A method for determining the anhydride value in anhydride-containing copolymers after derivatization

Abstract

The application provides a method for determining the acid anhydride value in a copolymer containing acid anhydride after derivatization, which comprises the following steps: after the reaction material of the copolymer containing acid anhydride and the acid anhydride group is subjected to a derivatization reaction by a derivatization reagent, the residual content of the derivatization reagent is detected by liquid chromatography, and the acid anhydride value in the copolymer containing acid anhydride is calculated. The application indirectly determines the acid anhydride value content in the copolymer containing acid anhydride by adopting the liquid chromatography external standard method to analyze the consumption of the derivatization reagent, avoids the interference of the hydrolyzed dicarboxylic acid and other acidic substances in the copolymer containing acid anhydride on the test result, has high detection accuracy, and thus better controls and optimizes the performance and downstream application of the copolymer containing acid anhydride.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and in particular to a method for determining the acid anhydride value in copolymers containing acid anhydrides after derivatization. Background Technology

[0002] Olefin-anhydride copolymers are polymeric compounds copolymerized from olefins and anhydride monomers. The olefin monomers can be ethylene, styrene, propylene, etc., while the anhydride monomers can be maleic anhydride, phthalic anhydride, etc. Olefin-anhydride copolymers possess good thermal stability, chemical resistance, and mechanical properties, and can be used to prepare polymeric materials, coatings, adhesives, etc. Among these, olefin-maleic anhydride copolymers are widely used in printing inks, coatings, adhesives, and plastics, exhibiting good adhesion and water resistance. The anhydride value of an olefin-anhydride copolymer refers to the content of anhydride groups in the copolymer, and it has a significant impact on the copolymer's properties. The magnitude of the anhydride value directly affects the copolymer's chemical reactivity, thermal stability, adhesion, and solubility.

[0003] Therefore, in practical applications, accurately determining the anhydride value of olefin-anhydride copolymers is of great significance for ensuring product quality and optimizing their application performance.

[0004] The main method for detecting the anhydride value of olefin-anhydride copolymers is chemical titration: ASTM-D3644 is currently the most commonly used method for determining anhydride content. It utilizes an excess of strong alkali (sodium hydroxide or potassium hydroxide) to react with the anhydride in the olefin-anhydride copolymer, and then uses acid-base titration to determine the remaining strong alkali in the system. The titration endpoint is the disappearance of the indicator color, and the anhydride content in the olefin-anhydride copolymer is calculated.

[0005] The few literature reports on the anhydride functional group content of olefin-anhydride copolymers mainly focus on differences in chemical titration hydrolysis methods. Zhou Wen et al. (see "Determination of Anhydride Content in Styrene-Maleic Anhydride Random Copolymers", Zhou Wen et al., Modern Plastics Processing and Application, Vol. 10, No. 5, pp. 19-21) used pyridine as a catalyst, and the olefin-anhydride copolymer could be completely hydrolyzed after standing at room temperature for 4 hours. Liao Zhengfu et al. (see "Synthesis and Performance Study of Styrene / Maleic Anhydride Copolymers", Liao Zhengfu et al., Elastomers, pp. 19-21) used excess sodium hydroxide solution as a hydrolysis reagent, heated under reflux for 1 hour, and then titrated the excess sodium hydroxide with hydrochloric acid. Pan Wenhui et al. ("Determination of Anhydride Functional Group Content in Styrene-Maleic Anhydride Copolymers", Proceedings of the 20th China Copper Clad Laminate Technology Symposium) used pyridine as a catalyst to hydrolyze styrene-maleic anhydride copolymers under reflux conditions.

