Lactic acid-vinyl copolymer, binder composition and paste for calcination

Abstract

To provide: a lactic acid-vinyl copolymer for a paste for calcination having excellent calcination property, having no visually recognizable insoluble matter and capable of dissolving in a solvent, and having effective rheological property when mixed with the solvent and little stringing property; a binder composition containing the lactic acid-vinyl copolymer; and a paste for calcination.SOLUTION: According to the invention, a lactic acid-vinyl copolymer for a paste for calcination is provided which is a lactic acid-vinyl copolymer containing a lactic acid unit derived from lactic acid and a vinyl monomer unit derived from vinyl monomer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lactic acid-vinyl copolymer, a binder composition, and a firing paste.

[0002] Inorganic particle-containing firing pastes used in manufacturing internal electrodes (for example, MLCCs (Multilayer Ceramic Capacitors)) contain ethyl cellulose (EC) or polyvinyl butyral (PVB) as binders.

[0003] Patent Document 1 discloses an invention relating to a dry film for an internal electrode of a multilayer ceramic capacitor, which is formed from a composition containing a conductive powder and an organic binder resin, and discloses that the binder resin contains ethyl cellulose and polyvinyl butyral. Furthermore, Patent Document 2 discloses a paste composition containing an inorganic substance, a binder resin, and a solvent, wherein the binder resin is at least one (co)polymer selected from a homopolymer of lactic acid and a copolymer of lactic acid and a copolymerizable monomer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-121744 [Patent Document 2] Japanese Patent Application Publication No. 9-142938 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional inorganic particle-containing sintering pastes using, for example, ethyl cellulose, etc., have a high residual carbon content after sintering and have poor sinterability. Furthermore, with the recent trend toward smaller capacitors, there is a demand for inorganic particle-containing sintering pastes in which the binder is uniformly dispersed throughout the paste, with excellent coatability and little stringiness, as well as binders for sintering pastes that can prepare such sintering pastes. However, conventional binders and sintering pastes using conventional binders have not been able to satisfy all of these requirements.

[0006] The present invention has been made in view of the above circumstances, and provides a lactic acid-vinyl copolymer for a firing paste that has excellent firing properties, is soluble in a solvent without any visually visible insoluble matter, and has effective rheological properties and little stringiness when mixed with a solvent, as well as a binder composition and a firing paste that contain the lactic acid-vinyl copolymer. [Means for solving the problem]

[0007] According to the present invention, there is provided a lactic acid-vinyl copolymer for use in a baking paste, which is a lactic acid-vinyl copolymer containing lactic acid units derived from lactic acid and vinyl monomer units derived from a vinyl monomer.

[0008] As a result of extensive research, the present inventors have found that a lactic acid-vinyl copolymer containing lactic acid units derived from lactic acid and vinyl monomer units derived from a vinyl monomer has excellent sinterability, is soluble in a solvent without any visually detectable insoluble matter, and when mixed with a solvent, has effective rheological properties and is less stringy, and serves as a binder for a sintering paste, which has led to the completion of the present invention.

[0009] Various embodiments of the present invention will be described below as examples, and the embodiments shown below can be combined with each other. [1] A lactic acid-vinyl copolymer containing lactic acid units derived from lactic acid and vinyl monomer units derived from a vinyl monomer, the lactic acid-vinyl copolymer being used in a baking paste. [2] A lactic acid-vinyl copolymer according to [1], which has a viscosity of 2.0 Pa·s or more as measured by the following method. <Viscosity measurement method> 1) 30% by mass of the lactic acid-vinyl copolymer and 70% by mass of butyl carbitol acetate or dihydroterpinyl acetate are placed in a sealed container, stirred at 2000 rpm in a planetary mixer until no undissolved material remains, degassed at 2200 rpm until no air bubbles remain, and then left to stand at 25°C for one day to prepare a lactic acid-vinyl copolymer solution. 2) A cone plate with a diameter of 20 mm and a cone angle of 0.975° was attached to the viscosity / viscoelasticity measuring device with a clearance of 23 μm. 0.1 g of the lactic acid-vinyl copolymer solution obtained in 1) was placed in the measuring section, and the shear rate was set to 0.01 sec at a set temperature of 25°C. -1 From 10,000 seconds -1 The shear rate was increased at a constant rate over 150 seconds to -1 Viscosity measurement at [3] A lactic acid-vinyl copolymer according to [1] or [2], wherein the ratio A / B of viscosity A to viscosity B measured by the following method is 3.0 or more. <Method for measuring viscosity A and viscosity B> 1) 30% by mass of the lactic acid-vinyl copolymer and 70% by mass of butyl carbitol acetate or dihydroterpinyl acetate are placed in a sealed container, stirred at 2000 rpm in a planetary mixer until no undissolved material remains, degassed at 2200 rpm until no air bubbles remain, and then left to stand at 25°C for one day to prepare a lactic acid-vinyl copolymer solution. 2) A cone plate with a diameter of 20 mm and a cone angle of 0.975° was attached to the viscosity / viscoelasticity measuring device with a clearance of 23 μm. 0.1 g of the lactic acid-vinyl copolymer solution obtained in 1) was placed in the measuring section, and the shear rate was set to 0.01 sec at a set temperature of 25°C. -1 From 10,000 seconds -1 The shear rate was increased at a constant rate over 150 seconds. -1 Viscosity A at shear rate of 9,000 sec -1Measure the viscosity B at [4] The lactic acid-vinyl copolymer according to any one of [1] to [3], having a weight-average molecular weight of 10,000 to 3,000,000. [5] The lactic acid-vinyl copolymer according to any one of [1] to [4], wherein the lactic acid-vinyl copolymer has a micro carbon residue content of 2.00% by mass or less. [6] The lactic acid-vinyl copolymer according to any one of [1] to [5], wherein the lactic acid-vinyl copolymer contains a vinyl polymer block, and the glass transition temperature of the vinyl polymer block is 0 to 100°C. [7] The lactic acid-vinyl copolymer according to any one of [1] to [6], wherein the lactic acid unit is bonded to a functional group contained in the vinyl monomer. [8] A lactic acid-vinyl copolymer according to [7], wherein the functional group is at least one functional group selected from the group consisting of a hydroxyl group, a carbonyl group, an epoxy group, an amino group, an isocyanate group, a thiol group, and an alkoxysilyl group. [9] The lactic acid-vinyl copolymer according to any one of [1] to [8], wherein the vinyl monomer comprises at least one of (meth)acrylic acid and a (meth)acrylic acid ester.

[10] The lactic acid-vinyl copolymer according to any one of [1] to [9], wherein the vinyl monomer comprises a vinyl monomer containing an alkyl group having 1 to 22 carbon atoms.

[11] The lactic acid-vinyl copolymer according to any one of [1] to

[10] , wherein a toluene solution of the lactic acid-vinyl copolymer containing 25% by mass of the lactic acid-vinyl copolymer and 75% by mass of toluene has an acid value of 0.1 mg KOH / g or more and 20.0 mg KOH / g or less.

[12] The lactic acid-vinyl copolymer according to any one of [1] to

[11] , wherein the lactic acid-vinyl copolymer contains 5.0% by mass to 99.9% by mass of the lactic acid units relative to 100% by mass of the lactic acid-vinyl copolymer.

[13] The lactic acid-vinyl copolymer according to any one of [1] to

[12] , which is a graft copolymer.

[14] A binder composition for preparing a paste for firing, comprising the lactic acid-vinyl copolymer according to any one of [1] to

[13] and a solvent.

[15] A binder composition for preparing a firing paste according to

[14] , wherein the ratio A' / B' of viscosity A' to viscosity B' measured by the following method is 3.0 or more. <Method for measuring viscosity A' and viscosity B'> A cone plate with a diameter of 20 mm and a cone angle of 0.975° was attached to the viscosity / viscoelasticity measuring device with a clearance of 23 μm, and the binder composition was set in the measuring section. The shear rate was set to 0.01 sec at a set temperature of 25°C. -1 From 10,000 seconds -1 The shear rate was increased at a constant rate over 150 seconds. -1 Viscosity A' at shear rate 9,000 sec -1 Measure the viscosity B' at

[16] A paste for firing, comprising the binder composition for preparing a paste for firing according to

[14] or

[15] and inorganic particles. [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain a lactic acid-vinyl copolymer for a baking paste, which has excellent baking properties, is soluble in a solvent without any visually visible insoluble matter, and has effective rheological properties and little stringiness when mixed with a solvent. More specifically, the lactic acid-vinyl copolymer of the present invention can be dissolved in a solvent without any visible insoluble matter, allowing for the preparation of a binder composition for a baking paste and a baking paste in which the binder is uniformly dispersed. Furthermore, the lactic acid-vinyl copolymer of the present invention has effective rheological properties when mixed with a solvent, i.e., has appropriate viscosity and pseudoplasticity, making it possible to prepare a baking paste with excellent coatability. Furthermore, the lactic acid-vinyl copolymer of the present invention, and the binder composition for preparing a baking paste and baking paste containing the lactic acid-vinyl copolymer, have excellent sinterability, leaving little or no residual carbon after the paste is baked. Furthermore, when the lactic acid-vinyl copolymer of the present invention is mixed with a solvent to form a lactic acid-vinyl copolymer solution, it is possible to obtain a baking paste that is less likely to produce stringiness and is less likely to cause problems such as overflow during printing. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below by illustrating embodiments of the present invention. The present invention is not limited by these descriptions. The features of the embodiments of the present invention described below can be combined with each other. Furthermore, each feature can be an invention independently.

