Accurate measurement method for hydrogen content in polysiloxane and application of accurate measurement method

Abstract

The invention relates to a method for accurately measuring the hydrogen content in polysiloxane and application of the method in determining the hydrogen content in simethicone, hydrogen-containing silicone oil, phenyl modified silicone oil, alkyl modified silicone oil or polyether modified silicone oil or in determining the hydrogen content in simethicone, hydrogen-containing silicone oil, phenyl modified silicone oil, alkyl modified silicone oil or polyether modified silicone oil prepared through hydrosilylation. The invention discloses application of the silicon hydrogen conversion rate of alkyl modified silicone oil or polyether modified silicone oil. The method comprises the following steps: S10, quantitatively weighing to-be-detected polysiloxane and an internal standard substance, and directly and uniformly mixing the to-be-detected polysiloxane and the internal standard substance to obtain a to-be-detected solution; s20, dissolving a predetermined amount of to-be-detected liquid in a deuterated reagent, and carrying out 1H NMR test to obtain at least one 1H NMR spectrogram about the to-be-detected liquid; and S30, analyzing the 1H NMR spectrogram of the to-be-detected liquid by using a nuclear magnetic data analysis processing auxiliary tool, and calculating the hydrogen content of the to-be-detected polysiloxane based on an analysis result and a hydrogen content calculation formula. The method is wide in applicability, simple and convenient to operate and accurate in result.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical analysis, and in particular to a method for detecting the hydrogen content in polysiloxane, and more particularly to a method for accurately measuring the hydrogen content in polysiloxane and application of the method to determining the hydrogen content in dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil or polyether-modified silicone oil, or application of the method to determining the silicon-to-hydrogen conversion rate of dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil or polyether-modified silicone oil prepared by a silicon-hydrogen addition reaction. Background Art

[0002] Polysiloxanes are polymers with a silicon-oxygen bond as the backbone and at least one organic group directly attached to a silicon atom. They are a class of high-performance functional materials that combine the characteristics of both inorganic and organic materials, including excellent properties such as reaction inertness, thermal stability, oxidation resistance, electrical insulation, and lubricity. They are known as "industrial vitamins." Silicone hydride (Si-H) is one of the primary active functional groups in the polysiloxane structure, and different products can be customized based on the hydrogen content. Silicone oils are often prepared through the hydrosilylation reaction of double-bond derivatives. The hydrogen content can be used to assess the completion of the hydrosilylation reaction. Therefore, the hydrogen content of polysiloxanes is a very important technical indicator.

[0003] Currently, the main methods for determining the hydrogen content in hydrogenated silicone oils include chemical titration, gasometrics, and infrared spectroscopy. Chemical titration generally involves reacting Si-H with bromine under acidic conditions to produce hydrogen bromide. Excess bromine reacts with potassium iodide, and the precipitated iodine is titrated with a standard sodium thiosulfate solution. While the chemical titration method has a wide range of applications, substances such as bromine and iodine are highly toxic, the testing process is cumbersome, and it also produces a large amount of waste liquid. Gasometrics utilizes the principle that Si-H bonds can be broken by aqueous alkali metal hydroxide solutions to release H2. The volume of H2 is measured using a gasometric tube method, and the hydrogen content is calculated using the gas state equation. CN 108490110A discloses a method for determining the hydrogen content of high-hydrogenated silicone oils using the gasometric principle, but the gasometric device requires high airtightness. CN 109696496B discloses a method for quantitatively measuring H2 content and thereby determining the hydrogen content using headspace gas chromatography. However, both methods disclosed in these patents can only determine hydrogenated silicone oils with high hydrogen contents and also generate waste liquid that pollutes the environment. The principle of infrared spectroscopy for determining the hydrogen content in hydrogenated silicone oil is to use Fourier transform infrared spectrometer for quantitative analysis. CN103674889A and CN112730320B published the use of mid-infrared and near-infrared spectrometers to establish a standard curve. The sample was measured at 2160 cm -1 and 5000~5200cm -1Substitute the absorbance into the standard curve to obtain the silicon-hydrogen content of hydrogenated silicone oil. This method is relatively quick and has a wide test content range, but it requires the use of hydrogenated silicone oil with known hydrogen content to establish a standard curve, and can only measure hydrogenated silicone oil and polyether-polysiloxane copolymers. In addition, amides, amines, cyanides, carbonyls and other substances are not detected at 2160 cm -1 and 5000~5200cm -1 There are absorption peaks, which affect the measurement results and require data refinement, resulting in larger errors.

