JP2017228413A - Conductive paste for lithium ion battery positive electrode, and mixture material paste for lithium ion battery positive electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste for a lithium ion battery positive electrode and a mixture material paste for the lithium ion battery positive electrode which are suppressed in high viscosity and gelatinization and have a viscosity easy to coat.SOLUTION: Disclosed is a conductive paste which contains: a dispersion resin (A); a polyvinylidene fluoride(B); an electrically conductive carbon (C); a solvent (D); and a hindered amine compound (E).SELECTED DRAWING: None

Description

  The present invention relates to a solvent-based conductive paste for a lithium ion battery positive electrode and a mixture paste for a lithium ion battery positive electrode containing polyvinylidene fluoride.

  The lithium ion secondary battery is a kind of non-aqueous electrolyte secondary battery, and is a secondary battery in which lithium ions in the electrolyte bear electric conduction. Lithium ion secondary batteries have excellent characteristics such as high energy density, excellent charge energy retention characteristics, and a small so-called memory phenomenon that reduces apparent capacity. 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 electrolyte, and the like. The positive electrode plate is obtained by forming a positive electrode mixture layer on the surface of a positive electrode core material. The positive electrode mixture layer is formed by applying a positive electrode mixture paste obtained by mixing an electrode active material to a conductive paste containing a conductive additive (carbon, etc.), a binder, and a solvent to the surface of the positive electrode core material and drying it. Can be manufactured.

  As described above, since the positive electrode mixture layer is produced by applying the positive electrode mixture paste on the surface of the positive electrode core material, the positive electrode mixture paste and the conductive paste as its constituent material have a low viscosity. It is required to be. Under such circumstances, there is known a method of adding a dispersing agent for dispersing a conductive additive in a conductive paste or dispersion (Patent Documents 1 and 2). A method using a specific vinyl alcohol polymer as a binder is also known (Patent Document 3). Here, polyvinylidene fluoride is useful for blending into a conductive paste as a binder between a metal oxide and a current collector, etc., but in a conductive paste blended with polyvinylidene fluoride, a basic substance is particularly useful. When included, there was a problem that the paste became highly viscous and gelled by storage.

JP 2013-89485 Japanese Unexamined Patent Publication No. 2014-193986 Japanese Patent Laid-Open No. 11-250915 JP 2001-196065 Japanese Patent Laid-Open No. 10-106579

  The problem to be solved by the present invention is to provide a lithium ion battery positive electrode conductive paste and a lithium ion battery positive electrode mixture paste that have high viscosity and reduced gelation and are easily coated.

  Under such circumstances, as a result of intensive studies, the present inventors have found that a hindered amine compound (E) is added to a conductive paste containing the dispersion resin (A), polyvinylidene fluoride (B), conductive carbon (C), and solvent (D). The present inventors have found that the above-mentioned problems can be solved by using in combination. The present invention is based on such novel findings.

Accordingly, the present invention provides the following sections:
Item 1. A conductive paste for a lithium ion battery positive electrode, comprising a dispersion resin (A), polyvinylidene fluoride (B), conductive carbon (C), a solvent (D), and a hindered amine compound (E).
Item 2. Item 2. The conductive paste for a lithium ion battery positive electrode according to Item 1, wherein the dispersion resin (A) contains a resin (A1) having a polycyclic aromatic hydrocarbon group.
Item 3. Item 3. The conductive paste for a lithium ion battery positive electrode according to Item 1 or 2, wherein the dispersion resin (A) contains a polyvinyl alcohol resin (A2).
Item 4. Item 4. The conductive paste for a lithium ion battery positive electrode according to any one of Items 1 to 3, wherein the conductive carbon (C) contains acetylene black.
Item 5. Item 5. The conductive paste for a lithium ion battery positive electrode according to any one of Items 1 to 4, wherein the conductive carbon (C) contains graphite.
Item 6. Item 6. The conductive paste for a lithium ion battery positive electrode according to any one of Items 1 to 5, wherein the solvent (D) contains N-methyl-2-pyrrolidone.
Item 7. Furthermore, an acidic compound is contained, The electrically conductive paste for lithium ion battery positive electrodes of any one of claim | item 1 -6 characterized by the above-mentioned.
Item 8. Item 8. The conductive paste for a lithium ion battery positive electrode according to any one of Items 1 to 7, wherein the water content in the conductive paste is less than 1.0% by mass.
Item 9. Item 9. The method for producing a conductive paste for a lithium ion battery positive electrode according to any one of Items 1 to 8, wherein mixing and / or pigment dispersion is performed in an atmosphere having a dew point of 10 ° C or lower.
Item 10. Item 10. A paste for a lithium ion battery positive electrode obtained by further blending an electrode active material with the conductive paste according to any one of items 1 to 9.
Item 11. Item 11. The lithium ion battery positive electrode composite paste according to item 10, wherein the lithium hydroxide content in the composite paste is less than 1.5% by mass based on the mass of the polyvinylidene fluoride (B). .
Item 12. Item 12. An electrode for a lithium ion battery positive electrode obtained by using the composite paste for a lithium ion battery positive electrode according to Item 10 or 11.
Item 13. Item 13. A lithium ion battery having the electrode for a lithium ion battery positive electrode according to Item 12.

  The conductive paste for lithium ion battery positive electrode and the composite paste for lithium ion battery positive electrode of the present invention have higher viscosity and gel than the conventional lithium ion battery positive electrode conductive or composite paste due to the above structural features. In particular, even when a basic compound is blended with the conductive or composite paste for a lithium ion battery positive electrode, the viscosity of the paste suitable for coating is suppressed. Is maintained.

Although the mechanism by which the conductive or composite paste for lithium ion battery positive electrode is gelled is not clarified, for example, the following mechanism is assumed. In the conductive or composite paste for a lithium ion battery positive electrode containing polyvinylidene fluoride (B) as in the present invention, the acidity of the proton adjacent to the fluorine group in the polyvinylidene fluoride is very high due to the electron withdrawing property of the fluorine group. Therefore, this proton elimination proceeds easily especially in basic conditions. Such proton desorption is presumed to proceed particularly easily when moisture is present in the conductive or composite paste. An anion is generated on the carbon after proton elimination, and the anion promotes elimination of the fluorine group, and a double bond is formed in the main chain of the polyvinylidene fluoride molecule. And it is estimated that the several polyvinylidene fluoride molecule | numerator which will have a double bond superposes | polymerizes, and further polymerizes, leading to a viscosity rise and gelatinization. In particular, since the electrode active material in the composite paste may contain the basic substance lithium hydroxide, high viscosity and gelation are significant in the composite paste.
In the present invention, polymerization of polyvinylidene fluoride molecules is performed by combining the components (A) to (D) with a hindered amine compound (E) having a function of trapping harmful radicals and preventing generation of new radicals. It is considered that the increase in viscosity and gelation of the lithium ion battery positive electrode conductive material or composite paste could be suppressed.

  On the other hand, Patent Documents 1 to 3 have no disclosure about blending a hindered amine compound into a conductive paste for a lithium ion battery positive electrode. Further, Patent Document 4 only describes a mixture paste for lithium ion battery positive electrode that is a water-based dispersion, and does not disclose a solvent-based mixture paste for lithium ion battery positive electrode and a conductive paste. In Patent Document 5, a composite oxide as an active material is added to and mixed with an organic solution of an organic compound for capturing oxygen radicals, and then the organic solvent is removed by drying to add the organic compound to the composite oxide. It only describes that a positive electrode is produced by obtaining a product and mixing it with a conductive agent and a binder (Patent Document 5, Claim 4, Examples, etc.). Therefore, in Patent Document 5, a conductive paste for a lithium ion battery positive electrode is produced, which contains a dispersion resin (A), polyvinylidene fluoride (B), conductive carbon (C), and a solvent (D). Is not disclosed at all, and the manufacturing method of the positive electrode is completely different from the present invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail.
It should be understood that the present invention is not limited to the following embodiments, and includes various modifications that are implemented without departing from the scope of the present invention.

  In the present specification, “(meth) acrylate” means acrylate and / or methacrylate, and “(meth) acrylic acid” means acrylic acid and / or methacrylic acid. “(Meth) acryloyl” means acryloyl and / or methacryloyl. “(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 (meth) acryloyl group, acrylamide group, vinyl group. , Allyl group, (meth) acryloyloxy group, vinyl ether group and the like.

The present invention relates to a lithium ion battery positive electrode conductive paste comprising a dispersion resin (A), polyvinylidene fluoride (B), conductive carbon (C), a solvent (D), and a hindered amine compound (E). It is a conductive paste for an ion battery positive electrode.

Dispersing resin (A)
As the dispersion resin (A) that can be used in the conductive paste of the present invention, those widely used in the field of the conductive paste for lithium ion battery positive electrodes to which the present invention belongs are widely used. it can.

  For example, resin (A1) which has a polycyclic aromatic hydrocarbon group, polyvinyl alcohol resin (A2), etc. are mentioned. In the present invention, the dispersion resin (A) preferably contains both the resin (A1) having a polycyclic aromatic hydrocarbon group and the polyvinyl alcohol resin (A2).

Resin (A1) having a polycyclic aromatic hydrocarbon group
The resin (A1) having a polycyclic aromatic hydrocarbon group that can be used in the conductive paste of the present invention is a monomer (A1-1) having a polycyclic aromatic hydrocarbon, based on the total amount of solid content of the monomer mixture. It is obtained by copolymerizing a monomer mixture containing 1 to 70% by mass. Therefore, in the present invention, the resin (A1) is a co-polymer of a monomer mixture containing 1 to 70% by mass of the monomer (A1-1) having a polycyclic aromatic hydrocarbon, based on the total solid content of the monomer mixture. It can also be called a polymer.

  Examples of the resin (A1) include acrylic resin, polyester resin, epoxy resin, polyether resin, alkyd resin, urethane resin, silicone resin, polycarbonate resin, silicate resin, chlorine resin, fluorine resin, and these. In particular, an acrylic resin is preferable.