[0012] 1. Lactic acid-vinyl copolymer The lactic acid-vinyl copolymer according to the present invention is a lactic acid-vinyl copolymer for use in a baking paste, containing lactic acid units derived from lactic acid and vinyl monomer units derived from a vinyl monomer. It is difficult for polylactic acid consisting only of lactic acid units to achieve solvent solubility, and it is also difficult for polymers consisting only of vinyl monomer units to achieve appropriate viscosity and pseudoplasticity when mixed with a solvent. According to the present invention, by containing both lactic acid units derived from lactic acid and vinyl monomer units derived from a vinyl monomer, a lactic acid-vinyl copolymer for use in a baking paste can be obtained that has excellent baking properties, is soluble in a solvent without visible insoluble matter, and has effective rheological properties and little stringiness when mixed with a solvent.

[0013] 1.1 Lactic acid unit The lactic acid-vinyl copolymer according to the present invention contains lactic acid units derived from lactic acid. The lactic acid units according to the present invention may contain at least one of L-lactic acid units and D-lactic acid units, and preferably contain L-lactic acid units and D-lactic acid units. The lactic acid units may be derived from at least one of meso-lactide, L-lactide, and D-lactide.

[0014] In the lactic acid-vinyl copolymer according to the present invention, when the total of the L-lactic acid units and D-lactic acid units contained in the lactic acid-vinyl copolymer is taken as 100% by mass, the L-lactic acid unit content can be, for example, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% by mass, or it can be within a range between any two of the values ​​exemplified here. For example, the L-lactic acid unit content can be 30 to 70% by mass. Furthermore, the D-lactic acid unit content can be, for example, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% by mass, or it can be within a range between any two of the values ​​exemplified here. For example, the D-lactic acid unit content can be 30 to 70% by mass.

[0015] 1.2 Vinyl monomer units The lactic acid-vinyl copolymer according to the present invention contains a vinyl monomer unit. A vinyl monomer according to one embodiment of the present invention refers to a monomer containing at least one vinyl group (carbon-carbon unsaturated double bond). The lactic acid-vinyl copolymer according to the present invention may contain one or more types of vinyl monomer units.

[0016] A lactic acid-vinyl copolymer according to one embodiment of the present invention may contain vinyl monomer units derived from unsaturated monocarboxylic acids such as (meth)acrylic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, and their esters, styrene, vinyl acetate, acrylonitrile, acrylamide, and derivatives thereof. The lactic acid-vinyl copolymer preferably contains vinyl monomer units derived from at least one of (meth)acrylic acid and a (meth)acrylic acid ester, more preferably vinyl monomer units derived from a (meth)acrylic acid ester, and even more preferably vinyl monomer units derived from a methacrylic acid ester. By including vinyl monomer units derived from the above vinyl monomers, a binder with superior sinterability and solvent solubility can be easily obtained.

[0017] A vinyl monomer is typically used in the lactic acid-vinyl copolymer according to one embodiment of the present invention. The vinyl monomer preferably includes a vinyl monomer containing an alkyl group having 1 to 22 carbon atoms, and more preferably includes a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group is within the above-mentioned range. The number of carbon atoms in the alkyl group may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or 22, or may be within a range between any two of the values ​​exemplified here. By using a vinyl monomer containing an alkyl group having the above-mentioned carbon number, a binder composition with a more appropriate viscosity can be obtained when mixed with a solvent. Furthermore, a lactic acid-vinyl copolymer according to one embodiment of the present invention more preferably contains a monomer unit derived from a vinyl monomer having an alkyl group of 1 to 7 carbon atoms (short-chain alkyl group-containing vinyl monomer) and a monomer unit derived from a vinyl monomer having an alkyl group of 8 to 18 carbon atoms (long-chain alkyl group-containing vinyl monomer). The number of carbon atoms of the short-chain alkyl group-containing vinyl monomer is, for example, 1, 2, 3, 4, 5, 6, or 7, and may be within a range between any two of the values ​​exemplified here. The number of carbon atoms of the long-chain alkyl group-containing vinyl monomer is, for example, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, and may be within a range between any two of the values ​​exemplified here. Using these in combination can further improve solvent solubility.

[0018] A lactic acid-vinyl copolymer according to one embodiment of the present invention preferably contains vinyl monomer units derived from a vinyl monomer containing a functional group. The functional group is preferably at least one selected from the group consisting of hydroxyl, carbonyl, epoxy, amino, isocyanate, thiol, and alkoxysilyl groups, and is preferably at least one of hydroxyl and epoxy groups. The vinyl monomer containing a functional group is preferably at least one of (meth)acrylic acid and (meth)acrylic acid esters containing a functional group. Examples include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, as well as epoxy group-containing vinyl monomers such as glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether. When the lactic acid-vinyl copolymer according to one embodiment of the present invention contains vinyl monomer units derived from a vinyl monomer having a functional group, it is also possible to obtain a lactic acid-vinyl copolymer in which the lactic acid monomer units are bonded (e.g., graft polymerized) starting from the functional group.

[0019] A lactic acid-vinyl copolymer according to one embodiment of the present invention may contain vinyl monomer units derived from a vinyl monomer that does not contain a functional group (e.g., the functional groups described above). The vinyl monomer that does not contain a functional group is preferably at least one of (meth)acrylic acid and (meth)acrylic acid esters that do not contain a functional group, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, and isodecyl (meth)acrylate. alkyl (meth)acrylates such as acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and behenyl (meth)acrylate; alkylene oxide-modified (meth)acrylates such as ethylene oxide-modified (meth)acrylate and propylene oxide-modified (meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate; isobornyl (meth)acrylate; (meth)acrylic acid aryl esters such as phenyl (meth)acrylate; (meth)acrylic acid aryloxyalkyl esters such as phenoxyethyl (meth)acrylate; and (meth)acrylic acid arylalkyl esters such as benzyl (meth)acrylate.

[0020] A lactic acid-vinyl copolymer according to one embodiment of the present invention preferably contains vinyl monomer units derived from a vinyl monomer containing a functional group and vinyl monomer units derived from a vinyl monomer not containing a functional group. The vinyl monomer containing a functional group may be a vinyl monomer containing a short-chain alkyl group, and the vinyl monomer not containing a functional group may be a vinyl monomer containing a long-chain alkyl group. The lactic acid-vinyl copolymer may contain 0.5 to 70% by mass of vinyl monomer units derived from a vinyl monomer containing a functional group, relative to 100% by mass of the total vinyl monomer units contained in the lactic acid-vinyl copolymer. The content of vinyl monomer units derived from a vinyl monomer containing a functional group may be, for example, 0.5, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70% by mass, or may be within a range between any two of the values ​​exemplified here. When the content of vinyl monomer units derived from a vinyl monomer containing a functional group is within the above range, it is easier to achieve a balance between the solvent solubility of the lactic acid-vinyl copolymer and other physical properties such as rheological properties.

[0021] 1.3 Other monomer units In the present invention, the lactic acid-vinyl copolymer is a polymer primarily composed of lactic acid units and vinyl monomer units. However, as long as the effects of the present invention are not impaired, it may contain components derived from other monomers as necessary. Examples of such other monomers include monomers having functional groups, such as hydroxyl, carbonyl, epoxy, amino, isocyanate, thiol, and alkoxysilyl groups. The other monomers may also include chain transfer agents used for molecular weight control, such as those described in "2. Method for Producing Lactic Acid-Vinyl Copolymer." The other monomers may also include monomers having functional groups capable of reacting with the functional groups of the vinyl monomers. Specific examples include diglycidyl ethers such as bisphenol A diglycidyl ether and polyalkylene oxide diglycidyl ether. The other monomer units may be incorporated into the main chain of the vinyl polymer, or may be included as side chains by reacting with the vinyl monomers having functional groups. The lactic acid-vinyl copolymer according to the present invention may contain, when the lactic acid-vinyl copolymer is taken as 100% by mass, monomer units other than lactic acid units and vinyl monomer units in an amount of, for example, 0, 5, 10, 15, or 20% by mass, or may contain a range between any two of the values ​​exemplified here. The lactic acid-vinyl copolymer according to the present invention may also be composed only of lactic acid units and vinyl monomer units.

[0022] 1.4 Content of each monomer unit A lactic acid-vinyl copolymer according to one embodiment of the present invention preferably contains 5.0 to 99.9% by mass of lactic acid units relative to 100% by mass of the lactic acid-vinyl copolymer. The lactic acid unit content may be, for example, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0, 65.0, 70.0, 75.0, 80.0, 85.0, 90.0, 95.0, or 99.9% by mass, or may be within a range between any two of the values ​​exemplified here. By setting the lactic acid monomer unit content below the upper limit, solvent solubility is easily maintained. Furthermore, by setting the lactic acid unit content above the lower limit, appropriate viscosity and pseudoplasticity can be obtained when mixed with a solvent. According to one embodiment of the present invention, even if the content of lactic acid monomers in a lactic acid-vinyl copolymer is very small, the presence of lactic acid monomer units improves pseudoplasticity when the lactic acid-vinyl copolymer is mixed with a solvent, and although the mechanism is not entirely clear, it is speculated as follows: The improvement in pseudoplasticity is thought to be related to hydrogen bonds between carboxylic acids of the lactic acid monomer units present at the terminals of the lactic acid-vinyl copolymer, and it is speculated that pseudoplasticity can be maintained even if the content of lactic acid monomer units in the entire lactic acid-vinyl copolymer is low (for example, even if the polylactic acid block is short), as long as the amount of lactic acid monomer units present at the terminals can be maintained to a certain extent.

[0023] A lactic acid-vinyl copolymer according to one embodiment of the present invention preferably contains 0.1 to 95.0% by mass of vinyl monomer units relative to 100% by mass of the lactic acid-vinyl copolymer. The content of vinyl monomer units may be, for example, 0.0, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0, 65.0, 70.0, 75.0, 80.0, 85.0, 90.0, or 95.0% by mass, or may be within a range between any two of the values ​​exemplified here.

