DD209639A5 - POLYMERS - Google Patents

Abstract

HYDROPHILIC MICROPOROESES DIAPHRAGM MADE FROM A FLUOROUS SUBSTRATE, TO WHICH AT LEAST ONE FUNCTIONAL MONOMER D. FORMULA I CF LOW 2 = CF (CF LOW 2) LOW NA, THE FORMULA II CF LOW 2 = CF-O- (CFX-CFX) DEEP MA, A DIKARBONIC ACID, THE D. GROUP OF FORMULA III-H HIGH 3 (COOH) -R HIGH 4 (COOH) - AND AT LEAST ONE NON-FUNCTIONAL MONOMER D. FORMULA IV CY LOW 2 = CYZ OR THE FORMULA V CONTAINS THE MOLARE RATIO OF COPIED FUNCTIONAL MONOMER TO NON-FUNCTIONAL MONOMER IN THE FIELD OF 2: 1 TO 1:20. THESE DIAPHRAGMS HAVE IMPROVED BENEFICIENCY FOR IMPROVED PERFORMANCE IN CHLORINE ALKALI CELLS.

Description

242328 1 Berlin, 27.10. S3

61 100 12/37

polymers

field of use the invention

The present invention relates to a method of rendering hydrophobic fluoropolymers hydrophilic.

In particular, the present invention relates to a process for the preparation of hydrophilic fluoropolymers which are suitable for use as microporous diaphragms in electrochemical cells, specifically those "cells which are used to electrolyze" alkali metal chloride solutions.

State of the art

Electrolytic cells are commonly used to produce chlorine and an alkali metal hydroxide solution by electrolysis of an alkali metal chloride solution. Such cells are known as chlor-alkali cells. In the present specification reference is made to chlor-alkali cells as well as to processes which are typical of electrolytic cells in general and in particular.

There are three general types of chlor-alkali cells: "mercury" cells, "diaphragm" cells and the more recently developed "merabran" cells.

In the membrane cell, the anodes and cathodes are separated by cation-active permselective membranes;

λ unw λ η λ

61 100 12/37

these are membranes which are selectively permeable so that they pass only from. For example, cationic selectively permeable membranes suitable for use in chlorine cells include those membranes made from synthetic organic copolymeric material containing cation-exchanging groups such as sulfonate carboxylate and phosphanate. Perm-selective membranes are non-porous.

On the other hand, diaphragmatic cells in which the anodes and cathodes are separated by porous diaphragms permit the passage of both positive and negative ions as well as the passage of the electrolyte.

When operating a diaphragm cell for the electrolysis of alkali metal chloride solutions in order to produce chlorine and Alkalimetailhydroxiden it is required _t that the flow of solutions through the tortuous microporous diaphragm is not impeded by gas bubbles in the porous network.

In general, diaphragms made of asbestos fibers have been used, which in turn suffer from the disadvantages that:

1) the lifetime of the fibrous asbestos network in the chlor-alkali cells is limited;

2) the handling of asbestos fibers under environmental aspects

61 100 12/37

42328 1

often undesirable; and

3) the thickness of the fibrous substance often limits the extent to which the distance between the electrodes can be reduced.

Alternatively, diaphragms consisting of fluoropolymer substances in sheet or fiber form and which are non-reactive with the cell fluids have been proposed. However, such diaphragms suffer from the problem that they are difficult to moisten hydrophobic and alkali metal chloride and -hydroxidlösungen to _e and that they tend consequently to bubbles filled with gas to develop in the porous network of the diaphragm. This can lead to blockage of the diaphragm, high voltages and mixing of the product gases hydrogen and chlorine.

Various methods have been proposed for rendering such diaphragms hydrophilic. For example, UK Patent 1,031,046 and Belgian Patent 794 SS9 of ICI Ltd. describe. Processes for microporous layer diaphragms to which a hydrophilic particulate inorganic additive such as titanium dioxide is added to impart hydrophilicity to the diaphragm matrix. For the same purpose, other additives such as surfactants have also been proposed. Such additives have the disadvantage that they

1) generally adversely affect the processing of the fluoropolymer to the fiber or sheet form;

61 100 12/37

42328!

2) are easily leached by the flow through the diaphragm and

3) to satisfactorily facilitate the initial moistening of the tortuous microporous network to a satisfactory degree.

Object of the invention

The aim of the invention is to avoid the disadvantages described.

Explanation of the essence of the invention

It is an object of the present invention to develop novel hydrophilic fluorocarbon membranes for use in chlor-alkali electrolysis cells and a process of rendering hydrophobic fluorocarbon polymers hydrophilic by graft copolymerizing certain monomers to the hydrophobic fluorocarbon polymer substrate.

According to the present invention, there is provided a hydrophilic fluoropolymeric diaphragm comprising a fluorine-containing substrate to which has been added by radiation grafting a mixture of monomers containing at least one functional monomer selected from the group of compounds of formula I.

