In this sector mouldings of high green strength are made by cold compression of ceramic powder produced beforehand by spray drying. In special ceramics it is important to have both high green strength in the moulding and the lowest possible viscosity in the aqueous ceramic slip, the necessary shear-dependent viscosity being achieved by the addition of Kuraray Poval™. If the slip needs to be further liquefied for particular uses, this can be done by adding Mowilith Ct 5 A approx 50% in solution, sodium hexametaphosphate and / or other dispersants.
In the case of low-viscosity compounds it should be noted that foaming may occur during vigorous mixing. To prevent this, additions of 0.02 – 0.3% defoamer, relative to Kuraray Poval™ (solid), are recommended. Kuraray Poval™ 3–83, 8–88, 18–88 and especially 4–88 (low ash), though also fully hydrolysed grades such as Kuraray Poval™ 10–98, have proved useful in the ceramics sector. These products are applied either alone or with an addition of up to 10% plasticizer (relative to Kuraray Poval™) such as glycerine, glycol, trimethylol propane, neopentyl glycol or polyglycol (up to a molar mass of 400). During development work on suitable formulations, consideration may be given to additions of paraffin emulsions or solutions of polyglycols with higher molar masses, the choice depending on the process technology.
Kuraray Co., Ltd.
