DE1049360B - Process for the production of ion exchange membranes - Google Patents

Description

GERMAN

F16881IVc / 12d

REGISTRATION DATE: FEBRUARY 19, 1955

NOTICE DEK REGISTRATION AND ISSUE OF THE EXPLORATION PAPER: 29 J A N U A R 1 9 5 9

To improve the stability of ion exchange membranes are often plastic frameworks in the form of fibers, fabrics, nets, sieves and Foils embedded in the membranes. There are only those plastics in question, which are under the Manufacturing conditions of the exchange resins are stable. However, these are largely hydrophobic and have completely different chemical and physical properties than the hydrophilic ion exchange resins, so that there is no firm bond between the synthetic fibers and the exchange substance. For this reason, the resistance of such exchange membranes is also insufficient in many cases.

If one condenses z. B. a thread made of polyvinylidene chloride in an exchange membrane, so can pull the same out of the finished, swollen membrane in the longitudinal direction without the Membrane is damaged. If the thread in the transverse direction is broken through the overlying If the membrane layer is pulled out, the hydrogel of the ion exchanger will crumble off completely the smooth surface of the thread.

If a membrane is produced, its thickness is about the same as that corresponds to an embedded plastic grid, so that essentially only the gaps between the grids are filled by the ion exchanger, it is found that especially with changes in swelling the exchanger filling of the grid gradually crumbles out. If you want to avoid this, you have to Make the membrane thicker and completely embed the support structure in the exchanger membrane, what but leads to an increase in the electrical resistance.

It has now been found that these disadvantages can be avoided by using polymers as framework substances for exchange membranes used from ethylene derivatives which have reactive atoms or groups of atoms, and these condensed on the surface with such compounds, which in turn during membrane production be bound to the ion exchanger.

For example, if you want to use a polyvinylidene chloride fabric as a support for an anion exchange membrane, which is obtained by condensing an amine with formaldehyde, you first condense the fabric surface with an amine, whereupon the fabric pretreated in this way is added together with the same or another condensable amine of CH ₂ O converts to the exchange membrane. In this way, the ion exchanger is chemically bonded to the structural substance, which would not take place without precondensation of the fiber with the amine. One in the same process for the production of ion exchange membranes

Applicant:

Paint factories Bayer Aktiengesellschaft, Leverkusen-Bayerwerk

Dr. Karl Haagen, Leverkusen-Bayerwerk, has been named as the inventor

Well-pretreated polyvinylidene chloride thread or wire cannot be pulled out of the membrane after it has condensed into the membrane without the membrane structure being destroyed at the same time. Suitable amines for carrying out this process are, for. B. aromatic mono- and polyamines and aliphatic polyamines which still contain reactive amine hydrogen atoms. In addition, compounds that are reacted with the structural substances are mono- and polyoxybenzenes in which the hydrogen of a phenol group has been partially replaced by alkali and which can still be condensed _{with CH 2 O.} The last-mentioned compounds also enable the production of cation exchange membranes. To pretreat the builder substance, it is generally sufficient to heat the same with the aqueous alkaline solution of the organic compound for a few hours to 90 to 100 ° C. and, after the solution has dripped off, to dry it at the same temperature. This treatment generally results in a darkening of the fiber. Under appropriate reaction conditions, the conversion of the fiber substance with the amine can take place to such an extent that the fiber strength suffers.

It is already known that this improves the properties of film-forming substances can that reactive substances can be added to them before shaping, at least contain two alkylenimine groups and optionally heated before, during or after the shaping thereby improving heat resistance and water resistance. Be opposed to this but the membrane supports or supports, the reactive

809,747 / $ 31

capable atoms or groups of atoms with such Pre-treated compounds that are able to react with the reactive atoms or groups of atoms, but which can still be condensed with formaldehyde.

It is also known, with the aid of halogen-containing macromolecules, by reaction with nitrogen-containing ones Bases to produce ion exchange membranes. While in this process z. B. polyvinylidene chloride serves to react with amines to form exchange membranes, this is in the present case Method used only as a supporting fabric, which has no ion-exchanging tasks. Only on the surface of the polyvinylidene chloride thread does a reaction take place with a Substance instead, which in turn is condensed to an ion exchanger. * ·

The pretreatment of the fiber is given by a few examples described:

example 1

A grid of thin polyvinylidene chloride wire is placed in an aqueous solution which Contains 15% phenol and 4% NaOH, heated to 95 to 100 ° C. The solution is then allowed to drain off and dry for a few hours at this temperature. The fiber, which has a brownish tinge has assumed, is now used to produce an ion exchange membrane, which is based on the following Way is obtained:

