DD267244A5 - PROCESS FOR PREPARING TITANIUM DIOXIDE PIGMENT - Google Patents

Abstract

The invention relates to a process for the preparation of titanium dioxide pigment by grinding and mixing a titania-containing material such as sorel slag with an alkali compound such as sodium hydroxide and roasting the mixture. The roasted material is ground in a stirred ball mill and then washed and filtered off. Thereafter, the solids residue is digested with hydrochloric acid. After filtering off the acid and washing, the solid residue is calcined to form a titania pigment. By precise control of the process conditions, it is possible to produce either a nodular or a needleless titanium dioxide pigment.

Description

For this 1 page drawing

Field of application of the invention

The invention relates to a process for the preparation of titanium oxide pigment from titanium dioxide-containing materials. In particular, it is a simplified and relatively inexpensive process for the preparation of a titanium oxide pigment in which the separation of the titanium from the titandloxidha!:! those substances or ores are not made by dissolution or conversion into a vaporizable liquid compound, but are separated from the impurities of the ore by solid-liquid reactions and are mechanically comminuted to P-size.

Characteristic of the known state of the art

Titanium Dioxide (TiO) is a well-known opacifying pigment for use in paints and coating coagulations, in plastics, and as a filler in paper and other materials. For example, various known methods of producing titanium dioxide include a conventional method, commonly referred to as the sulfate method and the chloride method.

In the sulphate process, the titanium becomes Titanium ore. with low titanium content, such as ammonium or sorol slag, dissolved with concentrated sulfuric acid and carefully separated from the Eisonsulfat formed in the process. Then, precipitation, washing and calcination are carried out to form titanium dioxide pigment.

In the chlorination process, titanium is pre-evaporated as the tetrahalide from high concentration titanium ores, such as Australian rutile (containing about 95% TiO ₂ ) or highly refined IImonite. This is followed by cleaning and oxidation.

The sulphate process and the chloride process are very complex ancestors and capital intensive, so that a relatively expensive titanium dioxide pigment results from these processes.

Object of the invention

The object of the invention is to provide means for obtaining a titanium dioxide pigment having either nodular or nadolfike particles.

Explanation of the essence of the invention

The invention is therefore directed to a process for the preparation of a titanium dioxide pigment with the steps:

(a) mincing a titania-containing material selected from sorel slag, prepared ilmenite, and chloride slag to a particle size of less than 10 microns.

(b) mixing the titanium dioxide-containing material with an alkali compound selected from alkali hydroxide, alkali carbonate and alkali oxide,

(c) roasting the mixture at a temperature of 700 ⁰ C-GOO ⁰ C,

(d) digesting the roasted material in hydrochloric acid and

(e) calcining the in the digestion step (d) gebildeton solid product at a temperature of 800 ° C-1000 ⁰ C to form a titanium dioxide pigment.

Figure 1 shows a schematic flow diagram of an embodiment according to which the method according to the invention can be carried out.

The starting material for the process according to the invention is a titanium-containing material, boisiolswoiso Sorolschlacko odor titanium slag. Various grades of sorel slag have been used in the present process. For example, the composition of a typical sorel slag (expressed as oxido) may consist of about 70 weight percent TiO ₂ and about 11 weight percent FeO as an impurity, with the remaining impurities including, for example, CaO, MgO, SiO ₂ , Al ₂ O , MnO, V ₃ O ₆ , Cr ₂ O ₃ and other oxides in traces.

Another type of sorel slag suitable for the present process may consist of about 78% by weight of TiO ₂ , about 8% by weight of FeO as an impurity and the other aforementioned impurities as rust.

The present invention is not limited to the use of sorel slag or an itanschlacko *. Other materials or particles containing titanium may be pre-wetted as starting materials for the erfindungsgomaßo method. For example, chloride slag may also be used. A typical chloride slurry may consist of 85 wt.% TiO _2, about 10 wt.% FeO as impurity and the remainder in the form of impurities as indicated above.

Another suitable starting material for the oromega-containing process gene may be an intermediate from the work-up of ilmenite, as described, for example, in US Pat. No. 3,825,419. A typical raw material that is formed during pre-pulping processing may consist of about 95% by weight of TiO ₂ , about 1% by weight of FeO impurity, and the remainder of impurities as previously indicated.

Examples of other titaniferous substances that can be twisted for the method according to the invention are titanium-containing substances which have been treated such that the proportion of titanium dioxide can react with alkali compounds when heated to temperatures of 700 ° C.-950 ° C. Suitable alkali metal compounds are, for example, alkali metal hydroxide, alkali metal carbonate or alkali metal oxide or mixtures thereof.

All of the equipment used in the process of the invention for milling, mixing, roasting, filtering and calcining and all other operations are common known facilities used for continuous or batch operation Micron is preferably a stirred ball mill or sand mill of the type described in US Pat. No. 2,581,414. The sand milling to which the invention is subjected to in order to comminute a material to a particle size of microns is described, for example, in US Patent No. 2,581,414. However, the grinding medium for such agitator ball mills is not limited to sand; It is also possible to use glass, steel, ceramic or other suitable grinding media having a spherical or beaded shape, generally with a diameter in the range of 0.5-3 mm.

The digestion is carried out in vessels whose internal surface parts or linings are resistant to the usual working conditions with respect to the acid used in the ancestor. Suitable materials for this Oborflächentoile are beispielsw eise glass, glass fiber reinforced plastics (polyester, Vmyloster, epoxy and anuore suitable plastics), Hasteloy (a nickel / molybdenum alloy), rubber, refractory metals (Ta, Zr, Cb) or acid-resistant bricks. In a preferred embodiment of the invention, the particle size of the titanium-containing material should be small enough that substantially all of the material will react with the alkaline amine Jung. In Figure 1 it is shown that the TiHn-containing starting material is ground first, for example with a hammer mill, to a size suitable for the purpose of a sand mill. The process according to the invention is described below as an example of the wounding of sorel slag as a titanium-containing material, but is not limited to this starting material or titanium slag.

