Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
  • B01J13/02—Making microcapsules or microballoons
  • B01J13/06—Making microcapsules or microballoons by phase separation
  • B01J13/14—Polymerisation; cross-linking
  • B01J13/18—In situ polymerisation with all reactants being present in the same phase
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/20—Compounding polymers with additives, e.g. colouring
  • C08J3/22—Compounding polymers with additives, e.g. colouring using masterbatch techniques
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/32—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof from compositions containing microballoons, e.g. syntactic foams
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K9/00—Use of pretreated ingredients
  • C08K9/10—Encapsulated ingredients
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
  • B01J13/02—Making microcapsules or microballoons
  • B01J13/06—Making microcapsules or microballoons by phase separation
  • B01J13/14—Polymerisation; cross-linking
  • B01J13/18—In situ polymerisation with all reactants being present in the same phase
  • B01J13/185—In situ polymerisation with all reactants being present in the same phase in an organic phase

Definitions

• the present invention relates to a thermally expandable microcapsule that is easy to handle and capable of producing a foamed molded product with good color development, and a foamable masterbatch and foamed molded product that use the thermally expandable microcapsule.
• Thermally expandable microcapsules are used in a wide range of applications, such as design imparting agents and weight-reducing agents, and are also used in foaming inks, lightweight paints such as wallpaper, and adhesives such as dismantling adhesives.
• 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.
• Patent Document 1 discloses a thermally expandable microcapsule encapsulating a volatile expansion agent, which is obtained by adding, while stirring, an oily mixture in which a volatile expansion agent such as a low-boiling point aliphatic hydrocarbon is mixed with a monomer, together with an oil-soluble polymerization catalyst, to an aqueous dispersion medium containing a dispersant, and then carrying out suspension polymerization.
• Patent Document 2 discloses heat-expandable microspheres containing a polymer made of a crosslinkable monomer having a (meth)acryloyl group and a reactive carbon-carbon double bond and a molecular weight of 500 or more.
• thermoly expandable microcapsules thermally expandable microspheres
• the thermally expandable microcapsules tend to float during storage, necessitating a stirring step before use or an additional stirring step, and thus poses a problem of poor handleability.
• the resulting foamed molded article also has a problem of poor color development, particularly when a black foamed molded article is produced.
• the present invention aims to provide a thermally expandable microcapsule that is easy to handle and capable of producing a foamed molded product with good color development, and a foamable masterbatch and foamed molded product that use the thermally expandable microcapsule.
• the present disclosure (1) is a thermally expandable microcapsule having a shell containing a polymer compound and a volatile expansion agent encapsulated as a core agent, the shell containing a specific gravity adjuster having a density of 2.3 g/ cm3 or more and 22 g/ cm3 or less.
• the present disclosure (2) is the thermally expandable microcapsule according to the present disclosure (1), in which the specific gravity adjuster is zirconium nitride.
• the present disclosure (3) is a thermally expandable microcapsule according to the present disclosure (1) or (2), in which the content of the specific gravity adjuster is 0.01% by weight or more and 30% by weight or less with respect to the entire thermally expandable microcapsule.
• the present disclosure (4) is a thermally expandable microcapsule according to any one of the present disclosures (1) to (3), in which the specific gravity adjuster is present inside the shell or on the surface of the shell.
• the present disclosure (5) is a thermally expandable microcapsule according to any one of the present disclosures (1) to (3), in which the specific gravity adjuster is present inside the shell and on the surface of the shell.
• the present disclosure (6) is a thermally expandable microcapsule according to any one of the present disclosures (1) to (5), having a true density of 1.08 g/ cm3 or more and 1.50 g/cm3 or less .
• the present disclosure (7) is a thermally expandable microcapsule according to any one of the present disclosures (1) to (6), which has a lightness (L* value) of 50 or less.
• the present disclosure (8) is a foamable masterbatch containing the thermally expandable microcapsule according to any one of the present disclosures (1) to (7) and a resin.
• the present disclosure (9) is a foamed molded article obtained by using the thermally expandable microcapsule according to any one of the present disclosures (1) to (7). The present invention will be described in detail below.
• the shell constituting the thermally expandable microcapsule which is one embodiment of the present invention contains a specific gravity adjusting agent.
• a specific gravity adjusting agent By including the above-mentioned specific gravity adjuster, when the thermally expandable microcapsules are used for ink or adhesive applications, for example, the thermally expandable microcapsules can be prevented from floating, thereby making it possible to improve the uniformity of the thermally expandable microcapsules.
