Patent US4436888A successfully refreshed from Google Patents.
US4436888A
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Method for making balanced low shrink tension polyolefin film
Assignee: EIDP Inc
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Filing: 1982-10-05
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Granted: 1984-03-13
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Expires: 2002-10-05
Abstract
Abstract Biaxially oriented, balanced, low shrink tension, heat-shrinkable polyolefin film having a shrink percent of at least 7% in both MD and TD at 110° C. and a shrink force of not greater than 2.2 MPa in both MD and TD at 110° C. is produced by a sequential hot/cold/hot/cold treatment of ordinary biaxially oriented, balanced, heat-shrinkable polyolefin film where the film is stretched and relaxed, respectively in the two hot stages of the treatment sequence.
Inventors
- 👤 Kerry J. Copple
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:57
CPC Classifications
B; B29; B29C; B29C55/00; B29C55/02; B29C55/04; B29C55/06; B29C55/065; B29C61/00; B29C61/06; B29C71/00; B29C71/02; B29K; B29K2023/00; B29L; B29L2007/00
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
174 words
A method for making a biaxially oriented polyolefin film with substantially balanced shrinkage of at least 7 percent at 110° C. and a substantially balanced shrink force of not more than 2.2 MPa as measured at 110° C., said method comprising the sequential steps of: (a) heating a biaxially oriented polyolefin heat-shrinkable film to a temperature of from 124°-138° C., (b) stretching the heated film resulting from step (a) in the longitudinal direction by a factor from 1.05 to 1.20, (c) cooling the stretched film resulting from step (b) to a temperature of not greater than 55° C. while maintaining the degree of stretch created in step (b), (d) heating the cooled film resulting from step (c) to a temperature of from 124°-138° C., (e) relaxing the heated film resulting from step (d) in the longitudinal direction by a factor of from 0.83 to 0.95, and (f) cooling the relaxed film resulting from step (e) to a temperature of not greater than 55° C. while maintaining the degree of relaxation created in step (e).
Claim 2
Independent Claim
174 words
A method for making a biaxially oriented polyolefin film with substantially balanced shrinkage of at least 7 percent at 110° C. and a substantially balanced shrink force of not more than 2.2 MPa as measured at 110° C., said method comprising the sequential steps of: (a) heating a biaxially oriented polyolefin heat-shrinkable film to a temperature of from 124°-138° C., (b) stretching the heated film resulting from step (a) in the longitudinal direction by a factor from 1.05 to 1.20, (c) cooling the stretched film resulting from step (b) to a temperature of not greater than 55° C. while maintaining the degree of stretch created in step (b), (d) heating the cooled film resulting from step (c) to a temperature of from 124°-138° C., (e) relaxing the heated film resulting from step (d) in the longitudinal direction by a factor of from 0.83 to 0.95, and (f) cooling the relaxed film resulting from step (e) to a temperature of not greater than 55° C. while maintaining the degree of relaxation created in step (e).
Claim 3
Dependent Claim
18 words
The method of claim 1 wherein the heating temperature in steps (a) and (d) is from 130°-135° C.
Claim 4
Dependent Claim
62 words
The method of claim 1 wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, copolymers of a major proportion of ethylene and a minor proportion of a normal aliphatic mono- alpha-olefinic hydrocarbon containing 4-8 carbons, copolymers of a major proportion of propylene and a minor proportion of a copolymerizable olefin selected from the group consisting of ethylene and iso-butylene.
Claim 5
Dependent Claim
19 words
The method of claim 3 wherein the polyolefin is a propylene/ethylene copolymer containing at least 97 weight percent propylene.
Claim 6
Dependent Claim
20 words
The method of claim 1 wherein the cooling temperature in steps (c) and (f) is not greater than 40° C.
Claim 7
Dependent Claim
143 words
The method of claim 1 wherein the heating, stretching, cooling and relaxing steps are carried out on a series of at least four temperature controlled process rolls such that the first of said process rolls is maintained at a temperture of 124°-138° C., the second of said process rolls is maintained at a temperature of not more than 55° C. and is rotated at a linear surface speed of 1.05-1.20 times the linear surface speed of the first roll, the third of said process rolls is maintained at a temperature of 124°-138° C. and is rotated at a linear surface speed approximately equal to the speed of the second roll, and the fourth process roll is maintained at a temperature of not more than 55° C. and is rotated at a linear surface speed of 0.83-0.95 times the speed of the third roll.
Claim 8
Dependent Claim
9 words
The product produced by the process of claim 1.
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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) | 1987-03-13 | 1987-09-12 | 1988-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-03-13 | 1991-09-12 | 1992-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-03-13 | 1995-09-12 | 1996-03-13 | $7700.00 | Window Closed / Lapsed |