EP0497850A1

EP0497850A1 - Aluminium oxide-based foams which are stable under the effect of water, bodies made therefrom and mixtures for their production

Info

Publication number: EP0497850A1
Application number: EP19900916271
Authority: EP
Inventors: Lutz Prof. Dr. RÖSCH; Beate Dr. Biller; Günter Dr. KRATEL
Original assignee: Wacker Chemie AG
Current assignee: Wacker Chemie AG
Priority date: 1989-10-31
Filing date: 1990-10-31
Publication date: 1992-08-12
Also published as: JPH04505000A; CA2069335A1; WO1991006516A1; DE3936230A1

Abstract

La présente invention se rapporte à des mousses stables sous l'aciton de l'eau à base d'oxyde d'aluminium, les corps qui en résultent ainsi que les mélanges servant à leur fabrication.The present invention relates to foams stable under the action of water based on aluminum oxide, the resulting bodies and the mixtures used for their manufacture.

Description

Under the action of water, stable foams based on aluminum oxide, bodies made from them and mixtures for their production

According to JP-A-45-28637 foams based on sodium aluminate are known. However, these foams are neither water- nor dimensionally stable.

Known inorganic foams, such as foam concrete, which are water- and dimensionally stable, have densities that are at least> 0.5 g / cm ³ .

Organic-based foams such as polystyrene or polyurethane are not suitable for use at higher temperatures, since they are either directly combustible or develop vapors which are harmful to health under the influence of heat.

The invention relates to stable foams based on aluminum oxide with a density of less than or equal to 0.3 g / cm ³ under the action of water.

Stable under the influence of water in the sense of the invention means that the foam has no visible change after exposure to water for 30 minutes (compare also in the examples under General). The foams according to the invention are heat-stable up to 1100 ° C., water-stable, dimensionally stable, mechanically processable and non-combustible.

Furthermore, neither harmful nor environmentally harmful substances are released during production.

The foams according to the invention preferably have a density in the range from 0.01 to 0.2 g / cm ³ .

The invention further relates to foams based on aluminum oxide which can be prepared from mixtures comprising A: substance of the general formula

MχA1 ⁰ _l 5 ₊₀ , 5x ^* YH2 °, where M means sodium or potassium, preferably sodium, x within the limits 0.5 to 3.0, preferably 0.7-1.5, and y are within the limits of 1.5 to 35.0, preferably 1.5 to 7.5,

B: 2 to 100% by weight (based on the amount of A used), preferably 4-15% by weight, of pyrogenic silica with a BET surface area of preferably 50 to 400 m ² / g,

C: 0 to 100% by weight (based on the amount of A used), preferably 0-10% by weight, of additives.

Substances of the general formula where M means sodium or potassium, preferably sodium, x within the limits 0.5 to 3.0, preferably 0.7-1.5, and y within the limits 1.5 to 35.0, preferably 1.5-7.5, can be obtained by mixing at least one compound of the general formulas

M ₂ 0, MOH, M ₂ C0 ₃ or MHC0 ₃ , where M means sodium or potassium, preferably sodium, with at least one compound of the formulas

AI (OH) ₃ , a- or -AI ₂ O ₃ and optionally water, where appropriate heating to temperatures of 20 to 110 ° C. for 2 to 24 hours.

KOH, NaOH and Na2CO ₃ are preferably used.

The components mentioned are depending on the to be achieved

Parameters x and y used in the required proportions.

Commercially available alkali aluminates, especially sodium aluminates, of the general formula can also be used

M A1 ⁰ 1/5 _{+ 0} , 5 ^* yH2 ^θ / are used, where x and y have the meaning given above.

Compounds selected from the groups of metal oxides, metal nitrides, metal silicates, carbonates, in particular metal carbonates, hydrogen carbonates, in particular metal hydrogen carbonates, silicones and / or organic substances, are preferably used as additives C. Preferred examples of such compounds are SiO 2, SnO 2, I2O ₃ , MgO, CaO, TiO 2, r O 2 _/ Fe 2 O ₃ , FeTi O ₃ , ZrSi O 4 and other silicates, ZnO, CuO, B2O ₃ , (NH) 2 CO ₃ , Na 2 CO ₃ , NaH CO ₃ , K2CO ₃ , MgC0 ₃ , CaC0 ₃ , oxalates, formates, wood flour, cellulose, cotton, sugar as well as silicone oils, paraffin oils, petrol and alcohols.