• the density of the specific gravity adjuster has a lower limit of 2.3 g/cm 3 and an upper limit of 22 g/cm 3. By setting the density within the above range, it is possible to prevent the thermally expandable microcapsules from floating and to increase the uniformity of the thermally expandable microcapsules.
• the density of the specific gravity adjuster is preferably 3.0 g/cm 3 in lower limit and 15.0 g/cm 3 in upper limit, more preferably 4.0 g/cm 3 in lower limit and more preferably 8.0 g/cm 3 in upper limit.
• the density of the specific gravity adjuster can be measured by a true density meter.
• the specific gravity adjusting agent may have, for example, a spherical, fibrous, tabular, or polygonal shape.
• the specific surface area of the specific gravity adjuster is preferably 5 m 2 /g or more and 300 m 2 /g or less.
• the specific surface area can be measured by measuring a nitrogen adsorption isotherm using a surface area/pore size analyzer (NOVA4200e, manufactured by Quantachrome Instruments) and calculating the specific surface area of the specific gravity adjuster from the measurement results in accordance with the BET method.
• Examples of the specific gravity adjuster include metals alone, as well as metal nitrides, carbides, oxides, oxynitrides, etc.
• the metal it is preferable to use at least one selected from the group consisting of zirconium, iron, copper, cobalt, nickel, manganese, titanium, and tin.
• the specific gravity adjuster examples include zirconium nitride, boron carbide, boron carbonitride, alumina, magnesium hydroxide, magnesium oxide, zinc oxide, iron oxide, ferrite, mullite, cordierite, silicon nitride, silicon carbide, titanium black, titanium oxide, barium titanate, tin oxide, zirconium oxide, magnesium fluoride, aluminum nitride, magnesium carbonate, aluminum hydroxide, and iron-manganese-copper oxide.
• zirconium nitride is more preferred because it has excellent dispersibility in resin, can impart a black color, and can increase density with the addition of a small amount.
• the specific gravity adjuster is preferably colored, and is particularly preferably black.
• the primary average particle size of the specific gravity adjuster is preferably 1 nm in lower limit and 5000 nm in upper limit, more preferably 5 nm in lower limit and 1000 nm in upper limit, still more preferably 7 nm in lower limit and still more preferably 150 nm in upper limit. By setting it within the above range, the specific gravity adjuster is easily dispersed.
• the primary average particle size can be measured by forming a thin film so as to pass through the vicinity of the center of the thermally expandable microcapsules dispersed in the embedding resin, and then observing the thin film using a transmission electron microscope or the like.
• the preferred lower limit of the content of the specific gravity adjuster is 0.01% by weight, and the preferred upper limit is 30% by weight, based on the total weight of the thermally expandable microcapsules.
• the content 0.01% by weight or more floating of the thermally expandable microcapsules can be suppressed.
• the more preferred lower limit is 0.3% by weight, the more preferred upper limit is 15% by weight, the even more preferred upper limit is 12% by weight, and the even more preferred upper limit is 10% by weight.
• the content of the specific gravity adjusting agent can be determined, for example, by heating the thermally expandable microcapsule in air to 1000° C. at a rate of 10° C./min and maintaining the temperature at 1000° C.
• the content of the specific gravity adjusting agent is calculated as (A-B)%.
• the shell constituting the thermally expandable microcapsule which is one embodiment of the present invention contains a polymer compound.
• the polymer compound is preferably a polymer of a monomer composition containing a nitrile monomer and a monomer having a carboxyl group.
• nitrile monomer is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, ⁇ -chloroacrylonitrile, ⁇ -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.
• the preferred lower limit of the content of the nitrile monomer in the monomer composition is 40% by weight, and the preferred upper limit is 90% by weight.
• the gas barrier properties of the shell can be improved and the expansion ratio can be improved.
• the heat resistance can be improved and yellowing can be prevented.
• the more preferred lower limit is 50% by weight, and the more preferred upper limit is 80% by weight.
• 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 their anhydrides, and monoesters of unsaturated dicarboxylic acids and their derivatives. These may be used alone or in combination of two or more kinds.
• 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.
• acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid are particularly preferred.
• the preferred lower limit of the content of the monomer having a carboxyl group in the monomer composition is 5% by weight, and the preferred upper limit is 50% by weight. By making it 5% by weight or more, the maximum foaming temperature can be increased, and by making it 50% by weight or less, the foaming ratio can be improved.
• the more preferred lower limit is 10% by weight, and the more preferred upper limit is 30% by weight.
• the monomer composition preferably contains a crosslinkable monomer having two or more double bonds in the molecule.
• the crosslinkable monomer acts as a crosslinking agent.
