DD155820A1 - PROCESS FOR PRODUCING CERAMIC PRODUCTS - Google Patents

Abstract

The invention relates to the production of ceramic products that are used as Sanitaer- and baukeramische articles, stoneware, porcelain and corrosion and heat-resistant building materials. The object of the invention is to save the natural and synthetic fluxes required for the production of ceramic products and to enable the use of novel raw materials. At the same time total energy consumption u. Number of process stages for the manufacture of the products can be increased. The fluxes, which are traditionally contained in the ceramic offset, are replaced by water-soluble alkali and alkaline earth compounds, and the viscous fractions Schlaemmkaolin u. Clay completely or partly by raw clay, raw kaolin and partially bound kaolin. This mixture is dimmed, ground, spray-granulated molded by pressing and sintered in a known manner. Alkalis or salts can be used as the water-soluble alkali or alkaline earth compounds. It can be produced in this way ceramic products that reach or exceed the values of conventional articles in terms of strength and whiteness.

Description

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Title of the invention

Process for the production of ceramic products

Field of application, the invention

The invention relates to a process for the production of ceramic products which can be used as sanitaryware and building ceramic articles, stoneware, household and industrial porcelain, electrotechnical and chemical-technical porcelain as well as corrosion and heat-resistant building materials such as acid-resistant stones and the like.

Characteristic of the Known Technical Solutions It is known that ceramic offsets are composed in a traditional manner from the components slurry kaolin and / or clay, quartz or quartz sand as well as feldspar and / or feldspar sand or feldspathic rocks (Haase, T. "Keramik"). In special cases, alumina (DL-PS 23.685), mullite-rich calcined kaolin and lime and dolomite (Haase, T. "ceramics") can also be introduced into the offset. The ingredients Schlämmkaolin and clay give the ceramic mass in conjunction with a certain water content of a high degree of flexibility, as required for shaping, for example by extrusion. During the shaping of such plastic masses, the alignment of the particles results in the formation of textures. These textures, in conjunction with the shrinkage that occurs on the molded article during drying and sintering, can result in deformation and cracks in the article. Furthermore, different material properties are measured in different spatial directions.

The components feldspar, feldspar sand, lime and dolomite have a sintering-promoting flux effect in the offset. Equal-

In time they are characterized by the fact that the alkalis and alkaline earths are present in them in water-insoluble form. In place of said natural fluxes, fluxes prepared for synthetic use have also been proposed for use in ceramic displacement. This concerns, for example, a synthetic flux with Feldspatähnlichen properties, which can be made of Schlämmkaolin, alkali compounds added with the addition of natural feldspar or feldspar sand by pressing, sintering and subsequent crushing (DL-PS 116,594) and up to 60 weight percent can be included in a porcelain offset. In this method, it is to be criticized that for the synthesis of the flux high additional investment and energy costs through the process stages pressing, sintering and grinding are required.

It was :, furthermore, a method in which, with complete abandonment of the viscous components clay and Schlämmkaolin ceramic offsets of feldspar and synthetic mullite and optionally clay and Zirkonsi.likat are constructed and these completely unplastic offsets by modern shaping methods, such as Isostatic pressing, molded (DT-OS 1,646,395). A disadvantage is that these non-plastic discontinuities require very high compressive pressures or the addition of expensive organic binders and plasticizers in order to be able to be molded into articles of sufficiently high green strength. In addition, also here for the synthesis of the non-plastic components, such as the mullite * plant, cost and energy-intensive additional process stages are required. As a result, for example, two high-temperature processes must be operated - once for synthesizing the resulting in the subsequent ceramic fire phases such as mullite and glass phase and on the other hand, the actual ceramic fire for the production of the product.

Object of the invention

The object of the invention is to save in the production of ceramic products, the natural and synthetic flux and to use other raw materials, so as to achieve a reduction in the process stages required for the production and the total energy expenditure while maintaining or improving the properties of the products.

