JP2003327482A - Pore forming material for ceramic composition and hydrated pore forming material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pore forming material less liable to break particles in the mixing or molding a ceramic composition and capable of easily holding the plasticity in the molding and the pore forming material containing water. <P>SOLUTION: The pore forming material for the ceramic composition is one kind of a particle selected from the group consisting of a solid resin particle, a hollow resin particle, a thermally expanding micro-capsule and a thermally expanded micro-capsule which have a polar group (preferably a group having hydrophilicity) on the surface. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pore-forming material for a ceramic composition and a water-containing pore-forming material. Specifically, the present invention relates to a pore-forming material for a ceramic composition and a water-containing pore-forming material that are preferably used for manufacturing a porous ceramic filter or the like.

[0002]

2. Description of the Related Art In recent years, as a porous ceramic filter, a partition wall of a honeycomb structure made of cordierite has a porous structure, and such partition wall is passed to allow a fluid such as gas to flow. Various porous honeycomb filters having a filter function have been proposed.
It is used as a filter for collecting particulates of exhaust gas discharged from a diesel car (a diesel particulate filter).

In such a porous ceramic filter, the average pore diameter (hereinafter referred to as pore diameter) of the porous material and the porosity are very important factors that determine the performance of the filter, and especially the diesel particulate matter. In the case of a porous ceramic filter such as a filter, a filter having a large pore size and a large porosity is desired in view of the collection efficiency of fine particles, pressure loss, and collection time.

Conventionally, in order to achieve the above-mentioned demand, a method using a pore-forming material has been studied. For example, a porous ceramic filter can be obtained by firing a ceramic molded body containing various pore-forming materials at a high temperature. However, in order to obtain a ceramic filter, it is also desired to mold a ceramic molded body with dimensional accuracy.

Therefore, for example, Japanese Patent Laid-Open No. 5-330943
The publication describes that by using graphite as a pore-forming material, a porous ceramic product with good dimensional accuracy can be obtained. However, an unfired ceramic composition is difficult to maintain an appropriate plasticity suitable for molding processing, its fluidity decreases with the passage of time and becomes brittle, and a ceramic molded body with good dimensional accuracy is stably manufactured. It was difficult. Further, when the ceramic composition is mixed, the pore-forming material may be destroyed, and the pore-forming material may not function sufficiently. In particular, resin particles and hollow particles with little burning calories are easily broken.

[0006]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, the object of the present invention is to prevent the particles from being broken during mixing or molding of the ceramic composition and to easily maintain the plasticity during molding. To provide a pore material.

[0007]

The pore-forming material for a ceramic composition according to claim 1 is a solid resin particle having a polar group on the surface, hollow resin particle, heat-expandable microcapsule, and heat-expanded material. It is characterized by being at least one kind of particles selected from the group consisting of microcapsules.

The pore-forming material for a ceramic composition according to claim 2 is the pore-forming material for a ceramic composition according to claim 1, wherein the polar group has hydrophilicity.

The pore-forming material for a ceramic composition according to claim 3 is the pore-forming material for a ceramic composition according to claim 1, wherein the polar group has a carboxyl group.

The pore-forming material for a ceramic composition according to claim 4 is the pore-forming material for a ceramic composition according to any one of claims 1 to 3, wherein the thermally expanded microcapsules are heat-expandable microcapsules in water. The microcapsules obtained by expanding by heat treatment in 1.

The water-containing pore-forming material according to claim 5 is from claim 1 to
The powder comprising the pore-forming material for a ceramic composition according to any one of 4 above contains water and is in a state of either powder, slurry or dispersion.

A hydrous pore-forming material according to claim 6 is the hydrous pore-forming material according to claim 5, characterized in that it contains a fluidity-imparting agent and water.

The present invention will be described in detail below. The pore-forming material for a ceramic composition of the present invention is at least one selected from the group consisting of solid resin particles having a polar group on the surface, hollow resin particles, thermally expandable microcapsules, and thermally expanded microcapsules. It is characterized by being seed particles. The presence of the polar group on the surface makes it difficult for the particles to be broken during the mixing and molding of the ceramic composition, and can easily maintain the plasticity during molding.

