JP2014105222A - Viscosity-reducing agent, slurry for exhaust emission control catalyst and method of producing the same, and internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity-reducing agent with which an exhaust emission control catalyst can be prepared by applying the viscosity-reducing agent onto a base material for the catalyst with a small number of times and uniformly and involving little clog, and to provide a slurry for the exhaust emission control and a method of producing the same.SOLUTION: There is provided the viscosity-reducing agent for reducing viscosity of a slurry for an exhaust emission control catalyst including heat resistant inorganic oxide carrying noble metals, a water soluble metal compound and a dispersant. The viscosity-reducing agent contains a copolymer (X) composed of a (meth)acrylic acid (A) unit and a (meth)acrylic acid alkoxy polyoxyalkylene (B) unit, and has the content of the (meth)acrylic acid (A) unit of 50 to 70 mol% and the content of the (meth)acrylic acid alkoxy polyoxyalkylene (B) unit of 50 to 30 mol% based on the molar numbers of the (meth)acrylic acid (A) unit and the (meth)acrylic acid alkoxy polyoxyalkylene (B) unit.

Description

  The present invention relates to a viscosity reducing agent, a slurry for exhaust gas purification catalyst, a method for producing an exhaust gas purification catalyst, and an internal combustion engine.

  An exhaust gas purification catalyst using cerium nitrate, aluminum nitrate or the like as a water-soluble co-catalyst is known (Patent Documents 1, 2, etc.).

JP 58-170540 A Japanese Patent Laid-Open No. 59-066345

If a water-soluble cocatalyst is used, the viscosity of the slurry containing the water-soluble cocatalyst tends to increase, and clogging or non-uniformity occurs when this slurry is applied to the catalyst substrate. There is. And in order to eliminate this problem, the solid content concentration of the slurry is lowered and applied to the catalyst base material. However, it is necessary to increase the number of times of application by the amount of the low solid content concentration, and the productivity is lowered. There is a problem that the production cost increases.
An object of the present invention is to solve the above-mentioned problem, that is, a viscosity reducing agent that can be applied to a catalyst substrate uniformly and with a small number of times and with less clogging to prepare an exhaust gas purification catalyst, An object is to provide a slurry for an exhaust gas purification catalyst and a method for producing the same.

The thinning agent of the present invention is characterized in that it is a thinning agent for reducing the viscosity of a slurry for exhaust gas purification catalyst containing a heat-resistant inorganic oxide carrying a noble metal, a water-soluble metal compound and a dispersion medium,
Containing a copolymer (X) composed of (meth) acrylic acid (A) units and (meth) acrylic acid alkoxypolyoxyalkylene ester (B) units;
Based on the number of moles of the (meth) acrylic acid (A) unit and the (meth) acrylic acid alkoxypolyoxyalkylene ester (B) unit, the content of the (meth) acrylic acid (A) unit is 50 to 70 mol%, The gist is that the content of the (meth) acrylic acid alkoxypolyoxyalkylene ester (B) unit is 50 to 30 mol%.

  The feature of the slurry for exhaust gas purification catalyst of the present invention is that it comprises the above-mentioned viscosity reducing agent, a heat-resistant inorganic oxide carrying a noble metal, a water-soluble metal compound and a dispersion medium.

The manufacturing method of the exhaust gas purification catalyst of the present invention is characterized by a slurrying step (1) in which the above-mentioned viscosity reducing agent, a heat-resistant inorganic oxide supporting a noble metal, a water-soluble metal compound and a dispersion medium are uniformly mixed and dispersed. ),
The gist includes a coating step (2) for applying a slurry to a substrate to obtain a coated substrate, and a drying and firing step (3) for drying and firing the coated substrate to obtain an exhaust gas purification catalyst. To do.

  The feature of the internal combustion engine of the present invention is that the exhaust gas purifying catalyst manufactured by the above manufacturing method is mounted.

  The viscosity reducing agent of the present invention can reduce the viscosity of a slurry for exhaust gas purification catalyst containing a heat-resistant inorganic oxide carrying a noble metal, a water-soluble metal compound and a dispersion medium. Therefore, by using the exhaust gas slurry using the thinning agent of the present invention, it is possible to prepare an exhaust gas purification catalyst by applying it to the catalyst base material with a small number of times and with less clogging.

  Since the slurry for exhaust gas purification catalyst of the present invention uses the above-described thinning agent, the viscosity can be lowered, and it can be uniformly applied to the exhaust gas purification catalyst base material with a small number of times and with less clogging. can do. Therefore, when the slurry for exhaust gas purification catalyst of the present invention is used, an exhaust gas purification catalyst can be prepared with high productivity (low cost).

  Since the method for producing an exhaust gas purifying catalyst of the present invention uses the above-described thinning agent, it can be uniformly applied to the exhaust gas purifying catalyst substrate with a small number of times and with less clogging. Therefore, according to the method for producing an exhaust gas purification catalyst of the present invention, an exhaust gas purification catalyst can be prepared with high productivity (low cost).

  Since the internal combustion engine of the present invention is equipped with the exhaust gas purification catalyst manufactured by the above manufacturing method, it can be made cheaper.

It is the perspective view which showed typically the honeycomb type base material used in the Example.

<Thickening agent>
The (meth) acrylic acid (A) unit includes an acrylic acid unit and a methacrylic acid unit.

  The content (mol%) of the (meth) acrylic acid (A) unit is 50 based on the number of moles of the (meth) acrylic acid (A) unit and the (meth) acrylic acid alkoxypolyoxyalkylene ester (B) unit. -70 are preferable, More preferably, it is 52-68, Most preferably, it is 54-66. Within this range, the viscosity reducing effect is further improved.

  The (meth) acrylic acid alkoxy polyoxyalkylene ester (B) unit includes an acrylic acid alkoxy polyoxyalkylene ester unit and a methacrylic acid alkoxy polyoxyalkylene ester unit.

  Examples of oxyalkylene include oxyalkylene having 2 to 4 carbon atoms (oxyethylene, oxypropylene and oxybutylene). Of these, oxyethylene is preferred.

  The polyoxyalkylene may be composed of one kind of oxyalkylene or may be composed of two or more kinds of oxyalkylene. When composed of two or more oxyalkylenes, the bonding mode may be block, random, or a mixture thereof. Among these, it is preferable that it is comprised from oxyethylene or it is comprised from 2 or more types of oxyalkylene containing oxyethylene, More preferably, it is comprised from oxyethylene. That is, the (meth) acrylic acid alkoxypolyoxyalkylene ester (B) unit is preferably a (meth) acrylic acid alkoxypolyoxyethylene ester (B1) unit.

