具体实施方式：
[0018]The material for fused deposition modeling type three-dimensional modeling (hereinafter sometimes referred to as material for modeling) of the present invention is described concretely below.
[0019]The material for modeling of the present invention is preferably obtained by blending (including) one or more selected from the group consisting of a styrene-based resin (B1) obtained by copolymerizing an aromatic vinyl-based monomer (B1) and a vinyl cyanide-based monomer (b2), a thermoplastic resin (B2) having a glass transition temperature of 20° C. or lower, and a plasticizer (B3).
[0020]The material for modeling of the present invention is preferably a material for modeling satisfying any one or more of the following [Condition 1] to [Condition 3] in addition to the above-mentioned condition.
[0021][Condition 1] A styrene-based resin (B1) obtained by copolymerizing an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2) and a polylactic acid resin (A) are blended (contained), and the loading (content) of the styrene-based resin (B1) is 10 parts by weight to 900 parts by weight relative to 100 parts by weight of the content of the polylactic acid resin (A).
[Condition 2] A polylactic acid resin (A) and a thermoplastic resin (B2) having a glass transition temperature of 20° C. or lower are blended (contained), and the loading (content) of the thermoplastic resin (B2) having a glass transition temperature of 20° C. or lower is 5 parts by weight to 400 parts by weight relative to 100 parts by weight of the content of the polylactic acid resin (A).
[Condition 3] A polylactic acid resin (A) and a plasticizer (B3) are blended (contained), and the loading (content) of the plasticizer (B3) is 5 parts by weight to 30 parts by weight relative to 100 parts by weight of the content of the polylactic acid resin (A).
[0022]Therefore, the material for fused deposition modeling type three-dimensional modeling of the present invention is particularly preferably a material for fused deposition modeling type three-dimensional modeling obtained by blending 10 to 900 parts by weight of a styrene-based resin (B1) obtained by copolymerizing an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2), and/or 5 to 400 parts by weight of a thermoplastic resin (B2) having a glass transition temperature of 20° C. or lower, and/or 5 to 30 parts by weight of a plasticizer (B3) relative to 100 parts by weight of a polylactic acid resin (A).
(Polylactic Acid Resin (A))
[0023]The material for modeling of the present invention is obtained by blending a styrene-based resin (B1), a thermoplastic resin (B2) having a glass transition temperature of 20° C. or lower, or a plasticizer (B3), each described below, with a polylactic acid resin (A). A material for modeling capable of being molded at lower temperatures can be obtained by blending the polylactic acid resin (A).
[0024]Generally, one conceivable method for molding at a low temperature and lowering a melt viscosity may be a method of blending a thermoplastic resin having a low glass transition temperature (Tg) (e.g., a Tg lower than the glass transition temperature (Tg) of the styrene-based resin (B1) described below (approximately 100 to 110° C.)). Examples of known thermoplastic resins being commercially widely distributed and available at a relatively low price and being lower in Tg than the styrene-based resin (B1) include nylon 6 (PA6) (Tg is approximately 50° C.), nylon 66 (PA66) (Tg is approximately 50° C.), polyethylene terephthalate (PET) (Tg is approximately 80° C.), and polybutylene terephthalate (PBT) (Tg is approximately 22 to 30° C.). Such a thermoplastic resin, however, readily crystallizes and the melting point (Tm) thereof is equal to or higher than 200° C., and in order to melt such a thermoplastic resin sufficiently, it is necessary to perform heating at 220° C. or more.
[0025]The polylactic acid resin (A) in the present invention is a polymer including L-lactic acid (L-form) and/or D-lactic acid (D-form) as a main constituent. The term “main constituent” as used herein means any constituent occupying 50 mol % or more of all constituents. The polymer contains L-lactic acid and/or D-lactic acid preferably in an amount of 70 mol % or more, more preferably in an amount of 90 mol % or more, relative to all the constituents.
[0026]Especially, from the viewpoint of mechanical properties, it is preferable to use a polylactic acid resin including L-form or D-form in a content of 80% (mol %) or more of all lactic acid components of the polylactic acid resin (A), and the L-form or D-form content is more preferably 85% or more.
[0027]On the other hand, while the upper limit of the content of L-lactic acid or D-lactic acid, which is a constituent of the polylactic acid resin (A), is not particularly limited, it is preferably 99% (mol %) or less, more preferably 97% or less from the viewpoint of reducing optical purity and suppressing the advance of crystallization. The optical purity of the polylactic acid resin (A) is particularly preferably 97% or less.
