DE2240228A1 - PROCESS AND EQUIPMENT FOR MANUFACTURING HEAT-RESISTANT AND / OR THERMAL-INSULATING MATERIAL - Google Patents

Description

"Process and device for the production of heat-resistant and / or heat-insulating material"

The invention relates to a method and a device for the production of heat-resistant or refractory material, in particular, but not exclusively of material for poor insulation at high temperatures. .

Good thermal insulation material or a good thermal insulator should fulfill its functions satisfactorily within a wide temperature range - and should also under the influence external forces as well as the effects of moisture (e.g. wetting, dampening, dampening or penetration) and (exhaust) Drying remain intact, as may be required, for example, in accordance with the relevant recognized standards is.

For solid heat-insulating material or for solid heat insulators, it is generally stated that the denser Such a material is, that is to say the less air it contains, the higher its thermal conductivity is, from which it follows that good WärnieiBolatoren or good heat insulating material should contain as many cavities as this

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to be agreed with the requirements for material strength: The more cavities, interfaces or intermediate surfaces and dislocations or defects of the arms. encounter on their way, the lower the apparent Thermal conductivity of the material in question. Therefore, this thermal conductivity is determined by the distribution, Affects the size and number of cavities.

If the insulating material can absorb water, the material properties deteriorate, because the thermal conductivity of water is about twenty five times is greater than that of dry air at ambient temperature. Therefore, it is desirable for such a material to have water repellent properties.

The invention is based on the object of providing a method and a device that enable the production of parts made of heat-insulating material, for example in the form of thick (blocks) or thin (foils) plates or panels or as molded parts, which have a predeterminable dry density and correspondingly desired thermal insulation properties with sufficient strength.

Accordingly, the invention is based on the knowledge that with a mixture of perlite and sodium silicate this of the invention The underlying object can be achieved by influencing or adjusting the dry density of the used Perlites, the proportions of solids in a wet mixture of perlite and a sodium silicate solution as well the size of the pressure or pressure applied to this mixture in compression molds or printing forms before drying

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Compression. In this mixture used according to the invention, the perlite and an aqueous solution of sodium silicate are the basic materials, whereby perlite is known for its non-flammability and its resistance to higher temperatures and is a naturally occurring siliceous rock in the form of volcanic glass, which has a concentric shell structure , while the aqueous solution of sodium silicate (Na ₂ O SiO ^ ₅ ) is a binder for binding the perlite * particles, which is obtained from a melt of sand and sodium carbonate formed in a glass melting furnace. The size of the pressure that can be applied depends on the grain size and is limited by the size of the pressure that can still be applied without destroying the porous honeycomb structure, which destroys the number of cavities and thus an increase the thermal conductivity would be caused.

At a given constant pressure and for a given thickness of the finished part (finished product), that the greater the mass of the wet mix, the more compact and dense the finished product, i.e. the less is the proportion of voids between the particles in a given volume of dry matter.

These findings are based on that of the invention The underlying object is achieved in that in a method for producing heat-resistant and / or heat-insulating Material made from a mixture of perlite and sodium

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According to the invention, a mixture is mixed together silicate which is predominantly perlite with a dry density within a range of 48 to 1 ^ 6 kg / m ^ in one contains aqueous solution of sodium silicate or sodium silicate powder mixed with water, in such a way that it contains the pesticides including dissolved pesticides between 55 and 75 percent by weight of the mixture make up that a molded part is pressed from this mixture and then this is dried, this being the compaction factor is essentially determined by the equation

CF = ^DD

WD x PS

whereby

CP = ratio of the height of the molded part before

Compression to the height of the molding after compression for a given constant Cross-section of the molded part,

DD = dry density of the compressed material;

WD = wet density, and

PS = proportion of solids in the total mixture,

The corresponding proportions of the individual constituents are advantageously selected in such a way that the density of the compressed and dried molded part is substantially equal to or greater than the density of the uncompressed one wet molding.

