Method for measuring hydroxyl value of polycaprolactone triol by utilizing nuclear magnetic resonance hydrogen spectrum
阅读说明：本技术 一种利用核磁共振氢谱测量聚己内酯三元醇羟值的方法 (Method for measuring hydroxyl value of polycaprolactone triol by utilizing nuclear magnetic resonance hydrogen spectrum ) 是由 刘阳 王晓宇 于 2019-10-22 设计创作，主要内容包括：本发明提供一种利用核磁共振氢谱测量聚己内酯三元醇羟值的方法,包括如下步骤：(1)将分析样品加入至核磁管中；(2)将核磁管放置于核磁共振分析仪内,并选择对应的分析方案,对样品进行扫描,得到样品核磁共振氢谱；(3)对样品核磁共振氢谱中各结构特征峰面积进行积分,并根据各结构H原子个数比与特征峰强度比之间的关系,计算样品的平均聚合度n,进而计算出聚己内酯三元醇样品的平均相对分子质量及具体羟值。本发明的方法具有分析过程简单快速、分析结果准确性高、分析设备运行稳定等特点,为聚己内酯三元醇类样品羟值的计算提供了一种简单、快速、准确的检测方法。(The invention provides a method for measuring hydroxyl value of polycaprolactone triol by utilizing nuclear magnetic resonance hydrogen spectrum, which comprises the following steps: (1) adding an analysis sample into a nuclear magnetic tube; (2) placing the nuclear magnetic tube in a nuclear magnetic resonance analyzer, selecting a corresponding analysis scheme, and scanning a sample to obtain a nuclear magnetic resonance hydrogen spectrum of the sample; (3) integrating the characteristic peak areas of all structures in the nuclear magnetic resonance hydrogen spectrum of the sample, calculating the average polymerization degree n of the sample according to the relation between the atomic number ratio of all structures and the characteristic peak intensity ratio, and further calculating the average relative molecular mass and the specific hydroxyl value of the polycaprolactone triol sample. The method has the characteristics of simple and quick analysis process, high accuracy of analysis results, stable operation of analysis equipment and the like, and provides a simple, quick and accurate detection method for the calculation of the hydroxyl value of the polycaprolactone triad sample.)
1. A method for measuring the hydroxyl value of polycaprolactone triol by utilizing nuclear magnetic resonance hydrogen spectrum is characterized by comprising the following steps:
(1) adding an analysis sample into a nuclear magnetic tube;
(2) placing the nuclear magnetic tube in a nuclear magnetic resonance analyzer, selecting a corresponding analysis scheme, and scanning a sample to obtain a nuclear magnetic resonance hydrogen spectrum of the sample;
(3) and integrating the characteristic peak areas of all structures in the nuclear magnetic resonance hydrogen spectrum of the sample, and calculating the specific hydroxyl value of the polycaprolactone triol according to the characteristic peak areas.
2. The method for measuring the hydroxyl value of polycaprolactone triol by using the nuclear magnetic resonance hydrogen spectrum according to claim 1, wherein the method comprises the following steps: the nuclear magnetic resonance analyzer is off-line equipment, and the resonance atomic nucleus is1H, the resonance frequency is 60 +/-0.5 MHz.
3. The method for measuring the hydroxyl value of polycaprolactone triol by using the nuclear magnetic resonance hydrogen spectrum according to claim 1, wherein the nuclear magnetic resonance analyzer is set under the conditions that the total sampling points are 8192, the relaxation time is more than or equal to 2s, the probe temperature is 30 +/-5 ℃, and the nuclear magnetic resonance hydrogen spectrum chemical shift interval is about-2 ~ 12 ppm.
4. The method for measuring the hydroxyl value of polycaprolactone triol by using nuclear magnetic resonance hydrogen spectroscopy according to claim 1, wherein the method comprises the following steps: the polycaprolactone triol is mainly prepared by polymerizing an epsilon-caprolactone monomer and trimethylolpropane, and the molecular formula is C6H14O3·(C6H10O2)nStructural formula is
Degree of polymerization n = (n)1+n2+n3)。
5. The method for measuring the hydroxyl value of polycaprolactone triol by using the nuclear magnetic resonance hydrogen spectrum according to claim 1, wherein the method comprises the following steps: the molecular structure of the polycaprolactone triol contains-CH3、-CH2A, -OH group, wherein-CH2The structures of the groups connected are mainly divided into four types: is and straight chain middle-CH3、-CH2linked-CH2A group; -CH attached to C atom in ester group2A group; ③ CH attached to the O atom of the ester group2A group; tetra and-OH linked to-CH2A group.
