EP2539295A2

EP2539295A2 - Heat-insulating refractory high-temperature resistant molded article

Info

Publication number: EP2539295A2
Application number: EP11709864A
Authority: EP
Inventors: Rainer Angenendt; Peer Genth
Original assignee: Tdh - Technischer Dammstoffhandel GmbH
Current assignee: Tdh - Technischer Dammstoffhandel GmbH
Priority date: 2010-02-24
Filing date: 2011-02-23
Publication date: 2013-01-02
Also published as: WO2011104008A2; DE102010009148A1; WO2011104008A3; DE102010009148B4

Abstract

A heat-insulating refractory high-temperature resistant molded article which is suitable for continuous service temperatures of 1200 to 1600°C and contains several light-weight fillers, a reaction product of the thermal hardening of a binder and fibers and/or wollastonite, is characterized by containing fly ash cenospheres and blown closed-cell volcanic rock cenospheres as the light-weight fillers, by containing fluxing agents and by containing silicon dioxide as the reaction product of the thermal hardening of the binder.

Description

Heat-insulating fireproof high temperature resistant molding

The invention relates to a heat-insulating refractory high-temperature resistant molded part containing a plurality of lightweight fillers, a binder and fibers and / or wollastonite, for applications up to about 1600 ° C.

The term lightweight fillers is to be understood here as high-melting mineral granules of low density, for example fly ash, expanded volcanic rocks, expanded perlite, etc.

In the present application "finely divided" is not in the sense of a certain small grain size, but in the sense of "powdery" or "granular" in

Unlike "lumpy" used, so it does not depend on a specific grain size or particle size distribution.

State of the art

Refractory bricks are formed refractory products with a total porosity> 45% and an application temperature of at least 800 ° C. ASTM C 155-70 and DIN EN 1094 define the temperature at which the shrinkage of the material after 24 h or 12 h is not more than 2% and a maximum density.

Starting from the chemism are light refractory bricks in aluminum silicate

To divide lightweight refractory bricks, silicate bricks, zirconia and corundum light bricks. The greatest importance and spread comes to the aluminum silicate light bricks (chamotte and mullite bricks).

For the production of raw materials based on A1 ₂ 0 ₃ , Si0 ₂ and possibly CaO are used. As an alumina carrier are raw materials such as clay, kaolin, chamotte,

Sillimanite, andalusite, kyanite and mullite and alumina, alumina hydrate and corundum used.

In addition to the fine-grained raw materials, coarse-grained, porous raw materials such as lightweight chamotte and hollow spheres made from corundum and mullite are also used.

Known refractory bricks have a bulk density of 0.5 to 1.4 g / cm ³ , a

Thermal conductivity from 0.13 to 1.3 W / mK at 400 ° C, from 0.17 to 1.2 W / mK at 800

CONFIRMATION COPY 2011/000872

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° C, from 0.23 to 1.1 W / mK at 1200 ° C and an application temperature range of 1000 ° C to 1800 ° C. (Source: G. Routschka, H. Wuthnow, Paperback refractory materials, 4th edition 2007, Vulkan-Verlag GmbH, Essen) S. 354 - 360). German Offenlegungsschrift DE 10 2007 012 489 A1 describes exclusively insulating and exothermic feeders from the foundry industry. Speiser is a term from the foundry industry and refers to geometric sprues on castings, in the form of the voids volume deficit is to be placed during the casting solidification and which are removed in the cleaning process of the castings again. The feeders themselves are destroyed in this process (disposable parts).

A feeder has the task of avoiding the formation of voids (cavities) in a casting, and has other different tasks in a casting mold:

• Control of the solidification direction of the cast melt (if possible

directed towards the feeder)

• compensation for the reduction in the specific volume of the potted

Melt during the phase transition liquid / solid

• Venting of the casting mold during the casting process (exception: blank feeder) "Feeder variants": Natural feeder, isolating feeder, exotherm feeder: By isolating or additionally heating up the feeder after the casting process, the

Speiserabmessungen be kept smaller, resulting in a material saving (better casting casting).

The exothermic feeders described in DE 10 2007 012 489 A1 contain thermally similar mixtures which are very dangerous and have led to extreme fires in some factories. The thermite reaction is a redox reaction in which aluminum is used as a reducing agent, e.g. Iron (III) oxide to reduce iron. The mixture is called thermite:

Fe ₂ 0 ₃ + 2 AI -> 2 Fe + A1 ₂ 0 ₃

The reaction products are alumina and elemental iron. The reaction is very exothermic, ie under strong heat. The ignition medium used is barium peroxide with magnesium.

