DE2609123A1 - Anhydrite compsn. for casting, flooring and coatings - contains activators trialkali phosphate flow agent and surfactant - Google Patents

Abstract

Synthetic and/or natural anhydrite contg. 0.3-3.0 wt.% free CaO or the equivalent amt. of Ca(OH)2, activators and opt. water, also contains 0.1-3.0 wt.% trialkali phosphate (I) opt. is not >1.5 wt.% flour agent (II) and >0.1 wt.% surfactant (III). (I) acts as a strong activator as well as inhibiting the commencement of hardening without affecting the quality of the anhdrite. The compsn. may be used for self leveling flooring, casting, filing of voids e.g. in mining or as coatings. In an example, anhydrite contg. 1% CaO, K3PO4, and flour agent were mixed with water to give a water-binder coefficient of 0.35. The compsn. was cast and remained fluid for 60 min. After 24 hours the compsn. hardened with a smooth surface.

Description

Setting stimulator

The present invention relates to a mixture and a method for the production of solid bodies on the basis of anhydrite and additives, through stimulation the setting process using trialkali phosphate and calcium oxide, in a preferred Embodiment it relates to the stimulation of the setting process between anhydrite and water using trialkali phosphate and calcium oxide in the presence of a liquefier and a wetting agent.

The production of solids from anhydrite and water with participation of stimulators for the setting process is known. Contains commercial anhydrite consistently free calcium oxide as a stimulator, sulfates are used as additional stimulators, especially alkali sulfates are used.

The preference for potassium sulfate as an additional stimulator is based on the fact that this in contrast to sodium sulfate on the resulting solids does not cause any efflorescence, see DT-OS 2 530 728. Without these additives, purer binds Anhydrite does not come off, even those that already contain calcium oxide are technical not applicable.

It is also known that the water requirement of a mixture of anhydrite and can significantly reduce water by adding condensers. This measure is important because mixtures of anhydrite and water, as a result of the slow Stiffening, tend to segregate due to sedimentation.

It is also desirable to control the water content of such mixtures to keep low, as the strength of the resulting body by this measure is increased.

Such mash, consisting of anhydrite and water with the addition of Suggest and if necessary. Liquefiers show two important characteristics when used the setting process, namely the start of stiffening and the degree of hydration.

According to the well-known test procedure, the beginning of the stiffening is designated the period of time until an incision with a knife is made in the flat mass no longer disappears automatically by the confluence of the mass.

The surface of the in a mold or mash poured onto a surface or a bottom without an outer surface Influence. The start of stiffening also marks the end of the period in which the mash can be conveyed by pumps. This is especially important if the production of the mash takes place at a location remote from the application, as is usually the case when casting cavities in mining, for example.

The degree of hydration indicates what proportion of the anhydrite is in the Has converted the setting process into the dihydrate of calcium sulfate. Because education of dihydrate the essential process for the formation of a solid from anhydrite and water, the aim is to achieve the highest possible degree of hydration.

The classic stimulation achieved with potassium sulfate and calcium oxide Degree of hydration up to over 70% if it succeeds in keeping the mass long enough before it dries out to protect. These values are definitely with regard to the achievable strength satisfactory. In contrast, the course is unsatisfactory for some areas of application the stiffening. The alkali sulfate settles when mashed with water with the Ca (OH) 2 contained in anhydrite partially to gypsum, CIS04. 2H20 to, being at the same time Alkali hydroxide is formed. This plaster of paris forms extraordinarily in the hydration process effective crystal nuclei for those formed from the anhydrite when it is hydrated Plaster. This nucleation shortens the time until the start of stiffening all the more drastically, the higher the number of stimulators chosen. This causes a an early increase in viscosity, so that these no longer flow freely can.

Such an increase in viscosity occurs in various applications very annoying. For example, it is extremely hindering when you have the mash Must convey by pumping over a longer distance if in the hose line already stiffening occurs. In the same way, this stiffening interferes with Pouring the mash into larger flat areas that are expected to be Mash runs independently to form a smooth, even surface, as it does when making it of e.g. flowing screeds is the case.

