Inorganic ultrafiltration of microfiltration membrane modified b

Details Inorganic ultrafiltration of microfiltration membrane modified b Inorganic ultrafiltration of microfiltration membrane modified b

1988-12-19

1991-02-12

Spear, Frank

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

210490, 21050037, 21050038, B01D 1300

Patent

active

049921789

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to ultrafiltration or microfiltration membranes more particularly usable for the separation of proteins.
More specifically, it applies to membranes having a separating layer of a microporous organic material, e.g. membranes constituted by a macroporous support coated with a microporous layer giving the desired separation characteristics to the membrane. In this case, the macroporous support can be made from different inorganic materials, e.g. of carbon or metal oxide. The microporous layer can be constituted by one or more metal oxides, e.g. zirconia, alumina or aluminous spinels, carbides, fluorides, etc.
Although inorganic ultrafiltration or microfiltration membranes have satisfactory characteristics for a large number of separations, the aim is to improve the separation performance characteristics of such membranes and possibly their selectivity with a view to the use thereof for protein separation.
Liquid phase separation processes using membranes and involving reverse osmosis, electrodialysis, ultrafiltration and similar methods have been studied to a significant extent over the past few years. The membranes used can be made from an organic or an inorganic material. Organic membranes for the deionization of liquids by reverse osmosis are e.g. described in French Patent No. 2 388 583 and U.S. Pat. No. 4 125 462. These Patents make use of organic membranes which are coated with a charged polyelectrolyte layer, such as a charged hydrophilic polymer, in order to give them the property of repelling certain ions, such as cations. In this case, the polymer cationic polyelectrolyte layer must have a molecular mass, e.g. exceeding 100 000 and preferably exceeding 500 000, in order to obtain the desired ion rejection or repulsion characteristics.
For the separation of proteins by ultrafiltration, it is possible to use inorganic or organic membranes as described in European Patent No. 22 696, or organic polymer membranes, as described in European Patent No. 190 558.
When using organic polymer membranes, problems are encountered in carrying out a separation on an industrial scale, because these polymer membranes generally have inadequate mechanical performance characteristics. Moreover, it is preferable to use inorganic membranes, which have superior mechanical properties.
However, the use of inorganic membranes causes other problems because the separating layers of said membranes and which are often oxide based, is not completely inert. Thus, the latter is obtained from highly active, finely divided particles and it still has surface charges, which make it sensitive to mineral salts. In addition, in operation, mineral salts can clog the finer pores.
The invention relates to an inorganic membrane usable for the separation of proteins, which is as effective as organic membranes without being sensitive to the action of mineral salts and which also has better mechanical properties and in certain cases an improved selectivity for separation of proteins.
The inorganic ultrafiltration or microfiltration membrane according to the invention has an inorganic material separating layer and is characterized in that it comprises, prior to being used for an ultrafiltration or microfiltration operation, at least one hydrophilic copolymer or polymer having a molecular mass at the most equal to 10.sup.5, adsorbed on or in the separating layer of the inorganic membrane with a view to modifying the separating properties.
In the membrane according to the invention, the hydrophilic polymer with a molecular ma$s below 10.sup.5 adsorbed on or in the separating layer of the inorganic membrane, makes it possible to neutralize the residual charges of said separating layer and make it insensitive to clogging by mineral salts. Moreover, the choice of an appropriate hydrophilic copolymer or polymer makes it possible to modify the conditions of transfer of proteins through the ultrafiltration or microfiltration membrane and to vary certain properties of the membrane such as its selectivity with respect to solutes

REFERENCES:
patent: 3061518 (1962-10-01), Auerswald et al.
patent: 4125462 (1978-11-01), Latty
patent: 4250029 (1981-02-01), Kiser et al.
patent: 4762619 (1988-08-01), Gaddis et al.
patent: 4780210 (1988-10-01), Hsia

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