[0028]From the viewpoint of moldability, the upper limit of the content of the L-form or the D-form is preferably 98% (mol %) or less, more preferably 97% or less, even more preferably 96% or less, most preferably 95% or less. Warpage can be suppressed by suppressing crystallization.
[0029]The polylactic acid resin (A) may be one in which another copolymerization component other than lactic acid has been copolymerized as long as the object of the present invention is not impaired. Examples of such another copolymerization components include polyvalent carboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, and lactones. Specific examples include polyvalent carboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodiumsulfoisophthalic acid, and 5-tetrabutylphosphoniumsulfoisophthalic acid; polyhydric alcohols, such as ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerol, trimethylolpropane, pentaerythritol, bisphenol A, an aromatic polyhydric alcohol prepared by making ethylene oxide undergo addition reaction to bisphenol A, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; hydroxycarboxylic acids, such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, and hydroxybenzoic acid; lactones, such as glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, and δ-valerolactone. One or two or more of such copolymerization components may be used.
[0030]The polylactic acid resin (A) to be used for the material for fused deposition modeling type three-dimensional modeling according to embodiments of the present invention is a polymer including L-lactic acid and/or D-lactic acid as main constituents, and it can contain another copolymerization component other than lactic acid. Examples of such other copolymerization units include units formed from polyvalent carboxylic acids, such as the aforementioned polyvalent carboxylic acids and anthracenedicarboxylic acid, the aforementioned polyhydric alcohols, the aforementioned hydroxycarboxylic acids, and the aforementioned lactones. Usually, the content of such copolymerization units is preferably 0 to 30 mol %, more preferably 0 to 10 mol % where the amount of all monomer units is taken as 100 mol %.
[0031]It is also preferable to use a polylactic acid resin in combination such that an L-form or D-form content of 80% or more is achieved.
[0032]The polylactic acid resin (A) to be used in an embodiment of the present invention may be a modified resin and, for example, use of a maleic anhydride-modified polylactic acid resin, an epoxy-modified polylactic acid resin, an amine-modified polylactic acid resin, or the like is a preferred embodiment because not only heat resistance but also mechanical properties are thereby improved.
[0033]As a method for producing the polylactic acid resin (A) in an embodiment of the present invention, there can be used a polymerization method known in the art, examples of which include a direct polymerization method from lactic acid and a ring-opening polymerization method via a lactide.
[0034]The polylactic acid resin (A) in an embodiment of the present invention is not particularly limited with respect to its molecular weight and molecular weight distribution, and the weight average molecular weight thereof is preferably 100,000 or more, more preferably 150,000 or more, most preferably 180,000 or more. From the viewpoint of flowability during molding, the upper limit of the weight average molecular weight is preferably 400,000 or less. The weight average molecular weight as used herein is a polymethyl methacrylate (PMMA)-equivalent weight average molecular weight measured by gel permeation chromatography (GPC).
[0035]Although the polylactic acid resin (A) is not particularly limited with respect to its molecular weight and molecular weight distribution as long as it is substantially moldable as described above, the polylactic acid resin (A) is known to undergo its thermal decomposition self-catalytically by a carboxyl group located at an end of its molecule, and from the viewpoint of inhibition of the thermal decomposition, the weight average molecular weight is preferably 50,000 or more, more preferably 100,000 or more. On the other hand, from the viewpoint of enabling the material for modeling to be molded at lower temperatures and further lowering the melt viscosity, the weight average molecular weight is preferably 400,000 or less, more preferably 300,000 or less, even more preferably 200,000 or less (as described above, the weight average molecular weight as used herein is a polymethyl methacrylate (PMMA)-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent).
(Styrene-Based Resin (B1))
[0036]The styrene-based resin (B1) to be used in an embodiment of the present invention denotes a copolymer obtained by copolymerizing at least an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2). Moreover, it also may be a copolymer obtained by further copolymerizing an alkyl unsaturated carboxylate-based monomer (b3) and/or another vinyl-based monomer (b4) copolymerizable therewith according to need. Use of the styrene-based resin (B1) makes it possible to obtain a material capable of affording a modeled article excelling in surface polishability.
[0037]The styrene-based resin (B1) can be obtained by subjecting a monomer mixture including an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2) and, according to need, an alkyl unsaturated carboxylate-based monomer (b3) and/or another vinyl-based monomer (b4) copolymerizable therewith to bulk polymerization, bulk suspension polymerization, solution polymerization, precipitation polymerization or emulsion polymerization each known in the art.
