Liquid purification or separation – Filter – Material
Patent
1997-11-07
2000-01-25
Fortuna, Ana
Liquid purification or separation
Filter
Material
21050027, 21050028, B01D 3900
Patent
active
060174552
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a porous aromatic polyether ketone membrane and a process for preparing the same. More particularly, the present invention relates to a porous aromatic polyether ketone membrane which has excellent heat and chemical resistance, low elution characteristics and an excellent balance of water permeability and fractionating characteristics and which is useful as a separation membrane, and a process for preparing the same.
BACKGROUND ART
Porous membranes are used as separation membranes in various industrial fields. For example, the membranes are widely used for the preparation of ultrapure water in the field of semiconductor production, the removal of a very small amount of iron contained in cooling water at power plants and filtration or the removal of microorganisms in medical appliances and in the pharmaceutical and food industries. The current trend is one of continuing expansion in the range and volume of the application and use of such membranes. Above all, the demand for porous membranes excellent in heat and chemical resistance is on the increase. For example, in the semiconductor production field, it is desirable to raise the temperature of ultrapure water in order to effectively wash the fine regions of semiconductors with the water. Therefore, porous membranes are in demand from which ion fractions, organic substances or the like are eluted in small quantities at high temperatures and which are excellent in heat and chemical resistance. At thermal or nuclear power plants, separation membranes are in demand which have particularly excellent heat resistance and which make it possible to stably remove cruds (particulate substances mostly comprising iron) from steam condensates having a temperature of 100 degrees C. or higher for a long period without cooling the steam condensates.
At present, materials used for porous membranes include cellulose derivatives such as cellulose acetate, etc. and polymers such as polyacrylonitrile resins, polyamide resins, polymethyl methacrylate resins, polysulfone resins, polyvinylidene floride resins, polyethylene resins, polycarbonate resins, etc., and membranes prepared from these materials are widely employed for ultrafiltration or microfiltration. However, the membranes of these materials are inferior in heat, chemical and boiling water resistance, so that the membranes are not suitable for the aforesaid uses. For the above-mentioned reasons, attention has been paid to aromatic polyether ketones as materials for filtration membranes because of their extreme excellence in heat and chemical resistance. Therefore, attempts have been made to develop porous membranes made from aromatic polyether ketones.
For example, JP-A-3-21333 (corresponding to EP-A-8894) and JP-B-6-34912 propose separation membranes comprising sulfones of polyether ether ketones which are aromatic polyether ketones and processes for preparing the membranes. Membranes of such sulfones, however, are known to swell in water (Macromolecules, 86, p.18, 1985). Further, the membranes dissolve, intensely swell or deform in organic solvents such as acetone, alcohols, tetrahydrofuran, dimethyl formamide, so that their application range is limited. The proposed membranes, therefore, cannot be employed in fields that require the high performance of filtration membranes.
Furthermore, porous non-sulfonated aromatic polyether ketone membranes from melt or wet processes and the production processes thereof have been proposed.
Referring to the melt processes, for example, JP-B-5-33267 (corresponding to U.S. Pat. No. 4,755,540) and JP-A-3-106424 (corresponding to EP-A-417908) propose processes for preparing porous membranes useful as separation membranes wherein aromatic polyether ketones, thermoplastic polymers which are imcompatible with said aromatic polyether ketones, and plasticizers are melt compounded under heat at high temperatures to obtain mixtures, which are formed into desirable shapes, cooled and washed to remove said imcompatible thermoplastic polymers
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Hachiya Hiroshi
Shimoda Teruyoshi
Asahi Kasei Kogyo Kabushiki Kaisha
Fortuna Ana
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