• the strength of the shell can be increased, and the cell walls are less likely to break during thermal expansion.
• the crosslinkable monomer includes 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.
• 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, 1,4-butanediol di(meth)acrylate, etc.
• di(meth)acrylate of polyethylene glycol having a weight average molecular weight of 200 to 600 may be used.
• trifunctional (meth)acrylate examples include trimethylolpropane tri(meth)acrylate, ethylene oxide modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, triallyl formal tri(meth)acrylate, etc.
• tetrafunctional or higher (meth)acrylate examples include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc.
• trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and difunctional (meth)acrylates such as polyethylene glycol provide relatively uniform crosslinking to the shell mainly composed of acrylonitrile.
• the preferred lower limit of the content of the crosslinkable monomer in the monomer composition is 0.1% by weight, and the preferred upper limit is 1.0% by weight.
• the more preferred lower limit of the content of the crosslinkable monomer is 0.15% by weight, and the more preferred upper limit is 0.9% by weight.
• the monomer composition preferably contains other monomers other than the nitrile monomer, the monomer having a carboxyl group, and the crosslinkable monomer.
• 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.
• (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.
• the preferred lower limit of the content of the other monomer in the monomer composition is 0.1% by weight, and the preferred upper limit is 45% by weight.
• the dispersibility of the composition using the thermally expandable microcapsules can be improved, and by making it 45% by weight or less, the gas barrier properties of the cell walls can be improved, and the thermal expansion properties can be improved.
• the more preferred lower limit of the content of the other monomer is 0.3% by weight, and the more preferred upper limit is 40% by weight.
• a polymerization initiator is added to the monomer composition in order to polymerize the monomers.
• the polymerization initiator for example, dialkyl peroxide, diacyl peroxide, peroxy ester, peroxy dicarbonate, azo compound, etc. are suitably 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.
• Further 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.
• peroxy esters such as cumyl peroxy neodecanoate and ( ⁇ , ⁇ -bis-neodecanoylperoxy)diisopropylbenzene; bis(4-t-butylcyclohexyl)peroxydicarbonate, di-n-propyl-oxydicarbonate, and diisopropyl peroxydicarbonate.
• peroxydicarbonates such as di(2-ethylethylperoxy)dicarbonate, dimethoxybutylperoxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate.
• examples of the compound 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).
• 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).
• the preferred lower limit of the weight average molecular weight of the polymer compound constituting the 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, and if it exceeds 2,000,000, the strength of the shell may become too high, resulting in a decrease in the expansion ratio.
• the shell constituting the thermally expandable microcapsule according to one embodiment of the present invention preferably further contains at least one inorganic compound selected from the group consisting of Si-based compounds and Mg-based compounds.
• the inorganic compound By including the inorganic compound, it is possible to suppress fusion of the thermally expandable microcapsules to each other in the resin during molding.
• the inorganic compound is different from the specific gravity adjuster.
• Si-based compound and Mg-based compound preferably contain an oxide, hydroxide, carbonate or hydrogen carbonate of silicon or magnesium.
• These Si-based compounds and Mg-based compounds may be used alone or in combination of two or more kinds.
• Examples of the Si-based compound include colloidal silica, silicic acid sol, water glass No. 3, 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. Among these, magnesium hydroxide is preferred.
• inorganic compounds examples include calcium phosphate, aluminum hydroxide, ferric hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, etc.
• inorganic salts such as sodium chloride and sodium sulfate, alkali metal nitrite, stannous chloride, stannic chloride, potassium dichromate, etc. may also be added as necessary.
• the inorganic compound is preferably in the form of fine particles.
• the primary particle size (average primary particle size) is preferably 0.5 ⁇ m or less, more preferably 5 to 100 nm (0.1 ⁇ m). By keeping the size within the above range, it is possible to suppress fusion between the thermally expandable microcapsules in the resin during molding.
• the primary particle size can be measured by observation using a scanning electron microscope (Regulus 8220, manufactured by Hitachi High-Technologies Corporation).
• the density of the inorganic compound is preferably 1.0 g/cm 3 or more and 5.0 g/cm 3 or less. The density of the inorganic compound can be measured in the same manner as the density of the specific gravity adjuster.
• the content of the inorganic compound is 0.01% by weight, preferably 7% by weight, based on the total amount of the thermally expandable microcapsules. By making it 0.01% by weight or more, it is possible to suppress the fusion of the thermally expandable microcapsules in the resin during molding. By making it 7% by weight or less, it is possible to further improve the resin dispersibility during molding. A more preferable lower limit is 0.3% by weight, and a more preferable upper limit is 5% by weight.
