JP6914790B2 - Method for manufacturing conductive paste for positive electrode of lithium ion battery and mixture paste for positive electrode of lithium ion battery - Google Patents

Description

The present invention relates to a method for producing a conductive paste for a positive electrode of a lithium ion battery and a mixed material paste for a positive electrode of a lithium ion battery.

A lithium ion secondary battery is a type of non-aqueous electrolyte secondary battery, and is a secondary battery in which lithium ions in the electrolyte are responsible for electrical conduction. Lithium-ion secondary batteries have excellent characteristics such as high energy density, excellent charge energy retention characteristics, and small so-called memory phenomenon in which apparent capacity is reduced. Therefore, lithium ion secondary batteries are used in a wide range of fields such as mobile phones, smartphones, personal computers, hybrid vehicles, and electric vehicles.

Here, the lithium ion secondary battery mainly includes a positive electrode plate, a negative electrode plate, a separator for insulating the positive electrode plate and the negative electrode plate, a non-aqueous electrolytic solution, and the like. The positive electrode plate has a positive electrode mixture layer formed on the surface of the positive electrode core material. The positive electrode mixture layer is obtained by applying a positive electrode mixture paste, which is a mixture of a conductive paste containing a conductive additive (carbon, etc.), a binder and a solvent, and an electrode active material to the surface of the positive electrode core material, and drying the paste. , Can be manufactured.

Since the positive electrode mixture layer is manufactured by applying the positive electrode mixture paste to the surface of the positive electrode core material as described above, the positive electrode mixture paste and the conductive paste which is a constituent material thereof have low viscosity. Is required to be. Under such circumstances, a method of adding a dispersant for dispersing the conductive auxiliary agent in the conductive paste or the dispersion liquid is known (Patent Documents 1 and 2). Further, a method of using a specific vinyl alcohol-based polymer as a binder is also known (Patent Document 3). Further, a method of using a copolymer of a monomer mixture containing a monomer having a polycyclic aromatic hydrocarbon as a dispersion resin is also known (Patent Documents 4 and 5).

However, in the technical field to which the present invention belongs, the development of a method for reducing the viscosity of the conductive paste and the positive electrode mixture paste is still eagerly desired.

Japanese Unexamined Patent Publication No. 2013-89485 Japanese Unexamined Patent Publication No. 2014-193986 Japanese Unexamined Patent Publication No. 11-250915 JP-A-2017-98240 JP-A-2017-98241

An object to be solved by the present invention is to provide a mixture paste for a positive electrode of a lithium ion battery, which has a viscosity that suppresses high viscosity and is easy to apply.

Under such circumstances, as a result of diligent studies, the present inventors used a resin having a polycyclic aromatic hydrocarbon group and / or an amide group as at least a part of the dispersed resin, and further, a dispersed resin and polyvinylidene fluoride (B). ), Conductive carbon (C), and solvent (D) are dispersed to obtain a dispersion, and then a dispersion resin is further added to the obtained dispersion. I found that it could be solved. The present invention is based on such novel findings.

Therefore, the present invention provides the following sections:
Item 1. A step of dispersing a mixed solution containing a dispersion resin (A-1), polyvinylidene fluoride (B), conductive carbon (C), and a solvent (D) to obtain a dispersion.
Next, the step of adding the dispersion resin (A-2) to the dispersion liquid,
A method for producing a conductive paste for a positive electrode of a lithium ion battery, wherein the dispersed resin (A-1) and / or the dispersed resin (A-2) has a polycyclic aromatic hydrocarbon group and / or an amide group. Including methods.
Item 2. Item 1 is characterized in that the total content of the dispersed resin (A-1) and the dispersed resin (A-2) is 0.1 to 10 parts by mass based on 100 parts by mass of the conductive carbon (C). The method described.
Item 3. Item 2. The method according to Item 1 or 2, wherein the mass ratio of the dispersed resin (A-1) and the dispersed resin (A-2) is 99/1 to 50/50.
Item 4. Item 6. The method according to any one of Items 1 to 3, wherein the dispersed resin (A-1) and the dispersed resin (A-2) contain a resin having a hydroxyl group.
Item 5. Item 6. The method according to any one of Items 1 to 4, wherein the dispersed resin (A-2) contains a resin having a polycyclic aromatic hydrocarbon group.
Item 6. Item 6. The method according to any one of Items 1 to 4, wherein the dispersed resin (A-1) contains a resin having a polycyclic aromatic hydrocarbon group.
Item 7. Regarding the dispersed resin (A-1) and the dispersed resin (A-2), the amount of resin adsorbed on the conductive carbon (C) measured under the following conditions was 30 mg / g or more for the dispersed resin (A-1). Item 6. The method according to any one of Items 1 to 6, wherein the dispersed resin (A-2) has an adsorption amount of 10 mg / g or more and less than 30 mg / g.
[Adsorption amount measurement conditions (carbon)]
80 mg of resin, 2 g of conductive carbon, and 1000 g of N-methyl-2-pyrrolidone are mixed well and left at room temperature for 1 week. Then, the precipitate (pigment) is removed, and the supernatant is quantified by gel permeation chromatography (GPC) to calculate the amount of resin adsorbed on the pigment.
Item 8. A method for producing a mixture paste for a positive electrode of a lithium ion battery, which comprises a step of mixing an electrode active material with the conductive paste obtained by the method according to Items 1 to 7.
Item 9. Regarding the dispersed resin (A-1) and the dispersed resin (A-2), the amount of the dispersed resin adsorbed on the electrode active material measured under the following conditions is less than 5 mg / g for the dispersed resin (A-1). Item 8. The production method according to Item 8, wherein the dispersed resin (A-2) has an adsorption amount of 5 mg / g or more.
[Adsorption amount measurement conditions (electrode active material)]
80 mg of the resin, 2 g of the electrode active material, and 1000 g of N-methyl-2-pyrrolidone are mixed well and left at room temperature for 1 week. Then, the precipitate (pigment) is removed, and the supernatant is quantified by gel permeation chromatography (GPC) to calculate the amount of resin adsorbed on the pigment.
Item 10. Item 8. A method for producing a positive electrode mixture layer of a lithium ion battery, which comprises a step of applying a mixture paste obtained by the method according to Item 8 or 9 to a current collector.
Item 11. Item 10. A method for manufacturing a lithium ion battery, which comprises a step of installing a positive electrode, a negative electrode, and an electrolyte having a positive electrode mixture layer obtained by the method according to Item 10 in a battery case.

The method for producing a conductive paste for a positive electrode of a lithium ion battery and a mixed material paste for a positive electrode of a lithium ion battery of the present invention is a lithium ion battery positive electrode in which higher viscosity is suppressed than conventional ones due to the above-mentioned structural features. Conductive or mixed material paste can be obtained.

Hereinafter, embodiments for carrying out the present invention will be described in detail.
It should be noted that the present invention is not limited to the following embodiments, and should be understood to include various modifications implemented without changing the gist of the present invention.

Further, in the present specification, "(meth) acrylate" means acrylate and / or methacrylate, and "(meth) acrylic acid" means acrylic acid and / or methacrylic acid. In addition, "(meth) acryloyl" means acryloyl and / or methacryloyl. In addition, "(meth) acrylamide" means acrylamide and / or methacrylamide. The "polymerizable unsaturated monomer" means a monomer having a polymerizable unsaturated group capable of radical polymerization, and examples of the polymerizable unsaturated group include a (meth) acryloyl group, an acrylamide group, and a vinyl group. , Allyl group, (meth) acryloyloxy group, vinyl ether group and the like. Further, in the present specification, the term pigment is described as a concept including conductive carbon, electrode active material and the like.

Method for Producing Conductive Paste for Lithium Ion Battery Positive Electrode In the present invention, a mixed solution containing a resin (A-1), polyvinylidene fluoride (B), conductive carbon (C), and a solvent (D) is dispersed and dispersed. The process of getting
Next, the step of adding the resin (A-2) to the dispersion liquid,
A method for producing a conductive paste for a positive electrode of a lithium ion battery, wherein the resin (A-1) and / or the resin (A-2) has a polycyclic aromatic hydrocarbon group and / or an amide group. , Provide a method.

The total solid content of the dispersed resin (A-1) in the conductive paste solid content for the positive electrode of the lithium ion battery obtained by the production method of the present invention is usually 25% by mass or less, preferably 15% by mass or less. This is preferable from the viewpoints of viscosity at the time of pigment dispersion, pigment dispersibility, dispersion stability, production efficiency and the like. The total solid content of the dispersed resin (A-1) in the solid content of the conductive paste for the positive electrode of the lithium ion battery obtained by the production method of the present invention is usually 0.1% by mass or more, preferably 0. It is preferably 5% by mass or more. The total solid content of the dispersed resin (A-2) in the conductive paste solid content for the positive electrode of the lithium ion battery obtained by the production method of the present invention is usually 25% by mass or less, preferably 15% by mass or less. This is preferable from the viewpoints of viscosity at the time of pigment dispersion, pigment dispersibility, dispersion stability, production efficiency and the like. The total solid content of the dispersed resin (A-2) in the solid content of the conductive paste for the positive electrode of the lithium ion battery obtained by the production method of the present invention is usually 0.1% by mass or more, preferably 0. It is preferably 2% by mass or more. The total solid content of the dispersed resins (A-1) and (A-2) in the conductive paste solid content for the positive electrode of the lithium ion battery obtained by the production method of the present invention is usually 30% by mass or less, preferably 30% by mass or less. 20% by mass or less is preferable from the viewpoints of viscosity at the time of pigment dispersion, pigment dispersibility, dispersion stability, production efficiency and the like. Further, the total solid content of the dispersed resins (A-1) and (A-2) in the conductive paste solid content for the positive electrode of the lithium ion battery obtained by the production method of the present invention is usually 0.2% by mass. As mentioned above, it is preferably 0.7% by mass or more.

The solid content of polyvinylidene fluoride (B) in the solid content of the conductive paste for the positive electrode of the lithium ion battery of the present invention is usually 1% by mass or more and less than 30% by mass, preferably 2% by mass or more and 25% by mass. %, More preferably 4% by mass or more, and less than 20% by mass is preferable from the viewpoint of battery performance. The solid content of the conductive carbon (C) in the solid content of the conductive paste for the positive electrode of the lithium ion battery of the present invention is usually 30% by mass or more and less than 97% by mass, preferably 50% by mass or more and 94% by mass. Less than, more preferably 70% by mass or more, and less than 91% by mass is preferable from the viewpoint of battery performance. The content of the solvent (D) in the conductive paste for the positive electrode of the lithium ion battery of the present invention is usually 30% by mass or more and less than 95% by mass, preferably 45% by mass or more and less than 92% by mass. Preferably, 60% by mass or more and less than 90% by mass is preferable from the viewpoint of drying efficiency and paste viscosity.

