Method for testing CTAB (cetyltrimethyl ammonium bromide) specific surface area of carbon black

Abstract

The invention provides a method for testing the CTAB (Cetyltrimethyl Ammonium Bromide) specific surface area of carbon black. The testing method comprises the following steps: sequentially carrying out first mixing and solid-liquid separation on a carbon black sample and a hexadecyl trimethyl ammonium bromide solution to obtain a first mixture; titrating unadsorbed cetyltrimethylammonium bromide in the first mixture by adopting a sodium sulfosuccinate dioctyl ester solution until the end point, and recording the consumed volume of the cetyltrimethylammonium bromide; the solid-liquid separation comprises centrifugation and multi-stage filtration; establishing a calculation formula S =-S0 * (V0-V) / (b * m) of the CTAB specific surface area of the carbon black sample; and carrying out the above steps on a carbon black to-be-tested product with unknown CTAB specific surface area to obtain a volume test value of the dioctyl sodium sulfosuccinate corresponding to the carbon black to-be-tested product, and substituting the volume test value and the mass into a calculation formula for calculation to obtain the CTAB specific surface area of the carbon black to-be-tested product. The testing method is safe, reliable and easy to operate, and meanwhile the testing result is high in accuracy and good in repeatability.

Description

Technical Field

[0001] This invention relates to the field of rubber technology, and more specifically, to a method for testing the CTAB specific surface area of ​​carbon black. Background Technology

[0002] Carbon black is a commonly used reinforcing and coloring agent for tires, and the characterization of carbon black raw materials and recycled carbon black is of great significance. The reinforcing effect of carbon black on rubber is usually considered in terms of the accessibility of rubber molecules to the surface of carbon black aggregates. Accessibility is mainly affected by two factors: firstly, carbon black aggregates contain small micropores into which rubber molecular chains cannot enter; secondly, the surface of carbon black aggregates is rough, preventing larger rubber molecular chains from contacting the concave surfaces of the rough surface. Therefore, the pores within the carbon black aggregates and the concave surfaces of the rough surface cannot provide reinforcement. Thus, using the adsorption surface area of ​​hexadecyltrimethylammonium bromide (CTAB) can characterize the smooth surface area of ​​carbon black, thereby more effectively reflecting its reinforcing properties.

[0003] The principle of the CTAB method for testing the smooth specific surface area of ​​carbon black is as follows: Because CTAB molecules are quite large, they cannot adsorb onto the microporous surface of carbon black. Therefore, the CTAB specific surface area reflects the effective contact area between carbon black and rubber molecules. The isothermal adsorption curve of carbon black in CTAB aqueous solution has a relatively long, flat segment of a monomolecular adsorption layer. The adsorption of CTAB by carbon black is not affected by tar-like substances or functional groups containing hydrogen or oxygen on its surface. Mechanical stirring or ultrasonic vibration can quickly bring adsorption to equilibrium. After filtering out the dispersed colloidal carbon black, the amount of unadsorbed CTAB is titrated with sodium dioctyl sulfosuccinate (OT). The experimental results are used to determine the CTAB specific surface area based on industrial coloring reference carbon black ITRB or industrial reference carbon black (IRC4#).

[0004] However, current methods for testing the CTAB specific surface area of ​​carbon black suffer from problems such as poor repeatability of test results, difficulty in separating carbon black from CTAB solution, and the need to add formaldehyde solution to prepare OT standard solution, which may cause harm to the environment and personnel. Therefore, there is an urgent need to develop a new method for testing the CTAB specific surface area of ​​carbon black. Summary of the Invention

[0005] The main objective of this invention is to provide a method for testing the CTAB specific surface area of ​​carbon black, in order to solve the problems in the existing methods for testing the CTAB specific surface area of ​​carbon black, such as the difficulty in separating carbon black from CTAB solution, resulting in poor repeatability of test results and the fact that OT standard solution is not environmentally friendly.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for testing the CTAB specific surface area of ​​carbon black is provided. The method includes: Step S1, sequentially mixing and separating a carbon black sample and a hexadecyltrimethylammonium bromide solution to obtain a first mixture; titrating the unadsorbed hexadecyltrimethylammonium bromide in the first mixture with a sodium dioctyl sulfosuccinate solution until the endpoint, and recording the volume of sodium dioctyl sulfosuccinate solution consumed; the solid-liquid separation includes sequential centrifugation and filtration, wherein the filtration is multi-stage filtration; the sodium dioctyl sulfosuccinate solution is sodium dioctyl sulfosuccinate and water; Step S2, when the carbon black sample consists of n industrial reference carbon blacks of different masses with known CTAB specific surface areas, after Step S1, the volume test value of the corresponding sodium dioctyl sulfosuccinate solution for each industrial reference carbon black is obtained, with the mass of the industrial reference carbon black as the abscissa and the volume of the sodium dioctyl sulfosuccinate solution as the ordinate. The volume test value of sodium dioctyl sulfosuccinate solution is used as the ordinate to plot a calibration curve, and a linear regression equation is obtained, which is y=bx+V0; where n≥3; Step S3, the calculation formula for the CTAB specific surface area of ​​the carbon black sample is established as S=-S0×(V0-V) / (b×m); where S0 is the standard value of the CTAB specific surface area of ​​industrial reference carbon black, V0 is the ordinate of the calibration curve, b is the slope of the calibration curve, V is the volume of sodium dioctyl sulfosuccinate consumed for the carbon black sample, and m is the mass of the carbon black sample; Step S4, when the carbon black sample is a carbon black test sample with an unknown CTAB specific surface area, the carbon black test sample has undergone step S1 to obtain the volume test value of sodium dioctyl sulfosuccinate corresponding to the carbon black test sample. The volume test value of sodium dioctyl sulfosuccinate and the mass of the carbon black test sample are substituted into the calculation formula in step S3 to calculate the CTAB specific surface area of ​​the carbon black test sample.

[0007] Further, in step S1 above, the carbon black sample is a dried carbon black sample; the drying temperature is 125℃, and the drying time is 1~3h; the mass ratio of the dried carbon black sample to the volume of the hexadecyltrimethylammonium bromide solution is 0.01g / mL; and / or, the molar concentration of the hexadecyltrimethylammonium bromide solution is 0.01mol / L; and / or, the molar concentration of the sodium dioctyl sulfosuccinate solution is 0.0022mol / L.

[0008] Further, in step S1 above, the first mixing method is shaking; the first mixing time is 30~45 min, and the shaking frequency is 200~300 r / min; and / or, step S1 further includes: adding a titration auxiliary solution and water to the first mixture and then performing titration; wherein, the volume ratio of the first mixture, the titration auxiliary solution and water is 5:15:15~40; the titration auxiliary solution is an octylphenyl polyoxyethylene ether solution; and / or, using a turbidimeter to monitor the endpoint time and record the volume of sodium dioctyl sulfosuccinate solution consumed.

[0009] Furthermore, in step S1 above, the centrifugation time is 20~60 min, and the centrifugation speed is 4000~9000 r / min.

[0010] Furthermore, filtration is performed using a filter membrane, and as the number of filtration stages increases sequentially, the pore size of the filter membrane decreases accordingly; and / or, the pore size of the filter membrane is 0.05~0.25μm; the filtration pressure is 0.1~0.5MPa.

[0011] Furthermore, the multi-stage filtration includes a first-stage filtration, a second-stage filtration, and a third-stage filtration performed sequentially; wherein, the first-stage filtration is performed using a filter membrane with a pore size of 0.22~0.25μm; the second-stage filtration is performed using a filter membrane with a pore size of 0.1~0.15μm; and the third-stage filtration is performed using a filter membrane with a pore size of 0.05~0.08μm.

[0012] Furthermore, in step S2 above, the mass of the industrial reference carbon black is 0.1~1.5g; and / or, n is 3~8.

[0013] Furthermore, in step S3 above, the industrial reference carbon black is of type ITRB and / or IRC4#; when the industrial reference carbon black is of type ITRB, S0 is 83.0 × 10⁻⁶. 3 m 2 / kg; when the industrial reference carbon black is IRC4#, S0 is 78.5×10 3 m 2 / kg; and / or, V0 is 22.102~22.502, b is -15.050~-15.554.

[0014] Further, in step S4 above, the grade of the carbon black sample to be tested is selected from any one or more of the N100 series, N200 series, N300 series, N500 series, N600 series, and N700 series; the NSA specific surface area of ​​the carbon black sample to be tested is 20 × 10⁻⁶. 3 ~151×10 3 m 2 / kg, the mass of the carbon black sample to be tested is 0.28~1.37g.

[0015] Furthermore, when the carbon black sample to be tested is of the N100 series, and the NSA specific surface area of ​​the N100 series is 125×10⁻⁶, 3 ~151×10 3 m 2 When the carbon black sample is 0.28~0.32g, the mass of the sample is 0.28~0.32g; and / or, when the grade of the carbon black sample is N200 series, and the NSA specific surface area of ​​N200 series is 97×10⁻⁶. 3 ~129×10 3 m 2 When the carbon black sample is 0.33~0.37 g / kg, the mass of the carbon black sample to be tested is 0.33~0.37 g; and / or, when the grade of the carbon black sample to be tested is N300 series, and the NSA specific surface area of ​​N300 series is 75×10⁻⁶. 3 ~103×10 3 m 2 When the carbon black sample is 0.38~0.42 g / kg, the mass of the carbon black sample is 0.38~0.42 g; and / or, when the grade of the carbon black sample is N500 series or N600 series, and the NSA specific surface area of ​​N500 series and N600 series is independently 27×10⁻⁶ g / kg. 3 ~45×10 3 m 2 When the carbon black sample is 0.88~0.92g, the mass of the sample is 0.88~0.92g; and / or, when the grade of the carbon black sample is N700 series, and the NSA specific surface area of ​​N700 series is 20×10⁻⁶. 3 ~39×10 3 m 2 When the carbon black sample is 1.33~1.37g, the mass of the sample is 1.33~1.37g.

[0016] The technical solution of this invention utilizes carbon black nanoparticles with small particle sizes. Especially after stirring, ultrasonicating, or vibrating, the carbon black disperses into even smaller aggregates. Currently, most methods use 0.15 μm filter membranes for solid-liquid separation of carbon black and hexadecyltrimethylammonium bromide (CTAB). The pore size of the filter membrane is larger than the diameter of some carbon black particles, making complete separation of the carbon black suspension impossible. Furthermore, only one pressure filtration makes the filtrate difficult to clarify, resulting in poor accuracy of the CTAB specific surface area test results for carbon black. This application, however, employs a centrifugation + multi-stage filtration model after the initial mixing of the carbon black sample and the CTAB solution. Centrifugation filters out large carbon black particles, and multi-stage filtration filters carbon black of different particle sizes step by step, thereby improving the separation effect between carbon black particles and the CTAB solution, achieving complete separation, and solving the problem of easy permeation of carbon black. This improves the accuracy and repeatability of the CTAB surface area detection for carbon black. Furthermore, the sodium dioctyl sulfosuccinate (OT) solution of this application is formaldehyde-free, improving the safety and environmental friendliness of the test. Specifically, in step S2, this application obtains the corresponding volumes of OT solution consumed by n industrial reference carbon black samples of different masses through step S1, thereby establishing a linear regression equation between the mass of the industrial reference carbon black and the volume of OT consumed. This allows the determination of V0 and b in the formula for calculating the CTAB specific surface area of ​​carbon black in step S3. Substituting the corresponding OT volume V obtained from step S1 for a carbon black sample of mass m into the formula in step S3 yields its corresponding CTAB specific surface area. In summary, the test method for the CTAB specific surface area of ​​carbon black of this application is safe, reliable, easy to operate, and yields highly accurate and repeatable test results. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0018] As analyzed in the background section of this application, the existing methods for testing the CTAB specific surface area of ​​carbon black have problems such as the difficulty in separating carbon black from CTAB solution, resulting in poor repeatability of test results and the environmental unfriendliness of OT standard solution. In order to solve the above problems, this application provides a method for testing the CTAB specific surface area of ​​carbon black.

[0019] In a typical embodiment of this application, a method for testing the CTAB specific surface area of ​​carbon black is provided. The method includes: Step S1, sequentially mixing and separating a carbon black sample and a hexadecyltrimethylammonium bromide solution to obtain a first mixture; titrating the unadsorbed hexadecyltrimethylammonium bromide in the first mixture with a sodium dioctyl sulfosuccinate solution until the endpoint, and recording the volume of sodium dioctyl sulfosuccinate solution consumed; the solid-liquid separation includes sequential centrifugation and filtration, with multi-stage filtration; the sodium dioctyl sulfosuccinate solution is sodium dioctyl sulfosuccinate and water; Step S2, when the carbon black sample consists of n industrial reference carbon blacks of different masses with known CTAB specific surface areas, after Step S1, the volume test value of the corresponding sodium dioctyl sulfosuccinate solution for each industrial reference carbon black is obtained, with the mass of the industrial reference carbon black as the x-axis and the volume of sodium dioctyl sulfosuccinate as the y-axis. The volume test value of the octyl ester solution is used as the ordinate to plot the calibration curve and obtain the linear regression equation, which is y=bx+V0; where n≥3; Step S3, the calculation formula for the CTAB specific surface area of ​​the carbon black sample is established as S=-S0×(V0-V) / (b×m); where S0 is the standard value of the CTAB specific surface area of ​​industrial reference carbon black, V0 is the ordinate of the calibration curve, b is the slope of the calibration curve, V is the volume of sodium dioctyl sulfosuccinate consumed for the carbon black sample, and m is the mass of the carbon black sample; Step S4, when the carbon black sample is a carbon black test sample with an unknown CTAB specific surface area, the carbon black test sample has undergone step S1 to obtain the volume test value of sodium dioctyl sulfosuccinate corresponding to the carbon black test sample. The volume test value of sodium dioctyl sulfosuccinate and the mass of the carbon black test sample are substituted into the calculation formula in step S3 to calculate the CTAB specific surface area of ​​the carbon black test sample.

[0020] Carbon black consists of nanoparticles with small particle sizes. Especially after stirring, sonicating, or vibrating, carbon black disperses into even smaller aggregates. Currently, most methods use 0.15 μm filter membranes for solid-liquid separation of carbon black and hexadecyltrimethylammonium bromide (CTAB). The pore size of these membranes is larger than the diameter of some carbon black particles, making complete separation of the carbon black suspension impossible. Furthermore, only one pressure filtration makes the filtrate difficult to clarify, resulting in poor accuracy of the CTAB specific surface area test results for carbon black. This application addresses this issue by employing a centrifugation + multi-stage filtration approach after the initial mixing of the carbon black sample and the CTAB solution. Centrifugation filters out large carbon black particles, and multi-stage filtration filters out carbon black particles of different sizes, thereby improving the separation effect between carbon black particles and the CTAB solution, achieving complete separation, and solving the problem of easy permeation of carbon black. This improves the accuracy and repeatability of the CTAB surface area detection for carbon black. Furthermore, the sodium dioctyl sulfosuccinate (OT) solution of this application is formaldehyde-free, improving the safety and environmental friendliness of the test. Specifically, in step S2, this application obtains the corresponding volumes of OT solution consumed by n industrial reference carbon black samples of different masses through step S1, thereby establishing a linear regression equation between the mass of the industrial reference carbon black and the volume of OT consumed. This allows the determination of V0 and b in the formula for calculating the CTAB specific surface area of ​​carbon black in step S3. Substituting the corresponding OT volume V obtained from step S1 for a carbon black sample of mass m into the formula in step S3 yields its corresponding CTAB specific surface area. In summary, the test method for the CTAB specific surface area of ​​carbon black of this application is safe, reliable, easy to operate, and yields highly accurate and repeatable test results.

