CN114112965B - Method for detecting trace moisture in isocyanate and application of method in online monitoring - Google Patents

Method for detecting trace moisture in isocyanate and application of method in online monitoring Download PDF

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CN114112965B
CN114112965B CN202010891614.9A CN202010891614A CN114112965B CN 114112965 B CN114112965 B CN 114112965B CN 202010891614 A CN202010891614 A CN 202010891614A CN 114112965 B CN114112965 B CN 114112965B
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isocyanate
sample
diethyl ether
catalyst
carbon dioxide
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CN114112965A (en
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徐丹
陈良进
李楠
王普照
国欣
吴雪峰
张宏科
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Wanhua Chemical Group Co Ltd
Wanhua Chemical Ningbo Co Ltd
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Wanhua Chemical Ningbo Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications

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Abstract

The invention provides a method for monitoring trace moisture in isocyanate and an application of on-line monitoring, which comprises the following steps: the isocyanate and water are passed through a membrane carrying the isocyanate-reactive catalyst bis (3-amidomorpholino) diethyl ether to form carbon dioxide, the carbon dioxide content formed is determined and converted to the moisture content in the isocyanate. The invention greatly reduces the detection limit of water in isocyanate by using an indirect measurement method, the measurement precision can meet the requirement of monitoring the isocyanate production, and the invention can monitor whether the production device leaks water or not in time, thereby avoiding larger safety accidents.

Description

Method for detecting trace moisture in isocyanate and application of method in online monitoring
Technical field:
the invention belongs to the field of isocyanate production quality and production safety monitoring, and provides a method for detecting trace moisture in isocyanate and an online monitoring application thereof.
The background technology is as follows:
isocyanates are important raw materials for polyurethane materials, which are generally produced by: firstly producing amine corresponding to isocyanate, then carrying out phosgenation reaction on the amine and phosgene to generate crude products containing isocyanate products, and obtaining pure products by separation means such as rectification, evaporation, recrystallization and the like.
In the isocyanate production process, the production reaction of the precursor amine involves water, possibly brought downstream due to incomplete dehydration; under the humid condition in summer, the device possibly permeates water vapor in the environment due to improper pipelines, heat exchangers, improper packaging and the like, and the water vapor can react with NCO active groups in isocyanate in production, storage and transportation systems and the like to generate urea substances which are difficult to dissolve in isocyanate. The accumulation of urea in the reactor causes pipeline blockage, which can cause serious potential safety hazard; on the other hand, after water is fed in the packaging and transportation process, the reaction temperature is low (30-50 ℃), the reaction speed is low, and when isocyanate products pass through a packaging filter, moisture does not react in time to generate urea and is filtered and removed, so that moisture is brought into a packaging barrel or a tank car to react with isocyanate slowly, the isocyanate raw materials used by users are turbid, the quality of downstream products is affected, and complaints of customers are caused.
At present, the determination of the moisture in the isocyanate is mainly carried out by off-line sampling, laboratory chromatography and spectrometry, a great amount of manpower and material resources are consumed in off-line determination, and the time required by the sample feeding and manual analysis processes is longer, so that the quality of the isocyanate at the sampling moment cannot be accurately represented; on the other hand, the sample is inevitably contacted with air during the sampling process, and the measurement result is not the true condition of the sample in the wet summer. On-line analysis of the moisture in isocyanate at home and abroad is rarely reported, as disclosed in the published patent CN107703096A, the moisture of an isocyanate sample is directly measured by a near infrared method by utilizing the characteristic near infrared absorption wavelength of water, but the method has a lot of problems: on one hand, the near infrared model is seriously influenced by the type of isocyanate sample, the temperature and the pressure of the environment where the near infrared model is positioned, the correction coefficients under different conditions are greatly different, and modeling is complicated; on the other hand, the quantitative limit of the near infrared analyzer on water analysis is generally above 0.005%, and in practice, the laboratory offline analysis shows that the water content in the normal isocyanate sample is often lower than the value, so that the monitoring value of the near infrared method on the normal isocyanate may cause larger fluctuation due to system reasons, cause false alarm of DCS and cause unnecessary trouble.
Therefore, it is necessary to achieve an immediate, accurate on-line analysis of the moisture in isocyanate strands and packaged products.
The invention comprises the following steps:
the invention provides a method for monitoring trace moisture in isocyanate and an online monitoring application, which greatly reduces the detection limit of water in the isocyanate by using an indirect measurement method, can meet the requirement of monitoring the isocyanate production, can timely monitor whether a production device leaks water, and avoids larger safety accidents.
In order to achieve the above object, the present invention provides a method for detecting trace moisture in isocyanate, comprising the steps of: the isocyanate and water are passed through a membrane loaded with an isocyanate-reactive catalyst di (3-amide morpholino) diethyl ether to form carbon dioxide, and the content of the carbon dioxide formed is measured and converted into the moisture content in the isocyanate; the isocyanate-reactive catalyst bis (3-amide morpholinyl) diethyl ether has the following structural formula:
R 1 is catechol ethyl, R 2 Is C1-C5 alkyl or phenyl, preferably methyl, ethyl or phenyl.
According to the method provided by the invention, the isocyanate sample is selected from one or more of diphenylmethane diisocyanate, diphenylmethane polyisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and phenyl isocyanate; preferred are diphenylmethane diisocyanate and isomers thereof, including one or more of 4, 4-diphenylmethane diisocyanate, 2-diphenylmethane diisocyanate.
The diphenylmethane diisocyanate and isomers thereof are preferably selected from one or more of 4, 4-diphenylmethane diisocyanate, 2-diphenylmethane diisocyanate.
The isocyanate-reactive catalyst di (3-amidomorpholino) diethyl ether is prepared by preparing a precursor di (3-carboxymorpholino) diethyl ether, and then carrying out a chloracylation reaction with thionyl chloride and a subsequent nitrogen acylation reaction to load the precursor di (3-carboxymorpholino) diethyl ether on a membrane, wherein the precursor di (3-carboxymorpholino) diethyl ether has the following structural formula:
the preparation method of the precursor di (3-carboxyl morpholinyl) diethyl ether comprises the following steps:
(1) Weighing 3-carboxyl morpholine with certain mass, and dissolving in solvent reagent;
(2) Adding a catalyst, preferably dripping diethyl ether into 3-carboxyl morpholine at a constant speed, and carrying out reflux reaction after the mixture is mixed to a required ratio;
(3) The isocyanate-reactive catalyst di (3-carboxyl morpholinyl) diethyl ether pure product is obtained through separation and purification.
