DE3314145A1 - Fine-grained granular material of expanded perlite or vermiculite and method for the production thereof - Google Patents

Abstract

A fine-grained granular material of expanded perlite or vermiculite suitable in particular as an additive for insulating coatings consists of granules the material of which is converted to cellular glass at least on the surface of the granules. For the production of the granular material the raw perlite or raw vermiculite is subjected to a pretreatment which consists of a hydrothermal conversion of at least the surface layer, by which the melting point of the material is lowered below its expansion temperature. This hydrothermal conversion of the surface layer can be effected in a known manner.

Description

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Applicant: ütuttj-art, .-. Ien ^l . . · Ί. 1 " ■ *

Mr P 4-330 '.i / W.

Dr. Alo.y.s vfiistefeld Panoramaweg 17

7035 Waidenbuch

Representative:

Kohler - Schwindling - Späth patent attorneys Hohentwielstrasse 4-1

7000 Stuttgart 1

Fine-grained granules made from expanded perlite or vermiculite and ancestors to it Manufacturing

The invention relates to a fine-grain granulate made of expanded material Perlite or vermiculite.

BATH ORIGINAL

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From DE-OS 29 09 652 is a lightweight, pourable Granules made of foamed perlite are known, with the core of which is a jacket made of glass and / or ceramic material connected is. This coat has the purpose of being loosened up by puffing up and therefore easily disintegrating Solidify perlite so that it can be used as an aggregate material in the manufacture of lightweight building blocks and building panels using binders is suitable. In principle, it seems possible to use a similar material using vermiculite. The known material is said to be produced in that the Perlite is coated with liquid water glass either in its raw state or in the foamed state, to which, if necessary, silicate minerals, ground glass, aluminum silicate and similar substances can also be added, to give the glass or ceramic jacket greater strength.

The known material has the disadvantage that the creation of a sufficiently strong cladding layer requires the use of a Requires a very large amount of glass and / or ceramic material, because with a very fine-grained granulate that The surface area to volume ratio of the granules is very large. The consequence of this is that the creation of the surface layer in relation to the price of the raw perlite requires considerable costs, and that still very much cheap, low density of expanded perlite due to the relatively heavy glass and / or ceramic jacket is increased very much, so that no granules can be obtained in this way, as it is per se for the Production of components with a low volume weight and good thermal insulation would be required.

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It also appears questionable whether the material known from DE-OS 29 09 can be produced on an industrial scale, since the waterglass layers will presumably have the consequence that the individual grains of the granulate flow of the manufacturing process stick together, so that it is not easily possible, a free-flowing and preferably to obtain pearl-shaped material.

The foamed or expanded materials previously used in the construction industry for thermal insulation purposes were therefore also of a different type. In particular, plate-shaped insulation materials made of foamed plastics or mineral fibers were used for thermal insulation purposes. Such insulating materials require the formation or application of special insulating layers which, because of their lack of mechanical stability and weather resistance, have to be provided with additional protective layers. Attempts have also been made to develop heat-insulating plasters that can take on both the protective function of a normal plaster and the role of a heat-insulating layer, but the thermal insulation that can be achieved with such an insulating plaster is still very low. The reason for this is that the previously available additives, which are supposed to bring high insulation values, either do not have very high insulation values themselves, such as brick chippings _y or, for example, granulates made of foamed plastics, do not have sufficient strength to be able to work in this way to be used in large quantities, as would be required for good thermal insulation.

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As far as other expanded mineral materials with high strength and low thermal conductivity are available, such as expanded clay or foam glass granules, these materials have a grain size of more than 3 mm, so that it is difficult to produce components with a perfect surface. In particular, such coarse-grained granules are unsuitable as additives for plastering mortar. Expanded perlite and vermiculite have excellent heat-insulating properties because they are loosened to a large extent by expansion, but, as already mentioned above, the loosening leads to a very poor stability of the expanded grains. Although perlite and vermiculite change to a plastic state at high temperatures, so that a kind of vitrification could occur, through which the granules would lose a very high strength, but the granulate would have to for a considerable time after expansion for this purpose the expansion temperature are heated with the result that the parts become unstable by softening and for this reason also collapse, but on the other hand would also stick together or sintered together. It is therefore not to be expected that a useful product could be obtained in this way.

