Composition for expandable microcapsule

Abstract

To provide a composition for expandable microcapsules, expandable microcapsules, and a method for producing expandable microcapsules capable of yielding expandable microcapsules that achieve a balance between superior foaming properties and high blackness.SOLUTION: The present invention provides a composition for expandable microcapsules for producing expandable microcapsules in which a volatile blowing agent is encapsulated as a core agent in a shell, the composition for expandable microcapsules containing a black coloring material, a pigment derivative, a dispersant, and a polymerizable monomer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a composition for thermally expandable microcapsules that can produce thermally expandable microcapsules that have both excellent foaming properties and a high degree of blackness. [Background technology]

[0002] Thermally expandable microcapsules are used in a wide range of applications, including as design additives and weight-reducing agents, and are also used in foaming inks, wallpapers, and other lightweight paints. As such thermally expandable microcapsules, those in which a volatile expanding agent that becomes gaseous at a temperature below the softening point of the shell polymer is encapsulated in a thermoplastic shell polymer are widely known.

[0003] As such a thermally expandable microcapsule, for example, Patent Document 1 discloses a thermally expandable microcapsule containing carbon black as a black material inside the shell. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2021 / 221160 Summary of the Invention [Problem to be solved by the invention]

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

[0006] The present invention aims to provide a composition for thermally expandable microcapsules, which can produce thermally expandable microcapsules that have both excellent foaming properties and blackness, a thermally expandable microcapsule, and a method for producing thermally expandable microcapsules. [Means for solving the problem]

[0007] Disclosure 1 relates to a composition for thermally expandable microcapsules for producing thermally expandable microcapsules in which a volatile expanding agent is encapsulated in a shell as a core agent, and the composition for thermally expandable microcapsules contains a black material, a pigment derivative, a dispersant, and a polymerizable monomer. Disclosure 2 is the composition for thermally expandable microcapsules according to Disclosure 1, wherein the content of the organic solvent in the composition for thermally expandable microcapsules is 70% by weight or less. Disclosure 3 relates to a composition for thermally expandable microcapsules according to Disclosure 1 or 2, 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. Disclosure 4 relates to the composition for thermally expandable microcapsules according to Disclosure 3, wherein the carbonaceous black pigment is carbon black. The present disclosure 5 is the composition for thermally expandable microcapsules according to any one of the present disclosures 1 to 4, wherein the black material has primary particles with a number average particle size of 10 nm or more and 100 nm or less. Disclosure 6 is the composition for thermally expandable microcapsules according to any one of Disclosures 1 to 5, wherein the content of the black material is 1% by weight or more and 40% by weight or less. Disclosure 7 is the composition for thermally expandable microcapsules according to any one of Disclosures 1 to 6, wherein the pigment derivative is at least one selected from the group consisting of azo pigments and phthalocyanine pigments. Disclosure 8 of the present invention is the composition for thermally expandable microcapsules according to any one of Disclosures 1 to 7 of the present invention, wherein the polymerizable monomer is a radically polymerizable monomer. Disclosure 9 is a thermally expandable microcapsule obtained using the composition for thermally expandable microcapsules according to any one of Disclosures 1 to 8. Disclosure 10 is a method for producing thermally expandable microcapsules using the composition for thermally expandable microcapsules described in any one of Disclosures 1 to 8. The present invention will be described in detail below.

[0008] The present invention relates to a composition for thermally expandable microcapsules for producing thermally expandable microcapsules in which a volatile expanding agent is encapsulated in a shell as a core agent, and the composition contains a black material, a pigment derivative, a dispersant, and a polymerizable monomer. By including the black material, the blackness of the obtained thermally expandable microcapsules can be increased, and the light-blocking properties and appearance performance can be further improved. The black material exhibits black color by absorbing all light rays in sunlight, including the visible light range. Although general black pigments exhibit 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 greatly to heat generation.