In the preparation of the precursor di (3-carboxymorpholino) diethyl ether, the mass ratio of the 3-carboxymorpholino to the diethyl ether is 5-20:1, preferably 8-10:1.
In the preparation of the pre-product di (3-carboxyl morpholinyl) diethyl ether, the solvent is one or more of tetrahydrofuran, acetonitrile, N-N-dimethylformamide, N-methylpyrrolidone and cyclohexane, preferably N-N-dimethylformamide; the mass ratio of the 3-carboxyl morpholine to the solvent is 1:1.5-8, preferably 1:2-4.
In the preparation of the precursor di (3-carboxyl morpholinyl) diethyl ether, the temperature of the reaction system is 60-120 ℃, and the maximum temperature is the temperature of a reaction solvent.
In the preparation of the pre-product di (3-carboxyl morpholino) diethyl ether, the catalyst is one or more of hydroxide, halide and carbonate of alkali metal, preferably single type of potassium iodide, potassium bromide and sodium carbonate; the mass ratio of 3-carboxymorpholine to catalyst is 20-80:1, preferably 30-50:1.
In the preparation of the precursor di (3-carboxyl morpholinyl) diethyl ether, in the reaction process, the diethyl ether serving as a reactant is completely dripped into the reaction mixture to be 100%, the dripping speed is 0.5-3%/min, preferably 0.7-1.5%/min, and the reaction time is 4-8h.
In the preparation of the catalyst of the present invention, in the step (3), the separation and purification modes required to be involved are extraction, reduced pressure distillation, atmospheric distillation and recrystallization, and specific operations are as follows:
(1) Taking a liquid phase sample after the reaction, and carrying out normal pressure distillation or extraction to remove the solvent; the distillation temperature should be higher than the boiling point of the solvent and not higher than 220 ℃.
(2) Distilling the sample prepared in the step (1) under reduced pressure to remove redundant reaction raw materials and solvents; the conditions of reduced pressure distillation are a pressure of 20 to 40mmHg, preferably 25 to 30mmHg, and a temperature of 180 to 230 ℃, preferably 195 to 205 ℃. (3) Recrystallizing the sample prepared in the step (2) to obtain a pure product. The solvent of choice for recrystallization may be ethyl acetate, acetonitrile or acetone, preferably acetonitrile.
The invention provides a preparation method of an isocyanate-reactive catalyst supported film, which comprises the following steps:
(1) Adding thionyl chloride and a catalyst required by the reaction into a pre-product di (3-carboxyl morpholino) diethyl ether, wherein the mass ratio of the di (3-carboxyl morpholino) diethyl ether to the thionyl chloride is 1:3-20, preferably 1:5-8; heating and refluxing, and removing thionyl chloride by rotary evaporation to obtain an intermediate di (3-acyl chloride morpholinyl) diethyl ether, wherein the intermediate di (3-acyl chloride morpholinyl) diethyl ether has the following structure;
the catalyst required for the reaction may be any one of amide, tertiary amine and carbonate, preferably N-N-dimethylformamide. The mass ratio of the di (3-carboxyl morpholino) diethyl ether to the catalyst is 50-400:1, preferably 80-150:1. The temperature of the reaction system is 60-120 ℃ and the reaction time is 2-8h;
(2) Cleaning the base film with a solvent, and naturally airing;
the base film may be a polyvinylidene fluoride film (PVDF) or a polytetrafluoroethylene film (PTFE), preferably a polyvinylidene fluoride film (PVDF); the cleaning solvent can be one or more solvents selected from methanol, ethanol, acetone, and ultrapure water, preferably acetone;
(3) After the basal membrane is soaked in a dopamine solution, constructing a polydopamine mediating layer on the surface of the basal membrane;
the dopamine solution is a mixed solution of dopamine, buffer salt and water, and the pH value of the solution is 5-9; wherein the concentration of dopamine in the solution is 5-20mg/mL, and the buffer salt can be one or more of phosphate, ammonium salt and organic salt, preferably any one of potassium dihydrogen phosphate-dipotassium hydrogen phosphate and Tris-HCl. The buffer salt concentration is 30-200mM, preferably 80-150mM. The soaking time is 12-24h, and the soaking system temperature is 30-60 ℃.
(4) And (3) immersing the base film of the medium layer in the solvent containing the intermediate di (3-acyl chloride morpholinyl) diethyl ether, and finally converting the intermediate di (3-acyl chloride morpholinyl) diethyl ether into the catalyst di (3-amide morpholinyl) diethyl ether by nitrogen acylation reaction, wherein the catalyst di (3-amide morpholinyl) diethyl ether is loaded on the base film.
The solvent in the supporting reaction can be one or more of amide, acetone and cyclohexane, preferably N-N-dimethylformamide; the concentration of the di (amide morpholino) diethyl ether solution is 5-20mg/mL. The soaking time is 12-24h, and the soaking temperature is 40-80 ℃.
(5) Immersing the membrane loaded with the catalyst of di (3-amide morpholinyl) diethyl ether in the step (4) in a blocking agent to finish blocking.
The capping agent may be one or more of the acid chlorides, preferably acetyl chloride. The end capping reaction time is 6-12h; the end capping temperature is selected to be normal temperature, and the mass ratio of the end capping agent to the catalyst is 300-1000:1.
The invention also provides an application of the method in on-line monitoring of trace moisture in isocyanate production, comprising the following steps:
step one, a membrane loaded with an isocyanate-reactive catalyst bis (3-amide morpholinyl) diethyl ether is arranged at the inlet end of on-line measuring equipment;
And secondly, starting a measuring device by controlling measuring equipment, introducing a sample at a position to be measured into a buffer tank through a sample output pipeline which is arranged in advance when the moisture content of the sample is monitored on line at the position related to the device, introducing the sample into the on-line measuring device through the buffer tank, regulating the temperature of an isocyanate sample through the buffer tank, enabling a certain mass of isocyanate sample to pass through a film loaded with a catalyst by using a pump, reacting the isocyanate with trace moisture to generate carbon dioxide, measuring the generated carbon dioxide content by using a carbon dioxide on-line measuring instrument, and automatically calculating the moisture content converted into the isocyanate. According to the method provided by the invention, the water content online measuring equipment in the step one comprises a control measuring device, a buffer tank, a sample conveying pump, a reaction device containing a catalyst load membrane, a measuring air chamber, a carbon dioxide online measuring instrument and related connecting pipelines which are connected through pipelines. The water on-line measuring equipment is connected with a site to be measured through a material pipeline, the material pipeline is firstly connected into a buffer tank, materials in the buffer tank are introduced into a measuring chamber through a delivery pump, after measurement is carried out, a sample pressing piston in the measuring chamber presses a sample into the lower space of a nested catalyst membrane, after reaction, the sample flows out to a measured sample chamber again, and finally, the sample is introduced into a waste liquid tank; and the gas generated by the reaction enters a measuring gas chamber with a carbon dioxide on-line measuring instrument to finish analysis and measurement. The whole online moisture measuring device is positioned in a constant-temperature closed space.
