Thermal cracking carbon black iodine absorption value test method

Abstract

The invention discloses a thermal cracking carbon black iodine absorption value test detection method, and relates to the technical field of material detection. The method comprises the following steps: drying thermal cracking carbon black at 125 DEG C for 1 hour to remove water, weighing 0.5 g of a sample, stirring and adsorbing with 0.04730 mol / L iodine solution at the rotating speed of 10-30 r / min for 10-30 minutes, carrying out centrifugal separation at the rotating speed of 3000-5000 r / min, ensuring that no residual carbon black exists in supernate through light transmittance detection, titrating with 0.03940 mol / L sodium thiosulfate solution, and calculating an iodine absorption value by combining a blank test. The innovation point is an exclusive drying process, dynamic adsorption-centrifugation synergy and a quantitative quality control system. The method has the beneficial effects that the detection period is shortened to be within 1 hour, the measurement error is reduced to + / -1.5%, the problems of insufficient adsorption separation and the like of a conventional method are solved, and the method is suitable for carbon black quality control in the fields of waste tire recovery and the like.

Description

Technical Field

[0001] The present invention relates to the field of material testing technology, and in particular to the field of thermal cracking carbon black recycling and utilization. It specifically provides a test method for the iodine absorption value of thermal cracking carbon black, which is suitable for rapid and accurate detection in quality monitoring of thermal cracking carbon black production lines and recycling scenarios. Background Art

[0002] The iodine adsorption value of carbon black is a core indicator of its specific surface area and is directly related to its reinforcing properties in applications such as rubber and coatings. Thermal carbon black, a byproduct of the pyrolysis of organic matter like scrap tires, possesses complex surface functional groups and highly dispersed particles. Therefore, its iodine adsorption testing requires targeted process optimization.

[0003] The current common carbon black iodine absorption value test standards (such as GB / T 3780.1-2018) are mainly designed for conventional furnace carbon black. When used for thermal cracking carbon black, there are the following technical bottlenecks:

[0004] Insufficient adsorption: The oxygen-containing groups on the surface of thermal cracking carbon black are easily chemically adsorbed with iodine. Conventional stirring speed (<10r / min) and time (<10min) are difficult to break through the mass transfer resistance, resulting in adsorption failure to reach equilibrium, and the error rate can reach more than ±5%;

[0005] Low separation efficiency: When the average particle size of carbon black particles is less than 50nm, conventional centrifugal speed (less than 3000r / min) cannot effectively settle them. The residual carbon black in the supernatant will consume the titrant, resulting in deviation in the calculation of the iodine absorption value.

[0006] Significant moisture interference: Thermal carbon black easily absorbs environmental moisture during production (moisture content can reach 3%-5%). Existing drying conditions (such as 105°C) make it difficult to completely remove bound water, resulting in dilution of the iodine solution and affecting detection accuracy.

[0007] Based on this, a test method for the iodine absorption value of thermal cracking carbon black is now provided, which can eliminate the disadvantages of the existing device. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for testing the iodine absorption value of thermal cracking carbon black, which solves the problem of inconvenience in use in the prior art.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A test method for iodine absorption value of thermal cracking carbon black, step 1: sample pretreatment: drying the thermal cracking carbon black in an oven at 125°C for 1 hour and cooling to room temperature;

[0011] Step 2: Weighing: Weigh 0.5 g of dry sample into a centrifuge bottle, recorded as m, with an accuracy of 0.1 mg;

[0012] Step 3: Adsorption and centrifugation: Add 25 mL of 0.04730 mol / L iodine-potassium iodide solution to the centrifuge bottle, stir for 10-30 minutes at a speed of 10-30 rpm, and then centrifuge at 3000-5000 rpm for 3-5 minutes;

[0013] Step 4: Supernatant treatment: Pour out the supernatant. If there is floating carbon black, repeat centrifugation and pouring until there is no obvious floating carbon black.

[0014] Step 5: Titration: Take 20 mL of the supernatant and titrate with 0.03940 mol / L sodium thiosulfate solution until it turns light yellow. Add 3-5 drops of starch solution and continue titrating until the light purple disappears. Record the volume V1.

[0015] Step 6: Blank test: record the blank titration volume V0;

[0016] Step 7: Data processing: According to the formula Calculate the iodine absorption value, where C is the concentration of the iodine solution.

[0017] On the basis of the above technical solutions, the present invention also provides the following optional technical solutions:

[0018] In an optional solution, the method of cooling to room temperature in step 1 is: placing the dried sample in a desiccator to cool, and the cooling time is ≤30 minutes.

[0019] In an optional solution: in step 3, the stirring speed is 20 r / min, the stirring time is 20 min, the centrifugal speed is 4000 r / min, and the centrifugal time is 4 min.

