Thermally expandable microsphere, master batch, composition, and foam-molded body

Abstract

The purpose of the present invention is to provide: thermally expandable microspheres capable of reducing the occurrence of gum when molding a foam-molded body; and an application thereof.　Thermally expandable microspheres according to the present invention each comprise an outer shell containing a polymer and a foaming agent included in the outer shell and vaporized when being heated. The solubility parameter of the polymer is 13 (cal / cm3)1 / 2 or less. The polymer is preferably a polymer having a polymerizable component containing a carboxyl group-containing monomer. The weight proportion of the carboxyl group-containing monomer in the polymerizable component is preferably 20-70 wt%.

Description

Heat-expandable microspheres, masterbatch, composition and foam-molded product

[0001] The present invention relates to heat-expandable microspheres, a masterbatch, a composition, and a foam-molded article.

[0002] Heat-expandable microspheres (heat-expandable microcapsules), which are microparticles with a thermoplastic resin outer shell and a blowing agent encapsulated inside, are characterized by expanding upon heating. Furthermore, masterbatches obtained by kneading these heat-expandable microspheres with a base resin also have the characteristic of expanding upon heating. These heat-expandable microspheres and masterbatches are used in a wide range of applications, for example, by blending them with a base resin and molding them to produce molded articles. Heat treatment during molding causes the heat-expandable microspheres to expand, which not only reduces the weight of the molded article but also imparts design features, cushioning properties, and the like to the molded article.

[0003] As such heat-expandable microspheres, Patent Document 1 proposes heat-expandable microcapsules having an outer shell made of a polymer composed of 15 to 75% by weight of a nitrile monomer, 10 to 65% by weight of a monomer having a carboxyl group, 0.1 to 20% by weight of a monomer having an amide group, and 0.1 to 20% by weight of a monomer having a cyclic structure in its side chain, and encapsulating a blowing agent.

[0004] WO 2004 / 058910

[0005] The heat-expandable microspheres disclosed in Patent Document 1 have excellent heat and solvent resistance, and excellent foaming properties over a wide range of high temperatures, making them suitable for foam molding of thermoplastic resins, thermosetting resins, and other materials at resin molding temperatures of 200°C or higher. However, when foam molding is performed using the heat-expandable microspheres disclosed in the Patent Document, deposits called "smear," such as granular base resin and expanded heat-expandable microspheres, are generated and accumulate near the discharge outlet of the molding machine. Furthermore, the generated smear may be mixed into the molded product or adhere to the surface of the molded product, thereby degrading the appearance of the molded product.

[0006] Therefore, an object of the present invention is to provide heat-expandable microspheres that can reduce the occurrence of resin deposits during the formation of foamed articles, and uses thereof.

[0007] As a result of extensive investigations, the present inventors have found that specific heat-expandable microspheres can solve the above problems, and have arrived at the present invention. That is, the present invention includes the following aspects.

[0008] <1> Heat-expandable microspheres comprising an outer shell containing a polymer and a blowing agent encapsulated in the outer shell and vaporized by heating, wherein the solubility parameter of the polymer is 13 (cal / cm ３ ) １／２ Heat-expandable microspheres having the following structure. <2> Heat-expandable microspheres according to <1>, wherein the polymer is a polymer of a polymerizable component containing a carboxyl group-containing monomer. <3> Heat-expandable microspheres according to <2>, wherein the weight ratio of the carboxyl group-containing monomer in the polymerizable component is 20 to 70 wt %. <4> Heat-expandable microspheres according to <2> or <3>, wherein the polymerizable component further contains at least one monomer selected from the group consisting of a (meth)acrylic acid amide monomer and a (meth)acrylic acid ester monomer. <5> Heat-expandable microspheres according to <4>, wherein the weight ratio of the at least one monomer selected from the group consisting of a (meth)acrylic acid amide monomer and a (meth)acrylic acid ester monomer in the polymerizable component is 5 to 70 wt %. <6> Heat-expandable microspheres according to any one of <2> to <5>, wherein the weight ratio of acrylonitrile in the polymerizable component is less than 20 wt %. <7> A masterbatch comprising the heat-expandable microspheres according to any one of <1> to <6> and a base resin, wherein the base resin has a melt flow rate of more than 60 g / 10 min and a melting point equal to or lower than the expansion initiation temperature of the heat-expandable microspheres. <8> The masterbatch according to <7>, wherein the melting point is 60 to 130°C. <9> The masterbatch according to <7> or <8>, wherein the content of the heat-expandable microspheres is 35 to 300 parts by weight per 100 parts by weight of the base resin. <10> A composition comprising the heat-expandable microspheres according to any one of <1> to <6> and at least one masterbatch according to any one of <7> to <9>, and a matrix component. <11> A foam-molded article obtained by molding the composition according to <10>.

[0009] The heat-expandable microspheres of the present invention can reduce the occurrence of sludge during foam molding. The masterbatch of the present invention contains the heat-expandable microspheres, which can reduce the occurrence of sludge during foam molding. The composition of the present invention contains at least one selected from the heat-expandable microspheres and the masterbatch, which can reduce the occurrence of sludge during foam molding. The molded article of the present invention, which is obtained by molding the composition, has good appearance and is lightweight.

[0010] [Heat-Expandable Microspheres] The heat-expandable microspheres of the present invention comprise a polymer-containing shell and a blowing agent encapsulated in the shell that vaporizes upon heating, and the microspheres as a whole exhibit heat-expandability (the property that the entire microspheres expand upon heating). The heat-expandable microspheres preferably have a core-shell structure consisting of a polymer-containing shell and a core that essentially contains a blowing agent.

[0011] The heat-expandable microspheres of the present invention are made of a polymer having a solubility parameter of 13 (cal / cm ３ ) １／２ In the present invention, the solubility parameter is sometimes simply referred to as the SP value. When the solubility parameter of the polymer forming the shell of the heat-expandable microspheres is 13 (cal / cm ３ ) １／２ When the solubility parameter is equal to or less than 9.0, it is considered that the solubility parameter is close to that of the matrix component, which increases the compatibility between the heat-expandable microspheres and the matrix component, and reduces the occurrence of sludge during molding. The solubility parameter is preferably 9.0 to 13 (cal / cm ３ ) １／２ , more preferably 10 to 12.8 (cal / cm ３ ) １／２ , and more preferably 11 to 12.8 (cal / cm ３ ) １／２ is.

