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CN-122003590-A - Device and method for deriving the viscosity of a molten polymer

CN122003590ACN 122003590 ACN122003590 ACN 122003590ACN-122003590-A

Abstract

An apparatus (1) for deriving the viscosity of a molten polymer comprises a pipe (10) having an inlet (10I) and an outlet (10U) and being traversed by a flow of molten polymer material, a sensor system (13) operatively in contact with the molten polymer material flowing in the pipe (10) to measure a pressure value and, if required, a temperature value and to generate a measurement signal, a processing unit (14) connected to the sensor system (13) to receive the measurement signal and/or the plurality of measurement signals and programmed to process the measurement signals to derive an estimate of the viscosity of the molten polymer material flowing in the pipe (10). The sensor system (13) includes an optical fiber defining at least one or more differential pressure sensors located inside the conduit (10) to operatively contact the molten polymeric material and, if desired, a temperature sensor.

Inventors

  • FABRIZIO PUCCI
  • Fioreno Palinello
  • Julia Domenici
  • Alberto Di Giacomo

Assignees

  • 萨克米伊莫拉机械合作社合作公司

Dates

Publication Date
20260508
Application Date
20231017

Claims (20)

  1. 1. An apparatus (1) for deriving the viscosity of a molten polymer, comprising: -a conduit (10) having an inlet (10I) and an outlet (10U) and being traversed by a flow of molten polymeric material; -a sensor system (13) operatively in contact with the molten polymeric material flowing in the pipe (10) to measure pressure values and generate measurement signals; a processing unit (14) connected to the sensor system (13) to receive the measurement signal and programmed to process the measurement signal to derive an estimate of the viscosity of the molten polymeric material flowing in the pipe (10), Characterized in that the sensor system (13) comprises an optical fiber defining a differential pressure sensor located inside the pipe (10) to be in operative contact with the molten polymeric material.
  2. 2. The device (1) according to claim 1, wherein the optical fiber ends in an end point (133), the end point (133) being located inside the pipe (10) to be in contact with the molten polymer material.
  3. 3. The device (1) according to claim 2, wherein the optical fiber comprises a reflective layer (136) in direct contact with the end point (133).
  4. 4. The device (1) according to one or more of the preceding claims, wherein said end point (133) defines said differential pressure sensor.
  5. 5. The device (1) according to one or more of the preceding claims, wherein said optical fiber further defines a temperature sensor located in the interior (I) of said duct (10) to be in operative contact with said molten polymeric material.
  6. 6. The device (1) according to one or more of the preceding claims, wherein the processing unit (14) is programmed to derive an apparent viscosity value of the molten polymer material flowing in the pipe (10) based on the measurement signal, and is further programmed to apply a rabinowtsch or Weissenberg-rabinowtsch correction to the apparent viscosity value in order to derive a corresponding actual viscosity value.
  7. 7. The device (1) according to claim 6, wherein the processing unit (14) is programmed to also derive a shear rate value of the molten polymer flowing in the pipe (10).
  8. 8. The device (1) according to one or more of the preceding claims, wherein the duct (10) has a first section with a first cross-sectional dimension (D2) for the plastic material flow and a second section with a second cross-sectional dimension (D3) for the plastic material flow, the second cross-sectional dimension (D3) being smaller than the first cross-sectional dimension (D2), and wherein the optical fiber comprises a first sensorized section located in the first section of the duct (10) and a second sensorized section located in the second section of the duct (10).
  9. 9. The device (1) according to one or more of the preceding claims, wherein said duct (10) has a longitudinal section oriented along a longitudinal axis (X), and wherein said optical fiber has an effective section located inside said duct (10) and oriented parallel to said longitudinal axis (X).
  10. 10. The device (1) according to claim 9, comprising a guiding element (12), the guiding element (12) having an outer portion (12A) located outside the duct (10) and an inner portion (12B) extending into the interior of the duct (10), the guiding element (12) defining internally a channel having an inlet formed in the outer portion (12A) of the guiding element (12) and an outlet formed in the inner portion (12B) of the guiding element (12), wherein the optical fiber has an initial section, the initial section being housed in the channel and being located upstream of the effective section, the effective section being located downstream of the outlet of the channel.
  11. 11. The device (1) according to claim 10, wherein the channel in the inner portion (12B) of the guiding element (12) defines a curve such that the outlet of the channel is oriented parallel to the longitudinal axis (X).
  12. 12. The device (1) according to one or more of claims 9 to 11, wherein the effective section of the optical fiber is at least 10mm long.
  13. 13. The device (1) according to one or more of the preceding claims, wherein said optical fiber has a core (13A) made of glass and an outer sheath (13C) made of stainless steel.
  14. 14. The device (1) according to claim 13, wherein the optical fiber further comprises an intermediate sheath (13C') made of ceramic material.
  15. 15. An apparatus (L) for continuously processing plastic materials, comprising: -an extruder (2) configured to receive a raw plastic as an input and to produce a stream of molten plastic material as an output; -a processing machine (3) configured to perform processing on the plastic in a continuous cycle; -a connecting duct for feeding the molten plastic fed out from the extruder (2) to the processing machine (3); -a device (1) for deriving the viscosity of a molten polymer according to one or more of the preceding claims, wherein the duct (10) of the device (1) is formed by a portion of the connecting duct.
  16. 16. The apparatus (L) according to claim 15, comprising a controller configured to adjust one or more process parameters related to the activity of the extruder (2), wherein the controller is connected to the processing unit (14) to receive an estimate of the viscosity of the molten polymeric material and is programmed to adjust the one or more process parameters in accordance with the estimate of the viscosity of the molten polymeric material.
  17. 17. A method for deriving the viscosity of a molten polymer comprising the steps of: -delivering the molten polymeric material through a conduit (10) having an inlet (10I) and an outlet (10U); -generating a measurement signal representative of a pressure value via a sensor system (13) operatively in contact with the molten polymeric material flowing in the pipe (10); Processing the measurement signal to derive an estimate of the viscosity of the molten polymeric material flowing in the pipe (10), Characterized in that the sensor system (13) comprises an optical fiber defining a differential pressure sensor located in the interior (I) of the pipe (10) to be in contact with the molten polymer material.
  18. 18. The method of claim 17, wherein the optical fiber terminates at an end point (133), the end point (133) being located inside the pipe (10) to be in contact with the molten polymeric material.
  19. 19. The device (1) according to claim 18, wherein the optical fiber comprises a reflective layer (136) in direct contact with the end point.
  20. 20. The device (1) according to one or more of claims 17 to 19, wherein said end point (133) defines said differential pressure sensor.