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Explanation of the essence of the invention

The invention has for its object to provide a process for the production of ceramic products with improved properties, processing offsets without natural Feldspäte or without sintered synthetic flux with simultaneously reduced content of plastic components and reduces the number of process stages and the total energy expenditure compared to known methods become. According to the invention, the object is achieved in that the natural Feldspäte and / or synthetic flux in the offset replaced by appropriate levels of water-soluble alkali and / or alkaline earth and the vapourous Schlämmkaolin and / or clay completely or partially by raw clay, Rohkaolin and / or teilgeschlämmten Kaolin exchanged, this mixture verschlimmert, ground, processed by suitable methods such as spray drying into granules and molded by dry pressing or isostatic pressing and sintered in a known manner. The natural feldspars and / or synthetic fluxes can be partially or completely replaced by water-soluble alkali and / or alkaline earth compounds. , An inventive feature is that Rohkaolin or teilgeschlämmter kaolin is introduced in proportions of 5 to 99.5 weight percent in the total dry offset. It is also advantageous to limit the content of viscous components in the dry offset to = 40 percent by weight in order to achieve an improvement in the pressing properties of the mass. Another feature of the invention is characterized in that the alkali or alkaline earth compounds are introduced into the ceramic offset in solid or dissolved form as salts or alkalis or mixtures thereof, wherein the Oxidgehalte imtrockenen total offset 0.5 to 15 weight percent , preferably 2-8 Make up weight percent.

Example examples

The invention will be explained in more detail below with reference to two embodiments. According to a first embodiment, an inventively constructed offset, which corresponds in the chemical composition of a traditional dish porcelain mass, is composed as follows:

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32.5% by weight Rohkaolin 64.8% by weight Schlämmkaolin

2.7% by weight K ₀ O; which in the form of KOH or K ₀ CO ₀

c. 2 3

may be present

 2nd example

A quartz-richer mass according to the invention is composed as follows: '97.1 weight percent Rohkaolin 2.9 weight percent K ₀ O, which in the form of KOH or K ₀ CO ₀

may be present.

The preparation of these offsets is carried out in the same way by mixing with water to form a slurry and fine grinding in a drum mill on Verarbeitungs'feinheit traditional porcelain masses. The ground slurry becomes a compressible one in a spray drying process. Processed granules. After dry pressing or isostatic pressing at a pressure

of for example 100 N / mm and the sintering in rapid firing (total burning time 2 - 2.5 hours) or normal firing (total burning time 10 - 15 hours) at 1400 degrees Celsius Ausbrenntemperatur to obtain IVerkstoffe with the following properties in the unglazed state: Normal firing: -

Example 1 Example 2

2 bending strength (N / mm) > 60 > 95 Water absorption (%) 0 0 linear burning shrinkage (%) 8-10 11 Quick fire; example 1 Example 2

Flexural strength. (N / mm)> 60 88-94

iAvoid {%) 0 0

linear firing shrinkage {%) 8 - 10 8-9

Content (%) - 79-84

All compacts have breaking strength> 4 N / mm in the raw state without the addition of organic binders.

The high tVeißgehalt of Example 2, obtained in rapid firing under oxidizing atmosphere, is due to the low pollutant content of the mass (TiO "+ FepO" = 0.2 weight percent). , "- 5 -

Claims (1)

, Process for the production of ceramic products, wherein in a known manner an offset is acidified with the addition of water, ground, processed by spray drying into a compressible granulate and by known methods of pressing and sintering to a ceramic material, characterized in that the offset of natural and / or synthetic aluminosilicate substances with water-soluble alkali and / or alkaline earth metal compounds is produced. , A method according to item 1, characterized in that the dry offset of Rohkaolin or teilgeschlämtem kaolin in proportions of 5 to 99.5 weight percent and with the remaining portions of water-soluble alkali and / or Erdalkaliver-. and slurried kaolins. , Method according to item 1, characterized in that the water-soluble alkali and / or alkaline earth compounds are introduced in the form of lyes and / or salts in solid and / or dissolved form in the offset, wherein the oxide contents in the offset amount to 0.5 to 15 weight percent , , Method according to points 1, 2 and 3, characterized in that the granules produced from the offset by spray drying is processed under simultaneous action of pressure and temperature to the ceramic semi-finished or finished product.