Pigmentary titanium dioxide and its preparation

 

(57) Abstract:

The invention relates to pigment rutelinae titanium dioxide, the method of its production and can be used in the production of paints, plastics and laminated plates on a paper basis. The invention consists in the pigment comprising particles of titanium dioxide with the besieged them cerium oxide in an amount of 0.01-1 wt.% and dense amorphous silica in an amount of 1-8 wt.% from the amount of titanium dioxide. The pigment may be optionally coated with aluminum hydroxide in the amount of 2-4 wt.% from the amount of titanium dioxide. A method of obtaining a pigment is added to the water slurry of particles rutlege titanium dioxide water soluble compound of cerium in an amount of 0.01-1 wt.% in terms of cerium oxide on the quantity of titanium dioxide, which when reacted with acid or alkali besieging cerium oxide, then add a water-soluble silicate in the amount of 1-6 wt.% and mineral acid to precipitate at least at pH 8 dense amorphous silica, the slurry is continuously stirred and maintain the temperature of 60-100oC during the whole deposition process. In addition to the sludge add water dissolve the military strength, superior resistance to photochemical decomposition. 2 C. and 13 C.p. f-crystals, 1 table.

The invention relates to pigmentary titanium dioxide and the way it was received.

Pigmentary titanium dioxide, in particular rutelinae titanium dioxide, is used in many products requiring a high degree of strength. For example, rutelinae titanium dioxide is widely used in paints, plastics and laminated plastics on a paper basis. However, in cases where such products are exposed to ultraviolet radiation, decomposition and discoloration of the pigment is accelerated. Thus, there is a need for improved titanium-dioxide pigment with a high resistance, resulting in increased service life of articles containing this pigment.

The closest analogue of the invention is U.S. patent N 4450012, which discloses pigments coated with rutile a mixed phase comprising retelny pigment mixed phase having a first coating of oxide or gidrirovannoe metal oxide selected from tetravalent titanium, zirconium, tin and mixtures thereof, and a final coating of oxide or gidrirovannoe aluminum oxide. Also disclosed pic is new or titanium dioxide, zirconium, tin or mixtures thereof on calcined and crushed retelny pigment mixed in the aqueous phase of the suspension, the subsequent deposition of the final layer of oxide or gidrirovannoe aluminum oxide on the already coated with the pigment, washing and drying twice covered rutlege pigment.

The present invention meets the above described requirements and eliminates the disadvantages of the known prior art by creating a pigmentary titanium dioxide having improved strength, i.e., improved resistance to photochemical decomposition. Durable pigment titanium dioxide consists of particles rutile titanium dioxide precipitated with them cerium oxide and dense (thick) amorphous silicon dioxide. The cerium oxide is preferably present on the particles of titanium dioxide in an amount of from 0.01 to 1 wt. from titanium dioxide and dense amorphous silica is preferably present in an amount of from 1 to 8 wt. from titanium dioxide.

Particles of titanium dioxide with the besieged them cerium oxide and thick amorphous silicon dioxide is also preferably include an external coating of precipitated water (hydrated) oxide of aluminum. The latter is preferably part of the NT is obtained by formation of a water slurry of particles rutile titanium dioxide with the addition thereto of a water soluble compound of cerium, which when interacting with acid or alkali besieging the cerium oxide particles of titanium dioxide. Acid or alkali is added to the slurry to cause the precipitation of cerium oxide on the particles of titanium dioxide. Then the slurry was added water-soluble silicate and a mineral acid, in order to obtain particles of titanium dioxide precipitate dense amorphous silica. Optionally, the order of deposition may be changed, i.e., first precipitated thick amorphous silicon dioxide, and then the oxide of cerium.

The preferred deposition coating of an aqueous aluminum oxide particles of titanium dioxide with the besieged them cerium oxide and thick amorphous silicon dioxide is carried out by adding to the slurry is acidic or alkaline aluminum compounds which, in contact with acid or alkali besieging particles aqueous alumina. Alkali or acid is added to the slurry, either simultaneously or after the addition of aluminum compounds.

Thus, the main objective of the invention is to provide an improved high strength pigment dioxide and develop the way it was received.

Other and additional objectives of the invention, and Yeghia preferred variant of the invention, given in the following description.

Durable pigment titanium dioxide includes particles rutile titanium dioxide precipitated with them cerium oxide and thick amorphous silicon dioxide. In addition, the particles preferably include an external coating of an aqueous aluminum oxide to increase the dispersion ability and optical properties of the pigment.

