| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | March 16, 2004 |
| PATENT TITLE |
Process for coating a surface |
| PATENT ABSTRACT | The invention relates to a process for coating a surface through graft polymerization, characterized in that before graft polymerization, the surface is modified, in the presence of an amine of formula: ##STR1## wherein R.sub.1 is hydrogen or a group R.sub.4, R.sub.2 and R.sub.3 are each independently a group R.sub.4, and R.sub.4 is [-1,2-C.sub.2 -C.sub.3 alkylen-T-].sub.n -H wherein T is O or NH and n is a number from 1 to 3, by a compound having a functional group: ##STR2## wherein R.sub.5 to R.sub.7 are each C.sub.1 -C.sub.4 alkyl. The amount of amine is preferably from 5 to 500 g/m.sup.2 of surface of the substrate particle. The amount of the trialkoxysilane compound is preferably from 0.1 to 2 g/m.sup.2 of surface of the substrate particle. The process for coating a surface is particularly useful for effect pigments |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | May 17, 2002 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT REFERENCES CITED |
R. Simon et al., J. Am. Chem. Soc., Vol 104, No. 7, (1982), pp. 2031-2034. C.-G. Wu et al., Chemistry of Materials, vol. 9, No. 2, pp. 399-402, Feb. 1997. A. Hebeish et al., Die Angewandte Macromolekulare Chemie vol. 157, pp. 153-163 (1988). W. Watt et al., Pl. & Polymer Conf. No. 4 (1971) pp. 23-31. Derw. Abst. 1993-408771 of JP 5306143 (1993). Derw. Abst. 1987-007929 [02] for DD 238994 (1986). Derw. Abst. 1987-007928 [02] for DD 238993 (1986). Abst. for DE 19502231 (1995). Abst. for DE 4317019 (1993). Derw. Abst. 1978-07042A of JP 52146436 (1977). Derw. Abst. 1983-42425K of JP 58049479 (1983). |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A process for coating a surface through graft polymerization, characterized in that before graft polymerization, said surface is modified, in the presence of an amine of formula: ##STR7## wherein R.sub.1 is hydrogen or a group R.sub.4, R.sub.2 and R.sub.3 are each independently a group R.sub.4, and R.sub.4 is [-1,2-C.sub.2 -C.sub.3 alkylene-T-].sub.n -H wherein T is O or NH and n is a number from 1 to 3, by a compound having a functional group: ##STR8## wherein R.sub.5 to R.sub.7 are each C.sub.1 -C.sub.4 alkyl. 2. A process for coating a surface through graft polymerisation according to claim 1, wherein the amount of amine of formula: ##STR9## is from 5 to 500 g/m.sup.2 of surface of the substrate particle. 3. A process for coating a surface through graft polymerisation according to claim 1, wherein R.sub.1 is hydrogen. 4. A process for coating a surface through graft polymerisation according to claim 1, wherein R.sub.4 is [-1,2-ethylene-T-].sub.n -H. 5. A process for coating a surface through graft polymerisation according to claim 1, wherein T is O. 6. A process for coating a surface through graft polymerisation according to claim 1, wherein n is 1. 7. A process for coating a surface through graft polymerisation according to claim 1, wherein R.sub.5 to R.sub.7 are, independently of each other, methyl or ethyl. 8. A process for coating a surface through graft polymerisation according to claim 1, wherein the compound having a functional group: ##STR10## is titanium tetraisopropoxide. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
This invention relates to a collection of loose composite plateletlike particles comprising a core and at least one coating layer consisting essentially of a compound having from 60 to 95% by weight of carbon and from 5 to 25% by weight of nitrogen, the balance to 100% being selected from elements of the group consisting of hydrogen, oxygen and sulfur, as well as to processes for the manufacture thereof, to polymer compositions containing it, and to the use thereof as effect pigments. Effect (or luster) pigments are reflective flat particles that show at least partly specular reflection of the incident light. In a surface painted with effect pigments, for example, the effect pigment particles in the paint usually orient themselves substantially parallel to the surface, so that the colored paint surface when illuminated by a fixed white light source shows a luster effect and may appear in different colors according to the angle at which it is viewed and the nature of the effect pigment. A high-quality coloured effect pigment should impart highly saturated colors to the medium in which it is incorporated at all viewing angles. An optically variable pigment should also have a large difference in color between different viewing angles (high goniochromaticity). The visual difference between two colors is best reflected by the .DELTA.E* value in the L*a*b* color system (CIE-LAB 1986). Different types of effect pigments are able to impart effects to varying degrees; for example, simple metal particles, for example aluminium flakes, mainly produce differences in brightness (high .DELTA.L*), which in combination with transparent colored pigments leads to the so-called metallic flop effect. In effect pigments, color is mainly produced by interference of light. Such pigments are particles that have been coated with a thin layer of a colorless or colored substance; the color effect depends on the thickness of the coating layer and may manifest itself both in the brightness (L*) and in the hue (H*). The goniochromaticity arises because the optical path length of the reflected beam is different at different angles to the surface. Interference pigments can be prepared from any known plate-like particles, for example from plate-like organic or inorganic colored pigments, such as .beta.-copper phthalocyanine, 3,4,9,10-peryienetetracarboxylic acid diimides, fluororubins or .alpha.