Thermally expandable microspheres, masterbatches, compositions, and foamed molded articles

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

[Technical Field]

[0001] The present invention relates to thermally expandable microspheres, masterbatches, compositions, and foamed molded articles. [Background technology]

[0002] Thermally expandable microspheres (thermally expandable microcapsules), which are fine particles with a thermoplastic resin outer shell and a foaming agent inside, have the characteristic of expanding when heated. Furthermore, the masterbatch obtained by kneading these thermally expandable microspheres with a base resin also has the characteristic of expanding when heated. These thermally expandable microspheres and masterbatches are used in a wide range of applications. For example, they can be mixed with a base resin and molded to produce molded articles. The heat treatment applied during molding causes the thermally expandable microspheres to expand, not only reducing the weight of the molded article but also imparting aesthetic appeal and cushioning properties to it.

[0003] As an example of such thermally expandable microspheres, Patent Document 1 proposes a thermally expandable microcapsule having a polymer outer shell composed of 15-75% by weight of a nitrile monomer, 10-65% by weight of a monomer having a carboxyl group, 0.1-20% by weight of a monomer having an amide group, and 0.1-20% by weight of a monomer having a cyclic structure in its side chain, and containing a blowing agent. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2004 / 058910 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The thermally expandable microspheres disclosed in Patent Document 1 are excellent in heat and solvent resistance, have excellent foaming properties over a wide range in the high-temperature region, and can also be used for foam molding of thermoplastic resins and thermosetting resins with a resin molding temperature of 200 °C or higher. However, when foam molding is performed using the thermally expandable microspheres disclosed in the above patent document, deposits called "meyani", such as particulate matter of the base resin and expanded thermally expandable microspheres, occur and accumulate near the discharge port of the molding apparatus. Furthermore, the generated meyani mixes into the molded body or adheres to the surface of the molded body, deteriorating the appearance of the molded body.

[0006] Therefore, an object of the present invention is to provide thermally expandable microspheres and their uses capable of reducing the generation of meyani when molding a foam molded body.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have found that specific thermally expandable microspheres can solve the above problems and have reached the present invention. That is, the present invention includes the following aspects.

[0008] <1> A thermally expandable microsphere including an outer shell containing a polymer and a foaming agent encapsulated in the outer shell and vaporizing by heating, wherein the solubility parameter of the polymer is 13 (cal / cm 3 ) 1 / 2 The following thermally expandable microspheres. <2> The thermally expandable microsphere according to <1>, wherein the polymer is a polymer of a polymerizable component containing a carboxyl group-containing monomer. <3> The thermally expandable microsphere according to <2>, wherein the weight ratio of the carboxyl group-containing monomer in the polymerizable component is 20 to 70% by weight. <4> The thermally expandable microsphere according to <2> or <3>, wherein the polymerizable component further contains at least one selected from (meth)acrylamide-based monomers and (meth)acrylate-based monomers. <5> The weight percentage 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. <4> The thermally expandable microspheres described above. <6> The weight percentage of acrylonitrile in the polymerizable component is less than 20% by weight. <2> ~ <5> A thermally expandable microsphere as described in any of the following. <7> <1> ~ <6> A masterbatch comprising a thermally expandable microsphere and a base resin as described in any of the above, wherein the melt flow rate of the base resin is greater than 60 g / 10 min, and the melting point of the base resin is less than or equal to the expansion start temperature of the thermally expandable microsphere. <8> The melting point is 60 to 130°C. <7> The masterbatch described above. <9> The content of the thermally expandable microspheres is 35 to 300 parts by weight per 100 parts by weight of the base resin. <7> or <8> The masterbatch described above. <10> <1> ~ <6> The thermally expandable microspheres described in any of the following and <7> ~ <9> A composition comprising at least one masterbatch selected from any of the masterbatches described in the above, and a matrix component. <11> <10> A foamed molded article obtained by molding the composition described above. [Effects of the Invention]

[0009] The heat-expandable microspheres of the present invention can reduce the generation of adhesive residue when forming foamed molded articles. Since the masterbatch of the present invention contains the above-mentioned thermally expandable microspheres, the generation of smegma can be reduced when molding foamed molded articles. Since the composition of the present invention contains at least one selected from the above-mentioned thermally expandable microspheres and masterbatch, it is possible to reduce the generation of smegma when molding a foamed molded article. Since the molded article of the present invention is made by molding the above composition, it has a good appearance and is lightweight. [Modes for carrying out the invention]

[0010] [Thermally expandable microspheres] The thermally expandable microspheres of the present invention include an outer shell containing a polymer and a foaming agent encapsulated in the outer shell and vaporized by heating, and exhibit thermal expandability as a whole (the property that the whole microspheres expand by heating). As the form of the thermally expandable microspheres, it is preferable to have a core-shell structure composed of an outer shell (shell) containing a polymer and a core containing a foaming agent as an essential component.