CF ₂ = CF (CF ₂ J _n A ^:

and the formula II

CF ₂ = 'CF-O- (CFX-CFX) _m A

comprises

61 100 12/37

24 2 3 28 1 -β-

in which A represents carboxyl, Alkoxykarbonyl, Hydroxyalkoxykarbonyl _v, cyano, hydroxysulfonyl, Fluorsulf onyl or the group -CO-NR ¹ R ^2, in which latter formula R ¹ and R ² inde gig from hydrogen and a C _1, .. C _g alkyl can be selected;

('an X is fluorine, the other X is selected from chloro, fluoro and a trifluoromethyl group, η is an integer from 1 to 12, m is an integer from 1 to 3, the diaphragm further includes unsaturated dicarboxylic acids or their derivatives which contain the group aer formula III

- C C -

I 1

COOH COOH

in which R and R - identical or unequally - or represents hydrogen, fluorine and chlorine, hydrogen, fluorine, chlorine and C ... C _c alkyl group or a Cg-halogenierte.C ^ ... are Alkyigruppe or together form a double bond; it also contains at least one non-functional monomer from the group of aliphatic vinylaronomers of formula IV

CY ₀ = CYZ

and aromatic vinyl monomers of the formula V

423

61 100 12/37 - 6 -

in which Y is hydrogen or fluorine, Z is hydrogen, fluorine or chlorine and W is hydrogen, a C ₁ ... Cg-alkyl, C ₂ ... C, - alkenyl, a halogenated C... C, --Alkyl or a halogenated C ^ ... Cg alkenyl.

By the term "functional monomers" is meant the presence of the cation exchange groups in the monomer such as carboxylic acid and sulfonic acid; or reference is made to groups which can be easily converted to cation exchange groups, as is the case, for example, with carboxylic acid esters and amides and nitriles. The term "non-functional monomers" refers to the absence of any ion-exchange group in those monomers.

The molar ratio of co-grafted functional monomer to nonfunctional monomer is in the range of 2: to 1: 20. Preferably, the molar ratio is in the range of 2: 1 to 1: 3.

The preferred fluorochemical substrate is a homopolymer or copolymer of fluorinated ethylene, especially a homopolymer or copolymer of vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene or hexafluoropropylene. Typically preferred substrates are polytetrafluoroethylene (PTFE); Polychlorotrifluoroethylene (PCTFE) and FEP; the latter is the common name for the copolymer of tetrafluoroethylene and hexafluoropropylene, with the hexafluoropropylene incorporated in said copolymer being present in a range of 3.5 to 12.5 % M / M.

The preferred functional monomers of the formula I, as they

2 3 2

61 100 12/37 - 7 -

can be used in our process include pentafluorobutene acid and C _1, C 2-alkylpentafluorobutenoates such as methyl pentafluorobutenoate and ethyl pentafluorobutenoate. A preferred functional monomer of formula II is trifluorovinylsulfonyl fluoride. Preferred functional monomers of the formula III are maleic acid, 1,2-difluoromaleic acid, acetylenedicarboxylic acid and amides derived from these acids, anhydrides and C ₁ ... Cg-Aikylester.

Preferred non-functional monomers of the formula IV are tetrafluoroethylene and chlorotrifluoroethylene. Preferred non-· functional monomers of the formula V are styrene and its halogenated derivatives such as o _<# ß, ß-Trifluorstyren and divinylbenzene and its halogenated derivatives such as QC, ß # ß "C <'»ß' * ß '-Hexafluordivinylbenzen "

By co-grafted functional and non-functional monomers on a polymeric substrate we mean that the functional and non-functional monomers form copolymer side chains on the polymeric substrate such that the functional monomer is attached to the substrate via a non-functional monomer.

The molecular structures of one type of the resins of the diaphragm of the present invention can be schematically represented as follows;

61 100 12/37

4232

(Polymer substrate)

(N)

(F)

(N)

wherein F and N represent the mer units derived from the functional and non-functional monomers, respectively; T is a polymeric chain terminating group or a polymeric substrate;

a, ο and d are 1 or more than 1, c is zero or 1 or more than 1.

It is appreciated that this illustration does not cover all possible configurations of the side chains of the resins of the present invention; For example, the scope of the invention, those side chains comprise, which branched configurations, and / or an ordered or random manner the distribution is to have functional and nichtfunktionellen.mer-cinheiten; the same applies to those side chains which have more than one type of functional unit and / or more than one type of non-functional unit.

61 100 12/37

24 2 3 28 1 -9-

In a further embodiment of our invention, we provide a process for producing a hydrophilic fluoropolymeric diaphragm according to the above definition, the method being composed of the radiation Kopfropfung of at least one functional monomer according to the above description and the Kopfropfung of minde- ( '·; least one non-functional monomer as described above on a fluoropolymeric diaphragm, which in turn comprises a polymer or copolymer of a fluorinated ethylene as described above.

It is a characteristic of this method that all side chains formed by the grafting process are linked to the polymeric substrate diaphragm by at least one of the non-functional raer units derived from the non-functional monomer. In this way, the non-functional i-monomer provides a screening group by which the non-functional monomers can be grafted onto the polymeric substrate.

In this process, the functional monomeric material and the non-functional monomeric material are mixed in proportions such that the molar ratio of the monomers present is in the range of from 1:20 to 9: 1. Preferably, the molar ratio is in the range of 1: 4 to 4: 1, but even better are the monomeric substances in a proportion even more approximate to equimolar ratios, i. h, in the range of 2: 1 to 1: 2 mixed together to obtain the preferred resins of the invention.