-Fe.sub.2 O.sub.3, from metal flakes, such as aluminium, copper or bronze flakes, or from silicatic particles. However, the demands made of pigments are constantly increasing, so that the conventional effect pigments are unable fully to meet today's high expectations, particularly in high-quality applications such as automotive lacquers. For example, many effect pigments which would be desirable from the point of view of hue often exhibit inadequate light or weather stability, and many interference pigments are lacking chroma (C*, saturation) and opacity. In many cases, too, the mechanical strength of the effect pigments is not satisfactory. For example upon dispersion into an ink or paint composition, the coatings may break or peel off, leading to insatisfactory coloristics. This happens particularly with flat, smooth coatings which are desirable for coloristic reasons. Another problem is that it is very difficult to make relatively thick coatings without forming agglomerates, thus impairing the optical properties. The preparation of fine black pigments through oxydative pyrolysis at 200-350.degree. C. of acrylonitrile-based polymer particles treated with an adhering aminosiloxane is disclosed in JP-63/142066-A. This process leads to an uniformly shaped black powder, which contains only traces of nitrogen and does not produce any luster effect or goniochromaticity. DD 238 994 discloses organophilic colored fillers consisting of small clay or kaolin particles (.O slashed.<2 .mu.m) embedded in a matrix based on conducting polymers, which are obtained by calcination of a ceramic mass of clay and a polymer such as acrylonitrile at a temperature between 150.degree. C. and 50.degree. C. below the clay's decomposition point. Yet, these composite fillers are of brown to black color, without any luster effect or goniochromaticity, and their components are not arranged regularly. DD 238 993 discloses organophilic colored fillers consisting of small clay or kaolin particles (.O slashed.<2 .mu.m) embedded in a matrix containing amorphous carbon, which are obtained by calcination of a ceramic mass of clay and a polymer such as acrylonitrile at a temperature above the clay's decomposition point. Additional components such as mica may be contained in amounts up to 20% by weight. Yet, these composite fillers are of brown to black color, without any luster effect or goniochromaticity, and their components are not arranged regularly. U.S. Pat. No. 5,322,561 relates to conductive flaky pigments, the conductive coating of which consists of a metal oxide pigment layer doped with additional metal oxide particles and containing interdispersed carbon black particles. The color is however black to pale and silvery grey, with quite a low chroma. U.S. Pat. No. 3,087,827 discloses the deposition of carbon onto a TiO.sub.2 layer from hydrocarbons, fatty acids, fats or soaps at 700-1000.degree. C. The carbon fills into the minute spaces between the TiO.sub.2 particles, even when deposited at the end of the process. Total absence of oxygen is required in order to avoid undesirable soot or particulate carbon formation. Moreover, the products are insatisfactory light stable as is known from U.S. Pat. No. 5,501,731. U.S. Pat. No. 5,271,771 discloses carbon-containing effect pigments which are obtained through simultaneous deposition of carbon and a metal on a plate-like substrate, and subsequent redox reaction between the metal oxide in the pigment's undercoat and the metal in the pigment's topcoat, together with precipitation of carbon, at high temperatures under reducing conditions. It is however not possible to deposit the carbon-containing layer without altering the system's optical properties. Dark effect pigments are known from DE-OS 195 02 231, which are coated with soot embedded in or overlaid with titanium oxide. They are obtained by coating a plateletlike core mechanically with soot particles, precipitating thereon titanium hydroxide and a metallic reducing agent, and pyrolizing the obtained composite at about 500-1000.degree. C. under inert conditions. The chroma is somewhat improved but at the detriment of the lightness which is much too low. U.S. Pat. No. 4,076,551 discloses pigments coated with a metal hydroxide or bismuth oxychloride layer and carbon black particles incorporated therein. Example 3 discloses a blue mica/TiO.sub.2 interference pigment coated with 3% of carbon black and 0.73% Al.sub.2 O.sub.3, which exhibits a strong dark blue powder color with a lively blue shimmer and may be heated to 300.degree. C. for 40 minutes without any gloss or color change. However, the amount of carbon which can be fixed is limited and depends on the pigment's available surface area. For mica flakes, it does not exceed about 15 mg/m.sup.2, the carbon in excess remaining in suspension and affecting the luster. In addition, it is very difficult to disperse the carbon black in aqueous media, and the coating is irregular, so that the color and the goniochromaticity do not meet today's requirements to a satisfactory extent. U.S. Pat. No. 5,501,731 claims that some of above lacks may be solved by coating plateletlike silicatic substrates with carbon-containing metal compounds (such as Cr.sup.III acac.sub.3) and compounds of the formula [(CH.sub.2 O).sub.1-6 ].sub.x (such as sugars or starch), and then decomposing the carbon-containing compounds on the surface of the substrate particles under oxygen-excluding conditions. Very smooth coatings can allegedly be obtained when the decomposition takes place from the gas phase. However, this process leads to coatings containing high amounts of a metal--the ratio Cr/C is 0.92 in example 1 and 1.50 in example 2. Consequently, it is only suitable for very thin layers, generally 1-20 nm, preferably 1-10 nm. Furthermore, a substantial amount of the metal is detached from the coating upon thermal decomposition, leading to a highly undesirable contamination with metallic particles which affect the coloristic properties and can be abrasive or develop an undesired catalytic activity when the pigment is incorporated into a high molecular weight organic material. U.S. Pat. No. 5,364,467 and U.S. Pat. No. 5,662,738 finally disclose luster pigments based on plateletlike metallic substrates comprising a