiation can be produced.

[0131] In addition, as a volatile expanding agent, a thermally decomposable compound that becomes gaseous through thermal decomposition by heating can be used.

[0132] In one embodiment of the present invention, the optical density (OD value) of the thermally expandable microcapsules is preferably 0.5 or higher. By setting it to 0.5 or higher, a black coating or black matrix that balances high opacity and deep blackness can be obtained. A more preferred lower limit is 0.8, and a more preferred upper limit is 1.6.

[0133] It should be noted that optical density (OD value) can be measured using a Macbeth concentration meter or similar device.

[0134] As an embodiment of the present invention, the preferred lower limit of the maximum foaming temperature (Tmax) of the thermally expandable microcapsules is 170°C. By setting it to 170°C or higher, the heat resistance is increased, and when the composition containing the thermally expandable microcapsules is applied in high-temperature areas, the rupture and shrinkage of the thermally expandable microcapsules can be prevented. In addition, the 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 more preferred upper limit is 240°C.

[0135] It should be noted that, 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 microcapsules are heated from room temperature while their diameter is measured.

[0136] As an embodiment of the present invention, the preferred lower limit of the maximum displacement (Dmax) of the thermally expandable microcapsules, as determined by thermomechanical analysis, is 10 μm. If it is 10 μm or more, the foaming ratio is increased, and the desired foaming performance can be obtained. A more preferred lower limit is 20 μm, a further preferred lower limit is 100 μm, and an even more preferred lower limit is 300 μm. In addition, the preferred upper limit of the above-mentioned maximum displacement is 2000 μm, a more preferred upper limit is 1800 μm, and a further preferred upper limit is 1500 μm.

[0137] It should be noted that the above maximum displacement refers to the value when the diameter of the specified amount of thermally expandable microcapsules reaches its maximum while being heated from room temperature and their diameter is measured.

[0138] Furthermore, the preferred upper limit for the foaming start temperature (Ts) is 185°C. By setting it below 185°C, foaming becomes easier, and the desired expansion ratio can be achieved. The preferred lower limit is 130°C, and the more preferred upper limit is 180°C.

[0139] As an embodiment of the present invention, the preferred lower limit of the volume average particle size of the thermally expandable microcapsules is 5 μm, and the preferred upper limit is 45 μm. If it is 5 μm or more, the resulting molded article has moderate bubbles, and therefore the foaming ratio is sufficient; if it is 45 μm or less, the resulting coating has moderate bubbles, and therefore the appearance is good. A more preferred lower limit is 7 μm, and a more preferred upper limit is 35 μm.

[0140] The volume-average particle size of the aforementioned thermally expandable microcapsules can be determined using a particle size distribution measuring device based on laser diffraction and scattering.

[0141] Furthermore, the thickness of the shell constituting the thermally expandable microcapsule, as an embodiment of the present invention, is preferably 2 μm or more and 6 μm or less. The thickness of the shell can be measured simultaneously when measuring the area (% value) from the outer surface where at least 50% of the black material exists.

[0142] The method for manufacturing thermally expandable microcapsules, which is one embodiment of the present invention, is not particularly limited. For example, it can be manufactured by performing the following steps: a step of preparing a black material dispersion containing a black material, a pigment derivative, a dispersant, and a medium; a step of preparing an aqueous dispersion medium containing an inorganic compound; a step of mixing an oily mixture containing a monomer composition and a volatile expanding agent with the black material dispersion and dispersing it in an aqueous dispersion medium; and a step of polymerizing the aforementioned monomers.

[0143] As the above-mentioned monomer composition, monomer compositions containing the above-mentioned nitrile monomers, monomers having carboxyl groups, crosslinking monomers, and other monomers can be used.

[0144] In manufacturing thermally expandable microcapsules as one embodiment of the present invention, a step is performed to prepare a black material dispersion containing a black material, a pigment derivative, a dispersant, and a polymerizable monomer (medium). Specifically, for example, the black material, dispersant, pigment derivative, polymerizable monomer, and a desired polymerization initiator are added to a container, and dispersion is performed using a disperser, thereby preparing a black material dispersion containing the black material, pigment derivative, dispersant, and polymerizable monomer.

[0145] The above-mentioned dispersant has the function of inhibiting the aggregation of black materials and improving dispersion stability.

[0146] The above dispersant usually comprises: a unit that easily adsorbs to the black material and a unit that easily adsorbs to substances other than the black material represented by polymerizable monomers (has affinity for substances other than the black material). Each unit may be included in one structure of the dispersant. Alternatively, polymers containing each unit may be condensed (chemically bonded). In addition, monomers forming each unit may also be copolymerized. Alternatively, the dispersant may be produced by methods other than these, and may also be produced by combining these methods.