[0011] The solubility parameter of the polymer forming the outer shell of the thermally expandable microspheres of the present invention is 13 (cal / cm 3 ) 1 / 2 or less. In the present invention, the solubility parameter may be simply referred to as the SP value. When the solubility parameter of the polymer forming the outer shell of the thermally expandable microspheres is 13 (cal / cm 3 ) 1 / 2 or less, the value becomes close to the solubility parameter of the matrix component, and it is considered that the compatibility between the thermally expandable microspheres and the matrix component is increased, and it becomes possible to reduce the occurrence of streaks when forming a molded body. 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 , still more preferably 11 to 12.8 (cal / cm 3 ) 1 / 2 .

[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 (pages 147 to 154)". The SP value can be calculated from the following formula (I) using the cohesive energy (E coh ) of the atomic group constituting the structural unit of the polymer and the molar volume (V) of the atomic group constituting the structural unit. The cohesive energy (E cohThe values ​​for the molar volume (V) of the atomic group were referenced from "POLYMER ENGINEERING AND SCIENCE, February, 1974, Vol.14, No.2, Robert F. Fedors (pp. 147-154)". Also, 1 J was defined as 0.239 cal. SP value = [ΣE coh / ΣV] 1 / 2 (I)

[0013] For example, a structural unit derived from acrylonitrile has one secondary carbon (-CH2-) group, one tertiary carbon (-CH<) group, and one nitrile group (-CN). The cohesive energy E of each of these groups coh The molar volume V is as follows: -CH2-:E coh =1180.7 cal / mol, V=16.1 cm 3 / mol -CH<:E coh = 819.7 cal / mol, V = -1.0 cm 3 / mol -CN::E coh =6101.7 cal / mol, V=24.0 cm 3 / mol Therefore, calculating the above values ​​based on 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 is the result.

[0014] Furthermore, the structural unit derived from methacrylonitrile has one primary carbon (-CH3) group, one secondary carbon (-CH2-) group, one quaternary carbon (>C<) group, and one nitrile group (-CN). Here, the cohesive energy E of the primary carbon (-CH3) group and the quaternary carbon (>C<) group. coh The molar volume V is as follows: -CH3:Ecoh =1125.7 cal / mol, V=33.5 cm 3 / mol >C<:E coh =351.3 cal / mol, V=-19.2 cm 3 / mol Therefore, in the same manner as with acrylonitrile, the SP value (SP(MAN)) of the structural unit formed by methacrylonitrile (methacrylonitrile structural unit) is: 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 is the result.

[0015] Furthermore, the SP value (SP(P)) of a polymer consisting of acrylonitrile structural units and methacrylonitrile structural units, wherein the proportion of acrylonitrile structural units in the polymer is a1% by weight and the proportion of methacrylonitrile structural units is a2% by weight, can be calculated according to the following formula (II). SP(P)=(SP(AN)×a1+SP(MAN)×a2) / (a1+a2) (II)

[0016] Furthermore, the above formula (II) can be generalized not only to polymers consisting of the above-mentioned specific structural units, but also to polymers having other structural units, as shown in the following formula (III). SP value = (SP1 × a1 + SP2 × a2 + ... + SP n ×a n ) / (a1+a2+···+a n ) (III) Here, SP1 is the SP value of the first structural unit in the polymer, and a1 is its weight percentage (%) in the polymer. Furthermore, SP2~SP n These are the SP values ​​of the 2nd to nth structural units in the polymer, respectively, a2 to a n These represent the weight percentage (%) of each component in the polymer. If the polymer is a polymer of polymerizable components described later, then the above a1~an This represents the weight percentage of each monomer in the polymerizable components.

[0017] In the present invention, the polymer forming the outer shell is preferably a polymer of polymerizable components that include a monomer having one (radical) polymerizable carbon-carbon double bond (hereinafter sometimes referred to as a monomer component). Such a polymer is preferable because it efficiently encapsulates the blowing agent and has high expansion performance. The weight ratio of structural units derived from each monomer component in the polymer is the weight ratio of each monomer component to the polymerizable component. Furthermore, the polymerizable component may further contain monomers having at least two (radical) polymerizable carbon-carbon double bonds (hereinafter sometimes referred to as crosslinking agents). The monomer component and the crosslinking agent are components capable of addition reactions, and the crosslinking agent is a component that can introduce a crosslinked structure into the thermoplastic resin (A). In the polymer, the weight ratio of structural units derived from each crosslinking agent is the weight ratio of each crosslinking agent to the polymerizable component.

