CA1109474A

CA1109474A - Polymerisable disulphimide derivatives containing maleic imide groups and their use

Info

Publication number: CA1109474A
Application number: CA322,885A
Authority: CA
Inventors: Klaus Elfert; Hans J. Rosenkranz; Helmut Ritter
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1978-03-07
Filing date: 1979-03-05
Publication date: 1981-09-22
Also published as: EP0004287B1; ES478338A1; DK93779A; EP0004287A2; EP0004287A3; DE2960207D1; JPS54122270A; IL56787A0

Abstract

POLYMERISABLE DISULPHIMIDE DERIVATIVES
CONTAINING MALEIC IMIDE GROUPS AND THEIR USE

Abstract of the Disclosure Compounds corresponding to the general formula wherein Ar denotes a benzene or naphthalene group;
R1 and R2 are identical or different and denote H, CH3, F or Cl;
R3 and R4 are identical or different and denote H, phenyl, branched-chain or linear alkyl having from 1 to 6 C-atoms, branched-chain or linear hydroxyalkyl having from 1 to 6 C-atoms, Cl or F; and X denotes H, Na, K or NH4.
1 to 50 % by weight of said compounds, 50 to 99 % by weight of acrylonitrile and 0 to 30 % by weight of at least one further monomer copolymerisable with acrylonitrile may be copolymerized. The copolymers are suitable for producing semi-permeable membranes which may be used for reverse osmosis and ultrafiltration.

Description

11~9474 This invention relates to new unsaturated monomer~
containing maleic imido and disulphimide groups (i.e.
di~ulphonyl amino groups) and to a process for their preparation.
In numerou~ synthetic polymer product~, certain properties and combinations of properties can be obtained or improved by incorporating ~trongly acidic components a~ comonomer~ in the polymer chain. Particu-larly important among the~e propertie~ are the capacity to ab~orb ba~ic triphenyl methane dyes, anti-electro-~tatic propertie~, acceptability to the ~kin in the ca~e of ~ynthetic i'ibres and the wetting power of gla~s fibre~
and of pigments. Although a broad range of polar monomers i~ available, e.g. acrylic acid, maleic acid, acrylamide or hydroxyethyl acrylate, the ef$ect~ obtained by chemical incorporation of these monomer unit~ are frequently in~u~ficient 80 that it i9 necessary to resort to highly polar systems, preferably with acidic components.
However, only a small number of comonomers which introduce strongly acidic groups into synthetic resins polymeri~ed by radical polymerisation has hitherto been available. Virtually the only comonomer~ of this type which are of any technical interest are methallyl ~ul-phonic acid and vinyl sulphonic acid, and even these have certain disadvantages. Methallyl sulphonic acid is particularly disadvantageous owing to its high transier constant, i.e. the quantity in which these monomers can be incorporated in synthetic resins is limited, and in addition the overall reaction velocity is reduced and the molecular weights of the resulting polymers are correspondingly reduced. Vinyl sulphonic acid can only be handled in the iorm of an aqueous solution on account of its instability, and this entails additional costs, e.B. for transport and storage.
Furthermore, it ha~ been dlsclosed, inter alia in Le A 18 595 , 1~9~4 British Petent No. 867,006, that (meth)acryloyl amino-benzene-benzene disulphimides ean be prepared by the reaction Or halide~ oi (meth)acrylic acid with amino-benzene-benzene-di~ulphimides and can be used as comonomers ~or radical polymerisation. From the general iormula on page 1 of the said specification, it i8 also possible, by a mosale-llke ~uxtaposition, to eonstruet 3-earboxy (meth)acryloyl-aminoaryl-aryl-di~ulphimide (i.e. (methyl)maleic acid monoamidoaryl-aryl-disulphamide) correspondine to the following formula:
H(CH3) 0 0 n n HOOC-CH_C-C-NH-arylene-S-NH-S-aryl n n n O O O
which is used as a starting material for the preparation of the monomers according to the invention or formed as an intermediate product. In the general iniormation given in the afore~aid British Patent Speciiication on page 2, lines 34 to 41, it is recommended to prepare ~ueh eompounds by the reaetion oi maleie aeid anhydride with disulphiDides which contain primary amino groups.
The British Patent Speeiiication eontains no iurther details about the reaetion eonditions or any practieal examples. Ii the reaetion oi maleie aeid anhydride with aminobenzene-benzene-disulphimides is carried out by the usual methods, for example aeeording to U.S.
Patent No. 3,018,290, eolumn 5, lines 42 - 47, i.e. in suitable solvents~ using the reaetants in approximately equimolar proportions, the N-substituted maleie amido aeids are not only obtained in very poor yields but are also highly eontaminated.
It is also known that the N-substituted maleie amido aeids may be converted into the corresponding maleie imide der~vatives by eyelodehydration in organie Le A 18 ~

