DE1294941B - Process for the production of diaphragms, in particular diaphragms for fuel elements - Google Patents

Description

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The present invention relates to an exchanger, carbon black and graphite powder suitable. Metal driving for the production of diaphragms, in particular oxides, for example magnesium oxide, as well as metal earths Diaphragms for fuel elements. powders can then be used as fillers

The use of diaphragms in fuel when they are opposed to alkaline or acidic elements is known. For example, at 5 trolytes of the fuel element are resistant. The the particle diameter of the fillers in the French additional patent specification 87,850 is described for the purpose Fuel cell asbestos diaphragms moderately depending on the applied separator a support conditions containing the electrolyte and desired volume porosity Adjust the framework and the electrodes on both sides.

built in to thereby reduce the risk of penetration. The diaphragm is formed according to the inventors Reaction gases at operating pressure in the electrode on metal nets, however, are at bare avoid lytes. electrophoretic deposition of the fillers and

The production of binder-containing asbestos dia binders often receive diaphragms that have a phrasing is usually done in such a way that one shows an uneven texture and approaches one another Made of asbestos fibers and a binding agent, with too large pores and trapped air bubbles for example plastic, an aqueous suspension can possess. Because of the resulting posed, the binding agent is absorbed on the fibers wrestles mechanical strength and gas-permeable and from the slurry formed in this way, these diaphragms are for fuel elements, Then separates off the water again. The ones operated with higher gas pressures are not Shanks of the ao available after drying and pressing.

Diaphragms are largely made up of the It has now been shown that the above-mentioned

The binder used is determined. due to the structure of the separation surfaces

It has now been found that diaphragms th difficulties be eliminated by köninsbesondere diaphragms for fuel elements, NEN, characterized in that the electrophoretic deposition of a dispersion of the starting materials or off 25 of the filler or fillers and binders with gear and binding agents with particular advantage sedimentation The fillers or binders can be produced if the starting materials or are combined, whereby for sedimentation all particles not migrating in the electrical starting materials and binders by electrophoresis are used or electrophoresis and sedimentation are deposited,
will. 30 The electrodes are in the combined dis-

The separation of the starting materials, subsequently arranged horizontally, namely is located referred to as fillers, the electrode on which the diaphragm of the Anode, which is either a highly polished metal. Deposition takes place below the counter electrode. In surface or an electrically conductive mesh. In most cases this will be the anode. Deposition a polished metal surface is used, 35 ■ When applying a DC voltage to the electronics The deposited coatings in the damp soil now migrate to the colloid dissolved or dispersed state or after drying or sintering of yeasted binder particles due to their negative The base is lifted off and, as diaphragms, charged with the filler particles, which enforced will. If necessary, however, the knife can be smaller than 1 μ for the mesh-shaped anode deposited diaphragms also from nickel meshes 40 and are deposited there; one diminution is lifted off will. tion of the mesh cross section takes place. Filler-

The separation on nets is particularly useful for particles with a through advantage above 1μ, However, if large-area diaphragms and asbestos fibers get smaller knives in the elek thickness and high mechanical strength, Irish field produced little or no evaluation should, as is the case with fuel elements of 45 mobility. Under the influence of the gravitational field Case is. The metal networks, which are opposite to the electro- it comes to a sedimentation, the filler part lytes The fuel cell must be resistant to falling on the electrophoretically deposited take on the function of a support frame. Components and are firmly anchored there. Of the

The use of metal nets, in particular deposited film, is permitted after drying or Nickel nets as a carrier for the deposited dia- 50 hardening as a diaphragm in fuel elements phragmen, is also advantageous because the me- is very well suited, with gas tightness and electrical networks even before the separation of the diaphragm resistance from the added binder men in a prefabricated plastic frame.