61 100 12/37

242328 1 -ίo-

The mixture of monomeric substances must be in liquid form; if necessary, use a conventional solvent to obtain a solution of the substances. Usually, one of the monomeric materials will itself provide the liquid phase which dissolves the other monomeric material.

On the other hand, and more advantageously, the solvent employed may be one which penetrates and swells the substrate material, thereby enabling the monomer solution to be substantially absorbed by the substrate material. Suitable solvents include toluene and xylene, and chlorinated hydrocarbons such as trichlorotrifluoroethane as well as oligomers of tetrafluoroethylene such as the tetramer and pentamer of tetrafluoroethylene.

It is further within the scope of the invention that the substrate material be pre-swollen prior to adding the monomers with such solvents. The advantage of such a procedure is that only minimal amounts of solvent must be used.

All known methods of radiation grafting can be used. For example, the substrate and the monomeric materials may be co-exposed to continuous or intermittent irradiation, or the substrate may also be pre-irradiated before being contacted with the monomeric materials. Preferably, the substrate and the monomeric materials are

24 2 3 28 1

61 100 12/37

4,

- 11 -

jointly irradiated; the substrate is immersed in the liquid phase containing the mixed monomeric materials, and the whole is exposed to irradiation with & rays, X-rays or an electron beam, but preferably with α- rays.

(It is essential in the process of the invention that both the functional monomeric material and the non-functional monomeric material co-exist during the grafting process so that the free radicals produced by the irradiation will both graft the non-functional groups onto the substrate and cooperate initiate the copolymerization of the functional and non-functional monomeric materials to form the chains characterizing the resins of the invention The grafting process is preferably carried out in the absence of oxygen.

In those instances where a derivative of the functional monomer such as maleic anhydride is used in the grafting process, subsequent chemical treatment such as hydrolysis is required to bring the dikarboxylate derivative into the active acid form.

It is also within the scope of our invention to introduce further cation exchange active groups into the resins, which include a substrate as well as functional and non-functional groups. The additionally active Grupoen are replaced by

61 100 12/37

4 2 3 28 1

- 12 -

Mixed modification of existing groups introduced. For example, the non-functional groups in the side chains can be sulfonated and / or carboxylated to yield active resins with increased ion exchange capacity and wettability.

In another embodiment of our process according to the invention, the functional and non-functional monomers as defined above are subjected to radiation grafting onto fluoropolymeric substrate material in particulate form such as in the form of beads or powder. The co-grafted product is then processed into a diaphragm. This can be done by any of the conventional methods, such as by stretching the resin. Compared to the direct co-grafting of the preformed diaphragm, however, this is the less preferred variant, since it is possible in the direct co-grafting to achieve the desired hydrophilicity by grafting the monomeric material only on the surfaces of the hikropores in the diaphragm , whereby the amount of required monomeric material can be reduced.

Most suitable way of carrying out the invention

Radiation co-grafting of the functional and non-functional linking monomers to the polymeric substrate appears to be determined by two competing reactions. One of these reactions is the desired co-grafting of the functional monomer onto the nonfunctional binding monomer, which in turn depends on the polyfunctional monomer.

61 100 12/37

242328 1

- 13 -

The substrate is grafted. The second reaction is the copolymerization of the monomers. In a preferred embodiment, since the rate of copolymerization may be greater than the desired co-grafting, we complete the already described process of radiation co-grafting of functional and nonfunctional linking monomers to fluorine-containing polymeric hydrocarbon substrate insofar as we include at least one polymerization inhibitor and at least one polymerization inhibitor Add chain transfer

 In this embodiment, higher levels of co-grafting can be achieved; typically the degree of copolymerization is increased by three or more times. The resins of our improved process have a higher ion exchange capacity; When such resins are incorporated in diaphragms for use in electrolytic cells, considerably better performance is achieved in these cells.

The preferred polymerization inhibitors for use in our method of the invention include, for example, quinone inhibitors such as p-senzquinone, naphthaquinone and hydroquinone in the presence of oxygen; inorganic inhibitors such as copper acetate, and compounds such as 2,2,6,6-tetramethyl-4-oxopiperidine oxide, 2,2,6, S-tetramethylpiperazine M-oxide and ghloranil.

The inhibitor concentration used in the method according to the invention is in the range of 0.001 to 2 % M / M of the total mixture of functional and monomer monomers and donor excimer substances - preferably they are present in the

61 100 12/37

242323 1 -14 -

Range of O, 01 ... 0.5 % M / M.

Since the radiation co-grafting is preferably carried out in a liquid medium, it is advantageous if the chain transfer agents are also solvents for the monomers. Preferred chain transfer solvent solvents include, for example, chloroform, carbon tetrachloride, dimethylformamide and mixtures thereof. Suitable geras are, for example, chloroform. Carbon tetrachloride, dimethylformamide and mixtures thereof. Examples of suitable mixtures are carbon tetrachloride / chloroform (1: 1) and carbon tetrachloride / dimethylformamide (1: 9). The concentration of the monomers in the chain transfer solvent is in the range of 10 to 50 % M / M, preferably in the range of 30 to 50 % M / M.

Solid chain transfer agents are less preferred because additional solvents may be required to provide a liquid medium for the radiation co-grafting. If solid chain transfer agents are used, then the M / M ratio of such chain transfer agents to the monomers should be in the same range as mentioned above for the preferred chain transfer solvent.

