DE2335755C3 - Water-insoluble, random copolymers and their use as cation exchangers - Google Patents

Description

wherein R 'is a hydrogen atom or an alkyl chemical Treatment introduced into a polymer film, which does not contain any ion exchange groups. Process (a) enables simple production, however, it is extremely difficult to uniformly disperse the ion exchange powder over a large area, and the resulting membrane has low electrical conductivity. In method (b) the film formation must be carried out at the same time as the polymerization, and a highly skilled worker is required for this procedure. The resulting film is also generally brittle, and therefore one must be extremely careful when using it. The technology involved in the process (c) has recently been further developed, and ionic

and
(B) Units of Formula 2

hC-H

R ²
C-

(CH ₂ ),
COO (CH ₂ J _1n SO ₃ M

(2)

group with 1 to 4 carbon atoms means .5 exchange membranes with relatively good properties

can be made using this process. However, it is extremely difficult to get one Ion exchange group uniformly introduce into the entire surface of a large film, and the formation

of the basic film and the introduction of the ion exchange groups must be done under controlled, mild conditions, which is complicated and meticulous Requires compliance with the reaction conditions

British Patent 12 18 712 discloses a method for making ion exchange membranes described, in which a copolymer of ethylene and vinyl alcohol with a sulfone such as propane sultone is implemented, whereby from the solution of the resulting, modified copolymer a mem-

bran is formed. This modified copolymer has a side chain of the sulfoalkyl ether type and differs in the side chain from the copolymer according to the invention, which is an ester-like one Contains side chain. Ls therefore has poor thermal stability and at the time of its production cannot be melt-deformed. The processing of this copolymer must therefore be done by potting, using solutions that require complicated and careful control. Will

modified copolymers of the sulfoalkyl ether type melt-molded by conventional methods, then occurs thermal decomposition of the copolymers. This lowers the content of sulfonic acid groups, and the resulting ion exchange membrane possesses

where R ^{2 is} a hydrogen atom or a methyl group, I is 0 or an integer from 5 to 8, m3 or 4 and M is a hydrogen atom or an alkali metal atom, the amount of the units of the formula 2 being 0.1 to 5 meq / g copolymer .

2. Use of the copolymers according to Claim 1 as a cation exchanger.

Ion exchange membranes have in recent years Years of increasing importance because of the

Desalination of sea water and other salt contains a reduced efficiency. In contrast

tender liquids and in the manufacture of fuel cells. The best method of producing ion-exchangeable membranes or ion-exchangeable fibers is to use a melt, such a phenomenon is not observed in the case of the ester-like modified copolymers according to the invention.
Jn the French patent specification 12 03 683 is

or solution of the ion exchanger and 50 described an InterpolymAisat which is a copoly-

then process them. The known styrene type ion exchangers are generally highly crosslinked and impossible to melt. Since it is insoluble in all solvents, it comprises merizate which contains the unit of formula 2 of the copolymers of the invention. In the French patent, however, no such -olefins are mentioned, which represent the units (1) and which are a

it is impossible to convert them from their solutions.

work.

In view of this situation, known ion exchange membranes have been made, for example, by using (a) a method in which an insoluble, infusible ion exchange resin powder is dispersed in a polymer capable of forming a film, and then such a polymer is processed into films; in another method (b) becomes a monomer. which has an ion-exchangeable group, condenses or polymerizes with a crosslinking agent, and at the same time a film is formed; in a method (c) the anion exchange group is through mers are. A specific example listed is styrene. The procedure of the French The copolymer obtained in the patent specification has a suitable thermal stability, but it cannot Melt-deformed into films or other objects. The casting process must be used for processing be used. Furthermore, the thermal stability of the film is extremely poor, and thereby problems arise in practical use. It has now been found that the disadvantages of Ion exchangers, the sulfone-modified copolymers can be eliminated by water-insoluble random copolymers with a

Molecular weight from 5000 to 1000 (XK), consisting

out
(A) Units of Formula 1

(D

wherein R 'represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and
(B) Units of Formula 2

H
-C-

R ²
-C-

(CH ₂ ),
COOiCH ₂ ) ", S0 ₃ M

(2)

CH ₂ = CH (CH _{2) 8} COOH

35

where K ^{2 is} a hydrogen atom or a methyl group, / 0 or an integer from 5 to 8, m 3 or 4 and M is a hydrogen atom or an alkali metal atom, the amount of the units of the formula 2 being 0.1 to 5 meq / g copolymer amounts to.

The invention is therefore based on the object of creating a cation-exchangeable copolymer, which can be processed by melt molding and which has excellent cation exchange capacity and exchange rate and has suitable thermal and mechanical properties and which can be easily regenerated.

Specific examples of -olefins which lead to units (1) are ethylene, propylene. 1-butene, 4-methyl-1-pentene, i.e. H. «-Olefine with the unit of Formally, in which R 'denotes hydrogen, methyl, ethyl and isobutyl.

Specific examples of compounds which give the unit (2) are sulfopropyl ester or sulfobutyl ester of acrylic acid, methacrylic acid and omega-ethylenically unsaturated aliphatic carboxylic acids or the alkali metal salts thereof, for example the sodium and potassium salts.

Specific examples of omega-ethylenically unsaturated aliphatic carboxylic acids

CH ₂ = CH (CH _{2) 5} COOH
CH ₂ = CH (CH ₂ COOH J ₆
CH ₂ = CH (CH _{2) 7} COOH

The resulting copolymer can practically not be used.

The water-insoluble copolymer can be obtained by copolymerizing an -olefin having 1 to 6 carbon atoms with a sulfopropyl ester, sulfobutyl ester or an alkali metal salt of acrylic acid, methacrylic acid and omega-ethylenically unsaturated aliphatic carboxylic acids having 8 to 11 carbon atoms in the presence of a catalyst. You can also copolymerize the α-olefin with the unsaturated carboxylic acid in the presence of a catalyst and then react the copolymer with propane sultone and / or butane sultone. The above copolymerization reaction can be carried out at room temperature up to 300 ^° C. and atmospheric pressure up to 400 kg / cm ² in the presence of a radical catalyst and a catalyst of the Ziegler type.

If the group —SO ₃ M in the resulting water-insoluble copolymer is —SO ₃ H, the copolymer can be treated by known processes, ie it can be treated with a solution of an alkali such as sodium hydroxide or potassium hydroxide, the —SO ₃ H- Group is converted into the alkali salt. On the other hand, when the group - SO ₃ M of the copolymer is an alkali metal salt, it can be treated with a solution of a mineral acid such as hydrochloric acid to convert this group to the SO ₃ H group. This treatment can take place before or after the formation of the ion exchange membranes or fibers. The latter process is preferably used to prepare the modified olefin copolymers.

Preferred examples of water-insoluble copolymers which contain the cation-exchangeable according to the invention Products are

1. a water-insoluble random copolymer containing (A ') units of the formula 1'

C-

C-

(Γ

and (B ') units of the formula 2'

C-

R ²
-C-

COO (CH ₂ ), "SO ₃ MJ

55

The amount of unit of the formula 2 is 0.1 to Smequiv., Preferably 0.5 to 3 meequiv., Per gram of water-insoluble copolymer. If the amount of units of the formula 2 is greater than the above range, the melt deformability of the resulting copolymer becomes poor, and the swellability of the resulting cation exchanger with respect to water increases, whereby the performance of the copolymer as an ion exchange membrane is reduced or whereby the ^ ₅ mechanical strength of the film drops sharply. When the amount of the units of Formula 2 is extremely small. the ion exchange capacity is too small, and that contains where R ² , m and M have the same meanings as given in formula 2.

In this copolymer, the amount of unit of the formula (2 ') is 0.1 to 5 meq / g copolymer.

2. A water-insoluble copolymer with (A ") olefin units of the following formula 1"

(J '

wherein R 'denotes a hydrogen atom, a methyl, ethyl and / or an isobutyl group, and (B ")

Units of the following formula 2 "

H
C-

H
C-

(CH ₂ J _5. ,
COO (CH ₂ LSO ₃ M

where m and M are the definitions given in formula 2 own.

In this copolymer, the amount is Unit of the formula 2 "0.1 to 5 meq / g copolymer.

The water-insoluble random copolymer according to the invention has molecular weights in a broad range from 5000 to 1 million. It has a melt index (ASTM D-1238-70), determined at a load of 2.160 g for copolymers of the ethylene type at 190 ^° C., of the propylene type at 230 ° C., of approximately 0.1 to 100 and a Vicat softening point ( ASTM D-1525-70) from 60 to 250 ⁰ C.

Since the water-insoluble copolymer according to the invention is not crosslinked, it is thermoplastic. Since it also contains a sulfonic acid group or a salt thereof through an ester bond, it possesses extremely high thermal stability. The polymer can be used to form ion exchange membranes or ion exchange fibers deformed by known molding processes such as melt extrusion or compression molding will. The preferred deformation temperature is 200 to 350 ° C, and one can at this point additives common to copolymers, such as an antioxidant, agents that absorb ultraviolet light, Lubricants or lubricants or agents that prevent damage from copper, or add the usual pigments, these being well dispersed. These additives can according to known Process are mixed, for example, you can use different mixing devices such as mixers, Use kneaders or rollers. Since the copolymer according to the invention in a mixture it can be dissolved from two solvents that have different polarities its solutions can be deformed into films or fibrous shapes. For example, you can use a solvent mixture made of decalin and dimethyl sulfoxide or a solvent mixture of tetralin and hexaalkylphosphotriamide.

Soft and transparent membranes can be produced from the copolymers according to the invention, which can be stored in a dry state without impairing the mechanical properties will.

The properties given in the examples were determined as follows:

1. Exchange capacity

The sample is dissolved in a 1N aqueous solution. Hydrochloric acid immersed for one day. The Η-shape membrane that you get is washed several times with pure water and then for 1 day in a 1N aqueous solution of sodium chloride immersed. The acid released in the solution by the exchange becomes quantitative determined using an aqueous solution of potassium hydroxide of known concentration and determines the exchange capacity.

2. Water content

On the surface of a membrane in the Na form. that in 1-N aqueous solution of sodium chloride is sufficient was equilibrated, the water is wiped away and the membrane is at 45 "C and reduced Print dried. The water content is determined ίο.

3. Electrical resistance

This is the product that is obtained by taking the electrical resistance in a vertical direction of the membrane, determined in an aqueous 1N NaCl solution, multiplied by the area of the membrane. It is called "sheet resistance". (The dimension is ohm cm '.)

4. Transport number

A 0.5 N aqueous sodium chloride solution is made up

a 2.5 N aqueous sodium chloride solution was separated using a membrane which is saturated with a 1.5 N aqueous sodium chloride solution. The electromotive force (E) at this time is calculated.

5. Intrinsic viscosity

The intrinsic viscosity [</] is in Decalin at 135 C.

6. Molecular weight

The molecular weight (M _1. ) Is calculated by inserting the obtained value [»,] into the formula

[,,] = 1.88 x 10 " ⁴ A /, ⁰ ^ ¹

for the ethylene type copolymer and in the formula [,,] = 1.10 · ΙΟ " ⁴ M, ^om for the propylene type copolymer.

If M in the units of the formula 2 represents alkali metal, the measurement of the intrinsic viscosity [/,] is carried out as follows:

1 g of the copolymer is added to 20 ml of a 1N aqueous hydrochloric acid solution and Left for 24 hours. After sufficient washing with water, the copolymer becomes under reduced Print dried. After the sample of the copolymer was subjected to atomic absorption analysis was to confirm that it does not contain sodium, the intrinsic viscosity [//] becomes each Copolymer sample determined in decalin at 135 ° C.

example 1

100 g of an ethylene / acrylic acid copolymer (90 mol percent ethylene units and 10 percent Acrylic acid units, melt index 10 g / 10 min.) Are dissolved in 11 p-xylene by heating. 155 ml Ethanolic 2N sodium hydroxide solution is added over the course of one hour while stirring. The mixture is then refluxed for 1 hour.

After cooling, the product is washed well with methanol and dried under reduced pressure, all carboxylic acid groups contained in the copolymer being converted into the sodium salt form. 100 g of the copolymer (completely neutralized) and 37 g of 1,3-propane sultone are added to 1 l of p-xylene and ^{heated at 130 °} C. for one hour to complete the reaction

to effect. After cooling, the reaction product is washed well with acetone and reduced Pressure dried, 160 g of a colorless, powdery sulfopropylated ethylene copolymer with a melt index of 0.5 g / 10 min., a molecular weight of 51,000 and a Vicat softening point of 71 ° C.

The copolymer is extracted with boiling methanol for 24 hours and then elemental analysis is performed carried out. It is found that there are 1.75 mmoles of sulfur / g of sulfopropylated ethylene copolymer contains. An atomic absorption analysis shows that it contains 1.75 mmol sodium / g copolymer.

The modified ethylene copolymer was molded at 240 ° C into a 0.1 mm thick film under pressure, and the properties of the cation exchange membrane were examined. The results are in Table 1 listed.

Comparative example 1

According to the process described in British patent specification 12 18 712, spirobi-2,2'-propanesultone and propanesultone are reacted with a vinyl alcohol-ethylene copolymer, a modified ethylene copolymer being obtained which contains 1.41 mmol of sulfonic acid groups / g of dried product . The resulting modified ethylene copolymer is ^{deformed at 180 °} C. under pressure to form a 0.3 mm thick film, and the properties as a cation exchange membrane are determined. The results obtained are shown in Table I.

Comparative example 2

According to the process described in French patent specification 12 03 683, styrene, 3-sulfo-1-propyl acrylate (sodium salt) and benzoyl peroxide are polymerized, a polymer being formed which contains 1.52 mmoles of sulfonic acid groups / g of dried product. Films could not be made by compression molding this polymer at elevated temperatures of 150 to 250X. Therefore, the polymer was dissolved in dimethylformamide to form a 5% solution, and the solution was spread on a glass plate, followed by drying at 90 ° C for one day and then heating under reduced pressure at 70 ° C for 10 hours. A 0.1 mm thick film was obtained, and the properties of the film as a cation exchange membrane were examined. The results obtained are shown in Table I.

Table I.

Electrical resistance (ohm cm ² )
Transport number of
Cations in the
membrane
Thermal
Stability*)

Example 1 Comparative Comparative Example 1 example 2

1.6 119.7 11.2
0.96 0.80 0.89

0.995

0.36

*) The thermal stabilities of the in example 1 and in the comparative example 1 obtained copolymers were determined according to the following method:

Content of sulfonic acid groups according to the
Thermal _ film formation (mmol / dried copolymer)
Stability of sulfonic acid group content before

Film formation (mmole dried copolymer)

The content of sulfonic acid groups in the copolymer after film formation was determined by using the sulfur content of the sample after determining the water content as described above Elemental analysis found and then found the sodium content by taking an atomic absorption spectrum recorded. The copolymer according to the invention has a very good thermal stability, on the other hand the copolymer described in Comparative Example 1 has very poor thermal stability owns. The thermal stability of Comparative Example 2 was not determined because in this sample the Film formation was done in a different way.

Film strength (kg / cm ² )

(ASTM D-638-70) Exchange capacity of the moist membrane (mEqiiiv. / g ■ moist membrane) Water content (Weight percent)

250

230

25.2

Examples 2 and 3

1. Production of a water-insoluble
random copolymers A

Propylene was copolymerized with undecylenic using titanium trichloride and diethylaluminum chloride as catalyst, with a propylene undecylenic acid copolymer, containing 1.13 mmol carboxylic acid groups / g copolymer and an intrinsic viscosity [ "], determined in decalin at 135 ⁰ C, of 1, 9OdIg owned, received. If 100 g of this copolymer were heated under reflux for 1 hour in a mixture of 100 ml of a 10% strength aqueous solution of sodium hydroxide and 1 liter of methanol, the carboxylic acid groups contained in the copolymer were converted into the sodium salt. 100 g of this copolymer (sodium salt) and 21 g of 1,3-propane sultone were added to 11 p-xylene and reacted at 130 ° C. for 2 hours. The reaction product was washed well with acetone , dried under reduced pressure to obtain 109 g of a colorless powdery product (sulfopropylated propylene copolymer). The copolymer was extracted with boiling methanol for 24 hours, and then with the extract

6o carried out an elemental analysis. It was found that there was 0.970 mmoles of sulfur per gram of sulfopropylated propylene copolymer. An atomic 0.57 2 ^ 8 absorption analysis showed that 0.969 mmoles of sodium g

Copolymer were present. This, sulfopropy-

65 lated propylene copolymers had an intrinsic molecular weight Viscosity [r,] of 2.1 dl / g, a molecular weight of 13.0 35.0 224000. a Vicat softening point of 138 ° C

and a melt index of 2.1 g / 10 min.

