DE2534097C3 - Process for making a nonwoven microporous membrane material from asbestos fiber - Google Patents

Description

Claim 1, characterized

1 to 15 minutes and finally the obtained ^ gJ ^^ E Ge ^ mtheition pretty much

^{the Knsta11} - äÄh ⁱ Ä ^E jst

3. The method according to one of claims 1 and 2, to be obtained, explains the oeirachtliche number of characterized in that a mixture of _{5 is} already tried

holds and the weight ratio of filler to 30 for so-called

Latex + asbestos is preferably 1 to 25: 1. "D ^^^^^^^^^^ i

4. The method according to claim 1, characterized in that they are formed themselves. This way of working is with

shows that the pore-forming agent calcium cells with finger-shaped ^^ oden are particularly useful

carbonal is one that can be obtained by immersing yourself in a moderately. The We. development of this ^ IeJrn * has

, 0 to 25gew _h -% acetic acid solution for 35 * ^% "££££ $ £ * ^^ Ά

removed for at least 24 hours. Td that on the other hand for reasons of performance and

the efficiency, the current densities can be increased.

This has two consequences: first has the meaning

40 of the deposited diaphragms decreased in favor of the prefabricated diaphragms; Farther

The invention relates to the production of micro-have obtained by depositing asbestos

porous membranes as diaphragms in electrolysis diaphragms * £££ * £ {? α] Κ? Α

^ It is well known that the diaphragm behaves in a 45. It is also known that the Abidtoden of

ElectroWse cell like a porous medium that gives the asbestos fibers a difficult to adjust position

toSS ^ with low voltage drop and rosity leads and ^^ J ^ Jrtm

the electrolyte flows from a chamber in the disadvantages of the non-solidified structures ^ on -

the other allowed. This results in a complex, namely: Sources J ^ * ^d «^ ™ *"'

of mechanical, electrical and hydraulic 5 <> whereby a minimum distance between dw »E ^ troden

Conditions that are all the more critical as is required in the and the difficulty of thin layers

to obtain modern electrolysis cells with high current density with low voltage drop d. _e

work must be carried out, unless this is not justified- instability of the diaphragm during electrolysis,

bare voltage losses have to be accepted. in the event of business interruptions and "m s.tu" -

The required properties are actually countered. _it "i _n ; _w "i _a i, r, .n current. From a mechanical point of view, this should be for this reason: Since a genre has been looking for a well-defined and dimensionally stable diaphragm, diaphragms consisting of a micro-space and a plastic membrane with a porous plastic membrane base have to be homogeneous. A swelling of the diaphragm should be avoided electrolytes against resistant polymers, at the same time it should give off gases, which sometimes form inside it. I have already tried to find the different values.

From an electrical point of view, the diaphragm can be combined with one another through various options. So is from the

marked its relative resistance. Including FR-PS 21 23 514 known a homogeneous Su pen sum

one understands the relationship between the resistance of the asbestos fibers and fillers such as bentonite

Electrolyte-soaked diaphragm to the resistance of the 65 and this suspension with an acid-proof

Mix Flektrolvten latex.

It hl been found that this relative resistance are known from CH-PS 5 50 272 already mchtgewebte

It is tied to the porosity of the diaphragm, but oriented felt-like membrane materials for

3 4

Electrolytic cells known that are manufactured, in k mn, advantageously calcium carbonate in one

the thermoplastic fibers to a mat carded grain size from 2 to 50 μπι.

so that the fibers are essentially parallel. The aqueous latex preferably has a solid

are to each other, whereupon this mat transversely to the content of 50 to 60%.

Fiber direction under increased temperature and pressure 5 Mixing or kneading is carried out slowly

is solidified. So this is a running mixer, like <100 rpm. As a plasticizer

purely organic fleece material, which z. B. serve as particular oils, such as mineral oils

Diaphragm in batteries is suitable whose requirements are made from petroleum with emulsifiers.

