Method and device for detecting conversion rate of polymeric monomer in isocyanate reaction liquid and polymerization inhibition method

Abstract

The invention relates to a method and a device for detecting the conversion rate of a polymeric monomer in an isocyanate reaction solution and a polymerization inhibition method of the isocyanate reaction solution. The detection method comprises the following steps: detecting the temperature T and the refractive index Y of a to-be-detected isocyanate reaction solution, substituting the temperature T and the refractive index Y into a linear equation of the corresponding relation of the reaction temperature, the refractive index and the conversion rate, and determining the conversion rate alpha in the to-be-detected isocyanate reaction solution. The construction method of the linear equation comprises the following steps: providing an isocyanate reaction liquid standard substance; the isocyanate reaction liquid standard substance comprises n reaction liquid standard samples with different conversion rates. Detecting the refractive index Y of each reaction liquid standard sample at different temperatures T, and performing linear fitting on the refractive index Y and the temperature T to obtain a plurality of linear equations N: Y = kn * T + bn; performing linear fitting on the intercept bn of the linear equation N and the conversion rate alpha of the reaction liquid standard sample, and replacing the bn with Y-knxT1 to obtain a linear equation.

Description

Technical Field

[0001] The present application relates to the technical field of rapid detection of isocyanate polymerization reactions, and in particular to a detection method and a testing device for the conversion rate of polymerization monomers in an isocyanate reaction solution, and a method for inhibiting the polymerization of an isocyanate reaction solution. Background Art

[0002] Polyisocyanates are important basic raw materials for polyurethanes. Aliphatic isocyanates such as hexamethylene diisocyanate (HDI) polymer series and pentamethylene diisocyanate (PDI) polymer series have excellent physical and chemical properties such as weather resistance, friction resistance and yellowing resistance, and have therefore been widely used as polyurethane coatings for high-end equipment and facilities such as outdoor buildings, transportation facilities, offshore vessels, and aerospace. Aromatic isocyanates such as diphenylmethane diisocyanate (MDI) polymer series have excellent chemical stability, thermal insulation and sound insulation properties, and are widely used as polyurethane powders for refrigeration equipment, transportation vehicles and other equipment.

[0003] The preparation process of polyisocyanate is mainly to make polymerizable monomers such as HDI, PDI and MDI undergo self-polymerization reaction under the action of catalyst. In the self-polymerization reaction, trimer is one of the main polymer products, but as the polymerization reaction or reaction time increases, high polymers such as pentamer and heptamer with higher molecular weight will be further generated. The generation of these high polymers will affect the performance and application range of the product. Therefore, in the preparation process of polyisocyanate, it is necessary to monitor the degree of polymerization reaction, that is, the conversion rate of the polymer, so as to add the inhibitor at the appropriate time to obtain the desired polymerization product.

[0004] At present, the main method for testing the degree of polyisocyanate polymerization reaction is gel chromatography (GPC). This method requires dilution of the reaction solution and has the disadvantages of long detection time, difficult sample preparation and the need to consume mobile phase. Summary of the invention

[0005] Based on this, the present application provides a detection method and testing device for the conversion rate of polymerized monomers in isocyanate reaction liquid, and a polymerization inhibition method. The detection method provided in the present application can obtain the conversion rate by the temperature and refractive index of the isocyanate reaction liquid to be tested, which has the advantages of no need for dilution and quick detection.

[0006] In a first aspect of the present application, a method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution is provided, comprising the following steps:

[0007] Detecting the temperature T and the refractive index Y of the isocyanate reaction liquid to be tested, substituting the temperature T and the refractive index Y into a linear equation of the corresponding relationship between the reaction temperature, the refractive index and the conversion rate, and determining the conversion rate α in the isocyanate reaction liquid to be tested;

[0008] The step of constructing the linear equation includes:

[0009] Providing an isocyanate reaction solution standard; the isocyanate reaction solution standard comprises n reaction solution standard samples with different conversion rates, and the conversion rate α of the reaction solution standard samples is known;

[0010] Detect the refractive index Y of each of the reaction liquid standard samples at different temperatures T, perform linear fitting on the refractive index Y and the temperature T, and obtain a linear equation N of the corresponding relationship between the refractive index Y and the temperature T in the plurality of the reaction liquid standard samples; the linear equation N is: Y=k n ×T+b n , k n is the slope, b n is the intercept;

[0011] The intercept b of the linear equation N is n The conversion rate α of the reaction solution standard sample is linearly fitted, and then b n Use Y-k n ×T to obtain the linear equation.

[0012] In one embodiment, the detection method has one or more of the following features:

[0013] (1) The linear equation N R 2 ≥0.98;

[0014] (2) R of the linear equation 2 ≥0.99;

[0015] (3) The conversion rate of the reaction solution standard sample is less than 100%.

