Analysis method of chemical structure in polyurethane

Abstract

The invention discloses a method for analyzing a chemical structure in polyurethane, which comprises the following steps of: hydrolyzing polyurethane under a first microwave hydrolysis condition, and analyzing a monomer structure contained in the polyurethane after the hydrolysis is completed; and hydrolyzing the polyurethane under a second microwave hydrolysis condition, and analyzing the proportion of the monomers by using nuclear magnetism after the hydrolysis is completed. According to the method, the sample is pretreated through microwave hydrolysis, and unknown polyurethane can be quickly and efficiently decomposed into small molecules through the thermal effect and the non-thermal effect of microwaves, so that analysis on the chemical structure composition of the polyurethane is realized. The method has the advantages of simplicity in operation, short time consumption, low sample consumption and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical analysis, and more specifically, to a method for analyzing the chemical structure of polyurethane. Background Art

[0002] Polymer materials are important materials that are indispensable in modern industry and life. They have complex chemical structures and diverse properties. In order to better understand and utilize these materials, it is crucial to accurately analyze their chemical structures. Traditional methods for analyzing the chemical structure of polymer materials require complex sample pretreatment, which is time-consuming, sometimes requires high temperature and high pressure, and has high safety risks. Existing methods for analyzing the chemical structure of polymer materials mainly analyze the polymer materials as a whole through various analytical instruments and techniques, such as infrared spectroscopy, nuclear magnetic resonance, and mass spectrometry. In addition, some researchers have tried to use autoclave hydrolysis to pre-treat polymer materials, and then perform chemical structure analysis through other analytical methods. Although the existing methods for analyzing the chemical structure of polymer materials can meet the needs to a certain extent, there are still some problems and limitations. First, traditional infrared spectroscopy analysis methods often cannot accurately analyze polymer monomers and are limited to overall functional group characterization. Secondly, research and development have high requirements for accurate determination of the chemical monomer structure in polymer materials. Therefore, how to develop a new method that is simple to operate, safe, efficient, thoroughly deconstructed, and the monomers are kept intact, and can accurately analyze the chemical structure of polymer materials, is a problem that needs to be solved in this field. Summary of the invention

[0003] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0004] Another object of the present invention is to provide a method for analyzing the chemical structure of polyurethane, which uses microwave hydrolysis to pre-treat the sample, and utilizes the thermal effect and non-thermal effect of microwaves to quickly and efficiently decompose the unknown polyurethane into small molecules, thereby realizing the analysis of its chemical structure composition. This method has the advantages of simple operation, short time consumption, and low sample consumption.

[0005] In order to achieve these purposes and other advantages according to the present invention, a method for analyzing the chemical structure of polyurethane is provided, comprising the following steps: hydrolyzing the polyurethane under a first microwave hydrolysis condition, and analyzing the monomer structure contained therein after the hydrolysis is completed; hydrolyzing the polyurethane under a second microwave hydrolysis condition, and analyzing the ratio between the monomers thereof by nuclear magnetic resonance after the hydrolysis is completed.

[0006] Furthermore, the concentration of the alkaline solution in the first microwave hydrolysis condition is greater than the concentration of the alkaline solution in the second microwave hydrolysis condition.

[0007] Preferably, the concentration of the alkaline solution in the first microwave hydrolysis condition is at least 1.3 M greater than the concentration of the alkaline solution in the second microwave hydrolysis condition.

[0008] Furthermore, the concentration of the alkaline solution in the second microwave hydrolysis condition is 0.02-0.10M.

[0009] Preferably, before setting the first microwave hydrolysis condition, the functional groups of the polyurethane are first identified, and the microwave hydrolysis conditions of the polyurethane are set according to the functional groups. When there are 4 or more characteristic peaks of functional groups in the 500-800nm ​​region, the microwave frequency is first set to 2.5-5GHz, and when there are less than 4, the microwave frequency is first set to 1.5-2.5GHz; when there are 6 or more characteristic peaks of functional groups in the 800-1200nm region, the microwave frequency is then set to 3.5-6GHz, and when there are less than 6, the microwave frequency is then set to 2.5-3.5GHz.

