CN-121994944-A - Method for measuring free acrylonitrile content in acrylonitrile-butadiene rubber

Abstract

The invention relates to a method for measuring the free acrylonitrile content in acrylonitrile-butadiene rubber, which comprises the steps of weighing a measured (H) NBR sample, placing the measured (H) NBR sample in a headspace bottle, then transferring a BHT-THN solution, capping and sealing the solution, sending the solution into a headspace gas chromatography-mass spectrometry combined instrument, measuring the total ion flow chromatogram, integrating chromatographic peaks from acrylonitrile to obtain peak areas, and substituting the peak areas into a standard working curve of free acrylonitrile concentration and peak areas to obtain the free acrylonitrile content in the measured (H) NBR sample. Compared with the prior art, the invention solves the problem of difficult detection of the free acrylonitrile in the (H) NBR, and can further improve the accuracy, the detection limit and the like of the detection of the free acrylonitrile content in the (H) NBR.

Inventors

• XIONG FENG
• GONG GUANGBI
• ZHANG XIAOFAN
• WANG SIZHI
• ZHANG YUTIAN
• ZHAO GUIJUN
• LIU ZHONGSHI
• ZHENG HONGBING
• CHEN FEI
• HAN YAN

Assignees

• 中石油(上海)新材料研究院有限公司
• 中国石油天然气股份有限公司

Dates

Publication Date

20260508

Application Date

20241108

Claims (10)

1. 1. A method for measuring the content of free acrylonitrile in acrylonitrile-butadiene rubber is characterized by weighing a measured (H) NBR sample, placing the measured (H) NBR sample in a headspace bottle, then removing a BHT-THN solution, capping and sealing the sample, sending the sample into a headspace gas chromatography-mass spectrometry combined instrument, measuring the total ion flow chromatogram of the sample, integrating chromatographic peaks from acrylonitrile to obtain peak areas, and substituting the peak areas into a standard working curve of the concentration and the peak areas of free acrylonitrile to obtain the content of free acrylonitrile in the measured (H) NBR sample.
2. 2. The method for determining the free acrylonitrile content in an acrylonitrile-butadiene rubber according to claim 1, wherein the (H) NBR sample to be tested is NBR, partially hydrogenated or fully hydrogenated NBR.
3. 3. The method for determining the free acrylonitrile content in the acrylonitrile-butadiene rubber according to claim 1, wherein the mass concentration of BHT in the BHT-THN solution is 180-220mg/L, and the addition amount of the tested (H) NBR sample and the BHT-THN solution is 0.3g:4-6L.
4. 4. The method for determining the free acrylonitrile content in the acrylonitrile-butadiene rubber according to claim 1, wherein in the headspace gas chromatography-mass spectrometer, the headspace gas chromatography conditions are: detecting by a single four-stage rod mass spectrum detector; the headspace heating temperature is 90-120 ℃, the headspace balance time is 30-300 min, the sample injection needle temperature is 110 ℃, the transmission line temperature is 120 ℃, the sample injection pressurization is 15psi, the sample injection pressurization time is 1.0min, and the sample injection time is 0.1min; the temperature of the gas chromatograph sample inlet is 200 ℃, the split ratio is 50:1, and the carrier gas is helium.
5. 5. The method for measuring the free acrylonitrile content in the acrylonitrile-butadiene rubber according to claim 4, wherein the temperature is raised to 50 ℃ for 5min, 5 ℃ per min to 150 ℃ for 20min; The volume fraction purity of the helium is higher than 99.999%.
6. 6. The method according to claim 4, wherein the chromatographic column is an HP-FFAP polyethylene glycol nitrobenzene modified capillary column with a column specification of 50m x 0.32mm x 0.5. Mu.m.
7. 7. The method for determining the free acrylonitrile content in the acrylonitrile-butadiene rubber according to claim 1, wherein in the headspace gas chromatography-mass spectrometer, mass spectrometry detection conditions are as follows: The temperature of the chromatographic-mass spectrometry interface is 150 ℃; The ion source of the mass spectrum is an electron ionization source EI, the temperature is 200 ℃, and the electron energy is 70eV; the mass analyzer is a four-level rod mass analyzer; The scanning mode is ion monitoring mode quantification; The mass spectrum scanning range is 33-300 m/z; the solvent delay time is 1 to 5 minutes.
8. 8. The method according to claim 7, wherein the intensity of the characteristic ion m/z=53 is extracted in the scanning mode.
9. 9. The method for determining the free acrylonitrile content in an acrylonitrile-butadiene rubber according to claim 1, wherein the NBR without free acrylonitrile is added to eliminate the matrix effect when establishing a standard working curve.
10. 10. The method for measuring the free acrylonitrile content in the acrylonitrile-butadiene rubber according to claim 1, wherein the process conditions for establishing the standard working curve are the same as those for measuring the chromatographic peak area of the (H) NBR sample to be measured.

