Molded body

Abstract

The present invention provides a molded body which has excellent flame retardancy and in which a poor appearance due to surface irregularities is unlikely to occur. The present invention is a molded body including hollow particles each containing, in a shell, a resin and a flame retardant, wherein the hollow particles have a number average particle diameter of 3-200 μm.

Description

Molded body

[0001] The present invention relates to a molded article.

[0002] Hollow particles having voids inside the particle are used in an extremely wide range of fields, such as various molded products such as injection molded products, injection compression molded products, extrusion molded products, and hollow molded products, as well as wallpaper, paints, sealants, pressure-sensitive adhesives, and diffusion materials, for the purposes of weight reduction, light diffusion, pore formation, imparting heat insulation properties, sound insulation properties, low dielectric properties, imparting impact resistance, improving rigidity, improving texture, preventing sink marks, improving coatability, and the like.

[0003] Known examples of such hollow particles include hollow resin particles obtained by using a special surfactant, as described in Patent Document 1. Such thermoplastic hollow resin particles have superior light diffusing properties compared to spherical resin particles that do not have a hollow structure, and are therefore said to provide excellent effects when used as a light diffusing material, such as in a light diffusion plate.

[0004] Japanese Patent Application Laid-Open No. 2020-045399

[0005] On the other hand, when producing a molded product using hollow particles, it is required to impart flame retardancy, but when a molded product is produced by mixing conventional hollow particles with a general flame retardant, the flame retardancy is insufficient, and there is also a problem that the surface of the obtained molded product becomes uneven, which impairs the appearance.

[0006] An object of the present invention is to provide hollow particles that can be used to obtain molded articles that have excellent flame retardancy and are less likely to suffer from poor appearance due to surface irregularities, and to provide molded articles using such hollow particles.

[0007] The present disclosure (1) is a molded article comprising hollow particles containing a resin and a flame retardant in a shell, the hollow particles having a number-average particle diameter of 3 to 200 μm. The present disclosure (2) is the molded article according to the present disclosure (1), in which the flame retardant comprises at least one selected from the group consisting of phosphorus-based flame retardants and halogen-based flame retardants. The present disclosure (3) is the molded article according to any one of the present disclosures (1) to (2), in which the content of the flame retardant is 0.01 wt% or more and 10 wt% or less based on the total weight of the hollow particles. The present disclosure (4) is the molded article according to any one of the present disclosures (1) to (3), further comprising at least one flame-retardant compound selected from the group consisting of phosphorus-based flame retardants and halogen-based flame retardants. The present invention is described in detail below. The hollow particles may have a void core or may contain a liquid or the like in the core, but it is preferable that the core be void. The voids have the advantages of preventing dimensional changes even when heat is applied to the molded body, and of reducing the amount of volatile matter from the liquid. Furthermore, when expanded particles or the like are used, the presence of unexpanded particles can result in an insufficient reduction in specific gravity, but when hollow particles are used, all particles can contribute to the reduction in specific gravity, allowing the specific gravity of the molded body to be reduced efficiently.

[0008] The hollow particles constituting the molded article according to one embodiment of the present invention contain a flame retardant in the shell. The inclusion of the flame retardant can improve the flame retardant properties of the molded article. As a result, the molded article can achieve both excellent flame retardancy and good appearance. Furthermore, the inclusion of the flame retardant increases affinity with resins, improving dispersibility. As a result, a molded article having uniform cells can be produced. In the present invention, the shell may contain a component equivalent to the flame retardant. The shell may contain the flame retardant and resin separately, or the flame retardant and resin may be integrated. The flame retardant is a substance that, when added to flammable materials such as plastics, wood, and fibers, can impart flame retardancy to the resulting material.

[0009] Examples of the flame retardant include phosphorus-based flame retardants, halogen-based flame retardants, nitrogen-containing flame retardants, inorganic flame retardants, etc. Among these, those containing at least one selected from the group consisting of phosphorus-based flame retardants and halogen-based flame retardants are preferred, and phosphorus-based flame retardants are preferred because they have high flame retardant properties and low environmental pollution.

[0010] Examples of the phosphorus-based flame retardant include aromatic phosphate esters, aliphatic phosphate esters, halogen-containing phosphate esters, polymerizable phosphorus compounds, phosphates, polyphosphates, and phosphorus-based spiro compounds. Examples of the aromatic phosphate esters include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, and aromatic pentaerythritol diphosphonate. Examples of the fatty acid phosphate esters include trioctyl phosphate. Examples of the halogen-containing phosphate esters include tris(halopropyl)phosphate and tris(haloethyl)phosphate. Examples of the polymerizable phosphorus compounds include vinyl phosphonate and allyl phosphonate.

[0011] Examples of the phosphate salts include melamine orthophosphate, piperazine orthophosphate, melamine pyrophosphate, piperazine pyrophosphate, calcium phosphate, magnesium phosphate, etc. Examples of the polyphosphate salts include ammonium polyphosphate, melamine polyphosphate, melamine melam melem polyphosphate, piperazine polyphosphate, etc. Among these, ammonium polyphosphate is preferred.

[0012] "Melamine" or "piperazine" in the above examples of phosphates and polyphosphates includes N,N,N',N'-tetramethyldiaminomethane, ethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-diethylethylenediamine, 1,2-propanediamine, 1 , 3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, trans-2,5-dimethylpiperazine, 1,4-bis(2-aminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, acetoguanamine, benzoguanamine, acrylguanamine, 2,4-diamino-6-nonane 2,4-diamino-6-hydroxy-1,3,5-triazine, 2-amino-4,6-dihydroxy-1,3,5-triazine, 2,4-diamino-6-methoxy-1,3,5-triazine, 2,4-diamino-6-ethoxy-1,3,5-triazine, 2,4-diamino-6-propoxy-1,3,5-triazine, 2,4-diamino-6-isopropoxy-1,3,5-triazine, 2,4-diamino-6-methyl- Compounds with names substituted with melamine cyanurate, melamine pyrophosphate, butylenediguanamine, norbornenediguanamine, methylenediguanamine, ethylenedimelamine, trimethylenedimelamine, tetramethylenedimelamine, hexamethylenedimelamine, and 1,3-hexylenedimelamine can also be used.