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According to another feature of the invention, it is special advantageous, according to a previous classification of the mineral according to grain sizes of the different Particle-sized use to which the raw perlite? Particles rely when heated 871 C into the shape of hollow spherical particles. The pearlite particles expanded in this way can continue classified or mixed with coarse, medium or fine grain, or where possible it can be Perlite of a single available class - for example, a medium grain containing both coarse and fine grains - be used. In order to achieve high thermal insulation that is compatible with the strength requirements, it is according to the invention furthermore advantageous if the product contains at least a part of coarse grain, which gaps which, in contrast to free air, represent small closed volumes filled with air. After a Another feature of the invention, the proportion of sodium silicate should be kept as small as possible, since as a result of its use in aqueous form it is possible for voids to form with free air when the product exposed to elevated temperature. The less sodium silicate is used, the lower the volume of the product for a given weight, the greater and the shorter the time required for drying.

As far as the commercially available types of sodium silicate in liquid form are concerned, according to the invention those are particularly suitable which have an average solid content of 34 to 37 % and an average specific weight

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from 7ο to 75 ° TWADELL scale and a viscosity between 7 ° and loo centipoise. However, you can if necessary, can be further diluted. It can also optionally contain sodium silicate in powder form Find use, as will be described below.

According to a further feature of the invention, a water-repellent liquid can be used as a further component of the mixture or compound are added to make the dry heat insulating material water repellent; therefor Aqueous siliconates such as water-soluble ones are particularly suitable Sodium methyl siliconate, which is used as an integral part of the mixture. In certain cases it may be more practical to first coat the perlite particles with sodium methyl siliconate either in the expansion phase the pearlite grain or in the phase of the production of thermal insulation material to coat. Furthermore, it can be more convenient to cover the dry insulating material with a top ^ surface coating made of siliconate to provide this To impart the ability to repel water spray.

A continuous water repellency is particularly advantageous when the insulating material is to be sawed for installation purposes, or then, when situations arise where the insulating material may be exposed to water showers, such as when blasting off in boiler houses or when burst pipes occur.

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A suitable liquid water-repellent agent has been found under the trade name "Dow-Corning 772" Product proven. As a powdery water-repellent agent under the trade name "Dow-. Corning Integral XW6-0909 "available, silicone-based established water-repellent compound proved to be advantageous.

Optionally, no more than 20 weight percent lightweight additions can be added, such as flaked vermiculite, pulverized fuel ash, or coal ash cenospheres.

According to an advantageous development of the method according to the invention, to increase the wet and dry strength of the material, especially if it is a low-density material, built into the mixture of fibers which are compatible with the other components of the mixture. As an example of such lines glass fibers may be mentioned, in particular alkali-resistant glass fibers, which in contrast to ordinary glass fibers are not attacked by the alkali contained in the sodium silicate, • water repellants and fuel ash, when incorporated into the mixture in chopped up form. In doing so, the fiberglass is applied to the outer surface of the insulating material Material applied, these can be used in the form of tissue, if this is a good one Has connection with the material, the fabric improves the flexural strength of the insulating material, and at the same time the abrasion resistance and the dust repellency on the surface can be increased. If only dust repellency is

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calls for this, known methods such as spraying can be used can be used with sodium silicate.

The density range within which the mixture of the invention can be used is wide and extensive down from 128 kg / m for insulating material with lower Thermal conductivity up to 64o kg / nr for products in the form of foils or thin sheets, which are more suitable are used as refractory materials for the sheathing of structural steel, walls and doors, for example.

For high temperature insulating materials (temperatures 121 C exceeding) according to the invention, there is a preferred range between 128 to 15.57 kg / nr density, the Materials lying in this range have a thermal conductivity between 0.093 and 0.144 W / m ° C at a peak temperature at the end face of 593 ° C and a middle one Temperature of J21 C.

For heat insulating materials for medium and low temperature ranges appear thick plates (blocks), which only have coarse grain, more suitable.

