KR101017914B1 - Method for adjusting the deviation of molecular weight by monitoring the water contents in the preparation of the polytetramethylene ether gylcol - Google Patents

Abstract

The present invention relates to a method for preparing polytetramethylene ether glycol by ring-opening polymerization of tetrahydrofuran using heteropoly acid and / or a salt thereof as a catalyst, in particular polytetramethylene by monitoring the water content during the polymerization process. It relates to a method of controlling the average molecular weight deviation of ether glycol. The present invention provides a method for producing polytetramethylene ether glycol from tetrahydrofuran using heteropolyacid as a catalyst. It provides a method for producing polytetramethylene ether glycol, characterized in that for controlling the variation in the molecular weight of the polytetramethylene ether glycol produced.

Tetrahydrofuran, Polytetramethylene EtherGlycol, Heteropoly Acid, Molecular Weight Fine Control, NIR, Near Infrared Spectroscopy

Description

Method for adjusting the deviation of molecular weight by monitoring the water contents in the preparation of the polytetramethylene ether gylcol}

The present invention relates to a method for preparing polytetramethylene ether glycol by ring-opening polymerization of tetrahydrofuran using heteropoly acid and / or a salt thereof as a catalyst, in particular polytetramethylene by monitoring the water content during the polymerization process. It relates to a method of controlling the average molecular weight deviation of ether glycol.

Polytetramethylene ether glycol (hereinafter referred to as "PTMG") is an industrially useful polymer as the main raw material, oil additive and softener of polyurethane used for polyurethane elastic fibers and synthetic leather. Polytetramethylene ether glycol needs to have an optimum average molecular weight depending on the industrially required use.

When polytetramethylene ether glycol is used as a raw material for elastic fibers represented by polyurethane fibers, it is necessary to adjust the molecular weight as desired because the molecular weight of polytetramethylene ether glycol affects elastic action, especially recovery of elastic fibers. . The molecular weight deviation is within ± 50 molecular weight, preferably within ± 30 molecular weight. Molecular weight deviation is an important item when polytetramethylene ether glycol is supplied for spandex which is an elastic fiber. In the first reaction to produce spandex, PTMG and methyl diisocyanate (hereinafter referred to as "MDI") are equivalently reacted to form a polymer, wherein a smaller molecular weight variation of polytetramethylene ether glycol is advantageous. If the molecular weight deviation is ± 30 it is not necessary to adjust the MDI input ratio to PTMG in the reaction, it can give the stability of the process in forming the spandex polymer. That is, since the less the molecular weight variation of the produced PTMG, the post-processability is advantageous, a method of reducing the molecular weight variation by an appropriate method has been required.

Polytetramethylene ether glycol generally used has two relative molecular weights of 1,000 and 2,000. Polytetramethylene ether glycol having a relative molecular weight of 1,000 is reacted with toluene diisocynate to produce high strength rubber having good abrasion resistance, oil resistance, and excellent adaptability to low temperature environments. In addition, polytetramethylene ether glycol having a relative molecular weight of 2,000 may react with 4-phenylmethyl diisocyanate to produce urethane elastic fibers. This elastic fiber is characterized by high strength and elasticity similar to that of natural rubber.

In the process of producing PTMG using heteropoly acid, after separating the organic layer and the catalyst layer from the reaction effluent, the density of the catalyst layer is measured and the average molecular weight is adjusted by adjusting the amount of water supplied to the reactor so as to maintain this value. The method is generally known. However, in this case, the temperature of the catalyst layer may change depending on the time to be left to affect the density value, and it is difficult for the density value of the catalyst layer to accurately indicate the activity of the reaction.

Another known method for adjusting the average molecular weight in a manufacturing process using heteropolyacids is disclosed in US Pat. No. 5,395,959. This patent describes a method for controlling the average molecular weight in the polymerization of PTMG using heteropolyacids. In detail, the conductivity is measured during the reaction process, and the proton (water) supply amount is controlled in the reaction system by using the same. More specifically, the correlation between the molecular weight and the molecular weight distribution of the reaction product and the conductivity measured in the polymerization system is calculated, and then the amount of water supplied is adjusted to maintain the conductivity of the catalyst layer corresponding to the required molecular weight, thereby obtaining a uniform average molecular weight. To obtain polytetramethylene ether glycol.