[0013] In the present invention, one of the above phosphates and polyphosphates may be used alone, or two or more selected from the above phosphates and polyphosphates may be mixed and used as an intumescent flame retardant. Furthermore, one or more selected from the above phosphates and polyphosphates may be mixed with a metal oxide and used as an intumescent flame retardant. Examples of metal oxides to be used in combination with one or more selected from the above phosphates and polyphosphates include zinc oxide, magnesium oxide, calcium oxide, silicon dioxide, titanium oxide, manganese oxide (MnO, MnO ２ ), iron oxide (FeO, Fe ２ O ３ , Fe ３ O ４ ), copper oxide, nickel oxide, tin oxide, aluminum oxide, calcium aluminate, etc. Among these, zinc oxide, magnesium oxide, and calcium oxide are preferred. When one or more selected from the above phosphates and polyphosphates are used in combination with a metal oxide, the mass ratio thereof is preferably adjusted as follows. From the viewpoint of improving flame retardancy, the mass ratio of one or more selected from phosphates and polyphosphates to the metal oxide [total mass of phosphate and polyphosphate / mass of metal oxide] is preferably 4 or more and 100 or less, more preferably 6 or more and 50 or less, and even more preferably 10 or more and 35 or less. That is, the ratio of the total mass of the above phosphate and polyphosphate to the mass of the metal oxide is preferably 4 to 100, more preferably 6 to 50, and even more preferably 10 to 35.

[0014] The phosphazene compound is an organic compound having a -P=N- bond in the molecule. As the phosphazene compound, one represented by the following general formula (1) is preferred because it has a relatively high decomposition temperature:

[0015]

[0016] In the above formula (1), R １ ~R ６each independently represents an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, an amino group, or a halogen atom. Examples of such phosphazene compounds include "SPB-100" commercially available from Otsuka Chemical Co., Ltd.

[0017] The phosphorus-based spiro compound is not particularly limited as long as it is a spiro compound having a phosphorus atom. A spiro compound is a compound having a structure in which two cyclic compounds share one carbon, and a spiro compound having a phosphorus atom is a compound in which at least one of the elements constituting the two cyclic compounds is a phosphorus atom. As the phosphorus-based spiro compound, for example, a compound having a structure represented by the following formula (2) in the molecule is preferably used. In formula (2), * indicates a linking portion to other substituents.

[0018]

[0019] Examples of the nitrogen-containing flame retardant include triazine derivatives, tris(2-hydroxyethyl)isocyanurate, tris(2,3-epoxypropyl)isocyanurate, melamine cyanurate, benzoguanamine, melamine, etc., and those containing oxygen in the structure are preferred. Note that the nitrogen-containing flame retardant in this specification refers to a flame retardant that does not contain phosphorus.

[0020] The halogen-based flame retardant is preferably a chlorine-based flame retardant or a bromine-based flame retardant. Examples of the chlorine-based flame retardant include chlorinated paraffin and chlorinated polyethylene perchloropentacyclodecane. The bromine-based flame retardant is not particularly limited as long as it contains bromine in its molecular structure. Examples of the brominated flame retardant include decabromodiphenyl ether, octabromodiphenyl ether, tetrabromobisphenol A (TBBA), TBBA epoxy oligomer, TBBA carbonate oligomer, TBBA bis(dibromopropyl ether), TBBA bis(aryl ether), decabromodiphenylethane [bis(pentabromophenyl)ethane], 1,2-bis(2,4,6-tribromophenoxy)ethane, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, 2,6-or(2,4-)dibromophenol homopolymer, brominated polystyrene, polybrominated styrene, ethylene bistetrabromophthalimide, hexabromocyclododecane, hexabromobenzene, pentabromobenzyl acrylate monomer, and pentabromobenzyl acrylate polymer. Among these, decabromodiphenylethane is preferred from the viewpoint of flame retardancy. These bromine-based flame retardants may be used alone or in combination of two or more. Note that the halogen-based flame retardants do not include halogen-based phosphorus-based flame retardants, nitrogen-containing flame retardants, and inorganic flame retardants.

[0021] Examples of the inorganic flame retardant include metal compounds such as metal oxides, metal hydroxides, and metal salts, etc. Examples of the metal compounds include zirconium oxide, aluminum hydroxide, dawsonite, calcium aluminate, gypsum dihydrate, calcium hydroxide, zinc borate, barium metaborate, borax, kaolin clay, calcium carbonate, molybdenum compounds, ammonium aluminum hydroxycarbonate, ferrocene, and tin compounds.

[0022] The flame retardant may be used in combination with a flame retardant synergist. This allows for a synergistic effect with the flame retardant, improving flame retardancy and reducing the amount of flame retardant used. In particular, when a halogen-based flame retardant is used as the flame retardant, the flame retardant synergist reacts with the halogen-based flame retardant during combustion to form a non-flammable halide. This produces an oxygen-shielding effect.

[0023] The flame retardant aid is preferably an antimony-based flame retardant aid, such as antimony trioxide or antimony pentoxide, and examples of commercially available products include "PATOX-M," "PATOX-MK," and "PATOX-K" manufactured by Nippon Seiko Co., Ltd.

[0024] From the viewpoint of a synergistic effect with the flame retardant, the content of the flame retardant aid is preferably 20 to 80 parts by weight, more preferably 30 to 70 parts by weight, and even more preferably 40 to 60 parts by weight, relative to 100 parts by weight of the flame retardant.

[0025] The melting point of the flame retardant is preferably 240 to 600° C., more preferably 250 to 550° C., and even more preferably 255 to 500° C. By setting the melting point within the above range, the flame retardant is easily melted by the heat during combustion, and combustion of the molded body can be suppressed.

[0026] The flame retardant is preferably in the form of fine particles (flame-retardant fine particles). In this case, the average particle diameter of the flame retardant is preferably 10 nm or more and 5000 nm or less, more preferably 50 nm or more and 1000 nm or less. By setting the average particle diameter within the above range, the flame-retardant fine particles are dispersed in the resin. That is, the average particle diameter of the flame retardant is preferably 10 to 5000 nm, more preferably 50 to 1000 nm. The average particle diameter can be measured, for example, by observation using a particle size distribution measuring device (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.).

[0027] The flame retardant has a specific surface area of ​​500 m ２ / g or less, and more preferably 5 to 300m ２ / g. By setting the specific surface area within the above range, the flame retardant is dispersed in the resin. 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 flame retardant from the measurement results in accordance with the BET method.

[0028] The preferred lower limit of the flame retardant content is 0.01 wt % and the preferred upper limit is 10 wt % based on the total hollow particle content. By setting the content at 0.01 wt % or more, fusion between hollow particles in the resin during molding can be suppressed. Setting the content at 10 wt % or less can increase the strength of the shell and further improve appearance performance. A more preferred lower limit is 0.3 wt %, a more preferred upper limit is 9 wt %, an even more preferred upper limit is 8 wt %, and an even more preferred upper limit is 7 wt %. That is, the flame retardant content is preferably 0.01 to 10 wt %, more preferably 0.3 to 9 wt %, even more preferably 0.3 to 8 wt %, and even more preferably 0.3 to 7 wt %. The flame retardant content can be determined by thermogravimetric analysis. The flame retardant content can also be calculated from the amounts of flame retardant and other components added during the manufacturing process.

