JP2023084547A - Acrylic polymer, sintering binder composition, and sintering paste - Google Patents

Abstract

To provide an acrylic polymer (A) that can be blended in a sintering binder composition to improve the strength of a green sheet prepared from a sintering paste comprising the sintering binder composition without impairing the pyrolytic properties of the sintering binder composition.SOLUTION: An acrylic polymer (A) is blended in a sintering binder composition, the acrylic polymer (A) comprising a constitutional unit (a) represented by formula (1). In the formula (1), R1 is a hydrogen atom or a methyl group, and R2 is methylene group, an ethylene group or an ethoxyethylene group.SELECTED DRAWING: None

Description

The present invention relates to an acrylic polymer, a binder composition for firing, and a paste for firing, and more specifically, an acrylic polymer blended in a binder composition for firing, and a binder composition for firing containing the acrylic polymer. and a firing paste containing the firing binder composition.

Regarding a firing binder composition to be blended in a firing paste for producing a sintered body of inorganic powder, Patent Document 1 discloses polyvinyl butyral, a carboxyl group-containing acrylic monomer, and a nitrogen-containing acrylic monomer. and an acrylic polymer synthesized by polymerizing an acrylic monomer containing at least one in an organic solvent in the presence of polyvinyl butyral without reacting with polyvinyl butyral. , is disclosed. A green sheet can be molded from a firing paste containing a firing binder composition and an inorganic powder, and the green sheet is fired to produce a sintered body of the inorganic powder. A sintered body of inorganic powder can be applied to electrodes and conductor wiring in various electronic devices, dielectric layers in laminated capacitors, and the like.

According to the technique described in Patent Document 1, it is possible to utilize the advantages of both the impartation of high strength to the green sheet by polyvinyl butyral and the good thermal decomposability of the acrylic polymer, and a highly stable binder for firing. A composition can be provided.

Japanese Patent No. 5767737

The inventor proceeded with research and development to further improve the strength of the green sheet in order to further improve the handleability of the green sheet while maintaining the thermal decomposability of the binder composition for firing.

An object of the present invention is to increase the strength of a green sheet produced from a firing paste containing a firing binder composition without impairing the thermal decomposability of the firing binder composition by adding it to the firing binder composition. An object of the present invention is to provide an acrylic polymer (A) that can be enhanced, a binder composition for firing containing the acrylic polymer (A), and a paste for firing containing the binder composition for firing.

The acrylic polymer (A) according to the first aspect of the present invention is an acrylic polymer (A) to be blended in the binder composition for firing, and the structural unit (a) represented by formula (1) is have.

In formula (1) above, R ₁ is a hydrogen atom or a methyl group, and R ₂ is a methylene group, an ethylene group or an ethoxyethylene group.

A binder for firing according to one aspect of the present invention contains the acrylic polymer (A).

A firing paste according to an aspect of the present invention contains the firing binder composition and an inorganic powder.

According to the present invention, by blending in the binder composition for firing, the strength of the green sheet produced from the paste for firing containing the binder composition for firing is increased without impairing the thermal decomposability of the binder composition for firing. An acrylic polymer that can be enhanced, a firing binder composition containing the acrylic polymer, and a firing paste containing the firing binder composition can be provided.

An embodiment of the present invention will be described below. It should be noted that the following embodiment is merely one of various embodiments of the present invention, and the present invention can be modified in various ways according to its design.

1. Acrylic Polymer The acrylic polymer (A) according to the present embodiment is blended in the binder composition for firing. The acrylic polymer (A) is synthesized by polymerizing polymerizable monomers containing (meth)acrylic compounds. A (meth)acrylic compound is a compound having a (meth)acryloyl group. In this specification, "(meth)acrylic" means at least one of "acrylic" and "methacrylic", that is, it is a generic concept of "acrylic" and "methacrylic". .

The acrylic polymer (A) has a structural unit (a) represented by formula (1).

In formula (1), _R1 is a hydrogen atom or a methyl group, and _R2 is a methylene group, an ethylene group or an ethoxyethylene group.

According to the present embodiment, by blending the acrylic polymer (A) in the binder composition for firing, the binder composition for firing containing the binder composition for firing can be obtained without impairing the thermal decomposability of the binder composition for firing. The strength of green sheets made from the paste can be increased.