Process 1
The method of the present invention includes a step of dispersing a mixed liquid containing a resin (A-1), polyvinylidene fluoride (B), conductive carbon (C), and a solvent (D) to obtain a dispersion liquid (the present invention). The process may be referred to as step 1). In the step 1, each component described above is subjected to, for example, a dispersion, a paint shaker, a sand mill, a ball mill, a roll mill, a pebble mill, an LMZ mill, a DCP pearl mill, various mixers, a planetary ball mill, a homogenizer, a biaxial kneader, and a thin film swirl type. This can be done by uniformly mixing and dispersing using a conventionally known disperser such as a high-speed mixer.

The conductive paste for the positive electrode of a lithium ion battery obtained by the production method of the present invention can be used for producing a mixture paste for the positive electrode of a lithium ion battery by mixing with an electrode active material, as will be described later.

Dispersed resin (A-1)
As the dispersion resin (A-1), a resin used in the field of batteries to which the present invention belongs can be appropriately used. However, in the present invention, at least one of the dispersed resin (A-1) and the dispersed resin (A-2) contains a resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group. It is a feature. To that extent, the dispersed resin (A-1) may or may not contain a resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group.

Resin having a polycyclic aromatic hydrocarbon group and / or an amide group (AI)
The resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group is a monomer (AI-1) having a polycyclic aromatic hydrocarbon and / or a (meth) acrylamide compound (AI-2). ), For example, a monomer mixture containing a total of 1 to 70% by mass of a monomer (AI-1) having a polycyclic aromatic hydrocarbon and a (meth) acrylamide compound (AI-2). Can be obtained by In this case, the resin (AI) is a total of 1 to 70 masses of the monomer (AI-1) having a polycyclic aromatic hydrocarbon and the monomer (AI-2) based on the total amount of the solid content of the monomer mixture. It can also be rephrased as a copolymer of a monomer mixture containing%. Further, a resin having a polycyclic aromatic hydrocarbon group can also be obtained by synthesizing a resin having no polycyclic aromatic hydrocarbon and then adding a polycyclic aromatic hydrocarbon.

Examples of the type of resin (AI) include acrylic resin, polyester resin, epoxy resin, polyether resin, alkyd resin, urethane resin, silicone resin, polycarbonate resin, silicate resin, chlorine resin, fluororesin, and polyvinyl. Examples thereof include resins and composite resins thereof, and acrylic resins are particularly preferable.

In addition, in this specification, a "derivative" is obtained by changing a small part (may be a plurality of parts) in a molecule by introduction of a functional group, substitution of an atom, or other chemical reaction with respect to a certain compound. Means a compound that is For example, naphthalene contains one or more functional groups such as an alkyl group, an alkoxy group, a hydroxyl group, a sulfonic acid group, a carboxyl group, an amino group, a nitro group, a halogen atom, an aryloxy group, an alkylthio group and an arylthio group. The introduced compound is a naphthalene derivative.

Monomer with polycyclic aromatic hydrocarbons (AI-1)
Examples of the polycyclic aromatic hydrocarbon of the monomer (AI-1) having a polycyclic aromatic hydrocarbon include a naphthalene ring, an anthracene ring, a triphenylene ring, a tetraphene ring, a tetracene ring, a kekulene ring, and a pyrene ring. Examples thereof include hydrocarbon groups having a pentacene ring, a hexacene ring, a heptacene ring, a coronen ring, and a kekulene ring, and derivatives thereof. In a preferred embodiment of the present invention, the monomer (AI-1) having a polycyclic aromatic hydrocarbon is one of the above polycyclic aromatics having a naphthalene ring, that is, a polymerizable unsaturated having a naphthyl group. Examples thereof include monomers or derivatives thereof. Examples of the polymerizable unsaturated monomer having a naphthyl group or a derivative thereof include a polymerizable unsaturated monomer having a naphthyl group represented by the formula (3) described later or a derivative thereof (AI-1-2). ..

The monomer (AI-1) having a polycyclic aromatic hydrocarbon is a polymerizable unsaturated monomer (AI-1) having a polycyclic aromatic hydrocarbon represented by the following formula (2). Is preferable.

(In the formula, R represents a hydrogen atom or a methyl group, A represents a polycyclic aromatic hydrocarbon group, W may or may not be present. If W is present, W is a carbon atom, When the number of nitrogen atoms and / or oxygen atoms is 1 to 20 and W is absent, W is directly bonded to A.) The "polymerizable unsaturated monomer" is a polymerization capable of radical polymerization. It means a monomer having a sex unsaturated group, and examples of the polymerizable unsaturated group include (meth) acryloyl group, acrylamide group, vinyl group, allyl group, (meth) acryloyloxy group, vinyl ether group and the like. ..

Specific examples of the polymerizable unsaturated monomer (AI-1-1) having a polycyclic aromatic hydrocarbon include vinylnaphthalene, naphthyl (meth) acrylate, naphthylalkyl (meth) acrylate, and vinyl anthracene. , Anthracenyl (meth) acrylate, anthracenylalkyl (meth) acrylate, vinyl pyrene, pyrenyl (meth) acrylate, pyrenyl alkyl (meth) acrylate, vinyl chrysene, vinyl naphthalene, vinyl pentacene, and derivatives thereof. .. In addition, a polymerizable unsaturated group monomer having a reactive functional group such as a glycidyl group or an isocyanate group and a polycyclic aromatic hydrocarbon having a functional group that reacts with the reactive functional group are reacted with each other. .. Any combination of functional groups that react with each other can be preferably used, but a combination of a carboxyl group and a glycidyl group, an amino group and a glycidyl group, and a hydroxyl group and an isocyanate group is more preferable. Specifically, for example, glycidyl (meth) acrylate and 1-naphthylacetic acid, 2- (meth) acryloyloxyethyl isocyanate and 1-naphthol, 2- (meth) acryloyloxyethyl isocyanate and 1- (2-naphthyl) ethanol. Examples include the combination of. These can be used alone or in combination of two or more.

Among them, the polymerizable unsaturated monomer (AI-1-1) having a polycyclic aromatic hydrocarbon is a polymerizable unsaturated monomer having a naphthyl group represented by the following formula (3) or a derivative thereof (AI-I). -1-2) is preferable.

(In the formula, R represents a hydrogen atom or a methyl group, and X and Y may be the same or different, and the hydrogen atom, alkyl group, alkoxy group, alkoxycarbonyloxy group, phosphoryloxy group, hydroxyl group and sulfone. Indicates any of an acid group, a carboxyl group, an amino group, a nitro group, a halogen atom, an aryloxy group, an alkylthio group or an arylthio group. If W is present, W is the number of carbon atoms, nitrogen atoms and / or oxygen atoms. Is an organic group or a single bond of 1 to 20.)
Examples of the polymerizable unsaturated monomer having a naphthyl group or a derivative thereof (AI-1-2) include vinylnaphthalene, naphthyl (meth) acrylate, naphthylalkyl (meth) acrylate, and derivatives thereof. .. These can be used alone or in combination of two or more.

Among them, the naphthyl (meth) acrylate or a derivative thereof (AI-1-2) is preferably a naphthyl (meth) acrylate represented by the following formula (4) or a derivative thereof (AI-1-3). ..

(In the formula, R represents a hydrogen atom or a methyl group, and X and Y may be the same or different, and the hydrogen atom, alkyl group, alkoxy group, hydroxyl group, sulfonic acid group, carboxyl group and alkoxycarbonyloxy. Indicates either a group, a phosphoryloxy group, an amino group, a nitro group, a halogen atom, an aryloxy group, an alkylthio group or an arylthio group.)
Examples of the naphthyl (meth) acrylate or a derivative thereof (AI-1--3) include 1-naphthyl (meth) acrylate, 2-naphthyl (meth) acrylate, and derivatives thereof. The seeds can be used alone or in combination of two or more.

Among them, the naphthyl (meth) acrylate or its derivative (AI-1-3) is a 4-substituted-1-naphthyl (meth) acrylate (AI-1--4) represented by the following formula (5). Is preferable.

(In the formula, R represents a hydrogen atom or a methyl group, and Z represents a hydroxyl group or an alkoxy group having 1 to 8 carbon atoms.)
When Z, which is a substituent in the above formula (5), is an alkoxy group, the number of carbon atoms of the alkoxy group is usually 1 to 8, preferably 1 to 4, and more preferably 1 to 2. Especially preferably 1.

Examples of the 4-substituted-1-naphthyl (meth) acrylate (AI-1--4) include 4-methyl-1-naphthyl (meth) acrylate and 4-ethyl-1-naphthyl (meth) acrylate, 4 −methoxy-1-naphthyl (meth) acrylate, 4-ethoxy-1-naphthyl (meth) acrylate, 4-hydroxy-1-naphthyl (meth) acrylate, 2-methoxy-4-hydroxy-1-naphthyl (meth) acrylate , 2-ethoxy-4-hydroxy-1-naphthyl (meth) acrylate, 2-hydroxy-4-methoxy-1-naphthyl (meth) acrylate, 2-hydroxy-4-ethoxy-1-naphthyl (meth) acrylate, 4 Examples thereof include −methoxycarbonyloxy-1-naphthyl (meth) acrylate, 4-phenoxycarbonyloxy-1-naphthyl (meth) acrylate, 4-phosphoryloxy-1-naphthyl (meth) acrylate, and derivatives thereof. Can be used alone or in combination of two or more.

The reason why the pigment-dispersed resin having a polycyclic aromatic hydrocarbon of the present invention is effective in the dispersibility and stability of the pigment is not known in detail, but for example, the pigment has an aromatic ring. In this case, it is considered that this is because it is stabilized by the π-π interaction between the pigment and the pigment-dispersed resin. The π-π interaction is a dispersion force acting between aromatic rings, and is also called a stacking interaction because the two aromatic rings tend to be stabilized in an arrangement like a stack of coins.

The reason why the substituent of the 4-substituted-1-naphthyl (meth) acrylate (AI-1--4) is effective in the dispersibility and stability of the pigment is not known in detail. For example, it is speculated that having a substituent increases the electrostatic potential of the aromatic ring and enhances the affinity with the pigment.