[0147] The above dispersant generally preferably comprises: an adsorption moiety that easily adsorbs to black materials and pigments, and a side chain moiety solvated with a solvent represented by a polymerizable monomer.

[0148] Examples of the above adsorption moiety include: moieties containing polar functional groups such as a moiety containing an amino group, a moiety containing an imino group, a moiety containing a carboxyl group, a moiety containing a sulfo group, and a moiety containing a hydroxyl group, or moieties containing an aromatic ring, and the like.

[0149] Examples of the above side chain moiety include: a moiety containing a polyalkylene group, a moiety containing a polyoxyalkylene group, a moiety containing a polyether group, a moiety containing a polyester group, a moiety containing a polyamide group, a moiety containing a poly(meth)acrylic acid group, a moiety containing a polyurethane group, and the like.

[0150] Examples of the above dispersant include: polyacrylic-based, polyether-based, polyurethane-based, polyamide-based, polyimide-based, poly(meth)acrylic acid, polycarboxylic acid-based such as polymaleic acid (anhydride), polyamine-based, and polyester-based dispersants that have poly(meth)acrylate, polylactone, polyalkylene oxide, etc. as a main chain or side chains, and dispersants having quaternary ammonium salts introduced into a part thereof. These dispersants may be used alone or in combination of two or more.

[0151] Examples of the above polyether-based dispersant include polyoxyalkylene, polyether phosphate amine, polyether phosphate, polyether ester amine, and the like.

[0152] Examples of the above polyester-based dispersant include polycaprolactone, polylactic acid, and the like.

[0153] Examples of the dispersant obtained by chemically bonding the unit that easily adsorbs to the black material and the unit having affinity for substances other than the black material include: condensation products of polycaprolactone and polyalkyleneimine, condensation products of polycaprolactone and polyallylamine, condensation products of polylactide and polyalkyleneimine, condensation products of polylactide and polyallylamine, and amine salts of polyetherester acid, and the like.

[0154] Commercially available dispersants include, for polyurethane systems, Disperbyk-161, 166, and 167 (BYK-Chemie Japan), and Solsperse 55000 and 76500 (Lubrizol Japan); for polycarboxylate systems, Disperbyk-106, 110, and 111, Solsperse 36000 and 41000, and EFKA-5060 (BASF Japan); and for polyamine systems, Disperbyk-116 and 130, Solsperse 24000, 32000, 33000, 35000, 86000, J200, EFKA-4046, and AJISPER (Ajinomoto Fine-Techno). PB821, PB822, PB824, and PB881; as carboxyl-containing polymer dispersants, examples include FLOWLEN G-700, FLOWLEN G-900, and FLOWLEN GW-1500 manufactured by Kyoei Chemical Co., Ltd.; as polyester dispersants, examples include Solsperse 35000, Solsperse 39000, and T-6000, T-8000E, and T-9100 manufactured by Kawaken Fine Chemicals Co., Ltd.; as polyacrylic acid dispersants, examples include Efka4701, Efka4585, Efka4780 (manufactured by BASF), DISPERBYK-2012 (manufactured by BYK), FLOWLEN DOPA-35, FLOWLEN DOPA-17HF, and FLOWLEN... DOPA-15BHFS (manufactured by Kyoei Co., Ltd.); as a polyether system, examples include DISPARLON 234 and DISPARLON 325 (manufactured by Kusunoki Chemical Co., Ltd.). Among these, from the viewpoint of dispersibility of black materials, Solsperse J200, Solsperse 35000, and Solsperse 39000 are preferred.

[0155] The preferred lower limit of the content of the dispersant relative to the total black material dispersion is 0.01% by weight, and the preferred upper limit is 20% by weight. Setting it to 0.01% by weight or more can suppress the aggregation of the black material. Setting it to 20% by weight or less can suppress the aggregation of the black material caused by the interaction between the dispersants. A more preferred lower limit is 0.1% by weight, a further preferred lower limit is 0.3% by weight, a more preferred upper limit is 15% by weight, a further preferred upper limit is 10% by weight, and an even more preferred upper limit is 5% by weight.

[0156] The aforementioned pigment derivatives (dispersing agents) refer to compounds in which acidic or basic groups are introduced as substituents into pigment molecules. By containing pigment derivatives, they function as dispersing agents, adjusting the dispersibility of black materials and the properties of the resulting thermally expandable microcapsules.

[0157] Examples of pigments that form the matrix of the aforementioned pigment derivatives include: phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, perylene pigments, diketopyrrolopyrrole pigments, azo pigments, benzimidazolinone pigments, dioxazine pigments, quinacridone pigments, and isoindoline pigments.