The percentage of the structural unit (a) is preferably 2% by mass or more and 20% by mass or less with respect to the acrylic polymer (A). When the percentage of structural units (a) is 2% by mass or more, the hardness of the green sheet can be particularly increased, and when this percentage is 20% by mass or less, the green sheet can have appropriate flexibility. . Therefore, the strength of the green sheet can be particularly enhanced by the structural unit (a). The percentage of this structural unit (a) is more preferably 2.5% by mass or more, and even more preferably 5% by mass or more. Moreover, the percentage of the structural unit (a) is more preferably 17.5% by mass or less, and even more preferably 15% by mass or less.

The acrylic polymer (A) may have a structural unit (b) represented by formula (2).

In formula (2), R ₃ is a hydrogen atom or a methyl group, and R ₄ is a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms.

The structural unit (b) allows the acrylic polymer (A) to have good properties as a binder such as moldability and thermal decomposability.

The percentage of the structural unit (b) is, for example, 5% by mass or more and 95% by mass or less relative to the acrylic polymer (A). The percentage of this structural unit (b) is more preferably 10% by mass or more, and even more preferably 15% by mass or more. Moreover, the percentage of the structural unit (b) is more preferably 90% by mass or less, and even more preferably 85% by mass or less.

The acrylic polymer (A) may have a structural unit (c) which is a residue of an unsaturated monomer having a carboxyl group. In this case, the affinity between the acrylic polymer (A) and the inorganic powder in the firing paste can be enhanced, so that the firing paste can be easily formed into a sheet and the strength of the green sheet can be increased. can be further enhanced.

When the acrylic polymer (A) has the structural unit (c), the percentage of the structural unit (c) is preferably 1% by mass or more and 10% by mass or less relative to the acrylic polymer (A). It is more preferable if the percentage of this structural unit (c) is 2% by mass or more. Moreover, the percentage of this structural unit (c) is more preferably 5% by mass or less.

Structural unit (c) contains, for example, structural unit (C1) represented by formula (3).

In formula (3), _R5 is a hydrogen atom or a methyl group, and _R6 is a hydrogen atom or a substituent represented by formula (4).

In formula (4), _R7 is a methylene group or an ethylene group, and _R8 is a methylene group or an ethylene group.

The acrylic polymer (A) may contain a structural unit (d) which is a residue of an unsaturated monomer containing a hydroxyl group. In this case, the affinity between the acrylic polymer (A) and the inorganic powder in the firing paste can be enhanced, and the intramolecular interaction can be enhanced. and the strength of the green sheet can be further increased.

When the acrylic polymer (A) has the structural unit (d), the percentage of the structural unit (d) is preferably 30% by mass or more and 60% by mass or less relative to the acrylic polymer (A). The percentage of this structural unit (d) is more preferably 35% by mass or more, and even more preferably 40% by mass or more. Moreover, the percentage of the structural unit (d) is more preferably 55% by mass or less, and even more preferably 50% by mass or less.

Structural unit (d) contains, for example, structural unit (D1) represented by formula (5).

In formula (5), R ₉ is a hydrogen atom or a methyl group, and R ₁₀ is a hydroxyalkyl group having 1 to 4 carbon atoms.

The acrylic polymer (A) may have a structural unit (a) and a structural unit (b) as structural units, and the structural unit (a), the structural unit (b), and the structural unit (c) are may have a structural unit (a), a structural unit (b), and a structural unit (d), and may have a structural unit (a), a structural unit (b), a structural unit (c), and a structural unit (d).

In addition, the acrylic polymer (A) has a structural unit (hereinafter referred to as a structural unit (e)) other than the structural unit (a), the structural unit (b), the structural unit (c), and the structural unit (d). may or may not have. When the acrylic polymer (A) has the structural unit (e), the percentage of the structural unit (e) is preferably 10% by mass or less relative to the acrylic polymer (A).

Examples of unsaturated ethylenic monomers capable of forming the structural unit (e) include benzyl (meth)acrylate, (3-phenoxyphenyl)methyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropyleneglycol (meth)acrylate, polyethyleneglycol (meth)acrylate, polypropyleneglycol (meth)acrylate, Examples include glycidyl (meth)acrylate, 2-acetoacetoxyethyl (meth)acrylate, and allyl (meth)acrylate.