[0012] In the present invention, the SP value is a value calculated by the Fedors method described in "POLYMER ENGINEERING AND SCIENCE, February 1974, Vol. 14, No. 2, Robert F. Fedors (pp. 147-154)". The SP value is the cohesive energy (E ｃｏｈ ) and the molar volume (V) of the atomic groups constituting the structural unit, it can be calculated from the following formula (I). ｃｏｈ The values ​​of the molecular weight (Mg) and the molar volume (V) of the atomic group were taken from "POLYMER ENGINEERING AND SCIENCE, February 1974, Vol. 14, No. 2, Robert F. Fedors (pp. 147-154)." 1J was set to 0.239 cal. SP value = [ΣE ｃｏｈ / ΣV] １／２ (I)

[0013] For example, the structural unit derived from acrylonitrile has a secondary carbon (-CH ２ It has one tertiary carbon (-CH<) atomic group, one nitrile group (-CN) atomic group. The cohesive energy E ｃｏｈ and molar volume V are as follows: ２ -: E ｃｏｈ =1180.7cal / mol, V=16.1cm ３ / mol -CH<:E ｃｏｈ =819.7cal / mol, V=-1.0cm ３ / mol -CN::E ｃｏｈ =6101.7cal / mol, V=24.0cm ３ / mol From this, when the above value is calculated based on the above formula (I), the SP value (SP(AN)) of the structural unit formed by acrylonitrile (acrylonitrile structural unit) is: SP(AN)=[(1180.7+819.7+6101.7) / (16.1-1.0+24.0)] １／２ =14.4(cal / cm ３ ) １／２ This becomes:

[0014] In addition, the structural unit derived from methacrylonitrile is a primary carbon (-CH ３ ) group, one secondary carbon (-CH ２ It has one primary carbon (-C<) atomic group, one quaternary carbon (>C<) atomic group, and one nitrile group (-CN) atomic group. ３ ) atomic group and quaternary carbon (>C<) atomic group cohesive energy E ｃｏｈ and molar volume V are as follows: ３ : E ｃｏｈ =1125.7cal / mol, V=33.5cm ３ / mol >C<:E ｃｏｈ =351.3cal / mol, V=-19.2cm ３ / mol From this, the SP value (SP(MAN)) of the structural unit (methacrylonitrile structural unit) formed by methacrylonitrile in the same manner as for acrylonitrile is given by: SP(MAN)=[(1125.7+1180.7+351.3+6101.7) / (33.5+16.1-19.2+24.0)] １／２ =12.7(cal / cm ３ ) １／２ This becomes:

[0015] The polymer is composed of acrylonitrile structural units and methacrylonitrile structural units, and the proportion of the acrylonitrile structural units in the polymer is a １ % by weight, the proportion of methacrylonitrile structural units is a ２ The SP value of the polymer in weight percent (SP(P)) can be calculated according to the following formula (II): SP(P) = (SP(AN) x a １ + SP (MAN) x a ２ ) / (a １ +a ２ ) (II)

[0016] Furthermore, the above formula (II) can be generalized to the following formula (III) for polymers having other structural units as well as polymers having the above specific structural units: SP value=(SP １ ×a １ +SP ２ ×a ２ +...+SP ｎ×a ｎ ) / (a １ +a ２ +...+a ｎ ) (III) where SP １ is the SP value of the first structural unit in the polymer, and a １ is the weight percentage (%) of the polymer. ２ ~SP ｎ are the SP values ​​of the second to nth structural units in the polymer, respectively, and a ２ ~a ｎ are the weight percentages (%) of the polymer. １ ~a ｎ is the weight ratio of each monomer in the polymerizable component.

[0017] In the present invention, the polymer forming the outer shell is preferably a polymer of a polymerizable component containing a monomer having one (radically) polymerizable carbon-carbon double bond (hereinafter, sometimes referred to as the "monomer component"). Such a polymer is preferable because it allows the blowing agent to be efficiently encapsulated and provides high expansion performance. The weight proportion of the structural units derived from each monomer component in the polymer is the weight proportion of each monomer component in the polymerizable component. The polymerizable component may further contain a monomer having at least two (radically) polymerizable carbon-carbon double bonds (hereinafter, sometimes referred to as the "crosslinking agent"). The monomer component and the crosslinking agent are components capable of undergoing an addition reaction, and the crosslinking agent is a component capable of introducing a crosslinked structure into the thermoplastic resin (A). The weight proportion of the structural units derived from each crosslinking agent in the polymer is the weight proportion of each crosslinking agent in the polymerizable component.

[0018] The monomer component is not particularly limited, but examples thereof include nitrile monomers such as acrylonitrile, methacrylonitrile, fumaronitrile, and maleonitrile; halogenated vinyl monomers such as vinyl chloride; halogenated vinylidene monomers such as vinylidene chloride; vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl butyrate; unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, and maleic acid, itaconic acid, fumaric acid, and citric acid. carboxyl group-containing monomers such as unsaturated dicarboxylic acids such as maleic acid and chloromaleic acid, anhydrides of unsaturated dicarboxylic acids, and unsaturated dicarboxylic acid monoesters such as monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, (meth)acrylic acid ester-based monomers such as acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate; (meth)acrylamide-based monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; maleimide-based monomers such as N-phenylmaleimide and N-cyclohexylmaleimide; styrene-based monomers such as styrene and α-methylstyrene; ethylenically unsaturated monoolefin-based monomers such as ethylene, propylene, and isobutylene; vinyl ether-based monomers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl ketone-based monomers such as vinyl methyl ketone; N-vinyl-based monomers such as N-vinylcarbazole and N-vinylpyrrolidone; and vinyl naphthalene salts. A part or all of the carboxyl groups of the carboxyl group-containing monomer may be neutralized during or after polymerization. Acrylic acid and methacrylic acid may be collectively referred to as (meth)acrylic acid, and (meth)acrylate means acrylate or methacrylate, and (meth)acrylic means acrylic or methacrylic.These monomer components may be used alone or in combination of two or more.

[0019] The polymerizable component is not particularly limited, but containing a carboxyl group-containing monomer as a monomer component is preferred because it improves the heat resistance of the heat-expandable microspheres. Furthermore, containing a carboxyl group-containing monomer is preferred because it facilitates the adjustment of the solubility parameter of the polymer within the above range. When the polymerizable component contains a carboxyl group-containing monomer as a monomer component, the weight percentage of the carboxyl group-containing monomer in the polymerizable component is not particularly limited, but is preferably 20 to 70 wt %, more preferably 25 to 65 wt %, and even more preferably 30 to 60 wt %. A weight percentage of 20 wt % or more tends to improve the heat resistance of the heat-expandable microspheres. A weight percentage of 70 wt % or less tends to prevent the shell from becoming too rigid, thereby improving the expandability.