[0010] Furthermore, the hydrolysis temperature of the first microwave hydrolysis condition is 160-200° C., the hydrolysis time is 2-4 hours, the alkali concentration is 1.4-2.3 M, the reaction solvent is an alcohol-containing aqueous solution, and the volume ratio of alcohol to water is (2.5-3):1.

[0011] Furthermore, the hydrolysis temperature of the second microwave hydrolysis condition is 160-200° C., the hydrolysis time is 2-4 hours, the reaction solvent is an alcohol-containing aqueous solution, and the volume ratio of alcohol to water is (10-20):1.

[0012] Furthermore, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0013] Furthermore, the alcohol comprises one or more combinations of methanol, ethanol and isopropanol.

[0014] Preferably, the specific steps of analyzing the ratio between the monomers by NMR are: adjusting the pH of the solution after hydrolysis to 5-6, adding a deuterated reagent, performing NMR testing after complete dissolution, and calculating the ratio between the monomers based on the integrated area ratio of the representative functional group characteristic peaks.

[0015] Furthermore, the deuterated reagent is one or more combinations of deuterated water, deuterated methanol or deuterated DMSO.

[0016] The present invention has at least the following beneficial effects:

[0017] The present invention utilizes microwave pretreatment technology to quickly and efficiently decompose unknown polyurethane into small molecules, thereby realizing the analysis of the monomer structure of its components. This method has the advantages of simple operation, short time consumption, and low sample consumption;

[0018] The present invention uses a relatively small alkali concentration under the second microwave hydrolysis condition, which can reduce the concentration of inorganic salts and avoid adsorption of monomers after microwave hydrolysis, thereby affecting the analysis of the ratio between monomers after polyurethane hydrolysis.

[0019] In the first microwave hydrolysis condition of the present invention, the microwave frequency is set according to the gradient of the number of functional groups in the wavelength region, which can promote the complete hydrolysis of polyurethane and reduce the damaged monomer structure;

[0020] When performing nuclear magnetic resonance testing, the present invention adjusts the pH to 5-6, which can promote the dissolution of the test substance, improve the peak shape of the nuclear magnetic resonance test result, completely dissolve the test substance, and make the calculated monomer ratio in the polyurethane more accurate.

[0021] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the NMR spectrum in step five of Example 1 of the present invention.

[0023] Figure 2 This is the NMR spectrum in step 5 of Example 2 of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below.

[0025] The present invention provides a method for analyzing the chemical structure of polyurethane, comprising the following steps:

[0026] S1, hydrolyzing the polyurethane under the first microwave hydrolysis condition, and analyzing the monomer structure contained therein after the hydrolysis is completed;

[0027] In an embodiment of the present invention, in order to avoid excessively high inorganic salt concentration, adsorption of monomers, and affecting the analysis of the ratio between monomers after polyurethane hydrolysis, when setting microwave conditions, the concentration of the alkaline solution in the first microwave hydrolysis condition is greater than the concentration of the alkaline solution in the second microwave hydrolysis condition; preferably, the concentration of the alkaline solution in the first microwave hydrolysis condition is at least 1.3M greater than the concentration of the alkaline solution in the second microwave hydrolysis condition, preferably 1.32M. Generally, the concentration of the alkaline solution under the first microwave condition is 1.4 to 2.3M.