• the content of the inorganic compound can be calculated from the weights of the monomer composition forming the thermally expandable microcapsules, the volatile expanding agent, and the specific gravity adjusting agent.
• the weight ratio of the inorganic compound to the specific gravity adjuster 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 the resin dispersibility during molding.
• a more preferred lower limit is 0.3, an even more preferred lower limit is 0.5, a more preferred upper limit is 300, and an even more preferred upper limit is 200.
• the specific gravity adjuster and inorganic compound may be present inside or on the surface of the shell of the thermally expandable microcapsule, or may be present inside and on the surface of the shell. In a preferred embodiment of the present invention, the specific gravity adjuster is preferably contained inside the shell.
• the locations of the specific gravity adjusting agent and inorganic compound can be confirmed using a transmission electron microscope or the like after a thin film is prepared so as to pass through the vicinity of the center of the thermally expandable microcapsules dispersed in the embedding resin.
• the shell may contain a metal cation.
• the metal cation reacts with the carboxyl group to ionically crosslink the copolymer, improving heat resistance, and making it possible to obtain a thermally expandable microcapsule that does not burst or shrink for a long time in a high temperature range.
• the elastic modulus of the shell is unlikely to decrease even in a high temperature range, even when a molding process such as kneading molding, calendar molding, extrusion molding, or injection molding is performed in which a strong shear force is applied, the thermally expandable microcapsule does not burst or shrink.
• 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 valence of metal cation varies depending on the type of metal.
• the metal cation is not particularly limited as long as it is a metal cation that reacts with the carboxyl group of the copolymer to ionically crosslink the copolymer, and examples thereof include ions such as 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.
• the combination is not particularly limited, but it is preferable to use an alkali metal ion in combination with a metal cation other than the above alkali metal.
• an alkali metal ion By having the above alkali metal ion, functional groups such as carboxyl groups can be activated, and the reaction between the metal cation other than the above alkali metal and the carboxyl group of the copolymer can be promoted.
• the alkali metal include Na, K, and Li.
• the shell may further contain stabilizers, UV absorbers, antioxidants, antistatic agents, flame retardants, silane coupling agents, colorants, etc., as necessary.
• a volatile expanding agent is encapsulated as a core agent in the shell.
• the volatile expanding agent is a substance that becomes gaseous at a temperature equal to or lower than the softening point of the polymer constituting the shell, and is preferably a low-boiling organic solvent.
• volatile expanding agent examples include low molecular weight hydrocarbons such as ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, petroleum ether, isooctane, octane, decane, isododecane, dodecane, and hexanedecane.
• low molecular weight hydrocarbons such as ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, petroleum ether, isooctane, octane, decane, isododecane, dodecan
• chlorofluorocarbons such as CCl 3 F, CCl 2 F 2 , CClF 3 , and CClF 2 -CClF 2 ; and tetraalkylsilanes such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane.
• chlorofluorocarbons such as CCl 3 F, CCl 2 F 2 , CClF 3 , and CClF 2 -CClF 2
• tetraalkylsilanes such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane.
• thermally expandable microcapsule among the above-mentioned volatile expanding agents, it is preferable to use a low-boiling point hydrocarbon having a carbon number of 5 or less. By using such a hydrocarbon, it is possible to obtain a thermally expandable microcapsule having a high expansion ratio and capable of rapidly starting to expand. Moreover, a pyrolytic compound that decomposes when heated to become gaseous may be used as the volatile expanding agent.
• the thermally expandable microcapsules of the present invention have a true density of preferably 1.08 g/ cm3 or more at the lower limit and 1.50 g/ cm3 at the upper limit. By keeping the true density within the above range, the uniformity of the thermally expandable microcapsules can be improved.
• a more preferable lower limit is 1.10 g/ cm3
• a more preferable upper limit is 1.40 g/ cm3 .
• the true density can be measured using a true density meter (Ultrapyc 5000, manufactured by Anton Parr, etc.) under conditions of a pressure of 12 psi, a temperature of 25° C., and a gas type of helium.
• the thermally expandable microcapsule of the present invention has a lightness (L* value) of preferably 1 at its lower limit and 50 at its upper limit.
• L* value preferably 1 at its lower limit and 50 at its upper limit.
• a more preferable lower limit of the L* value is 5, and a more preferable upper limit thereof is 40.
• the lightness (L* value) is an index indicating the brightness of a color tone. A larger L* value indicates a lighter color tone, and a smaller L* value indicates a darker color tone.
• the L* value can be measured using a spectrophotometer in accordance with JIS Z 8722:2009.