In the case of the mixture according to the invention, for a given thickness or for a given dry volume and for a given constant pressing pressure from the weight of the wet mixture used the required dry weight as follows be determined:

Let it be:

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W = percentage of liquid parts in the mixture χ = percentage of pesticides in the liquid part in relation to the total mixture, i.e.

w (100 - a) - 100

y = percentage of pearl stone (perlite) in the mixture

ζ = expected dry weight of the end product, i.e. required density χ required volume

a = percentage of water in the sodium silicate solution

b - percentage of pesticides in this latter solution.

then

the total wet weight = 1ΟΟ · ζ »χ ₊ ζ» y

Μ * + J) (x + y)

becomes additional dry material, for example powdered Fuel-Asehe, it must be in the dry weight the mix must be taken into account. If m is the proportion of dry additives, the result is the total wet weight to

lQO · ζ «(x} ₊ ζ · y 4: ζ · m

b (χ + y + m) (x + y + m) (x + y + m)

The invention is explained in more detail below by means of examples described.

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EXAMPLE I

Coarse-grain perlite $ 26>

Medium-grain perlite 13 %

Fine-grain perlite 13 %

Sodium Silicate (diluted with $ 32 water

48 %

Wet density of the mixture 19 ^, 38 kg / m ⁵

Wet weight of the pressed material 0.451 kg

Volume of the pressed material o, ool3 m

Dry density of the finished product 220 kg / nr

Modulus of rupture of the dry finished product _p

3.02 kg / cm

Compaction factor 1.785

The dry finished product obtained from this mixture remains intact in the state soaked with water within the limits given by the relevant standards. Will the dry finished product is immersed in water for one (l) minute, but 281 percent by weight of water is absorbed. If, on the other hand, it is desired to impart a high level of moisture repellency, the above mixture becomes a water-repellent one Additive added, preferably sodium methyl siliconate in an amount of up to 5 percent by weight in relation to all components of the mixture. In this way it becomes a more stable heat insulating one Material obtained, as this has greater resistance to the ingress of moisture. Affected thereby Sodium methyl siliconate in no way affects the strength of the finished product, as can be seen from Example II below.

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EXAMPLE II

Coarse-grain perlite. 25 %

Medium-grain perlite 12.5 %

Fine-grain perlite 12.5 %

Sodium silicate as in Example I: 46 %. Sodium methyl siliconate (diluted to

5 % solids concentration) 4 %

Wet density of the mixture 202.15 kg / m ⁵

Wet weight of pressed material 0.463 kg

Volume of the pressed material 0.0013 m

Dry density of the finished product 219 kg / m ⁵

Breaking modulus 3 * 02 kp / cm

Compaction factor 1 * 764

Absorption after one minute of immersion in water, 1 percent by weight

It may come in handy to remove the water repellant sodium silicate prior to adding it to the solids to be added in the manner still to be described.

In the next example, the pearlite was omitted by spraying on dilute sodium methyl siliconate. It was found that in this case this Perlite some time after this coating for the production of pressed heat insulating material with good Water repellency can be used:

EXAMPLE III

Coarse-grain perlite 26 % all three beMittel-grain perlite 13 % layers with sodium

Fine-grain perlite 13 % methyl siliconate

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Sodium silicate as in Example I: 48 % wet density of the mixture 194.38 kg / m "'

Wet weight of the pressed material 0.459 kg Volume of the pressed material 0.001j5 m ^J Dry density of the finished product 224 kg / m Compression factor 1.817

Absorption after one minute of immersion

in water 5 percent by weight

Optionally, a water repellent powder can be incorporated into this mixture.

EXAMPLE IV

Coarse-grain pearlite 52 % sodium silicate as in Example I 47.5 % "Dow-Corning XW6-09O9 water repellent" 0.5 % NaG density of the mixture 22 ^, 3 kg / m- ⁵ wet weight of the pressed Material 0.425 kg Volume of the pressed material 0.001 Jj m Dry density of the finished product 222.07 kg / nr Compression factor 1.467 Absorption after one minute of immersion in water Io percent by weight

EXAMPLE V

Fine-grain perlite 5o %

Sodium Sj-LIKAT diluted with 25 ° / o water

5o %

Wet density of the mixture 120.1 kg / nr

Wet weight of the pressed material 0.329 kg, volume of the pressed material 0.00lj5 m

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-ζ.

