Title of Invention	"RUTILE-BASED PIGMENT AND A METHOD FOR THE PRODUCTION THEREOF"
Abstract	There is disclosed finely divided, brilliant, and highly opaque rutile-based pigment, which comprises a nickel- antimony rutile yellow featuring a color saturation C* of 52 to 55 acc. to DIN 5033, at a color hue angle h of 96° to 98° and a particle size distribution with a diameter range between 50 and 1000 nm, which in case of a mon-, bi-, tri or oligomodal-type maxima distribution may feature a majorizing (primary) maximum between 230 and 400 nm, and a secondary maximum of less than 25% of the primary maximum in a diameter range between 400 and 1000 nm in case of bi-or oligomodal distributions.

Title of Invention

"RUTILE-BASED PIGMENT AND A METHOD FOR THE PRODUCTION THEREOF"

Abstract

There is disclosed finely divided, brilliant, and highly opaque rutile-based pigment, which comprises a nickel- antimony rutile yellow featuring a color saturation C* of 52 to 55 acc. to DIN 5033, at a color hue angle h of 96° to 98° and a particle size distribution with a diameter range between 50 and 1000 nm, which in case of a mon-, bi-, tri or oligomodal-type maxima distribution may feature a majorizing (primary) maximum between 230 and 400 nm, and a secondary maximum of less than 25% of the primary maximum in a diameter range between 400 and 1000 nm in case of bi-or oligomodal distributions.

