DE3230962A1 - Process for producing a binder based on hydrated magnesium oxide - Google Patents

Abstract

A process for producing a dry and storable binder based on magnesium hydroxide and magnesium salt hydrates is described, according to which caustic burnt magnesite mixed with recycled material is treated with water at temperatures of up to 100 DEG C, then dried and intensively mixed in the dry state with magnesium chloride hexahydrate or magnesium sulphate heptahydrate.

Description

KALI UND SALZ AKTIENGESELLSCHAFT, Friedrich-Ebert-Str. 16Q

kassel

Process for the production of a binder based on hydrated magnesium oxide

July 28, 1982 CE-Dl / ri

Kali und Salz AG · ":;' : '.'. ' ·"· ·*'?8th . July 1982

Magnesia cements, also known as Sorel cements can, as is well known, by mixing caustic burned magnesite, the so-called «oyster, and magnesium chloride solution or magnesium chloride hexahydrate and water or magnesium sulfate solution can be produced. As with this mixing already the mixture begins to set, this mixture can only be prepared on site and / or grounded. Through the admixture of aggregates, such as sand, especially one

IQ agreed grain structure, to such magnesia-cement mixes mortars are created that can be processed into interior construction floors with a particularly high load-bearing capacity. Since such a mortar also contains organic fibers, such as wood flour or wood shavings, without any problems and without essential Including strength reduction, can benefit from it elastic and heat-insulating floors are manufactured.

For the preparation of these magnesia cements or mortars however, difficulties arise from the fact that the so-called causer even with the origin of the magnesite from a deposit from batch to batch may have considerable deviations in its composition and in its properties to which the Magnesia cement and mortar compounds react sensitively. For these reasons it is necessary prior to processing a new Kauster batch for magnesia cement or mortar perform optimal MgO-MgCl "-HO ratio .

3Q Another technical difficulty is posed by the exothermic reaction of magnesium oxide with the Magnesium chloride and water released VJarms in the Processing of magnesia cements that depends on the reaction rate, which on the

Kali und Salz AG. * ::.::. ··. . . * · "July 20, 1982

Activity of the caustic is determined. Succeeds at the processing of magnesia cements does not affect the heat of reaction in a certain proportion to their formation from the magnesia-cement mixture, so the resulting products tend to form undesirable cracks.

To solve these problems, DE-PS 739 164 recommends using magnesia cements instead of magnesium oxide or the caustic should also include magnesium hydroxide

Set IQ. For this, however, it is necessary to use a magnesium chloride solution to use such a concentration that in the mixture including the water introduced with the magnesium hydroxide, the magnesium chloride concentration is between 21 and 27 wt .-? o. The rate of formation of the oxychloride can according to this Process can be accelerated by adding measured amounts of active magnesium oxide. This method However, it also requires special care with regard to compliance with the proportions of the Starting materials and their particularly good mixing, which can only be used on site by particularly experienced Professionals can be done.

In order to reduce the problems of processing magnesia cements here as well, DE-PS 832 565 a dry premix for processing as magnesia cement is described. These premixes are obtained from aqueous mixtures of magnesium hydroxide and magnesium chloride solution by dehydration, free magnesium hydroxide and chloride must be retained in addition to the oxychloride formed. These dry premixes need at the place of processing, if necessary after adding additives, Can only be mixed and processed with water.

Kali und Salz AG ':::.' ■ '.'. · ". '. · " 28. July 1982

According to DE-PS 839 622, this procedure is varied in that pastes made from magnesium hydroxide and chloride solutions are used which contain 100 to 700 parts by weight of magnesium hydroxide with 10 to 30 parts by weight of magnesium hydroxide MgCl ₉ content included.

From a publication by the "Forschungsgemeinschaft Bauen und Wohnen "(1966), volume 80, page 57, it is known that the weight ratios magnesium chloride to magnesium oxide in screed compounds should be around 1: 2.5 to 3.5, but in no case less than 1: 2.

Furthermore, it has already been proposed in OE-PS 29 21 245 to mix magnesium hydroxide with chloride in powder form intimately to form a dry magnesia mortar, the weight ratio of MgO: MgCl _{9 should be} between 0.8 and 2.0. Such dry magnesia mortar masses have the advantage that they can be stored and mixed with water in constant proportions at the place of processing. However, the magnesium hydroxide must be produced separately by a conventional method.

This gave rise to the task of finding a way to enable this separate production of the magnesium hydroxide obsolete for magnesia mortar dry matter without sacrificing the benefits of magnesium hydroxide containing dry masses of magnesia mortar.

A process for the production of a dry, storable binder based on magnesium hydroxide was developed and magnesium salt hydrates found.

