EP3047079A1

EP3047079A1 - Silicic acid mixtures and use thereof as insulation material

Info

Publication number: EP3047079A1
Application number: EP14758334.8A
Authority: EP
Inventors: Wolfgang Knies; Hans Eiblmeier
Original assignee: Wacker Chemie AG
Current assignee: Wacker Chemie AG
Priority date: 2013-09-18
Filing date: 2014-08-27
Publication date: 2016-07-27
Also published as: JP2016539909A; DE102013218689A1; CN105556043A; US20160230383A1; WO2015039843A1; KR20160058859A

Abstract

1. The invention relates to silicic acid mixtures and use thereof as insulation material. 2.1 The problem to be solved by the invention was the providing of a cost-effective mixture based on silicic acid which can be used for insulation, wherein said mixture contains as small a volume as possible of chemically produced silicic acid and a high proportion of silicon-containing by-products or waste products, without substantially reducing the insulating properties. 2.2 This problem is solved by a mixture of silicic acid and more than 50 wt.-% silicon-containing ash, which contains no perlite, wherein the silicon-containing ash preferably comprises rice husk ash and silica fume. The invention further relates to a method for producing insulation material by producing the mixture according to the invention and introducing the mixture into a sleeve, wherein no sintering step occurs in the method. Mixtures of differing compositions were correspondingly processed into a vacuum insulation panel and the insulating properties were compared based on the measured thermal conductivity. 2.2 The mixture according to the invention can be used as an insulation material, in particular for housing insulation.

Description

Silica mixtures

and their use as thermal insulation material

The invention relates to a mixture of silica and more than 50 wt .-% silicon-containing ash containing no perlite, a process for the production of thermal insulation material by preparing the mixture according to the invention and introducing the mixture into a shell, wherein no sintering takes place in the process. Another object of the invention is the use of the thermal insulation material according to the invention in particular in the building insulation.

Thermal insulation (also called thermal insulation) is an important aspect for reducing energy consumption. Thermal insulation is intended to reduce the passage of heat energy through a shell to protect an area from either cooling or heating. Thermal insulation is therefore used to minimize the heating requirements of buildings, to allow for technical processes or to reduce their energy requirements, as well as in the transport of temperature-sensitive goods, e.g. biological or medical products. For example, while the insulation of refrigerators or hotplates is well known, thermal insulation of buildings has recently become increasingly important.

Depending on the application temperature, different requirements are placed on the thermal insulation material (also called insulating material). The reason for this is that the known heat transfer mechanisms, ie transmission through (1) gas line, (2) solid state line and / or (3) radiation change with temperature. At ambient temperature, for example, the convection of air is of greater importance than the radiation conductivity (3), the influence of which, however, greatly increases at higher temperatures or in vacuum systems. Thermal insulation materials must take this into account. Because at high temperatures the Transmission through gases (1) is of lesser importance, also the pore structure loses its importance. In the case of moldings which are to be used at high temperatures, the mechanical strength of the heat-insulating body also gains importance, for which reason corresponding thermal insulation materials usually contain further constituents, such as, for example, binders or hardeners. Such components would lead to a drastic deterioration of the thermal insulation at room temperature. For thermal insulation different materials are in use. One of these is mixtures of microporous powders which, when admixed with additives either as molded bodies, play a role directly in the high-temperature insulation or as so-called vacuum insulation panels in the thermal insulation at ambient temperature.

A number of blends based on microporous inorganic oxides, e.g. Silica, in particular fumed silica, which are used for thermal insulation (see, for example, US Pat. No. 5,911,903). These have the disadvantage that chemically prepared silica such as e.g. Fumed silica is relatively expensive and thus the total cost of thermal insulation material are very high. From DE 199 54 474 it is known that a mixture based on dried, cleansed of foreign matter and dusted seaweed for thermal insulation can be used, since this has a high boron and silica content. No further chemically produced silicic acid is added to this mixture.

Both in order to reduce the high costs of thermal insulation mixtures and insulating materials due to the use of chemically produced silica, as well as to use the good insulation of biogenic material, the mixtures and moldings based on silica, in particular pyrogenic ner silica, for use in thermal insulation more favorable silicon dioxide-containing components added as by-products or waste products and the proportion of chemically produced silica, in particular fumed silica, kept as low as possible.