[0024] 1.5 Structure of lactic acid-vinyl copolymer A lactic acid-vinyl copolymer according to one embodiment of the present invention may contain a vinyl polymer block. The vinyl polymer block may be a vinyl polymer block consisting of one type of vinyl monomer unit, or may be a vinyl (co)polymer block consisting of two or more types of vinyl monomer units. For example, the vinyl polymer block may contain at least one of vinyl monomer units derived from a vinyl monomer containing a functional group and vinyl monomer units derived from a vinyl monomer not containing a functional group, and preferably contains vinyl monomer units derived from a vinyl monomer containing a functional group and vinyl monomer units derived from a vinyl monomer not containing a functional group, and may be a polymer block in which these monomer units are randomly polymerized.

[0025] The vinyl polymer block preferably has a glass transition temperature of 0 to 100°C. The glass transition temperature may be, for example, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100°C, or may be within a range between any two of the values ​​exemplified here. When the glass transition temperature of the vinyl polymer block is within the above range, the handleability of the firing paste using a lactic acid-vinyl copolymer as a binder can be improved. The glass transition temperature can be theoretically determined using Fox's equation based on the weight fraction of the monomers blended as raw materials and the glass transition temperature of the homopolymer of the monomers. Specifically, it can be calculated by the method described in the Examples.

[0026] The vinyl polymer block preferably has a weight-average molecular weight of 3,000 to 1,000,000, more preferably 8,000 to 700,000. The weight-average molecular weight may be, for example, 3,000, 5,000, 8,000, 10,000, 20,000, 30,000, 50,000, 70,000, 100,000, 200,000, 300,000, 500,000, 700,000, or 1,000,000, or may be within a range between any two of the values ​​exemplified here. By having the weight-average molecular weight of the vinyl polymer block within the above range, the solvent solubility, viscosity, and pseudoplasticity of the lactic acid-vinyl copolymer can be more appropriately adjusted.

[0027] A lactic acid-vinyl copolymer according to one embodiment of the present invention preferably has lactic acid units bonded to functional groups contained in vinyl monomers, and the functional groups are preferably at least one selected from the group consisting of hydroxyl, carbonyl, epoxy, amino, isocyanate, thiol, and alkoxysilyl groups.

[0028] A lactic acid-vinyl copolymer according to one embodiment of the present invention may contain a polylactic acid block. The polylactic acid block may contain lactic acid monomer units derived from at least one of meso-lactide, L-lactide, and D-lactide, and the polylactic acid block may contain at least one of L-lactic acid units and D-lactic acid units, and may be a polymer block in which the L-lactic acid units and D-lactic acid units are randomly polymerized.

[0029] A lactic acid-vinyl copolymer according to one embodiment of the present invention may contain a polylactic acid block and a vinyl polymer block. A lactic acid-vinyl copolymer according to one embodiment of the present invention may be a block copolymer (particularly a diblock copolymer) or a graft copolymer containing a polylactic acid block and a vinyl monomer block. A diblock copolymer is likely to have suitable viscosity and pseudoplasticity. A graft copolymer is likely to have suitable pseudoplasticity.

[0030] A lactic acid-vinyl copolymer according to one embodiment of the present invention may be a graft copolymer. The graft copolymer may include a backbone containing vinyl monomer units and branch chains containing lactic acid monomer units. The branch chains containing lactic acid monomer units may be bonded to functional groups contained in the vinyl monomers contained in the backbone.

[0031] 1.6 Physical properties of lactic acid-vinyl copolymer <Viscosity of lactic acid-vinyl copolymer solution> The lactic acid-vinyl copolymer according to one embodiment of the present invention can be deformed at a shear rate of 0.01 sec at 25°C. -1 From 10,000 seconds-1 The shear rate was increased at a constant rate over 150 seconds. -1 The viscosity A of the lactic acid-vinyl copolymer solution is preferably 2.0 Pa s or more. The viscosity A of the lactic acid-vinyl copolymer solution may be, for example, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0, 100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 700.0, 800.0, 900.0, or 1000.0 Pa s, or may be within a range between any two of the values ​​exemplified here. By having the viscosity as described above, the binder composition can be prepared into a firing paste having excellent coatability.

[0032] The lactic acid-vinyl copolymer according to one embodiment of the present invention is soluble in water at a shear rate of 0.01 sec at 25°C. -1 From 10,000 seconds -1 When the shear rate was increased at a constant rate over 150 seconds, -1 The viscosity B of the lactic acid-vinyl copolymer solution in the above range is preferably 0.05 to 2.0 Pa·s. The viscosity B of the lactic acid-vinyl copolymer solution is, for example, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1.0, 1.1.0, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0, and may be within a range between any two of the values ​​exemplified here. By having such a viscosity, the binder composition can be used to prepare a firing paste with excellent coatability.

[0033] The lactic acid-vinyl copolymer solution according to one embodiment of the present invention is heated at 25°C at a shear rate of 0.01 sec -1 From 10,000 seconds -1 The shear rate was increased at a constant rate over 150 seconds. -1 Viscosity A and shear rate at 9000 sec -1Preferably, the ratio A / B of the viscosity A to the viscosity B at shear rate is 3.0 or greater. A / B is, for example, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0, 100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 700.0, 800.0, 900.0, or 1,000.0 Pa s, and may be within a range between any two of the values ​​exemplified here. That is, the lactic acid-vinyl copolymer solution according to one embodiment of the present invention preferably exhibits pseudoplasticity, in which the viscosity decreases as the shear rate increases.

[0034] Here, the lactic acid-vinyl copolymer solution means a solution containing 30% by mass of lactic acid-vinyl copolymer and 70% by mass of butyl carbitol acetate or dihydroterpinyl acetate. That is, it is preferable that a lactic acid-vinyl copolymer according to one embodiment of the present invention satisfies at least one of the following requirements. The viscosity of a lactic acid-vinyl copolymer butyl carbitol acetate solution containing 30% by mass of lactic acid-vinyl copolymer and 70% by mass of butyl carbitol acetate satisfies the above requirements. The viscosity of a lactic acid-vinyl copolymer dihydroterpinyl acetate solution containing 30% by mass of lactic acid-vinyl copolymer and 70% by mass of dihydroterpinyl acetate satisfies the above requirements. In addition, the viscosity of both the lactic acid-vinyl copolymer butyl carbitol acetate solution and the lactic acid-vinyl copolymer dihydroterpinyl acetate solution may satisfy the above requirement.

[0035] The viscosity of a lactic acid-vinyl copolymer solution can be controlled by adjusting the types and amounts of lactic acid units and vinyl monomer units contained in the lactic acid-vinyl copolymer, as well as the weight-average molecular weight and structure. The viscosity of a lactic acid-vinyl copolymer solution at 25°C and at each shear rate can be measured using a rotational viscometer, for example, a rheometer, and can be measured by the following method, specifically, the method described in the Examples. <Method for measuring viscosity A and viscosity B> 1) 30% by mass of the lactic acid-vinyl copolymer and 70% by mass of butyl carbitol acetate or dihydroterpinyl acetate are placed in a sealed container, stirred at 2000 rpm in a planetary mixer until no undissolved material remains, degassed at 2200 rpm until no air bubbles remain, and then left to stand at 25°C for one day to prepare a lactic acid-vinyl copolymer solution. 2) A cone plate with a diameter of 20 mm and a cone angle of 0.975° was attached to the viscosity / viscoelasticity measuring device with a clearance of 23 μm. 0.1 g of the lactic acid-vinyl copolymer solution obtained in 1) was placed in the measuring section, and the shear rate was set to 0.01 sec at a set temperature of 25°C. -1 From 10,000 seconds -1 The shear rate was increased at a constant rate over 150 seconds. -1 Viscosity A at shear rate of 9,000 sec -1 Measure the viscosity B at As the planetary mixer, a planetary mixer called "Awatori Rentaro" manufactured by THINKY can be used, and as the viscosity and viscoelasticity measuring device, a viscosity and viscoelasticity measuring device called "Discovery HR30" manufactured by TA Instruments can be used.

[0036] <Weight average molecular weight> The lactic acid-vinyl copolymer according to one embodiment of the present invention preferably has a weight-average molecular weight of 10,000 to 3,000,000. The weight-average molecular weight may be, for example, 10,000, 50,000, 100,000, 200,000, 300,000, 500,000, 1,000,000, 2,000,000, or 3,000,000, or may be within a range between any two of the values ​​exemplified here. By setting the weight-average molecular weight within the above range, it is easy to achieve a balance between the solvent solubility, viscosity, and pseudoplasticity of the lactic acid-vinyl copolymer.

[0037] The weight-average molecular weight can be determined by a GPC method, specifically, under the conditions described in the Examples. The weight-average molecular weight can be controlled by adjusting the polymerization conditions.

[0038] <Solvent solubility> When the lactic acid-vinyl copolymer according to one embodiment of the present invention is dissolved in a solvent (for example, when a lactic acid-vinyl copolymer butyl carbitol acetate solution containing 30% by mass of the lactic acid-vinyl copolymer and 70% by mass of butyl carbitol acetate is prepared, and / or when a lactic acid-vinyl copolymer dihydroterpinyl acetate solution containing 30% by mass of the lactic acid-vinyl copolymer and 70% by mass of dihydroterpinyl acetate is prepared), it is preferable that no insoluble matter is visible to the naked eye.

[0039] The solvent solubility can be evaluated under the conditions described in the Examples, specifically. The solvent solubility can be controlled by adjusting the types and amounts of lactic acid units and vinyl monomer units contained in the lactic acid-vinyl copolymer, as well as the weight-average molecular weight and structure.

[0040] <Micro carbon residue> The lactic acid-vinyl copolymer according to one embodiment of the present invention preferably has a micro carbon residue of 2.00% by mass or less, and the micro carbon residue may be, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, 1.90, or 2.00% by mass, or may be within a range between any two of the values ​​exemplified here.