In addition, a method of adjusting the molecular weight by measuring conductivity is disclosed in Chinese Laid-Open Patent CN1156515. However, US Patent No. 5,395,959, in contrast to adjusting the amount of water supplied by measuring the conductivity of the catalyst layer, the present patent determines the amount of water to be injected into the reaction system by measuring the conductivity of the organic material of the upper layer of the reactants.

Both methods succeeded in shortening the reaction response time according to the residence time by installing a separate small material separator and shortening the settling time, but since the whole catalyst amount does not exist in an ionized form affecting the conductivity, There is a problem that the accuracy of the conductivity value is poor. In addition, when measuring the conductivity of the upper organic layer, since the upper layer contains a certain amount of catalyst, when considering this content, the accuracy of measuring the conductivity is poor. In particular, if the residence time in the material separator is insufficient, the accuracy cannot be guaranteed due to the heterogeneity of the catalyst.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of effectively controlling the average molecular weight of polytetramethylene ether glycol when preparing polytetramethylene ether glycol alone or by mixing heteropoly acid and / or salt thereof as a catalyst.

In order to solve the above problems, according to a preferred embodiment of the present invention, in the method for producing polytetramethylene ether glycol from tetrahydrofuran using a heteropolyacid as a catalyst, the tetrahydrofuran monomer to be introduced, generated during the reaction It provides a method for producing polytetramethylene ether glycol, characterized in that by controlling the moisture content of the organic material layer and the tetrahydrofuran monomer to be recovered by controlling the variation in the molecular weight of the polytetramethylene ether glycol is finally produced.

According to another suitable embodiment of the present invention, the monitoring of the amount of moisture is characterized in that in real time using NIR (Near Infrared Spectroscopy).

According to another suitable embodiment of the present invention, the control of the water content is characterized in that the control of the water content of the monomer introduced based on the difference with the reference water content.

According to another suitable embodiment of the present invention, the molecular weight deviation of the polytetramethylene ether glycol to be produced is within ± 30.

The present invention makes it possible to predict the variation of the final molecular weight in advance by measuring the moisture in the reaction system as well as the entire system as a method of measuring the moisture of the charged and recovered monomers. In addition, by measuring the moisture in the system in real time, process variables can be adjusted quickly, which is advantageous for stable operation of commercial plants. In particular, when measuring moisture by NIR (Near Infrared Spectroscopy), it may be disadvantageous in catalyst or other mixing systems, but in monomer alone, moisture can be measured within an error range of 10 to 20 ppm, which is different from Karl-Fisher used offline. Measurements can be made within the same level of error. In addition, as the calibration data continues to increase, the moisture content can be measured within a few ppm error range, which can be useful in commercial plants.

The present inventors studied a method for controlling the average molecular weight of polytetramethylene ether glycol which is easy to operate during commercialization while maintaining a constant coordination number of the catalyst during the reaction. As a result, after monitoring the water content such as the water content of the tetrahydrofuran monomer introduced, the water content in the organic layer in the reactor, and the water content of the recovered monomer, the correlation between the variation of the average molecular weight and the effective In addition, it was found that a control method capable of maintaining a uniform molecular weight produced by controlling the amount of input water accurately.

At this time, as a device for measuring and monitoring moisture, various instruments can be used, but NIR (Near Infrared Spectroscopy) is used, which can accurately measure moisture content in organic solvents. Although NIR is used for various purposes, it is particularly advantageous for the measurement of moisture in organic solvents and in the present invention, the moisture content can be accurately measured. NIR was equipped with 4 to 6 probes in the cycler so that each probe could be installed in several places during the process, and at the same time, it can receive information and monitor it in real time. This has the advantage of being high.

