CN116165236A - Method for testing silicon hydroxyl content in MQ silicon resin - Google Patents

Abstract

The invention discloses a method for testing the content of silicon hydroxyl in MQ silicon resin, which comprises two detection modes, wherein one mode is to quantitatively represent the mass fraction of the silicon hydroxyl in the MQ silicon resin synthesized by a water glass method by adopting a solid-state nuclear magnetic resonance silicon spectrum; and the mass fraction of silicon hydroxyl in the MQ silicon resin synthesized by the tetraethoxysilane method is quantitatively characterized by combining a solid-state nuclear magnetic resonance silicon spectrum and a liquid-state nuclear magnetic resonance hydrogen spectrum. Therefore, the invention is used for quantitatively representing the absolute content of silicon hydroxyl in the MQ silicon resin, and has the characteristics of simple operation, no influence of water or other impurities and high accuracy.

Description

A test method for silanol content in MQ silicone resin

Technical Field

The invention belongs to the technical field of polymer material detection, and specifically relates to a method for testing the silanol content in MQ silicone resin.

Background Art

MQ silicone resin is a special type of polysiloxane resin. It is a polysiloxane with a three-dimensional spherical or highly branched structure, which is formed by hydrolysis and condensation of monofunctional siloxane segments (R ₃ SiO _1/2 , referred to as M segments) and tetrafunctional siloxane segments (SiO _4/2 , referred to as Q segments) with Si-O bonds as the skeleton. Its typical (planar) chemical structure is shown in Figure 1. Compared with organic polymer compounds, MQ silicone resin has better high temperature resistance, water repellency, chemical resistance, electrical insulation, weather resistance, flexibility, film-forming property, adhesion and excellent mechanical properties. It has been widely used in pressure-sensitive adhesives, liquid silicone rubber reinforcement, cosmetics, high temperature resistant coatings, release agents and other fields. At present, there are two main 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 segment monomers and water glass as Q segment monomers; while the latter is formed by hydrolysis and condensation reaction with ethyl orthosilicate as Q segment precursor and (partial) end-capping with M segment monomers. Whether MQ silicone resin is synthesized by water glass method or silicate method, its physical and chemical properties are greatly dependent 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 silanol content. Since the silanol content determines the reactivity and polarity of MQ silicone resin, in production practice, accurate measurement of the silanol content in MQ silicone resin is crucial for people to understand the relationship between the structure and performance of MQ silicone resin and its downstream applications.

At present, the testing methods for silanol content 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 Silicone Materials, 2015, 29(05), 395-398.), etc. Among them, the titration method requires more samples, expensive reagents, and requires a blank control group, and the steps are cumbersome; the reaction gas chromatography method uses the active hydrogen on SiOH to react with TiCl ₄ , CH ₃ MgI, LiAlH _4, etc. to generate gas, but this method has high requirements for the purity of the product, not only requires the removal of surface adsorbed substances, requires no side reactions in the reaction, but also requires the drawing of calibration curves, and the steps are cumbersome; the isotope exchange method requires degassing before the exchange reaction, the reaction conditions are harsh, and the test cycle is long; the thermogravimetric analysis method needs to be combined with the LiAlH ₄ titration method to obtain a calibration curve first, the steps are cumbersome, and the internal silicon hydroxyl groups may cause weight loss errors; the attenuated total reflection infrared spectroscopy method also needs to use the reaction chromatography method to first determine the hydroxyl content of the sample, 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 method are all hydroxyl groups on the surface of the material, and it is difficult to accurately obtain the hydroxyl groups inside the material. Therefore, it is urgent to develop a simple and effective method that can accurately characterize the absolute content of silicon hydroxyl groups in MQ silicone resin.