Industrial applicability

Hydrophilic diaphragms according to the invention show improved properties, in particular with regard to their wettability by the fluids present in electrolytic cells; As a result, they find particular application in electrolysis cells;

61 100 12/37

242328 1 -is

find other electrochemical systems application; for example as separators in batteries, fuel elements and electrolysis cells «

The invention will be illustrated but not limited in the following by examples in which all ion exchange capacities refer to highly alkaline conditions; d. h, all carboxylic acid and sulfonic acid groups act as exchange sites. Unless otherwise stated, all percentages and percentages are by weight.

Exemplary embodiment 1

100 g of commercial "KEL-F" powder (registered trade name for the homopolymer of chlorotrifluoroethylene), free of additives and with a particle size of about 150 sieve size, were suspended in monochlorobenzene (300 ml) which also contained 10.0 g (0.096 mol) Styrene and 9.4 g (0.096 mol) of maleic anhydride contained. The suspension was carried out in a reaction vessel equipped with stirrer, gas inlet and outlet ports and cooling devices. The suspension was exposed to Garama radiation.

Before and during the Garnma irradiation, a stream of nitrogen gas was bubbled through the contents of the vessel. The vial contents were heated to 52.5C with continuous stirring and exposed to gamma-irradiation at a dose level of 250 krad / hr for a total of 4.5 hours. The irradiated mixture received the total dose of

61 100 12/37

42328 1

- 16 -

1125 krad, then irradiation were adjusted _t heating and stirring. The grafted resin powder was quantitatively transferred to an i.V. column and freed from unreacted monomers, solvents and undesirable by-products. Finally, the resin was converted to the acid form and dried in a drying oven at 60.degree.

The percent of grafting calculated by representing the increase in resin as a percentage of the mass of grafted resin produced was 2.25 %. The ion exchange capacity determined by titration was 0.18 meq / g.

Since the ion exchange capacity is related to the amount of functional monomer incorporated by grafting (maleic anhydride), it provides a measure of the hydrophilicity achieved by the radiation co-grafting method of the present invention. Assuming equi-polar proportions of the groups as derived from the styrenic and maleic anhydride monomers in the polymeric side chains grafted onto the "KEL-F" skeleton, the theoretical ion exchange capacity of a grafted-on resin would be 2.25 g 0.20 mg / g. Infrared spectrum testing of the product has demonstrated the presence of dicarboxylic acid and styrene in the molecular structure of the resin.

When added to an aqueous medium containing 25, iM / M sodium chloride, the hydrolyzed resin was wetted by the solution and sank to the bottom of the solution, -The fluoro

51 100 12/37

24 2 3 28 1 -

17 -

Polymer powder could not be wetted by the solution prior to grafting and hydrolyzation and had formed a white surface film on the liquid.

This resin is pressed to form a film, then a microporous diaphragm is made by a technique known in the art, such as calendering, which film is stretched X-Y dimensionally until the desired pore size is achieved. The diaphragm is constructed by successive layers of stretched film to the desired size. The hydrophilicity of the resin remains unchanged during this manufacturing process, so that the hydrophilic properties are transferred to the final diaphragm.

Embodiments 2 to 5

Using the method described in Example 1, graft copolymers of styrene-maleic anhydride according to the invention were prepared on "KEL-F" powder, although using different total monomer concentrations (while keeping the molar ratios of the monomers constant) in order to refer to them produce different levels of grafts, which in turn result in different exchange capacities of the grafted product resin, as shown in Table 1.

61 100 12/37

Ir "; O

Table 1

21 , 0 53 '3 126 »6 286 , 6 19 , 7, 50 , 7 120 , 0 266 , 6 1 25 3 12 5 , 06 S , 01

Embodiment. 2 3 4

Monomer concentration in monochlorobenzene

Styrene g / l

Maleic anhydride g / l Percent grafting% Theoretical ionic strength

exchange capacity mEq / g .0,11 0,28 0,4-4 0,57 Measured ion exchange capacity mäq / g 0,09 χ 0,40. χ

χ = not determined

The infrared analysis confirmed the presence of dicarboxylic acid and styrene in the molecular structure of the grafted resin products. All hydrolyzed resins were wettable with 25% sodium chloride solution.

These resins were processed into microporous diaphragms according to the manner described in Example 1.

Examples 6 to S

These exemplary embodiments illustrate the products according to the invention whose fluorine-containing hydrocarbon polymer substrate differs from that of the Ausfup.gsbeispisle i to 5

61 100 12/37

242328 1 -i9-

is divorced «

In these embodiments, styrene and maleic anhydride were subjected to graft copolymerization to "FLUQN" powder which is a homopolymer of tetrafluoroethylene by the method of the present invention ("FLUON" is a registered trademark of Imperial Chemical Industries Ltd.). The conditions already described in Example 1 were used. The percentage grafts and ion exchange capacities of the product resins in their acid form, as obtained using different monomer concentrations, are shown in Table 2.