[0021] In one embodiment of this application, in step S1, the carbon black sample is a dried carbon black sample; the drying temperature is 125°C, and the drying time is 1~3h; the mass ratio of the dried carbon black sample to the volume ratio of the hexadecyltrimethylammonium bromide solution is 0.01g / mL; the molar concentration of the hexadecyltrimethylammonium bromide solution is 0.01mol / L; and / or, the molar concentration of the sodium dioctyl sulfosuccinate solution is 0.0022mol / L.

[0022] It is preferable to dry the carbon black sample to constant weight, controlling the drying temperature and time within the aforementioned range. This helps remove moisture from the carbon black sample, thereby improving the accuracy of the detection results. It is also preferable to control the ratio of the mass of the dried carbon black sample to the volume of the hexadecyltrimethylammonium bromide solution, as well as the molar concentration of the hexadecyltrimethylammonium bromide solution, within the aforementioned range. This helps CTAB to be fully adsorbed onto the surface of the carbon black, thereby improving the accuracy of subsequent titration results. Furthermore, it is preferable to control the molar concentration of the sodium dioctyl sulfosuccinate solution within the aforementioned range. This helps in titrating the amount of unadsorbed CTAB, thereby improving the accuracy and efficiency of the titration.

[0023] In one embodiment of this application, in step S1 above, the first mixing method is shaking; the first mixing time is 30~45min, and the shaking frequency is 200~300r / min; step S1 above further includes: adding titration auxiliary solution and water to the first mixture and then performing titration; wherein, the volume ratio of the first mixture, titration auxiliary solution and water is 5:15:15~40; the titration auxiliary solution is octylphenyl polyoxyethylene ether solution (OP solution); and / or, using a turbidimeter to monitor the endpoint time and record the volume of sodium dioctyl sulfosuccinate solution consumed.

[0024] Preferably, the mixing method, time, and oscillation frequency are within the above range, which helps to disperse carbon black aggregates and allow CTAB to be fully adsorbed on the surface of carbon black, thereby improving the accuracy of measuring the CTAB specific surface area of ​​carbon black.

[0025] Adding the aforementioned titration aid solution to the first mixture is preferred. This helps promote the dissolution of the carbon black sample and hexadecyltrimethylammonium bromide solution in water. Controlling the volume ratio of the first mixture, titration aid solution, and water within the aforementioned range helps promote the complete dissolution of the carbon black sample and hexadecyltrimethylammonium bromide solution, and facilitates mechanical stirring of the instrument below the liquid surface, thereby ensuring thorough stirring. Using a turbidimeter to monitor the endpoint is preferred. This helps to monitor changes in the solution's turbidity in real time, thus enabling immediate identification of changes in solution properties during titration. In particular, when residual carbon black particles or complexes in the solution begin to decrease or disappear, the turbidity value will change significantly. Using a turbidimeter helps reduce errors introduced by subjective visual judgment, thereby improving the accuracy of endpoint determination and the overall accuracy of the test.

[0026] In one embodiment of this application, in step S1, the centrifugation time is 20-60 min and the centrifugation speed is 4000-9000 r / min.

[0027] Since carbon black consists of nanoparticles, with the primary particle size of commonly used carbon black being tens of nanometers, although the number of primary particles generated after shaking is small and most are aggregates, some small-diameter particles will still pass through even when using a 0.15μm filter membrane directly, thus affecting the test results. Therefore, this application first centrifuges the carbon black particles to help separate the larger particles, which is beneficial for subsequent multi-stage filtration and improves the solid-liquid separation effect. If the centrifugation speed is too high, it may cause mechanical damage to the carbon black particles, affecting the accuracy of the specific surface area measurement results; if the centrifugation speed is too low, the large carbon black particles cannot be effectively separated from the CTAB solution. Therefore, it is preferable that the centrifugation time and speed are within the above range to help separate the large carbon black particles from the CTAB solution first, thereby improving the accuracy and repeatability of the test results.

[0028] In one embodiment of this application, a filter membrane is used for filtration. As the number of filtration stages increases sequentially, the pore size of the filter membrane decreases accordingly; and / or, the pore size of the filter membrane is 0.05~0.25μm; the pressure of multi-stage filtration is 0.1~0.5MPa.

[0029] Traditional high-pressure, single-pore membrane filtration can lead to problems such as carbon black nanoparticle permeation and incomplete separation. This application preferably employs multi-stage filtration, where the pore size of the membrane decreases progressively with each filtration stage. Controlling the pore size within the aforementioned range helps to gradually filter out fine carbon black particles, reducing the probability of permeation and achieving thorough separation of carbon black and CTAB solution. Existing methods typically use filtration pressures of 0.4–0.7 MPa, while the preferred multi-stage filtration pressure falls within this range, helping to reduce the probability of permeation during filtration. In summary, the multi-stage filtration method employed in this application facilitates effective separation of carbon black and unadsorbed CTAB solution, thereby significantly improving the accuracy of the detection results.

