Title of Invention

INTENSELY COLOURED RED EFFECT PIGMENTS .

Abstract

The present invention relates to intensely coloured red effect pigments comprising iron oxide-coated SiO2 flakes, where the total thickness of the effect pigments is not greater than 500 nm (+/- 30 nm). The present invention likewise relates to processes for the preparation of these pigments in which SiO2 flakes are coated with iron oxide, where the thicknesses of the SiO2 flakes and of the iron-oxide layers are selected in such a way that the total thickness of the red effect pigments is not greater than 500 nm (+/- 30 nm), and to the use of these pigments in cosmetics, paints, coatings, plastics, films, in security printing, in security features in documents and identity papers, for colouring seed, for colouring foods or in medicament coatings and for the preparation of pigment compositions and dry preparations.

Full Text

Intensely coloured red effect pigments The present invention relates to intensely coloured red effect pigments comprising iron oxide-coated SiO2 flakes, where the total thickness of the effect pigments is not greater than 500 nm (+/- 30 nm). The present inven- tion likewise relates to processes for the preparation of these pigments in which SiO2 flakes are coated with iron oxide, where the thicknesses of the SiO2 flakes and the iron-oxide layers are selected in such a way that the total thickness of the red effect pigments is not greater than 500 nm (+/- 30 nm), and to the use of these pigments in cosmetics, paints, coatings, plastics, films, in security printing, in security features in documents and identity papers, tor colouring seed, for colouring foods or in medicament coatings and for the preparation of pigment compositions and dry preparations. The use of red lustre or effect pigments is widespread. Pigments of this type have become indispensable in automobile paints, decorative coatings of all types and in the colouring of plastics, in paints and printing inks and in applications in decorative cosmetics. In the matrix surrounding them, these pigments ideally align themselves parallel to the surface of the coating and exhibit their optical action through a complex interplay of interference, re- flection and absorption of the incident light. A bright colour and high lustre are the focus of interest for the various applications. Pigments of this type are generally prepared by coating flake-form mica with metal-oxide layers, in particular iron-oxide layers. Mica, in particular, has the disadvantage that the thickness of the substrate varies in a broad range and cannot be set specifically, which results in light transmission and reflection at the substrate occurring in a substantially uncontrollable man- ner, even in the case of transparent substrates, and therefore being unus- able in a specific manner. WO 93/08237 discloses flake-form red pigments which consist of a silicon dioxide matrix as substrate which is coated with an iron-oxide layer The thickness of the matrix here can be set in a broad range. The red pigments described in WO 93/08237 have the disadvantage that, when tilted towards flatter viewing angles, they exhibit a brownish hue, which is undesired. Rather, there is a need for intensely coloured red effect pigments having a pure red hue and high lustre. In addition, the substrates have a thickness of 500 nm and the thicknesses of the applied layers are preferably 20-250 nm. Overall, pigments having a relatively large total thickness are thus obtained. However, this is unfavourable for many applications, since the applicational properties of the pigments are impaired, a phenomenon which is described, for example, by P. Hoffmann, W. Duschek, New Effect Pigments, in report volume DFG 41, 1999, 50, 123-132. In coating applications, for example, thick pigments exhibit problems with the target parallel alignment. The un- favourable geometry of the relatively thick pigment particles makes the desired alignment parallel to the surface more difficult in the binder system. Relatively thick pigment particles tend to line up at an angle to one another, and consequently the light is no longer reflected in the optimum direction and scattering effects reduce the directed lustre. In addition, applicational disadvantages arise, such as, for example, an increased haze effect (lustre fog) and a worse distinctness of image (DOI) of the pigment-containing coatings. Furthermore, colouristic disadvantages arise merely through the fact that the high mass of the individual particles for the same mass weight means that there is a considerably smaller number of pigment particles in the coating application. This has disadvantageous effects on the hiding power, the lustre and the overall colour impression. The desired properties therefore can only be achieved with difficulty in the case of thick pigment particles. The object was therefore to find red effect pigments having improved opti- cal properties, in particular having a pure red hue, which can be employed universally in a very wide variety of applications without exhibiting applica- tional disadvantages. The above-mentioned object is achieved by pigments according to the pre- sent invention. The present invention accordingly relates to intensely col- oured red effect pigments