(Meta) Acrylamide Compound (AI-2)
As the (meth) acrylamide compound (AI-2), those known per se can be used without particular limitation, and specifically, for example, acrylamide, methacrylamide, 2-acrylamide-2-methylpropanesulfonic acid. , N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide butyl ether, N-methylolmethacrylamide butyl ether, N-ethylacrylamide, N-ethylmethacrylamide, Nn-propylacrylamide, N-n-propylmethacrylamide , N-Isopropyl Acrylamide, N-Isopropyl Acrylamide, N-Cyclopropyl Acrylamide, N-Cyclopropyl Acrylamide, Diacetone Acrylamide, Diacetone Acrylamide, N-Hydroxymethylacrylamide, N-Hydroxymethyl Methulamide, N-Hydroxy Ethylacrylamide, N-hydroxypropylacrylamide, N-hydroxybutylacrylamide, N-hydroxypentylacrylamide, N-hydroxymethyl-N-ethylacrylamide, N-methyl-N-hydroxyethylacrylamide, N, N-dihydroxymethylacrylamide, N , N-dihydroxyethylacrylamide, N, N-dihydroxypropylacrylamide, N, N-dihydroxybutylacrylamide, N, N-dihydroxypentylacrylamide, N-hydroxymethylmethacrylamide, N-hydroxyethylmethacrylate, N-hydroxypropylmethacryl Amid, N-Hydroxybutyl Acrylamide, N-Hydroxypentyl Acrylamide, N-Hydroxymethyl-N-Eethyl Acrylamide, N-Methyl-N-Hydroxyethyl Acrylamide, N, N-Dihydroxymethyl Acrylamide, N, N -Dihydroxyethyl methacrylamide, N, N-dihydroxypropyl methacrylamide, N, N-dihydroxybutyl methacrylamide, N, N-dihydroxypentyl methacrylamide, N, N-dihydroxybutyl (meth) acrylamide, and N- [Tris ( Hydroxymethyl) methyl) acrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide, N-methyl, N-ethylacrylamide, N-me Chill, N-ethyl methacrylamide, N-methylol acrylamide methyl ether, N-methylol methacrylamide methyl ether, N-methylol acrylamide ethyl ether, N-methylol methacrylamide ethyl ether, N-methylol acrylamide propyl ether, N-methylol methacrylamide. Propyl ether, N-methylolacrylamide butyl ether, N-methylolmethacrylamide butylether, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide , N, N-Dipropylaminoethyl (meth) acrylamide and other amino group-containing (meth) acrylamide compounds, methacryloyloxyethyltrimethylammonium chloride (acrylester DMC, trade name, manufactured by Mitsubishi Rayon Co., Ltd.) and other quaternary ammonium bases. Examples thereof include a contained acrylamide compound and acryloylmorpholin. These can be used alone or in combination of two or more.

Of these, a (meth) acrylamide compound represented by the following formula (7) is preferable.
CH ₂ = C (-R ₁ ) -C (= O) -N (-R ₂ ) -R ₃ ... Equation (7)
_{R 1} in the above formula (7) is a hydrogen atom or a methyl group, and R ₂ and R ₃ may be different or the same, and may be at least one selected from a hydrogen atom, an organic group having a hydroxyl group, and an alkyl group. It is preferable to have. Further _{, it is more preferable that both or one of R 2} and R ₃ is an organic group having a hydroxyl group, and specifically, for example, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N- Hydroxypropyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide, N-hydroxymethyl-N-ethyl (meth) acrylamide, N-methyl-N-hydroxyethyl (meth) acrylamide, N-ethyl-N-hydroxyethyl (Meta) acrylamide, N-hydroxyethyl-N-butyl (meth) acrylamide, N-hydroxybutyl-N-butyl (meth) acrylamide, N, N-dihydroxymethyl (meth) acrylamide, N, N-dihydroxyethyl (meth) ) It is particularly preferable that it is at least one selected from acrylamide, N, N-dihydroxypropyl (meth) acrylamide, N, N-dihydroxybutyl (meth) acrylamide, and N- [tris (hydroxymethyl) methyl) acrylamide.

Polymerizable unsaturated monomers other than polymerizable unsaturated monomers (AI-1) and (meth) acrylamide compounds (AI-2) having polycyclic aromatic hydrocarbons The polycyclic aromatic hydrocarbon groups and / or amides described above. The resin (AI) having a group includes a polymerizable unsaturated monomer (AI-1) having a polycyclic aromatic hydrocarbon and / or a (meth) acrylamide compound (AI-2) and optionally the (A). It can be obtained by (co) polymerization of polymerizable unsaturated monomers other than I-1) and (AI-2). The polymerizable unsaturated monomer other than the polymerizable unsaturated monomer (AI-1) having a polycyclic aromatic hydrocarbon is not particularly limited as long as it is a polymerizable unsaturated monomer usually used in the synthesis of acrylic resin. It can be used, for example, an alkyl (meth) acrylate having 3 or less carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and isopropyl (meth) acrylate, and n-butyl (meth). ) Acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) ) Acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate , Alkyl or cycloalkyl (meth) acrylates such as tricyclodecanyl (meth) acrylates; polymerizable unsaturated compounds having isobornyl groups such as isobornyl (meth) acrylates; polymerizable with adamantyl groups such as adamantyl (meth) acrylates. Unsaturated compounds; aromatic ring-containing polymerizable unsaturated monomers such as benzyl (meth) acrylate, styrene, α-methylstyrene, vinyltoluene; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3- A monoesteride of a (meth) acrylic acid such as hydroxypropyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate and a divalent alcohol having 2 to 8 carbon atoms, the (meth) acrylic acid and 2 to 8 carbon atoms. Ε-caprolactone modified product of monoesterate with divalent alcohol, allyl alcohol, hydroxyl group-containing polymerizable unsaturated monomer such as (meth) acrylate having a polyoxyalkylene chain having a hydroxyl group at the molecular end; (meth) acrylic acid , Maleic acid, crotonic acid, β-carboxyethyl acrylate and other carboxyl group-containing polymerizable unsaturated monomers; (meth) acrylonitrile, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate. , Glycidyl (meth) acrylate and amine compounds Nitrogen-containing polymerizable unsaturated monomer that does not contain a urethane bond such as an adduct of Polymerizable unsaturated monomer having urethane bond such as reaction product of; glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl Epoxy group-containing polymerizable unsaturated monomer such as (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allylglycidyl ether; (meth) acrylate having a polyoxyethylene chain having an alkoxy group at the molecular end; 2 -Polymerically unsaturated monomers having sulfonic acid groups such as sulfoethyl (meth) acrylate, allyl sulfonic acid, 4-styrene sulfonic acid, sodium salt and ammonium salt of these sulfonic acids; 2-acryloyloxyethyl acid phosphate, 2- Polymerizable unsaturated monomers having a phosphate group such as methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy). ) Polymerizable unsaturated monomer having an alkoxysilyl group such as silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane; perfluorobutylethyl (meth) acrylate, perfluoro Perfluoroalkyl (meth) acrylate such as octylethyl (meth) acrylate; polymerizable unsaturated monomer having fluorinated alkyl group such as fluoroolefin; polymerizable unsaturated monomer having photopolymerizable functional group such as maleimide group; molecule (Meta) acrylate having a polyoxyethylene chain having an alkoxy group at the end; allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1 , 3-butylene glycol di (meth) acrylate, trimerol propantri (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopenti Luglycoldi (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol di (meth) acrylate, 1,1,1-tris Hydroxymethyl ethanedi (meth) acrylate, 1,1,1-tris hydroxymethyl ethanetri (meth) acrylate, 1,1,1-tris hydroxymethyl propanetri (meth) acrylate, triallyl isocyanurate, diallyl terephthalate, divinyl Examples thereof include polymerizable unsaturated monomers having two or more polymerizable unsaturated groups such as benzene in one molecule. These can be used alone or in combination of two or more.

Among them, it is preferable to contain at least one kind of styrene, and it is more preferable to contain 5 to 65% by mass of styrene based on the total amount of the polymerizable unsaturated monomer component.

Further, from the viewpoint of forming a three-dimensional repulsion layer of the resin and ensuring the stability of the pigment dispersion paste, the polyalkylene glycol macromonomer can be contained based on the total amount of the polymerizable unsaturated monomer component.

The polyalkylene glycol macromonomer is a nonionic polymerizable unsaturated monomer represented by the following formula (6), and specific examples of such a monomer include polyethylene glycol (meth) acrylate and polypropylene glycol. Examples thereof include (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, and ethoxypolyethylene glycol (meth) acrylate. Of these, polyethylene glycol (meth) acrylate and polypropylene glycol (meth) acrylate are particularly preferable.
CH ₂ = C (R ₁ ) COO (C _n H _2n O) _m −R ₂ ... Equation (6)
[In the formula, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m is an integer of 4 to 60, particularly 4 to 55, and n is 2. It is an integer of ~ 3, where m oxyalkylene units (C _n H _2n O) may be the same or different from each other. ]
Synthesis of Resin (AI) Having Polycyclic Aromatic Hydrocarbon Group and / or Amid Group The resin (AI) having a polycyclic aromatic hydrocarbon group and / or amide group is in the presence of a radical polymerization initiator. In addition, it can be obtained by a radical polymerization method known per se, such as a method of solution polymerization in an organic solvent or a method of emulsion polymerization in an aqueous medium.

Examples of the radical polymerization initiator used for the polymerization include cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, and 1,1-bis (tert-butylperoxy) -3,3. 5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, n-butyl-4,4-bis (tert-butylperoxy) valerate, cumenehydroperoxide, 2,5-dimethylhexane-2 , 5-Dihydroperoxide, 1,3-bis (tert-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, diisopropylbenzene peroxide , Tert-Butyl cumyl peroxide, decanoyyl peroxide, lauroyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, di-tert-amyl peroxide, bis (tert-butylcyclohexyl) peroxydicarbonate, Peroxide polymerization initiators such as tert-butylperoxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tert-butylperoxy-2-ethylhexanoate; 2,2 ´-Azobis (isobutyronitrile), 1,1-azobis (cyclohexane-1-carbonitrile), azocusmen, 2,2 ´-azobis (2-methylbutyronitrile), 2,2 ′-azobisdimethylvalero Nitrile, 4,4'-azobis (4-cyanovaleric acid), 2- (t-butylazo) -2-cyanopropane, 2,2'-azobis (2,4,4-trimethylpentane), 2,2' Examples thereof include azo-based polymerization initiators such as -azobis (2-methylpropane) and dimethyl2,2'-azobis (2-methylpropionate). These can be used alone or in combination of two or more.

The solvent used for the above polymerization or dilution is not particularly limited, and examples thereof include water, an organic solvent, and a mixture thereof. Examples of the organic solvent include hydrocarbon solvents such as n-butane, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane and cyclobutane; aromatic solvents such as toluene and xylene; and methylisobutylketone and the like. Ketone solvents; ether solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol; ethyl acetate, n-butyl acetate, isobutyl acetate, Ester-based solvents such as ethylene glycol monomethyl ether acetate and butyl carbitol acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and diisobutyl ketone; alcohol-based solvents such as ethanol, isopropanol, n-butanol, sec-butanol and isobutanol. Solvent: Equamid (trade name, manufactured by Idemitsu Kosan Co., Ltd., amide solvent), N, N-dimethylformamide, N, N-dimethylacetamide, N-methylformamide, N-methylacetamide, N-methylpropioamide, N Conventionally known solvents such as amide-based solvents such as −methyl-2-pyrrolidone can be mentioned. These can be used alone or in combination of two or more.

In solution polymerization in an organic solvent, a method in which a polymerization initiator, a polymerizable unsaturated monomer component, and an organic solvent are mixed and heated while stirring, and an organic solvent is placed in a reaction vessel in order to suppress a temperature rise of the system due to reaction heat. The polymerizable unsaturated monomer component and the polymerization initiator are mixed and dropped or separated and dropped over a predetermined time while being charged and stirring at a temperature of 60 ° C to 200 ° C and blowing an inert gas such as nitrogen or argon as necessary. The method of polymerizing is used.

The polymerization can generally be carried out for about 1 to 10 hours. After each stage of polymerization, an additional catalyst step may be provided to heat the reaction vessel while dropping a polymerization initiator as needed.