are fundamentally different from a membrane. Advantageously, in the course of the material, such as the following components, calculated for the chlor-alkali second stage, are applicable to electrolysis. 1 part asbestos, applied: 10 to 100 parts fillers, According to other procedures, diaphragms 1 to 100 parts polytetrafluoroethylene in latex, 0.5 to large pore volume, are obtained by adding 2 parts plasticizer and 1 to 20 parts water, a surface-active agent into the asbestos fiber The shaping is preferably carried out on a suspension introduces. Unfortunately, it is with this work- i ₅ roller mill whose rollers run at the same speed or at different speeds despite the improvements achieved. This form of mastering the formation of the coagulum can be facilitated by working with something, above all the electrolytic properties of the elevated temperature, preferably by using diaphragms. at 30 to 80; C for 1 to 15 min.Then this difficulty is based on the one hand on the type ₂₀ is the formed fleece or the web more expediently the polymer used (usually dried in polytetrafluorine manner, then sintered and then the ethylene, which requires high pressures for shaping, pore-forming filler is removed, and likes to retain trapped gases) and sintering is preferably carried out at a temperature, on the other hand, on the fineness of the fillers with a defined point above the crystal melting point (= conversion grain size distribution transition to the amorphous state, i. e. completely non-woven microporous Membranmatcrials from) the disappearance of the polymers, preferably in an asbestos fiber as diaphragms for electrolytic cells which operate at 25 to 75 ° C and the overlying temperature with high yield and high current densities. Thus, at 330 min to 37o ⁰ C, within 2 to 20th

According to the invention, this object is thereby achieved. The sintering time depends on the sintering temperature and

resolves that for the production of a nonwoven one also depends on the thickness and the composition

micro-porous membrane material made of asbestos fibers from the web. .

£ 2 first process asbestos fibers with min- The poien-forming agent can be used in a simple manner

at least one extractable filler is dry-mixed, removed, namely by at least 24 h Emin In the second stage, a polytetrafluoroethylene 35 immerses the sintered and cooled web in a

If necessary, add the latex with a plasticizer, under aqueous, 10 to ² % weak acid.

Stirring DZW kneading adds, in a, third stage of preferably 25% acetic acid, which optionally e, n

the mass is rolled into a fleece web, which is then

is festiet and, in a further stage, contains extractable urea.

Ee 'filler is removed with pore formation. Finally, it is more advantageous that the membrane is preferred in the first stage in 5 to 30 minutes at a stirring speed of at least 800 rpm by immersion in alcohol, for example, alcohol, optionally in a partial vacuum, degassed in the second stage 1 to 15 min with a kneading machine, of course, varying intrinsic speed of a maximum of 100 rpm and in the shafts can be achieved by combining this method of operation with a fritted stage in 1 to 15 minutes on a roller frame 45 whose methods of operation are known per se. 30 to 8O ⁰ C worked, whereupon it is then; Such consist, for example, that the held product is sintered, namely the preferential membrane is reinforced by being applied to a mesh or tissue above the melting point of the crystal in 2 to 20 minutes; It is also possible to-Ah starting mixture is preferably 1 part by weight sammengeseLte structures generated by a au-A <fhestfasern 10 to 100 parts by weight calcium carbonate 50 other depositions of a plurality of layers, as a filler, 1 to 100 parts by weight Latex solid, υ.5, which differ in the composition of the applied up to 2 parts by weight of plasticizer and 1 to 20 parts by weight of mixture. .. parts of water, so that the weight ratio of the web is characterized by the non-microporous latex to polytetrafluoroethylene + asbestos, preferably due to the very high proportion of filler, which means that the total composition is 55%, with advantages Chrysotile is used as asbestos, amosite the weight ratio of filler to latex polymer or crocidolite. The filler can be an asbestos preferably (1 to 25): 1. ? utlZ ^ geae ^ nenfaUs be inorganic material. In microporous state, the erfinrfindin ^ sgemäße method is distinguished allows before dung modern membrane by J * large pore

the filling 60 volume and your

For example calcium carbonate, colloidal stood from 1.5 to 10.

S Slox.de or any other material, the following examples are for further explanation

which can ultimately be removed or destroyed tion of the invention.

25th

example 1

In a first stage, 20 parts by weight of chrysotile asbestos fibers - length 0.5 to 5 mm, density 2.3 to 2.5 g / cm ^s , mean diameter 18 mm - and 400 parts by weight of commercially available calcium carbonate 15 to 20 μΐη mixed (101, 3800 rpm, 10 min) and the mixture worked through at a speed of 45 rpm.

100 parts by weight of a 60% strength by weight commercial polytetrafluoroethylene dispersion (mean particle diameter 0.25 μm) and 21 parts of plasticizer (mineral oil with emulsifier) were added to this first mixture. The whole thing was worked through for 2 minutes and then shaped on the rolling mill (length 70 cm, 2 minutes, 50 ^° C.). The web was 2 h at 9O ⁰ C and then dried for 1 hour at 180 ⁰ C.

Example 2

The procedure was as in Example 1 and the obtained Product also sintered in 6 min at 350 ° C.

Example 3

Example 2 was repeated and the sintered product was then immersed in a 25% acetic acid solution for 96 hours dipped to loosen the filler.

Example 4

The procedure was as in Example 3, but degassed for a further 30 minutes at a partial vacuum of 740 mm Hg.