first layer of metal oxide, a second, nonselectively absorbing layer of carbon, metal or metal oxide, and optionally a third layer of metal oxide. There is however no example wherein the second layer is carbon. Notwithstanding the statement that a carbon layer may be made by thermal decomposition of a compound containing at least 1 oxygen for every 2 carbon atoms (such as PVA, sorbitol or sugars), this method does not enable to make regularly coated, isolated particles. Instead, very irregularly coated particles are obtained together with agglomerates which consist of several platelets linked together at different dihedric angles by a bridging carbonaceous mass. Consequently, the coloristic properties of these luster pigments are still not satisfactory. The instant invention's object is to provide effect pigments that meet today's requirements to an especially high degree even in high-quality applications. The effect pigments according to the invention possess superior optical properties, such as high reflectivity, brilliance, luster and opacity. Those of the instant effect pigments which are coloured display a high chroma coupled with interesting flop effects, for example goniochromaticity. Their outstanding light stability and chemical and mechanical properties render them particularly suitable for use in all customary kind of substrates, including water-based coating systems, wherein there is surprisingly no need for an additional stabilizing treatment even in the case of metallic cores. The invention relates to a collection of composite plateletlike particles comprising a core and at least one coating layer consisting essentially of a compound having from 60 to 95% by weight of carbon and from 5 to 25% by weight of nitrogen, the balance to 100% being selected from elements of the group consisting of hydrogen, oxygen and sulfur. Said coating is hereafter also referred to as a nitrogen doped carbon coating. The compound's carbon content is preferably from 70 to 90% by weight. The hydrogen content is preferably from 0.5 to 5% by weight. The nitrogen content is preferably from 13 to 22% by weight. The sulfur content is preferably below 1% by weight, most preferably nil. Preferably, there is a vast majority of loose particles, wherein a single core is surrounded by the instant nitrogen doped carbon coating. The number of loose particles is very preferably at least 80%, most preferably at least 95%, of the total number of loose and agglomerated particles. The nitrogen doped carbon coating around a core most preferably consists essentially of planar macromolecules arranged parallel to each other. Each core is preferably surrounded by one inventive coating. Suitable core substrates for the luster pigments of the invention are transparent, partially reflectant or reflectant. Examples thereof are flat metallic or silicatic particles, graphite, Fe.sub.2 O.sub.3, MoS.sub.2, talc or glass flakes, and plateletlike crystals of .beta.-phthalocyanine, fluororubine, red perylenes or diketopyrrolopyrroles. Silicatic particles are preferred, in particular light-colored or white micas, for example sericite, kaolinite, muscovite, biotite, phlogopite or related vermiculite, or any synthetic mica. Flakes of preferably wet-ground muscovite are particularly preferred, althought it is of course also possible to use other natural micas or artificial micas. Another preferred embodiment is the use of flat metallic particles as the core. In contrast to previously known coatings, the instant coating can advantageously be made at temperatures below the melting point of the core metal, surprisingly enabling the preparation of perfectly shaped, coated metal flakes. Preferably, metal flakes are coated at temperatures below any phase change, as compared with their phase at room temperature. Examples of suitable metallic particles are flakes of Ag, Al, Au, Cu, Cr, Fe, Ge, Mo, Ni, Si, Ti, or alloys thereof, such as brass or steel, preferably Al flakes. Depending on the material, a natural optically non-interfering oxide layer may form on the surface of metallic particle. Partially reflecting cores have preferably a reflectance of at least 35% of the light falling vertically on its surface in the range from 380 to 800 nm. Surprising effects are obtained with all types of core materials. The cores may be colorless or colored and may consist of a single substance or of a combination of substances. The instant pigments preferably also comprise an intermediate coating between the core and the nitrogen doped carbon coating, which intermediate coating may consist, for example, of one or more layers of Prussian blue, MgF.sub.2 or, especially, of a metal or mixed-metal oxide or oxide hydrate. Such pigments are well known to the person skilled in the art, for example from DE 32 07 936, EP 0 096 284 or U.S. Pat. No. 5,026,429. The intermediate layer has preferably a thickness of from 0.01 to 1 .mu.m. On silicatic core particles, the intermediate layer consists preferably of a metal oxide, oxide hydrate or halide such as titanium, zirconium, tin, iron, chromium or zinc oxide, bismuth oxychloride or mixtures thereof, ontop which an optional protective layer may preferably also be applied to increase the stability, for example a layer of a metal oxide such as silicon or aluminium oxide. Of particular importance are micas, which are coated with highly refractive colorless metal oxides or oxide hydrates. Particularly preferred are intermediate coatings of zirconium dioxide or titanium dioxide; very particularly preferred is a coating of titanium dioxide. A very particular interest is given to micas having a dielectric coating layer of thickness from 0.03 to 0.3 .mu.m. The intermediate coating layer may also consist of a pack of multiple layers, for example from 2 to 20 layers. The skilled artisan knows many types of multiple layers, which are all suitable, and which effects can be obtained therewith. If desired, a layer of a colorless metal oxide or oxide hydrate can for