Thermitgemische are not explosives and can be brought to implementation (inflammation) only by a very large heat input (activation energy). The burning process is a strongly exothermic reaction (up to 3000 ° C). Since burning thermite does not require external oxygen, the reaction can not be stifled and in any environment - even under sand or water - be ignited and continue to burn. Extinguishing tests with water and moisture lead to a further redox reaction, in which the water is reduced by the less noble metals and thus metal oxide and hydrogen are formed:

2 AI + 3H ₂ 0 -> 3H ₂ + A1 ₂ 0 ₃

2 Fe + 3 H ₂ O -> 3 H ₂ + Fe ₂ 0 ₃

The presence of water is therefore a great danger in the Thermitreaktion and leads to the explosive ejection of glowing substances and explosive hydrogen-oxygen mixtures (oxyhydrogen). Thermit mixtures must therefore be stored dry.

The formulations listed in DE 10 2007 012 489 A1 in paragraphs [0053] and [0054] have a water content of about 1.5 to 2.5%. These are thus powdered blends that are obviously produced exclusively for the core shooting process.

In the core shooter, base material mixed with binder with a certain firing pressure and possibly defined working temperature is introduced into a core mold (the "core box"). After hardening or precuring of the casting core thus produced, it is installed in the casting mold. Depending on the binder used for curing the molding material, so-called cold box or hot box core shooting machines are used. The blends in the present patent application contain significantly more water. In the recipe, the water content is at least 10 wt% and larger. The blends in the present patent application therefore correspond to their consistency ramming masses or plastic masses. The binders listed in DE 10 2007 012 489 A1 are exclusive

Thermoplastics. Thermoplastics, also known as plastomers, are plastics that can be deformed in a specific temperature range (thermo-plastic). This process is reversible, that is, it can be repeated as often as desired by cooling and reheating to the molten state, as long as not using the so-called thermal decomposition of the material by overheating. Thermoplastics are mainly processed by injection molding, which is similar to the core shooting method described in DE 10 2007 012 489 AI. The thermoplastics include z. Acrylonitrile-butadiene-styrene (ABS), polyamides (PA), polylactate (PLA), polymethylmethacrylate (PMMA), polycarbonate (PC),

Polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyetheretherketone (PEEK) and polyvinyl chloride (PVC). The longest known thermoplastic is celluloid.

In no way are the properties of thermoplastic binders to be compared with the hybrid binders described in the present patent application which must ensure strength over a wide temperature range.

A burning of the products described in DE 10 2007 012 489 AI is not possible. They would disintegrate or ignite and burn with thermite. A use is then no longer possible.

The reduction of the emission in DE 10 2007 012 489 AI is only for the protection of the mold, but not the environment or to avoid fire hazards, etc.

carried out. The emission is considerably higher than in our products. In the mixtures of DE 10 2007 012 489 A1, only refractory materials are used as lightweight filler

Cenospheres of Si0 ₂ (but there is not really), A1 ₂ 0 ₃ (does not exist in said grain size) and aluminum silicate, but no fibers and no expanded volcanic ash, etc. as in the present patent application. The products shown in DE 10 2007 012 489 A1 can be used for the applications described in the present patent application on the basis of their

Do not use properties. The invention is therefore not obvious from DE 10 2007 012 489 AI.

Task and solution of the invention

The invention has for its object to provide extremely stable moldings of the type mentioned, which have a density of less than 1.0 g / cm ³ , to about a maximum of 1500 ° C virtually no shrinkage, namely less than 1.0%, and show up to this temperature no external or internal cracks and no crumbling and for continuous temperatures up to about 1600 ° C are suitable and the one clearly show higher cold compressive strength than refractory bricks comparable gross density and comparable thermal conductivity show.

This object is achieved according to the invention in a refractory molding of the type mentioned by the features of claim 1.

Advantageous embodiments of the invention are set forth in the subclaims.

The geometry of the molded parts is basically no limit. Bricks, pipes, hollow bodies and other molded parts can be produced.