According to the method provided by the invention, the control measuring equipment in the step two is a controller for starting the system, and the connected external host can set automatic analysis time, and can also be used for forcedly starting the system manually.
The constant temperature value of the online moisture measuring device is 50-95 ℃, preferably 70-80 ℃. The temperature should be kept constant in a range of not more than 1% to 10%, preferably 1% to 2%.
The buffer tank is a closed container which is connected before the catalyst loading film to stabilize the temperature of the isocyanate sample, so that the temperature of the isocyanate sample pumped into the film is consistent with the temperature of the reaction system. The residence time of the isocyanate sample in the buffer tank is 2 to 10min, preferably 3 to 5min.
The adjusting parameters of the sample conveying pump are as follows: when the isocyanate sample is transferred to the moisture on-line measuring equipment, the transfer amount of the isocyanate sample is 30-200g, preferably 50-80g; the pressure of the permeable membrane is 30-300KPa, preferably 50-100KPa.
The contact area of the catalyst loading film and the isocyanate sample is 20-100cm 2 Preferably 50-80cm 2 。
The measuring air chamber is connected with the catalyst loading film through the air pipeline, carbon dioxide generated by the catalytic reaction of isocyanate and moisture through the catalyst diffuses into the measuring air chamber, and the carbon dioxide content in the air chamber is measured by the carbon dioxide on-line measuring instrument. The volume of the measuring air chamber is 10-50L, preferably 15-25L;
According to the method provided by the invention, the carbon dioxide on-line measuring instrument can be of various types sold in the market meeting the measuring requirement, the measuring principle is preferably a non-dispersive mid-infrared light-emitting method, the carbon dioxide has strong absorption to light in a mid-infrared band region of 4.26 mu m, the absorption energy and the gas content are in good linear relation, the absorption energy is converted by a circuit to obtain the carbon dioxide concentration, and the moisture content of isocyanate is calculated by the volume of an air chamber and the transmission quantity of isocyanate.
The carbon dioxide on-line measuring instrument probe is arranged inside the air chamber to measure the carbon dioxide content in the air chamber. The mounting position of the probe is 10% -90% of the height of the air chamber, preferably 40% -50%; preferably, the carbon dioxide on-line measuring instrument probe is an immersed optical fiber probe. More preferably, the immersion carbon dioxide on-line meter probe is a retractable probe.
The probe material of the carbon dioxide on-line tester is one or more selected from stainless steel, hastelloy and ceramic, and preferably 316L stainless steel according to the property of isocyanate material flow.
According to the method provided by the invention, a period of time is required for the chemical reaction involved in the second step and the generated carbon dioxide to diffuse into the air chamber to realize content balance, so that after the isocyanate sample is completely coated, the content of the carbon dioxide in the air chamber is measured in a delayed manner, and then the measured isocyanate sample is discharged. The measurement delay time of the carbon dioxide on-line measuring instrument is 0.5-10min, preferably 2-4min.
According to the method provided by the invention, in the second step, the measurement data such as the transmission speed, the transmission time and the measurement value of the carbon dioxide on-line measuring instrument of the isocyanate sample are transmitted into the PC host through the optical cable, and the host calculates the moisture content in the isocyanate sample.
According to the method provided by the invention, in the second step, the host machine realizes automatic conversion of the measured value of the carbon dioxide into the moisture content of the isocyanate, and the moisture content is required to be corrected and established through a system measurement model which is confirmed in advance and is input into an analysis system. According to the method provided by the invention, preferably, the establishment of the analysis model comprises the following steps: and (3) analyzing the isocyanate sample of the correction set by the method disclosed by the invention to obtain an analysis measurement value, correlating the analysis measurement value with the known content of the isocyanate sample, and establishing an analysis model by a multivariate data regression analysis method.
In a preferred embodiment, the established analytical model is subjected to a deviation test.
In a preferred embodiment, the multivariate data regression analysis method is a partial least squares regression method.
In a preferred embodiment, the isocyanate sample collected includes both the on-line, tank car, canned raw sample, and the experimental sample with the moisture added manually.
In a preferred embodiment, the corrected set has an isocyanate sample number of not less than 20. The moisture content of the calibration set is from 0.0003 to 0.03%, preferably from 0.0008 to 0.016%, based on 100% by weight of the total isocyanate sample.
According to the method provided by the invention, preferably, for improving the measurement essence of the moisture content of isocyanate samplesDegree, the established analytical model correlation coefficient (R 2 ) The error between the predicted value and the actual value is required to be higher than 0.985, and the actual working condition requirement is required to be met.
According to the method provided by the invention, the measurement data such as the transmission quantity of the isocyanate sample, the measured value of the carbon dioxide content and the like are transmitted into the PC host through the optical cable, and the host calculates the moisture content in the isocyanate sample according to the pre-set moisture content analysis model.
According to the method provided by the invention, preferably, the sample moisture content data of the monitored site is transmitted to a DCS picture of a control room in a wired or wireless mode, and a DCS high limit alarm is set at the same time; more preferably, the DCS alarm minimum value is 0.008-0.012% of the moisture content.
By utilizing the method provided by the invention, the moisture content of the isocyanate sample in the system can be monitored in real time at different key sites of the isocyanate production system, and the sites needing to be monitored are as follows: heat exchanger seal head of side draw point of rectifying tower, pipeline with sample effusion, buffer tank, product packaging pipeline, etc.
According to the method provided by the invention, each measuring site can realize continuous monitoring of the moisture of the isocyanate sample at preset time intervals. In a preferred embodiment, the sample measurement and data collection interval for the site to be monitored is 10-30 minutes.
The invention has the positive effects that:
(1) A catalyst for efficiently catalyzing the reaction of isocyanate and water is prepared and is loaded on a membrane; through the catalytic effect of the membrane, isocyanate penetrating through the membrane reacts with moisture contained in the isocyanate to generate carbon dioxide; therefore, the water detection with higher detection limit and difficult detection is converted into carbon dioxide detection which is easy to realize trace analysis, the analysis detection limit is greatly reduced, and the measurement accuracy is further improved.
