Measuring device and method for determining the rheological properties of viscous polymer substances

Abstract

The invention relates to a measuring device and a method for determining the rheological properties of a viscous polymer substance, wherein the measuring device comprises a rheometer having a container for accommodating the substance and a rotating element which can be positioned inside the container, wherein the measuring device provides a relative rotation between the rotating element and the container about a rotation axis, which defines an axial direction parallel to the rotation axis and a radial direction perpendicular to the rotation axis, wherein the measuring device comprises one or more normal force sensors for detecting at least a component of a normal force exerted onto the container or the rotating element in the axial direction and a radial force sensor for detecting a radial force exerted onto the container in the radial direction.

Description

Technical Field

[0001] This invention relates to a measuring apparatus and method for determining the rheological properties of viscous polymers. Background Technology

[0002] Rotational rheometers are known to be used to measure the rheological properties of liquids, such as viscosity. EP 2 078 949 A2 discloses the use of a rheometer for measuring the viscosity of highly viscous substances. A known rheometer has a measuring chamber for receiving the highly viscous substance and a cone that can rotate inside the measuring chamber to rotate the highly viscous substance. Viscosity is derived from the torque required to generate the rotating cone. For accurate measurements of the highly viscous substance, it is crucial that the highly viscous substance rotates with the cone and does not slip relative to the inner surface of the chamber. To ensure adequate adhesion and / or friction between the highly viscous substance and the cone, the measuring chamber is closed and the highly viscous substance is pressurized to a pressure significantly higher than atmospheric pressure.

[0003] US 4,173,142 A discloses a rotational viscometer for measuring polymeric substances. The rotational viscometer operates on the principle of plate-to-cone or plate-to-plate and includes a chamber for accommodating the polymeric substance whose viscosity is to be measured, an upper counter rotating measuring surface and a lower counter rotating measuring surface within the chamber, and a force measuring device located within a housing for measuring the cumulative force acting perpendicularly to one of the measuring surfaces.

[0004] US2011 / 0100098A discloses a rheometer with multiple normal force sensors but no container. Therefore, the rheometer is not suitable for containing pressurized, highly viscous substances.

[0005] EP2063249A2 discloses a rheometer having a material container for containing ingredients under controlled temperature or controlled pressure and two rotatable mixing elements within the cavity of the material container. This known rheometer does not have a normal force sensor. Summary of the Invention

[0006] It has been found that, in addition to the normal force, the relative rotation between the rotating element and the measuring chamber also results in a slight increase in the force measured in the radial direction. This slight increase can be detected and combined with the detected normal force to calculate various rheological properties of viscous polymeric substances. A drawback of known rotational rheometers, such as those disclosed in EP 2 078 949 A2, is that although they have a pressure sensor, this sensor is only arranged to measure pressure before the rotation of the rotating element. Furthermore, neither EP 2 078 949 A2 nor EP 2 063 249 A2 discloses any normal force sensor. US 4,173,142A and EP 2 063 249 A2 disclose force measuring devices for measuring the normal force, but do not disclose radial force sensors.

[0007] Another drawback of EP 2 078 949 A2 is that high pressure itself promotes or influences the behavior of highly viscous substances, which can lead to inaccuracies in some measured rheological properties. In particular, due to the enclosed nature of the measuring chamber, the behavior of highly viscous substances may be inconsistent, especially towards the circumferential walls of the measuring chamber used to detect radial forces. Higher viscosity requires higher pressure. Therefore, the negative impact of pressure increases significantly with increasing viscosity. Depending on the applied pressure (if any), the viscometer of US4,173,142 A will have the same drawback.

[0008] In EP 2 063 249 A2, the measured load on the shaft is independent of the radial force applied to the container in the radial direction. Furthermore, EP 2 063 249 A2 does not recognize any inconsistent behavior of the feed when pressurized to high pressure toward or near the circumferential wall of the container.

[0009] The purpose of this invention is to provide a measuring apparatus and method for determining the rheological properties of viscous polymers, wherein the measuring apparatus can improve its measuring capability.

[0010] According to a first aspect, the present invention provides a measuring apparatus for determining the rheological properties of a viscous polymer, wherein the measuring apparatus includes a rotational rheometer having a container for containing the viscous polymer and a rotating element positionable within the container, wherein the measuring apparatus is arranged to provide relative rotation between the rotating element and the container about a rotation axis, the rotation axis defining an axial direction parallel to the rotation axis and a radial direction perpendicular to the rotation axis, wherein the measuring apparatus includes one or more normal force sensors for detecting at least a component of the normal force applied to the container or the rotating element in the axial direction and a radial force sensor for detecting a radial force applied to the container in the radial direction.

[0011] Relative rotation causes shearing of the viscous polymer, during which the viscous polymer applies a normal force in the axial direction to the container, a radial force on the circumferential wall, and an internal force in the flow direction. Detection signals representing the normal and radial forces can be combined to calculate the fluid properties of the viscous polymer, such as the "first normal stress difference" and the "second normal stress difference".

[0012] US 2011 / 100098 A1 relates to rheometers without containers.

[0013] EP 2 063 249 A2 discloses a rheometer having a material holding container for containing ingredients at a controlled temperature or pressure and two mixing elements rotatable within the cavity of the material holding container. EP 2 063 249 A2 also discloses a transducer arranged to decompose the lateral displacement transmitted via a bearing to the drive coupling housing through the drive coupling shaft due to the torque generated at the fulcrum of the drive coupling device during the rotation of the bevel gear. The load applied by the ingredients is distinguished from the radial force applied to the material holding container in the radial direction by detecting the radial displacement of the shaft or its housing element. In particular, the force generating the torque measured by the transducer is a tangential force. By definition, these forces are perpendicular to the radial force measured by the radial force sensor in the measuring device according to the first aspect of the invention. The relationship between the tangential force and the radial force is unknown and therefore cannot be derived from the torque measured by the transducer of EP 2 063 249 A2. Therefore, EP 2 063 249 A2 does not disclose a normal force sensor for detecting at least the component of the normal force applied to the material holding container in the axial direction, nor does it disclose a radial force sensor for detecting the radial force applied to the container in the radial direction (i.e., at the circumferential wall of the container).