After comminution with a hammer mill, the sorel slag is preferably comminuted in an agitating ball mill with sand as grinding media to an average particle size of about 15 μm. Preferably, a particle size of otwa is 10 μm. Especially minimized is the crushing of the starting material by sand milling to a maximum particle size of 10μηι or smaller. Particles larger than 15 μm may include impurities that can not be easily removed from the starting material in the subsequent process steps.

After the sorel slag is milled to the preferred particle size, it is mixed intensively with an alkali binder, for example, an alkali hydroxide, an alkali carbonate, an alkali oxide or a mixture thereof. Suitable alkalis include sodium, potassium, lithium, rubidium, cesium or mixtures thereof. The preferred compound is an alkali hydroxide, most preferably sodium hydroxide, because it reacts readily with the finely-ground sorel slag. Hereinafter, the method of the present invention using sodium hydroxide as the preferred alkoxide compound will be described, but it is not limited to the use of this alkaline material.

Sodium hydroxide may be mixed with the Sorelsuhlacken material prior to roasting and mixing is preferably done during sand milling or before comminution in a stirred ball mill. The mixture of Sorelschlacko and sodium hydroxide may contain about 30 parts by weight or more of sodium hydroxide per 100 Gow'chtstoilo Sorelschlacko. Preferred are from 30-60 weight of sodium hydroxide to about 100 weight parts of sorel slag. Particularly preferred is a weight ratio of sorel slag: sodium hydroxide of from 100: 35 to 100: 45. The use of a ratio of sorel slag to sodium hydroxide higher or lower than the range of 100: 30 to 100: 60 is possible, but may result in an unsatisfactory titanium dioxide pigment. If the titanium dioxide-containing material used contains more than 70% by weight of TiO ₂ , the proportion of hydroxide in the mixture is correspondingly increased.

After sand grinding, the mixture of sorel slag and sodium hydroxide is heated or roasted: at temperatures of 700 ° C-950 ° C for a period of 1-3 hours. At roasting temperatures above 95O ⁰ C may result in a hard ocer clinker-like material and below 700 ⁰ C, the reaction between sodium hydroxide and Sorelschlacko may be incomplete. It is therefore preferred to roast the mixture for 1.5-2 hours at temperatures of 800 ° C-870 ° C. Preferably, the roasted mixture is then milled to a particle size of 0.5-2 pm as previously described It is believed that during the roasting, the titanium dioxide contained in the mixture reacts with the sodium hydroxide to form sodium titanate Some of the impurities present in the material may also be submerged with the particulate hydroxide For example, when sodium hydroxide is used, alkali metal salts such as sodium vanadate, sodium chromate, sodium aluminate, and potassium silicate are formed as impurities which are readily soluble in water, and these impurities are therefore preferably, at least partially a dissolved by washing with water after roasting to reduce its content. Most preferably, it is essential to remove all of the interfering amounts of the contaminants. Other compounds present in the starting material, such as iron oxide, magnesium oxide and calcium oxide, are soluble in mineral acids, such as hydrochloric acid, and are removed during the digorization described below. After the water-soluble impurities have been washed out or dissolved from the roasted material, the remaining insoluble alkali titanate is diluted with the additional insoluble oxides in hydrochloric acid. Preferably, about 6 normal (N) HCl acid is used because a weaker acid is not as effective as that of about 6N. A stronger acid can be effectively twisted in a pressure vessel, but tends to approach a concentration of 6 N when boiling in an open container. It is therefore within the scope of the invention to use acid concentrations from 5N to 12N. However, if a higher concentration of acid (as 6N that is the azootrope boiling point of HCI at 108 ⁰ C is used, a pressure vessel is required. It is therefore more practical to work at atmospheric pressure at standardatmosphärischem pressure digesting at 8O can be ⁰ C been executed or higher and is preferably carried out under reflux at a temperature of 9O ⁰ C to 110 ° C, very particularly preferably at 108 ⁰ C for a period of 10-120 minutes, preferably 10-40 minutes. higher temperatures may be used, However, they require pressurized equipment, which may be done one or more times, preferably at least twice.

A nodular or spherical or needle-shaped form of the titanium dioxide particles is obtained as a function of the residence time of the roasted Materia 'ι (sodium titanate) In 6N HCl at a temperature below 90 ° C. Wonn the 6 N-acid suspension in the digestion step is slowly heated to its boiling point of 108 ⁰ C (less than 5 ° C per minute), the process substantially bulbous or spherical titanium dioxide is obtained. Elno acicular particle shape is obtained when the temperature during the Digoriorons of the mixture is increased very quickly, or by using an acid concentration below 4N upon heating and increasing the Aciditöt to 6N when the temperature has exceeded 9O ⁰ C.

In a preferred embodiment of the invention, the roasted material is mixed with HCl at room temperature (for example, from 20 ° C-30 ° C). The mixture of roasted material and acid is then heated slowly until the Siedopunkt of the acid with a rate of about 5 ⁰ C per minute or less, preferably at a speed of 2 ⁰ C per minute to 3 ⁰ C per minute, and most preferably at a rate of 2C per minute or slower. It is believed that the nodular sodium tltanate material is formed during digestion.

In either case, to prepare nodular or acicular particles, the suspension of the washed, roasted material in about 6N HCl is refluxed for a time sufficient to complete the digestion. The boiling point, which varies with the pressure used, is in the range of 90 ° C to 111 ⁰ C and is preferably about 108 ° C.

The digestion is essentially after 10-15min. Completed. Digestion times up to about 120 min. May be used, but preferably a digestion time of 10-40 min. Higher heating rates and times may be used, but a pressure vessel may then be required.