[0020] When the polymerizable component contains a carboxyl group-containing monomer, it is preferred, although not limited thereto, to further contain at least one monomer selected from the group consisting of a (meth)acrylamide monomer and a (meth)acrylic ester monomer, since this improves the heat resistance of the heat-expandable microspheres. When the polymerizable component contains at least one monomer selected from the group consisting of a (meth)acrylamide monomer and a (meth)acrylic ester monomer, the weight ratio of the at least one monomer selected from the group consisting of a (meth)acrylamide monomer and a (meth)acrylic ester monomer in the polymerizable component is not limited, but is preferably 5 to 70% by weight, more preferably 8 to 60% by weight, and even more preferably 8 to 50% by weight. A weight ratio of 5% by weight or more tends to improve the heat resistance of the heat-expandable microspheres. A weight ratio of 70% by weight or less tends to prevent the shell from becoming too rigid, thereby improving the expandability. When the polymerizable component contains a (meth)acrylamide-based monomer or a (meth)acrylic acid ester-based monomer, the content of the (meth)acrylamide-based monomer or the (meth)acrylic acid ester-based monomer may be in the above weight ratio.

[0021] The weight proportion of acrylonitrile in the polymerizable component is not particularly limited, but is preferably less than 20% by weight. Having the weight proportion of acrylonitrile in the polymerizable component within the above range is preferable in that the rigidity of the outer shell is adjusted and the expandability is improved. Furthermore, having the weight proportion of acrylonitrile in the polymerizable component within the above range is preferable in that the solubility parameter of the polymer can be easily adjusted within the above range. The weight proportion of acrylonitrile in the polymerizable component is more preferably 15% by weight or less, even more preferably less than 13% by weight, and particularly preferably 10% by weight or less.

[0022] The polymerizable component may contain methacrylonitrile. The polymerizable component containing methacrylonitrile is preferred because it improves the gas barrier properties of the outer shell. Furthermore, the polymerizable component containing methacrylonitrile is preferred because it makes it easier to adjust the solubility parameter of the polymer to the above range. The weight percentage of methacrylonitrile in the polymerizable component is not particularly limited, but is preferably 0 to 70% by weight, more preferably 5 to 60% by weight.

[0023] As described above, the polymerizable component may contain a crosslinking agent. When the polymerizable component contains a crosslinking agent, the outer shell has a crosslinked structure, improving gas barrier properties and expanding performance. The crosslinking agent is not particularly limited, and examples thereof include alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate; diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, PEG#200 di(meth)acrylate, and PEG#400 di(meth)acrylate. Polyalkylene glycol di(meth)acrylates such as acrylate, PEG #600 di(meth)acrylate, PEG #1000 di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol #400 di(meth)acrylate, and polypropylene glycol #700 di(meth)acrylate; ethoxylated bisphenol A di(meth)acrylate (EO addition 2 to 30); Propoxylated bisphenol A di(meth)acrylate; Propoxylated ethoxylated bisphenol A di(meth)acrylate; Glycerin di(meth)acrylate; Polybutadiene di(meth)acrylate; Polyisoprene di(meth)acrylate; 2-hydroxy-3-acryloyloxypropyl methacrylate; Dimethylol-tricyclodecane di(meth)acrylate; Divinylbenzene; Ethoxylated glycerin triacrylate; 1,3,5-tri(meth)acrylate Examples of such crosslinking agents include bifunctional monomers, trifunctional monomers, and tetrafunctional or higher functional monomers such as acryloyl hexahydro 1,3,5-triazine, triallyl isocyanurate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,2,4-trivinylbenzene, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. These crosslinking agents may be used alone or in combination of two or more.

[0024] The weight proportion of the crosslinking agent in the polymerizable component is not particularly limited, but is preferably 0 to 10% by weight, more preferably 0.1 to 5% by weight, even more preferably 0.15 to 3% by weight, particularly preferably 0.2 to 2% by weight, and most preferably 0.3 to 1.5% by weight.

[0025] The blowing agent is a component that vaporizes upon heating and is encapsulated in the outer shell of heat-expandable microspheres. This allows the heat-expandable microspheres as a whole to exhibit thermal expandability (the property of expanding the entire microsphere upon heating). The blowing agent is not particularly limited, and examples thereof include hydrocarbons having 1 to 13 carbon atoms, such as methane, ethane, propane, (iso)butane, (iso)pentane, (iso)hexane, (iso)heptane, (iso)octane, (iso)nonane, (iso)decane, (iso)undecane, (iso)dodecane, and (iso)tridecane; hydrocarbons having more than 13 but not more than 20 carbon atoms, such as (iso)hexadecane and (iso)eicosane; petroleum ethers, such as normal paraffins and isoparaffins having an initial boiling point of 150 to 260°C and / or a distillation range of 70 to 360°C; and Examples of suitable blowing agents include hydrocarbons such as distillates; halogenated hydrocarbons having 1 to 12 carbon atoms, such as methyl chloride, methylene chloride, chloroform, and carbon tetrachloride; fluorine-containing compounds such as hydrofluoroethers; silanes having an alkyl group having 1 to 5 carbon atoms, such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane; and compounds that thermally decompose to form gases upon heating, such as azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, and 4,4'-oxybis(benzenesulfonylhydrazide). The blowing agent may be composed of a single compound or a mixture of two or more compounds. The blowing agent may be linear, branched, or cyclic, with aliphatic blowing agents being preferred. Furthermore, the blowing agent preferably contains hydrocarbons having 8 or more carbon atoms, as this increases the maximum expansion temperature of the heat-expandable microspheres, and preferably contains hydrocarbons having 6 or fewer carbon atoms, as this increases the efficiency of the expansion of the heat-expandable microspheres.

[0026] The content of the blowing agent in the heat-expandable microspheres of the present invention is defined as the percentage of the weight of the blowing agent encapsulated in the heat-expandable microspheres relative to the total weight of the heat-expandable microspheres. There are no particular limitations on the content of the blowing agent, but it is preferably 2 to 40% by weight, more preferably 4 to 35% by weight, even more preferably 5 to 30% by weight, and particularly preferably 6 to 25% by weight. When the encapsulation rate is within the above range, leakage of the blowing agent to the outside during thermal expansion tends to be less likely, and expandability tends to be improved.

[0027] The expansion onset temperature (Ts) of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 120 to 200°C, more preferably 130 to 180°C, even more preferably 140 to 180°C, and particularly preferably 150 to 170°C. An expansion onset temperature of 120°C or higher tends to improve the heat resistance of the heat-expandable microspheres. An expansion onset temperature of 200°C or lower tends to improve the expansion performance.

[0028] The maximum expansion temperature (Tmax) of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 155°C or higher, more preferably 155 to 250°C, even more preferably 160 to 230°C, particularly preferably 165 to 210°C, and most preferably 170 to 200°C. A maximum expansion temperature of 155°C or higher tends to provide sufficient heat resistance. The expansion onset temperature (Ts) and maximum expansion temperature (Tmax) of the heat-expandable microspheres are measured by the methods described in the Examples.

[0029] The average particle size of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 1 to 200 μm, more preferably 5 to 100 μm, even more preferably 5 to 60 μm, and particularly preferably 10 to 50 μm. An average particle size of 1 μm or more tends to improve the expansion performance of the heat-expandable microspheres. An average particle size of 200 μm or less tends to improve the appearance of the resulting molded article. The coefficient of variation (Cv) of the particle size distribution of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 10 to 40%, more preferably 15 to 35%. The average particle size and particle size distribution of the heat-expandable microspheres are measured by the methods described in the Examples.

