A device and method for online measurement of polymer melt index

Abstract

The present invention discloses a device and method for online measuring the melt index of a polymer melt; the device comprises a measuring mold, a waveguide rod, an ultrasonic transducer, a pressure sensor and a temperature sensor; the waveguide rods are evenly distributed on both sides of the mold; a temperature sensor / pressure sensor is installed in the middle of the waveguide rod, and the ultrasonic transducer is tightly fitted to the waveguide rod; the present invention uses the device for online measuring the melt index of the polymer melt to measure ultrasonic signals in real time, and a background calculation program calculates changes in physical parameters such as density and flow rate of the polymer melt in the mold flow channel, thereby obtaining the melt index of the polymer melt; the method can realize real-time online monitoring of the melt index of the polymer during the extrusion process, overcomes the shortcomings of low efficiency and feedback lag of traditional offline measurement of the melt index, and provides a simple and fast method for real-time adjustment of extrusion process parameters and monitoring of extruded product quality.

Description

Technical Field

[0001] The present invention relates to the field of testing rheological properties during the extrusion process of polymer materials, and in particular to a device and method for online measuring the melt index of a polymer melt. Background Art

[0002] Melt index is a critical physical property parameter in the polymer extrusion process. It indicates the fluidity of the polymer under certain pressure and temperature. A higher value indicates better fluidity, and vice versa. Rapid and accurate measurement of this parameter is crucial for characterizing the viscosity and flow characteristics of molten polymers, adjusting production processes, monitoring the quality of extruded polymer products, and ultimately improving product quality.

[0003] Existing methods for measuring the melt index of polymer melts primarily rely on melt index meters. However, this offline testing method is time-consuming and labor-intensive, and cannot meet the automation requirements of continuous production and timely feedback control in process industries. It also exhibits significant lags in guiding timely adjustments to polymer processing techniques. Installing existing melt index meters on polymer processing lines still requires offline weighing of the melt mass extruded from the runner over a specific period of time, failing to solve the problem of real-time automated calculation of the melt index of polymer melts and making them unsuitable for processing scenarios requiring rapid, real-time testing. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings and deficiencies of the above-mentioned prior art and to provide an apparatus and method for online measurement of the melt index of a polymer melt. The present invention solves the technical problems of traditional measurement methods, such as the need for offline measurement, cumbersome and time-consuming detection steps, and delayed feedback of detection results.

[0005] The present invention can collect ultrasonic signals online during the continuous processing of polymers to calculate the melt index of the melt, thereby achieving the purpose of real-time optimization and adjustment of processing parameters and improving the quality of polymer material processing products.

[0006] The present invention is achieved through the following technical solutions:

[0007] An apparatus for online measurement of the melt index of a polymer melt, comprising a detection device for detecting the rheological properties of a polymer melt 11 in a flow channel of a mold 12; the detection devices are distributed on both sides of the mold 12;

[0008] The detection device includes a first waveguide rod 1, a second waveguide rod 4, a temperature sensor 3, a third waveguide rod 9, a fourth waveguide rod 6 and a pressure sensor 8; wherein,

[0009] The first waveguide probe 1, the second waveguide probe 4 and the temperature sensor 3 are located on one side of the mold 12, and the connection line of the three is collinear and parallel to the flow direction of the polymer melt 11;

[0010] The third waveguide probe 9 , the fourth waveguide probe 6 and the pressure sensor 8 are located on the other side of the mold 12 , and the connecting line of the three is collinear and parallel to the flow direction of the polymer melt 11 .

[0011] Ends of the first waveguide probe 1 , the second waveguide probe 4 , the third waveguide probe 9 and the fourth waveguide probe 6 extend into the flow channel and are flush with the inner wall of the mold.

[0012] The axes of the first waveguide probe 1 and the third waveguide probe 9 are collinear; the axes of the second waveguide probe 4 and the fourth waveguide probe 6 are collinear.

[0013] The first waveguide rod 1 has a built-in first ultrasonic transducer 2;

[0014] The second waveguide rod 4 is equipped with a second ultrasonic transducer 5;

[0015] The third waveguide rod 9 is equipped with a third ultrasonic transducer 10;

[0016] The fourth waveguide rod 6 is equipped with a fourth ultrasonic transducer 7;

[0017] The second ultrasonic transducer 5 transmits an ultrasonic signal, and the fourth ultrasonic transducer 7 and the third ultrasonic transducer 10 receive the ultrasonic signal.

[0018] The first ultrasonic transducer 2 operates in two modes: reflection and transmission. The second ultrasonic transducer 5 , the third ultrasonic transducer 10 and the fourth ultrasonic transducer 7 operate in a transmission mode.

