CN112684058B - Method for measuring DTBP content in polypropylene melt-blown material - Google Patents
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Abstract
The invention discloses a method for measuring the DTBP content in a polypropylene melt-blown material, which comprises the following steps: s1, dissolving a DTBP standard sample and an internal standard substance in an extracting agent to obtain a standard solution; s2, analyzing the standard solution through gas chromatography, and calculating to obtain a correction factor of the DTBP; s3, freezing and crushing the polypropylene melt-blown material to obtain polypropylene melt-blown granules, and extracting the polypropylene melt-blown granules by using an extracting agent at the temperature of 20-40 ℃ to obtain an extraction liquid which is a DTBP pretreatment sample; s4, adding the internal standard substance into the DTBP pretreatment sample to obtain a sample to be detected, analyzing the sample to be detected through gas chromatography, and calculating to obtain the DTBP content in the polypropylene melt-blown material; the extraction agent is acetone, ethanol or toluene, and the internal standard substance is one or more of n-hexane, n-pentane, n-octane or ethyl acetate. According to the invention, the polypropylene melt-blown material is crushed at a low temperature, the DTBP is extracted at a low temperature, and the residual amount of the DTBP in the polypropylene melt-blown material can be accurately measured by selecting a specific kind of extracting agent and an internal standard substance.
Description
Technical Field
The invention relates to the field of DTBP analysis, in particular to a method for measuring the DTBP content in a polypropylene melt-blown material.
Background
DTBP is an organic peroxide, and is widely used as a cross-linking agent of unsaturated polyester and silicon rubber, a polymerization initiator of monomer, a polypropylene modifier, a rubber vulcanizing agent and the like, ordinary polypropylene can obtain melt-blown materials with high melt index by adding DTBP as a degrading agent, and the state has standard requirements on the residual amount of DTBP in the melt-blown materials, so that the DTBP content in the polypropylene melt-blown materials needs to be accurately measured.
The existing detection method for DTBP residual quantity mainly uses gas chromatography and iodineAnd (4) measuring. The iodometry method mainly comprises the steps of dissolving toluene in a refluxing manner, cooling, adding FeCl 3 The glacial acetic acid solution precipitates the plastic and is then filtered and transferred to the volumetric flask, but the iodometry method gives the total amount of all substances capable of oxidizing the iodide in the sample, not the exact content of DTBP, and is time-consuming, reagent-consuming and environmentally unfriendly.
Chinese patent application CN111220726A discloses a method for measuring DTBP content by gas chromatography, which adopts an internal standard method, and adopts internal standard substance n-octane and solvent to select n-pentane, n-hexane and n-heptane by gas chromatography analysis. However, this patent only relates to DTBP samples which are liquid per se and does not relate to a method for pre-treatment of DTBP in polypropylene.
Lipeyl et al (Lipeyl, liu lan Zhen. Gas chromatography for the determination of di-t-butyl-ether peroxide [ J ] in polypropylene. Synthetic fiber industry, 1981 (05): 27-29.) disclose a pretreatment method for DTBP: heating toluene for refluxing to dissolve polypropylene, and separating DTBP from toluene by using an ice salt cooling and suction filtration method. However, the self-accelerating decomposition temperature of DTBP is 80 ℃, and the DTBP is easy to decompose under the condition of heating reflux, so that the detection error of the residual amount of DTBP is larger; the ice salt suction filtration mode is troublesome, the error is large, and the repeatability is poor; the peaks of toluene and DTBP in gas chromatography are difficult to separate effectively, and further the DTBP content cannot be determined accurately.
Therefore, it is necessary to develop a method for measuring the DTBP content in the polypropylene melt-blown material, which can accurately measure the DTBP residual amount in the polypropylene melt-blown material.
Disclosure of Invention
The invention provides a method for measuring the content of DTBP in polypropylene melt-blown material, which can accurately measure the residual amount of DTBP in the polypropylene melt-blown material, and aims to overcome the defect of inaccurate measurement of the content of DTBP in the polypropylene melt-blown material in the prior art.