[0038]The aromatic vinyl-based monomer (b1) is not particularly limited, and specific examples thereof include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, c-ethylstyrene, p-ethylstyrene, and p-t-butylstyrene. Especially, styrene or α-methylstyrene is preferably used. These may be used individually or in combination. The monomer components constituting the styrene-based resin (B1) contain the aromatic vinyl-based monomer (b1) preferably in a content of 20% by weight or more, more preferably in a content of 50% by weight or more.
[0039]There is no particular limitation with respect to the vinyl cyanide-based monomer (b2), and specific examples thereof include acrylonitrile, methacrylonitrile and ethacrylonitrile. Especially, acrylonitrile is preferably used. These may be used individually or in combination.
[0040]From the viewpoint of improving the productivity and the mechanical strength of a filament to be obtained using a material for modeling, the monomer components constituting the styrene-based resin (B1) contain the vinyl cyanide-based monomer (b2) preferably in a content of 15% by weight or more, more preferably in a content of 20% by weight or more.
[0041]There is no particular limitation with respect to the alkyl unsaturated carboxylate-based monomer (b3), an ester of an alcohol having 1 to 6 carbon atoms and (meth)acrylic acid is suitable. Such an ester may further have a substituent and examples of such a substituent include a hydroxy group and chlorine. Specific examples of the alkyl unsaturated carboxylate-based monomer (b3) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, and 2,3,4,5-tetrahydroxypentyl (meth)acrylate. Especially, methyl methacrylate is preferably used. These may be used individually or in combination. The term “(meth)acrylic acid” as used herein denotes acrylic acid or methacrylic acid.
[0042]The other vinyl-based monomer (b4) has no particular limitations as long as it can be copolymerized with the aromatic vinyl-based monomer (b1), the vinyl cyanide-based monomer (b2) and, according to need, the alkyl unsaturated carboxylate-based monomer (b3), and specific examples thereof include maleimide-based monomers, such as N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, and N-phenylmaleimide, vinyl-based monomers having a carboxyl group or a carboxylic anhydride group, such as acrylic acid, methacrylic acid, maleic acid, monoethyl maleate, maleic anhydride, phthalic acid, and itaconic acid, vinyl-based monomers having a hydroxy group, such as 3-hydroxy-1-propene, 4-hydroxy-1-butene, cis-4-hydroxy-2-butene, trans-4-hydroxy-2-butene, 3-hydroxy-2-methyl-1-propene, cis-5-hydroxy-2-pentene, trans-5-hydroxy-2-pentene, and 4,4-dihydroxy-2-butene, vinyl-based monomers having an amino group or its derivative, such as acrylamide, methacrylamide, N-methylacrylamide, butoxymethylacrylamide, N-propylmethacrylamide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, phenylaminoethyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallyl amine, N-methylallylamine, and p-aminostyrene, and vinyl-based monomers having an oxazoline group, such as 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl-oxazoline, and 2-styryl-oxazoline. These may be used individually or in combination.
[0043]While there is no particular limitation with the molecular weight of the styrene-based resin (B1), from the viewpoint of securing extrusion stability at the time of producing a filament obtained using a material for modeling and mechanical strength necessary for collecting a filament by winding it around a bobbin, the weight average molecular weight is preferably 50,000 or more, more preferably 80,300 or more. On the other hand, from the viewpoint of further lowering the melt viscosity at low temperatures of a filament obtained using a material for modeling, the weight average molecular weight is preferably 400,000 or less. The weight average molecular weight as referred to herein denotes a polystyrene-equivalent weight average molecular weight measured by GPC using tetrahydrofuran as a solvent.
[0044]Specific examples of the styrene-based resin (B1) to be used in the present invention include acrylonitrile-styrene (AS) resin and methyl methacrylate-acrylonitrile-styrene (MAS) resin. Two or more of them may be used in combination: for example, AS resin and MAS resin may be used in combination.
[0045]The loading of the styrene-based resin (B1) in the material for modeling of the present invention is 10 to 900 parts by weight relative to 100 parts by weight of the polylactic acid resin (A). When the loading of the styrene-based resin (B1) is less than 10 parts by weight, the surface polishability of a 3D modeled article is insufficient, and when the loading of the styrene-based resin (B1) exceeds 900 parts by weight, the warpage becomes greater. The loading of the styrene-based resin (B1) is preferably 30 parts by weight or more, more preferably 100 parts by weight or more. On the other hand, the loading of the styrene-based resin (B1) is preferably 300 parts by weight or less, more preferably 250 parts by weight or less.
