CA1114276A - Method of obtaining membrane-type separators - Google Patents
Method of obtaining membrane-type separatorsInfo
- Publication number
- CA1114276A CA1114276A CA307,758A CA307758A CA1114276A CA 1114276 A CA1114276 A CA 1114276A CA 307758 A CA307758 A CA 307758A CA 1114276 A CA1114276 A CA 1114276A
- Authority
- CA
- Canada
- Prior art keywords
- sandwich
- grafting
- film
- heating element
- activated
- 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
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/38—Graft polymerization
- B01D2323/385—Graft polymerization involving radiation
Landscapes
- Cell Separators (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE :
The present invention relates to a method for the production of membrane battery separators by grafting a vinyl monomer to a polyolefin film, activated by ultraviolet irradiation, and heating the film. The grafting is effected in a five-layer sandwich which com-prises the activated polyolefin film, covered from both sides with cellulose material, impregnated with the monomer or its solution and pressed from each side by an inert pol-ymer band enclosing the reaction space. The sandwich is then pressed from 10 to 45 minutes against a heater with a pressure towards the surface of the heating element of from 10 to 30 g/cm2, the layers of the sandwich being bands endless in length, the sandwich being passed over the sur-face of the heating element at a velocity of 1 to 100 m/hour.
The present invention relates to a method for the production of membrane battery separators by grafting a vinyl monomer to a polyolefin film, activated by ultraviolet irradiation, and heating the film. The grafting is effected in a five-layer sandwich which com-prises the activated polyolefin film, covered from both sides with cellulose material, impregnated with the monomer or its solution and pressed from each side by an inert pol-ymer band enclosing the reaction space. The sandwich is then pressed from 10 to 45 minutes against a heater with a pressure towards the surface of the heating element of from 10 to 30 g/cm2, the layers of the sandwich being bands endless in length, the sandwich being passed over the sur-face of the heating element at a velocity of 1 to 100 m/hour.
Description
Z7~
This invention relates to a me-thod for -the produc-tion of membrane separator~ for alkali accumulator bat-teries.
A method for the production of membrane separator~ is known(US Patent No. 3427206), according -to which a gamma-ray irradiated polyethylene film is wound-up together with cellulose cloth in a multi-layer spool, and iS -then immersed into a vessel containing a monomer, which is grafted to the polyethylene under the action of gamma-irradiation dur:lng 70 to 130 hours.
~ he drawbacks of this me-thod are its rather slow rate, the non-uniform grafting along the length of the film, the impossibility to effect in production-line conditions~ as well a~ the necessity to use expensive and dangerous gamma-ray source~.
~ n attempt to improve -this method is disclosed in West-German Patent Np. 2144253 (16.03.1972). According to i-t, the process of grafting is effected in a pack compri~ing tQn layers of polymer material, which are insulated in between by gla~s partitions. The grafting monomer is applied in advance to the polymer material, the pack is closed and subjected to irradiation with X- or gamma-rays in a medium of iner-t gas or vacuum. Exept for the posslbili-ty of better temperature con-trol in a thinner layer, this method features all drawbacks of the aforementioned.
According to another method for the production of mem-brane separators for alkali batteries (US Patent No. 3.955.014), the polyethylene film, which is irradiated with UV light, is wound-up together with cellulose''cloth or paper in a multi-layer spool, which is then impregnated with methacrylic acid, being grafted to the polyethylene film by heating at 70 to 90C during 60 to 90 min. ' ~ he drawbac~s of this method lie in the difficulties of dissipating the reaction heat, the non-uniform grafting along the length of the film, as well as in the interrupted character of the process.
Z7~
According to an East-German Pa-tent (DD~ No. 89244, 12.04.1972) J the wounding-up of a spool is avoided, and -the graf-ting is effected on a layer of polymer film, which is placed in a pack between -two surface3 of thin cellulose material, impregna~
-ted with the monomer and enclosed between two metal surfaces.
