MXPA06007995A - Highly reflective interference pigments with dark absorption color - Google Patents

Abstract

Highly reflective interference effect pigments with dark absorption color are obtained by reducing platy titanium dioxide. The present effect pigments may be used in cosmetics, plastics, inks, and coatings including solvent and water borne automotive paint systems.

Description

It is not toxic. The titanium dioxide may be in the anatase form as described, for example, in U.S. Patent Nos. 3,087,827, 3,087,828, 3,418,146 and 3,437,515, or in the crystalline form of rutile as described in U.S. Patent 4,038,099. The metal oxide on the mica substrate has a high refractive index and provides optical effects, including high luster and reflectivity, cover, interference reflection color if the metal oxide coating is thick enough, and absorption color if the metal oxide contains a colored material. Mica, on the other hand, has a low refractive index and essentially functions only as a carrier, substrate making almost no contribution to the optical effect that is performed. The substrate pigments coated with metal oxide do not exhibit dark absorption colors. The glossy, presumably dark interference pigments have been prepared using the chemical vapor deposition techniques as described in European patents Nos. 0579091 and 0571836. A description of the production of dark, particularly black, surface coatings, are found in U.S. Patent 5,356,471. This result is achieved by coating a platelet-like substrate with a silane followed by pyrolysis, for example at temperatures which are preferably greater than 700 ° C in a gas atmosphere, preferably inert, not oxidation. The process leads to the formation of a layer on the surface of the pigment containing black Si02 glass containing silicon oxycarbide and / or carbon black. In U.S. Patent 5,286,291, a pigment containing carbon black is achieved by fixing the carbon black on a substrate by means of a surfactant and an organic silane compound. The products of these patents are usually characterized by being low in reflectivity and poor in color purity. The use of carbon black is not - a very efficient process due to the majority of platelets being treated may not be properly coated. As a result, the methods mentioned in the above are characterized by increased production costs, which are difficult to precisely control and involve multiple stages. There is, therefore, still a need for highly intense interference pigments with a dark absorption color that can be made by a simple and cost-effective process. It is the object of this invention to provide such pigments and a process by means of which they can be prepared. BRIEF DESCRIPTION OF THE INVENTION This invention relates to highly reflective interference pigments having a dark absorption color. Such pigments have been surprisingly achieved by reducing the surface of a laminated titanium dioxide or self-supporting plate. Thus, the present invention provides an effect pigment comprising laminated titanium dioxide which is substantially free of substrate and has a surface comprising reduced titanium oxide. Although the reduction of Ti0-containing pigments known hitherto have been shown to generate dark absorption pigments (See BASF PALIOCROM® Blue Silver L 6000 pigment reported to be 70-75 percent mica coated with 21 percent by weight reduced Ti02 and tin), the pigments of this invention are significantly different in that they are substantially substrate-free (as defined below) and unexpectedly maintain their high degree of color purity and reflectivity across the gold-to-green color spectrum after reduction treatment. Prior to the present invention, it was observed that color and brilliance were lost as the degree of reduction increases, especially with mica-based pigments, to the extent that the quality of interference was compromised. Nevertheless, when the self-supporting or laminated Ti02 of the present invention is employed, this loss of quality is negligible, resulting in a product with high opacity, excellent color, and reflectivity. Furthermore, and even more unexpectedly, the pigments of this invention not only maintain their appearance of original interference but currently appear to advance in optical thickness as the reduction process intensifies. Thus, for example, a yellow self-supporting Ti02 will move from yellow to deep gold to olive green. By controlling the degree of reduction of titanium dioxide, several dark absorption shadows can be obtained without compromising the reflection or purity of color. Thus, an interference effect pigment with a dark absorption color of superior reflection and color purity can be achieved or the reduction can be carried out so that the resulting color pigment is completely opaque with a metallic appearance. DESCRIPTION OF THE INVENTION In accordance with the present invention, laminated titanium dioxide plates are subjected to reduction. As used herein, the phrase "laminated Ti02" or "self-supporting Ti02" as described, for example, in the commonly assigned U.S. patents, 4,192,691 and 5,611,851 incorporated herein by reference in their entireties. herein, the phrase "substantially substrate free" means that it contains less than about 60 weight percent substrate based on the total weight of the effect pigment US Patent 4,192,691 employs an aqueous solution of hydrofluoric acid and an acid mineral such as sulfuric acid to dissolve the pigment mica.It is also disclosed and illustrated the use of this solvent for removing the mica from a mica coated with titanium dioxide having a surface layer of either iron or chromium oxide. U.S. Patent 5,611,851 employs a combination of a mineral acid and a phosphoric acid followed by an extractive solution using u n alkali Although the process of US Pat. No. 5,611,851 is preferred, other methods can be employed to obtain the titanium dioxide platelets used in the present invention. For example, the types of titanium dioxide platelets suitable for use in this invention can be prepared by removing gypsum from gypsum