Accordingly, the invention is based on the object of providing fine-grained granules of the type mentioned at the beginning create, the density of which does not differ significantly from that of the expanded perlite or vermiculite and that still has a very high strength. The fine grain of the granulate should also be preserved stay.

This object is achieved according to the invention in that the material forming the granules at least on the granule surface is converted into foam glass.

In the case of the material according to the invention, there is accordingly also an outer, glassy or ceramic-like layer, which gives the granules high strength, but this layer is not one Sheath made of a material completely different from the core made of foamed perlite, but it is the vitrified or sintered core material itself. As for the transformation of the material forming the granules at the Grain surface in foam glass no appreciable amounts of additional material are required, has the invention Granules essentially have the same density as the previously known, expanded perlite or vermiculite, and the costs for the production of these granules remain extremely low.

The granulate according to the invention has a similar structure and strength to sand and can therefore just as sand processed with binders, especially in connection with hydraulic binders. In particular allowed it is the fine grain to use the granulate according to the invention as an aggregate for cleaning. The little Volume weight also makes it possible to set the proportion of granules in the plaster very high and still relatively to apply thick layers of plaster, which then have similarly good thermal insulation values as the granulate itself. As it is the granulate according to the invention is a very stable, water-resistant aggregate, the strength of which

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properties that come close to those of sand are such Insulating plasters also weatherproof, so that the invention for the first time offers the possibility of producing external plasters that are weatherproof and at the same time guarantee a high level of thermal insulation. The difficulties that have arisen so far with multilayer thermal insulation on the outside, can when using such plasters that have been produced using the granulate according to the invention, no longer occur.

With regard to the special importance that is attached to the production of such heat-insulating plasters, the subject is the invention also the use of the granules according to the invention as an additive for such insulating plasters.

The invention also relates to a method for producing the granulate according to the invention, in which, similar to that in the process known from DE-OS 29 09 652, the pearlite or possibly also vermiculite is subjected to a pretreatment and then made to expand by heating. at In the method according to the invention, however, the pretreatment does not consist in the application of an additional material, which then forms the glass or ceramic jacket, namely water glass and additional silicate minerals, but rather in a hydrothermal transformation of at least the surface layer of the unexpanded pearlite or vermiculite grains, which lowers the melting temperature of the material below its expansion temperature. As a consequence of this the converted material softens during expansion for some time before the expansion temperature is reached, and

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This changes into a glass-like state in which, when suddenly the pearlite or vermiculite grains expand takes place, forms a kind of foam glass structure, which gives the individual granules a very high level of strength confers. For this, however, it is not necessary to bring in additional amounts of a material which the Glass or ceramic cladding, but it is the perlite or vermiculite itself, albeit in a transformed form, which takes on a glass-like structure and thus gives it high strength.

The method according to the invention can be carried out in two stages, by first running the conversion process and the raw perlite with converted surface layer bloated at a later point in time. The raw perlite provided with the transformed surface layer is very stable and storable, so that it is suitable as an intermediate product because of its higher density better suited for transport than the puffed granules. The granules could be expanded in a rotary kiln, for example take place directly at the construction site or on the construction site near Baustoffplätzeri .. Accordingly, the invention should also extend to a fine-grained perlite or vermiculite, the grains of which at least on the surface are hydrothermally converted.

Process for the hydrothermal conversion of silicate-containing Minerals which lower the melting temperature of the minerals are known per se. Ks can such per se known methods also in the case of the method

for the production of the granules according to the invention are used. Thus it is in particular possible. To mix the raw perlite or raw vermiculite with addition of water with the chemical conversion means, and 1 to 2 hours of heating at 100 to 14O ⁰ C. Depending on the use of the conversion agent and the duration of the conversion, the thickness of the surface layer that has been covered by the conversion process is different. If the product with a converted surface layer is to be stored and / or shipped as an intermediate product, must. the transformation is followed by a drying process. Immediately after the conversion or after the drying, the product obtained can be expanded in a conventional manner. A more intensive conversion that penetrates further into the core can be obtained by heating the material mixed with a conversion agent under a steam pressure of at least 2 bar. In this way, a conversion of the entire granule material can be achieved so that, after the expansion, a product is obtained in which the individual granules consist entirely of foam glass. Such a product would have. but a higher density than a granulate which is only glassy on its surface without the compressive strength increasing significantly, so that a complete conversion of the particles into a glassy state should only be useful in exceptional cases.

