US3844865A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of making stretch-oriented porous films
Assignee: 3M Co
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Filing: 1972-06-06
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Granted: 1974-10-29
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Expires: 1992-06-06
Abstract
Abstract Porosity (preferably microporosity) can be introduced into a polymeric film by (1) dispersing finely divided particles of a non-hygroscopic inorganic salt such as calcium carbonate into a suitable polymer, e.g., by milling, (2) forming a film of the filled polymer, and (3) stretching the film to provide good porosity and water absorptive or transmissive characteristics. It is unnecessary to leach out the particles of the inorganic salt, and the resulting porous film is useful in laminates, adhesive tapes, gas permeable containers, first aid dressings, and the like even though it still contains these particles.
Inventors
- 👤 R Elton
- 👤 J Louw
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 01:04
CPC Classifications
B; B29; B29C; B29C55/00; B29C55/02; B29C55/04; A; A61; A61L; A61L15/00; A61L15/16; A61L15/42; A61L15/425; B29C55/10; B29C55/12; C; C08; C08L; C08L75/00; C08L75/04; Y; Y10; Y10T; Y10T428/00; Y10T428/25; Y10T428/258
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
167 words
A PROCESS FOR MAKING A POROUS STRUCTURE COMPRISING THE STEPS OF: A. DISPERSING PARTICLES OF AN INORGANIC PORE NUCLEATING AGENT LESS THAN 250 MICRONS IN SIZE INTO A FILM-FORMING ORGANIC POLYURETHANE POLYMER TO FORM A FILLED POLYMER COMPOSITION, B. HEAT-FORMING A FILM LESS THAN 80 MILS IN THICKNESS FROM THE FILLED POLYMER COMPOSITION OF STEP (A) C. STRETCH-ORIENTING SAID FILM AT LEAST 1.5 TIMES ITS ORIGINAL LENGHT ALONG AT LEAST ONE AXIS OF THE FILM TO PROVIDE A STRETCH-ORIENTED FILM OF REDUCED THICKNESS AND AN AREA ENLARGE BY A FACTOR OF AT LEAST 1.5, WHEREBY SAID STRETCHORIENTED FILM IS PROVIDED WITH AN INTERCONNECTED NETWORK OF VOIDS AND A MOISTURE VAPOR TRANSMISSION OF AT LEAST 500 MICROGRAMS/CM2HR. FOR A RELATIVE HUMIDITY DIFFERENCE ON OPPOSITE SIDES OF SAID STRETCH-ORIENTED FILM OF NO LESS THAN 100 PERCENT/60 PERCENT, AND D. ADHERING SAID STRETCH-ORIENTED FILM HAVING SAID DECREASED THICKNESS AND ENLARGED AREA TO A POLYMERIC LAYER WITHOUT ANY PRIOR OR SUBSEQUENT REMOVAL OF SAID INORGANIC PORE NUCLEATING AGENT FROM SAID FILM.
Claim 2
Dependent Claim
167 words
A PROCESS FOR MAKING A POROUS STRUCTURE COMPRISING THE STEPS OF: A. DISPERSING PARTICLES OF AN INORGANIC PORE NUCLEATING AGENT LESS THAN 250 MICRONS IN SIZE INTO A FILM-FORMING ORGANIC POLYURETHANE POLYMER TO FORM A FILLED POLYMER COMPOSITION, B. HEAT-FORMING A FILM LESS THAN 80 MILS IN THICKNESS FROM THE FILLED POLYMER COMPOSITION OF STEP (A) C. STRETCH-ORIENTING SAID FILM AT LEAST 1.5 TIMES ITS ORIGINAL LENGHT ALONG AT LEAST ONE AXIS OF THE FILM TO PROVIDE A STRETCH-ORIENTED FILM OF REDUCED THICKNESS AND AN AREA ENLARGE BY A FACTOR OF AT LEAST 1.5, WHEREBY SAID STRETCHORIENTED FILM IS PROVIDED WITH AN INTERCONNECTED NETWORK OF VOIDS AND A MOISTURE VAPOR TRANSMISSION OF AT LEAST 500 MICROGRAMS/CM2HR. FOR A RELATIVE HUMIDITY DIFFERENCE ON OPPOSITE SIDES OF SAID STRETCH-ORIENTED FILM OF NO LESS THAN 100 PERCENT/60 PERCENT, AND D. ADHERING SAID STRETCH-ORIENTED FILM HAVING SAID DECREASED THICKNESS AND ENLARGED AREA TO A POLYMERIC LAYER WITHOUT ANY PRIOR OR SUBSEQUENT REMOVAL OF SAID INORGANIC PORE NUCLEATING AGENT FROM SAID FILM.
Claim 3
Dependent Claim
16 words
A method according to claim 1 wherein said polymeric layer is a layer of pressure-sensitive adhesive.
Claim 4
Dependent Claim
27 words
A method according to claim 2 wherein the pore nucleating agent in said filled polymer composition comprises a water-insoluble salt with a melting point above 200* C.
Claim 5
Dependent Claim
14 words
A method according to claim 3 wherein said pore nucleating agent is calcium carbonate.
Claim 6
Dependent Claim
27 words
A method according to claim 1 wherein said stretch-oriented film is adhered along its peRiphery to at least one non-porous film to form a gas permeable container.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-28 | 1978-04-29 | 1978-10-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-28 | 1982-04-29 | 1982-10-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-28 | 1986-04-29 | 1986-10-29 | $7700.00 | Window Closed / Lapsed |