(1) Compared with the off-line analysis method in the laboratory, the method eliminates the measurement positive interference caused by the introduction of moisture in the air due to sampling, and the measured sample can flow back into the device, so that a series of problems of occupational health, waste liquid treatment and the like caused by manual sampling and off-line analysis contact with isocyanate samples are avoided.
(2) Compared with the laboratory off-line analysis method, the measurement time is obviously shortened (< 10 min), which is equivalent to monitoring the product quality condition inside the current device in near real time. And production personnel can rapidly diagnose and process abnormal conditions according to the online analysis data, so that larger accidents caused by further leakage of moisture are avoided. Meanwhile, the turbidity phenomenon caused by infiltration of a large amount of moisture into the production device by the delivery material of the customer can be avoided, customer complaints are reduced, and manpower and material resources for examining specific problems of the device are also reduced. In the current laboratory method, the measurement period is as long as several hours, and in the time of waiting for the analysis result, the production personnel can not confirm the specific condition of the current device, the production is continued, and the hidden trouble and accident caused by the longer measurement period should be avoided by optimizing the analysis method.
Description of the drawings:
the foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descriptions of exemplary embodiments of the invention as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the invention.
FIG. 1 shows a schematic diagram of an in-line measuring device for moisture in isocyanate.
The reference numerals shown are described as follows:
1: device site, 2: buffer tank, 3: sample pressing piston, 4: sample area to be reacted, 5: catalyst-supporting film, 6: waste liquid tank, 7: reacted sample area, 8: air chamber, 9: capnometer host, 10: a capnometer probe;
wherein the catalyst-supporting film is located at a lower position of the sample area to be reacted. The buffer tank is connected with a site to be sampled of the device through a heat preservation pipeline.
FIG. 2 shows a plot of the true moisture content in isocyanate samples versus laboratory instrument analysis content.
FIG. 3 shows a plot of the true moisture content of an isocyanate sample versus the carbon dioxide content generated after reaction by an on-line analysis device.
Fig. 4 shows a correlation curve between two sets of measured values obtained for isocyanate samples by laboratory analysis methods, on-line assay device analysis methods, respectively.
The specific embodiment is as follows:
the technical features and contents of the present invention will be described in detail below by way of specific examples. It is to be understood, however, that the invention may be embodied in other various forms and should not be limited to the specific embodiments set forth herein.
The analytical test method comprises the following steps:
1. carbon dioxide online determination:
the carbon dioxide on-line analyzer is selected from MCP-200 infrared analyzer of AAI company in U.S., a heat-resistant protection device is additionally arranged, and the probe is made of 316L stainless steel.
2. Laboratory detection method for determining the water content in isocyanate samples:
basic principle of analysis of water content in isocyanate samples: at humidity of<In 5% environment, accurately weighing 75g of isocyanate sample to be measured, transferring into a sample area to be reacted of a designed on-line measuring device, immediately applying 100Kpa pressure by a sample pressing piston to make the sample contact with a catalytic membrane (supported catalyst membrane 1) for reaction, wherein the total contact area of the catalytic membrane is 70cm 2 Transferring all samples to a reacted sample area after passing through the sample, and after delaying for 4min, measuring the concentration of the reaction product carbon dioxide diffused into the air chamber by a carbon dioxide tester, wherein the probe is positioned at 50% of the height of the measuring air chamber, and the volume of the air chamber is 20L; from this measurement value, the water content in the sample was indirectly obtained. The specific analysis steps are as follows:
(1) In n groups of 500mL sample bottles, the same mass of isocyanate sample to be tested was added, followed by different mass of water (m 1 、m 2 、m 3 …m n ) The reaction and the instrument analysis were carried out under the above conditions to determine the corresponding measured value of the carbon dioxide concentration in the sample (S in terms of 1 、S 2 、S 3 …S n )；
(2) In 1 20mL sample bottle, adding the isocyanate sample to be tested with the same mass as each group of samples in (1) but not adding water,directly carrying out reaction and instrument analysis according to the conditions to determine the corresponding measured value of the carbon dioxide concentration in the sample, wherein the measured value is S 0 。
(3) In the water addition amount (m 1 、m 2 、m 3 …m n ) As x-axis, corresponds to the increase in carbon dioxide concentration measurement value (i.e., S 1 -S 0 、S 2 -S 0 、S 3 -S 0 …S n -S 0 ) Taking the y axis, determining the slope k, namely the first derivative value of the water addition quantity and the measured value of the carbon dioxide concentration;
(4) And (3) carrying out reaction and instrument analysis on the isocyanate sample to be detected according to the conditions, wherein the water content n= (S/k)/m, S is a corresponding carbon dioxide concentration measurement value in the sample, and m is the sample addition amount.
In the above laboratory test method, the analytical instrument used is selected from the group consisting of:
(1) Avance III 400M nuclear magnetic resonance spectrometer from Bruker, germany. An Ultrashield 400 magnet, a 5mm Dual (13C, 1H) Dual core probe was configured.
(2) The yield of the precursor di (3-carboxymorpholino) diethyl ether in the examples was quantified by liquid chromatography:
1260 liquid chromatograph, with DAD detector, agilent company, usa;
chromatographic column: CAPCELL PAK-C18 5 μm, 4.6X1250 mm;
gradient elution:
time(min) methanol (%, v/v) 0.1% phosphoric acid (%, v/v)
0 10 90
7 10 90
15 80 20
20 10 90
30(end) 10 90
0.1% phosphoric acid, 1mL phosphoric acid was dissolved in 1L ultra pure water
Column temperature: 40 ℃, flow rate: 1.0mL/min, sample injection amount: 30 μl, UV detector wavelength: 210nm of
(3) The yield of di (3-acid chloride morpholino) diethyl ether in the examples was quantified by elemental chlorine analysis: the method comprises the steps of (1) analyzing a Muti EA 5000 element analyzer of Analytikjena, carrying out a chlorine detector, a liquid injector, diluting a sample with chromatographic grade acetone (without chlorine element) by 500 times, analyzing, quantifying by a standard addition method of a chlorine standard oil sample, and finally calculating the relative content of a di (3-acyl chloride morpholinyl) diethyl ether molecule in the reaction product of the embodiment according to the chlorine element content of the sample.