comprising iron oxide-coated SiO2 flakes, where the total thickness of the effect pigments is not greater than 500 nm (+/- 30 nm). The present invention likewise relates to processes for the preparation of these pigments in which SiO2 flakes are coated with iron oxide, where the thicknesses of the SiO2 flakes and the iron-oxide layers are selected in such a way that the total thickness of the red effect pigments is not greater than 500 nm (+/- 30 nm). The pigments according to the invention are distinguished by a particularly intense and pure red colour effect. The red effect pigments surprisingly exhibit only a very slight colour flop effect, or none at all, and are free from the interfering brown hue of other red pigments with iron-oxide layers. In addition, the pigments according to the invention have the advantage that they can be employed in a very wide variety of applications, where they exhibit improved applicational properties, for example a reduced haze effect and a better distinctness of image (DOI) in coating applications or a better skin feel in cosmetic formulations. Owing to the advantageous properties, the effect pigments according to the invention are universally suitable for a large number of applications of a very wide variety of types. The present invention accordingly also relates to the use of these pigments in cosmetics, paints, coatings, plastics, films, in security printing, in security features in documents and identity papers, for colouring seed, for colouring foods or in medicament coatings and for the preparation of pigment compositions and dry preparations. The pigments according to the invention are based on synthetic SiO2 flakes as substrate which have a uniform layer thickness and are preferably pre- pared in accordance with International Application WO 93/08237 on a con- tinuous belt by solidification and hydrolysis of a water-glass solution. Uni- form layer thickness here is taken to mean a layer-thickness tolerance of from 3 to 10%, preferably from 3 to 5%, of the total dry layer thickness of the particles. The flake-form silicon dioxide particles are generally in amor- phous form. Synthetic flakes of this type have the advantage over natural materials, such as, for example, mica, that the layer thickness can be adjusted with regard to the desired effects and the layer-thickness tolerance is limited. The diameter of the substrates is usually between 1 and 250 urn, preferably between 2 and 100 urn. Their thickness is between 250 and 400 nm and preferably from 330 to 350 nm. The average aspect ratio of the flake-form substrates, i.e. the ratio of the average length measurement value, which here corresponds to the average diameter, to the average thickness meas- urement value, is usually from 5 to 200, preferably from 20 to 150 and par- ticularly preferably from 30 to 120. The said substrates in the pigments according to the invention are coated with iron-oxide layers, in particular with haematite layers (α-Fe2O3). The thickness of the individual iron-oxide layers is between 30 and 150 nm, preferably from 50 to 130 nm. It is essential for the present invention that the total thickness of the red effect pigments is not greater than 500 nm (+/- 30 nm). The coating of the SiO2 flakes with iron oxide may be present either only on the two largest opposite surfaces or in a sheathing manner; the SiO2 flakes are preferably completely sheathed with iron oxide. In cross section, the following pigment structure arises from this: Fe2O3/SiO2/Fe2O3 The sum of the thicknesses of the total of three layers must not exceed the requisite 500 nm (+/- 30 nm). In order to optimise the desired pure red hue, precise matching of the thick- nesses of the substrate and of the iron-oxide layers is advantageous. The following distributions of the thicknesses for the substrates and the individ- ual iron-oxide layers are particularly preferred here: Thickness of the Thickness of the two Total thickness of the SiO2 matrix [nm] Fe2O3 layers (each) [nm] red pigments [nm] 250 125+/-15 500+/-30 300 100+/-15 500+/-30 350 75+/-15 500+/-30 400 50+/-15 500+/-30 In a further embodiment of the present invention, the effect pigments according to the invention can furthermore be provided with an additional stabilising organic coating as outer layer. Examples of such coatings are given, for example, in EP 0 632 109, US 5,759,255, DE 43 17 019, DE 39 29 423, DE 32 35 017, EP 0 492 223, EP 0 342 533, EP 0 268 918, EP 0 141 174, EP 0 764 191, WO 98/13426 or EP 0 465 805, the disclo- sure content of which is incorporated herein by way of reference. Effect pig- ments comprising an organic coating, for example of organosilanes or organotitanates or organozirconates, additionally, besides the above-men- tioned optical properties, exhibit increased stability to weathering influ- ences, such as, for example, moisture and light, which is of particular inter- est for industrial coatings and in the automobile sector. The stabilisation can be improved by inorganic components of the additional coating. Over- all, the respective proportions for the additional stabilising coating should be selected in such a way that the optical properties of the effect pigments according to the invention are not significantly influenced. The present invention likewise