DD155820B1 - METHOD FOR PRODUCING CERAMIC SUBSTITUTES - Google Patents

Description

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embodiment

The invention will be explained in more detail with reference to 18 exemplary embodiments.

example 1

The inventively constructed offset, which corresponds in the chemical composition of a traditional dish porcelain mass, is composed as follows:

32.5% by weight crude kaolin

64.8% by weight of Schlämmkaolin

2.7% by weight of K ₂ O, which may be in the form of KOH or K ₂ CO _3. The processing of the batch is carried out by mixing with water to give a slurry and fine grinding in a drum mill on a processing unit of traditional porcelain masses. The ground slicker is processed in a spray-drying process into a compressible granulate. After dry pressing or isostatic pressing at a pressure of 100 N / mm ² and the sintering in rapid firing (total duration 2-2.5 hours) or normal firing (total duration of 10-15 hours) at 1400 degrees Celsius burnout to obtain a material having the following properties unglazed: normal firing:

Bending strength (N / mm ² )> 60

Water absorption (%) 0

linear firing shrinkage (%) 8-10

Fast firing:

Bending strength (N / mm ² )> 60

Water absorption (%) 0

linear firing shrinkage (%) 8-10

The compacts have breaking strength> 4 N / mm ² in the raw state without the addition of organic binders.

Example 2

A quartz-richer mass is composed according to the invention as follows:

97.1% by weight of crude kaolin

2.9% by weight of K ₂ O, which may be in the form of KOH or K ₂ CO _3. The preparation and further processing of the offset are carried out as in Example 1. A material with the following properties was obtained in the unglazed state: Normal firing:

Bending strength (N / mm ² )> 95

Water absorption (%) 0

linear burning shrinkage (%) 11

Fast firing:

Flexural strength (N / mm ² ) 88-94

Water absorption (%) 0

linear firing shrinkage (%) 8-9

Whiteness (%) 79-84

The compacts have without addition of organic Bindemitte) in the raw state breaking strengths> 4N / mm ² . The high white content, achieved in rapid firing under oxidizing atmosphere, is due to the low pollutant content of the mass (TiO ₂ + Fe ₂ O ₃ = 0.2Gew .-%).

Example 3

The offset according to the invention is composed as follows: 99.5% by weight partially ground kaolin (21.5% Al ₂ O ₃ ) 0.5% by weight KOH (caustic potash, solid, anhydrous) The batch was mixed with water and placed in a drum mill the fineness of a stoneshift offset crushed. Thereafter, the slurry is spray-dried and the granules compacted by pressing. It was possible to produce compacts with a raw breaking strength> 2.5 N / mm ² . The compacts were sintered at 1 200 ⁰ C. The sintered material has typical earthenware properties:

Flexural strength (N / m ² ) 18-20

Water absorption (%) 16-18

The color of the piece is pure white

This can ben glazed wt, u: n, d.Tbei the glaze firing is preferably carried out at 1 080-1 150 ° C.

Example 4

The offset according to the invention is composed as follows: 5% by weight crude kaolin 15% by weight CaCl ₂ (solid, anhydrous) 80% by weight slurry kaolin (31% Al ₂ O ₃ ) The offset was prepared as described in Example 3, spray-dried and pressed. The blanks have a raw breaking strength of> 2.8 N / mm ² . They were sintered at 1100 ° C and have typical characteristics of a limestone:

Flexural strength (N / mm ² ) 20

Water intake (%) 18

The color of the piece is pure white

This piece of glass can be glazed, the glaze firing is preferably at 1 050-1 080 ⁰ C.

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Example 5

The offset according to the invention is composed as follows: 9.1% by weight KOH (caustic potash, solid, anhydrous) 25.0% by weight NaOH (20% strength) 65.9% by weight crude kaolin The batch is made up to a slurry with water and crushed in drum mills to a particle size <63μ.Γη. The slurry is spray-dried and the granules are compacted by isostatic pressing (P = 50 MPa). The compacts have a raw breaking strength> 4 N / mm ² . After sintering at> 1 200 ⁰ C they have the following properties: bending strength (N / mm ² ) 9.0 ... 15.0

Water absorption (%)

Whiteness {%)

Example 6

The offset consisting of 99.5% by weight of crude kaolin 0.5% by weight of K ₂ O (in the form of KOH or K ₂ CO ₃ ) is mixed with water and comminuted to <0.1 mm in a drum mill. The further processing takes place by spray drying and by isostatic pressing. The moldings are sintered at 1400 ° C. Thereafter, the material has a white body with <10Vol .-% residual porosity and a flexural strength> 15,0 N / mm ² . The material can be used for small-sized insulating parts.

