WO1980000078A1

WO1980000078A1 - Process for manufacturing porous glass and porous glass obtained by such process

Info

Publication number: WO1980000078A1
Application number: PCT/CH1979/000094
Authority: WO
Inventors: H Schuerch; G Bayer
Original assignee: H Schuerch; G Bayer
Priority date: 1978-06-21
Filing date: 1979-06-21
Publication date: 1980-01-24
Also published as: CH637097A5

Abstract

The known technique for manufacturing porous glass with closed pores, wherein the glass foam is rapidly cooled and nearly frozen, gives a relatively thin pore glass. Nevertheless, in order to improve the thermal insulation characteristics of the porous glass, which are essential when it is used as construction and insulating material, a relatively coarse porous structure is desired. To obtain such a structure, the glass foam is submitted to inflation until most part of the lamillar walls situated between the different bubbles of the foam are tom and a plurality of neighbouring bubbles merge into a single cavity. During inflation, the influence of heat on the glass foam is maintained after its formation and/or the ratio between the average gas pressure in the foam bubbles and the pressure acting from outside on the foam is raised to a value higher than the value of this ratio obtained with the formation of the foam and/or the surface tension of the glass forming the lamellar walls, opposing to the gas being in the bubbles of the foam as well as the resistance to the glass pressure are brought down to values lower than those obtained with the formation of the foam.

Description

Process for the production of foam glass and foam glass produced thereafter

The invention relates to a process for producing closed-pore foam glass, in which a crude mixture containing at least glass powder and blowing agent is heated to temperatures above the transformation range of the glass forming the glass powder until the blowing agent is

O PI Chemical reactions and / or gas elimination and / or evaporation develop a blowing gas that initially forms spherical bubbles within the raw mixture cake that has been baked together by softening the glass powder grains, which then grow with the further gas development while the cake is inflated until the neighboring bubbles collide with one another and with the other Then, with formation of lamella-like walls between the individual bubbles, they assume a polyhedral shape and the cake thus passes into a glass foam formed by the lamella-like walls between approximately polyhedral foam bubbles adjoining one another on all sides. The invention further relates to foam glass produced by this method.

Method ^* it are the aforementioned type is already known for some time, for example, US Patent No. 2,233,608 and 3,811,851, the CH-PS 426 601 and 473 741, the DT-PS ^'2,028,666 and the book "silicates" W Hinz, VEB Verlag Berlin, 1971, volume 2, pages 267, 268 and 283, 28 However, with these known processes it was only possible to produce foam glass with relatively small pore sizes, the maximum being of the order of millimeters. For example, in the named CH-PS pore sizes in the range from 0.2 to 2 mm and in the mentioned DT-PS pore sizes in the range from 0.1 to 1 mm as realizable values of the pore size. The reason for this lies in the process technology used in the known processes, after the aforementioned transition of the cake into a glass foam formed by the lamella-like walls between approximately polyhedral foam bubbles adjacent to one another on all sides, ie when the so-called optimal , foaming, the heating of the glass foam with an abrupt drop in temperature, which is referred to in practice as a temperature shock, is abruptly stopped to temperatures lying within or just a little above the transformation range mentioned, because with this quenching the polyhedral glass foam formed is frozen so to speak, so that one further development of the foam is no longer possible, and in the state described as optimal foaming, polyhedron glass foams can at most have pore sizes in the raw mixtures of waste glass powder and a few percent blowing agents used reach the order of millimeters. In addition, according to the view that was previously valid in the professional world - which is expressed, for example, in terms of "optimal foaming" - was another Development of the foam for manufacturing reasons is not at all desirable, on the contrary, such a development should be prevented by the deterrent and instead the state of "optimal foaming" should be maintained and frozen, so to speak, because one is due to bad experimental Experience feared that the polyhedron would collapse in further development beyond the state of the so-called optimal foaming. In the professional world there was also the opinion that a more favorable foam glass structure than that of the so-called "real polyhedron foam" would not be possible and that improvements could only be achieved with regard to the fine structure, for example as in the above-mentioned CH PS described - with regard to the internal structure of the lamella-like walls mentioned or - as described in the above-mentioned DT-PS - with regard to the uniformity of the foaming at all points within the foam glass produced.

In fact, however, the foam glass produced according to the previously known methods with the structure of a "real polyhedron foam" is by no means optimal with regard to the requirements to be placed on foam glass in practice. Because in practice, foam glass -

^ - as can be seen in almost all related publications and publications - mainly used as a building and insulating material, and there it is primarily the thermal insulation properties of the foam glass that matter. Of course, the strength properties of the foam glass also play an important role in this area of application, but in this respect there are usually so large reserves ^* that a reduction in strength within these reserves can easily be accepted in favor of improving the thermal insulation properties, and from this it follows that a foam glass structure is to be regarded as optimal with regard to the requirements in practice if it has the best thermal insulation properties of all of the foam foam structures that are possible lying there. The thermal insulation properties of a foam glass structure are now essentially determined by the shape and cross section of the aforementioned lamellar walls forming the foam glass, or in other words, the heat conduction of foam glass essentially results from the heat flow flowing over the lamellar walls in the direction of the temperature gradient, while that of the cavities enclosing the lamella-like walls practically not at all

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OMPI or only contribute to the heat treatment to a very small extent. As a result, the ratio of the volume d lamella-like walls to the total volume of the foam glass or the density of the foam glass which is proportional to this ratio with the density of the foam-glass material forming the lamella-like walls is of decisive importance for the heat conduction, because it should be clear be that the greater the percentage of the volume of the heat-conducting lamellar walls or the smaller the percentage of the volume of the non-heat-conducting cavities in the total volume of the foam glass, the greater the heat conduction. Therefore, in order to arrive at comparable ratios when comparing the thermal insulation properties of different foam glass structures, one has to start from the same density of the viewing glasses to be compared with each other, different foam glass structure and of course also from the same foam glass material for the lamella-like walls of the foam glasses to be compared. Since, given the density of a foam glass or the predetermined ratio k of the volume V of the lamella-like walls to the total volume Vges of the foam glass, provided that the foam glass structure is essentially the same at all points of the foam glass each wafer-thin foam glass pane cut out in any cross-sectional plane of the foam glass has a predetermined volume ratio

Vw / Vtot = k ^r Unlock computationally forming ratio Δvw / Δvges

Vw / Vges = k of the product of the total cross-sectional area F of the lamella-like walls and the pane thickness d corresponding volume Δv = dF of the lamella-like walls in the foam glass pane to the product of the total area Fges of the foam area and the total volume corresponding to the pane thickness d

Δvges = d.Fges "the Schaumg ^& lasscheibe has' is at a

Foam glass of a predetermined density with essentially the same foam glass structure at all points of the foam glass in any cross-sectional plane the ratio Fw / 'Fges = d.Fw /' d.Fges = Δv2 / 'Δvges ^* = Vw / Vges k of the total cross-section F of the lamellar walls to the entire cross-sectional area Fges at the interface is equal to the constant k and thus the percentage

Share of the total cross section F of the lamella-like

Walls on the cross-sectional area Fg _{are the} same size in every Q-section plane, regardless of the special foam glass structure of the foam glass in question. With the same density and the same foam glass material as well as uniform structure distribution

OMPI Foam glass blocks of the same dimensions in mutually corresponding cross-sectional planes, even with different foam glass structures, have the same overall cross sections of the lamella-like walls. If, in addition, the cross-sectional areas in these foam glasses are the same in all cross-sectional planes perpendicular to the temperature gradient direction, then, according to the above, the total cross-sections of the lamellar walls in all these cross-sectional planes are also the same size, again also with different foam glass structures of the individual foam glass blocks. In this case, the thermal resistance which such a foam glass block represents is proportional to the ratio of the mean length of the current paths of the heat flow flowing through the foam glass block in the direction of the temperature gradient to the overall cross section of the lamellar walls which is of equal size in all cross-sectional planes perpendicular to the temperature gradient direction , and since this overall cross-section of the lamella-like walls is the same under the aforementioned conditions, which apply to comparable conditions, even with foam glass blocks with different foam glass structures, differences in thermal resistance only arise with different foam glass structures if the different foam glass structures

^ ( For different mean lengths, the current paths of the heat flows flowing through these foam glass blocks with different foam glass structures result. The specific heat resistance of a foam glass structure is therefore a maximum or, in other words, the heat insulation properties of a foam glass structure are optimal if this structure results in the greatest possible mean length of the current paths of the heat flow flowing through the foam glass structure. The yardstick for the mean length of the current paths is the ratio of the effective mean current path length to the thickness of the foam glass block or to the fictitious current path length resulting in the temperature gradient direction when the heat flow passes straight through the foam glass structure. This ratio of the effective to the active current path length is greater, the further the heat flow has to run back and forth transversely to the temperature gradient direction as it passes through the foam glass structure, or the greater the proportion of the path segments running transverse to the temperature gradient direction in the total current path length. Since the current paths, as already mentioned above, run almost exclusively within the lamella-like walls, a foam glass structure with regard to their heat insulation properties is then

OMPI _j . IPO optimal if the largest possible portion of the lamella-like walls runs transversely to the temperature gradient or the smallest possible portion in the temperature gradient direction, or in other words if the F of the cavities enclosed by the lamellar walls has the greatest possible lateral deviations of the effe tive current paths from the assigned fictitious current paths running directly in the temperature gradient direction through the foam glass structure. However, this is not the case with the foam glass manufactured according to the previously known processes with the structure of a "real polyhedron, because in the case of a real polyhedron foam i the shape of the cavities is roughly spherical and in this case the effective mean current path length is approximately 20% greater than the length of a fictional current of rectilinearly leading through the foam glass structure, while with other foam glass structures, such as structures with lenticularly flattened cavities, a ratio of the effective to the positive current length of two or more or approximately twice as good thermal insulation properties as that of the foam glass produced by the known methods come ka

The invention was therefore based on the object of producing a method of the type mentioned at the outset to create a foam glass which, owing to its structure with regard to the requirements to be placed on foam glass in practice, has overall more favorable properties and, in particular, better thermal insulation properties than the foam glass with the structure of real polyhedron foam produced according to the known methods.