• the preferred lower limit of the maximum foaming temperature (Tmax) of the thermally expandable microcapsule according to one embodiment of the present invention is 170°C.
• Tmax maximum foaming temperature
• the maximum foaming temperature means the temperature at which the diameter of a thermally expandable microcapsule becomes maximum (maximum displacement) when the diameter of the thermally expandable microcapsule is measured while being heated from room temperature.
• the maximum displacement (Dmax) measured by thermomechanical analysis is preferably 10 ⁇ m at its lower limit. If it is less than 10 ⁇ m, the expansion ratio decreases and the desired expansion performance may not be obtained.
• the more preferred lower limit is 20 ⁇ m
• the even more preferred lower limit is 100 ⁇ m
• the even more preferred lower limit is 300 ⁇ m.
• the preferred upper limit of the maximum displacement is 2000 ⁇ m
• the more preferred upper limit is 1800 ⁇ m
• the even more preferred upper limit is 1500 ⁇ m.
• the above-mentioned maximum displacement amount refers to the value at which the diameter of a predetermined amount of thermally expandable microcapsules as a whole becomes maximum when the diameter of the predetermined amount of thermally expandable microcapsules is measured while being heated from room temperature.
• the preferred upper limit of the foaming start temperature (Ts) is 185°C. By setting the temperature at 185°C or lower, foaming becomes easy and the desired foaming ratio can be achieved.
• the preferred lower limit is 130°C, and the more preferred upper limit is 180°C.
• the preferred lower limit of the volume average particle diameter of the thermally expandable microcapsule according to one embodiment of the present invention is 5 ⁇ m, and the preferred upper limit is 45 ⁇ m. If it is less than 5 ⁇ m, the bubbles in the resulting molded product are too small, so the expansion ratio may be insufficient, and if it exceeds 45 ⁇ m, the bubbles in the resulting molded product are too large, so there may be problems in terms of appearance.
• the more preferred lower limit is 7 ⁇ m, and the more preferred upper limit is 35 ⁇ m.
• the volume average particle size of the thermally expandable microcapsules can be measured using a laser diffraction/scattering particle size distribution measuring device or the like.
• the method for producing the thermally expandable microcapsules which are one embodiment of the present invention, is not particularly limited, but they can be produced, for example, by carrying out the steps of preparing an aqueous dispersion medium containing a specific gravity adjuster and an inorganic compound, dispersing an oily mixture containing a monomer composition and a volatile expansion agent in the aqueous dispersion medium, and polymerizing the monomers.
• a composition containing the above-mentioned nitrile monomer, a monomer having a carboxyl group, a crosslinkable monomer, and other monomers can be used.
• the first step is to prepare an aqueous dispersion medium.
• an aqueous dispersion medium containing a specific gravity adjuster and an inorganic compound is prepared by adding water, a specific gravity adjuster, an inorganic compound, and, if necessary, an auxiliary stabilizer to a polymerization reaction vessel.
• auxiliary stabilizer examples include condensation products of diethanolamine and aliphatic dicarboxylic acids, and condensation products of urea and formaldehyde.
• Other examples include polyvinylpyrrolidone, polyethylene oxide, polyethyleneimine, tetramethylammonium hydroxide, gelatin, methylcellulose, polyvinyl alcohol, dioctyl sulfosuccinate, sorbitan esters, various emulsifiers, etc.
• a condensation product or a water-soluble nitrogen compound may be added.
• 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.
• water-soluble nitrogen compounds examples include polyvinylpyrrolidone, polyethyleneimine, polyoxyethylene alkylamines, polydialkylaminoalkyl (meth)acrylates such as polydimethylaminoethyl methacrylate and polydimethylaminoethyl acrylate.
• polydialkylaminoalkyl (meth)acrylamides such as polydimethylaminopropyl acrylamide and polydimethylaminopropyl methacrylamide
• polyvinylpyrrolidone is preferably used.
• the aqueous dispersion medium containing the above-mentioned specific gravity adjuster, inorganic compound, auxiliary stabilizer, and optionally a dispersant is prepared by mixing with deionized water, and the pH of the aqueous phase is appropriately determined depending on the type of specific gravity adjuster, inorganic compound, and auxiliary stabilizer used.
• a Si-based compound such as colloidal silica
• polymerization is carried out using an acidic aqueous dispersion medium, and to make the aqueous dispersion medium acidic, an acid such as hydrochloric acid is added as necessary to adjust the pH of the system to 3 to 4.
• a Mg-based compound such as magnesium hydroxide or calcium phosphate is used as the inorganic compound
• polymerization is carried out using an alkaline aqueous dispersion medium adjusted to a pH of 8 to 11.
