KURARAY POVAL™ as a Temporary Binder

Ceramic compounds

KURARAY POVAL is outstandingly suitable as a temporary binder and plasticizer for ceramic compounds. It breaks down almost entirely into water and carbon dioxide when a ceramic moulding is fired. The possible applications depend essentially on the nature of the ceramic compound and the moulding process. The quantities used vary considerably, depending on the technology applied, in the range 0.1 – 5%, relative to the dry mix. KURARAY POVAL is particularly effective as a temporary binder in special ceramics (technical ceramics). 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.      

Advantages of using KURARAY POVAL as a temporary binder in the ceramics sector:

  • Low viscosity of the aqueous slip before drying and hence less water to evaporate (energy saving)
  • Low binder requirement
  • Low ash content (electroceramics)
  • Little waste through breaking (re-usable)
  • Smooth burn-out profile
  • Low shrinkage during firing No clogging of screens, filters and moulds