According to the invention, this is achieved in a method of the type mentioned at the outset by subjecting the glass foam to a post-expansion process in order to achieve a coarse-pore foam structure until the predominant part of the lamella-like walls between the individual foam bubbles is torn open and in each case a large number of adjacent foam bubbles have united into a single cavity and that for this purpose the heat effect on the glass foam is further maintained after its formation and / or the ratio of the mean gas pressure in the foam bubbles to the pressure acting on the glass foam from the outside _. a value above the value of this ratio achieved with the formation of the glass foam and / or the surface tension of the glass forming the lamella-like walls compared to the gas in the foam bubbles and the toughness of the glass forming the lamella-like walls

OMPI ^IPO Values are brought below the values of surface tension or toughness achieved with the formation of the glass foam.

The present method has advantages in two respects with regard to improvements in the thermal insulation properties of the foam glass produced. First of all, by further expanding the glass foam in the post-expansion process with the volume of the lamella-like walls remaining the same, the total volume of the foam glass is increased and thus the density of the foam glass is reduced, which, according to the above explanations, leads to a reduction in the percentage of the total cross-section of the lamella-like Walls at the cut surface of a cross section through the foam glass and thus lead to an increase in the specific thermal resistance of the foam glass produced, which is inversely proportional to this percentage, or to an improvement in the thermal insulation properties of the foam glass. Furthermore, there is a substantial improvement in the thermal insulation properties of the foam glass produced by the combination of a plurality b of adjacent foam bubbles, achieved with the present method, into a single cavity. In comparison to those that form in this association

f In contrast to the roughly spherical foam bubbles, the cavities which are relatively large in relation to the pore size of the foam bubbles generally have considerably larger dimensions in the horizontal direction than in the vertical direction and, because of the resulting large-pore foam glass structure, have essentially lenticularly flattened cavities to relatively large lateral deviations of the effective current paths of the heat flow from the assigned fictitious heat flow paths running directly in the vertical direction through the foam glass structure and accordingly to a relatively large ratio of the effective to the fictitious current path length, which is a problem in the above statements substantial increase in the specific thermal resistance of the foam glass proportional to this ratio, or a corresponding improvement in the thermal insulation properties of the foam glass. Overall, the increase in the ratio of effective to fictitious current path length in conjunction with the present method, in conjunction with the reduction in density mentioned, enables improvements in the thermal insulation properties of foam glass up to a factor of 2 and above.

In a preferred embodiment of the present method, the glass foam is

(- OMPI ^'_ Process heated to a temperature which is above the temperature prevailing at the formation of the glass foam and thereby both the gas pressure in the foam bubbles to a value above the pressure value achieved with the formation of the glass foam and the surface tension and toughness of the glass to values below the with the formation of the glass foam brought values of surface tension and toughness. In this preferred embodiment of the present method, the glass show is preferably heated in the post-expansion process to a temperature e which is 50 ° C. to 100 ° C. above the temperature prevailing when the glass foam is formed.

Ante of a substance can also advantageously be added to the blowing agent, which substance only enters into a gas-developing chemical reaction with one of the substances contained in the glass foam in the area of the temperature prevailing in the formation of the glass foam or above it. If the reaction temperature of this reaction is in the range of the temperature prevailing during the formation of the glass foam, then only through this gas-developing reaction can the gas pressure in the bubbles in the post-expansion process be brought to a value above the pressure value g achieved with the formation of the glass foam, i.e. in this case is to be carried out

( of the post-expansion process only a further heat effect on the glass foam after its formation, but no increase in temperature of the same is necessary. Nevertheless, the glass foam can of course also be heated in this case beyond the temperature prevailing during its formation, for example to accelerate the course of the reaction of the gas-developing reaction and / or to further increase the gas pressure in the foam bubbles and to reduce the surface tension and toughness of the glass. If, on the other hand, the reaction temperature of the gas-generating reaction is above the temperature prevailing when the glass foam is formed, further heating of the glass foam in the post-expansion process is absolutely necessary to initiate the reaction, at least down to the reaction temperature, ie in these circumstances, in In the post-expansion process, the temperature increase to the reaction temperature or the resulting increase in gas pressure in the foam bubbles and the resulting reduction in surface tension and toughness of the glass are effective before the gas pressure in the foam bubbles increases further Effect of the gas-evolving chemical reaction begins. The reaction temperature should therefore not be significantly above that in the formation of the glass foam

OMPI W prevailing temperature, if the post-inflation process is to be based primarily on the gas-evolving chemical reaction.

Instead of such fractions of a substance which enters into a gas-developing chemical reaction with one of the substances contained in the glass foam, or in addition to this, the blowing agent can also advantageously have fractions of a substance which is vaporizable in the post-expansion process and which is inert towards the substances contained in the glass foam the temperature prevailing during the formation of the glass foam is added. In this case, too, for the same reasons as explained above for the reaction temperature of a gas-evolving reaction, the evaporation temperature should expediently not be substantially above the temperature prevailing in the formation of the glass foam if the post-expansion process is primarily based on the evaporation of the said inert substance, but the evaporation temperature must in any case be higher than the temperature prevailing during the formation of the glass foam, since otherwise there is a risk that the foam glass to be produced collapses during the post-expansion process.

Finally, in addition to the chemically reacting substance and / or the vaporizable substance mentioned, or instead of the blowing agent, the blowing agent can also advantageously contain portions of a substance which can be decomposed in the post-expansion process and which is at a decomposition temperature above the temperature prevailing during the formation of the glass foam Splits off gas, added. Here, too, the decomposition temperature should expediently not be substantially above the temperature prevailing when the glass foam is formed, if the post-expansion process is primarily to be based on the elimination of gas during the decomposition.

When using substances which evolve and / or evaporate and / or decompose and thereby release gas in the post-expansion process as a blowing agent, the reaction or evaporation or decomposition temperature is not significantly above that in the formation of the glass foam prevailing temperature, the further inflation of the glass foam until the combination of a plurality of adjacent foam bubbles into a single cavity is caused mainly by gas pressure rise in the foam bubbles above the pressure value achieved with the formation of the glass foam, while at one without

OMPI such substances carried out in the blowing agent, solely based on tere heating of the glass foam beyond the post-inflation process prevailing in its formation, the further expansion of the glass foam is primarily based on reductions in the surface tension and the toughness of the glass.

In the present process, the glass foam is expediently formed in the temperature range between 750 ° C. and 900 ° C., and the post-expansion process is advantageous at temperatures in the temperature range from 800 ° C. to 1000 ° C. or when fillers are added up to 1150 ° C. carried out.

For procedural reasons and in view of the technical effort and in particular the energy required for the production of foam glass according to the present method, it is expedient to subject the glass foam to the post-expansion process immediately after its formation. In general, however, it is also possible and in certain cases, such as when using glass powder with an exceptionally strong decrease in the surface tension and toughness of the glass above the temperature of the formation of the glass foam, to use the glass foam only after an intermediate connection Cooling phase to the post-inflation process and then reheat. The glass foam can expediently be cooled to room temperature in the cooling phase and then heated again to a temperature above the temperature prevailing when the glass foam is formed in order to carry out the post-expansion process.

The invention further relates to foam glass produced according to the present method, which is characterized in that the major part of the total cavity volume of the foam glass is formed by cavities, each of which has a cross-sectional area of at least one cross-sectional plane running through the cavity has at least 0.5 cm.

In a preferred embodiment of the foam glass produced by the present method, the majority of the cavities have at least 0.5 cm 2

Cross-sectional area in each case the cross-section with the largest cross-sectional area of the cavity in question has at least one, preferably two, intersecting at right angles, which is larger than the dimension of the cavity in the normal direction thereof

Are cross section. With a particular advantage for the heat. The majority of the cavities with at least 0.5 cm cross-sectional

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OMPI be flat in at least approximately the same, in essence union with the normal direction mentioned, the flattening direction roughly approximated lenticular.

It can also be advantageous in the foam glass produced by the present method, at least for

2 of the majority de «. Cavities with at least 0.5 cm cross-sectional area on the interior walls of the cavity have a metallic coating deposited. Foam glasses with such a metallic coating on the cavity inner walls generally have, among other things, a relatively high brittle fracture resistance.

The invention is explained in more detail below on the general principles of manufacturing technology and some examples of the present method.

For the production of foam glass by the method lying v, a 50 to 99.5% by weight, preferably 80 to 99% by weight, crude mixture containing glass powder is expediently used.

In the present method, preference is given to glass for the glass powder, at least for the most part, with a transformation which is at least partially within the temperature range from 500 ° C. to 600 ° C.

« ^• §> area used.

In the present process, in particular when the foam glass produced is used as buss and insulating material, it is advantageously possible to use at least partially pulverized waste glass as the glass powder for the raw mixture. For the production of foam glass for the building industry, waste glass consisting essentially of usage glasses, preferably bottle glass and other container glass and pane glass, is expediently used. For the production of foam glass for technical devices, in particular for thermal insulation and high temperature stresses, waste glass consisting of device glasses, preferably borosilicate glass and / or low-melting lead glass and / or high-melting silica glass, is expediently used.

The waste glass is expediently broken into glass fragments of less than 5 mm in size in a jaw crusher, and the chips are then ground in a vibrating disc mill or a ball mill to give glass powder with grain sizes of up to 1 mm at most. As a rule, the glass powder obtained in this way is used directly for the raw mixture in the present process, that is to say without being divided into grain fractions. In particular in the production of foam glass for the building industry according to the present method

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OMPI For cost reasons, it is advisable to set the upper limit of the size range of the glass powder grains after grinding the chippings as high as possible, or just as permissible for a flawless ablation of the present method, since, of course, given the disk vibration or ball mill the longer and therefore the cost of the grinding process, the finer the glass chips have to be ground or the smaller the maximum grain size forming the upper limit of the grain size range of the glass powder grains. In this context, it should be mentioned that in the present process, even with a maximum grain size of 1 m, a flawless process sequence and good quality of the foam glass produced can be expected if the raw mixture contains, besides glass powder and blowing agent, certain fine-grained additives, such as clay, for example, whereas in the known processes for the production of foam glass usually only glass powder with a maximum grain size in the order of tenths of a millimeter can be processed.