[0004] At present, the main method for determining the hydrogen content of downstream products is an improved chemical method in which the solvent CCl4 is replaced with CHCl3. Although this method has a wide range of applications and accurate measurement results, it also has problems such as complex operation, time-consuming and labor-intensive operation, and the generation of a large amount of waste liquid.

[0005] In order to measure the hydrogen content in polysiloxane more accurately, simply and universally, and to accelerate the upgrading and development of high-quality silicone products, it is necessary to develop an efficient and accurate hydrogen content measurement method. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for accurately measuring the hydrogen content in polysiloxane and its application, which solves the problems of the prior art such as the cumbersome determination of hydrogen content, large errors, and large amount of wastewater. The method of the present invention is to use quantitative nuclear magnetic resonance hydrogen spectroscopy ( 1 H qNMR (H qNMR) is a rapid method for determining the hydrogen content of polysiloxanes. The test scope is primarily for polysiloxanes with no signal peaks at the hydrogen chemical shift of 6.80-6.85, such as dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, and polyether-modified silicone oil. This method has a wide test range, is fast and simple to operate, requires little sample, and provides relatively accurate results.

[0007] According to a first aspect of the present invention, there is provided a method for accurately measuring the hydrogen content in polysiloxane, comprising the following steps:

[0008] S10. Quantitatively weigh the polysiloxane to be tested and the internal standard, and directly mix the two to obtain a test solution, wherein the internal standard is 1 In the H NMR spectrum, a single strong peak is generated in the area where there is no signal of the polysiloxane to be measured;

[0009] S20. Take a predetermined amount of the test solution and dissolve it in a deuterated reagent. 1 H NMR test, obtain at least one about the liquid to be tested 1 H NMR spectrum;

[0010] S30. Analyze the liquid to be tested using nuclear magnetic data analysis and processing auxiliary tools 1H NMR spectrum, and the hydrogen content of the polysiloxane to be tested is calculated based on the analysis results and the hydrogen content calculation formula.

[0011] In an embodiment of the present invention, in step S30, the hydrogen content of the polysiloxane to be tested is determined based on the following formula 1:

[0012]

[0013] Wherein, [H] represents the hydrogen content, I si-H It represents the integral area of the corresponding signal generated by the hydrogen nuclei of Si-H in the polysiloxane to be tested, I std It represents the integral area of the corresponding signal generated by the characteristic hydrogen nuclei in the internal standard, N std Indicates the number of hydrogen nuclei in the internal standard that generate corresponding signals, M std Represents the relative molar mass of the internal standard, m x and m std Respectively represent the mass of the polysiloxane to be tested and the internal standard, P std Indicates the purity of the internal standard.

[0014] In an embodiment of the present invention, in step S10, the mass ratio of the polysiloxane to be measured to the internal standard substance is 1:1.1 to 1.1:1, and the internal standard substance is bromoform.

[0015] In an embodiment of the present invention, in step S30, the hydrogen content of the polysiloxane to be tested is determined based on the following formula 2:

[0016]

[0017] Among them, the P std Greater than or equal to 98%.

[0018] In an embodiment of the present invention, the formula 1 is obtained based on the following formula:

[0019]

[0020] Among them, P x Indicates the purity of the analyte, I x It represents the integrated area of the corresponding signal generated by the hydrogen nuclei of the characteristic functional groups of the analyte.