  In this specification, a “derivative” is obtained by changing a small part (or a plurality of parts) in a molecule by introducing a functional group, substituting an atom, or other chemical reaction with respect to a certain compound. Means a compound. For example, naphthalene has 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 having polycyclic aromatic hydrocarbon (A1-1)
Examples of the polycyclic aromatic hydrocarbon of the monomer (A1-1) having a polycyclic aromatic hydrocarbon that can be used in the pigment dispersion resin of the present invention include a naphthalene ring, an anthracene ring, a triphenylene ring, a tetraphen ring, Examples thereof include a hydrocarbon group having a tetracene ring, a chrysene ring, a pyrene ring, a pentacene ring, a hexacene ring, a heptacene ring, a coronene ring and a keklen ring, and derivatives thereof. In preferable embodiment of this invention, as a monomer (A1-1) which has a polycyclic aromatic hydrocarbon, what has a naphthalene ring among the said polycyclic aromatics, ie, the polymerizable unsaturated monomer which has a naphthyl group, Or the derivative (A1-2) is mentioned. As the polymerizable unsaturated monomer having a naphthyl group or a derivative thereof (A1-2), for example, a polymerizable unsaturated monomer having a naphthyl group represented by the formula (3) described later or a derivative thereof (A1-1-2) Etc.

  The monomer (A1-1) having a polycyclic aromatic hydrocarbon is a polymerizable unsaturated monomer (A1-1-1) having a polycyclic aromatic hydrocarbon represented by the following formula (2). It is preferable.

(Wherein R represents a hydrogen atom or a methyl group, A represents a polycyclic aromatic hydrocarbon group, W may or may not be present. When W is present, W is a carbon atom, An organic group having 1 to 20 nitrogen atoms and / or oxygen atoms, and when W is not present, W is directly bonded to A.) “Polymerizable unsaturated monomer” is a polymer capable of radical polymerization. Means a monomer having a polymerizable 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 (A1-1-1) having a polycyclic aromatic hydrocarbon include vinyl naphthalene, naphthyl (meth) acrylate, naphthylalkyl (meth) acrylate, vinylanthracene, Anthracenyl (meth) acrylate, anthracenyl alkyl (meth) acrylate, vinylpyrene, pyrenyl (meth) acrylate, pyrenylalkyl (meth) acrylate, vinyl chrysene, vinyl naphthacene, vinyl pentacene, and derivatives thereof may be mentioned. Also included are those obtained by reacting a polymerizable unsaturated group monomer having a reactive functional group such as a glycidyl group or an isocyanate group with a polycyclic aromatic hydrocarbon having a functional group that reacts with the reactive functional group. . Any combination of functional groups that react with each other can be suitably used, but a combination of a carboxyl group and a glycidyl group, an amino group and a glycidyl group, or a hydroxyl group and an isocyanate group is more preferable. Specifically, for example, glycidyl (meth) acrylate and 1-naphthyl acetic acid, 2- (meth) acryloyloxyethyl isocyanate and 1-naphthol, 2- (meth) acryloyloxyethyl isocyanate and 1- (2-naphthyl) ethanol And the like. These can be used alone or in combination of two or more.

  Among these, as the polymerizable unsaturated monomer (A1-1-1) having a polycyclic aromatic hydrocarbon, a polymerizable unsaturated monomer having a naphthyl group represented by the following formula (3) or a derivative thereof (A1-1) -2).

(In the formula, R represents a hydrogen atom or a methyl group, X and Y may be the same or different, and a hydrogen atom, alkyl group, alkoxy group, alkoxycarbonyloxy group, phosphoryloxy group, hydroxyl group, sulfone) 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, and when W is present, W is the number of carbon atoms, nitrogen atoms and / or oxygen atoms. Is an organic group of 1 to 20 or a single bond.)
Examples of the polymerizable unsaturated monomer having a naphthyl group or a derivative thereof (A1-1-2) include vinyl naphthalene, naphthyl (meth) acrylate, naphthylalkyl (meth) acrylate, and derivatives thereof. These can be used alone or in combination of two or more.

  Especially, it is preferable that naphthyl (meth) acrylate or its derivative (A1-1-2) is naphthyl (meth) acrylate or its derivative (A1-1-3) represented by following formula (4).

(In the formula, R represents a hydrogen atom or a methyl group, X and Y may be the same or different, and a hydrogen atom, alkyl group, alkoxy group, hydroxyl group, sulfonic acid group, carboxyl group, alkoxycarbonyloxy group) Group, phosphoryloxy group, amino group, nitro group, halogen atom, aryloxy group, alkylthio group or arylthio group.)
As said naphthyl (meth) acrylate or its derivative (A1-1-3), 1-naphthyl (meth) acrylate, 2-naphthyl (meth) acrylate, these derivatives, etc. are mentioned, for example, These are 1 type. Can be used alone or in combination of two or more.

  Among these, naphthyl (meth) acrylate or a derivative thereof (A1-1-3) is a 4-substituted-1-naphthyl (meth) acrylate (A1-1-4) represented by the following formula (5). 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 formula (5) is an alkoxy group, the number of carbon atoms of the alkoxy group is usually 1 to 8, preferably 1 to 4, more preferably 1 to 2, Particularly preferred is 1.

  Examples of the 4-substituted-1-naphthyl (meth) acrylate (A1-1-4) include 4-methyl-1-naphthyl (meth) acrylate, 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- Methoxycarbonyloxy-1-naphthyl (meth) acrylate, 4-phenoxycarbonyloxy Examples include -1-naphthyl (meth) acrylate and 4-phosphoryloxy-1-naphthyl (meth) acrylate, or derivatives thereof, and these can be used alone or in combination of two or more. .

  The reason why the pigment dispersion resin having the 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 to be stabilized by the π-π interaction between the pigment and the pigment dispersion resin. The π-π interaction is a dispersion force acting between the aromatic rings and is also called a stacking interaction because it tends to be stabilized in an arrangement in which two aromatic rings are stacked with coins.

  Further, the reason why the substituent of the 4-substituted-1-naphthyl (meth) acrylate (A1-1-4) is effective in the dispersibility and stability of the pigment is not known in detail. It is speculated that by having a substituent, the electrostatic potential of the aromatic ring is increased and the affinity with the pigment is increased.

Polymerizable unsaturated monomer other than the polymerizable unsaturated monomer (A1-1) having a polycyclic aromatic hydrocarbon The resin (A1) that can be used in the present invention is a polymerizable unsaturated monomer having a polycyclic aromatic hydrocarbon. It can be obtained by copolymerizing the monomer (A1-1) and a polymerizable unsaturated monomer other than (A1-1). As the polymerizable unsaturated monomer other than the polymerizable unsaturated monomer (A1-1) having a polycyclic aromatic hydrocarbon, any polymerizable unsaturated monomer usually used in the synthesis of an acrylic resin can be used without any particular limitation. For example, alkyl (meth) acrylates having 3 or less carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, 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 Such as (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, tricyclodecanyl (meth) acrylate, etc. Alkyl or cycloalkyl (meth) acrylate; polymerizable unsaturated compound having an isobornyl group such as isobornyl (meth) acrylate; polymerizable unsaturated compound having an adamantyl group such as adamantyl (meth) acrylate; benzyl (meth) acrylate, styrene , Α-methylstyrene, vinyltoluene and other aromatic ring-containing polymerizable unsaturated monomers; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydride Monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms such as loxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate, (meth) acrylic acid and 2 to 8 carbon atoms Of ε-caprolactone, monoesterified with dihydric alcohol, N-hydroxymethyl (meth) acrylamide, allyl alcohol, hydroxyl group-containing polymerizability such as (meth) acrylate having a polyoxyalkylene chain having a hydroxyl group at the molecular end Unsaturated monomers; carboxyl group-containing polymerizable unsaturated monomers such as (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate; (meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl ( (Meth) acrylate, N, N-diethylaminoethyl ( Nitrogen-containing polymerizable unsaturated monomers not containing urethane bonds such as meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, adducts of glycidyl (meth) acrylate and amine compounds; isocyanate group-containing polymerizable unsaturated Polymerizable unsaturated monomer having a urethane bond such as a reaction product of a monomer and a hydroxyl group-containing compound or a reaction product of a hydroxyl group-containing polymerizable unsaturated monomer and an isocyanate group-containing compound; glycidyl (meth) acrylate, β-methylglycidyl Contains epoxy groups such as (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether Polymerizable unsaturated monomer; (meth) acrylate having polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth) acrylate, allylsulfonic acid, 4-styrene Polymerizable unsaturated monomers having a sulfonic acid group such as sodium salt and ammonium salt of these sulfonic acids; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, Polymerizable unsaturated monomers having a phosphate group such as 2-methacryloyloxypropyl acid phosphate; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) sila , Polymerizable unsaturated monomers having an alkoxysilyl group such as γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane; perfluorobutylethyl (meth) acrylate, perfluorooctyl Perfluoroalkyl (meth) acrylate such as ethyl (meth) acrylate; polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; polymerizable unsaturated monomer having a photopolymerizable functional group such as maleimide group; (Meth) acrylate having a polyoxyethylene chain in which is an alkoxy group; allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) a Acrylate, 1,3-butylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol Di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol di (meth) acrylate, 1,1,1-trishydroxymethylethanedi (meth) acrylate, 1,1,1 -1 polymerizable unsaturated group such as trishydroxymethylethane tri (meth) acrylate, 1,1,1-trishydroxymethylpropane tri (meth) acrylate, triallyl isocyanurate, diallyl terephthalate, divinylbenzene Polymerizable unsaturated monomers having two or more in the child and the like. These can be used alone or in combination of two or more.