114~9474 solvents at 0 - 100C in the presence of acetic acid anhydride and catalysts such as nickel salts and tertiary amines (see German Oifenlegungsschrift No.

2,040,094), or in anhydrides of lower fatty acids such as acetic acid anhydride at temperatures above 25C in the presence of catalysts such as tertiary amines (see U.S. Patents Nos. 3,018,290 and 3,018,292). However, no N-substituted maleic imides in which the N-substituent is a diaryl sulphimide have yet been disclosed.
The present invention provides compounds corresponding to the general formula (I):

.. .
Rl - C - C
/Ar S02 ,N S02 Ar (I) R2 ~ C - C 3 R4 wherein Ar denotes a benzene or naphthalene group, pre~erably a benzene group;
Rl and R2 may be identical or different and denote H, CH3, F or Cl, preferably H or CH3;
R3 and R4 may be identical or difierent and denote H, phenyl, straight-chain or branched-chain alkyl with 1 - 6 C-atoms, straight-chain or branched-chain hydroxy-alkyl with 1 - 6 C-atoms, Cl or F, preferably H; and X denotes H, Na, K or NH4, preierably H or Na.
The invention also provides a process for the preparation of N-substituted maleic imide derivatives by the reaction of maleic acid anhydride or a maleic acid anhydride which iB substituted by CH3, F or Cl, wlth an aminoaryl-aryl-disulphimide, followed by cyclo-dehydration of the resulting N-substituted maleic amido Le A 18_595 :

4'74 acid in an anhydride of a ~aturated $atty acid having a maximum Or 5 C-atom~ in the pre~ence of a cataly~t, characteri~ed in that the reaction Or the maleic acid anhydride or ~ub~tituted maleic acid anhydride with the ~inoaryl-aryl-di~ulphimide 1~ carried out in the melt with or without a cataly~t and the maleic acid anhydride i9 u~ed in a 1 to 5 tlme~ molar exce~ over the amino-aryl-aryl di~ulphimide.
The proce~s take~ place in accordance with the following reaction scheme, in which the variou~ ~ymbol~
have the meaning indicated for formula (I):
n (A) (2 to 6 mol) Rl - C - C \
ll O + H2N-Ar-S02-N-S02-Ar.
R2 ~ C - C R3 X R4 O (a) ~olvent-free, ~ (cataly~t) (B) Hooc-csc-coNH-Ar-so2-N-so2-Ar + (1 to 5 mol) RlR2 R3 X R4,, (b) Rl - C - C
Il ~

O
cyclodehydratlon 0 catalyQt n ~ ~saturated iatty acid anhydride Rl - C - C~
ll N - Ar - S02 - N - S02 - Ar + H20 " R3 X R4 Le A 18 595 , _ ~lV9474 The ~minoaryl-aryl_disulphimides (a) used as starting materials ior reaction (A) (see reaction scheme) are either known in the llterature (see Methoden der Organischen Chemie, Houben-Weyl, Volume 11/1, (1957), page 368) or csn be prepared by known methods (see Germsn Pstent No. 757,262, Germsn Auslegeschrift No.
1,249,259 snd U.S. Patent No. 2,374,934). The reaction with the substituted or unsubstituted maleic acid anhydride (citraconie acid anhydride may also be used) i9 carried out solvent-rree, i.e. at temperatures of about 60 to 180C, preferably 100 to 140C, using irom 2 to 6 mol, preferably irom 3 to 5 mol oi anhydride to one mol of the disulphimide. The excess of anhydride can easily be removed subsequently by distillation under vacuum or by extraction with a suitable solvent.
As catalysts for reaction (A) there may be used tertiary amines corresponding to the following formula:

