HU211191B - Process for producing ceramic shaped-bodies - Google Patents

Abstract

The invention relates to a process for producing light ceramic shaped parts, in particular bricks or the like, with a perlite being used as porosity-inducing agent.

Description

FIELD OF THE INVENTION The present invention relates to the production of lightweight ceramic bodies containing perlite as a weight loss additive having a dry bulk density of less than 2.0 g / cm ³ .

The effect of thinning and pore-forming agents, especially in the field of brick production, has long and often been studied.

Mackedanz gave a summary of this in Sprechsaal 9/80. in your booklet on page 559.

Although pore-forming additives such as sawdust, paper sludge and plastic foam significantly reduce the bulk density of the tile, the compression strength of the molds thus produced must also be taken into account. Adding sawdust does not reduce the bulk density of the tile, but the compressive strength values are relatively good, while "Styropor" (styrene powder) drastically reduces the bulk density, but at the same time, the compressive strength is greatly reduced, as Mackedanz writes.

In the introductory part of DE-OS 2,853,709, other pore-forming grains, such as peat, coal dust, perlite, straw or flotation pellets, are not of great practical importance because they have similar disadvantages as described above.

DE-OS 2,853,709. According to the disclosure document, said additives can be used only when a combustible, powdery or fine-grained material is mixed with and foamed. In this way, foam-like combustible granules having a loose structure are produced. It has been mentioned as a particular advantage that the high-shake additive has a higher calorific value than that of the solid particles, which is good for furnace firing because it saves heating energy.

They also mention perlite administration. They point out that mixing untreated perlite with the raw material often fails to produce the desired result because the perlite particles crush when pressed. According to the German disclosure, the stability of the granules can only be guaranteed if they are introduced into the foam together with powdered carbon or the like.

Such a two-part process, in which the additive is first processed into foam and then blended with the foam, is obviously relatively expensive for the production of bulk products such as brick or the like.

The additive perl introduced into the clay matrix is crushed when the mixture mass is pressed, as described in DEOS 2,853,709. disclosure document and as confirmed in DE-PS 3 614 943. in U.S. Pat. In the latter place, expanded glass-coated perlite particles are recommended for the production of clay bricks.

Glass-coated perlite particles become so solid that, when mixed with the clay matrix, they can withstand compression or similar molding without crushing.

However, in this case too, the additive has to be processed separately (coated with a glass-like coating) before being added to the clay matrix, which results in additional time and expense. not always bearable in the manufacture of bricks or the like.

No. AT-PS 252,091. It is known from the patent that the perlite in the expanded state absorbs a lot of water. In order to reduce this water uptake, the flowable or dormant still hot perlite particles in the expansion process are sprayed with an aqueous solution of silicone resin and mixed with the sprayed particles.

Finally, DE-AS 1 253 133 is incorporated herein by reference. A method for treating perlite, in which perlite is soaked or sprayed and centrifuged with a binder, impregnated, liquid or liquid binder and impregnant, has become known from US Patent Publication No. 3,600,151. The purpose of spraying is to bring the water-soluble impregnating agent into contact with the perlite. Finally, the material so treated is dried.

Our task was to enable the porous additive, such as perlite, to be stabilized in a cheaper and simpler manner than that of the prior art, so that it would not be fragmented by mixing and shaping with clay.

Surprisingly, it has been found that the stability of the expanded perlite can be dramatically increased by uptake of a liquid, preferably water. Stabilization of each pearl particle will be greatest if the total open pore volume is preferably filled by a liquid. The fluid may be introduced into open pores in various ways and ways. The liquid may also be introduced in a completely separate operation, for example by immersing the expanded perlite in a liquid, or by spraying the expanded perlite particles through, for example, a suitable water jet on the sidewall of the conveyor passing through the perlite. However, because of the consistency of the clay, this can be too much, as the clay, together with its own moisture, can make the mixture too wet. In this case, it is suggested that before mixing with the clay, only a fraction of the total amount of water theoretically absorbed by the open pore volume is added to the expanded perlite. However, at least 50% by weight of the amount theoretically required must be added to mix the perlite homogeneously with the clay. In this case, due to the high capillary activity of the open pores, the amount of water missing for "full saturation" is absorbed by the perlite from the clay. Very porous perlite particles can also be considered as "clay drying agents", but larger surface pores may be filled with clay matrix material, from which moisture also migrates into the capillaries of the perlite due to suction. In any case, a sufficient quantity of liquid must be provided to ensure that the open pore volume of the perlite is completely filled with liquid. At the same time, care must be taken to ensure that the clay perlite mixture is ultimately of a consistency that permits its further processing. Accordingly, the total amount of liquid should be added to the amount of liquid added to the clay and externally added so that the open pores of the

Even when filled, the consistency of the clay.perlite mixture should meet the requirements of further processability.