[0009] The OD value of the black material has a preferred lower limit of 0.1 and a preferred upper limit of 5.0. A more preferred lower limit is 0.5, a more preferred upper limit is 4.0, and an even more preferred upper limit is 3.0. By keeping the OD value within the above ranges, 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 on an acrylic resin (coating thickness: 10 μm) containing 5% by weight of the black material. In this specification, the optical density (OD value) is defined as the intensity of light incident on the optical density variable element, I0, and the intensity of light transmitted through the element, I T When X=-log(I T This refers to the value X expressed as (X = 1 / I0). The optical density (OD value) can be measured using a color difference meter, a Macbeth densitometer, or the like.

[0010] Examples of the black material include black pigments, black dyes, black conductive polymers, etc. 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. Of 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 carbon-based black pigment include carbon black, graphite, activated carbon, graphene, carbon nanotubes, etc. Of these, carbon black is preferred. Examples of the oxide-based black pigments include titanium black, iron oxide, magnetite, cuprous oxide (cuprous oxide), and composite oxide black pigments whose main metal components are copper and chromium, copper and manganese, copper, iron and manganese, or cobalt, chromium and iron. Examples of the nitride-based black pigment include zirconium nitride. Examples of the organic black pigment include aniline black (CI Pigment Black 1). Of these, carbon black is more preferred because it has excellent heat resistance, excellent dispersibility in resin, and can impart a uniform black color. The black pigment is preferably a black pigment having an aromatic functional group. By using the black pigment having an aromatic functional group, the aromatic functional group of the black pigment interacts with the aromatic group 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 the black pigment having an aromatic functional group include carbon black and carbon nanotubes (both of which have an aromatic functional group).

[0011] Examples of the black dye include inorganic black dyes and organic black dyes, with organic black dyes being 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 (trade name Solvent Black 27, manufactured by Chuo Synthetic Chemical Industry Co., Ltd.).

[0012] 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 (trade name Solvent Black 3, manufactured by Chuo Synthetic Chemical Industry Co., Ltd.). Examples of the azine-based black dye include ChuoBlack F5 (trade name Solvent Black 7, manufactured by Chuo Synthetic Chemical Industry Co., Ltd.), which is known as

[0013] Examples of the black conductive polymer include polythiophene, polydopamine, polypyrrole, polyaniline, polyphenylene vinylene, polyphenylene, polyacetylene, polyquinoxaline, polyoxadiazole, polybenzothiadiazole, etc., and polymers having multiple conductive skeletons thereof. 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.

[0014] Among the above black materials, black materials in the form of fine particles (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 10 nm or more and 100 nm or less, even more preferably 12 nm or more and 80 nm or less, and particularly preferably 15 nm or more and 75 nm or less. By ensuring that the diameter is within the above range, the black fine particles are dispersed in the resin, resulting in a uniform hue (black). The above average primary particle size can be measured using a scanning electron microscope (SEM).

[0015] The preferred lower limit of the content of the black material is 1 wt % relative to the total composition for thermally expandable microcapsules, and the preferred upper limit is 40 wt %. By making the content 1 wt % or more, it is possible to further improve the light-blocking properties and appearance performance. By making the content 40 wt % or less, it is possible to further improve the dispersibility of the black material. A more preferred lower limit is 3 wt %, an even more preferred lower limit is 5 wt %, an even more preferred lower limit is 10 wt %, an even more preferred lower limit is 15 wt %, an especially preferred lower limit is 20 wt %, a more preferred upper limit is 35 wt %, an even more preferred upper limit is 30 wt %, and an even more preferred upper limit is 25 wt %.

[0016] The black material mentioned above has a specific surface area of ​​500m 2 / g or less, and more preferably 300m 2 / g or less. There is no particular lower limit to the specific surface area, but from the viewpoint of increasing the degree of blackness, it is 1 m 2 / g or more is preferable, and 5m 2 By adjusting the content within the above range, the black material is dispersed in the resin, and the hue (black color) becomes uniform. The specific surface area can be measured by measuring the 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.