Description

Method for measuring free acrylonitrile content in acrylonitrile-butadiene rubber Technical Field The invention belongs to the technical field of acrylonitrile content measurement, and relates to a method for measuring the content of free acrylonitrile in acrylonitrile-butadiene rubber. Background Hydrogenated nitrile rubber (HNBR) is a rubber material with a highly saturated molecular backbone, which is mainly prepared by hydrogenation of nitrile rubber (NBR, i.e. acrylonitrile-butadiene rubber). The acrylonitrile unit in the HNBR molecular chain provides excellent oil resistance and high tensile strength of the material, while the hydrogenated butadiene unit can provide good heat resistance, aging resistance and low temperature performance, and the residual small amount of butadiene can still provide unsaturated bonds required for rubber crosslinking, so that the elastic characteristics of the butadiene unit can be maintained. Therefore, HNBR has wide application in the fields of automobiles, petroleum, mechanical industries and the like, and particularly in the fields of static and dynamic seal rubber seals and the like, such as oil resistance, aging resistance, high temperature resistance, tear resistance, compression deformation resistance and the like. Acrylonitrile in HNBR is divided into combined acrylonitrile and free acrylonitrile, and the content of the acrylonitrile determines various application performances of HNBR. The present method for measuring the bound acrylonitrile mainly comprises infrared spectroscopy, gas chromatography, kjeldahl nitrogen determination method and the like (Xu Jiao, tan Shuaixia, yao Zhiping, and the like; the research progress of the bound acrylonitrile content measurement in NBR [ J ]. Special rubber products, 2014,35 (05): 74-80.). The catalyst of NBR in the hydrogenation reaction process can be deactivated due to the fact that the content of free acrylonitrile is too high, the content of free acrylonitrile can influence the end use of products, and the content of free acrylonitrile is definitely required to be limited in the export process of domestic NBR users and NBR products, so that the detection of the content of free acrylonitrile is particularly important. At present, the content of free acrylonitrile is mainly measured by a headspace gas chromatography (petrochemical industry, 2015,44 (06): 758-761), the standard adding recovery rate of the method is 94.8% -98.6%, the relative standard deviation is less than 3.0% (n=6), the minimum detection limit of the method is 1.8mg/kg, and the detection limit and the accuracy of the method can be seen to be improved. Therefore, the method has important practical significance for further improving the accuracy and the detection limit of the free acrylonitrile content detection in the (H) NBR so as to realize the high-precision detection of the free acrylonitrile in the (H) NBR. Disclosure of Invention The invention aims to provide a method for measuring the free acrylonitrile content in acrylonitrile-butadiene rubber, so as to further improve the accuracy and the detection limit of the free acrylonitrile content detection in (H) NBR. The aim of the invention can be achieved by the following technical scheme: A method for measuring the content of free acrylonitrile in acrylonitrile-butadiene rubber includes such steps as weighing the sample of (H) NBR to be measured, loading it in overhead bottle, moving the solution of BHT-THN, sealing, loading it in overhead gas chromatograph-mass spectrometer, measuring the total ion flow chromatogram, integrating the chromatographic peak from acrylonitrile to obtain peak area, and substituting it in the standard working curve of concentration and peak area of free acrylonitrile to obtain the content of free acrylonitrile in the sample of (H) NBR to be measured. Further, the (H) NBR sample to be tested is NBR, partially hydrogenated or fully hydrogenated NBR. Further, in the BHT-THN solution, the mass concentration of the BHT (2, 6-di-tert-butyl-4-methylphenol) is 180-220mg/L, and the addition amount of the tested (H) NBR sample and the BHT-THN (tetrahydronaphthalene) solution is 0.3g:4-6L. Further, in the headspace gas chromatography-mass spectrometer, the headspace gas chromatography conditions are: detecting by a single four-stage rod mass spectrum detector; the headspace heating temperature is 90-120 ℃, the headspace balance time is 30-300 min, the sample injection needle temperature is 110 ℃, the transmission line temperature is 120 ℃, the sample injection pressurization is 15psi, the sample injection pressurization time is 1.0min, and the sample injection time is 0.1min; the temperature of the gas chromatograph sample inlet is 200 ℃, the split ratio is 50:1, and the carrier gas is helium. Further, the temperature-raising program is that the column temperature is kept at 50 ℃ for 5min, and the temperature is raised to 150 ℃ for 20min; The volume fraction purity of the helium is