Of course, it is also possible with the present method and is advantageous for certain uses of the foam glass produced, the glass splinters to be ground more finely, for example down to a maximum grain size of 0.5 mm or in special cases even up to a maximum grain size of 0.25 mm. This is mainly possible if the aforementioned fine-grained additives are undesirable due to the intended use or for other reasons. In this case, the raw mixture should expediently contain a proportion of very fine-grained glass powder, preferably with grain sizes below 50 u, and for this purpose it is generally necessary to grind the glass splinters more finely than up to a maximum grain size of 1 mm. In the case of direct use of the glass powder resulting from the grinding process for the raw mixture, one can either proceed so that the glass splinters are ground down to such a small maximum grain size that the proportion of very fine particles which increases as the maximum grain size decreases Glass grains in the glass powder obtained correspond to the required proportion of very fine-grained glass powder in the raw mixture, or a part of the glass splinters can still have a first predetermined maximum grain size of, for example, 0.5 mm, with the proportion of very fine-grained glass powder is below the required value and the other part of the glass splinters up to a second predetermined maximum Grind the grain size of, for example, 0.25 mm, in which the proportion of very fine-grained glass powder is already above the required value, and select the ratio of one part to the other such that the mixture of the glass powder resulting from the two parts has the required proportion contains very fine-grained glass powder. Another possibility, which comes into consideration in particular in the production of foam glass for technical devices and other special purposes, is to divide the glass powder resulting from the grinding process into several grain fractions, for example using a vibrating sieve machine, and the glass powder to be used for the raw mixture then put together from certain proportions of the different grain fractions corresponding to the requirements in the production of the foam glass in question. The glass powder can advantageously consist of glass grains of a first grain fraction with medium-sized grains, for example with a grain size between 125 and 250 u, a second grain fraction with fine grains, for example with grain sizes between 50 and 125 u and a third grain fraction with very fine grains, for example with grain sizes below 50 u, and the proportions of the individual grain fractions can be used to achieve the densest possible grain packing

-

^ expediently chosen such that the spaces between grains of the second grain fraction remaining in a uniform mixture of the grain fractions between the grains of the first grain fraction and the gaps still remaining between the grains of the first and second grain fractions of grains of the third grain fraction tion are filled out. However, since the latter possibility involves several additional process steps in the production of the glass powder, namely the division of the glass grains resulting from the grinding process into grain fractions, the dimensioning of the proportions of the different grain fractions required for the composition of the glass powder, and finally the mixture of these fractions, making them necessary, their use is mainly limited to the cases where the use of glass powder with a very specific grain size distribution is of essential importance for a flawless process sequence in the production of the foam glass or for the quality of the foam glass produced.

In the present process, a fine-grained material is expediently used as blowing agent, which material is obtained by chemical reaction with a substance contained in the raw mixture or which forms when the same is heated and / or by thermal dissociation and / or by process

^■ OMPI Evaporation or sublimation developed a blowing gas that only at a temperature above the transition d raw mixture to a viscous mass marking the bonding temperature of the glass grains forming the glass powder, preferably at a temperature above 600 ° C, reaches a partial pressure that corresponds to the raw mix corresponds to the external pressure acting on the cake, and this already at a temperature below the flow temperature of the raw mixture cake which marks the transition of the raw mixture cake to a thin, flowing mass which causes the bubbles forming to rise to the surface, preferably at a temperature below 900 ° C., the temperature required for bubble formation. the sum of the external pressure acting on the ro-mix cake and that due to the surface tension? on the inner wall of a bubble excess pressure of p = 4Ö / d corresponding to the blowing agent grain of the size d.

To avoid unnecessary additional consumption of blowing agents which do not participate in the formation of bubbles and also to avoid unfavorable influences of the blowing agent on the consistency of the glass forming the glass foam, in the present process it is advisable only to add one in the mass forming the raw mixture cake

4S_≥. less than 1 percent by weight of the mass of soluble, preferably mass-insoluble, blowing agent is used.

In particular, a substance from the group of substances comprising the alkaline earth carbonates, silicon carbides and talc and the oxides of manganese, cobalt, copper, nickel and iron or a mixture of several of these substances can advantageously be used as blowing agents in the present process. With particular advantage, the blowing agent can consist at least partially of silicon monocarbide. In addition to pure silicon monocarbide, mixtures of the same with at least one oxide of the metals manganese, cobalt, copper, nickel and iron can also be used. The use of silicon monocarbide as an essential component of the blowing agent has, as will be explained in more detail below with reference to an exemplary embodiment, in particular considerable advantages for the course of the post-blowing process. In the present method, favorable results are also achieved with a blowing agent consisting at least partly of talc. A mixture of talc and calcite or of talc and calcite and brown stone or of talc and at least one oxide of the metals manganese, cobalt, copper, nickel and iron is preferably used as blowing agent. Furthermore could

OMPI In the present process, very good results can also be achieved with blowing agents consisting at least partly of calcite.

With regard to the external nature of the blowing agent, it should be noted in the present process that a granular material with an average grain size preferably in the range between 5 and 2 of the intended average foam bubble size of the glass foam is expediently used as the blowing agent. A fine-grained agent can advantageously be used as blowing agent Mater with grain sizes below 100 u, preferably below 20 u, can be used. If a granular material developing the expanding gas mainly by thermal dissociation and / or evaporation above the transformation range of the glass is used as the blowing agent, then the grain sizes of the blowing agent grains should be expedient to achieve a glass foam with larger foam bubbles around the individual grains, preferably essentially over 10 u, preferably over 20 u, because with thermally dissociative o evaporating blowing agents, a foam bubble forms around each blowing agent, the final size of which is primarily determined by the volume of fibers resulting from complete dissociation or damaging of the blowing agent in question, and with grain sizes below 10 u Lively

"3 (__ is less than 0.2 mm and in the case of a glass foam consisting of such fine foam bubbles, the post-blowing process is relatively difficult because, for example, over 100 ^* 000 foam bubbles have to be combined to form a 1 cm cavity. If, on the other hand, a granular material which develops the blowing gas mainly through chemical reaction above the transformation region of the glass is used as blowing agent, then the grain sizes of the blowing agent grains should be used to achieve the largest possible ratio of reaction area to the amount of reaction substance or from grain surface to grain volume are expediently substantially below 10 u, because experience has shown that chemically reacting blowing agents result in larger foam bubbles than would be expected from the grain size of the blowing agent granules and the resulting volume of the gaseous reaction product, and then of course, the focus is on the point of the fastest possible reaction and thus the largest possible ratio of grain surface to grain volume.

In the foam glass produced by the present process, the individual cavities formed by combining a plurality of adjacent foam bubbles within the foam glass are approximately the same be large - which is generally aimed at with regard to the best possible heat insulation properties of the foam glass - then it is an advantage if foam bubbles of the glass foam, which is used in the post-blowing process, are approximately the same size, and that to achieve, a granular material is expediently used as the blowing agent, which consists essentially of grains of uniform size with a size tolerance of less than 20% compared to a nominal value of the grain size in order to achieve glass foam with foam bubbles of approximately uniform size around the individual grains.

With regard to the amount of blowing agent required for the present process, the principle generally applies that the percentage by weight of the blowing agent in the total weight of the raw mixture is greater than 1.2 times the ratio of the sum of the molecular weight numbers of the molecules required to form a molecule of the expanding gas of the blowing agent to the product of the density of the foam glass and the temperature value in ° K should be the absolute temperature prevailing in the formation of the glass foam. As a guideline, one can assume that this percentage is at least three times that Ratio should be. Upwards there is no mandatory maximum value for the weight fraction of the blowing agent in the total weight of the raw mixture, but it has been shown in practice that this weight fraction should expediently be below 10%.

In particular, the following guidelines apply to the measurement of the proportion by weight of the blowing agent in the total weight of the raw mixture:

If a granular material is used as the blowing agent, this material is only open at temperatures above the sealing temperature at which the blowing agent granules are essentially gas-tightly enclosed by the mass forming the raw mixture cake and which is still open in the temperature range between the transition of the raw mixture the porous viscous mass-marking adhesive temperature of the glass grains forming the glass powder and the flow temperature of the raw mixture cake, which marks the transition of the raw mixture cake to a thin, flowing mass, which causes the bubbles forming to rise to the surface, a blowing gas with an external pressure which acts on the raw mixture cake developed partial pressure, then the weight fraction of the blowing agent in the total weight of the raw mixture should suitably be less than 2.5% and preferably between 1% and 2%

IPO lie. These low proportions by weight are quite sufficient in this case because a loss of blowing gas because of the gas-tight enclosure of the blowing agent granules practically does not occur before the gas is formed. If, on the other hand, a granular material is used as the blowing agent, a blowing gas with a partial pressure above the external pressure acting on the raw mixture cake is developed even at temperatures below the aforementioned sealing temperature, then the weight fraction of the blowing agent in the total weight of the raw mixture should in any case be greater than 1 % and preferably be between 2% and 5%, because in this case there is a not inconsiderable loss of blowing gas due to the raw mixture cake which is still open-pore below the surrounding temperature, which loss must be compensated for by a correspondingly higher proportion by weight of the blowing agent in the total weight of the raw mixture.

. If a material is also used as blowing agent which contains soluble constituents in the mass forming the raw mixture cake, then the proportion by weight of each of these constituents to the total weight of the raw mixture should expediently be greater than and preferably the proportion by weight of the constituent in question which is soluble in the raw mixture cake at least twice as large

- like this soluble weight fraction.

In the present process, a material which contains constituents which react chemically with one another at a reaction temperature above the transformation range of the glass forming the glass powder and which produce at least part of the expansion gas as a reaction product can also be used as blowing agent with particular advantage which are preferably inert and insoluble in the mass forming the raw mixture cake. The reaction temperature should expediently be in the range between the above-mentioned ambient temperature and the above-mentioned flow temperature of the raw mixture cake. With such blowing agents, a precise control of both the blowing and the blowing agent can be achieved by a suitable choice of the mutually reacting blowing agent components in relation to the reaction temperature in conjunction with a suitable selection of the parts by weight of these reacting blowing agent components based on the total weight of the raw mixture Achieve post-inflation process.

To achieve certain properties of the foam glass produced by the present process and / or to influence the course of the process during its production, the raw mixture can be used in addition to the two

W1PO Basic components glass powder and blowing agent, certain additives, such as fillers, fluxes, coloring additives, mixing liquids, etc., are added. In particular, the following guidelines essentially apply to the addition of such additives to the raw mixture:

To increase the flow temperature of the raw mixture cake, which marks the transition of the raw mixture cake to a thin, flowing mass, which causes bubbles to rise to the surface, and / or the temperature at which the blowing agent granules are essentially gas-tightly enclosed by the mass forming the raw mixture cake , an inert filler or one which reacts with a substance contained in the raw mixture or which is formed when it is heated can expediently be added to the raw mixture. Such fillers generally increase the viscosity of the viscous mass forming the raw mixture cake. In the present process, this can be of particular importance for the post-expansion process, since the post-expansion process is in most cases at temperatures above that when the glass foam is formed prevail the so-called inflation temperature and should on the other hand to avoid difficulties with

O Sequence below the flow temperature mentioned can be carried out, so that an increase in toughness and thus the flow temperature can be of considerable advantage at relatively high expansion temperatures. The filler used in the present process is primarily a substance from the group of substances comprising quartz powder, fireclay powder, kaolin, corundum powder and clay, or a mixture of several of these substances. In general, the filler used should expediently be as fine-grained as possible and have average grain sizes of less than 10011, preferably less than 10 u, which is generally given or realizable with the abovementioned substances. The weight fraction of the filler in the total weight of the raw mixture should expediently be below 50% and preferably in the range between 10% and 30 l.

