Small-hole pipe calibration method for measuring median particle size of aluminum hydroxide by particle counting analyzer

Abstract

The invention discloses a small-hole tube calibration method for determining the median particle size of aluminum hydroxide by a particle counting analyzer, and belongs to the technical field of aluminum hydroxide detection. The method comprises the following steps: S1, preparing an aluminum hydroxide sample for calibration; s2, primary calibration: carrying out primary calibration on the small-hole tube by using latex ball standard particles according to an operation instruction of a particle counting analyzer to obtain a primary calibration KD value; s3, correcting the standard particles: taking the primary calibration KD value as a parameter, measuring the median particle diameter D50 of the aluminum hydroxide standard sample by using a particle counting analyzer to obtain a D50 measured value of the aluminum hydroxide standard sample, and calculating to obtain a reference diameter of the corrected standard particles; and S4, secondary calibration: using the reference diameter of the corrected standard particle to calibrate the small hole pipe again to obtain the KD value of the hole pipe for measurement. The method can solve the problem that the aluminum hydroxide particle size analysis result easily has large deviation when the solid spherical latex particles are used for calibration.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum hydroxide detection, and in particular to a small-bore tube calibration method for measuring the median particle size of aluminum hydroxide by a particle counting analyzer. Background Art

[0002] Alumina production control and product sales both require the D50 value of the median particle size of aluminum hydroxide to regulate production and product shipment. Aluminum hydroxide sold externally requires a fast and accurate analysis report. The key to determining D50 is to determine the particle size distribution of the material. Currently, there are mainly five methods for determining particle size distribution: screening method, sedimentation method, resistance method, laser method, and electron microscopy method. Among them, the sedimentation method has problems such as cumbersome operation, long time consumption, and complex calculation. The laser method has problems such as the results are greatly affected by the distribution model and the resolution is slightly low. The electron microscopy method has problems such as poor representativeness, measurement is easily affected by human factors, and reproducibility is slightly poor. Therefore, the more commonly used methods are screening method and resistance method.

[0003] The screening method has the disadvantages of long sample preparation time, each particle size requires an analytical sieve of corresponding size for screening, frequent screen replacement, and poor operating environment. The particle size percentage is obtained by weighing the sample weight on each sieve layer after screening, and only the percentages of several particle sizes such as 45μm, 90μm, and 150μm can be determined, and the accurate value of D50 cannot be obtained; secondly, the screening method needs to go through sample drying, preparation, vibrating, data processing and other processes, which is time-consuming. Obviously, the screening method cannot fully meet the needs of rapid and accurate determination of aluminum hydroxide D50.

[0004] In the resistance method, a particle counting analyzer is usually used to measure the particle size distribution of aluminum hydroxide. The instrument uses the principle of the resistance method for measurement: after the sample is stirred, the sample particles are dispersed in the electrolyte solution and a uniform suspension is formed by stirring. The suspension is sucked through an insulating tube containing a small hole (a small hole tube); there is an electrode on each side of the small hole tube, and a current is loaded between the two electrodes. When the particles pass through the small hole on the insulating wall of the small hole tube, it will cause a change in the resistance value between the two electrodes. The pulse value of this change is amplified and counted, and its height is analyzed. By applying the particle size calibration constant, the number distribution of the volume equivalent sphere diameter can be obtained.

[0005] According to the working principle of the particle counting analyzer, the electric pulse signal is converted into a particle size value, and the particle size calibration constant of the small hole tube must be applied. In the current analysis work, the particle size calibration constant is obtained by directly measuring the standard particles provided by the equipment manufacturer and statistically analyzing the results. Since the standard particles provided by the manufacturer are solid spherical latex particles, and aluminum hydroxide is a non-spherical inorganic substance, there are obvious differences in shape and material between the two. Therefore, the particle size calibration constant obtained by using solid spherical latex particles is not suitable for aluminum hydroxide samples in actual applications, which can easily cause large deviations in the particle size analysis results of aluminum hydroxide. Summary of the invention