The additives can be suspended or dissolved as a powder or in a solvent, preferably water, if necessary, together with component B during the preparation of component A, to give the mixtures used according to the invention. The foaming is preferably carried out by heating to 200 to 1200 ° C, in particular 300 to 800 ° C, at heating rates of at least 8 ° C / min, in particular 10 - 200 ° C / min and at the pressure of the surrounding atmosphere, ie 1020 hPa or un ¬ approximately 1020 hPa, the mixtures optionally being presented in forms which can be of any geometric shape. However, higher or lower pressures can be used if necessary. In addition to conventional heating and contact with a hot object with sufficient heat capacity, for example metal plates or ceramic plates, the energy can also be supplied by means of microwaves or thermal radiation.

A further embodiment of the invention are mixtures for

Production of foams based on aluminum oxide

A: Substance of the general formula ^M χAlo _{1 5+} o _f 5 _X -yH ₂ o, where M means sodium or potassium, preferably sodium, x within the limits 0.5 to 3.0, preferably 0.7-1 , 5, and y are within the limits of 1.5 to 35.0, preferably 1.5 to 7.5,

B: 2 to 100% by weight (based on the amount of A used), preferably 4 to 15% by weight, of pyrogenically produced silica with a BET surface area of preferably 50 to 400 m ² / g,

C: 0 to 100% by weight (based on the amount of A used), preferably 0-10% by weight of additives.

They can be obtained by mixing components A, B and C in the proportions indicated. A further embodiment of the invention are mats or sanitary napkins for producing foams based on aluminum oxide, which can be produced from a carrier material and mixtures comprising A: substance of the general formula

Mχ ^Alo l, 5 + 0.5χ-Y ^H 2θ, where M means sodium or potassium, preferably sodium, x within the limits 0.5 to 3.0, preferably 0.7-1.5, and y within the limits are from 1.5 to 35.0, preferably 1.5 to 7.5,

The mixtures are preferably bonded to the carrier material by impregnation or application. The application can take place continuously or discontinuously, mechanically, mechanically or by spraying. It is then dried at temperatures of preferably 20 to 120 ° C. Nonwovens or woven fabrics made of inorganic and / or organic fibers, e.g. Glass fiber fleece and glass fiber fabrics or from organic materials such as cotton, linen, cellulose and synthetic fibers are used. Nonwovens and fabrics made from mixtures of inorganic and organic fibers as well as absorbent materials such as paper and thin cardboard are also possible. The carrier materials preferably have a thickness of 0.1 to 3 mm, in particular 0.2 to 0.6 mm.

Glass fiber mats and gauze bandages stabilized with starch are used in particular. Another embodiment of the invention comprises plastic compositions for the production of foams based on aluminum oxide which can be prepared by aging mixtures

A: Substance of the general formula MχAlO 1/5 _{+ 0} , 5χ-γH ₂ θ, where M means sodium or potassium, preferably sodium, x within the limits 0.5 to 3.0, preferably 0.7-1, 5 and y are within the limits of 1.5 to 35.0, preferably 1.5 to 7.5, B: 2 to 100% by weight (based on the amount of A used), preferably 4-15 % By weight, fumed silica with a BET surface area of preferably 50 to 400 m ² / g, C: 0 to 100% by weight (based on the amount of A used), preferably 0-10% by weight of additives.

Shaped parts such as skins or foils are preferably formed from these plastic materials, which can then be converted into molded articles consisting of foams based on aluminum oxide. Release agents can be used to prevent sticking during shaping.

The aging of the liquid base mixture is preferably carried out by storing the substance in an open or closed vessel, depending on the temperature, preferably from 0 to 80 ° C. for 1 to 7 days. At a temperature of 20 ° C, a duration of 7 days and at a temperature of 50 ° C, a duration of 3 days has proven itself. In particular, the aging is carried out at the temperature of the surrounding atmosphere at about 20 to 25 ° C. for a period of 5 to 7 days. A further embodiment of the invention are solid compositions for the production of foams based on aluminum oxide which can be prepared by drying mixtures comprising A: substance of the general formula

^M x ^Alo l, 5 + 0.5χ-Y ^H 2 °, where M means sodium or potassium, preferably sodium, x within the limits 0.5 to 3.0, preferably 0.7-1.5, and y are within the limits of 1.5 to 35.0, preferably 1.5 to 7.5,

After drying, which can be carried out, for example, by freeze drying, spray drying or by air drying, if appropriate with heating to temperatures in the range from 20 to 110 ° C., the masses obtained are comminuted into powders if necessary.