Dry density of the finished product 1βθ, 2 kg / nr Compression factor 2.11

Such mixtures according to the invention, as shown in the are produced in the manner described below, before they are formed by pressing a few days in stored in tightly closed containers. However, mixtures of dry mixture components alone can also be used which later, when compression molding is desired, are moistened with water. For example the following dry mix was prepared:

EXAMPLE VI

Coarse-grain perlite. 4o %

Medium-grain perlite 20 %

Pein-Korn Perlite 20 %

Sodium silicate in powder form 19 % Water repellent in powder form 1 fo

The above mixture was gradually moistened by adding water in the proportion of about one part Water to two parts pesticides (in parts by weight)

Wet weight of pressed material 0.4095 kg

• χ

Wet density of the mixture 189.53 kg / nr

/ Volume of the pressed material 0.001J no

Dry density of the finished product 210 kg / nr

Rupture modulus 2.8 kp / cm ²

Compression factor. 1.662 absorption after one minute immersion in

Water '0.7 percent by weight

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Absorption after three hours of immersion in

Water 6 weight

percentages

Though the addition of pulverized fuel ashes apparently no increase in the strength of the finished product, this addition has the advantage of low cost and less absorbency than pearlite. Because the ash has a greater density than Has perlite, this increases the weight of the dried finished product. By including such ashes you can Thermal insulating materials can be manufactured within a wide range of density, such as the following Mixture examples show:

EXAMPLE VII

Fine-grain perlite 40 %

Sodium silicate (undiluted) 4o %

Powdered fuel ash 20 %

Wet density of the mixture 290.2 kg / m- ⁵

Wet weight of the pressed material

0.58 kg

Volume of the pressed material 0.0013 nr Dry density of the finished product 332 kg / nr

2 breaking modulus 3.86 kg / cm

Compaction factor 1.5 ^

EXAMPLE VIII

Orob grain perlite 23.5 %

Medium-grain perlite 11.75 %

Fine-grain perlite 11.75 %

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"¹⁵; 22A0228

Sodium Silicate (as in Example i) 4 % Powdered Oil Ash. 6 %

Sodium methyl siliconate ..4 %

Wet density of the mixture 215 kg / nr

Wet weight of the pressed material 0.46 kg

Volume of the pressed material 0.0013 m

Dry density of the finished product 224 kg / nr

Modulus of rupture 3.16 kgf / cm

Compaction factor 1.648 -

Thermal insulating materials made from the above described Mixtures can be prepared, a pre-determined one Have dry density or be adjusted to this. The general rule is that those with dry densities are above 32o kg / no also have good fracture moduli. Reduced in the process the apparent thermal conductivity increases with increasing density. It may now be desirable to have a heat insulating material with low density, but also with a good breaking modulus and good water repellency. One way to improve the strength values of insulating materials formed from such mixtures consists in their use of glass-fiber reinforcement, in particular of reinforcing glass fibers in the form of fabric panels, which on a or several outer surfaces of the dry heat insulator are adhesively applied. In order to - a - embrittlement of the fibers in To prevent this, the drying temperature should be limited to 75 ° G.

The following example illustrates the effect of the mentioned use of glass fibers in connection with such mixtures, this following example with can be compared to the above example II, in which no such glass fibers are used:

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EXAMPLE IX

Coarse grain perlite 24.76 %

Medium-grain perlite 12.38 %

Pein-Korn Perlite 12.38 %

Sodium silicate (as in example I) 45.16 % sodium methyl siliconate 3.79 %

Alkali (lye) resistant glass fibers 1 * 53 %

Wet density of mixture 204, 1 kg / m. Wet weight of pressed material 0.45 kg Volume of the pressed material 0.0013 m

Dry density of the finished product 218 kg / nr breaking module 3 * 4 kp / cm

Compression factor 1.728

Absorption after one minute of immersion

in water 2.0 %

A comparison shows that the glass fibers increase the modulus of rupture by about 11 % .

