JP3692682B2 - Manufacturing method of ceramic molded body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a ceramic molded body.
[0002]
The cast molding of the present invention relates to a method that can be suitably used for products having a complicated shape or a thick shape, can be net-shaped, and can obtain a molded body in an extremely short time compared to conventional cast molding.
[0003]
[Prior art]
In recent years, ceramic parts having complicated shapes have been required for mechanical structural parts, decorative parts, electronic parts and the like that require heat resistance and durability.
[0004]
In many cases, these parts have complicated shapes in accordance with required high functions. Ceramics are excellent in heat resistance, durability, corrosion resistance, and wear resistance, but have a problem that it is extremely difficult to form or process into a complicated shape.
[0005]
For this reason, various molding methods have been studied, and complex shapes that could not be produced by mold press or rubber press molding, such as cast molding, injection molding, extrusion molding, and sheet molding, can be easily performed with a near net shape. Yes.
[0006]
Of these, conventional casting is a method of obtaining a molded body by pouring slurry into a water-absorbing mold and forming a walled layer. Although this method is inferior in productivity as compared with press molding or plastic molding, it is possible to form a large and complicated shape, and the equipment cost for molding is low, and it is a method suitable for small-scale production. However, the conventional cast molding method has the disadvantages that it is worn out or clogged by repeated use of the mold, resulting in a decrease in dimensional accuracy and cracking when the molded product is dried. . In view of this, a casting molding method is proposed in Japanese Patent Application Laid-Open No. 8-133844, in which a binder mainly composed of an unsaturated polymer and a cross-linked body containing a vinyl group or an acrylic group is used as an organic binder to be mixed with the ceramic powder and is cured. Has been.
[0007]
[Problems to be solved by the invention]
However, since these organic binders are not water-soluble and are soluble only in organic solvents, there are concerns about the impact of the scattered organic solvents on the exhaust equipment and the human body, which poses practical problems.
[0008]
[Means for Solving the Problems]
The object of the present invention can basically be achieved by the following constitution. That is, “in the casting of alumina, zirconia, or a composite ceramic thereof, the main component is a mixture of a crosslinkable component comprising a water-soluble epoxy resin and a crosslinker comprising an amine compound. A method for producing a ceramic molded body in which a mixture of a crosslinkable water-soluble binder and alumina, zirconia, or a composite ceramic powder thereof is filled in a mold and reaction-cured to form a molded body. The compounding amount of the curing agent with respect to the water-soluble binder is added so that the curing agent is 1 to 4 parts by weight with respect to 10 parts by weight of the crosslinkable water-soluble binder, and the reaction- cured molded body is humidified or adjusted after demolding. “A method for producing a ceramic molded body, comprising drying the ceramic molded body in a wet atmosphere.”
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the contents of the present invention will be described in detail.
[0010]
The crosslinkable water-soluble binder in the present invention, it is necessary that a mixture of cross-linking component and the crosslinking agent. As the crosslinkable component , a water-soluble epoxy resin is required, and as the crosslinker, an amine compound is required . In other words, it is a binder mainly composed of a cross-linked body containing a water-soluble epoxy resin and an amine compound, and a mixture of this binder and ceramic powder is filled in a mold and reacted and cured to form a molded body. It is necessary to.
[0011]
The water-soluble epoxy resin of the present invention has the most common types such as glycidyl ether, glycidyl ester, methyl glycidyl ether, cyclohexene oxide, and epoxidized polybutadiene, but the glycidyl ether type cures smoothly even at room temperature. Suitable as curable resin.
[0012]
For this, it is preferable to use a commercially available polycarboxylic acid-based or polyacrylic acid-based dispersant.
[0013]
Examples of epoxy resin curing agents include compounds having amino groups, carboxyl groups or hydroxyl groups, and amine compounds are particularly effective. Amine compounds include primary, secondary, and tertiary amines in which 1, 2 or 3 of ammonia is replaced with hydrocarbons. Moreover, it is called monoamine, diamine, triamine, or polyamine depending on the number of amines in one molecule, and further classified into aliphatic, alicyclic, and aromatic amines depending on the type of hydrocarbon. In the present invention, any amine compound can be used.
