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Patent US4721591A successfully refreshed from Google Patents.
US4721591A
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Method for the preparation of cross-linked polyethylene foams and foams produced by the method
Assignee: BP CHEMICALS FOAMS BUSINESS SA
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Filing: 1986-07-01
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Granted: 1988-01-26
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Expires: 2006-07-01
Abstract
Abstract A foam of cross-linked polyethylene having microcell structure is prepared using a chemical cross-linking initiator having a 10 hours half life temperature of from 80° to 110° C. In a preferred embodiment, the chemical cross-linking agent is employed in combination with co-cross-linking agent such as triallyl cyanurate.
Inventors
- 👤 John S. Cheng-Shiang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:00
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/04; C08J9/06; C08J9/10; C08J9/0014; C08J2323/00; C08J2323/02; C08J2323/04; Y; Y10; Y10S; Y10S264/00; Y10S264/18; Y10S264/65
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
158 words
A method for the preparation of a cross-linked microcellular foam of a low density polyethylene or a blend of low density polyethylene with one or more other polymer(s), the method comprising the steps of mixing the low density polyethylene, a blowing agent, a cross-linking initiator, and if employed, other polymer(s) and additives, forming the resulting mixture into a sheet material without substantially cross-linking the olefinic polymer(s) and without substantial decomposition of the blowing agent, thereafter continuously producing from the sheet material a significantly cross-linked microcellular foam by pre-heating the sheet material at a temperature of from 150° C. to less than 180° C. for a period of less than 15 minutes, and subsequently heating the pre-heated sheet at a second and higher temperature, for a period of less than 15 minutes to produce the significantly cross-linked microcellular foam wherein the cross-linking agent has a ten hour half-life temperature of more than 80° C. and less than 110° C.
Claim 2
Independent Claim
158 words
A method for the preparation of a cross-linked microcellular foam of a low density polyethylene or a blend of low density polyethylene with one or more other polymer(s), the method comprising the steps of mixing the low density polyethylene, a blowing agent, a cross-linking initiator, and if employed, other polymer(s) and additives, forming the resulting mixture into a sheet material without substantially cross-linking the olefinic polymer(s) and without substantial decomposition of the blowing agent, thereafter continuously producing from the sheet material a significantly cross-linked microcellular foam by pre-heating the sheet material at a temperature of from 150° C. to less than 180° C. for a period of less than 15 minutes, and subsequently heating the pre-heated sheet at a second and higher temperature, for a period of less than 15 minutes to produce the significantly cross-linked microcellular foam wherein the cross-linking agent has a ten hour half-life temperature of more than 80° C. and less than 110° C.
Claim 3
Dependent Claim
25 words
A method as claimed in claim 1 characterised in that the foaming mixture further comprises a co-cross-linking agent having two or more ethylenically unsaturated groups.
Claim 4
Dependent Claim
21 words
A method as claimed in claim 2 characterised in that the co-cross-linking agent is triallyl cyanurate, diallyl phthalate or butanediol diacrylate.
Claim 5
Dependent Claim
26 words
A method as claimed in claim 1 characterised in that the cross-linking initiator has a ten hour half life temperature of from 85° to 100° C.
Claim 6
Dependent Claim
15 words
A method as claimed in claim 4 characterised in that the cross-linking initiator is 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane.
Claim 7
Dependent Claim
37 words
A method as claimed in claim 1 characterised in that the pre-heating is conducted for a period of less than 10 minutes, and the temperature during the pre-heating is in the range of 150° to 170° C.
Claim 8
Dependent Claim
38 words
A method as claimed in claim 1 characterised in that the heating at the second and higher temperature is conducted for a period of less than 10 minutes, and the higher temperature is from 190° to 240° C.
Claim 9
Dependent Claim
48 words
A method as claimed in claim 1 wherein the sheet material is formed by extruding a blend of the low density polyethylene, the cross-linking initiator, the blowing agent, and if employed, the co-cross-linking agent and other polymeric materials and additives at extrusion temperatures of 90° to 125° C.
Claim 10
Dependent Claim
49 words
A method as claimed in claim 8 wherein the sheet material is prepared by dry blending a proportion of the total amount of the olefinic polymer(s) with the cross-linking initiator and blowing agent, and blending the resulting mixture with the remaining amount of olefinic polymer(s) prior to its extrusion.
Claim 11
Dependent Claim
33 words
A method as claimed in claim 1 wherein the composition is substantially free of aromatic carboxylic or aliphatic fatty acid salts of transition metals of groups 7 or 8 of the perioxic table.
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) | 1991-01-25 | 1991-07-27 | 1992-01-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-25 | 1995-07-27 | 1996-01-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-25 | 1999-07-27 | 2000-01-26 | $7700.00 | Window Closed / Lapsed |