Binder for firing and paste composition for firing

Abstract

This binder for firing contains an aliphatic polycarbonate having a carbonate structure in a main chain and a hydrocarbon group having 2-8 carbon atoms in a side chain. The aliphatic polycarbonate has a weight average molecular weight of 50,000-170,000 inclusive. The aliphatic polycarbonate preferably has a structural unit represented by general formula (1a). In the formula, R1, R2, R3 and R4 are each independently a hydrogen atom or a hydrocarbon group, and at least one thereof is a hydrocarbon group having 2-8 carbon atoms.　According to the binder for firing, the solid matter of the carbon compound derived from the binder does not remain in a sintered product, carbon dioxide can be used as a production raw material, carbon dioxide is not substantially discharged during firing, and adhesion to metal is high.

Description

Firing binder and firing paste composition

[0001] The present invention relates to a binder for firing and a paste composition for firing.

[0002] Sintered bodies obtained by sintering inorganic powders such as metal powders and ceramic powders have conventionally been used in various fields, for example, for producing electrodes, conductor wiring, multilayer capacitors, etc. in various electronic devices.

[0003] To produce the sintered body, a paste composition for firing, which is a mixture of inorganic powder and a binder for firing, is formed into a desired shape, preheated as necessary, and then fired to sinter the inorganic powder.

[0004] As an example of such a sintering binder, Patent Document 1 proposes a low-temperature sintering binder resin composition containing 100 parts by weight of a (meth)acrylate polymer (A) having a functional group capable of forming a hydrogen bond with a hydroxyl group, 20 to 200 parts by weight of an organic compound (B) having three or more hydroxyl groups, and 100 parts by weight or less of an organic solvent (C) having a boiling point of 150°C or higher.

[0005] Japanese Patent Application Laid-Open No. 2006-160791

[0006] However, the acrylic sintering binder as disclosed in Patent Document 1 has a problem in that solid carbon compounds remain in the sintered body after sintering.

[0007] Furthermore, depending on the application of the sintered body, adhesion to a metal member (e.g., copper, aluminum, etc.) with which the sintered body or the sintering binder comes into contact may be required. However, the acrylic sintering binder as disclosed in Patent Document 1 has low adhesion to metals, and it has been necessary to use an additive or the like to improve adhesion.

[0008] In recent years, global warming and the resulting environmental destruction have become major problems, and carbon dioxide is thought to be one of the main causes. Therefore, reducing carbon dioxide emissions in the process of producing various materials and effectively utilizing the carbon dioxide that is emitted can be said to be helpful in protecting the environment.

[0009] The present invention has been made in view of the above-described circumstances, and aims to provide a sintering binder and a sintering paste composition that do not leave behind any solid carbon compound derived from the binder in the sintered body, can use carbon dioxide as a manufacturing raw material, does not substantially emit carbon dioxide during sintering, and has high adhesion to metals.

[0010] In order to achieve the above object, first, the present invention provides a sintering binder containing an aliphatic polycarbonate having a carbonate structure in its main chain and a hydrocarbon group having 2 to 8 carbon atoms in its side chain, wherein the aliphatic polycarbonate has a weight-average molecular weight of 50,000 or more and 170,000 or less (Invention 1).

[0011] The aliphatic polycarbonate in the above invention (Invention 1) decomposes upon firing, producing a cyclic carbonate as the main product. Therefore, it emits virtually no carbon dioxide during firing, and binder-derived carbon compound solids are unlikely to remain in the sintered body. Furthermore, the aliphatic polycarbonate has a relatively low weight-average molecular weight of 50,000 or more and 170,000 or less, which further reduces the likelihood of binder-derived carbon compound solids remaining in the sintered body. Furthermore, the cyclic carbonate product can be reused as a solvent or electrolyte for lithium-ion batteries. Furthermore, the aliphatic polycarbonate can be produced using carbon dioxide as a raw material, thereby enabling effective utilization of carbon dioxide. Furthermore, the aliphatic polycarbonate has a hydrocarbon group having 2 to 8 carbon atoms in its side chain, which facilitates a glass transition temperature below room temperature and improves wettability to adherends, resulting in excellent adhesion to metals at room temperature.

[0012] In the above invention (invention 1), it is preferable that the 50% thermal decomposition temperature in an atmosphere at atmospheric pressure with an oxygen concentration of 5% or less is 255° C. or more and 300° C. or less (invention 2).

[0013] In the above inventions (Inventions 1 and 2), it is preferable that the 99% thermal decomposition temperature in an atmosphere at atmospheric pressure with an oxygen concentration of 5% or less is 400° C. or less (Invention 3).

[0014] In the above inventions (Inventions 1 to 3), it is preferable that the adhesion strength measured when the layer of the sintering binder having a thickness of 20 μm is peeled off from an aluminum plate at a peel angle of 180° and a peel rate of 300 mm / min is 0.3 N / 25 mm or more (Invention 4).

[0015] In the above inventions (Inventions 1 to 4), the hydrocarbon group having 2 to 8 carbon atoms is preferably a linear hydrocarbon group (Invention 5).

[0016] In the above inventions (Inventions 1 to 5), it is preferable that the aliphatic polycarbonate has a structural unit represented by the following general formula (1a) (Invention 6). (In the formula, R １ , R ２ , R ３ and R ４ are each independently hydrogen or a hydrocarbon group, and at least one is a hydrocarbon group having 2 to 8 carbon atoms.

[0017] In the above inventions (Inventions 1 to 6), it is preferable that the composition is for forming a metal oxide precursor sintered body or a metal oxide sintered body (Inventions 7 and 8), or that the composition is used for forming a metal oxide precursor sintered foil on a substrate or for forming a metal oxide sintered foil on a substrate (Inventions 9 and 10).

[0018] In the above inventions (Inventions 1 to 10), the storage modulus at 23° C. is preferably 1.0 MPa or more and 50 MPa or less (Invention 11).

[0019] In the above inventions (Inventions 1 to 11), the glass transition temperature (Tg) is preferably −15° C. or higher and 25° C. or lower (Invention 12).

[0020] In the above inventions (Inventions 1 to 12), it is preferable that the elongation at break when formed to a thickness of 0.5 mm and a width of 10 mm and stretched at a measurement temperature of 23°C, a measurement length of 10 mm, and a tensile speed of 200 mm / min is 100% or more (Invention 13).

[0021] In the above inventions (Inventions 1 to 13), it is preferable that the maximum stress when formed to a thickness of 0.5 mm and a width of 10 mm and stretched to the breaking elongation at a measurement temperature of 23°C, a measurement length of 10 mm, and a tensile speed of 200 mm / min is 10 MPa or less (Invention 14).

[0022] Secondly, the present invention provides a paste composition for firing (Invention 15), which contains a metal oxide precursor powder or a metal oxide powder and the above-mentioned binder for firing (Inventions 1 to 14).

[0023] In this specification, the term "metal oxide precursor" is a general term for a substance that can become a metal oxide when fired in an oxygen atmosphere. However, firing in an oxygen atmosphere is not a prerequisite. In addition, in this specification, the term "metal oxide precursor sintered foil" refers to a composite of a metal oxide precursor sintered body and a foil-like member such as a metal foil, and the term "metal oxide sintered foil" refers to a composite of a metal oxide sintered body and a foil-like member such as a metal foil.

[0024] According to the sintering binder and sintering paste composition of the present invention, no solid carbon compound derived from the binder remains in the sintered body, carbon dioxide can be used as a manufacturing raw material, carbon dioxide is not substantially emitted during sintering, and adhesion to metals is high.

[0025] Hereinafter, an embodiment of the present invention will be described. [Binder for sintering] A binder for sintering according to one embodiment of the present invention (hereinafter sometimes referred to as "binder for sintering B") contains an aliphatic polycarbonate (hereinafter sometimes referred to as "aliphatic polycarbonate A") having a carbonate structure in the main chain and a hydrocarbon group having 2 to 8 carbon atoms in the side chain.

[0026] When aliphatic polycarbonate A is decomposed by firing, the main product is cyclic carbonate. Therefore, carbon dioxide is not substantially emitted during firing, and solid carbon compounds derived from the binder are less likely to remain in the sintered body. Furthermore, since the weight-average molecular weight of aliphatic polycarbonate A is relatively low, at 50,000 or more and 170,000 or less, carbon compounds derived from the binder are less likely to remain in the sintered body (this effect may be referred to as "carbon residue suppression" hereinafter). Furthermore, the cyclic carbonate product can be reused as a solvent or electrolyte for lithium-ion batteries. Furthermore, as described below, aliphatic polycarbonate A can be produced using carbon dioxide as a production raw material, thereby enabling effective utilization of carbon dioxide.

[0027] Furthermore, since the aliphatic polycarbonate A has hydrocarbon groups with 2 to 8 carbon atoms in its side chains, its glass transition temperature tends to be below room temperature, improving its wettability to adherends and thereby exhibiting excellent adhesion to metals at room temperature. Specifically, the adhesion between a firing paste composition using firing binder B and a metal member, the adhesion between metal oxide precursor powders in a firing paste composition containing firing binder B and a metal oxide precursor powder, and the adhesion between metal members via firing binder B (firing paste composition) are excellent. Note that when the hydrocarbon groups in the side chains of aliphatic polycarbonate A are only those with 0 or 1 carbon atom, adhesion to adherends is low at room temperature.

