Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-10-10
2003-03-18
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S418000, C106S499000
Reexamination Certificate
active
06533858
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to platy pigments with a highly adherent colorant.
Colored lustrous pigments are known in which the lustrous pigment part is a natural pearlescent material or synthetic pearlescent substance (also called nacreous pigments) and the colors are a wide variety of inorganic and organic coloring agents or dyestuffs. The processes used to make colored lustrous pigments in prior art encountered numerous difficulties among which the following are noteworthy: severe bleeding of the color on filtration of the coated product from the suspension; poor adherence to the surface of the pigment in that the color could be washed off with water; difficulty of retaining luster with increased color intensity; and nonuniform distribution of the colorant on the pigment surface.
The foregoing problems are in part described in U.S. Pat. No. 4,084,983. This patent relates to the use of titanium dioxide-coated-mica pigments to produce colors due to interference phenomena and additional color effects achieved by coating organic dyes on the surface of these pigments. In an attempt to overcome the problems encountered in the art, the dyestuff is chemically bound on the surface of the pigment with the help of a laking reagent. For example, one laking reagent used was aluminum chloride which on hydrolysis produced layers of aluminum hydroxide with which the dye reacted to form the insoluble color lake, thereby permitting it to deposit on the surface of the pigment. Although this approach particularly addresses the problem of poor adherence of the organic dye on the surface of the pigment, the problem of heavy bleeding of the uncoated dye remained severe. The failure of the previous art to control this problem was a serious obstacle in developing a suitable process of preparing colored lustrous pigments of superior quality.
A significant advance in the art is described in U.S. Pat. No. 4,968,351. This provides an efficient laking process which is practical and economical for preparing dye-coated pigments with strong color intensity and superior luster.
Another significant advance in the art is described in U.S. Pat. No. 4,755,229 in connection with combination pigments, i.e., pearlescent pigments further coated with an absorption pigment, so-called because it absorbs some portion of the visible spectrum. Absorption pigments which are not soluble in water and which cannot be formed in place from a water-soluble reactant(s) are deposited using an oxide or hydroxide of a polyvalent cation and an anionic polymeric substance. Since that procedure was developed in the 1980's, the conditions to which such colored nacreous pigments have been subjected have become even more severe, thereby requiring further improvements in color adhesion. Furthermore, that process was particularly adopted for use in products which are subjected to inherently more severe processing conditions during manufacturing, as for instance, incorporation into a mass of plastic.
A pearlescent pigment having improved humidity resistance and weatherability is described in U.S. Pat. No. 5,759,255. This pigment is realized by a metal oxide-coated mica pearlescent pigment which has an aluminum or an aluminum-cerium combined with a hydrolyzed silane coupling agent treated surface. It has now been surprisingly discovered that the hydrolyzed silane coupling agent treatment when used in conjunction with the pigments of the aforementioned U.S. Pat. No. 4,755,229 give rise to improved non-bleeding, non-agglomerated, lustrous colored nacreous pigments with excellent weatherability.
SUMMARY OF THE INVENTION
This invention relates to colored lustrous pigments of superior quality and to processes for producing them. More particularly, the invention pertains to colored lustrous platy materials, especially metal oxide-coated substrate nacreous or pearlescent pigments, which are colored with an absorption colorant and contain a hydrolyzed silane coupling agent treated surface and a process for producing such pigments. The products of the invention are preferably chromium-free. They exhibit improved adhesion of the colorant coupled with enhanced weatherability. The products are of particular use in liquid coating such as the solvent and water borne automotive paint systems combining a pigmented basecoat and a clear top coat.
The invention thus provides a lustrous colored platy substrate, e.g., a nacreous pigment comprising metal oxide-coated substrate nacreous pigment particles, whose surface has been coated with a first coating layer comprising anionic polymeric substance and water-insoluble colored pigment, said pigment having a second coating layer thereon consisting essentially of hydrated aluminum oxide or combination of hydrated cerium and aluminum oxide and a coating of hydrolyzed silane coupling agent on or intermingled with said second coating. The pigment is essentially non-bleeding and non-agglomerated, i.e., bleeding is substantially reduced if not eliminated compared to prior art pigments.
The invention also provides method of producing the pigment by combining an aqueous suspension of platelets with an aqueous suspension of a water-insoluble colored pigment containing an anionic polymeric substance, and thereafter forming a coating consisting essentially of a hydrated aluminum oxide or combination of hydrated aluminum-cerium oxide on the platelets and combining said platelets with a hydrolyzed silane coupling agent simultaneously or subsequently with the formation of said coating.
DESCRIPTION OF THE INVENTION
In accordance with the present invention, a superior pigment, e.g., a combination nacreous pigment, is produced basically in accordance with the process described in the aforementioned U.S. Pat. No. 4,755,229, which is hereby incorporated by reference, and then is post-treated with a hydrolyzed complexing agent.
The substrate to be treated can be any platy material such as mica flakes, titanium dioxide, sericite, kaolin, gypsum, bismuth oxychloride, glass and the like. Suitable mixtures of platy substrates may also be used. Usable coated platelets are exemplified by titanium dioxide-, zirconium dioxide- and/or iron oxide-coated mica or coated glass. The substrate may also be an optically variable pearlescent or effect pigment.
Preferred are the well-known metal-oxide coated mica or glass nacreous or pearlescent pigments. The metal oxide coated substrate nacreous pigments are well known and are exemplified by titanium dioxide and/or iron oxide coated mica. Such pigments are described, inter alia, in U.S. Pat. Nos. 3,437,515; 3,418,146; 3,087,828 and 4,038,099. A preferred nacreous pigment is titanium dioxide coated mica. The mica flake substrates generally have a length of about 1-75 microns, preferably about 5-35 microns, and a thickness between about 0.3 and 3 microns. Usually, the titanium dioxide or other metal oxide will be coated on the substrate surface to a thickness of about 20-350 nanometers or such that it is about 50 to 500 mg/m
2
, depending on the specific surface area of the substrate in m
2
/g. Depending on the thickness of the metal oxide coating, the pigments can exhibit interference or reflection colors of blue, green, yellow, red, etc.
Absorption pigments which are water insoluble, transparent (i.e. substantially non-light scattering) and which cannot be formed in situ from a water soluble reactant(s) but which may be highly dispersed in water or water-alcohol containing anionic polymer are suitable for the invention. These include, for example, carbon black and organic pigments in the following groups: azo compounds, anthraquinones, perinones, perylenes, pyrroles such as diketopyrrolo pyrroles, quinacridones, thioindigos, dioxazines and phthalocyanines and their metal complexes. The pigments, depending on their color intensity, are used in a concentration range of about 0.01% to about 30% based on the weight of platy substrate, preferably 0.1% to 10%.
Colors may be adjusted if desired by mixing combination pigments. In general, it is preferred to mix pigments of t
Cacace Deborah
Fuller Daniel S.
Bell Mark L.
Dickstein , Shapiro, Morin & Oshinsky, LLP
Engelhard Corporation
Manlove Shalie
LandOfFree
Effect pigments with improved colorant adhesion does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Effect pigments with improved colorant adhesion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Effect pigments with improved colorant adhesion will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3009587