[0028] In the embodiment of the present invention, in order to completely hydrolyze, keep the monomer structure intact, and reduce the damaged monomer structure, before setting the first microwave hydrolysis condition, the functional groups of the polyurethane are first identified, and the microwave hydrolysis conditions of the polyurethane are set according to the functional groups. When there are 4 or more characteristic peaks of functional groups in the 500-800nm ​​region, the microwave frequency is first set to 2.5-5GHz, and when there are less than 4, the microwave frequency is first set to 1.5-2.5GHz; when there are 6 or more characteristic peaks of functional groups in the 800-1200nm region, the microwave frequency is later set to 3.5-6GHz, and when there are less than 6, the microwave frequency is later set to 2.5-3.5GHz. The microwave reaction time set first is 30-60 minutes, and the microwave reaction time set later is 60-120 minutes.

[0029] In an embodiment of the present invention, the hydrolysis temperature of the first microwave hydrolysis condition is 160-200°C, the hydrolysis time is 2-4 hours, the concentration of the alkaline solution is 1.4-2.3M, the reaction solvent is an aqueous solution containing alcohol, and the volume ratio of alcohol to water is (2.5-3): 1. Microwaves cause water and methanol to generate high pressure in a closed tank, which increases the boiling point. The microwave synthesizer in the embodiment of the present invention can heat water to 260°C.

[0030] In an embodiment of the present invention, the specific steps for analyzing the monomer structure contained therein are: adding an appropriate amount of pure water to the solution after the hydrolysis is completed to separate the soluble components and the insoluble components; concentrating the soluble components, then dissolving and extracting, separating the aqueous phase and the organic phase, concentrating and purifying them respectively, and analyzing them using analytical instruments, such as nuclear magnetic resonance, GCMS, LCMS, GPC, etc.; drying the insoluble components, and testing them using instruments such as SEM and energy dispersive spectrometer (EDS). If the insoluble matter is an inorganic matter, the insoluble matter is calcined in a muffle furnace, and the residue is measured by XRD.

[0031] The determined composition of polyurethane includes but is not limited to E300, TDA, PTMG, PPG and other substances.

[0032] S2. Hydrolyze the polyurethane under the second microwave hydrolysis condition. After the hydrolysis is completed, use nuclear magnetic resonance to analyze the ratio of its monomers.

[0033] In an embodiment of the present invention, the alkali concentration in the second microwave hydrolysis condition is 0.02-0.10M, preferably 0.04-0.08M.

[0034] In an embodiment of the present invention, the hydrolysis temperature of the second microwave hydrolysis condition is 160-200° C., the hydrolysis time is 2-4 hours, the reaction solvent is an alcohol-containing aqueous solution, and the volume ratio of alcohol to water is (10-20):1.

[0035] In an embodiment of the present invention, the microwave frequency and the time setting of the microwave frequency change interval of the second microwave hydrolysis condition refer to the first microwave hydrolysis condition.

[0036] In an embodiment of the present invention, the specific steps of using nuclear magnetic resonance to analyze the ratio between its monomers are: adjust the pH of the solution after hydrolysis to 5-6, concentrate, add deuterated reagent, perform nuclear magnetic resonance test after complete dissolution, and calculate the ratio between each monomer according to the integral area ratio of the representative functional group characteristic peak. In the above embodiment, adjusting the pH to 5-6 can help dissolution, improve the peak shape of the area to be analyzed, facilitate integral calculation, and make the calculated monomer ratio more accurate. The pH adjustment is carried out using hydrochloric acid, and the concentration of hydrochloric acid is 5-10wt%. The concentration of hydrochloric acid should not be too high, which will damage the hydrolyzate, nor too low, which will greatly increase the water content and increase the difficulty of removal.

[0037] In an embodiment of the present invention, the deuterated reagent is one or more combinations of deuterated water, deuterated methanol or deuterated DMSO.

[0038] In an embodiment of the present invention, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0039] In an embodiment of the present invention, the alcohol comprises one or more combinations of methanol, ethanol, and isopropanol.

[0040] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0041] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0042] <Example 1>

[0043] Step 1: Select the polishing pad to be analyzed, peel off the unknown polyurethane sample from the polishing pad, and crush it.