For example, DE 43 20 506 a molded body with a layer of burned biogenic material, with a

Is connected layer of fumed silica, for insulation, especially in the night power storage area or for a variety of electrical appliances such. Stoves and refrigerators available. The total body contains in addition to fumed silica cheap rice husk ash and inorganic hardeners. The use of hardener has the disadvantage that it lowers the heat-insulating properties of a mixture or of a shaped body.

DE 10 2006 045 451 discloses thermal insulation material in which part of the fumed silica is replaced by less expensive biological material. The proportion of biogenic or biological material that is burned and evt. pretreated and / or post-treated, is at most 50 wt .-%. The thermal insulation material is intended for radiant heaters and should therefore meet certain purity requirements. DE 30 20 681 also provides a mixture of silicic acid and biogenic material for high-temperature thermal insulation, in particular for the isolation, protection or treatment of metal baths during their processing or transport, which additionally contains organic binder in the form of a slurry Is added to cellulose. However, the addition of binders has the disadvantage that it increases the thermal conductivity of the resulting thermal insulation mixture and thus reduces the heat-insulating properties. In addition, DE 2847807 adds the thermal insulation mix with perlite. Also DE 93 02 904 claims a thermal insulation mixture containing perlite according to the invention. The addition of perlite has the disadvantage that the heat-insulating properties and the me chanical stability are reduced.

There is therefore a need to switch from chemically produced silica-based thermal insulation systems to mixtures containing cheaper components. For example, thermal insulation materials based on fumed silica are considered, the hollow glass spheres of the company 3M (Scotchlite) such as e.g. which contain the K, S or iM series, one finds a linear increase in the thermal conductivity with increasing amount of glass hollow spheres with simultaneously decreasing amount of fumed silica. Thus, the lower the proportion of costly fumed silica and the higher the proportion of cheaper silicon-containing constituents, the lower the heat-insulating properties become. The present invention therefore provides a low-cost silica-based mixture which can be used for thermal insulation without substantially reducing the heat-insulating properties, the mixture comprising a small amount of chemically produced silica and a proportion of at least 50% by weight. - contains% silicic by-products or waste products but no perlite.

Surprisingly, it was found that liziumhaltiger using si ashes a significantly lower heat ^¬ conductivity occurs in a mixture based on chemically produced silica, as they would be expected with linear dependence of the thermal conductivity of the percentage of additive in the mixture. This is particularly surprising when a high proportion of silicon-containing ashes is set to. Therefore, a significant advantage of the mixture according to the invention is that it is inexpensive and at the same time has very good heat-insulating properties. It is particularly advantageous that the heat-insulating properties of the mixture according to the invention compared to a mixture of pure silica without the addition of silicon-containing ashes are only slightly lower, while they are significantly higher than mixtures which consist only of silicon-containing ashes.

It has been found that for use as a thermal insulation material more than 50% by weight of silicon-containing ashes can be used in the mixture and thereby the amount of silica can be reduced without the thermal conductivity of the mixture compared to the silicic acid mixture without silicon-containing

To increase ashes by a factor of more than 2.5, preferably more than 2, more preferably more than 1.5 and in particular more than 1.2. The addition of silicon in the form of cheap silicon-containing ashes replaces some of the silica. According to the invention, the mixture contains more than 50% by weight of silicon-containing ashes, preferably more than 60% by weight, more preferably more than 65% by weight and especially preferably more than 70% by weight

o.

Even when using more than 60 wt .-% or more than 70 wt .-% silicon-containing ash in the mixture according to the invention this has the advantage that it is characterized by values for thermal conductivity, which are significantly lower than when only silicon-containing ash is used in the mixture (cf., for example, Example 1 with 5 and Example 8 with 6).

It was completely unexpected that the thermal insulation effect of a mixture of silica and silicon-ash such as rice husk ash or waste silica, despite the high thermal conductivity ^¬ ability of siliceous ash is much lower in pure form in gerin- gen proportions of the raw material silica. Due to this surprising result, it is possible to put einzu- silica in the mixture has a high proportion of silicon pockets at the same time redu ^¬ ed proportion of the raw material and this to USAGE example for thermal insulation ^¬ that without reducing the insulating properties significantly. This can significantly reduce costs.