Too early stiffening constitutes for some important areas of application a crucial handicap.

In addition, there are fluctuations in the processing of anhydrite in the stiffening, the causes of which are still largely unexplained.

The use of, known from the technology of gypsum hemihydrate Retarding the setting process (see Ullmann, 3rd edition, volume 8, pages 120-123 ) separates during processing from anhydrite, as this is the case with Anhydrite also the formation of hydration and thus the strength of the resulting Delay the body in an undesirable way.

Additives that intervene in the processing process, such as Retarders, liquefiers and stimulators show in the case of anhydrite and gypsum hemihydrate largely identical effects.

Since gypsum hemihydrate sets relatively quickly, the retarders have one greater application-related importance as a stimulator, with anhydrite this is the other way around.

From an investigation into the effects of various additives the setting behavior of gypsum hemihydrate (W.C. Riddel, Rock Products 57 (1954) October issue, Page 109, ref. Zement-Kalk-Gips, 1955, page 409 ff) shows that trisodium phosphate and triammonium phosphate cause a drastic delay.

The setting times increase with an addition of 1 percent by weight of this Substances in plaster of paris from 30 minutes to 600 or 42C minutes. At the same time will a significant reduction in tensile strength was observed.

DRP 198 100 even explicitly states the use of 0.1 surprisingly claimed up to 1.0% alkali phosphate as a retarder for gypsum it has now been found that trialkali phosphate has a strong stimulating effect on synthetic and natural arhydrite in the presence of calcium oxide.

Equally surprising is the fact that with this strong stimulus a significant delay in the onset of stiffening is associated. It could also it will be found that this new type of stimulation increases the quality fluctuations tin anhydrite, which lead to differences in the start of setting, largely eliminated will.

With the well-known analogy in the effect of the stimulators and retarders on anhydrite and on gypsum hemihydrate is therefore the stimulation of anhydrite by trialkali phosphate completely unexpected.

The present invention is therefore a mixture of Anhydrite with a content of 0.3 to 3.0 percent by weight of free calcium oxide or the equivalent amount of calcium hydroxide, stimulators and optionally water, the is characterized in that this mixture contains 0.1 to 3.0 percent by weight of trialkali phosphate as a stimulator and, if necessary, up to 1.5 percent by mass of a commercially available condenser and contains up to 0.1 mass% of a surfactant, and a method for the production of molded articles and / or coatings from synthetic and / or natural anhydrite as a binder, characterized in that the anhydrite 0.3 up to 3.0 percent by mass of free calcium oxide or the equivalent amount of calcium hydroxide contains and 0.3 to 3.0 percent by mass of trialkali phosphate is used as a stimulator, and the use of mixtures with synthetic and / or natural anhydrite for the production of self-leveling screeds and / or grouting and filling of cavities and / or as coatings.

Anhydrite, with e.g. 1% free calcium oxide and 0.6 mass percent tripotassium phosphate stimulated, reaches one after storage for 7 days in a humid atmosphere Degree of hydration from 80 to 85%. The same anhydrite shows under the same conditions when excited with 2% potassium sulfate a degree of hydration of only 70 to 75%. The start of stiffening of the anhydrite excited with potassium sulfate was in this case Comparison observed at 7 minutes. When excited with 0.6% tripotassium phosphate the onset of stiffening did not occur until after 45 minutes. So the stiffening runs when using potassium sulfate as a stimulator, it increases approximately linearly with time, while advantageously, when stimulated with phosphates, the mash can flow longer and so that it remains processable. The stiffening then also takes place within a shorter period of time.

The following table shows a comparison with other phosphates, the results reported were obtained by the following procedure: 100 g more synthetic Anhydrite, with a content of 1.3 mass percent free calcium oxide, were with Put 400 ml of water in a bowl using a stirrer to form a thin paste stirred. The salts indicated in the first column, in the previously dissolved in the quantity indicated in the second column. After 24 hours it was the hydration (mass percentage calcium sulfate dihydrate) after being powdered Substance washed out the not yet bound water with acetone and the Substance was dried to constant weight at 6000, determined analytically. At the same time, the strength was increased by pressing in a wooden stick with a cross section of 1 cm2 judged by the still moist mass.

