JPH01192727A - Preparation of titanium dioxide pigment - Google Patents

Abstract

PURPOSE: To relatively inexpensively produce a titanium dioxide pigment by a simplified process for production by pulverizing TiO₂-contg. raw materials, mixing this materials with an alkaline metal compd., then roasting the mixture, digesting the mixture with hydrochloric acid and calcining the formed solid product.

CONSTITUTION: The TiO₂-contg. raw materials (e.g.: Sorel slag, high-grade ilmenite, etc.) are pulverized and thereafter, the TiO₂-contg. raw materials are mixed with an alkaline metal compd. selected from an alkaline metal hydroxide, alkaline metal carbonate and alkaline metal oxide. At this time, the mixture composed of the TiO₂-contg. raw materials, the alkaline metal compd. and water is preferably treated with a sand mill to a grain size of <15 μ. This mixture is then roasted at 700 to 900°C and water-insoluble impurities are washed away from the roasted raw materials. The remaining water-insoluble alkaline metal titanate is digested with the hydrochloric acid together with another insoluble oxide. The digestion temp. is preferably 90 to 110°C. The solid product formed by the digestion stage is calcined at 800 to 1100°C to obtain the TiO₂ pigment. The Tie, pigment is relatively inexpensively obtd. by the simple method according to the constitution described above.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a method for preparing titanium dioxide pigment from raw materials containing titanium dioxide. More specifically, the titanium values in the raw material or ore containing titanium dioxide are separated from the impurities of the ore by a solid-liquid reaction without being solubilized or converted into an evaporable liquid compound, and then machined. It would be desirable to provide a simplified and relatively inexpensive method for preparing titanium dioxide pigments that are micronized to pigment size.

This method provides a means to obtain titanium dioxide pigments in the form of nodular or acicular particles.

[Conventional technology]

Titanium dioxide (Ties) is a well-known opaque pigment useful in paints and coatings, plastic materials, and as a filler in paper and other materials.

Various known methods for producing titanium dioxide include, for example, the conventional methods commonly referred to as the "sulfuric acid" method and the "chlorine" method.

The "sulfuric acid" method includes ilmenite or Sorel slag (s
The method involves solubilizing titanium values in low grade titanium ores such as orelslag with concentrated sulfuric acid and carefully removing the ferrous sulfate produced in this way. This is followed by precipitation, washing and calcination to produce pigmentary titanium dioxide.

The "chlorine" process involves extracting the titanium values from high-grade titanium ores, such as Australian rutile (which contains about 95 percent Ti) or beneficent and very highly graded ilmenite, into tetrahalogens. This includes volatilizing it as a chemical compound.

This is then purified and oxidized.

[Problem to be solved by the invention]

The sulfuric acid and chlorine processes are very complex and capital intensive, so that titanium dioxide pigments made by these processes are relatively expensive products.

[Means and Effects for Solving the Problems] Therefore, the present invention provides the following steps: (a) titanium dioxide-containing raw material selected from Sorel slag, ilmenite whose grade has been improved by beneficiation, and chloride slag is reduced to less than 101 na; (b) mixing the titanium dioxide-containing raw material with an alkali metal compound selected from alkali metal hydroxides, alkali metal carbonates, and alkali metal oxides; (c) this (d) Digesting the bi-baked material with hydrochloric acid; and (e) Digesting the solid product produced in the digestion step at a temperature of 800-100°C.
Calcining at a temperature of 0<0>C to produce a titanium dioxide pigment.

An example of a general flowchart in which the present invention can be implemented is shown in the first part.
As shown in the figure.

The starting material for the process of the invention is a titanium-containing raw material, such as Sorel slag. Various grades of Sorel slag can be used in the method of the present invention. For example, the composition of one representative grade of Sorel slag, expressed as an oxide, is approximately 70 weight percent TiO□;
Approximately 11 weight percent is FeO as an impurity, and the remainder is impurities (including, for example, Cab, Mgo,
5iOz, A 1zOs+MnO, C2oS+ Cr
zOx, and other oxides as trace impurities). Another grade of Sorel slag useful in the process of the present invention may consist of approximately 78 weight percent TiOz, approximately 8 weight percent FeO as an impurity, and remaining impurities such as those listed above.

It should be understood that the present invention is not limited to Sorel slugs. Within the scope of this invention are other raw materials or ores containing titanium as starting materials for this invention. For example, "chloride slag" may be used in the method of the invention. A typical chloride slag is approximately 8
It may consist of 5 weight percent TiO□, approximately 10 weight percent FeO as an impurity, and the remaining impurities such as those listed above.

Another suitable raw material for the process of the invention may be an intermediate product produced by carrying out a process for upgrading ilmenite as described in US Pat. No. 3,825,419. A typical material produced by carrying out the above upgrading method has approximately 95 weight percent Tt.
Q□, approximately 1 weight percent FeO as an impurity
, and the remaining impurities as listed above.

Examples of other titanium-containing materials that can be used in the method according to the invention include those whose titanium dioxide portion becomes reactive with alkali metal compounds when heated to temperatures between 700 and 950°C. Any treated titanium-containing material. The alkali metal compounds used herein include, for example, alkali metal hydroxides, alkali metal carbonates, alkali metal oxides, or mixtures thereof.

In the process of the present invention, all of the operations used for grinding, mixing, bi-firing, filtering, and calcination, as well as all other operations, are carried out by conventional equipment suitable for continuous or batch operation. It will be done. In order to grind the titanium-containing starting material to micron size, for example, US Pat.
of the type described and exemplified in No. 81414,
Preferably, a "sand mill" is used. here,
The "sand mill" method is, for example, US Pat. No. 258141
A method of grinding raw materials to micron particle size using equipment of the type described and exemplified in No. 4. However, the grinding media used in such equipment is not limited to sand, but may be spherical or bead-shaped - for boat fishing, glass, steel, ceramic, or any other material in the range of 0.5 to 3 fl in diameter. Any suitable grinding media may be used.