[0006] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art and to provide a small-bore tube calibration method for measuring the median particle size of aluminum hydroxide by a particle counting analyzer. After the calibration of the present invention, the particle counting analyzer is used for measurement, which can meet the needs of quickly and accurately measuring the D50 of aluminum hydroxide and can solve the problem that the use of solid spherical latex particles for calibration easily causes large deviations in the particle size analysis results of aluminum hydroxide.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] A small-bore tube calibration method for measuring the median particle size of aluminum hydroxide by a particle counting analyzer comprises the following steps:

[0009] S1. Prepare aluminum hydroxide sample for calibration: take aluminum hydroxide and prepare aluminum hydroxide standard sample by sieving method;

[0010] S2. Primary calibration: Use latex ball standard particles to perform primary calibration on the small hole tube, i.e., the insulating tube containing small holes, according to the operating procedures of the particle counting analyzer to obtain the primary calibration KD value;

[0011] S3. Corrected standard particles: Using the primary calibration KD value as a parameter, use a particle counting analyzer to measure the median particle size D50 of the aluminum hydroxide standard sample, and obtain the D50 measured value of the aluminum hydroxide standard sample. The reference diameter of the corrected standard particles is obtained by calculation. The specific calculation formula is as follows: response factor = D50 true value of the aluminum hydroxide standard sample / D50 measured value of the aluminum hydroxide standard sample, reference diameter of the corrected standard particles = response factor × peak particle size of the latex ball standard particles;

[0012] S4. Secondary calibration: Use the reference diameter of the corrected standard particles as the peak particle diameter and calibrate the orifice tube again according to the operating procedures of the particle counting analyzer to obtain the KD value of the orifice tube for measurement.

[0013] Furthermore, in step S1, the preparation method of the aluminum hydroxide standard sample includes the following steps: taking aluminum hydroxide, sieving it using a three-layer sieve combination of 80μm, 90μm, and 100μm, and the sieve layer sequence is 100-90-80 from top to bottom, and after sieving, taking equal weights of the 90μm sieve and the sieve under the sieve to mix them to obtain an aluminum hydroxide standard sample with a D50 of 90μm; that is, the true value of D50 of the obtained aluminum hydroxide standard sample is 90μm.

[0014] Furthermore, the small-pore tube is a tube with a pore size of 200-400 μm.

[0015] Furthermore, in step S2, the peak particle size of the latex ball standard particles is as follows: the peak particle size of the latex ball standard particles for 200μm pore tubes is 10-20μm, the peak particle size of the latex ball standard particles for 280μm pore tubes is 14-28μm, and the peak particle size of the latex ball standard particles for 400μm pore tubes is 20-40μm.

[0016] Furthermore, the small-pore tube is a 280 μm pore tube, corresponding to a peak particle size of a latex ball standard particle of 19.98 μm.

[0017] Furthermore, the primary calibration and the secondary calibration are both performed by calibrating the pinhole tube 10 times, and the average value is taken to obtain the KD value.

[0018] The present invention also provides a method for measuring the median particle size of aluminum hydroxide using a particle counting analyzer, specifically, using the KD value of the measuring hole tube obtained by the above method to measure the median particle size of aluminum hydroxide, comprising the following steps:

[0019] (1) preparing an electrolyte: preparing an electrolyte by mixing sodium chloride with deionized water;

[0020] (2) Sample preparation: Add the aluminum hydroxide sample to be tested into the electrolyte, mix well and transfer into a beaker;

[0021] (3) Sample analysis: Place the beaker containing the sample to be tested into a particle counting analyzer, and use the KD value of the measuring orifice tube obtained in claim 1 to perform measurement according to the instrument operating procedures to obtain the median particle size D50 of aluminum hydroxide.

[0022] Furthermore, in step (1), sodium chloride and deionized water are used to prepare an electrolyte with a mass concentration of 2%, and the electrolyte is filtered through a 0.22 μm filter membrane.

