DE2609124A1 - Setting initiators for calcium sulphate slurries - consist of alkali and/or acid fluorides - Google Patents

Abstract

Mixts. of calcium sulphate (anhydrite or gypsum) usual additives and opt. water and/or other filters, contg. 0.3-3 pts. alkali fluoride and/or acid fluoride per 100 pts. CaSO4 as initiator of settling. Used for the mfr. of solid articles or coatings e.g. floor surfaces, by casting, also for the prod. of porous building blocks. No sedimentation of the mixts. occurs over a wide range of solids contents, the CaF2 formed by reaction with CaO present in the CaSO4 acting as a powerful suspending agent. Mfr. of foam products by addn. of foaming surfactant and H2O2 is improved, the fluoride preventing reactiong of CaO and H2O2, and stabilising the foam structure.

Description

Setting stimulator

The present invention relates to a mixture and a method for the production of solid bodies and / or coatings based on calcium sulphates, Additions and, if necessary, water by stimulating the setting process with alkali fluoride and calcium oxide. A particular embodiment of the method relates to neglect the so excited mixtures.

The production of solids from calcium sulfates and water in The presence of stimulators is known. As calcium sulfates here can be more synthetic and / or natural anhydrite and / or gypsum with different water contents are used will.

Commercially available anhydrite, for example, usually contains 0.3 to 3.0 % free calcium oxide. This must also be seen as a stimulus, but it is its effect only unfolds in the presence of a second stimulator. Together with the Calcium oxide is used as the most effective stimulant sulfates, preferably alkali sulfates. Potassium sulphate is particularly preferred here because it contains e.g.

in contrast to sodium sulphate with otherwise the same effect on the solids does not cause efflorescence (see DT-OS 2 330 728).

For the sake of simplicity, the present invention is exemplified below described on the basis of anhydrite, but the explanations apply in the same sense for plasters with different water contents.

When mashing the anhydrite with water and sulphatic stimulants The calcium oxide contained in the anhydrite combines with the sulfate to form calcium sulfate dihydrate around. This forms very effective crystal nuclei for the hydration of the anhydrite resulting dihydrate. However, the amount of water required for mashing is exceeded the minimum amount necessary for the formation of dihydrates, especially if one is pourable produces thin-bodied mashes that are required for most applications. Anhydrite or hemihydrate of gypsum bind about 19% water during hydration. For mashing e.g. with anhydrite about 25-50% and e.g. with stucco about 45 to 100% water required, based on the solid used. Thinner suspensions tend to be When standing for a longer period of time, it separates due to sedimentation of the anhydrite. It is therefore very difficult to fill completely by pouring out molds or cladding to achieve these forms.

It is known that the water content of such suspensions by can reduce the use of so-called liquefiers without the The fluidity of the suspension deteriorates. Such suspensions are less prone for sedimentation as the same, without the addition of liquefiers.

By reducing the amount of water required, one obtains from Mashes that were produced with the addition of liquefiers, molded bodies with increased density and increased compressive strength. One disadvantage in use from Liquefaction consists in the fact that this foam forms in the mash cause. This foam rises to the surface and in the poured mass forms a porous layer when it hardens. When pouring a screed from e.g.

Anhydrite, water and additives makes this porous layer an uncomfortable one Disturbance of the surface. It must be carried out by mechanical measures after hardening removed.

The condensation product, for example, is known as a liquefier Fcrmaldehyde and sulfonic acid of di-toluyl ether are used. Other condensers used are e.g. sulphonic acids of melamine derivatives and those in DT-PS 1 238 831, DT-OS 2 341 923 and Oe-PS 263 607 have been described.

The devices used in technology for mashing anhydrite are all of a relatively simple design, as they are among those prevalent on a construction site Conditions must work properly. There are therefore frequent fluctuations in the dosage of the raw materials, in particular the solid anhydrite. Despite the The use of liquefaction can therefore temporarily arise suspensions that lead to Tend to sedimentation.

The use of liquefiers therefore solves the problem of sedimentation only partially. The bridging of fluctuations in the solids content of the mash and the disturbances caused by this cannot be solved with it. It therefore exists the urgent need for a system of auxiliaries that prevent sedimentation prevent effectively in a wide range of solids content in the mash, without impairing the valuable properties of the resulting solids.