The digestion step must be carried out in a vessel that has an interior surface or lining that is resistant under normal operating conditions to the acid utilized in the process. Suitable materials for such internal parts include, for example, glass, FRP (glass fiber reinforced polymer composite), polyester, vinyl ester,
Epoxy resin or other suitable plastic, Hastelloy
(Product name) (Ni/No alloy), rubber, refractory metal (Ta
, Zr, Cb) or acid-resistant brick.

According to a preferred embodiment of the invention, the particle size of the titanium-containing feedstock should be small enough to allow all or substantially all of the feedstock to be reacted with the alkali metal compound. Referring to FIG. 1, the titanium-containing starting material is first ground to a size suitable for sand milling, such as by hammer milling.

In the following, the present invention will be described in detail using Sorel slag as a raw material containing titanium, but as mentioned above, the raw material is not limited to Sorel slag.

After the hammer milling step, the Sorel slag is preferably sand milled to an average particle size of about 157/11, more preferably about 10 IM. Even more preferably, the starting material may be sand milled to a maximum particle size of 1On or less. Particles larger than about 15 - will incorporate impurities that cannot be easily removed from the starting material in subsequent processing steps of the invention.

After grinding the Sorel slag to the desired particle size, it is homogeneously mixed with an alkali metal compound, such as an alkali metal hydroxide, an alkali metal carbonate, an alkali metal oxide, or a mixture thereof. Alkali metals such as sodium, potassium, lithium, rubidium, cesium, or mixtures thereof can be used.

Preferred compounds are alkali metal hydroxides, and more preferably sodium hydroxide, since it readily reacts with finely ground Sorel slag feedstock. In the following, the present invention will be described in detail using sodium hydroxide as the preferred alkali metal compound, but it should be understood that the present invention is not limited thereto.

Sodium hydroxide may be mixed with the Sorel slag feed prior to the bi-firing step and preferably during the sand milling step described above, or alternatively prior to the sand milling step. The mixture of Sorel slag and sodium hydroxide can contain about 30 parts by weight or more of sodium hydroxide per 100 parts by weight Sorel slag.

Preferably, 30 to 60 parts by weight of sodium hydroxide are used to about 100 parts by weight of Sorel slag.

More preferably, the weight ratio of Sorel slag to sodium hydroxide is from 100:35 to 100:4.
Up to 5. Although it is possible to operate with ratios of Sorel slag to sodium hydroxide greater than or less than the range of 100:30 to 100:60, doing so would result in a poor titanium dioxide pigment product. When using raw materials with a Ti(h content of more than 70 weight percent), the amount of sodium hydroxide in the mixture increases accordingly.

After the sand milling step, the mixture of Sorel slag and sodium hydroxide is heated or bi-baked at a temperature of 700-950 η for 1-3 hours. Bi-firing temperatures above 950°C may result in hard materials or talin forces, and below 700°C the reaction between the sodium hydroxide and Sorel slag may not be complete.

Therefore, the mixture should be heated at a temperature of 800-870 °C to 1.5-2
Time-baking is preferred. Preferably, the bi-fired mixture is subsequently ground to a particle size of 0.5 to 2 digits. As mentioned above, the fine particles facilitate the removal of impurities during subsequent processing of the bi-fired material.

It is believed that during the bi-firing process, the titanium dioxide contained in the mixture reacts with the sodium hydroxide to form sodium titanate. Some of the impurities in the feedstock will also react with the particular hydroxide used to form alkali metal salts, which will be in extractable form. For example, when using sodium hydroxide, impurities in the form of alkali metal salts include sodium vanadate, sodium chromate, sodium aluminate, and sodium silicate, which are readily soluble in water. do. These impurities are therefore preferably reduced, at least partially dissolved in water, by washing after the bi-firing step, or - preferably, substantially completely free of harmful amounts of impurities. 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 ()ICl) and are present during the digestion process discussed below. will be removed.

After water-soluble impurities have been washed away or dissolved from the bi-fired material, the remaining insoluble alkali metal titanate is digested with hydrochloric acid along with other insoluble oxides. It is preferred to use about 6 normal (N) hydrochloric acid because much weaker acids are not as effective as about 6N. Stronger acids may be used in pressurized vessels, although they tend to approach 6N when boiled in vessels open to the atmosphere. Therefore, it is entirely within the scope of this invention to use acids ranging from as low as 5N to as high as 12N. However, if the concentration exceeds 6N (which is an HC,l azeotrope boiling at 108°C), a pressure vessel is required. Therefore, it is more practical to operate at atmospheric pressure.

At standard atmospheric pressure, the digestion step is preferably carried out at a temperature of 90 to 110 °C, preferably at reflux, for a period in the range of 10 to 120 minutes at or above 80 °C, preferably at 108 °C. can be carried out for 10 to 40 minutes. Higher temperatures can be used, but a pressurized vessel will be required. The digestion step can be carried out once or more than once, but preferably it is carried out at least twice.

Nodular or acicular titanium dioxide particle shapes are obtained depending on how long the bi-calcined material (sodium titanate) is allowed to remain in 6NII at temperatures below about 90°C.Digestion step If a 6N acid suspension is heated slowly (at a rate of less than 5 °C/sin) to its boiling point of 108 °C, this operation yields titanium dioxide that is essentially nodular. The particle shape of increases the temperature of the digestion mixture very quickly or
or as a result of using an acid concentration of less than 4N in the heating step and increasing the acidity to 6N when the temperature exceeds 90°C.

In a preferred embodiment of the invention, the bi-fired material is combined with hydrochloric acid at room temperature (i.e. 20-30°C). The mixture of the bi-baked material and hydrochloric acid is then slowly heated to the boiling point of the hydrochloric acid at a rate of about 5°C/win or less, preferably at a rate of 2-b, more preferably 2°C/w.
heating at a rate of in or less. It is believed that nodular sodium titanate is formed during this digestion process.