Table of stimulators stiffening hydration strength start in degrees according to type amount minutes 24 hours 24 hours K2S04 0.5% 14 28% hard KH2P ° 4 0.5 ffi 70 13% soft 2HP04 0.5% 56 29% soft KDP04 0.5% 56 34% very hard Na4P207 0.5% 30 4% very soft NaH2P04 0.5% 52 8% very soft K2S04 2.0% 6 50% very hard K3P04 2.0% 15 50 s very hard The advantage of the inventive excitation with However, trialkali phosphate is not only evident in the greater range of variation in the Start of stiffening, but also in the strength of the anhydrite due to the setting emerging body. The masses excited by acidic phosphates or diphosphate show no practically usable hardening despite considerable degrees of hydration.

For the anhydrite that sets with water to form a solid body There are many areas of application, two particularly important ones are potting and filling of cavities, for example in mining, and the potting of self-leveling Screeds. In both cases, the mash must be in a free-flowing area for as long as possible State, but also afterwards to a body of high strength freeze. In mining, the mash is often transported over a relatively long distance from the place of production pumped to the point of application. A premature stiffening was the delivery hoses clog and thus cause a malfunction. Making a self-leveling Screed requires a mash that remains free flowing until the entire Area is filled or filled.

In general, one mash, the start of stiffening, is sufficient for these applications is not less than 30 minutes.

By means of the excitation with trialkali phosphate it is possible to achieve this value to hold or even to exceed without affecting the strength of the hardened Mass is reduced.

In the process according to the invention it is possible to use all alkalis to use in the form of trialkali phosphates. Their effect is the same, the use of rubidium and cesium salts is likely to be severely restricted due to their price be. Trisodium phosphate can cause efflorescence on the surface of the resulting solids lead, wherever these do not interfere, this is preferred according to the invention used phosphate. Should these possibly

Tripotassium phosphate is used to avoid efflorescence.

In the method according to the invention, the anhydrite to excite required trialkali phosphates are used as such or only in use Phosphoric acid or acid phosphates and alkali compounds are synthesized.

The amount of trialkali phosphate required for excitation is generally m at 0.3 to 3.0% by mass of anhydrous substance, preferably at 0.5 to 2.0 Mass percent, very preferably 0.5 to 1.5 mass percent, based on the amount of synthetic and / or natural anhydrite. It is largely based on the setting time expected in the mash and can be determined by a simple preliminary experiment be determined.

Upwards is the addition of trialkali phosphate due to the content of the anhydrite is limited to free calcium oxide. The alkali metal phosphate is said to be those quantities do not exceed that to a complete reaction with the contained in the anhydrite Calcium oxide is required when the reaction product is an Ilydroxylapatit of the composition 3 Ca3 (P04) 2. Ca (OH) 2 ar, geno, .men, corresponding to a molar ratio of e.g.

K3 P04 to calcium oxide as 6 to 10. For the stimulation according to the invention however, a significantly lower proportion of trialkali phosphate in the also suffices Excitation system.

Another advantage of the excitation with tri-alkali phosphate results when pouring the settable suspensions of anhydrite and water, with addition of so-called condensers.

The excitation of such liquefiers allows the water content of these To significantly reduce suspensions without increasing the viscosity. A very good one Liquefier is the condensation product of formaldehyde and sulfonic acid Di-Toluyläthers, other usable liquefiers are well known, they are e.g. described in OE-PS 263 607 as well as DT-OS 1 238 831 and DT-OS 2 341 923, e.g. Condensation products from formaldehyde with sulfonated aromatic ethers, imines, Sulfones, cycloalkanes, aceto and / or benzoguanamine sulfonic acids or naphthalenesulfonic acid derivatives or melamine resins.

The anhydrite to water ratio is generally around 0.2 up to 0.6% by weight, preferably at about 0.25 to 0.45% by weight.

