JP2000119055A - Slurry for cold casting use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molded product excellent in demoldability and having physical properties nearly equivalent to those of the corresponding burnt product in a cold process by compounding a specified proportion of a rock powder clay composition in an emulsion containing a specified proportion of an acrylic urethane mixed resin with a specific mixing ratio followed by conducting a slurry cast molding. SOLUTION: This molded product with high mechanical strength is obtained by compounding 1-1.8 pts.wt. of a rock powder clay composition in 1 pt.wt. of an emulsion containing 3-20 wt.% of an acrylic urethane mixed resin with the mixing weight ratio: acrylic resin/urethane resin of (16:1) to (110:1) followed by conducting a slurry cast molding; wherein the rock powder clay composition is such one as to use plastic clay fine powder as vehicle and rock powder as skeletal material; and the slurry cast molding process is carried out as follows: the slurry is cast into a gypsum mold and left to stand, the water in the slurry is then diffused and absorbed from the surface of the mold into the pores of the gypsum to effect forming a slurry layer of lower water content on the surface of the mold, and an excess of the slurry is allowed to flow out of the mold to effect affording a molded product of desired thickness which is then demolded and air-dried on dried at a low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unheated casting slurry which is capable of obtaining a molded article having properties similar to those of fired porcelain without heating, and which is excellent in demoldability.

[0002]

2. Description of the Related Art Conventionally, porcelain has been obtained by pouring a firing slurry into a gypsum mold, molding and firing. In other words, when the slurry for firing is poured into a gypsum mold and allowed to stand, the water in the gypsum mold has less moisture as the water in the gypsum diffuses into the pores in the gypsum from the surface of the gypsum mold. This layer becomes thicker in proportion to the length of the standing time, so after standing for an appropriate period of time, excess slurry is poured out of the mold to obtain a shaped object having a desired thickness. And after demolding and drying, 1050
It has been practiced to obtain ceramics by firing at 1200 ° C.

[0003]

However, in this case, not only equipment for firing at a high temperature is required, but also
Since various techniques, labor and time are required for firing, there is a disadvantage that the cost is extremely high. Also, in the case of this type of firing mud, after removing it from the plaster mold,
Because it is premised that firing will be performed to make ceramics,
Without firing, it was very brittle and unusable.

[0004] Even in this kind of firing slurry, in order to maintain the strength enough to be handled before firing, the bonding force is exhibited only before firing, and after firing, it burns and remains on the ceramic. Although a binder that does not use it may be used, even if a firing slurry using such a binder is used as a non-heat-casting slurry, in the case of a complex shape, it is difficult to remove the mold and it does not fire. And high strength could not be obtained, so it was not possible to produce something close to the same as ceramics that used firing mud.

[0005] Regarding the use of the binder, techniques of using an acrylic emulsion are also disclosed. However, any of these techniques can also be performed by adding an acrylic emulsion to the slurry to work as a slurry. Although there is some improvement in the properties and strength of the molded body, there is a drawback that the impact resistance is essentially inferior.

[0006] In view of the above situation, the present invention is to realize a molded product having excellent demoldability and having properties similar to those of a fired product by non-heating by ordinary slip casting using a gypsum mold. The purpose is to provide a slurry that can be used.

[0007]

According to the present invention, a mixing ratio of 16:
A non-heated mixture comprising 1 to 1.8 parts by weight of a rock powder clay composition per 1 part by weight of an emulsion containing 3 to 20% by weight of an acrylic urethane mixed resin of 1 to 110: 1. It is a casting slurry.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The slurry of the present invention is intended for casting without heating, so that a sufficiently strong bond can be obtained without heating and the function of cast molding with gypsum, particularly without deteriorating the demolding. In addition, it is necessary that the mold can be released in a short time. For this purpose, a rock powder clay composition is used, and the solid content in the acrylic urethane mixed resin emulsion is used as a binder. This acrylic urethane mixed resin emulsion has the fluidity of unheated slurry and the removal from gypsum. It does not inhibit the mold.