[0021] In an embodiment of the present invention, in step S30, the analysis result includes 1 The integrated area of the corresponding signal generated by the hydrogen nuclei of Si—H in the polysiloxane to be tested and the integrated area of the corresponding signal generated by the characteristic hydrogen nuclei in the internal standard generated on the H NMR spectrum.

[0022] In an embodiment of the present invention, in step S10, the polysiloxane to be tested and the internal standard are weighed in a range of 0.100 g to 0.2000 g using a 1 / 10,000 precision balance, accurate to four decimal places; and the polysiloxane to be tested and the internal standard are uniformly mixed by ultrasound.

[0023] In an embodiment of the present invention, in step S20, the predetermined amount is 20 mg to 100 mg, and 1 During H NMR testing, the number of scans ranged from 16 to 64.

[0024] In an embodiment of the present invention, in step S20, the deuterated reagent includes one of deuterated chloroform, deuterated dimethyl sulfoxide and deuterated tetrahydrofuran, and the amount of the deuterated solvent is 0.6-1.0 mL.

[0025] According to a second aspect of the present invention, there is provided an application of the method for accurately measuring the hydrogen content in polysiloxane according to the present invention in determining the hydrogen content in dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil or polyether-modified silicone oil, or in determining the silicon-to-hydrogen conversion rate of dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil or polyether-modified silicone oil prepared by a hydrosilylation reaction.

[0026] The present invention uses quantitative nuclear magnetic resonance hydrogen spectroscopy technology to measure the hydrogen content, which requires a small amount of sample and is recyclable; the test is fast and time-saving; and the accuracy is high. The present invention not only uses quantitative nuclear magnetic resonance hydrogen spectroscopy technology to measure the hydrogen content of polysiloxanes, but also uses quantitative nuclear magnetic resonance hydrogen spectroscopy technology to measure the conversion rate of silicon-hydrogen reactions, and has a wider range of applications. In addition, the present invention selects tribromoform as an internal standard, which can test aromatic polysiloxanes such as phenyl (this type of functional group peaks at 7 to 8), and the test range is wider. Moreover, tribromoform is used as an internal standard, and there is no need to prepare a standard solution, which makes the operation more convenient, greatly improving the convenience of the test and easy to promote and apply.

[0027] Furthermore, the accurate hydrogen content measurement method provided by the present invention allows for rapid and accurate determination of the hydrogen content of polysiloxane polymers, as well as the silicon-to-hydrogen conversion rate in the hydrosilylation reaction. This accelerates the development and upgrading of high-quality organosilicon products. Furthermore, since polysiloxane is one of the most commonly used and important materials in titanium dioxide organic processing, the method described herein also lays the foundation for the development of new titanium dioxide products and for improving the quality and efficiency of existing titanium dioxide products. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic flow chart showing a method for accurately measuring the hydrogen content in polysiloxane provided by the present invention is shown;

[0029] Figure 2An embodiment of the present invention is shown 1 H NMR spectrum;

[0030] Figure 3 Another embodiment of the present invention is shown 1 H NMR spectrum;

[0031] Figure 4 According to another embodiment of the present invention, 1 H NMR spectrum. DETAILED DESCRIPTION

[0032] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in the present invention, it is readily apparent to those skilled in the art that various modifications are feasible without departing substantially from the teachings of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other replacements, modifications, variations, and deletions may be made to the design, operating conditions, and parameters of the following exemplary embodiments.