[0018] There are no particular limitations on the monomer components, but examples include nitrile monomers such as acrylonitrile, methacrylonitrile, fumaronitrile, and maleonitrile; vinyl halogenated monomers such as vinyl chloride; vinylidene halogenated 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, as well as maleic acid, itaconic acid, fumaric acid, and citra. Carboxyl group-containing monomers such as unsaturated dicarboxylic acids like 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 Examples include (meth)acrylic acid ester monomers such as rilate, 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 monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; maleimide monomers such as N-phenylmaleimide and N-cyclohexylmaleimide; styrene monomers such as styrene and α-methylstyrene; ethylene unsaturated monoolefin monomers such as ethylene, propylene, and isobutylene; vinyl ether monomers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl ketone monomers such as vinyl methyl ketone; N-vinyl monomers such as N-vinylcarbazole and N-vinylpyrrolidone; and vinylnaphthalene salts. In carboxyl group-containing monomers, some or all of the carboxyl groups may be neutralized during or after polymerization. Acrylic acid or methacrylic acid together may also be called (meth)acrylic acid, (meth)acrylate means acrylate or methacrylate, and (meth)acrylic means acrylic or methacrylic.These monomeric components may be used individually or in combination of two or more.

[0019] While there are no particular limitations on the polymerizable components, the inclusion of a carboxyl group-containing monomer as a monomer component is preferable because it improves the heat resistance of the thermally expandable microspheres. Furthermore, the inclusion of a carboxyl group-containing monomer is preferable because it makes it easier to adjust 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% by weight, more preferably 25 to 65% by weight, and even more preferably 30 to 60% by weight. When the weight percentage is 20% by weight or more, the heat resistance of the thermally expandable microspheres tends to improve. When the weight percentage is 70% by weight or less, the rigidity of the outer shell does not become too high, and the expandability tends to improve.

[0020] When the polymerizable component contains a carboxyl group-containing monomer, there are no particular limitations, but it is preferable to further include at least one selected from (meth)acrylamide monomers and (meth)acrylic acid ester monomers as a monomer component, as this improves the heat resistance of the thermally expandable microspheres. When the polymerizable component contains at least one monomer selected from (meth)acrylamide monomers and (meth)acrylic acid ester monomers as a monomer component, the weight percentage of at least one monomer selected from (meth)acrylamide monomers and (meth)acrylic acid ester monomers in the polymerizable component is not particularly 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. When the weight percentage is 5% by weight or more, the heat resistance of the thermally expandable microspheres tends to improve. When the weight percentage is 70% by weight or less, the rigidity of the outer shell does not become too high, and the expandability tends to improve. When the polymerizable component includes a (meth)acrylamide monomer or a (meth)acrylic acid ester monomer, the weight of the (meth)acrylamide monomer or the (meth)acrylic acid ester monomer should be in the above weight ratio.

[0021] The weight percentage of acrylonitrile in the polymerizable component is not particularly limited, but is preferably less than 20% by weight. Having the weight percentage of acrylonitrile in the polymerizable component within the above range is preferable because it adjusts the rigidity of the outer shell and improves expandability. Furthermore, having the weight percentage of acrylonitrile in the polymerizable component within the above range is preferable because it makes it easier to adjust the solubility parameter of the polymer within the above range. The weight percentage 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 inclusion of methacrylonitrile in the polymerizable component is preferable because it improves the gas barrier properties of the outer shell. Furthermore, the inclusion of methacrylonitrile is preferable because it makes it easier to adjust the solubility parameters of the polymer within 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 bridging structure, improving gas barrier properties and expansion performance. There are no particular limitations on the crosslinking agent, but examples include alkane diol 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; polyalkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)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; and ethoxylated bisphenol A di(meth)acrylate (EO addition 2-30); Propoxylated bisphenol A di(meth)acrylate; Propoxylated ethoxylated bisphenol A di(meth)acrylate; Glycerin di(meth)acrylate; Polybutadiene di(meth)acrylate; Polyisoprene(meth)acrylate; 2-Hydroxy-3-acryloyloxypropyl methacrylate; Dimethylol-tricyclodecane di(meth)acrylate; Divinylbenzene; Ethoxylated glycerin triacrylate; 1,3,5-tri(meth) Examples of crosslinking agents include difunctional 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, as well as tetrafunctional monomers or monomers with four or more functions. These crosslinking agents may be used individually or in combination of two or more.