For example, one made of Plexiglas, welded in. Both electrophoresis can be used as a binder can. In this way, 55 paints in which the plastics are completely in water colloid, extremely stable and easily sealable construction solutions, as well as plastic dispersions and solution parts for fuel cells are produced in this way, gene can be used.

that on a plastic frame first both commercially available electrophoresis paints, for example

on the side a nickel mesh with an inner mesh based on acrylic acid ester and / or styrene Support frame welded in and then based on acrylic acid esters and / or melamine resins as well Both outer nickel nets, which are based on vinyl chloride, are deposited prior to their use Makes diaphragms. The first of the diaphragms in the one specified by the manufacturer Limited space then forms verelement in a fuel mix ratio with fully desalinated water the electrolyte compartment while the electrodes thin and for several hours at room temperature the diaphragm surface are applied. 65 temperature homogenized by stirring and after addition

The fillers used in the process are several hours in a ball mill after that of the filler Invention of asbestos fibers, asbestos powder and mica treated. The solids content of the baths produced Flour is preferred, but ionic is between 5 and 40 percent by weight, based on

3 4

the entire bath liquid, but preferably designated between the container, with 2 made of a nickel mesh

15 and 25 percent by weight. existing and attached to the bracket 3 anode

After the deposition on highly polished metal and with 4 the cathode. 5 represents a tap for that surfaces, but in particular nickel nets, are the drainage of the bath liquid 6, which consists of 16 weights manufactured diaphragms with 5 percent asbestos powder with a grain diameter of Rinsed fully deionized water and slowly im 1 to 20 μ, 4 weight percent binder based

Oven cured at temperatures up to 180 ° C. Acrylic acid ester and polystyrene and 80 weight

The hardening time of the plastics is about 20 percent water.

up to 80 minutes and takes place according to the specifications of the The diameter of the electrodes was 70 mm,

Manufacturer. io the bath temperature 25 ° C and the voltage 150 V.

The deposition voltage is between 60 and 300 V. When the current is switched on, the anode

According to another embodiment of the invention, a current density of 3 A / dm ² measured during

However, as a binder, it is also possible to use a 1 minute deposition to 0.03 A / dm ^{2 of} conventional aqueous plastic dispersions.

As a pressure test showed, the basis is polyvinyl chloride, acrylic acid ester, vinyl chloride, the diaphragm produced after drying vinylidene chloride, vinyl ether and isobutylene. Curing and hardening gas-tight to over 1 atm.
The bath liquid is produced in the same way. In an analogous manner, a diaphragm was produced in a manner similar to that used for electrophoresis paints, ie the dispersion plastic dispersion and asbestos fibers. The sions are initially ao bath liquid with fully demineralized water, a from 10 percent by weight to a solids content of 5 to 20 percent by weight polyvinyl chloride dispersion, 2.5 percent by weight and, after homogenization, asbestos fibers and 87.5 percent by weight of water are added with fillers offset. The ratio of connective suspension used. However, a ratio of 1 5 divorce the voltage was 8 V. The current density are, preferably:: during Abmittel to fillers can be between 1: 1 and 1 as 1.5 at the anode was made after switching on of the current _t selected. The deposition voltage is between 5 within one ^; Minute from 0.3 to 0.02 ÄVdm ² . and 60 V, but preferably at 50 V. The diaphragm was gas-tight up to 0.5 atm and ¹ The made of plastic dispersions and filler showed in 6 n-KOH, an electrical resistance of the diaphragms are either when clearing Ö, 4Q / cmV ■,,.:. (::.
temperature-dried or a heat treatment. In another example, the electrolytic process was subjected to up to about 130 ° C, which in many cases resulted in an increase in strength relative to the solid content , 4.5 percent by weight asbestos fibers and

Finally, 92.5 percent by weight of water cannot be used as a binder. That at 50 V in one

Aqueous plastic solutions are used at- 35 half a minute on a nickel mesh with a

for example solutions of polystyrene in an aromatic mesh size of 0.3 mm deposited diaphragm

Hydrocarbons. In this embodiment the was gas-tight to over 1.1 atmospheres and had 6 n-KOH

Invention are ion exchangers as fillers, with an electrical resistance of 0.4 Ω / cm ² .