[0014] Furthermore, neither US 2011 / 100098 A1 nor EP 2 063 249 A2 acknowledges the problem of the different radial behavior of the ingredients before and after rotation. This may be because the pressure of the ingredients is lower than that used when pressurizing high-viscosity polymers.

[0015] Based on the objective disclosures of US 2011 / 100098 A1 and EP 2 063 249 A2, there is no incentive for those skilled in the art to add a radial force sensor for detecting radial forces applied to a container in the radial direction (i.e., at the circumferential wall of the container).

[0016] In a preferred embodiment, the radial force sensor is located at or within the circumferential wall. Therefore, the radial force can be measured directly at the circumferential wall.

[0017] In another preferred embodiment, the radial force sensor is a pressure sensor. A pressure sensor measures the force (typically expressed in Newtons) per unit area (typically in square meters), thus generating a pressure value, typically expressed in Pascals (Pa) or bar.

[0018] In another preferred embodiment, one step in the calculation involves subtracting the radial force, based on a detection signal from the radial force sensor indicating the radial force, from the normal force applied to the container or the rotating element in the axial direction at the outer diameter. Initially, a radial force sensor was added to measure the radial force applied to the container in the radial direction only during pressurization of the viscous polymer material before the rotating element rotates, i.e., setting the pressure before the normal force measurement. After the correct pressure was set, the detection signal from the radial force sensor was no longer monitored. However, unexpectedly, a difference was found between the radial force measured before the rotating element rotates and the radial force during the rotation of the rotating element. Upon further investigation of this difference, it was considered that the increase in radial force during the rotation of the rotating element might be due to an unexpected side effect of the Weissenberg effect on the normal force applied to the container in the normal direction, which also appears to contribute to the increase in radial force at the circumferential walls of the container. The inventors arrived at the surprising insight that the value of the radial force during the rotation of the rotating element can be used in the above calculations to determine the second normal stress difference “N2”.

[0019] More preferably, the one or more characteristics include one or more of a "first normal stress difference" and a "second normal stress difference". These characteristics can be used to calculate or predict other characteristics, such as extrusion swelling.

[0020] In another embodiment, the one or more normal force sensors include a first normal force sensor for detecting at least the component of the normal force applied to the container or the rotating element in the axial direction at a first radial distance from the axis of rotation, and a second normal force sensor for detecting at least the component of the normal force applied to the container or the rotating element in the axial direction at a second radial distance from the axis of rotation greater than the first radial distance. Normal force detection has proven unreliable due to the effects of pressure and / or container boundaries. In particular, the region radially outside the rotating element can be problematic because it marks the transition between a region of viscous polymeric material rotating with the rotation of the rotating element and a remaining region in which the viscous polymeric material rotates more slowly or not at all. A normal force sensor positioned at this transition will inevitably overlap with both regions and thus produce unreliable detection results. Furthermore, when the normal force sensor is positioned close to the radial boundary of the container, the detection results will become inconsistent due to pressure accumulation relative to the radial boundary.

[0021] As proposed in this invention, by utilizing at least two normal force sensors to detect normal forces at two different radial distances, normal forces at other radial distances can be predicted, calculated, interpolated, and / or extrapolated. Thus, normal forces can be determined for radial distances where actual detection of normal forces is difficult or unreliable.

[0022] In a preferred embodiment, the plurality of normal force sensors further includes a third normal force sensor for detecting at least the component of the normal force applied to the container or the rotating element in the axial direction at a third radial distance from the axis of rotation greater than the second radial distance. The normal force detected at the third radial location can be used to more accurately predict, calculate, interpolate, and / or extrapolate the normal force at other radial distances. In particular, it has been found that the normal force exhibits an exponential relationship with the radial distance. Therefore, the normal forces at the three radial locations can be used to determine the parameters of this exponential relationship.

[0023] In another embodiment, the rotating element has an outer diameter, wherein the control unit is arranged to calculate, by interpolation or extrapolation, the normal force applied to the container in the axial direction at the outer diameter of the rotating element based on detection signals from the plurality of normal force sensors indicating the normal force at a corresponding radial distance from the axis of rotation. As previously stated, the normal force at the outer diameter of the rotating element cannot be reliably determined by the normal force sensors. Therefore, the value is interpolated or extrapolated based on the detection signals from the normal force sensors.

[0024] In one embodiment, all of the plurality of normal force sensors are arranged to detect the normal force between the rotation axis and the outer diameter, wherein the control unit is arranged to calculate, by means of extrapolation, the normal force applied to the container or the rotating element at the outer diameter of the rotating element in the axial direction. By arranging all the normal force sensors in the region between the rotation axis and the outer diameter, contamination of the detection results from the normal force sensors by the inconsistent behavior of the viscous polymer material outside the outer diameter can be prevented.

[0025] In another embodiment, the normal force has an exponential relationship with the radial distance, which can be expressed on a logarithmic scale as a linear equation with a slope and an intercept. The control unit is arranged to determine the slope and intercept of the linear equation using the normal force detected by the first normal force sensor and the normal force detected by the second normal force sensor. The control unit is also arranged to calculate, via the linear equation, the normal force applied to the container or the rotating element in the axial direction at the outer diameter of the rotating element. Therefore, the exponential relationship can be simplified to a linear relationship, thereby requiring only normal forces from two different radial distances to calculate the normal force at any other radial location.

[0026] In another embodiment, the rotating element has an outer diameter, wherein the container includes a circumferential wall extending concentrically about a rotation axis, wherein the circumferential wall of the container has an inner diameter concentric with the outer diameter of the rotating element, wherein the inner diameter is larger than the outer diameter to form a gap between the rotating element and the circumferential wall. The circumferential wall causes unpredictable and / or inconsistent behavior of viscous polymeric substances, particularly at or near the circumferential wall. This problem is particularly pronounced under high pressures, i.e., pressures exceeding thirty bar or fifty bar. The gap effectively reduces this negative impact.