With optimal dosing of the condenser, the water requirement is reduced a pumpable suspension by 33%, i.e. from approx. 45 parts of water to 100 parts 30 parts anhydrite Water to 100 parts of anhydrite.

When mashing anhydrite, liquefier, water and potassium sulfate as a stimulator, in a device common in the construction industry, is formed in the mash a very fine bubble foam.

This collects on the surface when the mash is poured and forms a porous layer there after hardening.

Attempts to prevent this foam formation by using defoamers are so far unsuccessful. The subsequent mechanical removal of the porous Layer on the hardened anhydrite, for example in the production of Screeds represent an additional workload.

In the case of the inventive excitation with trialkali phosphate it was found that that the bubbles that form are much larger than those that form e.g. Form of stimulation with potassium sulfate. They can be seen on the surface by simple Destroy the smear with e.g. a rubber squeegee or a straightedge while this mash still shows no incipient stiffening. The delayed stiffening the excitation with trialkali phosphate obviously facilitates the destruction the bubble structure on the surface.

Furthermore, it was found that these surface bubbles spontaneously develop decompose when you mash a small amount of a surfactant clogs. Alkali salts of the sulphite waste liquors, for example, have proven to be particularly effective Ammonium lignin sulfonate, also alkyl sulfonates, alkylaryl sulfonates, olefin sulfonates and alkyl sulfuric acid esters.

The effect of these surface-active substances is already through Additions of 0.01 percent by weight, based on the weight of the anhydrite, in full Scope secured. Additions above 0.05 percent by mass are generally not necessary. Understandably, this spontaneous breakdown of the bubbles works best in the still thin mash. This effect is all the more surprising as these substances are known as typical auxiliaries for the production of foams.

In addition to the substances mentioned above, the mixtures according to the invention can be used still other inert auxiliaries can be added, such as porous fillers and / or fibers, as well as coloring materials, sand, sound and heat insulating materials, Synthetic resins, strength-increasing substances, corrosion inhibitors, antifreeze agents Etc.

Quartz powder, quartz sand and / or bricks can be used as inert fillers split can be used. The volume weight is increased by adding specially porous fillers of the shed masses humiliated. This measure is because of the achieved Weight saving is particularly important for filling rooms in the construction industry. Used Both inorganic lightweight fillers, such as expanded clay, can be blown for this purpose Perlite, expanded vermicullite and similar substances, as well as organic light fillers, such as cork, styrofoam or other foams. Among the fibers are the inorganic, such as glass fibers, glass wool, rock wool, basalt wool, are preferred, but use is other fibers are just as possible.

The mixture according to the invention and the method should be based on the following examples are explained in more detail So much for the If a liquefier is used in the following examples, it is the condensation product from formaldehyde and the sulfonic acid of di-toluyl ether.

Comparative Example A In a mashing device for continuous Production of the anhydrite suspension, with an output of 1400 kg / hour of solids, was carried out a solid mixture according to the following recipe used 1400 kg synthetic anhydrite with 1.0% free CaO 28 kg potassium sulfate 10 kg liquefier.

This was done while maintaining a water-binder ratio mashed by 0.3. The resulting mash was prepared in a flat shape poured in with a layer height of 3 cm. After a short time the Surface of the mass A fine bubble foam, which is also intense Did not let slip by. After about 25 minutes of pouring it had to the mass is leveled with the help of a straightedge because of the incipient stiffening especially where freshly poured mass came together with those that had been shed 25 minutes ago. The hardened within 24 hours Mass into a solid body, the surface of which is partially covered with fine bubbles was. The bubbles could be rubbed off, but a porous surface structure remained obtain. The individual bubbles were less than 0.5 mm in diameter.

