A method for detecting nitrogen-containing functional monomers in water-soluble acrylic resin

Abstract

The present application relates to the field of analytical detection, and more particularly to a method for detecting nitrogen-containing functional monomers in water-soluble acrylic resin. The steps include S1. preparing a water-soluble acrylic resin sample; S2. respectively performing Py-GCMS testing, FTIR testing and organic element analysis testing on the water-soluble acrylic resin sample; S3. analyzing the test results to determine the content of nitrogen-containing functional monomers in the water-soluble acrylic resin sample. The combination of FTIR testing, Py-GCMS testing and organic element analysis can accurately identify and analyze the synthetic monomers in the water-soluble acrylic product. By controlling the thickness of the sample and correcting the coefficient of the sample's transmittance data, the qualitative and quantitative analysis of nitrogen-containing functional monomers (such as acrylonitrile and acrylamide) in the resin can be achieved, and the detection results are more accurate, providing reliable data support for the component analysis of water-soluble acrylic resin products.

Description

Technical Field

[0001] The present invention relates to the field of analysis and detection, and in particular to a method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin. Background Art

[0002] In the functionalization modification of acrylic resins, the introduction of nitrogen-containing monomers has become a core approach to improving the material's water resistance, crosslinking density, and surface properties. However, existing detection systems often face multiple technical bottlenecks when accurately analyzing the types and contents of such monomers. Currently, the Kjeldahl method and the Dumas method are commonly used to analyze the nitrogen content in acrylic resins. The Kjeldahl method is a traditional analytical method that measures nitrogen content through sample digestion, ammonia conversion, and acid titration. The Dumas method converts organic nitrogen into ammonia by burning the sample, and then measures the ammonia content through a chemical reaction. However, these methods have low test accuracy and are unable to accurately locate nitrogen-containing functional monomers and determine the results. This results in a lack of detection technology support for resin analysis, and there are still technical blind spots.

[0003] Chinese patent application CN115902008A discloses a method for testing residual monomers in polyacrylate pressure-sensitive adhesives. The method involves completely dissolving the sample in dichloromethane to release the residual monomers. A large amount of methanol is then added to flocculate the acrylate pressure-sensitive adhesive polymer, separating the polymer from the residual monomers and ensuring accurate results. However, this method is only suitable for measuring conventional acrylic monomers and has limited detection capabilities for nitrogen-containing functional monomers.

[0004] The technical limitations of detection methods have severely hampered the development of high-performance acrylic resins. In the development of novel bio-based nitrogen-containing monomers (such as chitosan derivatives) and all-nitrogen heterocyclic crosslinkers, traditional methods are unable to accurately quantify trace active sites and struggle to distinguish the contributions of monomers in copolymerized and physically mixed states. Furthermore, industry standards for residual monomer limits (such as the gas chromatography-mass spectrometry method specified in SN / T3342-2012) further expose the inadequate capture capacity of existing technologies for trace targets in complex matrices. When salt-forming agents or crosslinking networks are present in the sample, the phase separation efficiency during the pretreatment stage decreases, directly leading to fluctuations in detection sensitivity. Therefore, developing a new method that can overcome spectral interferences, accurately trace nitrogen forms, and adapt to the needs of industrial rapid detection has become an inevitable choice for promoting the functionalization upgrade of acrylic resins. Summary of the Invention

[0005] A first aspect of the present invention provides a method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin, comprising the following steps:

[0006] S1. Prepare a water-soluble acrylic resin sample;

[0007] S2. Perform Py-GCMS (pyrolysis-gas chromatography mass spectrometry) test, FTIR (Fourier transform infrared spectroscopy) test and organic element analysis test on the water-soluble acrylic resin sample respectively;

[0008] S3. Analyze the test results to determine the nitrogen-containing functional monomer in the water-soluble acrylic resin sample and its content.