It has been found that the setting process of the anhydrite with water stimulate very effectively with alkali fluorides in the presence of free calcium oxide can. The present invention therefore provides a mixture of calcium sulfate binders, Additives and optionally water and / or auxiliaries, characterized in that that this mixture - based on 100 parts of calcium sulfate - 0.3 to 3 parts of alkali metal fluoride and / or contains acidic fluorides as stimulators.

Surprisingly, those according to the invention also show with alkali metal fluoride and calcium oxide excited mashes in a very wide range of solids content no sedimentation. Apparently this forms from calcium oxide and alkali fluoride at The calcium fluoride produced by mashing is an extraordinarily powerful suspension aid.

DT-OS 2 418 608 teaches the use of soluble aluminum fluorides as a retarder for the setting of hardenable calcium sulphates. All the more surprising was therefore the inventive effect of alkali fluoride as a stimulator for setting of settable calcium sulphates.

It is also known that, for example, in the production of phosphoric acid from calcium phosphate and sulfuric acid a gypsum is obtained, the contamination of which is caused by Fluoride allows further processing only after extensive cleaning. The DT-AS 1 950 658 describes such a method for cleaning plaster and the disturbances of the setting process caused by fluoride. Here is pointed out that the hydrolysis of silicofluorides produces simple fluorides, without eliminating the disturbances.

In the anhydrite formed during the production of hydrogen fluoride Depending on the process, a residue of fluoride may also remain, this is but in the form of the insoluble and therefore ineffective calcium fluoride. The inventive Stimulation of the Abb indevorgan ges of anhydrite and water by means of calcium oxide and Alkali fluoride, leads to a hydration of the anhydrite, that of the classical stimulation is at least equivalent to alkali sulphate and calcium oxide.

According to the classic method, mashes are obtained that are only available in a very narrow range of solids content can be processed without sedimentation can. The mashes produced according to the invention show a broader range the solids content in which sedimentation is prevented.

In addition to the calcium oxide, 0.1 to 3 z alkali are used as stimulants fluoride and / or acidic fluoride used.

In those cases in which efflorescence on the resulting solids are not desired, potassium fluoride is preferred. Acid fluorides are used there where the stiffening effect is more strongly promoted than the stimulation of the setting process should be, this can be the case, for example, when foaming these masses. As acidic fluorides, e.g. all alkali hydrogen fluorides can be used which Use of sodium and potassium hydrogen fluorides is for the same reasons as preferred for the alkali fluorides.

The free calcium oxide contained in anhydrite should be compared to fluorides be present in excess, assuming complete conversion to calcium fluoride.

All alkali fluorides are stimulators for the purposes of the present invention effective, but in practice the use of sodium fluoride and potassium fluoride should be used be preferred, since lithium fluoride is relatively sparingly water-soluble and the homologues For reasons of price, rubidium and cesium fluoride are unlikely to be considered.

In a mixing bowl, 1000 g of anhydrite, the one content of 1.2% of free calcium oxide, with the specified amount of water and the The stimulant described in each case is mixed into a mash and then poured into a flat Potted bowl with a layer thickness of about 2 cm.

The pourability of the fresh mash and the deposition were determined in each case of water on the surface of the poured layer after 30 minutes qualitatively judged.

Tabel Liquefier Liquefier Wuser 15 g K2SO4 - 300 ml stiff mass, not pourable 15 g K2SO4 10 g 300 ml thin liquid clear sedimentation 15 g K2SO4 10 g 100 ml very thin liquid, strong sedimentation 10 g KF - 300 ml thick, still pourable, no sedi- mentation 10 g KF - 400 ml easily pourable, no sedimentation 10 g KF - 450 ml thin, no sedimentation 10 g KF 10 g 300 ml thin liquid, no sedimentation The comparison illustrated in the table above shows that when using, for example, potassium fluoride as a stimulator, the mashed mass does not show any sedimentation of the anhydrite despite a high addition of water. Another advantage can be seen in the fact that the addition of a condenser can even be dispensed with entirely without the risk of sedimentation.

It was also found that die'mit excited with alkali fluoride and calcium oxide Mashing from anhydrite and water works in an excellent way with the addition of a Allow foaming wetting agent to foam, this is a variant of the method.

The production of porous bodies based on anhydrite is achieved by foaming a gypsum-water mixture, with 0.1-1.0 parts of a water-soluble as a special additive Aluminum compound can be used. The omission itself takes place through catalytic Decomposition of hydrogen peroxide, preferably by means of more soluble in an alkaline medium Manganese compounds.

