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US4613441A Expired / Lapsed US ⏱️ 0.0 years remaining

Thermoplastic resin porous membrane having an increased strength factor

Assignee: Asahi Kasei Corp
•
Filing: 1983-04-20
•
Granted: 1986-09-23
•
Expires: 2003-04-20
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Abstract

Abstract A porous membrane formed of a thermoplastic resin having a critical surface tension of not higher than 35 dyn/cm and having a three-dimensional network structure is provided. Communicating pores having a porosity of at least 60% and an average pore diameter of 0.1 to 2.0 microns are formed in the porous membrane. The strength factor F defined by the following formula is at least 1 as measured in any direction: F=A/[B(1-α)], wherein A is the tensile strength at break of the membrane, B is the tensile strength at break of a non-porous film formed of the same resin and α is the porosity fraction of the membrane. The thickness of the porous membrane is 5 to 500 microns. The porous membrane is prepared by a process wherein a porous membrane formed of a thermoplastic resin having a critical surface tension of not higher than 35 dyn/cm and having a three-dimensional network structure including communicating pores having an average pore diameter of 0.05 to 1 micron with a porosity of 30 to 70%, is subjected to a space drawing operation in at least one direction at a temperature between 50° C. lower than the melting or softening point of the thermoplastic resin and 5° C. lower than the melting or softening point of the thermoplastic resin.

Inventors

  • 👤 Mitsuo Kohno
  • 👤 Shigeki Katayama
  • 👤 Kazuo Matsuda

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-24 10:37
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0023; B01D67/0025; B01D67/0027; B01D69/00; B01D69/02; H; H01; H01M; H01M50/00; H01M50/40; H01M50/489; H01M50/491; H01M50/494; Y; Y02; Y02E; Y02E60/00; Y02E60/10

Claims Analysis

Total Claims: 8
Claim 1
Independent Claim 203 words
A thermoplastic resin porous membrane which is formed of a thremoplastic resin having a critical surface tension of from 20 to 33 dyn/cm and having a three-dimensional network structure wherein communicating pores having a porosity of at least 60% and an average pore diameter of 0.1 to 2.0 microns are formed; the porous membrane having a strength factor F defined by the following formula (1): F=A/(B(1-α)) (1) wherein A stands for the tensile strength at break of the porous membrane, B stands for the tensile strength at break of a non-porous film formed of the same resin and α stands for the porosity fraction of the porous membrane, of at least 1 as measured in any direction, a modulus factor F' defined by the following formula (2): F'=C/(D(1-α)) (2) wherein C stands for the tensile stress of the porous membrane at 5% deformation, D stands for the tensile stress of a non-porous film formed of the same resin at 5% deformation and α stands for the porosity fraction of the porous membrane, of at least 0.2 as measured in any direction; a maximum pore diameter not larger than 3.25 times the average pore diameter and a thickness of from 5 to 500 microns.
Claim 2
Dependent Claim 203 words
A thermoplastic resin porous membrane which is formed of a thremoplastic resin having a critical surface tension of from 20 to 33 dyn/cm and having a three-dimensional network structure wherein communicating pores having a porosity of at least 60% and an average pore diameter of 0.1 to 2.0 microns are formed; the porous membrane having a strength factor F defined by the following formula (1): F=A/(B(1-α)) (1) wherein A stands for the tensile strength at break of the porous membrane, B stands for the tensile strength at break of a non-porous film formed of the same resin and α stands for the porosity fraction of the porous membrane, of at least 1 as measured in any direction, a modulus factor F' defined by the following formula (2): F'=C/(D(1-α)) (2) wherein C stands for the tensile stress of the porous membrane at 5% deformation, D stands for the tensile stress of a non-porous film formed of the same resin at 5% deformation and α stands for the porosity fraction of the porous membrane, of at least 0.2 as measured in any direction; a maximum pore diameter not larger than 3.25 times the average pore diameter and a thickness of from 5 to 500 microns.
Claim 3
Dependent Claim 67 words
A thermoplastic resin porous membrane as set forth in claim 1, wherein the quantity of deformation caused when the membrane is subjected to a tensile stress corresponding to 5% of the tensile stress at break of the porous membrane at 20° C. for 100 hours is not more than 15%, and the quantity of residual deformation after removal of said tensile stress is not larger than 5%.
Claim 4
Dependent Claim 37 words
A thermoplastic resin porous membrane as set forth in claim 1, wherein the areal shrinkage at a temperature of 50° C. lower than the melting or softening point of the thermoplastic resin is not larger than 5%.
Claim 5
Dependent Claim 19 words
A thermoplastic resin porous membrane as set forth in claim 1, wherein the thermoplastic resin is high density polyethylene.
Claim 6
Dependent Claim 17 words
A thermoplastic resin porous membrane as set forth in claim 1, wherein the thermoplastic resin is polypropylene.
Claim 7
Dependent Claim 18 words
A thermoplastic resin porous membrane as set forth in claim 1, wherein the thermoplastic resin is polyvinylidene fluoride.
Claim 8
Dependent Claim 19 words
A thermoplastic resin porous membrane as set forth in claim 1, wherein the thermoplastic resin is an ethylene/tetrafluoroethylene copolymer.

References Cited (Backward Citations)

US3558764A Cited
US3953566A Cited
US4187390A Cited
US3679538A Cited
GB1576228A Cited
US4190707A Cited
US4250002A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1989-09-22 1990-03-24 1990-09-23 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1993-09-22 1994-03-24 1994-09-23 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1997-09-22 1998-03-24 1998-09-23 $7700.00 Window Closed / Lapsed

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