RU2391309C1 - Method of making ceramic objects - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to fine ceramic technology and can be used in making ceramic products for various purposes. The ceramic slip preparation method involves preliminary thermal treatment of clay material with quarry moisture through hydrothermal treatment in an autoclave at saturated vapour temperature of 168-250C for 3-60 minutes with an accelerated mode of raising and decreasing vapour pressure, preparation of the slip through wet grinding, moulding, drying and roasting. The accelerated mode of raising vapour pressure is achieved by releasing vapour from a used autoclave with stabilised material into an autoclave with already loaded starting material. ^ EFFECT: increased strength, reduced water absorption and density of products. ^ 2 cl, 1 ex, 3 tbl

Description

The invention relates to the technology of fine ceramics and can be used in the manufacture of ceramic products for various purposes.

A known method of manufacturing ceramic products, including grinding in a ball mill clay materials, rocky materials, water and electrolytes to a residue on sieve No. 006 of not more than 2%, followed by stabilization of the slip for 5-7 days. Next, the products are molded by casting in plaster molds, drying and firing the castings at a temperature of 1180-1280 ° C [Moroz I.I. Technology of porcelain and faience products / I.I. Moroz. - M .: Stroyizdat, 1984. - 334 p.].

The disadvantages of this method are the variability of the properties of clay raw materials, the duration of the process of stabilization of the slip, the need to use expensive electrolytes, low physical and mechanical characteristics of the finished product.

There is also a method for preliminary preparation of clay raw materials by heat treatment at a temperature of 600-700 ° C in a rotary kiln [A.S. 317635 USSR, IPC ⁷ С04В 33/00. The method of preparation of ceramic products / V.I. Utkin (USSR). - No. 1434354 / 29-33; declared 04/27/70; publ. 10/19/71. Bull. No. 31. - 2 p.].

The disadvantages of this method are the destruction of the structure and a partial change in the phase composition of clay raw materials after heat treatment, a decrease in the rheological properties of clays and kaolins, and a deterioration in the physicomechanical characteristics of finished products obtained by molding by molding.

The invention is aimed at stabilizing the structure of clay raw materials in the process of their preparation, improving the rheological properties of slip based on clay and kaolin, increasing the strength of finished ceramic products based on stabilized raw materials.

The technical result according to the invention is achieved by the fact that clay raw materials with a career humidity of 15-25% are preliminarily subjected to hydrothermal treatment at temperatures of 151-263 ° C for 3-60 minutes with an accelerated mode of rising and depressurizing steam, which is carried out by venting steam from a spent autoclave with stabilized feed in an autoclave with the feed material already loaded.

Example. Kaolins of the Glukhovetsky (22 wt.%), Prosyanovsky (2 wt.%) And Kyshtymsky (5 wt.%) Deposits, clay: Granitik-Vesko (9 wt.%), Ceramic-Vesko (12 wt.%) And Latensky LT -1 (3 wt.%) Is subjected to hydrothermal treatment at temperatures of 151-263 ° C and saturated steam pressures of 0.5-5 MPa. Further, clay materials, as well as Vishnevogorsk feldspar (15 wt.%), Quartz sand (22 wt.%), The battle of sanitary products (10 wt.%), Water glass (0.5 wt.%) Are wet milled with humidity 32% The rheological characteristics of the finished slips are presented in table 1. Examples 3 and 8 in table 1 are negative.

Table 1 Rheological characteristics of injection slips No. The method of processing clay raw materials Processing conditions Expiration time after 30 s, s The coefficient of thickening Temperature ° C Vapor pressure, MPa one By analogy - - fourteen 7.5 2 According to the prototype 600 - 16 9.1 3 The proposed method 151 0.5 12 8.9 four 168 0.8 eleven 2.6 5 183 1,0 8 1.5 6 223 2.5 8 1,2 7 250 4.0 7 1,1 8 263 5,0 7 1,2

In the methods of processing clay according to the analogue (holding the slurry in time for 5 days) and the prototype (processing clay at a temperature of 600 ° C) (examples 1 and 2 of Table 1), slip agents have high thickening coefficients, which makes them unsuitable for molding products using injection technologies .

Processing in hydrothermal conditions at a temperature of 151 ° C (0.5 MPa) (example 3) does not lead to stabilization of raw materials and a significant decrease in the coefficient of thickening - a negative example by the proposed method. The increase in temperature (168-250 ° C) and pressure (0.8-4 MPa) of hydrothermal stabilization of clays helps to streamline the structure of clay raw materials and significantly improve the rheological characteristics of multicomponent ceramic suspensions (examples 4-7 table 1). A further increase in temperature to 263 ° C and pressure up to 5 MPa (example 8) is impractical because it requires additional energy costs and complicates the process without significant improvement in the properties of the slip - a negative example by the proposed method.

Hydrothermal stabilization of clays and improvement of the rheological characteristics of the slip is carried out during the processing of 3-60 minutes (examples 2-6 table 2).

table 2 Rheological characteristics of injection slips No. The time of hydrothermal processing of clay raw materials at a temperature of 183 ° C, min Expiration time after 30 s, s The coefficient of thickening one No processing fourteen 7.5 2 one 12 5,0 3 3 10 2.6 four 10 8 1,5 5 thirty 8 1,2 6 60 8 1,1 7 120 8 1,1

Reducing the processing time to 1 min does not provide complete heating and the necessary structural stabilization (example 1, table 2) - a negative example by the proposed method. Increasing the hydrothermal stabilization time to 120 or more minutes is also impractical (example 7), since it requires additional energy costs without significantly improving the properties of the slip — a negative example by the proposed method.

From the obtained slip products are molded into plaster molds, dried and fired at a temperature of 1180 ° C. Physico-mechanical characteristics of the finished products are presented in table.3. Hydrothermal stabilization of clay raw materials has a significant impact on the sintering and formation of the properties of ceramic products. The physico-mechanical characteristics of ceramics increase almost 2 times, which is associated with a more uniform implementation of structural phase transformations during sintering and the formation, ultimately, of a more perfect structure of the ceramic crock.

Table 3 Physico-mechanical properties of ceramic samples No. Clay processing Density, kg / m ³ Water absorption,% Compressive strength, MPa one By analogy 2290 1,1 86 2 According to the prototype 2180 5.1 48 four According to the proposed method at a temperature of 183 ° C for 30 minutes 2330 0.6 151

To increase the productivity of hydrothermal processing equipment, the rise in steam pressure and temperature during processing should be carried out with maximum intensity. This can only be achieved by discharging steam from an autoclave that has already been used up in the production cycle to a second autoclave with raw materials loaded. In this case, a quick but smooth decrease in temperature is achieved in the first autoclave with already stabilized raw materials. As a result, the maximum ordering of the crystalline structure of clay materials is ensured.

The proposed method allows to stabilize the structure and properties of clay raw materials, to reduce the viscosity of clay suspensions by 5-10 times or the amount of injected thinner, to form a necessary set of properties of injection slips and obtain ceramic products with high physical and mechanical characteristics.

Claims (2)

1. A method of preparing ceramic slips, including preliminary heat treatment of clay raw materials with quarry moisture, preparing a slurry by wet grinding, molding, drying and firing, characterized in that the clay raw material is preliminarily subjected to hydrothermal treatment in an autoclave at saturated steam temperatures of 168-250 ° C for a time 3-60 min with accelerated mode of lifting and depressurizing steam pressure. 2. The method of producing ceramic products according to claim 1, characterized in that the accelerated mode of raising the vapor pressure is carried out by dumping the steam from the spent autoclave with stabilized raw materials into the autoclave with the source material already loaded.