[0029] In the present invention, the flame retardant may be present inside the shell of the hollow particle, on the shell surface, or on the inner surface of the shell. When the flame retardant is present inside the shell, the appearance of the molded article can be improved. Furthermore, it is preferable that the hollow particle has an outermost layer, and that the outermost layer contains the flame retardant. This configuration further improves dispersibility in the resin during molding. Furthermore, the flame retardant may be present both on the shell surface and inside the shell, in which case poor appearance of the molded article can be suppressed and flame retardancy can be improved. The location of the flame retardant can be confirmed using a transmission electron microscope or the like after preparing a thin film that passes near the center of the hollow particles dispersed in the embedded resin.

[0030] The hollow particles constituting the molded article according to one embodiment of the present invention contain a resin in the shell. The resin is preferably a polymer of a monomer composition, such as an unsaturated carboxylic acid monomer, a nitrile monomer, a polyfunctional monomer, a conjugated diene monomer, or a vinyl monomer. Two or more of these may be used in combination to form a copolymer. It is particularly preferred to use a polyfunctional monomer alone or to use an unsaturated carboxylic acid monomer and a nitrile monomer in combination.

[0031] The unsaturated carboxylic acid monomer is preferably a (meth)acrylic acid ester or an unsaturated carboxylic acid. The (meth)acrylic acid ester is preferably an alkyl methacrylate such as methyl methacrylate, ethyl methacrylate, or n-butyl methacrylate, or an alicyclic, aromatic, or heterocyclic methacrylate such as cyclohexyl methacrylate, benzyl methacrylate, or isobornyl methacrylate.

[0032] Examples of the unsaturated carboxylic acid include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, as well as maleic acid, itaconic acid, fumaric acid, citraconic acid, and chloromaleic acid. Monoesters of the unsaturated dicarboxylic acids may also be used. Examples of the monoesters of the unsaturated dicarboxylic acids 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.

[0033] 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.

[0034] Examples of the polyfunctional monomer include monomers having two or more radically polymerizable double bonds, and specific examples include divinylbenzene, di(meth)acrylate, and tri- or higher functional (meth)acrylates. Examples of the di(meth)acrylate include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Other examples include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane di(meth)acrylate, and dimethylol-tricyclodecane di(meth)acrylate. Furthermore, di(meth)acrylate of polyethylene glycol having a weight average molecular weight of 200 to 600 may also be used. Examples of the trifunctional (meth)acrylates 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)acrylates include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc. Among these, trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and bifunctional (meth)acrylates such as polyethylene glycol provide relatively uniform crosslinking to the acrylonitrile-based shell. By including the polyfunctional monomer, the strength of the shell can be enhanced.

[0035] Examples of the conjugated diene monomer include butadiene, isoprene, and chloroprene. Examples of the vinyl monomer include vinyl chloride, vinylidene chloride, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

[0036] The resin may contain a thermosetting resin. Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, urea resin, polyimide resin, and bismaleimide resin. Among these, epoxy resin and phenol resin are preferred.

[0037] The epoxy resin is not particularly limited, and examples thereof include bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, dicyclopentadiene epoxy resins, and glycidylamine epoxy resins. Examples of the phenol resins include novolac phenol resins, resol phenol resins, and benzylic ether phenol resins. Of these, novolac phenol resins are preferred.

[0038] The thermosetting resin preferably has two or more functional groups reactive with carboxyl groups per molecule. Having two or more functional groups reactive with carboxyl groups can further strengthen the curing properties of the thermosetting resin. In particular, when the monomer composition contains a monomer having a carboxyl group, the heat generated during heating causes the carboxyl group and the thermosetting resin to bond more strongly, significantly improving heat resistance and durability. The thermosetting resin preferably does not have a radically polymerizable double bond.

[0039] Examples of the functional group reactive with the carboxyl group include a glycidyl group, a phenol group, a methylol group, and an amino group. Of these, a glycidyl group is preferred. The functional groups reactive with the carboxyl group may be the same or two or more different groups.

[0040] When the flame retardant and the resin are integrally contained, the resin preferably contains a polymer of a monomer composition containing a flame-retardant monomer. Examples of the flame-retardant monomer include phosphorus atom-containing monomers and halogen-containing monomers. Examples of the phosphorus atom-containing monomer include phosphoric acid derivatives, phosphine derivatives, phosphinic acid derivatives, phosphonic acid derivatives, phosphorane derivatives, and phosphazene derivatives.

[0041] Examples of the phosphoric acid derivatives include 2-acryloyloxyethyl phosphate, 2-methacryloyloxyethyl phosphate, 2-acryloyloxypropyl phosphate, 2-methacryloyloxypropyl phosphate, di(2-acryloyloxyethyl)phosphate, di(2-methacryloyloxyethyl)phosphate, di(2-acryloyloxypropyl)phosphate, di(2-methacryloyloxypropyl)phosphate, methyl-2-acryloyloxyethyl phosphate, and methyl-2-methacryloyloxyethyl. Phosphate, methyl-2-acryloyloxypropyl phosphate, methyl-2-methacryloyloxypropyl phosphate, ethyl-2-acryloyloxyethyl phosphate, ethyl-2-methacryloyloxyethyl phosphate, ethyl-2-acryloyloxypropyl phosphate, ethyl-2-methacryloyloxypropyl phosphate, propyl-2-acryloyloxyethyl phosphate, propyl-2-methacryloyloxyethyl phosphate, propyl-2-acryloyloxypropyl phosphate, propyl-2 -methacryloyloxypropyl phosphate, butyl-2-acryloyloxyethyl phosphate, butyl-2-methacryloyloxyethyl phosphate, butyl-2-acryloyloxypropyl phosphate, butyl-2-methacryloyloxypropyl phosphate, phenyl-2-acryloyloxyethyl phosphate, phenyl-2-methacryloyloxyethyl phosphate, phenyl-2-acryloyloxypropyl phosphate, phenyl-2-methacryloyloxypropyl phosphate, tri(2-acryloyloxyethyl tri(2-methacryloyloxyethyl)phosphate, tri(2-acryloyloxypropyl)phosphate, tri(2-methacryloyloxypropyl)phosphate, dimethyl-2-acryloyloxyethyl phosphate, dimethyl-2-methacryloyloxypropyl phosphate, dimethyl-2-methacryloyloxypropyl phosphate, diethyl-2-acryloyloxyethyl phosphate, diethyl-2-methacryloyloxyethyl phosphate,Examples of the acryloyloxypropyl phosphate include diethyl-2-acryloyloxypropyl phosphate, diethyl-2-methacryloyloxypropyl phosphate, dipropyl-2-acryloyloxyethyl phosphate, dipropyl-2-methacryloyloxyethyl phosphate, dipropyl-2-acryloyloxypropyl phosphate, dipropyl-2-methacryloyloxypropyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxypropyl phosphate, dibutyl-2-methacryloyloxypropyl phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, diphenyl-2-acryloyloxypropyl phosphate, and diphenyl-2-methacryloyloxypropyl phosphate.