[0009] Currently, there are certain limitations in the detection of water-soluble acrylic resin, and it is difficult to qualitatively and quantitatively analyze the nitrogen-containing functional monomer information in the resin. Although Py-GCMS test, FTIR test and organic element analysis test can obtain some information, there is still a problem of low accuracy of test results. For example, although the pyrolysis-gas chromatography mass spectrometry technology can infer the monomer structure through characteristic cracking fragments, it has significant limitations in identifying amide groups and other easily decomposed functional groups: low content of acrylamide is difficult to retain complete molecular information, and indirect correlation of fragment ion peaks is required, which not only increases the complexity of analysis, but also may lead to misjudgment under the interference of homologues. In addition, although the organic element analysis method can determine the total nitrogen content, it cannot distinguish the source attribute of nitrogen - the acrylamide monomer in the resin, the residual initiator nitrogen-containing byproduct or environmental pollutants show the same nitrogen signal in element analysis, which causes systematic deviation between the quantitative results and the true monomer content. Under such background, the present application innovatively provides an analysis method for nitrogen-containing functional monomers in water-soluble acrylic resin, which combines Py-GCMS (pyrolysis-gas chromatography mass spectrometry) test, FTIR (Fourier transform infrared spectroscopy) test and organic element analysis test, and can qualitatively and quantitatively analyze the nitrogen-containing functional monomers in the resin, and the determination result is accurate, which provides strong support for the detection means for the analysis of acrylic resin.

[0010] In some embodiments, S1 includes: taking the water-soluble acrylic resin to be tested, heating to remove moisture and processing into a thin film to obtain a water-soluble acrylic resin sample.

[0011] Optionally, the heating temperature in S1 is 100-160℃, and the heating time is 2-6h.

[0012] More optionally, the heating temperature in S1 is 105℃, and the heating time is 4h.

[0013] More optionally, the heating temperature in S1 is 160℃, and the heating time is 4h. The present application sets the sample preparation scheme as follows: the sample is heated at 100-160℃ for 2-6h to obtain a dried sample, and the dried sample is sent for FTIR, Py-GCMS and organic element analysis, which effectively avoids the pollution and loss of the sample during the splitting process.

[0014] Optionally, the thickness of the water-soluble acrylic resin sample is 2-50 μm; more optionally 5-20 μm, for example 10 μm. It is found that if the sample is not controlled in thickness during sample preparation, the analysis process of the infrared test data will be affected, and the accuracy of the corresponding test results will be reduced, and the reliability of the detection method will be affected. When the thickness of the resin sample is 10 μm, the signals of different depths are avoided from being superimposed together, and the accuracy and reliability of the infrared test results are improved.

[0015] In some embodiments, the raw materials for preparing the water-soluble acrylic resin include synthetic monomers, basic compounds, initiators and solvents.

[0016] The synthetic monomers of the water-soluble acrylic resin can include, for example, acrylic acid, methacrylic acid, acrylonitrile, acrylamide, methyl methacrylate, ethyl methacrylate, styrene, ethyl acrylate, butyl acrylate, lauryl acrylate, isooctyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycidyl methacrylate, N-methylol acrylamide, and the like.

[0017] Optionally, the synthetic monomers of the water-soluble acrylic resin include acrylic acid, methacrylic acid, acrylonitrile and acrylamide.

[0018] Optionally, the initiator includes a persulfide, which can include, for example, ammonium persulfate, potassium persulfate, sodium persulfate, and the like.

[0019] The solvent can be water.

[0020] In some optional embodiments, the test conditions of the FTIR test include a resolution of 2-5 cm -1 , and a scanning number of 20-40.

[0021] More optionally, the resolution is 4 cm -1 , and the scanning number is 32.

[0022] The FTIR test is specifically performed by using an ATR (attenuated total reflection) method.

[0023] In some optional embodiments, the test conditions of the Py-GCMS test include:

[0024] Chromatographic column specifications: 30m*0.25mm*0.25um; column oven temperature: 50-65℃; injection port temperature: 300-350℃; injection mode: split; split ratio: (90-110): 1; temperature program: 50-65℃, hold for 1-3min; increase to 300-350℃ at 10-20℃ / min, hold for 10-15min; ion source temperature: 200-250℃; interface temperature: 300-350℃; scan ion scanning range: 20-700amu; cracker interface temperature: 280-320℃; oven temperature: 500-600℃.

