Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-07-07
2001-04-17
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
Reexamination Certificate
active
06217701
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
This invention relates to desiccant containers. More specifically, this invention relates to a composition of material for use in a desiccant container comprising a combination of calcium chloride and starch.
2. Prior Art
Desiccant containers which absorb water vapor, water, liquids and the like are well known in the art. Generally, these containers are comprised of a water or water vapor permeable packaging material formed from fibrous or film products securely sealed together at the edges of the packaging. The packaging material encapsulates a desiccant material, such as silica gel. The volume of water or water vapor absorbed by the desiccant container is generally determined by the absorbent capacity of the desiccant material contained within the container.
One type of desiccant container absorbs both water vapor and liquid water by permitting both to pass through the packaging material to be absorbed by the desiccant material. In some circumstances, the packaging material for this type of product dissolves to permit the desiccant material contained within the desiccant container to have direct contact with the liquid.
Another type of desiccant container absorbs water vapor but not liquid water. The packaging material for this type of desiccant container is designed to prevent water absorbed within the desiccant container as water vapor from being released from the desiccant container in the form of liquid water.
There are many common products that are utilized as desiccating agents. Among the most common used include silica gel, calcium sulfate, calcium fluoride, activated charcoal, molecular sieves, lithium chloride, calcium chloride and other such products. A common list of these drying agents is contained, for example, in Kirk-Othmer,
Encyclopedia of Chemical Technology
, Volume 7, pages 378-398. Common desiccating agents for use in conventional desiccant containers are also disclosed in U.S. Pat. No. 5,114,003, which discloses the use of a montmorillonite clay, silica gel, molecular sieve, calcium oxide, calcium sulfate and calcium chloride. The use of silica gel, alumino silicate, alumina, activated charcoal and molecular sieves as desiccating agents are disclosed in U.S. Pat. No. 4,464,261.
Commercial grade calcium chloride is a widely used desiccant due to its low cost and high degree of hygroscopicity. Calcium chloride compacted in the form of particles or beads is used as a drying agent, for example, in U.S. Pat. No. 3,923,944.
Mixtures and combinations of other materials have been combined with calcium chloride to form desiccating products. For example, polyethylene glycol was mixed with calcium chloride to form a desiccant product in U.S. Pat. No. 3,779,936. In addition, U.S. Pat. No. 3,334,468 discloses the use of sodium chloride or sodium carbonate with calcium chloride. Further, the combination of calcium chloride with magnesium, lithium or ammonium salts is disclosed, for example, in U.S. Pat. No. 3,885,926. The use of calcium chloride with a metal, for example, iron fillings, is disclosed in U.S. Pat. No. 1,798,862. Further, the use of activated carbon with calcium chloride as a desiccant product is disclosed in U.S. Pat. No. 2,027,093.
U.S. Pat. No. 3,390,511 discloses the use of calcium chloride placed on a carrier material for use as a gas dryer desiccant. The preferred material that is utilized as the carrier for the calcium chloride is sodium chloride. See also, U.S. Pat. No. 3,334,468. The desiccant product in U.S. Pat. No. 3,390,511 preferably comprised about 90 to 97 percent sodium chloride as the carrier and about 10 to about 3 percent calcium chloride. In addition, sodium dichromate and trisodium phosphate in minor amounts may be included in the product. While the preferred carrier for the calcium chloride was sodium chloride, other disclosed carriers included sugar, potassium chloride, potassium nitrate, sodium nitrate and starch. See column 3, line 33. The percentage of calcium chloride used in this product was 10 percent or less, because the major component of the product was the carrier.
One of the problems in the utilization of calcium chloride as a desiccating agent is that when the water is absorbed, it forms a liquid mixture on the surface of the calcium chloride. This is discussed in U.S. Pat. No. 3,334,468. With conventional desiccant products this liquid may leak which can cause problems, for example, if the desiccant product is used in storage containers.
While these references disclose the use of calcium chloride as a desiccant either alone or combined with a number of different compositions, there is still the need for improved desiccant products utilizing calcium chloride.
Therefore it is an object of this invention to disclose a desiccant composition containing calcium chloride as its major component.
It is a still further object of this invention to disclose a desiccant composition containing calcium chloride mixed with a significant amount of starch to form the desiccant composition.
It is a still further object of the invention to disclose a desiccant composition contained within a packaging material, wherein the desiccant composition is a combination of calcium chloride and starch, preferably a modified starch.
It is a still further object of this invention to disclose a desiccant composition containing calcium chloride where water absorbed by the calcium chloride does not leak from the desiccant container.
It is a still further object of this invention to disclose a desiccant composition contained within a packaging material wherein the desiccant composition prevents leakage of water from within the package by use of a starch, preferably a modified starch.
These and other objects and features of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description, drawings and claims. The description, along with the accompanying drawings, provides a selected example of the construction of the product and process to illustrate the invention.
SUMMARY OF INVENTION
In accordance with the present invention there is provided a desiccant composition comprising calcium chloride and starch, wherein the calcium chloride comprises at least about 5 to about 95 percent of the composition by weight and the starch from about 5 to about 95 percent of composition. In the preferred embodiment calcium chloride comprises from about 20 to about 95 percent of the composition by weight while the starch comprises from about 5 to about 80 percent of the composition by weight. While the starch used may be unmodified, in a preferred embodiment, it is a modified starch, preferably a modified corn starch.
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Kirk-Othmer, “Drying Agents”, Encyclopedia of Chemical Technology, vol. 7, pp. 378-398.
Rix Matthew Lee
Shelley Richard M.
Ball Michael W.
Cox Scott R.
Haran John T.
United Catalysts Inc.
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