The polymer foil, which is grafted in advance, is proces~ed in a solution of an initia-tor (peroxide~q or azo-compounds)~ The at-tai-ned degree of grafting after heating during 8 to 10 hours at 70 C
does not exceed ~0~. The use of an initiator appears a~ a draw-back of the method, while -the low degree of grafting makes it inapplicabl~ for the production of grafted membranes of high ionic conductance.
For the correct operation of the alkali bat-tery, the resistance of the membrane separators in 40~ potassium hydroxide at 22C must be from 0.06 to 0.15 Ohm.cm2, depending on the pur-pose of the battery, and the deviations from the average value of the resistance must not exceed + 30%. This requires the develop-ment of a method, which avoids all aforementioned drawbacks.
It is, -therefore, a general object of the present in-vention to provide a method for the production of membrane ~epara-tors, which ensure a high degree of grafting (over 80%) the polye-thylene film9 as well as a great uniformity along the length and width of the film.
The gist of the inven-tion lies in the grafting of a vinyl monomer to a polyole~in film7 activated by UV irradiation, the grafting being effected in a five-layer sadwich, comprising an activated polyolefin film, covered from both sides by cellulose material impregnated with the monomer or its solution and pressed form each side by an inert polymer band, enclosin~ the reaction 3 space. me cellulose material u~ as a carrier of the mono~ is bleached and non-finished cloth from natural cotton, such as cheese cloth, with a thick ness of 150 to 200 mlcrons and a density of about 10 fibres per cenb~ter.
.~
The material of -the .inert polymer foil is a ~biaxialJ.y oriented polyester film with a thickness oE 80 to 150 microns. The layers of the sandwich are not limited in length, and the sandwich is transported over the surEace of a heating element at a constant velocity of 1 to 100 m/hour at a pressure from 10 to 30 g/cm2 and temperature from 85 to 95C, which is maintained at an accuracy of + 1C for 10 to 45 minutes.
The basic advantages of this method is that the grafting proceed isothermally, and as a result, the produced sep-arator film is featured by a high uniformity of its properties, as well as by the possibility for continuous production-line use of the process and its total automation. Moreover, conditions provided to reduce to a minimum the process waste, to reduce the monomer consumption, to reduce the quantity of materials to be renderea harmless, as well as for its total securing and hygienization.
For a better understanding of the invention, reference should be made to several examples, which are intended to explain it rather than to limit its scope.
EXAMPLE I.
The low density polyethylene film, activated by UV
irradiation, with a density of about 0.925 g/cm , a melt index of about 2 g/10 min and a thickness of about 35 microns is covered from both sides with well dried paper of bleached cellulose with a weight of about 20 g/m2 and a density of about 0.3 g/cm3, which does not contain any impregnators, fillers, pigments or other ad-mixtures. Each of both paper layers is impregnated with about 0.3 .
to 0.05 lit/m2 distilled methacrylic acid, containing less than 5 microgrammes per liter inhibitor, and then each paper layer is covered by a polyester film with a thichness of 80 to 150 microns.
The obtained five-layer sandwich is pressed tightly to a heater, heated at 88 + 1C at a pressure of 10 to 20 g/cm during 25 min for the ac-complishment of the polymerization process~ The grafted polyethylene film is alkalized in 5 to 10~ p~sium hydroxide at .
, ~, ~ 3 -. . ~ . .
.
, .
, . .
~$~ '7~
60 to 70C during 20 to 30 minute~. The io~c resistance of ~he thus produced membrane separator in 400~o potassium hydroxide at 22~C is less than 0.12 ohms.cm , the degree of grafting determined by the increase of the film weight is higher than 8~% while the tensile strenght of the dry film is higher than 150 kg/cm2.
Example II.
The five-layer sandwich not limited in length, prepared in accordance with example I, is passed under pressure over one or more heating sur~aces (flat or rounded), heated at 88 + l C
at such a velocity as to endure a stay of the sandwich over the heating surface for about 20 minutes. After the alkalization, the produced membrane ~eparator obtains properties; as described in ~xample I.
~xample III.