Full Text	The invention relates to a fine-particle, bright, and highly opaque rutile-based pigment without the addition of impurities by reactive metal components and to a method for the production of such pigments. Nickel antimony titanium yellow pigments are by nature pale yellow pigments with high opacity. Overdyeing with high quality organic pigments makes it possible to obtain highly saturated full- tone colors with which the entire color spectrum can be covered, with the exception of blue and violet hues. This overcoloring results in a synergy between the relatively high opacity of the cost-effective nickel antimony titanium yellow and the great color intensity of the organic overcoloring pigments, which are generally quite expensive. This effect can also be obtained using titanium white; however, overcoloring always leads to greater brightening, that is, to less saturation, due to the high whitening power of titanium white pigments. Another disadvantage of titanium white overcoloring is the photocatalytic effect of titanium white pigments, which leads to a sharp decrease in the light-fastness and weather- fastness of the expensive organic color components. Consequently, full hues based on titanium white "age" some four-times faster than mixtures of the same organic color components with nickel antimony titanium yellow. In the past, this decisive use of nickel antimony titanium yellow was seldom used because the nickel titanium pigments currently available on the market are abrasive (grain-hard and sharp- edged), have poor gloss, and are inferior in terms of covering capacity compared to titanium white. Moreover, the following economic background should be considered: Nickel antimony titanium yellows account for relatively small market shares among titanium pigments, as the following figures demonstrate: titanium white world market: 4,000,0001, titanium yellow world market: 20,000 t, of which chromium antimony titanium yellow: 16,000 t, of which nickel antimony titanium yellow: 4,000 t. The annual tonnage of chromium antimony titanium yellow is disproportionate to that of nickel antimony titanium yellow. As colored pigments, nickel antimony titanium yellows offer merely an unsatisfactory option for replacing the 100,000 annual tons of lead sulfochromate and molybdate red pigments pursuanttorthe hazardous materials laws and environmental protection laws that have become increasingly stringent since 1980. The reason for this is the deficiencies, considered unchangeable, that are manifested in particular by the inadequate opacity, compared to titanium white and to chromium and cadmium yellows and by inadequate gloss and high abrasiveness. These three deficiencies are the result of one and the same cause, specifically a mean particle, size, primarily of the nickel antimony titanium yellow, that is too large and that is an average of 1000 - 2000 nm in the best qualities found on the market, while the optimum opacity of a pigmentary coloring agent is attained with a particle size of 300 nm and with optimized grain shape and surface. A pigment loses about 20% of its opacity when the mean particle diameter is greater than 500 nm. Finer commercial type according to the prior art are regularly slightly doped and greatly whitened, and in addition due to their high grinding costs expensive, highly doped, high-fired products are unknown because they are inconsistent in terms of color. Surface enlargement when the mean particle diameter is 300 nm should be avoided for color pigments because they become transparent when they drop below a particle diameter of about half the wavelength of the light reflected by them, which is undesirable for applications for nickel antimony titanium yellow pigments. When the hardness of the particles is high, abrasiveness increases for spiky and sharp-edged particles. The goal is therefore also to produce isometric particles (rhombi) that are chamfered or have beveled flattened or rounded areas on the corners. This cannot be obtained using a coating in accordance with DE-A-2 936 746 that acts in cooperation with surfactant agents such as a slip agent and which additionally requires its own processing step and the use of auxiliary agents as the subject matter of the invention. Nevertheless, for avoiding color effects under different types of illumination (metamerism), a relatively smooth surface and also approximate uniformity of the (projected) edge lengths should be obtained; a spherical shape is unattainable under any conditions, however. Talcing the aforesaid into account, the relevant prior art shall be addressed: In the past, a mean particle size of 300 nm has not been reached by any manufacturer with satisfactory results for highly doped and/or fully annealed nickel or chromium antimony rutile yellow pigments (TiO2 antimony titanium yellows. In fact, thelsmali dopings described therein inter alia with antimony and chromium at low firing temperatures lead to a pigment with a narrow grain size distribution and corresponding fineness, sometimes also due to the softer grain of the mixed phase oxide pigments described therein. However, there are still also limits for hue creation in terms of how the reactive iron content can assume uncontrollable amounts if a non-metallic mill with resistant lining is not used as it is inventively in this case. Still, with a product according to the prior art in DE-A-3 202 158, increased photoactivity, and with appropriate very fine grinding, a high degree of whitening must be accepted. If iron abrasion is permitted in the milling process, the material grays and leads inter alia to disturbances in PVC-based matrices. This is true even for mixed phase rutile-based oxide pigments that contain iron bound as a non-reactive component in the crystal lattice of the rutile, as in example 3 of DE-A-3 202 158, In accordance with the teaching of DE-A-3 202 158, a coloristically favorable grain size distribution is attained when low doping, relatively low firing temperature, and wet milling are combined. However, this application does not provide any information on grain size distribution and specifies the type of milling only imprecisely. In the case of titanium dioxide, synthesis during the chloride method with the adjustment of the TiCl4 burner and mixing in of agglomeration-preventing sand in the subsequent cooling and conveying process has already found a practical path for adjusting optimized particle size distributions (d50 = approx. 280 nm for light of 550 nm wavelength) (see inter alia: Winkler, J: "Titanium Dioxide", Hannover: Vincentz, 2003; ISBN 3-87870-148-9; pp. 35 - 37;51-58). Although in this method small quantities of aluminum chloride are metered to the titanium tetrachloride for "rutilization", it being unresolved how many lattice places in the rutile are really occupied by aluminum ions, this method is not promising e.g. using the addition of antimony and nickel chlorides to titanium tetrachloride upstream of the burner. Separation and inhomogeneous volatility of metal chlorides and metal oxychlorides prior to the lattice insertion of the metal ions is observed. A lengthy afterglow period leads to reagglomeration. The Ishihara Company is particularly active in the prior art. This is demonstrated by worldwide patent applications. These include for instance EP 1245 646 (Al, corresponds to US-A-6 576 052), in which a fine-particle TiO2 obtained from the chloride process, already 100 to 400 nm mean grain size, is re-ground to a corresponding fine primary grain size during a siloxane post- treatment and coating with aluminum phosphate using a jet mill. According to EP-A-1 273 555 (corresponds to US 6 616 746), the same grain fineness of the raw pigment for coating is used with multivalent alcohols and hydrolyzed amino silanes and/or aluminum hydroxide. The procedure is the same as the foregoing. Good dispersibility of the photostabilized products is claimed. For grinding, the pigment is comminuted after or during addition of the coating and stabilization reagents at a temperature of 120 to 300 °C in a jet mill or a similar "fluid energy mill" that permits a hydrolysis reaction of the amino siloxanes and other reactive components and prevents any reagglomeration during the coating process. This patent relates only to TiO2 in rutile modification (which is preferably formed by the additions of aluminum). After working up the batch, the coating is principally to act in a manner that prevents agglomeration and is photostabilizing, i.e. lastingly moderates the photocatalytic effects of the pigment. Wet grinding of rutiles, that is also rutile yellow pigments, in high-intensity bead mills is prior art e.g. in accordance with DE-A-3 930 098. These are sold by a number of different specialty companies. The option provided e.g. in DE-A-4 106 003 to obtain an a priori finer grain structure and thus save a grinding process by "alloying" the firing batch for a rutile brown pigment with small quantities of cerium, inter alia, cannot be performed with chromium and nickel titanium pigments due to the brighter hues that are more sensitive to fluctuations in doping. Basically many companies seem to prefer wet precipitation to the actual synthesis of the pigment and thus create a "wet precursor" which is imprinted with the grain distribution and thus the fineness, which is maintained even until after calcination and final fine grinding. The hydroxyl groups on the surface of the freshly precipitated oxides and hydroxides represent a good precursor for the diffusive penetration of the rutile lattice, which also has numerous vacancies, with foreign metal ions after evaporating the water above 150 °C. However, the finer grain sizes possible due to the lower firing temperature are not of reproducible color intensity. The diameter still fluctuates between 800 and 1200 nm. Proceeding from the prior art described in the foregoing, the object of the invention was to suggest a fine-particle, bright, and highly opaque rutile-based pigment that is distinguished by superior opacity, gloss, and lower abrasiveness. Moreover, it should have the smallest possible or no iron content, for instance in the ppm range in any case. Moreover, the invention should suggest a method with which such a pigment can be produced in a particularly economical manner. This object is inventively attained using a fine-particle, bright, and highly opaque rutile-based pigment that is characterized in that it has a grain size distribution with particle diameters between 50 and 1000 nm and for mono-, bi-, tri-, or oligomodal frequency distribution has a primary maximum between 230 and 400 nm, whereby for a bi- or multimodal frequency distribution where necessary a secondary maximum occurs, at less than 25% of the primary maximum, between 400 and 1000 nm, in particular between about 400 and 900 nm. It is particularly preferred when the claimed primary maximum is between 280 and 340 nm and/or the secondary maximum is between 480 and 800 nm. Furthermore, it is preferred when the mean particle diameter of the pigment is between 80 and 1000 nm, in particular between 80 and 900 nm. The range of 120 to 600 nm is very particularly preferred. Moreover, in individual cases it is advantageous when the pigment has an asymmetrically shaped monomodal frequency distribution for the particle diameter with a maximum between 250 and 390 nm, in particular between 280 and 340 nm. As is consequently evident, the particle size for the type described should be considered an essential feature of the present invention. This shall be explained in greater detail in terms of the technology. Surprisingly, it has been demonstrated that the sharp grain size distribution must sit on a "base", which as needed can also have secondary maximums in the amount of up to 15%, primarily 5%. Without this explanation being limiting or exhaustive, this special embodiment of a sharply asymmetrical, bi- or oligomodal grain distribution or a "deep drag" for attaining optimum brightness and saturation can be traced back to the need for providing optimum space filling in the matrix by approaching a specific portion of the pigment on the "Fuller curve". As long as they remain the minority, the finest portions in small diameters (150 nm themselves can certainly cause the absorption edge of the pigment to be steeper due to stronger absorption, which likewise causes intensification of the Raleigh scattering, resulting in improved brightness. The grain shape must also receive the required "polishing" in order to be able to work itself optimally into a matrix, improve the gloss, and protect the normal application tools. This can be done effectively and in the same work step in the inventive method, which will be described in the following, by adding auxiliary agents. The grain surface is abraded, using the selected method and appropriate additives and coatings, to the round shape, which helps to moderate the abrasiveness of the particles and to improve the flowability of highly-pigmented preparations in later use. The tendency of fine rutile pigments to agglomerate is now effectively addressed during creation, i.e., in the grinding batch, which will be described in greater detail. In the abstract, the invention includes in particular the following pigments: a highly doped, fully annealed nickel antimony rutile yellow, a chromium antimony rutile yellow that is just as highly doped and fully annealed, and a titanium dioxide, preferably made of synrutile precursors, each in rutile structure, that is just annealed and only weakly doped with foreign parts. The inventive fine-particle, bright, and highly opaque rutile-based pigments also result in excellent gloss values. A pigment in accordance with the invention is distinguished in that it has a 20° reflectometer gloss value of at least 42 according to DIN 67 530 and a 60° reflectometer gloss value of at least 80, in particular a 20° reflectometer gloss value of at least 50, in particular 55 to 70 , and a 60° reflectometer gloss value of at least 83, in particular 83 to 93. The excellent covering power of the claimed pigments is particularly valuable. These are distinguished in that the covering power in accordance with DIN 55 987 is greater than 100% relative to a standard rutile pigment comparison substance, in particular is greater than 110%, and in particular is between 115 and 130%. Neither dry grinding used today as the state of the art nor conventional sand/bead mills are suitable for producing the inventive pigment of the type characterized. These known methods attain only mean particle sizes of 600 to 1200 nm, which results from the curves in enclosed Fig. 1. In the figure, the ribbed line represents a conventional commercial product A that was dry jet-milled, while the dashed line represents a conventional commercial nickel antimony titanium yellow, "TY70", from the Ishihara Company, that was milled in a conventional manner by means of a bead or jet mill. The uniform solid line represents a pigment in accordance with the invention. It demonstrates covering power improved by 25% and substantially improved gloss. The type of production shall be described in greater detail in the following, although it should be stated that a micromedia mill with 1.2 mm diameter grinding bodies was employed. The uniform solid line in Fig. 1 that represents the invention demonstrates a clear leap in quality compared to the ribbed and dashed lines. The optimum grain size distribution in terms of the primary maximum, between about 230 and 400 nm, could be one reason for the improved properties observed. Figs. 2 through 5 should also be mentioned in connection with Fig. 1. Figs. 2, 3, and 4 each represent an electron-microscopic image of the products represented in Fig. 1 in terms of particle size. Fig. 2 is TY70, the Ishihara conventional commercial pigment, Fig. 3 is the conventional commercial product A Get-milled), and Fig. 3 [sic] is the inventive nickel antimony rutile yellow pigments. The comparison demonstrates that the inventive pigment has a clearly smaller particle size. The present invention also proves to be valuable because it no longer has any regular increase in remission across all wavelengths, due to the sharpness of the grain size distribution, but rather has a maximum in the yellow range of the spectrum (about 570 to 600 nm). This simultaneously prevents the b* values from decreasing excessively because then the brightness (that is, the non- wavelength-specific remission) would increase excessively. Fig. 5 represents nickel antimony rutile yellow products in the CIELab color space. It is evident from this that the inventive products include a new color location compared to the products according to the prior art. First, this demonstrates that this is a product that differs from the prior art products. On the other hand, the invention expands the spectrum of stable pigments with a yellow hue. It is therefore of particular advantage for nickel antimony rutile yellows that the CIELab color location has a color saturation C* of 52 to 55 at a color hue angle h of 96 to 98° according to DIN 5033. The subject matter of the present invention is also a method for producing the pigments in accordance with the invention. It is characterized in that an inorganic mixed phase oxide pigment with rutile structure is treated by means of high-speed grinding in an aqueous suspension in an agitator ball mill with resistant lining until the grab size distribution described in the foregoing has been attained. Preferably the grinding unit and the grinding tools have a wear-resistant and inert coating. Preferably the resistant lining material for the (high-speed) agitator ball mill is an inert and wear-resistant ceramic material, in particular in the form of a heat-conductive ceramic material for assisting in cooling. Alternatively, it is preferred that the resistant lining material for the agitator ball mill is an inert and wear-resistant plastic, e.g. polyurethane. Additional information regarding the method. It is preferred that resistant grinding pearls with a diameter of about 0.2 to 1.7 mm, in particular from about 0.5 to 1.2 mm, are used in the milling unit in an analogous manner for coating. The temperature during fine grinding is preferably between about 20 and 90 °C, in particular between about 40 and 60 °C. Moreover, it is useful that the fine grinding is performed in the framework of the inventive method using a recirculation method, the mean dwell time of the ground material in the agitator ball mill being 4 to 44 min, in particular 10 to 18 min. It is useful that the circumferential speed of the rotor in the agitator ball mill is 5 to 19 m/s, in particular 10 to 12 m/s. In addition, in the framework of the invention the fill level is usefully planned to be advantageous. It is preferred that the fill level of the agitator ball mill with grinding bodies is about 60 to 90 vol.%, in particular about 70 to 80 vol.