In either case, to obtain a nodular or acicular particle shape, a suspension of about 6 NHtJ of washed bi-calcined material is boiled at reflux for a period that substantially completes the digestion process.

The boiling point varies depending on the pressure, but is in the range of 90 to 111°C, preferably about 108°C. Digestion is 10
Virtually complete in ~15 minutes.

Although digestion times of up to about 120 minutes can be used,
Preferably the digestion time is 10-40 minutes. Faster heating rates and shorter times may be used, but pressurized equipment will be required.

During the digestion process, the alkali metal titanates formed are believed to hydrolyze to amorphous hydrated Ti(h·nHzO), and iron oxides are available as ferric chloride and ferric chloride. Iron chloride and other impurities in the acid suspension are removed, for example by centrifugation or filtration, and optionally disposed of or further processed to recover unreacted acid. The insoluble amorphous titanium dioxide residue is washed with a fluid such as water to further remove soluble impurities. The titanium dioxide (TiOx) is then recovered from the water, for example by filtration or centrifugation. After that,
A white residual cake results.

Iron impurities in titanium dioxide pigments are believed to be responsible for the non-white pigments. Preferably, the iron content of the titanium dioxide pigment is less than 520 ppm, more preferably 200 ppm.
less than pm.

Amorphous titanium dioxide is preferably heated for 30 to 60 minutes at 8
By calcination at temperatures ranging from 00 to 1000 °C, Ti
1t is converted to its crystalline rutile form. More preferably, a temperature of 875-925°C is used for 30 minutes to 1 hour. This is because undesirable discoloration of the resulting pigment is minimized and lower temperatures are less effective in converting the product to its desired crystalline form.

If the crystalline rutile product obtained after calcination is severely agglomerated in the form of needles or nodules, it may be comminuted or ground in a sand mill. The final particle size for the acicular species is between 0.05 and 0.3-thick.
and the length is 0.1 to 1.0, preferably the thickness is about 0.
．． 2 tna and a length of about 0.7-, its value as an opacifier dictates a narrow optimum size range.

If the crystalline rutile product has a nodular shape,
The average particle size of the titanium dioxide particles is less than about 1 nanometer, preferably about 0.3 nanometers.

The product titanium dioxide can be used as a pigment in any of the typical applications in which opaque pigments are utilized.

By way of example only and without limiting the scope of the invention, the titanium dioxide pigment obtained by the method of the invention can be used as an opacifier in paints, papers, or plastics. The hiding power of this product (o
pacifying power) and brightness (brig.
htness) is determined by measuring its light scattering coefficient and reflectance. The pigment obtained by the method of this invention is
Preferably, the light scattering coefficient is about 2000 cm2/
g, preferably greater than #4000 cm2/g, more preferably greater than about 900 M/g,
and the brightness is greater than 80%, preferably 85-93%
It is.

The following examples illustrate the invention, but it should not be limited thereto.

〔Example〕

■A sample of approximately 75-g Sorel slag ore ground in an earthen hammer mill with approximately 70 weight percent TiOz and approximately 30 weight percent impurities.60
0 g was dispersed in 450 ml of water.

The Sorel slag in the suspension was mixed with a steel ball (s) with a diameter of 1.5 mm.
Sandmill was used for 120 minutes at 1000 rpm using a Teelshot 800-. The sand mill used had a cylindrical grinding vessel with an inner diameter of 11.5 cm and a height of 19 CJ, an air turbine-driven rotating shaft, and two 8.5 cm diameter polyurethane disc impellers spaced 4 (J) apart. It was a vertical water-cooled laboratory sand mill made of stainless steel.The circumferential speed of this impeller was 4.4 m/S.The rotation speed was controlled by an optical tachometer. Upon completion, the maximum size of the Sorel slag particles was about 10 Jna, the average size was about 5-, after removing the steel balls from the slag suspension by sieving through a sieve with an opening of 0.5 M. 2 in slag suspension
Add 40 g of anhydrous sodium hydroxide (NaOH),
Then mixed thoroughly. Next, Sorcil Slag/N
The mixture with an aOH ratio of 100/40 was evaporated to dryness in air at 120° C. in a shallow dish. A Weber Brothers rub mill was used to break up any agglomerates formed after drying and obtain a homogeneous mixture.
The dried material was hammer milled using a BrothersLab Mill) S-500. The resulting fine powder was placed in a porcelain crucible for 2 hours in the air.
It was baked at a temperature of 820°C for a time. 1 of the baked substances
A 50 g sample was ground in a mortar to eliminate lumps formed after baking and dispersed in 350-g water.

The bi-fired material and water were sand milled for 30 minutes at 11,000 rpm using 700 ml of 1.2×1 diameter glass beads. Glass beads were used in place of steel balls in this sand milling process to avoid discoloration of the material caused by steel balls.

After removing the beads by sieving, the dispersion of the sand milled bi-calcined material and water was centrifuged. The solid residue (solid content) obtained after centrifugation was redispersed in water, and centrifuged again to wash. Washing was repeated twice.

Next, the above solid content was dissolved in 6N hydrochloric acid 1000aZ (approximately 1
00° C.) and boiled for 90 minutes at a temperature of about 108° C. in an open beaker while stirring with a magnetic stirrer. The acidic liquid containing solids was centrifuged. The solids were washed twice with water and dried in air at 120°C. The dried solids were then calcined at 900° C. for 1 hour.

The resulting white calcined product has a density of 4.14 g
/aJ, and X-ray diffraction analysis showed that the calcined product had a rutile structure. Electron transmission microscopy (el
ectron translation yaic
roscopy showed pigment-grade titanium dioxide particles with needle-like shape. The particle size of this acicular pigment is 0.05 to 0.3 Ina thick and 0.1 to 1 Ina long. It was in the range of 0 μm.