[0044] Step 2: Select 14 mL of methanol aqueous solution with a volume ratio of 10:4 as the reaction solvent and place it in a closed reactor. The alkali concentration in the reaction solvent is 1.4 M NaOH. Place 1 g of the crushed polyurethane sample in a closed reactor for microwave decomposition. The microwave frequency is 2.4 GHz, the microwave hydrolysis time is 160 minutes, and the hydrolysis temperature is 180°C.

[0045] Step 3: Add pure water to the microwave reactor and filter out insoluble matter and filtrate.

[0046] Step 4: Take the filtrate and spin dry it. After the filtrate is spin dried, add water and ethyl acetate for dissolution and extraction, separate the aqueous phase and the organic phase, and concentrate them separately. After the aqueous phase is concentrated, purify it, and take samples of each purified sample for nuclear magnetic resonance, GCMS, LCMS, and GPC. After the organic phase is concentrated, purify it, and take samples of each purified sample for nuclear magnetic resonance, GCMS, LCMS, and GPC.

[0047] The insoluble matter obtained by filtration is dried and tested by SEM and energy dispersive spectrometer (EDS) to determine its chemical composition; if it is inorganic, the insoluble matter is incinerated in a muffle furnace and the incineration residue is measured by XRD.

[0048] The monomer structure contained in the unknown polyurethane sample is analyzed based on the detection results of the above instruments.

[0049] Step 5: Analyze the ratio between each monomer. After the composition of the polyurethane compound is determined, select 10.5mL of methanol-water solution with a volume ratio of 10:1 as the reaction solvent and place it in a closed reactor. The alkali concentration is 0.045M. Take a small amount of polyurethane (about 20mg) and place it in a closed reactor for microwave decomposition. Set the microwave frequency to 2.4GHz and the temperature to 180°C. React for 160 minutes. After the reaction is completed, remove the reaction solution and place it in a beaker. Rinse the closed reactor with 15mL of methanol, combine it into the reaction solution and concentrate it completely. Add a mixed solution of deuterated methanol and deuterated water in a mass ratio of 2:1, dissolve it completely, test the NMR, and calculate the composition ratio between the monomers based on the integrated area of ​​the characteristic peaks of the functional groups. The NMR spectrum is as follows Figure 1 shown.

[0050] <Example 2>

[0051] Step 1: Select the same polishing pad as in Example 1, peel off the unknown polyurethane sample from the polishing pad, crush it, and analyze it using a Thermo Scientific infrared spectrometer to determine the type of functional groups. It was found that there were characteristic peaks of 6 functional groups in the range of 500 to 800 nm, and characteristic peaks of 4 functional groups in the range of 800 to 1200 nm.

[0052] Step 2: Select 14 mL of methanol aqueous solution with a volume ratio of 10:4 as the reaction solvent and place it in the reactor. The alkali concentration in the reaction solvent is 1.4 M NaOH. Place 1 g of the crushed polyurethane sample in the reactor for microwave decomposition. The microwave frequency is first set to 3.5 GHz for hydrolysis for 60 minutes, and then to 3.0 GHz for microwave hydrolysis for 100 minutes. The hydrolysis temperature is 180°C.

[0053] Step 3: Add pure water to the microwave reactor and filter out insoluble matter and filtrate.

[0054] Step 4: Take the filtrate and spin dry it. After the filtrate is spin dried, add water and ethyl acetate for dissolution and extraction, separate the aqueous phase and the organic phase, and concentrate them separately. After the aqueous phase is concentrated, purify it, and take samples of each purified sample for nuclear magnetic resonance, GCMS, LCMS, and GPC. After the organic phase is concentrated, purify it, and take samples of each purified sample for nuclear magnetic resonance, GCMS, LCMS, and GPC.

[0055] The insoluble matter obtained by filtration is dried and tested by SEM and energy dispersive spectrometer (EDS) to determine its chemical composition; if it is inorganic, the insoluble matter is incinerated in a muffle furnace and the incineration residue is measured by XRD.