In recent years, with the development of photoelectric detection technology, nuclear magnetic resonance spectroscopy (NMR) has been widely used for qualitative and quantitative analysis of various organic and inorganic components and structures. For example, the invention patent with publication number CN114316269A records that the silicon nuclear magnetic resonance spectrum can be used to test the content of silanol and alkoxy in the MQ resin sample prepared by the silicate method, and the mass percentage of silicon hydroxy and ethoxy in the MQ silicone resin sample can be obtained, thereby judging the aging resistance of the MQ silicone resin structure when applied to silicone pressure-sensitive adhesives. However, it should be noted that no matter whether it is liquid or solid silicon nuclear magnetic resonance spectrum, the proportion of Q segments (Q ³ and Q ⁴ segments) in the MQ resin sample prepared by the silicate method cannot be accurately obtained.

Summary of the invention

The invention aims to provide a method for testing the content of silanol in MQ silicone resin. The method is respectively for MQ silicone resins synthesized by a water glass method and a ethyl orthosilicate method. Due to their different structures, the method directly detects the silanol by solid-state nuclear magnetic resonance silicon spectrum, or detects the silanol by combining solid-state nuclear magnetic resonance silicon spectrum with liquid nuclear magnetic resonance hydrogen spectrum. The method can be used to quantitatively characterize the absolute content of silanol in the MQ silicone resin. The method has the characteristics of simple operation, no influence of water or other impurities, and high accuracy.

The present invention is achieved by the following technical solution: A method for testing the silanol content in MQ silicone resin, comprising the following detection methods:

Ⅰ. Solid-state NMR silicon spectroscopy was used to quantitatively characterize the mass fraction of silanol groups in MQ silicone resin synthesized by the water glass method;

Ⅱ. The mass fraction of silanol groups in MQ silicone resin synthesized by the ethyl orthosilicate method was quantitatively characterized by combining solid-state silicon nuclear magnetic resonance spectroscopy and liquid hydrogen nuclear magnetic resonance spectroscopy.

The MQ silicone resin synthesized by the water glass method contains at least a ^Q3 chain segment represented by the following formula (1):

（1）。

(1).

The MQ silicone resin synthesized by the tetraethyl orthosilicate method contains at least a ^Q3 chain segment represented by the following formula (1) or the following formula (2):

（1）

(1)

（2）

(2)

In formula (2), R is CH ₂ CH ₃ .

The MQ silicone resin synthesized by the water glass method or the MQ silicone resin synthesized by the ethyl orthosilicate method contains at least one of the following groups: hydrogen, methyl, vinyl, phenyl, chloropropyl, and (methyl)acrylate.

In the method I, for the MQ silicone resin synthesized by the water glass method, the molar number of its Q ³ chain link is first determined to be the molar number of silanol. By integrating the M chain link, Q ³ chain link and Q ⁴ chain link on the solid-state NMR silicon spectrum respectively, the silanol content in the MQ silicone resin synthesized by the water glass method can be calculated.

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

（3）

(3)

为M链节的积分面积、

为Q³链节的积分面积、

为Q⁴链节的积分面积、a为OH的摩尔质量、b为M链节的摩尔质量、c为Q³链节的摩尔质量、d为Q⁴链节的摩尔质量。In formula (3),

is the integral area of the M chain link,

is the integrated area of Q ³ chain link,

is the integrated area of the ^Q4 chain segment, a is the molar mass of OH, b is the molar mass of the M chain segment, c is the molar mass of the Q3 ^chain segment, and d is the molar mass of the ^Q4 chain segment.

In the method II, for the MQ silicone resin synthesized by the tetraethyl orthosilicate method, the molar number of its ^Q3 chain segment is first determined to be the sum of the molar numbers of silanol and alkoxy groups, and then the content of alkoxy groups is first determined by liquid nuclear magnetic resonance hydrogen spectrum, and then the M chain segment, ^Q3 chain segment and ^Q4 chain segment are integrated separately on the solid-state nuclear magnetic resonance silicon spectrum to calculate the silanol content in the MQ silicone resin synthesized by the tetraethyl orthosilicate method.

