Gasket structure

Abstract

A gasket structure for multi-section electrolytic cells and electric dializers, which is capable of preventing the leakage of the electrolyte by a combination of a resilient soft material and a hard material and preventing deformation of guide passages adjacent liquid inlet and outlet openings.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to gasket structures for multi-sectional electrolytic cells and dialyzers and, more particularly, to gasket structures which reduces the thickness of electrolytic sections or compartments of the electrolytic cells and dialyzers to reduce the size of the cells and dialyzers thereby providing an economic advantage of reducing the voltage in use. More specifically, the invention concerns multi-sectional electrolytic cells and dialyzers which are produced by stacking gasket structures to constitute electrolytic or dialytic cells, electrodes and partition walls and pressing the stack with a press, for instance a filter press, to integrally fix the individual parts in respective positions to thereby form inside electrolytic or dialytic cells and common liquid passages.

2. Description of the Prior Art

In the usual electrolytic or dialytic cell structures constructed with gasket sheets, the sheets themselves should serve as the gasket, so that they are made of resilient materials. Therefore, guide passages in the individual cells to which the common liquid ducts or passages are open are likely to be deformed. Also, it is extremely difficult to prevent the leakage of the liquid.

By way of example, in a known cell structure in which the individual electrolytic sections or compartments formed by respective frame members are mutually communicated with common passages open to the individual sections at respective guide passages defined by respective spacers, ion exchange films or walls on opposite sides of the individual passage ways and soft material frame members adjacent to the ion exchange walls partly migrate into recesses formed in the frame members for the guide passages, causing leakage between adjacent cells. It is extremely difficult to prevent this leakage which is inherent in the above cell structure, so that safe operation of the cell cannot be expected.

SUMMARY OF THE INVENTION

An object of the invention is to provide a gasket structure which consists of a combination of resilient soft material parts and hard material parts, and with which liquid leakage can be sufficiently prevented to ensure safe operation of the cell structure.

The invention features a gasket structure which comprises a first gasket sub-structure consisting of a sheet of a resilient, soft material having an excellent electric insulating property and formed with holes constituting common passages and a central opening and guide wall members made of a hard material difficult to deform and having an excellent electric insulating property, said members being formed with respective holes each communicating with the corresponding one of said holes formed in said sheet and with a guide passage defined by said sheet and the corresponding one of said members. The gasket also includes a pair of second gasket substructures each including a second sheet of a hard material difficult to deform and having an excellent electric insulating property and a third sheet of a soft material, said second and third sheets being formed with holes forming said common passages and respective openings forming said compartment, the first sub-structure is sandwiched between a pair of the second sub-structures. If necessary, the second gasket sub-structure may include a further sheet of a resilient, soft material having an excellent electric insulating property and formed with holes constituting the afore-said common passages and a central opening constituting the afore-said compartment, said further sheet being provided on the side of the second sheet of the hard material opposite to the third sheet of the soft material. The term "hard material" herein means a material having a such hardness that the hard material sheet itself is not substantially compressed when the associated soft material sheet is compressed when pressed by the hard sheet with such a fastening force as not to cause liquid leakage. In other words, the hard material and soft material are distinguished from each other according to the compressive strain; the soft material should be compressed by pressing, whereas the hard material should not be substantially compressed. More specifically, when the soft material sheet is compressed by about 10 percent by pressing a stack of hard and soft material sheets, the hard material sheet should not be compressed more than 0.5 percent, desirably not more than 0.1 percent. Also, the guide wall members which are made of a hard material should be thinner than the soft material sheet.

By stacking gasket structures mentioned above together with electrodes and partition wall memberes and integrally securing the stack parts to one another by means of a press, for instance a a filter press, it is possible to produce an electrolitic or dialytic cell structure without deforming the guide passages, so that the leakage within the cell structure and leakage to the outside of the structure may be sufficiently prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a gasket sub-structure according to the invention.

FIG. 2 is a section taken along line 2--2 in FIG. 1.

FIG. 3 is a perspective view of a different gasket sub-structure according to the invention and which provides guide passages.

FIG. 4 is a section taken along line 4--4 in FIG. 3.