[0030] The maximum volume expansion ratio of the heat-expandable microspheres of the present invention is not particularly limited, but is preferably 5 to 200, more preferably 10 to 200, and even more preferably 15 to 200. An expansion ratio of 5 or more tends to result in lightweight molded articles. An expansion ratio of 200 or less tends to result in molded articles with good appearance.

[0031] The heat-expandable microspheres of the present invention can be produced by a method comprising the steps of dispersing an oily mixture containing a polymerizable component, a blowing agent, and a polymerization initiator in an aqueous dispersion medium and polymerizing the polymerizable component (hereinafter sometimes referred to as the polymerization step).

[0032] The polymerization initiator is not particularly limited, and examples thereof include peroxides, azo compounds, etc. The peroxide is not particularly limited, and examples thereof include peroxydicarbonates such as diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and dibenzyl peroxydicarbonate; diacyl peroxides such as dilauroyl peroxide and dibenzoyl peroxide; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; peroxyketals such as 2,2-bis(t-butylperoxy)butane; hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; dialkyl peroxides such as dicumyl peroxide and di-t-butyl peroxide; and peroxyesters such as t-hexyl peroxypivalate and t-butyl peroxyisobutyrate. The azo compound is not particularly limited, and examples thereof include 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), and 1,1'-azobis(cyclohexane-1-carbonitrile).

[0033] The amount of the polymerization initiator to be added is not particularly limited, but in terms of achieving the effects of the present invention, it is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, and even more preferably 0.2 to 5 parts by weight, relative to 100 parts by weight of the polymerizable component.

[0034] The aqueous dispersion medium used in the polymerization step is a medium containing water, such as ion-exchanged water, as a main component for dispersing the oily mixture, and may further contain alcohols, such as methanol, ethanol, and propanol, or hydrophilic organic solvents, such as acetone. In the present invention, "hydrophilic" means a state in which the aqueous dispersion medium can be arbitrarily mixed with water. The amount of the aqueous dispersion medium used is not particularly limited, but is preferably 100 to 1,000 parts by weight per 100 parts by weight of the polymerizable component.

[0035] The aqueous dispersion medium may further contain an electrolyte. Examples of the electrolyte include sodium chloride, magnesium chloride, calcium chloride, sodium sulfate, magnesium sulfate, ammonium sulfate, and sodium carbonate. These electrolytes may be used alone or in combination of two or more. The content of the electrolyte is not particularly limited, but is preferably 0.1 to 50 parts by weight per 100 parts by weight of the aqueous dispersion medium.

[0036] The aqueous dispersion medium may contain at least one water-soluble compound selected from the group consisting of water-soluble 1,1-substituted compounds having a structure in which at least one hydrophilic functional group selected from a hydroxyl group, a carboxylic acid (salt) group, and a phosphonic acid (salt) group and a heteroatom are bonded to the same carbon atom, polyalkyleneimines having a structure in which an alkyl group substituted with at least one hydrophilic functional group selected from a carboxylic acid (salt) group and a phosphonic acid (salt) group is bonded to a nitrogen atom, water-soluble ascorbic acids, water-soluble polyphenols, water-soluble B vitamins, potassium dichromate, alkali metal nitrites, metal (III) halides, boric acid, and water-soluble phosphonic acids (salts). In the present invention, "water-soluble" means a state in which 1 g or more of the compound dissolves in 100 g of water. The amount of the water-soluble compound contained in the aqueous dispersion medium is not particularly limited, but is preferably 0.0001 to 1.0 part by weight, more preferably 0.0003 to 0.1 part by weight, and even more preferably 0.001 to 0.05 part by weight, relative to 100 parts by weight of the polymerizable component.

[0037] In addition to the electrolyte and water-soluble compound, the aqueous dispersion medium may contain a dispersion stabilizer or a dispersion stabilization aid. Examples of dispersion stabilizers include tribasic calcium phosphate, magnesium pyrophosphate obtained by metathesis, calcium pyrophosphate, colloidal silica, alumina sol, and magnesium hydroxide. These dispersion stabilizers may be used alone or in combination of two or more. The amount of dispersion stabilizer is not particularly limited, but is preferably 0.05 to 100 parts by weight, more preferably 0.2 to 70 parts by weight, per 100 parts by weight of the polymerizable component. Examples of dispersion stabilization aids include polymeric dispersion stabilization aids, and surfactants such as cationic surfactants, anionic surfactants, zwitterionic surfactants, and nonionic surfactants. These dispersion stabilization aids may be used alone or in combination of two or more.

[0038] The aqueous dispersion medium is prepared, for example, by blending water (ion-exchanged water) with, as necessary, an electrolyte, a water-soluble compound, a dispersion stabilizer, a dispersion stabilization assistant, etc. The pH of the aqueous dispersion medium during polymerization is appropriately determined depending on the types of the water-soluble compound, dispersion stabilizer, and dispersion stabilization assistant.

[0039] In the method for producing the heat-expandable microspheres of the present invention, polymerization may be carried out in the presence of sodium hydroxide and zinc chloride. In the method for producing the heat-expandable microspheres of the present invention, an oily mixture is suspended and dispersed in an aqueous dispersion medium so as to produce spherical oil droplets having a predetermined particle size.

[0040] Examples of methods for suspending and dispersing the oily mixture include general dispersion methods such as stirring with a homomixer (e.g., manufactured by Primix Corporation), methods using a static dispersing device such as a static mixer (e.g., manufactured by Noritake Engineering Co., Ltd.), membrane suspension, and ultrasonic dispersion. The dispersion in which the oily mixture is dispersed in the aqueous dispersion medium as spherical oil droplets is then heated to initiate suspension polymerization. It is preferable to stir the dispersion during the polymerization reaction, and the stirring may be gentle enough to prevent, for example, floating of the spherical oil droplets and settling of the heat-expandable microspheres after polymerization.

[0041] The polymerization temperature can be freely set depending on the type of polymerization initiator, but is preferably controlled within a range of 30 to 100°C, more preferably 40 to 90°C. The time for maintaining the reaction temperature is preferably about 1 to 20 hours. The initial polymerization pressure is not particularly limited, but is in the range of 0 to 5 MPa, more preferably 0.1 to 3 MPa, in gauge pressure.

[0042] The resulting slurry is filtered using a centrifuge, pressure press, vacuum dehydrator, or the like to obtain a wet powder with a moisture content of 10 to 50% by weight, preferably 15 to 45% by weight, and more preferably 20 to 40% by weight. The resulting wet powder is then dried using a tray dryer, indirect heating dryer, fluidized bed dryer, vacuum dryer, vibration dryer, flash dryer, or the like to obtain a dry powder. The moisture content of the resulting dry powder is preferably 8% by weight or less, more preferably 5% by weight or less. To reduce the content of ionic substances, the resulting wet or dry powder may be washed with water and / or redispersed, then refiltered and dried. The slurry may also be dried using a spray dryer, fluidized bed dryer, or the like to obtain a dry powder. The wet powder and dry powder can be selected appropriately depending on the intended use.