[0027] However, when the gap is too large, a portion of the viscous polymer will rotate more slowly or stop rotating altogether. This also leads to unpredictable and / or inconsistent behavior of the viscous polymer, particularly at the transition between its rotating and non-rotating portions. Therefore, it is preferable to set the gap size within a range that achieves a balance between reducing the negative impact of the circumferential wall on the detection results and introducing new negative impacts caused by the difference in rotational speed of the viscous polymer. It has been found that detection results can be improved when the size of the gap in the radial direction is in the range of two to fifty percent of the outer diameter. Detection results can be further improved when the size of the gap in the radial direction is in the range of two to fifteen percent of the outer diameter. In practical embodiments with an outer diameter of approximately fifty millimeters, it is preferred that the size of the gap in the radial direction is in the range of one to five millimeters.

[0028] In another embodiment, the container includes a first end wall that closes a circumferential wall in the axial direction on one side of the rotating element and a second end wall that closes a circumferential wall in the axial direction on the opposite side of the rotating element, wherein each of the one or more normal force sensors is located at or within one of the end walls of the container. Preferably, all the normal force sensors are located within the same end wall. Therefore, the normal force sensors can be optimally positioned to detect normal forces in the axial direction perpendicular to the surface of the end wall.

[0029] In another embodiment, the axis of rotation extends vertically or substantially vertically, wherein the first end wall is arranged axially above the rotating element. Preferably, the plurality of normal force sensors are located at or in the first end wall of the container. More preferably, the first end wall is a lid for opening and closing the container. Therefore, the sensors are easily accessible for maintenance purposes.

[0030] In an alternative embodiment, the one or more normal force sensors are located on the rotating element. The normal force generated by the shearing of the polymer is applied in two directions parallel to the axis of rotation, i.e., applied to both the container and the rotating element. Therefore, the normal force can be detected at the container or the rotating element, or optionally even at both.

[0031] In another embodiment, the one or more normal force sensors are arranged to detect the component of the normal force in a detection direction extending in the range of zero to thirty degrees relative to the axis of rotation. The detection direction may be slightly tilted relative to the axis of rotation, particularly when one of the container and the rotating element does not have a surface perpendicular to the axis of rotation, i.e., in the case of a conical rotating element or a conical container. As long as the component of the normal force can be detected within the specified range, vector decomposition can be used to calculate the actual normal force within or parallel to the axis of rotation.

[0032] Alternatively, the one or more normal force sensors are arranged to detect the normal force in a detection direction parallel to the axis of rotation. In this case, the detected normal force approximately corresponds to the actual normal force.

[0033] In another embodiment, the container arrangement is configured to contain a viscous polymeric substance at a pressure higher than ambient pressure. The arrangement of one or more normal force sensors or another pressure sensor is configured to detect the pressure exerted on the container by the viscous polymeric substance when the rotating element is stationary due to the pressure of the polymeric substance. The measuring device further includes a control unit electrically connected to the one or more normal force sensors, wherein the control unit is configured to distinguish between the pressure generated by the viscous polymeric substance when the rotating element is stationary and the normal force generated by the rotation of the rotating element. Therefore, the effect of pressurization, i.e., the basic pressure, can be subtracted from the forces detected by the normal force sensor and / or radial force sensor to accurately determine the contribution of rotation to the normal and radial forces detected by the respective sensors.

[0034] In another embodiment, the first and second normal force sensors are offset relative to each other in a circumferential direction about the axis of rotation. This is particularly convenient when the normal force sensors are too large to be physically arranged side by side in a straight line.

[0035] According to a second aspect, the present invention provides a method for determining the rheological properties of a viscous polymer using a measuring device according to a first aspect of the present invention, wherein the method comprises the following steps:

[0036] - Fill the container with a viscous polymer material;

[0037] - Pressurize the viscous polymer material to a pressure higher than ambient pressure;

[0038] - Provide relative rotation between the rotating element and the container to shear the viscous polymer in the container;

[0039] -At least detect the component of the normal force exerted on the container or the rotating element in the axial direction by the shear-viscosity polymer; and

[0040] - Detect the radial force exerted on the container in the radial direction by the viscous polymer material.

[0041] The method and its embodiments relate to the practical implementation of the measuring device and its corresponding embodiments according to the first aspect of the present invention, and therefore have the same technical advantages, which will not be repeated hereafter.

[0042] In a preferred embodiment, the rotating element has an outer diameter, wherein the method includes the steps of: calculating a normal force applied in the axial direction to the container or the rotating element at the outer diameter of the rotating element based on detection signals from the one or more normal force sensors; and

[0043] - The normal and radial forces applied to the container or the rotating element in the axial direction at the outer diameter are used as parameters for calculating one or more properties of the viscous polymer.

[0044] In another embodiment, one of the calculations involves subtracting the radial force, based on a detection signal from the radial force sensor indicating the radial force, from the normal force applied to the container or the rotating element in the axial direction at the outer diameter.

[0045] In another embodiment, the one or more characteristics include one or more of a "first normal stress difference" and a "second normal stress difference".

[0046] In another embodiment, the one or more normal force sensors include a first normal force sensor at a first radial distance from the axis of rotation and a second normal force sensor at a second radial distance from the axis of rotation greater than the first radial distance, wherein the method includes the steps of: using the first normal force sensor and the second normal force sensor respectively to detect at least the components of the normal force applied to the container or the rotating element by the shear-viscosity polymer at the first radial distance and the second radial distance.

[0047] In a preferred embodiment, the plurality of normal force sensors further includes a third normal force sensor located at a third radial distance from the axis of rotation greater than the second radial distance, wherein the method further includes the step of: using the third normal force sensor to detect at least the component of the normal force applied to the container or the rotating element in the axial direction at the third radial distance.