Table 2

Embodiment 6 7 S

Monomer concentration in monochlorobenzene

Styrene g / l

Maleic anhydride g / l Percent grafting % Theoretical ion output capacity mEq / g Measured ion exchange capacity meq / g

χ = not determined

21.0 33.7 143.3 19.7 31.7 135.0 0.75 1.22 3.12 0.06 0.11 0.23 0.08 / ν

61 100 12/37

242 3 2

- 20 -

Infrared analysis confirmed the presence of dicarboxylic acid and styrene in the molecular structure of the grafted resin products.

These resins were processed into microporous diaphragms according to the manner described in Example 1,

Embodiments 9 to 12

Treatment of product samples of some of the foregoing embodiments with a known method for substituting sulfonate groups in the styrene groups yielded sulfonated resins having the ion exchange capacities listed in Table 3.

Table 3 Unsupported product . Ex, 1 Ionenaus 31 exchange capacity tnäq / ausf . Ex, 2 Theoretically 17 Measured Example no. ausf , -3Sp, 4 0 64 0.26 9 ausf . Ex. 7 0 17 0.13 10 ausf O, 0.52 11 0 0.13 12

The ion exchange capacities of these sulfonated resins all exceeded the ion exchange capacities of their non-sulfonated analogs.

61 100 12/37

2Λ 2 3 28 1

- 21 -

Embodiment 15

100 g of "KEL-F" powder similar to that used in embodiment 1 was suspended in 300 ml of a solution of maleic anhydride and tetrafluoroethylene in toluene. The solution contained 0.7 g / kg maleic anhydride and 0.7 g / kg tetrafluoroethylene,

The suspension was frozen by immersion of its container in liquid nitrogen. She was degassed and exposed to the recovery of room temperature. The degassing operation was repeated three times, then the container was sealed.

The solution in the closed container was heated to 70 C and held for 24 h at this temperature. Subsequently, the container and container contents were subjected to a total of 50 hours of gamma irradiation at a dose rate of 100 krad / h.

After irradiation, the vessel was again immersed in liquid nitrogen, as a precaution, the suspension was frozen with the tetrafluoroethylene before opening the container. The powder was washed free of unreacted and ungrafted homopolymer monomers. It turned out that one 20 ^; ijige grafting had taken place. The powder was then pressed to form a film; the film was then hydrolyzed. The ion exchange capacity of the hydrolyzed film was found to be 0.54 meq / g. On the basis of the percentage

61 iOO 12/37

4 23 28 ί

- 22 -

Grafting and ion exchange capacity was calculated to be about 1: 3 molar ratio of functional to non-functional groups in the side chains grafted onto the "KEL-F" substrate.

Embodiment 14

In this embodiment, the advantage of using a swelling solvent is demonstrated.

4 g of "KSL-F" powder similar to the powder used in Example 1 was dipped in hot xylene. The powder swelled and absorbed a quantity of xylene equal to about 7 % of the powder mass. Excess xylene was removed. To the swollen powder was added an equimolar mixture of styrene and maleic anhydride. After 12 hours, the excess liquid phase was decanted off and the swollen powder was irradiated with the absorbed monomers under nitrogen at 80 krad / h for 24 hours ,

After removal of any homopolymer formed and removal of any unreacted monomers, the powder was hydrolyzed.

On the basis of the mass increase, it could be calculated that a 10% graft had taken place.

The ion exchange capacity of the resin was found to be .1.1 meq / g; assuming grafting of styrene and maleic acid in equimolar proportions

61 100 12/37

242328 1 - ₂ 3-

anhydride would indicate this to be a ll, 0% grafting.

This resin was processed into a microporous diaphragm by the procedure described in Example 1.

Exemplary embodiments 15 to 26

These embodiments demonstrate the use of gamma irradiation on perfluorinated films or powders in the presence of unsaturated perfluorinated monomers containing functional or functional ion exchange groups.

De, a sample of the monomer (5.0 g) was dissolved in sin glass reaction vessel, is introduced and mixed with 5.0 g unsaturated, perfluorinated monomer or monomer Gemiscb. The halt I _n the reaction vessel was frozen in liquid nitrogen and placed under vacuum to remove the existing system in the air.

After thorough evacuation, the vacuum pump was disconnected, the contents of the vessel allowed to thaw and reach room temperature. This process, in the following referred to as degassing, was repeated three times before the Reaktionsgafäß was closed.

When this technique was used, the contents of the reaction vessel were in a de facto oxygen-free atmosphere. In addition, the prepared samples were then stored for a period of 24 hours at selected temperatures to obtain an equilibrium state.

61 .100 12/37 ό L O 1 - 24 -

maintains "

Thereafter, the reaction vessel was placed in an irradiation cell room and exposed for 120 hours to gamma rays emitted from a cobalt-60 source corresponding to an intensity equivalent of 10 krad / h,

In some experiments, a solvent - trifluorotrichloroethylene - was added at the concentration listed in Table 4. The simultaneously irradiated content of the reaction vessel was given a completely absorbed dose of 1.2 Mrad; After completion of the irradiation, the contents of the glass reaction vessel were frozen in liquid nitrogen before opening the vessel. The grafted substrate (foil or powder) was washed free with a suitable solvent of unreacted monomer and homopolymer and dried to constant weight in a vacuum drier at 60 ° C.

The Pfropfungs percentage (expressed as the mass increase of the film as a percentage of the mass of the grafted film), the infrared spectra OCE grafted film (carbonyl absorption at a frequency of 1795 cm ~) and the ion exchange capacity (expressed as meq / g) used to characterize the modified psrfluorinated substrate produced by gamma irradiation.