[0043] [Masterbatch] The masterbatch of the present invention contains the above-mentioned heat-expandable microspheres and a base resin, and is a foam molding component that can be used to produce foamed molded articles. The base resin contained in the masterbatch of the present invention is a component that is kneaded together with the heat-expandable microspheres to form the masterbatch.

[0044] The base resin has a melt flow rate (hereinafter sometimes referred to as MFR) of more than 60 g / 10 min and a melting point below the expansion initiation temperature of the heat-expandable microspheres. A base resin with an MFR of more than 60 g / 10 min increases the fluidity of the masterbatch when melted, allowing the heat-expandable microspheres to disperse and expand uniformly during molding of a composition containing the masterbatch, reducing specific gravity variations and further reducing the occurrence of resin buildup during molding. The MFR of the base resin is preferably more than 60 g / 10 min and not more than 500 g / 10 min, more preferably 65 to 400 g / 10 min, and even more preferably 70 to 300 g / 10 min. The MFR of the base resin is measured using a capillary rheometer in accordance with JIS K7210 at a temperature of 190°C and a load of 2.16 kg.

[0045] The melting point of the base resin is not particularly limited as long as it is equal to or lower than the expansion initiation temperature of the heat-expandable microspheres. However, it is preferably at least 5°C lower than the expansion initiation temperature of the heat-expandable microspheres, more preferably at least 10°C lower than the expansion initiation temperature of the heat-expandable microspheres, and even more preferably at least 20°C lower than the expansion initiation temperature of the heat-expandable microspheres.

[0046] The melting point of the base resin is not particularly limited as long as it is equal to or lower than the expansion initiation temperature of the heat-expandable microspheres, but is preferably 60 to 130°C, more preferably 65 to 120°C, even more preferably 70 to 120°C, and particularly preferably 75 to 110°C. A melting point of 60°C or higher tends to suppress fusion of masterbatches. A melting point of 130°C or lower tends to improve expandability.

[0047] The base resin is not particularly limited as long as it has the above-mentioned properties, and examples thereof include ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, silane-crosslinkable ethylene-vinyl acetate copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-ethyl (meth)acrylate copolymer, ethylene-butyl (meth)acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, low-density polyethylene (LDPE), silane-crosslinkable low-density polyethylene, low-density linear low-density polyethylene (L-LDPE), silane-crosslinkable linear Examples of suitable base resins include olefin-based polymers such as linear low-density polyethylene, chlorinated polyethylene, modified polyethylene containing a carboxyl group, polypropylene, silane-crosslinkable polypropylene, and modified polypropylene containing a carboxyl group; polyvinyl chloride; acrylic resins; styrene-based polymers such as acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, styrene-butadiene copolymers, and polystyrene; polycarbonates; polyester-based polymers such as polyethylene terephthalate and polybutylene terephthalate; and urethane-based polymers such as thermoplastic polyurethane and urethane-based elastomers, and these may be used alone or in combination of two or more. Furthermore, the base resin may contain a matrix component, which will be described later.

[0048] The base resin preferably contains an olefin-based polymer, as this improves the dispersibility of heat-expandable microspheres. The content of the olefin units constituting the olefin-based polymer is not particularly limited, but is preferably 60 to 100% by weight, more preferably 70 to 100% by weight, even more preferably 75 to 100% by weight, and particularly preferably 80 to 100% by weight. A content within the above range tends to improve the dispersibility of heat-expandable microspheres. The olefin units are not particularly limited, but are preferably olefins having 2 to 10 carbon atoms, and preferably contain ethylene. When the olefin units contain ethylene, the content of the ethylene units constituting the olefin-based polymer is not particularly limited, but is preferably 50 to 100% by weight, more preferably 60 to 100% by weight, even more preferably 70 to 100% by weight, and particularly preferably 75 to 100% by weight.

[0049] When the base resin contains an olefin-based polymer, the weight percentage of the olefin-based polymer in the base resin is not particularly limited, but is preferably 10 to 100% by weight, more preferably 30 to 100% by weight, even more preferably 50 to 100% by weight, and particularly preferably 80 to 100% by weight. When the weight percentage is within the above range, the dispersibility of heat-expandable microspheres tends to be improved. The base resin may also consist of an olefin-based polymer.

[0050] The content of heat-expandable microspheres in the masterbatch of the present invention is not particularly limited, but is preferably 35 to 300 parts by weight, more preferably 50 to 250 parts by weight, even more preferably 60 to 200 parts by weight, and particularly preferably 75 to 150 parts by weight, per 100 parts by weight of the base resin. A content of 35 parts by weight or more tends to more easily maintain the mechanical properties of the matrix component constituting the resulting foamed molded article. A content of 300 parts by weight or less tends to improve the dispersibility of the heat-expandable microspheres during the production of the molded article.

[0051] In addition to the heat-expandable microspheres and base resin, the masterbatch of the present invention may further contain other components, such as stabilizers, lubricants, fillers, and molding additives, such as dispersibility improvers. The stabilizers are not particularly limited, and examples thereof include phenolic stabilizers such as pentaerythrityl tetrakis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] and triethylene glycol bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate]; phosphorus-based stabilizers such as tris(mononylphenyl)phosphite and tris(2,4-di-t-butylphenyl)phosphite; and sulfur-based stabilizers such as dilauroyl dipropionate. These may be used alone or in combination of two or more. The lubricants are not particularly limited, and examples thereof include polyethylene wax; glycerin fatty acid esters such as glycerin monostearate and diglycerin stearate; and fatty acids such as stearic acid. These may be used alone or in combination of two or more.

[0052] The filler is not particularly limited, and examples thereof include plant fibers such as wood flour and kenaf, organic fibers such as polyethylene fibers, polypropylene fibers, nylon fibers, and polyester fibers; inorganic fibers such as glass fibers (including those coated with metal) and carbon fibers (including those coated with metal), potassium titanate, asbestos, silicon carbide, silicon nitride, ceramic fibers, metal fibers, aramid fibers, barium sulfate, calcium sulfate, calcium silicate, calcium carbonate, magnesium carbonate, antimony trioxide, zinc oxide, titanium oxide, magnesium oxide, iron oxide, molybdenum disulfide, magnesium hydroxide, aluminum hydroxide, mica, talc, kaolin, pyrophyllite, bentonite, sericite, zeolite, wollastonite, alumina, clay, ferrite, graphite, gypsum, glass beads, glass balloons, and inorganic particles of quartz, and these may be used alone or in combination of two or more. The dispersibility improver is not particularly limited, but examples thereof include aliphatic hydrocarbons, process oils such as paraffin oil and aromatic oil, and liquid paraffin, and one or more of these may be used in combination.