The rock powder clay composition used in the present invention uses a plastic clay fine powder as a molding material capable of being formed into any shape, and provides a skeletal material capable of imparting strength and maintaining a stable shape. As rock powder. The above-mentioned plastic clay is an inorganic clay which has plasticity and can be formed (shaped) into a desired shape, and is a fine powder of clay, kaolin, montmorillonite, bentonite, pyroflight, sericite and the like. is there. The above-mentioned rock powder, which imparts strength to the compact, includes silica, quartz, feldspar, pumice, volcanic ash, pottery stone, silica stone and the like.

As the rock powder clay composition used in the present invention, for example, a hydrated rock powder clay composition purified by filtration or the like or a hydrated rock powder clay composition further densified by pressing can be used. As the rock powder clay composition, a water-containing rock powder clay composition obtained by removing one or more of the above-mentioned rock powder and one or more of the plastic clay by elutriation and purifying and then dehydrating by a filter press is used. Can be. As the clay, those commercially available as discotic or irregular shaped chunks as ceramic materials can be used. When using a commercially available elutriated hydrated rock powder clay composition, it is preferable to further use a plastic clay. The use of the purified or further densified hydrated rock powder clay composition makes it possible to obtain a stronger strength even with a small amount of the synthetic resin added, and also to reduce the amount of the synthetic resin used to reduce the amount of gypsum. The effect of shortening the time for removing from the mold and improving the working efficiency can be obtained. In addition, coloring agents such as titanium oxide, inorganic pigments, and organic pigments can be used as needed.

The acrylic urethane mixed resin emulsion used in the present invention is an acrylic ester copolymer such as a polyacrylate, a polymethacrylate, an acrylate / styrene copolymer, a methacrylate / styrene copolymer. A powder of a blend of an acrylic resin fine powder such as a methacrylic acid ester copolymer and a urethane resin fine powder is in a state of being dispersed in water, and is usually an emulsion of an acrylic resin fine powder and urethane. It is obtained by mixing an emulsion of a fine resin powder, and may be an emulsion of a mixture of a fine acrylic resin powder and a fine urethane resin powder, or may be obtained by another manufacturing method. The particle size of each fine powder of acrylic resin and urethane resin is desirably about 0.05 to 0.5 microns. The pH of the emulsion is particularly preferably 7 to 8.

This acrylic urethane mixed resin emulsion is usually prepared as an emulsion having a solid content (acrylic resin, urethane resin) having an average concentration of about 40 to 50%, and then mixed with water to form an aqueous solution (a thin concentration). Emulsion), whose solid content in the aqueous solution is 3 to 20% by weight, particularly 8 to 16% by weight, and more preferably 11 to 16% by weight.
15% by weight is particularly preferred. If the solid content in the aqueous solution is less than 3% by weight, the strength tends to decrease,
If it exceeds 20% by weight, the fluidity and shrinkage of the slurry tend to be poor.

The mixing ratio of the acrylic resin and the urethane resin is from 16: 1 to 110: 1. Within this range, a resin having a high strength can be obtained, and the releasability is excellent. In particular, the range of 40: 1 to 90: 1 is most preferable.

In general, the composition of the slurry is such that the ratio of the rock powder clay composition to the aqueous solution (dilute emulsion) 1 is 1 to 1.8, particularly preferably 1 to 1.5. If the rock powder clay composition is less than 1 with respect to the aqueous solution 1, the preferable function of the slurry is impaired, and if it exceeds 1.8, the strength is reduced.

Various additives such as a deflocculant, a fungicide, and a coloring agent can be used in combination with the non-heat-casting slurry of the present invention. For example,
The deflocculant is intended to provide sufficient fluidity even when the amount of water used is reduced. In addition, extremely good fluidity can be given by dripping the deflocculant into the gel suspension obtained by mixing and stirring the rock powder clay composition and the aqueous solution (lightly concentrated emulsion).

Examples of the peptizer include inorganic salts such as sodium silicate, sodium hydroxide, sodium carbonate, sodium phosphate and sodium aluminate, and organic substances such as diethylamine, dipropylamine, monoamylamine and monoethylamine. But not limited to.