The brightness (Roo) of the pigment is 88.4% based on the measurement of the light reflectance of the fume magnesium oxide surface, which has a reflectance of 100%, and its scattering coefficient (S) is 68.
It was 35cj/g. The iron (Fe) content of the pigment is
It was 520 ppm as measured by line fluorescence analysis.

The primary function of (S) and (ROo) titanium dioxide pigments is to provide opacity to materials such as paint, paper, plastics, etc. It is incorporated as a homogeneous dispersion. Of the many ways used to express the hiding power of pigments, the term scattering coefficient is particularly meaningful and can be easily measured accurately and reproducibly.

The principle of this test is to apply a thin film of pigment over a black sheet of glass such that this film is slightly translucent, i.e. approximately 80 to 90% of the reflectance of a thick, completely opaque film.
% reflectance. Another coating of the same dispersion is applied onto a white glass plate and thickened so that further increases in thickness do not change its light reflectance. Measure the reflectance (R and Roo) of these two films, respectively, and measure the weight it (W) (weight of dry film per unit area! (g/d)) of the film coating covering the black glass plate. and the scattering coefficient S (c+J/g) is defined by Kubelker-Munk's theory of light scattering (Kubelka-?1unk
Theory) (Zeitschrift, fur T.
ech, Physik, 12,593.1931). The reflectance measurement ROo of a film over a white glass plate is often referred to as brightness. A table based on the Kubelker-Munk equation can be found in Mttton-Jacobsen's paper "New Charts for Calculating Scattering Coefficients and Hiding Power" (Official D
igest.

September 1963, pp. 871-913). R1
Once R and W are known, S can be easily calculated using the table in the above paper. Example A below further explains how to determine S.

Hereinafter, the margin-penetrating pigment is dispersed in water, and a small amount of a binder is added as a film-forming agent to form a cohesive film when the dispersion is cast onto a glass plate for reflectance measurement. Since the opacity of the film is very sensitive to the pigment to binder volume ratio, this ratio must be kept exactly constant and the presence of the binder must weaken the hiding power of the pigment to an appreciable extent. must be held at a high enough level to prevent The test was performed at a pigment volume concentration of 70.00 percent (pigment volume equals 70.00 percent of the total volume of solids, and total volume of solids equals the volume of pigment plus the volume of binder). , and the film is slightly translucent when cast with a 37-way applicator onto a black glass plate (with a reflectance of approximately 80-90 percent of that of a thick, fully opaque film of the same dispersion). The solids content should be low enough so that A solids volume of approximately 4 percent is a suitable level for a titanium dioxide dispersion (pigment volume plus binder volume equals 4 percent of the total volume of the dispersion), with S and R∞ An example of a titanium dioxide pigmented coating composition for testing is listed in Table A below.

Table A, 1) Nalcochemical Campa, :l--(Nalco
"Narco (ChemicalCo+5pany)"
An anionic polyacrylic acid ester dispersant commercially available under the trade name Nalco) 2324J.

2) The Dow Chemical Company
A carboxylated styrene-butadiene latex commercially available under the trade name Dow Latex 620AJ by Che+wical Company.

In the above composition, the pigment volume concentration is 70.00
percent, and the volume of solids in the dispersion is 4.00 percent.

Pigments, water, and dispersants were supplied by Brinkmann Instrument Company.
Using a homogenizer commercially available under the trade name "rPT45/80 Brinkmann Homogenizer" by NTS Company, mix for 5 minutes at speed setting 4. Then add Dow Latex 620,
Stir the mixture on speed setting 2 for 5 minutes.

Pacific Scientific Company (Pac
The Gardner Laboratory, a division of the International Scientific Company
A Bird Film applicator with a width of 15C11 and a gap of 0.037, commercially available from
or) is placed on top of a 50 x 50 cm black glass plate (reflectance = 0) and a dispersion of approximately 3- is placed in front of the applicator. Draw the applicator down evenly along the glass plate at a uniform speed. Dry the film in a horizontal position at room temperature. Using a Bird applicator with a gap of 75μ, the same dispersion was applied to a white glass plate (reflectance = 8
5. Pull down along 6).

After drying these films for about 2 hours, an area of 32-5
A 6.25 cm x 6.25 cm rectangular template is placed over the coating on a black glass plate and the outer coating of the template is removed with a razor blade, leaving a 32aJ rectangular patch on the black glass plate. Next, Eastman Kodak Company ([!astman Kodak Cos+-pany
Photovolt (P
Use a reflectometer to measure the reflectance of the punch on the black glass plate and the coating on the white glass plate.The punch on the black glass plate is then removed with a razor blade and weighed on an analytical balance. do.

The following values are examples.

R=79.5 Roo=92.0 W=0.0186 g/32c+4 or 0.000577 g/cm2 Table 8 on page 895 of the paper by Mitzton-Jacobsen mentioned above and the above for given R and Roo From the value of , the scattering power (SW) is 4
．． It turns out that it is equal to 09. Scattering 46 can then be calculated as follows.

W 0.000577 = 7088cj/g Sample 6 of Sorel slag with approximately 70 weight percent Ti01 and approximately 30 weight percent impurities.
00g was ground in a sand mill as in Example 1. The suspension ground with steel balls contained 57% slag. 175 g of this suspension (=100 g of solid slag
) was mixed with anhydrous sodium carbonate (Na, C03), the suspension was dried, processed with a hammer mill, and 1050
It was baked at t for 2 hours.

Crush the baked hard material in a mortar to 3.6 μm.
bits, then hammer milled to a fine powder, which was further sand milled using glass beads as in Example I.

This bi-calcined material is dispersed in water, separated in a centrifuge, washed as in Example 1, digested in 10QQd of 6NHC1 for 90 minutes, followed by separation and washing of the solids as in Example 1. did. After baking at 900° C. for 1 hour, a white pigment with a rutile structure and a density of 4.10 g/aJ was obtained.

The brightness of this pigment was 78.3%, and the scattering coefficient (S) was 4128 cj/g.

