CH683425A5 - Silicate foam moulding used as noise protecting element - comprises first layer of larger open cells and second layer of smaller closed cells facing the first layer - Google Patents

Abstract

Silicate foam moulding comprises a 1st surface of larger open cells and a 2nd surface, of smaller closed cells, lying opposite the 1st surface. The moulding has decreasing cell size with increasing closed cell structure from the 1st to 2nd surface. Prodn. of the moulding is also claimed. The moulding is produced by mixing a liquid/pasty compsn. contg. liquid alkali metal silicate, inorganic fillers and azodicarboxylic diamide, as reactive hardener, with a water-based foam, moulding the foam mixt., and hardening at elevated temp. (at least 50 deg.C) below the decomposition temp. of the hardener. Organic fillers, pref. powdered plastic waste, are pref. additionally used. USE/ADVANTAGE - The moulding can be used as a noise protecting element and in self-supported vertical appts.. The moulding has good noise absorption and improved mechanical properties.

Description

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description

The invention relates to a silicate-based foam body according to the preamble of claim 1 and a method for its production.

DE-C 3 923 284 discloses an inorganic foam body made of a foamed and hardened mixture of alkali water glass and fillers. This foam body is produced by mixing the starting materials with a chemical blowing agent, for example with azodicar-bondiamide, and heating the mixture to a temperature in the region of the decomposition temperature of the blowing agent. The foam bodies obtained have an irregular structure in which open and closed cells and cells of different sizes are irregularly distributed.

The use of azodicarbondiamide as a blowing agent for foaming ceramic compositions is also described in DE-A 1 796 260. Here, too, the composition to be foamed is heated to a temperature in the range of the decomposition temperature of the chemical blowing agent. The decomposition temperature is given as 200 ° C for azodicarbondiamide. The described procedure leads to a foam with an irregular cell structure. The production is also problematic because the relatively high temperatures make the necessary control of the foaming process difficult.

The known foam bodies have an irregular cell structure and are unsatisfactory in terms of their sound absorption properties.

The aim of the present invention is therefore to propose a foam body based on alkali silicate which does not have the disadvantages listed above and in particular has good sound absorption and improved mechanical properties.

This aim is achieved by the features of the characterizing part of claims 1 and 7, respectively. Particularly preferred embodiments of the invention form the subject matter of claims 2 to 6 and 8 to 15.

The foam bodies according to the invention have, on their first surface with the open, larger cells, excellent sound absorption in the area relevant for sound insulation. The second surface with the smaller closed cells and the adjoining zone with a similar cell structure have a mechanical strength that allows the foam bodies according to the invention to be arranged in a self-supporting, preferably vertical, arrangement. Fasteners such as screws, nails, etc. can also be attached to this second, denser side of the foam body.

The internal structure of the foam body according to the invention is characterized by a regular structure. It is possible to distinguish parallel zones in the foam body that continuously differ from the first surface to the second changing cell structure. With the smaller cells and the presence of more closed cells over the thickness of the foam body according to the invention, its compressive strength increases continuously from the first to the second surface. The structure and thickness of the individual zones can be controlled by the process parameters during manufacture. The suitable parameters can be determined by preliminary tests.

In the production of the foam body according to the invention, on the one hand a mixture of the starting materials or constituents and on the other hand, separated from the constituents, a water-based foam is produced by mechanical ventilation. The mixture of the starting materials and the mechanically generated foam are mixed with one another so that the material forming the foam body is in foam form even before the curing reaction begins. The foam-like mixture is filled into molds, whereupon the pre-formed foam is only hardened by increasing the temperature. Since the foam is not only formed during the curing reaction, the uniform temperature distribution within the mold is of no importance with regard to the internal structure of the resulting foam body. Therefore, according to the invention, relatively large shapes can be used and correspondingly large foam bodies with a regular internal structure can be produced.