For the preparation is based on an aqueous mass, which are prepared by known shaping processes, subsequent drying and thermal treatment in various stages from 950 to about 1450 ° C. For example, the following molding methods are suitable:

• Vibration presses with low load,

Isostatic pressing,

Manual or mechanical stamping or ramming for complex shapes or smaller number of parts to be manufactured,

· Extrusion or extrusion process,

• Slip casting, especially for special parts, but also for larger blocks, whereby the water content of the masses produced for slip casting is about 10 to 20% higher. Before firing, careful and complete drying is recommended to avoid drying cracks or flaws after firing. Drying may take place at room temperature or at temperatures of approx. 70 ° C

be made. When fired at 950 to 1050 ° C, the kaolin present in the plastic starting material is converted into spinel and quartz, which then serves as a binder for the not yet melted at this temperature volcanic rocks.

Another fire at around 1250 ° C causes spinel + quartz pseudo-mullite to form. For applications above 1350 ° C, a further fire at approx. 1400 ° C is necessary. The pseudo-mullite now completely transforms to mullite and cristobalite. Drying and fire do not change the microstructure of the fixed cenospheres up to their softening or melting point. The microcellularly blown volcanic rocks melting above 1000 ° C serve above 1150 ° C with the silica and kaolin as a flux. SEM images have been used to demonstrate that this flux distributes uniformly across the cenospheres and coats them.

While the cenospheres remain unchanged during the fire, the surface of the cenospheres can be adjusted to the requirements in a targeted manner by adding or exchanging minerals and melts in the flux. With approximately the same densities and thermal properties can

Molded parts are produced in the coated surfaces of the cenospheres, depending on the aggregate e.g. the acid chamotte SS85 (85% <= SiO 2 <93%) or the aluminum-rich stones, enamel and sintered mullite stones M60 (55%> = A1203 <65%). Thus, lightweight flameproof, can be used up to 1600 ° C moldings with adapted to the intended use surfaces of the cenospheres.

Properties and production of the plastic mass, which serves as starting material for the production of the heat-insulating refractory molding according to the invention

The content of fibers and / or wollastonite serves to cohesion of the mass in the wet state. The hybrid binder provides for the cohesion after drying at temperatures up to about 200 ° C due to the organic component and at higher temperatures by the sintering of the silica particles. The kaolin used and the silica sol are also a binder, which at elevated

Temperature unfolds its function. The light fillers, namely the microcellularly expanded volcanic rocks and the cenospheres provide the necessary volume and a relatively low density compared to the prior art. The microcellularly inflated volcanic rocks soften at temperatures above about 1000 ° C and higher and then serve as a flux and binder between the

high temperature resistant cenospheres.

It is also advantageous if high-melting additives such as silicon carbide, carbon, corundum, etc. are included to chemical, thermal and mechanical property and durability of the molding and starting material, such as viscosity,

Printer softening point, temperature resistance, shrinkage behavior and other properties can be set specifically. The microcellular expanded volcanic stones are surface treated to protect against water attack in the plastic masses and mortars, thereby rendering the masses shelf stable. On the one hand inflated cellular volcanic rock in the form of nonporous hollow granules is used as light filler. In the case of porous hollow granules, on the other hand, the bulk density would increase, more glue and more minerals would be required, the masses would become duller and thus would be worse to process and the porosity of the end product would increase significantly.

fly ash

The main constituent of the composition according to the invention are fly ash cenospheres, which in particular have a proportion of from 20 to 45% by weight.

Fly ash is the solid, disperse (particulate, particulate, dusty) residue of burns, which is due to its high dispersity (fineness) discharged with the flue gases. Fly ash is produced in large quantities in

Thermal power plants and waste incineration plants and there must be separated by filters from the flue gases. The particle size ranges from about 1 μπι to 1 mm.

Particle shapes include both smooth, massive spheres and hollow spheres (so-called cenospheres), platelets, fibers and agglomerates. The density is 2.2 to 2.4 kg / dm ³ , the bulk density is between 0.9 to 1.1 kg / dm ³ . The composition of the fly ash strongly depends on the fuel (lignite or

Hard coal) and extends from residual carbon and minerals (quartz) to toxic substances such as heavy metals (arsenic to zinc) and dioxins. The fly ash also acts as a carrier of adsorbed pollutants. While pure, uniform, consistent fuels such as hard coal provide a good usable fly ash, the brown coal fly ash (BFA) is composed of many different substances. Due to their chemical and physical properties, such as the pozzolanic reactivity, the spherical grain shape and the grain distribution, hard coal fly ash (SFA) in particular is a high - quality secondary raw material and is found in the

Construction a variety of uses.

