US4230658A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for preparing biaxially drawn thermoplastic polyester film
Assignee: Unitika Ltd
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Filing: 1979-03-26
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Granted: 1980-10-28
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Expires: 1999-03-26
Abstract
Abstract A biaxially drawn thermoplastic polyester film is prepared by concurrent-biaxially drawing a thermoplastic polyester film by a tenter method at a drawing temperature higher than the glass transition temperature of the thermoplastic polyester while maintaining the preheating temperature of the film just prior to drawing at a level greater than the drawing temperature and maintaining the subsequent heat-treating temperature immediately after drawing lower than the preheating temperature and carrying out a reheat-treating process in a plurality of steps while elevating the temperature in each step over a substantially equal temperature range.
Inventors
- 👤 Kazuo Matsukura
- 👤 Kunio Murakami
- 👤 Tsugio Nagasawa
- 👤 Tadashi Hayashi
- 👤 Akiyoshi Kozuma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:37
CPC Classifications
B; B29; B29C; B29C55/00; B29C55/02; B29C55/10; B29C55/12; B29C55/16; B29C71/00; B29K; B29K2067/00
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
130 words
In a process for preparing a biaxially drawn thermoplastic polyester film by concurrently-biaxially drawing a thermoplastic polyester film by a tenter technique, the improvement comprising the sequential steps of: (a) preheating a thermoplastic polyester film in a preheating zone to a temperature higher than the temperature at which the film is to be drawn; (b) concurrently biaxially drawing said preheated film at a temperature greater than the glass transition temperature of the polyester; (c) heat treating said drawn polyester film in a heat treating zone at a temperature less than the preheating temperature; and (d) progressively heating said heat treated film at increasingly higher temperature levels in a plurality of steps in a reheating zone, wherein the increments of temperature increase between progressively higher temperature levels are about the same.
Claim 2
Dependent Claim
130 words
In a process for preparing a biaxially drawn thermoplastic polyester film by concurrently-biaxially drawing a thermoplastic polyester film by a tenter technique, the improvement comprising the sequential steps of: (a) preheating a thermoplastic polyester film in a preheating zone to a temperature higher than the temperature at which the film is to be drawn; (b) concurrently biaxially drawing said preheated film at a temperature greater than the glass transition temperature of the polyester; (c) heat treating said drawn polyester film in a heat treating zone at a temperature less than the preheating temperature; and (d) progressively heating said heat treated film at increasingly higher temperature levels in a plurality of steps in a reheating zone, wherein the increments of temperature increase between progressively higher temperature levels are about the same.
Claim 3
Dependent Claim
23 words
The process according to claim 1, wherein the temperature of the pre-heating step is not greater than 50° C. over the drawing temperature.
Claim 4
Dependent Claim
38 words
The process according to claim 1, wherein the temperature of the heat treating step just after drawing is less than 50° C. below the preheating temperature and is higher than the glass transition temperature of the thermoplastic polyester.
Claim 5
Dependent Claim
41 words
The process according to claim 1, wherein said film is preheated for a period of 0.5 seconds to 20 seconds in a preheating zone and is heat treated in said heat-treating zone for a period of 0.2 seconds to 15 seconds.
Claim 6
Dependent Claim
72 words
The process according to claim 1, wherein the thickness of said film is less than 4μ after the drawing step and the treating time T 1 (seconds) in the preheating zone is in the range defined by the expression: ##EQU3## wherein t represents the thickness (μ) of the film after drawing, z is the elongation ratio and the time T 2 (seconds) in the heat-treating zone is within the range of ##EQU4##
Claim 7
Dependent Claim
17 words
The process according to claim 1, 2, 3, 4 or 5, wherein the thermoplastic polyester is polyethyleneterephthalate.
Claim 8
Dependent Claim
17 words
The process according to claim 1, 2, 3, 4 or 5, wherein the thermoplastic polyester is polybutyleneterephthalate.
Claim 9
Dependent Claim
20 words
The process according to claim 1, wherein said plurality of steps in said reheating zone number up to five steps.
Claim 10
Dependent Claim
28 words
The process according to claim 1, wherein the temperature in the heat treating zone is within the range of 5° C. to 30° C. below said preheating temperature.
Claim 11
Dependent Claim
21 words
The process according to claim 1, wherein the deviations between the incremental increases in temperature are no more than 15° C.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-10-28 | 1984-04-28 | 1984-10-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-10-28 | 1988-04-28 | 1988-10-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-10-28 | 1992-04-28 | 1992-10-28 | $7700.00 | Window Closed / Lapsed |