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Porous ceramic bodies and process for their preparation

a porous ceramic and process technology, applied in the field of porous ceramic bodies and process for their preparation, can solve the problems of insufficient natural porosity, disadvantageous strength reduction, and open porosity not only reducing melt strength, so as to improve porosity, improve mechanical strength, and reduce weight

Inactive Publication Date: 2013-12-12
IMERYS CERAMICS FRANCE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The process achieves lightweight porous ceramics with improved porosity, thermal and electrical insulation, and maintained mechanical strength, reducing water absorption and bulk density, making them suitable for applications like tableware and construction materials.

Problems solved by technology

This natural porosity can be insufficient for application situations where it is important to assure a good thermal and electrical insulation, in addition to refractory properties, and where a reduced weight is required.
In fact, while the introduction of voids in the ceramic material has very positive effects on thermal and electrical insulation properties of the material and also allows a reduced weight, the presence of voids may also lead to a disadvantageous strength reduction.
Open porosity not only reduces melt strength, but also allows water and moisture to penetrate in the ceramic body, which is undesired for many traditional ceramic applications; in fact, open porosity is determined by the pores which are connected to the surface of the ceramic and linked, with each other.
Nevertheless, the obtained porous ceramics are still unsatisfactory as regards mechanical strength.
Further problems associated to the use of high amounts of porogens are caused by the quick decomposition and combustion of the porogens upon heating, which may lead to cracking in a moulded body.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

examples

[0067]The following examples are given for illustrative and not limiting purposes.

[0068]The following commercial products were used in the preparation of the coated porogens of the process of the invention and in the comparative examples:

[0069]JRS101: cellulose fibres, having length of 100 μm and medium diameter of 20 μm, commercialized by Rettenmeyer.

[0070]JRS200: cellulose spherical particles, having diameter of 200 μm, commercialized by Rettenmeyer.

[0071]JRS FIC500P: cellulose fibres, having length of 500 μm and medium diameter of 30 μm, commercialized by Rettenmeyer.

[0072]CaCO3: Calcit, Type K6 / L II commercialized by Franz Mandt GmbH, particle size D50 of 5.6 μm.

[0073]The coated porogens used in the process of the invention were obtained as follows.

[0074]Porogen 1

[0075]In a 3-neck round glass-bottle, 1.8g of polyvinyl alcohol (Polyviol®, commercialized by Wacker Polymer Systems GmbH & Co. KG) was added to 100 ml water, and the mixture was heated at about 95° C. under stirring fo...

examples 1-6

[0086]The standard mixture for porcelain PP910B, commercialized by Imerys Tableware Deutschland GmbH (comprising 57% wt. of a mixture of kaolins, 42% wt. pegmatite and 1% wt. polyvinyl alcohol) was used as ceramic precursor; the porcelain mixture of Example 6 was the same, but containing about 2% wt. polyvinyl alcohol (Polyviol®, commercialized by Wacker Polymer Systems GmbH & Co. KG).

[0087]50 g of said mixture (154 g in Example 6) were added under stirring to 70 ml of water (300 ml in Example 6) thus forming a slurry; the porogens reported in Table 1, in the amounts indicated therein, were added to the slurry, and the resulting mixture was homogenized by mixing.

[0088]100 g of the ceramic slurry were dried cautiously at 60° C., maintaining the mixture homogeneous under stirring. The dried ceramic cake, having a moisture content of about 7-8% wt., was crushed to small particles (average diameter lower than 300 μm) and sieved on a screen of 500 μm. The thus obtained ready-to-press pow...

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Abstract

A process for producing a porous ceramic body may include: a) mixing a coated porogen with a silicate or an oxide ceramic precursor, wherein the porogen is decomposable to gaseous decomposition products and optionally solid products upon heating, and is coated with a coated agent; b) forming a green body from the mixture obtained in step (a); and c) firing the green body obtained in step (b) to obtain the ceramic body, whereby the porogen decomposes to form pores within the ceramic body, and the coating agent is deposited at the inner surface of the pores. The porogen may be coated with a coating agent which, upon firing, is deposited at the inner surface of the ceramic pores, so that porous ceramics having decreased weight and improved porosity are obtained, while maintaining good mechanical strength. A green body and porous ceramic body obtainable with the above-mentioned process are also described.

Description

FIELD OF THE INVENTION[0001]The present invention concerns a process for preparing lightweight porous ceramics by using porogens coated with a coating agent; the porous ceramic bodies obtained after decomposition of the porogen upon firing show an advantageous density reduction without a significant impairment of the mechanical strength, a more homogeneous total porosity and improved closed porosity.BACKGROUND OF THE INVENTION[0002]Ceramic materials are commonly provided with a natural porosity determined by the composition and the grain structure of the raw materials, and by the driving out of the water during drying and firing. This natural porosity can be insufficient for application situations where it is important to assure a good thermal and electrical insulation, in addition to refractory properties, and where a reduced weight is required.[0003]Various ceramic products with higher porosity levels have been developed in the art; the incorporation of pores is commonly obtained ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C04B38/00
CPCC04B38/0096C04B33/24C04B33/30C04B2235/664C04B2235/77C04B2235/96Y10T428/249956C09C3/063C04B38/0054C04B38/0058C04B38/0061C04B38/0074C04B38/065C04B38/068C04B38/0635C04B38/067
Inventor MUELLER-ZELL, AXEL
Owner IMERYS CERAMICS FRANCE