~he grafting is e~fected in accordance with examples I
or II, with the difference, -that the stay over the heater is 15 to 18 minutes. The resistance of the membrane separator after its alkalization is from 0.20 to 0.25 ohms.cm2, the degree of grafting is about 70%, while their tensile streng-th is higher than 180 kg/cm2.
Example IV.
The grafting i9 effected in accordance with examples I or II, however with the difference, tha-t the temperature of the heater is 85 + 1C, while the stay duration of the sandwich over the heater is 35 to 40 minutes. lhe properties of -the grafted film after its alkalization are as indicated in example I, however the tensile strength attaining up to 220 kg/cm2.
Exam~le V.
~he grafting is effected in accordance with examples I to IV, however with the difference, that instread of paper there is used non-finished cloth from natural bleached co-tton, such as - . : . , :
'7Ç~
~heese cl~th, wi.~h a 'chicl~ess o:E 150 to 200 microns and a density of 8 to 10 fibres per cm. '~he produced membrane separator i~ featured by -the corresponding characteristics, a~ indica-ted in exampleY
I to IV, inclusively Example VI.
The grafting is effected in accordance with examples I, II or V, however instead of lOO~o distilled methacrylie acid there is used 70-80~o solution in toluene or xylene. The produeed membrane separator is featured by the characteristics indicated in example I.
Example VII.
~ he grafting is effeeted in accordance with examples I, II or V, however instead of 100~ distilled methacrylic acid there i9 used its 85... 95yo solu-tion in tetraehloromethane. ~he produeed membrane separator is featured by the characteristics in-dicated in example I.
Example VIII.
qlhe grafting is effected in aceordanee with examples I, II, V, VI or VII~ however with -the differenee, tha-t the thick-ness o~ the polyethylene film is 80 microns instead of 35 microns,the number of cloth or paper layers on each side of the polye-thylene film is -two instead of one, the quantity of methacrylic acid or its solutions is from 0.5 to 0.9 lit/m2, while the duration of stay is about 45 minutes, qlhe resistance of the produced membrane separator is abou-t 0.3 ohms~cm .
.
- . . . .
.
This invention relates to a me-thod for -the produc-tion of membrane separator~ for alkali accumulator bat-teries.
A method for the production of membrane separator~ is known(US Patent No. 3427206), according -to which a gamma-ray irradiated polyethylene film is wound-up together with cellulose cloth in a multi-layer spool, and iS -then immersed into a vessel containing a monomer, which is grafted to the polyethylene under the action of gamma-irradiation dur:lng 70 to 130 hours.
~ he drawbacks of this me-thod are its rather slow rate, the non-uniform grafting along the length of the film, the impossibility to effect in production-line conditions~ as well a~ the necessity to use expensive and dangerous gamma-ray source~.
~ n attempt to improve -this method is disclosed in West-German Patent Np. 2144253 (16.03.1972). According to i-t, the process of grafting is effected in a pack compri~ing tQn layers of polymer material, which are insulated in between by gla~s partitions. The grafting monomer is applied in advance to the polymer material, the pack is closed and subjected to irradiation with X- or gamma-rays in a medium of iner-t gas or vacuum. Exept for the posslbili-ty of better temperature con-trol in a thinner layer, this method features all drawbacks of the aforementioned.
According to another method for the production of mem-brane separators for alkali batteries (US Patent No. 3.955.014), the polyethylene film, which is irradiated with UV light, is wound-up together with cellulose''cloth or paper in a multi-layer spool, which is then impregnated with methacrylic acid, being grafted to the polyethylene film by heating at 70 to 90C during 60 to 90 min. ' ~ he drawbac~s of this method lie in the difficulties of dissipating the reaction heat, the non-uniform grafting along the length of the film, as well as in the interrupted character of the process.
Z7~
According to an East-German Pa-tent (DD~ No. 89244, 12.04.1972) J the wounding-up of a spool is avoided, and -the graf-ting is effected on a layer of polymer film, which is placed in a pack between -two surface3 of thin cellulose material, impregna~
-ted with the monomer and enclosed between two metal surfaces.
