Gas separation: processes – Solid sorption – Inorganic gas or liquid particle sorbed
Reexamination Certificate
2001-02-13
2002-05-14
Smith, Duane (Department: 1724)
Gas separation: processes
Solid sorption
Inorganic gas or liquid particle sorbed
C095S141000
Reexamination Certificate
active
06387160
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improved insulated glass windows. The present invention also relates to a matrix incorporating the improved zeolite adsorbent compound. More particularly, the invention relates to the use of the improved zeolite adsorbent compound in insulated glass windows.
BACKGROUND OF THE INVENTION
Zeolites are well-known adsorbents which have been used in insulated glass windows between the glass panes, either alone or within a matrix. Generally, the zeolites are disposed along the periphery of the space enclosed by the glass panes, and the zeolites adsorb water vapor from the space between the panes to prevent the formation of a fog between the panes. The zeolite functions as a molecular sieve having pores into which the material being adsorbed passes. The pores in the molecular sieve have apertures of a size sufficient to permit the molecules of the material being adsorbed to pass-through, but small enough to block materials not adsorbed. Such molecular sieve zeolites for use in insulated glass windows are disclosed in U.S. Pat. Nos. 4,151,690, 4,141,186 and 4,144,196.
Zeolites are known to have pore sizes ranging between about 3 and about 10 angstroms. Insulating glass windows generally consist of two panes of glass separated by an air space. Generally, the zeolites are placed in a channel along the perimeter of the window pane, or incorporated in a matrix around the parameter. The matrix typically comprises a polymer well-known in the art and into which the activated zeolite is bound. Zeolites with pore sizes greater than about 3, are typically used to adsorb gaseous components in the air space. These gaseous components which can be adsorbed by such zeolites include oxygen and nitrogen, as well as water and organic vapors. When the temperature rises or the pressure lowers, the oxygen and nitrogen are released from the zeolite adsorbent. This phenomenon is known as out-gassing. When these zeolites are used in a matrix between the glass panes of a window, they adsorb oxygen and nitrogen when cooled (as during the evening hours) and then release the gases when the glass is heated (as during the daytime hours). This adsorption and desorption of gases can result in pressure variations in the enclosed air space between the glass panes. Such fluctuation can lead to window problems such as excessive deflection or inflection, or window failures from excessive flexing of the seal surrounding the window edges. Such out-gassing can also lead to a loss of adhesion between the glass panes and the matrix when the matrix is cured. The loss of adhesion generally results from the formation of bubbles in the matrix which then migrate to the adhesive-to-glass surface when such gases are released by the adsorbent.
In addition to the above gases in the enclosed air space between the glass panes, there are traces of the solvent from the matrix or inserts within the panes of the window. Over the life of the window, the matrix or other internal components in the window release solvent molecules which are larger than can be accommodated by the small pore adsorbents. In an effort to capture this solvent and keep it from forming a cloud, or a “chemical fog”, and to prevent the chemical fog from condensing on the glass panes, a larger pore zeolite selective for the adsorption of the solvent molecules is included in the adsorbent material in the matrix or in the desiccant material.
U.S. Pat. Nos. 4,141,186 and 4,144,196 attempt to solve this problem by using zeolite adsorbents with pore sizes of about three angstroms or less in size so that oxygen and nitrogen molecules cannot enter into the pores, thus preventing the adsorption and desorption of these gases. In another patent, U.S. Pat. No. 4,151,690, it is disclosed that zeolite adsorbents with larger pore sizes can be pre-treated by adsorption of a low molecular weight polar material to partially suppress the undesirable adsorption of the gases.
U.S. Pat. No. 3,868,299 to Ulisch discloses the use of an adsorbent designed for use in multiple layer, or multi-layer, insulating glass windows comprising a small-pore zeolite in combination with a large-pore adsorbent and, optionally, a clay binder. Ulisch discloses that small-pore zeolites include sodium zeolite A, and large-pore adsorbents include faujasite, active carbon, silica gel, aluminum oxide and mixtures thereof. Kaolin, attapulgite, bentonite, waterglass, gellable silica sols and mixtures thereof are disclosed as suitable binders. Ulisch discloses that the adsorbent materials are prepared by methods known in the art as oil dropping, wherein a suspension of the adsorbent materials is stirred with an aqueous stable silica sol to form a free-flowing suspension which is subsequently introduced to a liquid immiscible with water to form droplets of the required size. The bead granulates formed are removed from the liquid as completely homogeneous bead granulates. The bead granulates are screened, dried, and dehydrated in hot air at about 350° C. Bead granulates produced in this manner represent the most common beads for use in insulating glass windows and, typically, have bulk densities ranging from about 0.640 gm/cc (40 lbs/ft
3
) to about 0.960 gm/cc (60 lbs/ft
3
) and range in size from about 10 to about 40 mesh.
Others such as U.S. Pat. No. 4,835,130 to Box, and hereby incorporated by reference, disclose the preparation of adsorbents for use in multi-pane windows by providing a zeolite material having a mixture of at least two zeolites having a pore size of 4 angstroms and a zeolite having a pore size up to and including 10 angstroms, which has been out-gassed by heating the zeolite to drive out gases and water vapor. The zeolite material is covered with a fluid such as a paraffinic, naphthenic, or aromatic oil which is impervious to nitrogen or oxygen and the covered zeolitic material is incorporated into a sealant matrix such as butyl, resin, zinc oxide, carbon black, aromatic resin, and silane.
U.S. Pat. No. 4,476,169 relates to an adsorbent material for multi-layer glazing wherein an adsorbent in the spacers consists of a granular zeolite having a core of synthetic zeolite with a clay binder wherein the core has more zeolite than the particle as a whole, and a shell of synthetic zeolite with a clay binder wherein the shell has more clay than in the particle as a whole, and of particles of activated carbon coated with synthetic latex.
Although combinations of small pore zeolite A and larger pore zeolites such as zeolite X have been used in insulated glass windows, the problem of out-gassing from the zeolite in the matrix which leads to the accelerated failure of the insulated glass window has not been resolved. Even though attempts have been made to maximize the amount of the small pore zeolite relative to the large pore zeolite, the problem of the large pore zeolite adsorbing air as well as solvent has not been resolved. When 13X zeolite is employed in the adsorbent mixture, the insulated window out-gassing problem often results.
It is an objective of the present invention to provide an adsorbent material for use in insulated glass windows which has a reduced capacity for adsorbing selected gases from air while retaining the capacity to prevent premature failure of insulated glass windows by release of solvent molecules.
It is an objective of the present invention to provide a large pore zeolite material which has a reduced affinity for the adsorption of air when used in insulated glass windows.
It is an objective of the present invention to mitigate the out-gassing problem in insulated glass windows by reducing the amount of nitrogen adsorbed by the adsorption material using an improved zeolitic adsorbent.
SUMMARY OF THE INVENTION
It was surprisingly discovered that the nitrogen adsorption capacity of a faujasite-type zeolite in insulated glass windows can be significantly reduced by low levels of ion-exchange of the FAU-type zeolite with an alkali metal without significantly reducing the adsorption of solvents. It was discovered that the nitrogen
Dangieri Thomas J.
Greenlay Nanette
Goldberg Mark
Lawrence Frank M.
Nolinaro Frank S.
Smith Duane
Tolomei John G.
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