■ A 600 g sample of hammer milled Sorel slag containing approximately 70 weight percent titanium dioxide and approximately 30 weight percent impurities was sand milled using steel balls as in Example 1.

The sieved steel balls were washed with water. The wash water was mixed with the ground slag suspension. The solids content of the suspension with water was 45.9 percent.

327 g sample of slag suspension (150 g solid slag)
) was mixed with 52.5 g of anhydrous sodium hydroxide to give a slag/NaOH ratio of 100:35. The mixture was evaporated to dryness at 120°C, then ground in a hammer mill and bi-calcined at 800°C for 2 hours. Without further grinding in a sand mill, the bi-calcined material was then dispersed in water and centrifuged. The separated solids were washed twice with water by redispersing them in water and centrifuging them again. The washed bi-calcined material was then boiled for 1 hour in 10100O 6NHCj2 in an open beaker. After digestion with acid solution, the solids were separated and washed twice by centrifugation.

The solids were then redispersed in 300-ml of water and 700-
Grinding was performed in a sand mill using glass beads at 11,000 rpm for 60 minutes. After sieving to remove the glass beads, the white opaque suspension was mixed with an equal volume of 12NH (/
! were mixed and boiled in an open beaker for 10 minutes (final boiling point was approximately 108°C).

The solids were then separated, washed twice with water, and
Dry at ℃. The solids were then calcined at 900° C. for 1 hour. Density is 4.0g/cm and iron content is 150
A pigmented titanium dioxide which is ppa+ was obtained.

The brightness of this pigment was 88.9% and the scattering coefficient (S) was 3760 td/g.

■Sample 3 of Sorel slag crushed with steel balls prepared in Soil Example 3
27 g (150 g of solid slag) was mixed with 45 g of anhydrous sodium hydroxide (slag/NaOH ratio = 10
0/30). The mixture was evaporated to dryness at 120° C., followed by hammer milling and baking as in Example 3. The two digestion steps and other processing steps were also performed as in Example 3. This example was conducted to determine the effect of reducing the amount of sodium hydroxide added to the Sorel slag feed of Example 3 on the properties of the final pigment.

After calcination, the titanium dioxide pigment obtained had a pale yellow color, and the iron content was 8300 ppm.

The brightness of this pigment was approximately 50%.

Scatterer #! The value of 1(S) was not measured.

5) A 600 g sample of hammer milled Sorel slag with approximately 70 weight percent titanium dioxide and approximately 30 weight percent impurities was dispersed in 480 g of a 50% NaOH solution (slag/NaOH ratio = 10).
0/40), this suspension was processed in the sand mill described in Example 1 using 800-grade steel balls at 900 rpm for 150 minutes. The particle size of the solid particles of the sand milled suspension was up to about 13 particles, with an average size of about 74 particles.

After sieving the steel balls from the suspension, the suspension was dried at 120°C, hammer milled and bi-calcined at 850°C for 2 hours.

A 150 g sample of the bi-fired material was sand milled using 700-g glass beads and 350-g water at 11000 rpm for 10 minutes. After removing the glass peas through a sieve, the solids are separated using a centrifuge and washed for two
I went around. The solid residue obtained in the centrifugation H& was then dispersed in 500-10.8N IIcβ and boiled at 107° C. for 25 minutes under reflux. The solid content was separated from the acid solution by centrifugation and washed once with water. The centrifuged solids were redispersed in 500rn1 of 7NHIJ and boiled at 108°C for 30 minutes under reflux. The solid content was separated from the acid solution by centrifugation and washed three times.

The centrifuged solids were dried at 120°C and 90°C.
Calcined for 45 minutes at 0°C. A pigmented titanium dioxide with an iron content of 65 ppm was obtained. The brightness of this pigment is 9
0.5%, scattering coefficient (S) is 4472a+1/
It was g.

A 400 g sample of hammer milled Sole's slag containing approximately 70 weight percent titanium dioxide and approximately 30 weight percent impurities was dispersed in 280 g of water and 180 g of anhydrous sodium hydroxide.
Slag/NaOH ratio = 100/45).

This suspension was processed in the sand mill described in Example 1 using a 1.5 mm steel ball 600-mm at 1350 rpm for 150 minutes.

After sieving off the steel balls, the sandmilled suspension was dried at 120°C, ground in a hammer mill and bi-fired at 840°C for 2 hours.

A 150 g sample of the bi-calcined material was dispersed in 350 mj of water and milled in a sand mill at 1000 rpa+ for 10 min.
．． It was pulverized using a 2-piece glass pea 700-. After sieving the glass peas, the suspension was centrifuged and washed twice. The washed centrifuge cake weighed 234g and contained 96g of water. Therefore, the yield of solid bi-fired material was 138 g. This cake was dispersed in 300 mj of water and 605 mj of 12 NH (J). The liquid portion ended up being 7.3 N HCl, which became 6 N after neutralization of the solids. Digested at 108 °C under reflux. The solid content was separated from the acid solution by centrifugation, washed twice, then dispersed again in 600-6NIIIJ and digested for another 20 minutes, and then the solid content was separated by centrifugation. Washing was carried out twice.Next, the solid content was reduced to 120
It was dried at 900°C and calcined for 1 hour at 900°C. A titanium dioxide pigment with an iron content of 30 ppm was produced. The brightness of this pigment is 90.1% and the scattering coefficient (S) is 61
It was 7M/g.

■1 In this example, the Socil Slag/NaOH ratio is 10015.
I changed it to 0 and processed it as follows.

A 600 g sample of hammer milled Sorel slag with approximately 70 weight percent titanium dioxide and approximately 30 weight percent impurities was added to 400n+7
1.5 wr steel balls 8 were dispersed in water and milled in a sand mill as described in Example 1 for 120 minutes at 1800 rpm.
It was ground using 00-. Steel balls were removed by sieving.