Example 1:
method for synthesizing isocyanate-reactive catalyst precursor bis (3-carboxymorpholino) diethyl ether example 1:
400g of 3-carboxyl morpholine is dissolved in 1000g N-N-dimethylformamide, the mixture is added into a reactor equipped with a thermometer and a reflux condenser, the temperature of the reaction system is controlled to be 100 ℃, 10g of potassium iodide is added, 40g of diethyl ether dichloride is dripped into the reactor at a flow rate of 0.4g/min, stirring reflux reaction is carried out, and the reaction is carried out for 30min after the dripping is finished. Cooling at normal temperature, separating phase, wherein the solid phase is 3-carboxyl morpholine hydrochloride and potassium iodide (which can be recycled after being treated by sodium hydroxide), and the liquid phase is distilled at 160 ℃ under normal pressure to remove solvent N-N-dimethylformamide; then distilling under reduced pressure at 200 ℃ under 25mmHg to remove redundant 3-carboxyl morpholine, thus obtaining crude product; the crude product is recrystallized by acetonitrile, and the di (3-carboxyl morpholinyl) diethyl ether is obtained by suction filtration, and the yield is 84%. The reaction formula is as follows:
1 H NMR(CDCl 3 12.39 (s, 2H), 4.43 (s, 4H), 4.03 (d, j=12.1 hz, 2H), 3.77 (d, j=12.1 hz, 2H), 3.57-3.61 (m, 4H), 3.34 (t, j=11.1 hz, 2H), 2.62-2.72 (m, 4H). Method for synthesizing isocyanate-reactive catalyst precursor bis (3-carboxymorpholino) diethyl ether example 2:
400g of 3-carboxyl morpholine is dissolved in 2000g N-methyl pyrrolidone, and then the mixture is added into a reactor equipped with a thermometer and a reflux condenser, the temperature of the reaction system is controlled to be 120 ℃,20 g of sodium carbonate is added, 60g of diethyl ether dichloride is dripped into the reactor at a flow rate of 0.3g/min, stirring reflux reaction is carried out, and the mixture is then subjected to heat preservation reaction for 30min after the dripping is finished. Cooling at normal temperature, separating phase, wherein the solid phase is 3-carboxyl morpholine hydrochloride and sodium carbonate (which can be recycled after being treated by sodium hydroxide), and the liquid phase is distilled at 205 ℃ under normal pressure to remove solvent N-methylpyrrolidone; then distilling under reduced pressure at 200 ℃ under 25mmHg to remove redundant 3-carboxyl morpholine, thus obtaining crude product; the crude product is recrystallized by acetonitrile, and the product di (3-carboxyl morpholinyl) diethyl ether is obtained by suction filtration, and the yield is 91%.
1 H NMR(CDCl 3 12.68 (s, 2H), 4.48 (s, 4H), 4.09 (d, j=12.1 hz, 2H), 3.59 (d, j=12.1 hz, 2H), 3.62-3.64 (m, 4H), 3.39 (t, j=11.1 hz, 2H), 2.84-2.90 (m, 4H). Method for synthesizing isocyanate-reactive catalyst precursor bis (3-carboxymorpholino) diethyl ether example 3:
400g of 3-carboxyl morpholine is dissolved in 750g of tetrahydrofuran, the solution is added into a reactor equipped with a thermometer and a reflux condenser, the temperature of the reaction system is controlled to be 60 ℃, 6g of potassium bromide is added into the reactor, 20g of dichlorodiethyl ether is dripped into the reactor at a flow rate of 0.5g/min, stirring reflux reaction is carried out, and the reaction is carried out for 60min after the dripping is finished. Cooling at normal temperature, separating phase, wherein the solid phase is 3-carboxyl morpholine hydrochloride and potassium bromide (which can be recycled after being treated by sodium hydroxide), and the liquid phase is distilled at 80 ℃ under normal pressure to remove solvent tetrahydrofuran; then distilling under reduced pressure at 200 ℃ under 25mmHg to remove redundant 3-carboxyl morpholine, thus obtaining crude product; the crude product is recrystallized by acetonitrile, and the product di (3-carboxyl morpholinyl) diethyl ether is obtained by suction filtration, and the yield is 75%.
1 H NMR(CDCl 3 ,500MHz):12.55(s,2H),4.45(s,4H),4.13(d,J＝12.1Hz,2H),3.48(d,J＝12.1Hz,2H),3.68-3.70(m,4H),3.33(t,J＝11.1Hz,2H),2.74-2.81(m,4H).
Example 2:
preparation method of the supported isocyanate-reactive catalyst film example 1;
700g of thionyl chloride is added into 100g of di (3-carboxyl morpholinyl) diethyl ether, then 1g N-N-dimethylformamide is added dropwise, heating reflux is carried out for 3 hours at 80 ℃, redundant thionyl chloride and N-N-dimethylformamide are removed by rotary evaporation, and the membrane active matrix di (3-acyl morpholinyl) diethyl ether can be obtained, the yield is 92%, and the reaction formula is as follows:
1 H NMR(CDCl 3 ,500MHz):4.44(s,4H),4.09(d,J＝12.1Hz,2H),3.84(d,J＝12.1Hz,2H),3.57-3.61(m,4H),3.23(t,J＝11.1Hz,2H),2.62-2.72(m,4H).
And cleaning the polyvinylidene fluoride (PVDF) film with an acetone solvent, and naturally airing. And (3) soaking the cleaned membrane material in a dopamine buffer solution (10 mg/mL dopamine+ 50mM Tris+50mM HCl aqueous solution) for 18h at 50 ℃ to construct a polydopamine mediated layer on the membrane surface. Soaking a basal membrane for constructing a polydopamine dielectric layer in 10mg/mL of N-N-dimethylformamide solution of di (3-acyl chloride morpholinyl) diethyl ether for 18h at 50 ℃ to load a catalyst; finally, soaking the catalyst-loaded membrane in acetyl chloride with the mass of 500 times of that of the catalyst at normal temperature for 8 hours, and finishing end capping to obtain a catalyst-loaded membrane 1, wherein the reaction formula is as follows: r represents catecholethyl.