[0041] The term "micro carbon residue" refers to the carbon residue determined by the micro method. Specifically, a sample is weighed into a test container, placed in a furnace, and heated to 500°C under specified conditions in a nitrogen atmosphere. The temperature is then maintained at 500°C for 15 minutes. The test container is then allowed to cool, after which the sample is weighed and the percentage of the mass lost relative to the initial mass (mass%) is calculated to determine the carbon residue. Specifically, the micro carbon residue can be determined by the method described in the Examples. The micro carbon residue can be adjusted by controlling the types and amounts of lactic acid units and vinyl monomer units contained in the lactic acid-vinyl copolymer.

[0042] <95% weight loss temperature (TD95)> The lactic acid-vinyl copolymer according to one embodiment of the present invention preferably has a 95% weight loss temperature (TD95) of less than 400° C. The TD95 may be, for example, 350, 355, 360, 365, 370, 375, 380, 385, 390, or 395° C., or less than 400° C., or may be within a range between any two of the values ​​exemplified here.

[0043] TD95 refers to the temperature at which a sample loses 95% of its weight when heated at a rate of 10°C / min, and can be determined using a thermogravimetric differential thermal analyzer by the method described in the Examples. TD95 can be adjusted by controlling the types and amounts of lactic acid units and vinyl monomer units contained in the lactic acid-vinyl copolymer solution.

[0044] <Stringability> In the lactic acid-vinyl copolymer according to one embodiment of the present invention, when a glass rod is pierced into a lactic acid-vinyl copolymer solution adjusted to have a viscosity A of 5 Pa s in an environment of 25°C and pulled up 10 cm, it is preferable that the time required for the thread-like solution existing between the solution surface and the glass rod to break is 4 seconds or less.

[0045] Specifically, the stringiness can be determined by the method described in the Examples. The stringiness can be adjusted by controlling the types and amounts of lactic acid units and vinyl monomer units contained in the lactic acid-vinyl copolymer.

[0046] <Acid value> In one embodiment of the present invention, the acid value of a lactic acid-vinyl copolymer toluene solution is preferably 0.1 mgKOH / g or more and 20.0 mgKOH / g or less. The acid value may be, for example, 0.1, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, or 20.0 mgKOH / g, or may be within a range between any two of the values ​​exemplified here. The acid value is thought to correlate with the amount of carboxylic acid of the lactic acid units present at the terminals of the lactic acid-vinyl copolymer. For example, when the lactic acid-vinyl copolymer is a graft copolymer, it is thought to correlate with the number of branch chains.

[0047] Here, the lactic acid-vinyl copolymer toluene solution can contain 25% by mass of lactic acid-vinyl copolymer and 75% by mass of toluene. The acid value can be measured by dissolving a sample in a solvent and performing potentiometric titration using a 0.1 mol / L potassium hydroxide ethanol solution, specifically by the method described in the Examples. The acid value can be adjusted by adjusting the types and amounts of lactic acid units and vinyl monomer units contained in the lactic acid-vinyl copolymer as well as the polymerization conditions, thereby controlling the weight-average molecular weight and structure of the lactic acid-vinyl copolymer.

[0048] The lactic acid-vinyl copolymer according to the present invention is a lactic acid-vinyl copolymer for a sintering paste and can be suitably used as a binder for the sintering paste. As described above, the lactic acid-vinyl copolymer according to the present invention has been found for the first time to have excellent sinterability due to the presence of lactic acid units and vinyl monomer units, to be soluble in a solvent without visible insoluble matter, and to function as a binder for a sintering paste that exhibits effective rheological properties and little stringiness when mixed with a solvent. The present invention makes it possible to obtain a sintering paste in which the binder is uniformly dispersed, has excellent coatability, little stringiness, and little carbon remains after sintering. This enables pattern formation without problems, even in the manufacture of increasingly smaller capacitors, and provides the benefit of reducing the risk of defects in the resulting capacitors because no organic substances derived from the binder remain.

[0049] 2. Manufacturing method of lactic acid-vinyl copolymer The method for producing the lactic acid-vinyl copolymer according to the present invention is not particularly limited, but it can be produced, for example, by the following method. A method for producing a lactic acid-vinyl copolymer according to one embodiment of the present invention includes the steps of: a vinyl (co)polymerization step in which a raw material containing one or more vinyl monomers is polymerized to obtain a vinyl (co)polymer; and A lactic acid-vinyl copolymer polymerization step in which a raw material containing the vinyl (co)polymer and lactic acid is polymerized to obtain a lactic acid-vinyl copolymer. may include:

[0050] 2.1 Vinyl (co)polymer polymerization process In the vinyl (co)polymer polymerization step, a raw material containing one or more vinyl monomers is polymerized to obtain a vinyl (co)polymer. In the vinyl (co)polymer polymerization step, for example, a conventionally known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. can be used, and among these, solution polymerization is preferred.

[0051] Specifically, a reaction vessel is charged with raw materials containing one or more vinyl monomers, and optionally a chain transfer agent, a solvent, etc., and then a polymerization initiator is added under an inert gas atmosphere such as nitrogen gas, and the reaction is carried out for 2 to 20 hours while maintaining the reaction system at a temperature of usually 50 to 90° C., preferably 60 to 90° C. Further, during the polymerization reaction, additional polymerization initiator, chain transfer agent, monomer, and solvent may be added as appropriate.

[0052] The raw material may contain a vinyl monomer having a functional group and a vinyl monomer having no functional group, and specific examples of the vinyl monomer having a functional group and the vinyl monomer having no functional group and the blending ratio thereof are as described above.

[0053] Examples of solvents that can be used include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, and ethylene glycol diacetate; and water. During the vinyl (co)polymer polymerization step, lactides such as meso-lactide, L-lactide, and D-lactide, which will serve as raw materials for the next step, may be added to the reaction system in advance. In this case, lactide does not contribute to the polymerization reaction.

[0054] Examples of the polymerization initiator include azo-based initiators and peroxide-based polymerization initiators. Examples of azo initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoylazo)isobutyronitrile, and 2-phenylazo-4-methoxy-2,4-dimethyl Examples of azo compounds include valeronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) dihydrate, 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-cyanopropanol), and dimethyl-2,2'-azobis(2-methylpropionate).

[0055] The chain transfer agent may include a thiol compound (mercaptan). Specific examples include alkyl mercaptans such as n-octyl mercaptan and t- or n-dodecyl mercaptan; hydroxyl group-containing mercaptans such as 2-mercaptoethanol, thioglycerol, and 3-mercaptohexan-1-ol; carboxyl group-containing mercaptans such as thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 4-mercaptobutanoic acid, 6-mercaptohexanoic acid, 11-mercaptoundecanoic acid, 3-mercaptopyruvate, 2-mercaptobenzoic acid, 3-mercaptobenzoic acid, 4-mercaptobenzoic acid, and thiomalic acid; and alkoxysilane-containing mercaptans such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane. Other examples include polyfunctional thiols such as pentaerythritol tetrakis(3-mercaptopropionate), styrene dimers such as α-methylstyrene dimer, and naphthoquinone compounds. When a chain transfer agent is used, it can be used in an amount within a range of preferably 0.01 to 5.00 parts by mass, more preferably 0.02 to 3.00 parts by mass, and even more preferably 0.03 to 2.50 parts by mass, relative to 100 parts by mass of the monomer.

[0056] The polymerization initiator, chain transfer agent, and solvent may be used alone or in combination of two or more. The weight-average molecular weight of the vinyl (co)polymer can be adjusted by adjusting the type and amount of the polymerization initiator and chain transfer agent, as well as polymerization conditions such as polymerization temperature and time.

[0057] 2.2 Lactic acid-vinyl copolymer polymerization process In the lactic acid-vinyl copolymer polymerization step, raw materials containing a vinyl (co)polymer and lactic acid are further polymerized to obtain a lactic acid-vinyl copolymer. In the lactic acid-vinyl copolymer polymerization step, for example, a conventionally known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization can be used, and among these, solution polymerization is preferred.

[0058] In a lactic acid-vinyl copolymer polymerization process according to one embodiment of the present invention, lactide is subjected to ring-opening polymerization using tin octoate or the like. Specifically, raw materials containing a vinyl (co)polymer and lactic acid, and optionally a solvent, are charged into a reaction vessel, and a catalyst is added under an inert gas atmosphere such as nitrogen gas. The temperature inside the reaction vessel is adjusted to 150 to 210°C, preferably 160 to 200°C, and the reaction is carried out for 2 to 20 hours. Additional catalyst, monomer, and solvent may be added as needed during the polymerization reaction.

[0059] The raw material containing lactic acid can contain lactide, which is a cyclic dimer, and can contain at least one of meso-lactide, L-lactide, and D-lactide.

[0060] A catalyst can be used for the polymerization, and examples of the catalyst include organic tin compounds such as tin lactate, tin tartrate, tin dicaprylate, tin dilaurate, tin dipaltimate, tin distearate, tin dioleate, tin α-naphthenate, tin β-naphthenate, and tin octoate; tin powder; zinc powder, zinc halide, zinc oxide, organic zinc compounds; titanium compounds such as tetrapropyl titanate; zirconium compounds such as zirconium isopropoxide; and antimony compounds such as antimony trioxide. The amount of catalyst added can be 0.001 to 1 part by mass, or 0.005 to 0.5 parts by mass, per 100 parts by mass of the raw materials, such as lactide.

[0061] In the lactic acid-vinyl copolymer polymerization step according to one embodiment of the present invention, polylactic acid blocks are formed. For example, when the vinyl (co)polymer used as the raw material has functional groups, it is thought that a structure will be formed in which the polylactic acid blocks are bonded to the functional groups. By adjusting the type and amount of catalyst, as well as polymerization conditions such as polymerization temperature and time, it is possible to adjust the weight-average molecular weight and structure of the polylactic acid block and lactic acid-vinyl copolymer, as well as the physical properties of the lactic acid-vinyl copolymer.