Surprisingly, it has now been found that alkali metal fluorides and / or acid fluorides as stimulators with the corresponding reaction products in the mash prevent the reaction of calcium oxide with hydrogen peroxide and at the same time stabilize the resulting foam structure.

According to the method described above, a mixture of anhydrite with potassium sulfate as a stimulator, a water-soluble aluminum salt as a stabilizer for the foam and potassium permanganate as a catalyst for the decomposition of the hydrogen peroxide mashed with water. An aqueous solution of hydrogen peroxide is then added to this mash and a foaming wetting agent added, the mass then in a few seconds foams up. It would be an advantage if you had the wetting agent at the same time as the anhydrite and the other additives during mashing.

As the preferred wetting agents, however, as alkali salts of alkyl sulfonic acids react alkaline, the aluminum salt would precipitate prematurely as aluminum hydroxide and thus become ineffective.

In contrast, alkali fluorides and / or acidic fluorides show none harmful reaction with the wetting agents and can therefore have their combined effect as stimulators for the calcium sulfates and as stabilizers for the foam fully exercise. The wetting agents used are, for example, alkyl sulfonates with 10-16 carbon atoms in the alkyl radical, alkyl aryl sulfonates and their modified derivatives are used and, as manganese compounds, e.g. all soluble manganese salts e.g. inorganic acids such as permanganates, manganese sulfates, Magnan nitrate etc.

The process is simplified because now all additives, with the exception of the hydrogen peroxide, dissolved in the water used for mashing can be.

This advantage is particularly evident when it is carried out continuously of the process in the mashing devices customary in structural engineering.

Such foamed masses can ztB. for the production of porous Light building blocks are used. The convenient dosage of the hydrogen peroxide succeeds it, simply and re-producible, the volume weight of the lightweight building blocks to the desired Set values.

If an acceleration of the setting process is desired, this can be done by mixing the slowly setting anhydrite with the quickly setting gypsum hemihydrate take place. Another way of regulating the setting speed is through the use of so-called retarders is possible, here all known retarders, E.g. alkaline hydrolysates of keratins, etc. are used, as well as all others Retarders known from the processing of gypsum hemihydrate (see Ullmann, 3rd edition, volume 8, pages 120-123).

Another area of application for these foamed masses is that Potting of insulating layers or filling layers under a screed, in particular when this screed is also poured, e.g. a non-foamed one Anhydrite suspension, is applied.

The inventive excitation of such suspensions with alkali fluoride thus on the one hand allows the production of screed layers without the previous ones Procedure highly disruptive Sedimentation of the anhydrite, on the other hand but also the stabilization of such suspensions after foaming, here results in the broad consistency of the composition of the foamed insulating layer and the load-bearing cover layer when pouring screed a good connection between the two superimposed layers.

The invention is to be described in more detail with the aid of the following examples will.

Comparative Example 1 In a vessel with a capacity of about 5000 ml 1000 g of anhydrite containing 1.3% free calcium oxide were stirred into 600 ml of water. 0.1 g of potassium permanganate was used as the decomposition catalyst and 0.013 as the wetting agent g Na alkyl sulfonate dissolved in the mash with stirring.

This mash was made by stirring in 10 ml of a 35% strength hydrogen peroxide solution foamed. The mass foams within 30 seconds of adding the hydrogen peroxide to a volume of about 2000 ml.

The foam structure of this mass partially disintegrated with formation coarse gas bubbles that burst after about 20 minutes, before the anhydrite suspension was stiffened.

Example 1 600 ml of water were placed in a vessel with a capacity of about 5000 ml submitted, in which 10 g of potassium fluoride were dissolved.

1000 g of anhydrite of the same quality as in Comparative Example 1, as well as 0.1 g of potassium permanganate and 0.013 g of Na alkyl sulfonate stirred in.

This suspension was then stirred in 10 ml of a 35% hydrogen peroxide solution foamed. The mass foams within 30 Seconds to a volume of about 2300 ml.

The foam structure was so stable that the liquid foam could not be Shed decay in molds and solidified there without loss of volume.

After completion of the setting process and drying, one obtained a foam body with a density of 500 kg / m3 and a compressive strength of 15 kg / cm².