Solid compositions for the production of foams based on aluminum oxide are also obtained from mixtures comprising A: mixture consisting of

0.5 to 3.0 mol of MOH and 1 mol of AI (OH) ₃ or 0.5 mol to 3.0 mol of M ₂ CO ₃ or 1.0 mol to 6.0 mol of MHCO ₃ and 1 mol of AI2O ₃ , where M means sodium or potassium, preferably sodium, B: 2 to 100% by weight (based on the amount of A used), preferably 4 to 15% by weight, of pyrogenic silica with a BET surface area of preferably 50 to 400 m ² / g and C: 0 to 100% by weight (based on the amount of A used), preferably 0-10% by weight of additives.

When producing the mixture consisting of MOH and Al (OH) ₃ , the temperature should not be greater than 200 ° C., in particular ^* within the range from 5 to 30 ° C. In the preparation of the mixture consisting of M2CO ₃ or MHCO ₃ and Al ₂ O ₃ , temperatures of 700 to 1200 ° C. and reaction times of 2 to 24 hours are preferably used.

The solid masses which can be produced in this way are preferably used for the production of foamable molded parts such as sheets, in particular the solid masses produced by drying being used. The dry powder is shaped into foamable molded parts such as sheets by pressing at temperatures up to 150 ° C.

Foams based on aluminum oxide are used in particular as sound insulation, thermal insulation, sealing compound, non-combustible packaging material and / or insulating material.

Examples:

Generally

Unless otherwise stated, for the foaming tests, approx. 10 g of the corresponding foam base substance were placed in a preparation glass (capacity 50 ml, length 10 cm, diameter 2.5 cm) and, at the specified temperature, open for 15 minutes in an electric glass Oven, a vacuum drying cabinet (pressure 73 mbar) or in a microwave oven (700 W power). To determine the water solubility, foam samples were placed in a dist. Given water filled beaker. A foam that shows no visible changes after 30 minutes is said to be water-resistant.

example 1

3.68 kg (92 mol) of solid NaOH (99%) in 3.6 kg (200 mol) of distilled water are placed in a 20 l round-bottom flask with protective gas feed, reflux condenser and mechanical stirring. Water dissolved. 6.24 kg (80 mol) of Al (OH) ₃ (powdered, pure) are added to the resulting hot solution with vigorous stirring and the contents of the flask are heated to 80-90 ° C. After about 5 hours, a clear, slightly beige colored solution was formed. After cooling, the solution is kept in a closed container.

Foaming tests:

Electric oven 300 ° C: white large-pored foam,

Density 0.4 g / cm ³ 600 ° C: white large-pored foam,

Density 0.2 g / cm ³ vacuum drying cabinet 350 ° C: white large-pored foam,

Density 0.1 g / cm ³ microwave: white large-pored foam,

Density 0.1 g / cm ³ All foams are readily water-soluble.

Example 2

100 g of the substance obtained in Example 1 are mixed with 10 g of pyrogenic silica (BET 200 m ² / g) and ren homogeneously mixed. Foaming tests are carried out with the viscous liquid obtained.

Foaming tests:

Electric oven 300 ° C: white, fine-pored foam,

Density 0.1 g / cm ³ 600 ° C: white, fine-pored foam,

Density 0.02-0.04 g / cm ³ 700 ° C: white, fine-pored foam, density 0.02-0.04 g / cm ³ vacuum drying cabinet 350 ° C: white, large-pored foam,

Density 0.04-0.08 g / cm ³ microwave: white, large-pored foam,

Density 0.08 g / cm ³

The foams are all water resistant.

Example 3

20 g of the substance from Example 2 are placed in an Alsint dish at 1100 ° C. in the electric oven. A white, soft, water-resistant foam with a density of 0.08 g / cm ³ forms within 10 minutes.

Example 4

100 g of the substance obtained in Example 1 are mixed with 6 g of pyrogenic silica (BET 200 m ² / g) and mixed homogeneously by stirring. A foaming test is carried out in the electric oven at 600 ° C. with the viscous liquid obtained. A white, fine-pored, water-resistant foam with a density of 0.1 g / cm ^{3 is obtained} . Example 5

100 g of the substance obtained in Example 1 are mixed with 20 g of pyrogenic silica (BET 200 m ² / g) and mixed homogeneously by stirring. A foam test is carried out in the electric oven at 600 ° C. with the viscous mass obtained. A white, very fine-pored, water-resistant foam with a density of 0.08 g / cm ^{3 is obtained} .

