Important requirements for carriers for adsorption separation of water-soluble biopolymers such as proteins (hereinafter referred to as "proteins, etc.") are to have such a chemical structure for the carrier to exhibit sufficient hydrophilic properties, active sites for causing a hydrophobic interaction with proteins, etc., and a proper skeleton structure and a proper specific surface area for efficient contact with proteins, etc.
A crosslinked and insolubilized polysaccharide, e.g., agarose, as a carrier with an alkyl group being introduced is known as such an adsorbent. Having a saccharide chain skeleton, such an adsorbent, however, has insufficient physical strength for industrial use. An adsorbent comprising a porous body, e.g., silica gel, having introduced thereinto a hydrophobic functional group has been proposed, but it is also unsuitable for industrial use due to lack of chemical stability against acid or alkali.
A polymer obtained by reacting glycidyl methacrylate with a crosslinking agent, hydrolyzing the glycidyl group of the resulting crosslinked copolymer, and then reacting the copolymer with a fatty acid chloride is known for use as a carrier for reverse phase partition chromatography as disclosed in JP-A-2-36351 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). Further, a spherical porous hydrophilic crosslinked polymer obtained by suspension polymerization of a hydrophilic methacrylic ester having at least one ether linkage per molecule with a crosslinking agent is known useful as a carrier for gel chromatography as disclosed in JP-A-60-55009.
However, in the process wherein glycidyl methacrylate is polymerized as a monomer, followed by hydrolysis of the glycidyl group in the presence of a mineral acid, etc. as a catalyst, hydrolysis takes place on not only the glycidyl group but the ester moiety to produce a carboxyl group so that the resulting polymer fails to have sufficient performance properties as a chromatographic adsorbent for proteins, etc. In using a hydrophilic methacrylic ester having the specific structure, there is a problem in that specific polymerization conditions must be selected.