US4255381A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Textured surface polypropylene film
Assignee: General Electric Co
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Filing: 1979-03-15
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Granted: 1981-03-10
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Expires: 1999-03-15
Abstract
Abstract An improved process of producing a predetermined textured surface on a polypropylene film is disclosed including the steps of extruding the polypropylene into a stalk, cooling the stalk to crystallize the polypropylene, passing the stalk through a heating zone and biaxially stretching the stalk into a thin film. The stalk emanating from the extruder has a section primarily temperature controlled and correlated to the stalk velocity to cause extensive, continuous and uniform spherulite formation with a predominantly type III polypropylene crystal structure on the outer surface of the stalk, which upon subsequent inflation of the stalk causes the desired texture to occur.
Inventors
- 👤 John W. Eustance
- 👤 Stanley Y. Hobbs
- 👤 Emilie L. Carley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:11
CPC Classifications
H; H01; H01G; H01G4/00; H01G4/002; H01G4/018; H01G4/06; H01G4/14; H01G4/18; B; B29; B29C; B29C55/00; B29C55/28; B29C59/00; B29D; B29D7/00; B29D7/01; B32; B32B; B32B27/00; B32B27/32; H01G4/32; B29C48/00; B29C48/001; B29C48/0018; B29C48/0019; B29C48/03; B29C48/09; B29C48/10; B29K; B29K2995/00; B29K2995/0037; B29K2995/0072; Y; Y10; Y10S; Y10S264/00; Y10S264/47
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
155 words
In the bubble process for producing thermoplastic polypropylene film where molten thermoplastic polypropylene material is extruded by a die into a tubular stalk form and the stalk passes coaxially over a cooling mandrel for crystallization thereof and formation of a frost line, the improvement of producing hazy film which comprises: (a) continuously effecting an elevated and constant temperature at the outer stalk surface at a predetermined position between said die and the frost line to cause a skin effect to appear coextensively with the outer surface of said tubular stalk, said skin effect comprising spherulites of type III crystal structure in an outer layer of said stalk; (b) insufflating said stalk to provide a biaxially oriented bubble; and (c) collapsing and slitting said bubble to provide a film having one surface coextensively and uniformly covered by overlapping pattern of fibroid irregularities so that the total haze measurement of said film is greater than 20 percent.
Claim 2
Dependent Claim
155 words
In the bubble process for producing thermoplastic polypropylene film where molten thermoplastic polypropylene material is extruded by a die into a tubular stalk form and the stalk passes coaxially over a cooling mandrel for crystallization thereof and formation of a frost line, the improvement of producing hazy film which comprises: (a) continuously effecting an elevated and constant temperature at the outer stalk surface at a predetermined position between said die and the frost line to cause a skin effect to appear coextensively with the outer surface of said tubular stalk, said skin effect comprising spherulites of type III crystal structure in an outer layer of said stalk; (b) insufflating said stalk to provide a biaxially oriented bubble; and (c) collapsing and slitting said bubble to provide a film having one surface coextensively and uniformly covered by overlapping pattern of fibroid irregularities so that the total haze measurement of said film is greater than 20 percent.
Claim 3
Dependent Claim
11 words
The process of claim 1 wherein said polypropylene comprises isotactic polypropylene.
Claim 4
Dependent Claim
20 words
The process of claim 1 wherein said predetermined position is spaced from said die and closely adjacent said frost line.
Claim 5
Dependent Claim
19 words
The process of claim 1, wherein said elevated temperature is caused by applying separate heating means to said stalk.
Claim 6
Dependent Claim
163 words
In a process for producing polypropylene film wherein molten polypropylene material is extruded through a die into a stalk form and said stalk is cooled to crystallize the polypropylene, after which the stalk is passed through a heating zone and thereafter is biaxially stretched into a thin film, the improvement of producing a predetermined textured surface on said film comprising: (a) continuously effecting an elevated and constant predetermined temperature at said extruder of between about 425° F. and 475° F.; (b) maintaining a predetermined constant tension in said biaxially stretching process to reduce the thickness of said film below about 1 mil (25.4μ); (c) reducing said extrusion temperature and increasing said tension to enhance and maintain an increased growth of type III crystal structure layer on said stalk; and (d) causing said type III crystal structure to melt in said heating zone while being biaxially stretched to provide a textured surface on said film defined by a space factor of above about 5.0%.
Claim 7
Dependent Claim
163 words
In a process for producing polypropylene film wherein molten polypropylene material is extruded through a die into a stalk form and said stalk is cooled to crystallize the polypropylene, after which the stalk is passed through a heating zone and thereafter is biaxially stretched into a thin film, the improvement of producing a predetermined textured surface on said film comprising: (a) continuously effecting an elevated and constant predetermined temperature at said extruder of between about 425° F. and 475° F.; (b) maintaining a predetermined constant tension in said biaxially stretching process to reduce the thickness of said film below about 1 mil (25.4μ); (c) reducing said extrusion temperature and increasing said tension to enhance and maintain an increased growth of type III crystal structure layer on said stalk; and (d) causing said type III crystal structure to melt in said heating zone while being biaxially stretched to provide a textured surface on said film defined by a space factor of above about 5.0%.
Claim 8
Dependent Claim
47 words
The process of claim 5, additionally comprising the step of providing a controlled temperature gradient between the inside and the outside of said stalk prior to crystallization to enhance and maintain an increased growth of type III crystal structure layer on the outside of said film stalk.
Claim 9
Dependent Claim
10 words
The process of claim 5, wherein polypropylene comprises isotactic polypropylene.
Claim 10
Dependent Claim
19 words
The process of claim 6 wherein said temperature gradient is caused by applying separate heating means to said stalk.
Claim 11
Dependent Claim
21 words
The process of claim 6 wherein said temperature gradient is caused by separate means preventing heat transfer away from said stalk.
Claim 12
Dependent Claim
80 words
The process of claim 6 wherein said stalk moves over a mandrel in the range of from about 10 to 12 meters per minute and is from about 15 to 20 mils (0.381 mm to 0.510 mm) in wall thickness and said temperature and tension cause a shearing action in the outer surface of said stalk and the formation of a coextensive skin effect on the outer surface thereof comprising a dense layer of spherulites of type III crystal structure.
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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) | 1984-03-09 | 1984-09-08 | 1985-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-09 | 1988-09-08 | 1989-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-09 | 1992-09-08 | 1993-03-10 | $7700.00 | Window Closed / Lapsed |