CA1144520A - Bonding of fibers for diaphragms in electrolytic cells - Google Patents
Bonding of fibers for diaphragms in electrolytic cellsInfo
- Publication number
- CA1144520A CA1144520A CA000309661A CA309661A CA1144520A CA 1144520 A CA1144520 A CA 1144520A CA 000309661 A CA000309661 A CA 000309661A CA 309661 A CA309661 A CA 309661A CA 1144520 A CA1144520 A CA 1144520A
- Authority
- CA
- Canada
- Prior art keywords
- fibers
- improvement
- slurry
- cementing agent
- diaphragm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE:
Diaphragms for electrolytic cells have improved operating efficiency by cementing the diaphragm material which is a fibrous slurry deposited on a screen associated with a cathode, with a fluorinated hydrocarbon bonding agent.
Diaphragms for electrolytic cells have improved operating efficiency by cementing the diaphragm material which is a fibrous slurry deposited on a screen associated with a cathode, with a fluorinated hydrocarbon bonding agent.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention-The present invention pertains to diaphragms for electrolytic cells. More particularly, the present invention pertains to materials of construction for diaphragms for electrolytic cells. Even more particularly, the present inven-tion pertains to the bonding of the fibers of the diaphragm materials.
1. Field of the Invention-The present invention pertains to diaphragms for electrolytic cells. More particularly, the present invention pertains to materials of construction for diaphragms for electrolytic cells. Even more particularly, the present inven-tion pertains to the bonding of the fibers of the diaphragm materials.
2. Prior ~rt-In copending Canadian Patent Application Number 244,710, entitled aThermopLastic Fibers as Separators or Diaphragms in Electrochemical Cells, filed on January 29, 1976, there is disclosed the use of discrete fibers of thermoplastic materials as a diaphragm for use in electrolytic cells. The invention disclosed in the copending application provides suitable replacement or asbestos as a diaphragm material.
~1~45ZO
As is known to those skilled in the art, conventionally asbestos is employed as the diaphragm material. Asbestos has many advantages as a diaphragm material. These advantages have been reported and detailed a plurality of times. Yet, ~hcre exis~ a plurallty oE dlsadvan~a~cs a~endan~ on tho u~o of asbestos diaphragms, such as swelling of the diaphragm, etc.
Although the inventlon of the abovementioned copending application provides more than adequate substitutive materials for asbestos, there still e~ists a need for improving diaphragms.
Contemporaneously, it would be advantageous to improve the fiber diaphragms of the copending application. It is to this to which the present invention is directed.
SUMMARY OF THE INVENTION
In accordance with the present invention, diaphragm materials for use in electrolytic cells have the fibers thereof cemented by incorporating into the fibers a cementing material. The cementin material contemplated for use herein, preferably com~rises a ~luorohydrocarbon.
The~fluorohydrocarbon is used in amounts ranging from about 10% to 30% by weight, based upon the weight of the fibers. The~f~uorohydrocarbon is deployed as a solution thereof in a solvent thereoE, or as a dry powder material.
In practicing the present invention, the diaphragm fibers are contacted with the cement solution or a fiber slurry is admixed with dry cementing agent. After deposition of the fibers on the cathode screen, the screen is washed with water. Thereafter, the diaphragm is heat treated to bond the fibers to each other as well as to the cathode screen.
The present invention is efficacious with respect to asbestos fibers as well as thermoplastic and thermoset fibers.
For a more complete understanding of the presentinvention, reference is made to the following detailed description and accompanying examples.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, diaphragms for electrolytic cells have the fibers thereof cemented to each other, as well as to the screen assoclated with the cathode with a fluorohydrocarbon or other cementing agent.
As is known to those skilled in the art, diaphragms are generally prepared by depositing a fibrous slurry onto acathode support. Usually, the slurry is vacuum deposited to densify and compact the slurry. Such methods of preparing diaphragms, as noted, are well known.