[0048] In another embodiment, the rotating element has an outer diameter, and the method further includes the step of interpolating or extrapolating detection signals from the plurality of normal force sensors indicating the normal force at a corresponding radial distance from the axis of rotation.

[0049] In one embodiment, the plurality of normal force sensors detect the normal force between the rotation axis and the outer diameter, wherein the method includes the step of extrapolating the detected normal force to determine the normal force applied to the container or the rotation element in the axial direction at the outer diameter of the rotation element.

[0050] In another embodiment, the normal force has an exponential relationship with the radial distance, which can be expressed on a logarithmic scale as a linear equation with a slope and an intercept, wherein the method includes the steps of: determining the slope and intercept of the linear equation using the normal force detected by the first sensor and the normal force detected by the second normal force sensor, and calculating the normal force applied to the container or the rotating element in the axial direction at the outer diameter of the rotating element via the linear equation.

[0051] In another embodiment, the method includes the following steps:

[0052] - Detect the pressure exerted on the container by the viscous polymer due to the pressure of the viscous polymer when the rotating element is stationary; and

[0053] - Distinguish between the pressure generated by the viscous polymer material when the rotating element is stationary and the normal force generated by the rotation of the rotating element.

[0054] The aspects and features described and illustrated in the specification may be applied individually, as far as possible. These individual aspects, especially those described in the appended dependent claims, may become the subject of a divisional patent application. Attached Figure Description

[0055] The invention will be explained based on exemplary embodiments shown in the accompanying drawings, wherein:

[0056] Figure 1 An isometric view of a measuring device according to a first embodiment of the present invention is shown;

[0057] Figure 2 It shows according to Figure 1 A schematic cross-section of the measuring device;

[0058] Figure 3 It shows Figure 2 The cross-section and the forces measured at various locations along the cross-section;

[0059] Figure 4 The first graph is shown, which illustrates the exponential relationship between normal force and radial distance;

[0060] Figure 5The second graph is shown, which illustrates the result after logarithmic scaling. Figure 4 The linear relationship between the normal force and the radial distance; and

[0061] Figure 6 A schematic cross-section of an alternative measuring device according to a second embodiment of the present invention is shown. Detailed Implementation

[0062] Figure 1 , 2 Figures 3 and 4 illustrate a measuring device 1 for determining the rheological properties of a viscous or highly viscous polymeric material 9 according to an exemplary first embodiment of the present invention, such as... Figure 2 and 3 As shown in the diagram, the measuring device 1 can be used, for example, to determine, calculate, or predict one or more properties of an elastomeric material (particularly rubber blends used in the tire manufacturing industry). Typically, elastomeric materials are tested under different conditions (e.g., at different temperatures or pressures).

[0063] like Figure 1 As shown, the measuring device 1 includes a rotational viscometer or rheometer 2. The rheometer 2 is provided with a chamber or container 3 defining an internal volume for containing the polymer 9 and a rotating element 4 positionable within the container 3. The measuring device 1 is arranged to provide relative rotation between the rotating element 4 and the container 3 about a rotation axis S. The rotation axis S defines an axial direction A parallel to the rotation axis S and a radial direction R perpendicular to the rotation axis S. Preferably, the rotation axis S extends vertically or substantially vertically. Thus, the rotating element 4 rotates in a horizontal plane. In this exemplary embodiment, the rotating element 4 is rotated about the rotation axis S to obtain relative rotation between the rotating element 4 and the container 3. Alternatively, the container 3 may rotate relative to the rotating element 4, similar to a rotating cylinder forming the measuring chamber of US4,173,142 A.

[0064] The measuring device 1 also includes a driver 7 for driving the rotating element 4 to rotate about the rotation axis S and an extruder 8, the extruder 8 being arranged in fluid communication with the container 3 to supply the polymer 9 into the container 3 of the rheometer 2. When the container 3 is completely filled with the polymer 9, the extruder 8 is controlled to pressurize the polymer 9. Specifically, the pressure P of the polymer 9 in the container 3 is increased to a level higher than the ambient pressure around the measuring device 1. More specifically, the pressure P is increased to a level exceeding thirty bar, preferably exceeding fifty bar, and most preferably exceeding one hundred bar.

[0065] The extruder 8 and / or rheometer 2 may be further provided with one or more heating elements (not shown) to control the temperature of the polymer 9. The measuring device 1 may be further provided with a torque transducer or sensor (not shown) to measure the torque applied to the rotating element 4.

[0066] In this exemplary embodiment, the container 3 includes a circumferential wall 30 extending in a circumferential direction around the axis of rotation S. The circumferential wall 30 is circular or substantially circular. The circumferential wall 30 is concentric with the circumference of the rotating element 4. The container 3 also includes a first end wall 31 that closes the circumferential wall 30 in the axial direction A on one side of the rotating element 4 and a second end surface or wall 32 that closes the circumferential wall 30 in the axial direction A on the opposite side of the rotating element 4. In this exemplary embodiment, the first end surface or wall 31 is arranged above the rotating element 4 in the axial direction A. More specifically, the first end wall 31 is a lid for opening and closing the container 3, i.e., for maintenance purposes. Figure 1 The cover is shown in the open position. When closed, the cover is fixed relative to the circumferential wall 30 to form a rigid or substantially rigid first end wall 31.

[0067] like Figure 1 As shown in the optimal configuration, the rotating element 4 has a circular or approximately circular circumference. The circumference defines the outer diameter D1, as... Figure 2 and 3 As shown in the illustration. Preferably, the outer diameter D1 is in the range of forty to one hundred millimeters. In this particular example, the outer diameter D1 is approximately fifty millimeters. In the illustrated embodiment, the rotating element 4 is a double-sided cone or a double cone. Alternatively, the rotating element 4 may be shaped as a single-sided cone, a single cone, or a suitably shaped disc or plate.

