FR2512592A1 - METHOD FOR SEALING AN ELECTROCHEMICAL CELL AND THAT BATTERY - Google Patents

Abstract

THE INVENTION RELATES TO AN ELECTROCHEMICAL BATTERY AND A PROCESS FOR SEALING IT. THE ELECTROCHEMICAL BATTERY ACCORDING TO THE INVENTION USES, AS ELECTRICAL INSULATOR, A POLYAMIDE HAVING AN AMINE NUMBER LESS THAN 8 AND FORMING A SEAL, A BARREL 13 OR OTHER ELEMENT PLACED BETWEEN CAP 11 AND BOX 12 OF BATTERY 10, THIS MATERIAL WHICH CAN ALSO BE USED TO ENSURE WATERPROOFING AND PREVENT LEAKS CAUSED BY ALKALINE ELECTROLYTE. THE POLYAMIDE USED MAY BE STRAIGHT CHAIN OR BRANCHED CHAIN, AND IT IS PRACTICALLY NON-STICKY. FIELD OF APPLICATION: MINIATURE BATTERIES FOR WATCHES, HEARING DEVICES, ETC.

Description

The invention relates generally to electrochemical cells, and

more particularly

  batteries using insulation and sealing materials.

  One of the difficulties encountered in the manufacture and use of alkaline batteries, including batteries containing an alkaline electrolyte, lies in the possibility of wetting metal surfaces by the electrolyte. This wettability has been determined to be one of the main causes of leaking alkaline batteries, because the electrolyte, by wetting the surface of the metal casing of the electrolytic material, can actually "seep" at the interface of the seal which is conventionally arranged between the metal casing and the other metal surfaces usually serving as contacts for the

external current of the battery.

  Various topics have been suggested in the art

  to be used as water-borne

  or as seals, and these materials are therefore disposed between the adjacent metal surfaces to provide both electrical isolation between these surfaces and form an effective seal between the surfaces to prevent the "seepage" of the alkaline electrolyte In particular, United States Patent No. 3,922,178 discloses a

  particular sealing composition comprising a poly-

  fatty amide which has an amine value higher than

  Viron 10, which is intended to form an effective obstacle to stop the alkaline electrolyte, and thus prevents the appearance of "oozing", as well as the degradation of certain elements of the cell by contact with the electrolyte

alkaline.

  In addition, in the case of the manufacture of button-type alkaline cells, it is desirable that the seal or sealant be substantially tack free to facilitate transportation and application.

  automated during the manufacture of the battery.

  It is therefore desirable to develop other

  Polyamide-based seals and sealants

  both the advantageous characteristics of flexibility, adhesiveness, virtually complete absence of stickiness, and resistance to seepage of the electrolyte,

  making them suitable for use in alkaline batteries

lines of all types.

  The invention generally relates to a

  electrochemical cell containing a certain amount of electricity

  alkaline trolyte and having one or more surfaces

  subject to wetting by this electrolyte, the battery used

  for these surfaces, a polyamide having a

amine less than 8.

  The invention relates more particularly to

  electrochemical cell having a recess housing

  an anode, a cathode and a quantity of alkaline electrolytic material, at least one cap

  aligned with the housing, and at least one electrical insulator

  that disposed between the battery cap and the housing,

  a polyamide having an amine value of less than 8

  locating the electrical insulator or being disposed on the surfaces of this insulator in contact with the housing and

Hood.

  The invention also relates to a method for

  seal an electrochemical cell as described above.

  above, which consists, in a first form, of using a sealing material in the immediate vicinity of the surfaces subject to wetting by an alkaline electrolyte, this material comprising a polyamide having an amine value of less than 8. wherein the electrochemical cell comprises an electrical insulator and a sealing material, the method comprises coating the insulator surfaces, in contact with the housing and the battery cap, with a sealing material comprising a polyamide having an amine value of less than 8 In addition, the electrical insulator can be prepared from

current polyamides.

  Piles prepared in accordance with the invention have greater leak resistance and better sealing characteristics, including

  resistance to "seepage" of the alkaline electrolyte.

  The invention will be described in more detail in

  view of the annexed drawing as an example, which is by no means

  tatif and in which the single figure is an elevation, with partial section, of the electrochemical cell according to the invention. According to the invention, alkaline cells which use on or in

  subject to wetting by an alkaline electrolyte, a poly-

  amide having an amine value of less than 8.