Rl - N - R3 wherein Rl, R2 and R3 may be identical or difierent and denote alkyl groups ha~ing from 1 to 4 C-atoms. Cyclic tertiary amlnes such as pyridine, N-Cl-C4-alkylated morpholines, piperidines, piperazines and triethylene diamine (Dabco) may also be used.
The above-mentioned catalysts are preferably used in quantltieq of from 0.2 to 2 % by weight, based on the 25 quantity oi~ substituted or unsubstituted maleic acid an-hydride put into the process.
Cyclodehydration of the maleic acid monoamidoaryl-aryl-disulphimides (b) may be carried out by known methods, for example the methods according to U.S. Patents Nos. 3,018,290 and 3,018,292 or German Offenlegungsschrift No. 2,040,094. It is preierably carried out by the method disclosed in U.S. Patent No. 2,444,536, i.e. in an Le A 18 595 l~V~4~4 anhydride of a saturated fatty acid having from 2 to 5 C-atoms, such a~ acetic acid anhydride, in the presence of alkali metal salts of these i'atty acids having from 2 to 5 C-atoms, such as ~odium acetate, at temperatures ranging from about 25C to below the decomposition point of the reactants or of the maleic amido acid-disulphimide formed, in particular at 60 to 100C.
The anhydride Or the fatty acid having from 2 to 5 C-atoms is preferably used in a 1 to 10 times molar quantity, in particular a 5 to 8 times molar quantity, based on 1 mol of maleic amido acid disulphimide. The quantities of alkali metal salts of the aforesaid C2 -C5 fatty acids added, in particular of sodium acetate, preferably amount to from 5 to 20 % by weight of the quantity of anhydride of the fatty acid anhydride put into the process. The excess of anhydride used and the fatty acid formed may be distilled off after cyclodehydration, optionally in a vacuum, and the maleic imido disulphimide may be isolated after crystallization or it may be obtained by the addition of a suitable precipitating agent, suah as a lower alcohol(C1-C4 carbon atoms), water (pH = 7), acetone, etc. before dlstillation.
The maleic lmido-disulphimides according to the invention can easily be copolymerised by radical copolymerisation, they are easily handled and stored as solid powders and they are also dietinguished by being - obtainable by exceptionally simple methods of preparation.
The monomers according to the invention may be polymerised by radical polymerisation. A particularly preferred variation of such polymeriBation iB the copolymerisation with monomers such as (meth)acrylic acid, (meth)acrylamide, (meth)acrylic acid esters having from 1 to 12 C-atoms, preferably from 1 to 4 C-atoms in the alcohol component, butadiene, ~tyrene, maleic acid, fumaric acid, vinyl chloride~ vinylidene chloride, vinyl Le A 18 595 7~

acetate, malcic imides, vinyl pyrrolidone, vinyl carba~ole, vinyl pyridine, vinyl caprolactam or acrylonitrile.
The copolymers with acrylonitrile may be used for the production of fibres if they contain the compounds according to the invention in proportions of, preferably, from 1 to 5% by weight. These fibres are distinguished from the known polyacrylonitrile products by their improved dye absorption with basic dyes; they are also more acceptable to the skin.
New semi-permeable membranes of copolymers of maleic imidoaryl-aryl-disulphimides and acrylonitrile can be made and used for reverse osmosis and ultra-filtration.
Reverse osmosis and ultra-filtration are methods of separating substances. This separation takes place by passing an aqueous solution under pressure over the surface of a semi-permeable membrane so that the solvent and possibly a proportion of the dissolved substances pass through the membrane while the other components of the solution are held back by the surface of the membrane and can be concentrated in the solution.
Technically the most important of these membranes are those made of cellulose derivatives, in particular cellulose acetate. In spite of their efficiency in allowing water to pass through and separating substances, they have various disadvantageous properties which limit their general usefulness. These include their lack of chemical resistance, in particular their sensitivity to hydrolysis at high and low pH values, and their sensitivity to degradation by microorganisms. This causes deterioration of the membrane properties in the course of time.
Membranes of polyacrylonitrile have already been produced for reverse osmosis. These membranes have a certain capacity to retain salts .

