Patent ID: 7838035

Claim:
A free-flowing, microsphere powder comprising at least one monomer selected from the group consisting of: (a) acrylic acid and salts thereof; (b) methacrylic acid and salts thereof; (c) 2-hydroxyethyl acrylate; and, (d) 2-hydroxyethyl methacrylate wherein (a), (b), (c), (d) or a mixture thereof is crosslinked with a crosslinking agent selected from the group consisting of: N,N′-methylene-bis-acrylamide; N,N′-methylene-bis-methacrylamide; N-methylolacrylamide, N-methylolmethacrylamide; glycidyl acrylate; glycidyl methacrylate; polyethylene glycol diacrylate; polyethylene glycol dimethacrylate; polyvalent metal salts of acrylic acid and methacrylic acid; divinyl benzene phosphoacrylates; divinylbenzene; divinylphenylphosphine; divinyl sulfone; 1,3-divinyltetramethyldisiloxane; 3,9-divinyl-2,4,8,10-tetraoxaspiro[5,5]undecane; phosphomethacrylates; ethylene glycol diglycidyl ether; glycerin triglycidyl ether; glycerin diglycidyl ether; and polyethylene glycol diglycidyl ether, wherein the microsphere powder has a bulk density of at least 0.5 g/cm 3 , a water uptake of at least 70 grams of water per gram of powder, said powder comprising individual microspheres having cell voids therein, wherein the cell voids consist essentially of closed cell voids, and wherein said microspheres have (i) an individual density between about 0.9 and 2 g/cm 3 , (ii) substantially spherical shape, (iii) rapid swell wherein substantially full swell is reached within 15 seconds upon exposure to water, (iv) deformability when substantially fully swollen with water, and (v) a substantial resistance to fracture when swelled in water and passed through a small bore needle in a flowing aqueous medium, wherein a minimum of 15 milligrams of said powder being capable, when substantially fully swollen, to form an occlusion at a preselected location in flexible, substantially nonexpandable tubing, said tubing having an internal diameter of 1.58 mm and a wall thickness of 1.59 mm, to withstand a water pressure as high as about 110 mm Hg in said tubing without dislodging said occlusion from its preselected location.