example be combined with a layer of a colored metal oxide or oxide hydrate. Or, layers having a high refractive index (.gtoreq.2.0) and layers having a low refractive index (.ltoreq.2.0) may be alternated. Multiple layer coatings are generally known as Fabry-Perot systems, many of which are known also in pigments technology, such as in U.S. Pat. No. 5,135,812. On metallic flakes, the intermediate layer consists preferably of a metal oxide, oxide hydrate or halide such as titanium, zirconium, tin, iron, chromium or zinc oxide, bismuth oxychloride or mixtures thereof Particularly preferred is a coating of silicium dioxide. Particles coated with the above intermediate layers and their use as effect pigments are generally known per se, for example from DE 14 67 468, EP 0 045 851, DE 32 37 264, DE 36 17 430, EP 0 298 604, EP 0 388 932 and EP 0 402 943. Metal oxide-coated mica platelets are also commercially available under the names Iriodin.RTM. (E. Merck, Darmstadt), Flonac.RTM. (Kemira Oy, Finland), Mearlin.RTM. (Mearl Corporation, New York/USA) and Infinite Color.RTM. (Shisheido, Japan). Coated metal flakes are also commercially available unter the names Chroma Flair.RTM. (Flex Products, Inc, Santa Rosa, Calif./USA) and Paliochrom.RTM. (BASF, Germany). The size of the core particles is not critical per se and can be adapted to the particular use. Generally, the particles have a length from about 1 to 200 .mu.m, in particular from about 5 to 100 .mu.m, and thicknesses from about 0.05 to 5 .mu.m, preferably from 0.1 to 2 .mu.m, in particular about 0.5 .mu.m. Particles having a plateletlike shape are understood to be such having two essentially flat and parallel surfaces, with an aspect ratio length to thickness of from about 2:1 to about 1000:1, and a length to width ratio of from 3:1 to 1:1. The nitrogen doped carbon coating may for example be prepared by any method known in the art, and then adsorbed onto the substrate particles, or may be prepared by methods known per se in the presence of the substrate particles, such as emulsion polymerisation. It is however preferably prepared directly on the plateletlike substrate particles, starting for example from monomers. With the latter new method, a much more regular coating is obtained and the number of loose particles is increased, giving surprising better coloristics. The nitrogen doped carbon coating has for example a thickness of from 1 nm to 1 .mu.m, preferably of from 1 nm to 300 nm. Further preferences for particular coating compounds are given below. Above the nitrogen doped carbon coating, the instant effect pigments may optionally also be coated with an outer coating, which may consist of one or more layers of various materials according to the function to be performed. For example, the outer coating may consist of a transparent or selectively absorbing dielectric material of any kind, the specific electrical resistance of which according to the customary definition is at least 10.sup.10 .OMEGA..multidot.cm. Where appropriate, the outer coating preferably consists of a metal oxide, oxide hydrate or metal fluoride, for example of TiO.sub.2, ZrO.sub.2, SiO, SiO.sub.2, SnO.sub.2, GeO.sub.2, ZnO, Al.sub.2 O.sub.3, V.sub.2 O.sub.5, Fe.sub.2 O.sub.3, Cr.sub.2 O.sub.3, MgO, MgF.sub.2, CuO or PbTiO.sub.3, or a mixture thereof. Special preference is given to those metal oxides or oxide hydrates which are neither dissolved nor etched by the solvents used in many applications. Expediently, the outer coating should not impair the colorative properties of the coating system according to the invention located beneath it, but retain them as far as possible or even improve them. The person skilled in the art will know which material is suitable for which function, and which thicknesses are adequate. The outer coating may protect the underlying coatings from chemical or mechanical influences. In this case, its refractive index is preferably as similar as possible to that of the external medium in which the pigment is intended to be embedded. Particularly preferred, the outer coating has a refractive index of from 1.33 to 1.71, although materials having high refractive indices may also be used. The thickness of a protective outer coating is most adequately no greater than 200 nm, preferably no greater than 100 nm, especially no greater than 50 nm. The outer coating may, however, also reflect part of the incident light, or refract the incident light and the light reflected by the core, generating interference effects. In this case, its refractive index is preferably as high as possible, for example above 2.0. The thickness of a reflective outer coating is most adequately from 100 to 400 nm. Of course, the outer coating may also consist of multiple layers, for example such as described above for the intermediate coating. When the outer coating consists of more than one layer, then it is preferably composed of alternate layers of a dielectric material and an instant nitrogen doped carbon coating or a semitransparent metal. All figures are schematic cuts orthogonal to the largest surface of the instant particles. FIG. 1 shows a single composite particle with a nitrogen doped carbon coating [1] around an aluminium flake core particle [2]; around the particle, there is air as an outer medium [3]. FIG. 2 shows a single particle with a nitrogen doped carbon coating [4] around a mica core particle [5]; around the particle, there is also air as an outer medium [6]; there is however an additional layer of TiO.sub.2 [7] between the coating [4] and the inner core [5]. FIG. 3 shows a single particle with a nitrogen doped carbon coating [8] around a core particle [9] with an additional layer of TiO.sub.2 [11] between the coating [8] and the core [9]; around the particle, there is also air as an outer medium [10]; there is however an additional layer of SiO.sub.2 [12] on the coating [8]. FIG. 4 shows several particles according to FIG. 3 [13] embedded in a polymer layer [14]. The instant nitrogen