[0158] Examples of substituents mentioned above include sulfonic acid group, sulfonic acid salt-forming group, sulfonic acid amide group, phthalimide methyl group, amino group, imino group, nitro group, carboxyl group, amide group, hydroxyl group, and phosphate group.

[0159] Preferably, the pigments are derivatives of phthalocyanine pigments, quinacridone pigments, azo pigments, and diketopyrrolopyrrole pigments, and more preferably derivatives selected from at least one of azo pigments and phthalocyanine pigments. By using pigment derivatives having these parent structures, the dispersibility and dispersion stability of black materials can be improved, and further, the foaming properties and blackness when forming thermally expandable microcapsules can be made more excellent.

[0160] The preferred lower limit of the content of the aforementioned pigment derivatives relative to the total black material dispersion is 0.001% by weight, and the preferred upper limit is 20% by weight. Setting it to 0.001% by weight or more can suppress the aggregation of the black material. Setting it to 20% by weight or less can suppress the aggregation of the black material caused by the interaction between the pigment derivatives. A more preferred lower limit is 0.01% by weight, a further preferred lower limit is 0.1% by weight, a more preferred upper limit is 15% by weight, a further preferred upper limit is 10% by weight, and an even more preferred upper limit is 5% by weight.

[0161] The aforementioned black material dispersion contains a medium.

[0162] The medium is not particularly limited as long as it can disperse the black material, but preferably a polymerizable monomer.

[0163] The polymerizable monomers mentioned above are preferably free radical polymerizable monomers, and more preferably nitrile monomers or monomers containing carboxyl groups. It should be noted that the polymerizable monomers mentioned above may be the same as or different from the monomers described above.

[0164] In the manufacture of thermally expandable microcapsules, which is one embodiment of the present invention, a step of preparing an aqueous dispersion medium is performed. As a specific example, an aqueous dispersion medium containing a black material and an inorganic compound is prepared by adding water, an inorganic compound, and a desired auxiliary stabilizer to a polymerization reactor.

[0165] Examples of auxiliary stabilizers mentioned above include the condensation products of diethanolamine and aliphatic dicarboxylic acids, and the condensation products of urea and formaldehyde. Other examples include polyvinylpyrrolidone, polyethylene oxide, polyethyleneimine, tetramethylammonium hydroxide, gelatin, methylcellulose, polyvinyl alcohol, dioctyl sulfosuccinate, sorbitan anhydride, and various emulsifiers.

[0166] In addition to auxiliary stabilizers, condensation products and water-soluble nitrogen compounds can also be added.

[0167] As the condensation product mentioned above, the condensation product of diethanolamine and aliphatic dicarboxylic acid is preferred, and the condensation product of diethanolamine and adipic acid and the condensation product of diethanolamine and itaconic acid are particularly preferred.

[0168] Examples of the aforementioned water-soluble nitrogen compounds include: polyvinylpyrrolidone, polyethyleneimine, polyoxyethylene alkylamine, and poly(meth)acrylate dialkylaminoalkyl esters, represented by poly(dimethylaminoethyl methacrylate) and poly(dimethylaminoethyl methacrylate). Other examples include: poly(dialkylaminoalkyl(meth)acrylamide), represented by poly(dimethylaminopropylacrylamide) and poly(dimethylaminopropylmethacrylamide), polyacrylamide, polycationic acrylamide, polyamine sulfone, and polyallylamine. Polyvinylpyrrolidone is particularly suitable for use among these.

[0169] An aqueous dispersion medium containing the aforementioned inorganic compounds, auxiliary stabilizers, and dispersants as needed is prepared by mixing with deionized water. The pH of the aqueous phase is appropriately determined based on the type of inorganic compound and auxiliary stabilizer used. For example, when using Si-based compounds such as colloidal silica as the inorganic compound, polymerization is carried out using an acidic aqueous dispersion medium. To make the aqueous dispersion medium acidic, an acid such as hydrochloric acid is added as needed to adjust the pH of the system to 3-4. On the other hand, when using Mg-based compounds such as magnesium hydroxide and calcium phosphate as the inorganic compounds, polymerization is carried out using an alkaline aqueous dispersion medium with a pH adjusted to 8-11.

[0170] Next, in the method for manufacturing thermally expandable microcapsules, a step is performed to disperse an oily mixture containing a monomer composition and a volatile expander, as well as a black material dispersion, in an aqueous dispersion medium.

