Patent US3651547A successfully refreshed from Google Patents.
US5015667A
Expired / Lapsed
US
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Pre-foamed beads of polyethylene base resin
Assignee: JSP Corp
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Filing: 1988-11-02
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Granted: 1991-05-14
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Expires: 2008-11-02
Abstract
Abstract A method of forming pre-foamed beads of a polyethylene-base resin are disclosed. The polyethylene-base resin has been obtained by crosslinking a starting polyethylene-base resin having a density greater than 0.940 g/cm3 and the pre-foamed beads have a crosslinking degree of 10-45% gel content. The pre-foamed beads can provide a molded articles having excellent rigidity and dimensional accuracy and showing superb dimensional stability under heat.
Inventors
- 👤 Shohei Yoshimura
- 👤 Hideki Kuwabara
- 👤 Toru Yamaguchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 10:42
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/22; C08J9/228; C08J9/16; C08J2323/00; C08J2323/02; C08J2323/04
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
140 words
A method of forming prefoamed beads with a crosslinking degree of 10 to 45% gel content, comprising the steps of: chemically crosslinking a starting bead-like polyethylene-base resin having a density greater than 0.940 g/cm 3 to a crosslinking degree of 10 to 45% gel content; charging the crosslinked bead-like polyethylene-base resin, a foaming agent and a dispersion medium into a closed vessel; agitating and heating the resulting admixture at a temperature of from (the melting point of the resin -2° C.) to (the melting point of the resin +30° C.); and releasing the crosslinked bead-like polyethylene-base resin and dispersion medium into an atmosphere of a pressure lower than the internal pressure of the closed vessel thereby causing the crosslinked bead-like polyethylene-base resin to expand by an apparent expansion ratio in the range of from at least 15 to about 45.
Claim 2
Independent Claim
140 words
A method of forming prefoamed beads with a crosslinking degree of 10 to 45% gel content, comprising the steps of: chemically crosslinking a starting bead-like polyethylene-base resin having a density greater than 0.940 g/cm 3 to a crosslinking degree of 10 to 45% gel content; charging the crosslinked bead-like polyethylene-base resin, a foaming agent and a dispersion medium into a closed vessel; agitating and heating the resulting admixture at a temperature of from (the melting point of the resin -2° C.) to (the melting point of the resin +30° C.); and releasing the crosslinked bead-like polyethylene-base resin and dispersion medium into an atmosphere of a pressure lower than the internal pressure of the closed vessel thereby causing the crosslinked bead-like polyethylene-base resin to expand by an apparent expansion ratio in the range of from at least 15 to about 45.
Claim 3
Dependent Claim
21 words
A method as defined in claim 1 wherein said crosslinking step and said foaming step are performed in the same vessel.
Claim 4
Dependent Claim
20 words
A method as defined in claim 1 wherein said crosslinking step and said foaming step are performed in different vessels.
Claim 5
Dependent Claim
47 words
A method as defined in claim 1 wherein said crosslinking step includes adding a crosslinking agent to the starting polyethylene-base resin; dispersing the polyethylene-base resin and the crosslinking agent in a dispersing medium; and heating while simultaneously agitating the dispersion to a temperature sufficient to provide crosslinking.
Claim 6
Dependent Claim
36 words
A method as defined in claim 4 wherein said dispersing step includes adding a dispersing agent selected from the group consisting of particulate aluminum oxide, titanium oxide, basic magnesium carbonate, basic zinc carbonate, and calcium carbonate.
Claim 7
Dependent Claim
20 words
A method as defined in claim 1 wherein said crosslinking step includes exposing the starting polyethylene-base resin to electron beams.
Claim 8
Dependent Claim
27 words
A method as defined in claim 1 wherein the polyethylene-base resin is selected from the group consisting of ethylene homopolymer, ethylene-propylene copolymer, ethylene-butene copolymer and ethylene-pentene copolymer.
Claim 9
Dependent Claim
21 words
A method as defined in claim 7 wherein said polyethylene-base resin contains ethylene in an amount of at least 95 weight-%.
Claim 10
Dependent Claim
27 words
A method as defined in claim 1 wherein the density ρ of the starting polyethylene-base resin is in accordance with the following relation: 0.940 g/cm.sup.3 <ρ≦0.970 g/cm.sup.3
Claim 11
Dependent Claim
25 words
A method as defined in claim 4 wherein said crosslinking agent is selected from the group consisting of dicumylperoxide, di-t-butylperoxide, t-butylcumylperoxide, α,α-bis(t-butylperoxy)-p-diiospropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane.
Claim 12
Dependent Claim
28 words
A method as defined in claim 4 wherein said crosslinking agent is added in an amount of 0.1-2.0 parts by weight per 100 parts of the polyethylene-base resin.
Claim 13
Dependent Claim
29 words
A method as defined in claim 4 wherein said heating step is performed at a temperature range of 130°-180° C. over a period of about 0.5 to 5 hours.
Claim 14
Dependent Claim
25 words
A method as defined in claim 4 wherein said dispersing medium is selected from the group consisting of water, ethylene glycol, glycerin, methanol, and ethanol.
Claim 15
Dependent Claim
29 words
A method as defined in claim 1 wherein the pre-foamed beads have an internal pressure decreasing velocity coefficient k of at most 0.35 at 25° C. and 1 atm.
Claim 16
Dependent Claim
14 words
A method as defined in claim 1 wherein the foaming agent is carbon dioxide.
Claim 17
Dependent Claim
25 words
A method as defined in claim 1 wherein the foaming agent is selected from the group consisting of propane, butane, pentene, hexane, dichlorodifluoromethane, and dichlorotetrafluoroethane.
Claim 18
Dependent Claim
29 words
A method as defined in claim 1 wherein said foaming step includes adding the charging agent in an amount of 0.15-0.40 mole per 100 g of the bead-like resin.
Claim 19
Dependent Claim
25 words
A method as defined in claim 1 wherein said dispersing medium is selected from the group consisting of water, ethylene glycol, glycerin, methanol, and ethanol.
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) | 1994-05-13 | 1994-11-12 | 1995-05-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-05-13 | 1998-11-12 | 1999-05-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-05-13 | 2002-11-12 | 2003-05-14 | $7700.00 | Window Closed / Lapsed |