Furthermore, in method II, when the alkoxy content is determined by liquid NMR hydrogen spectrum, the internal standard method is used to measure the MQ silicone resin by liquid NMR hydrogen spectrum, and the CH ₂ in the internal standard reagent Q ³ chain segment on the NMR hydrogen spectrum is integrated respectively to calculate the OCH ₂ CH ₃ content in the MQ silicone resin.

The formula _for calculating the content of _OCH2CH3 in MQ silicone resin is shown in the following formulas (4) and (5):

（4）

(4)

（5）

(5)

为内标物的质量、

为MQ硅树脂的质量，

为内标物中H原子的质量分数、

为Q³链节中的CH₂中2个H原子占MQ硅树脂的质量分数、X为核磁氢谱图上MQ硅树脂中Q³链节中CH₂峰和内标试剂中CH₂峰的积分面积之比、a为OCH₂CH₃摩尔质量、b为Q³链节中的CH₂中2个H原子的摩尔质量。In formulas (4) and (5),

is the mass of the internal standard,

For the quality of MQ silicone resin,

is the mass fraction of H atoms in the internal standard,

is the mass fraction of the 2 H atoms in CH ₂ in the Q ³ chain in the MQ silicone resin, X is the ratio of the integrated area of the CH ₂ peak in the Q ³ chain in the MQ silicone resin and the CH ₂ peak in the internal standard reagent on the H NMR spectrum, a is the molar mass of OCH ₂ CH ₃ , and b is the molar mass of the 2 H atoms in CH ₂ in the Q ³ chain.

In method II, the formula for calculating the silanol and alkoxy groups of MQ silicone resin by integrating the solid-state NMR silicon spectrum is shown in the following formula (6):

（6）

(6)

为M链节的积分面积、

为Q³链节的积分面积、

为Q⁴链节的积分面积、a为OH的摩尔质量、b为M链节的摩尔质量、c为Q³链节的摩尔质量、d为Q⁴链节的摩尔质量；In formula (6),

is the integral area of the M chain link,

is the integrated area of Q ³ chain link,

is the integrated area of ^Q4 chain segment, a is the molar mass of OH, b is the molar mass of M chain segment, c is the molar mass of Q3 ^chain segment, d is the molar mass of Q4 ^chain segment;

The silanol content in the MQ silicone resin is obtained by subtracting the alkoxy content determined by the liquid H NMR spectrum from the silanol and alkoxy content calculated by the solid-state NMR silicon spectrum method.

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

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

（7）

(7)

和

分别代表羟基的质量和MQ硅树脂的质量。In formula (7),

and

represent the mass of hydroxyl group and the mass of MQ silicone resin respectively.

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

(1) The method of the present invention is based on solid-state NMR silicon spectroscopy to characterize MQ silicone resin. It is convenient and rapid, does not require pretreatment, and is applicable to MQ silicone resins with different synthesis methods and different organic groups. It is not affected by acid and alkali residues, moisture and other impurities in the sample.

(2) Compared with the existing characterization methods for the hydroxyl content of MQ silicone resin, the method of the present invention can accurately obtain the silanol content on the surface and inside of MQ silicone resin simultaneously by solid-state NMR silicon spectroscopy, which is an absolute method for measuring the mass fraction of silanol.

(3) The present invention specifically adopts different detection methods for MQ silicone resins prepared by different synthesis methods, namely: solid-state nuclear magnetic resonance silicon spectroscopy can be used to characterize the MQ silicone resin prepared by the water glass method, and solid-state nuclear magnetic resonance silicon spectroscopy and liquid nuclear magnetic resonance hydrogen spectroscopy are combined to determine the MQ silicone resin prepared by the tetraethyl orthosilicate method, which can improve the accuracy of the silanol content in the MQ silicone resin, especially the MQ silicone resin prepared by the tetraethyl orthosilicate method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is the structural formula of MQ silicone resin (R ₁ , R ₂ , R ₃ are organic groups, including hydrogen, methyl, vinyl, phenyl, chloropropyl, (meth)acrylate, etc., wherein R ₁ , R ₂ , R ₃ may be the same or different).