• a step of dispersing the oily mixture containing the monomer composition and the volatile expansion agent in an aqueous dispersion medium is carried out.
• a process is carried out in which an oily mixture containing a monomer composition and a volatile swelling agent is dispersed in an aqueous dispersion medium.
• the monomer composition and the volatile swelling agent may be added separately to the aqueous dispersion medium to prepare an oily mixture in the aqueous dispersion medium, but usually, the two are mixed in advance to prepare an oily mixture, and then added to the aqueous dispersion medium.
• the oily mixture and the aqueous dispersion medium may be prepared in separate containers, and the oily mixture may be dispersed in the aqueous dispersion medium by mixing while stirring in another container, and then added to the polymerization reaction vessel.
• an inorganic compound is present at the interface between the oil droplets of the oily mixture and the aqueous dispersion medium, and as a result, an inorganic compound can be present on the surface of the obtained thermally expandable microcapsule.
• a polymerization initiator is used to polymerize the above monomers.
• the polymerization initiator may be added to the above oily mixed liquid in advance, or may be added after the aqueous dispersion medium and the oily mixed liquid are stirred and mixed in a polymerization reaction vessel.
• the above process may be carried out by adding the specific gravity adjuster and, if necessary, the dispersant to the monomer composition instead of the aqueous dispersion medium.
• the specific gravity adjuster used can be present inside the thermally expandable microcapsules.
• Examples of a method for emulsifying and dispersing the above-mentioned oily mixture in an aqueous dispersion medium to a predetermined particle size include a method of stirring the mixture using a homomixer (e.g., manufactured by Tokushu Kika Kogyo Co., Ltd.) or a method of passing the mixture through a static dispersion device such as a line mixer or an element-type static disperser.
• the aqueous dispersion medium and the polymerizable mixture may be supplied separately to the static dispersing device, or a dispersion liquid which has been previously mixed and stirred may be supplied.
• the thermally expandable microcapsules which are one embodiment of the present invention, can be manufactured 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 manufactured by such a method have a high maximum foaming temperature, excellent heat resistance, and will not burst or shrink even when molded in a high temperature range.
• the foamable masterbatch containing the thermally expandable microcapsules and resin (base resin) of the present invention is also one aspect of the present invention.
• the ink containing the thermally expandable microcapsules and resin can also be used as a foamable ink.
• the composition containing the thermally expandable microcapsules and resin of the present invention is preferably used for applications such as adhesives, rubber chips, foam chips, flooring materials, rock consolidation materials, paints, coating materials, reinforcing fibers, composite materials, electronic components, and molding materials.
• the molding materials are preferably used for molding by injection molding, extrusion molding, blow molding, rotational molding, vacuum molding, inflation molding, calendar molding, slush molding, dip molding, foam molding, fused deposition modeling, inkjet method, stereolithography method, laser sintering method, etc.
• the resin used for the base resin is not particularly limited, and thermoplastic resins and curable resins used in normal foam molding can be used.
• the thermoplastic resin include polyolefins such as low-density polyethylene (LDPE) and polypropylene (PP), polyvinyl acetate, ethylene-vinyl acetate copolymer (EVA), vinyl chloride, polystyrene, thermoplastic elastomers, and ethylene-methyl methacrylate copolymer (EMMA).
• LDPE, EVA, EMMA, etc. are preferred because they have a low melting point and are easy to process. These may be used alone or in combination of two or more kinds.
• the curable resin examples include epoxy resin, (meth)acrylic resin, urethane resin, phenol resin, cyanate resin, isocyanate resin, maleimide resin, benzoxazine resin, silicone resin, fluorine resin, polyimide resin, and phenoxy resin.
• the curable resin preferably contains an epoxy resin.
• 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.
• the method for producing the expandable master batch is not particularly limited, but for example, raw materials such as a base resin and various additives are pre-kneaded using a unidirectional twin-screw extruder or the like. Next, the mixture is heated to a predetermined temperature, a blowing agent such as thermally expandable microcapsules is added, and the mixture is further kneaded, and then cut into pellets of a desired size using a pelletizer to form a master batch.
• a pellet-shaped master batch may be produced by kneading raw materials such as a base 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.
• the present invention also provides a foamed molded product obtained by using the above-mentioned thermally expandable microcapsules and foamable master batch.
• the above-mentioned thermally expandable microcapsules can be suitably used in applications requiring post-processing at high temperatures, and therefore a foamed sheet having high appearance quality such as a concave-convex shape can be obtained, and the foamed sheet can be suitably used for applications such as wallpaper for homes.