%. In an exceptional case, it is preferred that pre-comminution occurs upstream of the inventive method. This usefully occurs in a ball mill, likewise made of resistant material, metal contact with the ground material being largely prevented. This is one reason that iron content is largely prevented in the inventive pigments. In other words, this means that the iron content is determined solely by the parameters of the raw materials and is thus in any case in the ppm range. Regarding the history of the inventive method it should be stated: After initial experiments with highly doped and fully annealed nickel titanium yellow as for the teaching of DE-A- 3 202 158 with high-speed agitator ball mills failed due to unsatisfactory color consistency, it was surprisingly found that the grinding efficiency improved dramatically in connection with chemically and mechanically resistantly lined agitator ball mills and ceramic fine grinding bodies. Preferably the lining should be non-metallic. It could comprise plastic, but it could also comprise ceramic. Therefore a sharp grain size distribution with about 320 nm mean particle diameter, close to the optimum, can be attained with relatively low grinding complexity, the grain size distribution additionally also having a steep course that conforms to the objective. The refitting of the agitator ball mill, mentioned in the foregoing in terms of the metal-free lining, was thus extremely important for conducting the new inventive wet milling method successfully. The inventive pigments and also the inventive method have particular value, which is evidenced by numerous advantages: for instance, the grinding efficiency can be promoted using the surfactant polymers, mentioned in the foregoing, specifically using differently substituted polysiloxane compounds and polar substituted long-chain alkanes. The polysiloxanes primarily effect hydrophobization of the per se polar surface of the inorganic pigment particle. During subsequent working in into nonpolar binding agents (solvent-containing resin) or other polymer materials (polyolefins), the hydrophobization of the pigment surface leads to clearly more rapid rewetting and thus to less wear. Under the selected grinding conditions, highly disperse oxides of silicon or aluminum prove to be the solution to hydrodynamic problems, in addition to adjusting an optimal ion strength and therefore viscosity with a salt of an oxygen acid of for instance sulfur or phosphorus. Using the aforesaid compounds it is therefore possible to obtain particularly advantageous controllability when optimizing the inventive method. The present invention overcomes the aforesaid deficiencies of prior art nickel antimony titanium yellow pigments and leads, optionally using a modified finish process, to yellow pigments with substantially improved opacity and substantially improved gloss that is the equivalent of that of titanium white; at the same time the color intensity is improved compared to low-doped rutiles that are annealed at lower reaction temperatures, which is clearly evidenced in Fig. 5. In accordance with the object, the invention thus includes a new application area for highly doped rutile pigments. In summary, the advantages of the inventive pigment can be depicted as follows: It is distinguished from the prior art product by improved gloss, low whiteness/less brightening, relatively high color saturation, and extremely high covering power, not usable in the past in this class of material, with low photoactivity for fine-particle rutiles compared to the prior art. Furthermore, in practice it does not demonstrate any disadvantageous abrasivity or any interaction of any grinding residues with the application matrix. In particular it is essentially free of reactive metals or metal compounds, in particular reactive iron compounds. The invention shall be explained in the following in greater detail using various examples, although this shall not be construed as a limitation. Example 1: Step 1: Pre-comminution It is advantageous to have a conventional pre-comminution step upstream of fine grinding in order to limit the duration of grinding. This can occur according to the following variations, and the ground material is then fed directly to the inventive process (these are actually processes in accordance with the prior art, which are only included for the sake of completeness and to demonstrate the general applicability of the invention): Ball mill/roller block 40% suspension (4 kg pigment and 6 L water) of the raw pigment: is ground with 25-mm ceramic balls on the roller block for 60 to 90 min. Sand mill: Horizontal PU-lined sand mill with Ottawa sand or zircon silicate grinding beads (Rimax) with a diameter of 2.5 to 2.8 mm. There are 1 to 2 passes with 600 to 800 kg 40% suspension per hour. The temperature must be kept below 60 °C. Although a jet mill for dry pre-comminution with subsequent slurrying of the raw pigment to the 40% suspension is very effective and does not cause any wear, it is very complex and time- consuming to manage and is therefore expensive. Corundum disc mill: Pre-comminution of the raw pigment particles into a 40% suspension has a throughput that is too low, but can be used trial-wise. Example 2: Step 2: Inventive wet grinding The 10 kg of the 40% suspension of the nickel titanium raw pigment from Example 1 are adjusted to a pH of 6 - 6.5 with 10% sulfuric acid, and if necessary adjusted to conductivity of 2000 to 2500 µS/cm by adding sodium sulfate solution, in order to obtain a stable, pumpable suspension having a viscosity of 600 - 700 mPas. A Lehmann "FM 20" mill lined with a special heat-conductive ceramic material for cooling is used. Example 2a: Pass grinding The suspension is pumped through the mill 3 times, passes 1 and 2 with grinding balls (cerium- stabilized zircon oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4 mm, the third pass with grinding balls 0.7 to 1.2 mm (cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L) at a throughput of 600 g suspension per minute; this is equal to a dwell time of 130 to 150 sec per pass, that is, a total dwell time of 10 min. The mill is set to a circumferential speed of 12 m/sec. The grinding temperature is no more than 45 °C. Example 2b: Circulatory grinding 1 pass with grinding balls (cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4 mm (72 vol.% of the grinding space), then circulatory grinding for 30 to 60 min with a throughput of 900 g suspension per min, which equals total dwell time of 6 to 12 min and 4 to 8 theoretical passes. It is necessary to check the pH after each pass or every 30 min during circulatory grinding. If the pH rises above 6.5, it must be corrected by adding sulfuric acid. The mill is set for a circumferential speed of 11 m/sec. After 45 minutes have elapsed, 20 g (0.2%) Nuosperse 2008, a fatty amine salt of an ethoxylated and partially phosphatized polymer oleyl alcohol are added for conditioning and grinding continues for an additional 15 min. If the suspension becomes thin, the viscosity must be raised by adding no more than 50 g sodium dihydrogen phosphate, and if necessary more additional sulfuric acid. The grinding temperature is no more than 45 °C. Example 3: Adding additives After fine grinding in accordance with Example 2b, the pigment is washed until the conductivity of the excess liquid is 500 to 800 µS/cm. The suspension is concentrated by means of centrifuge decanter or filter press to a solid content of 55 to 65%. Then additional 2.5% sodium sulfate is added to the slurry, the viscosity is adjusted to 620 Pas with equal parts by weight of sodium phosphate and sulfuric acid, an additional quick pass (dwell time performed with grinding balls (cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4 mm. An excellently covering yellow pigment is obtained that has optimum gloss in the coating. There are no detectable differences between the pigment in accordance with the method in Example 2A and in accordance with the method in Example 2B. Example 4: Adding additives: After fine grinding in accordance with Example 2b, the pigment is washed until the conductivity of the excess liquid is 500 to 800 µS/cm. The suspension is concentrated by means of centrifuge decanter or filter press to a solid content of 60%. Then additional 3% non-ionic, modified fatty acid derivative (commercial product) and 100 g "Aerosil" are added to the slurry, and an additional quick pass (dwell time (cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4 mm (same filling as before). An excellently covering yellow pigment is obtained that has optimum gloss in the coating. It is not possible to detect a feared matting effect from the Aerosil There are no detectable differences between the pigment in accordance with the method in Example 2A and in accordance with the method in Example 2B. Example 5: Adding additives After fine grinding in accordance with Example 2b, the pigment is washed until the conductivity of the excess liquid is 500 to 800 µS/cm. The suspension is concentrated by means of centrifuge decanter or filter press to a solid content of 60%. Then additional 2% a [sic] polydimethyl siloxane (aqueous emulsion) is added to the slurry to reduce abrasivity, in addition 35 g "aluminum oxide C" from the Degussa Company (commercial product), an additional quick pass (dwell time oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4 mm (same filling as before). After separation, an excellently covering, bright yellow pigment is obtained that has optimum gloss in the coating. There are no detectable differences between the pigment in accordance with the method in Example 2A and in accordance with the method in Example 2B. Example 6: Variations in the auxiliary agents To illustrate how independent the pigment properties are in accordance with this invention, deviating from the wording of these examples the following auxiliary agents are used in variations that are reasonable to experts in the field without this having a significantly further improving effect on the result, in contrast to DE-A-2 936 746: Modified fatty acid derivatives 1. Fatty amine salt of a polymer oleyl alcohol, ethoxylated and phosphatized, and 2. Non-ionic, modified fatty acid derivative Polysiloxane compounds 1. With polyether group-modified siloxane 2. Alkylaryl-modified polysiloxane Nanodisperse aluminum oxide or silicic acids Aluminum oxide C (Degussa) Aerosils The following can be used as grinding balls: 1.7 to 2.4 mm cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L 0.7 to 1.2 mm cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L 0.6 to 0.8 mm yttrium-stabilized zircon oxide balls, bulk density 3.6 kg/L 0.8 to 1.0 mm yttrium-stabilized zircon oxide balls, bulk density 2.8 kg/L 2.5 to 2.8 mm zircon silicate balls, bulk density 2.4 kg/L Example 7: Evaluation After filtration and drying, a bright, highly opaque, and fine-particle yellow pigment is obtained. In comparison, the pigment in accordance with Example 4 is as follows (Table 1): See Fig. 1 enclosed in the attachment with regard to the particle size in the products compared in the foregoing. The described commercial product A was obtained according to common multistage jet-milling methods until no more improvement could be attained. Grain shape and particle size can be seen and compared in enclosed Figures 2, 3, and 4 in raster electron- microscope images. The round polished shape that is responsible for some of the favorable application technology properties is evident. Example 8: Non-voluntary confirmation of success for inventive improved nickel antimony titanium yellow pigment The efficacy of the invention is documented primarily by the following incident, highlighted briefly and without any disturbing effects (the pigment is also resistant to leaching), during the development of the product, even though it may seem to be an unorthodox example: Pilot production began after preliminary results from Examples 1 - 6 were evaluated. Because of an error in handling, small quantities of very fine nickel antimony rutile yellow pigment traveled out of the mill into the receptacle for the waste water basin (clear side). The pigment was deposited as an extremely well covering, uniform, and intensely luminous lemon yellow coating on the walls and fittings of the waste water preparation system. The "result" looked like it had been applied with a roller or sprayed on in a clean, covering manner. The bright green substrate of the building and the various pipes, fixtures, and cables did not have any more yellow hue nuances in the midday sunlight. The color effect initially led one to think of doped bismuth vanadate or even lead chromate, which could not be disproved without chemical analysis. If one is mindful that all of this occurred without auxiliary agents, the practical value of the improvement from the invention becomes quite clear. Example 9: Variation of the ground substance: other rutile-based pigments Trial as in Examples 1 and 2A, but, instead of with nickel antimony rutile yellow, with "off- white" titanium dioxide, obtained from a synrutile using the method according to DE-A-101 03 977, which according to the method described therein, but in contrast to Example 3 of DE-A-3 202 158, is obtained directly and does not contain any more "reactive iron". A batch is produced according to Examples 1 and 2A, but a "synrutile" with 97% TiO2 is used instead of a synthetic mixed phase color pigment. Similarly significant improvements result, in this case with regard to improved brightness, opacity, and gloss, which include the use of a "synrutile" in a direct manner (i.e. without refining methods, using the chloride or sulfate process, that are otherwise usual for TiO2) for pigment applications in the sector of pastel white colors. In the context of this invention, the qualitative evaluation furthermore leads to the conclusion that the inventive method is applicable to all grain-hard or highly agglomerated pigments that are based on titanium dioxide in a rutile structure, without having to pay for these advantages with weak color for lack of adequate doping, with sharply increased photoactivity, with a significantly increased expenditure of energy and/or non-specific graying due to metal abrasion of the grinding aggregate. Example 10: Comparison of measured gloss values for commercial product A, inventive nickel antimony rutile yellow, and Ishihara TY70 commercial pigment, which were compared in the foregoing. The measured gloss values are determined according to DIN 67 530. An alkyd melamine stoving enamel (55% solid content) was used for the testing system. For this, 80 g resin, 20 g pigment, and 120 g glass beads (2 mm) were weighed into a polypropylene beaker and shaken for 20 minutes on a Scandex shaker. The pigmented resin was applied to a white testing chart (Leneta Form WH) with a wet film thickness of 200 um using a film drawing device (Erichsen Company, model 509 MCIII) and fired for 30 min at 130 °C. Then the reflectometer values were determined with standard illuminant D 65. Example 11: Determining covering power Covering power was determined according to DIN 55 97 using standard light D65 (daylight, northern hemisphere, corresponding to emission radiation of the black body heated to 6504 K), using an oxidatively drying alkyd resin. For this, 70 g resin, 30 g pigment, and 120 g glass beads (2 mm) were weighed into a polypropylene beaker and shaken for 20 min on a Scandex shaker. The pigmented resin was applied to black/white contrast cards with wet film thicknesses of 60 to 400 µm using a film drawing device (Erichsen Company, model 509 MCIII) with a type 421/II Erichsen Company step rake. After the resin film was dried, the color spacing DE was determined over black and white substrates according to DIN 6174 and applied graphically against the reciprocal value of the film thickness at which the color spacing is DE = 1. This was determined both for the described nickel titanium pigments and for a titanium dioxide pigment for the rutile modification. The covering power in Table II is provided relative to titanium dioxide. The concentration of the tested pigments was less than the critical pigment volume concentration (CPVK). WE CLAIM: 1. Finely divided, brilliant, and highly opaque rutile-based pigment, which comprises a nickel- antimony rutile yellow featuring a color saturation C* of 52 to 55 acc. to DIN 5033, at a color hue angle h of 96° to 98° and a particle size distribution with a diameter range between 50 and 1000 nm, which in case of a mon-, bi-, tri or oligomodal-type maxima distribution may feature a majorizing (primary) maximum between 230 and 400 nm, and a secondary maximum of less than 25% of the primary maximum in a diameter range between 400 and 1000 nm in case of bi-or oligomodal distributions. 2. Pigment as claimed in claim 1, wherein the mean particle diameter is between 80 and 1000 nm, in particular, between 80 and 600 nm, and/or wherein a secondary maximum at less than 25% of the primary maximum occurs between 400 and 900 nm. 3. Pigment as claimed in claim 1 or 2, having an asymmetrically shaped mono-modal-type maxima distribution of particle size diameters with a maximum between 250 and 390 nm, preferably between 280 and 340 nm. 4. Pigment as claimed in any of claims 1 to 3, which, when subject to application of standard DIN 67530 illuminant "D65" for trial conditions enumerated in Example 10, is featuring a 20° reflectometer gloss value of at least 42, and a 60° reflectometer value of at least 80, in particular a 20° reflectometer gloss value of at least 50, in particular 55 through 70, and a 60° reflectometer gloss value of at least 83, in particular 83 through 93, without requiring application of auxiliary agents that remain on the pigment. 5. Pigment as claimed in any of claims 1 to 4, which has, in accordance with DIN 55987 using standard illuminant "D65" for trial conditions enumerated in Example 11, a hiding power in excess of 100%, in particular exceeding 110%, relative to a standard titanium dioxide rutile pigment as comparative substance. 6. Pigment as claimed in claim 5, having a hiding power between 115% and 130% according to DIN 559987. 7. Process of manufacturing a finely divided, brilliant, and highly opaque pigment based on nickel-antimony rutile yellow as claimed in any of claims 1 to 6, wherein a nickel-antimony rutile yellow pigment is subjected to high-speed milling of its aqueous suspension in an agitator ball mill having resistant iron-free lining, until any one of the particle size specification, recited in said claims 1 to 6, is attained. 8. Process as claimed in claim 7, wherein the milling device and grinding tools are equipped with a wear-resistant and inert lining. 9. Process as claimed in claim 7 or 8, wherein iron-free and resistant grinding beads of an inert and abrasion-resistant material, having diameter of 0.2 to 1.7 mm, in particular 0.5 to 1.2 mm, are used in said milling device. 10. Process as claimed in any of claims 7 to 9, wherein ultrafine grinding is performed at temperatures between 20 and 90°C, in particular between 40 and 60°C. 11. Process as claimed in any of claims 7 to 10, wherein the grinding is performed using a recirculation flow scheme, the mean dwell time of the ground material in the agitator ball mill being 4 to 44 minutes, in particular 10 to 18 minutes. 12. Process as claimed in any of claims 7 to 11, wherein the perimeter speed of the rotor in said agitator ball mill is 5 to 19 m/s, in particular 10 to 12 m/s. 13. Process as claimed in any of claims 7 to 12, wherein the filling level of said agitator ball mill with grinding bodies is about 60 to 90 vol.-%, in particular 70 to 80 vol.-%. 14. Process as claimed in any of claims 7 to 13, wherein pre-condition occurs upstream of said process in a ball mill equally made of resistant material which prevents the ground material from coming into contact with metal. 15. Process as claimed in claim 14, wherein said resistant material is an inert and abrasion-resistant material. 16. Process as claimed in claim 14, wherein the resistant material is a heat-conductive ceramic material. 17. Process as claimed in any of claims 7 to 16, wherein said resistant lining material for the agitator ball mill is an inert and abrasion-resistant polymer plastic or an inert and wear-resistant ceramic material. ABSTRACT RUTILE-BASED PIGMENT AND A METHOD FOR THE PRODUCTION THEREOF There is disclosed finely divided, brilliant, and highly opaque rutile-based pigment, which comprises a nickel- antimony rutile yellow featuring a color saturation C* of 52 to 55 acc. to DIN 5033, at a color hue angle h of 96° to 98° and a particle size distribution with a diameter range between 50 and 1000 nm, which in case of a mon-, bi-, tri or oligomodal-type maxima distribution may feature a majorizing (primary) maximum between 230 and 400 nm, and a secondary maximum of less than 25% of the primary maximum in a diameter range between 400 and 1000 nm in case of bi-or oligomodal distributions.

