CA1063669A - Spiral-wrapped multi-layer cell separator - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Inner and outer spiral-wrapped layers with adhesive between them form a sleeve. The adhesive is then activated.
The outer layer covers at least the adjoining edges of the inner layer.

Description

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The invention relates to a galvanie primary element with spirally-wrapped multi-layer separator.
More particularly, the subjeet of the invention is a separator sleeve for eylindrical eells having MnO2, Ag20, AgO
or HgO depolarizer, or rather a depolarizer of mixtures of these eompounds and alkaline eleetrolytes, in ~hieh prefabrieated separator sleeves are used whieh are made of matting, fabric, or mieroporous foils. The matting, fabrie or foil are preferably produeed of eotton, polyamide, polypropylene, or polaeryl nitrile fibers or mixtures of these produets.
Separators for alkaline primary elements having - cylindrical form are produced and inserted into the eells by the most varied processes.
The best-known proce~s inYolves forming a rectangular piece o$ matting or fabric into a tube ~hieh is then inserted into the cell. The lower end of thîs ~rapping or tube is elosed o~f by a pushed-in bottom eap of the same material. The dis-advantages of this pro~ess, partieularly for eylindrieal eells , of small diameter, resides in that there are many difficulties 2a involved in aeeomplishing such wrapping and insertion automatical-ly and using maehlnery. In partieular, the hottom eaps, after ; h~ying heen pushed in, are pa~tially pulled out again by the insertion plunger due to a pinching e~fect.
In aecordanee ~;th another known process, two - separator strips superposed at right anglea are pushed into the cylindrical cell over guide shoulders in such a m~nner that one strip width constitutes at leaat one-half the eircumference of the separator slee~e. The outer strip facing the previously . ~ .'.: .
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3~69 inserted rin~-shaped positive electrode then bridges the two adjacent edges of the inner separator strip. Its disadvantage is that it is difficult to mechanize, Particularly disadvan-tageous is the fact that the ends of the strips protrude without guidance or support, so that during insertion of the sealing elements the strip ends are susceptible to uncontrollable bending.
Still another known type of separators are pre-fabricated sleeves with folded-over bottoms. The sleeves are wrapped in three layers from a rectangular piece and then glued together. A disadvantage of these is the longitudinal seam.
Especially when synthetic matting is used, this leads to a deformation of the circular cross-section and hence to non-`~ uniform adj~cency of the separator sleeves to the positive c~lindrical electrodes. Moreover, the manufacture o~ such .. . .. .
i sleeves is very costl~. ~
Separators which are ~rapped in the form of a spiraland inserted in alkaline cylindrical cells are disclosed in German patent publication (Au$1egeschrift) 1 421 582. Eowever, 2Q no disclosure is~ provided there o~ their construction and method of manu~acture.
Accordingly, the present invention has as its object the manufacture of a separator slee~e made of spiral-wrapped ~ material~
; It is another object to provide such a sleeYe which can be produced simply and continuously in large quantities.
`~ Still another object is to provlde such a separatox slee~e which is capable of absorbing the introduced electrolyte . ~ , .
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~636691 in the shortest possible time, of distributing it, and binding it in place, thereby achieving ~oth separation and positioning of the electrolyte layer ~etween anode and cathode.
: These objects and others which will appear are achieved in accordance with the invention by making the separator sleeve of an inner spiral-wrapped layer and an outer absorbent spiral-wrapped layer. These are joined together by an adhesive layer in the form of a synthetic plastic foil, ~ wrapped spirally ahout the inner layer and covering the inner .~ 10 layer at least in the region of adjoining edges. Both the inner and outer layer may be of microporous foil. However, it .
is also possible to us:e a pore-free foil ~or the inner layer and an a~sorbent microporous- foil for the outer layer.
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: For further details, reference i5 made to the .
discussion which follows i.n the light of the accompanying drawing, wh.erein the single figure .illustrates. somewhat dia~rammatlcally the technique for manu~acturing an embodiment ; of the invention and also the resulti.ng product.
In th.~t figure, there is shown an inner layer 1, the 2Q adhesive layer 2, and th.e outer layer 3. All of these are .rapped about ~nding mandreI~,4. $pray nozzles 5 are diagrammatically illustrated for spraying on of ~ater or solvent. The direction of ~ovement is indicated by arrow 6. .: .
I The matti.ngs or ~abrics shown preferahly have thicknesses of `. a~out a . 1 to Q.2 millimeters and stri.p w~.dths: of about 10 to 20 mi.llimeters............................................................... .
.~ Thé adhesi~e layer is pre~e.rably of s~nthetic plastic ~oil and may consist of polyvinyl alcohol. However, cellulose , .
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deriyatives may also be used.
The preferred process for the manufacture of such a separator sleeve involves wrapping the inner layer 1 spirally upon a mandrel. Upon this layer an adhesive layer 2 is spirally placed. Vpon these layers there is then wrapped spirally an absorbent outer layer prov~ded wi.th.:a solvent. It will be understood that the inner layer, the synthetic plastic foil and the outer layer may also be spirally ~ound consecutively upon . each other and thereafter the entire ~inding-may be sprayed with a solYent for the synthetic plastic foil or synthetic plastic middle layer.
~ By using, in accordance wi.th the invention, a foil-. like adhesiYe layer, numerous special advanta~es accrue. If the indiyîdual layers were joined simply by a low viscosity adhesive, . during manufacture this would penetrate ~nto th.e matting and distribute itself so quickly that i.nsuffi.cient adhesive effect would remain for attachment of the s~econd layer of matting. In ~
addition, the matting6 would then have los:t a large part of .:
their absorpti.veness for the ele.ctrolyte ~hich.they must 2a ~ubsequently take up. On the other hand, use of a high viscosity adhesiYe would lead to the formation of surface film on the .. matting, and this~ pronounced film format~on would cause the .
adhe5iYe to act as. a strong inhibitor to the separator properties. The sol~ent in s~uch.an adhesiYe layer would have to be elim~nated through.extended evaporati.on or drying periods duri.ng spi.ral ~rapping; ~therwise, up~n removal of the sleeve from the machine, the spiral could again unrayel.
When adhesi~es are used which are redi.ssolved by ,~ -:

