JPH01215750A - Slip-casting molding method - Google Patents

Abstract

PURPOSE:To easily obtain molded products of uniform density in any shapes, by casting a self-curing slip containing a specific binder and a curing agent into a mold and demolded after curing. CONSTITUTION:A self-curing slip is prepared, preferably by combining 100pts.wt. of a ceramic powder such as alumina powder, with 13-20pts.wt. of water, 1-10pts.wt. of an alkali-soluble phenolic resin of 30-75wt.% solid content, as a binder, and 0.1-10pts.wt. in other words, 10-100wt.%, based on the phenolic resin, of an ester or lactone from aliphatic monohydric or polyhydric alcohol and carbonic acid or 2-6C aliphatic carboxylic acid such as glycerol triacetate as a curing agent. Then, the slip is cast into a mold having a flexible cavity (e.g., made of rubber), cured, then the molded product is taken out of the mold, then cut or ground.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a method for producing a ceramic sintered body by pouring slurry containing refractory materials such as ceramic powder and metal powder into a mold to form a molded body. Related to the slip casting molding method in the manufacturing process, the slip casting molding method and cutting or grinding of the molded body are particularly suitable for producing molded bodies with complex shapes, shapes that cannot be released from the mold due to a reverse slope, and molded bodies with cavities. It is related to.

(Prior art) Usually, the mold used for slip casting of ceramics has a plaster mold.Since plaster has fine pores, it has the ability to absorb the dispersion liquid (mainly water) in the slip (ffiL). Therefore, the plaster mold for solidifying the slip is usually a split mold, which complicates the shape of the molded product and requires a large number of split molds. The slip is solidified and separated from the split mold to obtain a molded body of a desired shape (hereinafter referred to as a "green body").

(Problem M to be solved by the invention) Since the strength of the green body obtained by such a method is weak, it is difficult to remove a complex-shaped green body with many unevenness and internal cavities from a plaster mold. is prone to cracking and deformation, and when a large number of split molds are required, the production and assembly of plaster molds becomes complicated, and cracks occur in the green body after molding. Furthermore, repeated use of the plaster mold causes wear and clogging, reducing the dimensional accuracy of the green body.

In slip casting using a mold that absorbs the dispersion liquid in the slip as in the above method, if the green body has a thick interior and a thin wall part, the assimilation of the thick part is delayed compared to the thin wall part, and the fractional liquid absorption of the mold is As the amount increases, the absorption function of the dispersion liquid decreases. Therefore, a density distribution occurs inside the green body, and cracks and deformation due to the density distribution are likely to occur during the drying and firing process. Furthermore, when the slip is poured into a mold with a complex shape or a shape with a thin wall, and the slip comes into contact with the mold, the dispersion liquid in the slip is absorbed into the mold, so the fluidity of the slip decreases in the thin wall, and the molded product filling defects are likely to occur. In addition, hollow shapes have various drawbacks, such as the shrinkage effect of slip assimilation, which tends to cause cracks in the green body that is restrained by the core mold, and the shape of the green body is subject to various restrictions. Green bodies are difficult to cut or grind due to their low strength and brittleness.

(Means for Solving the Problems) The present invention is a molding method in which a slip is poured into a mold and a green body is removed from the mold after the slip has hardened, in which a water-soluble phenol resin and an organic acid ester are added to and mixed with the slip. This method is characterized by hardening the slip.

When a water-soluble phenol resin and an organic acid ester are added and mixed with the slip, the viscosity is low at first and exhibits moderate fluidity, but the viscosity gradually increases and eventually hardens. This is because the ester of the curing agent hydrolyzes to become carboxylic acid and alcohol, and the carboxylic acid causes a neutralization reaction with the alkali metal of the metal phenolate, promoting electron transfer of the phenolic anion, and as a result, methylol is activated and rapidly It is believed that the slip hardens by condensation to form methylene or methyl ether bonds.

The phenolic resin used in the present invention is an aqueous solution of an alkaline phenol-formaldehyde resin obtained by reacting phenol with formaldehyde in the presence of an alkali having essentially the same molar amount as the phenol.

Furthermore, the esters used in the present invention may be of any type as long as they cause the above-mentioned reaction, and are usually composed of chain-like mono-, di-, tri-, or polyhydric alcohols having 2 to 10 carbon atoms and 1 carbon atoms. esters with carbonic acid or chain carboxylic acids having 2 to 6 carbon atoms, and furthermore, so-called lactones in which a carboxylic acid group and an alcohol group are ester-bonded within their own molecules.

Typically, glycerin monoacetate, glycerin diacetate, glycerin triacetate, ethylene carbonate, propylene carbonate, propiolactone,
Examples include gamma butyrolactone and epsilon caprolactone.

This hardening effect makes it possible to obtain a green body, but if the slip contains more water, binder, hardener, etc. than necessary, the green body may be formed poorly, and the sintered density and strength of the sintered body may deteriorate. It is also possible to add and mix a small amount of water, dispersant, etc. to the ceramic powder, binder, and hardening agent to give it plasticity, and obtain a molded body using a molding method such as press molding or extrusion. be.

