MXPA01002740A - Reduction pigments - Google Patents

Abstract

The present invention relates to thin, wafer-shaped titanium dioxide reduction pigments based on SiO2 wafers, in addition to the use thereof in colorants, paints, plastics, printing inks and glazes for ceramics and glass.

Description

REDUCTION PIGMENTS FIELD OF THE INVENTION The present invention relates to pigments for the reduction of titanium dioxide in the form of platelets, thin platelets based on SiO 2 and their use in paints, varnishes, plastics, inks. printing and varnish for ceramics and glass.

BACKGROUND OF THE INVENTION The known titanium dioxide reduction pigments are based on the use of mica or titanium dioxide platelets as the base substrate. The titanium dioxide is precipitated onto the uncoated or coated base substrates and subsequently reduced to titanium suboxides. The reducing agents used are generally gaseous reducing agents such as hydrogen or ammonia or metals, for example silicon or titanium.

REF. : 127205 The U.S. No. 4,948,631 describes a process for the preparation, in particular, of pigments for bluish bead luster or gloss using ammonia to reduce pigments of mica coated with titanium dioxide of 750 to 850 ° C. JP H4-20031 describes a process for the preparation of a colored coated mica pigment by mixing a mica pigment coated with titanium dioxide with titanium and reducing the resulting mixture in a vacuum of 500 to 1000 ° C. DE-A-196 18 562 discloses a titanium dioxide reduction pigment consisting of titanium dioxide, titanium suboxides and optionally a titanium oxide nitrite or additional metal dioxide. This pigment is obtained by solidifying an aqueous solution of a thermally hydrolysable titanium compound on an endless belt, which separates the resulting layer, coating the resulting titanium dioxide platelets with additional titanium dioxide in a wet process, drying and optionally calcining. and treatment in a non-oxidizing gas atmosphere.

However, the known pigments are disadvantageous because they have insufficient hiding power and / or no unstable color.