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subsequently introduced liquid solvent, the sleeve end of the separator which protrudes from the tubular positive electrode can again unra~el and cause short-circuits in the cell if the zinc paste contacts the posi:ti.ve electrode.
For the adhesive layer, there is therefore preferably wrapped a stri.p of synthetic plastic, as for example, in accordance with the following process-.
After the first layer of separator matting or fabric has been -mounted on the wi.nding mandreI, there follows a strip of polyvinyl alcohol foil, preferably of a thickness of between about O.Q2 to 0.~.4 mi.llimeters which i5 soluble either warm or ~ cold. Thi.s layer ma~ be wrapped over the first layer diagonally, or in al;gnment w-ith'it, or overlappingly. The third layer then consists agai.n of suitable matting material. However, in the case of polyvinyl alcohbl foil, th;~:s has prev;.ously been passed through an aqueous b~th.'and'is therefore. soaked with water`
Th.e ~etted stxip is wrapped over the previously spirally mounted poly~inyl alcohbl foil, which is thereby dissolved throughout its entire thickness. rt thereby develops strong adhesive 20. pxoperties and e~fe.cts the adhesi.on between the two matting layers. The polyviny1 alcohol foil acts as adhesive and also `.' as separator m~teri.al, in a manner wh.i.ch. i.s known in itself.
In lieu of a clo~ed pol~vinYl alcohol strip, a -' perforate.d foil or a fa~ric strip of polyvinyl alcohol may also -`' be used. A narro~ stri.p ~ay also be used to merely glue the ~ gap togethe~. Wetting may, for example, also be accomplished j hy sprayi.ng o~ the outer matting layer whi:ch previously had . been wrapped in the dry state. Through radiation or hot air the ` ' .'. .