To reduce the bonding temperature marking the transition of the raw mixture to a still open-pore viscous mass, the glass forming the glass powder and / or the temperature at which the blowing agent granules are essentially gas-tightly enclosed by the mass forming the raw mixture cake and / or the flow temperature marking the transition of the raw mixture cake to a thin, flowing mass which causes the bubbles which form to rise to the surface of the raw mixture cake can be added to the raw mixture expediently reducing the viscosity of the raw mixture cake. The addition of fluxes is particularly considered when the gas development of the blowing agent to be used starts at relatively low temperatures and the above-mentioned ambient temperature would be above the temperature at which the gas evolution begins without the addition of flux to the raw mixture. In this case, the enclosure temperature is expediently reduced to a value which is below half the temperature at which the gas evolution of the blowing agent begins by adding a flux. Boric acid or lithium carbonate can advantageously be used as the flux. In this case, the weight fraction of the flux in the total weight of the raw mixture should preferably be between 0.2% and 1%.

For the production of colored foam glass according to the present process, a color-imparting additive can also be added to the raw mixture, preferably a substance from which the transition metal oxides and chromates, as well as nickel monoxide, manganese dioxide, cobalt (III) oxide, iron (III) oxide , Chromium (III) oxide and vanadium (V) oxide group of substances or a mixture of several of these substances. It should be noted that various of these substances, and in particular the metal oxides specified, can simultaneously act as blowing agents, which must be taken into account when selecting the blowing agent to be used and also when measuring the proportion by weight of the total weight of the raw mixture. In special cases, the coloring additive alone can simultaneously form the blowing agent. The proportion by weight of the coloring additive in the total weight of the raw mixture should generally be kept as low as possible and should preferably be between 0.5% and 10%. It may also be advantageous for the course of the process of the present method to preferably mix the crude mixture with a stirring liquid in order to simplify the achievement of a uniform distribution of its constituents in the mixture and / or to improve the blowing process and an associated increase in the strength of the foam glass produced with water to mix into a dough and then stir in dough form until an essentially homogeneous mixture is formed and then to dry the dough at elevated temperature, preferably in the temperature range between 100 ° C. and 120 ° C. If a flux is also to be added to the raw mixture in addition to such a mixing liquid, then is Flux is advisable to use a substance that is soluble in the mixing liquid, preferably water with boric acid as the mixing liquid, and to dissolve the flux in the mixing liquid before mixing the mixing liquid with the raw mixture.

Such mixing of the raw mixture with water or another liquid is not absolutely necessary in the present process. Rather, in many cases there is also the possibility of heating the raw mixture to carry out the expanding process in the dry state, and of course this has the advantage that the aforementioned process step of drying the raw mixture dough can be saved. In these cases, which are possible, for example, when silicon monocarbide is used as the main constituent of the blowing agent, the raw mixture is mixed, preferably stirred and then carried out, in order to achieve a uniform distribution of its constituents in the mixture in the dry state until an essentially homogeneous mixture is formed of the swelling process in the dry state.

To produce foam glass moldings according to the present process, the raw mixture can be heated in appropriate forms. By ver Using forms in which the raw mixture is heated can also prevent the raw mixture cake from running apart during the expansion or post-expansion process. Molds made of ceramic or metal, preferably scale-free steel, can advantageously be used for this purpose, which should expediently be able to be dismantled from the mold in order to simplify the removal of the foam glass molded body produced. In order to prevent the foam glass from sticking or adhering to the inner walls of the molds, it is furthermore expedient to provide the molds with a coating of a suspended gypsum-sand mixture or koalin-graphite mixture on their inner walls before the raw mixture is introduced. This is especially true for metal molds because there is a relatively high risk of such adherence. If, as explained above, the raw mixture is mixed with a mixing liquid to form a raw mixture dough, then when using molds for heating the raw mixture, it is generally advantageous if the raw gerough dough only after it has been introduced is dried into the mold, because the dough fills the lower part of the mold completely and evenly, which cannot usually be achieved with already dried chunks of raw mixture. In addition, the raw mixture dough can be introduced into the

? UREA OMPI

WIPO In any case, when using continuous furnaces for the heating of the raw mixture, the mold is in most cases dried in the same oven or the pre-zone in which the raw mixture is subsequently heated to the expansion or post-expansion temperatures when the mold passes through the oven.

In the present method for producing a molded foam body, it is advantageously possible to use an essentially closed, dismantled mold with a cavity adapted to the dimensions of the molded glass body and into the mold a product corresponding to the volume of the cavity and the intended density of the molded glass body The amount by weight of the raw mixture is introduced. In this case, the raw mixture is expediently mixed in the dry state and introduced into the mold, since in closed molds the removal of the vapor of the mixing liquid which arises when drying the moist mixed raw mixture causes certain difficulties. However, it is of course also possible to introduce the raw mixture in a moist state, only then either the mold should only be closed after the raw mixture has dried or small openings should be provided at the top of the mold through which the steam flows out can. When introducing the raw mixture in the moist state, it must also be taken into account that the amount by weight of the introduced moist raw mixture must be greater by the weight of the mixing liquid contained therein than when it is introduced in the dry state. In general, the production of foam glass moldings with such closed molds has the advantage of a high degree of shape accuracy of the foam glass bodies produced, provided that suitable process management and a suitable composition of the raw mixture ensure that the foam that forms in the expansion process and in the post-expansion process Glass foam that expands further completely fills the cavity enclosed by the mold at the end of the post-expansion process, and this can generally be achieved if the glass foam in the final phase of the post-expansion process has a sufficient low toughness to adapt seamlessly to the shape of the cavity walls to be able to. However, the effort for the production of foam glass moldings when using molds and in particular closed molds is relatively high, because in addition to the investments required for the molds, there is also a considerable amount of work involved in preparing (assembling and slurrying) the molds before the start of the procedure and the

-GU E_ä OMPI

Λ. WIPO - the same is required after the end of the procedure. This manufacturing effort can be reduced in the case of simple shaping of the foam glass moldings to be produced, such as, for example, rectangular blocks, by using a shaft furnace with the cross section of the moldings to be produced, instead of individual molds running through a continuous furnace, to which raw mixture is continuously fed in on the exit side which, on the output side, like an extruder, continuously delivers a foam glass rod with the cross section of the molded articles to be produced, but firstly, such shaft furnaces require a considerably higher investment outlay than the conventional continuous furnaces because of the complicated conveying device, and secondly each individual molded article then has to have the foam produced ¬ glass rod are cut off, so that the use of such a shaft furnace can not achieve a really significant reduction in manufacturing costs.

On the other hand, in the present method, a substantial reduction in the production outlay for foam glass moldings can be achieved, if either molds, such as thin-walled individual molds a prebaked or dried clay, are used, ie after completion of the manufacturing process, an integrated component, such as, for example, forming a sheathing for the molded article produced, or if it is possible to compact to a high degree of dimensional accuracy or if rounded forms can be accepted at the corners and edges of the molded articles to be produced. In the latter case, the use of molds can be dispensed with entirely if a substance which increases the toughness of the raw mixture cake or the glass foam is added to the raw mixture to prevent the raw mixture cake or the glass foam from diverging during the blowing or post-blowing process. In addition to other clay and koalin, such substances are very suitable. When dispensing with molding, however, it is necessary that the raw mixture already as an intrinsically stable molded body, the weight (in the dry or dried state) of which corresponds approximately to the weight of the molded foam body to be produced and the dimensions of which are proportional to the dimensions of the molded body to be produced, is introduced into the furnace used to heat the raw mixture. This can be achieved when using clay as a toughness-increasing substance in that the raw mixture is mixed with the clay and relatively little water, thus producing a plastically deformable mass. is put, which is then brought into the shape of said Eigensta bile molded body and is dried in this state before de introduction into the oven used to heat the raw mixture. Other possibilities for the image of said intrinsically stable molded body consist in a dry pressing of the raw mixture or in the use of adhesive additives to the raw mixture, however the formation from a plastically deformable mass made with clay has proven to be the simplest and cheapest method. When dispensing with molds, it should generally be noted that the intended temperature values and heating times during the expansion and post-expansion process are observed exactly, that the temperature increase during the expansion process is kept as low as possible compared to the expansion process, which can be achieved, for example, by blowing agents with components that react with one another and that unnecessary excesses of blowing agent not intended to cover any losses are avoided. If these conditions are met, a relatively good dimensional accuracy of the foam glass moldings produced can still be achieved in spite of the absence of molds.

The following general guidelines apply to the conduct of the proceedings in the present proceedings: The raw mixture is dried or dried in a preheated oven, the temperature of which is below the enclosing temperature, at which the blowing agent granules are essentially gas-tightly enclosed by the mass forming the raw mixture cake - and which are preferably between 400 ° C. and 700 ° C. lies, or introduced into a furnace zone of appropriate temperature and first heated in the furnace or the furnace zone to approximately the temperature prevailing there. Subsequently, the raw mixture cake that forms, preferably within 20 to 60 minutes, by increasing the oven temperature or moving it to a higher temperature zone to the temperature required to form the glass foam, in the temperature range between the surrounding temperature and the transition of the raw mixture cake a low-viscosity blowing temperature of the raw mixture cake which allows the forming bubbles to rise to the surface and which preferably falls in the range from 700 ° C. to 900 ° C. The post-expansion process is then carried out and the foam glass formed thereafter, preferably within less than 30 minutes, by reducing the oven temperature or moving it to an oven zone

^~ W £

OMPI lower temperature at least to a temperature close to the upper limit of the transformation range of the glass forming the foam glass, preferably temperature falling to e in the lower part of the transformation range, cooled and then, preferably with the interposition of an aftermath serving to influence the material properties of the finished foam glass process, let it cool to room temperature. Advantageously, the foam glass formed is only briefly cooled to a temperature falling in the transformation region of the glass forming the foam glass, preferably in the lower part thereof, after the post-expansion process and then in a minimum internal stress to achieve minimal internal stresses the tempering process used in the foam structure is heated again to a temperature above the transformation range and then gradually to a temperature below the transform in a cooling process lasting several hours cooled and then then allowed to cool to room temperature, preferably in an environment having room temperature. In a production of foam glass of the present method in larger scale ^', for example in the production of blocks of foam glass, it is the purpose of efficient production of advantage wen the raw mixture is heated up to the formation of foam glass and the subsequent cooling of the foam glass formed is carried out in a tunnel or pusher furnace and by gradual or continuous workpiece displacement in furnace zones of different temperatures and control of the speed of the workpieces through the furnace or individual oven zones a predetermined temporal temperature profile of the heating and cooling processes is observed.