In preparing diaphragms in accordance herewith, any suitable material can be used. Representative materials include, for example, both thermoset and thermoplastic fibers, as well as inorganic fibrous materials. Withln the class of useful fibrous materials are, inter alia, asbestos, polyolefins, polycarbonates, polyesters, polyamide~, and the like, as well as mixtures thereof. Representative compounds include, for example, polyethylene, polypropylene, hexamethylene adipamide and other nylons, polyethylene terephthalate, poly-4-methylpentene-1, poly(tetramethylene) terephthalate, polystyrene-polyvinylidene chloride copolymers, chlorinated polyvinyl chloride, polycarbonates of 2-(4-hydroxymethyl) propane (Bisphenol A), polyphenylene oxide and the like, as well as mixtures thereof.
Preferably, the diaphragm material is asbestos.
.
Because of the hydrophobic nature of the thermo-plastic fibers, as well as the properties of the other fibers upon bonding, it is necessary to include within the internal structure or matrix of the fibers, per se, a hydrophilic material to ensure the wetting ability of the fibers. Any wetting agent that can withstand the processing parameters can be effectively utilized. The wetting agent or surfactant can either be organic or inorganic. Suitable organlc wetting agents are the nonionic and anionic sur-factants.
Useful nonionic surfactants include the oxyalky-lene condensates of ethylene diamine, such as the ethylene oxide-propylene oxide block copolymers prepared by the se~uential additlon thereof to ethylene diamine, and as described in U.S. Patent Number 2,979,528.
Other useful organic wetting agents include poly-I oxyeth~lene alkylphenols, polyoxyethylene alcohols, polyoxy-ethylene esters of fatty acids, polyoxyethylene mercaptans, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyol ourfactants and the like.
Suitable inorganic wetting agents which can be internally incorporated into the thermoplastic fibers include, for example, mica, titanates, such as barium titanate and potassium titanate, talc, vermiculite, titanium dioxide, boron nitrides, kaolinite, diatomaceous earth and clays, as well as mixtures thereof.
Preferred wettlng agents are perfluorinated fatty acids or alcohols or sulfonate-based surfactants.
The use of these wetting agents is more particularly lQ described in the above-referred to copending canadian application n 244,710.
~ he cementing agents herein, as previously noted, preferably are fluorohydrocarbons. Although any cementing agent that is capable of resisting chemical attack in an electrolytic cell can be utilized, the fluorohydrocarbons have been found to be eminently useful. Usually, the cementing agents are utilized where the diaphragm material is non-fluorinated, or wh,ere the fibers, per se, are not self-bonding, but the use of these agents is applicable with all fibers.
The cementing agent or cement is employed in an amount ranging from about ten to thirty percent, by weight thereof, based on the weight of the fiber. Preferably, the cement is employed in an amount ranging from about fifteen to twenty-five percent, by weight thereof, based on the weight of the fiber.
The cementing agent can be employed as a dry powder or as a solution thereof in a suitable non-reactive solvent.
Also, fibers of the cementing agent can be utilized. It has been found that when fibers of the cementing agent are admixed with an asbestos slurry, the fibers remain in the slurry as discrete particles thereof.
When employed as a powder, the agent is admixed with the fiber slurry prior to its deposition on the cathode 1~445ZO
screen.
Where deployed-as a solution, one useful method for applying the solution is achieved by first depositing the fiber slurry on the cathode screen and thereafter, contacting the deposited fibrous diaphragm with the cement solution.
Useful fluorohydrocarbon cementing agents contem-plated for use in the present invention include, for example, fluorinated ethylene and propylene copolymers, polyethylene-tetrafluoroethylene, polyethylenechlorotrifluoroethylene,polychlorotrifluorethylene, polyvinylidene fluoride, copoly-mers of chlorotrifluoroethylene, as well as mixtures thereof.
Suitable solvents for deploying the fluorohydro-carbon as a solution include nitrobenæene, hexachlo~obenzene, and ~he llkc. ~cncrallyj a onc ~o ~cn pcrccn~ y wcigllt, solution is utillzed.