[0019] The distance between the first waveguide rod 1 and the second waveguide rod 4 is greater than or equal to the maximum diameter of the temperature sensor 3;

[0020] The distance between the third waveguide rod 9 and the fourth waveguide rod 6 is greater than or equal to the maximum diameter of the pressure sensor 8 .

[0021] The inner ends of the first ultrasonic transducer 2 , the second ultrasonic transducer 5 , the third ultrasonic transducer 10 and the fourth ultrasonic transducer 7 are flush with the inner wall surface of the mold 12 .

[0022] A method for online measurement of the melt index of a polymer melt comprises the following steps:

[0023] Step 1: Heat the polymer melt 11 to fill the flow channel of the mold 12, and the temperature sensor 3 and the pressure sensor 8 collect the temperature and pressure of the polymer melt 11 during the extrusion process;

[0024] Step 2: Using a reflection method, measure the reflection coefficient R when the ultrasonic waveguide rod and the melt two-phase interface propagates and the sound velocity C in the polymer melt 11;

[0025] Step 3: The ultrasonic sensor located upstream of the flow channel uses the reflection method to transmit and receive ultrasonic signals, specifically, it uses the ultrasonic transducer located upstream of the flow channel to collect ultrasonic signals in a single-transmit and single-receive manner; according to Calculate the acoustic impedance Z of the polymer melt 11 in the flow channel of the mold 12 melt , substitute Get the density ρ of the polymer melt 11;

[0026] Among them, Z rod is the known acoustic impedance of the waveguide probe, and C is the propagation speed of ultrasonic waves in the melt;

[0027] Step 4: Use the transmission method to make the two ultrasonic transducers on one side of the mold 12 send ultrasonic signals at the same time, and the ultrasonic transducer on the other side of the mold 12 receives the ultrasonic signals from the opposite side, and obtain the upstream ultrasonic signal R1(t) and the downstream ultrasonic signal R2(t) of the flow channel. According to the cross-correlation method, the time displacement of the polymer melt 11 from the upstream position to the downstream position is obtained as t, which is obtained by Thus, the flow velocity v of the polymer melt 11 is obtained, where L is the distance between two adjacent ultrasonic transducers on the same side of the mold 12;

[0028] Step 4: Repeat steps 1 to 3 within 8-10 minutes, and obtain the function of polymer melt density ρ changing with time ρ(t), melt flow rate v changing with time v(t) by numerical fitting method, and calculate The melt index MI of the polymer melt is obtained, where t1-t0=8-10 minutes and S is the cross-sectional area of ​​the mold flow channel.

[0029] Compared with the prior art, the present invention has the following advantages and effects:

[0030] The present invention employs an online device for measuring the melt index of a polymer melt, which is located on both sides of a mold 12. The detection device includes a first waveguide probe 1, a second waveguide probe 4, a temperature sensor 3, a third waveguide probe 9, a fourth waveguide probe 6, and a pressure sensor 8. The first waveguide probe 1, the second waveguide probe 4, and the temperature sensor 3 are located on one side of the mold 12, with the line connecting the three being collinear and parallel to the flow direction of the polymer melt 11. The third waveguide probe 9, the fourth waveguide probe 6, and the pressure sensor 8 are located on the other side of the mold 12, with the line connecting the three being collinear and parallel to the flow direction of the polymer melt 11. Through this arrangement, the present invention can online measure the density and flow rate of the melt flowing in the mold runner, establish a functional relationship between the melt density, the speed of sound, and time, and obtain the melt mass by solving the definite integral of the product of the melt flow rate through the runner interface and the melt density over time within approximately 10 minutes, thereby achieving real-time online calculation of the melt index of the melt without affecting the normal extrusion production of the polymer material.

[0031] The present invention has an ingenious concept and simple and easy technical means. It not only overcomes the limitations of traditional melt index measurement methods, such as offline measurement, time-consuming and labor-intensive measurement process, and untimely feedback of measurement results, but also has many substantial advantages such as saving time, online monitoring, feedback adjustment, and improving production efficiency and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The figure is a schematic structural diagram of the device for online measuring the melt index of a polymer melt according to the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in further detail below with reference to specific embodiments.

[0034] like Figure 1 As shown, the present invention discloses a device for online measuring the melt index of a polymer melt;

[0035] The device includes a detection device for detecting the rheological properties of the polymer melt 11 in the flow channel of the mold 12; the detection device is distributed on both sides of the mold 12;

[0036] The detection device includes a first waveguide rod 1, a second waveguide rod 4, a temperature sensor 3, a third waveguide rod 9, a fourth waveguide rod 6 and a pressure sensor 8; wherein,

[0037] The first waveguide probe 1, the second waveguide probe 4 and the temperature sensor 3 are located on one side of the mold 12, and the connection line of the three is collinear and parallel to the flow direction of the polymer melt 11;

[0038] The third waveguide probe 9 , the fourth waveguide probe 6 and the pressure sensor 8 are located on the other side of the mold 12 , and the connecting line of the three is collinear and parallel to the flow direction of the polymer melt 11 .