[0171] Specifically, the process involves mixing an oily mixture containing a monomer composition and a volatile expanding agent, along with a dispersion of a black material, and dispersing them in an aqueous dispersion medium. In this step, the monomer composition, volatile expanding agent, and black material dispersion can be added separately to the aqueous dispersion medium to prepare the oily mixture. However, typically, all three are pre-mixed to prepare an oily mixture containing the black material before being added to the aqueous dispersion medium. Alternatively, the oily mixture and aqueous dispersion medium can be prepared in separate containers beforehand, and then mixed while stirring in another container to disperse the oily mixture in the aqueous dispersion medium before adding it to the polymerization reaction vessel. In this step, an inorganic compound can be present on the aqueous dispersion medium side of the interface between the oil droplet and the aqueous dispersion medium, wherein the oil droplet contains the oily mixture containing the black material. As a result, the inorganic compound can be present on the surface of the obtained thermally expandable microcapsules. Furthermore, in this process, the black material exists on the oily mixture side containing the black material at the interface between the oil droplet and the aqueous dispersion medium, wherein the oil droplet contains the oily mixture containing the black material. As a result, in the shell of the obtained thermally expandable microcapsule, when the thickness direction from the outer surface to the inner surface is set to 0 to 100%, more than 50% of the aforementioned black material can be present in the area within 15% from the outer surface.

[0172] It should be noted that, in order to use a polymerization initiator for the polymerization of the above monomers, the polymerization initiator can be added to the above oily mixture containing the black material in advance, or it can be added after the aqueous dispersion medium and the oily mixture containing the black material are stirred and mixed in the polymerization reaction vessel.

[0173] Methods for emulsifying and dispersing the aforementioned oily mixture containing black material in an aqueous dispersion medium at a specified particle size include: stirring using a homogenizer (e.g., manufactured by a special chemical company), and passing it through a static dispersion device such as a pipeline mixer or a component-type static disperser.

[0174] It should be noted that the above-mentioned static dispersion device can be supplied with an aqueous dispersion medium and a polymerizable mixture, or it can be supplied with a pre-mixed and stirred dispersion.

[0175] As one embodiment of the present invention, the thermally expandable microcapsules can be manufactured by performing the following steps: heating the dispersion obtained by the above steps to polymerize the monomers; and cleaning the dispersion. The thermally expandable microcapsules manufactured by this method have a high maximum foaming temperature and excellent heat resistance, and will not crack or shrink even when applied in high-temperature areas.

[0176] Foaming masterbatch containing the above-mentioned thermally expandable microcapsules and thermoplastic resin (base resin) is also one of the inventions.

[0177] The thermoplastic resin used in the above-mentioned base resin is not particularly limited, and thermoplastic resins commonly used in foam molding can be used. Specifically, examples of the above-mentioned thermoplastic resins 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).

[0178] Among these, LDPE, EVA, and EMMA are preferred due to their low melting point and ease of processing. They can be used individually or in combination of two or more.

[0179] The content of the aforementioned thermally expandable microcapsules in the foaming 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 relative to 100 parts by weight of the aforementioned thermoplastic resin.

[0180] There are no particular limitations on the method for manufacturing the aforementioned foaming masterbatch. Examples include: pre-mixing a base resin such as a thermoplastic resin and various additives using a co-rotating twin-screw extruder, heating to a predetermined temperature, adding a foaming agent such as thermally expandable microcapsules, further mixing, and then cutting the resulting mixture into desired sizes using a granulator to produce granules, thus creating the masterbatch. Alternatively, a granulated masterbatch can be manufactured by mixing a base resin such as a thermoplastic resin and raw materials such as thermally expandable microcapsules using an intermittent mixer and then granulating them using a granulator.

[0181] There are no particular limitations on the type of mixing machine mentioned above, as long as it can perform mixing without damaging the thermally expandable microcapsules. Examples include pressure kneaders and Banbury mixers.

[0182] Furthermore, the foamed molded articles obtained using the aforementioned thermally expandable microcapsules and foaming masterbatch are also part of this invention. In particular, the aforementioned thermally expandable microcapsules are also suitable for applications requiring post-processing at high temperatures, thus yielding foamed sheets with high appearance quality such as textured surfaces, suitable for applications such as residential wallpaper.

[0183] Specifically, the above-mentioned thermally expandable microcapsules or foaming masterbatch containing the above-mentioned thermally expandable microcapsules are mixed with a matrix resin and molded to obtain a foamed molded body.

[0184] There are no particular limitations on the forming method for the aforementioned foamed molded articles. Examples include compounding, calendering, extrusion, and injection molding. In the case of injection molding, there are no particular limitations on the process. Examples include the short shot method, in which a portion of resin material is added to the mold and foamed, and the core retraction method, in which the mold is filled with resin material and then opened to the desired foaming degree.