Further, from the viewpoint of forming a three-dimensional repulsive layer of resin and ensuring the stability of the pigment dispersion paste, a polyalkylene glycol macromonomer can be contained on the basis of the total amount of polymerizable unsaturated monomer components.
The polyalkylene glycol macromonomer is a nonionic polymerizable unsaturated monomer represented by the following formula (6), and specific examples of such a monomer include, for example, polyethylene glycol (meth) acrylate, polypropylene glycol (Meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate and the like can be mentioned. 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 ··· formula (6)
[Wherein, 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 Is an integer of ˜3, where the m oxyalkylene units (C _n H _2n O) may be the same or different from each other. ]
Further, it preferably contains at least one (meth) acrylamide compound. As the (meth) acrylamide compound, those known per se can be used without particular limitation. Specific examples include acrylamide, methacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N-methylacrylamide. N-methylmethacrylamide, N-methylolacrylamide butyl ether, N-methylol methacrylamide butyl ether, N-ethylacrylamide, N-ethylmethacrylamide, Nn-propylacrylamide, Nn-propylmethacrylamide, N-isopropylacrylamide N-isopropylmethacrylamide, N-cyclopropylacrylamide, N-cyclopropylmethacrylamide, diacetone acrylamide, diacetone methacrylamide, N-hydroxy Methylacrylamide, N-hydroxymethylmethacrylamide, N-hydroxyethylacrylamide, N-hydroxypropylacrylamide, N-hydroxybutylacrylamide, N-hydroxypentylacrylamide, N-hydroxymethyl-N-ethylacrylamide, N-methyl-N- Hydroxyethyl acrylamide, N, N-dihydroxymethyl acrylamide, N, N-dihydroxyethyl acrylamide, N, N-dihydroxypropyl acrylamide, N, N-dihydroxybutyl acrylamide, N, N-dihydroxypentyl acrylamide, N-hydroxymethyl methacrylamide N-hydroxyethyl methacrylamide, N-hydroxypropyl methacrylamide, N-hydroxybutyl methacryl N-hydroxypentyl methacrylamide, N-hydroxymethyl-N-ethyl methacrylamide, N-methyl-N-hydroxyethyl methacrylamide, N, N-dihydroxymethyl methacrylamide, 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-methyl, 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-methylol methacrylamide butyl ether, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N -Amino group-containing (meth) acrylamide compounds such as dipropylaminoethyl (meth) acrylamide, methacryloyloxye Le trimethylammonium chloride (ACRYESTER DMC, tradename, manufactured by Mitsubishi Rayon Co., Ltd.) Quaternary ammonium salt group-containing acrylamide compounds such as, can be exemplified acryloyl morpholine. These can be used alone or in combination of two or more.
Especially, it is preferable that it is a (meth) acrylamide compound represented by following formula (7).
CH ₂ = C (—R ₁ ) —C (═O) —N (—R ₂ ) —R ₃ (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 are at least one selected from a hydrogen atom, an organic group having a hydroxyl group, and an alkyl group. Preferably there is. Further, it is more preferable that both or one of R ₂ and R ₃ is an organic group having a hydroxyl group. 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 (Meth) acrylamide, N-hydroxyethyl-N-butyl (meth) acrylamide, N-hydroxybutyl-N-butyl (meth) acrylamide, N, N-dihydroxymethyl (meth) acrylamide, N, N-dihydroxyethyl (meta) ) Acrylamide, N, N Dihydroxypropyl (meth) acrylamide, N, and particularly preferably at least one selected from N- dihydroxy-butyl (meth) acrylamide, and N- [tris (hydroxymethyl) methyl) acrylamide.

Synthesis of Resin (A1) Having Polycyclic Aromatic Hydrocarbon Group Resin (A1) having a polycyclic aromatic hydrocarbon group that can be used in the conductive paste of the present invention is organic in the presence of a radical polymerization initiator. It can be obtained by a radical polymerization method known per se, such as a solution polymerization method in a solvent or an emulsion polymerization method in an aqueous medium.

  Examples of the radical polymerization initiator used for polymerization include cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, 1,1-bis (tert-butylperoxy) -3,3, 5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, n-butyl-4,4-bis (tert-butylperoxy) valerate, cumene hydroperoxide, 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, decanoyl Oxide, lauroyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, di-tert-amyl peroxide, bis (tert-butylcyclohexyl) peroxydicarbonate, tert-butylperoxybenzoate, 2,5- Peroxide-based polymerization initiators such as dimethyl-2,5-di (benzoylperoxy) hexane and tert-butylperoxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1 , 1-azobis (cyclohexane-1-carbonitrile), azocumene, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobisdimethylvaleronitrile, 4,4′-azobis (4- Cyanovaleric acid), 2- (t-butylazo) -2-cyanopropane, 2,2′-azobis ( 2,4,4-trimethylpentane), 2,2'-azobis (2-methylpropane), dimethyl 2,2'-azobis (2-methylpropionate), and the like. . These can be used alone or in combination of two or more.

  There is no restriction | limiting in particular as a solvent used for said superposition | polymerization or dilution, Water, an organic solvent, or its mixture etc. can be mentioned. 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; methyl isobutyl ketone 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 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 solvent such as alcohol, isopropanol, n-butanol, sec-butanol, isobutanol, etc .; Ecamide (trade name, manufactured by Idemitsu Kosan Co., Ltd., amide solvent), N, N-dimethylformamide, N, N- Conventionally known solvents such as amide solvents such as dimethylacetamide, N-methylformamide, N-methylacetamide, N-methylpropioamide, N-methyl-2-pyrrolidone and the like can be mentioned. These can be used alone or in combination of two or more.

  In solution polymerization in an organic solvent, a polymerization initiator, a polymerizable unsaturated monomer component, and an organic solvent are mixed and heated while stirring, and the organic solvent is added to the reaction vessel to suppress the temperature rise of the system due to reaction heat. While being stirred at a temperature of 60 ° C. to 200 ° C. while introducing an inert gas such as nitrogen or argon as necessary, the polymerizable unsaturated monomer component and the polymerization initiator are mixed or dropped over a predetermined time. Or the like is used.

  The polymerization can be generally performed for about 1 to 10 hours. You may provide the additional catalyst process which heats a reaction tank, dripping a polymerization initiator as needed after superposition | polymerization of each step.

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

The resin (A1) can be made into a resin solution substituted with a solid or an arbitrary solvent by removing the solvent and / or replacing the solvent after completion of the synthesis. As the substitution solvent, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, propylene glycol monomethyl ether, alcohol solvents and the like are preferable.
As a method for removing the solvent, it may be carried out by heating at normal pressure or may be removed under reduced pressure. As a solvent replacement method, the replacement solvent may be added at any stage before, during or after the solvent removal.

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

Polyvinyl alcohol resin (A2)
As the polyvinyl alcohol resin (A2), a resin obtained by copolymerizing a polymerizable unsaturated group-containing monomer (A2a-1) represented by the following formula (1) and another polymerizable unsaturated monomer (this specification) In this specification, it may be simply indicated as polyvinyl alcohol resin (A2a) or resin (A2a)), sulfonic acid-modified polyvinyl alcohol resin (A2b) (in this specification, simply indicated as polyvinyl alcohol resin (A2b) or resin (A2b)) And a polyvinyl alcohol resin (A2c) other than the resin (A2a) and the resin (A2b) (in this specification, it may be simply referred to as a polyvinyl alcohol resin (A2c) or a resin (A2c)). :

Wherein R ₁ , R ₂ , R ₃ and R ₄ are the same or different and 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 _At least one of ₂ , R ₃ and R ₄ is a hydroxyl group, and X may or may not be present, and when X is present, X is a linked chain composed of one or more atoms. ).
In the present invention, as the polyvinyl alcohol resin (A2), a polyvinyl alcohol resin (A2a) and / or a polyvinyl alcohol resin (A2b) can be preferably used, but a polyvinyl alcohol resin (A2c) is also used in combination. Is preferred.

Polyvinyl alcohol resin (A2a)
The polyvinyl alcohol resin (A2a) is a resin obtained by copolymerizing the polymerizable unsaturated group-containing monomer (A2a-1) represented by the formula (I) and other polymerizable unsaturated monomers. In the present invention, “a resin having a polymerizable unsaturated group-containing monomer (A2a-1) as one of the constituent components” means (co) polymerization of raw material monomers including the polymerizable unsaturated group-containing monomer (A2a-1). Means the resin obtained. Similarly, in the present invention, the resin “having monomer X as a constituent component” means a resin obtained by (co) polymerizing a raw material containing monomer X. The polyvinyl alcohol resin (A2a) is not sulfonic acid-modified and can be clearly distinguished from the sulfonic acid-modified polyvinyl alcohol resin (A2b).

R ₁ , R ₂ , R ₃ and R ₄ in the polymerizable unsaturated group-containing monomer (A2a-1) represented by the formula (1) are the same or different and are a hydrogen atom, a hydrocarbon group, a hydroxyl group or methylol. And at least one selected from the group, 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. X in the monomer represented by the formula (1) may or may not be present. When X is not present, it is a single bond, and when X is present, it is a linkage composed of one or more atoms. Is a chain. Such a linking chain is not particularly limited, but may be alkylene (for example, linear or branched alkylene having 1 to 6 carbon atoms) or alkenylene (for example, linear or branched chain having 2 to 6 carbon atoms). Alkenylene having 1 to 2 double bonds (preferably 1), alkynylene (for example, straight chain or branched chain having 2 to 6 carbon atoms, preferably 1 to 2 triple bonds (preferably 1) alkynylene), hydrocarbon groups such as phenylene and naphthylene (these hydrocarbon groups may be substituted by halogen such as fluorine, chlorine and bromine), and -O-,-(R- O) _m -,-(O-R) _m -,-(R-O) _m -R-, -C (= O)-, -R (-OH)-, -C (= O) -O- , -RC (= O) -O-, -C (= O) -O-R-, -C (= O) -N (-R)-, -C ═O) —N (—R) —R—, —R—C (═O) —N (—R) —, —R—C (═O) —N (—R) —R—, and the like. It is done. (The above R are each independently an arbitrary substituent, preferably a hydrogen atom or an alkyl group. 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) is preferably a linking chain selected from NH—CH 2 —, and more preferably a single bond (X does not exist).

Specific examples of the monomer (A2a-1) include, for example, a ring-opened product of hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, 2-propen-1-ol, and 1-propene-1,3-diol. 1-propen-2-ol, 2-methyl-2-propen-1-ol, 2-buten-1-ol, 2-methyl-2-buten-1-ol, 1-methyl-2-buten-1- All, 2-butene-1,4-diol, 1-butene-3,4-diol, 2-methyl-2-butene-1,4-diol, 4-penten-2-ol, 3-pentene-1- All, 4-penten-2-ol, 4-penten-1-ol, 1-pentene-4,5-diol, 2-pentene-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- Examples thereof include dihydroxyethyl (meth) acrylamide and derivatives thereof.
These can be used alone or in combination of two or more. Of these, those having two or more hydroxyl groups are preferred.
In addition, the total number of carbon atoms and oxygen atoms in X, R ₃ , and R ₄ in the monomer (A2a-1) represented by the formula (1) is preferably 3 or more.

  The content of the polymerizable unsaturated group-containing monomer (A2a-1) in the resin (A2a) is preferably in the range of 0.01 to 20% by mass, and in the range of 0.1 to 15% by mass. It is more preferable that it is in the range of 0.5 to 10% by mass. In the present invention, “the content ratio of the polymerizable unsaturated group-containing monomer (A2a-1) in the resin (A2a)” refers to the polymerizable unsaturated group-containing monomer in the monomer mixture as the raw material of the resin (A2a) ( It means the content ratio of A2a-1). Therefore, the content ratio of the polymerizable unsaturated group-containing monomer (A2a-1) in the resin (A2a) is 0.1 to 20% by mass. The resin (A2a) is a polymerizable unsaturated group-containing monomer. It means that it is a copolymer of raw material monomers containing 0.1 to 20% by mass of (A2a-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 that is the raw material of the resin Y. Therefore, the content ratio of the polymerizable unsaturated group-containing monomer X in the resin Y being a mass% means that the resin Y is a copolymer of raw material monomers containing the monomer X in a mass%. .

  The other polymerizable unsaturated monomer copolymerized with the polymerizable unsaturated group-containing monomer (A2a-1) is not particularly limited as long as it is a monomer copolymerizable with the monomer (A2a-1). Specifically, for example, fatty acid vinyl esters such as vinyl acetate; olefinic monomers such as ethylene and propylene; (meth) acryloyl group-containing monomers such as alkyl (meth) acrylates; allyl ethers such as allyl glycidyl ether; Examples thereof include vinyl halide compounds such as vinyl chloride, vinylidene chloride and vinyl fluoride; vinyl ethers such as alkyl vinyl ether. These can be used individually by 1 type or in combination of 2 or more types, Especially, fatty acid vinyl ester (A2a-2) is preferable. Specific examples of the fatty acid vinyl ester (A2a-2) include, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl caprylate, vinyl caproate, vinyl laurate, and vinyl myristate. , Vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl octylate, vinyl monochloroate, vinyl benzoate, vinyl cinnamate, vinyl crotonate, divinyl adipate, and derivatives thereof, among which vinyl acetate is preferred. .

Further, it is preferable from the viewpoint of dispersibility and solubility that the resin (A2a) obtained by copolymerization is saponified to hydrolyze all or part of the fatty acid vinyl ester units to 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%, still more preferably in the range of 86 to 100 mol%, and 88 to 99. It is particularly preferable that the amount be in the range of .9 mol%.
In other words, the resin (A2a) is polymerized by saponifying a copolymer of at least one polymerizable unsaturated group-containing monomer (A2a-1) and at least one fatty acid vinyl ester (A2a-2). It is particularly preferable that the resin is a resin comprising a polymerizable unsaturated group-containing monomer (A2a-1), a fatty acid vinyl ester (A2a-2), and vinyl alcohol (A2a-3) as constituent components.

  Normally, when the degree of saponification (high polarity) is high, the adsorptivity to inorganic pigments such as carbon is improved, but the solubility in a solvent (NMP, etc.) is reduced, and a three-dimensional repulsive layer cannot be formed, resulting in poor dispersibility It will be. However, in the present invention, the reason why the resin (A2a) having the polymerizable unsaturated group-containing monomer (A2a-1) as one of the constituents has an effect on the dispersibility of the conductive paste is specific to the side chain of the resin. By introducing the functional group, a relatively bulky side chain functional group becomes a steric hindrance, so that the melting point of the resin can be lowered, and the crystallinity of the resin can be lowered by hydrogen bonding of a specific hydroxyl group. Therefore, it is considered that the solubility in the solvent and the adsorptivity to the pigment were compatible.

  The polymerization method of the resin (A2a) can be produced by a polymerization method known per se, for example, a solution polymerization method in an organic solvent, but is not limited to this, for example, bulk polymerization or emulsification Polymerization or suspension polymerization may be used. When solution polymerization is performed, continuous polymerization or batch polymerization may be performed, and the monomers may be charged all at once, may be charged separately, or may be added continuously or intermittently.

  The polymerization initiator used in the solution polymerization is not particularly limited. Specifically, for example, azobisisobutyronitrile, azobis-2,4-dimethylpareronitrile, azobis (4-methoxy-2) Azo compounds such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, and peroxidation such as 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate Products; percarbonate compounds such as diisopropylpropyloxycarbonate, di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate; t-butylperoxyneodecanate, α-cumylperoxyneodecanate , T-butyl par Perester compounds such as carboxymethyl neodecanate; azobisdimethylvaleronitrile can be used a known radical polymerization initiator such as azo-bis-methoxy valeronitrile.

  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 moiety in the molecule in an alcohol solution such as methanol in the presence of an alkali catalyst or an acid catalyst.
Examples of the alkali catalyst that can be used include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, and potassium methylate, alcoholates, and the like. As the acid catalyst, for example, an inorganic acid aqueous solution such as hydrochloric acid or sulfuric acid, or an organic acid such as p-toluenesulfonic acid can be used, but sodium hydroxide is preferably used.
The temperature of the saponification reaction is not particularly limited, but is preferably 10 to 70 ° C, more preferably 30 to 40 ° C. Although reaction time is not specifically limited, It is desirable to carry out in 30 minutes-3 hours.

The resin (A2a) can be made into a resin solution substituted with a solid or an arbitrary solvent by removing the solvent and / or replacing the solvent after completion of the synthesis. As the substitution solvent, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, propylene glycol monomethyl ether, alcohol solvents and the like are preferable.
As a method for removing the solvent, it may be carried out by heating at normal pressure or may be removed under reduced pressure. As a solvent replacement method, the replacement solvent may be added at any stage before, during or after the solvent removal.

Sulfonic acid-modified polyvinyl alcohol resin (A2b)
The sulfonic acid-modified polyvinyl alcohol resin (A2b) is a polyalcohol resin provided with sulfonic acid by the following production method. Moreover, the polyvinyl alcohol resin (A2b) does not contain the polymerizable unsaturated group-containing monomer (A2a-1) represented by the formula (I) and can be clearly distinguished from the polyvinyl alcohol resin (A2a).
(1) A method in which a compound containing a sulfonic acid group and a polymerizable unsaturated group is copolymerized with a fatty acid vinyl ester such as vinyl acetate, and the resulting polymer is further saponified.
(2) A method of Michael addition of vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid or the like to polyvinyl alcohol.
(3) A method of heating polyvinyl alcohol with a sulfate compound solution (sulfuric acid aqueous solution, sodium sulfite aqueous solution or the like).
(4) A method of acetalizing polyvinyl alcohol with a sulfonic acid group-containing aldehyde compound.
(5) A method of polymerizing polyvinyl alcohol by allowing a compound having a functional group such as alcohol having a sulfonic acid group, aldehyde, and thiol to coexist as a chain transfer agent.

  Any of the production methods can be suitably used, but the compound (1) containing a sulfonic acid group and a polymerizable unsaturated group and other polymerizable unsaturated monomers (especially fatty acid vinyl esters such as vinyl acetate are preferred). ) And the resulting polymer is further saponified.

  As the above compound containing a sulfonic acid group and a polymerizable unsaturated group (in this specification, simply referred to as a polymerizable unsaturated monomer having a sulfonic acid group), a compound that can be copolymerized with a fatty acid vinyl ester Can be used without particular limitation. Specifically, for example, olefin sulfonic acids such as vinyl sulfonic acid, isoprene sulfonic acid, ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid; sodium sulfopropyl 2-ethylhexyl Sulfoalkylmalates such as malate, sodium sulfopropyltridecylmalate, sodium sulfopropyleicosylmalate; sulfoalkyl (meth) such as 2- (meth) acrylamide-2-methylpropanesulfonic acid, sodium N-sulfoisobutyleneacrylamide Ak 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfonic acid, 3-methacryloyloxy-2-hydroxypropanesulfonic acid, 3-acryloyloxypropanesulfonic acid, sulfoethyl (meth) acrylate, sodium methacrylate-4- Sulfoalkyl (meth) acrylates such as styrene sulfonate and sodium 2-sulfoethyl acrylate; allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, styrene sulfonic acid, oleyl 2-hydroxy- [3-allyloxy] -propyl sulfosuccinate An ammonium salt etc. are mentioned, These can be used individually by 1 type or in combination of 2 or more types.

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 sodium salt or potassium salt, or an ammonium salt.
The content of the polymerizable unsaturated monomer having a sulfonic acid group in the sulfonic acid-modified polyvinyl alcohol resin (A2b) 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 (A2b)” means the content ratio of the monomer having a sulfonic acid group in the monomer mixture as a raw material of the resin (A2b). Therefore, the content ratio of the monomer having a sulfonic acid group in the resin (A2b) is 0.1 to 10% by mass. The resin (A2b) is 0.1 to 10 mass by mass of the monomer having a sulfonic acid group. % Is a copolymer of raw material monomers.

  The other polymerizable unsaturated monomer copolymerized with the compound containing the sulfonic acid group and the polymerizable unsaturated group is not particularly limited as long as it is a monomer copolymerizable with the polymerizable unsaturated monomer having a sulfonic acid group. It can be used without. [However, it is limited to monomers other than the polymerizable unsaturated group-containing monomer (A2a-1). Specifically, for example, fatty acid vinyl esters such as vinyl acetate; olefinic monomers such as ethylene and propylene; (meth) acryloyl group-containing monomers such as alkyl (meth) acrylates; allyl ethers such as allyl glycidyl ether; vinyl chloride , Vinyl halide compounds such as vinylidene chloride and vinyl fluoride; and vinyl ethers such as alkyl vinyl ether. These can be used individually by 1 type or in combination of 2 or more types, Among these, fatty acid vinyl ester is preferable. As fatty acid vinyl ester, 1 type (s) or 2 or more types can be used suitably from the fatty acid vinyl ester illustrated by fatty acid vinyl ester (A2a-2), and especially vinyl acetate is preferable.

  The saponification degree of the sulfonic acid-modified polyvinyl alcohol resin (A2b) 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 preferable that it is in the range of 88 to 99.9 mol%.