A preferred formulation of the present invention is 13 to 2 parts of water, 1 to 10 parts of water-soluble phenol resin, and 0.1 to 10 parts of organic acid ester to 100 parts of ceramic powder. Since each compound layer varies depending on the 1h conditions such as shape, size, and molding method, the conductivity 1a is determined experimentally for each case.

With this configuration, when a self-hardening slip is poured into the mold, a green body with no density distribution can be obtained, and at the same time, the resulting molded product is strong and will not chip or become porous due to cutting or grinding. It is now possible to process molded products of any shape without causing damage.

In addition, since the slip flow is good, it can be filled to every corner of any mold, and the solidified molded product is strong, so it can be
Even in the case of a molded article having an f1l shape that is difficult to release, the use of a flexible mold makes it easy to release the molded article, making it possible to manufacture molded articles of any shape.

A rubber mold is used as the flexible mold, for example, silicone rubber mold 1 is used. 2 is a mold for fixing the rubber mold, and generally a plaster mold is used. A resin mold or a metal mold may be used for this pond. Depending on the shape of the green body, a slip prepared with phenol resin, organic acid ester, etc. is poured into mold 1, and the slip is kept in mold 1 for a certain period of time. Leave it in there. After the slip has hardened, the mold 2 is separated from the mold 1, and then the mold 1 is separated from the hardened slip or green body.

Ceramic sintered bodies in any shape can be obtained by drying and firing the thus obtained molded product in any shape using a rigid or flexible mold.

(Example) Next, Examples 1, 2, and 3 will be shown to explain the slip casting molding method in more detail, but the present invention is not limited to the following examples unless it exceeds the gist. .

Example 1 Alumina (center particle size 0.6 μm) 100-layer water
16 parts by weight dispersant 0.
Alumina balls were added to the raw materials in the 5-layer plate and pulverized and mixed for one day, and the solid content was 5011 parts per 100 parts by weight of the mixture.
4 parts by weight of a water-soluble phenol resin in the ffi part and 15 parts by weight of glycerin triacetate as an organic acid ester were added to prepare a slip that was adjusted to be uniformly dispersed, and then vacuum defoamed, and the slip was fixed in a plaster mold to make silicone rubber. It was poured into a mold and left for 1 hour. The green body was then cut out from the silicone rubber mold. There was no cracking or deformation in the green body, and a high-density alumina sintered body was obtained after drying and firing for a specified period of time. Note that the water-soluble phenol resin used in this example was manufactured as follows.

304.2 Kg of phenol, 411.3 Kg of 37% formalin and 7.7 Kg of phenol were placed in a steam heated jacketed reaction vessel.
Add Kg of water and start heating while stirring. At 50°C, 13.1 kg of a 48% caustic soda aqueous solution is first heated, followed by 261.2 kg of a 48.7% caustic soda aqueous solution. Sexual speed should not exceed 80°C.

Continue stirring until the viscosity is 500 cps/2
When the temperature reaches 5°C, stop heating and allow to cool. The viscosity was adjusted to Mr& with alkaline water, 2.5 kg of silane was added, and the mixture was thoroughly mixed to obtain the desired phenol resin.

Example 2 Zirconia (center particle size 0.6 μm) 100 layers (3 mol% ittria added) Water
13 Weight part dispersant 0.
Alumina balls were added to 4 parts by weight of water-soluble phenol resin (50 parts by weight of solid content fi) and a binder, and the mixture was mixed in a ball mill for one day to prepare a slip.
Add 2 parts by weight of glycerin monoacetate to 0 parts by weight and adjust to evenly disperse! ! The mixture was degassed under vacuum, poured into a silicone rubber mold fixed with a plaster mold, and left for 8 hours. After the slip had hardened, the green body was released from the silicone rubber mold. Green body <mm・25
After drying and firing for a predetermined period of time, a high-density zirconia sintered body 1 was obtained with no cracking or deformation.

Example 3 A slip was prepared by the method described in Example 1 and a green body was formed. Cutting was then performed using a lathe to obtain a green body having the desired shape.

(Effects of the Invention) As explained above, according to the present invention, a green body can be easily obtained by pouring a slip containing a water-soluble phenol resin as a binder and an organic acid ester as a hardening agent into a mold. In addition, a desired green body can be obtained by cutting the green body.

Patent applicant: Hodogaya Ashland Co., Ltd. Toyama Prefecture Handbook continuation supplementary edition (self-published) June 23, 1986

Claims (5)

[Claims] 1. In a molding method in which a self-hardening slip is poured into a mold having a cavity and the molded body is removed from the mold after the slip has hardened, the binder of the slip is an alkali water-soluble phenolic resin and the curing agent is an organic acid ester. Slip casting molding method is characterized by: 2. The solid content of alkaline water-soluble phenolic resin is 30
The slip casting method according to claim 1, characterized in that the amount is 75% by weight. 3. 10 hardening agent for alkaline water-soluble phenolic resin
The slip casting molding method according to claim 1, characterized in that the addition amount is 100% by weight. 4. A method for producing a molded body, which comprises molding by the slip casting molding method according to claim 1, 2, or 3, and then cutting or grinding the molded body. 5. 5. A method for manufacturing a molded article according to claims 1, 2, 3, and 4, characterized in that a flexible mold is used.