Process for preparing hydrogels as spherical beads of large size
AssigneeCiba-Geigy Corporation
InventorsKarl F. Mueller, Sonia J. Heiber, Walter L. Plankl
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Abstract
The disclosure describes an improved process for the preparation of uniform, spherical beads of up to 5 mm diameter of a crosslinked, water-insoluble hydrogel by suspension polymerization in a concentrated aqueous salt solution of 95-30% by weight of a monoolefinic water-soluble monomer containing at least 5% of a hydroxy substituted hydrophilic vinyl monomer with 5-70% by weight of a terminal diolefinic macromer crosslinking agent in the presence of water-insoluble, gelatinous, strong water-bonding inorganic metal hydroxides as suspending agents in the absence of excess alkali. The hydrogels have a host of pharmaceutical and industrial uses.
Claims26
An improved process for preparing essentially uniform spherical beads of up to 5 mm diameter of a crosslinked, water-insoluble hydrogel by suspension polymerization of (A) 95 to 30% by weight of the hydrogel of a water-soluble monoolefinic monomer or mixture of said water-soluble monomers, and from 0 to 70% by weight based on the total monomer of a water-insoluble monoolefinic monomer or mixture of said water-insoluble monomers, with the proviso that the final hydrogel does not contain over 60% by weight of said water-insoluble monomer components, with (B) 5 to 70% by weight of the hydrogel of a polyolefinic crosslinking macromer of the formula ##STR9## wherein a is 1 or 2, R.sub.1 is a polycondensate chain having a molecular weight from about 200 to about 8,000 which contains hydrocarbon residues connected via ether, ester, amide or urea linkages or is a polysiloxane of molecular weight between 400 and 8,000;
- R.sub.2 is hydrogen, methyl or --CH.sub.2 COOR.sub.4 ;
- R.sub.4 is hydrogen or alkyl of 1 to 10 carbon atoms;
- R.sub.3 is hydrogen or --COOR.sub.4 with the proviso that at least one of R.sub.2 and R.sub.3 is hydrogen;
- X is an oxygen atom, --COO-- or --CONR.sub.5 ;
- R.sub.5 is hydrogen or alkyl of 1 to 5 carbon atoms;
- Y is a direct bond or the radical R.sub.6 --Z.sub.1 --CONH-- R.sub.7 NHCO--Z.sub.2 --;
- R.sub.6 is linked to X and represents branched or linear alkylene of 1 to 7 carbon atoms;
- Z.sub.1 is an oxygen atom or --NR.sub.5 --;
- Z.sub.2 is Z.sub.1 or a sulfur atom;
- and R.sub.7 is the diradical of an aliphatic, alicyclic or aromatic diisocyanate with the proviso that in case X is oxygen, Y is different from a direct bond and R.sub.2 and R.sub.3 are hydrogen, with a polymerization initiator in a concentrated aqueous inorganic salt solution wherein the improvement comprises
- carrying out the suspension polymerization with monoolefinic monomers containing at least 5% by weight of the total monomers of a hydroxy substituted hydrophilic vinyl monomer;
- employing as the crosslinking agent a polyolefinic macromer having a molecular weight from about 400 to about 8,000 and
- utilizing from 0.01 to 5% by weight, based on the hydrogel, of a suspending agent selected from the water-insoluble, gelatinous, strongly water-bonding, inorganic metal hydroxides and metal hydroxy salts in the absence of excess alkali or free hydroxyl ions.
Dependencies are inferred from the claim text.