  The degree of polymerization of the polyoxyalkylene is preferably from 1 to 100, more preferably from 4 to 60, and particularly preferably from 10 to 40, from the viewpoint of a viscosity reducing effect.

  The alkoxy group in the alkoxy polyoxyalkylene includes a hydrocarbon group having 1 to 30 carbon atoms, and a linear alkyloxy group, a branched alkyloxy group, and the like can be used.

  Linear alkyl alkoxy groups include methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy, pentadecyloxy , Hexadecyloxy, heptadecyloxy, octadecyloxy, nonadecyloxy, icosyloxy, henicosyloxy, docosyloxy, tricosyloxy, tetracosyloxy, heptacosyloxy, hexacosyloxy, heptacosyloxy, octacosyloxy, nonacosyloxy And triaconyloxy and the like.

  Examples of branched alkylalkoxy groups include isopropyloxy, isobutyloxy, t-butyloxy, isopentyloxy, neopentyloxy, isohexyloxy, 2-ethylhexyloxy, isotridecyloxy, isooctadecyloxy, and isotriaconcyloxy Is mentioned.

  Among these alkoxy groups, a linear alkyloxy group is preferable from the viewpoint of a viscosity reducing effect, etc., more preferably a linear alkyloxy group having 1 to 18 carbon atoms, and particularly preferably methoxy, ethoxy and octadecyloxy.

  The content (mol%) of the (meth) acrylic acid alkoxypolyoxyalkylene ester (B) unit is the number of moles of the (meth) acrylic acid (A) unit and the (meth) acrylic acid alkoxypolyoxyalkylene ester (B) unit. Is preferably 30 to 50, more preferably 32 to 48, and particularly preferably 34 to 46. Within this range, the viscosity reducing effect is further improved.

  The copolymer (X) is composed of other ethylenically unsaturated monomers (C) in addition to (meth) acrylic acid (A) and (meth) acrylic acid alkoxypolyoxyalkylene ester (B). Can be included as

  The other ethylenically unsaturated monomer (C) is not particularly limited as long as it can be copolymerized with (meth) acrylic acid (A) and (meth) acrylic acid alkoxypolyoxyalkylene ester (B). Examples thereof include carboxylic acid, ethylenically unsaturated carboxylate, olefin, ethylenically unsaturated nitrile and ethylenically unsaturated amide.

  Examples of the ethylenically unsaturated carboxylic acid include ethylenically unsaturated monocarboxylic acid and ethylenically unsaturated dicarboxylic acid.

  Examples of ethylenically unsaturated monocarboxylic acids include aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, and aromatic monocarboxylic acids.

  As the aliphatic monocarboxylic acid, an aliphatic carboxylic acid monomer other than (meth) acrylic acid can be used, and crotonic acid, 3-butenoic acid, 2-pentenoic acid, 3-pentenoic acid, 4-pentenoic acid, 3- Methyl-2-butenoic acid, 3-methyl-3-butenoic acid, 2-methyl-3-butenoic acid, 2-methyl-2-butenoic acid, 2-ethyl-2-propenoic acid, 2-hexenoic acid, 4- Methyl-2-pentenoic acid, 2-methyl-2-pentenoic acid, 2-heptenoic acid, 4,4-dimethyl-2-pentenoic acid, 2-octenoic acid, 3-methyl-2-heptenoic acid, 2-nonenoic acid , 3-methyl-2-octenoic acid, 2-decenoic acid and 2-hydroxypropenoic acid.

  Examples of the alicyclic monocarboxylic acid include 1-cyclopentenecarboxylic acid, 3-cyclopentenecarboxylic acid, 4-cyclopentenecarboxylic acid, 1-cyclohexenecarboxylic acid, 3-cyclohexenecarboxylic acid, 4-cyclohexenecarboxylic acid, and 1-cycloheptene. Carboxylic acid, 3-cycloheptenecarboxylic acid, 4-cycloheptenecarboxylic acid, 5-cycloheptenecarboxylic acid, 1-cyclooctenecarboxylic acid, 3-cyclooctenecarboxylic acid, 4-cyclooctenecarboxylic acid, 5- Cyclooctenecarboxylic acid, 1-cyclononenecarboxylic acid, 3-cyclononenecarboxylic acid, 4-cyclononenecarboxylic acid, 5-cyclononenecarboxylic acid, 1-cyclodecenecarboxylic acid, 3-cyclodecenecarboxylic acid, 4-cyclo Dekencarboxylic acid and 5-cyclodekaenka Bonn acid and the like.

  As aromatic monocarboxylic acids, o-styrene carboxylic acid, p-styrene carboxylic acid, cinnamic acid, atropic acid, 5-vinyl-1-naphthalene carboxylic acid, 4-vinyl-1-naphthalene carboxylic acid and 4-vinyl- Examples include 1-anthraquinone carboxylic acid.

  Examples of unsaturated dicarboxylic acids include aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, aromatic dicarboxylic acids, and intramolecular acid anhydrides thereof.

  Examples of aliphatic dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, butenedioic acid, 2-pentenedioic acid, 3-pentenoic acid, 4-pentenoic acid, 2-methyl-2-butene Acid, 2-ethyl-2-propenoic acid, 2-hexenedioic acid, 2-heptenedioic acid, 2-octenoic acid, 3-methyl-2-heptenedioic acid, 2-nonenedioic acid, 2-decenedioic acid and Examples include 2-hydroxyptenelodioic acid.

  Examples of the alicyclic dicarboxylic acid include 1,2-cyclopentene dicarboxylic acid, 1,3-cyclopentene dicarboxylic acid, 1,4-cyclopentene dicarboxylic acid, 1,2-cyclohexene dicarboxylic acid, 1,3-cyclohexene dicarboxylic acid, 4-cyclohexene dicarboxylic acid, 1,2-cycloheptene dicarboxylic acid, 1,3-cycloheptene dicarboxylic acid, 1,4-cycloheptene dicarboxylic acid, 1,5-cycloheptene dicarboxylic acid, 1,2- Cyclooctene dicarboxylic acid, 1,3-cyclooctene dicarboxylic acid, 1,4-cyclooctene dicarboxylic acid, 1,5-cyclooctene dicarboxylic acid, 1,2-cyclononene dicarboxylic acid, 1,3-cyclononene dicarboxylic acid, 1,4-cyclononene dicarboxylic acid, 1,5-cyclononene dicarboxylic acid, 1,2-cyclodecenedicarboxylic acid, 1,3-cyclodecenedicarboxylic acid, 1,4-cyclodecenedicarboxylic acid, 1,5-cyclodecenedicarboxylic acid and the like can be mentioned.