The results presented in Table 4 indicate that the perfluorinated hydrophobic substrate was grafted with unsaturated perfluorinated monomer which was functional

61 100 12/37

2 3 2 8 1 - ²⁵ -

or has functional ion exchange groups.

The following abbreviations are used in the tablets and in the description:

TFE = tetrafluoroethylene

PTFE = polytetrafluoroethylene

PEP = copolymer of tetrafluoroethylene and

hexafluoropropylene

PFBA = perfluorobutene acid

MPF3 = methyl perfluorobutenoate

MAA = methacrylic acid

IEC = ion exchange capacity

The sizes are given in microns and refer to the thickness, if they are foils; in the case of powders, the indication refers to the particle size.

These films and powders are processed into microporous diaphragms according to the procedure described in Embodiment Example 1.

61 100 12/37

242328 1

- 26 -

Taoelle 4 size Monomer concentration % M / M PFBA MPF3 - Solvent concentration % M / M C / Pfrop fung IEC fläq / g 175 100 - - 2.5 0.13 Execution ex. substratum 2 ... 100 100 - 3.6 0.21 15 PTFE foil 175 - 100 - 1.4 - 16 PTFE powder 2 ... _ - - 2.2 0.11 17 PTFE foil 125 100 100 - 1.6 - IS PTFE powder 125 -  mm - 1.2 - 19 FEP film 175 30 30 70 3,1 ' 0.15 20 FEP film 175 - - 70 2.4 0.11 21 PTFE foil 125 30 30 70 2.5 0.13 22 PTFE foil 125th - - 70 1.3 - 23 FEP film 2 .., 30 30 70 ι α 0.20 24 FE? foil 2 ... 70 2.3 0.11 25 PTFE powder 26 PTFE powder , 5 »5 .5 ► 5

61 100 12/37

4232

- 27 -

Embodiments 27 to 33

In these embodiments, the conditions selected in the previous embodiments were repeated except that the irradiation grafting was performed at the temperatures shown in Table 5 with the results shown in the same table.

Table 5

Ausf.- Substrate Size Monomer Conversion % lemp * IEC

bsp. center medium Pfropcu mäq /

% M / M concentration ° g

PF3A. MPF3 tration

27 PTFE foil 175 100 - 28 FTFc film 175 IOU 100 29 PTFE foil 175 - 100 30 PTFE foil 175 - - 31 FEP film 125 ICO - 32 FEP film · 125 100 100 33 FEP film 125 - 100 34 FEP 125

3.1 35

3.9 OO 0.21 2.1

3.0 80 0.13

2.2

3.1 30 0.15

2.6 80 0.11

ί-OiXi

61 100 12/37

242328 1.

- 28 -

1 2 3 4 5 6 7 8th 9 35 PTFE foil 175 30 - 70 3.5 50 0.17 36 PTFE foil 175 - 30 70 3.0 50 - 37 FEP film 125 30 - 70 3.0 50 0.15. 38 FEP film 125 - 30 70 2.5 50 - Working Example e 39 to 43

In these embodiments, the general conditions of Embodiments 15 to 26 have been maintained; the only exception was that the temperature of the mixture during irradiation was 50 ° C and that the solvent was varied in the manner shown in Table 6 to give the results also shown in Table 6.

In each case, the substrate was 175 micron PTFE film,

  61 100 12/37

24 2 328 1 - 29 - Solvent concentration % M / M CV / 0 Pfrop test IEC meq / g table 6 70 3.4 0.17 Solvent medium 70 3.3 0.20 Ex. Monomer concentration % M / M PFBA MPF3 CF ₂ ClCFCl ₂ 70 70 1.2 1 * 8 mm 39 30 water 70 2.1 0.03 40 30 Methanol tetrachloro carbon 41 42 30.- 30 Carbon tetrachloride 43 -

The grafted films were processed into microporous diaphragms by the method described in Example 1.

Exemplary embodiments 44 to 49

These embodiments had the same conditions as Embodiments 15 to 26; it illustrates: the use of a mixture of two functional monomers.

61 100 12/37

4232

- 30 -

Table 7

Ausf, - substrate size Monomerkon- solution % bsp.

center medium Pfrop meq / g

% M / M concentration PFBA MPFB MAA tration

44 PTFE foil 45 PTFE foil 46 PTFE powder 47 PTFE powder 48 FEP film 49 FEP film

175 25 - 25 175 - 25 25

2 ... 5 25

2 ... 5

125 25

125

25

25 25

25 25

50 17.6 0.78 50 20.0 0.44 50 28.0 0.95 50 31.2 1.12 50 9.5 0.41 50 * 12,1 0.35

Embodiment 50

This embodiment illustrates the i-insert of the graft inhibitor alpha-pinene.