FIG. 2 is a solid-state NMR silicon spectrum of a methyl MQ silicone resin having a higher hydroxyl content.

FIG3 is a solid-state NMR silicon spectrum of a methyl MQ silicone resin having a medium hydroxyl content.

FIG. 4 is a solid-state NMR silicon spectrum of a methyl MQ silicone resin having a lower hydroxyl content.

FIG. 5 is a solid-state NMR silicon spectrum of a vinyl MQ silicone resin.

FIG. 6 is a solid-state NMR silicon spectrum of a phenyl MQ silicone resin.

FIG. 7 is a solid-state NMR silicon spectrum of MQ silicone resin (i.e., Wacker 803) prepared by a tetraethyl orthosilicate (TEOS) method.

FIG8 is a liquid NMR hydrogen spectrum of MQ silicone resin (i.e., Wacker 803) prepared by the tetraethyl orthosilicate (TEOS) method.

DETAILED DESCRIPTION

The invention objectives, technical solutions and beneficial effects of the present invention are further described in detail below.

It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the claimed invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs.

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

The present invention adopts two methods for measurement. One is to characterize the MQ silicone resin prepared by the water glass method by solid-state nuclear magnetic resonance silicon spectroscopy; the other is to characterize the MQ silicone resin prepared by the ethyl orthosilicate method by a combination of solid-state nuclear magnetic resonance silicon spectroscopy and liquid nuclear magnetic resonance hydrogen spectroscopy. The specific test methods can be summarized as follows:

Method 1: using solid-state nuclear magnetic resonance silicon spectroscopy to quantitatively characterize the mass fraction of silanol in MQ silicone resin synthesized by the water glass method. The specific steps are as follows:

S1. Collection of solid-state NMR spectra of MQ silicone resin

Experimental samples: various MQ silicone resins synthesized by the water glass method; dosage 50 ~ 500 mg;

Experimental instruments: silicon nuclear magnetic resonance spectrometer;

Experimental parameters: magnetic field strength 11.746 T; aperture 89 mm; 7 mm magic angle probe, double resonance mode and dual gas path support; 10 ms contact time and 0.5 ~ 1.0 s pulse repetition time; scan number ²ⁿ (n ≥ 7) times.

S2. Analysis of solid-state NMR spectra of MQ silicone resin

First, the peaks of the collected solid-state NMR spectrum are assigned. The peak area of the M segment in MQ silicone resin is generally between 30 and -6 ppm, while the Q segment generally has separate peaks, namely Q ³ (-90 to -104.5 ppm) and Q ⁴ (-104.5 to -120ppm). The peak areas of M, Q ³ and Q ⁴ can be integrated separately. The structures and general integration ranges of Q ³ and Q ⁴ are as follows:

Quantitative calculation of silanol content in S3.MQ silicone resin

The chemical composition of the M segment is determined according to the type of end-capping agent used in the synthesis process. For example, if (CH ₃ ) ₃ SiOSi(CH ₃ ) ₃ or (CH ₃ ) ₃ SiCl is used for end-capping, the M segment is (CH ₃ ) ₃ SiO _1/2 . The same logic can be applied to other situations.

The calculation formula of silanol mass fraction is as follows:

（3）

(3)

为M链节的积分面积、

为Q³链节的积分面积、

为Q⁴链节的积分面积、a为OH的摩尔质量、b为M链节的摩尔质量、c为Q³链节的摩尔质量、d为Q⁴链节的摩尔质量。In formula (3),

is the integral area of the M chain link,

is the integrated area of Q ³ chain link,

is the integrated area of the ^Q4 chain segment, a is the molar mass of OH, b is the molar mass of the M chain segment, c is the molar mass of the Q3 ^chain segment, and d is the molar mass of the ^Q4 chain segment.