[0030] In one embodiment of this application, the multi-stage filtration includes a first-stage filtration, a second-stage filtration, and a third-stage filtration performed sequentially; wherein, the first-stage filtration is performed using a filter membrane with a pore size of 0.22~0.25μm; the second-stage filtration is performed using a filter membrane with a pore size of 0.1~0.15μm; and the third-stage filtration is performed using a filter membrane with a pore size of 0.05~0.08μm.

[0031] Optimizing the pore size of each stage of the multi-stage filtration within the above-mentioned range helps to separate carbon black particles of different sizes, thereby further improving the separation effect of carbon black particles and CTAB solution.

[0032] Preferably, the pore size of the filter membrane in the second stage of filtration is 0.07~0.15μm smaller than that in the first stage of filtration, and the pore size of the filter membrane in the third stage of filtration is 0.02~0.1μm smaller than that in the second stage of filtration. This helps to further improve the separation effect of carbon black particles and CTAB solution, thereby further improving the accuracy and repeatability of CTAB specific surface area testing.

[0033] In one embodiment of this application, in step S2, the mass of industrial reference carbon black is 0.1~1.5g; and / or, n is 5~8.

[0034] Optimizing the number of carbon black samples n of different qualities and the quality of industrial reference carbon black within the above range helps to construct a more reliable standard curve, thereby obtaining a more accurate linear regression equation.

[0035] In one embodiment of this application, in step S3, the industrial reference carbon black is of type ITRB and / or IRC4#; when the industrial reference carbon black is of type ITRB, S0 is 83.0 × 10⁻⁶. 3 m 2 / kg; when the industrial reference carbon black is IRC4#, S0 is 78.5×10 3 m 2 / kg; and / or, V0 is 22.102~22.502, b is -15.050~-15.554.

[0036] The selection of the above-mentioned industrial reference carbon black, based on its known CTAB specific surface area, standard use in the rubber industry, and wide application, helps to construct a more accurate and reliable formula for calculating the CTAB specific surface area of ​​carbon black.

[0037] In one embodiment of this application, in step S4 above, the grade of the carbon black sample to be tested is selected from any one or more of the N100 series, N200 series, N300 series, N500 series, N600 series, and N700 series; the NSA specific surface area of ​​the carbon black sample to be tested is 20×10³~151×10³. 3 m 2 / kg, the mass of the carbon black sample to be tested is 0.28~1.37g.

[0038] The CTAB specific surface area of ​​all the carbon black samples mentioned above can be obtained using the testing method of this application with high accuracy. The principle for weighing samples according to the type of carbon black is that the larger the specific surface area, the smaller the sample weight. Currently, for known carbon black series, most schemes determine the sample weight based on the CTAB specific surface area. For unknown carbon black types, the sample weight is determined using nitrogen adsorption specific surface area or iodine adsorption value, which introduces certain errors. This application determines the mass based on the NSA specific surface area of ​​the carbon black sample, which helps to quickly and initially obtain its NSA specific surface area. The mass of the carbon black sample in this application's test can then be adjusted accordingly, thereby improving the efficiency of the CTAB specific surface area test.

[0039] In one embodiment of this application, when the carbon black sample to be tested is of the N100 series, and the NSA specific surface area of ​​the N100 series is 125 × 10⁻⁶, 3 ~151×10 3 m 2 When the carbon black sample is 0.28~0.32g, the mass of the sample is 0.28~0.32g; and / or, when the grade of the carbon black sample is N200 series, and the NSA specific surface area of ​​N200 series is 97×10⁻⁶. 3 ~129×10 3 m 2When the carbon black sample is 0.33~0.37 g / kg, the mass of the carbon black sample to be tested is 0.33~0.37 g; and / or, when the grade of the carbon black sample to be tested is N300 series, and the NSA specific surface area of ​​N300 series is 75×10⁻⁶. 3 ~103×10 3 m 2 When the carbon black sample is 0.38~0.42 g / kg, the mass of the carbon black sample is 0.38~0.42 g; and / or, when the grade of the carbon black sample is N500 series or N600 series, and the NSA specific surface area of ​​N500 series and N600 series is independently 27×10⁻⁶ g / kg. 3 ~45×10 3 m 2 When the carbon black sample is 0.88~0.92g, the mass of the sample is 0.88~0.92g; and / or, when the grade of the carbon black sample is N700 series, and the NSA specific surface area of ​​N700 series is 20×10⁻⁶. 3 ~39×10 3 m 2 When the carbon black sample is 1.33~1.37g, the mass of the sample is 1.33~1.37g.

[0040] Based on their NSA specific surface area, the carbon black samples from the different series mentioned above are preferably within the above-mentioned range. Following the principle that the larger the specific surface area, the smaller the sample weight, it helps CTAB to be fully adsorbed on the surface of the carbon black, thereby improving the accuracy of the CTAB specific surface area of ​​the carbon black.

[0041] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0042] Example 1

[0043] Preparation: Prepare a pH 7 buffer solution by dissolving 2.722 g of potassium dihydrogen phosphate, 4.260 g of disodium hydrogen phosphate, and 1.169 g of sodium chloride in a 1 dm³ solution. 3 A buffer solution was obtained by mixing water. A 0.01 mol / L solution of hexadecyltrimethylammonium bromide (CTAB) and a 0.0022 mol / L solution of sodium dioctyl sulfosuccinate (OT) were prepared. The OT solution was obtained by mixing OT and water. After the OT solution was prepared, it was magnetically stirred for 48 hours, and after being tightly sealed, it was placed in a cool and dry place for 12 days before use.