doped carbon layers are best prepared by forming on the substrate particles a layer of a polymer containing nitrogen and carbon atoms, and then heating the substrate particles coated with the polymer containing nitrogen and carbon atoms under slightly oxydative conditions as described below. Thus, the invention also relates to a process for preparing a collection of composite plateletlike particles comprising a core and at least one coating layer consisting essentially of a compound having from 60 to 95% by weight of carbon and from 5 to 25% by weight of nitrogen, the balance to 100% being selected from elements of the group consisting of hydrogen, oxygen and sulfur, comprising the steps of (a) suspending plateletlike particles in a liquid; (b) optionally adding a surface modifier, a polymerisation catalyst or both; (c) before or after step (b), adding one or more polymers containing nitrogen and carbon atoms, or one or more monomers which are capable to polymerize to said polymer; (d) effecting a polymeric coating layer to be formed on the surface of said plateletlike particles from the polymers or monomers added at step (c); (e) isolating said plateletlike particles having said polymeric coating layer from the suspension; and (f) heating said plateletlike particles having said polymeric coating layer to a temperature of from 100.degree. C. to 1000.degree. C. in a gaseous environment. With this process, it is surprisingly possible to form very consistent, regular nitrogen doped carbon coatings of thickness from 1 nm to 1 .mu.m, preferably from 1 nm to 300 nm. There is no need for complex and expensive equipment, such as necessary for vapor deposition. The plateletlike particles may be any core particles as described above. It is possible, and in many cases most convenient, to use already coated plateletlike particles, many of which are commercially available. In this case, the starting particles' coating should preferably be chosen according to the desired intermediate coating of the instant pigments. Following known methods, it is however also possible to modify the starting particles' coating between steps (a) and (b), for example to etch the surface or the upper layer, or to add one or more coating layers. This enables to manufacture an extremely broad choice of effect pigments. The liquid may for example be any usual solvent which does not react with the other chemicals used in the instant process, apart of with a reactive metal compound if applicable. Examples of liquids are water or customary organic solvents, for example ethers, alcohols, ketones, nitriles, nitro compounds, unsubstituted or substituted aliphatic or aromatic hydrocarbons, or mixtures thereof. Usual liquids are known to the skilled artisan and can be found in handbooks, such as Techniques of Chemistry, vol II Organic Solvents, 3.sup.rd ed. Arnold Weissberger, Wiley-Interscience 1970. Suitable liquids are such wherein the polymeric coating to be formed is not totally soluble. Preferred liquids are C.sub.1 -C.sub.4 alcohols, water and mixtures thereof, water being most preferred. The amount of liquid is not critical at all, and may vary for example from 1 to 1000 parts by weight, based on the weight of the plateletlike particles. Surface modifiers may for example be surfactants, acids or bases, reactive metal compounds or polar polymers. Suitable surfactants are for example neutral, cationic, anionic or amphoteric surfactants. Suitable acids or bases are for example mineral or organic acids, such as phosphoric acid, acetic acid or sebacic acid, or mineral or organic bases, such as sodium hydroxide, ammonia or primary, secondary or tertiary amines. Suitable reactive metal compounds are such which bond to or form a deposit of metal oxide, oxide hydrate or hydroxide on the surface of a substrate particle in the presence of the liquid, which may be involved in the reaction as long as it does not totally inhibit it. For example, N-(3-(trimethoxysilyl)-propyl)pyrrole may be used, which is known from J. Amer. Chem. Soc. 104, 2031-4 (1982) and Chemistry of Materials 9/2, 399-402 (1997) to anchor polypyrroles on n-type semiconductors such as silicon and silicon oxide, or titanium or zirconium salts such as Ti(OiPr).sub.4 or Zr(acac).sub.4. Suitable polar polymers are for example compounds having a molecular weight (M.sub.w) of from about 1000 to about 100000 and repeating units carrying polar groups, such as polyvinyl alcohol, cellulose or derivatives thereof. Most preferred are polyvinyl alcohol derivatives, for example a polyvinyl alcohol with sulfonate or silanol groups, and cellulose derivatives, for example carboxymethylcellulose or cellulose thiocarbonate. Additional chemicals may be added to facilitate surface modification through reactive metal compounds, for example acids or bases, preferably ammonia or primary, secondary or tertiary amines. Highly surprisingly, it has now been found that amines of formula: ##STR3## wherein R.sub.1 is hydrogen or a group R.sub.4, R.sub.2 and R.sub.3 are each independently a group R.sub.4, and R.sub.4 is [-1,2-C.sub.2 -C.sub.3 alkylene-T-].sub.n -H wherein T is O or NH and n is a number from 1 to 3, give excellent results in combination with compounds having a functional group: ##STR4## wherein R.sub.5 to R.sub.7 are each C.sub.1 -C.sub.4 alkyl. Hence, the invention also relates to a process for coating a surface through graft polymerization, characterized in that before graft polymerization, said surface is modified, in the presence of an amine of formula ##STR5## wherein R.sub.1 is hydrogen or a group R.sub.4, R.sub.2 and R.sub.3 are each independently a group R.sub.4, and R.sub.4 is [-1,2-C.sub.2 -C.sub.3 alkylene-T-].sub.n -H wherein T is O or NH and n is a number from 1 to 3, by a compound having a functional group: ##STR6## wherein R.sub.5 to R.sub.7 are each C.sub.1 -C.sub.4 alkyl. The amount of amine is preferably from 5 to 500 g/m.sup.2 of surface of the substrate particle. The amount of the trialkoxysilane