[0025] More optionally, the test conditions of the Py-GCMS test include:

[0026] Chromatographic column specifications: 30m*0.25mm*0.25um; column oven temperature: 60℃; injection port temperature: 320℃; injection mode: split; split ratio: 100:1; temperature program: 60℃, hold for 2min; increase to 320℃ at 20℃ / min, hold for 13min; ion source temperature: 230℃; interface temperature: 320℃; solvent delay: 0.6min; scan ion range: 29-600amu; cracker interface temperature: 300℃; oven temperature: 550℃.

[0027] The Py-GCMS test was performed using a PGC (portable gas chromatograph), such as the Shimadzu GCMS-QP2020 gas chromatograph-mass spectrometer. The chromatographic column was a TG-5silMS, and the pyrolyzer was a FrontierLab PY-3030D.

[0028] Optionally, in S2, the transmittance of the nitrogen-containing functional monomer of the water-soluble acrylic resin is obtained by Py-GCMS testing, the transmittance is coefficient-corrected, and the influencing factor of the mass ratio of the nitrogen-containing functional monomer is calculated based on the corrected transmittance, and the mass content of the nitrogen-containing functional monomer of the water-soluble acrylic resin is determined based on the calculation of the influencing factor.

[0029] More optionally, the calculation formula of the impact factor is:

[0030]

[0031] Wherein: n is the influencing factor, x and y are the transmittances of different nitrogen-containing functional monomers, and a and b are the mass contents of different nitrogen-containing functional monomers (x and a correspond to the same nitrogen-containing functional monomer, and y and b correspond to the same nitrogen-containing functional monomer).

[0032] The nitrogen-containing functional monomers include acrylonitrile and acrylamide. In the above formula, n is the influencing factor, x is the transmittance of acrylonitrile, y is the transmittance of acrylamide, a is the mass content of acrylonitrile, and b is the mass content of acrylamide.

[0033] For example, in water-soluble acrylic acid, the total amount of acrylamide (molecular weight 71) and acrylonitrile (molecular weight 53) is about 15%, and the infrared spectrum shows that the concentration of acrylamide at 1665 cm -1 The transmittance is x%, 2240cm -1 If the intensity transmittance is y%, then the mass content ratio of acrylamide to acrylonitrile is x:((10-14)y). Assuming x:y=1:3, the mass content range of acrylamide is 1.00-1.36%, and the mass content of acrylonitrile is 13.64-14%. The error mass content range is within 0.5%.

[0034] This method uses precise infrared spectroscopy analysis and transmittance coefficient correction to accurately measure the acrylamide and acrylonitrile contents in water-soluble acrylic resin samples. The corrected data not only improves the accuracy of the measurement results but also makes the mass distribution of acrylamide and acrylonitrile more specific, reducing the error range to less than 0.5%. This provides reliable data support for the subsequent development and analysis of water-soluble acrylic resin products.

[0035] Optionally, the test conditions of the organic element analysis test include: combustion tube temperature: 1050-1200° C.; reduction tube temperature: 800-920° C.; helium flow rate: 100-300 mL / min; oxygen flow rate: 10-20 mL / min.

[0036] More optionally, the test conditions of the organic element analysis test include: combustion tube temperature: 1170° C.; reduction tube temperature: 850° C.; helium flow rate: 200 mL / min; oxygen flow rate: 13 mL / min.

[0037] Beneficial effects:

[0038] The present invention provides a method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin, which has the following advantages:

[0039] (1) The present invention explores a new analytical method that combines multiple technical means. With the help of FTIR testing, Py-GCMS testing and organic element analysis, it can accurately identify and analyze the synthetic monomers in water-soluble acrylic acid products, especially the qualitative and quantitative analysis of nitrogen-containing functional monomers in the products.

[0040] (2) The present application controls the thickness of the sample, effectively improves the accuracy of the FTIR test result, and can quickly judge the main synthetic monomers in the water-soluble acrylic acid product. The FTIR test method adopted is simple to operate, the result is accurate, and provides strong support for the quality control of the product.

[0041] (3) The present application corrects the transmittance coefficient of the sample after Py-GCMS testing, calculates the influence factor of the nitrogen-containing functional monomer after calibration, and further calculates the mass content of the nitrogen-containing functional monomer (such as acrylonitrile and acrylamide) in the sample based on the influence factor, so that the data obtained by this method is more accurate.