Kali und Salz AG / · \ \ . · : [■ - '., ["' 28; July 1982

Thereafter, according to the invention

a) burned in a first stage from magnesite Causter at a temperature of 20 to 100 C. in a weight ratio of 1: 0.7 to 1.5 with returned material (A) from this stage and - based on the MgO content of the Kauster used - mixed with water in a molar ratio of 1: 0.9 to 1.2, for one or stacked for several hours, separated into return goods (A) and product (A), the latter from this first stage is carried out,

b) in a second stage, the product (A) is dried at a temperature of about 150 ° C. and becomes the product (B) marry,

c) in a third stage the product (B) in a weight ratio of 1: 0.6 to 1.5 with magnesium chloride hexahydrate or intimately mixed with magnesium sulfate heptahydrate in a weight ratio of 1: 0.9 to 1.6.

The hydration of magnesite burned causter occurs due to the low reactivity of the in it The magnesium oxide contained therein is considerably slower than, for example, the hydration of quick lime. At temperatures around 20 C, the hydration of the cage is largely complete after four days. These Slow hydration proceeds through a dough-like phase leading to a very late hydration solid mass solidified. According to both the dough-like phase as well as the solidification to a solid mass avoided in that the to be used Causter in a weight ratio of 1: 0.7 to 1.5 returned material is added, which is already largely hydrated is. As a result, the reaction mixture always remains even when the water is subsequently added fine-grained to crumbly, if the amount of water related to the MgO content of the freshly used masticatory

■ * ^c - ^ MnI MnO is 0.9 to 1.2 mol of water.

Kali und Salz AG *. :: '. : '..' "- '" 28 ·. July 1982

The causer is particularly advantageous in this first Process stage with still M / poor return material premixed, whereupon the mixture, preferably in a rotating drum or a paddle mixer, by injecting warm water or blowing in saturated steam to a certain temperature preheated to about 100 ° C. and therein a water content of 0.9 to 1.2 mol per mol of freshly added MgO is set. After a residence time of 1 to 2 hours, the product obtained is converted into returned material (A) and product (A) separated, which are further processed according to the invention.

Even if this resulting hydration product is stacked for one or more hours it can only too with magnesium chloride hexahydrate be mixed with a binder that hardens in a more or less short time on storage.

For this reason, the product (A) becomes the first stage the method of the invention in a second stage at a temperature of about 150 C before it is dried Product (B) is finely ground. That will be beneficial Product (A) in this process stage to a content dried in free water from 8 to 10% by weight and less. The resulting dry material is then Grind fine to the product (B).

The product (B) is then mixed with finely ground magnesium chloride hexahydrate in a weight ratio of 1: 0.6 to 1.5 or in a weight ratio of 1: 0.9 to 1.6 with also finely ground magnesium sulfate heptahydrate to the dry one and storable binder intimately mixed, which is advantageously packed airtight in plastic bags will .

Kali und Salz AG * ::::: "." * · .. · July 25, 1982

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As a stimulator and to shorten the setting time of the binder produced according to the invention, this in a weight ratio of 1: 0.08 to 0.075 additionally active magnesium oxide with an iodine number of 80 to 120 are mixed in. However, the same effect is also achieved if a subset of the product (B), preferably 5 to 20 wt .-? I, briefly, i.e. for about 5 minutes, to a temperature of It is heated to 400 to 450 C and then quickly cooled before moving on to the third stage of the process of the invention is introduced.

By the amount of that contained in the dry mix active magnesium oxide, the time from mixing the dry mixture with water to the start of solidification, as stated in the draft of DIN regulation 273, part 1, of February 1977 and its determination is described, can be varied in such a way that with decreasing Amount of active magnesium oxide increases the time between starting and the start of solidification is, from 10 minutes to 3 hours.

According to the process of the invention, without the need for separate production of magnesium hydroxide dry and storable binders based on magnesium hydroxide and magnesium salt hydrates are generated, which after mixing with water, preferably in amounts of 15 to 30 wt .-? o of the weight of the dry binder, reproducible in the same Set time lag to products with the same mechanical and physical properties.

Lean substances, such as wood shavings, sand, stones, broken glass, car tire chips, into the mix-up be introduced. Here the water

Kali und Salz AG · "* ::": '":'. '.' \ '>-'"28. July 1982

to take into account the absorption of these lean substances and, if necessary, use a correspondingly larger amount of water when mixing.

The manufactured using the invention The paste-like mixture ultimately produced by the binder must be converted into the desired form before the start of solidification te form. The shaped body obtained after setting has the same volume as the shaped body pulpy mass. The method according to the invention opens up the possibility of without separate manufacture of magnesium hydroxide a clearly defined binder in terms of its composition produce that in predetermined times to an efflorescence-free Product of constant volume and excellent mechanical and physical properties sets.