  Normally, when the degree of saponification (high polarity) is high, the adsorptivity to inorganic pigments such as carbon is improved, but the solubility in a solvent (NMP, etc.) is reduced, and a three-dimensional repulsive 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 (A2b) has an effect on the dispersibility of the conductive paste is that a relatively bulky side chain is introduced by introducing a specific functional group into the side chain of the resin. The functional group (functional group containing sulfonic acid) lowers the melting point of the resin due to steric hindrance, and the crystallinity of the resin decreases due to the highly polar side chain functional group (functional group containing sulfonic acid). Therefore, it is considered that the solubility in the solvent and the adsorptivity to the pigment were compatible.

  As a polymerization method of the resin (A2b), the same method as the resin (A2a) described above can be used.

Polyvinyl alcohol resin (A2c) other than resin (A2a) and resin (A2b)
The dispersion resin (A) that can be used in the conductive paste of the present invention does not contain the polymerizable unsaturated group-containing monomer (A2a-1), and has a saponification degree of 30 to 100 mol% that is not modified with sulfonic acid. Alcohol resin (A2c) can be contained. In the present invention, the “polyvinyl alcohol resin not containing a polymerizable unsaturated group-containing monomer (A2a-1)” means (co) polymerization of raw material monomers not containing a polymerizable unsaturated group-containing monomer (A2a-1). It means the resulting polyvinyl alcohol resin. The “polyvinyl alcohol resin not modified with sulfonic acid” means a polyvinyl alcohol resin obtained by (co) polymerization of a raw material monomer not containing a sulfonic acid group, or a sulfonic acid group formed by the above-described modification or the like. It means a resin not added.

  The polyvinyl alcohol resin (A2c) 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 for the fatty acid vinyl ester (A2a-2) can be suitably used, and among them, vinyl acetate is preferable.

The polyvinyl alcohol resin (A2c) can be obtained by copolymerizing with a polymerizable unsaturated monomer other than the fatty acid vinyl ester. [However, it is limited to monomers other than the polymerizable unsaturated group-containing monomer (A2a-1) and the polymerizable unsaturated monomer having a sulfonic acid group. ]
The polymerizable unsaturated monomer copolymerizable with the fatty acid vinyl ester is not particularly limited as long as it is a monomer other than the polymerizable unsaturated group-containing monomer (A2a-1) and the polymerizable unsaturated monomer having a sulfonic acid group. For example, olefin monomers such as ethylene and propylene; (meth) acryloyl group-containing monomers such as alkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and glycidyl (meth) acrylate; allyl glycidyl ether and the like Allyl ethers; vinyl halide compounds such as vinyl chloride, vinylidene chloride and vinyl fluoride; vinyl ethers such as alkyl vinyl ether and 4-hydroxy vinyl ether. These can be used alone or in combination of two or more.

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

  The polymerization method of the polyvinyl alcohol resin (A2c) is a polymerization method known per se, for example, a method of producing a polyvinyl acetate by solution polymerization of vinyl acetate in an alcoholic organic solvent and saponifying it. Although it can manufacture, it is not restricted to this, For example, bulk polymerization, emulsion polymerization, suspension polymerization, etc. may be sufficient. When solution polymerization is performed, continuous polymerization or batch polymerization may be performed, and the monomers may be charged all at once, may be charged separately, or may be added continuously or intermittently.

  The polymerization initiator used in the solution polymerization is not particularly limited. Specifically, for example, azobisisobutyronitrile, azobis-2,4-dimethylpareronitrile, azobis (4-methoxy-2) Azo compounds such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, and peroxidation such as 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate Products; percarbonate compounds such as diisopropylpropyloxycarbonate, di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate; t-butylperoxyneodecanate, α-cumylperoxyneodecanate , T-butyl par Perester compounds such as carboxymethyl neodecanate; azobisdimethylvaleronitrile can be used a known radical polymerization initiator such as azo-bis-methoxy valeronitrile.

  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 (A2c) are not particularly limited and can be saponified by a known method. Generally, it can carry out by hydrolyzing the ester part in a molecule | numerator in presence of an alkali catalyst or an acid catalyst in alcohol solutions, such as methanol.
Examples of the alkali catalyst that can be used include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, and potassium methylate, alcoholates, and the like. As the acid catalyst, for example, an inorganic acid aqueous solution such as hydrochloric acid or sulfuric acid, or an organic acid such as p-toluenesulfonic acid can be used, but sodium hydroxide is preferably used.
The temperature of the saponification reaction is not particularly limited, but is preferably 10 to 70 ° C, more preferably 30 to 40 ° C. Although reaction time is not specifically limited, It is desirable to carry out in 30 minutes-3 hours.

The polyvinyl alcohol resin thus obtained preferably has a degree of polymerization of 100 to 4,000, and more preferably 100 to 3,000.
The degree of saponification is usually in the range of 30 to 100 mol%, preferably in the range of 32 to 85 mol%.
In the present invention, the degree of saponification of the polyvinyl alcohol resin (A2c) refers to the proportion (mol%) of the fatty acid vinyl ester-derived constituent units contained in the polyvinyl alcohol resin (A2c) in which the ester bond is hydrolyzed. means. The saponification degree can be measured by completely saponifying the polyvinyl alcohol resin with an alkaline substance such as sodium hydroxide and measuring the amount of the obtained fatty acid salt (for example, acetate). (Complete saponification can be confirmed by infrared absorption analysis.)
The polyvinyl alcohol resin (A2c) may be a commercially available product.

The polyvinyl alcohol resin (A2c) can be made into a resin solution that is replaced with a solid or an arbitrary solvent by removing the solvent and / or replacing the solvent after completion of the synthesis. As the substitution solvent, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, propylene glycol monomethyl ether, alcohol solvents and the like are preferable.
As a method for removing the solvent, it may be carried out by heating at normal pressure or may be removed under reduced pressure. As a solvent replacement method, the replacement solvent may be added at any stage before, during or after the solvent removal.

  In the conductive paste of the present invention, the high-polarity resin (A2a) and / or (A2b) and the relatively low-polarity polyvinyl alcohol resin (A2c) are used in combination to make the resins compatible with each other. It is considered that the solvent solubility and the pigment adsorptivity were further compatible.

  When the dispersion resin (A) includes the resin (A1) having a polycyclic aromatic hydrocarbon group and the polyvinyl alcohol resin (A2), the blending ratio is not limited, but the solid content of the dispersion resin (A) is 100 mass. The solid content of the resin (A1) having a polycyclic aromatic hydrocarbon group is usually 5 to 95 parts by mass, preferably in the range of 10 to 50 parts by mass, and the solid content of the polyvinyl alcohol resin (A2). Usually, it is preferable to set it as the range of 5-95 mass parts, Preferably it is the range of 50-90 mass parts from a viewpoint of a viscosity and battery performance. When the polyvinyl alcohol (A2) contains both the polyvinyl alcohol resin (A2a) and / or (A2b) and the polyvinyl alcohol (A2c), the blending ratio is not limited, but the polyvinyl alcohol resin (A2a) and the resin (A2b) From the viewpoint of viscosity and battery performance, the solid content of polyvinyl alcohol (A2c) is usually 5 to 100 parts by mass, preferably 15 to 70 parts by mass with respect to 100 parts by mass of the total solids. preferable.

You may mix | blend resin other than said resin (A1) and resin (A2) arbitrarily with other resin dispersion resin (A). For example, acrylic resin other than resin (A1) and resin (A2), polyester resin, epoxy resin, polyether resin, alkyd resin, urethane resin, silicone resin, polycarbonate resin, silicate resin, chlorine resin, polyvinylidene fluoride (PVDF ) -Based fluororesin, polyvinyl pyrrolidone resin, polyvinyl alcohol resin, polyvinyl acetal resin, and composite resins thereof. These resins can be used alone or in combination of two or more. Especially, it is preferable to use together and use at least 1 sort (s) of resin chosen from polyvinyl acetal resin, polyvinylpyrrolidone resin, and a fluororesin. Further, these resins can be blended in the conductive paste as a pigment dispersion resin or as an additive resin after pigment dispersion.

Polyvinylidene fluoride (B)
As the polyvinylidene fluoride, those used for dispersing a conductive additive in the field of the conductive paste for a lithium ion battery positive electrode to which the invention belongs can be widely used. The weight average molecular weight of the 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.

Conductive carbon (C)
Examples of the conductive carbon (C) include acetylene black, furnace black, thermal black, channel black, ketjen black, vulcan, carbon nanotube, graphene, vapor grown carbon fiber (VGCF), and graphite. Preferably, acetylene black, graphite, etc. are mentioned, More preferably, acetylene black etc. are mentioned. 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 a solvent (D), the solvent used for superposition | polymerization or dilution of resin (A3) which has the polycyclic aromatic hydrocarbon group mentioned above can be used suitably. Specific examples of the preferred solvent (D) include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, propylene glycol monomethyl ether, methanol and the like, preferably N-methyl-2-pyrrolidone and the like. Is mentioned. These solvent can be used individually by 1 type or in mixture of 2 or more types.
The conductive paste of the present invention preferably has a water content of less than 1.0% by mass, more preferably less than 0.7% by mass, and 0.5% by mass based on the total amount of paste. More preferably, it is less than. In the present invention, the water content of the conductive paste is measured by the Karl Fischer coulometric titration method. Specifically, a Karl Fischer moisture meter (Kyoto Electronics Industry Co., Ltd., product name: MKC-610) was used, and a moisture vaporizer (ADP-611, Kyoto Electronics Co., Ltd.) provided in the device was used. The preset temperature can be measured as 130 ° C. When the water content in the conductive paste is 1.0% by mass or more, storage stability and the like are inferior, and thus the conductive paste of the present invention can be said to be a substantially non-aqueous conductive paste.

Hindered amine compound (E)
As the hindered amine compound (E) that can be used in the present invention, a known compound such as a low molecular weight compound or a high molecular weight compound can be used without particular limitation. Specifically, for example, as a low molecular weight compound, Is a reaction product of bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and octane (molecular weight 737) 70 And consisting of 30% by weight of polypropylene and 30% by weight of polypropylene; bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] Methyl] butyl malonate (molecular weight 685); bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl -1,2,2,6,6-pentamethyl-4-piperidyl sebacate mixture (molecular weight 509); bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (molecular weight 481); tetrakis (2 , 2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 791); tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 847); 2,2,6,6-tetramethyl-4-piperidyl-1,2,3,4-butanetetracarboxylate and tridecyl-1, Mixture of 2,3,4-butanetetracarboxylate (molecular weight 900); 1,2,2,6,6-pentamethyl-4-piperidyl-1,2,3,4-butanetetra Rubokishireto and tridecyl-1,2,3,4-butane tetracarboxylic mixtures rate (molecular weight 900), and the like.