DESCRIPTION OF THE INVENTION It is an object of the present invention to provide a titanium dioxide reduction pigment in the form of a high gloss or glossy platelet which does not have the disadvantages described above and is notable for the high hiding power and unstable color. This object is achieved according to the invention by a platelet-shaped color pigment based on a Si02 platelet coated with titanium dioxide, one or more titanium sub-oxides and optionally with at least one additional metal oxide, non-metallic oxide and / or titanium oxynitrides. In the coating, the concentration of titanium dioxide is at a maximum near the surface of the substrate and gradually decreases in the direction of the pigment surface, and the concentration of any additional metal oxide present is at a maximum at the surface of the pigment and gradually decreases in the direction of the surface of the substrate, the coating layer comprising the mixed phases of these oxides. The inventive titanium dioxide reduction pigments based on SiO2 platelets are remarkable for luster or gloss, high hiding power and unstable color. The invention therefore provides thin titanium reduction pigments based on SiO2 platelets, which are coated with titanium dioxide, titanium suboxides and optionally at least additional metal oxide, non-metallic oxide and / or titanium oxynitride. The invention in a similar manner provides for the use of the pigments of the invention in paints, printing inks, plastics, coatings, especially automotive coatings, and varnish for ceramics and glasses. The pigments of the invention are based on SiO2 platelets. These generally have a thickness between 10 nm and 1000 nm, preferably between 300 and 500 nm. The area in the other two dimensions is between 2 and 200 μm, especially between 5 and 150 μm. Such pigments are produced in an endless belt, for example, and are based on a platelet-shaped matrix as described in WO 93/08237. The SiO2 platelets are provided with one or more layers of metal oxide, at least one layer which is a layer of TiO2. The Ti02 layer is 10 to 1000 nm, preferably 40 to 50 nm, thick. The metal oxides or metal oxide mixtures in Si02 platelets coated with Ti02 are zirconium oxide, zinc oxide, iron oxide and / or chromium oxide and also mixtures of i2 / Fe203. The coating of the Si02 platelets can be carried out, for example, as described in WO 93/08237 (chemical coating for moisture) or DE-A-196 14 637 (CVD process). Preferably, the SiO2 platelets are chemically coated by moisture. The additional metal oxide present in the pigment of the invention in addition to the titanium oxide and titanium suboxides may be the oxidation product of the reducing agent used. This is in particular an oxide of the elements Li, Na, K, Mg, Ca, Al, Si, Cr, Zr, Zn and Fe. This metal oxide is present in the pigment of the invention in a concentration of 2 to 30% by weight, preferably 1 to 5% by weight, based on the amount of the titanium dioxide. The reducing agents used are gaseous reducing agents, for example hydrogen or solid reducing agents in the form of metal powders, metal alloys, metal borides, metal carbides or metal silicides. The preference is given to use metallic / non-metallic powders such as boron, aluminum, silicon, zinc or iron and especially silicon or combinations of the same. The usual reducing agents such as alkali metals can be used in liquid or gaseous phase. In addition to possible reducing agents include hydrides such as LiH or CaH2. It is also possible to use combinations of these reducing agents with each or some other. The Si02 platelets coated with Ti02 and optionally an additional metal oxide and the reducing agent are mixed in a ratio of 100 to 1 to 5: 1. In a particular embodiment, the pigment of the invention can additionally comprise carbon black, which is either applied directly to the silicon oxide particles in the form of platelets or is precipitated in the silicon dioxide particles in the form of platelets. together with titanium dioxide in a process by humidity. The details are more particularly described in the German documents OPI DE 195 02 231, DE 42 22 372 and U.S. Pat. 4,076,551. The Si02 platelets coated with titanium dioxide are completely mixed with the solid reduction agents described above in a ratio of 100: 1 to 5: 1 and treated at more than 600 ° C, preferably in the range from 700 to 1100 ° C. , in a non-oxidizing atmosphere for more than 10 minutes, preferably for 15 to 60 minutes. The reduction reaction goes faster in the presence of a halide, preferably a chloride. The particular preference is given to LiCl, NaCl, KCl, MgCl 2, CaCl 2, CuCl 2, CrCl 3, MnCl 2, FeCl 2, FeCl 3, CoCl 2, NiCl 2 or CeCl 3. The reaction temperature can be reduced by 150 to 300 ° C in the presence of chloride, for example CaCl 2. The chloride could preferably be anhydrous. The amounts of halide can vary from 0.1 to 40% by weight, preferably 0.5 to 10% by weight, based on the Si02 platelet coated with Ti02. The pigment of the invention can be additionally coated with firmly adhering, sparingly soluble organic or inorganic dyes. The preference is given to use lacquers, especially aluminum lacquers. To this end, a layer of aluminum hydroxide is precipitated by wet chemical means and laced in a second step using a lacquer. The process is known from DE 24 29 762 and DE 29 28 287. The preference is also given to an additional coating with salt complex pigments, especially cyanoform complexes, for example Prussian blue and Turnbull blue., as described in EP 0 141 173 or DE-C-23 13 332. The pigment of the invention can also be coated with organic dyes, especially dyes of phthalocyanine or metal phthalocyanine and / or indantrone, according to the DE 40 09 567. To this end, the pigment is suspended in a solution of the dye and the suspension is then combined with a solvent in which the dye is insoluble or soluble escás amenté. It is also possible to use metal chalcogenides or metal chalcogenide and carbon black hydrates for an additional coating. To produce the color pigments of the invention, Si02 platelets coated with Ti02 are mixed with at least one solid reduction agent, preferably an alkaline earth metal, B, Al, Si, Zn, Fe, LiH, CaH2, A14C3 , Mg2Si, MgSi2, Ca2Si or CaSi2, and the mixture is calcined in a non-oxidizing gas atmosphere above 600 ° C for more than 10 minutes. The mixture of the pigment and the reducing agent used to produce the reduction pigments of the invention frequently have talc added to it in amounts of 0.1 to 10% by weight, especially 0.1 to 2.0% by weight, to improve the flowability of the pigments reduced. The reduction reaction takes place in a non-oxidizing gas atmosphere, for example, N2, Ar, He, C02, CxXy, H2, NH3, of which N2 or Ar are preferred. The preference is given in addition to nitrogen-hydrogen mixtures having a hydrogen content. preferably 3% by volume. In the case of N2 or NH3, TiN or TiON can also be formed as well as Ti02-? The reduction at temperatures of = 800 ° C for a period of more than 10 minutes, preferably 15 minutes to 60 minutes, leads to the production on the Si02 platelets of the mixed solid suboxides or bronze oxides in the form of solid powders, soft. The reaction is explained with reference to certain examples: 1000 ° C 2A1 + 6 Ti02 / Si A1203 x 3 Ti203 / Si Ar 1000 ° C 2A1 + 3 Ti02 / Si * A120- 3 TiO / Si * Ar 1000 ° C Si + 6 Ti02 / Si Si02 x 2 Ti305 / Si N; 1000 ° C Yes + 4 Ti02 / Si * Si2 x 2 TÍ3O5 / YES N: If * = platelets of Si02 The color effect of the pigments is generally controllable through the variation - particle size of the Si02 platelet (smaller particles lead to a silky, smooth luster or shine, larger particles to a luster or radiant glow) Thickness of the titanium dioxide layer (interference color) of the nature of the solid reduction agent (low potential reduction gives bluish black output, high potential reduction gives black to blackish-yellow output) and - of the amount of agent solid reduction.