The pigment-dispersed resin of the present invention obtained as described above preferably has a weight average molecular weight in the range of preferably 1,000 to 100,000, more preferably 3,000 to 50,000.

The resin (AI) can be made into a solid or a resin solution replaced with an arbitrary solvent by removing the solvent and / or substituting the solvent after the completion of the synthesis. As the substitution solvent, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, propylene glycol monomethyl ether, alcohol-based solvent and the like are preferable.

As a method for removing the solvent, heating may be performed at normal pressure, or the solvent may be removed under reduced pressure. As a method of solvent replacement, the replacement solvent may be added at any stage before desolving, during desolving, or after desolving.

In the present specification, the number average molecular weight and the weight average molecular weight are the holding times (holding capacity) measured by using a gel permeation chromatograph (GPC), and the holding time of standard polystyrene having a known molecular weight measured under the same conditions. It is a value obtained by converting to the molecular weight of polystyrene by (retention capacity). Specifically, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) is used as a gel permeation chromatograph, and "TSKgel G-4000HXL", "TSKgel G-3000HXL", and "TSKgel G-2500HXL" are used as columns. And "TSKgel G-2000HXL" (trade name, both manufactured by Tosoh Corporation) can be measured under the conditions of mobile phase tetrahydrofuran, measurement temperature 40 ° C., flow velocity 1 mL / min and detector RI. can.

Polyvinyl alcohol resin (A II)
In the present invention, the dispersed resin (A-1) may contain a polyvinyl alcohol resin (AII). The polyvinyl alcohol resin (A II) is a resin obtained by copolymerizing a polymerizable unsaturated group-containing monomer (A IIa-1) represented by the following formula (1) with another polymerizable unsaturated monomer (A II). In the present specification, it may be simply referred to as polyvinyl alcohol resin (A IIa) or resin (A IIa)), sulfonic acid-modified polyvinyl alcohol resin (A IIb) (in the present specification, simply polyvinyl alcohol resin (A IIb)). Or resin (A IIb)), and polyvinyl alcohol resin (A IIc) other than resin (A IIa) and resin (A IIb) (in the present specification, simply polyvinyl alcohol resin (A IIc) or resin. (Sometimes referred to as (AIIC))):

(In the formula, R ₁ , R ₂ , R ₃ and R ₄ are at least one selected from the group consisting of a hydrogen atom, a hydrocarbon group, a hydroxyl group and a methylol group, and R ₁ , R are the same or different. _{2. At} least one of R ₃ and R ₄ is a hydroxyl group. Further, X may or may not be present, and when X is present, X is a connecting chain consisting of one or more kinds of atoms. ).

In the present invention, the polyvinyl alcohol resin (A IIa) and / or the polyvinyl alcohol resin (A IIb) can be preferably used as the polyvinyl alcohol resin (A II), but the polyvinyl alcohol resin (A IIc) is also used in combination. It is preferable to use it.

Polyvinyl alcohol resin (A IIa)
The polyvinyl alcohol resin (A IIa) is a resin obtained by copolymerizing a polymerizable unsaturated group-containing monomer (A IIa-1) represented by the above formula (1) with another polymerizable unsaturated monomer. In the present invention, the "resin containing a polymerizable unsaturated group-containing monomer (A IIa-1) as one of its constituent components" is a raw material monomer containing a polymerizable unsaturated group-containing monomer (A IIa-1) (co-). ) Means a resin obtained by polymerization. Similarly, in the present invention, the resin having monomer X as a constituent means a resin obtained by (co) polymerizing a raw material containing monomer X. Further, the polyvinyl alcohol resin (A IIa) is not sulfonic acid-modified and can be clearly distinguished from the sulfonic acid-modified polyvinyl alcohol resin (A IIb).

_{R 1} , R ₂ , R ₃ and R ₄ in the polymerizable unsaturated group-containing monomer (A IIa-1) represented by the formula (1) are the same or different, and are the same or different hydrogen atoms, hydrocarbon groups, hydroxyl groups, and the like. It is at least one selected from the methylol groups, and at least one of R ₁ , R ₂ , R ₃ and R ₄ (for example, 1 to 3 is preferable, and 2 to 3 is more preferable) is a hydroxyl group. Further, X in the monomer represented by the above formula (1) may or may not be present, and if it is not present, it is a single bond, and if X is present, it is a linkage consisting of one or more kinds of atoms. It is a chain. Such a linking chain is not particularly limited, but may be an alkylene (for example, a linear or branched alkylene having 1 to 6 carbon atoms) or an alkenylene (for example, a linear or branched alkylene having 2 to 6 carbon atoms). , Alkenylene having 1 to 2 (preferably 1) double bonds), alkynylene (eg, linear or branched chain with 2 to 6 carbon atoms, and 1 to 2 triple bonds (preferably) In addition to hydrocarbon groups such as alkynylene), phenylene, and naphthylene (these hydrocarbon groups may be substituted with halogens such as fluorine, chlorine, and bromine), -O-,-(R-). _{O) m -, - (O} -R) m -, - (R-O) m -R -, - C (= O) -, - R (-OH) -, - C (= O) -O- , -RC (= O) -O-, -C (= O) -OR-, -C (= O) -N (-R)-, -C (= O) -N (-R) ) -R-, -RC (= O) -N (-R)-, -RC (= O) -N (-R) -R-, and the like. (R above is an arbitrary substituent independently, and a hydrogen atom and an alkyl group are preferable. In addition, m is an integer of 1 or more.)
Among them, a single bond (X does not exist), a hydrocarbon group, an ester group [-C (= O) -O-], an amide group [-C (= O) -NH-], an amide methyl group [-C (=) O) It is preferable that it is a link chain selected from NH-CH2-], and it is more preferable that it is a single bond (X does not exist).

Specific examples of the monomer (A IIa-1) include, for example, hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate ring-opening product, 2-propene-1-ol, and 1-propene-1,3-. Diol, 1-propen-2-ol, 2-methyl-2-propen-1-ol, 2-butene-1-ol, 2-methyl-2-butene-1-ol, 1-methyl-2-butene-1 -Ol, 2-butene-1,4-diol, 1-butene-3,4-diol, 2-methyl-2-butene-1,4-diol, 4-pentene-2-ol, 3-pentene-1 -Ol, 4-Penten-2-ol, 4-Penten-1-ol, 1-Penten-4,5-diol, 2-Penten-1,5-diol, N-hydroxymethyl (meth) acrylamide, N- Hydroxyethyl (meth) acrylamide, N-hydroxyisopropyl (meth) acrylamide, N- (1-methyl-2-hydroxyethyl) (meth) acrylamide, 2,3-dihydroxypropyl (meth) acrylamide, 1,2-dihydroxyethyl Examples thereof include (meth) acrylamide and derivatives thereof.

These can be used alone or in combination of two or more. Among them, those having two or more hydroxyl groups are preferable.

Further, it is preferable that the total number of carbon atoms and oxygen atoms in _{X, R 3} and R ₄ in the monomer (A IIa-1) represented by the formula (1) is 3 or more.

The content ratio of the polymerizable unsaturated group-containing monomer (A IIa-1) in the resin (A IIa) is preferably in the range of 0.01 to 20% by mass, preferably 0.1 to 15% by mass. It is more preferably within the range, and particularly preferably within the range of 0.5 to 10% by mass. In the present invention, the "content ratio of the polymerizable unsaturated group-containing monomer (A IIa-1) in the resin (A IIa)" means the polymerizable unsaturated group in the monomer mixture which is the raw material of the resin (A IIa). It means the content ratio of the contained monomer (A IIa-1). Therefore, the content ratio of the polymerizable unsaturated group-containing monomer (A IIa-1) in the resin (A IIa) is 0.1 to 20% by mass, that the resin (A IIa) is polymerizable unsaturated. It means that it is a copolymer of a raw material monomer containing 0.1 to 20% by mass of a group-containing monomer (A IIa-1). Similarly, the "content ratio of the monomer X in the resin Y" means the content ratio of the monomer X in the monomer mixture which is the raw material of the resin Y. Therefore, the content ratio of the polymerizable unsaturated group-containing monomer X in the resin Y is a mass%, which means that the resin Y is a copolymer of the raw material monomer containing the monomer X in a mass%. ..

The other polymerizable unsaturated monomer copolymerizing with the polymerizable unsaturated group-containing monomer (A IIa-1) is not particularly limited as long as it is a monomer copolymerizable with the monomer (A IIa-1). Specifically, for example, fatty acid vinyl esters such as vinyl acetate; olefin-based monomers such as ethylene and propylene; (meth) acryloyl group-containing monomers such as alkyl (meth) acrylates; allyls such as allylglycidyl ethers. Ethers; vinyl halide-based compounds such as vinyl chloride, vinylidene chloride, and vinyl fluoride; vinyl ethers such as alkyl vinyl ethers and the like can be mentioned. These can be used alone or in combination of two or more, and among them, fatty acid vinyl ester (A IIa-2) is preferable. Specific examples of the fatty acid vinyl ester (A IIa-2) include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caproate, vinyl laurate, and myristic acid. Examples include vinyl, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl octylate, vinyl monochloroate, vinyl benzoate, vinyl cinnate, vinyl crotonate, divinyl adipate, and derivatives thereof, among which vinyl acetate is used. preferable.

Further, it is preferable from the viewpoint of dispersibility and solubility that the resin (A IIa) obtained by copolymerization is saponified to hydrolyze all or a part of the fatty acid vinyl ester units into vinyl alcohol units. ..

The degree of saponification is preferably in the range of 50 to 100 mol%, more preferably in the range of 70 to 100 mol%, further preferably in the range of 86 to 100 mol%, and 88 to 99. It is particularly preferably in the range of 9.9 mol%.
In other words, the resin (A IIa) by saponifying a copolymer of at least one polymerizable unsaturated group-containing monomer (A IIa-1) and at least one fatty acid vinyl ester (A IIa-2). Is particularly preferably a resin containing a polymerizable unsaturated group-containing monomer (A IIa-1), a fatty acid vinyl ester (A IIa-2), and a vinyl alcohol (A IIa-3) as constituents.

Normally, when the degree of saponification (high polarity) is increased, the adsorptivity to inorganic pigments such as carbon is improved, but the solubility in a solvent (NMP, etc.) is reduced, and a three-dimensional repulsion layer cannot be formed, resulting in poor dispersibility. It will be. However, in the present invention, the reason why the resin (A IIa) containing the above-mentioned polymerizable unsaturated group-containing monomer (A IIa-1) as one of the constituents has an effect on the dispersibility of the conductive paste is that the side chain of the resin is effective. By introducing a specific functional group into the resin, the relatively bulky side chain functional group becomes a steric hindrance to lower the melting point of the resin, and the hydrogen bond of a specific hydroxyl group lowers the crystallinity of the resin. Therefore, it is considered that the solubility in the solvent and the adsorptivity to the pigment were compatible with each other.

The polymerization method of the resin (AIIIa) can be produced by a polymerization method known per se, for example, a method of solution polymerization in an organic solvent, but the polymerization method is not limited to this, and for example, bulk polymerization or It may be emulsion polymerization, suspension polymerization or the like. When solution polymerization is carried out, continuous polymerization or batch polymerization may be performed, the monomers may be charged all at once, may be charged separately, or may be added continuously or intermittently.