[0020] In an optional scheme: the "no obvious floating carbon black" in step 4 is judged by the following method: the transmittance of the supernatant is ≥95% (detection wavelength 450nm). If it does not meet the standard, repeat centrifugation (4000r / min, 3min), and the number of repetitions is ≤3 times.

[0021] In one optional solution: the titration endpoint judgment standard in step 5 is: the light purple color disappears and does not recover within 30 seconds, and the titration volume is recorded with an accuracy of 0.01 mL.

[0022] In an optional solution: the calculation result of the formula in step 7 is retained to 4 significant figures, and the error of parallel sample detection is ≤2%.

[0023] In an optional solution, the concentration of the iodine-potassium iodide solution is calibrated with a reference substance, with an error of ≤0.1%; and the sodium thiosulfate solution is prepared as a reference reagent.

[0024] In an optional solution, the thermal cracking carbon black is a by-product of the thermal decomposition of waste tires, and its moisture content is reduced to below 0.3% through a drying process at 125°C.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Improved anti-interference ability: The 125°C drying process reduces the sample moisture content to below 0.3% (compared to the 1.2% moisture content of conventional 105°C drying), eliminating the dilution effect of water on the iodine solution concentration and improving the stability of the test results by 3 times;

[0027] 2. Breakthrough in detection efficiency: The total time for adsorption-centrifugation is controlled within 1 hour (50% shorter than the 2-hour process in GB / T 3780.1). Combined with an automatic titration device, it can realize assembly line detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a comparison diagram of the method of the present invention and the existing method. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0030] Instrument and reagent standardization

[0031]

[0032]

[0033] Refinement of operating procedures

[0034] Sample drying process:

[0035] Preheat the drying oven to 125°C, stabilize for 30 minutes, then place 1.0 g of thermal cracking carbon black in an aluminum weighing bottle (5 cm in diameter, 2 cm in depth) with the bottle cap half open.

[0036] After drying for 1 hour, immediately take out the weighing bottle with tweezers, cover the bottle tightly, move it into a desiccator (filled with color-changing silica gel), and cool it for 30 minutes (control the ambient humidity ≤40% RH).

[0037] Adsorption-centrifugal coordinated control

[0038] Stirring stage: Place the centrifuge bottle in the center of the magnetic stirrer with the magnet size matching the centrifuge bottle (φ5mm×10mm), set the speed to 20r / min, and stir for 20min. During this period, observe the color change of the solution (initial dark red, the color becomes lighter after adsorption);

[0039] Centrifugation stage: Place the centrifuge bottle into the centrifuge within 30 seconds after the stirring is completed, and place a blank centrifuge bottle of equal mass in a symmetrical position. Centrifuge at 4000r / min for 4 minutes. After centrifugation, let it stand for 2 minutes before opening the lid to avoid disturbing the sediment.

[0040] Accurate determination of titration endpoint

[0041] Titration speed control: Initial drop rate is 10 drops / second, slow down to 1 drop / second when approaching light yellow, and add drop by drop until the solution turns straw yellow;

[0042] When to add starch indicator: When the light transmittance of the solution reaches "light yellow" as visually judged (approximately corresponding to the residual volume of 5mL after sodium thiosulfate titration), immediately add 3 drops of starch solution. At this time, the solution should show a stable blue-purple color. Continue titrating until the blue-purple color completely disappears and does not recover within 30 seconds.

[0043] Quality Control System

[0044]

[0045] Comparative Examples and Data Verification

[0046] Example 1: Method of the present invention (optimization parameters)

[0047] Key parameters: drying at 125°C for 1 hour, stirring at 20 r / min for 20 minutes, centrifugation at 4000 r / min for 4 minutes, and light transmittance testing once to meet the standard.

[0048] Test results:

[0049] Sample moisture content: 0.28%

[0050] Iodine absorption value: I1 = 125.6 g / kg, I2 = 126.1 g / kg (error of parallel samples 0.4%)

[0051] Blank titration volume V0 = 22.50 mL, sample titration volume V1 = 15.20 mL

[0052] Total time: 55 minutes

[0053] Measurement error (compared with the standard value): ±1.2% (the standard value is 127.0 g / kg determined by the BET method)

[0054] Example 2: GB / T 3780.1-2018 method (conventional parameters)

[0055] Key parameters: drying at 105°C for 2 hours, stirring at 5 rpm for 40 minutes, centrifugation at 2000 rpm for 10 minutes, transmittance not tested

[0056] Test results:

[0057] Sample moisture content: 1.15%

[0058] Iodine absorption value: I1 = 118.3 g / kg, I2 = 122.7 g / kg (parallel sample error 3.7%)

[0059] Blank titration volume V0 = 22.45 mL, sample titration volume V1 = 16.80 mL

[0060] Total time: 120 minutes

[0061] Measurement error (compared with the standard value): -6.1% (significantly lower due to insufficient adsorption and water dilution of the iodine solution)

[0062] Example 3: Drying temperature comparison test (other parameters are the same);

[0063]

[0064] Example 4: Centrifugal speed comparison test (other parameters are the same)

[0065]

[0066] Data comparison and advantage analysis

[0067] (1) Core indicator comparison table

[0068]

[0069] Advantages Summary

[0070] Efficiency breakthrough: Through high-efficiency drying at 125°C (1 hour vs. traditional 2 hours) and strong centrifugation at 4000 rpm (4 minutes vs. traditional 10 minutes), the detection cycle is shortened to within 1 hour, making it suitable for real-time monitoring of production lines.