Example 6

100 g of the substance obtained in Example 1 are mixed with 20 g of pyrogenic silica (BET 200 m ² / g) and mixed homogeneously by stirring. A further 10 g of fumed silica are then incorporated using a kneader. A foam test is carried out in an electric oven at 600 ° C. with the viscous mass obtained. A white, fine-pored, water-insoluble foam with a density of 0.4 g / cm ^{3 is obtained} . At 900 ° C foaming temperature, it has a density of 0.2 g / cm ³ .

Example 7

100 g of the substance obtained in Example 1 are mixed with 10 g of pyrogenic silica (BET 400 m ² / g) and mixed homogeneously by stirring. A foaming test is carried out in the electric oven at 600 ° C. with the viscous liquid obtained. A white, water-resistant, very fine-pored foam with a density of 0.035 g / cm ^{3 is obtained} . Example 8

100 g of the substance obtained in Example 1 are mixed with 10 g of pyrogenic silica (BET 50 m ² / g) and mixed homogeneously by stirring. A foaming test is carried out in the electric oven at 600 ° C. with the viscous liquid obtained. A white, fine-pored, water-resistant foam with a density of 0.06 g / cm ^{3 is obtained} .

Example 9

100 g of the substance obtained in Example 1 are each mixed with 10 g of one of the additives below and mixed homogeneously by stirring. With the viscous liquids obtained, foaming tests are carried out in an electric oven at 600 ° C. In most cases, there is only very little foaming. When B ₂ O ₃ , (NH4) ₂ CO ₃ , Al (OH) ₃ , SiO ₂ (highly disperse) or sugar are added, water-soluble foams with densities between 0.06 g / cm ³ and 0.1 g / cm ^{3 are obtained} .

Additives used:

(BET 56 m ² / g)

3 µm, 1 = 0.1-20 cm

100 g of the substance obtained in Example 1 are each mixed with 10 g of fumed silica (BET 200 m ² / g) and with 10 g of one of the additives listed in Example 9 and mixed homogeneously by stirring. With the obtained viscous masses, foaming tests are carried out in an electric oven at 600 ° C. Foaming is obtained in all cases. The density of the foams is between 0.025 g / cm ³ and 0.3 g / cm ³ . All foams are water stable. Example 11

184 g (4.6 mol) of NaOH are dissolved in 180 g (10 mol) of water in a 5 1 plastic barrel, 312 g (4 mol) of powdered Al (OH) 3 and 58 g of pyrogenic silica (BET 200 m ² / g). The barrel is closed and rolled on a roller stand for 10 hours. Foam tests are carried out with the resulting homogeneous mass. Foams are obtained which are of the same quality as those in Example 2.

Example 12

460 g (11.5 mol) of solid NaOH, 780 g (10 mol) of powdered Al (OH) ₃ , 169 g of fumed silica ( BET 200 m ² / g) and 27 g (1.5 mol) dist. Water was added and the mixture was heated to 80-90 ° C. for 5 hours with vigorous stirring. Then allowed to cool. A foaming test is carried out in an electric oven at 600 ° C. with the resulting mixture. A fine-pored, water-resistant foam with a density of 0.07 g / cm ^{3 is obtained} .

Example 13

Analogously to Example 12, 460 g (11.5 mol) of NaOH, 780 g (10 mol) of Al (OH) ₃ , 169 g of pyrogenic silica (BET 200 m ² / g) and 630 g (35 mol) of dist. Set water and a foaming test in an electric oven at 600 ° C with the resulting mixture. A large-pore, water-resistant foam with a density of 0.09 g / cm ^{3 is obtained} . Example 14

Analogously to Example 12 28.1 g (0.5 mol) of KOH, 26 g (0.65 mol) of NaOH, 78 g (l mol) of Al (OH) _3, 16.9 g of pyrogenic silicic selsäure (BET 200 m ² / g) and 45 g (2.5 mol) dist. Implemented water. The foaming test at 600 ° C in an electric oven produces a white, hard, fine-pored, water-resistant foam with a density of 0.2 g / cm ³ .