[0033] In order to solve the limitations of existing polysiloxane hydrogen content detection methods such as being cumbersome, having large errors, and producing a large amount of wastewater, the present invention provides a method for accurately measuring the hydrogen content in polysiloxane. The method utilizes quantitative nuclear magnetic resonance spectroscopy (qNMR) technology that is simple to operate and non-destructive to determine, and adopts high-purity, low-viscosity, and tribromoform with a peak position of δ=6.83 as an internal standard, which can be fully mixed with the polysiloxane liquid and dissolved in a deuterated solvent. The test range of this method is mainly for polysiloxanes with hydrogen spectrum chemical shifts of 6.80 to 6.85, such as dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, and polyether-modified silicone oil, which have no signal peaks. The test range is wide, the operation is fast and simple, the sample dosage is small, and the results are accurate. This method can be used to quickly evaluate the completion of the hydrosilylation reaction during the synthesis of polysiloxane and the measurement of the silicon hydrogen content in the product.

[0034] Nuclear magnetic resonance quantitative technology can integrate qualitative identification and quantitative determination. Compared with other analytical techniques, it does not require its own reference material, does not require the separation of multi-component samples, can simultaneously determine multiple components in a mixture, and has simple sample pretreatment. Its basic principle is that the intensity of the detected magnetic nuclear resonance signal is proportional to the number of corresponding nuclei. Since hydrogen is the main element that constitutes organic molecules and is widely distributed, 1 The natural abundance of H nuclei is high, so hydrogen nuclei have high sensitivity and a wide range of applications. It is the most commonly used one-dimensional nuclear magnetic resonance technology. The present invention is to use quantitative nuclear magnetic resonance spectroscopy based on internal standard method ( 1 HqNMR) is a detection method for quantitative analysis of the hydrogen content of the polysiloxane to be tested.

[0035] Specifically, according to the first aspect of the present invention, a method for accurately measuring the hydrogen content in polysiloxane is provided, such as Figure 1 As shown, it includes the following steps:

[0036] S10. Quantitatively weigh the polysiloxane to be tested and the internal standard, and directly mix the two to obtain a test solution, wherein the internal standard is 1 In the H NMR spectrum, a single strong peak is generated in the area where there is no signal of the polysiloxane to be measured;

[0037] S20. Take a predetermined amount of the test solution and dissolve it in a deuterated reagent. 1 H NMR test, obtain at least one about the liquid to be tested 1 H NMR spectrum;

[0038] S30. Analyze the liquid to be tested using nuclear magnetic data analysis and processing auxiliary tools 1 H NMR spectrum, and the hydrogen content of the polysiloxane to be tested is calculated based on the analysis results and the hydrogen content calculation formula.

[0039] In step S10, it is particularly important to select an internal standard. The internal standard needs to be stable in nature, non-hygroscopic, high in purity, non-toxic, and non-reactive with the sample to be tested. The most important thing is to produce a single strong peak in the area where there is no polysiloxane signal to be tested. The present invention analyzes the nuclear magnetic resonance spectra of polysiloxanes such as various dimethyl silicone oils, hydrogenated silicone oils, phenyl-modified silicone oils, alkyl-modified silicone oils, and polyether-modified silicone oils, as well as the chemical shift and peak type analysis of various commonly used internal standards such as bromoform, 1,1,2,2-tetrabromoethane, 1,3,5-tribromobenzene, and 1,3,5-trimethoxybenzene, and preferably uses bromoform as the internal standard for the detection of hydrogen content in dimethyl silicone oil, hydrogenated silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, and polyether-modified silicone oil. Another advantage of choosing bromoform is that, compared to a solid internal standard, bromoform, which is liquid at room temperature, can be directly mixed with the polysiloxane to be tested. This eliminates the need to prepare separate standard solutions of the internal standard and the polysiloxane to be tested using several milliliters of a high-cost deuterated reagent (e.g., the steps involved in preparing the standard solutions, such as volume adjustment, transfer, and mixing). This greatly simplifies the process and saves time and cost.