60 g of anhydrous sodium hydroxide was dissolved in this slag suspension containing 120 g of Sorel slag, placed in a shallow dish and dried in an oven at 120°C.

The dried material was ground in a hammer mill and heated to 840°C.
I baked it for 2 hours. The bi-fired material was dispersed in 350 mJ of water and ground in a sand mill using 700-mm glass beads with a diameter of 1.2 mm at 1000 rpm for 10 minutes. The firing material was manufactured by W&R Polton Ltd. (W&R
Bolton, Ltd.
perN1541) J, using a filter paper with a pore size of approximately 74, with a diameter of 15 aa.
The mixture was vacuum filtered using a Puchner funnel and washed with approximately 2 F of water.

The washed bi-fired material was then treated with 1000-6NHC1
The mixture was digested for 20 minutes at 108° C. under reflux.

Then, 7 grams of a 1 percent solution of the first flocculant was added. This added first flocculant was incorporated into U.S. Pat.
The Dow of the type generally described in No. 48
It was a cationic homopolymer manufactured by The Chemical Company. The flocculated suspension was vacuum filtered and washed on the filter with 21 portions of water. The filter cake was dispersed in 1000-6N) lcjl at about 30°C and the temperature was lowered to 1
Gradually (within about 20 minutes) raise the temperature to a boiling point of 0.8°C,
The temperature was maintained for 20 minutes. Next, 1000-g cold water and 7 g of a 1 percent solution of a second flocculant were added. This second flocculant was also manufactured by The Dow Chemical Company and was a slightly anionic homopolymer of solid acrylamide with a degree of hydrolysis of 1 to 5 percent. pH of second flocculant = 3 and 25°C
The viscosity of a 0.5 percent solids aqueous solution is 31 to 50
It was in the cP range. The flocculated suspension was vacuum filtered and washed with 2N water, followed by drying at 120°C. solid content 9
Calcined at 00°C for 1 hour.

Electron micrographs showed pigments with nodular or nonacicular shapes. X-ray diffraction analysis confirmed that the pigment had a rutile structure. Scattering coefficient 0) value 4;! 240
8rd/g, brightness was 83.9%.

In this example, pigment titanium dioxide was produced using a titanium-containing raw material called chloride slag, containing approximately 85 weight percent titanium dioxide and approximately 15 weight percent impurities. The particle size of the raw material was approximately 840 um.

A 400 g sample of this raw material was mixed with 200 g of anhydrous sodium hydroxide and 300 g of water. Using the sand mill described in Example 1, the above raw materials were ground using 1.5 fl steel balls at 1500 rpm for 240 minutes to an average particle size of about 10 mm. After sieving the steel balls from the sandmilled suspension, the suspension was dried at 120°C, ground in a hammer mill, and bi-fired at 840°C for 2 hours.

A 150 g sample of the bi-fired material was dispersed in 350-g water and ground in a sand mill with 700-g glass beads at 1000 rpm+ for 10 minutes. After removing the glass beads from the suspension, the suspension was centrifuged. The centrifuge cake was washed four times. The centrifuge cake was refluxed in 1000-6NIIl.
Digested for 20 minutes at 08°C. At the end of the digestion, 5 g of a 1 percent solution of the first flocculant described in Example 7 was added to the digested material and the flocculated suspension was vacuum filtered. The filter cake was then washed on the filter with 1000+ nl of water.

The washed filter cake was digested once more for 20 minutes at 108° C. under reflux in 1000 −1 of 6NH.

After digestion, 5 grams of a 1 percent solution of the second flocculant described in Example 7 was added to the digested material. The flocculated suspension was then vacuum filtered and washed on the filter with 21 g of water. The filter cake was then dried at 120°C. The solids were calcined at 900°C for 1 hour. Dispersion coefficient (S) is 5
A pigmented titanium dioxide of 670 m/g and a brightness of 89.0 percent was obtained.

- A 500 g sample of hammer milled Sorel slag containing approximately 78 weight percent titanium dioxide and approximately 22 weight percent impurities was dispersed in 350 a/ml of water and milled by sand milling as described in Example 1.
18 at 1800 rpm using 5 n+ steel balls 800-
Milled for 0 minutes. The circumferential speed of the impeller was 8 m/s.

The crushed slag was sieved through a 425μ sieve to remove steel balls. The steel balls were rinsed with water and the water was mixed with the ground slag described above to form a slag suspension with a solids content of 24.5 percent ft.

612 g of this slag suspension (150 g of solid slag)
), add 67.5 g of anhydrous sodium hydroxide to Sorel slag/Na0)! The ratio was set to 100/45. The mixture was evaporated to dryness in a shallow dish at 120°C. The dried material was ground in a hammer mill to obtain a uniform fine powder. Next, this powder was heated to 840°C in a porcelain crucible for 1 hour.
It was heated or baked for 50 minutes. The baked material was cooled and pulverized in a mortar. This bi-calcined material was then dispersed in 350 mm of water and 1 mm in diameter as the grinding media.
, 2fl of Glass Peas 700+d was used for 10 minutes at 180 rpm in the laboratory sand mill described above. The sand milled bi-calcined material was sieved to remove beads, water was added to 1500- and vacuum filtered through a 15 cm diameter Buchner funnel using No. 541 Whatman filter paper. About 2c! The filter cake, now 1.2 mm thick, was washed on the filter with about 2 Il of water. The solids content of the filter cake was 62.6%.

The washed filter cake was diluted with 200 mZ of 12N) lcj! water at 300 mZ! was added to the mixture. This mixture, which has a normality of about 4.4, was heated to a temperature of 100° C. in a four-necked 21 glass flask equipped with a reflux condenser, thermometer, stirrer, and stopcocked funnel. did. After that, to raise the acidity to 6N, add 40% to the flask.
0-12NHIJ was added. The temperature instantly dropped to 85℃, but this temperature dropped to 6NIC within 5 minutes!
The boiling point of 108°C was reached. The mixture was boiled for 20 minutes and then 7 grams of a 1 percent solution of the first flocculant described in Example 7 was added to the mixture with continued stirring, diluted with cold water to 2000-.