Description

Device and method for deriving the viscosity of a molten polymer Technical Field The present invention relates to an apparatus and a method for deriving the viscosity of a molten polymer. Background Viscosity sensors are used to measure or estimate the viscosity of liquids (e.g., molten plastic, ink, sludge, or petroleum) in a variety of different industrial environments. In general, in particular with respect to the processing of plastics, an extruder is used to produce a flow of liquid plastics (alternatively, a piston or other device may be used instead), downstream of which there are processing devices, such as moulding machines (which is the case in beverage lines for forming caps or parisons) or other machines for performing other treatments (for example, the production of plastic films or segments). The use of sensors in the field of plastics processing is known, for example, from the patent documents US5197633A, US20190315048A1, US5303141A, US20200324311A1, US10137679B2 and US6492485B1. For example, patent document US5197633a describes the use of a proximity sensor made of optical fibers to measure the flow rate of molten plastic. Regarding the measurement of viscosity, several solutions are known, for example, from patent documents US2019250086, US5708197A, US5197633A, US4425790A, CN104568663a and CN 204439494U. For example, the solution proposed in US4425790a involves measuring differential pressure measurements in a mould delivering molten plastic. However, this solution means that a device dedicated to viscosity measurement is constructed and is complex and expensive, since it requires the use of branch pipes and dedicated pumps, for example. Thus, there remains a need for a reliable and mechanically simple system for deriving the viscosity of a fluid (e.g., liquid plastic) flowing in a pipe. Disclosure of Invention It is an object of the present invention to provide a device and a method for deriving the viscosity of a liquid, in particular but not exclusively a molten polymer, to overcome the above-mentioned drawbacks of the prior art. In particular, it is an object of the present invention to provide a device and a method for deriving the viscosity of a liquid, in particular but not exclusively a molten polymer, which are reliable and simple and therefore inexpensive. These objects are fully achieved by the devices and methods of the present disclosure as characterized in the appended claims. The present disclosure relates to a device (or system) for deriving a viscosity of a liquid. The concepts and features described in this disclosure may be applied to derive the viscosity of any liquid, or the viscosity of a liquid or semi-liquid substance made to flow in a pipe, such as ink, petroleum, sludge, or molten plastic. In particular, the concepts of the present disclosure are applicable to deriving the viscosity of newtonian and non-newtonian, pseudoplastic fluids. The remainder of the disclosure focuses on applications to molten plastics, that is, applications where the liquid whose viscosity is to be derived is molten plastic, but the disclosure does not lose generality accordingly (thus, it should be understood that terms such as "molten plastic" or "molten polymeric material" used in the disclosure may be replaced by the term "liquid"). The molten polymer flows in the pipe. In an example embodiment, the conduit forms part of a device. The conduit has an inlet and an outlet. The apparatus includes a sensor system. The sensor system includes one or more sensors. The sensor system is configured to capture a measurement signal representative of one or more quantities that depend on a physical state of the molten polymer flowing in the pipe. More specifically, the sensor system measures the pressure value (and if necessary also the temperature value) of the molten plastic flowing in the pipe. In an example embodiment, the sensor system is operably in contact with the molten polymeric material flowing in the conduit. Thus, the sensor system is operably in contact with the molten polymeric material flowing in the conduit to capture a pressure value (and, if desired, a temperature value), and the measurement signal generated by the sensor system is representative of the captured pressure value. The apparatus further comprises a processing unit. For example, the processing unit includes a memory and a processor. The processing unit is connected to the sensor system to receive the processing signal and process it. The processing unit is programmed to derive an estimate of the viscosity of the molten polymeric material flowing in the pipe based on the measurement signal. The sensor system includes a fiber optic sensor. More specifically, the sensor system includes an optical fiber that defines a differential pressure sensor. In an example embodiment, an optical fiber defining a differential pressure sensor is positioned inside the conduit so as to be in operable contact with the molten polymeric mater