In order to solve the technical problems, the invention adopts the technical scheme that:
a method for measuring the DTBP content in a polypropylene melt-blown material comprises the following steps:
s1, dissolving a DTBP standard sample and an internal standard substance in an extracting agent to obtain a standard solution;
s2, analyzing the standard solution through gas chromatography to obtain peak areas of the DTBP and the internal standard substance in the standard solution, and calculating to obtain a correction factor of the DTBP according to the peak areas and the mass of the DTBP and the internal standard substance;
s3, freezing and crushing the polypropylene melt-blown material to obtain polypropylene melt-blown granules with the grain size of 0.1-0.6 mm, and extracting the polypropylene melt-blown granules by using an extracting agent at the extraction temperature of 20-40 ℃ to obtain an extract liquid which is a DTBP pretreatment sample;
s4, adding the internal standard substance into the DTBP pretreatment sample to obtain a sample to be detected, analyzing the sample to be detected through gas chromatography under the same analysis condition as the standard solution to obtain peak areas of the DTBP and the internal standard substance, and calculating through a correction factor of the DTBP to obtain the DTBP content in the polypropylene melt-blown material;
the extracting agent is acetone or ethanol,
the internal standard substance is one of n-hexane, n-pentane, n-octane or ethyl acetate.
Since the polypropylene melt-blown material is difficult to be completely dissolved in an organic solvent at normal temperature, DTBP cannot be completely extracted, and heating can accelerate the solution of the polypropylene melt-blown material but can decompose DTBP. The inventor researches and discovers that decomposition and loss of DTBP can be effectively avoided by crushing and extracting the polypropylene melt-blown material under the freezing condition, the extraction efficiency of the DTBP can be improved, and more accurate DTBP content can be measured.
Acetone and ethanol have excellent extraction efficiency on DTBP, and in gas chromatography analysis, the acetone and the ethanol have good separation degrees with the normal hexane, the normal pentane, the normal octane and the ethyl acetate which are internal standard substances of the invention, and can be completely distinguished from the detection peak of DTBP. Therefore, by selecting acetone and ethanol as extracting agents and n-hexane, n-pentane, n-octane and ethyl acetate as internal standard substances, DTBP detection peaks with extremely high separation degree can be obtained under gas chromatography analysis, so that the accurate content of DTBP can be calculated.
Preferably, the extractant is acetone and the internal standard substance is n-hexane.
Preferably, the content of DTBP in the DTBP standard sample is more than or equal to 99wt.%.
Preferably, the mass ratio of the DTBP to the internal standard substance in the standard solution is (1-3) to 1.
Preferably, the temperature of the freeze-pulverization is 0 ℃ or less.
Preferably, the freeze-crushing is freezing using liquid nitrogen.
On one hand, liquid nitrogen can provide extremely low freezing temperature, and on the other hand, DTBP is not easy to decompose and lose under the inert gas environment.
Preferably, the time for the freeze-pulverization is 10 to 30 seconds.
The short crushing time ensures that the polypropylene melt-blown material generates less heat and avoids the decomposition of peroxide.
Preferably, the extraction temperature in step S3 is 30 to 40 ℃.
Preferably, the extraction in step S3 is by using ultrasonic extraction, shaking extraction or soaking extraction.
More preferably, the ultrasonic extraction is ultrasonic extraction using a flowing water bath.
Because ultrasound is a high-energy process, the temperature of the water bath is continuously increased, so that DTBP is decomposed in the extraction process and the accurate content cannot be measured. By using the flowing water bath, the influence of ultrasonic temperature rise on DTBP is effectively avoided.
Preferably, the concentration of the internal standard substance in the sample to be tested in the step S4 is 0.1-0.5 mg/mL.
Preferably, the detection conditions of the gas chromatograph are as follows:
the temperature of the sample inlet is 70-120 ℃, the temperature of the detector is 200-250 ℃, the sample injection amount is 0.2-2 mu L, the split ratio is 15-30 2 The flow rate is 0.5-1.2 mL/min, the hydrogen flow rate is 40mL/min, and the air flow rate is 400mL/min.
Preferably, the temperature raising program of the chromatographic column is: the temperature is initially 40-80 ℃, and is maintained for 3-10 min, and then the temperature is increased to 150-240 ℃ at the speed of 10-30 ℃/min, and is maintained for 1-10 min.
Preferably, the chromatography column is a packed column or a capillary chromatography column.
