SK45299A3 - Method for preparing coloured pigments with titanium dioxide base - Google Patents

Abstract

The invention concerns a method for preparing coloured pigments with titanium dioxide base comprising the calcination of octahedrite dioxide until complete transformation of the octahedrite titanium dioxide into rutile titanium dioxide, in which is used an octahedrite titanium dioxide having a rutile phase temperature of at least 1000 DEG C and a proportion of sulphate, expressed in SO3, of at most 1 wt. %.

Description

The invention relates to a process for the preparation of color pigments based on the titanium dioxide phase. The invention also relates to color pigments obtained by this process.

Color pigments have been used as a color substance in plastic materials, paints and varnishes, as well as in the cosmetics and pharmaceuticals sectors.

These major artistic pigments are usually prepared by (i) mixing anatase titanium dioxide with one or more pigment additives, (ii) subsequently crushing and (iii) calcining.

BACKGROUND OF THE INVENTION

Color pigments must meet certain criteria, in particular they must be stable to temperature, light and decomposition by acid or alkaline chemical agents. DE 36 04 317 offers color pigments with improved thermostability containing from 0.1 to 2% by weight of magnesium, in addition to a triple system composed of titanium, antimony and chromium.

In essence, the colors of the pigments do not change the shade of e.g. when added to plastic materials or varnishes, or when exposed to particularly severe climatic conditions.

Similarly, EP 318 783 recommends the addition of lithium in an amount of 0.01 to 0.25% by weight in order to limit the tendency of the rutile phase pigments consisting of chromium and antimony to change color under cooling conditions.

. 9th

However, the dyeing of rutile phase pigments currently used in industry is not always satisfactory in terms of shade intensity and color saturation.

SUMMARY OF THE INVENTION

The invention offers a solution to the problem of intensifying shades by improving the process for preparing titanium dioxide-based color pigments. The color pigments obtained in this way offer a palette of colors that are more intense than the colors commercially available.

The invention relates to a process for the preparation of color pigments based on titanium dioxide, including calcination of anatase titanium dioxide up to complete conversion of anatase titanium dioxide to rutile titanium dioxide using anatase titanium dioxide having a rutilization temperature of at least 1000 ° C and preferably at 1060 ° C. a sulfate level expressed in SO3 of at most 1% by weight, but preferably less than 0.8% by weight.

According to a first essential characteristic of the invention, the titanium dioxide used must have a sulfate level expressed in SO3 of at most 1% by weight. preferably less than 0.8. It has been found that initiation with anatase titanium dioxide with an excess sulfate level provides a pigment shade that is not sufficiently intense. More preferably, the sulfate level is as low as possible.

The sulfate level is readily determined by a skilled person using any of the commonly used methods, e.g. X-ray florescence.

The sulfate content of the titanium dioxide anatase dioxide can be controlled during its production.

The initial anatase titanium dioxide, which may be used in the process in accordance with the invention, is prepared by commonly used methods. In this sense, Ullman Band (vol. 18, p. 574) and Kirk Othmer (vol. 23, p. 146) can be found. optimal

The process for obtaining anatase titanium dioxide comprises three steps of (1) hydrolyzing the titanium sulfate solution, (2) filtering the hydrolyzate, and (3) washing the filtrate with water.

In particular, the sulfate content of the titanium dioxide can be checked during the third step during the washing of the filtrate.

According to a second essential characteristic of the invention, the titanium dioxide used must have a rutilization temperature of at least 1000 ° C, but preferably of 1060 ° C and more.

The control of the rutilization temperature of titanium dioxide is usually carried out during the synthesis of titanium dioxide. The degree of purity of the anatase phase of the anatase phase of titanium dioxide may control this temperature: the closer the level of anatase titanium dioxide approaches 100%, the higher the rutilization temperature.

The anatase level may be adjusted in step (1) by introducing seed crystals into the hydrolysis medium. This serves to guide the nature of the hydrolyzate formed: depending on the nature of the titanium dioxide seed crystals introduced, the resulting hydrolyzate, mainly composed of anatase titanium dioxide, will contain a higher or lower percentage of rutile titanium dioxide, with the aim of reducing the percentage.

Anatase titanium dioxide having the necessary characteristics required in the process of the invention are available on the market e.g. through the Rhône-Poulenc Company. The titanium dioxide marketed by the Rhône-Poulenc Company under the trade name G5 is a powder. The Rhône-Poulenc Company also supplies titanium dioxide also in the form of a sol under the name S 5-300.

The rutization temperature, which is not always indicated by the manufacturer, can be easily determined by the skilled worker by implementing the following workflow.