The thermal conductivity λ denotes the specific heat-insulating properties of a substance. The smaller the value, the better the heat-insulating effect. The thermal conductivity has the unit watts per meter and Kelvin (W / mK). It is temperature dependent. Their inverse is the specific thermal resistance. The thermal conductivity values for various substances vary by many orders of magnitude. High values are required for heat sinks. In contrast, an insulating material is a material with low thermal conductivity, which is used for thermal insulation.

The thermal conductivity of a sample as a function of the measuring temperature can be determined, for example, with the aid of a heat flow meter according to DIN EN 12939, DIN EN 13163 and DIN EN 12667 at a temperature of 10 ° C to 40 ° C. Preferably, a heat flow meter (HFM) from Netzsch (Selb) is used, particularly preferably the lambda meter HFM 436 from Netzsch. The thermal conductivity of the sample is preferably measured at a temperature of 10 ° C.

Silica in the context of the invention means chemically produced oxides of silicon and is commercially available as a raw material lent. The term silica accordingly includes precipitated silica and fumed silica. The salts of the acids, referred to as silicates, are not included. The silica is preferably pyrogenically prepared silica. This includes, for example, HDK® from Wacker Chemie AG (Burghausen), Cabosil Fa. Cabot and Aerosil® Evonik Industries (location).

Silica is characterized by good heat-insulating properties, which manifests itself in a low thermal conductivity (see Example 4). Although mixtures without silica exclusively based on silicon-containing ashes in general have a significantly higher value for the thermal conductivity (see Examples 5 and 6), the thermal conductivity of the mixture according to the invention containing at least 50 wt .-% silicon-containing ash at a measuring temperature of 10 ° C. compared to the mixture in which the amount of silicon-containing ash has been replaced by pure silicic acid has only been increased by a factor of less than 2.5, preferably less than 2 and particularly preferably less than 1.5 (compare Examples 1-3 and 7-8). Therefore, the addition of chemically produced silica in the mixture is not completely eliminated.

The thermal conductivity of the mixture according to the invention is preferably less than 0.009 W / mK, more preferably less than 0.005 W / mK and especially less than 0.004 W / mK, at a measuring temperature of 10 ° C.

A preferred object of the invention is that the silica in the mixture is fumed silica. This has for example in the insulation to the advantage that it has an increased insulating ability, since it has a lower moisture content and lower moisture absorption than precipitated silicic acids due to the manufacturing process. For this reason, for example, the support cores of vacuum insulation panels are made predominantly of fumed silica.

Fumed silicas generally have a specific surface area (after BET measurement) of 30 to 500 m ² / g. The A- amount of fumed silica, which is preferably between 25 and 49 wt .-%, depends on this BET surface area. The higher the BET surface area, the lower the amount used to achieve comparable thermal insulation. Therefore, preferably small amounts of a fumed silica having a high BET surface area are used, particularly preferably HDK® N20, T30 or T40 (Wacker Chemie) having a specific surface area of more than 170 m ² / g.

The specific surface area of a silica is preferably determined in accordance with DIN 9277/66132 by BET measurement (according to Brunauer, Emmett and Teller) by nitrogen adsorption.

Ash refers to the remaining inorganic constituents from the combustion of organic matter, ie living organisms such as plants or animals or fossil fuels. The solid inorganic residues are a mixture of carbonates, sulfates, phosphates, chlorides and silicates of the alkali metals and alkaline earth metals, and iron oxides and the like. These can be mixed with smaller amounts of unburned organic material. It is particularly preferred that the organic material is completely burned and that the ash consists exclusively of inorganic constituents.

According to the invention, silicon-containing ash consists of more than 70% by weight, preferably more than 80% by weight and more preferably more than 85% by weight of silicon dioxide, the proportion being particularly preferred by means of chemical analysis, preferably by digestion with hydrofluoric acid analogous to the determination of silica, as described in US Pharmacopeia USP 36 NF 31, can be determined. An example of an inventive safety-liziumhaltige ash, which is preferably used is rice hull ash ^¬ (also called rice hull ash) in the combustion of rice husk residues in the production of rice is created and is currently deposited for the most part, thus representing a cheap raw material. It is therefore preferred that the silicon-containing ash in the mixture contains rice husk ash, more preferably the siliceous ash in the mixture is exclusively rice-shell ashes. It consists of more than 90% by weight of silicon dioxide (see www.refra.com/bioqene silica) and can be obtained from many rice mills located in rice-producing countries.