[0016] In one embodiment, the reaction solution standard sample and the isocyanate reaction solution to be tested contain the same type of polymerizable monomers;

[0017] Optionally, the polymerizable monomer includes one or more of hexamethylene diisocyanate, pentamethylene diisocyanate and diphenylmethane diisocyanate; and / or,

[0018] In the plurality of linear equations N, the plurality of slopes k n The deviation is ≤ 0.00001; and / or,

[0019] Among the n reaction solution standard samples with different conversion rates, n is an integer ≥4.

[0020] In one embodiment, the detection method has one or more of the following features:

[0021] (1) When the polymerizable monomer is hexamethylene diisocyanate, the slope k1 is -0.00041 to -0.00039;

[0022] (2) When the polymerizable monomer is pentamethylene diisocyanate, the slope k1 is -0.00041 to -0.00039.

[0023] In one embodiment, the linear equation is: α=100%-[K(Yk n ×T)+B]×100%; where α is the conversion rate, K is -3000~-2000, and B is 4000~4800.

[0024] In one embodiment, the preparation steps of the isocyanate reaction solution to be tested include:

[0025] The polymerizable monomers and the catalyst are mixed, and the obtained mixture is heated to a polymerization temperature to prepare the isocyanate reaction solution to be tested.

[0026] In one embodiment, the preparation step of the isocyanate reaction solution to be tested has one or more of the following characteristics:

[0027] (1) The catalyst includes one or more of a quaternary ammonium base catalyst, a quaternary ammonium salt catalyst and a silane amine catalyst;

[0028] (2) The polymerization temperature is 40°C to 100°C.

[0029] In one embodiment, the detection method has one or more of the following features:

[0030] (1) The conditions for detecting the isocyanate reaction liquid to be tested include: passing the isocyanate reaction liquid to be tested through an Abbe refractometer, and reading the temperature T and the refractive index Y of the isocyanate reaction liquid to be tested;

[0031] (2) The test conditions for the conversion rate of the reaction solution standard sample include: testing the conversion rate α of the reaction solution standard sample by gel chromatography;

[0032] (3) The test conditions for the conversion rate of the reaction solution standard sample include: using an Abbe refractometer to detect the refractive index Y and temperature T of the isocyanate reaction solution standard sample.

[0033] In a second aspect of the present application, a method for inhibiting polymerization of an isocyanate reaction solution is provided, comprising the following steps:

[0034] Taking the isocyanate reaction liquid to be tested, and testing the conversion rate of the polymerized monomer in the isocyanate reaction liquid to be tested by the detection method described in any one of the embodiments of the first aspect of the present application;

[0035] When the conversion rate of the isocyanate reaction solution to be tested reaches the expected conversion rate, an inhibitor is added to inhibit polymerization.

[0036] In a third aspect of the present application, a test device for the conversion rate of polymerization monomers in an isocyanate reaction solution is provided, comprising:

[0037] A polymerization reaction module, wherein the polymerization reaction module is suitable for containing the isocyanate reaction liquid to be tested,

[0038] A detection module, the detection module is connected to the polymerization reaction module, and the detection module is suitable for detecting the temperature and refractive index of the isocyanate reaction liquid to be tested;

[0039] A data acquisition module, wherein the data acquisition module is connected to the detection module, and the data acquisition module is suitable for collecting the temperature and refractive index measured by the detection module, and calculating the conversion rate of the isocyanate reaction liquid according to a linear equation; wherein the linear equation is obtained by the detection method described in any one of the embodiments of the first aspect of the present application.

[0040] The method for detecting the conversion rate in the isocyanate reaction solution provided in the present application has at least the following beneficial effects:

[0041] The detection method provided by the present application can determine the conversion rate of the polymerized monomer in the isocyanate reaction liquid to be tested based on the temperature and refractive index of the isocyanate reaction liquid to be tested. The operation is simple and there is no need to pre-treat the reaction liquid. At the same time, the detection method also has the advantage of fast detection speed. It can obtain conversion rate data in real time during the reaction process, so that the operator can grasp the reaction dynamics in time and accurately control the reaction process to accurately inhibit polymerization at the inhibition end point. In addition, the method has high accuracy and good repeatability. The detection model established based on temperature and refractive index is stable and reliable, which reduces the production deviation caused by detection error, and is convenient for actual production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the structure of a testing device for the conversion rate of polymerization monomers in an isocyanate reaction solution of the present application;

[0043] Figure 2 is the fitting curve of the linear equation N in the reaction solution standard samples A1 to A5 of Example 1 of the present application;

[0044] Figure 3 It is the fitting curve of the linear equation N in the reaction solution standard samples B1~B6 of Example 2 of the present application.

