CS230769B1 - Process for preparing ceramic dough - Google Patents

Abstract

The invention relates to a method for preparing ceramic dough from granulate, which was produced by drying a suspension of ceramic mass containing deflocculating agents. The essence of the invention lies in the fact that the granulate is kneaded with a solution or dispersion containing 0.01 to 2.0 wt. % flocculating agents, preferably with a solution of magnesium sulfate, acetic acid or calcium hydroxide, to a dough of the desired consistency. Flocculating agents are preferably either mixed into the suspension from returnable waste and the suspension thus prepared is kneaded together with the granulate to a dough of the desired consistency, or deflocculating agents are mixed into the suspension and the suspension thus prepared is dried separately or in any ratio with the suspension to granulate.

Description

The present invention relates to a process for the preparation of ceramic dough having better rheological properties, higher mechanical strength after drying, while reducing the energy consumption of the preparation.

The ceramic dough has been made by kneading the granulated mass prepared by spray-drying the deflocculated suspension with water or water. a suspension of a return ceramic mass. The deflocculants present in forming the dough give rise to distinctly oriented textures, which makes it difficult to diffuse water from the product and further increases the anisotropy of shrinkage. The consequence is either a deformation of shape or more often a breach of the integrity of the product. Therefore, it has always been necessary to step away from deflocculation, and it is therefore necessary to produce thick-walled and more demanding products so far from doughs which do not contain declocating agents. This, however, has an adverse effect on the energy efficiency of the preparation of granulated nmota resp. granulation in a spray drier, since the deflocculants cannot be treated with a high solids concentration suspension which would meet the needs of spray drying due to its theological properties. It is known to solve this problem based on the fact that the effect of some deflocculating agents, in particular based on ammonium salts, is degraded during spray drying. However, this solution has some major disadvantages. The effectiveness of ammonium salt deflocculating agents is insufficient for many clay raw materials, so that the range of raw materials useful in this case is severely limited. Furthermore, the degradation of the effect of deflocculating agents in spray drying is never complete, and therefore the adverse consequences of the presence in the dough are more or less manifested.

The prior art methods of preparing ceramic dough from granulate improve the invention. SUMMARY OF THE INVENTION The granulate produced by drying a ceramic slurry containing a de-flocculating agent is bent with a solution or dispersion containing 0.01 to 2.0 wt. flocculating agents, preferably with a solution of magnesium sulfate, acetic acid or calcium hydroxide, to the dough of the desired consistency. The amount of the addition and the type of flocculating agents are controlled on the basis of the required technological properties of the processed ceramic mass. In the treatment of recyclable wastes Ceramic masses are advantageous to process the slurry from the recyclable wastes in two ways. Either flocculating agents are added to the slurry and the slurry 3e so treated together with the granulate to form a batter of desired consistency, or deflocculating agents are added to the slurry and the slurry thus treated is dried separately or in any ratio with the freshly prepared ceramic slurry to granulate.

The main advantages of this method of making ceramic dough are that ceramic materials containing deflocculating agents can be made into thick-walled and shape-intensive products without significant texture orientation, which facilitates the diffusion of water from the product during drying without distorting or breaking its integrity. Said preparation process, compared to only deflocculated ceramic mass, accelerates its filterability by up to 50%, while the values of mechanical strengths can be maintained or higher compared to the starting untreated mass.

Example 1

In the production of electroporcelain mass with a composition of 44% by weight. kaolins and clays, 55 wt. % of flake and Al 2 O 5, 21 wt. According to the invention, 2.5 kg of a protective colloid-type deflocculant - Humitan F (or Vanisperse) - are added to the freshly prepared suspension containing 1,000 kg of raw materials and 670 kg of water as a solution before adding kaolin. A suspension with an apparent viscosity of 0.16 Pas, as determined on a rotary viscometer at D = 457.4 s @ -1, is obtained.

After dewatering in a spray drier, a granulate is obtained which is sprinkled with a MgSO4 flocculant solution. For example, 250 kg of a 0.4% MgSO4 solution are added per 1000 kg of dry matter, where flocculation occurs due to cation exchange. After kneading, a suitable plastic dough is obtained.

- 3,230,769

The process according to the invention results in a reduction in the water content of the slurry from 850 kg to 670 kg based on 1000 kg of dry electroporcelain mass, an increase in mechanical bending strength of 20% compared to the untreated mass. Compared to the raw material »The proposed flocculation leads to an increase in filterability of 3% compared to the original raw material and compared to the deflocculated material by 50%, which is a measure of the formation of a suitable structure of the formed blank.

* Example 2

In the production of the electroporcelain mass of the same composition as in Example 1, 2 parts of the deflocculated return suspension are added to 1 part fresh deflocculated suspension. The apparent viscosity of the slurries is the same as in Example 1. The return waste is deflocculated with NH4OH to the apparent viscosity value shown in Example 1. By using an electrolyte which decomposes at a higher spraying temperature, no decomposition occurs at repeated deflocculation and flocculation to accumulate divalent and trivalent cations or protective colloids in the mass. A solution containing 0.12% by weight was used to flocculate the dried granulate. of acetic acid based on the dry weight of the porcelain mixture. Does flocculation occur through a dream mechanism _? pH. After kneading, the dough properties of Example 1 were obtained.

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Example 3

The electroporcelain composition of Example 1 was treated in the same manner except that a solution containing 0.41 wt.% Was used to flocculate the dried granulate. calcium hydroxide, based on the dry weight of the porcelain mass.

The invention can be used for technologies where it is formed from a plastic dough prepared either with a deliberately deflocculated suspension, or from a suspension which exhibits these properties based on the raw materials used or the distribution water used _.

Claims (3)

Process for preparing a ceramic dough from a granulate produced by drying a ceramic slurry containing deflocculating agents, characterized in that the granulate is kneaded with a solution or dispersion containing 0.01 to 2.0 wt. flocculating agents, preferably with a solution of magnesium sulphate, acetic acid or calcium hydroxide, based on the dry matter of the ceramic mass, to the dough of the desired consistency. 2. A process according to claim 1, wherein the flocculating agents are admixed with the granular recyclable slurry prior to kneading with the granulate. 5. A process according to claim 1, wherein the slurry prepared from the recyclable ceramic waste is deflocculated by the addition of 0.01 to 1% by weight. deflocculating agents and dried to the granulate alone or in admixture with a freshly prepared suspension.