[0185] Another aspect of the present invention relates to a hollow particle formed by thermally expanding the thermally expandable microcapsules of the present invention, wherein a black material is attached to or partially embedded in the outer surface of a shell containing a polymer compound. This other aspect of the present invention exhibits excellent blackness.

[0186] Another embodiment of the hollow particles of the present invention can be produced, for example, by heating the thermally expandable microcapsules of the present invention to cause them to expand thermally. It should be noted that in this other embodiment of the present invention, the shell structure, the black material, and the polymer compound are the same as those of the thermally expandable microcapsules of the present invention, and therefore their description is omitted.

[0187] Invention Effects

[0188] According to the present invention, it is possible to produce thermally expandable microcapsules that achieve both excellent foaming properties and blackness, foaming masterbatches using the thermally expandable microcapsules, foamed molded articles, and hollow particles. Furthermore, according to the present invention, it is possible to produce thermally expandable microcapsules with a small difference in blackness before and after foaming. Detailed Implementation

[0189] The present invention will be described in more detail below with examples, but the present invention is not limited to these examples.

[0190] (Example 1)

[0191] (Preparation of thermally expandable microcapsules)

[0192] Carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Co., Ltd., with a primary average particle size of 24 nm and a specific surface area of ​​110 m²) used as a black material 2 0.13 parts by weight of Solsperse 39000 (polyester-based dispersant, manufactured by Lubrizol Corporation, Japan) as a dispersant [polymeric dispersant] for carbon black, 0.026 parts by weight of Solsperse 5000S (phthalocyanine pigment derivative, manufactured by Lubrizol Corporation, Japan) as a dispersing aid, and 30 parts by weight of methacrylonitrile and 20 parts by weight of acrylonitrile as media were dispersed using a bead mill to obtain a carbon black dispersion.

[0193] 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 reactor. Next, an oily mixture containing the proportions shown in Table 1, 30 parts by weight of volatile expanding agent, 20 parts by weight of methyl methacrylate, 50.2 parts by weight of carbon black dispersion, and polymerization initiators (0.8 parts by weight of 2,2'-azobis(2,4-dimethylpentanones) and 0.6 parts by weight of 2,2'-azobis(2,4-dimethylpentanones)) was added to the aqueous dispersion medium and suspended to prepare a dispersion.

[0194] The obtained dispersion was homogenized and mixed, then placed in a nitrogen-replaced pressure polymerizer and reacted at 60°C for 21 hours under pressure (0.5 MPa) to obtain the reaction product. The obtained reaction product was repeatedly filtered and washed with water before drying to obtain thermally expandable microcapsules.

[0195] (Examples 2-6)

[0196] The black material, polymeric dispersant, and dispersing aid were added in the amounts shown in Table 1, and the process was otherwise the same as in Example 1, to obtain thermally expandable microcapsules. It should be noted that in Examples 2-6, methacrylonitrile and acrylonitrile were also added as a medium when preparing the carbon black dispersion.

[0197] (Examples 7-14, 25, 26)

[0198] The black materials shown in Tables 1 and 2 were used as the black materials, and the thermally expandable microcapsules were obtained by operating in the same manner as in Example 4. It should be noted that the details of CB2-CB9, titanium black, and zirconium nitride are shown below. It should also be noted that in Examples 7-14, 25, and 26, methacrylonitrile and acrylonitrile were also added as a medium when preparing the carbon black dispersion.

[0199] CB2: #2650, manufactured by Mitsubishi Chemical, with a primary average particle size of 13 nm and a specific surface area of ​​370 m². 2 / g

[0200] CB3: MA230, manufactured by Mitsubishi Chemical, with a primary average particle size of 30 nm and a specific surface area of ​​74 m². 2 / g

[0201] CB4: MA14, manufactured by Mitsubishi Chemical, with a primary average particle size of 40 nm and a specific surface area of ​​56 m². 2 / g

[0202] CB5: MA285, manufactured by Mitsubishi Chemical, with a primary average particle size of 40 nm and a specific surface area of ​​60 m². 2 / g

[0203] CB6: #95, manufactured by Mitsubishi Chemical, with a primary average particle size of 40 nm and a specific surface area of ​​55 m². 2 / g

[0204] CB7: #240, manufactured by Mitsubishi Chemical, with a primary average particle size of 45 nm and a specific surface area of ​​64 m². 2 / g

[0205] CB8: MA220, manufactured by Mitsubishi Chemical, with a primary average particle size of 55 nm and a specific surface area of ​​36 m². 2 / g

[0206] CB9: #5, manufactured by Mitsubishi Chemical, with a primary average particle size of 76 nm and a specific surface area of ​​29 m². 2 / g

