DE1542626A1 - Process for the manufacture of silicon dioxide - Google Patents

Description

concerning processes for the production of silicon dioxide »

The invention relates to the production of silicon » dioxydο

The process for producing finely divided silicon dioxide, which is suitable, among other things, as a filter aid and as a falling agent for paints or varnishes, plastics and paper, consists essentially of digesting sepiolite (meerschaum) with aqueous mineral acid. Sepiolite is a hydrated magnesium silicate mineral. The effect of such SSuredigerierung consists in extracting

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ID ^ ZOZO

and soluble in the magnesium and hydroxyl content as well of the extractable impurities, such as iron, which is present in the sepiolite, so that essentially pure silicon dioxide remains as a solid residue that is easily removed. separated, dried and ground.

The sepiolite can be used in granulated form, but it is preferably finely divided, for example so that the particles can pass through a sieve with a mesh size of 0.152; 0.076 or 0.038 mm (100, 200, or 400 BS mesh).

According to a preferred embodiment of the method finely distributed sepiolite, which is expediently passed through a sieve with mesh size of 0.152 mm (100 BS) is processed into a dilute aqueous slurry using a high speed stirrer with aqueous hydrochloric acid being added to the slurry so that a final solids content of no more than 5 6ew. % adjusts. The amount and Concentration of the acid added can be varied within wide limits, but it is preferred that the acidified mash is at least 1 normal

The acidified porridge is then boiled, preferably under reflux conditions ο When using 1 normal acid

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the extraction is normally essentially complete after 10 minutes of boiling. Usually there is no partially achieved if you cook for longer than 30 minutes · Slightly longer cooking times should be achieved with lower acid concentrations be respected. Even though acid values higher than 1 η can be used, they do not, however, give any appreciable advantage in terms of the cooking time when using of 1 η acid is required * Any strong, inorganic acid can be used for extraction, e.g. Hydrochloric acid, Sulfuric acid or nitric acid. Of these acids, hydrochloric acid is preferred.

When the cooking level is finished, the remaining, solid Material separated by filtering, decanting, centrifuging or another suitable method · It is then washed and dried. Washing the separated Th solid material with water can be followed by washing with an organic solvent that is miscible with water, such as ethyl alcohol (methylated spirit) or acetone, in order to remove water from the material «In this case the organic solvent can be removed from the material by heating to lower temperatures than them to remove ron water are needed «At temperatures, which are required to dry the material that comes with

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Water alone has been washed, eB "80 ⁰ C or above, there is a tendency for the particles to agglomerate, which is why the finished product is more difficult to grind"

The following examples serve to explain the invention according to the procedure ",

Example 1:

A 0.152 mm (100 BS) mesh size sepiolite was used in Water dispersed using a high speed stirrer until a 7.5 weight percent dispersion was obtained. Portions of this dispersion, weighing ron 53.76 g, were placed in a conical flask and with 25 ml of 3 η Hydrochloric acid added. The concentration of acid in the mixture was 1 normal, and the mixture contained 5% by weight Solids. A condenser was inserted into the neck of the flask * and different samples of the porridge were cooked for different times. The contents of the flask were swirled by hand until the boiling point was reached »At this stage the viscosity of the pulp was eliminated and the mixture was boiled vigorously with no further stirring required was "

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When the boiling was stopped, the flask was cooled to about 50 ° C and the slurry was sucked through a weighed filter paper. The residue was washed with 100 ml of hot water and sucked dry. The filter cake and the filter paper were removed and dried in an oven at 150 ⁰ C. A non-acidified sample (53.75 g) of the pulp was filtered and dried in this manner to determine the dry sepiolite content of the pulp.The following results were obtained:

cooking time
Min. Residue
(G) Weight loss
(G) Percentage loss
on dry se-
piolit 0 3,321 ti? 10 2,190 Iol31 34.1 20th 2.145 1,186 35o7 40 2.117 1,204 36.3 80 1,690 1,651 49.1

The weight percent loss after 20 and 40 hours of long cooking, that is approximately 36 %, is essentially in accordance with the theoretical weight loss, 33%, calculated on the basis that sepiolite is a pure material and essentially that all of the magnesium and the lattice hydroxyl content was extracted. The difference is due to the present