[0006] However, none of the above methods can avoid the interference of hydrolyzed dicarboxylic acids and other acidic substances in the anhydride copolymer on the test results, thus affecting the accuracy of the results. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a method for determining the acid anhydride value in copolymers containing acid anhydrides after derivatization. This method avoids the interference of the hydrolyzed carboxylic acid moiety or other acidic substances on the measurement results in the chemical titration method. Compared with the titration method, this method is more accurate and reliable, and can more accurately determine the acid anhydride value in copolymers containing acid anhydrides, thereby better controlling and optimizing its performance and downstream applications.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for determining the anhydride value in anhydride-containing copolymers after derivatization, the method comprising:

[0010] The reaction material of the copolymer containing anhydride is subjected to derivatization reaction with an anhydride group by a derivatization reagent, and the remaining content of the derivatization reagent is detected by liquid chromatography to calculate the anhydride value in the copolymer containing anhydride.

[0011] It is worth noting that the anhydride-containing copolymers targeted in this invention differ from conventional maleic anhydride and other small-molecule anhydrides. When small-molecule anhydride compounds undergo hydrolysis, acid radicals can be directly distinguished using chromatographic detection. However, anhydride-containing copolymers are essentially combinations of compounds with different molecular weights. When detected chromatographically, they exhibit broad peaks, making quantitative detection difficult, and their accuracy is not superior to chemical titration. Furthermore, anhydride-containing copolymers are easily affected by water, carbon dioxide, and other elements in the air, resulting in the presence of acidic impurities or the generation of dibasic acids or small-molecule acids through hydrolysis. Chemical titration detects the total acid content in the anhydride-containing copolymer, failing to exclude interference from these impurities. To address this challenge, this invention first uses a derivatizing reagent to react with the anhydride groups in the anhydride-containing copolymer, and then uses liquid chromatography to determine the remaining derivatizing reagent, thereby calculating the anhydride value in the anhydride-containing copolymer. This detection method effectively avoids the influence of hydrolyzed dibasic acids in the anhydride-containing copolymer on the detection results and also avoids the influence of other acidic substances.

[0012] Preferably, the molar ratio of the anhydride-containing copolymer to the derivatizing reagent is 1:2 to 10, for example, it can be 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] Preferably, the temperature of the derivatization reaction is 80 to 100°C, for example, 80°C, 83°C, 85°C, 87°C, 89°C, 92°C, 94°C, 96°C, 98°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] Preferably, the derivatization reaction is carried out under reflux conditions.

[0015] Preferably, the derivatization reaction time is 50 to 100 min, for example, 50 min, 56 min, 62 min, 67 min, 73 min, 78 min, 84 min, 89 min, 95 min or 100 min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the derivatizing agent is a hydrazine compound and / or an acylhydrazine compound.

[0017] The key to this invention lies in the derivatization reagent. On one hand, the derivatization reagent must react fully with the acid anhydride; that is, almost all the acid anhydride in the sample must react with the derivatization reagent to ensure detection accuracy. Simultaneously, the derivatization reagent must not react with acidic substances such as acids to eliminate the influence of acids on the detection of acid anhydride. On the other hand, the product of the reaction between the derivatization reagent and the acid anhydride must not interfere with the detection of the derivatization reagent itself during liquid chromatography, enabling accurate quantitative testing of the derivatization reagent. Through extensive research, this invention selects hydrazine compounds and / or acylhydrazine compounds, which have the advantage of rapid reaction speed.

[0018] Preferably, the derivatizing agent comprises any one or a combination of at least two of 1-dimethylaminonaphthalene-5-sulfonylhydrazine, benzenesulfonylhydrazine, 2,4,6-triisopropylbenzenesulfonylhydrazine, 4-fluorobenzenesulfonylhydrazine, 4-hydrazino-N,N-dimethylaniline, 4-chlorophenylhydrazine, or 4-(triethylamine)benzenesulfonylhydrazine, wherein a typical but non-limiting combination is the combination of 1-dimethylaminonaphthalene-5-sulfonylhydrazine and benzenesulfonylhydrazine, and 2,4,6-triisopropylbenzenesulfonylhydrazine. Combinations of hydrazine and benzenesulfonyl hydrazine, combinations of 1-dimethylaminonaphthalene-5-sulfonyl hydrazine and 2,4,6-triisopropylbenzenesulfonyl hydrazine, combinations of 4-fluorobenzenesulfonyl hydrazine and benzenesulfonyl hydrazine, combinations of 1-dimethylaminonaphthalene-5-sulfonyl hydrazine and 4-fluorobenzenesulfonyl hydrazine, combinations of 4-hydrazyl-N,N-dimethylaniline and benzenesulfonyl hydrazine, combinations of 1-dimethylaminonaphthalene-5-sulfonyl hydrazine and 4-(triethylamine)benzenesulfonyl hydrazine, preferably 1-dimethylaminonaphthalene-5-sulfonyl hydrazine.

