CS249398B1 - Process for preparing semipermeable membranes based on sulfonated poly (oxy- (2,6-dimethyl-1,4-phenylene)) - Google Patents

Abstract

The solution relates to the preparation of semipermeable membranes based on sulfonated poly(oxy(2,6- -dimethyl-1,4-phenylene)), suitable for ultrafiltration of aqueous solutions. The subject of the solution is a method for preparing semipermeable membranes based on sulfonated poly(oxy(2,6-dimethyl-1,4-phenylene)), characterized in that a solution containing 2 to 20 wt. % sulfonated poly(oxy-2,6-dimethyl-1,4-phenylene)) insoluble in pure methanol, but soluble in chloroform or in a mixture of chloroform with methanol, is cast onto a smooth inert substrate, the solvent is allowed to spontaneously evaporate from the cast film on the substrate for 10 s to 8 minutes, and then the film on the substrate is allowed to coagulate in a bath consisting of alcohol and the membrane is removed from the inert substrate. Membranes prepared in the described manner have good ultrafiltration parameters, good mechanical properties and good stability over a wide range of temperatures, pH and are resistant to a number of organic substances.

Description

The present invention relates to the preparation of semipermeable membranes based on sulfonated poly (oxy- (2,6-dimethyl-1,4-phenylene)) suitable for ultrafiltration of aqueous solutions.

The ultrafiltration membranes must meet a number of requirements. At the pressure applied, it should have the greatest permeability to water with good selectivity, i.e. the ability to retain macromolecular substances in the concentrate and to pass low molecular weight substances into the permeate. The membrane must have good mechanical properties and it is advantageous to be resistant to organic solvents and microbiological attack and to be able to operate without degradation and changes over the greatest possible pH and temperature range.

Poles (oxy- (2,6-dimethyl-1,4-phenylene)) (abbreviated as PPO) is a polymer that meets the following requirements for material for ultrafiltration membranes: it has high mechanical strength, mechanical properties practically unchanged at higher temperatures, it is stable over a wide pH range and resistant to a variety of organic solvents (encyclopedia of Polymer Science and Technol. 10, pp. 92-111, Interscience Publ. 1969).

The preparation of ultrafiltration membranes from unmodified PPO is described (L. Broens et al., Desalination 22, 205-219, 1977). Membranes based on non-sulfonated poly (oxy- (2,6-dimethyl-1,4-phenylene)) (abbreviated PPO) are prepared by first preparing a solution of PPO in a chlorinated solvent with the addition of a small amount of a bad solvent such as 1-butanol.

The solution is poured onto a support, immersed in a cast film in a bath consisting of a liquid which is miscible with the solvents used and is a precipitating agent for unsulfonated PPO, for example, lower alcohols (methanol). The membranes prepared retained albumin well (molecular weight 69,000) but were poorly water-permeable due to the low hydrophilicity of the polymer.

The hydrophilicity of PPO can be increased by its sulfonation. Reverse osmosis membranes of saline solutions (ABLaConti et al.) Were prepared from methanol-soluble sulfonated PPO having an ion exchange capacity of 1.8 to 2.7 meq / g of dry polymer (corresponding to the sulfur content of the 6 to 9% polymer). Osmosis Membrane Res 1972, 263-84 (EdLonsdale, Plenum: New York) These membranes were resistant to hydrolysis, degradation over a wide range of temperatures (25-74 ° C) and pH (5-13) in baths containing organic and inorganic substances.

SUMMARY OF THE INVENTION The present invention provides a process for the preparation of semipermeable poles based on sulfonated poles (oxy- (2,6-dimethyl-1,4-phenylene)), characterized in that a solution comprising a poly (permeable) poly (sulphonated poly). 2 to 20 wt. of sulfonated poly (oxy- (2,6-dimethyl-1,4-phenylene)) insoluble in pure methanol but soluble in chloroform or chloroform-methanol mixtures, is poured onto a smooth inert substrate, leaving the cast film on the substrate for 10 s to 8 minutes to spontaneously evaporate the solvent, and then the film on the substrate is allowed to coagulate in an alcohol bath and the membrane is removed from the inert substrate.

The more concentrated the sulphonated (oxy- (2,6-dimethyl-1,4-phenylene)) (PPO) casting solution (PPO) is, the denser the resulting membrane is, ie the macromolecular rejection is greater and the water flow is less.

As the solvent for the casting solution, a mixture of a chlorinated solvent such as chloroform, trichlorethylene, 1,2-dichloroethane with a poor solvent or a sulfonated PPO precipitate which is miscible with the chlorinated solvent used or an aromatic hydrocarbon such as benzene, toluene or a bad solvent aromatic hydrocarbon mixture is used. or a sulfonated PPO precipitate that is miscible with the aromatic hydrocarbon.

Poor solvents or precipitates of sulfonated PPO include, for example, alcohols such as methanol, 1-butanol, 1-octanol, etc., ketones such as ethyl methyl ketone, acetone, amides such as dimethylformamide, organic acid esters such as butyl acetate, ethyl acetate, ethers such as dioxane and dimethyl sulfoxide. The more poor solvent or precipitant the casting solution contains, the more the resulting membrane is permeable to both water and macromolecular substances.

The cast film solvent is allowed to evaporate for 10 s to 8 minutes. The longer the evaporation time, the denser the resulting membrane.

As a coagulation bath, an alcohol such as methanol, ethanol, propanol is used. Membranes precipitated into ethanol or propanol are denser than membranes precipitated into methanol. Membranes precipitated at lower temperatures are denser than membranes precipitated at higher temperatures.

