Sintering binder resin composition

Abstract

The objective is to provide a sintering binder resin composition that exhibits excellent slurry dispersibility, ease of molding, and yields molded products with high strength and density. [Solution] The present invention relates to a sintering binder resin composition comprising a polymer (A) of reaction components including styrenes (a1), a monomer having a polar group and one ethylenically unsaturated group (a2), an alkyl mono(meth)acrylate without a polar group (a3), and a poly(meth)acrylate (a4).

Description

[Technical Field] 【0001】 This invention relates to a binder resin composition for sintering. [Background technology] 【0002】 Sintered bodies are used in decorative parts, electronic components, filters, biomaterials, etc. Known manufacturing methods include, for example, a method in which a slurry is prepared by mixing and dispersing powder in a sintering binder resin composition, which is then dried with a spray dryer or the like to form a granule, which is then molded with a pressure press, cut, polished, etc., and then sintered; and a method in which the slurry is formed into a sheet using a doctor blade or the like to form a green sheet, which is then dried and sintered. 【0003】 Conventional sintering binder resin compositions used were those containing butyral resin dissolved in organic solvents. However, due to environmental regulations, these have been replaced by water-based binder resin compositions, with polyvinyl alcohol and polyvinyl acetate becoming the mainstream. However, these resin compositions tend to aggregate when formed into a slurry, resulting in poor slurry dispersibility, uneven molded products, and a high likelihood of sintering defects. 【0004】 As a technique to improve dispersibility, for example, it is known to use an aqueous binder consisting of a copolymer obtained by copolymerizing a powder with an unsaturated carboxylic acid monomer and a component containing a specific epoxy group (Patent Document 1). However, although the dispersibility of the slurry is improved, it is not sufficient. 【0005】 Furthermore, molded products before sintering are required to have high density and strength. Higher strength and / or density generally leads to reduced fracture when handling them as green ceramic materials, and is said to improve the quality of the sintered body. 【0006】 As a means of increasing density and strength, for example, there is a known invention of ceramic precursor materials in which a condensed polymer of polyamide-polyamine or a cross-linked polyamide is blended with a binder resin to a powder (Patent Document 2). However, although density and strength are increased, they are not sufficient, and because there is an excess of carboxylic acid, the condensed polymer does not have primary amino groups at its ends, resulting in poor slurry dispersibility. 【0007】 Furthermore, if carboxylic acid groups remain at the polymer ends of the crosslinked polyamide, ester bonds remain when reacted with epoxy resin, and the binder composition after crosslinking undergoes hydrolysis, leading to a decrease in viscosity over time and a reduction in density and strength when used as a molded product before sintering. [Prior art documents] [Patent Documents] 【0008】 [Patent Document 1] Japanese Patent Publication No. 2005-162572 [Patent Document 2] Special Publication No. 2001-525310 [Overview of the Initiative] [Problems that the invention aims to solve] 【0009】 The present invention aims to provide a sintering binder resin composition that exhibits excellent slurry dispersibility, ease of molding, and yields molded products with high strength and density. [Means for solving the problem] 【0010】 The present inventors, through diligent research, have found that a sintering binder resin composition containing a specific polymer solves the aforementioned problem, and have completed the present invention. That is, the present invention relates to the following sintering binder resin composition. 【0011】 1. A sintering binder resin composition comprising a polymer (A) of reaction components including styrenes (a1), a monomer having a polar group and one ethylenically unsaturated group (a2), an alkyl mono(meth)acrylate without a polar group (a3), and a poly(meth)acrylate (a4). 【0012】 2. The sintering binder resin composition described in item 1 above, wherein the glass transition temperature is between -60°C and 60°C. 