As a method for obtaining the particles having a polar group on the surface, for example, a monomer having a polar group, a multifunctional monomer and a mixed monomer composed of other monomers, and a non-polymerizable organic solvent are used. Are mixed to prepare a monomer solution, and the monomer solution is suspended in a polar solvent, and then the monomer component is polymerized to obtain resin particles encapsulating the non-polymerizable organic solvent. It can be obtained by removing the organic solvent. The obtained particles are hollow resin particles.

In the above-mentioned polymerization method, when the non-polymerizable organic solvent is a highly volatile solvent, heat-expandable microcapsules can be obtained. When the heat-expandable microcapsules are heated above the softening point of the shell polymer, the contained organic solvent is volatilized and expanded to obtain hollow heat-expanded microcapsules. Further, solid resin particles can be obtained unless a non-polymerizable organic solvent is used in the above-mentioned polymerization method.

Further, the heat-expandable microcapsules can be heat-treated in a polar medium typified by water to obtain heat-expanded microcapsules containing many polar groups on the particle surface. Therefore, the particles are less likely to be broken when the ceramic composition is mixed or molded. Further, the ceramic composition can be imparted with plasticity and can be easily molded. In addition, it also exhibits excellent dispersibility in the ceramic composition.

That is, the thermally expanded microcapsules superior to the thermally expanded microcapsules obtained by the dry heat treatment can be obtained. Probably, it is considered that the polar group is trapped inside the shell when it is thermally expanded by the dry heat treatment, while the polar group is likely to appear on the surface of the shell layer when the heat treatment is performed under the wet condition. Therefore, it is presumed that the microcapsules can be made to contain water by being heated in water and expanded in water, so that the ceramic composition does not have an excess or deficiency of water lost in the ceramic composition during molding, and it becomes difficult to dry. To be done.

It is presumed that the large number of polar groups present on the surface of the shell layer facilitates dispersion of the microcapsules in the ceramic. That is, the thermally expanded microcapsules absorb excess water contained in the ceramic composition, while providing the water contained in the microcapsules to the ceramic composition as the ceramic composition dries. Therefore, the ceramic composition is kept in an appropriate amount of water, and the binder resin such as methyl cellulose can maintain a strong shape-retaining force for a long time. Therefore, the ceramic composition is tough and yet retains sufficient plasticity, and a tough and light fired ceramic product is easily obtained. It was also found that the dispersibility of the microcapsules is further enhanced by adding an aggregating inhibitor such as a silane compound to the thermally expanded microcapsules before the wet heat treatment.

The thermally expanded microcapsules are
It is preferable to make the particle sizes uniform by a method such as classification. The particles having a small particle size may include unexpanded microcapsules that could not be expanded by the heat treatment. By removing these particles, the water retention capacity of the ceramic composition can be efficiently increased. The presence of unexpanded microcapsules can be confirmed from the phenomenon that the true specific gravity of the thermally expanded microcapsules is reduced by removing the particles having a small particle size.

Examples of the polar group of the monomer having the polar group include, for example, a carboxyl group, a glycidyl group, an amino group, an amide group, an ester group, a pyridyl group, a hydroxyl group, an alkoxyl group, a sulfonyl group, a phosphoric acid group and a phosphorus group. Examples thereof include acid ester group, nitro group, cyano group and the like. As a preferable monomer, a mixed monomer including a hydrophilic monomer can be mentioned. The polar group on the surface of the pore-forming material preferably has hydrophilicity, and the monomer having the polar group is preferably a hydrophilic monomer. Since the hydrophilic monomer has a higher affinity for a polar solvent than an organic solvent, it is considered that the hydrophilic monomer is localized at the oil droplet interface in the oil droplets suspended in the monomer solution. Easy to form the surface part of the wall surface.

The hydrophilic monomer preferably has a solubility in water of 1% by weight or more, for example, methyl (meth) acrylate, (meth) acrylonitrile, (meth) acrylamide, (meth) acrylic acid, Glycidyl (meth) acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate
, Dimethylaminomethyl methacrylate, vinyl pyridine, 2-acryloyloxyethyl phthalic acid, itaconic acid, fumaric acid, maleic anhydride, 2-methacryloyloxyethyl succinic acid and the like. Among them, methyl (meta) is easy to adjust the hardness and softness of resin particles.
Acrylate and glycidyl (meth) acrylate are preferable, and maleic anhydride, methacrylic acid, succinic acid and the like are preferable in that they have an acidic functional group on the surface. These may be used alone or in combination of two or more.