compound is preferably from 0.1 to 2 g/m.sup.2 of surface of the substrate particle. The adequate reaction temperature is from -20 to 150.degree. C., preferably from 20 to 80.degree. C., most preferably from 50 to 80.degree. C. The reaction time is adequately from about 1/4 to about 100 hours, preferably from 1 to 10 hours. R.sub.1 is preferably hydrogen. The alkylene group within R.sub.4 is preferably ethylene. T is preferably O. n is preferably 1. R.sub.5 to R.sub.7 are preferably methyl or ethyl. Most preferred are combinations of two or more preferred features. Preferably, ammonia is also added to improve the surface modification even further. The modified surfaces are particularly well suited as substrates for graft polymerisation. The graft polymers obtained thereon do surprisingly adhere better to the substrate, and they are very homogeneous and substantially of constant thickness. Polymerisation catalysts are for example thermo- or photoinitiators, as well as graft polymerisation catalysts, such as compounds of transition metal elements and lanthanides having multiple oxidation states and capable of undergoing a redox reaction with suitable reagents, for example compounds of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Tc, Pd, Re, Os, Ir, Pt, Au, Hg, Ce, Sm, Eu and Yb. Preferred polymerisation catalysts are salts of Ce.sup.III or Ce.sup.IV. It is known, which polymerisation catalysts are suitable for polymerizing which of the monomers used in the instant invention. It is preferred that both a surface modifier and a polymerisation catalyst are added in step (b), which is preferably performed, most preferably before step (c). The polymer containing nitrogen and carbon atoms has preferably unsaturated bonds. Examples are a polypyrrole, a polyamide, a polyaniline, a polyurethane, a nitrile rubber or a melamin-formaidehyde resin, which may be used alone in mixtures together with other polymers, such as polythiophene, polyacetylene, polyparaphenylene or polyparaphenylene-sulphide. Preferred polymers are homo- and copolymerisates of acrylonitrile, acrylamide, methacrylonitrile, methacrylamide, crotononitrile and crotonamide, such as, most preferred, polyacrylonitrile. The monomer capable to polymerize to said polymer is for example a pyrrole derivative, acrylonitrile, methacrylonitrile, crotononitrile, acrylamide, methacrylamide or crotonamide, preferably acrylonitrile, methacrylonitrile or crotononitrile, most preferably acrylonitrile. All above-mentioned liquids, surfactants, reactive metal compounds, polar polymers, thermo- and photoinitiators, graft polymerisation catalysts, and nitrogen containing polymers and monomers are known compounds, most of which are commercially available. Effecting the polymeric coating layer to be formed is performed in analogy to methods which are known per se and depend on the materials added in step (c) and optionally (b). Polar polymers may for example be coated by simply stirring at a temperature of from 0 to 100.degree. C. Emulsion or graft polymerization require more sophisticated procedures, which are however also known per se. U.S. Pat. No. 4,057,683 discloses the graft polymerisation of vinyl polymers on inorganic substrates having hydroxy groups. Die Angewandte Macromolekulare Chemie 157, 153-163 (1988) discloses vinyl grafting onto cotton fabric using ceric-cellulose thiocarbonate redox system. U.S. Pat. No. 4,315,959 discloses the graft polymerisation of methyl methacrylate onto TiO.sub.2 coated with a first layer of polyvinyl alcohol and a transition metal complex. Isolating the coated particles is done by standard methods, such as for example filtrating or centrifugating, then washing the residue with a common solvent or with water and drying, for example batchwise in an oven or continuously in a spray-dryer. The coated particles are then preferably heated to a temperature of from 100.degree. C. to 100.degree. C. in a gaseous environment. The preferred temperature range is from 150 to 600.degree. C. In this step, most hydrogen atoms and hydroxy groups are eliminated, and the coating gets a high degree of unsaturation and crosslinking, as well as a very dark color. In an ideal case, the whole coating around each core becomes completely unsaturated, with as much conjugated double bonds as possible. Generally, the temperature suitable for obtaining this result is known for the bulk nitrogen containing polymers or might be chosen in analogy thereto for related materials. Alternatively or in addition to heating, equivalent treatments having the same result may also be used. The gaseous environment ensures that there is a minimum of contact between the particles during step (f). It is preferred to slightly agitate the particles, for example in a fluidized bed, in order that gravity does not cause them to stick together. High shear and high pressures on the particles should suitably be avoided. The gas to be used depends on the temperature and should not induce a reduction. It is preferred to use an oxygen-containing gas, such as air, at temperatures of from 100.degree. C. to 300.degree. C., and inert gasses, such as nitrogen or argon, at temperatures from about 200 to 1000.degree. C. If the temperature should exceed 300.degree. C., then it is preferred to heat in 2 steps, an oxygen-containing gas being used up to a temperature of from 200 to 300.degree. C., and an inert gas afterwards when the temperature is increased above it. This 2-step heating process, which has been disclosed to increase the yield of carbon fibers [presentation by W. Watt at the Plastics & Polymer Conference n.degree. 