Full Text

The invention relates to a fine-particle, bright, and highly opaque rutile-based pigment without
the addition of impurities by reactive metal components and to a method for the production of
such pigments.
Nickel antimony titanium yellow pigments are by nature pale yellow pigments with high opacity.
Overdyeing with high quality organic pigments makes it possible to obtain highly saturated full-
tone colors with which the entire color spectrum can be covered, with the exception of blue and
violet hues. This overcoloring results in a synergy between the relatively high opacity of the
cost-effective nickel antimony titanium yellow and the great color intensity of the organic
overcoloring pigments, which are generally quite expensive.
This effect can also be obtained using titanium white; however, overcoloring always leads to
greater brightening, that is, to less saturation, due to the high whitening power of titanium white
pigments. Another disadvantage of titanium white overcoloring is the photocatalytic effect of
titanium white pigments, which leads to a sharp decrease in the light-fastness and weather-
fastness of the expensive organic color components. Consequently, full hues based on titanium
white "age" some four-times faster than mixtures of the same organic color components with
nickel antimony titanium yellow.
In the past, this decisive use of nickel antimony titanium yellow was seldom used because the
nickel titanium pigments currently available on the market are abrasive (grain-hard and sharp-
edged), have poor gloss, and are inferior in terms of covering capacity compared to titanium
white. Moreover, the following economic background should be considered:
Nickel antimony titanium yellows account for relatively small market shares among titanium
pigments, as the following figures demonstrate: titanium white world market: 4,000,0001,
titanium yellow world market: 20,000 t, of which chromium antimony titanium yellow: 16,000
t, of which nickel antimony titanium yellow: 4,000 t.

