DE2505713C2 - Improvement of the filtration of titanium dioxide hydrolyzate sludge - Google Patents

Description

35

assume, where / ι = 0 to 10 and Rj = H or CH), with the provisos that only R ₁ or R _{2 is} a Ci- to C ₁ -alkyl radical and when X is NR ₁ R ₂ , R is not Assumes importance of an alkoxy radical.

3. The method according to any one of claims 1 to 2, characterized in that the filter aids are added in amounts of 0.01 to 1 wt .-%, based on the TiO ₂ solids content of the suspension.

4. The method according to any one of claims 1 to 3, characterized in that the filter aid at * 5 is added at a temperature of more than 30 ° C.

5. The method according to any one of claims I to 3, characterized in that the addition of the organosulfur compounds takes place during or after the hydrolysis of titanium sulfate solutions.

6. The method according to any one of claims I to 4, characterized in that 0.02 to 0.5 wt .-%, based on TiO ₂ solids content of the suspension of a Ci ₂ - to Cu-alkylsulfonic acid mixture are added to the titanium dioxide llydrolyzate suspension.

7. The method according to any one of claims I to 4, characterized in that 0.02 to 0.5 wt .-%, based on TiO ₂ solids content of the suspension of a Ci ₂ - to Cu-alkylarylsulfonic acid mixture for the titanium dioxide hydrolyzate suspension / jgcsetzt . ^ O

65

Today, titanium dioxide pigments are manufactured using the chloride or cleavage process. In the SuI-fat method, TlO ₂ raw materials, e.g. B. llmenite. Leucoxene or rutile or products enriched with TiO> such as slag digested with sulfuric acid and converted into soluble metal sulphates - During the digestion of the raw materials, a digestion cake is formed, which is dissolved with water and separated from the gangue and undigested parts and then fed to the hydrolysis.

The hydrolysis is carried out by heating to temperatures of 90 ° C. or above with generation or addition of germs. The formed titanium dioxide hydrai is filtered, washed, in the presence of reducing substances bleached and after adjusting with doping substances burned to pigment.

An essential and laborious step during the Production involves separating the titanium dioxide hydrolyzate from the mother liquor (»dilute acid«). Since particularly finely divided products are present here, complex processes have to be used. Technically the problem was solved by using plate filters. Filtration and washing of the titanium dioxide hydrolysates this method is expensive and time consuming. Long loading and washing times are included the use of the filter plates is necessary. Furthermore, considerable filtration losses occur in this process due to finely divided product that runs through the filter and thus gets into the dilute acid. Such product proportions are lost for pigment production, affect the economy of the process and burden the subsequent work-up of the waste dilute acid.

In DE-OS a process for the production of titanium dioxide by hydrolysis of titanium sulfate is described, in which the titanium sulfate solution prior to hydrolysis with a polymer or copolymer of an ester of Acrylic or methacrylic acid is mixed with an amino alcohol of a certain formula. That remaining in solution Flocculant thus also has an effect on the filtration of the hydrolyzate.

From US-PS 30 23 162 it is known that in the separation of water from aqueous suspensions by means of filtration by adding flocculants the formation of impermeable filter cakes, which extremely slow filtration speeds are avoided. As a flocculant during work-up A polymeric ester of methacrylic or acrylic acid is called from acidic titanium sulphate pulp.

The object of the present invention is to improve the filterability of finely divided titanium dioxide hydrolyzate sludges. In particular, the filtering and washing times should be shortened and the proportion of suspended matter in the Filirat be decreased.

The present invention relates to a method to accelerate the filtration speed and reduce the filtration losses of titanium dioxide hydrolyzate sludge by adding a filter aid before, during or after the hydrolysis of a Titanium sulphate solution, which is characterized by this. that organosulfates, organosulfonates, Organosulfonic acid amides or mixtures of these sulfur-containing compounds with 10 to 24 carbon atoms are added and the tilane dioxide hydrolyzate sludge is filtered off after the hydrolysis has ended.