7~

but a low permeability to water (S.W. Saltonstall Jr. et al., OSW Res. Der.
Progr. Report No. 220 (1966)). Ionic acrylonitrile copolymers have been described in German Auslegeschriften Nos. 2,145,183 and 2,346,011. Although these substances have a high permeability to water, they are only suitable for the filtration of solutions of macromolecular substances, i.e. for the separation of relatively high molecular particles.
No membranes are therefore as yet available which have both a high permeability to water and a high selectivity for substances in the range of medium molecular weights without the disadvantages described above of the usual cellulose acetate membranes.
It has now been found that membranes which do not have the dis-advantageous properties of conventional membranes based on cellulose acetate can be obtained from maleic-imido aryl-aryl-disulphimide/acrylonitrile copolymers. These membranes have a low separation limit of about 500 and permeability to water, but still one which is considerably greater than, for example, that of membranes produced from pure polyacrylonitrile.
Applicants copending divisional application provides semi-permeable membranes based on copolymers of acrylonitrilelmonomers containing disulphimide groups, characterised in that the copolymers consist of copolymerised units of (I) 50 - 99 % by weight, preferably 80 - 95% by weight, of acrylonitrile, (II) 1 - 50 % by weight, preferably 5 - 20 % by weight, of at least one monomer corresponding to the general formula (I):

_ g _ 1~)9~4 Rl - C - C~
2 ~ 2 ~ (I) R2 ~ C - C R3 X R4 o wherein Ar denotes a benzene or naphthalene group, preferably a benzene group;
Rl and R2 may be identical or different and denote H, CH3, F or Cl, preferably H or CH3;
R3 and R4 . may be identical or difierent and de-note H, phenyl, straight-chain or branched-chain alkyl having from 1 -6 C-atoms, straight-chain or branched-chain hydroxyalkyl having from 1 - 6 C-atoms, Cl or F, preferably H, and X denotes H, Na, K or NH4, preferably H or Na, and (III) 0 - 30 ~ by welght, preferably 0 - 15 ~ by weight, of at least one other olefinically unsaturated monomer which is copolymerisable with acrylonitrile, the sum of the percentage contents of (I) to (III) being in all cases 100.
- The following are mentioned as further examples of oleiinically unsaturated monomers (III) which are copolymerisable with acrylonitrile:
(meth)acrylic acid, (meth)acrylamide, (meth)acrylic acid alkyl esters having.irom 1 - 12, preierably from 1 - 4 C-atoms in the alcohol component, hydroxyalkyl-(meth)-acrylates havlng irom 2 - 4 C-atoms in the ~kyl group, sulphoalkyl-(meth)acrylates having from 2 - 4 C-atoms in the alkyl group, maleic acid, vinyl chloride and vinyli-dene chloride. The above-mentioned monomers are preierred;
iurther examples include butadiene, styrene, iumaric acid, Le A 18 595 .. ..

7~

maleic acid sem;-amide optlonally mono or di-substituted hy Cl - C4 alkyl groups on the n;trogen; male;c imide optionally substituted by Cl- C4 alkyl or by phenyl on the nitrogen; vinyl pyrrolidone, vinyl pyridine or methacrylic acid salicylate ~salicylic acid-~-methacrylate).
Preparation of the copolymers from monomers (I) to (III) is carried out by conventional methods, for example the method described in German Patent No. 1,089,548.
The monomer units are built into the resulting copolymers in a substantially statistical distribution. Although it is possible in principle to vary the molecular weights of the polymers according to the invention within wide limits by Icnown methocls, polymers having relative viscosities in the range of about 1.6 to 4.6 are particularly suitable for the production of membranes.
The membranes may be prepared, for example, as follows: a homogenous solution of the copolymer obtained from monomers (I) to (III) (= polymer) is prepared in a suitable solventl preferably a solvent of the amide type.
From 5 - 35 % by weight of the polymer, based on the total quantity of ; polymer and solvent, are dissolved in a polar aprotic solvent with the addition of from 1 - 10 % by weight of an alkali metal salt or alkaline earth metal salt, preferably LiCl, LiBr, LiNO3, MgCl2, CaCl2 or CaBr2, or an organic amine such as triethylamine, tripropylamine, pyridine, ethanolamine or triethanolamine. The following solvents are preferred: dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidone, hexamethyl phosphoric acid triamide, dimethyl sulphoxide, and mixtures of these solvents. Heating may be employed to accelerate the solution process.
This casting solution is used for the production of 11~7~