The polymer foil, which is grafted in advance, is proces~ed in a solution of an initia-tor (peroxide~q or azo-compounds)~ The at-tai-ned degree of grafting after heating during 8 to 10 hours at 70 C
does not exceed ~0~. The use of an initiator appears a~ a draw-back of the method, while -the low degree of grafting makes it inapplicabl~ for the production of grafted membranes of high ionic conductance.
For the correct operation of the alkali bat-tery, the resistance of the membrane separators in 40~ potassium hydroxide at 22C must be from 0.06 to 0.15 Ohm.cm2, depending on the pur-pose of the battery, and the deviations from the average value of the resistance must not exceed + 30%. This requires the develop-ment of a method, which avoids all aforementioned drawbacks.
It is, -therefore, a general object of the present in-vention to provide a method for the production of membrane ~epara-tors, which ensure a high degree of grafting (over 80%) the polye-thylene film9 as well as a great uniformity along the length and width of the film.
The gist of the inven-tion lies in the grafting of a vinyl monomer to a polyole~in film7 activated by UV irradiation, the grafting being effected in a five-layer sadwich, comprising an activated polyolefin film, covered from both sides by cellulose material impregnated with the monomer or its solution and pressed form each side by an inert polymer band, enclosin~ the reaction 3 space. me cellulose material u~ as a carrier of the mono~ is bleached and non-finished cloth from natural cotton, such as cheese cloth, with a thick ness of 150 to 200 mlcrons and a density of about 10 fibres per cenb~ter.
.~
The material of -the .inert polymer foil is a ~biaxialJ.y oriented polyester film with a thickness oE 80 to 150 microns. The layers of the sandwich are not limited in length, and the sandwich is transported over the surEace of a heating element at a constant velocity of 1 to 100 m/hour at a pressure from 10 to 30 g/cm2 and temperature from 85 to 95C, which is maintained at an accuracy of + 1C for 10 to 45 minutes.
The basic advantages of this method is that the grafting proceed isothermally, and as a result, the produced sep-arator film is featured by a high uniformity of its properties, as well as by the possibility for continuous production-line use of the process and its total automation. Moreover, conditions provided to reduce to a minimum the process waste, to reduce the monomer consumption, to reduce the quantity of materials to be renderea harmless, as well as for its total securing and hygienization.
For a better understanding of the invention, reference should be made to several examples, which are intended to explain it rather than to limit its scope.
EXAMPLE I.
The low density polyethylene film, activated by UV
irradiation, with a density of about 0.925 g/cm , a melt index of about 2 g/10 min and a thickness of about 35 microns is covered from both sides with well dried paper of bleached cellulose with a weight of about 20 g/m2 and a density of about 0.3 g/cm3, which does not contain any impregnators, fillers, pigments or other ad-mixtures. Each of both paper layers is impregnated with about 0.3 .
to 0.05 lit/m2 distilled methacrylic acid, containing less than 5 microgrammes per liter inhibitor, and then each paper layer is covered by a polyester film with a thichness of 80 to 150 microns.
The obtained five-layer sandwich is pressed tightly to a heater, heated at 88 + 1C at a pressure of 10 to 20 g/cm during 25 min for the ac-complishment of the polymerization process~ The grafted polyethylene film is alkalized in 5 to 10~ p~sium hydroxide at .
, ~, ~ 3 -. . ~ . .
.
, .
, . .
~$~ '7~
60 to 70C during 20 to 30 minute~. The io~c resistance of ~he thus produced membrane separator in 400~o potassium hydroxide at 22~C is less than 0.12 ohms.cm , the degree of grafting determined by the increase of the film weight is higher than 8~% while the tensile strenght of the dry film is higher than 150 kg/cm2.
Example II.
The five-layer sandwich not limited in length, prepared in accordance with example I, is passed under pressure over one or more heating sur~aces (flat or rounded), heated at 88 + l C
at such a velocity as to endure a stay of the sandwich over the heating surface for about 20 minutes. After the alkalization, the produced membrane ~eparator obtains properties; as described in ~xample I.