By silicon deposits in plant stalks also straw and whole plant ashes such. Ashes of grasses and reeds to a silicon content of about 70 wt .-% and can be used according to the invention.

It is advantageous if the rice husk ash still contains soot residues, since these also act as an IR blocker.

The silicon-containing ash of combustion furnaces resulting from the disposal of silicon-containing exhaust gases or residues is, for example, another cheap product which can be used according to the invention. These include, among other things, the filter residue of the flue gas cleaning in the silicon production, such products are usually under the name Silica Fume on the market. The silicon-containing ash according to the invention preferably comprises silica fume. However, it is also possible to use other ashes which are typically produced when disposing of silicon-containing waste. Characteristic of these cheap fillers is that they generally do not have a defined surface according to BET, and in some cases with other elements such as e.g. Aluminum, iron, etc. are contaminated.

It is particularly preferred that the silicon-containing ash of the mixture according to the invention consists of rice husk ash and silica fume. Most preferably, it is composed of equal parts rice husk ash and silica fume. Thermal insulation systems for higher application temperatures often contain additional constituents, such as hardeners or binders.

A hardener, also called curing agent, is an additive to synthetically produced adhesives (glues) and paints (reaction paint), which sets the curing in motion or accelerates it. It consists of acids or salts. A preferred object of the invention is that at most 1% by weight, particularly preferably at most 0.5% by weight and especially preferably at most 0.1% by weight of hardener is added to the mixture according to the invention. Moreover, it is preferred that no inorganic hardener is added to the mixture, more preferably no curing agent is added at all. In this way, the costs are reduced and the thermal conductivity of the mixture kept low because hardeners reduce the thermal insulation properties of a mixture. The mixture preferably contains no alkali silicate solution used as hardener in the prior art.

Binders are substances by which solids with a fine degree of dispersion (eg powder) are glued to one another or to a substrate. Binders are usually added in liquid form to the fillers to be bound and mixed intensively so that they are evenly distributed and all particles of the filler are wetted uniformly with the binder. In particular, when using liquid binders have the disadvantage that when mixed with liquids, the pores of the particles of the mixture filled and the contacts between the particles are increased, thereby increasing the thermal conductivity and the insulation deteriorates accordingly. Due to the nature of the binder, the filler can be given new processing and material properties. For higher application temperatures, binders such as polyvinyl alcohol, molasses, sodium hexametaphosphate, Portland cement, Sodium silicate, precipitated calcium carbonate listed.

A preferred subject matter of the invention is that the mixture according to the invention is added to at most 1% by weight, more preferably at most 0.5% by weight and especially preferably at most 0.1% by weight of binder. In addition, it is particularly preferred that no cellulose-based pulp such as pulp is added to the mixture according to the invention. Furthermore, preference is given to adding at least no organic binder, particularly preferably no binder at all, to the mixture according to the invention. By dispensing with additives for the mixture according to the invention such as binders, it is possible, for example when used in thermal insulation, to keep the thermal conductivity low despite the high proportion of the mixture of by-products and waste products in the form of silicon-containing ashes. At the same time the costs are reduced.

Perlite is a volcanic rock, which due to its chemical composition corresponds to a natural glass. The pearlite rock contains bound water, which evaporates on rapid heating and leads to popcorn-like structures (ceramic hollow spheres). The resulting pumice-like products with thin pore walls are used in the prior art, inter alia, as thermal insulation materials. It has a thermal conductivity of about 0.04-0.07 W / mK and due to its structure a low mechanical stability.

The mixture according to the invention is characterized in that it contains no perlite. This has the advantage that it contains no fragments of perlite when using pressing processes, such as the production of moldings or even the pressure of the vacuum, for example, exerted on the core of a vacuum insulation panel. Another object of the invention is the preferred addition of infrared (IR) opacifier (also called IR blocker) for the mixture according to the invention. If a material which already acts as an IR blocker is used as the silicon-containing ash, which is usually the case, for example, when rice husk ash is used, no further separate IR blocker is added. IR opacifiers are substances that reduce heat radiation due to their composition and structure due to scattering and absorption processes. Examples of opacifiers include ilmenite, titanium oxide / rutile, silicon carbide, iron II / iron III mixed oxide, ^' chromium dioxide, zirconium oxide, manganese dioxide, iron oxide, silica, alumina and zirconium silicate, and mixtures thereof. Preferably, Russian and silicon carbide are used. It is preferred that the opacifiers have an absorption maximum in the infrared range between 1.5 and 10 μm.