When the unheated casting slurry of the present invention is poured into a gypsum mold and allowed to stand, the water in the slurry is diffused and absorbed into the pores in the gypsum from the surface of the gypsum mold, so that the gypsum mold surface is removed. After a layer of low-moisture plasma is formed, allow it to stand for an appropriate amount of time, then pour out excess mud from the mold,
A molded article having a desired thickness can be obtained, demolded, and further dried naturally or at a low temperature to obtain a molded article having high strength. By using the slurry to which the synthetic resin emulsion is added, a molded product can be obtained with exactly the same molding conditions as those of conventional slurry casting. Furthermore, it is possible to obtain a solid and beautiful molded object by curing by simply removing moisture by natural drying or low-temperature drying,
In addition, since it can be released in a short time, a great deal of labor and cost during conventional heating and firing are reduced,
Enables time savings.

In particular, by purifying or further densifying the particles constituting the substrate, it is possible to increase the strength of the bond, promote the absorption of moisture into the gypsum, and remove the mold in an extremely short time. Since the amount of urethane resin added is reduced to promote water absorption and the strength of the molded product can be maintained high, the water absorption time can be shortened without losing the strength, and the flow into the gypsum mold (30 cm or less) It can be shortened to about one hour from release to release.

[0019]

Hereinafter, Examples and Comparative Examples of the present invention will be described in detail. In addition, the characteristics of the obtained non-heat-casting slurry and the molded article molded therefrom were measured by the following methods. 1. Specific gravity Unheated casting slurry was flowed into a 50 cc graduated cylinder to measure its volume, and its weight was measured to calculate its specific gravity. 2. Fluidity When the unheated casting slurry was flowed into the gypsum mold, the fluidity was visually evaluated in three stages (○: good, Δ: poor, Δ: extremely poor). 3. Stability over time The fluidity of the unheated casting slurry after standing for one week was visually evaluated in three stages (○: good, Δ: poor, Δ: extremely poor).

4. Volume shrinkage rate When the length of the longest side of the modeled object was x and the amount of change in the length due to shrinkage was a, the volume shrinkage was calculated by the following equation. This calculation method is based on the calculation method described in "Intelligible Industrial Ceramics" by Yoichi Motoki. 4. Volume shrinkage (%) = (3a / x) × 100 Breaking strength and bending strength The shaped object is processed into 60mm × 25mm × 3mm and SUN RHEO M
ETER COMPAC-100 MODEL CR-100 (SUN SCIENTIFIC CO, LT
D.). 6. Warping distortion The warping distortion of the formed object is visually evaluated in three stages (○: good, △:
Poor, Δ: extremely poor).

Example 1 83 g of an acrylic acid ester / styrene copolymer emulsion (Polysol AP-4710, manufactured by Showa Polymer Co., Ltd., solid content 50%, pH 9, average particle size 0.1 to 0.2 μm)
And urethane resin emulsion (Adekabon titer HUX-240 manufactured by Asahi Denka Kogyo Co., Ltd., solid content 30%, pH
(7-8, average particle size: 0.1 μm) 2 g was put into a beaker, and stirred for about 30 minutes with a stirrer to prepare 85 g of an acrylic urethane mixed resin emulsion. Next, as shown in Table 1, 10 g of kaolin (KM kaolin), elutriated hydrated rock powdered clay composition [white porcelain clay (kaolin, sericite, feldspar) manufactured by Ando Ceramics Co., Ltd., moisture content 24%] 56 g ,
1.3 g of titanium oxide powder, a total of 67.3 g, was put into a 300 cc beaker, and a stainless steel pallet knife (18 ×
(110 x 0.5 mm) and manually mixed for about 1 minute to prepare a powder mixture.

Put 6.5 g of the previously prepared acrylic urethane mixed resin emulsion and 26 g of water into a 100 cc beaker, and slowly slow the mixture for about 1 hour using the same palette knife as described above.
By stirring manually for 3 minutes, a total of 32.5 g of the aqueous solution was prepared. A 32.5 g aqueous solution was charged into a 300 cc beaker containing 67.3 g of the powder mixture, and was manually kneaded for about 1 minute with the same pallet knife as above to obtain a gel-like clay.
0.2 g of sodium silicate No. 3 as a deflocculant was added dropwise and further stirred to obtain about 100 g of a non-heating casting slurry.

