DE2209476B2 - Use of synthetic MonocalciumsUikat - Google Patents

Description

The invention relates to the use of synthetic monocalcium silicate.

From DE-PS 5 68 832 a process for the production of refractory products is known, which in the are essentially formed from wollastonite of great purity, which does not contain magnesium oxide and does not contain more than 0.2% Contains aluminum oxide by melting the corresponding raw materials and the melted Mixture is solidified in molds. 4> This is a delicate process as the cooling down must be done slowly; the products obtained are expensive because of the high price of those used Starting materials, so that the process is only of interest to the glass industry, where materials> <· Great purity works.

Furthermore, from FR-PS 15 24 501 a ceramic product is known which is produced by molding, drying and firing a quantity of fritted wollastonite with an additive such as clay. The *>"> Preparation of fritted wollastonite requires a fine grinding and a very homogeneous mixture of the components. In addition, the demands on the temperature control for the frit are very high, so that it is difficult to perform a uniform production in furnaces of large wi dimensions. Therefore this process seems to be limited to the production of small quantities.

DE-OS 19 25 060 describes a process for the production of a synthetic monocalcium silicate with essentially the composition of naturally occurring wollastonite, starting from a mixture of quartz sand and lime used in equal parts, which are reacted at elevated temperature , adding up to 15% naturally occurring clay with proportions of Na ₂ O and / or K ₂ O to the mixture, melting the mixture, drawing off the melt and quenching it to achieve an at least partially glass-like end product

The object of the invention is to open up an advantageous field of application for the synthetic product produced in this way. This object is achieved in that clay with a content of at least 25% Al ₂ O ₃ in a monocalcium silicate: clay ratio of 40:60 is added to the monocalcium silicate obtained in this way, the mixture is shaped, dried and at temperatures of 1100-1300 ° C is burned. It has been found that the synthetic monocalcium silicate, when it is processed with one or more refractory clays and fired with these, the manufacture of articles with such a remarkable heat-resistant properties permits it to be used to 1200 ⁰ C.

There have already been compositions based on refractory according to the known combustion process Clays, alumina, mullite, zircon, cordierite and other elements with good refractory properties are produced. However, these materials are quite difficult to manufacture, they are also expensive and very brittle. Further considering the previously known low fire resistance materials, theirs is Resistance to temperature fluctuations is very low.

According to the invention, the properties of the synthetic monocalcium silicate mentioned are used to produce materials for ovens and temperature-resistant objects with dimensions of several square centimeters and thicknesses that can be reduced to a few millimeters, which have ^{good strength at use temperatures of up to 1200 0} C, and one at room temperature have increased mechanical strength and sufficient mechanical strength at the temperatures of use, have good resistance to rapid temperature fluctuations and, in view of their various properties, can be sold at an extremely favorable price.

The mixture can be shaped by moistening it in the powdery state or by forms a slip from the mixture and introduces it into a mold.

Obtained in this way products having the furnace construction or for temperature-resistant articles which are used at temperatures up to 1200 ⁰ C, the desired strength properties.

The invention is illustrated in more detail by the following examples.

example 1

A synthetic monocalcium silicate was made from a mixture of raw products made, which was composed of equal parts by weight as follows:

Containing silicate rock
73% SiO ₂
4.7% Al ₂ O ₃ and
10% CaO
Grain size 50 to 70 mm,

containing natural lime

55.9% CaO
Grain size 50 to 100 mm.

The mixture was continuously fed into a flame furnace where it was melted at 1320 ° C. It was then quenched as it exited the furnace

There were 32 parts by weight of the end product with the following composition

Start-up time
Firing level

5h

25 min at 1200 ^° C.

SiO ₂

Al ₂ O ₃ ;

CaO
MgO

K ₂ OI-Na ₂ O
Burning loss

51.50% 3.25% 1.40%

40.60% 0.50% 1.50% 1.00%

taken with a crystallinity of 45%.

