A testing method for the content of silanol groups in MQ silicone resin

Abstract

The present invention discloses a method for testing the content of silanol groups in MQ silicone resin, including two detection methods. One is to quantitatively characterize the mass fraction of silanol groups in MQ silicone resin synthesized by the water glass method using solid-state nuclear magnetic resonance silicon spectroscopy; the other is to quantitatively characterize the mass fraction of silanol groups in MQ silicone resin synthesized by the tetraethyl orthosilicate method by combining solid-state nuclear magnetic resonance silicon spectroscopy and liquid-state nuclear magnetic resonance hydrogen spectroscopy. It can be seen therefrom that the present invention directly detects the MQ silicone resin synthesized by the water glass method and the tetraethyl orthosilicate method respectively by using solid-state nuclear magnetic resonance silicon spectroscopy due to their different structures, or detects them by combining solid-state nuclear magnetic resonance silicon spectroscopy and liquid-state nuclear magnetic resonance hydrogen spectroscopy, which can be used to quantitatively characterize the absolute content of silanol groups in MQ silicone resin, and has the characteristics of simple operation method, not being affected by water or other impurities, and high accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer material detection. Specifically, it is a method for testing the content of silanol groups in MQ silicone resin. Background Art

[0002] MQ silicone resin is a special type of polysiloxane resin, which is composed of monofunctional siloxane linkages (R3SiO 1 / 2 , abbreviated as M linkages) and tetrafunctional siloxane linkages (SiO 4 / 2 , abbreviated as Q linkages). Through hydrolysis and condensation, a polyorganosiloxane with a three-dimensional spherical or highly branched structure is formed with Si-O bonds as the backbone. Its typical (planar) chemical structure is as Figure 1 shown. Compared with organic polymer compounds, MQ silicone resin has good high-temperature resistance, water repellency, chemical resistance, electrical insulation, weather resistance, flexibility, film-forming property, adhesiveness and excellent mechanical properties, and has been widely used in fields such as pressure-sensitive adhesives, reinforcement of liquid silicone rubber, cosmetics, high-temperature resistant coatings, and release agents. At present, there are mainly two methods for synthesizing MQ silicone resin, namely the water glass method and the silicate method. Specifically, the former is formed by hydrolysis and condensation reaction with organochlorosilane or various disiloxanes as M-linkage monomers and water glass as Q-linkage monomers; while the latter is formed by using tetraethyl (ortho) silicate as the Q-linkage precursor and capped with M-linkage monomers (partially) after hydrolysis and condensation reaction. Whether it is MQ silicone resin synthesized by the water glass method or the silicate method, its physical and chemical properties greatly depend on the chemical composition and structure of the resin, such as the type of R group, M / Q value, molecular weight and distribution, three-dimensional topological structure, and the content of silanol groups. Since the content of silanol groups will determine the reactivity and polarity of MQ silicone resin, therefore, in production practice, accurately measuring the content of silanol groups in MQ silicone resin is crucial for people to understand the relationship between the structure and properties of MQ silicone resin and its downstream applications.

[0003] Currently, the testing methods for the content of silanol groups include: titration method (J. Am. Chem. Soc., 1951, 73(5):2367-2368.), reaction gas chromatography (J. Phys. Chem., 1969, 73, 11, 3947–3953.), isotope exchange method (Langmuir, 1991,7(8): 1695-1701.), thermogravimetric analysis (Langmuir, 2003, 19(1), 160-165.), attenuated total reflection infrared spectroscopy (Organic Silicon Materials, 2015, 29(05), 395-398.), etc. Among them, the titration method requires a large amount of samples, expensive reagents, and a blank group for comparison, with cumbersome steps; the reaction gas chromatography method utilizes the active hydrogen on SiOH to react with TiCl4, CH3MgI, LiAlH4, etc. to generate gases, but this method has high requirements for the purity of the products. It not only requires removing the adsorbed substances on the surface, no side reactions in the reaction, but also needs to draw a calibration curve, with cumbersome steps; the isotope exchange method requires degassing treatment before the exchange reaction, with harsh reaction conditions and a long testing cycle; the thermogravimetric analysis method needs to combine with the LiAlH4 titration method to obtain a calibration curve first, with cumbersome steps, and the internal silanol groups may cause weight loss errors; the attenuated total reflection infrared spectroscopy method also needs to rely on the reaction chromatography method to measure the hydroxyl content of the sample first, and then provide a standard sample, measure the spectrum, and draw a calibration curve. In addition, affected by the diffusion rate and diffusion degree, the hydroxyl groups measured by the above methods are all the hydroxyl groups on the surface of the material, and it is difficult to accurately obtain the hydroxyl groups inside the material. Therefore, there is an urgent need to develop a simple and effective method that can accurately characterize the absolute content of silanol groups in MQ silicone resin.