for example an anion exchanger on polystyrene- The diaphragm produced in this way has in the dried

basis, particularly suitable. 4 ° neten condition an asbestos fiber content of 86.5%

The deposition voltage here is appropriate and a binder content of 13.5%.

moderately 300 V. Depending on the solution used, F i g. Figure 2 shows one made according to the invention

medium and plastics, the component for fuel elements is dried, in which the fine

Diaphragms at room temperature or lightly meshed nickel nets 7 and 9 and the coarse mesh

higher temperature. 45 Nickemetz 8 into the parts labeled 10 and 11

The separation of the diaphragms can, however, be welded into the Plexiglas frame. On the

According to the invention on highly polished metal surfaces nickel nets 7 and 9 are each through

or electrically conductive networks without additional electrophoresis or electrophoresis and sediment

Liche sedimentation take place. This procedure deposited diaphragms 12 and 13, which the

Variant is particularly important when 50 include electrolyte compartment 14. On the diaphragms

Fillers metals and / or metal oxides used 12 and 13 can be powdery, sintered

and applied to an addition of binding agents in mesh or mesh-shaped electrodes,

is drawn. Diaphragms produced in this way, for example by welding the nickel meshes into the

made of carbonylnickel, must be made after the removal of the Plexiglas frame and the subsequent deposition

Divorce, however, is still to be sintered. 55 of the diaphragms is now a particularly favorable one

In all embodiments of the invention, perfect adhesion and separation of the frame and diaphragm can be achieved for and stable sealing between fuel cells.
Diaphragms require thorough cleaning and degreasing of the support surfaces. If necessary, the main feature is that the carrier materials can also be subjected to a suitable selection of the starting materials and additional pretreatment, for example separating conditions for the desired pickling or phosphating. Properties of the diaphragms can be set

With the help of the following figures and examples. By choosing a specific grain frack now the subject of the invention explains in more detail tion of the filler and variation of the amount will. 65 The binder and filler ratio can be, for example,

In Fig. 1 is first an arrangement for rejecting a fixed volume porosity or gas separation of diaphragms can be achieved by electrophoresis tightness and conductivity. Depending on and sedimentation. With 1 a bath can be used as a binder for plastics.

The diaphragms are also hydrophilic or hydrophobic be. Furthermore, two or more layers can be deposited one after the other, for example a hydrophilic layer can be combined with a hydrophobic layer.

It goes without saying that the diaphragms produced by the new process cannot be used limited to fuel elements. For example, they can also be used as diaphragms in electrolysers and accumulators are used.

Claims (11)

Patent claims: 1. Process for the production of diaphragms, in particular diaphragms for fuel elements from a dispersion of the starting materials or starting materials and binders, characterized in that that the starting materials or starting materials and binders by electrical ao phoresis or electrophoresis and sedimentation are deposited. 2. The method according to claim 1, characterized in that the diameter of the through Electrophoresis deposited starting materials as or binders is at most 1 μ. 3. Process according to claims 1 and 2, characterized in that the starting materials inorganic substances, for example asbestos, mica, metal and / or metal oxide, are used will. 4. The method according to claims 1 and 2, characterized in that as starting materials Ion exchangers are used. 5. Process according to claims 1 to 3, characterized in that electrophoresis paints are used as binders can be used. 6. Process according to Claims 1 to 3, characterized in that plastic dispersions are used as binders can be used. 7. The method according to claims 1 and 4, characterized in that as a binder in plastics dissolved in inorganic solvents are used. 8. The method according to claims 1 to 7, characterized in that the diaphragms on the anode are deposited. 9. The method according to claims 1 to 8, characterized in that the diaphragms on electrically conductive networks are deposited. 10. The method according to claims 1 to 8, characterized in that the diaphragms on highly polished metal surfaces deposited and after drying, curing or sintering of the documents are withdrawn. 11. The method according to claims 1 to 10, characterized in that the anode and Cathode are arranged horizontally. 1 sheet of drawings