Moreover, the acrylic polymer (A) preferably does not have a structural unit (e1) which is a residue of a polyfunctional monomer having two or more polymerizable unsaturated groups in one molecule. When the acrylic polymer (A) has the structural unit (e1), the percentage of the structural unit (e1) is preferably 5% by mass or less relative to the acrylic polymer (A). In this case, excessive thickening of the binder composition for firing containing the acrylic polymer (A) can be suppressed, and deterioration of moldability of the paste for firing containing the binder composition for firing can be prevented. . In addition, when the acrylic polymer (A) does not have the structural unit (e1), or the percentage of the structural unit (e1) is 5% by mass or less with respect to the acrylic polymer (A), the binder composition for firing The combustibility of the material is further improved. It is presumed that this is because a three-dimensional network is less likely to be formed in the skeleton of the acrylic polymer (A), so that the depolymerization of the acrylic polymer (A) during combustion is less likely to be inhibited. be done.

The acrylic polymer (A) is synthesized, for example, by a solution polymerization method. For example, a reactive solution is prepared by blending a solvent with a polymerizable monomer, which is a raw material for the acrylic polymer (A), and a polymerization initiator. A polymerizable monomer is a monomer corresponding to each constitutional unit of the acrylic polymer (A). A chain transfer agent may be added to the reactive solution. The acrylic polymer (A) is synthesized by polymerizing the polymerizable monomer by stirring this reactive solution while heating it in an inert atmosphere.

The solvent is not particularly limited as long as it can dissolve or disperse the polymerizable monomer and the acrylic polymer (A). Solvents include, for example, toluene, xylene, ethanol, 2-propanol, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, phenyl propylene glycol, phenyl glycol, texanol, benzyl alcohol, phenyl diglycol, terpineol, dihydroterpineol, dihydroterpineol. pinyl acetate, cyclohexanone, cyclopentanone, ethylene glycol, 1,4-butanediol, diethylene glycol, tetraethylene glycol, 1,3-butylene glycol, dipropylene glycol, tripropylene glycol, octanediol, 2,4-diethyl- It contains at least one selected from the group consisting of 1,5-pentanediol, diethylene glycol monobutyl ether, butyl carbitol acetate, solvent naphtha, and the like.

Polymerization initiators include, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(2,4-dimethyl-4-methoxy azo compounds such as valeronitrile); 4-dichlorobenzoyl peroxide, t-butyl peroxypivalate, o-methylbenzoyl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t -butyl peroxy-2-ethylhexanoate, cyclohexanone peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, lauroyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, and di-t - Contains at least one selected from the group consisting of butyl peroxide and the like.

Chain transfer agents are, for example, n-dodecyl mercaptan, 2,4-diphenyl-4-methyl-1-pentene, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, 2-ethylhexyl thioglycolate, 2,3- It contains at least one selected from the group consisting of dimercapto-1-propanol and α-methylstyrene dimer.

The weight average molecular weight of the acrylic polymer (A) is, for example, 50,000 or more and 250,000 or less. This weight average molecular weight is a relative average weight molecular weight in terms of standard polystyrene measured by gel permeation chromatography.

2. Binder composition for firing The binder composition for firing contains the acrylic polymer (A) described above. The binder composition for firing may further contain a solvent, if necessary. Moreover, the binder composition for firing may further contain additives such as a dispersant and a plasticizer, if necessary.

The binder composition for firing may further contain a polyfunctional amine compound (B). When the binder composition for firing contains the polyfunctional amine compound (B), the strength of the green sheet can be further increased. This is because the cyclocarbonate group in the structural unit (a) in the acrylic polymer (A) and the cyclocarbonate group in the structural unit (a) in the acrylic polymer (A) are mixed in the process of preparing the firing paste from the firing binder composition and further in the process of producing the green sheet from the firing paste. It is presumed that this is because the reaction with the amino group in the functional amine compound (B) forms a urethane bond, thereby forming a crosslinked structure.

An example of the structure formed by the reaction of acrylic polymer (A) and polyfunctional amine is shown in formula (6).

In formula (6), each _R11 is independently a hydrogen atom or a methyl group, each _R12 is independently a methylene group, an ethylene group or an ethoxyethylene group, and A is the residue of the polyfunctional amine compound (B). is.

