DD151565A3 - METHOD FOR PRODUCING POLISHED EARTH - Google Patents

Abstract

The invention relates to a method for producing a polishing clay from aluminum trihydroxide. The aim of the invention is a cheap and energy-saving method for producing a Poliertonerde with very low amount of inferiority. For this purpose, the starting material used is bayerite with a residual moisture content of less than 3% by weight and a grain size between 45 and 125 m, ie in a continuously operating vibratory mill with at least two mixing chambers connected in series, with residence times of 30 minutes per grinding chamber while maintaining the initial structure, with a degree of comminution of 8 to 10 is ground. The starting material treated in this manner is then exposed to a temperature between 620 and 700 degrees for 36 to 48 hours and then cooled to 20 to 30 degrees C over 24 hours.

Description

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Title of the invention Process for the production of polishing earth

Field of application of the invention

The invention relates to a process for the production of polishing earth from aluminum trihydroxide.

Characteristic of the known technical

solutions

In DD-PS IO4315 a process for the preparation of a polishing body based on alumina is described which uses hydrargillite as a starting material. The hydrargillite 8 to 16 hours exposed to a temperature between 150 and 30O ⁰ C, subsequently calcined at 950 to 1050 ⁰ C and then cooled gradually. The product is then finally classified. This process has a number of disadvantages: in the initial stage of the annealing process, hydrothermal processes occur, which favor the formation of oc-alo-3 which is unfavorable for the polishing process and causes fogging,

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This reduces the quality of the final product. The application of polishable material is based on the feedstock, only about 30%, the amount of resulting inferior qualities is thus considerable. In addition, the end product must be subjected to stream classification in a classifier. However, this stream classification does not guarantee a sufficient separation limit due to the density differences present in the grain

Screen classification is no longer economically feasible in the case of technical implementation with a grain boundary of 45 / fcw.

The process is energy consuming, the stepwise cooling difficult to effect, the chamotte capsules used as auxiliary material expensive and of low life, the starting material expensive.

Object of the invention

The aim of the invention is a cheap and energy-saving process for the production of a polishing earth with a very low incidence of inferior qualities,

Explanation of the essence of the invention

The invention has for its object to provide a process for the production of polishing clay from aluminum trihydroxide, which allows, avoiding hydrothermal processes during annealing and waiving a gradual cooling, from relatively cheap starting materials, without a final classification process, high quality Produce polishing earth with high yield.

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According to the invention, this object has been achieved by using, as starting material, either Bayerit or Uordstrand.it or a mixture of both. In this case, the starting material has a residual moisture content of less than 3% by mass. Its grain size is between 45 and 125 ^ m, It is in a continuous vibrating mill, with at least two series-connected grinding chambers, z. B. a twin-tube vibratory mill, wherein prevail in the first grinding chamber at a residence time of 10 to 50 minutes, preferably 30 minutes, temperatures between 110 ⁰ C and 180 ⁰ C and in the second or subsequent grinding chambers, with the same residence times between 200 and 28O ⁰ C lie.

The starting material is comminuted while maintaining the starting structure, with a degree of comminution of 8 to 10, based on the average particle diameter. The thus-treated and crushed material is annealed for 36 to 48 hours at temperatures between 620 and 700 ⁰ C and then cooled to 20 bia 30 ⁰ C in a cooling time of 24 hours.

The process according to the invention has the advantages that the structure present in the starting material and essential for the polishing effect is destroyed neither by the milling process itself nor by the thermal decomposition into another form. In this case, the course of the thermal degradation and the resistance of the mold, which represents the final product, ie the polishing earth, γ / enig by foreign ions such as ITa, K, Fe, influenced.

In addition, a surface activation takes place in the tube vibrating mills. Processes that lead to the formation of undesirable forms for the polishing effect and to alpha - Al ₂ Oo hardly take place.

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The cooling regime is simple due to the tumble cooling, the use of metal capsules makes the work easier, they are also cheaper and longer life than Schaiaottekapseln, The application of polishable material is always over 80 %.

embodiment

The invention will be explained in more detail below using an exemplary embodiment.

Bayerit was used as starting material with a residual moisture content of less than 3% by mass, and its grain size ranged between 45 and 125. The bayerite had a layered, spherulitic structure in a continuously operating vibratory mill with two grinding chambers connected in series, here a twin-tube vibratory mill, ground.

The residence times in the individual grinding chambers were 30 minutes; the temperatures in the first grinding chamber between 110 and 180 ⁰ C, in the second milling chamber between 200 and 280 ⁰ C, the starting material was comminuted with a degree of comminution of 8 to 10, based on the average grain diameter.

As a result of this grinding process and the associated thermal treatment, the initial structure was largely retained in the comminuted material. There was extensive surface activation,

The crushed material was then calcined immediately in regard Metallkapsein for 40 hours at temperatures zv / 620 and 700 ⁰ C. The cooling was carried out by a tumble cooling, in which the material was cooled to 20 ⁰ C within 24 hours. The final product was a high quality polishing clay. The yield was 88 %.

Claims (1)

21,675 7 -s invention claim A process for the production of polishing earth from aluminum trihydroxide, characterized in that as starting material bayerite and / or Jordstrandstrandit having a residual moisture content of less than 3 percent by mass and a particle size between 45 and Λ25ΜΜ use, which in a continuously operating vibrating mill with at least two series mixing chambers , at residence times of 10 to 50 minutes, preferably 30 minutes per grinding chamber, with a degree of comminution of 8 to 10, based on the average grain diameter, ground, then the crushed material for 36 to 48 hours heated to a temperature between 620 and 700 ⁰ C. , and then cooled in a cooling time of 24 hours at 20 to 30 ⁰ C.