The polymerization initiator used in solution polymerization is not particularly limited, but specifically, for example, azobisisobutyronitrile, azobis-2,4-dimethylpareronitrile, and azobis (4-methoxy-2). , 4-Dimethylpaleronitrile) and other azo compounds; acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate and other peroxides Substances; Percarbonate compounds such as diisoppilperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate; t-butylperoxyneodecanate, α-cumylperoxyneodecanate , T-Butylperoxyneodecanate and other perester compounds; known radical polymerization initiators such as azobisdimethylvaleronitrile and azobismethoxyvaleronitrile can be used.

The polymerization reaction temperature is not particularly limited, but can usually be set in the range of about 30 to 200 ° C.

The conditions for saponification are not particularly limited, and saponification can be performed by a known method. For example, it can be carried out by hydrolyzing the ester portion in the molecule in the presence of an alkali catalyst or an acid catalyst in an alcohol solution such as methanol.

As the alkali catalyst, for example, hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate and the like, alcoholates and the like can be used. As the acid catalyst, for example, an aqueous inorganic acid solution such as hydrochloric acid or sulfuric acid or an organic acid such as p-toluenesulfonic acid can be used, but it is desirable to use sodium hydroxide.

The temperature of the saponification reaction is not particularly limited, but is preferably in the range of 10 to 70 ° C, more preferably 30 to 40 ° C. The reaction time is not particularly limited, but it is desirable to carry out the reaction in the range of 30 minutes to 3 hours.

The resin (AIIIa) can be made into a solid or a resin solution replaced with an arbitrary solvent by removing the solvent and / or substituting the solvent after the completion of the synthesis. As the substitution solvent, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, propylene glycol monomethyl ether, alcohol-based solvent and the like are preferable.

As a method for removing the solvent, heating may be performed at normal pressure, or the solvent may be removed under reduced pressure. As a method of solvent replacement, the replacement solvent may be added at any stage before desolving, during desolving, or after desolving.

Sulfonic acid-modified polyvinyl alcohol resin (A IIb)
The sulfonic acid-modified polyvinyl alcohol resin (A IIb) is a polyalcohol resin to which sulfonic acid is added by the following production method. Further, the polyvinyl alcohol resin (A IIb) does not contain the polymerizable unsaturated group-containing monomer (A IIa-1) represented by the above formula (1), and is clearly distinguished from the polyvinyl alcohol resin (A IIa). can.
(1) A method of copolymerizing a compound containing a sulfonic acid group and a polymerizable unsaturated group with a fatty acid vinyl ester such as vinyl acetate, and further saponifying the obtained polymer.
(2) A method of adding Michael sulfonic acid, 2-acrylamide-2-methylpropane sulfonic acid, or the like to polyvinyl alcohol.
(3) A method of heating polyvinyl alcohol with a sulfuric acid compound solution (sulfuric acid aqueous solution, sodium sulfite aqueous solution, etc.).
(4) A method for acetalizing polyvinyl alcohol with a sulfonic acid group-containing aldehyde compound.
(5) A method for polymerizing polyvinyl alcohol by allowing a compound having a functional group such as an alcohol having a sulfonic acid group, an aldehyde and a thiol to coexist as a chain transfer agent.

Any production method can be preferably used, but in particular, the compound containing the sulfonic acid group and the polymerizable unsaturated group of (1) and other polymerizable unsaturated monomers (particularly fatty acid vinyl esters such as vinyl acetate are preferable. ), And the obtained polymer is further saponified.

As the compound containing the sulfonic acid group and the polymerizable unsaturated group (in the present specification, it may be simply referred to as a polymerizable unsaturated monomer having a sulfonic acid group), a compound capable of copolymerizing with a fatty acid vinyl ester. If it is, it can be used without particular limitation, and specifically, for example, olefin sulfonic acid such as vinyl sulfonic acid, isoprene sulfonic acid, ethylene sulfonic acid, allyl sulfonic acid, metaallyl sulfonic acid; sodium sulfopropyl 2-ethylhexyl. Sulfoalkyl malates such as malate, sodium sulfopropyl tridecyl malate, sodium sulfopropyl eicosyl malate; sulfoalkyl (meth) such as 2- (meth) acrylamide-2-methylpropanesulfonic acid, N-sulfoisobutylene acrylamide sodium. Acrylamide; 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfonic acid, 3-methacryloyloxy-2-hydroxypropanesulfonic acid, 3-acryloyloxypropanesulfonic acid, sulfoethyl (meth) acrylate, sodium methacrylate-4-4- Sulfoalkyl (meth) acrylates such as styrene sulfonate, sodium 2-sulfoethyl acrylate; allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, styrene sulfonic acid, oleyl 2-hydroxy- [3-allyloxy] -propyl sulfosuccinate Examples thereof include ammonium salts, and these can be used alone or in combination of two or more.

In the present invention, the sulfonic acid group may be in the form of a free acid, or may be in the form of an alkali metal salt such as a sodium salt or a potassium salt, an ammonium salt or the like.
The content ratio of the polymerizable unsaturated monomer having a sulfonic acid group in the sulfonic acid-modified polyvinyl alcohol resin (A IIb) is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass. In the present invention, the "content ratio of the monomer having a sulfonic acid group in the resin (A IIb)" means the content ratio of the monomer having a sulfonic acid group in the monomer mixture which is the raw material of the resin (A IIb). Therefore, the content ratio of the monomer having a sulfonic acid group in the resin (A IIb) is 0.1 to 10% by mass, that is, the resin (A IIb) contains a monomer having a sulfonic acid group of 0.1 to 0.1. It means that it is a copolymer of a raw material monomer containing 10% by mass.

The other polymerizable unsaturated monomer copolymerizing with the compound containing the sulfonic acid group and the polymerizable unsaturated group is particularly limited as long as it is a monomer copolymerizable with the polymerizable unsaturated monomer having a sulfonic acid group. Can be used without. [However, it is limited to monomers other than the polymerizable unsaturated group-containing monomer (A IIa-1). ] Specifically, for example, a fatty acid vinyl ester such as vinyl acetate; an olefin monomer such as ethylene and propylene; a (meth) acryloyl group-containing monomer such as alkyl (meth) acrylate; an allyl ether such as allyl glycidyl ether; vinyl chloride. , Vinyl halide compounds such as vinylidene chloride and vinyl fluoride; vinyl ethers such as alkyl vinyl ethers and the like. These can be used alone or in combination of two or more, and among them, fatty acid vinyl ester is preferable. As the fatty acid vinyl ester, one or more of the fatty acid vinyl esters exemplified in the fatty acid vinyl ester (A IIa-2) can be preferably used, and vinyl acetate is particularly preferable.

The saponification degree of the sulfonic acid-modified polyvinyl alcohol resin (A IIb) is preferably in the range of 30 to 100 mol%, more preferably in the range of 50 to 100 mol%, and in the range of 86 to 100 mol%. It is more preferably in the range of 88 to 99.9 mol%, and particularly preferably in the range of 88 to 99.9 mol%.

Normally, when the degree of saponification (high polarity) is increased, the adsorptivity to inorganic pigments such as carbon is improved, but the solubility in a solvent (NMP, etc.) is reduced, and a three-dimensional repulsion layer cannot be formed, resulting in poor dispersibility. It will be. However, in the present invention, the reason why the sulfonic acid-modified polyvinyl alcohol resin (A IIb) has an effect on the dispersibility of the conductive paste is that the side chain of the resin is introduced with a specific functional group so that the side chain is relatively bulky. The chain functional group (functional group containing sulfonic acid) becomes a steric obstacle to lower the melting point of the resin, and the highly polar side chain functional group (functional group containing sulfonic acid) improves the crystallinity of the resin. Since it can be reduced, it is considered that both the solubility in the solvent and the adsorptivity to the pigment can be achieved at the same time.

As the polymerization method of the resin (A IIb), the same method as that of the resin (A IIa) described above can be used.

Polyvinyl alcohol resin (A IIc) other than resin (A IIa) and resin (A IIb)
The dispersed resin (A) does not contain the polymerizable unsaturated group-containing monomer (A IIa-1), and contains a polyvinyl alcohol resin (A IIc) having a saponification degree of 30 to 100 mol% that has not been sulfonic acid-modified. be able to. In the present invention, the "polyvinyl alcohol resin containing no polymerizable unsaturated group-containing monomer (A IIa-1)" is a raw material monomer containing no polymerizable unsaturated group-containing monomer (A IIa-1) (co). It means a polyvinyl alcohol resin obtained by polymerization. Further, the "polyvinyl alcohol resin not modified with sulfonic acid" refers to a polyvinyl alcohol resin obtained by (co) polymerization of a raw material monomer containing no sulfonic acid group or a polyvinyl alcohol resin having a sulfonic acid group formed by the above-mentioned modification or the like. It means a resin that has not been added.

The polyvinyl alcohol resin (A IIc) can be obtained by a polymerization method known per se, for example, by polymerizing and hydrolyzing a fatty acid vinyl ester typified by vinyl acetate.

As the fatty acid vinyl ester, one or more of the fatty acid vinyl esters exemplified in the fatty acid vinyl ester (A IIa-2) can be preferably used, and vinyl acetate is particularly preferable.

The polyvinyl alcohol resin (A IIc) can be obtained by copolymerizing with a polymerizable unsaturated monomer other than the fatty acid vinyl ester. [However, this is limited to monomers other than the polymerizable unsaturated group-containing monomer (A IIa-1) and the polymerizable unsaturated monomer having a sulfonic acid group. The polymerizable unsaturated monomer copolymerizable with the fatty acid vinyl ester is particularly limited as long as it is a monomer other than the polymerizable unsaturated group-containing monomer (A IIa-1) and the polymerizable unsaturated monomer having a sulfonic acid group. Can be used without, for example, olefinic monomers such as ethylene and propylene; (meth) acryloyl group-containing monomers such as alkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and glycidyl (meth) acrylate; allylglycidyl. Allyl ethers such as ethers; vinyl halide compounds such as vinyl chloride, vinylidene chloride and vinyl fluoride; vinyl ethers such as alkyl vinyl ethers and 4-hydroxyvinyl ethers can be mentioned. These can be used alone or in combination of two or more.

In the following, the description will be made mainly with reference to vinyl acetate, but the present invention is not limited thereto.

The above-mentioned polymerization method of polyvinyl alcohol resin (A IIc) is a polymerization method known per se, for example, a method such as solution polymerization of vinyl acetate in an alcohol-based organic solvent to produce polyvinyl acetate and saponification thereof. However, the present invention is not limited to this, and for example, bulk polymerization, emulsion polymerization, suspension polymerization, or the like may be used. When solution polymerization is carried out, continuous polymerization or batch polymerization may be performed, the monomers may be charged all at once, may be charged separately, or may be added continuously or intermittently.