Since the polyfunctional amine compound (B) tends to leave a residue when burned, it is not preferable to incorporate it into the binder composition for firing. However, in the present embodiment, when the binder composition for firing contains the polyfunctional amine compound (B), the polyfunctional amine compound (B) bonds with the cyclocarbonate group of the acrylic polymer (A) to form a urethane bond. When formed, it is less likely to leave a residue. Therefore, in the present embodiment, the thermal decomposability of the binder composition for firing is less likely to be inhibited by the polyfunctional amine compound (B).

Also, the reaction between the acrylic copolymer and the polyfunctional amine compound occurs mainly during the process of drying the baking paste to produce the green sheet. Therefore, during preparation of the binder composition for firing and preparation of the paste for firing, gelation and thickening due to the reaction between the acrylic copolymer and the polyfunctional amine compound are unlikely to occur. Problems such as deterioration of handleability in preparation of the firing paste and deterioration of formability when producing a green sheet from the firing paste are less likely to occur.

The polyfunctional amine compound preferably contains an aliphatic diamine. In this case, the green sheet can have moderate flexibility, and therefore the strength of the green sheet can be further improved.

The aliphatic diamine preferably contains at least one of ethylenediamine and hexamethylenediamine. In this case, the strength of the green sheet can be further improved.

Polyfunctional amines may include tri- or higher functional amines, such as polyethyleneimine. Polyethyleneimine can also improve the strength of the green sheet.

The proportion of amino groups contained in the polyfunctional amine compound is preferably 95 mol % or more and 105 mol % or less with respect to the cyclocarbonate groups of the acrylic polymer (A). When the ratio of the polyfunctional amine is 95 mol % or more, the strength of the green sheet can be further improved. Moreover, if this ratio is 105 mol% or less, the thermal decomposability of the binder composition for firing is less likely to be inhibited. This ratio is more preferably 97 mol % or more, and even more preferably 99 mol % or more. Further, this ratio is more preferably 103 mol % or less, and even more preferably 101 mol % or less.

3. Firing Paste The firing paste contains a firing binder composition and inorganic powder.

The inorganic powder can contain an appropriate powder according to the application of the firing paste. For example, inorganic powders include gold, copper, silver, nickel, palladium, alumina, zirconia, bismuth, titanium oxide, barium titanate, alumina nitride, silicon nitride, boron nitride, silicate glass, lead glass, _CaO.Al2O . _{3.SiO2 based inorganic glass , MgO.Al2O3.SiO2 based} inorganic glass _, and _{LiO2.Al2O3.SiO2} based inorganic glass. can.

The amount of the firing binder composition and the amount of the inorganic powder in the firing paste are such that good applicability of the firing paste and good properties of the element obtained by sintering the firing paste are maintained. is preferably adjusted as appropriate. For example, the amount of the inorganic powder with respect to 100 parts by mass of the binder composition for firing is 20 parts by mass or more and 4000 parts by mass or less.

When using the firing paste, for example, the firing paste is first formed into a sheet. The method for forming the baking paste is, for example, screen printing, dispensing, or doctor blade method, but is not limited to these. Further, the sheet-like baking paste is dried by heating. At this time, the conditions for heating the baking paste for drying are, for example, a heating temperature of 100° C. or higher and 200° C. or lower, and a heating time of 1 hour or longer and 10 hours or shorter. The firing paste may first be air dried at room temperature and then further dried by heating. As a result, the solvent in the binder composition for firing volatilizes. Moreover, when the binder composition for baking contains a polyfunctional amine compound, the reaction between the acrylic polymer (A) and the polyfunctional amine compound proceeds. A green sheet is thus produced. In this embodiment, as already explained, the green sheet can have high strength.

By heating the green sheet, the firing binder composition is thermally decomposed and the inorganic powder is sintered. Thereby, a sintered body of the inorganic powder is produced. At this time, the conditions for heating the firing paste for sintering are, for example, a heating temperature of 500° C. or more and 1500° C. or less and a heating time of 1 hour or more and 24 hours or less. In the present embodiment, as already explained, the binder composition for firing can have good thermal decomposability. difficult to remain.

A method of producing a sintered body using a firing paste is particularly suitable for producing dielectric layers in multilayer capacitors. However, the application of the sintered body is not limited to the dielectric layer, and the sintered body can constitute appropriate elements such as electrodes, conductor wiring, and insulating layers.

Specific examples of this embodiment will be presented below. However, this embodiment is not limited to the following examples.