[0004] In recent years, with the development of optoelectronic detection technology, nuclear magnetic resonance spectroscopy (NMR) has been widely used for the qualitative and quantitative analysis of the components and structures of various organic and inorganic substances. For example, the invention patent with the publication number CN114316269A records that the content of silanol groups and alkoxy groups in the MQ resin sample prepared by the silicate method can be tested by nuclear magnetic resonance silicon spectrum, and the mass percentage content of silanol groups and ethoxy groups in the MQ silicone resin sample can be obtained. Thus, the structure of the MQ silicone resin can be judged for its aging resistance performance when applied to silicone pressure-sensitive adhesives. However, it should be noted that whether it is liquid or solid nuclear magnetic resonance silicon spectrum, it is impossible to accurately obtain the ratio of Q linkages (Q 3 and Q 4 linkages) in the MQ resin sample prepared by the silicate method. Summary of the Invention

[0005] The object of the present invention is to provide a method for testing the content of silanol groups in MQ silicone resin. For MQ silicone resins synthesized by the water glass method and the tetraethyl orthosilicate method respectively, due to their different structures, solid-state nuclear magnetic resonance silicon spectroscopy is directly used for detection, or a combination of solid-state nuclear magnetic resonance silicon spectroscopy and liquid-state nuclear magnetic resonance hydrogen spectroscopy is used for detection. It can be used to quantitatively characterize the absolute content of silanol groups in MQ silicone resin, and has the characteristics of simple operation method, not being affected by water or other impurities, and high accuracy.

[0006] The present invention is achieved by the following technical solutions: A method for testing the content of silanol groups in MQ silicone resin, including the following detection methods:

[0007] Ⅰ. Using solid-state nuclear magnetic resonance silicon spectroscopy to quantitatively characterize the mass fraction of silanol groups in MQ silicone resin synthesized by the water glass method;

[0008] Ⅱ. Using a combination of solid-state nuclear magnetic resonance silicon spectroscopy and liquid-state nuclear magnetic resonance hydrogen spectroscopy to quantitatively characterize the mass fraction of silanol groups in MQ silicone resin synthesized by the tetraethyl orthosilicate method.

[0009] The MQ silicone resin synthesized by the water glass method contains at least Q 3 linking units shown in the following formula (1):

[0010] (1).

[0011] The MQ silicone resin synthesized by the tetraethyl orthosilicate method contains at least Q 3 linking units shown in the following formula (1) or formula (2):

[0012] (1)

[0013] (2)

[0014] In formula (2), R is CH2CH3.

[0015] The MQ silicone resin synthesized by the water glass method or the MQ silicone resin synthesized by the tetraethyl orthosilicate method contains at least one of the following groups: hydrogen, methyl, vinyl, phenyl, chloropropyl, (meth)acrylate group.

[0016] In the method Ⅰ, for the MQ silicone resin synthesized by the water glass method, first, it is determined that the number of moles of its Q 3 linking units is the number of moles of silanol groups. By integrating the M linking units, Q 3 linking units and Q 4 linking units on the solid-state nuclear magnetic resonance silicon spectrum respectively, the content of silanol groups in the MQ silicone resin synthesized by the water glass method can be calculated.