[0040] Using tribromoform, the hydrogen content of various polysiloxanes including dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, and polyether-modified silicone oil can be accurately measured. Among them, the mass ratio of the polysiloxane to be measured and the internal standard can be 1:1.1 to 1.1:1. In one embodiment, a one-tenth precision balance can be used to weigh the polysiloxane to be measured and the internal standard, and the weighing range of the polysiloxane to be measured and the internal standard is 0.100g to 0.2000g, accurate to four decimal places. After weighing, the two are mixed evenly to obtain a liquid to be measured. The liquid to be measured can be a transparent or opaque liquid, as long as the two reach a stable and uniform state after mixing. In one embodiment, the polysiloxane to be measured and the internal standard can be ultrasonicated for 5 to 25 seconds to fully mix the two.

[0041] In step S20, a proper amount of the mixed solution to be tested is dissolved in a deuterated reagent, placed in a nuclear magnetic resonance tube, and subjected to spectrometry on a Bruker 400 nuclear magnetic resonance spectrometer. 1 H NMR test. In the embodiment of the present invention, the mass range of the sample of the test liquid is between 20mg and 100mg. The deuterated reagent can be one of deuterated chloroform, deuterated dimethyl sulfoxide, deuterated tetrahydrofuran, etc., and the amount of the deuterated solvent is between 0.6 and 1.0mL. 1 During H NMR testing, the number of scans is 16 to 64. In one embodiment, the number of scans is 16. In other embodiments, the number of scans can be set as needed. Since the number of scans is proportional to the signal intensity, an appropriate number of scans can be selected based on the required signal intensity.

[0042] In step S30, the NMR data analysis and processing auxiliary tool is used to analyze the liquid to be tested. 1 HNMR spectrum. In one embodiment, the nuclear magnetic data analysis and processing auxiliary tool can be MestReNova software, which can be used to obtain the integrated area of the corresponding signal generated by the hydrogen nuclei of the characteristic functional groups of the test liquid and the integrated area of the corresponding signal generated by the characteristic hydrogen nuclei in the internal standard. For example, the integrated area can be automatically generated by the software, or the operator can manually select a specific peak, and then the software automatically generates the integrated area of the selected specific peak.

[0043] The present invention is based on the principle that the integrated area of the resonance signal peak of hydrogen nuclei is proportional to the number of corresponding hydrogen nuclei, that is, it satisfies the following formula:

[0044]

[0045] Among them, I x , I std They represent the integral areas of the corresponding signals generated by the hydrogen nuclei of the characteristic functional groups of the analyte and the characteristic hydrogen nuclei in the internal standard; N x、N std Respectively represent the number of hydrogen nuclei of the characteristic functional groups in the analyte and the characteristic hydrogen nuclei in the internal standard that generate corresponding signals; M x 、M std Represent the relative molar masses of the analyte and the internal standard respectively; m x 、m std Represent the masses of the analyte and the internal standard respectively; P std is the purity of the internal standard; P x Indicates the purity of the analyte in the sample.

[0046] The hydrogen content refers to the amount of silicon-hydrogen (Si-H) contained in every 100g of polysiloxane, and also refers to the hydrogen content on the silicon-hydrogen bond. Therefore, when testing the hydrogen content in polysiloxane, Nx = 1. Based on this, the formula 1 of the present invention can be derived based on the above formula:

[0047]

[0048] Wherein, [H] represents the hydrogen content, I si-H It represents the integral area of the corresponding signal generated by the hydrogen nuclei of Si-H in the polysiloxane to be measured, I std It represents the integral area of the corresponding signal generated by the characteristic hydrogen nuclei in the internal standard, N std Indicates the number of hydrogen nuclei in the internal standard that produce corresponding signals, M std Indicates the relative molar mass of the internal standard, m x and m std Respectively represent the mass of the analyte, i.e. the polysiloxane to be measured and the internal standard, P std Indicates the purity of the internal standard.

[0049] When the internal standard is bromoform, based on M being 252.731 g / mol, substitute M into formula 1. std , the formula 2 of the present invention is obtained:

[0050]

[0051] Among them, P std Greater than or equal to 98%.