[0019] Preferably, the derivatizing reagent is added to the derivatization reaction in the form of a derivatizing reagent solution.

[0020] Preferably, the concentration of the derivatization reagent solution is 3 to 30 wt%, for example, it can be 3 wt%, 6 wt%, 9 wt%, 12 wt%, 15 wt%, 18 wt%, 21 wt%, 24 wt%, 27 wt%, or 30 wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] Preferably, the solvent of the derivatization reagent solution includes anhydrous DMF and / or anhydrous DMA.

[0022] Preferably, the molecular weight of the anhydride-containing copolymer is ≥3000, for example, it can be 3000, 13000, 24000, 35000, 46000, 56000, 67000, 78000, 89000 or 100000, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 3000 to 100000.

[0023] Preferably, the anhydride-containing copolymer includes an olefin-anhydride copolymer.

[0024] Preferably, the anhydride-containing copolymer is first dissolved in an organic solvent and then subjected to a derivatization reaction.

[0025] Preferably, the organic solvent comprises anhydrous DMF and / or anhydrous DMA.

[0026] Preferably, the ratio of the anhydride-containing copolymer to the organic solvent is 0.01 to 0.1:1 g / mL, for example, it can be 0.01:1 g / mL, 0.02:1 g / mL, 0.03:1 g / mL, 0.04:1 g / mL, 0.05:1 g / mL, 0.06:1 g / mL, 0.07:1 g / mL, 0.08:1 g / mL, 0.09:1 g / mL or 0.1:1 g / mL, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the mobile phase for detection by liquid chromatography includes a first mobile phase and a second mobile phase.

[0028] Preferably, the first mobile phase is water.

[0029] Preferably, the second mobile phase is methanol.

[0030] Preferably, the volume ratio of the first mobile phase to the second mobile phase is (30-70):(30-70), for example, it can be 30:30, 30:30, 30:30, 30:30, 30:30, 30:30, 30:30, 30:30, 30:30, 30:30, or 30:30, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the flow rate of the mobile phase in the liquid chromatography detection is 0.8 to 1.2 mL / min, for example, it can be 0.8 mL / min, 0.85 mL / min, 0.89 mL / min, 0.94 mL / min, 0.98 mL / min, 1.03 mL / min, 1.07 mL / min, 1.12 mL / min, 1.16 mL / min or 1.2 mL / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0032] Preferably, the instrument used for liquid chromatography detection is an Agilent 1260II high-performance liquid chromatograph.

[0033] Preferably, the chromatographic column used for liquid chromatography detection is an Agilent XDB-C18.

[0034] Preferably, the detector used for liquid chromatography detection is a VWD detector.

[0035] Preferably, the size of the chromatographic column used for liquid chromatography detection is 5μm×4.6mm×250mm.

[0036] Preferably, the column temperature for liquid chromatography detection is 30-40°C, for example, 30°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the wavelength of the monitor for liquid chromatography detection is 220–240 nm, and more preferably 230 nm.

[0038] Preferably, the injection volume in the liquid chromatography detection is 1.0 to 10.0 μL, for example, it can be 1.0 μL, 2 μL, 3 μL, 4 μL, 5 μL, 6 μL, 7 μL, 8 μL, 9 μL or 10.0 μL, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the liquid chromatography detection employs an isocratic elution procedure.

