CS218316B1 - A method for producing gypsum products with controlled mechanical strength - Google Patents

Abstract

The invention relates to a method of processing gypsum into gypsum products, in which a gypsum suspension of any concentration is dewatered and expanded by pressure filtration at a pressure of 10 to 100 MPa, while the bending strength of the moldings in the range of up to 70 MPa is controlled by the filtration pressure and fillers.

Description

The invention relates to a process for processing gypsum into gypsum products.

Heretofore, gypsum products have been made by casting a gypsum slurry in water into molds of various materials. The strength of the products thus prepared depends on the type of gypsum and mainly on the water content of the gypsum slurry. The water content of the gypsum suspension is usually 40%. This relatively high water content determines the high porosity of the gypsum products and hence the low mechanical strength.

The water content cannot be reduced in the present treatment, even if it is 3 times higher than the theoretical need for hydration, since the gypsum slurry with decreasing water content leads to an increase in viscosity and a loss of casting properties, - workability.

According to the invention, a number of drawbacks common to the prior art gypsum process can be overcome by the fact that gypsum suspensions with an arbitrarily high water content, an amount for hydration and preferably higher than required in the above-mentioned conventional operation are treated by pressure filtration in a pressure range of 10 to 100. MPa in a metal matrix whose punch is porous, thus allowing excess water to flow. The die closed by the punch defines the shape of the product.

During pressure filtration, the suspension is thickened in the first phase and further dewatered and compacted by further increasing the compression pressure so that the final gypsum molding contains little more water than theoretically required for complete hydration. This achieves the maximum strength of the plaster molding.

This maximum achievable molding strength can also be reduced either by using lower compression pressures or by using 10 to 90% fillers, preferably solid, microporous, such as fine quartz, fireclay, ground gypsum dihydrate from discarded products.

The moldings produced according to this process are dried in a manner customary for gypsum products, i.e. at a temperature of less than 60 ° C.

The process according to the invention is described in more detail in the following examples.

Example 1

In the usual processing, u

6

The sample of S-Gypsum at a water coefficient of 0.7 reached a flexural strength after drying of 3.8 MPa. In the process according to the invention, a suspension containing 60% of water was prepared, thoroughly mixed and dewatered by means of pressure filtration, the compacting being carried out at a final pressure of 40 MPa. The molding contained only 18% of water and, after drying, showed a bending strength of 30 MPa.

Example 2

In a similar manner to Example 1, α-gypsum was treated. The bending strength up to 7 MPa was achieved in the normal processing, with a pressure filter ^! 55 MPa. Example 3

When using a / 3-paris and 30% filler (silica sand of less than 60 _(microns] was obtained by pressure filtration of the bending strength of 25 MPa.

He attaches

When used (3-gypsum with micro-porcelain fireclay with grain size up to 60 μ vη in the amount of 70%), a pressure bending strength of 4.1 MPa was achieved by pressure filtration.

Example 5

Using x-gypsum in admixture with 80% gypsum from discarded gypsum products with a grain size below 0.2 mm and a filtration pressure of 50 MPa, a bending strength of the molding of 6.0 MPa was achieved.

The process according to the invention has a number of advantages. In addition to the possibility of achieving high mechanical strength of the gypsum products, it is far less energy-intensive, since 3 times less water evaporates from the lumps during drying. In addition, a much higher work productivity can be achieved in this way. Working in the ceramics industry is also reduced by the use of this method by eliminating the need for model and reproduction equipment.

Claims (2)

печет Process for the manufacture of gypsum products having controlled mechanical bending strength up to 70 MPa, characterized in that the gypsum slurry with water is dewatered and compacted by filtration at a pressure of 10 to 100 MPa, the pressure being controlled by the desired degree of compacting. YNÁLEZU 2. Process according to claim 1, characterized in that 10 to 90% by weight of a filler, preferably a solid microporous substance, based on the weight of the gypsum, is added to the aqueous gypsum suspension.