[0028] Furthermore, the aliphatic polycarbonate A exhibits low-temperature decomposition due to a specific reaction, specifically a backbiting reaction, due to the carbonate structure in the main chain. Therefore, the sintering binder B according to the embodiment can be sintered at a relatively low temperature. This low-temperature decomposition property of the aliphatic polycarbonate A is exhibited not only in air but also in an inert atmosphere. Therefore, even when a metal that is easily oxidized during sintering in air is present, sintering can be performed at a relatively low temperature in an inert atmosphere while preventing oxidation of the metal.

[0029] Furthermore, since the weight average molecular weight of the aliphatic polycarbonate A is relatively low, at 50,000 or more and 170,000 or less, the coating property and processability of the firing paste composition (slurry) containing the aliphatic polycarbonate A are good.

[0030] From the viewpoint of the above-mentioned effects, particularly the ability to suppress carbon residue, the weight average molecular weight (Mw) of the aliphatic polycarbonate A is preferably from 50,000 to 160,000, particularly from 54,000 to 120,000, and even more preferably from 58,000 to 80,000. The weight average molecular weight (Mw) in this specification and the number average molecular weight (Mn) described below are values ​​measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0031] The number average molecular weight (Mn) of the aliphatic polycarbonate A is preferably from 10,000 to 150,000, more preferably from 15,000 to 100,000, particularly preferably from 20,000 to 80,000, and even more preferably from 30,000 to 60,000, which makes the above-mentioned effects, particularly the ability to suppress carbon residue, even more excellent.

[0032] The molecular weight distribution PDI (Mw / Mn) of the aliphatic polycarbonate A is preferably 1.00 to 7.00, more preferably 1.05 to 5.00, particularly preferably 1.10 to 3.00, and further preferably 1.15 to 2.00.

[0033] The 99% thermal decomposition temperature of aliphatic polycarbonate A in an atmosphere at atmospheric pressure and an oxygen concentration of 5% or less is preferably 400°C or less, more preferably 380°C or less, more preferably 350°C or less, particularly preferably 320°C or less, and even more preferably 310°C or less. This means that aliphatic polycarbonate A has excellent low-temperature decomposition properties even in an inert atmosphere, and can be fired at a relatively low temperature even in an inert atmosphere. In this embodiment, the use of aliphatic polycarbonate A makes it possible to achieve the above-mentioned 99% thermal decomposition temperature. Although the lower limit of the 99% thermal decomposition temperature is not particularly limited, from the viewpoint of volatilizing the solvent at a temperature above its boiling point after coating of the slurry, it is preferably 270°C or more, particularly preferably 280°C or more, and even more preferably 290°C or more. Note that the thermal decomposition temperature in this specification is measured by thermogravimetric analysis (TGA), and details are as shown in the test examples described below.

[0034] The 50% thermal decomposition temperature of the aliphatic polycarbonate A in an atmosphere at atmospheric pressure with an oxygen concentration of 5% or less is preferably 300°C or less, more preferably 295°C or less, more preferably 290°C or less, particularly preferably 285°C or less, and even more preferably 280°C or less. This tends to improve low-temperature decomposition properties in an inert atmosphere. The lower limit of the 50% thermal decomposition temperature is preferably 255°C or more, more preferably 260°C or more, particularly preferably 265°C or more, and even more preferably 270°C or more. This makes it possible to widen the difference between the boiling point of the slurry and that of the solvent, thereby preventing decomposition of the aliphatic polycarbonate A when the slurry is heated to volatilize the solvent after application.

[0035] The 10% thermal decomposition temperature of aliphatic polycarbonate A in an atmosphere of atmospheric pressure with an oxygen concentration of 5% or less is preferably 285° C. or less, more preferably 280° C. or less, more preferably 275° C. or less, particularly preferably 270° C. or less, and even more preferably 265° C. or less. There are no particular restrictions on the lower limit of the 10% thermal decomposition temperature, but it is preferably 210° C. or more, particularly preferably 235° C. or more, and even more preferably 250° C. or more.

[0036] The 5% thermal decomposition temperature of the aliphatic polycarbonate A in an atmosphere of atmospheric pressure with an oxygen concentration of 5% or less is preferably 280° C. or less, more preferably 275° C. or less, more preferably 270° C. or less, particularly preferably 265° C. or less, and even more preferably 260° C. or less. There are no particular restrictions on the lower limit of the 5% thermal decomposition temperature, but it is preferably 210° C. or more, particularly preferably 230° C. or more, and even more preferably 245° C. or more.

[0037] The 99% thermal decomposition temperature of the aliphatic polycarbonate A in air is preferably 395°C or lower, more preferably 375°C or lower, more preferably 345°C or lower, particularly preferably 315°C or lower, and even more preferably 305°C or lower. This means that the aliphatic polycarbonate A has excellent low-temperature decomposition properties, and can be fired at a relatively low temperature. In this embodiment, the use of the aliphatic polycarbonate A makes it possible to achieve the above-mentioned 99% thermal decomposition temperature. Although the lower limit of the 99% thermal decomposition temperature is not particularly limited, from the viewpoint of volatilizing the solvent at a temperature above its boiling point after coating of the slurry, it is preferably 265°C or higher, particularly preferably 275°C or higher, and even more preferably 285°C or higher.

[0038] The 50% thermal decomposition temperature of the aliphatic polycarbonate A in air is preferably 295° C. or lower, more preferably 290° C. or lower, more preferably 285° C. or lower, particularly preferably 280° C. or lower, and even more preferably 275° C. or lower. There are no particular restrictions on the lower limit of the 50% thermal decomposition temperature, but it is preferably 250° C. or higher, particularly preferably 255° C. or higher, and even more preferably 260° C. or higher.

[0039] The 10% thermal decomposition temperature of the aliphatic polycarbonate A in air is preferably 280° C. or lower, preferably 275° C. or lower, more preferably 270° C. or lower, particularly preferably 265° C. or lower, and even more preferably 260° C. or lower. There are no particular restrictions on the lower limit of the 10% thermal decomposition temperature, but it is preferably 205° C. or higher, particularly preferably 230° C. or higher, and even more preferably 245° C. or higher.

[0040] The 5% thermal decomposition temperature of the aliphatic polycarbonate A in air is preferably 275° C. or lower, more preferably 270° C. or lower, more preferably 260° C. or lower, particularly preferably 255° C. or lower, and even more preferably 250° C. or lower. There are no particular restrictions on the lower limit of the 5% thermal decomposition temperature, but it is preferably 200° C. or higher, particularly preferably 225° C. or higher, and even more preferably 240° C. or higher.

[0041] The adhesion strength measured when the layer of sintering binder B (20 μm thick) is peeled off from an aluminum plate having a layer of sintering binder B (20 μm thick) formed thereon at a peel angle of 180° and a peel rate of 300 mm / min is preferably 0.3 N / 25 mm or more, more preferably 0.5 N / 25 mm or more, particularly preferably 1 N / 25 mm or more, and even more preferably 5 N / 25 mm or more. This indicates high adhesion to metals. In this embodiment, the use of aliphatic polycarbonate A can achieve the above-mentioned excellent metal adhesion. The upper limit of the adhesion strength is not particularly limited, but from the viewpoint of exhibiting blocking properties when the adhesion strength is too high, it is preferably 20 N / 25 mm or less, particularly preferably 18 N / 25 mm or less, and even more preferably 15 N / 25 mm or less. The adhesive strength in this specification basically refers to the adhesive strength measured by the 180-degree peeling method in accordance with JIS Z0237:2000, and the specific test method is as shown in the test examples below.

[0042] Here, the hydrocarbon group having 2 to 8 carbon atoms in the aliphatic polycarbonate A is preferably a linear hydrocarbon group, which makes it easier to achieve the above-mentioned adhesive strength.

[0043] The glass transition temperature (Tg) of the aliphatic polycarbonate A is preferably 25°C or lower, particularly preferably 20°C or lower, and even more preferably 18°C ​​or lower. This allows excellent adhesion to metals, particularly aluminum, to be exhibited at room temperature, making it easier to achieve the above-mentioned adhesion. In this embodiment, the use of an aliphatic polycarbonate A having a hydrocarbon group in the side chain with 2 to 8 carbon atoms makes it possible to achieve the above-mentioned low glass transition temperature (Tg). From the viewpoint of film strength, the glass transition temperature (Tg) is preferably −15°C or higher, more preferably −8°C or higher, particularly preferably 0°C or higher, and even more preferably 10°C or higher. In this specification, the glass transition temperature (Tg) is measured by differential scanning calorimetry (DSC), and details are as shown in the test examples described below.

[0044] The storage modulus of the aliphatic polycarbonate A at 23°C is preferably 50 MPa or less, more preferably 40 MPa or less, particularly preferably 30 MPa or less, and even more preferably 20 MPa or less. This allows excellent adhesion to metals, particularly aluminum, to be exhibited at room temperature, making it easier to achieve the above-mentioned adhesion strength. The lower limit of the storage modulus is preferably 1.0 MPa or more, more preferably 2.0 MPa or more, particularly preferably 8 MPa or more, and even more preferably 12 MPa or more. This allows excellent adhesion to metals, particularly aluminum, to be maintained at room temperature, making it easier to achieve the above-mentioned adhesion strength. The method for measuring the storage modulus in this specification is as shown in the test examples described below.

