DE1671796C3 - Acid-resistant separator for accumulators - Google Patents

Description

The invention relates to acid-resistant separators for accumulators, which are placed between the electrode plates be inserted to short-circuits in the accumulator as well as dissolving out the chemical substances to prevent from the electrode plates, namely a separator, which consists of a plate with a number of im There is spaced apart ribs which are provided on at least one side of the plate.

It is common practice, provided in fluid-sealed batteries with ribs separator to be used to the exact spacing of the accumulators ^ ₀ renplatten from each other to be observed and to provide sufficient space for the circulation of the liquid electrolyte and for the escape of gas released during the operation. The ribs must withstand the compressive forces acting on them, which could lead to a reduction in the protective distance, ie to warping or expansion of the panels. Of the polymeric materials hitherto used to produce the ribs, vinyl chloride polymers, including their copolymers, have proven to be particularly suitable. Cellular ribs are often used to achieve the desired spacing with a minimum amount of polymeric material.

Recently, the number has increased dramatically of accumulators, the method Trokkenlade be prepared by the so-called, in which isolated the individual battery cells and the batteries are made under conditions in which the ribs of the battery separator temperatures are _s0 up to 6O ⁰ C exposed . The battery separators are then removed from the accumulators, washed acid-free and dried at temperatures in the range from 121 to 177 ° C for up to 10 minutes. When ribs of cellular structure are subjected to these conditions, deformation of the ribs can occur to such an extent that their thickness decreases by up to 15% or the cellular structure of the ribs completely collapses, with the result that the channels necessary for the escape of gases are opened (, ₀ close, the battery plates are no longer kept at the correct distance, and that the tendency for the plate material to loosen out increases.

An acid-proof separator with ribs with r, _s cell structure has now been developed which has sufficient resistance to compressive forces in the accumulator and at the same time is practically stable even against the relatively high temperatures that occur during the dry charging process, although the ribs are compared to compact ones Ribs (without blowing agent) have a relatively low density.

The invention relates to an acid-resistant separator for accumulators, consisting of a plate and a number of spaced apart plasticized vinyl chloride polymers manufactured ribs with cell structure, which are arranged on at least one side of the plate, the is characterized in that the ribs 10 to 100 parts by weight of plasticizer mixture for the vinyl chloride polymer, based on 100 parts by weight of vinyl chloride polymer, and that the plasticizer mixture from a dialkyl fumarate or maleate. Maleic anhydride and a smaller amount Consists of alkyl phthalate.

The plasticizer mixture is one that crosslinks itself, i. H. under the action of heat in Polymerized in the presence of a catalyst; it is therefore referred to as a "crosslinking plasticizer". Accordingly, after heating to flux the mixture, the ribs consist of a hardened one Blending the vinyl chloride polymer with the crosslinked plasticizer. The hardened ribs have a closed cell structure with practically uniform pore size. The fumarate (or maleate) and the Maleic anhydride are the predominant components and thus the main reactants. Of the Dialkyl fumarates and maleates, diisooctyl fumarate is particularly preferred. A preferred mix consists of equal parts by weight of diisooctyl fumarate and maleic anhydride with a smaller amount on allyl phosphate and a catalyst which forms free radicals. A free radical forming catalyst z. B. di-tert-butyl peroxide or azo (bis-isobutyro) nitrile, is generally used to accelerate homopolymerization necessary.

The blowing agents are preferably used in finely divided form, ie in a particle size of about 1 to 3 μm. They are selected and matched to the catalysts so that their decomposition temperature is somewhat below the final melting temperature of the vinyl resin mixture. A difference between the maximum melting temperature and the Zerset / .ungstemperatur of the blowing agent of about 15 to 30 ⁰ C has proved to be suitable. Such a selection of the blowing agent makes it possible to achieve expansion when the resin mixture still has a relatively tough, gel-like consistency, ie when it is not yet so liquid that the development of gas leads to perforation of the surface of the mass and on the other hand is no longer so tough that sufficient expansion of the gas is prevented. There are a large number of blowing agents useful in producing the desired cell structure in the ribs; this includes, among others

Azodicarbonamide,

Dinitrosopentamethylene tetramine,

Diazoaminobenzene,

p, p'-oxybis (benzenesulfonylhydrazide),

Sodium carbonate, ammonium carbonate and

Ammonium hydrogen carbonate.
The nitrogen-forming compounds are particularly suitable. The amount of blowing agent can vary between about 0.5 and 10% by weight, based on the total resin. If 2 to 5% by weight are used, good pore formation is achieved.

According to one embodiment of the invention, a conventional plasticizer is added in addition to the crosslinking plasticizer. The ratio of crosslinking plasticizer to conventional plasticizer can be in the range from 20 to 100%, based on the vinyl chloride polymer.