[0017] The composition for thermally expandable microcapsules of the present invention contains a dispersant. The dispersant has the function of suppressing aggregation of the black material and improving dispersion stability. The dispersant preferably comprises an adsorbing portion that is generally easily adsorbed to the pigment and a side chain portion that solvates with a solvent such as a polymerizable monomer. Examples of the adsorption moiety include a moiety containing a polar functional group such as a moiety containing an amino group, a moiety containing an imino group, a moiety containing a carboxyl group, a moiety containing a sulfone group, or a moiety containing a hydroxyl group, or a moiety containing an aromatic ring. Examples of the side chain portion include a portion containing polyalkylene, a portion containing polyoxyalkylene, a portion containing polyether, a portion containing polyester, a portion containing polyamide, a portion containing poly(meth)acrylic, and a portion containing polyurethane. Examples of the dispersant 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, etc., incorporated into a portion thereof. These dispersants can be used alone or in combination of two or more. Examples of the polyether dispersant include polyether phosphate ester amine, polyether phosphate ester, and polyether ester acid amine. Examples of the polyester dispersant include polycaprolactone, polylactic acid, condensates of polycaprolactone and polyalkyleneimine, condensates of polycaprolactone and polyallylamine, condensates of polylactic acid and polyalkyleneimine, and condensates of polylactic acid and polyallylamine. 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 Efka4701, Efka4585, and Efka4780 (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 Chemical Co., Ltd.). Among these, Solsperse J200, Solsperse 35000, and Solsperse 39000 are more preferred from the viewpoint of dispersibility of black materials. The dispersant is preferably a polymer dispersant.

[0018] The preferred lower limit of the content of the dispersant is 0.1 wt % and the preferred upper limit is 10 wt % based on the total composition for thermally expandable microcapsules. By setting the content at 0.1 wt % or more, aggregation of the black material can be suppressed. By setting the content at 10 wt % or less, aggregation due to interactions between dispersants can be suppressed. The more preferred lower limit is 0.5 wt %, the more preferred upper limit is 8 wt %, the even more preferred upper limit is 7 wt %, and the even more preferred upper limit is 6 wt %.

[0019] The composition for thermally expandable microcapsules of the present invention contains a pigment derivative. The pigment derivative is a compound in which an acidic group or a basic group is introduced as a substituent into a pigment. The pigment derivative acts as a dispersing aid, allowing the dispersibility of the black material and the properties of the resulting thermally expandable microcapsules to be adjusted. Examples of pigments that serve as the parent skeleton of the pigment derivatives 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 a sulfonic acid group, a sulfonic acid base, a sulfonic acid amide group, a phthalimidomethyl group, an amino group, an imino group, a nitro group, a carboxyl group, an amide group, a hydroxyl group, and a phosphate group. Among these, derivatives of phthalocyanine pigments, quinacridone pigments, azo pigments, and diketopyrrolopyrrole pigments are preferred, and derivatives of at least one selected from the group consisting of azo pigments and phthalocyanine pigments are preferred. Furthermore, as the pigment derivatives, those in which a sulfonic acid group has been introduced into a pigment are preferably used. By using pigment derivatives having these base skeletons, the dispersibility and dispersion stability of the black material can be improved, and furthermore, when made into thermally expandable microcapsules, the foaming properties and blackness can be improved.

[0020] The preferred lower limit of the content of the pigment derivative in the thermally expandable microcapsule composition of the present invention is 0.1% by weight, and the preferred upper limit is 10% by weight, based on the total weight of the thermally expandable microcapsule composition. By setting the content at 0.1% by weight or more, aggregation of the black material can be suppressed. By setting the content at 10% by weight or less, aggregation of the black material due to interactions between the pigment derivatives can be suppressed. A more preferred lower limit is 0.3% by weight, a more preferred upper limit is 8% by weight, an even more preferred upper limit is 6% by weight, and an even more preferred upper limit is 4% by weight.

[0021] The composition for thermally expandable microcapsules of the present invention contains 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 monomer described later. In the present invention, the term "polymerizable monomer" refers to a monomer used in combination with a black material among the raw material monomers of the polymer constituting the shell of the thermally expandable microcapsule. Furthermore, a composition consisting of monomers other than the "polymerizable monomer" among the raw material monomers of the polymer constituting the shell of the thermally expandable microcapsule is referred to as a monomer composition.

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

[0024] The polymerizable monomer may contain 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.

[0025] The crosslinkable monomer may be a monomer having two or more radically polymerizable double bonds, and specific examples thereof include divinylbenzene, di(meth)acrylate, tri- or higher functional (meth)acrylate, and the like. 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, a 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 are crosslinked relatively uniformly in the shell mainly composed of acrylonitrile.