4 (1971)], gives particularly surprising good results in the case of polyacrylonitrile coatings. The duration of the heat treatment depends on the coating's chemical constitution as well as from the equipment to be used. It may vary from as short as a few seconds (such as 10 s) to a few days (such as 1 week). Preferably, for batch operations reaction times from 1/2 to 30 h are chosen, reaction times from 1 to 10 h being most preferred. Highly surprising it has been found, that it is possible to obtain very regular, homogeneous and continuous coatings in an extremely wide range of thicknesses. Coatings of, for example, polypyrrole or pyrolysed polyacrylonitrile, the thickness of which is below 1 .mu.m, are new. Instant coatings of conductive polymers, the thickness of which is below 300 nm, preferably below 50 nm, can be used very advantageously not only in pigment technology but also in other applications, for example in optical devices such as displays. The luster pigments and luster pigment mixtures of the present invention are advantageously useful for many purposes, such as the coloring of plastics, glasses, ceramic products, decorative cosmetic preparations and particularly coatings, especially automotive coatings, and inks, especially security printing inks. All customary printing processes can be employed, for example screen printing, intaglio printing, bronze printing, flexographic printing and offset printing. The pigments of the present invention are also advantageously useful for these purposes in admixture with transparent and hiding white, colored and black pigments and also commercial transparent, colored and black luster pigments based on metal oxide-coated mica and metal pigments, platelet-shaped iron oxides, graphite, molybdenum sulfide and platelet-shaped organic pigments. The pigment according to the invention can be embedded with excellent results in any high molecular weight organic material for the pigmenting thereof. Such high molecular weight organic materials are described hereinafter. The amount of high molecular weight organic material may be as desired and is, for example, from 10.sup.-3 to 10.sup.3 parts by weight, preferably from 10.sup.-2 to 10.sup.2 parts by weight, based on 1 part by weight of pigment according to the invention. The substance compositions according to the invention may comprise other customary constituents, for example wetting agents or texture-improving agents, the amount of which may be as desired, but is preferably from 0 to 30% by weight in total, based on the total weight of the substance composition. The pigment according to the invention is embedded in the high molecular weight organic material, for example, by mixing or dispersing, if desired in the presence of a suitable liquid which can be removed again once the dispersion is complete. If desired, stirrers or roller mills or any other customary mixing devices may be used as dispersing devices for that purpose. If desired, a cationic, anionic, zwitterionic or non-ionic wetting agent of any kind may be added to the dispersion mixture. The substance compositions according to the invention can be isolated from the dispersion mixture, for example, by filtration or concentration by evaporation of the liquid. The high molecular weight organic material for the pigmenting of which the pigments or substance compositions according to the invention may be used may be of natural or synthetic origin. It may involve, for example, natural resins, drying oils, rubber or casein, or natural substances modified thereby, such as chlorine rubber, oil-modified alkyd resins, viscose, and cellulose ethers or esters, such as ethyl cellulose, cellulose acetate, cellulose propionate, cellulose acetobutyrate or nitrocellulose, but especially fully synthetic organic polymers (duroplastics and thermoplastics), as are obtained by polymerisation, polyconden-sation or polyaddition. From the class of the polymerisation resins there may be mentioned especially polyolefins, such as polyethylene, polypropylene or polyisobutylene, also substituted polyolefins, such as polymers of vinyl chloride, vinyl acetate, styrene, acrylonitrile, acrylic acid or methacrylic acid esters or butadiene, and copolymers of the mentioned monomers, such as, especially, ABS or EVA. Of the group of the polyaddition resins and polycondensation resins there may be mentioned the condensation products of formaldehyde with phenols, the so-called phenol plastics, and the condensation products of formaldehyde with urea, thiourea and melamine, the so-called aminoplastic resins, the polyesters used as surface-coating resins, and both saturated, for example alkyd resins, and unsaturated, for example maleic resins, also linear polyesters and polyamides, polyurethanes or silicones. The mentioned high molecular weight compounds may be present individually or in mixtures, in the form of plastic masses or melts. They may also be in the form of their monomers or in the polymerised state in dissolved form as film formers or binders for paints or printing inks, for example boiled linseed oil, nitrocellulose, alkyd resins, melamine resins and urea-formaldehyde resins or acrylic resins. Depending on the intended application, it proves advantageous to use the effect pigments or effect pigment compositions according to the invention as toners or in the form of preparations. Depending on the conditioning process or intended application, it may be advantageous to add specific amounts of texture-improving agents to the effect pigment before or after the conditioning process, provided that such agents do not have an adverse effect when the effect pigments are used in the dyeing of high molecular weight organic materials, especially polyethylene. There come into consideration as such agents especially fatty acids having at least 18 carbon atoms, for example stearic acid or behenic acid, or their amides or metal salts, especially magnesium salts, as well as plasticisers, waxes, resin acids, such as abietic acid, colophonium soap, alkylphenols or aliphatic alcohols, such as stearyl alcohol or aliphatic 1,2-dihydroxy compounds having from 8 to 22 carbon atoms, such as 1,2-dodecanediol, also modified colophonium maleic resins or fumaric acid colophonium resins. The texture-improving agents are preferably added in amounts of from 0.1 to 30% by weight, especially from 2 to 15% by