A Structural Analysis Method for Ethoxylated Trimethylolpropane

Abstract

The present invention provides a structural analysis method for ethoxylated trimethylolpropane, comprising: reacting a sample of ethoxylated trimethylolpropane to be analyzed with a derivatization reagent to obtain a derivatized liquid sample; putting the derivatized liquid sample into a nuclear magnetic resonance tube and adding a deuterated reagent; sending the sample dissolved in the deuterated reagent into a nuclear magnetic resonance spectrometer for hydrogen spectrum testing to obtain nuclear magnetic resonance hydrogen spectrum data; processing and analyzing the obtained sample hydrogen spectrum data, correcting the baseline, determining peaks and peak integration, and then calculating the molecular weight of ethoxylated trimethylolpropane and the grafting rate of terminal hydroxyl groups. By performing derivatization pretreatment on the ethoxylated trimethylolpropane sample with acetic anhydride and then combining with nuclear magnetic resonance hydrogen spectrum analysis means, the present invention avoids the integral interference of the terminal hydroxyl groups of ethoxylated trimethylolpropane on the overlapping methylene spectral peaks on the EO chain, and can quickly and simply determine the average molecular weight of ethoxylated trimethylolpropane.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer material analysis, and particularly relates to a method for analyzing the structure of ethoxylated trimethylolpropane. Background Art

[0002] Photopolymerizable monomers, also known as reactive diluents, are low-molecular compounds containing unsaturated groups, mainly used to adjust the viscosity of photocuring systems. Monomers are required to have good solubility in oligomers and have unsaturated groups that can participate in polymerization. Monomers are generally classified into mono-functional monomers and multi-functional monomers according to the number of functional groups participating in photopolymerization. The most commonly used free-radical multi-functional monomers are mainly acrylate esters, including trimethylolpropane trimethacrylate (TMPTA), dipropylene glycol diacrylate (DPGDA), etc.

[0003] Ethoxylated trimethylolpropane triacrylate (EO-TMPTA) is the second-generation reactive diluent developed in recent years at home and abroad, and is widely used in special radiation curing coatings, inks and adhesives for mobile electronic devices, automobiles, wind power and solar cells. Introducing a flexible chain into the molecule is the most significant feature of the second-generation diluent structure. In terms of performance, while ensuring high activity and high solubility, the shrinkage stress, flexibility, adhesion to substrates, etc. of the cured film are greatly improved. In addition, low skin irritation is also one of the characteristics of the second-generation reactive diluent.

[0004] As one of the main raw materials for synthesizing EO-TMPTA, the structural differences of ethoxylated trimethylolpropane play a decisive role in the use performance of the finished product. Since ethoxylated trimethylolpropane is a multi-component polymer, conventional molecular weight testing methods are limited to the chemical determination of hydroxyl value, and general gas and liquid phase methods can only compare the relative molecular weight sizes between different samples, making it difficult to judge the average molecular weight of the samples. In addition, since trimethylolpropane has three sites that can react with ethylene oxide (EO), ethoxylated trimethylolpropane with a low EO number will inevitably have exposed hydroxyethyl groups without EO attachment and side chains with multiple EO attachments. The activity differences of these terminal hydroxyl groups with different structures when reacting with acrylic acid will affect the overall performance of the diluent. Therefore, qualitative and quantitative analysis of the terminal hydroxyl group structure of ethoxylated trimethylolpropane can provide an important basis for the quality control and performance judgment of this product. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a method for analyzing the structure of ethoxylated trimethylolpropane. This analysis method combines acetic anhydride derivatization with nuclear magnetic resonance hydrogen spectrum to qualitatively and quantitatively analyze the molecular weight of ethoxylated trimethylolpropane and its terminal hydroxyl group structure, providing an important basis for the quality control and performance judgment of this product. The technical solution of the present invention is as follows:

[0006] First aspect, the present invention provides a structural analysis method for ethoxylated trimethylolpropane, comprising:

[0007] Step 1: React the ethoxylated trimethylolpropane sample to be analyzed with a derivatization reagent to obtain a derivatized liquid sample;

[0008] Step 2: Place the derivatized liquid sample into a nuclear magnetic tube and add a deuterated reagent;

[0009] Step 3: Send the sample dissolved in the deuterated reagent into a nuclear magnetic resonance spectrometer for proton nuclear magnetic resonance test to obtain proton nuclear magnetic resonance data;

[0010] Step 4: Process and analyze the obtained sample proton nuclear magnetic resonance data, correct the baseline, determine peaks and perform peak integration, and then calculate the molecular weight of ethoxylated trimethylolpropane and the grafting rate of terminal hydroxyl groups.

[0011] Further, in the step 1, the mass ratio of ethoxylated trimethylolpropane to the derivatization reagent is: 1:1 to 20.

[0012] Further, the derivatization reagent is acetic anhydride, acetyl chloride or other acid anhydride reagents.

[0013] Further, in the step 1, the reaction temperature for derivatization is 80 - 200 °C, and the derivatization time is at least 0.5 h.

[0014] Preferably, in the step 1, the ethoxylated trimethylolpropane sample to be analyzed is formulated with acetic anhydride at a mass ratio of 1:10, and reacted in a closed system at 150 °C for 1.5 h to obtain a derivatized liquid sample.

[0015] Further, in the step 2, the volume ratio of the derivatized liquid sample to the deuterated reagent is 1:1 - 1:50.

[0016] Preferably, the deuterated reagent is deuterated chloroform, and the volume ratio of the sample to be measured to deuterated chloroform is 1:20.

[0017] Preferably, in the step 3, a 600M nuclear magnetic resonance spectrometer is used.

[0018] Further, in the step 4, the MestReNova software is used to process and analyze the obtained sample proton nuclear magnetic resonance data.

[0019] Further, in the step 4, the calculation formula for the molecular weight is: (I 1 / I 2 ×3 - 6) / 4×44 + 134.2, where I 1 is the sum of the integrated areas of four groups of peaks in the chemical shift range of δ = 3.1 - 4.4, and I 2It is the integral area of the peak at the chemical shift δ = 0.85.

[0020] Further, in the step 4, the calculation formula of the terminal hydroxyl grafting rate is: I 3 / I 4 × 100%, where I 3 is the integral area at the chemical shift δ = 4.20, and I 4 is the sum of the integral areas at the chemical shifts δ = 4.20 and 4.01.

[0021] In the present invention, the ethoxylated trimethylolpropane sample is pretreated by derivatization with acetic anhydride, and then combined with the nuclear magnetic resonance hydrogen spectrum analysis method, which avoids the integral interference of the terminal hydroxyl group of ethoxylated trimethylolpropane on the overlapping methylene spectral peaks on the EO chain, and can quickly and simply determine the average molecular weight of ethoxylated trimethylolpropane. In addition, by introducing the performance index of the grafting rate, it provides an important basis for the quality control and performance judgment of this product. Description of the Drawings

[0022] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum data of ethoxylated trimethylolpropane in Example 1 of the present invention.

[0023] Figure 2 It is the comparison of the nuclear magnetic resonance hydrogen spectrum data of continuous tests of ethoxylated trimethylolpropane in Example 1 of the present invention.

[0024] Figure 3 It is the comparison of the nuclear magnetic resonance hydrogen spectrum data of ethoxylated trimethylolpropane before (Figure (1)) and after (Figure (2)) derivatization in Example 1 of the present invention.

[0025] Figure 4 It is the nuclear magnetic resonance hydrogen spectrum data after derivatization of PEG400. Detailed Embodiments

[0026] In the description of the present invention, it should be noted that for those not specified in the examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained by purchasing in the market.

[0027] The following further describes the present invention in detail in conjunction with the drawings and specific embodiments to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention. The protection scope of the present invention includes but is not limited to the following embodiments. Any modification made to the details and forms of the technical solution of the present invention without departing from the spirit and scope of the present application falls within the protection scope of the present invention.

[0028] Example 1

[0029] In this example, the structural analysis process of ethoxylated trimethylolpropane was investigated as follows:

[0030] 1. Instruments and Reagents

[0031] 600M nuclear magnetic resonance spectrometer (Bruker, Germany);

[0032] The ethoxylated trimethylolpropane sample was provided by Zhejiang Huangma Science and Technology Co., Ltd.; deuterated chloroform was purchased from Qingdao Tenglong Microwave Technology Co., Ltd.; acetic anhydride, analytical grade.

[0033] 2. Sample Pretreatment

[0034] Derivatization: Take 0.20 g of the ethoxylated trimethylolpropane sample to be analyzed in a 10 mL capped reaction flask, add 2.0 mL of acetic anhydride, and heat and react at 150 °C for 1.5 hours.

[0035] 3. Testing Method

[0036] The samples before and after derivatization were respectively analyzed by 600 MHz nuclear magnetic resonance hydrogen spectrum. The hydrogen spectrum parameters are as follows: the measurement temperature is 25 °C, the observation frequency is 600.21 MHz, the number of sampling points is 64k, the spectral width is 11904 Hz, the 90° pulse width is 9.3 us, the acquisition time is 2.75 s, the number of dummy scans is 2, and the number of accumulations is 32. The obtained hydrogen spectrum data of the samples were processed using MestReNova software.

[0037] 4. Result Analysis

[0038] As Figure 1 shown is the nuclear magnetic resonance hydrogen spectrum result of ethoxylated trimethylolpropane before derivatization. From Figure 1 the shown hydrogen spectrum, it can be found that the hydrogen spectrum peaks of the undervivatized ethoxylated trimethylolpropane mainly consist of three parts, namely the peaks at chemical shifts δ = 0.85, 1.34, and around 3.59. Among them, the peak at chemical shift δ = 0.85 is the methyl peak at the end of ethoxylated trimethylolpropane. After setting the integral area of the peak at δ = 0.85 to 3, the peak area at chemical shift δ = 1.34 is exactly 2, and this peak is the peak of the methylene group connected to the methyl at the end of ethoxylated trimethylolpropane. In addition, the remaining methylene groups in the structure of ethoxylated trimethylolpropane are all connected to oxygen atoms, and the hydrogen spectrum peaks of these methylene groups are all concentrated at around δ = 3.59, with a total integral area of 22.25.

[0039] Due to the severe overlap of the hydrogen spectrum peaks at the chemical shift δ = 3.59, little structural information can be directly obtained from the hydrogen spectrum. Considering this part as a whole, it can be obtained that the number of EO contained in this sample is about 4.1, and thus its molecular weight is 312.9 g / mol. However, the hydroxyl value of this product is about 610 mg KOH / g, and the molecular weight calculated from the hydroxyl group is 275.9 g / mol, showing a large difference between the two.

[0040] The 1H NMR of the same ethoxylated trimethylolpropane sample was continuously measured four times, and the obtained spectra were magnified at the chemical shift δ = 3.2 - 3.9. From Figure 2 it can be seen that the peak patterns of the spectra obtained each time are different. The active hydrogen of the hydroxyl group moves within this chemical shift range and participates in the integral calculation of the molecular weight as the methylene group of EO. As a result, the molecular weight of ethoxylated trimethylolpropane obtained from NMR will be on the high side, making the structural interpretation of ethoxylated trimethylolpropane by 1H NMR more meaningless.

[0041] To avoid the integral interference of the terminal hydroxyl group of ethoxylated trimethylolpropane on the overlapping methylene group peaks in the EO chain, the sample was derivatized with acetic anhydride according to the experimental method in step 2. From Figure 3 the comparison of the spectral peaks of (1) and (2) below, it can be seen that the overlapping spectral peaks at about δ = 3.57 before derivatization are well separated in chemical shift after acetic anhydride derivatization, and can be roughly divided into four groups of peaks, with their chemical shifts at about δ = 4.20, 4.01, 3.65 and 3.35 respectively. Similarly, setting the integral area of the spectral peak at about δ = 0.85 to 3, it can be seen that the total integral area of these four groups of peaks is 18.76, which is less than the total integral area before derivatization. This means that the active hydrogen of the terminal hydroxyl group of ethoxylated trimethylolpropane has disappeared after derivatization, and the spectral peaks in the chemical shift range are the true methylene group peaks. From the integral area of 18.76, the number of EO contained in ethoxylated trimethylolpropane can be obtained as 3.2, and thus its molecular weight is 275.0 g / mol, which is consistent with the hydroxyl value measurement result of this product.