a film by applying the solution to a glass or metal surface or any other suitable substrate, e.g. a continuously moving belt or a drum, to form on it a layer of from 150 - 5no ~ in thickness.
The solvent is partly evaporated off by heat treatment. The film is dried at a temperature of from 40 - 150~C for 2 - 60 minutes. This step may be omitted, depending on the des;red membrane properties of the fi]m.
After a cooling phase of several minutcs, the film is immersed in - a precipitation bath and left therein for about 60 minutes. The liquids used for precipitation may be solvents which are miscible with the organic solvent of the casting solution and possibly also capable of dissolving the ~ salt, but are non-solvents for the polyamide. Water, methanol, ethanol and - i-propanol, with the optional additon of salts such as CaC12, are suitable for this purpose. I~ater is the preferred precipitating agent. The tempera-ture of the precipitation bath may be in the region of from 0 - 50C and is : preferably from 0 - 25C.
The membranes according to the invention may be used in the form of foils, pipes, flexible tubes or hollow fibres. The techniques employed for the manufacture of tubes, pipes and hollow fibres accord with the processes described above. The methods known to the expert for the production of pipes, tubes and hollow fibres oi polymer solutions are employed.
The membranes may be used for concentrating or recovering usable substances and removing unwanted substances, e.g. in the treatment of effluents from the dyestuff, paper and textile industry.
The membranes produced from the polymers are preferably asymmetric membranes which are characterised by the following :~ `

-,-. ~ ' structure: The selective separating layer proper is extremely thin and merges almost continuou~ly into an underlying layer of the same material which has a porous structure and serves us a substrate or supporting layer.
One advantage of such membranes is that all the substan-ces are separated on the surface of the membrane, where they can be removed by the stream of solution supplled.
The life of the membranes is thereby increased since the membrane~ cannot 90 readily become blocked.
To determine the membrane properties, the completed membrane is applied to a porous sintered plate o~ metal on which a filter paper is placed, and the whole arrangement is inserted in a pressure filtration apparatus in which various solutions of test substances in water are pumped over the membrane surface at room temperature and at various pressures. The pump output is 21.5 litres per hour and the effective membrane surface about 40 cm2.
The throughput Or water, in terms oi litres/m2 per day (= 1/m2d) i9 a measure of the filtration power of the membrane. The percentage retention is normally defined a~ rollows:
Concentration of dissolved substance in filtrate 25 Retention = 1 - - x 100.
Concentration of dissolved substance in starting solution The membranes~ according to the invention have a high permeability to water but at the same time they are capable of separating substances having a molecular weight Or 500 i'rom subs,tances having molecular weights in the regionof 100. The molecular weight of the dissolved component Or components is to be regarded as a measure oi~ the retention or separation.
These membranes are used for the concentration, Le A 18 595 removal or recovery of var;ous substances from aqueous solutions by reverse osmosis, ultra-filtration or similar processes.
The ~ercentages given in the Exclmples are percentages hy weight unless otherwise indicated.
Example 1 2.2 kg of 3- amino-N-(phenylsulphonyl)-henzene sulphonamide and 2.8 kg of maleic acid anhyclride are heated to about 110 to 120~C and 2 ml of triethylamine are added as catalyst. After about 2 hours, the temperature is slowly raised to 150C and excess maleic acid anhyclride is distilled off under vacuum. Thc reaction mixture is then cooled to llO~C (an isolated sample of 3-maleic acid-aminoamidebenzene-henzcne-disulphimide melts at 185C) and 4.5 kg of acetic acid anhydride and 490 g of sodium acetate (anhydrous) are added. After about 40 minutes at lOO~C, acetic acid and anhydride are distilled off at 20 Torr so that the crude product crystallizes.
The residue is then treated with about 5 litres of isopropanol and suction-filtered. The yield of 3-maleic imido-benzene-benzene-disulphimide is 2.3 kg, corresponding to 84% of the theoretical yield; Mp 157 - 160~C.
IR: VcO = 1720 (s)/1785 (w) cm The yields in E~xamples 1 and 2 are based on the quantity of 3-amino-N-(phenylsulphonyl)-benzene sulphamide put into the process.
Example 2 40 g of 3-amino-N-(phenylsulphonyl)-benzene sulphonamide and 25 g of methyl maleic acid anhydride are heated to 120 - 130~C, and a small quantity of triethylamine is added as catalyst. After about 2 hours, the temperature is raised to 175C and excess methyl maleic acid anhydride is distilled off under vacuum. When P~