The annual tonnage of chromium antimony titanium yellow is disproportionate to that of nickel
antimony titanium yellow. As colored pigments, nickel antimony titanium yellows offer merely
an unsatisfactory option for replacing the 100,000 annual tons of lead sulfochromate and
molybdate red pigments pursuanttorthe hazardous materials laws and environmental protection
laws that have become increasingly stringent since 1980. The reason for this is the deficiencies,
considered unchangeable, that are manifested in particular by the inadequate opacity, compared
to titanium white and to chromium and cadmium yellows and by inadequate gloss and high
abrasiveness.
These three deficiencies are the result of one and the same cause, specifically a mean particle,
size, primarily of the nickel antimony titanium yellow, that is too large and that is an average of
1000 - 2000 nm in the best qualities found on the market, while the optimum opacity of a
pigmentary coloring agent is attained with a particle size of 300 nm and with optimized grain
shape and surface. A pigment loses about 20% of its opacity when the mean particle diameter is
greater than 500 nm. Finer commercial type according to the prior art are regularly slightly
doped and greatly whitened, and in addition due to their high grinding costs expensive, highly
doped, high-fired products are unknown because they are inconsistent in terms of color.
Surface enlargement when the mean particle diameter is 300 nm should be avoided for color
pigments because they become transparent when they drop below a particle diameter of about
half the wavelength of the light reflected by them, which is undesirable for applications for
nickel antimony titanium yellow pigments. When the hardness of the particles is high,
abrasiveness increases for spiky and sharp-edged particles. The goal is therefore also to produce
isometric particles (rhombi) that are chamfered or have beveled flattened or rounded areas on the
corners. This cannot be obtained using a coating in accordance with DE-A-2 936 746 that acts in
cooperation with surfactant agents such as a slip agent and which additionally requires its own
processing step and the use of auxiliary agents as the subject matter of the invention.

Nevertheless, for avoiding color effects under different types of illumination (metamerism), a
relatively smooth surface and also approximate uniformity of the (projected) edge lengths should
be obtained; a spherical shape is unattainable under any conditions, however.
Talcing the aforesaid into account, the relevant prior art shall be addressed:
In the past, a mean particle size of 300 nm has not been reached by any manufacturer with
satisfactory results for highly doped and/or fully annealed nickel or chromium antimony rutile
yellow pigments (TiO2 antimony titanium yellows. In fact, thelsmali dopings described therein inter alia with antimony
and chromium at low firing temperatures lead to a pigment with a narrow grain size distribution and corresponding fineness, sometimes
also due to the softer grain of the mixed phase oxide pigments described therein. However, there
are still also limits for hue creation in terms of how the reactive iron content can assume
uncontrollable amounts if a non-metallic mill with resistant lining is not used as it is inventively
in this case. Still, with a product according to the prior art in DE-A-3 202 158, increased
photoactivity, and with appropriate very fine grinding, a high degree of whitening must be
accepted. If iron abrasion is permitted in the milling process, the material grays and leads inter
alia to disturbances in PVC-based matrices. This is true even for mixed phase rutile-based oxide
pigments that contain iron bound as a non-reactive component in the crystal lattice of the rutile,
as in example 3 of DE-A-3 202 158,
In accordance with the teaching of DE-A-3 202 158, a coloristically favorable grain size
distribution is attained when low doping, relatively low firing temperature, and wet milling are
combined. However, this application does not provide any information on grain size distribution
and specifies the type of milling only imprecisely.
In the case of titanium dioxide, synthesis during the chloride method with the adjustment of the
TiCl4 burner and mixing in of agglomeration-preventing sand in the subsequent cooling and
conveying process

has already found a practical path for adjusting optimized particle size distributions (d50 =
approx. 280 nm for light of 550 nm wavelength) (see inter alia: Winkler, J: "Titanium Dioxide",
Hannover: Vincentz, 2003; ISBN 3-87870-148-9; pp. 35 - 37;51-58). Although in this
method small quantities of aluminum chloride are metered to the titanium tetrachloride for
"rutilization", it being unresolved how many lattice places in the rutile are really occupied by
aluminum ions, this method is not promising e.g. using the addition of antimony and nickel
chlorides to titanium tetrachloride upstream of the burner. Separation and inhomogeneous
volatility of metal chlorides and metal oxychlorides prior to the lattice insertion of the metal ions
is observed. A lengthy afterglow period leads to reagglomeration.
The Ishihara Company is particularly active in the prior art. This is demonstrated by worldwide
patent applications. These include for instance EP 1245 646 (Al, corresponds to US-A-6 576
052), in which a fine-particle TiO2 obtained from the chloride process, already 100 to 400 nm
mean grain size, is re-ground to a corresponding fine primary grain size during a siloxane post-
treatment and coating with aluminum phosphate using a jet mill. According to EP-A-1 273 555
(corresponds to US 6 616 746), the same grain fineness of the raw pigment for coating is used
with multivalent alcohols and hydrolyzed amino silanes and/or aluminum hydroxide. The
procedure is the same as the foregoing. Good dispersibility of the photostabilized products is
claimed. For grinding, the pigment is comminuted after or during addition of the coating and
stabilization reagents at a temperature of 120 to 300 °C in a jet mill or a similar "fluid energy
mill" that permits a hydrolysis reaction of the amino siloxanes and other reactive components
and prevents any reagglomeration during the coating process. This patent relates only to TiO2 in
rutile modification (which is preferably formed by the additions of aluminum). After working up
the batch, the coating is principally to act in a manner that prevents agglomeration and is
photostabilizing, i.e. lastingly moderates the photocatalytic effects of the pigment.
Wet grinding of rutiles, that is also rutile yellow pigments, in high-intensity bead mills is prior
art e.g. in accordance with DE-A-3 930 098. These are sold by a number of different specialty
companies.
The option provided e.g. in DE-A-4 106 003 to obtain an a priori finer grain structure and thus
save a grinding process by "alloying" the firing batch for a rutile brown pigment with small
quantities of cerium, inter alia, cannot be performed with chromium and nickel titanium
pigments due to the brighter hues that are more sensitive to fluctuations in doping.

Basically many companies seem to prefer wet precipitation to the actual synthesis of the pigment
and thus create a "wet precursor" which is imprinted with the grain distribution and thus the
fineness, which is maintained even until after calcination and final fine grinding. The hydroxyl
groups on the surface of the freshly precipitated oxides and hydroxides represent a good
precursor for the diffusive penetration of the rutile lattice, which also has numerous vacancies,
with foreign metal ions after evaporating the water above 150 °C. However, the finer grain sizes
possible due to the lower firing temperature are not of reproducible color intensity. The diameter
still fluctuates between 800 and 1200 nm.
Proceeding from the prior art described in the foregoing, the object of the invention was to
suggest a fine-particle, bright, and highly opaque rutile-based pigment that is distinguished by
superior opacity, gloss, and lower abrasiveness. Moreover, it should have the smallest possible
or no iron content, for instance in the ppm range in any case. Moreover, the invention should
suggest a method with which such a pigment can be produced in a particularly economical
manner.
This object is inventively attained using a fine-particle, bright, and highly opaque rutile-based
pigment that is characterized in that it has a grain size distribution with particle diameters
between 50 and 1000 nm and for mono-, bi-, tri-, or oligomodal frequency distribution has a
primary maximum between 230 and 400 nm, whereby for a bi- or multimodal frequency
distribution where necessary a secondary maximum occurs, at less than 25% of the primary
maximum, between 400 and 1000 nm, in particular between about 400 and 900 nm. It is
particularly preferred when the claimed primary maximum is between 280 and 340 nm and/or
the secondary maximum is between 480 and 800 nm. Furthermore, it is

preferred when the mean particle diameter of the pigment is between 80 and 1000 nm, in
particular between 80 and 900 nm. The range of 120 to 600 nm is very particularly preferred.
Moreover, in individual cases it is advantageous when the pigment has an asymmetrically shaped
monomodal frequency distribution for the particle diameter with a maximum between 250 and
390 nm, in particular between 280 and 340 nm.
As is consequently evident, the particle size for the type described should be considered an
essential feature of the present invention. This shall be explained in greater detail in terms of the
technology. Surprisingly, it has been demonstrated that the sharp grain size distribution must sit
on a "base", which as needed can also have secondary maximums in the amount of up to 15%,
primarily 5%. Without this explanation being limiting or exhaustive, this special embodiment of
a sharply asymmetrical, bi- or oligomodal grain distribution or a "deep drag" for attaining
optimum brightness and saturation can be traced back to the need for providing optimum space
filling in the matrix by approaching a specific portion of the pigment on the "Fuller curve". As
long as they remain the minority, the finest portions in small diameters (150 nm themselves can certainly cause the absorption edge of the pigment to be steeper due to stronger
absorption, which likewise causes intensification of the Raleigh scattering, resulting in improved
brightness.
The grain shape must also receive the required "polishing" in order to be able to work itself
optimally into a matrix, improve the gloss, and protect the normal application tools. This can be
done effectively and in the same work step in the inventive method, which will be described in
the following, by adding auxiliary agents. The grain surface is abraded, using the selected
method and appropriate additives and coatings, to the round shape, which helps to moderate the
abrasiveness of the particles and to improve the flowability of highly-pigmented preparations in
later use. The tendency of fine rutile pigments to agglomerate is now effectively addressed
during creation, i.e., in the grinding batch, which will be described in greater detail.
In the abstract, the invention includes in particular the following pigments: a highly doped, fully
annealed nickel antimony rutile yellow, a

