Material residence time distribution detection device, extrusion system and detection method

Abstract

The invention relates to a material retention time distribution detection device which comprises an optical instrument, a moving device, a left-right limiting device and an up-down limiting device, the moving path of the moving device is parallel to the discharging direction of an extruder, the optical instrument is connected with the moving device, and a probe of the optical instrument is arranged towards the discharging path of the extruder. The left-right limiting device and the up-down limiting device are arranged on a discharging path of the extruder and used for detecting the tracer agent contained in the extruded material strip; the left-right limiting device and the up-down limiting device are arranged on the discharging path of the extruder; the left-right limiting device can limit left-right movement of the material strip, the up-down limiting device can limit up-down movement of the material strip, it is ensured that when the optical instrument detects the tracer agent contained in the material strip, the material strip and the optical instrument are kept relatively stable, and then accurate detection of the content of the tracer agent in the material strip is achieved; therefore, stay time distribution data with higher accuracy can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of polymer processing, and in particular to a material residence time distribution detection device, an extrusion system and a detection method. Background Art

[0002] Residence time (RT) is one of the key parameters that need to be paid attention to in the processing and molding of polymers in extrusion equipment. RT can reflect the total processing time of the material from entering to leaving the extrusion equipment. However, due to the difference in the speed of different particles, the final result of RT is often expressed in the form of a distribution function, that is, the residence time distribution (RTD). The analysis and study of residence time is of great significance for revealing the extrusion process. The residence time can be used to evaluate the mixing ability of the extrusion equipment and provide a reference for determining the equipment structure (such as screw configuration, etc.) and process parameters (such as screw speed, feed rate and processing temperature, etc.) suitable for special materials.

[0003] In the prior art, a tracer is often added to the material in the extrusion equipment and the extruded material is subjected to tracer detection to indirectly obtain the residence time distribution. However, the tracer content measured by the residence time distribution measurement device known in the prior art is often not very accurate, resulting in inaccurate residence time distribution. At the same time, the aforementioned device has high requirements on application scenarios and detection materials.

[0004] Therefore, there is an urgent need for a more accurate material residence time distribution detection device, extrusion system and detection method. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a material residence time distribution detection device, which limits the material strip by left and right limit devices and upper and lower limit devices, thereby ensuring the stability of the material strip during the measurement process and thereby improving the accuracy of the data measured by the device.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A material residence time distribution detection device comprises: an optical instrument, a motion device, a left and right limit device and an upper and lower limit device, wherein the motion path of the motion device is parallel to the discharge direction of an extruder, the optical instrument is connected to the motion device, the probe of the optical instrument is arranged toward the discharge path of the extruder to detect a tracer contained in the extruded material strip, the left and right limit device and the upper and lower limit device are both arranged on the discharge path of the extruder, the left and right limit device is used to limit the left and right movement of the material strip, and the upper and lower limit device is used to limit the up and down movement of the material strip.

[0008] Preferably, it also includes a resistance detection device, which is connected to the motion device, and the resistance detection device includes a positive plate and a negative plate connected to a power supply, the positive plate and the negative plate are spaced apart, and both the positive plate and the negative plate are in contact with the material strip.

[0009] Preferably, the left and right limiting devices are connected to the moving device.

[0010] Preferably, it further comprises a supporting mechanism, wherein the supporting mechanism is arranged between the moving device and the extruder, and the supporting mechanism comprises material rollers distributed on both sides of the moving path of the material strip, and the material rollers abut against the material strip.

[0011] Preferably, the extrusion speed of the material strip matches the movement speed of the movement device.

[0012] An extrusion system using the material residence time distribution detection device comprises an extruder and the material residence time distribution detection device.

[0013] Preferably, it further comprises a traction device, wherein the traction device is arranged on the discharge path of the extruder, and the traction device is arranged corresponding to the discharge port of the extruder.

