Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2002-11-19
2004-03-16
Le, H. Thi (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C210S754000, C210S755000, C548S311100
Reexamination Certificate
active
06706395
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to halogenated hydantoins, and more particularly to rapidly dissolving halogenated hydantoin powders (particularly BCDMH powder) with improved flow, decreased dust, improved wetability, and increased density.
BACKGROUND OF THE INVENTION
One of the most pervasive problems in the paper making industry is the growth of biological organisms that interfere with the manufacturing process or negatively impact the quality of the finished paper. These organisms typically form into slimes on the machines, which can then become incorporated into the paper. Slimes in paper can affect paper quality, and accordingly may affect the profitability of the mill. Slimes in the paper can also lead to “slime tears” during the papermaking process, which may require the machine to be shut down and restarted. Shut downs also can have a large effect on the profitability of the mill, due to the high capital cost associated with papermaking. Additionally, slimes in the paper may also cause unwanted tastes and odors, again affecting paper quality and mill profitability.
Historically, paper mills have used chemical treatments in conjunction with periodic shut downs to control biological fouling. Most commonly, chlorine or non-oxidizing biocides have been used in those treatments. Unfortunately though, chlorine presents handling and discharge problems, while non-oxidizing biocides often have limited efficacy and can be very expensive.
The halogenated hydantoin bromochlorodimethylhydantoin (“BCDMH”) has been used successfully in the cooling water and process industries because of its generally good handling and discharge characteristics, as well as its superior efficacy. Some problems remain, however, that limit the utility of BCDMH in paper mills. For example, the trend in the paper industry is to “close” mills, which means more water is recycled, less fresh water is used, and less wastewater is discharged. This means that less fresh water is available in the mill for various uses, and the mill is more sensitive to the addition of fresh water because of water and chemistry balances. Because the most common forms of BCDMH—tablets and granules—require large amounts of relatively clean water to dissolve, their use is limited in the paper manufacturing process.
As an alternative to tablets and granules, BCDMH powder has been available for several years. It provides the advantage of a “quick dissolving” product in markets where this is critical because of the limited availability of fresh water. However, several other issues remain, particularly regarding flowability, dusting, wetability, and bulk density. From the flowability standpoint, powdered BCDMH frequently exhibits variable rates of flow, leading to inconsistent amounts of feed. From the dusting standpoint, the product has been very dusty, making it inconvenient to handle and sometimes requiring the use of respirators or other air purification systems. From the wetability standpoint, the product, because of a portion of its small particle size, expresses difficulty in wetting, and tends to float on the surface in the mixing tank, rather than forming a suspension. From the density standpoint, the product is fluffy and light in appearance and weight, which requires larger and more costly packaging.
A need therefore exists for new powdered halogenated hydantoin products that meets the requirements for improved flow, reduced dust, improved wetability, and increased density. The present invention addresses that need.
SUMMARY OF THE INVENTION
Briefly describing one aspect of the present invention, powdered halogenated hydantoin products such as BCDMH are prepared to provide the following particle size distribution: (a) 70-100% halogenated hydantoin particles sized between 80 mesh and 200 mesh; (b) 0-20% particles sized larger than 80 mesh; and (c) 0-10% particles sized smaller than 200 mesh. These powdered products have superior dissolution and flow characteristics, with reduced dusting, improved wetability, and increased density when compared to prior art products.
In another aspect of the present invention the powdered halogenated hydantoin products are prepared to provide the following particle size distribution: (a) 90-100% halogenated hydantoin particles sized between 60 mesh and 200 mesh; (b) 0-5% particles sized larger than 60 mesh; and (c) 0-5% particles sized smaller than 200 mesh.
One object of the present invention is to provide BCDMH compositions having improved flowability, reduced dusting, improved wetability, and increased density.
Other objects and advantages will be apparent from the following description of the preferred embodiments.
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patent: 6495698 (2002-12-01), Howarth
patent: 6508954 (2003-01-01), Elnagar et al.
Harrison Alan D.
Sisk J. Patrick
Biolab Services, Inc.
Le H. Thi
Woodard Emhardt Moriarty McNett & Henry LLP
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