Example 15

204 g (2 mol) of anhydrous Al2O ₃ (powder, 98.5% purity) and 212 g (2 mol) of anhydrous Na ₂ CO ₃ (powder, 99.5% purity) are homogenized in a laboratory mill. The mixture obtained is loosely filled into an Alsint tube (120 cm long, inner diameter 5.4 cm). In order to prevent the powder from falling out, the ends of the tube are loosely closed with Kerlan fiber (aluminum silicate fiber). The tube is inserted into a tube furnace and heated while rotating according to a specific temperature program (temperature program: heating from 20 ° C to 400 ° C within 2 h, holding at 400 ° C for 2 h, then heating to 800 ° C within 2 h , keep at this temperature for 1.5 h, continue to heat up to 1100 ° C within 1.5 h, keep at this temperature for 1.5 h, then switch off the heating and allow to cool to 20 ° C). While the temperature program is running, the pipe N2 is blown to discharge the resulting CO 2 gas. 164 g of this powdery substance, which only contains traces of carbonate, are mixed with 180 g of dist. Water and 24.4 g of pyrogenic silica (BET 200 m ² / g) were added and the mixture was stirred vigorously at 20 ° C. for 3 h. Here, some solution occurs, the rest is suspended. Foaming tests are carried out analogously to Example 2 with the mixture obtained. In all conditions, foams are obtained which have almost the same properties as those in Example 2 exhibit.

Example 16

In a 500 ml round-bottomed flask with protective gas feed, reflux condenser and mechanical stirring, 100 g of sodium aluminate (84.4% content, Na ₂ θ / Al ₂ θ ₃ = 1.32, 15.6% molar ratio) are used as protective gas. Water), 11 g of powdered Al (OH) ₃ and 67 ml of water combined and heated to 90 ° C. with stirring for 3 h. The mixture is then left to cool and a test of the resulting mixture is carried out in an electric oven at 600 ° C. The result is a very soft, flaky, water-soluble foam.

Example 17

100 g of the substance prepared according to Example 16 are mixed with 10 g of pyrogenic silica (BET 200 m ² / g) and homogenized. Foam tests with this mixture analogous to Example 2 give foams under all conditions which have almost the same properties as those in Example 2.

Example 18

13.4 g (0.33 mol) of solid NaOH, 23.4 (0.3 mol) of Al (OH) ₃ powder and 3.7 g of pyrogenic silica (BET 200 m ² / g) are homogenized in a laboratory beater. Foaming tests are carried out on the resulting gray-white powder. A foaming test in an Alsint dish at 1000 ° C. in an electric oven yields a fine-pored, water-resistant foam with a density of 0.06 g / cm ³ . Example 19

A mixture prepared analogously to Example 2 with 10% pyrogenic silica (BET 200 m ² / g) is stored in the closed vessel for 1 week at 20 ° C. During this time, the mass "ages" and a tough dough (plastic mass) is created. 5.9 g of this dough are rolled out into a 0.4 mm thick sheet of size 9.2 × 6.2 cm and dried at 120 ° C. for 1 1/2 hours. The fur is placed on a 2 cm thick, 30 x 30 cm large, metal plate heated to 600 ° C and on the fur a 2 cm thick, 2.7 kg heavy metal plate, also heated to 600 ° C. The fur foams up within a minute and a 1.65 cm thick, almost rectangular foam plate measuring 9.4 cm x 6.4 cm is created. The plate has a density of 0.045 g / cm ³ and is water-stable.

Example 20

A sample of the plastic mass from Example 19 is rolled out to a 0.4 mm thick skin and then dried either at 20 ° C. or at elevated temperature (up to 120 ° C.). This creates a firm, dry plate. The plate is placed in an electric oven at 600 ° C. The plate foams within 10 minutes. An approx. 2.3 cm thick irregular foam plate is created. The foam is largely small-pored, water-resistant and has an average density of 0.03 g / cm ³ .

Example 21-

A solid, dry, non-foamed sheet from Example 20 is broken and then ground to a powder in a laboratory beater. Foaming tests are carried out with the powder. You get foams in all conditions have almost the same properties as those produced in Example 2.

Example 22

36 g of the powder prepared in Example 21 are pressed at 20 ° C. and a pressure of 248 kg / cm ² to form a round plate (thickness = 1.2 cm, φ = 6.0 cm). The plate is placed in an electric oven at 600 ° C. A white, very hard foam body with a very irregular surface is obtained, which is approximately 6.2 cm high and 7.7 cm thick. The density is 0.2 g / cm ³ . The same sheet of compressed foam base powder is foamed between two 600 ° C hot metal sheets (coating weight 8.3 kg). A white solid foam with a density of 0.25 g / cm ^{3 is obtained} . Both foams are water resistant.