[0068] like Figure 2 and 3 As shown, the circumferential wall 30 extends concentrically around the axis of rotation S at the inner diameter D2. Preferably, the inner diameter D2 is larger than the outer diameter D1 to form a gap X between the rotating element 4 and the circumferential wall 30. The gap X in the radial direction R has a size in the range of two to fifty percent of the outer diameter D1, more preferably in the range of two to fifteen percent of the outer diameter D1. Based on the outer diameter D1 of the rotating element 4 of approximately fifty millimeters, the size of the gap (X) in the radial direction (R) is in the range of one to twenty-five millimeters, more preferably in the range of one to seven point five millimeters, and most preferably about four millimeters.

[0069] The relative rotation or counter-rotation between the rotating element 4 and the container 3 causes shear or shear flow in the polymer 9, which stretches the originally randomly arranged polymer in the shear direction. The polymer has a tendency to return to its initial random arrangement, which generates stress in the polymer 9, particularly in the direction perpendicular to the shear direction (i.e., in or parallel to axial direction A). This phenomenon is known as the "Weisenberg effect." As a result, the normal force (in...) Figure 3(Illustrated schematically by arrows F1, F2, F3, and F4) The polymer material 9 is applied to the container 3. The normal forces F1, F2, F3, and F4 act on the container 3 in the axial direction A or parallel to the axial direction A, particularly on its first end wall 31 and / or second end wall 32.

[0070] like Figure 1 and 2 As shown, the measuring device 1 also includes a plurality of normal force transducers or sensors 51, 52, 53 for measuring or detecting normal forces F1, F2, F3 applied to the container 3 in the axial direction A. The plurality of normal force sensors 51, 52, 53 are located at or within one of the end walls 31, 32 of the container 3. In this exemplary embodiment, the plurality of normal force sensors 51, 52, 53 are located in the first end wall 31 (i.e., the lid of the container 3). Therefore, the plurality of normal force sensors 51, 52, 53 are easily accessible for maintenance purposes.

[0071] Preferably, the measuring device 1 further includes a radial force transducer or sensor 54 for measuring or detecting the radial force F5 exerted by the polymer 9 on the container 3 in the radial direction R. The radial force sensor 54 is located at or within the circumferential wall 30.

[0072] In this exemplary embodiment, the plurality of normal force sensors 51, 52, 53 and / or radial force sensors 54 are pressure sensors that measure the force (typically expressed in Newtons) per unit area (typically expressed in square meters), thereby generating a pressure value, typically expressed in Pascals (Pa) or Bars. The normal force sensors 51, 52, 53 detect the force in a detection direction G perpendicular to the surface area being measured. In this exemplary embodiment, the detection direction G is parallel to the rotation axis S and / or the axial direction A.

[0073] like Figure 2 As shown, the measuring device 1 further includes a control unit 6, which is operatively and / or electronically connected to one or more of a plurality of normal force sensors 51, 52, 53 and / or radial force sensors 54 to receive detection signals from the respective sensors 51, 52, 53, 54 indicating the forces detected by the respective sensors 51, 52, 53, 54. Preferably, the control unit 6 is also operatively and / or electronically connected to the driver 7 and / or the extruder 8 to control the driver and / or the extruder 8 in response to the detection signals received from the plurality of normal force sensors 51, 52, 53 and / or radial force sensors 54.

[0074] like Figure 1 and 2As best shown, at least two of the plurality of normal force sensors 51, 52, and 53 are arranged at different radial distances R1, R2, and R3 from the rotation axis S. In particular, in the illustrated example, the plurality of normal force sensors 51, 52, and 53 include a first normal force sensor 51 for detecting a normal force F1 in the axial direction A at a first radial distance R1 from the rotation axis S, and a second normal force sensor 52 for detecting a normal force F2 in the axial direction A at a second radial distance R2 from the rotation axis S greater than the first radial distance R1. In this particular example, the plurality of normal force sensors 51, 52, and 53 also include a third normal force sensor 53 for detecting a normal force F3 in the axial direction A at a third radial distance R3 from the rotation axis S greater than the first radial distance R1.

[0075] like Figure 1 As best shown, the first normal force sensor 51 and the second normal force sensor 52 are offset relative to each other in the circumferential direction C about the rotation axis S. Alternatively, the normal force sensors 51, 52, and 53 can be arranged side by side in a line in the radial direction R, provided that they can be physically accommodated within the available space in the radial direction R. In this particular example, all of the multiple normal force sensors 51, 52, and 53 are physically located between the rotation axis S and the outer diameter D1 of the rotating element 4 and / or arranged to detect the normal forces F1, F2, and F3 between the rotation axis S and the outer diameter D1 of the rotating element 4.

[0076] The following will refer to Figure 1-5 The method for determining the rheological properties of the viscous polymer 9 using the above-described measuring device 1 is explained.

[0077] Figure 1 One scenario is illustrated where the container 3 of the measuring device 1 is opened for maintenance, i.e., cleaning the container 3 after a previous cycle of the method. The lid of the container 3 can be closed to form a closed internal volume, such as... Figure 2 and 3 As shown in the diagram, container 3 is now ready to receive the viscous polymer material 9 from extruder 8.

[0078] When the extruder 8 fills the container 3 with the viscous polymer 9, the rotating element 4 remains stationary relative to the container 3. Therefore, the Weissenberg effect has not yet occurred, and once the substance 9 has completely filled the container 3, the pressure P exerted on the container 3 by the viscous polymer 9 should be uniform or substantially uniform in all directions. Subsequently, the extruder 8 can be controlled by the control unit 6 to increase the pressure P of the viscous polymer 9 to a level greater than the ambient pressure. During this process, one or more of a plurality of normal force sensors 51, 52, 53 and / or radial force sensors 54 can be used to monitor the pressure P in the container 3. Once the preset or predetermined pressure P is reached, the extruder 8 remains in its current position such that the pressure P is no longer regulated by the extruder 8. Subsequently, while the rotating element 4 remains stationary, i.e., before the rotation of the rotating element 4, the pressure P exerted on the container 3 by the polymer 9 is detected. This pressure P can be stored in the memory or circuitry of the control unit 6 for later reference.

