Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-07-25
2001-04-17
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S064000, C521S065000, C521S071000, C521S072000
Reexamination Certificate
active
06218440
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OF DEVELOPMENT
Not applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates hydrophilic crosslinked porous polymeric materials and methods for preparing such materials. In one embodiment, the hydrophilic polymeric materials are produced in the form of microbeads.
2. Description of the Related Art
Crosslinked porous polymeric materials are disclosed. in U.S. Pat. No. 4,522,953 (Barby et al., issued Jun. 11, 1985). The disclosed polymeric materials are produced by polymerization of “water-in-oil” emulsions having a relatively high ratio of water to oil, typically on the order of 70% or more. These emulsions are termed “high internal phase emulsions” and are known in the art as “HIPEs.” The HIPEs disclosed in U.S. Pat. No. 4,522,953 comprise an oil continuous phase including a monomer and a crosslinker and an aqueous discontinuous phase. Such emulsions are prepared by subjecting the combined oil and water phases to agitation in the presence of an emulsifier. Polymers are produced from the resultant emulsion by heating or other means. The polymers are then washed to remove any unpolymerized emulsion components.
The disclosed porous polymers have rigid structures characterized by cavities interconnected by pores in the cavity walls. By choosing appropriate component and process conditions, HIPE polymers with void volumes of 70% or more can be achieved. These materials thus have a very high capacity for absorbing and retaining liquids.
Although the polymerization of oil-phase monomer and crosslinker described by Barby and others produced hydrophobic HIPE polymers, such polymers could be made hydrophilic by conjugation with hydrophilic groups. For instance, U.S. Pat. No. 4,536,521 (Haq, issued Aug. 20, 1985) discloses that HIPE polymers can be sulfonated to produce a sulfonated polymeric material that exhibits a high capacity for absorption of ionic solutions. Other functionalized HIPE polymers prepared by a similar process have been disclosed in U.S. Pat. No. 4,611,014 (Jomes et al., issued Sep. 9, 1986) and U.S. Pat. No. 4,612,334 (Jones et al., Sep. 16, 1986).
Initially processes for making HIPE polymers produced blocks of polymeric material the size and shape of the vessel used for polymerization. A problem with producing HIPE polymers in block form was that it is very difficult to wash unpolymerized emulsion components out of blocks of low density, highly absorbent material. Attempts to address this problem by grinding the blocks into particles were unsatisfactory because both the drying and milling processes are costly, and there is a limit to the size of the particles produced by milling.
The state of the art was significantly advanced by producing HIPE polymers in the form of microbeads, as disclosed in U.S. Pat. No. 5,583,162 (Li et al., issued Dec. 10, 1996) and International Application No. PCT/US95/06879 (WO 95/33553, published Dec. 14, 1995). The disclosed “HIPE microbeads” are produced by polymerization of a suspension of HIPE droplets. A key feature of one polymerization method described in International Application No. PCT/US95/06879 was the use of a film-forming stabilizer to reduce leakage of the discontinuous phase of the HIPE from HIPE droplets into the medium in which the droplets were dispersed. This aspect of the method helped preserve the HIPE-like structure of the droplets upon conversion to microbeads.
It is desirable to produce hydrophilic polymeric materials having a HIPE-like structure directly, i.e., by polymerizing hydrophilic monomers. The polymerization of hydrophilic monomers in an “oil-in-water-in-oil” emulsion is described in U.S. Pat. No. 4,742,086 (Masamizu, issued May 3, 1988). According to this process, an oil-in-water emulsion is prepared and added to a hydrophobic dispersing medium. The process is disclosed as useful for preparing polymeric beads from oil-in-water emulsions that are less than 70% oil (internal) phase. Thus, the resultant hydrophilic beads are not HIPE microbeads.
BRIEF SUMMARY OF THE INVENTION
The present invention includes a process based upon polymerization of hydrophilic monomers, which produces porous crosslinked hydrophilic polymeric materials directly. This process provides the significant advantage of allowing the preparation of hydrophilic polymers from HIPEs (i.e., emulsions containing about 70% to about 99% internal phase).