1~4S20 Il~ practicin~ the ~resellt invelltion~ it should be notcd it is also preferred that whcre uscd, the tnerrno-plastic fibers have a fiber di~meter of from about 0.05 to forty microns.
The d:iaphra~ms hcreof are prepared by eithcr:
(a) depositing the slurry, wlth the cernenting agent in adrnixture therewith~ on a cathode screen, or (b) depositing the fibers on the screen and, then, contacting the fibers with the cementing agent.
After the fibers are deposited on the screen, the so-prepared diaphragm is, then, washed with water. It has been found that washing the diaphragm rerno~es electrolytes therefrom. Electrolytes are ordinarily present in the slurry from which the diaphragms are prepared. This is e~pecially true with respect to asbestos diaphragms formed from asbestos slurries.
Furthermore, it has been found that the fallure to wash the diaphragm has a deleterious effect thereupon.
The electrolyte salts, if not washed out, crystall:i~e upon heat treatment. This, in turn, produces a diaphragm with an exc~ssive pore size. Thus, the performance of such diaphragms is well below what it should be thereby negating the utility thereof. By washing the diaphragms after fiber deposition on the screen, the electrolyte salts are remo~ed.
In washing the diaphragm, by any convenient mode, - i 11445ZO
,, distilled water is utilized.
After the diaphragm has been washed with the water, it is, then, heat treated to bond the fibers to each other as well as to the cathode screen.
Heat treating is carrled out at a temperature ranging from about 100C to about 300C for a period of from about one-half to about one hour. This, of course, varies according to the selected fiber used for the diaphragm.
For a more complete understanding of the present invention, reference is made to the following examples thereof. In the examples, which are illustrative rather than limitative of the invention, all parts are by weight, absent indications to the contrary.
EXAMPLE I
To a conventional two percent, by weight, asbestos slurry containing 0.5% by weight, based on the weight of the asbestos, of FLUORAD FC-126* fluorohydrocarbo~ surfactant, is added twenty percent, by weight, based on the weight of the asbestos, of polyethylenechlorotrifluoroethylene powder., The powder is mixed with the slurry to render the slurry unlform.
The slurry is then deposited onto a cathode screen by vacuum deposition substantially as described in Example I
of the above referenced, copendlng canadian application n ~44,710 ~~~~
.
Thereafter, the diaphragm is washed with distille~ water by vacuum suction of the water through the diaphragm. The diaphragm is then dried in an oven at about 100C, to remove excess water, for eight hours.
Thereafter, the diaphragm is heat treated to bond the asbestos fibers to each other as well as to the cathode, at 260C for one hoùr.
The diaphragm is then mounted in a test chlor-alkali cell and brine electrolysis was carried out there-within. The cell having the diaphragm mounted therewithinproduces 130 grams per liter of caustic at 95% current efficiency.
EXAMPLE II
, This example illustrates the use of a cementing agent with a self-bonding fiber.
Following the procedure of Example I of the above referenced, copending Canadian application n 244,710, a polyethylene chlorotrifluoroethylene fiber slurry containing the same surfactant as defined therein is deposited on a cathode screen. After deposition and washing, the fiber-screen assembly is dried in a vacuum oven at 100C for a period of about eight hours to remove excess water. The dried fibers are then impregnated with a one percent solution of poly-ethylene chlorotrifluoroethylene in nitrobenzene at 70C
as a cementing agent. This is achieved by immersing the assembly within the solution. Thereafter, the impregnated fiber-screen assembly is heated at 250C for about one-half hour to bond the fibers to each other as well as to the screen .1 ., 1, ~i C
1~4SZO
The cathode is thcn deployed ln a brine electrolysls test cell. m e cell produced a caustic concentration of 130 grams per liter with a 90~ current effici.ency.
Having, thus, described the inventign, what is claiméd is: .
~1~45ZO
As is known to those skilled in the art, conventionally asbestos is employed as the diaphragm material. Asbestos has many advantages as a diaphragm material. These advantages have been reported and detailed a plurality of times. Yet, ~hcre exis~ a plurallty oE dlsadvan~a~cs a~endan~ on tho u~o of asbestos diaphragms, such as swelling of the diaphragm, etc.