[0042] To judge the correct attribution of the four groups of peaks after acetic anhydride derivatization, trimethylolpropane and PEG400 were derivatized with acetic anhydride in the same way respectively. The 1H NMR data of PEG400 after derivatization are as Figure 4As shown in the figure, by comparing the NMR data after derivatization, it can be known that the peak at chemical shift δ = 4.20 is the hydrogen on the methylene group connected to the hydroxyl group at the end of the EO chain, and the peak at chemical shift δ = 4.01 is the hydrogen on the hydroxymethyl group of trimethylolpropane that is not connected to the EO chain. The sum of the integrated areas of these two peaks is exactly 6.0, which is in line with the structural composition of ethoxylated trimethylolpropane. Considering the structure, after the terminal hydroxyl group is acetylated, the electron-withdrawing effect of the ester group is stronger than that of the hydroxyl group, causing the hydrogen on the methylene group connected to the terminal hydroxyl group, which was originally at about δ = 3.57, to shift to a lower field, and the chemical shift increases. Also, because the α-H of the original terminal hydroxyl group of the EO chain is affected not only by the ester group but also by the electron-withdrawing effect of the ether bond at the other end, after the methylene group at the end of the EO chain is derivatized with acetic anhydride, the final chemical shift is slightly larger than that of the methylene group of the hydroxymethyl group.

[0043] In addition, the chemical shift of the peak at δ = 3.65 changes little compared with the chemical shift before derivatization, so it is inferred that it is the hydrogen on the inner methylene group of the EO chain that has nothing to do with the terminal hydroxyl group. Finally, the peak at chemical shift δ = 3.35 is the hydrogen on the hydroxymethyl group of trimethylolpropane connected to the EO chain. The sum of the integrated area of this peak and the peak at δ = 4.20 is also exactly 6.0, which also fits well with the structural composition of ethoxylated trimethylolpropane. From the splitting, the main body of this peak shows a singlet state, which also conforms to its structural feature of having no adjacent methylene groups.

[0044] After completing the peak assignment, the grafting rate of ethoxylated trimethylolpropane, that is, the proportion of hydroxyethyl groups connected to the EO chain, can be obtained by using the test method of derivatization with acetic anhydride combined with nuclear magnetic resonance hydrogen spectrum ( 1 1H-NMR). As Figure 3 shown, the proportion of hydroxyethyl groups connected to the EO chain in this test sample among all hydroxyethyl groups is about 58.7% (the ratio of the integrated area at chemical shift δ = 4.20 to the sum of the integrated areas at chemical shifts δ = 4.20 and 4.01). This structural index is difficult to obtain by other analytical methods. For example, there are more than ten components measured by conventional gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), which are difficult to assign. Even if the structures of each component can be determined, the quantitative data obtained without an internal standard are not reliable.

[0045] Example 2

[0046] Using the method described in Example 1, the derivatization reagent was changed to acetyl chloride, and the others were the same as in Example 1. Another batch of ethoxylated trimethylolpropane sample B from Zhejiang Huangma Technology Co., Ltd. was selected, and the molecular weight and grafting rate data of the sample were measured.

[0047] Example 3

[0048] Using the method described in Example 1, the derivatization reagent was changed to phthalic anhydride, and the rest was the same as in Example 1. Another batch of ethoxylated trimethylolpropane sample C from Zhejiang Huangma Science & Technology Co., Ltd. was selected, and the molecular weight and grafting rate data of the sample were measured.

[0049] Example 4

[0050] Using the method described in Example 1, another batch of ethoxylated trimethylolpropane sample D from Zhejiang Huangma Science & Technology Co., Ltd. was selected, and the molecular weight and grafting rate data of the sample were measured.