[0052] As mentioned above, the NMR data analysis and processing auxiliary tool can obtain the integral area of the corresponding signal generated by the hydrogen nuclei of the characteristic functional groups of the test liquid and the integral area of the corresponding signal generated by the characteristic hydrogen nuclei in the internal standard. That is, the analysis results of the tool can at least include the integral area of the corresponding signal generated by the characteristic hydrogen nuclei of the test liquid. 1 The integrated area of the corresponding signal generated by the hydrogen nuclei of Si-H in the polysiloxane to be tested and the integrated area of the corresponding signal generated by the characteristic hydrogen nuclei in the internal standard generated on the H NMR spectrum can be used to calculate the hydrogen content of the polysiloxane to be tested based on the analysis results and according to Formula 2.

[0053] Specifically, the chemical shift of Si-H in the polysiloxane to be tested is δ = 4.72-4.69, and the peak type is a single peak or multiple peaks; the chemical shift of the internal standard bromoform is δ = 6.86, and the peak type is a single strong peak. The spectrum is analyzed using MestReNova software. According to formula 2, the integrated area I of the characteristic hydrogen nuclear resonance signal peak at δ = 4.72-4.69 and δ = 6.86 is x , I std and the mass m of the polysiloxane to be measured and the internal standard bromoform x 、m std , the hydrogen content of the polysiloxane to be tested can be calculated quickly and accurately.

[0054] The present invention provides a method for accurately measuring the hydrogen content in polysiloxane. The method has wide applicability, is simple to operate, and produces accurate results. It can accelerate the upgrading and development of high-quality organosilicon products and has good application prospects.

[0055] According to a second aspect of the present invention, there is provided the use of the method for accurately measuring the hydrogen content in polysiloxanes according to the present invention for determining the hydrogen content in dimethyl silicone oil, hydrogenated silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, or polyether-modified silicone oil, or for determining the silicon-to-hydrogen conversion rate of dimethyl silicone oil, hydrogenated silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, or polyether-modified silicone oil produced by a hydrosilylation reaction. By using dimethyl silicone oil, hydrogenated silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, or polyether-modified silicone oil as the polysiloxane to be measured in the steps of the above method, the hydrogen content thereof and the silicon-to-hydrogen conversion rate of the hydrosilylation reaction can be accurately measured.

[0056] The present invention will be further described and illustrated below with reference to the following examples. The siloxanes AC tested in the following examples were laboratory-prepared and all exhibited a peak in the proton chemical shift range of 6.80 to 6.85, including dimethyl silicone oil, hydrogenated silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, or polyether-modified silicone oil. Both bromoform and deuterated reagents were commercially available, for example, from the Aladdin reagent brand.

[0057] Example 1

[0058] (1) Weigh 0.2003 g of polysiloxane A to be tested and 0.1998 g of bromoform (99.5% purity) into a 2 mL sampling bottle, sonicate for 20 seconds, mix thoroughly, and set aside.

[0059] (2) Take 30 mg of the mixture; dissolve it in 0.7 mL of deuterated chloroform, place it in an NMR tube, and perform NMR spectrometry on a Bruker 400 NMR spectrometer. 1 H NMR test, 16 scans;

[0060] (3) 1 The H NMR spectrum and the corresponding characteristic hydrogen nuclear resonance signal peak integral area are shown in the attached Figure 2 As shown, according to Formula 2, the hydrogen content of the polysiloxane A to be tested [H]=0.3957×(0.6683×0.1998)×99.5%÷(1.0000×0.2003)=0.2625.

[0061] (4) The hydrogen content of the polysiloxane A to be tested was tested using a chemical titration method. After a sodium thiosulfate titration experiment (the specific testing method can be found in the literature and will not be described in detail here), the hydrogen content [H] was calculated to be 0.2545, which is basically consistent with the result obtained by the measurement method of the present invention with a relative error of 3.1%.