The sulfur-containing filter aids to be used according to the invention are acids. Salts or sulfonic acid amides, which are characterized by the general Let formula I represent:

R-SO ₂ -XI

whereby

R for a straight-chain or branched alkyl or alkoxy radical with 10 to 20 carbon atoms, a cycloalkyl radical with 5 to 7 carbon atoms, an aliphatic-aromatic radical with 12 to 24 carbon atoms,
X stands for OM or NR ₁ R ₂ ,
whereby

M = NH ₄ *, Na *, K *, Ca ² * _{I / 2} , Mg ² * _{I / 2} , R, and R ₂ independently of one another the meaning of hydrogen,
Ci- to C4-alkyl or the rest

j- CH-

assume, where ;; = 0 to 10 and Rj = H or CHj,
with the provisos that only R ₍ or R _{2 is} a Ci- to C ₄ -alkylresi and when X stands for NR ₁ R ₂ , R does not assume the meaning of an alkoxy radical.

Compounds which correspond to the formula I include, for example, sodium salts of alkyl sulfuric acid esters with 10 to 20, preferably 12 to 18 carbon atoms in the alkyl group for use. Examples of this are substances such as stearyl sulfate, miryslil sulfate, lauryl sulfate or cetyl sulfate. Another of the general formula I corresponding preferably used for use Nairiumalkylsulfonate represent a group of substances straight-chain alkyl radical with 10 to 20, preferably 12 to 18 carbon atoms. Such compounds are as commercially available emulsifiers or dispersing aids are known. They are made by adding paraffin, Hydrocarbons and subsequent saponification with Sodium hydroxide solution obtained (H. Beyer, Leh book of organic chemistry, II., 12th edition, p. 195, 1966, S.-Hirzel-Verlag Leipzig).

As further compounds corresponding to general formula I, sulfonic acid amides are preferred straight-chain alkylsulfonic acid alkanol or dialkanol amides with 12 to 18 carbon atoms in the alkyl group and 2 to 3 carbon atoms in the hydroxyalkyl radical («= 1) for use, for example alkylsulfonic acid alcohol and diethanolamide. Such products are easily accessible by known methods Implementation of the sulfochlorinated paraffins with alkanol or dialkanolamines or with ammonia and then Alkoxylation (F. Asinger, Chemistry and Technology of Paraffin Hydrocarbons, 1956, Akademie-Verlag Berlin pp. 395 to 474).

The concentration and amount of the surface-active compounds added are not critical and can be up to several% by weight, based on the TiO ₂ solids content of the suspension. For economic reasons, about 0.01 to 1.0% by weight, preferably 0.02 to 0.5% by weight, is preferred. It is essential to add the compounds to the titanium dioxide hydrolyzate suspension before filtration.

Surprisingly, the organosulfates and organosulfonates are effective, regardless of whether the compounds are added before, during or after the hydrolysis. It is particularly easy to add during and at the end of the hydrolysis. The temperature of the Tltandioxid-Hydrolysatschlümme upon addition of the compounds of the invention may vary over a range of about 30 to 12O ⁰ C, preferably 80 to 120 ° C range. This independence from the dosage temperature is desirable because it allows the active compounds to be added during the hydrolysis at temperatures of normally 100 ° C and more. Even after the hydrolysis has ended, use at higher temperatures of more than 50 ° C is preferred, Since the distribution of the compounds is favored at higher temperatures. In addition to the increase in the filtration rate, the reduced titanium dioxide content in the filtrate is a considerable advance. Furthermore, the measures according to the invention to use organosulfur compounds of the combined heating described also reduce the filtration losses after the bleaching and after the addition of setting chemicals prior to calcination of titanium dioxide hydrolyzate slurries.

The following examples serve to illustrate the present invention:

example 1

The hydrolysis of a black solution containing, inter alia, 236 g / l titanium sulphate (expressed as TiO ₂ ) and 108 g / l iron end sulfate, was carried out according to Blumenfeldverrahren (US Pat. No. 1,795,467 and US Pat. No. 3,518,053). For this purpose, 3240 ml of solution were heated to 96 ° C. and added to 550 ml of water at 96 ° C. over the course of 16 minutes. The mixture was heated to the boil and refluxed for 4 hours to complete the hydrolysis. By adding 710 ml of water, the concentration was reduced to 169 g / l TiO ₂ during the boiling process.