chromium antimony rutile yellow that is just as highly doped and fully annealed, and a titanium
dioxide, preferably made of synrutile precursors, each in rutile structure, that is just annealed and
only weakly doped with foreign parts.
The inventive fine-particle, bright, and highly opaque rutile-based pigments also result in
excellent gloss values. A pigment in accordance with the invention is distinguished in that it has
a 20° reflectometer gloss value of at least 42 according to DIN 67 530 and a 60° reflectometer
gloss value of at least 80, in particular a 20° reflectometer gloss value of at least 50, in particular
55 to 70 , and a 60° reflectometer gloss value of at least 83, in particular 83 to 93. The excellent
covering power of the claimed pigments is particularly valuable. These are distinguished in that
the covering power in accordance with DIN 55 987 is greater than 100% relative to a standard
rutile pigment comparison substance, in particular is greater than 110%, and in particular is
between 115 and 130%. Neither dry grinding used today as the state of the art nor conventional
sand/bead mills are suitable for producing the inventive pigment of the type characterized.
These known methods attain only mean particle sizes of 600 to 1200 nm, which results from the
curves in enclosed Fig. 1. In the figure, the ribbed line represents a conventional commercial
product A that was dry jet-milled, while the dashed line represents a conventional commercial
nickel antimony titanium yellow, "TY70", from the Ishihara Company, that was milled in a
conventional manner by means of a bead or jet mill. The uniform solid line represents a pigment
in accordance with the invention. It demonstrates covering power improved by 25% and
substantially improved gloss. The type of production shall be described in greater detail in the
following, although it should be stated that a micromedia mill with 1.2 mm diameter grinding
bodies was employed. The uniform solid line in Fig. 1 that represents the invention
demonstrates a clear leap in quality compared to the ribbed and dashed lines. The optimum grain
size distribution in terms of the primary maximum, between about 230 and 400 nm, could be one
reason for the improved properties observed.
Figs. 2 through 5 should also be mentioned in connection with Fig. 1. Figs. 2, 3, and 4 each
represent an electron-microscopic image of the products represented in Fig. 1 in terms of particle
size. Fig. 2 is TY70, the Ishihara conventional commercial pigment,

Fig. 3 is the conventional commercial product A Get-milled), and Fig. 3 [sic] is the inventive
nickel antimony rutile yellow pigments. The comparison demonstrates that the inventive
pigment has a clearly smaller particle size.
The present invention also proves to be valuable because it no longer has any regular increase in
remission across all wavelengths, due to the sharpness of the grain size distribution, but rather
has a maximum in the yellow range of the spectrum (about 570 to 600 nm). This simultaneously
prevents the b* values from decreasing excessively because then the brightness (that is, the non-
wavelength-specific remission) would increase excessively.
Fig. 5 represents nickel antimony rutile yellow products in the CIELab color space. It is evident
from this that the inventive products include a new color location compared to the products
according to the prior art. First, this demonstrates that this is a product that differs from the prior
art products. On the other hand, the invention expands the spectrum of stable pigments with a
yellow hue. It is therefore of particular advantage for nickel antimony rutile yellows that the
CIELab color location has a color saturation C* of 52 to 55 at a color hue angle h of 96 to 98°
according to DIN 5033.
The subject matter of the present invention is also a method for producing the pigments in
accordance with the invention. It is characterized in that an inorganic mixed phase oxide
pigment with rutile structure is treated by means of high-speed grinding in an aqueous
suspension in an agitator ball mill with resistant lining until the grab size distribution described
in the foregoing has been attained. Preferably the grinding unit and the grinding tools have a
wear-resistant and inert coating. Preferably the resistant lining material for the (high-speed)
agitator ball mill is an inert and wear-resistant ceramic material, in particular in the form of a
heat-conductive ceramic material for assisting in cooling. Alternatively, it is preferred that the
resistant lining material for the agitator ball mill is an inert and wear-resistant plastic, e.g.
polyurethane.

Additional information regarding the method. It is preferred that resistant grinding pearls with a
diameter of about 0.2 to 1.7 mm, in particular from about 0.5 to 1.2 mm, are used in the milling
unit in an analogous manner for coating. The temperature during fine grinding is preferably
between about 20 and 90 °C, in particular between about 40 and 60 °C. Moreover, it is useful
that the fine grinding is performed in the framework of the inventive method using a
recirculation method, the mean dwell time of the ground material in the agitator ball mill being 4
to 44 min, in particular 10 to 18 min. It is useful that the circumferential speed of the rotor in the
agitator ball mill is 5 to 19 m/s, in particular 10 to 12 m/s. In addition, in the framework of the
invention the fill level is usefully planned to be advantageous. It is preferred that the fill level of
the agitator ball mill with grinding bodies is about 60 to 90 vol.%, in particular about 70 to 80
vol.%.
In an exceptional case, it is preferred that pre-comminution occurs upstream of the inventive
method. This usefully occurs in a ball mill, likewise made of resistant material, metal contact
with the ground material being largely prevented. This is one reason that iron content is largely
prevented in the inventive pigments. In other words, this means that the iron content is
determined solely by the parameters of the raw materials and is thus in any case in the ppm
range.
Regarding the history of the inventive method it should be stated: After initial experiments with
highly doped and fully annealed nickel titanium yellow as for the teaching of DE-A- 3 202 158
with high-speed agitator ball mills failed due to unsatisfactory color consistency, it was
surprisingly found that the grinding efficiency improved dramatically in connection with
chemically and mechanically resistantly lined agitator ball mills and ceramic fine grinding
bodies. Preferably the lining should be non-metallic. It could comprise plastic, but it could also
comprise ceramic. Therefore a sharp grain size distribution with about 320 nm mean particle
diameter, close to the optimum, can be attained with relatively low grinding complexity, the
grain size distribution additionally also having a steep course that conforms to the objective.

The refitting of the agitator ball mill, mentioned in the foregoing in terms of the metal-free
lining, was thus extremely important for conducting the new inventive wet milling method
successfully. The inventive pigments and also the inventive method have particular value, which
is evidenced by numerous advantages: for instance, the grinding efficiency can be promoted
using the surfactant polymers, mentioned in the foregoing, specifically using differently
substituted polysiloxane compounds and polar substituted long-chain alkanes. The polysiloxanes
primarily effect hydrophobization of the per se polar surface of the inorganic pigment particle.
During subsequent working in into nonpolar binding agents (solvent-containing resin) or other
polymer materials (polyolefins), the hydrophobization of the pigment surface leads to clearly
more rapid rewetting and thus to less wear. Under the selected grinding conditions, highly
disperse oxides of silicon or aluminum prove to be the solution to hydrodynamic problems, in
addition to adjusting an optimal ion strength and therefore viscosity with a salt of an oxygen acid
of for instance sulfur or phosphorus. Using the aforesaid compounds it is therefore possible to
obtain particularly advantageous controllability when optimizing the inventive method.
The present invention overcomes the aforesaid deficiencies of prior art nickel antimony titanium
yellow pigments and leads, optionally using a modified finish process, to yellow pigments with
substantially improved opacity and substantially improved gloss that is the equivalent of that of
titanium white; at the same time the color intensity is improved compared to low-doped rutiles
that are annealed at lower reaction temperatures, which is clearly evidenced in Fig. 5. In
accordance with the object, the invention thus includes a new application area for highly doped
rutile pigments.
In summary, the advantages of the inventive pigment can be depicted as follows: It is
distinguished from the prior art product by improved gloss, low whiteness/less brightening,
relatively high color saturation, and extremely high covering power, not usable in the past in this
class of material, with low photoactivity for fine-particle rutiles compared to the prior art.
Furthermore, in practice it does not

demonstrate any disadvantageous abrasivity or any interaction of any grinding residues with the
application matrix. In particular it is essentially free of reactive metals or metal compounds, in
particular reactive iron compounds.
The invention shall be explained in the following in greater detail using various examples,
although this shall not be construed as a limitation.
Example 1: Step 1: Pre-comminution
It is advantageous to have a conventional pre-comminution step upstream of fine grinding in
order to limit the duration of grinding. This can occur according to the following variations, and
the ground material is then fed directly to the inventive process (these are actually processes in
accordance with the prior art, which are only included for the sake of completeness and to
demonstrate the general applicability of the invention):
Ball mill/roller block
40% suspension (4 kg pigment and 6 L water) of the raw pigment: is ground with 25-mm ceramic
balls on the roller block for 60 to 90 min.
Sand mill:
Horizontal PU-lined sand mill with Ottawa sand or zircon silicate grinding beads (Rimax) with a
diameter of 2.5 to 2.8 mm. There are 1 to 2 passes with 600 to 800 kg 40% suspension per hour.
The temperature must be kept below 60 °C.
Although a jet mill for dry pre-comminution with subsequent slurrying of the raw pigment to the
40% suspension is very effective and does not cause any wear, it is very complex and time-
consuming to manage and is therefore expensive.
Corundum disc mill: Pre-comminution of the raw pigment particles into a 40% suspension has a
throughput that is too low, but can be used trial-wise.