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necessary drying proces:s on the ~inding mandre.l can be accelerated.
.- In place of polyvinyl alcohol foils or fabrics, it is . possible to utilize synthetic plastic foils which are dissolved or activated by suitable solvents. Very well suited for this purpose are cellulos:e derivatives such as cellulose acetate or ~ cellulose triacetate, which are also effecti~e and known for use as separators. There too, the u6e of woven or perforated strips is possible Cacetate rayon). ~s sol~ent there is suitable, for example, dich.lormethane ~methylene chloride) or .. . . .
:: acetone. As a furth.er possibilit~, synthetic foils may be used which. are. also activated into adhesive by means of solvents, but which.later disintegra-te under the influence of the solvent li.quid. These su~tances include, for example, polycarbonate . or polyester foils. As solvents there are then suitable methyl chloride and ethylene chlorIde ~r, in the case of polyester foils, benzyl alcohol or resorcinol solution.
~ ~hat may be parti.cularly appropriate is to make the :t inner layer of cellulose acetate foil which is not soluble in water, the intermediate layer of a polyvinyl alcohol foil which ;s susceptible of acti.vation by water, and as the outer layer a cellulose m~tting or s~nthetic matti.ng. ~nother especially desirable possi~ility in~olves using as the inner layer a poly-vinyl alcohol or cellulose foil which is not soluble in the solvent, to use as the intermed~ate layer cellulose acetate ; foil which i.s s~sceptible to acti~at;on with the solvent, and to use as the outer layer a cellulose or synthetic plastic matting layer.
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The particular advantages of these spiral windings of the separator foil with intermediate adhesive foil which also possesses separator activity reside especially in the possibility of continuous production at high rates. sy using an adhesive foil, trouble-free predetermined distribution of the adhesive is achieved. If foils are us:ed which are glued together with matting layers, only individual fibers. of the outer fiber surface contact each other. The foils do not penetrate into the matting material, as would be the case with adhesives or liquids, and there arises a floating film layer which. does not diminish : the absorptive properties of the separator layers. Moreover it .
is possible to use perforated or ~oven layers, which is not -.
possible when an adhesive i5 used. When necessary, e.g. for ~g20, ~gO or HgO depolarizers, the adhesi.ve foil can remain in the form of a pore.-free film and act as additional separator.

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Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A spiral-wrapped multi-layer separator sleeve for a galvanic primary element, said sleeve comprising:
an inner spiral-wrapped layer;
an outer absorbent spiral-wrapped layer; and an adhesive layer joining the inner and outer layers, the adhesive layer being in the form of a spiral wrapped upon the inner layer, and covering at least the adjoining edges of the inner layer.

2. The separator of claim 1 wherein both the inner and outer layers are of microporous foil.

3. The sleeve of claim 1 wherein the inner layer is a pore-free foil and the outer layer is an absorbent microporous foil.

4. The sleeve of claim 1 wherein the synthetic foil forming the adhesive layer is of polyvinyl alcohol.

5. The sleeve of claim 1 wherein the foil-forming adhesive layer is of cellulose derivative.

6. A glavanic primary element including the sleeve of claim 1 and positive and negative electrodes separated by the sleeve.

7. The element of claim 6 wherein the outer absorbent layer of the sleeve contains an alkaline electrolyte.

8. The method of manufacturing a sleeve according to claim 1, wherein the inner layer is spirally wrapped upon a winding mandrel, the adhesive layer is spirally applied to this inner layer, and the absorbent outer layer equipped with a solvent is then spirally wrapped upon the adhesive layer.

9. The method of manufacturing a sleeve according to claim 1 wherein the inner layer, the adhesive layer and the outer layer are successively spirally wrapped upon each other and thereafter the assembly is sprayed with a solvent for the adhesive layer.