Pollutant-free fly ash is used in the building materials industry according to DIN EN 450 as an additive in cement and concrete. Furthermore, the fly ash can be used for the production of bricks made of sand-lime brick or aerated concrete. In road and earthworks, the fly ash is used together with Gesteinskömung as a building material for unbound base courses.

(Source: Wikipedia)

Only the fraction of the cenospheres is used in the compositions according to the invention, since the density in the range of 0.5-0.9 g / ml and the bulk density of 0.3-0.6 g ml are considerably lower.

Kaolin / Silica Kieselsol Kaolin, also referred to as china clay or aluminum silicate, is a fine, iron-free, white rock containing as its main constituent kaolinite, a weathering product of feldspar.

The kaolin used as a film covers the high-melting light filler and forms a solid structure even at about 900 ° C. The strength of the structure and the

Shrinkage is affected by the ratio of kaolin / silica / silica sol and their distribution.

Another advantage of the used mixture of kaolin silica silica sol is that the mass after hardening is hard and mechanically stable.

The high mechanical stability without shrinkage at temperatures up to about 1600 ° C according to the invention by the interaction of the essential components

• high melting light filler cenospheres,

· (T up to 1650 ° C)

• microcellular puffed volcanic rock

• kaolin, silica, silica sol • Mineral aggregates such as corundum, quartz, mullite,

Calcium magnesium silicates, chrome ore, zirconium silicate, etc.

Ceramic or other refractory fibers and / or wollastonite

reached.

It is also proposed that a binder mixture of several

Binders is used with a binding effect in different temperature ranges. The innovation of the product according to the invention is, in particular, that suitable, complementary binder systems are used, for. B. the

Hybrid binder, which already has the support structures made of fibers in the

Drying under room temperature with the light filler (expanded volcanic rocks) sufficient to fix the structure to about 200 ° C. By mineral binders, z. As kaolin, which are already included, as well as the silica contained in the hybrid binder, this structure is sufficiently strong reinforced from about 900 ° C, that at the respective desired application temperatures also no shrinkage. Above 1050 ° C serve the softening microcellular distended

Volcanic rocks as a flux for the additional minerals and as a fixation for the cenospheres. Due to the cavities formed by the melting, stresses can be buffered by increasing the temperature and expanding within the mass.

If temperatures continue to rise, additional chemical changes take place, depending on the aggregate. The fixation of the cenospheres remains untouched up to their softening point and thus guarantees the dimensional stability. Particularly innovative is that the different binders and the high-melting mineral granules in terms of increasing the temperature increase solidification of these materials so complemented that a dimensionally stable and constant weight product with different adjustable structures, densities and strengths up to the maximum application temperature.

A key customer benefit when using the products according to the invention is that in addition to the desired goal of efficient high-temperature insulation a Significant cost savings in the area of opportunity costs for customers can be realized. The reduction of these costs is achieved primarily by improving the energy balance and also the life cycle assessment by reducing emissions for the customer.

Further important advantages of the products according to the invention:

• Non-flammable

• Low weight

• High temperature resistance

· Low thermal conductivity

• Good strength properties

• Easy installation and processing

• Many combination options

• Low alkalinity

· Non-hygroscopic

• Chemical resistant

• Good electrical insulation

• Recyclable

• Landfillable

Perlite (English: perlite) referred to in geosciences an altered (chemically and physically transformed) volcanic glass (obsidian) and is thus one of the rocks. The so-called pearlitic structure is formed here by approximately pea-sized glass beads. Perlite contains up to 2% water and has a density of about 900 to 1000 kg / m ³ (bulk density of crude perlite). By annealing to about 800 ° C to 1000 ° C, perlite inflates to the fifteen to twenty times its original volume and then has a bulk density of 50 to 100 kg / m ³ and a thermal conductivity of λ = 0.040 to 0.070 W / mK. According to the invention, these perlites can not be used because of the porosity.