The membranes prepared as described have good ultrafiltration parameters, good mechanical properties and good stability over a wide range of temperatures, pH, and are resistant to many organic substances.

The invention is described in more detail in the examples without being limited thereto.

He did

10% wt. a solution of sulfonated poly (oxy- (2,6-dimethyl-1,4-phenylene)) (polymer contains 1.10% S) in a mixed solvent of chloroform-1-butanol (solvent ratio 94: 6 wt.) was applied by casting knife (slot height 350 µm) on a glass plate at 25 ° C. The solvent was allowed to evaporate from the deposited film for 1.5 minutes, then the coated film plate was immersed in a 10 ° C methanol bath warm. The film coagulated and after 15 minutes the membrane was removed from the glass plate. In the prepared membrane, methanol was replaced with water by immersion in a water bath. The finished membrane at 0.1 MPa had a water permeability of 0.16 mh · MPa ¹ and dextran rejection with a molecular weight of 10,000 81%.

Examples 2-13

In Examples 2-13, the general procedure of Example 1 was followed, with the specific conditions shown in Table I.

Table 1

Example Sulfur content of polymer (%) Polymer concentration in the casting solution (% by weight) Solvent composition (weight ratio) Time odpa- verification (min) Coagulation bath Water permeability (mh ^-1 . MPa) Rejection dextran (md. mass) (%) 2. 2.06 6.3 chloroform-methanal, 89:11 0.5 methanol 20 ° 0.21 70 000 84 3. 1.10 10 trichlorethylene- -1-octand 85:15 2 methanol 20 ° 1.68 500 000 98 4. 1.10 10 trichlorethylene-1- -1-octand 92: 7 3 methanol 20 ° 0.31 70 000 85 5. 1,28 12.5 trichlorethylene dioxane, 87:13 , 0.25 methanol 20 ° 0.17 40 000 57 6. 1,28 12.5 trichlorethylene- -dimethylfermamide, 87:13 4,5 methanol 20 ° 0.06 10 000 55 7. 1,28 9.9 chloroform-butyl acetate, 94: 6 , 0.5 methand 20 ° 0.13 40 000 93 8. 1,28 10 benzene-1-butane, 93: 7 3.5 methand 20 ° 0.20 40 000 67 9. 1,28 10 toluene, 100 8 1-propand 20 ° 0.09 70 000 55 10. 1,28 9.9 chloroform- -dimethylsulfoxide, 92: 7 1.5 methand 20 ° 0.17 70 000 70

Table 1 - continued

Example Sulfur content of polymer (%) Polymer concentration in the casting solution (% by weight) Solvent composition (weight ratio) Evaporation time (min) Coagulation bath Water permeability (mh ^-1 .MPa) Regulation dextran (mol. wt.) (%) 11. 1,28 9.9 chloroform- -dimethylsulfoxide, 92: 7 0.75 ethanol 20 ° 0.13 70 000 30 12. 1,28 7.6 1,2-dichloroethane- -ethylenemethylketone, 89:11 3 methanol 20 ° 0.06 40 000 94 13. 0.61 10 chloroform-1-octanol, 92: 8 1.5 methanol 0.12 70 0'j0 92

Comparative Example 1

10% wt. a solution of the non-sulfonated pole (oxy-2,6-dimethyl-1,4-phenylene)) in a mixed solvent of chloroform-1-butanol (solvent ratio 85:15 w / w) was applied with a casting knife (slot height 350 µm) on a glass plate at 25 ° C. The solvent was allowed to evaporate from the deposited film for 30 seconds, then the coated glass plate was immersed in a 10 ° C methanol bath warm. The film coagulated and after 15 minutes the membrane was removed from the glass plate. In the prepared membrane, methanol was replaced with water by immersion in a water bath. The finished membrane had a water permeability of 0.03 mh ^-1 .MPa ^-1 and a dextran rejection having a molecular weight of 10,000 62% at 0.3 MPa.

Comparative Example 2

Preparation procedure as in Comparative Example 1, but using a mixed solvent of chloroform-1-butanol 90:10 wt. The finished membrane was not water permeable at 0.3 MPa.

Claims (3)

A process for the preparation of semipermeable poles based on sulfonated poles (oxy- (2,6-dimethyl-1,4-phenylene)), characterized in that a solution containing 5 to 20 wt. of the sulfonated poly (oxy- (2,6-dimethyl-1,4-phenylene)) insoluble in pure methanol but soluble in chloroform or chloroform-methanol mixture is poured onto a smooth inert substrate, leaving the cast film on the substrate for 10 s to 8 minutes to spontaneously evaporate the solvent, and then the film on the substrate is allowed to coagulate in an alcohol bath and the membrane is removed from the inert substrate. 2. A process for the preparation of semipermeable membranes according to claim 1, characterized in that the solvent used for the preparation of the casting solution is a mixture of a chlorinated solvent with a poor solvent or a sulfonated pole (oxy- (2,6-dimethyl-1,4-phenylene)). it is miscible with the chlorinated solvent or aromatic hydrocarbon used, or a mixture of the aromatic hydrocarbon with a poor solvent or a sulphonated pole (oxy- (2,6-dimethyl-1,4-phenylene)), which is miscible with the aromatic solvent. , 3. A process for the preparation of semipermeable membranes according to claim 1, wherein the coagulation bath is an alcohol, for example methanol, ethanol or 1-propanol.