FIG. 5 is a sectional view showing an electrolytic cell structure constructed by using gasket structures according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one preferred embodiment of the invention, guide passages of one electrolytic or dialytic section or compartment in communication with supply and exhaust liquid passages are defined by respective guide wall members of a hard material difficult to deform, said guide wall members being fitted in a sheet thicker than the wall members and made of a resilient soft material. The sheet of soft material is sandwiched between two sheets of a hard material. Thus, when the structure is compressed, the closeness of the contact between the hard and soft material sheets is enhanced without causing the substantial deformation of the guide passages, thus leakage of the liquid within the cell structure and to the outside of the cell structure may be sufficiently prevented. In order to provide an enhanced leakage prevention effect according to the invention, the resilient soft material sheets are desirably compressed by about 5 to 20 percent. Further, the guide wall members which are thinner than the soft material sheet member in which they are fitted should be brought into contact with the two opposite side hard material sheets when the afore-said soft material is compressed by pressing. Preferably, the thickness of the guide wall members is substantially equal to the thickness of the compressed soft material sheet compressed by about 5 to 20 percent. Since the guide passages are not deformed, the flow resistance in them may be maintained constant.

The invention will now be described in conjunction with an embodiment thereof with reference to the accompanying drawing. Referring to FIGS. 1 and 2, reference numeral 11 designates a rectangular sheet made of a hard material and difficult to deform, and reference numeral 12 designates a rectangular sheet made of a soft and resilient material. Both these sheets are electrically insulating. These sheets 11 and 12 are bonded together. They are formed near their four corners with holes 13, 14, 15 and 16 which constitute respective common ducts or passages common for them and the other sheet members. They are also formed with central rectangular openings 17 and 18 to form an electrolytic cell or compartment. The overall gasket structure is generally designated at 5.

Referring now to FIGS. 3 and 4, there is shown a different gasket structure 6, which comprises by a rectangular sheet 21 of a soft and resilient material. It is formed near its two opposite corners with holes 24 and 25. It is also formed with a central rectangular opening 27 to form an electrolytic compartment. At its other opposite corners than those mentioned above with recesses or depressions 19 and 20 terminate in the central opening 27. Elongate wall members 28 and 29 made of a material slightly harder than the sheet 21 are fixed in position in respective upper and lower portions of the opening 27. They serve to define respective guide passages 30 and 31. They are formed in their portions occupying the recesses 19 and 20 with respective holes 23 and 26. The dimensions and shape of the central rectangular window defined by the sheet 21 and the wall members 28 and 29 are designed to be the same as those of the central opening of the structure 5. Thus, when the individual structures are assembled together, their respective openings and windows define electrolytic cells or compartments.

In accordance with the invention, such hard or quasi-hard synthetic resins such as hard vinyl chloride, heat-resisting vinyl chloride, polypropylene, hard polyethylene, "polyacetal" and glass fiber reinforced resins as well as ebonite which are difficult to deformed and are excellent electrical insulators are used as the hard material of the sheet 11 and wall members 28 and 29, while such resilient materials such as soft vinyl chloride, soft polyethylene and various rubbers which are soft and have excellent electric insulating properties are used for the sheets 12 and 21.

FIG. 5 shows, in section, an electrolytic cell structure assembled from the afore-described gasket structures according to the invention. A gasket structure 5 having holes 13, 14, 15 and 16 for the common passages 35 and 36, for instance the one nearest to the left end, has its one side in contact with one side of a structure 6 having guide walls 28 and 29 and holes 23 and 26, whose other side is in turn in contact with another gasket structure 5b, which is the same as but inverted with respect to the first structure 5. This gasket structures comprises a gasket group, which has its one side in contact with a composite electrode 38 and its other side in contact with a partition wall 39, which is in turn in contact with a second gasket group having the same construction as but inverted with respect to the first. The second gasket group is in turn in contact with a second composite electrode. In this manner, cathodic and anodic electrolytic compartments 40 and 41 are formed with respective gasket groups individually consisting of two gasket structures 5 and one gasket structure 6 alternately inverted, and which are separated with alternately intervening composite electrode 38 and partition wall 39. Each composite electrode 38 has its cathode side define a cathodic compartment and its anode side define an anodic compartment. The electrodes 38 and partition walls 39 are surrounded by respective outer frame members 45 and 46 respectively formed with holes 43 and 44 for the common passages 35 and 36. Appropriate spacers 47 of material such as soft vinyl chloride, polyethylene, polypropylene and "Saran" (a tradename) are disposed within the individual compartments 40 and 41. The sheets, electrodes and partition wall members stacked in the afore-described manner are integrated together by pressing the stack with a press, thus producing an electrolytic cell strucure. In the electrolytic cells, the materials of the various parts should be selected by taking the operating cell temperature, electrolyte materials and electrolitic products into consideration. In the electrolytic cell structure using the gasket structures according to the invention, most of the inner walls in contact with the electrolyte are made of a hard material, so that the resistance to chemicals and to heat required for the soft materials according to the invention may be alleviated. Also, it is possible to select inexpensive materials. Thus, the invention is particularly beneficial, for instance, for table salt electrolytic cells.