1. Preparation of Polymer A 1-liter four-necked flask equipped with a reflux condenser, thermometer, nitrogen purge tube and stirrer was used as a reaction vessel. Into this reaction vessel, materials other than the polymerization initiator among the materials shown in Table 1-3 were charged, and the inside of the reaction vessel was heated under a nitrogen stream. When the inside of the reaction vessel reached 80°C, a polymerization initiator was added, and the polymerization reaction was carried out at 80°C for 6 hours. After the reaction, the reaction vessel was cooled, and a solvent was added so that the solution in the reaction vessel contained 30% by mass of non-volatile matter, thereby obtaining a polymer solution.

A weight average molecular weight in the polymer solution was measured. The weight average molecular weight is a relative average molecular weight obtained by converting the calibration curve measured by gel permeation chromatography using a standard polymer, and the measurement conditions are as follows.
- Apparatus name: Prominence HPLC system (manufactured by Shimadzu Corporation).
- Columns: KF-805, KF-803, KF-801 (series) (manufactured by Showa Denko KK).
- Mobile phase: tetrahydrofuran.
- Flow rate: 1 mL/min.
- Detector: Differential refractive index detector.
- Temperature: 40°C.
- Molecular weight standard: polystyrene.

In Comparative Production Example 4, the weight-average molecular weight was not measured because the polymer solution gelled.

Further, details of raw materials indicated by abbreviations in Tables 1-3 are as follows. In Table 1-3, the monomers corresponding to structural unit (a), structural unit (b), structural unit (c) and structural unit (d) are represented as (a), (b), (c) and Shown in column (d).
-CCMA: (2-oxo-1,3-dioxolan-4-yl)-methyl methacrylate.
-MMA: methyl methacrylate.
-BMA: n-butyl methacrylate.
- EHMA: 2-ethylhexyl methacrylate.
-LMA: n-dodecyl methacrylate.
-CHMA: cyclohexyl methacrylate.
-BA: n-butyl acrylate.
-MAA: methacrylic acid.
- MOES: 2-methacryloyloxyethyl succinic acid.
- AA: acrylic acid.
- AOES: 2-acryloyloxyethyl succinic acid.
- HEMA: 2-hydroxyethyl methacrylate.
-HPMA: 2-hydroxypropyl methacrylate.
- PEGDMA: polyethylene glycol diacrylate #600.
- PGM: propylene glycol methyl ether.
-MSD: α-methylstyrene dimer.
- AIBN: 2,2'-azobisisobutyronitrile.

2. Preparation of Green Sheet Raw materials shown in Table 4-7 were mixed and stirred for 10 minutes using a stirring and defoaming device to prepare a firing paste. The firing paste was applied onto a polyethylene terephthalate film and allowed to air dry at room temperature for 12 hours, followed by Examples 7, 8, 15-18, 23-30 and Comparative Example 2 at 100°C Examples 1-6, 9-14, 19-22 and Comparative Examples 1, 3, 4 and 5 were heated at 150° C. for 60 minutes. Thus, a green sheet having a thickness of 200 μm for evaluation was produced.

The details of the raw materials indicated by abbreviations in Tables 4-7 are as follows.
-BT-01: Barium titanate, manufactured by Sakai Chemical Industry Co., Ltd.
- PGM: propylene glycol methyl ether.
-BYK-102: An anionic polymerization initiator, manufactured by BYK-Chemie, product number BYK-102.
- PEG400: polyethylene glycol #400.
- DOA: bis(2-ethylhexyl) adipate.
- HT-510: polyethylene glycol-polypropylene glycol alkyl ether. No. HT-510 manufactured by NOF Corporation.
- PVB: polyvinyl butyral. Manufactured by Sekisui Chemical Co., Ltd., product name S-REC BH-3.
- PEI: Polyethylenimine. Nippon Shokubai Co., Ltd., product name Epomin SP-003.

3. Evaluation (1) Tensile strength A sample having a width of 1 cm and a length of 6 cm was cut out from the prepared green sheet. Using a tensile tester (manufactured by Shimadzu Corporation, Model No. AGS-1kNX), the tensile strength (maximum stress) of the sample was measured at a tensile speed of 20 mm/min.