[0062] Furthermore, the calculated hydrogen content can be used to calculate the silicon-hydrogen conversion rate in the polysiloxane. For example, in this example, polysiloxane A is prepared by the hydrosilylation reaction of a 0.75% hydrogen-containing silicone oil with an olefin. Therefore, the silicon-hydrogen conversion rate of this reaction is (0.75 - 0.2625) ÷ 0.75 × 100% = 65%, which can be used to assess the completion of the hydrosilylation reaction.

[0063] Example 2

[0064] (1) Weigh 0.2180 g of polysiloxane B to be tested and 0.2035 g of bromoform (99.5% purity) into a 2 mL sampling bottle, sonicate for 20 seconds, and mix thoroughly to obtain the test solution for later use;

[0065] (2) Take 30 mg of the test solution, dissolve it in 0.7 mL of deuterated chloroform, put it in an NMR tube, and perform NMR spectrometry on a Bruker 400 NMR spectrometer. 1 H NMR test, 16 scans;

[0066] (3) 1 The H NMR spectrum and the corresponding characteristic hydrogen nuclear resonance signal peak integral area are shown in the attached Figure 3 As shown, according to Formula 2, the hydrogen content of the polysiloxane B to be tested [H] is calculated as [H] = 0.3957 × (0.1166 × 0.2035) × 99.5% ÷ (1.0000 × 0.2180) = 0.0429.

[0067] (4) The hydrogen content of the polysiloxane B to be tested was tested using a chemical titration method. After titration experiments (the specific testing method can be found in the literature and will not be described in detail here), the hydrogen content [H] was calculated to be 0.0419, which is basically consistent with the result obtained by the measurement method of the present invention with a relative error of 2.3%.

[0068] Example 3

[0069] (1) Weigh 0.2046 g of polysiloxane C to be tested and 0.2098 g of bromoform (99.5% purity) into a 2 mL sampling bottle, sonicate for 20 seconds, mix thoroughly, and set aside.

[0070] (2) Take 30 mg of the mixture; dissolve it in 0.7 mL of deuterated chloroform, place it in an NMR tube, and perform NMR spectrometry on a Bruker 400 NMR spectrometer. 1 H NMR test, 16 scans;

[0071] (3) 1 The H NMR spectrum and the corresponding characteristic hydrogen nuclear resonance signal peak integral area are shown in the attached Figure 4 As shown, according to Formula 2, the hydrogen content of the polysiloxane C to be tested is calculated as [H] = 0.3957 × (0.1056 × 0.2098) × 99.5% ÷ (1.0000 × 0.2046) = 0.0426.

[0072] (4) The hydrogen content of the polysiloxane B to be tested was tested using a chemical titration method. After a sodium thiosulfate titration experiment (the specific testing method can be found in the literature and will not be described in detail here), the hydrogen content [H] was calculated to be 0.0430, which is basically consistent with the result obtained by the measurement method of the present invention with a relative error of 0.9%.

[0073] As demonstrated in Examples 1-3 above, the method described herein can accurately determine the hydrogen content of a polysiloxane, as verified by chemical titration. Furthermore, the method is simple to operate and highly cost-effective. Furthermore, the calculated hydrogen content can be used to further determine the completion of the hydrosilylation reaction of the polysiloxane.

[0074] In summary, the present invention utilizes nondestructive quantitative nuclear magnetic resonance spectroscopy based on internal standard method ( 1 This method uses high-purity, low-viscosity bromoform (with a peak at δ = 6.83) as an internal standard to quantitatively analyze the hydrogen content of the polysiloxane being tested. Compared to other analytical techniques, this method requires no internal reference, does not require separation of multicomponent samples, and simplifies sample pretreatment. It covers polysiloxanes with no peaks in the H chemical shift range of 6.80 to 6.85, including dimethyl silicone oil, hydrogenated silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil, and polyether-modified silicone oil. This method offers a wide testing range, requires minimal sample volume, is simple to operate, and offers high accuracy.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. If the present invention is modified or replaced with equivalents without departing from the spirit and scope of the present invention, it should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for accurately measuring the hydrogen content in polysiloxane, characterized in that: The following steps are involved: S10. Quantitatively weigh the polysiloxane to be tested and the internal standard, and directly mix the two to obtain a test solution, wherein the internal standard is 1 In the H NMR spectrum, a single strong peak is generated in the area where there is no signal of the polysiloxane to be measured; S20. Take a predetermined amount of the test solution and dissolve it in a deuterated reagent. 1 H NMR test, obtain at least one about the liquid to be tested 1 H NMR spectrum; S30. Analyze the liquid to be tested using nuclear magnetic data analysis and processing auxiliary tools 1 H NMR spectrum, and the hydrogen content of the polysiloxane to be tested is calculated based on the analysis results and the hydrogen content calculation formula.

