Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2001-12-17
2003-07-22
Bell, Bruce F. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S631000, C204S632000, C204S633000, C204S634000
Reexamination Certificate
active
06596137
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a bipolar membrane capable of dissociating water at a low voltage.
BACKGROUND ART
The bipolar membrane is an ion-exchange membrane having a structure in which a cation-exchange membrane and an anion-exchange membrane are stuck together to dissociate the water into protons and hydroxyl ions. There have been proposed a variety of methods for their preparation.
For example, there have been proposed:
a method of sticking a cation-exchange membrane and an anion-exchange membrane together using a mixture of polyethyleneimine and epichlorohydrin, and adhering them together by curing (Japanese Examined Patent Publication (Kokoku) No. 3962/1957;
a method of adhering a cation-exchange membrane and an anion-exchange membrane together using an ion-exchange adhesive (Japanese Examined Patent Publication (Kokoku) No. 3961/1959);
a method of press-adhering a cation-exchange membrane and an anion-exchange membrane together by applying thereto a fine powdery ion-exchange resin or a paste-like mixture of an anion-exchange or cation-exchange resin and a thermoplastic substance (Japanese Examined Patent Publication (Kokoku) No. 14531/1960);
a method of applying a paste-like substance of a vinyl pyridine and an epoxy compound onto the surface of a cation-exchange membrane, followed by the irradiation with radioactive rays (Japanese Examined Patent Publication (Kokoku) No. 16633/1963);
a method of adhering a sulfonic acid-type high-molecular electrolyte and allylamines onto the surface of the anion-exchange membrane, followed by crosslinking by the irradiation with ionizing radioactive rays (Japanese Examined Patent Publication (Kokoku) No. 4113/1976);
a method of depositing a mixture of a dispersion of an ion-exchange resin and a matrix polymer on the surface of the ion-exchange membrane, the ion-exchange resin having an electric charge of a polarity opposite to that of the ion-exchange membrane (Japanese Unexamined Patent Publication (Kokai) No. 37190/1978, International Patent Application No. 502673/1999);
a method of forming a nonionic layer containing a chemically active moiety, and converting the active moiety into a cationic or anionic exchange group (Japanese Unexamined Patent Publication (Kokai) No. 210638/1985); and
a method in which a sheet obtained by impregnation-polymerizing a polyethylene film with a styrene or a divinyl benzene is held by a stainless steel frame, one side thereof is sulfonated, the sheet is, then, removed, and the remaining portion is chloromethylated, followed by the aminnation (U.S. Pat. No. 3,562,139).
There has further been reported that a bipolar membrane having a low water dissociation voltage can be obtained by applying particular metal ions onto the surfaces of cation- and anion-exchange membranes, and by stacking the the two ion-exchange membranes one upon the other with the application of pressure (Electrochem. Acta, Vol. 31, pp. 1175-1176, 1986). However, the thus prepared bipolar membrane permits the water dissociation voltage to be raised within a relatively early time, and permits air bubbles and water bubbles to evolve between the cation- and anion-exchange membranes. Besides, the bipolar membrane itself is easily split into the cation- and anion-exchange membranes.
There has further been proposed a bipolar membrane in which an inorganic ion-exchange membranes is interposed between the anion- and cation-exchange membranes (Japanese Unexamined Patent Publication (Kokai) Nox. 172557/1994, 172558/1994, 263896/1994, 3051/1995, 11021/1995 and 11022/1995). However, this bipolar membrane has a problem of lacking stability.
There have further been proposed a bipolar membrane obtained by joining an anion-exchange member containing fine particles of a metal oxide and a cation-exchange membrane together (Japanese unexamined Patent Publication (Kokai) No. 269217/1996) and a bipolar membrane obtained by providing an intermediate layer between the anion-exchange membrane and the cation-exchange membrane, the intermediate layer comprising fine particles of a metal oxide and anion exchange groups (Japanese Unexamined Patent Publication (Kokai) No. 87853/1998). These bipolar membranes exhibit considerably favorable properties accompanied, however, by a problem in that the water dissociation voltage increases under a high current density condition.
The present invention is to provide a bipolar membrane which exhibits a low water dissociation voltage for extended periods of time under a high current density condition and a high current efficiency, maintaining good durability without developing blister or peeling of membrane.
DISCLOSURE OF THE INVENTION
In view of the above-mentioned problems, the present inventors have conducted keen study and, as a result, have proposed the invention by discovering the fact that there can be easily obtained a bipolar membrane permitting the water dissociation voltage to rise little under a high current density condition, and featuring a high current efficiency and excellent durability.
That is, the present invention provides a bipolar membrane comprising a cation-exchange membrane and an anion-exchange membrane which are joined together, wherein ion-exchange resin particles having ions of a metal of an atomic number 20 to 90 or having complex ions of said metal are existing on the junction interface between the cation-exchange membrane and the anion-exchange membrane.
The invention further provides a bipolar membrane comprising a cation-exchange membrane and an anion-exchange membrane which are joined together, wherein ion-exchange groups having ions of a metal of an element No. 20 to 90 or having complex ions of said metal are existing on at least one surface facing the junction interface of the cation-exchange membrane and the anion-exchange membrane, and ion-exchange resin particles having ions of a metal of an element No. 20 to 90 or having complex ions of said metal are existing on the junction interface between the cation-exchange membrane and the anion-exchange membrane.
The bipolar membrane according to the invention is obtained by joining the cation-exchange membrane and the anion-exchange membrane together. There is no particular limitation on the cation-exchange membrane, and any known cation-exchange membrane can be used. For example, there can be used a membrane obtained by introducing cation exchange groups such as sulfonic acid groups or carboxylic acid groups into a styrene-divinylbenzene resin or a polysulfone resin. From the standpoint of use of the bipolar membrane, in particular, it is desired to use a cation-exchange membrane having sulfonic acid groups in which the exchange groups are dissociated even under acidic conditions. The cation-exchange membrane may be of any kind and type such as the one of the polymerization type, homogeneous type, nonhomogeneous type, or the one with or without a reinforcing member. Even the ion-exchange membrane such as the one comprising the cation-exchange membrane containing anion exchange groups to some extent can be used as the cation-exchange membrane of the present invention to a sufficient degree provided the transport number of the cations is not smaller than 90%.
Though there is no particular limitation, it is desired that the cation-exchange membrane usually has a thickness of from 10 to 400 &mgr;m and, preferably, from 30 to 200 &mgr;m. From the standpoint of voltage drop and transport number, it is desired that the ion-exchange capacity is from 0.5 to 3.0 meq/g and, more particularly, from 0.7 to 2.5 meq/g. To suppress the bipolar membrane from developing blister, further, it is desired that the surfaces of the cation-exchange membrane is finely coarsened by using a sand-paper or the like.
There is no particular limitation on the anion-exchange membrane used in the invention, and any known anion-exchange membrane can be used. For example, there can be used a membrane obtained by introducing anion exchange groups such as quaternary ammonium groups, pyridinium groups or amino groups into the styrene-divinylbenzene resin or t
Hanada Fumio
Nago Satoshi
Bell Bruce F.
Sherman & Shalloway
Tokoyama Corporation
LandOfFree
Bipolar membrane does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bipolar membrane, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bipolar membrane will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3004809