In each case, these are water-saturated perlite particles, the pores of which are not removed during mixing with the liquid clay matrix. This is mainly due to the surface tension of the water. This can be confirmed, optimized by the presence of a surfactant. In some cases it may be advantageous to introduce the liquid into the pearlitic pores under low pressure, whereby the pores of smaller cross-section may be filled with liquid.

The clay-perlite mixture thus formed can be processed in a conventional manner.

Whether working in an extruder (screw press) or in a batch press, the fragmentation of water-filled perlite particles is noteworthy. An incompressible fluid, such as water, stabilizes the fragile backbone of the expanded perlite particle itself more effectively if the water is filled with virtually the entire pore volume, even after shaping (i.e., the fluid remains in the pores).

The water is then expelled from the pores during normal plowing and the product is then burnt in the usual way.

Depending on the selected firing temperature, the perlite will either burn or at least partially form a molten phase which solidifies into a glassy skeleton, which further enhances the mechanical strength of the molded bodies.

At today's relatively desirable firing temperatures, it should always be taken into account that due to the large pore volume of expanded perlite, otherwise desirable for thermal insulation

- a certain reduction in the density of the tiles should not be too detrimental to the strength.

It is surprising in two respects that perl can be used effectively as a post-molding agent. It is known from the prior art that, on the one hand, perlite cannot be used as an additive for technical reasons and, on the other hand, if it is used, a reduction in the strength of the perlite particles is to be expected.

It is true that dry pearl grains are very difficult or difficult to use. they cannot be mixed in a normal clay matrix. The surface of the perlite particles is obviously too coarse to allow homogeneous mixing.

Even if we were satisfied with the inhomogeneous clay / perlite mixture, it would not be possible to make it a technically usable product, because - as described

- the pearl particles would fragment during molding. And so the desired porosity would not develop.

This deficiency is likely to be overcome by providing glazed glaze for the perlite particles, but it is an unbearable technical expense.

Although not particularly simple, the process of the present invention allows for the introduction and homogeneous distribution of perlite into the clay matrix in a very efficient and surprisingly simple manner. Water obviously acts as a lubricant and at the same time, as we have written, stabilizes the individual particles. As described above, the amount of water may not be any and is determined by the desired consistency.

We recommend the use of perlite with a particle size of less than 6 mm but in most applications less than 6 mm. Fine pearlite with a particle size of less than 1 mm should preferably not be used because it absorbs relatively much water, which has to be discarded at a later date, and provides little effective porosity from a thermal point of view. Therefore, in the case of greasy clay, the preferred particle size is between 1 and 6 mm.

The liquid to be used is primarily water. But it can also be used in industrial plants. During combustion, the harmful parts of this water, such as heavy metals, can be incorporated into the ceramic vase of the ceramic product.

Perl must be added in such a way that the finished product has a drying crude density of less than 2.0 g / cm ³ , preferably less than 1.7 g / cm ³ .

Generally, 50-500 l perlite is added to 1000 kg of clay.

Preferably 100-250 liters of perlite are added to 1000 kg of clay.

Of course, when it comes to clay matrix, this means not only pure material but also ingredients that are common in ceramic moldings.

Otherwise, the processing can essentially take place in the usual way and manner. If this also includes the use of a collar passage, the perlite dosing according to the invention can be administered only after leaving the collage passage. This is because the material is subjected to very high mechanical stress in the collision passage and even water-stabilized perlite particles would be broken.

In contrast, it has been shown that water-saturated perlite particles do not break in any continuous or batch press when operated under normal pressure. An example of the first is an extruder, the second an elbow press. In addition, during compression, the skeleton formed by the larger pores is almost completely retained in the granules.

