EP0410792A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Double bubble process for making strong, thin films
Assignee: Cryovac LLC
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Filing: 1990-07-27
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Granted: —
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Expires: 2010-07-27
Abstract
Abstract Polymeric, thin oriented films can be made by use of a combination of a hot blown process and a blown bubble process, i.e. a double bubble process. The resulting film has use in replacing PVC for in store stretch wrap applications. Very low density polyethylene, VLDPE, is an especially preferred material for this process. It may be used as a monolayer, or as one layer of a multilayer structure. In practising the invention, the polymer is extruded and hot blown, and heated to a temperature above its orientation temperature. This heating can be accomplished by the use of a heated liquid reservoir or sock disposed at the lower end of the primary bubble, inside the bubble. The hot blown heated film is then passed through a first set of pinch rolls, re-inflated into a blown bubble, and collapsed at a second set of pinch rolls. Thin, tough and elastic packaging materials are obtained by this process.
Inventors
- 👤 Henry George Schirmer
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 18:42
CPC Classifications
B; B32; B32B; B32B37/00; B32B37/14; B32B37/15; B32B37/153; B29; B29C; B29C55/00; B29C55/28; B29C55/30; B32B27/00; B32B27/06; B32B27/08; B32B27/30; B32B27/306; B32B27/32; B32B27/322; B29K; B29K2023/00; B29K2023/04; B29K2023/06; B29K2023/08; B29K2023/083; B29K2025/00; B32B2553/00
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
77 words
A method of making a thin oriented polymeric film comprising: a) extruding the polymer as a melt stream through a tubular die; b) hot blowing the extruded film; c) heating the hot blown film to a temperature above its orientation temperature; d) directing the heated film through a first set of pinch rolls; e) reinflating the hot blown film by a blown bubble process; and f) collapsing the reinflated film through a second set of pinch rolls.
Claim 2
Independent Claim
77 words
A method of making a thin oriented polymeric film comprising: a) extruding the polymer as a melt stream through a tubular die; b) hot blowing the extruded film; c) heating the hot blown film to a temperature above its orientation temperature; d) directing the heated film through a first set of pinch rolls; e) reinflating the hot blown film by a blown bubble process; and f) collapsing the reinflated film through a second set of pinch rolls.
Claim 3
Dependent Claim
23 words
A method according to claim 1 wherein the extruded film is hot blown at a blow-up ratio of between about 1.5:1 and 3:1.
Claim 4
Dependent Claim
32 words
A method according to claim 1 or 2 wherein the hot blown film is passed in communication with a heated liquid medium before being directed through the first set of pinch rolls.
Claim 5
Independent Claim
28 words
A method according to any one of claims 1 to 3 wherein the heated liquid medium is hot water, hot oil, hot emulsion, hot wax or propylene glycol.
Claim 6
Independent Claim
51 words
A method according to any one of the preceding claims wherein the hot blown film is oriented at a ratio of between about 1:1 and 5:1 in the transverse direction and/or wherein the hot blown film is oriented at a ratio of between about 1:1 and 5:1 in the machine direction.
Claim 7
Independent Claim
31 words
A method according to any one of the preceding claims wherein the film is a monolayer film which comprises very low density polyethylene, ethylene vinyl acetate copolymer, or a mixture thereof.
Claim 8
Independent Claim
23 words
A method according to any one of claims 1 to 5 wherein the film is a monolayer film which comprises high density polyethylene.
Claim 9
Independent Claim
18 words
A method according to any one of claims 1 to 5 wherein the film is a multilayer film.
Claim 10
Dependent Claim
36 words
A method according to claim 8 wherein the film comprises a core layer comprising very low density polyethylene, ethylene vinyl acetate copolymer, or a blend thereof; and two outer layers comprising an olefinic polymer or copolymer.
Claim 11
Dependent Claim
41 words
A method according to claim 9 wherein the olefinic polymer or copolymer of the outer layers comprises ethylene vinyl acetate copolymer, very low density polyethylene, ethylene acrylic acid copolymer, ethylene methacrylic acid copolymer, or a blend of any of these materials.
Claim 12
Dependent Claim
44 words
A method according to claim 10 wherein the ethylene vinyl acetate copolymer of the outer layers comprises a blend of two ethylene vinyl acetate copolymer resins or wherein the ethylene vinyl acetate copolymer of the outer layers is blended with very low density polyethylene.
Claim 13
Dependent Claim
49 words
A method according to claim 9, 10 or 11 further comprising an intermediate layer, disposed between the core layer and each outer layer respectively, comprising ethylene vinyl acetate copolymer, very low density polyethylene, ethylene acrylic acid copolymer, ethylene methacrylic acid copolymer, or a blend of any of these materials.
Claim 14
Independent Claim
22 words
A method according to any one of the preceding claims wherein the film has a thickness of less than about 1 mil.
Claim 15
Dependent Claim
25 words
A thin biaxially oriented packaging film comprising a layer of very low density polyethylene, said film having a thickness of less than about 1 mil.
Claim 16
Dependent Claim
25 words
A thin biaxially oriented packaging film comprising a layer of very low density polyethylene, said film having a thickness of less than about 1 mil.
Claim 17
Dependent Claim
19 words
A film according to claim 14 obtainable by a process according to any one of claims 1 to 13.
Claim 18
Dependent Claim
35 words
A package comprising a semi-rigid or rigid tray and a thin oriented polymeric film made by the method of any one of claims 1 to 13 or a film according to claim 14 or 15.
Claim 19
Independent Claim
110 words
An apparatus for making thin, oriented polymeric film comprising: a) means for extruding the polymer as a melt stream through a tubular die; b) means for hot blowing the extruded film to form a primary bubble; c) means for heating the hot blown film to a temperature above its orientation temperature; d) a first set of pinch rolls through which the heated film is directed; e) a second set of pinch rolls by means of which the heated film, after reinflation by a blown bubble process, is collapsed; and f) means for circulating a heated liquid to and from a reservoir disposed at the lower end of the primary bubble.
Claim 20
Independent Claim
110 words
An apparatus for making thin, oriented polymeric film comprising: a) means for extruding the polymer as a melt stream through a tubular die; b) means for hot blowing the extruded film to form a primary bubble; c) means for heating the hot blown film to a temperature above its orientation temperature; d) a first set of pinch rolls through which the heated film is directed; e) a second set of pinch rolls by means of which the heated film, after reinflation by a blown bubble process, is collapsed; and f) means for circulating a heated liquid to and from a reservoir disposed at the lower end of the primary bubble.
References Cited (Backward Citations)
No citation records indexed.
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