[0023]

[Table 1]

The powder / water solution ratio in Table 1 was obtained as follows. The water content of white porcelain clay is about 24%,
3.44 g, and the powder / water solution ratio was (67.3-1).
3.44) ÷ (32.7 + 13.44) = 1.17. Further, the unheated casting slurry was defoamed with a vacuum defoaming machine for 5 minutes to obtain a usable unheated casting slurry. The specific gravity measured by the above means was 1.4. Its fluidity and stability over time were excellent.

Next, a gypsum mold prepared in advance with the above-mentioned non-heat-casting slurry (inner shape: horizontal 30 mm × vertical 150 mm)
× 5 mm in depth), allowed to stand for 1 hour, demolded, and air-dried for 2 days to obtain a molded article.

The volume shrinkage after air drying was 14% as shown in Tables 1 and 2. Also, as shown in Table 1, the breaking strength, bending strength and warpage were excellent.

[0027]

[Table 2]

Example 2 As shown in Table 1, the input amount of the acrylic urethane mixed resin emulsion was changed from 6.5 g to 8.5 g, and the amount of water was 26 g.
The procedure was the same as that in Example 1 except that the weight was changed to 24 g. The specific gravity of the obtained unheated casting slurry was 1.4, and the fluidity and the stability over time were excellent. The volume shrinkage after air drying was 14 as shown in Tables 1 and 2.
%, And the breaking strength, bending strength and warpage were excellent as shown in Table 1.

Example 3 As shown in Table 1, the input amount of the acrylic urethane mixed resin emulsion was changed from 6.5 g to 10.5 g, and the amount of water was 26
Example 1 was repeated except that the g was changed to 22 g. The specific gravity of the obtained unheated casting slurry was 1.4, and the fluidity and the stability over time were excellent. The demolding time was 1 hour. Table 1 shows the volume shrinkage after air drying.
As shown in Table 2, the fracture strength, bending strength and warpage were excellent, as shown in Table 1.

Example 4 As shown in Table 1, the amount of the acrylic urethane mixed resin emulsion was changed from 6.5 g to 12.5 g and the amount of water was 26
The procedure was the same as in Example 1 except that g was changed to 20 g. The specific gravity of the obtained unheated casting slurry was 1.4, and the fluidity and the stability over time were excellent. The demolding time was 1 hour. Table 1 shows the volume shrinkage after air drying.
As shown in Table 2, the fracture strength, bending strength, and warpage were excellent, as shown in Table 1.

Comparative Examples 1 to 3 The same procedures as in Example 1 were carried out, except that an unmodified acrylic resin emulsion was used instead of the acrylic urethane mixed resin emulsion. In this case, the amount of the acrylic resin used was such that the resin solid content of the acrylic urethane mixed resin emulsion of Example 1 was the same. In Comparative Examples 1 to 3, only the amount of water was changed. The physical properties of the obtained unheated casting slurry are as shown in Table 3, and the breaking strength is particularly 3770, 5490, 5810.
g / mm ^2, which was considerably inferior to each of the examples. The powder / water solution ratio in Table 3 is the same as in Table 1.

[0032]

[Table 3]

[0033]

The unheated casting slurry of the present invention is molded by using the conventional technique of casting into a gypsum mold.
In addition, the molded product can be easily removed in a short time, and the molded product that has been removed from the molded product has physical properties close to those of a baked product, a good coloring effect and a smooth feel, and fine expressions can be easily adopted. Molding is possible. Further, the gypsum mold casting technology using the non-heating casting slurry of the present invention,
Since the sintering step is not required, the economical and technical effects are extremely large due to the simplicity of handling, the simplification of equipment used, and the reduction of time.

Claims (1)

[Claims] 1. A rock powder clay composition of 1 to 1.8 parts by weight is mixed with 1 part by weight of an emulsion containing 3 to 20% by weight of an acrylic urethane mixed resin having a mixing ratio of 16: 1 to 110: 1. Unheated casting mud characterized by the following.