  Examples of the aromatic dicarboxylic acid include o, p-styrene dicarboxylic acid, o, p-styrene dicarboxylic acid, 4-vinyl-1,2-naphthalenedicarboxylic acid and 4-vinyl-1,3-anthraquinone dicarboxylic acid. .

  Examples of intramolecular acid anhydrides of unsaturated dicarboxylic acids include maleic anhydride, itaconic anhydride, and citraconic anhydride.

Examples of the ethylenically unsaturated carboxylate include alkali metal salts, alkaline earth metal salts, amine salts, ammonium salts and / or quaternary organic ammonium salts of ethylenically unsaturated carboxylic acids.
The ethylenically unsaturated carboxylic acid includes the ethylenically unsaturated monocarboxylic acid and the ethylenically unsaturated dicarboxylic acid described for the ethylenically unsaturated carboxylic acid.

Examples of the alkali metal salt include lithium, potassium and sodium salts.
Examples of the alkaline earth metal salt include salts such as calcium or magnesium.
As an amine salt, salts, such as a C2-C6 aliphatic amine, a C3-C6 alicyclic amine, or a C6-C8 aromatic amine, are mentioned.

  Examples of the aliphatic amine include ethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, 2-amino-2-methylpropanol, dimethylethanolamine, diethylethanolamine, and ethylenediamine.

  Examples of alicyclic amines include cyclopropylamine, cyclobutylamine, cyclopentylamine, and cyclohexylamine.

  Examples of the aromatic amine include aniline, pyridine, piperidine, benzylamine, and phenylenediamine.

  As the quaternary organic ammonium salt, an organic ammonium salt having 4 to 8 carbon atoms can be used, such as tetramethylammonium salt, tetraethylammonium salt, trimethylethylammonium salt, N-methylpyridinium salt and N-methylimidazolium salt. Is mentioned.

  Examples of the olefin include α-olefins having 2 to 20 carbon atoms (ethylene, propylene, butylene, hexylene, octylene, undecylene, tetradecylene, and nonadecylene), diisobutylene, butadiene, piperylene, chloroprene, pinene, limonene, indene, and cyclopentadiene. , Bicyclopentadiene, ethylidene norbornene and the like.

  Examples of the ethylenically unsaturated nitrile include (meth) acrylonitrile, cyanopropene and cyanopentene.

  Examples of the ethylenically unsaturated amide include (meth) acrylamide, N-methyl (meth) acrylamide, N-2-hydroxymethyl (meth) acrylamide, N- (2-aminoethyl) (meth) acrylamide and N- (2- And dimethylaminoethyl) (meth) acrylamide.

  When other ethylenically unsaturated monomer (C) units are included, the content (mol%) of the other ethylenically unsaturated monomer (C) units is (meth) acrylic acid (A) units and ( Based on the number of moles of the (meth) acrylic acid alkoxypolyoxyalkylene ester (B) unit, 0.1-20 are preferable, more preferably 0.5-15, and particularly preferably 1-10, but other ethylene. Most preferably, it does not contain a unit of the unsaturated monomer (C).

  The weight average molecular weight (Mw) of the copolymer (X) is preferably from 5,000 to 100,000, more preferably from 10,000 to 80,000, particularly preferably from 15,000, from the viewpoint of the viscosity reducing effect. 60,000.

  The weight average molecular weight (Mw) is measured by gel permeation chromatography (GPC) using (poly) ethylene glycol of known molecular weight as a standard substance (for example, column temperature 40 ° C., eluent methanol: ion exchange) Water: sodium acetate = 800: 1200: 15 (weight ratio), flow rate 0.8 ml / min, sample concentration: 0.4 wt% eluent solution.).

  The copolymer (X) can be obtained using a usual vinyl monomer polymerization method, and suspension polymerization, bulk polymerization, solution polymerization, etc. can be applied as the polymerization method. From the viewpoint of productivity, solution polymerization is possible. Is preferred.

  A polymerization catalyst can be used for the polymerization. As the polymerization catalyst, an ordinary polymerization catalyst or the like is used, and azo compounds, persulfates, inorganic peroxides, redox catalysts, and organic peroxides are included. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 4,4′-azobis-4-cyanovaleric acid, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile, 2, 2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-albonitrile), 2,2'-azobis (2,4,4-trimethylpentane), dimethyl 2,2 ' -Azobis (2-methylpropionate), 2,2'-azobis [2- (hydroxymethyl) propionitrile], 1,1'-azobis (1-acetoxy-1-phenylethane) and the like. Examples of the salt include ammonium persulfate, potassium persulfate, sodium persulfate, etc. Examples of the inorganic peroxide include perborate and hydrogen peroxide. Examples of the redox catalyst include ascorbic acid-hydrogen peroxide, etc. Examples of the organic peroxide include benzoyl peroxide, etc. These polymerization catalysts may be used alone or in combination. Of these, persulfates and azo compounds are preferred, more preferred are persulfates and 2,2′-azobisisobutyronitrile, and particularly preferred are ammonium persulfate, potassium persulfate, and sodium persulfate.

  When the polymerization catalyst is used, the amount (% by weight) of the polymerization catalyst is preferably 3 to 100, more preferably 8 to 80, and particularly preferably 10 to 60, based on the weight of the constituent monomer.

  Moreover, you may use the chain transfer agent for radical polymerization as needed. Chain transfer agents include thiocarboxylic acids (n-lauryl mercaptan, mercaptoethanol, mercaptopropanol, etc.), thiolic acids (thioglycolic acid, thiomalic acid, etc.), secondary alcohols (isopropanol, etc.), amines (dibutylamine, etc.) And hypophosphites (sodium hypophosphite, etc.).

  When the chain transfer agent is used, the amount (% by weight) of the chain transfer agent is preferably 0.01 to 10, more preferably 0.05 to 5, particularly preferably based on the weight of the constituent monomer. 0.1-1.

In the case of solution polymerization and suspension polymerization, the solvent includes water (tap water, ion exchange water, industrial water, etc.), alcohol solvent (methanol, ethanol, isopropyl alcohol, etc.) and / or aromatic solvent (toluene, xylene, etc.). Etc. can be used. Among these, water, a mixed solvent of water and an alcohol solvent are preferable, a mixed solvent of water and alcohol is more preferable, and a mixed solvent of ion-exchanged water and isopropyl alcohol is particularly preferable.
When a solvent is used, the amount (% by weight) used is preferably 50 to 900, more preferably 60 to 800, and particularly preferably 100 to 600, based on the total weight of the constituent monomers.