[0042] Examples of the halogen-containing monomer include 2,4,6-tribromophenyl methacrylate, 2,4,6-tribromophenyl acrylate, 2,4-dichlorostyrene, 2,4-dibromostyrene, 2,4,6-trichlorostyrene, 2,4,6-tribromostyrene, pentachlorostyrene, pentabromostyrene, pentabromobenzyl acrylate, and pentabromobenzyl methacrylate.

[0043] The preferred lower limit of the content of the flame-retardant monomer in the monomer composition is 0.1 wt %, and the preferred upper limit is 25 wt %. By setting the content of the flame-retardant monomer to 0.1 wt % or more, it is possible to improve the flame retardancy when hollow particles are used, and by setting the content to 25 wt % or less, it is possible to improve the strength of the shell. The more preferred lower limit of the content of the flame-retardant monomer is 0.3 wt %, and the more preferred upper limit is 22 wt %. That is, the content of the flame-retardant monomer is preferably 0.1 to 25 wt %, and more preferably 0.3 to 22 wt %.

[0044] A polymerization initiator is added to the monomer composition to polymerize the monomers. Suitable examples of the polymerization initiator include dialkyl peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, and azo compounds. Specific examples include dialkyl peroxides such as methyl ethyl peroxide, di-t-butyl peroxide, and dicumyl peroxide; and diacyl peroxides such as isobutyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and 3,5,5-trimethylhexanoyl peroxide. Other examples include t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, and 1,1,3,3-tetramethylbutyl peroxyneodecanoate. Other examples include peroxyesters such as cumyl peroxy neodecanoate and (α,α-bis-neodecanoylperoxy)diisopropylbenzene; bis(4-t-butylcyclohexyl)peroxydicarbonate, di-n-propyl-oxydicarbonate, and diisopropyl peroxydicarbonate. Further examples include peroxydicarbonates such as di(2-ethylethylperoxy)dicarbonate, dimethoxybutyl peroxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate. Additionally, other examples include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 1,1'-azobis(1-cyclohexanecarbonitrile).

[0045] The preferred lower limit of the weight-average molecular weight of the resin constituting the shell is 50,000, and the preferred upper limit is 2,000,000. By making it 50,000 or more, the strength of the shell can be improved, and by making it 2,000,000 or less, the strength of the shell can be prevented from becoming too high. That is, the weight-average molecular weight of the resin constituting the shell is preferably 50,000 to 2,000,000. The weight-average molecular weight is a value determined by measuring by gel permeation chromatography (GPC) using DMF as a solvent and calculated in terms of polymethyl methacrylate. Examples of columns used when measuring the weight-average molecular weight calculated in terms of polymethyl methacrylate by GPC include HSPgel RT MB-H (manufactured by Waters), and examples of molecular weight standards include M-75 (manufactured by Shodex).

[0046] The shell may contain a metal cation. When the copolymer constituting the shell contains a carboxyl group, the metal cation reacts with the carboxyl group to ionically crosslink the copolymer, improving heat resistance and enabling hollow particles to be produced that do not burst or shrink for long periods of time at high temperatures. Furthermore, since the elastic modulus of the shell is unlikely to decrease even at high temperatures, the hollow particles do not burst or shrink even when subjected to molding processes that apply strong shear forces, such as kneading, calendaring, extrusion, and injection molding. The ionic crosslinking described above means that crosslinks are formed between free carboxyl groups present as side chains of the copolymer. The number of carboxyl groups arranged per monovalent metal cation varies depending on the metal type.

[0047] The metal cation is not particularly limited as long as it reacts with the carboxyl groups of the copolymer to ionically crosslink the copolymer, and examples thereof include ions of Li, Na, K, Zn, Mg, Ca, Ba, Sr, Mn, Al, Ti, Ru, Fe, Ni, Cu, Cs, Sn, Cr, and Pb. These may be used alone or in combination of two or more. Among these, Ca, Zn, and Al ions are preferred, with Zn ions being particularly preferred. When two or more of the metal cations are used, the combination is not particularly limited, but it is preferable to use an alkali metal ion in combination with a metal cation other than the alkali metal. The presence of the alkali metal ion activates functional groups such as carboxyl groups, thereby promoting the reaction between the metal cations other than the alkali metal and the carboxyl groups of the copolymer. Examples of the alkali metal include Na, K, and Li.

[0048] The shell may further contain, as necessary, a stabilizer, an ultraviolet absorber, an antioxidant, an antistatic agent, a silane coupling agent, a coloring agent, and the like.

[0049] The number-average particle diameter of the hollow particles constituting the molded article according to one embodiment of the present invention has a lower limit of 3 μm and an upper limit of 200 μm. By setting the diameter to 3 μm or more, the porosity of the resulting molded article can be increased, and by setting the diameter to 200 μm or less, the appearance of the molded article can be improved. The lower limit of the number-average particle diameter is preferably 5 μm, more preferably 15 μm, and a preferred upper limit is 150 μm, more preferably 100 μm, even more preferably 80 μm, particularly preferably 60 μm, and especially more preferably 50 μm. That is, the number-average particle diameter of the hollow particles is 3 to 200 μm, preferably 5 to 150 μm, more preferably 15 to 100 μm, even more preferably 15 to 80 μm, particularly preferably 15 to 60 μm, and especially more preferably 15 to 50 μm. The CV value (coefficient of variation) of the average particle diameter of the hollow particles is preferably 40% or less, more preferably 30% or less, and even more preferably 20% or less. A CV value of 40% or less ensures uniform cell counts in the resulting molded body, resulting in a uniform thickness. Furthermore, the cells present on the surface of the molded body are also uniform, resulting in an excellent appearance. While there are no particular restrictions on the preferred lower limit, 0% is preferred. The number-average particle diameter of the hollow particles can be measured by measuring the particle diameters of at least 50 hollow particles in a cross section obtained by cutting the molded body using a SEM or the like and calculating the average value. When the cross section of the hollow particles is not a perfect circle, the average value of (maximum diameter + minimum diameter) / 2 is used as the particle diameter. The CV value can also be calculated during the measurement.