[0046]There is no particular limitation with respect to the loading of the polylactic acid resin (A) in the material for modeling of the present invention as long as it is within the range of the present invention, and the loading can be adjusted as occasion calls according to the use method and the use environment of a modeled article obtained using a material for modeling obtained. For example, when paint or the like is applied to a modeled article, the loading of the polylactic acid resin (A) in the material for modeling to be used for such a modeled article is preferably 50 parts by weight or less relative to 100 parts by weight in total of the styrene-based resin (B1) and the polylactic acid resin (A) because the styrene-based resin (B1) excels in paintability. Moreover, when a modeled article is displayed in a vehicle, the modeled article preferably has a heat distortion temperature of about 80° C., and the loading of the polylactic acid resin (A) in the material for modeling to be used for such a modeled article is preferably 30 parts by weight or less relative to 100 parts by weight in total of the styrene-based resin (B1) and the polylactic acid resin (A). On the other hand, from the viewpoint of enabling molding at lower temperatures, the loading of the polylactic acid resin (A) is preferably adjusted to 5 parts by weight or more relative to 100 parts by weight in total of the styrene-based resin (B1) and the polylactic acid resin (A).
[0047]Next, an effect produced by a material for fused deposition modeling type three-dimensional modeling obtained by compounding a styrene-based resin (B1) obtained by copolymerizing an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2) and a polylactic acid resin (A) is described.
[0048]First, as a material for three-dimensional modeling using the FDM method, a composition including an amorphous thermoplastic resin selected from the group consisting of a blend of polyphenylene ether and impact-resistant polystyrene, a blend of polyphenylsulfone and amorphous polyamide, and a blend of polyphenylsulfone, polysulfone, and amorphous polyamide (see, for example, WO 2002/093360), a composition composed of a copolymer obtained by graft-copolymerizing an aromatic vinyl compound in the presence of a specific rubbery polymer and a polymer obtained by polymerizing an aromatic vinyl compound (see, for example, JP-A-2007-51237), and the like have been proposed.
[0049]Generally, in a three-dimensionally modeling method using the FDM method, stacking such a material for modeling to become smooth and flattened on a building table requires reduction in melt tension and therefore it is necessary to heat a filament formed from the material for modeling such that the melt viscosity falls within a proper range. Although the material for modeling disclosed in WO 2002/093360 A excels in mechanical strength and the resin composition disclosed in JP-A-2007-51237 excels additionally in thermal stability, in order to melt these materials for modeling to attain a proper melt viscosity, high heating temperature is required.
[0050]On the other hand, 3D printing devices adopting the FDM method have been spreading to common households or educational facilities as described previously. Moreover, properties required with modeled articles themselves have been changing and high mechanical strength which has conventionally been required may not be required.
[0051]Thus, it is preferable that a material for modeling can be melted at a lower temperature than the material for modeling proposed in WO 2002/093360 A or JP-A-2007-51237 and, as a result, electric power consumption or gas emitted from a material for modeling can be reduced.
[0052]When such a property is required, the material for three-dimensional modeling of the present invention preferably incorporates a styrene-based resin (B1) produced by copolymerizing an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2), and a polylactic acid resin (A).
[0053]When a modeled article is produced with a 3D printing device using the FDM method using a material for fused deposition modeling type three-dimensional modeling prepared by mixing a styrene-based resin (B1) and a polylactic acid resin (A) (or a filament, particle, or pellet prepared by molding the material), it is possible to produce a modeled article at a lower temperature than the material for modeling proposed in WO 2002/093360, JP-A-2007-51237 or the like.
[0054]While the polylactic acid resin (A) is a crystalline resin, it has little progress of crystallization in the absence of a nucleating agent or auxiliary agent that promotes crystallization, and the Tg of the polylactic acid resin (A) is generally 55 to 60° C., which is generally lower than the Tg of the styrene-based resin (B1). Incorporation of the polylactic acid resin (A) having such a characteristic into the styrene-based resin (B1) can, for example, enable molding at lower temperatures than a case of using ABS as a material for modeling.
[0055]A material for fused deposition modeling type three-dimensional modeling obtained by compounding a styrene-based resin (B1) and a polylactic acid resin (A), and a filament, particle or pellet for a 3D printing device using the same are lower in melt viscosity than conventional materials for modeling proposed in WO 2002/093360, JP-A-2007-51237, etc., and thus, they can be molded at lower temperature than such materials for modeling. For this reason, compared with these materials for modeling, the electric power consumption required by modeling and the gas emitted from a material for modeling may be reduced successfully. Due to such effects, 3D printing devices can be spread more for common households and educational facilities.