[0062] 3. Binder Composition A binder composition according to one embodiment of the present invention contains the above-described lactic acid-vinyl copolymer and a solvent, and can be used to prepare a paste for firing.

[0063] A binder composition according to one embodiment of the present invention contains a lactic acid-vinyl copolymer as a binder, and may contain a binder other than a lactic acid-vinyl copolymer. Examples of binders that the binder composition according to one embodiment of the present invention may contain in addition to the lactic acid-vinyl copolymer include ethyl cellulose and polyvinyl butyral. The binder composition according to one embodiment of the present invention preferably contains 50% by mass or more of the lactic acid-vinyl copolymer, preferably 80% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of the binder. The content of the lactic acid-vinyl copolymer based on 100% by mass of the binder may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, or may be within a range between any two of the values ​​exemplified here. A binder composition according to one embodiment of the present invention may also contain only the lactic acid-vinyl copolymer as the binder.

[0064] 3.1 Solvent The solvent that may be contained in the binder composition according to one embodiment of the present invention is not particularly limited, and known solvents can be used. The solvent preferably has excellent compatibility with the lactic acid-vinyl copolymer according to the present invention. For example, when a lactic acid-vinyl copolymer solution containing 30% by mass of the lactic acid-vinyl copolymer according to the present invention and 70% by mass of the solvent is prepared, it is preferable that no visible residue remains. Furthermore, the boiling point of the solvent is preferably 150 to 300°C, more preferably 200 to 290°C, and even more preferably 220 to 280°C. Examples of the solvent include alcohol-based solvents and ester-based solvents.

[0065] Examples of alcohol-based solvents include cycloalkanols such as cyclohexanol, terpineol (including α-, β-, and γ-isomers, or any mixture thereof), terpene alcohols (e.g., monoterpene alcohols) such as dihydroterpineol, dihydroterpineol, myrtenol, sobrerol, menthol, carveol, perillyl alcohol, pinocarveol, sobrerol, verbenol, dipropylene glycol, and butyl carbitol.

[0066] Examples of ester-based solvents include butyl carbitol acetate (BCA), dihydroterpinyl acetate (DHTA), butyl glycol acetate (BMGAC), diethylene glycol alkyl ether acetate (here, examples of alkyl include ethyl, propyl, n-butyl, etc.; the same applies below), acetates such as ethylene glycol alkyl ether acetate, ethylene glycol diacetate, and propylene glycol alkyl ether acetate, 2,2,4-trimethylpentane-1,3-diol mono-iso-butyrate, 2,2,4-trimethylpentane-1,3-diol mono-iso-butyrate ether, dipropylene glycol monomethyl ether, diethylene glycol alkyl ether, ethylene glycol alkyl ether, and dipropylene glycol alkyl ether.

[0067] Among the above, the solvent preferably contains at least one of ester solvents, more preferably at least one of butyl carbitol acetate (BCA), butyl glycol acetate (BMGAC), dihydroterpineol acetate (DHTA), terpineol, and dihydroterpineol, and even more preferably at least one of butyl carbitol acetate (BCA) and dihydroterpineol acetate (DHTA).

[0068] A binder composition according to one embodiment of the present invention may contain 1 to 40% by mass of binder when the binder composition is taken as 100% by mass. The binder content when the binder composition is taken as 100% by mass may be, for example, 1, 5, 10, 15, 20, 25, 30, 35, or 40% by mass, or may be within a range between any two of the values ​​exemplified here.

[0069] The binder composition according to one embodiment of the present invention may contain other additives as needed, as long as the effects of the present invention are not impaired. Examples of other additives include dispersants, surfactants, antioxidants, flame retardants, plasticizers, lubricants, and mold release agents.

[0070] 3.2 Physical properties of binder composition <Viscosity> The binder composition according to one embodiment of the present invention is a binder composition having a shear rate of 0.01 sec at 25°C. -1 From 10,000 seconds -1 The shear rate was increased at a constant rate over 150 seconds. -1 Preferably, the viscosity A' in the above range is 2.0 Pa·s or more. The viscosity A of the binder composition is, for example, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0, 100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 700.0, 800.0, 900.0, or 1000.0 Pa·s, and may be within a range between any two of the values ​​exemplified here. By having the above viscosity, the binder composition can be used to prepare a firing paste with excellent coatability.

[0071] The binder composition according to one embodiment of the present invention is a binder composition having a shear rate of 0.01 sec at 25°C. -1 From 10,000 seconds -1 When the shear rate was increased at a constant rate over 150 seconds, -1Preferably, the viscosity B' in this range is 0.05 to 2.0 Pa s. The viscosity B may be, for example, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1.0, 1.1.0, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0, and may be within a range between any two of the values ​​exemplified here. By having such a viscosity, the binder composition can be used to prepare a firing paste with excellent coatability.

[0072] The binder composition according to one embodiment of the present invention is a binder composition having a shear rate of 0.01 sec at 25°C. -1 From 10,000 seconds -1 The shear rate was increased at a constant rate over 150 seconds. -1 Viscosity A' and shear rate at 9,000 sec -1 Preferably, the ratio A' / B' to the viscosity B' at this shear rate is 3.0 or greater. A' / B' is, for example, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0, 100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 700.0, 800.0, 900.0, or 1000.0 Pa s, and may be within a range between any two of the values ​​exemplified here. In other words, the binder composition according to one embodiment of the present invention preferably exhibits pseudoplasticity, in which the viscosity decreases as the shear rate increases.

[0073] The viscosity of the binder composition can be controlled by adjusting the type, amount, and weight-average molecular weight of each monomer unit in the lactic acid-vinyl copolymer, as well as the type and amount of the binder and solvent. The viscosity of the binder composition at each shear rate at 25°C can be measured using a rotational viscometer, such as a rheometer, by the following method, specifically, by the method described in the examples. <Method for measuring viscosity A' and viscosity B'> A cone plate with a diameter of 20 mm and a cone angle of 0.975° was attached to the viscosity / viscoelasticity measuring device with a clearance of 23 μm, and the binder composition was set in the measuring section. The shear rate was set to 0.01 sec at a set temperature of 25°C. -1 From 10,000 seconds -1 The shear rate was increased at a constant rate over 150 seconds. -1 Viscosity A' at shear rate 9,000 sec -1 Measure the viscosity B' at As the viscosity / viscoelasticity measuring device, a TA Instruments viscosity / viscoelasticity measuring device "Discovery HR30" can be used.

[0074] <Solvent solubility> The binder composition according to one embodiment of the present invention preferably does not contain any undissolved binder matter that is visible to the naked eye.

[0075] <Micro carbon residue> The binder composition according to one embodiment of the present invention preferably has a micro carbon residue of 2.00% by mass or less. The micro carbon residue may be, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, 1.90, or 2.00% by mass, or may be within a range between any two of the values ​​exemplified here. The micro carbon residue can be specifically determined by the method described in the Examples.

[0076] <95% weight loss temperature (TD95)> The binder composition according to one embodiment of the present invention preferably has a 95% weight loss temperature (TD95) of less than 400°C. The TD95 may be, for example, 350, 355, 360, 365, 370, 375, 380, 385, 390, or 395°C, or less than 400°C, or may be within a range between any two of the values ​​exemplified here. Specifically, the TD95 can be determined using a thermogravimetric differential thermal analyzer by the method described in the examples.

[0077] <Stringability> In a binder composition according to one embodiment of the present invention, when a glass rod is pierced into a lactic acid-vinyl copolymer solution adjusted to a viscosity A of 5 Pa s in an environment of 25°C and pulled up 10 cm, it is preferable that the time required for the thread-like solution existing between the solution surface and the glass rod to break is 4 seconds or less. Specifically, the threadability can be determined by the method described in the examples.

[0078] 4. Firing paste A firing paste according to one embodiment of the present invention includes the binder composition and inorganic particles. Known powders suitable for various applications can be used as the inorganic particles. Examples of inorganic particles include gold, silver, copper, nickel, palladium, ITO, alumina, zirconia, titanium oxide, barium titanate, aluminum nitride, silicon nitride, boron nitride, various glass powders, inorganic phosphors, graphite powder, and solder powder. These particles can be used alone or in combination of two or more. For example, silver, copper, nickel, and nickel can be used to prepare a firing paste for use in printing wiring patterns by screen printing or the like, with nickel being preferred. A firing paste according to one embodiment of the present invention can be used for multilayer ceramic capacitors (MLCCs), for example, for internal electrodes of MLCCs. For example, a firing paste according to one embodiment of the present invention can be used for internal electrodes containing nickel as inorganic particles.

[0079] The formulation of the firing paste is appropriately adjusted so that the firing paste has good coatability and the sintered body obtained by sintering the firing paste has various good properties. For example, when forming internal electrodes or conductor wiring for use in MLCCs, etc., the firing paste can be molded using a known molding method, such as a screen printing method, a dispensing method, or a doctor blade method, to obtain a molded body of the desired shape. The obtained molded body is then heated and dried at an appropriate temperature as needed, and then fired to remove the binder in the firing paste, sinter the inorganic powder, and obtain a sintered body. The firing paste containing the lactic acid-vinyl copolymer of the present invention has excellent coatability, can be molded using, for example, the above-mentioned method, has little stringiness, is less likely to cause problems such as overflow during printing, and can obtain electrodes and conductor wiring with little residual carbon derived from the lactic acid-vinyl copolymer after firing, resulting in a low risk of defects. [Example]

[0080] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited to these examples.

