JPS61181611A - Slip casting molding method and mold for molding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a slip casting molding method in which a molded product is made by casting a slip of particles such as ceramic grains or metal grains, and a mold for molding. A molding method and molding method especially suitable for making molded products with complex shapes! Regarding type 4.

[Background of the invention]

The mold used for slip casting of ceramics is usually a split υ type and a draft angle is added to separate the mold after slip casting from the solidified slip molded body (hereinafter referred to as "green body"). and,
The obtained green body is sintered to produce a finished ceramic product.0 When slip casting is used to form a molded body with a complex external shape and cavity shape and high dimensional accuracy, it has conventionally been necessary to use a large number of main molds and center molds. A common method was to combine the molds to form a desired mold. However, this method requires a large number of man-hours to manufacture and assemble a large number of main molds and cores, and the green body is likely to crack during the process of dehumidifying the green body and the process of removing the mold and core.

Further, this method can only be applied when the core has a shape that allows it to be pulled out from the slip molded body after solidification.

Therefore, as a method for removing the mold after slip casting in such cases, for example, as disclosed in Japanese Patent Publication No. 58-125658, sintering is performed with the mold still installed.
There is a method of disintegrating and removing the mold after that. However, with this method, the green body is dried by leaving it in the air with the mold installed, and the green body is sintered with the mold installed. Cracks occur in the molded product due to shrinkage and deformation of the green body. Judging from its structure, this reference does not assume the use of a core. However, as disclosed in Japanese Patent Application Laid-open No. 176107/1983, slipping is applied to a hot water disintegrable gypsum mold. After pouring and solidifying the slip to form a green body, there is a method of removing the gypsum mold by immersing the (green body + mold) in hot water of approximately 85°C or higher.

However, this method uses a relatively large amount (0.5-5%) to prevent the green body from disintegrating due to water absorption during soaking.
) is added to the slip, but this does not affect the mechanical properties of the sintered crystal, and it may take a long time to disintegrate it deep into the mold with hot water. In some cases, removal of the mold is extremely difficult.

In other words, when a long and slender core (i.e. a core with a large length/diameter value) is cast in a hydrothermally disintegrable mold and a slip is cast around the core, the proportion of the hot water contact area to the total surface area of the core increases. The smaller the value, the longer it takes to remove the template.

[Purpose of the invention]

In view of the above, an object of the present invention is to provide a slip casting molding method and a mold that are suitable for preventing cracking of molded products and molding complex-shaped products by making it possible to remove the mold immediately after solidification of the slip. shall be.

[Summary of the invention]

The present invention is a molding method in which a slip using water or an organic bath agent as a medium is cast in a 114 m space, and the mold is removed after the slip has solidified, and the mold is molded with a water-soluble organic binder. It is something.

In this case, the developed aggregate is alumina (AtzOs) +
MgO, zircon sand, silica sand, or resin particles insoluble in the slip medium used are used.

Examples of water-soluble synthetic organic binders include polyvinyl alcohol (PVA), water-soluble isobutane-maleic anhydride copolymer, polyacrylamide (PAAm), and polyethylene oxide (PEO).

Polyvinylpyrrolidone (PVP), water-soluble vinyl acetate copolymer, acrylic copolymer, polyethylene glycol (PFJG), methylcellulose (MC).

One or more organic substances such as carboxymethyl cellulose (CMC), hydroxypropyl cellulose (CHPC), and water-soluble wax are used in the form of a solution in water. Alternatively, natural water-soluble binders such as starch, glue, and gum arabic may also be used.

The mixing ratio of bone machine, binder P, and water depends on workability during mold making, mold dry strength, absorbency of solvent (water or organic bath agent, e.g. ethanol, acetonate) in the slip, and the mold after absorbing water. This value is determined on a case-by-case basis depending on the disintegrability of the material and is not uniformly determined.

However, as a general rule of thumb, the amount of binder is 15 to 10 parts by weight and the water is 120 to 30 parts by weight per 9100 parts by weight of aggregate particles.