Method 2: using solid-state silicon nuclear magnetic resonance spectroscopy and liquid hydrogen nuclear magnetic resonance spectroscopy to quantitatively characterize the mass fraction of silanol in MQ silicone resin synthesized by ethyl orthosilicate method. The specific steps are as follows:

S1. Collection of NMR spectra of MQ silicone resin

S1.1. Collection of liquid H NMR spectra

Experimental sample preparation: Use a clean NMR tube to weigh the internal standard reagent m ₁ (mg) and the MQ silicone resin sample m ₂ (mg), add the deuterated reagent, and wait until the internal standard reagent and the silicone resin are completely dissolved in the deuterated reagent before testing.

Experimental instruments: Nuclear magnetic resonance hydrogen spectrometer;

Experimental parameters: magnetic field strength 9.4 T; using 5 mm two-in-one probe.

S1.2. Collection of solid-state NMR silicon spectra

Experimental sample: commercial MQ silicone resin synthesized by ethyl orthosilicate method; dosage 50 ~ 500 mg;

Experimental instruments: silicon nuclear magnetic resonance spectrometer;

Experimental parameters: magnetic field strength 11.746 T; aperture 89 mm; 7 mm magic angle probe, double resonance mode and dual gas path support; 10 ms contact time and 0.5 ~ 1.0 s pulse repetition time; scan number ²ⁿ (n ≥ 7) times.

S2. Analysis of NMR spectra of MQ silicone resin

S2.1. Analysis of liquid H-NMR spectra

First, the peaks of the H NMR spectrum are assigned. The CH ₂ peak of the internal standard reagent (1,4-dioxane) is generally between 4.0 and 3.5 ppm, while the Q ³ chain Si-OR in the MQ silicone resin produced by the tetraethyl orthosilicate method may be H or CH ₂ CH ₃ , as shown below:

Roughly speaking, the vast majority of R in the MQ silicone resin Q ³ prepared by the ethyl orthosilicate method is H, and the proportion of CH ₂ CH ₃ is extremely small and negligible. The silanol content can be calculated according to Technical Scheme 1;

Strictly, we need to first calculate the content of trace Si-OCH ₂ CH ₃ based on liquid nuclear magnetic hydrogen spectrum (internal standard method), where the peak of CH ₂ generally appears at 1.3 ~ 0.8 ppm. The internal standard reagent (1,4-dioxane, cyclohexane, dimethyl sulfoxide or hydroquinone can be used. The present invention takes 1,4-dioxane as an example) and the characteristic peak area of CH ₂ in Q ³ are integrated respectively. The specific integration interval is as follows:

S2.2. Solid-state NMR analysis is the same as step S2 of method 1

Quantitative calculation of silanol content in S3.MQ silicone resin

S3.1. According to the nuclear magnetic hydrogen spectrum, the mass fraction of H atoms in each molecule is converted to the ratio of its integrated area, and the mass fraction of Si-OCH ₂ CH ₃ (or Si-OCH ₃ ) is calculated. The specific calculation method is as follows:

（4）

(4)

（5）

(5)

为内标物的质量、

为MQ硅树脂的质量、

为内标物中H原子的质量分数、

为Q³链节中的CH₂中2个H原子占MQ硅树脂的质量分数、X为核磁氢谱图上MQ硅树脂中Q³链节中CH₂峰和内标试剂中CH₂峰的积分面积之比、a为OCH₂CH₃摩尔质量、b为Q³链节中的CH₂中2个H原子的摩尔质量。In formulas (4) and (5),

is the mass of the internal standard,

For the quality of MQ silicone resin,

is the mass fraction of H atoms in the internal standard,

is the mass fraction of the 2 H atoms in CH ₂ in the Q ³ chain in the MQ silicone resin, X is the ratio of the integrated area of the CH ₂ peak in the Q ³ chain in the MQ silicone resin and the CH ₂ peak in the internal standard reagent on the H NMR spectrum, a is the molar mass of OCH ₂ CH ₃ , and b is the molar mass of the 2 H atoms in CH ₂ in the Q ³ chain.