[0207] Titanium black: UF-8, manufactured by Mitsubishi Materials, with a primary average particle size of 20 nm and a specific surface area of ​​25 m². 2 / g

[0208] Zirconium nitride: UB-2, manufactured by Mitsubishi Materials, with a primary average particle size of 40 nm and a specific surface area of ​​40 m². 2 / g

[0209] (Examples 15-24, 27, 28)

[0210] Except for mixing the black material, polymeric dispersant, dispersing aid, and monomer composition as shown in Tables 1 and 2, the procedure was the same as in Example 4 to obtain thermally expandable microcapsules. It should be noted that details of the polymeric dispersant and dispersing aid are shown below. It should also be noted that in Examples 15-24, 27, and 28, methacrylonitrile and acrylonitrile were also added as a medium when preparing the carbon black dispersion.

[0211] [Polymer dispersant]

[0212] Polyacrylic acid based: Efka4701 (manufactured by BASF)

[0213] Polyether-based: DISPARLON 234 (manufactured by Kusumoto Chemical Co., Ltd.)

[0214] [Dispersing agent]

[0215] Azo pigment derivative: Solsperse 22000 (manufactured by Lubrizol).

[0216] Quinacridone pigment derivatives: sulfonic acid derivatives of quinacridone red

[0217] Diketopyrrolopyrrole pigment derivatives: sulfonic acid derivatives of diketopyrrolopyrrole

[0218] (Comparative Example 1)

[0219] Carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Co., Ltd., with a primary average particle size of 24 nm and a specific surface area of ​​110 m²) used as a black material 2 A carbon black dispersion was obtained by dispersing 6.89 parts by weight of Solsperse 39000 (manufactured by Lubrizol Corporation of Japan) as a dispersant for carbon black, 1.38 parts by weight of methacrylonitrile as a medium, and 30 parts by weight of acrylonitrile and 20 parts by weight of acrylonitrile as media using a bead mill.

[0220] 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 reactor. Next, an oily mixture containing the proportions shown in Table 2, 30 parts by weight of volatile expanding agent, 20 parts by weight of methyl methacrylate, 50.3 parts by weight of carbon black dispersion, and polymerization initiators (0.8 parts by weight of 2,2'-azobis(2,4-dimethylpentanones) and 0.6 parts by weight of 2,2'-azobis(2,4-dimethylpentanones)) was added to the aqueous dispersion medium and suspended to prepare a dispersion.

[0221] The obtained dispersion was homogenized and mixed, then placed in a nitrogen-replaced pressure polymerizer and reacted at 60°C for 21 hours under pressure (0.5 MPa) to obtain the reaction product. The obtained reaction product was repeatedly filtered and washed with water before drying to obtain thermally expandable microcapsules.

[0222] (Compare Examples 2 and 3)

[0223] Except for using the black material shown in Table 2 as the black material, the procedure was the same as in Example 4 to obtain thermally expandable microcapsules. It should be noted that the same titanium black as in Example 25 was used, and the same zirconium nitride as in Example 26 was used.

[0224] (Comparative Example 4)

[0225] 300 parts by weight of water and carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Co., Ltd., with a primary average particle size of 24 nm and a specific surface area of ​​110 m²) were added to the polymerization reactor. 2 After adding 4.6 parts by weight of Solsperse 39000 (manufactured by Lubrizol Corporation, Japan) as a dispersant [polymeric dispersant] for carbon black, 0.92 parts by weight of Solsperse 5000S (phthalocyanine pigment derivative, manufactured by Lubrizol Corporation, Japan) as a dispersing aid, 10 parts by weight of colloidal silica (manufactured by Asahi Denka Corporation 20% by weight) as a dispersing stabilizer, 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF Corporation), and 1.8 parts by weight of 1N hydrochloric acid, the following were added in the proportions shown in Table 2: 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 polymerization initiator (0.8 parts by weight of 2,2'-azobis(2,4-dimethylpentanonitrile) and 0.6 parts by weight of 2,2'-azobis(2,4-dimethylpentanonitrile)). The mixture was then suspended to prepare a dispersion.

[0226] The obtained dispersion was homogenized and mixed, then placed in a nitrogen-replaced pressure polymerizer and reacted at 60°C for 21 hours under pressure (0.5 MPa) to obtain the reaction product. The obtained reaction product was repeatedly filtered and washed with water before drying to obtain thermally expandable microcapsules.

