FR2554641A1 - MINERAL LOAD CLOSURE ELEMENTS FOR GALVANIC BATTERIES - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO MINERAL-LOADED CLOSING ELEMENTS FOR GALVANIC BATTERIES. FOLLOWING THE INVENTION IS USED TO FORM THESE CLOSING ELEMENTS A THERMOPLASTIC MATERIAL WITH A MINERAL LOAD, INERT WITH RESPECT TO ELECTROLYTES, FOR EXAMPLE POLYPROPYLENE, POLYETHYLENE AND THEIR COPOLYMERS, THE MINERAL LOAD OF TONALCATE, FOR EXAMPLE. OF CALCIUM, MICA OR ANY OTHER MATERIAL INERT TOWARDS ELECTROLYTES, THE RESISTANCE TO BURST OR RUPTURE OF A MEMBRANE OF THERMOPLASTIC MATERIAL WITH A LOAD THAT IS LOWER AND CAN BE MORE EASILY PREDICTED AND CONTROLLED.

Description

The present invention relates to batteries

  sealed galvanic devices, such as alkaline batteries

  mayors and others, and it relates more specifically to

  sealing elements, which are hereinafter referred to as closure elements, for such cells, these elements being produced or molded from a thermoplastic material having a filler, for example polypropylene having a mineral charge,

  such as talc, calcium carbonate or mica.

  The general construction of a galvanic

  cylindrical watertight is such that its constituent parts

  The main batteries are assembled in a box and the battery is then closed by a closure element placed in the open end of this box. The closure element pockets an electrolyte leak from the cell and isolates the electrode contacts from this cell one

compared to each other.

  A closure element will advantageously

  also the release of hydrogen gas out of the stack to reduce pressure build-up inside

  of it, while also preventing an increase

  loss of moisture and oxygen or carbon dioxide infiltration into the interior of the

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  battery. In addition, the closure element is usually

  manufactured to have a thin section or mem-

  molded brane, such as a breakable membrane forming an expulsion zone, which membrane has a reduced cross-sectional thickness relative to the thickness of the surrounding material, to ensure that the stack can be degassed under certain conditions when a high build up of gas pressure occurs inside the cell, and thus to exclude a rupture

of it.

  In connection with the present invention, there are provided closure elements for use in sealed cylindrical cells, these closure elements

  being molded, usually injection molded, to the

  of a thermoplastic material, inert to the

  the electrolyte, comprising a charge, for example

  lypropylene, polyethylene, (and in particular a polyethylene

  lysulfone for high temperature applications), as well as their copolymers, comprising from 5 to 45% by weight

  the weight of a mineral charge, which may be chosen

  in the group consisting of talc (theoretically

  anhydrous magnesium silicate Mg3SiO10 (OH) 2], carbon

  calcium and mica. Depending on the purpose for which the closure element is used, this element can be annealed or not. When polypropylene is annealed, it can be at temperatures of 70 to 155 C (other

  temperatures suitable for other thermoplastics

  such as copolymers of polypropylene and

  polyethylene). The annealing can be advantageously carried out

  in an oven or tunnel with air circulation. In most cases, a mineral-filled polypropylene, and in particular a talc-filled polypropylene, is

  particularly interesting, from what we have

  acetate. Examples of closure elements and their

  placed in batteries have been described in the

  Belgian vests No. 895,361 and 896,976 of the plaintiff. The injection-molded plastic parts, which are made from a talc-filled polypropylene, can be produced with practically no surface depressions or depressions, i.e. irregularities or surface cavitations,

  may be of particular importance when

  me closing elements comprising a membrane.

  Moreover, since the parts can be molded without

  safety, tolerances and conditions of the molding

  which these pieces are formed are less critical.

  - A mineral filler, such as talc, may allow lower molding temperatures. In

  in addition, a mineral filler, such as talc, may increase

  bring the creaminess to the surface of the thermo-

  plastic, so that it can act as a

  internal molding. This is particularly useful because

  external release agents, such as silicates,

  cones, can soil the molded parts and that this stain could in turn cause a gas release inside the battery. The mineral filler (talc, calcium carbonate or mica) would not cause such a gas release inside the cell. As there is less shrinkage after molding, especially with higher concentrations of filler, such as talc. , of the order of 20 to 40%, there is a larger

  certainty that the sealing and isolation elements

  will be molded more precisely. Finally, the cost

  unit of plastic parts with mineral charge

  may be lower than that achieved with

materials without charge.

