US5012503A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for sterilization of polyvinyl alcohol gel by γ-ray
Assignee: Sumitomo Bakelite Co Ltd
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Filing: 1987-11-04
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Granted: 1991-04-30
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Expires: 2007-11-04
Abstract
Abstract This invention relates to a method for sterilization, by irradiation with γ-ray, of a hydrogel obtained by freezing an aqueous polyvinyl alcohol solution and then thawing it or by partially dehydrating (3% or more in weight reduction rate of the frozen body) the aqueous polyvinyl alcohol solution as it is frozen under vacuum and by selecting dosage of the γ-ray of 3-10 Mrad, stable sterilization effect can be obtained with less soluble decomposition products. Especially, this method is effective and most suitable as a method for sterilization of polyvinyl alcohol hydrogel molded article for medical use.
Inventors
- 👤 Masao Nambu
- 👤 Tadayuki Onishi
- 👤 Masayuki Onohara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 07:59
CPC Classifications
A; A61; A61L; A61L2/00; A61L2/02; A61L2/08; A61L2/081; A61L2103/00; A61L2103/05
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
89 words
A method for sterilization of polyvinyl alcohol gel while decreasing by-product deterioration rates to about 0.0095% or less comprising: irradiating with γ-ray, (A) a hydrogel obtained by freezing thawing an aqueous polyvinyl alcohol solution so that the number of times of accumulative freezing amounts to 2-8 times, or (B) a hydrogel in a range of dehydration rate of 3-30% obtained by subjecting an aqueous polyvinyl alcohol solution in the frozen state to vacuum partial dehydration; wherein the irradiation dosage of γ-ray is from about 3.5 to about 7 Mrad.
Claim 2
Independent Claim
89 words
A method for sterilization of polyvinyl alcohol gel while decreasing by-product deterioration rates to about 0.0095% or less comprising: irradiating with γ-ray, (A) a hydrogel obtained by freezing thawing an aqueous polyvinyl alcohol solution so that the number of times of accumulative freezing amounts to 2-8 times, or (B) a hydrogel in a range of dehydration rate of 3-30% obtained by subjecting an aqueous polyvinyl alcohol solution in the frozen state to vacuum partial dehydration; wherein the irradiation dosage of γ-ray is from about 3.5 to about 7 Mrad.
Claim 3
Independent Claim
142 words
A method for sterilization of polyvinyl alcohol while decreasing by-product deterioration rates to about 0.0095% or less comprising taking a medical hydrogel molded product of polyvinyl alcohol in a range of dehydration rate of 3-30% obtained by pouring an aqueous polyvinyl alcohol solution having a saponification degree of 95 mol % or more and an average polymerization degree of 1000 or more in a mold and repeatedly freezing thawing it so that the number of times of accumulative freezing amounts to 2-8 times or subjecting the aqueous polyvinyl alcohol solution in the frozen state to vacuum partial dehydration, putting frozen state material in a bag or container having oxygen barrier properties, deaerating the bag or container to produce a vacuum or place inert gas therein, sealing the bag or container and irradiating with γ-rays of from about 3.5 to about 7 Mrad.
Claim 4
Independent Claim
142 words
A method for sterilization of polyvinyl alcohol while decreasing by-product deterioration rates to about 0.0095% or less comprising taking a medical hydrogel molded product of polyvinyl alcohol in a range of dehydration rate of 3-30% obtained by pouring an aqueous polyvinyl alcohol solution having a saponification degree of 95 mol % or more and an average polymerization degree of 1000 or more in a mold and repeatedly freezing thawing it so that the number of times of accumulative freezing amounts to 2-8 times or subjecting the aqueous polyvinyl alcohol solution in the frozen state to vacuum partial dehydration, putting frozen state material in a bag or container having oxygen barrier properties, deaerating the bag or container to produce a vacuum or place inert gas therein, sealing the bag or container and irradiating with γ-rays of from about 3.5 to about 7 Mrad.
Claim 5
Dependent Claim
22 words
A method for sterilization of polyvinyl alcohol gel according to claim 2 wherein the hydrogel molded product contains a medicine embedded therein.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-04-29 | 1994-10-29 | 1995-04-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-04-29 | 1998-10-29 | 1999-04-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-04-29 | 2002-10-29 | 2003-04-30 | $7700.00 | Window Closed / Lapsed |