weight, based on the end product. Accordingly, the invention relates also to a substance composition comprising an effective pigmenting amount of a pigment as defined above and a high molecular weight organic material. In general, the pigment is contained in the substance composition in the form of a plurality of individual pigment particles surrounded by organic material. The pigment according to the invention may be contained in the substance composition according to the invention in an amount of from 0.01 to 70% by weight, based on the high molecular weight organic material. If the pigment according to the invention has an outer coating consisting of a high molecular weight organic material, then that material and the high molecular weight organic material that is to be pigmented may be different or, preferably, identical. If the two high molecular weight organic materials are different, it is advisable to ensure that they are readily compatible. The person skilled in the art will know which high molecular weight organic materials are compatible with one another. In that case, it is especially preferable for the two high molecular weight organic materials to have similar refractive indices. If the substance composition according to the invention is subjected to further processing undiluted as a pigmented high molecular weight organic material, then the amount of pigment according to the invention is preferably from 0.1 to 20% by weight, based on the total weight of the substance composition according to the invention. If, by contrast, the substance composition according to the invention is used as a master batch for pigmenting another high molecular weight organic material, then the amount of pigment according to the invention is preferably from 20 to 70% by weight, based on the total weight of the substance composition according to the invention. For the pigmenting of organic materials, the effect pigments or effect pigment compositions according to the invention may be used on their own. However, it is also possible, for the purpose of achieving different shades of color or color effects, to add to the high molecular weight organic substances, in addition to the effect pigments or effect pigment compositions according to the invention, other coloring constituents, such as white, colored, black or effect pigments in any desired amounts. If colored pigments are used in admixture with the pigments or substance compositions according to the invention, then the total amount is preferably from 0.1 to 20% by weight, based on the high molecular weight organic material. The preferred combination of an effect pigment according to the invention with a colored pigment of a complementary color has especially high goniochromaticity, test coatings of the effect pigment and test coatings of the colored pigment having a difference in hue (.DELTA.H*) of from 150 to 210. Colour values relate to the CIE L*a*b* (L*C*H*) color coordinates for normal light type D65 and CIE 1964 10.degree.-observer (D.sub.65.sup.10.degree.). The pigmenting of the high molecular weight organic substances using the pigments or substance compositions according to the invention is carried out, for example, as follows: such a pigment or such a substance composition, if desired in the form of a master batch, is mixed with those substrates using roller mills, mixing apparatuses or grinding apparatuses. The pigmented material is then brought into the desired final form by methods known per se, such as calendering, compression moulding, extrusion, coating, casting or injection moulding. Any additives customary in the plastics industry, for example plasticisers, fillers or stabilisers, may be incorporated into the polymers in the usual amounts before or after incorporation of the pigment. In particular, in order to prepare non-rigid mouldings or to reduce their brittleness, it is desirable to incorporate plasticisers, for example esters of phosphoric acid, phthalic acid or sebacic acid, into the high molecular weight compounds before shaping. For the pigmenting of paints and printing inks, the high molecular weight organic materials and the effect pigments or effect pigment compositions according to the invention, if desired together with customary additives, for example fillers, other pigments, siccatives or plasticisers, are finely dispersed or dissolved in a common organic solvent or solvent mixture. It is possible for the individual components to be dispersed or dissolved separately, or for several components to be dispersed or dissolved together, and only then for all the components to be combined. When dispersing an effect pigment according to the invention in the high molecular weight organic material to be pigmented, and when processing a substance composition according to the invention, it is preferable to maintain conditions under which only relatively low shear forces occur, so that the effect pigment is not comminuted into smaller fragments. The permissible shear force corresponds approximately to that which is permissible for the flat core, the gentle dispersion of which in a high molecular weight organic material is generally well known to the person skilled in the art. The resulting color effects, for example in plastics, paints or ink prints, preferably in paints or ink prints, especially in paints, are distinguished by excellent properties, especially by high brilliance, reflectivity and opacity as well as excellent color fastness as mentioned above. Accordingly, the invention relates also to a method for pigmenting high molecular weight organic material by incorporating an effective pigmenting amount of an effect pigment according to the invention or of an effect pigment composition according to the invention into said high molecular weight organic material. If the high molecular weight material to be pigmented is a paint, then it is especially a speciality paint, especially an automotive lacquer. |
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