[0081] A vinyl copolymer was prepared according to the following procedure. <Manufacturing example A-1> A 1-L flask equipped with a stirrer, gas inlet tube, thermometer, and reflux condenser was charged with 200 parts by weight of a monomer and solvent mixture consisting of 50 parts by weight of isobutyl methacrylate (iBMA) and 50 parts by weight of 2-hydroxyethyl methacrylate (HEMA) as monomers, and 100 parts by weight of methyl ethyl ketone (MEK) as solvent. Nitrogen gas was introduced into the flask through the gas inlet tube at a flow rate of 0.3 L / min for 30 minutes while stirring and purging with nitrogen. The mixture in the flask was then heated to 75°C. Next, while maintaining the mixture in the flask at 75°C, 0.5 parts by weight of V-601 (dimethyl-2,2'-azobis(2-methylpropionate)) was added as a polymerization initiator five times every 30 minutes. The temperature of the contents in the flask was maintained at 75°C by appropriately heating and cooling. Eight hours after the initial addition of the polymerization initiator, the mixture was cooled to room temperature to obtain a vinyl copolymer solution. The obtained vinyl copolymer solution was dried at 105° C. for 8 hours to prepare vinyl copolymer 1. The weight average molecular weight of the obtained vinyl copolymer 1 was 516,000.

[0082] <Manufacturing example A-2> Vinyl copolymer 2 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 50 parts by mass of isobutyl methacrylate (iBMA), 50 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 100 parts by mass of ethyl acetate (EtAc), and 2 parts by mass of thioglycerol (TGL) as a chain transfer agent, for a total of 202 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 2 was 11,000.

[0083] <Manufacturing example A-3> Vinyl copolymer 3 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 80 parts by mass of isobutyl methacrylate (iBMA), 20 parts by mass of 2-hydroxyethyl methacrylate (HEMA), and 100 parts by mass of ethyl acetate (EtAc), totaling 200 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 3 was 287,000.

[0084] <Manufacturing example A-4> Vinyl copolymer 4 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 200 parts by mass, consisting of 90 parts by mass of isobutyl methacrylate (iBMA), 10 parts by mass of 2-hydroxyethyl methacrylate (HEMA), and 100 parts by mass of ethyl acetate (EtAc). The weight-average molecular weight of the resulting vinyl copolymer 4 was 140,000.

[0085] <Manufacturing example A-5> Vinyl copolymer 5 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 90 parts by mass of isobutyl methacrylate (iBMA), 10 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 100 parts by mass of ethyl acetate (EtAc), and 0.2 parts by mass of thioglycerol (TGL) as a chain transfer agent, for a total of 200.2 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 5 was 63,000.

[0086] <Manufacturing example A-6> A 1-L flask equipped with a stirrer, gas inlet tube, thermometer, and reflux condenser was charged with 300 parts by mass of a monomer and solvent mixture consisting of 90 parts by mass of isobutyl methacrylate (iBMA) and 10 parts by mass of 2-hydroxyethyl methacrylate (HEMA) as monomers, 1 part by mass of polyvinyl alcohol (PVA) as a polymer dispersion stabilizer, and 200 parts by mass of water as a solvent, along with 0.5 parts by mass of V-601 as a polymerization initiator. Nitrogen gas was introduced into the flask through the gas inlet tube at a flow rate of 0.3 L / min for 30 minutes with stirring to replace the atmosphere with nitrogen. The mixture in the flask was then heated to 75°C. The mixture was heated and cooled to maintain the temperature at 75°C and allowed to react for an additional 3 hours. After 3 hours from the addition of the initiator, the mixture was cooled to room temperature to obtain a vinyl copolymer emulsion. The resulting vinyl copolymer emulsion was cooled to room temperature, filtered, and then dried at 105°C for 8 hours to prepare vinyl copolymer 6. The weight-average molecular weight of the resulting vinyl copolymer 6 was 440,000.

[0087] <Manufacturing example A-7> Vinyl Copolymer 7 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 95 parts by mass of isobutyl methacrylate (iBMA), 5 parts by mass of 2-hydroxyethyl methacrylate (HEMA), and 200 parts by mass of water, totaling 300 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 7 was 682,000.

[0088] <Manufacturing example A-8> A vinyl copolymer 8 / meso-lactide mixture was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 95 parts by mass of isobutyl methacrylate (iBMA), 5 parts by mass of 2-hydroxyethyl methacrylate (HEMA), and 100 parts by mass of meso-lactide (mLA), totaling 200 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 8 was 193,000.

[0089] <Manufacturing example A-9> Vinyl copolymer 9 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 90 parts by mass of stearyl methacrylate (SMA), 10 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 90 parts by mass of ethyl acetate (EtAc), 10 parts by mass of toluene (To), and 0.1 parts by mass of thioglycerol (TGL) as a chain transfer agent, for a total of 200.1 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 9 was 82,000.

[0090] <Manufacturing example A-10> Vinyl copolymer 10 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 70 parts by mass of stearyl methacrylate (SMA), 30 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 80 parts by mass of ethyl acetate (EtAc), 20 parts by mass of toluene (To), and 0.1 parts by mass of thioglycerol (TGL) as a chain transfer agent, totaling 200.1 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 10 was 95,000.

[0091] <Manufacturing example A-11> Vinyl copolymer 11 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 200 parts by mass, consisting of 90 parts by mass of stearyl methacrylate (SMA), 10 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 80 parts by mass of ethyl acetate (EtAc), and 20 parts by mass of toluene (To). The weight-average molecular weight of the resulting vinyl copolymer 11 was 320,000.

[0092] <Manufacturing example A-12> Vinyl copolymer 12 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 96 parts by mass of stearyl methacrylate (SMA), 4 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 80 parts by mass of ethyl acetate (EtAc), 20 parts by mass of toluene (To), and 0.1 parts by mass of thioglycerol (TGL) as a chain transfer agent, for a total of 194.1 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 12 was 74,000.

[0093] <Manufacturing example A-13> Vinyl copolymer 13 was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 9096 parts by mass of stearyl methacrylate (SMA), 4 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 80 parts by mass of ethyl acetate (EtAc), and 20 parts by mass of toluene (To), totaling 194 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 13 was 217,000.

[0094] <Manufacturing example A-14> A vinyl copolymer 13 / meso-lactide mixture was prepared in the same manner as in Production Example A-1, except that the monomer and solvent mixture was 99 parts by mass of isobutyl methacrylate (iBMA), 1 part by mass of 2-hydroxyethyl methacrylate (HEMA), and 50 parts by mass of meso-lactide (mLA), totaling 150 parts by mass. The weight-average molecular weight of the resulting vinyl copolymer 14 was 142,000.

[0095] Using the vinyl copolymer prepared by the above procedure, a lactic acid-vinyl copolymer was prepared by the following procedure. <Manufacturing example B-1> A 1-liter flask equipped with a stirrer, gas inlet tube, thermometer, and reflux condenser was charged with 100 parts by weight of a monomer / polymer mixture consisting of 96 parts by weight of meso-lactide (mLA) and 4 parts by weight of vinyl copolymer 1. The contents of the flask were heated to 180°C while nitrogen gas was introduced into the flask through the gas inlet tube at a flow rate of 0.3 L / min, followed by stirring and nitrogen substitution. Next, while maintaining the contents of the flask at 180°C, 0.03 parts by weight of tin octoate was added as a catalyst. The contents of the flask were heated and cooled to maintain the temperature at 180°C, and the reaction was continued for another 3 hours. Three hours after the addition of the catalyst, the contents were cooled to room temperature, yielding lactic acid-vinyl copolymer 1. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 1 was 1,871,000.

[0096] <Manufacturing example B-2> Lactic acid-vinyl copolymer 2 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass in total, consisting of 50 parts by mass of mLA and 50 parts by mass of vinyl copolymer 2. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 2 was 136,000.

[0097] <Manufacturing example B-3> Lactic acid-vinyl copolymer 3 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass in total, consisting of 83 parts by mass of mLA and 17 parts by mass of vinyl copolymer 3. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer was 1,448,000.

[0098] <Manufacturing example B-4> Lactic acid-vinyl copolymer 4 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass in total, consisting of 50 parts by mass of mLA and 50 parts by mass of vinyl copolymer 4. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 4 was 374,000.

[0099] <Manufacturing example B-5> Lactic acid-vinyl copolymer 5 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 90 parts by mass of mLA and 10 parts by mass of vinyl copolymer 4. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 5 was 694,000.

[0100] <Manufacturing example B-6> Lactic acid-vinyl copolymer 6 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 97.5 parts by mass of mLA and 2.5 parts by mass of vinyl copolymer 4. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 6 was 1,055,000.

[0101] <Manufacturing example B-7> Lactic acid-vinyl copolymer 7 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass in total, consisting of 90 parts by mass of mLA and 10 parts by mass of vinyl copolymer 5. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 7 was 899,000.

[0102] <Manufacturing example B-8> Lactic acid-vinyl copolymer 8 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass in total, consisting of 70 parts by mass of mLA and 30 parts by mass of vinyl copolymer 6. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 8 was 1,292,000.

[0103] <Manufacturing example B-9> Lactic acid-vinyl copolymer 9 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 60 parts by mass of mLA and 40 parts by mass of vinyl copolymer 7. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 9 was 1,244,000.

[0104] <Manufacturing example B-10> Lactic acid-vinyl copolymer 10 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 50 parts by mass of mLA and 50 parts by mass of the vinyl copolymer 8 / meso-lactide mixture. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 10 was 533,000.

[0105] <Manufacturing example B-11> Lactic acid-vinyl copolymer 11 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 90 parts by mass of mLA and 10 parts by mass of vinyl copolymer 9. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 11 was 1,122,000.

[0106] <Manufacturing example B-12> Lactic acid-vinyl copolymer 12 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 103 parts by mass in total, consisting of 90 parts by mass of mLA and 13 parts by mass of vinyl copolymer 10. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 12 was 531,000.