[0040] As a preferred technical solution of the present invention, the method includes the following steps:

[0041] A copolymer containing anhydride with a molecular weight ≥3000 is dissolved in anhydrous DMF and / or anhydrous DMA. The resulting solution is then subjected to a derivatization reaction with a 3–30 wt% derivatizing reagent solution. The molar ratio of the copolymer containing anhydride to the derivatizing reagent is 1:2–10. The derivatization reaction is carried out under reflux at 80–100 °C for 50–100 min. The remaining content of the derivatizing reagent in the obtained reaction mixture is then determined by liquid chromatography, and the anhydride value in the copolymer containing anhydride is calculated.

[0042] The mobile phase for liquid chromatography detection includes water and methanol, with a volume ratio of water to methanol of (30–70):(30–70), and a flow rate of 0.8–1.2 mL / min.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] (1) The method for determining the acid anhydride value in copolymers containing acid anhydride after derivatization provided by the present invention reverses the content of acid anhydride functional groups by measuring the consumption of the derivatization reagent 1-dimethylaminonaphthalene-5-sulfonylhydrazine; it solves the problem that chemical titration cannot deduct the trace amounts of carboxylic acid functional groups that may have been hydrolyzed in the sample, resulting in the measured value being higher than the actual value.

[0045] (2) The method for determining the anhydride value in copolymers containing anhydrides after derivatization provided by the present invention has the advantages of fast analysis speed, high sensitivity and high recovery rate, with RSD≤0.42% and quantitative method recovery rate of 98.41~102.36%, and the accuracy and precision of detection are guaranteed.

[0046] (3) The method for determining the anhydride value in copolymers containing anhydrides after derivatization provided by the present invention has a fast derivatization reaction rate and few by-products, and can accurately detect the anhydride content in olefin-maleic anhydride copolymers. Attached Figure Description

[0047] Figure 1 This is the test spectrum of the 1-dimethylaminonaphthalene-5-sulfonylhydrazine standard in Example 1 of the present invention.

[0048] Figure 2 This is the test spectrum after derivatization in Embodiment 1 of the present invention.

[0049] Figure 3 This is the standard curve of 1-dimethylaminonaphthalene-5-sulfonylhydrazine in Example 1 of the present invention. Detailed Implementation

[0050] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0051] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0052] Example 1

[0053] This embodiment provides a method for determining the anhydride value in anhydride-containing copolymers after derivatization, the method comprising the following steps:

[0054] Liquid chromatography conditions: Agilent 1260II high performance liquid chromatograph, Agilent XDB-C18 liquid chromatograph column (5μm×4.6mm×250mm); detector: VWD; detector wavelength: 230nm; flow rate: 1.0mL / min; injection volume: 5.0μL; isocratic program: the volume ratio of the first mobile phase (ultrapure water) to the second mobile phase (methanol) is 50:50; run time: 20min.

[0055] Determination of the standard curve: Accurately weigh 0.10 g (accurate to 0.0001 g) of 1-dimethylaminonaphthalene-5-sulfonylhydrazine (purity ≥99.00%) into a 50 mL volumetric flask, dissolve and dilute to volume with methanol, and prepare a primary standard stock solution. Weigh 0.2 g, 0.4 g, 0.6 g, 0.8 g, and 1.0 g of the primary standard stock solution into 50 mL volumetric flasks, dilute to volume with methanol, and prepare standard solutions of 4 mg / L, 8 mg / L, 12 mg / L, 16 mg / L, and 20 mg / L, respectively. Under the above chromatographic conditions, the standard solutions of different concentrations were measured, the peak areas of the target components were recorded, and a peak area-concentration standard curve was plotted to obtain the linear equation of the standard curve. The chromatogram of the 1-dimethylaminonaphthalene-5-sulfonylhydrazine standard is shown below. Figure 1 As shown, the standard curve obtained is as follows: Figure 3 As shown, the linear equation is y = 77.80x + 0.68, and the linear correlation coefficient R0 is... 2 =0.9998.