In the present invention, a polytetramethylene ether glycol having a specific range of number average molecular weight is prepared by polymerizing a heteropoly acid or a salt of a heteropoly acid alone or using a mixture of a heteropoly acid and a salt thereof and polymerizing tetrahydrofuran, which is a starting monomer. do. In the heteropolyacid catalyst of the present invention, a heteropoly acid having a coordination number of 3 to 5 or a salt of a heteropoly acid alone or mixed is added to tetrahydrofuran to form a catalyst layer, and then to a reactor. In addition, the catalyst layer containing heteropoly acid may be separated from the mixed solution (PTMG + catalyst layer) passing through the reactor according to specific gravity and recycled back to the reactor.

In the present invention, the molecular weight deviation means a deviation from the required PTMG molecular weight value, that is, a deviation from a target value of PTMG to be produced in the process. Molecular weight can be measured in various ways, but the molecular weight value of the present invention is measured by titration of the weight ratio of the terminal OH group in the total weight of the polymer, and the fact that the deviation occurs means that the molecular weight value changes compared to the target value. do. This variation is defined as the deviation.

Hereinafter, a method of controlling molecular weight variation in the manufacturing process of polytetramethylene ether glycol according to the present invention will be described with reference to FIG. 1.

First, the tetrahydrofuran monomer is supplied to the THF reservoir 11 in which the NIR probe 21 for water measurement is installed, and water is supplied from the water input device 10 and then stirred. The moisture in the THF reservoir 11 is measured and tetrahydrofuran containing an appropriate amount of water is introduced into the reactor 12. A heteropoly acid having a coordination number of 3 to 5 and / or a salt thereof is prepared alone or by mixing a mixture with tetrahydrofuran to prepare a catalyst layer in advance and add it to the reactor 12. It is preferable that the reactor 12 maintains temperature at 40-80 degreeC. At this time, the NIR probe 21 installed in the THF reservoir 11 measures the moisture content of the THF.

In the polymerization of THF using heteropolyacids and / or salts thereof alone or in combination as a catalyst, the reaction system forms an emulsion solution in which two phases, an organic phase containing a polymer and a catalyst phase, are dispersed in the form of liquid droplets. The polymerization is thought to be carried out on a catalyst. As polymerization proceeds, polytetramethylene ether glycol dissolved in the catalyst phase begins to be distributed between the catalyst phase and the organic phase. The water supplied with THF is distributed in the coordination water in the catalyst phase and also by the equilibrium concentration in the organic phase and, as the reaction proceeds, exists as a hydroxyl group at the end of the reactant.

The produced reactant is transferred to the catalyst specific gravity separation tank 13, and kept at room temperature for a predetermined time (40 minutes to 1 hour). In the catalyst gravity separation tank 13, the catalyst layer and the organic phase layer are separated, and the organic phase layer is recovered and transferred to the evaporator 14, and the catalyst layer is transferred to the reactor 12 again. The NIR probe 22 is installed on the line transferred from the catalyst gravity separation tank 13 to the evaporator 14 to measure the moisture content of the organic phase layer to be transferred.

The organic phase layer transferred to the evaporator 14 is classified into final polytetramethylene ether glycol and THF monomer by distillation, THF monomer is separated by distillation, and passed through the monomer recovery tank heat exchanger 15 to the monomer recovery passage 16. Transferred. At this time, the NIR probe 23 is installed on the line transferred from the recovery tank heat exchanger 15 to the monomer recovery tank 16 to measure the moisture content of the recovered THF. In addition, the NIR probe 24 is also installed for the final produced PTMG to measure the moisture content.

In the present invention, the amount of water in the THF monomer, the organic layer, and PTMG is measured at each step by using the NIR probes 21 to 24 installed in the respective parts. When the water input device 10 that can be added to the water separately is installed, using the flow regulator 101 and the control device 102, when the molecular weight of the PTMG molecular weight to be produced with respect to the generated PTMG molecular weight is large, Reduce the water input and increase the water input if the molecular weight decreases. The correlation between the THF monomer water input and the water content of the THF monomer recovered and the average molecular weight of the polymerized polytetramethylene ether glycol can be obtained. At this time, while monitoring the moisture measurement of the reaction system to control the moisture according to the correlation, in this case it can reduce the deviation of the final molecular weight.