6. The method for measuring the hydroxyl value of polycaprolactone triol by using the nuclear magnetic resonance hydrogen spectrum according to claim 1, wherein the method comprises the following steps: in the NMR spectrum of the polycaprolactone triol sample, obvious characteristic peaks appear in five areas of-0.55-0.93 ppm, 0.93-1.89 ppm, 1.89-2.79 ppm, 2.79-3.64 ppm and 3.64-5.11 ppm, and the corresponding structures are-CH3Radical, and straight chain middle-CH3、-CH2group-bound-CH2Group, -CH attached to C atom of ester group2Radical, -CH attached to the O atom of-OH2Group, -CH attached to O atom in ester group2The relative content of the group-OH group is small, so that the characteristic peak signal of the H atom is weak, and the characteristic peak is covered by the characteristic peak within the range of 3.64-5.11 ppm.
7. The method for measuring the hydroxyl value of polycaprolactone triol by using the nuclear magnetic resonance hydrogen spectrum according to claim 1, wherein the method comprises the following steps: in the NMR spectrogram of the polycaprolactone triol sample, the total area of three characteristic peaks in a-0.55-2.79 ppm region can be set as X1The total area of two characteristic peaks in the 2.79-5.11 ppm region can be X2The ratio of the total number of H atoms in each structure in the two regions is X1/X2。
8. The method for measuring the hydroxyl value of polycaprolactone triol by using the nuclear magnetic resonance hydrogen spectrum according to claim 4, wherein the method comprises the following steps: in the polycaprolactone triol structure, -CH3Radical, and straight chain middle-CH3、-CH2group-bound-CH2Group, -CH attached to C atom of ester group2The total number of H atoms in the three structures of the group is 8n +5, and the-CH is connected with the O atom in the-OH2Group, -CH attached to O atom in ester group2The total number of H atoms in the three structures of the group and the-OH group is 2n +9, so that there is (8 n + 5)/(2 n + 9) = X1/X2。
9. According toThe method for measuring the hydroxyl value of polycaprolactone triol by using nuclear magnetic resonance hydrogen spectroscopy as claimed in claim 8, characterized in that: the total number of epsilon-caprolactone monomers participating in polymerization reaction in the polycaprolactone triol structure, namely the polymerization degree n, can be determined according to the ratio X of the characteristic peak areas of the two regions1/X2And (6) performing calculation.
10. The method for measuring the hydroxyl value of polycaprolactone triol by using nuclear magnetic resonance hydrogen spectroscopy according to claim 9, wherein: the average relative molecular mass M of the polycaprolactone triol can be calculated according to the value of n, namely M =134+114 n; let the hydroxyl value of polycaprolactone triol be Q, then Q =1000 × 56.1 × 3/M = 168300/M.
Technical Field
The invention belongs to the field of polycaprolactone triol analysis, and particularly relates to a method for measuring a hydroxyl value of polycaprolactone triol by using nuclear magnetic resonance hydrogen spectrum.
Background
The polycaprolactone triol is one of polycaprolactone polyols (PCL for short), and has important industrial effect. For example, elastomers, coatings, adhesives, and the like, such as elastic optical fibers, potting adhesives, coatings, foams, resins, microcellular elastomers/foams, sealants, footwear materials, tubing, and the like, are widely used. It can improve the wear resistance, hydrolysis resistance and other performances of paint, elastomer and adhesive.
In general, polycaprolactone polyols are prepared by ring-opening polymerization of caprolactone monomers, initiators (polyols), catalysts (tetrabutyl titanate, tetraisopropyl titanate, stannous octoate, etc.). For polycaprolactone triol, an epsilon-caprolactone monomer and trimethylolpropane are mostly adopted as an initiator and polymerized under the action of a catalyst.