  The applicant has discovered that one achieves significant mechanical advantages when using a thermoplastic material with a load. These

  benefits include the fact that we have better

  sealing and degassing characteristics for which

  relates to the closure element. A thermoplastic material

  loaded tick has a lower coefficient of

  linear thermal energy, which is closer to the coefficient

  linear thermal expansion of the metal casing

  that is used for the assembly of the cell.

  gives a better seal, especially after

  thermal cycles. The thermoplastic material having a filler has a higher compressive strength than the no-load material, which

  which gives a better seal to the crimp. This characteristic

  This is even more important when the sealing and insulation elements are annealed. The annealing stabilizes the dimensions of the sealing and insulation elements, that is to say that the physical dimensions of the parts become constant, and annealing also releases any internal stresses that may occur.

  have been created during the molding process.

  The load acts as the concentration agent of

  constraints to allow a rupture of the membrane

  ne or degassing zone occurs with deformation

  minimum of this membrane. When a closure element

  re having a charge is annealed, thereby releasing

  the internal constraints of any molding, the pressure

  The rupture rate of the membrane increases relatively less than the corresponding increase imparted by annealing.

  of a material without charge, A material loaded and re-

  bake better predicting breaking strength

of a membrane.

  At the same time, the use of a material

  charged thermoplastic reduces the space requirements

  by ensuring that the degassing diaphragm that can break will break with less stretching than a material

  thermoplastic without load, and without excessive accumulation

  sive pressure in the stack. In addition, one can mold

  a thicker membrane, which allows tolerances

  wider molding rims, while still remaining

  within the limits of the tolerances for degassing.

  In addition, since it takes less vertical space to allow rupture of the degassing membrane, the closure element can be placed slightly higher in the casing, which allows the establishment

  a greater amount of active ingredient in the

  the. As the charged thermoplastics of the invention allow permeation of hydrogen, the stack in which the closure member is installed

  can be degassed by exudation. Degassing by exudation

  This allows a sufficient escape of hydrogen from the cell, thus reducing the possibility of degassing.

  of the cell by rupture of the membrane. This is also

  important in that the amount of the constituent

  gaseous release and mercury corrosion

  re, which may need to be placed in the stack, especially

  alkaline batteries, can be reduced by

  very considerable, which not only resulted in

  a more satisfactory product from the point of view of

  but also better working conditions

  for the entire battery and appreciable savings.

  An advantage arising from the present invention

  when compared with a glass-filled nylon, when used for

  elements of battery closing, is that the thermic

  moplastic with a load is much less

  throws into a dissolution during an exposure to an

  trolyte, for example to a solution of hydroxide

  40% potassium. This is how a polypropylene to load

  talc, calcium carbonate or mica decomposes

  will not pose, even during an exposure for long periods of time, for example 4 weeks, to 71 C to

  of KOH, which is done by a nylon with

  re. In the filled thermoplastic materials contemplated in the present case, ie containing a filler such as talc, calcium carbonate or mica, in amounts of 5 to 45% and usually from 40%, the filler is very finely ground or consists of a finely particulate material and is such that when inside the thermoplastic sealing and sealing element

  molded, there is no superficial exposure of the material

  load in the molded part. In this respect, particularly with regard to the use of talc

  As a filler, it is preferred to use a quantity of

  20% but up to 40% of this talc, as

  charge, especially in polypropylene.

  As mentioned, annealing brings cer-

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  benefits by relieving the internal molding stresses that have occurred, and by stabilizing

  physical dimensions of the sealing and insulation element

  molded, but even if the closure element is not annealed, superior behavior can be achieved

  compared to a no-load product of a similar design

  Milaire. This is due to the fact that there is a wider

  tolerance in the production of the membrane part

  the closing element, so that it can be

  ler in a greater thickness, and this with a better possibility of predicting the breaking pressure and in any case to accommodate some breaking pressures a little

  higher, without getting close to the pressure to which

  the cathode casing would serve, in

  as for the release of the entire closure element

  and, as a result, the breaking of the stack.

  A typical analysis of polypropylene

  Talc load is given below.