The process according to the invention can be used to produce all kinds of clay articles of low density and thus good thermal insulation in the dry state. Examples are masonry bricks, roof tiles, chandeliers, roof bricks, basement pipes, chimney bricks or the like. The process is predominantly suitable for the production of porous products, but can also be used for the production of e.g. clinker - the structure of which is comparable to that of the stone hub - and these pieces need only be burned until the open pores disappear. It is also possible to burn the clay / perlite mixture and then process it into the appropriate chamotte product.

Examples

Starting materials:

- Expanded perlite with a particle size of less than 4 mm, with a shaking density of 80 kg / m ³ , a pure density of 2,1 g / cm ³ and a chemical composition by weight:

HU 211 191 B

Sio ₂ 67.0 A1 ₂ O ₃ 13.2 TiO ₂ 0.4 Na ₂ O 6.4 K ₂ O 4.5 CaO 1.3 MgO 0.3 FeO 0.7 Fe ₂ O ₃ 0.7 remaining: contamination

- Clays A, B and C with a chemical composition by weight:

THE B C SiO ₂ 71.7 60.1 46.8 A1 ₂ O ₃ 13.4 16.8 12.7 Na ₂ O 0.4 1.4 0.3 K ₂ O 2.2 4.2 2.0 CaO 0.6 0.2 14.5 MgO 1.3 2.7 2.3 Fe ₂ O ₃ 4.8 6.7 4.4 TiO ₂ 1.0 1.1 1.0 CaCo ₃ 0.2 0.6 24.9 remaining: contamination

Example 1

1 expanded expanded perlite was mixed in a stirrer for 3 minutes with 300-300 kg of clay A, B and C and 5 L of water, and the mixture was processed into bricks at 1.2 MPa in an extruder.

The bricks are dried to a residual moisture of 1.0% by weight and then fired at 850 ° C in a tunnel furnace. The dry raw density of the burnt bricks (raw density of the "burnt clay") is 1,6 g / cm ² .

Example 2

1 250 500 to 500 kg expanded perlite and B into clay »and mixed with 1 feeder proper mixer 25 1 water for 5 minutes, the mixture was worked up téglává nyerstéglaprésben ^_1 8 to 10 MPa. 2% by weight of surfactant excipient (surfactant) was added to the water prior to loading into the mixer.

The bricks were dried to a residual moisture of 1.0% by weight and then fired at 850 ° C in a tunnel furnace. The dry raw density of the burnt bricks (raw density of the "burnt clay") is 1.4 g / cm ³ .

PATENT CLAIMS

Claims (10)

PATIENT INDIVIDUAL POINTS A method for producing ceramic moldings having a dry bulk density of less than 2.0 g / cm ³ in dry weight, expanded perlite, expanded as a weight-reducing additive, characterized in that an open pore volume of a perlite having a particle size of less than 10 mm is optionally mixed with a surfactant; preferably filled with water - completely filled, and at the same time or evenly distributed in the clay matrix of the perlite, then the body of the mixture is formed and dried and then burned. Process according to claim 1, characterized in that water is used as a liquid. Method according to claim 1 or 2, characterized in that prior to filling the perlite pores, the liquid is mixed with a known amount of surfactant. 4. The method of claim 3, wherein the surfactant is a surfactant. 5. Method according to any one of claims 1 to 3, characterized in that the amount of perlite required for the production of burnt bodies having a dry density of less than 1.7 g / cm ^{3 is} mixed with the clay matrix. 6. Method according to any one of claims 1 to 5, characterized in that 50 to 500 liters of perlite are added to 1000 kg of clay. 7. The method of claim 6, wherein 100 to 250 liters of perlite are added. 8. Referring to Figures 1-7. A method according to any one of claims 1 to 3, characterized in that the liquid saturated perlite is added to the clay matrix after a colloidal route and prior to molding. 9. Method according to one of Claims 1 to 5, characterized in that molds are formed from the clay matrix mass mixed with the perlite, and thus bricks are pressed. 10. References 1-9. A method according to any one of claims 1 to 6, characterized in that a perlite having a particle size of 1-6 mm and a density of 80-130 kg / m ^{3 is} used. Published by the National Inventory Office, Budapest Responsible for the release: Head of Department, Gyurcsekné Philipp Clarisse ARCANUM Databases - BUDAPEST