[0045] Description of Reference Numerals

[0046] Polymerization reaction module-10, detection module-20, data acquisition module-30. DETAILED DESCRIPTION

[0047] The following is a further complete and clear description of the detection method and test device for the conversion rate of the polymerized monomers in the isocyanate reaction solution of the present application, as well as the polymerization inhibition method, in conjunction with specific examples. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0048] The self-polymerization reaction of isocyanate monomer occurs in the isocyanate reaction liquid to be tested. During the reaction, isocyanate monomer is consumed and polymerization product is generated. As the polymerization reaction progresses or the reaction time increases, the proportion of isocyanate monomer (i.e., polymerization monomer) in the isocyanate reaction liquid to be tested gradually decreases, and the proportion of polymerization product gradually increases. Therefore, by measuring the content of polymerization monomer in the isocyanate reaction liquid, or measuring the content of polymerization product, the degree or conversion rate of the polymerization reaction can be characterized.

[0049] Based on this, the first aspect of the present application provides a method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution, comprising the following steps:

[0050] The temperature T and the refractive index Y of the isocyanate reaction liquid to be tested are detected, and the temperature T and the refractive index Y are substituted into a linear equation of the corresponding relationship between the reaction temperature, the refractive index and the conversion rate to determine the conversion rate α in the isocyanate reaction liquid to be tested.

[0051] The detection method provided by the present application can determine the conversion rate in the isocyanate reaction liquid to be measured based on the temperature and refractive index of the isocyanate reaction liquid to be measured, and the operation is simple, and there is no need to pre-treat the reaction liquid. Meanwhile, the detection method also has the advantage of fast detection speed, and it can obtain conversion rate data in real time during the reaction process, so that the operator can grasp the reaction dynamics in time and accurately control the reaction process, and accurately perform inhibition at the inhibition end point to obtain the expected polymer product. In addition, the detection method can also be applied to high-throughput screening catalysts, accurately detect the conversion rate when different catalysts participate in the reaction, and then batch screen and quickly obtain the most suitable catalyst for catalytic activity. Further, the method has high accuracy and good repeatability, and the detection model established based on temperature and refractive index is stable and reliable, which reduces the production deviation caused by detection error, and is convenient for actual production and application.

[0052] In one example, the steps of constructing the linear equation include:

[0053] S10, providing an isocyanate reaction solution standard; the isocyanate reaction solution standard comprises n reaction solution standard samples with different conversion rates, and the conversion rate α of the reaction solution standard samples is known.

[0054] S20, detecting the refractive index Y of each of the reaction liquid standard samples at different temperatures T, performing linear fitting on the refractive index Y and the temperature T, and obtaining a linear equation N of the corresponding relationship between the refractive index Y and the temperature T in the plurality of the reaction liquid standard samples; the linear equation N is: Y=k n ×T+b n , k n is the slope, b n is the intercept.

[0055] S30, intercepts b of the plurality of linear equations N n The conversion rate α of the reaction solution standard sample is linearly fitted, and then b n Use Y-k n ×T to obtain the linear equation.

[0056] It can be understood that in step S20, when performing linear fitting on the refractive index Y and the temperature T, in order to improve the accuracy of the fitting, the corresponding point values ​​of the refractive index Y and the temperature T are multiple, so as to offset the influence of the test error. The number of data points selected when performing linear fitting on the refractive index Y and the temperature T is ≥4.

[0057] At the same time, in order to avoid the problem of increased workload caused by a large amount of testing, further, the number of data points selected when performing linear fitting on the refractive index Y and the temperature T is 4 to 15.

[0058] In addition, since in step S10, the isocyanate reaction liquid standard includes multiple reaction liquid standard samples with different conversion rates. Therefore, a linear equation N of the corresponding relationship between the refractive index Y and the temperature T will be obtained for one reaction liquid standard sample; multiple linear equations N will be obtained for multiple reaction liquid standard samples. The inventors surprisingly found that when the types of monomers included in the isocyanate reaction liquid are the same, the slopes of the linear equations N are almost exactly the same. Therefore, at this time, a universal linear equation N of the corresponding relationship between the refractive index Y and the temperature T in the isocyanate reaction liquid standard can be obtained; the linear equation N is: Y=k n ×T+b n , k n is a fixed value, b n is the intercept.

[0059] As mentioned above, multiple reaction solution standards will obtain multiple linear equations N, and the slope k of multiple linear equations N is nThe values ​​are the same, and the main difference is the intercept value. The inventors found that the greater the conversion rate, the greater the intercept value of the corresponding linear equation N. The above findings show that the relationship between the refractive index, temperature and conversion rate can present a good one-to-one linear relationship, so the conversion rate of the monomer in the reaction liquid can be obtained by measuring the refractive index and temperature values ​​in the reaction liquid. The specific method is: in step S30, the intercept b of the linear equation N of multiple reaction liquid standard samples is used. n A linear equation can be obtained by linearly fitting the conversion rate α corresponding to multiple reaction solution standards. n As a constant, the intercept b can be n Use as Yk n ×T is substituted to obtain the linear equation of reaction conversion rate, temperature and refractive index.

[0060] In one example, the linear equation N of R 2 ≥0.98.

[0061] In one example, the R of the linear equation 2 ≥0.99.