[0044] Step S1: First, the carbon black sample is dried in an oven at 125℃ for 1 hour. A mass m of the dried carbon black sample is added to 30 mL of CTAB solution for a first mixing process of 40 min using shaking at a frequency of 240 r / min. After shaking, the sample undergoes solid-liquid separation. Specifically, it is centrifuged for 30 min at a speed of 4000 r / min. Then, multi-stage filtration is performed: the supernatant after centrifugation is first filtered through a 0.22 μm pore size filter membrane at a pressure of 0.1–0.5 MPa; the filtrate is then filtered through a 0.1 μm pore size filter membrane at a pressure of 0.1–0.5 MPa; and finally, the filtrate is filtered through a 0.05 μm pore size filter membrane at atmospheric pressure. The resulting first mixture is in a clear state. Transfer 5 mL of the first mixture to a clean, transparent plastic cup, add 15 mL of titration aid solution OP, then add 40 mL of pure water, and titrate using OT solution. Record the volume V of OT solution consumed when the endpoint is reached.

[0045] In step S2, the five masses m are successively 0.2g, 0.3g, 0.4g, 0.5g, and 0.6g, and the CTAB specific surface area of ​​each is 83.0×10⁻⁶. 3 m 2 After each of the industrial reference carbon black ITBs ( / kg) undergoes step S1, the corresponding OT solution volume test values ​​are 19.063 mL, 17.796 mL, 16.128 mL, 14.617 mL, and 12.916 mL, respectively. A calibration curve is plotted with the mass of the industrial reference carbon black ITBs as the abscissa and the volume test value of the consumed OT solution as the ordinate, yielding the linear regression equation y = -15.454x + 22.302.

[0046] Step S3: Establish the formula for calculating the CTAB specific surface area of ​​the carbon black sample as S = -S0 × (V0 - V) / (b × m); where the standard value of the CTAB specific surface area of ​​the industrial reference carbon black ITRB is S0 = 83.0 × 10⁻¹⁰. 3 m 2 / kg, V0 is the ordinate of the calibration curve in step S2, V0=22.302; b is the slope of the calibration curve in step S2, b=-15.454; V is the volume of OT solution consumed for titrating the carbon black sample, and m is the mass of the carbon black sample.

[0047] In step S4, the carbon black test sample N134 with a mass of m of 0.3g is processed through step S1 to obtain the volume test value V of the OT solution consumed by the carbon black test sample. The volume test value of the OT solution and the mass of the carbon black test sample are substituted into the formula in step S3 to calculate the CTAB specific surface area S of the carbon black test sample.

[0048] Example 2

[0049] The difference from Example 1 is that in step S4, the carbon black test sample is N115. After step S1, the volume test value V of the OT solution consumed by the carbon black test sample is obtained. The volume test value of the OT solution and the mass of the carbon black test sample are substituted into the formula in step S3 to calculate the CTAB specific surface area S of the carbon black test sample.

[0050] Example 3

[0051] The difference from Example 1 is that in step S4, the carbon black test sample N774 is processed through step S1 to obtain the volume test value V of the OT solution consumed by the carbon black test sample. The volume test value of the OT solution and the mass of the carbon black test sample are substituted into the formula in step S3 to calculate the CTAB specific surface area S of the carbon black test sample.

[0052] Example 4

[0053] The difference from Example 1 is that in step S1, after shaking, the sample is subjected to solid-liquid separation. Specifically, it is first centrifuged for 50 minutes at a speed of 7000 r / min. Then, multi-stage filtration is performed. The supernatant after centrifugation is first filtered through a filter membrane with a pore size of 0.24 μm at a pressure of 0.1~0.5 MPa. The filtrate is then filtered through a filter membrane with a pore size of 0.14 μm at a pressure of 0.1~0.5 MPa. Finally, the filtrate is filtered through a filter membrane with a pore size of 0.06 μm at atmospheric pressure. The resulting first mixture is in a clear state.

[0054] In step S2, the linear regression equation is y = -15.453x + 22.308.

[0055] Step S3: Establish the formula for calculating the CTAB specific surface area of ​​the carbon black sample as S = -S0 × (V0 - V) / (b × m); where the standard value of the CTAB specific surface area of ​​the industrial reference carbon black ITRB is S0 = 83.0 × 10⁻¹⁰. 3 m 2 / kg, V0 is the ordinate of the calibration curve in step S2, V0=22.308; b is the slope of the calibration curve in step S2, b=-15.453; V is the volume of OT solution consumed for titrating the carbon black sample, and m is the mass of the carbon black sample.

[0056] In step S4, the carbon black test sample N134 is processed through step S1 to obtain the volume test value V of the OT solution consumed by the carbon black test sample. The volume test value of the OT solution and the mass of the carbon black test sample are substituted into the formula in step S3 to calculate the CTAB specific surface area S of the carbon black test sample.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that 2.5 mL of a 37% formaldehyde solution was added to the OT solution.

