DE3230962C2 - Process for the production of a binder based on hydrated magnesium oxide - Google Patents

Abstract

A process for the production of a dry and storable binder on the basis of magnesium hydroxide and magnesium salt hydrates is described, according to which a caustic mixed with returned material and burned from magnesite is treated with water at temperatures of up to 100 ° C, then dried and with magnesium chloride hexahydrate or magnesium chloride hexahydrate. Magnesium sulfate heptahydrate is intensively mixed dry.

Description

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 (RA) from this stage and - based on the MgO content of the Kauster used - mixed with water in a molar ratio of 1: 03 to 1.2, temporarily stacked for one or more hours, separated into return material (RA) 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 approx. 150 0} C and ground to the product (B),

c) in a third stage the product (B) is intimately mixed in a weight ratio of 1: 0.6 to 13 with magnesium chloride hexahydrate or in a weight ratio of 1 : 0 to 1.6 with magnesium sulfate heptahydrate.

2. The method according to claim 1, characterized in that in step a) the Kauster premixed with warm return material, in the ^{heated to a temperature of about 100 0} C and vigorously agitated mixture of the water content is adjusted by supplying water and / or steam and after a residence time of 1 to 2 hours, the product (A) separated from this mixture is introduced into stage b).

3. Process according to Claims 1 to 2, characterized in that the product (A) in step b) a free water content of 8 to 10% is dried.

4. Process according to Claims 1 to 3, characterized in that the product in step c) in a weight ratio 1: 0.08 to 0.075 active magnesium oxide with an iodine number of 80 to 120 in addition is admixed.

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 0} C, then quickly cooled and introduced into the third stage.

Magnesia cements, which are also known as Sorel cements, can be known by mixing of caustic burned magnesite, the so-called caustic, and magnesium chloride solution or magnesium chloride hexahydrate and water or magnesium sulfate solution can be produced. Since the setting of the mixture begins with this mixing, this mixture can only be prepared on site. By adding aggregates, how sand, especially a certain grain structure, is formed into such magnesia-cement mixes Mortar that can be processed into interior construction floors with a particularly high load-bearing capacity. There such a Mortar also contains organic fibers such as wood flour or wood shavings, trouble-free and without any significant reduction in strength integrates, it can advantageously be used to manufacture elastic and heat-insulating floors will.

For the preparation of these magnesia cements or mortars, however, difficulties arise from the The fact that the so-called causter even if the magnesite comes from a deposit from batch

ίο there are considerable deviations in its composition for each batch and can have in its properties on which the magnesia cement or mortar masses react sensitively. For these reasons it is necessary to process a new Kauster batch on magnesia cement or mortar Voi Investigations to set the optimal MgO-MgCb-H2O ratio in each case perform.

Another technical difficulty is the heat released during the exothermic reaction of the magnesium oxide with the magnesium chloride and water during the processing of magnesia cements, which is dependent on the reaction rate, which is determined by the activity of the caustic. If, when processing Magncsia cements, it is not possible to dissipate the heat of reaction in a certain ratio to its generation from the magnesia-cement mixture, the resulting products tend to form undesirable cracks.
In order to solve these problems, DE-PS 7 39 164 recommends using magnesium hydroxide in magnesia cements instead of magnesium oxide or Kauster. To do this, however, it is necessary to use a magnesium chloride solution of such a concentration that the magnesium chloride concentration in the mixture, including the water introduced with the magnesium hydroxide, is between 21 and 27% by weight. The rate of formation of the oxychloride can be accelerated according to this process by adding measured amounts of active magnesium oxide. However, this process also requires special care with regard to maintaining the proportions of the starting materials and their particularly thorough mixing, which can only be carried out on site by particularly experienced specialists.

In order to reduce the problems of processing magnesia cements here too, DE-PS 8 32 565 describes a dry premix for processing as magnesia cement. These premixes are made from aqueous mixtures of magnesium hydroxide and magnesium chloride solution Obtain drainage, with free magnesium hydroxide and chloride in addition to the oxychloride formed must be preserved. These dry premixes may need more at the place of processing Mixing of aggregates, only to be mixed and processed with water.

According to DE-PS 8 39 622, this procedure is varied in that pastes of magnesium hydroxide and chloride solutions are used which contain 100 to 700 parts by weight of magnesium chloride solution with 10 to 30% by weight of MgCl _{2 per 100 parts by weight of magnesium hydroxide} Content included.

From a publication by the "Research Association for Building and Living" (1966), issue 80, page 57, is known that the weight ratio of magnesium chloride to magnesium oxide in screed masses is about 1: 2.5 up to 3.5, but under no circumstances should be less than 1: 2.

It has also been proposed in DE-PS 29 21 245 to intimately mix magnesium hydroxide with chloride in powder form to form a dry magnesia mortar, the weight ratio of MgO: MgCl _{2 being} 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 that 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.