• 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. According to the present invention, it is possible to improve the gas barrier properties and durability during thermal expansion, and also to improve the expansion ratio and heat resistance.
• the molding method for the foamed molded body is not particularly limited, and examples include kneading molding, calendar molding, extrusion molding, and injection molding.
• injection molding the process is not particularly limited, and examples include the short-short method, in which a portion of the resin material is placed in a mold and foamed, and the core-back method, in which the mold is filled with the resin material and then opened to the desired point of foaming.
• thermoly expandable microcapsule that is easy to handle and capable of producing a foamed molded article having good color development, and a foamable masterbatch and a foamed molded article using the thermally expandable microcapsule.
• thermally expandable microcapsules of the present invention are added to foaming ink or the like, it is possible to prevent the thermally expandable microcapsules from being unevenly distributed in the foaming ink, thereby making it possible to make the thermally expandable microcapsules uniform.
• the primary average particle size and density of the inorganic compounds, and the primary average particle size, specific surface area, and density of the specific gravity adjuster shown below were measured using the method described above.
• a true density meter (Pycnometer UltraPYC5000 micro, manufactured by Anton Parr) was used to measure the density.
• Example 1 (Preparation of Thermally Expandable Microcapsules) An aqueous dispersion medium was prepared by adding 30 parts by weight of colloidal silica (manufactured by Asahi Denka Corporation, average primary particle size: 20 nm, density: 2.2 g/ cm3 ) as an inorganic compound (dispersant) and 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF) to 250 parts by weight of ion-exchanged water and mixing them. 20% by weight of acrylonitrile, 30% by weight of methacrylonitrile, 20% by weight of methacrylic acid, and 30% by weight of methyl methacrylate were mixed to obtain a monomer composition of a homogeneous solution.
• colloidal silica manufactured by Asahi Denka Corporation, average primary particle size: 20 nm, density: 2.2 g/ cm3
• polyvinylpyrrolidone manufactured by BASF
• this monomer composition 100 parts by weight of this monomer composition were dispersed by adding 0.8 parts by weight of an amine-based dispersant (Solsperse 39000, manufactured by Lubrizol Corporation) as an additive and 4.1 parts by weight of zirconium nitride (UB-2, manufactured by Mitsubishi Materials Corporation, primary average particle size: 35 nm, specific surface area: 35 m 2 /g, density: 6.4 g/cm 3 ) as a specific gravity adjuster, and then charged in an autoclave.
• an amine-based dispersant Solsperse 39000, manufactured by Lubrizol Corporation
• UB-2 zirconium nitride
• the obtained reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules.
• the obtained thermally expandable microcapsules were added to an embedding resin (Technovit 4000, manufactured by Kulzer) so that the particle content was 3% by weight, and dispersed to prepare a resin embedding thermally expandable microcapsules.
• a thin film was prepared using a microtome (EM UC7, manufactured by LEICA) so as to pass through the vicinity of the center of the thermally expandable microcapsules dispersed in the embedding resin, and the location of the specific gravity adjuster was confirmed using a transmission electron microscope (JEM-2100, manufactured by JEOL Ltd.), confirming that the specific gravity adjuster was present inside the shell.
• Example 2 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that 0.03 parts by weight of an amine-based dispersant (Solsperse 39000, manufactured by Lubrizol Corporation) and 0.1 parts by weight of zirconium nitride (UB-2, manufactured by Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m2 /g, density: 6.4 g/ cm3 ) were added as a specific gravity adjuster.
• an amine-based dispersant Solsperse 39000, manufactured by Lubrizol Corporation
• UB-2 zirconium nitride
• Example 3 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that 0.3 parts by weight of an amine-based dispersant (Solsperse 39000, manufactured by Lubrizol Corporation) and 1.4 parts by weight of zirconium nitride (UB-2, manufactured by Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m2 /g, density: 6.4 g/ cm3 ) were added as a specific gravity adjuster.
• an amine-based dispersant Solsperse 39000, manufactured by Lubrizol Corporation
• UB-2 zirconium nitride
• Example 4 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that 1.4 parts by weight of an amine-based dispersant (Solsperse 39000, manufactured by Lubrizol Corporation) and 6.8 parts by weight of zirconium nitride (UB-2, manufactured by Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m2 /g, density: 6.4 g/ cm3 ) were added as a specific gravity adjuster.
• an amine-based dispersant Solsperse 39000, manufactured by Lubrizol Corporation
• U-2 zirconium nitride
• Example 5 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that 2.7 parts by weight of an amine-based dispersant (Solsperse 39000, manufactured by Lubrizol Corporation) and 13.7 parts by weight of zirconium nitride (UB-2, manufactured by Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m2 /g, density: 6.4 g/ cm3 ) were added as a specific gravity adjuster.
