Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2002-04-19
2004-01-06
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S331000, C428S421000, C428S422000, C428S523000, C524S423000, C524S433000
Reexamination Certificate
active
06673436
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a moisture absorbing formed body.
BACKGROUND ART
Electronic devices such as batteries, capacitors (condensers), display units and so forth are steadily heading for further down sizing and weight reduction. These electronic parts are sealed, without exception, with a rubber sealant or a resin adhesive such as UV-curable resin in the stage of sealing the outer housing. However, when such a sealing technique is used, the moisture penetrating through the sealant during storage or use detracts from the performance of the electronic parts. Thus, the moisture finding its way into an electronic device may cause a degradation or corrosion of electronic parts within the device. For example, in a battery or capacitor using an organic electrolyte, contamination of the electrolyte with water causes not only changes in electrical conductivity, electrolysis of the invading water, etc. but also a voltage depression across the terminals and distortion and leakage of the housing due to evolution of gases. Thus, owing to the moisture infiltrating into electronic devices, the functional stability and reliability of the devices can hardly be maintained.
To overcome this disadvantage, the so-called hermetic sealing or metal welding might be considered. However, with such techniques, swelling of the package housing or distortion of the housing due to internal pressure reduction would occur to induce chemical changes in the internal functional component materials.
On the other hand, in the stage of assembling such as electronic device, it is practically impossible to control humidity at 0 throughout the stage. Therefore, for example, in the aging stage after completion of an electronic device, it is indispensable to absorb the moisture which has infiltrated into the electronic device during its assembling. However, as mentioned above, there has not been established a technology by which the moisture infiltrating into an electronic device can be absorbed infallibly and easily.
DISCLOSURE OF INVENTION
A primary object of the present invention, therefore, is to overcome the above-mentioned drawbacks of the prior art and provide an formed body capable of absorbing the moisture infiltrating into the interior of a device, such as an electronic device, with ease and without fail.
In view of the above disadvantage of the prior art, the inventor of the present invention did intensive investigations and found that a herein-defined moisture absorbing shaped article is capable of accomplishing the above object. The inventor has accordingly perfected this present invention.
The present invention, therefore, relates to the following moisture absorbing formed bodies.
1. A moisture absorbing formed body comprising a hygroscopic agent and a resinous component.
2. A moisture absorbing formed body according to Paragraph
1
wherein the hygroscopic agent comprises at least one member selected from the group consisting of the oxides and sulfates of alkaline earth metals.
3. A moisture absorbing formed body according to Paragraph
1
wherein the hygroscopic agent is at least one member selected from the group consisting of CaO, BaO and SrO.
4. A moisture absorbing formed body according to Paragraph
1
wherein the hygroscopic agent is a powder having a specific surface area of not less than 10 m
2
/g.
5. A moisture absorbing formed body according to Paragraph
1
wherein the hygroscopic agent is a powder having a specific surface area of not less than 40 m
2
/g.
6. A moisture absorbing formed body according to Paragraph
1
wherein the hygroscopic agent accounts for 30-95 weight %of the moisture absorbing formed body.
7. A moisture absorbing formed body according to Paragraph
1
wherein the resinous component is at least one member selected from the group consisting of fluorine-containing resin, polyolefin resin, polyacrylic resin, polyacrylonitrile resin, polyamide resin, polyester resin and epoxy resin.
8. A moisture absorbing formed body according to Paragraph
1
further comprising a gas absorbent.
9. A moisture absorbing formed body according to Paragraph
8
wherein the gas absorbent comprises an inorganic porous substance.
10. A moisture absorbing formed body according to Paragraph
1
, the surface of which is covered wholly or in part with a resinous covering layer.
11. A moisture absorbing formed body according to Paragraph
1
, wherein the resinous component has been fibrillated.
12. A moisture absorbing formed body according to Paragraph
1
, wherein the hygroscopic agent is a powder composed of at least one member selected from the group consisting of CaO, BaO and SrO which has a specific surface area of not less than 10 m
2
/g and the resinous component is a fluorine-containing resin (fluororesin).
13. A moisture absorbing formed body according to Paragraph
12
wherein the fluorine-containing resin has been fibrillated.
14. A moisture absorbing formed body according to Paragraph
1
for electronic device use.
The moisture absorbing formed body of the present invention comprises a hygroscopic agent and a resinous component. The morphology or geometry of the moisture absorbing formed body is not restricted but can be judiciously selected according to the mode of use, purpose of use, and site of use of the end product, among other variables, thus including sheets, pellets, plates, films, grains (granules), and so forth.
The hygroscopic agent need only be a substance having at least the function of absorbing moisture but is preferably a compound which adsorbs moisture and retains its solid state even upon adsorption of moisture. Among examples of such compound are various metal oxides and salts of metals with inorganic or organic acids but it is particularly preferable to use at least one member selected from the group consisting of the oxides of alkaline earth metals and sulfates.
The oxides of alkaline earth metals include, for example, calcium oxide (CaO), barium oxide (BaO), magnesium oxide (MgO), and strontium oxide (SrO), or the like.
As the sulfates, there can be mentioned lithium sulfate (Li
2
SO
4
), sodium sulfate (Na
2
SO
4
), calcium sulfate (CaSO
4
), magnesium sulfate (MgSO
4
), cobalt sulfate (CoSO
4
), gallium sulfate (Ga
2
(SO
4
)
3
), titanium sulfate (Ti(SO
4
)
2
), and nickel sulfate (NiSO
4
), among others. Aside from the above oxides and sulfates, organic compounds having hygroscopic properties can also be used as the hygroscopic agent in accordance with the present invention.
As the hygroscopic agent for use in the present invention, an alkaline earth metal oxide is preferred. Particularly preferred is at least one member selected from the group consisting of CaO, BaO and SrO. The most preferred is CaO.
The hygroscopic agent for use in the present invention is formulated preferably in a powdery form. In this case, the specific surface area (BET specific surface area) of the powder should be generally not less than 10 m
2
/g, preferably not less than 30 m
2
/g, particularly not less than 40 m
2
/g. As the hygroscopic agent in powdery form, the CaO (powder) obtainable by heating calcium hydroxide at a temperature not over 900° C. (preferably not over 700° C., most preferably not over 500° C. (particularly 490-500° C.)), can be used with advantage. In the practice of the present invention, a CaO powder having a BET specific surface area of not less than 10 m
2
/g, preferably not less than 30 m
2
/g, particularly not less than 40 m
2
/g, can be used most advantageously.
On the other hand, the resinous component is not particularly restricted provided that the water-removing action of the hygroscopic agent is not interfered with, and a gas-permeable polymer (that is to say a polymer or resin having low gas barrier properties) can be used with advantage. For example, there can be mentioned fluorine-containing resin, polyolefin resin, polyacrylic resin, polyacrylonitrile resin, polyamide resin, polyester resin, epoxy resin, and polycarbonate resin. The degree of gas permeability may be judiciously selected according to the use and desired charact
Fujimori Masayuki
Kawaguchi Yohei
Nishino Atsushi
Ohyama Kaneto
Uchibori Teruo
Dynic Corporation
Knobbe Martens Olson & Bear LLP
Nakarani D. S.
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