【0013】 3. A sintering binder resin composition according to item 1 or 2, further comprising elastomer (B). [Effects of the Invention] 【0014】 The sintering binder resin composition of the present invention exhibits excellent slurry dispersibility, ease of molding, and high strength and density when formed into a molded product. [Modes for carrying out the invention] 【0015】 The sintering binder resin composition of the present invention contains a polymer (A) of reaction components including styrenes (a1) (hereinafter referred to as component (a1)), a monomer (a2) having a polar group and one ethylenically unsaturated group (hereinafter referred to as component (a2)), an alkyl mono(meth)acrylate (a3) ​​without a polar group (hereinafter referred to as component (a3)), and poly(meth)acrylate (a4) (hereinafter referred to as component (a4)). Polymer (A) may be used alone or in combination of two or more types. (Meth)acrylate means methacrylate or acrylate. 【0016】 (a1) Examples of components include styrene, α-methylstyrene, β-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, and dimethylstyrene. These may be used individually or in combination of two or more. 【0017】 As the usage amount of the component (a1), from the viewpoint that the strength of the molded article obtained using the polymer (A) to be produced is likely to increase, based on 100% by weight of all the reaction components, it is preferably 10 to 70% by weight, more preferably 20 to 50% by weight. Here, all the reaction components mean the components excluding the polymerization initiator, solvent, and additive described later (the same applies hereinafter). 【0018】 The component (a2) is a monomer having a polar group and one ethylenically unsaturated group. The polar group means a functional group having polarity, for example, a group having an atom other than carbon and hydrogen such as an amino group, a carboxy group, a hydroxy group, a sulfonyl group, etc. Also, the ethylenically unsaturated group means a carbon-carbon double bond or a carbon-carbon triple bond. These may be used alone or in combination of two or more. 【0019】 Examples of the component (a2) include monomers having an amino group and one ethylenically unsaturated group such as vinylamine, allylamine, 3-buten-1-amine, N,N-dimethylvinylamine, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, N,N-diethylaminopropyl (meth)acrylamide, etc. (hereinafter, may be abbreviated as monomers having an amino group); Monomers having a carboxy group and one ethylenically unsaturated group such as (meth)acrylic acid (methacrylic acid, acrylic acid), acrylic anhydride, itaconic acid, itaconic anhydride, fumaric acid, maleic acid, maleic anhydride, etc. (hereinafter, may be abbreviated as monomers having a carboxy group); Monomers having a hydroxy group and one ethylenically unsaturated group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, etc. (hereinafter, may be abbreviated as monomers having a hydroxy group); Examples include monomers having a sulfonyl group such as vinylsulfonic acid and methallylsulfonic acid and one ethylenically unsaturated group (hereinafter sometimes abbreviated as a monomer having a sulfonyl group). These may be used alone or in combination of two or more. 【0020】 Further, as the monomer having an amino group, a quaternized salt of these monomers may be used. The quaternized salt means a product obtained by reacting a monomer having an amino group with a quaternizing agent. Examples of the quaternized salt include inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as acetate. Examples of the quaternizing agent include methyl chloride, benzyl chloride, dimethyl sulfate, epichlorohydrin and the like. 【0021】 Furthermore, as the monomer having a carboxy group, a monomer having a hydroxy group, and a monomer having a sulfonyl group, they can also be used in the form of salts such as alkali metal salts such as sodium and potassium, and ammonium salts. 【0022】 Among them, from the viewpoint that the strength of the molded product obtained using the polymer (A) to be produced is likely to increase, a monomer having any one of an amino group, a carboxy group or a hydroxy group and one ethylenically unsaturated group is preferable, and N,N-dimethylaminoethyl (meth)acrylate, (meth)acrylic acid (methacrylic acid, acrylic acid), 2-hydroxyethyl (meth)acrylate are more preferable. 【0023】 The amount of the component (a2) used is preferably 1 to 40% by weight, more preferably 5 to 15% by weight, based on 100% by weight of all the reaction components, from the viewpoint that the strength of the molded product obtained using the polymer (A) to be produced is likely to increase. 