[0050] The hollow particles constituting the molded article according to one embodiment of the present invention preferably have a ratio (A / B) of the average particle diameter (A) of the flame retardant to the shell thickness (B) of 0.01 to 5.0. By setting the ratio within this range, both flame retardancy and appearance can be achieved. A more preferred lower limit is 0.1, and a more preferred upper limit is 4.0. The shell thickness is preferably 0.05 μm or more and 1.5 μm or less. Furthermore, the hollow particles preferably have a ratio (B / C) of the shell thickness (B) to the average particle diameter (C) of the hollow particles of 0.0001 to 0.1. The shell thickness can be measured by measuring the shell thickness of 10 hollow particles in a cross section obtained by cutting the molded article using a SEM or the like at any five locations per particle and calculating the average value.

[0051] The method for producing the hollow particles constituting the molded article, which is one embodiment of the present invention, is not particularly limited. For example, the hollow particles can be produced by carrying out the steps of preparing an aqueous dispersion medium containing a dispersant, adding a monomer composition, a flame retardant, and a hollowing agent, and polymerizing the monomers.

[0052] In the production of hollow particles constituting the molded article according to one embodiment of the present invention, a step of preparing an aqueous dispersion medium is first carried out. Specifically, for example, an aqueous dispersion medium containing a dispersant is prepared by adding water, a dispersant, and optionally a co-stabilizer to a polymerization reaction vessel.

[0053] As the dispersant, it is preferable to use at least one inorganic compound selected from the group consisting of Si-based compounds and Mg-based compounds, in addition to an emulsifier such as polyvinyl alcohol. By containing the inorganic compound, it is possible to suppress fusion between hollow particles during molding. From the viewpoint of improving the flame retardancy of the resulting molded body, it is preferable to use an inorganic compound. Note that the inorganic compound is different from the flame retardant.

[0054] The Si-based compound and Mg-based compound preferably contain an oxide, hydroxide, carbonate, or hydrogencarbonate of silicon or magnesium. These Si-based compounds and Mg-based compounds may be used alone or in combination of two or more.

[0055] Examples of the Si-based compounds include colloidal silica, silicate sol, No. 3 water glass, sodium orthosilicate, sodium metasilicate, etc. Among these, colloidal silica is preferred. Examples of the Mg-based compounds include magnesium oxide, magnesium hydroxide, magnesium oxide hydroxide, hydrotalcite, dihydrotalcite, magnesium carbonate, basic magnesium carbonate, magnesium calcium carbonate, magnesium phosphate, magnesium hydrogen phosphate, magnesium pyrophosphate, magnesium borate, etc. Among these, magnesium hydroxide is preferred.

[0056] 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.

[0057] The inorganic compound is preferably in the form of fine particles. When the inorganic compound is in the form of fine particles, the primary particle diameter is preferably 0.5 μm or less, more preferably 5 to 100 nm (0.1 μm). By keeping the diameter within this range, fusion between hollow particles 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).

[0058] The preferred lower limit of the amount of the dispersant added relative to the total monomer composition is 0.5% by weight, and the preferred upper limit is 30% by weight. By setting the amount to 0.5% by weight or more, aggregation during hollow particle production can be suppressed. By setting the amount to 30% by weight or less, dispersibility can be further improved. A more preferred lower limit is 1% by weight, and a more preferred upper limit is 25% by weight. That is, the amount of the dispersant added is preferably 0.5 to 30% by weight, and more preferably 1 to 25% by weight.

[0059] 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, dioctyl sulfosuccinate, sorbitan ester, various emulsifiers, etc.

[0060] In addition to the co-stabilizer, a condensation product or a water-soluble nitrogen compound may be added. As the condensation product, a condensation product of diethanolamine and an aliphatic dicarboxylic acid is preferred, and a condensation product of diethanolamine and adipic acid or a condensation product of diethanolamine and itaconic acid is particularly preferred.

[0061] Examples of the water-soluble nitrogen compounds include polyvinylpyrrolidone, polyethyleneimine, polyoxyethylene alkylamine, polydialkylaminoalkyl(meth)acrylates such as polydimethylaminoethyl methacrylate and polydimethylaminoethyl acrylate, polydialkylaminoalkyl(meth)acrylamides such as polydimethylaminopropyl acrylamide and polydimethylaminopropyl methacrylamide, polyacrylamide, polycationic acrylamide, polyamine sulfone, and polyallylamine. Among these, polyvinylpyrrolidone is preferably used.

[0062] An aqueous dispersion medium containing the dispersant and, if necessary, a co-stabilizer is prepared by blending it with deionized water, and the pH of the aqueous phase is determined appropriately depending on the types of dispersant and co-stabilizer used. For example, when a Si-based compound such as colloidal silica is used as the dispersant, polymerization is carried out using an acidic aqueous dispersion medium, and to make the aqueous dispersion medium acidic, an acid such as hydrochloric acid is added as necessary to adjust the pH of the system to 3 to 4. On the other hand, when a Mg-based compound such as magnesium hydroxide or calcium phosphate is used as the inorganic compound, polymerization is carried out using an alkaline aqueous dispersion medium adjusted to a pH of 8 to 11.

[0063] Next, in the method for producing hollow particles, a step of adding a monomer composition, a flame retardant, and a hollowing agent is carried out. In this step, the monomer composition, the flame retardant, and the hollowing agent may be added separately to an aqueous dispersion medium to prepare an oily mixture in the aqueous dispersion medium. However, typically, the two may be mixed together to form an oily mixture, which is then added to the aqueous dispersion medium. In this case, the oily mixture and the aqueous dispersion medium may be prepared in separate containers, and the oily mixture may be dispersed in the aqueous dispersion medium by stirring and mixing in the separate containers, and then added to the polymerization reaction vessel. In this step, the dispersant can be present at the interface between the oil droplets of the oily mixture and the aqueous dispersion medium. A polymerization initiator is used to polymerize the monomer. The polymerization initiator may be added to the oily mixture in advance, or after stirring and mixing the aqueous dispersion medium and the oily mixture in the polymerization reaction vessel. The flame retardant and dispersant may be added to the aqueous dispersion medium or after. Furthermore, when the flame retardant and the polymer compound are integrated, a monomer composition containing a flame-retardant monomer may be used without adding a flame retardant. In particular, the average particle size of the resulting hollow particles can be controlled by adjusting the components of the hollow particles (especially the monomer and hollowing agent) and the amounts added, or by adjusting the reaction process during production of the thermally expandable microcapsules. Examples of adjustments to the reaction process include thoroughly pre-stirring the oily mixture before emulsifying and dispersing it in the aqueous dispersion medium, or by emulsifying and dispersing the oily mixture in the aqueous dispersion medium to a predetermined particle size. In particular, the amount of hollowing agent added is preferably 50 to 2,800 parts by weight per 10 parts by weight of the monomer composition.