relates to processes for the preparation of these pigments in which SiO2 flakes are coated with iron oxide, where the thicknesses of the SiO2 flakes and of the iron-oxide layers are selected in such a way that the total thickness of the red effect pigments is not greater than 500 nm (+/- 30 nm). The respective matching of the thicknesses of the substrates to the thicknesses of the applied iron-oxide layers has already been explained above. The coating with iron-oxide layers can be carried out by wet-chemical methods and/or by CVD or PVD processes. The processes according to the invention for the preparation of the effect pigments are preferably wet-chemical processes in which use can be made of the known wet-chemical coating technologies developed for the prepara- tion of pearlescent pigments, which are described, for example, in the fol- lowing publications: DE 14 67 468, DE 19 59 988, DE 20 09 566, DE 22 14 545, DE 22 15 191, DE 22 44 298, DE 23 13 331, DE 25 22 572, DE 31 37 808, DE 31 37 809, DE 31 51 343, DE 31 51 354, DE 31 51 355, DE 32 11 602, DE 32 35 017. For the coating, the SiO2 flakes are suspended in water and coated with iron oxide by addition and precipitation of corresponding inorganic metal compounds, with the pH necessary for the precipitation of iron oxide being set and kept constant by simultaneous addition of acid or base, and the coated substrate is subsequently separated off from the aqueous suspen- sion, dried and optionally calcined, with the layer thicknesses of the individ- ual layers being set in such a way that, after drying and optional calcination, the thickness of the pigment is not greater than 500 nm (+/- 30 nm). The calcination temperature is generally between 250 and 1000°C, in par- ticular between 350 and 900°C. In principle, CVD or PVD processes for the coating of particles with iron oxide are also suitable for the preparation of the pigments according to the invention. Processes of this type are described, for example, in W. Oster- tag, Nachr. Chem. Tech. Lab 1994, 42, 849. It is necessary here for the substrate to be kept in uniform motion during the vapour-deposition process in order that a homogeneous coating of all particle surfaces is ensured. In addition, in a process which is likewise in accordance with the invention, an organic coating can additionally be applied as outer layer. Examples of coating processes of this type are given, inter alia, in EP 0 632 109, US 5,759,255, DE 43 17 019, DE 39 29 423, DE 32 35 017, EP 0 492 223, EP 0 342 533, EP 0 268 918, EP 0 141 174, EP 0 764 191, WO 98/13426 or EP 0 465 805. Examples of organic coatings and the associated advan- tages have already been described above under the structure of the pig- ments according to the invention. The process step of application of the organic coating can follow directly after the other steps of the process ac- cording to the invention. The substances applied here only have a propor- tion by weight of from 0.1 to 5% by weight, preferably from 0.5 to 3% by weight, in the pigment as a whole. The effect pigments according to the invention can be employed in a variety of applications. Accordingly, the present invention likewise relates to the use of the pigments according to the invention in cosmetics, paints, coat- ings, plastics, films, in security printing, in security features in documents and identity papers, for colouring seed, for colouring foods or in medica- ment coatings and for the preparation of pigment compositions and dry preparations. In the case of cosmetics, the effect pigments according to the invention are particularly suitable for products and formulations in decorative cosmetics, such as, for example, nail varnishes, colouring powders, lipsticks or eye- shadows, soaps, toothpastes, etc. The effect pigments according to the invention can of course also be combined in the formulations with cosmetic raw materials and assistants of all types. These include, inter alia, oils, fats, waxes, film formers, preservatives and assistants which generally deter- mine the applicational properties, such as, for example, thickeners and Theological additives, such as, for example, bentonites, hectorites, silicon dioxide, Ca silicates, gelatine, high-molecular-weight carbohydrates and/or surface-active assistants, etc. The formulations comprising effect pigments according to the invention may be of the lipophilic, hydrophilic or hydropho- bic type. In the case of heterogeneous formulations having discrete aque- ous and non-aqueous phases, the particles according to the invention may be present in each case in only one of the two phases or alternatively dis- tributed over both phases. The pH values of the aqueous formulations can be between 1 and 14, pref- erably between 2 and 11 and particularly preferably between 5 and 8. The concentrations of the effect pigments according to the invention in the for- mulation are unlimited. They may - depending on the application - be between 0.001 (rinse-off products, for example shower gels) and 99% (for example lustre-effect articles for particular applications). The effect pig- ments according to the invention may furthermore also be combined with cosmetic active ingredients. Suitable active ingredients are, for example, insect repellents, UV A/BC protection