[0056] Derivatization reaction: Take 0.5000g (accurate to 0.0001g) of the ethylene-maleic anhydride copolymer sample to be tested (average molecular weight 50000) into a pre-weighed 100mL reflux tube, add 10mL of anhydrous DMF to dissolve it, and slowly add 50mL of derivatization solution to the tube (for about 30 minutes). Accurately weigh 6.0g (accurate to 0.0001g) of 1-dimethylaminonaphthalene-5-sulfonylhydrazine into a 50mL volumetric flask and dilute to volume with anhydrous DMF. After the addition is complete, rinse the inner wall of the volumetric flask with a small amount of DMF and pour it into the reflux tube. Heat the mixture to reflux at 90℃ for 60 minutes, and accurately weigh the total weight of the reflux tube and the reaction solution. Weigh 0.5g of the mixed reaction solution into a 50mL volumetric flask, dilute to volume with methanol and shake well to obtain the reaction material.

[0057] Liquid chromatography detection: The diluted sample solution was measured under the above chromatographic conditions, and the peak area of ​​1-dimethylaminonaphthalene-5-sulfonylhydrazine was recorded. The peak area was substituted into the peak area-concentration standard curve to obtain the remaining amount of 1-dimethylaminonaphthalene-5-sulfonylhydrazine after the derivatization reaction. The true content of acid anhydride in the copolymer containing acid anhydride was then calculated.

[0058] like Figure 2 As shown, the retention time of 1-dimethylaminonaphthalene-5-sulfonylhydrazine was 6.4 min, and the elution time of DMF was 2.8 min, with no interference from 1-dimethylaminonaphthalene-5-sulfonylhydrazine. This indicates that the liquid chromatography method is suitable for the quantitative analysis of the content of the derivatization reagent 1-dimethylaminonaphthalene-5-sulfonylhydrazine.

[0059] Precision testing:

[0060] Six samples of the same batch of polyethylene-maleic anhydride copolymer of different masses were weighed. The sample preparation conditions were the same as those in Example 1 for the derivatization reaction process. The samples were analyzed using the chromatographic conditions of Example 1. The peak area of ​​1-dimethylaminonaphthalene-5-sulfonylhydrazine was recorded. The remaining amount of 1-dimethylaminonaphthalene-5-sulfonylhydrazine after the derivatization reaction was obtained by substituting the peak area-concentration standard curve. The true content of anhydride in the copolymer containing anhydride was calculated by reverse calculation. The relative standard deviation (RSD) was calculated based on the measured content. The results are shown in Table 1.

[0061] Table 1

[0062]

[0063] As can be seen from Table 1, the RSD of the results obtained by this method meets the precision requirements and has good repeatability.

[0064] Accuracy test:

[0065] Nine portions of 1-dimethylaminonaphthalene-5-sulfonylhydrazine solution with known component content were weighed and added to the polyethylene-maleic anhydride copolymer sample. Then, 1-dimethylaminonaphthalene-5-sulfonylhydrazine standard solution was added quantitatively. The chromatographic conditions described above were used for determination, and the spiked recovery rate of liquid chromatography was calculated. The results are shown in Table 2.

[0066] Table 2

[0067]

[0068] As can be seen from Table 2, the recovery rate of the analytical method is between 98.79% and 101.12%, indicating that the detection accuracy of the method provided by this invention is guaranteed.

[0069] Five portions of 10% polyethylene-maleic anhydride DMF solution were prepared. Polyethylene-maleic anhydride copolymer was added to each solution, and an excess of 1-dimethylaminonaphthalene-5-sulfonylhydrazine standard solution was added. The sample preparation and detection were carried out using the method provided in Example 1. The molar number of anhydride was calculated to conduct a spiked recovery experiment. The results are shown in Table 3.

[0070] Table 3

[0071]

[0072]

[0073] As can be seen from Table 3, the recovery rate of the analytical method is between 98.41% and 102.36%, indicating that the detection accuracy of the method provided by the present invention is guaranteed.