[0107] <Manufacturing example B-13> Lactic acid-vinyl copolymer 13 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 50 parts by mass of mLA and 50 parts by mass of vinyl copolymer 11. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 13 was 92,000.

[0108] <Manufacturing example B-14> Lactic acid-vinyl copolymer 14 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 50 parts by mass of mLA and 50 parts by mass of vinyl copolymer 9. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 14 was 193,000.

[0109] <Manufacturing example B-15> Lactic acid-vinyl copolymer 15 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 50 parts by mass of mLA and 50 parts by mass of vinyl copolymer 12. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 15 was 116,000.

[0110] <Manufacturing example B-16> Lactic acid-vinyl copolymer 16 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass in total, consisting of 50 parts by mass of mLA and 50 parts by mass of vinyl copolymer 13. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 16 was 578,000.

[0111] <Manufacturing example B-17> Lactic acid-vinyl copolymer 17 was prepared in the same manner as in Production Example B-1, except that the monomer / polymer mixture was 100 parts by mass, consisting of 33.3 parts by mass of mLA and 66.7 parts by mass of the vinyl copolymer 14 / meso-lactide mixture. The weight-average molecular weight of the resulting lactic acid-vinyl copolymer 17 was 146,000.

[0112] Using the lactic acid-vinyl copolymer obtained above and other compounds as binders, binder compositions were prepared according to the following procedure.

[0113] [Example 1] 30 parts of lactic acid-vinyl copolymer 1 and 70 parts of BCA as a solvent were placed in a sealed container, and the mixture was stirred at 2000 rpm in a THINKY planetary mixer "Awatori Rentaro" until no undissolved material remained, and then degassed at 2200 rpm until no air bubbles remained, and then allowed to stand at 25°C for 1 day to obtain binder composition 1. The measurement results of the physical properties of binder composition 1 and lactic acid-vinyl copolymer 1 are shown in Table 3.

[0114] [Example 2] Binder composition 2 was obtained in the same manner as in Example 1, except that lactic acid-vinyl copolymer 2 was used instead of lactic acid-vinyl copolymer 1 and DHTA was used instead of BCA. The measurement results of the physical properties of binder composition 2 and lactic acid-vinyl copolymer 2 are shown in Table 3.

[0115] [Example 3] Binder composition 3 was obtained in the same manner as in Example 1, except that lactic acid-vinyl copolymer 3 was used instead of lactic acid-vinyl copolymer 1. The measurement results of the physical properties of binder composition 3 and lactic acid-vinyl copolymer 3 are shown in Table 3.

[0116] [Example 4] Binder composition 4 was obtained in the same manner as in Example 2, except that lactic acid-vinyl copolymer 4 was used instead of lactic acid-vinyl copolymer 2. The measurement results of the physical properties of binder composition 4 and lactic acid-vinyl copolymer 4 are shown in Table 3.

[0117] [Example 5] Binder composition 5 was obtained in the same manner as in Example 1, except that lactic acid-vinyl copolymer 5 was used instead of lactic acid-vinyl copolymer 1. The measurement results of the physical properties of binder composition 5 and lactic acid-vinyl copolymer 5 are shown in Table 3.

[0118] [Example 6] Binder composition 6 was obtained in the same manner as in Example 1, except that lactic acid-vinyl copolymer 6 was used instead of lactic acid-vinyl copolymer 1. The measurement results of the physical properties of binder composition 6 and lactic acid-vinyl copolymer 6 are shown in Table 3.

[0119] [Example 7] Binder composition 7 was obtained in the same manner as in Example 1, except that lactic acid-vinyl copolymer 7 was used instead of lactic acid-vinyl copolymer 1. The measurement results of the physical properties of binder composition 7 and lactic acid-vinyl copolymer 7 are shown in Table 3.

[0120] [Example 8] Binder composition 8 was obtained in the same manner as in Example 1, except that lactic acid-vinyl copolymer 8 was used instead of lactic acid-vinyl copolymer 1. The measurement results of the physical properties of binder composition 8 and lactic acid-vinyl copolymer 8 are shown in Table 3.

[0121] [Example 9] Binder composition 9 was obtained in the same manner as in Example 2, except that lactic acid-vinyl copolymer 9 was used instead of lactic acid-vinyl copolymer 2. The measurement results of the physical properties of binder composition 9 and lactic acid-vinyl copolymer 9 are shown in Table 3.

[0122] [Example 10] A binder composition 10 was obtained in the same manner as in Example 2, except that lactic acid-vinyl copolymer 10 was used instead of lactic acid-vinyl copolymer 2. The measurement results of the physical properties of binder composition 10 and lactic acid-vinyl copolymer 10 are shown in Table 3.

[0123] [Example 11] A binder composition 11 was obtained in the same manner as in Example 1, except that lactic acid-vinyl copolymer 11 was used instead of lactic acid-vinyl copolymer 1. The measurement results of the physical properties of binder composition 11 and lactic acid-vinyl copolymer 11 are shown in Table 3.

[0124] [Example 12] A binder composition 12 was obtained in the same manner as in Example 1, except that lactic acid-vinyl copolymer 12 was used instead of lactic acid-vinyl copolymer 1. The measurement results of the physical properties of binder composition 12 and lactic acid-vinyl copolymer 12 are shown in Table 3.

[0125] [Example 13] Binder composition 13 was obtained in the same manner as in Example 2, except that lactic acid-vinyl copolymer 13 was used instead of lactic acid-vinyl copolymer 2. The measurement results of the physical properties of binder composition 13 and lactic acid-vinyl copolymer 13 are shown in Table 3.

[0126] [Example 14] Binder composition 14 was obtained in the same manner as in Example 2, except that lactic acid-vinyl copolymer 14 was used instead of lactic acid-vinyl copolymer 2. The measurement results of the physical properties of binder composition 14 and lactic acid-vinyl copolymer 14 are shown in Table 3.

[0127] [Example 15] Binder composition 15 was obtained in the same manner as in Example 2, except that lactic acid-vinyl copolymer 15 was used instead of lactic acid-vinyl copolymer 2. The measurement results of the physical properties of binder composition 15 and lactic acid-vinyl copolymer 15 are shown in Table 3.

[0128] [Example 16] Binder composition 16 was obtained in the same manner as in Example 2, except that lactic acid-vinyl copolymer 16 was used instead of lactic acid-vinyl copolymer 2. The measurement results of the physical properties of binder composition 16 and lactic acid-vinyl copolymer 16 are shown in Table 3.

[0129] [Example 17] Binder composition 17 was obtained in the same manner as in Example 2, except that lactic acid-vinyl copolymer 17 was used instead of lactic acid-vinyl copolymer 2. The measurement results of the physical properties of binder composition 17 and lactic acid-vinyl copolymer 17 are shown in Table 3.

[0130] [Comparative Example 1] Five parts of ethyl cellulose and 95 parts of DHTA as a solvent were placed in a sealed container, and the mixture was stirred at 2000 rpm in a THINKY planetary mixer "Awatori Rentaro" until no undissolved material remained, and then degassed at 2200 rpm until no air bubbles remained, and then allowed to stand at 25°C for one day to obtain binder composition 17. The measurement results of the physical properties of binder composition 17 and EC are shown in Table 3.

[0131] Comparative Example 2 Binder composition 18 was obtained in the same manner as in Example 2, except that poly-iBMA (PiBMA) was used instead of lactic acid-vinyl copolymer 2. Table 3 shows the measurement results of the physical properties of binder composition 18 and poly-iBMA.

[0132] Comparative Example 3 A binder composition 19 was obtained in the same manner as in Example 1, except that polylactic acid was used instead of lactic acid-vinyl copolymer 1. The measurement results of the physical properties of binder composition 19 and polylactic acid are shown in Table 3.

[0133] The vinyl copolymer, the lactic acid-vinyl copolymer (binder), and the binder composition were evaluated according to the following procedures. <Glass transition temperature of vinyl copolymer> The glass transition temperature of the vinyl copolymer was theoretically calculated using the weight fraction of the monomers blended as raw materials and the glass transition temperature of the homopolymer of the monomers, using the Fox equation below. The results are shown in Table 1. 1 / Tg=w1 / Tg1+w2 / Tg2+...+w i / Tg i +...+w N / Tg N Tg: Glass transition temperature of vinyl copolymer (K) Tg i : Glass transition temperature (K) of homopolymers of N types of vinyl monomers w i : Weight fraction of each of N types of vinyl monomers (where w1 + w2 + ... + w i +...+w N =1)

[0134] <Weight average molecular weight> The weight average molecular weight and molecular weight distribution of the vinyl copolymer and lactic acid-vinyl copolymer were measured using GPC (gel permeation chromatography) under the following conditions. The results are shown in Tables 1 and 2. Measuring device: HLC-8120GPC (Tosoh Corporation) GPC column configuration: The following five columns (all manufactured by Tosoh Corporation) (1) TSK-GEL G7000HXL (2) TSK-GEL GMHXL (3) TSK-GEL GMHXL (4) TSK-GEL G2500HXL Sample concentration: Dilute with tetrahydrofuran to 1.5 mg / cm3 Mobile phase solvent: tetrahydrofuran Flow rate: 1ml / min Column temperature: 40℃

[0135] <Solvent solubility> The solubility of each binder in DHTA (dihydroterpinyl acetate) and BCA (butyl carbitol acetate) was evaluated. 70 parts by mass of organic solvent and 30 parts by mass of binder were placed in a sealed container, and the mixture was stirred at 2000 rpm for 20 minutes using a THINKY rotating and revolving mixer called "Awatori Rentaro," and then degassed at 2200 rpm for 5 minutes. After that, 10 g of the sample was removed from the sealed container and placed on a glass plate, approximately 5 cm thick. 2 After spreading the binder on the surface, the solubility of the binder in the solvent was evaluated visually according to the following evaluation criteria. ◯: The sample placed on the glass plate was uniformly dissolved in the organic solvent, and no insoluble matter was observed. ×: A large amount of insoluble matter was observed in the sample placed on the glass plate.