  The polymerization reaction temperature is preferably about 40 to 130 ° C., and the polymerization reaction time is preferably about 1 to 15 hours.

  In addition, you may superpose | polymerize, dripping the whole quantity or one part of a structural monomer. Moreover, you may superpose | polymerize, dripping the whole quantity or one part of a polymerization catalyst. Moreover, you may superpose | polymerize, dripping the whole quantity or one part of a solvent with a structural monomer or a polymerization catalyst. On the other hand, the entire amount of the solvent may be charged in a polymerization tank and polymerization may be performed while removing the solvent. Among these, from the viewpoint of productivity and the like, the method of dropping the whole amount of the constituent monomer and the polymerization catalyst and the method of dropping a part of the solvent together with the constituent monomer or the polymerization catalyst are preferable, and more preferably the constituent unit. In this method, the entire amount of the monomer and the polymerization catalyst is dropped together with a part of the solvent.

The form of the copolymer (X) is not particularly limited, and may be liquid or solid.
When the copolymer (X) is liquid, it means a state in which the copolymer (X) is dissolved or dispersed in an aqueous solvent. In this case, the copolymer (X) may be obtained by suspension polymerization or solution polymerization without removing all the solvent, or the copolymer (X) obtained by bulk polymerization or the like may be dissolved in an aqueous solvent. Alternatively, it may be obtained by dispersing.
Examples of the aqueous solvent include water, alcohols having 1 to 6 carbon atoms (such as ethyl alcohol, methyl alcohol, ethylene glycol and diethylene glycol), and ketones having 1 to 6 carbon atoms (such as methyl isobutyl ketone and acetone). You may use individually or in mixture.

On the other hand, when the copolymer (X) is solid, it may be a solid made of the copolymer (X), or may be a powder having the liquid copolymer (X) supported on the powder. .
In the case of a solid comprising the copolymer (X), it may be obtained by bulk polymerization, or after the solution or dispersion containing the copolymer (X) is obtained by suspension polymerization or solution polymerization, the solvent is removed. May be obtained.
As a method for removing the solvent from the solution or dispersion containing the copolymer (X), known methods such as a dry pulverization method, a freeze pulverization method, a spray dryer method, and a drum dryer method can be used. Of these, the dry pulverization method and the spray dryer method are preferred.
The size (mm; maximum length) of the solid copolymer (X) is preferably 0.01 to 5, more preferably 0.05 to 3 from the viewpoint of the solubility of the thinning agent of the present invention. Especially preferably, it is 0.08-1.
When the liquid copolymer (X) is supported on a powder, examples of the powder include heat-resistant inorganic oxides, activated carbon, calcium carbonate, zeolite, shirasu balloon, and bentonite.
As a method for supporting the liquid copolymer (X) on these powders, the powder and the liquid copolymer (X) can be obtained by using a known stirring mixer (such as a ribbon mixer and a Henschel mixer). A method of stirring and mixing can be applied.
Among the forms of the copolymer (X), a liquid is preferable, and a state where the copolymer (X) is dissolved in an aqueous solvent is more preferable.

In addition to the copolymer (X), the thinning agent of the present invention may contain other components (such as a surfactant and / or an aqueous solvent).
As the surfactant, nonionic, cationic, anionic or amphoteric surfactants can be used.

  Nonionic surfactants include alkylphenol alkylene oxide (alkylene oxide having 2 to 4 carbon atoms unless otherwise specified) adduct, higher fatty acid alkylene oxide adduct, polyhydric alcohol fatty acid ester, higher alkyl amine alkylene oxide. Examples include adducts, alkylene oxide adducts of higher fatty acid amides, alkylene oxide adducts of acetylene glycol, and polyoxyalkylene-modified silicones (polyether-modified silicones).

  Cationic surfactants include higher alkylamine salts, higher alkylamine alkylene oxide adducts, solomin A type cationic surfactants, sapamin A type cationic surfactants, Arcobel A type cationic surfactants, and imidazoline type cationic surfactants. Agents, higher alkyltrimethylammonium salts, higher alkyldimethylbenzylammonium salts, sapamine-type quaternary ammonium salts and pyridinium salts.

  Examples of the anionic surfactant include fatty acid salts, α-olefin sulfonates, alkylbenzene sulfonic acids and salts thereof, alkyl sulfate esters, alkyl ether sulfates, N-acyl alkyl taurates, and alkyl sulfosuccinates. It is done.

  Examples of amphoteric surfactants include higher alkylaminopropionates and higher alkyldimethylbetaines.

  When the surfactant is contained, the content (% by weight) is preferably 0.1 to 20, more preferably 0.5 to 10, particularly preferably 1 based on the weight of the copolymer (X). ~ 5. Within this range, the viscosity reducing effect is further improved.

Examples of the aqueous solvent include those described above.
When the aqueous solvent is contained, the content (% by weight) is preferably 10 to 1000, more preferably 50 to 900, particularly preferably 100 to 600, based on the weight of the copolymer (X).

  When the thinning agent of the present invention contains other constituents, the thinning agent of the present invention is obtained by uniformly mixing (uniformly dissolving or uniformly dispersing) the copolymer (X) and other constituents. can get.

  The viscosity reducer of the present invention can effectively reduce the viscosity of a slurry for exhaust gas purification catalyst containing a heat-resistant inorganic oxide supporting a noble metal, a water-soluble metal compound and a dispersion medium. Even if a material other than the viscosity reducing agent of the present invention is used, the viscosity of the slurry cannot be effectively reduced. This is considered to be based on the type and content of the constituent monomer of the copolymer (X) contained in the viscosity reducing agent. For example, if one of the monomers constituting the copolymer (X) is changed to another monomer, the effect of the present invention can no longer be obtained.

<Slurry for exhaust gas purification catalyst>
The heat-resistant inorganic oxide is not limited as long as it can support a noble metal without being deteriorated even at a high temperature (900 ° C. or higher), and includes at least one selected from the group consisting of zirconia, alumina, silica, titania, magnesia and ceria. Can be mentioned.

