DD154097A1 - METHOD FOR PRODUCING MAGNESIUM OXIDE FOR SYNTHESIS RUBBER - Google Patents

Abstract

The invention relates to the preparation of an effective magnesia blend component for d. Vulkanisationsregelnden addition in Polychloroprenmischungen. The aim of the invention is to reduce the expense of producing the active ingredient MgO in magnesium oxide dispersions in such a way that the usual wet-chemical redistribution process via the magnesium bicarbonate is avoided. The object is to design the manufacturing process so that the product has the same use value for Polychloroprenmischungen as the previously used umgefaellte product. Magnesium carbonate-containing raw materials or secondary raw materials, which are given a particularly fine-crystalline and surface-active state by gentle firing conditions, are gently comminuted with simultaneous air classification. Certain fine fractions, which have a particularly high specific surface, are separated and kneaded with organic paste excipients to vulkanisationsregelnden oxide paste. The invention can be used to convert magnesium carbonate raw material or secondary raw material directly into a well suited MgO active ingredient for dispersions which, e.g. T. also in the presence of zinc oxide, in polychloroprene mixtures has age-protective effect.

Description

224 937 - * -

Process for the preparation of magnesium oxide for synthetic rubbers

Field of application of the invention

The invention relates to a process for the preparation of vinylalkoxide which is used as an additive in elastomers, in particular polychloroprene mixtures for inhibiting scorching or as protection against tarnishing.

Characteristic of the known technical solutions It is known that in the vulcanization of elastomers, in particular polychloroprene mixtures, premature scorching can be prevented by the addition of magnesium oxide with certain properties. For the curing of such polymers, it is also common to use mixtures of magnesium oxide with zinc oxide.

The disadvantages of the application of the oxides in powder form, in particular their poor distribution in the vulcanizate, which leads to inhomogeneity and thus to quality fluctuations, are known to be overcome by dispersion of the metal oxides in suitable organic substances. For this purpose the chemicals intended for use in coated form are used. For the purpose of homogenization and increase in effectiveness, plasticizers, surface-active agents and metal soaps or fatty acids are contained in the metal oxide materials used as pastes or dispersions.

These application forms have eliminated the quality losses that have occurred in the final product and reduced the magnesium oxide content per 100 parts of elastomer from 4 to 3 parts. To achieve this purpose, a magnesium oxide is used

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which is characterized by a high specific surface area and activity ·

 Such magnesium oxides are now obtained by a process which, depending on the raw material, is always carried out according to the same costly principle. The process is the so-called "PATTIRSOII Seeing Process", i. to the extraction of magnesium oxide by way of production of magnesium hydrogen carbonate solution by leaching of magnesium oxide or hydroxide-containing suspensions, cleaning the alkalis, their boiling and preparation to the basic carbonate with Piltrations- and drying process, as well as its calcination and grinding to oxide powder. From the basic magnesium carbonate produced during the dissolving process, particularly surface-active magnesium oxide species can be obtained by appropriate control of the process conditions. This possibility results from the fact that the ITetzbenebenständo in the crystal lattice of the carbonate are about twice as large, ie those which theoretically derived from the oxide obtained therefrom get. With careful thermal cleavage of the carbonate can therefore be obtained a fine-pored, active intermediate stage. This modification represents the product which is used for the elastomers, in particular polychloroprene missions as magnesium oxide powder, paste or dispersion on the basis of its preferred physical properties.

The operation of this Umlöseprozesees is associated with a high process, cost and energy consumption and high material losses, so that the high price of the magnesia pastes or magnesium oxide / zinc oxide pastes is essentially determined because of this costly mixture component »

Aim of the invention

It is an object of the invention to eliminate the disadvantages of the prior art described and to find ways to produce magnesium oxide modifications which, when used in elastomers, in particular polychloroprene mixtures, give the paste form or as a dispersion the same positive effects, but over the prior art less process, cost and energy consuming to produce are ·

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224 937

Explanation of the ", reading of the penance

The Erfindimg has for its object to develop a process for the preparation of magnesium oxide, bypassing the wet chemical route, in which is obtained using the well-known in the prior art crystallographic principle for producing an intermediate state in the crystal lattice active magnesium oxide

It has now surprisingly been found that in the milling of raw magnesia fired under mild conditions, easily miscible fractions are obtained having the same physical properties as known from the redissolved oxide and required for the preparation of effective magnesia pastes for elastomers, in particular polychloroprene blends and dispersions become·