[0136] <Micro carbon residue> Measurement of micro carbon residue was performed using a micro carbon residue tester (ACR-M3) manufactured by Tanaka Scientific Instruments Manufacturing Co., Ltd. Specifically, approximately 2,0000 g (mass M2) of binder was weighed into a precisely weighed test container (glass, φ20.8 mm x height 80 mm, volume 10 mL, mass M1) and placed in the coking furnace of the tester. Nitrogen was then flowed into the coking furnace at a flow rate of 600 mL / min for 10 minutes, replacing the interior of the furnace with a nitrogen atmosphere. Next, while flowing nitrogen at a flow rate of 150 mL / min, the coking furnace was heated from room temperature to 500 °C at a heating rate of 10 °C / min. The temperature of the coking furnace was then maintained at 500 °C ± 2 °C for 15 minutes, after which heating was stopped and the nitrogen flow rate was increased to 600 mL / min to cool the coking furnace. After the temperature inside the coking furnace dropped below 250 °C, the test container was removed and allowed to cool to room temperature in a desiccator. Thereafter, the mass M3 of the test container containing the heated binder was precisely weighed, and the micro carbon residue (%) was calculated using the following formula 1. {(M3-M1) / M2}×100 (Formula 1)

[0137] <95% weight loss temperature (TD95)> Approximately 5.00 mg of binder was weighed out into an aluminum sample container with a diameter of 5 mm, and the temperature was raised from 30°C to 500°C at a rate of 10°C / min in a nitrogen atmosphere using a thermogravimetric differential thermal analyzer (STA7300) manufactured by Hitachi High-Tech Corporation, and the relationship between temperature and weight change was evaluated. The weight before heating was taken as 100%, and the temperature at which the weight had decreased by 95% was taken as the 95% weight loss temperature (TD95) [°C].

[0138] <Stringability> In an environment of 25°C, a binder was dissolved in a solvent (BCA or DHTA) listed in Table 3 at a ratio such that the viscosity A was 5 Pa s. A glass rod was pierced into the solution and pulled up 10 cm, and the time required for the thread-like solution present between the surface of the solution and the glass rod to break was measured and evaluated according to the following criteria. In Examples 1, 3, 5 to 8, 11, 12 and Comparative Example 3, BCA was used as the solvent, and in the other Examples and Comparative Examples, DHTA was used as the solvent. If it's less than 4 seconds: Yes If it exceeds 4 seconds: ×

[0139] <Acid value> 1 g of a toluene solution containing 25% by weight of binder and 75% by weight of toluene was added to 100 ml of a mixed solvent of 66% by weight of toluene and 34% by weight of ethanol, and the mixture was adjusted until the sample was completely consumed. Potentiometric titration was performed with a 0.1 mol / L potassium hydroxide ethanol solution using an automatic titrator (AUT-701) manufactured by DKK-TOA, and the inflection point of the resulting titration curve was used as the endpoint. The acid value was calculated using the following formula 2. A=(B×f×5.611) / S A: Acid number B: Amount (ml) of 0.1 mol / l potassium hydroxide ethanol solution used in titration f: Factor of 0.1 mol / l potassium hydroxide ethanol solution S: Mass of binder used in measurement (g)

[0140] <Viscosity A, B and viscosity ratio at each shear rate> The viscosity of the lactic acid-vinyl copolymer solution (binder composition) of the present invention was measured using a TA Instruments viscosity / viscoelasticity measuring device "Discovery HR30." Specifically, the measurement temperature was set to 25°C, and 0.1 g of the binder composition was placed in a measuring section equipped with a cone plate having a diameter of 20 mm and a cone angle of 0.975° and a clearance of 23 μm. The shear rate was set to 0.01 sec. -1 From 10,000 seconds -1 The viscosity A at a shear rate of 1 sec-1 when the shear rate is increased at a constant rate over 150 seconds is -1 The viscosity B at the shear rate of 0.01 sec was measured. The viscosity ratio A / B was also calculated. -1 From 10,000 seconds -1 "Increase the shear rate at a constant rate over 150 seconds to 100%" means that the shear rate is increased by 10 times every 25 seconds. For example, the shear rate 25 seconds after the start of measurement is 0.1 sec. -1 The shear rate after 50 seconds from the start of measurement was 1 sec -1 This becomes:

[0141] [Table 1]

[0142] [Table 2]

[0143] [Table 3]

Claims

1. A lactic acid-vinyl copolymer containing lactic acid units derived from lactic acid and vinyl monomer units derived from a vinyl monomer, the lactic acid-vinyl copolymer being used in a baking paste.

2. The lactic acid-vinyl copolymer according to claim 1, A lactic acid-vinyl copolymer having a viscosity of 2.0 Pa·s or more as measured by the following method. <Viscosity measurement method> 1) 30% by mass of the lactic acid-vinyl copolymer and 70% by mass of butyl carbitol acetate or dihydroterpinyl acetate were placed in a sealed container, stirred at 2000 rpm in a planetary mixer until no undissolved material remained, degassed at 2200 rpm until no air bubbles remained, and then allowed to stand at 25°C for one day to prepare a lactic acid-vinyl copolymer solution. 2) A cone plate with a diameter of 20 mm and a cone angle of 0.975° was attached to the viscosity / viscoelasticity measuring device with a clearance of 23 μm, and 0.1 g of the lactic acid-vinyl copolymer solution obtained in 1) was placed in the measuring section. The viscosity was measured at a set temperature of 25°C and a shear rate of 0.01 sec. －１ From 10,000 seconds －１ Shear rate 1 sec when increased at a constant rate over 150 seconds －１ Viscosity measurement at

3. The lactic acid-vinyl copolymer according to claim 1 or 2, A lactic acid-vinyl copolymer having a ratio A / B of viscosity A to viscosity B measured by the following method of 3.0 or more. <Method for measuring viscosity A and viscosity B> 1) 30% by mass of the lactic acid-vinyl copolymer and 70% by mass of butyl carbitol acetate or dihydroterpinyl acetate were placed in a sealed container, stirred at 2000 rpm in a planetary mixer until no undissolved material remained, degassed at 2200 rpm until no air bubbles remained, and then allowed to stand at 25°C for one day to prepare a lactic acid-vinyl copolymer solution. 2) A cone plate with a diameter of 20 mm and a cone angle of 0.975° was attached to the viscosity / viscoelasticity measuring device with a clearance of 23 μm, and 0.1 g of the lactic acid-vinyl copolymer solution obtained in 1) was placed in the measuring section. The viscosity was measured at a set temperature of 25°C and a shear rate of 0.01 sec. －１ From 10,000 seconds －１ The shear rate was increased at a constant rate over 150 seconds. －１ Viscosity A at shear rate of 9,000 sec －１ Measure the viscosity B at

4. 3. The lactic acid-vinyl copolymer according to claim 1, wherein the weight-average molecular weight is 10,000 to 3,000,000.

5. 3. The lactic acid-vinyl copolymer according to claim 1, wherein the lactic acid-vinyl copolymer has a micro carbon residue content of 2.00% by mass or less.

6. The lactic acid-vinyl copolymer according to claim 1 or 2, The lactic acid-vinyl copolymer contains a vinyl polymer block, A lactic acid-vinyl copolymer, wherein the glass transition temperature of the vinyl polymer block is 0 to 100°C.

7. 3. The lactic acid-vinyl copolymer according to claim 1, wherein the lactic acid unit is bonded to a functional group contained in the vinyl monomer.

8. 8. The lactic acid-vinyl copolymer according to claim 7, wherein the functional group is at least one functional group selected from the group consisting of a hydroxyl group, a carbonyl group, an epoxy group, an amino group, an isocyanate group, a thiol group, and an alkoxysilyl group.

9. 3. The lactic acid-vinyl copolymer according to claim 1, wherein the vinyl monomer comprises at least one of (meth)acrylic acid and a (meth)acrylic acid ester.

10. 3. The lactic acid-vinyl copolymer according to claim 1, wherein the vinyl monomer comprises a vinyl monomer containing an alkyl group having 1 to 22 carbon atoms.

11. 3. The lactic acid-vinyl copolymer according to claim 1, wherein a toluene solution of the lactic acid-vinyl copolymer containing 25% by mass of the lactic acid-vinyl copolymer and 75% by mass of toluene has an acid value of 0.1 mgKOH / g or more and 20.0 mgKOH / g or less.

12. 3. The lactic acid-vinyl copolymer according to claim 1, wherein the lactic acid-vinyl copolymer contains 5.0 to 99.9% by mass of the lactic acid units relative to 100% by mass of the lactic acid-vinyl copolymer.

13. 3. The lactic acid-vinyl copolymer according to claim 1, wherein the lactic acid-vinyl copolymer is a graft copolymer.

14. A binder composition for preparing a baking paste, comprising the lactic acid-vinyl copolymer according to claim 1 or 2, and a solvent.

15. A binder composition for preparing a firing paste according to claim 14, comprising: A binder composition having a ratio A' / B' of viscosity A' to viscosity B' measured by the following method of 3.0 or more. <Method for measuring viscosity A' and viscosity B'> A cone plate with a diameter of 20 mm and a cone angle of 0.975° was attached to a viscosity / viscoelasticity measuring device with a clearance of 23 μm, and the binder composition was set in the measuring section. The set temperature was 25° C. and the shear rate was 0.01 sec. －１ From 10,000 seconds －１ The shear rate was increased at a constant rate over 150 seconds. －１ Viscosity A' at shear rate of 9,000 sec －１ Measure the viscosity B' at

16. A paste for firing, comprising the binder composition for preparing a paste for firing according to claim 14 and inorganic particles.

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