It is further possible to subject the pigments to a subsequent coating to further increase clarity, weathering and chemical stability or to facilitate handling. of the pigment, especially its incorporation in several media. Useful back coatings include for example the process described in DE-C 22 15 191, DE-A 31 51 354, DE-A-32 35 017 or DE-A-33 34 598. Due to the properties of the pigments of the invention which are very good even without these additional measures, these substances, if applied additionally, which is optional, only account for about 0 to 5% by weight, especially about 0 to 3% by weight, of the whole pigment. The pigment of the invention has a superior luster or gloss and a very uniform thickness compared to the titanium dioxide reduction pigments of the prior art. The standard deviation known as thickness tolerance does not exceed 10%. The flat parallel surface and the reduced thickness tolerance of the pigment particles provide a very high color purity and very high color fastness. The pigments of the invention are compatible with a multiplicity of color systems, preferably in the field of varnishes, paints, printing inks, plastics, glasses and ceramics. The invention is also provided for the use of the reduction pigments alone or in combination with other pigments, dyes and / or organic or inorganic fillers in formulations such as paints, printing inks, varnishes, plastics and glasses. The invention similarly provides pigment mixtures comprising the reduction pigments of the invention in combination with commercially available pigments, for example organic and inorganic color pigments, effect pigments. As well as the titanium reduction pigments, the pigment mixtures preferably include all the effect pigments familiar to the person skilled in the field of the effect pigment, for example pigments with a matic effect composed of aluminum, copper, zinc, tin and its alloys, of which aluminum and bronze and gold alloys in particular are preferred. In addition, the pigment blends of the invention preferably include iron oxide in the form of an uncoated or coated platelet, aluminum flakes or coated aluminum flakes. Such effect pigments are produced by BASF under the name Pa 1 i ocrom (R), by Ec ka rt - Wer ke under the name Standart (R > and by Flex. Pearl polish or gloss pigments are also suitable, BiOCl, functional pigments, LCPs (Liquid Crystal Pigments), holographic pigments, glass or graphite platelets coated with one or more metallic oxides, and BiOCl, pearl luster or glitter pigments, mica flake pigments coated with one or more more metal oxides are available, for example, from Merck KGaA, Darmstadt under the factory name of Iriodin (R), the latter being known, for example, from German patents and patent applications 14 67 468, 19 59 988, 20 09 566, 22 14 545, 22 15 191, 22 44 298, 23 13 331, 25 22 572, 31 37 808, 31 37 809, 31 51 343, 31 51 354, 31 51 355, 31 11 602 and 32 53 017. Mica pigments coated with Fe203 and / or TiO2 are used in particular. Both natural and synthetic mica are useful as silicate sheet. The titanium reduction pigments are miscible in any proportion with one or more fillers, dyes, organic and inorganic pigments. The proportion of the titanium reduction pigment for commercially obtainable pigments or dyes is preferably within the range of 10: 1 to 1:10. The pigment mixture of the invention is simple and easy to handle. The pigment mixture can simply be stirred in the application system. This is not necessary for the trituration and complicated dispersion of the pigments. The pigment mixture of the invention is useful for pigment varnishes, printing inks, plastics, agricultural films, lower pastes, seed coatings, food coloring or drug coatings. The concentration of the pigment mixture in the application system to be pigmented is generally between 0.01 and 50% by weight, preferably between 0.1 and 5% by weight, based on the total solids content of the system. The concentration of the pigment mixture in the application system to be pigmented depends on the specific application case. Plastics comprising the inventive pigment mixture of titanium reduction pigment and pearlescent and / or effect gloss pigment and / or effect in amounts of 0.1 to 50% by weight, especially 0.5 to 7% by weight, often have an effect of special flash. In the coatings sector, especially automotive coatings, the mixture of pigment pigment reduction titanium and pigment gloss or bead shine and / or effect is used in amounts of 0.5 to 10% by weight. The pigment mixture of the invention has the advantage in coatings that the desired unstable color effect is obtained from a single layer coating (single layer systems or as a base coat constructed in 2 layers). This unstable color is very different even in diffuse light.