Example 7

The offset, consisting of

5% by weight partially ground kaolin (21% Al ₂ O ₃ ) 92.3% by weight slurry kaolin (flux-rich, eg kaolin rope seat) 2.7% by weight K ₂ O (in the form of KOH or K ₂ CO ₃ ) is mixed with water, comminuted to <90μΓη in a drum mill and spray-granulated. The granules with a humidity of 2.5% is isostatically pressed at 15-30 MPa and dense sintered at 1 350-1 400 ⁰ C to a material with porcelain properties.

Example 8

The offset consisting of 70% by weight partially ground kaolin (<0.1 mm, 70% quartz) 67.3% by weight slurry kaolin (37% quartz) 2.7% by weight K ₂ O (in the form of KOH or K ₂ CO ₃ ) is mixed with water, comminuted to <90 μm in a drum mill and spray-dried. The granules are processed according to Example 7 and you get a material with porcelain properties.

Example 9

The offset consisting of 70% by weight partially ground kaolin (<0.12 mm, 65% quartz) 27.1% by weight slurry kaolin (85% clay substance) 2.9% by weight K ₂ O (in the form of KOH or K ₂ CO ₃ ) is made up with water, ground to <40dt and spray-dried. The granules are pressed at a pressure> 100 MPa into moldings and dense sintered at 1300-1 350 ⁰ C. The material has typical properties of a technical porcelain, in particular:

electrical breakdown strength (kV / mm)> 30

open porosity (%)

Bending strength (N / mm ² )> 95

Example 10

The offset, consisting of 78.9 wt .-% Rohkaolin 6.1 wt .-% KOH (solid, anhydrous) 15.0 wt .-% NaOH (20%) is mixed with water and in the drum mill to <63μΓη crushed. The slurry is spray dried and isostatically pressed at 50 MPa. The moldings have a raw breaking strength of> 3N / mm ² . After sintering at> 1 25O ⁰ C, the porcelain-like sintered products have a flexural strength of> 90 N / mm ² .

Example 11

The offset, consisting of

99.3% by weight of crude kaolin

0.7% by weight of Ca (OH) ₂ (dry) is mixed with water and ground in the drum mill to a fineness of earthenware offsets. This is followed by spray drying and isostatic pressing of the granules. After sintering at 1200 ° C, the products have a pure white body with 15-19% water absorption and a flexural strength of> 18N / mm ² .

Example 12

The offset, consisting of

96.4% by weight of crude kaolin

3.6% by weight of Ca (OH) ₂ (dry) is processed according to Example 11. After sintering at 115o C ⁰ is obtained a white-like earthenware body with <19% water absorption, and a bending strength 5:18 N / mm ^2. The shards can be glazed, wherein the glaze is preferably baked at 1 080-112O ⁰ C.

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Example 13

The offset, consisting of 80 wt .-% Rohkaolin 20 wt .-% Ca (OH) ₂ (dry) is processed according to Example 11. After sintering, which should take place at temperatures> 1 200 ° C, depending on the sintering temperature, porous or dense, pure white shards with the following properties are obtained:

Flexural strength (N / mm ² ) 30-60

Water absorption (%) 0-10

Example 14

The offset, consisting of 80.8 wt .-% Rohkaolin

16.2% by weight Ca (OH) ₂ (dry)

3.0 wt .-% KOH (solid, anhydrous) is mixed with water, ground to <60μ.Γη, spray-dried and isostatically pressed. The sintering is preferably carried out at 1150-1 250 ⁰ C. There are pure white porous to dense shards obtained with a flexural strength of 30 to 85 N / mm ² and a water absorption of 0-15%.

Example 15

The offset, consisting of 87.0 wt .-% Rohkaolin 10.0 wt .-% Ca (OH) ₂ (dry) 3.0 wt .-% KOH (solid, anhydrous) is processed according to Example 14. After sintering at> 1 200 ° C white shards are obtained, which have depending on the residual porosity earthenware to porcelain properties.

Example 16

The offset, consisting of 94.0 wt .-% Rohkaolin 3.0 wt .-% Ca (OH) ₂ (dry) 3.0 wt .-% KOH (solid, anhydrous) is mixed with water, to a fineness of <60μΓη crushed and spray dried. The granules with a humidity of 2% is isostatically pressed at a pressure of s 100MPa. The moldings are densely sintered at> 1300 ⁰ C and then exhibit typical properties of technical porcelain.