In addition to the thermal aftertreatment mentioned above, the foam glass produced by the present process can also be subjected to a mechanical aftertreatment to improve its material properties, specifically in that the foam glass formed in the warm plastic state at a temperature above the Transformation area of the glass forming the foam glass is deformed. In order to increase the rigidity in a predetermined load direction, the foam glass can expediently be squeezed together in the direction transverse to this load direction, the cavities formed in the post-expansion process being flattened out in a lenticular manner by combining a plurality of adjacent foam bubbles. The foam glass can also be used to increase the heat Insulation in a predetermined direction of heat flow in the direction parallel to this heat flow direction are squeezed together, the cavities formed in the post-expansion process also being flattened like a lens. Furthermore, the foam glass can be pulled apart or extruded in a predetermined loading direction in a direction parallel to this loading direction in order to increase the rigidity, the cavities formed in the post-expansion process being drawn out in a spindle-like manner, and finally the foam glass can be extended to increase the Thermal insulation is pulled apart or extruded in all directions perpendicular to an axial direction in the direction parallel to this axial direction, the cavities formed in the afterblowing process also being drawn out in a spindle-shaped manner. Of the abovementioned possibilities for improving the material properties of the foam glass, the achievable increase in thermal insulation in a predetermined direction of heat flow by squeezing the foam glass in the direction parallel to the heat flow direction is of particular importance, because the possibility of a further improvement of the Thermal insulation properties of the Scha produced by the present method glases results. It should be mentioned again in this connection that the supply in the Nachblähprozess Vereini¬ by each of a plurality of adjacent foam bubbles formed cavities have anyway in the horizontal direction is usually considerably larger dimensions than ^'in verti¬ Kaler direction and accordingly, in any case in the vertical direction are substantially flattened in a lenticular shape (the horizontal and vertical directions refer to the position of the foam glass during manufacture

_ process). By squeezing the foam glass together in the vertical direction, this already existing lenticular flattening can be strengthened and a further improvement in the heat insulation properties of the foam glass can be achieved in this vertical direction.

The deformability of the foam glass in the thermoplastic state can also be used to add the foam glass produced in the course of a mechanical aftertreatment. to deform a foam glass molded body of a predetermined shape. This possibility is of importance, in particular for the case mentioned above, that the use of molds in the production of foam glass moldings is dispensed with entirely, and therefore the foam glass moldings produced

OMPI do not have a high level of shape accuracy, because here the required or desired shape accuracy can now be achieved by reshaping the foam glass moldings as part of a mechanical aftertreatment.

In general, the present method leads, provided that the raw mixture or the glass foam formed in the expansion process is heated essentially uniformly, to at least approximately the same temperatures over the entire volume of the raw mixture or glass foam - as they are used with the usual manner In any case, with a suitable procedure or sufficient dwell times, the furnace is generally achieved - to an essentially uniform foam glass structure of the foam glass produced over the entire foam glass volume. In special cases, however, it may also be desirable to produce foam glass with a partly coarse-pored and partly fine-pored foam glass structure. This can be achieved in the present method in that an inhomogeneous temperature distribution with areas of substantially higher temperature than the temperature prevailing during the formation of the glass foam in the areas provided for coarse-pore foam glass structure and areas of the same in the glass foam during the post-expansion process or only an insignificantly higher temperature than the temperature prevailing during the formation of the glass foam is generated in the areas provided for fine-pored foam glass structure. The inhomogeneous temperature distribution can advantageously be generated by heat radiation with different intensities in the different radiation directions. For example, l ^'ässt by the fact that the foam glass during Nachblähprozesses a is heated in a predetermined direction on the Glas¬ foam radiant heat source prepared foam glass having a gradually coarse merges in the predetermined direction to fine-pored foam glass structure.

The strength of the foam glass produced according to the present method is in general despite its coarse-pored structure due to the cavities formed in the post-expansion process by combining a plurality of adjacent foam bubbles. and despite the resulting reduction in strength compared to foam gas with a fine-pored structure resulting from this coarse pore structure, it is still far above the strengths required in practice, for example when foam glass is used as a building material. However, as with all other glass products and also with foam glass with fine porous structure the reserves in breaking strength due to the brittleness of glass only low. An increase in the breaking strength and in particular the brittleness breaking strength of the foam glass is therefore of essential importance. Such an increase can be achieved with the present method in that on the inner walls of the cavities formed in the post-expansion process by combining a plurality of adjacent foam bubbles substantially above the wall surface, homogeneous in the finished foam glass to compressive stresses along the wall surfaces leading surface layers are generated. These upper surface layers can advantageously be produced by surface chemical reaction of the material forming the cavity walls with at least one substance located in the cavities, forming a reaction product with a lower thermal expansion than that of the wall material. Another advantageous possibility is to produce the surface layers by means of a material which forms a self-contained coating over the wall surfaces and has a lower thermal expansion than that of the wall material, by means of a coating which adheres to the interior of the cavities from the atmosphere. The upper surface layers can also advantageously by

^^ a substance which precipitates from the atmosphere within the cavities on the interior walls of the cavity and then dissolves superficially in the wall material and which forms a solution with the wall material of less thermal expansion than that of the pure wall material. Finally, in the case of appropriate compositions of the material forming the cavity walls, it is also expedient to proceed in such a way that the surface layers are produced by a material which is contained in the wall material and diffuses to the wall surfaces by heat treatment. The surface layers are preferably produced under the conditions of the post-expansion process during the same. To form the surface layers, a substance from the group of substances comprising the suicides, nitrides, tianates, zirconates and the rare earths or a mixture of several of these substances can expediently be added to the raw mixture. Instead of this or in addition thereto, the crude mixture for forming the surface layers is advantageously a metal oxide, an oxide of the metals nickel, copper and iron, or a mixture of preferably more metal oxides conces- ^■ sets. Another advantageous possibility is to add clay to the raw mixture to form the surface layers. In the following, some special exemplary embodiments of the present method are described in more detail with all the details that are important for the method.

example 1

A mixture of 98% by weight of glass powder with a maximum grain size of 125 u and 2% by weight of powdered silicon carbide with a maximum grain size of 10 u was used as the raw mixture. The raw mixture was mixed thoroughly and then shaken dry in a mold. The open mold filled with the crude mixture up to about 30% of its height was then in an oven within a period of 3 hours to the temperature of 650 above the transformation range of the waste glass used for the glass powder, which range from 500 ° C. to 600 ° C. ° C heated at this temperature, which is still below the enclosure temperature of approx. 680 to 720 ° C, at which the silicon carbide grains are essentially gas-tightly enclosed by the mass forming the raw mixture cake, the silicon carbide used as blowing agent develops, as by an examination of the Atmosphere in the furnace could not be established, no blowing gas. After heating to 650 ° C, the mold with the inside contained, still open-pore raw mixture cakes from glued together glass grains and silicon carbide grains distributed in the interspaces between the glass grains heated to the expansion temperature of approx. 880 ° C. within approx. 25 minutes. During this heating, the raw mixture cake initially changes into a viscous mass in the temperature range from 680 ° C to 720 ° C, from which the silicon carbide grains distributed therein are sealed gas-tight, and from about 750 ° C then a chemical reaction of the silicon carbide with the Silicon dioxide contained in the crude mixture, in which carbon monoxide and carbon dioxide are formed and which are likely according to the following reaction equations

2 Si0 ₂ + SiC 3 SiO + CO and

3 Si0 ₂ + SiC 4 SiO + CO.

expires. The resulting carbon oxides form the expanding gas, which initially causes a small bubble to form around each silicon carbide grain. With the formation of these bubbles, the reaction between the silicon carbide and the silicon dioxide slows down considerably because the carbon oxide gases contained in the bubbles increase the surface area of the silicon carbide grain in the bubble.

OMPI to » ^WIP ° ^" Insulate partly from the viscous mas surrounding the balase and thus from the silicon dioxide. However, the gas pressure in the bubbles is relatively high because of the still fairly high toughness at these temperatures and the large surface tension of the viscous mass forming the raw mixture cake. With further heating to the blowing temperature, however, both the toughness and the surface tension of the mass forming the raw mixture cake decrease sharply, so that the bubbles under high gas pressure can now increase successively with this decrease. As a result, the mass forming the raw mixture cake is gradually foamed and begins to rise in shape. To-

• When the blowing temperature of approx. 880 ° C is reached in the oven, the temperature increase is stopped and the blowing temperature is maintained for about 2 to 5 minutes. During this time, the mass in the mold continues to increase until the raw mixture cake has passed into a glass foam formed by lamellar walls between mutually adjacent, approximately polyhedral foam bubbles. The end of this transition phase can be recognized by the fact that the initially rapid increase in mass in the form slows down more and more. At this point the night

^ 't / OO blowing process is initiated and the temperature in the furnace is raised to 950 ° C. in about 10 minutes. As a result, the increase in the mass in the mold accelerates again and then stops almost completely after the 10 minutes. Simultaneously with this further increase in the mass in the mold during the post-expansion process, the previously almost smooth surface of the mass becomes increasingly uneven, which is obviously due to the fact that relatively large voids are created within the mass by combining a plurality of adjacent foam bubbles and the Cavities that arise immediately below the surface of the mass due to expansion cause the surface of the mass to rise in its central regions. The post-expansion process is terminated at the latest when one of these cavities bursting directly beneath the surface of the mass bursts. The operations during the Nach¬ blähprozesses within the process defined in the previous bulking glass foam are essentially the following ^': With the expansion temperature of about 880 ° C of the glass foam is still relatively fine pores, ie, the individual foam bubbles of the glass foam have dimensions in Be¬ range between approx. 0.5 and 2 mm, which can easily be determined by the fact that the glass foam is cools and cuts open indirectly after the swelling process. With the further heating of the glass foam during the post-expansion process, firstly, the toughness and surface tension of the glass forming the glass foam continue to drop sharply, and secondly, the pressure within the individual foam bubbles increases both due to the increase in temperature and due to a chemical reaction between the in the carbon dioxide contained in the bubbles and the rest of the silicon carbide grain still remaining in the foam bubble, in which the carbon dioxide is reduced by the silicon carbide to form silicon to carbon monoxide. The free silicon produced in this reaction beats. to stick as _? essentially a self-contained coating on the inner walls of the cavities formed in the post-expansion process by combining adjacent foam bubbles. The silicon coatings on the cavity inner walls can be readily determined on the finished foam glass. The increase in pressure due to the chemical reaction results from the fact that two molecules of carbon monoxi are formed from one molecule of carbon dioxide in the reaction. The reaction probably only starts at temperatures above 900 ° C. It may also be