Preparation method of the supported isocyanate-reactive catalyst film example 2;
adding 1200g of thionyl chloride into 100g of di (3-carboxyl morpholinyl) diethyl ether, then dripping 0.5g of triethylamine, heating and refluxing for 7h at 65 ℃, removing redundant thionyl chloride and triethylamine by rotary evaporation to obtain membrane active matrix di (3-acyl morpholinyl) diethyl ether, the yield is 87%,
1 H NMR(CDCl 3 ,500MHz):4.35(s,4H),4.08(d,J＝12.1Hz,2H),3.81(d,J＝12.1Hz,2H),3.49-3.57(m,4H),3.28(t,J＝11.1Hz,2H),2.69-2.79(m,4H).
and cleaning the polyvinylidene fluoride (PVDF) film with an acetone solvent, and naturally airing. And (3) soaking the cleaned membrane material in a dopamine buffer solution (15 mg/mL dopamine+150 mM dipotassium hydrogen phosphate+10 mM potassium dihydrogen phosphate aqueous solution) for 12 hours at the temperature of 55 ℃ to construct a polydopamine mediated layer on the membrane surface. Soaking a basal membrane for constructing a polydopamine dielectric layer in 15mg/mL acetone solution of di (3-acyl chloride morpholinyl) diethyl ether for 12h at the temperature of 75 ℃ to load a catalyst; and finally, soaking the catalyst-loaded membrane in acetyl chloride with the mass of 500 times of that of the catalyst at normal temperature for 6 hours to finish end capping, thereby obtaining the catalyst-loaded membrane 2.
Preparation method of the supported isocyanate-reactive catalyst film example 3;
400g of thionyl chloride is added into 100g of di (3-carboxyl morpholinyl) diethyl ether, 2g of sodium carbonate is added dropwise, heating reflux is carried out for 3 hours at the temperature of 110 ℃, redundant thionyl chloride and sodium carbonate are removed by rotary evaporation and filtration, thus obtaining membrane active matrix di (3-acyl morpholinyl) diethyl ether with the yield of 94%;
1 H NMR(CDCl 3 ,500MHz):4.39(s,4H),4.04(d,J＝12.1Hz,2H),3.80(d,J＝12.1Hz,2H),3.52-3.54(m,4H),3.29(t,J＝11.1Hz,2H),2.63-2.74(m,4H).
and cleaning the polyvinylidene fluoride (PVDF) film with an acetone solvent, and naturally airing. And (3) soaking the cleaned membrane material in a dopamine buffer solution (6 mg/mL dopamine+40 mM ammonium chloride+5 mM ammonia water solution) for 24 hours at 35 ℃ to construct a polydopamine mediating layer on the membrane surface. Soaking a basal membrane for constructing a polydopamine dielectric layer in 5mg/mL cyclohexane solution of bis (3-acyl chloride morpholinyl) diethyl ether for 24 hours at the temperature of 45 ℃ to load a catalyst; and finally, soaking the catalyst-loaded membrane in acetyl chloride with the mass of 500 times of that of the catalyst at normal temperature for 12 hours to finish end capping, thereby obtaining the catalyst-loaded membrane 3.
Example 3:
according to the method provided by the invention, an online measuring device is designed, as shown in fig. 1, and the following is an application example of the device for loading the membrane catalyst under different preparation methods.
Application example 1 of the on-line measuring device:
Introducing the sample into a buffer tank through a device site which is confirmed in advance, keeping the temperature at 80+/-1 ℃ for 5min, metering by a buffer load balance, transferring 75g of diphenylmethane diisocyanate sample into a sample area to be reacted, immediately applying 100Kpa pressure by a sample pressing piston to enable the sample to contact a catalytic membrane (supported catalyst membrane 1) for reaction, wherein the total contact area of the catalytic membrane is 70cm 2 After all samples have passed through, they are transferred to the reacted sample zone and after a further delay of 4min, the concentration of the reaction product carbon dioxide diffused into the gas chamber is determined by a capnometer, wherein the probe is at 50% of the height of the measuring gas chamber, the volume of the gas chamber is 20L. The sample in the reacted sample area is transferred to a waste liquid tank, can be treated as waste liquid according to the requirement, and can also be returned to the original device site.
On-line assay device application example 2:
introducing the sample into a buffer tank through a device site confirmed in advance, keeping the temperature at 50+/-1 ℃ for 5min, metering by a buffer load balance, and introducing 120g of toluene diisocyanides into a sample area to be reactedAcid ester sample, immediately applying 200Kpa pressure by a sample pressing piston to make the sample contact with a catalytic membrane (supported catalyst membrane 2) for reaction, wherein the total contact area of the catalytic membrane is 90cm 2 After all samples have passed through, they are transferred to the reacted sample area and after a further delay of 4min, the concentration of the reaction product carbon dioxide diffused into the gas chamber is determined by a capnometer, wherein the probe is at 30% of the height of the measuring gas chamber and the volume of the gas chamber is 30L. The sample in the reacted sample area is transferred to a waste liquid tank, can be treated as waste liquid according to the requirement, and can also be returned to the original device site.
On-line assay device application example 3:
introducing the sample into a buffer tank through a device site which is confirmed in advance, keeping the temperature constant for 5min at 90+/-3 ℃, metering by a buffer load balance, introducing 40g of hexamethylene diisocyanate sample into a sample area to be reacted, immediately applying 50Kpa pressure by a sample pressing piston to enable the sample to contact a catalytic membrane (supported catalyst membrane 3) for reaction, wherein the total contact area of the catalytic membrane is 40cm 2 After all samples have passed through, they are transferred to the reacted sample area and after a further delay of 7min, the concentration of the reaction product carbon dioxide diffused into the gas chamber is determined by a capnometer, wherein the probe is at 70% of the height of the measuring gas chamber and the volume of the gas chamber is 10L. The sample in the reacted sample area is transferred to a waste liquid tank, can be treated as waste liquid according to the requirement, and can also be returned to the original device site.
Example 4:
according to the method provided by the invention, in order to obtain the on-line measurement result of the water content of the isocyanate sample, a result model of the water content of the isocyanate sample and the carbon dioxide content generated by the reaction of the sample in an on-line measurement device is established, and the method comprises the following specific steps of:
(1) Collecting 20 diphenylmethane diisocyanate samples with different sites, different times and different 4,4/2,4 isomerism ratios of the device, analyzing the water content in the samples by using the laboratory analysis method to determine the MDI sample with the lowest water content, manually adding water with different contents into the sample, wherein the water content is respectively 0-0.015%, and the water is distributed in an arithmetic progression to obtain a group of samples with different water contents The total number of samples was 20, and the laboratory analysis content of the moisture content of the set of samples was determined using laboratory analysis methods. The correlation curve of the real moisture content of the sample and the laboratory analysis content is shown in FIG. 2, and the correlation coefficient R 2 The laboratory analysis results can be approximated as being able to characterize the true moisture content of the isocyanate sample, = 0.9988.