223 g of phenoxyacetic acid (wet 81.8 ° / oig) are introduced and dissolved by heating at 95 to 100 ⁰ C in 40 ml of water are then at the same temperature with stirring, 255; into the solution of 100 g of sulfuric acid (lOO ° / oig. g of 2,4-benzaldehyde-disulfonic acid sodium (moist 59%), based on the molecular weight 266, are entered. The temperature is now increased to 105 to 110 ° C. and held until the benzaldehyde-disulfonic acid is consumed clear, viscous, deep cherry red solution. the mixture is allowed to cool slightly and then 215 g of formalin (40% strength) and 250 g of phenoxyacetic acid (81.8 ° / oig) was added and the mixture heated to about 8O ⁰ C. the temperature rises now without supply of heat further up to 106 ° C., with refluxing taking place. After the temperature has fallen to about 100 ° C. 90 g of paraformaldehyde are added all at once and the temperature is now kept at 95 ° C. until a viscous solution originated . The same is poured onto a glass plate on which the above grid is placed and, after covering it with a second plate, heated to 90 ° C. in the cupboard. A reddish, clear membrane is obtained which contains sulfo and carboxyl groups in a ratio of 1: 4. When the hydrogen form of the exchanger is converted into the sodium form, the swelling of the membrane increases considerably. At the same time, however, their strength properties deteriorate. If the membrane is to be used in the sodium form, one proceeds according to patent 915 036 and condenses a compound into the exchange molecule which does not contain any exchange-active atomic group, but is polyfunctional with regard to its reactivity towards aldehydes.

In the present example, 215 g of formalin solution and 520 g of phenoxyacetic acid were added furthermore 200 g of diphenyl ether or naphthalene are added and the amount of paraformaldehyde is increased 220 g increased. In addition, if one proceeds as indicated above, one also obtains one in the sodium form stable exchange membrane.

Example 2

A fabric made of polyvinylidene chloride is in a saturated, aqueous aniline solution, which is still undissolved Contains aniline, heated to 95 ° C for several hours and dried after the solution has dripped off. The tissue has turned blackish brown and becomes in

ίο the usual way as a support fabric for an ion exchange membrane is used, which is obtained as follows:

650 g of Phenoxäthyltrirnethylammoniumchlorid C ₈ -H ₅ OCH ₂ CH ₂ -N (CHs) ₃ Cl, which by reaction

was obtained from phenoxyethyl chloride with trimethylamine, together with 255 g of diphenyl ether, 350 g of paraformaldehyde and 730 g of sulfuric acid (70%) heated to 60 to 70 ° C. with stirring. the The temperature rises without additional heat input

ao 109 ° C and stays there for about 15 minutes Altitude, with refluxing taking place. The viscous condensation product obtained in this way is poured out on glass plates. The above tissue is then placed on top and pressed into the solution. Man

as is heated to 90 ° C for about 16 hours and receives a bright, slightly cloudy anion exchange membrane, which contains bound quaternary nitrogen atoms.

Instead of aniline, it is also possible to use the reaction product of phenoxyethyl chloride with polyethylenepolyamine, which reacts with CH ₂ O both on still unsubstituted amine hydrogen and on reactive nuclear hydrogen atoms of the phenoxy group and can form bridges to ion exchange molecules.

Substances used as connecting links, which after binding to the fiber are still free phenolic OH groups or substitutable H atoms on nitrogen atoms can of course can also be used for membranes in which epichlorohydrin acts as a crosslinker.

Example 3

A polyvinylidene fabric is in a solution of 40 g of polyethyleneimine (50%) in 100 ecm of water Heated to 97 ° C for 18 hours. The solution in which Cl is detectable is poured off and the tissue is dried at 110 ° C. Further processing takes place as in example 2.

Example 4

A polyvinylidene fabric is made in a melt of 22 g of resorcinol and 8 g of 50% sodium hydroxide solution Heated for 20 hours in a boiling water bath and then washed with water and dried. That The fabric has got an olive hue. Further processing takes place as in example 1.

Claims (5)

Claim: Process for the production of ion exchange membranes from formaldehyde condensable Compounds using membrane supports or supports made from polymers of these Ethylene derivatives which contain reactive atoms or groups of atoms, characterized in that that the surface of the membrane support or support is pretreated with such compounds, which are able to react with the reactive atoms or groups of atoms, but after they have taken place Reaction still contain more condensable hydrogen atoms, whereupon after the 5 6 Dry the pretreated supports with the documents considered: the same or with other condensable German Patent No. 901 844; . French compounds with the addition of formaldehyde Patent No. 1 040 122, or analogous compounds to exchange membranes in known manner reacted for 5 ^Contemplated prior patents: are. German Patent No. 915 036. O 809 747/315 1.59