SK39694A3 - Method of production of stiffnesses and transparental siliceous filler - Google Patents

Abstract

siliceous filler the produces from solutions silicates al alkaline, metal and of hydrochloric in two degrees. Types degree my two steps grounded in adding different quantity sour sol to solution of silicate. After each uploads sour sol the formation Nuta suspension allowed ripen 10 until 50 minutes, while her pH the keeps on the worth higher than 10 and then the sus pension neutralizes acid, acid to h sheet music PHA Second After neutralization suspension the pH back adjust on the value 5 until 6.8 adding hydroxide sodium him, hydroxide carbonate or hydroxide ammonium

Description

Technical field

The invention relates to a process for the production of a solidified silica filler from solutions of alkali metal silicates and hydrochloric acid in several rings.

The prior art

The prior art processes for the production of precipitated siliceous fillers are based on aqueous solutions of alkali metal silicates, most commonly sodium silicate, i. water glass. These solutions react with acids to precipitate a fine silica hydrogel (GB 1 105 618 and 1 132 831, respectively). In other processes, the silicate solution is treated with acids in the presence of precipitants e.g. sodium chloride (GB 1,043,282).

According to U.S. Pat. No. 2,601,235, a silica hydrogel is prepared by simultaneous addition of dilute waterglass and sulfuric acid to an alkali silica sol at well-defined concentration levels. time and temperature conditions. Other known processes for precipitating a silica hydrogel from a sodium silicate solution use acid-reactive gases such as e.g. sulfur dioxide or carbon dioxide (GB 945 523, 1 122 588, 1 122 589 and DE 1 117 552, respectively). A different process is described in CS 239 831, in which the siliceous filler is prepared by a two-step neutralization of the silicate using an acidic silica sol. The resulting hydrogel suspension is finally neutralized to pH 5 to 4 with acid. The disadvantage of this process is that the silica filler thus prepared has a relatively low transparency in the rubber mixtures.

SUMMARY OF THE INVENTION

The aforementioned drawbacks are eliminated by the process for the production of the reinforcing and transparent silica filler according to the invention, which is based on this. that the filler is prepared with solutions of alkali metal silicates and inorganic acids (e.g. hydrochloric acid). In the first step, an acidic silica sol solution is prepared by mixing the silicate solution into an acid solution, which in the second step is mixed at temperatures above 90 ° C with another silicate solution in two steps. In the first step, 30-50% of the volume of the acid sol is admixed and in the second 50-70% of the volume of the acid sol, followed by a ripening period of 10 to 50 minutes, maintaining the pH of the resulting suspension above 10, then neutralizing the suspension with acid. (e.g. hydrochloric acid), the neutralization being brought to pH i 2.

After the final neutralization of the suspension to pH 2, the pH can be brought back to a pH of 5 to 6.8 with an alkaline-reactive salt solution selected from the group consisting of sodium hydroxide, potassium hydroxide or ammonium hydroxide. It has been found that it is also possible to add an acidic electrolyte-containing silica sol, selected from the group consisting of alkali metal chlorides, preferably sodium chloride, which is prepared by adding the electrolyte to the inorganic acid solution and / or acid solo directly.

Exemplary S uctio n e n e n e n e n e

Example 1

1300 liters of water are added to the 1200 liters of 37% (w / w) hydrochloric acid present in the reactor and 4150 liters of sodium silicate solution with a silica to sodium oxide ratio in mol% equal to or greater than 3.1 are added with vigorous stirring, the added sodium silicate is 13.4 wt%.

The resulting acid sol of silicic acid is added to 26,400 liters of ounium silicate solution. which contains 5.5% by weight of silica and is heated to 95 ° C in the lance by adding 2100 liters of acid sol over 15 days. The hot reads: - leave for 20 min. aging, with gentle stirring at a temperature of at least 93 ^c, no. then, for 20 minutes, with stirring, the pH is 4449 liters of acid sol. The temperature is maintained at about 95 ° C and the pH of the suspension after addition of all the sol is above 10 / month and aged with gentle stirring for a further 30 minutes, then diluted dilute saline acid is added over a period of about 10 minutes. the suspension reaches a value of 2. The suspension is then converted into a filter press, freed from the mother liquor and washed thoroughly with water. Finally, they are dried and crushed to the desired grain size.

Example

To 1190 liters of water glass having a density of 1.36 to 1.38 g ^-3 is added 1290 liters of water. to form a dilute sodium silicate solution containing 12 to 16 wt% silica.

of concentrated hydrochloric acid flow by dilution in the reactor, 2780 liters of hydrochloric acid having a concentration of 10-14 wt% HCl are prepared. The above diluted water glass solution is metered into this dilute acid with stirring and at room temperature to form an acidic silica sol. The second reactor was charged with 2000 liters of 1.38 g- ³ water glass, which was diluted with 14900 liters of water. The reactor is heated to a temperature close to the boiling point (96-98 ° C) and 2300 liters of acid sol are continuously added to the hot water glass solution with stirring over 10 minutes. After 10 minutes, the temperature of the mixture in the reactor matures for more than 92 minutes

while the pH of the suspension remains above 10. The suspension is aged again at a temperature of about 95 ° C for 45 minutes, then neutralized with concentrated hydrochloric acid to a further 15 ° C over the course of

2960 liters of acid solo.

oH value equal to. The suspension was allowed to cool. Filter on a wash and wash with water. The filter cake is washed with water and the suspension is dried in a spray dryer

P r i K .1 and h 3

The procedure was as in Example 1, except that the neutralized suspension at pH 7 was back-adjusted to pH 5-6.8 with sodium or ammonium hydroxide solution prior to filtration.

Example 4

The procedure is as in Example 2, except that 300 kg of sodium chloride is dissolved in a dilute hydrochloric acid solution for the preparation of the acid sol.

Example 5

The procedure is as in Example 2 with the difference. that 350 kg of potassium chloride is dissolved in the acid sol.

Industry usability

The filler prepared according to the invention can be used in the rubber industry for mixing into rubber mixtures.

Claims (3)

L. A process for the production of a reinforcing and transparent silica additive from a solution of alkali metal silicates and hydrochloric acid, in which, in a first stage, an acidic silica sol solution is prepared by mixing the silicate solution into an acid solution which is mixed in a second stage at temperatures. above 90 ^l 'T. with a further silicate solution in two steps, in the first step 30 to 50% by volume of the acid sol and in the second step 50 to 70% by volume of the acid sol to the silicate solution, characterized in that after each addition of the acidic silica sol the suspension is left It matures for 10 to 50 minutes, maintaining the pH of the maturing suspension at a value greater than 10, and then neutralizing the suspension with a hydrochloric acid solution to a pH of 5. 2.0. The process for producing a reinforcing and transparent silica filler according to claim 1, characterized in that after the suspension has been neutralized to a pH of 2, the pH is readjusted to a value of 5 reacting salt solutions including sodium hydroxide, ammonium hydroxide. with addition of an alkali selected from the group of potassium hydroxide or A process for producing a reinforcing and transparent silica filler according to claim 1, characterized in that an acidic electrolyte-containing silica sol selected from the group of salts of strong acids and alkali metals, preferably sodium chloride, is added.