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OfHGiNAL INSPECTED

▼ on extractable impurities, such as bise, in the sepiolite used. The further weight loss the 80 minutes of boiling may be due to the peptization of the silicon dioxide. This reduces the Yield of silicon dioxide obtained, and cooking should not continue beyond the point at which the magnesium and lattice hydroxyl content of the sepiolite is extracted has been,

Example 2t

716 g of a 7.5% pulp of undried sepiolite with a mesh size of 0.152 nt ClOO BS) in water were refluxed with 333 ml of 3 η hydrochloric acid for 20 minutes. The mixture was ^{cooled to about 50 °} C. and filtered. The residue was washed with hot, distilled water, redispersed in hot water, the dispersion was divided into two parts and each part was filtered again.

The residue from the first portion (sample A) was ^{dried in an oven at 80 °} C .; a hard, compact mass was obtained which could only be ground with difficulty

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OfHGlNAl INSPECTED

The residue of the "broad fraction (sample B) was washed twice on the filter" it hot, methyl i th he fuel and washed twice with acetone and then dried in oven at 60 ⁰ C. The product obtained could be easily pulverized with the exception of a few isolated hard lumps.

The apparent specific gravity and oil absorption of Samples A and B were determined and compared with the values of commercial silica used under the Trade names "Tluosil" and "Gasil" are available says «The following results were obtained;

sample 0.152 «κ
(100 msh) Spec "weight (o / ml) Sample A 0.053 m
(300 mesh} 0.16 Sample A 0.053 ma.
(300 «esh) 0 "13 Sample B default 0.077 Fluosil 23 0.066 Gaeil 644 0.045 Gasir 35 0.113 Gaeil 64 0.165 Gasll 93 0.171 Gasil 937 0.191 Gasil 200 1,224 Gasil 0.40

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The linseed oil absorption was determined according to the information in British Standard Specification B ₀ p. 1795: 1952 Appendix C; the following results were obtained:

Ölabsorptlon Sample Wt.%

Sample B default 130-140 Fluosil 23 190 Gasil 644 270 Gasil 64 160 Gasil 160 Example 3:

A 1 η sulfuric acid solution was made from 15.4 kg (34 lbs.) Of 98% sulfuric acid in 291 l (64 gallons) of water. To this stirred acid solution was added 15.9 kg (35 lbs.) Of sepiolite which had been ground to a particle size of 5 to 10 μm. A slurry was obtained with an initial solids content of 5% by weight. The slurry was brought to the boiling point and refluxed for 20 minutes. After cooling to room temperature, the solid silica residue was filtered off, washed with water and dried at 105 ° C. for 12 hours. The silica yield was 10.093 kg (22.25 lbs. ") Which corresponds to a weight loss of 36.4%.

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OFHGiNAL INSPECTEO

The product had after grinding in a hammer mill an apparent specific gravity of 0.08 g / nl and an oil absorption value of 161%.

Claims

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Claims (5)

Claims 1. Process for the manufacture of silicon dioxide, thereby characterized in that sepiolite is digested with aqueous mineral acid and the insoluble silicon dioxide residue is removed isolated from the mix 2. The method according to Ansoruch 1, characterized in that sepiolite is used, which by a sieve with a mesh size of 0.152; 0.076 or 0.088 ml works " 3. The method according to claim 1 or 2, characterized in that » mark i ch.net that you can use a mineral acid adding dilute aqueous paste of sepiolite " 4 «, method according to claim 1 to 3, characterized in that the concentration of Keeps mineral acid in the initial mixture of sepiolite and aqueous mineral acid at at least 1 normal o 5. Method according to Anaprv.ch 1 to 4, thereby cy β mark The mineral acid used is hydrochloric acid. 0098U / 1569 BATH ORIGINAL - Ii - 6 _O method according Änsoruch 1 to 5, characterized geke η η is characterized in that one uses a starting mixture of sepiolite and aqueous mineral acid, the solid content is not more than 5 wt.%. 7ο The method according to claim 1 to 6, characterized in that one after the insoluble residue the separation of the mixture first with water and then with a water-miscible organic solvent washes and finally dries " 009814/1569 BATH ORIGINAL