【0024】 (a3) Component is an alkyl mono(meth)acrylate that does not have a polar group. Examples of (a3) ​​component include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl(meth)acrylate, t-butyl(meth)acrylate, n-pentyl(meth)acrylate, isopentyl(meth)acrylate, neopentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, n- Aliphatic alkyl mono(meth)acrylates such as octyl(meth)acrylate, isooctyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-nonyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, tri-n-decyl(meth)acrylate, n-lauryl(meth)acrylate, n-myristyl(meth)acrylate, n-palmityl(meth)acrylate, n-stearyl(meth)acrylate, isostearyl(meth)acrylate, etc. Examples include alicyclic alkyl mono(meth)acrylates such as cyclohexyl (meth)acrylate, norbornyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentanyloxyethyl (meth)acrylate. These may be used individually or in combination of two or more. 【0025】 In particular, aliphatic mono(meth)acrylates are preferred, and n-butyl(meth)acrylate and 2-ethylhexyl(meth)acrylate are more preferred, from the standpoint of improving the density of the molded product obtained using the polymer (A) produced. 【0026】 (a3) The amount of component used is preferably 30 to 90% by weight, more preferably 40 to 70% by weight, with the total reaction components being 100% by weight, in order to improve the density of the molded product obtained using the polymer (A) produced. 【0027】 (a4) Component is a poly(meth)acrylate, meaning a monomer having two or more (meth)acryloyl groups. Note that (meth)acryloyl group means either a methacryloyl group or an acryloyl group. 【0028】 (a4) For example, the components are: Alkane diol di(meth)acrylates such as ethylene glycol di(meth)acrylate (ethanediol di(meth)acrylate), 1,2-propylene glycol di(meth)acrylate (1,2-propanediol di(meth)acrylate), 1,3-propanediol di(meth)acrylate, 2,2-dimethylpropanediol di(meth)acrylate (neopentyl glycol di(meth)acrylate), 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediool di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, etc. Cycloalkanediol di(meth)acrylates such as cyclohexanedimethanol di(meth)acrylate and tricyclodecanedimethanol di(meth)acrylate; Trimethylolpropane poly(meth)acrylates such as trimethylolpropane tri(meth)acrylate and ditrimethylolpropanetetra(meth)acrylate; Glycerin poly(meth)acrylates such as glycerin di(meth)acrylate and glycerin tri(meth)acrylate; Polyalkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene di(meth)acrylate, polytetramethylene di(meth)acrylate, and polytetramethylene di(meth)acrylate; Pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, or a mixture thereof, or pentaerythritol poly(meth)acrylate (a mixture containing pentaerythritol mono(meth)acrylate may also be used). Dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, or mixtures thereof of dipentaerythritol poly(meth)acrylate (a mixture containing dipentaerythritol mono(meth)acrylate may also be used). Tripentaerythritol tetra(meth)acrylate, tripentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, tripentaerythritol octa(meth)acrylate, or tripentaerythritol poly(meth)acrylate, which are mixtures thereof; Triacryloyl triazines such as 1,3,5-triacryloyl-1,3,5-triazine and 1,3,5-triacryloylhexahydro-1,3,5-triazine; Alkylene oxide modified products of a mixture of two or more selected from the group consisting of alkylene oxide modified bisphenol A di(meth)acrylate, alkylene oxide modified trimethylolpropane tri(meth)acrylate, alkylene oxide modified ditrimethylolpropane tetra(meth)acrylate, alkylene oxide modified glycerin tri(meth)acrylate, alkylene oxide modified polyglycerin (meth)acrylate, alkylene oxide modified pentaerythritol di(meth)acrylate, alkylene oxide modified pentaerythritol tri(meth)acrylate, alkylene oxide modified pentaerythritol tetra(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate and pentaerythritol (meth)tetraacrylate, alkylene oxide modified dipen Examples of alkylene oxide-modified poly(meth)acrylates include taerythritol poly(meth)acrylate (wherein "poly" refers to any of the di, tri, tetra, penta, or hexa isomers, but may also refer to mixtures of two or more of these), alkylene oxide-modified tripentaerythritol poly(meth)acrylate (wherein "poly" refers to any of the di, tri, tetra, penta, hexa, hepta, or octa isomers, but may also refer to mixtures of two or more of these), etc. (Examples of alkylene oxides include methylene oxide, ethylene oxide, propylene oxide, butylene oxide, etc. Also, alkylene oxide modification can be rephrased as alkoxylation (for example, ethylene oxide modification is ethoxylation, propylene oxide modification is propoxylation, etc.)). 