[0051] The test results of the molecular weight and grafting rate of the ethoxylated trimethylolpropane samples in Examples 1-4 are shown in Table 1:

[0052] Table 1 Test results of the molecular weight and grafting rate of ethoxylated trimethylolpropane samples in different batches

[0053] Batch Peak 1 Peak 2 Peak 3 Peak 4 Total EO Number NMR Molecular Weight Grafting Ratio Hydroxyl Value Hydroxyl Value Molecular Weight Example 1 A 3.52 2.48 9.22 3.51 18.73 3.18 274.2 58.7％ 609.3 276.2 Example 2 B 3.51 2.49 9.21 3.51 18.72 3.18 274.1 58.5％ 610.2 275.8 Example 3 C 3.39 2.60 8.40 3.40 17.79 2.95 263.9 56.6％ 635.2 265.0 Example 4 D 3.48 2.52 9.21 3.48 18.69 3.17 273.8 58.0％ 611.8 275.1

[0054] From the test results of the four different batches of samples, there are indeed differences in molecular weight among different batches, and the results measured by the method of the present invention are relatively consistent with the chemical titration test results of hydroxyl value, which can be used as a supplementary test method to mutually confirm the test data of ethoxylated trimethylolpropane. In addition, relatively stable test results can be obtained with the 3 selected derivatization reagents: acetic anhydride, acetyl chloride, and phthalic anhydride. However, considering the comprehensive factors of safety in use, easy availability of raw materials, and cost, acetic anhydride is the best choice.

[0055] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for structural analysis of ethoxylated trimethylolpropane, characterized in that: It includes: Step 1, reacting the ethoxylated trimethylolpropane sample to be analyzed with a derivatization reagent to obtain a derivatized liquid sample; Step 2, putting the derivatized liquid sample into a nuclear magnetic tube and adding a deuterated reagent; Step 3, sending the sample dissolved in the deuterated reagent into a nuclear magnetic resonance spectrometer for proton NMR test to obtain nuclear magnetic resonance proton spectrum data; Step 4, processing and analyzing the obtained sample proton spectrum data, correcting the baseline, peak determination and peak integration, and then calculating the molecular weight of ethoxylated trimethylolpropane and the grafting rate of terminal hydroxyl groups; The derivatization reagent is acetic anhydride, acetyl chloride or phthalic anhydride; The grafting rate of the terminal hydroxyl group is the proportion of hydroxyethyl groups connected with ethylene oxide chains in all hydroxyethyl groups.

2. The method for structural analysis of ethoxylated trimethylolpropane according to claim 1, characterized in that: In the said Step 1, the mass ratio of ethoxylated trimethylolpropane to the derivatization reagent is 1:1 - 20.

3. The method for structural analysis of ethoxylated trimethylolpropane according to claim 1, characterized in that: In the said Step 1, the reaction temperature for derivatization is 80 - 200 °C, and the derivatization time is at least 0.5 h.

4. The method for structural analysis of ethoxylated trimethylolpropane according to claim 3, characterized in that: In the said Step 1, the ethoxylated trimethylolpropane sample to be analyzed is formulated with acetic anhydride at a mass ratio of 1:10, and reacted in a closed system at 150 °C for 1.5 h to obtain a derivatized liquid sample.

5. The method for structural analysis of ethoxylated trimethylolpropane according to claim 1, characterized in that: In the said Step 2, the volume ratio of the derivatized liquid sample to the deuterated reagent is 1:1 - 50.

6. The method for structural analysis of ethoxylated trimethylolpropane according to claim 1 or 5, characterized in that: The deuterated reagent is deuterated chloroform, and the volume ratio of the sample to be measured to deuterated chloroform is 1:

20.

7. The method for structural analysis of ethoxylated trimethylolpropane according to claim 1, characterized in that: In the said Step 4, the obtained sample proton spectrum data is processed and analyzed using MestReNova software.

8. The method for structural analysis of ethoxylated trimethylolpropane according to claim 7, characterized in that: In step 4, the molecular weight calculation formula is: ( I 1 / I 2 ×3 - 6) / 4×44 + 134.2, I 1 is the sum of the integral areas of four groups of peaks in the chemical shift range of δ = 3.1 - 4.4, I 2 is the integral area of the peak at the chemical shift δ = 0.

85.

9. The method for structural analysis of ethoxylated trimethylolpropane according to claim 7, characterized in that: In the said step 4, the calculation formula for the grafting rate of the terminal hydroxyl group is: I 3 / I 4 × 100%, I 3 is the integral area at the chemical shift δ = 4.20, I 4 is the sum of the integral areas at the two chemical shifts δ = 4.20 and 4.01.

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