Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2001-07-17
2003-06-17
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S031600, C106S031900, C106S441000, C106S456000, C524S398000, C524S399000, C524S407000, C524S492000
Reexamination Certificate
active
06579356
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to various aspects related to brown pigments containing iron and chromium. In particular, the present invention relates to brown pigments having desirable weathering characteristics, methods of making the brown pigments, plastics and other materials containing the brown pigments, and methods of using the brown pigments.
BACKGROUND OF THE INVENTION
Iron oxide is often used with other components to make brown Complex Inorganic Color Pigments (CICP). A CICP is a pigment made by heating a number of different metal oxides. Relatively large, coarse, and/or hard particles often lead to problems in some CICP applications.
The large, coarse, and/or hard CICP particles may be employed in substances such as concrete. However, CICP particles used for coloring coatings, plastics, lacquers and synthetic resins are typically subjected to intensive grinding. The disadvantages associated with intensive grinding include the undesirable formation dust, difficulties in measuring the ground CICP particles, and difficulties in dispensing with the ground CICP particles.
Moreover, in order for CICP particles used for coloring coatings, plastics, lacquers and synthetic resins, high temperature stability is often required since these materials are often processed or exposed to high temperatures. Coatings, plastics, lacquers and synthetic resins also typically require pigments with good weathering characteristics since lengthy exposure to the outdoor environment is common. In the case of vinyl siding for homes, outdoor exposure lasts many years. Many brown pigments unfortunately lack good weathering characteristics.
The ability to tint pigments is also a desirable characteristic. A pigment with high tinting strength has broader applications and may be used in a number of different settings. Unfortunately, many brown pigments lack strong tinting characteristics.
Some brown CICP formulations have one or two desirable properties as well as several undesirable properties. For example, some brown pigments are strong, but have poor weathering characteristics, poor heat resistance, weak tinting strength, undesirable color shades, and/or costly starting materials. Specifically, conventional PBr 29 is strongly brown but has poor weathering characteristics. It is therefore not commonly employed in outdoor applications where such characteristics are required. Conventional PY 164 (based on manganese-antimony-titanium), often employed as a brown pigment, has good weathering characteristics, but poor tinting strength.
Given these circumstances, when employing a brown CICP formulation, one must accept a compromise on at least one desirable property. There is thus an unmet need in the art for a brown CICP formulation having many desirable properties including good weathering.
SUMMARY OF THE INVENTION
The present invention provides brown CICP formulations that possess high pigment strength, excellent weathering characteristics, high temperature resistance, and excellent tinting strength. The brown CICP formulations of the present invention possess many desirable characteristics thus minimizing the compromises typically required when selecting a brown pigment.
One aspect of the invention relates to a brown pigment composition with excellent weathering resistance containing iron oxide, chromium oxide, and one or more alumina and/or silica components. Another aspect of the invention relates to a method of making a brown pigment involving combining iron oxide, chromium oxide, and one or more alumina and/or silica components to form a mixture and heating the mixture to provide brown pigment particles. Yet another aspect of the invention relates to a plastic composition containing a major amount of a plastic material and a minor amount of a brown pigment composition containing iron oxide, chromium oxide, and one or more alumina and/or silica components.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides brown iron-chromium pigments that possess at least one of high pigment strength, good weathering characteristics, high tinting strength, high temperature resistance, small particle size, stable during handling, stable to oxidation, and highly dispersible.
The brown iron-chromium pigments contain at least three components; namely, iron oxide, chromium oxide, and one or more alumina and/or silica components. The brown iron-chromium pigments optionally contain other components such as a binder, dispersant, and/or mineralizer. The iron oxide and chrome oxide form a crystal structure typically represented by the formula [Fe,Cr]
2
O
3
, corresponding to a PBr 29 pigment, wherein the crystal structure contains more iron than chromium.
The iron oxide of the brown iron-chromium pigments contributes to the strength of the pigment. Iron oxide primarily contains yellow iron oxide; that is, Fe
2
O
3
.H
2
O or FeOOH (hydrated iron (III) oxide). Forms of yellow iron oxide include &agr;-FeOOH and &ggr;-FeOOH. Other forms of iron oxide, which may be used in addition to yellow iron oxide include Fe
3
O
4
(iron (II, III) oxide) also known as FeO.Fe
2
O
3
, Fe
2
O
3
(iron (III) oxide including &agr;-Fe
2
O
3
and/or &ggr;-Fe
2
O
3
), Fe(OH)
2
, and Fe(OH)
3
. Iron oxides are commercially available and/or may be made from iron oxide precursors.
Although not necessary, it is preferred to employ iron oxide or iron oxide precursors having a relatively small particle size. For example, iron oxide having an average particle size (by weight) of about 5 &mgr;m or less is employed. In another embodiment, iron oxide having an average particle size (by weight) of about 1 &mgr;m or less is employed.
In one embodiment, the brown iron-chromium pigments of the present invention contain from about 30% to about 80% by weight of iron oxide. In another embodiment, the brown iron-chromium pigment contains from about 35% to about 75% by weight of iron oxide. In yet another embodiment, the brown iron-chromium pigment contains from about 40% to about 70% by weight of iron oxide.
The chromium oxide of the brown iron-chromium pigments contributes to the strength of the pigment. Chromium oxide primarily contains Cr
2
O
3
(chromium (III) oxide), but may also contain chromium (VI) oxide. In one embodiment, the brown iron-chromium pigments do not contain chromium (VI) oxide, or contain less than about 0.001% by weight chromium (VI) oxide. Chromium oxide is commercially available and/or may be made from chromium oxide precursors. Chromium oxide precursors include chromium acetate, chromium bromide, chromium chloride, chromium fluoride, chromium nitrate, and chromium sulfate.
Although not necessary, it is preferred to employ chromium oxide or chromium oxide precursors having a relatively small particle size. For example, chromium oxide having an average particle size (by weight) of about 5 &mgr;m or less is employed. In another embodiment, chromium oxide having an average particle size (by weight) of about 2 &mgr;m or less is employed.
In one embodiment, the brown iron-chromium pigments of the present invention contain from about 5% to about 50% by weight of chrome oxide. In another embodiment, the brown iron-chromium pigment contains from about 10% to about 45% by weight of chromium oxide. In yet another embodiment, the brown iron-chromium pigment contains from about 15% to about 40% by weight of chromium oxide.
In some instances, the ratio of iron to chromium in the resultant pigment falls within a suitable range for maximizing color strength and/or maintaining crystal structure indicative of a PBr 29 pigment. This crystal structure is represented by the formula [Fe,Cr]
2
O
3
. This structure is determined/confirmed using X-ray diffraction. In this connection, in one embodiment, the ratio of iron to chromium is from about 1:1 to about 5:1 by weight (which also corresponds to the amounts of iron oxide and chromium oxide initially combined). In another embodiment, the ratio of iron to chromium is from about 1.5:1 to about 4:1 by weight. In yet another embodiment, the ratio
Gall Mark Edward
Loucka William Gerald
Richardson John Gilbert
Engelhard Corporation
Keller Raymond F.
Koslow C. Melissa
Manlove Shalie A.
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