Patent US4370291A successfully refreshed from Google Patents.
US4370291A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing polyester film
Assignee: Toray Industries Inc
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Filing: 1981-09-21
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Granted: 1983-01-25
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Expires: 2001-09-21
Abstract
Abstract A biaxially oriented polyester film which is well balanced between sliding properties and transparency and having an enhanced uniformity in thickness is prepared by a process wherein a polyester, predominantly comprised of polyethylene terephthalate, is extruded into a sheet form extrudate; the extrudate is quenched to a temperature of below Tg to obtain a solidified, substantially amorphous film; the film is drawn in the longitudinal direction at a drawing ratio of larger than 2.4 but smaller than 6.5; the film is quenched; and then, the film is drawn in the transverse direction at a drawing ratio of at least 2.5. The drawing in the longitudinal direction is carried out in two steps wherein: (i) in the first drawing step, the substantially amorphous film is drawn in one or more stages at a total drawing zone length (l 1 ) of at least 50 mm so that the resulting polyester film possesses a birefringence of 1×10 -3 to 12×10 -3 ; (ii) the drawn film is kept, without being quenched to a temperature of not higher than the Tg, in contact with a roll maintained at 100° to 130° C.; and then, (iii) in the second drawing step, the film is drawn at a drawing ratio of larger than 1.6 but smaller than 2.7 in one stage at a drawing zone length of shorter than l 1 /2.
Inventors
- 👤 Takahiko Kazama
- 👤 Yuji Okamura
- 👤 Saburo Fujita
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:56
CPC Classifications
B; B29; B29C; B29C55/00; B29C55/02; B29C55/10; B29C55/12; B29C55/14; B29C55/143; B29C55/04; B29C55/06; B29C55/065; B29C35/00; B29C71/00; B29K; B29K2067/00
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
225 words
An improvement in a process for producing a polyester film which comprises melt-extruding a polyester predominantly comprised of polyethylene terephthalate into an extrudate in sheet form; quenching the extrudate to a temperature of below Tg to obtain a solidified, substantially amorphous film; drawing the film in the longitudinal direction at a drawing ratio (λt) of larger than 2.4 but smaller than 6.5; quenching the longitudinally drawn film and; then, drawing the quenched film at a drawing ratio of at least 2.5 in the transverse direction; said improvement comprising conducting said drawing in the longitudinal direction in two steps wherein: (i) in the first drawing step, the substantially amorphous film is drawn in one or more stages at a total drawing zone length (l 1 ) of at least 50 mm so that the resulting polyester film possesses a birefringence of from 1×10 -3 to 12×10 -3 ; (ii) the drawn film is kept, without being quenched to a temperature not higher than the glass transition temperature, in contact with a roll maintained at a temperature of from 100° to 130° C.; and then, (iii) in the second drawing step, the film is drawn at a drawing ratio (λ 2 ) of larger than 1.6 but smaller than 2.7 in one stage at a drawing zone length (l 2 ) of shorter than l 1 /2.
Claim 2
Dependent Claim
225 words
An improvement in a process for producing a polyester film which comprises melt-extruding a polyester predominantly comprised of polyethylene terephthalate into an extrudate in sheet form; quenching the extrudate to a temperature of below Tg to obtain a solidified, substantially amorphous film; drawing the film in the longitudinal direction at a drawing ratio (λt) of larger than 2.4 but smaller than 6.5; quenching the longitudinally drawn film and; then, drawing the quenched film at a drawing ratio of at least 2.5 in the transverse direction; said improvement comprising conducting said drawing in the longitudinal direction in two steps wherein: (i) in the first drawing step, the substantially amorphous film is drawn in one or more stages at a total drawing zone length (l 1 ) of at least 50 mm so that the resulting polyester film possesses a birefringence of from 1×10 -3 to 12×10 -3 ; (ii) the drawn film is kept, without being quenched to a temperature not higher than the glass transition temperature, in contact with a roll maintained at a temperature of from 100° to 130° C.; and then, (iii) in the second drawing step, the film is drawn at a drawing ratio (λ 2 ) of larger than 1.6 but smaller than 2.7 in one stage at a drawing zone length (l 2 ) of shorter than l 1 /2.
Claim 3
Dependent Claim
26 words
A process according to claim 1 wherein, in the first drawing step (i), the substantially amorphous film is drawn 1.2 to 3.0 times its original length.
Claim 4
Dependent Claim
19 words
A process according to claim 1 wherein said first drawing (i) is carried out in one to four stages.
Claim 5
Dependent Claim
23 words
A process according to claim 1 wherein said first drawing (i) is carried out at a temperature of from 100° to 150° C.
Claim 6
Dependent Claim
31 words
A process according to claim 1 or 3 wherein the drawing zone length (l 1i ) in each stage in the first drawing step (i) is not longer than 800 mm.
Claim 7
Dependent Claim
30 words
A process according to claim 1 wherein, in the step (ii), the drawn film is kept in contact with the roll for a period of from 0.012 to 1.43 seconds.
Claim 8
Dependent Claim
30 words
A process according to claim 1 wherein, in the step (ii), the drawn film is kept in contact with the roll for a period of from 0.027 to 0.61 second.
Claim 9
Dependent Claim
26 words
A process according to claim 1 wherein the drawing zone length (l 2 ) in the second drawing step (iii) is not longer than 100 mm.
Claim 10
Dependent Claim
28 words
A process according to claim 1 wherein, in the second drawing step (iii), the film is drawn at a drawing rate (V) of larger than 5×10 4 %/min.
Claim 11
Dependent Claim
23 words
A process according to claim 1 wherein said second drawing (iii) is carried out at a temperature of from 100° to 150° C.
Claim 12
Dependent Claim
69 words
A process according to claim 1 wherein said drawing in the longitudinal direction is carried out at a drawing ratio (λt) of from 3.6 to 6.5; said drawing in the transverse direction is carried out at a drawing ratio of from 3.0 to 4.0 and at a temperature of from 100° to 140° C.; and the biaxially drawn film is heat-treated at a temperature of 150° to 240° C.
Claim 13
Dependent Claim
99 words
A process according to claim 1 wherein said drawing in the longitudinal direction is carried out at a drawing ratio of from 2.4 to 6.0; said drawing in the transverse direction is carried out at a drawing ratio of from 2.5 to 3.5 and at a temperature of from 85° to 130° C.; and the biaxially drawn film is again drawn in the longitudinal direction at a drawing ratio of from 1.2 to 3.0 and at a temperature of from 80° to 160° C. and, then, the film is heat-treated at a temperature of from 130° to 240° C.
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) | 1986-01-24 | 1986-07-26 | 1987-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-01-24 | 1990-07-26 | 1991-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-01-24 | 1994-07-26 | 1995-01-25 | $7700.00 | Window Closed / Lapsed |