  Polypropylene resin, without load, can

  have a melt index of 10 to 15. After charging, the

  Dice of fusion will have been reduced to about 6 to 10.

  Talc is a white powdery substance

  dusty, in blister packs or small tables, not containing asbestos

  a chemical analysis that may be in the inter-

  following valleys: Constituents% by weight MgO 20-32% SiO2 16-46% CaO 9-30%

A1203 0.5-4%

Fe203 0.2-4%

PF 8-20%

  [PF (loss on ignition) represents the percentage

  of carbon dioxide released during the heating of the talc].

  An example of the distribution of the dimensions

  Sieve lengths can be in the following ranges: Sieve to% wt. mesh 44 microns 100% microns 94-97% microns 75-90% microns 40-60% microns 18-32% 4 microns 14-24% 3 microns 9-17% 2 microns 5-10% 1 micron 4-4%

  Normal dry gloss is 84-94; den-

  in the packed state: 0.96-1.28 kg / dm; density at the state

  free: 0.38-0.88 kg / dm3; specific weight: 2.8-2.9; ab-

  oil sorption: 20 to 35 g / 100 g of talc; pH: 9-10.5; finesse Hegman: 13.5; 100% of the material goes through a

  mesh sieves of 0.074 mm, and 98-99.9% pass through a

meshed with 0.043 mm.

  Calcite (calcium carbonate) ground similar

  would show the following characteristics: Constituents% by weight CaCO3 95-98% MgCO3 1-2%

A1203 0.05-0.2%

  2 3 Fe203 0.01-0.2% SiO2 0.1-1% MnO 0.01% copper undetected moisture 0.25% organic layer 0.5-2% (normally silane) An example of granulometry of this material

  includes: 100% particles less than 15 microns (par-

  spherical particles), 95 to 99% less than 10 microns, 75

  85% less than 5 microns, 40 to 60% less than 2.5

  crons, and 20 to 40% less than 1 micron. The average particle size may be of the order of 2.5 microns, with a specific gravity of about 2.7 and a

refraction of about 1.55.

  Various embodiments according to the invention

are given below.

Example 1

  A number of AA-type closure members (upper pieces) have been molded using

  nylon, unfilled polypropylene, and polypropylene

  with a charge of 20% of talc. Half of the polypropylene closure elements have been annealed,

  while the other half was not. All members

  closures have been installed completely in

  batteries with formation of a tight seal by crimping

  ge, except that the outer shell was not placed on the piles, and leakage observations were

  after various attempts at storage and use.

  tion. Leakage observations revealed, for example,

  that, after a week's storage at high temperatures,

  followed by one week of temperature stabilization

  ambient temperature, annealed closure elements and

  Nylon fittings had an essential failure

  one (equal to one in thirty) in the first case and no failure in the second, the non-annealed elements having a higher failure. Other closure elements were stored at a slightly lower but still elevated temperature for two weeks, followed by an additional week of stabilization at room temperature, and failure was noted.

  of a nylon element and a non-load element,

  say that no element carrying a load was

of failure.

  Other closing elements have been

  subject to storage at a very low temperature

  one week, followed by temporary stabilization

  room temperature for an additional week, and

  much better behavior has been

  closing devices with a load and having been re-

  cooked (one in thirty) than the nylon elements

  twenty out of thirty showed a failure.

  Similarly, an application of thermal cycles to another batch of elements, since a low temperature

  to a relatively high temperature, followed by

  stabilization at room temperature, showed a failure of only two of the load-bearing and annealed elements out of thirty, while fifteen

  Nylon out of 30 had

  faillance. Other samples were stored at room temperature for 1 day, then they were

  1.5 A charge, and all batteries are

  zaient. On the other hand, other closure elements were stored at high temperature for several days, then receiving a load of 1.5 A; with the elements

  polypropylene having a charge and having been

  when cooked, there was a degassing of three out of three,

  say that one of the three batteries with a nylon closure element was breaking a lot more

violent.

Example 2

  We have molded a number of elements of

  closure for AA, C and D batteries, all these

  containing degassing membranes which may

  break, molded into these elements and having thick

  from 0.08 mm to 0.12 mm; among the samples

  some were molded without talcum, some with 20% talcum and some with

a load of 40% talc.