[0039] Ends of the first waveguide probe 1 , the second waveguide probe 4 , the third waveguide probe 9 and the fourth waveguide probe 6 extend into the flow channel and are flush with the inner wall of the mold.

[0040] The axes of the first waveguide probe 1 and the third waveguide probe 9 are collinear; the axes of the second waveguide probe 4 and the fourth waveguide probe 6 are collinear.

[0041] The first waveguide rod 1 has a built-in first ultrasonic transducer 2;

[0042] The second waveguide rod 4 is equipped with a second ultrasonic transducer 5;

[0043] The third waveguide rod 9 is equipped with a third ultrasonic transducer 10;

[0044] The fourth waveguide rod 6 is equipped with a fourth ultrasonic transducer 7;

[0045] The second ultrasonic transducer 5 transmits an ultrasonic signal, and the fourth ultrasonic transducer 7 and the third ultrasonic transducer 10 receive the ultrasonic signal.

[0046] The first ultrasonic transducer 2 operates in two modes: reflection and transmission. The second ultrasonic transducer 5 , the third ultrasonic transducer 10 and the fourth ultrasonic transducer 7 operate in a transmission mode.

[0047] The distance between the first waveguide rod 1 and the second waveguide rod 4 is greater than or equal to the maximum diameter of the temperature sensor 3;

[0048] The distance between the third waveguide rod 9 and the fourth waveguide rod 6 is greater than or equal to the maximum diameter of the pressure sensor 8. To avoid interference during installation, the temperature sensor 3 and the pressure sensor 8 are collinear and can be located on either side of the mold 12.

[0049] The inner ends of the first ultrasonic transducer 2 , the second ultrasonic transducer 5 , the third ultrasonic transducer 10 and the fourth ultrasonic transducer 7 are flush with the inner wall surface of the mold 12 .

[0050] The method for detecting the rheological properties of polymer melts of the present invention can be implemented by the following steps:

[0051] Step 1: After the polymer melt 11 is heated and melted, it flows into and fills the flow channel of the mold 12 and is extruded from the outlet to complete the processing and production;

[0052] Step 2: The temperature sensor 3 and the pressure sensor 8 respectively collect the temperature of the polymer melt 11 and the flow channel pressure of the mold 12;

[0053] Step 3: The first ultrasonic transducer 2 uses the reflection method to transmit and receive ultrasonic signals. The sound waves enter the polymer melt 11 along the first waveguide rod 1 and are reflected back from the wall of the mold 12, carrying information about the physical properties of the polymer material. The propagation velocity C of the sound waves in the melt and the density ρ of the melt can be calculated based on the ultrasonic signal echo.

[0054] Step 4: Using the transmission method for measurement; the first ultrasonic transducer 2, the second ultrasonic transducer 5, the third ultrasonic transducer 10 and the fourth ultrasonic transducer 7 work simultaneously;

[0055] Among them, the first ultrasonic transducer 2 and the second ultrasonic transducer 5 send ultrasonic signals at the same time; the third ultrasonic transducer 10 receives the sound wave signal from the first ultrasonic transducer 2, and the fourth ultrasonic transducer 7 receives the sound wave signal from the second ultrasonic transducer 5, and obtains the upstream echo signal R1(t) and the downstream echo signal R2(t); According to the principle of cross-correlation method, the time displacement t of the melt moving from the position below the first waveguide rod 1 to the position below the second waveguide rod 4 can be obtained, and it is obtained by The melt flow rate v can be obtained, where L is the distance between the first ultrasonic transducer 2 and the second ultrasonic transducer 5;

[0056] Step 5: Repeat steps 2, 3, and 4 within 8-10 minutes, measure the melt density ρ and melt flow rate v at different times, use the numerical fitting function to obtain ρ(t) and v(t), and calculate The melt index MI of the polymer melt is obtained, where t1-t0=10 minutes and S is the cross-sectional area of ​​the flow channel in the mold.

[0057] Through the above steps, the melt index MI of the polymer melt at the temperature and pressure within this period of time (about 10 minutes) is finally obtained.

[0058] The waveguide rods of the present invention, i.e., the first waveguide rod 1, the second waveguide rod 4, the third waveguide rod 9 and the fourth waveguide rod 6, can be of any shape. Their function is to isolate the ultrasonic transducer from the high-temperature and high-pressure melt environment, transmit ultrasonic waves, reduce the influence of the near-field area of ​​the acoustic wave, and obtain a stable ultrasonic signal.

[0059] As described above, the present invention can be implemented better.