It is believed that, during the digestion, the resulting alkali titanate hydrolyzes to amorphous, water-containing TiO ₂ .xHjO and the iron oxides dissolve as ferro- and ferric chloride. The iron chlorides and other impurities in the sauron suspension are removed, for example by centrifugation or filtration and optionally further treatment for the recovery of unreacted acid. The insoluble amorphous titanium dioxide residue is washed with a liquid such as water to remove further soluble impurities. Subsequently, the titanium dioxide is recovered from the water, for example by filtering or centrifuging. A white residue cake results from this step.

It is believed that the iron impurities in the titanium dioxide pigment are the cause of non-white pigment.

Preferably, the titanium dioxide pigment contains less than 520 ppm Fe and most preferably less than 200 ppm.

The amorphous titanium dioxide is calclniert preferably during 30-60 min., At temperatures in the range of 800 ⁰ C-1000'C to convert doe titanium dioxide in the crystalline rutile form. Most preferably, a temperature of 875 ° C-92b ° C during 30MIn. to 1 hour, because the undesirable discoloration of the resulting pigment is minimal and low temperatures are not as effective in converting the product to the desired crystalline form.

If the crystalline rutile product, which is either acicular or nodular in shape, is highly agglomerated after calcination, it may be powdered or ground with a sand mill. The final particle size for the needle-shaped version is from 0.05 to 0.3 μm thick and from 0.1 to 1 μm in length, preferably about 0.2 μm thick and about 0.7 μm in length. Its value as opacifying pigment is determined by a narrow main grain size range.

When the crystalline rutile product has a nodular form, the titanium dioxide particles have an average particle size of less than about 1 μνη, and preferably about 0.3 μηι.

The titanium dioxide can be used as a pigment in any conventional application for which opacifierondon pigments are used. For example, the titanium dioxide pigment of the process according to the invention can be used as opacifiers in paints, paper or plastics. The opacity and the brightness of the product are determined by measuring the scattering coefficient and the reflection. The pigment prepared according to the invention has a light scattering coefficient of above 2OOOcm ² / g, preferably above 4000 cm ² / g and most preferably

above 9000 cmVg and a brightness of more than 80% and preferably of 85-93% measured in accordance with the procedures given in Examples 1 and 12.

The following Belspiolo illustrate the present invention without limiting it.

example 1

A Mustor of 600g Sorelschlackenenerz, which was crushed by means of a hammer mill to a particle size of about 75μηι and with a content of about 70Gow .-% TiO ₂ and about 30Gew .-% impurity was dispersed in 450ml of water. The sorel slag suspension was in a sand mill with 800ml steel balls of a diameter of 1.5mm at 1000 rpm 120Min. gemahlon. The sand mill used was a vertical, water-cooled, stainless steel laboratory sand grinder with a 11.5 cm inner diameter cylindrical grinding bowl and an air turbine driven shaft and 2 8.5 cm diameter polyurethane disc impellers, spaced 4 cm apart. The peripheral speed of the impellers was 4.4m / s. The speed was controlled by an optical tachometer. After completion of the sand milling, the upper particle size of the Sorelschlacketeilchen was about 10μηι and the mitto particle size about 5μπν After separating the Stahlkugoln from dor slag suspension through a sieve with openings of 0.5mm 240g anhydrous sodium hydroxide (NaOH) the Schlackensuspenslon were added and mixed homogeneously.

The mixture had a Sorel slag / NaOH ratio of 100/40 and was then dried in a shallow dish in air at 120 ° C. In order to break agglomerates formed after dehydration and to obtain a homogeneous solution, the dried material was ground by means of an Elnar hammer mill (Wuber Brothers Lab Mill S-500). The resulting fine powder was roasted in porcelain containers for two hours at a temperature of 820 ° C. A 150 g sample of the roasted material was pulverized in a mortar to remove any lumps formed during roasting and dispersed in 350 ml of water. The roasted material and water were ground in a Sandmühlo with 700ml glass beads with a diameter of 1.2mm for 30min. at 1000 revolutions per minute. The glass beads were used in the milling instead of the steel shot to avoid discoloration of the material by steel shot.

After removing the grinding beads from the ground roasted material, the aqueous dispersion was centrifuged. The solid residue after centrifugation was washed and redispersed in water and centrifuged again. The washing was repeated twice.

The solids were then suspended in 1000 ml β N HCl Süure of about 100 ⁰ C and dispersed heated iiuf a boiling temperature of about 108 ⁰ C in olnem open vessel with stirring using a magnetic stirrer for 90 min. The acidic mother liquor containing the solids was centrifuged. The solids were washed twice with water u ^ d in air at 120 ⁰ C dried.

Thereafter, the dried solids were calcined at 900 ° C for one hour.

The density of the obtained white calcined product was 4.14 g / cm ³ and the X-ray diffraction pattern analysis showed that the calcined product had a rutile structure. Under the electron microscope, it was found that the titanium dioxide pigment particles were needlelike. The particle size of the nadelförmigon Pigmentos was in the range of 0.05 to 0.3μηι thickness and 0.1-1.0 μηι Läntje.

The brightness (Rw) of the pigment was 88.4% based on the measurement of the light reflectance of a magnesium oxide surface

with 100% reflection and its co-efficacy (S) was 6,835cmVg. The iron content (Fe content) of the pigment was determined by X-ray fluorescence analysis to be 520 ppm.

Determination of the scattering coefficient (S) and the brightness (R °°)

The main function of a titanium dioxide pigment is to make materials opaque to machon, such as paints, paper, plastics, etc., in which it is incorporated in the form of a uniform dispersion. There are many ways to express the opacity of an opacifying pigment. The scattering coefficient is particularly suitable for this and can easily be determined accurately and reproducibly.