The conventional plasticizers suitable for use in the invention include:

Dioctyl phthalate, diisooctyl phthalate,

Dodecyl phthalate, di (n-octyl, n-decyl) phtha! At,

Acetyl tributyl citrate, dioctyl sebacate,

Dihexyl adepate,

2-ethylhexyldiphenyl-phosphate and

Tricresyl phosphate '

In addition to these conventional plasticizers, an extender for the Find plasticizers use, such. B. naphthenic products of the petroleum industry.

In addition to the resin, the plasticizer and the blowing agent, the compositions can be used to produce the Additional modifying additives can be added to the separator ribs. These include fillers such as anhydrous calcium sulfate, talc, wood flour, clay, diatomaceous earth and asbestos; further stabilizing agents such as sodium silicate sulfate, tetranium pyrophosphate, tribasic lead silicate sulfate, calcium stearate, organotin complexes, epoxy resins and epoxidized oils or so-called hydrochloric acid removers; furthermore pigments such as carbon black, titanium dioxide and aluminum powder; then Dispersants such as zinc resinate, lecithin, glycol stearate, propylene glycol laurate and glycerin monooleate; Finally, blowing agent catalysts, e.g. metal soaps such as lead stearate, zinc stearate, zinc octoate and dibasic lead phosphate.

A typical mass for the production of ribs according to the invention is composed as follows:

Parts by weight Vinyl chloride polymers 100 Crosslinking plasticizers 10 to 100 Conventional plasticizer 20 to 100 filler 50 to 100 Blowing agent 0.5 to 10 Blowing agent catalyst 0.5 to 1.0 Forming free radicals catalyst 0.015 to 6

In a particularly preferred embodiment of the invention, the crosslinking plasticizer mixture used in an amount of 15 to 60 parts by weight per 100 parts by weight of vinyl chloride polymers.

The following examples are intended to illustrate the invention without intending to be a restriction. The stated masses were extruded onto plates after the ingredients had been mixed together. The mass was then ^{subjected to a temperature of 2O4 C} C for 30 seconds in order to activate the blowing agent and to melt the polymer. In the following examples, the crosslinking plasticizer consisted of 1 part by weight of diisooctyl fumarate, 1 part by weight of maleic anhydride and 0.25 part by weight of allyl phthalate.

Table 1 Example no. 2 3 4th Comparison ¹ 100 100 100 attempt 100 I. 1 1 100 Polyvinyl chloride 1 I. 1 1 1 Azodicarbonamide 1 60 60 60 1 Zinc octoate 60 60 15th 60 60 Dioctyl phthalate 15th 1.5 1.5 3 - Crosslinking plasticizer 3 78.8 74.2 68.0 - Di-tert-butyl peroxide 86.6 50 Shore A hardness

The above experiments show that, according to the invention, by using the crosslinking plasticizer, a considerable increase in Shore hardness is achieved compared to a composition which does not contain this crosslinking plasticizer. This will have the desired hardness and compressive strength as well

Table 2

the required stability against deformation due to heating despite lower density compared to solid ones, Achieved blowing agent-free masses.

In the experiments summarized in Table 2, the blowing agent was through for 13 seconds constant heating to 260 to 293 ° C decomposes.

Polyvinyl chloride Example no. 6th / ' - 8th - Comparative 0.089 Azodicarbonamide 100 100 100 search 1.298 - Zinc octoate 5 1 1 1 (Plastisol) 2.7% Calcium sulfate 100 1 1 1 100 Crosslinking plasticizer 1 95 95 95 - Conventional plasticizer I. 20th 20th 20th - Di-tert-butyl peroxide 95 b0 40 40 95 Rib thickness (in cm) 20th 0.75 1 1 _ Rib density (g / cm ³ ) 60 0.140 0.089 0.089 60 Decrease in rib thickness after 1 0.961 0.881 0.833 - Dry loading at 138 ° C 0.089 0.5% 0.800 1.25%

The above examples show that according to the invention even with a significantly reduced rib density a significantly improved compressive strength is achieved under dry loading conditions.

The method used to create the separator ribs is not critical. The single ones Ingredients are mixed together and then extruded or in some other suitable manner in a Applied separator plate and then exposed to a temperature that activates the blowing agent, for Sufficient fluxing the mixture and polymerizing the crosslinking plasticizer.

The ribs can be used with any conventional separator plate. To such Sheets include microporous sheets made of rubber or plastics such as polyethylene or polyvinyl chloride, or from cellulose fabrics impregnated with a polymer. The expression "Scheiderplatte" in the context of the present description denotes both a flat, porous plate and Plates with embossed depressions of the type mentioned above, which are used as separators for accumulators Find use.

Claims (1)

Claim: Acid-resistant separator for accumulators, consisting of a plate and a number of spaced apart ribs made of plasticized vinyl chloride polymers with a cell structure, which are arranged on at least one side of the plate, characterized in that the ribs 10 to 100 parts by weight of plasticizer mixture for the vinyl chloride poly -, ₀ mers, based on 100 parts by weight of vinyl chloride polymers, and that the plasticizer mixture consists of a dialkyl fumarate or maleate. Maleic anhydride and a smaller amount of alkyl phthalate.