[0056] The monomer structure contained in the unknown polyurethane sample is analyzed based on the detection results of the above instruments.

[0057] Step 5: Analyze the ratio between each monomer. After the composition of the polyurethane compound is determined, select 10.5mL of methanol-water solution with a volume ratio of 10:1 as the reaction solvent and place it in a closed reactor. The alkali concentration is 0.045M. Take a small amount of polyurethane (about 20mg) and place it in a closed reactor for microwave decomposition. The microwave frequency is first set to 3.5GHz for hydrolysis for 60 minutes, and then set to 3.0GHz for microwave hydrolysis for 100 minutes. The temperature is 180°C. After the reaction is completed, remove the reaction solution and place it in a beaker. Rinse the closed reactor with 15mL of methanol, combine it into the reaction solution and concentrate it completely. Add a mixed solution of deuterated methanol and deuterated water in a mass ratio of 2:1, dissolve it completely, test the nuclear magnetic resonance, and calculate the composition ratio between each monomer based on the integrated area of ​​the characteristic peaks of the functional groups. The nuclear magnetic spectrum is as follows Figure 2 shown.

[0058] <Example 3>

[0059] Step 1: Select the same polishing pad as in Example 1, peel off the unknown polyurethane sample from the polishing pad, crush it, and analyze it using a Thermo Scientific infrared spectrometer to determine the type of functional groups. It was found that there were characteristic peaks of 6 functional groups in the range of 500 to 800 nm, and characteristic peaks of 4 functional groups in the range of 800 to 1200 nm.

[0060] Step 2: Select 14 mL of methanol aqueous solution with a volume ratio of 10:4 as the reaction solvent and place it in the reactor. The alkali concentration in the reaction solvent is 1.4 M NaOH. Place 1 g of the crushed polyurethane sample in the reactor for microwave decomposition. The microwave frequency is first set to 3.5 GHz for hydrolysis for 60 minutes, and then to 3.0 GHz for microwave hydrolysis for 100 minutes. The hydrolysis temperature is 180°C.

[0061] Step 3: Add pure water to the microwave reactor and filter out insoluble matter and filtrate.

[0062] Step 4: Take the filtrate and spin dry it. After the filtrate is spin dried, add water and ethyl acetate for dissolution and extraction, separate the aqueous phase and the organic phase, and concentrate them separately. After the aqueous phase is concentrated, purify it, and take samples of each purified sample for nuclear magnetic resonance, GCMS, LCMS, and GPC. After the organic phase is concentrated, purify it, and take samples of each purified sample for nuclear magnetic resonance, GCMS, LCMS, and GPC.

[0063] The insoluble matter obtained by filtration is dried and tested by SEM and energy dispersive spectrometer (EDS) to determine its chemical composition; if it is inorganic, the insoluble matter is incinerated in a muffle furnace and the incineration residue is measured by XRD.

[0064] The monomer structure contained in the unknown polyurethane sample is analyzed based on the detection results of the above instruments.

[0065] Step 5: Analyze the ratio between each monomer. After determining the substances contained in the polyurethane, select appropriate conditions for overall hydrolysis. Select 10.5mL of methanol aqueous solution with a volume ratio of 10:1 as the reaction solvent and place it in a closed reactor. The alkali concentration is 0.045M. Take a small amount of polyurethane (about 20mg) and place it in a closed reactor for microwave decomposition. The microwave frequency is first set to 3.5GHz for hydrolysis for 60 minutes, and then set to 3.0GHz for microwave hydrolysis for 100 minutes. The temperature is 180°C. After the reaction is completed, remove the reaction solution and place it in a beaker. Use 15mL of methanol to rinse the closed reactor, merge it into the reaction solution, concentrate it completely, add 8wt% hydrochloric acid solution to adjust the pH to 5-6, and after concentration, add deuterated DMSO to dissolve it completely. Test the nuclear magnetic resonance and calculate the composition ratio between each monomer based on the characteristic peak area of ​​the functional group.