Although the inventlon of the abovementioned copending application provides more than adequate substitutive materials for asbestos, there still e~ists a need for improving diaphragms.
Contemporaneously, it would be advantageous to improve the fiber diaphragms of the copending application. It is to this to which the present invention is directed.
SUMMARY OF THE INVENTION
In accordance with the present invention, diaphragm materials for use in electrolytic cells have the fibers thereof cemented by incorporating into the fibers a cementing material. The cementin material contemplated for use herein, preferably com~rises a ~luorohydrocarbon.
The~fluorohydrocarbon is used in amounts ranging from about 10% to 30% by weight, based upon the weight of the fibers. The~f~uorohydrocarbon is deployed as a solution thereof in a solvent thereoE, or as a dry powder material.
In practicing the present invention, the diaphragm fibers are contacted with the cement solution or a fiber slurry is admixed with dry cementing agent. After deposition of the fibers on the cathode screen, the screen is washed with water. Thereafter, the diaphragm is heat treated to bond the fibers to each other as well as to the cathode screen.
The present invention is efficacious with respect to asbestos fibers as well as thermoplastic and thermoset fibers.
For a more complete understanding of the presentinvention, reference is made to the following detailed description and accompanying examples.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, diaphragms for electrolytic cells have the fibers thereof cemented to each other, as well as to the screen assoclated with the cathode with a fluorohydrocarbon or other cementing agent.
As is known to those skilled in the art, diaphragms are generally prepared by depositing a fibrous slurry onto acathode support. Usually, the slurry is vacuum deposited to densify and compact the slurry. Such methods of preparing diaphragms, as noted, are well known.
In preparing diaphragms in accordance herewith, any suitable material can be used. Representative materials include, for example, both thermoset and thermoplastic fibers, as well as inorganic fibrous materials. Withln the class of useful fibrous materials are, inter alia, asbestos, polyolefins, polycarbonates, polyesters, polyamide~, and the like, as well as mixtures thereof. Representative compounds include, for example, polyethylene, polypropylene, hexamethylene adipamide and other nylons, polyethylene terephthalate, poly-4-methylpentene-1, poly(tetramethylene) terephthalate, polystyrene-polyvinylidene chloride copolymers, chlorinated polyvinyl chloride, polycarbonates of 2-(4-hydroxymethyl) propane (Bisphenol A), polyphenylene oxide and the like, as well as mixtures thereof.
Preferably, the diaphragm material is asbestos.
.
Because of the hydrophobic nature of the thermo-plastic fibers, as well as the properties of the other fibers upon bonding, it is necessary to include within the internal structure or matrix of the fibers, per se, a hydrophilic material to ensure the wetting ability of the fibers. Any wetting agent that can withstand the processing parameters can be effectively utilized. The wetting agent or surfactant can either be organic or inorganic. Suitable organlc wetting agents are the nonionic and anionic sur-factants.
Useful nonionic surfactants include the oxyalky-lene condensates of ethylene diamine, such as the ethylene oxide-propylene oxide block copolymers prepared by the se~uential additlon thereof to ethylene diamine, and as described in U.S. Patent Number 2,979,528.
Other useful organic wetting agents include poly-I oxyeth~lene alkylphenols, polyoxyethylene alcohols, polyoxy-ethylene esters of fatty acids, polyoxyethylene mercaptans, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyol ourfactants and the like.
Suitable inorganic wetting agents which can be internally incorporated into the thermoplastic fibers include, for example, mica, titanates, such as barium titanate and potassium titanate, talc, vermiculite, titanium dioxide, boron nitrides, kaolinite, diatomaceous earth and clays, as well as mixtures thereof.
Preferred wettlng agents are perfluorinated fatty acids or alcohols or sulfonate-based surfactants.
The use of these wetting agents is more particularly lQ described in the above-referred to copending canadian application n 244,710.