[0053] The specific gravity of the masterbatch of the present invention is not particularly limited, but is preferably 0.8 g / mL or more, more preferably 0.8 to 1.2 g / mL, even more preferably 0.85 to 1.1 g / mL, and particularly preferably 0.9 to 1.1 g / mL. When the specific gravity is 0.8 g / mL or more, the amount of expanded heat-expandable microspheres contained in the masterbatch tends to be small, and the expandability tends to be improved. The specific gravity of the masterbatch is measured by the method described in the Examples.

[0054] The expansion ratio of the masterbatch is not particularly limited, but is preferably 5 to 120 times, more preferably 10 to 100 times, and even more preferably 15 to 75 times. When the expansion ratio is 5 times or more, a lightweight foamed molded article tends to be easily obtained. When the expansion ratio is 120 times or less, a foamed molded article with a good appearance tends to be easily obtained.

[0055] The cross-sectional shape of the masterbatch of the present invention, when cut perpendicular to its length, can be determined appropriately depending on the intended use of the masterbatch, and examples thereof include circular, elliptical, polygonal, star-shaped, and hollow circular shapes. The length of the masterbatch of the present invention can be determined appropriately depending on the intended use, and is preferably 1 to 5 mm, more preferably 2 to 4 mm, and even more preferably 2.5 to 3.5 mm. A length within this range tends to improve the dispersibility of heat-expandable microspheres during the production of molded articles. The major axis length of the masterbatch of the present invention, cut perpendicular to its length, can be determined appropriately depending on the intended use, and is preferably 1 to 5 mm, more preferably 2 to 4 mm, and even more preferably 2.5 to 3.5 mm. A major axis length within this range tends to improve the dispersibility of heat-expandable microspheres during the production of molded articles.

[0056] The masterbatch of the present invention can be produced by any method that involves mixing heat-expandable microspheres and a base resin, preferably a method that uniformly disperses them. Examples of methods for producing the masterbatch include a pre-mixing step (1) and a pelletizing step (2). (1) The base resin is melt-mixed in advance using a mixer such as a roll, kneader, pressure kneader, or Banbury mixer. The pre-mixing step then involves adding heat-expandable microspheres and, if necessary, other components to the molten base resin to prepare a pre-mixed mixture. (2) The pelletizing step involves feeding the pre-mixed mixture into an extruder such as a single-screw extruder, twin-screw extruder, or multi-screw extruder, extruding the molten mixture into a desired shape and thickness, and pelletizing the extruded mixture using a hot-cut pelletizer.

[0057] The masterbatch of the present invention can be produced by extruding a strand of the desired thickness from an extruder and cutting it to the desired length using a cutter. The strand thickness during masterbatch production can be adjusted by adjusting the diameter of the extruder's strand die and the strand take-up speed. The masterbatch must be produced at a temperature lower than the expansion initiation temperature of the heat-expandable microspheres, otherwise the heat-expandable microspheres will expand. To prevent the heat-expandable microspheres from expanding, it is usually recommended to produce the masterbatch at a temperature at least 5°C lower than the expansion initiation temperature.

[0058] [Composition and foam-molded article] The composition of the present invention contains at least one selected from the heat-expandable microspheres and the masterbatch described above, and a matrix component. The composition of the present invention may contain the heat-expandable microspheres and a matrix component. Alternatively, the composition may contain the masterbatch and a matrix component. Foam-molded articles can be produced by molding the composition of the present invention, and the generation of resin deposits during the production of foam-molded articles can be reduced.

[0059] The matrix component is not particularly limited, and examples thereof include polyvinyl chloride; polyvinylidene chloride; polyvinyl alcohol; ethylene-based copolymers such as ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-ethyl (meth)acrylate copolymer, and ethylene-butyl (meth)acrylate copolymer; ionomers; polyolefin-based resins such as low-density polyethylene, high-density polyethylene, polypropylene, polybutene, polyisobutylene, polystyrene, and polyterpene; styrene-based copolymers such as styrene-acrylonitrile copolymer and styrene-butadiene-acrylonitrile copolymer; polyacetal; polymethyl methacrylate; cellulose acetate; polycarbonate; Examples of the resin include polyester resins such as ethylene terephthalate and polybutylene terephthalate; polyamide resins such as nylon 6 and nylon 66; thermoplastic polyurethane; tetrafluoroethylene; ionomer resins such as ethylene-based ionomers, urethane-based ionomers, styrene-based ionomers, and fluorine-based ionomers; polyacetal; thermoplastic resins such as polyphenylene sulfide; thermoplastic elastomers such as polyurethane-based elastomers, styrene-based elastomers, olefin-based elastomers, polyamide-based elastomers, and polyester-based elastomers; and bioplastics such as polylactic acid (PLA), cellulose acetate, polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), and starch resins, and one or more of these may be used in combination. The matrix component may be the above-mentioned base resin.

[0060] The matrix component is not particularly limited, but preferably contains a thermoplastic elastomer in order to achieve the effects of the present invention. The matrix component also preferably contains at least one selected from an olefin-based elastomer and a styrene-based elastomer. The weight percentage of the thermoplastic elastomer in the matrix component is not particularly limited, but is preferably 30 to 100% by weight, more preferably 50 to 100% by weight, and particularly preferably 70 to 100% by weight.

[0061] The content of heat-expandable microspheres in the composition of the present invention is not particularly limited, but is preferably 0.01 to less than 35 parts by weight, more preferably 0.1 to 30 parts by weight, even more preferably 0.5 to 20 parts by weight, and particularly preferably 1 to 15 parts by weight, per 100 parts by weight of the matrix component. A content within this range tends to enable the production of lightweight foamed molded articles with good appearance.

[0062] When the composition contains a masterbatch, the content of the masterbatch in the composition is not particularly limited as long as it corresponds to the content of the heat-expandable microspheres, but is preferably 0.05 to 50 parts by weight, more preferably 0.1 to 30 parts by weight, even more preferably 1 to 20 parts by weight, and particularly preferably 3 to 10 parts by weight, per 100 parts by weight of the matrix component. A content of 0.05 parts by weight or more tends to make it easier to obtain lightweight foamed molded articles. A content of 50 parts by weight or less tends to make it easier to obtain foamed molded articles with good appearance.

[0063] The composition of the present invention may contain, in addition to the heat-expandable microspheres, masterbatch and matrix component, molding additives such as the stabilizers, lubricants, fillers and dispersibility improvers described above, as long as the effects of the present invention are achieved.

[0064] The composition of the present invention can be produced by mixing at least one selected from the group consisting of heat-expandable microspheres and a masterbatch with a matrix resin in a ribbon mixer or a counter-rotor mixer while controlling the temperature to be lower than the expansion-initiation temperature of the heat-expandable microspheres and, if necessary, lower than the melting point or softening point of the base component or matrix component of the masterbatch.

