DE2750839A1 - INORGANIC FOAM - Google Patents

Description

275Ü339

T.EDTKE - BUHUNG - K.NNE - GROUP

Dipl.-Chem. G. Buehling

- Dipl.-Ing. R. Kinne

Dipl.-Ing. P. Grape

Bavariaring 4, P.O. Box 20 2403 8000 Munich 2

Tel .: (0 89) 53 96 53 Telex: 5-24845 tipat cable: Germaniapatent Munich

November 14, 1977

B 8532

ICI case Q.29173

Imperial Chemical Industries Limited London, UK

Inorganic foam

The invention relates to inorganic foams, in particular to solid foams made from minerals.

Vermiculite is a phyllosilicate mineral with a Layer structure. Vermiculite can be caused to swell by the action of aqueous salts, and then the Structure of the vermiculite, i.e. the swollen vermiculite can be broken down by mechanical action split into extremely thin lamellae. Other phyllosilicate minerals, e.g. hydrobiotites or chlorite vermiculites, also contain a substantial proportion of vermiculite layers and can also be in the same or in

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be made to swell in a similar manner. These minerals, which contain vermiculite layers, also lead to thin lamellae and are included in the minerals that can be used in the present invention. For the production of the inorganic foam according to the invention, the use of the vermiculite lamellae is preferred.

The Amneläerin patent application 14764/76, which is pending at the same time, uses a solid, inorganic foam described, which has a cell structure made up of the mineral vermiculite. This foam was made from a aqueous suspension of small vermiculite lamellae produced by swelling and splitting of the mineral in the presence was obtained from water. According to the invention has now surprisingly found that it is easier to produce a solid, inorganic foam from these vermiculite suspensions by applying electromagnetic energy to the suspension.

In the method according to the invention for producing a solid foam from the mineral vermiculite applies electromagnetic energy with a frequency between 1o4 Hz and 10 Hz through an aqueous suspension of vermiculite lamellae through, wherein the suspension is preferably held by a vapor-permeable pad. Included bubbles of water vapor are formed by the absorption of electromagnetic energy in the suspension Cause the suspension to swell, forming a foam from which further water vapor is removed until a solid foam forms.

over the entire frequency range mentioned above the electromagnetic energy is absorbed preferentially by the water of the aqueous suspension, causing it to rapid heating of the water, resulting in

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rapid formation of water vapor and swelling of the Suspension leads as long as it is still mobile. Compared to other processes where the water is in the Suspension is heated in order to provide steam for expanding the foam is produced according to the invention Process a more uniform product. If the electromagnetic heating is continued, the foam will under-dry Formation of a solid product, which is a solid foam made of vermiculite lamellas, which is directly from an aqueous suspension or paste of the vermiculite lamellae was produced by a single drying process. If Desirably, the puffing effect can be achieved by the absorption of the applied energy inside the suspension formed water vapor can be supported by stirring the suspension before heating, e.g. by means of a mechanical Whorls or percussion. As soon as a self-supporting foam has formed, the electromagnetic heating can stop and, if desired, the water vapor can be removed by using other heating methods, for example using away from warm air. Alternatively, warm air can be used to preheat the vermiculite suspension, before electromagnetic heating.

As the foam is dried, a large volume of water vapor is created and the suspension becomes preferred held by a vapor-permeable pad. The base can be a porous material such as a sintered structure made of ceramic or plastic or a woven structure made of fibers or wire. The pad is preferably flexible and is suitably in the form of a trough or ribbon and can, for example, enter the electromagnetic field and moved out of the field. A layer of woven fibers, e.g. made of textile fibers, including nylon, rayon, cotton wool, Linen, jute and especially glass or polyester

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Fibers are suitable, preferred. Paper can be used as a permeable lining material along with a coarse mesh or Screen cloth can be used as a supporting base.

When the suspension of the mineral is heated, the foam swells and can advantageously be placed under the Weight of a layer of a permeable material as used for the underlay or, alternatively, under the weight of a layer of paper or some other thin, porous material that can be pulled down, when the foam is dry, allow it to swell. If for the dry foam obtained as the end product If a predetermined depth or thickness is required, provision can be made to remove the foam while it is drying only can swell to a predetermined extent. For this purpose one can put a Attach a hard or semi-hard, permeable membrane to limit the swelling of the foam when the suspension is heated and suppress. A foam product is then obtained which is permeable in a composite structure between Layers located that can be removed when the foam is dry or, alternatively, that are in place can be left to give the foam product a to give increased strength.

