Liquid purification or separation – Filter – Material
Reexamination Certificate
1997-04-23
2001-11-20
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Filter
Material
C210S500270, C210S500340, C210S500350, C210S500380, C210S500390, C210S500410, C210S500420, C264S041000, C264S048000, C264S049000, C264S425000, C428S315700
Reexamination Certificate
active
06319404
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel process for the preparation of a porous material and a porous material prepared by the preparation process. The porous material according to the present invention can be used as a microfiltration membrane, ultrafiltration membrane, reverse osmosis membrane, dialysis membrane, adsorbent, bioreactor, biosensor, artificial organs, etc.
BACKGROUND OF THE INVENTION
Microporous membranes are used in filtration and separation of protein, colloid, bacteria, virus, salts, etc. in various separation processes used in the arts of chemical industry, electronic industry, pharmaceutical industry, food industry, disposal of waste liquid, medical treatment (including medical instrument such as artificial organs, examination), water purification, etc. Porous materials such as porous bead and porous fiber are used as adsorbents for substances, e.g., solvent or protein, dissolved in water, adsorbents for gaseous substance, fillers for chromatography, carriers for enzyme in bioreactor or biosensor, etc.
As the process for the preparation of a microporous membrane (hereinafter occasionally referred simply to as “membrane”) there has been most widely used a so-called wet process which comprises shaping a polymer solution, optionally drying somewhat the surface of said polymer solution, and then allowing said polymer solution to come in contact with a coagulating solution miscible with the solvent in said solution so that the polymer is coagulated in a network pattern. However, the wet process is disadvantageous in that only a solvent-soluble-polymer, i.e., linear polymer can be used. The resulting membrane exhibits a poor heat resistance, pressure resistance and fastness to filtration (compaction). Further, the membrane can be hardly modified, making it difficult to prepare a hydrophilic membrane. If it is tried to prepare a hydrophilic membrane for the purpose of inhibiting fouling (drop of flux due to fouling of membrane), which is the greatest weak point in membrane filtration, the resulting membrane swells in water and thus exhibits a poor compaction resistance. Further, the polymer material comprising a hydrophilic group incorporated therein can swell in water during the preparation of the membrane, making it possible to prepare a membrane having a small pore diameter. Moreover, the resulting membrane is alcohol-soluble and thus can be hardly purified. Accordingly, the preparation of a hydrophilic membrane requires complicated steps of preparing a non-hydrophilic membrane and then surface-coating the non-hydrophilic membrane to render it hydrophilic.
On the other hand, U.S. Pat. No. 5,236,588 discloses a process for the preparation of a microporous membrane which comprises shaping a mixture of an energy ray-polymerizable monomer and/or oligomer and a poor solvent which is miscible with said energy ray-polymerizable monomer and/or oligomer but doesn't dissolve or subject said energy ray-polymerizable monomer and/or oligomer thereinf to gelation, optionally drying somewhat the surface of the mixture, and then irradiating the material with energy ray to effect polymerization and phase separation at the same time. In accordance with this process, the use of a multifunctional compound as the monomer and/or oligomer makes it possible to prepare a crosslinked polymer membrane. Thus, a membrane having excellent heat resistance and compaction resistance can be obtained. Further, the addition of a hydrophilic material to the monomer and/or oligomer makes it easy to prepare a hydrophilic membrane. However, this process, too is disadvantageous in that if it is tried to prepare a hydrophilic membrane having a small cut-off molecular weight, only a membrane having a small flux can be obtained.
The foregoing difficulties are encountered in membranes as well as in porous materials such as porous bead and porous fiber.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a porous material having excellent fouling resistance, heat resistance and compaction resistance and a widely and arbitrarily designed pore diameter and a process for the preparation thereof. Another object of the present invention is to provide a porous material adapted for adsorption having broadly controlled surface properties and pore diameter and excellent heat resistance and strength and a process for the preparation thereof.
The inventors made extensive studies of the solution to the foregoing problems. As a result, it was found that a process for the preparation of a porous material which comprises shaping a polymerizable solution (I) comprising as essential components a crosslinking-polymerizable vinyl monomer and/or oligomer (a) and a solvent (B) capable of dissolving said monomer and/or oligomer (a) therein and subjecting a crosslinked polymer (A) obtained by crosslinking polymerization of said monomer and/or oligomer (a) to gelation, crosslinking-polymerizing the polymerizable solution (I) to produce a gel formed product of crosslinked polymer (A), and then allowing the gel formed product to come in contact with a coagulating solution (C) which is compatible with said solvent (B) but doesn't subject the crosslinked polymer (A) to gelation so that it is coagulated has the following features:
(i) Excellent fouling resistance, heat resistance and compaction resistance can be provided and the pore diameter can be arbitrarily designed to a wide range in the preparation of a membrane;
(ii) In the preparation of a porous material adapted for adsorption, the surface properties and pore diameter can be widely controlled. Thus, a porous material having an excellent heat resistance and strength can be obtained; and
(iii) Among the porous materials obtained according to the foregoing preparation process, a porous material made of a semi IPN (interpenetrating polymer network) type polymer alloy of a crosslinked polymer (A) with a non-crosslinked polymer (D) which is soluble in the solvent (B) but insoluble in the coagulating solution (C) is excellent in physical properties such as strength, hardness and heat resistance as well as in chemical and biological properties such as non-adsorptivity and selective adsorptivity of protein and thus is particularly desirable. The present invention has been thus worked out.
In order to solve the foregoing problems, the present invention provides the following inventions:
(1) A process for the preparation of a porous material, which comprises shaping a polymerizable solution (I) containing as essential components a crosslinking-polymerizable vinyl monomer and/or oligomer (a) and a solvent (B) capable of dissolving said monomer and/or oligomer (a) therein and subjecting a crosslinked polymer (A) obtained by the crosslinking polymerization of said monomer and/or oligomer (a) to gelation, crosslinking-polymerizing the polymerizable solution (I) to produce a gel formed product of crosslinked polymer (A), and then allowing the gel formed product to come in contact with a coagulating solution (C) which is compatible with said solvent (B) but doesn't subject said crosslinked polymer (A) to gelation so that it is coagulated and rendered porous;
(2) The process for the preparation of a porous material defined in Clause (1), wherein said polymerizable solution (I) comprises a non-crosslinked polymer (D) which is soluble in said solvent (B) but insoluble in said coagulating solution (C).
(3) The process for the preparation of a porous material defined in Clause (2), wherein the content of said crosslinking-polymerizable vinyl monomer and/or oligomer (a) in the resin component contained in said polymerizable solution (I) is from 10 to 90% by weight.
(4) The process for the preparation of a porous material defined in any one of Clauses (1) to (3), wherein said crosslinking-polymerizable vinyl monomer and/or oligomer (a) comprises a multifunctional monomer and/or oligomer in an amount of not less than 10% by weight.
(5) The process for the preparation of a porous material defined in any one of Clauses (1) to (3), wherein s
Anazawa Takanori
Miyajima Miyuki
Watanabe Yasuko
Zhang Husheng
Armstrong Westerman Hattori McLeland & Naughton LLP
Dainippon Ink & Chemicals Inc.
Fortuna Ana
LandOfFree
Process for the preparation of porous material and porous... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the preparation of porous material and porous..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of porous material and porous... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2586373