In contrast, microcellularly-expanded volcanic rocks are suitable for the purposes of the invention, produced according to new environmentally friendly and energy-saving methods, and achieve properties and technical values that expand from older, porous ones

Volcanic rocks ("expanded perlites") differs. Microcellular, expanded volcanic rock is a filler from the group of aluminum silicates and consists of spherical ("honeycomb"), rod-shaped and flaky particles resulting in high packing densities and higher bond strengths than conventional hollow microspheres due to mechanical and cohesive bonding forces. Targeted surface coatings enable an advantageous bond with the inorganic or organic matrix. This results in less shrinkage and better technical properties. Commercially available is blown impregnated perlite z. B. under the trade name NOBLITE® (product of the company NOBLITE, Route de Claye, F-77181 LE PIN, France) and Technoperl® (product of Europerl Germany, D-94032 Passau, Nibelungenplatz 4).

Fibers used according to the invention

In particular, ceramic and / or mineral high-melting fibers and / or organic high-melting fibers, for example carbon fibers, are used. Wollastonite is also possible.

Ceramic fibers or ceramic fibers are fibers

inorganic, non-metallic material. Originally, only polycrystalline inorganic materials were called ceramic. Meanwhile, however, there are various polymers, so-called precursors, produced by pyrolysis amorphous fibers, which are referred to by their properties as ceramic fibers. The distinction to amorphous glass fibers, which are not counted among the ceramic fibers, is best made possible by the manufacturing process (glass fibers from glass melt, amorphous ceramic fibers from polymeric precursors by pyrolysis). The ceramic fibers are classified into oxidic and non-oxidic.

On oxidic ceramic fibers fibers based on alumina and silica in different proportions and in part even with additional boron oxide or zirconium oxide are known. Mixed oxide fibers of 85% A1 ₂ 0 ₃ and 15% Si0 ₂ are also referred to as mullite fibers. All of these fibers are polycrystalline.

Non-oxide, industrially produced fibers (other than carbon fibers) have various types of silicon carbide fibers known. Starting polymers are almost exclusively so-called poly-carbosilanes. These are polymers of hydrocarbons in which individual carbon atoms have been replaced by silicon atoms or silanes in which individual silicon atoms have been replaced by carbon atoms. Additives crosslink the polymers in a hardening process so that they can be used after the P2011 / 000872

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Spinning process in the pyrolysis not simply evaporate, but - as in the production of carbon fibers - are converted into an amorphous, usually non-stoichiometric, still free carbon-containing SiC ceramic fiber. In special manufacturing processes, it is also possible to produce very finely crystalline and pure SiC fibers with significantly improved high-temperature properties.

Hybrid Binding Agent Used According to the Invention Preferably, an organic-inorganic hybrid binder is used which is obtainable under the trade name COL.9 from BASF. It contains 50 to 100 nm composite particles containing amorphous silica particles 5 and a polymer 6 based on n-butyl acrylate and methyl methacrylate (see Figure 1). The particles are dispersed in water. Due to the stickiness of the particles due to the polymer content is obtained an excellent binder for low temperatures, up to about 200 ° C. At elevated temperatures, the polymer fraction decomposes and the silica particles remain and thus preserve the structure, wherein the silica particles also forms a solid framework at a correspondingly high temperature. Shrinkage therefore does not occur at low or elevated

Temperature up. The binder has a solids content of about 35 to 40% by weight. The silicate content, based on the solids content, is 30 to 50 wt .-%.

Silica used according to the invention

Preferably, a surface-treated silica is used. Silica is an intimate mixture of finely divided silica and kaolinite. For example, the Neuburg Siliceous Earth is known, which is preferably used according to the invention. For better wettability with water, the silica is treated with a silane so that the individual particles have a functional hydrophilic surface.

Such an activated silica is available under the trade name "AKTISIL EM" from Hoffmann Mineral GmbH, Neuburg (Danube) Here, the silica is treated with 3-epoxypropyloxipropyltrimethoxysilane.This so-called activated silica can be used in powder form the use of a mixture of silica sol and kaolin / kaolinite. Production examples and example formulations for the plastic mass used to produce the molded parts

preparation

First, mix all the liquid components of the recipe; then the components are weighed separately according to the recipe. step 1

Mixer to be used: e.g. beba compulsory mixer

All liquid raw materials should be mixed with the water (avoid foaming); then the fibers are picked by hand and wetted with the water mixture until they are completely moistened.

Level 2

Addition of the first half of the cenospheres. Now mix with the lid closed. Mixing time: approx. 10 minutes, stage 3

Now, the addition of mineral aggregates such as kaolin, corundum, silica, etc. takes place.

Mixing time: 20 minutes

The premix now has a creamy consistency and may no longer contain lumps. If there are any lumps left, rasp them by hand, mix again with the same setting until there are no more lumps.