The use of a mixture of hydrous alkali silicates, boric acid and aluminum hydroxide as conversion agents. In addition, the Reaction mixture of powdery basic rock materials, in particular in the form of or with an anorthite content,

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can be added. Further advantageous additives to the reaction mixture are hydrated lime and glass dust.

In the above-mentioned use of alkali metal silicates, boric acid and aluminum hydroxide as conversion agents, use is made of the fact that hydrous alkali metal silicates, especially sodium metasilicate-5-hydrate, easily reacts with aluminum hydroxide in the presence of boric acid to form boric acid-containing alkali aluminum silicates in the composition mf ^ O .AlgO nSic ^ .pEL ^ O + qH-, ΒΟ ^ react, and that the reaction products change ^{into a pyroplastic state at temperatures below 800 0} C and thus below the expansion temperature of perlite or vermiculite. If basic rock materials in powder form are added to the reaction mixture, these materials are dissolved or at least partially dissolved at the conversion temperature, so that they take part in the conversion reaction in particular when they contain anorthite Ca Z / Al-Si

OqjI included. True, perlite is an acidic rock with a ο

Silica content from 70 to 77 # and an AlpCU content of ■ $ 12 to $ 15, however, perlite also becomes perlite with the addition of one basic substance dissolved in the same way. The above-mentioned Ca (OH) 2 is such a basic substance which is preferably is used in the method of the invention.

The pyroplasticity obtained even at low temperatures is also due to the contribution of water and boric acid. For example, pure melts K _o S.ip0 _c at 1015 ⁰ C. The addition of 8% water lowers the melting point to about 500 ° C, and it may by a further

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Addition of boric acid already melts in the area of the transformation temperatures of 120 to 140 ° C mentioned above take place when with a water pressure from 1 to 2 bar is worked out. Instead of boric acid, another polybasic, weak to medium-strength, oxygen-containing acid can also be used Acid of a non-metal can be used. In order to achieve the advantageous overpressure of water vapor in some cases To achieve 1 to 2 bar, the conversion step can take place in a closed vessel that is equipped with a appropriate pressure relief valve is provided. When converting to make it easier for large-scale production the atmosphere creates a closed layer of sodium aluminum silicates in gel form on the surface of the grains, which is able to read the silicate grains of the material from the surface during further heating and a sufficiently thick surface layer before the expansion temperature is reached in the pyroplastic state to move.

The use of hydrated lime Ca (OH) 2 as a conversion agent has the particular advantage that, when used in excess, it also serves as a separating agent for the granulate particles. Furthermore, the highest strength values for the granulate according to the invention are achieved in a particularly economical manner. The effect as a conversion agent on perlite takes place according to the following scheme:

Na ₂ O.AlpO, .10SiO ₂ + Ca (OH) ₂ + 3H ₂ O =

OaO. Al ₂ O ^ .4-SiO ₂ .4H ₂ O + Na ₅ 0.3SiO ₂ + 3SiO ₂ .

The first compound in the above equation is perlite, which is formed by treatment with hydrated lime and water

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at elevated temperature results in a gel containing laumontite. The conversion with hydrated lime can also be promoted by adding high molecular weight polyphosphates (NaPCU) will.

The invention is described and explained in more detail below with the aid of a few examples.

example 1

1 kg of raw perlite with a grain size of 0.1 to 1 mm was mixed with 165 g of a mineral mixture of 15 g of Al (QH) ₅ , 45p; Ca (OH) ₂ , 70g perlite dust and 35g Glasraehl (waste glass) mixed well. The mixture was then moistened with 100 ml of an aqueous solution in which 40 g of Na ₂ SiO ₅ ^ H ₃ O and 16.3 g of H ₃ BO _{5 were} dissolved and worked through again thoroughly. The batch was then heated in the atmosphere and approx.

Maintained for 2 hours at a temperature between 120 and 140 ^° C. and finally dried. In this way, a granular and free-flowing preliminary product was maintained, which consisted of granules with a hydrothermally converted surface. This precursor was then heated to the expansion temperature. The end product was examined for its properties according to the test methods described below. Thereafter, the density was ο.15 g / cm, the compression at 10 kg / cm stamp pressure 40% and the compressive strength

19 kec / cm ² .