The meaning of water in the reaction system has two meanings. First, it controls the strength of the reaction by controlling the activation energy of the catalyst used. Second, the role of terminator in which the polymerization reaction occurs after the ring opening of tetrahydrofuran occurs and the reaction is terminated by reacting with water molecules. Will be When water is supplied in excess of the amount participating as a terminator in the reaction system, it affects the reaction catalyst activity, so the balance of water content is very important and thus monitoring and controlling it are the most important factors in controlling the molecular weight of PTMG.

The amount of added water is adjusted according to the percentage change in the moisture content of the water measuring apparatuses 21 to 24 at each stage. The input water is constant and the reaction temperature or other conditions of the reactor are constant, but changing the water content of the moisture measuring devices 21-24 means that the activation energy of the reaction and the terminal ratio in the overall reaction are changing. By monitoring and feeding back, it is possible to minimize the deviation of the generated PTMG molecular weight.

Moisture measurement device (21 ~ 24) by monitoring the amount of water inputted by measuring the change in the water content of each series, and displayed the change in the generated PTMG molecular weight. The amount of water is controlled through the flow controller 101 shown in FIG. 1, and the amount of water introduced is adjusted as a result of moisture monitoring. Changes in the reaction conditions occur over time, resulting in a change in the amount of water, and monitoring in real time to detect the amount of water rising in the water measuring device (21 to 24) and to be input in the amount (percentage unit) accordingly. To control the amount of water.

The moisture content is adjusted over time, and the reference moisture state converges to the target point. The theoretical added water content during the reaction can be determined according to the molecular weight of the desired PTMG. The moisture content is monitored through a moisture measuring device while maintaining the standard moisture content, and after 1 hour, the moisture content change% is calculated from the standard moisture content, and the input water amount is adjusted by reflecting the changed moisture content%. At this time, if the change moisture content is less than 1%, the input moisture content is not controlled.

In the following the invention is described in detail by way of examples, but the examples presented are for clarity of understanding and should not be construed as limiting the invention.

 <Example 1>

100 kg of tetrahydrofuran monomer and 250 cc of water are supplied to the monomer reservoir equipped with the NIR probe and stirred. The tetrahydrofuran monomer containing water is transferred to the reactor, and a catalyst layer prepared using phosphotungstic acid having a coordination number of 3 to 5 and tetrahydrofuran is introduced into the reactor and reacted while maintaining a temperature of 60 ° C. The resulting reactants are transferred to a continuous settling tank and separated into a catalyst layer and an organic phase layer. The separated catalyst layer is transferred back to the reactor, the organic phase layer is transferred to the evaporator, tetrahydrofuran is sent to the monomer recovery tank, and polytetramethylene ether glycol is collected in the storage tank. At this time, the water content was measured using NIR probes installed on the line and the polytetramethylene ether storage tank transferred to the monomer recovery tank. The moisture content and the molecular weight of the final polytetramethylene ether glycol measured at each step are shown in Table 1 below.

As shown in Table 1, the water content of each step at 1 hour after the start of the reaction was compared with the water content (reference water content) of each step of the reaction start step, and the average of the difference was about 1%. Therefore, the water input amount was adjusted from 250cc / hr to 247.5 cc / hr by adjusting the water input amount of 2.5cc, which is 1% of 250cc / hr. The water content at each stage was specified 2 hours after the start of the reaction while the adjusted amount of water was added. At 2 hours, the water content was similar to the reference water content of 0hr level, so the water input was restored to the reference water content of 250cc / hr. Thereafter, the moisture content was measured at 1 hour intervals while maintaining the same moisture content, and the difference from the standard moisture content was calculated. Since the difference was less than 1%, the water input was maintained at 250 cc / hr. Six hours after the start of the reaction, the mean difference with the reference moisture content was lowered to 1.2%. At this time, the amount of water input was increased again by 1.2% (250cc / hr-> 253cc / hr) to proceed with the reaction.

Adjusting the reaction in this way ensures the uniformity of the reaction is shown in Table 1 the molecular weight of the produced PTMG. The deviation of the PTMG molecular weight produced at each step was 2000 ± 30 daltons. Table 1 shows the hourly moisture monitoring values and molecular weight values up to 6hr, after which the moisture content and molecular weight values at times that differ by more than 1% from the reference moisture content. The value at each time not shown in Table 1 is 250 cc / hr of water input. The molecular weight of the final polytetramethylene ether glycol was measured by OH titration (OH Titration, ASTM D4274-05 Standard Test Methods for Testing Polyurethane Raw Materials: Determination of Hydroxyl Numbers of Polyols).