[0062] In one example, the conversion rate of the reaction solution standard is less than 100%. It is understandable that since the refractive index is actually the refractive index of the incompletely converted monomer mixture to be detected, the presence of polymerized monomers is required in multiple reaction solution standards. Furthermore, the conversion rates of multiple reaction solution standards are controlled at 0-60%, and the linear equation obtained by fitting is more linear. That is, the conversion rate of the reaction solution standard is 0-60%.

[0063] In one example, the reaction solution standard sample and the isocyanate reaction solution to be tested include the same type of polymerizable monomers.

[0064] When the types of polymerizable monomers included in the reaction solution standard sample and the isocyanate reaction solution to be tested are the same, the linear equations of the corresponding relationship between the reaction temperature, the refractive index and the conversion rate are also exactly the same. Therefore, for isocyanate reaction systems of the same type of polymerizable monomers, this method can be applied to detect the conversion rate, whether in the laboratory stage or in the industrial large-scale production stage, without the need to re-establish the detection method for different reaction batches or reaction scales.

[0065] Illustratively, the polymerizable monomer includes one or more of hexamethylene diisocyanate, pentamethylene diisocyanate, and diphenylmethane diisocyanate.

[0066] In one example, in the plurality of linear equations N, the plurality of slopes k nThe deviation is ≤0.00001. The present application found that when the types of polymerization monomers included in the reaction solution standard sample are the same, the slope values ​​obtained by fitting the linear equation N are almost the same, and the multiple slopes k n The deviation is ≤0.00001. Therefore, the general linear equation N for the corresponding relationship between the refractive index Y and the temperature T in the isocyanate reaction solution standard can be obtained; the linear equation N is: Y=k n ×T+b n , k n is a fixed value, b n is the intercept.

[0067] In one example, when the polymerizable monomer is hexamethylene diisocyanate, the slope k n is -0.00041 ~ -0.00039. Specifically, k n The values ​​include, but are not limited to, -0.00039, -0.000395, -0.000398, -0.0004, -0.000402, -0.000405, -0.000408 or -0.00041, or a range consisting of any two of the above point values ​​as endpoint values.

[0068] More specifically, when the polymerizable monomer is hexamethylene diisocyanate, the slope k n For example, the linear equation N of the corresponding relationship between the refractive index Y and the temperature T in the isocyanate reaction solution standard is: Y = -0.0004 × T + b n .

[0069] In one example, when the polymerizable monomer is pentamethylene diisocyanate, the slope k n is -0.00041 ~ -0.00039. Specifically, k n The values ​​include, but are not limited to, -0.00039, -0.000395, -0.000398, -0.0004, -0.000402, -0.000405, -0.000408 or -0.00041, or a range consisting of any two of the above point values ​​as endpoint values.

[0070] More specifically, when the polymerizable monomer is pentamethylene diisocyanate, the slope k n For example, the linear equation N of the corresponding relationship between the refractive index Y and the temperature T in the isocyanate reaction solution standard is: n = -0.0004×T+b n .

[0071] In one example, the linear equation is: α=100%-[K(Ykn ×T)+B]×100%; where α is the conversion rate, K is -3000~-2000, and B is 4000~4800.

[0072] In step S30, the intercept b n After linear fitting of Y2 and conversion rate, the obtained linear curve corresponds to the relationship between the content of polymerized monomers in the isocyanate reaction solution to be tested and the temperature and refractive index. For example, Y2= K(Yk n ×T)+B is the relationship between the polymerized monomer content Y2 in the isocyanate reaction solution to be tested and the temperature T and the refractive index Y. Since the sum of the polymerized monomer content and the polymerized product content in the isocyanate reaction solution to be tested, or the sum of the polymerized monomer content and the conversion rate is 100%, the linear equation is: α=100%-[K(Yk n ×T)+b n ]×100% can represent the relationship between conversion rate, temperature and refractive index. In addition, as mentioned above, when the monomers included in the isocyanate reaction solution to be tested are the same, k n The values ​​are almost the same, multiple of the slope k n The deviation is ≤0.00001. Therefore, the slope k n The value can be a certain value. Therefore, in the linear equation, there are only two variables: temperature T and refractive index Y.

[0073] For example, in the linear equation, the value of K includes but is not limited to -3000, -2950, ​​-2933, -2932, -2931, -2930.9, -2930.8, -2930.7, -2930.6, -2930.5, -2930.4, -2930, -2900, -2850, -2800, -2750, -2730, -2728, -2727.5, -2727.4, -2727.4, -2727.3, -2727.2, -2727, -2720, -2700, -2500, -2400, -2300, -2200, -2100 or -2000.

[0074] For example, in the linear equation, the value of B includes but is not limited to 4020, 4050, 4070, 4075, 4078, 4079, 4080, 4081, 4082, 4085, 4090, 4100, 4200, 4300, 4350, 4370, 4372, 4375, 4376, 4376.1, 4376.2, 4376.3, 4376.5, 4377, 4380, 4390, 4400, 4500, 4600, 4700 or 4800.