When a slip using water as a medium is cast into the above mold, if the mold is thin, the mold can collapse with only the water in the slip, but if the mold is thick, sufficient moisture can be obtained from the slip for collapse. In cases where this is not possible, (1) it is preferable to reduce the mold wall thickness, and for this purpose, a hollow core is provided inside the thick-walled core; (11) moisture is added to the external mold to improve the collapsibility of the mold. , G11) , (+)(l
It is even more effective to use methods such as i) in combination.

In other words, measures such as keeping the mold wall thickness as thin as possible, and providing one or more appropriate holes in the main mold or core to facilitate the addition of moisture are effective in eliminating mold collapse. It is effective for

Also, as a method of adding moisture, '! It is also effective to add it in the form of a mist. Furthermore, in a high humidity cha/par (
One method of removing mold collapse is to leave the mold (mold + green body) for a predetermined period of time to allow the mold to absorb moisture.

In the present invention, a slip using water as a medium is cast into a mold made by hardening aggregate particles with a water-soluble organic binder, and the mold absorbs water in the slip and solidifies the slip. The phenomena that make it easier to collapse are as follows.

As shown in Figure 1 (a), (b) l (C),
The aggregate particles l in the mold are coated with a water-soluble organic binder 2 when not dried (see (a)), but when the mold is dried and hardened, the moisture evaporates and a large number of fine particles are formed inside the mold. Hole 3
is formed, and when a slip is cast into this solid HfJ, water, which is a medium in the slip, enters into the pores 3 by capillary action and becomes a water-soluble binder 21! Since it is made to dissolve, its cohesive strength is significantly weakened and each aggregate particle 1 becomes independent. (See (C)).

Looking at this phenomenon from a macroscopic perspective, as the mold absorbs the water in the slip, it gradually transitions to a state where it can collapse deep into the interface with the slip, but on the other hand, the slip releases water as a medium. As the density increases, the degree of solidification increases, eventually leading to the formation of green bodies.

This green body gradually shrinks during the subsequent dehydration process. On the other hand, since the mold absorbs moisture, it tends to swell, albeit slightly.

Ordinary plaster molds do not lose their strength even if they absorb water in the slip, so the green body is susceptible to cracking due to the stress generated during the contraction of the green body and the swelling process of the mold.However, in the present invention, Since the mold softens as it absorbs water, the mold does not at all prevent minute deformations such as convergence that occur during the green body production process. In other words, the green body is a mold (
Since it does not receive any external force from the main mold or core,
No stress is generated on the green body, so no cracks occur at all. Therefore, even when the mold is rough and the mold is complicated, or when a core is sometimes used, each part is equal to the depth, and there is no slippage. Since the water necessary for disintegration removal is absorbed from the slip, each part of the mold can be disintegrated evenly.0 Note that if the mold wall thickness is large and the amount of moisture in the slip is insufficient to remove the mold, use an external source. As mentioned above, adding water is effective.

Molds are formed by compacting aggregate particles, a water-soluble binder, and a water mixture, but the molding time can be shortened by imparting fluidity to the mold material.

Basically, to impart fluidity, it is sufficient to increase the water content. However, the moisture in polyviolet is not easy to evaporate.

Therefore, an alternative method is to prepare an alcoholic solution of a water-soluble binder that is stable in the form of a hydrate at room temperature, and add to it the amount of water necessary to fix it as crystal water, or a slightly smaller amount of water. It is preferable to impart fluidity to the mold by adding fluidity to the mold.

As described above, since the softening of the mold progresses simultaneously with the solidification of the slip, it is possible to mold ceramic molded products of complex shapes extremely easily without any cracks.

Furthermore, since the present invention uses an organic binder, it is similar to the case where a non-material water-soluble binder (for example, 2CO3) is used.
) If a water-soluble mold and a gypsum mold are used in combination, the gypsum mold will be eroded and the number of times the gypsum mold can be used repeatedly will be extremely small; (10 The binder in the water-soluble mold will diffuse into the green body. It does not have any problems such as easily causing quality deterioration of the molded product, reacting with θID slip, and affecting the PH of the slip.