For the energy that is used, the frequency range from 10 Hz to 10 Hz is preferred, including this range most of the so-called "microwave" and "radio frequency" range of the electromagnetic spectrum.

Vermiculite is a dielectric material and shows

beyond that defined for the application according to the invention Frequency range very small dielectric losses, while water over most of this range considerable Shows losses and absorbs much more energy than the vermiculite. The electromagnetic energy can be used in a known manner

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are used, in particular by means of electrical generators, generating high voltage alternating electromagnetic fields, these generators are suitable in known heating devices, for example in a microwave oven or in a dielectric or radio frequency heater from which currently many versions in the trade are built-in.

The suspension of the mineral may suitably contain from 10% to 70% by weight vermiculite solids, and In this way the viscosity of the suspensions can range from a free-flowing liquid to a viscous pulp or even a thick paste.

The energy output that is required to evaporate the water from the vermiculite suspension depends firstly on the mass of the water present and, secondly, on the required rate of evaporation. It may be desired be to vary the evaporation rate over a small range to get the water as fast as possible to evaporate, insofar as this results in the formation of a uniform Can agree foam, the evaporation time is suitably between less than a minute and 15 minutes. The mass of water in the laboratory can vary between a few grams and about 1 kg, while at hundreds of kilograms may be enforced in a process on an industrial scale.

It has been found that, for a small scale operation, between 0.1 kW and 20 kW is suitably for a Operation on a larger scale, however, requires 100 kW or more of electrical power.

The term "solid inorganic foam" used in the present specification means one 2-phase dispersion of a gas in a solid, the solid phase being an essentially coherent, inorganic Cell structure is. Small amounts of

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organic materials may be present, which have been either added intentionally or inadvertently present, however, the organic material is not an essential part of the cell structure, although it's own transactions of the cell structure can be modified in a useful manner. In the removal of the water from an aqueous dispersion of vermiculite lamellae the lamellae come together to form a coherent layer. The cell walls of the cell structure of the foam according to the invention accordingly obtain their mechanical strength mainly from the self-adhesion of the flakes when the water is removed. Depending on the final equilibrium water content, the solid foam structure can deform or bend under moderate stress, but does not normally crumble.

During the procedure in which the foam is inflated and then the water vapor is removed from the foam is changed, the foam, which is first fully flexible and then has a self-supporting shape, in which the cell structure does not collapse even if the heating is stopped or interrupted.

The cellular vermiculite is considered to be heat-resistant

and heat insulating material suitable as a foam filling

for troughs and cavities, or for coating the outside of materials such as wood or Steel structures can be used, in both cases the vermiculite foam as a fire protection layer works. A composite structure provided according to the invention with vermiculite foam inside, which if necessary .with Layers of wood veneer, paper, asbestos, mica or plastic or is connected to a vermiculite layer, forms suitable decorative panels or panels for building purposes. One can use suitable, fire-resistant and / or sound-absorbing

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Manufacture panels and panels for the construction industry, if the vermiculite foam is placed between plasterboard or layers of thermosetting synthetic resin, e.g. melamine synthetic resin, brings into a composite structure. For some applications it may be necessary to use the vermiculite foam waterproofing treatment such as that disclosed in our co-pending UK patent application 14551/77 of the applicant is described.

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

example 1

A sample of vermiculite mineral was obtained after treatment with an aqueous solution of n-butylammonium chloride in Brought water to the source. A suspension of vermiculite lamellae was obtained by splitting in a Greaves HS mixer, obtained by evaporation to form a slurry containing between 15 wt% and 25 wt% solids, was concentrated.

Various examples of this pulp were made from glass-framed troughs (36.3 cm by 12.7 cm) with bottoms 5 brought a polyester braid, previously with a silicone mold release agent and which had been sprayed in a microwave oven, through glass slides in a Approximately 1.3 cm from the bottom of the oven. held, found. When the oven was used a Rotax model MH / 1500/50 that had an output of 0.5 kW to 1.5 kW at 2450 MHz. The pulps became even heated, and a foam quickly began to swell. A boundary was placed above the troughs, see above that only a predetermined depth of foam could form against another braid. The heating was continued for about 7 minutes, and after that time

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the three of them had turned into dry, firm foam.