S3.2. According to the solid-state NMR silicon spectrum, the calculation method is the same as that of technical solution 1. At this time, the sum of the mass fractions of Si-OH and Si-OCH ₂ CH ₃ is calculated based on Q ³ .

S3.3. Subtract the results obtained in S3.2 and S3.1 to obtain the mass fraction of OH.

Several typical embodiments are listed below to illustrate the specific implementation of the present invention. Of course, the protection scope of the present invention is not limited to the following embodiments. For detailed processes and parameters, refer to the above-mentioned test method of the present invention.

Embodiment 1:

In this example, solid-state NMR silicon spectroscopy was used to characterize a methyl MQ silicone resin (synthesized by the water glass method) with a relatively high hydroxyl content, and an NMR spectrum was obtained, see FIG2 .

First, the peaks in the NMR spectrum were assigned. The single peak at 30 to -6 ppm was the M chain segment, and the double peak at -90 to -120 ppm was the Q ³ and Q ⁴ chain segments, respectively. The peaks were integrated to obtain the proportion of each chain segment.

The M segment of methyl MQ silicone resin is (CH ₃ ) ₃ SiO _1/2 , so it can be calculated according to the following formula:

The silanol content of the methyl MQ silicone resin in this embodiment is calculated to be 5.83%.

Embodiment 2:

In this example, solid-state NMR silicon spectroscopy was used to characterize a methyl MQ silicone resin (synthesized by the water glass method) with a medium hydroxyl content, and an NMR spectrum was obtained, see FIG3 .

First, the peaks of the NMR spectrum were assigned. The single peak at 30 to -6 ppm was the M chain segment, and the double peak at -90 to -120 ppm was the Q ³ and Q ⁴ chain segments, respectively. The peaks were integrated to obtain the proportion of each chain segment.

The M segment of methyl MQ silicone resin is (CH ₃ ) ₃ SiO _1/2 , so it can be calculated according to the following formula:

The silanol content of the methyl MQ silicone resin in this embodiment is calculated to be 3.93%.

Embodiment 3:

In this example, solid-state NMR silicon spectroscopy was used to characterize a methyl MQ silicone resin (synthesized by the water glass method) with a relatively low hydroxyl content, and an NMR spectrum was obtained, see FIG4 .

First, the peaks of the NMR spectrum were assigned. The single peak at 30 to -6 ppm was the M chain segment, and the double peak at -90 to -120 ppm was the Q ³ and Q ⁴ chain segments, respectively. The peaks were integrated to obtain the proportion of each chain segment.

The M segment of methyl MQ silicone resin is (CH ₃ ) ₃ SiO _1/2 , so it can be calculated according to the following formula:

The silanol content of the methyl MQ silicone resin in this embodiment is calculated to be 1.62%.

Embodiment 4:

In this example, a vinyl MQ silicone resin (synthesized by the water glass method) was characterized by solid-state NMR silicon spectroscopy to obtain an NMR spectrum, see FIG5 .

First, the peaks in the NMR spectrum were assigned, among which the peak at 30 to -6 ppm was the M chain segment, and the double peak at 90 to -120 ppm was the Q ³ and Q ⁴ chains, respectively. The peaks were integrated to obtain the proportion of each chain segment.

There are two types of end-capping agents for vinyl MQ silicone resin, and therefore two types of M segments, namely CH ₂ =CH(CH ₃ ) ₂ SiO _1/2 and H(CH ₃ ) ₂ SiO _1/2 . Therefore, the calculation can be performed according to the following formula:

The silanol content of the vinyl MQ silicone resin in this embodiment is calculated to be 1.62%.