[0017] Furthermore, in Method I, the formula for calculating the silanol content of MQ silicone resin by solid-state nuclear magnetic resonance silicon spectrum integration is shown in the following formula (3):

[0018] (3)

[0019] In formula (3), is the integral area of the M link; is Q 3 the integral area of the link; is Q 4 the integral area of the link; a is the molar mass of OH; b is the molar mass of the M link; c is Q 3 the molar mass of the link; d is Q 4 the molar mass of the link.

[0020] In Method II, for the MQ silicone resin synthesized by the tetraethyl orthosilicate method, first, it is determined that the number of moles of the Q 3 link is the sum of the number of moles of silanol and alkoxy groups. Then, the content of alkoxy groups is first determined by liquid nuclear magnetic resonance hydrogen spectrum, and then the M link, Q 3 link and Q 4 link on the solid-state nuclear magnetic resonance silicon spectrum are integrated respectively, and the silanol content in the MQ silicone resin synthesized by the tetraethyl orthosilicate method can be calculated.

[0021] Furthermore, in Method II, when using liquid nuclear magnetic resonance hydrogen spectrum to determine the alkoxy content, the internal standard method is adopted. The MQ silicone resin is measured by liquid nuclear magnetic resonance hydrogen spectrum. The CH2 in the Q 3 link of the internal standard reagent in the nuclear magnetic resonance hydrogen spectrum is integrated respectively, and the content of OCH2CH3 in the MQ silicone resin is calculated.

[0022] The formulas for calculating the content of OCH2CH3 in the MQ silicone resin are shown in the following formulas (4) and (5):

[0023] (4)

[0024] (5)

[0025] In formulas (4) and (5), is the mass of the internal standard; is the mass of the MQ silicone resin, is the mass fraction of H atoms in the internal standard; is Q 3 the mass fraction of 2 H atoms in CH2 of the link in the MQ silicone resin; X is the Q in the MQ silicone resin on the nuclear magnetic resonance hydrogen spectrum 3The ratio of the integrated area of the CH2 peak in the chain link to the integrated area of the CH2 peak in the internal standard reagent, a is the molar mass of OCH2CH3, b is Q 3 and is the molar mass of 2 H atoms in CH2 in the chain link.

[0026] In Method II, the formulas for calculating the silanol groups and alkoxy groups of MQ silicone resin by solid-state nuclear magnetic silicon spectroscopy integration are shown in the following formula (6):

[0027] (6)

[0028] In formula (6), is the integrated area of the M chain link, is Q 3 is the integrated area of the chain link, is Q 4 is the integrated area of the chain link, a is the molar mass of OH, b is the molar mass of the M chain link, c is Q 3 is the molar mass of the chain link, d is Q 4 is the molar mass of the chain link;

[0029] Subtracting the alkoxy group content determined by liquid nuclear magnetic resonance hydrogen spectroscopy from the silanol group and alkoxy group contents calculated by the above solid-state nuclear magnetic silicon spectroscopy method gives the silanol group content in the MQ silicone resin.

[0030] In Method II, 1,4-dioxane, cyclohexane, dimethyl sulfoxide, or hydroquinone is used as the internal standard reagent.

[0031] It should be noted that the silanol group content involved in the present invention refers to the mass percentage of hydroxyl groups in the MQ silicone resin, that is:

[0032] (7)

[0033] In formula (7), and respectively represent the mass of the hydroxyl group and the mass of the MQ silicone resin.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] (1) The method of the present invention is based on solid-state nuclear magnetic silicon spectroscopy to characterize MQ silicone resin, which is convenient and fast, does not require pretreatment, and is applicable to MQ silicone resins with different synthesis methods and different organic groups, and is not affected by acid-base residues, moisture, and other impurities in the sample.

[0036] (2) Compared with the existing characterization methods for the hydroxyl content of MQ silicone resin, the solid-state nuclear magnetic silicon spectrum can accurately obtain the silicon hydroxyl contents on the surface and inside of MQ silicone resin simultaneously, and it is an absolute method for measuring the mass fraction of silicon hydroxyl.

[0037] (3) The present invention specifically adopts different detection methods for MQ silicone resins prepared by different synthesis methods, that is: the solid-state nuclear magnetic resonance silicon spectrum method can be used to characterize the MQ silicone resin prepared by the water glass method, and the solid-state nuclear magnetic resonance silicon spectrum and the liquid-state nuclear magnetic resonance hydrogen spectrum methods are combined to determine the MQ silicone resin prepared by the tetraethyl orthosilicate method, which can improve the accuracy of the silicon hydroxyl content in MQ silicone resin, especially for the MQ silicone resin prepared by the tetraethyl silicate method. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the structural formula of MQ silicone resin (R1, R2, R3 are organic groups, including hydrogen-containing, methyl, vinyl, phenyl, chloropropyl, (meth)acrylate groups, etc. Among them, R1, R2, R3 can be the same or different).

[0039] Figure 2 is the solid-state nuclear magnetic silicon spectrum of a methyl MQ silicone resin with a relatively high hydroxyl content.

[0040] Figure 3 is the solid-state nuclear magnetic silicon spectrum of a methyl MQ silicone resin with a medium hydroxyl content.

[0041] Figure 4 is the solid-state nuclear magnetic silicon spectrum of a methyl MQ silicone resin with a relatively low hydroxyl content.

[0042] Figure 5 is the solid-state nuclear magnetic silicon spectrum of a vinyl MQ silicone resin.

[0043] Figure 6 is the solid-state nuclear magnetic silicon spectrum of a phenyl MQ silicone resin.

[0044] Figure 7 is the solid-state nuclear magnetic silicon spectrum of an MQ silicone resin (i.e., Wacker 803) prepared by the tetraethyl orthosilicate (TEOS) method.

[0045] Figure 8 is the liquid-state nuclear magnetic hydrogen spectrum of an MQ silicone resin (i.e., Wacker 803) prepared by the tetraethyl orthosilicate (TEOS) method. DETAILED DESCRIPTION OF THE INVENTION

[0046] Hereinafter, the object of the invention, the technical solution and the beneficial effects of the present invention will be further described in detail.

[0047] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the claimed invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the present invention pertains.

[0048] The present invention can detect the content of silanol groups in MQ silicone resins with different synthesis methods and different organic groups, and can accurately obtain the content of silanol groups on the surface and inside of MQ silicone resins, with high accuracy.

[0049] The present invention uses two methods for measurement. One is for MQ silicone resins prepared by the water glass method, and solid-state nuclear magnetic resonance silicon spectroscopy is used for characterization; the other is for MQ silicone resins prepared by the tetraethyl orthosilicate method, and a combination of solid-state nuclear magnetic resonance silicon spectroscopy and liquid nuclear magnetic resonance proton spectroscopy is used. The specific test methods can be summarized as follows:

[0050] Method 1: Quantitative characterization of the mass fraction of silanol groups in MQ silicone resins synthesized by the water glass method using solid-state nuclear magnetic resonance silicon spectroscopy. The specific steps are as follows:

[0051] S1. Collection of solid-state nuclear magnetic resonance silicon spectrum of MQ silicone resin

[0052] Experimental samples: Various MQ silicone resins synthesized by the water glass method; dosage 50 - 500 mg;

[0053] Experimental instrument: Nuclear magnetic resonance silicon spectrometer;

[0054] Experimental parameters: Magnetic field strength 11.746 T; aperture 89 mm; use a 7 mm magic angle probe, double resonance mode and use a double gas path support; use a contact time of 10 ms and a pulse repetition time of 0.5 - 1.0 s; number of scans 2 n (n ≥ 7) times.

[0055] S2. Analysis of solid-state nuclear magnetic resonance silicon spectrum of MQ silicone resin

[0056] First, the peaks in the collected solid-state nuclear magnetic resonance spectrum are assigned. The peak region of the M link in MQ silicone resin is generally at 30 - -6 ppm, while the Q link generally splits into peaks, which are Q 3 (-90 - -104.5 ppm) and Q 4 (-104.5 - -120 ppm). The above M, Q 3 and Q 4 peak regions can be integrated respectively. The structures and general integration intervals of Q 3 and Q 4 are as follows:

[0057]

[0058]

[0059] Quantitative calculation of the content of silanol groups in S3.MQ silicone resin