In order to sufficiently increase the polarity of the outer wall surface of the resin particles, the proportion of the hydrophilic monomer is 10 to 10 of the monomer component.
It is preferably 99.9% by weight, and more preferably 30 to 99.9% by weight.

As the polyfunctional monomer constituting the monomer component, for example, di (meth) acrylate, tri (meth) acrylate, etc. are preferably used. Examples of the di (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,6- Hexanediol di (meth) acrylate, trimethylolpropane di (meth) acrylate and the like can be mentioned. Examples of the tri (meth) acrylate include trimethylolpropane tri (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and the like. To be

Examples of polyfunctional monomers other than the above are, for example, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, diallyl phthalate, diallyl maleate. Examples thereof include di- or triallyl compounds such as diallyl fumarate, diallyl succinate and triallyl isocyanurate, and divinyl compounds such as divinylbenzene and butadiene.

These polyfunctional monomers can be used alone or in combination of two or more kinds.

In order to increase the compression resistance of the resin particles and prevent the particles from agglomerating during the polymerization, the proportion of the polyfunctional monomer is 0.1 to 30% by weight of the monomer component. It is preferably 0.3 to 5% by weight.

The other monomer constituting the above-mentioned monomer component is added for the purpose of improving mechanical strength, chemical resistance and moldability, and the kind is not particularly limited. For example, ethyl (meth) acrylate is used. , Propyl (meth) acrylate, butyl (meth) acrylate, cumyl methacrylate, cyclohexyl (meth) acrylate, mistyryl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate -Aryl (meth) acrylates such as styrene; aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene; vinyl esters such as vinyl acetate and vinyl propionate; vinyl chloride, chloride Halogen-containing monomers such as vinylidene; ethylene, propylene, butadiene and the like. These may be used alone or in combination of two or more.

If the amount of the above-mentioned other monomer is too large, the hydrophilicity of the monomer component is lowered and the outer wall of the resin particles is prevented from being formed. Therefore, the amount of the monomer component is 89.9% by weight or less. Is preferred, more preferably 69.
It is 9% by weight or less.

It is desirable that the non-polymerizable organic solvent added to the monomer component is localized in the central portion of the oil droplet in the oil droplet suspended in the monomer solution, and has a solubility in water of 0.
It preferably has a hydrophobicity of not more than 2% by weight, and the kind thereof is not particularly limited, but for example, butane, isobutane,
Pentane, hexane, cyclohexane, toluene, xylene and the like are preferably used. Among them, butane, isobutane, pentane, hexane and cyclohexane, which have high volatility, are more preferable.

If the amount of the non-polymerizable organic solvent added is too small, the porosity of the particles will be low, and if it is too large, the porosity will be too high and the strength of the particles will be reduced, so 100 parts by weight of the monomer component is added. On the other hand, it is preferably 1 to 400 parts by weight, more preferably 10 to 200 parts by weight.

In the pore-forming material of the present invention, it is preferable that the powder of the pore-forming material for the ceramic composition contains water and is in a state of either powder, slurry or dispersion.

In addition to water, it is more preferable that a fluidity-imparting agent is contained in order to improve the fluidity of the ceramic composition. Thereby, the particles are less likely to be broken and the plasticity at the time of molding becomes good. Examples of the fluidity-imparting agent defined in the present invention include electrolytes, acids, salts of acidic substances, salts of basic substances and neutralized salts. Of these, substances that can be hydrolyzed by water in the ceramic composition are preferable.

The above-mentioned acid is not particularly limited, and examples thereof include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as phosphoric acid and carboxylic acid. Specific examples thereof include melamine sulfonic acid and hydroxy poly. Examples thereof include carboxylic acid, polyethylene carboxylic acid, polyalkyl sulfonic acid, alkylnaphthalene sulfonic acid, melamine sulfonic acid, polycarboxylic acid and polystyrene sulfonic acid. The above-mentioned salt is not particularly limited as long as it is a compound in which a cation and an anion are generated in the form of neutralizing the charge, and examples thereof include an acid salt and a basic salt, and an addition compound of an organic base and an acid.
Among them, an addition compound of an organic base and an acid is preferable, and examples thereof include naphthalene sulfonate, alkylallyl sulfonate, amylene / maleic anhydride copolymer soda salt (“Quinflo-540” manufactured by Nippon Zeon Co., Ltd., Quinfro
542 ”), a partial amide ammonium salt of an amylene-maleic anhydride copolymer (“ Queenflo-
543 ") are preferably used. These may be used alone or in combination of two or more.