The cerium oxide is preferably present on the particles of titanium dioxide in an amount of from 0.01 to 1 wt. from TiO2dense amorphous silica is preferably present in the particles in an amount of from 1 to 8 wt. from TiO2and the external coating of an aqueous aluminum oxide (in those cases when it is incorporated into particles) deposited on them in quantity (in terms of aluminum oxide) from 2 to 4 wt. from titanium dioxide.

Particles rutile titanium dioxide preferably receive a "chloride" way, i.e. by oxidation in the vapor phase of titanium tetrachloride, sodium hydroxide and sodium hexametaphosphate, followed by the addition of titanium dioxide. Optionally, the suspension (slurry) is subjected to wet grinding using a sand mill, followed by screening of small solid particles and residue sand.

PEFC is acid or alkali besieging the cerium oxide particles of titanium dioxide. Examples of acidic compounds of cerium, which can be used in the process are cerium salts of mineral acids, in particular sulfate or nitrate of cerium. Used acidic compound of cerium causes the precipitation of cerium oxide due to interaction with the alkali, in particular the alkali metal hydroxide. Another option may be used alkali metal salts of cerium, in particular ammonium sulfate or nitrate of cerium, which interact with acid, for example sulphuric, for deposition of CeO2. In a preferred embodiment, the water soluble compound of cerium is a cerium nitrate and reactive with him alkali is an aqueous solution of sodium hydroxide. The connection of the cerium is introduced into the aqueous suspension in an amount (in terms of oxide of cerium) from 0.01 to 1 wt. from fine particles of TiO2in suspension, more preferably in the range of 0.02 to 0.05 wt. from titanium dioxide. Acid or alkali is added to the suspension in an amount sufficient to interact with the compound of cerium and subsequent deposition of cerium oxide particles.

After the deposition of cerium oxide is completed, the particles of titanium dioxide are coated with a dense silica, which before the AI from a solution of water-soluble silicate while maintaining the pH of the slurry is more than 8, preferably in the range from 9 to 11. The deposition of a thick silicon dioxide reach by adding to the suspension a water-soluble silicate and the simultaneous or sequential addition of mineral acid. Preferably an aqueous solution of water-soluble silicate is added to the slurry, together with a solution of mineral acid while maintaining the pH of the slurry in the range of 9-10,5, resulting in the particles deposited dense amorphous silica. An aqueous solution of water-soluble silicate is preferably a solution of sodium silicate and mineral acid preferably is a solution of sulfuric acid. Water-soluble silicate is added to the suspension in the amount (in terms of silica) from 1 to 8 wt. from the content of the particles of titanium dioxide in the slurry, more preferably in the range from 1 to 6 wt. from titanium dioxide. Mineral acid is added in sufficient quantity to maintain the pH in the above range of values.

During the deposition of the oxide of cerium and dense amorphous silica particles of titanium dioxide aqueous suspension is continuously stirred in the temperature range from 60 to 100oC, preferably at 70

After deposition on the particles of cerium oxide and thick amorphous silicon dioxide is preferable in order to improve the dispersion capability and optical properties of the particles were applied external coating of an aqueous aluminum oxide. This is achieved by adding an acidic or alkaline aluminum compounds, which when interacting with alkali or acid besieging particles aqueous alumina. Examples of the acidic aluminum compounds are aluminum salts of mineral acids, such as sulfate or aluminum nitrate. Examples of alkaline compounds of aluminum are the aluminates of alkali metals such as sodium aluminate. Acidic or alkaline compound of aluminum added to the suspension in the amount (in terms of aluminum oxide) from 2 to 4 wt. from the content of titanium dioxide, more preferably in the range from 2.5 to 3.5 wt. Alkali or acid is administered in sufficient quantity to or after the addition of aluminum compounds. Preferably as added aluminum compounds to use sodium aluminate in the form of its aqueous solution, which simultaneously interacts with the aqueous solution of sulfuric acid.

After deposition of the oxide of cerium, dense amorphous silica and optional water aluminum oxide particles of titanium dioxide mixture is preferably filtered, washed and dried. Optionally, the dried product is ground, treated with air conditioning, in particular trimethylaluminum, and passed through a jet mill.

The quantitative content of the various reagents used to obtain pigments proposed in the present invention, as the concentration of the applied solution can be established by any expert working in this field of technology.