filters (for example OMC, B3, MBC), anti-ageing active ingredients, vitamins and derivatives thereof (for example vitamin A, C, E, etc.), self-tanning agents (for example DHA, erythrulose, inter alia), and further cosmetic active ingredients, such as, for example, bisabolol, LPO, ectoine, emblica, allantoin, bioflavonoids and derivatives thereof. On use of the effect pigments in paints and coatings, all areas of application known to the person skilled in the art are possible, such as, for example, powder coatings, automobile paints, printing inks for gravure, offset, screen or flexographic printing, and coatings in outdoor applications. The paints and coatings here may be, for example, radiation-curing, physically drying or chemically curing. For the preparation of printing inks or liquid coatings, a multiplicity of binders, for example based on acrylates, methacrylates, poly- esters, polyurethanes, nitrocellulose, ethylcellulose, polyamide, polyvinyl butyrate, phenolic resins, maleic resins, starch or polyvinyl alcohol, amino resins, alkyd resins, epoxy resins, polytetrafluoroethylene, polyvinylidene fluorides, polyvinyl chloride or mixtures thereof, in particular water-soluble grades, are suitable. The coatings can be powder coatings or water- or sol- vent-based coatings, where the choice of the coating constituents is subject to the general knowledge of the person skilled in the art. Common poly- meric binders for powder coatings are, for example, polyesters, epoxides, polyurethanes, acrylates or mixtures thereof. In addition, the effect pigments according to the invention can be used in films and plastics, thus, for example, in agricultural sheeting, infrared- reflective films and sheets, gift foils, plastic containers and mouldings for all applications known to the person skilled in the art. Suitable plastics for incorporation of the effect pigments according to the invention are all com- mon plastics, for example thermosets or thermoplastics. A description of the possible applications and suitable plastics, processing methods and additives is given, for example, in RD 472005 or in R. Glausch, M. Kieser, R. Maisch, G. Pfaff, J. Weitzel, Perlglanzpigmente [Pearlescent Pigments], Curt R. Vincentz Verlag, 1996, 83 ff., the disclosure content of which is incorporated herein. In addition, the effect pigments according to the invention are also suitable for use in security printing and in security-relevant features for, for example, counterfeiting-proof cards and identity papers, such as, for example, entry tickets, personal identity cards, banknotes, cheques and cheque cards and for other counterfeiting-proof documents. In the area of agriculture, the effect pigments can be used for colouring seed and other starting materials, in addition in the foods sector for pigmenting foods. The effect pigments according to the invention can likewise be employed for pigmenting coat- ings in medicaments, such as, for example, tablets or dragees. In the above-mentioned areas of application, the effect pigments according to the invention are likewise suitable for use in mixtures with organic dyes and/or pigments, such as, for example, transparent and opaque white, col- oured and black pigments, and with flake-form iron oxides, organic pig- ments, holographic pigments, LCPs (liquid crystal polymers) and conven- tional transparent, coloured and black lustre pigments based on metal oxide-coated flakes based on mica, glass, AI2O3, Fe2O3, SiO2, etc. The effect pigments according to the invention can be mixed with commercially available pigments and fillers in any ratio. Fillers which may be mentioned are, for example, natural and synthetic mica, nylon powder, pure or filled melamine resins, talc, glasses, kaolin, oxides or hydroxides of aluminium, magnesium, calcium, zinc, BiOCI, bar- ium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, carbon, and physical or chemical combinations of these substances. There are no restrictions regarding the particle shape of the filler. It can be flake- form, spherical or needle-shaped, for example, in accordance with require- ments. The effect pigments according to the invention are furthermore suitable for the preparation of flowable pigment compositions and dry preparations comprising one or more particles according to the invention, binders and optionally one or more additives. The term dry preparations is also taken to mean preparations which comprise from 0 to 8% by weight, preferably from 2 to 8% by weight, in particular from 3 to 6% by weight, of water and/or of a solvent or solvent mixture. The dry preparations are preferably in the form of pellets, granules, chips, sausages or briquettes and have particle sizes of 0.2-80 mm. The dry preparations are used, in particular, in the preparation of printing inks and in cosmetic formulations. The complete disclosure content of all patent applications, patents and publications mentioned above is incorporated into this application by way of reference. The following examples are intended to explain the invention in greater detail, but without restricting it. Examples Example 1: 100 g of SiO2 flakes (365 nm in thickness) are heated to 75°C in 2 I of demineralised water. 