[0075] Further, when the polymerizable monomer included in the isocyanate reaction liquid to be tested is hexamethylene diisocyanate, the linear equation of the corresponding relationship among the reaction temperature, the refractive index and the conversion rate is α=100%-[-2727.4×(Y+0.0004×T)+ 4080.0]×100%.

[0076] Further, when the polymerizable monomer included in the isocyanate reaction solution to be tested is pentamethylene diisocyanate, the linear equation of the corresponding relationship among the reaction temperature, the refractive index and the conversion rate is α=100%-[-2930.7 (Y+0.0004×T)+ 4376.3]×100%.

[0077] In one example, the steps of preparing the isocyanate reaction solution to be tested include:

[0078] The polymerizable monomers and the catalyst are mixed, and the obtained mixture is heated to a polymerization temperature to prepare the isocyanate reaction solution to be tested.

[0079] In one example, the catalyst includes one or more of a quaternary ammonium base catalyst, a quaternary ammonium salt catalyst, and a silane amine catalyst.

[0080] In one example, the polymerization temperature is 40° C. to 100° C. For example, the polymerization temperature includes but is not limited to 40° C., 45° C., 50° C., 55° C., 58° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C. or 100° C., or a range formed by any two of the above point values ​​as endpoint values.

[0081] In one example, the conditions for detecting the isocyanate reaction solution to be tested include:

[0082] The isocyanate reaction liquid to be tested flows through an Abbe refractometer, and the temperature T and the refractive index Y of the isocyanate reaction liquid to be tested are read.

[0083] The online Abbe refractometer is connected to the isocyanate reaction liquid to be tested. At this time, the temperature and refractive index of the isocyanate reaction liquid to be tested can be detected in real time, and the conversion rate of the isocyanate reaction liquid to be tested can be obtained in real time through a linear equation. This can effectively reduce the inhibition hysteresis caused by long detection time, so that the inhibition operation can be accurately implemented according to the expected conversion rate.

[0084] In one example, an Abbe refractometer is used to detect the refractive index Y and temperature T of the isocyanate reaction solution standard.

[0085] In one example, the test conditions for the conversion rate of the reaction solution standard sample include: using gel chromatography to test the conversion rate α of the reaction solution standard sample.

[0086] The general method of using gel chromatography is to pass the reaction solution standard sample through the chromatographic column and separate it according to the molecular weight. The separated components pass through the detector in sequence, record the signals of different components, and calculate the conversion rate based on the signals and related calibration curves. It can be understood that the present application does not limit the specific operating steps of obtaining the conversion rate of the reaction solution standard sample by gel chromatography.

[0087] For example, the step of obtaining the conversion rate of the reaction solution standard sample includes: diluting the reaction solution standard sample with a solvent to obtain a diluent. The diluent is separated through a chromatographic column with a mobile phase, and a refractive index detector (RID) detects the refractive index difference between the reaction solution standard sample and the solvent, and converts it into an electrical signal output to obtain a gel permeation chromatography (GPC) chromatogram. In the chromatogram, the horizontal axis is the retention time, and the vertical axis is the signal intensity (mV) corresponding to the refractive index difference. According to the principle of gel permeation chromatography, compounds peak in order from large to small according to molecular weight. The chromatogram is integrated by GPC software to determine parameters such as the area and retention time of each peak, thereby obtaining information such as the molecular weight distribution of the reaction solution standard sample, and then obtaining the conversion rate.

[0088] In a second aspect of the present application, a method for inhibiting polymerization of an isocyanate reaction solution is provided, comprising the following steps:

[0089] Taking the isocyanate reaction liquid to be tested, and testing the conversion rate of the polymerizable monomer in the isocyanate reaction liquid to be tested by using the detection method described in any example of the first aspect of the present application;

[0090] When the conversion rate of the isocyanate reaction solution to be tested reaches the expected conversion rate, an inhibitor is added to inhibit polymerization.

[0091] In one example, the expected conversion rate is 30% to 40%. For example, the expected conversion rate includes but is not limited to 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%.

[0092] See also Figure 1 In a third aspect of the present application, a test device for the conversion rate of polymerization monomers in an isocyanate reaction solution is provided, comprising:

[0093] A polymerization reaction module 10, wherein the polymerization reaction module 10 is suitable for containing the isocyanate reaction liquid to be tested,

[0094] A detection module 20, the detection module 20 is connected to the polymerization reaction module 10, and the detection module 20 is suitable for detecting the temperature and refractive index of the isocyanate reaction liquid to be detected;

[0095] The data acquisition module 30 is connected to the detection module 20 and is suitable for collecting the temperature and refractive index measured by the detection module 20 and calculating the conversion rate of the isocyanate reaction solution according to a linear equation.

[0096] Wherein, the linear equation is: α=100%-[K(Yk n ×T)+B]×100%; α is the conversion rate, K is -3000~-2000, N is 4000~4800, k1 is a constant, Y is the refractive index, and T is the temperature.