The following examples are provided to further illustrate the improved titanium-dioxide pigments and methods for their preparation.

Example 1. Rutilio titanium dioxide, obtained by vapor-phase oxidation of titanium tetrachloride in the presence of 1.5 wt. aluminum oxide, suspended in water with a sufficient quantity of sodium hexametaphosphate and sodium hydroxide, resulting in the stable d is Itanium sand mill is diluted to 18.7 wt. solids and pass through a standard 325 sieve to remove small solid particles and residue sand.

A portion of the sludge (4610 g) containing an equivalent amount of titanium dioxide (864 g), placed in a suitable vessel equipped with a stirrer and heater. The temperature was raised to 70oC, the pH of the dispersion is 8.8.

To the dispersion was added with stirring for 10 min a solution of cerium nitrate (33 ml) with a concentration of cerium oxide 260 g/l After the addition of cerium nitrate measured the pH of the dispersion is 1. After 10 minutes of incubation, the pH of the dispersion is raised to 9.4 for 14 min by adding 144,7 ml of sodium hydroxide solution (110 g/l).

The variance leave for 15 minutes for curing. Then for 58 min there was added 240,3 ml solution of sodium silicate containing the equivalent amount of silicon dioxide (of 142.8 g/l) at a ratio of silica: sodium oxide of 2.86: 1, and during this period the pH of the dispersion support of 9.4 by adding to 72.4 ml of sulfuric acid with a concentration of 10% by volume.

After a 30-minute incubation, the pH was adjusted to 7.5 using 26,7 ml of sulfuric acid (10 vol.), the temperature of the dispersion is reduced from 70oC to 5 the version for 20 minutes add the sodium aluminate solution (reach 201.9 ml), containing 93,5 g/l of aluminum oxide and of 174.4 g/l of sodium oxide. When the pH of the dispersion reaches 10, simultaneously add sulfuric acid (10 vol. ) to maintain pH in the range of 10-10,5. The total volume is 216,9 ml After adding the aluminum oxide dispersion leave on 79 minutes; during this time the pH decreased from 10.2 to 9.2. After that, the pH is further reduced to 7.5 with the help of 21.6 ml of sulfuric acid (10 vol.). After an additional 30-minute incubation, and minor adjustment of pH to return it to the value of 7.5, the suspension is washed to remove soluble salts and dried at 105oC. the Dried product is milled and treated with 0.35% trimethylaluminum and passed through a jet mill.

Photocatalytic activity of the obtained product was measured by the method described, for example, in the literature: T. I. Brownbridge and J. R. Brand, Photocatalytic Activity of Titanium Dioxide Pigment, Surface Coating Australia, September 1990, 6-11 (article presented at the annual 32nd Congress of the SCAA, Perth, USA, Sept. 1990). This test mainly includes the following stages: distribution of about 0.2 g TiO2in 40 ml of isopropanol spectral purity; the impact on a mixture of TiO2/isopropanol ultraviolet radiation; control at the time of formation of acetone in the test mixture; ODA is measured velocities by a factor of 103. The calculated value is proportional to the magnitude of climatic obtained under conditions of accelerated tests titanium-dioxide pigment.

The pigment product obtained in accordance with the above example, has a zero value photocatalytic activity. This result indicates a very high degree of strength.

Example 2. In example 2, which does not involve the use of oxide of cerium, work with another portion of the suspension rutile titanium dioxide obtained by the method of example 1, consisting of 4615 g suspension, equivalent to 865 g of titanium dioxide. Using the same vessel as in example 1, the suspension is heated to 70oC, pH this is 8.8. To increase to 9.4 add 4.5 mg of sodium hydroxide. To the stirred dispersion was added 242 ml of the same sodium silicate solution as in example 1. This solution, equivalent of 34.6 g of silicon dioxide, is added dropwise within 60 minutes During this addition the pH value constant support by simultaneous injection of sulfuric acid solution (10 vol. in the number of 76.4 ml After injection dispersion leave to ripen for 30 minutes the pH is then reduced to 7.5 by adding within 21 min add 203,5 ml of the same sodium aluminate solution, as in example 1. When the pH of the dispersion reaches a value of 10, at the same time add sulfuric acid (10 vol.) to maintain pH in the range of 10-10,5. After the addition of aluminum oxide, the mixture is left for 45 minutes during which time the pH increases between 10.3 to 10.4. After completion of the ripening period reduce pH to 7.5 by adding sulfuric acid (10 vol.) the number 106,9 ml within 30 minutes after the 30 minute incubation, and minor adjustment of pH to return it to the value of 7.5, the suspension is filtered, washed and dried at 105oC. the Dried product is milled and treated with 0.35% trimethylaluminum and passed through a jet mill. Photocatalytic activity of the sample is 1, what is worse compared with the sample treated with cerium oxide in accordance with example 1.