[0024] The weight percentage 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 foaming agent is a component that vaporizes when heated and is encapsulated within the outer shell of the thermally expandable microspheres. As a result, the thermally expandable microspheres as a whole exhibit thermal expandability (the property of the entire microsphere expanding when heated). There are no particular limitations on the foaming agent, but examples include hydrocarbons with 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 with more than 13 carbon atoms but 20 or less such as (iso)hexadecane and (iso)eicosane; pseudocumene, petroleum ether, and petroleum such as normal paraffins and isoparaffins with an initial boiling point of 150 to 260°C and / or a distillation range of 70 to 360°C. Examples include hydrocarbons such as fractional distillates; halides of 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 alkyl groups with 1 to 5 carbon atoms, such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane; and compounds that generate gas through thermal decomposition upon heating, such as azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, and 4,4'-oxybis(benzenesulfonylhydrazide). The foaming agent may consist of one compound or a mixture of two or more compounds. The foaming agent may be linear, branched, or cyclic, and is preferably aliphatic. Furthermore, it is preferable that the blowing agent contains hydrocarbons with 8 or more carbon atoms because this improves the maximum expansion temperature of the thermally expandable microspheres, and it is preferable that the blowing agent contains hydrocarbons with 6 or fewer carbon atoms because this allows the thermally expandable microspheres to expand more efficiently.

[0026] The foaming agent content in the thermally expandable microspheres of the present invention is defined as the percentage of the weight of the foaming agent contained within the thermally expandable microspheres relative to the total weight of the thermally expandable microspheres. The content of the foaming agent is not particularly limited, but is preferably 2 to 40% by weight, more preferably 4 to 35% by weight, even more preferably 5 to 30% by weight, and most preferably 6 to 25% by weight. When the content is within the above range, the foaming agent is less likely to leak out to the outside during heating and expansion, and the expandability tends to improve.

[0027] The expansion start temperature (Ts) of the thermally 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 most preferably 150 to 170°C. When the expansion start temperature is 120°C or higher, the heat resistance of the thermally expandable microspheres tends to improve. When the expansion start temperature is 200°C or lower, the expansion performance tends to improve.

[0028] The maximum expansion temperature (Tmax) of the thermally 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. When the maximum expansion temperature is 155°C or higher, the microspheres tend to have sufficient heat resistance. The expansion start temperature (Ts) and maximum expansion temperature (Tmax) of the thermally expandable microspheres are determined by the method described in the examples.

[0029] The average particle size of the thermally 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. When the average particle size is 1 μm or more, the expansion performance of the thermally expandable microspheres tends to improve. When the average particle size is 200 μm or less, the appearance of the resulting molded article tends to be good. The coefficient of variation (Cv) in the particle size distribution of the thermally 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 thermally expandable microspheres are determined by the method described in the examples.

[0030] The maximum volume expansion ratio of the thermally expandable microspheres of the present invention is not particularly limited, but is preferably 5 to 200 times, more preferably 10 to 200 times, and even more preferably 15 to 200 times. When the expansion ratio is 5 times or more, a lightweight molded article tends to be obtained. When the expansion ratio is 200 times or less, the appearance of the resulting molded article tends to be good.

[0031] In the present invention, a method for producing the thermally expandable microspheres includes a step of dispersing an oily mixture containing a polymerizable component, a foaming agent, and a polymerization initiator in an aqueous dispersion medium, and polymerizing the polymerizable component (hereinafter sometimes referred to as the polymerization step).

[0032] There are no particular limitations on the polymerization initiator, but examples include peroxides and azo compounds. There are no particular limitations on the peroxides, but examples 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. There are no particular limitations on the azo compounds, but examples 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-carbonitride).

[0033] The amount of polymerization initiator is not particularly limited, but in order to achieve 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 per 100 parts by weight of polymerizable component.

[0034] The aqueous dispersion medium used in the polymerization process is a water-based medium, such as deionized water, that disperses an oily mixture, and may further contain alcohols such as methanol, ethanol, or propanol, or hydrophilic organic solvents such as acetone. In this invention, hydrophilicity means being miscible with water. The amount of aqueous dispersion medium used is not particularly limited, but is preferably 100 to 1000 parts by weight per 100 parts by weight of polymerizable component.

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

[0036] The aqueous dispersion medium may contain at least one water-soluble compound selected from 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 is bonded to the same carbon atom and a heteroatom; 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 vitamin B compounds; potassium dichromate; alkali metal nitrite salts; metal (III) halides; boric acid; and water-soluble phosphonic acid (salts). In this invention, "water-soluble" means a state in which 1 g or more dissolves per 100 g of water. The amount of 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 parts by weight, and even more preferably 0.001 to 0.05 parts by weight, per 100 parts by weight of polymerizable component.

[0037] The aqueous dispersion medium may contain, in addition to electrolytes and water-soluble compounds, dispersion stabilizers and dispersion stabilization aids. Examples of dispersion stabilizers include tricalcium phosphate, magnesium pyrophosphate obtained by a double decomposition method, calcium pyrophosphate, colloidal silica, alumina sol, and magnesium hydroxide. These dispersion stabilizers may be used individually 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 polymerizable component. Examples of dispersion stabilization aids include polymer-type dispersion stabilization aids, cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, and other surfactants. These dispersion stabilization aids may be used individually or in combination of two or more types.

[0038] Aqueous dispersion media are prepared, for example, by adding electrolytes, water-soluble compounds, dispersion stabilizers, and dispersion stabilization aids to water (ion-exchanged water) as needed. The pH of the aqueous dispersion media during polymerization is appropriately determined depending on the type of water-soluble compound, dispersion stabilizer, and dispersion stabilization aid used.

[0039] In the thermally expandable microspheres of the present invention, polymerization may be carried out in the presence of sodium hydroxide and zinc chloride in the manufacturing method. In the present invention, the method for producing the thermally expandable microspheres involves suspending and dispersing an oily mixture in an aqueous dispersion medium so that spherical oil droplets of a predetermined particle size are prepared.

[0040] Methods for suspending and dispersing oily mixtures include, for example, stirring with a homomixer (e.g., manufactured by Primix Co., Ltd.), using a static dispersion device such as a static mixer (e.g., manufactured by Noritake Engineering Co., Ltd.), and general dispersion methods such as membrane suspension and ultrasonic dispersion. Next, suspension polymerization is initiated by heating the dispersion, in which the oily mixture is dispersed as spherical oil droplets in an aqueous dispersion medium. During the polymerization reaction, it is preferable to stir the dispersion, and the stirring should be done gently, for example, to prevent the spherical oil droplets from floating to the surface and the thermally expandable microspheres after polymerization from settling.

[0041] The polymerization temperature can be freely set depending on the type of polymerization initiator, but is preferably controlled within the range of 30 to 100°C, and more preferably within the range of 40 to 90°C. The time for maintaining the reaction temperature is preferably about 1 to 20 hours. There are no particular limitations on the initial polymerization pressure, but it is in the range of 0 to 5 MPa, and more preferably within the range of 0.1 to 3 MPa in gauge pressure.

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

[0043] [Masterbatch] The masterbatch of the present invention comprises the above-mentioned thermo-expandable microspheres and base resin, and is for foam molding that can be used when manufacturing foamed molded articles. The base resin contained in the masterbatch of the present invention is a component that is mixed together with thermally expandable microspheres, and is a component that forms the masterbatch.

[0044] The base resin has a melt flow rate (hereinafter sometimes referred to as MFR) exceeding 60 g / 10 min, and its melting point is below the expansion initiation temperature of thermally expandable microspheres. Having a base resin MFR of over 60g / 10min increases the fluidity of the masterbatch when it melts. This allows the thermally expanding microspheres to disperse and expand uniformly when molding the composition containing the masterbatch, reducing variations in specific gravity and thus making it easier to reduce the generation of mold residue during molding. The MFR of the base resin is preferably greater than 60 g / 10 min and 500 g / 10 min or less, 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 under conditions of a measurement temperature of 190°C and a load of 2.16 kg, in accordance with JIS K7210.

[0045] The melting point of the base resin is not particularly limited as long as it is below the expansion start temperature of the thermally expandable microspheres, but preferably it is 5°C or more lower than the expansion start temperature of the thermally expandable microspheres, more preferably 10°C or more lower than the expansion start temperature of the thermally expandable microspheres, and even more preferably 20°C or more lower than the expansion start temperature of the thermally expandable microspheres.

[0046] Furthermore, the melting point of the base resin is not particularly limited as long as it is below the expansion start temperature of the thermally 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. If the melting point is 60°C or higher, fusion between masterbatches tends to be suppressed. If the melting point is 130°C or lower, the expandability tends to improve.

[0047] The base resin is not particularly limited as long as it has the above characteristics, but examples 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), and silane-crosslinkable linear Examples include olefin polymers such as chain-like low-density polyethylene, chlorinated polyethylene, modified polyethylene containing carboxyl groups, polypropylene, silane-crosslinked polypropylene, and modified polypropylene containing carboxyl groups; polyvinyl chloride; acrylic resin; styrene polymers such as acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, styrene-butadiene copolymer, and polystyrene; polycarbonate; polyester polymers such as polyethylene terephthalate and polybutylene terephthalate; and urethane polymers such as thermoplastic polyurethane and urethane elastomers. One or more of these may be used in combination. Furthermore, the base resin may use the matrix components described later.

[0048] The base resin is preferable if it contains an olefin-based polymer, as this improves the dispersibility of the thermally expandable microspheres. Furthermore, while there are no particular limitations on the content of olefin units constituting the olefin polymer, it 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. When the content is within the above range, the dispersibility of the thermally expandable microspheres tends to improve. The olefin unit is not particularly limited, but it is preferably an olefin having 2 to 10 carbon atoms, and preferably contains ethylene. When the olefin unit contains ethylene, the content of ethylene units constituting the olefin 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 most preferably 75 to 100% by weight.

[0049] When the base resin contains an olefin polymer, the weight percentage of the olefin 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 most preferably 80 to 100% by weight. When the weight percentage is within the above range, the dispersibility of the thermally expandable microspheres tends to improve. Alternatively, the base resin may consist of an olefin polymer.

[0050] The content of thermally 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 base resin. When the content is 35 parts by weight or more, the mechanical properties of the matrix components constituting the resulting foamed molded article tend to be more easily maintained. When the content is 300 parts by weight or less, the dispersibility of the thermally expandable microspheres tends to improve during the production of the molded article.

[0051] The masterbatch of the present invention may further contain other components in addition to the thermally expandable microspheres and base resin, such as molding additives including stabilizers, lubricants, fillers, and dispersibility enhancers. There are no particular limitations on the stabilizers, but examples 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. One or more types may be used in combination. There are no particular limitations on the lubricant, but examples include polyethylene wax; glycerin fatty acid esters such as glycerin monostearate and diglycerin stearate; and fatty acids such as stearic acid. One or more of these may be used in combination.

[0052] There are no particular limitations on the fillers, but examples include plant fibers such as wood powder 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 quartz inorganic particles, and one or more of these may be used in combination. There are no particular limitations on the dispersibility improver, but examples include aliphatic hydrocarbons, process oils such as paraffin oil and aroma oil; liquid paraffin, etc., 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, thermally expandable microspheres contained in the masterbatch is small, and the expandability tends to improve. The specific gravity of the masterbatch is determined 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, it tends to be easier to obtain a lightweight foamed molded product. When the expansion ratio is 120 times or less, it tends to be easier to obtain a foamed molded product with a good appearance.

[0055] In the masterbatch of the present invention, the shape of the cross-section when cut with a plane perpendicular to its length can be appropriately determined depending on the intended use of the masterbatch, but examples include circular, elliptical, polygonal, star-shaped, hollow circular, etc. The length of the masterbatch of the present invention is determined appropriately depending on its application, but is preferably 1 to 5 mm, more preferably 2 to 4 mm, and even more preferably 2.5 to 3.5 mm. When the length is within the above range, the dispersibility of the thermally expandable microspheres tends to improve during the manufacture of the molded article. In the masterbatch of the present invention, the length of the major axis of the cross-section in a plane perpendicular to its longitudinal direction is appropriately determined depending on the application, but is preferably 1 to 5 mm, more preferably 2 to 4 mm, and even more preferably 2.5 to 3.5 mm. When the length of the major axis is within the above range, the dispersibility of thermally expandable microspheres tends to improve during the manufacture of the molded article.

[0056] The method for manufacturing the masterbatch of the present invention may be any method of mixing thermally expandable microspheres and a base resin, and a method of uniformly dispersing them is preferred. Examples of methods for manufacturing the masterbatch include a manufacturing method that includes the pre-kneading step shown in (1) below and the pelletizing step shown in (2) below. (1) The base resin is pre-melted and kneaded using a kneader such as a roller, kneader, pressure kneader, or Banbury mixer. Next, a pre-kneading step is performed in which thermally expandable microspheres and, if necessary, other components are added to the molten base resin to prepare a pre-kneaded product. (2) A pelletizing process in which the pre-mixed material obtained above is fed into an extruder such as a single-screw extruder, twin-screw extruder, or multi-screw extruder to extrude the molten mixture into the desired shape and thickness, and then pelletized using a hot-cut pelletizer.

[0057] Furthermore, the masterbatch of the present invention can be manufactured by extruding strands of a desired thickness from an extruder and cutting them to a desired length using a cutting machine. During the manufacturing of the masterbatch, the thickness of the strands can be adjusted by the diameter of the extruder's strand die and the strand winding speed, etc. When manufacturing a masterbatch, the temperature must be below the expansion initiation temperature of the thermally expandable microspheres; otherwise, the microspheres will expand. Generally, to prevent the expansion of the thermally expandable microspheres, it is best to manufacture the masterbatch at a temperature at least 5°C lower than the expansion initiation temperature.

[0058] [Composition and foamed molded article] The composition of the present invention comprises at least one selected from the above-mentioned thermally expandable microspheres and the above-mentioned masterbatch, and a matrix component. The composition of the present invention may also comprise the above-mentioned thermally expandable microspheres and a matrix component. Alternatively, the composition may comprise the above-mentioned masterbatch and a matrix component. By molding the composition of the present invention, a foamed molded article can be manufactured, and the generation of moldy residue during the manufacturing of the foamed molded article can be reduced.

[0059] There are no particular limitations on the matrix components, but examples 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 resins such as low-density polyethylene, high-density polyethylene, polypropylene, polybutene, polyisobutylene, polystyrene, and polyterpenes; styrene-based copolymers such as styrene-acrylonitrile copolymer and styrene-butadiene-acrylonitrile copolymer; polyacetal; polymethyl methacrylate; cellulose acetate; polycarbonate; and polyethylene. Examples include polyester resins such as ethylene terephthalate and polybutylene terephthalate; polyamide resins such as nylon 6 and nylon 66; thermoplastic polyurethanes; 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. One or more of these may be used in combination. The matrix component may be the base resin described above.

[0060] The matrix component is not particularly limited, but it is preferable to include a thermoplastic elastomer in order to achieve the effects of the present invention. Furthermore, it is preferable that the matrix component includes at least one selected from olefin-based elastomers and styrene-based elastomers. The weight percentage of 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 most preferably 70 to 100% by weight.

[0061] The content of thermally expandable microspheres in the composition of the present invention is not particularly limited, but is preferably 0.01 parts by weight or more and 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. When the content is within the above range, it tends to be possible to produce a lightweight foamed molded article with a good appearance.

[0062] If the composition contains a masterbatch, the amount of masterbatch in the composition is not particularly limited as long as it is equal to the amount of the thermally 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. When the amount is 0.05 parts by weight or more, it is easier to obtain a lightweight foamed molded article. When the amount is 50 parts by weight or less, it is easier to obtain a foamed molded article with a good appearance.

[0063] The composition of the present invention may contain, to the extent that it achieves the effects of the present invention, molding additives such as the aforementioned stabilizers, lubricants, fillers, and dispersibility enhancers, in addition to the thermally expandable microspheres, masterbatch, and matrix components.

[0064] A method for producing the composition of the present invention involves mixing at least one selected from thermally expandable microspheres and a masterbatch with a matrix resin using a ribbon-type mixer or a sub-axis rotor-type mixer, while controlling the temperature to be lower than the expansion start temperature of the thermally expandable microspheres and, if necessary, lower than the melting point or softening point of the base component and matrix component of the masterbatch.

[0065] Methods for molding the foamed molded article of the present invention include injection molding, extrusion molding, blow molding, calendering, press molding, and vacuum molding. The foaming ratio of the foamed molded article of the present invention is not particularly limited, but is preferably 1.1 to 5 times. When the foaming ratio is 1.1 times or more, the article tends to be lighter. When the foaming 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 foaming 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 foaming ratio is more preferably 4 times, even more preferably 3 times, and particularly preferably 2 times.

[0066] Applications of the foamed molded articles of the present invention include, for example, 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. [Examples]

[0067] The following describes specific examples of the thermally expandable microspheres of the present invention. The present invention is not limited to these examples. In the following examples and comparative examples, unless otherwise specified, "%" means "weight percent" and "parts" means "parts by weight". Furthermore, for simplicity, in the following, thermally expandable microspheres may 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 thermally expandable microspheres] As the measuring device, a laser diffraction scattering particle size distribution analyzer (MT3000II) manufactured by Microtrac-Bell Corporation was used to measure the average particle size and particle size distribution. The D50 value obtained by volume-based measurement was used as the average particle size.

[0069] [Expansion onset temperature (Ts) and maximum expansion temperature (Tmax) of thermally expandable microspheres] A DMA (DMA Q800 model, 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 of 5.6 mm, thickness of 0.1 mm) on top of the microsphere layer. The sample height was measured while a force of 0.01 N was applied to the sample from above using a pressure bar. The sample was heated from 20°C to 350°C at a heating rate of 10°C / min while a force of 0.01 N was applied using the pressure bar, and the displacement of the pressure bar in the vertical direction was measured. The temperature at which displacement in the positive direction began was defined as the expansion start temperature (Ts), and the temperature at which the maximum displacement was observed was defined as the maximum expansion temperature (Tmax).

[0070] [Measurement of the specific gravity of the masterbatch] The specific gravity of the masterbatch was measured using the following 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, dried, and its weight (WB1) was weighed. The weighed volumetric flask was then accurately filled with isopropyl alcohol up to the meniscus, and its weight (WB2) was weighed. Another 100 mL volumetric flask was emptied, dried, and its weight (WS1) was weighed. Approximately 50 mL of masterbatch was filled into the weighed volumetric flask, and its weight (WS2) was weighed. Finally, the weight (WS3) of the volumetric flask filled with isopropyl alcohol up to the meniscus, ensuring no air bubbles were present, was weighed. Then, the specific gravity (d) of the masterbatch was calculated by introducing the obtained WB1, WB2, WS1, WS2, and WS3 into the following formula. d={(WS2-WS1)×(WB2-WB1) / 100} / {(WB2-WB1)-(WS3-WS2)}

[0071] [Measurement and evaluation of eye discharge amount] A foamed molded body was obtained by extruding the resulting composition using a Laboplast Mill (ME-25, single-screw extruder) and a strand die (nozzle diameter 3.0 mm). Extrusion molding was performed for 30 minutes, starting 5 minutes after the raw material composition was fed into the extruder and extrusion from the strand die began. Under the molding conditions described above, the weight of the die deposits accumulated near the discharge port of the strand die in 30 minutes was measured. The measured weight of the die deposits was evaluated based on the following indicators, with a score of ○ or higher being considered acceptable. ◎: Eye discharge amount is 25mg or less, good condition. ○: The amount of eye discharge is over 25mg but 50mg or less, which is slightly good. ×: The amount of eye discharge exceeds 50mg, which is unacceptable.