[0014]
Curing of the epoxy resin with an amine-based curing agent causes the active hydrogen of the primary amine to react with the epoxy group to form a secondary amine, and the secondary amine reacts with the epoxy group to cure. Further, the generated tertiary amine polymerizes the epoxy group.
[0015]
In general, in order for the cured product to be a crosslinked polymer, the curing agent needs 3 or more active hydrogens in one molecule and 2 or more amino groups. The compounding amount of the curing agent with respect to the epoxy resin is optimal when the epoxy group and the active hydrogen are equimolar, and actually the cured product has a glass transition temperature, heat resistance, etc. when both the aliphatic and aromatic polyamines are equimolar. Be the best.
The curing rate by the amine varies depending on the type of amine, the blending amount, and the type of epoxy resin.
[0016]
The epichlorohydrin condensate, which is a glycidyl ether type resin, is almost cured at room temperature by an aliphatic amine, but an aromatic amine is slow to cure at room temperature and requires heat curing. In addition, when the blending amount does not extremely increase or decrease more than the chemical equivalent, the apparent curing is faster as the amine amount is larger, and it is slower when the blending amount is smaller. In practice, the curing rate can be adjusted using this.
[0017]
Powder, casting Until now molding is difficult, alumina, zirconia, Contact and applicable to all of these composite ceramic. However, it is desirable that the raw material powder is well pulverized and dispersed in advance.
[0018]
Pure water is used in an amount of 15 to 70 parts by weight with respect to 100 parts by weight of the ceramic powder. If it is less than 15 parts by weight, the solvent is insufficient and the viscosity of the slurry becomes high, so that the slurry does not reach the details of the mold and the moldability is lowered. If it is 70 parts by weight, the water content becomes too high, making it difficult to release after curing, and the drying time also becomes longer. A more preferable slurry is obtained when the pure water is more preferably used in an amount of 25 to 50 parts by weight. Further, it is preferable to use 2 to 10 parts by weight of a binder and 0.1 to 5 parts by weight of a dispersant with respect to 100 parts by weight of the ceramic powder.
[0019]
The slurry thus prepared is sufficiently pulverized and mixed with a general pulverizer such as an attrition mill, a bead mill, or a ball mill. Preferably, the following curing agent is added to the binder so as to be 1 to 4 parts by weight with respect to 10 parts by weight of the binder, and further mixed for several minutes to several tens of minutes.
[0020]
The slurry is taken out from the container of the pulverizer to another container, and before pouring into the mold, it is preferable to defoam in vacuum for 5 to 60 minutes under a reduced pressure of 10 torr or less. The casting method is performed under reduced pressure, increased pressure, or normal pressure as in conventional casting.
[0021]
In the cast molding of the present invention, the molded body is solidified while retaining a considerable amount of water. Therefore, when gypsum like a conventional mold is used, water is absorbed from the slurry and the shape of the molded body is distorted or cracks are generated. Therefore, it is very important to use a casting mold that does not absorb water. It is preferable to use various plastics or metals for the mold material that does not absorb water.
[0022]
It is preferable that a mold release agent such as silicon or fluorine is applied to the surface of the mold that contacts the slurry in advance because it is very easy to remove the mold.
[0023]
In the reaction curing, since the curing agent is injected and then solidified in 2 to 20 hours at room temperature, the mold is removed at a certain degree of shape retention. As a guideline, if the slurry does not drip even if the mold is turned upside down, the mold can be removed.
[0024]
It is preferable to dry the ceramic molded body taken out from the mold while humidifying or adjusting the humidity so that the relative humidity is 40% to 75% . This is because the water is rapidly dehydrated, cracks are not generated, deformation of the molded body is prevented, and drying is performed efficiently. Since the inside of the molded body is particularly difficult to dry, if it is dried to some extent, it is dried at 50 to 200 ° C. in a thermostat or vacuum dried, or the center of the molded body that is retained by microwaves using a microwave oven is heated. In addition, the water retention amount is desirably 0.5% by weight or less.