【0029】 These (a4) components may be used individually or in combination of two or more. Among them, alkanediol di(meth)acrylate and alkylene oxide-modified poly(meth)acrylate are preferred because they tend to increase the strength of the molded product obtained using the polymer (A) produced, and 1,6-hexanediol di(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate (ethoxylated pentaerythritol tetra(meth)acrylate), and ethylene oxide-modified dipentaerythritol hexa(meth)acrylate (ethoxylated dipentaerythritol hexa(meth)acrylate) are more preferred. 【0030】 The amount of component (a4) used is preferably 0.1 to 10% by weight, more preferably 1 to 5% by weight, relative to 100% by weight of the total of components (a1), (a2), and (a3), in order to increase the strength of the molded product obtained using the polymer (A) produced. 【0031】 As the reaction components, monomers other than components (a1) to (a4), namely (a5) (hereinafter referred to as component (a5)), may also be used. Examples of component (a5) include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and Nt-butyl(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N,N-diisopropyl(meth)acrylamide; and N,N'-alkylene(meth)acrylamides such as N,N'-methylenebis(meth)acrylamide and N,N'-ethylenebis(meth)acrylamide. Examples include bis(meth)acrylamide; monomers having a trialyl group such as triallyl isocyanurate, triallyl trimellitate, triallylamine, and triallyl(meth)acrylamide; vinyl carboxylates such as vinyl acetate and vinyl propionate; nitriles such as acrylonitrile; mercaptans such as 2-mercaptoethanol and n-dodecyl mercaptan; alcohols such as ethanol, isopropyl alcohol, and n-pentyl alcohol; aromatic compounds such as α-methylstyrene dimer, ethylbenzene, isopropylbenzene, and cumene; and carbon tetrachloride. These may be used individually or in combination of two or more. 【0032】 The amount of component (a5) used is preferably 30% by weight or less, and more preferably 20% by weight or less, relative to 100% by weight of the total of components (a1), (a2), and (a3). 【0033】 The method for producing polymer (A) includes polymerizing components (a1) to (a4), and optionally component (a5), in the presence of a polymerization initiator, and the order and method of addition (simultaneous, divided, dropwise, or a combination thereof) are not particularly limited. The polymerization reaction may be carried out under an atmosphere of an inert gas such as nitrogen or argon, and the pressure can be freely selected from atmospheric pressure, pressurized, or reduced pressure. Furthermore, surfactants and solvents may be used in the polymerization. 【0034】 The polymerization conditions include, for example, a temperature of typically 30 to 90°C, preferably 50 to 80°C, and a time of typically 1 to 6 hours, preferably 2 to 4 hours. 【0035】 Examples of polymerization initiators include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate; azo polymerization initiators such as 2,2'-azobis(2-amidinopropane) hydrochloride; and hydrogen peroxide. These may be used individually or in combination of two or more. The amount of polymerization initiator used is preferably 0.1 to 8 parts by weight, and more preferably 1 to 4 parts by weight, per 100 parts by weight of the total reaction components. 【0036】 Additionally, although optional, a reducing agent may be used in combination to facilitate the generation of radicals from organic peroxides. Examples of reducing agents include sulfites such as sodium sulfite; bisulfites such as sodium bisulfite; triethanolamine, cuprous sulfate, etc. 【0037】 Examples of surfactants include cationic surfactants, nonionic surfactants, and anionic surfactants. These can be used individually or in combination of two or more types. 【0038】 Examples of cationic surfactants include dodecyltrimethylammonium chloride, tetradecyldimethylbenzylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, and octadecyldimethylbenzylammonium chloride. These may be used individually or in combination of two or more. 【0039】 Examples of commercially available cationic surfactants include "Kachiogen H" and "Kachiogen L" (both manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Cotamin 24P," "Cotamin 86P Corn," "Cotamin 60W," and "Cotamin 86W" (all manufactured by Kao Corporation). 【0040】 Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene styrylphenyl ethers, polyoxyalkylene alkyl esters, polyoxyalkylene sorbitan alkyl esters, condensation products of alkylene oxides and aliphatic amines, and ethylene oxide-propylene oxide polymers. These may be used individually or in combination of two or more. 【0041】 In the preceding paragraph, examples of oxyalkylene groups include oxyethylene, oxypropylene, oxyisoprene, and oxybutylene groups. Examples of alkyl groups include n-hexyl, isohexyl, n-heptyl, n-octyl, isooctyl, 2-ethylhexyl, n-decyl, isodecyl, n-undecyl, n-dodecyl (lauryl), n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, and n-octadecyl groups. 