The rutilization temperature is generally defined as the temperature at which 50 wt% of the anatase phase of the anatase titanium dioxide has been converted to the rutile phase by

-4kalcinácie. According to the embodiment, the rutilization temperature is determined by high temperature X-ray diffractometry.

To get the temperature), this determinate calcination is a sample held in a closed. the chamber rises quickly

The regular interval diffractometer determines 0.032 ° C in 10 second steps.

if the influence of external parameters (such as given rise conditions takes place under very precise operating conditions: during impact titanium dioxide is placed on a flat platinum substrate and • an ore (no air flow), eg in a closed chamber. Temperature at 5 ° C / min up to 1250 ° C.

The measurements are carried out between 650 ° C and 1250 ° C. A diofractogram is drawn in ch (eg every 50 ° C), the increment of time during the angular range from 10 ° to 60 °, recorded

Preliminary fields are performed in this way with reference samples of 100% rutile phase or 100% anatase phase.

The position of the bands corresponding to the anatase or rutile titanium dioxide is determined on the obtained reference diffractograms.

An experiment is then carried out under the same conditions on the sample of titanium dioxide to be analyzed.

By comparing the surface area of the most intense band of the two phases with those indicated on the diffractograms drawn for the reference samples, a calculation is made for each temperature of the rutile phase fraction formed.

The rutilization temperature is reached when the percentages of the rutilization phase and the anastasis phase are equal.

According to the invention, the rutilization temperature must be at least 1000 ° C, preferably 1060 ° C. A temperature of less than 1000 ° C is insufficient to enhance shades and color saturation.

In accordance with the present invention, the method comprises the steps of: mixing titanium dioxide anatase with at least one pigmentary additive; triturating the resulting mixture and calcining in an oxygen atmosphere.

The mixing of the titanium dioxide anatase with one or more pigmentary additives may be carried out dry or may be initiated with an aqueous suspension.

In order to facilitate the mixing process, a titanium dioxide anatase with a specific BET surface area of at least 250 g / m ² [sic m / g] is recommended.

A specific BET surface is understood to be the specific surface area measured by the BET method, ie. nitrogen adsorption in accordance with standard 03663-78, based on the BRUNAUEREMMETT-TELLER method described in the journal, The Journal of the American Society, 60, 309 (1938). When titanium dioxide is present in the form of an aqueous suspension (e.g., a sol), the aqueous suspension is sprayed before measuring its specific surface area.

When the mixing process a) is carried out dry, the titanium dioxide anatase consists of a powder consisting of particle aggregates. The average size of such agglomerates is in the range of 1 to 2 µm and the average particle size of them is in the range of 40 to 60 nm.

Such a powder can preferably be obtained in an artistic manner, with the following steps:

- hydrolysis of the titanium sulphate solution,

- filtration of the solution thus obtained,

- rinsing the filtrate with water,

redissolve the filtrate in water, and

spraying the resulting suspension.

According to another article, the mixing a) may be carried out in a solution in which the titanium dioxide anatase particles are first suspended in a liquid medium, the average

- (3The particle size is between 40 and 60 nm. In this case, water is removed from the liquid suspension prior to comminution and calcination. This second cell is advantageous because its application produces pigments with more intense colors than the first cell. in accordance with which the mixing process (a) is started dry with an appropriate titanium dioxide anatase powder.

In all cases, reducing the particle size facilitates the mixing process.

A liquid suspension based on titanium dioxide anatase can be obtained by following the following steps:

- hydrolysis of titanium sulphate.

- filtration of this hydrolysis,

- rinsing the filtrate in water.

- redistributing the filtrate in an acidified medium, such as nitric acid or a hydrochloric acid solution. At this stage, the use of sulfuric acid will be limited to prevent sulfate levels from rising.

The ingredients are identical to those commonly used in art. The following are selected, for example, from compounds of the transition elements Sb, Cr, Ni, Co, Zn, Cu, Mn, and W and are found either in oxygenated form (especially SbiO 2, CnCl 2, NiO, CuO, MnO and WCb) or in the form of oxidizable in an oxygen atmosphere, such as a degree of calcination.

Preferably, a mixture of titanium dioxide and chromium and antimony compounds is selected, wherein the molar ratio of antimony and chromium is close to 1, for example 0.8 to 1.2.

For the sake of clarity, it should be noted that calcination can take place in an oxygen or air atmosphere, with temperatures between 800 and 1400 ° C being preferred.

Mineral additives (in the art called mineralizers), such as sodium floride, sodium chloride, potassium chloride, calcium floride, or calcium chloride, may be added to the titanium dioxide-based composition prior to comminution and calcination. It is also

-1, the addition of lithium compounds such as e.g. those disclosed in EP 318 783 (carbonate, floride, chloride, oxide, hydroxide, sulphate, nitrate, phosphate, lithium antimony or lithium titanium), or magnesium compounds, as recommended for example in DE 36 04 317 (magnesium carbonate and oxide).

The invention also relates to color pigments which are obtained by the above process. These color pigments can be used on plastic materials, paints and varnishes, as well as in the cosmetic and galenite areas.

Finally, the invention relates to the use of titanium dioxide anatase having a rutilization temperature of at least 1000 ° C, preferably 1060 ° C and a sulfate level expressed in SO _{3 of} at most 1% by weight, preferably less than 0.8%, useful for preparing color pigments based on titanium dioxide.

DETAILED DESCRIPTION OF THE INVENTION

The following examples serve to facilitate the understanding of the invention without limiting it.

Example 1.

Determination of rutilization temperature of titanium dioxide anatase.

The samples used in the following examples have the following characteristics:

- sample 1: G5 powder produced by Rhône Poulenc Company. This titanium dioxide has a BET specific surface area of 300 m ² / g and a sulfate level, expressed in SO _{3, of} less than 0.8% by weight; the powder is in the form of clusters of particles with an average size of these clusters approaching 1.5 µm.

- sample 2: a comparable powder having a BET specific surface area greater than 250 m ² / g and a sulphate level, expressed in SO _{3 of} 5% by weight; the powder exists in the form of clusters of particles with an average size of these clusters approaching K1.5 µm.

-8Rutilization temperatures of these samples are measured as follows:

First, the test samples of the powders at high temperature are examined by X-ray diffraction (diffraction). 100% anatase and 100% rutilization powders were used to determine the structural bands corresponding to the anatase and rutile phases. Each test sample is placed on a flat platinum substrate in a closed chamber. The chamber temperature is gradually increased at a rate of 5 ° C / min. Diffraction is recorded at 650,700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200 and 1250 ° C, subject to the following conditions:

- Acquisition time: 10s

- angular range from 10 ° to 60 ° in steps of 0,032 °.

Bands corresponding to the rutile and anatase phases are localized.

The same measurements are made with samples 1 and 2. The thus obtained diffracciograms make it possible to evaluate the percentage of the rutile and anatase phases by comparing the surfaces with the most intense bands of both phases with the diffracciograms of the test samples.

The result is then plotted as curves representing the percentage changes in rutile and anatase phase versus temperature. The curves obtained according to patterns 1 and 2 allow a simple graphical determination of the rutilization temperature.

Diagram 1 corresponds to Sample 1, which shows a rutilization temperature of 1080 ° C.

Diagram 2 corresponds to Sample 2, which shows a rutilization temperature of 850 ° C.

In accordance with the invention, only the powder of Sample 1 can be used in the process as its rutilization temperature is above 1000 ° C.

Example 2

Preparation of color pigments based on titanium dioxide anatase at 1080 ° C.

-9Patty powder. chromium (Cr ₂ O ₂ ) tablets.

Then these are subsequently crushed to the oxygen atmosphere.

The following sample 3: has a full v sample 4: has a full v.

Chemical vz. chromium trioxide, titanium dioxide from sample 1 (see Example 1) is mixed with antimony oxide (Sb.sub.2). The mixture is formed into a lump for 12 hours at 920 ° C under an oxygen atmosphere, crushed and re-calcined, initially for 12 hours at 980 ° C in about 4 hours in air at 970 ° C. Two samples of orange colored pigments are prepared in the manner thus obtained:

ec (Tio, 9Cr ₀ , o ₅ Sbo, o5) 0 ₂ cec (Tio, 99Cro, oo5Sbo, 005) 02.

ec of the resulting compound is adjusted using the appropriate amount: for antimony and titanium dioxide.

Both of these? Pigments are tested for color saturation.

Coloring is quantified by chromatic coordinates L *, a * and b * according to the CIE system (L *, a *, b *) from roll 1 1976 as defined by the Lighting Commission and published in the French * Review. 2 Noriem (Recueil des Normes Francaises (AFNOR)), colorimetric color no. X08-12 (H83). They are determined using a DATACOLOR colorimeter manufactured by SCIEN.FIC PACIFIC.

L * gives the measurement reading and provides information about the color brightness.

a * and b * express the false tendencies:

a positive value of a * indicates red, a negative value of a * indicates green, a positive value of b * else. the negative value of b * ir indicates blue.

L * thus schematically - represents the transition from white to black (clarity), and * the transition from green to red and the 1 'transition from blue to yellow.