(2) The carbon dioxide content of the 20 isocyanate samples added with moisture in (1) after the reaction was measured by an on-line analyzer, and all the reaction conditions of the on-line analyzer were the same as those of example 1 in example 3.
(3) Correlating the real moisture content of 20 isocyanate samples added with moisture in the step (1) with the carbon dioxide content generated by the reaction after the on-line analysis device, and establishing a quantitative model of the water content of the diphenylmethane diisocyanate sample by using a partial least squares regression method, wherein a correlation curve of the real moisture content of the sample and the carbon dioxide content in the reactor is shown in figure 3, and a correlation coefficient R 2 = 0.9926, the modeling results are ideally reliable, so the reactor produced carbon dioxide content can accurately describe the moisture content in the isocyanate.
(4) Using the established quantitative model, the rest 19 diphenylmethane diisocyanate samples in (1) were subjected to moisture analysis by an on-line analysis device, and compared with the moisture content obtained by the laboratory analysis method in (1), the correlation curves of the two analysis methods being shown in FIG. 4, the correlation coefficient R 2 = 0.9885, the maximum deviation is 0.0005%, and the accuracy of the online analysis value determined by the model can meet the requirement of device production.
Example 5:
the on-line reactor and analysis result model of example 3 and example 4 were applied to on-line moisture measurement of MDI product tank samples, and the specific steps were as follows:
(1) Installing the on-line reactor described in example 3 at a specified position corresponding to the specified height of the MDI product feed line and the storage tank;
(2) The carbon dioxide concentration values collected at each site are transmitted to a PC host, the PC host calculates the water content of the sample using the data and the analysis result model established in example 4, the calculation result is transmitted to the DCS screen of the control room, and the measurement can be manually operated for 30 minutes or longer.
(3) When the analyzed moisture content is higher than a set alarm value (the set alarm value is set to be 0.001%), the DCS gives an alarm, an operator needs to switch the high-moisture-content MDI product into an unqualified product tank in time, and meanwhile immediately checks whether leakage points exist near the position, and the high-moisture-content MDI product can be switched back into a normal product tank until the analyzed value is recovered to the normal back.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation, and various modifications and adaptations of various embodiments will be apparent to those skilled in the relevant arts.

Claims (32)

1. A method for detecting trace moisture in isocyanate comprising the steps of: the isocyanate and water are passed through a membrane loaded with an isocyanate-reactive catalyst bis (3-amidomorpholino) diethyl ether having the following formula to form carbon dioxide, the carbon dioxide content formed is measured and converted to the moisture content in the isocyanate:
；
wherein R is 1 Is catechol ethyl, R 2 Is C1-C5 alkyl or phenyl.
2. The method of claim 1, wherein R 2 Is methyl, ethyl or phenyl.
3. The method according to claim 1, wherein the isocyanate is selected from one or more of diphenylmethane diisocyanate and isomers thereof, diphenylmethane polyisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, phenyl isocyanate.
4. A process according to claim 3, wherein the diphenylmethane diisocyanate and isomers thereof are selected from one or more of 4, 4-diphenylmethane diisocyanate, 2-diphenylmethane diisocyanate.
5. The method of claim 1, wherein the isocyanate-reactive catalyst di (3-amidomorpholino) diethyl ether is prepared by preparing a precursor di (3-carboxymorpholino) diethyl ether, and then carrying out a chloroacylation reaction with thionyl chloride and a subsequent nitroxylation reaction, wherein the precursor di (3-carboxymorpholino) diethyl ether is supported on a membrane and has the following structural formula:
the preparation method of the precursor di (3-carboxyl morpholinyl) diethyl ether comprises the following steps:
(1) Dissolving 3-carboxymorpholine in a solvent;
(2) Adding a catalyst, adding diethyl ether into 3-carboxyl morpholine, and carrying out reflux reaction after the mixture ratio is reached;
(3) The di (3-carboxyl morpholinyl) diethyl ether is obtained by separation and purification.
6. The process according to claim 5, wherein the mass ratio of 3-carboxymorpholine to diethyl ether is from 5 to 20:1; and/or the temperature of the reaction system is 60-120 ℃; and/or dripping diethyl ether into 3-carboxyl morpholine at uniform speed, wherein the dripping speed is 0.5-3%/min, and the reaction time is 4-8h, with the total dripping speed of the diethyl ether as a reactant being 100%.
7. The process according to claim 6, wherein the mass ratio of 3-carboxymorpholine to diethyl ether is 8-10:1; and/or the drop rate is 0.7-1.5%/min.
8. The method according to any one of claims 5 to 7, wherein the solvent is one or more of tetrahydrofuran, acetonitrile, N-dimethylformamide, N-methylpyrrolidone, cyclohexane; and/or the mass ratio of the 3-carboxyl morpholine to the solvent is 1:1.5-8.
9. The method according to any one of claims 5-7, wherein the catalyst is one or more of an alkali metal hydroxide, halide, carbonate; the mass ratio of the 3-carboxyl morpholine to the catalyst is 20-80:1.
10. The method according to any one of claims 5 to 7, wherein the method for preparing the isocyanate-reactive catalyst supported film comprises the steps of:
(1) Adding thionyl chloride and a catalyst required by the reaction into di (3-carboxyl morpholinyl) diethyl ether, heating and refluxing, and removing thionyl chloride by rotary evaporation to obtain an intermediate di (3-acyl morpholinyl) diethyl ether, wherein the substance has the following structural formula;
(2) Cleaning the base film with a solvent, and naturally airing;
(3) After the basal membrane is soaked in a dopamine solution, constructing a polydopamine mediating layer on the surface of the basal membrane;
(4) Soaking the base film of the medium layer constructed in the step (3) in a solvent containing an intermediate di (3-acyl chloride morpholinyl) diethyl ether, carrying out nitrogen acylation reaction on the intermediate di (3-acyl chloride morpholinyl) diethyl ether, and finally converting into a catalyst di (3-amide morpholinyl) diethyl ether and loading the catalyst di (3-amide morpholinyl) diethyl ether on the base film;
(5) Immersing the membrane loaded with the catalyst di (3-amide morpholinyl) diethyl ether in the step (4) in a blocking agent to finish blocking.
11. The method according to claim 10, wherein: in the step (1), the mass ratio of the di (3-carboxyl morpholinyl) diethyl ether to the thionyl chloride is 1:3-20; and/or the catalyst is any one of amide, tertiary amine and carbonate; and/or the mass ratio of the di (3-carboxyl morpholino) diethyl ether to the catalyst is 50-400:1; and/or the temperature of the reaction system is 60-120 ℃ and the reaction time is 2-8h.