(2) Reactivity of polyfunctional amine compound (B) For each of Examples 2, 4, 6, 8, 10, 12, 14, 15, 16, 18 to 30 using the polyfunctional amine compound (B), Infrared absorption analysis of the green sheet was carried out under conditions of an ambient temperature of 25°C. Also, among raw materials for green sheets, a mixture of a polymer solution and a polyfunctional amine compound (B) was prepared. This mixture was also subjected to infrared absorption analysis at an atmospheric temperature of 25°C.

As a result, when the intensity of the absorption peak near 1790 cm ^-1 in the infrared absorption spectrum of the green sheet is less than 10% of the intensity of the absorption peak near 1790 cm ^-1 in the infrared absorption spectrum of the mixture, "A", 10% or more A case of less than 20% was evaluated as "B", and a case of more than 20% was evaluated as "C".

(3) Sinterability The sample obtained by drying the polymer solution used to make the green sheet and evaporating the solvent was measured with a simultaneous differential thermal and thermogravimetric measurement device (TG-DTA8122 manufactured by Rigaku Co., Ltd.). was used, under the conditions of an air atmosphere, a temperature increase rate of 10°C/min, and a temperature range of 25°C to 500°C.

As a result, based on the weight of the sample at 25 ° C., the weight loss rate of the sample at 500 ° C. is 99% or more, "A", 98% or more and less than 99%, "B", 95% or more. A case of less than 98% was evaluated as "C", and a case of less than 95% was evaluated as "D".

The above results are shown in Table 4-7.

As shown in the above results, in Examples 1 to 30, since the binder composition for firing containing the acrylic polymer (A) having the structural unit (a) represented by formula (1) is used, It was found that the green sheet was excellent in strength and the binder composition for firing was excellent in sinterability.

In Comparative Examples 1 to 3, since a binder composition for firing containing a polymer having no structural unit (a) represented by formula (1) is used, the polymer has excellent firing properties, but green It was found that the strength of the sheet was inferior to that of any of the examples. In addition, Comparative Example 4 had a crosslinked structure resistant to thermal decomposition during the formation of the green sheet, so the sinterability of the polymer was slightly inferior. In Comparative Example 5, since polyvinyl butyral is contained as a binder, the strength of the green sheet is excellent, but the sinterability is low.

Claims (13)

An acrylic polymer (A) blended in a binder composition for firing,
Having a structural unit (a) represented by formula (1),

In the above formula (1), R ₁ is a hydrogen atom or a methyl group, R ₂ is a methylene group, an ethylene group or an ethoxyethylene group,
Acrylic polymer. Further having a structural unit (b) represented by formula (2),

In the above formula (2), R ₃ is a hydrogen atom or a methyl group, and R ₄ is a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms.
The acrylic polymer according to claim 1. Further having a structural unit (c) which is a residue of an unsaturated monomer having a carboxyl group,
The acrylic polymer according to claim 1 or 2. The structural unit (c) contains a structural unit (C1) represented by formula (3),

In the formula (3), R ₅ is a hydrogen atom or a methyl group, R ₆ is a hydrogen atom or a substituent represented by the formula (4),

In the formula (4), R ₇ is a methylene group or an ethylene group, R ₈ is a methylene group or an ethylene group,
The acrylic polymer according to claim 3. Further having a structural unit (d) which is a residue of an unsaturated monomer containing a hydroxyl group,
The acrylic polymer according to any one of claims 1 to 4. The structural unit (d) contains a structural unit (D1) represented by the following formula (5),

In the above formula (5), R ₉ is a hydrogen atom or a methyl group, R ₁₀ is a hydroxyalkyl group having 1 to 4 carbon atoms,
The acrylic polymer according to claim 5. The percentage of the structural unit (a) is 2% by mass or more and 20% by mass or less with respect to the acrylic polymer (A).
The acrylic polymer according to any one of claims 1 to 6. Containing the acrylic polymer (A) according to any one of claims 1 to 7,
Binder composition for firing. Further containing a polyfunctional amine compound (B),
The binder composition for firing according to claim 8. The polyfunctional amine compound (B) contains an aliphatic diamine,
The binder composition for firing according to claim 9. The aliphatic diamine contains at least one of ethylenediamine and hexamethylenediamine,
The binder composition for firing according to claim 10. The polyfunctional amine compound (B) contains polyethyleneimine,
The binder composition for firing according to claim 9. Containing the binder composition for firing according to any one of claims 8 to 12 and an inorganic powder,
baking paste.