[0026] The polymerizable monomer preferably contains a monomer other than the nitrile monomer, the monomer having a carboxyl group, and the crosslinkable monomer. By containing the other monomer, the miscibility of the thermally expandable microcapsules with a matrix resin such as a thermoplastic resin is improved, and a foamed molded article using the thermally expandable microcapsules has an 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, and in particular, methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate, or alicyclic, aromatic, or heterocyclic methacrylic acid esters such as cyclohexyl methacrylate, benzyl methacrylate, and isobornyl methacrylate are preferred.

[0027] The preferred lower limit of the content of the polymerizable monomer in the thermally expandable microcapsule composition of the present invention is 50% by weight, and the preferred upper limit is 98% by weight, based on the total weight of the thermally expandable microcapsule composition. By setting the content at 50% by weight or more, the foaming properties of the thermally expandable microcapsules can be improved. By setting the content at 98% by weight or less, the blackness of the thermally expandable microcapsules can be increased. A more preferred lower limit is 60% by weight, a more preferred upper limit is 95% by weight, an even more preferred upper limit is 90% by weight, and an even more preferred upper limit is 85% by weight.

[0028] In the composition for thermally expandable microcapsules of the present invention, the polymerizable monomer and an organic solvent may be used in combination. In the present invention, a "medium" refers to a substance containing at least one of a "polymerizable monomer" and an "organic solvent." When a polymerizable monomer and an organic solvent are used in combination, the "medium" contains a "polymerizable monomer" and an "organic solvent." Examples of the organic solvent that can be used include aromatic organic solvents such as toluene and xylene, aliphatic organic solvents such as n-hexane, alicyclic organic solvents such as cyclohexane and methylcyclohexane, ketone organic solvents such as methyl ethyl ketone, and alcohol organic solvents such as methanol and ethanol.

[0029] The composition for thermally expandable microcapsules of the present invention preferably contains substantially no organic solvent. In this case, the content of organic solvent in the entire composition for thermally expandable microcapsules is preferably 70% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less, particularly preferably 10% by mass or less, and most preferably 0% by mass. This can improve the foaming performance of the thermally expandable microcapsules.

[0030] A polymerization initiator may be added to the composition for thermally expandable microcapsules of the present invention in order to polymerize the polymerizable monomer. As the polymerization initiator, for example, dialkyl peroxide, diacyl peroxide, peroxyester, peroxydicarbonate, azo compound, etc. are preferably used. 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, dimethoxybutylperoxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate. Additionally, 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).

[0031] The composition for thermally expandable microcapsules of the present invention may contain a polymerization inhibitor. By including the polymerization inhibitor, excessive polymerization of the polymerizable monomer can be prevented, and the foaming uniformity of the thermally expandable microcapsules can be further improved. As the polymerization inhibitor, for example, nitroso-based, hydroxyamine-based, quinone-based, and phenol-based inhibitors are preferably used. Examples of the nitroso-based compounds include cupferron and N-nitroso-N-phenylhydroxylamine aluminum. Examples of the hydroxylamine-based compounds include N,N-diethylhydroxylamine. Examples of the quinone-based compounds include benzoquinone, t-butylhydroquinone, 4-t-butylpyrocatechol, and hydroquinone. Examples of the phenol-based compounds include p-methoxyphenol and 2,6-di-t-butyl-4-methylphenol. Among these, p-methoxyphenol and the like are preferably used.

[0032] The composition for thermally expandable microcapsules of the present invention may further contain at least one inorganic compound selected from the group consisting of Si-based compounds and Mg-based compounds. By including the inorganic compound, it is possible to prevent the resulting thermally expandable microcapsules from fusing together. The inorganic compound is different from the black material.

[0033] The Si-based compound and Mg-based compound preferably contain oxides, hydroxides, carbonates or hydrogen carbonates of silicon and magnesium. These Si-based compounds and Mg-based compounds may be used alone or in combination of two or more.

[0034] Examples of the Si-based compound 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 compound 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. Of these, magnesium hydroxide is preferred.

[0035] 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.