The volume average particle diameter (μm) of the heat-resistant inorganic oxide is preferably 0.1 to 100, more preferably 0.2 to 50, and particularly preferably 0.3 to 10 from the viewpoint of catalyst performance.
In addition, the volume average particle diameter is a laser diffraction particle size analyzer conforming to JIS Z8825-1: 2001 (for example, Microtrac Model No. manufactured by Lees & Northrup). MT3300EX}, a measurement dispersion prepared by adding a measurement sample to water so that the measurement sample concentration is 0.1% by weight, measured at a measurement temperature of 25 ± 5 ° C., and 50% cumulative volume average particle diameter As required.

As the noble metal, nitrogen oxide (NO _x ) can be reduced to nitrogen (N ₂ ), carbon monoxide (CO) can be oxidized to carbon dioxide (CO ₂ ), and hydrocarbon (hydrocarbon) can be converted to carbon dioxide and So-called three-way catalysts can be used without limitation as long as they can be oxidized to water, and examples thereof include platinum, palladium and rhodium.

  The loading amount (% by weight) of the noble metal can be appropriately determined depending on the type of exhaust gas, the exhaust gas treatment amount, and the like.

  As a method for supporting a noble metal on a heat-resistant inorganic oxide, a known method (for example, an impregnation method; a method of impregnating and supporting a catalyst metal solution on an inorganic oxide carrier such as alumina or silica) can be applied as it is. .

  As the water-soluble metal compound, any metal compound that dissolves in water (0 to 100 ° C., preferably 5 to 60 ° C.) can be used without limitation. Organic acid metal salts (preferably having 1 to 6 carbon atoms), metal nitrates , At least one selected from the group consisting of metal oxynitrates, metal hydroxides and metal nitrites.

  The metal atom constituting the water-soluble metal compound includes at least one selected from the group consisting of aluminum, cerium, zirconium, barium, lanthanum and bismuth.

Specific examples of the water-soluble metal compound include the following metal compounds.
(1) Aluminum compound Aluminum nitrate and the like.

(2) Cerium compounds Cerium nitrate, cerium ammonium nitrate, cerium acetate, cerium malate, cerium tartrate, cerium citrate, and the like.

(3) Zirconium compound Zirconium nitrate, zirconium oxynitrate, zirconium oxyacetate, and the like.

(4) Barium compounds Barium nitrate, barium hydroxide, barium nitrite, barium formate, barium acetate, barium propionate, barium hydroxyacetate, barium lactate, barium glycerate, barium malate, barium tartrate, barium citrate and the like.

(5) Lanthanum compounds Lanthanum nitrate and lanthanum acetate.

(6) Bismuth compounds Bismuth nitrate, bismuth oxynitrate, bismuth formate, bismuth acetate, bismuth propionate, bismuth hydroxyacetate, bismuth lactate, bismuth glycerate, bismuth malate, bismuth tartrate, bismuth citrate, and the like.

  Examples of the dispersion medium include water and a mixed solvent of water and a water-soluble organic solvent. Of these, water is preferred.

  Examples of the water-soluble organic solvent include alcohols having 1 to 3 carbon atoms (such as methanol, ethanol, isopropanol, ethylene glycol, and propylene glycol), ketones having 1 to 3 carbon atoms (such as acetone, methyl ethyl ketone, and dimethyl sulfoxide), and those having 4 to 4 carbon atoms. 6 ethers such as diethyl ether, tetrahydrofuran, dioxane, diethylene glycol and triethylene glycol.

  The content of the thinning agent is preferably such that the content (% by weight) of the copolymer (X) is 0.5 to 20 based on the weight of the heat-resistant inorganic oxide carrying the noble metal, The amount is preferably 2 to 18, particularly preferably 5 to 16. Within this range, the viscosity reducing effect is further improved.

  The content of the water-soluble metal compound is preferably such that the content (% by weight) of the metal atom is 0.1 to 70 based on the weight of the heat-resistant inorganic oxide carrying the noble metal, more preferably 0. The amount of 3 to 60, particularly preferably 7 to 54. Within this range, the catalyst performance is further improved.

  The content (% by weight) of the dispersion medium can be appropriately determined depending on the catalyst specifications.

  In the slurry for exhaust gas purification catalyst of the present invention, other additives (antifoaming agent, thickening agent, etc.) in addition to the above-mentioned thinning agent, heat-resistant inorganic oxide supporting noble metal, water-soluble metal compound and dispersion medium ) May be contained.

  The slurry for the exhaust gas purification catalyst of the present invention is not limited in the production method as long as it can uniformly mix and disperse the viscosity reducing agent, the heat-resistant inorganic oxide supporting the noble metal, the water-soluble metal compound, and the dispersion medium. It can be obtained by slurrying. When slurrying, it can be appropriately sealed or cooled so that the solvent does not evaporate.

The viscosity (mPa · s) of the exhaust gas purifying catalyst slurry is preferably about 10 to 10,000, more preferably 100 to 8,000, and particularly preferably 200 to 7,000.
The viscosity is measured according to JIS K7117-1: 1999 {25 ° C.} {for example, Brookfield type rotational viscometer HBDV-III, manufactured by Brookfield, Inc.}.

<Method for producing exhaust gas purification catalyst>
In the slurrying step (1), the above-mentioned viscosity reducing agent, the heat-resistant inorganic oxide supporting the noble metal, the water-soluble metal compound and the dispersion medium are uniformly mixed and dispersed to obtain a slurry. The uniform mixing and dispersion is as described above. It can be carried out with a known mixing and dispersing machine.

In the coating step (2), the base material has heat resistance (up to about 900 to 1000 ° C.) and is not limited as long as it has corrosion resistance (no corrosion against exhaust gas), and ceramics and stainless steel are preferable. Can be used for Examples of the ceramic include cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ). The shape of the substrate can be appropriately determined depending on the application.

  When the exhaust gas purification catalyst is for an internal combustion engine, the base material is preferably a monolith type base material that communicates between the inlet end side and the outlet end side, and more preferably communicates between the inlet end side and the outlet end side. It is a honeycomb type substrate.

As a coating method, there is no limitation as long as the coated substrate can be obtained by applying the slurry to the substrate.
When the base material is a monolith type base material that communicates between the inlet end side and the outlet end side, the coating step (2) is a transfer coating in which the slurry is applied by a method of transferring the slurry from the inlet end side toward the outlet end side. It may be a step (21) or a dip coating step (22) of coating by a method of immersing the substrate in the slurry. Of these, the transfer coating step (21) is preferable, and more preferably, the outlet end side is made more negative than the inlet end side, and the pressure difference between the inlet end side and the outlet end side causes the inlet end side to the outlet end side. This is a transfer coating process in which the slurry is coated by a method of transporting the slurry toward it. As the transfer coating step (21), the method disclosed in JP 2008-302304 A is a reference.
When the slurry is transferred by the pressure difference between the inlet end side and the outlet end side, the outlet end side may be depressurized, the inlet end side may be pressurized, and the outlet end side is depressurized. You may pressurize an end side.
The coating amount can be appropriately determined depending on the type of exhaust gas, the exhaust gas treatment amount, and the like.