[0071] Accuracy Leap:

[0072] Moisture control: drying at 125°C to reduce the moisture content to less than 0.3%, eliminating the iodine solution dilution error (Example 3 demonstrates that the error is reduced from -4.6% to -1.1%);

[0073] Enhanced separation: Centrifugation at 4000 r / min resulted in a sedimentation rate of >99% for particles with a diameter ≥20 nm, a 73% reduction in the amount of carbon black residue in the supernatant (Example 4), and a reduction in titration error.

[0074] Improved stability: Standardized operating procedures (such as transmittance detection and titration endpoint control) reduce the error of parallel samples from 3.7% to 0.4%, meeting the requirements for inter-laboratory data comparison.

[0075] (2) Application scenario adaptability

[0076] Scrap tire recycling companies: can quickly test the quality of thermal black batches and reduce the defective product rate from 8% to below 2%;

[0077] Third-party testing agencies: Under the same equipment conditions, testing efficiency increased by 50%, and the annual testing volume of a single instrument increased from 1,200 batches to 2,400 batches;

[0078] Research Laboratory: Providing accurate surface area evaluation data for thermal carbon black surface modification research, shortening experimental cycles by 30%.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for testing the iodine adsorption value of thermal cracking carbon black, characterized by: The following steps are involved: Step 1: Sample pretreatment: Dry the thermal carbon black in an oven at 125 °C for 1 h and cool to room temperature; Step 2: Weighing: Weigh 0.5 g of dry sample into a centrifuge bottle, recorded as m, with an accuracy of 0.1 mg; Step 3: Adsorption and centrifugation: Add 25 mL of 0.04730 mol / L iodine-potassium iodide solution to the centrifuge bottle, stir for 10-30 minutes at a speed of 10-30 rpm, and then centrifuge at 3000-5000 rpm for 3-5 minutes; Step 4: Supernatant treatment: Pour out the supernatant. If there is floating carbon black, repeat centrifugation and pouring until there is no obvious floating carbon black. Step 5: Titration: Take 20 mL of the supernatant and titrate with 0.03940 mol / L sodium thiosulfate solution until it turns light yellow. Add 3-5 drops of starch solution and continue titrating until the light purple disappears. Record the volume V1. Step 6: Blank test: record the blank titration volume V0; Step 7: Data processing: According to the formula Calculate the iodine absorption value, where C is the concentration of the iodine solution.

2. The method for testing the iodine adsorption value of thermal cracking carbon black according to claim 1, wherein: The method of cooling to room temperature in step 1 is: placing the dried sample in a desiccator to cool, and the cooling time is ≤30min.

3. The method for testing the iodine adsorption value of thermal cracking carbon black according to claim 1, wherein: In step 3, the stirring speed is 20 r / min, the stirring time is 20 min, the centrifugal speed is 4000 r / min, and the centrifugal time is 4 min.

4. The method for testing the iodine adsorption value of thermal cracking carbon black according to claim 1, wherein: The absence of obvious floating carbon black in step 4 is judged by the following method: the transmittance of the supernatant is ≥95% (detection wavelength 450nm). If it does not meet the standard, repeat centrifugation (4000r / min, 3min), and the number of repetitions is ≤3 times.

5. The method for testing the iodine adsorption value of thermal carbon black according to claim 1, wherein: The titration endpoint judgment criteria in step 5 are: the light purple color disappears and does not recover within 30 seconds, and the titration volume is recorded with an accuracy of 0.01 mL.

6. The method for testing the iodine adsorption value of thermal cracking carbon black according to claim 1, wherein: The calculation result of the formula in step 7 is retained to 4 significant figures, and the error of parallel sample detection is ≤2%.

7. The method for testing the iodine adsorption value of thermal carbon black according to claim 1, wherein: The concentration of the iodine-potassium iodide solution is calibrated with a reference substance, with an error of ≤0.1%; the sodium thiosulfate solution is prepared as a reference reagent.

8. The method for testing the iodine adsorption value of thermal carbon black according to claim 1, wherein: The thermal cracking carbon black is a by-product of the thermal decomposition of waste tires, and its moisture content is reduced to below 0.3% through a drying process at 125°C.

Images