[0014] A material residence time distribution detection method, using the material residence time distribution detection device, comprises the following steps:

[0015] Step S1: After the extruder is stably extruding, adding a tracer to the raw material in the extruder;

[0016] Step S2: performing tracer detection on the material strips extruded by the extruder through a signal detector;

[0017] Step S3: Calculate the residence time distribution and the cumulative residence time distribution according to the signal detected by the signal detector.

[0018] Preferably, the step S2 further comprises:

[0019] Step S21: performing color difference detection on the material strips by an optical instrument to obtain an optical analog signal;

[0020] Step S22: Perform resistance detection on the material strip by means of a resistance detection device to obtain an electrical analog signal.

[0021] Preferably, in step S3, the function of the residence time distribution changing with time and the cumulative residence time distribution changing with time is as follows:

[0022] The residence time optical simulation signal distribution density function E(t) is:

[0023]

[0024] The residence time optical simulation signal distribution density function F(t) is:

[0025]

[0026] Where: c(t) represents the blackness of the raw material detected by the optical instrument;

[0027] The time of adding the tracer is recorded as t = 0;

[0028] The distribution density function of the residence time electrical simulation signal E'(t) is:

[0029]

[0030] The cumulative residence time electrical simulation signal distribution function F'(t) is:

[0031]

[0032] Where: R(t) represents the resistance value of the raw material in the detection section of the online detection platform;

[0033] The time when the tracer is added is recorded as t=0.

[0034] Compared with the prior art, the present invention has achieved the following technical effects:

[0035] In the material residence time distribution detection device disclosed in the present application, the left and right limit devices and the upper and lower limit devices are all arranged on the discharge path of the extruder. The left and right limit devices can limit the left and right movement of the material bar, and the upper and lower limit devices can limit the up and down movement of the material bar, thereby ensuring that during the process of the optical instrument detecting the tracer contained in the material bar, the material bar can remain relatively stable with the optical instrument, thereby ensuring the accurate detection of the tracer content in the material bar, and therefore, more accurate residence time distribution data can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0037] Attached Figure 1 A schematic diagram of an embodiment of the present invention;

[0038] Attached Figure 2 This is a schematic diagram of the change of residence time distribution over time in the present invention;

[0039] Attached Figure 3 Schematic diagram of cumulative residence time distribution over time in the present invention

[0040] Among them, 1. optical instrument; 2. motion device; 3. extruder; 4. resistance detection device; 5. supporting mechanism; 6. traction device; 7. computer. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The purpose of the present invention is to provide a material residence time distribution detection device, which limits the material strip by left and right limit devices and upper and lower limit devices, thereby ensuring that the material strip can remain relatively stable with the optical instrument and improving the accuracy of the data measured by the device.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] refer to Figure 1-3 The material residence time distribution detection device disclosed in the embodiment of the present invention comprises: an optical instrument 1, a moving device 2, a left and right limit device and an upper and lower limit device, wherein the movement path of the moving device 2 is parallel to the discharge direction of the extruder 3, the optical instrument 1 is mounted on the moving device 2, and can move synchronously with the moving device 2, the optical probe of the optical instrument 1 faces the discharge path of the extruder 3 to detect the tracer contained in the material strip extruded by the extruder 3, the left and right limit device and the upper and lower limit device are arranged on the discharge path of the extruder 3, the left and right limit device and the upper and lower limit device are arranged at intervals, and the left and right limit device is used to limit the left and right movement of the material strip The upper and lower limit devices are used to limit the up and down movement of the material strip; its working principle is as follows: the extruded material strip is limited by the left and right limit devices and the upper and lower limit devices, ensuring that the material strip can move forward stably in a certain direction. At this time, the motion device 2 drives the optical instrument 1 to move forward synchronously with the material strip, and detects the tracer in the material strip through the light emitted by the optical probe. Under the action of the left and right limit devices and the upper and lower limit devices, the material strip can always remain relatively stable with the optical instrument 1, avoiding the problem that the optical instrument 1 cannot accurately detect the tracer content in the material strip due to the deviation of the material strip, thereby obtaining residence time distribution data with higher accuracy.