  In the firing step (3), the drying conditions are not limited as long as the coated substrate can be dried, and known conditions (for example, 240 to 260 ° C., 0.5 to 2 hours) can be applied. The baking conditions are not limited as long as the coated substrate is dried and then baked to burn off the organic components, and those that can be oxidized can be oxidized. Known conditions (for example, 450 to 900 ° C., 0.5 to 2 hours) ) Is applicable.

The exhaust gas purification catalyst produced by the production method of the present invention can be applied without limitation as long as it is an exhaust gas to be purified, and is suitable for exhaust gas discharged from internal combustion engines, factories, industrial waste treatment plants, and the like. Of these, it is most suitable for exhaust gas discharged from an internal combustion engine.
The internal combustion engine equipped with the exhaust gas purification catalyst produced by the production method of the present invention can be installed in an automobile, a motorcycle, an agricultural machine, a civil engineering construction machine, or the like.

Hereinafter, unless otherwise specified, “part” means “part by weight” and “%” means “% by weight”.
<Example 1>
Into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, 500 parts of ion-exchanged water, 200 parts of isopropyl alcohol and 0.5 part of 2-mercaptoethanol are added, and 50 parts of acrylic acid and methoxypolyoxyacrylate are stirred. 400 parts of ethylene (degree of polymerization of oxyethylene: 23) ester and 100 parts of 40% aqueous sodium persulfate aqueous solution were reacted in a sealed manner while dropping from a separate dropping line at a constant rate over 3 hours. The reaction temperature was maintained at 80-100 ° C. After completion of the dropwise addition, the mixture was kept at 95 to 100 ° C. for 3 hours, and then isopropyl alcohol was removed under reduced pressure while dropping (hydrolyzing) 150 parts of ion-exchanged water, followed by addition of water to adjust the concentration to 30%. Thickener (1) [acrylic acid (66 mol%)-methoxypolyoxyethylene acrylate (degree of polymerization: 23) ester (34 mol%) copolymer (x1)] was obtained. The weight average molecular weight of the copolymer (x1) was 30,000.

  The weight average molecular weight (Mw) is a gel permeation chromatography (GPC) method (column temperature 40 ° C., eluent methanol: ion-exchanged water: sodium acetate = 800: 1200 using (poly) ethylene glycol of known molecular weight as a standard substance. : 15 (weight ratio), flow rate 0.8 ml / min, sample concentration: 0.4 wt% eluent solution) (hereinafter the same).

<Example 2>
Into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, 600 parts of ion-exchanged water and 0.5 part of 2-mercaptoethanol are added, and under stirring, 155 parts of acrylic acid, ethoxypolyoxyethylene acrylate (oxyethylene) Degree of polymerization: 2) 400 parts of ester and 100 parts of 40% aqueous sodium persulfate aqueous solution were reacted in a sealed manner while dropping at a constant rate over 3 hours from separate dropping lines. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the mixture was kept at 95-100 ° C. for 3 hours, and then added with water to adjust the concentration to 30%. The viscosity reducing agent (2) of the present invention [acrylic acid (50 mol%)-ethoxypolyoxyacrylate] Ethylene (degree of polymerization of oxyethylene: 2) ester (50 mol%) copolymer (x2)] was obtained. The weight average molecular weight of the copolymer (x2) was 50,000.

<Example 3>
Into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, 50 parts of ion-exchanged water and 750 parts of isopropyl alcohol are added and, under stirring, 58 parts of acrylic acid, 2-ethylhexyloxypolyoxyethylene acrylate (polymerization of oxyethylene) Degree: 8) Polyoxypropylene (Polymerization degree of oxypropylene: 6) 600 parts of ester and 100 parts of 40% aqueous sodium persulfate aqueous solution were allowed to react in a sealed manner while being dropped from a separate dropping line at a constant rate over 3 hours. It was. The reaction temperature was maintained at 80-100 ° C. After completion of the dropwise addition, the mixture was kept at 95 to 100 ° C. for 3 hours, and then isopropyl alcohol was removed under reduced pressure while dropping (hydrolyzing) 150 parts of ion-exchanged water, followed by addition of water to adjust the concentration to 30%. (3) [acrylic acid (54 mol%)-acrylic acid 2-ethylhexyloxypolyoxyethylene (oxyethylene polymerization degree: 8) polyoxypropylene (oxypropylene polymerization degree: 6) ester (46 mol) %) Copolymer (x3)]. The weight average molecular weight of the copolymer (x3) was 6,000.

<Example 4>
500 parts of ion exchange water, 100 parts of isopropyl alcohol and 2.5 parts of 2-mercaptoethanol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer. Under stirring, 50 parts of methacrylic acid, octadecyloxypolymethacrylate methacrylate 700 parts of oxyethylene (degree of polymerization of oxyethylene: 30) ester and 100 parts of 40% sodium persulfate aqueous solution were each reacted in a sealed state while dropping from a separate dropping line at a constant rate over 3 hours. The reaction temperature was maintained at 80-100 ° C. After completion of the dropwise addition, the mixture was kept at 95 to 100 ° C. for 3 hours, and then isopropyl alcohol was removed under reduced pressure while dropping (hydrolyzing) 150 parts of ion-exchanged water, followed by addition of water to adjust the concentration to 30%. Thickener (4) [methacrylic acid (58 mol%)-octadecyloxypolyoxyethylene methacrylate (degree of polymerization of oxyethylene: 30) ester (42 mol%) copolymer (x4)] was obtained. The weight average molecular weight of the copolymer (x4) was 9,000.

<Example 5>
Into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, 500 parts of ion-exchanged water and 0.1 part of 2-mercaptoethanol are added, and 35 parts of methacrylic acid, methoxypolyoxyethylene methacrylate (of oxyethylene) are stirred. Degree of polymerization: 90) 700 parts of ester and 100 parts of 40% aqueous sodium persulfate aqueous solution were reacted in a sealed manner while dropping at a constant rate over 3 hours from separate dropping lines. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the mixture was kept at 95 to 100 ° C. for 3 hours, and then added with water to adjust the concentration to 30%. The viscosity reducing agent (5) of the present invention [methacrylic acid (70 mol%)-methoxy polyoxymethacrylate] Ethylene (degree of polymerization of oxyethylene: 90) ester (30 mol%) copolymer (x5)] was obtained. The copolymer (x5) had a weight average molecular weight of 100,000.

