System and method for continuously manufacturing cured membranes

Patent metadata

Field	Value
Publication number	US-10112334-B2
Application number	US-201314385864-A
Country	US
Kind code	B2
Filing date	Mar 20, 2013
Priority date	Mar 20, 2012
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

A method of continuously manufacturing a cured membrane includes continuously compounding and mixing a vulcanizable rubber composition in a mixing extruder while continuously removing gasses from the vulcanizable rubber composition during mixing with a vacuum. The vulcanizable rubber composition may be continuously extruded to form an extrudate, which may be continuously calendered to form a green membrane. The green membrane may be continuously cured, such as by a hot air conveyor curing system, to form a cured membrane.

First claim

What is claimed is:

1. A method of continuously manufacturing a cured membrane, the method comprising:
mixing EPDM rubber, filler, oil and curative within a mixing extruder to form a vulcanizable rubber composition;
subjecting the vulcanizable rubber composition to a reduced pressure by applying a vacuum to form a vulcanizable rubber composition with reduced levels of entrapped gases;
extruding the vulcanizable rubber composition with reduced levels of entrapped gases to form a continuous partially-cured extrudate, where said step of extruding takes place at a temperature between 120 and 160° C.;
calendaring the partially-cured extrudate to form a partially-cured membrane; and
curing the partially-cured membrane to form a substantially cured membrane, where said step of curing is devoid of elevated pressures.

2. The method of claim 1 , wherein the step of mixing includes conveying the vulcanizable rubber composition downstream toward an outlet end of the mixing extruder.

3. The method of claim 1 , wherein the step of mixing includes back-mixing the vulcanizable rubber composition in a portion of the mixing extruder.

4. The method of claim 1 , wherein the step of mixing includes maintaining a temperature of the vulcanizable rubber composition at any point along a length of the mixing extruder within +/−5° C. of a desired temperature.

5. The method of claim 1 , wherein the step of mixing includes maintaining a temperature of the vulcanizable rubber composition at all points on a section plane through the mixing extruder within a temperature variance of +/−5° C.

6. The method of claim 1 , where the rubber is added to the mixing extruder at a feed throat, and where the curative is added to the mixing extruder downstream of the feed throat.

7. The method of claim 1 , wherein the step of curing includes forcing hot air across the partially-cured membrane.

8. The method of claim 1 , wherein the step of curing includes applying heat and pressure to the partially-cured membrane.

9. The method of claim 1 , wherein the step of curing includes applying an electronic beam to the partially-cured membrane.

10. A continuous method of manufacturing a cured membrane comprising:
charging rubber, filler, oil, and a curative to a mixing extruder; mixing the rubber, filler, oil and curative to form a vulcanizable rubber composition;
subjecting the vulcanizable rubber composition to a reduced pressure by applying a vacuum within the mixing extruder to form a vulcanizable rubber composition with reduced levels of entrapped gases;
extruding the vulcanizable rubber composition with reduced levels of entrapped gases to form a continuous partially-cured extrudate, where said step of extruding takes place at a temperature between 120 and 160° C.;
applying a compressive force to the partially-cured extrudate to form a partially-cured membrane; and
applying energy to the partially-cured membrane to form a substantially cured membrane, where a total processing time of the method after charging, including the steps of mixing, subjecting the composition to a reduced pressure, extruding, applying a compressive force, and applying energy to the partially-cured membrane is less than 2.0 hours, and where the time from said step of charging rubber, filler, oil, and curative to a mixing extruder to said step of applying compressive force to the partially-cured extrudate is less than 8 minutes.

11. The method of claim 10 , where the total processing time from the step of charging the curative through the step of extruding the vulcanizable rubber composition is less than 7 minutes.

12. The method of claim 10 , where the total processing time from the step of charging the curative through the step of applying a compressive force to the extrudate is less than 7 minutes.

13. The method of claim 10 , where a total elapsed time between the steps of extruding the vulcanizable rubber composition and applying a compressive force to the extrudate is less than 20 seconds.

14. The method of claim 10 , wherein residence time of the curative within the mixing extruder is less than 6 minutes.

15. The method of claim 10 , where the vulcanizable rubber composition is between approximately 120 and 160° C. at the time of extruding.

16. The method of claim 10 , where the vulcanizable rubber composition is between approximately 130 and 150° C. at the time of extruding.

17. The method of claim 10 , where the vulcanizable rubber composition is between approximately 135 and 145° C. at the time of extruding.

Assignees

• Firestone Building Prod Co Llc
• Firestone Building Prod Co Llc

Inventors

• Douglas Bruce
• Hubbard Michael
• Wang Hao

Classifications

• B29C48/39

  a first extruder feeding the melt into an intermediate location of a second extruder · CPC title

• B29C43/22

  of articles of indefinite length · CPC title

• B29K2021/00

  Use of unspecified rubbers as moulding material · CPC title

• B29C48/385

  using two or more serially arranged screws in separate barrels · CPC title

• B29L2007/008

  Wide strips, e.g. films, webs · CPC title