~xample III.
~he grafting is e~fected in accordance with examples I
or II, with the difference, -that the stay over the heater is 15 to 18 minutes. The resistance of the membrane separator after its alkalization is from 0.20 to 0.25 ohms.cm2, the degree of grafting is about 70%, while their tensile streng-th is higher than 180 kg/cm2.
Example IV.
The grafting i9 effected in accordance with examples I or II, however with the difference, tha-t the temperature of the heater is 85 + 1C, while the stay duration of the sandwich over the heater is 35 to 40 minutes. lhe properties of -the grafted film after its alkalization are as indicated in example I, however the tensile strength attaining up to 220 kg/cm2.
Exam~le V.
~he grafting is effected in accordance with examples I to IV, however with the difference, that instread of paper there is used non-finished cloth from natural bleached co-tton, such as - . : . , :
'7Ç~
~heese cl~th, wi.~h a 'chicl~ess o:E 150 to 200 microns and a density of 8 to 10 fibres per cm. '~he produced membrane separator i~ featured by -the corresponding characteristics, a~ indica-ted in exampleY
I to IV, inclusively Example VI.
The grafting is effected in accordance with examples I, II or V, however instead of lOO~o distilled methacrylie acid there is used 70-80~o solution in toluene or xylene. The produeed membrane separator is featured by the characteristics indicated in example I.
Example VII.
~ he grafting is effeeted in accordance with examples I, II or V, however instead of 100~ distilled methacrylic acid there i9 used its 85... 95yo solu-tion in tetraehloromethane. ~he produeed membrane separator is featured by the characteristics in-dicated in example I.
Example VIII.
qlhe grafting is effected in aceordanee with examples I, II, V, VI or VII~ however with -the differenee, tha-t the thick-ness o~ the polyethylene film is 80 microns instead of 35 microns,the number of cloth or paper layers on each side of the polye-thylene film is -two instead of one, the quantity of methacrylic acid or its solutions is from 0.5 to 0.9 lit/m2, while the duration of stay is about 45 minutes, qlhe resistance of the produced membrane separator is abou-t 0.3 ohms~cm .
.
- . . . .
.
Claims (4)
1. In a method for the production of membrane battery separators by grafting a vinyl monomer to a polyolefin film, activated by ultraviolet irradiation, and heating the film, the improvement which comprises effecting the grafting in a five-layer sandwich comprising the activated polyolefin film, covered from both sides with cellulose material, impregnated with the monomer or its solution and pressed from each side by an inert polymer band enclosing the reaction space, pressing the sandwich from 10 to 45 minutes against a heater with a pressure towards the surface of the heating element of from 10 to 30 g/cm2, the layers of the sandwich being bands endless in length, the sandwich being passed over the surface of the heating element at a velocity of 1 to 100 m/hour.
2. A method according to claim 1, wherein as cellulose material there is used bleached and non-finished cloth of natural cotton, such as cheese cloth, with a thickness of 150 to 200 microns and a density of about 10 fibers per cm.
3. A method according to claim 1, wherein the inert polymer hand is a biaxially oriented polyester film with a thickness of 80 to 150 microns.
.
.
4. A method according to claim 1, wherein the tem-perature of the surface of the heating element is from 85 to 95°C
and is maintained with an accuracy of + 1°C.
and is maintained with an accuracy of + 1°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA307,758A CA1114276A (en) | 1978-07-20 | 1978-07-20 | Method of obtaining membrane-type separators |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA307,758A CA1114276A (en) | 1978-07-20 | 1978-07-20 | Method of obtaining membrane-type separators |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1114276A true CA1114276A (en) | 1981-12-15 |
Family
ID=4111931
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA307,758A Expired CA1114276A (en) | 1978-07-20 | 1978-07-20 | Method of obtaining membrane-type separators |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1114276A (en) |
-
1978
- 1978-07-20 CA CA307,758A patent/CA1114276A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |