US4891173A
Expired / Lapsed
US
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Process for producing a crosslinked and oriented polyethylene film
Assignee: Tonen General Sekiyu KK
•
Filing: 1988-09-08
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Granted: 1990-01-02
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Expires: 2008-09-08
Abstract
Abstract A crosslinked and oriented polyethylene film superior in clarity as well as moistureproofness and having an improved stretchability is produced by a process for producing a crosslinked and oriented polyethylene film such that the degree of crosslinking inwardly decreases across the thickness of the film, comprising using a polyethylene having a density of at least 0.935 g/cm 3 , a melt index of 0.5 to 20 g/10 min and a high-load melt index to melt index ratio of 40 to 200.
Inventors
- 👤 Keichiro Saitoh
- 👤 Yasushi Itaba
- 👤 Minoru Izawa
- 👤 Tadao Yoshino
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 04:14
CPC Classifications
C; C08; C08J; C08J3/00; C08J3/24; C08J3/245; C08J5/00; C08J5/18; C08J2323/00; C08J2323/02; C08J2323/04
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
92 words
A process for producing a crosslinked and oriented polyethylene film such that the degree of crosslinking inwardly decreases across the thickness of the film to form outer layer portions of the film each having gel fractions of between 20 to 70% and a middle layer portion of the film having a gel fraction between 0 to 5%, comprising using a polyethylene having a density of at least 0.935 g/cm 3 , a melt of 0.5 to 20 g/10 min and a high-load melt index to melt index ratio of 40 to 200.
Claim 2
Dependent Claim
92 words
A process for producing a crosslinked and oriented polyethylene film such that the degree of crosslinking inwardly decreases across the thickness of the film to form outer layer portions of the film each having gel fractions of between 20 to 70% and a middle layer portion of the film having a gel fraction between 0 to 5%, comprising using a polyethylene having a density of at least 0.935 g/cm 3 , a melt of 0.5 to 20 g/10 min and a high-load melt index to melt index ratio of 40 to 200.
Claim 3
Dependent Claim
24 words
A process as claimed in claim 1, wherein the polyethylene is crystalline ethylene homopolymer or ethylene-α-olefin copolymer produced by the medium- or low-pressure process.
Claim 4
Dependent Claim
40 words
The process as claimed in claim 1, wherein the polyethylene is produced by polymerizing ethylene in two stages to control the melt index and thereby forming a polyethylene consisting of a high molecular weight component and low molecular weight component.
Claim 5
Dependent Claim
57 words
The process as claimed in claim 3, wherein the high molecular weight component has a density of at least 0.93 g/cm 3 and a melt index of 0.01 to 1 g/10 min, and the low molecular weight component has a density of at least 0l95 g/cm 3 and a melt index of 5 to 1000 g/10 min.
Claim 6
Dependent Claim
25 words
The process as claimed in claim 1, wherein the polyethylene is obtained by blending a high molecular weight polyethylene and a low molecular weight polyethylene.
Claim 7
Dependent Claim
57 words
The process as claimed in claim 5, wherein the high molecular weight polyethylene has a density of at least 0.93 g/cm 3 and a melt index of 0.01 to 1 g/10 min, and the low molecular weight polyethylene has a density of at least 0.95 g/cm 3 and a melt index of 5 to 1000 g/10 min.
Claim 8
Dependent Claim
41 words
The process as claimed in claim 1, wherein the polyethylene is further mixed with at least one member selected from the group consisting of low density polyethylenes and linear low density polyethylene in a proportion of at most 10% by weight.
Claim 9
Dependent Claim
141 words
A process for producing a crosslinked and oriented polyethylene film, which comprises melting and extruding a high density polyethylene having a density of at least 0.935 g/cm 3 , a melt index of 0.5 to 20 g/10 min and a high-load melt index tomelt index ratio of 40 to 200, followed by cooling and solidifying to form a stock sheet with a thickness of 210 to 2000 μm, crosslinking the opposite surfaces of the stock sheet in such a manner that the degree of crosslinking decreases from said surfaces inwardly to produce a sheet wherein the opposite outer layer portions of the sheet each have gel fractions of 20 to 70% and the middle layer portion of the sheet has gel fractions of 0 to 5%, and then heating and stretching the crosslinked sheet under conditions to orient the polyethylene molecules.
Claim 10
Dependent Claim
141 words
A process for producing a crosslinked and oriented polyethylene film, which comprises melting and extruding a high density polyethylene having a density of at least 0.935 g/cm 3 , a melt index of 0.5 to 20 g/10 min and a high-load melt index tomelt index ratio of 40 to 200, followed by cooling and solidifying to form a stock sheet with a thickness of 210 to 2000 μm, crosslinking the opposite surfaces of the stock sheet in such a manner that the degree of crosslinking decreases from said surfaces inwardly to produce a sheet wherein the opposite outer layer portions of the sheet each have gel fractions of 20 to 70% and the middle layer portion of the sheet has gel fractions of 0 to 5%, and then heating and stretching the crosslinked sheet under conditions to orient the polyethylene molecules.
Claim 11
Dependent Claim
41 words
The process as claimed in claim 8, wherein the outer layer portions are crosslinked and the middle layer portion is an uncrosslinked film, the thickness ratio of the outer layer portion/middle layer portion/outer layer portion thereof ranging from 1:0.1:1 to 1:10:1.
Claim 12
Dependent Claim
20 words
The process as claimed in claim 8, wherein the crosslinking is carried out by irradiating both surfaces of the sheet.
Claim 13
Dependent Claim
26 words
The process as claimed in claim 8, wherein the stretching is carried out at least in one direction with a draw ratio of at least 300%.
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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) | 1993-01-01 | 1993-07-03 | 1994-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-01 | 1997-07-03 | 1998-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-01 | 2001-07-03 | 2002-01-02 | $7700.00 | Window Closed / Lapsed |