<Example 6>
Into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, 500 parts of ion-exchanged water, 120 parts of isopropyl alcohol and 0.1 part of 2-mercaptoethanol are added, and under stirring, 48 parts of methacrylic acid, methoxypolyoxymethacrylate methacrylate. 350 parts of ethylene (degree of polymerization of oxyethylene: 23) ester and 100 parts of 40% sodium persulfate aqueous solution were reacted in a sealed state while dropping each at a constant rate over 3 hours from separate dropping lines. The reaction temperature was maintained at 80-100 ° C. After completion of the dropwise addition, the mixture was kept at 95 to 100 ° C. for 3 hours, and then isopropyl alcohol was removed under reduced pressure while dropping (hydrolyzing) 150 parts of ion-exchanged water, followed by addition of water to adjust the concentration to 30%. Thickener (6) [methacrylic acid (64 mol%)-methacrylic acid methoxypolyoxyethylene (degree of polymerization of oxyethylene: 23) ester (36 mol%) copolymer (x6)] was obtained. The weight average molecular weight of the copolymer (x6) was 25,000.

<Comparative Example 1>
500 parts of ion exchange water, 100 parts of isopropyl alcohol and 2 parts of 2-mercaptoethanol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, and 400 parts of acrylic acid and 40% aqueous sodium persulfate solution 100 are added with stirring. The parts were reacted in a sealed manner while dropping at a constant rate over 3 hours from separate drop lines. The reaction temperature was maintained at 80-100 ° C. After completion of dripping, after maintaining at 95-100 ° C. for 3 hours, isopropyl alcohol was removed under reduced pressure while dripping (hydrating) 150 parts of ion-exchanged water, and then water was added to adjust the concentration to 30%. (7) [polyacrylic acid type polymer (x7)] was obtained. The polymer (x7) had a weight average molecular weight of 15,000.

<Comparative example 2>
Into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, 600 parts of ion-exchanged water and 0.2 part of 2-mercaptoethanol are added, and under stirring, 155 parts of acrylic acid, ethoxypolyoxyethylene acrylate (oxyethylene) Degree of polymerization: 2) 600 parts of ester and 100 parts of 40% aqueous sodium persulfate aqueous solution were reacted in a sealed manner while dropping at a constant rate over 3 hours from separate dropping lines. The reaction temperature was maintained at 80-100 ° C. After completion of dripping, after maintaining at 95-100 ° C. for 3 hours, isopropyl alcohol was removed under reduced pressure while dripping (hydrating) 150 parts of ion-exchanged water, and then water was added to adjust the concentration to 30%. Thickener (8) [acrylic acid (40 mol%)-acrylic acid ethoxypolyoxyethylene (degree of polymerization of oxyethylene: 2) ester (60 mol%) copolymer (x8)]. The weight average molecular weight of the copolymer (x8) was 90,000.

<Comparative Example 3>
Into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, 500 parts of ion-exchanged water, 100 parts of isopropyl alcohol and 0.5 part of 2-mercaptoethanol are added and, under stirring, 85 parts of methacrylic acid, octadecyloxypolymethacrylate methacrylate. 400 parts of oxyethylene (degree of polymerization of oxyethylene: 30) ester and 100 parts of 40% sodium persulfate aqueous solution were each reacted in a sealed state while dropping from a separate dropping line at a constant rate over 3 hours. The reaction temperature was maintained at 80-100 ° C. After completion of dripping, after maintaining at 95-100 ° C. for 3 hours, isopropyl alcohol was removed under reduced pressure while dripping (hydrating) 150 parts of ion-exchanged water, and then water was added to adjust the concentration to 30%. Thickener (9) [methacrylic acid (80 mol%)-octadecyloxypolyoxyethylene methacrylate (degree of polymerization of oxyethylene: 30) ester (20 mol%) copolymer (x9)] was obtained. The weight average molecular weight of the copolymer (x9) was 40,000.

<Example 7>
After uniformly mixing 80 parts of the dispersion medium (1) {ion-exchanged water} and 6.9 parts of the thinning agent (1) obtained in Example 1, a heat-resistant inorganic oxide (1 ) {Γ-alumina, specific surface area 100 m ² / g} 13 parts are added, and uniformly dispersed and mixed with a stirrer, water-soluble metal compound (1) {aluminum nitrate nonahydrate, Wako Pure Chemical Industries, Ltd.} 13 The slurry (1) for exhaust gas purifying catalyst of this invention was obtained by adding a part and mixing uniformly with a stirrer.

<Example 8>
Exhaust gas of the present invention in the same manner as in Example 7, except that “water-soluble metal compound (1)” was changed to “water-soluble metal compound (2) {lanthanum nitrate hexahydrate, Nacalai Tesque, Inc.}” A purification slurry (2) was obtained.

<Example 9>
Exhaust gas purification slurry of the present invention (excluding the water-soluble metal compound (1)) was changed to “water-soluble metal compound (3) {barium acetate, Nacalai Tesque Co., Ltd.}” in the same manner as in Example 7. 3) was obtained.

<Example 10>
Except that “6.9 parts of the thickener (1) obtained in Example 1” was changed to “2.2 parts of the thickener (2) obtained in Example 2”, the same as in Example 7. Thus, an exhaust gas purifying slurry (4) of the present invention was obtained.

<Example 11>
“Thickener (1) obtained in Example 1” was changed to “Thickener (3) obtained in Example 3”, and “Water-soluble metal compound (1)” was changed to “Water-soluble metal compound”. Exhaust gas purification slurry (5) of the present invention was obtained in the same manner as in Example 7 except that it was changed to (3) ".

<Example 12>
“6.9 parts of the viscosity reducer (1) obtained in Example 1” was changed to “2.2 parts of the viscosity reducer (4) obtained in Example 4” and “water-soluble metal compound (1) ) 13 parts "was changed to" 1.7 parts of water-soluble metal compound (3) "in the same manner as in Example 7 to obtain an exhaust gas purification slurry (6) of the present invention.

<Example 13>
Exhaust gas purification slurry of the present invention in the same manner as in Example 7, except that "Thickener (1) obtained in Example 1" was changed to "Thickener (5) obtained in Example 5". (7) was obtained.

<Example 14>
Exhaust gas purification slurry of the present invention in the same manner as in Example 7, except that "Thickener (1) obtained in Example 1" was changed to "Thickener (6) obtained in Example 6". (8) was obtained.