[0023] Furthermore, in step (2), graded sampling is adopted, and a total of 15 g of the aluminum hydroxide sample to be tested is taken from multiple locations, 200 mL of electrolyte is added and mixed, and then 5 mL is taken with a syringe and injected into a beaker containing 200 mL of electrolyte.

[0024] Furthermore, the particle counting analyzer is an MS3 particle counter or an MS4e particle counting analyzer.

[0025] The beneficial effects of the present invention are as follows:

[0026] The present invention first uses standard particles to determine the particle size calibration constant of the small-bore tube, and then uses aluminum hydroxide for supplementary correction. Through the above improvements, the particle size analysis of aluminum hydroxide determined by the particle counting analyzer is more in line with the actual situation. In the comparative analysis with the screening method, the analysis results of the two are similar and meet the requirements, and the problem that the use of solid spherical latex particles for calibration easily causes a large deviation in the particle size analysis result of aluminum hydroxide can be solved.

[0027] After calibration by the method of the present invention, the particle counting analyzer is used to measure the aluminum hydroxide D50, and the results can be obtained quickly and accurately. Compared with the screening method, it has the following advantages: the screening method requires drying, mixing, sampling, screening, brushing, weighing, calculation and other steps, the process is long and cumbersome, there are many influencing factors, and the analysis results are easily affected by personal operating skills; while the present invention only samples, measures, and derives the results, the process is simple, and the process is easy to standardize. The screening method cannot issue an accurate D50 value; while the present invention can directly obtain the accurate D50 value of the sample. The screening method sample analysis takes more than 180 minutes; while the present invention only takes about 15 minutes, and the work efficiency is improved by more than 10 times. The dry sampling of the screening method has a lot of dust, the vibration process is noisy, and there is a possibility of mechanical damage; while the wet sampling of the present invention has less dust, and there is no obvious noise during the operation process. In summary, the method of the present invention can accurately determine the aluminum hydroxide D50 value to meet the production and sales needs; at the same time, it significantly improves the working environment, significantly reduces the time of contact with dust and noise; in addition, it improves work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Comparison of analysis results of -45μm with different calibration methods;

[0029] Figure 2 This is a statistical chart of the measurement results of the D50 monitoring sample. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] Example 1

[0032] A small-bore tube calibration method for measuring the median particle size of aluminum hydroxide by a particle counting analyzer comprises the following steps:

[0033] S1. Prepare aluminum hydroxide sample for calibration: weigh 50g aluminum hydroxide and sieve it using a three-layer sieve combination of 80μm, 90μm, and 100μm, with the sieve layer sequence being 100-90-80 from top to bottom. After sieving for 15 minutes, take 7.5g of the material on and under the 90μm sieve and mix them evenly to obtain an aluminum hydroxide standard sample with a median particle size D50 of 90μm; that is, the true value of D50 of the obtained aluminum hydroxide standard sample is 90μm.

[0034] S2. Primary calibration: The particle counting analyzer uses an MS3 particle counter. After the instrument is turned on and running stably, the small-bore tube (280μm bore tube) is calibrated using the latex ball standard particles with a peak particle size of 19.98um distributed by the instrument manufacturer according to the operating procedures of the particle counting analyzer. Calibrate 10 times and take the average value to obtain the primary particle size calibration constant, that is, the primary calibration KD value of 388.0; the specific data are shown in Table 1 below.

[0035] Table 1

[0036]

[0037] S3. Corrected standard particles: Using the primary calibration KD value as a parameter, input 388.0 into the particle counting analyzer, and use the particle counting analyzer to measure the median particle size D50 of the aluminum hydroxide standard sample. Measure 10 times and take the average value to obtain D50 of 102.3 μm, which is the D50 measured value of the aluminum hydroxide standard sample. The reference diameter (particle size) of the corrected standard particles is obtained by calculation. The specific calculation formula is as follows: response factor = true value of D50 of the aluminum hydroxide standard sample / measured value of D50 of the aluminum hydroxide standard sample, that is, response factor = 90 / 102.3 = 0.88; reference diameter of corrected standard particles = response factor × peak particle size of latex ball standard particles, that is, reference diameter of corrected standard latex ball particles = 19.98 × 0.88 = 17.58 μm; specific data are shown in Table 2 below.