【0042】 Examples of commercially available nonionic surfactants include "Neugen EA," "Neugen EM," "Neugen ES," "Neugen SD," "Neugen TDS," and "Neugen XL" (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and "Softanol" (manufactured by Kao Corporation). 【0043】 Examples of anionic surfactants include polyoxyalkylene alkyl sulfates, polyoxyalkylene alkylphenyl ether sulfates, sulfate esters of higher alcohols, phosphate esters of higher alcohols, alkyl sulfonates, alkylphenyl ether sulfonates, alkyldiphenyl ether sulfonates, alkylbenzene sulfonates, naphthalene sulfonates, formaldehyde condensates of naphthalene sulfonates, lignin sulfonates, alkyl sulfosuccinates, polyoxyalkylene alkyl sulfosuccinates, polyoxyalkylene phenyl ether sulfosuccinates, polyoxyalkylene alkylphenyl ether sulfosuccinates, and polyoxyalkylene styrylphenyl ether sulfosuccinates. These may be used individually or in combination of two or more. Specific examples of oxyalkylene groups are those described in the previous paragraph. 【0044】 Examples of commercially available anionic surfactants include "Aqualon AR," "Aqualon KH," "High High Tenol LA," "High Tenol N," and "High Tenol NF" (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and "Emal 10," "Emal 2F," and "Emal 20" (all manufactured by Kao Corporation). 【0045】 The amount of surfactant used is preferably 0.1 to 10 parts by weight, and more preferably 1 to 5 parts by weight, per 100 parts by weight of the total reaction components. 【0046】 Examples of solvents include water such as tap water, deionized water, industrial water, pure water, and ultrapure water; alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, isobutyl alcohol, n-hexyl alcohol, n-octyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and diacetone alcohol; and ethers such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. These may be used individually or in combination of two or more. Water is preferred among these. When using a solvent, it is preferable to adjust the polymerization concentration to 20-60% by weight. 【0047】 The resulting polymer (A) may contain, for example, anti-slip agents, preservatives, rust inhibitors, pH adjusters, defoaming agents (such as silicone-based defoaming agents), thickeners, fillers, antioxidants, pigments, dyes, and the like. 【0048】 Examples of the polymer (A) obtained by the above manufacturing method include solutions, emulsions, and the like. 【0049】 The resulting polymer (A) has a glass transition temperature that is preferably between -60°C and 60°C. Having the glass transition temperature within this range makes it easier to increase the strength of molded articles obtained using the resulting polymer (A). Similarly, the glass transition temperature is more preferably between -50°C and 40°C, and even more preferably between -30°C and 20°C. 【0050】 The glass transition temperature (Tg) of polymer (A) is the value obtained by converting T (unit: K) obtained from (Equation 1) to °C, where "T" is the weight fraction of each reactant that makes up polymer (A) (w1, w2, w3, ..., w n ) (Unit: weight %) and the glass transition temperature (t1, t2, t3, ..., t) when it is a homopolymer. n It is calculated using (unit: K). 【0051】 (Equation 1) 1 / T = (Fraction of each reactant by weight / Sum of the glass transition temperatures (t) when the reactant is a homopolymer) / (Fraction of all reactants by weight) =(w1 / t1+w2 / t2+w3 / t3+···+w n / t n ) / (w1+w2+w3+···+w n ) 【0052】 The glass transition temperature (t) of the reaction component when it is a homopolymer refers to the glass transition temperature of the polymer produced by polymerizing only that reaction component alone. For example, specific values ​​are described in Wiley-Interscience's "POLYMER HANDBOOK FOURTH EDITION" (2003). In this invention, we adopted the values ​​from the chemical manufacturer's website or product catalog, or, if not described in these sources, the values ​​described in Japanese Patent Publication No. 2021-155862. 【0053】 Furthermore, the volume-average particle size of polymer (A) is preferably 10 nm to 200 nm, and more preferably 30 nm to 100 nm, from the standpoint of facilitating stable dispersion of polymer (A) particles when preparing the slurry. The volume-average particle size here is the value measured using a light scattering particle size analyzer (product name "ELSZ-2", manufactured by Otsuka Electronics Co., Ltd.). 