[0064] Examples of methods for emulsifying and dispersing the oily mixture in an aqueous dispersion medium to a predetermined particle size include stirring using a homomixer (e.g., manufactured by Tokushu Kika Kogyo Co., Ltd.) or a homogenizer, or passing the mixture through a static dispersion device such as a line mixer or an element-type static disperser. The average particle size of the resulting hollow particles can also be controlled by adjusting the stirring force (e.g., rotation speed) during stirring. The aqueous dispersion medium and the monomer composition may be supplied separately to the static dispersion device, or a dispersion liquid that has been mixed and stirred in advance may be supplied. Furthermore, the flame retardant may be added after adjusting the average particle size by a pulverization / dispersion treatment or the like. Examples of methods for the pulverization / dispersion treatment include a crusher, a mill (e.g., a wet or dry bead mill, a ball mill, a jet mill, a planetary mill), a blender, and the like.

[0065] The hollowing agent is a substance for forming a hollow portion that becomes the core. The hollowing agent is preferably an organic solvent with a boiling point of −50 to 100° C., as this is easy to handle when drying is performed in the hollowing step.

[0066] Examples of the hollowing agent include low molecular weight hydrocarbons such as n-butane, isobutane, butane, butene, isobutene, n-pentane, 2-methylbutane (isopentane), neopentane, n-hexane, cyclohexane, heptane, petroleum ether, isooctane, and octane. Other examples include ethyl acetate, methyl ethyl ketone, acetone, methylene chloride, chloroform, and carbon tetrachloride. Of these, 2-methylbutane, cyclohexane, isobutane, n-butane, n-pentane, n-hexane, isooctane, isododecane, and mixtures thereof are preferred. These hollowing agents may be used alone or in combination. Alternatively, a pyrolytic compound that decomposes into a gaseous form upon heating may be used as the hollowing agent.

[0067] The hollow particles constituting the molded article according to one embodiment of the present invention can be produced by subjecting the dispersion obtained through the above-described steps to a step of polymerizing the monomer by heating and pressurizing the dispersion, and a step of washing the dispersion. In particular, in the step of polymerizing the monomer, the number average particle diameter of the obtained hollow particles can be controlled by setting the heating temperature to 40 to 100°C and the pressurizing pressure to 0.2 to 1.0 MPa.

[0068] The molded article according to one embodiment of the present invention contains a base resin in addition to the hollow particles. The base resin is preferably a thermoplastic resin. 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, olefin-based thermoplastic elastomers (TPV), and ethylene-methyl methacrylate copolymer (EMMA). Among these, LDPE, EVA, EMMA, and the like are preferred due to their low melting points and ease of processing. These may be used alone or in combination of two or more.

[0069] The content of the hollow particles in the molded article according to one embodiment of the present invention is not particularly limited, but a preferred lower limit is 1 part by weight and a preferred upper limit is 90 parts by weight per 100 parts by weight of the base resin.

[0070] In addition to the hollow particles and base resin, a flame-retardant compound may be added to the molded article, which is one embodiment of the present invention. The flame-retardant compound refers to a flame-retardant component contained in addition to the flame retardant contained in the hollow particles. The flame-retardant compound may be the same as the flame retardant. The flame-retardant compound preferably contains at least one selected from the group consisting of phosphorus-based flame retardants and halogen-based flame retardants. The content of the flame-retardant compound in the molded article is not particularly limited, but a preferred lower limit is 1 part by weight and a preferred upper limit is 90 parts by weight per 100 parts by weight of the base resin.

[0071] In the molded article according to one embodiment of the present invention, the ratio (A / C) of the average particle size (A) of the flame retardant contained in the hollow particles to the average particle size (C) of the flame-retardant compound is preferably 0.0016 to 1.0. By keeping the ratio within the above range, flame retardancy can be further improved. The average particle size of the flame-retardant compound is preferably 1,000 nm or more and 300,000 nm or less, more preferably 3,000 nm or more and 250,000 nm or less. That is, the average particle size of the flame-retardant compound is preferably 1,000 to 300,000 nm, more preferably 3,000 to 250,000 nm. The average particle size of the flame-retardant compound can be measured by observation using a particle size distribution analyzer (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.) or the like.

[0072] In one embodiment of the molded article of the present invention, the content of the flame-retardant element is preferably 0.001 wt% or more and 10 wt% or less relative to the entire molded article. By setting the content of the flame-retardant element to 0.001 wt% or more, the flame retardancy of the molded article can be improved, and by setting it to 10 wt% or less, the strength can be improved. A more preferred lower limit of the content of the flame-retardant element is 0.01 wt%, an even more preferred lower limit is 0.1 wt%, a particularly preferred lower limit is 0.3 wt%, a more preferred upper limit is 7 wt%, an even more preferred upper limit is 5 wt%, and a particularly preferred upper limit is 4 wt%. That is, the content of the flame-retardant element is preferably 0.001 to 10 wt%, more preferably 0.01 to 7 wt%, even more preferably 0.1 to 5 wt%, and particularly preferably 0.3 to 4 wt%. The content of the flame-retardant element can be measured by solid-state NMR measurement. The flame-retardant element refers to elements such as phosphorus, halogen elements, or elements such as antimony, aluminum, and tin. Among these, phosphorus and halogen elements are preferred, and phosphorus element is particularly preferred.

[0073] In particular, the hollow particles can be used to obtain molded articles having high appearance quality, such as uneven shapes, and can be suitably used for applications such as automotive interior materials and residential wallpaper. The molding method of one embodiment of the molded article of the present invention is not particularly limited, and examples thereof include kneading molding, calendar molding, extrusion molding, and injection molding.

[0074] According to the present invention, a molded article can be obtained that has excellent flame retardancy and is less likely to have poor appearance due to surface irregularities. Furthermore, according to the present invention, the dispersion of hollow particles in the molded article is improved. As a result, a molded article having uniform cells can be obtained.