At this time, the measured molecular weight value according to the monitoring and control of the moisture content in each system is shown in Table 1. In particular, it can be seen that the width of the variation in the molecular weight of PTMG changes in proportion to the change in moisture content.

<Comparative Example 1>

The same reactor and the same reaction as in Example 1 while controlling the molecular weight of the final produced PTMG was controlled by the density (Density) of the catalyst layer recovered in the catalyst gravity separation tank. The catalyst layer density was controlled to ± 0.003 g / cm ³ by controlling the amount of water introduced while monitoring the generated PTMG molecular weight. At this time, the molecular weight of PTMG was able to control the variation of molecular weight to 2000 ± 50 level when the reaction proceeded for 30 hours or more. The density of the catalyst layer recovered from the separation tank is measured through a density meter (Density Meter) and at the same time taking a sample to measure the molecular weight. When the molecular weight deviation is more than 1% of the target molecular weight, the water input is changed by the% of molecular weight deviation occurrence. Considering the residence time in the reactor, the reaction time took 10-20 hours until the molecular weight was changed after the water was added, so that the molecular weight variation of the produced PTMG was ± 50 even if the catalyst bed density was controlled.

Table 1 shows the catalyst layer density through the measurement of the moisture content. The change of catalyst layer density relative to moisture deviation was relatively insensitive and the variation of the significant digits of the third decimal point was controlled within ± 0.001.

division Standard moisture content and difference average (%) Water input
(cc / hr) Moisture Measurement (21)
(ppm) Moisture measurement
(22)
(ppm) Moisture Measurement (23)
(ppm) Moisture Measurement (24)
(ppm) Molecular Weight
(dalton) Catalyst bed
density
(g / cm ³⁾ 0hr Water content 250 2000 2300 3400 1980 2005 2.050 1hr 1.1 250 → 247.5 2020 2328 3431 1998 1983 2.049 2hr 0.2 247.5 → 250 1998 2301 3402 1990 2006 2.050 3hr 0.1 250 1995 2303 3403 1978 2014 2.050 4hr 0.2 250 2003 2308 3404 1983 2022 2.050 5hr 0.4 250 2008 2310 3407 1988 2026 2.050 6hr 1.2 250 → 253 1977 2270 3660 1968 2029 2.049 10hr 1.0 250 → 247.5 2019 2327 3433 1998 1990 2.049 16hr 1.2 250 → 253 1978 2275 3663 1973 2022 2.050 28hr 1.0 250 → 247.5 2025 2327 3435 2000 1985 2.050 34hr 1.0 250 → 252.5 2018 2325 3428 1992 2020 2.050 38hr 1.0 250 → 252.5 2017 2326 3429 1990 2018 2.051

1 shows a process for preparing polytetramethylene ether glycol according to the present invention.

* Brief description of reference numbers

10. Water input device

11. THF reservoir

12. Reactor

13. Catalyst specific gravity separation tank

14. Evaporator

15. Monomer Recovery Tank Heat Exchanger

16. Monomer Recovery Tank

101. Flow regulator

102. Control

21-24. Moisture Measurement Device

Claims (4)

In the process for producing polytetramethylene ether glycol from tetrahydrofuran using heteropoly acid as a catalyst, After measuring the water content of the added tetrahydrofuran monomer, the water content of the organic material layer generated during the reaction and the water content of the tetrahydrofuran monomer recovered, and then adjust the amount of water supplied to the reaction system based on the difference between the reference water content and the final production A method for producing polytetramethylene ether glycol, characterized by adjusting the molecular weight variation of polytetramethylene ether glycol. The method of claim 1, wherein the monitoring of the amount of water is performed in real time using Near Infrared Spectroscopy (NIR). delete The method for preparing polytetramethylene ether glycol according to claim 1, wherein the molecular weight deviation of the polytetramethylene ether glycol to be produced is within ± 30.

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