DD231338A1 - METHOD FOR PRODUCING FIRE-RESISTANT HEAT-DRYING FORMKOERPER AND GEMENGE - Google Patents

Abstract

The invention relates to a process for the production of porous refractory materials from porous granules, which are used in particular in high-temperature pores in metallurgy, the ceramic, refractory, glass and in the cement industry. The object of the invention is to improve such marked performance properties of such products as reduction of bulk density and heat conductivity and increase in edge strength. According to the invention, the object is achieved by adding water-insoluble fine particles of special shape, which hinder the penetration of the binding matrix into the porous granules, in addition to the usual binders to porous granules. The refractory heat-insulating shaped bodies and mixtures produced according to the invention are distinguished from conventional products based on porous granules by a higher utility value and by a lower susceptibility to breakage in the production process.

Description

Application of the invention

The invention relates to a method for producing refractory thermally insulating moldings and mixtures, which can be used in metallurgy, the ceramic, glass, refractory and in the cement industry.

Characteristic of the known technical solutions

For the production of refractory thermally insulating moldings and mixtures mixtures of porous grains are mixed with suitable binders and molded by known methods, inter alia. Subsequently, the curing takes place by chemical means or by ceramic bond.

The porous grains used for the production of refractory thermally insulating moldings and blends have a high open porosity mainly due to the process of their preparation. In the processing of such porous grains with a high proportion of open porosity to moldings and blends there is the disadvantage that the binder partially penetrate during mixing by capillary action in the porous grain. The binders can thus no longer or only to a lesser extent do justice to their actual task of bringing the porous grains into a firm bond.

This gives moldings with lower strength, especially with reduced edge strength.

To compensate for this undesirable phenomenon, it is possible to increase the binder content. Due to the high price of many refractory binders, this leads to increased production costs.

The filling of the pores is also undesirable because it reduces the porosity of the moldings and blends.

There is an increase in the bulk density and the thermal conductivity of the products.

Furthermore, the chemistry of the products can be changed in an undesirable direction.

Known technical solutions to the problem of construction based on a sealing of the porous granules with epoxy resin (DDR patent no. 139249) or on a hydrophobing of the porous aggregates with silicone oil, fatty acids, resins or asphalt (BRD AS 3001893, USA 4,235,460) , The disadvantage of these solutions is that when using materials for sealing or hydrophobing of the granules, the solid bond between binder matrix and grain is severely impaired.

Another known technical solution to the problem is based on the addition of Vermiculitglimmer in combination with hydrophobierenden additives such as organic metal complexes and cationic fatty acid derivatives BRD Patent 2606511).

Here, the vermiculite semipermeable form colloidal membranes that prevent the ingress of water in porous aggregates temporarily. The application of this solution to the problem also leads to a reduced bond strength between matrix and porous aggregate. In addition, this method reduces the fire resistance of thermal insulation materials by contamination with alkali compounds.

Object of the invention

The object of the invention is to produce refractory thermally insulating moldings and mixtures of porous granules with increased edge strength and minimized increase in bulk density of the starting granules.

Explanation of the essence of the invention

The invention has for its object to produce refractory heat-insulating moldings and mixtures based on porous granules, which are distinguished from known solutions by a lower content of binders, higher edge strength, lower bulk density and lower thermal conductivity. According to the invention the object is achieved in that porous granules are added in addition to the usual binder water-insoluble fine particles in needle-like, rod-shaped or fibrous form, which may consist of organic or inorganic substances. The water-insoluble fine particles are to be intimately mixed with the porous granules. The addition of the fine particles can be carried out directly to the porous grain with subsequent mixing. The usual ceramic or chemical binder is mixed in this case last.

Another possibility is to mix the water-insoluble fine particles directly with the binder or with mixing water and then mix under the porous granules. Finally, the particles according to the invention should not be added to the mixture because this reduces their effect.

The surprising effects of the invention are that:

the water-insoluble fine particles, still favored by their large surface due to their shape, are enveloped by the chemical and / or ceramic binders by chemical reactions and / or adhesion and deposit fines of the binding matrix on their surface. As a result, the binders are increasingly retained in the intermediate grain spaces of the porous granules. They are thus no longer available for a filling of pores; the water-insoluble fine particles coated with binder components cover open pores of the porous granules and thus close pore openings. By means of a filtering effect, this prevents further penetration of fines of the binding matrix into the interior of the pores;

the coated with binder matrix fine particles between the porous grains bond bridges that give the moldings after drying, the chemical or ceramic curing a firm bond without a dense grain packing of the binding matrix is absolutely necessary. This promotes the intended high porosity of the products.

An inventive feature of the production of refractory thermally insulating moldings and blends is that the water-insoluble fine particles in the range of 0.05 to 10mm total length have a length to diameter ratio of between 600: 1 and 20: 1.

Based on the dry refractory base components of the moldings and mixtures, the proportion of these particles should be between 1 and 10% by mass.