[0042] (4) The present application realizes the accurate quantification of nitrogen-containing functional monomers such as acrylonitrile and acrylamide by qualitative analysis by Py-GCMS, combined with the relative quantification of FTIR infrared spectrum and organic element analysis. This achievement provides an important basis for the formula optimization and performance improvement of the water-soluble acrylic acid product.

[0043] (5) In order to ensure the accuracy and reliability of the analysis, the present application formulates a complete sample disassembly scheme. The scheme specifies the collection, processing and disassembly steps of the sample in detail, effectively avoiding the pollution and loss of the sample in the disassembly process. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is the total ion flow chart of the dried sample of No. 1 sample;

[0045] Figure 2 is the Py-GCMS test result (retention time: 1.635 min, acrylonitrile) of the dried sample of No. 1 sample;

[0046] Figure 3 is the Py-GCMS test result (retention time: 1.735 min, acrylonitrile fragment) of the dried sample of No. 1 sample;

[0047] Figure 4 is the Py-GCMS test result (retention time: 6.215 min, polyacrylonitrile fragment) of the dried sample of No. 1 sample;

[0048] Figure 5 is the Py-GCMS test result (retention time: 7.325 min, polyacrylamide fragment) of the dried sample of No. 1 sample;

[0049] Figure 6 is the Py-GCMS test result (retention time: 7.550 min, polyacrylamide fragment) of the dried sample of No. 1 sample;

[0050] Figure 7Py-GCMS test result of the sample dried at 1 (retention time: 10.895 min, polyacrylonitrile fragment);

[0051] Figure 8 Py-GCMS test result of the sample dried at 1 (retention time: 11.815 min, polyacrylonitrile fragment);

[0052] Figure 9 FTIR test result graph of the sample dried at 1; DETAILED DESCRIPTION

[0053] Note: If not specified, the instruments and reagents used in the present application are commercially available.

[0054] EMBODIMENT

[0055] The embodiment provides a detection method of a nitrogen-containing functional monomer in a water-soluble acrylic resin, and comprises the following steps:

[0056] S1. Preparing a water-soluble acrylic resin sample: taking the water-soluble acrylic resin to be detected, heating to remove water and processing into a film to obtain a water-soluble acrylic resin sample;

[0057] S2. respectively performing FTIR test, Py-GCMS test and organic element analysis test on the water-soluble acrylic resin sample;

[0058] S3. analyzing the test results to determine the nitrogen-containing functional monomer in the water-soluble acrylic resin sample and the content of the nitrogen-containing functional monomer.

[0059] The heating temperature in S1 is 105 DEG C, and the heating time is 4 h.

[0060] The thickness of the water-soluble acrylic resin sample is 10 μm.

[0061] The water-soluble acrylic resin to be detected in the embodiment is a self-made standard product. The raw materials for preparing the water-soluble acrylic resin include synthetic monomers (see Table 1 for information), an alkaline compound (sodium hydroxide), 0.5 g of an initiator (ammonium persulfate) and 100 mL of a solvent (water).

[0062] The addition amount of the synthetic monomer is 100 g.

[0063] Table 1

[0064]

[0065] Note: The values in Table 1 represent the addition amount of the raw materials, and the unit is wt%; " / " represents no addition.

[0066] The preparation steps of the water-soluble acrylic resin include: adding a synthetic monomer, an alkaline compound, and an initiator to water in sequence, heating to 70° C. to perform a free radical polymerization reaction for 6 hours to obtain a water-soluble acrylic resin, which is a homemade standard product; and preparing samples No. 1 to No. 4 according to the component information in Table 1.

[0067] The FTIR test adopts the ATR method, and the test conditions are: resolution of 3cm -1 , the number of scans is 32.

[0068] The test conditions of the Py-GCMS test include:

[0069] Chromatographic column: TG-5silMS, specifications 30m*0.25mm*0.25um; column oven temperature: 60℃; injection port temperature: 320℃; injection mode: split; split ratio: 100:1; temperature program: 60℃, hold for 2min; increase to 320℃ at 20℃ / min, hold for 13min; ion source temperature: 230℃; interface temperature: 320℃; solvent delay: 0.6min; Scan ion scanning range: 29-600amu; cracker is Frontier Lab PY-3030D, interface temperature: 300℃, oven temperature: 550℃.