[0079] When the rotating element 4 rotates, the Weissenberg effect causes the viscous polymer 9 to apply normal forces F1, F2, F3, and F4 to the container 9 in or parallel to the axial direction A. The control unit 6 is arranged to distinguish between the storage pressure generated by the pressure P of the polymer 9 when the rotating element 4 is stationary and the normal forces F1, F2, F3, and F4 generated by the rotation of the rotating element 4. The control unit 6 can, for example, subtract the storage pressure from the detection signals from the multiple normal force sensors 51, 52, and 53, or cancel the storage pressure relative to the detection signals from the multiple normal force sensors 51, 52, and 53, to obtain the net contribution of the normal forces F1, F2, and F3 to the actual forces measured at the respective sensors 51, 52, and 53.

[0080] Using the Navier-Stokes equations, it has been found that the normal forces F1, F2, F3, and F4 caused by the rotation of rotating element 4 have an exponential relationship with the radial distances R1, R2, R3, and R4. Specifically, the normal forces F1, F2, F3, and F4 are highest near the rotation axis S and decrease exponentially in the radially outward direction, such as... Figure 4 As shown in the figure. The normal forces F1, F2, F3, and F4 can also be expressed as functions of the natural logarithm (ln) or plotted on a logarithmic scale, which would result in a linear relationship, such as... Figure 5 As shown in the figure, the linear relationship can be defined by a linear equation with a slope (a) and an intercept (b).

[0081] Normal forces F1, F2, F3, and F4 can be used to calculate the fluid properties of viscous polymers, such as the "first normal stress difference" typically denoted by "N1" and the "second normal stress difference" typically denoted by "N2". The "normal stress difference" is well-known in tire manufacturing and is used to predict the behavior of rubber compounds, particularly extrusion swell. However, normal force detection has proven unreliable due to the influence of the pressure and / or container 3 boundaries. An alternative is the absence of boundaries in the radial direction R, i.e., no circumferential wall 30; however, this makes it impossible to contain the pressurized material 9 and measure the radial force F5.

[0082] The measuring device 1 according to the invention uses the exponential and / or linear relationships described above to predict, calculate, interpolate, or extrapolate the normal force at any radial distance from the axis of rotation S based on the detection of normal forces F1, F2, F3 at a finite number of radial distances R1, R2, R3. Specifically, detecting the normal forces F1, F2, F3 at radial positions F1, F2, F3 is more reliable or less susceptible to the influence of pressure or the boundary of the container 3.

[0083] In cases where multiple normal force sensors 51, 52, and 53 include only the first normal force sensor 51 and the second normal force sensor 52, or where a third or additional normal force sensor is not used, it can be achieved by using, for example... Figure 5 The linear relationship shown predicts, calculates, interpolates, and / or extrapolates the normal force at any radial distance from the axis of rotation S at the outer diameter D1. Specifically, the normal force F1 detected by the first normal force sensor 51 and the normal force F2 detected by the second normal force sensor 52 are used to determine the constituent forces. Figure 5 The slope (a) and intercept (b) of the basic linear equation of the line.

[0084] In the case where multiple normal force sensors 51, 52, 53 include three or more normal force sensors 51, 52, 53, the normal forces F1, F2, F3 detected at the corresponding normal force sensors 51, 52, 53 are used to determine the composition. Figure 4 The basic exponential relationship of the curve.

[0085] In any of the above cases, the normal force at any radial distance from the axis of rotation S can be determined based on the normal forces F1, F2, F3 detected at a finite number of radial distances R1, R2, R3.

[0086] Alternatively, the normal force F4 at the outer diameter D1 of the rotating element 4 can be directly detected by a single normal force sensor (not shown), provided there is sufficient space at the location to accommodate the single normal force sensor. Furthermore, due to the fact that the normal force F4 is the average value of the detection area of ​​the normal force sensor and the negative impact of the polymer material 9 slowing down or remaining stationary radially outside the outer diameter D1, the detection accuracy of the normal force F4 at the outer diameter D1 may be slightly worse than its extrapolation.

[0087] like Figure 3 As shown, the normal force F4 at the outer diameter D1 of the rotating element 4 (i.e., at a fourth radial distance R4 from the axis of rotation S) is particularly important because it is used to determine the "second normal stress difference". More specifically, the "second normal stress difference" is calculated by subtracting the radial force F5, which is based on the detection signal from the radial force sensor 54 indicating the radial force F5, from the normal force F4 applied to the container 3 at the outer diameter D1 in the axial direction A. The "first normal stress difference" can then be used to calculate the "first normal stress difference" in a manner known per se to predict various properties of the viscous polymer 9, particularly extrusion swell.

[0088] It has been found that the relative rotation of the rotating element 4 with respect to the container 3 also results in a slight increase in the force measured in the radial direction R (i.e., by the radial force sensor 54). However, the radial force F5 detected at the radial force sensor 54 in the radial direction R is affected by the presence of the circumferential wall 30 and the gap X between the circumferential wall 30 and the rotating element 4. However, when the gap X is too large, a portion of the viscous polymer 9 will rotate more slowly or stop rotating altogether. The gap X is selected within the previously specified range to minimize the influence of the circumferential wall 30 on the detection results of the radial force sensor 54, while preventing the introduction of further negative effects due to the slowing down of the viscous polymer 9.

[0089] Figure 6 An alternative measuring device 101 according to an exemplary second embodiment of the present invention is shown. The alternative measuring device 101 differs from the aforementioned measuring device 1 in that its viscometer or rheometer 102 includes normal force sensors 151, 152, and 153 located at or on the rotating element 104. Therefore, the normal force sensors 151, 152, and 153 are arranged to detect the normal forces F1, F2, and F3 applied to the rotating element 104.