In the context of the production of highly porous heat-insulating shaped bodies and mixtures, it may be advantageous to remove the water-insoluble fine particles according to the invention again in the starting state of the products because their advantageous effects are no longer needed.

An inventive feature of the production of refractory thermally insulating moldings and mixtures is therefore that the particles according to the invention consist of organic material such as pulp, which decomposes on heating to use temperature.

Another feature of the present invention of producing refractory thermally-insulating molded bodies and blends is that the fine particles of the invention themselves act as additional binders, melting at elevated temperatures or reacting with the binder matrix and porous granules to form mineral neodymium to form fixed bond bridges.

For such applications, in particular fine particles of the invention are suitable, which can be selected from the group of glasses.

A further feature of the invention is that the refractory moldings and mixtures to 50 to 95 wt .-% of porous granules in the grain size> 0.5 mm and 5 to 50 wt .-% binder matrix in the grain size> 0.5 mm and be brought to 6 to 30 wt .-% based on the dry matter mixing water to a moisture-moist consistency.

As porous granules, substances such as foam chamotte, perlite, ceramic hollow spheres, hollow spherical corundum, expanded clay, light granules, lightweight concrete granules and porous slags can be selected.

In addition to known refractory substances such as kaolin, clay, refractory oxides, mullite, chamotte, the binding matrix can also contain cements, organic binders and / or chemical binders such as waterglass, ethylsilicate solutions and phosphate binders in addition to the mixing water.

embodiment

The invention will be explained in more detail below with reference to two examples: Example 1

A refractory light gray granules with 72% Al ₂ O 3 content and the main mineral phase mullite, composed of the grain fractions 0.5 to 5mm to 85% by mass and 0 to 0.5mm to 15% by mass, becomes a slurry consisting of organic fibers in water to 3l Ma .-% added to the light stone granules and mixed. The slurry of fibers and water has a fiber content of 10% by mass.

Subsequently, a binder matrix of the following composition is admixed with a proportion of 58% by mass, based on the light-weight granules

 Component proportion in% by weight

Kaolin 36

Toner hydrate 30

Dextrin solution 15% 10 ^c

Water 24

This gives a soil-moist mass, which can be processed by pressing into moldings. The addition of the water-insoluble fine particles leads to a similar mass without this additive in pressed and then fired at 1550 ° C moldings to the following properties: Feature conventional inventive

Molded body

Bulk density [g / cm ³ ] 1.35 1.14 Cold pressure strength [MPa] 3 3 thermal conductivity 0.61 0.54 at 1 000 ⁰ C [W / m K] Particularities: low edge strength, significantly higher by much scrap Edge resistance in when handled dried State by little committee

Example 2

70 wt .-% of a Kaolinschaumschamotte in grain size Obis 10mm, 20% <0.5 mm, are admixed with 3Ma .-% Kaolinwolle the classification temperature 1250 ⁰ C and covered with 36 wt .-% water to the Kaolinschaumschamotte. Finally, 27% by mass, based on the dry mass constituents, of a bond consisting of 50% clay, 48% fireclay flour and 2% sulfur dioxide powder are mixed in. This gives a good mouldable mixture, which can be processed by pressing, drying and firing to refractory shaped bricks. The moldings have about 8% lower bulk density and increased edge strength compared to comparable stones made of granules. The stones are easy to handle after drying.

Claims (8)

Invention claim: 1. A process for producing refractory thermally insulating moldings and mixtures, characterized in that porous granules are added in addition to the usual binder water-insoluble fine particles in needle-like, rod-shaped or fibrous form, which may consist of organic or inorganic substances. 2. The method according to claim 1, characterized in that the water-insoluble fine particles have a length of 0.05 mm to 10 mm at a ratio of length to diameter between 600: 1 to 20: 1 and that the addition of such particles 1 to 10 % By weight, based on the dry refractory base components. Process according to claims 1 and 2, characterized in that the water-insoluble fine particles themselves act as an additional binder in that they melt at elevated temperatures or react with the binding matrix and the porous granules to form mineral neoplasms. 4. The method according to claim 1,2 and 3, characterized in that the particles according to the invention are selected from the group of glasses. 5. The method according to claim 1 and 2, characterized in that the particles according to the invention consist of pulp. 6. The method according to claim 1, characterized in that the refractory moldings and mixtures to 50 to 95 wt .-% of porous granules in the grain size> 0.5 mm and 5 to 95 wt .-% of binder matrix in the grain size 0, 5mm are composed. 7. The method according to claim 1 and 6, characterized in that are selected as porous granules substances such as foam fireclay, perlite, ceramic hollow spheres, Hohlkugelkorund, expanded clay, light granules, lightweight concrete granules and porous slags. 8. The method according to claim 1 and 6, characterized in that the binder matrix may be composed of conventional binders and their combinations such as clay, kaolin, refractory oxides, chamotte, MuIMt, organic binders, cement and chemical binders such as water glass, ethyl silicate solutions and phosphate binders.