[0045] Aliphatic polycarbonate A is formed into a thickness of 0.5 mm and a width of 10 mm, and when subjected to a tensile test at a measurement temperature of 23°C, a measurement length of 10 mm, and a tensile speed of 200 mm / min, the breaking elongation is preferably 100% or more, more preferably 1000% or more, particularly preferably 3000% or more, and even more preferably 5000% or more. This results in excellent flexibility and a high degree of freedom in designing the shape of the resulting sintered body. The specific method of the tensile test is as shown in the test examples described below.

[0046] When the aliphatic polycarbonate A is subjected to the tensile test and stretched to the breaking elongation, the maximum stress is preferably 10 MPa or less, more preferably 7 MPa or less, particularly preferably 5 MPa or less, and even more preferably 3 MPa or less. This results in excellent flexibility and a high degree of freedom in designing the shape of the resulting sintered body. The lower limit of the maximum stress is preferably 0.01 MPa or more. This ensures the strength required when preparing a firing paste.

[0047] The ether bond ratio in the aliphatic polycarbonate A is preferably 20% or less, more preferably 10% or less, particularly preferably 5% or less, and even more preferably 1% or less. This improves decomposition properties and provides excellent carbon residue suppression. The ether bond ratio in this specification is measured as shown in the test examples described later. Note that the -O- bond in the carbonate bond (-O-C(=O)-O-) does not qualify as an ether bond.

[0048] 1. Components The components contained in the sintering binder B according to this embodiment are described below. (1) Aliphatic polycarbonate (1-1) Structure of aliphatic polycarbonate The aliphatic polycarbonate A used in the sintering binder B is a polycarbonate whose main chain is composed only of carbonate groups (—O—C(═O)—O—) and aliphatic groups, and has a structure in which divalent aliphatic groups constituting the main chain are linked by carbonate groups.

[0049] The aliphatic polycarbonate A may have a carboxylic acid ester bond (-C(=O)-O-) in its main chain, but preferably does not have one. When the aliphatic polycarbonate A does not have a carboxylic acid ester bond in its main chain, the aliphatic polycarbonate A does not include a polymer having a polycarbonate skeleton obtained by reacting a carboxylic acid or a derivative thereof with an alcohol to form an ester bond in the main chain. Here, examples of the carboxylic acid derivative include carboxylic acid anhydrides and carboxylic acid halides that are capable of forming an ester bond.

[0050] The aliphatic polycarbonate A may have a urethane bond (—NH—C(═O)—O—) in its main chain, but preferably does not have one. When the aliphatic polycarbonate A does not have a urethane bond in its main chain, the aliphatic polycarbonate A does not include a polymer having a polycarbonate skeleton obtained by reacting a compound having an isocyanate group with an alcohol to form a urethane bond in the main chain.

[0051] Furthermore, the aliphatic polycarbonate A may have an ether bond (—O—) in its main chain.

[0052] The aliphatic polycarbonate A may or may not have either or both of a carboxylic acid ester bond and a urethane bond in its side chain, but from the viewpoint of preventing metal corrosion, it is preferable that the aliphatic polycarbonate A does not have a carboxylic acid ester bond in its side chain.

[0053] The aliphatic polycarbonate A may, for example, be one having a structural unit represented by the following general formula (1).

[0054] (In the formula, X is a divalent aliphatic hydrocarbon group having a substituent.)

[0055] In the formula, X is a divalent aliphatic hydrocarbon group having a substituent, and the aliphatic hydrocarbon group may be linear, branched, or cyclic, or may have both a linear structure and a cyclic structure. The cyclic aliphatic hydrocarbon group may be monocyclic or polycyclic.

[0056] Regarding X, the aliphatic hydrocarbon group "having a substituent" means an aliphatic hydrocarbon group in which one or more hydrogen atoms have been substituted with a group (substituent) other than a hydrogen atom.

[0057] The substituent of the aliphatic hydrocarbon group is not particularly limited, and examples thereof include a hydroxy group, a halogen atom, an alkoxy group, an alkenyl group, an alkenyloxy group, an aryl group, a heteroaryl group, an aryloxy group, a heteroaryloxy group, an alkylsilyl group, an alkylsilyloxy group, and the like. Thus, the aliphatic polycarbonate may or may not have an aromatic group in a side chain branched from the main chain, as long as the groups other than the carbonate group constituting the main chain are aliphatic groups. Note that, from the viewpoint of preventing metal corrosion, it is preferable that the aliphatic polycarbonate does not have a carboxy group as a substituent.

[0058] Examples of the halogen atom in the above substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0059] Examples of the alkoxy group in the above substituent include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group, and the like, and the alkoxy group in the R １ and the like.

[0060] Examples of the alkenyl group in the above substituent include a vinyl group, an allyl group, a 1-methylethenyl group, a 2-methylethenyl group, a 1-cyclohexenyl group, a 2-cyclohexenyl group, a 3-cyclohexenyl group, and the like, and R １ and the like.

[0061] Examples of the alkenyloxy group in the substituent include an ethenyloxy group, a 2-propenyloxy group, a 1-methylethenyloxy group, a 2-methylethenyloxy group, a 1-cyclohexenyloxy group, a 2-cyclohexenyloxy group, and a 3-cyclohexenyloxy group, which are monovalent groups formed by bonding an oxygen atom to the above-mentioned alkenyl group.

[0062] The aryl group in the above-mentioned substituent may be either monocyclic or polycyclic, and preferably has 6 to 13 carbon atoms. Examples thereof include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, and a xylyl group (dimethylphenyl group). One or more hydrogen atoms of these aryl groups may be further substituted with one or more hydrogen atoms of these aryl groups or with one or more hydrogen atoms of the aryl groups described below. １ The aryl group having such a substituent preferably has 6 to 13 carbon atoms, including the carbon number of the substituent.

[0063] The heteroaryl group in the above-mentioned substituent may be either monocyclic or polycyclic. Such heteroaryl groups may be, for example, the aforementioned aryl groups in which one or more carbon atoms constituting the aromatic ring skeleton are substituted with heteroatoms, either singly or together with the hydrogen atoms bonded to those carbon atoms, and thus have aromaticity. Alternatively, they may be cyclic unsaturated aliphatic hydrocarbon groups having three or more carbon atoms in which one or more carbon atoms constituting the ring skeleton are substituted with heteroatoms, either singly or together with the hydrogen atoms bonded to those carbon atoms, and thus have aromaticity. Examples of such heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, selenium atoms, and phosphorus atoms. However, from the standpoint of safety and environmental protection of decomposition products generated during firing, it is preferable that heteroatoms other than oxygen atoms, particularly nitrogen atoms and sulfur atoms, are not included. This is because decomposition products containing nitrogen atoms or sulfur atoms may become toxic gases. The number of heteroatoms constituting the aromatic ring skeleton is not particularly limited, but is preferably 1 to 2. When the number of heteroatoms constituting the aromatic ring skeleton is two or more, these heteroatoms may all be the same, all be different, or only some may be the same.

[0064] In this specification, for example, a group having a structure in which an aromatic hydrocarbon group and an aromatic heterocyclic group are condensed is referred to as an aromatic heterocyclic group.

[0065] Examples of the aryloxy group in the above substituent include a phenoxy group, a 1-naphthoxy group, a 2-naphthoxy group, and other monovalent groups formed by bonding an oxygen atom to the above-mentioned aryl group.

[0066] Examples of the heteroaryloxy group in the above substituent include a monovalent group formed by bonding an oxygen atom to the above heteroaryl group.

[0067] The alkylsilyl group in the above substituent may be any of a monoalkylsilyl group, a dialkylsilyl group, and a trialkylsilyl group. In such an alkylsilyl group, the alkyl group bonded to the silicon atom may be any of a linear, branched, and cyclic group, and may have both a chain structure and a cyclic structure. The cyclic alkyl group may be either a monocyclic or a polycyclic group. Examples of the alkyl group bonded to the silicon atom include, for example, R １ The alkyl groups in the above groups are the same as those in the above groups.

[0068] In the dialkylsilyl group and trialkylsilyl group, the alkyl groups may be the same or different from one another. In the trialkylsilyl group, the three alkyl groups may all be the same or different, or only two may be the same.

[0069] Examples of the alkylsilyloxy group in the above-mentioned substituent include a monovalent group formed by bonding the above-mentioned alkylsilyl group to an oxygen atom, such as a dimethylsilyloxy group, an ethylmethylsilyloxy group, a trimethylsilyloxy group, an ethylmethyl-n-propylsilyloxy group, and an ethyldimethylsilyloxy group.

[0070] The number of substituents possessed by the aliphatic hydrocarbon group is not particularly limited, and may be one or more, or all hydrogen atoms may be substituted with substituents. The aliphatic hydrocarbon group having a substituent preferably has a total carbon number including the substituent of 4 or more. The total carbon number including the substituent is preferably 10 or less, more preferably 8 or less, and particularly preferably 6 or less. When the total carbon number including the substituent is within the above range, the aliphatic hydrocarbon group can achieve both layer-forming ability and decomposability.

[0071] In the above-described aliphatic hydrocarbon group, when the number of substituents is two or more, these substituents may be the same or different. That is, two or more substituents may all be the same, all may be different, or only some may be the same. Furthermore, the bonding position of the substituent in the above-described aliphatic hydrocarbon group is not particularly limited, but it is preferable that the terminal end of the substituent is the terminal end of the side chain, and it may be a carbon atom constituting the main chain in X or a carbon atom at the terminal of the side chain.