[0045] In addition, when the device is performing detection, the optical instrument 1 does not need to come into contact with the material bar or the molten polymer in the extruder throughout the process, and the light emitted by the optical instrument 1 only needs to irradiate the surface of the material bar, ensuring that the detection result will not be affected by factors such as process temperature and material transmittance, making the application scenarios of the device more extensive.

[0046] It can be understood that: under the premise of being able to reciprocate in a direction parallel to the discharging direction, the motion device 2 can be a known structure such as a telescopic cylinder, a cam mechanism, a crank slider structure, a stepping motor, a drag chain structure, etc., and no specific limitation is made here.

[0047] Furthermore, the left and right limit devices and the upper and lower limit devices can both be clamping plate type limit devices or clamping roller type limit devices; the specific clamping plate type limit device includes at least one pair of clamping plates arranged on both sides of the material strip movement path, the material strip passes between the two clamping plates, and the gap between the two clamping plates is greater than or equal to the size of the material strip; the clamping roller type limit device includes at least one group of rotating rollers arranged on both sides of the material strip movement path, the material strip passes between the two rotating rollers, and the gap between the two rotating rollers is greater than or equal to the size of the material strip. More preferably, a driving device is provided at the end of the rotating roller to enable the rotating roller to actively rotate.

[0048] As a preferred embodiment, it also includes a resistance detection device 4, which is connected to the motion device 2 and can move synchronously with the motion device 2. The resistance detection device 4 includes a positive plate and a negative plate connected to a power supply, the positive plate and the negative plate are arranged at intervals, and both the positive plate and the negative plate are in contact with the material strip; those skilled in the art can understand that: the material strip raw material itself is not conductive, but the tracer is conductive, that is, the material strip added with the tracer is conductive, and the conductivity of the material strip is proportional to the content of the tracer, the positive plate, the negative plate, the material strip and the power supply form a closed loop to detect the resistance of the material strip, and then the content of the tracer in the material strip can be obtained, and the combination of resistance detection and optical signal detection is adopted to further improve the accuracy of the detected data.

[0049] Preferably, the resistance detection device 4 also includes a base, which is mounted on the motion device 2, and the positive plate and the negative plate are connected to the base through a telescopic mechanism, so that the positive plate and the negative plate can be extended in a direction close to the material strip or retracted in a direction away from the material strip.

[0050] As a preferred embodiment, the left and right limit devices are arranged between the upper and lower limit devices and the extruder 3. Furthermore, the left and right limit devices are connected to the moving device 2. The left and right limit devices can move synchronously with the moving device 2 together with the optical instrument 1, further ensuring that the detected position of the material strip always remains relatively stable with the probe of the optical instrument 1.

[0051] As a preferred embodiment, it also includes a supporting mechanism 5, which is arranged between the moving device 2 and the extruder 3. The supporting mechanism 5 includes material rollers distributed on both sides of the moving path of the material strip, and the material rollers abut against the material strip, thereby further improving the stability of the material strip during movement.

[0052] Furthermore, the extrusion speed of the material strip and the movement speed of the moving device 2 can be infinitely adjusted; more preferably, the extrusion speed of the material strip matches the movement speed of the moving device 2.

[0053] The present invention further discloses an extrusion system using the material residence time distribution detection device, comprising an extruder 3 and the material residence time distribution detection device.

[0054] Furthermore, the extrusion system also includes a traction device 6, which is arranged on the discharge path of the extruder 3, and the traction device 6 is arranged corresponding to the discharge port of the extruder 3; it can be understood that: the left and right limit devices, the upper and lower limit devices, the supporting mechanism 5 and the moving device 2 are all arranged between the extruder 3 and the traction device 6, and the traction device 6 can be used to guide the material strip to move stably in a certain direction, thereby further improving the stability of the material strip during movement.

