SE436312B - ELECTRICAL ACCUMULATORS SEPARATOR - Google Patents

Description

7907260-9 active battery electrodes are known, for example, from DE Offenlegungsschrift No. 1 771 227. The strips or spacers are obtained here by punching out a foil material of the desired thickness and glued, welded or pressed into parallel paths on the actual separator. In another known method according to DE Offenlegungsschrift 1 269 212, a thermosetting plastic mixture in the form of parallel strands is applied to the actual porous separator foil by extrusion and the product is passed through an air-permeable oven with a set temperature, at which the strands melt on the substrate this, which is impregnated with partially cured phenol-formaldehyde resin.

Since the strips can only go in longitudinal paths to ensure a necessary passage of the ascending oxygen bubbles, the separator has only good stability in one direction, while in the other direction it can easily be folded or pressed.

A separator of the type initially indicated is previously known. ' The same means a solution to the problem of providing a separator, in particular for lead-acid accumulators or starter batteries, which in addition to their actual function as a highly porous diaphragm also has a good rigidity over the entire surface and which despite a narrow installation makes it possible to the charge gases to leave the electrolyte without difficulty.

This problem has been solved by connecting the side facing the positive electrode to a plastic mesh structure.

The connection with the actual base material only needs to be maintained per se until the separator has taken its place in the cell forever between the electrodes of different polarity. The task of the network is that as far as possible an extremely flexible base material can be manipulably stabilized during the manufacturing process to the rigid separator.

The base material in the separator as above is a highly porous foil, consisting of an acid-resistant thermoplastic. The suitable material is polyethylene, but preferably polypropylene. A known polypropylene film has e.g. a thickness of about 25 μm and a porosity of 35%, the diameter of the pores being less than 0.1 μm. The pores of this foil may be considered uåèššáèo-9 as discrete, slightly separated channels from one surface to the other. The resulting extremely smooth structure gives the foil extremely favorable mechanical and electrical properties for its intended use.

On one side of the base material of the separator, a mesh structure of a plastic has been adhered, which is suitably selected from the same group of thermoplastics, but which may also be a thermosetting plastic. ' The net structure serves as a spacer, the separator in all directions obtaining an increased bending strength, which the known laminar structures such as the initially mentioned strip separators only incompletely show. Only in conjunction with the mesh-like spacer layer, over which the florin-thin foil is to some extent stretched, can it perform its separator function optimally.

The net structure itself may be formed by intersecting parallel groups of plastic rods or wires.

According to the present invention, the mesh structure is a stretch plastic, which in a similar manner as a stretch metal is made of a smooth strip material. The basis for this stretch processing is a stretch process known per se, which the plastic material in the net structure has to thank for its dimensional stability.

By stretching, most linear plastics undergo a significant increase in strength during a simultaneous decline in the elongation. The stabilization is due to the fact that the generally welded-together wire molecules, when stretched, arrange themselves into crystal-like structures in which the intermolecular binding forces are strengthened.

On the basis of the above, a separator of the initially stated type is characterized in that the body consists of a stretch plastic, the mesh structure of which belongs to the strip parts of different widths, only strip sections of smaller width occurring in a direction in which electrolysis gases are intended to escape, and that the stretch plastic is thermally bonded to the base foil.

A stretch deformation is available both for glassy amorphous thermoplastics and at room temperature partially crystalline thermoplastics such as polyethylene and polypropylene. In the latter case, it is advantageous to carry out the stretching at elevated temperature, in the range 100 - 150 ° C (hot forming temperature), which is already close to the melting range of the crystals. In any case, one should choose such a high deformation temperature that a subsequent rapid cooling can still be carried out to a temperature below the so-called the freezing temperature, whereby the thermoelastic state range is passed. The shape change then becomes permanent up to the crystallite melting range, at least at the usual operating temperatures.

The stretch plastic overlay of the separator according to the invention preferably has steps of different thicknesses. The steps with the smaller thickness are arranged in the stretching network in such a way that passages are formed in the direction of preference for the passage of the electrolyte gases after the separator has been installed tightly between the electrode plates. Such a design of the stretch plastic can be achieved in different ways. Then e.g. the slits, with which the plastic foil is provided in exactly the same way as when stretching a metallic strip material, are displaced relative to each other according to a predetermined pattern in such a way that the surfaces between the slits through the knives of the stretching tool become stronger and less strong. expressed to the sides. In this case, it is possible to obtain webs with less thick steps with a zigzag-shaped course. Another possibility of obtaining larger and smaller step thicknesses next to each other is that the otherwise equal, in a uniform manner arranged the wear knives of the stretching tool are partially and in a certain order replaced with punch knives.

The connection of the net structure with the microporous base material to a uniform body can, due to the special properties of the thermoplastics, be carried out in such a way that the surfaces intended for connection to each other are heated to incipient softening and compressed under light pressure, and the base material with an iron is ironed on the mesh structure. However, the heating time should be short measured and the temperature set so that the surfaces become sticky and evenly welded together when using pressure.

For this purpose, it is advantageous to conduct the microporous base material and the stretch plastic, both in strip form, separately over heatable rollers, which they leave with the temperature necessary for gluing on the side facing the roll surface. . Immediately afterwards, the belts are taken up by two closely spaced breaking rollers and are easily compressed between them. The gap width between the breaking rollers must only be slightly less than the thickness of the finished product in order to avoid an undesired flat rolling of the solidified stretch plastic.

Fig. 1 shows a laminate separator according to the invention, consisting of the microporous base foil 1 and a stretch plastic overlay 2. The dashed lines pass over preferred passages for the gas; which are formed by reducing the step thicknesses in these areas.

The total layer thickness of the laminate separator corresponds to the thickness of conventional separators in starter batteries.

Claims (1)

1. vsavzso-si PATENT REQUIREMENTS Separator for electric accumulators, in particular lead-acid accumulators, with a microporous base foil (1), the side of which faces the positive electrode is provided with a spacer in the form of a plastic body, k ä It is characterized in that the body consists of a stretch plastic (2), the mesh structure of which belongs to the strip parts has different widths, only strip sections with a smaller width occurring in the direction in which electrolysis gases are intended to escape, and that the stretch plastic is thermally connected to the base foil.