12. The method according to claim 11, wherein: in the step (1), the mass ratio of the di (3-carboxyl morpholinyl) diethyl ether to the thionyl chloride is 1:5-8; and/or the catalyst is N-N-dimethylformamide; and/or the mass ratio of the di (3-carboxyl morpholino) diethyl ether to the catalyst is 80-150:1.
13. The method according to claim 10, wherein: the dopamine solution in the step (3) is a mixed solution of dopamine, buffer salt and water, and the pH value of the solution is 5-9; the buffer salt is one or more of phosphate, ammonium salt and organic salt; and/or buffer salt concentration of 30-200mM; and/or soaking time is 12-24h, and soaking system temperature is 30-60 ℃.
14. The method according to claim 13, wherein: the concentration of the dopamine in the step (3) in the solution is 5-20mg/mL, and the buffer salt is any one of potassium dihydrogen phosphate-dipotassium hydrogen phosphate and Tris-HCl; and/or the buffer salt concentration is 80-150mM.
15. The method according to claim 10, wherein: the solvent in the step (4) is one or more of amide, acetone and cyclohexane; the concentration of the di (3-acyl chloride morpholinyl) diethyl ether solution is 5-20mg/mL, and/or the soaking time is 12-24h, and the soaking temperature is 40-80 ℃.
16. The method according to claim 10, wherein: the end capping agent in the step (5) is one or more of acyl chloride substances; and/or the end capping reaction time is 6-12h, and/or the mass ratio of the end capping agent to the catalyst is 300-1000:1.
17. The method of claim 16, wherein: the end capping agent in the step (5) is acetyl chloride.
18. Use of the method according to any of claims 1 to 17 for in-line monitoring of trace moisture in isocyanate production, characterized in that it comprises the steps of:
step one, a membrane loaded with an isocyanate-reactive catalyst bis (3-amide morpholinyl) diethyl ether is arranged at the inlet end of on-line measuring equipment;
And secondly, starting a measuring device by controlling measuring equipment, regulating the temperature of an isocyanate sample through a buffer tank, allowing the isocyanate sample to pass through a film loaded with a catalyst, reacting the isocyanate with trace moisture to generate carbon dioxide, measuring the generated carbon dioxide content by using a carbon dioxide on-line measuring instrument, and converting the carbon dioxide content into the moisture content in the isocyanate.
19. The use according to claim 18, wherein the on-line measuring device comprises a control measuring device, a buffer tank, a sample transfer pump, a reaction apparatus containing a catalyst-carrying membrane, a measuring gas chamber and an on-line carbon dioxide meter connected by a pipeline; the probe of the carbon dioxide on-line measuring instrument is arranged inside the air chamber, and the installation position is 10% -90% of the height of the air chamber.
20. The use according to claim 19, wherein the carbon dioxide on-line measuring probe is mounted inside the air chamber at a position of 40% -50% of the height of the air chamber; the probe of the carbon dioxide on-line measuring instrument is an immersed optical fiber probe.
21. The use according to claim 18, wherein the isocyanate sample is fed into the buffer tank via the site to be measured, the sample is fed into the reaction device comprising the catalyst-loaded membrane via the sample-feeding pump, the gas resulting from the reaction is fed into the measuring chamber, and the measuring data is transmitted via the optical fiber after the data is collected by the on-line measuring instrument in the chamber.
22. The use according to any one of claims 18 to 21, wherein in step one the operating temperature of the on-line measuring device is 50-95 ℃; the temperature should be kept constant, and the constant range is not higher than 1% -10%; and/or the volume of the air chamber is 10-50L.
23. The use according to claim 22, wherein in step one, the operating temperature of the on-line measuring device is 70-80 ℃; the temperature should be kept constant, and the constant range is not higher than 1% -2%; and/or the air chamber volume is 15-25L.
24. The use according to any one of claims 18 to 21, wherein in step two, the isocyanate sample is subjected to the membrane reaction in advance with the temperature adjusted by a buffer tank to match the sample temperature with the temperature of the on-line measuring device, and the buffer time is 2 to 10min.
25. The use according to claim 24, wherein in step two the buffering time is 3-5min.
26. The use according to any one of claims 18 to 21, wherein in step two the isocyanate sample is transported in an amount of 30 to 200g; and/or the sample film-penetrating pressure is 30-300KPa; and/or the contact area of the catalyst-supporting film and the isocyanate sample is 20-100cm 2 The method comprises the steps of carrying out a first treatment on the surface of the And/or the measured delay time is 0.5-10min.
27. The use according to claim 26, wherein in step two the isocyanate sample is transported in an amount of 80-100g; and/or the sample film-penetrating pressure is 50-100KPa; and/or the contact area of the catalyst-supporting film and the isocyanate sample is 50-80cm 2 The method comprises the steps of carrying out a first treatment on the surface of the And/or the measured delay time is 2-4min.
28. The use according to any one of claims 18 to 21, wherein in step two, the transmission amount of the isocyanate sample, the measured value of the carbon dioxide content, the specific site of the equipment and the measurement time are transmitted to the PC host computer through the optical cable, the calculation of the moisture content in the isocyanate sample is performed by the host computer, the analysis model of the measured value of the carbon dioxide content corresponding to the isocyanate sample with different moisture content is built first, and the correspondence is entered into the host computer to realize the automatic calculation.
29. The use according to claim 28, wherein the establishment of the analytical model comprises the steps of: introducing the isocyanate sample of the calibration set into a reactor provided with a membrane containing isocyanate-reactive catalyst di (3-amide morpholino) diethyl ether, performing online analysis to obtain an analysis measurement value, correlating the analysis measurement value with the known content of the analysis measurement value, and establishing an analysis model by a multivariate data regression analysis method; and/or the number of isocyanate samples of the correction set is not less than 20, and the moisture content of the isocyanate samples of the correction set is 0.0003-0.03% (w/w) based on 100% of the total weight of the isocyanate samples of the correction set.
30. The use of claim 29, wherein the multivariate data regression analysis method is a partial least squares regression method; and/or, the isocyanate sample moisture content of the calibration set is 0.0008-0.016% (w/w).
31. The use according to claim 29, characterized in that the sample moisture content data of the monitored site is transmitted to the control room DCS screen by means of a PC host in a wired or wireless manner, while setting a DCS high limit alarm; and/or the sample measurement and data acquisition interval of the site to be monitored is 10-30min.
32. The use of claim 31, wherein the DCS alarm minimum value is 0.008-0.012% of moisture content.
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