[0036] 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 of the thermally expandable microcapsules in the resin during molding can be suppressed. The primary particle diameter can be measured by observation using a scanning electron microscope (Regulus 8220, manufactured by Hitachi High-Technologies Corporation).

[0037] The content of the inorganic compound is 0.01% by weight, preferably 7% by weight, based on the total composition for 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.

[0038] 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 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.

[0039] The composition for thermally expandable microcapsules of the present invention 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 a long time at high temperatures. Furthermore, because the elastic modulus of the shell is unlikely 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 molding, calendar molding, extrusion molding, and injection molding. The above-mentioned ionic crosslinking means that crosslinks are formed between free carboxyl groups present as side chains of the copolymer. The number of carboxyl groups arranged per one metal cation varies depending on the metal species.

[0040] The metal cation is not particularly limited as long as it reacts with the carboxyl group 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, and Zn ions are particularly preferred. Although the combination of two or more of the above metal cations is not particularly limited, it is preferable to use an alkali metal ion in combination with a metal cation other than the alkali metal ion. The presence of the alkali metal ion activates functional groups such as carboxyl groups, thereby promoting the reaction between the metal cation other than the alkali metal and the carboxyl group of the copolymer. Examples of the alkali metal include Na, K, and Li.

[0041] The L* value of the composition for thermally expandable microcapsules is preferably 0.5 or more and 20 or less, more preferably 15 or less, and even more preferably 10 or less. The L* value of the thermally expandable microcapsule composition can be measured using a spectrophotometer. Specifically, 5 mL of the thermally expandable microcapsule composition is placed in a vial (AS ONE, No. 2), and the L* value (SCE) can be measured from the bottom of the vial using a spectrophotometer (Konica Minolta, CM-26dG).

[0042] The composition for thermally expandable microcapsules, which is one embodiment of the present invention, can be prepared by mixing and stirring a black material, a pigment derivative, a dispersant, and a polymerizable monomer.

[0043] After carrying out the process of preparing a composition for thermally expandable microcapsules, which is one embodiment of the present invention, thermally expandable microcapsules can be produced by carrying out the process of preparing an aqueous dispersion medium containing an inorganic compound, the process of dispersing a monomer composition, an oily mixture containing a volatile expanding agent, and the composition for thermally expandable microcapsules of the present invention in the aqueous dispersion medium, and the process of polymerizing the above-mentioned monomers.

[0044] When producing thermally expandable microcapsules, a step of preparing an aqueous dispersion medium is carried out. Specifically, for example, an aqueous dispersion medium containing an inorganic compound is prepared by adding water, an inorganic compound, and, if necessary, a co-stabilizer to a polymerization reaction vessel.

[0045] 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.

[0046] In addition to the co-stabilizer, a condensation product and a water-soluble nitrogen compound may also 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.

[0047] 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, polyacrylamides, polycationic acrylamides, polyamine sulfones, and polyallylamines. Among these, polyvinylpyrrolidone is preferably used.

[0048] 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. The pH of the aqueous phase is determined appropriately depending on the type of inorganic compound and co-stabilizer used. For example, when a silicon-based compound such as colloidal silica is used as the inorganic compound, polymerization is carried out using an acidic aqueous dispersion medium. To acidify the aqueous dispersion medium, an acid such as hydrochloric acid is added as needed to adjust the pH of the system to 3 to 4. On the other hand, when a magnesium-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.

[0049] Next, in the method for producing thermally expandable microcapsules, a step is carried out in which an oily mixture containing a monomer composition and a volatile expanding agent, and a composition for thermally expandable microcapsules are dispersed in an aqueous dispersion medium. Specifically, a process is performed in which an oily mixture containing a monomer composition and a volatile expanding agent is mixed with a composition for thermally expandable microcapsules and dispersed in an aqueous dispersion medium. In this process, the monomer composition, the volatile expanding agent, and the composition for thermally expandable microcapsules may be added separately to an aqueous dispersion medium to prepare a black material-containing oily mixture in the aqueous dispersion medium. However, typically, the three are mixed together to form a black material-containing oily mixture, which is then added to the aqueous dispersion medium. In this process, the oily mixture and the aqueous dispersion medium may be prepared in separate containers, and the black material-containing 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 process, an inorganic compound is 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, resulting in the inorganic compound being present on the surface of the resulting thermally expandable microcapsules. Furthermore, in this process, the black material may be present on the black material-containing oily mixture side at the interface between the oil droplets of the black material-containing oily mixture and the aqueous dispersion medium. A polymerization initiator is used to polymerize the monomers. The polymerization initiator may be added to the oily mixture in advance, or may be added after the aqueous dispersion medium and the oily mixture are stirred and mixed in a polymerization reaction vessel.