The polymerization initiator used in solution polymerization is not particularly limited, but specifically, for example, azobisisobutyronitrile, azobis-2,4-dimethylpareronitrile, and azobis (4-methoxy-2). , 4-Dimethylpaleronitrile) and other azo compounds; acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate and other peroxides Substances; Percarbonate compounds such as diisoppilperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate; t-butylperoxyneodecanate, α-cumylperoxyneodecanate , T-Butylperoxyneodecanate and other perester compounds; known radical polymerization initiators such as azobisdimethylvaleronitrile and azobismethoxyvaleronitrile can be used.

The polymerization reaction temperature is not particularly limited, but can usually be set in the range of about 30 to 200 ° C.

The saponification conditions for producing the polyvinyl alcohol resin (AIIC) are not particularly limited, and saponification can be performed by a known method. Generally, it can be carried out by hydrolyzing the ester portion in the molecule in the presence of an alkali catalyst or an acid catalyst in an alcohol solution such as methanol.

As the alkali catalyst, for example, hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate and the like, alcoholates and the like can be used. As the acid catalyst, for example, an aqueous inorganic acid solution such as hydrochloric acid or sulfuric acid or an organic acid such as p-toluenesulfonic acid can be used, but it is desirable to use sodium hydroxide.

The temperature of the saponification reaction is not particularly limited, but is preferably in the range of 10 to 70 ° C, more preferably 30 to 40 ° C. The reaction time is not particularly limited, but it is desirable to carry out the reaction in the range of 30 minutes to 3 hours.

The polyvinyl alcohol resin obtained in this manner preferably has a degree of polymerization of 100 to 4,000, more preferably 100 to 3,000.
The saponification degree is usually in the range of 30 to 100 mol%, preferably in the range of 32 to 94 mol%.

In the present invention, the saponification degree of the polyvinyl alcohol resin (A IIc) is the ratio (mol%) of the constituent units derived from the fatty acid vinyl ester contained in the polyvinyl alcohol resin (A IIc) in which the ester bond is hydrolyzed. ) Means. The degree of saponification can be measured by completely saponifying a polyvinyl alcohol resin with an alkaline substance such as sodium hydroxide and measuring the amount of the obtained fatty acid salt (for example, acetate). (It can be confirmed by infrared absorption analysis whether it is completely saponified.)
The polyvinyl alcohol resin (A IIc) may be a commercially available product.

The polyvinyl alcohol resin (A IIc) can be made into a solid or a resin solution replaced with an arbitrary solvent by removing the solvent and / or substituting the solvent after the completion of the synthesis. As the substitution solvent, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, propylene glycol monomethyl ether, alcohol-based solvent and the like are preferable.

As a method for removing the solvent, heating may be performed at normal pressure, or the solvent may be removed under reduced pressure. As a method of solvent replacement, the replacement solvent may be added at any stage before desolving, during desolving, or after desolving.

In the conductive paste of the present invention, the resins are compatible with each other by using the high-polarity resin (A IIa) and / or (A IIb) in combination with the relatively low-polarity polyvinyl alcohol resin (A IIc). It is considered that the mixture further achieved both solvent solubility and pigment adsorption.

When the dispersed resin (A) contains a resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group and a polyvinyl alcohol resin (AI II), the blending ratio thereof is not limited, but the dispersed resin (A) The solid content of the resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group is usually 5 to 95 parts by mass, preferably 10 to 50 parts by mass with respect to 100 parts by mass of the solid content of A). The range, the solid content of the polyvinyl alcohol resin (A II), is usually in the range of 5 to 95 parts by mass, preferably in the range of 50 to 90 parts by mass, from the viewpoint of viscosity and battery performance. When the polyvinyl alcohol (A II) contains both the polyvinyl alcohol resin (A IIa) and / or (A IIb) and the polyvinyl alcohol (A IIc), the blending ratio thereof is not limited, but the polyvinyl alcohol resin (A IIa) The solid content of polyvinyl alcohol (A IIc) is usually in the range of 5 to 100 parts by mass, preferably in the range of 15 to 70 parts by mass, based on 100 parts by mass of the total solid content of the resin (A IIb) and the resin (A IIb). It is preferable from the viewpoint of viscosity and battery performance.

Other Dispersed Resin The dispersed resin (A) may be optionally blended with a resin other than the above-mentioned resin (AI) and resin (AI II). For example, acrylic resins other than resins (AI) and resins (AI II), polyester resins, epoxy resins, polyether resins, alkyd resins, urethane resins, silicone resins, polycarbonate resins, silicate resins, chlorine-based resins, polyvinylidene fluorides. Examples thereof include fluororesins other than (PVDF), polyvinylpyrrolidone resins, polyvinyl alcohol resins, polyvinyl acetal resins, and composite resins thereof. These resins can be used alone or in combination of two or more. Among them, it is preferable to use at least one resin selected from polyvinyl acetal resin, polyvinylpyrrolidone resin, and fluororesin in combination. Further, these resins can be blended in the conductive paste as a pigment-dispersed resin or as an additive resin after pigment dispersion.

Further, in the present invention, the dispersed resin (A-1) preferably contains a resin containing a hydroxyl group. The ratio of the solid content of the resin containing a hydroxyl group to the solid content of the dispersed resin (A-1) is preferably 1 to 100% by mass, more preferably 50 to 100% by mass.

Polyvinylidene fluoride (B)
As the polyvinylidene fluoride, those in cultivated land can be widely used in the field of conductive paste for positive electrode of lithium ion battery to which the invention belongs. The weight average molecular weight of polyvinylidene fluoride is not particularly limited, but is usually preferably 10,000 to 2,000,000, more preferably 50,000 to 1,700,000, and particularly preferably 100,000 to 1,500,000. preferable. The polyvinylidene fluoride may be used as a dispersion resin for conductive carbon, or may be added after dispersion of conductive carbon.

Conductive carbon (C)
As the conductive carbon (C), the conductive carbon used in the field of the battery to which the present invention belongs can be appropriately used. Examples of the conductive carbon (C) include acetylene black, furnace black, thermal black, channel black, Ketjen black, vulcan, carbon nanotubes, graphene, vapor-grown carbon fiber (VGCF), graphite and the like. Preferred are acetylene black, graphite and the like, and more preferably acetylene black and the like. Further, in a preferred embodiment of the present invention, the conductive carbon (C) may contain both acetylene black and graphite. These conductive carbons can be used alone or in combination of two or more.

Solvent (D)
As the solvent (D), those known in the field of the conductive paste for the positive electrode of a lithium ion battery can be widely used, and the above-mentioned resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group can be widely used. A solvent other than water used for polymerization or dilution can be preferably used. Specific examples of the preferable solvent (D) include, for example, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, propylene glycol monomethyl ether, methanol and the like, and preferably N-methyl-2-pyrrolidone and the like. Can be mentioned. These solvents can be used alone or in admixture of two or more.

Other Components The conductive paste for the positive electrode of the lithium ion battery may contain components other than the above components (A-1), (A-2), (B), (C), and (D), and is dehydrated. Agents and additives can be used. A step of dispersing a mixed solution containing a resin (A-1), polyvinylidene fluoride (B), conductive carbon (C), and a solvent (D) to obtain a dispersion liquid; then, the above dispersion liquid. The step of adding the dispersed resin (A-2) to the mixture; between these steps; may be added at any stage after the step of adding the dispersed resin (A-2).

Dehydrating agent As the dehydrating agent, known dehydrating agents can be used without particular limitation as long as they have a dehydrating action. It may be a solid dehydrating agent that does not dissolve in the solvent (D) of the conductive paste, or it may be a dehydrating agent that dissolves in the solvent (D). Specifically, for example, solid dehydrating agents such as zeolite, silica gel, calcium oxide, molecular sieve, active alumina, barium oxide, calcium hydride, sodium sulfate; trimethyl phosphate, tri-2-propyl phosphate, tributyl phosphate. , Phosphate esters such as tetraisopropylethylenephosphonate; phosphine oxides such as tolubutylphosphinoxide, trioctylphosphine oxide, triphenylphosphine oxide; orthoesteric acid methyl ester, orthoesteric acid ethyl ester, orthoacetate methyl ester, orthoacetate ethyl ester , Orthoesters such as orthoester benzoic acid ethyl ester; oxalic anhydride, acetic anhydride, propionic acid anhydride, butyric anhydride, benzoic acid anhydride, trifluoroacetic anhydride, disulfate, dinitrogen pentoxide, diphosphate , Diphosphory pentoxide, diphosphorus trioxide, hydride pentoxide, arsenic trioxide, methanesulfonic anhydride, trifluoromethanesulfonic anhydride, acid anhydrides such as sulfobenzoic anhydride, and the like. Can be used alone or in combination of two or more.

Additives Examples of additives include neutralizers, pigment dispersants, defoamers, preservatives, rust inhibitors, plasticizers, binders and the like.

Examples of the pigment dispersant and / or binder include acrylic resins other than the above dispersion resin (A) and polyvinylidene fluoride, polyester resins, epoxy resins, polyether resins, alkyd resins, urethane resins, silicone resins, and polycarbonate resins. , Silicate resin, chlorine-based resin, fluorine-based resin, polyvinylpyrrolidone resin, polyvinyl alcohol resin, polyvinyl acetal resin, and composite resins thereof. These resins can be used alone or in combination of two or more.

Step 2
The method of the present invention further includes a step of adding the dispersion resin (A-2) to the dispersion obtained by the above step (in the present invention, the step may be referred to as step 2). In the step 2, the dispersion resin (A-2) is added to the dispersion liquid, and in a typical embodiment, these are used, for example, a dispenser, a paint shaker, a sand mill, a ball mill, a roll mill, a pebble mill, an LMZ mill, and a DCP pearl mill. , Various mixers, planetary ball mills, homogenizers, twin-screw kneaders, thin film swirl type high-speed mixers, and other conventionally known dispersers can be used for uniform mixing.

Dispersed resin (A-2)
As the dispersion resin (A-2), a resin used in the field of batteries to which the present invention belongs can be appropriately used. However, in the present invention, at least one of the dispersed resin (A-1) and the dispersed resin (A-2) contains a resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group. It is a feature. To that extent, the dispersed resin (A-2) may or may not contain a resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group.

In the method of the present invention, the conductive carbon (C) is first produced by mixing the raw materials containing the dispersed resin (A-1), polyvinylidene fluoride (B), conductive carbon (C), and solvent (D). After the dispersion, the dispersion resin (A-2) is further added. This is done by dispersing with a dispersion resin (A-1) having a strong adsorption force to the conductive carbon, sufficiently dispersing and stabilizing the conductive carbon with the dispersion resin (A-1), and then the conductive carbon and the electrode active material. This is because the addition of the dispersion resin (A-2) having an appropriate adsorption force to both of the above has the effect of lowering the viscosity of the mixture paste containing a large amount of the electrode active material.

When the dispersed resin (A-2) contains a resin (AI) having a polycyclic aromatic hydrocarbon group and / or an amide group, the resin (AI) is blended with the dispersed resin (A-1). As a resin, the same resin as described above can be used. When the dispersed resin (A-2) contains a resin other than the polyvinyl alcohol resin (A II) and / or the resin (AI) and the resin (A II), the dispersed resin (A-1) can be used as these resins. ), The same resin as described above can be used.

