Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1999-11-08
2001-07-10
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S404000, C106S415000, C106S493000, C106S494000, C106S495000, C106S496000, C106S497000, C106S498000, C106S499000
Reexamination Certificate
active
06258158
ABSTRACT:
The present invention relates to a process for pigmenting a porous metal oxide by applying a solution of a soluble pigment derivative and regenerating the organic pigment by heating, whereby the organic pigment is deposited into the metal oxide's pores. The invention also relates to pigmented porous metal oxides and materials comprising a solid substrate and a surface layer of a pigmented metal oxide.
BACKGROUND OF THE INVENTION
Porous materials are commonly coloured with dyes that are applied, for example, as stains. In order to achieve satisfactory colouring results with this method a requirement is that the porous material to be coloured has a high and uniform affinity for the dye. Porous materials coloured with dyes possess, however, a light stability which is very unsatisfactory especially in outdoors applications. This is particularly a problem in the case of materials which are themselves highly weather-fast, such as metal oxides, because the colour undesirably disappears much earlier than the material is itself altered.
Another method of imparting a coloured appearance to porous materials is to provide them with a pigmented coating. This method, however, has the disadvantage that the visual appearance of porous materials such as metal oxides is changed. This is a great disadvantage, especially with metal oxides, since it is their properties, especially their transparency when applied in thin layers, that are the most prized. In addition, a pigmented coating is generally much less stable to weather and chemicals than, for example, the metal oxides onto which they are coated. With time, pigmented coatings decrease in gloss, fade and eventually become brittle and finally peel off.
U.S. Pat. No. 4,066,816 discloses the deposition of undefined inorganic pigmentary material onto at least 3 &mgr;m, preferably 15-30 &mgr;m thick porous aluminium oxide layers. However, very little colouration is achieved unless the pore diameter is increased, and this process is hardly useful for commercial purposes because of the predominant bronze tone (muddiness). U.S. Pat. No. 4,310,586 teaches to grow a second oxide film beneath the inorganic deposits, but this process is very difficult to control as a whole, as the colour results from optical interference and small thickness variations of the deposits or the second oxide film lead to undesirably large colour changes. Moreover, the products have less satisfactory chemical and physical properties than usual oxide layers.
U.S. Pat. No. 5,585,189 dicloses an electrophoresis process for pigmenting anodic oxide films on aluminium. However, it is necessary to increase the pore size to 50 to 250 nm, whereby the visual appearance and the weathering properties are impaired due to the rough surface. In addition, this process does not lead to satisfactory results with high performance red pigments such as diketo-pyrrolo-[3,4-c]-pyrroles and quinacridones.
Hence, the coloration of metal oxides or of materials comprising a solid substrate and a surface layer of a metal oxide has long been a problem with no satisfactory solution.
EP 648 770 and EP 648 817 disclose carbamate-functional, soluble chromophores which can be converted to the corresponding pigments by being heated to relatively high temperatures, with the ensuing elimination of the carbamate radicals. These compounds are suitable for the mass colouring of polymers and, according to EP 654 711, for the colouring of resists and of polymer coatings to which they are applied. Compounds of the same type but with improved properties are known from EP 742 556, WO 98/32802, WO 98/45757, WO 99/01511, CH-98/1922 and CH-99/702.
U.S. Pat. No. 5,243,052 discloses carbonates of quinophthalones, which are of limited solubility and can be used in heat-sensitive recording systems. The leuco dye is embedded within a polymer, preferably in polyethyloxazoline.
Soluble derivatives of triphenylmethane dyes are known from U.S. Pat. No. 4,828,976. They are likewise used in heat-sensitive recording systems, together with a binder such as cellulose acetate-butyrate, polyvinyl pyrrolidone or copolymerized ethylene/maleic anhydride.
EP 742 556, furthermore, describes textured pigmentary coatings which are prepared from soluble or meltable precursors and which cover all of or part of a substrate surface. The substrates mentioned include fibres and fabrics. It has been found, however, that these pigmentary coatings fail to entirely meet high requirements especially in terms of their rub fastness.
SUMMARY OF INVENTION
Also known, finally, are numerous heat-sensitive recording systems in which colourless precursors of colourants—as solids, in the form, for example, of aqueous suspensions, together with binders and with or without fillers—are incorporated as the recording layer. For example, JP 04/124,175 describes leucoindigoid derivatives. Colourants in solid form, however, such as conventional pigments, make hardly any entry into the pores but for the most part remain, undesirably, on the surface.
It has now surprisingly been found that porous metal oxides and materials comprising a solid substrate and a surface layer of a metal oxide can be coloured without impairing their properties if fragmentable pigment precursors in melted or dissolved form are introduced into the pores and then converted thermally to organic pigments. The porous surface is then still functionally available for any desired subsequent treatment, such as sealing, glueing, bonding, marking, laminating or coating, entirely or only in part, by any of the many known techniques routinely used in the field. The pigmented materials may advantageously also be cut, milled, bent or joined identically to the non-pigmented materials. Consequently, either finished articles or raw material, as desired, can be coloured prior to processing, shaping or assembling.
It is, surprisingly, also possible to obtain non-bleeding, very high colour saturations (chroma) by using high pigment concentrations. Thus, pigmented metal oxides of fine particle size can be used as pigments for colouring high molecular mass organic material. The results are excellent with respect to hue and chroma as well as also to the transparency, when the porous material has a refraction index similar to that of the substrate into which it is incorporated. Very advantageously, these products are less dusting and are more easily incorporated into substrates than usual transparent pigments, and rheology problems can be avoided. Particles comprising a layer of a pigmented porous metal oxide may be used themselves as pigments, too.
The resulting colorations are surprisingly strong in colour, fast to weathering, light and heat, rubbing, water and solvent, and are also optically highly uniform provided the material itself is uniform in its porosity.
DETAILED DESCRIPTION OF INVENTION
The present invention accordingly provides a process for preparing a coloured metal oxide or a material comprising a solid substrate and a layer of a coloured metal oxide, wherein the coloured metal oxide or metal oxide layer comprises an effective colouring amount of an organic pigment, which process comprises
(a) treating a porous metal oxide or a material comprising a surface layer of a porous metal oxide with a solution or melt of a soluble pigment precursor such that at least part of the pigment precursor enters the pores of the metal oxide, and
(b) regenerating said organic pigment within the pores, through fragmentation of the pigment precursor that has entered the pores of the metal oxide in accordance with treatment (a), by means of heating or irradiation,
with the proviso that the coloured metal oxide is not pumice, fired clay, unglazed porcelain, gypsum, concrete, kieselguhr, silica gel or a zeolite.
Porous metal oxides are preferably colourless or only slightly coloured, such as the oxides of elements of the periodic table's groups 2, 3, 4, 12, 13 and 14 (IUPAC) and mixtures thereof, for example the oxides of Al, Si, Zr, Mg or Ti. Very particularly preferred are porous oxides of aluminium or an al
Bugnon Philippe
Homma Seiji
Verhoustraeten Patrick
Bell Mark L.
Ciba Specialty Chemicals Corp.
Crichton David R.
DiVerdi Michael J.
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