* §B to unite adjacent foam bubbles and thus to form the relatively large cavities, tearing open the walls between the individual foam bubbles initiated or favored by the reaction, because the processes of the reaction in the individual foam bubbles are undoubtedly not exactly the same, so that during the The course of the reaction gives rise to pressure differences between the individual foam bubbles which, if the height is sufficient, could cause the walls between the individual foam bubbles to tear open. In addition, the amount of silicon carbide still present in the individual foam bubbles is also of different sizes, so that pressure differences between the individual foam bubbles could also result from the fact that the reaction and thus the pressure increase in the foam bubbles, where the silicon carbide is used up ceases while the reaction and thus the increase in pressure in the other foam bubbles continues. In any case, there is reason to believe that all of the silicon carbide is used up, and no residues of silicon carbide grains could be found in the finished foam glass. In addition to this possibility that the tearing of the walls between the individual foam bubbles is caused by pressure differences between the foam bubbles, there is of course also the possibility that the tearing open of the walls mainly due to the sharp drop in surface tension and toughness of the glass forming the walls with the further increasing temperature and the decrease in the wall thickness of the walls associated with the further expansion of the foam bases, with a simultaneous increase in those acting on the walls Tensile stresses is attributable. In any case, the cavities formed during the post-expansion process by combining foam bubbles have dimensions in the order of magnitude of centimeters, which can also be readily determined by cutting the finished, cooled foam glass. Following the post-blowing process, the resulting foam glass is cooled within 20 minutes to the temperature of 510 ° C in the lower part of the transformation area of the glass forming the foam glass, and this rapid cooling, so to speak, freezes the foam glass structure achieved at the end of the post-blowing process . The thermal stresses resulting from this rapid cooling in the foam glass are then removed in a tempering process which serves to achieve minimal residual stresses in the foam structure. For this purpose, the glass is heated again to 620 ° C within 15 minutes and then in a cooling process lasting over 5 hours.

<W

£ gradually cooled to the temperature of 480 ° C below the transformation range of the glass forming the foam glass. Because of the extremely slow cooling when passing through the transformation area, no thermal stresses arise in the foam glass during this cooling process. After this cooling process has ended, the mold is then removed from the oven and allowed to cool to room temperature in an ambient temperature environment. Since the foam glass is already completely solidified below the transformation region, no residual stresses can arise in the foam glass during this relatively rapid cooling to room temperature. The finished foam glass is then removed from the mold.

The resulting foam glass has a density of 0.143 g / cm and a foam structure with essentially regularly distributed, slightly lenticularly flattened cavities which have a diameter of between 1 and 2 cm in the horizontal direction (in relation to the position of the foam glass during the manufacturing process) have dimensions between 0.8 and 1.4 cm in the vertical direction and are coated on their inner walls with a thin silicon layer. The lenticular flattening of the cavities probably arises in part only during the aforementioned Cooling process, because it could be observed that the foam glass sagged somewhat in the mold during the cooling process.

Example 2

The process explained in Example 1 was repeated for a raw mixture of 82 percent by weight glass powder with a maximum grain size of 1 mm and 3 percent by weight of powdered silicon monocarbide with a maximum grain size of 50 u and 15 percent by weight clay with a maximum grain size of 20 u, but for heating the The raw mixture was not used in a mold, but the raw mixture was mixed with water and formed into a cuboid and then g was dried at 120 ° C. for about 3 hours and then placed in this cuboid mold in the oven used to heat the raw mixture. The temperatures and heating or Cooling times in the heating of the raw mixture, the blowing process, the post-blowing process, the rapid cooling of the foam glass formed after the post-blowing process, the tempering process and the subsequent slow cooling of the foam glass were essentially the same as in Example 1, but in the transition phase vo The subsequent slow cooling at the temperature of 620 ° C a mechanical

, * ( shaping of the foam glass body formed in the tough plastic state for the final shaping and for further flattening of the slightly lenticularly flattened cavities within the foam glass body. The finished cuboidal foam glass body had a density of 0.161 g / cm and, in comparison to Example 1, was similarly distributed but somewhat smaller cavities with a somewhat stronger flattening.

Example 5

In this and all the following examples, the process sequence is qualitatively the same as in Example 1 and also the heating and cooling times and the heating temperature of the raw mixture of about 650 ° C. and the final temperatures of the subsequent expansion process Cooling down of approx. 510 ° C., the subsequent tempering process of approx. 620 ° C. and the subsequent 5-hour cooling process of approx. 4.80 ° C. are essentially the same as in example 1, because they are for the waste glass used is the same in all cases and the above-mentioned temperatures and times result from the properties of the glass used for the powder. Furthermore, this and the following example have in common with example 2 that the raw mixture with water

OMPI is stirred and formed into a cuboid, which was then subjected to a three-hour drying process at approx. 120 ° C and then introduced without a mold into the oven used to heat the raw mixture. Different from Examples 1 and 2 in this and the following examples are only the compositions of the raw mixture, in particular with regard to the blowing agents used and other additives to the raw mixture and with regard to the grain sizes of the glass powder, the blowing agents used and the type resulting therefrom and the course of the expansion and post-expansion process dependent final temperatures of the expansion and post-expansion process and the properties of the foam glasses produced. For this and all other examples, only these different characteristics are therefore given in tabular form below.

Composition of the raw mixture: 97.3 percent by weight of glass powder with a maximum grain size of 0.25 m,

2.0 weight percent calcite

0.7% by weight boric acid (dissolved in the mixing water. Final temperature of the blowing process: 800 ° C. Final temperature of the post-blowing process: 850 ° C

Density of manufactured

Foam glass: 0.126 g / cm 3 average diameter of the cavities: 1, 1 cm average height of the cavities: 0.8 cm

Example 4

Composition of the raw mixture:

94% by weight glass powder with a maximum grain size of 0.4 mm,

3 weight percent calcite

3% by weight talc

Final temperature blowing process: 780 ° C

Final post-inflation process temperature: 830 ° C

Density of the manufactured

Foam glass: 0.153 g / cm average diameter of the cavities: 1.25 cm average height. the cavities: 0.9 cm

'Example 5

Composition of a raw mixture:

93.7 percent by weight glass powder with a maximum grain size of 0.25 mm

2.0 weight percent calcite

2.0 percent by weight talc

2.0 percent by weight of manganese dioxide

0.3 percent by weight boric acid (dissolved in mixing water)

Final temperature blowing process: 780 ° C

Final post-inflation process temperature: 830 ° C

^ _ ^~ E i

OMPI Λ. WIPO. ₃ Density of the foam glass produced: 0.137 g / cm average diameter of the cavities: 1.35 cm average height of the cavities:. 1.05 cm

Example 6

Composition of the raw mixture:

93.5 percent by weight glass powder with a maximum grain size of 0.3 mm

3.0 weight percent silicon monocarbide

3.0 weight percent manganese dioxide

0.5 percent by weight boric acid (dissolved in the mixing water

Final temperature blowing process: 860 ° C

Final post-inflation process temperature: 920 ° C

Density of the manufactured

Foam glass: 0.132 g / cm average diameter of the cavities: 1.6 cm average height of the cavities: 1.1 cm

Example 7

Composition of the raw mixture:

86 percent by weight glass powder with a maximum grain size of 0.5 mm

3 weight percent silicon monocarbide

3 percent by weight manganese dioxide

8 weight percent clay

Final temperature blowing process: 890 ° C

Final temperature post-inflation process: 960 ° C 3 Density of the foam glass produced: 0.154 g / cm average diameter of the cavities: 1.3 cm average height of the cavities: 0.9 cm

Claims

Patent claims

1. Process for the production of closed-pore foam glass, in which a raw mixture containing at least glass powder and blowing agent is heated to temperatures above the transformation range of the glass forming the glass powder until the blowing agent is caused by chemical reactions and / or gas elimination and / or Evaporation evolves a blowing gas, which initially forms spherical bubbles within the raw mixture cake that has been baked by softening the glass powder granules, which continue to grow with the further development of gas while the cake is inflated until the adjacent bubbles collide and then, with further growth, form lamellar walls the individual bubbles take on a polyhedral shape and the cake is thus covered in a glass foam formed by the lamella-like walls between the mutually adjacent, approximately polyhedral foam bubbles goes, characterized in that the glass foam is subjected to a post-expansion process to achieve a coarse-pore foam structure until the major part

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____ the lamella-like walls between the individual foam bubbles is torn open and a plurality of adjacent foam bubbles are united to form a single cavity, and that for this purpose the heat effect on the glass foam is maintained after its formation and / or the ratio of the average gas pressure in the foam bubbles to the pressure acting on the glass foam from the outside to a value above the value of this ratio achieved with the formation of the glass foam and / or the surface tension of the glass forming the lamellar walls relative to the gas in the foam bubbles and the toughness of the glass forming the lamellar walls is brought to values below the values of the surface tension or toughness achieved with the formation of the glass foam.

2. The method according to claim 1, characterized in that the glass foam in the Nachblähpro¬ process is heated to a temperature which is above the. During the formation of the glass foam and thereby both the gas pressure in the foam bubbles to a value the pressure value achieved with the formation of the glass foam as well as the surface tension and toughness of the glass to values below those with values of surface tension and toughness achieved in the formation of the glass foam.

3. The method according to claim 2, characterized in that the glass foam in the Nachblähpro¬ process is heated to a temperature which is 50 ° C to 100 ° C above the prevailing temperature during the formation of the glass foam.

4. The method according to claim 1 or 2, characterized in that portions of the blowing agent are added to a substance which contains a gas-developing chemical reaction with one of those in the glass foam which occurs only in the region of the temperature prevailing in the formation of the glass foam or above it ¬ NEN substances and thereby blow the gas pressure in the show in the post-inflation process is brought to a value above the pressure value achieved with the formation of the glass foam.