«09 646/299

Example 1 Comparative Comparative Example 1 Example 2

100

10

2. Production of a water-insoluble
random copolymers B

100 g of a commercially available ethylene / sodium methacrylate copolymer (ethylene content 85 percent by weight, degree of neutrality 20%) were dissolved in 1 l of paraxylene by heating. 80 ml of a 2N ethanolic sodium hydroxide solution were added over the course of one hour with stirring. The mixture was refluxed for 1 hour. The product was washed well with methanol and dried under reduced pressure; the unneutralized carboxylic acid groups contained in the copolymer were converted into sodium salt groups. 100 g of this copolymer (completely neutralized) and 35 g of 1,3-propanesultone were added 11 paraxylene and ^{reacted at 130 °} C. for one hour. The product was washed well with acetone and dried under reduced pressure, giving 119 g of a colorless, powdery product (sulfopropylated ethylene copolymer). The copolymer was extracted with boiling methanol for 24 hours. The extract was subjected to elementary analysis, and it was found that the sulfur was present in the copolymer in an amount of 1.37 mmol / g of the sulfopropylated ethylene copolymer. Atomic absorption analysis indicated that 1.35 mmol of sodium was present. This sulfopropylated ethylene copolymer had a taste index of 0.7 g / 10 min., A molecular weight of 51,000 and a Vicat softening point of 70 ^° C.

3. Each of Copolymers A and B above was molded under pressure to produce a 0.15 mm thick film. The properties of the film as a cation exchange membrane were determined. The results are shown in Table I. \. It has been found that both water-insoluble random copolymers have satisfactory properties and can therefore be used as cation exchange membranes.

Table 11

Examples
2 3 Water-insoluble statistical A. B. Copolymer Film Strength (kg cm ² ) 200 250 Exchange capacity of the damp 0.75 1.01 Membrane (mEquiv. / G moist Membrane) Water content (weight percent) 21.2 20.4 Electrical resistance 10.8 5.4 (Ohm cm ² ) Transport number of the cations 0.89 0.93 in the membrane

Example 4

An ethylene acrylic acid copolymer (83 mole percent ethylene units and 17 mole percent acrylic acid units, Melt index 3OgIOm. [- /) 0.14dl g] was treated in the same manner as described in Example 3 to completely remove the carboxylic acid groups to neutralize.

100 g of this copolymer (sodium salt) and 6Oj; 1,3-propane sultone was added to 1 l of refined p-xylene and the mixture was stirred at 130 ° C. for one hour. The product was well washed with acetone, and at a reduced D ^r piece dried to obtain a modified copolymer having a melt index of 0.1 g 10 min., A molecular weight of 42 500 and a Vicat softening point of 6Γ C received. This modified copolymer was subjected to elemental analysis and it was found that this sulfopropylic ethylene copolymer contained 2.43 mmol of sodium copolymer. Alom absorption analysis showed that it contained 2.45 mmoles of sodium c thereof.

To prove the cation-exchanging properties the modified ethylene copolymer obtained in this way was aui in 500 ml of a 1N aqueous solution Added hydrochloric acid and then stored for 24 hours. After washing with water it became the product dried under reduced pressure

Atomic absorption analysis showed that this copolymer did not contain sodium. 20 g of the treated modified ethylene copolymer were in 1: a solvent mixture of 90 percent by weight p-xylene and 20 percent by weight dimethyl sulfoxide

given and heated ^{to 140 r C.} After the resulting polymer solution had gradually been poured into acetone with stirring, porous, cotton-like fibers (C) were obtained.

50 g of modified propylene copolymer

4c made in the same way as described in Example 2 were treated with hydrochloric acid in the same manner as described above. 20 g of the treated modified copolymer were given ir 11 of a solvent mixture containing 80 Gc-

weight percent decalin and 20 weight percent di methyl sulfoxide, and then the product was dissolved by heating to 140 ° C. This polymer solution was gradually added to acetone, se porous, cotton-like fibers were obtained (D).

Each of the fibers C and D was tightly filled in a glass tube having an inner diameter of 3 cm so that the height of the fiber layer was 20 cm. From the bottom of the tube, a 0.01 N aqueous sodium hydroxide solution in an amount of 10 ml

Sec. Passed through. The outlet from the top of the tube was titrated with a 0.001N aqueous solution of hydrochloric acid. You could find no sodium hydroxide.

Claims (1)

Patent claims: 1. Water-insoluble random copolymers with a molecular weight of 5,000 to 1,000,000, consisting of (A) Units of Formula 1 -C- R '
CH Π)