A considerable improvement in the flexural strength can be achieved by applying glass fiber fabric to the upper and lower sides of flat plates made of pressed mixtures or otherwise shaped elements such as thermal insulation for pipelines. With good adhesion to the heat-insulating material, the fabric gives hold, and with tension and pressure gives way and prevents destruction of the surface. Such an application of glass fiber reinforcements is particularly effective in the case of heat-insulating material that contains water-repellent agents.

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EXAMPLE X

Eight sample panels are made from mixtures which are components of the same type and texture as in Example II. The top and bottom of each of these sample panels are covered with a fiberglass fabric coated, which has glass strands that are continuously parallel at a distance of about 25 mm from each other towards each other, with this fabric adding about 14 grams to the weight of each panel. The adhesion of the fiberglass fabric on the dried heat insulating material is made with an adhesive causes which from one part a polyvinyl acetate emulsion to five parts undiluted liquid sodium silicate consists.

Wet weight of the pressed mixture 0.4 kg / plate

Volume of the pressed material per plate 0.0013 m

Dry density of the sample panels without fabric 208 kg / nr

Dry density of the sample panels with fabric 218 kg / nr

Mean breaking modulus 6.11 kg / cm

It can be seen that the surface fabric improves the modulus of rupture by about 75%. Fractional

Modules that exceed 7 * 03 kp / cm can be achieved, provided the adhesive can dry in air or at least at a temperature not exceeding 50 ° C,

Adhesives consisting of polyvinyl acetate emulsion are also used as adhesives for attaching fiberglass fabrics and water usable.

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The above-described examples of mixtures according to the method according to the invention are for thermal insulation Material suitable that is intended for temperatures not exceeding 600 C.

The invention is not limited to a method for producing heat-insulating material, but rather relates to it also a facility to carry out this procedure.

An advantageous embodiment of such a invention Device for the production of plates, thick panels or blocks or other molded parts from the invention insulating material is described below with reference to the drawings.

Show it :

Fig. 1 schematically shows a complete device for carrying out the invention Procedure, and

2 schematically shows an advantageous expansion of a device according to Pig. I.

The mixing device of the embodiment according to Pig. I consists essentially of a cylindrical drum 1, which rests on rollers 2 in the example shown, but which can also be held, for example, by pivot pins; this drum 1 can be set in rotation at an adjustable speed by means of a motor j5 with the interposition of an Öebetriebes or a belt drive with a drive ring 4. The axis of the drum 1, the length of which is at least twice its diameter, is opposite the horizontal

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downwards in the direction of 'to the outlet end in Fig. 1 for right end too slightly inclined. The arrangement is such that this inclination is adjustable. The open ones The ends of the drum 1 rotate in elastic seals 5 'which are attached to fixed end plates 6 are. On the inside of the cylinder wall of the drum 1, guide vanes 7 are attached in a spiral shape in such a way that that material entering the drum 1 is conveyed in the direction of its exit end. From the end plate 6 a flexible cleaning brush 8 is also held, which is used to scrape off all material, that could attach itself to the drum wall. However, this includes all parts that come into contact with the wet mixture come coated with a material to which this mixture does not stick easily, for example one fluorinated material. If necessary, an electrical heating device 9 can be provided which at least part of the length of the drum 1 surrounds the creation of a heated zone to reduce the Viscosity of the sodium silicate used is used.