[0074] Comparison with chemical titration:

[0075] Five samples of polyethylene-maleic anhydride copolymer from different batches were weighed and prepared according to the conditions described in Example 1. The samples were analyzed using the chromatographic conditions described above. The peak area of ​​the remaining derivatizing reagent, 1-dimethylaminonaphthalene-5-sulfonylhydrazine, was recorded. The content of the remaining 1-dimethylaminonaphthalene-5-sulfonylhydrazine was calculated using a standard curve. The actual content of the anhydride functional groups was then inferred and compared with the anhydride content determined by chemical titration. The results are shown in Table 4.

[0076] Table 4

[0077] EMA-1 65.42 66.01 EMA-2 70.36 71.03 EMA-3 69.55 69.98 EMA-4 67.96 68.66 EMA-5 63.23 63.83

[0078] As shown in Table 4, the anhydride value of ethylene-maleic anhydride copolymer determined by chemical titration is higher than that determined by derivatization liquid chromatography. Furthermore, the chemical titration method, which involves directly hydrolyzing and measuring the carboxylic acid functional groups to infer the anhydride functional group content, has the disadvantage of failing to account for trace amounts of carboxylic acid functional groups that may have been hydrolyzed in the sample, thus leading to higher measured values. Using derivatization liquid chromatography to determine the anhydride content of polyethylene-maleic anhydride copolymer can eliminate the interference of hydrolyzed acids in the detection.

[0079] Anti-interference experiment:

[0080] Four samples of the same batch of polyethylene-maleic anhydride copolymer were weighed and prepared according to the conditions in Example 1. 0 g, 0.01 g, 0.02 g, and 0.03 g of maleic acid were added to each sample, respectively. The samples were analyzed under the chromatographic conditions described above. The peak area of ​​the remaining derivatizing reagent, 1-dimethylaminonaphthalene-5-sulfonylhydrazine, was recorded. The content of the remaining 1-dimethylaminonaphthalene-5-sulfonylhydrazine was calculated using a standard curve. The actual content of the anhydride functional groups was then compared with the anhydride content determined by chemical titration. The results are shown in Table 5.

[0081] Table 5

[0082]

[0083] As can be seen from Table 5, with the increase of maleic acid, the anhydride content measured by the method of determining the anhydride value in the copolymer containing anhydride after derivatization provided by the present invention did not change significantly or showed an increasing trend; while the anhydride content measured by chemical titration gradually increased with the addition of maleic acid, indicating that the method provided by the present invention can resist acid interference and has higher detection accuracy.

[0084] Example 2

[0085] This embodiment provides a method for determining the anhydride value in anhydride-containing copolymers after derivatization, the method comprising the following steps:

[0086] Liquid chromatography conditions: Agilent 1260II high performance liquid chromatograph, Agilent XDB-C18 liquid chromatograph column (5μm×4.6mm×250mm); detector: VWD; detector wavelength: 230nm; flow rate: 1.2mL / min; injection volume: 10.0μL; isocratic program: the volume ratio of the first mobile phase (ultrapure water) to the second mobile phase (methanol) is 30:50; run time: 30min.

[0087] Determination of standard curve: The standard curve was determined under the liquid chromatography conditions described above, following the steps in Example 1.

[0088] Derivatization reaction: Take 0.5000g (accurate to 0.0001g) of the ethylene-maleic anhydride copolymer sample to be tested (average molecular weight 30000) into a pre-weighed 100mL reflux tube, and add 20mL of anhydrous DMF to dissolve it; slowly add 50mL of derivatization solution to the tube (about 30min, accurately weigh 7.0g (accurate to 0.0001g) of 1-dimethylaminonaphthalene-5-sulfonylhydrazine into a 50mL volumetric flask, and dilute to volume with anhydrous DMF). After the addition is complete, rinse the inner wall of the volumetric flask with a small amount of DMF and pour it into the reflux tube. Heat the mixture to reflux at 95℃ for 100min, and accurately weigh the total weight of the reflux tube and the reaction solution. Weigh 0.5g of the mixed reaction solution into a 50mL volumetric flask, dilute to volume with methanol and shake well to obtain the reaction material.