As a high molecular weight compound, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6 -Tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}] (molecular weight 2,000-3,100); dimethyl succinate and 4-hydroxy -2,2,6,6-tetramethyl-1-piperidineethanol polymer (molecular weight 3,100-4,000); N, N ', N ", N"'-tetrakis- (4,6-bis -(Butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10-diamine (molecular weight 2, 286) and the above dimethyl succinate and 4- Polymer mixture of droxy-2,2,6,6-tetramethyl-1-piperidineethanol; dibutylamine, 1,3,5-triazine, N, N′-bis (2,2,6,6-tetra Examples include polycondensates (molecular weight 2,600-3,400) of methyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine. be able to.
These can be used alone or in combination of two or more.

  Moreover, as a commercial item of the said hindered amine compound, for example, HALS292, CHIMASSORB119, CHIMASSORB2020, CHIMASSOVIN944, TINUVIN622, TINUVINUVIN783, TINUVIN111, TINUVIN111, TINUVIN492, TINUVIN491, TINUVIN491, TINUVIN4953 , TINUVIN 770, TINUVIN XT850, TINUVIN XT855, TINUVIN 440, TINUVIN NOR371 (above, manufactured by Ciba Japan Co., Ltd.), ADK STAB LA-52, Adekasta LA-57, ADK STAB LA-62, ADK STAB LA-67, ADK STAB LA-63, ADK STAB LA-68LD, ADK STAB LA-82, ADK STAB LA-87, ADK STAB LA-501, ADK STAB LA-502XP, ADK STAB LA-503, ADK STAB LA-77, Adekastab LX-335, Adecanol UC-605 (manufactured by ADEKA), Sanol LS770, Sanol LS765, Sanol LS292, Sanol LS440, Sanol LS744, Sanol LS2626, Sanol LS944 (and above, Sankyo) Lifetech Co., Ltd.), Hostavin N20, Hostabin N24, Hostabin N30, Hostabin N321, Hostabin PR31, Hostabin 305 0, hostabin 3051, hostabin 3052, hostabin 3053, hostabin 3055, hostabin 3058, hostabin 3063, hostabin 3212, hostabin TB01, hostabin TB02, Nylostab S-EED (above, Clariant Japan Co., Ltd.), Tomissorb 77 ( Yoshitomi Fine Chemical Co., Ltd.), SIASORB UV3346, Siasorb UV3529, Siasorb UV3853 (Sun Chemical Co., Ltd.), SUMISORB TM61 (Sumitomo Chemical Co., Ltd.), Goodlite UV3159, Good Light UV3034, Goodlight UV3150, Goodlight 3110 × 128 (above BF Goodrich Co., Ltd.), Ubinu (UVINUL) 4049, Uvinul 4050, or the like of Uvinul 5050 (or BASF (Ltd.)) can be mentioned.

Acidic compound (F)
The conductive paste for a lithium ion battery positive electrode of the present invention may further contain an acidic compound (F). The aforementioned double bond formation in the main chain of polyvinylidene fluoride and polymerization of polyvinylidene fluoride are manifested under basic conditions. Therefore, by adding the acidic compound (F), it is possible to suppress the polymerization of polyvinylidene fluoride and the accompanying increase in viscosity and gelation of the conductive paste for a lithium ion battery positive electrode. It does not specifically limit as an acidic compound (F), Either an inorganic acid and an organic acid can also be used. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like. Examples of the organic acid include carboxylic acid compounds and sulfonic acid compounds. Carboxylic acid compounds include formic acid, acetic acid, propionic acid, butyric acid, tartaric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, (meth) acrylic acid, crotonic acid, fumaric acid, Examples include maleic acid, itaconic acid, citraconic acid, and fluoroacetic acid. Examples of the sulfonic acid compound include methanesulfonic acid, paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid. Further, anhydrides, hydrates, or acidic compounds in which a part of the acidic compound is a salt can also be used. These can be used alone or in combination of two or more.

Other additives In the conductive paste for a lithium ion battery positive electrode, components other than the above components (A), (B), (C), (D), (E), and (F) (shown as other additives) May be included). Examples of other additives include neutralizers, pigment dispersants, antifoaming agents, preservatives, dehydrating agents, rust preventing agents, plasticizers, and binders (binders).

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

Production Method of Conductive Paste for Lithium Ion Battery Positive Electrode of the Present Invention The total amount of the solid content of the dispersion resin (A) in the solid content of the conductive paste for a lithium ion battery positive electrode of the present invention is usually 30% by mass or less, preferably 20 The 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. Moreover, in preferable embodiment of this invention, from the electroconductive viewpoint of a coating film, the total amount of solid content of the dispersion resin (A) in the conductive paste solid content for lithium ion battery positive electrodes of this invention is normal. 20 mass% or less, preferably 0.1 to 15 mass%, more preferably 1.0 to 10 mass%.

  The solid content of polyvinylidene fluoride (B) in the solid content of the conductive paste for a lithium ion battery positive electrode of the present invention is usually 0.5% by mass or more and less than 30% by mass, preferably 3% by mass or more, and Less than 25% by mass, more preferably 5% by mass or more and less than 20% by mass is suitable. The solid content of the conductive carbon (C) in the solid paste for the lithium ion battery positive electrode of the present invention is usually 50% by mass or more and less than 100% by mass, preferably 60% by mass or more and 100% by mass. Less than, more preferably 70% by mass or more and less than 100% by mass is suitable from the viewpoint of battery performance. The content of the solvent (D) in the conductive paste for a lithium ion battery positive electrode of the present invention is usually 50% by mass or more and less than 100% by mass, preferably 70% by mass or more and less than 100% by mass. Preferably 80 mass% or more and less than 100 mass% are suitable from the point of drying efficiency and paste viscosity. The solid content of the hindered amine compound (E) in the solid content of the conductive paste for the lithium ion battery positive electrode of the present invention is usually 1% by mass or more and less than 500% by mass based on the mass of the polyvinylidene fluoride (B). From the viewpoint of viscosity and storage stability, it is preferable that the content is 10% by mass or more and less than 300% by mass, more preferably 20% by mass or more and less than 150% by mass. When mix | blending acidic compound (F) with the conductive paste for lithium ion battery positive electrodes of this invention, the compounding quantity of acidic compound (F) in the conductive paste solid content for lithium ion battery positive electrodes is the mass of polyvinylidene fluoride (B). Is usually 0.1% by weight or more and less than 10% by weight, preferably 0.5% by weight or more and less than 7% by weight, more preferably 1% by weight or more and less than 5% by weight. It is preferable from the viewpoint of storage stability. In the present invention, the conductive paste for a lithium ion battery positive electrode preferably has a water content of less than 1.0% by mass and less than 0.6% by mass from the viewpoint of viscosity and storage stability. Is more preferable, and it is especially preferable that it is less than 0.4 mass%.

The conductive paste for a lithium ion battery positive electrode of the present invention comprises the components described above, for example, paint shaker, sand mill, ball mill, pebble mill, LMZ mill, DCP pearl mill, planetary ball mill, homogenizer, biaxial kneader, thin film swirl type It can be prepared by uniformly mixing and dispersing using a conventionally known disperser such as a high-speed mixer. In the present invention, in the production of the conductive paste for a lithium ion battery positive electrode, mixing and / or pigment dispersion is performed in an atmosphere having a dew point of 10 ° C. or less, more preferably a dew point of 7 ° C. or less, and even more preferably a dew point of 5 ° C. or less. Is preferable from the viewpoints of viscosity and storage stability.
Although it is preferable to remove moisture as much as possible, since moisture is mixed into the conductive paste from raw materials and air, at least 0.01% by mass or more of moisture can be contained. Moreover, the water | moisture content of 0.06 mass% or more may be contained on the relationship of an installation or a manufacturing process.

  As will be described later, the conductive paste for a lithium ion battery positive electrode of the present invention can be mixed with an electrode active material and used to produce a lithium ion battery positive electrode mixture paste.

Lithium-ion battery positive electrode composite paste The present invention provides a lithium-ion battery positive electrode composite paste obtained by further blending an electrode active material with the conductive paste.

As an electrode active material , for example, lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), LiNi _1/3 Co _1/3 Mn _1/3 O _And lithium composite oxide such as ₂ . These electrode active materials can be used individually by 1 type or in mixture of 2 or more types. The solid content of the electrode active material in the solid paste solid content of the lithium ion battery positive electrode 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 in terms of battery capacity, battery resistance, and the like.

Method for Producing Lithium Ion Battery Positive Electrode Paste The lithium ion battery positive electrode composite paste of the present invention is prepared by first preparing the above-described lithium ion battery positive electrode conductive paste, and applying the lithium ion battery positive electrode conductive paste to the conductive paste. It can be obtained by blending an active material. Moreover, the lithium ion battery positive electrode composite paste of the present invention includes the aforementioned component (A), component (B), component (C), component (D), component (E), and optionally component (F). Other components may be mixed with the electrode active material.

  The total amount of the solid content of the dispersion resin (A) in the solid paste solid content for the lithium ion battery positive electrode of the present invention is usually 0.001 to 20 mass%, preferably 0.005 to 10 mass%. Is preferable in terms of battery performance, paste viscosity, and the like.