distillation is completed (an isolated ~ample oi 3-methyl-maleic acid-monoamido benzene-benzene-di~ulphimide melts at 165C), 94 g of acetic acid anhydride and 9 g Or sodium acetate are added at about 90C. The reaction mixture is cooled aiter about 30 minutes and the solid product i~ ~uctlon-iiltered and washed with isopropanol. Yield Or 3-methyl-maleic-imidobenzene-benzene-disulphimide: 44 g, corresponding to 90~ oi the theoretical yield;
Mp(isopropanol) = 171C.
IR: VcO = 1720 (8) : 1775 (w) cm 1.
Example ~
5 g oi 3-maleic-imidobenzene-benzene-disulphimide rrom Example 1 snd 20 g Or methacrylic acid are di9901ved in 30 ml Or methanol and heated under rerlux after the addition of 0.5 g oi azodiisobutyronitrile.
Polymerisation is stopped aiter 80 minutes and the viscous solution is added dropwise to acetone to precipitate a polymer product. The product is puriiied by redi9901ving it in methanol and precipitating it irom acetone. A copolymer consisting oi 15~ by weight oi 3-maleic-imidobenzene-benzene-disulphimide units and 85 by weight oi methacrylic acid units is obtained. The amounts incorporated were determined in each case irom the S-analysi~ data.
Example 4 5 g oi 3- maleic-imidobenzene-benzene-disulphimide and lOg o$ methacrylic acid are copolymerised in the same way as in E~ample 3. The copolymer contains 24 by weight oi 3-maleic-imidobenzene-benzene-disulphon-imide units and 76~ by weight o~ methacrylic acid units.
Example 5 A.) CoPolvmers Or ~-maleic-imidobenzene-benzene-disulphimide (sodium salt) with acrYlonitrile 53 g Or acrylonitrile and 5.9 g oi a compound Le A 18 595 ~1~94~4 corresponding to the following rormula:
o ¢N ~SO2-N-SO
o Na are heated to 60C in 760 ml of water. The pH i~
then adjusted to 3 with dilute sulphuric acid and polymeri~ation is started by the addition Or 0.7 g o~
potassium peroxodi~ulphate and 2.9 g of sodium sulphite.
After 5 hour~, the precipitated copolymer i~ suction-iiltered, washed until neutral and dried. The copolymer contains about 94.6 ~ by weight Or acrylonitrile units and 5.4~ by weight Or built-in units oi 3-maleic-imido-benzene-benzene-disulphimide (sodium salt) determined by sulphur analysis.
' ~ rel: 2.70 (0.5 g/100 ml in N-methylpyrrolidone) The sodium salt Or maleic-imidobenzene-benzene-disulphimide i8 obtained rrom the aqueous solution Or the disulphimide by the addition Or aqueous sodium hydroxide and concentration Or the aqueous solution by evaporation iol~wed by crystallization.
B.) Production of membrane A solution was prepared irom 15 g oi the polymer desoribed above, 4.5 g oi CaC12 and 130.5 g or N-methyl pyrrolidone by stirring and heating to 60C. A casting solution ready ior use was obtained by riltration and removal oi any remaining air bubbles.
A iilm 250 ,u in thickness was applied to a glass plate an,d then heated to 50C on a hot plate iOI' 20 minutes. Aiter a cooling phase oi 10 minutes, the iilm was immersed in an ice/water bath and leit therein ior 30 minutes. During this time, the iilm became detached irom the glass plate. The iinished membrane was stored in water ~t room temperature.
Le A 18 595 11~9~74 The results obtained rrom examination Or the membrane are shown in the following Table:
Substance Concentration ~etention Through-l/m d NaCl 1 0 Sodium lauryl sulphate 1 73 3100 Congo red 0.1 99.9 3400 Pressure: 20 bar Example 6A) Copolymerisation Or 3-maleic-imidobenzene-benzene-disulphimide with acrylonitrile 53 g Or acrylonitrile and 13.25 g Or 3-maleic-imido benzene-benzene-disulphimide are dissolved in 760 ml Or water. The pH is adjusted to 3 with dilute sulphuric~acid and polymerisation is started at 60C
by the addition Or 0.7 g Or potassium peroxodisulphate and 2.9 g oi sodium sulphite. Arter 5 hours, the precipi-tated polymer i9 suction-riltered, washed and dried. It contains approximately 91.8 ~ by weight Or built-in acrylonitrile units and 8.2 % by weight Or built-in units oi 3-maleic-imidobenzene-benzene-disulphimide.
~Zel 2.65 (0.5 g/100 ml in N-methyl pyrrolidone).
B) Production oi membrane 10 g oi the polymer described above, 3 g oi CaC12 and 87 g Or N-methyl pyrrolidone were used to prepare a casting solution. The castlng solution was ca~t to rorm a iilm 250 y in thickness which was dried at 60C
ior 20 minutes.
The membrane is iound to have a retention Or 99.9 (Congo red, 0.1%) and a permeability to water Or 2,100 l/m2/d at a pressure oi 20 bar.