The dry perlite is fed into the drum 1 through an opening 10, optionally provided with a slide, in the end plate 6 at the end of the feed of the drum, if necessary together with other dry mixture components. These mixture components are supplied from a storage bunker 11 in an addition amount which is determined by a metering device 12 which can regulate the addition amount volumetrically or in terms of weight and which can be adjusted to change the addition amount. The storage bunker 11 is - possibly together with a storage bunker for a further .Trommel - supplied via a main feed line, which in turn is fed via a vacuum conveyor lh from a bunker: 15, which

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is kept filled directly from a perlite sintering plant or from other sources of supply. If necessary more than one pesticide conveyor can be provided, e.g. B. separate conveyors for coarse grain and fine grain perlite and for powdered oil ash. Means not shown in the drawing Introduction of chopped up glass fibers, which are either chopped up in advance or by means of a pressure air operated Cutting device can be cut into pieces, can also be provided in the end plate 6.

At the same end of the drum 1 are also a sodium silicate solution and possibly other. «liquid mixture components, such as liquid water repellants, by means of an air-operated spray tube 16 - or also via an air-free spray tube - which essentially in the axial direction protrudes into the drum, introduced in regulated quantities. The length of the spray tube 16 and the Number of jet openings depend on the required Spray speed. The liquid components are supplied from a tank 17, which by means of a thermostat can be maintained at a predetermined temperature, the gravity feed from a head tank takes place, which is fed via a pump 19 from the tank 17, this pump 19 by a float in the tank is regulated automatically. The liquid components pass from the tank 18 via a line 16 through a control head through which compressed air is supplied at 22.

Sodium methyl siliconate is advantageously introduced into the drum 1 at its outlet end. As in Fig. 1 shown, this is a spray tube 23 from a tank fed via a controllable spray head 25, the latter

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at 26 is supplied with compressed air.

Also from Fig. 1 it can be seen that glass fibers advantageously through an opening 27 at the dispensing end the drum 1 are inserted; these glass fibers are from a storage tank 28 via a control head 29 by means of taken at 30 supplied compressed air.

Dry material entering the drum 1 becomes picked up by the guide vanes 7 and passed through them to a point where it is through an artificial ' small mist made of sodium silicate or sodium silicate

by

and liquid water repellant through / gravity fall through, so that the material is coated in this way with these substances. Through the. Inclination of Drum 1 and by the action of the guide vanes 7, the moistened material is in the direction of the discharge end to be promoted, the components of the mixture being thrown together and mixed through and through at the same time will. Sodium methyl siliconate and / or glass fibers in this way, if necessary, also mixed in on the way to the end of the dispensing process.

The mixture is removed through an opening in the Wall 6 at the output end of the drum 1 above a setting Able weir 3I · Through a chimney 32 above the discharge end the drum 1 is air by means of a fan through a filter 33 or through a cyclone collector sucked in, thereby evacuating airborne micro-sized particles to prevent pollution will,

The wet mixture is immediately or via a Belt conveyor 3 ^ unloaded into troughs or forms, or else on an endlessly rotating belt conveyor with shielding side walls. In the illustrated embodiment of the

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Device according to the invention, the removal takes place in forms 35, one after the other from a collecting station. at 36 coming to the removal point on a conveyor 37 are brought up. The conveyor 37 is operated intermittently by means of limit switches and the filled molds are simply fed by an accelerating conveyor 38 to a pressing station 38 (FIG. 2) which has a fixed plate 39 , the position of which can be adjusted in the vertical direction and thus the material thickness or thickness, and a hydraulic or pneumatic ram 40 for lifting each individual mold 35 and thus for compacting the material to the required (set strength / thickness) and density.

When unloading onto a conveyor , the mixture can be conveyed through this under pressure rollers and through a storage device with gradually converging side and top walls. If necessary, the conveyor can work in start-stop mode in order to enable a periodic pressing operation.

After completion of the compaction, the material is in a state that allows the removal of the side retaining walls of the molds or conveyors, so that the sides z. B. a pressed, molded thick plate (a block) can be exposed prior to drying of the molding. As can be seen from FIG. 2, the mold is removed in a station 41 with a conveyor 42, from which the mold parts (blocks, etc.) are passed on to an endlessly rotating conveyor 44 in a

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Drying station with one or more high-frequency heaters45. Because of the relatively low water content However, if necessary, conventional air drying of the material can also be carried out.