[0059] In step S1, the solid-liquid separation is performed only once using a 0.15μm filter membrane at a pressure of 0.7MPa.

[0060] In step S2, the linear regression equation is y = -14.994x + 22.427.

[0061] Step S3: Establish the formula for calculating the CTAB specific surface area of ​​the carbon black sample as S = -S0 × (V0 - V) / (b × m); where the standard value of the CTAB specific surface area of ​​the industrial reference carbon black ITRB is S0 = 83.0 × 10⁻¹⁰. 3 m 2 / kg, V0 is the ordinate of the calibration curve in step S2, V0=22.427; b is the slope of the calibration curve in step S2, b=-14.994; V is the volume of OT solution consumed for titrating the carbon black sample, and m is the mass of the carbon black sample.

[0062] In step S4, the carbon black test sample N134 with a mass of m of 0.3g is processed through step S1 to obtain the volume test value of the OT solution consumed by the carbon black test sample. The volume test value of the OT solution and the mass of the carbon black test sample are substituted into the formula in step S3 to calculate the CTAB specific surface area S of the carbon black test sample.

[0063] Test method:

[0064] Three sets of parallel tests were conducted on the carbon black samples from the above examples and comparative examples to evaluate the repeatability of the test method. The results are shown in Table 1.

[0065] Table 1

[0066]

[0067] In multi-stage filtration, the first and second stages are performed manually, therefore, their pressure is within the range mentioned above.

[0068] The CTAB specific surface area of ​​the carbon black sample is within the industry range. The CTAB specific surface area S of the carbon black sample obtained from the test method embodiments of this application were all within the range of their true values ​​in three parallel tests. This demonstrates that the test method of this application has high accuracy and good repeatability.

[0069] The OT solution in Comparative Example 1 contained formaldehyde, which could be harmful to the environment and personnel. Furthermore, only a 0.15μm filter membrane was used for solid-liquid separation. The pore size of the membrane was larger than the diameter of some carbon black particles, making it impossible to completely separate the carbon black and CTAB solution. Additionally, only one pressure filtration was performed, resulting in a difficult-to-clarify filtrate and a significant deviation in the CTAB specific surface area test results for the carbon black.

[0070] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0071] Carbon black consists of nanoparticles with small particle sizes. Especially after stirring, sonicating, or vibrating, carbon black disperses into even smaller aggregates. Currently, most methods use 0.15 μm filter membranes for solid-liquid separation of carbon black and hexadecyltrimethylammonium bromide (CTAB). The pore size of these membranes is larger than the diameter of some carbon black particles, making complete separation of the carbon black suspension impossible. Furthermore, only one pressure filtration makes the filtrate difficult to clarify, resulting in poor accuracy of the CTAB specific surface area test results for carbon black. This application addresses this issue by employing a centrifugation + multi-stage filtration approach after the initial mixing of the carbon black sample and the CTAB solution. Centrifugation filters out large carbon black particles, and multi-stage filtration filters out carbon black particles of different sizes, thereby improving the separation effect between carbon black particles and the CTAB solution, achieving complete separation, and solving the problem of easy permeation of carbon black. This improves the accuracy and repeatability of the CTAB surface area detection for carbon black. Furthermore, the sodium dioctyl sulfosuccinate (OT) solution of this application is formaldehyde-free, improving the safety and environmental friendliness of the test. Specifically, in step S2, this application obtains the corresponding volumes of OT solution consumed by n industrial reference carbon black samples of different masses through step S1, thereby establishing a linear regression equation between the mass of the industrial reference carbon black and the volume of OT consumed. This allows the determination of V0 and b in the formula for calculating the CTAB specific surface area of ​​carbon black in step S3. Substituting the corresponding OT volume V obtained from step S1 for a carbon black sample of mass m into the formula in step S3 yields its corresponding CTAB specific surface area. In summary, the test method for the CTAB specific surface area of ​​carbon black of this application is safe, reliable, easy to operate, and yields highly accurate and repeatable test results.

[0072] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing the CTAB specific surface area of ​​carbon black, characterized in that, The testing method includes: Step S1: The carbon black sample and hexadecyltrimethylammonium bromide solution are sequentially mixed and separated into solid and liquid components to obtain a first mixture; the unadsorbed hexadecyltrimethylammonium bromide in the first mixture is titrated with sodium dioctyl sulfosuccinate solution until the endpoint is reached, and the volume of sodium dioctyl sulfosuccinate solution consumed is recorded; the solid-liquid separation includes sequential centrifugation and filtration, and the filtration is multi-stage filtration; the sodium dioctyl sulfosuccinate solution is sodium dioctyl sulfosuccinate and water; Step S2: When the carbon black sample consists of n industrial reference carbon blacks of different masses and with known CTAB specific surface areas, the industrial reference carbon blacks undergo the same process as in Step S1 to obtain the volumetric test values ​​of the sodium dioctyl sulfosuccinate solution corresponding to each industrial reference carbon black. A calibration curve is plotted with the mass of the industrial reference carbon black as the abscissa and the volumetric test value of the sodium dioctyl sulfosuccinate solution as the ordinate, yielding a linear regression equation: y = bx + V0; where n ≥ 3. Step S3: Establish the formula for calculating the CTAB specific surface area of ​​the carbon black sample as S = -S0 × (V0 - V) / (b × m); where S0 is the standard value of the CTAB specific surface area of ​​industrial reference carbon black, V0 is the ordinate of the calibration curve, b is the slope of the calibration curve, V is the volume of sodium dioctyl sulfosuccinate consumed for the carbon black sample, and m is the mass of the carbon black sample. Step S4: When the carbon black sample is a carbon black test sample with an unknown CTAB specific surface area, the carbon black test sample undergoes step S1 to obtain the volume test value of sodium dioctyl sulfosuccinate corresponding to the carbon black test sample. The volume test value of sodium dioctyl sulfosuccinate and the mass of the carbon black test sample are substituted into the calculation formula in step S3 to calculate the CTAB specific surface area of ​​the carbon black test sample.