Example 3. Example 3 demonstrates the advantage achieved even at low contents CeO2.

836 g suspension rutile titanium dioxide prepared by the method described above, but with a solids content of 30% and a specific gravity of 1.3, heated to 80oC. the pH Value of the dispersion when it is 8.4. This value increased to 10 by the addition of 9.5 ml of sodium hydroxide. Then to the hot Sucina. The pH value constant support by simultaneous injection of a solution of sodium hydroxide (200 g/l) in the amount of 4.1 ml After injection dispersion leave to ripen for 15 minutes the pH Value of the dispersion is then reduced to 9.4 by the addition of 95% sulfuric acid in an amount of 0.4 ml.

Then within 121 minutes added to it 154,8 ml of sodium silicate solution at a content of silicon dioxide 216 g/l and the ratio of silica: sodium oxide 3,22, and during this time the pH of the dispersion maintain constant by simultaneous addition of 7.2 ml of 95% sulfuric acid. After the deposition of the silicon dioxide dispersion leave on for 15 minutes, then reduce the pH to 8 by the addition of 2.1 ml of 95% sulfuric acid.

73,6 ml of a solution of sodium aluminate with an aluminum oxide content of 250 g/l is added to the mixture for 20 minutes During this operation, the pH constant support 8 by adding to 19.3 ml of 95% sulfuric acid, and then reduce to 5.6 and leave for 15 minutes Then after an additional minor adjustment of pH to return it to a value of 5.6, the suspension is filtered, washed and dried at 106oC.

The dried product is milled and treated with 0.35% of the districts is this sample (0,47) was the best compared to the activity, defined in example 2.

Example 4. In the following example, which does not involve the use of cerium oxide together with thick amorphous silicon dioxide, 824 g suspension rutile titanium dioxide prepared according to the procedure described in example 1, but with a solids content of 30% and a specific gravity of 1.3, heated to 80oC. After the addition of 2.9 ml of sodium hydroxide solution pH increases from 8.5 to 9.4.

To the dispersion within 120 min add 152,6 ml of sodium silicate solution described in example 3. At this time maintain a constant pH by adding 7 ml of 95% sulfuric acid. After the introduction of silicon dioxide, the suspension is left to ripen for 15 minutes the pH is then reduced to 8 by adding 2 ml of 95% sulfuric acid.

72,5 ml of the same sodium aluminate solution as in example 3, is added to the mixture for 20 minutes At this time maintain a constant pH by adding 16 ml of 95% sulfuric acid. At the end of the process of adding sodium aluminate reduce pH to 5.6 with 1.5 ml of 95% sulfuric acid. After a 15-minute ripening and additional minor adjusting the pH of the mixture is filtered, washed and dried at 105oC. Wyss the x2">

The measured value of the photocatalytic activity of this sample, which is 1.16, equivalent to the activity obtained for the pigment of example 2, but this is worse than the pigments of examples 1 and 3.

Example 5. In this example, the cerium oxide precipitated after conducting the deposition of dense amorphous silica. 838 g of a suspension of titanium dioxide as described in example 1, but with a solids concentration of 30% and a specific gravity of 1.3, is placed in the reaction vessel and increase the temperature to 80oC. After the addition of 3.2 ml of a solution of sodium hydroxide (200 g/l) pH increases from 8.6 to 9.4.

To this dispersion within 120 min add 155, 2mm ml of the same sodium silicate solution used in example 3. At this time maintain a constant pH by simultaneous addition of 7.2 ml of 95% sulfuric acid. After the introduction of silicon dioxide, the suspension is left to ripen for 15 minutes

Next, to the mixture for 3.5 min type of 6.4 ml of the previously used solution of nitrate of oxide of cerium. At this time maintain a constant pH when a 9.4 by adding 13 ml of a solution of sodium hydroxide (200 g/l). Then the dispersion is left to ripen for 15 min, after which the pH decrease is the thief of sodium aluminate (73,7 ml), used in example 3. At this time maintain a constant pH at 8 by adding at 16.1 ml of 95% sulfuric acid. After the introduction of aluminum oxide in the pH of the suspension is reduced to 5.6 by the addition of 1.8 ml of 95% sulfuric acid and the mixture is left to ripen for 15 minutes

Then at the end of this period and minor adjusting the pH of the suspension is filtered, washed and dried at a temperature of 105oC. the Dried product is milled and treated with 0.35% trimethylaluminum and passed through a jet mill. The measured value of the photocatalytic activity of this sample is 0.13.