[0060] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for online measurement of the melt index of a polymer melt, characterized in that This is achieved by using a device for online measurement of the melt index of the polymer melt; The device for online measuring the melt index of a polymer melt comprises a detection device for detecting the rheological properties of the polymer melt (11) in the flow channel of a mold (12); the detection device is distributed on both sides of the mold (12); and is characterized in that: The detection device comprises a first waveguide rod (1), a second waveguide rod (4), a temperature sensor (3), a third waveguide rod (9), a fourth waveguide rod (6) and a pressure sensor (8); wherein, The first waveguide rod (1), the temperature sensor (3) and the second waveguide rod (4) are sequentially located on one side of the mold (12), and the connection lines of the three are collinear and parallel to the flow direction of the polymer melt (11); The third waveguide rod (9), the pressure sensor (8) and the fourth waveguide rod (6) are sequentially located on the other side of the mold (12), and the lines connecting the three are collinear and parallel to the flow direction of the polymer melt (11); The first waveguide rod (1) has a built-in first ultrasonic transducer (2); The second waveguide rod (4) is equipped with a second ultrasonic transducer (5); The third waveguide rod (9) is equipped with a third ultrasonic transducer (10); The fourth waveguide rod (6) is equipped with a fourth ultrasonic transducer (7); The second ultrasonic transducer (5) transmits an ultrasonic signal, and the fourth ultrasonic transducer (7) and the third ultrasonic transducer (10) receive the ultrasonic signal; The first ultrasonic transducer (2) operates in two modes: reflection and transmission; the second ultrasonic transducer (5), the third ultrasonic transducer (10), and the fourth ultrasonic transducer (7) operate in a transmission mode; The implementation steps are as follows: Step 1: heating the polymer melt (11) so that it fills the flow channel of the mold (12), and the temperature sensor (3) and the pressure sensor (8) collect the temperature and pressure of the polymer melt (11) during the extrusion process; Step 2: Using the reflection method, measure the reflection coefficient R of the ultrasonic wave when it propagates at the interface between the waveguide rod and the melt and the sound velocity C in the polymer melt (11); Step 3: The first ultrasonic transducer (2) located upstream of the flow channel uses a reflection method to transmit and receive ultrasonic signals; Calculate the acoustic impedance Z of the polymer melt (11) in the flow channel of the mold (12) melt , substitute The density ρ of the polymer melt (11) is obtained; Among them, Z rod is the known acoustic impedance of the waveguide probe, and C is the propagation speed of ultrasonic waves in the melt; Step 4: Using the transmission method, the first ultrasonic transducer (2) and the second ultrasonic transducer (5) on one side of the mold (12) simultaneously transmit ultrasonic signals, the third ultrasonic transducer 10 on the other side of the mold (12) receives the acoustic wave signal from the first ultrasonic transducer (2) on the opposite side, and the fourth ultrasonic transducer 7 receives the acoustic wave signal from the second ultrasonic transducer (5), and obtains the upstream ultrasonic signal R1(t) and the downstream ultrasonic signal R2(t) of the flow channel. According to the cross-correlation method, the time t for the polymer melt (11) to move from the upstream position to the downstream position is obtained, and is obtained by Thus, the flow rate v of the polymer melt (11) is obtained, where L is the distance between the adjacent first ultrasonic transducer (2) and the second ultrasonic transducer (5) on the same side of the mold (12); Step 5: Repeat steps 2 to 4 within 8-10 minutes, and obtain the function of polymer melt density ρ changing with time ρ(t), and the function of melt flow rate v changing with time v(t) by numerical fitting method, and calculate The melt index MI of the polymer melt is obtained, where t1-t0=8-10 minutes and S is the cross-sectional area of ​​the mold flow channel.

2. The method for online measurement of polymer melt index according to claim 1, characterized in that: The ends of the first waveguide rod (1), the second waveguide rod (4), the third waveguide rod (9) and the fourth waveguide rod (6) extend into the flow channel and are flush with the inner wall surface of the mold (12).

3. The method for online measurement of polymer melt index according to claim 1, characterized in that: The axes of the first waveguide rod (1) and the third waveguide rod (9) are collinear; the axes of the second waveguide rod (4) and the fourth waveguide rod (6) are collinear.

4. The method for online measurement of polymer melt index according to claim 1, characterized in that: The distance between the first waveguide rod (1) and the second waveguide rod (4) is greater than or equal to the maximum diameter of the temperature sensor (3); The distance between the third waveguide rod (9) and the fourth waveguide rod (6) is greater than or equal to the maximum diameter of the pressure sensor (8).

5. The method for online measurement of polymer melt index according to claim 1, characterized in that: The inner ends of the first ultrasonic transducer (2), the second ultrasonic transducer (5), the third ultrasonic transducer (10) and the fourth ultrasonic transducer (7) are flush with the inner wall surface of the mold (12).

Images