Example 2

It was prepared in the specified Example 1 and mixture heated in a closed vessel to a temperature between 120 and 140 ⁰ C and SSTD at this temperature for approx. 2 held. The vessel was provided with a valve,

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which opened at 2 bar water vapor overpressure, so that the conversion took place at overpressure. In this way the pearlite grains were transformed deeper from the surface, so that in the subsequent flatulence of the dried A stronger pyroplastic shell was created from the preliminary product and the end product despite an even lower one Volume weight possessed an even higher strength.

Example 3

Examples 1 and 2 were repeated using vermiculite with a grain size of 0.8 to 2 mm as the starting material. Here too, after the expansion, which ^{took place at 1000 °} C., a granular material with a hard surface was obtained.

Example 4-

1 kg of crude perlite was mixed with 95 6 of a mineral mixture which consisted of 15 g Al (OH) ₅ , 4-5 g Ca (OH) ₂ and 55 g glass powder. The raw perlite used came from Hungarian deposits, was dark gray to black in color and was very fine-grained. The maximum grain size was 1 mm, and a portion of $ 70 had a grain size of less than 0.5 nm. The above-mentioned mixture was moistened with 100 ml of an aqueous solution which contained 30 g of a potassium silicate powder, which consisted of 28% of K ₂ O and 70 _{% of SiO 2} , and in which 20 g of _{Ka 2 O.S1O 2} .5H ₂ O and 23g Borax B ^, Op. 10H ₂ O were dissolved. The moistened and again

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Well-worked mixture was ^{heated to about 120 0} G, with the result that the alkali silicates and Al (OH), in the presence of borates, with the formation of a sodium aluminum silicate with the composition

mMepO. Al ₂ O ₅ .nSi0 ₂ .pII ₂ 0 + qH ^ BO,

reacted. The sodium aluminum silicate was in gel form after the reaction. The gel surrounded the pearlite grains as a shell with good wetting, while the Ca (OH) p was present as a separating agent between the pearlite grains withdrawn with the gel, so that a shell that was impervious to the atmosphere could develop around each individual grain without interference from the neighboring grains . The shell ensures that moisture is retained under it over a longer period of time. In this regard, the presence of boric acid is also beneficial because boric acid has the ability to retain water for a long time. The constant moisture content over a longer period of time enables the perlite to be dissolved or at least partially dissolved and thus a continuous conversion into water-containing alkali aluminum silicate with the excess of alkali metal silicates present. The alkali aluminum silicate contributes to increasing the pyroplasticity when the granular and free-flowing preliminary product is heated to the expansion temperature. The pyroplastic shell obtained in this way is the guarantee for the production of stable pearlite grains during the flatulence.

Here, too, the mass was about 2 ütd. kept at 120 ⁰ C and finally getrockneb. As expected, a uniform, free-flowing, granular material was produced.

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hold, which was then blown in p-leicher way like raw pearl it. This resulted in granules whose grains were loosened in the core and which was foamed from the surface. The foaming is due to the fact that potassium silicate had been used in the mixture, which, with 8% water, ^{reduced the melting point from 1015 °} C. to about 500 ⁰ C experiences, and that the further addition of boric acid even a üchmelzunp; in the range of the transition temperature used.

Example 5

1 kg of raw perlite from Hungarian deposits with a grain size of 0.1-1 mm was mixed dry _{with 65 g of hydrated lime Ca (OH) 2.} The amount of hydrated lime can be increased up to 100 g. The mixture was diluted with 100 ml of an aqueous jWolgen polyphosphate (NaPO,) moistened and again worked well. The mixture was then heated in the atmosphere, and about 2 hours. Maintained at a temperature of 120 ⁰ C and by dewatering (activation) geterocknet. During the holding time, the above-described conversion with hydrated lime took place with the help of the high molecular weight polyphosphate, which forms water-soluble complexes with the alkaline earth ions. The complex formation is to be understood as an ion exchange reaction in which sodium ions are exchanged for Ca ions. The released Na ions react with the surface of the pearlite grains without the formation of sodium aluminum silicates in gel form or activate the corresponding reaction

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the Ca ions with the pearlite surface. The gels form one Cover around the pearlite grains and ensure that the moisture under the cover over a longer period of time remains until it comes to dehydration (activation) and drying. It got such a grainy and Obtain free-flowing preliminary product, which was then expanded in the same way as raw perlite. The properties of the final product were the following:

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Volume weight 0.20 g / cm, compression at 100 N / cm stamp pressure 30% and a compressive strength of 300 N / cm.