[0050] 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 dispersion device. The aqueous dispersion medium and the polymerizable mixture may be supplied separately to the static dispersing device, or a dispersion liquid that has been mixed and stirred in advance may be supplied.

[0051] Thermally expandable microcapsules can be produced by subjecting the dispersion obtained through the above-mentioned steps to a step of polymerizing the monomers by heating, and a step of washing. Thermally expandable microcapsules produced by such a method have a high maximum foaming temperature, excellent heat resistance, and do not burst or shrink even when coated at high temperatures.

[0052] A foamable masterbatch can be produced by adding a thermoplastic resin (base resin) to the thermally expandable microcapsules.

[0053] 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, EMMA, etc. are preferred because they have low melting points and are easy to process. These may be used alone or in combination of two or more.

[0054] 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.

[0055] 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 a desired size using a pelletizer to form the 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 kneading machine is not particularly limited as long as it can knead the thermally expandable microcapsules without destroying them, and examples thereof include a pressure kneader and a Banbury mixer.

[0056] Furthermore, the thermally expandable microcapsules and the expandable masterbatch can be used to obtain foamed molded articles. In particular, the thermally expandable microcapsules can be suitably used in applications requiring post-processing at high temperatures, and therefore can be used to obtain foamed sheets having high appearance quality, such as uneven shapes, which can be suitably used for applications such as residential wallpaper. Specifically, the thermally expandable microcapsules or a foamable masterbatch containing the thermally expandable microcapsules are kneaded with a matrix resin, and the mixture is molded to obtain a foamed molded article.

[0057] 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. [Effects of the Invention]

[0058] According to the present invention, it is possible to provide a composition for thermally expandable microcapsules, thermally expandable microcapsules, and a method for producing thermally expandable microcapsules that can produce thermally expandable microcapsules that have both excellent foaming properties and blackness. DETAILED DESCRIPTION OF THE INVENTION

[0059] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0060] Example 1 [Preparation of composition for thermally expandable microcapsules] A container was charged with 3 parts by weight of Solsperse 39000 (a polyester-based dispersant, manufactured by Lubrizol Japan Co., Ltd.) as a polymer dispersant, 0.5 parts by weight of Solsperse 5000S (a phthalocyanine-based pigment derivative, manufactured by Lubrizol Japan Co., Ltd.) as a dispersing aid (pigment derivative), 76.5 parts by weight of methacrylonitrile [MAN], a polymerizable monomer, as a medium, and carbon black (CB1, MA100, manufactured by Mitsubishi Chemical Corporation, primary average particle diameter 24 nm, specific surface area 110 m) as a black material. 2 20 parts by weight of carbon black (carbon black / g) was added and dispersed in a bead mill to obtain a composition for thermally expandable microcapsules (carbon black dispersion). In the examples and comparative examples, the primary average particle size of the black material was measured using an SEM, and the specific surface area was measured using the BET method. The composition for thermally expandable microcapsules was composed of 20% by weight of CB1, 3% by weight of dispersant, 0.5% by weight of dispersing aid, and 76.5% by weight of methacrylonitrile.

[0061] [Preparation of thermally expandable microcapsules] 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), and 1.8 parts by weight of 1N hydrochloric acid to a polymerization reaction vessel. Next, an oily mixture consisting of 15 parts by weight of isopentane, 10 parts by weight of isooctane, 20 parts by weight of methyl methacrylate, 30 parts by weight of methacrylic acid, 20 parts by weight of acrylonitrile as a volatile swelling agent, a thermally expandable microcapsule composition measured to have a carbon black content of 4% by weight, 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)) was added to the aqueous dispersion medium and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, then placed in a nitrogen-purged pressure polymerization vessel and reacted at 60°C for 21 hours under pressure (0.5 MPa), yielding a reaction product. The resulting reaction product was repeatedly filtered and washed with water, and then dried to yield thermally expandable microcapsules.