This example was used for comparison.

The filtration properties of the hydrolyzates were determined with the aid of an immersion filter at 50 ° C. and 600 Torr negative pressure, which was covered with a Dralon filter cloth and had a filter area of 100 cm ² (method I). The filter cloth was loaded at different suction times (t) and the solids content of the washed hydrolyzate filter cake was determined by annealing at 1000 ° C. for two hours (Ta *. 1, column 2). In addition, in Table 2, Column 2, the filtration performance is given as kg / h · m ^{2 of} TiO ₂ residue as a function of the loading time (t).

Example 2

The hydrolysis was carried out as indicated in Example 1, but according to the invention 0.07% by weight (based on the amount of TiOj) sodium alkyl (C | ₂ - to C _T «-) sulfonai was added to the water in the water. The determination of the filtration capacity is; in Tab. 1 and 2 dem

so compared to example 1. This clearly shows the improvement in the rate of filtration. With a loading time of 6 minutes, the hydrolyzate without alkyl sulfonic acid has a filtration rate (per cm ² ) of 68 mg TlO ₂ / min, while the hydrolyzate after the inventive addition of alkyl (C, 2- to Ci «-) sulfonate a A value of 81 mg TiOj / min results, which corresponds to an increase of 19%.

Table 1

Loading time (t) Weight of the calcined filter cake (g) (min.) Example 1 Example 2

36.3

40.7
45.7

41.5
48.2
56.6

Table 2

Loading time
(min.)

Filter performance in kg / m ² - h
Example I Example 2

43.6 49.8 40.7 48.2 34.2 42.5

A simplified measuring arrangement (method II), which consisted of a filter bag with a filter area of 25 cm ² , to which a constant pre-pressure of 60 Torr was connected, also provided comparable values for the filtration speeds. For this purpose, 50 ml of hydrolyzate were poured onto the suction filter at a temperature of 50 ° C. and, after applying the negative pressure, the filtration time was measured up to the point in time at which the surface lost its gloss. To determine the washing time 50 ml of water (20 ⁰ C) was added to the filter cake after completion Filtrierzeitbestimmung and the time up to the recurrence of the matte surface. In good agreement with the immersion filter tests, a filtration time of 330 seconds was measured for the hydrolyzate from Example 1 and a value of 280 seconds for the hydrolyzate from Example 2. This results in filtration rates (per cm ² ) of 60 mg TiO ₂ / min for the comparative experiment and 71 mg for the product of the process according to the invention and thus an increase of 18%.

Another advantage of the process according to the invention is the lowering of the total filtration losses (Sum of the losses in filtration after hydrolysis, bleaching and adjustment). The filtration losses of the hydrolyzate from Example 1 amounted to a total of 2.66%, while the product from Example 2 showed a total loss of 1.82% was determined. The yield could thus by the process according to the invention 0.83% can be increased.

Example 3

A hydrolyzate prepared according to Example 1 was treated 5 minutes before the hydrolysis was stopped with 0.1% sodium-alkyl- (C, ₂ -bis Ci ₄ -) benzenesulfonal (based on the TiOi content) in the form of a 5% aqueous solution and cooked until the hydrolysis is complete. Before the addition of the sulfonate according to Method II, the hydrolyzate had a filtration rate of 390 seconds and then 240 seconds, which corresponds to an improvement of 38% after the addition of the compound effective according to the invention.

Example 4

3240 ml of a black solution with 235 g / l titanium sulfate (expressed as TiOj) and 119 g FeSO ₄ / l were heated to 96 ° C and added to 440 ml water at 96 ° C in the course of 15 minutes. The mixture was then heated to a temperature of 105 ° C. and left there for 4 hours to complete the hydrolysis. A final dilution of 169 g / l TiO _{2 was} set with 820 ml of water.