  Polyamides which can be used in accordance

  According to the invention, fatty polyamides, the preparation and properties of which are described generally in pages 597 to 615 of volume 10 of "The

  Encyclopedia of Polymer Science and Technology ", Inter-

  Science Publishers (John Wiley & Sons, Inc.), New York, United States of America In general, polyamides are

  prepared by reacting a polyacid with a polyamine amine

  Polyacids may include

  straight-chain and branched-chain alkyl

  for example, unsaturated fatty acids derived from vegetable oils, and other sources The present polyamides may therefore comprise known materials

  under the name of fatty polyamides having both a structural

  straight chain and a branched chain structure.

  The polyamides according to the invention possess

  advantageously amine numbers between 1 and 8.

  In particular, polyamides suitable for use in the present invention are marketed by the

  HB Fuller Company, Minneapolis, Minnesota, USA

  United States of America, under the name "FULL-MELT" resins. One of these resins, designated FM-8200, is a fatty polyamide having an amine number generally ranging from about 6 to about 7. Another resin, designated FM8050, is

  also an acid-terminated fatty polyamide and possess

  With an amine number of about 1 While the foregoing materials are indicated, the present invention encompasses

  the use of other polyamides available in the

  merce, having amine numbers included in the abovementioned ranges, such as polyamide "Union Camp 2645"

  (amine number = 8) and the polyamide "Henkel Macro-

  melt 6239 "(amine number equal to 7).

  The polyamides according to the invention can be used in a variety of ways depending on the particular application desired. For example, polyamides can be formed to make seals, gaskets or guns that can be used as electrical insulators in various alkaline cells. In a variant,

  the polyamide can be used as a composition of water

  or adhesive, applied to such fittings, seals or guns at the time of their placement between

  adjacent metal surfaces in these stacks.

  The polyamides according to the invention can be used alone, or in admixture with adjuvants such as diluents, modifiers and hardeners,

  as desired, for the purpose of modifying the physical properties of

of these polyamides.

  In the case where the polyamides according to the invention are used as coating, they can be applied by known methods, for example in the molten state or in

  solution in a solvent such as an alcohol / hydrocarbon mixture

  The methods of application of polyamides, such as those suggested above, are known and not

not within the scope of the invention.

  The single figure represents a particular example

  The battery shown in the figure is a battery-button 10 which represents the type of battery generally suitable for hearing aids, watches and other applications, in which: it is desired that the battery operate at a continuous rate but

  The cell has a common metal anode 14

  zinc or cadmium, the preferred anodic material being amalgamated zinc.

  anode can also be used.

  A housing 12 encloses a common cathode 17

  It is made from a material such as mercuric oxide, silver oxide and the like, with silver oxide being preferred. The cathode 17 is isolated from the anode 14, in the embodiment described by a porous separator

  16 and an absorbent spacer 15, the spacer 15 contains

  An alkaline electrolyte such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) for ionic conductivity. The housing 12 functions both as a cathode current collector and as a positive terminal for the pile, while the top or the cap

  11 of the stack, in direct contact with the anode 14, function-

  not as anode current collector and as a negative terminal

  The top 11 of the battery and the housing 12 may be made of conductive materials such as stainless steel, nickel or nickel-plated steel, and the inner surfaces of the top 11 of the cell may be coated. of a suitable metal such as tin,

copper, silver or gold.

  The top 11 of the stack is centered relative

  to the boot 12, as shown, but it is isolated electrically

  An electrical insulator, such as a plastic barrel 13, resiliently engaged in position,

  may be provided, as shown and, in accordance with the

  vention, the barrel 13 can be prepared from a poly-

  amide having an amine value of less than 8 In this case, the barrel 13 provides an effective one-piece seal which prevents any interstitial "seepage" of the alkaline electrolyte between the contacting surfaces, either from above 11 of the and stack 13 and casing 12 and barrel 13. In addition to the use of polyamides described herein, as a material that can be used for the preparation of barrel 13, the invention also relates to the use of polyamides cited as adhesive coating applied between the housing 12 and the top 11 of the stack, either in place of the barrel 13, or as a coating disposed above the surfaces of the barrel 13 which make contact with the corresponding adjacent surfaces 2 S of the boot 12 and above it of the mile Thus, as shown in the figure, these contact surfaces of the barrel 13

  may be provided with a sealant composition or

  adhesive position which can be dispensed in a fluid form so that, when positioning the barrel 13 between the adjacent surfaces of the housing 12 and the top 11 of the stack, the sealing material forms a barrier layer which is impermeable to way that the electrolyte

  alkaline can not infiltrate or destroy it.