The pore-forming material of the present invention preferably contains a water-retaining agent because it can easily retain plasticity when water is added during molding. Further, when the pore-forming material contains water in advance before being added to the ceramic composition, a water-retaining effect on the pore-forming material powder can be obtained.

Examples of the water retention agent include glycerin, ethylene glycol, diethylene glycol, ethylene glycol monoalkyl ether, diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, and dimethyl. Polyglycol ethers such as sulfoxide, methyl polysiloxane, methyl polycyclosiloxane, methylphenyl polysiloxane,
Copolymers of dimethyl siloxane and methyl (polyoxyethylene) siloxane, copolymers of dimethyl siloxane and methyl (polyoxyethylene) siloxane and methyl (polyoxypropylene) siloxane, methyl polysiloxane and methyl polycyclosiloxane In addition to liquid silicone compounds such as mixed liquids, mixed liquids of trimethylsiloxysilicic acid and methylpolysiloxane, lepurinic acid,
3-methoxybutyl acetate, 3-methoxy-1-butanol, 3-methyl-3-methoxybutanol, 3-
Methyl-1,5-pentanediol, methyl ethyl ketone oxime, methyl isobutyl carbitol, formamide, formalin, 1,5-pentanediol, pentaerythritol, 1,6-hexanediol, propylene glycol monomethyl ether -Tel, Propylene Glyco-
, Dipropylene glycol, γ-butyl lactone,
1,4-butanediol, 1,3-butanediol, 4
-Hydroxy-2-butanone, neopentyl glycol,
Butyl lactate, ethyl lactate, trimethylolpropane, trimethylolethane, triacetin, thioglycol, thioglycerol, diacetone alcohol
, Sebacic acid, 3,3-dimethoxypropionitrile, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, dimethyl sulfoxide, 1,3-dihydroxyacetone, ethyleneglyco- Ludiacetate, cyclohexanone dimethyl acetal, cyclohexanone, cyclohexano-
, Tetrahydrofurfuryl alcohol, glyoxylic acid, octandiol, ethylene cyanohydrin, ethylene glycol monomethyl ether, ethylene glyco-
Rumonoethyl ether, ethylene glycol monobutyl ether, ethylene glycol, diethylene glycol
, Diethylene glycol dimethyl ether, triethylene glycol, ethylene carbonate, isoprene glycol, 2,5-dimethyl-3-hexyne-2,5-
Diol, 2,5-dimethyl-2,5-hexanedio-
And glycerin, N-methyl-2-pyrrolidone, sulfolane, 1,2,6-hexanetriol and the like. These may be used alone or in combination of two or more.

It has also been found that when polyvinyl alcohol is attached to the surface of the pore-forming material of the present invention, the dispersibility in the ceramic composition is improved.

The ceramic composition in which the pore-forming material is mixed with a ceramic raw material such as an inorganic mixture can be usually molded into a ceramic molded body of an appropriate shape by extrusion molding or the like, and dried and then fired. Thus, a porous ceramic filter can be manufactured.

[0038]

EXAMPLES Examples of the present invention will be described below.
It is not limited to the following example. (Examples 1 to 5 and Comparative Examples 1 and 2) The monomer components, the non-polymerizable organic solvent and the polymerization initiator in the compounding amounts shown in Table 1 were mixed and stirred to prepare a monomer solution. It was mixed with the polar medium shown in No. 1, ion-exchanged water was further added, and the mixture was stirred with a homogenizer to prepare a suspension monomer solution.
On the other hand, ion-exchanged water was put into a 20-liter polymerization vessel equipped with a stirrer, a jacket, a reflux condenser and a thermometer. Then, stirring was started to depressurize the inside of the polymerization vessel to deoxygenate the inside of the vessel, then nitrogen was injected to return the pressure to atmospheric pressure, the inside was made into a nitrogen atmosphere, and then the above suspension monomer solution was added. The ingredients were added all at once in the polymerization vessel, and the temperature of the polymerization vessel was raised to 80 ° C. to initiate polymerization. Polymerization was completed in 5 hours, and after aging for 1 hour, the polymerization vessel was cooled to room temperature. After dehydrating the slurry with a dehydrator (centre),
It was dried sufficiently to obtain heat-expandable microcapsules.