1120 ml of FeCI3 solution (corresponds to 130% of Fe2O3) are added with stirring. The pH of the reaction mixture is kept con- stant at 3 by addition of sodium hydroxide solution (30%). After addition of the FeCU solution, the pH is raised to pH 5 using sodium hydroxide solution (30%). The product is filtered off and rinsed with demineralised water. After drying at 110°C, the product is calcined at 800°C. The pigment prepared in this way exhibits the colour behaviour shown in Figure 1 (-A-). Comparative Example: 100 g of SiO2 flakes (445 nm in thickness) are heated to 75°C in 1 I of demineralised water. 237 ml of FeCI3 solution (corresponds to 27.5% of Fe2O3) are added with stirring. The pH of the reaction mixture is kept con- stant at 3 by addition of sodium hydroxide solution (30%). After addition of the FeC l3 solution, the pH is raised to pH 5 using sodium hydroxide solution (30%). The product is filtered off and rinsed with demineralised water. After drying at 110°C, the product is calcined at 800°C. The pigment prepared in this way exhibits the colour behaviour shown in Figure 1 (-♦-). Figure 1 shows the colouristic situation through a comparison of effect pig- ments having different red hues and different colour flop behaviour. The colour curves here show the change in the colour values in the a,b colour system, which is obtained if a paint card containing the pigment is tilted from the perpendicular angle (90 degrees plan view) to 180 degrees (hori- zontal axis is the a axis, from left = green to right = red, vertical axis is the b axis, from bottom = blue to top = yellow). Typical iron-oxide mica pigments (-•-) are comparatively weak in colour and exhibit no colour flop. The typical brownish hue on tilting is not evident in the curve. A typical SiO2 flake pigment having an iron-oxide coating as described in WO 93/08237 (-♦-) does not exhibit a clear red in the initial hue. On tilting, a strong colour flop occurs; in the example it changes to green. The colouring of the pigment according to the invention (-A-) shows a saturated red which also remains a red on tilting. The colour always remains in one quadrant of the a,b colour system, and the colour flop is very small. WE CLAIM: 1. Intensely coloured red effect pigments comprising iron oxide-coated SiO2 flakes, where the total thickness of the effect pigments is not greater then 500 nm (+/- 30 nm). 2. Effect pigments as claimed in claim 1, wherein the diameter of the SiO2 flakes is between 1 and 250 μm and othe thickness of the SiO2 flakes is between 250 and 400 nm. 3. Effect pigments as claimed in claim 1 or 2, wherein the thickness of the SiO2 flakes is 250,300,350 or 400nm. 4. Effect pigments as claimed in claims 1 to 3 wherein the iron oxide is haematite (α-Fe2O3). 5. Effect pigments as claimed in one of claims 2 to 4, wherein the thickness of the iron-oxide layers is from 30 to 150 nm. 6. Effect pigments as claimed in one of claims 1 to 5, wherein an organic coating is additionally applied to the effect pigments. 7. Process for the prtparation of effect pigments as claimed in claim 1 wherein SiO2 flakes are coated with iron oxide by wet-chemical methods and/or by chemical vapour deposition (CVD) or plasma vapour deposition (PVD) processes, where the thickness of the SiO2 flakes end of the ion-oxide layers ere selected in such a way that the total thickness of the red effect pigments is not greater than 500nm (+/- 30 nm). 8. Process as claimed in claim 7 wherein the coating with iron oxide is carried out in such a way that the thickness of the layers is between 30 and 150 nm. 9. Cosmetics, paints, coatings, plastics, films , in security printing, in security features in documents and identity papers, for colouring seed, for colouring foods or in medicament coatings and for the preparation of pigment compositions and dry preparations comprising the effect pigments as claimed in claim 1. Dated this 26th day of DECEMBER, 2005 The present invention relates to intensely coloured red effect pigments comprising iron oxide-coated SiO2 flakes, where the total thickness of the effect pigments is not greater than 500 nm (+/- 30 nm). The present invention likewise relates to processes for the preparation of these pigments in which SiO2 flakes are coated with iron oxide, where the thicknesses of the SiO2 flakes and of the iron-oxide layers are selected in such a way that the total thickness of the red effect pigments is not greater than 500 nm (+/- 30 nm), and to the use of these pigments in cosmetics, paints, coatings, plastics, films, in security printing, in security features in documents and identity papers, for colouring seed, for colouring foods or in medicament coatings and for the preparation of pigment compositions and dry preparations.

Documents:

1181-kol-2005-granted-abstract.pdf

1181-kol-2005-granted-claims.pdf

1181-kol-2005-granted-correspondence.pdf

1181-kol-2005-granted-description (complete).pdf

1181-kol-2005-granted-drawings.pdf

1181-kol-2005-granted-examination report.pdf

1181-kol-2005-granted-form 1.pdf

1181-kol-2005-granted-form 18.pdf

1181-kol-2005-granted-form 2.pdf

1181-kol-2005-granted-form 3.pdf

1181-kol-2005-granted-form 5.pdf

1181-kol-2005-granted-gpa.pdf

1181-kol-2005-granted-reply to examination report.pdf

1181-kol-2005-granted-specification.pdf

1181-kol-2005-granted-translated copy of priority document.pdf