阅读说明：本技术 一种利用近红外光谱仪分析聚四亚甲基醚二醇分子量的方法 (Method for analyzing molecular weight of polytetramethylene ether glycol by using near-infrared spectrometer ) 是由 王晓敏 余灵柱 于艳 梁娟 于 2019-10-12 设计创作，主要内容包括：一种利用近红外光谱仪分析聚四亚甲基醚二醇分子量的方法,工艺步骤：(1)从工艺生产线收集范围交广的分子量样品,并手动滴定,确定具体分子量；(2)使用近红外光谱仪对不同分子量样品进行扫描,收集一定量的谱图；(3)类比大量分析谱图,找出不同分子量谱图之间不同之处,建立分析数据模型；(4)使用数据模型对手动分析分子量样品进行分析,确定与手动分析误差,优化模型,提高模型精确度；(5)使用近红外分析方法配合工艺生产。通过近红外分析技术,对不同分子量的PTMEG进行分析,得到相对应的谱图,建立分析方法,准确快速分析出PTMEG分子量,从原来手动滴定需3个小时到使用近红外光谱分析仅10分钟,分析快速,准确度高。(A method for analyzing the molecular weight of polytetramethylene ether glycol by using a near infrared spectrometer comprises the following process steps: (1) collecting molecular weight samples from a process production line, manually titrating the samples, and determining the specific molecular weight; (2) scanning samples with different molecular weights by using a near-infrared spectrometer, and collecting a certain amount of spectrogram; (3) simulating a large number of analysis spectrograms, finding out the difference between different molecular weight spectrograms, and establishing an analysis data model; (4) analyzing the manual analysis molecular weight sample by using a data model, determining the error with the manual analysis, optimizing the model and improving the accuracy of the model; (5) the product is produced by using a near infrared analysis method and matching with a process. The PTMEG with different molecular weights is analyzed by a near infrared analysis technology to obtain a corresponding spectrogram, an analysis method is established, the PTMEG molecular weight is accurately and quickly analyzed, the analysis is quick and the accuracy is high from 3 hours of original manual titration to only 10 minutes of near infrared spectrum analysis.)

1. A method for analyzing the molecular weight of polytetramethylene ether glycol by using a near infrared spectrometer is characterized by comprising the following specific process steps:

(1) collecting molecular weight samples from a process production line, manually titrating the samples, and determining the specific molecular weight;

(2) scanning samples with different molecular weights by using a near-infrared spectrometer, and collecting a certain amount of spectrogram;

(3) simulating a large number of analysis spectrograms, finding out the difference between different molecular weight spectrograms, and establishing an analysis data model;

(4) analyzing the manual analysis molecular weight sample by using a data model, determining the error with the manual analysis, optimizing the model and improving the accuracy of the model;

(5) the product is produced by using a near infrared analysis method and matching with a process.

Technical Field

The invention belongs to the field of analysis and detection application of coal chemical industry, and particularly relates to a method for analyzing the molecular weight of polytetramethylene ether glycol (PTMEG) by using a near-infrared spectrometer.

Background

Polytetramethylene ether glycol (PTMEG) is a homopolymer obtained by cationic ring-opening polymerization of Tetrahydrofuran (THF) monomer in the presence of catalyst, and is a linear polyether glycol with primary hydroxyl end group, which is white waxy solid at normal temperature, melts into transparent and colorless liquid when the temperature exceeds room temperature, is easily dissolved in alcohol, ester, ketone, aromatic hydrocarbon and chlorinated hydrocarbon, and is insoluble in aliphatic hydrocarbon and water. PTMEG is mainly used for the production of polyurethane elastomers, polyurethane elastic fibers (spandex) and ester ether copolymerized elastomers.

The molecular weight is used as one of important indexes in the PTMEG production process and is also a factor influencing the downstream production of spandex quality, the molecular weight is analyzed in the prior national standard GB/T25254-2010 industrial polytetramethylene ether glycol (PTMEG) by stipulating, hydroxyl functional groups in the PTMEG are manually titrated, the components are obtained by calculation by using a calculation formula, and volatile toxic substances such as acylating agent, isopropanol and the like are used in the process; some laboratories may also use the Inweda procedure, in which PTMEG is dissolved thoroughly in a THF (tetrahydrofuran) mixture of acetonitrile and excess p-toluenesulfonyl isocyanate (TSI) and stirred for 10min, the hydroxyl groups can react with TSI to form acidic carbamates, water is added to convert unreacted isocyanate to sulfonamides (thoroughly reacted for 5min), the acidic carbamates are directly titrated potentiometrically with 0.1mol/L tetrabutylammonium hydroxide-isopropanol (TBAH) standard solution, and the molecular weight of PTMEG is calculated from the volume of consumed TBAH.