[0060] According to the types of end-capping agents used in the synthesis process, determine the chemical composition of the M link. For example, if it is end-capped with (CH3)3SiOSi(CH3)3 or (CH3)3SiCl, the M link is (CH3)3SiO 1 / 2 , and so on for other cases,

[0061] The calculation formula for the mass fraction of silanol groups is as follows:

[0062] (3)

[0063] In formula (3), is the integral area of the M link, is Q 3 the integral area of the link, is Q 4 the integral area of the link, a is the molar mass of OH, b is the molar mass of the M link, c is Q 3 the molar mass of the link, d is Q 4 the molar mass of the link.

[0064] Method 2: Quantitative characterization of the mass fraction of silanol groups in MQ silicone resin synthesized by the tetraethyl orthosilicate method by combining solid-state nuclear magnetic resonance silicon spectrum and liquid nuclear magnetic resonance hydrogen spectrum. The specific steps are as follows:

[0065] S1. Acquisition of the nuclear magnetic resonance spectrum of MQ silicone resin

[0066] S1.1. Acquisition of liquid nuclear magnetic resonance hydrogen spectrum

[0067] Experimental sample preparation: Use a clean nuclear magnetic resonance tube, weigh the internal standard reagent m1 (mg) and the MQ silicone resin sample m2 (mg), add deuterated reagent, and wait until the internal standard reagent and the silicone resin are completely dissolved in the deuterated reagent before testing.

[0068] Experimental instrument: Nuclear magnetic resonance hydrogen spectrometer;

[0069] Experimental parameters: Magnetic field strength 9.4 T; Use a 5 mm two-in-one probe.

[0070] S1.2. Acquisition of solid-state nuclear magnetic resonance silicon spectrum

[0071] Experimental sample: Commercial MQ silicone resin synthesized by the tetraethyl orthosilicate method; dosage 50 - 500 mg;

[0072] Experimental instrument: Nuclear magnetic resonance silicon spectrometer;

[0073] Experimental parameters: Magnetic field strength 11.746 T; aperture 89 mm; using a 7 mm magic angle probe, double resonance mode and using a dual gas path support; using a contact time of 10 ms and a pulse repetition time of 0.5 - 1.0 s; number of scans 2 n (n ≥ 7) times.

[0074] Analysis of the NMR spectrum of S2.MQ silicone resin

[0075] S2.1. Analysis of the liquid nuclear magnetic resonance hydrogen spectrum

[0076] First, assign the peaks in the nuclear magnetic resonance hydrogen spectrum. The CH2 peak interval of the internal standard reagent (1,4-dioxane) is generally in the range of 4.0 - 3.5 ppm, while in the MQ silicone resin prepared by the tetraethyl orthosilicate method, the Q 3 in the Si-O-R link of the chain may be H or CH2CH3, as shown below:

[0077]

[0078] Roughly, in the MQ silicone resin prepared by the tetraethyl orthosilicate method, most of the R in Q 3 is H, and the proportion of CH2CH3 is extremely small and can be ignored. According to Technical Solution 1, the content of silanol groups can be calculated;

[0079] Strictly speaking, we need to first calculate the content of trace Si-OCH2CH3 according to the liquid nuclear magnetic resonance hydrogen spectrum (internal standard method). Among them, the CH2 peak generally appears at 1.3 - 0.8 ppm. Integrate the internal standard reagent (1,4-dioxane, cyclohexane, dimethyl sulfoxide or hydroquinone can be used, and 1,4-dioxane is taken as an example in the present invention) and the CH2 characteristic peak region in Q 3 respectively. The specific integration intervals are as follows:

[0080]

[0081] S2.2. Solid-state nuclear magnetic resonance silicon spectrum analysis is the same as step S2 of Method 1

[0082] S3. Quantitative calculation of the silanol group content in MQ silicone resin

[0083] S3.1. According to the nuclear magnetic resonance hydrogen spectrum, convert the mass fraction of H atoms in their respective molecules to the mass fraction of Si-OCH2CH3 (or Si-OCH3) based on the ratio of their integral areas. The specific calculation method is as follows:

[0084]

[0085] (4)

[0086] (5)

[0087] In formulas (4) and (5), is the mass of the internal standard substance,[[]] is the mass of the MQ silicone resin,[[]] is the mass fraction of H atoms in the internal standard substance,[[]] is Q,[[]] 3 The mass fraction of 2 H atoms in CH2 in the Q chain link in the MQ silicone resin, X is the ratio of the integral area of the CH2 peak in the Q chain link in the MQ silicone resin to the CH2 peak in the internal standard reagent in the nuclear magnetic hydrogen spectrum diagram,[[]] 3 is the molar mass of OCH2CH3,[[]] a is Q,[[]] b is Q,[[]] 3 The molar mass of 2 H atoms in CH2 in the Q chain link.[[]]

[0088] S3.2. According to the solid-state nuclear magnetic silicon spectrum, the calculation method is the same as that in Technical Solution 1. At this time, based on Q,[[]] 3 The calculated value is the sum of the mass fractions of Si-OH and Si-OCH2CH3.[[]]

[0089] Subtract the result obtained in S3.2 from the result obtained in S3.1, and the mass fraction of OH can be obtained.[[]]

[0090] The following uses several typical embodiments to illustrate the specific implementation manners of the present invention. Of course, the protection scope of the present invention is not limited to the following embodiments. For the detailed process and parameters, refer to the above test method of the present invention.[[]]

[0091] Example 1:[[]]

[0092] In this example, the solid-state nuclear magnetic silicon spectrum method is used to characterize a methyl MQ silicone resin with a relatively high hydroxyl content (synthesized by the water glass method), and a nuclear magnetic spectrum diagram is obtained. See Figure 2 .

[0093] First, assign the peaks in the nuclear magnetic spectrum diagram. Among them, the single peak at 30 to -6 ppm is the M link, and the doublets at -90 to -120 ppm are the Q 3 and Q 4 chain links, respectively integrate them, and obtain the proportion of each chain link.[[]]

[0094] The M link of the methyl MQ silicone resin is (CH3)3SiO 1 / 2 , therefore, the following formula can be used for calculation:[[]]

[0095]

[0096]

[0097] The silanol content of the methyl MQ silicone resin in this example is calculated to be 5.83%.

[0098] Example 2:

[0099] In this example, solid-state nuclear magnetic silicon spectroscopy was used to characterize a methyl MQ silicone resin with a medium hydroxyl content (synthesized by the water glass method), and a nuclear magnetic spectrum was obtained. See Figure 3 .

[0100] First, the peaks in the nuclear magnetic spectrum were assigned. Among them, the single peak at 30 to -6 ppm is the M link, and the doublets at -90 to -120 ppm are the Q 3 and Q 4 links, respectively. Integrating each gives the proportion of each link.

[0101] The M link of the methyl MQ silicone resin is (CH3)3SiO 1 / 2 , so the following formula can be used for calculation:

[0102]

[0103]

[0104] The silanol content of the methyl MQ silicone resin in this example is calculated to be 3.93%.

[0105] Example 3:

[0106] In this example, solid-state nuclear magnetic silicon spectroscopy was used to characterize a methyl MQ silicone resin with a low hydroxyl content (synthesized by the water glass method), and a nuclear magnetic spectrum was obtained. See Figure 4 .

[0107] First, the peaks in the nuclear magnetic spectrum were assigned. Among them, the single peak at 30 to -6 ppm is the M link, and the doublets at -90 to -120 ppm are the Q 3 and Q 4 links, respectively. Integrating each gives the proportion of each link.

[0108] The M link of the methyl MQ silicone resin is (CH3)3SiO 1 / 2 , so the following formula can be used for calculation:

[0109]

[0110]

[0111] The silanol content of the methyl MQ silicone resin in this example is calculated to be 1.62%.

[0112] Example 4:

[0113] In this example, solid-state nuclear magnetic silicon spectroscopy was used to characterize a vinyl MQ silicone resin (synthesized by the water glass method), and a nuclear magnetic spectrum was obtained. See Figure 5 .