Example 23

A thin gauze bandage (cotton) is impregnated with the mixture obtained in Example 2 and then dried in a forced-air drying cabinet for 15 minutes. A firm, almost non-sticky, flexible bandage is obtained. If this bandage is placed in the electric oven at 500 ° C, it will foam within 10 minutes. If the bandage is placed in several layers around a metal tube and this is then placed in the electric furnace at 500 ° C., foaming also occurs and the metal tube is completely foamed where it was surrounded by the bandage. If the foamed metal pipe is placed in a 750 ° C oven, the gauze bandage is burned without destroying the foam structure. The foam obtained is water-resistant. Example 24

A plastic mass produced analogously to Example 19 is heated to 100 ° C. and stirred. Under these conditions, the mass becomes liquid again. The liquid mass is applied thinly (0.5 mm) to a 0.3 mm thick glass fiber mat either using a spatula or a roller applicator. The mat is then dried in a forced-air drying cabinet at 100 ° C. for 15 minutes. You get a dry mat, but it is highly elastic. A 10 x 10 cm piece of this mat is placed in an electric oven. An almost rectangular 2.4 cm thick, foamed, water-resistant plate with an average density of 0.04 g / cm ^{3 is obtained} .

Another sample of 10 x 10 cm of this mat is foamed analogously to Example 19 between two 600 ° C hot metal plates (print run: 28 g / cm ² ). A 1.5 cm thick, foamed, water-resistant plate made of fine-pored foam with a density of 0.07 g / cm ^{3 is obtained} .

Example 25

A sample of the plastic mass from Example 19 is at 110 ° C for 15 min. heated long. Here, the raw material liquefies. The liquid mass is poured into a round (inner diameter 18.9 cm), 600 ° C hot graphite mold and the whole thing at 600 ° C for 20 min. long put in an electric oven. Within 10 min. foams the mass. The result is a cylindrical foam body with a slightly branched foam crown. This inhomogeneous, upper part is cut off and a stable, water-resistant, fine-pored foam plate of 2 cm thickness, 18.9 cm diameter and a density of 0.06 g / cm ³ remains.

Claims

- SLD-

Claims

Under the action of water, stable foams based on aluminum oxide with a density of less than or equal to 0.3 g / cm ³ .

Foams can be produced on the basis of aluminum oxide

Mixtures containing

A: Substance of the general formula where M means sodium or potassium, x within the

Limits 0.5 to 3.0 and y within the limits of

1.5 to 35.0, B: 2 to 100% by weight (based on the amount of A used) pyrogenic silica, C: 0 to 100% by weight (based on the amount of A used)

Additives.

Mixture for the production of foams based on

Containing alumina

A: Substance of the general formula

MχAl0 _{1 5 + G} , 5x ^* Y ^H 2θ, where M means sodium or potassium, x within the

Limits 0.5 to 3.0 and y within the limits of

Additives.

Bodies containing foams based on aluminum oxide which can be produced from mixtures according to claim 3. - 1 -

5. Mats or pads for the production of foams based on aluminum oxide can be produced from a support material and mixtures

A: Substance of the general formula

^MA l ° l, 5 + 0.5x * YH2θ, where M means sodium or potassium, x within the

Limits 0.5 to 3.0 and y within the limits of

Additives.

6. mats or sanitary napkins according to claim 5, characterized gekennzeich¬ net that the carrier material consists of a nonwoven or woven fabric made of inorganic and / or organic fibers, paper or cardboard.

7. body containing foams based on aluminum oxide producible from mats or pads according to claim 5 or 6.

8. Containing plastic compositions for the production of foams based on aluminum oxide by aging of mixtures

Limits 0.5 to 3.0 and y within the limits of

Additives. 9. body containing foams based on aluminum oxide producible from compositions according to claim 8

10. Solid masses for the production of foams based on aluminum oxide can be prepared by drying mixtures containing

Limits 0.5 to 3.0 and y within the limits of

Additives.

11. Solid masses for the production of foams based on aluminum oxide can be produced from mixtures comprising A: mixture consisting of

0.5 to 3.0 mol of MOH and 1 mol of Al (OH) ₃ or 0.5 mol to 3.0 mol of M ₂ CO ₃ or 1.0 mol to 6.0 mol of MHCO3 and 1 mol of Al ₂ θ ₃ , where M is sodium or potassium,

B: 2 to 100% by weight (based on the amount of A used) of pyrogenic silica,

C: 0 to 100% by weight (based on the amount of A used) of additives.

12. body containing foams based on aluminum oxide producible from compositions according to claim 10 or 11

13. Use of foams based on aluminum oxide as sound insulation, thermal insulation, sealing compound, packaging material and / or insulating material.