2. The test method according to claim 1, characterized in that, In step S1, the carbon black sample is a dried carbon black sample; the drying temperature is 125℃, and the drying time is 1~3h; The ratio of the mass of the dried carbon black sample to the volume of the hexadecyltrimethylammonium bromide solution is 0.01 g / mL; And / or, the molar concentration of the hexadecyltrimethylammonium bromide solution is 0.01 mol / L; And / or, the molar concentration of the sodium dioctyl sulfosuccinate solution is 0.0022 mol / L.

3. The test method according to claim 1 or 2, characterized in that, In step S1, the first mixing method is oscillation; the first mixing time is 30~45min, and the oscillation frequency is 200~300r / min; And / or, step S1 further includes: adding a titration auxiliary solution and water to the first mixture and then performing the titration; wherein the volume ratio of the first mixture, the titration auxiliary solution and the water is 5:15:15~40; the titration auxiliary solution is an octylphenyl polyoxyethylene ether solution; And / or, the time of the endpoint is monitored using a turbidimeter, and the volume of the sodium dioctyl sulfosuccinate solution consumed is recorded.

4. The test method according to any one of claims 1 to 3, characterized in that, In step S1, the centrifugation time is 20-60 minutes and the centrifugation speed is 4000-9000 r / min.

5. The test method according to any one of claims 1 to 4, characterized in that, The filtration is performed using a filter membrane, and as the number of filtration stages increases sequentially, the pore size of the filter membrane decreases accordingly; and / or, the pore size of the filter membrane is 0.05~0.25μm; the filtration pressure is 0.1~0.5MPa.

6. The test method according to claim 5, characterized in that, The multi-stage filtration includes a first-stage filtration, a second-stage filtration, and a third-stage filtration performed sequentially; wherein, the first-stage filtration is performed using a filter membrane with a pore size of 0.22~0.25μm; the second-stage filtration is performed using a filter membrane with a pore size of 0.1~0.15μm; and the third-stage filtration is performed using a filter membrane with a pore size of 0.05~0.08μm.

7. The test method according to any one of claims 1 to 6, characterized in that, In step S2, the mass of the industrial reference carbon black is 0.1~1.5g; and / or, n is 3~8.

8. The test method according to any one of claims 1 to 7, characterized in that, In step S3, the industrial reference carbon black is of type ITRB and / or IRC4#; when the industrial reference carbon black is of type ITRB, S0 is 83.0 × 10⁻⁶. 3 m 2 / kg; when the industrial reference carbon black is of type IRC4#, the SO is 78.5 × 10 3 m 2 / kg; And / or, the V0 is 22.102~22.502, and the b is -15.050~-15.

554.

9. The test method according to any one of claims 1 to 8, characterized in that, In step S4, the grade of the carbon black sample to be tested is selected from any one or more of the N100 series, N200 series, N300 series, N500 series, N600 series, and N700 series; the NSA specific surface area of ​​the carbon black sample to be tested is 20 × 10⁻⁶. 3 ~151×10 3 m 2 / kg, where the mass of the carbon black sample to be tested is 0.28~1.37g.

10. The test method according to claim 9, characterized in that, When the grade of the carbon black to be tested is N100 series, and the NSA specific surface area of ​​the N100 series is 125×10⁻⁶. 3 ~151×10 3 m 2 When the carbon black sample is 0.28~0.32g, the mass of the sample is 0.28~0.32g. And / or, when the carbon black sample to be tested is of the N200 series, and the NSA specific surface area of ​​the N200 series is 97 × 10⁻⁶. 3 ~129×10 3 m 2 When the carbon black sample is 0.33~0.37g, the mass of the sample is 0.33~0.37g. And / or, when the carbon black sample to be tested is of the N300 series, and the NSA specific surface area of ​​the N300 series is 75 × 10⁻⁶. 3 ~103×10 3 m 2 When the carbon black sample is 0.38~0.42g, the mass of the sample is 0.38~0.42g. And / or, when the carbon black sample to be tested is from the N500 series or the N600 series, and the NSA specific surface area of ​​the N500 series and the N600 series is independently 27 × 10⁻⁶. 3 ~45×10 3 m 2 When the carbon black sample is 0.88~0.92g, the mass of the sample is 0.88~0.92g. And / or, when the carbon black sample to be tested is of the N700 series, and the NSA specific surface area of ​​the N700 series is 20 × 10⁻⁶. 3 ~39×10 3 m 2 When the carbon black sample is 1.33~1.37g, the mass of the sample is 1.33~1.37g.

Images