[0075] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0076] (Example 1) [Production Example 1] (Production Example 1: Preparation of Hollow Particles) 2.0 parts by weight of polyvinyl alcohol (PVA, manufactured by Mitsubishi Chemical Corporation, GH-20, viscosity 40 to 46 mPa·s, degree of saponification 86.5 to 89.0 mol%) as a dispersant was added to 250 parts by weight of ion-exchanged water and mixed to prepare an aqueous medium. Furthermore, 10 parts by weight of divinylbenzene as a monomer composition was added to 200 parts by weight of cyclohexane and mixed to prepare a homogeneous solution. To this homogeneous solution, 0.2 parts by weight of an amine salt of polyether ester acid (Disparlon-234, manufactured by Kusumoto Chemicals Co., Ltd.) as an additive, 0.26 parts by weight of ammonium polyphosphate (Exolit AP423, manufactured by Clariant Chemicals, crushed) as a flame retardant, and 0.8 parts by weight of a polymerization initiator (2,2′-azobisisobutyronitrile) were added, and the mixture was crushed and dispersed using a bead mill, followed by mixing in an autoclave. (Oil-based Mixture) The ammonium polyphosphate in the oil-based mixture had an average particle size of 150 nm. It was then added to an aqueous medium and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, placed in a nitrogen-purged pressure polymerization vessel, and reacted at 60°C for 20 hours under pressure (0.5 MPa), to obtain a reaction product. The resulting reaction product was repeatedly filtered and washed with water, and then dried to obtain hollow particles. The resulting hollow particles were added to an embedding resin (Technovit 4000, manufactured by Kulzer) and dispersed to prepare a hollow particle-embedded resin. A thin film was prepared using a microtome (EM UC7, manufactured by LEICA) so as to pass through the center of the hollow particles dispersed in the embedding resin. The location of the flame retardant was confirmed using a transmission electron microscope (JEM-2100, manufactured by JEOL Ltd.). The presence of the flame retardant was confirmed on the shell surface and inside of the hollow particles.

[0077] (Preparation of Molded Article) 80 parts by weight of polypropylene resin and 20 parts by weight of polyethylene resin were mixed with 40 parts by weight of the obtained hollow particles, 0.5 parts by weight of 2,6-di-t-butyl-p-cresol as an antioxidant, 0.3 parts by weight of dilauryl thiodipropionate, 3.2 parts by weight of trimethylolpropane trimethacrylate as a crosslinking aid, and 15 parts by weight of ammonium polyphosphate (Exolit AP462, manufactured by Clariant, average particle size: 20 μm) as a flame retardant compound to obtain a resin composition. A molded article was prepared from the obtained resin composition using an 8-inch roll at 130°C.

[0078] (Example 2) [Production Example 2] Hollow particles [Production Example 2] were produced in the same manner as in Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 500 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0079] Example 3 Hollow particles were produced in the same manner as in Production Example 2. Then, a molded body was produced in the same manner as in Example 2, except that the amount of hollow particles added was 60 parts by weight.

[0080] Example 4 Hollow particles were prepared in the same manner as in Production Example 2. Then, Fireguard FCX-210 (spirocyclic diphosphonate compound, Teijin Limited, melting point: 250°C, specific surface area: 1.0 m) was used as the flame retardant compound instead of ammonium polyphosphate (Exolit AP462, Clariant). ２ A molded body was prepared in the same manner as in Example 2 except that a 100% cellulose ester (100% cellulose ester) was used.

[0081] (Example 5) [Production Example 3] Hollow particles [Production Example 3] were produced in the same manner as in Production Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 800 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0082] (Example 6) [Production Example 4] Hollow particles [Production Example 4] were prepared in the same manner as in Production Example 2, except that ammonium polyphosphate (Exolit AP423, manufactured by Clariant, pulverized) was used as the flame retardant, and a molded body was prepared in the same manner as in Example 1. The average particle size after pulverization and dispersion treatment using a bead mill was 80 nm.

[0083] (Example 7) [Production Example 5] Hollow particles [Production Example 5] were prepared in the same manner as in Production Example 2, except that ammonium polyphosphate (Exolit AP423, manufactured by Clariant, pulverized) was used as the flame retardant, and a molded body was prepared in the same manner as in Example 1. The average particle size after pulverization and dispersion treatment using a bead mill was 250 nm.

[0084] (Example 8) [Production Example 6] Hollow particles [Production Example 6] were prepared in the same manner as in Production Example 2, except that ammonium polyphosphate (Exolit AP423, manufactured by Clariant, pulverized) was used as the flame retardant, and a molded body was prepared in the same manner as in Example 1. The average particle size after pulverization and dispersion treatment using a bead mill was 350 nm.

[0085] (Example 9) [Production Example 7] Instead of ammonium polyphosphate (Exolit AP423, manufactured by Clariant, crushed), a flame retardant (Fireguard FCX-210, manufactured by Teijin Limited, crushed, average particle size: 150 nm, melting point: 250°C, specific surface area: 1.0 m) was used. ２ Hollow particles [Production Example 7] were produced in the same manner as in Production Example 2 except that 100g of cellulose acetate was used. A molded article was produced in the same manner as in Example 1.

[0086] (Example 10) [Production Example 8] Instead of 0.26 parts by weight of ammonium polyphosphate (Exolit AP423, manufactured by Clariant, crushed), 0.26 parts by weight of decabromodiphenylethane (SAYTEX8010, manufactured by Albemarle Japan, crushed, average particle size: 150 nm, melting point: 350°C) was used as a flame retardant. Antimony trioxide (PATOX-M, manufactured by Nippon Seiko Co., Ltd., crushed, melting point: 656°C, specific surface area: 3.0 m) was further used as a flame retardant aid. ２ Hollow particles [Production Example 8] were produced in the same manner as in Production Example 2 except that 0.13 parts by weight of cellulose acetate / g was used, and a molded article was produced in the same manner as in Example 1.

[0087] (Example 11) [Production Example 9] Hollow particles [Production Example 9] were prepared in the same manner as in Production Example 2, except that 9 parts by weight of divinylbenzene and 1 part by weight of 2-(methacryloyloxy)ethyl phosphate (Phosmer M, manufactured by Unichemical Corporation) were used instead of 10 parts by weight of divinylbenzene, and a molded body was prepared in the same manner as in Example 1.

[0088] (Example 12) [Production Example 10] To 250 parts by weight of ion-exchanged water were added 75 parts by weight of sodium chloride, 30 parts by weight of colloidal silica containing 20% ​​by weight of an active ingredient, 2.0 parts by weight of polyvinylpyrrolidone, and 0.6 parts by weight of ethylenediaminetetraacetic acid tetrasodium salt, and the pH of the resulting mixture was adjusted to 2.0 to 3.0 to prepare an aqueous dispersion medium. Separately, to a monomer composition of 0.2 parts by weight of acrylonitrile, 5.5 parts by weight of methacrylonitrile, 0.3 parts by weight of methacrylic acid, and 4 parts by weight of methyl acrylate, 0.2 parts by weight of an amine salt of polyether ester acid (Disparlon-234, manufactured by Kusumoto Chemicals Co., Ltd.), and 0.39 parts by weight of ammonium polyphosphate (Exolit AP423, manufactured by Clariant, pulverized) as a flame retardant, 500 parts by weight of cyclohexane as a hollowing agent, and 1.6 parts by weight of a liquid containing 50% di-sec-butyl peroxydicarbonate as an active ingredient were added, and a pulverization dispersion treatment was carried out using a bead mill. Next, the mixture was charged into an autoclave and mixed. The ammonium polyphosphate in the oily mixture had an average particle size of 150 nm. Thereafter, the mixture was added to an aqueous medium and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed using a homogenizer, then charged into a nitrogen-purged pressure polymerization vessel and reacted at 60°C for 20 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 hollow particles [Production Example 10]. Furthermore, a molded body was produced using the resulting hollow particles in the same manner as in Example 1.