An optionally modified liquid alkali silicate, for example water glass, is used as silicate in an amount of advantageously 30 to 35% by weight. Inorganic fillers, preferably a particle size corresponding to the sieve fraction below 400 n, are mixed into the water glass. Suitable inorganic fillers are those of the ceramic industry, such as quartz powder, kaolin, wollastonit, talc, aluminum oxide and aluminum hydroxide. Part of the inorganic filler can also be cement or powdered brick derivatives. The proportion of inorganic fillers is advantageously 40 to 50% by weight. Up to 15% by weight of the total filler amount of organic fillers, such as powdered plastic waste, can be mixed with the inorganic filler.

Organic or inorganic fibers such as glass or metal fibers are suitable as reinforcing fibers. They are advantageously used in an amount of 0.3 to 1% by weight.

The amount of azodicarbondiamide used as reactive hardener is advantageously 2.5 to 4% by weight.

The one for transferring the basic mixture, i.e. the mixture of starting materials, foam used in the foam mold is created by intimate mechanical ventilation of a system of 2

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CH 683 425 A5

for example water / epoxy resin, water / polyvinyl chloride, water / styrene-butadiene, water / artificial proteins (peptones and / or peptides), water / detergents or water / wetting agents. A foam with a maximum weight of 100 g is preferably used. Based on the basic mixture of the components, 5 to 20% by weight of the mechanically produced foam is generally used.

The row structure of the foam bodies according to the invention is shown schematically in the single figure.

The foam body 1 has a first upper surface 2 with large open cells 3 and a second lower surface 4 with small closed cells 5. Zones 6, 7, 8 are located between the two areas 2, 4, the cell structure of which is increasingly open from bottom to top and has increasingly larger cells in the same direction.

The invention is further illustrated by the following examples.

example 1

8700 g of quartz powder (43.5% by weight) are mixed with 800 g of azodicarbondiamide (4% by weight). 6800 g of sodium silicate (34% by weight) are then added. 3600 g (18% by weight) of a foam of water / epoxy resin produced by mechanical ventilation is mixed into the resulting pasty yellow mass with stirring. Finally, 100 g (0.5% by weight) of glass fiber chips are slowly added with stirring. The foam-like mass obtained is placed in a mold provided with a release agent. Curing takes place in an oven for 3.5 hours at 90 to 110 ° C. Ammonia is generated during the hardening reaction. After curing, the foam body is dried at 110 to 120 ° C for 1.5 hours and then solidified at 170 to 180 ° C for 2 hours. Before cutting, the foam bodies are cooled to below 100 ° C under controlled conditions.

After removing any unwanted crust, the foam body of 540 x 540 x (80-100) mm obtained has the following properties:

density

270-320 kg / m3

Water content

4.5-5.5% by weight

Thermal conductivity x

0.0624 W / m • K

Sound absorption level a

90% between 400 and 2000 Hertz

Compressive strength

0.13+ 0.03 MPa (Zone A)

0.36 ± 0.04 MPa (Zone B)

0.66 ± 0.1 MPa (Zone C)

Frost resistance

4-5 12h cycles

Weather resistance for a few days

Brand code

6q. (according to VKF guidelines)

Zones A through C correspond to the top, middle and bottom in the figure. The sound absorption coefficient a was measured according to DIN standard 52215, the thermal conductivity according to X ISO-DIS 8301, the pressure resistance according to SIA standard 215 1978 and the fire index (BKZ) according to SIA standard 183/2. To determine the frost resistance, the foam body was subjected to a test with 2 daily cycles: 1) immersed in water for 8 hours at -18 ° C, 45 minutes at room temperature and 2) in water for 14.5 hours at -18 ° C, 45 minutes immersed at room temperature.

Example 2

A water-repellent foam is produced according to the procedure of Example 1 with the following composition:

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CH 683 425 A5

5920 g

Quartz flour

37%

640 g

Azodicarbondiamide

4%

5890 g

Na silicate

36.5%

800 g

Water repellent additive

5%

2720 g

Mechanical foam

17%

80 g

Glass fiber schnitzel

0.5%

A silicone was used as a water repellent additive. Known aluminum compounds such as alcoholates, carboxylates and tristearates are also suitable for this purpose.