coated Ti02 or by burning graphite from Ti02-coated graphite. The dissolution of glass from a glass base coated with Ti02 also provides a useful substrate in this invention as various network techniques. Although there are several routes for preparing Ti02 platelets which can then be further coated, the Ti02 substrate of US Pat. No. 5,611,851 is still preferred in order to obtain maximum reflectivity and color purity. Initially using a substrate helps the production of the relatively smooth and regular titanium dioxide surfaces needed to achieve the high quality effect pigments, and the subsequent removal of the mica (refractive index 1.5) and other substrate and its replacement with air (Rf 1.0), allows the benefit of the refractive index of Ti02 (2.6-2.9) that is made more completely. A useful laminated Ti02 is commercially available from Engelhard Corporation. The titanium dioxide platelets used in the present invention generally have an average longer dimension of about 1 to about 75 μm, and preferably about 2 to about 35 μm. Platelets can have a thickness of about 5 to about 600 nm and such thickness is more preferably about 20 to about 400 nm. The Ti02 is preferably in the crystalline form of rutile but may also be in the anatase form. The use of laminated Ti02 that is substantially free of substrate provides useful effect pigments and it is possible to further decrease the amount of the substrate present in the effect pigment. Nevertheless, the need to eliminate a lot of the substrate helps the manufacturing cost. Also, because the center of the TiO? It is essentially hollow, the pigment has to be more brittle, which, in turn tends to complicate its use in applications where the pigment is subjected to more stringent conditions. Thus, the pigment substantially free of substrate present is useful in certain applications that require a firmer pigment such as or automotive paints. The laminated Ti02 is preferably used at least about 40 weight percent of the substrate based on the total weight of the effect pigment and more preferably at least about 20 weight percent of the effect pigment. In order to achieve the effect pigments of the present invention, the laminated titanium dioxide is subjected to the action of a reducing agent for a time and under conditions which cause the surface of the platelets to be reduced. For example, titanium dioxide platelets can be heated in a reducing gas atmosphere. Typical "reducing gases" include ammonia, hydrogen, volatile hydrocarbons and mixtures thereof Such reducing agents are preferably used in a mixture with an inert gas such as nitrogen.The reduction is preferably carried out at an elevated temperature of about 675-850 ° C when the ammonia is used as the reducing agent and higher temperatures are generally used when the ammonia / hydrocarbon mixtures are used.According to the desired degree of reduction, the temperature and residence time can be varied so that either a pure color pigment, highly reflective with a dark absorption color or a completely opaque pigment can be prepared. The degree of reduction can be quantified by spectrophotometric methods to determine the color purity and degree of reflectivity / absorption. Opacity values can be determined by measuring the film thickness on a spray panel that equals the cover values. In general, the thickness of the reduced material needed for a given degree of concealment is inversely proportional to the opacity. Thus, since the material becomes more opaque, a thinner reduction layer is needed to complete the cover-up compared to a control substance such as Al flakes. The reduction process leads to the formation of the reduced titanium species which have oxidation states less than 4, such as Ti305, Ti20 and TiO. The reduced laminated titanium dioxide pigments of the present invention are very different from the reduced titanium dioxide coated mica, such as those commercially available under the name of pigment PALIOCROM & (BASF), as well as other substrate pigments coated with Ti02. Illustrative of other pigments are those based on silicate platelets coated with titanium dioxide that have been heated in the reduction atmosphere and contain a coating 11 colorless having a reflective index up to 1.8 coated by a colorless coating having a refractive index of at least 2.0, such as titanium dioxide, which is described in US Pat. No. 6,139,414. The resulting pigment can be used in any application whereby the effect pigments have been used up to now such as, for example, in cosmetics, plastics, inks and coatings' including automotive solvent and water-borne paint systems. The products of this invention have unlimited use in all types of automotive and industrial paint applications, especially in the organic color coating and the ink field where deep color intensity is required, for example, these pigments can be Use in mass tone or as styling agents for all types of automotive and non-automotive vehicle spray paint.Also, they can be used in all, clay / Formica / wood / glass / metal / enamel / ceramic. porous or porous pigments can be used in powder coating compositions, can be incorporated into plastic articles, prepared for the toy industry or the home.These pigments can be impregnated into fibers to impart new and aesthetic coloration to clothing and carpeting, can be used to improve the appearance of shoes, rubber and floor 12 vinyl / marble, vinyl lining boards, all other vinyl products. In addition, these colors can be used in all types of scale models. The aforementioned compositions in which the compositions of this invention are useful are well known to those of ordinary skill in the art. Examples include printing inks, nail enamels, lacquers, thermoplastic and thermosetting materials, natural resins and synthetic resins. Some non-limiting examples include polystyrene and its mixed polymers, polyolefins, in particular polyethylene and polypropylene, polyacrylic compounds, polyvinyl compounds, for example polyvinyl chloride and polyvinyl acetate, polyesters and rubber and also filament made