[0227] (Comparative Example 5)

[0228] Carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Co., Ltd., with a primary average particle size of 24 nm and a specific surface area of ​​110 m²) used as a black material 2 The carbon black dispersion was obtained by dispersing the following ingredients in a bead mill: 0.13 parts by weight of Solsperse 39000 (polyester-based dispersant, manufactured by Lubrizol Corporation, Japan) as a dispersant [polymeric dispersant], 0.026 parts by weight of Solsperse 5000S (phthalocyanine pigment derivative, manufactured by Lubrizol Corporation, Japan) as a dispersing aid, and 50 parts by weight of methyl ethyl ketone as a medium.

[0229] 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 reactor. Next, an oily mixture containing the proportions shown in Table 2, including 60 parts by weight of volatile expanding agent, 40 parts by weight of methyl methacrylate, 50.2 parts by weight of carbon black dispersion, and polymerization initiators (0.8 parts by weight of 2,2'-azobis(2,4-dimethylpentanones) and 0.6 parts by weight of 2,2'-azobis(2,4-dimethylpentanones), was added to the aqueous dispersion medium and suspended to prepare a dispersion.

[0230] The obtained dispersion was homogenized and mixed, then placed in a nitrogen-replaced pressure polymerizer and reacted at 60°C for 21 hours under pressure (0.5 MPa) to obtain the reaction product. The obtained reaction product was repeatedly filtered and washed with water before drying to obtain thermally expandable microcapsules.

[0231] (Comparative Example 6)

[0232] Add 300 parts by weight of water, 3 parts by weight of carbon black (CB10, Aqua-Black #001, manufactured by Tokai Carbon, with an average primary particle size of 50 nm) as a black material, 10 parts by weight of colloidal silica (manufactured by Asahi Denka Co., Ltd., 20% by weight) as a dispersion stabilizer, 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF), and 1.8 parts by weight of 1N hydrochloric acid to a polymerization reaction vessel. Then add 30 parts by weight of volatile expanding agent, 20 parts by weight of methacrylonitrile, 30 parts by weight of acrylonitrile, 20 parts by weight of acrylonitrile, 30 parts by weight of methyl methacrylate, 20 parts by weight of methacrylic acid, and polymerization initiator (0.8 parts by weight of 2,2'-azobis(2,4-dimethylpentanonitrile) and 0.6 parts by weight of 2,2'-azobis(2,4-dimethylpentanonitrile)) in the proportions shown in Table 2 to suspend the mixture and prepare a dispersion.

[0233] The obtained dispersion was homogenized and mixed, then placed in a nitrogen-replaced pressure polymerizer and reacted at 60°C for 21 hours under pressure (0.5 MPa) to obtain the reaction product. The obtained reaction product was repeatedly filtered and washed with water before drying to obtain thermally expandable microcapsules.

[0234] (Evaluation Method)

[0235] The performance of the obtained thermally expandable microcapsules was evaluated using the following methods. The results are shown in Tables 1 and 2.

[0236] (1) Evaluation of thermally expandable microcapsules

[0237] (1-1) Average particle size (before foaming)

[0238] The average particle size (volume average particle size) of the obtained thermally expandable microcapsules was determined using a laser diffraction-scattering particle size distribution measuring device (LS 13 320, Beckman Coulter).

[0239] (1-2) Location of the black material

[0240] Thermally expandable microcapsules were added to an embedding resin (Oken Epok 812, manufactured by Oken Shoji Co., Ltd.) at a particle content of 3% by weight to disperse them, thus preparing a thermally expandable microcapsule embedding resin. Thin films were fabricated from the obtained embedding resin using a microtome (EM UC7, manufactured by LEICA Co., Ltd.). Cross-sectional images of the shells of the thermally expandable microcapsules with the largest diameter at observation were taken using a transmission electron microscope (ARM-200F, manufactured by NEC Corporation).

[0241] Then, image analysis was performed using the 3D image analysis software Dragonfly (made by Object Research Systems) and the open-source image analysis software Fiji (ImageJ). The analysis steps are as follows.

[0242] For the cross-sectional images, deep learning using Dragonfly (algorithm: U-Net) was employed to extract the black material through image segmentation (recognition). Additionally, Fiji was used to extract the thermally expandable microcapsules and inner surface (shell / core interface) through binarization of the cross-sectional images. Then, a distance map was performed on the extracted thermally expandable microcapsule images to obtain a distance map image from the outer surface. After performing Image Calculator on the distance map image and the extracted inner surface image, a Histogram was performed to obtain the 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, after performing Image Calculator on the distance map image and the extracted black material image, Analyze Particles was performed to obtain the distance data of the black material from the outer surface. The average value of the distance data in each region of the black material was used as the distance of each black material from the outer surface.

[0243] Then, the location of each black material from the outer surface of the shell is calculated according to the following formula.