[0097] For example, the polymerization reaction module 10 includes but is not limited to a reactor.

[0098] For example, the detection module 20 includes but is not limited to an Abbe refractometer.

[0099] By way of example, the data acquisition module 30 includes but is not limited to a recorder or a distributed control (DCS) system.

[0100] The above-mentioned testing device is used, wherein the Abbe refractometer can directly detect the temperature and refractive index of the reaction liquid in the reactor. The Abbe refractometer is connected to a recorder or a DCS control system, and after signal transmission, it can be directly substituted into a linear equation to directly read the reaction conversion rate of the reaction liquid.

[0101] In one example, the Abbe refractometer is calibrated using pure water.

[0102] The following further specific examples are provided to explain the present application in detail. It should also be understood that the following examples are only used to further explain the present application and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application belong to the scope of protection of the present application. The specific process parameters of the following embodiments are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not necessarily limited to the specific values ​​of the embodiments below.

[0103] Example 1

[0104] (1) Construction of linear equations

[0105] An isocyanate reaction solution standard is provided; the isocyanate reaction solution standard includes 5 reaction solution standards with different conversion rates, which are respectively recorded as reaction solution standard A1, reaction solution standard A2, reaction solution standard A3, reaction solution standard A4 and reaction solution standard A5; the conversion rates of reaction solution standard samples A1-A5 are known; wherein the conversion rates of reaction solution standard samples A1-A5 are determined by gel chromatography GPC integration equipped with a differential refractive index detector RID, and the conversion rates of reaction solution standard samples A1-A5 are shown in Table 1. The monomer type included in the reaction solution standard samples A1-A5 is PDI.

[0106] The reaction liquid standard samples A1 to A5 were respectively passed through the online Abbe refractometer, and the temperature T and refractive index Y data of the reaction liquid standard samples were respectively read. The refractive index Y and the temperature T were linearly fitted to obtain the linear equation N of the corresponding relationship between the refractive index Y and the temperature T in the reaction liquid standard samples; the fitting curves of the linear equation N in the reaction liquid standard samples A1 to A5 are shown as follows: Figure 2 And as shown in Table 1.

[0107] Table 1

[0108]

[0109] Depend on Figure 2 As shown in Table 1, the linear equation N of the isocyanate reaction solution standard satisfies Y= -0.0004 T+ b n , R 2 ≥0.99.

[0110] The intercept b of the reaction solution standard samples A1~A5 n The linear equation Y2 = -2930.7×(Y+0.0004×T)+4376.3(R 2 =0.988), where Y2×100% is the PDI monomer content. Conversion rate α=100%-[-2930.7 (Y+0.0004×T)+ 4376.3]×100%.

[0111] (2) Determination of conversion rate in isocyanate reaction solution

[0112] Build a conversion rate test device: connect the online Abbe refractometer to the reactor and the recording instrument respectively.

[0113] Add 1 kg of PDI to the reactor, heat to the reaction temperature of 70°C~80°C, add dropwise the catalyst diluted with alcohol (wherein the catalyst type is quaternary ammonium salt TMR-2, and the total amount of catalyst added is 1 g), take samples during the reaction stage and record the relevant Abbe data (refractive index, temperature) of the isocyanate reaction liquid to be tested, and use the conversion rate α=100%-[-2930.7 (Y+0.0004×T)+4376.3]×100% formula to calculate the conversion rate of the isocyanate reaction liquid to be tested at different stages.

[0114] In order to verify the accuracy of the conversion rate detection in the isocyanate reaction liquid to be tested in this application, samples are taken while the reaction liquid is online tested at different stages, and the samples are integrated by gel chromatography (GPC) to obtain the conversion rate for comparison. The steps of GPC integration include: using a gel chromatography (GPC) equipped with a differential refractive index detector (RID) to detect the conversion rate, specifically including: integrating the curve through GPC software to determine the ratio of the area of ​​the monomer peak to the total area, thereby obtaining the GPC monomer ratio and the GPC conversion rate.

[0115] The conversion rate, GPC conversion rate and the error between them calculated using the conversion rate formula are shown in Table 2.

[0116] Table 2

[0117]

[0118] Example 2

[0119] (1) Construction of linear equations

[0120] An isocyanate reaction solution standard is provided; the isocyanate reaction solution standard includes 6 reaction solution standards with different conversion rates, which are respectively recorded as reaction solution standard B1, reaction solution standard B2, reaction solution standard B3, reaction solution standard B4, reaction solution standard B5 and reaction solution standard B6; the conversion rates of reaction solution standard samples B1 to B6 are known; wherein the conversion rates of reaction solution standard samples B1 to B6 are determined by gel chromatography GPC integration equipped with a differential refractive index detector RID, and the conversion rates of reaction solution standard samples B1 to B6 are shown in Table 3. The monomer type included in the reaction solution standard samples B1 to B6 is HDI.

