Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Viscosity
Reexamination Certificate
1999-07-01
2001-02-06
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Viscosity
C073S863610, C073S864340, C422S093000, C137S110000, C137S115030
Reexamination Certificate
active
06182503
ABSTRACT:
The present invention relates generally to the measurement of rheological characteristics of flowing materials and pertains, more specifically, to the on-line measurement of such characteristics as the viscosity of flowing materials, such as polymer melts, for purposes of control of manufacturing processes involving flowing materials, such as molten plastics.
Rheological testing equipment has been available for a very long time in conducting laboratory measurements of certain important characteristics of flowing materials, such as polymer melts, used in various manufacturing processes. Thus, properties such as viscosity and melt flow index of polymer melts are being measured in the laboratory with increasing accuracy. More recently, efforts have been directed toward the measurement of these characteristics on-line, during the manufacturing process itself, in order to provide constant, closer control over the quality of the material utilized in the process. On-line measurement requires equipment which not only is relatively easy to use and maintain, but which is responsive, and which avoids disturbing the manufacturing process being monitored.
Among the more successful on-line rheometers available currently are capillary rheometers which divert a portion of a polymer melt from the main stream of molten plastic, conduct measurements on the diverted melt, and then either discard the diverted melt or return the diverted melt to the process main stream. In U.S. Pat. No. 4,817,416, the disclosure of which is incorporated herein by reference thereto, there is disclosed an on-line capillary rheometer and techniques for conducting on-line measurements of the type described above. In U.S. Pat. No. 5,347,852, the disclosure of which is incorporated herein by reference thereto, the capability of such on-line rheometers is extended to enable effective use in connection with the control of processes where measurements must be conducted quickly and response time must be held to a minimum, such as processes in which polymers are blended, alloyed or reacted.
The present invention accomplishes still further reductions in response time while increasing the accuracy and effectiveness of Theological measurements conducted on-line. As such, the present invention attains several objects and advantages, some of which are summarized as follows: Enables truly on-line measurements for attaining quicker response and more accurate control of manufacturing processes involving flowing materials, such as polymer melts; allows on-line measurements to be made in a flowing material, such as a polymer melt, diverted from the process main stream with decreased residence time of the diverted material in the measuring apparatus, increased accuracy and quicker response; permits the conduct of on-line measurements with a minimal intrusion into the process being monitored; permits increased versatility in the nature and extent of the information derived from on-line measurements of flowing materials, such as polymer melts, as well as increased accuracy in the information itself; enables ease of installation and use in connection with current manufacturing equipment and techniques; allows ready adaptation for use in connection with a wide variety of materials and operating conditions; enables the maintenance of a continuous flow of material diverted from the process main stream for assuring a supply of fresh material to a rheometer for regular accurate Theological measurements; delivers material to a rheometer for on-line measurements, the material being delivered continuously and at a stabilized temperature for increased accuracy of measurement; allows continuous measurements to be accomplished by an on-line rheometer at selected different volumetric flow rates through the rheometer, while maintaining an essentially constant flow rate in the material diverted from the process main stream for accomplishing accuracy over a range of measurements; and provides a simple and rugged construction for economical manufacture and reliable long-term service.
The above objects and advantages, as well as further objects and advantages, are attained by the present invention, which may be described briefly as apparatus for conducting on-line rheological measurements in a process flowing material carried in a process main stream so as to provide process control information based upon the viscosity of the process flowing material, utilizing a rheometer in which diverted material from a first conduit communicating with the process main stream is delivered downstream to an entrance of a capillary passage having a predetermined volumetric flow capacity, and passes from an exit of the capillary passage to a second conduit, while measuring means measures the viscosity of the diverted material in the capillary passage, the apparatus comprising: an inlet site located in close proximity to the entrance of the capillary passage; an inlet pump having an entrance communicating with the first conduit, and an exit communicating with the inlet site for delivering a volumetric flow of diverted material to the inlet site; a metering pump having an entrance communicating with the exit of the capillary passage, and an exit communicating with the second conduit for drawing a portion of the volumetric flow of diverted material from the inlet site through the capillary passage; a parallel flow passage having an inlet located at the inlet site, between the exit of the inlet pump and the entrance of the capillary passage, in close proximity to the entrance of the capillary passage, and an outlet communicating with the second conduit at a location downstream of the exit of the metering pump; and a parallel passage pump for moving a balance of the volumetric flow of the diverted material from the inlet site through the parallel flow passage to the second conduit so as to assure that a continuous supply of fresh diverted material is available at the inlet site, in close proximity to the entrance of the capillary passage.
Further, the invention includes a method for conducting on-line rheological measurements in a process flowing material carried in a process main stream so as to provide process control information based upon the viscosity of the process flowing material, utilizing a rheometer in which diverted material from a first conduit communicating with the process main stream is delivered downstream to an entrance of a capillary passage having a predetermined volumetric flow capacity, and passes from an exit of the capillary passage to a second conduit, while measuring means measures the viscosity of the diverted material in the capillary passage, the method comprising: providing a volumetric flow of diverted material at an inlet site located in close proximity to the entrance of the capillary passage; drawing a portion of the volumetric flow of diverted material from the inlet site through the capillary passage; and moving a balance of the volumetric flow of diverted material from the inlet site through a parallel passage to assure a continuous supply of fresh diverted material at the inlet site, in close proximity to the entrance of the capillary passage.
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Garritano Ronald F.
Mode Paul G.
Jacob Arthur
Rheometric Scientific, Inc.
Wiggins David
Williams Hezron
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