[0090] In this example, since the rotating element 104 is slightly tapered, the detection direction G of the normal force sensors 151, 152, and 153 is also slightly tilted or offset relative to the rotation axis S. Specifically, the detection direction G is within a range of 0 to 30 degrees relative to the rotation axis S, preferably within a range of 0 to 15 degrees. Therefore, the normal force sensors 151, 152, and 153 are arranged to detect at least the components of the normal forces F1, F2, and F3 acting on the rotating element 104 in the axial direction S. In other words, the normal force sensors 151, 152, and 153 are arranged to detect the components of the normal forces F1, F2, and F3 in the detection direction G tilted relative to the rotation axis S. The control unit 6 can be arranged to calculate the normal forces F1, F2, and F3 based on the detection signals from the respective normal force sensors 151, 152, and 153, i.e., through vector decomposition.

[0091] Alternatively, the rotating element 104 may be plate-shaped, while the container 3 may have tapered end walls (not shown). Normal force sensors 151, 152, and 153 may be located in either the rotating element 104 or the container 3.

[0092] It should be understood that the above description, which illustrates the operation of the preferred embodiments, is not intended to limit the scope of the invention. Many variations will be apparent to those skilled in the art from the above discussion, but they will still be covered by the scope of the invention.

[0093] In summary, the present invention relates to a measuring apparatus and method for determining the rheological properties of a viscous polymer, wherein the measuring apparatus includes a rheometer having a container for containing the substance and a rotating element positionable within the container, wherein the measuring apparatus provides relative rotation between the rotating element and the container about a rotation axis, the rotation axis defining an axial direction parallel to the rotation axis and a radial direction perpendicular to the rotation axis, wherein the measuring apparatus includes one or more normal force sensors for detecting at least the component of the normal force applied to the container or the rotating element in the axial direction and a radial force sensor for detecting the radial force applied to the container in the radial direction.

[0094] List of reference numerals

[0095] 1. Measuring device

[0096] 2. Viscometer or rheometer

[0097] 3 chambers or containers

[0098] 30 Zhou Xiangbi

[0099] 31 First end wall

[0100] 32 Second end wall

[0101] 4 Rotating elements

[0102] 51 First normal force sensor

[0103] 52 Second normal force sensor

[0104] 53 Third normal force sensor

[0105] 54 Radial Force Sensor

[0106] 6 Control Unit

[0107] 8. Extruder

[0108] 9. Viscous polymers

[0109] 101 Alternative measuring device

[0110] 102 Viscometer or rheometer

[0111] 151 First normal force sensor

[0112] 152 Second normal force sensor

[0113] 153 Third normal force sensor

[0114] 104 Rotating elements

[0115] a slope

[0116] b. Intercept

[0117] Axial direction

[0118] C. Circumferential direction

[0119] D1 outer diameter

[0120] D2 inner diameter

[0121] F Normal force

[0122] F1 Normal force at the first radial distance

[0123] Normal force at the second radial distance F2

[0124] Normal force at the third radial distance F3

[0125] Normal force at the fourth radial distance F4

[0126] G detection direction

[0127] Ln Natural Logarithm

[0128] P pressure

[0129] R radial direction

[0130] R1 First radial distance

[0131] R2 Second radial distance

[0132] R3 Third radial distance

[0133] R4 Fourth radial distance

[0134] S-axis of rotation

[0135] X gap

Claims

1. A measuring device for determining the rheological properties of viscous polymers, wherein, The measuring device includes a rotational rheometer having a container for containing a viscous polymeric substance and a rotating element capable of being positioned inside the container. The measuring device is arranged to provide relative rotation between the rotating element and the container about a rotation axis, the rotation axis defining an axial direction parallel to the rotation axis and a radial direction perpendicular to the rotation axis. The measuring device includes one or more normal force sensors for detecting at least a component of the normal force applied to the container or the rotating element in the axial direction and a radial force sensor for detecting a radial force applied to the container in the radial direction. The rotating element has an outer diameter. The measuring device further includes a control unit electrically connected to the one or more normal force sensors. The control unit is arranged to calculate, based on detection signals from the one or more normal force sensors, the normal force applied to the container or the rotating element in the axial direction at the outer diameter of the rotating element. One of the calculations involves subtracting the radial force, based on a detection signal from the radial force sensor indicating the radial force, from the normal force applied to the container or the rotating element in the axial direction at the outer diameter.

2. The measuring device according to claim 1, wherein, The radial force sensor is located at or within the circumferential wall.

3. The measuring device according to claim 1, wherein, The radial force sensor is a pressure sensor.

4. The measuring device according to claim 1, wherein, One or more characteristics include one or more of "first normal stress difference" and "second normal stress difference".

5. The measuring device according to claim 1, wherein, The one or more normal force sensors include a first normal force sensor and a second normal force sensor. The first normal force sensor is used to detect at least the component of the normal force applied to the container or the rotating element in the axial direction at a first radial distance from the rotation axis. The second normal force sensor is used to detect at least the component of the normal force applied to the container or the rotating element in the axial direction at a second radial distance from the rotation axis greater than the first radial distance.

6. The measuring device according to claim 5, wherein, The plurality of normal force sensors also include a third normal force sensor for detecting at least the component of the normal force applied to the container or the rotating element in the axial direction at a third radial distance from the axis of rotation greater than the second radial distance.

7. The measuring device according to claim 5, wherein, The control unit is arranged to calculate, by means of interpolation or extrapolation, the normal force applied to the container or the rotating element in the axial direction at the outer diameter of the rotating element, based on detection signals from the plurality of normal force sensors indicating the normal force at a corresponding radial distance from the axis of rotation.

8. The measuring device according to claim 7, wherein, All of the plurality of normal force sensors are arranged to detect the normal force between the rotation axis and the outer diameter, wherein the control unit is arranged to calculate, by means of extrapolation, the normal force applied to the container or the rotation element in the axial direction at the outer diameter of the rotation element.