The mixture, now approximately 3N, was vacuum filtered. The filter cake was washed on the filter with 21 portions of water.

The solids content of this filter cake was 32.5 percent.

This filter cake, weighing 323 g (solid content 105 g), was dispersed in a solution of 280-g water and 200-g 12NH (J). This mixture was placed in a four-loaf flask and heated to 100°C. .Then, this mixture
0af's 12NHCj! added. The temperature was increased to the boiling point of 108°C of 6NHC and held at this temperature for 20 minutes. The mixture was diluted to 2000 with cold water. Seven grams of a 1 percent solution of the second flocculant described in Example 7 was added to this mixture while stirring continued. The mixture was filtered and washed as after the first digestion.

The filter cake, approximately 3 cm thick, was dried at 120° C. and then ground in a mortar. Grind the cake at 900℃
I baked it for 1 hour. The calcined material was immediately placed in a large porcelain shallow dish and exposed to air to cool at room temperature. Pigment titanium dioxide was obtained.

, X-ray diffraction analysis revealed that the pigment was rutile, and its density was 4.1 g/c+J.

This pigment had a scattering coefficient (S) of 6900c+J/g and a brightness of 92.2%. The crystal habit was needle-like.

- Dioxide as in Example 9, except that the Sorel slag/NaOH ratio was changed to 100/40 and the sodium hydroxide was added to the Sorel slag before sand milling rather than after the Sorel slag was sand milled. A titanium pigment was produced.

The needle-shaped pigment has a scattering coefficient (S) of 8900c.
m2/g, and the brightness was 91.0%.

Benilite cyclic process (Benilite Cyclic method)
ic Process) was used as the starting material for this example. This black material is approximately 93 weight percent titanium dioxide and approximately 7 weight percent impurities, and has a particle size of approximately 2.
It was 5 On.

A 400 g sample of this raw material was mixed with 200 g of sodium hydroxide and 350 g of water and ground in the sand mill described in Example 1 using 600 rsl of 1.5 steel balls at 1600 rpm for 90 minutes. The sand milled material contained particles with an average particle size of less than about 10-. After sieving to remove steel balls, the ground material was dried at 120°C, ground in a hammer mill, and bi-fired at 840°C for 2 hours. A 170 g sample of the bi-fired material was dispersed in 350-g water and ground in a sand mill with 700-g glass beads at 1600 rpm for 10 minutes. After sieving to remove beads,
The suspension was centrifuged and the centrifuge cake was washed twice with water.

This centrifugation cake is 1000-6NHCj! The mixture was digested for 20 minutes under reflux. The solid content was separated from the acid solution by centrifugation and washed. As expected 10001&1
Digestion in 6NIIC It was performed once more, followed by centrifugation and washing. The solids were dried at 120°C and then calcined at 900°C for 1 hour.

A pigmented titanium dioxide having a needle-like shape was obtained.

This pigment had a scattering coefficient (S) of 4260 ad/g and a brightness of 90.0%.

Table 1 below summarizes the above examples except Example 2.8.11.

Margin below 劃”

A sample of Sorel slag with a particle size of approximately 74 m was obtained from QrT-FERET TITANE, INC., a Canadian company. A 1200 g sample of this Sorel slag and 480 g of sodium hydroxide (NaOlt) were placed in a laboratory sand mill containing 11 steel balls 1.2 m in diameter and approximately 1000 g of water. This mixture was then sand milled until the maximum particle size (largest dimension) of the Sorel slag was 10. The weight ratio of slag/NaOH in the mixture was 100/40. After sieving to remove the steel balls, the mixture was dried in an oven at a temperature of 100°C. The dried material was processed in a hammer mill to crush the agglomerates that formed after drying.

The hammer milled material was then bi-calcined at a temperature of 875° C. for 2 hours. The bi-calcined material is passed through a grinder to crush the agglomerates formed after bi-firing, and then this bi-calcined material is milled in a sand mill to approximately 700 rn! of water and 11 zirconium oxide beads with a diameter of 1.2 mm for 5 minutes. After sieving to remove the beads, the suspension is vacuum filtered and the filter cake is soaked twice with water, each approximately 1.
1 water was used for washing.

A sample of 194 g of bi-fired material on a dry weight basis was
++! The digestion process was carried out as follows: the temperature of the 6N solution (i.e. the mixture of bi-calcined material and hydrochloric acid) was kept at room temperature (20°C).
)Met. The temperature was then slowly increased to the boiling point of the 6N hydrochloric acid solution at a rate of about 5° C./.mu.m, and the solution was refluxed for 15 minutes. When calculating the normality of hydrochloric acid, the amount of water in the wet filter cake was taken into account. A flocculant, namely SEPARA, is added to this digestion suspension.
N)? Three grams of a 1 percent solution of IG-205 (trade name of The Dow Chemical Company) was added. The suspension was filtered and washed twice with water, each using 11 portions of water. Redisperse the filter cake in water and add 800
Digestion was carried out again in the same manner as the first digestion with 6N HCl in d. The same amount of flocculant was added to the suspension as during the first digestion. The suspension was then vacuum filtered and washed as during the first digestion. The filter cake was dried at a temperature of 110° C. for about 3 hours. The dried material was then calcined at a temperature of 900° C. for 1 hour. The resulting rutile pigment had a distinct nodular particle shape.

A portion of the calcined material was placed at a depth of about 1.3 am and a diameter of 2
The dry brightness of the calcined material was measured by filling a 5 cm sample vial cap and measuring the reflectance of the sample using a photovolt with a blue filter. The instrument was first calibrated by using a white standard chip of known brightness of 86.9 with a blue filter. The dry brightness of the calcined material in this example was 88.0 percent.