Example 2: Step 2: Inventive wet grinding
The 10 kg of the 40% suspension of the nickel titanium raw pigment from Example 1 are
adjusted to a pH of 6 - 6.5 with 10% sulfuric acid, and if necessary adjusted to conductivity of
2000 to 2500 µS/cm by adding sodium sulfate solution, in order to obtain a stable, pumpable
suspension having a viscosity of 600 - 700 mPa*s. A Lehmann "FM 20" mill lined with a
special heat-conductive ceramic material for cooling is used.
Example 2a: Pass grinding
The suspension is pumped through the mill 3 times, passes 1 and 2 with grinding balls (cerium-
stabilized zircon oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4 mm, the third pass with grinding
balls 0.7 to 1.2 mm (cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L) at a throughput
of 600 g suspension per minute; this is equal to a dwell time of 130 to 150 sec per pass, that is, a
total dwell time of 10 min. The mill is set to a circumferential speed of 12 m/sec. The grinding
temperature is no more than 45 °C.
Example 2b: Circulatory grinding
1 pass with grinding balls (cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4
mm (72 vol.% of the grinding space), then circulatory grinding for 30 to 60 min with a
throughput of 900 g suspension per min, which equals total dwell time of 6 to 12 min and 4 to 8
theoretical passes. It is necessary to check the pH after each pass or every 30 min during
circulatory grinding. If the pH rises above 6.5, it must be corrected by adding sulfuric acid. The
mill is set for a circumferential speed of 11 m/sec.
After 45 minutes have elapsed, 20 g (0.2%) Nuosperse 2008, a fatty amine salt of an ethoxylated
and partially phosphatized polymer oleyl alcohol are added for conditioning and grinding
continues for an additional 15 min. If the suspension becomes thin, the viscosity must be raised
by adding no more than 50 g sodium dihydrogen phosphate, and if necessary

more additional sulfuric acid. The grinding temperature is no more than 45 °C.
Example 3: Adding additives
After fine grinding in accordance with Example 2b, the pigment is washed until the conductivity
of the excess liquid is 500 to 800 µS/cm. The suspension is concentrated by means of centrifuge
decanter or filter press to a solid content of 55 to 65%. Then additional 2.5% sodium sulfate is
added to the slurry, the viscosity is adjusted to 620 Pa*s with equal parts by weight of sodium
phosphate and sulfuric acid, an additional quick pass (dwell time performed with grinding balls (cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L) 1.7 to
2.4 mm.
An excellently covering yellow pigment is obtained that has optimum gloss in the coating. There
are no detectable differences between the pigment in accordance with the method in Example 2A
and in accordance with the method in Example 2B.
Example 4: Adding additives:
After fine grinding in accordance with Example 2b, the pigment is washed until the conductivity
of the excess liquid is 500 to 800 µS/cm. The suspension is concentrated by means of centrifuge
decanter or filter press to a solid content of 60%. Then additional 3% non-ionic, modified fatty
acid derivative (commercial product) and 100 g "Aerosil" are added to the slurry, and an
additional quick pass (dwell time (cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4 mm (same filling as
before).
An excellently covering yellow pigment is obtained that has optimum gloss in the coating. It is
not possible to detect a feared matting effect from the Aerosil There are no detectable
differences between the pigment in accordance with the method in Example 2A and in
accordance with the method in Example 2B.

Example 5: Adding additives
After fine grinding in accordance with Example 2b, the pigment is washed until the conductivity
of the excess liquid is 500 to 800 µS/cm. The suspension is concentrated by means of centrifuge
decanter or filter press to a solid content of 60%. Then additional 2% a [sic] polydimethyl
siloxane (aqueous emulsion) is added to the slurry to reduce abrasivity, in addition 35 g
"aluminum oxide C" from the Degussa Company (commercial product), an additional quick pass
(dwell time oxide balls, bulk density 3.7 kg/L) 1.7 to 2.4 mm (same filling as before).
After separation, an excellently covering, bright yellow pigment is obtained that has optimum
gloss in the coating. There are no detectable differences between the pigment in accordance with
the method in Example 2A and in accordance with the method in Example 2B.
Example 6: Variations in the auxiliary agents
To illustrate how independent the pigment properties are in accordance with this invention,
deviating from the wording of these examples the following auxiliary agents are used in
variations that are reasonable to experts in the field without this having a significantly further
improving effect on the result, in contrast to DE-A-2 936 746:
Modified fatty acid derivatives
1. Fatty amine salt of a polymer oleyl alcohol, ethoxylated and phosphatized, and
2. Non-ionic, modified fatty acid derivative
Polysiloxane compounds
1. With polyether group-modified siloxane
2. Alkylaryl-modified polysiloxane
Nanodisperse aluminum oxide or silicic acids
Aluminum oxide C (Degussa)
Aerosils

The following can be used as grinding balls:
1.7 to 2.4 mm cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L
0.7 to 1.2 mm cerium-stabilized zircon oxide balls, bulk density 3.7 kg/L
0.6 to 0.8 mm yttrium-stabilized zircon oxide balls, bulk density 3.6 kg/L
0.8 to 1.0 mm yttrium-stabilized zircon oxide balls, bulk density 2.8 kg/L
2.5 to 2.8 mm zircon silicate balls, bulk density 2.4 kg/L
Example 7: Evaluation
After filtration and drying, a bright, highly opaque, and fine-particle yellow pigment is obtained.
In comparison, the pigment in accordance with Example 4 is as follows (Table 1):

See Fig. 1 enclosed in the attachment with regard to the particle size in the products compared in
the foregoing. The described commercial product A was obtained according to common
multistage jet-milling methods until no more improvement could be attained. Grain shape and
particle size can be seen and compared in enclosed Figures 2, 3, and 4 in raster electron-
microscope images. The round polished shape that is responsible for some of the favorable
application technology properties is evident.
Example 8: Non-voluntary confirmation of success for inventive improved nickel antimony
titanium yellow pigment

The efficacy of the invention is documented primarily by the following incident, highlighted
briefly and without any disturbing effects (the pigment is also resistant to leaching), during the
development of the product, even though it may seem to be an unorthodox example:
Pilot production began after preliminary results from Examples 1 - 6 were evaluated. Because
of an error in handling, small quantities of very fine nickel antimony rutile yellow pigment
traveled out of the mill into the receptacle for the waste water basin (clear side). The pigment
was deposited as an extremely well covering, uniform, and intensely luminous lemon yellow
coating on the walls and fittings of the waste water preparation system. The "result" looked like
it had been applied with a roller or sprayed on in a clean, covering manner. The bright green
substrate of the building and the various pipes, fixtures, and cables did not have any more yellow
hue nuances in the midday sunlight. The color effect initially led one to think of doped bismuth
vanadate or even lead chromate, which could not be disproved without chemical analysis. If one
is mindful that all of this occurred without auxiliary agents, the practical value of the
improvement from the invention becomes quite clear.
Example 9: Variation of the ground substance: other rutile-based pigments
Trial as in Examples 1 and 2A, but, instead of with nickel antimony rutile yellow, with "off-
white" titanium dioxide, obtained from a synrutile using the method according to DE-A-101 03
977, which according to the method described therein, but in contrast to Example 3 of DE-A-3
202 158, is obtained directly and does not contain any more "reactive iron". A batch is produced
according to Examples 1 and 2A, but a "synrutile" with 97% TiO2 is used instead of a synthetic
mixed phase color pigment. Similarly significant improvements result, in this case with regard
to improved brightness, opacity, and gloss, which include the use of a "synrutile" in a direct
manner (i.e. without refining methods, using the chloride or sulfate process, that are otherwise
usual for TiO2) for pigment applications in the sector of pastel white colors.
In the context of this invention, the qualitative evaluation furthermore leads to the conclusion
that the inventive method is applicable to all grain-hard or highly

agglomerated pigments that are based on titanium dioxide in a rutile structure, without having to
pay for these advantages with weak color for lack of adequate doping, with sharply increased
photoactivity, with a significantly increased expenditure of energy and/or non-specific graying
due to metal abrasion of the grinding aggregate.
Example 10: Comparison of measured gloss values for commercial product A, inventive nickel
antimony rutile yellow, and Ishihara TY70 commercial pigment, which were compared in the
foregoing.
The measured gloss values are determined according to DIN 67 530. An alkyd melamine
stoving enamel (55% solid content) was used for the testing system. For this, 80 g resin, 20 g
pigment, and 120 g glass beads (2 mm) were weighed into a polypropylene beaker and shaken
for 20 minutes on a Scandex shaker. The pigmented resin was applied to a white testing chart
(Leneta Form WH) with a wet film thickness of 200 um using a film drawing device (Erichsen
Company, model 509 MCIII) and fired for 30 min at 130 °C. Then the reflectometer values were
determined with standard illuminant D 65.