[0089] Liquid chromatography detection: The diluted sample solution was measured under the above chromatographic conditions, and the peak area of ​​1-dimethylaminonaphthalene-5-sulfonylhydrazine was recorded. The peak area was substituted into the peak area-concentration standard curve to obtain the remaining amount of 1-dimethylaminonaphthalene-5-sulfonylhydrazine after the derivatization reaction. The true content of acid anhydride in the copolymer containing acid anhydride was then calculated.

[0090] Example 3

[0091] This embodiment provides a method for determining the anhydride value in anhydride-containing copolymers after derivatization, the method comprising the following steps:

[0092] Liquid chromatography conditions: Agilent 1260II high performance liquid chromatograph, Agilent XDB-C18 liquid chromatograph column (5μm×4.6mm×250mm); detector: VWD; detector wavelength: 230nm; flow rate: 0.8mL / min; injection volume: 2.0μL; isocratic program: volume ratio of first mobile phase (ultrapure water) to second mobile phase (methanol) 70:30; run time: 25min.

[0093] Determination of standard curve: The standard curve was determined under the liquid chromatography conditions described above, following the steps in Example 1.

[0094] Derivatization reaction: Take 0.5000g (accurate to 0.0001g) of the ethylene-maleic anhydride copolymer sample to be tested (average molecular weight 60000) into a pre-weighed 100mL reflux tube, and add 15mL of anhydrous DMF to dissolve it; slowly add 50mL of derivatization solution to the tube (about 30min, accurately weigh 5.0g (accurate to 0.0001g) of 1-dimethylaminonaphthalene-5-sulfonylhydrazine into a 50mL volumetric flask, and dilute to volume with anhydrous DMF). After the addition is complete, rinse the inner wall of the volumetric flask with a small amount of DMF and pour it into the reflux tube. Heat the mixture to reflux at 85℃ for 45min, and accurately weigh the total weight of the reflux tube and the reaction solution. Weigh 0.5g of the mixed reaction solution into a 50mL volumetric flask, dilute to volume with methanol and shake well to obtain the reaction material.

[0095] Liquid chromatography detection: The diluted sample solution was measured under the above chromatographic conditions, and the peak area of ​​1-dimethylaminonaphthalene-5-sulfonylhydrazine was recorded. The peak area was substituted into the peak area-concentration standard curve to obtain the remaining amount of 1-dimethylaminonaphthalene-5-sulfonylhydrazine after the derivatization reaction. The true content of acid anhydride in the copolymer containing acid anhydride was then calculated.

[0096] Example 4

[0097] This embodiment provides a method for determining the anhydride value in a copolymer containing anhydride after derivatization. The method is the same as in Example 1 except that 1-dimethylaminonaphthalene-5-sulfonylhydrazide is replaced with 4-hydrazino-N,N-dimethylaniline, and will not be described again here.

[0098] Example 5

[0099] This embodiment provides a method for determining the anhydride value in a copolymer containing anhydride after derivatization. The method is the same as in Example 1 except that 1-dimethylaminonaphthalene-5-sulfonylhydrazine is replaced with 4-chlorophenylhydrazine, and will not be repeated here.

[0100] Example 6

[0101] This embodiment provides a method for determining the anhydride value in a copolymer containing anhydride after derivatization. The method is the same as in Example 1 except that 1-dimethylaminonaphthalene-5-sulfonylhydrazine is replaced with 4-(triethylamine)benzoylhydrazine, and will not be repeated here.

[0102] Example 7

[0103] This embodiment provides a method for determining the anhydride value in anhydride-containing copolymers after derivatization. The method is the same as in Example 1 except that all anhydrous DMF is replaced with anhydrous DMA, and will not be described again here.

[0104] The same batch of samples as those measured in Example 1 were tested using the above-described embodiment. The relative standard deviation was calculated using the above-described precision test method, and the average value of 6 tests was given. The average recovery rate of the entire test method for 5 samples was measured using the above-described accuracy test method. The results are shown in Table 6.