[0065] Methods for molding the foamed molded article of the present invention include injection molding, extrusion molding, blow molding, calendar molding, press molding, vacuum molding, etc. The expansion ratio of the foamed molded article of the present invention is not particularly limited, but is preferably 1.1 to 5 times. When the expansion ratio is 1.1 times or more, the foamed molded article tends to be lightweight. When the expansion ratio is 5 times or less, the deterioration of the mechanical properties of the foamed molded article tends to be reduced. The lower limit of the expansion ratio is more preferably 1.2 times, even more preferably 1.4 times, and particularly preferably 1.5 times. On the other hand, the upper limit of the expansion ratio is more preferably 4 times, even more preferably 3 times, and particularly preferably 2 times.

[0066] Examples of uses of the foamed molded article of the present invention include automotive components such as door trims, instrument panels, glass runs, body seals, and bumpers; building materials such as window frame seals, door gaskets, and flooring materials; shoe soles; and artificial cork.

[0067] Examples of the heat-expandable microspheres of the present invention are described below in detail. However, the present invention is not limited to these examples. In the following examples and comparative examples, "%" means "% by weight" and "parts" means "parts by weight" unless otherwise specified. Furthermore, for simplicity, heat-expandable microspheres will be referred to as "microspheres," the base resin as "resin," and the matrix component as "matrix."

[0068] [Measurement of average particle size and particle size distribution of heat-expandable microspheres] The average particle size and particle size distribution were measured using a laser diffraction / scattering particle size distribution analyzer (MT3000II) manufactured by Microtrac Bell Co., Ltd. The D50 value determined by volume-based measurement was used as the average particle size.

[0069] [Expansion Onset Temperature (Ts) and Maximum Expansion Temperature (Tmax) of Heat-Expandable Microspheres] A DMA (DMA Q800, manufactured by TA Instruments) was used as the measuring device. A sample was prepared by placing 0.5 mg of microspheres in an aluminum cup with a diameter of 6.0 mm and a depth of 4.8 mm, and placing an aluminum lid (diameter 5.6 mm, thickness 0.1 mm) on top of the microsphere layer. A pressure of 0.01 N was applied to the sample from above using a pressure probe, and the sample height was measured. The sample was heated from 20°C to 350°C at a heating rate of 10°C / min while applying a pressure of 0.01 N using the pressure probe, and the displacement of the pressure probe in the vertical direction was measured. The temperature at which displacement in the forward direction began was defined as the expansion onset temperature (Ts), and the temperature at which the maximum displacement occurred was defined as the maximum expansion temperature (Tmax).

[0070] [Measurement of Specific Gravity of Masterbatch] The specific gravity of the masterbatch was measured using the following measurement method. The specific gravity was measured by the immersion method (Archimedes method) using isopropyl alcohol in an atmosphere with an ambient temperature of 25°C and a relative humidity of 50%. Specifically, a 100 mL volumetric flask was emptied and dried, and the weight of the volumetric flask (WB1) was measured. The weighed volumetric flask was then filled with isopropyl alcohol exactly up to the meniscus, and the weight of the volumetric flask filled with 100 mL of isopropyl alcohol (WB2) was measured. The 100 mL volumetric flask was also emptied and dried, and the weight of the volumetric flask (WS1) was measured. Approximately 50 mL of the masterbatch was filled into the weighed volumetric flask, and the weight of the volumetric flask filled with the masterbatch (WS2) was measured. The volumetric flask filled with the masterbatch was then filled exactly up to the meniscus with isopropyl alcohol, ensuring no air bubbles were introduced, and the weight (WS3) was measured. The obtained WB1, WB2, WS1, WS2, and WS3 were then introduced into the following formula to calculate the specific gravity (d) of the masterbatch: d = {(WS2 - WS1) x (WB2 - WB1) / 100} / {(WB2 - WB1) - (WS3 - WS2)}

[0071] [Measurement and Evaluation of the Amount of Gunk] The obtained composition was extrusion molded using an extrusion molding machine, Laboplastomill (ME-25, single-screw extruder, manufactured by Toyo Seiki Seisakusho) and a strand die (nozzle diameter 3.0 mm) as a mold, to obtain a foamed molded article. The raw material composition was charged into the extrusion molding machine, and extrusion was carried out for 30 minutes, starting 5 minutes after extrusion from the strand die. Under the above molding conditions, the weight of gunk accumulated near the discharge outlet of the strand die over 30 minutes was measured, and the measured gunk weight was evaluated based on the following index, with ○ or higher being considered pass. ⊚: The gunk amount was 25 mg or less, good. ○: The gunk amount was more than 25 mg and 50 mg or less, fair. ×: The gunk amount was more than 50 mg, poor.

[0072] [Measurement of specific gravity of foam molded article] Measurement was carried out using a Shimadzu top-pan electronic analytical balance (AX200, manufactured by Shimadzu Corporation) in the solid specific gravity measurement mode (immersion method).

[0073] [Surface condition of foam molded article] The surface condition of the foam molded article was visually judged and rated according to the following criteria: ⊚: No peeling or dents were observed on the surface of the foam molded article, good; ○: A few small peelings or dents were observed on the surface of the foam molded article, fairly good; ×: Many large peelings or dents were observed on the surface of the molded article, poor.

[0074] <Production Example A1> 150 g of sodium chloride, 50 g of colloidal silica containing 20% ​​active ingredient, 1 g of polyvinylpyrrolidone, and 0.5 g of ethylenediaminetetraacetic acid tetrasodium salt were added to 600 g of ion-exchanged water, and the pH was adjusted to 3.0 to prepare an aqueous dispersion medium. Separately, 25 g of acrylonitrile, 175 g of methacrylonitrile, 72 g of methacrylic acid, 17 g of methacrylamide, 11 g of styrene, 1.2 g of ethylene glycol dimethacrylate, 7.5 g of di(2-ethylhexyl)peroxydicarbonate (P-OPP), 40 g of isopentane, and 40 g of isooctane were mixed to prepare an oily mixture. The aqueous dispersion medium and the oily mixture were mixed, and the resulting mixture was dispersed in a homomixer (TK Homomixer, manufactured by Plamix Co., Ltd.) at 10,000 rpm for 1 minute to prepare a suspension. The suspension was transferred to a 1.5-liter pressure reactor and purged with nitrogen. The initial reaction pressure was adjusted to 0.35 MPa, and polymerization reaction was carried out at a polymerization temperature of 60°C for 20 hours with stirring at 80 rpm. After polymerization, the product was filtered and dried to obtain microspheres 1. The physical properties of the obtained heat-expandable microspheres are shown in Table 1.