5. The method according to claim 1 or 2, characterized in that the blowing agent proportions of a vaporisable in the post-expansion process, compared to the substances contained in the glass foam with a substance above the temperature prevailing during the formation of the glass foam, are added and thereby the gas pressure in the foam bubble in the post-expansion process is brought to a value above the pressure value achieved with the formation of the glass foam.

6. The method according to claim 1 or 2, characterized in that portions of a decomposable substance in the post-expansion process, which splits off at a temperature above the prevailing temperature during the formation of the glass foam, gas is added to the blowing agent and thereby the gas pressure in the foam bubbles in the post-blowing process are brought to a value above the pressure value achieved with the formation of the glass foam.

7. The method according to any one of the claims

1 to 6, characterized in that the formation of the glass foam takes place in the temperature range between 750 ° C and 900 ° C and the post-expansion process is carried out at temperatures in the temperature range from 800 ° C to 1000 ° C.

8. The method according to any one of the claims

1 to 7, characterized in that the glass foam is subjected to the post-expansion process immediately after its formation.

9. The method according to any one of claims 1 to 7, characterized in that the glass foam only after the interposition of a cooling phase, the post-expansion. process and is reheated for this purpose.

10. The method according to claim 9, characterized in that the glass foam is cooled to room temperature in the cooling phase and is heated to carry out the post-expansion process to a temperature above the temperature prevailing during the formation of the glass foam.

11. The method according to any one of claims 1 to 10, characterized in that a raw mixture containing 50 to 99.5 weight percent, preferably 80 to 99 weight percent glass powder is used.

12. The method according to any one of claims 1 to 11, characterized in that for the Glaspul¬ ver at least for the most part glass with a min least partially within the temperature range of

500 ° C to 600 ° C lying transformation range is used.

13. The method according to any one of claims 1 to 12, characterized in that at least partially pulverized waste glass is used as glass powder for the raw mixture.

14. The method according to claim 13, characterized in that for the production of foam glass for the construction industry essentially from use glasses, pre- preferably bottle glass and other container glass as well as disc glass, existing waste glass is used.

15. The method according to claim 13, characterized in that existing waste glass is used for the production of foam glass for technical devices essentially from device glasses, preferably borosilicate glass and / or low-melting lead glass and / or high-melting silica glass.

16. The method according to any one of the claims 13 to 15, characterized in that the waste glass is broken up in a jaw crusher into glass fragments of less than 5 mm in size and the splinters are ground in a disc vibrating mill or a ball mill to glass powder with grain sizes of up to 1 mm at most and the glass powder thus obtained is used directly for the raw mixture.

17. The method according to any one of claims 1 to 16, characterized in that glass powder with grain sizes below 1 mm is used for the raw mixture.

18. The method according to any one of claims 1 to 17, characterized in that a fine-grained material is used as blowing agent, which is contained in the raw mixture by chemical reaction with one or during the heating of the same forming substance and / or by thermal dissociation and / or by evaporation or sublimation, a blowing gas develops which only at a temperature above the transition temperature of the raw mixture to a viscous mass marking the bonding temperature. the glass grains forming the glass powder, preferably at a temperature above 600 ° C., reaches a partial pressure which corresponds to the external pressure acting on the raw mixture cake and already at a temperature below which the transition of the raw mixture cake to a thin liquid which changes Forming bubbles to the surface let-Mas marking flowing temperature of the raw mixture cake, preferably at a temperature below 900 ° C, the necessary for blowing, the sum of the external pressure acting on the raw mixture cake and the surface tension caused by the surface tension C_f on the inner wall of a a bubble overpressure LΛ \ ~ = 4CJ / d corresponding partial pressure reached around a blowing agent grain produced by the large d-forming bubble.

19 .. The method according to any one of claims 1 to 18, characterized in that a in the Ro mixed cake forming mass only less than 1% by weight of the mass soluble, preferably in the

yf ___ O Bulk insoluble blowing agent is used.

20. The method according to any one of claims 1 to 19, characterized in that a substance from which the alkaline earth carbonates, silicon carbides and talc and the oxides of manganese, cobalt, copper, nickel and iron or a mixture of several of these substances is used as blowing agent .

21. The method according to claim 20, characterized in that the blowing agent consists at least partially of silicon monocarbide.

22. The method according to claim 21, characterized in that a mixture of silicon monocarbide and at least one oxide of the metals manganese, cobalt, copper, nickel and iron is used as blowing agent.

23. The method according to claim 20, characterized in that the blowing agent consists at least partially of talc.

24. The method according to claim 23, characterized in that a mixture of talc and calcite or of talc and calcite and brown stone or talc and at least one oxide of the metals manganese, cobalt, copper, nickel and iron is used as blowing agent.

25. The method according to claim 20, characterized in that the blowing agent at least in part consists of calcite.

26. The method according to any one of claims 1 to 25, characterized in that a granular material with an average particle size of between 6 and 20% of the envisaged average bubble size of the gloss foam is used as blowing agent.

27. The method according to any one of claims 1 to 26, characterized in that a fine-grained material with grain sizes below 100 u,. preferably less than 20 u.

28. The method according to any one of claims 1 to 27, characterized in that a granular material developing the expanding gas mainly by thermal dissociation and / or evaporation above the transformation region of the glass is used as the blowing agent, the grain sizes of which are used to achieve a Glass foam with larger foam bubbles around the individual grains are essentially above 10 u, preferably above 20 u.

29. The method according to patent claim 27, characterized in that the blowing agent is a blowing agent which mainly develops through chemical reactions which occur above the transformation region of the glass granular material is used, the grain sizes of which in order to achieve the largest possible ratio of the reaction area to the amount of reactant or from the grain surface to the grain volume are substantially below 10 u.

30. The method according to any one of claims 1 to 29, characterized in that a granular material is used as blowing agent, which is used to achieve a glass foam with foam bubbles of approximately uniform size around the individual grains essentially from grains of uniform size with a size below 20 % tolerance lies in relation to a nominal value of the grain size.

31. The method according to any one of claims 1 to 30, characterized in that the percentage by weight of the blowing agent in the total weight of the crude mixture is greater than 1.2 times the ratio of the sum, the molecular weight numbers of the molecules required to form a molecule of the expanding gas Blowing agent to the product of the density number corresponding to the intended density of the foam glass and the temperature value in ° K is the absolute temperature prevailing when the glass foam is formed.

32. The method according to any one of claims 1 to 31, characterized in that a raw mixture

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Λ, ^{^} WlPO ^~ is used in which the weight fraction of the blowing agent in the total weight of the raw mixture is less than 10%.

33. Method according to one of the claims

1 to 32, characterized in that a granular material is used as blowing agent, which is only at temperatures above the surrounding temperature at which the blowing agent granules are enclosed in a gas-tight manner by the mass forming the raw mixture cake and which in the temperature range between the transition of the Raw mixture to a still open-pore viscous mass marking the adhesive temperature of the glass grains forming the glass powder and the transition temperature of the raw mixture cake to ^{1 "of} a thin, flowing mass of the resulting bubbles that rise to the surface of the raw mixture cake, a blowing gas with a higher than that developed partial pressure acting on the raw mixture cake and that the weight fraction of the blowing agent in the total weight of the raw mixture is less than 2.5% and is preferably between 1% and 2%.

34. Method according to one of the claims

1 to 32, characterized in that a granular material is used as blowing agent, which already at temperatures below the enclosure temperature at which

f O the blowing agent granules are essentially gas-tightly enclosed by the mass forming the raw mixture cake and the temperature range between the bonding temperature of the glass grains forming the glass powder and the transition of the raw mixture cake to a still porous viscous mass that marks the transition of the raw mixture cake to one low-viscosity, the flowing temperature of the raw mixture cake that causes the bubbles to rise to the surface, a blowing gas develops with a partial pressure above the external pressure acting on the raw mixture cake, and that the weight fraction of the blowing agent in the total weight of the raw mixture is greater than Is 1% and is preferably between 2% and 5%.

35. Method according to one of the claims 1 to 34, characterized in that a material is used as blowing agent which contains soluble components in the mass forming the raw mixture cake, and that the weight proportion of each of these components in the total weight of the raw mixture is greater as. the proportion by weight of the constituent in question which is soluble in the raw mixture cake and is preferably at least twice as large as this soluble proportion by weight.

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36. Method according to one of the claims

1 to 19, characterized in that the blowing agent used is a material which contains constituents which chemically react with one another at a reaction temperature above the transformation range of the glass forming the glass powder and as a reaction product produce at least part of the blowing gas and preferably as opposed to one another the mass forming the raw mixture cake is inert and insoluble in it.

37. The method according to claims 33 and 36, characterized in that the reaction temperature lies in the range between the said sealing temperature and the flow temperature of the raw mixture cake

38. Method according to one of the claims 1 to 37, characterized in that the raw mixture to increase the flow temperature of the raw mixture cake and / or the sealing temperature, which marks the transition of the raw mixture cake to a thin, flowing mass, which causes the bubbles to rise to the surface, in which the blowing agent granules are essentially gas-tightly enclosed by the mass forming the raw mixture cake, an inert filler or a filler which reacts with substances contained in the raw mixture or is formed when it is heated is added.

39. Method according to claim 38, characterized in that a substance from the group of substances comprising the substances quartz powder, chamotte powder, kaolin, corundum powder and clay or a mixture of several of these substances is used as the filler and the proportion by weight of the filler in the total weight of the raw mixture ¬ preferably under. 50% lies.

40. Method according to one of the claims

1 to 39, characterized in that the raw mixture for reducing the transition temperature of the raw mixture to a still open-pore viscous mass marking temperature of the glass forming the glass powder and / or the temperature at which the blowing agent granules from the mass forming the raw mixture cake are enclosed essentially gas-tight and / or the flux reducing the viscosity of the raw mixture cake is added to the transition temperature of the raw mixture cake to a thin, flowing mass of the raw mixture cake that causes the bubbles to rise to the surface.

41. The method according to claim 40, characterized in that boric acid or lithium carbonate is used as the flux and the weight fraction of the flux in the total weight of the raw mixture is preferred.

OMPI as between 0.2 I and 1 I.

42. The method according to any one of claims 1 to 41, characterized in that the raw mixture for the production of colored foam glass, a coloring additive, preferably a substance from which the transition metal oxides and chromates as well as nickel monoxide, manganese dioxide, cobalt (III) - oxide, iron (III) oxide, chromium (III oxide and vanadium (V) oxide) substance group or, a mixture of several of these substances, is added and the proportion by weight of the coloring additive in the total weight of the raw mixture - preferably between 0.5 and 10%.