of viscous ethers and cellulose , cellulose esters, polyamides, polyurethanes, polyesters, for example polyglycol terephthalates, and polyacrylonitrile. For a well-rounded introduction to a variety of pigment applications, see Temple C. Patton, editor, The Pigment Handbook, volume II, Applications and Markets, John Wiley and Sons, New York (1973). Also, see for example, with respect to the ink: R.H. Leach, editor, the Printing Ink Manual, fourth edition, Van Nostrand Reinhold (International) Co. Ltd., London (1988), particularly pages 282-591; with respect to paintings: C.H. I will, 13 Protective Coatings, Technology Publishing Co. Pittsburgh (1994), particularly pages 93-288. The above references are incorporated herein by reference to their teaching of ink, paint and plastic compositions, formulations and vehicles in which the compositions of this invention can be used including amounts of colorant. For example, the pigment can be used at a level of 10 to 15% in a photolithographic ink, with the remainder being a vehicle containing gelled and ungelled hydrocarbon resins, alkyd resins, wax compounds and aliphatic solvent. The pigment can be used, for example, at a level of 1 to 10% in an automotive paint formulation along with other pigments which may include titanium dioxide, acrylic networks, conglutinating agents, water or solvents. The pigment can also be used, for example, at a level of 20 to 30% in a plastic-colored concentrate in the polyethylene. In the field of cosmetics, these pigments can be used in the eye area and in all external and rinsing applications. Thus, they can be used in hairsprays, face powder, leg makeup, insect repellent lotion, cake / cream, nail polish, nail polish remover, perfume lotion, and shampoos from all types (gel or liquid). In addition, you can 14 use in shaving cream (concentrated in spray, without brush, in foam), burnishing bar for the skin, makeup for the skin, hair grooming, eyeshadow (liquid, ointment, powder, stick, pressure or cream), eyeliner, cologne bar, cologne, cologne emollient, bubble bath, body lotion (moistening, cleansing, analgesic, astringent), after shave lotion, after milk bath and sun block lotion. For a review of cosmetic applications, see Cosmetics: Science and Technology, 2nd Ed., Eds: MS Balsam and Edward Sagarin, Wiley-Interscience (1972) and de Navarre, the Chemistry and Science of Cosmetics, 2nd Ed., Volumes 1 and 2 (1962), Van Nostrand Co. Inc., Inc., Volumes 3 and 4 (1975), Continental Press, both of which are incorporated herein by reference. In order to further illustrate the invention, several non-limiting examples will be set forth below. In these examples, as well as throughout the balance of this specification and claims, all parts and percentages are by weight and all temperatures are in degrees Centigrade unless otherwise indicated. Example 1 A load of 3-5 grams of laminated titanium dioxide having a pearly appearance that has been prepared according to the procedure set forth in Example 1 of US Pat. No. 5,611,851 and which is substantially free of substrate was placed in a quartz cup vessel and placed in a tube furnace. The furnace was filled with nitrogen since the tube was heated to 675 ° C. When that temperature was reached, the nitrogen gas was replaced with ammonia gas for a period of one hour. The resulting pigment was a pure, highly refractive color interference pigment with a dark absorption color. Examples 2-7 Example 1 was repeated substituting laminated titanium dioxides having appearances of gold, orange, red, violet, blue and green. The resulting pigments were pure, highly refractive color interference pigments with a dark absorption color. Example 8 The procedure of Example 1 was repeated except that the temperature of the ammonia reduction was maintained at 800 ° C. The resulting pigment was opaque and exhibited a good color with a metallic appearance. Example 9 The pigment of Example 1 can be formulated into a powder eye shadow as follows: The following materials are mixed and completely dispersed: Ingredients by weight 16 ? E? RL ALC TCA® (Talc) 18 ME? BIMICA® SVA (Mica) 20 Myristate Magnesium 5 Silica 2 CLOISONNÉB Red 42 C (mica coated with red Ti02) 20 CLOISONNÉ® Violet 525C (mica coated with Ti02 violet) 13 CLOISONNm Nu-Antique Blue 626CB (mica coated with Ti02 / mica coated with iron oxide) 2 CLOISONNÉ® Cerise Flaiabé 550Z (mica covered with iron oxide) 2 Preservatives and Antioxidant qs Then 7 parts of octyl palmitate and a part of isostearyl neopentanoate are heated and mixed until uniform, while the resulting mixture is sprayed into the dispersion and mixing is continued. The mixed material is pulverized and then 5 parts of Cloisonne Red 424C and 5 parts of the pigment of Example 1 are added and mixed until a uniform powder eye shadow is obtained. Example 10 The pigment of Example 1 can be formulated in a lipstick as follows. 17 The following amounts of the listed ingredients are placed in a heated container and the temperature rises to 85 ± 3 ° C. • Parts by weight Candelilla wax 2.75 Carnauba wax 1.25 Beeswax 1.00 Ceresin wax 5.90 Ozocerite wax 6.75 Microcrystalline wax 1.40 Oleic alcohol 3.00 Isostearyl palmitate 7.50 Isostearyl isostearate 5.00 Capric / Capric triglyceride 5.00 Bis-Diglicerilpolyalcohol adipate 2.00 Alcohol of Acetylated Lanolin 2.50 Sorbitan Tristearate 2.00 Aloe Vera 1.00 Castor Oil 37.50 Red 6 Lake 0.25 Tocopheryl Acetate 0.20 Phenoxyethanol, isopropylparaben, and butylparaben 1.00 Antioxidant q. s. Then, 14 parts of the pigment of Example 1 is add and mix until all of the pigment is well dispersed. The fragrance is added as desired and mixed with agitation. The resulting mixture is emptied into molds at 75 ± 5 ° C, allowed to cool and flamed in lipsticks. Various changes and modifications can be made in the products and the process of the present invention without departing from the spirit and scope thereof. The various embodiments that have been disclosed herein were for the purpose of further illustrating the invention but were not intended to limit it.