More preferably, the chromatography column is a capillary chromatography column. Optionally, the chromatographic column is an Agilent capillary chromatographic column HP 101, the length of the column is 50m, the inner diameter of the column is 0.32mm, and the thickness of a liquid membrane is 0.3 μm.
The correction factor of DTBP in the invention is calculated according to the following formula:
F＝(A s *M i )/(A i *M s )；
in the formula, A s = peak area of internal standard in calibration solution,
A i = peak area of DTBP standard in calibration solution,
M s = mass of internal standard in calibration solution,
M i = mass of DTBP standard in calibration solution.
DTBP content C in the invention i (mg/kg) was calculated according to the following formula:
C i ＝(F*Ms`*Ai’)/(m*As’)*1000；
wherein Ai' = peak area of DTBP in the sample to be detected;
as' = peak area of internal standard substance in sample to be measured;
f = correction factor for DTBP;
ms' = mass of internal standard in solution to be tested (mg);
m = polypropylene melt-blown pellet mass (g).
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the polypropylene melt-blown material is crushed at low temperature, and the DTBP is extracted at low temperature, so that a DTBP pretreatment sample with extremely low DTBP content loss is obtained, a DTBP chromatographic peak is effectively separated by selecting a specific kind of extractant and an internal standard substance, and the residual amount of the DTBP in the polypropylene melt-blown material can be accurately measured.
Detailed Description
The present invention will be further described with reference to the following embodiments.
The starting materials in the examples and comparative examples are commercially available as follows:
see table 1.
Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.
Example 1
Example 1A standard solution was provided and subjected to gas chromatography to obtain a calibration factor for DTBP.
Preparation of a standard solution: accurately weighing the internal standard substance and the DTBP standard sample, diluting the internal standard substance and the DTBP standard sample to a certain volume by using an extracting agent, and shaking up and mixing to obtain a standard solution.
The standard solution comprises the following components in percentage by weight: 0.5g of DTBP standard sample, 0.5g of internal standard substance n-hexane and 50ml of extracting agent acetone.
The detection conditions of the gas chromatography are as follows:
the temperature of a sample inlet is 80 ℃, the temperature of a detector is 200 ℃, the sample injection amount is 1 mu L, the split ratio is 20 2 The flow is 1mL/min, the hydrogen flow is 40mL/min, and the air flow is 400mL/min;
the chromatographic column is Agilent capillary chromatographic column HP 101, the length of the column is 50m, the inner diameter is 0.32mm, and the thickness of a liquid film is 0.3 μm; the temperature rising program of the chromatographic column is as follows: the temperature is increased to 160 ℃ at the speed of 10 ℃/min after the initial temperature of 50 ℃ is maintained for 3min, and the temperature is maintained for 10min.
The correction factor for DTBP is calculated according to the following formula:
F＝(A s *M i )/(A i *M s )；
in the formula, A s = peak area of internal standard in calibration solution,
A i = peak area of DTBP standard in calibration solution,
M s = mass of internal standard in calibration solution,
M i = mass of DTBP standard in calibration solution.
Examples 2 to 15
In order to verify the reliability and accuracy of the extraction and gas chromatography methods, the recovery rate of the polypropylene powder added with known amount of DTBP needs to be tested.
Examples 2 to 5 provide a quantitative DTBP polypropylene.
Preparing quantitative DTBP polypropylene: accurately measuring a DTBP standard sample and polypropylene powder, and vibrating and blending in an acetone solvent to prepare the quantitative DTBP polypropylene.
The quantitative DTBP polypropylene of examples 2-5 has the contents of the respective components shown in Table 2.
TABLE 2 quantitative DTBP Polypropylene component contents of examples 2-5
Examples 6 to 15 the recovery rates of DTBP were measured for quantitative DTBP polypropylenes A to D, respectively, by the following methods:
extracting the quantitative DTBP polypropylene by using an extracting agent to obtain an extract liquid as a pretreatment sample; adding the internal standard substance into the pre-treated sample to obtain a sample to be detected; and (3) analyzing the sample to be detected by gas chromatography under the same analysis condition as the standard solution, measuring the DTBP content, and calculating the recovery rate of the DTBP.