  The solid content of polyvinylidene fluoride (B) in the solid paste solid content of the lithium ion battery positive electrode of the present invention is usually 0.1% by mass or more and less than 3% by mass, preferably 0.5% by mass. Above and below 2.5% by mass, more preferably above 1% by mass and below 2% by mass are suitable. The solid content of the conductive carbon (C) in the solid content of the lithium ion battery positive electrode paste of the present invention is usually 0.01 to 30% by mass, preferably 0.05 to 20% by mass, more preferably. 0.1-15 mass% is suitable from the point of battery performance. The content of the solvent (D) in the lithium ion battery positive electrode mixture paste of the present invention is usually 0.1 to 60% by mass, preferably 0.5 to 50% by mass, more preferably 1 to 45%. Mass% is preferable from the viewpoint of electrode drying efficiency and paste viscosity. The solid content of the hindered amine compound (E) in the solid paste solid content for the lithium ion battery positive electrode of the present invention is usually 1% by mass or more and 500% by mass based on the mass of the polyvinylidene fluoride (B). Less than, preferably 10% by mass or more and less than 300% by mass, more preferably 20% by mass or more and less than 150% by mass is suitable from the viewpoint of viscosity and storage stability. When the acidic compound (F) is blended in the lithium ion battery positive electrode composite paste of the present invention, the amount of the acidic compound (F) in the lithium ion battery positive electrode composite paste solid is determined to be polyvinylidene fluoride (B). Is usually 0.1% by weight or more and less than 10% by weight, preferably 0.5% by weight or more and less than 7% by weight, more preferably 1% by weight or more and less than 5% by weight. It is preferable from the viewpoint of viscosity and storage stability. In the present invention, the lithium hydroxide content in the lithium ion battery positive electrode mixture paste is suppressed to less than 1.5 mass%, more preferably less than 1 mass%, based on the mass of polyvinylidene fluoride (B). It is preferable to prevent gelation. In the present invention, the lithium hydroxide content can be measured by a method in which the mixture paste is overdiluted with deionized water and centrifuged, and then the supernatant is neutralized and titrated with hydrochloric acid.

The lithium ion battery positive electrode composite paste of the present invention preferably contains as little moisture as possible. The moisture content is preferably less than 1.0% by mass, more preferably less than 0.6% by mass, and particularly preferably less than 0.4% by mass. Since moisture is mixed into the composite paste from the conductive paste or the atmosphere, at least 0.01% by mass or more of moisture can be contained. Moreover, the water | moisture content of 0.06 mass% or more may be contained on the relationship of an installation or a manufacturing process.
In addition, said moisture content is content contained in mixture paste, Comprising: It is not moisture content contained in the positive mix layer which dried the composite paste. In the process of drying the composite paste, it is considered that part or all of the water contained in the composite paste evaporates.

Method for Producing Lithium Ion Battery Positive Electrode As described above, the positive electrode mixture layer of the lithium ion secondary battery is coated with the lithium ion battery positive electrode mixture paste on the surface of the positive electrode core material and dried. Can be manufactured. Moreover, as a use of the electrically conductive paste for lithium ion battery positive electrodes of this invention, it can use also as a primer layer between a positive electrode core material and a synthetic layer besides using as a paste of a compound material layer.
The method of applying the lithium ion battery positive electrode composite paste can be performed by a method known per se using a die coater or the like. The coating amount of the lithium ion battery positive electrode mixture paste is not particularly limited. 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 follows. As temperature of a drying process, it can set suitably in 80-200 degreeC, for example, Preferably in the range of 100-180 degreeC. As time of a drying process, it can set suitably within the range of 5 to 120 second, for example, Preferably it is 5 to 60 second.
In the drying step, it is preferable from the viewpoint of battery performance that the hindered amine compound (E) contained in the composite paste of the present invention is evaporated or sublimated as much as possible and does not remain in the positive electrode mixture layer as a dry film.

  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, “parts” indicates mass parts, and “%” indicates mass%.

Manufacture of pigment dispersion resin
Production and production example 1 of resin (A1) having a polycyclic aromatic hydrocarbon group
In a reaction vessel equipped with a stirring and heating device and a cooling tube, 300 parts of propylene glycol monomethyl ether was charged and maintained at 110 ° C. after purging with nitrogen. Into this, the monomer mixture shown below was dripped over 3 hours.
<Monomer mixture>
4-hydroxy-1-naphthyl methacrylate 300 parts styrene 200 parts n-butyl acrylate 300 parts 2-hydroxyethyl acrylate 200 parts 2,2′-azobis (2-methylbutyronitrile) 40 parts 1 hour after the end of dropping A solution prepared by dissolving 5 parts of 2,2′-azobis (2-methylbutyronitrile) in 100 parts of propylene glycol monomethyl ether was added dropwise over 1 hour. After the completion of dropping, this was further maintained at 110 ° C. for 1 hour, then discharged and dried with a hot air dryer. Resin No. having a polycyclic aromatic hydrocarbon group having a solid content of 100% finally. One solution was obtained. Resin No. having a polycyclic aromatic hydrocarbon group 1 had a weight average molecular weight of 10,000.

Production Examples 2-7
Resin No. 1 having a polycyclic aromatic hydrocarbon group with the same composition and production method as in Production Example 1 except that the monomer composition of Production Example 1 is the type and blending amount shown in Table 1 below. 2-7 solutions were prepared.

Production Production Example 8 of Polyvinyl Alcohol Resin (A2a) Containing Polymerizable Unsaturated Group-Containing Monomer (A2a-1) 8
In a reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer, 90 parts by mass of vinyl acetate as a polymerizable monomer and 10 parts by mass of 2-butene-1,4-diol, methanol as a solvent, polymerization initiation A copolymer of azobisisobutyronitrile as an agent was carried out at a temperature of about 60 ° C., and then unreacted monomers were removed under reduced pressure to obtain a resin solution. Next, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, washed well, and then dried with a hot air dryer. Finally, a polyvinyl alcohol resin No. 1 having a polymerization degree of 300, a saponification degree of 92 mol%, and a polymerizable unsaturated group-containing monomer (A2a-1) content of 10% by mass. 1 was obtained.

Production Example 9
In a reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer, 90 parts by mass of vinyl acetate as a polymerizable monomer and 10 parts by mass of 1-butene-3,4-diol, methanol as a solvent, polymerization initiation After carrying out a copolymerization reaction at a temperature of about 60 ° C. using azobisisobutyronitrile as an agent, unreacted monomers were removed under reduced pressure to obtain a resin solution. Next, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, washed well, and then dried with a hot air dryer. Finally, a polyvinyl alcohol resin No. 1 having a polymerization degree of 300, a saponification degree of 92 mol%, and a polymerizable unsaturated group-containing monomer (A2a-1) content of 10% by mass. 2 was obtained.

Production Example 10
In a reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer, 90 parts by mass of vinyl acetate as a polymerizable monomer and 10 parts by mass of 1-pentene-4,5-diol, methanol as a solvent, polymerization initiation After carrying out a copolymerization reaction at a temperature of about 60 ° C. using azobisisobutyronitrile as an agent, unreacted monomers were removed under reduced pressure to obtain a resin solution. Next, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, washed well, and then dried with a hot air dryer. Finally, a polyvinyl alcohol resin No. 1 having a polymerization degree of 300, a saponification degree of 92 mol%, and a polymerizable unsaturated group-containing monomer (A2a-1) content of 10% by mass. 3 was obtained.

Production and production example 11 of sulfonic acid-modified polyvinyl alcohol resin (A2b)
In a reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer, 97 parts by mass of vinyl acetate as a polymerizable monomer and 3.0 parts by mass of sodium allyl sulfonate, methanol as a solvent, azo as a polymerization initiator After carrying out a copolymerization reaction at a temperature of about 60 degrees using bisisobutyronitrile, unreacted monomers were removed under reduced pressure to obtain a resin solution. Next, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, washed well, and then dried with a hot air dryer. Finally, polyvinyl alcohol resin No. 1 having a polymerization degree of 300, a saponification degree of 92 mol%, and a sulfonic acid group-containing polymerizable unsaturated monomer content of 3.0 mass% 4 was obtained.

Production and production example 12 of polyvinyl alcohol resin (A2c)
A reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer, and a temperature of about 60 degrees using vinyl acetate as a polymerizable monomer, methanol as a solvent, and azobisisobutyronitrile as a polymerization initiator. After carrying out the copolymerization reaction, the unreacted monomer was removed under reduced pressure to obtain a resin solution. Next, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, washed well, and then dried with a hot air dryer. Finally, a polyvinyl alcohol resin No. 5 having a polymerization degree of 500 and a saponification degree of 50 mol% was used. 5 was obtained.

Production Example 13
A reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer, and a temperature of about 60 degrees using vinyl acetate as a polymerizable monomer, methanol as a solvent, and azobisisobutyronitrile as a polymerization initiator After carrying out the copolymerization reaction, the unreacted monomer was removed under reduced pressure to obtain a resin solution. Next, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, washed well, and then dried with a hot air dryer. Finally, a polyvinyl alcohol resin No. 5 having a polymerization degree of 500 and a saponification degree of 70 mol% was used. 6 was obtained.

Production Example 14
A reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer, and a temperature of about 60 degrees using vinyl acetate as a polymerizable monomer, methanol as a solvent, and azobisisobutyronitrile as a polymerization initiator. After carrying out the copolymerization reaction, the unreacted monomer was removed under reduced pressure to obtain a resin solution. Next, a methanol solution of sodium hydroxide was added to carry out a saponification reaction, washed well, and then dried with a hot air dryer. Finally, a polyvinyl alcohol resin No. 5 having a polymerization degree of 500 and a saponification degree of 90 mol% was used. 7 was obtained.

Production Example 1 of Conductive Paste
Polyvinyl alcohol resin No. 1 obtained in Production Example 1. 1 30 parts (solid content 30 parts), acetylene black 1200 parts, KF polymer W # 7300 (trade name, polyvinylidene fluoride, manufactured by Kureha) 220 parts, N-methyl-2-pyrrolidone 8500 parts, and TINUVIN 144 100 parts The mixture was mixed and dispersed in a ball mill for 5 hours to obtain a conductive paste X-1. In addition, each process of mixing, pigment dispersion | distribution, and discharge | emission was performed in the atmosphere with a dew point of 4.5 degreeC.

Examples 2-31 and Comparative Examples 1-3
Conductive pastes X-2 to X-34 were produced in the same manner as in Example 1 except that the conductive paste composition was changed to Table 2 below. In addition, the resin compounding quantity in a table | surface is a value of solid content.
The moisture content in the table was measured using a Karl Fischer moisture meter (product name: MKC-610, manufactured by Kyoto Electronics Industry Co., Ltd.).

(Note 1) TINUVIN 144: trade name, manufactured by Ciba Geigy, hindered amine compound, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl)- 4-Hydroxyphenyl] methyl] butyl malonate.
(Note 2) HALS292: trade name, manufactured by Ciba Geigy, hindered amine compound, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl (1,2,2,6,6-pentamethyl-) 4-piperidyl) mixture with sebacate.
(Note 3) TINUVIN123: trade name, manufactured by Ciba Geigy, hindered amine compound, decanedioic acid bis (2,2,6,6-tetramethyl-1- (octyloxy) -4-piperidinyl) ester, 1,1-dimethyl Reaction product of ethyl hydroperoxide and octane.