Then, in Examples 1 to 4 among the obtained heat-expandable microcapsules, they were expanded in heated dry air to obtain heat-expanded microcapsules. In addition, in Example 4, sieving was performed to substantially remove microcapsules of 20 μm or less. In Example 5, high-pressure steam was blown into the thermally expandable microcapsules dispersed in water to thermally expand the microcapsules to obtain thermally expanded microcapsules. The true specific gravities of the thermally expanded microcapsules of Example 4 and Example 5 were almost the same.

Cordierite 28 as a ceramic raw material
An extrudable ceramic composition was obtained by kneading 4 g of heat-expandable microcapsules (85% by weight of water, 15% by weight of heat-expandable microcapsules) containing 3 g, 14.2 g of methylcellulose and water. It was Next, the obtained ceramic composition was shaped by an extrusion molding method to obtain an unfired ceramic molded body (kneaded clay).

The following evaluation was performed using the obtained ceramic molded body, and the results are shown in Table 1. (Puddle hardness) Using the obtained ceramic formed body (kneaded clay), penetration measurement (AN201 penetration tester manufactured by Nippon Oil Testing Machine Industry Co., Ltd.) was performed. The load was set to 200 g, and how much the needle penetrated into the sample puddle for 5 seconds (0.1 mm) was measured. (Puddle density): As for the characteristic against particle breakage, the lower the value, the better the obtained ceramic molded body (kneaded clay) was cut into a certain volume, and the weight was measured using each sample piece. . After that, the density was calculated by dividing by the volume and evaluated according to the following criteria. ◎: Less than 1.4 ○: 1.4 or more and less than 1.6 △: 1.6 or more and less than 1.7 ×: 1.7 or more (comprehensive judgment): From the better judgment, ◎, ○, △, × It was evaluated on a 4-point scale. ⊚: Kneaded clay density is less than 1.4 and kneaded clay hardness is less than 150. ◯: When the kneaded clay density is 1.4 or more and less than 1.6 and the kneaded clay hardness is less than 200, or the kneaded clay density is less than 1.4 and the kneaded clay hardness is 150 or more and less than 200. Δ: When the kneaded clay density is 1.6 or more and less than 1.7 and the kneaded clay hardness is less than 200, or when the kneaded clay hardness is 200 or more at all kneaded clay densities. X: Other than the above.

[0042]

[Table 1]

The components used in Table 1 are as follows. AN: acrylonitrile MMA: methyl methacrylate MAA: methacrylic acid MAH: maleic anhydride HOMS: 2-methacryloyloxyethyl succinic acid ST: styrene monomer IBOA: isobornyl acrylate

[0044]

EFFECTS OF THE INVENTION The pore-forming material for a ceramic composition and the pore-forming material containing water according to the present invention have the above-mentioned constitution, and the particles are not easily broken during the mixing and molding of the ceramic composition, and the plasticity during molding is improved. Can be easily held.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiyuki Kosaka             1259 Izumi, Mizuguchi-cho, Koga-gun, Shiga Sekisui Chemical Co., Ltd.             Within the corporation (72) Inventor Masahiro Yamanaka             1259 Izumi, Mizuguchi-cho, Koga-gun, Shiga Sekisui Chemical Co., Ltd.             Within the corporation

Claims (6)

[Claims] 1. A solid resin particle having a polar group on its surface,
A pore forming material for a ceramic composition, which is at least one kind of particles selected from the group consisting of hollow resin particles, thermally expandable microcapsules, and thermally expanded microcapsules. 2. The pore-forming material for a ceramic composition according to claim 1, wherein the polar group has hydrophilicity. 3. The pore-forming material for a ceramic composition according to claim 1, wherein the polar group is a carboxyl group. 4. The ceramic composition according to claim 1, wherein the thermally expanded microcapsule is a microcapsule obtained by expanding the thermally expandable microcapsule by heating in water. Hole forming material. 5. A powder comprising the pore-forming material for a ceramic composition according to claim 1, which contains water and is in a state of powder, slurry or dispersion. Water-containing pore forming material. 6. The water-containing pore-forming material according to claim 5, which contains a fluidity-imparting agent and water.