[0070] The Py-GCMS test was conducted using a PGC (portable gas chromatograph) device, specifically a Shimadzu GCMS-QP2020 gas chromatograph-mass spectrometer from Japan.

[0071] The test conditions for the organic element analysis test include: combustion tube temperature: 1170° C.; reduction tube temperature: 850° C.; helium flow rate: 200 mL / min; oxygen flow rate: 13 mL / min; and a sample injection volume of 0.1 g.

[0072] Performance Testing

[0073] The water-soluble acrylic resin (sample 1) that was heated to remove moisture was subjected to Py-GCMS testing. The total ion elution curve was shown in the figure. Figure 1 .

[0074] The Py-GCMS test results of samples 1 to 4 are shown in Figures 2 to 8 .

[0075] From the results in the figure, it can be seen that when the retention time is 1.635min, the characteristic peak of acrylonitrile appears in the spectrum; when the retention time is 1.735min, the characteristic peak of methacrylonitrile appears in the spectrum; when the retention time is 6.215min, the characteristic peak of acrylonitrile dimer appears in the spectrum; when the retention time is 7.325min, the characteristic peak of acrylamide fragment appears in the spectrum; when the retention time is 7.550min, the characteristic peak of polyacrylamide fragment appears in the spectrum; when the retention time is 10.895min, the characteristic peak of polyacrylonitrile appears in the spectrum; when the retention time is 11.815min, the characteristic peak of polyacrylamide appears in the spectrum. Further analysis of these results yields the following conclusions:

[0076] 1) When acrylonitrile was used as the synthetic monomer, the samples could be decomposed and recombined to obtain information on methacrylonitrile. According to the Py-GCMS area normalization method, the mass ratio of acrylonitrile to methacrylonitrile may be in the range of (1.56-6.96):1.00.

[0077] 2) When acrylamide is used as a synthetic monomer, due to its high polarity, the final elution information in the Py-GCMS is relatively small. However, analysis can be performed using the proton peak of polyacrylamide (acrylamide dimer). Sample results show that information on the dimer of acrylamide can be detected when the content of acrylamide in the acrylic resin is 10%.

[0078] Based on the above results, the testing method of the present invention can be used to perform qualitative analysis on nitrogen-containing functional monomers (such as acrylonitrile and acrylamide) in acrylic resin.

[0079] The FTIR test results of the dried sample No. 1 are shown in Figure 9 .

[0080] Based on the FTIR test results of each sample, the concentration of acrylonitrile and acrylamide in the sample was quantitatively analyzed. The specific analysis steps are as follows:

[0081] 1) According to the characteristic absorption peak of acrylonitrile (2240cm -1 ) and the characteristic absorption peak of acrylamide (1665 cm -1 ) intensity comparison, combined with the calibration coefficient to calibrate the transmittance of acrylonitrile and acrylamide. The specific operation is: open the infrared spectrum of the sample, process the data in sequence, obtain the absorbance, automatically calibrate the baseline, process the data again, obtain the transmittance, save the data in CSV format, and obtain the sample at 2240cm -1 and 1665cm -1 The transmittance under the characteristic peak is calibrated by determining the calibration coefficient based on the actual mass ratio of acrylonitrile and acrylamide in the sample, and the transmittance result of the sample is calibrated by the calibration coefficient.

[0082] 2) According to the calibrated transmittance, set the influence factor n, and calculate n using the following formula:

[0083]

[0084] Wherein, a is the mass content of acrylonitrile, b is the mass content of acrylamide, and x is the characteristic absorption peak of acrylonitrile (2240 ​​cm -1 ) under the transmittance, y is the characteristic absorption peak of acrylamide (1665cm -1 The calculation results of the influencing factors are shown in Table 2.

[0085] Table 2

[0086]

[0087] According to the calculation results in the above table, the influence coefficient factor of acrylonitrile relative to acrylamide is about 10-14, and the mass content of acrylamide and acrylonitrile in the sample can be further calculated.