In the production and processing process of polycaprolactone triol, the indexes for evaluating the product mainly comprise hydroxyl value, acid value, moisture, viscosity, chroma and the like. The hydroxyl value is used as a key analysis index for inspecting the product quality, and has important significance for the evaluation process of the product. The hydroxyl value refers to the number of milligrams of potassium hydroxide (mgKOH/g) with equivalent hydroxyl content in each gram of sample, and the current general detection method is mainly an anhydride-pyridine potentiometric titration method. The method has high temperature requirement, is complex to operate, and is easy to generate some human errors in the analysis process; meanwhile, the whole analysis process is long in time, and the analysis efficiency is low. Therefore, it is necessary to develop a method for accurately and rapidly determining the hydroxyl value.
The nmr analysis technique is a technique in which nmr phenomenon is applied to molecular structure measurement. For the determination of organic molecular structures, nuclear magnetic resonance spectroscopy plays a very important role, and together with ultraviolet, infrared and mass spectra, it is known by organic chemists as the "four-broad spectrum".
NMR analysis is a non-contact molecular structure detection technology, and can be used for rapidly analyzing and detecting heavy, viscous and light-tight samples. Nuclear magnetic resonance spectroscopy is currently mainly focused on the H spectrum, due to the possibility of generating a nuclear magnetic resonance signal1The abundance of H atoms in nature is very high, and nuclear magnetic resonance signals generated by the H atoms are very strong and easy to detect.
The development of NMR analysis technology in the 50 th of the 20 th century, and the rapid development of NMR technology in more than sixty years has become an important research means in the contemporary analysis field, and is widely applied to the research fields of physics, chemistry, biology, medical treatment, geology, materials and the like. The NMR technology can deeply detect the internal structure of the sample without damaging the sample, and has the advantages of high analysis speed, high efficiency and accurate result, so the application development of the NMR technology in the petroleum raw material or product analysis field of the petrochemical industry is rapid in recent years. However, no report related to the rapid detection of indexes such as the hydroxyl value of the polycaprolactone polyol substance by using a 60MHz nuclear magnetic resonance analyzer is available at present.
Disclosure of Invention
In order to improve the analysis efficiency of the hydroxyl value of the polycaprolactone triol, the invention provides a method for measuring the hydroxyl value of the polycaprolactone triol by utilizing a nuclear magnetic resonance hydrogen spectrum, which comprises the following steps:
(1) adding an analysis sample into a nuclear magnetic tube;
(2) placing the nuclear magnetic tube in a nuclear magnetic resonance analyzer, selecting a corresponding analysis scheme, and scanning a sample to obtain a nuclear magnetic resonance hydrogen spectrum of the sample;
(3) and integrating the characteristic peak areas of all structures in the nuclear magnetic resonance hydrogen spectrum of the sample, and calculating the specific hydroxyl value of the polycaprolactone triol according to the characteristic peak areas.
The nuclear magnetic resonance analyzer is off-line equipment, and the resonance atomic nucleus is1H, the resonance frequency is 60 +/-0.5 MHz.
The nuclear magnetic resonance analyzer is set with total sampling points of 8192, relaxation time of not less than 2s, probe temperature of about 30 deg.c, preferably 25 ~ 35 deg.c, and chemical shift interval of nuclear magnetic resonance hydrogen spectrum of-2 ~ 12 ppm.
The polycaprolactone triol is mainly prepared by polymerizing an epsilon-caprolactone monomer and trimethylolpropane, and the molecular formula is C6H14O3·(C6H10O2)nThe structural formula is shown in figure 1, and the polymerization degree n = (n)1+n2+n3)。
The molecular structure of the polycaprolactone triol contains-CH3、-CH2A, -OH group, wherein-CH2The structures of the groups connected are mainly divided into four types: is and straight chain middle-CH3、-CH2The groups are connected; ② is connected with C atom in ester group; connecting with O atom in ester group; and fourthly, connecting with-OH.