Example 17

The offset, consisting of

65.3% by weight crude kaolin 30.0% by weight slurry kaolin 4.0% by weight Ca (OH) ₂ (dry) 2.0% by weight KOH (solid, anhydrous) is triturated with water to a fineness <60μηη ground and spray dried. The granules with a moisture content of 2 ± 0.5% is isostatically compacted at a pressure of 20-50 MPa and the compacts are dense sintered at 1350-1 380 ⁰ C. The material has typical characteristics of dish porcelain.

Example 18

The offset, consisting of

99.4% by weight partly ground kaolin (<0.12 mm, 65% quartz) 0.5% by weight Ca (OH) ₂ (dry)

0.1 wt .-% KOH (solid, anhydrous) is processed according to Example 11. The sintered products have typical properties of earthenware.

Claims (1)

-1- 208 631 Invention claim: A process for producing a ceramic offset of Rohkaolin, teilgeschlämmtem kaolin and slurried kaolin, characterized in that 0.5-15 wt .-% alkali and / or alkaline earth metal oxide in the form of water-soluble alkali and / or alkaline earth salts or lye is used. Field of application of the invention The invention relates to a method for producing a ceramic offset, can be made from the products that are used as plumbing and building ceramic articles, stoneware, household and business china, electrical and chemical-technical porcelain and corrosion and heat resistant materials such as acid-resistant stones and the like are applicable. Characteristic of the known technical solutions It is known that ceramic offsets are composed of the components kaolin and / or clay, quartz or quartz sand and feldspar and / or feldspar sand or feldspar-containing rocks in a traditional manner (Haase, T. "Keramik".) In special cases, alumina may also be used (DD-PS 23685), mullitreicher fired kaolin and lime and dolomite (Haase, T. "ceramic") are introduced into the offset. The constituents kaolin and clay impart to the ceramic mass, in conjunction with a certain water content, a high degree of plasticity, as required for shaping, for example by extrusion. The quality of the kaolins and / or clays for the offset depends on the intended use. During the formation of such plastic masses, texturing is achieved by aligning the particles. 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 sand, feldspar, lime and dolomite have a sintering-promoting flux effect in the offset. They are characterized in that the alkalis or alkaline earths are present in them in water-insoluble form. Alkalis in water-soluble form are introduced into ceramic offsets in proportions of not more than 0.15% only as suspension stabilizers or leveling agents in order to obtain a stable casting slip. In place of said natural fluxes, fluxes prepared synthetically for use in ceramic displacement have been proposed. This relates, for example, to a synthetic flux having feldspar-like properties, which may be made from slurry kaolin, alkali compounds added with natural feldspar or feldspar sand by pressing, sintering and subsequent comminution (DL-PS 116,594) and up to 60% by weight in a porcelain batch. 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. Furthermore, a process has been disclosed in which ceramic displacements of feldspar and synthetic mullite and, if appropriate, alumina and zirconium silicate are built up completely without the viable components of clay and kaolin and these completely unplastic offsets are obtained by modern shaping processes, for example by isostatic pressing. be formed (DT-OS 1,646,395). The disadvantage here is that these non-plastic displacements require very high compression pressures or the addition of expensive organic binders and plasticizers in order to be able to be molded into articles having a sufficiently high pipe strength. In addition, also here for the synthesis of the 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 the natural and synthetic fluxes produced in the manufacture of ceramic products and at the same time 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. Explanation of the essence of the invention The invention has for its object to provide a method for producing a ceramic offset, without using natural Feldspäte or synthetically produced flux, said offset should be processed in an advantageous manner to ceramic products. The object is achieved in that, in addition to Rohkaolin, teilgeschlämmten kaolin and Schlämmkaolin according to the invention in the production of the ceramic offset 0.5-15Gew .-% alkali and / or alkaline earth metal oxide in the form of water-soluble alkali and / or alkaline earth salts or lye as a flux is used. The composition according to the invention is deslimed, ground, processed into granules by suitable processes, such as spray-drying, for example by pressing or isostatic pressing, and the moldings are sintered in a known manner The water-soluble alkali and / or alkaline earth compounds are converted into the ceramic Offset introduced in solid or dissolved form. The advantage of the method according to the invention is that the synthetic flux or expensive natural flux can be easily replaced by readily available water-soluble alkali and / or alkaline earth metal compounds. Furthermore, larger amounts of Rohkaolin or teilgeschlämeten kaolin can be introduced into the ceramic offset, without the quality of the ceramic products produced from the offset deteriorates. This saves the cost of kaolin processing.