43. Method according to one of the claims

1 to 42, characterized in that the raw mixture for the production of magnetic foam glass with an overlying relative permeability constant is an additive of ferromagnetic substances and / or substances which form ferromagnetic substances under the conditions of the swelling or post-blowing process, preferably a substance from the group of substances comprising nickel monoxide, cobalt (III) oxide, iron (III) oxide and iron or a mixture of several of these substances, and the proportion by weight of this additive in the total weight of the raw mixtures is preferably between 0.2% and 10 % lies.

44. The method according to any one of claims 1 to 43, characterized in that the raw mixture to simplify the achievement of a uniform distribution of its components in the mixture and / or to improve the blowing process and an associated increase in the strength of the foam glass produced a mixing liquid, preferably with water, is mixed into a dough and then stirred in dough form until an essentially homogeneous mixture is formed, and the dough is then heated at elevated temperature, preferably in the temperature range between 100 ° C. and 130 ° C. ¬ is dried.

45. Method according to claims 40 and 44, characterized in that a substance soluble in the mixing liquid, preferably boric acid soluble in water, is used as the flux and the flux is dissolved in the mixing liquid before the mixing liquid is mixed with the raw mixture .

46. The method according to any one of the claims 1 to 43, characterized in that the crude mixture to achieve a uniform distribution ^'Be¬ its constituents in the mixture in the dry state until the Ent stehung a substantially homogeneous mixture durch¬ mixed, preferably stirred, is and then to management of the blowing process is heated in the dry state.

47. The method according to any one of claims 1 to 46, characterized in that the raw mixture is heated in a mold to prevent the raw mixture cake from running apart during the blowing or post-blowing process, ^" preferably in a mold made of dried or fired clay or other ceramics or in a suitably dismantled metal form made of scale-free steel or another metal.

48. The method according to claim 47, characterized in that the mold is provided on its inner walls with a coating of a slurried gypsum-sand mixture or kaolin-graphite: mixture before the introduction of the ro mixture.

• 49. Method according to claims 44 and 47 or 48, characterized in that the raw mixture dough is dried after being introduced into the mold.

50. The method according to claim 47, 48 or 49, characterized in that a closed or closable mold with a cavity adapted to the dimensions of the foam glass body is used for producing a foam glass molded body and in the shape of a product of the volume of the cavity and the intended A corresponding amount of weight of the raw mixture is introduced into the density of the foam glass molded body.

51. The method according to claim 47, 49 or 50, characterized in that for the production of an at least partially encased foam glass molded body, a mold forming the shell of the molded body produced after completion of the manufacturing process, preferably a thin-walled mold made from pre-fired or dried clay or ceramic, is used.

52. Method according to one of the claims

1 to 46, characterized in that a substance which increases the toughness of the raw mixture cake is added to the raw mixture to prevent the raw mixture cake from running apart during the blowing or post-blowing process.

53. Method according to claims 39,

44 and 52, characterized in that aluminum silicate, preferably from the material group comprising clay, kaolin and pyrophillite, is used as the toughness of the raw mixture cake.

54. The method according to claim 52 ^"barren ^53,: characterized in that for the production of a foam glass body having at least partially überdecktem foamed glass solid core or carrier in the crude mixture before a core or carrier body, preferably made of ceramic, is introduced when it is heated.

55. The method according to any one of claims 1 to 54, characterized in that the raw mixture i dry or dried state in a preheated oven whose oven temperature is below the enclosure temperature at which the blowing agent granules are enclosed in a gas-tight manner by the composition forming the mixture cake and is preferably between 400 ° C. and 700 ° C. or is introduced into a furnace zone of appropriate temperature and is initially heated in the furnace or the furnace zone to approximately the temperature prevailing there and the crude mixture cake which forms subsequently, preferably within 20 up to 60 minutes, by increasing the oven temperature or moving it to a higher temperature in the oven zone to the temperature required to form the glass foam, in the temperature range between the surrounding temperature and the transition of the raw mixture cake to a thin liquid that allows the bubbles to rise to the surface e marking the flowing temperature of the raw mixture cake and preferably further heating temperature falling in the range from 700 ° C to 900 ° C and then the post-expansion process is carried out and the formed

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(Λ Foam glass thereafter, preferably within less than 30 minutes, by reducing the furnace temperature or moving to a lower temperature furnace zone to at least a temperature close to the upper limit of the transformation range of the glass forming the foam glass, preferably to a temperature falling in the lower part of the transformation region is cooled and then allowed to cool to room temperature, preferably with the interposition of an aftertreatment process serving to influence the material properties of the finished foam glass.

56. Method according to one of the claims 1 to 55, characterized in that the foam glass formed, after the post-expansion process, is briefly cooled to a temperature falling in the transformation region of the glass forming the foam glass, preferably in the lower part thereof, and then in a tempering process used to achieve minimal internal stresses in the foam structure is heated again to a temperature above the transformation range and then gradually to a temperature below in a cooling process which lasts for several hours

Ar- IPO of the transformation region is cooled and then then allowed to cool to room temperature, preferably in an environment having room temperature.

57. The method according to any one of claims 1 to 56, characterized in that the heating of the raw mixture until the formation of foam glass and the subsequent cooling of the foam glass formed is carried out in a tunnel or batch furnace and by gradual or continuous workpiece displacement in furnace zones of different temperatures and Controlling the throughput speed of the workpieces through the furnace or the individual furnace zones, a predetermined temporal temperature profile of the heating and cooling processes is maintained.

58. The method according to any one of claims 1 to 57, characterized in that the foam glass is formed in the hot plastic state at a temperature above the Transformationsbe ^'rich of the sight glass forming the glass is deformed structure.

59. The method according to claim 58, characterized in that the foam glass is squeezed together to increase the rigidity in a predetermined loading direction in the direction transverse to this loading direction and thereby through in the post-inflation process

O Unification of a plurality of adjacent foam bubbles each created in a lenticular shape.

60. Method according to claim 58, characterized in that the foam glass is squeezed together in order to increase the thermal insulation in a predetermined heat flow direction in the direction parallel to this heat flow direction, and as a result the cavities formed in the post-expansion process by combining a plurality of adjacent foam bubbles are flattened in a lenticular shape become.

61. The method according to claim 58, characterized in that the foam glass is pulled apart or extruded to increase the rigidity in a predetermined loading direction in the direction parallel to this loading direction, and thereby the resulting in the post-blowing process by combining a plurality of adjacent foam bubbles Cavities are drawn out in a spindle-shaped manner.

62. Method according to claim 58, characterized in that the foam glass is pulled apart or extruded in order to increase the thermal insulation in all directions perpendicular to an axial direction in the direction parallel to this axial direction and thereby the in

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^ the postblowing process is drawn out in a spindle-like manner by combining a plurality of adjacent foam bubbles.

63. The method according to claim 58, characterized in that the foam glass is deformed into a foam glass molded body of a predetermined shape.

64. The method according to any one of claims 1 to 63, characterized in that for the production of foam glass with a partially coarse-pored and partly fine-pored foam structure in the glass foam during the post-expansion process, an inhomogeneous temperature distribution with areas of significantly higher temperature than the temperature in the formation of the glass foam the areas intended for coarse-pored foam structure and areas of the same or only slightly higher temperature than the temperature forming during the formation of the glass foam are produced in the areas provided for fine-pored foam structure.

65. The method according to claim 64, characterized in that the glass foam for the production of foam glass with a foam structure gradually transitioning from coarse to fine porosity in a predetermined direction during the post-expansion process from a radiation in the predetermined direction onto the glass foam

*% Heat source is heated.

66. The method according to any one of claims 1 to 65, characterized in that to increase the breaking strength, in particular the brittle fracture resistance, of the foam glass on the inner walls of the cavities formed in the post-blowing process by combining a plurality of adjacent foam bubbles in each case substantially above the wall surface homogeneous surface layers leading to compressive stresses along the wall surfaces in the finished foam glass are produced.

67. The method according to claim 65, characterized in that the surface layers are produced by surface chemical reaction of the material forming the cavity walls with at least one substance located in the cavities to form a reaction product with a lower thermal expansion than that of the wall material.

68. The method according to claim 65, characterized in that the surface layers produce a substance with less thermal expansion than that of the wall material due to a coating which adheres to the interior walls of the cavity and forms a self-contained coating over the wall surfaces become.

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69. The method according to claim 66, characterized by the fact that the surface layers are produced by a substance which is deposited on the interior walls of the cavity from the atmosphere within the cavities and then dissolves in the wall material, and which with the wall material is a solution of less Forms thermal expansion than that of the pure wall material.

70. The method according to claim 66, characterized by the fact that the surface layers are produced by a substance contained in the wall material and diffusing to the wall surfaces by heat treatment

71. Method according to one of the claims 66 to 70, characterized in that the surface layers are produced under the conditions of the post-expansion process during the same.

72. Method according to one of the claims 66 to 71, characterized in that a substance from the group of substances comprising the suicides, nitrides, titanates, zirconates and rare earths or a mixture of several of these substances is added to the raw mixture to form the surface layers.

73. The method according to any one of claims 66 to 71, characterized in that the raw mixture

_ a metal oxide, preferably an oxide of the metals nickel, copper and iron, or a mixture of several metal oxides is added to form the surface layers.

74. The method according to any one of claims 66 to 73, characterized in that clay is added to the raw mixture to form the surface layers.

75. Foam glass produced according to the method according to one of claims 1 to 74, characterized in that the major part of the total cavity volume of the foam glass is formed by cavities, each of which has a cross-sectional shape in at least one cross-sectional plane running through the cavity. area of at least 0.5 cm 2, preferably, at least

2 1 cm. ^*

76. Foam glass according to claim 75, characterized in that with the majority of the cavities

2 at least 0.5 cm cross-sectional area in each case the cross-section with the largest cross-sectional area of the cavity in question has at least one, preferably two, intersecting at right angles, the diameter which is larger than the dimension of the cavity in the normal direction this cross section are.

77. Foam glass according to claim '76, characterized in that the majority of the cavities with little 2 at least 0.5 cm cross-sectional area are flattened in an approximately lenticular manner in at least approximately the same flattening direction, which essentially corresponds to the normal direction mentioned.

78. Foam glass according to one of the claims

75 to 77, characterized in that at the Mehrzah

2 of the cavities with a cross-sectional area of at least 0.5 cm is deposited on the inside of the cavity walls by a metallic coating.