[0072] The substituted aliphatic hydrocarbon group described above is preferably an alkylene group having a substituent, and more preferably an ethylene group having a substituent. When the aliphatic hydrocarbon group is an alkylene group, particularly an ethylene group, the glass transition temperature (Tg) of the aliphatic polycarbonate is lowered, and low-temperature decomposition properties are improved.

[0073] The aliphatic polycarbonate A preferably has a structural unit represented by the following general formula (1a) (hereinafter sometimes abbreviated as "structural unit (1a)").

[0074] In the formula, R １ , R ２ , R ３ and R ４ are each independently a hydrogen atom or a hydrocarbon group, and at least one is a hydrocarbon group having 2 to 8 carbon atoms.

[0075] The number of carbon atoms in the hydrocarbon group having 2 to 8 carbon atoms is preferably smaller from the viewpoint of decomposability, and specifically, 2 is particularly preferred, while the number of carbon atoms is preferably larger from the viewpoint of adhesion, and specifically, 8 is particularly preferred.

[0076] The hydrocarbon groups are preferably independently unsubstituted or substituted alkyl or alkoxy groups. The hydrocarbon groups (alkyl and alkoxy groups) may be linear, branched, or cyclic, and may have both a chain structure and a cyclic structure, but are preferably linear from the viewpoint of easily satisfying the above-mentioned physical properties, particularly the glass transition temperature (Tg). The cyclic hydrocarbon groups may be monocyclic or polycyclic.

[0077] Examples of the linear or branched alkyl group include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, a 2-methylpentyl group, an n-heptyl group, a 2-methylhexyl group, a 2-ethylhexyl group, an n-octyl group, an isooctyl group, etc. Among these, from the viewpoint of making it easier to satisfy the above-mentioned physical properties, in particular the glass transition temperature (Tg), an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-octyl group, or an isooctyl group is preferred, and an ethyl group or an n-octyl group is particularly preferred.

[0078] Examples of the cyclic alkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and further include those in which one or more hydrogen atoms of these cyclic alkyl groups have been substituted with a linear, branched, or cyclic alkyl group. Here, examples of the linear, branched, or cyclic alkyl group that substitutes a hydrogen atom include R １ ~R ４ Examples of the alkyl group in the formula (I) include those exemplified above.

[0079] Examples of the linear or branched alkoxy group include an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, an n-pentyloxy group, an isopentyloxy group, an n-hexyloxy group, a 2-methylpentyloxy group, an n-heptyloxy group, a 2-methylhexyloxy group, a 2-ethylhexyloxy group, an n-octyloxy group, and an isooctyloxy group; １ ~R４ Examples of such a monovalent group include a linear or branched alkyl group having an oxygen atom bonded thereto.

[0080] Examples of the cyclic alkoxy group include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group. １ ~R ４ Examples of such a monovalent group include a cyclic alkyl group having an oxygen atom bonded thereto.

[0081] R １ ~R ４ When the alkyl group or alkoxy group in the formula (I) has a substituent, examples of the substituent include a hydroxy group, a halogen atom, an alkoxy group, an alkenyl group, an alkenyloxy group, an aryl group, a heteroaryl group, an aryloxy group, a heteroaryloxy group, an alkylsilyl group, an alkylsilyloxy group, and the like. These substituents are the same as the substituents when the aliphatic hydrocarbon group described above has a substituent.

[0082] R １ ~R ４ The number of substituents that the alkyl group or alkoxy group has in the formula (I) is not particularly limited, and may be one or more, or all hydrogen atoms may be substituted with substituents. The alkyl group or alkoxy group having a substituent preferably has the number of carbon atoms, including the number of carbon atoms of the substituent, within the above-mentioned range.

[0083] R １ ~R ４ When the alkyl group or alkoxy group in has two or more substituents, these substituents may be the same or different from one another. That is, the two or more substituents may all be the same, all be different, or only some may be the same.

[0084] The bonding position of the substituent in the alkyl group or alkoxy group is not particularly limited. For example, in the case of an alkyl group, the bonding position is preferably the terminal part (the carbon atom at the end of the alkyl group opposite to the carbon atom bonded to the ethylene group).

[0085] R having a substituent１ ~R ４ Examples of the alkyl group having a substituent include a hydroxyalkyl group, a haloalkyl group, an alkoxyalkyl group, an arylalkyl group, a heteroarylalkyl group, an aryloxyalkyl group, a heteroaryloxyalkyl group, an alkylsilylalkyl group, and an alkylsilyloxyalkyl group. １ ~R ４ When has a substituent, the hydrogen atom is similarly substituted with the substituent.

[0086] In the structural unit (1a), R １ ~R ４ At least one of, particularly preferably R １ ~R ４ Preferably, one of R is an alkyl group having 2 to 8 carbon atoms, and from the viewpoint of decomposability, a smaller number of carbon atoms is preferable, specifically, an alkyl group having 2 carbon atoms is particularly preferable, and from the viewpoint of adhesion, a larger number of carbon atoms is preferable, specifically, an alkyl group having 8 carbon atoms is particularly preferable. １ ~R ４ When one of the groups is an alkyl group having 2 to 8 carbon atoms, the remaining group is preferably a hydrogen atom.

[0087] In this embodiment, the aliphatic polycarbonate A may have only one type of structural unit or two or more types, and when there are two or more types, the combination and ratio can be appropriately selected depending on the purpose. For example, when the aliphatic polycarbonate A has the structural unit (1a), the aliphatic polycarbonate A may or may not have a structural unit other than the structural unit (1a). The structural unit (1a) that the aliphatic polycarbonate A has may be only one type or two or more types, and the structural unit other than the structural unit (1a) may be only one type or two or more types.

[0088] In the aliphatic polycarbonate A of the present embodiment, the proportion of the structural unit (1a) relative to the total amount of structural units is preferably 90 mol% or more, more preferably 95 mol% or more, even more preferably 97 mol% or more, particularly preferably 99 mol% or more, and may be 100 mol%.

[0089] Specifically, the aliphatic polycarbonate A in this embodiment is preferably polybutylene carbonate, a polybutylene carbonate derivative, polydecylene carbonate, or a polydecylene carbonate derivative. The sintering binder B using the aliphatic polycarbonate A is more likely to satisfy the above-mentioned physical properties, particularly the thermal decomposition temperature and adhesive strength.

[0090] (1-2) Method for Producing Aliphatic Polycarbonate The aliphatic polycarbonate A used in this embodiment is, for example, a polycarbonate produced by oxidizing carbon dioxide (CO ２ ) and a monomer that polymerizes to form an aliphatic group in the main chain, in the presence of a metal catalyst, while controlling the water content to a predetermined level or less, as necessary. For example, an aliphatic polycarbonate A having a structural unit (1a) can be produced by a manufacturing method that includes a step of polymerizing carbon dioxide and a compound represented by the following general formula (1b) (an alkylene oxide (epoxide) or a derivative thereof, hereinafter sometimes abbreviated as "compound (1b)") in the presence of a metal catalyst, while controlling the water content to a predetermined level or less, as necessary, as shown below (see, for example, WO 2011 / 142259). In this specification, unless otherwise specified, the term "monomer" refers to a compound that polymerizes with carbon dioxide in such a way that the main chain is formed of an aliphatic group. Furthermore, the term "derivative" refers to a compound in which one or more hydrogen atoms of the original compound are substituted with a group (substituent) other than a hydrogen atom, and the "substituent" here refers to the R １ ~R ４ When the group has a substituent, the substituents are the same as those of the group.

[0091] (In the formula, R １ , R ２ , R３ and R ４ is the same as above; and n is an integer of 2 or more.

[0092] In the formula, R １ ~R ４ represents R in the general formula (1a) described above. １ ~R ４ Furthermore, n is an integer of 2 or more, and represents the number of structural units (1a) in the aliphatic polycarbonate A.

[0093] Preferred examples of compound (1b) include 1-butene oxide, 2-butene oxide, 1,2-butylene oxide, isobutylene oxide, 1-pentene oxide, 2-pentene oxide, 1-hexene oxide, 1-octene oxide, 1,2-decylene oxide, etc. Among these, compound (1b) is more preferably 1,2-butylene oxide, a derivative of 1,2-butylene oxide, 1,2-decylene oxide, or a derivative of 1,2-decylene oxide.

[0094] The monomer used in the polymerization reaction step (e.g., compound (1b) and a monomer other than compound (1b)) may be one type or two or more types. When two or more types are used, the combination and ratio thereof may be appropriately adjusted depending on the purpose.

[0095] Examples of metal catalysts used in the polymerization reaction step include metal salen complex catalysts, composite metal cyanide complex catalysts (DMC catalysts), organometallic catalysts, etc. Among these, metal salen complex catalysts or DMC catalysts are preferred from the viewpoint of exhibiting high polymerization activity. As the metal salen complex catalyst, cobalt salen complex is more preferred, and as the DMC catalyst, Zn ３ (Cо[CN] ６ ) ２ The metal catalyst may be used alone or in combination of two or more kinds.

[0096] The amount of metal catalyst used during the polymerization reaction is preferably 0.001 to 10 parts by mass, and particularly preferably 0.01 to 3 parts by mass, per 100 parts by mass of the monomer used, which allows the polymerization reaction to proceed more easily.