  The polyamide used as sealing material in accordance with the invention can be used with

  joints prepared from materials other than poly-

  amide cited Thus, for example, the barrel 13 may be made of an insulating material such as "nylon" or

  polyolefins such as polyethylene or polyethylene

  propylene, and it can then be used with the material

sealing according to the invention.

  As mentioned earlier, the class of

  polyamides covered by the present invention is particularly

  useful for the fact that these polyamides are practically

  This property has proved to be

  In the process of being treated, particularly in the case where the guns and sealing compositions are used in the automated manufacture of button cells. The fact that the sealing compositions are not tacky or sticky makes it possible to transport them to at the point of application during battery assembly, by automated means, because the frequency of congestion and

  equipment outages are significantly reduced or eliminated.

  In addition, the absence of stickiness or

  sticky promotes the uniformity of the coating

  which, as a result, improves surface contact

  between the metal and the adhesive, resulting in a decrease in

  Sensitive failure of leaks.

  The invention also relates to a method for sealing an electrochemical cell comprising a housing, a certain amount of alkaline electrolyte and at least one

  surface subjected to wetting undesired by the electrolyte.

  This method consists in providing, on this surface or on the surfaces, a certain amount of a polyamide having an amine value of less than 8.

  coated with polyamide, or prepared from poly-

  amide, in the case of joints, guns and others.

  The invention also relates to a method of

  manufacture of electrochemical cells consisting of

  blowing the container, the alkaline electrolyte and the battery cap so as to place a sealing material or an electrical insulator or both between the cap and the housing. This method consists in using an electrical insulator prepared from the described polyamides and, in one embodiment, this isolator can be

  used alone In another form of the process of the invention

  the insulator may be coated with a certain amount of a sealing composition comprising the polyamides according to the invention, which sealing composition has been transported to the coating station by automatic equipment. the assembly of the electrochemical cells is accelerated by the possibility of the polyamides described to be transported by means

largely automated.

  The manner in which the polyamide class described is used may also vary with respect to the shapes

  described, for example, the poly-

  amides can be applied to a substrate in the form of

  thin coating, spraying, immersion or otherwise.

  It goes without saying that many modifications can be made to the stack described and shown

  without departing from the scope of the invention.

Claims (10)

  A method for sealing an electrochemical cell (10) comprising a casing (12) which contains a certain   amount of an alkaline electrolytic material, and a   chon (11) battery centered relative to the housing, the method being characterized in that it consists in arranging between   the boot and hood a certain amount of a poly-   amide having an amine value of less than 8.   Process according to Claim 1, characterized in that the polyamide is disposed between the casing and the   cap of the battery in the form of an electrical insulator than preformed (13).   3 Process according to claim 1, characterized   in that the polyamide is used as a water-resistant material   applied on the surfaces of a preformed electrical insulator (13) and in contact with the casing and the cap of the pile.   Process according to Claim 3, characterized in that the electrical insulator is prepared from a   polyamide having an amine value of less than 8.   Method according to one of claims 2 and   3, characterized in that the polyamide is practically not sticky.   6 Electrochemical cell, characterized in that it comprises a casing (12), a certain amount of alkaline electrolyte disposed in this casing, and at least one surface subject to wetting by the alkaline electrolyte, at least a portion of said surface having some   quantity of a polyamide having an amine to 8.   Electrochemical cell according to Claim 6, characterized in that the surface is situated between the   container and a cap (11) of the stack.   Electrochemical cell according to Claim 7, characterized in that the polyamide is arranged in the form of a pre-formed electrical insulator (13) placed between the boot and the hood. 22592   Electrochemical cell according to Claim 7, characterized in that the polyamide is disposed between the surface of a preformed electrical insulator (13),   contact with the housing, and said battery cap.   Electrochemical cell according to one of claims 8 and 9, characterized in that the polyamide is branched chain.   11 Electrochemical cell according to one of the   8 and 9, characterized in that the polyamide is practically not sticky.