[0072] [Measurement of specific gravity of foamed molded material] The measurement was performed using a Shimadzu top-loading electronic analytical balance (AX200, manufactured by Shimadzu Corporation) in solid specific gravity measurement mode (liquid immersion method).

[0073] [Condition of the surface of the foamed molded product] The surface condition of the foamed molded product was visually inspected and evaluated using the following indicators. ◎: No peeling or dents were observed on the surface of the foamed molded product; it is in good condition. ○: A few minor peeling and indentations were observed on the surface of the foamed molded body, but the overall quality is relatively good. ×: The molded surface shows many large peels and dents, indicating a defect.

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

[0075] <Manufacturing examples A2~A5, manufacturing comparative examples a1~a3> Except for changing the reaction conditions shown in Table 1, thermally expandable microspheres were obtained in the same manner as in Production Example A1. The physical properties of the obtained thermally expandable microspheres are shown in Table 1. The abbreviations in Table 1 have the following meanings. AN: Acrylonitrile, SP(AN): 14.4 (cal / cm³) 3 ) 1 / 2 MAN: Methacrylonitrile, SP(MAN): 12.7 (cal / cm) 3 ) 1 / 2 AA: Acrylic acid, SP(AA): 14.0 (cal / cm³) 3 ) 1 / 2 MAA: Methacrylic acid, SP(MAA): 12.5 (cal / cm³) 3 ) 1 / 2 MAAm: Methacrylamide, SP(MAAm): 16.3 (cal / cm²) 3 ) 1 / 2 MMA: Methyl methacrylate, SP(MMA): 9.9 (cal / cm³) 3 ) 1 / 2 St: Styrene, SP(St): 10.6 (cal / cm) 3 ) 1 / 2 EDMA: Ethylene glycol dimethacrylate, SP(EDMA): 11.2 (cal / cm³) 3 ) 1 / 2

[0076] [Table 1]

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

[0078] <Manufacturing examples B2 to B8, manufacturing comparative examples b1 to b3> Except for changing the formulation conditions and manufacturing conditions of the masterbatch in manufacturing example B1 to those shown in Tables 2 and 3, masterbatches were obtained in the same manner as in manufacturing example B1. The physical properties of the obtained masterbatches are shown in Tables 2 and 3. The abbreviations used in Tables 2 and 3 have the following meanings. Resin 1: Ethylene-vinyl acetate copolymer, manufactured by Tosoh Corporation, UltraCen® 720, specific gravity 0.947, melting point 67℃, 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® 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. Petrocene (registered trademark) 353, specific gravity 0.915, melting point 98℃, 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., Aclift® CM5021, specific gravity 0.94, melting point 67°C, melt flow rate 450 g / 10 min, olefin unit content 72% by weight, ethylene unit content 72% by weight

[0079] [Table 2]

[0080] [Table 3]

[0081] <Example 1> Six parts by weight of the masterbatch (MB1) obtained in Production Example B1 and 100 parts by weight of Matrix 1 (olefin-based elastomer, Milastomer® 8032BS, manufactured by Mitsui Chemicals, Inc., specific gravity 0.89) were mixed to obtain a composition. The obtained composition was extruded using the extruder and strand die described in "Measurement and Evaluation of Meysin Content" above to obtain a strand-shaped foamed molded body. The physical properties of the obtained foamed molded body are shown in Table 4. The molding conditions were set to 200°C for the cylinder and strand die temperature (molding temperature) of the extrusion molding machine, and 25 rpm for the screw rotation speed. The time the composition remained in the molding machine during this process was 3.5 minutes.

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

[0083] [Table 4]

[0084] [Table 5]

[0085] Tables 4-5 show that the solubility parameter of the polymer contained in the outer shell of the thermally expandable microsphere is 13 (cal / cm³). 3 ) 1 / 2 The following conditions indicate that the generation of lint can be reduced when molding foamed products. On the other hand, the solubility parameter of the polymer contained in the outer shell is 13 (cal / cm³). 3 ) 1 / 2 If this value is exceeded, it indicates that the generation of smegma during the molding of the foamed product has not been reduced. [Industrial applicability]

[0086] The thermally expandable microspheres of the present invention can be used in the manufacture of foamed molded articles by molding processes such as injection molding, extrusion molding, and press molding. The resulting foamed molded articles can be used as sound insulation materials, heat insulation 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 / cm²). ３ ) １／２ The following: The melt flow rate of the base resin is 70 to 500 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.

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