DTBP content C i (mg/kg) was calculated according to the following formula:
C i ＝(F*Ms`*Ai’)/(m*As’)*1000；
wherein Ai' = peak area of DTBP in the sample to be detected;
as' = peak area of internal standard substance in sample to be detected;
f = correction factor for DTBP;
ms' = mass (mg) of internal standard substance in solution to be detected;
m = polypropylene melt-blown pellet mass (g).
The specific parameters of the measurement methods of examples 6 to 15 are shown in Table 3.
TABLE 3 measurement method specific parameters of examples 6 to 15
Examples 16 to 22
Examples 16 to 22 the DTBP residual amounts of 5 commercially available polypropylene melt-blown materials were measured by:
freezing and crushing the polypropylene melt-blown material to obtain polypropylene melt-blown granules, extracting the polypropylene melt-blown granules by using an extracting agent at the extraction temperature of 40 ℃, wherein the extraction mode is ultrasonic extraction by using a flowing water bath to obtain an extraction liquid which is a DTBP pretreatment sample;
and adding normal hexane into the DTBP pretreatment sample to obtain a sample to be detected, analyzing the sample to be detected by gas chromatography under the same analysis condition as the standard solution, and calculating to obtain the DTBP content in the polypropylene melt-blown material.
The specific parameters of the measurement methods of examples 16 to 22 are shown in Table 4.
TABLE 4 measurement method specific parameters of examples 16 to 22
Comparative examples 1 to 4
Comparative examples 1 to 4 the recovery rates of DTBP in the quantitative DTBP polypropylene A were measured, respectively, by the following methods:
extracting the quantitative DTBP polypropylene A by using an extracting agent to obtain an extract liquid as a pretreatment sample; adding the internal standard substance into the pretreatment sample to obtain a sample to be measured; and (3) analyzing the sample to be detected by gas chromatography under the same analysis condition with the standard solution, measuring the DTBP content, and calculating the recovery rate of the DTBP.
The specific parameters of the measurement methods of comparative examples 1 to 4 are shown in Table 5.
TABLE 5 concrete parameters of measuring methods of comparative examples 1 to 4
Comparative examples 5 to 11
Comparative examples 5 to 11 the DTBP residual amounts of 5 commercially available polypropylene melt-blown materials were measured by the following methods:
in comparative examples 5-9, the polypropylene melt-blown material was not pulverized, and the polypropylene melt-blown material was extracted directly with an extractant at 40 ℃ in a manner of ultrasonic extraction using a flowing water bath to obtain an extract as a DTBP pretreatment sample;
comparative examples 10 to 11 polypropylene melt-blown materials were pulverized to obtain polypropylene melt-blown pellets, which were extracted with an extractant at 40 ℃ in a fluidized water bath ultrasonic extraction manner to obtain an extract as a DTBP pretreatment sample;
and adding normal hexane into the DTBP pretreatment sample to obtain a sample to be detected, analyzing the sample to be detected by gas chromatography under the same analysis condition as the standard solution, and calculating to obtain the DTBP content in the polypropylene melt-blown material.
The specific parameters of the measurement methods of comparative examples 5 to 11 are shown in Table 6.
TABLE 6 concrete parameters of measuring methods of comparative examples 5 to 11
Test results
(1) Test of recovery of DTBP
The DTBP recovery is calculated according to the following formula:
DTBP recovery = (DTBP detection value/DTBP standard weight) × 100%.
The DTBP recovery of each quantitative DTBP polypropylene of examples 6 to 15 is shown in Table 7.
TABLE 7 DTBP recovery rates of examples 6 to 15
The DTBP recovery of the quantitative DTBP polypropylene in comparative examples 1 to 4 is shown in Table 8.
TABLE 8 DTBP recovery for comparative examples 1-4
| 1 | 2 | 3 | 4 | |
| DTBP detection value (mg) | 5.004 | 7.506 | 6.0048 | 7.806 |
| DTBP recovery (%) | 50 | 75 | 60 | 78 |
It can be seen that the DTBP content in the polypropylene can be accurately determined by extracting at 20-40 ℃ and selecting the specific types of extracting agents and internal standard substances, and the recovery rate of the DTBP is more than or equal to 90 percent.
In comparative examples 1 to 4, too high an extraction temperature resulted in decomposition of DTBP; the DTBP is difficult to be completely extracted due to the excessively low extraction temperature; toluene is used as an extracting agent, cannot be completely distinguished from DTBP and detection peaks of an internal standard substance, and cannot be used for measuring the accurate content of DTBP; the use of ultrasonic extraction at normal temperature also leads to thermal decomposition of DTBP.