The scattering coefficient of this calcined material was determined by the following procedure.

That is, 15 g of a pigment sample and 0.5 g of sodium tripolyphosphate were placed in 70 g of water and dispersed for 5 minutes using a high-speed disperser. Next, to this suspension was added 3.1 g of latex sold under the trade name Rhoplex B-100 by Rohm and Haas Co. and Triton X-
0.5 g of a surfactant sold at 100 was added and gently stirred by hand for about 3 minutes. Drop-down coatings of this suspension were applied using a Mylar (E, 1. DuPont) using a 37-point Bird film applicator.
Dupont de Nemours (E, 1. Dupont de NeI
It was applied to a 504-thick transparent plastic sheet of the trade name Iours & Co.) and dried in an oven at a temperature of 100° C. for 3 minutes. A 5C11 x 5CIII square sample of coated mirror sheet was weighed and then 50
It was mounted on an optically flat black glass plate of IX 12.5 cm.

Propylene glycol was used to ensure optical contact. Regarding this sample, the reflectance R8 on black glass was measured using a photovolt. 50IIX5
(The coating on the mirror sheet of J was washed off, the mirror sheet was dried, and then weighed to determine the coating weight 1w per unit area. The practical neighbor value Roo for an infinitely opaque coating is as follows: A drop-down coating was applied on a sheet of 50μ mirror, allowed to dry, and the process was repeated until the maximum reflectance was reached as measured by photovoltage.R1, Rω, and Using the value of W, we use the paper by Michael Jakobsen, ``A New Diagram J for Calculating Scattering Coefficients and Hiding Powers'' (Official Digest.

The scattering power value SW was determined using the table published in September 1963, pp. 871-913). The scattering coefficient S was then calculated using the following formula:

In this example, the scattering coefficient of the calcined material is 3336
cm2/g.

The iron content of the calcined material was determined using ionic coupled plasma spectroscopy.
electrometry). In this example, the iron content of the calcined material was 200 ppm+.

Margin below

[Brief explanation of the drawing]

FIG. 1 is a schematic flow diagram of one way in which the method of the present invention may be implemented.

Claims (1)

[Claims] 1. The following steps: (a) pulverizing the raw material containing titanium dioxide; (b) converting the raw material containing titanium dioxide into alkali metal hydroxide, alkali metal carbonate, and an alkali metal compound selected from alkali metal oxides; (c) bi-firing this mixture at a temperature of 700-900°C; (d) digesting the bi-baked material with hydrochloric acid; e) Calcining the solid product produced in the digestion step at a temperature of 800-1000<0>C to form a titanium dioxide pigment. 2. The titanium dioxide-containing raw material is selected from Sorel slag, high-grade ilmenite, and chloride slag,
2. The method of claim 1, wherein the alkali metal compound is an alkali metal hydroxide, and the weight ratio of Sorel slag to alkali metal hydroxide is from 100:30 to 100:60. 3. Treat the mixture of the titanium dioxide-containing raw material, the alkali metal compound, and water with a sand mill to reduce the particle size to 15%.
2. The method of claim 1, further comprising the step of reducing to less than .mu.m. 4. The method of claim 3, wherein the titanium dioxide-containing feedstock is Sorel slag and the alkali metal compound is sodium hydroxide, and the mixture is sand milled to a particle size of less than 10 μm. 5. A claim comprising filtering solubilized material from the bi-firing mixture after step (c) and filtering hydrated amorphous titanium dioxide material from the acid treatment step after step (d). The method according to item 1, 2, or 3. 6. Grinding the bi-firing mixture of step (c) in water with a sand mill and filtering the solubilized substance from the bi-firing mixture;
The bi-firing mixture of step (c) was heated to 90-110% with hydrochloric acid.
producing the hydrated amorphous titanium dioxide material of step (d) from the acid solution by digestion at a temperature of 0.degree. C. and washing the titanium dioxide material prior to calcination.
A method according to any one of claims 1 to 5. 7. Digesting the bi-calcined material for 10-120 minutes;
A method according to any one of claims 1 to 6. 8. Any one of claims 1 to 7, which includes a step of finely pulverizing the particles of the calcination product to have a nodular shape to an average particle size of about 0.3 μm. The method described in. 9. If the calcined product has a needle-like shape, finely pulverize it to a length of 0.1 to 1.0 μm and a thickness of 0.05 to 0.3 μm.
8. A method according to any one of claims 1 to 7, comprising forming micron particles. 10. Brightness of the produced titanium dioxide pigment after calcination (
10. The method according to claim 1, wherein R^∞) is between 88 and 94 percent. 11. The method according to any one of claims 1 to 10, wherein the titanium dioxide pigment produced after calcination has a scattering coefficient (S) of 2000 to 9000 cm^2/g. 12. The method according to any one of claims 1 to 11, wherein the iron content of the titanium dioxide pigment produced after calcination is between 30 and 600 ppm. 13. Bringing the mixture of the bi-calcined material and acid to its boiling point;
2. The method of claim 1, further comprising heating at a rate sufficient to form a nodular material. 14. The method of claim 13, wherein the mixture of bi-firing material and acid solution is heated to its boiling point of 90-110C at a rate of less than 5C/min. 15. Bringing the mixture of the bi-calcined material and acid to its boiling point;
2. The method of claim 1, comprising heating at a rate and acidity sufficient to form a needle-shaped material. 16. The method of claim 15, wherein the acidity of the mixture of bi-firing material and acid is maintained below 4N during the heating step and increased to 6N when the temperature exceeds 90<0>C. 17. The method according to claim 12 or 13, wherein the titanium dioxide pigment produced after calcination has a scattering coefficient (S) of 1500 to 5000 cm^2/g. 18. Claim 12, 13, or 1, wherein the iron content of the titanium dioxide pigment produced after calcination is less than 520 ppm.
The method described in 4. 19. Claim 1, wherein the digestion step is performed at least twice.
The method described in any one of to 18.