• an amine-based dispersant Solsperse 39000, manufactured by Lubrizol Corporation
• U-2 zirconium nitride
• Example 6 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that 8.2 parts by weight of an amine-based dispersant (Solsperse 39000, manufactured by Lubrizol Corporation) and 41 parts by weight of zirconium nitride (UB-2, manufactured by Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m2 /g, density: 6.4 g/ cm3 ) were added as a specific gravity adjuster.
• an amine-based dispersant Solsperse 39000, manufactured by Lubrizol Corporation
• U-2 zirconium nitride
• Example 7 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that titanium black (12S, manufactured by Mitsubishi Materials Corporation, average primary particle size: 62 nm, specific surface area: 22.5 m2 /g, density: 4.3 g/ cm3 ) was used instead of zirconium nitride (UB-2, manufactured by Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m2 /g, density: 6.4 g/ cm3 ) as the specific gravity adjuster.
• titanium black manufactured by Mitsubishi Materials Corporation, average primary particle size: 62 nm, specific surface area: 22.5 m2 /g, density: 4.3 g/ cm3
• U-2 zirconium nitride
• Example 8 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that iron-manganese-copper oxide (Cu[Fe,Mn]O 4 ) (TM Black 3550, Dainichiseika Color & Chemicals Mfg. Co., Ltd., average primary particle size: 60 nm, specific surface area: 45 m 2 /g, density: 4.8 g/cm 3 ) was used instead of zirconium nitride (UB-2, Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m 2 /g, density: 6.4 g/cm 3 ) as the specific gravity adjuster.
• Cu[Fe,Mn]O 4 TM Black 3550, Dainichiseika Color & Chemicals Mfg. Co., Ltd., average primary particle size: 60 nm, specific surface area: 45 m 2 /g, density: 4.8 g/cm 3
• Example 9 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that ferrite (Fe 3 O 4 ) (EMG1400, Ferrotec Corporation, average primary particle size: 10 nm, density: 5.0 g/cm 3 ) was used instead of zirconium nitride ( UB -2, Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m 2 /g, density: 6.4 g/cm 3 ) as the specific gravity adjuster.
• ferrite Fe 3 O 4
• EMG1400 Ferrotec Corporation
• zirconium nitride UB -2, Mitsubishi Materials Corporation, average primary particle size: 35 nm, specific surface area: 35 m 2 /g, density: 6.4 g/cm 3
• Example 10 Thermally expandable microcapsules and foaming ink were prepared in the same manner as in Example 1, except that the monomer compositions and core agents shown in Table 1 were used.
• Example 2 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that silica (SiO 2 , PM-09, Tokuyama Corporation, primary average particle size: 40 nm, density: 2.2 g/cm 3 ) was used instead of zirconium nitride (UB-2, Mitsubishi Materials Corporation, primary average particle size: 35 nm, specific surface area: 35 m 2 /g, density: 6.4 g/cm 3 ) as the specific gravity adjuster.
• silica SiO 2 , PM-09, Tokuyama Corporation, primary average particle size: 40 nm, density: 2.2 g/cm 3
• U-2 zirconium nitride
• Example 3 Thermally expandable microcapsules and foamed ink were prepared in the same manner as in Example 1, except that carbon black (MA14, Mitsubishi Chemical Corporation, primary average particle size: 40 nm, density: 1.9 g/cm 3 ) was used instead of zirconium nitride (UB-2, Mitsubishi Materials Corporation, primary average particle size: 35 nm, specific surface area: 35 m 2 /g, density: 6.4 g/cm 3 ) as the specific gravity adjuster.
• carbon black MA14, Mitsubishi Chemical Corporation, primary average particle size: 40 nm, density: 1.9 g/cm 3
• U-2 zirconium nitride
• Ts foaming start temperature
• Dmax maximum displacement
• Tmax maximum foaming temperature
• Ts thermomechanical analyzer
• 25 ⁇ g of a 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 temperature increase rate of 5° C./min with a force of 0.1 N applied from above, and the displacement in the vertical direction of the measuring probe was measured.
• the temperature at which the displacement started to increase was taken as the foaming start temperature
• the maximum value of the displacement was taken as the maximum displacement
• the temperature at the maximum displacement was taken as the maximum foaming temperature.
• thermoly expandable microcapsule that is easy to handle and capable of producing a foamed molded article having good color development, and a foamable masterbatch and a foamed molded article using the thermally expandable microcapsule.

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