(Thermoplastic Resin (B2) the Glass Transition Temperature of which is 20° C. or Lower)
[0056]As the thermoplastic resin (B2) the glass transition temperature of which is 20° C. or lower to be used in an embodiment of the present invention, polyester, thermoplastic elastomer, a graft copolymer prepared by graft polymerizing a monomer mixture component described below to a thermoplastic elastomer, etc. can be used. In the present invention, the “polyester” is a general term including aliphatic polyester resin, aliphatic aromatic polyester resin, alicyclic polyester resin, and aromatic polyester.
[0057]Use of the thermoplastic resin (B2) the glass transition temperature of which is 20° C. or lower makes it possible to obtain a material capable of affording a modeled article than develops little warpage and excels in surface polishability. Moreover, the use of (B2) can increase the mechanical strength of a filament and a modeled article obtained using a material for modeling because the impact strength of the material for modeling is enhanced and the softness is increased thereby. The filament obtained using a material for modeling is generally discharged through a hole provided in the head of an extruder and collected by winding around a bobbin, and the breakage thereof at the time of winding around the bobbin can be inhibited through improvement in mechanical strength. Moreover, it can improve ease-of-use of 3D printing device users and safety can also be improved because the filament itself is made resistant to breakage and even if the filament is broken, the fractured section has a low tendency to be sharp. Furthermore, the machinability of a modeled article can be improved through the improvement in mechanical strength of the modeled article, and it becomes easier to polish the surface thereof with a scraper or the like in order to smoothen the surface and fracture in processing with a drill or the like can be inhibited.
[0058]Examples of the aliphatic polyester resin include polyethylene succinate, polybutylene succinate, polybutylene adipate, polyethylene adipate, polybutylene (succinate/adipate), polyethylene (succinate/adipate), polyhydroxy butyrate, and polyhydroxy (butyrate/hexanoate). Herein “/” means copolymerization.
[0059]Examples of the aliphatic aromatic polyester resin include polybutylene (terephthalate/succinate), polyethylene (terephthalate/succinate), polybutylene (terephthalate/adipate), polyethylene (terephthalate/adipate), polyethylene (terephthalate/sulfoisophthalate), polybutylene (terephthalate/sebacate), and polyethylene (terephthalate/sebacate).
[0060]As the thermoplastic resin (B2) the glass transition temperature of which is 20° C. or lower, use of at least one selected from copolymerized polyester resins and thermoplastic elastomers is preferable from the viewpoint of low warpage of a 3D modeled article.
[0061]Of the polyester resins provided as examples previously, examples of the copolymerized polyester resin include polybutylene (succinate/adipate), polyethylene (succinate/adipate), polyhydroxy(butyrate/hexanoate), polybutylene (terephthalate/succinate), polyethylene (terephthalate/succinate), polybutylene (terephthalate/adipate), polyethylene (terephthalate/adipate), polyethylene (terephthalate/sulfoisophthalate), polybutylene (terephthalate/sebacate), and polyethylene (terephthalate/sebacate).
[0062]As the thermoplastic elastomer to be used in an embodiment of the present invention, any of a (co)polymer, a random copolymer, a block copolymer, and a graft copolymer can be used.
[0063]Examples of said (co)polymer, random copolymer, and block copolymer include an ethylene-propylene copolymer, an ethylene-propylene-nonconjugated diene copolymer, an ethylene-butene-1 copolymer, acrylic rubbers, an ethylene-acrylic acid copolymer and its alkali metal salts (so-called ionomer), an ethylene-glycidyl (meth)acrylate copolymer, an ethylene-alkyl (meth)acrylate copolymer (for example, an ethylene-methyl acrylate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-butyl acrylate copolymer, and an ethylene-methyl methacrylate copolymer), an ethylene-vinyl acetate copolymer, an acid-modified ethylene-propylene copolymer, diene rubber (for example, polybutadiene, polyisoprene, and polychloroprene), a copolymer of diene with a vinyl monomer (for example, a styrene-butadiene random copolymer, a styrene-butadiene block copolymer, a styrene-butadiene-styrene block copolymer, a styrene-isoprene random copolymer, a styrene-isoprene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-ethylene-butylene-styrene block copolymer, a styrene-ethylene-propylene-styrene block copolymer, and a butadiene-acrylonitrile copolymer) or its hydrogenated product, polyisobutylene, a copolymer of isobutylene with butadiene or isoprene, natural rubber, thiokol rubber, polysulfide rubber, silicone rubber, polyurethane rubber, polyether rubber, epichlorohydrin rubber, polyester-based elastomer, or polyamide-based elastomer. Moreover, polymers crosslinked with various crosslinkers, polymers having various microstructures, e.g., cis-structure and trans-structure, and a multilayer structure polymer composed of a core layer and one or more shell layers covering the core layer can also be used.