Example 5 teaches that the actually effective ions in the conversion are alkali ions. In Examples 1 to 3 and 5 there are sodium ions that are produced by hydrolysis or be free by base exchange, in Example 4- are it is predominantly potassium ions. In pursuit of this As a result, conversion tests were carried out with dilute sodium hydroxide solution without further additives. Examining the End products obtained from such conversion products gave values similar to those obtained in Example 5 Values largely matched.

Since handling such strong alkalis as sodium or potassium hydroxide in the building materials industry means unfamiliar work and furthermore, there is a risk that if the reaction agent is incompletely converted, it will later be used of the end product in mortar mixtures Swelling and blowing phenomena in those produced with such mortar mixtures If the plaster layers are disfigured, the use appears

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alkaline solutions are currently unsuitable as a conversion agent. Instead, it is again on the special economical and cheap procedure in Example 5 referenced.

The granules according to the invention are in terms of density (Bulk density) in the range of 0.10 - 0.20 g / cm, In this area there is practically a linear dependency between density and compression at certain Load when the granular bulk material in a steel cylinder by compression at a certain stamp pressure is compressed. The load used in this

was 100 N / cm. Depending on the volume weight, the following percentage compaction was determined:

Sample no. Compression in%
at 100 N / cm ²
load 7th
Volume weight in g / cnr 1 50 0.1 2 A-O 0.15 3 30th 0.20

It is common to use the 50% compaction

to designate the measured load in N / cm as the compressive strength of the pearlite. For this it is therefore necessary to compress each sample to 50% during the measurement. After that Sample No. 1 has a compressive strength of 100 N / cm '

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In our experiments, it makes more sense for practical application to use compaction with the same load 100 N / cm, to be measured according to the table above.

In Examples 1 and 5, densities of 40 and 30%, respectively, were measured, that is, the decrease in volume through the stamp pressure of 100 N / cm, based on the original volume times 100 - for the sake of completeness the compressive strength of samples 2 and 3 is also given:

Sample 2 has a compressive strength of 190 N / cm and

Sample 3 is 300 N / cm.

Claims (12)

33HH5 Claims j 1. fine-grained granules of expanded perlite or vermi-V_yculit, characterized in that the material forming the granules is at least on the granule surface in Foam glass is converted. 2. A method for producing the granules according to claim 1, in which granular perlite or vermiculite is subjected to a pretreatment and then heated to expand it is brought, characterized in that the pretreatment in a hydrothermal conversion at least the surface layer of the non-expanded pearlite or vermiculite grains, through which the melting temperature of the material is reduced below its expansion temperature. 3. The method according to claim 2, characterized in that the raw perlite or raw vermiculite mixed with the addition of water with chemical conversion agents and ^{heated to 100 to 14O 0} C for 1 to 2 hours, whereupon the material converted in this way at least on the surface, if necessary after prior drying, it is inflated in a conventional manner. 4-. Process according to Claim 3, characterized in that the material mixed with a conversion agent is heated under a steam pressure of at least 1 bar. 33HH5 5. The method according to claim 3 or 4, characterized in that that as a conversion agent a mixture of hydrous alkali silicates, a polybasic, oxygen-containing Acid of a non-metal, in particular boric acid, and aluminum hydroxide is used. 6. The method according to any one of claims 3 to 5 *, characterized in that that the reaction mixture powdery basic rock materials, especially in the form of or containing anorthite. 7. The method according to claim 6, characterized in that the reaction mixture hydrated lime ζ "αε ·» β1; ζΐ is » 8. The method according to any one of claims 3 to 7 »thereby characterized in that the reaction mixture has high molecular weight Polyphosphates are added. 9. The method according to any one of claims 3 to 7, characterized in that that glass dust is added to the reaction mixture. 10. Fine-grain perlite or vermiculite with a treated surface, characterized in that at least the Surface of the granules is hydrothermally converted. ^ 1 · Process for the production of the fine-grained perlite or Vermiculite according to claim 9, characterized in that the conversion of the surface takes place according to the method according to any one of claims 3 to 8. 12. Use of the granules according to claim 1 as an aggregate for insulating plaster.