[0114] First, the peaks in the nuclear magnetic spectrum were assigned. Among them, the peaks at 30 to -6 ppm are M linkages, and the doublets at 90 to -120 ppm are Q 3 and Q 4 linkages. Integrating each of them gives the proportion of each linkage.

[0115] There are two types of end-capping agents for the vinyl MQ silicone resin, so there are two corresponding M linkages, namely CH2=CH(CH3)2SiO 1 / 2 and H(CH3)2SiO 1 / 2 . Therefore, the calculation can be carried out according to the following formula:

[0116]

[0117]

[0118] From this calculation, the silanol content of the vinyl MQ silicone resin in this example was found to be 1.62%.

[0119] Example 5:

[0120] In this example, solid-state nuclear magnetic silicon spectroscopy was used to characterize a phenyl MQ silicone resin (synthesized by the water glass method), and a nuclear magnetic spectrum was obtained. See Figure 6 .

[0121] First, the peaks in the nuclear magnetic spectrum were assigned. Among them, the singlet at 30 to -6 ppm is the M linkage, and the peaks at -90 to -105 ppm and -105 to -120 ppm are Q 3 and Q 4 linkages. Integrating each of them gives the

[0122] The M linkage of the phenyl MQ silicone resin is C6H5(CH3)2SiO 1 / 2 . Therefore, the calculation can be carried out according to the following formula:

[0123]

[0124]

[0125] From this calculation, the silanol content of the phenyl MQ silicone resin in this example was found to be 1.58%.

[0126] Example 6:

[0127] In this example, liquid nuclear magnetic resonance hydrogen spectrum and solid nuclear magnetic resonance silicon spectrum were used to characterize the MQ silicone resin synthesized by the tetraethyl orthosilicate method (TEOS method), and the nuclear magnetic resonance hydrogen spectrum and silicon spectrum were obtained respectively. See Figure 7 and Figure 8 .

[0128] Peak deconvolution analysis was performed on the curves. Among them, according to the nuclear magnetic resonance hydrogen spectrum (internal standard method), the mass fraction of Si-OCH2CH3 can be calculated; then, according to the nuclear magnetic resonance silicon spectrum method Q 3 The sum of the mass fractions of Si-OCH2CH3 and Si-OH was calculated by partial integration, and the OH mass fraction of the MQ silicone resin by the tetraethyl orthosilicate method was obtained by subtraction.

[0129] Quantitative calculation of silanol groups:

[0130] According to the nuclear magnetic resonance hydrogen spectrum, the mass fraction of Si-OCH2CH3 was calculated as follows:

[0131]

[0132]

[0133]

[0134] According to the solid-state nuclear magnetic resonance silicon spectrum, the calculation is as follows:

[0135]

[0136] First, let the molar proportion of CH3CH2O-SiO 3 in Q 3 / 2 be x, so the molar proportion of HO-SiO 3 / 2 is 0.29 - x, then it can be calculated that:

[0137]

[0138] Solving gives x = 0.13,

[0139]

[0140] From this, the silanol group content of the MQ silicone resin in this example was calculated to be 1.89%.

[0141] For the MQ silicone resins of Examples 1 to 6, the silanol group content in them was calibrated by the titration method at the same time. The silanol group contents of Examples 1 to 6 above and the silanol group contents calibrated by the titration method were summarized as shown in the following table:

[0142]

[0143] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A test method for the content of silanol groups in MQ silicone resin, characterized in that: Including the following detection methods: Ⅰ. Quantitatively characterizing the mass fraction of silanol groups in MQ silicone resin synthesized by the water glass method using solid-state nuclear magnetic resonance silicon spectroscopy; Ⅱ. Quantitative characterization of the mass fraction of silanol groups in MQ silicone resin synthesized by tetraethyl orthosilicate method by combining solid-state nuclear magnetic resonance silicon spectroscopy and liquid nuclear magnetic resonance hydrogen spectroscopy: First, it is determined that the number of moles of its Q 3 linking units is the sum of the number of moles of silanol groups and alkoxy groups. Then, the content of alkoxy groups is first determined by liquid nuclear magnetic resonance hydrogen spectroscopy, and then the M linking units, Q 3 linking units and Q 4 linking units on the solid-state nuclear magnetic resonance silicon spectroscopy are integrated respectively, and the content of silanol groups in the MQ silicone resin synthesized by tetraethyl orthosilicate method can be calculated.