Level 4

Now the second half of the cenosphere has to be kneaded under the mass. Mixing time: 15 minutes

Level 5 Addition of microcellular expanded volcanic rock. Then mix with the lid closed.

Mixing time: 25 minutes

Depending on the type of processing, the mass must correspond to a loose bed to a pourable mortar.

The now completed mixture is now used by means of one of the above molding methods for the production of the moldings of the invention.

Basically, all shaping methods are possible, which are suitable for semi-dry masses on plastic masses up to pourable masses. Especially in the case of processes with pressure or high shear forces such as extrusion, it is important to pay attention to the limited load capacity of the lightweight fillers.

example recipe

200 kg approach:

Water 60.00 kg

Ceramic fiber "Altra" B80 from Rath 8, 10 kg

Binder "C0L.9" from Fa. BASF 2.00 kg

Silica sol "Levasil 200A / 30" from Akzo Nobel Chemicals 8,20 kg

Aluminum hydroxide Trefil 744-300 EST from Fa. Quarzwerke 20.40 kg "Cenosphere W300" from Omega Minerals 51, 40 kg Micro-cellular expanded volcanic rock "Noblite 200 EC"

from Fa. Noblite 21, 60 kg

Silica "Aktisil EM" from Fa. Hoffmann Mineral 10.40 kg

Corundum "Sepasil EK-R 220 MST" from Fa. Quarzwerke 17.90 kg

Claims

claims

Heat-insulating refractory high-temperature resistant molding, which is suitable for continuous use temperatures of 1200 to 1600 ° C and several lightweight fillers, a reaction product of the thermal curing of a

Contains binders and fibers and / or wollastonite,

characterized,

that there are cenospheres of fly ash and billowing closed-cell volcanic rock as light fillers that flux it and that it

Silica as a reaction product of the thermal curing of the binder.

2. molding according to claim 1,

characterized,

that it contains a uniform type of fibers or a mixture of different fibers, in particular ceramic fibers, having a softening point of at least 1200 ° C and / or wollastonite.

Molding according to claim 1,

marked by

the following composition:

Cenospheres of 30-60% by weight of microcellular expanded volcanic rock of 10 -40% by weight of silica (SiO 2) of 40-70% by weight of aluminum oxide (A1203) of 15-65% by weight of fibers up to 10% by weight Wollastonite up to 30% by weight

Molding according to claim 1,

characterized,

that high-melting additives such as silicon carbide, carbon, corundum are included. 5. molding according to claim 1,

characterized,

that it is trained as standard stone, brick, oven door or

Thermal insulation board or

as a lining for trolleys in ceramic kilns or

as inner insulation the lid of transport crucibles for liquid metal or as inner insulation of the transport crucible for liquid metal or

as gutter for liquid metal or

as Feuerwendestein for power plant and industrial plant construction or as a cover plate for bogies in furnaces for ceramics and porcelain.

Molding according to one of the preceding claims,

producible by molding a plastic mass and drying and firing,

the mass containing fibers and / or wollastonite and water and at least two light fillers and a flux,

that as light fillers cenospheres of fly ash and expanded closed cell volcanic ash are used, which are superficial

Water protection layer are equipped,

in that the composition contains as binder a hybrid organic-inorganic binder containing silica and an organic polymer, and in that the composition contains kaolin or kaolinite as flux and silica, preferably silica sol, in particular silica.

Molded part according to claim 6,

characterized,

that the hybrid binder used in the plastic mass contains particles which in turn are composed of amorphous silica particles (5) which contain as binder a polymer (6) based on acrylate,

in particular n-butyl acrylate and methyl methacrylate.

Molded part according to claim 6,

characterized,

that in the plastic mass is used a modified silica containing silica-kaolinite particles whose surface is coated with a wetting agent, in particular a silane.

Molded part according to claim 6,

characterized, that the plastic mass contains a uniform type of fibers or a mixture of different fibers, in particular ceramic fibers, with a softening point of at least 1200 ° C and / or wollastonite.

Molded part according to claim 6,

characterized,

that the plastic mass has the following composition:

Cenospheres 20 to 45% by weight microcellular expanded volcanic rock 5 to 20% by weight

Hybrid binder 1 to 6% by weight

Fibers up to 6% by weight

Wollastonite to 15% by weight modified silica 3 to 15% by weight.

Rest of water.