Furthermore, unlike other conventional methods, there is no need to immerse (mold + green body) in hot water before sintering, and sintered crystals can be obtained by slip casting with no restrictions on shape.

[Embodiments of the invention]

Examples of the present invention will be described below.

[Example 1] 1100 parts by weight of Az2o3 (250-325 mesh) and 120 parts by weight of an aqueous solution of 5-inch polyvinyl alcohol (PVA) were added at a time and mixed uniformly to form a mold material.

The core 4 shown in FIG. 2 was molded from the above molding material using a wooden mold prepared separately, and main molds 5 and 6 made of plaster were also molded. Core 4 was sufficiently dried and hardened at 100°C. Moreover, the main molds 5 and 6 made of plaster were sufficiently dried at 60°C. Thereafter, these main molds and cores were assembled to form a predetermined mold cavity.

Next, 100 parts by weight of At20al having an average particle size of 2ttm.

An alumina slip 8 prepared by uniformly mixing 116 parts by weight of water with a small amount of deflocculating agent and Pf (adjusting agent) was poured into the cavity 7 of the mold and left for one hour.

After the slip solidified, the core 4, which was removed from the main plaster mold 5.6, had absorbed the moisture in the slip, so its cohesive strength was extremely low, and it could be easily disintegrated and removed. . Furthermore, no cracking was observed in the green body.

[Example 2] At203 (250-325 mesh) $ 100
A mold material was prepared by kneading 20 parts by weight of a 5% aqueous solution of polyacrylamide (pAAm), and molded using a separately prepared wooden mold according to Example 1.
A core was made by sufficiently drying and curing at ℃, and assembled together with a separately molded plaster main mold 5.6. Add this to Sialon powder 11
00 parts by weight of water, 140 parts by weight of water, a peptizer, a sintering aid, and the like were added and homogeneously mixed together, and the sialo/slip 8 was cast into the mold cavity 7 and left for one hour. As a result, Example 1
Similarly, core 4 could be easily removed, and no cracks were observed in the green body.

[Example 3] A casing having the shape shown in FIG. 4 was created by slip casting using the method and mold of the present invention.

This casing has 7 lunges 9. Fastening groove 10. The inside has a spiral flow path 11 and has an extremely complicated shape, so it is difficult to use conventional casting! ! ! ! It was not possible to mold the material using the slip casting method.

Zircon sand (250-325 powder) 1100Xjt
parts, 5% polyvinylpyrrolidone (PVP) water g solution 115
Mix the weight parts uniformly to adjust the mold material and fill it into a separately prepared hard Si rubber core holder to create a spiral core.
After that, it was thoroughly dried at 100°C, and a mold was assembled together with a separately molded half-split main mold of stone fJ. Thereafter, an alumina slip similar to that in Example 1 was cast and left for 2 hours.

Afterwards, the main plaster mold was removed. Since the water-disintegratable spiral core according to the present invention sufficiently absorbs the moisture in the slip, the -type caking strength was significantly reduced and could be easily disintegrated and removed.

After drying this alumina green body in the air,
By drying at 0°C (to completely remove free water) and then slowly heating from room temperature to 1700°C for 2 hours, a casing as an alumina sintered crystal with no cracks and good mechanical properties was obtained.

[Example 4] The present invention was applied to molding the screw-shaped rotor shown in FIG.

In the case of such a shape, the conventional slip casting method using a stone-Ill mold requires the mold to be divided into an extremely large number of pieces, resulting in a decrease in dimensional density and damage to the green body during multiple demolding of Paris, making molding impossible. It was extremely difficult. Therefore, a screw-shaped model identical to that shown in FIG. 4 was separately foam-molded from expanded polystyrene using a mold. One-component RTV silicone rubber was applied to a thickness of about 50 μm on the entire second surface of the model 12 except for the top 15 and cured to form an insoluble coating film 13.

