JPH0818299B2 - High-strength cast molding manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for obtaining a molded product having high green strength by a slurry casting molding method.

(Prior Art) The sludge casting method has been widely used in the ceramics field for a long time, but it is easy to form complicated shapes uniformly and is suitable for various small-volume production with low equipment cost. Due to its advantages, its application in the field of fine ceramics is spreading in recent years.

(Problems to be Solved by the Invention) However, it is difficult to increase the green strength of a molded body by cast molding, and it is difficult to obtain a large green strength particularly in a base material that does not use clay as in the field of fine ceramics.

Organic binders such as carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), sodium alginate, acrylic resin, and starch can be added to increase the green strength. Not only does it have a large effect on the characteristics of the slurry, such as impairing the characteristics and reducing the inking rate, but it also has the drawback that it is absorbed by the mold and causes clogging, resulting in deterioration of the mold. There was a limit and it was hard to say that it was an effective method.

Therefore, an object of the present invention is to find a casting method capable of obtaining a molded product having high green strength without greatly affecting the characteristics of the slurry and the properties of the mold.

(Means for Solving the Problem) The present invention has been found as a result of earnest research for achieving this object. The method for producing a high-strength cast-molded article is the addition of zirconium chloride to polyvinyl alcohol or a derivative thereof. The resulting polyvinyl alcohol polymer is mixed with ceramics casting slurry in an amount of 0.1 to 5% by weight and cast-molded, and the resulting molded body is heat-treated at 50 to 150 ° C.

 The present invention will be described in detail below.

The polyvinyl alcohol polymer used in the method for producing a cast molded article according to the present invention is polyvinyl alcohol or a derivative thereof to which zirconium chloride is added (Japanese Patent Publication No. 50386386), which is used to prepare a ceramic cast slurry. Sometimes added together with the raw materials and mixed with a ball mill, or added into the prepared slurry and mixed with a stirrer. Since this additive is mainly composed of a polyvinyl alcohol-based polymer, it has excellent storage stability in a sludge state and is extremely stable even when left for a long time without causing viscosity increase or gelation. However, when the sludge becomes alkaline at pH 8 or above, it gels, so the sludge should be kept at pH 8 at all times.
It is important to keep the following neutral or slightly acidic.

The amount of polyvinyl alcohol polymer added to the slurry is 0.1 to 5% by weight, more preferably 0.2 to 2% by weight.
Is appropriate. If the addition amount is less than 0.1%, the effect of increasing the strength is not sufficient, and if it exceeds 5% by weight, not only the drying becomes difficult but also it takes a long time to decompose the organic matter due to excessive firing. .

The slurry to which the polyvinyl alcohol polymer has been added is then poured into a plaster mold and cast molding is performed. That is,
Using the water absorption of the plaster mold, the surface of the plaster mold is inlaid with a base material to obtain a molded body.

The obtained molded product is left as it is at room temperature in a water-containing state or is heat-treated at 50 to 150 ° C., so that the polyvinyl alcohol-based polymer in the matrix has zirconium as a cross-linking agent between polyvinyl alcohol molecules. In order to form

In this method, if the cutting occurs during the drying process, such as thick wall, complicated shape, or large shrinkage of the base material by drying, after heating in air with saturated humidity of 60 ° C or more, dry it. Good. Also, because the strength of the molded body is extremely low, so that it is likely to break during the process of taking out from the gypsum mold, heat the whole gypsum mold in air with a saturated humidity of 60 ° C or higher, and then remove it from the mold. Is appropriate.

Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples. In the examples, parts and% mean parts by weight and% by weight, respectively.

Example. To 100 parts of fine alumina having an average particle diameter of 0.5 μm, 0.6 part of a special polyacrylic acid copolymer (trade name C-24, manufactured by Nippon Kayaku Co., Ltd.) as a deflocculant and 31 parts of water were added. , Mixed with a ball mill to make alumina slurry, and zirconium chloride added to polyvinyl alcohol polymer as a binder (trade name ZIM-100, manufactured by Takamatsu Yushi Co., Ltd.),
Add 0.4 parts and 1 part respectively, mix well with a ball mill, then pour into a plaster mold and 14 mmφ x 140 mm
The round bar-shaped sample of was molded, demolded, and put in a dryer at 60 ° C. to dry.

Besides, polyvinyl alcohol (trade name PA-05, manufactured by Shin-Etsu Chemical Co., Ltd.), acrylic emulsion (trade name WA-320, Mitsui Toatsu Chemical Co., Ltd.) as binders, respectively.
The properties of a slurry to which a water-soluble acrylic resin (trade name: KS-900, manufactured by Nippon Kayaku Co., Ltd.) was added were examined and used as a comparative example.

The inking rate is indicated by the thickness of the gypsum 20 minutes after pouring sludge into the gypsum mold. Also, the dry strength of the cast moldings is shown in the table.

In addition, PVA, AE, SAR
“A” means each of the above-mentioned polyvinyl alcohol, acrylic emulsion, and water-soluble acrylic resin.

The dry strength of the product without the binder was extremely low at 10.0 kgf / cm ^2, and there was a problem in handling the product. Dry strength is 25.0kgf / cm ² by adding 0.4% of polyvinyl alcohol.
However, the inking rate was low and there was a problem in practical use. Further, in the acrylic resin-based binder that has been widely used in recent years, a dry strength of 40 to 50 kgf / cm ² cannot be obtained unless the added amount is 1 to 2%. On the other hand, in the case of using the polyvinyl alcohol-based polymer of the present invention, both the viscosity of the slurry and the inking rate are not inferior to others, and the dry strength is 61.0 kgf / cm ² when added in a small amount of 0.4%. The addition of 1.0% resulted in a further 90 kgf / cm ² .

Furthermore, when this sample was fired at 1620 ° C. for 2 hours, a sintered body having a relative density of 99.5% was obtained, and it was found that the addition of the polyvinyl alcohol polymer did not have any adverse effect on the compaction of the molded body. It was

(Effect of the invention) As is clear from the results of the above examples, according to the present invention, only the green strength of the molded product is significantly improved without significantly changing the properties of the slurry such as the water content and the inking rate of the cast slurry. Therefore, it is particularly useful for cast molding of non-clay-based materials such as fine ceramics, which tend to cause insufficient green strength.

Claims (1)

[Claims] 1. A polyvinyl alcohol-based polymer obtained by adding zirconium chloride to polyvinyl alcohol or a derivative thereof is mixed with ceramics casting slurry in an amount of 0.1 to 5% by weight and the mixture is cast-molded. ~ 15
A method for producing a high-strength cast-molded product, characterized by performing heat treatment at 0 ° C.