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Kali und Salz AG. ·; _.:.: * · "* - 'July 26, 1982

.: ".. ^: ,. - .. ^:: .. ^: * ^: .- ^: -: _ei: _ _D1 / _ri 3230962

example 1

100 parts by weight of a caustic made of magnesite with 90% by weight of MgO content are 140 parts by weight Return material (A) mixed and incorporated into this mixture 40 parts by weight of water. After that, will the mixture is temporarily stacked for 96 hours and in 140 parts by weight of return material and in 140 parts by weight of product (A) divided.

The product (A) is then brought to a temperature of 150 ° C. in a drying drum and the Free water content of the product reduced to 5% by weight. The dried material then becomes fine as a flour Grind to the product (B).

133 parts by weight of product (B) are mixed with 142 parts by weight of finely ground magnesium chloride hexahydrate and with 8 parts by weight of active magnesium oxide (iodine number 100) mixed intensively and placed in airtight sealed polyethylene bags packaged.

In this packaging, the binding agent can be stored indefinitely and does not lose its binding effect.

100 parts by weight of the binder are mixed with 20 parts by weight Made up of water and shaped into a standard body. The setting of the mass begins 200 minutes later and is finished 260 min afterwards. After 26 days, the standard body has a flexural strength of

2 2

9.2 N / mm and a compressive strength of 38 N / mm.

Kali und Salz AG ■. ;;. . * '..? θ. July 1982

Example 2

110 parts by weight of a caustic made of magnesite with 92% by weight MgQ content are used in the first Stage mixed with 90 parts by weight of return material (A) and this mixture in a rotating drum with hot water sprayed and treated with saturated steam so that the heated to a temperature of 100 C mixture a Water volume of 49.5 Geu. -Share has recorded. To a residence time of 90 min, the mixture is divided into 90 parts by weight of returned material (A) and 159 parts by weight of product (A) divided up.

In the second stage, the 159 parts by weight of product (A) are brought to a content of 150 ° C. at a temperature dried in free water of 4% by weight and fine as flour Grind to product (B). 29 parts by weight of this dry product are quickly raised in a rotary kiln heated to a temperature of 430 C, held at this temperature for a period of 5 minutes and then rapidly cooled to ambient temperature. There remain 25 parts by weight of preheated product (B), which in the third stage with the remaining 116 parts by weight of product (B) and 158 parts by weight of ground magnesium chloride hexahydrate to be intimately mixed with the binder, which is packed in polyethylene bags that are airtight be locked.

In this packaging, the binding agent can be stored indefinitely without losing its binding effect.

100 parts by weight of the binder are mixed with 19 parts by weight of water and formed into a screed. Setting begins 120 minutes thereafter and is completed 280 minutes thereafter. After 26 days, the screed has a flexural tensile strength of 9 N / mm and a compressive strength of 41 N / mm ² .

Claims (5)

Kali und Salz AG * ::::: * .. * '..' ■ : 28. July 1982 Claims J process for the preparation of a dry, storable binder based on magnesium hydroxide and magnesium salt hydrates, characterized in that a) Causter burnt from magnesite in a first stage at a temperature of 20 to 100 ⁰ C in a weight ratio of 1: 0.7 to 1.5 with return material (A) from this stage and - based on the MgQ content of the Kauster used - mixed with water in a molar ratio of 1: 0.9 to 1.2, temporarily stacked for one or more hours, separated into return material (A) and product (A), the latter being carried out from this first stage, b) in a second stage, the product (A) is dried at a temperature of about 150 ° C. and becomes the product (B) is married, c) in a third stage the product (B) in the Weight ratio from 1: 0.6 to 1.5 with magnesium chloride hexahydrate or in a weight ratio of 1: 0.9 to 1.6 with magnesium sulfate heptahydrate is intimately mixed. 2. The method according to claim 1, characterized in that in step a) the caustic is premixed with warm return material, in which the water content is adjusted by adding water and / or steam, and afterwards, in which the mixture is heated to a temperature of about 100 C and is agitated vigorously the product (A) separated from this mixture is introduced into stage b) with a residence time of 1 to 2 hours. Potash and Salt Ad ■ .'-..- 'ZB. July 1982 3. Process according to Claims 1 to 2, characterized in that the product (A) in step (b) is dried to a free water content of 8 to 10% . 4. Process according to Claims 1 to 3, characterized in that active magnesium oxide with an iodine number of 80 to 120 is additionally admixed with the product in stage c) in a weight ratio of 1: 0.08 to 0.075. 5. The method according to claims 1 to 3, characterized in that a portion of the product (B) is briefly heated to a temperature of 400 to 450 C and then rapidly cooled down.