In the present invention, the dispersed resin (A-2) preferably contains a resin containing a hydroxyl group. The ratio of the solid content of the resin containing a hydroxyl group to the solid content of the dispersed resin (A-2) is preferably 1 to 100% by mass, more preferably 50 to 100% by mass.

Further, in the present invention, it is preferable that both the dispersed resin (A-1) and the dispersed resin (A-2) contain a resin containing a hydroxyl group.

The dispersion resin (A-1) and the dispersion resin (A-2) may have the same composition, but it is preferable to use those having different compositions.

In the present invention, from the viewpoint of dispersibility and viscosity of the conductive paste and the mixture paste, the total content of the dispersed resin (A-1) and the dispersed resin (A-2) is 100 parts by mass of the conductive carbon (C). As a reference, it is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass. Further, in the present invention, the mass ratio of the dispersed resin (A-1) and the dispersed resin (A-2) is 99/1 to 50/50 from the viewpoint of the dispersibility and viscosity of the conductive paste and the mixture paste. It is preferable to have.

Further, in the present invention, the dispersed resin (A-2) is a polycyclic aromatic hydrocarbon group and / or from the viewpoint of dispersibility of the electrode active material in the subsequent method for producing the mixture paste for the positive electrode of the lithium ion battery. It is preferable to contain a resin having an amide group (AI) (preferably a resin having a polycyclic aromatic hydrocarbon group).

Further, in the present invention, from the viewpoint of dispersibility and viscosity, the amount of the resin adsorbed on the conductive carbon (C) measured under the following conditions with respect to the dispersed resin (A-1) and the dispersed resin (A-2) is determined. The dispersion resin (A-1) preferably has an adsorption amount of 30 mg / g or more, and the dispersion resin (A-2) preferably has an adsorption amount of 10 mg / g or more and less than 30 mg / g.
[Adsorption amount measurement conditions (carbon)]
80 mg of resin, 2 g of conductive carbon, and 1000 g of N-methyl-2-pyrrolidone are mixed well and left at room temperature for 1 week. Then, the precipitate (pigment) is removed, and the supernatant is quantified by gel permeation chromatography (GPC) to calculate the amount of resin adsorbed on the pigment.
As the GPC, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) was used.

Method for Producing Lithium Ion Battery Positive Electrode Paste The present invention provides a method for producing a lithium ion battery positive electrode mixture paste, which comprises a step of mixing an electrode active material with the conductive paste obtained by the method of the present invention described above. do.

The total solid content of the dispersed resin (A-1) in the solid content of the mixture paste for the positive electrode of the lithium ion battery of the present invention is usually 0.001 to 15% by mass, preferably 0.005 to 7% by mass. Is preferable from the viewpoint of battery performance, paste viscosity, and the like. The total solid content of the dispersed resin (A-2) in the solid content of the mixed material paste for the positive electrode of the lithium ion battery of the present invention is usually 0.001 to 15% by mass, preferably 0.005 to 7% by mass. Is preferable from the viewpoint of battery performance, paste viscosity, and the like. The total solid content of the dispersed resins (A-1) and (A-2) in the solid content of the mixed material paste for the positive electrode of the lithium ion battery of the present invention is usually 0.002 to 20% by mass, preferably 0. It is preferably 0.01 to 10% by mass from the viewpoints of battery performance, paste viscosity and the like.

The solid content of polyvinylidene fluoride (B) in the solid content of the mixture paste for the positive electrode of the lithium ion battery of the present invention is usually 0% by mass or more and less than 3% by mass, preferably 0.1% by mass or more. And less than 2.5% by mass, more preferably 0.5% by mass or more, and less than 2% by mass is preferable.

The solid content of the conductive carbon (C) in the solid content of the mixed material paste for the positive electrode of the lithium ion battery of the present invention is usually 0.01 to 30% by mass, preferably 0.05 to 20% by mass, more preferably. 0.1 to 15% by mass is preferable from the viewpoint of battery performance.

The content of the solvent (D) in the mixture paste for the positive electrode of the lithium ion battery of the present invention is usually 0.1 to 60% by mass, preferably 0.5 to 50% by mass, and more preferably 1 to 45% by mass. Is suitable from the viewpoint of electrode drying efficiency and paste viscosity.

Further, in the present invention, from the viewpoint of dispersibility and viscosity, the amount of the dispersed resin adsorbed on the electrode active material measured under the following conditions with respect to the dispersed resin (A-1) and the dispersed resin (A-2) is dispersed. The resin (A-1) preferably has an adsorption amount of less than 5 mg / g, and the dispersed resin (A-2) preferably has an adsorption amount of 5 mg / g or more.
[Adsorption amount measurement conditions (electrode active material)]
80 mg of the resin, 2 g of the electrode active material, and 1000 g of N-methyl-2-pyrrolidone are mixed well and left at room temperature for 1 week. Then, the precipitate (pigment) is removed, and the supernatant is quantified by gel permeation chromatography (GPC) to calculate the amount of resin adsorbed on the pigment.
As the GPC, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) was used.

Electrode active material As the electrode active material, those known in the field of the mixture paste for the positive electrode of a lithium ion battery can be widely used. For example, lithium composite oxides such as lithium nickel oxide (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium cobalt oxide (LiCoO ₂ ), LiNi _1/3 Co _1/3 Mn _1/3 O _{2 and the like.} Can be mentioned. These electrode active materials can be used alone or in combination of two or more. The solid content of the electrode active material in the solid content of the mixture paste for the positive electrode of the lithium ion battery of the present invention is usually 70% by mass or more and less than 100% by mass, preferably 80% by mass or more and less than 100% by mass. It is preferable from the viewpoint of battery capacity, battery resistance, and the like.

The amount of lithium hydroxide can be measured by a method in which the electrode active material is overdiluted with a solvent such as deionized water, centrifuged, and then the supernatant is neutralized and titrated with hydrochloric acid.

Method for manufacturing electrode for lithium ion battery positive electrode As described above, the positive electrode mixture layer of a lithium ion secondary battery is formed by applying a mixture paste for a positive electrode of a lithium ion battery to the surface of a positive electrode core material and drying it. Can be manufactured. Further, the conductive paste for the positive electrode of the lithium ion battery obtained by the production method of the present invention can be used not only as a paste for a mixture layer but also as a primer layer between a positive electrode core material and a synthetic layer. ..

The method of applying the mixture paste for the positive electrode of the lithium ion battery can be performed by a method known per se using a die coater or the like. The amount of the mixture paste for the positive electrode of the lithium ion battery is not particularly limited, but for example, the thickness of the positive electrode mixture layer after drying is in the range of 0.04 to 0.30 mm, preferably 0.06 to 0.24 mm. Can be set as. The temperature of the drying step can be appropriately set in the range of, for example, 80 to 200 ° C., preferably 100 to 180 ° C. The time of the drying step can be appropriately set within the range of, for example, 5 to 120 seconds, preferably 5 to 60 seconds.

Hereinafter, the present invention will be described in more detail with reference to examples.

Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited thereto. In each example, "part" indicates a mass part and "%" indicates a mass%.

Manufacture of dispersed resin
Production of Polycyclic Aromatic Ring-Containing Resin Production Example 1
300 parts of propylene glycol monomethyl ether was charged into a reaction vessel equipped with a stirring and heating device and a cooling tube, and the temperature was maintained at 105 ° C. after nitrogen substitution. The monomer mixture shown below was added dropwise thereto over 3 hours.
<Monomer mixture>
4-Hydroxy-1-naphthyl methacrylate 250 parts 2-methoxy-4-hydroxy-1-naphthyl acrylate 250 parts styrene 50 parts 2-hydroxyethyl acrylate 50 parts N, N-dimethylacrylamide 200 parts N-ethyl-N-hydroxyethyl 200 parts of acrylamide 2,2'-azobis (2-methylbutyronitrile) 40 parts 1 hour after the completion of dropping, 5 parts of 2,2'-azobis (2-methylbutyronitrile) in propylene glycol A solution dissolved in 100 parts of monomethyl ether was added dropwise over 1 hour. After completion of the dropping, the mixture was kept at 105 ° C. for 1 hour, discharged, and dried in a hot air dryer. Finally, the polycyclic aromatic ring-containing resin No. 1 having a solid content of 100%. I got 1. Polycyclic aromatic ring-containing resin No. 1 had a weight average molecular weight of 11,000.

Production Examples 2-4
The polycyclic aromatic ring-containing resin No. 1 has the same composition and production method as that of Production Example 1 except that the monomer composition of Production Example 1 is the type and blending amount shown in Table 1 below. 2 to 4 were manufactured.

Production of polyvinyl alcohol resin Production example 5
In a reaction vessel equipped with a thermometer, a recirculation cooling tube, a nitrogen gas introduction tube and a stirrer, 90 parts by mass of vinyl acetate and 10 parts by mass of 2-butene-1,4-diol as polymerizable monomers, methanol as a solvent, and polymerization initiation. After copolymerizing azobisisobutyronitrile as an agent at a temperature of about 60 ° C., unreacted monomers were removed under reduced pressure to obtain a resin solution. Then, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, and the mixture was thoroughly washed and then dried with a hot air dryer. Finally, the polyvinyl alcohol resin No. with a degree of polymerization of 300 and a degree of saponification of 95 mol%. I got 1.

Production example 6
In a reaction vessel equipped with a thermometer, a recirculation cooling tube, a nitrogen gas introduction tube and a stirrer, 90 parts by mass of vinyl acetate and 10 parts by mass of 1-butene-3,4-diol as polymerizable monomers, methanol as a solvent, and polymerization initiation. A copolymerization reaction was carried out at a temperature of about 60 ° C. using azobisisobutyronitrile as an agent, and then unreacted monomers were removed under reduced pressure to obtain a resin solution. Then, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, and the mixture was thoroughly washed and then dried with a hot air dryer. Finally, the polyvinyl alcohol resin No. with a degree of polymerization of 300 and a degree of saponification of 95 mol%. I got 2.

Production example 7
In a reaction vessel equipped with a thermometer, a recirculation cooling tube, a nitrogen gas introduction tube and a stirrer, 90 parts by mass of vinyl acetate and 10 parts by mass of 1-pentene-4,5-diol as polymerizable monomers, methanol as a solvent, and polymerization initiation. A copolymerization reaction was carried out at a temperature of about 60 ° C. using azobisisobutyronitrile as an agent, and then unreacted monomers were removed under reduced pressure to obtain a resin solution. Then, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, and the mixture was thoroughly washed and then dried with a hot air dryer. Finally, the polyvinyl alcohol resin No. with a degree of polymerization of 300 and a degree of saponification of 95 mol%. I got 3.

Production Example 8
In a reaction vessel equipped with a thermometer, a recirculation cooling tube, a nitrogen gas introduction tube and a stirrer, 97 parts by mass of vinyl acetate and 3.0 parts by mass of sodium allylsulfonate as a polymerizable monomer, methanol as a solvent, and azo as a polymerization initiator. After a copolymerization reaction was carried out using bisisobutyronitrile at a temperature of about 60 ° C., unreacted monomers were removed under reduced pressure to obtain a resin solution. Then, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, and the mixture was thoroughly washed and then dried with a hot air dryer. Finally, the polyvinyl alcohol resin No. with a degree of polymerization of 300 and a degree of saponification of 95 mol%. I got 4.