[0121] The reaction liquid standard samples B1 to B6 were respectively passed through the online Abbe refractometer, and the temperature T and refractive index Y data of the reaction liquid were respectively read. The refractive index Y and temperature T were linearly fitted to obtain the linear equation N of the corresponding relationship between the refractive index Y and temperature T in the reaction liquid standard sample; the fitting curves of the linear equation N in the reaction liquid standard samples B1 to B6 are as follows: Figure 3 And as shown in Table 3.

[0122] Table 3

[0123]

[0124] Depend on Figure 3 As shown in Table 3, the linear equation N of the isocyanate reaction solution standard satisfies Y = -0.0004 T + b n , R 2 ≥0.99.

[0125] The intercept b of the reaction solution standard samples B1~B6 n The linear equation Y2 = -2727.4×(Y+0.0004×T)+4080.0(R 2 =0.981), where Y2×100% is the HDI monomer content. Conversion rate α=100%-[-2727.4×(Y+0.0004×T)+ 4080.0]×100%.

[0126] (2) Determination of conversion rate in isocyanate reaction solution

[0127] Build a conversion rate test device: connect the online Abbe refractometer to the reactor and the recording instrument respectively.

[0128] 1 kg of HDI was added to the reactor, and the reaction temperature was heated to 70°C-80°C. A catalyst diluted with alcohol was added dropwise (wherein the catalyst type was quaternary ammonium salt TMR-2, and the total amount of catalyst added was 1 g). During the reaction stage, samples were taken and the relevant Abbe data (refractive index, temperature) of the isocyanate reaction liquid to be tested were recorded. The conversion rate of the isocyanate reaction liquid to be tested at different stages was calculated using the conversion rate α=100%-[-2727.4×(Y+0.0004×T)+4080.0]×100% formula.

[0129] In order to verify the accuracy of the conversion rate detection in the isocyanate reaction liquid to be tested in this application, samples were taken while the reaction liquid was online detected at different stages, and the samples were integrated by gel chromatography GPC to obtain the conversion rate for comparison. The steps of GPC integration include: using a gel chromatography (GPC) equipped with a differential refractive index detector (RID) to detect the conversion rate, specifically including: integrating the curve through GPC software, determining the ratio of the area of ​​the monomer peak to the total area, thereby obtaining the GPC monomer ratio and the GPC conversion rate. The conversion rate calculated using the conversion rate formula, the GPC conversion rate, and the error between the two are shown in Table 4.

[0130] Table 4

[0131]

[0132] As can be seen from Table 2 and Table 4, the conversion rate test results calculated by the linear equation in the present application are in good agreement with the GPC test results, and the absolute error is less than 0.5%. Therefore, the conversion rate detection method provided in the present application can obtain the instantaneous conversion rate of the reaction by detecting the temperature and refractive index of the isocyanate reaction solution to be tested, which can effectively reduce the detection time and greatly improve the production efficiency.

[0133] Example 3

[0134] Example 3 provides a method for screening inhibition points using the detection method of the present application when PDI is selected as a monomer, comprising the following steps:

[0135] Build the test device: connect the online Abbe refractometer to the reaction kettle, separation kettle and recording instrument respectively.

[0136] 8 kg of PDI was added to the reactor, the outlet of the reactor was connected to the inlet of the separation reactor, and the Abbe refractometer was suitable for recording the temperature and refractive index of the reactor and the separation reactor. The specific steps include: heating the reactor to 40 ° C, dropping TMR-2 catalyst, and when the reaction conversion rate was calculated to be about 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80%, 1 kg of the reaction liquid in the reactor was transferred to the separation reactor through a pipeline, and 1 / 8 of the initial catalyst amount of inhibitor was added to the separation reactor. After the inhibition was complete, the reaction liquid was transferred out for treatment (wherein the conversion rate was calculated using the formula α=100%-[-2930.7 (Y+0.0004×T)+ 4376.3]×100%). Finally, the obtained reaction liquid was subjected to molecular / thin film treatment, and the obtained products were tested for viscosity, color value, and monomer residue. The test results are shown in Table 5.

[0137] Table 5

[0138]

[0139] It can be seen from the test results in Table 5 that when the conversion rate is too high, the viscosity of the obtained polymer product is too large, and the color value increases significantly, and the product quality is not conducive to downstream high-end applications. When the conversion rate is less than 20%, the yield of the polymer product is low at this time. Therefore, the inhibition end point of the TMR-2 catalyst in Example 3 can be set to 30%~40% to obtain a polymer product with excellent comprehensive properties such as color value and viscosity and a higher yield. The detection method of the conversion rate provided in the present application can avoid the hysteresis of the inhibition caused by the long detection time, so that the inhibition operation can be accurately implemented according to the expected conversion rate. After the polymer after the inhibition is treated by molecules / films, an ideal product that meets expectations can be obtained. Therefore, the method provided in the present application has the significant advantages of rapid detection and fixed-point inhibition.