Claims (10)

19 CLAIMS 1. An effect pigment, characterized in that it comprises laminated titanium dioxide which is substantially free of substrate and has a surface comprising reduced titanium oxide.

2. The effect pigment according to claim 1, characterized in that it comprises a plurality of platelets from about 1 to about 25 μm in the maximum dimension and a thickness from about 5 to about 600 nm.

3. The effect pigment according to claim 2, characterized in that the platelets have a maximum dimension of about 2 to about 15 μm and a thickness of about 20 to about 400 n.

4. The effect pigment according to claim 3, characterized in that the titanium dioxide in the area other than the surface is in the rutile crystalline form.

5. The effect pigment according to claim 4, characterized in that the effect pigment contains less than about 40 weight percent of the substrate based on the total weight of the effect pigment.

6. The effect pigment according to claim 4, characterized in that the effect pigment it contains less than about 20 weight percent substrate based on the total weight of the effect pigment.

7. In a paint or ink composition including a pigment, the improvement characterized in that it comprises the pigment which is an effect pigment according to claim 1.

8. In a plastic composition including a pigment, the improvement characterized in that it comprises the pigment which is an effect pigment according to claim 1.

9. In a cosmetic composition including a pigment, the improvement characterized in that it comprises the pigment which is an effect pigment according to claim 1.

10. Paint - automotive, characterized in that it comprises the paint according to claim 17.