The foam body obtained had the following properties:

Density 300-400 kg / m3

Frost resistance 100 2-day cycles as described on page 6 The frost resistance was measured as indicated in Example 1.

Example 3

The foam body obtained by the process according to Example 1 was subjected to a surface treatment. It was sprayed with a water-repellent preparation. As the following test results show, the frost resistance of the foam body according to the invention was greatly increased as a result:

treatment

Frost resistance none

4 2-day cycles as described on page 6 with silicones

60

with siloxanes

100

with epoxy resins

»100

with acrylic resins

»100

The frost resistance was measured as indicated in Example 1.

Example 4

To improve the compressive strength and the hardness of the foam bodies according to the invention, they were impregnated with a preparation of 2000 g of water and 1000 g of a potassium silicate modified with an elastomer and dried in a forced air oven at 80 to 90 ° C. for 2 to 4 hours. The treatment was then repeated with a more concentrated solution of 1500 g water and 1500 g modified potassium silicate. The mixture was then dried for 2 to 4 hours at 80 to 90 ° C. and 2 to 4 hours at 105 to 115 ° C.

This treatment was also carried out with an epoxy resin solution and an aqueous polyvinyl chloride emulsion. The foam bodies obtained have a greatly improved compressive strength.

Compressive strength (MPa)

Treatment Zone A Zone B Zone C

no

0.13

+

0.03

0.36 ± 0.04

0.66

+

0.1

K-silicate

0.63

+

0.16

1.35 ± 0.26

1.68

+

0.18

Epoxy resin

0.61

+

0.15

0.79

±

0.21

aqueous PVC emulsion

0.25

+

0.03

0.54

±

0.12

The compressive strength was measured as indicated in Example 1.

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CH 683 425 A5

Example 5

In a combined treatment, foam bodies obtained according to Examples 1 and 2 were mechanically reinforced according to Example 4. That according to Example 1 was then subjected to a water-repellent treatment according to Example 3.

Claims (14)

Claims 1. Silicate-based foam body, characterized in that it has a first surface with larger open cells and a second surface opposite the first surface with smaller closed cells and a decreasing cell size with an increasingly closed cell structure from the first to the second surface via the foam body. 2. Foam body according to claim 1, characterized in that it has parallel zones with decreasing cell size from zone to zone and increasingly closed cell structure between the first and the second surface. 3. Foam body according to one of the preceding claims, characterized in that it has a density of less than 800 kg / m3. 4. Foam body according to one of the preceding claims, characterized in that it has a water-repellent finish. 5. Foam body according to one of the preceding claims, characterized in that it has a pressure-increasing equipment. 6. A process for producing a foam body according to any one of claims 1 to 5, characterized in that a liquid to pasty mass containing a liquid alkali metal silicate, inorganic fillers and as reactive hardener azodicarbondiamide is mixed with a water-based foam, the foam-like mixture in a mold introduces and cures at an elevated temperature, but at least 50 ° C, below the decomposition temperature of the reactive hardener. 7. The method according to claim 6, characterized in that drying the cured foam at an elevated temperature. 8. The method according to claims 6 or 7, characterized in that the dried foam is solidified with a further increase in temperature. 9. The method according to any one of claims 6 to 8, characterized in that reinforcing fibers are added to the foam-shaped mixture before curing. 10. The method according to any one of claims 6 to 9, characterized in that one additionally uses organic fillers, preferably powdered plastic waste. 11. The method according to any one of claims 6 to 10, characterized in that the pasty mass is admixed with a water-repellent component or the foam body obtained is treated with a water-repellent preparation. 12. The method according to any one of claims 6 to 11, characterized in that the foam body obtained is treated with a preparation which increases the compressive strength. 13. Use of the foam body of claims 1 to 5 as noise protection elements. 14. Use of the foam body according to claim 13 in a self-supporting vertical arrangement. 5