- 10The results shown in Table 1 below were recorded when measurements were taken on samples 3 and 4:

TABLE 1

pigment L * and * b * Sample 3 67.5 24 59 Sample 4 84 6 38

Example 3 (comparison) of color pigments based on titanium dioxide anatase at a rutilization temperature of 850 ° C.

From the titanium dioxide anatase of Sample 2 as described in Example 1 according to the procedure of Example 2, two color pigments (Sample 5 and 6) were prepared, the complete formulas of which are (T 10 ^ Cro.osSbo.osjCba (T 10 ^ Cro.oosSbo). .oosjCk

The measured chromatic data are shown in Table 2 below;

TABLE 2

pigment L * and * b * Sample 5 66 20 57 Sample 6 85.5 3 2 28.2

By comparing the pigments with the same chemical formulas (samples 3 and 5 on the one hand and samples 4 and 6 on the other), it is subsequently found that the pigments have higher a * and b * values and hence a more intense orange color due to the invention.

- 11Example 4,

Preparation of color pigments based on titanium dioxide anatase at a rutilization temperature of 1080 ° C.

The titanium dioxide used is in the form of a sol. It is manufactured by Rhône-Poulenc Company under reference number S5-300. The titanium dioxide under consideration has a BET surface area of 300 m ² / g and a sulfur level expressed in SO _{3 of} less than 0.8% by weight and a rutilization temperature of 1080 ° C. The dry extract from S5-300 is 20 wt. %.

Color titanium dioxide pigments are prepared by (i) mixing S5-300 sol with chromium nitride and antimony nitride, (ii) spraying the resulting liquid mixture, and (iii) calcining and crushing according to Example 2.

Two orange samples are prepared as follows:

- the complete formula of Sample 7 is: (Tio / jCro.osSbo.osjCb

- the complete formula of Sample 8 is (Tio, 99Cro, oojSbo, ooj) 02.

The chemical formula of pigments is treated with appropriate amounts of antimony nitride, chromium nitride and S5-300 sol.

Samples 7 and 8 were analyzed for color saturation. The results obtained are shown in Table 3:

TABLE 3

pigment L * and * b * Sample 7 68 24 61.5 Sample 8 85 8 41.2

By comparing the values for a * and b * for samples 3 and 7, on the one hand, and samples 4 and 8, on the other, it shows a higher coloring of the pigments of samples 7 and 8.

It has thus been shown that the pigments prepared from the titanium dioxide sol anatase of the present invention yield a higher shadow intensity.

Claims (11)

A process for the preparation of color titanium dioxide pigments, including calcination of titanium dioxide anatase until complete conversion of titanium dioxide anatase to rutile titanium dioxide, characterized in that the titanium dioxide anatase having a rutilization temperature of at least 1000 ° C, preferably 1060 ° C, is used. % of sulfur expressed in SO3 not more than 1 wt.%, preferably less than 0.8 wt. Method according to claim 1, characterized in that it comprises the following steps: admixing said titanium dioxide anatase with at least one pigmentary additive, crushing the resulting mixture, and calcining in an oxygen atmosphere. The method according to any one of claims 1 or 2, characterized in that the specific surface area of the BET anatase of titanium dioxide is at least 250 m ² / g. The process according to any one of claims 2 or 3, characterized in that step a) the mixing is carried out dry with titanium dioxide anatase powder. 5. The method of claim 4, wherein said powder consists of agglomerates of titanium dioxide particles having an average particle size in the range of 1 to 2 [mu] m and an average particle size of between 40 and 60 nm. A process according to any one of claims 2 or 3, characterized in that a) the mixing is started from a liquid suspension of titanium dioxide anatase, wherein water is removed from the suspension before the mixture is actually crushed. 147. A method according to claim 6, characterized in that. The liquid suspension comprises suspended titanium dioxide anatase particles having an average size in the range of 40 to 60 nm. Process according to any one of claims 2 to 7, characterized in that said pigmentary additives are selected from compounds of the transition elements Sb, Cr, Ni, Co, Zn, Cu, Mn and W, which are either in the form of oxides or in the form of oxides. in the form of oxygen-oxidizable compounds. Method according to claim 8, characterized in that in step a), said titanium dioxide anatase is mixed with antimony and chromium compounds, the molar ratio of antimony to chromium in the range of 0.8 to 1.2, preferably equal to 1. Process according to any one of claims 2 to 9, characterized in that the calcination is carried out at temperatures in the range 800 to 1400 ° C. Color titanium dioxide pigments obtained by any one of claims 1 to 10. Use of a titanium dioxide anatase having a rutilization temperature of at least 1000 ° C, preferably 1060 ° C and a sulfate level expressed in SO 3 of at most 1% by weight, preferably less than 0.8%, for the preparation of color titanium dioxide pigments.