It is furthermore a preferred object of the invention for the mixture according to the invention to contain fiber material. The amount of fiber material used in the mixture according to the invention is preferably not more than 10% by weight and more preferably not more than 5% by weight. A fiber is a thin and flexible structure in relation to its length. Examples of fiber materials, in addition to the many fibers based on organic polymers such as cellulose, polyethylene or polypropylene, glass wool, rock wool, basalt wool, slag wool and fibers obtained from smelting (for example by blowing, spinning or drawing), the aluminum and / or or silica, for example quartz glass fibers, ceramic fibers of soluble and insoluble type fibers containing at least 96% by weight of SiO ₂ and glass fibers such as E glass fibers and R glass fibers, as well as mixtures of one or more of said fiber types. Preferably, cellulose fibers, quartz glass fibers, ceramic fibers or glass fibers are used. They typically have a diameter of 0.1-15 μπι and a length of 1-25 mm. Another object of the invention is a process for the preparation of thermal insulation material, characterized in that the mixture described above is prepared and this mixture is introduced into a shell, wherein no sintering takes place in the process and the insulating material contains no pearlite.

First, the mixture according to the invention is prepared by intimately mixing together silicic acid, preferably fumed silica with silicon-containing ash, such as preferably rice husk ash or silica fume, fiber material, preferably cellulose fiber and optionally IR opacifier, preferably silicon carbide. For the preparation of the preferably powdery mixture, preference is given to a commercially available mixing apparatus or

Used mixing unit such as the Dispermat VL60 (Getzmann, Reichshof). It can e.g. Mixing units are used with mechanical mixing elements with low and / or high rotational speed. However, the individual components can also by introducing gas streams such. Air flows are mixed.

Another object of the invention is that the mixture according to the invention is introduced into a shell.

For this purpose, it is preferred that the mixture according to the invention is first enveloped by a first dust-tight envelope and then introduced according to the invention into a shell. The advantage of using a first shell is that it prevents dusts from escaping from the mixture in subsequent process steps, which, for example, occupy the seams to be welded of the second shell (vacuum film) and thus prevent airtight welding. It is therefore referred to below as a dust-tight envelope. As a shell can a commercial, air-permeable non-woven or foil bags are used.

The uncoated, coated or dust-tightly encased mixture is then more preferably introduced into a gas-tight envelope. Gas-tight means that this envelope is impermeable to air. It is therefore also referred to as an airtight film. The advantage of a gas-tight envelope is that it allows the application of a vacuum, which is why the thermal conductivity of the mixture is lower.

In the process for producing the thermal insulation material, no sintering step takes place. Sintering refers to a process for the production or modification of (factory) substances in which fine-grained, ceramic or metallic substances are usually heated under pressure increase by means of temperatures below their own melting temperatures.

This method is mainly used in the ceramic industry but also in metallurgy application, wherein granular or powdery substances are mixed and joined together by heat treatment. After the powder masses have been brought into the shape of the desired workpiece, either by pressing the powder masses or by shaping and drying, as happens in the production of Tongut, the so-called green compact is compacted by heat treatment below the melting temperature and cured.

Sintering allows the fusion of raw materials, which otherwise would not be possible or would be very difficult to combine to form a new substance. It works in three steps: First, the compaction of the green body takes place; in the second step, the porosity is substantially minimized and, finally, the desired strength of the materials is achieved. It is advantageous that this eliminates a time-consuming and costly process step.

In addition, the sintering process achieves a higher density of the thermal insulation material, which in turn leads to higher thermal conductivity. It was found in own experiments that even without the addition of silicon-containing ashes, the thermal conductivity of 0.003 W / mK only increases to values of 0.009 W / mK by sintering at a temperature of about 900 ° C. In contrast, although the drying is also a heat treatment, there is no chemical reaction during drying, since moisture is removed only from the ambient air.

The inventive method includes a drying step, but no sintering step.

It is a further preferred object of the invention to produce a shaped body from this mixture. The shaped body is preferably an insulating mat or insulating plate.