[0140] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0141] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the content of the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution, characterized in that: The following steps are involved: Detecting the temperature T and the refractive index Y of the isocyanate reaction liquid to be tested, substituting the temperature T and the refractive index Y into a linear equation of the corresponding relationship between the reaction temperature, the refractive index and the conversion rate, and determining the conversion rate α in the isocyanate reaction liquid to be tested; The step of constructing the linear equation includes: Providing an isocyanate reaction solution standard; the isocyanate reaction solution standard comprises n reaction solution standard samples with different conversion rates, and the conversion rate α of the reaction solution standard samples is known; Detect the refractive index Y of each of the reaction liquid standard samples at different temperatures T, perform linear fitting on the refractive index Y and the temperature T, and obtain a linear equation N of the corresponding relationship between the refractive index Y and the temperature T in the plurality of the reaction liquid standard samples; the linear equation N is: Y=k n ×T+b n , k n is the slope, b n is the intercept; The intercept b of the linear equation N is n The conversion rate α of the reaction solution standard sample is linearly fitted, and then b n Use Y-k n ×T to obtain the linear equation.

2. The method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution according to claim 1, characterized in that: The detection method has one or more of the following characteristics: (1) The linear equation N R 2 ≥0.98; (2) R of the linear equation 2 ≥0.99; (3) The conversion rate of the reaction solution standard sample is less than 100%.

3. The method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution according to claim 1 or 2, characterized in that: The type of polymerizable monomers included in the reaction solution standard sample and the isocyanate reaction solution to be tested is the same; Optionally, the polymerizable monomer includes one or more of hexamethylene diisocyanate, pentamethylene diisocyanate and diphenylmethane diisocyanate; and / or, In the plurality of linear equations N, the plurality of slopes k n The deviation is ≤ 0.00001; and / or, Among the n reaction solution standard samples with different conversion rates, n is an integer ≥4.

4. The method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution according to claim 3, characterized in that: The detection method has one or more of the following characteristics: (1) When the polymerizable monomer is hexamethylene diisocyanate, the slope k n -0.00041 ~ -0.00039; (2) When the polymerizable monomer is pentamethylene diisocyanate, the slope k n It is -0.00041 ~ -0.00039.

5. The method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution according to any one of claims 1 or 2, characterized in that: The linear equation is: α=100%-[K(Yk n ×T)+B]×100%; where α is the conversion rate, K is -3000~-2000, and B is 4000~4800.

6. The method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution according to claim 1 or 2, characterized in that: The preparation steps of the isocyanate reaction solution to be tested include: The polymerizable monomers and the catalyst are mixed, and the obtained mixture is heated to a polymerization temperature to prepare the isocyanate reaction solution to be tested.

7. The method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution according to claim 6, characterized in that: The preparation steps of the isocyanate reaction solution to be tested have one or more of the following characteristics: (1) The catalyst includes one or more of a quaternary ammonium base catalyst, a quaternary ammonium salt catalyst and a silane amine catalyst; (2) The polymerization temperature is 40°C to 100°C.

8. The method for detecting the conversion rate of polymerization monomers in an isocyanate reaction solution according to claim 1 or 2, characterized in that: The detection method has one or more of the following characteristics: (1) The conditions for detecting the isocyanate reaction liquid to be tested include: passing the isocyanate reaction liquid to be tested through an Abbe refractometer, and reading the temperature T and the refractive index Y of the isocyanate reaction liquid to be tested; (2) The test conditions for the conversion rate of the reaction solution standard sample include: testing the conversion rate α of the reaction solution standard sample by gel chromatography; (3) The test conditions for the conversion rate of the reaction solution standard sample include: using an Abbe refractometer to detect the refractive index Y and temperature T of the isocyanate reaction solution standard sample.

9. A method for inhibiting polymerization of an isocyanate reaction solution, characterized in that: The following steps are involved: Taking the isocyanate reaction liquid to be tested, and testing the conversion rate of the polymerization monomer in the isocyanate reaction liquid to be tested by the detection method according to any one of claims 1 to 8; When the conversion rate of the isocyanate reaction solution to be tested reaches the expected conversion rate, an inhibitor is added to inhibit polymerization.

10. A testing device for the conversion rate of polymerization monomers in isocyanate reaction liquid, characterized in that: include: A polymerization reaction module, wherein the polymerization reaction module is suitable for containing the isocyanate reaction liquid to be tested, A detection module, the detection module is connected to the polymerization reaction module, and the detection module is suitable for detecting the temperature and refractive index of the isocyanate reaction liquid to be tested; A data acquisition module, wherein the data acquisition module is connected to the detection module, and the data acquisition module is suitable for collecting the temperature and refractive index measured by the detection module, and calculating the conversion rate of the isocyanate reaction liquid according to a linear equation; wherein the linear equation is obtained by the detection method described in any one of claims 1 to 8.

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