~ he cementing agents herein, as previously noted, preferably are fluorohydrocarbons. Although any cementing agent that is capable of resisting chemical attack in an electrolytic cell can be utilized, the fluorohydrocarbons have been found to be eminently useful. Usually, the cementing agents are utilized where the diaphragm material is non-fluorinated, or wh,ere the fibers, per se, are not self-bonding, but the use of these agents is applicable with all fibers.
The cementing agent or cement is employed in an amount ranging from about ten to thirty percent, by weight thereof, based on the weight of the fiber. Preferably, the cement is employed in an amount ranging from about fifteen to twenty-five percent, by weight thereof, based on the weight of the fiber.
The cementing agent can be employed as a dry powder or as a solution thereof in a suitable non-reactive solvent.
Also, fibers of the cementing agent can be utilized. It has been found that when fibers of the cementing agent are admixed with an asbestos slurry, the fibers remain in the slurry as discrete particles thereof.
When employed as a powder, the agent is admixed with the fiber slurry prior to its deposition on the cathode 1~445ZO
screen.
Where deployed-as a solution, one useful method for applying the solution is achieved by first depositing the fiber slurry on the cathode screen and thereafter, contacting the deposited fibrous diaphragm with the cement solution.
Useful fluorohydrocarbon cementing agents contem-plated for use in the present invention include, for example, fluorinated ethylene and propylene copolymers, polyethylene-tetrafluoroethylene, polyethylenechlorotrifluoroethylene,polychlorotrifluorethylene, polyvinylidene fluoride, copoly-mers of chlorotrifluoroethylene, as well as mixtures thereof.
Suitable solvents for deploying the fluorohydro-carbon as a solution include nitrobenæene, hexachlo~obenzene, and ~he llkc. ~cncrallyj a onc ~o ~cn pcrccn~ y wcigllt, solution is utillzed.
1~4S20 Il~ practicin~ the ~resellt invelltion~ it should be notcd it is also preferred that whcre uscd, the tnerrno-plastic fibers have a fiber di~meter of from about 0.05 to forty microns.
The d:iaphra~ms hcreof are prepared by eithcr:
(a) depositing the slurry, wlth the cernenting agent in adrnixture therewith~ on a cathode screen, or (b) depositing the fibers on the screen and, then, contacting the fibers with the cementing agent.
After the fibers are deposited on the screen, the so-prepared diaphragm is, then, washed with water. It has been found that washing the diaphragm rerno~es electrolytes therefrom. Electrolytes are ordinarily present in the slurry from which the diaphragms are prepared. This is e~pecially true with respect to asbestos diaphragms formed from asbestos slurries.
Furthermore, it has been found that the fallure to wash the diaphragm has a deleterious effect thereupon.
The electrolyte salts, if not washed out, crystall:i~e upon heat treatment. This, in turn, produces a diaphragm with an exc~ssive pore size. Thus, the performance of such diaphragms is well below what it should be thereby negating the utility thereof. By washing the diaphragms after fiber deposition on the screen, the electrolyte salts are remo~ed.
In washing the diaphragm, by any convenient mode, - i 11445ZO
,, distilled water is utilized.
After the diaphragm has been washed with the water, it is, then, heat treated to bond the fibers to each other as well as to the cathode screen.
Heat treating is carrled out at a temperature ranging from about 100C to about 300C for a period of from about one-half to about one hour. This, of course, varies according to the selected fiber used for the diaphragm.
For a more complete understanding of the present invention, reference is made to the following examples thereof. In the examples, which are illustrative rather than limitative of the invention, all parts are by weight, absent indications to the contrary.
EXAMPLE I
To a conventional two percent, by weight, asbestos slurry containing 0.5% by weight, based on the weight of the asbestos, of FLUORAD FC-126* fluorohydrocarbo~ surfactant, is added twenty percent, by weight, based on the weight of the asbestos, of polyethylenechlorotrifluoroethylene powder., The powder is mixed with the slurry to render the slurry unlform.
The slurry is then deposited onto a cathode screen by vacuum deposition substantially as described in Example I
of the above referenced, copendlng canadian application n ~44,710 ~~~~
.