Embodiment 5:

In this example, solid-state NMR silicon spectroscopy was used to characterize phenyl MQ silicone resin (synthesized by the water glass method) to obtain an NMR spectrum, see FIG6 .

First, the peaks of the NMR spectrum were assigned, among which the single peak at 30 to -6 ppm was the M segment, and the peaks at -90 to -105 ppm and -105 to -120 ppm were the Q ³ and Q ⁴ segments, respectively. Each of them was integrated to obtain the identity of each segment.

The M segment of phenyl MQ silicone resin is C ₆ H ₅ (CH ₃ ) ₂ SiO _1/2 , so it can be calculated according to the following formula:

The silanol content of the phenyl MQ silicone resin in this embodiment was calculated to be 1.58%.

Embodiment 6:

In this embodiment, liquid H-NMR spectrum and solid-state Si-NMR spectrum are used to characterize the MQ silicone resin synthesized by the tetraethyl orthosilicate method (TEOS method), and H-NMR spectrum and Si-NMR spectrum are obtained, respectively, as shown in FIG7 and FIG8 .

The curve is subjected to peak analysis, wherein the mass fraction of Si- _OCH2CH3 can be calculated according to the H-NMR spectrum (internal standard method ₎ ; then the sum of the mass fractions of Si- _OCH2CH3 and Si- _OH is calculated according to the ^Q3 partial integration of the Si-NMR spectrum method, and the OH mass fraction of the MQ silicone resin by the tetraethyl orthosilicate method is obtained by subtracting them.

Quantitative calculation of silanol:

According to the nuclear magnetic hydrogen spectrum, the mass fraction of Si-OCH ₂ CH ₃ is calculated as follows:

According to the solid-state NMR silicon spectrum, the specific calculation is as follows:

First, let the molar proportion of CH ₃ CH ₂ O-SiO _3/2 in Q ³ be x, so the molar proportion of HO-SiO _3/2 is 0.29-x, then we can calculate:

Solving for x=0.13,

The silanol content of the MQ silicone resin in this embodiment was calculated to be 1.89%.

For the MQ silicone resins of Examples 1 to 6, the silanol content thereof was calibrated by titration. The silanol content of Examples 1 to 6 and the silanol content calibrated by titration were summarized as shown in the following table:

The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A method for testing the content of silicon hydroxyl in MQ silicon resin is characterized by comprising the following steps: the method comprises the following detection modes:

quantitatively characterizing the mass fraction of silicon hydroxyl in MQ silicon resin synthesized by a water glass method by adopting a solid-state nuclear magnetic resonance silicon spectrum;

and II, quantitatively characterizing the mass fraction of silicon hydroxyl in the MQ silicon resin synthesized by the tetraethoxysilane method by adopting the combination of a solid-state nuclear magnetic resonance silicon spectrum and a liquid-state nuclear magnetic resonance hydrogen spectrum.

2. The test method according to claim 1, wherein: the MQ silicon resin synthesized by the water glass method at least comprises Q shown in the following formula (1) ³ Chain links:

（1）。

3. the test method according to claim 1, wherein: the positive siliconThe MQ silicone resin synthesized by the ethyl ester method at least contains Q shown in the following formula (1) or the following formula (2) ³ Chain links:

（1）

（2）

in the formula (2), R is CH ₂ CH ₃ 。

4. The test method according to claim 1, wherein: the MQ silicon resin synthesized by the water glass method or the MQ silicon resin synthesized by the tetraethoxysilane method contains at least one of the following groups: hydrogen, methyl, vinyl, phenyl, chloropropyl, (meth) acrylate groups.