<Comparative Example 4>
Exhaust gas for comparison in the same manner as in Example 7, except that “thickening agent (1) obtained in Example 1” was changed to “comparative thinning agent (7) obtained in Comparative Example 1”. A purification slurry (9) was obtained.

<Comparative Example 5>
“Thickener (1) obtained in Example 1” was changed to “Comparative thinning agent (8) obtained in Comparative Example 2”, “Water-soluble metal compound (1)” was changed to “Water-soluble” A comparative exhaust gas purification slurry (10) was obtained in the same manner as in Example 7, except that the metal compound (3) {barium acetate, Nacalai Tesque, Inc.} was changed.

<Comparative Example 6>
Exhaust gas for comparison in the same manner as in Example 7, except that “thickening agent (1) obtained in Example 1” was changed to “comparative thinning agent (9) obtained in Comparative Example 3”. A purification slurry (11) was obtained.

<Comparative Example 7>
A comparative exhaust gas purification slurry (12) was obtained in the same manner as in Example 1, except that the “thickening agent (1) obtained in Example 1” was not used.

<Example 15>
While reducing the pressure on the outlet end side of the honeycomb type base material (connected between the inlet end side and the outlet end side, see FIG. 1) made of cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ) The inlet end side was attached to the slurry for exhaust gas purification catalyst (1) obtained in Example 7, and the slurry was applied to the inside of the honeycomb to obtain the coated substrate (1).
The coated substrate (1) was dried at 250 ° C. for 1 hour and then calcined at 500 ° C. for 1 hour to obtain an exhaust gas purification catalyst (1).

<Examples 16 to 22>
Except that the exhaust gas purification catalyst slurry (1) was changed to any one of the exhaust gas purification catalyst slurries (2) to (8), the coated substrates (2) to (8) were obtained in the same manner as in Example 15. After that, exhaust gas purification catalysts (2) to (8) were obtained.

<Comparative Examples 8-11>
Except that the exhaust gas purifying catalyst slurry (1) was changed to any of the comparative exhaust gas purifying catalyst slurries (9) to (12), the coated substrates (9) to (12 ), Exhaust gas purification catalysts (9) to (12) for comparison were obtained.

<Slurry viscosity>
About the slurry (1)-(12) for exhaust gas purification catalysts, the viscosity was measured using the Brookfield type rotational viscometer HBDV-III (made by Brookfield), and it showed in the following table.

Regarding the exhaust gas purification catalysts (1) to (12), the inlet end side of the cordierite honeycomb-type substrate is visually observed, the number of cells (hexagonal holes) being blocked is counted, and The clogging rate (%) was calculated.
(Clogging rate) = (Number of blocked cells) × 100 / (Total number of cells)

  When the exhaust gas catalyst slurry (Examples 15 to 22) using the thinning agent (Examples 1 to 6) of the present invention is used, the case of using the comparative slurry (Comparative Examples 8 to 11), There was little clogging and it could be applied uniformly to the substrate. Therefore, when the exhaust gas catalyst slurry of the present invention is used, it can be uniformly applied to the substrate with a small number of times and with less clogging, and an exhaust gas purification catalyst can be prepared with high productivity (low cost).

Claims (12)

A viscosity reducing agent for reducing the viscosity of a slurry for an exhaust gas purification catalyst containing a heat-resistant inorganic oxide supporting a noble metal, a water-soluble metal compound and a dispersion medium,
Containing a copolymer (X) composed of (meth) acrylic acid (A) units and (meth) acrylic acid alkoxypolyoxyalkylene ester (B) units;
Based on the number of moles of the (meth) acrylic acid (A) unit and the (meth) acrylic acid alkoxypolyoxyalkylene ester (B) unit, the content of the (meth) acrylic acid (A) unit is 50 to 70 mol%, Content of (meth) acrylic-acid alkoxypolyoxyalkylene ester (B) unit is 50-30 mol%, The viscosity reducing agent characterized by the above-mentioned. A slurry for exhaust gas purification catalyst, comprising the viscosity reducing agent according to claim 1, a heat-resistant inorganic oxide supporting a noble metal, a water-soluble metal compound, and a dispersion medium. The slurry according to claim 2, wherein the heat-resistant inorganic oxide is at least one selected from the group consisting of zirconia, alumina, silica, titania and ceria. The slurry according to claim 2 or 3, wherein the water-soluble metal compound is at least one selected from the group consisting of organic acid metal salts, metal nitrates, metal oxynitrates, metal hydroxides and metal nitrites. The slurry according to any one of claims 2 to 4, wherein the metal atom constituting the water-soluble metal compound is at least one selected from the group consisting of aluminum, cerium, zirconium, barium, lanthanum and bismuth. A slurrying step (1) for obtaining a slurry by uniformly mixing and dispersing the viscosity reducing agent according to claim 1, a heat-resistant inorganic oxide supporting a noble metal, a water-soluble metal compound and a dispersion medium,
It includes a coating step (2) for applying a slurry to a substrate to obtain a coated substrate, and a drying and firing step (3) for drying and firing the coated substrate to obtain an exhaust gas purification catalyst. A method for producing an exhaust gas purifying catalyst. The production method according to claim 6, wherein the heat-resistant inorganic oxide is at least one selected from the group consisting of zirconia, alumina, silica, titania and ceria. The process according to claim 6 or 7, wherein the water-soluble metal compound is at least one selected from the group consisting of organic acid metal salts, metal nitrates, metal oxynitrates, metal hydroxides and metal nitrites. The production method according to any one of claims 6 to 8, wherein the metal atom constituting the water-soluble metal compound is at least one selected from the group consisting of aluminum, cerium, zirconium, barium, lanthanum and bismuth. A monolithic base material in which the base material communicates between the inlet end side and the outlet end side;
The coating step (2) is a transfer coating step (21) in which the slurry is transferred from the inlet end side toward the outlet end side, or a dip coating step (22) in which the substrate is immersed in the slurry. The manufacturing method according to any one of claims 6 to 9. A monolithic base material in which the material communicates between the inlet end side and the outlet end side,
Coating step (2) is performed by a method in which the outlet end side is set to a negative pressure from the inlet end side and the slurry is transferred from the inlet end side to the outlet end side due to a pressure difference between the inlet end side and the outlet end side. The manufacturing method according to any one of claims 6 to 9, which is a transfer coating step. An internal combustion engine equipped with an exhaust gas purifying catalyst manufactured by the manufacturing method according to claim 6.

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