The following chemical reactions outline the chemistry of this analytical procedure.

And (3) generation of carbamate:

CH₃-Ar-SO₂-NCO+ROH→CH₃-Ar-SO₂-NHCOOR

removal of p-toluenesulfonyl peroxyisocyanate:

CH₃-Ar-SO₂-NCO+H₂O→CH₃-Ar-SO₂NH₂+CO₂

carbamate titration:

CH₃-Ar-SO₂-NHCOOR+OH→CH₃-Ar-SO₂-N-COOR+H₂O

the two measurement methods require 3 hours for analysis, are complicated and complicated in analysis, have more factors influencing the measurement accuracy, lead to process adjustment hysteresis, and have certain toxic action on human bodies by substances volatilized in the titration process.

Disclosure of Invention

The invention aims to provide a method for analyzing the molecular weight of polytetramethylene ether glycol (PTMEG) by a laboratory through a near-infrared spectrometer, which analyzes the PTMEG with different molecular weights through a near-infrared analysis technology under the conditions of not enlarging analysis errors and meeting analysis accuracy.

The technical scheme of the invention is as follows: a method for analyzing the molecular weight of polytetramethylene ether glycol by near infrared spectrometer. The method comprises the following specific process steps:

(1) collecting molecular weight samples from a process production line, manually titrating the samples, and determining the specific molecular weight;

(2) scanning samples with different molecular weights by using a near-infrared spectrometer, and collecting a certain amount of spectrogram;

(3) simulating a large number of analysis spectrograms, finding out the difference between different molecular weight spectrograms, and establishing an analysis data model;

(4) analyzing the manual analysis molecular weight sample by using a data model, determining the error with the manual analysis, optimizing the model and improving the accuracy of the model;

(5) the product is produced by using a near infrared analysis method and matching with a process.

Near Infrared (NIR) spectroscopy is a novel analytical technique that is simple and convenient to use and does not destroy the sample. It can simultaneously measure various chemical components and physical parameters in the sample. The NIR analysis technique requires substantially no chemical treatment of the sample, no organic solvents, no toxic waste, a typical 10 minute analysis time, and a rapid analysis speed!

The structure of the PTMEG molecule is relatively stable, when a sample is irradiated by infrared light with continuously changing frequency in a near infrared spectrum (780-2500 nm) region, the molecule absorbs radiation with certain frequency due to the transition of molecular vibration energy level (accompanied by rotation energy level), and the transmitted light intensity of the absorption region is reduced. Recording a curve of the relation between the percent transmittance and the wavelength of infrared light, establishing a corresponding analysis model through different molecular weights and different intensities of near-infrared absorption spectra, measuring samples with known molecular weights reversely, determining model analysis errors, and finally obtaining the molecular weight of an unknown sample in the molecular weight measurement of the unknown sample, wherein the implementation method is feasible.

The invention has the following remarkable effects:

1. the method comprises the steps of analyzing PTMEG with different molecular weights by a near-infrared analysis technology to obtain corresponding spectrograms, establishing an analysis method, accurately and quickly analyzing the molecular weight of the PTMEG, and realizing the purpose of quick analysis from 3 hours required by original manual titration analysis to only 10 minutes by using near-infrared spectroscopy, so that the analysis accuracy is improved, and the method is provided for production personnel to adjust the process in time;

2. the analyst can analyze in a non-toxic environment, the quality of an analysis environment is improved, the occupational disease probability of the analyst is reduced, and the working environment is safer;

3. the reagent amount used in analysis is reduced, the analysis cost is greatly reduced, the analysis cost is predicted to be reduced by 40-60 ten thousand yuan per year, and the method has obvious economic benefit.

Drawings

FIG. 1 is a molecular weight data model map established at the early stage of the method of the present invention.

FIG. 2 is a molecular weight data model map established at the later stage of the method of the present invention.

Detailed description of the invention

The method of the present invention will be further described with reference to the following examples, drawings and diagrams, which are provided for understanding of the present invention and are not intended to limit the scope of the present invention.