2. The test method according to claim 1, wherein: The Q contained in the MQ silicone resin synthesized by the water glass method contains at least the Q represented by the following formula (1) 3 linkage: （1）。 3. The test method according to claim 1, wherein: The MQ silicone resin synthesized by the tetraethyl orthosilicate method contains at least Q represented by the following formula (1) or formula (2). 3 Linkage: （1） （2） In formula (2), R is CH2CH3.

4. The test method according to claim 1, characterized in that: The MQ silicone resin synthesized by the water glass method or the MQ silicone resin synthesized by the tetraethyl orthosilicate method contains at least one of the following groups: hydrogen, methyl, vinyl, phenyl, chloropropyl, (meth)acrylate group.

5. The test method according to claim 1, characterized in that: In the first method, for the MQ silicone resin synthesized by the waterglass method, the number of moles of the Q 3 linking units is first determined to be the number of moles of silanol groups. By integrating the M linking units, Q 3 linking units, and Q 4 linking units respectively on the solid-state nuclear magnetic resonance silicon spectrum, the silanol group content in the MQ silicone resin synthesized by the waterglass method can be calculated.

6. The test method according to claim 5, characterized in that: The formula for calculating the silanol group content of MQ silicone resin by solid-state nuclear magnetic resonance silicon spectroscopy integration is shown in the following formula (3): （3） In formula (3), is the integrated area of the M link, is Q 3 the integrated area of the link, is Q 4 the integrated area of the link, a is the molar mass of OH, b is the molar mass of the M link, c is Q 3 the molar mass of the link, d is Q 4 the molar mass of the link.

7. The test method according to claim 1, characterized in that: When determining the alkoxy content by liquid nuclear magnetic resonance hydrogen spectroscopy, the internal standard method is adopted. The liquid nuclear magnetic resonance hydrogen spectroscopy of MQ silicone resin is measured, and the CH2 in the internal standard reagent and the CH2 in the Q 3 link in the nuclear magnetic resonance hydrogen spectrum are integrated respectively to calculate the content of OCH2CH3 in MQ silicone resin. The formulas for calculating the content of OCH2CH3 in MQ silicone resin are shown in the following formulas (4) and (5): （4） （5） In formulas (4) and (5), is the mass of the internal standard substance, is the mass of the MQ silicone resin, is the mass fraction of H atoms in the internal standard substance, is Q 3 the mass fraction of 2 H atoms in CH2 in the Q chain segment in the MQ silicone resin, X is the ratio of the integral area of the CH2 peak in the Q chain segment in the MQ silicone resin to the CH2 peak in the internal standard reagent in the 1H NMR spectrum, 3 is the ratio of the integral area of the CH2 peak in the Q chain segment of the MQ silicone resin to the CH2 peak in the internal standard reagent, a is the molar mass of OCH2CH3, b is Q 3 the molar mass of 2 H atoms in CH2 in the Q chain segment.

8. The test method according to claim 7, wherein: The formula for calculating the silanol groups and alkoxy groups of MQ silicone resin by solid-state nuclear magnetic resonance silicon spectroscopy integration is shown in the following formula (6): （6） In formula (6), is the integral area of the M link, is Q 3 the integral area of the link, is Q 4 the integral area of the link, a is the molar mass of OH, b is the molar mass of the M link, c is Q 3 the molar mass of the link, d is Q 4 the molar mass of the link; Subtracting the alkoxy group content determined by liquid nuclear magnetic resonance hydrogen spectroscopy from the contents of silanol groups and alkoxy groups calculated by the above solid-state nuclear magnetic resonance silicon spectroscopy method gives the silanol group content in the MQ silicone resin.

9. The test method according to claim 7, characterized in that: Using 1,4-dioxane, cyclohexane, dimethyl sulfoxide or hydroquinone as the internal standard reagent.

Images