【0054】 The sintering binder resin composition of the present invention may further contain an elastomer (B). The use of elastomer (B) has the effect of improving the density of the molded product obtained using the polymer (A) produced. Examples of elastomer (B) include rubber-based elastomers, polyurethane-based elastomers, polyalkylene glycol-based elastomers, polyester-based elastomers, polyamide-based elastomers, and olefin-based elastomers. These may be used individually or in combination of two or more. Among these, rubber-based elastomers, polyurethane-based elastomers, and polyalkylene glycol-based elastomers are preferred from the viewpoint of resin flexibility. 【0055】 Examples of rubber-based elastomers include natural rubber-based elastomers and synthetic rubber-based elastomers. 【0056】 As a natural rubber-based elastomer, either natural rubber or modified natural rubber obtained by modifying natural rubber with alkyl (meth)acrylate or the like can be used. 【0057】 Synthetic rubber elastomers are aqueous dispersions of synthetic polymers, and examples of synthetic polymers include styrene-butadiene rubbers such as polyisoprene, styrene-butadiene rubber (SBR), styrene-butadiene-alkyl(meth)acrylate rubber, styrene-butadiene-(meth)acrylic acid rubber, styrene-butadiene-acrylonitrile rubber, styrene-butadiene-vinylpyridine rubber, and styrene-butadiene-styrene block copolymer (SBS) rubber; styrene-isoprene (SI) rubber, and styrene-isoprene-styrene block copolymer (SBS). Examples include styrene-isoprene rubber such as IS) rubber; styrene-ethylene-butylene-styrene block copolymer (SEBS) rubber, styrene-ethylene-propylene-styrene block copolymer (SEPS) rubber, styrene-ethylene-propylene block copolymer (SEP) rubber, and other styrene-ethylene-propylene block copolymer (SEP) rubber; butadiene rubber such as methyl methacrylate-butadiene rubber and acrylonitrile-butadiene rubber (NBR); homopolymer rubbers such as polyisobutylene, polychloroprene (CR), and polybutadiene; recycled rubber, butyl rubber, etc. 【0058】 Examples of polyurethane elastomers include polyether polyurethane elastomers obtained from the reaction of polyether and polyisocyanate, and polyester polyurethane elastomers obtained from the reaction of polyester and polyisocyanate. These may be used individually or in combination of two or more types. 【0059】 Examples of polyalkylene glycol-based elastomers include polyethylene glycol, polypropylene glycol, and tetramethylene glycol. These may be used individually or in combination of two or more. 【0060】 Regarding the amount of elastomer (B) used, in order to improve the density of the molded product obtained using the polymer (A) produced, it is preferable to use 10 to 400 parts by weight, more preferably 20 to 300 parts by weight, and even more preferably 30 to 200 parts by weight, in terms of nonvolatile content, per 100 parts by weight of polymer (A). 【0061】 A method for producing the sintering binder resin composition of the present invention may include, for example, adding and mixing a polymer (A) with an elastomer (B) as needed. The aforementioned solvent may also be added during mixing. Furthermore, the mixture may be heated or cooled as appropriate during mixing. 【0062】 Examples of the sintering binder resin composition include solid, liquid, and emulsion forms. 【0063】 The sintering binder resin composition of the present invention may further contain additives such as antislip agents, preservatives, rust inhibitors, pH adjusters, defoaming agents (silicone-based defoaming agents, etc.), thickeners, fillers, antioxidants, pigments, dyes, and the aforementioned surfactants. 【0064】 One method of using the sintering binder resin composition of the present invention is to mix the resin composition, various powders, and, if necessary, the additives and sintering aids (e.g., silica, alumina, magnesium oxide, calcium oxide, etc.) to form a slurry, and then mold it into a molded product using a known molding method. In the above example of usage, the slurry can be dried to form granules for use, and the resulting molded product can be degreased and sintered by heating, with the conditions for these processes being set as appropriate. 【0065】 Examples of the powder include oxides such as alumina, magnesium, zirconia, titania, iron oxide, zinc oxide, silica, mica, etc.; complex oxides such as spinel and perovskite; non-oxides such as silicon carbide, titanium carbide, boron carbide, boron nitride, silicon nitride, aluminum nitride, carbon, etc.; colored pigments such as mica titanium, red iron oxide, aluminate, etc.; phosphorescent pigments, fluorescent pigments, etc. These may be used alone or in combination of two or more. 【0066】 Examples of the molding method include casting molding method, extrusion molding method, compression molding method, tape casting method, injection molding method, doctor blade method, coating method and other molding methods. 