9. The measuring device according to claim 7, wherein, The normal force has an exponential relationship with the radial distance, which can be expressed on a logarithmic scale as a linear equation with a slope and an intercept. The control unit is arranged to determine the slope and intercept of the linear equation using the normal force detected by the first normal force sensor and the normal force detected by the second normal force sensor. The control unit is also arranged to calculate, via the linear equation, the normal force applied to the container or the rotating element in the axial direction at the outer diameter of the rotating element.

10. The measuring device according to claim 1, wherein, The rotating element has an outer diameter, wherein the container includes a circumferential wall extending concentrically about a rotation axis, wherein the circumferential wall of the container has an inner diameter concentric with the outer diameter of the rotating element, wherein the inner diameter is larger than the outer diameter to form a gap between the rotating element and the circumferential wall.

11. The measuring device according to claim 10, wherein, The size of the gap in the radial direction is in the range of two to fifty percent of the outer diameter.

12. The measuring device according to claim 10, wherein, The size of the gap in the radial direction is in the range of two to fifteen percent of the outer diameter.

13. The measuring device according to claim 10, wherein, The gap has a radial dimension ranging from one to five millimeters.

14. The measuring device according to claim 1, wherein, The container includes a first end wall that closes a circumferential wall in the axial direction on one side of the rotating element and a second end wall that closes a circumferential wall in the axial direction on the opposite side of the rotating element, wherein each of the one or more normal force sensors is located at one end wall of the container or in one end wall of the container.

15. The measuring device according to claim 14, wherein, The rotation axis extends vertically, wherein the first end wall is arranged above the rotating element in the axial direction.

16. The measuring device according to claim 15, wherein, The one or more normal force sensors are located at or within the first end wall of the container.

17. The measuring device according to claim 16, wherein, The first end wall is the lid for opening and closing the container.

18. The measuring device according to claim 1, wherein, The one or more normal force sensors are located on the rotating element.

19. The measuring device according to claim 1, wherein, The one or more normal force sensors are arranged to detect the component of the normal force in a detection direction extending from zero to thirty degrees relative to the axis of rotation.

20. The measuring device according to claim 1, wherein, The one or more normal force sensors are arranged to detect normal force in a detection direction parallel to the axis of rotation.

21. The measuring device according to claim 1, wherein, The container arrangement is configured to contain a viscous polymer at a pressure higher than ambient pressure, wherein one or more of the one or more normal force sensors or another pressure sensor are arranged to detect the pressure exerted on the container by the viscous polymer due to the pressure of the viscous polymer when the rotating element is stationary, wherein the measuring device further includes a control unit electrically connected to the one or more normal force sensors, wherein the control unit is arranged to distinguish between the pressure generated by the pressure of the viscous polymer when the rotating element is stationary and the normal force generated by the rotation of the rotating element.

22. The measuring device according to claim 5, wherein, The first normal force sensor and the second normal force sensor are offset relative to each other in a circumferential direction about the axis of rotation.

23. A method for determining the rheological properties of a viscous polymer using the measuring apparatus according to claim 1, wherein, The method includes the following steps: - Fill the container with a viscous polymer; - Pressurize the viscous polymer material to a pressure higher than ambient pressure; - Provide relative rotation between the rotating element and the container to shear the viscous polymer in the container; - At least detect the component of the normal force exerted on the container or the rotating element in the axial direction by the shear-viscosity polymer; and - Detecting a radial force exerted on the container in the radial direction by a viscous polymer, wherein the rotating element has an outer diameter, wherein the method includes the steps of: calculating a normal force exerted on the container or the rotating element in the axial direction at the outer diameter of the rotating element based on detection signals from one or more normal force sensors; and - The normal and radial forces applied to the container or the rotating element in the axial direction at the outer diameter are used as parameters for calculating one or more properties of the viscous polymer, wherein one of the calculations involves subtracting the radial force, based on a detection signal from the radial force sensor indicating the radial force, from the normal force applied to the container or the rotating element in the axial direction at the outer diameter.

24. The method according to claim 23, wherein, One or more characteristics include one or more of "first normal stress difference" and "second normal stress difference".

25. The method according to claim 23, wherein, The one or more normal force sensors include a first normal force sensor at a first radial distance from the axis of rotation and a second normal force sensor at a second radial distance from the axis of rotation greater than the first radial distance, wherein the method includes the steps of: using the first normal force sensor and the second normal force sensor respectively to detect at least the components of the normal force applied to the container or the rotating element by the shear-viscosity polymer at the first radial distance and the second radial distance.

26. The method of claim 25, wherein, The plurality of normal force sensors also include a third normal force sensor at a third radial distance from the axis of rotation greater than the second radial distance, wherein the method further includes the step of: using the third normal force sensor to detect at least the component of the normal force applied to the container or the rotating element in the axial direction at the third radial distance.

27. The method according to claim 25, wherein, The method further includes the step of interpolating or extrapolating detection signals from the plurality of normal force sensors that indicate the normal force at a corresponding radial distance from the axis of rotation.

28. The method according to claim 27, wherein, The plurality of normal force sensors detect the normal force between the rotation axis and the outer diameter, wherein the method includes the following steps: extrapolating the detected normal force to determine the normal force applied to the container or the rotation element in the axial direction at the outer diameter of the rotation element.

29. The method according to claim 27, wherein, The normal force has an exponential relationship with the radial distance, which can be expressed on a logarithmic scale as a linear equation with a slope and an intercept. The method includes the following steps: using the normal force detected by the first normal force sensor and the normal force detected by the second normal force sensor to determine the slope and intercept of the linear equation, and calculating the normal force applied to the container or the rotating element in the axial direction at the outer diameter of the rotating element via the linear equation.

30. The method according to claim 23, wherein, The method includes the following steps: - Detect the pressure exerted on the container by the viscous polymer due to the pressure of the viscous polymer when the rotating element is stationary; and - Distinguish between the pressure generated by the viscous polymer material when the rotating element is stationary and the normal force generated by the rotation of the rotating element.

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