[0064]In producing such a (co)polymer, a random copolymer, and a block copolymer, such monomers as other olefins, dienes, acrylic acid, alkyl unsaturated carboxylate-based monomer (b3) (particularly preferably, an acrylate or a methacrylate) may be copolymerized. Of these thermoplastic elastomers, a polymer including acrylic units and a polymer including units having an acid anhydride group and/or a glycidyl group are preferable. Particularly preferable examples of the acrylic unit include a methyl methacrylate unit, a methyl acrylate unit, an ethyl acrylate unit, or a butyl acrylate unit, and preferable examples of the unit having an acid anhydride group or a glycidyl group include a maleic anhydride unit or a glycidyl methacrylate unit.
[0065]Examples of the graft copolymer to be used in the present invention include a product obtained by graft polymerizing a monomer mixed component including an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2) to a rubbery polymer (r).
[0066]Such a graft copolymer can be obtained, for example, by subjecting a monomer mixed component including an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2) to bulk polymerization, bulk suspension polymerization, solution polymerization, precipitation polymerization, or emulsion polymerization known in the art, in the presence of a rubber polymer (r). The graft copolymer can include not only a graft copolymer in which monomer components are graft polymerized to a rubbery polymer (r) but also a polymer of monomer components not having been grafted to a rubbery polymer (r). The monomer components to be graft polymerized include at least an aromatic vinyl-based monomer (b1) and a vinyl cyanide-based monomer (b2) and, according to need, an alkyl unsaturated carboxylate-based monomer (b3) and another vinyl-based monomer (b4) copolymerizable therewith. Examples of the aromatic vinyl-based monomer (b1), the vinyl cyanide-based monomer (b2), the alkyl unsaturated carboxylate-based monomer (b3), and another vinyl-based monomer (b4) copolymerizable therewith include those provided as examples of the monomers that constitute the styrene-based resin (B1).
[0067]When the styrene-based resin (B1) and the graft copolymer described above are mixed in the present invention, it is preferable to use the same monomer component in the same mixing ratio as those of the styrene-based resin (B1) as the monomer component to be graft polymerized from the viewpoint of dispersing the styrene-based resin (B1) and the graft copolymer more uniformly and thereby improving the appearance of a material for modeling, and a filament and a modeled article obtained using the material.
[0068]Although there is no particular limitation with the rubbery polymer (r), one the glass transition temperature of which is 0° C. or less is preferred, and diene rubber, acrylic rubber, ethylene rubber, etc. can suitably be used. Specific examples include polybutadiene, a styrene-butadiene copolymer, a styrene-butadiene block copolymer, an acrylonitrile-butadiene copolymer, a butyl acrylate-butadiene copolymer, polyisoprene, a butadiene-methyl methacrylate copolymer, a butyl acrylate-methyl methacrylate copolymer, a butadiene-ethyl acrylate copolymer, an ethylene-propylene copolymer, an ethylene-isoprene copolymer, and an ethylene-methyl acrylate copolymer.
[0069]Of these rubbery polymers, polybutadiene, a styrene-butadiene copolymer, a styrene-butadiene block copolymer, and an acrylonitrile-butadiene copolymer are preferably used from the viewpoint of improving mechanical strength more. These rubbery polymers can be used individually or in combination.
[0070]The weight average particle diameter of the rubbery polymer (r), which is not particularly limited, is preferably within the range of 0.05 to 1.0 μm, more preferably within the range of 0.1 to 0.5 μm. By adjusting the weight average particle diameter of the rubbery polymer into the range of 0.05 μm to 1.0 μm, it is possible to increase mechanical strength at a smaller loading and also possible to inhibit increase in melt viscosity. Herein the weight average particle diameter of the rubbery polymer (r) can be measured by the sodium alginate method disclosed in “Rubber Age, Vol. 88, p. 484-490, (1960), by E. Schmidt, P. H. Biddison,” namely, a method of determining a particle diameter at a 50% cumulative weight fraction from the cumulative weight fraction of sodium alginate concentration and a creamed weight ratio using the fact that the diameter of polybutadiene particles that cream varies depending upon t