The hydrolyzate had a filter time according to method II of 390 sea and was used for comparison for the following example 5.

Example 5

I ^: .inc according to Example 4 carried out hydrolysis was crl'indungsgcäß with 0.07 ",. N; ilriiim-alkyl- (Ci _; -

to Ci4-) sulfonate (based on the TiO ₂ content), the sulfonal being added as a 5% aqueous solution after half the amount of dilution water had been mixed in. After the hydrolysis had ended, the hydrolyzate had a filtration time of 270 seconds, which corresponds to a reduction in the filtration time of 31% compared with Example 4.

Example 6

In a series of experiments A to H, 100 ml of freshly prepared titanium dioxide hydrolyzate (solids content 12.5%) were in each case at 85 to 90 ° (with 1 ml of a 1.25% aqueous solution of the corresponding filter aid (0.1% based on TiO ₂ The filtration and washing times were determined according to method II. Table 3 shows the changes in the filtration and washing times in percent, the times of the hydrolyzate without additive (A) being set equal to 100 " .

As can be seen in the table. α , the organic sulfonic acids or sulfates or their salts used according to the invention show significant improvements, while compounds with a lower carbon number, such as. B. the benzenesulfonic acid (H), causes almost no change in the filtration properties and thus proves to be ineffective.

Table 3

Filter aid

Filtration line washing time

A without
B alkyl (Cu-C, g) sulfonate *)

C alkyl (C _{! 2} -C _u ) ^{benzene sulfonate a} )

D alkyl (Ci2-C, ₄ ) -suirat =)
E oleic acid-N-methyl-tauride ^a )

F Ethoxylated alkyl (C | ₂ -Cia) sulfonic acid amide

G Laurylbenzenesulfonic acid
H benzenesulfonic acid

100 100 72 85 72 85 83 90 72 88 76 75 75 82 97 100

Na-SaIz

Example 7

35 ml of a germ suspension ( _{containing 2.43 g of TiO 2} ) which was prepared from black solution and sodium hydroxide solution according to the Meckienburg process, US Pat. No. 1,758,528, was mixed at room temperature with 3000 ml of black solution (236 g / l YiO ₂ ; 108 g / l FeSO ₄ ) and 400 ml of water, heated to boiling within 25 minutes and kept the temperature constant at the boiling point for 4 hours. A final concentration of 165 g / l TiO _{2 was} set with 850 ml of dilution water.

As in Example 3, 0.1% sodium aJky'-ICn- to C ₁₄ -benzenesulfonate (based on the TiOj content) was added 5 minutes before the hydrolysis was stopped and the mixture was boiled until the hydrolysis had ended. The hydrolyzate had a filtration rate of 330 seconds before the addition of the sulfonal according to method II and then of 240 seconds, which corresponds to an improvement of 27 "after the addition of the crlindungsgcmü (3 active compound.

Claims (2)

Patent claims: 1. Process for accelerating the filtration speed and reducing the filtration Loss of titanium dioxide hydrolyzate sludge due to the addition of a filter aid before, during or after the hydrolysis of a titanium sulphate solution, characterized in that organosulphates, Organosulfonates, organosulfonic acid amides or mixtures of these sulfur-containing compounds with 10 to 24 carbon atoms added and the titanium dioxide hydrolyzate sludge be filtered off after the hydrolysis has ended. 2. The method according to claim 1, characterized in that sulfur-containing filter aids of the general formula R-SO ₂ -X 20th are used, where R represents a straight or branched alkyl or alkoxy radical with 10 to 20 carbon atoms, a cycloalkyl radical with 5 to 7 carbon atoms, an aliphatic-aromatic radical with 12 to 24 carbon atoms, X stands for OM or NR ₁ R ₂ , where M = NH /. Na ', K *, Ca ² V ₂ . Mg ² V ₂ . Ri and R ₂ independently of one another mean hydrogen, Ci- to Ct-alkyl or the remainder 30th - + CH ₂ - CH- OhH