The principle of this test is to form a thin layer of the pigment on a black glass plate, the film being slightly translucent, ie having a reflectance of about 80-90% of the reflectance of a thick, fully opaque film. Another layer of the same dispersion is applied to a white glass plate with a thickness such that a further increase in thickness does not change the light reflection. When the reflectivity of these two layers (R and R ") is measured and the weight (W) of the layer on the black plate is determined (dry layer weight per unit area, g / cm ² ), the scattering coefficient S (cm '/ g) can be calculated using the Kubelka-Munk Theory of Light Scattering! Zeitschrift für Techn. Physik, 12, 539, 1931). Reflection measurement of a layer on a white glass plate, Roo is often referred to as brightness. Tables based on the Kubolka-Munk equation are described in a publication by Mitton-Jacobsen, "New Graphs for Computing Scattering Coefficient and Hiding Power" Official Digest, September, 1963, pages 871-913 can easily be determined with knowledge of R, R °° and W. The following Example A shows a method for the determination of S.

Example A

A pigment is dispersed in water and a kloen amount of binder added as a film former so that a continuous layer is formed when the dispersion is poured onto glass plates for Refloxionsmessungon. Because the opacity of the film is very sensitive to the volume ratio of pigment binder, this ratio must be kept exactly constant and at a high enough level that the opacity of the pigment is not significantly reduced by the presence of the binder. The tests are carried out with a pigment volume co-concentration of 70% (pigment volume is 7% of the total solids volume and the total volume of solids is, the pigment volume plus binder volumone). The solids content is low enough so that the film, when applied to a black glass plate with a 37μμ applicator, is slightly translucent (with a reflectance of about 80-90% of the reflection of a single fully opaque layer of the same dispersion). A solids content of about 4% is a suitable level for titanium dioxide dispersions (pigment volume plus binder volume equal to 4% total volume of the dispersion). An example of a coating composition with a TiO.sub.i pigment for testing S and R oo is described in Table A below:

Table A

mass 15.00 density volume Volume of G 0.50 g / ml d. Firmly dispersion 3.06 matter ml TI0 ₂ -pigmont sample 4.20 3.57 3.57 Nalco 2324 dispersant ¹¹ 120.32 1.00 0.50 Binder, dispersant 138.88 1.04 1.53 3.11 (50.1 wt% solids) ²¹ water 1.00 120.32 5.10 127.50

An anionic polyacrylate dispersant sold under the trade designation "Nalc / 2324" by Nalco Chemical Company.

2 A carboxy lated styrene-butadiene latex sold under the trade designation Dow Latex 620A ™ by The Dow Chemical Company.

In the composition described above, the pigment volumcine concentration pvc was 70% and the solids volume of the dispersed solids was 4%.

Pigment, water and dispersant became 5 min. in a homogonizer available under the trade designation "ΡΤ45 / Θ0 Brinkmann Homogenizer" from Brinkmann Instruments Company The speed was 4. Then the Dow Latnx 620 was added and the mixture was stirred at a display scale 2 speed for five minutes.

A thin film applicator made by Gerdner Laboratory, a subsidiary of the Pacific Scientific Company with a width of 16 cm and a gap of 0.037 mm, is placed at the top of a 50 x 50 cm black glass plate (reflection "0) and about 3 ml of the dispersion in the applicator brought in. The applicator is pulled over the glass plate at a constant speed. The layer is dried at room temperature in a horizontal position. Using a Dünnschichtauftraggerätes with a gap of 75μιη the same dispersion was applied to a white glass plate (reflection 85.6),

After drying the layers for two hours, place a 5 x 6.25 cm right ankle stencil with a 32 cm ^{2 area} on the layer on the black plate and remove the coating outside the template with a razor blade so that there is a 32 cm square Surface remains on the black plate. Then, a photovoltage retroreflector with an external digital voltmeter and a 457 nanometer wavelength blue-light probe head sold under the trade name Wratten Filter by Eastman Kodak Company is used to reflect the pattern on the black plate and to measure the coating on the white plate. Then the sample is removed on the black glass plate with a razor blade and the weight determined with oinor analytical balance.

The sample had the following values: R - 79.5 Roo = 92.0 W = 0.0186 g / 32 cm ² or 0.000577 g / cm ¹

From Table 8 on page 895 of Mitton-Jacobsen's publication and the values of R and R ° o given above, the scattering force (SW) is determined to be 4.09. The scattering coefficient (S) can then be calculated as follows:

7088cm'g

S = - ^ 4ί9§

W 0.000577 g / cm ²

Example 2

A 600g sample of Sorel slag containing about 70% by weight TiO 2 and about 30% by weight impurity was then milled as in Belsnell 1. The steel meal refinery contained 57% slag *. 175 g of this suspension (= 100 g solid slag) was mixed with 67 g of anhydrous Na ₂ CO ₃ , dried, comminuted in a hammer mill and roasted at 1050 ° C for 2 hours. The hard, roasted material was crushed into 3.6 mm particles in a mortar and then further comminuted in a hammer mill to a fine powder, which was then ground in a sand mill with glass beads as in Example 1. The roasted material was dispersed in water and separated by centrifugation and washed as in Example 1. Digestion was then carried out in 1000 ml of 6N HCl for 90 min., Followed by separation of the solids and washing as in Example 1. After one hour of calcination, 900 ml. C, a white pigment having a rutile structure was obtained which had a density of 4.10 g / cm ^3. The pigment had a brightness of 78.3% and a scattering coefficient S of 4.128 cm ² / g.

Example 3

A sample of 600g sorel slag crushed in a hammer mill with about 70 wt% TiO 2; and about 30% by weight impurity was ground in a sand mill with steel shot as described in Example 1. The sieved steel shot was washed with water. The wash water was combined with the slag suspension. With this added water Wlos Wlos the suspension to a solids content of 45.9%.