[0038] Table 2

[0039]

[0040] S4. Secondary calibration: Use the reference diameter of the corrected standard particles of 17.58 μm and calibrate the orifice tube again 10 times according to the operating procedures of the particle counting analyzer, and take the average value to obtain the orifice tube KD value of 342.3 for the measurement; the specific data are shown in Table 3 below.

[0041] Table 3

[0042]

[0043] Determination of median particle size of aluminum hydroxide:

[0044] (1) Preparation of electrolyte: Use sodium chloride and deionized water to prepare an electrolyte with a mass concentration of 2%, and filter it through a 0.22 μm filter membrane. The blank value is required to be no more than 200.

[0045] (2) Sample preparation: Using graded sampling, take 15 g of aluminum hydroxide sample from multiple locations, add 200 mL of electrolyte, mix well, and then use a syringe to take 5 mL of the sample and inject it into an analysis beaker containing 200 mL of electrolyte.

[0046] (3) Sample analysis: Place the analysis beaker containing the sample to be tested into the MS3 particle counter, and input the KD value of the measurement orifice tube 342.3 into the MS3 particle counter. Perform the measurement according to the instrument operating procedures to obtain the original pulse signal file. Set the statistical method to "volume (mass)", add "D50" to the output item, export the data, and obtain the median particle size D50 of aluminum hydroxide.

[0047] like Figure 1 As shown, the -45μm percentage of the production samples was determined by calibration of Example 1 of the present invention and calibration with latex ball standard particles (i.e., only primary calibration was performed), and compared with the screening method. From the analysis results, it can be seen that the results of Example 1 are basically consistent with those of the screening method, while the results of calibration with latex ball standard particles have a large deviation.

[0048] Verification of operation correctness: When the operation is correct, the particle size analysis results of repeated measurements are consistent with the Poisson distribution. The specific verification is based on the repeated measurement results x 2 The test is based on the critical value not exceeding.

[0049] Specific operation: Repeat the measurement of aluminum hydroxide sample 6 times, record the total number of particles, and when the significance level p = 0.05 and the degree of freedom df = n-1 = 5, the x value of the measurement result 2 It is 5.47, which is less than the critical value of 11.07, indicating that the sample preparation and instrument operation are correct. The specific results are shown in Table 4 below.

[0050] Table 4

[0051]

[0052] Determination of the confidence interval of the measurement result: In the experiment, there is often a certain deviation between the measured value and the true value. According to the principle of statistics, when the confidence level is 95.44%, the confidence range is 2 times the standard deviation, and when the confidence level is 99.73%, the confidence range is 3 times the standard deviation. The aluminum hydroxide sample with a D50 of 90 microns was measured 100 times by the method of Example 1. It was statistically obtained that the confidence interval at the confidence level of 95.44% was 0.72 microns, and the confidence interval at the confidence level of 99.73% was 1.08 microns. The results are shown in Table 5 below.

[0053] Table 5D50 is the measurement result of 90 microns of aluminum hydroxide

[0054]

[0055]

[0056] Precision test: RSD of parallel tests

[0057] The D50 data of the unknown aluminum hydroxide sample was determined ten times using the method of Example 1, and the relative standard deviation was calculated to be 0.43%, which is much smaller than the target value of 5%, indicating that the method of the present invention has good precision. The results are shown in Table 6 below.

[0058] Table 6

[0059]

[0060] Accuracy test: single sample t test

[0061] The aluminum hydroxide sample with a D50 of 100 μm was measured 10 times using the method of Example 1, and the calculated t value was 0.61, which is less than t0.05 / 2,9=2.2620, indicating that at the 0.05 level, there is no difference between the measurement result and the true value, indicating that the method of the present invention has high accuracy. The results are shown in Table 7 below.