[0097] In the polymerization reaction step, it is also preferable to use a co-catalyst in combination with the metal catalyst. Examples of the co-catalyst include bis(triphenylphosphoranylidene)ammonium chloride, 4-dimethylaminopyridine, tetrabutylammonium chloride, tetrabutylammonium bromide, triphenylphosphine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 1,4-diazabicyclo[2.2.2]octane. One type of co-catalyst may be used alone, or two or more types may be used in combination.

[0098] The amount of the co-catalyst used in the polymerization reaction is preferably 0.001 to 20 parts by mass, and particularly preferably 0.01 to 14 parts by mass, per 100 parts by mass of the monomer used, which allows the polymerization reaction to proceed more easily.

[0099] The method for carrying out the polymerization reaction is not particularly limited as long as the target product can be obtained. For example, an autoclave may be charged with the above-mentioned monomer, metal catalyst, co-catalyst, and, if necessary, a solvent, and then the resulting mixture is mixed with carbon dioxide under pressure to cause the reaction.

[0100] The solvent used in the polymerization reaction as needed is not particularly limited, but is preferably an organic solvent. Examples of the organic solvent include aliphatic hydrocarbons such as pentane, hexane, octane, decane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as chloromethane, dichloromethane, chloroform, carbon tetrachloride, 1,1-dichloroethane, chlorobenzene, and bromobenzene; carboxylic acid esters such as ethyl acetate, propyl acetate, butyl acetate, and isobutyl acetate; carbonate esters such as dimethyl carbonate, diethyl carbonate, propylene carbonate, and 1,2-butylene carbonate; and lactams such as N-methylpyrrolidone.

[0101] The amount of the solvent used is preferably 50 to 10,000 parts by mass per 100 parts by mass of the monomer used, since this facilitates the polymerization reaction.

[0102] The pressure at which carbon dioxide is injected in the polymerization reaction is not particularly limited, but is preferably 0.1 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 0.1 to 5 MPa. When the pressure at which carbon dioxide is injected is equal to or greater than the above-mentioned lower limit, the polymerization reaction proceeds more easily. Furthermore, when the pressure at which carbon dioxide is injected is equal to or less than the above-mentioned upper limit, excessive use of carbon dioxide is suppressed, improving economic efficiency.

[0103] During the polymerization reaction, it is preferable to keep the amount of water in the reaction system at 5 mol % or less based on the amount (mol) of the metal catalyst used.

[0104] The reaction temperature during the polymerization reaction is not particularly limited, but is preferably 20°C or higher, and more preferably 40°C or higher. Furthermore, the reaction temperature during the polymerization reaction is preferably 100°C or lower, and more preferably 80°C or lower. By keeping the reaction temperature at or above the lower limit, the polymerization reaction is completed in a shorter time. By keeping the reaction temperature at or below the upper limit, side reactions are suppressed, and the yield of the aliphatic polycarbonate is improved.

[0105] The reaction time for the polymerization reaction may be appropriately adjusted depending on the reaction temperature, but is preferably 2 to 40 hours.

[0106] After the polymerization reaction is completed, known post-treatment procedures may be carried out as necessary, and the target aliphatic polycarbonate A may then be isolated by a known method. The resulting aliphatic polycarbonate A may be purified as necessary.

[0107] Carbon dioxide is a substance that causes global warming, but at the same time, it is emitted daily in various industrial sectors, and there is a need to reduce emissions on a global scale. In contrast, the above-mentioned production method uses carbon dioxide as a raw material, so it can fix carbon dioxide and is therefore excellent in terms of expanding the options for carbon resources.

[0108] The aliphatic polycarbonate A contained in the sintering binder B according to this embodiment may be one type or two or more types. When two or more types are used, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0109] (2) Other Components In addition to the aliphatic polycarbonate A, the binder B for sintering according to this embodiment may contain various additives, such as an acid / base generator that accelerates the decomposition of the aliphatic polycarbonate A, a sensitizer, an adhesion promoter, etc., as long as the desired low-temperature decomposition property, adhesion, and sintering performance are not impaired.

[0110] 2. Uses The sintering binder B according to this embodiment can be used for sintering various metals and ceramics, and is preferably used for sintering metal oxide precursors (production of metal oxide sintered bodies). As described above, the term "metal oxide precursor" is a general term for substances that can become metal oxides when sintered in an oxygen atmosphere. Preferred examples of the metal oxide precursor include simple metals or alloys such as gold, silver, copper, aluminum, nickel, and tungsten; metal carbides such as silicon carbide; and metal nitrides such as silicon nitride and aluminum nitride.

[0111] In addition, the firing binder B according to this embodiment is also preferably used for forming a metal oxide precursor sintered body or a metal oxide precursor sintered foil on a substrate, or for forming a metal oxide sintered body or a metal oxide sintered foil on a substrate. As the substrate, a metal oxide precursor member (including the concept of a metal oxide precursor foil) is preferably used, and a metal simple substance member such as copper or aluminum is particularly preferred.

[0112] As described above, the sintering binder B according to this embodiment has high adhesion to metals, and therefore can easily and efficiently manufacture a composite of a metal member and a metal sintered body or a metal oxide sintered body with high accuracy. Examples of such composites include a composite of an aluminum member and an aluminum sintered body, a composite of a copper member and an alumina sintered body, a composite of an alumina member and a copper sintered body, and a composite of an alumina member and a tungsten sintered body.

[0113] A composite of an aluminum member and an aluminum sintered body can be suitably used, for example, as an electrode material for an aluminum electrolytic capacitor. In this case, the aluminum member is preferably an aluminum base material, particularly an aluminum base material made of aluminum foil (aluminum foil base material). The electrode material for an aluminum electrolytic capacitor is preferably an aluminum base material having an aluminum sintered body formed on one or both sides thereof.

[0114] The composite of the copper member and the alumina sintered body can be suitably used, for example, as a power module substrate. In this case, the copper member is preferably a copper base material, particularly a copper base material (copper foil base material) made of copper foil. The power module substrate is preferably a copper base material having an alumina sintered body formed on one or both sides thereof.

[0115] The composite of the alumina member and the copper sintered body can be suitably used, for example, as a power semiconductor member. In this case, the alumina member is preferably an alumina base material. The power semiconductor member is preferably an alumina base material having a copper sintered body formed on one or both sides thereof.

[0116] [Paste composition for firing] The paste composition for firing according to this embodiment (hereinafter sometimes referred to as "paste composition C for firing") contains a metal oxide precursor powder and the binder for firing B according to the embodiment described above, and preferably further contains a solvent.

[0117] Preferred examples of the metal oxide precursor powder include gold powder, silver powder, copper powder, aluminum powder, nickel powder, tungsten powder, silicon carbide powder, silicon nitride powder, aluminum nitride powder, etc. The metal powder may be a powder made of the metal itself, or a powder made of an alloy of the metal.

[0118] The average particle size of the metal oxide precursor powder is preferably 0.3 to 15 μm, particularly preferably 0.8 to 10 μm, and even more preferably 1 to 6 μm. This allows the metal oxide precursor sintered body / metal oxide sintered body to exhibit the desired functions well. In this specification, the average particle size of the metal oxide precursor powder can be measured by measuring the powder itself using a laser diffraction / scattering method, or by observing the cross section of the sintered body with a scanning electron microscope.

[0119] The content of the metal oxide precursor powder in the firing paste composition C is preferably 30 to 79.5 mass %, and particularly preferably 40 to 70 mass %, which allows the metal oxide precursor sintered body to exhibit the desired functions and ensures adhesion to the substrate.

[0120] The content of the firing binder B in the firing paste composition C is preferably 0.5 to 35 mass %, and particularly preferably 0.75 to 10 mass %, which allows the paste composition C to have excellent adhesion to the substrate and to exhibit the desired functions as a metal oxide precursor sintered body.

[0121] The solvent that can be contained in the firing paste composition C is not particularly limited, and examples thereof include ketones such as methyl ethyl ketone (2-butanone), methyl isobutyl ketone, cyclohexanone, acetylacetone, and isophorone; ethers such as dioxane and tetrahydrofuran; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated carbons such as dichloromethane and dichloroethane; esters such as methyl acetate, ethyl acetate, and butyl acetate; isopropanol, butanol, cyclohexane, and the like. Examples of the solvent include alcohols such as diisopropyl ether and 1-decanol; cellosolves such as methyl cellosolve and ethyl cellosolve; glycol ethers or glycol ether acetates such as butyl carbitol, propylene glycol monomethyl ether acetate, butyl carbitol acetate (diethylene glycol monobutyl ether acetate), and ethyl carbitol acetate (diethylene glycol monoethyl ether acetate); cellosolve acetates; sulfoxides such as dimethyl sulfoxide; amides such as dimethylformamide and dimethylacetamide; etc. These solvents may be used alone or in combination of two or more.

[0122] The content of the solvent in the firing paste composition C is preferably 20 to 69.5% by mass, and particularly preferably 30 to 55% by mass, which provides excellent coatability and moldability and ensures adhesion to the substrate.

[0123] The firing paste composition C may contain other components such as a sintering aid and a surfactant, as needed. The sintering aid is not particularly limited, and for example, fluorides such as aluminum fluoride, potassium fluoride, and calcium fluoride can be used. The surfactant is not particularly limited, and for example, betaine-based, sulfobetaine-based, alkylbetaine-based, and other surfactants can be used.