σ = tensile strength in kg / cm ²

D = elongation at break (%)

L - lengthways

T = in the transverse direction ³ S

at a 8th T D. T thickness density games L. 43 18th L. 150 mm 1 34 17th 45 10 1.75 1.78 2 37 20th 7.5 120 1.75 1.72 3 19th 45 45 1.9 0.86 4th 15th 1.8 0.38

45

These examples show that one obtains membrane materials with well-defined properties that meet the different requirements depending on whether a diaphragm with greater or lesser density or stiffness, microporosity or not is sought.

Example 5 to 8

These examples were carried out according to Examples 1 to 4, but the kneading time increased 4 min and the rolling time extended to 3 min. The following table summarizes the various values :

60

at σ T D. T thickness density games L. 6.5 L. 40 mm g / cm ³ 5 14th 28 60 10 1.9 1.76 6th 28 22nd 15th 70 1.9 1.69 7th 29 20.5 30th 50 9.2 1.19 8th 40 30th 2 0.37

097

These examples show in comparison with the previous ones Examples of the adaptability of the procedure, according to which by modifying the procedural stages the properties of the process product can be varied.

Example 9

A sheet was produced according to the above examples and the same types of asbestos, latex and Filler used; the following working conditions were observed:

Calcium carbonate 800 parts by weight

Asbestos 40 parts by weight

Latex 200 parts by weight,

50% solids

Plasticizer 39 parts by weight

Mixing 3800 rpm, 10 min

Kneading 45 rpm, 2 min

Shaping up

Roller mill 2 min at 50 "C

Drying for 2 h at 100 ^° C

Sinter for 7 minutes at 35O ^D C

The filler was removed with a 25% acetic acid in 48 hours and 2 hours under a reduced pressure of mm Hg degassed.

The sheet obtained had the following properties:

Layer thickness 1.67 mm

Relative resistance 1.8

Permeability 0.27 cm ³ / min. cm ²

The relative resistance here is the quotient of the resistance of the diaphragm soaked with electrolyte and resistance of the electrolyte.

The permeability indicates the throughput of saline solution in cm ³ (electrolyte) per minute and per cm ² diaphragm under a pressure of 54 g / cm ² .

The diaphragm was used for electrolysis of a saline solution in a filter press cell with an iron cathode and metal anode, cathode distance 5 mm, used.

Current density 25 A / cm ²

Cell voltage at

State of equilibrium ... 3.47 V after 150 h

composition

the lye:

NaOH 125 to 130 g / l

Chlorate 0.8 to 1 g / l

Fluid pressure on the

Diaphragm 40 mm WS

Example 10

This example is identical to the previous one with the modification that a somewhat greater layer thickness of the diaphragm of 1.84 mm and a lower permeability of 0.08 ml / min · cm ^{2 were} achieved during rolling.

Current density 25 A / dm ²

Cell voltage in
State of equilibrium ... 3.4 V

composition

the lye:

NaOH 120 g / l

Chlorate 0.4 to 0.5 g / l

Liquid pressure

the diaphragm 150 mm WS

Example 11

The procedure was as in Example 9, with the difference that the mixture contained only 10 parts of asbestos fibers ; n stopped.

Layer thickness 1.43 mm

Relative resistance 1.7

Permeability 0.24 ml / min · cm ²

Current density 25 A / dm ^s

Cell voltage in
State of equilibrium ... 3.13 V

composition

the lye:

NaOH 125 g / l

Chlorate 0.8 to 0.9 g / l

Fluid pressure on the

Diaphragm 20 mm WS

Examples 12 and 13

It was worked as in the previous examples with the following modifications:

Calcium carbonate 500 parts by weight

Asbestos 20 parts by weight

Latex 200 parts by weight, 50% solids

Plasticizer ... 25 parts by weight layer thickness of the diaphragm 1.43 mm (example 12) or 2.63 mm (example 13).

Mix .
Kneading ..
Rollers ..
dry

Sintering

Removing the filler

Degas

Layer thickness

Relative resistance

permeability

Current density

Cell voltage

composition
the lye:

NaOH

Chlorate

Fluid pressure on the
Diaphragm

3800 rpm, 10 min 45 rpm, 2 min 15 s 2 min at 50 ⁰ C for 2 h at 90 ⁰ C and 2 hours at 18O ⁰ C 3minbei365 ° C for 90 h immersion in 25% acetic acid for 1.5 h vacuum 740 mm Hg 1.94 mm

2.8

0.14 ml / min · cm ² 25 A / dm * 3.25 V

118 g / l 0.9 g / l

28 mm WS

30th

45

The procedure was as in the previous example , with the modification that sintering was carried out at 250 ° C. for 11 minutes and the layer thickness of the diaphragm was 1.51 mm.