[0062] Table 7

[0063]

[0064] Stability verification: Aluminum hydroxide samples with a D50 of 90 microns were used as monitoring samples. Tracking monitoring was performed each time the measurement was performed. 2 times the standard deviation was used as the warning line and 3 times the standard deviation was used as the disposal line. The data was stable and the method was running well for three months. The results were as follows: Figure 2 shown.

[0065] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the definition of the claims.

Claims

1. A small-bore tube calibration method for measuring the median particle size of aluminum hydroxide by a particle counting analyzer, characterized in that: The steps include: S1. Prepare aluminum hydroxide sample for calibration: take aluminum hydroxide and prepare aluminum hydroxide standard sample by sieving method; S2. Primary calibration: Use latex ball standard particles to perform primary calibration on the pinhole tube according to the operating procedures of the particle counting analyzer to obtain the primary calibration KD value; S3. Corrected standard particles: Using the primary calibration KD value as a parameter, use a particle counting analyzer to measure the median particle size D50 of the aluminum hydroxide standard sample, and obtain the D50 measured value of the aluminum hydroxide standard sample. The reference diameter of the corrected standard particles is obtained by calculation. The specific calculation formula is as follows: response factor = D50 true value of the aluminum hydroxide standard sample / D50 measured value of the aluminum hydroxide standard sample, reference diameter of the corrected standard particles = response factor × peak particle size of the latex ball standard particles; S4. Secondary calibration: Use the reference diameter of the corrected standard particles and calibrate the orifice tube again according to the operating procedures of the particle counting analyzer to obtain the KD value of the orifice tube for measurement.

2. The method for calibrating a small-bore tube for measuring the median particle size of aluminum hydroxide by a particle counting analyzer according to claim 1, characterized in that: In step S1, the preparation method of the aluminum hydroxide standard sample includes the following steps: taking aluminum hydroxide, using a three-layer sieve combination of 80μm, 90μm, and 100μm for screening, the sieve layer sequence from top to bottom is 100-90-80, after screening, taking equal weight of the 90μm sieve and the sieve under the sieve, and mixing them to obtain an aluminum hydroxide standard sample with a median particle size D50 of 90μm; that is, the true value of D50 of the obtained aluminum hydroxide standard sample is 90μm.

3. The small-bore tube calibration method for measuring the median particle size of aluminum hydroxide by a particle counting analyzer according to claim 1, characterized in that: The small-pore tube is a tube with a pore size of 200-400 μm.

4. The method for calibrating a small-bore tube for measuring the median particle size of aluminum hydroxide by a particle counting analyzer according to claim 1, characterized in that: The primary calibration and the secondary calibration are both performed by calibrating the pinhole tube 10 times, and the average value is taken to obtain the KD value.

5. A method for measuring the median particle size of aluminum hydroxide using the KD value of the measuring hole tube calibrated according to claim 1, characterized in that: The steps include: (1) preparing an electrolyte: preparing an electrolyte by mixing sodium chloride with deionized water; (2) Sample preparation: Add the aluminum hydroxide sample to be tested into the electrolyte, mix well and transfer into a beaker; (3) Sample analysis: Place the beaker containing the sample to be tested into a particle counting analyzer, and use the KD value of the measuring orifice tube obtained in claim 1 to perform measurement according to the instrument operating procedures to obtain the median particle size D50 of aluminum hydroxide.

6. The method according to claim 5, characterized in that: In step (1), sodium chloride and deionized water are used to prepare an electrolyte with a mass concentration of 2%, and the electrolyte is filtered through a 0.22 μm filter membrane.

7. The method according to claim 5, characterized in that: In step (2), 15 g of the aluminum hydroxide sample to be tested is taken, added to 200 mL of electrolyte, mixed, and then 5 mL is taken with a syringe and injected into a beaker containing 200 mL of electrolyte.

8. The method according to claim 1 or 5, characterized in that: The particle counting analyzer is an MS3 particle counter or an MS4e particle counting analyzer.

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