Granular pigments useful to color concrete

Details Granular pigments useful to color concrete Granular pigments useful to color concrete

2002-06-20

2004-07-06

Koslow, C. Melissa (Department: 1755)

Compositions: coating or plastic

Materials or ingredients

Pigment, filler, or aggregate compositions, e.g., stone,...

C106S439000, C106S453000, C106S712000, C264S118000, C264S141000

Reexamination Certificate

active

06758893

ABSTRACT:

FIELD OF INVENTION
The present invention is directed to the manufacture of pigment granules, for example, iron oxide and chromium oxide pigments of a type useful for coloring concrete and other products. Granules made according to the processes of this invention often surprisingly produce coloring in concrete systems superior to that of the starting pigments.
BACKGROUND OF INVENTION
In General
Since at least the middle of the Nineteenth Century to the very present day, iron oxide has been used as the pigment of choice in an increasing variety of systems. Natural iron oxide actually was mined and used in paints before the American Civil War and such paint use continues, on a very large scale, into the twenty-first Century. Cosmetics, pharmaceuticals, waxes, coatings, inks, paper and a growing number of other new products continue to depend on iron oxide to provide the bright colors which some people believe define the vividness of modernity and our present time.
A major application of iron oxide (and chromium oxide) is in the pigmentation of cement and concrete products (e.g. paving slabs and blocks), and such colored concrete products are experiencing a growing and accelerating use throughout both the Western and Eastern worlds. Metal oxide pigments have been used in the form of a powder in the concrete business until very recently when customer preferences for a granule form became known.
Powdered metal oxide pigments are dusty, thereby giving rise to health hazards and making storage and handling difficult. Also, the powders are not free flowing and so cannot readily be conveyed through pipes, which become blocked by the powder. Further, the poor flowing properties of powders makes it hard to meter them using auger screws to ensure the correct proportion of pigment to base material (e.g., concrete).
Prior Developments
Similar problems are known in other industries (e.g., in the animal feedstuff industry). Such problems have been solved to a substantial extent by granulating the product. However methods of making these granules for concrete use have been difficult to optimize and are the subject of an ongoing investigation by many companies with much prior art reflecting the search for a process that is both effective in producing useful granules and is relatively inexpensive to implement. The guiding purpose of scientists working in the field has been to produce granules of sufficient strength to be transported and stored without breaking into dust and to simultaneously provide coloration properties to concrete close, or in rare cases equal, to that of the pigment itself. A substantial universe of patents has been issued in the field of this invention.
For example, Degussa U.S. Pat. No. 4,366,139 discloses granulating pigment used in the pigmentation of paper, cement, and concrete including specifically carbon blacks. Carbon blacks give rise to an even greater dusting problem than iron oxides since the particle size of carbon black powders are much smaller than that of iron oxide powders. Carbon blacks also suffer from the problem of floating on base material, which makes incorporation into the base material difficult. According to this patent, the twin problems of dusting and poor incorporation are solved by mixing carbon black with at least 30% water and optionally also a wetting or dispersing agent in an amount of 0.5 to 12% and preferably 5 to 10% (based on the amount of the carbon black) and subjecting the resulting mixture to compression forces in a pearlising machine to form pearls or granules. Depending on the nature and operation of the pearlising machine, the compression forces can be substantial.
U.S. Pat. No. 4,277,288 issued 1979 to Ciba Geigy discloses manufacturing pigment granules by forming a fluidized bed of pigment powder and adding into the bed an organic liquid or wax as a binder to promote granulation. A surfactant is also added.
U.S. Pat. No. 4,946,505 issued to Chemische Werke Brockhues A. G. discloses that no compression or briquetting forces at all must be applied to pigments during the formation of pigment granules for use in coloring of concrete and cement in order to obtain satisfactory production. This is achieved by an agglomeration technique (e.g., by drum granulizing machines). The agglomeration brings individual pigment particles into contact with each other in the presence of water and a binder (e.g., lignin sulphonate), whereupon the particles adhere to each other (coalesce) to form granules. Preferably, pigment granules are formed by spray drying a mixture of the pigment, water, and a binder. The method disclosed requires the presence of a considerable amount of binders to ensure that the pigment particles adhere to one another and use costly spray drying equipment.
Bayer U.S. Pat. No. 5,215,583 discloses building materials colored with pigments, for example iron oxide pigments, in the form of granules produced from a suspension of one or more pigments. The suspension also contains 0.05-5% of soluble salts, based on pigment weight.
U.S. Pat. No. 5,215,584 discloses building materials such as plaster, lime sand bricks, fiber cement parts, cast stones, roof tiles, and flagstone that are colored by incorporating organic granules produced from a suspension of one or more inorganic pigmenting agents and a hydrolyzed or poorly soluble compound of one or more ion types present per se as an essential constituent in one or more pigments.
U.S. Pat. No. 5,401,313 issued to Elementis Pigments, Inc. the assignee of this invention, describes a spray drying process wherein an added step of coating the pigment particles-with electric charges through use of a surface treatment is utilized.
U.S. Pat. No. 5,484,481 issued to Bayer discloses a process for the granulation of pigments for use in dyeing cement and concrete involving compacting pigment powders in the presence of a binder to form flakes; breaking up the flakes; and rounding the ground flakes using known techniques (e.g., using rotating pans or drums, which involve the application of water and a binder to the ground flakes).
Degussa U.S. Pat. No. 5,480,626 and U.K. Patent No. 0598318 disclose a process for the production of spherical granulates from powdered solids. The solids are uniformly moistened while being mixed in a mixer by the addition of a moistening agent and optionally a binder and other additives. The mixture is pressed through an annular die press having variable slippage between the annular die and press roller to yield cylindrical strands. The invention requires that the strands are then rounded in a rounding unit having a complicated and expensive ribbed plate to yield spherical granulates. The patent further teaches not to use extruders because of their high investment costs and the difficulties associated with slight moisture changes.
U.S. Pat. No. 5,853,476 issued to Elementis Pigments, Inc., shows a compaction process relying in a preferred embodiment on Bepex MS compactors to make granules for concrete coloration. While very effective, the process is relatively expensive. The patent teaches the use of recycling of oversize and undersize material streams in a process that both creates enhanced color in the concrete and saves the cost of waste disposal.
U.S. Pat. No. 5,634,970 issued to Bayer A. G. relates to a process for the coloration of organic media by granulated inorganic pigments. The possible processes discussed include spray granulation (spray drying via disc or nozzle) and pelletizing (mixer, fluidized bed granulation, disc or drum) and then describes the preferred invention as a multi-stage process compacted in a compactor (Bepex 200/50). U.S. Pat. No. 6,132,505 also issued to Bayer A. G. shows a related process to make pigment pellets for coloring building materials using both compaction and crushing steps with polyethylene glycols and similar water soluble liquids as required auxiliary substances.
U.S. Pat. Nos. 6,241,167 and 6,079,644 again to Bayer disclose processes for producing briquetted and pressed granular material and the use thereof for coloring building

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