Relative resistance 4.1 Permeability 0.18 ml / min · cm ^a Current density 25 A / dm *

Cell voltage at State of equilibrium ... 3.12 V

Lye:

NaOH 124 g / l

Chlorate 0.7 gfl Fluid pressure on the Diaphragm 70 ram WS

example 2.8 13th 3 12th 0.15 0.08 Relative resistance 25th 25th Permeability, ml / min · cm ² Current density, A / dm ² 3.04 3.63 Cell voltage in the same weight condition 120 140-150 Lye: 0.4 0.3 Na C H (g / l) 60 350 Chlorate (g / l) Fluid pressure on the iel 14 Diaphragm, mm WS E isp

Example 16

The same conditions as in Example 15 were used, with the modification that a other commercially available calcium carbonate was used and the layer thickness was 1.55 mm.

Relative resistance .... 2.2

Permeability 0.10 ml / cm ² · min

Current density 30 A / dm ²

Cell voltage 3.45V

composition
the lye:

NaOH 122 g / l

Chlorate lg / 1

Fluid pressure on the
Diaphragm 180 mm WS

Example 17

In this example, the following recipe was used worked using two commercially available calcium carbonate types:

A 320 parts by weight

B 80 parts by weight

Asbestos 20 parts by weight

Plasticizer 40 parts by weight

55

60

Real resistance 5.1 Permeability 0.19 ml / min Current density 30 A / dm * Cell voltage 3.42 V composition

the lye:

NaOH 125 g / l

Chlorate lg / 1

Fluid pressure on the Diaphragm 110 mm WS

cm*

Example IS Example 18

65 In this example, a sheet reinforced with a wire was used with the same recipe as before, made of galvanized steel fabric works in compliance with the following working conditions, wire diameter 0.25 mm, mesh size 1.41 editions: usable area 72%, weight 460 g / m *.

709613 / «

25th

Composition of the mixture:

Filler (calcium carbonate, 15 to

20 μm) 500 parts by weight

Asbestos 20 parts by weight

Polytetrafluoroethylene 100 parts by weight

Plasticizer 25 parts by weight

The working conditions were the same as in Example 9 with the difference that 15 minutes for one Temperature of 385 ° C was sintered.

Relative resistance 2.5

Permeability 0.15 cm ³ / min. cm ²

Properties of the non-reinforced membrane: Tensile strength:

in the longitudinal direction .... 16 kg / cm ²

in the transverse direction .... 8 kg / cm ² elongation:

lengthways ... 40%

in transverse direction 25%

Current density 30 A / dm ²

Cell voltage 3.36V

composition

the lye:

NaOH 120 g / l

Chlorate 0.9 g / l

Fluid pressure on the

Diaphragm 200 mm WS

Example 19

In this example, contrary to the method of operation of the previous examples, the two rolls of the rolling machine were used.

Driven at different speeds, and one twice as fast as the other.

Composition of the mixture:

Filler (calcium carbonate,

Diameter 15 to 20 μm) 400 parts by weight

Asbestos 20 parts by weight

Polytetrafluoroethylene 100 parts by weight

Plasticizer 26 parts by weight

Mixing 3800 rpm / 10 min

Kneading 45 rpm, 4 min

Drying for 2 h at 9O ⁰ C

Rolling 4 min, 50 ° C

Sintering 6 min, 350 ° C

Removal of fillers .. 84 h immersion in

25% acetic acid

Degassing 30 min negative pressure

750 mm Hg

Relative resistance 3.5

Permeability 0.17 cm ³ / min ■ cm ²

Current density 30 A / dm ²

Cell voltage 3.5 V

composition
the lye:

NaOH 130 to 140 g / l

Chlorate lg / 1

Fluid pressure on the

Diaphragm 110 mm WS

Claims (1)

also to the shape of the channels through which the electrolyte _{finally flows} , a diffusion through the mem- Patent claims: E'be prevented. Especially with the chloride Process for making a nonwoven alkali electrolysis must involve OH ion migration mixes, in one! .. stage a polytetrafluor- man the & * ^ tdictedes Sf ^^ beTaTch the Ethylene latex, if necessary with a plasticizer, then reduces its porosity but also the while stirring taw? Kneading admits, in a 3rd stage, voltage drop in the P ^ _c Äl de permeability rolls out from the crowd, a nonwoven web Toggle .In ^ '^ ^{Γ 1ι5} H'ns.cht to de ^ meab'lto is then solidified, and in another one of the diaphragms so se in ^ «J" Stage the extracted filler under pore- ^ KSS