【Examples】 【0067】 The present invention will be described below with reference to examples, but the present invention is not limited thereto. In the examples and comparative examples, "g", "parts" and "%" are based on weight unless otherwise specified. 【0068】 (Glass transition point of polymer (A)) The charged weight fraction (w1, w2, w3, ···, w n ) of each reaction component used and the glass transition point (t1, t2, t3, ···, t n ) when made into a homopolymer were substituted into Equation 1 to obtain T(K). For each reaction component, the numerical values described later were used for the glass transition point (t) when made into a homopolymer. The obtained T(K) was converted so that the unit became °C to obtain the glass transition point (Tg) of polymer (A). In Equation 1, the unit of the charged weight fraction of each reaction component is weight %, and the unit of the glass transition point is "K". The results are shown in Table 1. (Equation 1) 1 / T = (w1 / t1 + w2 / t2 + w3 / t3 + ··· + w n / t n ) / (w1 + w2 + w3 + ··· + w n ) 【0069】 (Volume average particle diameter of polymer (A)) 0.5 g of polymer (A) was placed in a sample bottle, diluted with 10 g of deionized water, and then measured using a light scattering particle size analyzer (product name: "ELSZ-2", manufactured by Otsuka Electronics Co., Ltd.). 【0070】 Example 1 In a reaction vessel equipped with a thermometer, condenser, stirrer, nitrogen inlet tube, and two dropping funnels, 2 parts of anionic surfactant (product name: "Hythenol LA-10", manufactured by Daiichi Kogyo Seiyaku Co., Ltd., non-volatile content: 95%) and 140 parts of deionized water were charged. After thoroughly replacing the oxygen in the reaction vessel with nitrogen, the temperature of the system was raised to 80°C while stirring. Next, a monomer solution prepared by mixing 20 parts of styrene, 10 parts of 2-hydroxyethyl acrylate, 65 parts of n-butyl acrylate, and 5 parts of 1,6-hexanediol acrylate was charged into dropping funnel (1), and an aqueous solution prepared by dissolving 3 parts of ammonium persulfate (3 parts per 100 parts of monomer) in 100 parts of deionized water was charged into dropping funnel (2). These solutions were added dropwise to the system over 2 hours, and after completion, the reaction was allowed to continue for another 2 hours to obtain an aqueous solution of polymer (A-1) with a non-volatile content of 30%. Table 1 shows the glass transition temperature and volume-average particle size of polymer (A-1) (the same applies hereafter). 【0071】 Examples 2-17, Comparative Examples 1-4 The composition and weight ratios shown in Table 1 were changed, and the process was carried out in the same manner as in Production Example 1 to obtain aqueous solutions of polymers (A-2) to (A-17) and (C-1) to (C-4), respectively. 【0072】 [Table 1] *1: The amount of component (a4) used is expressed as a weight percentage relative to 100% by weight of the total of components (a1), (a2), and (a3). 【0073】 The abbreviations for each reaction component in Table 1 represent the following compounds. • St: Styrene, glass transition temperature when used as a homopolymer: 100°C • HEA: 2-hydroxyethyl acrylate, glass transition temperature when homopolymerized: -15°C • AA: Acrylic acid, glass transition temperature when homopolymerized: 106°C • MAA: Methacrylic acid, glass transition temperature when homopolymerized: 185°C • DM: N,N-dimethylaminoethyl methacrylate, glass transition temperature when homopolymerized: 18°C • BA: n-butyl acrylate, glass transition temperature when homopolymerized: -55°C • BMA: n-butyl methacrylate, glass transition temperature when homopolymerized: 20°C • 2EHA: 2-ethylhexyl acrylate, glass transition temperature when homopolymerized: -68°C • 1,6-HDDA: 1,6-Hexanediol diacrylate, trade name: "A-HD-N", manufactured by Shin-Nakamura Chemical Industry Co., Ltd., glass transition temperature when homopolymerized: 63°C • E-PETA: Ethoxylated pentaerythritol tetraacrylate, trade name: "ATM-35E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd., glass transition temperature when homopolymerized: -40℃ • E-DPHA: Ethoxylated dipentaerythritol hexaacrylate, trade name: "A-DPH-12E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd., glass transition temperature when homopolymerized: 0°C 【0074】 <Performance evaluation when elastomer (B) is incorporated> Evaluation Example 1 A slurry was obtained by mixing 100 parts of alumina powder (product name: "Low Soda Alumina LS-710C", manufactured by Nippon Light Metal Co., Ltd., volume average particle size: 0.54 μm), 10 parts of an aqueous solution of polymer (A-1) (non-volatile content: 3 parts), 3 parts of styrene-butadiene rubber (product name: "SBL 0696", manufactured by ENEOS Material Co., Ltd.), and 100 parts of deionized water in a ball mill for 4 hours. 