It has been a method of preparing a dry, storable binder based on magnesium hydroxide UNII magnesium salt hydrates found h w'rd eriindun ^cT s ^CT eniäß

a) in a first stage from magnesite erbrannter caustic at a temperature of 20 to 100 ⁰ C in the weight ratio 1: 0.7 to 14, with recycled material (A) of this stage and - based on the MgO content of the Kausters used - in a molar ratio 1: 0.9 to 1.2 mixed with water, temporarily stacked for one or more hours, separated into return goods (RA) and product (A), the latter being carried out from this first step,

b) in a second stage the product (A) is ^{dried at a temperature of approx. 150 0} C and ground to the product (B),

c) in a third stage, the product (B) is intimately mixed in a weight ratio of 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

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. This slow one. Hydration proceeds via a dough-like phase that becomes a towards the end of hydration very solid mass solidified. According to the invention, both the dough-like phase and the solidification become too a solid mass avoided by adding the caustic to be used in a weight ratio of 1: 0.7 to 1.5 Return material that is already largely hydrated is mixed in. This means that the reaction mixture also remains In the subsequent admixture of the water always fine-grained to crumbly, if the on the MgO content of the freshly used Kauster amount of water per mole of MgO is 0.9 to 1.2 moles of water.

Particularly advantageously, the caustic is vorgemisciit in this first process stage with still warm return material and the mixture, preferably preheated in a rotating drum or a paddle mixer, by spraying warm water or blowing in saturated steam at a temperature of about 100 ⁰ C and therein per mole freshly supplied MgO is adjusted to a water content of 0.9 to 1.2 mol. After a residence time of 1 to 2 hours, the product obtained is separated into return material (RA) and product (A), which are further processed according to the invention.

Even if this resulting hydration product is stacked for one or more hours it can only be mixed with magnesium chloride hexahydrate to form a binder that is used in Storage hardened in a more or less short time

For this reason, the product (A) of the first stage of the process of the invention in a second stage at a temperature of about 150 ⁰ C dried

ίο before it is finely ground to product (B). Advantageous the product (A) in this process stage to a free water content of 8 to 10 wt .-% and less dried The dry material obtained in this way is then ground until the product (B) is fine.

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 likewise finely ground magnesium sulfate heptahydrate mixed intimately with the dry and storable binder, advantageously in plastic sacks is packed airtight.

As a stimulator and to shorten the setting time of the binder produced according to the invention, active magnesium oxide with an iodine number of 80 to 120 can additionally be added to it in a weight ratio of 1: 0.08 to 0.075. The same effect is, however, also be achieved if ε'κ-e subset of the product (B), preferably 5 to 20 wt .-%, for a short time, ie, about for a period of 5 min, to a temperature of 400 to 450 ⁰ C. heated and then rapidly cooled before being introduced into the third stage of the process of the invention.

The amount of active magnesium oxide contained in the dry mix can reduce the time it takes to get it on the dry mixture with water until the start of solidification, as described in the draft of the DIN regulation 273, Part 1, of February 1977 and its purpose is described, can be varied in such a way that that with decreasing amount of active magnesium oxide, the time between starting and the start of solidification is extended, namely 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% by weight of the weight of the dry binder, reproducible in the same time interval as products of the same mechanical and physical properties.

Lean substances such as wood chips, Sand, stones, broken glass, and car tire chips can be added to the mix. Here is the The water absorption capacity of these lean substances must be taken into account and, if necessary, when mixing to use a correspondingly larger amount of water.

The pulpy mixture ultimately produced using the binder produced according to the invention must be brought into the desired shape before solidification begins. The one after setting The molded body obtained has the same volume as the molded pulp-like mass. The inventive Process opens up the possibility of a regarding without a separate production of magnesium hydroxide its composition clearly defined

demittel to generate that in predetermined times an efflorescence-free product of constant volume and excellent mechanical and physical properties

example 1

lOOGew.-parts one? made of magnesite with 90% by weight MgO content burned Kausters are mixed with 140 parts by weight of return material (RA) and in this to Mixture incorporated 40 parts by weight of water. Then the mixture is stacked for 96 hours and in 140 parts by weight of returned material and divided into 140 parts by weight of product (A)

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 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 as well as intensively mixed with 8 parts by weight of acVvem magnesium oxide (iodine number 100) and sealed in airtight sealed polyethylene bags packed

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 of water and shaped into a standard body. Setting of the mass begins 200 minutes later and is completed 260 minutes later. After 26 days, the standard body has a flexural strength of 9.2 N / mm ² and a compressive strength of 38 N / n in the ² .

Example 2

35

110 parts by weight of a caustic made of magnesite with 92% by weight of MgO content are mixed in the first stage with 90 parts by weight of return material (RA) and this mixture is sprayed with hot water in a rotating drum and treated with saturated steam in such a way that that the heated to a temperature of 100 ⁰ C mixture has absorbed an amount of water of 49.5 parts by weight. After a residence time of 90 minutes, the mixture is divided into 90 parts by weight of returned material (A) and 159 parts by weight of product (A)

In the second stage, 159 parts by weight Product (A) are ground at a temperature of 150 ⁰ C to a content of free Waser of 4 wt .-% flour dried and finely product (B). From this Trokkenprodukt 29 parts by weight are heated in a rotary kiln rapidly to a temperature of 430 ⁰ C, for a period of 5 min at this temperature and then rapidly cooled to ambient temperature, there remain 25 parts by weight between heated product (B) , which are intimately mixed 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 form the binder, which is packed in polyethylene sacks that are hermetically sealed.

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 later and is completed 20 minutes later. After 26 days, the screed has a flexural tensile strength of 9 N / mm ² and a compressive strength of 41 N / mm ² .

Claims (1)

Patent claims: 1. Process for the production of a dry, storable Binder based on magnesium hydroxide and magnesium salt hydrates Mixing of the components in a weight ratio of less than 2, characterized in that that