Le A 18 595 ~1{)947g Example 7 A.) Copolymerisation of 3-maleic-imidobenzene-benzene-di~ulphimide with acrvlonitrile and methyl methacrylate 53 g of acrylonitrile, 3.12 g of methylmethacrylate and 6.25 g of 3-maleic-imidobenzene-benzene-disulphimide are dissolved in 780 ml of water under nitrogen at 60C
and the pH is adjusted to 3 with dilute sulphuric acid.
After the addltion of 0.7 g of potassium peroxodisulphate and 2.9 g of sodium ~ulphite, the reaction mixture is stirred for 5 hours at 60C, suction-filtered, washed until neutral and dried.
~rel: 1.98 (0.5 g/100 ml in N-methyl pyrrolidone) B.) Production of membrane 20 g oi the polymer described above and 6 g of CaC12 were dissolved in 174 g of N-methyl-pyrrolidone.
A 250 ~u film was prepared from this casting solution and dried at 60C ior 10 minutes.
At a pressure of 20 bar, the membrane was found to have a throughflow rate of 3,500 1/m2/d and a retention to Congo red (0.1~) Or 99.9~.
Comparison Example 12 g oi a homopolymer oi acrylonitrile are dissolved in 84.4 g of N-methyl pyrrolidone with the addition oi

3.6 g of CaC12. A iilm 250 y in thickness was formed irom this casting solution on a glass plate and the solvent was then evaporated off by heating to 70C ior 20 minutes, and the film was immersed in a precipitation bath (ice/water). The rate o* throughflow o~ water at 20 bar was found to be only 1,100 1/m2/d, and the retention Or Congo red was 99.9~.

Le A 18 595

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A compound corresponding to the general formula (I):

(I) wherein Ar denotes a benzene or naphthalene group;
R1 to R4 are identical or different and denote H, or lower alkyl; and X denotes H, Na, K or NH4.

2. 3-Maleic-imidobenzene-benzene-disulphimide.

3. 3-Methyl maleic-imidobenzene-benzene-disulphimide.

4. A process for the preparation of a compound corresponding to the general formula (I) as defined in claim 1, which comprises reacting maleic acid anhydride, or a maleic acid anhydride which is substituted by CH3, with an aminoaryl-aryl-disulphimide solvent-free with or without a catalyst, the maleic acid anhydride or substituted maleic acid anhydride being used in a 1 to 5 times molar excess over the amino-aryl-aryl-disulphimide; and cyclodehydration of the resulting N-substituted maleic amido acid in an anhydride of a saturated fatty acid having a maximum of 5 C-atoms, in the presence of a catalyst.