Such as. from US Pat. No. 5,950,450 or DE 43 39 435, the thermal conductivity of insulating material can be dramatically reduced if there is a vacuum in the system. Therefore, the mixture can be placed in a wrapper such as e.g. introduced a nonwoven bag and the shaped body formed in a non-porous shell such as a composite film are vacuum-sealed. The evacuation leads to a compression of the material. Due to their pore structure, silicic acids still have a reduced vacuum of less than 10 mbar. sufficient mechanical strength, without having the wrapper injurious edges.

Therefore, the use of the mixture for producing a vacuum insulation panel (VIP) is particularly preferred. The support Cores of the VIPs consist of microporous powders in the form of silica, silicon-containing ashes, fibers and / or IR blockers. Precipitated silicic acids have a higher moisture content due to the manufacturing process. This reduces the isolation ability of the entire VIP. For this reason, the support cores are made predominantly of fumed silica.

The production of VIPs preferably takes place in several steps:

First, the powdery mixture of the present invention is prepared as described above.

The resulting mixtures are then filled in an air-permeable envelope and these closed. For example, filling may be done manually (e.g., with a paddle) into a polypropylene film and sealed with heat-welding tongs.

Preferably, the filled nonwoven bags are dried. This can be done in a drying oven at temperatures higher than 40 ° C. The maximum drying temperature depends on the temperature stability of the casing and is preferably selected to be 10 ° C. below the melting temperature of the casing.

Subsequently, the filled casing are placed in an airtight film, applied a vacuum and welded. As a film, gas and vacuum-tight multilayer films can be used. Such films are available on the market and are offered for example by the companies Hanita Europe (Rüsselsheim) or Dow Wolff Cellulosics GmbH (Walsrode). The closing can be done with a commercial vacuum welding machine. The applied vacuum is <10 mbar, preferably 0.1 mbar.

Alternatively, moldings can first be produced from the mixtures in a pressing process, either in the dust-proof envelope or directly into the non-porous shell and can be welded under vacuum.

The mixture according to the invention is preferably used for thermal insulation. It is particularly advantageous that they are cost-effectively assembled, as well as simple and inexpensive to produce and has low thermal conductivity values. By dispensing with binder or hardener in the mixture, the thermal conductivity is kept low.

The mixture according to the invention is preferably used as thermal insulation at a temperature of up to 95 ° C., more preferably of up to 80 ° C. and in particular of up to 70 ° C. This temperature includes, among other things, the thermal insulation of buildings, but the high-temperature insulation of, for example, ovens, metal baths or hotplates.

EXAMPLES Example 1 A pulverulent mixture of fumed silica HDK® N20 (Wacker Chemie AG, Burghausen), rice husk ash (produced by burning the residues obtained from polishing of rice grains by Fa.) Was used with the aid of a mixer from Getzmann (Dispermat VL 60). Patum Rice Mill and Granary, Amphur Mueng, Thailand) and cellulose fiber (Schwarzwälder Textilwerke, Schenkenzell, short cut 6 mm). For a total of 800 g, the proportions were as follows:

30 wt. -% HDK® N20

65 wt. -% rice husk ash

5 wt .-% cellulose fiber

The resulting mixture was processed into a vacuum insulation panel by first filling it in a nonwoven bag (polypropylene, basis weight 27 g / m ² , Kreykamp GmbH, Nettetal) and this with the heat-welding tongs HZ (230 V, 540 W, Kopp, Reichenbach) was closed. The mixture was then dried at 55 ° C. for 10 hours in the drying oven Kelvitron (Heraeus, Hanau). The filled and dried nonwoven bag was then placed in an air-tight film (Hanita, Rüsselsheim) and vacuum-sealed at 0.1 mbar using a vacuum welding machine A300 (Multivac, Wolfertschwenden). The thermal conductivity measured in the heat flow meter (HFM, Netzsch, Selb) at 10 ° C according to the manufacturer's instructions is shown in Table 1.

Example 2:

The following mixture was used to prepare a VIP as detailed in Example 1: 30% by weight HDK® N20

60% by weight of silica fume

5 wt .-% silicon carbide

5 wt .-% cellulose fiber

The result of the thermal conductivity measurement at 10 ° C is re rum listed in Table 1.