[0075] <Preparation Examples A2 to A5, Preparation Comparative Examples a1 to a3> Heat-expandable microspheres were obtained in the same manner as in Preparation Example A1, except for changing the reaction conditions as shown in Table 1. The physical properties of the obtained heat-expandable microspheres are shown in Table 1. The abbreviations in Table 1 have the following meanings: AN: acrylonitrile, SP(AN): 14.4 (cal / cm ３ ) １／２ MAN: methacrylonitrile, SP (MAN): 12.7 (cal / cm ３ ) １／２ AA: acrylic acid, SP (AA): 14.0 (cal / cm ３ ) １／２ MAA: methacrylic acid, SP (MAA): 12.5 (cal / cm ３ ) １／２ MAAm: methacrylamide, SP (MAAm): 16.3 (cal / cm ３ ) １／２ MMA: methyl methacrylate, SP (MMA): 9.9 (cal / cm ３ ) １／２ St: styrene, SP (St): 10.6 (cal / cm３ ) １／２ EDMA: ethylene glycol dimethacrylate, SP (EDMA): 11.2 (cal / cm ３ ) １／２

[0076]

[0077] <Production Example B1> 100 parts of Resin 1 as a base resin and 100 parts of the microspheres 1 obtained in Production Example A1 were mixed and kneaded in a pressure kneader at 80°C for 1 minute, and the kneaded mixture was extruded at 70°C to form pellets, thereby obtaining a masterbatch (MB1). The physical properties of the obtained masterbatch are shown in Table 2.

[0078] <Production Examples B2 to B8, Production Comparative Examples b1 to b3> Masterbatches were obtained in the same manner as in Production Example B1, except that the masterbatch blending conditions and masterbatch production conditions of Production Example B1 were changed to those shown in Tables 2 and 3. The physical properties of the obtained masterbatches are shown in Tables 2 and 3. The abbreviations in Tables 2 and 3 have the following meanings. Resin 1: Ethylene-vinyl acetate copolymer, manufactured by Tosoh Corporation, Ultrathene (registered trademark) 720, specific gravity 0.947, melting point 67°C, melt flow rate 150g / 10min, olefin unit content 72% by weight, ethylene unit content 72% by weight. Resin 2: Ethylene-butene copolymer, manufactured by Sumitomo Chemical Co., Ltd., Excellen (registered trademark) FX558, specific gravity 0.89, melting point 79°C, melt flow rate 75g / 10min, olefin unit content 100% by weight, ethylene unit content 77.8% by weight. Resin 3: Low-density polyethylene, manufactured by Tosoh Corporation, Petrothene (registered trademark) 353, specific gravity 0.915, melting point 98°C, melt flow rate 145g / 10min, olefin unit content 100% by weight, ethylene unit content 100% by weight. Resin 4: Ethylene-methyl methacrylate copolymer, manufactured by Sumitomo Chemical Co., Ltd. Acryft (registered trademark) CM5021, specific gravity 0.94, melting point 67°C, melt flow rate 450g / 10min, olefin unit content 72% by weight, ethylene unit content 72% by weight

[0079]

[0080]

[0081] Example 1 Six parts by weight of the masterbatch (MB1) obtained in Production Example B1 was mixed with 100 parts by weight of Matrix 1 (an olefin-based elastomer, manufactured by Mitsui Chemicals, Inc., Milastomer® 8032BS, specific gravity 0.89) as a matrix component to obtain a composition. The resulting composition was extrusion-molded using the extruder and strand die described in the "Measurement and Evaluation of Residue Amount" section above to obtain a strand-shaped foamed molded article. The physical properties of the resulting foamed molded article are shown in Table 4. The molding conditions were as follows: the extruder cylinder and strand die temperatures (molding temperature) were set to 200°C, and the screw rotation speed was set to 25 rpm. The residence time of the composition in the molding machine was 3.5 minutes.

[0082] Examples 2 to 8, Comparative Examples 1 to 3 Foam molded articles were obtained in the same manner as in Example 1, except that the production conditions for the foam molded article in Example 1 were changed to those shown in Tables 4 and 5. The physical properties of the obtained foam molded articles are shown in Tables 4 and 5. Matrix 1: Olefin-based elastomer, Milastomer (registered trademark) 8032BS manufactured by Mitsui Chemicals, Inc., specific gravity 0.89, A-hardness 79 Matrix 2: Styrene-based elastomer, AR-SC-30 manufactured by Aronkasei Co., Ltd., specific gravity 0.89, A-hardness 26

[0083]

[0084]

[0085] From Tables 4 and 5, it can be seen that the solubility parameter of the polymer contained in the outer shell of the heat-expandable microspheres is 13 (cal / cm ３ ) １／２ On the other hand, when the solubility parameter of the polymer contained in the outer shell is 13 (cal / cm ３ ) １／２ If the temperature exceeds this range, it is clear that the occurrence of gum cannot be reduced when molding a foamed molded article.

[0086] The heat-expandable microspheres of the present invention can be used to produce foamed molded articles by injection molding, extrusion molding, press molding, etc. The foamed molded articles obtained can be used as sound-insulating materials, heat-insulating materials, heat-shielding materials, sound-absorbing materials, etc.

Claims

1. A masterbatch comprising thermally expandable microspheres and a base resin, The aforementioned thermally expandable microsphere comprises an outer shell containing a polymer and a foaming agent enclosed within the outer shell that vaporizes upon heating. The solubility parameter of the polymer is 13 (cal / cm³) 1 / 2 or less. The melt flow rate of the base resin is more than 60 g / 10 min, A masterbatch in which the melting point of the base resin is below the expansion initiation temperature of the thermally expandable microspheres, and the melting point is between 60 and 130°C.

2. The masterbatch according to claim 1, wherein the polymer is a polymer of a polymerizable component containing a carboxyl group-containing monomer.

3. The masterbatch according to claim 2, wherein the weight ratio of the carboxyl group-containing monomer to the polymerizable component is 20 to 70% by weight.

4. The masterbatch according to claim 2 or 3, wherein the polymerizable component further comprises at least one selected from (meth)acrylamide monomers and (meth)acrylic acid ester monomers.

5. The masterbatch according to claim 4, wherein the weight proportion of at least one selected from the (meth)acrylamide monomer and the (meth)acrylic acid ester monomer in the polymerizable component is 5 to 70% by weight.

6. The masterbatch according to claim 2 or 3, wherein the weight percentage of acrylonitrile in the polymerizable component is less than 20% by weight.

7. The masterbatch according to any one of claims 1 to 3, wherein the base resin comprises an olefin polymer, and the olefin units constituting the olefin polymer comprise ethylene units.

8. The masterbatch according to any one of claims 1 to 3, wherein the content of the thermally expandable microspheres is 35 to 300 parts by weight per 100 parts by weight of the base resin.

9. A composition comprising a masterbatch according to any one of claims 1 to 3 and a matrix component.

10. A foamed molded article obtained by molding the composition described in claim 9.