The NMR spectrum of the polycaprolactone triol sample shows five areas of-0.55-0.93 ppm, 0.93-1.89 ppm, 1.89-2.79 ppm, 2.79-3.64 ppm and 3.64-5.11 ppmDistinct characteristic peaks corresponding to the structures of-CH3Radical, and straight chain middle-CH3、-CH2group-bound-CH2Group, -CH attached to C atom of ester group2Radical, -CH attached to the O atom of-OH2Group, -CH attached to O atom in ester group2A group.
The relative content of the-OH groups is small, and the characteristic peak signal of the H atom is weak, so that the-OH groups are covered by the characteristic peak in the range of 3.64-5.11 ppm.
In the NMR spectrogram of the polycaprolactone triol sample, the total area of three characteristic peaks in a-0.55-2.79 ppm region can be set as X1The total area of two characteristic peaks in the 2.79-5.11 ppm region can be X2The ratio of the total number of H atoms in each structure in the two regions is the ratio X of the total area of the characteristic peak1/X2。
In the polycaprolactone triol structure, -CH3Radical, and straight chain middle-CH3、-CH2group-bound-CH2Group, -CH attached to C atom of ester group2The total number of H atoms in the three structures of the group is 8n +5, and the-CH is connected with the O atom in the-OH2Group, -CH attached to O atom in ester group2The total number of H atoms in the three structures of the group and the-OH group is 2n +9, so that there is (8 n + 5)/(2 n + 9) = X1/X2。
The total number of epsilon-caprolactone monomers participating in polymerization reaction in the polycaprolactone triol structure, namely the polymerization degree n, can be determined according to the ratio X of the characteristic peak areas of the two regions1/X2And (6) performing calculation.
The average relative molecular mass M of the polycaprolactone triol can also be calculated according to the value of n, namely M =134+114 n. Let the hydroxyl value of polycaprolactone triol be Q, then Q =1000 × 56.1 × 3/M = 168300/M, where "" means multiplicative.
The method for calculating the hydroxyl value of the polycaprolactone triol by utilizing the nuclear magnetic resonance hydrogen spectrum is mainly applied to the analysis process of the hydroxyl value of the polycaprolactone triol in related chemical enterprises.
The invention has the beneficial effects that:
(1) the NMR analysis technology related by the invention belongs to a non-contact analysis method, other chemical reagents are not required to be added in the analysis process, no harm is generated to the environment and human bodies, the sample can be directly recovered after analysis, special treatment is not required, and the method has good environmental protection benefit.
(2) The invention adopts the NMR analysis technology, can rapidly analyze indexes such as hydroxyl value, relative molecular mass and the like of the polycaprolactone triol, and greatly improves the overall analysis efficiency. As the NMR technology is high in analysis speed, the analysis time of a single sample is about 2-5 min, the analysis time is expected to be greatly reduced compared with the existing traditional analysis method, and the analysis efficiency is obviously improved.
(3) The invention adopts the NMR analysis technology to rapidly analyze indexes such as the hydroxyl value, the relative molecular mass and the like of the polycaprolactone triol, thereby greatly reducing the analysis cost. The current general analysis method mainly adopts an anhydride-pyridine potentiometric titration method, and has higher analysis cost; and by adopting the NMR analysis technology, only a nuclear magnetic tube and a disposable plastic dropper used for sampling are required to be consumed under normal conditions, no other reagent is needed, the equipment can stably run for a long time, and maintenance related cost is not needed, so that the overall cost is extremely low.
(4) The method adopts the NMR analysis technology to rapidly analyze indexes such as the hydroxyl value, the relative molecular mass and the like of the polycaprolactone triol, can provide sample analysis data for production in time, and is beneficial to an enterprise to timely and effectively adjust and optimize the production scheme of the polycaprolactone triol, so that the product quality is further improved, and the economic benefit of the enterprise is increased.
Drawings
FIG. 1 is a structural formula of polycaprolactone triol;
FIG. 2 is a hydrogen NMR spectrum of polycaprolactone triol (sample 1);
FIG. 3 is a NMR hydrogen spectrum of polycaprolactone triol (sample 2).
Detailed Description
The following detailed description of the present invention, taken in conjunction with the accompanying drawings and examples, is provided to enable the invention and its various aspects and advantages to be better understood. The specific embodiments and examples described below are for illustrative purposes only and are not intended to limit the invention.
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