Example 11: Determining covering power
Covering power was determined according to DIN 55 97 using standard light D65 (daylight,
northern hemisphere, corresponding to emission radiation of the black body heated to 6504 K),
using an oxidatively drying alkyd resin. For this, 70 g resin, 30 g pigment, and 120 g glass beads
(2 mm) were weighed into a polypropylene beaker

and shaken for 20 min on a Scandex shaker. The pigmented resin was applied to black/white
contrast cards with wet film thicknesses of 60 to 400 µm using a film drawing device (Erichsen
Company, model 509 MCIII) with a type 421/II Erichsen Company step rake. After the resin
film was dried, the color spacing DE was determined over black and white substrates according
to DIN 6174 and applied graphically against the reciprocal value of the film thickness at which
the color spacing is DE = 1. This was determined both for the described nickel titanium
pigments and for a titanium dioxide pigment for the rutile modification. The covering power in
Table II is provided relative to titanium dioxide. The concentration of the tested pigments was
less than the critical pigment volume concentration (CPVK).

WE CLAIM:
1. Finely divided, brilliant, and highly opaque rutile-based pigment, which comprises a nickel-
antimony rutile yellow featuring a color saturation C* of 52 to 55 acc. to DIN 5033, at a color hue
angle h of 96° to 98° and a particle size distribution with a diameter range between 50 and 1000 nm,
which in case of a mon-, bi-, tri or oligomodal-type maxima distribution may feature a majorizing
(primary) maximum between 230 and 400 nm, and a secondary maximum of less than 25% of the
primary maximum in a diameter range between 400 and 1000 nm in case of bi-or oligomodal
distributions.
2. Pigment as claimed in claim 1, wherein the mean particle diameter is between 80 and 1000 nm,
in particular, between 80 and 600 nm, and/or wherein a secondary maximum at less than 25% of the
primary maximum occurs between 400 and 900 nm.
3. Pigment as claimed in claim 1 or 2, having an asymmetrically shaped mono-modal-type
maxima distribution of particle size diameters with a maximum between 250 and 390 nm, preferably
between 280 and 340 nm.
4. Pigment as claimed in any of claims 1 to 3, which, when subject to application of standard DIN
67530 illuminant "D65" for trial conditions enumerated in Example 10, is featuring a 20° reflectometer
gloss value of at least 42, and a 60° reflectometer value of at least 80, in particular a 20° reflectometer
gloss value of at least 50, in particular 55 through 70, and a 60° reflectometer gloss value of at least 83,
in particular 83 through 93, without requiring application of auxiliary agents that remain on the
pigment.
5. Pigment as claimed in any of claims 1 to 4, which has, in accordance with DIN 55987 using
standard illuminant "D65" for trial conditions enumerated in Example 11, a hiding power in excess of
100%, in particular exceeding 110%, relative to a standard titanium dioxide rutile pigment as
comparative substance.
6. Pigment as claimed in claim 5, having a hiding power between 115% and 130% according to
DIN 559987.

7. Process of manufacturing a finely divided, brilliant, and highly opaque pigment based on
nickel-antimony rutile yellow as claimed in any of claims 1 to 6, wherein a nickel-antimony rutile
yellow pigment is subjected to high-speed milling of its aqueous suspension in an agitator ball mill
having resistant iron-free lining, until any one of the particle size specification, recited in said claims 1
to 6, is attained.
8. Process as claimed in claim 7, wherein the milling device and grinding tools are equipped with
a wear-resistant and inert lining.
9. Process as claimed in claim 7 or 8, wherein iron-free and resistant grinding beads of an inert
and abrasion-resistant material, having diameter of 0.2 to 1.7 mm, in particular 0.5 to 1.2 mm, are used
in said milling device.
10. Process as claimed in any of claims 7 to 9, wherein ultrafine grinding is performed at
temperatures between 20 and 90°C, in particular between 40 and 60°C.
11. Process as claimed in any of claims 7 to 10, wherein the grinding is performed using a
recirculation flow scheme, the mean dwell time of the ground material in the agitator ball mill being 4
to 44 minutes, in particular 10 to 18 minutes.

12. Process as claimed in any of claims 7 to 11, wherein the perimeter speed of the rotor in said
agitator ball mill is 5 to 19 m/s, in particular 10 to 12 m/s.
13. Process as claimed in any of claims 7 to 12, wherein the filling level of said agitator ball mill
with grinding bodies is about 60 to 90 vol.-%, in particular 70 to 80 vol.-%.
14. Process as claimed in any of claims 7 to 13, wherein pre-condition occurs upstream of said
process in a ball mill equally made of resistant material which prevents the ground material from
coming into contact with metal.

15. Process as claimed in claim 14, wherein said resistant material is an inert and abrasion-resistant
material.
16. Process as claimed in claim 14, wherein the resistant material is a heat-conductive ceramic
material.
17. Process as claimed in any of claims 7 to 16, wherein said resistant lining material for the
agitator ball mill is an inert and abrasion-resistant polymer plastic or an inert and wear-resistant
ceramic material.

ABSTRACT

RUTILE-BASED PIGMENT AND A METHOD FOR THE PRODUCTION THEREOF
There is disclosed finely divided, brilliant, and highly opaque rutile-based pigment, which
comprises a nickel- antimony rutile yellow featuring a color saturation C* of 52 to 55 acc. to DIN
5033, at a color hue angle h of 96° to 98° and a particle size distribution with a diameter range between
50 and 1000 nm, which in case of a mon-, bi-, tri or oligomodal-type maxima distribution may feature a
majorizing (primary) maximum between 230 and 400 nm, and a secondary maximum of less than 25%
of the primary maximum in a diameter range between 400 and 1000 nm in case of bi-or oligomodal
distributions.

Documents:

00911-kolnp-2007-assignment.pdf

00911-kolnp-2007-correspondence-1.1.pdf

00911-kolnp-2007-form-3-1.1.pdf

0911-kolnp-2007-abstract.pdf

0911-kolnp-2007-claims.pdf

0911-kolnp-2007-correspondence others.pdf

0911-kolnp-2007-descriptioncomplete.pdf

0911-kolnp-2007-drawings.pdf

0911-kolnp-2007-form1.pdf

0911-kolnp-2007-form3.pdf

0911-kolnp-2007-form5.pdf

0911-kolnp-2007-international publication.pdf

0911-kolnp-2007-international search authority report.pdf

0911-kolnp-2007-pct others.pdf

0911-kolnp-2007-priority document.pdf

911-KOLNP-2007-(05-07-2012)-CORRESPONDENCE.pdf

911-KOLNP-2007-(05-07-2012)-FORM-3.pdf

911-KOLNP-2007-ABSTRACT.pdf

911-KOLNP-2007-AMANDED CLAIMS.pdf

911-KOLNP-2007-ASSIGNMENT.pdf

911-KOLNP-2007-CORRESPONDENCE.pdf

911-KOLNP-2007-DESCRIPTION (COMPLETE).pdf

911-KOLNP-2007-DRAWINGS.pdf

911-KOLNP-2007-EXAMINATION REPORT REPLY RECIEVED.pdf

911-KOLNP-2007-EXAMINATION REPORT.pdf

911-KOLNP-2007-FORM 1.pdf

911-kolnp-2007-form 18.pdf

911-KOLNP-2007-FORM 2.pdf

911-KOLNP-2007-FORM 3 1.1.pdf

911-KOLNP-2007-FORM 3.pdf

911-KOLNP-2007-FORM 5.pdf

911-KOLNP-2007-GPA.pdf

911-KOLNP-2007-GRANTED-ABSTRACT.pdf

911-KOLNP-2007-GRANTED-CLAIMS.pdf

911-KOLNP-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

911-KOLNP-2007-GRANTED-DRAWINGS.pdf

911-KOLNP-2007-GRANTED-FORM 1.pdf

911-KOLNP-2007-GRANTED-FORM 2.pdf

911-KOLNP-2007-GRANTED-SPECIFICATION.pdf

911-KOLNP-2007-OTHERS 1.1.pdf

911-KOLNP-2007-OTHERS.pdf

911-KOLNP-2007-PETITION UNDER RULE 137.pdf

911-KOLNP-2007-REPLY TO EXAMINATION REPORT.pdf

« Previous Patent

Next Patent »

Patent Number

254626

Indian Patent Application Number

911/KOLNP/2007

PG Journal Number

48/2012

Publication Date

30-Nov-2012

Grant Date

27-Nov-2012

Date of Filing

14-Mar-2007

Name of Patentee

HEUBACH GMBH

Applicant Address

HEUBACHSTRASSE 7, 38685 LANGELSHEIM

Inventors:

#	Inventor's Name	Inventor's Address
1	HEUBACH RAINER	UNTERSBERGSTRASSE 104, A-5084 GROSSGMAIN

PCT International Classification Number

C09C 3/04,B02C 17/20

PCT International Application Number

PCT/EP2005/008892

PCT International Filing date

2005-08-16

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2004 040 384.8	2004-08-20	Germany