[0055] More preferably, the pulling speed of the pulling device 6, the extrusion speed of the material strip and the moving speed of the moving device 2 are kept consistent.

[0056] The present invention also discloses a material residence time distribution detection method, which uses the material residence time distribution detection device or extrusion system, and comprises the following steps:

[0057] First, after waiting for the extruder 3 to be able to stably extrude the material strips, a certain amount of tracer is instantaneously added to the raw material in the extruder 3; then, the material strips extruded by the extruder 3 are subjected to tracer detection through a signal detector; finally, a residence time distribution simulation signal variation curve graph and a cumulative residence time distribution simulation signal variation curve graph are calculated based on the signal detected by the signal detector.

[0058] As a preferred embodiment, the signal detector includes an optical instrument 1 and a resistance detection device 4. The optical instrument 1 performs color difference detection on the material strip to obtain an optical analog signal, and the resistance detection device 4 performs resistance detection on the material strip to obtain an electrical analog signal, and then the optical signal and the electrical signal can be combined to obtain the residence time distribution and the cumulative residence time distribution.

[0059] As a preferred implementation, the function of the residence time distribution changing with time and the cumulative residence time distribution changing with time is as follows:

[0060] Among them, the residence time optical simulation signal distribution density function E(t) is:

[0061]

[0062] The residence time optical simulation signal distribution density function F(t) is:

[0063]

[0064] Where: c(t) represents the blackness of the raw material detected by the optical instrument 1;

[0065] The time of adding the tracer is recorded as t = 0;

[0066] The distribution density function of the residence time electrical simulation signal E,(t) is:

[0067]

[0068] The cumulative residence time electrical simulation signal distribution function F,(t) is:

[0069]

[0070] Where: R(t) represents the resistance value of the raw material in the detection section of the online detection platform;

[0071] The time when the tracer is added is recorded as t=0.

[0072] As a preferred embodiment, the tracer is a lightness tracer or a darkness tracer. After the extruder 3 is stably extruded, a certain amount of lightness tracer or darkness tracer is instantaneously added into the extruder 3, and the optical instrument 1, the resistance detection device 4, the motion device 2 and the traction device 6 are started at the same time. After the material strip is extruded from the discharge port of the extruder 3, it passes through the supporting mechanism 5, the left and right limit devices, the upper and lower limit devices and the traction device 6 in sequence. The optical instrument 1 on the motion device 2 and the resistance detection device 4 are used in combination. At the beginning of a single measurement, the positive plate and the negative plate of the resistance detection device 4 are in contact with the material strip, and the optical instrument 1 starts to detect the color deviation of the raw material. During the test, the traction device 6 moves synchronously with the material strip along the forward direction of the material strip. At this time, the traction rate of the traction device 6 is consistent with the extrusion speed of the material strip and the movement speed of the motion device 2. After a single test is completed, the positive plate and the negative plate of the resistance detection device 4 are separated from the material strip, and the motion device 2 drives the optical instrument 1 and the resistance detection device 4 to quickly return to the test starting point and start the next measurement. This cycle is repeated, and the test results are sampled by the computer 7 and processed by the signal processing unit of the computer 7. The residence time distribution simulation signal changes with time curve is displayed in real time, and finally the cumulative residence time distribution simulation signal changes with time curve can also be displayed.

[0073] Preferably, during a single measurement, the moving device 2 and the material strip remain relatively still for at least 2 seconds.

[0074] Furthermore, the optical instrument 1 and the computer 7, and the resistance detection device 4 and the computer 7 can be connected by Bluetooth signal connection or wire connection.

[0075] Preferably, the optical instrument 1 is a spectrophotometer, and its working principle is the grating spectrophotometer.

[0076] As a preferred embodiment, the light source irradiation mode of the optical instrument 1 is diffuse lighting.