The object is therefore achieved according to the invention by a method in which crude, naturally occurring Kagnesiumkarbonat or magnesiunikarbonathaltiger secondary raw material is treated so gently, that although the bound carbon dioxide is excreted from the material for the most part, but the energy supplied not to form the crystalline oxide sufficient. Suitably, this is done in the 77eise _r that broken the material and 700-950 ⁰ C in conventional combustion facilities, such as is fired in a shaft furnace or rotary kilns, the abhängende on the residence time in the combustion zone and the Ctückgröße of the raw material most favorable temperature setting after measurable Properties of the produced oxide, such as the highest possible dissolution rate or Ilydratisierungsgeschwindigkeit to optimize. The resulting Branntgut is gently milled while simultaneously V / indsichtung in a spring roll grinding plant. The fraction obtained by air classification below 0.1 mm, advantageously below 0.04 mm, is used according to the invention for the production of the oxide pastes and for this purpose alone or in mixture with.! .Lagnesium oxide powders or magnesium oxide and zinc oxide powder mixtures in a submitted known mixture of organic pasta carriers incorporated «

embodiments

1 «Türkischei gelmagnesite is used in the jaw crusher on an in

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! Kiln processed by piece size broken * The grain bonding after the crusher is supposed to

for Schachtofenaurohratz 5 to 10 cm

for rotary kiln throughput be 10 to 30 mm.

After breaking the Rohmagagnesitgestein is burned at about 800 ⁰ C in the shaft furnace or rotary kiln, the exact temperature management is adapted to the residence time of the magnesite in the combustion zone of the furnace. The setting of the necessary firing conditions, in particular the temperature range, is determined kinetically, ie by determining the rate of dissolution of a sample of the spent material in acid, which must be as high as possible.

The burned material discharged from the kiln, which still contains about 3 to 4 mass% bound COp as a result of the gentle firing conditions, is coarsely crushed on the crusher after cooling and finely ground and sighted on a roller mill with a classifier. In the particle size range of 0.000 to 0.100 mm diameter, specific BET specific surface areas were measured on selected fired magnesite fractions: less than 0.100 mm 20 m 2 / g less than 0.040 mm 29 m 2 / g.

Magnesium oxide produced after the dissolving process has comparatively .specific surfaces around 15 to 25

In a Doppelmuldenknoter 23.5 kg plasticizer SE and 1.5 kg Rofacid TG5 are mixed while heated to 60 ⁰ C to this mixture 75 'kg of the Peinfraktion less than 0.040 mm added in portions and kneaded until a homogeneous pasty mixture is "

In a Polychloroprenvulkanisat according to conventional recipe, but with the application of 4 mass $ of this paste as KgO-. Component was produced, no age effect could be demonstrated »

2. Dried pulping and pilfer residues from the PATTIIiSON re-dissolving process are crushed in the roll crusher to a particle size of less than 20 mm ». The broken dry material is heated in a rotary kiln at 900 ^° C. and 10 minutes residence time in the burning zone of the

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Stove burned gently. After being cooled, the partially deacidified burned material is finely ground and sifted on a peder roll mill with classifier »

In the particle size range of less than 0.100 mm Durclimesser specific surface areas were measured at the aligned fraction of BET in the amount of

25 to 30 m ² / g measured.

The magnesium oxide obtained is processed with obtained according to Example 1 magnesium oxide and magnesium oxide from the redissolution process in the ratio 30:20:50 as described in Example 1 to a homogeneous pasty mixture.

In a polychloroprene vulcanizate according to a conventional formulation, which was prepared using 4% by mass of this paste as MgO component, no aging effect could be detected.

Claims (2)

'4 9Z7'6- He fi nds π or ucb 1, Process for the preparation of magnesium oxide for synthetic rubber, characterized in that magnesium karbonai; -containing raw material ejnem a gentle firing process at temperatures between 700 'and S50 ⁰ C subjected to vjird, the resulting Branntgut is ground and anechließend the leichtmahl bar en shares with a particle diameter less than 0.1 μm, preferably less than 0.04 mm. 2 ,. 1. The method of item, characterized in that _f magnesiuinhaltige as raw materials magneait-unkarbonathaltige raagneciumlcarbonathaltige residues or secondary raw materials for Anwcndi ^ ig Koumen. Process according to items 1 and 2 ^, characterized in that the grinding takes place gently, preferably in a Pederrollenmahlanlage in combination with an air classification.