Compound paste production example 32
8 parts of the conductive paste X-1 obtained in Example 1, active material particles (lithium nickel manganese oxide particles having a spinel structure represented by the composition formula LiNi _0.5 Mn _1.5 O _4. Average particle diameter 6 μm, 90 parts of a BET specific surface area of 0.7 m ² / g) and 57 parts of N-methyl-2-pyrrolidone were mixed to produce a composite paste Y-1.

Examples 33-62, Comparative Examples 4-6
Compound pastes Y-2 to Y-34 were produced in the same manner as in Example 32 except that the conductive paste was changed to the type shown in Table 3 below.

  Table 3 below shows the lithium hydroxide content (mass% based on the mass of vinylidene fluoride) in the composite paste and the results of evaluation tests described later (viscosity of the conductive paste, storage stability of the composite paste) , Battery performance). If at least one of the three evaluation tests yields an unacceptable evaluation result, the conductive paste and the composite paste are unacceptable.

Evaluation test <viscosity>
Using the cone and plate viscometer “Mars2” (trade name, manufactured by HAAKE), the viscosity of the conductive paste obtained in Examples and Comparative Examples was measured at a shear rate of 1.0 sec ⁻¹ and evaluated according to the following criteria. . As evaluation, S, A, B, and C are acceptable, and D is unacceptable.
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.

<Storage stability (viscosity increase rate)>
The composite pastes obtained in Examples and Comparative Examples were stored at a temperature of 25 ° C. for 2 days, and the initial viscosity and the viscosity after storage were compared. The viscosity was measured at a shear rate of 1.0 sec ⁻¹ using a cone and plate viscometer “Mars2” (trade name, manufactured by HAAKE), and the rate of increase in viscosity was evaluated by the following formula. As evaluation, S, A, B, and C are acceptable, and D is unacceptable.
Viscosity increase rate (%) = viscosity after storage / initial viscosity × 100-100
S: The viscosity increase rate (%) after storage is less than 10%.
A: The rate of increase in viscosity (%) after storage is 10% or more and less than 50%.
B: The rate of increase in viscosity (%) after storage is 50% or more and less than 100%.
C: The viscosity increase rate (%) after storage is 100% or more and less than 200%.
D: The viscosity increase rate (%) after storage is 200% or more.

<Battery performance (IV resistance increase rate)>
Battery performance (IV resistance increase rate) was evaluated using the composite paste obtained in Examples and Comparative Examples. The evaluation method was performed according to the following procedure.
(1) A conductive paste and a composite paste to be a blank are manufactured by the method shown in [Manufacture of a conductive paste to be a blank and a composite paste] below, and [Preparation of a positive electrode], [Preparation of a negative electrode] and [ A lithium ion secondary battery in which a positive electrode and a negative electrode were installed was constructed by the method shown in [Construction of Lithium Ion Secondary Battery]. Next, using the obtained lithium ion secondary battery, IV resistance was measured according to [Method of measuring IV resistance] described later.
(2) Lithium ions in which a positive electrode and a negative electrode were installed in the same manner as in (1) above, except that the composite pastes Y-1 to Y34 obtained in Examples and Comparative Examples were used instead of the blank composite paste A secondary battery was constructed and the IV resistance was measured. Subsequently, the IV resistance increase rate (%) relative to the blank was calculated and evaluated.
In addition, since there are three kinds of conductive carbon (acetylene black alone, acetylene black and graphite combined use, graphite alone), each was compared with a blank of the same kind of pigment. (Evaluation of the composite paste Y-26 is a blank of 600 parts of acetylene black and 600 parts of graphite, evaluation of the composite material paste Y-27 is a blank of 1200 parts of graphite, and other composite paste is a blank of 1200 parts of acetylene black)
The battery performance (IV resistance increase rate) was evaluated according to the following criteria. S, A, B, and C are acceptable and D is unacceptable.
S: IV resistance increase rate is less than + 3% compared to blank.
A: The IV resistance increase rate is + 3% or more and less than + 4.5% as compared with the blank.
B: IV resistance increase rate is + 4.5% or more and less than + 6% compared to the blank.
C: IV resistance increase rate is + 6% or more and less than + 8% as compared with the blank.
D: IV resistance increase rate is + 8% or more compared to blank.

[Manufacture of conductive paste and composite paste used as blank]
1200 parts of acetylene black, 220 parts of KF polymer W # 7300 (trade name, polyvinylidene fluoride, manufactured by Kureha) and 8500 parts of N-methyl-2-pyrrolidone were mixed and dispersed in a ball mill for 5 hours. A conductive paste without the addition of a polymerization inhibitor was obtained. (Each step was performed in an atmosphere with a dew point of 4.5 ° C.)
8 parts of the conductive paste, active material particles (lithium nickel manganese oxide particles having a spinel structure represented by the composition formula LiNi _0.5 Mn _1.5 O _4. Average particle diameter 6 μm, BET specific surface area 0.7 m ² / g ) 90 parts and 57 parts of N-methyl-2-pyrrolidone were mixed to produce a mixture paste containing no dispersant and no polymerization inhibitor, and this was used as a blank. Further, instead of 1200 parts of acetylene black, a blank of 600 parts of acetylene black and 600 parts of graphite and 1200 parts of graphite was also produced. (Manufacturing three types of blanks: acetylene black alone, acetylene black and graphite combined, and graphite alone)
[Preparation of positive electrode]
The composite paste is formed into a belt shape by a roller coating method so that the basis weight per side is 10 mg / cm ² (solid content basis) on both sides of a long aluminum foil (positive electrode current collector) having an average thickness of about 15 μm. The positive electrode active material layer was formed by applying and drying (drying temperature 80 ° C., 1 minute). The positive electrode active material layer supported on the positive electrode current collector was rolled with a roll press to adjust the properties.

[Preparation of negative electrode]
Natural graphite powder (C, average particle size: 5 μm, specific surface area: 3 m ² / g) as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener The negative electrode active material layer forming slurry is mixed with ion-exchanged water so that the mass ratio of these materials is C: SBR: CMC = 98: 1: 1 and the solid content concentration is about 45 mass%. Prepared. This slurry was applied in a belt-like manner on both sides of a long copper foil (negative electrode current collector) having an average thickness of about 10 μm by a roller coating method so that the basis weight per side is 7 mg / cm ² (solid content basis). Then, the negative electrode active material layer was formed by drying (drying temperature 120 ° C., 1 minute). This was rolled by a roll press to adjust the properties.

[Construction of lithium ion secondary battery]
The positive electrode sheet and the negative electrode sheet produced above were used as separator sheets (here, a three-layer structure in which polypropylene (PP) was laminated on both sides of polyethylene (PE) and having a thickness of 20 μm). The wound electrode body was produced by placing the electrodes facing each other and winding them in an elliptical shape. The produced electrode body is placed in a cylindrical battery case, and a non-aqueous electrolyte (here, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) is EC: DMC: EMC). = LiPF ₆ as a supporting salt was dissolved at a concentration of 1.0 mol / L in a mixed solvent containing a volume ratio of 3: 4: 3. And after welding a positive electrode terminal and a negative electrode terminal to the positive electrode collector and negative electrode collector which were exposed in the edge part of an electrode body, the battery case was sealed and the 18650 type lithium ion secondary battery was constructed.

[Method for measuring IV resistance]
The IV resistance of the cell for evaluation in an SOC of 60% state (SOC) was measured under an environment of −30 ° C. Here, the IV resistance is a constant current discharge at a predetermined current value (I) for 10 seconds, and the voltage (V) after the discharge is measured. Then, based on the predetermined current value (I) and the voltage (V) after the discharge, I plotted on the X axis and V on the Y axis, and based on the plot obtained by each discharge, An approximate straight line is drawn and the slope is taken as IV resistance. Here, the IV resistance (mΩ) was calculated based on the voltage (V) after each discharge obtained by performing constant current discharge at current values of 0.3C, 1C, and 3C.

Claims (13)

A conductive paste for a lithium ion battery positive electrode, comprising a dispersion resin (A), polyvinylidene fluoride (B), conductive carbon (C), a solvent (D), and a hindered amine compound (E). The conductive paste for a lithium ion battery positive electrode according to claim 1, wherein the dispersion resin (A) contains a resin (A1) having a polycyclic aromatic hydrocarbon group. Dispersion resin (A) contains polyvinyl alcohol resin (A2), The electrically conductive paste for lithium ion battery positive electrodes of Claim 1 or 2 characterized by the above-mentioned. Conductive carbon (C) contains acetylene black, The electrically conductive paste for lithium ion battery positive electrodes of any one of Claims 1-3 characterized by the above-mentioned. Conductive carbon (C) contains graphite, The electrically conductive paste for lithium ion battery positive electrodes of any one of Claims 1-4 characterized by the above-mentioned. The conductive paste for a lithium ion battery positive electrode according to any one of claims 1 to 5, wherein the solvent (D) contains N-methyl-2-pyrrolidone. Furthermore, an acidic compound is contained, The electrically conductive paste for lithium ion battery positive electrodes of any one of Claims 1-6 characterized by the above-mentioned. The conductive paste for a lithium ion battery positive electrode according to any one of claims 1 to 7, wherein the water content in the conductive paste is less than 1.0% by mass. The method for producing a conductive paste for a lithium ion battery positive electrode according to any one of claims 1 to 8, wherein mixing and / or pigment dispersion is performed in an atmosphere having a dew point of 10 ° C or lower. The mixture paste for lithium ion battery positive electrodes which mix | blends an electrode active material with the electrically conductive paste of any one of Claims 1-9. 11. The lithium ion battery positive electrode composite material according to claim 10, wherein the lithium hydroxide content in the composite paste is less than 1.5 mass% based on the mass of the polyvinylidene fluoride (B). paste. The electrode for lithium ion battery positive electrodes obtained using the mixed paste for lithium ion battery positive electrodes of Claim 10 or 11. The lithium ion battery which has an electrode for lithium ion battery positive electrodes of Claim 12.