5. The test method according to claim 1, wherein: in the mode I, aiming at MQ silicon resin synthesized by a water glass method, the Q of the MQ silicon resin is firstly identified ³ The mole number of chain units is the mole number of silicon hydroxyl groups, and the mole number of chain units is the mole number of M chain units and Q chain units on a solid-state nuclear magnetic silica spectrogram ³ Chain link and Q ⁴ The chain links are integrated respectively, so that the silicon hydroxyl content in the MQ silicon resin synthesized by the water glass method can be calculated.

6. The test method according to claim 5, wherein: the formula for calculating the silicon hydroxyl content of the MQ silicon resin by solid-state nuclear magnetic silica spectrum integration is shown in the following formula (3):

（3）

in the formula (3), the amino acid sequence of the compound,

for the integral area of the M chain link, +.>

Is Q ³ Integral area of the chain link->

Is Q ⁴ The integral area of the chain link,aIs the molar mass of OH,bIs the molar mass of M chain link,cIs Q ³ The molar mass of the chain links,dIs Q ⁴ Molar mass of the chain links.

7. The test method according to claim 1, wherein: in the mode II, aiming at the MQ silicon resin synthesized by the tetraethoxysilane method, the Q of the MQ silicon resin is firstly identified ³ The mole number of the chain units is the sum of the mole numbers of the silicon hydroxyl groups and the alkoxy groups, then the content of the alkoxy groups is firstly determined through liquid nuclear magnetic resonance hydrogen spectrum, and then the chain units M and Q on the solid nuclear magnetic silicon spectrum ³ Chain link and Q ⁴ The silicon hydroxyl content in the MQ silicon resin synthesized by the tetraethoxysilane method can be calculated by integrating the chain links respectively.

8. The test method according to claim 7, wherein: when the liquid nuclear magnetic resonance hydrogen spectrum is adopted to determine the alkoxy content, an internal standard method is adopted to measure the liquid nuclear magnetic hydrogen spectrum of the MQ silicon resin, and the CH in an internal standard reagent on the nuclear magnetic hydrogen spectrum is measured ₂ And Q ³ CH in chain link ₂ Respectively integrating to calculate OCH in MQ silicone resin ₂ CH ₃ Is added to the mixture according to the content of (3),

calculation of OCH in MQ Silicone ₂ CH ₃ The formulas of the content of (a) are shown in the following formulas (4) and (5):

（4）

（5）

in the formulas (4) and (5),

is the mass of the internal standard>

Is the mass of MQ silicone +.>

Is the mass fraction of H atoms in the internal standard substance, < >>

Is Q ³ CH in chain link ₂ Wherein 2H atoms account for the mass fraction of the MQ silicon resin, and X is Q in the MQ silicon resin on the nuclear magnetism hydrogen spectrogram ³ CH in chain link ₂ Peak and CH in internal standard reagent ₂ The ratio of the integral areas of the peaks,aIs OCH ₂ CH ₃ Molar mass of,bIs Q ³ CH in chain link ₂ Molar mass of 2H atoms.

9. The test method according to claim 8, wherein: the formula for calculating the silicon hydroxyl and alkoxy of the MQ silicone resin by solid-state nuclear magnetic silica spectrum integration is shown in the following formula (6):

（6）

in the formula (6), the amino acid sequence of the compound,

for the integral area of the M chain link, +.>

Is Q ³ Integral area of the chain link->

Is Q ⁴ The integral area of the chain link,aIs the molar mass of OH,bIs the molar mass of M chain link,cIs Q ³ The molar mass of the chain links,dIs Q ⁴ The molar mass of the chain links;

and subtracting the content of the alkoxy determined by the liquid nuclear magnetic resonance hydrogen spectrum from the content of the silicon hydroxyl and the alkoxy calculated by the solid nuclear magnetic silica spectrometry to obtain the content of the silicon hydroxyl in the MQ silicon resin.

10. The test method according to claim 8, wherein: 1, 4-dioxane, cyclohexane, dimethyl sulfoxide or hydroquinone is used as an internal standard reagent.

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