2. The method for accurately measuring the hydrogen content in polysiloxane according to claim 1, characterized in that: In step S30, the hydrogen content of the polysiloxane to be tested is determined based on the following formula 1: Wherein, [H] represents the hydrogen content, I si-H It represents the integral area of the corresponding signal generated by the hydrogen nuclei of Si-H in the polysiloxane to be tested, I std It represents the integral area of the corresponding signal generated by the characteristic hydrogen nuclei in the internal standard, N std Indicates the number of hydrogen nuclei in the internal standard that generate corresponding signals, M std Represents the relative molar mass of the internal standard, m x and m std Respectively represent the mass of the polysiloxane to be tested and the internal standard, P std Indicates the purity of the internal standard.

3. The method for accurately measuring the hydrogen content in polysiloxane according to claim 2, characterized in that: In step S10, the mass ratio of the polysiloxane to be tested to the internal standard substance is 1:1.1 to 1.1:1, and the internal standard substance is bromoform.

4. The method for accurately measuring the hydrogen content in polysiloxane according to claim 3, characterized in that: In step S30, the hydrogen content of the polysiloxane to be tested is determined based on the following formula 2: Among them, the P std Greater than or equal to 98%.

5. The method for accurately measuring the hydrogen content in polysiloxane according to claim 2, characterized in that: The formula 1 is obtained based on the following formula: Among them, P x Indicates the purity of the analyte, I x It represents the integrated area of the corresponding signal generated by the hydrogen nuclei of the characteristic functional groups of the analyte.

6. The method for accurately measuring the hydrogen content in polysiloxane according to claim 2, characterized in that: In step S30, the analysis result includes 1 The integrated area of the corresponding signal generated by the hydrogen nuclei of Si—H in the polysiloxane to be tested and the integrated area of the corresponding signal generated by the characteristic hydrogen nuclei in the internal standard generated on the H NMR spectrum.

7. The method for accurately measuring the hydrogen content in polysiloxane according to claim 1, characterized in that: In step S10, the polysiloxane to be tested and the internal standard are weighed in a range of 0.100 g to 0.2000 g using a 1 / 10,000 precision balance, accurate to four decimal places; and the polysiloxane to be tested and the internal standard are uniformly mixed by ultrasound.

8. The method for accurately measuring the hydrogen content in polysiloxane according to claim 1, characterized in that: In step S20, the predetermined amount is 20mg to 100mg, and 1 During H NMR testing, the number of scans ranged from 16 to 64.

9. The method for accurately measuring the hydrogen content in polysiloxane according to claim 1, characterized in that: In step S20, the deuterated reagent includes one of deuterated chloroform, deuterated dimethyl sulfoxide and deuterated tetrahydrofuran, and the amount of the deuterated solvent is 0.6 to 1.0 mL.

10. Use of the method for accurately measuring the hydrogen content in polysiloxane according to any one of claims 1 to 9 in determining the hydrogen content in dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil or polyether-modified silicone oil, or in determining the silicon-to-hydrogen conversion of dimethyl silicone oil, hydrogen-containing silicone oil, phenyl-modified silicone oil, alkyl-modified silicone oil or polyether-modified silicone oil prepared by a hydrosilylation reaction.

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