After grinding to a 20% residue of 100 μπι the material with 65 parts by weight of clay the following composition slurried to form a slip:

SiO ₂

AI ₂ O ₃

TiO ₂

Fe ₂ O ₃

CaO

MgO

K ₂ OH-Na ₂ O

Burn loss

51.10%

33.50%

1.60%

1.50%

0.15%

0.20%

0.90%

11.20%

The fineness of the clay corresponds to a 40% residue of 40μηι, the clay had the following mineralogical composition: kaolinite, muscovite, quartz, anatase (origin: Charentes basin).

After cooling and drying, the caked raw material was broken up and moistened with water to 8%. The product was evenly divided into the quantities necessary to cover the bottom of a mold of 150 χ 300 mm, after which each time for a few seconds at about 99 bar and then pressed at 393 bar.

Then the plate at 60 ⁰ C for 3 hours was dried, after which the drying temperature was raised to 110 °. ^{This was followed by firing in the kiln at a temperature gradually increasing to 1200 °} C. for 24 hours, taking into account the small dimensions of the kiln.

The burning time was then 1 hour.

Under these conditions, a perfectly flat plate was obtained which was free from warpage and crack and was 4 mm thick. The total shrinkage in relation to the dimensions of the mold was 2.5%, the porosity 7%, the flexural strength 217 bar and the fire resistance 137O ⁰ C.

Example 2

Following the procedure described in Example 1, smaller samples were produced with a shorter burning time manufactured:

The following properties were found:

Mechanic solidity:

197 bar flexural strength at room temperature,
Mechanical strength after 10 cycles up to 1100 °:
197 bar flexural strength at room temperature.
The introduction of the samples and their residence time in the lu oven took place automatically within 15 minutes.

No damage to the samples was found after the cyclic heat treatment

Resistance to twisting in heat:
45 bar at 1100 ⁰ C.

Example 3

According to the above procedure, panels of 100 100 10 mm were produced, they were in a tunnel oven Fired for a total cycle of 1.5 hours.

The panels obtained were not deformed and

had a mechanical strength of more than 148 bar. For further use as a refractory Materials it is advantageous in this case, initially

> 5 to approach more slowly with the temperature.

Example 4

30 parts by weight of completely crystalline silicate, which has a surface area of 2000 cm ² / g

jo was crushed and a particle size up to 2000 μτη possesses, and 70 parts by weight Westerwaldton to a slip. After solidification, drying and Re-moistening to 8% water, panels are pressed at 245.25 bar and fired at 1200 ° C.

j) In this way, earthenware tiles for floor coverings are obtained with the following properties:

Mechanic solidity:

392.4 bar (bending test)
_{4 ()} porosity:

0.5% (easily absorbed water)

Example 5

A composition consisting of 20 parts by weight of Charantes clay, the mineralogical composition of which comprises kaolinite, muscovite, quartz and anatase, 20 parts by weight of chamotte, 20 parts by weight of silicate with 55% crystallinity is used to to produce a shaped specimen from a slip with a density of 2 in in a plaster mold. After the complete solidification is fired at 1230 ⁰ C. Properties corresponding to the sanitary pottery are obtained:

Porosity:

6%
Mechanic solidity:

237.6 bar very little deformation.

The charges can contain inert components or · ■■ refractory materials such as fireclay, cordierite, zirconia etc. are added.

Claims (4)

Patent claims: 1.) Use of synthetic monocalcium silicate with essentially the composition ι naturally occurring wollastonite, made from a mixture of quartz sand and lime used in equal parts, which are reacted at an elevated temperature, with up to 15% of the mixture occurring naturally ι ο mende alumina with proportions of Na ₂ O and / or K ₂ O is added, the mixture is melted, the melt is drawn off and quenched to achieve an at least partially glass-like end product, clay with a content of at least 25% Al ₂ O ₃ in the ratio of monocalcium silicate: clay of 40:60 is added, the mixture is shaped, dried and ^{fired at temperatures of 1100 ... 1300 0} C, for the production of temperature-resistant products. 2.) A method for producing temperature-resistant products according to claim 1, characterized characterized in that the mixture is deformed moistened in powder form. 3.) Process for manufacturing temperature resistant> > diger products according to claim 1, characterized in that the mixture is used as a slip in a mold is introduced. 4.) The method according to any one of claims 2 or 3, characterized in that the mixture of w monocalcium silicate and clay refractory ingredients are added.