US3843761A
Expired / Lapsed
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Process for preparing a thermoplastic microporous film involving a cold stretching step and multiple hot stretching steps
Assignee: Celanese Corp
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Filing: 1973-05-30
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Granted: 1974-10-22
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Expires: 1993-05-30
Abstract
Abstract A process for the preparation of an open-celled microporous polymer film. The process includes the steps of cold stretching a non-porous, crystalline, elastic film significantly below the polymeric crystalline melting point of the polymer. The cold stretched film is then stretched, at a temperature slightly below the polymeric crystalline melting point of the film. The hot stretching procedure embodies a plurality of discrete sequential stretching operations.
Inventors
- 👤 I Hay
- 👤 H Bierenbaum
- 👤 L Daley
- 👤 D Zimmerman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:27
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0023; B01D67/0025; B01D67/0027; B29; B29C; B29C55/00; B29C55/02; B29C55/04; B29C55/06; B29C55/065; B29C67/00; B29C67/20; C; C08; C08J; C08J5/00; C08J5/18; C08J2323/00; C08J2323/02; C08J2323/10; C08J2359/00; C08J2359/02; Y; Y10; Y10S; Y10S264/00; Y10S264/73; Y10S428/00; Y10S428/91; Y10T; Y10T428/00; Y10T428/31
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
86 words
A PROCESS FOR THE PREPARATION OF AN OPEN-CELLED MICROPOROUS POLYMER FILM WHICH COMPRISES: UNIAXIALLY COLD STRETCHING A NON-POROUS, CRYSTALLINE, ELASTIC FILM AT A TEMPERATURE IN THE RANGE OF BETWEEN ABOUT -20* C, AND A TEMPERATURE 20*C, BELOW THE CRYSTALLINE MELTING POINT OF THE POLYMERIC FILM; AND SEQUENTIALLY HOT STRETCHING IN THE SAME DIRECTION THE COLD STRETCHED FILM IN A PLURALITY OF DISCRETE STRETCHING STEPS AT A TEMPERATURE IN THE RANGE OF BETWEEN ABOUT 20*C BELOW THE CRYSTALLINE MELTING POINT AND 5*C BELOW THE CRYSTALLINE MELTING POINT.
Claim 2
Dependent Claim
86 words
A PROCESS FOR THE PREPARATION OF AN OPEN-CELLED MICROPOROUS POLYMER FILM WHICH COMPRISES: UNIAXIALLY COLD STRETCHING A NON-POROUS, CRYSTALLINE, ELASTIC FILM AT A TEMPERATURE IN THE RANGE OF BETWEEN ABOUT -20* C, AND A TEMPERATURE 20*C, BELOW THE CRYSTALLINE MELTING POINT OF THE POLYMERIC FILM; AND SEQUENTIALLY HOT STRETCHING IN THE SAME DIRECTION THE COLD STRETCHED FILM IN A PLURALITY OF DISCRETE STRETCHING STEPS AT A TEMPERATURE IN THE RANGE OF BETWEEN ABOUT 20*C BELOW THE CRYSTALLINE MELTING POINT AND 5*C BELOW THE CRYSTALLINE MELTING POINT.
Claim 3
Dependent Claim
42 words
A process in accordance with claim 1 wherein the total amount of stretching which occurs in the cold and hot stretching steps is in the range of between about 10 to 300 percent, based on the initial length of the elastic film.
Claim 4
Dependent Claim
23 words
A process in accordance with claim 2 wherein the extension ratio is in the range of above about 0.10:1 to below about 0.99:
Claim 5
Dependent Claim
20 words
A process in accordance with claim 1 wherein the hot stretching step comprises about 2 to 30 discrete, sequential increments.
Claim 6
Dependent Claim
37 words
A process in accordance with claim 4 wherein each stretching increment occurs between adjoining hot stretch rolls, disposed in festoon relationship, wherein the downstream roll rotates at a speed greater than the adjoining up stream stretching roll.
Claim 7
Dependent Claim
30 words
A process in accordance with claim 1 wherein the film is formed from a polymer selected from the group consisting of polyolefins, polyacetals, polyamides, polyesters, polyalkylene sulfides and polyarylene oxides.
Claim 8
Dependent Claim
129 words
In a process for forming an open-celled microporous film comprising the steps of extruding a polymeric melt through a die, to form a film, taking up the film at a draw down ratio in the range of between about 20:1 to 200:1, annealing the film to form an elastic, non-open-celled film, thereafter uniaxially cold stretching the film at a temperature in the range of between about -20* C. and 20* C. below the crystalline melting temperature of the polymeric film, the improvement which comprises: thereafter hot stretching in the same direction the cold stretched film in a plurality of sequential discrete hot stretching increments at a film temperature in the range of between about 20* C. below the crystalline melting point and 5* C. below the crystalline melting point.
Claim 9
Dependent Claim
129 words
In a process for forming an open-celled microporous film comprising the steps of extruding a polymeric melt through a die, to form a film, taking up the film at a draw down ratio in the range of between about 20:1 to 200:1, annealing the film to form an elastic, non-open-celled film, thereafter uniaxially cold stretching the film at a temperature in the range of between about -20* C. and 20* C. below the crystalline melting temperature of the polymeric film, the improvement which comprises: thereafter hot stretching in the same direction the cold stretched film in a plurality of sequential discrete hot stretching increments at a film temperature in the range of between about 20* C. below the crystalline melting point and 5* C. below the crystalline melting point.
Claim 10
Dependent Claim
41 words
The improved process of claim 7 wherein the total amount of stretching which occurs in the cold and hot stretching steps is in the range of between about 10 to 300 percent, based on the initial length of the elastic film.
Claim 11
Dependent Claim
22 words
The improved process of claim 8 wherein the extension ratio is in the range of above about 0.10:1 to below about 0.99:1.
Claim 12
Dependent Claim
19 words
The improved process of claim 7 wherein the hot stretching step comprises about 2 to 30 discrete, sequential increments.
Claim 13
Dependent Claim
34 words
The improved process of claim 10 wherein each stretching increment occurs between adjoining hot stretch rolls, disposed in festoon relationship, wherein the downstream roll rotates at a speed greater than the adjoining upstream roll.
Claim 14
Dependent Claim
29 words
The improved process of claim 7 wherein the film is formed from a polymer selected from the group consisting of polyolefins, polyacetals, polyamides, polyesters, polyalkylene sulfides and polyarylene oxides.
Claim 15
Dependent Claim
121 words
A process for the preparation of an open-celled, microporous polypropylene film comprising the steps of: uniaxially cold stretching a non-porous, crystAlline, elastic film at a temperature in the range of between about 25* C. and below about 120* C.; hot stretching in the same direction the resulting cold stretched film in a plurality of discrete sequential increments at a temperature in the range of between about 120* C. and 150* C. to produce a film stretched, in the longitudinal or machine direction, in the range of between about 10 to 300 percent based on the initial length of the non-porous, elastic polypropylene film, said film formed at an extension ratio in the range of between above 0.10:1 but below about 0.99:1.
Claim 16
Dependent Claim
121 words
A process for the preparation of an open-celled, microporous polypropylene film comprising the steps of: uniaxially cold stretching a non-porous, crystAlline, elastic film at a temperature in the range of between about 25* C. and below about 120* C.; hot stretching in the same direction the resulting cold stretched film in a plurality of discrete sequential increments at a temperature in the range of between about 120* C. and 150* C. to produce a film stretched, in the longitudinal or machine direction, in the range of between about 10 to 300 percent based on the initial length of the non-porous, elastic polypropylene film, said film formed at an extension ratio in the range of between above 0.10:1 but below about 0.99:1.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-21 | 1978-04-22 | 1978-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-21 | 1982-04-22 | 1982-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-21 | 1986-04-22 | 1986-10-22 | $7700.00 | Window Closed / Lapsed |