Thereafter, the diaphragm is washed with distille~ water by vacuum suction of the water through the diaphragm. The diaphragm is then dried in an oven at about 100C, to remove excess water, for eight hours.
Thereafter, the diaphragm is heat treated to bond the asbestos fibers to each other as well as to the cathode, at 260C for one hoùr.
The diaphragm is then mounted in a test chlor-alkali cell and brine electrolysis was carried out there-within. The cell having the diaphragm mounted therewithinproduces 130 grams per liter of caustic at 95% current efficiency.
EXAMPLE II
, This example illustrates the use of a cementing agent with a self-bonding fiber.
Following the procedure of Example I of the above referenced, copending Canadian application n 244,710, a polyethylene chlorotrifluoroethylene fiber slurry containing the same surfactant as defined therein is deposited on a cathode screen. After deposition and washing, the fiber-screen assembly is dried in a vacuum oven at 100C for a period of about eight hours to remove excess water. The dried fibers are then impregnated with a one percent solution of poly-ethylene chlorotrifluoroethylene in nitrobenzene at 70C
as a cementing agent. This is achieved by immersing the assembly within the solution. Thereafter, the impregnated fiber-screen assembly is heated at 250C for about one-half hour to bond the fibers to each other as well as to the screen .1 ., 1, ~i C
1~4SZO
The cathode is thcn deployed ln a brine electrolysls test cell. m e cell produced a caustic concentration of 130 grams per liter with a 90~ current effici.ency.
Having, thus, described the inventign, what is claiméd is: .
Claims (9)
1. In a process for the manufacture of a diaphragm for an electrolytic cell of the type wherein a fibrous slurry is deposited on a screen associated with a cathode, the improvement which comprises:
(a) cementing the fibers of the slurry to each other by contacting said fibers with a fluorohydrocarbon cementing agent, and subsequently (b) washing the diaphragm with distilled water after deposition of the so-cemented slurry to remove electrolyte salts therefrom.
(a) cementing the fibers of the slurry to each other by contacting said fibers with a fluorohydrocarbon cementing agent, and subsequently (b) washing the diaphragm with distilled water after deposition of the so-cemented slurry to remove electrolyte salts therefrom.
2. The improvement of claim 1 which further comprises:
heat treating the diaphragm after washing .
heat treating the diaphragm after washing .
3. The improvement of claim 1, wherein the slurry is an asbestos slurry.
4. The improvement of claim 1, 2 or 3, wherein the fibers are contacted with the polyfluorohydrocarbon cementing agent by admixing the slurry with the cementing agent in a dry powder form, prior to deposition on the cathode.
5. The improvement of claim 1, 2 or 3, wherein the fibers are contacted with the polyfluorohydrocarbon cementing agent in solution after the slurry has been deposited on the cathode.
6. The improvement of claim 1 wherein the cementing agent is employed in an amount ranging from about ten to thirty percent, by weight thereof, based on the weight of the fibers.
7. The improvement of claim 5 wherein the cementing agent is employed in an amount ranging from about fifteen to twenty-five percent by weight thereof, based on the weight of the fibers.
8. The improvement of claim 1 wherein the cementing agent is selected from the group consisting of fluorinated ethylene and propylene copolymers, polyethylene tetrafluoroethylene, polyethylenechlorotrifluoroethylene, copolymers of chlorotrifluoroethylene, polychlorotrifluoro-ethylene, polyvinylidene fluoride and mixtures thereof.
9. The improvement of claim 8 wherein the cementing agent is polyethylenechlorotrifluoroethylene.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US82597477A | 1977-08-19 | 1977-08-19 | |
| US825,974 | 1977-08-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1144520A true CA1144520A (en) | 1983-04-12 |
Family
ID=25245363
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000309661A Expired CA1144520A (en) | 1977-08-19 | 1978-08-18 | Bonding of fibers for diaphragms in electrolytic cells |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1144520A (en) |
-
1978
- 1978-08-18 CA CA000309661A patent/CA1144520A/en not_active Expired
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| MKEX | Expiry |