[0124] To prepare the firing paste composition C, the metal oxide precursor powder, the firing binder B, a solvent, and, if necessary, other components may be mixed and kneaded.

[0125] It is preferable to adjust the amount of solvent in the firing paste composition C to a concentration and viscosity suitable for application and molding. For example, when applying, it is preferable to dilute the firing paste composition C with a solvent so that the solid content concentration is 10 to 60 mass %.

[0126] [Sintered body] A sintered body according to one embodiment of the present invention is obtained by firing the firing paste composition C according to the above-described embodiment. This sintered body may be a metal oxide precursor sintered body or a metal oxide sintered body.

[0127] The shape of the sintered body according to this embodiment is not particularly limited, and can be a desired shape such as a layer, a plate, a block, etc. Furthermore, the sintered body according to this embodiment has high adhesion to metals due to the use of the firing paste composition C containing the firing binder B, so it is preferable to form the sintered body in a form bonded to a metal member.

[0128] When the sintered body according to this embodiment is formed in a layer, the thickness of the sintered body is, for example, preferably 10 to 500 μm, particularly preferably 20 to 400 μm, and further preferably 30 to 300 μm.

[0129] To produce a sintered body according to the embodiment, first, the firing paste composition C is formed into a desired shape. For example, when producing a layered sintered body, it is preferable to apply the firing paste composition C to a desired object, such as a metal member. Furthermore, when producing a plate-shaped, block-shaped, or other sintered body, it is preferable to fill the firing paste composition C into a desired mold and mold it.

[0130] In either case, it is preferable to appropriately dry the firing paste composition C after coating and molding it. Examples of drying conditions include drying at a temperature of 20 to 300° C. for 1 to 30 minutes.

[0131] Examples of methods for applying the firing paste composition C include bar coating, knife coating, doctor blade, screen printing, roll coating, blade coating, die coating, gravure coating, curtain coating, and spray coating.

[0132] When the firing paste composition C is applied to a metal member, the layer of the firing paste composition C exhibits excellent adhesion to the metal member due to the action of the aliphatic polycarbonate A contained in the firing paste composition C. This results in very good handleability and enables the production of high-precision products with a good yield.

[0133] Next, the firing paste composition C formed into a desired shape is fired to obtain a sintered body. The firing method is not particularly limited, and examples thereof include a method of heating in a heating furnace.

[0134] The firing temperature is preferably a temperature between half the melting point (absolute temperature) of the material to be fired and below the melting point. This causes the firing binder B to thermally decompose, and the metal oxide precursor powder is baked to obtain a sintered body. In this embodiment, since the firing paste composition C uses the firing binder B containing the aliphatic polycarbonate A, which has excellent low-temperature decomposition properties, firing can be performed at a relatively low temperature as described above. Furthermore, when laminated on a metal member, the above-mentioned lower limit of the firing temperature results in better adhesion to the metal member. Furthermore, the above-mentioned upper limit of the firing temperature makes it easier to obtain a sintered body with a good shape.

[0135] The firing time is preferably 0.1 to 48 hours, particularly preferably 1 to 36 hours, and even more preferably 5 to 24 hours, which allows the metal oxide precursor powder to be sufficiently sintered and a good sintered body to be obtained.

[0136] The sintering atmosphere is preferably an oxygen-free atmosphere. The oxygen-free atmosphere may be an atmosphere of a single gas, an atmosphere of a mixed gas, or a vacuum atmosphere. Examples of the single gas include nitrogen, argon, helium, ammonia, and formaldehyde. Examples of the mixed gas include forming gas, such as nitrogen gas mixed with 5% or less by volume of hydrogen.

[0137] When forming a metal oxide precursor sintered body, an oxygen-free atmosphere, particularly a nitrogen atmosphere, is preferred from the viewpoint of preventing oxidation of the metal oxide precursor powder. The aliphatic polycarbonate A contained in the firing paste composition C exhibits low-temperature decomposition properties even in an oxygen-free atmosphere. Therefore, the sintered body according to the embodiment can be fired at a relatively low temperature while preventing oxidation of the metal.

[0138] From the viewpoint of preventing oxidation of the metal, the oxygen concentration in the oxygen-free atmosphere is preferably 5% by volume or less, more preferably 3% by volume or less, particularly preferably 0.5% by volume or less, and even more preferably 0.1% by volume or less.

[0139] The pressure condition of the sintering atmosphere may be any of atmospheric pressure, reduced pressure, and increased pressure.

[0140] As described above, when aliphatic polycarbonate A is decomposed by firing, the main product is cyclic carbonate. Therefore, carbon dioxide is not substantially emitted during firing, and no solid carbon compound derived from the binder remains in the sintered body according to the embodiment. Furthermore, the cyclic carbonate product can be reused as a solvent, an electrolyte for lithium-ion batteries, or the like.

[0141] [Sintered Composite] A sintered composite according to one embodiment of the present invention may be a sintered metal body formed on a substrate, or a sintered metal oxide body formed on a substrate. A preferred example of the substrate is a metal member, which may be a metal foil. The metal sintered metal may be a sintered metal foil, or the metal oxide sintered metal may be a sintered metal oxide foil.

[0142] Examples of the sintered composite according to this embodiment include a composite of an aluminum member (aluminum foil substrate) and an aluminum sintered body, a composite of a copper member (copper foil substrate) and an alumina sintered body, a composite of an alumina member and a copper sintered body, etc. The uses of these are as described above.

[0143] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0144] In this specification, when it is stated that "X to Y" (X and Y are any numbers), it means "X or more and Y or less" unless otherwise specified, and also means "preferably greater than X" or "preferably smaller than Y". Furthermore, when it is stated that "X or more" (X is any number), it means "preferably greater than X" unless otherwise specified, and when it is stated that "Y or less" (Y is any number), it also means "preferably smaller than Y" unless otherwise specified.

[0145] The present invention will be described in more detail below by showing examples, but the present invention is not limited to the following examples.

[0146] [Production Example 1] (Synthesis of Polymerization Catalyst-1) (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanecobalt(II) and pentafluorobenzoic acid were weighed out to a molar ratio of 1:1.1 and placed in a flask, to which was added dehydrated toluene. The flask was shielded from light with aluminum foil, and the reaction was carried out at room temperature for 20 hours. The chemical reaction formula is as follows: After completion of the reaction, the solvent was removed under reduced pressure, and the mixture was washed several times with an excess amount of hexane. This was then vacuum dried at room temperature to obtain a cobalt salen complex.

[0147]

[0148] [Production Example 2] (Synthesis of Polymerization Catalyst-2) Potassium hexacyanocobaltate (III) (K ３[Co(CN) ６ 1.33 g of zinc chloride solution (ZnCl) was dissolved in 20 mL of deionized water and heated to 50°C with vigorous stirring. ２ The resulting white suspension was dropped into a solution (11.42 g of t-butyl alcohol dissolved in a mixed solution of 60 mL of deionized water and 30 mL of t-butyl alcohol) over 45 minutes. The mixture was then vigorously stirred for 60 minutes. The resulting white suspension was centrifuged at 5,000 rpm to isolate a white solid. The isolated white solid was resuspended in a solution of t-butyl alcohol and deionized water (volume ratio of t-butyl alcohol:deionized water = 5:5) with vigorous stirring for 30 minutes. Subsequently, the isolation and resuspension by centrifugation was repeated several times while gradually increasing the amount of t-butyl alcohol relative to water (volume ratio of t-butyl alcohol:deionized water was changed from 6:4 to 7:3, 8:2, and 9:1). Finally, the white solid was resuspended in t-butyl alcohol and then isolated by centrifugation. The DMC catalyst, Zn, was then dried under vacuum at 50°C until a predetermined mass was obtained. ３ (Cо[CN] ６ ) ２ obtained.

[0149] Example 1 100 parts by mass of 1,2-butylene oxide as a raw material monomer, 0.6 parts by mass of the cobalt salen complex obtained in Production Example 1 as a catalyst, and 0.4 parts by mass of bis(triphenylphosphoranylidene)ammonium chloride as a co-catalyst were dissolved in 100 parts by mass of ethyl acetate to obtain a mixed liquid (solid content concentration: 50% by mass).

[0150] The interior of a 4 L autoclave equipped with a stirrer, a gas inlet tube, and a thermometer was previously purged with a nitrogen atmosphere, and the above mixture was then charged. Next, while stirring the resulting mixture, carbon dioxide gas was added until the reaction system reached 2 MPa. The temperature was then raised to 30°C, and the polymerization reaction was carried out for 18 hours while replenishment of carbon dioxide consumed by the reaction was performed. After completion of the reaction, the autoclave was cooled and depressurized, and the contents were diluted with ethyl acetate, followed by reprecipitation purification to remove the catalyst.

[0151] The resulting ethyl acetate solution was dried to obtain the resulting aliphatic polycarbonate. This aliphatic polycarbonate was polybutylene carbonate (PBC). This polybutylene carbonate (PBC) was used as the sintering binder in this example. Note that the number of carbon atoms in the hydrocarbon group of the side chain in the polybutylene carbonate was 2.

[0152] Example 2 100 parts by mass of 1,2-butylene oxide as a raw material monomer and 0.5 parts by mass of the DMC catalyst obtained in Production Example 2 as a catalyst were dissolved in 100 parts by mass of ethyl acetate to obtain a mixed liquid (solid content concentration: 50% by mass). Using the obtained mixed liquid, polybutylene carbonate (PBC) was prepared in the same manner as in Example 1. This polybutylene carbonate (PBC) was used as the firing binder in this example.