According to examples 6 to 15, the preferred extractant is acetone and the internal standard is n-hexane; preferably, the extraction temperature is 30-40 ℃, and ultrasonic extraction is carried out by using a flowing water bath.
(2) Determination of DTBP residual quantity of polypropylene melt-blown material
The DTBP residual quantity is calculated according to the following formula:
residual amount of DTBP = DTBP test value (mg)/weight of polypropylene meltblown (kg).
The residual DTBP level of the polypropylene meltblown in examples 16-22 is shown in Table 9.
TABLE 9 DTBP residual amounts of examples 16 to 22
The DTBP level of the polypropylene meltblown in comparative examples 5-11 is shown in Table 10.
TABLE 10 residual DTBP values of comparative examples 5 to 11
According to the DTBP residual quantity detection results of the examples 16-20 and the comparative examples 5-9, the detection value of the DTBP residual quantity is very low under the condition that the polypropylene melt-blown material is not crushed, and the crushed sample plays an important role in the accuracy of the test result.
When the polypropylene melt-blown material is crushed and the particle size is too large, or the polypropylene melt-blown material is crushed at normal temperature, the DTBP residual quantity detection value is inaccurate.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (6)
1. A method for measuring the DTBP content in a polypropylene melt-blown material is characterized by comprising the following steps:
s1, dissolving a DTBP standard sample and an internal standard substance into an extracting agent to obtain a standard solution;
s2, analyzing the standard solution through gas chromatography to obtain peak areas of the DTBP and the internal standard substance in the standard solution, and calculating to obtain a correction factor of the DTBP according to the peak areas and the mass of the DTBP and the internal standard substance;
s3, freezing and crushing the polypropylene melt-blown material to obtain polypropylene melt-blown granules with the average particle size of 0.1-0.6 mm, and extracting the polypropylene melt-blown granules by using an extracting agent at the extraction temperature of 20-40 ℃ to obtain an extraction liquid as a DTBP pretreatment sample;
s4, adding the internal standard substance into the DTBP pretreatment sample to obtain a sample to be detected, analyzing the sample to be detected by gas chromatography under the same analysis condition as the standard solution to obtain peak areas of the DTBP and the internal standard substance, and calculating by using a correction factor of the DTBP to obtain the DTBP content in the polypropylene melt-spray material;
the extracting agent is acetone or ethanol,
the internal standard substance is one or more of n-hexane, n-pentane, n-octane or ethyl acetate;
the temperature of the freezing and crushing is less than or equal to 0 ℃, and the time of the freezing and crushing is 10 to 30s;
the chromatographic column adopted by the gas chromatography in the S4 is an Agilent capillary chromatographic column HP 101, the length of the column is 50m, the inner diameter is 0.32mm, and the thickness of a liquid film is 0.3 mu m;
the detection conditions of the gas chromatography in the S4 are as follows: the temperature of a sample inlet is 70 to 120 ℃, the temperature of a detector is 200 to 250 ℃, the sample introduction quantity is 0.2 to 2 mu L, the split ratio is 15 to 30, and the carrier gas N 2 The flow is 0.5 to 1.2mL/min, the hydrogen flow is 40mL/min, and the air flow is 400mL/min;
the temperature rise program of the chromatographic column in the gas chromatography in the S4 is as follows: the temperature is initially kept for 3 to 10min at 40 to 80 ℃, and then is increased to 150 to 240 ℃ at the speed of 10 to 30 ℃/min, and is kept for 1 to 10min.
2. The method for detecting according to claim 1, wherein the mass ratio of DTBP to the internal standard substance in the standard solution is (1 to 3) to 1.
3. The assay method according to claim 1, wherein the cryo-pulverization is freezing using liquid nitrogen.
4. The method according to claim 1, wherein the extraction temperature in step S3 is from 30 ℃ to 40 ℃.
5. The method according to claim 1, wherein the extraction in step S3 is performed by ultrasonic extraction, shaking extraction or immersion extraction.
6. The assay of claim 5, wherein the ultrasonic extraction is ultrasonic extraction using a flowing water bath.
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