The results of the tests according to examples 1-5 are shown in table.

From the examples and tables, you can see that the proposed pigmentary titanium dioxide has a low photocatalytic activity and, consequently, high strength.

Thus, the present invention sufficiently allows you to accomplish goals and achieve all of the advantages, as already referred to, and characteristic of this invention. Although many changes can be carried out by experts of the relevant field of technology, such changes are in n the th titanium dioxide, characterized in that it comprises particles of titanium dioxide with the besieged them cerium oxide in an amount of 0.01 to 1.00 wt. and dense amorphous silica in an amount of 1 to 8 wt. from the amount of titanium dioxide.

2. Titanium dioxide under item 1, characterized in that it comprises cerium oxide in an amount of 0.02 to 0.5% of titanium dioxide.

3. Titanium dioxide on PP.1 and 2, characterized in that it includes a dense amorphous silicon dioxide in quantities of 1 to 6% of the amount of titanium dioxide.

4. Titanium dioxide under item 1, characterized in that the particles have an outer coating of precipitated aluminum hydroxide in amounts of 2 to 4 wt. from the amount of titanium dioxide.

5. A method of obtaining a pigment rutlege titanium dioxide comprising adding to the aqueous slurry of particles rutlege titanium dioxide water soluble compound of the metal, which when reacted with acid or alkali besieging the metal oxide on the particles of titanium dioxide, characterized in that as the water soluble compound of the metal is used as a compound of cerium in an amount of 0.01 to 1.00 wt. in terms of cerium oxide on the quantity of titanium dioxide, an acid or alkali is added in an effective amount for vzaimodeystviya in quantities of 1 to 6 wt. in terms of silicon dioxide on the quantity of titanium dioxide in mineral acid to precipitate at least at pH 8 dense amorphous silica, the slurry is continuously stirred and maintain a temperature of 60 100oWith throughout the deposition process.

6. The method according to p. 5, characterized in that as a soluble cerium compounds using cerium nitrate.

7. The method according to p. 5, characterized in that as the use of alkali hydroxide of sodium.

8. The method according to p. 5, characterized in that as a soluble silicate and a mineral acid using sodium silicate and sulfuric acid, respectively, in the form of aqueous solutions.

9. The method according to p. 6, characterized in that the cerium nitrate is used in a quantity of 0.02 to 0.50 wt. in terms of cerium oxide on the quantity of titanium dioxide.

10. The method according to p. 5, characterized in that in addition to the slurry is added an aqueous solution of sodium aluminate in an amount of 2.5 to 3.5 wt. in terms of aluminum oxide on the quantity of titanium dioxide and an aqueous solution of sulfuric acid to precipitate aluminum hydroxide.

11. The method according to p. 5, characterized in that it further perform filtering, washing and su is inuu acid is added to the slurry before adding the water-soluble cerium compounds and acid or alkali.

13. The method according to p. 5, wherein the slurry additionally add alkaline or acidic compound of aluminum in the boarding 2 4 wt. in terms of aluminum oxide on the quantity of titanium dioxide and acid or alkali to precipitate aluminum hydroxide particles of titanium dioxide.

14. The method according to p. 13, characterized in that as the aluminum compounds and acids using sodium aluminate and sulfuric acid, respectively, in the form of their aqueous solutions.

15. The method according to p. 14, characterized in that sodium aluminate is added in the amount of 2.5 to 3.5 wt. in terms of aluminum oxide on the quantity of titanium dioxide.

 

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1 tbl

FIELD: chemical industry; public health; medicine; production of the titanium dioxide composition.

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22 cl, 6 dwg, 3 tbl, 8 ex

FIELD: chemistry.

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EFFECT: reduction of rutile crystallisation temperature.

42 cl, 12 ex, 19 dwg

FIELD: chemistry.

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2 cl, 5 ex, 3 tbl

FIELD: chemistry.

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EFFECT: reduced temperature of titanium dioxide modification without surface contamination with hardly removable anions, or anatase form transmutation into rutile form.

2 cl, 9 ex

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