[0062] Examples 2 to 24 A composition for thermally expandable microcapsules and thermally expandable microcapsules were obtained in the same manner as in Example 1, except that the compositions and contents of the black material, polymer dispersant, pigment derivative, and medium were adjusted to those shown in Tables 1 and 2. Details of CB2 to CB9, titanium black, zirconium nitride, polymer dispersant, pigment derivative, and medium are shown below. [Black material] CB2: #2650, manufactured by Mitsubishi Chemical Corporation, average primary particle size 13 nm, specific surface area 370 m 2 / 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:MA220, manufactured by Mitsubishi Chemical Corporation, primary average particle size 55 nm, specific surface area 36 m 2 / g CB7: #95, manufactured by Mitsubishi Chemical Corporation, primary average particle size 40 nm, specific surface area 55 m 2 / g CB8: #5, manufactured by Mitsubishi Chemical Corporation, primary average particle size 76 nm, specific surface area 29 m 2 / g CB9: #240, manufactured by Mitsubishi Chemical Corporation, primary average particle size 45 nm, specific surface area 64 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 [Polymer dispersant] Polyacrylic: Efka4701 (BASF) Polyether type: Disparlon 234 (Kusumoto Chemicals Co., Ltd.) [Pigment derivatives] Azo-based: Solsperse 22000 (manufactured by Lubrizol) Quinacridone series: sulfonic acid derivatives of quinacridone red Diketopyrrolopyrrole system: sulfonic acid derivatives of diketopyrrolopyrrole [Medium] AN: Acrylonitrile MMA: methyl methacrylate MAN / MEK: methacrylonitrile / methyl ethyl ketone mixed solvent (weight ratio)

[0063] (Comparative Example 1) [Preparation of composition for thermally expandable microcapsules] A container was charged with 2 parts by weight of Solsperse 39000 (a polyester-based dispersant, manufactured by Lubrizol Japan) as a polymer dispersant, 78 parts by weight of methacrylonitrile [MAN], and carbon black (CB3, MA230, manufactured by Mitsubishi Chemical Corporation, primary average particle size 30 nm, specific surface area 74 m) as a black material. 2 20 parts by weight of carbon black (carbon black dispersion liquid) was added to the mixture and dispersed in a bead mill to obtain a composition for thermally expandable microcapsules (carbon black dispersion liquid). The composition of the thermally expandable microcapsule composition was 20% by weight of CB3, 2% by weight of dispersant, and 78% by weight of methacrylonitrile.

[0064] [Preparation of thermally expandable microcapsules] 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), 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 (20 parts by weight of methyl methacrylate, 30 parts by weight of methacrylic acid, 20 parts by weight of acrylonitrile), a thermally expandable microcapsule composition (measured so that the carbon black content was 4% by weight), 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 ratio shown in the table was added to the aqueous dispersion medium and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, then placed in a nitrogen-purged pressure polymerization vessel and reacted at 60°C for 21 hours under pressure (0.5 MPa), yielding a reaction product. The resulting reaction product was repeatedly filtered and washed with water, and then dried to yield thermally expandable microcapsules.

[0065] (Comparative Example 2) A composition for thermally expandable microcapsules and thermally expandable microcapsules were obtained in the same manner as in Comparative Example 1, except that MEK shown in Table 2 was used as the medium. Note that the medium in Comparative Example 2 did not contain a polymerizable monomer and consisted only of an organic solvent.

[0066] (Comparative Example 3) A composition for thermally expandable microcapsules and thermally expandable microcapsules were obtained in the same manner as in Example 3, except that MEK shown in Table 2 was used as the medium. Note that the medium in Comparative Example 3 did not contain a polymerizable monomer and consisted only of an organic solvent.

[0067] (Evaluation method) The performance of the obtained thermally expandable microcapsules was evaluated by the following method, and the results are shown in Tables 1 and 2.