Various vermiculite pulps were heated to form a foam:

1. Slurry with a solids content of 17.8% by weight without surfactant.

, Q 2nd slurry with a solids content of 23.6% by weight without surfactant.

3. Slurry with a solids content of 22% by weight without surface-active agent, which, however, before heating by whipping in a kitchen mixer (Kenwood Chef) had been aerated.

4. Slurry with a total solids content

24% by weight, which is a surfactant (fluorocarbon, 0.25% by weight) and that previously in a kitchen mixer (Kenwood Chef) by whipping with air had been transferred.

In each case, the result was a firm foam with small bubbles, which the strength between the individual vermiculite lamellas acting, mutual attraction was given.

Some foams have been made by a process in which the top and bottom layers are made of polyester braid was lined with a layer of vermiculite paper. The foam was made between the layers Vermiculite paper and the product that was obtained was a sheet of vermiculite foam made with smooth, non-foamed vermiculite surfaces.

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Example 2

A method similar to that in Example 1 was followed by aqueous pulps of vermiculite lamellae in made in the form of thick pastes and placed on troughs with a perforated bottom. The troughs were about 1.3 cm from the bottom of a radio frequency heating furnace with an output of 10 kW and a frequency of 80 MHz held. Various slurries with a solids content between 10% by weight and 25% by weight were foamed, thereby obtained the best results were obtained with slurries which had a solids content between 15% by weight and 20% by weight. It was found that it is necessary to limit the rise of the foam in order to prevent the formation of crevices or cracks on the upper surface of the foam. It was found that e.g.

a layer of porous paper is very effective for this purpose. You could put the paper on under your own weight leave the foam behind, or you could attach the paper to a solid overhead surface that acted to make the The thickness of the foam produced was limited. Samples of a free-rising foam (22.9 cm χ 22.9 cm 1.3 cm) with a final density of 0.1 g / ml after 15 minutes of heating from a slurry with a solids content of 17% and containing 0.2% of polypropylene glycol "5 methyl ethers. Smaller samples of foam were obtained from correspondingly smaller volumes of the same pulp after only 2 minutes of heating in the same oven. Under these conditions some scorching of the samples occurred and a radio frequency heater with a lower power was used applied with better results.

Example 3

A series of pastes made from vermiculite lamellae in water, differing in their solids content, was like described in Example 1, and according to the for the

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Forms 1 and 2 in the method described in Example 1 to form foams. The density of each foam was measured, and the relationship that existed between the density and the solids content of the paste used, was observed. The results are shown in the table below:

Total solids content (in% by weight)

Foam density (g / ml)

17.5 33.0 40.0 56.0 60.0 69.0

0.15 0.40 0.46 0.80 0.94 1.12

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Claims (10)

Claims 1 · Method of making a solid foam from the mineral vermiculite, characterized in that one 4 electromagnetic energy with a frequency between 10 Hz and 10 Hz through an aqueous suspension of vermiculite lamellae through it, whereby by the absorption of the electromagnetic energy in the suspension bubbles of Water vapor are formed, which cause a swelling of the suspension with the formation of a foam, from which one further Removes water vapor until a solid foam forms. 2. The method according to claim 1, characterized in that the water vapor is further removed by the application of electromagnetic energy continues. XI / 13 809820/0985 Drndnar Bank (monks) KIo. 3 »M4 PoMSChMk (some) loo. 670-43-8 " 1 7 b υ b J υ - 2 - B 8532 3. The method according to claim 1 or 2, characterized in that the aqueous suspension of the vermiculite lamellae by a vapor-permeable surface when applying the electromagnetic energy. 4. The method according to claim 3, characterized in that a flexible vapor-permeable base is used. 5. The method according to claim 4, characterized in that a layer of textile is used as a flexible base or fibrous material is used. 6. The method according to any one of the preceding claims, characterized in that a permeable membrane is provided, which comes in contact with the top surface of the foam as the foam expands. 7. The method according to any one of the preceding claims, characterized in that electromagnetic energy with a frequency between suspension applies. a frequency between 10 Hz and 10 Hz on the vermiculite 8. The method according to claim 7, characterized in that the energy by means of a microwave or radio frequency oven or - is using the heater. 9. The method according to claim 1, 7 or 8, characterized in that the aqueous suspension within a Trough or cavity by means of electromagnetic energy that is applied from outside the trough or cavity, makes it swell. 10. Solid foam from vermiculite lamellas, thereby characterized in that it has been produced by a method according to any one of the preceding claims. 809820/0985