[0066] <Comparative Example 1>

[0067] Steps 1 to 4 are the same as in Example 1, except that in step 5, the alkali concentration in the reaction solvent is 1.4 M NaOH.

[0068] The ratios of the monomer components measured after hydrolysis of the above Examples 1-3 and Comparative Example 1 are shown in Table 1 below.

[0069] Table 1

[0070]

[0071] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A method for analyzing the chemical structure of polyurethane, characterized in that: The following steps are included: The polyurethane is hydrolyzed under the first microwave hydrolysis condition, and after the hydrolysis is completed, the monomer structure contained therein is analyzed; the polyurethane is hydrolyzed under the second microwave hydrolysis condition, and after the hydrolysis is completed, the ratio between the monomers is analyzed by nuclear magnetic resonance.

2. The method for analyzing the chemical structure in polyurethane according to claim 1, characterized in that: The concentration of the alkaline solution in the first microwave hydrolysis condition is greater than the concentration of the alkaline solution in the second microwave hydrolysis condition; preferably, the concentration of the alkaline solution in the first microwave hydrolysis condition is at least 1.3 M greater than the concentration of the alkaline solution in the second microwave hydrolysis condition.

3. The method for analyzing the chemical structure in polyurethane according to claim 2, characterized in that: The alkali concentration in the second microwave hydrolysis condition is 0.02-0.10M.

4. The method for analyzing the chemical structure in polyurethane according to claim 1, characterized in that: Before setting the first microwave hydrolysis condition, the functional groups of the polyurethane are first identified, and the microwave hydrolysis conditions of the polyurethane are set according to the functional groups. When there are 4 or more characteristic peaks of functional groups in the 500-800nm ​​region, the microwave frequency is first set to 2.5-5GHz, and when there are less than 4, the microwave frequency is first set to 1.5-2.5GHz; when there are 6 or more characteristic peaks of functional groups in the 800-1200nm region, the microwave frequency is then set to 3.5-6GHz, and when there are less than 6, the microwave frequency is then set to 2.5-3.5GHz.

5. The method for analyzing the chemical structure in polyurethane according to claim 1, characterized in that: The hydrolysis temperature of the first microwave hydrolysis condition is 160-200° C., the hydrolysis time is 2-4 hours, the alkali concentration is 1.4-2.3 M, the reaction solvent is an alcohol-containing aqueous solution, and the volume ratio of alcohol to water is (2.5-3):

1.

6. The method for analyzing the chemical structure in polyurethane according to claim 1, characterized in that: The hydrolysis temperature of the second microwave hydrolysis condition is 160-200° C., the hydrolysis time is 2-4 hours, the reaction solvent is an alcohol-containing aqueous solution, and the volume ratio of alcohol to water is (10-20):

1.

7. The method for analyzing the chemical structure in polyurethane according to claim 5 or 6, characterized in that: The alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

8. The method for analyzing the chemical structure in polyurethane according to claim 5 or 6, characterized in that: The alcohol includes one or more combinations of methanol, ethanol and isopropanol.

9. The method for analyzing the chemical structure in polyurethane according to claim 1, characterized in that: The specific steps of using nuclear magnetic resonance to analyze the ratio between its monomers are as follows: after the hydrolysis is completed, the pH of the solution is adjusted to 5-6, and after concentration, a deuterated reagent is added, and after complete dissolution, a nuclear magnetic resonance test is performed, and the ratio between the monomers is calculated based on the integrated area ratio of the representative functional group characteristic peaks.

10. The method for analyzing the chemical structure of polyurethane according to claim 9, characterized in that: The deuterated reagent is one or more combinations of deuterated water, deuterated methanol or deuterated DMSO.

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