This process is carried out by forming and then polymerizing an emulsion including a hydrophilic monomer continuous phase and an oil discontinuous phase. The emulsion includes a hydrophilic monofunctional monomer, a polyfunctional crosslinker, an emulsifier having a hydrophobic cyclic head group and a hydrophilic tail, and an organic solvent. The use of an emulsifier having a hydrophobic cyclic head group and a hydrophilic tail has been found to be particularly effective in maintaining the stability of the emulsion during polymerization, especially when the emulsion is a HIPE.
This process can be used to produce hydrophilic polymers in a variety of forms, including microbeads. To produce hydrophilic microbeads, a stabilizer that is a film-forming compound is included in the emulsion, and the emulsion is added to an oil suspension medium to form a suspension of emulsion droplets. Polymerization then converts the emulsion droplets to microbeads. In one embodiment, the stabilizer is a natural or synthetic polymeric stabilizer.
The invention also includes porous crosslinked hydrophilic polymeric microbeads, in particular, hydrophilic microbeads produced by the process of the invention.
Also included are porous crosslinked hydrophilic polymeric microbeads having cavities joined by interconnecting pores, wherein at least some of the cavities at the interior of the microbeads communicate with the surface of the microbeads. At least approximately 10% of the microbeads are substantially spherical or substantially ellipsoidal or a combination thereof. The microbeads have a nominal void volume of at least about 70% and a water absorption capacity of at least about 5 grams of water per gram of dry polymer. Because of this high absorption capacity, these microbeads are useful in a variety of applications, including absorption of bodily fluids, absorption or transport of solvents or other chemicals, and scavenging of, e.g., aqueous fluids.
In one embodiment, the hydrophilic microbeads reach half maximal absorption capacity within 1 minute after immersion. These microbeads are particularly useful in applications requiring rapid absorption rates.
REFERENCES:
patent: 3255127 (1966-06-01), von Bonin
patent: 3460972 (1969-08-01), Nuck
patent: 3737337 (1973-06-01), Schnoring et al.
patent: 3822224 (1974-07-01), Gillan et al.
patent: 3879314 (1975-04-01), Gunning et al.
patent: 3891577 (1975-06-01), Kershaw et al.
patent: 3923704 (1975-12-01), Gunning et al.
patent: 3933579 (1976-01-01), Kershaw et al.
patent: 3943063 (1976-03-01), Morishita et al.
patent: 3988508 (1976-10-01), Lissant
patent: 4137380 (1979-01-01), Gunning et al.
patent: 4321332 (1982-03-01), Beresford et al.
patent: 4384975 (1983-05-01), Fong
patent: 4401456 (1983-08-01), Connick, Jr.
patent: 4522953 (1985-06-01), Barby et al.
patent: 4536521 (1985-08-01), Haq
patent: 4690825 (1987-09-01), Won
patent: 4741872 (1988-05-01), De Luca et al.
patent: 4818542 (1989-04-01), DeLuca et al.
patent: 4873091 (1989-10-01), Jankower et al.
patent: 4888309 (1989-12-01), Araya
patent: 4898734 (1990-02-01), Mathiowitz et al.
patent: 5064570 (1991-11-01), Rohringer
patent: 5071747 (1991-12-01), Hough et al.
patent: 5073365 (1991-12-01), Katz et al.
patent: 5135740 (1992-08-01), Katz et al.
patent: 5135872 (1992-08-01), Pouletty et al.
patent: 5145675 (1992-09-01), Won et al.
patent: 5154713 (1992-10-01), Lind
patent: 5169904 (1992-12-01), Ziemelis et al.
patent: 5246714 (1993-09-01), Dahlinder et al.
patent: 5292777 (1994-03-01), DesMarais et al.
patent: 5316774 (1994-05-01), Eury et al.
patent: 5352711 (1994-10-01), DesMarais
patent: 5354548 (1994-10-01), Araya et al.
patent: 5
Biopore Corporation
Foelak Morton
Maher David W.
McCutchen Doyle Brown & Enersen LLP
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