FEP film (2.0 g) was placed in a glass reaction vessel and treated with PFBA (9.0 g), alpha-pinene (0.12 g, 0.5, p total concentration), "Arclone" P (S, Og), Vv'asser (3.0 g) and ammonium perfluorooctanoate (0.025 g, 0.17 % total concentration). ("Arklone" · is a registered trademark

61 100 12/37

24 2 3 28 1 - ₃₁ -

for l, l, 2 ~ trichloro-l, 2,2-trifluoroethylene),

The mixture was frozen in liquid nitrogen, the air was evacuated, and the contents of the vessel were then allowed to stand at room temperature. This process of degassing was repeated three times, then TFE (3.0 g, free of any inhibitor) was introduced into the reaction vessel at liquid nitrogen temperature * The glass vessel was sealed and allowed to stand at room temperature overnight. It was then irradiated at ambient temperature for 120 hours at 10 krad / h. The mixture thus received a total dose of 1.2 Mrad; it was frozen again with liquid nitrogen before the glass jar was opened. The grafted film was collected, washed free of copolymers and unreacted monomers, and dried in a vacuum oven at 60 ° C.

The percent grafting was 47 %. The infrared spectrum of the polymerized film showed a carbonyl absorption frequency of 1 795 cm; the ion exchange capacity (IEC) determined by titration was 0.2 meq / g.

This film was processed according to the method described in Example 1 to form a microporous diaphragm,

Embodiments 51 to 55

The procedure of Example 50 was repeated except that * the concentration of the inhibitor alpha-pinene varies in the manner shown in Table 8

61 100 12/37

242328 1

• - 32 became

 Table 8

Ausf.- concentration % IEC bsp. of alpha-pinene grafting meq / g

/O

ο / _M / _M

51 0.00 52 0.05 53 0.1 54 1.0 55 2.5

61 0.11 53 - 59 0.10 35 0.12 10 0.04

Embodiments 56 to 58

The procedure of Example 36 was repeated, except that instead of the solvent "Arklone P" a same hatred of a listed in Table 9 solvent or Lösungsrnittelgeraisches was used.

Table 9

ZXJ

Ausf.- 'Solvent % IEC

bsp. Grafting meq / g

56 "Arclones" P / Chloro 60.0 0.02 f orm (1: 1)

57 carbon tetrachloride / 60.9 chloroform (1: 1)

53 chloroform 60.0

61 100 12/37

242328 1 -33-

Embodiments 59 to 66

These embodiments demonstrate the effect of gamma irradiation on a perfluorinated microporous diaphragm in the presence of unsaturated perfluorinated monomers containing functional or functional ion exchange groups.

The selected microporous diaphragm "Gorstex" (registered trademark of Gore Associates) has a pore size of about 100, u and a thickness of about 1500, u.

The "Goretex" diaphragm has pronounced hydrophobic properties, however, a modified hydrophilic diaphragm was obtained by the method of the present invention. "The procedure of Embodiments 15 to 26 was applied; the results obtained are shown in Table 10. In each case a dose rate of 15 krad / h was used to give a total dose of 1.25 Mrad. The solvent used was "Arclone" P.

61 100 12/37

4 2 3 2 8

I - 34 -

table

Ausf.- substrate and Monomerkon- solution % ι em- % bsp, size centering medium- Pfrop- mäq /

O / / Q PFBA M / M MPFB MAA conc. % M / M nature ⁰ C fung G 100 - - - - 35 4.8 0.28 - 100 - -, 35 5.1 0.25 100 - - - SO 5.6 0.31 100 - - 80 5.9 0.29 30 - - 70 35 3.8 0.20 - 30 - 70 35 4.1 0.18 25 - 25 50 35 26.3 0.91 25 25 50 35 30.5 1.06

59 "GoreteX"! 500

Claims (29)