[0077] Preferably, the color difference tracer is a masterbatch or master powder; more preferably, the color difference tracer is a combination of one or more of titanium dioxide, carbon black powder, iron oxide pigment, chrome yellow, cadmium pigment and zinc sulfide, but is not limited thereto.

[0078] As a preferred embodiment, the reflection result of the light irradiated onto the material strip is the reflectivity of the reflected light with a wavelength of 300-800nm.

[0079] More preferably, the content of the color difference tracer is 0.2-5g.

[0080] Furthermore, the length of the residence time not only reflects the mixing effect of the materials, but also indirectly affects the safety of the processing process. When the residence time is too long, although the materials can achieve a better mixing effect, they may also face risks such as over-plasticization and degradation of the materials, which may cause irreversible damage to the processing equipment; on the contrary, if the residence time is too short, the materials cannot be fully plasticized and mixed. Therefore, by studying and controlling the length of the residence time, it is possible to guide the material processing process to obtain better plasticization and mixing effects, and also effectively reduce the potential risks of the materials during the extrusion process, thereby improving the safety of the processing process.

[0081] Specifically, the above method is used to detect the raw materials extruded under different process parameters. After obtaining multiple sets of test data, the performance of the samples obtained under different process parameters is tested, and it can be reversely deduced that the material can obtain better melting and mixing effects within a certain residence time, thereby guiding the extrusion process of the raw material.

[0082] Example 1,

[0083] Polyethylene was fed at a feeding rate of 5 kg / h into a parallel co-rotating twin-screw extruder 3 with a screw speed of 100 rpm, a process temperature of 130-140-150-160-165-170-170-170-170°C (from the die head to the extrusion die), a screw diameter of 21.7 mm, and an aspect ratio of 54:1 to extrude material strips with a diameter of 3 mm. A color difference tracer was used with 0.5 mg of carbon black powder.

[0084] After testing, the average residence time was 185s, the 90% cumulative residence time was 295s, the 95% cumulative residence time was 345s, and the 97% cumulative residence time was 385s.

[0085] Example 2,

[0086] A formula consisting of 12% ethylene-vinyl acetate copolymer (EVA); 35% cellulose butyl acetate (CAB); 40% calcium carbonate (CaCO3); 8% diethyl phthalate (DEP); and 5% water was added at a feeding rate of 0.42 kg / h into a parallel co-rotating twin-screw extruder 3 with a screw speed of 15 rpm, a process temperature of 50-55-60-65-75-85-90-90-90°C (from the die head to the extrusion die), a screw diameter of 21.7 mm, and an aspect ratio of 54:1 to extrude material strips with a diameter of 3 mm. A color difference tracer was used, 0.5 mg of carbon black powder.

[0087] After testing, the average residence time was 1719s, the 90% cumulative residence time was 2427s, the 95% cumulative residence time was 2735, and the 97% cumulative residence time was 2946s.

[0088] Example 3,

[0089] Polyethylene was fed at a feeding rate of 12 kg / h into a parallel counter-rotating twin-screw extruder 3 with a screw speed of 100 rpm, a process temperature of 140-150-160-170-165-160°C (from die head to extrusion die), a screw diameter of 25 mm, and an aspect ratio of 23:1. The extrusion die was a pipe with a diameter of 26 mm, and 2 g of carbon black powder was used as a color difference tracer.

[0090] After testing, the average residence time results were: 90% of the cumulative residence time results were 267s, 95% of the cumulative residence time results were 455s, and 97% of the cumulative residence time results were 497s.

[0091] Example 4,

[0092] A formula consisting of 12% ethylene-vinyl acetate copolymer (EVA); 35% cellulose butyl acetate (CAB); 40% calcium carbonate (CaCO3); 8% diethyl phthalate (DEP); and 5% water is added at a feeding rate of 1.82 kg / h into a parallel counter-rotating twin-screw extruder 3 with a screw speed of 15 rpm, a process temperature of 60-70-75-85-75-70°C (from the die head to the extrusion die), a screw diameter of 25 mm, and an aspect ratio of 23:1. The extrusion die is a pipe with a diameter of 26 mm, and a color difference tracer is 2 g of carbon black powder.