[0088] For example, in water-soluble acrylic acid, the total amount of acrylamide (molecular weight 71) and acrylonitrile (molecular weight 53) is about 15%, and the infrared spectrum shows that the concentration of acrylamide at 1665 cm -1 The transmittance is x%, 2240cm -1 If the intensity transmittance is y%, then the mass content ratio of acrylamide to acrylonitrile is x:((10-14)y). Assuming x:y=1:3, the mass content range of acrylamide is 1.00-1.36%, and the mass content of acrylonitrile is 13.64-14%. The error mass content range is within 0.5%.

[0089] An organic element analyzer was used to determine the nitrogen content in samples 1 to 4. The N element in the standard was recorded as the theoretical nitrogen content N1, and the results of the organic element analyzer were recorded as the measured nitrogen content N2. The offset rate of the two test results was calculated (offset rate = (measured value - theoretical value) / measured value × 100%) and recorded in the table below.

[0090]

[0091] According to the calculation results in the above table, it can be seen that the deviation between the measured nitrogen content and the theoretical nitrogen content obtained by the organic element analyzer of the present invention is very small, with the offset rate as low as 0.1%. The measured nitrogen content results are basically consistent, indicating that the test results are highly accurate.

Claims

1. A method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin, characterized in that: The following steps are involved: S1. Prepare water-soluble acrylic resin sample; S2. Py-GCMS, FTIR, and organic element analysis were performed on the water-soluble acrylic resin samples. S3. Analyze the test results to determine the nitrogen-containing functional monomer and its content in the water-soluble acrylic resin sample; In S2, the nitrogen-containing functional monomers in the acrylic resin are qualitatively analyzed by Py-GCMS, the transmittance of the nitrogen-containing functional monomers in the water-soluble acrylic resin is obtained by FTIR testing, the transmittance is coefficient-corrected, and the influence factor of the mass ratio of the nitrogen-containing functional monomers is calculated based on the corrected transmittance, and the mass content of the nitrogen-containing functional monomers in the water-soluble acrylic resin is determined based on the influence factor; The nitrogen-containing functional monomers include acrylonitrile and acrylamide; The calculation formula of the impact factor is: Wherein: n is the influencing factor, x is the transmittance of acrylonitrile, y is the transmittance of acrylamide, a is the mass content of acrylonitrile, and b is the mass content of acrylamide.

2. The method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin according to claim 1, wherein Said S1 comprises: taking a water-soluble acrylic resin to be tested, heating it to remove moisture and processing it into a film to obtain a water-soluble acrylic resin sample; The thickness of the water-soluble acrylic resin sample is 2-50 μm.

3. The method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin according to claim 2, wherein: The heating temperature in S1 is 100-160° C., and the heating time is 2-6 hours.

4. The method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin according to claim 1, wherein The test conditions of the FTIR test include: a resolution of 2-5 cm -1 , the number of scans is 20-40.

5. The method for detecting nitrogen-containing functional monomers in water-soluble acrylic resin according to claim 1, wherein The test conditions of the Py-GCMS test include: Chromatographic column specifications: 30m*0.25mm*0.25um; column oven temperature: 50-65℃; injection port temperature: 300-350℃; injection mode: split; split ratio: (90-110):

1.

6. The method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin according to claim 5, wherein: The temperature program of the Py-GCMS test is: 50-65°C, hold for 1-3 minutes; increase to 300-350°C at 10-20°C / min, hold for 10-15 minutes.

7. The method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin according to claim 6, wherein: The test conditions of the Py-GCMS test also include: ion source temperature: 200-250°C; interface temperature: 300-350°C; Scan ion scanning range: 20-700amu; cracker interface temperature: 280-320°C, furnace temperature: 500-600°C.

8. The method for detecting nitrogen-containing functional monomers in a water-soluble acrylic resin according to claim 1, wherein The test conditions of the organic element analysis test include: combustion tube temperature: 1050-1200° C.; reduction tube temperature: 800-920° C.; helium flow rate: 100-300 mL / min; oxygen flow rate: 10-20 mL / min.

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