51 100 12/37 242328 1 .35. £ rfindunqsanspruch 1. Hydrophilic fluoropolymeric microporous diaphragm, characterized in that it comprises a fluorine-containing polymeric substrate to which a mixture of monomers has been attached by irradiation grafting; at least one functional monomer from the group of compounds of the formula I. CF ₂ = CF (CF ₂ J _n A,
and the formula II CF ₂ = CF-O- (CFS-CFX) _m A comprises in which A is carboxyl, alkoxycarbonyl, hydroxyalkoxycarbonyl, cyano, hydroxysulfonyl, fluorosulfonyl or the 12 Group -CO-NR R, where in the latter formula "R v. and R are independently selected from hydrogen, and a C .., Cg-alkyl; one X is fluorine, the other X is selected from chlorine, fluorine and a trifluoromethyl group; η is an integer of 1 ... 12, m is sin Integer of 1, .. 3; characterized by further comprising unsaturated dicarboxylic acids or their derivatives containing the group of formula III _C COOH COOH
contain, 61 100 12/37 2 3 28 1 - 2. A microporous diaphragm according to item 1, characterized in that the molar ratio of said functional monomer to said non-functional monomer is in the range of 2: 1 to 1: 3. 2 3 Z in which R and R "are identical or different for ϊί / asserstof f , fluorine, chlorine or a C,.. Cg-alkyl or a halogenated C ₁ .., C, - alkyl or together form a double bond; it further comprises at least one non-functional monomer from the group of aliphatic vinyl monomers of formula IV CY ₂ = CYZ and aromatic vinyl monomers of the formula V CY = CYZ where Y is hydrogen or fluorine, Z is hydrogen, fluorine or chlorine, and W is hydrogen, a C,. C ₁ -C 4 alkyl, C ₁ -C 4 alkeryl, C ₁ -C 4 halogenated halogen or C ₂ -C 4 halogenated, C ₁ -C 4 alkenyl; and wherein the molar ratio of co-grafted functional monomer to co-grafted non-functional monomer ranges from 2: 1 to 1:20. 3. A microporous diaphragm according to item 1 or 2, characterized in that it is in the fluorine-containing polymeric substrate to a homopolymer or copolymer of a 61 100 12/37 242328 1 - * - fluorinated ethylene. 4. A microporous diaphragm according to item 3, characterized in that the fluorinated ethylene is vinylidene fluoride. 5. A microporous diaphragm according to item 3, characterized in that the fluorinated ethylene is tetrafluoroethylene. 6. A microporous diaphragm according to item 3, characterized in that it is chlorotrifluoroethylene in the fluorinated ethylene. 7. A microporous diaphragm according to any one of items 3 to 6, characterized in that the copolymer includes hexafluoropropylene units. 8. A microporous diaphragm according to any one of items 1 to 3, characterized in that it is polytetrafluoroethylene in the fluorine-containing polymeric substrate. 9. A microporous diaphragm according to any one of items 1 to 3, characterized in that it is polychlorotrifluoroethylene in the fluorine-containing polymeric substrate. 10. A microporous diaphragm according to any one of items 1 to 3, characterized in that the fluorine-containing polymeric substrate is a copolymer of tetrafluoroethylene and hexafluoropropylene, wherein the incorporated in said copolymer hexafluoropropylene in a concentration range of 3.5 ... 12.5 % M / M is present. 61 100 12/37 11. Microporous diaphragm according to one of the items 1 to IG, characterized in that it is in the compounds of formulas I and II to pentafluorobutene, C. to C _ß -Alkylpentafluorbutenoate and Trifluorvinylsulfonylfluorid. 12. A microporous diaphragm according to item 11, characterized in that it is methylpentafluorobutenoate and Ethylpentafluorbutenoat said C * to Cg-Alkylpentafluorbutenoat. 13. A microporous diaphragm according to any one of items 1 to 10, characterized in that the compounds of formula III are f'laleinsäure, 1,2-Difluormaleinsä'ure-, acetylenic such as their anhydrides, amides and G ₁ to C _r Alkyl ester, 14. A microporous diaphragm according to any one of items 1 to 13, characterized in that it is tetrafluoroethylene and chlorotrifluoroethylene in the non-functional monomers of formula IV. 15. A microporous diaphragm according to any one of items 1 to 13, characterized in that the non-functional monomers of the formula V are styrene, c <, ß, ß-Trif luorstyren, divinylbenzene and οί, β, β, c <. ' , ß ', ß' ~ hexafluorodivinylbenzene. 16. A process for producing a microporous diaphragm according to any one of items 1 to 15, characterized 61 100 12/37 42328 1 - 39 - by irradiation grafting at least one above-defined functional monomer and at least one non-functional monomer as defined above onto a fluoropolymeric diaphragm which defines a polymer or copolymer of the type defined above. th kind and having the molar ratio, of ^radio-v - ^/ tionellem monomers to nonfunctional monomer in the range of 1: 1: 20 to 9th 17. Method according to item 16, characterized in that the molar ratio is in the range from 1: 4 to 4: 1, 18. The method according to item 16, characterized in that the molar ratio is in the range of 1: 2 to 2: 1. 19. The method according to any one of items 16 to 13, characterized in that the material which contains the diaphragm and the monomer mixture, jointly a Be . "" Radiation from gamma rays, X-rays or electron beams. 20. A method according to any one of items 16 to 19, characterized in that the mono Raeren mixture is dissolved in a solvent which is able to bring the diaphragm to the sources, 21. A method according to any one of items 16 to 19, characterized in that before the monomers are added the diaphragm is treated with a solvent capable of brining the diaphragm to swell, 61 iOO 12/37 42328 1 - 40 - 22. The method according to item 20 or 21, characterized in that the solvent is selected from toluene, xylene, trichlorotrifluoroethane and oligomers of tetrafluoroethylene. 23. Method according to one of the items 16 to 22 , characterized by .the fact that the monomer mixture additionally contains at least one polyraerization inhibitor and at least one chain transfer agent, 24. The method according to item 23, characterized in that the polyraerisatior .sinhibitor under p-benzoquinone _t naphthaquinone and hydroquinone in the presence of oxygen, copper acetate, 2,2,6,6-tetramethyl-4-oxopiperidine-l-oxide, 2, 2, 5, 6-tetratethylpiperazine N-oxide and chloranil are selected. 25. Method nach.Punkt 23 or 24, characterized in that the polymerization inhibitor is present in a concentration range of 0.001 to 2 % M / M - based on the Gesarat mixture of monomers and chain transfer agent. 26. The method according to item 25, characterized in that the concentration range is 0.01 to 0.5 % M / M. 27. The method according to any one of items 23 to 26, characterized in that it is the chain transfer agent is a solvent which is chloroform, carbon tetrachloride, dimethylformamide and their Ge 61 100 12/37 242328 1 _ ₄₁ _ mixing was selected. 28. The method according to any one of points 23 to 27, characterized in that the monomer concentration in the chain transfer solvent in the range of 10 to 60 % M / M. 29. The method according to item 28, characterized in that
said range is 30 to 50 % M / M.