[0089] (Example 13) [Production Example 11] Hollow particles [Production Example 11] were produced in the same manner as in Production Example 10, except that 3.3 parts by weight of acrylonitrile, 2.5 parts by weight of methacrylonitrile, 3 parts by weight of methyl acrylate, and 1.2 parts by weight of methyl methacrylate were used as the monomer composition, and a molded body was produced in the same manner as in Example 1.

[0090] (Example 14) [Production Example 12] Hollow particles [Production Example 12] were produced in the same manner as in Production Example 10, except that 2 parts by weight of acrylonitrile, 3 parts by weight of methacrylonitrile, 4 parts by weight of methacrylic acid, and 1 part by weight of methyl methacrylate were used as the monomer composition, and a molded body was produced in the same manner as in Example 1.

[0091] (Example 15) [Production Example 16] Hollow particles [Production Example 16] were produced in the same manner as in Production Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 100 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0092] (Example 16) [Production Example 17] Hollow particles [Production Example 17] were produced in the same manner as in Production Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 2,700 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0093] (Example 17) [Production Example 18] Hollow particles [Production Example 18] were produced in the same manner as in Production Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 3,500 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0094] (Example 18) [Production Example 19] Hollow particles [Production Example 19] were prepared in the same manner as in Production Example 2, except that the amount of ammonium polyphosphate (Exolit AP423, manufactured by Clariant Chemicals, pulverized) added was changed from 0.26 parts by weight to 0.52 parts by weight, and a molded body was prepared in the same manner as in Example 1.

[0095] (Example 19) [Production Example 20] Hollow particles [Production Example 20] were prepared in the same manner as in Production Example 2, except that the amount of ammonium polyphosphate (Exolit AP423, manufactured by Clariant Chemicals, pulverized) added was changed from 0.26 parts by weight to 1.12 parts by weight, and a molded body was prepared in the same manner as in Example 1.

[0096] (Example 20) [Production Example 21] Hollow particles [Production Example 21] were produced in the same manner as in Production Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 250 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0097] (Example 21) [Production Example 22] Hollow particles [Production Example 22] were produced in the same manner as in Production Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 90 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0098] Comparative Example 1 [Production Example 13] Hollow particles [Production Example 13] were produced in the same manner as in Production Example 1, except that no flame retardant was added, and a molded body was produced in the same manner as in Example 1.

[0099] (Comparative Example 2) [Production Example 14] Hollow particles [Production Example 14] were produced in the same manner as in Production Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 40 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0100] (Comparative Example 3) [Production Example 15] Hollow particles [Production Example 15] were produced in the same manner as in Production Example 1, except that the amount of cyclohexane added was changed from 200 parts by weight to 4,500 parts by weight, and a molded body was produced in the same manner as in Example 1.

[0101] (Evaluation Method) The performance of the obtained hollow particles and molded bodies was evaluated by the following methods. The results are shown in Tables 1 and 2.

[0102] (1) Evaluation of hollow particles (1-1) Measurement of number average particle diameter The particle diameters of at least 50 hollow particles in a cross section obtained by cutting the molded body were measured using a SEM or the like, and the average value was taken as the number average particle diameter.

[0103] (1-2) Shell Thickness The shell thickness of 10 hollow particles in a cross section obtained by cutting the molded body was measured by measuring the shell thickness at any five points using an FIB-SEM (Helios 650, FEI Corporation) and calculating the average value.

[0104] (1-3) Measurement of Flame-Retardant Element (P Element and Br Element) Content Using an NMR (ECZ-400R, manufactured by JEOL), a solid sample containing polyphosphoric acid was measured. 31 The content of the flame-retardant element (P element) was calculated by P-NMR measurement. In addition, the content of the flame-retardant element (Br element) was calculated by X-ray fluorescence measurement using decabromodiphenylethane as a standard sample with an X-ray fluorescence analyzer (EDX-800HS, manufactured by Shimadzu Corporation).

[0105] (2) Evaluation of Molded Articles (2-1) Surface Roughness The surface roughness (Rz value) of the molded article surface was measured using a 3D shape measuring instrument (manufactured by Keyence Corporation). The measured Rz value was evaluated according to the following criteria.

[0106] Less than 50 μm: ○○ 50 μm or more and 80 μm or less: ○ More than 80 μm and 100 μm or less: △ More than 100 μm: ×

[0107] (2-2) Flame Retardancy Evaluation The total burning time was measured and judged according to official standards (ISO 3582, JIS K6400-6, ASTM D4986). Specifically, a test piece (150±1×50±1×t [mm]) was held horizontally and then exposed to a 38 mm flame for 60 seconds. The total burning time was measured based on the burning rate and burning behavior at a 100 mm mark. A total burning time of 35 seconds or less was judged as ○, and a total burning time of more than 35 seconds was judged as ×.

[0108] (2-3) Evaluation of 25% Compression Strength The 25% compression strength of the molded product was measured at 23°C by a method in accordance with JIS K 6767. The obtained 25% compression strength was evaluated according to the following criteria: Less than 30 kPa: ◯ 30 kPa or more and less than 40 kPa: O 40 kPa or more and less than 50 kPa: Δ 50 kPa or more: ×

[0109] (2-4) Ratio of aggregation on surface The ratio of particles agglomerated by two or more on the surface (1 mm square) of the molded article (number of agglomerates of two or more / total number of particles) was counted using an optical microscope and evaluated according to the following criteria: Less than 85%: ◯ 85% or more but less than 95%: △ 95% or more: ×

[0110]

[0111]

[0112] According to the present invention, it is possible to provide hollow particles that can be used to obtain molded articles that have excellent flame retardancy and are less likely to suffer from poor appearance due to surface irregularities, and a molded article using the hollow particles.

Claims

1. A molded article comprising hollow particles containing a resin and a flame retardant in a shell, The hollow particles have a number average particle diameter of 3 to 200 μm, The molded article, wherein the shell has a thickness of 0.05 μm or more and 1.5 μm or less.

2. The molded article according to claim 1 , wherein the flame retardant comprises at least one selected from the group consisting of phosphorus-based flame retardants and halogen-based flame retardants.

3. 3. The molded article according to claim 1, wherein the content of the flame retardant is 0.01% by weight or more and 10% by weight or less based on the total weight of the hollow particles.

4. The molded article according to any one of claims 1 to 2, further comprising at least one flame-retardant compound selected from the group consisting of phosphorus-based flame retardants and halogen-based flame retardants.