[0068] (1) Evaluation of compositions for thermally expandable microcapsules (1-1) L* value measurement 5 mL of the obtained composition for thermally expandable microcapsules was placed in a vial (No. 2, manufactured by AS ONE Co., Ltd.), and the L* value (SCE) was measured from the bottom side of the vial using a spectrophotometer (CM-26dG, manufactured by Konica Minolta Co., Ltd.).

[0069] (2) Evaluation of thermally expandable microcapsules (2-1) Average particle size (before foaming) The primary average particle size (volume average particle size) of the obtained thermally expandable microcapsules was measured using a laser diffraction / scattering particle size distribution analyzer (LS 13 320, manufactured by Beckman Coulter).

[0070] (2-2) Measurement of foaming start 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 250°C at a heating rate of 5°C / min with a force of 0.1 N applied from above. The vertical displacement of the measuring probe was measured, and the temperature at which the displacement began to increase was defined as the foaming initiation temperature, the maximum value of the displacement as the maximum displacement, and the temperature at the maximum displacement as the maximum foaming temperature.

[0071] (2-3) Average particle size (after expansion), expansion ratio The microcapsules were expanded by heating at 200°C for 3 minutes in a heating oven (PHH-102, manufactured by Espec Corporation), and the primary average particle size (after expansion) of the expanded thermally expandable microcapsules was measured using a laser diffraction particle size distribution analyzer (LS 13 120, manufactured by Beckman Coulter). The expansion ratio was then calculated from "average particle size (after expansion) / average particle size (before expansion)" and evaluated according to the following criteria. If the expansion ratio was evaluated as ×, further evaluation was not performed.

[0072] ○○○: 3.0 times or more ○○: 2.5 times or more but less than 3.0 times ○: 2.0 times or more and less than 2.5 times △: 1.8 times or more but less than 2.0 times ×: Less than 1.8 times

[0073] (2-4) L* value measurement 100 mg of the obtained thermally expandable microcapsules were weighed into an aluminum pan and heated in an oven (PHH-102, manufactured by Espec Corporation) at 200° C. for 3 minutes to foam the thermally expandable microcapsules. The resulting foamed microcapsules were transferred to a vial (No. 2, manufactured by AS ONE Co., Ltd.), and the L* value (SCE) was measured from the bottom side of the vial using a spectrophotometer (CM-26dG, manufactured by Konica Minolta Co., Ltd.) and evaluated according to the following criteria.

[0074] ○○: Under 35 ○: 35 or more and less than 45 △: 45 or more and less than 60 ×:60 or more

[0075] [Table 1]

[0076] [Table 2] [Industrial Applicability]

[0077] According to the present invention, it is possible to provide a composition for thermally expandable microcapsules, thermally expandable microcapsules, and a method for producing thermally expandable microcapsules that can produce thermally expandable microcapsules that have both excellent foaming properties and blackness.

Claims

1. A composition for thermally expandable microcapsules for producing thermally expandable microcapsules in which a volatile expanding agent is encapsulated as a core agent in a shell, comprising: A composition for thermally expandable microcapsules, comprising a black material, a pigment derivative, a dispersant, and a polymerizable monomer.

2. 2. The composition for thermally expandable microcapsules according to claim 1, wherein the content of the organic solvent in the composition for thermally expandable microcapsules is 70% by weight or less.

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

4. The thermally expandable microcapsule composition according to claim 3 , wherein the carbonaceous black pigment is carbon black.

5. 3. The composition for thermally expandable microcapsules according to claim 1, wherein the black material has an average primary particle size of 10 nm or more and 100 nm or less.

6. 3. The composition for thermally expandable microcapsules according to claim 1, wherein the content of the black material is 1% by weight or more and 40% by weight or less.

7. 3. The composition for thermally expandable microcapsules according to claim 1, wherein the pigment derivative is at least one derivative selected from the group consisting of azo pigments and phthalocyanine pigments.

8. The composition for thermally expandable microcapsules according to claim 1 or 2, wherein the polymerizable monomer is a radically polymerizable monomer.

9. A thermally expandable microcapsule obtained by using the composition for thermally expandable microcapsules according to claim 1 or 2.

10. A method for producing thermally expandable microcapsules, using the composition for thermally expandable microcapsules according to claim 1 or 2.

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