[0153] Example 3 100 parts by mass of 1,2-hexene oxide as a raw material monomer and 0.1 parts by mass of the cobalt salen complex as a catalyst obtained in Production Example 1 were dissolved in 100 parts by mass of toluene to obtain a mixed liquid (solid content concentration: 50% by mass).

[0154] The interior of a 4 L autoclave equipped with a stirrer, a gas inlet tube, and a thermometer was previously purged with a nitrogen atmosphere, and the above mixture was then charged. Next, while stirring the resulting mixture, carbon dioxide gas was added until the reaction system reached 2 MPa. The temperature was then raised to 30°C, and the polymerization reaction was carried out for 18 hours while replenishment of carbon dioxide consumed by the reaction was performed. After completion of the reaction, the autoclave was cooled and depressurized, and the contents were diluted with ethyl acetate, followed by reprecipitation purification to remove the catalyst.

[0155] The resulting toluene solution was dried to obtain the resulting aliphatic polycarbonate. This aliphatic polycarbonate was polyhexene carbonate (PHC). This polyhexene carbonate (PHC) was used as the sintering binder in this example. Note that the number of carbon atoms in the hydrocarbon group of the side chain in polyhexene carbonate was 4.

[0156] Comparative Example 1 An aliphatic polycarbonate was prepared in the same manner as in Example 1, except that propylene oxide was used instead of 1,2-butylene oxide as the raw material monomer. This aliphatic polycarbonate was polypropylene carbonate (PPC). This polypropylene carbonate (PPC) was used as the binder for firing in this example. Note that the number of carbon atoms in the hydrocarbon group of the side chain in the polypropylene carbonate was 1.

[0157] Comparative Example 2 100 parts by mass of 1,2-decylene oxide as a raw material monomer and 0.1 parts by mass of the DMC catalyst obtained in Production Example 2 were dissolved in 100 parts by mass of ethyl acetate to obtain a mixed liquid (solid concentration: 50% by mass).

[0158] The interior of a 4 L autoclave equipped with a stirrer, a gas inlet tube, and a thermometer was previously purged with a nitrogen atmosphere, and the mixture was then charged. Next, while stirring the resulting mixture, carbon dioxide gas was added until the reaction system reached 4 MPa. The temperature was then raised to 60°C, and the polymerization reaction was carried out for 18 hours while replenishment of carbon dioxide consumed by the reaction was continued. After completion of the reaction, the autoclave was cooled and depressurized, and the contents were diluted with ethyl acetate, followed by reprecipitation purification to remove the catalyst.

[0159] The resulting ethyl acetate solution was dried to obtain the resulting aliphatic polycarbonate. This aliphatic polycarbonate was polydecylene carbonate (PDC). This polydecylene carbonate (PDC) was used as the binder for firing in this example. Note that the number of carbon atoms in the hydrocarbon group of the side chain in polydecylene carbonate was 8.

[0160] Comparative Example 3 100 parts by mass of 1,2-hexene oxide as a raw material monomer and 0.1 parts by mass of the DMC catalyst obtained in Production Example 2 as a catalyst were dissolved in 100 parts by mass of toluene to obtain a mixed liquid (solid content concentration: 50% by mass). Using the obtained mixed liquid, polyhexene carbonate (PHC) was prepared in the same manner as in Example 3. This polyhexene carbonate (PHC) was used as the firing binder in this example.

[0161] [Test Example 1] (Measurement of Molecular Weight) The weight average molecular weight (Mw) and number average molecular weight (Mn) of the binders for firing in the Examples and Comparative Examples were measured under the following conditions using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8320") and were measured in terms of standard polystyrene. In addition, the molecular weight distribution (PDI = Mw / Mn) was calculated from the obtained weight average molecular weight (Mw) and number average molecular weight (Mn). The results are shown in Table 1.

[0162] <GPC measurement conditions> Column: "TSK guard column Super H-H", "TSK gel Super HM-H", "TSK gel Super HM-H", and "TSK gel Super H2000" (all manufactured by Tosoh Corporation) connected in sequence Column temperature: 40°C Developing solvent: tetrahydrofuran (binder concentration 1% by mass) Injection volume: 20 μl Flow rate: 0.6 mL / min Detector: differential refractometer Standard sample: polystyrene

[0163] [Test Example 2] (Measurement of Glass Transition Temperature) The glass transition temperature (Tg) of the sintering binders of the Examples and Comparative Examples was determined by differential scanning calorimetry (DSC) using a "DSC Q2000" product manufactured by TA Instruments Japan Co., Ltd. Specifically, an aluminum pan was used as a container, and the temperature was increased from -70°C to 150°C at 10.0°C / min under a nitrogen atmosphere, held for 5 minutes, then decreased to -70°C at 10.0°C / min, held for 5 minutes, and then increased to 150°C at 10.0°C / min. The results are shown in Table 1.

[0164] [Test Example 3] (Measurement of Thermal Decomposition Temperature) The thermal decomposition temperatures of the firing binders of the Examples and Comparative Examples were measured under the following conditions using a thermogravimetric analyzer (TGA; Shimadzu Corporation, product name "DTG-60"). The 5% thermal decomposition temperature in nitrogen (Td5), the 10% thermal decomposition temperature in nitrogen (Td10), the 50% thermal decomposition temperature in nitrogen (Td50), the 99% thermal decomposition temperature in nitrogen (Td99), the 5% thermal decomposition temperature in air (Td5), the 10% thermal decomposition temperature in air (Td10), the 50% thermal decomposition temperature in air (Td50), and the 99% thermal decomposition temperature in air (Td99) were obtained. The results are shown in Table 1.

[0165] <TGA measurement conditions> Heating rate: 10°C / min Sample amount: 20 to 30 mg Measurement temperature range: 40°C to 550°C Measurement atmosphere: nitrogen / air Measurement pressure: atmospheric pressure The oxygen concentration in the nitrogen atmosphere was 0.1% or less.

[0166] [Test Example 4] (Evaluation of Residual Carbon Compounds - 1) After TGA measurement under a nitrogen atmosphere in Test Example 3, the aluminum pan was visually inspected to confirm the presence or absence of remaining carbon compounds. The remaining carbon compounds were then evaluated based on the following criteria. The results are shown in Table 2. A: The bottom of the aluminum pan was exposed and the metallic luster could be confirmed (= no remaining components) F: Combustion ash remained and the bottom of the aluminum pan was not visible

[0167] Test Example 5 (Evaluation of Residual Carbon Compounds -2) The firing binders of the Examples and Comparative Examples were sandwiched between two glass plates (AGC Inc., product name "Float Plate Glass FL3," 150 mm length x 70 mm width x 3 mm thickness) and heat-pressed for 5 minutes using a screw-type heater press (NPA Systems Corporation, product name "N4046-00") at 150°C and 200 N to form a binder layer with a thickness of 100 μm between the glass plates, and then cooled at room temperature. Next, the laminate was placed on a hot plate at 300°C and heated for 2 minutes. Thereafter, the state of the binder between the glass plates was confirmed. Then, the residual carbon compounds were evaluated based on the following criteria. The results are shown in Table 2. Note that "Evaluation of Residual Carbon Compounds -2" in Test Example 5 is an evaluation of residual carbon compounds under stricter conditions than "Evaluation of Residual Carbon Compounds -1" in Test Example 4. A... The binder decomposed, and the distance between the glass plates became less than 1 μm. F: The binder remained without being decomposed, or decomposed products remained between the glass plates, and the distance between the glass plates was 1 μm or more.

[0168] [Test Example 6] (Measurement of Ether Bond Ratio) The binders for firing of the Examples and Comparative Examples were dissolved in deuterated chloroform containing tetramethylsilane (TMS) as an internal standard so that the concentration was 3 mass %. １ The sample was subjected to H-NMR measurement under the following conditions: １ H-NMR measurement was carried out, and the content of ether bonds relative to the total amount (100 mol%) of carbonate bonds and ether bonds in each polymer was calculated. Specifically, the integral value from 4.7 to 5.2 ppm was calculated as the content of carbonate bonds. １ H, the integral value of 3.2 to 3.9 ppm is that of the ether bond ３ The H was calculated based on the following formula. The results are shown in Table 2. Ether bond content (%) = ether bond / 3 / (carbonate bond+ether bond / 3)

[0169] < １ H-NMR measurement conditions> Apparatus: Bruker, product name "AV-500" １H-NMR resonance frequency: 500 MHz Probe: 5 mmφ solution probe Deuterated solvent: deuterated chloroform (CDCl3) Internal standard substance: tetramethylsilane (TMS) Sample amount: 20 to 50 mg Measurement temperature: 25°C Number of accumulations: 16

[0170] [Test Example 7] (Adhesion Measurement-1) The sintering binders of Example and Comparative Example 1 were dissolved in toluene to prepare coating solutions with a solid content concentration of 30% by mass. The sintering binders of Comparative Examples 2 to 4 were dissolved in ethyl acetate to prepare coating solutions with a solid content concentration of 30% by mass.

[0171] The coating solution was applied to an aluminum plate (A1050P, thickness 0.5 mm) as an adherend using an applicator, and then heated and dried at 100° C. for 1 minute. In this way, a binder layer for firing having a thickness of 20 μm and a width of 25 mm was formed on the aluminum plate.