[0244] Presence of black material from the outer surface (%) = Distance of black material from the outer surface (pixel) / Shell thickness (pixel) × 100

[0245] Then, the frequency of the number of black material positions from the outer surface is calculated to be 50% of the positions from the outer surface of the black material, and the proportion (%) of black material positions from the outer surface is determined to be 50% or more.

[0246] In addition, the frequency of the number of black material positions from the outer surface was calculated to be 30% of the positions from the outer surface of the black material, and the proportion (%) of black material positions from the outer surface was determined to be 30% or more.

[0247] In addition, the frequency of the number of black material locations from the outer surface was calculated to be 70% of the locations from the outer surface, and the proportion (%) of black material locations from the outer surface was determined to be 70% or more.

[0248] (1-3) Determination of foaming start temperature, maximum displacement and maximum foaming temperature

[0249] The foaming initiation temperature (Ts), maximum displacement (Dmax), and maximum foaming temperature (Tmax) were determined using a thermomechanical analysis (TMA) apparatus (TMA450, TA Instruments). Specifically, a 25 μg sample was placed in an aluminum container with a diameter of 7 mm and a depth of 1 mm. Under a top-applied force of 0.1 N, the sample was heated from 80 °C to 220 °C at a heating rate of 5 °C / min. The vertical displacement of the measuring terminals was measured. The temperature at which the displacement began to rise was defined as the foaming initiation temperature, the maximum displacement was defined as the maximum displacement, and the temperature at which the maximum displacement was reached was defined as the maximum foaming temperature. It should be noted that in the foaming ratio described later, in the case of an evaluation marked "×", the foaming initiation temperature, maximum displacement, and maximum foaming temperature are not measured and are instead recorded as "-".

[0250] (1-4) Average particle size (after foaming), foaming ratio

[0251] After foaming by heating at 200°C for 3 minutes in a heating oven (PHH-102, Espec), the average particle size (after foaming) of the thermally expandable microcapsules was measured using a laser diffractometer (LS 13 120, Beckman Coulter). The foaming ratio was then calculated based on "average particle size (after foaming) / average particle size (before foaming)," and evaluated according to the following criteria.

[0252] 〇〇: 2.5 times or more

[0253] 〇: 2.0 times or more but less than 2.5 times

[0254] ×: Less than 2.0 times

[0255] (1-5) L* value determination

[0256] 100 mg of the obtained thermally expandable microcapsules were measured in an aluminum pan and heated at 200°C for 3 minutes in a heating oven (PHH-102, manufactured by Espec), thereby causing the thermally expandable microcapsules to foam.

[0257] The foamed microcapsules were transferred to tubular vials (manufactured by AS ONE, No. 2), and the L* value (SCE) was measured from the bottom side of the vials using a spectrophotometer (manufactured by KONICA MINOLTA, CM-26dG). The obtained L* value (blackness after foaming) was evaluated according to the following criteria.

[0258] It should be noted that in the above foaming ratio, in the case of "×" evaluation, the L* value is not measured and is recorded as "-".

[0259] In addition, the difference between the L* value (blackness before foaming) and the value measured by the above method for the thermally expandable microcapsules before foaming was calculated [blackness after foaming - blackness before foaming].

[0260] 〇〇: Less than 38

[0261] 〇: 38 or higher and less than 45

[0262] △: 45 and above but less than 55

[0263] ×:55 and above

[0264] [Table 1]

[0265]

[0266] [Table 2]

[0267]

[0268] Industrial availability

[0269] According to the present invention, it is possible to provide thermally expandable microcapsules that can achieve both excellent foaming properties and blackness, foaming masterbatches using the thermally expandable microcapsules, foamed molded articles, and hollow particles.

Claims

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

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

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

4. The thermally expandable microcapsule according to any one of claims 1 to 3, wherein, The primary average particle size of the black material is greater than 10 nm and less than 80 nm.

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

6. The thermally expandable microcapsule according to claim 1 or 2, wherein, More than 70 percent of the black material exists in the area within 15 percent of the outer surface.

7. The thermally expandable microcapsule according to claim 1 or 2, wherein, More than 30% of the black material is present in the area within 10% from the outer surface.

8. A foaming masterbatch comprising thermally expandable microcapsules and thermoplastic resin as described in any one of claims 1 to 7.

9. A foamed molded article, which is made using any one of the thermally expandable microcapsules of claims 1 to 7 or the foaming masterbatch of claim 8.

10. A hollow particle formed by thermally expanding a thermally expandable microcapsule according to any one of claims 1 to 7, wherein a black material is attached to the outer surface of a shell containing a polymer compound or a portion of the black material is embedded therein.

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