[0025]
The ceramic cast-molded body after drying is fired at 1200 to 2200 ° C. in the air, in an inert or reducing atmosphere, or under reduced pressure, depending on the type of ceramic. If necessary, pressure sintering may be necessary.
[0026]
【Example】
Hereinafter, the present invention will be specifically described with reference to the following examples. However, the present invention is not limited to this.
[0027]
Example 1
(Composition of ceramic slurry)
(1) Yttria partially stabilized zirconia added with 2.75 mol% ZrO _{2 of} inorganic powder Y ₂ O ₃ was prepared to have an average particle size of 0.12 μm, and this was used as a raw material powder. To the above powder, 0.375% by weight of Al ₂ O ₃ was added as a sintering aid.
[0028]
(2) Binder Polypropylene glycol diglycidyl ether was used at 5% by weight based on 100 g of powder.
[0029]
(3) Dispersant A polyacrylic acid surfactant was used and 1% by weight based on 100 g of the powder.
[0030]
(4) Solvent pure water was used and 40 wt% was used with respect to 100 g of the powder.
[0031]
The raw materials (1) to (4) were mixed with a ball mill at 80 rpm for 24 hours.
[0032]
(Production method of cast molding)
As a curing agent, 1- (2-aminoethyl) piperazine was added to the slurry so as to have a weight ratio of 5: 1 with respect to the binder, and further mixed and stirred in a ball mill for 5 minutes.
[0033]
The stirred slurry was transferred to a glass container, sufficiently defoamed under reduced pressure, poured into a mold and dried.
[0034]
The mold material was a non-water-absorbing material made of polypropylene resin, and drying was performed while adjusting the humidity so that the humidity was 70% at room temperature.
[0035]
(Drying and sintering method)
When it was cured to some extent, the molded body was removed from the mold and dried. Drying was performed at room temperature in an atmosphere adjusted to a humidity of 75%. By this drying, the cake-like lump became a strong molded body.
[0036]
The molded body was fired in the air in an electric furnace. The firing temperature was 1400 ° C. for 2 hours.
[0037]
(Evaluation of sintered body)
The structure of the sintered body was observed with a scanning electron microscope, and it was confirmed that the crystal grain size was 0.3 μm. Further, it was tetragonal zirconia substantially free of cubic crystals by X-ray diffraction, and the sintered body density by the Archimedes method was 6.06 grams / cubic centimeter.
[0038]
【The invention's effect】
The present invention provides a technique that does not gel at the time of preparation and has extremely good fluidity even at room temperature, and can be applied not only to casting molding but also to injection molding, sheet molding, extrusion molding, and the like. After filling into the mold and reaction hardening, there is no generation of cracks due to flow marks or shrinkage, good releasability, and no mass cracking or deformation occurs in the sintered body after firing. It is an excellent ceramic forming method.

Claims (4)

In casting of alumina, zirconia, or a composite ceramic thereof, a crosslinkable water solution mainly composed of a mixture of a crosslinkable component comprising a water soluble epoxy resin and a crosslinker comprising an amine compound. A method for producing a ceramic molded body comprising forming a molded body by filling a mold with a mixture of a functional binder and alumina, zirconia, or a composite ceramic powder thereof, and curing the reaction mold, the crosslinkable water-soluble binder Addition amount of curing agent with respect to 10 parts by weight of the crosslinkable water-soluble binder so that the curing agent is 1 to 4 parts by weight, and the reaction- cured molded body is dehumidified or humidified or conditioned A method for producing a ceramic molded body characterized in that the ceramic molded body is dried by the method. The method for producing a ceramic molded body according to claim 1, wherein zirconia is used as the ceramic. In the crosslinking agent active hydrogen 3 or more in one molecule, method of producing a ceramic molded body according to claim 1 or 2 amino groups as a main component a crosslinked conjugate comprising two or more amine compounds . The method for producing a ceramic molded body according to any one of claims 1 to 3, wherein the water-soluble epoxy resin is of a glycidyl ether type.