In the case of molded parts (blocks, plates or the like) produced in this way, one or more are sealed Surfaces desired, such surfaces can be in close contact with a surface or with a Surface heaters are brought, the temperature of which melts the material surface or surfaces brings.

If glass fiber fabric is to be applied to one or more product surfaces in order to increase the strength of the product increase, this can be done after the drying process. As can be seen from Fig. 2, has a The station serving for this purpose has a chamber 46 through which, for example, blocks etc. on a wire belt conveyor 47 be conveyed through. In this case, spray heads 48 are used to apply to the upper and lower surfaces of the panels, Blocks, etc. sodium silicate applied. The fiberglass fabric is applied to the coated surfaces and bonded to the moldings by passing the products thus obtained between infrared heaters 50. The finished product can then be packaged.

Such pressing, drying and other facilities könnenin compound having one or more mixing means (Fig. 1) operating in continuous or batch loading ¹ are used. For example, two or more drums 1 can be arranged on both sides of a common conveyor from which they are unloaded.

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It is also possible to use blocks or other products produced by the process according to the invention to be coated with a mixture similar to that of the products mentioned, if this mixture also contains sodium silicate is admixed.

Although the mixtures described above are preferred for use under high temperature conditions Working material are provided, so these can, if so desired, under conditions Find use, under which cold insulation or sound insulation is required.

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Claims (1)

Claims 1. A process for the production of heat-resistant and / or heat-insulating material from a mixture of perlite and sodium silicate, characterized by mixing a mixture consisting essentially of perlite with a dry density within a range of 48 to Ij5ö kg / nr with an aqueous solution of Sodium silicate or sodium silicate powder mixed with water, the proportion of solids including dissolved solids being between 55 and 75 percent by weight of the mixture, and by pressing molded parts from this mixture and then drying these molded parts, the compression factor in this pressing process is essentially given by the equation CF = - ^DD WD x PS where CF is the ratio of the height of the molded part before compression to the height of the molded part after compression for a given constant cross-section of the molded part, DD is the dry density of the compressed material, WD is its wet density and PS is the proportion of solids in the total mixture. 2. The method according to claim 1, characterized in that the proportions within the mixture are chosen such that the density of the compressed and dried molded part is substantially equal to or greater 309808/1010 - 2fr- is than the density of the uncompressed wet molding. • J5 · Method according to Claim 1 or 2, characterized in that a water-repellent agent such as sodium methyl siliconate or other water-repellent silicon compounds is or are added to the mixture as a further component of the mixture. 4. Process according to Claims 1 to 3, characterized in that the pearlite used consists of a mixture of pearlite grain sizes. 5. Process according to Claims 1 to 4, characterized in that a proportion of not more than 20 percent by weight of pulverized fuel ash or vermiculite is also added to the mixture as a constituent of the mixture. 6. Process according to Claims 1 to 5, characterized in that a proportion of glass fibers is added to the mixture as a reinforcing component of the mixture. 7. The method according to claims 1 to 6, characterized in that a reinforcing glass fiber fabric is adhered to at least one surface of the dried molded part. 8. Device for carrying out the method according to claims 1 to 7 * characterized by a mixing drum (l), means (I0-I5) for the regulated supply of perlite into the drum (l), means (l6-22) for the regulated supply 309808/1010 of sodium silicate in the drum (I), forms (55) _
or other shaping means to absorb the moist
Mixing from the drum (1), means (59-4o) for the controllable pressing of the formed moist mixture., As well as means (46-48) for drying the formed and pressed molded parts. 9. Device according to claim Q _s, characterized by means (25-26) for the regulated introduction of water-repellent agents into the drum (1). 10. Device according to claims 8 or 9 * characterized by means (27 -Jo) for the controlled introduction of glass fibers into the "drum (1) .. 11. Device according to claims 8 to lo, characterized by means (46-50) for the adhesive application of glass fiber fabric to at least one surface of the dried molded part. 309808/1010