A sample of 327g of the slag suspension (= 150g solids slag) was mixed with 52.5g of anhydrous NaOH to give a slag / NaOH ratio of 100:35. The mixture was dried at 120 ° C and then ground in a hammer mill and then roasted at 800 ⁰ C for two hours. Without further grinding in a stirred ball mill, the roasted material was dispersed in water and centrifuged. The separated solids were washed twice with water by redisporng fermentation in water and centrifuging. The washed gorosteto material was then boiled for one hour in 1000 ml of 6N HCl in an open beaker. After digestion in the acid, the solids were separated and washed twice in a centrifuge. The solids were then redispersed in 300 ml of water and ground with 700 ml of glass beads for 60 min. At 1000 revolutions / min in a sand mill. After screening the glass beads, the white opaque suspension was mixed with the same volume of 12N HCl and boiled for 10 min in an open beaker (the final boiling point was about 108 ° C.) The solids were then separated and washed twice with water and . dried at 120 ° C, the solids were then one hour at 900 ⁰ C cal: ined There was obtained a titanium dioxide pigment having a density of 4.0 g / cm ² and an iron content of 150ppm The Pigrr had ent brightness of 88,.. 9% and an S-value of 3.760 cmVg.

Verglelchsbelsplel3

A 327 g sample of Sorol slag milled with steel shot was suspended as in Example 3 (150 g solids slacko) and mixed with 45 g of anhydrous NaOH (S: heel / NaOH ratio 100/30). The mixture was evaporated to dryness and dried at 120 ° C, then ground in a hammer mill and roasted as in Example 3.

Two digestions and other precursors were carried out as in Example 3. This example was carried out to determine the effect of the reduced amount of NaOH added to zorlor slag, analogously to Example 3, on the properties of the pigment.

After calcination, a titania pigment was obtained which was leathery yellow in color and had an iron content of 8300 ppm. The pigment had a brightness of about 50%; the scattering coefficient was not determined.

Example 4

A 600 g sample of a hammer mill milled sorel slag containing about 70% by weight of TiO ₂ and about 30% by weight impurity was dispersed in 480 g of 5% NaOH solution (slag to NaOH ratio "100/40") 150 mm at 800 revolutions per minute with 800 ml steel meal, as in Example 1. The sand-milled suspension had a particle size of up to about 13 μm and an average particle size of about 7 μm Dried, ground in a hammer mill and roasted at 850 ° C for two hours.

Elno 150g Probo of the roasted material was made in a Sandmühlo with 700ml Glasporion and 350ml of water 10min. milled at 1000 revolutions per minute. By screening the glass beads, the solids were removed by centrifugation and washed twice with water. The solid obtained after centrifuging was then dispersed in 500 ml of 10.8 N HCl and at reflux 25MIn. cooked at 107 ⁰ C. The solids were centrifuged from the acidic mother liquor and washed once with water. The centrifuged solids were redispersed in 500 ml of 7N HCl and refluxed for 30 min. cooked at 108 ⁰ C. The solids were removed by centrifugation from the aqueous mother liquor and gassaschon three times with water. Dio centrifuged solids were dried to 12O ⁰ C and then 45Min. calcined at 900 ⁰ C. A titanium dioxide pigment was obtained with an Elsen content of 65 ppm. The pigment had a brightness of 90.5% and a scattering coefficient S of 4.472 cmVg.

Belsplol 5

A 400 g sample of sorel slag crushed in a hammer mill with about 70% by weight TiO ₂ and about 30% by weight impurity was dispersed in 280 ml water and 180 g anhydrous NaOH (slag / NaOH ratio - 100/45). The suspension was dissolved in a sand mill 150 min. milled at 1350 revolutions per minute and 600 ml steel shot of 1.5 mm diameter as described in Example 1. After sieving the steel shot, the suspension was dried at 12O ⁰ C, crushed in a hammer mill ur ^ then the material for two hours at 84O ⁰ C roasted. A sample of 150g dej roasted material was dispersed in SbOmI water uncin sand mill with 700ml glass beads of 1.2mm diameter 10Min. milled at 1000 revolutions per minute. After sieving off the glass beads, the suspension was centrifuged and washed twice with water. The washed centrifuged filter cake weighed 234 g / l and contained 96 g of water. The yield of roasted material was thus 138g. Dlosor cake was dispersed in 300 ml of water and 605 ml of 12N HCl. The liquid portion had a 7.3N HCl, which changed to 6N upon neutralization of solids. It was at reflux at 108 ⁰ C 20Min. digested. The solids were then centrifuged off in an aqueous mother liquor and washed twice with water, then redispersed in 600 ml of 6N HCl and further 20 min. Digesiert, followed by the separation of the solids and washing twice. The solids were then dried at 120 ° C and calcined at 900 ⁰ C for one hour. The titanium dioxide pigment obtained had an iron content of 30 ppm. The pigment had a brightness of 90.1% and an S-value of 6.170 cm ² / g.

Example 6

In this example, the Sorel slag / NaOH ratio was changed to 100/50 and as follows: A 600 g sample of Sorel slag milled in a hammer mill containing about 70% by weight of TiO ₂ and about 30% by weight. Contaminant was dispersed in 400ml of water and sandmilled with 800ml steel shot (1.5mm diameter) 120MIn. at 1800 revolutions per minute, as described in Example 1, milled. The steel shot was screened.