Example 1: Following the procedure described in Example 1, the following is carried out Mixture of solids mashed and poured: 1400 kg anhydrite with 1% free CaO 10 kg tripotassium phosphate, K3P04 10 kg liquefier The water-binding agent factor was set to a value of 0.35, this corresponded to 350 kg of water per 1000 kg Solid mixture. Pointed to a flat shape about 3 cm high after potting There are air bubbles on the surface with a diameter of 1.5 to 2.5 mm. These If they did not fall apart spontaneously, they could be removed by wiping them off with one Destroy a rubber squeegee or a straightedge. The poured mass remained until 60 For a few minutes it is so thin that the surface is self-acting without any special measures leveled. After 24 hours, the mass treated in this way had a smooth surface solidified into a solid.

Example 2: Following the procedure described in Example 1, the following was established Mixture of solids mashed and poured: 1400 kg anhydrite with 1.0 z free CaO 10 kg tripotassium phosphate, K3PO4 10 kg liquefier 0.07 kg wetting agent, sodium alkyl sulfonate with a chain length of the alkyl radical of 10 to 16 carbon atoms.

The water-binder factor was adjusted to a value of 0.35. After pouring, the liquid mass briefly formed on the surface Bubbles 1.5-2.5 mm in diameter that appear spontaneously after a few minutes disintegrated. Since the decay took place before the solidification occurred, smoothed the surface itself again.

After 24 hours the entire mass had a smooth, uniform surface stiffens.

The stiffener showed the same delay as in Example 2.

Example 3: Following the procedure described in Example 1, the following was established Mixture of solids mashed and poured.

1400 kg anhydrite with 1.0% free CaO 10 kg tripotassium phosphate, K3P04 6 kg liquefier 0.05 kg ammonium lignosulfonate.

The water-binder factor was adjusted to a value of 0.35. After pouring, the liquid mass briefly formed on the surface Bubbles 1.5-2.5 mm in diameter that appear spontaneously after a few minutes disintegrated. Since the disintegration occurred before the stiffening occurred, smoothed the surface itself again. After 24 hours, the entire mass was with solidified smooth uniform surface.

Claims (8)

Claims: 1. Mixture of synthetic and / or natural Anhydrite with a content of 0.3 to 3.0 percent by weight of free calcium oxide or the equivalent amount of calcium hydroxide, stimulants and optionally water, thereby characterized in that this mixture contains 0.1 to 3.0 percent by weight of trialkali phosphate and optionally up to 1.5 percent by mass of a liquefier and up to 0.1 percent by mass contains a surfactant. 2. Mixture according to claim 1, characterized in that this 0.5 Contains up to 2.0 percent by weight of trialkali phosphate as a stimulator. 3. Mixture of synthetic and / or natural anhydrite and additives according to claim 1 or 2, characterized in that a trialkali phosphate deficiency compared to the free calcium oxide is contained in the mixture. 4. Mixtures according to one or more of claims 1 to 3, characterized characterized in that a sulfonic acid condensed with formaldehyde is used as a liquefier Ditoluyl ethers and / or condensation products of formaldehyde with sulfonated aromatic secure, imines, sulfones, cycloalkanes, aceto and / or benzoguanamine sulfonic acids or naphthalenesulfonic acid derivatives or melamine resins are used. 5. Mixtures according to one or more of claims 1 to 4, characterized characterized in that as a surface-active substance ligninsulphonic acid or one their water-soluble salts and / or a sodium alkyl sulfonate with a chain length of the alkyl radical of 10 to 16 carbon atoms is used. 6. Mixtures according to one or more of claims 1 to 5, characterized characterized in that inert and / or porous fillers and / or fibers, Coloring materials, sand, sound and heat insulating materials, synthetic resins, strength-enhancing materials Substances, antifreeze and / or forroston inhibitors are used. 7. Process for the production of moldings and / or coatings of synthetic and / or natural anhydrite as a binder, characterized in that that the anhydrite 0.3 to 3.0 percent by mass of free calcium oxide or the equivalent Contains amount of calcium hydroxide and 0.3 to 3.0 percent by mass of trialkali phosphate as a stimulator be used. 8. Use of the prepared according to one or more of claims 1 to 6 Mixtures with synthetic and / or natural anhydrite for the production of self-leveling Screeds and / or potting and filling of cavities and / or as coatings.