The following example is given to illustrate the invention.

An electrolytic cell structure as shown in FIG. 5 was constructed with a press. Heat-resisting vinyl chloride was used for the sheets 11, nitrile rubber for the sheets 12 and 21, and hard polyethylene rubber sheets for the wall members 28 and 29. The sheets 11 had a thickness of 1.0 mm, the sheets 12 a thickness of 0.2 mm, the sheets 21 a thickness of 1.65 mm, and the wall members a thickness of 1.50 mm. The dimensions of the gaskets were selected to be 300 mm .times. 600 mm, while the dimensions of the electrolytic compartments were made to be 200 mm .times. 300 mm. The electrodes 38 each consisted of a titanium plate 2.8 mm thick having one side thereof plated with platinum to a thickness of 1.0 mm to provide a cathode and the other side plated with nickel to provide an anode. They were surrounded by nitril rubber outer frame members 45 and 46 and provided with leads 49. The partition walls 39 were each consisted of a positive ion substituted film based on stylene and divinyl benzene and had a thickness of 1.0 mm. Their outer dimentions were 240 mm .times. 340 mm, and they were surrounded by the outer frame members 48 made of a nitril rubber sheet formed with holes 42 and having the same thickness as them. For the spacers 47, polypropylene fiber was used. The common passages 44 constituted by holes 13, 23, 14 and 16, 26, 15 (passage of holes 13 being unseen) communicated with cathodic compartments, while the common pasages 45 constituted by holes 14, 24, 13 and 15, 25, 16 (passage of holes 15 being unseen) communicated with anodic compartments. Since the successive gasket groups each of gasket structures 5, 6 and 5b are alternately inverted, the cathodic and anodic compartments 40 and 41 are alternately defined, so that the liquids in both the former and latter compartments will not mix in the passages, and the exchange of ions is effected through the partition walls 39 separating adjacent cathodic and anodic compartments.

The electrolytic cell structure of the above example was operated for 24 hours under predetermined conditions, namely using 5N. NaCl and 5N. NaOH respectively as cathodic and anodic liquids, at a liquid temperature of 70.degree. C, at a current density of 15 A/dm.sup.2 and at an average speed of liquid flow through the electrolytic compartments of 10 cm/sec. As a result, no leakage of electrolitic liquids to the outside of the cell structure was found. Also, no liquid leakage within the cell structure was recognized from changes in the chlorine ion concentration in the anodic liquid as given in the Table below. Further, no bending or deformation of the parts defining the guide passages were found.

TABLE ______________________________________ Operating time (in hours) 0 6 12 18 24 Chlorine ion concentration in 25 23 21 21 20 anodic liquid (in ppm) ______________________________________

Claims

I claim:

1. A gasket structure for preventing leaks, said gasket structure comprising at least three gasket substructures, at least two of said substructures each including a first sheet of hard material and a second sheet of soft material wherein said sheet of soft material is thinner than said sheet of hard material and wherein said first and second sheets have a central opening and guide passages formed therein; said at least two gasket substructures being held together by pressure sufficient to compress said soft sheets without substantially compressing said hard sheets whereby leaks are prevented and said central opening and guide passages are not deformed and said third gasket substructure includes a sheet of soft resilient material and guide wall members of hard, resilient material said third gasket substructure having a central opening and guide passages corresponding to said central opening and guide passages formed by said at least two gasket substructures wherein said guide wall members are positioned within the central opening of said soft sheet and at least one of the guide passages of said third gasket substructures commuincates with said central opening.

2. The gasket of claim 1 wherein said third gasket substructure is sandwiched between said at least two gasket substructures.

3. The gasket structure of claim 2 wherein each of said at least two gasket substructures are inverted with respect to the succeeding and/or preceeding said at least two gasket substructures.