In 200 g of the slag suspension containing 120 g of sorel slag, 60 g of anhydrous NaOH were dissolved and dried in a flachon dish in an oven at 120 ° C. The dried material was crushed in a hammer mill and roasted at 840 ^° C. for two hours. The gc, esteto material was dispersed in 350 ml of water and ground in a sand mill with 700 ml glass sparge of 1.2 mm diameter for 10 min at 1000 cycles per min. After screening the glass beads, the ground roasted material was vacuum filtered with a Buchner funnel 15 cm in diameter and a filter paper with a pore size of about 7 μm (Whatman filter paper no. 541) and washed with 2 l of water. The washed roasted material was then digested at reflux in 1000 ml of 6N HCI at 108 ⁰ C for 20min. Then, 7 g of a 1% solution of a first flocculant was added. As a first flocculating agent, a cationic homopolymer was added by Dow Chemical Company as described in U.S. Patent No. 3,719,748. The precipitated suspension was then filtered with vacuum and washed with 21% water on the filter. The filter cake was then dispersed in 1000 ml of 6N HCI at about 30 ° C and the temperature gradually increased within 20 minutes to the boiling point of 108 ° C. and then kept at 20 ° C., then 1000 ml of cold water and 7 g of a 1% solution a second flocculant added. The second flocculant was a slightly anionic homopolymer of acrylamide in solid form with a degree of hydrolysis of 1-5%. The viscosity of a 0.5% solids aqueous solution at pH3 and 25 ⁰ C dos second flocculant was in the range of 31-50. <: p The flocculated suspension was vakuumfiltriort and washed with 21 water and then dried at 120 ° C The solids were calcined Oine hour at 900 ⁰ C under an electron microscope photographs show a bulbous, non-needle-shaped pigment DieRöntgenbeugung8Strukturana)... yse confirms that the pigment has a rutile structure, the S value was 2408 cm -1 / g and the brightness bet 83.9%.

Example 7 In this example, a titanium-containing material called chloride slag containing about 85% titanium dioxide by weight and

about 15% by weight impurities are used to make titanium dioxide pigment. The granuliei) material has one

Particle size of about 840pm. A 400g sample of this material was mixed with 200g of anhydrous NaOH and 300ml of water. The mixture was in

milled a sand mill as described in Example 1 with 700 ml of steel shot (1.5 mm diameter) at 1500 revolutions per minute during 240 minutes. to an average particle size below about 10 μνη. After screening the

Steel shot of the (lemahlenen suspension was dioso dried at 120 ° C, crushed in a hammer mill and

then roasted at 84O ⁰ C for two hours.

Elno 1BOg sample of roasted material was dispersed in 3BOmI of water and in a sand mill at 1000 rpm per min. and 700ml glass beads 10MIn. ground. The glass beads were suspended from the suspension and then centrifuged in suspension. The centrifuged cake was gowaschon four times. The centrifuged cake was then poured into 1000 ml of 6N HCl 20MIn. Degraded at 108 ° C under reflux. At the end of the digestion, Bg were added to a 1% solution of the first flocculant as in Example β and the precipitated suspension was vacuum filtered. The filter cake was washed on dom filter with 1000 ml of water. The washed filter cake was washed a second time in 10 μM b N HCI 20 min. Degraded at 108 ⁰ C under reflux. After digestion, tig were added to a 1% solution of the second flocculant as described in Example 6. The dormant suspension was then vacuum filtered and washed with 21% water on the dome filter. The filter cake was then dried at 110 ° C. The solids were calciniort one hour at 900 ⁰ C. The resulting titanium dioxide pigment had an S-Weri of 5.870 cm ^? / g and a brightness of 89.0%.

Example β

A BOOg sample in a hammer mill of ground sorel slag containing about 78% by weight of TiO ₂ and about 22% by weight. Impurities were dispersed in 350 ml of water and 180Min. with 180QUm turns per minute and 800ml 1.6mm Diameter steel shot in ninor sand mill, as described in Example 1. The peripheral speed of Stirrer actuator was 8m / sec. The crushed slag was screened through a 426 mm sieve to separate steel shot, Dbg steel shot

was washed with water and the wash water was combined with the ground slag to give a slag suspension having a solids content of 24.6%.

In this gelcoat suspension (= 150 g Foststoffschlacko) 67.5 g of anhydrous NaOH were introduced so that bin Sorol slag / NaOH ratio of 100/45 results. The mixture was dried in a shallow dish at 120 ° C

evaporated. The dried material was ground in a hammer mill to obtain a homogeneous fine powder.

The powder was then heated or roasted in a porcelain crucible at 840 ° C for 160 min. After dam cooling it was

crushed roasted material in a mortar. The roasted material was then dispersed in 350ml of water and spun at 1800 rpm for 10 minutes in a Laboratory Solvent recycle ball mill with 700 ml glass beads (1.2 mm diameter) as

Grinding medium ground. The ground, roasted material was then filtered from the beads and washed with 1500ml of water

diluted and vacuum filtered on a Buchner funnel 15cm in diameter and Whatman 541 filter paper. The

Filter cake was about 2 cm thick and was washed with 2 liters of water. The Foststoffgehalt of the filter cake was 62.6%. The washed filter cake was dispersed in 300 ml of water plus 200 ml of 12N HCl. The mixture was normal

about 4.4 and was placed in a 214 Hale flask with a reflux condenser, a thermometer and a stirrer and a

Feeding funnel introduced. The dispersion was heated to a temperature of 100 ⁰ C. After that was increased with the increase Acidity added to 6N 400ml 12N HCI. The temperature dropped briefly to 85 ⁰ C; after 5min. however, the temperature was

of 108 ⁰ C, the boiling point of BN HCI achieved. The mixture then became 20 min. boiled and then diluted with 2000ml cold water. Under continued stirring, 7 g of a 1% solution of the first flocculant, as in

Belwflc'ß described, added to the mixture. The Mischui ^ with about 3 N acid content was vacuum filtered, ¹ or filter cake on the filter washed with 21 water. The Solids content of the filter cake was 32.6%. The filter cake weighed 323g (solids content 105g) and was then dispersed in a solution containing 280ml of water plus

200ml 12N HCI. The mixture was placed in a 4-necked flask and heated to 100 ° C. Thereafter, 300 ml of 12N HCl was added. The temperature was raised to 108 ⁰ C, the boiling point of 6N HCl, and the mixture 20 min. on this

Temperature maintained. The mixture was then diluted to 100 ml of cold water. With continuous stirring

7g of a 1% solution of the second flocculant as described in Example 6. The mixture was filtered and washed as in the first digestion step.