Binder systems, "for example for colors and printing inks for size printing, tracing printing or screen printing, are advantageously pigmented using mixtures of titanium reduction pigment pigment and pearl gloss or pearl gloss and / or of effect and / or gold and aluminum bronze pastes of Ec ka rt -We r ke.The pigment mixture is incorporated into the printing ink in amounts of 2-50% by weight preferably 5-30%, especially 8-15 % by weight The printing inks comprising the pigment mixture of the invention exhibit a very light shade or color and are efficiently printable due to the low viscosity values The invention similarly provides pigment preparations comprising the pigments of reduction of titanium alone or combined with pigments, dyes, binders and optionally organic and inorganic additives in the form of a free-flowing granulate, substantially free of solvent. The granulates contain up to 95% by weight of the titanium reduction pigment. A pigment preparation produced by filling the pigment mixture of the invention with a binder and with water and / or an organic solvent and optionally additives before the paste dries and produces a compact particle form, for example granules, Pellets, briquettes, basic mixture, tablets, is particularly useful as a precursor for printing inks. The invention therefore also provides pigment preparations comprising the titanium reduction pigment of the invention. The examples below illustrate the phenomenon.

E j emplos Inventive example 1 100 g of Si02 platelets coated with Ti02 of 5-40 μm particle size of Merck KGaA are mixed with 0.76 g of silicon powder, 0.5 g of CaCl2 (anhydrous) and 1 g of talc and the mixture is completely homogenized. The pigment mixture was then calcined for 0.5 h at 900 ° C in a stream of N2. The product has a more obscure color tone. Color interference varies from reddish purple (steep viewing angle) to bluish green (small viewing angle).

Inventive Example 2 Color: 1.5% of Si02 platelets coated with 5-40 μm titanium suboxide of particle size prepared according to Example "1 1.0% iron oxide orange 0.7% copper titanium P.Br. 24/77310 0.7% Graphitan 7525 (from Ciba) 0.4% micronized Ti02, 35 nm Pigment: binder 38/100 This produced an olive base tone with silvery blue highlights, the coating exhibiting a variation in the descending drop to green.

Comparative Example: Color: 1.5% Iriodin (R) 9605 SW (mica pigment coated with titanium suboxide 10-40 μm particle size Merck KGaA) 1.0% iron oxide orange 0.7% chrome titanium P.Br. 24/77310 0.7% Graphitan 7525 0.5% iron oxide P4 42/77492 0.4% micronized Ti02, 35 nm Pigment: binder 38/100 This produced an olive base tone with silver blue highlights.

Inventive example 3: Color: 3.0% Si02 platelets coated with titanium suboxide according to Inventive Example 1 0.7% Graphitan 7525 0.5% phthalocyanine blue PB 15: 1/74160 0.3% carbon black P.BK. 7/77266 This provided a base tone of medium steel blue with silver blue highlights, which exhibits a downward drop to greenish.

Comparative Example: Color: 3.0% of Si02 platelets coated with 0.7% Graphitan dioxide. 7525 0.03% phthalocyanine blue PB 15: 1/74160 0.03% carbon black P.BK. 7/77266 This provided a base tone of medium steel blue, which exhibits a greenish downward drop. The rest is distinctly more transparent than in Example invention 3.

It is noted that in relation to this date the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property

Claims (10)

1. Reduction pigments based on SiO2 platelets, characterized in that Si02 platelets are coated with titanium dioxide, one or more titanium sub-oxides and optionally with at least one metal oxide, non-metallic oxide and / or titanium oxynitride.

2. Reduction pigments according to claim 1, characterized in that the other metallic oxides and / or non-metallic oxides are oxides of the elements Li, Na, K, Mg, Ca, B, Al, Si, Cr, Zr, Zn and Fe .

3. Reduction pigments according to claim 2, characterized in that the other metal oxide and / or non-metallic oxide is present in the pigment in an amount of 2 to 30% by weight based on the amount of titanium dioxide.

4. Process for the production of reduction pigments according to claim 1, characterized in that Si02 platelets coated with Ti02 and optionally at least one additional metal oxide are mixed with at least one solid reduction agent in a ratio of 100: 1 to 5: 1 and the mixtures are calcined in a non-oxidizing gas atmosphere at a temperature of more than 600 ° C.

5. Process according to claim 4, characterized in that the reducing agent is an alkaline earth metal, B, Al, Yes, Zn, Fe, LiH, CaH2, A1 C3, Mg2Si, MgSi2, Ca2Si or CaSi2.

6. Process according to claim 4 and 5, characterized in that Si02 platelets coated with Ti0 and optionally at least one additional metal oxide are mixed with a halide in an amount of 0.1 to 40% by weight.

7. Process according to claim 6, characterized in that the halide is preferably LiCl, NaCl, KCl, MgCl 2, CaCl 2, CuCl 2, CrCl 3, MnCl 2, FeCl 2, FeCl 3, CoCl 2, NiCl 2 or CeCl 3.

8. The use of the reduction pigments according to claim 1, alone or combined with commercially available pigments in paints, varnishes, printing inks, plastics and varnish for ceramics and glasses.

9. Formulations characterized in that they comprise a reduction pigment according to claim 1.

10. Dry preparation characterized in that they comprise a reduction pigment according to claim 1.