[0105] Table 6

[0106] Example 1 70.18 0.42 99.43 Example 2 70.21 0.39 99.39 Example 3 69.92 0.59 98.89 Example 4 62.99 3.12 90.33 Example 5 64.18 2.55 91.27 Example 6 50.27 7.45 74.12 Example 7 67.36 1.11 96.33

[0107] As can be seen from Table 6, the present invention preferably uses 1-dimethylaminonaphthalene-5-sulfonylhydrazine as a derivatization reagent, which has better derivatization efficiency and more accurate detection results.

[0108] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for determining the anhydride value in anhydride-containing copolymers after derivatization, characterized in that, The method includes: The acid anhydride value in the copolymer is calculated by using a derivatizing reagent to derivatize the acid anhydride groups in the copolymer. The remaining content of the derivatizing reagent is then detected by liquid chromatography. The derivatization reaction is carried out at a temperature of 80-100℃ and for a duration of 50-100 minutes. The anhydride-containing copolymer is an olefin-anhydride copolymer; The derivatizing agent is any one of 1-dimethylaminonaphthalene-5-sulfonylhydrazine, benzenesulfonylhydrazine, 2,4,6-triisopropylbenzenesulfonylhydrazine, 4-fluorobenzenesulfonylhydrazine, 4-hydrazino-N,N-dimethylaniline, 4-chlorophenylhydrazine or 4-(triethylamine)benzenehydrazine; The mobile phase for liquid chromatography detection includes a first mobile phase and a second mobile phase; the first mobile phase is water; the second mobile phase is methanol; the volume ratio of the first mobile phase to the second mobile phase is (30~70):(30~70); the flow rate of the mobile phase in the liquid chromatography detection is 0.8~1.2 mL / min; The chromatographic column used for liquid chromatography detection is an Agilent XDB-C18; the column size is 5μm×4.6mm×250mm; and the detection wavelength is 220~240nm.

2. The method according to claim 1, characterized in that, The molar ratio of the anhydride-containing copolymer to the derivatizing reagent is 1:2~10.

3. The method according to claim 1, characterized in that, The derivatization reaction was carried out under reflux conditions.

4. The method according to claim 1, characterized in that, The derivatizing agent is 1-dimethylaminonaphthalene-5-sulfonylhydrazine.

5. The method according to claim 1, characterized in that, The derivatizing reagent is added to the derivatization reaction in the form of a derivatizing reagent solution.

6. The method according to claim 5, characterized in that, The concentration of the derivatization reagent solution is 3~30wt%.

7. The method according to claim 5, characterized in that, The solvents for the derivatization reagent solution include anhydrous DMF and / or anhydrous DMA.

8. The method according to claim 1, characterized in that, The molecular weight of the anhydride-containing copolymer is ≥3000.

9. The method according to claim 8, characterized in that, The molecular weight of the anhydride-containing copolymer is 3,000 to 100,000.

10. The method according to claim 1, characterized in that, The anhydride-containing copolymer is first dissolved in an organic solvent and then undergoes a derivatization reaction.

11. The method according to claim 10, characterized in that, The organic solvents include anhydrous DMF and / or anhydrous DMA.

12. The method according to claim 10, characterized in that, The ratio of the anhydride-containing copolymer to the organic solvent is 0.01~0.1:1 g / mL.

13. The method according to claim 1, characterized in that, The method includes the following steps: A copolymer containing anhydride with a molecular weight ≥3000 is dissolved in anhydrous DMF and / or anhydrous DMA. The resulting solution is then subjected to a derivatization reaction with a derivatization reagent solution at a concentration of 3-30 wt%. The molar ratio of the copolymer containing anhydride to the derivatization reagent is 1:2-10. The derivatization reaction is carried out under reflux at 80-100°C for 50-100 min. The remaining content of the derivatization reagent in the obtained reaction material is then detected by liquid chromatography, and the anhydride value in the copolymer containing anhydride is calculated.

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