[0172] The adhesive side of a 25 mm wide polyester adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 31B") was attached to the binder layer for firing on the aluminum plate, and a 2 kg roller was rolled back and forth once to make it adhere tightly. Thereafter, the tape was left to stand for 30 minutes in an environment of 23°C and 50% RH, and this was used as a sample.

[0173] The sample was fixed to a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon"), and the firing binder layer was peeled from the aluminum plate at a 180° direction at a peel rate of 300 mm / min in accordance with JIS Z0237:2000 under an environment of 23°C and 50% RH (relative humidity). The value measured at this time (N / 25 mm) was taken as the adhesion strength. The results are shown in Table 2.

[0174] [Test Example 8] (Adhesion Measurement-2) For Examples 1 and 2 and Comparative Example 1, 95 parts by mass of alumina powder (manufactured by Sumika Alchem ​​Co., Ltd., product name "Advanced Alumina AA-2", median diameter 2.2 μm (measured by laser diffraction / scattering method)), 5 parts by mass of the firing binder of Examples 1 and 2 and Comparative Example 1, and 54 parts by mass of propylene glycol monomethyl ether acetate (PGMEA) as a solvent were mixed for 24 hours using zirconia balls (manufactured by AS ONE Corporation, product name "ZB-5") to prepare a coating liquid of a firing paste composition.

[0175] For Comparative Examples 2 to 4, 95 parts by mass of alumina powder (manufactured by Sumika Alchem ​​Co., Ltd., product name "Advanced Alumina AA-2", median diameter 2.2 μm (measured by laser diffraction / scattering method)), 5 parts by mass of the firing binder of Comparative Examples 2 to 4, and 43 parts by mass of a mixed solvent of toluene:n-butanol = 80:20 (mass ratio) as a solvent were mixed for 24 hours using zirconia balls (manufactured by AS ONE Corporation, product name "ZB-5") to prepare a coating liquid of a firing paste composition.

[0176] In Examples 1 and 2 and Comparative Example 1, the coating liquid was applied to aluminum (Al) foil (thickness: 20 μm) and copper (Cu) foil (thickness: 11 μm) as metal foils using an applicator, and then heated and dried for 5 minutes at 120° C. In this way, a firing paste composition layer having a thickness of 70 μm and a width of 25 mm was formed on the metal foil.

[0177] For Comparative Examples 2 to 4, the coating liquid was applied to aluminum foil (thickness: 20 μm) and copper foil (thickness: 11 μm) as the metal foil using an applicator, and then heated and dried for 5 minutes at 100° C. In this way, a firing paste composition layer having a thickness of 70 μm and a width of 25 mm was formed on the metal foil.

[0178] The adhesive surface of an adhesive tape (product name "PET50(A)PL Thin 8K" manufactured by Lintec Corporation) was attached to the firing paste composition layer on the metal foil. This laminate was formed into a size of 25 mm wide x 100 mm long, attached to a glass plate with double-sided tape, and left to stand for 12 hours in an environment of 23°C and 50% RH to prepare a sample.

[0179] The sample was fixed to a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon"), and the metal foil was peeled from the firing paste composition layer in a 180° direction at a tensile speed of 300 mm / min in accordance with JIS Z0237:2000 under an environment of 23°C and 50% RH (relative humidity). The value measured at this time (mN / 25 mm) was taken as the adhesion strength. The results are shown in Table 2.

[0180] In addition, since the firing paste composition layer of the example did not undergo cohesive failure when peeled off, it can be said that the firing binder of the example has high adhesion to the alumina powder (metal oxide precursor powder).

[0181] Test Example 9 (Evaluation of Paste Flexibility) The laminate of aluminum foil and firing paste composition layer produced in Test Example 8 was wrapped around rods with a diameter of 1 inch and 3 inches with the aluminum foil facing inside, and the presence or absence of cracks in the firing paste composition layer was visually determined. Then, paste flexibility was evaluated based on the following criteria. The results are shown in Table 2. A: No cracks occurred when wrapped around the 1-inch rod. F+: Cracks occurred when wrapped around the 1-inch rod, but no cracks occurred when wrapped around the 3-inch rod. F-: Cracks occurred when wrapped around both the 1-inch rod and the 3-inch rod.

[0182] [Test Example 10] (Evaluation of Slurry Processability) The coating liquid (slurry) of the firing paste composition prepared in Test Example 8 was applied to an aluminum foil using an applicator to form a coating film. The condition of this coating film was visually confirmed, and the slurry processability was evaluated based on the following criteria. The results are shown in Table 2. A... The coating film surface is smooth. F... The coating film surface is rough.

[0183] [Test Example 11] (Measurement of Storage Modulus) The firing binders of the Examples and Comparative Examples were formed into cylindrical shapes with a diameter of 8 mm and a thickness of 1 mm, which were used as samples. Using a viscoelasticity measuring device (manufactured by Anton Paar, device name "MCR300") and using parallel plates with a diameter of 8 mm as a measuring jig, the storage modulus (MPa) of the samples at each temperature was measured by a torsional shear method under the following conditions: test start temperature -20°C, test end temperature 150°C, heating rate 3°C / min, shear strain 0.05%, and frequency 1 Hz. From the measurement results, the storage modulus (MPa) at 23°C was obtained. The results are shown in Table 2.

[0184] [Test Example 12] (Tensile Test) The sintering binders of the Examples and Comparative Examples were formed into a rectangular shape measuring 10 mm wide x 30 mm long x 0.5 mm thick, which was used as a sample. The sample was attached to a tensile tester (Shimadzu Corporation, product name "Autograph AG-Xplus") with a chuck distance of 10 mm, and pulled at 23°C and a pulling rate of 200 mm / min until the sample broke. The breaking elongation (%) was measured, and the stress at each elongation was also measured to obtain the maximum stress (MPa). The results are shown in Table 2.

[0185]

[0186]

[0187] As can be seen from Tables 1 and 2, the sintering binders produced in the examples decompose at a relatively low temperature, allowing for sintering at a relatively low temperature. Furthermore, the sintering binders produced in the examples have high adhesion to metal oxide precursor powders and metals. Furthermore, the sintering binders produced in the examples have excellent carbon residue suppression properties even under harsh conditions, and also have excellent slurry processability. Furthermore, the sintering binders produced in the examples have a low glass transition temperature, a small storage modulus at room temperature, a large elongation at break, and a small maximum stress. Furthermore, the paste composition containing the metal oxide precursor powder is flexible, so cracks do not occur even when wrapped around a rod with a small diameter, and therefore, there is a high degree of freedom in designing the shape of the sintered body.

[0188] The sintering binder according to the present invention is suitable for producing, for example, a metal oxide precursor sintered body or a metal oxide sintered body, or a composite of either of these with a metal substrate.

Claims

1. A sintering binder containing an aliphatic polycarbonate having a carbonate structure in the main chain and a hydrocarbon group having 2 to 8 carbon atoms in the side chain, characterized in that the weight-average molecular weight of the aliphatic polycarbonate is 50,000 or more and 170,000 or less.

2. The binder for firing according to claim 1, characterized in that the 50% thermal decomposition temperature in an atmosphere at atmospheric pressure with an oxygen concentration of 5% or less is 255°C or higher and 300°C or lower.

3. The binder for firing according to claim 1, characterized in that the 99% thermal decomposition temperature in an atmosphere of atmospheric pressure and an oxygen concentration of 5% or less is 400°C or less.

4. The sintering binder according to claim 1, characterized in that the adhesion strength measured when the sintering binder layer is peeled off from an aluminum plate having a 20 μm-thick layer formed thereon at a peeling angle of 180° and a peeling rate of 300 mm / min is 0.3 N / 25 mm or more.

5. The binder for firing according to claim 1, wherein the hydrocarbon group having 2 to 8 carbon atoms is a linear hydrocarbon group.

6. The sintering binder according to claim 1, wherein the aliphatic polycarbonate has a structural unit represented by the following general formula (1a): (In the formula, R １ , R ２ , R ３ and R ４ are each independently a hydrogen atom or a hydrocarbon group, and at least one is a hydrocarbon group having 2 to 8 carbon atoms.

7. The sintering binder according to claim 1, which is used to form a sintered body of a metal oxide precursor.

8. The sintering binder according to claim 1, which is used to form a metal oxide sintered body.

9. The sintering binder according to claim 1, which is used to form a sintered foil of a metal oxide precursor on a substrate.

10. The sintering binder according to claim 1, which is used to form a sintered metal oxide foil on a substrate.

11. The binder for firing according to claim 1, characterized in that the storage modulus at 23°C is 1.0 MPa or more and 50 MPa or less.

12. The binder for firing according to claim 1, characterized in that the glass transition temperature (Tg) is -15°C or higher and 25°C or lower.

13. A binder for firing according to claim 1, characterized in that when formed to a thickness of 0.5 mm and a width of 10 mm and stretched at a measurement temperature of 23°C, a measurement length of 10 mm, and a tensile speed of 200 mm / min, the breaking elongation is 100% or more.

14. A binder for firing according to claim 1, characterized in that when formed to a thickness of 0.5 mm and a width of 10 mm and stretched to the breaking elongation at a measurement temperature of 23°C, a measurement length of 10 mm, and a tensile speed of 200 mm / min, the maximum stress is 10 MPa or less.

15. A firing paste composition comprising a metal oxide precursor powder and the firing binder according to any one of claims 1 to 14.

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