Manufacturing example 9
A reaction vessel equipped with a thermometer, a recirculation cooling tube, a nitrogen gas introduction tube and a stirrer, using vinyl acetate as a polymerizable monomer, methanol as a solvent, and azobisisobutyronitrile as a polymerization initiator at a temperature of about 60 ° C. After the copolymerization reaction was carried out in the above, the unreacted monomer was removed under reduced pressure to obtain a resin solution. Then, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, and the mixture was thoroughly washed and then dried with a hot air dryer. Finally, the polyvinyl alcohol resin No. with a degree of polymerization of 500 and a degree of saponification of 57 mol%. I got 5.

Production Example 10
A reaction vessel equipped with a thermometer, a recirculation cooling tube, a nitrogen gas introduction tube and a stirrer, using vinyl acetate as a polymerizable monomer, methanol as a solvent, and azobisisobutyronitrile as a polymerization initiator at a temperature of about 60 ° C. After the copolymerization reaction was carried out in the above, the unreacted monomer was removed under reduced pressure to obtain a resin solution. Then, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, and the mixture was thoroughly washed and then dried with a hot air dryer. Finally, the polyvinyl alcohol resin No. with a degree of polymerization of 500 and a degree of saponification of 75 mol%. I got 6.

Production Example 11
A reaction vessel equipped with a thermometer, a recirculation cooling tube, a nitrogen gas introduction tube and a stirrer, using vinyl acetate as a polymerizable monomer, methanol as a solvent, and azobisisobutyronitrile as a polymerization initiator at a temperature of about 60 ° C. After the copolymerization reaction was carried out in the above, the unreacted monomer was removed under reduced pressure to obtain a resin solution. Then, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, and the mixture was thoroughly washed and then dried with a hot air dryer. Finally, the polyvinyl alcohol resin No. with a degree of polymerization of 500 and a degree of saponification of 92 mol%. I got 7.

Production Example 1 of Conductive Paste
Dispersed Resin (A-1) [The polycyclic aromatic ring-containing resin No. 1 obtained in Production Example 1 1 4.8 parts (solid content 4.8 parts), the polyvinyl alcohol resin No. 1 obtained in Production Example 6 2 7.2 parts (solid content 7.2 parts), the polyvinyl alcohol resin No. 2 obtained in Production Example 7. 3 7.2 parts (solid content 7.2 parts), the polyvinyl alcohol resin No. obtained in Production Example 11 7 4.8 parts (solid content 4.8 parts)] total 24 parts, acetylene black 1200 parts, KF polymer W # 7300 (trade name, polyvinylidene fluoride, manufactured by Kureha, water content 100 ppm) 220 parts, N- 8500 parts of methyl-2-pyrrolidone and 6 parts of dehydrating agent (1.5 parts of diphosphorus pentoxide, 1.5 parts of acetic anhydride, 1.5 parts of methanesulfonic anhydride, 1.5 parts of orthoformic acid ethyl ester) The mixture was mixed and dispersed in a ball mill for 5 hours.
Subsequently, the dispersed resin (A-2) [Polycyclic aromatic ring-containing resin No. obtained in Production Example 1 11.2 parts (solid content 1.2 parts), polyvinyl alcohol resin No. 1 obtained in Production Example 6. 2 1.8 parts (solid content 1.8 parts), the polyvinyl alcohol resin No. 2 obtained in Production Example 7. 3 1.8 parts (solid content 1.8 parts), the polyvinyl alcohol resin No. obtained in Production Example 11 7 1.2 parts (solid content 1.2 parts)] was added in a total of 6 parts and stirred well to obtain a conductive paste X-1.

Examples 2-9, Comparative Examples 1-3
Conductive pastes X-2 to X-12 were produced in the same manner as in Example 1 except that the ones shown in Table 2 below were used. The resin blending amounts in the table are all solid content values.

Table 2 above shows the adsorption amounts of the dispersed resin (A-1) and the dispersed resin (A-2) with respect to acetylene black measured under the following conditions.
[Adsorption amount measurement conditions (carbon)]
80 mg of resin, 2 g of acetylene black, and 1000 g of N-methyl-2-pyrrolidone are mixed well and left at room temperature for 1 week. Then, the precipitate (pigment) is removed, and the supernatant is quantified by gel permeation chromatography (GPC) to calculate the amount of resin adsorbed on the pigment. As the GPC, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) was used.

Production Example 10 of Mixture Paste
100 parts of the conductive paste X-1 obtained in Example 1 and the active material particles (lithinel-structured lithium nickel manganese oxide particles represented by the _{composition formula LiNi 0.5} Mn _1.5 O _{4; average particle size 6 μm.} , BET specific surface area 0.7 m ² / g) 150 parts were mixed to produce a mixture paste Y-1.

Examples 11-18, Comparative Examples 4-6
Mixture pastes Y-2 to Y-12 were produced in the same manner as in Example 10 except that the ones shown in Table 3 below were used.

Table 3 above shows the adsorption amounts of the dispersed resin (A-1) and the dispersed resin (A-2) on the active material measured under the following conditions.
[Adsorption amount measurement conditions (electrode active material)]
80 mg of resin, 2 g of active material particles (lithium nickel-manganese oxide particles having a spinel structure represented by the composition formula LiNi0.5Mn1.5O4, average particle size 6 μm, BET specific surface area 0.7 m2 / g), and N-methyl-2. -Mix 1000 g of pyrrolidone well and leave at room temperature for 1 week. Then, the precipitate (pigment) is removed, and the supernatant is quantified by gel permeation chromatography (GPC) to calculate the amount of resin adsorbed on the pigment. As the GPC, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) was used.
In addition, the results of the evaluation test (viscosity of the conductive paste and the mixture paste) described later are shown in Table 3 above. If the evaluation result of failure is "D", the conductive paste and the mixture paste are all rejected.

Evaluation test <Viscosity of conductive paste>
^{The conductive pastes obtained in Examples and Comparative Examples were measured for viscosity at a shear rate of 1.0 sec -1} using a cone and plate viscometer "Mars2" (trade name, manufactured by HAAKE), and evaluated according to the following criteria. .. As an evaluation, S, A, B, and C pass, and D fails.
S: The viscosity is less than 1 Pa · s.
A: The viscosity is 1 Pa · s or more and less than 5 Pa · s.
B: The viscosity is 5 Pa · s or more and less than 30 Pa · s.
C: The viscosity is 30 Pa · s or more and less than 100 Pa · s.
D: The viscosity is 100 Pa · s or more.

<Viscosity of mixture paste>
^{The mixture pastes obtained in Examples and Comparative Examples were measured for viscosity at a shear rate of 1.0 sec -1} using a cone and plate viscometer "Mars2" (trade name, manufactured by HAAKE), and evaluated according to the following criteria. did.
In addition, the viscosity 1 hour after the preparation of the mixture paste having a large viscosity was measured. (The viscosity tends to decrease gradually over time.)
As an evaluation, S, A, B, and C pass, and D fails.
S: The viscosity is less than 5 Pa · s.
A: The viscosity is 5 Pa · s or more and less than 10 Pa · s.
B: The viscosity is 10 Pa · s or more and less than 20 Pa · s.
C: The viscosity is 20 Pa · s or more and less than 50 Pa · s.
D: The viscosity is 50 Pa · s or more.

Claims (11)

A step of dispersing a mixed solution containing a dispersion resin (A-1), polyvinylidene fluoride (B), conductive carbon (C), and a solvent (D) to obtain a dispersion.
Next, the step of adding the dispersion resin (A-2) to the dispersion liquid,
A method for producing a conductive paste for a positive electrode of a lithium ion battery, wherein the dispersed resin (A-1) and / or the dispersed resin (A-2) has a polycyclic aromatic hydrocarbon group and / or an amide group. only including,
The dispersion resin (A-1) contains either a naphthyl (meth) acrylate group and a resin having an acrylamide group; and a polyvinyl alcohol resin (AII).
The dispersion resin (A-2) contains either a resin having a naphthyl (meth) acrylate group and a polyvinyl alcohol resin (AII).
Solvent (D) contains N-methyl-2-pyrrolidone,
A method in which the viscosity of the conductive paste is less than 100 Pa · s. Claim 1 is characterized in that the total content of the dispersed resin (A-1) and the dispersed resin (A-2) is 0.1 to 10 parts by mass based on 100 parts by mass of the conductive carbon (C). The method described in. The method according to claim 1 or 2, wherein the mass ratio of the dispersed resin (A-1) and the dispersed resin (A-2) is 99/1 to 50/50. The method according to any one of claims 1 to 3, wherein the dispersed resin (A-1) and the dispersed resin (A-2) contain a resin having a hydroxyl group. The method according to any one of claims 1 to 4, wherein the dispersed resin (A-2) contains a resin having a polycyclic aromatic hydrocarbon group. The method according to any one of claims 1 to 4, wherein the dispersed resin (A-1) contains a resin having a polycyclic aromatic hydrocarbon group. Regarding the dispersed resin (A-1) and the dispersed resin (A-2), the amount of resin adsorbed on the conductive carbon (C) measured under the following conditions was 30 mg / g or more for the dispersed resin (A-1). The method according to any one of claims 1 to 6, wherein the dispersed resin (A-2) has an adsorption amount of 10 mg / g or more and less than 30 mg / g.
[Adsorption amount measurement conditions (carbon)]
80 mg of resin, 2 g of conductive carbon, and 1000 g of N-methyl-2-pyrrolidone are mixed well and left at room temperature for 1 week. Then, the precipitate (pigment) is removed, and the supernatant is quantified by gel permeation chromatography (GPC) to calculate the amount of resin adsorbed on the pigment. A method for producing a mixture paste for a positive electrode of a lithium ion battery, which comprises a step of mixing an electrode active material with the conductive paste obtained by the method according to claims 1 to 7 .
A method in which the viscosity of the mixture paste is less than 50 Pa · s . Regarding the dispersed resin (A-1) and the dispersed resin (A-2), the amount of the dispersed resin adsorbed on the electrode active material measured under the following conditions is less than 5 mg / g for the dispersed resin (A-1). The production method according to claim 8, wherein the dispersed resin (A-2) has an adsorption amount of 5 mg / g or more. [Adsorption amount measurement conditions (electrode active material)]
80 mg of the resin, 2 g of the electrode active material, and 1000 g of N-methyl-2-pyrrolidone are mixed well and left at room temperature for 1 week. Then, the precipitate (pigment) is removed, and the supernatant is quantified by gel permeation chromatography (GPC) to calculate the amount of resin adsorbed on the pigment. A method for producing a positive electrode mixture layer of a lithium ion battery, which comprises a step of applying a mixture paste obtained by the method according to claim 8 or 9 to a current collector. A method for manufacturing a lithium ion battery, which comprises a step of installing a positive electrode having a positive electrode mixture layer obtained by the method according to claim 10, a negative electrode, and an electrolyte in a battery case.