[0093] After testing, the average residence time was 2517s, the 90% cumulative residence time was 3075s, the 95% cumulative residence time was 3317s, and the 97% cumulative residence time was 3439s.

[0094] Adaptive changes made according to actual needs are all within the protection scope of the present invention.

[0095] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the invention. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

Claims

1. A material residence time distribution detection device, characterized in that: include: An optical instrument (1), a motion device (2), a left and right limit device and an upper and lower limit device, wherein the motion path of the motion device (2) is parallel to the discharge direction of the extruder (3), the optical instrument (1) is connected to the motion device (2), the probe of the optical instrument (1) is arranged toward the discharge path of the extruder (3) to detect the tracer contained in the extruded material strip, the left and right limit device and the upper and lower limit device are both arranged on the discharge path of the extruder (3), the left and right limit device is used to limit the left and right movement of the material strip, and the upper and lower limit device is used to limit the up and down movement of the material strip.

2. The material residence time distribution detection device according to claim 1, characterized in that: It also includes a resistance detection device (4), the resistance detection device (4) is connected to the motion device (2), the resistance detection device (4) includes a positive plate and a negative plate connected to a power source, the positive plate and the negative plate are spaced apart, and the positive plate and the negative plate are both in contact with the material strip.

3. The material residence time distribution detection device according to claim 1, characterized in that: The left and right limiting devices are connected to the moving device (2).

4. The material residence time distribution detection device according to claim 1, characterized in that: It also includes a supporting mechanism (5), which is arranged between the moving device (2) and the extruder (3), and the supporting mechanism (5) includes material rollers distributed on both sides of the moving path of the material strip, and the material rollers are in contact with the material strip.

5. The material residence time distribution detection device according to claim 1, characterized in that: The extrusion speed of the material strip matches the movement speed of the movement device (2).

6. An extrusion system using the material residence time distribution detection device according to any one of claims 1 to 5, characterized in that: It comprises an extruder (3) and the material residence time distribution detection device.

7. The extrusion system according to claim 6, characterized in that It also comprises a traction device (6), wherein the traction device (6) is arranged on the discharge path of the extruder (3), and the traction device (6) is arranged corresponding to the discharge port of the extruder (3).

8. A material residence time distribution detection method, using the material residence time distribution detection device according to claim 2, characterized in that: The following steps are involved: Step S1: After the extruder (3) is stably extruding, a tracer is added to the raw material in the extruder (3); Step S2: performing tracer detection on the material strips extruded by the extruder (3) by means of a signal detector; Step S3: Calculate the residence time distribution and the cumulative residence time distribution according to the signal detected by the signal detector.

9. The material residence time distribution detection method according to claim 8, characterized in that: The step S2 further comprises: Step S21: performing color difference detection on the material strips by using an optical instrument (1) to obtain an optical analog signal; Step S22: Perform resistance detection on the material strip by means of a resistance detection device (4) to obtain an electrical analog signal.

10. The material residence time distribution detection method according to claim 9, characterized in that: In step S3, the functions of the residence time distribution changing with time and the cumulative residence time distribution changing with time are as follows: The residence time optical simulation signal distribution density function E(t) is: The residence time optical simulation signal distribution density function F(t) is: Where: c(t) represents the blackness of the raw material detected by the optical instrument (1); The time of adding the tracer is recorded as t = 0; The distribution density function of the residence time electrical simulation signal E'(t) is: The cumulative residence time electrical simulation signal distribution function F'(t) is: Where: R(t) represents the resistance value of the raw material in the detection section of the online detection platform; The time when the tracer is added is recorded as t=0.

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