Example 2 In a commercially available device for continuous mashing of anhydrite or gypsum, consisting of a storage vessel with a conveyor for the solid, a stirrer in a mixing chamber, a water supply line with a metering device anhydrite was added to this mixing chamber and a sludge pump for discharging the mash mashed. In the water, based on the amount of anhydrite, there were the following Dissolved additives: 0.01% potassium permanganate, 0.0012% sodium alkyl sulfonate and 1% Potassium fluoride.

The ratio of anhydrite to water was 1: 0.6.

After exiting the mud pump it was connected to a Pipe piece entered into the mash by means of a metering pump hydrogen peroxide solution. The amount of hydrogen peroxide in the present example was set to 1% of a 35 % solution, based on the amount of solid.

The result was a foamed, liquid mass that would not disintegrate could be poured into prepared molds or shallow pits and without loss of volume froze.

The resulting porous bodies have a density of 500 kg / m³.

Comparative Example 3a In a 100 liter vessel. Content was under Stir the following mixture mashed: 50 kg anhydrite, 15 kg water, 0.7 kg potassium sulfate and 0.5 kg condenser.

The homogeneous mash was placed in a horizontal casing with 1 m2 Base area potted in a layer 3 cm high.

After about 30 minutes, a about 2 mm thick water layer formed.

Comparative Example 3b An attempt was made to use the same mixture as in Comparative example 3a, but mixing without the addition of liquefier. It was, however not possible to carry out the entire experiment because the resulting mass increases was stiff.

Example 4a This example was carried out analogously to comparative example 3a, however, instead of 0.7 kg of potassium sulfate, 0.5 kg of potassium fluoride was used.

It did not show up either within the first 30 minutes or later the surface of the mass, which has solidified into a solid body, a water separation.

Example 4b In a 100 liter vessel. Contents were stirring mashed the following mixture: 50 kg anhydrite, 20 kg water and 0.5 kg potassium fluoride.

The homogeneous mash was made into a horizontal form of casing 1 m2 base area potted in a layer 3 cm high. Neither within the first 30 minutes later, the surface of the mass, which had solidified, showed a water separation.

Claims (11)

Claims: 1) Mixture of calcium sulphate binders, additives and optionally water and / or auxiliaries, characterized in that these Mixture - based on 100 parts of binder - 0.3 to 3 parts of alkali fluoride and / or contains acid fluorides as stimulators. 2) Mixture according to claim 1, characterized in that the calcium sulfate component synthetic and / or natural anhydrite and / or gypsum with different water contents be used. 3) Mixture according to one or more of claims 1 to 2, characterized characterized in that this mixture contains 0.3 to 1.5 parts of a liquefier as an additive can be added. 4) mixture according to one or more of claims 1 to 3, characterized characterized in that condensation products of formaldehyde with sulfonated as liquefier aromatic ethers, imines, sulfones, cycloalkanes, aceto and / or benzoguanamine sulfonic acids or naphthalenesulfonic acid derivatives or melamine resins are used. 5) Mixture according to one or more of claims 1 to 4, characterized characterized in that this mixture - based on 100 parts of binder - 25 to Contains 100 parts of water. 6) Mixture according to one or more of claims 1 to 5, characterized characterized in that inert fillers and / or porous fillers are used as auxiliaries and / or fibers are used. 7) Process for producing moldings and / or coatings from calcium sulphate binders, additives and, if necessary, water and auxiliaries, characterized in that as a stimulator - based on 100 parts of binder - 0.3 up to 3 parts of alkali fluorides and / or acidic fluorides can be used. 8) Mixture of calcium sulphate binders, additives and optionally Water, characterized in that the mixture - based on 100 parts of binder - 0.3 to 3 parts of alkali fluorides and / or acidic fluorides as stimulators, 0.01 to 0.1 Parts foaming wetting agent and 0.01 to 1 part of a water-soluble manganese compound contains. 9) mixture according to claim 8, characterized in that this mixture with 0.3 to 5 parts of a 35% H202 solution, or corresponding amounts for others Concentrations, is foamed. 10) mixture according to one or more of claims 8 to 9, characterized characterized in that the mixture 0.3 to 1.5 parts liquefier and / or 0.05 to 0.5 parts of retarder are added. 11) Process for the production of moldings and / or coatings from calcium sulfate binders, additives and optionally water and / or Auxiliaries, characterized in that as stimulators - based on 100 parts of binder - 0.3 to 3 parts of alkali fluorides and / or acidic fluorides and, as a foaming agent, hydrogen peroxide is added.