The filter cake was about 3 cm thick and was dried at 12O ⁰ C and then zorkloinert in a mortar. The crumpled Filter cake was calcined at 900 ⁰ C for one hour. The calcined material immediately became flat The porcelain dish is introduced and cooled to room temperature in air. It was a Titandioxidpigment keep. X-ray diffraction analysis showed that it is a rutile pigment having a density of 4.1 g / cm ³ . The pigment showed

an S word of 6.900cm ² / g and a brightness of 92.2%. The crystal form was needle-shaped.

Example 9

A titania was prepared as described in Example 8 except that the ratio of slag / NaOH was changed to 100/40 and NaOH was added to the sorel slag before sand milling instead of dom sand grinding. The acicular pigment had an S value of 8.900 ncm ² / g and a brightness of 91.0%.

Example 10

A titanium-containing material that was obtained in the work-up of llmenit by the Benelite process by reduction and roasting and subsequent leaching with HCl. was used as the starting material for this Bolspiel. The black material contained about 93 wt .-% TiO ₂ and otwa 7 wt .-% impurities and had a particle size of about 250μπι on.

A 400g sample of this material was mixed with 200g NaOH and 350ml Vasser and ground in a sand mill as described in Example 1 with 600ml steel shot (1.5mm diameter) during 90 minutes. at 1600 revolutions per minute. The milled material contained particles with a mean particle size below about 10pm. The steel meal was poured off and the ground Matnrial dried at 12O ⁰ C, crushed in a hammer mill and then roasted at 84O ⁰ C for two hours. A 170g sample of the roasted material was dispersed in 350ml of water and ground in a sand mill using 700ml of glass beads at 1600 rpm for 10min. After sieving through beads, the suspension was centrifuged and the filter cake washed twice with water.

The bulk cake was then rücl'fluß with 1000ml β N HCI 20Min. digested. The solids were separated from the mother liquor and washed in a centrifuge. A second digestion step with 1000 ml of 6N HCl was carried out with subsequent separation and washing. The solids were dried at 120 ° C. and then calcined at f) ⁰ ° C. for 1 hour. A needle-shaped TiOj-Plgment was obtained. The pigment had an S-word of 4.260cm ² / g and a brightness of 90.0%

The following table gives the results of BoIs ₁ ^! ele, except examples 2,7 and 10, wioclor:

Tabollol

example relationship steel shot presence Number dor Eison- S Holligkoit No. Slag/ as a grinding agent from NaOH at Dlgorior- gohalt (Cm / g) (%) NaOH (U / min.) I.Mahlen steps (Ppm) 1 100Λ> 0 100/120 No 1 520 6,835 88.4 3 100/35 100/120 No 2 150 3,760 88.9 ό 100/30 100/120 No 2 8300 - 60.0 (Comparison) 4 100/40 900/150 Yes 2 65 4,472 90.5 5 100/45 1350/150 ia ? 30 6,170 90.1 6 100/50 1800/120 No 2 - 2,408 83.9 8th 100/45 1800/180 noin 2 - 6,900 92.2 9 100/40 1 800/180 ia 2 - 8,900 91.0

Example 11

A sample of sorel slag with a particle size of about 74) in QIT-FER ET TITANE, INC., CANADA was used as starting material. 1200 g of this sorel slag and 480 g of sodium hydroxide were placed in a laboratory atmosphere containing 111.2 mm diameter steel shot and about 1000 ml of water. The mixture was then ground until the maximum particle size of the sorel slag was 10μιη. The Gowichtsvorhältnls the slag / NaOH of the mixture was 100/40. After dom sieving the steel shot wurdo the mixture in an oven at 100 ⁰ C dried. The dried material was used to break up the agglomerates formed on drying in a Hammom homomahlon. The milled material was then roasted at 875 ^° C. for two hours. The gorosteto matorial was then passed through a mill to break the agglomerates formed on roasting. Sanding was then carried out for 5 min. In about 700 ml Wassor and 1 ml 1.2 mm Zirconoxidporlen. After screening the beads, the suspension was filtered by vacuum and the filter cake washed with water twice. Each was prewetted approximately 11 water for washing. A 194 g sample of the roasted material (based on dry sub-starch) was digested in 1000 ml of 6N HCl. The digestion step was carried out as follows:

The temperature of the βΝ solution (ie, the roasted material and dor acid mixture) batrug room temperature (2O ⁰ C), the temperature was then slowly added at a rate of about 5 ⁰ C per Minuto to the boiling point dor 6N increased acid solution and the glaze ι at reflux 15min. cooked. The amount of water in the wet filter cake was taken into account when calculating the normality of the HCl. As a flocculent, smlttol wurrian 3g 1% solution of SEPARAN MG-205 from the Dow Chemical Company to digested in suspension added. The suspension was filtered and washed twice with water, each using one liter of water. The filter cake was redispersed in water and digested a second time with 800 ml of 6N HCl in the same catwalk as in the first step. The total amount of filter aid was added to the suspension, vacuum filtered and washed as in the first digestion. Dor filter cake was dried at 110 ⁰ C 3 Stundon. The dried Maturial was then calcined for one hour boi 900 ⁰ C. The resulting rutile pigment had a pronounced nodular particle shape. The dry brightness of the calcined material was measured by placing a portion of the material in a 1.3 cm deep, 2.5 cm diameter sample vessel and measuring the reflection of the sample with a photovolt moter and a blue filter. The instrument was first calibrated prewiring a white standard with a brightness of 86.9 using the Blouffler. The brightness of the calcined material of the sample was 88.0%. The scattering coefficient of the calcined material was measured as follows:

15 g of the pigment and 0.5 g of sodium tripolyphosphate were dissolved in 70 g of water with a high-performance stirrer 5 MIn. disporgiort. Then, 3.1 g of polymer latex Rhoplox B-100 from Rohm & Haas Co. and 0.5 g of Triton X-100 surfactant, also from Rohm 8t Haas, were added to the dispersion and manually concentrated 3Min. touched. An effluent coating of the dispersion was applied to a RO Mm clear plastic film (Mylar from DuPont de Nemours & Co.) with a 37 μm thin layer applicator and dried in an oven at 100 ^° C. for 3 min. A sample 5 χ 5cm of the coated Mylar film was weighed and then placed on a 5 x 12.5cm optically flat black glass slide coated with propylene glycol. The propylene glycol was used to ensure optical contact. With dom photovoltmeter, the reflection was measured over the black glass Rb of the sample. The coating was washed off the 5 χ 5cm film and the film dried to determine the application weight per unit area (W). As a practical approximation to an opaque coating (Roo), the following was obtained: An effluent coating was applied to the 50mm Mylar. Applied film and dried and repeating the application until the maximum with the Fotovoltmeter detectable maximum reflection was reached. Using R ₈ , R °° and W and dom Strouwert SW, the strokou coefficient S was calculated using the formula by using Tabbollon of the publication by Mitton-Jacobsen

S =

SW W

The scattering coefficient of the sample of the calcined material was 3,33Gcm ^J / g.

The iron content of the calcined material was determined by plasma microscopy to be 200 ppm.

Claims (18)

1. A process for the preparation of a titanium dioxide pigment comprising the steps of: yes) crushing a Pt-containing material, (b) mixing the titanium dioxide-containing material with an alkali compound selected from alkali hydroxide, alkali carbonate and alkali oxide or a mixture thereof, (c) roasting the mixture at a temperature of 700 ^° C. to 900 ^° C., (D) digesting the roasted material i ι hydrochloric acid and (e) calcining the solid product formed in the digestion step (d) at a temperature of 800 ° C-1000 ° C to form a titania pigment. 2. The method according to claim 1, characterized in that the titandioxidhaltigo material is selected from Sorelschlacke, prepared llmenit and chloride slag and wherein the alkali compound used is alkali metal hydroxide and in which the weight ratio of SorelschlackeiAlkalihydroxid from 100: 30 to 100: 60. 3. The method according to claim 1, characterized in that crushing the mixture of titanium dioxide-containing material and the alkali compound with water in a sand mill to a particle size less than 15 microns. 4. The method according to claim 1, characterized in that one uses as titanium dioxide-containing material sorel slag and alkali compound as alkali metal hydroxide and comminuted their mixture with water in a sand mill to a particle size less than 10μηι. 6. Process according to Claims 1 to 4, characterized in that, following the roasting step (c), the material is dispersed in water and the dissolved material is filtered off from the roasted mixture and, following the acid treatment of step (d), a hydrous amorphous titanium dioxide material filtered off. 6. Procedure after everyone, '! of the preceding claims, characterized in that the mixture resulting from the roasting step (c) is comminuted with water in a sand mill and the dissolved material is removed from the roasted mixture, the roasted mixture in step (d) at a temperature of 90 ⁰ C-HO ⁰ C in hydrochloric acid and form with the acid a hydrated amorphous Titaridioxidmaterial * and that the titanium dioxide material is washed before calcination, Process according to any one of the preceding claims, characterized in that the roasted material is 10-120 min. digested with hydrochloric acid. 8. Process according to any one of the preceding claims, characterized in that, in the case of nodular particles, the calcined product is comminuted to an average particle size of about 0.3 μm. 9. The method according to any one of the preceding claims, characterized in that crushed in the case of acicular particles, the calcined product to a particle size of 0.1-1 μιη length and 0.05 to 0.3 μιη thickness. 10. The method according to any one of the preceding claims, characterized in that the titanium dioxide pigment obtained after calcination has a brightness (R «>) of 88-94%. Process according to any one of the preceding claims, characterized in that the titanium dioxide pigment obtained after calcination has a scattering coefficient (S) of 2,000 cm ² / g to 9,000 cmVg. 12. A method according to any one of the preceding claims, characterized in that the titanium dioxide pigment obtained after calcination has an iron content of 30 ppm to 600 ppm. 13. The method according to claim 1, characterized in that one heats the mixture of roasted material and acid with a sufficient speed for the formation of nodular particles to their boiling point. 14. The method according to claim 13, characterized in that the mixture of roasted material and acid at a rate of less than 5 ° C / min. to its boiling point of 90 ° C-11O ⁰ C orwärmt. 15. The method according to claim 1, characterized in that one heats the mixture of geröste'uim material and acid with a sufficient to form acicular particles speed to its boiling point. 16. The method according to claim 15, characterized in that maintaining the mixture of geröste ¹ em material and acid when heated to unter4N and increased to 6N when dieTemperaturvon 9O ⁰ C is exceeded. 17. The method according to claims 12 or 13, characterized in that the obtained after calcination Titandioxidpigmant has a scattering coefficient (S) of 1 500-5000cm ² / g. 18. The method according to claims 12,13 or 14, characterized in that the titanium dioxide pigment obtained after calcination has an iron content of less than 520 ppm. 19. The method according to any one of the preceding claims, characterized in that one carries out the digestion at least twice.