The top of this model is placed on a surface plate (not shown), and a wooden frame is installed around it. Next, 1203 particles 1xoO heavy parts,
A mold material 14 was prepared by adding 140 fc of a vinyl acetate emulsion water bath solution of 5 ml and mixing uniformly, and spraying acetone from the top 15 of the mold 12 filled around the rotor model. The volume of the styrofoam model is approximately 1
After shrinking to 730℃ and drying and curing the mold at 100'C, acetone was sprayed on the styrene model again and removed from the mold together with the rubber film applied to the surface.
Thereafter, it was dried and cured at 100C.

A sialon slip 17 similar to that in Example 2 was cast into the mold cavity 16 thus formed, and the moisture in the slip was absorbed into the mold and solidified. At this time, the mold according to the present invention had extremely good disintegration properties because the cohesive force of the mold was drastically reduced due to the absorption of water, and a green body could be obtained without damaging the threaded part of the rotor.

This sialon green body was gradually dried in the air, then dried in a 100°C oven to completely remove free moisture, heated slowly from room temperature, and sintered at 1800" CX 2 H under normal pressure to create a homogeneous sialon body. A rotor-fired crystal was obtained.

[Effects of the Invention] As explained above, according to the present invention, a water-soluble organic binder is mixed with insoluble aggregate particles such as Az2 OA powder to form a mold, and water or water is used as a medium. Since the mold is mainly made of slip material such as ceramics, the mold absorbs water from the slip and becomes soft and easily disintegrates.At the same time, the slip that has absorbed water increases its density over time and solidifies, eventually becoming a green body.

Therefore, according to the present invention, the following effects are brought about when molding ceramic products.

(i) Since the mold softens as the slip hardens, no cracks will occur in the green body even when using a main mold or core with a complicated shape.

(11) Since the mold softens by absorbing moisture from the slip, it is possible to easily mold even complex-shaped molded products that require a main mold and a core with thick concavities and convexities.

[Brief explanation of drawings]

Figures 1 (a), (b), and (C) are explanatory diagrams showing the principle of the mold used for molding of the present invention, Figure 2 is an explanatory diagram of an embodiment of the molding method of the present invention, Figures 3 and 4. The figure is an external view of a molded product to which the present invention is applied, and FIGS. 5 to 7 are explanatory diagrams of the molding method of the present invention. 1...Mold aggregate particles, 2...Water-soluble organic binder,
3... Holes, 4... Water-disintegratable core, 14... Water-disintegratable main mold, 5, 6... Gypsum main mold, 7, 16.
...Mold cavity, 8,17...Ceramic slip, 1
3...Insoluble coating film. 1st ward 3 days old 4th off T21

Claims (1)

[Scope of Claims] 1. A slip casting molding method in which a slip is cast into a mold and the mold is removed after the slip has solidified, the mold being molded with an organic water-soluble binder. 2. The slip casting molding method according to claim 1, wherein the mold aggregate is refractory particles such as alumina, magnesia, zircon sand, and silica sand. 3. The organic water-soluble binder is polyvinyl alcohol,
Water-soluble isoptane-maleic anhydride copolymer, polyacrylamide (PAAm), polyethylene oxide (
PEO), polyvinylpyrrolidone (PVP), water-soluble vinyl acetate copolymer, acrylic copolymer, polyethylene glycol (PEG), methylcellulose (MC),
The template according to claim 1, characterized in that the mold is made by dissolving one or more organic substances among carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), water-soluble wax, etc. in water. production method. 4. The mold according to claim 1, wherein the organic water-soluble sticky agent is one or more of starch, glue, and gum arabic dissolved in water. Molding method. 5. The method for making a mold according to claim 3 or 4, characterized in that alcohol is added to the binder to impart fluidity to the mold. 6. The slip casting molding method according to claim 1, wherein a cavity is provided in the mold to promote collapsibility. 7. The slip casting molding method according to claim 1, wherein after the slip has solidified to become a green body, moisture is added to the mold from the outside to promote the collapsibility of the mold. 8. A mold for slip casting, which is a molding method in which a slip is cast into the mold and the mold is removed after the slip has solidified, wherein the mold is molded with a water-soluble organic binder.