  A number of closure elements were chosen as controls and these elements were not

  immersed in a solution of potassium hydroxide,

  say that other groups of elements have been immersed in such a solution at room temperature for 2 weeks, or at a high temperature for 2 weeks,

  or at a very high temperature for 2 weeks.

  Then, out-of-pile degassing tests were performed, after which all the closure elements that had been stored while being immersed in KOH were immersed.

  showed degassing results quite comparable

  with those in the control group who had not been exposed to or immersed in KOH. In others

  In other words, all samples were chemically

resistant to the KOH solution.

  An important conclusion that can be drawn

  of these degassing tests is that the membrane or particles

  pressure relief devices for the degassing of

  Polypropylene-filled closures are not affected by high temperature alkaline electrolyte, and the membranes break so that the batteries degass at the same pressure both before and after

  long storage at high temperatures.

Example 3

  Other degassing tests were carried out, in which closure elements having degassing membranes having a thickness of 0.14 mm, molded in these

  elements, have been tried with varying

  the height above the membrane. The polypropylene closure elements without load did not degass or degassed at very high pressures in the case of small intervals, while 20% of the elements

  clogged with talc were degassed to

  reasonable. At an interval of 2.31 mm, one

  polypropylene closure without load and not

  cooked did not degass at a pressure of 5.85 MPa, while

  that a similar closure element

  Valve 3.68 mm degassed at 1.93 MPa. Polypropylene closure elements with 1% talcum charge, no

  annealed, degassed at 3.30 MPa, with the smallest

  mentioned above, and at 1.93 MPa at the highest

  interval, while poly-closure elements

  propylene with a 20% load of talc and having been annealed degassed at 2.89 MPa with the smallest

  at 2.75 MPa with the highest interval.

Example 4

  Nylon closure elements have been molded

  glass-filled, polypropylene without load, in poly-

  propylene of 20% of talc and polypropylene

  40% of talc, and stored at 71 C

  1 month in a KOH electrolyte. The solution,

  after storage, was acidified and showed

  lysis of traces of metallic elements. Except for a slightly higher amount of

  calcium released from the polypropylene closure elements

  binds 20% of talc, none of the iron

  polypropylene has shown an im-

any carrier of nickel, cadmium, strontium, cobalt, titanium, molybdenum, lead, copper, iron, vanadium, chromium, aluminum, silicon

  or calcium. Glass-filled nylon has, by way of

  Be shown that large quantities of titanium, copper, iron, vanadium, aluminum, silicon

and calcium have been dissolved.

  The shape of the sealing elements

  made of thermoplastic materials having a

  The present invention depends on design considerations that are outside the scope of the invention, but the designer may provide for broader tolerances.

  molding, and he can design membranes for

  thicker gassing with the assurance that the

  batteries will be the one expected, when these batteries se-

will be in use.

Claims (9)

  1. Closure element for galvanic cells sealed by crimping, characterized in that it comprises a thermoplastic material comprising 5 to 45% by weight of a filler, this thermoplastic material and this filler being each chemically inert with respect to of the electrolyte material to be used in the sealed cell, which element has a breakable degassing zone of reduced cross-sectional thickness relative to the thickness of the material surrounding it. degassing zone.   2. Closing element according to the claim   1, characterized in that the thermoplastic material is selected from polypropylene, polyethylene and   their copolymers, and the charge is chosen from the group   eg talc, calcium carbonate and it.   3. Closing element according to the claim   2, characterized in that it is made of polypropylene   with a load of talc.   4. Closing element according to the claim   3, characterized in that the amount of talc is at 40o%.   5. Closing element according to any one   than the preceding claims, characterized in that that it is subjected to annealing.   6. Closing element according to the claim   5, characterized in that the annealing takes place at a time from 70 to -155C.   7. Closing element according to the claim   5, characterized in that the annealing is done during   at least 1 hour at a temperature of 70 to 155 C.   8. Closing element according to claim   4, characterized in that the talc has a particular dimension   less than a maximum of 44 microns, at least 2% by weight of this talc having a size greater than 1 micron, with at least 18% being larger than 5 microns and at least 40% having more than microns.   9. Galvanic cell, characterized in that   comprises a casing sealed by crimping using   reading a closure element according to any one Claims 1 to 8.