【0075】 Evaluation Examples 2-17, Comparative Evaluation Examples 1-4 Slurries were obtained using aqueous solutions of polymers (A-2) to (A-17) and (C-1) to (C-4), respectively, by the same method as in Evaluation Example 1. 【0076】 (Dispersibility of slurry) Each slurry was placed in a test tube at 25°C to a liquid height of 10 cm and allowed to stand. After 24 hours, the height of the supernatant (cm) was measured, and the height of the supernatant relative to the liquid height before standing (10 cm) was calculated using (Equation 1) below (hereinafter referred to as the "supernatant ratio"), and the dispersibility was evaluated according to the following criteria. The results are shown in Table 2 (the same applies below). (Equation 1) Supernatant ratio (%) = {Height of supernatant (cm) / Height of liquid before standing (10cm)} × 100 【0077】 (Evaluation Criteria) ○: Supernatant ratio is less than 5% △: The ratio of supernatant liquid is 5% or more but less than 30%. ×: The ratio of supernatant liquid is 30% or more. 【0078】 (Preparation of molded products) Each slurry is dried in a spray dryer at 150°C (device name: "Spray Dryer GB-22", manufactured by Yamato Scientific Co., Ltd.) to obtain granules. The granules are then packed into rectangular molds (10 mm long x 100 mm wide) at a rate of 1 t / cm². 2 By applying a load and pressurizing the material, a disc-shaped molded product with a thickness of 1 mm was obtained. In this invention, the following evaluations were performed on the molded product in order to confirm the strength, density, etc., of the product containing the sintering binder resin composition. 【0079】 (Moldability) The resulting molded products were visually inspected, and their moldability was judged according to the following criteria. (Evaluation Criteria) ○: No cracks were observed in the molded product. △: Some cracks and chips are visible in the molded product. ×: The cracking is severe, and it is not possible to obtain a molded product of the specified size. 【0080】 (strength) The strength of each molded product at a temperature of 25°C was measured in accordance with JIS R1601. While JIS R1601 is originally a method for measuring the strength of sintered bodies, in this invention it was applied to molded products. 【0081】 (density) The weight (g) of each molded object was measured using a balance scale. Next, the thickness (mm) was measured using a digital thickness gauge. The volume was calculated from the area and thickness of a 14 mm diameter ceramic molded object, and the density was calculated using (Equation 2) below. (Formula 2) Density (g / cm 3 ) = Weight (g) / Volume (cm³) 3 ) 【0082】 [Table 2] 【0083】 <Performance evaluation without elastomer (B)> Evaluation Example 18 A slurry was obtained by mixing 100 parts of alumina powder (product name: "Low Soda Alumina LS-710C", manufactured by Nippon Light Metal Co., Ltd., volume average particle size: 0.54 μm), 10 parts of an aqueous solution of polymer (A-1) (non-volatile content: 3 parts), and 100 parts of deionized water in a ball mill for 4 hours. 【0084】 Evaluation Example 19, Comparative Evaluation Examples 5-6 Slurries were obtained using aqueous solutions of polymers (A-2), (C-1), and (C-2) in the same manner as in Evaluation Example 18. 【0085】 Using the slurries described above, the dispersibility of the slurries was evaluated in the same manner as described above. Molded articles were then prepared using these slurries, and their moldability, strength, and density were evaluated, respectively. The results are shown in Table 3. 【0086】 [Table 3] 【0087】 The results in Tables 2 and 3 show that molded articles obtained using the sintering binder resin composition of the present invention exhibit high strength and density. Furthermore, when these molded articles were sintered to form sintered bodies, the strength and density could be further improved.

Claims

[Claim 1] A sintering binder resin composition comprising a polymer (A) of reaction components including styrenes (a1), a monomer having a polar group and one ethylenically unsaturated group (a2), an alkyl mono(meth)acrylate without a polar group (a3), and a poly(meth)acrylate (a4). [Claim 2] The sintering binder resin composition according to claim 1, wherein the glass transition temperature of polymer (A) is -60°C or higher and 60°C or lower. [Claim 3] Furthermore, the sintering binder resin composition according to claim 1 or 2, further comprising elastomer (B).

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