Hydrophilic microporous polyolefin membrane
First Claim
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1. A composite microporous membrane structure comprising:
- a hydrophobic polyolefin microporous precursor membrane having external surfaces and having pores with internal pore surfaces; and
a water soluble hydrophilic polymer comprising polyethylene glycol diacrylate co-extensively applied to said surfaces in a thin liquid coating that is permanently photografted in solid state form onto the internal pore surfaces of the precursor membrane so that the thus grafted membrane structure is hydrophilic, essentially retains the same microporosity as the precursor membrane and is water wettable, and non-leachable.
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Abstract
A hydrophilic microporous membrane, is provided comprising a hydrophobic membrane substrate exemplified by a polyolefin or partially fluorinated polyolefin membrane. A process is also provided for preparing a hydrophilic membrane by grafting a water soluble polymer to the hydrophobic membrane substrate surface by irradiation means, e.g., ultraviolet irradiation. The invention further concerns a method for making the membrane and process means for filtering a fluid through such membrane.
89 Citations
14 Claims
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1. A composite microporous membrane structure comprising:
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a hydrophobic polyolefin microporous precursor membrane having external surfaces and having pores with internal pore surfaces; and a water soluble hydrophilic polymer comprising polyethylene glycol diacrylate co-extensively applied to said surfaces in a thin liquid coating that is permanently photografted in solid state form onto the internal pore surfaces of the precursor membrane so that the thus grafted membrane structure is hydrophilic, essentially retains the same microporosity as the precursor membrane and is water wettable, and non-leachable. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of making a hydrophilic microporous membrane comprising:
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forming a composite porous membrane formed from a microporous hydrophobic membrane substrate having external surfaces and pores with internal pore surfaces formed of a first polymer comprising polyolefin, said substrate being directly coated over its entire surfaces with a second polymer comprising polyethylene glycol-dialkylacrylate, said composite porous membrane having essentially the same porous configuration as said porous membrane substrate; by contacting said porous membrane substrate with a photografting solution of said second polymer and a photoinitiator in ethylene glycol, and exposing said second polymer to radiation ray treatment to graft said second polymer in situ over the entire surfaces of said substrate under conditions such that the thus grafted membrane is hydrophilic, essentially retains the same microporosity as the membrane substrate and is water wettable and non-leachable, while avoiding plugging of said pores. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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Specification