Example 3:

The following mixture was used to prepare a VIP as detailed in Example 1

25% by weight HDK® N20

35% by weight of rice husk ash

35% by weight of silica fume

5 wt .-% cellulose fiber

The result of the thermal conductivity measurement at 10 ° C is listed in T belle 1.

Example 4:

The following mixture was used to prepare a VIP as described in detail in Example 1:

85% by weight HDK® N20

5 wt .-% cellulose fiber

10 wt .-% silicon carbide

Example 5: The following mixture was used to prepare a VIP as detailed in Example 1:

95% by weight of rice husk ash

5 wt .-% cellulose fiber

The result of. Thermal conductivity measurement at 10 ° C is listed in Ta ble 1.

Example 6:

The following mixture was used to prepare a VIP as detailed in Example 1:

85% by weight of silica fume

5 wt .-% cellulose fiber

10 wt .-% silicon carbide

The result of the thermal conductivity measurement at 10 ° C is listed in Ta ble 1.

Example 7:

The following mixture was used to prepare a VIP as detailed in Example 1:

23.7% by weight HDK® N20

71.3% by weight of rice husk ash

5 wt .-% cellulose fiber

The result of the thermal conductivity measurement at 10 ° C is listed in Ta ble 1. Example 8: The following mixture was used to prepare a VIP as detailed in Example 1: 21.3 wt% HDK® N20

63.7 wt .-% silica fume

5 wt .-% cellulose fiber

10 wt .-% silicon carbide The result of the thermal conductivity measurement at 10 ° C is shown in Table 1.

Table 1:

λ = thermal conductivity at 10 ° C in W / mK (watts per meter and Kelvin)

All percentages are by weight.

The Si0 ₂ content of the rice husk ash was 91% by weight in all experiments. Example 9:

The following mixture was used to prepare a VIP as detailed in Example 1:

42.5% by weight of HD® N20

42.5% by weight hollow glass ball S25 (3M, St. Paul, USA)

5 wt .-% cellulose fiber

10 wt .-% silicon carbide

The result of the thermal conductivity measurement at 10 ° C is shown in ^Table 2.

Example 10:

The following mixture was used to prepare a VIP as detailed in Example 1:

85% by weight hollow glass ball S25 (3M, St. Paul, USA)

5 wt .-% cellulose fiber

10 wt .-% silicon carbide

The result of the thermal conductivity measurement at 10 ° C is shown in Table 2.

Table 2:

9 10

HDK®N20 42, 5% -

Glass bubbles 42, 5% 85%

Cellulose fiber 5% 5%

Silicon carbide 10% 10%

λ [W / mK] 7.0 -10 ^"3 1.1 -10 ^{" 2} λ = thermal conductivity at 10 ° C in W / mK (watts per meter and Kelvin)

All percentages are by weight.

Claims

claims

1. Mixture comprising silicic acid and more than 50 wt.% Silicon-containing ash, which does not contain perlite.

2. Mixture according to claim 1, characterized in that it is the fumed silica is fumed silica.

3. Mixture according to one of claims 1 or 2, characterized in that it contains more than 60 wt.% Of silicon-containing ash.

4. Mixture according to one of claims 1 to 3, characterized in that the silicon-containing ash consists of rice husk ash.

5. Mixture according to one of claims 1 to 3, characterized in that the silicon-containing ash contains silica fume.

6. Mixture according to one of claims 1 to 3, characterized in that the silicon-containing ash from Reisschalenasche and silica Fume consists.

7. Mixture according to one of claims 1 to 6, characterized in that IR opacifier is included.

8. Mixture according to one of claims 1 to 7, characterized in that fiber material is contained.

9. A process for the production of thermal insulation material, characterized in that a mixture according to any one of claims 1 to 8 is prepared and this mixture is introduced into a shell, wherein in the process, no sintering he follows and the insulating material contains no perlite.

10. The method according to claim 9, characterized in that da Dämmmaterial is processed into a shaped body.

11. The method according to claim 10, characterized in that the shaped body is an insulating mat, an insulating plate or a Vakuumisolationspaneel.

12. Use of the mixture according to one of claims 1 to 8 as thermal insulation material.

13. Use of the thermal insulation material prepared according to any one of claims 9 to 11 or according to claim 12 in the building dedämmung.