Gypsum & Lime

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The authors intended to improve the physical properties of plaster by moulding slaked lime with water soluble non-ionic highpolymers, investigated the physical properties of paste slaked lime moulded with one or two highpolymers [methyl cellulose (MC), polyvinyl alcohol (PVA), polyacrylamide (PAA), polyethylenoxide (PEO) and the effects of moulding on the hardened bodies and obtaied the following results.
1. In the case of moulding slaked lime with highpolymer aq solution which has the same viscosity, PEO remarkably increased the viscosity of slaked lime, but PVA little increased.
2. In the case that paste slaked lime moulded with highpolymer, indicate viscosity coefficient 20kg/sec near a standard softness, the results were as follows.
(1) Moulding quantity of PVA was 1.2% and its quantity was maximum among high polymers used. Moulding quantiny of PEO was 0.008-0.015%.
(2) Adding quantity of water had to increase about 20g/100g in moulding with PAA and to decrease about 12g/100g in PVA.
(3) Generally, flow value was rather small, hardness raised and water retention properties seemed somewhat to depend on adding quantity of water.
3. In the case of moulding with blended highpolymers, the blend of PEO and other highpolymer did not exhibit the moulding effects, though that of two of these MC. PVA. PAA made the effective physical properties changes.

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Sea-salt chemical gypsum is produced from concentrate brine and bitten. and its crystallization is affected by organic and inorganic substances.
It has been found in the present study that a fluctuation of 8-12 KMol and change in production ratio result when the company's manufatring facilities are used by fluctuation in the ion concentration of the row material and the SO₄^2- concentration even with inorganic substance.
The quality in this case is very stable and method of crystal growth by adjusting the production ratio, row material feed rate and production quality from the trend of crystallization was analyzed.
The relation of y=25.2-1.4 (4+x/5) (y=production quantity in KMol) (x= MgSO₄ g/L) was found during this analysis, the relative change in the flow rate of crystal growing tank and production ratio was confirmed and a production control diagram was prepared.

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